JP2022047509A - Method for Producing Cellulose Nanofiber-Containing Rubber Composition - Google Patents

Abstract

To provide a method capable of efficiently producing a rubber composition which has cellulose nanofibers uniformly dispersed therein and has suitable physical characteristics.SOLUTION: The method for producing a cellulose nanofiber-containing rubber composition includes a step of kneading a rubber component containing an ethylene-propylene-diene rubber, and an unmodified cellulose nanofiber dispersion in the presence of a water-soluble organic solvent having a boiling point of 150°C or higher and 220°C or lower and an SP value of 8.5-11.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a rubber composition containing cellulose nanofibers.

It is known that the rubber composition contains cellulose fibers as a filler to be blended in the rubber component to improve the physical properties of the obtained rubber (Patent Document 1). Examples of such cellulose fibers include microfibrillated cellulose. However, in general, microfibrillated cellulose is a wood pulp from which lignin is chemically removed for the purpose of bleaching and reducing the binding force between microfibril units to increase the efficiency of defibration into microfibril units. Microfibrillated cellulose, which is used as a raw material and is produced from wood pulp from which lignin has been removed, has hydrophilicity mainly derived from cellulose, and therefore has poor compatibility with the hydrophobic rubber component. Therefore, if an attempt is made to produce a fiber-reinforced rubber by directly blending microfibrillated cellulose into a rubber component, there is a problem that the dispersibility of the fiber deteriorates and the improvement of the physical properties of the obtained rubber is suppressed. ..

For example, Patent Document 1 describes a master batch of a rubber / cellulosic fiber obtained by stirring and mixing a cellulosic fiber having an average fiber diameter of less than 0.5 μm and a rubber latex, and a method for producing the same. As a result, the cellulosic fibers were uniformly dispersed in the rubber by mixing and drying a dispersion liquid in which cellulosic fibers having an average fiber diameter of less than 0.5 μm were fibrillated in water and rubber latex. A master batch of rubber / cellulosic fibers has been produced.
However, unlike the diene-based rubber synthesized by emulsion polymerization, ethylene propylene diene rubber is synthesized in a hydrocarbon-based solvent, so that the latex aqueous dispersion of ethylene propylene diene rubber is hardly distributed in the market, and the above-mentioned production The method is not available.

Further, in Patent Document 2, a dispersion in which cellulose fine fibers produced by mechanical defibration means are dispersed in toluene and a solution in which ethylene propylene diene rubber (EPDM) is dissolved in toluene are mixed and toluene is used. It is described that a master batch of cellulose fine fibers / EPDM is prepared by vaporizing, and then EPDM is kneaded and the master batch is put into the master batch and kneaded to finally prepare an uncrosslinked rubber composition. (Example 3-1).
However, when a water-insoluble organic solvent such as toluene is used, the cellulose nanofibers generally do not disperse and aggregate in the toluene solvent unless toluene is used from the time of producing the cellulose nanofibers. Mechanical defibration such as disc mills and high-pressure dispersion generates heat when defibrating cellulose, which is extremely dangerous when an organic solvent having a low flash point such as toluene is used.

In addition, cellulose nanofibers are offered on the market as an aqueous dispersion, but since cellulose nanofibers form hydrogen bonds and aggregate in the drying step of removing water from the aqueous dispersion, they can be combined with rubber components and resin components. In the compounding process of, the cellulose nanofibers could not exist in a highly deflated state, and the composite material could not be sufficiently reinforced by the cellulose nanofibers.
Therefore, a method of mixing a cellulose nanofiber aqueous dispersion with a rubber latex or a resin emulsion has been proposed (Patent Documents 3 and 4).
However, the composite materials produced by these methods may be affected by the properties of the rubber latex or resin emulsion. In addition, it could not be applied to rubber or resin that is not on the market as rubber latex or resin emulsion.

Japanese Unexamined Patent Publication No. 2006-206864 Japanese Unexamined Patent Publication No. 2019-163861 Japanese Unexamined Patent Publication No. 2015-98576 Japanese Unexamined Patent Publication No. 2016-29169

Therefore, an object of the present invention is to provide a method capable of efficiently producing a rubber composition in which cellulose nanofibers are uniformly dispersed and have suitable physical characteristics.

As a result of diligent studies for the purpose of developing a technique for sufficiently dispersing unmodified cellulose nanofibers in a rubber composition using a rubber component containing ethylene propylene diene rubber (EPDM), the present inventors have made a boiling point as a solvent. By using a water-soluble organic solvent having an SP value of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, cellulose nanofibers can be dispersed very uniformly and efficiently in the rubber composition, and can be obtained. They have found that the rubber composition has suitable physical properties and have completed the present invention.
Further, it is a mixed solvent of a water-soluble organic solvent having an SP value of 10 or more and a water-insoluble organic solvent having an SP value of 9 or less, and is a solvent of at least one of the water-soluble organic solvent and the water-insoluble organic solvent. Even when a mixed solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of the mixed solvent of 8.5 to 11 is used, the cellulose nanofibers are dispersed very uniformly and efficiently in the rubber composition. It was possible, and the resulting rubber composition was found to have suitable physical properties, which led to the completion of the present invention.

The first embodiment of the present invention is in the presence of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
With rubber components containing EPDM,
It has a step of kneading with an unmodified cellulose nanofiber dispersion.
The present invention relates to a method for producing a rubber composition containing cellulose nanofibers.

In the first embodiment, the step of swelling the rubber component containing EPDM with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, and the swollen rubber component and unmodified cellulose. It may have a step of kneading with the nanofiber dispersion.

In the first embodiment, a rubber component containing EPDM, which is swollen with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, is used.
A water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11
It may have a step of kneading with an unmodified cellulose nanofiber dispersion.

In the first embodiment, the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is selected from the group consisting of alcohol-based solvents, ether-based solvents and ester-based solvents1. It may be more than a seed.

In the first embodiment, the unmodified cellulose nanofiber dispersion may be a dispersion of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.

Further, the second embodiment of the present invention is a mixed solvent of a water-soluble organic solvent having an SP value of 10 or more and a water-insoluble organic solvent having an SP value of 9 or less, wherein the water-soluble organic solvent and the non-water-soluble organic solvent are used. In the presence of a mixed solvent in which the boiling point of at least one of the water-soluble organic solvents is 150 ° C. or higher and 220 ° C. or lower and the SP value of the mixed solvent is 8.5 to 11.
With rubber components including ethylene propylene diene rubber,
The present invention relates to a method for producing a cellulose nanofiber-containing rubber composition, which comprises a step of kneading with an unmodified cellulose nanofiber dispersion.

The second embodiment may include a step of swelling the rubber component containing ethylene propylene diene rubber with the mixed solvent, and a step of kneading the swelled rubber component with the unmodified cellulose nanofiber dispersion. ..

In the second embodiment, the rubber component containing ethylene propylene diene rubber swollen with the mixed solvent is used.
With the mixed solvent
It may have a step of kneading with an unmodified cellulose nanofiber dispersion.

In the second embodiment, the water-soluble organic solvent may be N-methylpyrrolidone or 1-methoxy-2-propanol, and the water-insoluble organic solvent may be butyl acetate or methoxybutyl acetate.

In the second embodiment, the unmodified cellulose nanofiber dispersion may be a dispersion of the mixed solvent.

In the first or second embodiment, the average fiber diameter of the unmodified cellulose nanofibers may be 20 to 1000 nm.

In the first or second embodiment, the unmodified cellulose nanofibers swollen with the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 or the mixed solvent are obtained. It may have a step of removing the water-soluble organic solvent or the mixed solvent so as to be 1% by weight or less from the dispersed rubber component.

In the first or second embodiment, the solid content concentration of the unmodified cellulose nanofibers in the cellulose nanofiber-containing rubber composition may be 3 to 30 phr.

According to the present invention, the unmodified cellulose nanofibers can be dispersed very uniformly and efficiently in the rubber composition in either the first or the second embodiment. The rubber molded product obtained by cross-linking the obtained rubber composition has high rubber hardness and elasticity, and therefore has suitable physical characteristics.

Hereinafter, embodiments of a method for producing a cellulose nanofiber-containing rubber composition according to the present invention will be described.

(First embodiment)
The method for producing a cellulose nanofiber-containing rubber composition according to the first embodiment of the present invention (hereinafter, also referred to as the production method according to the first embodiment) is
In the presence of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
With rubber components containing EPDM,
It has a step of kneading with an unmodified cellulose nanofiber dispersion.

In the production method according to the first embodiment, as described above, a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is used in the rubber composition. Unmodified cellulose nanofibers can be dispersed very uniformly and efficiently, and the rubber molded product obtained by cross-linking the obtained rubber composition has high rubber hardness and elasticity, so that it is suitable physics. It will have characteristics.

The water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 used in the production method according to the first embodiment has a rubber component and unmodified cellulose having a boiling point of 150 ° C. or higher. It is difficult to vaporize the nanofibers even during kneading, and the unmodified cellulose nanofibers are easily sufficiently dispersed in the rubber component. Further, since the organic solvent is water-soluble, the aggregation of the unmodified cellulose nanofibers is suppressed, and when the SP value is 8.5 to 11, the rubber component containing EPDM is easily swelled, and the unmodified cellulose is easily swelled. Nanofibers can be easily dispersed in the rubber component.
If the organic solvent to be used has a boiling point of 150 ° C. or higher and 220 ° C. or lower, an SP value of 8.5 to 11, or any of the water-soluble physical properties is out of the range, as described in the comparative example below. In addition, the rubber hardness tends to be low, the dispersibility of the unmodified cellulose nanofibers in the rubber component is poor, the rubber composition is difficult to knead, and the productivity tends to be poor.
Therefore, in the production method according to the first embodiment, using a water-soluble organic solvent having the boiling point and SP value in the specific range is to use a rubber composition having predetermined physical characteristics (hereinafter, first rubber). It is necessary to obtain the composition).

The SP value refers to a solubility parameter, and in the present invention, the value calculated by HSPiP ver.5.2.06 is used.

Examples of the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 include alcohol-based solvents, ether-based solvents, ester-based solvents and the like.
Examples of the alcohol solvent include 3-methoxybutanol, 3-methoxy-3-methyl-1-butanol, diacetone alcohol and the like.
Examples of the ether-based solvent include diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, ethylene glycol monobutyl ether, ethylene glycol monoterriary butyl ether, dipropylene glycol methyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, and propylene glycol n-propyl ether. , Triethylene glycol dimethyl ether and the like.
Examples of the ester solvent include diethylene glycol monoethyl ether acetate and ethyl lactate.
The water-soluble organic solvent may be used alone or in combination of two or more.
The type of the water-soluble organic solvent is not particularly limited, but 3-methoxy-3-methyl-1-butanol can be safely produced because the flash point disappears when the water ratio is 20% or more.

Further, in the production method according to the first embodiment, a water-soluble organic solvent other than the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 may be used in combination. ..

Examples of the other water-soluble organic solvent include N-methylpyrrolidone (boiling point 202 ° C., SP value 11.5), 1-methoxy-2-propanol (boiling point 120 ° C., SP value 10.2), and propylene glycol ( Boiling point 188 ° C., SP value 14.5), pyridine (boiling point 115 ° C., SP value 15.1), acetonitrile (boiling point 82 ° C., SP value 12.2), isopropyl alcohol (boiling point 82 ° C., SP value 13.3) , Ethyl alcohol (boiling point 78 ° C., SP value 13.3), methyl alcohol (boiling point 65 ° C., SP value 14.7) and the like.

When the other water-soluble organic solvent is used in combination with the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, the SP value of the obtained mixed solvent is 8.5 to 10 The ratio may be within the range of .1 and the ratio of the organic solvents to be mixed is not particularly limited.

In the present invention, the swelling refers to a state in which the force of the water-soluble organic solvent entering between the polymer molecules of the rubber component and trying to widen the molecules and the elasticity of the crosslinked mesh are balanced. The swelling depends on the affinity between the water-soluble organic solvent and the polymer of the rubber component, and the better the affinity between the two, the greater the swelling.

The rubber component used in the production method according to the first embodiment is the main component of the first rubber composition and contains solid EPDM in which latex rubber cannot be used, such as diene-based rubber.

The rubber component that can be used together with EPDM may be a solid rubber that swells in a water-soluble organic solvent having an SP value of 8.5 to 11, and is not particularly limited. For example, natural rubber, synthetic diene rubber, and natural rubber. Examples thereof include a mixture of rubber and synthetic diene-based rubber, and non-diene-based rubber other than these.

Examples of the natural rubber include natural rubber latex, technically rated rubber (TSR), smoked sheet (RSS), gutta-percha, natural rubber derived from Tochu, natural rubber derived from guayule, natural rubber derived from Russian dandelion, and resin component fermented rubber. Further, the natural rubber of the present invention also includes modified natural rubber such as epoxidized natural rubber, methacrylic acid-modified natural rubber, and styrene-modified natural rubber modified from these natural rubbers.

Examples of the synthetic diene-based rubber include styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), and styrene-isoprene-styrene block co-weight. Combined (SIS), styrene-butadiene-styrene block copolymer (SBS), ethylene-α-olefin copolymer rubber (SPO), ethylene-α-olefin-diene copolymer rubber, and modified synthetic diene-based rubbers thereof. Can be mentioned. The modified synthetic diene-based rubber includes a diene-based rubber obtained by a modification method such as main chain modification, single-ended modification, and double-ended modification. Here, examples of the modified functional group of the modified synthetic diene rubber include various functional groups such as an epoxy group, an amino group, an alkoxy group, a hydroxyl group, an alkoxysilyl group, a polyether group and a carboxyl group, and these functional groups are 1 The seed or two or more may be contained in the modified synthetic diene rubber.

The method for producing the synthetic diene rubber is not particularly limited, and examples thereof include emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, and cationic polymerization. Further, the glass transition point of the synthetic diene rubber is not particularly limited.

The cellulose nanofiber dispersion used in the production method according to the first embodiment is a liquid substance in which unmodified cellulose nanofibers are dispersed.

The unmodified cellulose nanofibers are those that have not been subjected to a modification treatment for modifying cellulose nanofibers obtained from a raw material plant.
Cellulose nanofibers are fiber materials derived from cellulose composed of skeletal components of plant cell walls obtained by finely loosening plant fibers. Examples of raw material plants for cellulose nanofibers include wood, bamboo, rice, potatoes, sugar cane, aquatic plants, and seaweeds.
Further, the cellulose nanofibers may be composed of cellulose alone or may be lignocellulosic nanofibers containing lignin.
Two or more kinds of these unmodified cellulose nanofibers may be mixed and used.

The unmodified cellulose nanofibers may have an average fiber diameter of 1000 nm or less, but from the viewpoint of being easily dispersed in the first rubber composition and easily obtaining suitable strength and elasticity, the unmodified cellulose nanofibers have a diameter of 50 to 500 nm. Is preferable.
The fiber length of the unmodified cellulose nanofibers is preferably 1 to 1000 μm from the viewpoint that it is easy to disperse in the first rubber composition and it is easy to obtain suitable strength and elasticity.
The average fiber diameter and fiber length in the present invention can be measured by a scanning electron microscope or an atomic force microscope.

In the production method according to the first embodiment, examples of the cellulose nanofiber dispersion include a dispersion of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
The content of the unmodified cellulose nanofibers in the cellulose nanofiber dispersion is not particularly limited, but may be adjusted to 1 to 30% by weight.

The method for dispersing the cellulose nanofibers in a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 may be any known method and is not particularly limited.
Further, the cellulose nanofibers are dispersed in water, and then the water is replaced with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, to prepare a cellulose nanofiber dispersion. May be good.

In the production method according to the first embodiment, as a method of kneading a rubber component containing EPDM in which a water-soluble organic solvent is swollen and a cellulose nanofiber dispersion to disperse unmodified cellulose nanofibers. ,for example,
1-1) A method comprising a step of kneading a rubber component containing EPDM and a cellulose nanofiber dispersion dispersed in a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
2-1) A step of swelling a rubber component containing EPDM with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, and a step of swelling the rubber component and a cellulose nanofiber dispersion. Methods involving kneading steps,

Specifically, as the method 1-1), a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is added to a rubber component containing EPDM kneaded with a kneader. Examples thereof include a method in which the cellulose nanofiber dispersion dispersed in the above is charged and the water-soluble organic solvent is vaporized while kneading the dispersion.
In addition, as the method of 2-1), a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is added to the rubber component containing EPDM kneaded by the kneader. The rubber component was swelled while kneading them, and then the cellulose nanofiber dispersion dispersed in a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 was added. A method of vaporizing the water-soluble organic solvent while kneading the rubber can be mentioned.
Further, in the method of 2-1), depending on the type of the kneading device and the type of the water-soluble organic solvent, a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is added. The step of swelling the rubber component while kneading can be omitted.
The water-soluble organic solvent kneaded with the rubber component and the water-soluble organic solvent used for the cellulose nanofiber dispersion may be of the same type or different.

The kneader includes a closed mixer (Banbury mixer, show mixer, kneader mixer, etc.), roll, extruder (Gordon plastic mixer, transfer mixer, cavity transfer mixer, pin type mixer, twin screw type extruder, etc.). And so on.

The temperature condition for swelling the rubber component may be any temperature as long as the rubber component does not crosslink, and may be appropriately adjusted depending on the type of the rubber component. The temperature is not particularly limited, but is preferably 80 to 130 ° C.
Further, the kneading time for swelling the rubber component is not particularly limited.

The temperature condition for vaporizing the water-soluble organic solvent while kneading may be any temperature as long as the rubber component does not crosslink, and is not particularly limited, but is preferably 100 to 150 ° C.
Further, the kneading may be continued until a water-soluble organic solvent cannot be confirmed around the first rubber composition, and the specific time is not particularly limited, but may be 1 to 3 hours.
Furthermore, by using the kneader and the organic solvent recovery device together, the water-soluble organic solvent can be recovered, and the regeneration is environmentally friendly and leads to cost reduction.

(Second embodiment)
The method for producing a cellulose nanofiber-containing rubber composition according to a second embodiment of the present invention (hereinafter, also referred to as a production method according to the second embodiment) is
A mixed solvent of a water-soluble organic solvent having an SP value of 10 or more and a water-insoluble organic solvent having an SP value of 9 or less (hereinafter, also referred to as a mixed solvent of the second embodiment), wherein the water-soluble organic solvent and the above-mentioned In the presence of a mixed solvent in which the boiling point of at least one of the water-insoluble organic solvents is 150 ° C. or higher and 220 ° C. or lower and the SP value of the mixed solvent is 8.5 to 11.
With rubber components including ethylene propylene diene rubber,
It has a step of kneading with an unmodified cellulose nanofiber dispersion.

In the production method according to the second embodiment, the water-soluble organic solvent having specific physical properties and the water-insoluble organic solvent having specific physical properties are mixed as described above, and the SP value of the obtained mixed solvent is set to 8. By adjusting to 5 to 11, the solvent is less likely to vaporize even when the rubber component and the unmodified cellulose nanofibers are kneaded, the unmodified cellulose nanofibers are easily sufficiently dispersed in the rubber component, and the unmodified cellulose nanofibers are not modified. The aggregation of the cellulose nanofibers is suppressed, the rubber component containing EPDM can be easily swollen, and the unmodified cellulose nanofibers can be easily dispersed in the rubber component. Therefore, similarly to the first embodiment, the rubber molded product obtained by cross-linking the rubber composition obtained by the production method according to the second embodiment (hereinafter referred to as the second rubber composition) has a rubber hardness. Because of its high elasticity and elasticity, it has suitable physical characteristics.
In the production method according to the second embodiment, the upper limit of the SP value of the water-soluble organic solvent and the lower limit of the SP value of the water-insoluble organic solvent are set to the SP of the mixed solvent of the second embodiment. It suffices if the value can be adjusted to a specific range, and there is no particular limitation.

Examples of the water-soluble organic solvent having an SP value of 10 or more include N-methylpyrrolidone (boiling point 202 ° C.), 1-methoxy-2-propanol (boiling point 120 ° C.), propylene glycol (boiling point 188 ° C.), and pyridine (boiling point 115 ° C.). ), acetonitrile (boiling point 82 ° C.), isopropyl alcohol (boiling point 82 ° C.), ethyl alcohol (boiling point 78 ° C.), methyl alcohol (boiling point 65 ° C.) and the like.
Examples of the water-insoluble organic solvent having an SP value of 9 or less include butyl acetate (boiling point 126 ° C.), methoxybutyl acetate (boiling point 172 ° C.), xylene (boiling point 140 ° C.), toluene (boiling point 110 ° C.), and mineral spirit (boiling point). 130-230 ° C) and the like.
In the production method according to the second embodiment, the boiling point of at least one of the water-soluble organic solvent having an SP value of 10 or more and the water-insoluble organic solvent having an SP value of 9 or less is 150 ° C. or more and 220 ° C. or less. The water-soluble organic solvent and the water-insoluble organic solvent may be selected so that the SP value of the mixed solvent of the second embodiment is 8.5 to 11.
Above all, from the viewpoint of excellent dispersibility of the mixed solvent of the second embodiment, N-methylpyrrolidone or 1-methoxy-2-propanol is used as the water-soluble organic solvent, and butyl acetate or methoxybutyl acetate is used as the water-insoluble organic solvent. It is preferable to use.

Regarding the mixing ratio of the water-soluble organic solvent and the water-insoluble organic solvent in the mixed solvent of the second embodiment, the SP value of the obtained mixed solvent of the second embodiment is in the range of 8.5 to 11. The mixing ratio may be adjusted, and there is no particular limitation.

The rubber component used in the production method according to the second embodiment is the main component of the second rubber composition. Specifically, any rubber component that can be used in the production method according to the first embodiment may be used. A detailed description of the rubber component will be omitted.

The cellulose nanofiber dispersion used in the production method according to the second embodiment is a liquid substance in which unmodified cellulose nanofibers are dispersed. Specifically, any cellulose nanofibers that can be used in the production method according to the first embodiment may be used. Detailed description of cellulose nanofibers will be omitted.

In the production method according to the second embodiment, as the cellulose nanofiber dispersion, a dispersion of a mixed solvent of the water-soluble organic solvent and the water-insoluble organic solvent (mixed solvent of the second embodiment) is used. Can be mentioned.
The content of the unmodified cellulose nanofibers in the cellulose nanofiber dispersion is not particularly limited, but may be adjusted to 1 to 30% by weight.

The method for dispersing the cellulose nanofibers in the mixed solvent of the second embodiment may be any known method, and is not particularly limited.
Further, the cellulose nanofibers may be dispersed in water, and then the mixed solvent of the second embodiment may be mixed to replace the water with the mixed solvent to prepare a cellulose nanofiber dispersion.

In the production method according to the second embodiment, the rubber component containing EPDM in which the mixed solvent of the second embodiment is swollen is kneaded with the cellulose nanofiber dispersion to disperse the unmodified cellulose nanofibers. As a method, for example,
1-2) A method comprising a step of kneading a rubber component containing EPDM and a cellulose nanofiber dispersion dispersed in the mixed solvent of the second embodiment.
2-2) A method including a step of swelling a rubber component containing EPDM with the mixed solvent of the second embodiment, and a step of kneading the swelled rubber component with a cellulose nanofiber dispersion.

Specifically, as the method of 1-2), the cellulose nanofiber dispersion dispersed in the mixed solvent of the second embodiment is added to the rubber component containing EPDM kneaded by the kneader. A method of vaporizing the mixed solvent of the second embodiment while kneading these can be mentioned.
Further, as the method of 2-2), the mixed solvent of the second embodiment is added to the rubber component containing EPDM kneaded by the kneader, and the rubber component is swollen while kneading them. Next, a method of adding the cellulose nanofiber dispersion dispersed in the mixed solvent of the second embodiment and kneading them to vaporize the water-soluble organic solvent can be mentioned.
Further, in the method of 2-2), depending on the type of the kneading device and the type of the organic solvent, the step of adding the mixed solvent of the second embodiment and kneading them while swelling the rubber component may be omitted. can.
The water-soluble organic solvent kneaded with the rubber component and the water-soluble organic solvent and the water-insoluble organic solvent used for the cellulose nanofiber dispersion may be the same type or different.

The kneading machine may be any device as long as it can be used in the manufacturing method of the first embodiment, and is not particularly limited.

The temperature condition for swelling the rubber component may be any temperature as long as the rubber component does not crosslink, and may be appropriately adjusted depending on the type of the rubber component. The temperature is not particularly limited, but is preferably 80 to 130 ° C.
Further, the kneading time for swelling the rubber component is not particularly limited.

The temperature condition for vaporizing the mixed solvent of the second embodiment while kneading may be any temperature as long as the rubber component does not crosslink, and is not particularly limited, but is preferably 100 to 150 ° C.
Further, the kneading may be continued until the mixed solvent of the second embodiment cannot be confirmed around the second rubber composition, and the specific time is not particularly limited, but is 1 to 3 hours. All you need is.
Further, by using the kneader and the organic solvent recovery device together, the mixed solvent of the second embodiment can be recovered, and the regeneration is environmentally friendly and leads to cost reduction.

Further, in the production method of the first or second embodiment, carbon black, a colorant, a filler, an oil, a plasticizer, a surfactant, a processing aid, etc. are contained in the obtained first or second rubber composition. Any component of may be added.
The timing of adding these optional components is not particularly limited, but in the case of the method 1-1) or 1-2) above, in the step of kneading the swollen rubber component and the cellulose nanofiber dispersion. If it is the step of kneading the rubber component and the water-soluble organic solvent or the mixed solvent of the second embodiment and the cellulose nanofiber dispersion, the method may be 2-1) or 2-2). good.

In the production method of the first or second embodiment, 1% by weight is added to the rubber component that is swollen with the water-soluble organic solvent or the mixed solvent of the second embodiment and in which the unmodified cellulose nanofibers are dispersed. The water-soluble organic solvent or the mixed solvent of the second embodiment may be removed as follows.
Examples of the method for removing the water-soluble organic solvent or the mixed solvent of the second embodiment from the rubber component include a method of continuing kneading while adjusting the temperature to a high level in the kneader, vacuum vacuum drying, and the like.
By removing the water-soluble organic solvent or the mixed solvent of the second embodiment in this way, a so-called masterbatch can be produced.

In the production method of the present invention, the dispersibility of the unmodified cellulose nanofibers in the first or second rubber composition is very excellent, so that the solid content concentration of the unmodified cellulose nanofibers is 3 to 30 phr ( The rubber molded product obtained by cross-linking the first or second rubber composition obtained by adjusting to per hungred rubber) has high rubber hardness and elasticity, and therefore has suitable physical properties. Will have.

The first or second rubber composition obtained by the production method of the present invention may be used for transmission belts, weather strips, anti-vibration rubbers, hoses, electric wire coatings, packings and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Production example of cellulose nanofiber dispersion]
970 parts by weight of purified water was added to 30 parts by weight of kraft pulp and stirred. Using a 6-inch mascoroider (Masuko Sangyo's stone mill type grinder), disperse while gradually reducing the clearance from the disk contact clearance, and when the contact clearance becomes 120 μm smaller, the end point is set and a buchnaroto is used. A cellulose nanofiber aqueous dispersion was prepared by filtering and concentrating until the cellulose nanofiber dispersion became 7.5% by weight (solid content concentration 7.5% by weight, average fiber diameter 80 to 200 nm, fiber length 100 μm).

Diethylene glycol dimethyl ether (manufactured by Toho Chemical Industry Co., Ltd .: water-soluble organic solvent having a boiling point of 162 ° C. and an SP value of 9.0) in 400 parts by weight of an aqueous dispersion of cellulose nanofibers having a solid content concentration of 7.5% by weight obtained as described above. Was added in an amount of 900 parts by weight and stirred.
Filtrate and concentrate the cellulose nanofiber dispersion to 400 parts by weight using Buchnaroth, then add 900 parts by weight of diethylene glycol dimethyl ether and stir, and filter to 400 parts by weight of the cellulose nanofiber dispersion using Buchnaroto. Concentration was performed. The water content of the obtained cellulose nanofiber dispersion was 10% or less. This cellulose nanofiber dispersion was used in subsequent examples.

[Example 1]
Diethylene glycol dimethyl ether (boiling point 162 ° C., boiling point 162 ° C., in 300 parts by weight of EPDM "EPT-4021H" (manufactured by Mitsui Chemicals, Inc.) being kneaded with a kneader (S-type double-arm kneader manufactured by Nihon Spindle Manufacturing Co., Ltd. (mixing capacity 1 L)) SP value 9.0) 60 parts by weight was added, and the rubber component was swollen while kneading at 100 ° C.
Then, while continuing the kneading, 500 parts by weight of the diethylene glycol dimethyl ether dispersion containing 6% by weight of the unmodified cellulose nanofibers (CNF) prepared in advance was added stepwise.
Then, kneading was continued while heating at 100 to 120 ° C., the diethylene glycol dimethyl ether was removed until the content of the diethylene glycol dimethyl ether became 1% by weight or less, and the rubber composition (solid content concentration of unmodified cellulose nanofibers 10 phr) was obtained. Obtained.

[Examples 2 to 6]
A rubber composition was obtained in the same manner as in Example 1 except that the organic solvent to be kneaded with EPDM and the organic solvent of the cellulose nanofiber dispersion were replaced with those shown in Table 1 below.
In the table, those in which the organic solvent is water-soluble are indicated by "∞".

[Comparative Examples 1 to 13]
A rubber composition was obtained in the same manner as in Example 1 except that the organic solvent to be kneaded with EPDM and the organic solvent of the cellulose nanofiber dispersion were replaced with those shown in Tables 2 and 3 below.

(Test Example 1)
The rubber hardness of the rubber compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 13 and the dispersibility of the unmodified cellulose nanofibers were evaluated by the following procedure.

[Rubber hardness]
1) 110 parts by weight of each rubber composition, 7.5 parts by weight of a cross-linking agent (DCP-40 (manufactured by NOF CORPORATION)), 5 parts by weight of zinc oxide and 1 part by weight of stearic acid are blended into two rolls. The mixture was kneaded at 70 to 80 ° C. for 10 minutes.
Next, the two rolls were operated to prepare a sheet having a thickness of 2.2 to 2.6 mm.
Then, using a metal frame having a thickness of 2 mm, heat pressing was performed at 170 ° C. for 20 minutes to carry out a cross-linking treatment to obtain a test piece having a thickness of 2 mm.
2) Three obtained test pieces were stacked to make a thickness of 6 mm, and 5 points were randomly measured with a digital durometer "GSD-719J-R (type A)" manufactured by Teclock, and the center value was defined as rubber hardness. did.

[Dispersity]
The presence or absence of coarse particles on the rubber surface after molding was visually confirmed and judged according to the following criteria.
"○" There are almost no coarse grains "△" There are many coarse grains that can be confirmed "×" There are many coarse grains that can be confirmed

[Comprehensive evaluation]
As an evaluation of production efficiency, kneading time was added and a comprehensive judgment was made based on the following criteria.
"○" Dispersibility is "○", rubber hardness is 75 or more and kneading time is less than 3 hours "△" Dispersibility is "○", rubber hardness is 75 or more, kneading time is 3 Those that satisfy one or two of less than time "x" Those with dispersibility of "x"

The results obtained are shown in Table 4.
From the results shown in Table 4, the rubber molded products of Examples 1 to 6 had high rubber hardness and coarse particles of unmodified cellulose nanofibers were not found in the rubber molded products, whereas the rubber molded products of Comparative Examples 1 to 6 were not found. The rubber molded product of No. 13 had a rubber hardness lower than that of Examples 1 to 6, and most of the evaluations of dispersibility were "Δ" or "x".
Further, when the rubber molded products were touched and confirmed, the rubber molded products of Examples 1 to 6 were deformed as compared with those of Comparative Examples 1 to 4, 7, and 13 in which the evaluation of dispersibility was "x". It was difficult and the elastic modulus was obviously high.
From the above, it can be seen that the rubber compositions obtained in Examples 1 to 6 can be suitably used for applications such as friction transmission belts, weather strips, anti-vibration rubbers, hoses, electric wire coatings, and packings.

Regarding the solvent types listed in Table 4,
"Diglyme" is diethylene glycol dimethyl ether,
"EDM" is diethylene glycol ethylmethyl ether,
"EDGAC" is ethyl diglycol acetate,
"Butyl cellosolve" is ethylene glycol n-butyl ether,
"Metobuta" is 3-methoxybutanol,
"Solfit" is 3-methoxy-3-methyl-1-butanol,
"Metose" is methoxybutyl acetate,
"PMA" is propylene glycol monomethyl ether acetate,
"Cellosolve acetate" is ethylene glycol monoethyl ether acetate,
"BDG" is a diethylene glycol monobutyl ether,
"PM" is propylene glycol monomethyl ether,
"NMP" is N-methyl-2-pyrrolidone,
"DMF" is dimethylformamide,
"PG" is propylene glycol,
"EG" indicates ethylene glycol.

[Example 7]
When butyl acetate and N-methyl-2-pyrrolidone were mixed in a volume ratio of 1: 1, it was confirmed that the SP value of the obtained mixed solvent was 10.1.
A rubber composition (solid content concentration of unmodified cellulose nanofibers: 10 phr) was obtained in the same manner as in Example 1 except that the above mixed solvent was used as a solvent.

[Examples 8 and 9, Comparative Examples 14 to 17]
A rubber composition (solid content concentration of unmodified cellulose nanofibers of 10 phr) was obtained in the same manner as in Example 7 except that the mixed solvent using the organic solvent shown in Table 5 was used.

The rubber hardness of the rubber compositions obtained in Examples 7 to 9 and Comparative Examples 14 to 17 and the dispersibility of the unmodified cellulose nanofibers were evaluated by the same procedure as in Example 1.
The results obtained are shown in Table 5.
From the results shown in Table 5, in the rubber molded products of Examples 7 to 9, the rubber hardness was high and coarse particles of unmodified cellulose nanofibers were not found in the rubber molded products, whereas the rubber molded products of Comparative Examples 14 to 14 to 9 were not found. The rubber molded product of No. 17 had a rubber hardness lower than that of Examples 1 to 6, and the evaluation of dispersibility was “Δ”.
Further, when the rubber molded product was touched and confirmed, the rubber molded product of Examples 7 to 9 was not easily deformed and had a high elastic modulus, like the rubber molded product of Example 1.
From the above, it can be seen that the rubber compositions obtained in Examples 7 to 9 can be suitably used for applications such as friction transmission belts, weather strips, anti-vibration rubbers, hoses, electric wire coatings, and packings.

[Reference example]
A rubber composition of a reference example was obtained by operating in the same manner as in Example 3 except that EPDM was changed to styrene butadiene rubber (product name: JSR 1502 JSR).
Next, 110 parts by weight of the rubber composition of the reference example, 1.5 parts by weight of sulfur, 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, and a thiazole-based vulcanization accelerator TMTD (Noxeller TT-P (Ouchi Shinko Kagaku Kogyo Co., Ltd.) )) 1 part by weight and 0.5 part by weight of thiazole-based vulcanization accelerator MBT (Noxeller MP (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)) in two rolls and mixed at 70-80 ° C for 10 minutes. Kneaded.
Next, the two rolls were operated to prepare a sheet having a thickness of 2.2 to 2.6 mm.
Then, using a metal frame having a thickness of 2 mm, heat pressing was performed at 150 ° C. for 20 minutes to carry out a cross-linking treatment to obtain a test piece having a thickness of 2 mm.
The rubber hardness, dispersibility, kneading time, and comprehensive evaluation of the obtained test piece were carried out based on Test Example 1. The results obtained are shown in Table 6.
From the results shown in Table 6, in the rubber molded product of the reference example, the rubber hardness was high and coarse particles of unmodified cellulose nanofibers were not found in the rubber molded product. Further, when the rubber molded product of the reference example was touched and confirmed, it was hard to be deformed and the elastic modulus was clearly high. Therefore, the rubber composition obtained in the reference example was a friction transmission belt, a weather strip, and a vibration-proof rubber. It can be seen that it can be suitably used for applications such as hoses, wire coatings, and packings.

Claims (13)

In the presence of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
With rubber components including ethylene propylene diene rubber,
A method for producing a cellulose nanofiber-containing rubber composition, which comprises a step of kneading with an unmodified cellulose nanofiber dispersion. A step of swelling a rubber component containing ethylene propylene diene rubber with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11, and a swelled rubber component and an unmodified cellulose nanofiber dispersion. The production method according to claim 1, further comprising a step of kneading. A rubber component containing ethylene propylene diene rubber swelled with a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11.
A water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11
The production method according to claim 1, further comprising a step of kneading the unmodified cellulose nanofiber dispersion. Claim 1 is that the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 is at least one selected from the group consisting of alcohol-based solvents, ether-based solvents and ester-based solvents. The manufacturing method according to any one of 3 to 3. The production method according to any one of claims 1 to 4, wherein the unmodified cellulose nanofiber dispersion is a dispersion of a water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11. .. A mixed solvent of a water-soluble organic solvent having an SP value of 10 or more and a water-insoluble organic solvent having an SP value of 9 or less, wherein the boiling point of at least one of the water-soluble organic solvent and the water-insoluble organic solvent is In the presence of a mixed solvent having a temperature of 150 ° C. or higher and 220 ° C. or lower and an SP value of the mixed solvent of 8.5 to 11.
With rubber components including ethylene propylene diene rubber,
A method for producing a cellulose nanofiber-containing rubber composition, which comprises a step of kneading with an unmodified cellulose nanofiber dispersion. The production method according to claim 6, further comprising a step of swelling a rubber component containing ethylene propylene diene rubber with the mixed solvent, and a step of kneading the swelled rubber component with an unmodified cellulose nanofiber dispersion. A rubber component containing ethylene propylene diene rubber swollen with the mixed solvent and
With the mixed solvent
The production method according to claim 6, further comprising a step of kneading the unmodified cellulose nanofiber dispersion. The production method according to any one of claims 6 to 8, wherein the water-soluble organic solvent is N-methylpyrrolidone or 1-methoxy-2-propanol, and the water-insoluble organic solvent is butyl acetate or methoxybutyl acetate. .. The production method according to any one of claims 6 to 9, wherein the unmodified cellulose nanofiber dispersion is a dispersion of the mixed solvent. The production method according to any one of claims 1 to 10, wherein the unmodified cellulose nanofibers have an average fiber diameter of 20 to 1000 nm. 1% by weight or less from the rubber component swelled with the water-soluble organic solvent having a boiling point of 150 ° C. or higher and 220 ° C. or lower and an SP value of 8.5 to 11 or the mixed solvent and in which unmodified cellulose nanofibers are dispersed. The production method according to any one of claims 1 to 11, further comprising a step of removing the water-soluble organic solvent or the mixed solvent. The production method according to any one of claims 1 to 12, wherein the solid content concentration of the unmodified cellulose nanofibers in the cellulose nanofiber-containing rubber composition is 3 to 30 phr.