JP2020094163A - Fibrous cellulose - Google Patents

Abstract

To provide fibrous cellulose excellent in dispersion stability and force-feeding property, and used for manufacturing a calcium carbonate powder-containing preceding agent for concrete pump force-feeding.SOLUTION: Fibrous cellulose is used for manufacturing a preceding agent for concrete pump force-feeding by mixing with calcium carbonate powder. The fibrous cellulose has an ionic group, and contains fine fibrous modified cellulose having a fiber width of 1,000 nm or less.SELECTED DRAWING: None

Description

The present invention relates to fibrous cellulose, in particular fibrous cellulose used for producing a precursor for concrete pumping by mixing with calcium carbonate powder.

In the foundation work of a building and the construction work of a concrete building, the work of driving concrete into a predetermined place is carried out.
In recent years, a method of transporting concrete supplied to a hopper to a predetermined pouring place using a concrete pump car has been widely adopted. In this method, concrete in a hopper is pumped into a pipe by using a concrete pump car, and the concrete is conveyed to a target pouring place through the pipe. Then, when concrete is pumped using a concrete pump and piping, cement paste or mortar mixed with water and cement as a preceding agent for pumping is pre-filled as a preceding agent for pumping in the hopper, and the preceding The agent is first fed into the pipe, and then the raw concrete is continuously fed into the pipe while pouring the raw concrete into the hopper for pressure feeding. In this way, the advance agent for pressure-feeding is sent first when only fresh uncured concrete (fluid concrete) is introduced without any treatment, and only mortar (cement paste) is contained among the components of concrete. This is because the tip of the concrete that adheres to the inner surface of the pump or the pipe and loses the mortar component with it may gradually separate and block the pipe.

In the method of using cement paste or mortar as a precursor for pressure feeding, the hardening reaction progresses during transportation or while waiting at the concrete driving destination, so it is necessary to make a detailed management plan for concrete driving work. In addition, this method requires a large amount to be used in order to obtain the required effects of cement paste and mortar, which are precursors for pressure-feeding, and the cement paste and mortar used for the precursor for pressure-feeding are discarded. In addition to being economically disadvantageous, cement paste and mortar are likely to adversely affect the quality of concrete.

Patent Document 1 discloses a pressure-feeding initiator for a concrete pump containing a water-absorbent resin, for the purpose of realizing a pressure-feeding initiator for a concrete pump that can smoothly start the pressure-feeding of concrete with a small amount of use. There is.

JP 2000-34461 A

The preceding agent for pressure feeding described in Patent Document 1 has a problem in that it is inferior in economic efficiency such as using a water-absorbent resin, and that the water-absorbent resin does not sufficiently absorb water depending on use conditions. ..
It is an object of the present invention to provide a fibrous cellulose which is used for producing a concrete pumping precursor for calcium carbonate powder, which is excellent in dispersion stability and pumping property.

The present inventors have found that the above problem can be solved by adopting fibrous cellulose that is substituted with an ionic group and contains fine fibrous modified cellulose having a fiber width of 1000 nm or less.
That is, the present invention relates to the following <1> to <7>.
<1> A fibrous cellulose used for producing a preceding agent for concrete pumping by mixing with calcium carbonate powder, wherein the fibrous cellulose has an ionic group and has a fiber width of 1000 nm or less. Fibrous cellulose, including some fine fibrous modified cellulose.
<2> The fibrous cellulose according to <1>, wherein the fibrous cellulose has a viscosity (solid content concentration 0.4% dispersion liquid, 23° C.) of 500 mPa·s or more.
<3> The fibrous cellulose according to <1> or <2>, wherein the fibrous cellulose has a thixotropic index (TI value) represented by the following formula (1) of 30 or more.
TI value=(viscosity at shear rate 1/s)/(viscosity at shear rate 1000/s) (1)
The above viscosity is the viscosity at 23° C. and 0.4% solid concentration dispersion.
<4> The fibrous cellulose according to any one of <1> to <3>, in which the content of calcium carbonate powder in the solid content of the preceding agent for pumping concrete pump is 50% by mass or more.
<5> The fibrous cellulose according to any one of <1> to <4>, in which a mixing amount of fibrous cellulose with respect to 100 parts by mass of the calcium carbonate powder is 0.0001 parts by mass or more and 100 parts by mass or less.
<6> The fibrous cellulose according to any one of <1> to <5>, in which the calcium carbonate powder contains a porous calcium carbonate powder.
<7> The fibrous cellulose according to any one of <1> to <6>, which is further mixed with at least one selected from a pigment, an antioxidant, and a pH adjuster.

ADVANTAGE OF THE INVENTION According to this invention, the fibrous cellulose which is excellent in dispersion stability and pumpability, and which is used for manufacturing the concrete pump pumping precursor containing calcium carbonate powder can be provided.

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

[Fibrous cellulose]
The fibrous cellulose of the present invention is used for producing a precursor for concrete pumping by mixing with calcium carbonate powder, and the fibrous cellulose has an ionic group and has a fiber width of 1000 nm or less. It contains fine fibrous modified cellulose (hereinafter, also simply referred to as "fine fibrous modified cellulose").
By adding the fibrous cellulose of the present invention to a pressure-feeding precursor containing calcium carbonate, the dispersion pump has excellent dispersion stability, and a concrete pump pressure-feeding precursor having excellent pumpability (hereinafter, "pressure-feeding precursor"). Alternatively, it is also referred to as "preceding agent").
Although the detailed reason why the above effects are obtained is unknown, some of them are presumed as follows.
The fibrous cellulose containing the fine fibrous modified cellulose exhibits a high thickening effect and a high particle dispersion effect by being added to water to form a slurry. On the other hand, the slurry has thixotropy and its viscosity decreases when it receives shear stress.
When mixed with calcium carbonate and used as a precursor for pumping concrete pumps, when the precursor is actually pumped into a pipe, the precursor for pumping contains water, which results in high dispersion stability against calcium carbonate. It is considered that excellent pumpability can be obtained while imparting the property. In particular, it is considered that since the fine fibrous cellulose has an ionic group, high dispersion stability with respect to calcium carbonate and excellent pumpability were obtained.
Hereinafter, the present invention will be described in more detail.

<Fine fibrous modified cellulose>
The fibrous cellulose of the present invention contains a fine fibrous modified cellulose, and the fine fibrous modified cellulose is a fibrous cellulose having a fiber width of 1,000 nm or less and is substituted with an ionic group. The fiber width of the fibrous cellulose and the fine fibrous modified cellulose can be measured by, for example, observing with an electron microscope.
The fibrous cellulose contains fine fibrous modified cellulose, and further has an unmodified fine fibrous cellulose having a fiber width of 1,000 nm or less, an unmodified fibrous cellulose having a fiber width of more than 1,000 nm, and a fiber width of 1. You may contain the fibrous modified cellulose which exceeds 000 nm and is substituted by the ionic group.
The content of the fine fibrous modified cellulose in the fibrous cellulose is preferably 30% by mass or more, more preferably 50% by mass, further preferably 70% by mass or more, still more preferably 90% by mass or more, and 100% by mass. It may be %. In the present invention, as the fibrous cellulose, an embodiment in which fine fibrous modified cellulose and unmodified fibrous cellulose having a fiber width of more than 1000 nm are mixed and used, or fibrous cellulose is added to the fine fibrous modified cellulose It also includes a mode in which a small amount of unmodified fine fibrous cellulose or modified or unmodified cellulose having a fiber width of more than 1000 nm is contained.

The fiber width of the fine fibrous modified cellulose is preferably 100 nm or less, more preferably 30 nm or less, and further preferably 8 nm or less. The fiber width is preferably 2 nm or more.
The average fiber width of the fine fibrous modified cellulose is, for example, 1000 nm or less. The average fiber width of the fine fibrous modified cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferable. By setting the average fiber width of the fine fibrous modified cellulose to 2 nm or more, it is possible to prevent the fine fibrous modified cellulose from being dissolved in water, and to more easily exhibit the effect of improving the dispersion stability and the pumpability of the fine fibrous modified cellulose. can do. The fine fibrous modified cellulose is, for example, a single fibrous cellulose.

The average fiber width of the fine fibrous modified cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fine fibrous modified cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and the suspension is cast on a hydrophilized carbon film-coated grid and observed by TEM. Use as a sample. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Then, observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times or 50000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observed image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber intersecting the straight line X and the straight line Y is visually read from the observed image satisfying the above conditions. In this way, at least three sets of observation images of the surface portions that do not overlap each other are obtained. Then, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thereby, the fiber width of at least 20 fibers×2×3=120 fibers is read. Then, the average value of the read fiber widths is set as the average fiber width of the fine fibrous modified cellulose.

The fiber length of the fine fibrous modified cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and 0.1 μm or more and 600 μm or less. Is more preferable. By setting the fiber length within the above range, it is possible to suppress the destruction of the crystalline region of the fine fibrous modified cellulose. Further, it becomes possible to set the slurry viscosity of the fine fibrous modified cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be determined by image analysis using TEM, SEM, or AFM, for example.

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

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

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

The fine fibrous modified cellulose in the present embodiment has an ionic group. When the fine fibrous modified cellulose has an ionic group, the dispersibility of the fibers in the dispersion medium (water) can be improved and the defibration efficiency in the defibration treatment can be increased. Further, when mixed with calcium carbonate powder to produce a precursor for pumping concrete by pump, it improves dispersibility of calcium carbonate in water and contributes to improvement of pumpability.
The ionic group may include, for example, one or both of an anionic group and a cationic group. In this embodiment, it is particularly preferable to have an anionic group as the ionic group.
The fine fibrous modified cellulose may have a nonionic group introduced in addition to the ionic group, and examples of the nonionic group include an alkyl group and an acyl group.

Examples of the anionic group as the ionic group include a phosphoric acid group or a group derived from a phosphoric acid group (sometimes referred to simply as a phosphoric acid group), a carboxy group or a group derived from a carboxy group (also referred to simply as a carboxy group) A) and a sulfone group or a group derived from a sulfone group (sometimes simply referred to as a sulfone group), and at least one selected from a phosphoric acid group and a carboxy group. It is more preferable, and a phosphoric acid group is particularly preferable.

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

In the formula (1), a, b and n are natural numbers (however, a=b×m). Of α ¹ , α ² ,..., α ⁿ and α′, a is O ⁻ and the rest is either R or OR. All α ⁿ and α′ may be O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon, respectively. It is a hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof.
Examples of the saturated-linear hydrocarbon group include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like. Examples of the saturated-branched hydrocarbon group include, but are not limited to, i-propyl group and t-butyl group. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like.
Examples of the unsaturated-straight chain hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated-branched hydrocarbon group include i-propenyl group and 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include a cyclopentenyl group and a cyclohexenyl group, but are not particularly limited. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

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

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

The amount of ionic groups introduced into the fibrous cellulose is, for example, preferably 0.10 mmol/g or more, more preferably 0.20 mmol/g or more, and 0.50 mmol/g per 1 g (mass) of the fibrous cellulose. It is more preferably at least g, and particularly preferably at least 1.00 mmol/g. The amount of ionic groups introduced into the fibrous cellulose is, for example, preferably 5.20 mmol/g or less per 1 g (mass) of the fibrous cellulose, more preferably 3.65 mmol/g or less. It is more preferably 50 mmol/g or less, still more preferably 3.00 mmol/g or less. By setting the introduction amount of the ionic group within the above range, it is possible to easily miniaturize the fiber raw material and enhance the stability of the fine fibrous modified cellulose. Further, by setting the introduction amount of the ionic group within the above range, the fibrous cellulose can exhibit good characteristics for improving dispersion stability and pumpability.
Here, the denominator in the unit of mmol/g indicates the mass of fibrous cellulose when the counter ion of the ionic group is a hydrogen ion (H ⁺ ).

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

In addition, since the denominator indicates the mass of the acid-type fibrous cellulose, the above-mentioned phosphate group introduction amount (mmol/g) indicates that the acid-type fibrous cellulose has the phosphate group amount (hereinafter, the phosphate group amount). (Called acid type)). On the other hand, when the counterion of the phosphate group is substituted with an arbitrary cation C so as to have a charge equivalent, the denominator is converted into the mass of the fibrous cellulose when the cation C is the counterion. Thus, the amount of phosphate groups in the fibrous cellulose having the cation C as a counterion (hereinafter, the amount of phosphate groups (C type)) can be obtained.
That is, it is calculated by the following calculation formula.
Phosphoric acid group amount (C type)=phosphoric acid group amount (acid type)/{1+(W-1)×A/1000}
A [mmol/g]: Total amount of anions derived from the phosphate group in the fibrous cellulose (value obtained by adding the amount of the strongly acidic group and the amount of the weakly acidic group of the phosphate group)
W: Formula weight per valence of cation C (for example, 23 for Na and 9 for Al)

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

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

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

<Method for producing fine fibrous modified cellulose>
(Fiber raw material containing cellulose)
The fine fibrous modified cellulose is produced from a fiber raw material containing cellulose.
The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulps include, for example, wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, and examples thereof include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP). ) And oxygen bleached kraft pulp (OKP) and other chemical pulps, semi-chemical pulp (SCP) and chemimiground wood pulp (CGP) and other semi-chemical pulps, groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) and the like. Mechanical pulp etc. are mentioned. The non-wood pulp is not particularly limited, but examples thereof include cotton-based pulp such as cotton linter and cotton lint, and non-wood-based pulp such as hemp, straw and bagasse. The deinked pulp is not particularly limited, and examples thereof include deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in a mixture of two or more kinds.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. Further, among wood pulp, the viewpoint of a high yield of fine fibrous modified cellulose at the time of defibration treatment with a large cellulose ratio, or a long fibrous modified cellulose of long fiber with a small decomposition of cellulose in the pulp and a large axial ratio From the viewpoint of being obtained, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. When long-fiber fine fibrous modified cellulose having a large axial ratio is used, the viscosity of the slurry containing the fine fibrous modified cellulose tends to increase.
As the fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used. Further, instead of a fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan may be used.

In order to obtain a fine fibrous modified cellulose having an ionic group as described above, an ionic group introducing step of introducing an ionic group into a fiber raw material containing the above-mentioned cellulose, a washing step, an alkali treatment step (neutralization Step) and the defibration treatment step in this order, and may have an acid treatment step instead of the washing step or in addition to the washing step. Examples of the ionic group introduction step include a phosphate group introduction step and a carboxy group introduction step. Each will be described below.

(Ionic group introduction step)
[Phosphate group introduction step]
In the phosphoric acid group introduction step, at least one compound selected from compounds capable of introducing a phosphoric acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose (hereinafter, also referred to as “compound A”) It is a step of acting on the fiber raw material containing. Through this step, a phosphoric acid group-introduced fiber is obtained.

In the phosphoric acid group-introducing step according to the present embodiment, the reaction between the fiber raw material containing cellulose and the compound A is performed in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). May be. On the other hand, the reaction of the fiber raw material containing cellulose and the compound A may be carried out in the absence of the compound B.
As an example of a method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state, or a slurry state can be mentioned. Among these, it is preferable to use the fiber raw material in the dry state or the wet state, and particularly preferable to use the fiber raw material in the dry state, because the reaction is highly uniform. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Compound A and compound B may be added to the fiber raw material in the form of powder or solution dissolved in a solvent, or heated to a melting point or higher and melted. Among these, since the reaction is highly uniform, it is preferable to add them in the form of a solution dissolved in a solvent, particularly in the 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, separately, or as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be dipped in the solution to absorb the liquid and then taken out. The solution may be added dropwise. In addition, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B are added to the fiber raw material, respectively, and then excess compound A and compound B are squeezed or filtered. May be removed.

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

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

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of the compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.
From the viewpoint of improving the uniformity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the homogeneity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.
The amount of the compound B added to the fiber raw material (extremely dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100% by mass or more and 350% by mass or less.

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

In the phosphoric acid group introduction step, it is preferable to add or mix the compound A or the like to the fiber raw material and then subject the fiber raw material to heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which the phosphoric acid group can be efficiently introduced while suppressing thermal decomposition or hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50° C. or higher and 300° C. or lower, more preferably 100° C. or higher and 250° C. or lower, and further preferably 130° C. or higher and 200° C. or lower. Further, for the heat treatment, equipment having various heat mediums can be used, and for example, a stirring dryer, a rotary dryer, a disk dryer, a roll type heater, a plate type heater, a fluidized bed dryer, an air stream. A drying device, a reduced pressure drying device, an infrared heating device, a far infrared heating device, or a microwave heating device can be used.
In the heat treatment according to the present embodiment, for example, the compound A or the like is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and the compound A or the like are kneaded or stirred with a kneader or the like. While heating, a method of heating can be adopted. This makes it possible to suppress unevenness in the concentration of the compound A or the like in the fiber raw material and more uniformly introduce the phosphate group into the surface of the cellulose fiber contained in the fiber raw material. This is because when water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A or the like is attracted to the water molecules by the surface tension and similarly moves to the surface of the fiber raw material (that is, uneven concentration of compound A). It is considered that this is caused by the fact that it is possible to suppress
In addition, the heating device used for the heat treatment always uses, for example, the water held by the slurry and the water generated by the dehydration condensation (phosphoric acid esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the device can be discharged to the outside. An example of such a heating device is a blower type oven. By constantly discharging the water in the device system, in addition to suppressing the hydrolysis reaction of the phosphoric acid ester bond, which is the reverse reaction of phosphoric acid esterification, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. it can. Therefore, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

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

The phosphate group introducing step may be performed at least once, but may be repeated twice or more. By performing the phosphoric acid group introduction step twice or more, it is possible to introduce many phosphoric acid groups into the fiber raw material. In the present embodiment, an example of a preferable mode is a case where the phosphate group introducing step is performed twice.

The amount of phosphoric acid groups with respect to the fiber raw material is, for example, preferably 0.10 mmol/g or more, more preferably 0.20 mmol/g or more, and 0.50 mmol/g or more per 1 g (mass) of fibrous cellulose. Is more preferable, and 1.00 mmol/g or more is particularly preferable. The amount of phosphate groups introduced into the fiber raw material is, for example, preferably 5.20 mmol/g or less, more preferably 3.65 mmol/g or less, and 3.00 mmol per 1 g (mass) of fibrous cellulose. /G or less is more preferable. By setting the amount of the phosphate group introduced within the above range, it is possible to facilitate miniaturization of the fiber raw material and enhance the stability of the fine fibrous modified cellulose.

[Carboxy group introduction step]
In the step of introducing a carboxy group, a fiber raw material containing cellulose is subjected to oxidation treatment such as ozone oxidation, Fenton's method, TEMPO oxidation treatment, a compound having a group derived from a carboxylic acid or a derivative thereof, or a group derived from a carboxylic acid. It is carried out by treating the compound with an acid anhydride or a derivative thereof.

The compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and citric acid and aconitic acid. Examples include tricarboxylic acid compounds. The derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an imidized product of an acid anhydride of a compound having a carboxy group and a derivative of an acid anhydride of a compound having a carboxy group. The imidization product of an acid anhydride of a compound having a carboxy group is not particularly limited, and examples thereof include imidization products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalic acid imide.
The acid anhydride of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. An acid anhydride is mentioned. The derivative of the acid anhydride of the compound having a carboxylic acid-derived group is not particularly limited, and examples thereof include compounds having a carboxy group such as dimethyl maleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride. Examples thereof include those in which at least a part of hydrogen atoms of the acid anhydride is substituted with a substituent such as an alkyl group or a phenyl group.

When the TEMPO oxidation treatment is performed in the carboxy group introduction step, for example, the treatment is preferably performed under the condition that the pH is 6 or more and 8 or less. Such treatment is also referred to as neutral TEMPO oxidation treatment. For the neutral TEMPO oxidation treatment, for example, sodium phosphate buffer (pH=6.8), pulp as a fiber raw material, and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst are used. It can be performed by adding nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by allowing sodium chlorite to coexist, the aldehyde generated during the oxidation process can be efficiently oxidized to the carboxy group.
Further, the TEMPO oxidation treatment may be performed under the condition that the pH is 10 or more and 11 or less. Such a treatment is also called an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be performed, for example, by adding nitroxy radicals such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidant to pulp as a fiber raw material. ..

The amount of the carboxy group introduced into the fiber raw material varies depending on the type of the substituent, but when introducing the carboxy group by TEMPO oxidation, for example, it is preferably 0.10 mmol/g or more per 1 g (mass) of the fibrous cellulose, It is more preferably 0.20 mmol/g or more, further preferably 0.50 mmol/g or more, and particularly preferably 0.90 mmol/g or more. Further, it is preferably 2.5 mmol/g or less, more preferably 2.20 mmol/g or less, and further preferably 2.00 mmol/g or less. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol/g or less per 1 g (mass) of fibrous cellulose.

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

(Alkaline treatment process)
When producing the fine fibrous modified cellulose, the ionic group-introduced fiber may be subjected to an alkali treatment between the ionic group-introducing step and the defibration treatment step described below. The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing the ionic group-introduced fiber in an alkali solution.
The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkali compound because of its high versatility. 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 water or a polar solvent containing a polar organic solvent such as an alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

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

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

(Acid treatment process)
When producing the fine fibrous modified cellulose, acid treatment may be performed on the ionic group-introduced fiber between the step of introducing the ionic group and the defibration treatment step described below. For example, the ionic 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 ionic group-introduced fiber in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic liquid used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less.
As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, 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, 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 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less based on the absolute dry mass of the ionic group-introduced fiber. Is more preferable.

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

In the defibration treatment step, for example, the ionic group-introduced fibers are preferably diluted with a dispersion medium to form a slurry. As the dispersion medium, water or one or more selected from organic solvents such as polar organic solvents 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, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol and glycerin. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and N-methyl-2-pyrrolidinone (NMP).
The solid content concentration of the fine fibrous modified cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the ionic group-introduced fiber in the dispersion medium may contain solid components other than the ionic group-introduced fiber such as urea having hydrogen bonding property.

<Physical properties of fibrous cellulose>
(viscosity)
In the present invention, the viscosity of the dispersion liquid (slurry) in which the solid content concentration of the fibrous cellulose is adjusted to 0.4% (0.4% by mass) at 23° C. is a viewpoint of further improving the dispersion stability of the calcium carbonate powder. Therefore, it is preferably 500 mPa·s or more, more preferably 1.0×10 ³ mPa·s or more, still more preferably 3×10 ³ mPa·s or more, still more preferably 5.0×10 ³ mPa·s. From the same viewpoint, it is preferably 1×10 ⁵ mPa·s or less, more preferably 7×10 ⁴ mPa·s or less, still more preferably 5×10 ⁴ mPa·s or less, still more preferably 3. It is 5×10 ⁴ mPa·s or less, more preferably 2.5×10 ⁴ mPa·s or less, and even more preferably 1.5×10 ⁴ mPa·s or less.
The above viscosity was measured by stirring the slurry in which the solid content concentration of the fibrous cellulose was adjusted to 0.4% at 1500 rpm for 5 minutes with a disperser, and then measuring the temperature at 23° C. and a relative humidity of 50% in an environment of 24. After standing for a period of time, measurement is performed using a B-type viscometer under the conditions of 23° C. and rotation speed of 3 rpm. More specifically, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD, which is a B-type viscometer, can be used. The measurement conditions are, for example, a liquid temperature of 23° C. and a viscometer rotation speed of 3 rpm, and the viscosity value at 3 minutes from the start of measurement is the viscosity of the dispersion liquid. The above-mentioned dispersion liquid may have the fibrous cellulose completely dissolved or may be in a dispersed state.

(TI value)
In the present invention, the thixotropic index (TI value) represented by the following formula (1) of the fibrous cellulose is preferably 30 or more, more preferably 50 or more, further from the viewpoint of obtaining a predecessor having more excellent pumpability. It is preferably 60 or more, more preferably 75 or more, still more preferably 90 or more.
And the upper limit is not particularly limited, but from the viewpoint of easy availability of fibrous cellulose and dispersion stability of the precursor, preferably 600 or less, more preferably 500 or less, further preferably 400 or less, still more preferably 350 or less. Is.
TI value=(viscosity at shear rate 1/s)/(viscosity at shear rate 1000/s) (1)
The above viscosity is the viscosity at 23° C. and 0.4% solid concentration dispersion.
The TI value is measured by the method described in the example.

[Preceding agent for concrete pumping]
The fibrous cellulose of the present invention is used to mix with calcium carbonate powder to make a precursor for concrete pumping.
In the present invention, the precursor for pumping concrete pump is usually in the form of powder or paste, and is dispersed by adding water before use, and the dispersion obtained by this is put into the hopper of the concrete pump. The "concrete pumping predecessor" does not mean only a powdery state, but also a dispersion in water.
Therefore, in the present invention, the fibrous cellulose is in a powder form such as a wet powder form, and may be present as a precursor for pumping which is a powder form as a whole when mixed with calcium carbonate. Is a state of dispersion (slurry), and when the powder containing calcium carbonate is made into an aqueous dispersion, a dispersion (slurry) containing fibrous cellulose is added and mixed with calcium carbonate, It may be used as an agent (dispersion liquid).

In the present invention, the amount of fibrous cellulose mixed with 100 parts by mass of calcium carbonate powder is preferably 0.0001 parts by mass or more, and more preferably 0.001 parts by mass, from the viewpoint of obtaining a precursor having excellent dispersion stability and pumpability. Parts by mass or more, more preferably 0.01 parts by mass or more, and from the same viewpoint, preferably 100 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 1 part by mass or less, and even more preferably 0. It is 1 part by mass or less.
The amount of fibrous cellulose mixed means the amount of dried fibrous cellulose mixed.

In the present invention, the preceding agent contains at least calcium carbonate.
The content of calcium carbonate in the solid content of the precursor is preferably 50% by mass, more preferably 60% by mass or more, further preferably from the viewpoint of excellent dispersibility and pumpability, and from the viewpoint of suppressing clogging of concrete pipes. Is 70% by mass or more, more preferably 80% by mass or more, and preferably 99.9% by mass or less.

The calcium carbonate may be light calcium carbonate such as precipitated calcium carbonate, or may be ground calcium carbonate obtained by crushing limestone, and is not particularly limited, but excellent performance as a precursor is obtained. From the viewpoint, it is preferable that the calcium carbonate powder has a small particle size. Moreover, you may use the calcium carbonate powder which carried out the particle size adjustment and the component adjustment.
Among these, it is preferable to contain a porous calcium carbonate powder from the viewpoint of exhibiting excellent performance as a precursor. Examples of the porous calcium carbonate include porous calcium carbonate obtained by adjusting the particle size and the components of fresh raw sludge.
Further, the calcium carbonate powder may contain fine powder calcium carbonate having a uniform particle shape, such as precipitated calcium carbonate.

In the present invention, the precursor may contain other components in addition to the calcium carbonate powder and the fibrous cellulose.
Examples of other components include inorganic powders other than calcium carbonate, water-absorbent resins, water-soluble resins, pigments, antioxidants, pH adjusters and the like. In the present invention, the fibrous cellulose is more preferably mixed with at least one selected from the group consisting of pigments, antioxidants, and pH adjusters.
Examples of the inorganic powder other than calcium carbonate include calcium hydroxide, hydrotalcite, calcium oxide and the like. The pigment may be either an inorganic pigment or an organic pigment. By including the pigment, the visibility of the discharged precursor agent is improved, and it becomes easy to monitor the discharge completion of the precursor agent. As the organic pigment, an organic fluorescent pigment is particularly preferable from the viewpoint of visibility.
Further, an antioxidant such as erythorbic acid or a pH adjuster may be added for the purpose of preventing oxidation or adjusting the pH. By adding an antioxidant, a pH adjuster and the like, the dispersibility of the preceding agent is further improved, and the corrosion in the pipe and the influence when mixed with concrete are reduced.

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

The fibrous cellulose used in each of the examples and comparative examples was produced by the following production example.
(Production Example 1)
(Preparation of phosphate group-introduced pulp)
As a raw material pulp, a softwood kraft pulp made by Oji Paper Co., Ltd. (solid content 93 mass %, basis weight 208 g/m ² sheet shape, Canadian standard freeness (CSF) measured in accordance with JIS P 8121 is 700 mL) It was used. This raw material pulp was subjected to phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to give 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. Was adjusted to obtain a chemical-impregnated pulp. Next, the obtained chemical liquid-impregnated pulp is heated for 200 seconds with a hot air dryer at 165° C. to introduce a phosphate group into the cellulose in the pulp to obtain a phosphate group-introduced pulp (hereinafter, also referred to as “phosphorylated pulp”). Obtained. Then, the phosphorylated pulp obtained was subjected to a washing treatment. The washing treatment was carried out by repeating the operation of pouring the pulp dispersion obtained by pouring 10 L of ion-exchanged water to 100 g of phosphorylated pulp (absolute dry mass) so that the pulp was uniformly dispersed, and then filtering and dehydrating. went. When the electric conductivity of the filtrate became 100 μS/cm or less, the washing end point was set.
Next, the phosphorylated pulp after washing was subjected to neutralization treatment as follows. First, the phosphorylated pulp after washing was diluted with 10 L of ion-exchanged water, and 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. .. Next, the phosphorylated pulp slurry was dehydrated to obtain a neutralized phosphorylated pulp. Next, the above washing treatment was performed on the phosphorylated pulp after the neutralization treatment.
The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on a phosphate group was observed around 1230 cm ⁻¹ , and it was confirmed that the phosphate group was added to the pulp. The amount of phosphoric acid groups (the amount of strong acidic groups) measured by the measuring method described later was 1.45 mmol/g. Also, the phosphorylated pulp obtained was tested and analyzed by an X-ray diffractometer, and it was found at two positions, that is, 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less. A typical peak was confirmed and it was confirmed to have a cellulose type I crystal.

(Preparation of fibrous cellulose dispersion)
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated once with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion liquid 1 containing fine fibrous modified cellulose. It was confirmed by X-ray diffraction that the fine fibrous modified cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous modified cellulose was measured with a transmission electron microscope, and it was 3 to 5 nm.
The amount of phosphoric acid groups (the amount of strongly acidic groups) of the fibrous cellulose measured by the measuring method described later was 1.45 mmol/g, and the degree of polymerization was 680.

(Production Example 2)
A fibrous cellulose dispersion 2 was obtained in the same manner as in Production Example 1 except that the fibrous cellulose was treated twice with a wet atomizer at a pressure of 200 MPa so that the degree of polymerization of fibrous cellulose was 590. ..

(Production Example 3)
Fibrous Cellulose Dispersion 3 was obtained in the same manner as in Production Example 1 except that the fibrous cellulose was treated 4 times at a pressure of 200 MPa with a wet atomizer so that the degree of polymerization of fibrous cellulose was 499. ..

(Production Example 4)
Fibrous Cellulose Dispersion Liquid 4 was obtained in the same manner as in Production Example 1 except that the treatment was performed 6 times at a pressure of 200 MPa with a wet atomizer so that the degree of polymerization of fibrous cellulose was 459. ..

(Production Example 5)
(Preparation of phosphate group-introduced pulp)
As a raw material pulp, a softwood kraft pulp made by Oji Paper Co., Ltd. (solid content 93 mass %, basis weight 208 g/m ² sheet shape, Canadian standard freeness (CSF) measured in accordance with JIS P 8121 is 700 mL) It was used. This raw material pulp was subjected to phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to give 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. Was adjusted to obtain a chemical-impregnated pulp. Next, the obtained chemical liquid-impregnated pulp was heated for 200 seconds with a hot air dryer at 165° C. to introduce a phosphate group into the cellulose in the pulp to obtain a phosphate group-introduced pulp (phosphorylated pulp). Then, the phosphorylated pulp obtained was subjected to a washing treatment. The washing treatment was carried out by repeating the operation of pouring the pulp dispersion obtained by pouring 10 L of ion-exchanged water to 100 g of phosphorylated pulp (absolute dry mass) so that the pulp was uniformly dispersed, and then filtering and dehydrating. went. When the electric conductivity of the filtrate became 100 μS/cm or less, the washing end point was set. The phosphorylated pulp after washing was further subjected to the above-mentioned phosphorylation treatment and the above-mentioned washing treatment once in this order.
Next, the phosphorylated pulp after washing was subjected to neutralization treatment as follows. First, the phosphorylated pulp after washing was diluted with 10 L of ion-exchanged water, and 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. .. Next, the phosphorylated pulp slurry was dehydrated to obtain a neutralized phosphorylated pulp. Next, the above washing treatment was performed on the phosphorylated pulp after the neutralization treatment.
The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on a phosphate group was observed around 1230 cm ⁻¹ , and it was confirmed that the phosphate group was added to the pulp. The amount of phosphoric acid groups (the amount of strong acidic groups) measured by the measuring method described later was 2.00 mmol/g. Also, the phosphorylated pulp obtained was tested and analyzed by an X-ray diffractometer, and it was found at two positions, that is, 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less. A typical peak was confirmed and it was confirmed to have a cellulose type I crystal.

(Preparation of fibrous cellulose dispersion)
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. The slurry was treated once with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion 5 containing fine fibrous modified cellulose. It was confirmed by X-ray diffraction that the fine fibrous modified cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous modified cellulose was measured with a transmission electron microscope, and it was 3 to 5 nm.
The amount of phosphoric acid groups (the amount of strongly acidic groups) of the fibrous cellulose measured by the measuring method described later was 2.00 mmol/g, and the degree of polymerization was 625.

(Production Example 6)
In Production Example 5, except that the fibrous cellulose was treated twice with a wet atomization device at a pressure of 200 MPa so that the amount of phosphoric acid groups in the fibrous cellulose was 2.00 mmol/g and the degree of polymerization was 536. Then, a fibrous cellulose dispersion liquid 6 was obtained.

(Production Example 7)
In Production Example 5, the same as Production Example 5 except that the fibrous cellulose was treated 4 times at a pressure of 200 MPa with a wet atomizer so that the amount of phosphate groups in the fibrous cellulose was 2.00 mmol/g and the degree of polymerization was 482. Then, a fibrous cellulose dispersion liquid 7 was obtained.

(Production Example 8)
In Production Example 5, the same as Production Example 5, except that the fibrous cellulose was treated 6 times at a pressure of 200 MPa with a wet atomization apparatus so that the amount of phosphate groups was 2.00 mmol/g and the degree of polymerization was 444. The fibrous cellulose dispersion liquid 8 was obtained.

(Production Example 9)
(Preparation of phosphite group-introduced pulp)
Except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate, the same operation as in Production Example 1 was repeated to prepare a phosphorous acid group-introduced pulp (hereinafter, also referred to as “phosphorylated pulp”). I said.)
Then, the obtained phosphorous-oxidized pulp was washed. In the washing treatment, a pulp dispersion obtained by pouring 10 L of ion-exchanged water to 100 g of phosphorous pulp (absolute dry mass) is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. I went by. When the electric conductivity of the filtrate was 100 μS/cm or less, the washing end point was set.
Then, the washed phosphorous acid pulp was neutralized as follows. First, after diluting the washed phosphite pulp with 10 L of ion-exchanged water, 1N sodium hydroxide aqueous solution is slightly added while stirring to give a phosphite pulp slurry having a pH of 12 or more and 13 or less. Obtained. Then, the phosphorous oxide pulp slurry was dehydrated to obtain a phosphorous acid pulp subjected to neutralization treatment. Next, the washing treatment was performed on the phosphorous acid pulp after the neutralization treatment.
The infrared absorption spectrum of the phosphorous-oxidized pulp thus obtained was measured using FT-IR. As a result, the absorption based on P=O of the phosphonic acid group, which is a tautomer of the phosphite group, was observed in the vicinity of 1210 cm ^-1 , and the phosphite group (phosphonic acid group) was added to the pulp. Was confirmed.
Moreover, when the obtained phosphorous phosphite pulp was tested and analyzed by an X-ray diffractometer, two positions of 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less were determined. Was confirmed to have a typical peak, and it was confirmed to have a cellulose type I crystal.

(Preparation of fibrous cellulose dispersion)
Ion-exchanged water was added to the obtained phosphorous oxide pulp to prepare a slurry having a solid content concentration of 2% by mass. The slurry was treated 6 times with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion 9 containing fine fibrous modified cellulose. It was confirmed by X-ray diffraction that the fine fibrous modified cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous modified cellulose was measured with a transmission electron microscope, and it was 3 to 5 nm.
The amount of phosphite group (the amount of strongly acidic group) of the fibrous cellulose measured by the measuring method described later was 1.80 mmol/g, and the degree of polymerization was 430.

(Production Example 10)
(Preparation of carboxy group-introduced pulp)
As a raw material pulp, a softwood kraft pulp made by Oji Paper Co., Ltd. (solid content 93 mass %, basis weight 208 g/m ² sheet shape, Canadian standard freeness (CSF) measured in accordance with JIS P 8121 is 700 mL) It was used. This raw pulp was subjected to TEMPO oxidation treatment as follows.
First, the raw material pulp corresponding to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), 10 parts by mass of sodium bromide, and 10 parts of water. It was dispersed in 1,000 parts by mass. Then, a 13 mass% sodium hypochlorite aqueous solution was added to 10 g of 1.0 g of pulp to start the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 or more and 10.5 or less, and the reaction was considered to be complete when no change in pH was observed.
Then, the obtained carboxy group-introduced pulp (hereinafter, also referred to as “TEMPO oxidized pulp”) was subjected to a washing treatment. The washing treatment is to dehydrate the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pour 5,000 parts by mass of ion-exchanged water, stir to uniformly disperse, and then repeat the operation of filtering and dehydrating. I went by. When the electric conductivity of the filtrate was 100 μS/cm or less, the washing end point was set.
Moreover, when the obtained TEMPO oxidized pulp was tested and analyzed by an X-ray diffractometer, it was found to be at two positions of 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less. A typical peak was confirmed and it was confirmed to have a cellulose type I crystal.

(Preparation of fibrous cellulose dispersion)
Ion-exchanged water was added to the obtained TEMPO oxidized pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated 6 times with a wet atomizer (manufactured by Sugino Machine Ltd., Starburst) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion liquid 10 containing fine fibrous modified cellulose.
The carboxy group content of the fibrous cellulose measured by the measuring method described later was 1.80 mmol/g, and the degree of polymerization was 336.

<Measurement method>
(Measurement of ionic group content of fibrous cellulose dispersion)
The ionic group content of the fibrous cellulose is a fibrous cellulose prepared by diluting a fibrous cellulose dispersion liquid containing the target fine fibrous modified cellulose with ion-exchanged water to a content of 0.2% by mass. The contained slurry was treated with an ion exchange resin and then titrated with an alkali to measure.
The treatment with an ion-exchange resin was performed by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; manufactured by Organo Co., Ltd., conditioned) to the slurry containing the fine fibrous modified cellulose, and performing a shaking treatment. After that, the resin and the slurry were separated by pouring onto a mesh having an opening of 90 μm.
In addition, titration using an alkali was performed by adding 50 μL of an aqueous 0.1 N sodium hydroxide solution to the slurry containing fine fibrous cellulose after the treatment with an ion exchange resin once every 30 seconds, and showing the electrical conductivity of the slurry. It was performed by measuring the change in the value of. The amount of ionic groups (mmol/g) is the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 1 or 2 in the measurement results as the solid content (g) in the slurry to be titrated. It was calculated by dividing.

(Measurement of degree of polymerization of fibrous cellulose)
The degree of polymerization of the fibrous cellulose was measured according to Tappi T230. That is, after measuring the viscosity (η ₁ ) measured by dispersing the fibrous cellulose to be measured in the dispersion medium and the blank viscosity (η ₀ ) measured only with the dispersion medium, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) were measured according to the following formulas.
η _SP =(η ₁ /η ₀ )-1
[Η]=η _sp /(c(1+0.28×η _sp ))
Here, c in the formula represents the concentration of fibrous cellulose at the time of viscosity measurement.
Further, the degree of polymerization (DP) of fibrous cellulose was calculated from the following formula.
DP=1.75×[η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

(Measurement of viscosity of fibrous cellulose dispersion)
The viscosity of the fibrous cellulose dispersion was measured as follows. First, the fibrous cellulose dispersion was diluted with ion-exchanged water so that the solid content concentration was 0.4%, and then stirred with a disperser at 1,500 rpm for 5 minutes. Then, the viscosity of the dispersion liquid thus obtained was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the dispersion liquid. Further, the dispersion liquid to be measured was allowed to stand for 24 hours in an environment of 23° C. and 50% relative humidity before the measurement. The liquid temperature of the dispersion liquid at the time of measurement was 23°C.

(Measurement of viscosity of fibrous cellulose dispersion by rheometer)
The fibrous cellulose dispersion was diluted with ion-exchanged water to a solid content concentration of 0.4%, and then the viscosity was measured using a rheometer (manufactured by HAAKE, RheoStress 6000). The shear rate was changed under the following conditions.
Measurement temperature: 23 ℃
Measuring jig: cone plate (diameter 40 mm, angle 1°)
Shear rate: 0.001 to 1000 sec ^-1
Number of data points: 100 points Data distribution: Log interval Measurement time: 5 minutes

(Calculation of TI value)
The viscosity was measured by a rheometer, and the value of viscosity (η ₁ ) measured under the condition of shear rate of 1 sec ⁻¹ was divided by the value of viscosity (η ₂ ) measured under the condition of shear rate of 1,000 sec ^−1. The obtained value was used as a thixotropic index value (TI value).
That is, the TI value was defined by the following formula.
TI value=η ₁ /η ₂
.eta.1: Viscosity was measured at a shear rate of 1 sec ^-1 .eta.2: viscosity measured under the conditions of a shear rate of 1,000 sec ^-1

(Preparation of antecedent for model pumping)
(Example 1)
100 parts by mass of porous calcium carbonate and 200 parts by mass of water were mixed, and 0.015 parts by mass of the fibrous cellulose dispersion 1 as a solid content was added thereto and well mixed to prepare a model pressure-feeding precursor.

(Examples 2 to 10)
In place of the fibrous cellulose dispersion 1, the fibrous cellulose dispersions 2 to 10 obtained in the above Production Examples 2 to 10 were used, respectively, to prepare a model pressure-feed advance agent in the same manner as in Example 1. did.

(Comparative Example 1)
A fibrous cellulose dispersion liquid 11 (manufactured by Sugino Machine Limited, IMa-10002) was used in place of the fibrous cellulose dispersion liquid 1 in the same manner as in Example 1 to prepare a model delivery precursor. ..

(Comparative example 2)
A model pressure-feeding precursor agent was prepared in the same manner as in Example 1 except that guar gum (manufactured by Tokyo Chemical Industry Co., Ltd.) was used.

(Reference example)
A model pressure-feeding precursor was prepared in the same manner as in Example 1 except that water was used instead of the fibrous cellulose dispersion 1.

<Evaluation method>
(Dispersion stability evaluation)
The model pressure-feeding precursors of Examples 1 to 10, Comparative Examples 1 and 2, and Reference Example were diluted with ion-exchanged water so as to have a solid content concentration of 1%, and added to a 10 mL screw vial bottle (manufactured by AS ONE Corporation). The mixture was collected and allowed to stand for 5 minutes. The distance from the bottom of the vial to the liquid surface was 3 cm. The dispersion stability was evaluated according to the following evaluation criteria. The results are shown in Table 1.
A: Good dispersion stability without separation B: Slight dispersion, but dispersion stability that does not cause any problems in use C: Significant separation is not observed and cannot be used. In addition, Example 1 and Comparative Example For No. 1, the distance between the liquid surface in the screw bottle and the interface between water and water generated by the separation was measured. The results are shown in Table 2.

[result]
As shown in Table 1, no separation of calcium carbonate was observed with time in the diluted solutions of the model pressure-feeding precursors of Examples 1, 3, 4, 7, and 8, indicating good dispersion stability. In addition, in Examples 2, 5, 6, 9, and 10, although there were some separations, dispersion stability showing no problem in use was shown. On the other hand, in the comparative example and the reference example, remarkable separation was observed.
In addition, as shown in Table 2, the distance between the boundary surface between the liquid surface in the screw bottle and the water generated by the separation was significantly smaller in Example 1 than in Comparative Example 1, and was allowed to stand for a long time. It also showed that it suppressed the separation and showed high dispersion stability.
From the above results, it was shown that the dispersion stability of calcium carbonate was improved in the precursor for pressure feeding containing the fibrous cellulose containing the fine fibrous modified cellulose substituted with the ionic group.

(Evaluation of pumpability)
A 50 mL disposable syringe (manufactured by Terumo Corp.) was filled with 10 g of the model pressure-feeding precursor of Example 1, Comparative Examples 1 and 2, and Reference Example, and the time required for extrusion of the entire amount was measured. The extrusion pressure at this time was about 0.1 kPa. The results are shown in Table 3.

[result]
Example 1 showed that the required time was about 30 seconds and that the extrusion was smooth, suggesting that it was effective in stabilizing the dispersion of the fine particles. On the other hand, in Comparative Examples 1 and 2 and Reference Example 1, the extrusion time that was twice as long as that in Example 1 was required.
It was shown that the precursor for pressure feeding containing the fibrous cellulose of the present invention is excellent in dispersion stability and can be pressure-fed at a lower pressure during pressure feeding.

By the fibrous cellulose of the present invention, it is possible to provide a precursor for concrete pump pumping containing calcium carbonate powder, which is excellent in dispersion stability and pumpability, and enables the smooth pumping of concrete through piping by using a small amount. Expected to start.

Claims (7)

A fibrous cellulose used for producing a precursor for concrete pumping by mixing with calcium carbonate powder,
A fibrous cellulose containing the fine fibrous modified cellulose having an ionic group and having a fiber width of 1000 nm or less. The fibrous cellulose according to claim 1, wherein the viscosity of the fibrous cellulose (solid content concentration 0.4% dispersion liquid, 23°C) is 500 mPa·s or more. The fibrous cellulose according to claim 1 or 2, wherein a thixotropic index (TI value) represented by the following formula (1) of the fibrous cellulose is 30 or more.
TI value=(viscosity at shear rate 1/s)/(viscosity at shear rate 1000/s) (1)
The above viscosity is the viscosity at 23° C. and 0.4% solid concentration dispersion. The fibrous cellulose according to any one of claims 1 to 3, wherein the content of the calcium carbonate powder in the solid content of the preceding agent for pumping concrete pump is 50% by mass or more. The fibrous cellulose according to claim 1, wherein a mixing amount of fibrous cellulose with respect to 100 parts by mass of the calcium carbonate powder is 0.0001 parts by mass or more and 100 parts by mass or less. The fibrous cellulose according to claim 1, wherein the calcium carbonate powder contains a porous calcium carbonate powder. The fibrous cellulose according to any one of claims 1 to 6, further mixed with at least one selected from a pigment, an antioxidant, and a pH adjuster.