JP6769510B2 - Method for producing fibrous cellulose, fibrous cellulose dispersion 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 fibers, in addition to fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Fine fibrous cellulose is attracting attention as a new material, and its uses are diverse.

Fine fibrous cellulose may be used, for example, as an additive for paints. In this case, the fine fibrous cellulose 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 studied to use cellulose nanofibers as a viscosity modifier.

International Publication No. 2018/01/2014 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 regard to such paints, attention has not been paid to the decrease in coating suitability due to the change in viscosity (thixotropy) due to the share applied before coating, and there is room for improvement in coating suitability. It was.

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

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 improved by adding the fine fibrous cellulose to the paint.
Specifically, the present invention has the following configuration.

[1] A fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorous acid group or a substituent derived from a phosphorous acid group.
When fibrous cellulose is dispersed in water to obtain a dispersion having a viscosity of 2500 mPa · s at 23 ° C. and the dispersion is stirred under the following stirring conditions, the viscosity change rate calculated by the following formula is within ± 50%. Fibrous cellulose;
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 recessed state of 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] When fibrous cellulose 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 200 mPa · s or more and 3000 mPa · s or less [1] or [ 2] The fibrous cellulose according to.
[4] The fibrous cellulose according to any one of [1] to [3] for paints.
[5] A fibrous cellulose dispersion liquid obtained by dispersing the fibrous cellulose according to any one of [1] to [4] in water.
[6] A cellulose fiber having a phosphorous acid group or a substituent derived from a phosphorous acid group is subjected to a defibration treatment to have a fiber width of 1000 nm or less, and a phosphorous acid group or a substituent derived from a phosphorous acid group. And the process of obtaining fibrous cellulose having
A method for producing fibrous cellulose, which comprises a step of subjecting fibrous cellulose to a thixotropic treatment.
[7] The method for producing fibrous cellulose according to [6], wherein the step of applying the thixotropy treatment is a step of reducing the degree of polymerization of fibrous cellulose to 300 or more and 500 or less.
[8] The method for producing fibrous cellulose according to [6] or [7], wherein the step of applying the thixotropy treatment is an ozone treatment step.

According to the present invention, it is possible to obtain fine fibrous cellulose capable of exhibiting excellent coating suitability when added to a paint.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphoric acid group. FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise to the fibrous cellulose-containing slurry having a carboxy group and the pH.

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

(Fine fibrous cellulose)
The present invention relates to a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorous acid group or a substituent derived from a phosphorous acid group. 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 recessed state of 2 cm, and the mixture is stirred at 23 ° C. for 24 hours.

In the present invention, when fine fibrous cellulose is used as a dispersion and the viscosity change rate when stirred under the above conditions is within ± 50%, excellent coating suitability is exhibited when added to a paint. 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 coating suitability. For example, even when the paint containing the fine fibrous cellulose of the present invention is stored or transported, the change in 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 a relatively strong share is applied to the paint by stirring the paint containing the fine fibrous cellulose of the present invention for a long time, 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 coating suitability of paints can be improved. Further, when the fine fibrous cellulose of the present invention is used as an additive for a coating material, the design and strength after coating can be improved. 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 is lowered by multiplying the dispersion by the share, 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, and particularly preferably -20% or more and 0% or less. The rate of change in viscosity of the dispersion calculated by the above formula is, for example, in an appropriate range depending on the type and conditions of treatment for the fine fibrous cellulose, the degree of polymerization of the fine fibrous cellulose and the amount of phosphite group introduced. It is achieved by controlling to.

In the present specification, the viscosity before and after stirring used for calculating the viscosity change rate of the dispersion is a 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 occur. That is, in the calculation formula of the viscosity change rate, the viscosity before stirring is the actually 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 performed later. Further, when adjusting the viscosity of the dispersion liquid before stirring to about 2500 mPa · s, the amount of 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. 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 to stir for 24 hours while maintaining a state in which the central portion of the liquid surface is recessed by 2 cm. The liquid temperature during stirring should be maintained at 23 ° C. Then, 1 minute after the end of stirring, the viscosity is measured using a B-type viscometer, the rotation speed is 6 rpm at 23 ° C., and the viscosity value 1 minute after the start of measurement is the viscosity after stirring.

When the fine fibrous cellulose of the present invention is dispersed in water 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 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, and 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, 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 fibrous cellulose as a cellulose molecule in water, and to make it easier to exhibit the effects of the fibrous cellulose on improving strength, rigidity and dimensional stability. it 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 prepare 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, destruction of the crystal region of the fibrous cellulose can be suppressed. 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 a 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, and further preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The degree of 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. In addition, sufficient viscosity can be easily obtained when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when fibrous cellulose is treated as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

The fibrous cellulose in the present 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 a method for producing fine fibrous cellulose described later.

The fibrous cellulose in the present embodiment has a phosphorous acid group or a substituent derived from the phosphorous acid group (also simply referred to as a phosphorous acid group). 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 a phosphorous acid group or a substituent derived from the phosphorous acid group. Further, the fine fibrous cellulose having a phosphorous acid group or a substituent derived from a phosphorous acid group can exhibit more excellent coating suitability when added to a coating material.

In the present invention, the phosphorous acid group or the substituent derived from the phosphorous acid group is, for example, a substituent represented by the following formula (2).

In equation (2), b is a natural number, m is an arbitrary number, and b × m = 1. α 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, an unsaturated-branched chain hydrocarbon group. , An unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. Above all, it is particularly preferable that α is a hydrogen atom. The α in the formula (2) does not include a group derived from the cellulose molecular chain.

Examples of the saturated-linear hydrocarbon group represented by α in the formula (2) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like, but are not particularly limited. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are 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 a vinyl group, an allyl group and the like, but are not particularly limited. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are 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 a phenyl group and a naphthyl group, but are not particularly limited.

Further, as the inducing group in α, 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 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 phosphorous acid 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 can be increased. It can also be increased.

Β ^{b +} in the formula (2) 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 is hard to yellow when the fiber raw material containing β is heated and is easily industrially used, but is not particularly limited.

The fine fibrous cellulose may have a phosphorous acid group or a group derived from the phosphorous acid group in addition to the phosphorous acid group or the substituent derived from the phosphorous acid group. The phosphoric acid group or the group derived from the phosphoric acid group may be, for example, a substituent represented by the following formula (1) or (3). The phosphoric acid group or the group derived from the phosphoric acid group may be a condensed phosphorus oxo acid group as represented by the following formula (3).

In the formula (1), a and b are natural numbers, and m is an arbitrary number (where a = b × m). a number of alpha and alpha 'are O ^- a and the remainder is OR. Here, 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, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (1) may be a group derived from a cellulose molecular chain.

In the formula (3), a and b are natural numbers, m is an arbitrary number, and n is a natural number of 2 or more (where a = b × m). ^{α 1, α 2, ···,} a number of alpha ⁿ and alpha 'is O ^- a and the remainder is either R or OR. Here, 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, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (3) may be a group derived from a cellulose molecular chain.

The specific examples of each group in the formulas (1) and (3) are the same as the specific examples of each group in the formula (2). Further, the formula (1) and specific examples beta ^{b +} a in (3) are the same as specific examples of beta ^{b +} in equation (2).

The fact that the fine fibrous cellulose has a phosphite group as a substituent means that the infrared absorption spectrum of the dispersion containing the fine fibrous cellulose was measured, and a tautomer of the phosphite group was measured around 1210 cm ^-1. This can be confirmed by observing the P = O-based absorption of a phosphonate group. In addition, the fact that the fibrous cellulose has a phosphoric acid group as a substituent means that the infrared absorption spectrum of the dispersion containing the fibrous cellulose is measured, and the absorption of the phosphoric acid group based on P = O is performed in the vicinity of 1230 cm ^-1. It can be confirmed by observing. Further, the fact that fibrous cellulose has a phosphite group or a phosphorous acid group as a substituent can be confirmed by a method of confirming a chemical shift by using NMR or a method of combining titration with elemental analysis.

The amount of phosphorous acid group introduced into the fibrous cellulose (the amount of the phosphorous acid group or the substituent derived from the phosphite group) is, for example, 0.10 mmol / g or more per 1 g (mass) of the fibrous cellulose. It is preferably 0.20 mmol / g or more, more preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more. Further, the amount of the phosphorous acid group introduced into the fibrous cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the fibrous cellulose, for example, 3 It is more preferably 0.00 mmol / g or less, further preferably 2.50 mmol / g or less, further preferably 2.00 mmol / g or less, and further preferably 1.50 mmol / g or less. It is more preferably 1.00 mmol / g or less, and particularly preferably 1.00 mmol / g or less. Here, the denominator in the unit mmol / g indicates the mass of fibrous cellulose when the counter ion of the phosphite group is a hydrogen ion (H ⁺ ). By setting the amount of the phosphorous 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 fibrous cellulose. Further, by setting the introduction amount of the phosphite group within the above range, the thixotropy property of the paint when fine fibrous cellulose is added to the paint can be lowered, thereby making the coating suitability more effective. Can be enhanced.

The amount of a phosphorous acid group (including a phosphorous acid group) introduced into the fibrous cellulose can be measured by, for example, a neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH 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 added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphoric acid group. The amount of the phosphorus oxo acid 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 strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. The titration curve shown in the upper part of FIG. 1 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 1 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, it is confirmed that there are two points where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociating acid of the fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point. The amount is equal to the amount of the second dissociating acid of the fibrous cellulose contained in the slurry used for the titration, and the amount of alkali required from the start to the second end point of the titration is the fibrous cellulose contained in the slurry used for the titration. Is equal to the total amount of dissociated acid. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxo acid group introduced (mmol / g). The amount of phosphorus oxo acid group introduced (or the amount of phosphorus oxo acid group) simply means the amount of the first dissociated acid.
In FIG. 1, the region from the start of titration to the first end point is referred to as a first region, and the region from the first end point to the second end point is referred to as a second region. For example, when the phosphoric acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of weakly acidic groups in the phosphoric acid group (also referred to as the second dissociated acid amount in the present specification) is apparently It decreases, 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 in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in the present specification) is the same as the amount of phosphorus atoms regardless of the presence or absence of condensation. Further, when the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so that the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, the titration curve has one point where the pH increment is maximized.

Since the denominator of the above-mentioned phosphorus oxo acid group introduction amount (mmol / g) indicates the mass of the acid-type fibrous cellulose, the phosphorus oxo acid group amount of the acid-type fibrous cellulose (hereinafter referred to as the phosphorus oxo acid group amount). (Called (acid type))). On the other hand, when the counterion of the phosphorus oxo acid 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. This makes it possible to determine the amount of phosphorus oxo acid groups (hereinafter, the amount of phosphorus oxo acid groups (C type)) possessed by the fibrous cellulose in which the cation C is a counter ion.
That is, it is calculated by the following formula.
Phosphoric acid group amount (C type) = Phosphoric acid group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total amount of anion derived from phosphoric acid group of fibrous cellulose (total amount of dissociated acid of phosphoric acid group)
W: Formula amount per valence of cation C (for example, Na is 23, Al is 9)

In the measurement of the amount of phosphorus oxo acid groups by the titration method, if the amount of one drop of the sodium hydroxide aqueous solution is too large or the titration interval is too short, the amount of phosphorus oxo acid groups will be lower than the original value. It may not be obtained. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, for example, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

In addition, which of the phosphite, the phosphoric acid, and the condensed phosphoric acid is the phosphoric acid detected when the phosphoric acid group, the condensed phosphoric acid group, or both is contained in addition to the phosphite group? As a method for distinguishing between, for example, a method of performing a treatment for cutting the condensed structure such as acid hydrolysis and then performing the above-mentioned titration operation, or a treatment for converting a phosphite group into a phosphate group such as an oxidation treatment. Examples thereof include a method of performing the above-mentioned titration operation after the operation.

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 even more preferably 460 or less. By setting the degree of polymerization of the fine fibrous cellulose within the above range, the thixotropy of the paint when the fine fibrous cellulose is added to the paint can be 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 an aqueous solution of copper ethylenediamine and the blank viscosity (referred to as η0) measured only with the 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 x [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "viscosity average degree of polymerization".

In the present invention, in particular, the degree of polymerization of the fine fibrous cellulose is 300 or more and 500 or less, and the amount of the phosphite group or the substituent derived from the phosphite group in the fine fibrous cellulose is 0.4 mmol / g or more. By setting the content to 1.0 mmol / g or less, the thixotropy property of the paint when fine fibrous cellulose is added to the paint can be further lowered, and thereby the coating suitability of the paint can be more effectively enhanced. it can. The degree of polymerization of the fine fibrous cellulose and the amount of the phosphorous acid group or the substituent derived from the phosphite group should be within an appropriate range so that the dispersion liquid in which the fine fibrous cellulose is dispersed exhibits low thixotropy. It is considered that this contributes to the coating suitability of the paint.

(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 pulp is preferably used 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 the present embodiment, one of the above types may be used alone, or two or more types 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, from the viewpoint of high cellulose ratio and high yield of fine fibrous cellulose during defibration treatment, long fiber fine fibrous cellulose having a small decomposition of cellulose in pulp and a large axial ratio can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. When long fiber fine fibrous cellulose having a large axial ratio is used, the viscosity tends to increase.

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

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

In the phosphorous acid 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 go. 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, a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state can be mentioned. Of these, 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, compound A and compound B may be added to the fiber raw material at the same time, separately, or 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, the required amounts of Compound A and Compound B may be added to the fiber raw material, or after the excess amounts of Compound A and Compound B are added to the fiber raw material, respectively, the surplus Compound A and Compound B are added by pressing or filtering. It may be removed.

The compound A used in this embodiment is at least one selected from a compound having a phosphorous acid group and a salt thereof. Examples of the compound having a phosphorous acid group include phosphorous acid, and examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of the compound having a phosphorous acid group include a lithium salt, a sodium salt, a potassium salt and an ammonium salt of phosphorous acid, and these can have various neutralization degrees. Of these, phosphorous acid and phosphorous acid are highly efficient in introducing phosphorous acid groups, are more likely to improve defibration efficiency in the defibration step described later, are low in cost, and are easy to apply industrially. Sodium salts of acids, potassium salts of phosphorous acid, or ammonium salts of phosphorous acid are preferably used.

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 atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the addition amount of phosphorus atoms 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.

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 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 is known to act as a good reaction catalyst.

In the phosphorous 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 phosphite 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, a microwave heating device, and a high frequency drying 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 phosphorous 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 the water content retained by the slurry and the water content generated by the dehydration condensation (phosphate 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, in addition to being able to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphate esterification, it is also possible to suppress the acid hydrolysis of the sugar chain in the fiber. it 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 phosphorous acid group introduced can be within a preferable range by setting the heating temperature and the heating time within an appropriate range.

The phosphorous acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphorous acid group introduction step two or more times, many phosphorous 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 phosphorous acid group introduction step is performed twice.

The amount of the phosphorous acid group introduced into the fibrous cellulose is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and more preferably 0.20 mmol / g or more per 1 g (mass) of the fine fibrous cellulose. It is more preferably 40 mmol / g or more, and particularly preferably 0.60 mmol / g or more. The amount of the phosphorous acid group introduced into the fibrous cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the fine fibrous cellulose, for example. It is more preferably 3.00 mmol / g or less, further preferably 2.50 mmol / g or less, further preferably 2.00 mmol / g or less, and even more preferably 1.50 mmol / g or less. Even more preferably, it is 1.00 mmol / g or less. By setting the amount of the phosphorous 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 phosphite group within the above range, the thixotropy property of the paint when fine fibrous cellulose is added to the paint can be lowered, thereby making the coating suitability more effective. Can be enhanced.

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

<Alkaline treatment process>
When producing fine fibrous cellulose, an alkali treatment may be performed on the fiber raw material between the phosphite group introduction step and the defibration treatment step described later. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the phosphorous acid group-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 the present embodiment, for example, sodium hydroxide or potassium hydroxide is preferably used 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 or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the 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 phosphorous acid group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10000% by mass or less, based on the absolute dry mass of the phosphorous acid group-introduced fiber. The following is more preferable.

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

<Acid treatment process>
When producing fine fibrous cellulose, the fiber raw material may be subjected to acid treatment between the step of introducing a phosphorous acid group and the defibration treatment step described later. For example, the phosphorous acid group 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 10% by mass or less, and more preferably 5% by mass or less, for example. 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 solution, 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 1,000% 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.

<Fiber processing>
Fine fibrous cellulose can be obtained by defibrating the phosphite-introduced fiber in the defibration treatment step. In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibrating apparatus is not particularly limited, but 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 crushed media and less likely to cause contamination.

In the defibration treatment step, for example, it is preferable to dilute the phosphorous acid group-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, glycerin and the like. Examples of ketones 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 mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the phosphorous acid group-introduced fiber in a dispersion medium may contain a solid content other than the phosphorous acid group-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 performing a thixotropy 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 thixotropy treatment to the fibrous cellulose. Is preferably included. 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 a thixotropic treatment. As described above, the defibration treatment step preferably further includes a step of introducing a phosphorous acid group into the cellulose fiber, and in addition to the step of introducing a phosphorous acid group, a washing step and an alkali. It is also preferable to further include a treatment step.

In the present specification, the step of applying the thixotropy treatment is a step of performing a treatment for reducing the thixotropy of the dispersion liquid containing fine fibrous cellulose. Specifically, the step of applying the thixotropy 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 thixotropy 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 thixotropy 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 sub-critical 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 sub-critical 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, for example, it is preferable to add it as an ozone / oxygen mixed gas. At this time, the ozone addition rate with respect 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 amorphous portions of cellulose, soluble cellooligosaccharides, and 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 hydrolyzes from the end of the cellulose molecule and is also called an exo-type or processive enzyme. The enzyme used in the enzyme treatment step is not particularly limited, but it is preferable to use endo-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, 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 (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 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 is in the above range, it means that the fibrous cellulose dispersion has high transparency and the fine fibrous cellulose is finely divided. When such a fibrous cellulose dispersion is added to the paint, the paint can exhibit excellent coating suitability. Here, the haze of the fibrous cellulose dispersion (fine fibrous cellulose concentration 0.2% by mass) is applied to 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 glass cell.

The fibrous cellulose dispersion may contain water and other additives in addition to the fine fibrous cellulose. Examples of other additives include antifoaming agents, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants, preservatives (for example, phenoxyethanol) and the like. In addition, the fibrous cellulose dispersion may contain a hydrophilic polymer, organic ions, or 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, polyacrylates, acrylic acid alkyl ester copolymer, urethane copolymer, cellulose derivative (hydroxy) Hydrophilic polymers such as ethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc .; Hydrophilic low molecules such as glycerin, sorbitol, ethylene glycol, etc. 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 painting vehicles such as automobiles, ships, aircraft, etc., for building materials, for daily necessities, etc.), inks, pharmaceuticals, and the like. it 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.

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>
[Manufacture of subphosphorylated fine fibrous cellulose dispersion]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheet, dissociated 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 phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to add 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. The amount was adjusted to be parts by mass, and a chemical-impregnated pulp was obtained. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 150 seconds to introduce a phosphorous acid group into the cellulose in the pulp to obtain a phosphorylated pulp.

Then, the obtained subphosphorylated pulp was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of subphosphorylated pulp is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. Was done by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

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

The infrared absorption spectrum of the obtained subphosphorylated pulp was measured using FT-IR. As a result, absorption based on P = O of the phosphonic acid group, which is a tautomer of the phosphite group, was observed around 1210 cm ^-1 , and the phosphite group (phosphonic acid group) was added to the pulp. Was confirmed. Further, when the obtained subphosphorylated pulp was tested and analyzed by an X-ray diffractometer, two positions were found: 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals. Regarding the obtained phosphorous acid pulp, the amount of phosphorous acid group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorous acid group amount] described later was 0.74 mmol / g. .. The total amount of dissociated acid was 0.78 mmol / g.

Ion-exchanged water was added to the obtained subphosphorylated 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 phosphite group (first dissociated acid amount) measured by the measuring method described later was 0.74 mmol / g.

<Manufacturing example 2>
A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1 except that the heating time of the chemical-impregnated pulp during subphosphorylation was 250 seconds. The amount of phosphite group (first dissociated acid amount) measured by the measuring method described later was 1.51 mmol / g.

<Manufacturing example 3>
A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1 except that the heating time of the chemical-impregnated pulp during subphosphorylation was 400 seconds. The amount of phosphite group (first dissociated acid amount) measured by the measuring method described later was 1.86 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. Alkaline TEMPO oxidation treatment was carried out on this raw material pulp 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 10000 parts by mass of water. Dispersed in parts. 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.

Next, 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, and then repeating the operation of filtration and dehydration. It was. 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 dehydrated sheet corresponding to 100 parts by mass of dry mass was dispersed in 10000 parts by mass of 0.1 mol / L acetate buffer (pH 4.8). Next, 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 with stirring at 500 rpm using a magnetic stirrer to obtain a pulp slurry.

Next, the obtained top-oxidized TEMPO oxide pulp was washed. The washing treatment is carried out by dehydrating the post-oxidized pulp slurry to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing the slurry, and then repeating the operation of filtering and dehydrating. It was. 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 oxidized 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 during 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 during 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>
(Lower thixotropy 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 ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was added and 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 viscosity change rate 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 later.

<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 later.

<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 later.

<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 later.

<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 later.

<Example 7>
(Lower thixotropy by enzyme treatment)
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 later.

<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 later.

<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 later.

<Example 10>
The enzyme-containing solution (AB Enzymes, ECOPULPR, enzyme content is about 5% by mass) is diluted 1000-fold with respect to 1000 g of the fine fibrous cellulose dispersion (solid content concentration 2% by mass, solid content 20 g). A low-thixogenized 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 later.

<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 later.

<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 later.

<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 sodium hypochlorite addition rate 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 later.

<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 later.

<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 later.

<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). In the same manner, a low-tixoneized fine fibrous cellulose dispersion was obtained. Sodium hypochlorite addition rate at this time is 1.02 × 10 ^-2 parts by mass relative to the fine fibrous cellulose 1 part by weight. The viscosity, degree of polymerization and viscosity change rate of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described later.

<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 later.

<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 later.

<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 later.

<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 later.

<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 later.

<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 later.

<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 later.

<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 later.

The sheet obtained by dehydrating and drying the fine fibrous cellulose obtained through the hypophosphating treatments of Examples 1 to 24 and Comparative Examples 1 to 3 was analyzed by FT-IR and found to be around 1210 cm ^-1 . P = O-based absorption of the phosphonic acid group, which is a tautomer of the phosphite group, was observed.

<Comparative example 1>
To 100 g of the subphosphorylated pulp obtained in Production Example 1 (solid content 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. The subphosphorylated pulp was then 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, degree of polymerization and viscosity change rate 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 subphosphorylated pulp obtained in Production Example 2 was used. The obtained fine fibrous cellulose dispersion was used as it was, and the viscosity, degree of polymerization and viscosity change rate 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 subphosphorylated pulp obtained in Production Example 3 was used. The obtained fine fibrous cellulose dispersion was used as it was, and the viscosity, degree of polymerization and viscosity change rate 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, degree of polymerization and viscosity change rate were measured by the method described later.

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

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

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

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

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

<Measurement>
[Measurement of phosphorus oxo acid group amount]
The amount of phosphite groups in the fine fibrous cellulose is a fiber prepared by diluting a 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-like cellulose-containing slurry was treated with an ion exchange resin and then titrated with an alkali.
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 fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
For titration using alkali, the change in pH value indicated by the slurry is measured while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry treated with an ion exchange resin every 5 seconds. I went by doing. The titration was carried out while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point divided by the solid content (g) in the slurry to be titrated was defined as the amount of phosphite groups (mmol / g).

[Measurement of carboxy group amount]
The carboxy group content of the fine fibrous cellulose is adjusted to 0.2% by mass by adding ion-exchanged water to the fine fibrous cellulose-containing slurry containing the target fine fibrous cellulose, and the treatment with an ion exchange resin is performed. After that, it was measured by performing a titration using an alkali.
The treatment with an ion exchange resin is carried out by adding a 1/10 volume of strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) to a slurry containing 0.2% by mass of fine fibrous cellulose for 1 hour. After the shaking treatment, the resin and the slurry were separated by pouring onto a mesh having a mesh size of 90 μm.
For titration using alkali, the change in pH value indicated by the slurry is measured while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry treated with an ion exchange resin every 5 seconds. I went by doing. By observing the change in pH while adding an aqueous sodium hydroxide solution, a titration curve as shown in FIG. 2 can be obtained. As shown in FIG. 2, in this neutralization titration, there is one point in which the increment (differential value of pH with respect to the amount of alkaline drop) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Observed. The maximum point of this increment is called the first end point. Here, the region from the start of titration to the first end point in FIG. 2 is referred to as a first region. The amount of alkali required in the first region is equal to the amount of carboxy groups in the slurry used for titration. Then, the amount of alkali (mmol) required in the first region of the titration curve is divided by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated, so that the amount of carboxy group introduced (mmol / g). ) Was calculated.
The above-mentioned amount of carboxy group introduced (mmol / g) is the amount of substituents per 1 g of mass of fibrous cellulose when the counterion of the carboxy group is hydrogen ion (H ⁺ ) (hereinafter, the amount of carboxy group (acid). Type)) is shown.

[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 at 1500 rpm for 5 minutes with a disperser. 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 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 fibers 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 x [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "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 1 and stirred with a disperser at 1500 rpm for 5 minutes. One minute after the end of stirring, the viscosity of the obtained fine fibrous cellulose dispersion was measured using a B-type viscometer (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 to a height of 5 cm, and the length was 5 cm, the width of the center was 2 cm, and the end. 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 coating suitability 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. The coating suitability of the fine fibrous cellulose-containing paint was evaluated on a four-point scale from the results of the liquid dripping of the paint and the sedimentation of the bright material.
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, a large amount of liquid dripping and sedimentation of the bright material are 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 coating suitability.

Claims (5)

A method for producing fibrous cellulose having a phosphorous acid group represented by the following formula (2) or a substituent derived from a phosphorous acid group and having a fiber width of 1000 nm or less.
Cellulose fibers having a phosphorous acid group represented by the following formula (2) or a substituent derived from a phosphorous acid group are subjected to a defibration treatment to have a fiber width of 1000 nm or less and the following formula (2). A step of obtaining a fibrous cellulose having a phosphorous acid group represented or a substituent derived from a phosphorous acid group, and
The fibrous cellulose includes a step of subjecting the fibrous cellulose to at least one selected from ozone treatment, enzyme treatment, hypochlorous acid treatment and subcritical water treatment.
When the fibrous cellulose obtained by the method for producing fibrous cellulose 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 following formula is used. A method for producing fibrous cellulose, wherein the calculated viscosity change rate 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. , Keep the center of the liquid level recessed by 2 cm and stir at 23 ° C. for 24 hours;

In equation (2), b is a natural number, m is an arbitrary number, and b × m = 1. α 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, an unsaturated-branched chain hydrocarbon group. , Unsaturated-cyclic hydrocarbon group or aromatic group. The method for producing fibrous cellulose according to claim 1, wherein the degree of polymerization of the fibrous cellulose obtained by the method for producing fibrous cellulose is 300 or more and 500 or less. When the fibrous cellulose obtained by the method for producing 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. The method for producing fibrous cellulose according to claim 1 or 2 below. The method for producing fibrous cellulose according to any one of claims 1 to 3, wherein the fibrous cellulose obtained by the method for producing fibrous cellulose is for a paint. A step of obtaining fibrous cellulose by the method for producing fibrous cellulose according to any one of claims 1 to 4.
A method for producing a fibrous cellulose dispersion liquid, which comprises a step of dispersing the fibrous cellulose in water.