JP7010206B2 - Fibrous cellulose - Google Patents

Description

The present invention relates to fibrous cellulose, particularly fibrous cellulose used to mix with calcium carbonate powder to produce a precursor for pumping concrete pumps.

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 casting place by using a concrete pump truck has been widely adopted. In this method, the concrete in the hopper is pumped into the pipe using a concrete pump truck, and the concrete is transported to the target casting place through the pipe. When concrete is pumped using a concrete pump and piping, cement paste or mortar mixed with water and cement as a pumping precursor is pre-filled in the hopper as a pumping precursor, and this pumping precedent is used. The agent is first sent into the pipe, and then the ready-mixed concrete is continuously sent into the pipe and pumped while pouring the ready-mixed concrete into the hopper. In this way, when the pre-hardened ready-mixed concrete (fluid concrete) is introduced without any treatment, only the mortar component (cement paste) among the constituents of the concrete is sent first. This is because the tip of the concrete that adheres to the surface inside the pump or the pipe and has lost the mortar content may gradually separate and block the pipe.

In the method using cement paste or mortar as a precursor for pumping, the hardening reaction proceeds during transportation or waiting at the concrete driving destination, so it is necessary to make a detailed management plan for the concrete driving work. Further, in this method, it is necessary to set a large amount of the cement paste or mortar used as the pumping precursor in order to obtain the required effect, and further, the cement paste or mortar used as the pumping precursor is discarded. Not only is it not economical, but 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 pumping of concrete with a small amount of use. There is.

Japanese Unexamined Patent Publication No. 2000-34461

The pumping precursor described in Patent Document 1 has problems such as inferior economic efficiency such as using a water-absorbent resin, and insufficient water absorption of the water-absorbent resin depending on the conditions of use. ..
An object of the present invention is to provide a fibrous cellulose used for producing a precursor for pumping a concrete pump containing calcium carbonate powder, which has excellent dispersion stability and pumping property.

The present inventors have found that the above-mentioned problems can be solved by adopting fibrous cellulose which 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 precursor for concrete pump pumping by mixing with calcium carbonate powder, wherein the fibrous cellulose has an ionic group and 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 viscosity of the fibrous cellulose (solid content concentration 0.4% dispersion, 23 ° C.) is 500 mPa · s or more.
<3> The fibrous cellulose according to <1> or <2>, wherein the fibrous cellulose has a thixotropic index (TI value) of 30 or more represented by the following formula (1).
TI value = (viscosity at shear rate 1 / s) / (viscosity at shear rate 1000 / s) (1)
The above viscosity is the viscosity of a dispersion liquid having a solid content concentration of 0.4% at 23 ° C.
<4> The fibrous cellulose according to any one of <1> to <3>, wherein the content of calcium carbonate powder in the solid content of the concrete pump pumping precursor is 50% by mass or more.
<5> The fibrous cellulose according to any one of <1> to <4>, wherein the mixed amount of the fibrous cellulose with respect to 100 parts by mass of the calcium carbonate powder is 0.0001 part by mass or more and 100 parts by mass or less.
<6> The fibrous cellulose according to any one of <1> to <5>, wherein 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.

According to the present invention, it is possible to provide a fibrous cellulose used for producing a precursor for pumping a concrete pump containing calcium carbonate powder, which is excellent in dispersion stability and pumping property.

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

[Fibrous cellulose]
The fibrous cellulose of the present invention is used for producing a precursor for concrete pump pumping by mixing with calcium carbonate powder, and the fibrous cellulose has an ionic group and 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 the preceding agent for pumping containing calcium carbonate, the preceding agent for pumping of a concrete pump having excellent dispersion stability and excellent pumping property (hereinafter, "preceding agent for pumping") Or "preceding agent") is obtained.
The detailed reason why the above effect is obtained is unknown, but some 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 adding it to water to form a slurry. On the other hand, the slurry has thixotropic properties and its viscosity decreases when it is subjected to shear stress.
When mixed with calcium carbonate to make a precursor for pumping concrete pumps, the precursor for pumping contains water when it is actually pumped into the pipe as a precursor, which results in high dispersion stability with respect to calcium carbonate. It is considered that excellent pumping property can be obtained while imparting sex. In particular, it is considered that the fine fibrous cellulose having an ionic group has obtained high dispersion stability with respect to calcium carbonate and excellent pumping property.
Hereinafter, the present invention will be described in more detail.

<Fine fibrous modified cellulose>
The fibrous cellulose of the present invention contains fine fibrous modified cellulose, and the fine fibrous modified cellulose is fibrous cellulose having a fiber width of 1,000 nm or less and is substituted with an ionic group. The fiber widths of the fibrous cellulose and the fine fibrous modified cellulose can be measured by, for example, observation with an electron microscope.
The fibrous cellulose contains fine fibrous modified cellulose, further, unmodified fine fibrous cellulose having a fiber width of 1,000 nm or less, unmodified fibrous cellulose having a fiber width of more than 1,000 nm, and a fiber width of 1,. It may contain fibrous modified cellulose over 000 nm and substituted with ionic groups.
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. May be%. In the present invention, as the fibrous cellulose, a mode in which fine fibrous modified cellulose and unmodified fibrous cellulose having a fiber width of more than 1000 nm are mixed and used, and fibrous cellulose is added to the fine fibrous modified cellulose. , A mode containing a small amount of unmodified fine fibrous cellulose and modified or unmodified cellulose having a fiber width of more than 1000 nm.

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. Further, 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 preferred. By setting the average fiber width of the fine fibrous modified cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous modified cellulose in water as a cellulose molecule, and it is easier to exhibit the effects of the fine fibrous modified cellulose on improving dispersion stability and pumping property. can do. The fine fibrous modified cellulose is, for example, monofibrous cellulose.

The average fiber width of the fine fibrous modified cellulose is measured as follows, for example, using an electron microscope. 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 this suspension is cast on a hydrophilized carbon film-coated grid for TEM observation. Use as a sample. 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 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 even more preferable. By setting the fiber length within the above range, it is possible to suppress the destruction of the crystal region of the fine fibrous modified cellulose. Further, it is 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 obtained by, for example, image analysis by TEM, SEM, or AFM.

The fine fibrous modified cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous modified cellulose has an I-type crystal structure can be identified in the diffraction profile obtained from the wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The ratio of the type I crystal structure to the fine fibrous modified cellulose is, for example, preferably 30% or more, more preferably 40% or more, still more preferably 50% or more. As a result, even better performance can be expected in terms of dispersion stability and pumping property. 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 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 value or more, it is easy to obtain sufficient viscosity when an aqueous dispersion of fine fibrous modified cellulose is produced. By setting the axial ratio to the above upper limit value or less, it is preferable in that handling such as dilution becomes easy when, for example, fibrous cellulose is treated as an aqueous dispersion.

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

The fine fibrous modified cellulose in this embodiment has an ionic group. Since 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 enhanced. Further, when a precursor for pumping concrete pumps is produced by mixing with calcium carbonate powder, the dispersibility of calcium carbonate in water is improved and the pumping property is improved.
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.
Further, 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.

Anionic groups as ionic groups include, for example, a phosphate group or a group derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxy group or a group derived from a carboxy group (also simply referred to as a carboxy group). There is), and at least one selected from 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 phosphate group and a carboxy group. It is more preferable, and it is particularly preferable that it is a phosphate group.

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 phosphoric acid group or a group derived from a phosphoric acid.
The phosphoric acid group is, for example, a divalent functional group obtained by removing a hydroxy group from phosphoric acid. Specifically, it is a group represented by -PO ₃ H ₂ . The group derived from the phosphoric acid group includes a group such as a salt of a phosphoric acid group and a phosphoric acid ester group. The group derived from the phosphoric acid group may be contained in the fine fibrous modified cellulose as a group (for example, a pyrophosphate group) in which the phosphoric acid group is condensed. Further, the phosphoric acid group may be, for example, a phosphite group (phosphonic acid group), and the group derived from the phosphoric acid group may be a salt of the phosphite group, a phosphite ester group, or the like. good.

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

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

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion, which does not easily yellow when the fiber raw material containing β is heated and is easily industrially used, but is not particularly limited.

The amount of the ionic group introduced in 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 g or more, and particularly preferably 1.00 mmol / g or more. Further, the amount of the ionic group introduced in the fibrous cellulose is 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, and even more preferably 3.00 mmol / g or less. By setting the amount of the ionic group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous 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 the dispersion stability and the pumping property.
Here, the denominator in the unit mmol / g indicates the mass of the fibrous cellulose when the counterion of the ionic group is a hydrogen ion (H ⁺ ).

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

Since the denominator of the above-mentioned phosphoric acid group introduction amount (mmol / g) indicates the mass of the acid-type fibrous cellulose, the phosphoric acid group amount of the acid-type fibrous cellulose (hereinafter referred to as the phosphoric acid group amount). (Called (acid type))). On the other hand, when the counterion of the phosphate group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is a counterion. This makes it possible to determine the amount of phosphate groups (hereinafter, the amount of phosphate groups (C type)) possessed by fibrous cellulose whose cation C is a counterion.
That is, it is calculated by the following formula.
Phosphoric acid group amount (C type) = Phosphoric acid group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total anion amount derived from the phosphate group of the fibrous cellulose (the sum of the strong acid group amount and the weakly acidic group amount of the phosphoric acid group).
W: Formulated amount of cation C per valence (for example, Na is 23, Al is 9)

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

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

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

<Manufacturing method of 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 it is preferable to use pulp because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, but is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp of this embodiment, one of the above may be used alone, or two or more of them may be mixed and used.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. In addition, among wood pulps, from the viewpoint of high cellulose ratio and high yield of fine fibrous modified cellulose during defibration treatment, long fiber fine fibrous modified cellulose with small decomposition of cellulose in pulp and large axial ratio is available. From the viewpoint obtained, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. When 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 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.

In order to obtain the above-mentioned fine fibrous modified cellulose into which an ionic group has been introduced, an ionic group introduction step, a washing step, and an alkali treatment step (neutralization) in which the ionic group is introduced into the above-mentioned fiber raw material containing cellulose Step), it is preferable to have a defibration treatment step in this order, and an acid treatment step may be provided instead of the washing step or in addition to the washing step. Examples of the ionic group introduction step include a phosphoric acid group introduction step and a carboxy group introduction step. Each will be described below.

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

In the phosphate group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). You may. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.
As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, there is a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state. Of these, since the reaction uniformity is high, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction uniformity is high, it is preferable to add the solution in the form of a solution dissolved in a solvent, particularly in the state of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, a required amount of compound A and compound B may be added to the fiber raw material, or an excess amount of compound A and compound B may be added to the fiber raw material, respectively, and then the surplus compound A and compound B may be added by pressing or filtering. It may be removed.

The compound A used in this embodiment may be any compound having a phosphorus atom and capable of forming an ester bond with cellulose, and may be phosphoric acid or a salt thereof, phosphoric acid or a salt thereof, dehydration condensed phosphoric acid or a salt thereof. Examples thereof include salts and anhydrous phosphoric acid (diphosphoric pentoxide), but the present invention is not particularly limited. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of the phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of the phosphate, sulphate, and dehydration-condensed phosphate include phosphoric acid, sulphite, or lithium salt of dehydration-condensed phosphoric acid, sodium salt, potassium salt, ammonium salt, and the like. It can be a sum.
Of these, phosphoric acid and phosphoric acid are highly efficient in introducing phosphoric acid groups, are more likely to improve defibration efficiency in the defibration process described later, are low in cost, and are easy to apply industrially. A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.

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

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

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

In the phosphoric acid group introduction step, it is preferable to add or mix the compound A or the like to the fiber raw material and then heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which the phosphate group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized bed drying device, and an air stream. A drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, and a microwave heating device can be used.
In the heat treatment according to the present embodiment, for example, a method of adding compound A or the like to a thin sheet-shaped fiber raw material by a method such as impregnation and then heating, or a method of kneading or stirring the fiber raw material and compound A or the like with a kneader or the like. It is possible to adopt a method of heating while heating. This makes it possible to suppress uneven concentration of the compound A or the like in the fiber raw material and more uniformly introduce the phosphoric acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A 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, the concentration unevenness of the compound A). 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 (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. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, and also to suppress the acid hydrolysis of the sugar chain in the fiber. can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

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

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

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

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

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

When the TEMPO oxidation treatment is performed in the carboxy group introduction step, it is preferable to perform the treatment under conditions of pH 6 or more and 8 or less, for example. Such a treatment is also referred to as a neutral TEMPO oxidation treatment. The neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and the like. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting with sodium chlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group.
Further, the TEMPO oxidation treatment may be carried out under the condition that the pH is 10 or more and 11 or less. Such a treatment is also referred to as an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. ..

The amount of carboxy group introduced into the fiber raw material varies depending on the type of substituent, but for example, when a carboxy group is introduced by TEMPO oxidation, it is preferably 0.10 mmol / g or more per 1 g (mass) of 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 by washing the ionic group-introduced fibers with, for example, water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleaning steps performed in each cleaning step is not particularly limited.

(Alkaline treatment process)
In the case of producing fine fibrous modified cellulose, the ionic group-introduced fiber may be treated with an alkali between the ionic 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 ionic 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 this embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water, a polar organic solvent exemplified by alcohol, and the like, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower.
The immersion time of the ionic group-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less.
The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the ionic group-introduced fiber. Is more preferable.

In order to reduce the amount of the alkaline solution used in the alkaline 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 alkaline 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 handleability.

(Acid treatment process)
In the case of producing fine fibrous modified cellulose, the ionic group-introduced fiber may be acid-treated between the step of introducing the ionic group and the defibration treatment step described later. For example, the ionic group introduction step, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.
The acid treatment method 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, 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 ionic group-introduced fiber. Is more preferable.

(Defibration processing process)
Fine fibrous cellulose can be obtained by defibrating the ionic group-introduced fiber in the defibration treatment step.
In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibration processing device 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 pulverized media and have less risk of contamination.

In the defibration treatment step, for example, it is preferable to dilute the ionic 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 and glycerin. Examples of the ketone include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monon-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotonic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.
The solid content concentration of the fine fibrous modified cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the ionic group-introduced fiber in a dispersion medium may contain a solid content other than the ionic group-introduced fiber such as urea having a hydrogen bond property.

<Physical characteristics of fibrous cellulose>
(viscosity)
In the present invention, the viscosity of the dispersion liquid (slurry) prepared by adjusting the solid content concentration of fibrous cellulose 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 as above, 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 is determined by stirring a slurry in which the solid content concentration of fibrous cellulose is adjusted to 0.4% at 1500 rpm for 5 minutes with a disperser, and then in an environment of 23 ° C. and 50% relative humidity before measurement. After allowing to stand for a while, the measurement is performed using a B-type viscometer under the conditions of 23 ° C. and a 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 3 minutes after the start of measurement is taken as the viscosity of the dispersion liquid. The dispersion liquid may be completely dissolved in fibrous cellulose 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, and further, from the viewpoint of obtaining a precursor having more excellent pumping property. It is preferably 60 or more, more preferably 75 or more, and even more preferably 90 or more.
The upper limit is not particularly limited, but is preferably 600 or less, more preferably 500 or less, still more preferably 400 or less, still more preferably 350 or less, from the viewpoint of availability of fibrous cellulose and dispersion stability of the precursor. Is.
TI value = (viscosity at shear rate 1 / s) / (viscosity at shear rate 1000 / s) (1)
The above viscosity is the viscosity of a dispersion liquid having a solid content concentration of 0.4% at 23 ° C.
The TI value is measured by the method described in the examples.

[Preceding agent for pumping concrete pump]
The fibrous cellulose of the present invention is used to mix with calcium carbonate powder to produce a precursor for pumping concrete pumps.
In the present invention, the precursor for pumping a concrete pump is usually in the form of powder or paste, and water is added and dispersed before use, and the dispersion liquid obtained thereby is charged into the hopper of the concrete pump. The "preceding agent for pumping concrete pump" does not mean only a powdery state, but also means a dispersion liquid dispersed in water.
Therefore, in the present invention, the fibrous cellulose may be in the form of a powder such as a wet powder, mixed with calcium carbonate, and may exist as an overall powdery precursor for pumping, and the fibrous cellulose may be present. Is the state of the dispersion liquid (slurry), and when the powder containing calcium carbonate is used as the aqueous dispersion, the dispersion liquid (slurry) containing fibrous cellulose is added, mixed with calcium carbonate, and preceded. It may be used as an agent (dispersion liquid).

In the present invention, the mixing amount of the fibrous cellulose with respect to 100 parts by mass of the calcium carbonate powder is preferably 0.0001 part by mass or more, more preferably 0.001 part by mass, from the viewpoint of obtaining a precursor having excellent dispersion stability and pumping property. More than parts, 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, still more preferably 0. .1 part by mass or less.
The mixed amount of the fibrous cellulose means the mixed amount as the dried fibrous cellulose.

In the present invention, the precursor 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, still more preferably, from the viewpoint of excellent dispersibility and pumpability, and from the viewpoint of suppressing blockage of the concrete pipe. 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 heavy calcium carbonate obtained by crushing limestone, and is not particularly limited, but obtains excellent performance as a precursor. From the viewpoint, it is preferable that the calcium carbonate powder has a small particle size. Further, calcium carbonate powder whose particle size and composition have been adjusted may be used.
Among these, it is preferable to contain 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 composition of raw concrete.
Further, the calcium carbonate powder may contain fine powdered 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 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 regulators.
Examples of the inorganic powder other than calcium carbonate include calcium hydroxide, hydrotalcite, and calcium oxide. Further, the pigment may be either an inorganic pigment or an organic pigment. By containing the pigment, the visibility of the preceding agent to be discharged is improved, and it becomes easy to monitor the end of discharging of the preceding 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 adjusting agent may be added for the purpose of preventing oxidation and adjusting the pH. By adding an antioxidant, a pH adjuster, or the like, the dispersibility of the precursor is further improved, and the corrosion in the piping and the influence when mixed in concrete are reduced.

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

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

(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 (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion 1 containing fine fibrous modified cellulose. By X-ray diffraction, it was confirmed that this fine fibrous modified cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous modified cellulose was measured using a transmission electron microscope, it was 3 to 5 nm.
The amount of phosphoric acid group (strong acid group amount) of the fibrous cellulose measured by the measuring method described later was 1.45 mmol / g, and the degree of polymerization was 680.

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

(Manufacturing Example 3)
In Production Example 1, the fibrous cellulose dispersion 3 was obtained in the same manner as in Production Example 1 except that the fibrous cellulose was treated four times at a pressure of 200 MPa with a wet atomizing device so that the degree of polymerization of the fibrous cellulose was 499. ..

(Manufacturing Example 4)
In Production Example 1, the fibrous cellulose dispersion 4 was obtained in the same manner as in Production Example 1 except that the fibrous cellulose was treated 6 times at a pressure of 200 MPa with a wet atomizing device so that the degree of polymerization of the fibrous cellulose was 459. ..

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

(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 (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion 5 containing fine fibrous modified cellulose. By X-ray diffraction, it was confirmed that this fine fibrous modified cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous modified cellulose was measured using a transmission electron microscope, it was 3 to 5 nm.
The amount of phosphoric acid group (strong acid group amount) of the fibrous cellulose measured by the measuring method described later was 2.00 mmol / g, and the degree of polymerization was 625.

(Manufacturing Example 6)
In Production Example 5, the same 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 amount of phosphoric acid group was 2.00 mmol / g and the degree of polymerization was 536. To obtain a fibrous cellulose dispersion liquid 6.

(Manufacturing Example 7)
In Production Example 5, the same as in Production Example 5 except that the fibrous cellulose was treated four times with a wet atomizer at a pressure of 200 MPa so that the amount of phosphoric acid group was 2.00 mmol / g and the degree of polymerization was 482. To obtain a fibrous cellulose dispersion 7.

(Manufacturing Example 8)
Same as Production Example 5 except that the fibrous cellulose was treated with a wet atomizer at a pressure of 200 MPa 6 times so that the amount of phosphoric acid group was 2.00 mmol / g and the degree of polymerization was 444. The fibrous cellulose dispersion 8 was obtained.

(Manufacturing Example 9)
(Preparation of phosphite-introduced pulp)
The same operation as in Production Example 1 was carried out except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate. I got.).
Then, the obtained subphosphorylated pulp was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of subphosphorized pulp is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. I went by that. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.
Next, the dephosphorylated pulp after washing was neutralized as follows. First, the washed subphosphorylated pulp is diluted with 10 L of ion-exchanged water, and then a 1N sodium hydroxide aqueous solution is slightly added while stirring to obtain a subphosphorylated pulp slurry having a pH of 12 or more and 13 or less. Obtained. Then, the subphosphorylated pulp slurry was dehydrated to obtain a neutralized subphosphorylated pulp. Next, the subphosphorylated pulp after the neutralization treatment was subjected to the above washing treatment.
The infrared absorption spectrum of the subphosphorylated pulp thus obtained 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 phosphorous acid group, was observed near 1210 cm ^-1 , and the phosphorous acid group (phosphonic acid group) was added to the pulp. Was confirmed.
In addition, when the obtained subphosphorylated pulp was tested and analyzed by an X-ray diffractometer, two positions were found: 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

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

(Manufacturing Example 10)
(Preparation of carboxy group-introduced pulp)
As raw material pulp, Oji Paper's softwood kraft pulp (solid content 93% by mass, basis weight 208 g / m ² sheets, separated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) is 700 mL) It was used. The raw material pulp was subjected to TEMPO oxidation treatment as follows.
First, the above raw pulp equivalent to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl), and 10 parts by mass of sodium bromide are added to 10 parts of water. It was dispersed in 000 parts by mass. Then, a 13 mass% sodium hypochlorite aqueous solution was added to 1.0 g of pulp so as to be 10 mmol, and the reaction was started. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10 or more and 10.5 or less, and the reaction was considered to be completed when no change was observed in the pH.
Next, the obtained carboxy group-introduced pulp (hereinafter, also referred to as “TEMPO oxide pulp”) was washed. In the washing treatment, the pulp slurry after TEMPO oxidation is dehydrated to obtain a dehydrated sheet, and then 5,000 parts by mass of ion-exchanged water is poured, stirred and uniformly dispersed, and then filtered and dehydrated is repeated. Was done by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.
Further, when the obtained TEMPO oxide pulp was tested and analyzed by an X-ray diffractometer, it was found at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed, and it was confirmed that it had cellulose type I crystals.

(Preparation of fibrous cellulose dispersion)
Ion-exchanged water was added to the obtained TEMPO oxide pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated with a wet atomizing device (manufactured by Sugino Machine Co., Ltd., Starburst) 6 times at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous modified cellulose.
The amount of carboxy group 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 amount of fibrous cellulose dispersion)
The amount of ionic group of fibrous cellulose is a fibrous cellulose prepared by diluting a fibrous cellulose dispersion containing a target fine fibrous modified cellulose with ion-exchanged water so that the content is 0.2% by mass. The contained slurry was treated with an ion exchange resin and then titrated with an alkali to measure the content.
For the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) having a volume of 1/10 was added to the fine fibrous modified cellulose-containing slurry and shaken. After that, it was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry.
For titration using alkali, a 0.1N sodium hydroxide aqueous solution is added to the fine fibrous cellulose-containing slurry treated with an ion exchange resin once every 30 seconds by 50 μL, and the electrical conductivity shown by the slurry is shown. This was done by measuring the change in the value of. The ionic group amount (mmol / g) is the alkali amount (mmol) required in the region corresponding to the first region shown in FIGS. 1 or 2 in the measurement results, and the solid content (g) in the slurry to be titrated. Calculated by dividing.

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

(Measurement of viscosity 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. Next, the viscosity of the dispersion liquid thus obtained was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of the measurement was taken as the viscosity of the dispersion. The dispersion to be measured was allowed to stand in an environment of 23 ° C. and a relative humidity of 50% for 24 hours before the measurement. The liquid temperature of the dispersion liquid at the time of measurement was 23 ° C.

(Measurement of viscosity of fibrous cellulose dispersion with a leometer)
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 leometer (RheoStress6000, manufactured by HAAKE). The shear rate was changed under the following conditions.
Measurement temperature: 23 ° C
Measuring jig: Cone plate (diameter 40 mm, angle 1 °)
Shear velocity: 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 is measured with a leometer and the viscosity value (η ₁ ) measured under the condition of shear rate 1 sec ^-1 is divided by the viscosity value (η ₂ ) measured under the condition of shear rate 1,000 sec ^-1 . The obtained value was taken as a thixotropic index value (TI value).
That is, the TI value was defined by the following formula.
TI value = η ₁ / η ₂
η1: Viscosity measured under the condition of shear rate 1 sec ^-1 η2: Viscosity measured under the condition of shear rate 1,000 sec ^-1

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

(Examples 2 to 10)
A precursor for model pumping was prepared in the same manner as in Example 1 except that the fibrous cellulose dispersions 2 to 10 obtained in Production Examples 2 to 10 were used instead of the fibrous cellulose dispersion 1. did.

(Comparative Example 1)
A precursor for model pumping was prepared in the same manner as in Example 1 except that the fibrous cellulose dispersion 11 (manufactured by Sugino Machine Limited, IMa-1002) was used instead of the fibrous cellulose dispersion 1. ..

(Comparative Example 2)
A precursor for model pumping 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 precursor for model pumping 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)
Examples 1 to 10, Comparative Examples 1 and 2, and the model pumping precursor of the reference example were diluted with ion-exchanged water so as to have a solid content concentration of 1%, and placed in a 10 mL screw vial bottle (manufactured by AS ONE Co., Ltd.). It was separated and allowed to stand for 5 minutes. The distance from the bottom of the vial to the liquid level 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: Dispersion stability with some separation but no problem in use C: Significant separation is observed and cannot be used. Also, Example 1 and Comparative Example. For No. 1, the distance between the liquid level in the screw bottle and the interface with water generated by the separation was measured. The results are shown in Table 2.

[result]
As shown in Table 1, in the diluted solution of the model pumping precursor of Examples 1, 3, 4, 7, and 8, no separation of calcium carbonate was observed with time, and good dispersion stability was shown. Further, in Examples 2, 5, 6, 9, and 10, although there was some separation, the dispersion stability was shown to be no problem in use. On the other hand, significant separation was observed in the comparative examples and the reference examples.
Further, as shown in Table 2, the distance between the liquid level in the screw bottle and the boundary surface between the water generated by the separation is significantly smaller in Example 1 than in Comparative Example 1, and the bottle is allowed to stand for a long time. It was also shown to suppress separation and show high dispersion stability.
From the above results, it was shown that the dispersion stability of calcium carbonate was improved in the pumping precursor to which the fibrous cellulose containing the fine fibrous modified cellulose substituted with an ionic group was added.

(Evaluation of pumpability)
A 50 mL disposable syringe (manufactured by Terumo Corporation) was packed with 10 g of Example 1, Comparative Examples 1 and 2, and a model pumping precursor of 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 the extrusion was smooth, suggesting that it effectively acts on the dispersion stabilization of the fine particles. On the other hand, in Comparative Examples 1 and 2 and Reference Example 1, an extrusion time more than twice that of Example 1 was required.
It was shown that the precursor for pumping containing the fibrous cellulose of the present invention is excellent in dispersion stability and can be pumped at a lower pressure during pumping.

The fibrous cellulose of the present invention can provide a precursor for pumping concrete pumps containing calcium carbonate powder, which has excellent dispersion stability and pumping property, and can smoothly pump concrete through piping with a small amount of use. Expected to start.

Claims (7)

A fibrous cellulose used to produce a precursor for pumping concrete pumps by mixing with calcium carbonate powder.
The fibrous cellulose comprising a fine fibrous modified cellulose having an ionic group and a fiber width of 1000 nm or less. The fibrous cellulose according to claim 1, wherein the fibrous cellulose has a viscosity (solid content concentration 0.4% dispersion, 23 ° C.) of 500 mPa · s or more. The fibrous cellulose according to claim 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 of a dispersion liquid having a solid content concentration of 0.4% at 23 ° C. The fibrous cellulose according to any one of claims 1 to 3, wherein the content of 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 any one of claims 1 to 4, wherein the mixed amount of the fibrous cellulose with respect to 100 parts by mass of the calcium carbonate powder is 0.0001 part by mass or more and 100 parts by mass or less. The fibrous cellulose according to any one of claims 1 to 5, 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 pigments, antioxidants, and pH regulators.

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