WO2017111103A1 - セルロースザンテートナノファイバー - Google Patents
セルロースザンテートナノファイバー Download PDFInfo
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- WO2017111103A1 WO2017111103A1 PCT/JP2016/088522 JP2016088522W WO2017111103A1 WO 2017111103 A1 WO2017111103 A1 WO 2017111103A1 JP 2016088522 W JP2016088522 W JP 2016088522W WO 2017111103 A1 WO2017111103 A1 WO 2017111103A1
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- cellulose
- xanthate
- nanofiber
- nanofibers
- treatment
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/40—Formation of filaments, threads, or the like by applying a shearing force to a dispersion or solution of filament formable polymers, e.g. by stirring
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B9/00—Cellulose xanthate; Viscose
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B16/00—Regeneration of cellulose
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B9/00—Cellulose xanthate; Viscose
- C08B9/02—Sulfidisers; Dissolvers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
- C08L1/08—Cellulose derivatives
- C08L1/22—Cellulose xanthate
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
- D01F2/06—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from viscose
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
- D01F2/06—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from viscose
- D01F2/08—Composition of the spinning solution or the bath
- D01F2/10—Addition to the spinning solution or spinning bath of substances which exert their effect equally well in either
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/14—Polymer mixtures characterised by other features containing polymeric additives characterised by shape
- C08L2205/16—Fibres; Fibrils
Definitions
- the present invention relates to a nanofiber manufactured from a cellulose material and a manufacturing method thereof.
- nanocellulose in which fibers constituting plant-derived cellulose material are subdivided to a fiber diameter of less than about 1 ⁇ m, has attracted attention.
- materials called nanocellulose materials differing depending on the size and aspect ratio have been proposed.
- materials called cellulose nanofibers, cellulose nanofibrils, fibrated cellulose, etc. mainly having a fiber diameter of about 4 to 100 nm and a length of 5 ⁇ m or more, have excellent properties as reinforcing fibers, and therefore are being manufactured and researched. It has been.
- Various names have been proposed for this material, but this material is referred to as cellulose nanofiber in this application.
- modified cellulose products having a size and aspect ratio similar to cellulose nanofibers are collectively referred to as nanofibers.
- Non-Patent Document 1 reports a method of defibration with a high-pressure homogenizer that pushes pulp slurry into a narrow gap and advances defibration by releasing the pressure.
- a mechanical method it is necessary to repeat the treatment several times in order to proceed with the defibration, and the energy required for the defibration treatment has become enormous.
- Patent Document 1 a method for removing lignin by pretreating the raw material with an acid before defibrating treatment to facilitate defibration is proposed in Patent Document 1 below. Since the applied external force can be reduced as compared with a method of applying a high pressure by a simple mechanical method, the resulting cellulose nanofiber is less damaged.
- Non-patent Document 2 a method for introducing a carboxyl group or a carboxymethyl group into cellulose to facilitate defibration is reported.
- pulp is treated in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (TEMPO) and sodium hypochlorite as an oxidizing agent
- TEMPO 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical
- sodium hypochlorite sodium hypochlorite
- cellulose microfibrils A carboxyl group can be efficiently introduced into the 6-position of cellulose constituting the fiber on the surface (Non-patent Document 2).
- a carboxymethyl group can be introduce
- TEMPO-oxidized cellulose introduced with a carboxyl group and carboxymethyl cellulose introduced with a carboxymethyl group are easier to fibrillate than unmodified cellulose. For this reason, compared with the process by the high pressure by a simple mechanical method, the frequency
- Patent Document 1 requires treatment for a long time with an acid or the like for delignification treatment, and the burden on pretreatment is large.
- TEMPO oxidized cellulose or carboxymethyl cellulose can be obtained instead of cellulose nanofibers themselves. These are modified from cellulose nanofibers. Moreover, it is difficult to return these TEMPO oxidized cellulose and carboxymethyl cellulose to cellulose, and cellulose nanofibers without modification could not be obtained from these modified nanofibers. In addition, the cellulose bond is also broken during the modification to introduce a carboxyl group, and the degree of polymerization of the obtained nanofiber equivalent is reduced to about 1/4 or less, and the obtained nanofiber equivalent is required. It was difficult to maintain strength. Furthermore, since this method uses expensive TEMPO, it is difficult to reduce the production cost of the resulting nanofibers.
- the present invention is to obtain a nanofiber having a high aspect ratio by suppressing a decrease in length while suppressing a processing burden at the time of manufacturing in order to obtain a fibrillated material corresponding to a nanofiber from a cellulose material.
- Another object of the present invention is to return the nanofibers to cellulose easily and with high yield so that cellulose nanofibers can be obtained efficiently.
- a cellulose-containing material is treated with an alkali metal hydroxide aqueous solution of 4% by mass or more and 9% by mass or less to produce alkali cellulose, and this alkali cellulose is reacted with carbon disulfide to form cellulose xanthate.
- the cellulose xanthate was defibrated to solve the above problems. This cellulose xanthate is considered to be more easily fibrillated than simple cellulose due to the presence of a xanthate group (—OCSS ⁇ ) introduced into any one of the 2, 3, and 6-position hydroxyl groups of cellulose.
- the nanofiber can be easily formed with a relatively low load. Since the burden of defibrating treatment is small and the cellulose fiber is not cut when the xanthate group is introduced, the cellulose fiber is not easily shortened throughout the process, and it is easy to obtain a long and high aspect ratio nanofiber. And this xanthate group can be rapidly returned to a hydroxyl group with an extremely high efficiency by acid treatment or heat treatment. By returning the xanthate group to the hydroxyl group, the cellulose xanthate nanofiber becomes a cellulose nanofiber.
- This production method is similar to the production method of producing cellophane from pulp via viscose, but has greatly different characteristics.
- pulp which is a material containing cellulose
- an aqueous alkali metal hydroxide solution having a high concentration of about 10% by mass to 30% by mass until the cellulose crystal region contained in the pulp is reached.
- An aqueous alkali metal hydroxide solution is infiltrated to form a cellulose II type alkali cellulose ([C 6 H 7 O 2 (OH) 2 (ONa)] n ) that has lost crystallinity.
- the average polymerization degree is about half from about 800 to about 400, and the fiber length is maintained.
- alkali cellulose which lost crystallinity and carbon disulfide (CS 2 ) are reacted to obtain cellulose xanthate ([C 6 H 7 O 2 (OH) 2 (OCSSNa)] n ).
- a solution obtained by dissolving cellulose xanthate in an aqueous alkali metal hydroxide solution is colloidal viscose. When this viscose is treated with dilute sulfuric acid and returned to cellulose, it is treated to form a film to produce cellophane.
- the greatest difference between the method according to the present invention and the conventional method for producing cellophane using viscose is in the concentration of the alkali metal hydroxide aqueous solution to be subjected to alkali treatment.
- the alkali metal hydroxide solution penetrates into the crystal region of cellulose and cannot maintain crystallinity, and nanofibers having crystallinity cannot be obtained.
- the cellulose-containing material is alkali-treated with a 4% to 9% by weight aqueous alkali metal hydroxide solution, so that the fibrillation treatment can be performed while maintaining the crystallinity to the extent that the physical properties as nanofibers can be maintained. It can be a pretreatment for easy xanthation.
- cellulose xanthate nanofibers can be obtained by an easy fibrillation treatment.
- cellulose xanthate can be easily obtained from the cellulose xanthate nanofiber by returning the cellulose xanthate to unmodified cellulose as necessary.
- This invention is the manufacturing method which obtains nanofiber from a cellulose material, and the nanofiber obtained.
- the cellulose material used as a material in the present invention refers to a material containing cellulose I type ⁇ -cellulose in a crystalline state. Even if it is ⁇ -cellulose, a material that has completely lost its crystalline state and has completely become cellulose type II cannot be suitably used.
- Specific materials include, for example, craft pulp and sulfite pulp processed from wood, biomass-derived materials such as wood flour and rice straw, paper-derived materials such as waste paper, filter paper and paper powder, powdered cellulose, and micro Examples thereof include processed cellulose products having crystallinity such as metric size microcrystalline cellulose. However, it is not limited to these examples.
- cellulose materials do not need to be pure ⁇ -cellulose, and may contain other organic substances such as ⁇ -cellulose, hemicellulose, and lignin, and inorganic substances in a removable range.
- cellulose simply refers to “ ⁇ -cellulose”.
- wood pulp it is preferable to use wood pulp because the length of the original cellulose fibers is easily maintained.
- alkali cellulose can be obtained by performing an alkali treatment in which the cellulose material is treated with an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide.
- an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide.
- sodium hydroxide is preferably used.
- the concentration of the alkali metal hydroxide aqueous solution needs to be 4% by mass or more, and preferably 5% by mass or more. If it is less than 4% by mass, the mercerization of cellulose does not proceed sufficiently, the amount of by-products generated during the subsequent xanthation cannot be ignored, and the yield also decreases. In addition, the effect of facilitating the defibrating process described later is insufficient.
- the concentration of the alkali metal hydroxide aqueous solution is preferably 9% by mass or less. If it exceeds 9% by mass, not only mercerization but also the alkali metal hydroxide solution penetrates into the crystalline region of the cellulose and the cellulose I type crystal structure cannot be maintained, and finally nanofibers are obtained. It becomes difficult to be.
- the time for the alkali treatment is preferably 30 minutes or more, and more preferably 1 hour or more. If it is less than 30 minutes, mercerization does not proceed sufficiently and the final yield may be too low. On the other hand, it is preferably 6 hours or less, and more preferably 5 hours or less. When mercerization is carried out for more than 6 hours, the production amount of alkali cellulose due to the extension of the time does not increase, and the productivity may decrease.
- the temperature of the alkali treatment is preferably around room temperature or a temperature that is heated by heat generation from room temperature.
- the treatment temperature is extremely low, such as under refrigeration conditions, the permeability of the alkaline solution to the cellulose tends to increase, and even if the alkali concentration is in the above range, the alkali hydroxide reaches the crystalline region of the cellulose.
- the metal solution may permeate and may make it difficult to maintain the cellulose I type crystal structure.
- the alkali metal hydroxide solution concentration is particularly preferably in the range of 4 mass% to 7 mass%. Such a tendency is not particularly observed at 10 ° C.
- an alkali metal hydroxide aqueous solution having a concentration of 4% by mass to 9% by mass is a preferable concentration as described above.
- an alkali metal hydroxide aqueous solution having a concentration of 4% by mass to 9% by mass is a preferable concentration as described above.
- the alkali cellulose obtained by the alkali treatment is subjected to solid-liquid separation thereafter to remove as much of the aqueous solution as possible. This is because in the next xanthate treatment, the reaction with less moisture is more likely to proceed.
- a solid-liquid separation method for example, a general dehydration method such as centrifugation or filtration can be used.
- the concentration of the alkali metal hydroxide contained in the alkali cellulose after the solid-liquid separation is preferably about 3% by mass or more and about 8% by mass. If it is too thin or too dark, work efficiency will deteriorate.
- the average xanthate substitution degree per glucose unit in this xanthation treatment is preferably 0.33 or more. That is, it is preferable that an average of 1/3 or more of all glucose units is substituted so as to have a (—OCSS ⁇ Na + ) group. This is because if the xanthate formation is not sufficient and the content of the (—OCSS ⁇ Na + ) group is too small, the effect of promoting the subsequent defibrating treatment cannot be obtained sufficiently.
- the average degree of xanthate substitution is 1, that is, if the average of at least one of the three (—OH) groups in the glucose unit of the original cellulose is a (—OCSS ⁇ Na + ) group, the yield And from the viewpoint of efficiency.
- the xanthate substitution degree is preferably 1.2 or less.
- the xanthate substitution degree is preferably 10 mol% (corresponding to a xanthate substitution degree of 0.33) or more, and 40 mol% (average xanthate substitution degree of 1.2). Or less), preferably 33.3 mol% (corresponding to an average xanthate substitution degree of 1.0) or less.
- the extra cost of supplying carbon disulfide is too high. If the total amount is replaced by carbon disulfide, the degree of sulfidization is about 33 mol% (the above-mentioned average xanthate substitution degree is 1) with about 24% by mass of carbon disulfide. Actually, the entire amount is not replaced, and it is considered that the unreacted portion remains.
- the contact time between carbon disulfide and alkali cellulose is preferably 30 minutes or more, more preferably 1 hour or more. This is because xanthate formation by contact with carbon disulfide proceeds rapidly, but it takes time for carbon disulfide to penetrate into the inside of alkali cellulose. On the other hand, if it is 6 hours, the penetration of the alkali cellulose lump after dehydration is sufficiently advanced, and the reactive xanthate formation is almost completed.
- This xanthation treatment is considered to increase the polarity of cellulose fibers (cellulose xanthate molecules) that retain crystallinity, increase the hydrophilicity, and improve the dispersibility by electrostatic repulsion of the xanthate group.
- the above-mentioned xanthated cellulose xanthate has a cellulose I type crystal structure, which is crystalline, contained in the original cellulosic material by mechanical defibrating treatment with a lighter load than conventional methods. While holding, cellulose xanthate nanofibers having a size and aspect ratio corresponding to the nanofibers can be obtained.
- the cellulose xanthate subjected to the above xanthate treatment can be easily defibrated by the repulsive action of the xanthate group.
- the load and frequency required for the defibrating treatment can be reduced. It is preferable to use water as the liquid used for the washing because the pH of the alkali is reduced and there is almost no risk of damaging the cellulose xanthate fiber itself. In washing, washing with running water or washing with repeated addition of water and dehydration may be used, but it is necessary to have little influence on the fiber length.
- the degree of washing when sodium hydroxide or potassium hydroxide is used as the alkali metal hydroxide, the pH of the slurry used for defibration after washing is preferably 10.5 or less, and more preferably 9.5 or less. preferable. Moreover, when using sodium hydroxide, the density
- xanthated cellulose xanthate it is preferable to disperse the xanthated cellulose xanthate after dispersing it in water.
- a method of defibrating treatment a general method can be used as long as the fiber length is not significantly reduced.
- a method of dispersing in water and defibrating with a rotary homogenizer, a bead mill, an ultrasonic disperser, a high-pressure homogenizer, a disc refiner, or the like can be given.
- the energy required by either method is significantly smaller than the energy required by the conventional method such as Patent Document 1.
- alkali metal ions such as Na + contained in the xanthate group of cellulose xanthate may be partially or entirely ion exchanged with other cations.
- the cation include hydrogen ions, other alkali metal ions such as potassium and lithium, monovalent metal ions such as silver, ammonium ions, aliphatic or aromatic ammonium, and the like. good.
- the salt may be replaced with a quaternary ammonium cation, which is a cation-substituted product, to be hydrophobized and then subjected to a fibrillation treatment in an organic solvent such as ethanol, dimethylformamide, or dimethylacetamide.
- Examples of the quaternary ammonium cation include tetrabutylammonium cation, tetrapropylammonium cation, tetraethylammonium cation, decyltrimethylammonium cation, dodecyltrimethylammonium cation, hexyldimethyloctylammonium cation, benzyltriethylammonium cation, and triethylphenylammonium cation. Can be mentioned.
- salt exchange that once replaces the alkali metal ion of the xanthate group of cellulose xanthate with a quaternary ammonium cation may be performed to form an ammonium salt, followed by defibrating treatment in water.
- the quaternary ammonium cation facilitates ionic dissociation and exhibits the effect of easy progress of defibration, and is effective when treatment in an aqueous system is desired after defibration.
- cellulose xanthate that has been defibrated once in an aqueous solvent such as water or an organic solvent is subjected to salt exchange in which an alkali metal ion is replaced with a quaternary ammonium cation. You may move to.
- the alkali metal ions contained in the defibrated cellulose xanthate or the cations once substituted therefor are ion-exchanged after the defibration and before the regeneration treatment, and then the ion-exchanged cellulose xanthate is obtained.
- the cation M n + to be ion-exchanged here hydrogen ions, alkali metal ions other than the original alkali metal ions such as Li + , Na + , K + , other monovalent metal ions such as Ag + , ammonium ions, etc. , Aliphatic or aromatic ammonium ions, and the like.
- the xanthated cellulose may contain functional groups other than hydroxyl groups.
- Cellulose xanthate nanofibers obtained by the above-described cellulose xanthate defibration treatment can be regenerated to obtain cellulose nanofibers. it can.
- this regeneration treatment the xanthate group (—OCSS ⁇ M n + ) is changed to the (—OH) group, and the cellulose xanthate is regenerated into cellulose.
- n is an integer of 1 to 3.
- An example of the regeneration treatment is a treatment using an acid. With the acid, the reaction for changing the xanthate group or its cation substituent to a hydroxyl group can proceed without causing a decrease in fiber length.
- an acid used here a mineral acid or an organic acid is mentioned, A mineral acid is preferable and hydrochloric acid, a sulfuric acid, nitric acid etc. are mentioned.
- the pH of the acid to be treated is preferably 3 or less.
- the cellulose xanthate nanofiber can be heated from the molecule of the cellulose xanthate nanofiber (including a cation substitution product in which an alkali metal ion is substituted with another cation M n + ).
- Cellulose nanofibers can be obtained by dissociating carbon sulfide and regenerating it into cellulose.
- the degree of regeneration can be adjusted by the heating time and temperature, but the heating temperature is preferably 40 ° C. or higher. The higher the temperature or the heating time, the shorter the regeneration time.
- the cellulose xanthate nanofiber to be heated may be a dry product or a slurry.
- the average sulfidity can be set to 0.1 mol% or less by the above regeneration treatment, after the regeneration treatment, further desulfurization treatment may be performed depending on the application. Further, a bleaching process may be performed together with the desulfurization process.
- the specific desulfurization method is not particularly limited, and general desulfurization methods can be applied in other fields. However, it is necessary that the fiber length of the cellulose nanofiber is not too short. For example, a treatment method using an aqueous sodium sulfide solution can be mentioned.
- the specific bleaching method is not particularly limited, and general bleaching methods can be applied in other fields. However, it is necessary that the fiber length of the cellulose nanofiber is not too short. For example, a treatment method using sodium hypochlorite or hydrogen peroxide water can be mentioned.
- Cellulose nanofibers obtained by regenerating cellulose xanthate nanofibers according to the present invention have sufficient average fiber diameter, a large fiber surface area, and sufficient fibers in which a decrease in the degree of polymerization from cellulose contained in the original cellulose material is suppressed. It has a long length and can be suitably used as a reinforcing fiber. This is because the degree of polymerization is reduced only by the alkali treatment among the above work steps, and the treatment can be performed with almost no decrease in the degree of polymerization in any of the xanthate treatment, the fibrillation treatment, and the regeneration treatment. Moreover, since the density
- the size of the cellulose xanthate nanofibers and cellulose nanofibers obtained by the present invention can be obtained with an average fiber length of 2 ⁇ m or more and 20 ⁇ m or less. This is because the degree of polymerization is unlikely to be lowered by treatments other than mercerization, and the average degree of polymerization tends to be about 300 to 800.
- the average degree of polymerization may become 300 or less by increasing the time of mercerization, but in that case, there are effects such as a decrease in yield and a decrease in aspect ratio.
- the average fiber diameter of individual fibers that are nanofibers is 4 nm or more and 100 nm or less, and has a sufficiently high aspect ratio, and can be suitably used as a reinforcing fiber.
- the average degree of sulfidation calculated from the average degree of sulfidation of the cellulose xanthate nanofibers can be adjusted to 0.1 mol% or more and 33.3 mol% or less depending on the purpose. The range of this value corresponds to 0.003 or more and 1 or less in terms of average xanthate substitution degree. Further, by adjusting the degree of defibration, the main component of the xanthate nanofiber can have an average fiber length of 2 ⁇ m to 100 ⁇ m and an average fiber diameter of 3 nm to 250 nm. In order to obtain a reinforcing effect by increasing the fiber surface area, it is preferable that the average fiber diameter is small.
- the fiber diameter is preferably 2 nm or more. Moreover, it is preferable that an average fiber diameter shall be 250 nm or less from the point which prevents mixing of fiber with insufficient defibration.
- the first characteristic of the nanofiber is that the viscosity of the slurry hardly changes due to temperature change. This is because the nanofibers are only dispersed in the slurry but not dissolved.
- the second property of the nanofiber includes thixotropy that improves fluidity when the slurry is rotated and stirred at a predetermined speed or higher. This is a characteristic that occurs when the fibers of the nanofibers are aligned in one direction when rotated at a certain speed or higher.
- Cellulose xanthate nanofibers and cellulose nanofibers are both nanofibers, but they have different properties and can be used for different applications.
- Cellulose nanofibers are generally said to have high thermal stability, high thermal stability, and hardly deteriorate even at 250 ° C. or higher. It is said that derivatized cellulose nanofibers are poor in thermal stability and deteriorate at about 150 to 200 ° C.
- Examples of derivatized cellulose nanofibers include cellulose xanthate nanofibers, TEMPO oxidized cellulose nanofibers, carboxymethylcellulose nanofibers, phosphorylated cellulose nanofibers, and the like.
- cellulose xanthate nanofibers are regenerated into cellulose nanofibers by heating, cellulose xanthate nanofibers can be used in a high heat environment as long as regeneration is allowed.
- Cellulose xanthate nanofibers can be used for reinforcing materials by addition to resins, rubber compositions, starch, etc., gas barrier materials, filter members, electronic device members, cosmetic members, thickeners, dispersants, and the like.
- Kraft pulp manufactured by Nippon Paper Industries Co., Ltd .: NBKP, ⁇ -cellulose content: 90% by mass, average degree of polymerization of ⁇ -cellulose of 1000) or less, hereinafter referred to as “NBKP”.
- Kraft pulp manufactured by Nippon Paper Industries Co., Ltd .: LBKP, ⁇ -cellulose content: 90% by mass, average degree of polymerization of ⁇ -cellulose 950, hereinafter referred to as “LBKP”.
- NDPT Sulphite pulp
- Powdered cellulose manufactured by Nacalai Tesque Co., Ltd .: powdered cellulose, ⁇ -cellulose content: 90% by mass, average polymerization degree of ⁇ -cellulose of 600
- microcrystalline cellulose manufactured by MERCK: Avicel, ⁇ -cellulose content: 90% by mass, ⁇ -cellulose average degree of polymerization of 300
- microcrystalline cellulose manufactured by MERCK: Avicel, ⁇ -cellulose content: 90% by mass, ⁇ -cellulose average degree of polymerization of 300
- -Softwood unbleached kraft pulp manufactured by Hyogo Pulp Industries: NUKP, ⁇ -cellulose content: 75% by mass, average degree of polymerization of ⁇ -cellulose of 1000) or less, sometimes referred to as “NUKP”.
- NUKP -Softwood unbleached kraft pulp
- LUKP ⁇ -cellulose content: 75 mass%, average degree of polymerization of ⁇ -cellulose 950
- Example 1 ⁇ Alkali treatment> NBKP was weighed so as to be 100 g of pulp solids (solid content including lignin as impurities in addition to ⁇ -cellulose, and their modified products, the same applies hereinafter). This was introduced into a 3 L beaker, and 2500 g of 8.5 mass% NaOH aqueous solution was added, and the mixture was stirred at room temperature for 3 hours for alkali treatment. The alkali-treated pulp was subjected to solid-liquid separation by centrifugation (filter cloth 400 mesh, 3000 rpm for 5 minutes) to obtain a dehydrated product of alkali cellulose. In this alkali cellulose dehydrated product, the NaOH content was about 7.5% by mass, and the pulp solid content was 27.4% by mass.
- the measurement of the NaOH content of the alkali cellulose dehydrate was performed as follows. In a 200 mL conical beaker, about 5 g of dehydrated alkali cellulose was precisely weighed, and 20 mL of a 0.5 mol / L sulfuric acid solution and a few drops of a phenolphthalein solution were added thereto. Thereafter, about 150 mL of boiled distilled water was added, and a stirrer chip was added, followed by stirring until the reddish purple color disappeared completely. This solution was neutralized and titrated with a 0.1 mol / L sodium hydroxide solution to obtain a titer. The NaOH content (concentration) was calculated from the obtained titer and the following formula (1).
- NaOH content (mass%) (0.5 ⁇ 2 ⁇ 20 ⁇ 0.1 ⁇ titrated amount (ml)) ⁇ 40 ⁇ 1000 ⁇ alkaline cellulose sampling amount ⁇ 100 (1)
- the method for measuring the pulp solid content was as follows.
- the alkaline cellulose in the conical beaker whose NaOH content was measured as described above was used as it was, and filtered under reduced pressure using GFP filter paper (GS-25 manufactured by ADVANTEC), which had been previously weighed. Was washed. After washing, the cellulose and filter paper were dried as they were with a dryer at 105 ° C. for 3 hours, and the weight was measured. Pulp solid content was computed from the measured weight and following formula (2).
- Pulp solid content (mass%) (weight after absolutely dry-filter paper weight) ⁇ alkali cellulose sampling amount ⁇ 100 (2)
- ⁇ Zanthate treatment> The alkali cellulose dehydrated product prepared above was weighed to a pulp solid content of 10 g, and introduced into an eggplant type flask. Into the eggplant-shaped flask, 3.5 g of carbon disulfide (35% by mass of pulp solid content) was introduced, and the sulfurization reaction was allowed to proceed at room temperature for about 4.5 hours to perform a xanthate treatment.
- the wet cellulose after the regeneration treatment was filtered using GFP filter paper (GS-25 manufactured by ADVANTEC), which had been weighed in advance, and washed thoroughly with distilled water to remove impurities, alkalis, carbon disulfide, and the like. . Then, it was completely dried to remove water, the mass of cellulose alone was measured, and the cellulose content relative to wet cellulose xanthate was calculated.
- the procedure of the Breede method was performed as follows. About 100 g of cellulose xanthate was precisely weighed into a 100 mL beaker, and 40 mL of saturated ammonium chloride solution (5 ° C.) was added.
- the sample was mixed well while crushing with a glass rod, allowed to stand for about 15 minutes, filtered through GFP filter paper (GS-25 manufactured by ADVANTEC), and thoroughly washed with a saturated ammonium chloride solution.
- the sample was placed in a 500 mL tall beaker together with the GFP filter paper, and 50 mL of 0.5 M sodium hydroxide solution (5 ° C.) was added and stirred. After standing for 15 minutes, it was neutralized with 1.5M acetic acid. (Phenolphthalein indicator) After neutralization, 250 mL of distilled water was added and stirred well, and 10 mL of 1.5 M acetic acid and 10 mL of 0.05 mol / L iodine solution were added using a whole pipette.
- This solution was titrated with 0.05 mol / L sodium thiosulfate solution. (1% starch solution indicator)
- the degree of sulfidization was calculated from the following formula (3) from the titration amount of sodium thiosulfate and the cellulose content of the sample. This degree of sulfidization is the ratio of groups substituted with xanthate groups among the hydroxyl groups in cellulose fibers.
- substitution degree is represented by following Formula (4) with respect to sulfidation degree.
- ⁇ SEM photo> The cellulose xanthate was freeze-dried at the stage where the defibration treatment was completed, and SEM observation was performed. As a result, fibers having a fiber diameter of 4 nm to 100 nm were observed. The photograph at that time is shown in FIGS. The magnification is 15000 times. On the other hand, many fibers having a length of about several tens of ⁇ m were observed. For this reason, it was visually recognized as a xanthate nanofiber that seems to have a high aspect ratio.
- ⁇ Fiber length measurement method The nanofiber slurry diluted to about 0.1% by mass with water was placed in a centrifuge tube and centrifuged at 9000 rpm for 10 minutes. The centrifugal supernatant was diluted to a slurry concentration of about 0.05% by mass and mixed with ethanol at a volume ratio of 1: 1. 20 ⁇ L of the mixed solution was dropped on a slide glass and allowed to dry naturally. After drying, safranin, which is a staining solution, was dropped and allowed to stand for about 1 minute, washed with running water and then naturally dried again, and observed with a microscope. A 1000-fold image obtained by microscopic observation was divided into 100, one nanofiber contained in one division (35 ⁇ m ⁇ 26 ⁇ m) was selected, and the fiber length for a total of 100 was measured.
- ⁇ Fiber diameter measuring method The nanofiber slurry diluted to about 0.1% by mass with water was placed in a centrifuge tube and centrifuged at 9000 rpm for 10 minutes. The centrifugal supernatant was diluted to a slurry concentration of about 0.03% by mass and mixed with tert-butyl alcohol at a volume ratio of 8: 2 (containing 20% tert-butyl alcohol). The mixture was lyophilized and SEM photographs were taken. 100 nanofiber fibers were selected from the 15000-fold image subjected to SEM observation, and the fiber diameter was measured. The values of fiber diameter and fiber length were the average of 100 points measured. The aspect ratio (fiber length / fiber diameter) calculated from the measured fiber diameter and fiber length was 15 to 5000.
- Example 1 both alkalization and xanthation proceeded sufficiently, and nanofibers that were sufficiently defibrated by the defibrating treatment described above were obtained.
- Example 1 ⁇ Confirmation of the transition of the crystal structure of cellulose xanthate> (Examples 2 to 4, Comparative Examples 1 to 3, Reference Example 1)
- the alkalinization treatment performed in Example 1 with 8.5% by mass aqueous sodium hydroxide solution was 7% by mass (Example 2), 8% by mass (Example 3), 9% by mass (Example 4), 10%.
- the IR of the cellulose made was measured. The result is shown in FIG. 3, and an enlarged view of the region around 1100 cm ⁇ 1 is shown in FIG.
- the IR measurement result of the original NBKP is described as Reference Example 1 for comparison.
- cellulose type I In cellulose type I, a peak near 1110 cm ⁇ 1 due to C—OH (near the vertical line of the IR spectrum) and a peak near 1060 cm ⁇ 1 due to C—O—C are observed, which are attributable to OH stretching vibration. The peak around 3300 cm ⁇ 1 is slightly sharp.
- the reference example NBKP has these features.
- the cellulose II type disappeared peak near 1110 cm -1 due to C-OH, the peak around 1060 cm -1 due to C-O-C decreases, the peak attributable to the OH stretching vibration 3600 Broad in the vicinity of ⁇ 3100 cm ⁇ 1 .
- cellulose nanofibers can be sufficiently obtained by defibration treatment of cellulose xanthate from 9% by mass or less from these IR spectra, but if it is 10% by mass or more, it becomes cellulose II type and has problematic properties as cellulose nanofibers. Has been confirmed to appear.
- Example 5 In Example 1, the treatment was performed in the same manner except that the amount of carbon disulfide introduced in the xanthate treatment was reduced to 1.2 g (12% by mass of pulp solid content). Although the average sulfidity decreased to 10.8 mol%, nanofibers could be obtained by defibration.
- Example 6 In Example 1, a planetary ball mill (manufactured by FRITSCH: P-6) was used instead of a homogenizer for defibration, and defibration was performed under conditions of a revolution speed of 500 rpm and 30 minutes. It was confirmed that nanofibers can be obtained without problems even if the defibration method is changed.
- Example 7 In Example 1, the pulp raw material to be used was changed to LBKP, the concentration of the sodium hydroxide aqueous solution was changed to 8% by mass, and the addition amount of carbon disulfide was 2.4 g (vs. pulp solid content of 24% by mass). Were processed according to the same procedure. Although the average sulfidity of cellulose xanthate was reduced to 25.2 mol%, defibration was performed without problems and nanofibers could be obtained.
- Example 8 In Example 1, the pulp raw material used was changed to NDPT, which is sulfite pulp, and the same procedure was followed except that the carbon disulfide addition rate was reduced to 1.2 g (vs. pulp solid content of 12% by mass). Went. Although the average sulfidity decreased to 11.4 mol%, defibration was performed without problems and nanofibers could be obtained.
- NDPT sulfite pulp
- Example 9 In Example 1, the pulp raw material used was changed to powdered cellulose, and the treatment was performed in the same procedure except that the concentration of the sodium hydroxide aqueous solution was changed to 8% by mass. Although the average sulfidity of cellulose xanthate was reduced to 26.1 mol%, defibration was performed without problems and nanofibers could be obtained.
- Example 10 In Example 9, the same procedure was followed except that the pulp raw material used was changed to microcrystalline cellulose. Although the average sulfidity of cellulose xanthate was reduced to 24.7 mol%, defibration was performed without any problem, and nanofibers could be obtained.
- Example 11 In Example 1, the produced cellulose xanthate was weighed into a beaker, and distilled water was added and dispersed. The mixture was filtered using GFP filter paper (GS-25 manufactured by ADVANTEC) and thoroughly washed with distilled water to remove impurities, alkalis, carbon disulfide and the like. All the washed cellulose xanthates were collected, and distilled water was added to form a washed slurry having a cellulose solid content of 0.5 mass%. The NaOH concentration of the slurry after washing was less than the lower limit of detection [0.1 mg / L] and pH 7.8.
- regeneration treatment heat treatment
- the slurry was freeze-dried to obtain a dried nanofiber, and IR was measured.
- IR IR spectrum corresponding to cellulose type I was obtained.
- the heat-treated slurry was sampled and placed in a 500 mL tall beaker. 50 mL of 0.5 M sodium hydroxide solution (5 ° C.) was added thereto and stirred, and when the average sulfidity was measured by the Breede method, it was less than 0.1 mol%, which is the lower limit of measurement. It was confirmed that the group was substituted with a hydroxyl group.
- the IR result is shown in FIG. Moreover, the average degree of polymerization after heat processing was 400, and became a numerical value which is not different from before heat processing.
- FIG. 1 An SEM photograph of the cellulose nanofiber after the regeneration treatment is shown in FIG. Compared to the xanthate nanofibers before regeneration treatment, the fiber diameter and fiber length are almost the same (average fiber diameter 25.8 nm, average fiber length 7.28 ⁇ m), and the nanofiber shape is maintained. confirmed.
- Example 12 The slurry after washing the cellulose xanthate in Example 11 was immersed in dilute hydrochloric acid and subjected to regeneration treatment (acid treatment) with acid over 30 minutes.
- regeneration treatment acid treatment
- the average degree of sulfidation after acid treatment was measured, it was less than 0.1 mol%, which is the lower limit of measurement. Therefore, it was confirmed that the xanthate group was substituted with a hydroxyl group by acid treatment.
- the IR measurement results are shown side by side in FIG. 5 showing the measurement results for the heat treatment. IR spectrum corresponding to cellulose type I is obtained in both regeneration by heating and regeneration by acid, and the crystal structure of cellulose type I is maintained in the cellulose nanofiber after regeneration. confirmed.
- the average fiber diameter was 25.0 nm and the average fiber length was 6.98 ⁇ m.
- Nanofibers were produced by the same procedure as in Example 1 except that the alkali concentration was changed to 4% by mass (Example 13), 5% by mass (Example 14), and 9% by mass (Example 15). The results are shown in Table 1.
- Example 16 ⁇ Cationic species change> (Example 16)
- the alkali metal salt used was changed from sodium hydroxide to potassium hydroxide, the concentration was changed to 9% by mass, and the other procedures were performed in the same manner.
- Cellulose xanthate having an average sulfidity of 28.7 mol% was defibrated to obtain nanofibers. (Nanofiber production rate: 72.7%, nanofiber sulfidity 23.5 mol%)
- Example 17 In Example 1, the produced cellulose xanthate was weighed into a beaker, and a saturated ammonium chloride solution was added and dispersed. The mixture was filtered using GFP filter paper (GS-25 manufactured by ADVANTEC) and washed thoroughly with distilled water to remove impurities, alkali, carbon disulfide, ammonium chloride and the like. All the washed cellulose xanthates were collected and fibrillated by the same procedure as in Example 1 to obtain cellulose xanthate nanofibers. The nanofiber production rate was 72.1%, and the sulfidity of the nanofiber was 26.5 mol%.
- GFP filter paper GS-25 manufactured by ADVANTEC
- Example 18 In Example 1, the produced cellulose xanthate was weighed into a beaker, and distilled water was added and dispersed. The mixture was filtered using GFP filter paper (GS-25 manufactured by ADVANTEC) and thoroughly washed with distilled water to remove impurities, alkalis, carbon disulfide and the like. All the washed cellulose xanthates were collected, a 5 wt% tetrabutylammonium hydride (TBAH) solution was added to form a slurry having a cellulose solid content of 1% by mass, and the mixture was stirred at room temperature for 1 hour. After stirring, the mixture was filtered again using GFP filter paper and thoroughly washed with distilled water.
- GFP filter paper GS-25 manufactured by ADVANTEC
- Example 2 All the washed cellulose xanthates were collected and fibrillated by the same procedure as in Example 1 to obtain cellulose xanthate nanofibers.
- the nanofiber production rate was 73.6%, and the sulfidity of the nanofiber was 24.5 mol%.
- Example 4 In Example 1, it processed by the same procedure except having changed the density
- Cellulose xanthate had an average sulfidity of 35.8 mol%, and xanthate nanofibers were not obtained after defibration treatment, resulting in gel-like pulverized products.
- the produced cellulose xanthate was regenerated and dried, and IR was measured. As a result, it was confirmed that the cellulose xanthate was of type II.
- Comparative Example 5 The treatment was performed in the same procedure except that the concentration of the aqueous sodium hydroxide solution was changed to 10% by mass in Comparative Example 1.
- Cellulose xanthate had an average sulfidity of 32.7 mol%, and a gel-like pulverized product was produced as in Comparative Example 1.
- Example 6 In Example 1, it processed by the same procedure except having changed the density
- Example 7 In Example 1, it processed by the same procedure except having changed the addition amount of carbon disulfide to 6g (6 mass% with respect to pulp solid content). The average degree of sulfidation of cellulose xanthate was 9.4 mol%, and defibration proceeded slightly, and nanofibers were obtained. However, the whole amount was not sufficiently converted into nanofibers, and pulverized products that were not defibrated remained.
- Example 8 In Example 1, it processed by the same procedure except having changed the addition amount of carbon disulfide to 70g (70 mass% with respect to pulp solid content). The average sulfidity of cellulose xanthate was 41.2 mol%, and nanofibers were obtained in the same manner as in Example 1. However, gel pulverized products were also mixed.
- Example 19 ⁇ Supplementary experiment in special temperature environment> (Example 19)
- the sodium hydroxide aqueous solution concentration was set to 7% by mass, and the working temperature was changed to 4 ° C., and the same procedure was performed.
- the nanofiber production rate was slightly decreased, it was confirmed that xanthate nanofibers were obtained.
- Example 19 when the sodium hydroxide aqueous solution concentration was 8% by mass, nanofibers were not generated, and the gel-like pulverized product remained.
- Example 20 ⁇ Comparison of energy required for defibration with conventional methods> (Example 20)
- the produced cellulose xanthate was weighed into a 5 L beaker with a hand, and distilled water was added and dispersed so that the slurry concentration became about 5%. Centrifugal dehydration using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh) and washing thoroughly with addition of distilled water to remove impurities, alkalis, carbon disulfide, etc. . All the washed cellulose xanthates were collected, and distilled water was added to make 10 kg of slurry having a cellulose solid content of 0.5% by mass.
- H-110A manufactured by Kokusan Co., Ltd., filter cloth 400 mesh
- the slurry was defibrated using a high-pressure homogenizer (Sanwa Engineering Co., Ltd. Model H20) by passing it three times at a flow rate of 2.5 L / min and a pressure of 38 to 52 MPa.
- Table 2 shows the nanofiber production rate at the end of each pass.
- the average degree of sulfidation of cellulose xanthate in each pass was 30 mol% to 31.8 mol%, and defibration was performed without any problems at the end of the third time, and nanofibers could be obtained.
- Example 20 when the nanofiber production rate, average fiber length, and average fiber diameter were measured in the nanofiber slurry at each pass point where the defibrating process was repeated, the results shown in Table 2 were obtained. When the nanofiber production rate of pass 1 in Example 20 was low, large fibers that were not defibrated were observed. Details of this example are shown in Table 3.
- Example 21 In Example 20, after all the washed cellulose xanthate was recovered, the concentration of 10 kg of slurry to which distilled water was added was changed to 1% by mass of cellulose solid content. The slurry was defibrated using the same high-pressure homogenizer and passed three times at a flow rate of 2.5 L / min and a pressure of 34 to 42 MPa. Table 3 shows the nanofiber production rate at the end of each pass. The average sulfidity of the cellulose xanthate in each pass was 30.0 mol% to 31.8 mol%, and defibration was performed without any problem, and nanofibers could be obtained.
- Example 22 In Example 20, 10 kg of slurry having a cellulose solid content of 0.5% by mass was measured with an ultrasonic disperser (UIP2000hd manufactured by Hieksher) at a flow rate of 2.5 L / min and an output of 2.34 to 2.48 kW. The fiber was defibrated after 5 passes. Table 3 shows the nanofiber production rate at the end of each pass. The average degree of sulfidation of cellulose xanthate at the end of the fifth round was 28.7 mol%. Therefore, defibration was performed without problems at the end of the fifth time, and nanofibers could be obtained.
- UCP2000hd manufactured by Hieksher ultrasonic disperser
- Example 9 In Example 1, the prepared alkali cellulose was weighed into a 5 L hand-held beaker, and distilled water was added and dispersed so that the slurry concentration was about 5%. Centrifugal dehydration was performed using a centrifugal dehydrator (H-110A manufactured by Kokusan Co., Ltd., 400 mesh filter cloth), and the mixture was sufficiently washed with distilled water to remove alkali. All the alkali cellulose after washing was collected, and distilled water was added to make 10 kg of slurry having a cellulose solid content of 0.5% by mass. This slurry was defibrated using a high-pressure homogenizer (Sanwa Engineering Co., Ltd.
- Example 11a For the cellulose xanthate converted into xanthate in Example 11, the degree of washing was changed to confirm the ease of defibrating treatment.
- distilled water was added to the cellulose xanthate before being washed after being xanthated to prepare 50 mL of a non-washed slurry of 0.5 mass%.
- the supernatant obtained by centrifuging this non-washed slurry at 3000 rpm for 10 minutes was collected with a whole pipette.
- Ten mL of the collected supernatant was neutralized with 0.01 N sulfuric acid using phenolphthalein as an indicator.
- the NaOH concentration was 0.41 g / L.
- the nanofiber production rate was measured as follows. First, distilled water was added to cellulose xanthate to prepare 50 mL of a 0.5% concentration slurry, and centrifuged at 3000 rpm for 10 min. A part of the supernatant after centrifugation was removed, and diluted slurry was prepared by adding water to adjust the NaOH concentration to 3/4 to 1/100 of the original solution (corresponding to Examples 11a to 11g). In addition, as a comparison, cellulose xanthate that was sufficiently filtered and washed (slurry pH: about 7, NaOH concentration: 0 g / L, Example 11) and cellulose xanthate that was sufficiently washed so as to have the same concentration as when not washed.
- Example 11h A slurry (Example 11h) in which NaOH was added to was prepared. About these, the fibrillation process was performed at 15000 rpm and 15 minutes similarly to Example 1, and the nanofiber production
- Example 11h in which NaOH was added to the once washed cellulose xanthate and adjusted to the same original NaOH concentration as Example 11a, had almost the same fibrillation result as Example 11a. For this reason, it has also been confirmed that the production rate does not change depending on the remaining amount of impurities removed by washing.
- Example 23 ⁇ Defibration in the presence of ammonia> (Example 23) The same operation as in Example 11 was performed to thoroughly wash the cellulose xanthate. After the washing, the same amount of ammonia as in Example 11a was added to the cellulose xanthate (pH 12.1) to replace the cation with ammonium ion, and then 15000 rpm, 15 min. The fibrillation treatment was performed at, and the nanofiber production rate was similarly determined. As a result, the nanofiber production rate was 71.7%, and the sulfidity of the nanofibers was 25.5 mol%.
- Example 24 ⁇ About other materials containing ⁇ -cellulose> (Example 24)
- the pulp material used was changed to NUKP (Needle Unbleached kraft pulp).
- NUKP Needle Unbleached kraft pulp
- Example 25 In Example 1, the same procedure was followed except that the pulp raw material used was changed to LUKP (Laubholz Unbleached kraft pulp). Although the average sulfidity of cellulose xanthate was reduced to 25.8 mol%, defibration was performed without any problem, and nanofibers could be obtained with a high yield. Nanofiber production rate: 83.4%.
- Example 20 a slurry having a concentration of 0.5% by mass (Example 20) and a slurry having a concentration of 1.0% by mass (Example 21)
- Example 20a was measured at temperatures of 20 ° C., 30 ° C., and 40 ° C.
- Example 21 was measured only at a temperature of 20 ° C.
- a comparison object of the behavior of the nanofiber about a 0.5 mass% slurry (Reference Example 3) of TEMPO oxidized cellulose nanofiber (produced by the method described in Non-Patent Document 2) which is a conventionally known nanofiber
- the viscosity was measured. The results are shown in Tables 6-8.
- Example 26 ⁇ Defibration treatment under organic solvent>
- the cellulose xanthate after washing in Example 18 was collected, and ethanol was added to make a slurry having a cellulose solid content of 0.5% by mass.
- the slurry was fibrillated with a homogenizer (manufactured by Nippon Seiki Seisakusho: AM-7) at 17000 rpm for 30 minutes to obtain cellulose xanthate nanofibers.
- the nanofiber production rate was 80.6%. According to this example, it was confirmed that the fibrillation treatment can be performed even in ethanol which is an organic solvent.
- Example 27 ⁇ Defibration treatment with other components mixed system> (Example 27)
- the produced cellulose xanthate was weighed into a beaker so that the solid content of cellulose xanthate was 1.2 g, and distilled water was added and dispersed.
- the mixture was filtered using GFP filter paper (GS-25 manufactured by ADVANTEC) and thoroughly washed with distilled water to remove impurities, alkalis, carbon disulfide and the like. All the cellulose xanthates after washing were collected. (Amount recovered 18 g, solid content 6.65%).
- the slurry was dried at 70 ° C. for 2 days, and then dried under reduced pressure to prepare a natural rubber master batch.
- X-ray CT was measured for the obtained natural rubber masterbatch, a clear fiber image and agglomerates were hardly observed.
- This CT image is shown in FIG.
- the fiber was defibrated to a size smaller than the resolution of CT and dispersed in natural rubber latex.
- fibers having a fiber diameter of 200 nm or less were observed. This example confirmed that defibration treatment in natural rubber latex was possible.
- the measurement conditions for X-ray CT are as follows.
- ⁇ Device SMX-160CT-SV3S manufactured by Shimadzu Corporation ⁇ Spatial resolution: 1.4 ⁇ m ⁇
- Example 27 (Comparative Example 10) In Example 27, the same evaluation was performed on a master batch prepared by adding cellulose xanthate to natural rubber latex and not performing the defibrating treatment. As a result, X-ray CT (shown in FIG. 8), SEM image. Then, cellulose xanthate fibers were observed.
- each nanofiber slurry used for the test was freeze-dried.
- Each procedure is as follows.
- Cellulose xanthate nanofiber The cellulose xanthate nanofiber slurry obtained in Example 11 was freeze-dried.
- TEMPO-oxidized cellulose nanofiber TEMPO-oxidized cellulose was prepared by the method described in Non-Patent Document 2, defibrated and then freeze-dried (Reference Example 3).
- Non-inventive cellulose nanofiber BinFi-s WMa10002 manufactured by Sugino Machine was freeze-dried (Reference Example 4).
- Cellulose xanthate nanofiber heat regenerated product The heat regenerated product obtained in Example 11 was desulfurized with a sodium sulfide solution, bleached with a sodium hypochlorite solution, washed with water and freeze-dried (Example) 11i).
- Cellulose xanthate nanofiber acid regenerated product The acid regenerated product obtained in Example 12 was desulfurized with a sodium sulfide solution, bleached with a sodium hypochlorite solution, washed with water and freeze-dried (Example) 12a).
- the lyophilized product of each nanofiber was measured by raising the temperature from room temperature to 400 ° C. at a rate of 10 ° C./min using TG-DTA (TG8120 manufactured by Rigaku).
- TG-DTA TG8120 manufactured by Rigaku.
- the results are shown in Table 9.
- Example 28 ⁇ Confirmation of paper strength enhancement effect by mixing with starch paste> (Examples 28 and 29) Using the cellulose xanthate produced in Example 1, the same washing and defibrating treatment as in Example 11 were performed to obtain a 0.5% by weight cellulose xanthate slurry.
- starch slurry was prepared by adding water to oxidized starch (Dynakote 68NB manufactured by GSL) at 25% by weight. This starch slurry was heated in a boiling bath to prepare a starch paste solution, and cooled in a water bath.
- the cellulose xanthate slurry is added so that the cellulose xanthate becomes 1% by weight (Example 28) or 2% by weight (Example 29) with respect to the starch solid content in the starch paste solution, and the total concentration Water was added so as to be 15% by weight.
- the slurry to which water was added was stirred and mixed with a homogenizer (8000 rpm, 5 min.) To prepare a coating solution. This coating solution was coated on both sides using a bar coater (No.
- Example 28 the coated paper coated with the starch paste without adding the cellulose xanthate slurry as the coating liquid was evaluated in the same manner (Comparative Example 11). Moreover, it evaluated similarly about the core for corrugated boards which does not apply a coating liquid (comparative example 12). The results are also shown in Table 10.
- the compressive strength (N) is measured according to the method of JIS P 8126 (corresponding to ISO 12192), and the obtained compressive strength is divided by the basis weight (g / m 2 ) to obtain the specific compressive strength (N ⁇ m 2 / g) was calculated.
- Example 28 the tensile strength was improved as compared with Comparative Example 11 in which the coating amount was the same. Therefore, it was found that the tensile strength of the coated paper is improved by adding cellulose xanthate nanofibers to the starch paste. Moreover, Example 29 which increased the ratio of the cellulose xanthate nanofiber further improved the tensile strength than Example 28. For this reason, it was shown that the tensile strength can be further improved according to the amount of cellulose xanthate nanofibers.
- Example 30 ⁇ Strengthening cellulose film strength by mixing with viscose> (Example 30) Using the cellulose xanthate prepared in Example 1, the same operation as in Example 11 was performed to obtain a 0.5% by weight cellulose xanthate slurry. This cellulose xanthate slurry was added to viscose (manufactured by Rengo Co., Ltd .: cellulose concentration 9.5%). The addition amount was adjusted so that the cellulose xanthate was 5% by weight with respect to the cellulose solid content in the viscose.
- This cellulose xanthate mixed viscose was stirred and mixed (8000 rpm, 5 min.) With a homogenizer, and then centrifuged (3000 rpm, 3 min.) For defoaming treatment.
- the cellulose xanthate mixed viscose after the defoaming treatment was added to a thickness of 10 mil.
- an applicator. (254 ⁇ m) was cast on a glass plate, solidified and regenerated (coagulation bath: 150 g / L sulfuric acid, 180 g / L sodium sulfate, about 30 ° C.), and then washed with water.
- Example 31 A film was produced in the same procedure as in Example 30, except that the cellulose xanthate of Example 1 was changed to the cellulose xanthate of Example 7, and evaluation was performed in the same manner.
- Example 30 In Example 30, a viscose to which cellulose xanthate slurry was not added was also evaluated by adding water to adjust the cellulose concentration to produce a film.
- Example 32a to 32d Using the cellulose xanthate prepared in Example 1, the same operation as in Example 11 was performed to obtain a 0.5% by weight cellulose xanthate slurry. Distilled water was added to the slurry, followed by centrifugation (10000 rpm, 20 minutes) to settle undefibrated material, and the supernatant was recovered as a nanofiber slurry (concentration 0.13%).
- starch slurry was prepared by adding water to oxidized starch (Dynakote 68NB manufactured by GSL) at 25% by weight.
- the cellulose xanthate slurry was added so that the cellulose xanthate was 1% by weight to 5% by weight with respect to the starch solid content in the starch slurry, and water was added so that the total concentration was 15% by weight. .
- the slurry was stirred and mixed (8000 rpm, 5 min.) With a homogenizer, and 100 mL was measured in a 100 mL measuring cylinder.
- the graduated cylinder was left standing to measure how much the starch powder settled from 100 mL every hour.
- the results are shown in Table 12. Moreover, it measured similarly about the starch slurry which does not add a cellulose xanthate as the comparative example 14.
- Example 33 ⁇ Confirmation of natural rubber sheet strength enhancement effect by mixing with natural rubber latex> (Example 33) -Preparation of Master Batch Using the cellulose xanthate prepared in Example 1, the same operation as in Example 20 was performed to obtain a 0.5 wt% cellulose xanthate slurry. This slurry is mixed with natural rubber latex (HA NR LATEX solid content 60%, ammonia 0.7%, manufactured by Regex Corp.) and 14% ammonia water (cellulose xanthate slurry addition amount is 100 parts by weight of natural rubber solid content) The mixture was stirred with a homogenizer (8000 rpm, 5 min.). After stirring and mixing, the slurry was dried at 70 ° C. for 2 days and then dried under reduced pressure to prepare a natural rubber master batch.
- natural rubber latex HA NR LATEX solid content 60%, ammonia 0.7%, manufactured by Regex Corp.
- 14% ammonia water cellulose xanthate slurry addition amount is 100 parts by
- the test piece is subjected to a tensile test (grip width: 50 mm, speed: 500 mm / min. Compliant with JIS K6251) using a tensile tester (Shimadzu Precision Universal Tester AG-1000D) to determine the stress at break and strain. Asked.
- the strain and stress at the breaking point were larger than those in Comparative Examples 15 and 16 below, and the strength was improved while maintaining the elongation, and the rubber characteristics were not impaired.
- the cellulose xanthate nanofiber containing sulfur suggested the interaction with rubber.
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Abstract
Description
・クラフトパルプ(日本製紙(株)製:NBKP、α-セルロース含有率:90質量%、α-セルロースの平均重合度1000)以下、「NBKP」と表記する。
・クラフトパルプ(日本製紙(株)製:LBKP、α-セルロース含有率:90質量%、α-セルロースの平均重合度950)以下、「LBKP」と表記する。
・サルファイトパルプ(日本製紙(株)製:NDPT、α-セルロース含有率:90質量%、α-セルロースの平均重合度830)以下、「NDPT」と表記する。
・粉末セルロース(ナカライテスク(株)製:粉末セルロース、α-セルロース含有率:90質量%、α-セルロースの平均重合度600)以下、「粉末セルロース」と表記する。
・微結晶セルロース(MERCK社製:アビセル、α-セルロース含有率:90質量%、α-セルロースの平均重合度300)以下、「微結晶セルロース」と表記する。
・針葉樹未晒しクラフトパルプ(兵庫パルプ工業製:NUKP、α-セルロース含有率:75質量%、α-セルロースの平均重合度1000)以下、「NUKP」と表記することがある。
・広葉樹未晒しクラフトパルプ(兵庫パルプ工業製:LUKP、α-セルロース含有率:75質量%、α-セルロースの平均重合度950)以下、「LUKP」と表記することがある。
<アルカリ処理>
NBKPをパルプ固形分(α-セルロースに加えて不純物であるリグニンなどを含む固形分、及びそれらの変性物を指す。以下同じ。)100gとなるように秤量した。これを3Lのビーカーに導入し、8.5質量%NaOH水溶液 2500gを入れ、室温にて3時間撹拌してアルカリ処理を行った。このアルカリ処理後のパルプを遠心分離(ろ布400メッシュ、3000rpmで5分間)により固液分離してアルカリセルロースの脱水物を得た。このアルカリセルロースの脱水物におけるNaOH含有率は約7.5質量%、パルプ固形分は27.4質量%であった。
上記で作製したアルカリセルロースの脱水物をパルプ固形分10gとなるように秤量し、ナス型フラスコに導入した。このナス型フラスコ内へ二硫化炭素を3.5g(対パルプ固形分35質量%分)導入し、室温で約4.5時間硫化反応を進行させてザンテート化処理を行った。
上記ザンテート化処理で作製したウェットなセルロースザンテートを2g精秤し、蒸留水50mLを添加してよく分散させ、2M塩酸 4mLを添加して、ザンテート基を水酸基に戻す再生処理を行った。再生処理後のウェットなセルロースをあらかじめ重量を測定したGFPろ紙(ADVANTEC社製GS-25)を使用してろ過し、蒸留水で十分に洗浄して、不純物、アルカリ、二硫化炭素等を除去した。その上で絶乾して水分を除去して、セルロースのみの質量を測定し、ウェットなセルロースザンテートに対するセルロース含有率を算出した。
また、セルロースザンテートについて、平均硫化度はBredee法により測定したところ、29.5mol%であった。なお、この硫化度はセルロースが有する2位、3位及び6位の全(-OH)基に対する値である。Bredee法の手順は次のように行った。100mLビーカーにセルロースザンテートを約1.5g精秤し、飽和塩化アンモニウム溶液(5℃)を40mL添加した。ガラス棒でサンプルを潰しながらよく混合し、約15分間放置後、GFPろ紙(ADVANTEC社製GS-25)でろ過して、飽和塩化アンモニウム溶液で十分に洗浄した。サンプルをGFPろ紙ごと500mLのトールビーカーに入れ、0.5M水酸化ナトリウム溶液(5℃)を50mL添加して撹拌した。15分間放置後、1.5M酢酸で中和した。(フェノールフタレイン指示薬)中和後蒸留水を250mL添加してよく撹拌し、1.5M酢酸 10mL、0.05mol/Lヨウ素溶液10mLをホールピペットを使用して添加した。この溶液を0.05mol/Lチオ硫酸ナトリウム溶液で滴定した。(1%澱粉溶液指示薬)チオ硫酸ナトリウムの滴定量、サンプルのセルロース含有量より次式(3)から硫化度を算出した。この硫化度は、セルロース繊維における水酸基のうち、ザンテート基に置換されている基の比率である。なお、置換度は硫化度に対して次式(4)で表される。
置換度=硫化度(mol%)/{(1/3)×100(mol%)}=硫化度/33.3……(4)
上記のセルロースザンテート中のセルロース含有率測定時に得られたセルロースについてIR測定を行った結果、セルロースI型に対応するピーク形状が観測された。
上記のザンテート化処理で作製したセルロースザンテートをセルロース固形分で0.25g秤量し、蒸留水50mLを添加して攪拌し、セルロース固形分0.5質量%のスラリーとした。このスラリーを、ホモジナイザー((株)日本精機製作所製:AM-7)を用いて17000rpmにて30分間かけて解繊処理してセルロースザンテートのナノファイバーを得た。
この解繊処理が終わった段階でセルロースザンテートを凍結乾燥させ、SEM観察を行ったところ、繊維径4nmから100nmの繊維が観察された。その際の写真を図1及び2に示す。倍率は15000倍である。一方、長さでは数十μm前後の繊維が多く観測された。このため、高アスペクト比と思われるザンテートナノファイバーであると視認された。
上記で解繊処理を行ったセルロースザンテートナノファイバーのスラリー(セルロース固形分0.5質量%)に蒸留水を添加してスラリー濃度を0.1質量%に調整した。このスラリーを遠心分離(10000rpm、20分間)して未解繊物を沈降させた。上清はナノファイバースラリーとして分離して三角フラスコに移し、沈降した未解繊物に蒸留水を添加して再度遠心分離を行い、未解繊物を洗浄した。未解繊物をるつぼに移して絶乾し、未解繊物の重量を測定した。未解繊物の重量と解繊処理したセルロースザンテート中のセルロース含有量より次式(5)から生成したセルロースザンテートナノファイバーの生成率を求めた。
水で約0.1質量%に希釈したナノファイバースラリーを、遠沈管に入れ、9000rpmにて10分間かけて遠心分離を行った。遠心上清をスラリー濃度約0.05質量%に希釈した上で、エタノールと体積比1:1で混合した。混合液をスライドガラス上に20μL滴下して自然乾燥させた。乾燥後、染色液であるサフラニンを滴下して約一分間静置し、流水で洗浄後に再度自然乾燥させ、顕微鏡観察を行った。顕微鏡観察を行った1000倍の画像を100分割し、1分割分(35μm×26μm)の中に含まれるナノファイバー一本選択して合計100本分の繊維長を測定した。
水で約0.1質量%に希釈したナノファイバースラリーを、遠沈管に入れ、9000rpmにて10分間かけて遠心分離を行った。遠心上清をスラリー濃度約0.03質量%に希釈した上で、tert-ブチルアルコールと体積比8:2(tert-ブチルアルコール20%含有)で混合した。混合液を凍結乾燥させ、SEM写真を撮影した。SEM観察を行った15000倍の画像からナノファイバー繊維100本選択し、繊維径を測定した。
繊維径、繊維長の値は測定した100点の平均とした。測定した繊維径、繊維長より算出したアスペクト比(繊維長/繊維径)は15~5000となった。
(実施例2~4、比較例1~3、参考例1)
実施例1において8.5質量%の水酸化ナトリウム水溶液で行ったアルカリ化処理を、7質量%(実施例2)、8質量%(実施例3)、9質量%(実施例4)、10質量%(比較例1)、11質量%(比較例2)、12質量%(比較例3)に替えた以外は同様の手順によって、それぞれで得られた解繊処理前のセルロースザンテートを再生させたセルロースのIRを測定した。その結果を図3に、1100cm-1前後の領域の拡大図を図4に示す。また、合わせて比較のために元のNBKPのIR測定結果を参考例1として記載する。
実施例1において、ザンテート化処理において導入する二硫化炭素の量を1.2g(対パルプ固形分12質量%分)に減少させた以外は同様の手順により処理を行った。平均硫化度は10.8mol%に減少したが、解繊してナノファイバーを得ることができた。
実施例1において、解繊する際にホモジナイザーの代わりに遊星式ボールミル(FRITSCH社製:P-6)を用い、公転回転数500rpm、30分間の条件で解繊を行った。解繊方法を変えても、問題なくナノファイバーを得ることができることが確かめられた。
実施例1において、用いるパルプ原料をLBKPに変え、水酸化ナトリウム水溶液の濃度を8質量%に変え、二硫化炭素の添加量を2.4g(対パルプ固形分24質量%分)として、それ以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は25.2mol%に減少したが、解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例1において、用いるパルプ原料をサルファイトパルプであるNDPTに変更し、二硫化炭素の添加率を1.2g(対パルプ固形分12質量%分)に減少させた以外は同様の手順により処理を行った。平均硫化度は11.4mol%に減少したが、解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例1において、用いるパルプ原料を粉末セルロースに変更し、水酸化ナトリウム水溶液の濃度を8質量%に変えた以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は26.1mol%に減少したが、解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例9において、用いるパルプ原料を微結晶セルロースに変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は24.7mol%に減少したが、解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例1において、作製したセルロースザンテートをビーカーに秤量し、蒸留水を添加して分散させた。GFPろ紙(ADVANTEC社製GS-25)を使用してろ過し、蒸留水で十分に洗浄して、不純物、アルカリ、二硫化炭素等を除去した。洗浄後のセルロースザンテートをすべて回収し、蒸留水を添加してセルロース固形分0.5質量%の洗浄後スラリーとした。この洗浄後スラリーのNaOH濃度は検出下限[0.1mg/L]未満であり、pH7.8であった。この洗浄後スラリーを、ホモジナイザー(日本精機製作所製:AM-7)を用いて17000rpmにて30分間かけて解繊処理してセルロースザンテートのナノファイバーを得た。以下の測定で実施例11のセルロースザンテートナノファイバーを用いる場合はこの成果物を基本とする。
実施例11におけるセルロースザンテートを洗浄した後のスラリーを、希塩酸中に浸して30分間かけて酸による再生処理(酸処理)を行った。酸処理後の平均硫化度を測定したところ、測定下限である0.1mol%未満であったので、酸処理によりザンテート基が水酸基に置換されていることが確認された。また、同様にIRを測定した結果を、加熱処理についての測定結果を示した図5に並べて示す。加熱による再生と酸による再生とのどちらであっても、セルロースI型に対応するIRスペクトルが得られており、再生後のセルロースナノファイバーにおいてもセルロースI型の結晶構造を維持していることが確認された。平均繊維径25.0nm、平均繊維長6.98μmであった。
アルカリ濃度を4質量%(実施例13)、5質量%(実施例14)、9質量%(実施例15)に変更した以外は実施例1と同様の手順によりナノファイバーを作製した。その結果を表1に示す。
(実施例16)
実施例1において、用いるアルカリ金属塩を水酸化ナトリウムから水酸化カリウムに変え、濃度を9質量%に変え、それ以外は同様の手順により処理を行った。平均硫化度は28.7mol%のセルロースザンテートを解繊してナノファイバーを得た。(ナノファイバー生成率:72.7%、ナノファイバー硫化度23.5mol%)
実施例1において、作製したセルロースザンテートをビーカーに秤量し、飽和塩化アンモニウム溶液を添加して分散させた。GFPろ紙(ADVANTEC社製GS-25)を使用してろ過し、蒸留水で十分に洗浄して、不純物、アルカリ、二硫化炭素、塩化アンモニウム等を除去した。洗浄後のセルロースザンテートをすべて回収し、実施例1と同様の手順により解繊処理してセルロースザンテートのナノファイバーを得た。ナノファイバー生成率は72.1%で、ナノファイバーの硫化度は26.5mol%あった。
実施例1において、作製したセルロースザンテートをビーカーに秤量し、蒸留水を添加して分散させた。GFPろ紙(ADVANTEC社製GS-25)を使用してろ過し、蒸留水で十分に洗浄して、不純物、アルカリ、二硫化炭素等を除去した。洗浄後のセルロースザンテートをすべて回収し、5wt%のテトラブチルアンモニウムヒドリド(TBAH)溶液を添加してセルロース固形分1質量%のスラリーとし、室温にて1時間撹拌した。撹拌後、再度GFPろ紙を使用してろ過し、蒸留水で十分に洗浄した。洗浄後のセルロースザンテートをすべて回収し、実施例1と同様の手順により解繊処理してセルロースザンテートのナノファイバーを得た。ナノファイバー生成率は73.6%で、ナノファイバーの硫化度は24.5mol%あった。
実施例1において、水酸化ナトリウム水溶液の濃度を11質量%に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は35.8mol%であり、解繊処理後にザンテートナノファイバーが得られずにゲル状の粉砕物が生じてしまった。作製したセルロースザンテートを再生処理して乾燥後、IRを測定した結果、セルロースII型となっていることが確認された。
比較例1に置いて、水酸化ナトリウム水溶液の濃度を10質量%に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は32.7mol%で、比較例1と同様にゲル状粉砕物が生じてしまった。
実施例1において、水酸化ナトリウム水溶液の濃度を3質量%に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は9.7mol%であり、解繊処理の際にナノファイバーの形状に解繊されず、パルプの状態を残した粉砕物のままとなってしまった。
実施例1において、二硫化炭素の添加量を6g(対パルプ固形分6質量%)に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は9.4mol%であり、解繊はわずかに進みナノファイバーが得られたものの、全量が十分にナノファイバー化されず、解繊されない粉砕物が残ってしまった。
実施例1において、二硫化炭素の添加量を70g(対パルプ固形分70質量%)に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は41.2mol%であり、実施例1と同様にナノファイバーが得られたが、ゲル状粉砕物も混在している結果となった。
(実施例19)
実施例1において、水酸化ナトリウム水溶液濃度を7質量%とし、作業温度を4℃に変更して同様の手順を行った。ナノファイバー生成率がやや低下したものの、ザンテートナノファイバーが得られていることが確認された。
実施例19において、水酸化ナトリウム水溶液濃度を8質量%としたところ、ナノファイバーが生成されず、ゲル状粉砕物のままとなってしまった。
(実施例20)
実施例1において、作製したセルロースザンテートを5L手付きビーカーに秤量し、スラリー濃度約5%となる様に蒸留水を添加して分散させた。遠心脱水機((株)コクサン社製H-110A、ろ布400メッシュ)を使用して遠心脱水し、蒸留水を添加しながら十分に洗浄して、不純物、アルカリ、二硫化炭素等を除去した。洗浄後のセルロースザンテートをすべて回収し、蒸留水を添加してセルロース固形分0.5質量%のスラリー10kgとした。このスラリーを、高圧ホモジナイザー(三和エンジニアリング(株) H20型)を用いて、流速2.5L/分、圧力38~52MPaで計3回パスさせて解繊処理した。各パス終了時点におけるナノファイバーの生成率を表2に示す。各パスのセルロースザンテートの平均硫化度は30mol%~31.8mol%で、3回目終了時点で解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例20において、洗浄後のセルロースザンテートをすべて回収した後、蒸留水を添加するスラリー10kgの濃度をセルロース固形分1質量%に変更した。このスラリーを、同じ高圧ホモジナイザーを用いて、流速2.5L/分、圧力34~42MPaで計3回パスさせて解繊処理した。各パス終了時点におけるナノファイバーの生成率を表3に示す。各パスのセルロースザンテートの平均硫化度は30.0mol%~31.8mol%で、解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例20において、セルロース固形分0.5質量%のスラリー10kgを、超音波分散機(hieksher社製 UIP2000hd)を用いて、流速2.5L/分、2.34~2.48kWの出力で計5回パスさせて解繊処理した。各パス終了時点におけるナノファイバーの生成率を表3に示す。5回目終了時点でのセルロースザンテートの平均硫化度は28.7mol%であった。したがって、5回目終了時点で解繊は問題なく行われており、ナノファイバーを得ることができた。
実施例1において、作製したアルカリセルロースを5L手付きビーカーに秤量し、スラリー濃度約5%となる様に蒸留水を添加して分散させた。遠心脱水機((株)コクサン社製H-110A、ろ布400メッシュ)を使用して遠心脱水し、蒸留水を添加しながら十分に洗浄して、アルカリを除去した。洗浄後のアルカリセルロースをすべて回収し、蒸留水を添加してセルロース固形分0.5質量%のスラリー10kgとした。このスラリーを、高圧ホモジナイザー(三和エンジニアリング(株) H20型)を用いて、流速2.5L/分、圧力38~52MPaで計3回パスさせて解繊処理したが、ナノファイバーの形状に解繊されず、パルプの状態を残した粉砕物のままとなってしまった。それぞれの解繊処理後のナノファイバー生成率を表4に示す。ザンテート化しない場合には、実施例17及び18と同じ圧力で解繊しようとしても、ほとんど解繊しないことが確認された。
(実施例11a~g)
実施例11でザンテート化したセルロースザンテートについて、洗浄の度合いを変更して解繊処理のし易さを確認した。まず、ザンテート化した後の洗浄前におけるセルロースザンテートに蒸留水を添加して、0.5質量%の非洗浄スラリー50mLを調製した。この非洗浄スラリーを3000rpm、10minで遠心分離した上清をホールピペットで採取した。この採取した上清10mLを、フェノールフタレインを指示薬として0.01N硫酸により中和滴定を行った。3回中和滴定を実施した平均を求めたところ、NaOH濃度は0.41g/Lであった。また、上清のpHをpH試験器で測定したところ11.2であった。
(実施例23)
実施例11と同様の操作を行い、セルロースザンテートを十分に洗浄した。洗浄後のセルロースザンテートに上記実施例11aと同モル量のアンモニアを添加することで(pH12.1)陽イオンをアンモニウムイオンに置換した後に、15000rpm、15min.にて解繊処理を行い、同様にナノファイバー生成率を求めた。その結果、ナノファイバー生成率は71.7%、ナノファイバーの硫化度は25.5mol%であった。
(実施例24)
実施例1において、用いるパルプ原料をNUKP(Needle Unbleached kraft pulp:針葉樹未晒しクラフトパルプ)に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は24.8mol%に減少したが、解繊は問題なく行われており、高い収率でナノファイバーを得ることができた。ナノファイバー生成率:81.4%であった。
実施例1において、用いるパルプ原料をLUKP(Laubholz Unbleached kraft pulp:広葉樹未晒しクラフトパルプ)に変更した以外は同様の手順により処理を行った。セルロースザンテートの平均硫化度は25.8mol%に減少したが、解繊は問題なく行われており、高い収率でナノファイバーを得ることができた。ナノファイバー生成率:83.4%であった。
(実施例20、21、参考例3)
ナノファイバー特有の性質である、粘度の非温度依存と、チクソ性とが発揮されているかを確認する。粘度の測定にあたっては、(株)トキメック製E形粘度計DVH-E(使用コーン:角度3°半径1.2cm)を使用して、20℃、30℃、40℃で測定回転数を1rpmから50rpmまで変更して粘度を測定した。実施例20、21において得られたセルロースザンテートナノファイバーを用いて、濃度0.5質量%としたスラリー(実施例20)と、濃度1.0質量%としたスラリー(実施例21)とについて粘度の測定を行った。実施例20aについては温度20℃、30℃、40℃について測定し、実施例21については温度20℃での測定のみ行った。また、ナノファイバーの挙動の比較対象として、従来知られたナノファイバーであるTEMPO酸化セルロースナノファイバー(非特許文献2記載の方法にて作製)の濃度0.5質量%スラリー(参考例3)についても、併せて粘度の測定を行った。その結果を表6~8に示す。
(実施例26)
実施例18における洗浄後のセルロースザンテートを回収し、エタノールを添加してセルロース固形分0.5質量%のスラリーとした。このスラリーを、ホモジナイザー(日本精機製作所製:AM-7)を用いて17000rpmにて30分間かけて解繊処理してセルロースザンテートのナノファイバーを得た。ナノファイバー生成率は80.6%であった。この実施例により、有機溶媒であるエタノール中でも解繊処理ができることが確かめられた。
(実施例27)
実施例1において、作製したセルロースザンテートをセルロースザンテート固形分が1.2gとなる様にビーカーに秤量し、蒸留水を添加して分散させた。GFPろ紙(ADVANTEC社製GS-25)を使用してろ過し、蒸留水で十分に洗浄して、不純物、アルカリ、二硫化炭素等を除去した。洗浄後のセルロースザンテートをすべて回収した。(回収量18g、固形分6.65%)。これと天然ゴムラテックス((株)レヂテックス社製 HA NR LATEX 固形分60%、アンモニア0.7%)40g、14%アンモニア水2gを混合し、ホモジナイザーにて解繊処理した。解繊処理後スラリーは解繊処理前と比較して増粘およびチクソ性がみられた。なお、粘度測定には、(株)トキメック製E形粘度計DVH-E(使用コーン:角度3°半径1.2cm)を使用して、20℃で測定回転数を1rpmから50rpmまで変更して粘度を測定した。解繊処理後スラリーを70℃にて2日間乾燥し、次いで減圧乾燥を行い、天然ゴムマスターバッチを作製した。得られた天然ゴムマスターバッチについてX線CTを測定したところ、明確な繊維像や凝集塊はほとんど観察されなかった。このCT画像を図7に示す。これにより、CTの分解能未満の大きさにまで解繊されており、天然ゴムラテックス中で分散していることが確かめられた。またSEM観察を行った結果、繊維径200nm以下のファイバーが観察された。この実施例により、天然ゴムラテックス中での解繊処理ができることが確かめられた。
・装置 : 島津社製 SMX-160CT-SV3S
・空間分解能 : 1.4μm
・管電圧 : 90kV、管電流 : 70μm
・SID: 400mm、SOD : 5mm
・ビュー数 1200(ハーフスキャン)
実施例27において、セルロースザンテートを天然ゴムラテックスに添加して解繊処理を行わないで作製したマスターバッチについても同様に評価を行った結果、X線CT(図8に示す。)、SEM画像ではセルロースザンテートの繊維が観察された。
<熱分解温度測定方法>
まず、試験に用いる各ナノファイバースラリーを凍結乾燥した。それぞれの手順は次の通りである。
・セルロースザンテートナノファイバー:実施例11で得られたセルロースザンテートナノファイバースラリーを凍結乾燥した。
・TEMPO酸化セルロースナノファイバー:非特許文献2に記載の方法でTEMPO酸化セルロースを作製し、解繊処理を行った後に凍結乾燥した(参考例3)。
・非本発明セルロースナノファイバー:スギノマシン製BinFi-s WMa10002を凍結乾燥した(参考例4)。
・セルロースザンテートナノファイバー加熱再生物:実施例11で得られた加熱再生処理物を、硫化ナトリウム溶液で脱硫処理、次亜塩素酸ナトリウム溶液で漂白処理後、水洗して凍結乾燥した(実施例11i)。
・セルロースザンテートナノファイバー酸再生物:実施例12で得られた酸再生処理物を、硫化ナトリウム溶液で脱硫処理、次亜塩素酸ナトリウム溶液で漂白処理後、水洗して凍結乾燥した(実施例12a)。
(実施例28、29)
実施例1にて作製したセルロースザンテートを使用し、実施例11と同様の洗浄、及び解繊処理を行い、0.5重量%のセルロースザンテートスラリーを得た。一方、酸化澱粉(GSL社製Dynakote68NB)に25重量%となる様に水を添加して澱粉スラリーを作製した。この澱粉スラリーを沸騰浴中で加熱して澱粉糊液を作製し、水浴中で冷却を行った。この澱粉糊液中の澱粉固形分に対して、セルロースザンテートが1重量%(実施例28)、又は2重量%(実施例29)となる様にセルロースザンテートスラリーを添加し、全体の濃度が15重量%となる様に水を添加した。水を添加したスラリーをホモジナイザーで撹拌混合(8000rpm、5min.)して塗工液を作製した。この塗工液を段ボール用中芯(レンゴー(株)製:坪量160g/m2)にバーコーター(No.7)を用いて両面塗工し、回転型乾燥機(ジャポー(株)製:L-3D)により120℃の温度環境で2分間乾燥させた。得られた紙をその後1日間にわたって23℃、50%R.H.の環境で調湿した。調湿後の坪量、圧縮強度(比圧縮強度)、引張強度(裂断長)を下記の方法で測定した。その結果を表10に示す。
実施例28において、セルロースザンテートスラリーを添加しない澱粉糊液をそのまま塗工液として塗工した塗工紙について同様に評価を行った(比較例11)。また、塗工液を塗工しない段ボール用中芯そのままについても同様に評価を行った(比較例12)。それらの結果も併せて表10に示す。
得られた塗工液を塗工した紙を絶乾して坪量(g/m2)を測定し、使用した原紙の絶乾坪量との差を求め、塗工量(g/m2)を算出した。
JIS P 8126(ISO12192に対応する。)の方法に従って圧縮強度(N)を測定し、さらに、得られた圧縮強度を坪量(g/m2)で割り、比圧縮強度(N・m2 /g)を算出した。
JIS P 8116(ISO1974に対応する。)に記載の方法に従って、引張強度(kN/m)を測定し、坪量の影響を除去するため、引張強度(kN/m)を(坪量×9.81÷1000)で割り、裂断長(km)を算出した。
(実施例30)
実施例1にて作製したセルロースザンテートを使用し、実施例11と同様の操作を行い、0.5重量%のセルロースザンテートスラリーを得た。このセルロースザンテートスラリーを、ビスコース(レンゴー(株)製:セルロース濃度9.5%)に添加した。添加量は、ビスコース中のセルロース固形分に対して、セルロースザンテートが5重量%となるように調整した。このセルロースザンテート混合ビスコースを、ホモジナイザーで撹拌混合(8000rpm、5min.)後、遠心分離(3000rpm、3min.)することで脱泡処理をした。脱泡処理後のセルロースザンテート混合ビスコースを、アプリケーターを使用して厚さ10mil.(254μm)でガラス板にキャストして、凝固・再生(凝固浴:150g/L硫酸、180g/L硫酸ナトリウム 約30℃)を行い、その後水洗した。水洗後、脱硫浴:10g/L硫化ナトリウム(約55℃)で脱硫処理を行い、脱硫処理後にさらに水洗した上でガラス板から剥がし、ウェットフィルムを得た。このウェットフィルムを吸水ろ紙(アドバンテック東洋(株)製:No.26-WA)に挟んでクーチロールで脱水後、回転型乾燥機(ジャポー(株)製:L-3D)により120℃の温度環境で2分間乾燥させてセルロースフィルムを得た。得られたセルロースフィルムをその後1日間にわたって23℃、50%R.H.の環境で調湿した。調湿したフィルム(各3枚)から引張試験用の試験片(ダンベル8号)を打ち抜き(n=5)、各試験片の厚みを測定した。試験片はオートグラフにて引張試験(つかみ幅:30mm、速度:20mm/min.)を行った。引張強度、伸度は以下のように算出した。その結果を表11に示す。
・伸度(%)= 破断点伸び(mm)/30mm × 100
実施例30において、実施例1のセルロースザンテートを実施例7のセルロースザンテートに変更した以外は同様の手順によりフィルムを作製し、同様に評価を行った。
実施例30において、セルロースザンテートスラリーを添加しないビスコースについても水を添加してセルロース濃度を調整してフィルムを作製し、同様に評価を行った。
(実施例32a~d)
実施例1にて作製したセルロースザンテートを使用し、実施例11と同様の操作を行い、0.5重量%のセルロースザンテートスラリーを得た。このスラリーに蒸留水を添加後、遠心分離(10000rpm、20分間)して未解繊物を沈降させ、上清をナノファイバースラリー(濃度0.13%)として回収した。一方、酸化澱粉(GSL社製Dynakote68NB)に25重量%となる様に水を添加して澱粉スラリーを作製した。この澱粉スラリー中の澱粉固形分に対してセルロースザンテートが1重量%~5重量%となる様に、セルロースザンテートスラリーを添加し、全体の濃度が15重量%となる様に水を添加した。水を添加した後、ホモジナイザーでスラリーを撹拌混合(8000rpm、5min.)し、100mLのメスシリンダーに100mL計量した。このメスシリンダーを静置して時間毎に澱粉粉体が100mLからどの程度沈降するか測定した。その結果を表12に示す。また、比較例14として、セルロースザンテートを添加しない澱粉スラリーについても同様に測定した。比較例14に比べて、実施例32a~32dはいずれも澱粉の沈降が遅くなることが確認された。
(実施例33)
・マスターバッチの作製
実施例1にて作製したセルロースザンテートを使用し、実施例20と同様の操作を行い、0.5重量%のセルロースザンテートスラリーを得た。このスラリーと天然ゴムラテックス((株)レヂテックス社製 HA NR LATEX 固形分60%、アンモニア0.7%)、14%アンモニア水を混合し(セルロースザンテートスラリー添加量は天然ゴム固形分100重量部に対して5重量部)、ホモジナイザーにて撹拌した(8000rpm、5min.)。撹拌混合後スラリーを70℃にて2日間乾燥し、次いで減圧乾燥を行い、天然ゴムマスターバッチを作製した。
得られたマスターバッチを50℃に加温した二本ロール(日本ロール製造(株) φ200mm×L500mmミキシングロール機)を使用して素練りし、次いで下記表13の配合通りにステアリン酸(ナカライテスク(株)製)、酸化亜鉛(ナカライテスク(株)製)、硫黄(ナカライテスク(株)製)、加硫促進剤(三新化学工業(株)製サンセラーNS-G)を添加混合し、厚さ2mm以上のコンパウンドシートを作製した。
得られたコンパウンドシートを金型に入れ、150℃、8分間圧縮成形して厚さ2mmの架橋体ゴムシート状を作製した。
得られた架橋ゴムシートからJIS3号形のダンベル形状に試験片を打ち抜き(n=5)、各試験片について厚みを測定した(n=3)。試験片は引張試験機((株)島津製作所 精密万能試験機 AG-1000D)にて引張試験(つかみ幅:50mm、速度:500mm/min.JIS K6251準拠)を行い、破断点応力、及びひずみを求めた。実施例33は下記の比較例15、16に比べて破断点のひずみ、応力が大きくなり、伸びを保ったまま、強度が向上し、ゴムの特性を損なわない結果となった。硫黄を含有するセルロースザンテートナノファイバーとなっていることで、ゴムとの相互作用が示唆された。
上記実施例において、セルロースザンテートスラリーを添加しない天然ゴムラテックスをそのまま乾燥してマスターバッチとして作製した架橋ゴムシートについて同様に評価を行った(比較例15)。また、セルロースザンテートナノファイバーの代わりにセルロースナノファイバー((株)スギノマシン製BiNFi-sWMa-10002)を添加したマスターバッチを使用して作製した架橋ゴムシートについても同様に評価を行った(比較例16)。それらの結果も併せて表14に示す。
Claims (7)
- セルロースザンテート又はセルロースザンテートのカチオン置換体を解繊処理する、セルロースザンテートナノファイバーの製造方法。
- セルロースを含有する材料を水酸化アルカリ金属水溶液で処理してセルロースI型を維持したアルカリセルロースを生成し、このアルカリセルロースを二硫化炭素と反応させてセルロースザンテートとし、
このセルロースザンテートを用いた請求項1に記載のセルロースザンテートナノファイバーの製造方法。 - 請求項1又は2に記載のセルロースザンテートナノファイバーの製造方法で得られたセルロースザンテートナノファイバーを再生処理する、セルロースナノファイバーの製造方法。
- セルロースの水酸基の何れかが下記式(1)で表されるザンテート基で置換されていることを特徴とするセルロースザンテートナノファイバー。
-CSS- Mn+ (1)
(カチオンMn+は、水素イオン、1価または多価金属イオン、アンモニウムイオン、脂肪族または芳香族アンモニウムイオンから選ばれる少なくとも1種。n=1,2,3) - 平均硫化度が0.1mol%以上33.3mol%以下であり、平均繊維長が2μm以上100μm以下であり、平均繊維径が3nm以上250nm以下であることを特徴とする請求項4に記載のセルロースザンテートナノファイバー。
- 請求項4又は5に記載のセルロースザンテートナノファイバーを再生することにより得られる、
平均繊維長が2μm以上100μm以下であり、平均繊維径が3nm以上250nm以下である、再生セルロースナノファイバー。 - 請求項4又は5に記載のセルロースザンテートナノファイバーを含有するゴム組成物。
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WO2021235501A1 (ja) | 2020-05-19 | 2021-11-25 | 王子ホールディングス株式会社 | 微細繊維状セルロース、分散液、シート、積層シート、積層体及び微細繊維状セルロースの製造方法 |
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Also Published As
Publication number | Publication date |
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EP3395837B1 (en) | 2021-12-15 |
US10662257B2 (en) | 2020-05-26 |
EP3395837A4 (en) | 2019-01-23 |
JPWO2017111103A1 (ja) | 2017-12-21 |
CN108350090B (zh) | 2020-08-14 |
US20180273644A1 (en) | 2018-09-27 |
EP3395837A1 (en) | 2018-10-31 |
JP6254335B2 (ja) | 2017-12-27 |
CN108350090A (zh) | 2018-07-31 |
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