JP7040576B2 - Method for Producing Fibrous Cellulose, Fibrous Cellulose Dispersion Liquid and Fibrous Cellulose - Google Patents

Description

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

Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products and the like. As the cellulose fiber, in addition to the 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 also known. Fine fibrous cellulose is attracting attention as a new material, and its uses are wide-ranging.

Fine fibrous cellulose may be used, for example, as an additive for paints. In this case, the fine fibrous cellulose can 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, it is considered to use cellulose nanofibers as a viscosity adjusting agent.

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, with respect to such paints, attention has not been paid to the decrease in coating suitability due to the change in viscosity (thixotropic property) due to the share applied before coating, and there is room for improvement in coating suitability. rice field.

Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of providing fine fibrous cellulose capable of exhibiting excellent coatability when added to a paint. rice field.

As a result of diligent studies to solve the above problems, the present inventors disperse fine fibrous cellulose in water to prepare a dispersion liquid, and when the mixture is stirred under predetermined conditions, the rate of change in viscosity before and after stirring ( %) Was obtained within a predetermined range, and it was found that the coating suitability of the paint could be enhanced by adding the fine fibrous cellulose to the paint.
Specifically, the present invention has the following configurations.

[1] Fibrous cellulose having a fiber width of 1000 nm or less.
When fibrous cellulose is dispersed in water to prepare 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;
Viscosity change rate (%) = (Viscosity after stirring-Viscosity before stirring) / Viscosity before stirring x 100
(Stirring conditions)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. is placed in a cylindrical container having a diameter of 10 cm to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a width of 2 cm at the center and a width of 1 cm at the end is used. The center of the liquid surface is maintained in a state of being recessed by 2 cm, and the mixture is stirred at 23 ° C. for 24 hours.
[2] The fibrous cellulose according to [1], wherein the degree of polymerization of the fibrous cellulose is 300 or more and 500 or less.
[3] 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 phosphate group or a substituent derived from a phosphate group.
[6] When fibrous cellulose is dispersed in water so as to be 0.4% by mass to prepare a dispersion liquid, 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.
[7] The fibrous cellulose according to any one of [1] to [6] for paints.
[8] A fibrous cellulose dispersion liquid obtained by dispersing the fibrous cellulose according to any one of [1] to [7] in water.
[9] A step of subjecting a cellulose fiber to a defibration treatment to obtain a fibrous cellulose having a fiber width of 1000 nm or less.
A method for producing fibrous cellulose, which comprises a step of applying a thixotropic treatment to fibrous cellulose.
[10] The method for producing fibrous cellulose according to [9], wherein the step of applying the thixotropic treatment is a step of reducing 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 applying the thixotropic treatment is an ozone treatment step.
[12] The method for producing fibrous cellulose according to any one of [9] to [11], further comprising 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 capable of exhibiting excellent coatability when added to a paint.

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and the electrical conductivity with respect to fibrous cellulose having a phosphoric acid group. FIG. 2 is a graph showing the relationship between the amount of NaOH added to the fibrous cellulose having a carboxy group and the electrical conductivity.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments and 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 the present specification, 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 prepare 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 is used. The rate of change is within ± 50%.
Viscosity change rate (%) = (Viscosity after stirring-Viscosity before stirring) / Viscosity before stirring x 100
(Stirring conditions)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. is placed in a cylindrical container having a diameter of 10 cm to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a width of 2 cm at the center and a width of 1 cm at the end is used. The center of the liquid surface is maintained in a state of being recessed by 2 cm, and the mixture is stirred at 23 ° C. for 24 hours.

In the present invention, by using fine fibrous cellulose as a dispersion and setting the viscosity change rate within ± 50% when stirring under the above conditions, excellent coating suitability is exhibited when added to paints. A possible fine fibrous cellulose 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 applicability. For example, even when the paint containing the fine fibrous cellulose of the present invention is stored or transported, the change in the viscosity of the paint is suppressed, so that liquid dripping during coating is suppressed and pigments and the like are added. 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 to give a relatively strong share to the paint, liquid dripping and pigments caused by a decrease in the viscosity of the paint It is possible to effectively suppress the sedimentation of additives such as.

The fine fibrous cellulose of the present invention is preferably used for paints, and as described above, the applicability of paints can be improved. Further, when the fine fibrous cellulose of the present invention is used as an additive for a paint, it is possible to improve the design and strength after coating. Therefore, the coating layer formed by applying the paint can exhibit excellent designability and scratch resistance.

The viscosity change rate of the dispersion calculated by the above formula may be within ± 50%, preferably within ± 40%, more preferably within ± 30%, and within ± 25%. It is more preferable, and it is particularly preferable that it is within ± 20%. The viscosity change rate of the dispersion liquid calculated by the above formula may be 0%. Usually, the viscosity of the dispersion liquid is often lowered by applying a share to the dispersion liquid, so that 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. The rate of change in viscosity of the dispersion calculated by the above formula is controlled within appropriate ranges, for example, the type and conditions of treatment for fine fibrous cellulose, the degree of polymerization of fine fibrous cellulose, and the amount of ionic substituents. 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 liquid is the viscosity value 1 minute after the start of measurement at 23 ° C. and a rotation speed of 6 rpm using a B-type viscometer. .. As the B-type viscometer, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD can be used. Since the viscosity before stirring is the viscosity of the dispersion adjusted so that the viscosity is about 2500 mPa · s, the measured value of the viscosity of the dispersion is preferably 2500 mPa · s, but an error of about ± 15%. May have occurred. That is, in the calculation formula of the viscosity change rate, the viscosity before stirring is the measured viscosity of the dispersion liquid adjusted so that the viscosity is about 2500 mPa · s, and is rotated at 23 ° C. using a B-type viscometer. It is a measured viscosity value 1 minute after the start of measurement at a speed of 6 rpm. However, when measuring the viscosity before stirring, put the fine fibrous cellulose dispersion into a cylindrical container with a diameter of 10 cm to a height of 5 cm, stir with a disperser at 1500 rpm for 5 minutes, and 1 minute from the end of stirring. The measurement will be made later. Further, when adjusting the viscosity of the dispersion liquid before stirring to about 2500 mPa · s, the amount of the fine fibrous cellulose 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% by mass, the viscosity of the dispersion liquid before stirring can be adjusted to about 2500 mPa · s.

In the calculation formula of the viscosity change rate, when measuring the viscosity after stirring, first, the dispersion liquid used for the viscosity measurement before stirring is further stirred by a stirrer. In this case, the pre-stirring dispersion is placed in a cylindrical container with a diameter of 10 cm, and the fine fibrous cellulose dispersion is placed up to a height of 5 cm. While maintaining a state in which the center of the liquid surface is recessed by 2 cm, the mixture is stirred for 24 hours. 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 so as to be 0.4% by mass to prepare a dispersion, the viscosity of the dispersion at 23 ° C. is preferably 200 mPa · s or more, preferably 300 mPa · s. The above is more preferable, 350 mPa · s or more is further preferable, and 400 mPa · s or more is particularly preferable. 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 having a fine fibrous cellulose concentration of 0.4% by mass can be measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). 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 a 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, for example, by observation 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 preferable. By setting the average fiber width of the fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the cellulose molecule in water and make it easier to exhibit the effects of the fibrous cellulose on improving strength, rigidity and dimensional stability. can. The fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of 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-coated grid to be a sample for TEM observation. And. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.

(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly 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 with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken 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, it is possible to suppress the destruction of the crystal region of the fibrous cellulose. It is also possible to set the slurry viscosity of the fibrous cellulose in an appropriate range. The fiber length of the fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

The fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fibrous cellulose has an I-type crystal structure can be identified in the diffraction profile obtained from the wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. The ratio of the type I crystal structure to the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, still more preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and the development of a low coefficient of linear thermal expansion. The crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 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 value or more, it is easy to form a sheet containing fine fibrous cellulose. Further, it is easy to obtain sufficient viscosity when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, it is preferable in that handling such as dilution becomes easy when, for example, fibrous cellulose is treated as an aqueous dispersion.

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

The fibrous cellulose in this 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 increasing 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. Further, as the nonionic substituent, for example, an alkyl group and an acyl group can be included. In this embodiment, it is particularly preferable to have an anionic group as the ionic substituent.

Examples of the anionic group as an ionic substituent include a phosphate group or a substituent derived from a phosphate group (sometimes referred to simply as a phosphate group), a carboxy group or a substituent derived from a carboxy group (simply a carboxy group). It is preferably at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxy group. It is more preferably one kind, and particularly preferably a phosphate group. Fine fibrous cellulose having a phosphoric acid group can exhibit more excellent coatability when added to a paint.

The substituent derived from the phosphoric acid group or the phosphoric acid group is, for example, a substituent represented by the following formula (1), and is generalized as a phosphoric acid group or a substituent derived from the phosphoric acid.
The phosphoric acid group is, for example, a divalent functional group obtained by removing a hydroxy group from phosphoric acid. Specifically, it is a group represented by -PO ₃ H ₂ . Substituents derived from phosphoric acid groups include substituents such as salts of phosphoric acid groups and phosphoric acid ester groups. The substituent derived from the phosphate group may be contained in the fibrous cellulose as a group (for example, a pyrophosphate group) in which the phosphate group is condensed. Further, the phosphoric acid group may be, for example, a phosphite group (phosphonic acid group), and the substituent derived from the phosphoric acid group is a salt of the phosphite group, a phosphite ester group, or the like. May be good.

In equation (1), a, b and n are natural numbers (where a = b × m). Of α ¹ , α ² , ..., α ⁿ and α', a is O ⁻ , and the rest is either R or OR. It is also possible that all of each αn and α'are O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain hydrocarbon, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing 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 chain hydrocarbon group include an i-propyl group and a t-butyl group, but the group is not particularly limited. 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-linear hydrocarbon group include, but are not limited to, a vinyl group, an allyl group and the like. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but the group is not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group and the like.

Further, as the inducing group in R, 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 with respect to the main chain or side chain of the above-mentioned various hydrocarbon groups. The group is mentioned, but it is not particularly limited. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R to the above range, the molecular weight of the phosphate group can be set to an appropriate range, the penetration into the fiber raw material is facilitated, and the yield of the fine cellulose fiber is increased. You can also do it.

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion, which does not easily yellow when the fiber raw material containing β is heated and is easily industrially used, 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 / g per 1 g (mass) of the fibrous cellulose. It is more preferably / g or more, and particularly preferably 0.60 mmol / g or more. The amount of the ionic substituent 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 fibrous cellulose. It is more preferably .50 mmol / g or less, further preferably 2.00 mmol / g or less, further 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 indicates the mass of the fibrous cellulose when the counterion of the ionic substituent is a hydrogen ion (H ⁺ ). By setting the amount of the ionic substituent to be introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose. Further, by setting the introduction amount of the ionic substituent within the above range, the thixotropy property of the paint material when fine fibrous cellulose is added to the paint material can be lowered, which makes the coating suitability more effective. Can be enhanced.

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 NaOH dropped and the electrical conductivity with respect to fibrous cellulose having a phosphoric acid group. The amount of the phosphate group introduced into the fibrous cellulose is measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target before the treatment with the strong acid ion exchange resin. Next, the change in electrical conductivity is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. As shown in FIG. 1, the electrical conductivity drops sharply at first (hereinafter referred to as "first region"). After that, the conductivity begins to increase slightly (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 by the point where the second derivative value of the conductivity, that is, the amount of change in the increment (slope) of the conductivity is maximized. 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 strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group causes condensation, the weakly acidic group is apparently lost, and the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups is consistent with the amount of phosphorus atoms regardless of the presence or absence of condensation. Therefore, when the term simply refers to the amount of phosphate group introduced (or the amount of phosphate group) or the amount of substituent introduced (or the amount of substituent), it means the amount of strongly acidic group. Therefore, the value obtained by dividing the amount of alkali (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 amount of phosphoric acid group introduced (mmol / mmol /). g).

FIG. 2 is a graph showing the relationship between the amount of NaOH added to the fibrous cellulose having a carboxy group and the electrical conductivity. The amount of the carboxy group introduced into the fibrous cellulose is measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target before the treatment with the strong acid ion exchange resin. Next, the 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 increase (slope) of the conductivity becomes almost constant, and then the increase (slope) of the conductivity increases. It is divided into the second area. The boundary point between the first region and the second region is defined by the point where the second derivative value of the conductivity, that is, the amount of change in the increment (slope) of the conductivity is maximized. The value obtained by dividing the amount of alkali (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 amount of carboxy group introduced (the amount of carboxy group introduced). mmol / g).

Since the denominator of the above-mentioned carboxy group introduction amount (mmol / g) is the mass of the acid type fibrous cellulose, the carboxy group amount of the acid type fibrous cellulose (hereinafter, the carboxy group amount (acid type)). ) Is shown. On the other hand, when the counterion of the carboxy group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is a counterion. Therefore, the amount of carboxy group (hereinafter, the amount of carboxy group (C type)) possessed by the fibrous cellulose in which the cation C is a counter ion can be obtained. That is, it is calculated by the following formula.
Amount of carboxy group (C type) = Amount of carboxy group (acid type) / {1+ (W-1) x (amount of carboxy group (acid type)) / 1000}
W: Formulated amount of cation C per valence (for example, Na is 23, Al is 9)

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

The degree of polymerization of the fine fibrous cellulose is preferably 300 or more, more preferably 320 or more, and even more preferably 340 or more. The degree of polymerization of the fine fibrous cellulose is preferably 500 or less, more preferably 490 or less, and further 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 lowered (lower thixotropy), thereby improving the coating suitability. Can be effectively enhanced.

The degree of polymerization of the fine fibrous cellulose is a value calculated from the pulp viscosity measured according to Tappi T230. Specifically, the viscosity (referred to as η1) measured by dispersing the fine fibrous cellulose to be measured in a copper ethylenediamine aqueous solution and the blank viscosity (referred to as η0) measured only with a dispersion medium are measured and then the ratio. Viscosity (ηsp) and 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 indicates the concentration of fine fibrous cellulose at the time of viscosity measurement.
Further, the degree of polymerization (DP) is calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes referred to as "viscosity average degree of polymerization".

In the present invention, in particular, the degree of polymerization of the fine fibrous cellulose is set to 300 or more and 500 or less, and the amount of ionic substituents in the fine fibrous cellulose is set to 0.4 mmol / g or more and 1.0 mmol / g or less. The thixotropic property of the paint when the fine fibrous cellulose is added to the paint can be further lowered, and thereby the coating suitability of the paint can be more effectively improved. Setting the degree of polymerization of fine fibrous cellulose and the amount of ionic substituents in appropriate ranges contributes to the low thixotropy of the dispersion liquid in which fine fibrous cellulose is dispersed, which makes it suitable for coating paints. Is expected to increase.

(Manufacturing method of fine fibrous cellulose)
<Fiber raw material>
Fine fibrous cellulose is produced from a fiber raw material containing cellulose. The fiber raw material containing cellulose is not particularly limited, but it is preferable to use pulp because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, but is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and 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), crushed wood 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 pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp of this embodiment, one of the above may be used alone, or two or more of them may be mixed and used. Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. Further, among wood pulps, it is possible to obtain long-fiber fine fibrous cellulose having a large cellulose ratio and a high yield of fine fibrous cellulose during defibration treatment, and having a small decomposition of cellulose in the pulp and a large axial ratio. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. It should be noted that the viscosity tends to be high when the fine fibrous cellulose of long fibers having a large axial ratio is used.

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians and bacterial cellulose produced by acetic acid bacteria can also 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 can also be used.

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

In the phosphate group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). You may. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.

As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, there is 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. Of these, since the reaction uniformity is high, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction uniformity is high, it is preferable to add the solution 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, may be added separately, or may be added as a mixture. The method for 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, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, a required amount of compound A and compound B may be added to the fiber raw material, or an excess amount of compound A and compound B may be added to the fiber raw material, respectively, and then the surplus compound A and compound B may be added by pressing or filtering. It 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, and specifically, phosphoric acid or a salt thereof, phosphoric acid or a salt thereof, and dehydration condensation. Examples thereof include phosphoric acid or a salt thereof, and anhydrous phosphoric acid (diphosphoric pentoxide), but the present invention is not particularly limited. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of the phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-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, sulphate, and dehydration-condensed phosphate include phosphoric acid, sulphite, or lithium salt of dehydration-condensed phosphoric acid, sodium salt, potassium salt, ammonium salt, and the like. It can be a sum. Of these, phosphoric acid and phosphoric acid are selected from the viewpoints of high efficiency of introduction of phosphoric acid group, easy improvement of defibration efficiency in the defibration process described later, low cost, and easy industrial application. 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 amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the phosphorus atomic weight, the amount of phosphorus atom added 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 atom 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 setting the addition amount of the phosphorus atom to the fiber raw material to be equal to or less than the above upper limit value, 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 compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.
From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

The amount of 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, and more preferably 10% by mass or more and 400% by mass or less. It is more preferably 100% by mass or more and 350% by mass or less.

In the reaction between the fiber raw material containing cellulose and compound A, for example, amides or amines may be contained in the reaction system in addition to compound B. 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, hexamethylenediamine and the like. Among these, triethylamine in particular is known to act 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 heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which the phosphate group can be efficiently introduced while suppressing the thermal decomposition and 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. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized layer drying device, and an air stream. A drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, and a microwave heating device can be used.

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

Further, the heating device used for the heat treatment always keeps water retained by the slurry and 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. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, and also to suppress the acid hydrolysis of the sugar chain in the fiber. can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

The heat treatment time is preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and 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 amount of the phosphoric acid group introduced can be within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

The phosphoric acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphoric acid group introduction step two or more times, many phosphoric acid groups can be introduced into the fiber raw material. In the present embodiment, as an example of a preferable embodiment, there is a case where the phosphate group introduction step is performed twice.

The amount of the phosphoric acid group 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 / g per 1 g (mass) of the fine fibrous cellulose. It is more preferably / g or more, and particularly preferably 0.60 mmol / g or more. The amount of the phosphoric acid group 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 .50 mmol / g or less, further preferably 2.00 mmol / g or less, further preferably 1.50 mmol / g or less, and particularly preferably 1.00 mmol / g or less. preferable. By setting the amount of the phosphoric acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose. Further, by setting the introduction amount of the ionic substituent within the above range, the thixotropy property of the paint material when fine fibrous cellulose is added to the paint material can be lowered, which makes the coating suitability more effective. Can be enhanced.

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

The compound having a group derived from a carboxylic acid is not particularly limited, and for example, a dicarboxylic acid compound such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, citric acid, aconitic acid and the like. Examples include tricarboxylic acid compounds. The derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an acid anhydride derivative of the compound having a carboxy group and an acid anhydride derivative of the compound having a carboxy group. The imide of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinic acidimide, and phthalateimide.

The acid anhydride of the compound having a group derived from a carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Acid anhydride is mentioned. The derivative of the acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited, but for example, a compound having a carboxy group such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride and the like. Examples thereof include those in which at least a part of the hydrogen atom of the acid anhydride is substituted with a substituent such as an alkyl group or a phenyl group.

When the TEMPO oxidation treatment is performed in the carboxy group introduction step, it is preferable to perform the treatment under conditions of pH 6 or more and 8 or less, for example. Such a treatment is also referred to as a neutral TEMPO oxidation treatment. The neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and the like. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting with sodium chlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group.

Further, the TEMPO oxidation treatment may be carried out under the condition that the pH is 10 or more and 11 or less. Such a treatment is also referred to as an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. ..

The amount of carboxy group introduced into fibrous cellulose varies depending on the type of substituent, but for example, when a carboxy group is introduced by TEMPO oxidation, it may be 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose. It is more preferably 0.20 mmol / g or more, further preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more. The amount of the carboxy group introduced into the fibrous cellulose is preferably 2.50 mmol / g or less, more preferably 2.00 mmol / g or less, and further 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, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose. Further, by setting the introduction amount of the carboxy group within the above range, the thixotropy property of the paint material when fine fibrous cellulose is added to the paint material can be lowered, thereby more effectively improving the coating suitability. Can be done.

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

<Alkaline treatment process>
In the case of producing fine fibrous cellulose, the fiber raw material may be treated with an alkali between the step of introducing an ionic substituent and the step of defibration treatment described later. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the ionic substituent-introduced fiber in an alkaline 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 this embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water, a polar organic solvent exemplified by alcohol, and the like, 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 alkaline solution in the alkaline 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 immersion time of the ionic substituent-introduced fiber in the alkaline solution in the alkaline 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 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to 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 alkaline 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 handleability.

<Acid treatment process>
In the case of producing fine fibrous cellulose, the fiber raw material may be acid-treated between the step of introducing an ionic substituent and the defibration treatment step described later. For example, the ionic substituent introduction step, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.

The method of the acid treatment is not particularly limited, and examples thereof include a method of immersing the fiber raw material in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably, for example, 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution 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, chloric acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. 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, and 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 is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the fiber raw material. Is more preferable.

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

In the defibration treatment step, for example, it is preferable to dilute the ionic substituent-introduced fiber with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and an organic solvent such as a polar organic solvent can be used. The polar organic solvent is not particularly limited, but for example, alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol and glycerin. Examples of the ketone include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monon-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotonic 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 appropriately set. Further, the slurry obtained by dispersing the ionic substituent-introduced fiber in a dispersion medium may contain a solid content other than the ionic substituent-introduced fiber such as urea having a hydrogen bond property.

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

In the present specification, the step of applying the thixotropic treatment is a step of performing a treatment for reducing the thixotropic property of the dispersion liquid containing fine fibrous cellulose. Specifically, the step of applying the thixotropic treatment is preferably a step of reducing 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 applying the thixotropic treatment is more preferably 320 or more, and further preferably 340 or more. Further, the degree of polymerization of the fine fibrous cellulose obtained in the step of applying the thixotropic treatment is more preferably 490 or less, and further preferably 460 or less.

Examples of the step of applying the low-tixo treatment include an ozone treatment step, an enzyme treatment step, a hypochlorous acid treatment step, and a subcritical water treatment step. The step of applying the low-tixo 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 is particularly preferably an ozone treatment step. preferable.

In the ozone treatment step, ozone is added to the fine fibrous cellulose dispersion (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 the fine fibrous cellulose contained in the fine fibrous cellulose dispersion (slurry) is preferably 1.0 × 10 ^-4 g or more, preferably 1.0 × 10 ^-3 g. The above is more preferable, and 1.0 × 10 ⁻² g or more is further preferable. The ozone addition rate with respect 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 (slurry), the mixture may be stirred for 10 seconds or more and 10 minutes or less under the 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 (slurry). The enzyme used at this time is preferably a cellulase-based enzyme. Cellulase-based enzymes are classified into the sugar hydrolase family based on the higher-order structure of the catalytic domain having the function of hydrolyzing cellulose. Cellulase-based enzymes are roughly classified into endo-glucanase and cellobiohydrolase according to their cellulolytic properties. Endo-type glucanase is highly hydrolyzable to the amorphous portion of cellulose, soluble cellooligosaccharides, or cellulose derivatives such as carboxymethyl cellulose, and randomly cleaves their molecular chains from the inside to reduce the degree of polymerization. In contrast, cellobiohydrolase decomposes the crystalline portion of cellulose to give cellobiose. In addition, cellobiohydrolase is hydrolyzed 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-type 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 with respect to 1 g of fine fibrous cellulose, and 1 It is more preferably 0.0 × 10 ^-5 g or more. The addition rate of the enzyme is preferably 1.0 × ^10-2 g or less with respect to 1 g of fine fibrous cellulose. After adding the enzyme to the fine fibrous cellulose dispersion (slurry), the mixture is stirred under the 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 the conditions of 90 ° C. or higher. It is preferable to inactivate the enzyme.

In the hypochlorous acid treatment step, sodium hypochlorite is added to the fine fibrous cellulose dispersion (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, and more preferably 1.0 × 10 -3 g or more with respect to 1 g of fine fibrous cellulose. It is more preferably 0 × 10 ⁻² g or more, and particularly preferably 1.0 × 10 ^-1 g or more. 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 (slurry), it is preferable to stir for 1 minute or more and 10 hours or less under the conditions of 10 ° C. or higher and 50 ° C. or lower.

In the sub-critical water treatment step, the fine fibrous cellulose dispersion (slurry) is subjected to high-temperature and high-pressure treatment to bring it into a sub-critical state. Fine fibrous cellulose is hydrolyzed in a subcritical state. Specifically, after the fine fibrous cellulose dispersion (slurry) is placed in the 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 increased. Pressurize to 10 MPa or more and 80 MPa or less, preferably 10 MPa or more and 20 MPa or less. The heating and pressurizing time at this time is preferably 0.1 seconds 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 dispersion for paints used for addition to paints.

The content of the 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 7.0% by mass or less, based on the total mass of the fibrous cellulose dispersion. 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, preferably 300 mPa · s. It is more preferably s or more, further preferably 350 mPa · s or more, and particularly preferably 400 mPa · s or more. 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 having a fine fibrous cellulose concentration of 0.4% by mass can be measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). 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, preferably 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, it means that the transparency of the fibrous cellulose dispersion liquid is high and the fineness of the fine fibrous cellulose is good. When such a fibrous cellulose dispersion is added to the paint, the paint can exhibit excellent coatability. Here, the haze of the fibrous cellulose dispersion (fine fibrous cellulose concentration 0.2% by mass) is placed in a liquid glass cell (manufactured by Fujiwara Seisakusho, MG-40, backlit path) having an optical path length of 1 cm. Is a value measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute) in accordance with JIS K 7136. The zero point measurement is performed with ion-exchanged water contained in the same glass cell.

The fibrous cellulose dispersion may contain water and other additives in addition to the fine fibrous cellulose. Examples of other additives include defoaming agents, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants, preservatives (eg, phenoxyethanol) and the like. Further, the fibrous cellulose dispersion liquid may contain a hydrophilic polymer, organic ions and the like as optional components.

The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above-mentioned cellulose fibers), and examples of the oxygen-containing organic compound include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, and modification. Distillate, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, polyvinylpyrrolidone, polyvinylmethyl ether, polyacrylic acid salts, acrylic acid alkyl ester copolymers, urethane copolymers, cellulose derivatives (hydroxyl) Hydrophilic polymers such as ethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose and the like; hydrophilic low molecules such as glycerin, sorbitol and ethylene glycol can be mentioned.

Examples of the organic ion include tetraalkylammonium ion and tetraalkylphosphonium ion. 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, cetyltrimethylammonium ion, stearyltrimethylammonium ion, octyldimethylethylammonium ion, lauryldimethylethylammonium ion, didecyldimethylammonium ion, lauryldimethylbenzylammonium ion and tributylbenzylammonium ion. Examples of the tetraalkylphosphonium ion include tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Further, examples of the tetrapropyl onium ion and the tetrabutyl onium ion include tetra n-propyl onium ion and tetra n-butyl onium ion, respectively.

(Use)
The fine fibrous cellulose of the present invention is preferably used as a thickener for various purposes. For example, the fine fibrous cellulose of the present invention can be used as an additive to foods, cosmetics, cement, paints (for vehicle painting of automobiles, ships, aircraft, etc., building materials, daily necessities, etc.), inks, pharmaceuticals, and the like. can. Further, the fine fibrous cellulose of the present invention can be applied to daily necessities by adding it to a resin-based material or a rubber-based material. Above all, the fine fibrous cellulose of the present invention is particularly preferably fine fibrous cellulose for paints.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

<Manufacturing example 1>
[Manufacturing of phosphorylated fine fibrous cellulose dispersion]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 208 g / m ² sheets, separated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) is 700 ml) It was used.

The 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 (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 140 ° C. for 200 seconds to introduce a phosphate group into the cellulose in the pulp to obtain a phosphorylated pulp.

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

Next, the phosphorylated pulp after washing was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide 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 phosphorylated pulp that had been neutralized. Next, the phosphorylated pulp after the neutralization treatment was subjected to the above washing treatment.

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

Further, when the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer, it was found 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 that it had cellulose type I crystals.

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 with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) 6 times at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

By X-ray diffraction, it was confirmed that this fine fibrous cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The amount of phosphoric acid group (strong acid group amount) measured by the measuring method described later was 0.80 mmol / g.

<Manufacturing example 2>
A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1 except that the drying temperature of the chemical-impregnated pulp at the time of phosphorylation was 165 ° C. The amount of phosphoric acid group (strong acid group amount) measured by the measuring method described later was 1.45 mmol / g.

<Manufacturing example 3>
A fine fibrous cellulose dispersion 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 phosphorylation treatment and the washing treatment once in this order. rice field. The amount of phosphoric acid group (strong acid group amount) measured by the measuring method described later was 2.00 mmol / g.

<Manufacturing example 4>
[Production of TEMPO Oxidized Fine Fibrous Cellulose Dispersion]
As the raw material pulp, softwood kraft pulp (undried) made by Oji Paper was used. The raw material pulp was subjected to alkaline TEMPO oxidation treatment as follows. First, the above-mentioned raw material pulp equivalent to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl), and 10 parts by mass of sodium bromide are added to 10,000 parts by mass of water. It was dispersed in the department. Then, a 13 mass% sodium hypochlorite aqueous solution was added to 1.3 mmol with respect to 1.0 g of pulp to initiate the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10 or more and 10.5 or less, and the reaction was considered to be completed when no change was observed in the pH.

Then, the obtained TEMPO oxide pulp was washed. The washing treatment is carried out by dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing the pulp slurry, and then repeating the operation of filtration and dehydration. rice field. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

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

Then, the obtained top-oxidized TEMPO oxide pulp was washed. The cleaning treatment is carried out by dehydrating the pulp slurry after additional oxidation to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing the pulp slurry, and then repeating the operation of filtration and dehydration. rice field. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

Further, when the obtained TEMPO oxide pulp was tested and analyzed by an X-ray diffractometer, it was found 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 that it had cellulose type I crystals.

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

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

<Manufacturing 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 at the time of the oxidation reaction was 3.8 mmol with respect to 1.0 g of pulp. The amount of carboxy group measured by the measuring method described later was 1.30 mmol / g.

<Manufacturing example 6>
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 at the time of the oxidation reaction was 10 mmol with respect to 1.0 g of pulp. The amount of carboxy group measured by the measuring method described later was 1.80 mmol / g.

<Example 1>
(Low thixotropic by ozone 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), 1 L of an 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 allowed to stand for 30 minutes. The ozone addition rate at this time was 1.0 × ^10-2 g with respect to 1 g of fine fibrous cellulose. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. In this way, the fine fibrous cellulose was reduced to thixotropy, and the viscosity, degree of polymerization, and rate of change in viscosity of the obtained low thixotropy 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, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, degree of polymerization and viscosity change rate 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 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 with respect to 1 g of fine fibrous cellulose. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 4 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, degree of polymerization and viscosity change rate of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 7>
(Lower thixotropy by enzyme treatment)
The enzyme-containing liquid (manufactured by AB Enzymes, ECOPULPR, enzyme content is about 5% by mass) with respect to 1000 g (solid content concentration 2% by mass, solid content 20 g) of the fine fibrous cellulose dispersion obtained in Production Example 1. ) 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 with respect to 1 g of fine fibrous cellulose. Then, the mixture was stirred at a temperature of 100 ° C. for 1 hour to inactivate the enzyme. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 10>
The enzyme-containing liquid (AB Enzymes, ECOPULPR, enzyme content is about 5% by mass) is diluted 1000 times with 1000 g of the fine fibrous cellulose dispersion (solid content concentration 2% by mass, solid content 20 g). A low-thixized fine fibrous cellulose dispersion 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 with respect to 1 g of fine fibrous cellulose. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 13>
(Lower thixotropy by treatment with sodium hypochlorite)
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 a sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added to room temperature. Was stirred for 1 hour. The addition rate of sodium hypochlorite at this time was 1.02 g with respect to 1 g of fine fibrous cellulose. The viscosity, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 13 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 13 except that the fine fibrous cellulose dispersion obtained in Production Example 3 was used. The viscosity, degree of polymerization and viscosity change rate 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 (solid content concentration 2% by mass, solid content 20 g). Similarly, a low-tixo-formated fine fibrous cellulose dispersion was obtained. The addition rate of sodium hypochlorite at this time is 1.02 × ^10-2 parts by mass with respect to 1 part by mass of fine fibrous cellulose. The viscosity, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 16 except that the fine fibrous cellulose dispersion obtained in Production Example 2 was used. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

<Example 19>
(Lower thixotropy by sub-critical water treatment)
The fine fibrous cellulose dispersion 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 the heating was completed, the reactor was cooled with water, and then the low thixotropic fine fibrous cellulose dispersion in the reactor was recovered. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 19 except that the heating time was set to 1 second. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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 was obtained in the same manner as in Example 1 except that the fine fibrous cellulose dispersion obtained in Production Example 4 was used. The viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate 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 an ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was added, and the temperature was 25 ° C. in a closed container. After stirring for 2 minutes, the mixture was allowed to stand for 30 minutes. The ozone addition rate at this time was 1.0 × ^10-2 g with respect to 1 g of fine fibrous cellulose. Then, the phosphorylated pulp was washed to remove residual ozone. Then, the obtained pulp was used to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) 6 times at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was used as it was, and the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described later.

<Comparative Example 2>
A fine fibrous cellulose dispersion 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. The obtained fine fibrous cellulose dispersion was used as it was, and the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described later.

<Comparative Example 3>
A fine fibrous cellulose dispersion 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. The obtained fine fibrous cellulose dispersion was used as it was, and the viscosity, the degree of polymerization and the rate of change in viscosity were measured by the methods described later.

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

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

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

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

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

<Comparative Example 9>
The fine fibrous cellulose dispersion obtained in Production Example 6 was used as it was, and 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 amount of phosphoric acid group of the fine fibrous cellulose is a fibrous form prepared by diluting the fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The cellulose-containing slurry was treated with an ion exchange resin and then titrated with an alkali for measurement.
For the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1/10 is added to the above fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. This was done by pouring onto a mesh with an opening of 90 μm to separate the resin and the slurry.
For titration using alkali, a 0.1 N sodium hydroxide aqueous solution is added to the fibrous cellulose-containing slurry treated with an ion exchange resin once every 30 seconds by 50 μL, and the electrical conductivity shown by the slurry is shown. This was done by measuring the change in the value of. For the amount of phosphoric acid group (mmol / g), the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 1 of the measurement results is divided by the solid content (g) in the slurry to be titrated. Calculated.

[Measurement of carboxy group amount]
The amount of carboxy group of the fine fibrous cellulose is a fibrous cellulose prepared by diluting the fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water so that the content is 0.2% by mass. The contained slurry was treated with an ion exchange resin and then titrated with an alkali to measure the content.
For the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1/10 is added to the above fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. This was done by pouring onto a mesh with an opening of 90 μm to separate the resin and the slurry.
In the titration using alkali, 50 μL of 0.1 N sodium hydroxide aqueous solution is added to the fibrous cellulose-containing slurry treated with an ion exchange resin once every 30 seconds to obtain the electrical conductivity of the slurry. This was done by measuring the change in value. For the carboxy group amount (mmol / g), the alkali amount (mmol) required in the region corresponding to the first region shown in FIG. 2 of the measurement results is divided by the solid content (g) in the slurry to be titrated. 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. Next, the viscosity of the dispersion liquid thus obtained was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of the measurement was taken as the viscosity of the dispersion. The dispersion to be measured was allowed to stand in an environment of 23 ° C. and a relative humidity of 50% for 24 hours 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 degree of polymerization of the fine fibrous cellulose were measured according to Tappi T230. After measuring the viscosity (referred to as η1) measured by dispersing the cellulose fiber to be measured in a dispersion medium and the blank viscosity (referred to as η0) measured only with 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 indicates the concentration of fine fibrous cellulose at the time of viscosity measurement.
Further, the degree of polymerization (DP) of the fine fibrous cellulose was calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes referred to as "viscosity average degree of polymerization".

[Measurement of viscosity change rate of fine fibrous cellulose dispersion]
The rate of change in viscosity 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 when measured by the method described later is about 2500 mPa · s, and the fine fibrous cellulose dispersion is 5 cm in a cylindrical container having a diameter of 10 cm. It was put into the height of the above, 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 (analog viscometer T-LVT manufactured by BLOOKFIELD). 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. The temperature of the dispersion at the time of measurement was 23 ° C.
(Stirring with a stirrer)
Next, the obtained fine fibrous cellulose dispersion having a viscosity of about 2500 mPa · s was placed in a cylindrical container having a diameter of 10 cm, and the fine fibrous cellulose dispersion was placed up to a height of 5 cm. Using an elliptical stirrer having a width of 1 cm, the mixture was stirred for 24 hours while maintaining a state in which the center of the liquid surface was recessed 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 with the stirrer, the viscosity of the fine fibrous cellulose dispersion was immediately measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). 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. The temperature of the dispersion at the time of measurement was 23 ° C.
(Calculation of viscosity change rate)
The rate of change in viscosity before and after stirring with the stirrer was calculated by the following formula.
Viscosity change rate (%) = (Viscosity after stirring-Viscosity before stirring) / Viscosity before stirring x 100

<Evaluation>
[Evaluation of paint aptitude]
The applicability of the paint using the fine fibrous cellulose dispersion obtained by the present invention was evaluated as follows.
(Preparation of fine fibrous cellulose-containing paint)
1 mass of bright material (aluminum paste WXM7640, manufactured by Toyo Aluminum Co., Ltd., aluminum concentration 58 to 61 mass%) with respect to 100 parts by mass of a fine fibrous cellulose dispersion having a viscosity of about 2500 mPa · s obtained by the same method as described above. The parts were added and stirred with a disperser at 1500 rpm for 5 minutes to obtain a fine fibrous cellulose-containing paint.
(Paint circulation and spray coating)
Next, the obtained fine fibrous cellulose-containing paint was circulated in the pipe for 24 hours by a pump-type circulation device. Immediately after the circulation was completed, 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, the presence or absence of sedimentation of the bright material in the fine cellulose-containing paint was visually confirmed during the coating. From the results of the liquid dripping of the paint and the sedimentation of the bright material, the coating suitability of the fine fibrous cellulose-containing paint was evaluated in four stages.
A: Liquid dripping and sedimentation of the bright material are not observed during coating after the paint is circulated, and the coating suitability is very good.
B: During coating after the paint is circulated, either liquid dripping or sedimentation of the bright material is observed, but it is slight and the coating suitability is good.
C: Liquid dripping and sedimentation of the bright material are observed during coating after the paint is circulated, and the coating suitability is slightly poor, but there is no problem in practical use.
D: During coating after the paint is circulated, liquid dripping and sedimentation of the bright material are often observed, and the coating suitability is poor, which poses a practical problem.

The paint using the fine fibrous cellulose obtained in the examples exhibited excellent coatability.

Claims (7)

Fibrous cellulose having a fiber width of 1000 nm or less,
The fibrous cellulose has an ionic substituent, and the ionic substituent is a phosphate group or a substituent derived from a phosphate group.
The phosphoric acid group or the substituent derived from the phosphoric acid group is represented by the following formula (1).

(In equation (1), a, b, and n are natural numbers (where a = b × m); a of α ¹ , α ² , ..., α ⁿ and α'is O ⁻ . The rest is either R or OR; R is a hydrogen atom, saturated-linear hydrocarbon group, saturated-branched chain hydrocarbon group, saturated-cyclic hydrocarbon group, unsaturated-, respectively. A linear hydrocarbon group, an unsaturated-branched chain hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof; β ^{b +} is a monovalent or higher cation consisting of an organic or inorganic substance. Ion.)
The amount of the ionic substituent is 0.10 mmol / g or more and 1.50 mmol / g or less.
The degree of polymerization of the fibrous cellulose is 300 or more and 500 or less.
When the fibrous cellulose is dispersed in water so as to be 0.4% by mass to prepare a dispersion liquid, the viscosity of the dispersion liquid at 23 ° C. is 200 mPa · s or more and 3000 mPa · s or less.
When the fibrous cellulose is dispersed in water to prepare 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 ± 3 . Fibrous cellulose within 0%;
Viscosity change rate (%) = (Viscosity after stirring-Viscosity before stirring) / Viscosity before stirring x 100
(Stirring conditions)
A dispersion having a viscosity of 2500 mPa · s at 23 ° C. is placed in a cylindrical container having a diameter of 10 cm to a height of 5 cm, and an elliptical stirrer having a length of 5 cm, a width of 2 cm at the center and a width of 1 cm at the end is used. The center of the liquid surface is maintained in a state of being recessed by 2 cm, and the mixture is stirred at 23 ° C. for 24 hours. The fibrous cellulose according to claim 1, wherein the viscosity change rate is −30% or more and 0% or less. The fibrous cellulose according to claim 1 or 2, wherein the degree of polymerization of the fibrous cellulose is 340 or more and 500 or less. The fibrous cellulose according to any one of claims 1 to 3, wherein the amount of the ionic substituent is 0.40 mmol / g or more and 1.50 mmol / g or less. The fibrous cellulose according to any one of claims 1 to 3, wherein the amount of the ionic substituent is 0.40 mmol / g or more and 1.00 mmol / g or less. The fibrous cellulose according to any one of claims 1 to 5 , which is used for paints. A fibrous cellulose dispersion liquid obtained by dispersing the fibrous cellulose according to any one of claims 1 to 6 in water.

Images