Elastomer composition and method for producing the same

Abstract

Provided is an elastomer composition having excellent elongation and breaking strength. [Solution] An elastomer composition containing 0.1 to 10 parts by weight of cellulose nanofiber powder per 100 parts by weight of elastomer, wherein the cellulose nanofiber powder contains 75 to 99% by weight of cellulose nanofiber, 0.5 to 20% by weight of phosphate ester, and 0.5 to 5.0% by weight of alkylammonium salt relative to the total weight of the cellulose nanofiber powder.

Description

[Technical Field]

[0001] The present invention relates to an elastomer composition, and more particularly to an elastomer composition having excellent elongation and strength at break, and a method for producing such an elastomer composition. [Background technology]

[0002] Elastomers are polymers that have viscoelasticity (meaning both viscosity and elasticity), and are generally amorphous polymers with a cross-linked network structure. They have the property of being deformed by small stresses and returning to their original shape when the stress is removed. Elastomer is a compound word made up of "elastic" and "polymer" and is often used synonymously with rubber, although rubber generally refers to vulcanized elastomers.

[0003] Meanwhile, cellulose nanofiber (also known as "Cellulose Nano Fiber"; hereafter referred to simply as "CNF") is a next-generation plant-derived material that is said to be five times stronger than steel at one-fifth the weight. Using cellulose nanofiber in automobiles, home appliances, and other products can reduce weight, improve energy efficiency, and is expected to make a significant contribution to combating global warming. Toward the social implementation of CNF, the Ministry of Economy, Trade and Industry and the Ministry of Agriculture, Forestry and Fisheries are collaborating to implement model projects in various fields, including automobiles, home appliances, and housing and building materials, to evaluate and verify the CO2 reduction effects and to demonstrate solutions to related issues.

[0004] As one application example of cellulose nanofibers, Patent Document 1 (JP 2023-133655 A) discloses a thermoplastic composite resin containing a thermoplastic resin, cellulose nanofibers, an ethylene-based copolymer, and a volatile substance. The thermoplastic resin is one or more selected from polyethylene, polypropylene, polystyrene, polylactic acid, ABS resin, vinyl chloride resin, elastomer-based resins, etc. The invention discloses that it is possible to provide a thermoplastic composite resin that can be produced using a simple process, contains a volatile substance, and has sustained release properties of the volatile substance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-133655 Summary of the Invention [Problem to be solved by the invention]

[0006] Lightly crosslinked polymers generally have a lower modulus and greater extensibility than other materials. Furthermore, elastomers allow the polymer chains to stretch under stress because they are held together by relatively weak intermolecular forces. This allows the elasticity of elastomers to be attributed to the ability of the chains to realign to dissipate stress.

[0007] Under normal conditions, the long molecular chains of elastomer materials are irregularly coiled. When a force is applied, they align in the direction of the tension, and when the force or tension is released, they return to their original configuration. This flexibility allows individual elastomers to be reversibly stretched up to several hundred percent. However, elastomers have low mechanical strength, with lower elongation and breaking strength than plastics and metals. They are often unsuitable for components that are subjected to loads in a stretched state.

[0008] The present invention has been completed in view of the above problems, and an object of the present invention is to provide an elastomer composition having excellent elongation and breaking strength in one embodiment. An object of the present invention is to provide a method for producing such an elastomer composition in another embodiment. [Means for solving the problem]

[0009] After extensive research, the inventors came up with the idea of ​​improving the tensile strength of elastomers when stretched by dispersing nano-sized fibers. Nanofibers include cellulose nanofibers (hereinafter sometimes referred to as "CNF"), carbon nanotubes, and nanofiberglass. They discovered that using CNF, which is the most flexible, can improve elongation and breaking strength.

[0010] Carbon nanotubes and nanofiberglass tend to have reduced elongation and may break. On the other hand, by incorporating specially treated cellulose nanofibers into an elastomer, the elongation and breaking strength of the crosslinked elastomer were excellent. The present invention was completed based on the above findings, and is exemplified below.

[0011] [Aspect 1] An elastomer composition comprising 0.1 to 10 parts by weight of cellulose nanofiber powder relative to 100 parts by weight of an elastomer, The cellulose nanofiber powder is an elastomer composition comprising, relative to the total weight of the cellulose nanofiber powder, 75 to 99% by weight of cellulose nanofibers, 0.5 to 20% by weight of a phosphate ester, and 0.5 to 5.0% by weight of an alkylammonium salt. [Aspect 2] 2. The elastomer composition of claim 1, wherein the elastomer is a polyolefin-based elastomer. [Aspect 3] 3. The elastomer composition according to aspect 1 or 2, wherein the cellulose nanofiber powder has an average fiber length in the range of 0.1 μm to 3.0 μm. [Aspect 4] The elastomer composition according to any one of Aspects 1 to 3, wherein the cellulose nanofiber powder has an average fiber diameter in the range of 0.5 nm to 10 nm. [Aspect 5] A method for producing an elastomer composition, comprising: Step A of preparing a cellulose nanofiber dispersion; A step B of supplying the cellulose nanofiber dispersion to a two-roll mill and rotating the two-roll mill to dry the cellulose nanofiber dispersion and obtain cellulose nanofiber powder; and A process C of adding 0.1 to 10 parts by weight of the cellulose nanofiber powder to 100 parts by weight of an elastomer and kneading them to obtain an elastomer composition. Including, The cellulose nanofiber dispersion is prepared to contain, in terms of solid content, 0.5 to 20% by weight of a phosphoric acid ester and 0.5 to 5.0% by weight of an alkylammonium salt. [Effects of the Invention]

[0012] According to one embodiment of the present invention, an elastomer composition having excellent elongation and breaking strength can be provided. According to yet another embodiment of the present invention, a method for producing such an elastomer composition can be provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating the structure and operating principle of a two-roll mill according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0015] (1. Cellulose nanofiber raw materials) Cellulose nanofibers are made by finely grinding cellulose, the main component of plant fibers, to nano-size particles, and are primarily made from wood pulp (the raw material for paper). They are used primarily to reinforce resin materials and prevent resin shrinkage at low temperatures. In the present invention, there are no particular limitations on the raw materials used for cellulose nanofibers.

[0016] Because cellulose nanofibers are typically plant-derived materials, they are in the form of a slurry dispersed in water when extracted from the plant. The solid content is typically 1 to 10% by weight. For example, when producing a powder dispersant from a cellulose nanofiber dispersion, it is first necessary to remove only the water from the cellulose nanofiber aqueous dispersion dispersed in water to extract the individual cellulose nanofibers. It is also conceivable that the individual cellulose nanofibers may be redispersed in water or a dispersing medium other than water, and then extracted again from the redispersion. Therefore, in the present invention, the dispersing medium in the cellulose nanofiber dispersion is not limited to water. However, the dispersing medium in the cellulose nanofiber dispersion is preferably water.

[0017] As mentioned above, the solids content of a cellulose nanofiber dispersion is usually 1 to 10% by weight, but it may also be further diluted to less than 1% by weight. Therefore, the cellulose nanofiber dispersion can also be pre-dried. There are no particular restrictions on the pre-drying method, and any conventional method can be used. The cellulose nanofiber dispersion can be pre-dried, for example, to a maximum solids content of 12% by weight, and then subjected to the roll drying method described below.

[0018] As described below, cellulose nanofiber powder is obtained by drying a cellulose nanofiber dispersion under specific conditions. The average fiber length of the cellulose nanofiber powder is preferably 0.1 μm or more. This is expected to improve dispersion stability. From this perspective, the average fiber length of the cellulose nanofiber powder is more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. If the average fiber length of the cellulose nanofiber powder is 0.1 μm or more, it will have a high aspect ratio relative to the average fiber diameter.

[0019] Furthermore, it is preferable that the average fiber length of the cellulose nanofiber powder is 3.0 μm or less. This prevents the cellulose nanofiber powder from becoming spherical during processing. From this perspective, it is more preferable that the average fiber length of the cellulose nanofiber powder is 2.5 μm or less, even more preferably 1.5 μm or less, and even more preferably 1.0 μm or less.

[0020] The average fiber length of the cellulose nanofiber powder refers to the D50 (median diameter) of the fibers of the cellulose nanofiber powder measured according to the laser diffraction / scattering method of JIS Z8825:2022.

[0021] The average fiber diameter of the cellulose nanofiber powder is preferably 0.5 nm or more. This is expected to improve dispersion stability. From this perspective, the average fiber diameter of the cellulose nanofiber powder is more preferably 0.7 nm or more, even more preferably 1 nm or more, and even more preferably 3 nm or more.

[0022] Furthermore, it is preferable that the average fiber diameter of the cellulose nanofiber powder is 10 nm or less. If the cellulose nanofiber powder becomes too thick, the aspect ratio decreases, and steric hindrance may occur, making it impossible to maintain interparticle distance. From this perspective, it is more preferable that the average fiber diameter of the cellulose nanofiber powder is 8 nm or less, even more preferably 7 nm or less, and even more preferably 5 nm or less.

[0023] The average fiber diameter of the cellulose nanofiber powder refers to the average particle diameter of the fibers of the cellulose nanofiber powder measured according to the dynamic light scattering method of JIS Z8828:2019.

[0024] (2. Cellulose nanofiber powder) Because cellulose nanofibers have a uniform diameter, a specific length direction, and are flexible, when the molecular chains in a coiled state before stretching are stretched, they move along with the molecular arrangement while maintaining their orientation. This movement occurs as if they are wrapping around the molecular chains of the elastomer, making them less likely to break and further increasing their rigidity. This reduces the resistance to external stress, wear, and sudden breakage in thinly stretched elastomer gaskets and processed fiber products, making them less likely to break. However, to take advantage of these advantages of cellulose nanofibers, proper dispersion is necessary. Therefore, in this embodiment, a powder made by chemically decorating a cellulose nanofiber slurry is used.

[0025] In one embodiment of the present invention, the cellulose nanofiber powder contains, relative to the total weight of the cellulose nanofiber powder, 75 to 99% by weight of cellulose nanofibers, 0.5 to 20% by weight of phosphate ester (including phosphate ester salts, the same applies below), and 0.5 to 5% by weight of alkylammonium salt.

[0026] If the amount of cellulose nanofibers is less than 75% by weight, the dispersing effect of the dispersant containing cellulose nanofibers as its core will be weakened. From this perspective, the amount of cellulose nanofibers is 75% by weight or more, preferably 78% by weight or more, more preferably 80% by weight or more, even more preferably 82% by weight or more, and even more preferably 85% by weight or more. On the other hand, if the amount of cellulose nanofibers exceeds 90% by weight, the effects of other components will be weakened, resulting in a reduced dispersing effect. From this perspective, the amount of cellulose nanofibers is 99% by weight or less, preferably 98% by weight or less, and more preferably 97% by weight or less.

[0027] In this embodiment, the cellulose nanofiber powder may contain a surfactant. Among the surfactants, it is particularly important to use phosphate esters and alkyl ammonium salts.

[0028] The amount of surfactant added is 1.0 to 25.0 wt% relative to the total weight of the cellulose nanofiber powder. If the amount of surfactant added is less than 1.0 wt%, the effect cannot be fully exerted. From this perspective, the amount of surfactant added is preferably 2.0 wt% or more, more preferably 3.0 wt% or more, and even more preferably 4.0 wt% or more. On the other hand, if the amount of surfactant added exceeds 25.0 wt%, the effect will plateau. From this perspective, the amount of surfactant added is preferably 20.0 wt% or less, more preferably 15.0 wt% or less, even more preferably 10.0 wt% or less, and even more preferably 7.0 wt% or less. The surfactant is usually added in the form of an aqueous solution, but it may also be added as a single substance.

[0029] Phosphate esters are compounds in which the hydroxyl groups of phosphoric acid (H3PO4) form ester bonds with the hydroxyl groups of alcohol or phenol, which changes the surface properties of cellulose. For example, when OH groups on the surface of cellulose are replaced with phosphate ester groups, the hydrophilicity changes and the hydrophobicity increases. This improves dispersibility in composite materials and interfacial adhesion. Surface modification with phosphate esters suppresses aggregation of CNFs and improves dispersibility in organic solvents. This can induce the diffusion of cellulose nanofibers into elastomers.

[0030] There are several types of phosphate esters. For example, monophosphate esters (monoesters), glucose-6-phosphate, AMP (adenosine monophosphate), diphosphate esters (diesters), triphosphate esters (triesters), trimethylphosphate esters, triphenylphosphate esters, tributylphosphate esters, etc. A particularly preferred example is BYK-142 (a phosphate salt of a high molecular weight copolymer, diluted with methylpyrrolidone acetate (MPA)) manufactured by BYK.

[0031] The amount of phosphate ester added is 0.5 to 20.0 wt% relative to the total weight of the cellulose nanofiber powder. If the amount of phosphate ester added is less than 0.5 wt%, its effect will not be fully exerted. From this perspective, the amount of alkylammonium salt added is preferably 1.0 wt% or more, more preferably 2.0 wt% or more, and even more preferably 3.0 wt% or more. On the other hand, if the amount of phosphate ester added exceeds 20.0 wt%, its effect will plateau. From this perspective, the amount of phosphate ester added is preferably 15.0 wt% or less, more preferably 10.0 wt% or less, even more preferably 8.0 wt% or less, and even more preferably 6.0 wt% or less. Note that phosphate ester is usually added in the form of an aqueous solution, but it may also be added as a single substance.

[0032] Examples of alkylammonium salts include, but are not limited to, distearyldimethylammonium chloride, behenyltrimethylammonium chloride, stearyltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, lauryltrimethylammonium chloride, benzalkonium chloride, etc. A particularly preferred example is BYK-9076 (a 50 to 60 mass % solution of alkylammonium salts of high molecular weight copolymers) manufactured by BYK.

[0033] The amount of alkylammonium salt added is 0.5 to 5.0 wt % relative to the total weight of the cellulose nanofiber powder. If the amount of alkylammonium salt added is less than 0.5 wt %, the effect cannot be fully exerted. From this perspective, the amount of alkylammonium salt added is preferably 1.0 wt % or more, more preferably 2.0 wt % or more, and even more preferably 3.0 wt % or more. On the other hand, if the amount of alkylammonium salt added exceeds 5.0 wt %, the effect will plateau. From this perspective, the amount of alkylammonium salt added is preferably 6.0 wt % or less. Note that alkylammonium salts are usually added in the form of an aqueous solution, but they may also be added as a single substance. However, it is preferable to add them in the form of an aqueous solution. Alkylammonium salts have the effect of preventing aggregation of cellulose nanofibers during the water reduction process.

[0034] The method for producing cellulose nanofiber powder of this embodiment includes step A of preparing a cellulose nanofiber dispersion, and step B of supplying the cellulose nanofiber dispersion to a two-roll mill and rotating the two-roll mill to dry the cellulose nanofiber dispersion and obtain cellulose nanofiber powder, where the cellulose nanofiber dispersion is prepared to contain 0.5 to 20% by weight of phosphate ester and 0.5 to 5% by weight of alkylammonium salt on a solids basis.

[0035] In step A of preparing a cellulose nanofiber dispersion, the types and amounts of each component of the cellulose nanofiber dispersion are as described above, and therefore will not be described here.

[0036] After step A, the cellulose nanofiber dispersion is fed into a two-roll mill, and the two-roll mill is rotated to remove the cellulose nanofiber dispersion and obtain a thick, dried cellulose nanofiber powder (step B).

[0037] By supplying the cellulose nanofiber dispersion to the middle of the two-roll mill, the cellulose nanofiber dispersion is absorbed into the roll gap (nip) (Figure 1). A characteristic of the two-roll mill is that before entering the nip, the input raw material rotates in the same direction as the rolls in the roll bank above the roll gap. At this time, the cellulose nanofibers maintain their orientation, and when they enter the nip, the fibers are aligned in the same direction. This causes shear shear in the nip while maintaining the orientation of the cellulose nanofibers. The raw material, whose boiling point is lowered by self-heating due to shear shear and the heating temperature of the two-roll mill, easily vaporizes, shortening the drying time. The distance between the rolls (clearance) is not particularly limited, but in this embodiment, it is preferably 0.3 to 1.5 mm.

[0038] The greater the rotation ratio (i.e., the difference in rotation speed) between the front roll and the rear roll in a two-roll mill, the faster the material will be cut into the nip. On the other hand, if the rotation ratio between the front roll and the rear roll is too high, the shear generated by the rotation ratio will be small and the time it takes for water to evaporate will be short, so it is preferable to set the rotation ratio to 1 to 3. Furthermore, if there is no rotation ratio, the cellulose nanofiber dispersion will not be able to cut into the nip and will tend to stagnate on the roll bank.

[0039] Due to the self-heating in the nip and the heat transfer from the heated two-roll mill, the intermolecular attraction of water molecules and the thermal energy cause the water molecules to attract each other in liquid form and interact with other nearby molecules. Under the sudden high temperature, the water molecules gain enough energy to overcome the intermolecular attraction with the fibers, and the water and alcohol instantly transition from liquid to gas. As mentioned above, the cellulose nanofibers enter the nip while maintaining their orientation, so they undergo vaporization in the same direction due to a steam explosion. This places little random stress on the cellulose nanofibers, allowing them to dry in a state close to their original form (with the double helix structure still largely intact).

[0040] Here, kneading machines other than two-roll mills, such as pressure kneaders, Banbury kneaders, and extruders, are considered. However, because these machines knead randomly, even if the water evaporates instantly, the cellulose nanofibers tend to entangle with each other and form lumps. Furthermore, conventional techniques such as freeze drying, drying ovens, and spray drying do not provide a means for imparting orientation to the cellulose nanofibers, and the drying process takes time, which tends to loosen the double helix structure and cause lumps. Therefore, two-roll processing offers advantages not available with conventional techniques. Note that a two-roll mill can be any device that can knead the raw materials between two rolls, and it may also have a third or subsequent roll.

[0041] Furthermore, if the surface temperature of the two-roll mill is too high, there is a risk that the cellulose nanofibers will be altered, and the surface will harden during powdering, making it difficult to produce fine particles, so the temperature is preferably 130°C or less, and more preferably 120°C or less. Therefore, in one embodiment of the present invention, the surface temperature of the two-roll mill is 95°C to 130°C.

[0042] As a result of the treatment with the two-roll mill, cellulose nanofiber powder is obtained. Note that the method described in Japanese Patent No. 7541411 can be used to dry the cellulose nanofibers, and the description thereof is incorporated herein in its entirety.

[0043] (3. Elastomer Composition) The elastomer composition of the present embodiment contains 0.1 to 10 parts by weight of cellulose nanofiber powder relative to 100 parts by weight of elastomer.

[0044] The elastomer that can be used in this embodiment is not limited and can be appropriately selected depending on the purpose. Examples include polyolefin-based elastomers, diene-based elastomers, polyurethane-based elastomers, polyester-based elastomers, and polyamide-based elastomers.

[0045] Polyolefin elastomers are soft resins containing a polyolefin resin and a rubber component, and may be those in which the rubber component is dispersed in the polyolefin resin or those in which the two are copolymerized. Examples include non-crosslinked thermoplastic olefin elastomers (TPOs) such as ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutene, polyisobutylene, chlorinated polyethylene, elastomers in which a polyolefin component and a rubber component are physically dispersed, and elastomers in which a polyolefin component and a rubber component are microphase-separated; and dynamically crosslinked thermoplastic olefin elastomers (TPVs), which are multiphase polymers obtained by dynamically heat-treating a mixture containing a matrix-forming resin component A (olefin resin component A) and a domain-forming rubber component B in the presence of a crosslinking agent, and have a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in the matrix (sea phase) of resin component A.

[0046] The diene-based elastomer may be selected from the group consisting of polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers.

[0047] Examples of polyurethane elastomers include polyurethane elastomers obtained by polymerizing polyols and polyisocyanates. Examples of polyols used in this polymerization include ester-type polyols, ether-type polyols, and polycarbonate-type polyols. Examples of ester-type polyols include polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene adipate (PHA), poly(3-methylpentane adipate) (PMPA), and polycaprolactone (PCL). Examples of ether-type polyols include polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetramethylene ether glycol (PTMG). Examples of polycarbonate-type polyols include polyhexamethylene carbonate diol (PHC) and co-condensates of polyhexamethylene carbonate with other ester-type polyols or ether-type polyols.

[0048] Examples of polyester elastomers include polyester-ether types that use polybutylene terephthalate (PBT) for the hard segment and polytetramethylene ether glycol (PTMG) for the soft segment, and polyester-ester types that use polybutylene terephthalate (PBT) for the hard segment and polybutylene adipate (PBA) for the soft segment. Any of these elastomers may be used alone or in combination of two or more.

[0049] Examples of polyamide elastomers include polyether ester types using nylon 6, nylon 11, or nylon 12 for the hard segment and polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene ether glycol (PTMG) for the soft segment, and polyether amide types using polypropylene diamine or polybutylene diamine for the soft segment. Any of these elastomers may be used alone or in combination of two or more.

[0050] The elastomer composition may contain any known crosslinking agent, crosslinking accelerator, and additives as long as they do not impair the effects of the present invention. The crosslinking agent may be, for example, sulfur. The crosslinking accelerator may be selected from, for example, zinc oxide, stearic acid, or equivalent compounds such as stearates, transition metal salts, guanidine derivatives (especially diphenylguanidine), and the like. The additives may include plasticizers, pigments, protective agents, heat stabilizers, anti-ozonants, antioxidants, and anti-fatigue agents. Furthermore, the elastomer composition may be combined with known thermoplastic resins to form a modified mixed compound.

[0051] The crosslinking agent can be added in an amount of, for example, 0.5 to 12 parts by weight, preferably 1 to 10 parts by weight, relative to 100 parts by weight of the elastomer.The vulcanization accelerator can be added in an amount of, for example, 0.5 to 10 parts by weight, preferably 0.5 to 8.0 parts by weight, relative to 100 parts by weight of the elastomer.

[0052] The elastomer composition of this embodiment contains 0.1 to 10 parts by weight of cellulose nanofiber powder per 100 parts by weight of elastomer. If the amount of cellulose nanofiber powder added is less than 0.1% by weight, the effect cannot be fully exerted. From this perspective, the amount of cellulose nanofiber powder added is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. On the other hand, if the amount of cellulose nanofiber powder added exceeds 10% by weight, the effect will plateau. From this perspective, the amount of cellulose nanofiber powder added is preferably 8 parts by weight or less, more preferably 5 parts by weight or less.

[0053] By incorporating the above-described chemically decorated and dried cellulose nanofiber powder into an elastomer composition, the cellulose nanofibers are well dispersed, and their effects are more pronounced, thereby improving the elongation and breaking strength of the elastomer.

[0054] The method for producing the elastomer composition of this embodiment includes, in addition to steps A and B for obtaining the cellulose nanofiber powder described above, step C of adding 0.1 to 10 parts by weight of cellulose nanofiber powder to 100 parts by weight of elastomer and kneading them to obtain the elastomer composition.

[0055] The kneading machine used in step C is not limited, and any known kneading machine can be used. For example, the cellulose nanofiber powder and the elastomer resin can be placed in a twin-screw extruder and kneaded.

[0056] In step C, in addition to the cellulose nanofiber powder, any known crosslinking agent, crosslinking accelerator, and other additives may be added together. [Example]

[0057] Examples of the present invention will be described below together with comparative examples. These examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0058] (Cellulose nanofiber powder production process) BYK BYK-142 (phosphate ester) and BYK BYK-9076 (alkylammonium salt) were placed in a container and mixed at room temperature for 10 minutes at 700 rpm using a dissolver mixer. To this mixture, an aqueous solution of cellulose nanofibers with a solid content of 8% by weight was added, and the mixture was mixed at room temperature for 5 minutes at 500 rpm using a dissolver mixer.

[0059] The mixture was placed in a two-roll mill manufactured by Yasuda Seiki Seisakusho Co., Ltd. (roll diameter: 8 inches, surface treatment: gloss plating, nip clearance: 0.5 mm). The amount placed was 300 g. The rolls were heated to a surface temperature of 120°C. Next, the two-roll mill was operated with the front roll rotating at 7 rpm and the rear roll at 6 rpm, and a sample of the dried product was taken after three rotations of the front roll (roll-processed CNF). The drying time was within 30 seconds.

[0060] The amount of each component in the dried cellulose nanofiber powder was confirmed by gas chromatograph mass analysis using a Shimadzu GC-MS series instrument. The entire composition was then heated in a ceramic crucible combustion chamber manufactured by Buhler Co., Ltd., to remove the carbonized material. The residue was then analyzed by FTIR analysis using an IRA1S series instrument manufactured by Shimadzu Corporation to confirm the peak elements. The water-soluble portion was analyzed by mass analysis using a Shimadzu Nexera series high-performance liquid chromatograph. The mass of each component was calculated from the results of these analyses. The cellulose nanofiber powder consisted of 92% CNF by weight, 6% phosphate ester salt, and 2% alkylammonium salt by weight.

[0061] (Process for producing elastomer composition) To demonstrate the differences in the functionality of the elastomer compositions, compounds were tested by combining a polypropylene (J-105G manufactured by Prime Polymer Co., Ltd.) with a relatively low elongation rate and an elastomer. The elastomer used was TAFMER® PN-2070 (polypropylene-α-alfin copolymer) manufactured by Mitsui Chemicals, Inc. The crosslinking agent used was Trexplain TPV manufactured by Mitsubishi Chemical Corporation. The aforementioned cellulose nanofiber powder was used as the filler. Furthermore, freeze-dried blank powder (100% CNF) dried in a Sansho Industry Co., Ltd. SF-10 freeze-drying device and kaolin nanopowder (Alumina sol10A manufactured by Kawaken Fine Chemical Co., Ltd., main component: alumina silica) were used as fillers for comparison. Furthermore, ZP (zinc oxide) manufactured by Dainichi Chemical Co., Ltd. was used as a heat stabilizer. The amounts of each component added are shown in Table 1.

[0062] The entire amount of each component was charged into a 20 L Henschel mixer manufactured by Nippon Coke and Engineering Co., Ltd., and after thorough mixing, the mixture was extruded at 230°C using a twin-screw extruder (model number: GT-110) manufactured by Ikegai Corporation to obtain a strand (string-like) having a diameter of 2.7 mm and a length of 200 mm.

[0063] [Table 1]

[0064] (Performance evaluation) The elongation (%) to break of each strand was measured using an Instron® 2603-080 Long Elongation XL Extensometer manufactured by Instron Corporation. Furthermore, each strand was cut into 3 mm pellets and fed into an inflation extrusion film molding machine (model LF250) manufactured by Altex Co., Ltd., where a 15 μm thick film was produced at 200°C. A4-sized pieces were cut from this film, and the number of pinholes in the film was counted. The results are shown in Table 1.

[0065] As can be seen from Table 1, the elastomer compositions using the cellulose nanofiber powder according to the present disclosure had excellent elongation and breaking strength. On the other hand, when the cellulose nanofiber powder was not subjected to the specified treatment, the improvement in elongation and breaking strength was limited.

Claims

1. An elastomer composition comprising 0.1 to 10 parts by weight of cellulose nanofiber powder per 100 parts by weight of elastomer, The cellulose nanofiber powder contains 75 to 99 wt% of cellulose nanofibers, 0.5 to 20 wt% of a phosphate ester, and 0.5 to 5.0 wt% of an alkylammonium salt, based on the total weight of the cellulose nanofiber powder; An elastomer composition in which OH groups on the surface of the cellulose nanofibers are substituted with phosphate ester groups of the phosphate ester.

2. The elastomer composition according to claim 1 , wherein the elastomer is a polyolefin-based elastomer.

3. The elastomer composition according to claim 1, wherein the average fiber length of the cellulose nanofiber powder is in the range of 0.1 μm to 3.0 μm.

4. The elastomer composition according to claim 1, wherein the cellulose nanofiber powder has an average fiber diameter in the range of 0.5 nm to 10 nm.

5. A method for producing an elastomer composition, comprising: Step A of preparing a cellulose nanofiber dispersion; A step B of supplying the cellulose nanofiber dispersion to a two-roll mill, heating the cellulose nanofiber dispersion to 95°C to 130°C, and rotating the two-roll mill to dry the cellulose nanofiber dispersion and obtain cellulose nanofiber powder; and Step C: adding 0.1 to 10 parts by weight of the cellulose nanofiber powder to 100 parts by weight of an elastomer and kneading them to obtain an elastomer composition Including, The cellulose nanofiber dispersion is prepared to contain, on a solids basis, 0.5 to 20 wt % of a phosphoric acid ester and 0.5 to 5.0 wt % of an alkylammonium salt.

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