JP2021161353A - Fibrous cellulose, fibrous cellulose-containing material, and molding - Google Patents

Abstract

To provide a fibrous cellulose that satisfactorily absorbs both of pure water and salt water.SOLUTION: A fibrous cellulose has a phosphorous acid group or a phosphorous acid group-derived substituent. When a sheet is formed by a predetermined sheet forming method and a liquid absorption rate of the sheet is calculated by a predetermined measuring method, the liquid absorption rate is 0.30 mm/s or more.SELECTED DRAWING: None

Description

The present invention relates to fibrous cellulose, fibrous cellulose-containing material and molded article.

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.

Normally, cellulose fibers are strongly bonded to each other by hydrogen bonds. Therefore, by chemically treating the cellulose fiber, a hydrophilic functional group (for example, a carboxy group, a cation group, a phosphoric acid group, etc.) is introduced into the hydroxy group on the surface of the cellulose to modify the cellulose fiber. Quality is being done.

For example, Patent Document 1 discloses a composition containing a phosphoric acid group or a cellulose fiber having a substituent derived from a phosphoric acid group. Here, a crosslinked structure of phosphoric acid groups is formed in at least a part of the cellulose fibers. Further, Patent Document 2 discloses a cellulose fine fiber in which a part of the hydroxy group of the cellulose fiber is replaced with a phosphorous acid group having a predetermined structure and an ester of phosphorous acid is introduced.

International Publication No. 2018/062501 Japanese Patent No. 6404382

When a sheet is formed from cellulose fibers, for example, the sheet may be required to have excellent water absorption of pure water. Further, not only pure water but also water absorption (salt water water absorption) for a solution containing salt may be required. In order to enhance these water absorbency, it has been studied to form a crosslinked structure on the cellulose fiber, but according to the study by the inventors. It has been difficult to achieve both pure water absorption and salt water absorption of a sheet containing fibrous cellulose at a high level. That is, to a certain extent, both pure water absorption and salt water absorption are compatible, but if an attempt is made to further increase the water absorption rate, there is a problem that only the pure water absorption rate becomes high and the salt water water absorption rate does not easily increase.

Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of providing fibrous cellulose having excellent water absorption in pure water and salt water.

As a result of diligent studies to solve the above problems, the present inventors appropriately control the production conditions of fibrous cellulose having a phosphite group or a substituent derived from the phosphite group. It has been found that, by setting the liquid absorption rate of the sheet when the sheet is formed from the fibrous cellulose within a predetermined range, the fibrous cellulose having excellent water absorption in pure water and salt water can be obtained.
Specifically, the present invention has the following configuration.

[1] A fibrous cellulose having a phosphorous acid group or a substituent derived from a phosphorous acid group, when a sheet is formed by the following sheet forming method and the liquid absorption rate is calculated by the following measuring method, the sheet Fibrous cellulose with a liquid absorption rate of 0.30 mm / s or more;
(Sheet formation method)
Ion-exchanged water is added to the fibrous cellulose to prepare a suspension having a solid content concentration of 0.3% by mass, and the suspension is poured onto a filter paper to obtain a wet sheet ^{having an absolute dry basis weight of 200 g / m 2.} The wet sheet is peeled off from the filter paper, placed on a stainless steel tray, and dried under the conditions of 23 ° C. and 50% relative humidity for 3 days; the dried sheet is pressed at a weighted pressure of 7.7 MPa for 1 minute. And use it as a sheet for measuring the liquid absorption rate;
(Liquid absorption rate)
A sheet for measuring the absorption rate is cut into a strip-shaped sample having a width of 5 mm and a length of 50 mm, and the end region of the sample from the longitudinal end to 5 mm is immersed in ion-exchanged water; from the longitudinal end to the longitudinal. The time t required for the ion-exchanged water to reach a distance point of 45 mm is measured, and the liquid absorption rate (mm / sec) is calculated using the following formula (1).
Liquid absorption rate (mm / sec) = 40 (mm) / t (sec) Equation (1)
[2] The fibrous cellulose according to [1], which further has a phosphoric acid group or a substituent derived from a phosphoric acid group.
[3] When the amount of the first dissociating acid in the fibrous cellulose is A1 and the total amount of the dissociating acid in the fibrous cellulose is A2, the value of A1 / A2 is 0.51 or more and 0.98 or less [1] or. The fibrous cellulose according to [2].
[4] A fibrous cellulose-containing product containing the fibrous cellulose according to any one of [1] to [3].
[5] A molded product formed from the fibrous cellulose according to any one of [1] to [3] or the fibrous cellulose-containing material according to [4].
[6] The molded product according to [5], which is in the form of a sheet.

According to the present invention, fibrous cellulose having excellent water absorption in pure water and water absorption in salt water can be obtained.

FIG. 1 is a graph showing the relationship between the amount of NaOH titrated and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group.

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.

(Fibrous cellulose)
The present invention relates to a phosphite group or a fibrous cellulose having a substituent derived from a phosphorous acid group. Here, when a sheet is formed from the fibrous cellulose of the present invention by the following sheet forming method and the liquid absorption rate is calculated by the following measurement method, the liquid absorption rate of the sheet is 0.30 mm / s or more.
(Sheet formation method)
Ion-exchanged water is added to the fibrous cellulose to prepare a suspension having a solid content concentration of 0.3% by mass, and the suspension is poured onto a filter paper to obtain a wet sheet ^{having an absolute dry basis weight of 200 g / m 2.} The wet sheet is peeled off from the filter paper, placed on a stainless steel tray, and dried under the conditions of 23 ° C. and 50% relative humidity for 3 days; the dried sheet is pressed at a weighted pressure of 7.7 MPa for 1 minute. And use it as a sheet for measuring the liquid absorption rate;
(Liquid absorption rate)
A sheet for measuring the absorption rate is cut into a strip-shaped sample having a width of 5 mm and a length of 50 mm, and the end region of the sample from the longitudinal end to 5 mm is immersed in ion-exchanged water; from the longitudinal end to the longitudinal. The time t required for the ion-exchanged water to reach a distance point of 45 mm is measured, and the liquid absorption rate (mm / sec) is calculated using the following formula (1).
Liquid absorption rate (mm / sec) = 40 (mm) / t (sec) Equation (1)

When a sheet is formed by the above sheet forming method and the liquid absorption rate is measured by the above method, the liquid absorption rate of the sheet may be 0.30 mm / s or more, preferably 0.32 mm / s or more. It is more preferably 0.35 mm / s or more, and further preferably 0.38 mm / s or more. Further, the liquid absorption rate of the sheet is preferably 20 mm / s or less. The liquid absorption rate of such a sheet is achieved by producing fibrous cellulose by a method for producing fibrous cellulose as described later and forming a sheet using the fibrous cellulose. Specifically, it is achieved by condensing at least a part of a phosphite group introduced into the fibrous cellulose or a substituent derived from the phosphorous acid group (hereinafter, also simply referred to as a phosphorous acid group). The form of condensation is not particularly limited, and may be, for example, a structure in which phosphite groups are dehydrated and condensed, or a structure in which phosphite groups and phosphoric acid groups are dehydrated and condensed. , A structure in which a phosphite group and a hydroxy group contained in fibrous cellulose are dehydrated and condensed may be used. The fibrous cellulose may contain a structure in which phosphoric acid groups are dehydrated and condensed, or may include a structure in which the phosphoric acid group and the hydroxy group contained in the fibrous cellulose are dehydrated and condensed. Further, the form of condensation may be one in which phosphite groups are condensed with each other via a structure derived from a cross-linking agent or the like, and a phosphite group and a phosphoric acid group are condensed through a structure derived from a cross-linking agent or the like. May be condensed, or a structure in which a phosphite group and a hydroxy group contained in the fibrous cellulose are condensed via a structure derived from a cross-linking agent or the like may be used. The fibrous cellulose may include a structure in which phosphoric acid groups are condensed with each other via a structure derived from a cross-linking agent or the like, and the phosphoric acid group and the fibrous cellulose may be contained through a structure derived from a cross-linking agent or the like. It may contain a structure in which the hydroxy groups contained therein are condensed.

In addition, in this specification, a substituent derived from a phosphite group or a phosphite group also includes a condensed structure of a phosphite group or a substituent derived from a phosphite group. For example, when a phosphite group and a phosphoric acid group are condensed to form a crosslinked structure between fibers, the fibrous cellulose contains a structure derived from the phosphite group and a structure derived from the phosphoric acid group, respectively. It will be. In the present specification, even in such a case, the fibrous cellulose has both a substituent derived from a phosphite group or a phosphite group and a substituent derived from a phosphoric acid group or a phosphoric acid group. Suppose you are.

Examples of the analysis method for forming a condensed structure between fibrous celluloses include a method using NMR and a method of combining various titration methods with elemental analysis. In the method using NMR, the formation of a condensed structure can be confirmed by measuring the chemical shift. Further, in the method of combining various titration methods with elemental analysis, the amount of P atoms measured by elemental analysis and the amount of first dissociated acid obtained from neutralization titration are compared. When the condensed structure is not formed, the amount of P atoms and the amount of the first dissociated acid are equal, but when the condensed structure is present, the amount of the first dissociated acid is smaller than the amount of P atoms. It can also be confirmed that the condensed structure was formed by reducing the amount of the first dissociated acid before and after the condensation reaction.

Since the fibrous cellulose of the present invention has the above-mentioned structure, it is excellent in pure water absorption and salt water absorption. The water absorption of pure water can be evaluated _{by, for example, the water absorption rate (I 0} ) when a sheet is formed from fibrous cellulose by the above method and the sheet is immersed in pure water. The amount of pure water absorbed by the sheet is a value measured in accordance with JIS K 7223: 1996, and the water absorption rate (I ₀ ) is a value calculated from the following formula.
Water absorption rate (I ₀ ) (%) = 100 x sheet water absorption (g) / sheet absolute dry weight (g)
The water absorption rate (I ₀ ) of the sheet is preferably 1300% or more, more preferably 1400% or more, and further preferably 1500% or more. The upper limit of the water absorption rate (I ₀ ) of the sheet is not particularly limited, but is preferably 100,000% or less.

Further, the water absorption of salt water can be evaluated _{by, for example, the water absorption rate (I 1} ) when a sheet is formed from fibrous cellulose by the above method and the sheet is immersed in a 0.1 N sodium chloride aqueous solution. The water absorption amount of the sodium chloride aqueous solution of the sheet is a value measured in accordance with JIS K 7223: 1996, and the water absorption rate (I ₁ ) is a value calculated from the following formula.
Water absorption rate (I ₁ ) (%) = 100 x sheet water absorption (g) / sheet absolute dry weight (g)
The water absorption rate (I ₁ ) of the sheet is preferably 700% or more, more preferably 800% or more, further preferably 900% or more, and particularly preferably 1000% or more. The upper limit of the water absorption rate (I ₁ ) of the sheet is not particularly limited, but is preferably 100,000% or less.

The salt water water absorption can also be evaluated by the reduction rate (%) of the water absorption rate. Here, the reduction rate (%) of the water absorption rate is an index showing the degree of decrease in the water absorption rate of salt water with respect to the water absorption rate of pure water. When the decrease rate (%) of the water absorption rate is small, it means that the amount of water absorption is not inferior to that of the case where pure water is absorbed even when salt water is absorbed. It can be determined that the smaller the reduction rate (%) of the water absorption rate, the better the water absorption of the salt water. The reduction rate (%) of the water absorption rate is a value calculated by the following formula.
Reduction rate of water absorption rate (%) = 100 x (I _0- I ₁ ) / I ₀
Here, the water absorption rate of pure water (I ₀ ) and the water absorption rate of the sodium chloride aqueous solution (I ₁ ) are values calculated by the above-mentioned method.
The reduction rate (%) of the water absorption rate calculated by the above method is preferably 70% or less, more preferably 65% or less, further preferably 60% or less, and 55% or less. More preferably, it is more preferably 50% or less, further preferably 40% or less, and particularly preferably 30% or less. The lower limit of the reduction rate (%) of the water absorption rate is not particularly limited and may be 0%.

The fiber width of the fibrous cellulose of the present invention is not particularly limited, and may be larger than 1000 nm and may be 1000 nm or less. Further, cellulose fibers having a fiber width of more than 1000 nm and cellulose fibers having a fiber width of 1000 nm or less may be mixed. For example, in the case of producing a sheet having excellent transparency, the fiber width of the fibrous cellulose is preferably 1000 nm or less, more preferably 100 nm or less, and further preferably 8 nm or less. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose.

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 may be larger than 1000 nm and may be 1000 nm or less. For example, when the average fiber width of the fibrous cellulose is larger than 1000 nm, it is preferably larger than 1 μm and 50 μm or less, more preferably larger than 1 μm and 40 μm or less, and further preferably larger than 1 μm and 30 μm or less. .. When the average fiber width of the fibrous cellulose is 1000 nm or less, it is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more. It is particularly preferably 10 nm or less. The fibrous cellulose may be a monofibrous cellulose, but the fibrous cellulose in the present specification also includes a fiber aggregate of the 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 when the fiber width is larger than 1000 nm, the fiber length is preferably 0.1 mm or more, more preferably 0.6 mm or more, for example. The fiber length is preferably 50 mm or less, more preferably 20 mm or less. When the fiber width is 1000 nm or less, the fiber length is preferably 0.1 μm or more, for example. The fiber length is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 600 μm or less. 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 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 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 fibrous cellulose. By setting the axial ratio to the above upper limit value or less, for example, when treating fibrous cellulose as a dispersion liquid, 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, 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 fibrous cellulose, which will be described later.

The fibrous cellulose of the present invention has a phosphorous acid group or a substituent derived from the phosphorous acid group (hereinafter, also simply referred to as a phosphorous acid group). Further, the fibrous cellulose of the present invention preferably further has a phosphoric acid group or a substituent derived from the phosphoric acid group (hereinafter, also simply referred to as a phosphoric acid group). In addition, in this specification, a substituent derived from a phosphoric acid group may be a salt of a phosphoric acid group or a phosphoric acid ester group. Further, the substituent derived from the phosphorous acid group may be a salt of the phosphorous acid group. The phosphite group also includes a structure in which a phosphite group is condensed, and the phosphoric acid group also includes a structure in which a phosphoric acid group is condensed.

The phosphoric acid group and the phosphorous acid group may be present in the same cellulose molecular chain (cellulose monofiber). For example, a phosphate group may be introduced into one glucose and a phosphite group may be introduced into the other glucose among the two glucose units which are the basic structures constituting cellulose. Further, the fibrous cellulose of the present invention may be a fiber aggregate of a cellulose molecular chain having a phosphoric acid group (cellulose single fiber) and a cellulose molecular chain having a phosphite group (cellulose single fiber). The fibrous cellulose of the present invention includes a cellulose molecular chain having both a phosphoric acid group and a phosphite group (cellulose monofiber), a cellulose molecular chain having a phosphoric acid group (cellulose monofiber), and phosphite. It may be a fiber aggregate of three kinds of single fibers of a cellulose molecular chain (cellulose single fiber) having a group. The condensed structure derived from the phosphorous acid group or the phosphoric acid group may be formed in the same fiber or may be formed among a plurality of fibers.

In the fibrous cellulose of the present invention, at least a part of the phosphite group forms a condensed structure with another phosphite group, a phosphoric acid group, or a hydroxy group in the fibrous cellulose. The form of condensation is not particularly limited, and may be, for example, a structure in which phosphite groups are dehydrated and condensed, or a structure in which phosphite groups and phosphoric acid groups are dehydrated and condensed. , A structure in which a phosphite group and a hydroxy group contained in fibrous cellulose are dehydrated and condensed may be used. Further, the fibrous cellulose may contain a structure in which phosphoric acid groups are dehydrated and condensed, or may include a structure in which the phosphoric acid group and the hydroxy group contained in the fibrous cellulose are dehydrated and condensed. Above all, the fibrous cellulose of the present invention preferably contains a structure in which a phosphite group and a phosphoric acid group are dehydrated and condensed. The form of condensation is not limited to dehydration condensation, and phosphite groups may be condensed with each other via a structure derived from a cross-linking agent or the like. The phosphoric acid group and the phosphoric acid group may be condensed, or the phosphite group and the hydroxy group of the fibrous cellulose may be condensed via a structure derived from a cross-linking agent or the like. Further, the fibrous cellulose may contain a structure in which phosphoric acid groups are condensed with each other via a structure derived from a cross-linking agent or the like, and in the phosphoric acid group and the fibrous cellulose via a structure derived from a cross-linking agent or the like. It may contain a structure in which the hydroxy groups contained in the above are condensed.

The fibrous cellulose of the present invention contains, at least in part, a structure represented by the following formula (A). In the following formula (A), * indicates a binding site with a cellulose molecular chain. The two * marks may be binding sites in the same fiber, and one * mark and the other * mark may be binding sites in different fibers.

In formula (A), a is 0 or a natural number, b is a natural number, m is an arbitrary number, and n is a natural number (where a = b × m). Of α ¹ , α ² , ..., α ⁿ , a are O ⁻ , and the rest are 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. Hydrocarbon groups, unsaturated-cyclic hydrocarbon groups, aromatic groups, or derivatives thereof. It is preferable that at least one of α ⁿ is R, and R is preferably a hydrogen atom. Further, n is preferably a natural number of 2 or more.

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

As the inducing group in R, a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted with respect to the main chain or side chain of the above-mentioned various hydrocarbon groups is used. However, it is not particularly limited. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R to the above range, the molecular weight of the condensed structure can be set to an appropriate range.

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include alkali metal ions 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 fibrous cellulose of the present invention contains a phosphite group that does not form a condensed structure. In addition, a phosphoric acid group may be further contained. In this case, the phosphorous acid group is, for example, a substituent represented by the following formula (2). The phosphoric acid group may be, for example, a substituent represented by the following formula (1).

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 groups, aromatic groups, or inducing groups 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.

In the formula (1), a and b are natural numbers, and m is an arbitrary number (where a = b × m). Of α and α', a are O ⁻ and the rest are 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. Hydrocarbon groups, unsaturated-cyclic hydrocarbon groups, aromatic groups, or derivatives thereof. The α in the formula (1) does not include a group derived from the cellulose molecular chain.

The saturated-linear hydrocarbon represented by α in the formula (2) or R in the formula (1) is a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, or an unsaturated-linear hydrocarbon. Specific examples of the hydrocarbon group, the unsaturated-branched chain hydrocarbon group, the unsaturated-cyclic hydrocarbon group, and the aromatic group include the same as the specific examples of each group of the formula (A). ..

Moreover, as a specific example of the inducing group in α of the formula (2) or R of the formula (1), the same as the inducing group of the formula (A) can be mentioned.

^{Β b +} in the formulas (1) and (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 alkali metal ions 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.

Further, the fibrous cellulose of the present invention may have a condensed phosphorus oxo acid group, and examples of the condensed phosphorus oxo acid group include a substituent represented by the following formula (3).

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). Of α ¹ , α ² , ..., α ⁿ and α', a are O ⁻ , and the rest are 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. Hydrocarbon groups, unsaturated-cyclic hydrocarbon groups, aromatic groups, or derivatives thereof. The α in the formula (3) does not include a group derived from the cellulose molecular chain.

The specific example of each group in the formula (3) is the same as the specific example of each group in the formula (1), and the specific example of β ^{b +} in the formula (3) is β in the formula (1). It is the same as the specific example of ^{b +.}

The fibrous cellulose may have other anionic groups in addition to the phosphoric acid group and the phosphorous acid group. Examples of such anionic groups include carboxy groups originally contained in pulp.

Further, the fibrous cellulose may include a structure in which the hydroxy groups of the fibrous cellulose are dehydrated and condensed, or a structure in which the hydroxy groups of the fibrous cellulose are condensed by a cross-linking agent other than phosphoric acid.

When the fibrous cellulose has a phosphite group and a phosphoric acid group, the molar ratio of the phosphite group to the phosphoric acid group (phosphoric acid group: phosphoric acid group) is 0.01: 99.99 to 99.99. : 0.01 is preferable, 1:99 to 99: 1 is more preferable, and 10:90 to 90:10 is even more preferable. That is, the molar ratio of the substituent represented by the above formula (2) to the substituent represented by the above formula (1) (formula (2): formula (1)) is 0.01: 99.99 to It is preferably 99.99: 0.01, more preferably 1:99 to 99: 1, and even more preferably 10:90 to 90:10. When the phosphite group and the phosphoric acid group form a condensed structure, the molar amount is converted by using the structure based on each group as the phosphite group or the phosphoric acid group. By setting the molar ratio of the phosphoric acid group to the phosphorous acid group within the above range, the water absorption of pure water and the water absorption of salt water of the fibrous cellulose can be more effectively enhanced.

The fact that the fibrous cellulose has a phosphite group as a substituent means that the infrared absorption spectrum of the dispersion containing the fibrous cellulose is measured, and phosphones, which are ^{metavariants of the phosphorous acid group, are measured in the vicinity of 1210 cm-1.} It can be confirmed by observing the absorption of the acid group based on P = O. 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 phosphoric acid group as a substituent can be confirmed by a method of confirming a chemical shift by using NMR, a method of combining titration with elemental analysis, or the like.

The amount of phosphorus oxo acid groups introduced into the fibrous cellulose (the amount of phosphorus oxo acid groups) is preferably 0.10 mmol / g or more, and more preferably 0.20 mmol / g or more per 1 g (mass) of the fibrous cellulose, for example. It is more preferably 0.50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of the phosphorus oxo 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. It is more preferably 00 mmol / g or less. Here, the unit mmol / g indicates the amount of substituents per 1 g of mass of fibrous cellulose when the counter ion of the phosphorus oxo acid group is a hydrogen ion (H ^+). The amount of the phosphoric acid group is total when the amount of the phosphoric acid group includes a phosphite group and a phosphoric acid group, or when the phosphoric acid group contains a phosphite group, a phosphoric acid group and a condensed phosphoric acid group. The amount of phosphoric acid groups. By setting the amount of the phosphorus oxo acid group introduced within the above range, the water absorption of pure water and the water absorption of salt water of the fibrous cellulose can be more effectively enhanced.

The amount of the phosphorus oxo 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 titrated and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group. The amount of the phosphorus oxo acid group introduced into the fibrous cellulose is measured, for example, as follows.
First, the fibrous cellulose is acid-treated. In the acid treatment of the fibrous cellulose, the fibrous cellulose is diluted with ion-exchanged water so that the content is 2% by mass, and a sufficient amount of a 1N aqueous hydrochloric acid solution is added little by little while stirring. Next, this pulp suspension was stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet, which was diluted again with ion-exchanged water, and 1000 parts of 1N aqueous hydrochloric acid solution was added to 100 parts by mass (absolute dry mass) of fibrous cellulose. Add by weight. By repeating this operation 5 times, the phosphorus oxo acid group contained in the fibrous cellulose is completely changed to the acid type. Further, the pulp suspension is stirred and uniformly dispersed, and then the operation of filtering and dehydrating to obtain a dehydrated sheet is repeated to sufficiently wash away excess hydrochloric acid. Then, the obtained acid-type fibrous cellulose is diluted so as to have a content of 0.2% by mass to prepare a suspension. If necessary, after the acid treatment, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution to the obtained suspension, 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, two points are confirmed 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. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated 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 total amount of the dissociating acid in the slurry used for the titration. Become equal. 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 fibrous cellulose contains a condensed phosphorus oxo acid group, the amount of weakly acidic groups in the phosphorus oxo acid group (also referred to as the second dissociated acid amount in the present specification) is apparently reduced, and the alkali required for the first region is used. The amount of alkali required for the second region is smaller than the amount. 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. 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, there is only one point on the titration curve where the pH increment is maximized.

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 if 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 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.

When the first dissociative acid amount (mmol / g) in the fibrous cellulose is A1 and the total dissociative acid amount (mmol / g) in the fibrous cellulose is A2, the value of A1 / A2 is 0.51 or more. Is more preferable, 0.64 or more is more preferable, and 0.70 or more is further preferable. Further, the value of A1 / A2 is preferably 0.98 or less, more preferably 0.90 or less, and further preferably 0.85 or less. Here, the amount of the first dissociating acid (A1) in the fibrous cellulose is the amount of alkali (mmol) required from the start to the first end point of the titration in the above-mentioned titration curve, and the solid content (g) in the slurry to be titrated. ) Divided by. That is, the first dissociated acid amount (A1) is a value obtained by dividing the amount of substance (mmol) of the acid that is ionized and neutralized in the first step by the solid content (g) in the slurry to be titrated. The total amount of dissociated acid (A2) in the fibrous cellulose is a value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated. That is, the total amount of dissociated acid (A2) is a value obtained by dividing the amount of substance (mmol) of all the acids that are ionized and neutralized at all stages by the solid content (g) in the slurry to be titrated. Therefore, the closer the value of A1 / A2 is to 1, the smaller the amount of weak acid (the number of weakly acidic groups in the phosphorus oxo acid group, etc.). In the embodiment of the present invention, by setting A1 and A2 to values satisfying the above conditions, the water absorption of pure water and the water absorption of salt water of the fibrous cellulose can be more effectively enhanced.

The value of A1 / A2 approaches 1 in either case when the phosphate group or the phosphite group is condensed or when the phosphite group is present. As a method for determining whether the factor that A1 / A2 approaches 1 is due to the condensation of a phosphoric acid group or a phosphite group or the presence of a phosphite group, for example, phosphorus such as acid hydrolysis is used. A method of performing the above-mentioned titration operation after performing a treatment for cutting the condensed structure of an acid or a phosphite group, or a treatment for converting a phosphite group into a phosphoric acid group such as an oxidation treatment, and then performing the above-mentioned titration operation. The method of doing this can be mentioned.

(Manufacturing method of fibrous cellulose)
The method for producing fibrous cellulose is derived from a phosphite group or a phosphite group by mixing a compound having a phosphite group and / or a salt thereof with a cellulose raw material and urea and / or a urea derivative. The step of obtaining a fibrous cellulose having a substituent is included. In this step, it is preferable to mix a compound having a phosphoric acid group and / or a salt thereof in addition to the compound having a phosphite group and / or a salt thereof. Further, in this step, it is preferable that at least a part of the phosphite group forms a condensed structure. In the present specification, the step of obtaining the fibrous cellulose is also referred to as a phosphorus oxo acid group introduction step.

<Cellulose raw material>
Fibrous cellulose is produced from a fiber raw material (cellulose 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 recycled 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, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable, from the viewpoint of obtaining long-fiber fibrous cellulose having a small decomposition of cellulose in the pulp and a large axial ratio.

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

<Linoxo acid group introduction process>
In the phosphorous acid group introduction step, a compound having a phosphorous acid group and / or a salt thereof is mixed with a cellulose raw material, and urea and / or a urea derivative are mixed, and a substitution derived from the phosphorous acid group or the phosphorous acid group is performed. This is a step of obtaining a fibrous cellulose having a group. In the phosphorus oxo acid group introduction step, the hydroxyl group of the fiber raw material containing cellulose reacts with the compound having a phosphite group and / or a salt thereof to obtain a phosphite group or a substituent derived from the phosphite group. Can be introduced. By this step, a cellulose raw material having a phosphorous acid group introduced therein can be obtained.

In the phosphoric acid group introduction step, it is preferable to further mix the compound having a phosphoric acid group and / or a salt thereof. That is, in the phosphoric acid group introduction step, a compound having a phosphite group and / or a salt thereof, a compound having a phosphoric acid group and / or a salt thereof, and urea and / or a urea derivative are mixed with the cellulose raw material. It is preferable that the step is to obtain a fibrous cellulose having a substituent derived from a phosphite group or a phosphite group and a substituent derived from a phosphoric acid group or a phosphite group. In the present specification, a compound containing a compound having a phosphorous acid group and / or a salt thereof and a compound having a phosphorous acid group and / or a salt thereof may be referred to as compound A, and urea and / or a compound thereof. The urea derivative may be referred to as 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 is highly homogeneous, it is preferable to add the mixture in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, 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 the present embodiment preferably contains at least a compound having a phosphite group and / or a salt thereof, and further preferably contains a compound having a phosphoric acid group and / or 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. Of these, from the viewpoints of high efficiency of introduction of phosphite group, low cost, and easy industrial application, phosphite, sodium phosphite salt, potassium phosphite salt, or Ammonium salts of phosphite are preferably used. Further, as the compound having a phosphoric acid group, phosphoric acid can be mentioned, and as the phosphoric acid, those having various puritys can be used, for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid. Can be used. Further, anhydrous phosphoric acid (diphosphorus pentoxide) may be used as the compound having a phosphoric acid group. Examples of the salt of the compound having a phosphoric acid group include a lithium salt, a sodium salt, a potassium salt, and an ammonium salt of phosphoric acid, and these can have various neutralization degrees. Of these, from the viewpoints of high efficiency of introduction of phosphoric acid group, low cost, and easy industrial application, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, or ammonium phosphate. Salt is preferably used. As the phosphoric acid, dehydration-condensed phosphoric acid (for example, pyrophosphoric acid, polyphosphoric acid, etc.) in which two or more molecules of phosphoric acid are condensed by a dehydration reaction may be 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. The amount of the compound A added is the total amount of the phosphorus oxo acid added. By setting the addition amount of the phosphorus atom to the fiber raw material within the above range, the introduction efficiency of the phosphorus oxo acid group can be further improved. On the other hand, by setting the addition amount of the phosphorus atom to the fiber raw material to be equal to or less than the above upper limit value, the effect of improving the yield and the cost can be balanced.

In the step of introducing a phosphoric acid group, when a compound having a phosphoric acid group and / or a salt thereof is mixed in addition to the compound having a phosphoric acid group and / or a salt thereof, the compound having a phosphoric acid group and / or The mixed molar ratio (phosphoric acid: phosphite) of the salt to the compound having a phosphoric acid group and / or the salt thereof is preferably 0.01: 99.99 to 99.99: 0.01. It is more preferably 1:99 to 99: 1, and even more preferably 10:90 to 90:10. By setting the ratio of each compound to be mixed as compound A within the above range, the water absorption of pure water and the water absorption of salt water of the fibrous cellulose can be more effectively enhanced. When the compound having a phosphoric acid group and / or a salt thereof is not further mixed in the step of introducing a phosphoric acid group, the compound having a phosphite group and / or its salt and the compound having a phosphoric acid group and / or The mixing molar ratio with the salt (phosphoric acid: phosphoric acid) is 100: 0.

Compound B used in this embodiment is urea and / or a urea derivative 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 in particular is known to act as a good reaction catalyst.

In the phosphorus oxo 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 a phosphorus oxo acid 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, compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. This makes it possible to suppress uneven concentration of the compound A in the fiber raw material and more uniformly introduce the phosphorus oxo 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. can. Therefore, it is possible to obtain fibrous cellulose having a high axial ratio.

The heat treatment time is, for example, preferably 200 seconds or more, more preferably 300 seconds or more, further preferably 350 seconds or more, and further preferably 400 seconds after the water is substantially removed from the fiber raw material. The above is particularly preferable. The heat treatment time is preferably 10,000 seconds or less, more preferably 5000 seconds or less, and even more preferably 3000 seconds or less. It is also possible to shorten the heating time by increasing the heat temperature. In the present embodiment, the condensation of at least a part of the phosphite group can be promoted by setting the heating temperature and the heating time as appropriate conditions, and as a result, when the liquid absorption rate of the predetermined sheet is measured. , It becomes easy to control the liquid absorption rate within a predetermined range.

In the phosphoric acid group introduction step, in addition to compound A and compound B, a condensing agent and a cross-linking agent are further added to condense phosphite groups with each other, phosphite group and phosphite group, or phosphite group. It may promote the condensation of each other and the formation of other crosslinked structures. Alternatively, a step may be provided in which a condensing agent or a cross-linking agent is separately acted on the phosphorus oxo acid group-introduced cellulose fiber obtained by reacting the compound A and the compound B with the fiber raw material.

The condensing agent used in the phosphorus oxo acid group introduction step is not particularly limited, and examples thereof include a carbodiimide compound, an imidazole compound, and a triazine compound. Examples of the carbodiimide compound include 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N, N'-dicyclohexylcarbodiimide (DCC). Examples of the imidazole compound include N-methylimidazole (NMI), a hydrochloride thereof, N, N'-carbonyldiimidazole (CDI) and the like. Examples of the triazine compound include 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride (DMT-MM).

When a condensing agent is used in the phosphorus oxo acid group introduction step, the molar amount of the condensing agent used is based on the total anion amount of the phosphorus oxo acid group or the group derived from the phosphorus oxo acid group contained in the fibrous cellulose from the viewpoint of reactivity. , 0.01 times or more and 20 times or less, more preferably 0.2 times or more and 15 times or less, and further preferably 0.5 times or more and 10 times or less. .. At that time, the temperature at the time of reaction is preferably 0 ° C. or higher and 100 ° C. or lower, and more preferably 5 ° C. or higher and 80 ° C. or lower. It is more preferably 10 ° C. or higher and 60 ° C. or lower. The reaction time is preferably 10 minutes or longer, more preferably 30 minutes or longer, and even more preferably 1 hour or longer. The reaction time is preferably 48 hours or less. The reaction time can be shortened by an operation for increasing the reactivity such as heating and refluxing.

Further, in the phosphorus oxo acid group introduction step, a cross-linking agent may be added instead of the condensing agent. Further, a cross-linking agent may be further added together with the condensing agent. When a cross-linking agent is added, condensation between phosphite groups, phosphite groups and phosphoric acid groups, or phosphoric acid groups is formed through a structure derived from the cross-linking agent. The cross-linking agent is not particularly limited, and examples thereof include polyhydric alcohols, polyhydric organic acids, polyhydric organic amines, and formaldehyde. Examples of the polyhydric alcohol include glycerin, sorbitol, ethylene glycol and the like. Examples of the polyhydric organic acid include oxalic acid, citric acid, tartaric acid, succinic acid, gluconic acid, phthalic acid, malic acid and the like. Examples of the polyvalent organic amine include ethylenediamine, 1,3-propanediamine, N, N-dimethylethylenediamine and the like.

The solvent used in the phosphorus oxo acid group introduction step is not particularly limited, but it is preferably a solvent in which the condensing agent or cross-linking agent used is dissolved. The solvent comprises, for example, water, methanol, tetrahydrofuran (THF), dimethylformamide (DMF), p-xylene, dichloromethane, ethyl acetate, N-methyl-2-pyrrolidinone (NMP), or at least two or more of the above solvents. Examples include a mixed solvent. Above all, it is more preferable to use a mixed solvent of tetrahydrofuran (THF) and dimethylformamide (DMF).

In the step of introducing a phosphoric acid group, when a compound having a phosphoric acid group and / or a salt thereof is further mixed in addition to the compound having a phosphoric acid group and / or a salt thereof, the phosphite group and the phosphoric acid group are mixed. It is also preferable that a condensed structure of However, also in this case, a condensed structure between phosphoric acid groups and a condensed structure between phosphite groups are formed at a constant ratio.

The phosphorus oxo acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphorus oxo acid group introduction step two or more times, many phosphorus oxo acid groups can be introduced into the fiber raw material.

<Washing process>
In the method for producing fibrous cellulose in the present embodiment, a washing step can be performed on the linoxoic acid group-introduced fiber, if necessary. The washing step is performed, for example, by washing the phosphorus oxo acid 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>
In the case of producing fibrous cellulose, the phosphoric acid group-introduced fiber may be subjected to an alkali treatment between the phosphorus oxo acid group-introducing 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 phosphoxoic 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 phosphorus oxo 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 10,000% by mass or less, for example, with respect to the absolute dry mass of the phosphorus oxo acid group-introduced fiber. Is more preferable.

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

<Acid treatment process>
In the case of producing fibrous cellulose, the phosphoric acid group-introduced fiber may be acid-treated between the step of introducing the phosphoric acid group and the defibration treatment step described later. For example, the phosphorus oxo acid group introduction step, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.

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

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the phosphorus oxo acid group-introduced fiber. Is more preferable.

<Fiber processing process>
When producing fibrous cellulose having a fiber width of 1000 nm, the method for producing fibrous cellulose may include a defibration treatment step. The defibration treatment step is a step of subjecting the phosphorus oxo acid group-introduced fiber to a micronization treatment to obtain a fibrous cellulose having a fiber width of 1000 nm or less. 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 phosphorus oxo 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 the 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 monon-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotonic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the phosphorus oxo acid group-introduced fiber in a dispersion medium may contain a solid content other than the phosphorus oxo acid group-introduced fiber such as urea having a hydrogen bond property.

(Filamentous cellulose-containing material)
The present invention may relate to the fibrous cellulose-containing material containing the fibrous cellulose described above. The fibrous cellulose-containing material preferably further contains a solvent and an optional component as described later, in addition to the above-mentioned fibrous cellulose.

Examples of the solvent that the fibrous cellulose-containing material may contain include water. Moreover, the solvent may be an organic solvent. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol and glycerin. Examples of ketones include acetone, methyl ethyl ketone and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, ethylene glycol mono t-butyl ether and the like. The solvent may be a mixed solvent of water and an organic solvent.

The fibrous cellulose-containing material may be in a liquid state, or may be in a solid state or a gel state. When the fibrous cellulose-containing material is liquid, the fibrous cellulose-containing material may be a fibrous cellulose-containing slurry. When the fiber width of the fibrous cellulose is 1000 nm or less, the fine fibrous cellulose-containing slurry obtained in the above-mentioned defibration treatment step may be a fibrous cellulose-containing substance. The fine fibrous cellulose-containing slurry may be concentrated or dried and then redispersed in a solvent to obtain a fine fibrous cellulose-containing slurry. In this case, the redispersion liquid becomes the fibrous cellulose-containing substance.

When the fibrous cellulose-containing material is a fibrous cellulose-containing slurry, the fibrous cellulose-containing slurry is preferably used for forming a molded body such as a sheet. That is, the fibrous cellulose-containing material of the present invention is preferably a composition for forming a molded product, and preferably a composition for forming a sheet.

When the fibrous cellulose-containing material of the present invention is in a solid state, its form is not particularly limited, but for example, it is preferably a sheet-like material or a powdery material, and more preferably a powdery material. preferable. Here, the powder or granular material is a powdery and / or granular substance. The powdery substance is smaller than the granular substance. Generally, the powdery substance refers to fine particles having a particle size of 1 nm or more and less than 0.1 mm, and the granular substance refers to particles having a particle size of 0.1 mm or more and 10 mm or less, but is not particularly limited. In the present specification, the powder or granular material may be referred to as powder. The particle size of the powder or granular material in the present specification can be measured and calculated by using a laser diffraction method. Specifically, it is a value measured using a laser diffraction / scattering type particle size distribution measuring device (Microtrac 3300EXII, Nikkiso Co., Ltd.).

The content of fibrous cellulose with respect to the total mass of the fibrous cellulose-containing material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more. preferable. The upper limit of the content of fibrous cellulose with respect to the total mass of the fibrous cellulose-containing material is preferably 99.9% by mass.

<Arbitrary ingredient>
The fibrous cellulose-containing material may further contain an optional component. Examples of the optional component include antifoaming agents, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants, preservatives and the like. In addition, the fibrous cellulose-containing slurry may contain a hydrophilic polymer, a hydrophilic small molecule, an organic ion, 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.), polyvinylpyrrolidone, polyvinylmethyl ether, polyacrylates, acrylic acid alkyl ester copolymer, urethane-based copolymer, cellulose derivative (hydroxyethyl cellulose, carboxy) Ethyl cellulose, carboxymethyl cellulose, etc.) and the like.

The hydrophilic small molecule is preferably a hydrophilic oxygen-containing organic compound, more preferably a polyhydric alcohol. Examples of the polyhydric alcohol include glycerin, sorbitol, ethylene glycol and the like.

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.

(Molded body)
The present invention may relate to the above-mentioned fibrous cellulose or a molded product formed from the above-mentioned fibrous cellulose-containing material. In the present specification, the molded body means a solid body formed into a desired shape or a solid body formed into a sheet. Examples of the molded product include sheets (including paper), beads, filaments, and the like. Above all, the molded product is preferably a sheet, beads or filament. When the molded product is bead-shaped, the particle size of the beads is preferably 0.1 mm or more and 10 mm or less. When the molded product is in the form of a filament, the width of the filament is preferably 0.1 mm or more and 10 mm or less, and the length of the filament is preferably 1 mm or more and 10000 mm or less.

Above all, the molded body is preferably in the form of a sheet. Above all, when a sheet is formed by the following sheet forming method and the liquid absorption rate is calculated by the following measurement method, the liquid absorption rate of the sheet may be 0.30 mm / s or more, and 0.32 mm / s or more. It is preferably 0.35 mm / s or more, and more preferably 0.38 mm / s or more. Further, the liquid absorption rate of the sheet is preferably 20 mm / s or less.
(Sheet formation method)
Ion-exchanged water is added to the fibrous cellulose to prepare a suspension having a solid content concentration of 0.3% by mass, and the suspension is poured onto a filter paper to obtain a wet sheet ^{having an absolute dry basis weight of 200 g / m 2.} The wet sheet is peeled off from the filter paper, placed on a stainless steel tray, and dried under the conditions of 23 ° C. and 50% relative humidity for 3 days; the dried sheet is pressed at a weighted pressure of 7.7 MPa for 1 minute. And use it as a sheet for measuring the liquid absorption rate;
(Liquid absorption rate)
A sheet for measuring the absorption rate is cut into a strip-shaped sample having a width of 5 mm and a length of 50 mm, and the end region of the sample from the longitudinal end to 5 mm is immersed in ion-exchanged water; from the longitudinal end to the longitudinal. The time t required for the ion-exchanged water to reach a distance point of 45 mm is measured, and the liquid absorption rate (mm / sec) is calculated using the following formula (1).
Liquid absorption rate (mm / sec) = 40 (mm) / t (sec) Equation (1)

When the molded product is a sheet, the thickness of the sheet is not particularly limited, but is preferably, for example, 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. The upper limit of the thickness of the sheet is not particularly limited, but may be, for example, 1000 μm. The thickness of the sheet can be measured, for example, with a stylus type thickness gauge (Millitron 1202D manufactured by Marl Inc.).

If the fiber width of the fibrous cellulose is larger than 1000 nm, the sheet may be paper. Moreover, the sheet may be a non-woven fabric. Since the fibrous cellulose of the present invention has excellent water absorption of pure water and salt water, the sheet may be used as a constituent member of various sanitary papers and absorbent articles.

When the fiber width of the fibrous cellulose is 1000 nm or less, a highly transparent sheet can be produced. In such a case, the haze of the sheet is, for example, preferably 2% or less, more preferably 1.5% or less, and further preferably 1% or less. On the other hand, the lower limit of the haze of the sheet is not particularly limited and may be, for example, 0%. Here, the haze of the sheet is, for example, a value measured using a haze meter (HM-150 manufactured by Murakami Color Technology Research Institute) in accordance with JIS K 7136.

The total light transmittance of the sheet is, for example, preferably 85% or more, more preferably 90% or more, and further preferably 91% or more. On the other hand, the upper limit of the total light transmittance of the sheet is not particularly limited and may be, for example, 100%. Here, the total light transmittance of the sheet is a value measured using, for example, JIS K 7361 and a haze meter (HM-150 manufactured by Murakami Color Technology Research Institute).

The basis weight of the sheet is not particularly limited, ^{but is preferably 10 g / m 2} or more, more preferably 20 g / m ² or more, and further preferably 30 g / m ² or more. The basis weight of the sheet is not particularly limited, but is preferably ^{200 g / m 2 or less, more preferably 180 g / m 2} or less, for example. Here, the basis weight of the sheet can be calculated in accordance with, for example, JIS P 8124.

The density of the sheet is not particularly limited, ^{but is preferably 0.1 g / cm 3} or more, more preferably 0.5 g / cm ³ or more, and further preferably 1.0 g / cm ³ or more. preferable. The density of the sheet is not particularly limited, ^{but is preferably 5.0 g / cm 3} or less, and ^{more preferably 3.0 g / cm 3} or less, for example. Here, the density of the sheet can be calculated by measuring the thickness and mass of the sheet after adjusting the humidity of a 50 mm square sheet under the conditions of 23 ° C. and 50% RH for 24 hours.

The content of fibrous cellulose in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and 5% by mass or more, based on the total mass of the sheet. Is more preferable, and 10% by mass or more is particularly preferable. On the other hand, the upper limit of the content of fibrous cellulose in the sheet is not particularly limited and may be 100% by mass or 95% by mass with respect to the total mass of the sheet.

The sheet may contain any component that may be included in the fibrous cellulose-containing slurry. Further, the sheet may contain water or an organic solvent.

(Manufacturing method of fibrous cellulose-containing sheet)
When the molded body is a sheet, the method for producing the sheet preferably includes a coating step of coating the fibrous cellulose-containing slurry on the substrate or a papermaking step of making the slurry, as will be described later.

<Coating process>
In the coating step, for example, a fibrous cellulose-containing slurry (hereinafter, also simply referred to as a slurry) is coated on a base material, and the sheet formed by drying the slurry is peeled off from the base material to obtain a sheet. can. Further, by using a coating device and a long base material, sheets can be continuously produced.

The material of the base material used in the coating process is not particularly limited, but a material having higher wettability to the fibrous cellulose-containing slurry (slurry) may suppress shrinkage of the sheet during drying, but it is dried. It is preferable to select a sheet in which the sheet formed later can be easily peeled off. Of these, a resin film or plate or a metal film or plate is preferable, but is not particularly limited. For example, resin films and plates such as polypropylene, acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polycarbonate, and polyvinylidene chloride, metal films and plates of aluminum, zinc, copper, and iron plates, and their surfaces are oxidized. , Stainless film or plate, brass film or plate, etc. can be used.

In the coating process, if the viscosity of the slurry is low and it develops on the base material, a dammed frame is fixed on the base material to obtain a sheet with a predetermined thickness and basis weight. You may. The frame for damming is not particularly limited, but it is preferable to select, for example, a frame in which the end portion of the sheet that adheres after drying can be easily peeled off. From this point of view, a resin plate or a metal plate molded is more preferable. In the present embodiment, for example, a resin plate such as a polypropylene plate, an acrylic plate, a polyethylene terephthalate plate, a vinyl chloride plate, a polystyrene plate, a polycarbonate plate, a polyvinylidene chloride plate, or a metal plate such as an aluminum plate, a zinc plate, a copper plate, or an iron plate. , And those whose surfaces are oxidized, stainless steel plates, brass plates and the like can be used. The coating machine for coating the slurry on the base material is not particularly limited, and for example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater, or the like can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the sheet can be made more uniform.

The slurry temperature and the atmospheric temperature when the slurry is applied to the substrate are not particularly limited, but are preferably, for example, 5 ° C. or higher and 80 ° C. or lower, more preferably 10 ° C. or higher and 60 ° C. or lower, and 15 ° C. It is more preferably 50 ° C. or lower, and particularly preferably 20 ° C. or higher and 40 ° C. or lower. When the coating temperature is equal to or higher than the above lower limit, the slurry can be coated more easily. When the coating temperature is not more than the above upper limit value, the volatilization of the dispersion medium during coating can be suppressed.

In the coating process, the slurry is based so that the finished basis weight of the sheet is preferably 10 g / m ² or more and 200 g / m ² or less, and more preferably 20 g / m ² or more and 180 g / m ^{2 or less.} It is preferable to apply the material. By coating so that the basis weight is within the above range, a sheet having excellent strength can be obtained.

As described above, the coating step includes a step of drying the slurry coated on the substrate. The step of drying the slurry is not particularly limited, but is performed by, for example, a non-contact drying method, a method of drying while restraining the sheet, or a combination thereof.

The non-contact drying method is not particularly limited, and for example, a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heat drying method) or a method of vacuum drying (vacuum drying method) is applied. can do. The heat drying method and the vacuum drying method may be combined, but the heat drying method is usually applied. Drying with infrared rays, far infrared rays, or near infrared rays is not particularly limited, but can be performed using, for example, an infrared device, a far infrared device, or a near infrared device.

The heating temperature in the heat drying method is not particularly limited, but is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 25 ° C. or higher and 105 ° C. or lower. When the heating temperature is set to be equal to or higher than the above lower limit value, the dispersion medium can be rapidly volatilized. Further, when the heating temperature is not more than the above upper limit value, it is possible to suppress the cost required for heating and suppress the discoloration of the fibrous cellulose due to heat.

<Papermaking process>
The papermaking process is performed by making a slurry with a paper machine. The paper machine used in the paper making process is not particularly limited, and examples thereof include continuous paper machines such as a long net type, a circular net type, and an inclined type, and a multi-layer paper making machine combining these. In the papermaking process, a known papermaking method such as hand-making may be adopted.

The papermaking process is performed by filtering and dehydrating the slurry with a wire to obtain a wet paper sheet, and then pressing and drying the sheet. The filter cloth used for filtering and dehydrating the slurry is not particularly limited, but it is more preferable that, for example, fibrous cellulose does not pass through and the filtration rate does not become too slow. Such a filter cloth is not particularly limited, but for example, a sheet made of an organic polymer, a woven fabric, or a porous membrane is preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE) are preferable. In the present embodiment, for example, a porous membrane of polytetrafluoroethylene having a pore size of 0.1 μm or more and 20 μm or less, polyethylene terephthalate having a pore size of 0.1 μm or more and 20 μm or less, a polyethylene woven fabric, or the like can be mentioned.

In the sheeting process, a method of producing a sheet from a slurry is, for example, a water-squeezed section in which a slurry containing fibrous cellulose is discharged onto the upper surface of an endless belt and a dispersion medium is squeezed from the discharged slurry to generate a web. This can be done using a manufacturing apparatus that includes a drying section that dries the web to produce a sheet. An endless belt is arranged from the watering section to the drying section, and the web generated in the watering section is conveyed to the drying section while being placed on the endless belt.

The dehydration method used in the papermaking process is not particularly limited, and examples thereof include a dehydration method usually used in the production of paper. Among these, a method of dehydrating with a long net, a circular net, an inclined wire or the like and then further dehydrating with a roll press is preferable. The drying method used in the papermaking process is not particularly limited, and examples thereof include methods used in the production of paper. Among these, a drying method using a cylinder dryer, a Yankee dryer, hot air drying, a near infrared heater, an infrared heater, or the like is more preferable.

(Use)
The fibrous cellulose of the present invention can be used, for example, as a reinforcing agent or an additive in cement, paints, inks, lubricants and the like. In addition, the molded product obtained by coating fibrous cellulose on a base material is a reinforcing material, an interior material, an exterior material, a packaging material, an electronic material, an optical material, an acoustic material, a process material, and a member of a transportation device. It is also suitable for applications such as electronic device members and electrochemical element members.

Further, by mixing the fibrous cellulose of the present invention with a solvent, a fibrous cellulose-containing slurry can be obtained, or a sheet in which fibrous cellulose is uniformly dispersed can be formed from the slurry. Further, the fibrous cellulose of the present invention can also be preferably used for mixing with an organic solvent containing a resin component. By mixing the fibrous cellulose of the present invention with an organic solvent containing a resin component, a resin composite in which the fibrous cellulose is uniformly dispersed can be formed. Similarly, a film can be formed using a fibrous cellulose-containing slurry and used as various films.

Further, the fibrous cellulose of the present invention can also be used for forming sanitary paper, constituent members of absorbent articles, and the like. Absorbent articles include, for example, disposable diapers, absorbent pads used for babies or incontinence, and sanitary napkins. In the absorbent article, the absorbent material is preferably used as a material constituting the absorbent body and peripheral members of the absorbent body.

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 limited by the specific examples shown below.

<Example 1>
[Manufacturing of phosphorus oxo oxide pulp]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheets, separated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) is 700 ml) It was used.

The raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphoric acid, phosphoric acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp, and 9 parts by mass of phosphoric acid and 24 parts by mass of phosphoric acid (phosphonic acid) are added. The amount was adjusted to 120 parts by mass of urea and 150 parts by mass of water to obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 600 seconds to introduce a phosphorus oxo acid group into the cellulose in the pulp to obtain phosphorus oxo oxide pulp A.

Next, ion-exchanged water was poured into the obtained phosphorus oxo-oxidized pulp A so that the solid content concentration was 2% by mass, dissociated with a tabletop disintegrator having a capacity of 2 L for 8 minutes, and then washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolutely dry mass) of phosphorus oxo-oxidized pulp A is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. I went by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

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

The infrared absorption spectrum of the phosphorus oxo-oxidized pulp A thus obtained was measured using FT-IR. As a result, absorption based on P = O phosphonic acid group is a tautomer of phosphorous acid in the vicinity of 1210cm ^-1, absorption based on P = O of phosphate groups was observed around 1230 cm ^-1, pulp It was confirmed that a phosphite group (phosphonic acid group) and a phosphoric acid group were added to.

Further, when the obtained phosphorus oxo oxide pulp A was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals. Regarding the phosphorus oxo oxide pulp A, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.30 mmol / g. The total amount of dissociated acid was 2.84 mmol / g.

[Preparation of sheet]
Ion-exchanged water was added to the phosphorus oxo oxide pulp A to prepare a suspension so that the solid content concentration was 0.3% by mass. The obtained suspension was filtered using a separate filter paper sandwiched between them to form a wet sheet having an ^{absolute dry basis weight of 200 g / m 2} on the filter paper (manufactured by ADVANTEC Toyo Co., Ltd., φ90 mm). The wet sheet was peeled off from the filter paper, placed on a stainless steel tray, and dried under the conditions of 23 ° C. and 50% relative humidity for 3 days. Both sides of the dried sheet were sandwiched between paper and a metal plate, and pressed with a mini hot press (MP-SNH, manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 23 ° C. and a weighted pressure of 7.7 MPa for 1 minute to obtain a sheet. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Example 2>
100 parts by mass (absolute dry mass) of the phosphorus oxo oxide pulp A obtained in Example 1 was diluted with ion-exchanged water so that the content was 2% by mass, and 1000 parts by mass of a 1N hydrochloric acid aqueous solution was added little by little while stirring. bottom. Next, this pulp suspension was stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet, which was diluted again with ion-exchanged water, and 1000 parts by mass of a 1N aqueous hydrochloric acid solution was added to 100 parts by mass of phosphorusoxo oxide pulp. By repeating this operation 5 times, the phosphorus oxo acid group contained in the phosphorus oxo oxide pulp was completely changed to the acid type. The obtained hydrous acid-type phosphorusoxo-oxidized pulp was repeatedly washed with acetone to completely remove the water contained in the pulp. 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride (DMT-MM) 16 was added to 100 parts by mass of the obtained absolute dry acid type phosphorusoxo oxide pulp. 11 parts by mass, 11 parts by mass of ethylenediamine, 4000 parts by mass of dimethylformamide (DMF), and 4000 parts by mass of tetrahydrofuran were added, and the reaction was carried out at 25 ° C. for 3 hours with stirring. After the reaction, the pulp was collected by filtration and washed repeatedly with ion-exchanged water to remove the DMT-MM salt and ethylenediamine remaining in the pulp. Then, the neutralization treatment was carried out in the same manner as in Example 1 to obtain phosphoroxo oxide pulp B. The infrared absorption spectrum of the phosphorus oxo oxide pulp B was measured using FT-IR. As a result, absorption based on P = O phosphonic acid group is a tautomer of phosphorous acid in the vicinity of 1210cm ^-1, absorption based on P = O of phosphate groups was observed around 1230 cm ^-1, pulp It was confirmed that a phosphite group (phosphonic acid group) was added to. Regarding the phosphorus oxo oxide pulp B, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 1.63 mmol / g. The total amount of dissociated acid was 2.23 mmol / g. Since the amount of the first dissociated acid in the phosphorus oxo oxide pulp B was smaller than that before the condensation reaction, it was confirmed that at least a part of the phosphite groups was condensed.
A sheet was obtained in the same manner as in Example 1 except that the phosphorus oxo oxide pulp B was used instead of the phosphorus oxo oxide pulp A. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Example 3>
Phosphoric acid oxidation in the same manner as in Example 1 except that the addition amounts of phosphoric acid and phosphite (phosphonic acid) in the phosphoric acid oxidation treatment were changed to 19 parts by mass of phosphoric acid and 16 parts by mass of phosphoric acid (phosphonic acid). Pulp C and a sheet were obtained. The infrared absorption spectrum of the phosphorus oxo oxide pulp C was measured using FT-IR. As a result, absorption based on P = O phosphonic acid group is a tautomer of phosphorous acid in the vicinity of 1210cm ^-1, absorption based on P = O of phosphate groups was observed around 1230 cm ^-1, pulp It was confirmed that a phosphite group (phosphonic acid group) and a phosphoric acid group were added to. Regarding the phosphorus oxo oxide pulp C, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.48 mmol / g. The total amount of dissociated acid was 3.26 mmol / g. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Example 4>
Phosphoric acid oxidation in the same manner as in Example 1 except that the addition amounts of phosphoric acid and phosphite (phosphonic acid) in the phosphoric acid oxidation treatment were changed to 28 parts by mass of phosphoric acid and 8 parts by mass of phosphoric acid (phosphonic acid). Pulp D and sheet were obtained. The infrared absorption spectrum of the phosphorus oxo oxide pulp D was measured using FT-IR. As a result, absorption based on P = O phosphonic acid group is a tautomer of phosphorous acid in the vicinity of 1210cm ^-1, absorption based on P = O of phosphate groups was observed around 1230 cm ^-1, pulp It was confirmed that a phosphite group (phosphonic acid group) and a phosphoric acid group were added to. Regarding the phosphorus oxo oxide pulp D, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.48 mmol / g. The total amount of dissociated acid was 3.14 mmol / g. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Example 5>
In the phosphorus oxo oxidation treatment, phosphorous acid was not added, the amount of phosphorous acid (phosphonic acid) added was changed to 33 parts by mass, and the heating time was set to 250 seconds. Pulp was made. Regarding the phosphorus oxo oxide pulp, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was 1. It was 79 mmol / g. The total amount of dissociated acid was 1.83 mmol / g.
A phosphorus oxo oxide pulp E was obtained in the same manner as in Example 2 except that 100 parts by mass (absolute dry mass) of the obtained phosphorus oxo oxide pulp was used instead of the phosphorus oxo oxide pulp A. The infrared absorption spectrum of the phosphorus oxo oxide pulp E was measured using FT-IR. As a result, ^{absorption based on P = O of the phosphonic acid group, which is a metamorphic form of the phosphite group, was observed around 1210 cm -1} , and the phosphite group (phosphonic acid group) was added to the pulp. Was confirmed. Regarding the phosphorus oxo oxide pulp E, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 1.13 mmol / g. The total amount of dissociated acid was 1.47 mmol / g. Since the amount of the first dissociated acid in the phosphorus oxo oxide pulp E was smaller than that before the condensation reaction, it was confirmed that at least a part of the phosphite groups was condensed.
A sheet was obtained in the same manner as in Example 1 except that the phosphorus oxo oxide pulp E was used instead of the phosphorus oxo oxide pulp A. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Comparative example 1>
In the phosphorus oxo oxidation treatment, phosphor oxo oxide pulp F and a sheet were obtained in the same manner as in Example 1 except that phosphorous acid was not added and the amount of phosphorous acid (phosphonic acid) added was changed to 33 parts by mass. The infrared absorption spectrum of the phosphorus oxo oxide pulp F was measured using FT-IR. As a result, ^{absorption based on P = O of the phosphonic acid group, which is a metamorphic form of the phosphite group, was observed around 1210 cm -1} , and the phosphite group (phosphonic acid group) was added to the pulp. Was confirmed. Regarding the phosphorus oxo oxide pulp F, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.06 mmol / g. The total amount of dissociated acid was 2.08 mmol / g. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Comparative example 2>
In the phosphorous oxidation treatment, phosphorous acid (phosphonic acid) was not added, and the amount of phosphoric acid added was changed to 38 parts by mass in the same manner as in Example 1 to obtain phosphorous oxide pulp G and a sheet. The infrared absorption spectrum of the phosphorus oxo oxide pulp G was measured using FT-IR. As a result, absorption ^{of the phosphate group based on P = O was observed around 1230 cm -1} , and it was confirmed that the phosphate group was added to the pulp. Regarding the phosphorus oxo oxide pulp G, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.50 mmol / g. The total amount of dissociated acid was 3.97 mmol / g. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Comparative example 3>
In the phosphorus oxo oxidation treatment, the heating time was changed to 300 seconds. Then, the washed phosphorus oxo oxide pulp was subjected to a second phosphorus oxo oxidation treatment, and the heating time at that time was set to 200 seconds. Then, a cleaning treatment was performed. Other operations were carried out in the same manner as in Comparative Example 2 to obtain phosphoroxo oxide pulp H and a sheet. The infrared absorption spectrum of the phosphorus oxo oxide pulp H was measured using FT-IR. As a result, absorption ^{of the phosphate group based on P = O was observed around 1230 cm -1} , and it was confirmed that the phosphate group was added to the pulp. Regarding the phosphorus oxo oxide pulp H, when the first dissociation acid amount was measured by the measurement method described in [Measurement of the first dissociation acid amount and the total dissociation acid amount (phosphoric acid group)], the first dissociation acid amount was measured. Was 2.15 mmol / g. The total amount of dissociated acid was 3,79 mmol / g. The liquid absorption rate and water absorption rate of the obtained sheet were measured by the method described later.

<Evaluation method>
<Measurement of first dissociated acid amount and total dissociated acid amount>
The amount of the first dissociated acid and the total amount of the dissociated acid were measured by the neutralization titration method. Specifically, after acid-treating the phosphorus oxo oxide pulp, the phosphorus oxo oxide pulp suspension was prepared by diluting it with ion-exchanged water so that the content was 0.2% by mass. Using a high-speed rotary defibrator (Clearmix-2.2S manufactured by M-Technique), mechanical treatment was performed at 21500 rpm for 5 minutes, and titration with alkali was performed to obtain the first dissociated acid amount and total dissociated acid. The amount was measured.
In the acid treatment of the phosphorus oxo oxide pulp, 100 parts by mass (absolute dry mass) of the obtained phosphorus oxo oxide pulp is diluted with ion-exchanged water so that the content becomes 2% by mass, and 1000 parts by mass of a 1N hydrochloric acid aqueous solution is stirred. Was added little by little. Next, this pulp suspension was stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet, which was diluted again with ion-exchanged water, and 1000 parts by mass of phosphorus oxo oxide pulp (absolutely dry mass) was added to 1000 1N aqueous hydrochloric acid solutions. By weight was added. By repeating this operation 5 times, the phosphorus oxo acid group contained in the phosphorus oxo oxide pulp was completely changed to the acid type. Further, the pulp suspension was stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. By repeating the operation, excess hydrochloric acid was sufficiently washed away.
In titration using alkali, a fast-rotating defibrator is used to prepare a phosphorus oxo oxide pulp suspension prepared by diluting the obtained acid-type phosphorus oxo oxide pulp with ion-exchanged water so that the content is 0.2% by mass. After mechanical treatment at 21500 rpm for 5 minutes using (Clearmix-2.2S manufactured by M-Technique), the pH value indicated by the slurry was added while adding 10 μL of 0.1 N sodium hydroxide aqueous solution every 30 seconds. The change in was measured. The titration was performed while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed 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 (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 of the phosphorus oxo oxide pulp in the slurry used for the titration. Further, the amount of alkali required from the start to the second end point of the titration becomes equal to the total amount of dissociated acid of the phosphorus oxo oxide pulp in the slurry used for the titration. The amount of alkali (mmol) required from the start of titration to the first end point was divided by the solid content (g) in the slurry to be titrated, and the value was defined as the first dissociating acid amount A1 (mmol / g). Further, the value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated was defined as the total amount of dissociated acid A2 (mmol / g).

<Measurement of liquid absorption rate of sheet>
The sheets obtained in Examples and Comparative Examples were cut into strip-shaped samples having a width of 5 mm and a length of 50 mm, and the end region from the longitudinal end side of the sample to 5 mm was immersed in ion-exchanged water. The time t required for the ion-exchanged water to reach a distance point of 45 mm in the longitudinal direction from the end edge in the longitudinal direction was measured, and the liquid absorption rate (mm / sec) was calculated using the following formula (1).
Equation (1) Liquid absorption rate (mm / sec) = 40 (mm) / t (sec)

<Measurement of water absorption rate of sheet>
For the sheets obtained in Examples and Comparative Examples, the water absorption rate I _{0 when immersed in pure water and the water absorption rate I 1} when immersed in a 0.1 N sodium chloride aqueous solution (salt water) were calculated. Specifically, it was calculated using the following formula (2) from the amount of water absorption of the sheet measured in accordance with JIS K 7223: 1996.
Formula (2) Water absorption rate I ₀ or I ₁ (%) = 100 × Sheet water absorption (g) / Sheet absolute dry weight (g)
Further, the reduction rate of the sheet water absorption rate was calculated using the following formula (3).
Equation (3) Reduction rate of water absorption rate (%) = 100 × (I ₀ −I ₁ ) / I ₀

In the examples, fibrous cellulose having excellent water absorption in pure water and water absorption in salt water was obtained. On the other hand, in the comparative example, both pure water absorption and salt water absorption were not compatible.

Claims (6)

When a fibrous cellulose having a phosphorous acid group or a substituent derived from a phosphorous acid group is formed by the following sheet forming method and the liquid absorption rate is calculated by the following measuring method, the liquid absorption of the sheet is performed. Fibrous cellulose with a velocity of 0.30 mm / s or more;
(Sheet formation method)
Ion-exchanged water is added to the fibrous cellulose to prepare a suspension having a solid content concentration of 0.3% by mass, and the suspension is poured onto a filter paper to obtain a wet sheet ^{having an absolute dry basis weight of 200 g / m 2.} The wet sheet is peeled off from the filter paper, placed on a stainless steel tray, and dried under the conditions of 23 ° C. and 50% relative humidity for 3 days; the dried sheet is pressed at a weighted pressure of 7.7 MPa for 1 minute. And use it as a sheet for measuring the liquid absorption rate;
(Liquid absorption rate)
A sheet for measuring the absorption rate is cut into a strip-shaped sample having a width of 5 mm and a length of 50 mm, and the end region of the sample from the longitudinal end to 5 mm is immersed in ion-exchanged water; from the longitudinal end to the longitudinal. The time t required for the ion-exchanged water to reach a distance point of 45 mm is measured, and the liquid absorption rate (mm / sec) is calculated using the following formula (1).
Liquid absorption rate (mm / sec) = 40 (mm) / t (sec) Equation (1) The fibrous cellulose according to claim 1, further comprising a phosphate group or a substituent derived from a phosphoric acid group. Claim 1 or 2 in which the value of A1 / A2 is 0.51 or more and 0.98 or less when the first dissociative acid amount in the fibrous cellulose is A1 and the total dissociative acid amount in the fibrous cellulose is A2. The fibrous cellulose described in. A fibrous cellulose-containing product containing the fibrous cellulose according to any one of claims 1 to 3. A molded product formed from the fibrous cellulose according to any one of claims 1 to 3 or the fibrous cellulose-containing product according to claim 4. The molded product according to claim 5, which is in the form of a sheet.

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