JP2021138818A - Production method of composite material, and composite material - Google Patents

Abstract

To provide a production method of a composite material that suppresses agglomeration of cellulose nanofibers and uniformly disperses the cellulose nanofibers in kneading the cellulose nanofibers and a thermoplastic elastomer.SOLUTION: A production method of a composite material of the present invention includes a preliminary kneading step S3 for kneading a textile material containing cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, and a thermoplastic elastomer in a hermetic type kneader to obtain a preliminary kneaded material, and a main kneading step S4 for kneading the preliminary kneaded material in a non-hermetic type kneader to obtain a composite material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a composite material and a composite material.

Cellulose nanofibers are a new material obtained by defibrating natural cellulose fibers into nano-sized fibers, and their effective use is expected in recent years.

For example, Patent Document 1 discloses a technique for adding cellulose nanofibers to a thermoplastic resin such as polyethylene in order to improve mechanical properties and the like. When the cellulose nanofibers are dried, they easily form hydrogen bonds with each other to form agglomerates. Therefore, it is a technical problem to uniformly disperse the cellulose nanofibers in the thermoplastic resin.

Therefore, in Patent Document 1, when a cationic surfactant and a polyhydric alcohol are added to an aqueous dispersion of cellulose nanofibers and water is removed from the mixture (aqueous dispersion), the polyhydric alcohol or the like is used. By interposing between the cellulose nanofibers, the aggregation of the cell roll nanofibers is suppressed. The dried product (fiber material) thus obtained contains a cationic surfactant and a polyhydric alcohol in addition to the cellulose nanofibers. The fiber material is kneaded together with the thermoplastic resin while being heated using an open roll. The polyhydric alcohol in the dried product is volatilized and removed during kneading.

Japanese Unexamined Patent Publication No. 2019-173253

When the dried product (fiber material) and the thermoplastic elastomer are kneaded with a non-sealed (open type) kneader such as an open roll, the cellulose nanofibers in the dried product are not sufficiently dispersed in the thermoplastic elastomer. In addition, the thermoplastic alcohol is volatilized and removed. When the polyhydric alcohol is removed, aggregation of cellulose nanofibers occurs in the thermoplastic elastomer during kneading, which has been a problem.

An object of the present invention is to provide a method for producing a composite material in which aggregation of cellulose nanofibers is suppressed during kneading of cellulose nanofibers and a thermoplastic elastomer, and cellulose nanofibers are uniformly dispersed.

When the fiber material containing the cellulose nanofibers, the cationic surfactant and the polyhydric alcohol and the thermoplastic elastomer are kneaded only by the non-sealed kneader, the present inventors, the cellulose nanofibers are contained in the thermoplastic elastomer. It was found that the polyhydric alcohol was volatilized and removed before it was sufficiently dispersed in the thermoplastic elastomer, resulting in agglomeration of the cellulose nanofibers in the thermoplastic elastomer.

Then, as a result of diligent studies to achieve the above object, the present inventors have previously put a fiber material containing cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, and a thermoplastic elastomer into a sealed kneader. It was found that the cellulose nanofibers can be uniformly dispersed in the thermoplastic elastomer while suppressing the aggregation of the cellulose nanofibers by kneading them in a non-sealed kneader. rice field.

The means for solving the above-mentioned problems are as follows. That is,
<1> A pre-kneading step of kneading a fiber material containing cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, and a thermoplastic elastomer with a closed kneader to obtain a pre-kneading material.
A method for producing a composite material, which comprises a main kneading step of kneading the pre-kneading material with a non-sealed kneader to obtain a composite material.

<2> The method for producing a composite material according to <1>, wherein the cellulose nanofibers have an average fiber diameter of 3 nm or more and 10 nm or less and an average aspect ratio of 20 or more and 350 or less.

<3> The above-mentioned <1> or <2>, wherein the cationic surfactant is at least one selected from the group consisting of a primary amine salt, a secondary amine salt, a tertiary amine salt and a quaternary ammonium salt. Method of manufacturing composite materials.

<4> The method for producing a composite material according to any one of <1> to <3>, wherein the polyhydric alcohol comprises at least one of a dihydric alcohol and a trihydric alcohol.

<5> The method for producing a composite material according to any one of <1> to <4>, wherein the thermoplastic elastomer contains a modified thermoplastic elastomer.

<6> In the pre-kneading step, the fiber material is blended with the thermoplastic elastomer so that the cellulose nanofibers are contained in a ratio of 30 parts by mass or less with respect to 100 parts by mass of the thermoplastic elastomer. The method for producing a composite material according to any one of 1> to <5>.

<7> The composite material according to any one of <1> to <6>, wherein the ratio of the polyhydric alcohol to the cellulose nanofibers in the fiber material is 1 to 20 times by mass ratio. Manufacturing method.

<8> In the fiber material, the ratio of the cationic surfactant to the cellulose nanofibers is 0.1 to 2.0 times by mass ratio, which is any one of <1> to <7>. The method for producing a composite material according to.

<9> A dispersion mixing step of mixing the cationic surfactant and the polyhydric alcohol in a precursor dispersion in which the cellulose nanofibers are dispersed in an aqueous solvent to obtain a CNF dispersion, and the CNF dispersion. The method for producing a composite material according to any one of <1> to <8>, which comprises a drying step of removing the aqueous solvent from the water to obtain the fiber material.

<10> A composite material produced by the method for producing a composite material according to any one of <1> to <9>.

According to the present invention, it is possible to provide a method for producing a composite material in which the aggregation of the cellulose nanofibers is suppressed and the cellulose nanofibers are uniformly dispersed at the time of kneading the cellulose nanofibers and the thermoplastic elastomer.

The flow chart which shows the manufacturing method of the composite material of this embodiment External photograph of each test sample of Example 3 and Comparative Example 2 SEM images of each test sample of Example 3, Comparative Example 1 and Comparative Example 2 A graph showing the results of tensile evaluation tests of Example 3, Comparative Example 1 and Comparative Example 2. A graph showing the results of tear strength evaluation tests of Example 3, Comparative Example 1 and Comparative Example 2. Graphs showing the results of tensile evaluation tests of Examples 1 to 4 and Comparative Example 1. Graph showing the result of tear strength evaluation test of Examples 1 to 4 A graph showing the results of tensile evaluation tests of Examples 3, 5 to 7 and Comparative Example 1. Graph showing the results of the tear strength evaluation test of Examples 3, 5 to 7 and Comparative Example 1. A graph showing the results of dynamic viscoelasticity evaluation of Example 3, Comparative Example 1 and Comparative Example 2. A graph showing the results of repeating the dynamic viscoelasticity evaluation of Example 3 twice.

[Manufacturing method of composite material]
FIG. 1 is a flow chart showing a method for producing a composite material of the present embodiment. As shown in FIG. 1, the method for producing a composite material of the present embodiment includes a dispersion liquid mixing step S1, a drying step S2, a pre-kneading step S3, and a main kneading step S4.

(Dispersion liquid mixing step S1)
The dispersion liquid mixing step S1 is a step of mixing a predetermined amount of a cationic surfactant and a predetermined amount of polyhydric alcohol in a precursor dispersion liquid in which cellulose nanofibers are dispersed in an aqueous solvent to obtain a CNF dispersion liquid. .. As the mixing means (stirring means), known mixing means can be used. As the mixing means, for example, those used in the miniaturization step described later can be adopted.

The precursor dispersion liquid is obtained by dispersing cellulose nanofibers in an aqueous solvent, and basically does not contain a cationic surfactant or a polyhydric alcohol. Water is mainly used as the aqueous solvent. As the water, distilled water, purified water, tap water and the like are used as long as the object of the present invention is not impaired. Further, as long as the object of the present invention is not impaired, an aqueous solvent other than water (for example, a lower alcohol such as methanol or ethanol) may be used as a part or all of the aqueous solvent.

Cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350. The average value of the fiber diameter and the aspect ratio of the cellulose nanofibers is an arithmetic mean value measured for at least 50 or more cellulose nanofibers in the field of view of an electron microscope. Cellulose nanofibers are provided as a cellulose nanofiber aqueous dispersion in which cellulose nanofibers are dispersed in water. Such a cellulose nanofiber aqueous dispersion may be used as a precursor dispersion in the dispersion mixing step S1. The precursor dispersion may contain cellulose oxide fibers. As the cellulose nanofibers, those obtained by various known methods can also be used.

The solid content of the cellulose nanofibers in the precursor dispersion is, for example, 0.01% by mass to 5% by mass, preferably 0.1% by mass to 2% by mass. When the cellulose nanofiber solid content in the precursor dispersion is in such a range, it is possible to prevent the drying step described later from taking too much time, and the cationic surfactant can be uniformly treated, and the cellulose nanofibers can be treated uniformly. It is easy to suppress the generation of agglomerates.

As a raw material for cellulose nanofibers, those derived from plant materials such as wood are used. As a method for producing cellulose nanofibers using a raw material of a vegetable material, for example, the raw material is chemically treated to make it easy to defibrate and then physically treated by a mechanical shearing force to defibrate the raw material. The raw material is physically defibrated and manufactured by a method using a known mechanical high shearing force such as a high-pressure homogenizer method, a grinder grinding method, a freeze crushing method, a strong shearing force kneading method, and a ball mill crushing method. Can be used.

Cellulose nanofibers may have anionic groups. Cellulose nanofibers having an anionic group can be obtained by further refining (defibrating) the raw material by introducing an anionic group when chemically treating the raw material or by physically defibrating the raw material. Be done. In the miniaturization step, it is easy to defibrate due to the repulsive action of the anionic group. Examples of the anionic group include a carboxylic acid group, a phosphoric acid group, a sulfonic acid group, a sulfuric acid group, phosphorous acid group, xanthate group (-OCSS ^-) and may be any one or more of these salts .. Examples of the cellulose nanofiber having an anionic group include an oxidized cellulose nanofiber having a carboxyl group or a salt of a carboxyl group, a phosphoric acid esterified cellulose nanofiber having a phosphate group or a salt of a phosphate group, a sulfate group or a sulfate. Sulfate-esterified cellulose nanofibers having a salt of the group, sulfate-esterified cellulose nanofibers having a phosphite group or a salt of a phosphite group, zanted cellulose nanofibers having a zantate group or a salt of a zantate group, etc. Can be mentioned. Examples of the cellulose oxide nanofibers include TEMPO cellulose oxide nanofibers and carboxymethylated cellulose nanofibers.

The aqueous dispersion (precursor dispersion) containing TEMPO oxidized cellulose nanofibers as the oxidized cellulose nanofibers is, for example, an oxidation step of oxidizing natural cellulose fibers to obtain oxidized cellulose fibers and a miniaturization step of refining the oxidized cellulose fibers. Obtained by a manufacturing method including.

In the oxidation step, water is added to the natural cellulose fiber as a raw material and treated with a mixer or the like to prepare a slurry in which the natural cellulose fiber is dispersed in water. Here, examples of natural cellulose fibers include wood pulp, cotton pulp, bacterial cellulose and the like. More specifically, examples of wood pulp include softwood pulp, broadleaf pulp and the like, examples of cotton pulp include cotton linter and cotton lint, and examples of non-wood pulp include cotton linter and cotton lint. Straw pulp, bagas pulp and the like can be mentioned. At least one of these can be used as the natural cellulose fiber.

In the oxidation step, in the case of TEMPO oxidation, natural cellulose fibers are oxidized in water using an N-oxyl compound as an oxidation catalyst to obtain oxidized cellulose fibers. As the oxidation step, a known method for oxidizing cellulose can be adopted. Examples of the N-oxyl compound that can be used as an oxidation catalyst for cellulose include 2,2,6,6-tetramethyl-1-piperidin-N-oxyl (hereinafter, also referred to as TEMPO), 4-acetamide-TEMPO, and the like. 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO and the like can be used. Oxidized cellulose fibers can be bundles of cellulose microfibrils. Oxidized cellulose fibers can be defibrated into cellulose nanofibers in the miniaturization step.

In the miniaturization step, the cellulose oxide fibers can be agitated in a solvent such as water, and cellulose nanofibers can be obtained. The stirring process in the miniaturization process includes, for example, a breaker, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic stirrer, and a household juicer mixer. Etc. can be used. The average value of the fiber diameters of the cellulose nanofibers in the aqueous dispersion thus obtained can be 3 nm to 10 nm, and further can be 3 nm to 4 nm. The average aspect ratio of the cellulose nanofibers in this aqueous dispersion can be 20 to 350, further 20 to 250, and further 50 to 200.

Further, the aqueous dispersion containing carboxymethylated cellulose as the oxidized cellulose nanofiber can be produced by, for example, a mercerization step, an etherification step, and a micronization step.

In the mercerization step, a natural cellulose fiber, a dispersion medium, and a mercerizing agent are mixed to perform a mercerization treatment. As the dispersion medium, for example, a lower alcohol alone or a mixture of two or more kinds and water is used. Lower alcohols include, for example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol and the like. As the mercerizing agent, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is used.

In the etherification step, after the mercerization treatment, a carboxymethylating agent is added to carry out an etherification reaction. The carboxymethylating agent is, for example, sodium monochloroacetate.

After the etherification reaction, the miniaturization step can be carried out in the same manner as the above-mentioned miniaturization step. For example, carboxymethylated cellulose nanofibers can be obtained by miniaturization treatment with a high-pressure homogenizer or the like. The carboxymethylated cellulose nanofibers thus obtained can have the same fiber diameter and aspect ratio as the TEMPO oxidized cellulose nanofibers.

The aqueous dispersion (precursor dispersion) containing phosphoric acid esterified cellulose nanofibers is, for example, a method of mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with a dry or wet cellulose fiber raw material, or a cellulose fiber raw material. It can be obtained by a method of adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to the dispersion liquid of. In these methods, usually, after mixing or adding a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative, dehydration treatment, heat treatment and the like are performed. Here, examples of the phosphoric acid or the phosphoric acid derivative include at least one compound selected from oxo acids containing a phosphorus atom, polyoxo acids, and derivatives thereof. As a result, a compound containing a phosphoric acid group or a salt thereof is dehydrated at the hydroxyl group of the glucose unit constituting cellulose to form a phosphoric acid ester, and the phosphoric acid group or a salt thereof is introduced. Cellulose fibers into which a phosphoric acid group or a salt thereof has been introduced can be subjected to the above-mentioned micronization step to obtain phosphoric acid esterified cellulose nanofibers. The phosphoric acid esterified cellulose nanofibers thus obtained can have the same fiber diameter and aspect ratio as the TEMPO oxidized cellulose nanofibers.

Cationic surfactants suppress the aggregation of cellulose nanofibers due to hydrogen bonds. The cationic surfactant comprises at least one selected from the group consisting of primary amine salts, secondary amine salts, tertiary amine salts and quaternary ammonium salts. The cationic surfactant can be a quaternary ammonium salt having a long-chain alkyl group having 1 to 40 carbon atoms (C number), preferably 2 to 20, and more preferably 8 to 18 carbon atoms. It can be inferred that the larger the number of carbon atoms, the higher the effect of suppressing aggregation due to hydrogen bonds of adjacent cellulose nanofibers. The salt can be chloride, bromide or the like.

Examples of the quaternary ammonium salt having a long-chain alkyl group having 1 to 40 carbon atoms include octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and chloride. Trimethylammonium salts such as octadecyltrimethylammonium; pyridinium salts such as octylpyridinium chloride, decylpyridinium chloride, dodecylpyridinium chloride, tetradecylpyridinium chloride, hexadecylpyridinium chloride, octadecylpyridinium chloride; Examples thereof include alkylammonium, dialkyldimethylammonium chloride, trimethylstearylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and the like.

In the CNF dispersion, the mass ratio of the cationic surfactant to the cellulose nanofibers (CNF) is, for example, 0.1 to 2 times, preferably 0.3 to 1 times. When the mass ratio is in such a range, it can act on the carboxyl group on the surface of the cellulose nanofibers, suppress the reaggregation of the cellulose nanofibers, obtain a good defibrated state in the resin, and process. Deterioration of sex is also suppressed.

The polyhydric alcohol can suppress the reaggregation of the cellulose nanofibers after dehydration drying by hindering the hydrogen bonding between the cellulose nanofibers even if the aqueous solvent is removed in the drying step described later. Further, it is possible to facilitate the defibration of the cellulose nanofibers in the kneading step (preliminary kneading step, main kneading step) described later. Polyhydric alcohols are alcohols excluding monohydric alcohols. Monohydric alcohol cannot be used because it has a lower boiling point than water.

Polyhydric alcohols have a higher boiling point than water. Since it has a boiling point higher than that of water, the polyhydric alcohol can remain in the fiber material even if the water evaporates through the drying step described later. Further, since the surfactant is adsorbed on the cellulose nanofibers, the cellulose nanofibers do not agglomerate and can maintain a stable dispersed state. In order to prevent the polyhydric alcohol from rapidly evaporating in the kneading step (preliminary kneading step, main kneading step) described later and causing reaggregation of cellulose nanofibers, the polyhydric alcohol is used at the kneading temperature in the kneading step described later. It is desirable to have a higher boiling point than.

The polyhydric alcohol consists of at least one of a dihydric alcohol and a trihydric alcohol. Examples of the dihydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol and the like. Examples of the trihydric alcohol include glycerin, trimethylolethane, trimethylolpropane, cyclohexanedimethanol and the like. As the polyhydric alcohol other than divalent and trivalent, for example, pentaerythritol, diglycerin, polyglycerin and the like may be contained. These may be used alone or in combination of two or more.

The mass ratio of the polyhydric alcohol to the cellulose nanofibers in the CNF dispersion is, for example, 1 to 20 times, preferably 3 to 10 times. When the mass ratio is in such a range, the cellulose nanofibers can be defibrated when the composite material is produced using the fiber material after the drying step S2, and the composite material can be easily produced.

(Drying step S2)
The drying step S2 is a step of removing the aqueous solvent from the CNF dispersion liquid to obtain a fiber material. As a method for removing the aqueous solvent from the CNF dispersion liquid, a known method can be used, and for example, it may be dried by heating or by a spray-drying method.

For example, the CNF dispersion may be poured into a container (such as a vat), and the container may be placed in an oven to evaporate the aqueous solvent at 30 ° C. to 100 ° C. In the drying step S2, the aqueous solvent may be completely removed from the CNF dispersion, or a small amount of the aqueous solvent may be left so that it can be removed in the subsequent steps.

The fiber material obtained in the drying step S2 contains cellulose nanofibers, a cationic surfactant and a polyhydric alcohol.

The ratio of the polyhydric alcohol to the cellulose nanofibers in the fiber material is, for example, 1 to 20 times, preferably 3 to 10 times, by mass ratio.

Further, in the fiber material, the ratio of the cationic surfactant to the cellulose nanofibers is, for example, 0.1 to 2 times, preferably 0.3 to 1 times, in terms of mass ratio.

(Preliminary kneading step S3)
The pre-kneading step S3 is a step of kneading a fiber material containing cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, and a thermoplastic elastomer with a closed kneader to obtain a pre-kneading material.

Examples of the thermoplastic elastomer include a styrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, a polybutadiene-based thermoplastic elastomer, and a polyisoprene-based thermoplastic elastomer. , Fluoro rubber-based thermoplastic elastomer and the like. These may be used alone or in combination of two or more.

As the thermoplastic elastomer, a styrene-based thermoplastic elastomer is preferable because it is easy to uniformly disperse the cellulose nanofibers.

Examples of the styrene-based thermoplastic elastomer include styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-propylene block copolymer (SEP), and styrene. Examples thereof include -ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS). These may be used alone or in combination of two or more.

As the thermoplastic elastomer, a modified thermoplastic elastomer having a reactive functional group capable of reacting with cellulose nanofibers (particularly, a hydroxyl group) may be used. Examples of the reactive functional group capable of reacting with the cellulose nanofibers include an acid anhydride group, a carboxyl group, an epoxy group, an oxazoline group, an isocyanate group and the like, and these may be used alone or in combination of two or more. .. Among these, an acid anhydride group is preferable as the reactive functional group from the viewpoint of good reactivity with cellulose nanofibers and the like.

The method for imparting a reactive functional group to the thermoplastic elastomer is not particularly limited, and a known method can be appropriately used. Examples of such a method include a method of adding an acid anhydride as a monomer during the synthesis of a thermoplastic elastomer. Examples of the acid anhydride include maleic anhydride, phthalic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, butenyl succinic anhydride and the like. .. These may be used alone or in combination of two or more.

Examples of the modified thermoplastic elastomer include maleic anhydride-modified styrene-based thermoplastic elastomers and maleic anhydride-modified olefin-based thermoplastic elastomers. These may be used alone or in combination of two or more. As the modified thermoplastic elastomer, an acid-modified styrene-based thermoplastic elastomer such as maleic anhydride-modified styrene-based thermoplastic elastomer is preferable. As the modified thermoplastic elastomer, a commercially available product (commercially available product) may be used.

Examples of the acid-modified styrene-based thermoplastic elastomer include maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer, maleic anhydride-modified styrene-ethylenepropylene-styrene copolymer, and maleic anhydride-modified styrene-butadiene. -Styrene copolymer, maleic anhydride-modified styrene-isoprene-styrene copolymer and the like can be mentioned. These may be used alone or in combination of two or more.

The introduction rate (modification rate) of the reactive functional group in the modified thermoplastic elastomer is determined by JIS-K2501: 2003.

In the pre-kneading step S3, a closed kneader is used for mixing the fiber material and the thermoplastic elastomer. The pre-kneading step S3 is a step performed in advance before the main kneading step S4 described later. The closed kneader is a device for kneading a fiber material and a thermoplastic elastomer in a closed space, and examples thereof include a Banbury mixer, an internal mixer, an intensive mixer, and a lab plast mill.

In the pre-kneading step S3, when the fiber material and the thermoplastic elastomer are kneaded using a closed kneader, the polyhydric alcohol is prevented from volatilizing and being removed from the kneaded product during the kneading. That is, in the preliminary kneading step S3, the cellulose nanofibers can be uniformly dispersed to some extent in the kneaded product (thermoplastic elastomer) while the polyhydric alcohol remains. Therefore, the presence of the polyhydric alcohol can suppress the aggregation of cellulose nanofibers.

In the preliminary kneading step S3, a high shearing force is applied to the thermoplastic elastomer, and the restoring force due to the elasticity of the thermoplastic elastomer can be used to deflate the cellulose nanofibers and disperse them in the thermoplastic elastomer. ..

The kneading temperature in the pre-kneading step S3 is appropriately set in consideration of the softening point (softening temperature) of the thermoplastic elastomer, the boiling point of the polyhydric alcohol, and the like.

For example, when the thermoplastic elastomer is a styrene-based thermoplastic elastomer (a modified styrene-based thermoplastic elastomer may be partially contained), the kneading temperature in the pre-kneading step S3 is set to, for example, 100 ° C. to 230 ° C. NS.

Further, the kneading time in the preliminary kneading step S3 is appropriately set in consideration of promotion of defibration of cellulose, heat of shearing on cellulose and base material, excessive evaporation of polyhydric alcohol, and the like. The kneading time in the preliminary kneading step S3 is set to, for example, 1 minute to 30 minutes.

In the preliminary kneading step S3, the fiber material is made into the thermoplastic elastomer so that the cellulose nanofibers are contained in a ratio of 30 parts by mass or less (preferably 1 to 15 parts by mass) with respect to 100 parts by mass of the thermoplastic elastomer. It is preferable to blend. When cellulose nanofibers are blended in such a ratio with respect to 100 parts by mass of the thermoplastic elastomer, it is easy to uniformly disperse the cellulose nanofibers in the thermoplastic elastomer.

In the pre-kneading step S3, the fiber material may be used in the form of a master batch that is previously mixed and dispersed in the thermoplastic elastomer.

The pre-kneading material is a material obtained by kneading a fiber material and a thermoplastic elastomer with a closed kneader. If necessary, components other than the fiber material and the thermoplastic elastomer may be added to the pre-kneading material as long as the object of the present invention is not impaired.

(Main kneading step S4)
This is a step of kneading the pre-kneading material with a non-sealing type kneader to obtain a composite material. The non-sealed kneader is a kneading device in which the part for kneading the pre-kneading material is open. Examples of such a non-sealed kneader include an open roll and the like.

The main kneading step S4 is a step performed following the pre-kneading step S, and during kneading, the cellulose nanofibers are uniformly dispersed in the kneaded product (thermoplastic elastomer) while gradually volatilizing the polyhydric alcohol. Can be done.

In the main kneading step S4, a high shearing force is applied to the thermoplastic elastomer, and the restoring force due to the elasticity of the thermoplastic elastomer can be used to deflate the cellulose nanofibers and disperse them in the thermoplastic elastomer. ..

The kneading temperature in the main kneading step S4 is appropriately set in consideration of the softening point (softening temperature) of the thermoplastic elastomer, the boiling point of the polyhydric alcohol, and the like. The kneading temperature in the main kneading step S4 is set to, for example, 100 ° C. to 230 ° C.

Further, the kneading time in the main kneading step S4 is appropriately set in consideration of promotion of defibration of cellulose, removal of polyhydric alcohol, damage due to shearing force to the base material and cellulose, and the like. The kneading time in the main kneading step S4 is set to, for example, 1 minute to 20 minutes.

In the main kneading step S4, the fiber material is made into the thermoplastic elastomer so that the cellulose nanofibers are contained in a ratio of 30 parts by mass or less (preferably 1 to 15 parts by mass) with respect to 100 parts by mass of the thermoplastic elastomer. It is preferable to blend. When cellulose nanofibers are blended in such a ratio with respect to 100 parts by mass of the thermoplastic elastomer, it is easy to uniformly disperse the cellulose nanofibers in the thermoplastic elastomer. In the kneading step S4, components other than the fiber material and the thermoplastic elastomer may be added as long as the object of the present invention is not impaired. After such a main kneading step S4, a composite material is obtained.

After the main kneading step S4, if necessary, a removal step of removing the polyhydric alcohol and the like in the mixed material may be performed by heat treatment using a reduced pressure oven or the like.

As described above, the composite material can be produced. As a method for producing the composite material, at least a pre-kneading step S3 and a main kneading step S4 may be provided.

In the composite material, the cellulose nanofibers are uniformly dispersed in the thermoplastic elastomer which is the base material without agglomeration. Such a composite material has excellent mechanical properties such as tensile strength and can be used for various purposes.

Hereinafter, the present invention will be described in more detail based on Examples. The present invention is not limited to these examples.

[Example 1]
<Water dispersion mixing process>
Using a commercially available TEMPO oxidized cellulose nanofiber aqueous dispersion (concentration 1%, precursor dispersion), add a predetermined amount of polyhydric alcohol to the dispersion, and use a mixer to mix them. , 60 seconds. A predetermined amount of cationic surfactant was further added to the obtained mixture, and the mixture was stirred for 90 seconds using the mixer to obtain a CNF dispersion liquid.

The cellulose nanofiber (CNF) is a TEMPO-oxidized cellulose nanofiber, the average fiber diameter of which is 3.3 nm, and the average aspect ratio is 160. Further, as the polyhydric alcohol, diethylene glycol (DEG) (manufactured by Wako Pure Chemical Industries, Ltd.) was used. Further, as the cationic surfactant (ammonium salt), n-hexadecyltrimethylammonium chloride (manufactured by Kanto Chemical Co., Inc.) was used.

<Drying process>
An aqueous solvent was removed from the CNF dispersion to obtain a fiber material. Specifically, the CNF dispersion was poured into a vat and dried in an oven at 40 ° C. for 96 hours to obtain a fiber material from which the aqueous solvent had been removed. The fiber material is adjusted so that the weight ratio of the fiber material is 5 times that of CNF1 and 0.5 times that of the cationic surfactant (ammonium salt).

<Preliminary kneading process>
The fiber material and a styrene-based thermoplastic elastomer (TPS, "Septon / 2002", manufactured by Kuraray Co., Ltd.) were kneaded using a closed kneader. Specifically, the mixture was subjected to a two-roll lab plast mill (an example of a closed kneader) at a temperature of 170 ° C. for 3 minutes at 30 rpm, followed by 7 minutes at 50 rpm (an example of a closed kneader). Kneading was carried out under rotating conditions (10 minutes in total).

The blending amount of the fiber material with respect to TPS was adjusted so that the amount of each component of the fiber material with respect to 100 parts by mass of TPS was 10 parts by mass of CNF, 50 parts by mass of DEG, and 5 parts by mass of the cationic surfactant, respectively.
<Main kneading process>
The kneaded product (pre-kneading material) obtained after the pre-kneading step was kneaded (elastic kneading) using an open roll (two rolls) which is a non-sealed kneader to obtain a composite material. The kneading temperature in the main kneading step was 160 to 180 ° C., and the kneading time was 20 minutes. The two roll speeds were set so that the surface speed ratio between the front side and the rear side was 1.15.

[Examples 2 to 4]
Composite materials of Examples 2 to 4 were prepared in the same manner as in Example 1 except that a part of TPS was replaced with modified TPS. Specifically, in the case of Example 2, 30 parts by mass of TPS is replaced with modified TPS, in the case of Example 3, 50 parts by mass is replaced with modified TPS, and in the case of Example 4, 70 parts by mass is replaced with modified TPS. Replaced with denatured TPS. As the modified TPS, "Tough Tech / M1943" (manufactured by Asahi Kasei Corporation) was used.

[Examples 5 to 7]
The composite materials of Examples 5 to 7 were prepared in the same manner as in Example 3 except that the blending amount of CNF contained in the fiber material was changed to each value (part by mass) shown in Table 3.

[Comparative Example 1]
A composite material was produced in the same manner as in Example 3 except that the pre-kneading step and the main kneading step were performed without blending the fiber material.

[Comparative Example 2]
A composite material was produced in the same manner as in Example 3 except that only kneading using an open roll (two rolls), which is a non-sealed kneader, was performed without performing the pre-kneading step. The kneading time in Comparative Example 2 was 20 minutes.

[Preparation of test sample]
The composites of each example and each comparative example were pelleted using a pelletizer. Then, the obtained pellets were used to prepare molded articles (test samples) for each test, which will be described later, using an injection molding apparatus.

[Appearance observation evaluation (confirmation of CNF aggregation inhibitory effect)]
By observing the test sample from the other side while illuminating the plate-shaped test sample (thickness: 1 mm) prepared from the composite material of Example 3 from one side, the composite material (kneading). The dispersion status of CNF existing in the object) was confirmed. Similarly, the dispersion status of CNF was confirmed in the test sample of Comparative Example 2. The results are shown in FIG.

FIG. 2 is an external photograph of each test sample of Example 3 and Comparative Example 2. A photograph of the test sample of Example 3 is shown on the left side of FIG. 2, and a photograph of the test sample of Comparative Example 2 is shown on the right side. Example 3 is a case where fibrous materials are blended so as to be 10 parts by mass of CNF and 50 parts by mass of DEG with respect to 100 parts by mass of thermoplastic elastomer (50 parts by mass of TPS + 50 parts by mass of modified TPS). At the time of kneading, a pre-kneading step of kneading with a closed kneader (laboplastomer) and a main kneading step of kneading with a non-sealed kneader (open roll) are performed. As shown in FIG. 2, in the test sample of Example 3, CNF was finely and uniformly dispersed in the kneaded product (thermoplastic elastomer) to the extent that it could not be visually confirmed, and no agglomerates of CNF were confirmed. rice field. As described above, in Example 3, it was confirmed that the effect of suppressing the aggregation of CNF by the DEF and the like contained in the fiber material was maintained even during the preliminary kneading of the kneaded product.

On the other hand, Comparative Example 2 has the same composition as that of Example 3, but the kneading method is different, and only the main kneading step of kneading with a non-sealed kneader (open roll) without performing the pre-kneading step is performed. This is the case. As shown in FIG. 2, in the test sample of Comparative Example 2, a large number of CNF agglomerates are scattered so as to spread in a plane. As described above, in Comparative Example 2, since the kneading was performed by the non-sealed kneader (open roll), the DEG was volatilized before the CNF was sufficiently dispersed in the kneaded product. It is presumed that the CNFs are agglomerated with each other.

[SEM observation evaluation]
For each of the test samples of Example 3, Comparative Example 1 and Comparative Example 2, SEM (Scanning Electron Microscope) images were acquired and observed, and the dispersion status of CNF present in the composite material (kneaded product) was observed. confirmed. The results are shown in FIG.

FIG. 3 is an SEM image of each test sample of Example 3, Comparative Example 1 and Comparative Example 2. The SEM image of Comparative Example 1 is shown at the left end of FIG. 3, the SEM image of Comparative Example 2 is shown at the right end, and the SEM image of Example 3 is shown between them. As shown in FIG. 3, in the test sample of Example 3, it was confirmed that the finely defibrated CNF was uniformly dispersed in the kneaded product (thermoplastic elastomer). On the other hand, in the test sample of Comparative Example 2, it was confirmed that CNF was present as a granular agglomerate. In Comparative Example 1, the fiber material is not included, and only 100 parts by mass of the thermoplastic elastomer (50 parts by mass of TPS + 50 parts by mass of the modified TPS) is used.

[Tension evaluation]
Each test sample of Examples 1 to 7 and Comparative Examples 1 and 2 was subjected to a tensile evaluation test in accordance with JIS-K6251.

Table 1 and FIG. 4 show the results of the tensile evaluation tests of Example 3, Comparative Example 1 and Comparative Example 2, respectively. Table 2 shows the results of the tensile evaluation tests of Examples 1 to 4, and FIG. 6 shows the results of the tensile evaluation tests of Examples 1 to 4 and Comparative Example 1. Table 3 and FIG. 8 show the results of the tensile evaluation tests of Examples 3, 5 to 7, and Comparative Example 1, respectively.

[Tear strength evaluation]
Each test sample of Examples 1 to 7 and Comparative Examples 1 and 2 was subjected to a tear strength evaluation test in accordance with JIS-K6252.

Table 1 and FIG. 5 show the results of the tear strength evaluation tests of Example 3, Comparative Example 1 and Comparative Example 2, respectively. Table 2 and FIG. 7 show the results of the tear strength evaluation tests of Examples 1 to 4, respectively. Table 3 and FIG. 9 show the results of the tear strength evaluation tests of Examples 3, 5 to 7, and Comparative Example 1, respectively.

As shown in Table 1 and FIG. 4, it was confirmed that the tensile stress when the elongation was 300% was higher in Example 3 than in Comparative Example 1 and Comparative Example 2. Although Example 3 and Comparative Example 2 basically have the same composition as each other, there is a large difference in tensile stress between them due to the difference in the kneading method. In Example 3, it is presumed that such a difference occurred because the cellulose nanofibers were uniformly dispersed in the thermoplastic elastomer in a fine state without agglomeration.

Further, as shown in Table 1 and FIG. 5, it was confirmed that among Example 3, Comparative Example 1 and Comparative Example 2, Example 3 had the highest tear strength.

As shown in Table 2 and FIG. 6, it was confirmed that Examples 2 to 4 containing the modified TPS had stronger tensile stress than Example 1 not containing the modified TPS. Further, as shown in Table 2 and FIG. 7, it was confirmed that Examples 2 to 4 containing the modified TPS had a larger tear strength than Example 1 not containing the modified TPS. From this, it was confirmed that the mechanical properties were improved by adding the modified thermoplastic elastomer to the thermoplastic elastomer.

As shown in Table 3 and FIG. 8, it was confirmed in Examples 3 and 5 to 7 that the tensile stress became stronger as the content of the cellulose nanofibers increased. Further, as shown in Table 3 and FIG. 9, it was confirmed in Examples 3 and 5 to 7 that the tear strength increased as the content of the cellulose nanofibers increased. As a result, it was confirmed that the mechanical properties are improved as the content of the cellulose nanofibers in the thermoplastic elastomer increases.

[Dynamic viscoelasticity evaluation 1]
The storage elastic modulus (E') was measured by performing dynamic viscoelasticity evaluation (DMA) under the conditions shown below for each of the test samples of Example 3, Comparative Example 1 and Comparative Example 2. The results are shown in FIG.

Measuring device: "DMA7100" (manufactured by Hitachi High-Tech Science Corporation)
Frequency: 1Hz
Measurement temperature: -100 ° C to 300 ° C
Temperature rise rate: 3 ° C / min
Measurement mode: Tensile test sample size: Length 20 mm x Width 4 mm x Thickness 1 mm

FIG. 10 is a graph showing the results of dynamic viscoelasticity evaluation of Example 3, Comparative Example 1 and Comparative Example 2. As shown in FIG. 10, the vertical axis of FIG. 10 is the storage elastic modulus E'(MPa), and the horizontal axis of FIG. 10 is the temperature (° C.). As shown in FIG. 10, the storage elastic modulus of Example 3 at 200 ° C. is higher than the storage elastic modulus of Comparative Example 2, and the thermal reinforcement effect of the thermoplastic elastomer CNF at high temperature is recognized. In the case of Comparative Example 1 composed of only a thermoplastic elastomer, the test sample broke at a temperature lower than 150 ° C.

[Dynamic viscoelasticity evaluation 2]
For the test sample of Example 3, the same dynamic viscoelasticity evaluation as above was performed by repeating the temperature rise from -100 ° C to 150 ° C and the subsequent temperature decrease from 150 ° C to -100 ° C twice in total. By doing so, the storage elastic modulus (E') was measured. The results are shown in FIG.

FIG. 11 is a graph showing the results of repeating the dynamic viscoelasticity evaluation of Example 3 twice. The vertical axis of FIG. 11 is the storage elastic modulus E'MPa, and the horizontal axis of FIG. 11 is the temperature (° C.). As shown in FIG. 11, the storage elastic modulus of the first temperature rise, the storage elastic modulus of the first temperature decrease, and the storage elastic modulus of the second temperature decrease overlap each other. It has almost the same curve. As described above, the test sample of Example 3 did not show a large difference in the result (storage elastic modulus E') even when the dynamic viscoelasticity evaluation was performed a plurality of times, and the thermoplastic elastomer was thermally reinforced by CNF. The effect could be confirmed.

S1 ... Dispersion liquid mixing step, S2 ... Drying step, S3 ... Preliminary kneading step, S4 ... Main kneading step

Claims (10)

A pre-kneading step of kneading a fiber material containing cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, and a thermoplastic elastomer with a closed kneader to obtain a pre-kneading material.
A method for producing a composite material, which comprises a main kneading step of kneading the pre-kneading material with a non-sealed kneader to obtain a composite material. The method for producing a composite material according to claim 1, wherein the cellulose nanofibers have an average fiber diameter of 3 nm or more and 10 nm or less and an average aspect ratio of 20 or more and 350 or less. The composite material according to claim 1 or 2, wherein the cationic surfactant is at least one selected from the group consisting of a primary amine salt, a secondary amine salt, a tertiary amine salt and a quaternary ammonium salt. Production method. The method for producing a composite material according to any one of claims 1 to 3, wherein the polyhydric alcohol comprises at least one of a dihydric alcohol and a trihydric alcohol. The method for producing a composite material according to any one of claims 1 to 4, wherein the thermoplastic elastomer contains a modified thermoplastic elastomer. Claims 1 to claim that the fiber material is blended with the thermoplastic elastomer so that the cellulose nanofibers are contained in a ratio of 30 parts by mass or less with respect to 100 parts by mass of the thermoplastic elastomer in the pre-kneading step. Item 5. The method for producing a composite material according to any one of Item 5. The method for producing a composite material according to any one of claims 1 to 6, wherein the ratio of the polyvalent alcohol to the cellulose nanofibers in the fiber material is 1 to 20 times by mass ratio. The composite according to any one of claims 1 to 7, wherein the ratio of the cationic surfactant to the cellulose nanofibers in the fiber material is 0.1 to 2.0 times by mass ratio. Material manufacturing method. A dispersion mixing step of mixing the cationic surfactant and the polyhydric alcohol in a precursor dispersion in which the cellulose nanofibers are dispersed in an aqueous solvent to obtain a CNF dispersion.
The method for producing a composite material according to any one of claims 1 to 8, further comprising a drying step of removing the aqueous solvent from the CNF dispersion liquid to obtain the fiber material. A composite material produced by the method for producing a composite material according to any one of claims 1 to 9.

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