Surface-treated nanocellulose masterbatch

Abstract

The objective of this invention is to provide a surface-treated nanocellulose masterbatch that yields a rubber composition exhibiting excellent homogeneous dispersion of nanocellulose, extensibility, hardness, water resistance, and tear resistance. A surface-treated nanocellulose masterbatch comprises a rubber component, nanocellulose, a methyl and / or linear resorcinol-formaldehyde initial condensate, and formaldehyde, obtained using an inorganic salt as a coagulant. Relative to 100 parts by weight of the rubber component, it contains 0.3 to 15 parts by weight of the nanocellulose; relative to 1 part by weight of the nanocellulose, it contains 0.03 to 1.2 parts by weight of the methyl and / or linear resorcinol-formaldehyde initial condensate, and 0.02 to 0.8 parts by weight of the formaldehyde. The aforementioned problem is solved by the surface-treated nanocellulose masterbatch described above.

Description

[0001] This application is a divisional application of the patent application filed on October 8, 2020, with application number 202080062651.7 and invention title "Surface-treated Nanocellulose Masterbatch". Technical Field

[0002] This invention relates to surface-treated nanocellulose masterbatch. Background Technology

[0003] Rubber compositions that make up tires and the like require substances with excellent properties such as elastic modulus (elongation) and hardness. Furthermore, techniques for incorporating fillers such as carbon black and silica into rubber compositions have been developed to improve these properties.

[0004] In addition, a technique (Patent Document 1) is known to provide an excellent rubber composition with good balance of excellent processability, rigidity, fracture properties and low flammability by dispersing chemically modified microfibrils of cellulose with cationic groups in a rubber composition.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6353169 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, because nanocellulose, such as chemically modified microfibrils, tends to aggregate and bundle during processes such as moisture removal, it is sometimes difficult to maintain the defibrilation to the nanoscale in the manufacture of masterbatches containing nanocellulose. This may prevent the production of rubber compositions with the desired properties from such masterbatches. Therefore, there is still room for further improvement in obtaining surface-treated nanocellulose masterbatches with uniform nanocellulose dispersion.

[0010] Therefore, the object of the present invention is to provide a surface-treated nanocellulose masterbatch, which can obtain a rubber composition with uniformly dispersed nanocellulose and excellent elongation, hardness, water resistance and crack resistance.

[0011] Methods for solving problems

[0012] To address the aforementioned issues, the inventors conducted in-depth research and discovered a surface-treated nanocellulose masterbatch. This masterbatch contains: a rubber component, nanocellulose, a resole-type and / or novolactic type resorcinol-formaldehyde initial condensate, and formaldehyde. Specifically, 100 parts by weight of the rubber component contains 0.3 to 15 parts by weight of the nanocellulose, and 1 part by weight of the resorcinol-formaldehyde initial condensate contains 0.03 to 1.2 parts by weight of the resorcinol-formaldehyde initial condensate and 0.02 to 0.8 parts by weight of the formaldehyde. This method yields a rubber composition with homogeneous dispersion of nanocellulose, maintaining elongation and hardness, excellent water resistance, and improved tear resistance, thus completing the present invention.

[0013] That is, the present invention is as follows [1] to [5].

[0014] [1]. A surface-treated nanocellulose masterbatch, comprising rubber components, nanocellulose, methyl and / or linear resorcinol-formaldehyde initial condensate, and formaldehyde.

[0015] Relative to 100 parts by weight of the rubber component, it contains 0.3 to 15 parts by weight of the nanocellulose.

[0016] Relative to 1 part by weight of the nanocellulose, it comprises 0.03 to 1.2 parts by weight of the initial condensate of the methyl and / or linear resorcinol-formaldehyde, and 0.02 to 0.8 parts by weight of the formaldehyde.

[0017] [2]. The surface-treated nanocellulose masterbatch as described in [1], wherein the rubber component comprises diene rubber and styrene-butadiene-vinylpyridine terpolymer.

[0018] [3]. The surface-treated nanocellulose masterbatch as described in [1] or [2] further comprises carbon black and / or silicon dioxide.

[0019] [4]. The surface-treated nanocellulose masterbatch as described in any one of [1] to [3] further comprises 0.1 to 15 parts by weight of unsaturated fatty acid metal salt relative to 100 parts by weight of the rubber component.

[0020] [5]. The surface-treated nanocellulose masterbatch as described in [4], wherein the unsaturated fatty acid metal salt is an acrylic acid metal salt and / or a methacrylate metal salt.

[0021] Invention Effects

[0022] According to the present invention, a surface-treated nanocellulose masterbatch can be obtained, which can produce a rubber composition that exhibits homogeneous dispersion of nanocellulose, maintains extensibility and hardness, has excellent water resistance, and also improves tear resistance. Detailed Implementation

[0023] The present invention will now be described.

[0024] This invention relates to a surface-treated nanocellulose masterbatch, comprising a rubber component, nanocellulose, a methyl and / or linear resorcinol-formaldehyde initial condensate, and formaldehyde. Relative to 100 parts by weight of the rubber component, the masterbatch contains 0.3 to 15 parts by weight of the nanocellulose; relative to 1 part by weight of the nanocellulose, the masterbatch contains 0.03 to 1.2 parts by weight of the methyl and / or linear resorcinol-formaldehyde initial condensate, and 0.02 to 0.8 parts by weight of the formaldehyde. This invention is also referred to below as "the surface-treated nanocellulose masterbatch of this invention".

[0025] First, as the rubber component incorporated in the surface-treated nanocellulose masterbatch of the present invention, common rubber components used in the rubber industry, such as diene rubber and butyl rubber, can be used. In the surface-treated nanocellulose masterbatch of the present invention, it is preferable to use a rubber latex as an aqueous dispersion, formed by dispersing this rubber component in water in a colloidal state, as a raw material. Furthermore, from the viewpoint of further improving the dispersibility of nanocellulose, etc., as described later, this rubber component is preferably a rubber component comprising diene rubber and a styrene-butadiene-vinylpyridine terpolymer (VP).

[0026] Furthermore, this diene-based rubber is a rubber component having double bonds in its polymer backbone, and examples include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), and isoprene rubber (IR). Moreover, the weight-average molecular weight of this diene-based rubber is preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000.

[0027] Here, in this invention, "weight-average molecular weight" refers to the "weight-average molecular weight" measured by gel permeation chromatography (GPC) with tetrahydrofuran as solvent, converted to standard polystyrene.

[0028] Furthermore, the surface-treated nanocellulose masterbatch of the present invention is a masterbatch containing nanocellulose that has undergone mechanical or chemical treatment (mechanical defibrillation or chemical modification, such as surface treatment by the action of the initial condensate of methyl and / or linear resorcinol-formaldehyde described later (the condensate is disposed close to the surface in at least a portion of the surface)). In the present invention, "nanocellulose" refers to extremely fine fibers composed of cellulose microfibrils with an average fiber diameter of 1 to 1000 nm, including cellulose nanofibrils (CNF) with an average fiber length of 0.5 to 5 μm and crystalline cellulose nanocrystals (CNC) with an average fiber length of 0.1 to 0.5 μm. Additionally, in the present invention, the surface-treated nanocellulose can also be simply referred to as "nanocellulose".

[0029] Cellulose used as a raw material for nanocellulose can be of either wood or non-wood origin (bacteria, algae, cotton, etc.), and there are no particular limitations. Methods for producing nanocellulose include, for example, adding water to the cellulose raw material, processing it using a mixer or similar device to prepare a slurry in which cellulose is dispersed in water, and then directly applying mechanical shear force to the slurry using a high-pressure or ultrasonic device to decellulose; and subjecting the slurry to chemical treatments such as oxidation, alkali treatment, or acid hydrolysis to modify the cellulose, making it easier to decellulose, and then applying mechanical shear force using a disperser or similar device to decellulose. By performing decellulose decomposition after such chemical treatment, cellulose can be broken down into finer and more uniform particles with lower energy, making it easier to obtain chemically modified nanocellulose. In addition, chemical treatments can be exemplified by agents such as 2,2,6,6-tetramethylpiperidine-1-oxide (hereinafter referred to as "TEMPO"), 4-acetamide-TEMPO, 4-carboxyl-TEMPO, 4-amino-TEMPO, 4-hydroxy-TEMPO, 4-phosphono-oxy-TEMPO, phosphate esters, periodic acid, alkali metal hydroxides, and carbon disulfide. Furthermore, chemical treatment can be performed after the mechanical defibrillation of cellulose. Moreover, in addition to the aforementioned chemical treatments, to further improve the affinity with rubber components, cellulase treatment, carboxymethylation, esterification, and cationic polymer treatment can be performed after the defibrillation step.

[0030] In this invention, since the affinity for the methyl and / or linear resorcinol-formaldehyde initial condensate described later is further enhanced, it is preferable to use nanocellulose having anion-forming groups (e.g., selected from one or more of carboxyl, phosphate, phosphite, xanthate, sulfonate, sulfate and thiol groups).

[0031] Furthermore, the average fiber diameter of the nanocellulose is 1–1000 nm, preferably 1–200 nm. Additionally, the average aspect ratio (average fiber length / average fiber diameter) of the nanocellulose is preferably 10–1000, more preferably 50–500. If the average fiber diameter is less than the above range and / or the average aspect ratio is greater than the above range, the dispersibility of the nanocellulose may decrease. Furthermore, if the average fiber diameter exceeds the above range and / or the average aspect ratio is less than the above range, the reinforcing properties of the nanocellulose may decrease.

[0032] In this invention, the "average fiber diameter" and "average fiber length" of nanocellulose refer to the average value of the fiber diameter and fiber length of at least 50 fibers when an aqueous dispersion of nanocellulose with a solid fraction of 0.05–0.1% by mass is prepared, observed by TEM or SEM, and the magnification is appropriately set according to the size of the fibers to obtain an electron microscope image. Furthermore, the average aspect ratio is calculated based on the average fiber length and average fiber diameter obtained in this way.

[0033] In this invention, the nanocellulose comprises 0.3 to 15 parts by weight, preferably 0.3 to 12 parts by weight, more preferably 0.4 to 10 parts by weight, even more preferably 0.4 to 8 parts by weight, and still more preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the rubber component, thereby obtaining a surface-treated nanocellulose masterbatch. If the nanocellulose content is less than 0.3 parts by weight relative to 100 parts by weight of the rubber component, it may not be possible to sufficiently improve the mechanical properties of the rubber composition obtained from the surface-treated nanocellulose masterbatch. Furthermore, if the nanocellulose content exceeds 15 parts by weight relative to 100 parts by weight of the rubber component, the cost of the obtained surface-treated nanocellulose masterbatch may increase, and there is also a possibility that the nanocellulose may not be uniformly dispersed.

[0034] Alternatively, in this invention, an aqueous dispersion of nanocellulose (with a solid fraction of about 0.1 to 10% by mass) can be formed and then mixed into rubber latex or the like, or nanocellulose with water removed can be mixed into rubber latex or the like.

[0035] Furthermore, the surface-treated nanocellulose masterbatch of the present invention contains, together with nanocellulose, a methyl and / or linear resorcinol-formaldehyde initial condensate and formaldehyde.

[0036] Here, in this invention, the so-called "resorcinol-formaldehyde initial condensate (RF resin)" is a condensate (oligomer) obtained by condensing resorcinol, a phenolic resin, and formaldehyde under a catalyst, and its degree of polymerization is preferably about 5 to 15. Furthermore, this resorcinol-formaldehyde initial condensate may also contain unreacted resorcinol and / or formaldehyde.

[0037] Furthermore, the hydroxymethyl condensate obtained by condensation reaction under alkaline catalysts such as sodium hydroxide and sodium carbonate with a resorcinol / formaldehyde molar ratio of 1 / 1 to 3 is a methyl resorcinol-formaldehyde initial condensate (the condensate represented by chemical formula (1) below (where n is the degree of polymerization)). The hydroxymethyl condensate obtained by condensation reaction under acidic catalysts such as oxalic acid with a resorcinol / formaldehyde molar ratio of 1 / 0.8 to 0.9 is a linear resorcinol-formaldehyde initial condensate (the condensate represented by chemical formula (2) below (where m is the degree of polymerization)). In the surface-treated nanocellulose masterbatch of the present invention, the resorcinol-formaldehyde initial condensate can be either methyl or linear, but the linear form is preferred.

[0038]

[0039] Furthermore, in this invention, relative to 1 part by mass of nanocellulose, the initial resorcinol-formaldehyde condensate contains 0.03 to 1.2 parts by mass, preferably 0.05 to 0.8 parts by mass, more preferably 0.06 to 0.6 parts by mass, and even more preferably 0.08 to 0.4 parts by mass. Additionally, formaldehyde contains 0.02 to 0.8 parts by mass, preferably 0.03 to 0.5 parts by mass, more preferably 0.04 to 0.4 parts by mass, and even more preferably 0.05 to 0.3 parts by mass. These adjustments are made to obtain the surface-treated nanocellulose masterbatch. If the initial resorcinol-formaldehyde condensate contains unreacted formaldehyde, the content of this unreacted formaldehyde is also included in the formaldehyde content of the surface-treated nanocellulose masterbatch of this invention. If these contents are below the above ranges, the nanocellulose may not be uniformly distributed, and the mechanical properties of the rubber composition obtained from the surface-treated nanocellulose masterbatch may not be sufficiently improved. Furthermore, if these contents exceed the above amounts, the tear resistance and elongation of the rubber composition obtained from the surface-treated nanocellulose masterbatch may actually decrease.

[0040] Furthermore, the surface-treated nanocellulose masterbatch of the present invention may also contain fillers. Examples of such fillers include carbon black, silica, clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, alumina, titanium dioxide, barium sulfate, lecithin, etc. These fillers can be used in combination or in combination of multiple types, especially carbon black and / or silica (fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, etc.), which is highly preferred from the viewpoint of improving the strength and hardness of the rubber composition obtained by the surface-treated nanocellulose masterbatch of the present invention, and making the nanocellulose more uniformly dispersed. The filler content in the surface-treated nanocellulose masterbatch of the present invention is preferably 10 parts by weight or more, more preferably 20 to 100 parts by weight, more preferably 30 to 80 parts by weight, and even more preferably 40 to 70 parts by weight, relative to 100 parts by weight of rubber component.

[0041] In addition, in this invention, "carbon black" refers to carbon particles with a diameter of about 3 to 500 nm that are manufactured industrially through quality control, and "silicon dioxide" refers to silicon dioxide (SiO2) or substances composed of silicon dioxide.

[0042] Here, an example of a method for manufacturing the surface-treated nanocellulose masterbatch of the present invention is described. First, nanocellulose containing 0.3 to 15 parts by mass relative to 100 parts by mass of the rubber component (solid component of the rubber latex), 0.03 to 1.2 parts by mass relative to 1 part by mass of the nanocellulose, and 0.02 to 0.8 parts by mass of formaldehyde are dispersed in rubber latex. If necessary, fillers or the like are further added to obtain a raw material dispersion in a paste state with a solid component concentration of 60% by mass or less. This dispersion method is not particularly limited and can be carried out by mechanical methods, etc. Furthermore, it is preferable to mix the nanocellulose in the rubber latex in the form of an aqueous dispersion, preferably with a concentration of 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. By keeping the concentration of the nanocellulose aqueous dispersion within such a range, the nanocellulose that has defibrinated in the aqueous dispersion can be dispersed more uniformly. Additionally, it is also preferable to mix the formaldehyde in the rubber latex in an aqueous solution (formalin).

[0043] Furthermore, the solid content concentration of the raw material dispersion is preferably 60% by mass or less, more preferably 2 to 50% by mass, and even more preferably 5 to 50% by mass. When the solid content concentration exceeds 60% by mass, the viscosity of the raw material dispersion increases, and its stability may also decrease.

[0044] Then, a coagulant is added to the raw material dispersion to cause the polymer components to coagulate and solidify. Water is removed by filtration, etc. The solidified material is washed as needed, the coagulant is removed, and the material is dried as needed to obtain the surface-treated nanocellulose masterbatch of the present invention.

[0045] Here, inorganic salts (sodium chloride, potassium chloride, etc.) and unsaturated fatty acid metal salts (acrylic acid metal salts, methacrylate metal salts, etc.) can be used as the coagulant.

[0046] In particular, when an unsaturated fatty acid metal salt is used as a coagulant, even if the surface-treated nanocellulose masterbatch contains the unsaturated fatty acid metal salt, the hardness and extensibility of the rubber composition obtained from the surface-treated nanocellulose masterbatch will not decrease. Therefore, the coagulation of the raw material dispersion and the washing of the coagulated solids can be omitted, which is even more preferable. As the unsaturated fatty acid metal salt, acrylic acid metal salts and / or methacrylate metal salts are very preferred. In addition, preferred metals as metal salts include, for example, sodium, potassium, calcium, magnesium, aluminum, zinc, neodymium, etc.

[0047] Furthermore, when using unsaturated fatty acid metal salts as coagulants, the unsaturated fatty acid metal salts are preferably contained in 0.1 to 15 parts by mass, more preferably 0.2 to 10 parts by mass, even more preferably 0.2 to 5 parts by mass, and even more preferably 0.2 to 2 parts by mass, and even more preferably 0.3 to 2 parts by mass, relative to 100 parts by mass of the rubber component. This is preferred because it allows the properties of the obtained rubber composition to be fully utilized without affecting the coagulation and solidification effects of the polymer components.

[0048] Furthermore, using the surface-treated nanocellulose masterbatch of the present invention, various additives commonly used in rubber compositions, such as fillers, silane coupling agents, zinc oxide (zinc oxide), stearic acid, adhesive resins, adhesives, kneading accelerators, anti-aging agents, waxes, processing aids, aromatic oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators, and crosslinking agents, can be appropriately mixed and kneaded in a known manner to form a rubber composition. Additionally, when obtaining the surface-treated nanocellulose masterbatch of the present invention, other additives besides vulcanizing agents, vulcanization accelerators, and crosslinking agents can also be added to the raw material dispersion.

[0049] The rubber composition obtained by using the surface-treated nanocellulose masterbatch of the present invention has homogeneous dispersion of nanocellulose, maintains extensibility and hardness and has excellent water resistance, thereby improving tear resistance.

[0050] The following describes embodiments of the present invention. The present invention is not limited to the following embodiments, and various modifications can be made within the technical concept of the present invention.

[0051] Example

[0052] (Test Example 1)

[0053] Masterbatch was prepared based on the raw materials shown in Table 1 below.

[0054] Specifically, a rubber latex composed of styrene-butadiene copolymer latex (SBR; manufactured by ZON Corporation, Nipol LX112, Japan) and styrene-butadiene-vinylpyridine terpolymer latex (VP; manufactured by ZON Corporation, Nipol LX2518FS, Japan) (solid content (dry rubber weight) 40.5% by mass, SBR to VP ratio 95:5), an aqueous dispersion of oxidized nanocellulose (manufactured by Nippon Paper Corporation, Cellenpia) (solid content 1.0% by mass), a linear resorcinol-formaldehyde initial condensate (RF resin (Smicanol (registered trademark) 700S, manufactured by Sumitomo Chemical Co., Ltd.), and a formaldehyde aqueous solution (manufactured by Kanto Chemical Co., Ltd., 37% solution) were mixed and dispersed at the mass ratios of the solid contents shown in Table 1 below to obtain a raw material dispersion in a paste state with a solid content concentration of less than 60% by mass (Examples 1-2 and Comparative Examples 2-3). In addition, as Comparative Example 1, the above-mentioned rubber latex and nanocellulose, along with dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) as a surfactant, were mixed and dispersed in the mass ratios shown in Table 1 below, and a paste-like raw material dispersion was also obtained. Furthermore, as Comparative Example 4, the above-mentioned rubber latex and carbon black (Sheet (registered trademark), manufactured by KH Tokai Carbon Co., Ltd.) were mixed and dispersed in the mass ratios shown in Table 1 below, and a paste-like raw material dispersion was also obtained.

[0055] Table 1

[0056]

[0057] Then, for the raw material dispersions of Examples 1-2 and Comparative Examples 1-4, sodium chloride was used as a coagulant for salting out coagulation. The coagulated material was then recovered, washed, and dried to obtain masterbatch. During washing, the sodium chloride was repeatedly rinsed five times while being filtered under reduced pressure using a Buchner funnel and distilled water was spread on the surface of the coagulated material. For drying, the washed coagulated material was spread out in a flat-bottomed tray and placed in a constant-temperature desiccator at 70°C for 24 hours. For each masterbatch obtained, zinc oxide (ZnO, produced by Zhengtong Chemical Industry Co., Ltd.), stearic acid (produced by Nippon Oil Co., Ltd.), a vulcanization accelerator (produced by Ouchi Shinsei Chemical Industry Co., Ltd., Noccel NS-P), and sulfur (produced by Shikoku Chemical Industry Co., Ltd., Muklon OT-20) were added. The mixture was then kneaded in an open roller and vulcanized under pressure at 160°C for 15 minutes in a 15cm × 15cm × 0.2cm mold to prepare vulcanized rubber test pieces. Then, for the obtained vulcanized rubber test pieces, a tensile test was performed at a tensile speed of 500 mm / min according to JIS K6251:2010, and the tensile stress (M100: MPa) at 100% elongation and the elongation at cut (= elongation at cut: Eb) were measured at room temperature (20°C). Furthermore, a tear test was performed at a tensile speed of 500 mm / min according to JIS K 6252:2015, and the tear stress (MPa) at break was measured at room temperature (20°C). In addition, an immersion test was conducted using water as the test liquid based on JIS K 6258:2016 to evaluate its water resistance.

[0058] These results are shown in Table 2 below. Note that for M100, Eb, and tear stress, the relative values ​​(index %) are shown when Comparative Example 1 is set to 100.

[0059] These results show that the surface-treated nanocellulose masterbatch of the present invention, containing oxidized nanocellulose, linear resorcinol-formaldehyde initial condensate, and formaldehyde in predetermined amounts, can yield a rubber composition that combines good extensibility and hardness, as well as good tear resistance (tear strength) and water resistance.

[0060] Table 2

[0061]

[0062] (Test Example 2)

[0063] Masterbatch was prepared using the raw materials shown in Table 3 below.

[0064] Specifically, a raw material dispersion in a paste state is obtained by mixing and dispersing a rubber latex composed of styrene-butadiene copolymer rubber latex (SBR; manufactured by Zen Co., Ltd., Nipol LX112) and styrene-butadiene-vinylpyridine terpolymer latex (VP; manufactured by Zen Co., Ltd., Nipol LX2518FS) (solid content (dry rubber) 40.5% by mass, SBR to VP ratio of 95:5), an aqueous dispersion of oxidized nanocellulose (manufactured by Nippon Paper Co., Ltd., Cellenpia) (solid content 1.0% by mass), a linear resorcinol-formaldehyde initial condensate (RF resin (Smicanol (registered trademark) 700S, manufactured by Sumitomo Chemical Co., Ltd.), and a formaldehyde aqueous solution (manufactured by Kanto Chemical Co., Ltd., 37% solution) at the mass ratios shown in the upper part of Table 3 below, to obtain a raw material dispersion with a solid content concentration of less than 60% by mass. Then, for the raw material dispersion, relative to 100 parts by mass of the solids component of the rubber latex, the amount of coagulant (sodium chloride was produced by Fuji Film and Kosei Pharmaceutical Co., Ltd., and acrylate was produced by Asada Chemical Co., Ltd.) shown in the lower part of Table 3 below was used for coagulation, and the coagulated material was then recovered and dried to obtain masterbatch (Examples 3-5 and Comparative Examples 5 and 7). Drying was performed by spreading the obtained coagulated material in a flat-bottomed pan and placing it in a constant-temperature desiccator at 70°C for 24 hours. In addition, Comparative Example 5 was washed before drying. This washing was performed by repeatedly washing away sodium chloride 5 times while filtering under reduced pressure using a Buchner funnel and sprinkling distilled water on the surface of the coagulated material. Furthermore, Comparative Example 6 could not be coagulated, and masterbatch was not obtained.

[0065] Table 3

[0066]

[0067] For each of the obtained master compounds, vulcanized rubber test pieces were prepared using the same method as in Test Example 1. The obtained vulcanized rubber test pieces were used to perform tensile tests at a tensile speed of 500 mm / min according to JIS K 6251:2010. The tensile stress (M100: MPa) at 100% elongation and the elongation at cut (= elongation at cut: Eb) were measured at room temperature (20°C).

[0068] These results, along with the cohesiveness of each masterbatch and the necessity of post-cohesion washing, are shown in Table 4 below. Note that for M100 and Eb, the relative values ​​(index %) are shown when Comparative Example 5 is set to 100.

[0069] These results show that the surface-treated nanocellulose masterbatch of the present invention, containing a specified amount of oxidized nanocellulose, linear resorcinol-formaldehyde initial condensate, and formaldehyde, and aggregated by a specified amount of unsaturated fatty acid metal salt (sodium acrylate or calcium acrylate), exhibits good cohesiveness and does not require post-aggregation washing. Furthermore, it demonstrates that a rubber composition with both good elongation and hardness can be obtained. Additionally, similar to Test Example 1, this rubber composition is also expected to have good water resistance and tear resistance.

[0070] Table 4

[0071]

[0072] This application claims priority based on Japanese Application Special Purpose 2019-186108, filed on October 9, 2019, the entire disclosure of which is incorporated herein by reference.

Claims

1. A surface-treated nanocellulose masterbatch, comprising rubber components, nanocellulose, methyl and / or linear resorcinol-formaldehyde initial condensate, and formaldehyde, obtained using an inorganic salt as a coagulant. The rubber component comprises diene rubber and styrene-butadiene-vinylpyridine terpolymer. Relative to 100 parts by weight of the rubber component, it contains 0.3 to 15 parts by weight of the nanocellulose. Relative to 1 part by weight of the nanocellulose, it comprises 0.03 to 1.2 parts by weight of the initial condensate of the methyl and / or linear resorcinol-formaldehyde, and 0.02 to 0.8 parts by weight of the formaldehyde.

2. The surface-treated nanocellulose masterbatch as described in claim 1 further comprises carbon black and / or silicon dioxide.

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