JP6384498B2 - Fibrous cellulose, resin composition and cellulose suspension - Google Patents

Description

  The present invention relates to a method for producing fine fibrous cellulose.

In recent years, there has been a growing trend to actively use reproducible resources. As a reproducible resource, for example, cellulose fiber is widely known. Among them, wood-derived cellulose fiber has been widely used mainly as a raw material for paper products.
When the cellulose fiber is refined to a fiber diameter of 1 μm or less, it can impart a new function to the resin and improve the physical properties of the resin when blended in the resin. An example of a physical property that can be improved by blending finely divided cellulose fibers (fine fibrous cellulose) into the resin is strength. In particular, for rubber for tires, interior / exterior materials for automobiles, housing members, housings for electrical products, etc., research and development of a technique for blending fine fibrous cellulose is being promoted for the purpose of improving strength.

  In order to enhance the effect of improving the strength of the resin by blending the fine fibrous cellulose, it is necessary to increase the dispersibility of the fine fibrous cellulose in the resin. In addition, in order for fine fibrous cellulose to be widely used in various applications, it is necessary to be manufactured at a high yield and at a low cost.

As a method for producing fine fibrous cellulose, for example, Patent Document 1 discloses a method of mechanically defibrating pulp containing a relatively large amount of lignin with respect to the cellulose mass. The fine fibrous cellulose obtained by the method described in Patent Document 1 has low hydrophilicity compared to the one not containing lignin, and is therefore considered to have excellent dispersibility when blended with a resin and a high strength improvement effect. Yes.
Moreover, as a manufacturing method of a fine fibrous cellulose, patent document 2 does not contain lignin at all, or contains a very small amount of lignin (lignin content is 0-5 mass%, preferably 0-1 mass%). A method of stirring a mixture of a fiber assembly and a liquid substance such as water is disclosed. According to this method, fine fibrous cellulose that is defibrated to a fiber width of 10 to 50 nm and is uniform and less damaged is obtained, and high strength is obtained when the cellulose is blended with a resin.

JP 2009-19200 A JP 2010-216021 A

The fibrous cellulose of the present invention has a fiber width of 2 nm or more and 1000 nm or less, a phosphoric acid group obtained by chemically modifying a part of the hydroxyl group of cellulose, a carbonyl group substituting a part of the hydroxyl group of cellulose , and a hydroxyl group of cellulose. It has at least one kind of substituent selected from carboxy groups whose parts are chemically modified or substituted , and is derived from unbleached chemical pulp or oxygen-bleached chemical pulp.
The resin composition of the present invention contains the fibrous cellulose and a resin.
The resin in the resin composition of the present invention preferably contains one or more selected from polyethylene, polystyrene, acrylic resin, polycarbonate, and polyethylene terephthalate.
The cellulose suspension of the present invention has a fiber width of 2 nm to 1000 nm, a phosphoric acid group obtained by chemically modifying a part of the hydroxyl group of cellulose, a carbonyl group substituting a part of the hydroxyl group of cellulose, and a hydroxyl group of cellulose. Including fibrous cellulose having at least one substituent selected from carboxy groups chemically modified or substituted, and derived from unbleached chemical pulp or oxygen bleached chemical pulp , and calculated by the following method: The supernatant yield is 52% by mass or more and 89% by mass or less .
<Calculation method>
Using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B), a slurry in which ion-exchanged water is added to the cellulose suspension to adjust the solid content concentration to 0.2% by mass (referred to as slurry A). Centrifugation is performed under the condition of 12000 G, and the obtained supernatant (referred to as slurry B) is recovered and the solid content concentration of the supernatant is measured. Subsequently, the supernatant yield of fibrous cellulose is calculated | required based on a following formula.
Supernatant yield (% by mass) = {(solid content concentration of slurry B) / (solid content concentration of slurry A)} × 100

  In view of the above circumstances, the present invention provides a method for producing fine fibrous cellulose that is excellent in dispersibility in a resin, has a high yield of fine fibrous cellulose in the defibrating step, and has a low cost for production. The task is to do.

  As a result of repeated research on a method for producing fine fibrous cellulose, the present inventors solve the problem by using a specific chemical pulp as a raw material and subjecting the cellulose suspension obtained from the pulp to chemical treatment. It was found to be an important technical element above.

The method for producing fine fibrous cellulose of the present invention includes a suspension preparation step for obtaining a cellulose suspension containing at least one of unbleached chemical pulp and oxygen-bleached chemical pulp, and the following (a) to (a) to the cellulose suspension. A chemical treatment step of applying at least one chemical treatment of (d);
And a defibrating step of performing a defibrating treatment on the cellulose suspension after the chemical treatment step.
(A) treatment of a dicarboxylic acid compound having two carboxy groups with an acid anhydride;
(B) Phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, pyrophosphoric acid Treatment with one or more selected from the group consisting of potassium, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate,
(C) treatment with ozone,
(D) Treatment with cellulase enzyme or hemicellulase enzyme

  According to the method for producing fine fibrous cellulose of the present invention, the yield of fine fibrous cellulose in the defibrating process is high, and the cost required for production is low. Moreover, the obtained fine fibrous cellulose is excellent in dispersibility when blended with a resin.

Hereinafter, the present invention will be described in detail.
<Fine fibrous cellulose>
The fine fibrous cellulose is an aggregate of cellulose molecules whose width (diameter) measured by observation with a scanning or transmission electron microscope is 2 nm to 1000 nm, and its crystal structure is type I (parallel chain). is there. Such fine fibrous cellulose is a fiber or rod-like particle whose width is remarkably smaller than the cellulose fiber used in ordinary paper products.
When the width of the fine fibrous cellulose is less than 2 nm, it dissolves in water as cellulose molecules, so that the physical properties (strength, rigidity and dimensional stability) as fine fibers are difficult to be expressed. On the other hand, when the width exceeds 1000 nm, it cannot be said to be a fine fiber, and since it is not different from a cellulose fiber used in a normal paper product, physical properties (strength, rigidity and dimensional stability) as a fine fiber are obtained. I can't.

Here, the fine fibrous cellulose has a type I crystal structure. In a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite, 2θ = It can be identified by having typical peaks at two positions near 14-17 ° and 2θ = 22-23 °.
Moreover, the measurement of the fiber width by electron microscope observation of fine fibrous cellulose is performed as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05 to 0.1% by mass is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. When wide fibers are included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight line X and the straight line Y is read for each image. Thus, at least 20 × 2 × 3 = 120 fiber widths are read. The fine fiber width in the present invention is an average value of the fiber widths thus read.

  The fiber length of the fine fibrous cellulose of the present invention is preferably 1 μm to 1000 μm. When the fiber length is less than 1 μm, it is difficult to obtain the strength improvement effect when the fine fibrous cellulose is combined with the resin. When the fiber length exceeds 1000 μm, the slurry viscosity of the fine fibrous cellulose becomes very high and becomes difficult to handle. The fiber length can be obtained by image analysis of TEM, SEM, or AFM. The said fiber length is a fiber length which occupies 30 mass% or more of a fine fiber.

  The axial ratio of the fine fibrous cellulose according to the present invention (the ratio of the fiber length to the fiber width, generally referred to as “aspect ratio”) is preferably in the range of 100 to 10,000. If the axial ratio is equal to or higher than the lower limit value, the effect of improving the strength when the fine fibrous cellulose is blended with the resin is further increased. If the axial ratio is equal to or lower than the upper limit value, the slurry viscosity of the fine fibrous cellulose is decreased. it can.

<Method for producing fine fibrous cellulose>
The manufacturing method of the fine fibrous cellulose of this invention has a suspension preparation process, a chemical treatment process, and a defibration process.

(Suspension preparation process)
The suspension preparation step is a step of preparing a cellulose suspension containing at least one of unbleached chemical pulp and oxygen bleached chemical pulp as a cellulose component.
The cellulose component contained in the cellulose suspension is preferably at least one of unbleached chemical pulp and oxygen-bleached chemical pulp, but unbleached chemical pulp and oxygen-bleached chemical as long as the effects of the present invention are not impaired. A small amount (preferably 7% by mass or less, more preferably 5% by mass or less) of a cellulose-containing material other than pulp may be included.

[Unbleached chemical pulp]
In describing the unbleached chemical pulp used in the present invention, first, a general chemical pulp will be described.
Pulp is a collection of fibers obtained by breaking down plants or waste paper. Pulp is divided into three types according to the type of raw material: wood pulp made from wood, non-wood pulp made from plants other than wood (straw, bamboo, flax, cotton linter, etc.), and waste paper pulp made from waste paper. It is done. Among these, wood pulp is further classified according to the method of unraveling the raw wood. Specifically, mechanical pulp (MP) obtained by mechanically grinding the raw material, chemical pulp (CP) obtained chemically by steaming the raw material with chemicals, etc. Is classified into semi-chemical pulp (SCP) obtained by subjecting to mechanical treatment.
Chemical pulp is further classified into kraft pulp (KP) and sulfite pulp (SP). Among them, kraft pulp accounts for most of the world's pulp production and is a typical chemical pulp.

  There are no particular restrictions on the wood used as the raw material for pulp. Conifers such as balsam fur, cedar, pine, and radiata pine, beech, hippopotamus, alder tree, oak, tab, shii, birch, poplar, tamo, dolphin, eucalyptus, mangrove, lauan, etc. can do. However, in the present invention, when making wood into pulp, it is preferable that the form of wood is not wood powder but chips. When the form of the wood is a chip, the fiber length of the obtained fine fibrous cellulose tends to be long, so that it is easy to obtain an effect of improving the strength when blended with a resin. Moreover, the cost of processing wood into chips is lower than the cost of processing wood into wood powder.

The kraft pulp is manufactured by sending the raw wood together with a mixture of caustic soda (sodium hydroxide) and sodium sulfide (sodium sulfide) into a digester and cooking under high temperature and high pressure. Examples thereof include a washing step of separating waste liquid from the digested product with a washing device, a selection step of selecting with a dust removing device such as a screen or a cleaner, and a bleaching step.
In the above production method, the cellulose fiber contained in the wood is separated from the lignin component by the cooking step, but the lignin component is not completely removed, and a certain amount of the lignin component remains.
A bleaching process is a process of removing the residual lignin component which is also a pulp coloring component, and aims at increasing the whiteness of a pulp. Therefore, it can also be regarded as a supplementary process or an extension process for removing the lignin component in the cooking process.
Usually, the bleaching process is performed by a method combining several kinds of bleaching processes. In the first stage of the bleaching step, oxygen bleaching is performed, and in the subsequent multistage bleaching, bleaching is performed with chlorine dioxide or ozone, and then bleaching is performed with hydrogen peroxide or chlorine dioxide. From the viewpoint of reducing the environmental load, it is preferable to use oxygen in the former stage bleaching to reduce the amount of chemicals used in the latter stage bleaching.
The method for producing sulfite pulp is the same as the method for producing kraft pulp except that sulfite and sulfite are used instead of caustic soda and sodium sulfide in the cooking step.

  The unbleached chemical pulp used in the present invention is a chemical pulp obtained without undergoing a bleaching step in the above kraft pulp or sulfite pulp manufacturing method. That is, it is a chemical pulp obtained only through a cooking process, a washing process, and a selection process. Therefore, unbleached chemical pulp does not incur the manufacturing cost generated in the bleaching process. Moreover, it can manufacture using the existing chemical pulp manufacturing equipment which has a bleaching process equipment as it is. Specifically, the chemical pulp that has passed through the selection process may be taken out before being sent to the bleaching process. If existing facilities are used, there is no need to install new large-scale facilities.

  Kraft pulp is preferred as the unbleached chemical pulp. Kraft pulp is superior in terms of environmental load and productivity because it produces less wastewater in the cooking process than sulfite pulp and produces more than kraft pulp.

[Oxygen bleached chemical pulp]
The oxygen bleached chemical pulp is a chemical pulp obtained by performing only the preceding oxygen bleaching treatment as a bleaching step in the production of the kraft pulp. Therefore, oxygen-bleached chemical pulp has a lower production cost than chemical pulp that has been subjected to all bleaching processes of multi-stage bleaching. Moreover, oxygen bleached chemical pulp can be manufactured using the existing chemical pulp manufacturing equipment as it is. Specifically, the chemical pulp subjected to the oxygen bleaching treatment may be taken out before being sent to the subsequent bleaching treatment. If existing facilities are used, there is no need to install new large-scale facilities.
Also in oxygen bleached pulp, kraft pulp is preferable like unbleached chemical pulp.

(Chemical treatment process)
The chemical treatment step is a step of subjecting the cellulose suspension to chemical treatment.
The chemical treatment in the present invention is at least one of the following (a) to (e).
(A) Treatment of a compound having a carboxy group with an acid anhydride (b) Treatment with a compound having a phosphate group (c) Treatment with ozone (d) Treatment with an enzyme (e) 2,2,6,6-tetramethyl Treatment with piperidinooxy radical (hereinafter referred to as “TEMPO”)

  As the degree of chemical treatment, the degree of substitution of cellulose after treatment is preferably in the range of 0.005 to 0.3, more preferably 0.01 to 0.25, 0.015 to More preferably, it becomes 0.2. Here, the degree of substitution refers to the number of three hydroxyl groups in the glucose skeleton of cellulose that are substituted with another substituent by chemical treatment. Since substitution to a carboxy group is important for substitution of a hydroxyl group with another substituent, the degree of substitution was calculated from the number of moles of carboxy group according to TAPPI T-237. If the degree of substitution is greater than or equal to the lower limit, the fibrillation is higher and the yield of fine fibrous cellulose is higher, and if the degree of substitution is less than or equal to the upper limit, the dispersibility of the resulting fine fibrous cellulose in the resin Becomes higher.

[Treatment of Compound Having Carboxy Group with Acid Anhydride]
In the treatment of the compound having a carboxy group with an acid anhydride, a part of the hydroxyl group of cellulose is chemically modified to a carboxy group by the acid anhydride of the compound having a carboxy group. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
Examples of the acid anhydride of the compound having a carboxy group include dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. These may be used individually by 1 type and may use 2 or more types together. Among the acid anhydrides, maleic anhydride and succinic anhydride are preferable because they are industrially easily used and easily gasified.

  In performing the chemical treatment with the acid anhydride of the compound having a carboxy group, it is preferable to dry the cellulose suspension in advance. Specifically, the water content of the cellulose suspension is set to 10% by mass or less. It is preferable to do. If the water content of the cellulose suspension is lowered, it becomes easy to obtain fine fibrous cellulose having a large aspect ratio. When fine fibrous cellulose having a large aspect ratio is added to the resin, the strength is easily improved.

  Although the mass ratio of the acid anhydride of the compound having a carboxy group with respect to the cellulose suspension is not particularly limited, it is 0.1 to 500 parts by mass with respect to 100 parts by mass of the solid content of the cellulose suspension. It is preferably 1 to 300 parts by mass, more preferably 25 to 75 parts by mass. If the mass ratio of the acid anhydride of the compound having a carboxy group is equal to or more than the lower limit, the effect of improving the yield of fine fibrous cellulose in the defibrating step becomes higher. However, if the above upper limit is exceeded, not only the yield improvement effect of fine fibrous cellulose in the defibration process will reach its peak, but all the lignin components contained in the cellulose suspension may be removed. .

  When performing the chemical treatment with the acid anhydride of the compound having a carboxy group, it is preferable to perform a heat treatment. The temperature during the heat treatment is not particularly limited, but is preferably 100 to 250 ° C. from the viewpoint of the thermal decomposition temperature of cellulose.

After the chemical treatment with the acid anhydride of the compound having a carboxy group, it is preferable to subject the cellulose suspension to an alkali treatment step of treating with an alkali solution. Although it does not restrict | limit especially as a method of an alkali treatment, For example, the method of immersing the cellulose suspension chemically treated with the acid anhydride of the compound which has a carboxy group in an alkaline solution is mentioned.
The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound. Examples of the inorganic alkali compound include sodium hydroxide, potassium hydroxide, calcium hydroxide and the like. Examples of the organic alkali compound include ammonia, aliphatic amines, and aromatic amines.
The solvent for the alkaline solution may be either water or an organic solvent, but is preferably a polar organic solvent, and more preferably an aqueous solvent containing at least water.

  In addition, after alkali treatment, in order to improve handleability, it is preferable to wash the alkali-treated cellulose suspension with water or an organic solvent before the defibrating step.

[Treatment with a compound having a phosphate group]
In the treatment with a compound having a phosphate group, a part of the hydroxyl group of cellulose is chemically modified to a phosphate group by the compound having a phosphate group. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples include tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. These may be used individually by 1 type and may use 2 or more types together. Of the above-mentioned compounds having a phosphate group, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferred from the viewpoint of easy industrial use.

  The mass ratio of the compound having a phosphate group to the cellulose suspension is not particularly limited, but the addition amount converted to phosphorus element is 0.1 with respect to 100 mass parts of the solid content of the cellulose suspension. It is preferably ˜500 parts by mass, more preferably 0.5 to 250 parts by mass, and even more preferably 1 to 100 parts by mass. If the mass ratio of the compound which has a phosphoric acid group is more than the said lower limit, the improvement effect of the yield of the fine fibrous cellulose in a fibrillation process will become higher. However, if the above upper limit is exceeded, not only the yield improvement effect of fine fibrous cellulose in the defibration process will reach its peak, but all the lignin components contained in the cellulose suspension may be removed. .

  When performing chemical treatment with a compound having a phosphate group, it is preferable to perform heat treatment. The temperature during the heat treatment is not particularly limited, but is preferably 100 to 250 ° C. from the viewpoint of the thermal decomposition temperature of cellulose.

[Treatment with ozone]
In the treatment with ozone, some hydroxyl groups of cellulose are replaced with carbonyl groups or carboxy groups. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
Ozone can be generated by supplying an oxygen-containing gas such as air, oxygen gas, or oxygen-added air to a known ozone generator.

The treatment with ozone is performed by exposing the cellulose suspension to a closed space / atmosphere in which ozone is present.
If the ozone concentration in the gas containing ozone is 250 g / m ² or more, there is a possibility of explosion, so it is necessary to be less than 250 g / m ² . However, if the concentration is low, the amount of ozone used is increased, and thus it is preferably 50 to 215 g / m ² . If the ozone concentration is equal to or higher than the lower limit, the handling of ozone is easy, and the effect of improving the yield of fine fibrous cellulose in the defibrating process is further increased.

  The amount of ozone added to the cellulose suspension is not particularly limited, but it is preferably 0.1 to 8 parts by mass with respect to 100 parts by mass of the solid content of the cellulose suspension. If the amount of ozone added is equal to or greater than the lower limit, the effect of improving the yield of fine fibrous cellulose in the defibrating step will be higher. However, when the above upper limit is exceeded, not only the yield improvement effect of fine fibrous cellulose in the defibrating process reaches its peak, but all lignin residual components in the cellulose suspension may be removed.

  The ozone treatment temperature is not particularly limited, and is appropriately adjusted within a range of 0 to 50 ° C. Further, the ozone treatment time is not particularly limited, and is appropriately adjusted within a range of 1 to 180 minutes.

  The cellulose suspension may be subjected to ozone treatment and then subjected to additional oxidation treatment. Examples of the oxidizing agent used for the additional oxidation treatment include chlorine compounds such as chlorine dioxide and sodium chlorite.

[Enzyme treatment]
In the treatment with an enzyme, the reason is not clear, but it is considered that the fibrillation is improved by attacking the crystal part of cellulose and loosening the bond.

As the enzyme, a cellulase enzyme or a hemicellulase enzyme is preferable.
Cellulase-based enzymes include the genus Trichoderma, the genus Acremonium, the genus Aspergillus, the genus Phanerochaete, the trametes, Trametes, Genus, Humicola (Bacteria), Bacillus (bacteria), Suehirotake (Basidiomycetes), Streptomyces (bacteria), Pseudomonas (bacteria), etc. Enzymes. Of these, filamentous fungal cellulase enzymes are preferred, and among the fungal cellulase enzymes, cellulase enzymes produced by Trichoderma bacterium (Trichoderma reesei or Hyporea jerorina) are abundant in types. It is more preferable because of its high productivity.

  The hemicellulase enzymes are xylanase, an enzyme that degrades xylan, mannanase, an enzyme that degrades mannan, arabanase, an enzyme that degrades araban, and an enzyme that degrades pectin. Examples include pectinase. Among these, xylase is preferable for cellulose suspension derived from hardwood, and mannase is preferable for cellulose suspension derived from conifer.

  The amount of enzyme added to the cellulose suspension is not particularly limited, and is appropriately adjusted depending on the type of enzyme, the type of wood (coniferous tree or hardwood), and the like.

  The pH of the cellulose suspension during the cellulase enzyme treatment is preferably a weakly acidic region (pH = 3.0 to 6.9) from the viewpoint of the reactivity of the enzyme reaction. On the other hand, the pH of the cellulose suspension during the hemicellulase enzyme treatment is preferably in a weakly alkaline region (pH = 7.1 to 10.0).

  The temperature during the enzyme treatment is not particularly limited, but is preferably 30 to 70 ° C, more preferably 35 to 65 ° C, and further preferably 40 to 60 ° C. If the temperature at the time of enzyme treatment is not less than the above lower limit value, the enzyme activity is unlikely to be lowered and the treatment time can be prevented from being prolonged, and if it is not more than the above upper limit value, inactivation of the enzyme can be prevented.

  The enzyme treatment time is preferably 0.5 to 24 hours. If processing time is more than the said lower limit, the effect of an enzyme process can fully be exhibited. On the other hand, if it is below the above upper limit, shortening of the fiber length due to the decomposition of the cellulose fibers can be suppressed, and the effect of improving the strength when blended into the resin can be sufficiently obtained. The enzyme treatment time can be adjusted by the kind of enzyme, temperature, pH and the like.

  It is preferable to deactivate the enzyme after the enzyme treatment. If the enzyme is deactivated, the enzymatic reaction is stopped and the progress of saccharification of the fiber is stopped, so that a decrease in yield can be prevented and shortening of the fiber length can be suppressed. Examples of the method for inactivating the enzyme include a method of adding an alkaline aqueous solution (preferably pH 10 or more, more preferably pH 11 or more) and a method of adding hot water at 80 to 100 ° C.

[Processing by TEMPO]
In the treatment with TEMPO, an oxidizing agent is reacted with the cellulose suspension in the presence of TEMPO and an alkali halide to chemically modify a part of the hydroxyl groups of cellulose to carboxy groups. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.

The alkali halide used as an oxidation catalyst together with TEMPO is not particularly limited, and alkali iodide, alkali bromide, alkali chloride, alkali fluoride and the like can be appropriately selected and used.
The oxidizing agent is not particularly limited, and sodium hypochlorite, sodium chlorite, sodium hypobromite, sodium bromite and the like can be appropriately selected and used.

  Although the usage-amount of an oxidation catalyst is not restrict | limited especially, it is preferable that TEMPO and an alkali halide are 0.1-15 mass parts, respectively with respect to 100 mass parts of solid content of a cellulose suspension. . If the addition amount of an oxidation catalyst is more than the said lower limit, the yield improvement effect of the fine fibrous cellulose in a defibrating process will become higher. However, if the upper limit is exceeded, the yield improvement effect of fine fibrous cellulose in the defibration process may reach its peak.

  The amount of the oxidizing agent used is not particularly limited, but is preferably 1 to 80 parts by mass with respect to 100 parts by mass of the solid content of the cellulose suspension.

  The pH of the suspension when the cellulose suspension is treated with TEMPO is appropriately adjusted according to the type of oxidizing agent used. The pH of the cellulose suspension is adjusted by appropriately adding a basic substance such as potassium hydroxide or ammonia, or an acidic substance such as acetic acid or oxalic acid.

The treatment temperature for treating the cellulose suspension with TEMPO is preferably in the range of 20 to 100 ° C., and the treatment time is preferably 0.5 to 4 hours.
Moreover, in order to perform the process by TEMPO uniformly, it is preferable to process, stirring with various stirring apparatuses.

(Defibration process)
The defibrating process is a process of performing a defibrating process on the chemically-treated cellulose suspension.
The equipment used for the defibrating treatment includes high-speed defibrator, grinder (stone mortar grinder), high-pressure homogenizer, ultra-high pressure homogenizer, high-pressure collision grinder, ball mill, bead mill, vibration mill, disk refiner, conical refiner, biaxial A conventionally known defibrating apparatus, such as a kneader, a homomixer under high-speed rotation, or a beater, can be appropriately selected and used.

(how to use)
The fine fibrous cellulose obtained by the above production method can be used as resin reinforcing fibers. If fine fibrous cellulose is mixed with resin, strength, rigidity, etc. can be improved.
As a mixing method when using fine fibrous cellulose as a reinforcing fiber, for example, a method of adding solid or slurry fine fibrous cellulose to melted resin and melt-kneading, resin emulsion and slurry And a method of mixing and dehydrating the fine fibrous cellulose.
The resin for mixing the fine fibrous cellulose may be either a thermoplastic resin or a thermosetting resin.
Thermoplastic resins include polyethylene (high pressure method low density polyethylene, linear low density polyethylene, high density polyethylene), polypropylene (homopolymer, random polymer, block polymer), polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene- Acrylic copolymer, acrylic resin, ABS resin, polylactic acid, polybutylene succinate, polyhydroxybutyrate, polyethylene adipate, polycaprolactone, polyethylene terephthalate, polybutylene terephthalate, polyamide, polycarbonate, polyacetal, polyphenylene oxide, fluorine resin, etc. Can be mentioned.
Examples of the thermosetting resin include an epoxy resin, an unsaturated polyester resin, a phenol resin, a urethane resin, a diallyl phthalate resin, and a melamine resin.
The above resins may be used alone or in combination of two or more.

  When high transparency is required, a transparent resin (for example, polystyrene, acrylic resin, polycarbonate, polyethylene terephthalate, etc.) is used as a resin to disperse fine fibrous cellulose, and is precipitated by centrifugation or the like after the defibrating step. It is preferable to use fine fibrous cellulose from which substances are removed.

(Function and effect)
The cellulose suspension containing unbleached chemical pulp and oxygen-bleached chemical pulp used in the present invention contains a larger amount of lignin component than the cellulose suspension containing bleached chemical pulp. In the conventional production method, when lignin is included, the yield in the defibrating process is reduced, but in the present invention, the chemical treatment is performed before the defibrating process is performed on the cellulose suspension. This prevents a decrease in the yield of fine fibrous cellulose.
In addition, unbleached chemical pulp or oxygen-bleached chemical pulp is less expensive to manufacture than chemical pulp that has been bleached because part or all of the bleaching process is omitted.
Moreover, the fine fibrous cellulose obtained by the production method of the present invention is excellent in dispersibility in the resin. The reason why the resin is excellent in dispersibility is not clear, but one reason is that a hydrophobic lignin component remains even after chemical treatment. In addition, since unbleached chemical pulp and oxygen bleached pulp have less fiber damage, the resulting fine fibrous cellulose is also less damaged, and when blended with a resin, localization due to fiber entanglement can be suppressed. .

Hereinafter, the present invention will be described with specific examples, but the present invention is not limited to the specific examples. Note that “%” and “parts” described in Examples and Comparative Examples are both “mass%” and “parts by mass”.
Moreover, in each Example and each Comparative Example, it was confirmed by the following method that fine fibrous cellulose was obtained.
That is, a supernatant liquid of a defibrated cellulose suspension described later was diluted with water to a concentration of 0.05 to 0.1% and dropped onto a carbon grid membrane subjected to a hydrophilic treatment. After drying, it was stained with uranyl acetate, and the width of the cellulose fiber was observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.). Based on the width, it was determined whether or not fine fibrous cellulose was contained.

<Treatment of Compound Having Carboxy Group with Acid Anhydride>
Example 1
A cellulose suspension containing hardwood unbleached kraft pulp (LUKP) mainly composed of eucalyptus as a cellulose component was dried at 105 ° C. for 3 hours to obtain a dry pulp having a moisture content of 3% or less. Next, 4 g of dried pulp and 2 g of maleic anhydride (50 parts with respect to 100 parts of pulp solid content) were filled in an autoclave and treated at 150 ° C. for 2 hours.
Next, the maleic anhydride-treated dry pulp was dispersed in 250 mL of a 0.8% sodium hydroxide aqueous solution, stirred and alkali-treated. The pH of the resulting cellulose suspension was about 12.5. Thereafter, the cellulose suspension after the alkali treatment was washed with ion-exchanged water until the pH became 8 or less.
Next, ion-exchanged water was added to the cellulose suspension after the alkali treatment to prepare a cellulose suspension having a solid content concentration of 0.5%. The cellulose suspension was defibrated for 30 minutes under the condition of 21500 rpm using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.). Obtained.

(Example 2)
After putting 50 g of hardwood unbleached kraft pulp (LUKP) (solid content mass) made from eucalyptus into a plastic bag and adding 2 parts of 2 molar caustic soda solution to 100 parts of LUKP solid content and mixing well The mixture was transferred to an autoclave equipped with a stirrer. Next, the reaction was carried out in the autoclave at an oxygen pressure of 0.5 MPa and a temperature of 100 ° C. for 60 minutes. After the reaction, the pulp was taken out of the container, washed with 5 times the amount of ion-exchanged water, and then dehydrated with a Buchner to obtain oxygen bleached kraft pulp (LOKP) using LUKP as a raw material.
A defibrated cellulose suspension was obtained in the same manner as in Example 1 except that the LOKP was used.

(Comparative Example 1)
A defibrated cellulose suspension was obtained in the same manner as in Example 1 except that softwood bleached kraft pulp (NBKP) was used as the cellulose component.

(Comparative Example 2)
A defibrated cellulose suspension was obtained in the same manner as in Example 1 except that hardwood bleached kraft pulp (LBKP) was used as the cellulose component.

[Evaluation]
When the cellulose contained in the defibrated cellulose suspensions of Examples 1 and 2 and Comparative Examples 1 and 2 was observed with a transmission electron microscope, it was confirmed that fine fibrous cellulose having a width of about 4 nm was contained. . Moreover, the cellulose maintained the cellulose I type crystal | crystallization by X-ray diffraction. Moreover, the measurement based on the infrared absorption spectrum by FT-IR showed absorption based on a carboxy group at 1580 to 1720 cm ⁻¹ , confirming the addition of maleic acid.

Moreover, about the defibrated cellulose suspension of the said Examples 1-2 and Comparative Examples 1-2, the supernatant yield after centrifuging was measured by the method as described below. The measurement results are shown in Table 1.
Moreover, the dispersibility with respect to resin of the fine fibrous cellulose contained in the defibrated cellulose suspension was evaluated as follows. Moreover, it evaluated about the cost of fine fibrous cellulose manufacture. Each evaluation result is shown in Table 1.

[Measurement of supernatant yield after centrifugation]
Ion exchange water is added to the defibrated cellulose suspension to adjust the slurry solids concentration to 0.2%, and the mixture is centrifuged at 12000G using a cooling high-speed centrifuge (Kokusan, H-2000B). The obtained supernatant was recovered, and the solid content concentration of the supernatant was measured. Based on the following formula, the supernatant yield of fine fibrous cellulose was determined.
Supernatant yield (%) = (Solid concentration of supernatant after centrifugation) ÷ (Solid concentration of defibrated cellulose suspension) × 100
The supernatant yield after centrifugation is the yield of fine fibrous cellulose obtained by excluding the aggregates of fine fibrous cellulose and the non-fine fibrous material having a large fiber width. The higher the is, the higher the yield of finer fine fibrous cellulose.

[Dispersibility]
Fine fibrous cellulose (supernatant liquid after centrifugation, concentration of about 0.5%) and anionic polyethylene latex (manufactured by Toho Chemical Co., Ltd., trade name E-2213, average particle size: 70 nm) are in a mass ratio of 5: 100. And a mixture of fine fibrous cellulose and polyethylene latex was obtained by stirring with a homogenizer. The obtained mixture was dried for 3 hours with a vacuum drier at 110 ° C., and the cross section of the obtained dried product was observed using a scanning electron microscope (voltage 10 kV, magnification 100 ×). This observed and evaluated the dispersion state of the fine fibrous cellulose in polyethylene.
As an evaluation method, the following criteria were used for evaluation based on the number of aggregates present in an electron micrograph (view expanded to 10 cm × 7 cm, 5 sheets).
A: There are almost no aggregates in the polyethylene composition.
○: There are aggregates in the polyethylene composition, but very few.
Δ: A little aggregate in the polyethylene composition.
X: There are many aggregates in a polyethylene composition.

[cost]
The cost evaluation is a relative evaluation assuming an industrial production.

In Example 1 obtained by treating LUKP with an acid anhydride of a compound having a carboxy group and then defibrating, the yield was high and the dispersibility of the obtained fine fibrous cellulose in the resin was high. Moreover, since the bleaching process of a pulp can be simplified, it was low-cost.
In Example 2 obtained by treating LOKP with an acid anhydride of a compound having a carboxy group and then defibrating, the yield was high and the dispersibility of the obtained fine fibrous cellulose in the resin was high. Moreover, since the bleaching process of a pulp can be simplified, it was low-cost.

<Chemical treatment with a compound having a phosphate group>
(Example 3)
6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate are dissolved in 19.62 g of water, and an aqueous solution of a phosphoric acid compound (hereinafter referred to as “phosphorylation reagent”).
)
Water was added to conifer unbleached kraft pulp (NUKP, moisture 50%, Canadian standard freeness (CSF) 550 ml measured according to JIS P8121) to a concentration of 4%. Then, using a double disc refiner, the irregular CSF (80 mesh plain weave, according to JIS P8121 except that the amount of pulp collected was 0.3 g) was beaten until 200 ml and the length average fiber length became 0.66 mm.
The cellulose suspension thus obtained was diluted to 0.3%, and a pulp sheet (thickness 200 μm) having a water content of 90% and a solid content (absolute dry mass) of 3 g was obtained by a papermaking method. This pulp sheet was immersed in 31.2 g of the phosphorylating reagent (80 parts by mass as the amount of phosphorus element with respect to 100 parts by mass of the dried pulp), and heated for 1 hour with an air dryer at 105 ° C. (Yamato Scientific Co., Ltd. DKM400). Further, heat treatment was performed at 150 ° C. for 1 hour to introduce phosphate groups into the cellulose fibers.
Subsequently, 500 ml of ion-exchanged water was added to the pulp sheet in which the phosphate group was introduced into the cellulose fiber, and the mixture was dehydrated after washing with stirring. The dehydrated sheet was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N sodium hydroxide aqueous solution was added little by little with stirring to obtain a cellulose suspension having a pH of 12 to 13. Thereafter, the cellulose suspension was dehydrated and washed by adding 500 ml of ion exchange water. This dehydration washing was repeated two more times.
Ion exchange water was added to the sheet obtained after washing and dehydration, and the mixture was stirred to obtain a 0.5 mass% cellulose suspension. This cellulose suspension is defibrated for 30 minutes at 21500 rpm using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.). Obtained.
When the cellulose contained in the defibrated cellulose suspension was observed with a transmission electron microscope, it was confirmed that fine fibrous cellulose having a width of about 4 nm was contained. Moreover, it was confirmed by X-ray diffraction that the cellulose maintained the cellulose I type crystal. Moreover, absorption based on a phosphate group was observed at 1320 to 1290 cm ⁻¹ by measurement of an infrared absorption spectrum by FT-IR, and addition of a phosphate group was confirmed.

(Comparative Example 3)
In Example 3, a defibrated cellulose suspension was obtained in the same manner as in Example 3 except that the treatment with the phosphorylating reagent and the alkali treatment were omitted.
When the cellulose contained in the defibrated cellulose suspension was observed with a transmission electron microscope, it was confirmed that fine fibrous cellulose having a width of about 4 nm was contained. Moreover, it was confirmed by X-ray diffraction that the cellulose maintained the cellulose I type crystal. However, addition of a phosphate group was not confirmed by measurement of an infrared absorption spectrum by FT-IR.

[Evaluation]
About Example 3 and Comparative Example 3, it carried out similarly to Examples 1-2 and Comparative Examples 1-2, measured the supernatant yield, and evaluated the dispersibility with respect to resin, and cost. Table 2 shows the measurement results and the evaluation results.

In Example 3 obtained by treating NUKP with a phosphorylating reagent and then defibrating, the yield was high and the dispersibility of the obtained fine fibrous cellulose in the resin was high. Moreover, since the bleaching process of a pulp can be simplified, it was low-cost.
In Comparative Example 3 obtained by fibrillating NUKP without treatment with a phosphorylating reagent, the yield was low. Moreover, since the production efficiency of the fine fibrous slurry was low, the cost was high.

<Chemical treatment with ozone>
[Production of oxygen bleached kraft pulp]
After putting 50 g of hardwood unbleached kraft pulp (LUKP) (solid content mass) made from eucalyptus into a plastic bag and adding 2 parts of 2 molar caustic soda solution to 100 parts of LUKP solid content and mixing well The mixture was transferred to an autoclave equipped with a stirrer. Next, the reaction was carried out in the autoclave at an oxygen pressure of 0.5 MPa and a temperature of 100 ° C. for 60 minutes. After the reaction, the pulp was taken out of the container, washed with 5 times the amount of ion-exchanged water, and then dehydrated with a Buchner to obtain oxygen bleached kraft pulp (LOKP) using LUKP as a raw material.
Also, the oxygen-bleached kraft pulp described above was used except that softwood unbleached kraft pulp (NUKP) made mainly of radiata pine was used instead of LUKP, and 2.5 parts of caustic soda solution was added to 100 parts of NUKP solid content. In the same manner as in the (LOKP) production method, oxygen bleached kraft pulp (NOKP) using NUKP as a raw material was obtained.

Example 4
[Ozone treatment]
After the LUKP was fluffed, sulfuric acid was added to adjust the pH to around 2, thereby obtaining a cellulose suspension having a solid content of 30 g. The obtained cellulose suspension was placed in a 3 L vinylidene chloride tedra bag, and ozone gas (200 g / m ³ ) generated by discharging oxygen was added to 100 parts of the solid content of the cellulose suspension. 1.0 part was added.
Next, the Tedra bag after the addition of ozone was shaken by hand so that the cellulose suspension and ozone sufficiently reacted, and then left at room temperature for 2 hours. After the reaction, the cellulose suspension was taken out, washed with 5 times the amount of ion-exchanged water, and dehydrated with a Buchner.

[Additional oxidation treatment]
In order to further oxidize the ozone-treated cellulose suspension, chlorous acid treatment was performed.
The treatment conditions were a temperature of 70 ° C., a cellulose suspension concentration of 3%, a pH of 4 to 5, and a 3 hour hold. After the reaction, the cellulose suspension was taken out, washed with 5 times the amount of ion-exchanged water, and dehydrated with a Buchner.

[Defibration processing]
After adding ion-exchanged water to the cellulose suspension subjected to the additional oxidation treatment and adjusting the concentration to 0.5%, using a high-speed defibrator (Cleamix-2.2S, manufactured by M Technique Co., Ltd.), 21500 rpm The defibrated cellulose suspension was obtained by defibration for 30 minutes under the conditions.

(Example 5)
A defibrated cellulose suspension was obtained in the same manner as in Example 4 except that the amount of ozone added was 2.5 parts. The ozone addition amount was adjusted by the ozone addition time (the same applies to the following examples).

(Example 6)
A defibrated cellulose suspension was obtained in the same manner as in Example 4 except that the amount of ozone added was 5.0 parts.

(Example 7)
A defibrated cellulose suspension was obtained in the same manner as in Example 4 except that LOKP was used instead of LUKP, and the amount of ozone added was 0.5 parts.

(Example 8)
A defibrated cellulose suspension was obtained in the same manner as in Example 7 except that the amount of ozone added was 1.5 parts.

Example 9
A defibrated cellulose suspension was obtained in the same manner as in Example 7 except that the amount of ozone added was 3.0 parts.

(Example 10)
A defibrated cellulose suspension was obtained in the same manner as in Example 4 except that NUKP was used instead of LUKP.

(Example 11)
A defibrated cellulose suspension was obtained in the same manner as in Example 5 except that NUKP was used instead of LUKP.

(Example 12)
A defibrated cellulose suspension was obtained in the same manner as in Example 6 except that NUKP was used instead of LUKP.

(Example 13)
A defibrated cellulose suspension was obtained in the same manner as in Example 7 except that NOKP was used instead of LOKP.

(Example 14)
A defibrated cellulose suspension was obtained in the same manner as in Example 8 except that NOKP was used instead of LOKP.

(Example 15)
A defibrated cellulose suspension was obtained in the same manner as in Example 9 except that NOKP was used instead of LOKP.

(Comparative Example 4)
A defibrated cellulose suspension was obtained in the same manner as in Example 7 except that ozone was not added.

(Comparative Example 5)
A defibrated cellulose suspension was obtained in the same manner as in Example 13 except that ozone was not added.

(Comparative Example 6)
Instead of LUKP, LBKP obtained by further three-stage bleaching (sequence: D-Ep-D, see Table 4 for the bleaching conditions in the D-Ep-D sequence) was used, and the amount of ozone added Was processed in the same manner as in Example 4 except that 5.0 parts was obtained to obtain a defibrated cellulose suspension.

(Comparative Example 7)
In place of LUKP, NBKP obtained by further three-stage bleaching (sequence: D-Ep-D, see Table 4 for bleaching conditions in the D-Ep-D sequence) is used, and the amount of ozone added Was processed in the same manner as in Example 4 except that 5.0 parts was obtained to obtain a defibrated cellulose suspension.

[Evaluation]
When the cellulose contained in the defibrated cellulose suspension obtained in each of Examples 4 to 15 and Comparative Examples 4 to 7 was observed with a transmission electron microscope, it was found that fine fibrous cellulose having a width of about 4 nm was contained. confirmed. Moreover, it was confirmed by X-ray diffraction that the cellulose of each example maintained the cellulose I type crystal.

  Moreover, about Examples 4-15 and Comparative Examples 4-7, it carried out similarly to Examples 1-2 and Comparative Examples 1-2, measured the supernatant yield, and evaluated the dispersibility with respect to resin, and cost. Table 3 shows the measurement results and the evaluation results.

In Examples 4 to 15 obtained by defibrillation after treating any of LUKP, LOKP, NUKP and NOKP with ozone, the yield was high and the dispersibility of the obtained fine fibrous cellulose in the resin was high. Moreover, since the bleaching process of a pulp can be simplified, it was low-cost.
In Comparative Example 4 obtained by defibrating LOKP without ozone treatment and Comparative Example 5 obtained by defibration of NOKP without ozone treatment, the yield was low. Therefore, the cost was high.
In Comparative Example 6 obtained by defibrating LBKP after ozone treatment, the dispersibility of the obtained fine fibrous cellulose in the resin was low. Moreover, since the pulp was sufficiently bleached, the cost was high.
In Comparative Example 7 obtained by defibrating NBKP after ozone treatment, the dispersibility of the obtained fine fibrous cellulose in the resin was low. Moreover, since the pulp was sufficiently bleached, the cost was high.

<Treatment with enzyme>
(Example 16)
[Enzyme treatment]
The above LUKP was made into a suspension having a solid content concentration of 0.5%, and beaten with a double disc refiner until the irregular CSF (according to JIS P8121 except that the amount of pulp collected was 0.3 g) was 200 ml. . Subsequently, 8 parts of cellulase enzyme “GC220” (Genencor) was added to 100 parts of pulp solids, adjusted to pH 4 to 5 and a temperature of 50 ° C., and treated for 3 hours. After 3 hours, the temperature was set to 90 ° C. to inactivate the enzyme. After the reaction, the pulp was taken out, washed with 5 times the amount of ion-exchanged water, and dehydrated with Buchner.

[Defibration processing]
After adding ion-exchanged water to the enzyme-treated cellulose suspension to adjust the concentration to 0.5%, using a high-speed defibrator (Cleamix-2.2S, manufactured by M Technique Co., Ltd.), conditions of 21500 rpm For 30 minutes to obtain a defibrated cellulose suspension.

(Example 17)
A defibrated cellulose suspension was obtained in the same manner as in Example 16 except that LOKP was used instead of LUKP.

(Example 18)
A defibrated cellulose suspension was obtained in the same manner as in Example 16 except that NUKP was used instead of LUKP.

(Example 19)
A defibrated cellulose suspension was obtained in the same manner as in Example 16 except that NOKP was used instead of LUKP.

(Comparative Example 8)
A defibrated cellulose suspension was obtained in the same manner as in Example 16 except that LBKP was used instead of LUKP.

(Comparative Example 9)
A defibrated cellulose suspension was obtained in the same manner as in Example 16 except that NBKP was used instead of LUKP.

[Evaluation]
When the cellulose contained in the defibrated cellulose suspension obtained in each of Examples 16 to 19 and Comparative Examples 8 to 9 was observed with a transmission electron microscope, it was found that fine fibrous cellulose having a width of about 4 nm was contained. confirmed. Moreover, it was confirmed by X-ray diffraction that the cellulose of each example maintained the cellulose I type crystal.

  About Examples 16-19 and Comparative Examples 8-9, it carried out similarly to Examples 1-2 and Comparative Examples 1-2, measured the supernatant yield, and evaluated the dispersibility with respect to resin, and cost. Table 5 shows the measurement results and the evaluation results.

In Examples 16 to 19 obtained by enzymatically treating any of LUKP, LOKP, NUKP and NOKP and then defibrating, the yield was high and the dispersibility of the obtained fine fibrous cellulose in the resin was high. Moreover, since the bleaching process of a pulp can be simplified, it was low-cost.
In Comparative Example 8 obtained by performing fibrillation after enzymatic treatment of LBKP, the dispersibility of the obtained fine fibrous cellulose in the resin was low. Moreover, since the pulp was sufficiently bleached, the cost was high.
In Comparative Example 9 obtained by carrying out enzyme treatment of NBKP and then defibrating, the dispersibility of the obtained fine fibrous cellulose in the resin was low. Moreover, since the pulp was sufficiently bleached, the cost was high.

Claims (4)

The fiber width is 2 nm or more and 1000 nm or less,
At least one kind of substitution selected from a phosphoric acid group obtained by chemically modifying a part of the hydroxyl group of cellulose, a carbonyl group substituted by a part of the hydroxyl group of cellulose , and a carboxy group obtained by chemically modifying or replacing a part of the hydroxyl group of cellulose. Fibrous cellulose having a group and derived from unbleached chemical pulp or oxygen bleached chemical pulp. A resin composition comprising the fibrous cellulose according to claim 1 and a resin. The resin composition according to claim 2, wherein the resin includes one or more selected from polyethylene, polystyrene, acrylic resin, polycarbonate, and polyethylene terephthalate. The fiber width is 2 nm or more and 1000 nm or less, and a phosphoric acid group obtained by chemically modifying a part of the hydroxyl group of cellulose, a carbonyl group substituted by a part of the hydroxyl group of cellulose, and a part of the hydroxyl group of cellulose are chemically modified or substituted. Comprising fibrous cellulose having at least one substituent selected from carboxy groups and derived from unbleached chemical pulp or oxygen bleached chemical pulp;
A cellulose suspension having a supernatant yield of 52% by mass or more and 89% by mass or less calculated by the following method.
<Calculation method>
Using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B), a slurry in which ion-exchanged water is added to the cellulose suspension to adjust the solid content concentration to 0.2% by mass (referred to as slurry A). Centrifugation is performed under the condition of 12000 G, and the obtained supernatant (referred to as slurry B) is recovered and the solid content concentration of the supernatant is measured. Subsequently, the supernatant yield of fibrous cellulose is calculated | required based on a following formula.
Supernatant yield (% by mass) = {(solid content concentration of slurry B) / (solid content concentration of slurry A)} × 100