JP7259158B2 - Foamed rubber molding, manufacturing method thereof, and sealing material using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a foamed rubber molded article containing biomass nanofibers, a method for producing the same, and a sealing material using the same.

Foamed rubber moldings obtained by crosslinking and foaming natural rubber and synthetic rubber have hitherto been used for underwater clothing, sealing materials, conveyor belts, roll surface members, and wire covering members because they are excellent in lightness and heat insulation. It is used for various purposes such as Among these, various sealing materials are used in a wide range of fields to prevent liquids such as water, lubricating oil and liquid fuel, and gases such as water vapor and various high pressure gases from leaking to the outside. In particular, sealing materials (also called rubber packings or sealing materials) for various vehicles such as automobiles and railroad vehicles are prone to leakage of various liquids such as fuel and lubricating oil to the outside, and foreign matter such as rainwater and dust inside. In order to prevent it from penetrating into the In addition, in various vehicles such as automobiles and railway vehicles, there are many places where such seal materials are used, and the frequency of replacement is high, so the seal materials are consumed in large amounts, and there is a demand for lower prices. It is

In recent years, foamed rubber moldings obtained by cross-linking rubber components such as natural rubber and synthetic rubber are compounded by adding fibers in order to strengthen the rubber-based materials. For example, Patent Literatures 1 to 6 and Non-Patent Literature 1 propose a rubber composition containing cellulose nanofibers and a rubber-based crosslinked foam molded article.

JP 2009-249449 A JP 2009-263417 A JP 2016-191007 A JP 2017-128663 A JP 2017-172676 A Japanese Patent No. 6143187

Cellulose nanocrystals reinforced foamed nitrile rubber nanocomposites, Carbohydrate Polymers, 2015, Vol.130, P.149-154

However, although Patent Documents 1, 2, 4 to 6 disclose rubber compositions reinforced with cellulose nanofibers, rubber-based crosslinked foamed moldings in which the inside of the rubber composition is made porous have not been sufficiently verified. not In addition, although the rubber-based cross-linked foamed molded article described in Patent Document 3 and Non-Patent Document 1 is reinforced with cellulose nanofibers, it is said that it is expensive to produce as a general-purpose product because the ratio of the rubber component is high. I had a problem.

In order to solve the above problems, the present invention provides an inexpensive foamed rubber molded article having high rubber elasticity, a method for producing the same, and a sealing material using the same.

In the first gist of the present invention, there is provided a foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler, wherein the filler is added in an amount of 85 parts by mass or more with respect to 100 parts by mass of the rubber component. It is 300 parts by mass or less, and the biomass nanofibers have an average fiber length of 700 nm or more and are oriented in a predetermined direction.

The second gist of the present invention is a foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler, wherein the filler is added in an amount of 85 parts by mass or more with respect to 100 parts by mass of the rubber component. It is 300 parts by mass or less, and in the foamed rubber molded article, an arbitrary direction is defined as a first direction, a direction perpendicular to the first direction is defined as a second direction, and the first direction is directed from the first direction to the second direction. 30 degrees clockwise from the first direction, 60 degrees clockwise from the first direction to the second direction, 30 degrees counterclockwise from the first direction to the second direction, and 30 degrees clockwise from the first direction to the second direction. Tensile strength was measured in accordance with JIS K 6251: 2010 for 60 degrees in the counterclockwise direction from the first direction to the second direction and six directions in the second direction, and each obtained Among the tensile strengths in the directions, the maximum tensile strength is T _max , and the tensile strength measured in the measurement direction at which the angle formed by the tensile strength at which T _max is measured is 90 degrees. Characterized by having a maximum tensile strength (T _max ) of 600 kPa or more, where T ₂ is the strength, and a ratio of T _max to T ₂ (T _max /T ₂ ) of 1.16 or more. It relates to a foamed rubber molding.

In the first and second gists of the present invention, the foamed rubber molding preferably has a 100% tensile stress of 580 kPa or more in any direction measured according to JIS K 6251:2010. In the first and second gists of the present invention, the foamed rubber molding preferably has a tensile strength of 800 kPa or more in any direction measured according to JIS K 6251:2010.

In the second gist of the present invention, it is preferable that T _max of the foamed rubber molding is 1000 kPa or more.

In the first and second gists of the present invention, the content of biomass nanofibers in the foamed rubber molded article is preferably 0.001% by mass or more and 10% by mass or less. In the first and second gists of the present invention, the average fiber diameter of the biomass nanofibers is 1 nm or more and 100 nm or less, the average fiber length is 800 nm or more and 20000 nm or less, and the ratio of the average fiber length to the average fiber diameter (average Fiber length/average fiber diameter) is preferably 10 or more and 10,000 or less.

In the first and second gists of the present invention, it is preferable that the foamed rubber molded article has a 25% compressive stress of 45 kPa or more measured according to JIS K 6767:1999. In the first and second gists of the present invention, the foamed rubber molded article preferably has an apparent density of 0.30 g/cm ³ or less as measured according to JIS K 6767:1999.

In the first and second gists of the present invention, it is preferable that the rubber component in the foamed rubber molding contains 5% by mass or more of natural rubber. In addition to natural rubber, the rubber component includes isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, brominated butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic rubber, At least one synthetic rubber selected from the group consisting of epichlorohydrin rubber, chlorosulfonated polyethylene, urethane rubber, silicone rubber and fluororubber may be included.

In the first and second gists of the present invention, the foamed rubber molded article comprises a latex containing at least one rubber component selected from the group consisting of natural rubber and synthetic rubber, and A rubber composition containing a masterbatch of biomass nanofibers obtained by mixing and solidifying the following dispersion of biomass nanofibers, a filler, a vulcanizing agent and a foaming agent is subjected to cross-linking and foaming. may

The present invention also provides the above-described method for producing a foamed rubber molded article, comprising a latex containing at least one rubber component selected from the group consisting of natural rubber and synthetic rubber, and a latex having a viscosity of 5500 mPa·s to 70000 mPa·s A rubber composition containing a biomass nanofiber masterbatch obtained by mixing and solidifying the following biomass nanofiber dispersion, a filler, a vulcanizing agent and a foaming agent is crosslinked and foamed to form a foamed rubber molding. It relates to a method for producing a foamed rubber molded article characterized by obtaining

In the dispersion liquid, the content of biomass nanofibers is preferably 0.05% by mass or more and 50% by mass or less.

The present invention also relates to a sealing material using the foamed rubber molded article.

In the present invention, a foamed rubber molded article contains a rubber component, biomass nanofibers, and a filler, and the fiber length of the biomass nanofibers is adjusted to a predetermined range, and the biomass nanofibers are added to a predetermined range in the foamed rubber molded article. Orientation in the direction makes it possible to provide an inexpensive foamed rubber molded article having high rubber elasticity and a sealing material using the same.

1 is a photograph (50000×) of cellulose nanofibers contained in an aqueous dispersion of cellulose nanofibers used in producing a foamed rubber molded article of Example 1, observed with a Schottky field emission scanning electron microscope. 3 is a photograph (50000×) of cellulose nanofibers contained in an aqueous dispersion of cellulose nanofibers used in producing a foamed rubber molded article of Comparative Example 3, observed with a Schottky field emission scanning electron microscope. 1 is a photograph (2000×) of a foamed rubber molded article of Example 1 observed with a scanning electron microscope. 1 is a photograph (5000×) of a foamed rubber molded article of Example 1 observed with a scanning electron microscope. 1 is a photograph (5000×) of a foamed rubber molded article of Comparative Example 1 observed with a scanning electron microscope. 4 is a photograph (5000×) of the foamed rubber molded article of Comparative Example 3 observed with a scanning electron microscope. FIG. 4 is a schematic diagram illustrating a method of sampling test pieces in six directions when measuring the tensile strength of a foamed rubber molded article.

The inventors of the present invention have earnestly studied how to reduce the cost while increasing the rubber elasticity of the foamed rubber molded article. As a result, in a foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler, the amount of the filler compounded was 85 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the rubber component, and the average fiber length was 700 nm. It has been found that by orienting the above biomass nanofibers in a predetermined direction, it is possible to obtain a foamed rubber molded article that is inexpensive and has good rubber elasticity. Normally, rubber elasticity decreases as the amount of filler compounded increases in rubber materials. By orienting in the direction of , the rubber elasticity could be enhanced. Alternatively, in a foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler, the amount of the filler compounded is 85 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the rubber component, and the adjacent measurement directions are In six directions with an angle of 30 degrees, the maximum tensile strength (T _max ) among the tensile strengths measured in accordance with JIS K 6251: 2010 is 600 kPa or more, and T _max and the T _max The ratio (T _max / T ₂ ) of the tensile strength (T ₂ ) measured in the measurement direction where the angle formed by the tensile strength with respect to the measurement direction is 90 degrees is 1.16 or more As a result, the inventors have found that a foamed rubber molded article which is inexpensive and has good rubber elasticity can be obtained. Generally, in rubber-based materials, when the amount of filler compounded increases, the rubber elasticity decreases. The rubber elasticity can be improved by having the It is presumed that the anisotropic tensile strength of the foam rubber molding is due to the orientation of the biomass nanofibers in a predetermined direction.

The foam rubber molding contains at least a rubber component, biomass nanofibers and a filler.

The rubber component is not particularly limited, but from the viewpoint of enhancing the dispersibility of biomass nanofibers and facilitating orientation in a predetermined direction, it preferably contains 5% by mass or more of natural rubber, more preferably 7% by mass or more, More preferably 10% by mass or more, still more preferably 20% by mass or more, even more preferably 25% by mass or more, particularly preferably 30% by mass or more. The upper limit of the ratio of the natural rubber component to the rubber component is not particularly limited, and the ratio of the natural rubber to the rubber component may be 100% by mass. and from the viewpoint of production costs, etc., the rubber component preferably contains 90% by mass or less of natural rubber, more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably It contains 60% by mass or less, particularly preferably 50% by mass or less. Specifically, the rubber component preferably contains 5% by mass or more and 90% by mass or less of natural rubber, more preferably 5% by mass or more and 75% by mass or less, and 7% by mass or more and 60% by mass or less. is more preferred.

The rubber component may contain synthetic rubber in addition to natural rubber. Although the rubber component is not particularly limited, for example, from the viewpoint of heat resistance, oil resistance, weather resistance, production cost, etc., natural rubber is 10% by mass or more and 90% by mass or less, and synthetic rubber is 10% by mass or more and 90% by mass. It preferably contains 20% by mass or more and 80% by mass or less of natural rubber, more preferably 20% by mass or more and 80% by mass or less of synthetic rubber, particularly preferably 25% by mass or more and 70% by mass or less of natural rubber, synthetic It contains 30% to 75% by mass of rubber, most preferably 30% to 60% by mass of natural rubber, and 40% to 70% by mass of synthetic rubber.

The synthetic rubber is not particularly limited, and examples thereof include diene rubbers and non-diene rubbers. Examples of the diene rubber include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and the like. Examples of the non-diene rubber include butyl rubber (also called isobutylene isoprene rubber, IIR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR), ethylene propylene rubber (EPM, ethylene propylene diene Rubber (EPDM), acrylic rubber (ACM), epichlorohydrin rubber (epichlorohydrin homopolymer (CO), epichlorohydrin/ethylene oxide copolymer (ECO), epichlorohydrin and allyl glycidyl ether (GCO) and terpolymers of ethylene oxide, epichlorohydrin and allyl glycidyl ether (GECO)), chlorosulfonated polyethylene (CSM), urethane rubber (U), silicone rubber, fluorine Examples thereof include rubber, etc. The synthetic rubbers may be used singly or in combination of two or more.

The synthetic rubber is not particularly limited, but isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, brominated butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic rubber, epi It preferably contains at least one selected from the group consisting of chlorohydrin rubber, chlorosulfonated polyethylene, urethane rubber, silicone rubber and fluororubber, styrene-butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, acrylic rubber, acrylonitrile-butadiene rubber It is more preferable to include at least one selected from the group consisting of

The biomass nanofibers have an average fiber length of 700 nm or more, and are preferably 800 nm or more, more preferably 1000 nm or more, still more preferably 1500 nm or more, and particularly preferably, from the viewpoint of being easily oriented in a predetermined direction. is greater than or equal to 1800 nm, most preferably greater than or equal to 2000 nm. Although the biomass nanofibers are not particularly limited, the average fiber length is preferably 20000 nm or less, more preferably 8000 nm or less, and even more preferably 5000 nm or less from the viewpoint of improving dispersibility. , particularly preferably 4000 nm or less, most preferably 3500 nm or less. Specifically, the biomass nanofibers preferably have an average fiber length of 800 nm or more and 20000 nm or less, more preferably 800 nm or more and 8000 nm or less, even more preferably 1000 nm or more and 5000 nm or less, and 1500 nm or more and 5000 nm or less. The following are more preferable.

Although the biomass nanofibers are not particularly limited, for example, from the viewpoint of being easily oriented in a predetermined direction, the average fiber diameter is preferably 1 nm or more and 100 nm or less, more preferably 10 nm or more and 80 nm or less, and particularly preferably. is 15 nm or more and 60 nm or less.

In the present invention, the "average fiber length and average fiber diameter of biomass nanofibers" refer to biomass nanofibers using a microscope capable of obtaining a clear image at a high magnification, for example, preferably 10,000 times or more, more preferably 20,000 times or more. is observed, 100 fibers are analyzed from the obtained image, and the arithmetic mean of the 100 fibers is calculated. Measurement of the average fiber length and average fiber diameter of biomass nanofibers is not particularly limited as long as it is a microscope capable of obtaining a sufficiently clear image at a magnification of 10000 times or more. ), a field emission scanning electron microscope (FE-SEM), a Schottky field emission scanning electron microscope, a scanning electron microscope (SEM), or the like can be used. In addition, when the biomass nanofibers are branched, the fiber length means the fiber length of the fiber including the branch with the largest fiber diameter. In addition, if the biomass nanofibers have a long fiber length and cannot be observed on one screen at a predetermined magnification of the microscope, the fiber length can be measured using the overall image obtained by connecting multiple screens on the software. can be done. An aqueous dispersion of cellulose nanofibers (cellulose nanofibers manufactured by Sugino Machine Co., Ltd., trade name BiNFi-s (registered trademark), product number: IMa- 10005"), which was observed with a Schottky field emission scanning electron microscope at a magnification of 50000. In addition, an aqueous dispersion of cellulose nanofibers (cellulose nanofibers manufactured by Sugino Machine Co., Ltd., trade name BiNFi-s (registered trademark), product number: FMa-10005") is shown in FIG. 2, which is a photograph of the cellulose nanofibers contained in FMa-10005") observed with a Schottky field emission scanning electron microscope at a magnification of 50000 times.

For example, from the viewpoint that the biomass nanofibers are easily oriented in a predetermined direction, the ratio of the average fiber length to the average fiber diameter (average fiber length/average fiber diameter) is preferably in the range of 10 or more and 10000 or less. It is more preferably in the range of 10 to 2000, even more preferably in the range of 15 to 500, particularly preferably in the range of 25 to 250, and most preferably in the range of 30 to 200.

The biomass nanofibers are fine fibrous substances with a fiber diameter of 1 nm or more and 1000 nm or less and an aspect ratio (fiber length/fiber diameter) of 5 or more and 10000 or less, which are obtained by miniaturizing biological raw materials. point to Examples of the biomass nanofibers include cellulose nanofibers (hereinafter also referred to as CNF), cellulose nanocrystals (CNC), cellulose nanowhiskers (CNW), chitin nanofibers, chitosan nanofibers, and microorganisms such as acetic acid bacteria. Bacterial nanofibers, etc. The cellulose nanofibers are produced by, for example, pulverizing fibrous cellulose that constitutes the cell walls of plants and wood, and chemically treating it (2,2,6,6-tetramethyl-1-piperidine-N-oxy radical and its derivatives). The chemical treatment used is an example.), which can be obtained by fibrillation. In addition, bacterial nanofibers (also called BNF, bacterial cellulose (BC), and bacterial cellulose nanofibers), which is a kind of cellulose nanofibers and produced by microorganisms such as acetic acid bacteria, are used to convert microorganisms such as acetic acid bacteria into waste glycerin. It can be obtained from cellulose ribbons that are synthesized and excreted by microorganisms when they run, by culturing them in a medium containing sugars. The chitin nanofibers can be obtained by pulverizing and fibrillating the shells of various crustaceans such as crabs and shrimps, for example. The chitosan nanofibers can be obtained, for example, by using the shells of various crustaceans such as crabs and shrimps as raw materials, pulverizing them, deacetylating them by alkali treatment, and defibrating them. The biomass nanofibers may be biomass nanofibers whose surfaces have been modified to be hydrophobic. The biomass nanofibers may be used singly or in combination of two or more.

The biomass nanofibers preferably contain cellulose nanofibers because of their easy availability and abundant variety. The cellulose nanofibers may be cellulose nanofibers whose surfaces have been modified to be hydrophobic. The cellulose nanofibers preferably have an aspect ratio of 10 to 10000, more preferably 10 to 2000, more preferably 15 to 500. It is particularly preferably in the range of 250 or less, and most preferably 30 or more and 200 or less.

The foamed rubber molded article is not particularly limited, but is used for applications that require hardness (hardness) and hardness when compressed (compressive stress), such as rubber elastic sealing materials that prevent the infiltration of water and lubricating oils, especially automobiles. And when used as a sealing material for various vehicles such as railway vehicles, the biomass nanofiber content is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less. 008% by mass or more and 2.3% by mass or less is particularly preferable, and 0.01% by mass or more and less than 1% by mass is most preferable.

Biomass nanofibers such as cellulose nanofibers are dispersed in polar liquids (polar solvents) such as water and various alcohols such as ethanol by utilizing their hydrophilicity from the viewpoint of handling. can be used. Of course, it is also possible to use a solid fine powder. Moreover, in order to improve dispersibility when mixed with various rubber components, biomass nanofibers may be chemically modified, or a coupling agent may be added. The chemically modified biomass nanofibers are not particularly limited, but for example, chemically modified cellulose nanofibers in which alkanoyl groups such as acetyl groups are introduced to the hydroxyl groups on the surface of the cellulose nanofibers, etc. The surface is modified to be hydrophobic. A cellulose nanofiber etc. are mentioned. The coupling agent is not particularly limited, and for example, a silane coupling agent, other known coupling agents, and the like can be used.

The foamed rubber molding contains 85 parts by mass or more and 300 parts by mass or less of a filler with respect to 100 parts by mass of the rubber component. From the viewpoint of cost and rubber elasticity, the foamed rubber molded article preferably contains 90 parts by mass or more and 250 parts by mass or less, more preferably 95 parts by mass or more and 200 parts by mass or less of a filler with respect to 100 parts by mass of the rubber component. more preferably 100 to 180 parts by mass, most preferably 100 to 150 parts by mass.

The filler (sometimes referred to as a reinforcing agent) is not particularly limited, and those used for rubber-based materials can be used as appropriate. Examples of the filler include light calcium carbonate, carbon black (CB), white carbon, talc, barium sulfate, magnesium carbonate, and mica. These may be used individually by 1 type, and may use 2 or more types together.

The foamed rubber molding also contains a vulcanizing agent and a foaming agent. In addition, if necessary, known vulcanization accelerators, vulcanization auxiliaries, vulcanization retarders (also called burn inhibitors or retarders), anti-aging agents, antioxidants, anti-ozonants, processing aids , softeners, flame retardants, antistatic agents, and the like.

The vulcanizing agent used for the foamed rubber molding is not particularly limited, and known ones can be used. Examples of the vulcanizing agent include sulfur (there are types such as powdered sulfur, precipitated sulfur, colloidal sulfur, and surface-treated sulfur), sulfur chloride, sulfur dichloride, selenium, inorganic vulcanizing agents such as tellurium, morpholine sulfur-containing organic compounds such as disulfides and alkylphenol disulfides; metal oxide vulcanizing agents such as hydrotalcite, magnesium oxide, trilead tetroxide, iron trioxide and titanium dioxide; and resin vulcanizing agents such as alkylphenol resins and modified alkylphenol resins. Sulfurizing agents, polyamine vulcanizing agents such as hexamethylenediamine carbamate, peroxides such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and peroxydicarbonates Vulcanizing agent (also referred to as a peroxide cross-linking agent, PO vulcanizing agent, PO cross-linking agent, peroxide vulcanizing agent, or peroxide cross-linking agent), p-quinonedioxime, p,p'-dibenzoyl A quinoid vulcanizing agent such as quinonedioxime (also referred to as a quinoid vulcanizing agent, a quinoid cross-linking agent, or a quinoid cross-linking agent) can be used. These vulcanizing agents may be used singly or in combination of two or more. These vulcanizing agents may be appropriately selected and used according to the rubber component.

The content of the vulcanizing agent in the foamed rubber molded article is not particularly limited, and can be adjusted according to the application. It may be added so that the ratio is 0.5 parts by mass or more and 20 parts by mass or less, or it is added so that the ratio is 1 mass part or more and 15 parts by mass or less. You may

The vulcanization accelerator is not particularly limited, but for example, aldehyde ammonia type, aldehyde amine type, guanidine type, thiourea type (also called thiourea type compound or thiourea type compound), thiazole type, thiuram type (also referred to as thiuram-based compounds), dithioate-based compounds, xanthate-based compounds, sulfenamide-based compounds (also referred to as sulfenamide-based compounds), and the like. Although the guanidine-based vulcanization accelerator is not particularly limited, for example, N,N'-diphenylguanidine, N,N'-diototolylguanidine and the like can be used. The thiourea-based vulcanization accelerator is not particularly limited, but may be, for example, ethylenethiourea (2-mercaptoimidazoline), N,N'-diethylthiourea, trimethylthiourea, N,N'-dibutylthiourea, or the like. can be done. The thiuram-based vulcanization accelerator is not particularly limited. Thiuram disulfide (TBTD), tetrabenzylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide and the like can be used. Although the xanthate-based vulcanization accelerator is not particularly limited, for example, xanthates and derivatives thereof can be used. The sulfenamide-based vulcanization accelerator is not particularly limited, but examples include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), Nt-butyl-2-benzothiazolylsulfenamide ( NS), N-oxydiethylene-2-benzothiazolylsulfenamide, N,N-diisopropyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, etc. can be done. One of the vulcanization accelerators may be used alone, or two or more thereof may be used in combination.

The content of the vulcanization accelerator in the foamed rubber molded article is not particularly limited, and can be appropriately adjusted according to the application. It may be added in a proportion of 0.2 parts by mass or more and 5 parts by mass or less, or may be added in a proportion of 0.3 parts by mass or more and 3 parts by mass or less. may be added as

Examples of the vulcanizing aid include, but are not limited to, metal oxide vulcanizing aids such as zinc oxide, red lead, and calcium oxide; various fatty acids such as stearic acid, oleic acid, and zinc stearate; and metal salts thereof. , triethanolamine and diethylene glycol. One of the vulcanizing aids may be used alone, or two or more thereof may be used in combination. Although the content of the vulcanization aid in the foamed rubber molded article is not particularly limited, for example, it may be added at a rate of 0.1 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the rubber component, You may add so that it may become the ratio of 0.5 to 20 mass parts, and may add so that it may become the ratio of 1 to 15 mass parts.

In the foamed rubber molded article, vulcanization additives, that is, vulcanizing agents, vulcanization accelerators, vulcanization aids and vulcanization retarders, are added according to the production method and the use of the resulting foamed rubber molded article. It can be adjusted and used as appropriate. The foamed rubber molding contains vulcanizing additives, i.e., vulcanizing agents, vulcanization accelerators, vulcanizing aids and vulcanization retarders, in a total amount of 0.1 parts by mass based on 100 parts by mass of the rubber component. It may be added so that the ratio is 50 parts by mass or less, it may be added so that the ratio is 0.5 parts by mass or more and 40 parts by mass or less, or 1 part by mass or more and 30 parts by mass or less. You may add so that it may become a ratio.

The processing aid is added to improve processability when various additives are added to the raw rubber component and kneaded. Examples of the processing aid include higher fatty acids, higher fatty acid metal salts, fatty acid esters, fatty acid amides, sulfur factice, sulfur chloride factice, sulfur factice made from hydrogenated rapeseed oil, white petrolatum, and paraffin wax. Examples of the higher fatty acids include palmitic acid, stearic acid, and oleic acid. One of the processing aids may be used alone, or two or more thereof may be used in combination. The content of the processing aid in the foamed rubber molded article is not particularly limited. It may be added at a ratio of 0.25 parts by mass to 30 parts by mass, or may be added at a ratio of 0.5 parts by mass to 25 parts by mass.

Examples of the softener include, but are not limited to, paraffinic oils other than chlorinated paraffin, naphthenic oils, phosphate ester oils other than chlorinated phosphate ester compounds, ester oils, petroleum resins, vegetable oils, liquid rubber, dioctyl phthalate (DOP), dioctyl sebacate (DOS), dioctyl azelate (DOZ) and the like. One of the softeners may be used alone, or two or more of them may be used in combination. The content of the softening agent in the foamed rubber molded article is not particularly limited. You may add so that it may become the ratio more than 55 mass parts or less, and may add so that it may become the ratio of 12 mass parts or more and 50 mass parts or less.

In the foamed rubber molded article, processing additives, that is, processing aids, softeners and anti-aging agents can be appropriately adjusted according to the production method and the intended use of the resulting foamed rubber molded article. The foamed rubber molded body contains processing additives, that is, processing aids, softeners and anti-aging agents in a total amount of 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component. It may be added, it may be added so that the ratio is 10 parts by mass or more and 85 parts by mass or less, or it may be added so that the ratio is 12 parts by mass or more and 75 parts by mass or less.

When the rubber component, biomass nanofibers, fillers, and other additives are mixed to form a rubber composition, a foaming agent is also added and kneaded, and the resulting rubber composition is pressurized and heated. The foaming agent foams to form a foamed rubber molding.

The foaming agent is not particularly limited, and for example, inorganic foaming agents such as sodium hydrogen carbonate and ammonium carbonate, as well as various organic foaming agents can be used. It is preferable to use an organic foaming agent in the foamed rubber molded article of the present invention.

The organic foaming agent is not particularly limited, and any known organic foaming agent can be used. Examples of the organic foaming agent include nitroso foaming agents, azo foaming agents, and hydrazide foaming agents.

The nitroso-based foaming agent is not particularly limited, but for example, N,N'-dinitrosopentamethylenetetramine (DPT) or the like can be used. Examples of the N,N'-dinitrosopentamethylenetetramine include "Cellular D (registered trademark)" manufactured by Eiwa Kasei Kogyo Co., Ltd., sponge paste No. 4 manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., and Sankyo Kasei Co., Ltd. A commercially available product such as "Cellmic (registered trademark) A" can be used.

The azo-based foaming agent is not particularly limited, but for example, diazoaminebenzene, azodicarbonamide, azobisisobutyronitrile, barium azodicarboxylate, and the like can be used. Examples of the azo foaming agent include "Vinihole (registered trademark) AC" and "Vinihole (registered trademark) AZ" manufactured by Eiwa Kasei Kogyo Co., Ltd., "Uniform (registered trademark) AZ" manufactured by Otsuka Chemical Co., Ltd., A commercially available product such as “Cellmic (registered trademark) C” manufactured by Sankyo Kasei Co., Ltd. can be used.

The hydrazide-based blowing agent is not particularly limited, but for example, p,p'-oxybisbenzenesulfonylhydrazide, benzenesulfonylhydrazide, toluenesulfonylhydrazide, hydrazodicarbonamide and the like can be used. Examples of the hydrazide-based foaming agent include "Cellmic (registered trademark) S, SX, SX-H" manufactured by Sankyo Kasei Co., Ltd., and "Neo Cellbon (registered trademark)" manufactured by Eiwa Kasei Kogyo Co., Ltd. A hydrazide-based foaming agent is preferably used in the foamed rubber molded article of one embodiment of the present invention.

One of the foaming agents may be used alone, or two or more thereof may be used in combination.

The foaming agent is preferably used in combination with a foaming aid such as zinc oxide or urea in order to lower the decomposition temperature of the foaming agent.

The content of the foaming agent (including foaming aid) in the foamed rubber molded article is not particularly limited, but for example, it is added at a rate of 3 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the rubber component. You may add so that it may become the ratio of 5 to 20 mass parts, and may add so that it may become the ratio of 7 to 15 mass parts.

The method of adding biomass nanofibers to the foamed rubber molded article is not particularly limited. For example, it may be added directly to the rubber component and kneaded with the rubber component to prepare a masterbatch containing biomass nanofibers at a high concentration. may be used as For example, if the biomass nanofibers (including biomass nanofibers whose surface is modified to be hydrophobic) are in powder form or in a dry state, they can be added directly to the rubber component and kneaded with the rubber component. good. Aqueous dispersions in which biomass nanofibers are dispersed in water (for example, gel-like dispersions can be mentioned, and available ones are BiNFi-s (registered trademark) available from Sugino Machine Co., Ltd., No. Rheocrysta (registered trademark) available from Ichi Kogyo Seiyaku Co., Ltd. and Auro Visco (registered trademark) available from Oji Holdings Co., Ltd.) are used, the biomass nanofiber aqueous dispersion and A masterbatch containing a high concentration of biomass nanofibers is prepared using various latexes including natural rubber and synthetic rubber such as chloroprene rubber, and the obtained masterbatch is mixed with fillers and other additives. can be kneaded by Further, if necessary, the obtained masterbatch, synthetic rubber, filler and other additives can be mixed and kneaded. In addition, dispersions in which biomass nanofibers are dispersed in nonpolar liquids, such as various organic solvents, oils, and various plasticizers, especially dispersions in which biomass nanofibers whose surfaces have been modified to be hydrophobic are dispersed in organic solvents When a liquid is used, a masterbatch containing biomass nanofibers at a high concentration is prepared by using the dispersion of biomass nanofibers and various latexes including synthetic rubbers such as natural rubber and chloroprene rubber. The batch, fillers and other additives can be mixed and kneaded, and various oils used as softeners and plasticizers (for example, paraffin oil) can be used as softeners and plasticizers in the process of kneading raw materials for foamed rubber moldings. ) can be replaced with a dispersion liquid in which biomass nanofibers are dispersed in a non-polar liquid, and the raw material for a foamed rubber molded article in which biomass nanofibers are dispersed can be kneaded. . Moreover, if necessary, the obtained masterbatch, natural rubber and/or synthetic rubber, fillers and other additives can be mixed and kneaded. Examples of the organic solvent include ketone solvents such as acetone and methyl ethyl ketone, alcohol solvents such as methanol and ethanol, and ester solvents such as ethyl acetate.

In the foamed rubber molded article, biomass nanofibers such as cellulose nanofibers are presumed to be oriented in the process of kneading the raw materials when producing the foamed rubber molded article, and are also oriented inside the resulting foamed rubber molded article. be done. After the kneading process, in the vulcanization/foaming process, the biomass nanofibers are thought to constrain the rubber molecules. The expansion of the rubber composition increases. The force that tries to constrain rubber molecules due to the orientation of biomass nanofibers changes depending on the direction in the rubber composition before vulcanization and foaming, and anisotropy in the degree of expansion appears in the vulcanization and foaming process (in a specific direction large expansion and small expansion in another direction), changes in the shape of the cell walls of the foamed rubber molded body, and anisotropy of mechanical properties in the obtained foamed rubber molded body, that is, in a specific direction On the other hand, it is presumed that the reinforcing effect is strongly expressed, and the ratio of the tensile strength in the direction perpendicular to the direction is 1.16 times or more. In the foamed rubber molded article of the present invention, since the biomass nanofibers are contained in an oriented state, even if the amount of the biomass nanofibers added is very small, the entire foamed rubber molded article is effectively reinforced, and the filler is is contained in a large amount, it is possible to increase rubber elasticity and improve mechanical properties such as tensile strength.

By observing the foamed rubber molded body using a transmission electron microscope, a field emission scanning electron microscope, a Schottky field emission scanning electron microscope, a scanning electron microscope, etc., the wall surfaces of the foam cells inside the foamed rubber molded body If the magnification is high enough, biomass nanofibers entrapped in the bubble cell walls can be observed. In addition, traces suggesting that biomass nanofibers such as cellulose nanofibers are oriented in a predetermined direction can be confirmed. 3 and 4 are photographs of a foamed rubber molded article according to one embodiment of the present invention observed with a scanning electron microscope. 3 and 4, it was confirmed that a ridge-like (rib-like) structure was formed on the cell wall surfaces of the foamed rubber molded article, and the ridge-like structure was extended in a specific direction. Fig. 5, in which a foamed rubber molded body containing no biomass nanofibers was observed with a scanning electron microscope, and Fig. 6, in which a foamed rubber molded body containing biomass nanofibers with a short fiber length was observed with a scanning electron microscope 3 and 4 cannot be confirmed on the wall surface of the air bubble cell, it can be concluded that such a change in the shape and structure of the wall surface of the air bubble cell is due to biomass nanofibers with an average fiber length of 700 nm or more. and its orientation.

In the present invention, the foamed rubber molded product is a master obtained by mixing various latexes including natural rubber and synthetic rubber such as chloroprene rubber with a dispersion such as an aqueous dispersion of biomass nanofibers and solidifying it. A rubber composition containing a batch (hereinafter also referred to as a "masterbatch of biomass nanofibers"), a filler, a vulcanizing agent and a foaming agent, and optionally natural rubber, synthetic rubber and other additives, It can be produced by vulcanization and foaming. The dispersion of biomass nanofibers may be an aqueous dispersion in which biomass nanofibers are dispersed in water, or a dispersion in which biomass nanofibers are dispersed in an organic solvent. In particular, in the case of biomass nanofibers whose surfaces have been modified to be hydrophobic, they can be suitably used as a dispersion in an organic solvent.

The content of biomass nanofibers contained in the biomass nanofiber masterbatch is not particularly limited. That is, since the biomass nanofibers need only be uniformly dispersed in the masterbatch, biomass nanofibers can be easily dispersed using a latex such as natural rubber or various latexes including synthetic rubbers such as chloroprene rubber. When producing a masterbatch containing nanofibers, the content of biomass nanofibers contained in the masterbatch may be 0.1% by mass or more and 50% by mass or less, or 0.5% by mass or more. The ratio may be 30 mass % or less, or the ratio may be 1 mass % or more and 25 mass % or less.

In the method for producing a foamed rubber molded article of the present invention, the viscosity of a dispersion such as an aqueous dispersion of biomass nanofibers is 5500 mPa·sec or more and 70000 mPa·sec or less. When the viscosity of the aqueous dispersion of biomass nanofibers satisfies the above range, it is easy to uniformly mix with various latexes including natural rubber and synthetic rubber such as chloroprene rubber, and manufacturing becomes easy. Although it depends on the concentration of biomass nanofibers, it is considered that the dispersion liquid contains a large amount of biomass nanofibers with a relatively long average fiber length. Strengthened. In the method for producing a foamed rubber molded article of the present invention, the viscosity of the biomass nanofiber dispersion such as an aqueous dispersion is preferably 6000 mPa·sec or more and 60000 mPa·sec or less, and preferably 7000 mPa·sec or more and 50000 mPa·sec or less. More preferably, it is 7300 mPa·sec or more and 45000 mPa·sec or less, particularly preferably. In the present invention, when measuring the viscosity of a dispersion such as an aqueous dispersion of biomass nanofibers, a commercially available B-type viscometer (VISCOMETER TVB-10, manufactured by Toki Sangyo Co., Ltd., rotor No. 4) is used. Measurement can be performed under the conditions of a rotation speed of 60 rpm and a measurement temperature of 25°C.

In the method for producing a foamed rubber molded article of the present invention, the concentration of biomass nanofibers in a dispersion such as an aqueous dispersion of biomass nanofibers is not particularly limited. The following are preferable. In the aqueous dispersion of biomass nanofibers, if the concentration of biomass nanofibers satisfies the above range, not only is it easier to handle dispersions such as dispersions, but also synthetic rubbers such as natural rubber and chloroprene rubber It is easy to uniformly mix with various latexes including, and production becomes easy. In the biomass nanofiber dispersion, the biomass nanofiber concentration is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and 0.8% by mass. % or more and 8 mass % or less, and most preferably 1 mass % or more and 4.5 mass % or less.

The rubber composition may contain vulcanization accelerators, vulcanization auxiliaries, vulcanization retarders, antioxidants, antioxidants, antiozonants, processing aids, softeners, fillers, reinforcing agents, if necessary. agents, flame retardants, antistatic agents, and the like. As the vulcanizing agent, foaming agent, vulcanization accelerator, vulcanizing aid, processing aid, softener and filler, those mentioned above can be used.

The rubber composition can be kneaded using a kneader or the like. The rubber composition after kneading is vulcanized and foamed at high temperature and high pressure to obtain a foamed rubber molding. In the vulcanization and expansion step, the temperature, pressure, and treatment time are not particularly limited, but from the viewpoint of workability and production cost, the temperature is in the range of 100 ° C. or higher and 200 ° C. or lower, and the pressure is in the range of 3 MPa or higher and 25 MPa or lower. and the time is preferably in the range of 5 minutes or more and 60 minutes or less. More preferably, the temperature ranges from 110° C. to 170° C., the pressure ranges from 5 MPa to 20 MPa, and the time ranges from 10 minutes to 45 minutes. The vulcanization and foaming may be one-stage foaming or two-stage foaming, but two-stage foaming is preferred.

When the rubber composition containing the biomass nanofibers is vulcanized and foamed at high temperature and high pressure, minute air bubbles are generated by the foaming agent in the rubber matrix. As these bubbles grow, they push aside the surrounding rubber matrix to form bubble cells. As the rubber matrix is displaced, the biomass nanofibers dispersed in that area are also oriented in a predetermined direction within the cell. Therefore, each cell of the obtained foamed rubber molded article is reinforced, and the rubber elasticity (for example, 100% tensile stress) and strength of the foamed rubber molded article are increased.

The foamed rubber molded article preferably has a 100% tensile stress in any direction measured in accordance with JIS K 6251:2010 of 580 kPa or more, more preferably 600 kPa or more, particularly 640 kPa or more. preferable. When the 100% tensile stress is within the range described above, the foamed rubber molded article is rich in rubber elasticity, increases in sealing performance, and becomes moderately hard. , soundproof rubber and sealing materials. The upper limit of the 100% tensile stress measured in accordance with JIS K 6251:2010 in the foamed rubber molded article is not particularly limited, but is preferably 1500 kPa or less, more preferably 1200 kPa or less, and particularly preferably. is 1000 kPa or less. In addition, in the foamed rubber molded article of the present invention, in the direction in which the biomass nanofibers intensively strengthened, when measuring the 100% tensile stress, the sample became hard, and the sample may break, making it impossible to measure. In such a case, a sample should be taken in a direction that makes an angle of 90° with this direction, and the 100% tensile stress should satisfy the above range.

Although the foamed rubber molded article is not particularly limited, for example, the tensile strength in any direction measured according to JIS K 6251:2010 is preferably 800 kPa or more, more preferably 840 kPa or more, and 900 kPa or more. is particularly preferred. As a result, the foamed rubber molded article becomes moderately hard, and can be suitably used as a sealing material for applications requiring strength and hardness, for example, vehicles such as automobiles and railroad vehicles. In the foamed rubber molded article, the upper limit of the tensile strength measured according to JIS K6251:2010 is not particularly limited, but it is preferably 2500 kPa or less, more preferably 2000 kPa or less, and 1800 kPa or less. 1700 kPa or less is most preferable.

In the foamed rubber molding, an arbitrary direction is defined as a first direction, a direction perpendicular to the first direction is defined as a second direction, and the first direction, the second direction, and the clockwise direction from the first direction to the second direction. in the direction of 30 degrees (third direction), in the clockwise direction from the first direction to the second direction in the direction of 60 degrees (fourth direction), in the counterclockwise direction from the first direction to the second direction 6 directions of 30 degrees (fifth direction) and 60 degrees counterclockwise from the first direction to the second direction (sixth direction) in accordance with JIS K 6251:2010 The tensile strength is measured, and the maximum tensile strength among the obtained tensile strengths is defined as _Tmax , and the angle formed by the tensile strength at which _Tmax is measured with respect to the measurement direction is 90 degrees. The maximum tensile strength (T _max ) is 600 kPa or more, and the ratio of T _max to T ₂ (T _max /T _{2 )} is 1.16 or more. is preferably The T _max is more preferably 800 kPa or more, still more preferably 1000 kPa or more, and particularly preferably 1200 kPa or more. Further, the ratio of T _max to T ₂ (T _max /T ₂ ) is more preferably 1.18 or more, still more preferably 1.2 or more, and most preferably 1.25 or more. . The upper limit of the ratio of T _max to T ₂ (T _max /T ₂ ) is not particularly limited, but may be 5 or less, 3 or less, 2.5 or less, 2 It may be below. Specifically, as shown in FIG. 7, an arbitrary direction represented by a straight line AA' is defined as a first direction, a direction perpendicular to the first direction represented by a straight line BB' is defined as a second direction, and the first direction is defined as a first direction. A direction, a second direction, 30 degrees clockwise from the first direction represented by arrow C' to the second direction (the third direction), a direction from the first direction represented by arrow D' to the second direction 60 degrees in the clockwise direction toward the direction (fourth direction), 30 degrees in the counterclockwise direction from the first direction represented by arrow E' to the second direction (fifth direction), And for a tensile test in the first direction, cut in each of the six directions of 60 degrees in the counterclockwise direction (sixth direction) from the first direction to the second direction represented by arrow F ' Test piece a, 2nd direction tensile test test piece b, 3rd direction tensile test test piece c, 4th direction tensile test test piece d, 5th direction tensile test test piece e, and Using a 6-direction tensile test specimen f, the tensile strength in 6 directions is measured in accordance with JIS K 6251: 2010, and among the obtained tensile strengths, the maximum tensile strength is T _{max T2} is the tensile strength measured in the direction of measurement that makes an angle of 90 degrees with respect to the direction of measurement in which the tensile strength at which T _max is measured.

Although the foamed rubber molded article is not particularly limited, for example, the 25% compressive stress measured in accordance with JIS K 6767:1999 is preferably 45 kPa or more, more preferably 50 kPa or more, and 55 kPa or more. It is particularly preferred to have As a result, the foamed rubber molded article is rich in rubber elasticity, improves sealing performance, and moderately hardens, making it suitable for applications requiring strength and hardness, such as sealing materials, anti-vibration rubbers, and sound-insulating rubbers. can be done. In the foamed rubber molded article of the embodiment, the upper limit of the 25% compressive stress measured according to JIS K 6767:1999 is not particularly limited, but it is preferably 150 kPa or less, more preferably 130 kPa or less. It is preferably 125 kPa or less, particularly preferably 120 kPa or less, most preferably 120 kPa or less.

The foamed rubber molded article preferably has an elongation at break in any direction measured in accordance with JIS K 6251:2010 of 25% or more, more preferably 50% or more, and 80% or more. is particularly preferred. It can be suitably used as a sealing material for applications requiring strength and hardness, for example, vehicles such as automobiles and railroad vehicles. Although the upper limit of the elongation at break is not particularly limited, it is preferably 250% or less, more preferably 200% or less.

In the foamed rubber molded article, the tensile strength may be a value that takes into consideration the balance with the elongation at break depending on the use of the foamed rubber molded article. When the foamed rubber molding is used as a sealing material that requires high rubber elasticity, high hardness, and high tensile strength, the elongation at break is 25% or more and 250% or less, and the tensile strength is 800 kPa. More preferably, the elongation at break is 50% or more and 200% or less, and the tensile strength is 840 kPa or more and 2000 kPa or less, and the elongation at break is 50% or more and 150% or less. and the tensile strength is particularly preferably 900 kPa or more and 1700 kPa or less.

The foamed rubber molding preferably has a hardness of 10 or more and 100 or less, more preferably 20 or more and 90 or less, as measured using an ASKER (registered trademark) rubber hardness tester (durometer) type C manufactured by Kobunshi Keiki Co., Ltd. is more preferable, and 25 or more and 85 or less is particularly preferable. When the hardness is within the range described above, the rubber elasticity is high and the sealability is enhanced, so that it can be suitably used as a sealing material for vehicles such as automobiles and railroad vehicles.

The apparent density of the foamed rubber molded article is not particularly limited because it depends on the type of rubber component contained in the foamed rubber molded article. The apparent density measured according to 7222:2005 is preferably 0.30 g/cm ³ or less, more preferably 0.25 g/cm ³ or less, and 0.20 g/cm ³ or less. is particularly preferred, and 0.18 g/cm ³ or less is most preferred. It can be suitably used as a sealing material for vehicles such as automobiles and railroad vehicles, and can contribute to weight reduction of the vehicle as a whole.

The foamed rubber molded article conforms to JIS K 6767: 1999 from the viewpoint of sealing performance and life when used as a sealing material, and has a 50% compression set of 35% or more measured 30 minutes after the load is removed. It is preferably 60% or less, more preferably 40% or more and 55% or less.

Since the foamed rubber molded article has high rubber elasticity and good hardness and strength, it can be suitably used as a sealing material for vehicles such as automobiles and railway vehicles.

EXAMPLES The present invention will be described in more detail below using examples. In addition, the present invention is not limited to the following examples.

(Example 1)
First, an aqueous dispersion of cellulose nanofibers (cellulose nanofibers manufactured by Sugino Machine Co., Ltd. "Product name BiNFi-s (registered trademark), product number: IMa-10005", an aqueous dispersion containing 5% by mass of cellulose nanofibers, viscosity : 35000 mPa s, average fiber diameter: 40 nm, average fiber length: 2300 nm, ratio of average fiber length to average fiber diameter (average fiber length/average fiber diameter): 57.5), and dispersing the cellulose nanofibers in water Liquid and natural rubber latex (solid content 60% by mass, ammonia-containing natural rubber latex purchased from S&S Japan Co., Ltd.) were added so that 2.3 parts by mass of cellulose nanofiber per 100 parts by mass of natural rubber. , stirred, solidified, and then dried to obtain a masterbatch. The obtained masterbatch of cellulose nanofibers contained 2.3 parts by mass of cellulose nanofibers with respect to 100 parts by mass of natural rubber.

Next, the cellulose nanofiber masterbatch and other additives were mixed at the blending ratios shown in Table 1 below, and kneaded for 60 minutes using a kneader.

The obtained rubber composition was aged at room temperature for 24 hours and then extruded with an extruder to obtain an unvulcanized sheet. The unvulcanized sheet was placed in a mold heated to 120° C. and press-vulcanized for 18 minutes while applying pressure (pressure 10 MPa) to foam (primary vulcanization). Next, it was placed in a mold heated to 155° C., press-vulcanized for 15 minutes while applying pressure (pressure of 10 MPa), and foamed (secondary vulcanization) to obtain a foamed rubber molding.

(Example 2)
A foamed rubber molded article was obtained in the same manner as in Example 1 except that the vulcanization time was changed to 16 minutes in the primary vulcanization.

(Comparative example 1)
A foamed rubber molded article was produced in the same manner as in Example 1, except that the natural rubber latex was solidified without adding cellulose nanofibers, and that the natural rubber and various additives were mixed at the blending ratios shown in Table 1 below. Obtained.

(Comparative example 2)
A foamed rubber molded article was produced in the same manner as in Example 2, except that the natural rubber latex was solidified without the addition of cellulose nanofibers, and that the natural rubber and various additives were mixed at the blending ratios shown in Table 1 below. Obtained.

(Comparative Example 3)
As an aqueous dispersion of cellulose nanofibers, an aqueous dispersion of cellulose nanofibers manufactured by Sugino Machine Co., Ltd. (“BiNFi-s (registered trademark), product number: FMa-10005”, water containing 5% by mass of cellulose nanofibers) dispersion liquid, viscosity: 5000 mPa s, average fiber diameter: 20 nm, average fiber length: 550 nm, ratio of average fiber length to average fiber diameter (average fiber length/average fiber diameter): 27.5) A foam rubber molding was obtained in the same manner as in Example 1.

The physical properties of the foamed rubber moldings obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were measured as follows, and the results are shown in Table 1 below. The cellulose nanofibers contained in the aqueous dispersion of cellulose nanofibers used in the production of the foamed rubber molded bodies of Examples 1, 2, and Comparative Example 3 were observed with a Schottky field emission scanning electron microscope (JEOL Ltd.). The fiber length and fiber diameter of the cellulose nanofibers were measured by observation with a Schottky field emission scanning electron microscope (manufactured by the company, product number: JSM-7001F). 3 shows a photograph (2000x) of the foamed rubber molded article of Example 1 observed with a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number "S-3000N"), and FIG. )showed that. FIGS. 5 and 6 show photographs (5000×) of the foamed rubber molded bodies of Comparative Examples 1 and 3, respectively, observed with a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number “S-3000N”). rice field.

(Tensile strength)
Measured according to JIS K 6251:2010. Specifically, in accordance with JIS K 6251: 2010, a dumbbell-shaped No. 2 test piece is fixed to a constant-speed tensile tester, pulled at a tensile speed of 500 ± 50 mm / min, and the test piece is cut. The value of the tensile strength was measured and defined as the tensile strength. As shown in FIG. 7, an arbitrary direction represented by a straight line AA' is defined as a first direction, and a direction perpendicular to the first direction represented by a straight line BB' is defined as a second direction. , from the first direction indicated by arrow C' to the second direction clockwise at 30 degrees (third direction), and from the first direction indicated by arrow D' to the second direction clockwise 60 degrees in the clockwise direction (fourth direction), 30 degrees in the counterclockwise direction from the first direction represented by arrow E' to the second direction (fifth direction), and in the direction of arrow F' A test piece for tensile test in the first direction, cut out in each of the six directions of 60 degrees in the counterclockwise direction (sixth direction) from the first direction to the second direction shown, 2 direction tensile test specimen b, 3rd direction tensile test specimen c, 4th direction tensile test specimen d, 5th direction tensile test specimen e, and 6th direction tensile test Using the test piece f for JIS K 6251: Measure the tensile strength in six directions in accordance with 2010, and among the obtained tensile strengths, the maximum tensile strength is T _max , and the T _max T ₂ was the tensile strength measured in the measurement direction at which the angle formed with the measurement direction in which the tensile strength was measured was 90 degrees.

(100% tensile stress)
Measured according to JIS K 6251:2010. Specifically, in accordance with JIS K 6251: 2010, a dumbbell-shaped No. 2 test piece is fixed to a constant-speed tensile tester, pulled at a tensile speed of 500 ± 50 mm / min, and the test piece is 100 The value of tensile stress when elongating by % was measured and defined as 100% tensile stress. In the measurement of the tensile strength, the direction in which the angle formed with respect to the measurement direction in which the tensile strength is maximized (hereinafter also referred to as the maximum direction) is perpendicular (hereinafter also referred to as the vertical direction.) 100% tensile stress was measured.

(elongation at break)
Measured according to JIS K 6251:2010. Specifically, in accordance with JIS K 6251: 2010, a dumbbell-shaped No. 2 test piece is fixed to a constant-speed tensile tester, pulled at a tensile speed of 500 ± 50 mm / min, and the test piece is cut. The length of the sample (the length between the chucks used to fix the sample) was measured, and the elongation at break of the sample was calculated from the original length of the sample piece. In the measurement of the tensile strength, the direction of measurement in which the tensile strength is maximized (hereinafter also referred to as the maximum direction) and the direction in which the angle formed with the maximum direction is perpendicular (hereinafter referred to as the vertical direction Also referred to as.) was measured elongation at break.

(25% compressive stress)
Measured according to JIS K 6767:1999. Specifically, in accordance with JIS K 6767: 1999, a test piece (20 mm × 20 mm × 20 mm) is compressed at a compression rate of 10 mm / min, and when strained 25%, that is, when the thickness of the sample is the original thickness Compressive stress was measured when it reached 75%.

(50% compression set)
Measured according to JIS K 6767:1999. Specifically, according to JIS K 6767:1999, first, a test piece (20 mm×20 mm×5 mm) was prepared at normal temperature (23±2° C.), and the initial thickness (T ₀ ) was measured. Next, it was compressed by applying a load to a state of being distorted by 50% from the initial thickness (T ₀ ), that is, a state in which the thickness became half of the initial thickness, and left for 22 hours. After compressing for 22 hours, the compression is released by removing the load, and the thickness (T _30m ) 30 minutes after releasing the compression (after removing the load) is measured using a dial thickness gauge, The 50% compression set was calculated by the following formula.
50% compression set after 30 minutes (%) = [( _T0 - _T30m )/ _T0 ] x 100

(hardness)
It was measured with ASKER (registered trademark) rubber hardness tester (durometer) C type manufactured by Kobunshi Keiki Co., Ltd. Specifically, a portion of the test piece having a thickness of 10 mm or more and 20 mm or less was selected, and the hardness was measured at that location. In addition, when the thickness of the test piece was less than 10 mm, the test pieces were stacked to adjust the thickness to the above range. At this time, the number of test pieces to be stacked was 3 or less.

(apparent density)
Measured according to JIS K 7222:2005, which is applied mutatis mutandis in JIS K 6767:1999.

As can be seen from the results of FIGS. 3 and 4, in the examples using cellulose nanofibers having an average fiber length of 700 nm or more, a ridge-like (rib-like) structure was formed on the cell walls of the foamed rubber molded body, It was confirmed that the ridged structure was stretched in a specific direction, and that the measured value of tensile strength changed greatly depending on the measurement direction. It is considered that the cellulose nanofibers are oriented in a predetermined direction. On the other hand, as can be seen from FIG. 5, in Comparative Example 1 containing no cellulose nanofibers, the ridged structure observed in FIGS. 3 and 4 was not observed. Since there is no directional dependence (anisotropy) in the tensile strength, the change in the structure occurring on the cell walls of the foamed rubber molded article of Example 1 shown in FIGS. It is presumed that the added biomass nanofibers are oriented in one direction due to the above addition of biomass nanofibers. In addition, in Comparative Example 3 using cellulose nanofibers with a short fiber length, it can be seen from FIG. 6 that the change in the foam cell wall surface of the foamed rubber molding confirmed in FIGS. 3 and 4 cannot be confirmed. In addition, since the measured value of tensile strength is constant and does not depend on the measurement, the cellulose nanofibers having an average fiber length of 550 nm added to the foamed rubber molded product of Comparative Example 3 are not oriented in a specific direction, It is assumed that they are randomly distributed.

As can be seen from Table 1, the foamed rubber molded bodies of Examples 1 and 2 had higher 100% tensile stress and higher rubber elasticity than the foamed rubber molded bodies of Comparative Examples 1-3.

Since the foamed rubber molded article of the present invention has excellent mechanical strength, high durability, and excellent manufacturing cost, it can be suitably used as various sealing materials, particularly sealing materials for vehicles such as automobiles and railroad vehicles. can.

AA' 1st direction
BB' second direction
C' Direction 30 degrees clockwise from the first direction to the second direction (third direction)
D' Direction 60 degrees clockwise from the first direction to the second direction (fourth direction)
E' Direction 30 degrees counterclockwise from the first direction to the second direction (fifth direction)
F' Direction 60 degrees counterclockwise from the first direction to the second direction (6th direction)
a test piece for tensile test in first direction b test piece for tensile test in second direction c test piece for tensile test in third direction d test piece for tensile test in fourth direction e test piece for tensile test in fifth direction f Test piece for tensile test in 6th direction

Claims (16)

A foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler,
In the foamed rubber molded article, the rubber component is crosslinked,
The amount of the filler compounded is 85 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the rubber component,
A foamed rubber molded article, wherein the biomass nanofibers have an average fiber length of 700 nm or more and are oriented in a predetermined direction. A foamed rubber molded article containing a rubber component, biomass nanofibers, and a filler,
In the foamed rubber molded article, the rubber component is crosslinked,
The amount of the filler compounded is 85 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the rubber component,
In the foamed rubber molding, an arbitrary direction is defined as a first direction, a direction perpendicular to the first direction is defined as a second direction, and the first direction is 30 degrees clockwise from the first direction to the second direction. 60 degrees clockwise from the first direction to the second direction 30 degrees counterclockwise from the first direction to the second direction 30 degrees counterclockwise from the first direction to the second direction The tensile strength is measured in accordance with JIS K 6251: 2010 in the direction of 60 degrees in the counterclockwise direction and in the second direction, and among the obtained tensile strengths, the maximum Tmax is the tensile strength of Tmax, and T2 is the tensile strength measured in the measurement direction at which the angle formed by the measurement direction in which the tensile strength at Tmax is 90 degrees is the maximum tensile strength A foamed rubber molded article having a thickness (Tmax) of 600 kPa or more and a ratio of Tmax to T2 (Tmax/T2) of 1.16 or more. 3. The foamed rubber molded article according to claim 1 or 2, having a 100% tensile stress in any direction measured according to JIS K 6251:2010 of 580 kPa or more. The foamed rubber molded article according to any one of claims 1 to 3, which has a tensile strength of 800 kPa or more in any direction measured according to JIS K 6251:2010. 3. The foamed rubber molded article according to claim 2, wherein Tmax of said foamed rubber molded article is 1000 kPa or more. The foamed rubber molded article according to any one of claims 1 to 5, wherein the content of biomass nanofibers in said foamed rubber molded article is 0.001% by mass or more and 10% by mass or less. The biomass nanofibers have an average fiber diameter of 1 nm or more and 100 nm or less, an average fiber length of 800 nm or more and 20000 nm or less, and a ratio of the average fiber length to the average fiber diameter (average fiber length/average fiber diameter) of 10 or more and 10000 or less. The foamed rubber molded article according to any one of claims 1 to 6. The foamed rubber molded article according to any one of claims 1 to 7, which has a 25% compressive stress of 45 kPa or more and 200 kPa or less measured according to JIS K 6767:1999. The foamed rubber molded article according to any one of claims 1 to 8, which has an apparent density of 0.30 g/cm ³ or less as measured according to JIS K 6767:1999. The foamed rubber molded article according to any one of claims 1 to 9, wherein the rubber component contains 5% by mass or more of natural rubber. In addition to natural rubber, the rubber component includes isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, brominated butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic rubber, The foamed rubber molded article according to any one of claims 1 to 10, comprising at least one synthetic rubber selected from the group consisting of epichlorohydrin rubber, chlorosulfonated polyethylene, urethane rubber, silicone rubber and fluororubber. The foamed rubber molded article according to any one of claims 1 to 11, wherein said biomass nanofibers are oriented in a predetermined direction on cell wall surfaces of said foamed rubber molded article. The foamed rubber molding is obtained by mixing a latex containing at least one rubber component selected from the group consisting of natural rubber and synthetic rubber, and a biomass nanofiber dispersion having a viscosity of 5500 mPa·s or more and 70000 mPa·s or less. 13. The rubber composition comprising a masterbatch of biomass nanofibers obtained by solidification, a filler, a vulcanizing agent and a foaming agent is crosslinked and foamed according to any one of claims 1 to 12 . foam rubber molding. A method for producing a foamed rubber molded article according to any one of claims 1 to 13 ,
Obtained by mixing and solidifying a latex containing at least one rubber component selected from the group consisting of natural rubber and synthetic rubber and a dispersion of biomass nanofibers having a viscosity of 5500 mPa·s or more and 70000 mPa·s or less. A method for producing a foamed rubber molded article, comprising cross-linking and foaming a rubber composition containing a biomass nanofiber masterbatch, a filler, a vulcanizing agent and a foaming agent to obtain a foamed rubber molded article. 15. The method for producing a foamed rubber molded article according to claim 14 , wherein the content of biomass nanofibers in said dispersion is 0.05% by mass or more and 50% by mass or less. A sealing material using the foamed rubber molding according to any one of claims 1 to 13 .

Images