JP2020063351A - Fibrous cellulose, fibrous cellulose dispersion and production method of fibrous cellulose - Google Patents

Abstract

To provide fine fibrous cellulose capable of exhibiting excellent coating suitability when added to a coating material.SOLUTION: The present invention relates to fibrous cellulose having a fiber width of 1000 nm or smaller, in which when the fibrous cellulose is dispersed in water to form a dispersion having the viscosity at 23°C of 2500 mPas, and the dispersion is agitated at a predetermined agitation condition, the viscosity change rate calculated by a following formula becomes within ±50%. Viscosity change rate (%)=(viscosity after agitation - viscosity before agitation)/viscosity before agitation×100.SELECTED DRAWING: None

Description

  The present invention relates to fibrous cellulose, a fibrous cellulose dispersion, and a method for producing fibrous cellulose.

  BACKGROUND ART Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products and the like. As cellulose fibers, in addition to fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, fine fibrous cellulose having a fiber diameter of 1 μm or less is known. Fine fibrous cellulose has been attracting attention as a new material, and its uses are diverse.

  Fine fibrous cellulose may be used, for example, as an additive for paints. In this case, the fine fibrous cellulose may function as a viscosity modifier in the paint. For example, Patent Document 1 discloses a bright pigment dispersion containing water, a viscosity modifier (A) and a scaly bright pigment (B). Further, Patent Document 2 discloses a bright pigment dispersion containing water, a scaly aluminum pigment and a cellulosic viscosity modifier. In Patent Documents 1 and 2, the use of cellulose nanofibers as a viscosity modifier is examined.

International Publication No. 2018/012014 International Publication No. 2017/175468

  Conventionally, cellulose nanofibers have been used in paints for the purpose of enhancing the dispersibility of pigments and the like. However, for such paints, attention has not been paid to the decrease in coating suitability due to the change in viscosity (thixotropic property) caused by applying a share before coating, and there is room for improvement in coating suitability. It was

  Therefore, in order to solve the problems of the prior art, the present inventors have advanced the study for the purpose of providing fine fibrous cellulose capable of exhibiting excellent coating suitability when added to a coating material. It was

As a result of intensive studies to solve the above problems, the present inventors have prepared a dispersion liquid by dispersing fine fibrous cellulose in water, and when stirring under predetermined conditions, the viscosity change rate before and after stirring ( It has been found that the coating suitability of the coating material can be enhanced by obtaining fine fibrous cellulose capable of adjusting (%) to a predetermined range and adding the fine fibrous cellulose to the coating material.
Specifically, the present invention has the following configurations.

[1] A fibrous cellulose having a fiber width of 1000 nm or less,
When fibrous cellulose is dispersed in water to obtain a dispersion having a viscosity of 2500 mPa · s at 23 ° C. and the dispersion is stirred under the following stirring conditions, the viscosity change rate calculated by the following formula is within ± 50%. Fibrous cellulose that becomes:
Viscosity change rate (%) = (viscosity after stirring−viscosity before stirring) / viscosity before stirring × 100
(Stirring condition)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. was put into a cylindrical container having a diameter of 10 cm up to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a central width of 2 cm, and an end width of 1 cm was used. While maintaining the state where the center of the liquid surface is depressed by 2 cm, the mixture is stirred at 23 ° C. for 24 hours.
[2] The fibrous cellulose according to [1], wherein the fibrous cellulose has a degree of polymerization of 300 or more and 500 or less.
[3] The fibrous cellulose is the fibrous cellulose according to [1] or [2], which has an ionic substituent.
[4] The fibrous cellulose according to [3], wherein the amount of ionic substituents in the fibrous cellulose is 0.10 mmol / g or more and 1.50 mmol / g or less.
[5] The fibrous cellulose according to [3] or [4], wherein the ionic substituent is a phosphoric acid group or a substituent derived from a phosphoric acid group.
[6] When a dispersion liquid is prepared by dispersing fibrous cellulose in water so as to be 0.4% by mass, the viscosity of the dispersion liquid at 23 ° C. is 200 mPa · s or more and 3000 mPa · s or less [1] to [ 5] The fibrous cellulose according to any one of 5).
[7] The fibrous cellulose according to any one of [1] to [6] for paints.
[8] A fibrous cellulose dispersion obtained by dispersing the fibrous cellulose according to any one of [1] to [7] in water.
[9] a step of subjecting cellulose fibers to a defibration treatment to obtain fibrous cellulose having a fiber width of 1000 nm or less,
A method for producing fibrous cellulose, comprising the step of subjecting fibrous cellulose to a treatment for reducing thixotropy.
[10] The method for producing fibrous cellulose according to [9], wherein the step of subjecting to a thixotropy treatment is a step of setting the degree of polymerization of fibrous cellulose to 300 or more and 500 or less.
[11] The method for producing fibrous cellulose according to [9] or [10], wherein the step of performing the thixotropy treatment is an ozone treatment step.
[12] The method for producing fibrous cellulose according to any one of [9] to [11], further including a step of introducing an ionic substituent into the cellulose fiber before the step of obtaining fibrous cellulose.

  According to the present invention, it is possible to obtain fine fibrous cellulose that can exhibit excellent coating suitability when added to a coating material.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and the electrical conductivity for fibrous cellulose having a phosphate group. FIG. 2 is a graph showing the relationship between the amount of dropped NaOH and the electrical conductivity for fibrous cellulose having a carboxy group.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

(Fine fibrous cellulose)
The present invention relates to fibrous cellulose having a fiber width of 1000 nm or less. In addition, in this specification, the fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose. Here, when the fibrous cellulose of the present invention is dispersed in water to obtain a dispersion having a viscosity at 23 ° C. of 2500 mPa · s, and the dispersion is stirred under the following stirring conditions, the viscosity calculated by the following formula The rate of change is within ± 50%.
Viscosity change rate (%) = (viscosity after stirring−viscosity before stirring) / viscosity before stirring × 100
(Stirring condition)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. was put into a cylindrical container having a diameter of 10 cm up to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a central width of 2 cm, and an end width of 1 cm was used. While maintaining the state where the center of the liquid surface is depressed by 2 cm, the mixture is stirred at 23 ° C. for 24 hours.

  In the present invention, the fine fibrous cellulose is used as a dispersion liquid, and the viscosity change rate when stirring is performed under the above conditions is within ± 50%, thereby exhibiting excellent coating suitability when added to a coating material. A fine fibrous cellulose capable of being obtained is obtained. Since the dispersion liquid in which the fine fibrous cellulose of the present invention is dispersed has low thixotropy, it can exhibit excellent coating suitability. For example, the coating containing the fine fibrous cellulose of the present invention is stored, or the viscosity change of the coating is suppressed even when transported, so that the liquid dripping during coating is suppressed and addition of a pigment or the like is suppressed. The sedimentation of the agent can be suppressed. Further, even when the paint containing the fine fibrous cellulose of the present invention is stirred for a long time, even when a relatively strong shear is applied to the paint, liquid sagging or a pigment caused by the decrease in the viscosity of the paint. It is possible to effectively suppress sedimentation of additives such as.

  The fine fibrous cellulose of the present invention is preferably used for paints, and as described above, the coating suitability of paints can be enhanced. In addition, when the fine fibrous cellulose of the present invention is used as an additive for paints, it is possible to improve the designability and strength after coating. Therefore, the coating layer formed by applying the coating material can exhibit excellent designability and scratch resistance.

  The viscosity change rate of the dispersion liquid calculated by the above formula may be within ± 50%, preferably within ± 40%, more preferably within ± 30%, and more preferably within ± 25%. It is more preferable that it is within ± 20%, and it is particularly preferable. The viscosity change rate of the dispersion liquid calculated by the above formula may be 0%. Usually, since the viscosity of a dispersion liquid is often lowered by applying a shear to the dispersion liquid, the viscosity change rate calculated by the above formula is often a negative value. That is, the viscosity change rate of the dispersion is preferably -50% or more and 0% or less, more preferably -40% or more and 0% or less, and further preferably -30% or more and 0% or less. , -25% or more and 0% or less is more preferable, and -20% or more and 0% or less is particularly preferable. Incidentally, the viscosity change rate of the dispersion calculated by the above formula, for example, the type and conditions of the treatment for the fine fibrous cellulose, the degree of polymerization of the fine fibrous cellulose and the amount of ionic substituents are controlled within respective appropriate ranges. It is achieved by doing.

  In the present specification, the viscosity before and after stirring used for calculating the viscosity change rate of the dispersion is a viscosity value after 1 minute from the start of measurement at a rotation speed of 6 rpm at 23 ° C. using a B-type viscometer. . As the B-type viscometer, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD Inc. can be used. Since the viscosity before stirring is the viscosity of the dispersion liquid adjusted so that the viscosity becomes about 2500 mPa · s, it is preferable that the actually measured value of the viscosity of the dispersion liquid be 2500 mPa · s, but the error is about ± 15%. May have occurred. That is, in the formula for calculating the rate of change in viscosity, the viscosity before stirring is the actually measured viscosity of the dispersion liquid adjusted to a viscosity of about 2500 mPa · s, and the viscosity was measured using a B-type viscometer at 23 ° C. It is a measured viscosity value 1 minute after the start of measurement at a speed of 6 rpm. However, when the viscosity before stirring is measured, the fine fibrous cellulose dispersion liquid is placed in a cylindrical container having a diameter of 10 cm to a height of 5 cm, stirred with a disperser at 1500 rpm for 5 minutes, and 1 minute from the end of stirring. The measurement will be performed later. Further, when adjusting the viscosity of the dispersion liquid before stirring to about 2500 mPa · s, the addition amount of the fine fibrous cellulose to be used is appropriately adjusted. For example, by adjusting the content of the fine fibrous cellulose with respect to the total mass of the dispersion liquid to 0.3 to 3.0 mass%, the viscosity of the dispersion liquid before stirring can be adjusted to about 2500 mPa · s.

  When measuring the viscosity after stirring in the formula for calculating the rate of change in viscosity, first, the dispersion liquid used for viscosity measurement before stirring is further stirred by a stirrer. In this case, the pre-stirring dispersion liquid was placed in a cylindrical container having a diameter of 10 cm, and the fine fibrous cellulose dispersion liquid was put up to a height of 5 cm to obtain an elliptical stirrer having a length of 5 cm, a central width of 2 cm, and an end width of 1 cm. Using the above, the mixture is stirred for 24 hours while maintaining the state where the center of the liquid surface is depressed by 2 cm. The liquid temperature during stirring should be maintained at 23 ° C. Then, 1 minute after the end of stirring, the viscosity is measured using a B-type viscometer, the rotation speed is 6 rpm at 23 ° C., and the viscosity value 1 minute after the start of measurement is the viscosity after stirring.

  When the fine fibrous cellulose of the present invention is dispersed in water to a concentration of 0.4% by mass to form a dispersion liquid, the viscosity of the dispersion liquid at 23 ° C. is preferably 200 mPa · s or more, and 300 mPa · s. More preferably, it is more preferably 350 mPa · s or more, still more preferably 400 mPa · s or more. Further, the viscosity of the dispersion liquid at 23 ° C. is preferably 3000 mPa · s or less, and more preferably 2500 mPa · s or less. The viscosity of the dispersion liquid having a fine fibrous cellulose concentration of 0.4 mass% can be measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions are 23 ° C., the rotation speed is 3 rpm, and the viscosity is measured 3 minutes after the start of measurement.

  The fibrous cellulose of the present invention is fine fibrous cellulose having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is more preferably 100 nm or less, further preferably 8 nm or less.

  The fiber width of the fibrous cellulose can be measured by, for example, observing with an electron microscope. The average fiber width of the fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Especially preferred. By setting the average fiber width of the fibrous cellulose to 2 nm or more, it is possible to prevent the fibrous cellulose from being dissolved in water and more easily exhibit the effect of improving the strength, rigidity, and dimensional stability of the fibrous cellulose. it can. The fibrous cellulose is, for example, monofilament cellulose.

  The average fiber width of the fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-covered grid to obtain a TEM observation sample. And When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Then, 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 fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.

(1) One straight line X is drawn at an arbitrary position in the observed 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 intersecting the straight line X and the straight line Y is visually read from the observed image satisfying the above conditions. In this way, at least three sets of observation images of the surface portions that do not overlap each other are obtained. Then, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thereby, the fiber width of at least 20 fibers × 2 × 3 = 120 fibers is read. Then, the average value of the read fiber widths is set as the average fiber width of the fibrous cellulose.

  The fiber length of the fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, breakage of the crystalline region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose within an appropriate range. The fiber length of the fibrous cellulose can be determined by image analysis using TEM, SEM, or AFM, for example.

  The fibrous cellulose preferably has a type I crystal structure. Here, the fact that the fibrous cellulose has an I-type crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418Å) monochromated with graphite. Specifically, it can be identified by having typical peaks at two positions near 2θ = 14 ° or more and 17 ° or less and around 2θ = 22 ° or more and 23 ° or less. The proportion of the I-type crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The crystallinity is determined by measuring the X-ray diffraction profile and using the pattern in a conventional manner (Seagal et al., Textile Research Journal, Vol. 29, page 786, 1959).

  The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit or more, it is easy to form a sheet containing fine fibrous cellulose. Further, it is easy to obtain sufficient thickening when the solvent dispersion is prepared. It is preferable that the axial ratio is not more than the above upper limit because handling such as dilution becomes easy when handling fibrous cellulose as an aqueous dispersion.

  The fibrous cellulose in the present embodiment has, for example, both a crystalline region and an amorphous region. In particular, fine fibrous cellulose having both a crystalline region and an amorphous region and a high axial ratio is realized by the method for producing fine fibrous cellulose described later.

  The fibrous cellulose in the present embodiment has, for example, at least one of an ionic substituent and a nonionic substituent. From the viewpoint of improving the dispersibility of the fibers in the dispersion medium and enhancing the defibration efficiency in the defibration treatment, it is more preferable that the fibrous cellulose has an ionic substituent. The ionic substituent may include, for example, one or both of an anionic group and a cationic group. The nonionic substituent may include, for example, an alkyl group and an acyl group. In this embodiment, it is particularly preferable to have an anionic group as the ionic substituent.

  Examples of the anionic group as the ionic substituent include a phosphoric acid group or a substituent derived from a phosphoric acid group (sometimes referred to simply as a phosphoric acid group), a carboxy group or a substituent derived from a carboxy group (simply a carboxy group). And at least one selected from the group consisting of a sulfone group and a substituent derived from a sulfone group (may be simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxy group. More preferably, it is one type, and particularly preferably a phosphate group. The fine fibrous cellulose having a phosphoric acid group can exhibit more excellent coating suitability when added to a coating material.

The phosphoric acid group or the substituent derived from the phosphoric acid group is, for example, a substituent represented by the following formula (1), and is generalized as a phosphorous acid group or a substituent derived from a phosphorous acid.
The phosphoric acid group is a divalent functional group corresponding to, for example, phosphoric acid from which a hydroxy group has been removed. Specifically, it is a group represented by —PO ₃ H ₂ . Substituents derived from a phosphoric acid group include substituents such as salts of phosphoric acid groups and phosphoric acid ester groups. The substituent derived from the phosphoric acid group may be contained in the fibrous cellulose as a group in which the phosphoric acid group is condensed (for example, a pyrophosphoric acid group). The phosphoric acid group may be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from the phosphoric acid group may be a salt of a phosphorous acid group, a phosphorous acid ester group, or the like. Good.

In the formula (1), a, b and n are natural numbers (however, a = b × m). Of α ¹ , α ² , ..., α ⁿ and α ′, a is O ⁻ , and the rest is either R or OR. Note that all of αn and α ′ may be O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group, respectively. It is a hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof.

  Examples of the saturated-linear hydrocarbon group include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like. Examples of the saturated-branched hydrocarbon group include, but are not limited to, i-propyl group and t-butyl group. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-straight chain hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated-branched hydrocarbon group include, but are not limited to, i-propenyl group and 3-butenyl group. Examples of the unsaturated-cyclic hydrocarbon group include a cyclopentenyl group and a cyclohexenyl group, but are not particularly limited. Examples of the aromatic group include, but are not limited to, a phenyl group and a naphthyl group.

  In addition, the derivative group in R is a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted to the main chain or side chain of the above-mentioned various hydrocarbon groups. Examples thereof include, but are not limited to, groups. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R in the above range, the molecular weight of the phosphoric acid group can be set in an appropriate range, the permeation into the fiber raw material is facilitated, and the yield of the fine cellulose fiber is increased. You can also

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or more cations composed of organic substances include aliphatic ammonium and aromatic ammonium, and examples of monovalent or more cations composed of inorganic substances include alkali metal ions such as sodium, potassium or lithium, Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but are not particularly limited. These may be applied alone or in combination of two or more. The cation having a valence of 1 or more consisting of an organic substance or an inorganic substance is preferably sodium or potassium ion which is less likely to be yellowed when a β-containing fiber raw material is heated and is industrially usable, but is not particularly limited.

The amount of the ionic substituent introduced into the fibrous cellulose is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.40 mmol per 1 g (mass) of the fibrous cellulose. / G or more is more preferable, and 0.60 mmol / g or more is particularly preferable. The amount of the ionic substituent introduced into the fibrous cellulose is, for example, preferably 3.65 mmol / g or less, and more preferably 3.00 mmol / g or less per 1 g (mass) of the fibrous cellulose. It is more preferably 0.50 mmol / g or less, further preferably 2.00 mmol / g or less, even more preferably 1.50 mmol / g or less, and particularly preferably 1.00 mmol / g or less. preferable. Here, the denominator in the unit mmol / g represents the mass of the fibrous cellulose when the counter ion of the ionic substituent is a hydrogen ion (H ⁺ ). By setting the introduction amount of the ionic substituent within the above range, the fiber raw material can be easily made finer and the stability of the fibrous cellulose can be enhanced. Further, by setting the introduction amount of the ionic substituent within the above range, it is possible to reduce the thixotropy of the paint when the fine fibrous cellulose is added to the paint, which makes the coating suitability more effective. Can be increased.

  The amount of the ionic substituent introduced into the fibrous cellulose can be measured, for example, by a conductivity titration method. In the measurement by the conductivity titration method, the introduction amount is measured by determining the change in conductivity while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fibrous cellulose.

  FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and the electrical conductivity for fibrous cellulose having a phosphate group. The amount of phosphate groups introduced into fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, a defibration process similar to the defibration process step described below may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin. Next, a change in electric conductivity is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in FIG. 1 is obtained. As shown in FIG. 1, the electrical conductivity sharply decreases at first (hereinafter, referred to as “first region”). After that, the conductivity starts to slightly increase (hereinafter, referred to as “second region”). After that, the increment of conductivity increases (hereinafter, referred to as “third region”). The boundary point between the second region and the third region is defined as the point where the second derivative of the conductivity, that is, the amount of change in the conductivity increment (slope) is maximum. Thus, three regions appear on the titration curve. Of these, the amount of alkali required in the first region is equal to the amount of strong acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weak acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid groups undergo condensation, apparently weak acidic groups are lost, and the amount of alkali required in the second region is smaller than the amount of alkali required in the first region. On the other hand, the amount of strongly acidic groups is the same as the amount of phosphorus atoms regardless of the presence or absence of condensation. For this reason, the term "phosphoric acid group introduced amount (or phosphoric acid group amount)" or "substituent group introduced amount (or substituent amount)" simply means the strongly acidic group amount. Therefore, the value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve obtained above by the solid content (g) in the slurry to be titrated is the phosphate group introduction amount (mmol / g).

  FIG. 2 is a graph showing the relationship between the amount of dropped NaOH and the electrical conductivity for fibrous cellulose having a carboxy group. The amount of the carboxy group introduced into the fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, a defibration process similar to the defibration process step described below may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin. Then, a change in electrical conductivity is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. In the titration curve, as shown in FIG. 2, after the electrical conductivity decreases, the first region until the conductivity increase (slope) becomes substantially constant, and then the conductivity increase (slope) increases. It is divided into the second area. The boundary point between the first region and the second region is defined as a point at which the second derivative of the conductivity, that is, the amount of change in the increment (slope) of the conductivity is maximized. Then, a value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated is the introduced amount of the carboxy group ( mmol / g).

In addition, since the denominator is the mass of the acid type fibrous cellulose, the carboxy group introduction amount (mmol / g) described above has the carboxy group amount of the acid type fibrous cellulose (hereinafter, the carboxy group amount (the acid type ))) Is shown. On the other hand, when the cation of the carboxy group is replaced with an arbitrary cation C so that the cation has a charge equivalent, the denominator should be converted into the mass of the fibrous cellulose when the cation C is the counterion. Thus, the amount of carboxy groups in the fibrous cellulose having the cation C as a counterion (hereinafter, the amount of carboxy groups (C type)) can be obtained. That is, it is calculated by the following calculation formula.
Amount of carboxy groups (C type) = amount of carboxy groups (acid type) / [1+ (W-1) × (amount of carboxy groups (acid type)) / 1000]
W: Formula weight per valence of cation C (for example, 23 for Na and 9 for Al)

  In the measurement of the amount of substituents by the titration method, when the titration interval of the sodium hydroxide aqueous solution is too short, the amount of substituents may be lower than it should be. Therefore, an appropriate titration interval, for example, 0.1N It is desirable to titrate 50 μL of the sodium aqueous solution every 30 seconds.

  The degree of polymerization of the fine fibrous cellulose is preferably 300 or more, more preferably 320 or more, and further preferably 340 or more. The degree of polymerization of the fine fibrous cellulose is preferably 500 or less, more preferably 490 or less, and even more preferably 460 or less. By setting the degree of polymerization of the fine fibrous cellulose within the above range, the thixotropy of the paint when the fine fibrous cellulose is added to the paint can be reduced (low thixotropy), and thus the coating suitability can be further improved. Can be effectively increased.

The degree of polymerization of the fine fibrous cellulose is a value calculated from the pulp viscosity measured according to Tappi T230. Specifically, the fine fibrous cellulose to be measured is dispersed in an aqueous solution of copper ethylenediamine (viscosity η1), and the blank viscosity (dispersion η0) measured only with the dispersion medium is measured. The viscosity (ηsp) and the intrinsic viscosity ([η]) are measured according to the following formulas.
ηsp = (η1 / η0) -1
[Η] = ηsp / (c (1 + 0.28 × ηsp))
Here, c in the formula represents the concentration of fine fibrous cellulose at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) is calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

  In the present invention, in particular, by setting the degree of polymerization of the fine fibrous cellulose to 300 or more and 500 or less, and the amount of the ionic substituent in the fine fibrous cellulose to 0.4 mmol / g or more and 1.0 mmol / g or less, When the fine fibrous cellulose is added to the paint, the thixotropy of the paint can be further reduced, whereby the applicability of the paint can be more effectively enhanced. Setting the degree of polymerization of fine fibrous cellulose and the amount of ionic substituents to appropriate ranges contributes to the low thixotropy of the dispersion liquid in which fine fibrous cellulose is dispersed, and thereby the coating suitability of the paint. Is expected to increase.

(Method for producing fine fibrous cellulose)
<Fiber raw material>
Fine fibrous cellulose is manufactured from a fiber raw material containing cellulose. The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulps include, for example, wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, and examples thereof include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton-based pulp such as cotton linter and cotton lint, and non-wood-based pulp such as hemp, straw and bagasse. The deinked pulp is not particularly limited, and examples thereof include deinked pulp made from waste paper. The pulp of this embodiment may be used alone or as a mixture of two or more kinds. Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. Further, among wood pulp, a viewpoint of a high yield of fine fibrous cellulose at the time of defibration treatment with a large cellulose ratio, and a long fiber fine fibrous cellulose with a small decomposition of cellulose in the pulp and a large axial ratio can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. The viscosity tends to increase when long-fiber fine fibrous cellulose having a large axial ratio is used.

  As the fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used. Further, instead of the fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan may be used.

<Phosphate group introduction step>
When the fine fibrous cellulose has a phosphate group, the step of producing the fine fibrous cellulose includes a phosphate group introduction step. In the phosphoric acid group introduction step, at least one compound selected from compounds capable of introducing a phosphoric acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose (hereinafter, also referred to as “compound A”) Is a step of acting on the fiber raw material containing. By this step, a phosphoric acid group-introduced fiber is obtained.

  In the phosphate group introducing step according to the present embodiment, the reaction of the fiber raw material containing cellulose and the compound A is performed in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). May be. On the other hand, the reaction of the fiber raw material containing cellulose and the compound A may be carried out in the state where the compound B does not exist.

  As an example of a method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state can be mentioned. Of these, it is preferable to use a fiber raw material in a dry state or a wet state, and particularly preferable to use a fiber raw material in a dry state, since the reaction is highly uniform. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. The compound A and the compound B may be added to the fiber raw material in the form of powder or in the form of a solution dissolved in a solvent, or in the state of being heated to a melting point or higher and being melted. Of these, since the reaction is highly uniform, it is preferable to add them in the form of a solution dissolved in a solvent, particularly in the state of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, separately, or as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid, and then taken out. The solution may be added dropwise. Also, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B are respectively added to the fiber raw material, and then excess compound A and compound B are squeezed or filtered. May be removed.

  Examples of the compound A used in this embodiment include compounds having a phosphorus atom and capable of forming an ester bond with cellulose. Specifically, phosphoric acid or a salt thereof, phosphorous acid or a salt thereof, dehydration condensation Examples thereof include phosphoric acid or a salt thereof, phosphoric anhydride (diphosphorus pentoxide), and the like, but are not particularly limited. As phosphoric acid, those having various purities can be used, and for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydrated condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of the phosphate, phosphite, and dehydrated condensed phosphoric acid salt include lithium salt, sodium salt, potassium salt, and ammonium salt of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid. It can be the degree of harmony. Of these, the efficiency of introduction of the phosphate group is high, the defibration efficiency is more easily improved in the defibration step described later, is low cost, and from the viewpoint of easy industrial application, phosphoric acid, phosphoric acid A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.

  The addition amount of the compound A to the fiber raw material is not particularly limited, but when the addition amount of the compound A is converted into the phosphorus atomic weight, the addition amount of the phosphorus atom to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by controlling the amount of phosphorus atoms added to the fiber raw material to be not more than the above upper limit, the effect of improving the yield and the cost can be balanced.

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of the compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.
From the viewpoint of improving the homogeneity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the homogeneity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

  The amount of the compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100% by mass or more and 350% by mass or less.

  In the reaction of the cellulose-containing fiber raw material with the compound A, in addition to the compound B, for example, amides or amines may be contained in the reaction system. Examples of the amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Of these, triethylamine is known to work particularly as a good reaction catalyst.

  In the phosphoric acid group introduction step, it is preferable to add or mix the compound A or the like to the fiber raw material and then subject the fiber raw material to heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which the phosphoric acid group can be efficiently introduced while suppressing thermal decomposition or hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. Further, for the heat treatment, equipment having various heat mediums can be used, and for example, a stirring dryer, a rotary dryer, a disc dryer, a roll heater, a plate heater, a fluidized bed dryer, an air stream. A drying device, a reduced pressure drying device, an infrared heating device, a far infrared heating device, or a microwave heating device can be used.

  In the heat treatment according to the present embodiment, for example, the compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and the compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. This makes it possible to suppress unevenness in the concentration of the compound A in the fiber raw material and more uniformly introduce the phosphate group into the surface of the cellulose fiber contained in the fiber raw material. This is because when water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules due to the surface tension and similarly moves to the surface of the fiber raw material (that is, uneven concentration of compound A It is thought to be due to the fact that it can be suppressed.

  In addition, the heating device used for the heat treatment always keeps, for example, the water retained by the slurry and the water generated by the dehydration condensation (phosphoric acid esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the device can be discharged to the outside of the device system. An example of such a heating device is a blower type oven. By constantly discharging water in the device system, in addition to suppressing the hydrolysis reaction of the phosphoric acid ester bond, which is the reverse reaction of phosphoric acid esterification, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. it can. Therefore, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

  The heat treatment time is, for example, preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and more preferably 10 seconds or more and 800 seconds or less after the water is substantially removed from the fiber raw material. Is more preferable. In the present embodiment, the introduction amount of the phosphate group can be set within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

  The phosphate group introducing step may be performed at least once, but may be repeated twice or more. By carrying out the phosphate group introduction step twice or more, many phosphate groups can be introduced into the fiber raw material. In the present embodiment, an example of a preferable mode is a case where the phosphate group introducing step is performed twice.

  The amount of phosphate groups introduced into the fibrous cellulose is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.40 mmol per 1 g (mass) of the fine fibrous cellulose. / G or more is more preferable, and 0.60 mmol / g or more is particularly preferable. The amount of phosphate groups introduced into the fibrous cellulose is, for example, preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less per 1 g (mass) of the fine fibrous cellulose. It is more preferably 0.50 mmol / g or less, further preferably 2.00 mmol / g or less, even more preferably 1.50 mmol / g or less, and particularly preferably 1.00 mmol / g or less. preferable. When the amount of the phosphate group introduced is within the above range, the fiber raw material can be easily made finer and the stability of the fine fibrous cellulose can be increased. Further, by setting the introduction amount of the ionic substituent within the above range, it is possible to reduce the thixotropy of the paint when the fine fibrous cellulose is added to the paint, which makes the coating suitability more effective. Can be increased.

<Carboxy group introduction step>
When the fine fibrous cellulose has a carboxy group, the production process of the fine fibrous cellulose includes a carboxy group introduction step. In the step of introducing a carboxy group, a fiber raw material containing cellulose is subjected to oxidation treatment such as ozone oxidation, Fenton's method, TEMPO oxidation treatment, or a compound having a carboxylic acid-derived group or a derivative thereof, or a carboxylic acid-derived group. It is carried out by treating the compound with an acid anhydride or a derivative thereof.

  The compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and citric acid and aconitic acid. Examples include tricarboxylic acid compounds. In addition, the derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an imidized product of an acid anhydride of a compound having a carboxy group and a derivative of an acid anhydride of a compound having a carboxy group. The imidization product of an acid anhydride of a compound having a carboxy group is not particularly limited, and examples thereof include imidization products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalic acid imide.

  The acid anhydride of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. An acid anhydride is mentioned. Further, the derivative of the acid anhydride of the compound having a group derived from a carboxylic acid is not particularly limited, but for example, a compound having a carboxy group such as dimethyl maleic anhydride, diethyl maleic anhydride, or diphenyl maleic anhydride. An acid anhydride in which at least a part of hydrogen atoms is substituted with a substituent such as an alkyl group or a phenyl group can be used.

  When the TEMPO oxidation treatment is carried out in the carboxy group introduction step, it is preferable to carry out the treatment, for example, under the condition that the pH is 6 or more and 8 or less. Such treatment is also referred to as neutral TEMPO oxidation treatment. For the neutral TEMPO oxidation treatment, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst are used. It can be performed by adding nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by allowing sodium chlorite to coexist, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group.

  Further, the TEMPO oxidation treatment may be performed under the condition that the pH is 10 or more and 11 or less. Such treatment is also referred to as alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be performed, for example, by adding nitroxyl radicals such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidant to pulp as a fiber raw material. .

  The introduction amount of the carboxy group to the fibrous cellulose varies depending on the kind of the substituent, but when introducing the carboxy group by TEMPO oxidation, for example, it is 0.10 mmol / g or more per 1 g (mass) of the fine fibrous cellulose. It is preferably 0.20 mmol / g or more, more preferably 0.40 mmol / g or more, particularly preferably 0.60 mmol / g or more. The amount of carboxy groups introduced into the fibrous cellulose is preferably 2.50 mmol / g or less, more preferably 2.00 mmol / g or less, and even more preferably 1.50 mmol / g or less. , 1.00 mmol / g or less is particularly preferable. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol / g or less per 1 g (mass) of fine fibrous cellulose. By setting the amount of the carboxy group introduced within the above range, the fiber raw material can be easily made finer, and the stability of the fibrous cellulose can be enhanced. Further, by setting the introduction amount of the carboxy group within the above range, it is possible to reduce the thixotropy of the paint when the fine fibrous cellulose is added to the paint, thereby more effectively improving the coating suitability. You can

<Washing process>
In the method for producing fine fibrous cellulose according to the present embodiment, a washing step can be performed on the ionic substituent-introduced fiber, if necessary. The washing step is performed, for example, by washing the ionic substituent-introduced fiber with water or an organic solvent. The washing step may be performed after each step described below, and the number of washings performed in each washing step is not particularly limited.

<Alkali treatment process>
In the case of producing fine fibrous cellulose, the fiber raw material may be subjected to alkali treatment between the ionic substituent introduction step and the defibration treatment step described later. The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing the ionic substituent-introduced fiber in an alkali solution.

  The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkali compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among these, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent such as an alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

  The temperature of the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersing time of the ionic substituent-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less, based on the absolute dry mass of the ionic substituent-introduced fiber. The following is more preferable.

  In order to reduce the amount of the alkaline solution used in the alkaline treatment step, the ionic substituent-introduced fiber may be washed with water or an organic solvent after the ionic substituent introduction step and before the alkali treatment step. After the alkali treatment step and before the defibration treatment step, it is preferable to wash the alkali-treated ionic substituent-introduced fiber with water or an organic solvent from the viewpoint of improving the handleability.

<Acid treatment step>
When producing fine fibrous cellulose, acid treatment may be performed on the fiber raw material between the step of introducing an ionic substituent and the defibration treatment step described below. For example, the step of introducing an ionic substituent, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.

  The method of acid treatment is not particularly limited, and examples thereof include a method of immersing the fiber raw material in an acid solution containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic liquid used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid and boric acid. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

  The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but for example, is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less based on the absolute dry mass of the fiber raw material. Is more preferable.

<Disentanglement treatment>
Fine fibrous cellulose is obtained by defibrating the ionic substituent-introduced fiber in the defibrating process. In the defibration processing step, for example, a defibration processing device can be used. The defibration processing device is not particularly limited, but includes, for example, a high-speed defibration machine, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision crusher, a ball mill, a bead mill, a disc refiner, a conical refiner, a twin-screw machine. A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, a beater, or the like can be used. Among the above-mentioned defibration treatment devices, it is more preferable to use a high-speed defibration machine, a high-pressure homogenizer, and an ultrahigh-pressure homogenizer, which are less affected by the grinding media and less likely to cause contamination.

  In the defibration treatment step, for example, the ionic substituent-introduced fiber is preferably diluted with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and propylene glycol monomethyl ether. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

  The solid content concentration of the fine fibrous cellulose during the defibration treatment can be set appropriately. Further, the slurry obtained by dispersing the ionic substituent-introduced fibers in the dispersion medium may contain solid components other than the ionic substituent-introduced fibers such as urea having hydrogen bonding property.

<Low thixotropic treatment>
The method for producing fine fibrous cellulose of the present invention preferably includes a step of further performing a low thixotropy treatment in addition to the steps described above. Specifically, as described above, a step of subjecting appropriately treated cellulose fibers to a defibration treatment to obtain fibrous cellulose having a fiber width of 1000 nm or less, and a step of subjecting the fibrous cellulose to a low thixotropy treatment. It is preferable to include. That is, the method for producing fine fibrous cellulose of the present invention preferably includes, for example, a step of subjecting the cellulose fiber to a defibration treatment and then a low thixotropy treatment. Before the defibration treatment step, as described above, it is preferable to further include a step of introducing an ionic substituent into the cellulose fiber, in addition to the step of introducing an ionic substituent, a washing step or an alkali. It is also preferable to further include a treatment step.

  In the present specification, the step of performing the thixotropy treatment is a step of reducing the thixotropy of the dispersion liquid containing fine fibrous cellulose. Specifically, the step of performing the thixotropy treatment is preferably a step of setting the degree of polymerization of fibrous cellulose having a fiber width of 1000 nm or less to 300 or more and 500 or less. The degree of polymerization of the fine fibrous cellulose obtained in the step of performing the thixotropy treatment is more preferably 320 or more, further preferably 340 or more. In addition, the degree of polymerization of the fine fibrous cellulose obtained in the step of performing the thixotropy treatment is more preferably 490 or less, further preferably 460 or less.

  Examples of the step of performing the thixotropy treatment include an ozone treatment step, an enzyme treatment step, a hypochlorous acid treatment step, and a subcritical water treatment step. The step of performing the low thixotropy treatment is preferably at least one selected from an ozone treatment step, an enzyme treatment step, a hypochlorous acid treatment step and a subcritical water treatment step, and particularly preferably an ozone treatment step. preferable.

In the ozone treatment step, ozone is added to the fine fibrous cellulose dispersion liquid (slurry). When adding ozone, it is preferable to add it as, for example, an ozone / oxygen mixed gas. At this time, the ozone addition rate to 1 g of fine fibrous cellulose contained in the fine fibrous cellulose dispersion (slurry) is preferably 1.0 × 10 ⁻⁴ g or more, and 1.0 × 10 ⁻³ g More preferably, it is more preferably 1.0 × 10 ⁻² g or more. The ozone addition rate to 1 g of fine fibrous cellulose is preferably 1.0 × 10 ¹ g or less. After adding ozone to the fine fibrous cellulose dispersion liquid (slurry), stirring may be performed for 10 seconds or more and 10 minutes or less under conditions of 10 ° C. or more and 50 ° C. or less, and then allowed to stand for 1 minute or more and 100 minutes or less. preferable.

  In the enzyme treatment step, the enzyme is added to the fine fibrous cellulose dispersion liquid (slurry). The enzyme used in this case is preferably a cellulase enzyme. Cellulase-based enzymes are classified into the sugar hydrolase family based on the higher-order structure of the catalytic domain having the hydrolysis reaction function of cellulose. Cellulase-based enzymes are roughly classified into endo-glucanase and cellobiohydrolase according to their cellulolytic properties. Endo-glucanase has a high hydrolyzability with respect to an amorphous portion of cellulose, soluble cellooligosaccharides, or a cellulose derivative such as carboxymethyl cellulose, and randomly cleaves their molecular chains from the inside to reduce the degree of polymerization. On the other hand, cellobiohydrolase decomposes the crystal part of cellulose to give cellobiose. Cellobiohydrolase hydrolyzes from the end of the cellulose molecule and is also called an exo-type or processive enzyme. The enzyme used in the enzyme treatment step is not particularly limited, but it is preferable to use endo-glucanase.

In the enzyme treatment step, the addition rate of the enzyme is preferably 1.0 × 10 ⁻⁷ g or more, more preferably 1.0 × 10 ⁻⁶ g or more, based on 1 g of the fine fibrous cellulose. More preferably, it is not less than 0.0 × 10 ⁻⁵ g. The enzyme addition rate is preferably 1.0 × 10 ⁻² g or less per 1 g of fine fibrous cellulose. After adding the enzyme to the fine fibrous cellulose dispersion liquid (slurry), the mixture is stirred under conditions of 30 ° C or higher and 70 ° C or lower for 1 minute or longer and 10 hours or shorter, and then placed under conditions of 90 ° C or higher. It is preferred to deactivate the enzyme.

In the hypochlorous acid treatment step, sodium hypochlorite is added to the fine fibrous cellulose dispersion liquid (slurry). The addition rate of sodium hypochlorite is preferably 1.0 × 10 ⁻⁴ g or more, more preferably 1.0 × 10 ⁻³ g or more, relative to 1 g of fine fibrous cellulose, and 1. It is more preferably 0 × 10 ⁻² g or more, and particularly preferably 1.0 × 10 ⁻¹ g or more. Further, the addition rate of sodium hypochlorite is preferably 1.0 × 10 ² g or less with respect to 1 g of fine fibrous cellulose. After adding sodium hypochlorite to the fine fibrous cellulose dispersion liquid (slurry), it is preferable to perform stirring for 1 minute or more and 10 hours or less under the condition of 10 ° C. or more and 50 ° C. or less.

  In the subcritical water treatment step, the fine fibrous cellulose dispersion liquid (slurry) is subjected to high temperature and high pressure treatment to bring it into a subcritical state. Fine fibrous cellulose is hydrolyzed in the subcritical state. Specifically, after the fine fibrous cellulose dispersion liquid (slurry) is placed in a reaction vessel, the temperature is raised to 150 ° C. or higher and 500 ° C. or lower, preferably 150 ° C. or higher and 350 ° C. or lower, and the pressure in the reaction vessel is adjusted. The pressure is applied to 10 MPa or more and 80 MPa or less, preferably 10 MPa or more and 20 MPa or less. The heating and pressing time at this time is preferably 0.1 second or more and 100 seconds or less, and more preferably 3 seconds or more and 50 seconds or less.

(Fibrous cellulose dispersion)
The present invention also relates to a fibrous cellulose dispersion liquid (also referred to as a fine fibrous cellulose-containing slurry or slurry) obtained by dispersing the above-mentioned fine fibrous cellulose in water. The fibrous cellulose dispersion may be, for example, a coating dispersion used for adding to a coating.

  The content of fine fibrous cellulose in the fibrous cellulose dispersion is preferably 0.1% by mass or more, and preferably 0.3% by mass or more, based on the total mass of the fibrous cellulose dispersion. More preferably, it is more preferably 0.5% by mass or more. The content of the fine fibrous cellulose is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and more preferably 6. 0% by mass or less with respect to the total mass of the fibrous cellulose dispersion liquid. It is more preferably 0% by mass or less.

  When the fibrous cellulose dispersion is a fibrous cellulose dispersion having a fine fibrous cellulose concentration of 0.4% by mass, the viscosity of the dispersion at 23 ° C. is preferably 200 mPa · s or more, and 300 mPa · s. s or more is more preferable, 350 mPa · s or more is further preferable, and 400 mPa · s or more is particularly preferable. Further, the viscosity of the dispersion liquid at 23 ° C. is preferably 3000 mPa · s or less, and more preferably 2500 mPa · s or less. The viscosity of the dispersion liquid having a fine fibrous cellulose concentration of 0.4 mass% can be measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions are 23 ° C., the rotation speed is 3 rpm, and the viscosity is measured 3 minutes after the start of measurement.

  When the fibrous cellulose dispersion is a fibrous cellulose dispersion having a fine fibrous cellulose concentration of 0.2% by mass, the haze of the dispersion is preferably 20% or less, and 15% or less. Is more preferable and 10% or less is further preferable. When the haze of the dispersion liquid is in the above range, the fibrous cellulose dispersion liquid has high transparency and fine fibrous cellulose is finely refined. When such a fibrous cellulose dispersion liquid is added to a paint, the paint can exhibit excellent coating suitability. Here, the haze of the fibrous cellulose dispersion (fine fibrous cellulose concentration: 0.2% by mass) was measured by using a glass cell for liquid (manufactured by Fujiwara, MG-40, reverse light path) having an optical path length of 1 cm. Is a value measured by using a haze meter (HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.) according to JIS K 7136. The zero point measurement is performed with ion-exchanged water contained in the glass cell.

  The fibrous cellulose dispersion may contain water and other additives in addition to the fine fibrous cellulose. Examples of other additives include antifoaming agents, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants and preservatives (for example, phenoxyethanol). Further, the fibrous cellulose dispersion may contain a hydrophilic polymer, an organic ion or the like as an optional component.

  The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above cellulose fiber), and examples of the oxygen-containing organic compound include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, and modified Starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, alkyl acrylate copolymers, urethane copolymers, cellulose derivatives (hydroxy Hydrophilic polymers such as ethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc .; hydrophilic low molecules such as glycerin, sorbitol, ethylene glycol and the like.

  Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Examples of the tetraalkylammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion, and lauryltrimethyl. Examples thereof include ammonium ion, cetyl trimethyl ammonium ion, stearyl trimethyl ammonium ion, octyl dimethyl ethyl ammonium ion, lauryl dimethyl ethyl ammonium ion, didecyl dimethyl ammonium ion, lauryl dimethyl benzyl ammonium ion, and tributyl benzyl ammonium ion. Examples of the tetraalkylphosphonium ion include tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Moreover, as a tetrapropyl onium ion and a tetrabutyl onium ion, a tetra n-propyl onium ion, a tetra n-butyl onium ion, etc. can be mentioned, respectively.

(Use)
The fine fibrous cellulose of the present invention is preferably used for various purposes as a thickener. For example, the fine fibrous cellulose of the present invention can be used as an additive to foods, cosmetics, cement, paints (for coating vehicles such as automobiles, ships, aircrafts, building materials, daily necessities, etc.), inks, pharmaceuticals, etc. it can. Further, the fine fibrous cellulose of the present invention can be applied to daily necessities by adding it to a resin material or a rubber material. Among them, the fine fibrous cellulose of the present invention is particularly preferably a fine fibrous cellulose for paint.

  The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. The materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following specific examples.

<Production Example 1>
[Production of phosphorylated fine fibrous cellulose dispersion]
As a raw material pulp, a softwood kraft pulp made by Oji Paper Co., Ltd. (solid content 93 mass%, basis weight 208 g / m ² sheet shape, Canadian standard freeness (CSF) 700 ml which is disaggregated and measured according to JIS P 8121) It was used.

  This raw material pulp was subjected to phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass of the raw material pulp (absolute dry mass) to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. Was adjusted as described above to obtain a chemical solution-impregnated pulp. Next, the obtained chemical-solution-impregnated pulp was heated for 200 seconds with a hot air dryer at 140 ° C. to introduce a phosphate group into the cellulose in the pulp to obtain phosphorylated pulp.

  Then, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment is carried out by repeating the operation of pouring the pulp dispersion obtained by pouring 10 L of ion-exchanged water to 100 g of phosphorylated pulp (absolute dry mass) so that the pulp is uniformly dispersed, and then filtering and dehydrating. went. When the electric conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

  Next, the phosphorylated pulp after washing was subjected to neutralization treatment as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and a 1N sodium hydroxide aqueous solution was added little by little with stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. . Next, the phosphorylated pulp slurry was dehydrated to obtain a neutralized phosphorylated pulp. Next, the above-mentioned washing treatment was performed on the phosphorylated pulp after the neutralization treatment.

The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on a phosphate group was observed around 1230 cm ^-1 , and it was confirmed that the phosphate group was added to the pulp.

Also, the phosphorylated pulp obtained was tested and analyzed by an X-ray diffractometer. At two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed and it was confirmed to have a cellulose type I crystal.

  Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated 6 times at a pressure of 200 MPa with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

  It was confirmed by X-ray diffraction that the fine fibrous cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous cellulose was measured with a transmission electron microscope, and it was 3 to 5 nm. The amount of phosphoric acid groups (the amount of strongly acidic groups) measured by the measuring method described later was 0.80 mmol / g.

<Production Example 2>
A fine fibrous cellulose dispersion liquid was obtained in the same manner as in Production Example 1 except that the chemical impregnated pulp at the time of phosphorylation was dried at 165 ° C. The amount of phosphoric acid groups (the amount of strongly acidic groups) measured by the measuring method described later was 1.45 mmol / g.

<Production Example 3>
A fine fibrous cellulose dispersion liquid was obtained in the same manner as in Production Example 2 except that the phosphorylated pulp after washing before the neutralization treatment was further subjected to the above phosphorylation treatment and the above washing treatment once in this order. It was The amount of phosphoric acid groups (the amount of strong acidic groups) measured by the measuring method described later was 2.00 mmol / g.

<Production Example 4>
[Production of TEMPO-oxidized fine fibrous cellulose dispersion]
Softwood kraft pulp (undried) made by Oji Paper Co., Ltd. was used as the raw material pulp. This raw material pulp was subjected to alkali TEMPO oxidation treatment as follows. First, the raw material pulp equivalent to 100 parts by mass of dry mass, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) 1.6 parts by mass, 10 parts by mass of sodium bromide, and 10000 parts by mass of water. Dispersed in parts. Next, a 13 mass% sodium hypochlorite aqueous solution was added to 1.3 g of 1.0 g of pulp to start the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 or more and 10.5 or less, and the reaction was considered to be complete when no change in pH was observed.

  Then, a cleaning process was performed on the obtained TEMPO oxidized pulp. The washing treatment is carried out by dewatering the pulp slurry after TEMPO oxidation to obtain a dewatering sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing, and then repeating the operation of filtering and dewatering. It was When the electric conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

  This dehydrated sheet was subjected to additional oxidation treatment of the remaining aldehyde group as follows. The above dehydrated sheet corresponding to 100 parts by mass of dry mass was dispersed in 10000 parts by mass of 0.1 mol / L acetate buffer solution (pH 4.8). Then, 113 parts by mass of 80% sodium chlorite was added, and the mixture was immediately sealed and then allowed to react at room temperature for 48 hours while stirring at 500 rpm using a magnetic stirrer to obtain a pulp slurry.

  Then, a washing treatment was performed on the obtained TEMPO-oxidized pulp having undergone additional oxidation. The washing treatment is performed by dewatering the pulp slurry after additional oxidation to obtain a dewatering sheet, and then pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing, and then repeating the operation of filtering and dewatering. It was When the electric conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

  Moreover, when the obtained TEMPO oxidized pulp was tested and analyzed by an X-ray diffractometer, it was found to be at two positions of 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed and it was confirmed to have a cellulose type I crystal.

  Ion-exchanged water was added to the obtained TEMPO oxidized pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated 6 times at a pressure of 200 MPa with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

  It was confirmed by X-ray diffraction that the fine fibrous cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous cellulose was measured with a transmission electron microscope, and it was 3 to 5 nm. The amount of carboxy groups measured by the measuring method described later was 0.70 mmol / g.

<Production Example 5>
A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 4 except that the amount of the sodium hypochlorite solution during the oxidation reaction was 3.8 mmol with respect to 1.0 g of pulp. The amount of carboxy groups measured by the measuring method described later was 1.30 mmol / g.

<Production Example 6>
A fine fibrous cellulose dispersion liquid was obtained in the same manner as in Production Example 4 except that the amount of the sodium hypochlorite solution during the oxidation reaction was 10 mmol with respect to 1.0 g of pulp. The amount of carboxy groups measured by the measuring method described later was 1.80 mmol / g.

<Example 1>
(Low thixolysis by ozone treatment)
To 1000 g of the fine fibrous cellulose dispersion liquid obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g), 1 L of ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was added, and the mixture was placed in a closed container. After stirring at 25 ° C for 2 minutes, the mixture was left standing for 30 minutes. At this time, the ozone addition rate was 1.0 × 10 ^-2 g per 1 g of fine fibrous cellulose. Then, the container was opened and stirred for 5 hours to volatilize ozone remaining in the dispersion liquid. Thus, the fine fibrous cellulose was subjected to low thixotropy, and the viscosity, the degree of polymerization and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 2>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 3>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 4>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 1 except that an ozone / oxygen mixed gas having an ozone concentration of 40 g / m ³ was used. The ozone addition rate at this time was 2.0 × 10 ⁻³ g per 1 g of fine fibrous cellulose. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 5>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 6>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 4 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 7>
(Low thixolysis by enzyme treatment)
Enzyme-containing liquid (ECOPULP R, manufactured by AB Enzymes, enzyme content is about 5% by mass) based on 1000 g of the fine fibrous cellulose dispersion liquid obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g). ) Was diluted 1000 times, 20 g was added, and the mixture was stirred at a temperature of 50 ° C. for 1 hour. The enzyme addition rate at this time was about 5.0 × 10 ⁻⁵ g per 1 g of fine fibrous cellulose. Then, the mixture was stirred at a temperature of 100 ° C. for 1 hour to deactivate the enzyme. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 8>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 7 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 9>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 7 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 10>
To 1000 g of fine fibrous cellulose dispersion (concentration of solid content: 2% by mass, solid content: 20 g), an enzyme-containing liquid (manufactured by AB Enzymes, ECOPULP R, enzyme content: about 5% by mass) was diluted 1000 times. A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 7 except that 4 g was added. The enzyme addition rate at this time was about 1.0 × 10 ⁻⁵ g per 1 g of fine fibrous cellulose. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 11>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 12>
A low-thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 13>
(Lower thixolysis by sodium hypochlorite treatment)
To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g), 170 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added, and the mixture was cooled to room temperature. It was stirred for 1 hour. At this time, the addition rate of sodium hypochlorite was 1.02 g per 1 g of fine fibrous cellulose. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 14>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 13 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 15>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 13 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 16>
Example 13 except that 1.70 g of a sodium hypochlorite solution (effective chlorine concentration: 12% by mass) was added to 1000 g of a fine fibrous cellulose dispersion liquid (solid content: 2% by mass, solid content: 20 g). In the same manner, a low thixotropic fine fibrous cellulose dispersion was obtained. At this time, the addition rate of sodium hypochlorite was 1.02 × 10 ^-2 parts by mass with respect to 1 part by mass of fine fibrous cellulose. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 17>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 16 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 18>
A low-thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 16 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 19>
(Lower thixotropy by subcritical water treatment)
The fine fibrous cellulose dispersion liquid obtained in Production Example 1 was placed in a reactor, heated to 200 ° C., and heated for 10 seconds. The pressure in the reactor at this time was 20 MPa. After completion of heating, the reactor was cooled with water, and the low thixotropic fine fibrous cellulose dispersion liquid in the reactor was recovered. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 20>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 19 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 21>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 19 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 22>
A low-thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 19 except that the heating time was 1 second. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 23>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 22 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 24>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 22 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 25>
A low thixotropic fine fibrous cellulose dispersion liquid was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion liquid obtained in Production Example 4 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 26>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion obtained in Production Example 5 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 27>
A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion obtained in Production Example 6 was used. The viscosity, the degree of polymerization, and the rate of change in viscosity of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Comparative Example 1>
To 100 g of phosphorylated pulp obtained in Production Example 1 (solid content concentration 20% by mass, solid content 20 g), 1 L of ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was added, and at 25 ° C. in a closed container. After stirring for 2 minutes, the mixture was left standing for 30 minutes. At this time, the ozone addition rate was 1.0 × 10 ^-2 g per 1 g of fine fibrous cellulose. Then, the phosphorylated pulp was washed to remove residual ozone. Then, using the obtained pulp, a slurry having a solid content of 2% by mass was prepared. This slurry was treated 6 times at a pressure of 200 MPa with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. Using the obtained fine fibrous cellulose dispersion as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative example 2>
A fine fibrous cellulose dispersion liquid containing fine fibrous cellulose was obtained in the same manner as in Comparative Example 1 except that the phosphorylated pulp obtained in Production Example 2 was used. Using the obtained fine fibrous cellulose dispersion as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative example 3>
A fine fibrous cellulose dispersion liquid containing fine fibrous cellulose was obtained in the same manner as in Comparative Example 1 except that the phosphorylated pulp obtained in Production Example 3 was used. Using the obtained fine fibrous cellulose dispersion as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative example 4>
Using the fine fibrous cellulose dispersion obtained in Production Example 1 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative Example 5>
Using the fine fibrous cellulose dispersion obtained in Production Example 2 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative example 6>
Using the fine fibrous cellulose dispersion obtained in Production Example 3 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative Example 7>
Using the fine fibrous cellulose dispersion obtained in Production Example 4 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative Example 8>
Using the fine fibrous cellulose dispersion obtained in Production Example 5 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Comparative Example 9>
Using the fine fibrous cellulose dispersion obtained in Production Example 6 as it was, the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described below.

<Measurement>
[Measurement of phosphate group amount]
The phosphate group amount of the fine fibrous cellulose is a fibrous substance prepared by diluting a fine fibrous cellulose dispersion liquid containing the target fine fibrous cellulose with ion-exchanged water to a content of 0.2% by mass. The cellulose-containing slurry was treated with an ion exchange resin and then titrated with an alkali for measurement.
The treatment with an ion exchange resin was carried out by adding 1/10 by volume of a strongly acidic ion exchange resin (Amber Jet 1024; Organo Co., Ltd., already conditioned) to the above-mentioned fibrous cellulose-containing slurry and performing a shaking treatment for 1 hour. , And the resin and the slurry were separated by pouring onto a mesh having an opening of 90 μm.
In addition, titration with an alkali was performed by adding 50 μL of a 0.1N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry after the treatment with the ion exchange resin once every 30 seconds while the electrical conductivity of the slurry was shown. It was carried out by measuring the change in the value of. The phosphate group amount (mmol / g) was obtained by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 1 in the measurement result by the solid content (g) in the titration target slurry. Calculated.

[Measurement of the amount of carboxy group]
The amount of carboxy groups in the fine fibrous cellulose is produced by diluting the fine fibrous cellulose dispersion liquid containing the target fine fibrous cellulose with ion-exchanged water to a content of 0.2% by mass. The contained slurry was treated with an ion exchange resin and then titrated with an alkali for measurement.
The treatment with an ion exchange resin was carried out by adding 1/10 by volume of a strongly acidic ion exchange resin (Amber Jet 1024; Organo Co., Ltd., already conditioned) to the above-mentioned fibrous cellulose-containing slurry and performing a shaking treatment for 1 hour. , And the resin and the slurry were separated by pouring onto a mesh having an opening of 90 μm.
In addition, titration with an alkali was performed by adding 50 μL of a 0.1 N sodium hydroxide aqueous solution once every 30 seconds to the fibrous cellulose-containing slurry after the treatment with the ion exchange resin, while measuring the electric conductivity of the slurry. This was done by measuring the change in value. The amount of carboxy groups (mmol / g) is obtained by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 2 in the measurement result by the solid content (g) in the titration target slurry. It was calculated.

[Measurement of viscosity of fine fibrous cellulose dispersion]
The viscosity of the fine fibrous cellulose dispersion was measured as follows. First, the fine fibrous cellulose dispersion was diluted with ion-exchanged water so that the solid content concentration was 0.4% by mass, and then stirred with a disperser at 1500 rpm for 5 minutes. Then, the viscosity of the dispersion liquid thus obtained was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the dispersion liquid. Further, the dispersion liquid to be measured was allowed to stand for 24 hours in an environment of 23 ° C. and a relative humidity of 50% before the measurement. The liquid temperature of the dispersion liquid at the time of measurement was 23 ° C.

[Measurement of specific viscosity and degree of polymerization of fine fibrous cellulose]
The specific viscosity and the degree of polymerization of the fine fibrous cellulose were measured according to Tappi T230. After measuring the viscosity (η1) measured by dispersing the cellulose fiber to be measured in a dispersion medium and the blank viscosity (η0) measured only in the dispersion medium, the specific viscosity (ηsp) and the intrinsic viscosity ([ η]) was measured according to the following formula.
ηsp = (η1 / η0) -1
[Η] = ηsp / (c (1 + 0.28 × ηsp))
Here, c in the formula represents the concentration of fine fibrous cellulose at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) of fine fibrous cellulose was calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as “viscosity average degree of polymerization”.

[Measurement of viscosity change rate of fine fibrous cellulose dispersion]
The viscosity change rate of the fine fibrous cellulose dispersion was measured as follows.
(Measurement of viscosity before stirring)
First, the fine fibrous cellulose dispersion is diluted with ion-exchanged water so that the viscosity is about 2500 mPa · s when measured by the method described below, and the fine fibrous cellulose dispersion is 5 cm in a cylindrical container having a diameter of 10 cm. To a height of 1, and stirred with a disperser at 1500 rpm for 5 minutes. One minute after the end of stirring, the viscosity of the obtained fine fibrous cellulose dispersion was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were a rotation speed of 6 rpm, and the viscosity value 1 minute after the start of measurement was taken as the viscosity of the dispersion liquid. The liquid temperature of the dispersion liquid at the time of measurement was 23 ° C.
(Stirring with stirrer)
Next, the obtained fine fibrous cellulose dispersion having a viscosity of about 2500 mPa · s was put into a cylindrical container having a diameter of 10 cm to a height of 5 cm, and the length was 5 cm, the central width was 2 cm, and the end was 2 cm. Using an elliptical stirrer having a width of 1 cm, stirring was performed for 24 hours while maintaining the state where the center of the liquid surface was depressed by 2 cm. The liquid temperature of the dispersion liquid during stirring was 23 ° C.
(Measurement of viscosity after stirring)
One minute after the end of stirring by the stirrer, the viscosity of the fine fibrous cellulose dispersion was immediately measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were a rotation speed of 6 rpm, and the viscosity value 1 minute after the start of measurement was taken as the viscosity of the dispersion liquid. The liquid temperature of the dispersion liquid at the time of measurement was 23 ° C.
(Calculation of viscosity change rate)
The rate of change in viscosity before and after stirring with a stirrer was calculated by the following formula.
Viscosity change rate (%) = (viscosity after stirring-viscosity before stirring) / viscosity before stirring × 100

<Evaluation>
[Evaluation of coating suitability of paint]
The coating suitability of the coating material using the fine fibrous cellulose dispersion liquid obtained by the present invention was evaluated as follows.
(Preparation of coating material containing fine fibrous cellulose)
1 part by mass of a luster color material (aluminum paste WXM7640, manufactured by Toyo Aluminum Co., Ltd., aluminum concentration 58-61% by mass) based on 100 parts by mass of a fine fibrous cellulose dispersion having a viscosity of about 2500 mPa · s obtained by the same method as above. Parts were added, and the mixture was stirred with a disperser at 1500 rpm for 5 minutes to obtain a fine fibrous cellulose-containing coating material.
(Paint circulation and spray coating)
Then, the obtained fine fibrous cellulose-containing paint was circulated in the pipe for 24 hours by a pump type circulation device. Immediately after the end of the circulation, a fine cellulose-containing paint was applied to the wall surface with a spray gun, and the presence or absence of liquid dripping was confirmed. In addition, during coating, the presence or absence of sedimentation of the glitter material in the fine cellulose-containing paint was visually confirmed. The coating suitability of the fine fibrous cellulose-containing coating material was evaluated on the basis of four results from the results of the liquid dripping of the coating material and the precipitation of the bright material.
A: No liquid dripping and no precipitation of the glittering material were observed during coating after circulation of the coating material, and coating suitability is very good.
B: Either liquid sagging or sedimentation of the glittering material is observed during coating after circulation of the paint, but it is slight, and coating suitability is good.
C: Dripping and sedimentation of the luster material were observed during coating after the paint was circulated, and coating suitability was somewhat poor, but there was no problem in practical use.
D: Liquid dripping and precipitation of the luster color material are often observed during coating after circulation of the coating material, resulting in poor coating suitability and practical problems.

  The coating material using the fine fibrous cellulose obtained in the examples exhibited excellent coating suitability.

Claims (12)

Fibrous cellulose having a fiber width of 1000 nm or less,
When the fibrous cellulose is dispersed in water to give a dispersion having a viscosity of 2500 mPa · s at 23 ° C. and the dispersion is stirred under the following stirring conditions, the viscosity change rate calculated by the following formula is ± 50. Fibrous cellulose within%;
Viscosity change rate (%) = (viscosity after stirring−viscosity before stirring) / viscosity before stirring × 100
(Stirring condition)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. was put into a cylindrical container having a diameter of 10 cm up to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a central width of 2 cm, and an end width of 1 cm was used. While maintaining the state where the center of the liquid surface is depressed by 2 cm, the mixture is stirred at 23 ° C. for 24 hours.   The fibrous cellulose according to claim 1, wherein the fibrous cellulose has a degree of polymerization of 300 or more and 500 or less.   The fibrous cellulose according to claim 1 or 2, wherein the fibrous cellulose has an ionic substituent.   The fibrous cellulose according to claim 3, wherein the amount of the ionic substituent in the fibrous cellulose is 0.10 mmol / g or more and 1.50 mmol / g or less.   The fibrous cellulose according to claim 3 or 4, wherein the ionic substituent is a phosphoric acid group or a substituent derived from a phosphoric acid group.   The viscosity at 23 ° C. of the dispersion liquid is 200 mPa · s or more and 3000 mPa · s or less when the fibrous cellulose is dispersed in water to 0.4% by mass to form a dispersion liquid. The fibrous cellulose according to any one of claims.   The fibrous cellulose according to any one of claims 1 to 6, which is used for paints.   A fibrous cellulose dispersion obtained by dispersing the fibrous cellulose according to any one of claims 1 to 7 in water. A step of subjecting a cellulose fiber to a defibration treatment to obtain fibrous cellulose having a fiber width of 1000 nm or less,
A method for producing fibrous cellulose, which comprises a step of subjecting the fibrous cellulose to a thixotropy treatment.   The method for producing fibrous cellulose according to claim 9, wherein the step of performing the thixotropy treatment is a step of setting the degree of polymerization of the fibrous cellulose to 300 or more and 500 or less.   The method for producing fibrous cellulose according to claim 9 or 10, wherein the step of performing the thixotropy treatment is an ozone treatment step.   The method for producing fibrous cellulose according to claim 9, further comprising a step of introducing an ionic substituent into the cellulose fiber before the step of obtaining the fibrous cellulose.

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