JP2020029423A - Dental material composition, dental material, and fine fibrous cellulose used for the dental material - Google Patents

Abstract

To provide a dental material composition that makes it possible to obtain a dental material with excellent mechanical strength such as flexural strength, without worsening a fluoride ion elution ability or while improving it, and a dental material obtained from the dental material composition, and provide a fine fibrous cellulose used for the dental material.SOLUTION: A dental material composition contains a fine fibrous cellulose with a fiber width of 1,000 nm or less and glass ionomer cement.SELECTED DRAWING: None

Description

  The present invention relates to a composition for a dental material, a dental material, and a fine fibrous cellulose used for the dental material.

Glass ionomer cement is crown-colored and has excellent biocompatibility, has stable untreated dentin adhesion and fluoride ion elution ability, and is used to fill restorations for teeth with carious defects Widely used for dental treatment.
Patent Document 1 discloses a dental glass ionomer liquid capable of obtaining a dental glass ionomer cement having high physical strength, particularly high compressive strength, of a cement mixture after curing while having the same operability as a conventional glass ionomer cement. For the purpose of providing 30 to 60% by mass of an α-β unsaturated carboxylic acid polymer and 0.1 to 10% by mass of colloidal silica and colloidal silica having an average particle size of 1 to 100 nm silica aqueous sol dispersed in a monodisperse state ₂ concentration from 1 to 50% by weight with respect to water, dental glass ionomer cement liquid consisting of 40 to 70% by weight as the balance of water is disclosed.

JP 2007/091689 A

What is widely used as a glass ionomer cement is mainly composed of polycarboxylic acid, fluoroaluminosilicate glass powder, and water, and is called a conventional glass ionomer cement. The conventional glass ionomer cement has a problem that the mechanical strength including bending strength is not sufficient.
Further, in the invention described in Patent Document 1, there is a problem that it is difficult to obtain a uniform liquid when blended, because the thickening effect of colloidal silica is too strong.

  The present invention provides a dental material composition capable of obtaining a dental material having excellent mechanical strength such as bending strength without reducing or improving the fluoride ion eluting ability, and a dental material obtained from the dental material composition. The purpose is to provide the material. A further object of the present invention is to provide fine fibrous cellulose used for the dental material.

The present inventors have found that the above-mentioned problems can be solved by a dental material containing fine fibrous cellulose and glass ionomer cement.
That is, the present invention relates to the following <1> to <9>.
<1> A composition for a dental material, comprising fine fibrous cellulose having a fiber width of 1,000 nm or less and glass ionomer cement.
<2> A dental material obtained by curing the dental material composition according to <1>.
<3> The dental material according to <2>, wherein the amount of fluoride ion eluted is from 50 μg / cm ² / week to 500 μg / cm ² / week.
<4> The dental material according to <2> or <3>, wherein the three-point bending strength is 7 MPa or more and 150 MPa or less.
<5> The dental material according to any one of <2> to <4>, having a compressive strength of 60 MPa or more and 500 MPa or less.
<6> The dental according to any one of <2> to <5>, wherein the content of the fine fibrous cellulose is 0.1% by mass or more and 50% by mass or less based on the total solid content of the dental material. material.
<7> The dental material according to any one of <2> to <6>, wherein the axial ratio of the fine fibrous cellulose is 20 or more and 10,000 or less.
<8> The dental material according to any one of <2> to <7>, wherein the fine fibrous cellulose has an ionic group.
<9> A fine fibrous cellulose having a fiber width of 1,000 nm or less, which is used for producing a dental material by being mixed with a glass ionomer cement.

  ADVANTAGE OF THE INVENTION According to this invention, the composition for dental materials which can obtain the dental material excellent in mechanical strength, such as bending strength, without reducing or improving fluoride ion elution ability was able to be provided. Further, according to the present invention, fine fibrous cellulose used for the dental material can be provided.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and the electric conductivity for a fiber raw material having a phosphate group. FIG. 2 is a graph showing the relationship between the amount of NaOH added to the fiber raw material having a carboxy group and the electrical conductivity. FIG. 3 is a graph showing the results of a three-point bending test in Examples and Comparative Examples. FIG. 4 is a graph showing the results of a compression test in Examples and Comparative Examples. FIG. 5 is a graph showing the measurement results of the fluoride ion elution amount in Examples and Comparative Examples.

[Dental material composition]
The composition for a dental material of the present invention contains fine fibrous cellulose having a fiber width of 1,000 nm or less, and a glass ionomer cement.
A dental material obtained from a composition for a dental material containing a conventional glass ionomer cement has insufficient mechanical strength, and further improvement in mechanical strength has been desired. In particular, the bending strength is not sufficient, and improvement in bending strength has been desired.
On the other hand, generally, when the mechanical strength is improved, the fluoride ion elution amount tends to decrease. Therefore, there has been a need for a dental material composition that can provide a dental material with improved mechanical strength without reducing or increasing the fluoride ion elution amount.
The present inventors have conducted intensive studies and found that the use of a composition for dental materials containing glass ionomer cement and a fine fibrous cellulose having a fiber width of 1,000 nm or less reduces the amount of fluoride elution. It has been found that a dental material having improved or less mechanical strength, particularly improved bending strength, can be obtained. The detailed mechanism by which the above effects can be obtained is unknown, but some are presumed as follows.
That is, it is considered that the fine fibrous cellulose functions as a filler in the dental material, thereby improving the mechanical strength such as bending strength. In addition, the fine fibrous cellulose has excellent dispersibility in the dental material composition, despite the fact that the fiber width is on the order of nanometers.
In the dental material containing fine fibrous cellulose, the reason why the amount of fluoride ion elution did not decrease is unknown, but surprisingly, the dental material of the present invention does not contain fine fibrous cellulose. Compared with the dental material, the elution amount of fluoride ion did not decrease or increased.

In the present invention, the term "composition for dental material" means a composition for dental material before hardening, which contains fine fibrous cellulose having a fiber width of 1,000 nm or less and glass ionomer cement. On the other hand, the “dental material” is formed by curing the dental composition.
Hereinafter, the present invention will be described in more detail.

<Fine fibrous cellulose>
The composition for a dental material and the dental material of the present invention contain fine fibrous cellulose, and the fine fibrous cellulose is a fibrous cellulose having a fiber width of 1,000 nm or less. The fiber width of the fibrous cellulose can be measured by, for example, observation with an electron microscope.

The fiber width of the fine fibrous cellulose is preferably 100 nm or less, more preferably 30 nm or less, and even more preferably 8 nm or less. Further, the fiber width is preferably 2 nm or more.
The average fiber width of the fine fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and more preferably 2 nm or more and 10 nm or less. Is particularly preferred. By controlling the average fiber width of the fine fibrous cellulose to 2 nm or more, dissolution in water as cellulose molecules is suppressed, and the effect of improving the strength, rigidity, and dimensional stability of the fine fibrous cellulose is more easily exhibited. be able to. The fine fibrous cellulose is, for example, a monofibrous cellulose.

The average fiber width of the fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared, and this suspension was cast on a carbon film-coated grid that had been subjected to a hydrophilization treatment, and a TEM observation sample was prepared. And In the case of including a wide fiber, an SEM image of a surface cast on glass may be observed. Next, observation with an electron microscope image is performed at a magnification of 1,000 times, 5000 times, 10,000 times, or 50,000 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) One 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 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 that intersects the straight line X and the straight line Y is visually read for an observation image satisfying the above conditions. In this way, at least three or more sets of observation images of the surface portions that do not overlap each other are obtained. Next, the width of the fiber that intersects the straight line X and the straight line Y is read for each image. Thereby, the fiber width of at least 20 fibers × 2 × 3 = 120 fibers is read. Then, the average value of the read fiber width is defined as the average fiber width of the fibrous cellulose.

  The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably, for example, 0.1 μm to 1000 μm, more preferably 0.1 μm to 800 μm, and more preferably 0.1 μm to 600 μm. More preferred. By setting the fiber length within the above range, destruction of the crystal region of the fine fibrous cellulose can be suppressed. Further, the slurry viscosity of the fine fibrous cellulose can be adjusted to an appropriate range. The fiber length of the fine fibrous cellulose can be determined by image analysis using, for example, TEM, SEM, or AFM.

The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous cellulose has the type I crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 °) 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 2θ = 22 ° or more and 23 ° or less.
The proportion of the type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The crystallinity can be determined by measuring the X-ray diffraction profile and using a pattern thereof according to a conventional method (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

  The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is preferably, for example, 20 or more and 10,000 or less, more preferably 50 or more and 1,000 or less, and 100 or more and 1 or less. More preferably, it is not more than 2,000. It is preferable that the axial ratio be equal to or more than the lower limit value, since the effect of improving the mechanical strength of the dental material is more excellent. It is preferable that the axial ratio be equal to or less than the upper limit, since handling such as dilution becomes easy when fine fibrous cellulose is treated as an aqueous dispersion.

In the dental material composition of the present invention and the dental material of the present invention described below, the content of fine fibrous cellulose is preferably 0.1% by mass or more and 50% by mass or less based on the total solid content mass. . It is preferable that the content of the fine fibrous cellulose is within the above range, since the dental material can have improved mechanical strength without reducing the elution amount of fluoride ions.
The content of the fine fibrous cellulose is more preferably at least 0.3% by mass, still more preferably at least 1.0% by mass, and still more preferably at least 3.0% by mass, based on the total solid mass of the dental material composition. % By mass or more. Further, the content is more preferably 30% by mass or less, further preferably 20% by mass or less, and still more preferably 10% by mass or less.

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

The fine fibrous cellulose in the present embodiment has, for example, at least one of an ionic substituent and a nonionic substituent. From the viewpoint of improving the dispersibility of the fibers in the dispersion medium and improving the defibration efficiency in the defibration treatment, it is more preferable that the fine fibrous cellulose has an ionic substituent. The ionic substituent may include, for example, one or both of an anionic group and a cationic group. The nonionic substituent may include, for example, an alkyl group, an acyl group, and the like. In the present embodiment, it is particularly preferable to have an anionic group as the ionic substituent.
The treatment for introducing an ionic substituent may not be performed on the fine fibrous cellulose.

  Examples of the anionic group as the ionic substituent include a phosphate group or a substituent derived from a phosphate group (sometimes referred to simply as a phosphate group), a carboxy group or a substituent derived from a carboxy group (simply a carboxy group). And at least one selected from a sulfone group or a substituent derived from a sulfone group (which may be simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxy group. One type is more preferred, and a phosphate group is particularly preferred.

  The phosphate group or a substituent derived from a phosphate group is, for example, a substituent represented by the following formula (1), and is generalized as a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid.

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 are either R or OR. Note that all of α ⁿ and α ′ may be O ⁻ . R represents a hydrogen atom, a saturated-straight-chain hydrocarbon group, a saturated-branched-chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-straight-chain hydrocarbon group, or an unsaturated-branched-chain hydrocarbon group, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative thereof.

  Examples of the saturated-linear hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group, but are not particularly limited. Examples of the saturated-branched hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not particularly limited to, a cyclopentyl group and a cyclohexyl group. Examples of the unsaturated-linear hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated-branched hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include 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.

Further, as the deriving group for 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 to a main chain or a side chain of the above various hydrocarbon groups. 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 to the above range, the molecular weight of the phosphate group can be adjusted to an appropriate range, facilitating penetration into the fiber material, and increasing the yield of fine cellulose fibers. You can also.

β ^{b +} is a monovalent or higher cation composed of an organic or inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include aliphatic ammonium or aromatic ammonium. Examples of the monovalent or higher cation composed of an inorganic substance include ions of an alkali metal such as sodium, potassium, or lithium; Examples include, but are not particularly limited to, cations of divalent metals such as calcium and magnesium, and hydrogen ions. These can 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 a sodium or potassium ion which is hardly yellowed when a fiber material containing β is heated and is industrially easily used, but is not particularly limited.

The phosphate group is a divalent functional group corresponding to, for example, a phosphoric acid obtained by removing a hydroxy group from phosphoric acid. Is specifically a group represented by -PO ₃ H _2. The substituent derived from the phosphate group includes substituents such as a salt of the phosphate group and a phosphate group. The substituent derived from the phosphate group may be contained in the fine fibrous cellulose as a group in which the phosphate group is condensed (for example, a pyrophosphate group).
Further, the phosphate group may be, for example, a phosphite group (phosphonate group), and the substituent derived from the phosphate group may be a salt of a phosphite group, a phosphite ester group, or the like. Is also good.

The amount of the ionic substituent introduced into the fine fibrous cellulose is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, per 1 g (mass) of the fine fibrous cellulose. It is more preferably at least 0.50 mmol / g, particularly preferably at least 1.00 mmol / g. The amount of the ionic substituent introduced into the fine fibrous cellulose is, for example, preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less per 1 g (mass) of the fine fibrous cellulose. And more preferably 3.00 mmol / g or less. By setting the introduction amount of the ionic substituent within the above range, the fineness of the fiber raw material can be facilitated, and the stability of the fine fibrous cellulose can be increased. Further, it is presumed that the introduction amount of the ionic substituent within the above range contributes to the improvement of the dispersibility in the dental material.
Here, the denominator in the unit of mmol / g indicates the mass of fibrous cellulose when the counter ion of the ionic substituent is a hydrogen ion (H ⁺ ).
The amount of the ionic substituent introduced into the fine fibrous cellulose can be measured, for example, by a conductivity titration method. In the measurement by the conductivity titration method, the amount of introduction is measured by determining the change in conductivity while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fine fibrous cellulose.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and the electric conductivity for fine fibrous cellulose having a phosphate group.
The amount of phosphate groups introduced into the fine fibrous cellulose is measured, for example, as follows.
First, a slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, before the treatment with the strongly acidic ion exchange resin, a fibrillation treatment similar to the fibrillation treatment step described later may be performed on the measurement target. Next, a change in electric conductivity is observed while adding an aqueous solution of sodium hydroxide, and a titration curve as shown in FIG. 1 is obtained. As shown in FIG. 1, the electrical conductivity sharply decreases at first (hereinafter, referred to as “first region”). Thereafter, the conductivity starts to slightly increase (hereinafter, referred to as “second region”). Thereafter, the increment of the conductivity increases (hereinafter, referred to as “third region”). Note that the boundary point between the second region and the third region is defined as the point at which the amount of change in the conductivity twice (ie, the increment (slope) of the conductivity) becomes maximum. Thus, three regions appear in 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. Become equal. When the phosphate group causes condensation, the weakly acidic group is apparently 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 the strongly acidic group matches the amount of the phosphorus atom regardless of the presence or absence of condensation. For this reason, simply referring to the phosphate group introduction amount (or phosphate group amount) or the substituent group introduction amount (or substituent amount) indicates a strongly acidic group amount. 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 / mmol). g).

Note that the above-mentioned phosphate group introduction amount (mmol / g) indicates the amount of phosphate groups (hereinafter referred to as phosphoric acid) contained in the acid-form fine fibrous cellulose since the denominator indicates the mass of the acid-form fine fibrous cellulose. (Referred to as a basic amount (acid type)). On the other hand, when the counter ion of the phosphate group is substituted by an arbitrary cation C so as to have a charge equivalent, the denominator is converted into the mass of the fine fibrous cellulose when the cation C is the counter ion. By doing so, the amount of phosphate groups (hereinafter, the amount of phosphate groups (C type)) of the fine fibrous cellulose having the cation C as a counter ion can be determined.
That is, it is calculated by the following formula.
Phosphate group amount (C type) = phosphate group amount (acid type) / {1+ (W-1) × A / 1000}
A [mmol / g]: total amount of anions derived from the phosphate groups of the fibrous cellulose (the value obtained by adding the amount of the strongly acidic groups and the amount of the weakly acidic groups of the phosphate groups)
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 dropping amount of NaOH and the electric conductivity for the fine fibrous cellulose having a carboxy group.
The amount of the carboxy group introduced into the fine fibrous cellulose is measured, for example, as follows.
First, a slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, before the treatment with the strongly acidic ion exchange resin, a fibrillation treatment similar to the fibrillation treatment step described later may be performed on the measurement target. Next, a change in electric conductivity is observed while adding an aqueous solution of sodium hydroxide, and a titration curve as shown in FIG. 2 is obtained. In addition, you may implement the defibration process similar to the defibration process process mentioned later with respect to a measurement object as needed. As shown in FIG. 2, the titration curve shows a first region where the increment (slope) of the conductivity becomes substantially constant after the decrease in the electric conductivity, and thereafter, the increment (slope) of the conductivity increases. It is divided into a second area. Note that the boundary point between the first region and the second region is defined as a point at which the amount of change in the conductivity twice (in other words, the increment (slope) of the conductivity becomes maximum). 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 slurry containing fine fibrous cellulose to be titrated is the amount of carboxy group introduced ( mmol / g).

In addition, since the denominator is the mass of the acid-form fine fibrous cellulose, the above-mentioned carboxy group introduction amount (mmol / g) is the amount of carboxy groups (hereinafter referred to as carboxy group amount ( Acid type). On the other hand, when the counter ion of the carboxy group is substituted by an arbitrary cation C so as to have a charge equivalent, the denominator is converted into the mass of the fine fibrous cellulose when the cation C is a counter ion. Thus, the amount of carboxy groups of the fibrous cellulose having the cation C as a counter ion (hereinafter, the amount of carboxy groups (C type)) can be determined.
That is, it is calculated by the following formula.
Carboxy group amount (C type) = Carboxy group amount (acid type) / {1+ (W-1) × (carboxy group amount (acid type)) / 1000}
W: Formula weight per valence of cation C (for example, 23 for Na and 9 for Al)

<Method for producing fine fibrous cellulose>
(Raw material containing cellulose)
The fine fibrous cellulose is produced from a fiber material containing cellulose (hereinafter, also simply referred to as “fiber material”).
The fiber material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulp includes, for example, wood pulp, non-wood pulp, and deinked pulp. Examples of the wood pulp include, but are not particularly limited to, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). And oxygen bleached kraft pulp (OKP); semi-chemical pulp such as semi-chemical pulp (SCP) and chemical ground wood pulp (CGP); groundwood pulp (GP); and thermomechanical pulp (TMP, BCTMP). And mechanical pulp. Non-wood pulp includes, but is not limited to, cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. Examples of the deinked pulp include, but are not particularly limited to, deinked pulp made from waste paper. As the pulp of this embodiment, one of the above-mentioned types may be used alone, or two or more types may be used in combination.
Among the above pulp, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. In addition, among wood pulp, a viewpoint that the cellulose ratio is large and the yield of fine fibrous cellulose at the time of defibration treatment is high, and the decomposition of cellulose in pulp is small, and fine fibrous cellulose of long fibers having a large axial ratio can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable. In addition, when fine fibrous cellulose of long fibers having a large axial ratio is used, the viscosity tends to increase.

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

  In order to obtain the fine fibrous cellulose into which the ionic substituent is introduced as described above, an ionic substituent introduction step of introducing the ionic substituent into the above-mentioned cellulose-containing fiber material, a washing step, and an alkali treatment step ( It is preferable to have a neutralization step) and a fibrillation treatment step in this order, and may have an acid treatment step instead of or in addition to the washing step. Examples of the ionic substituent introduction step include a phosphate group introduction step and a carboxy group introduction step. Hereinafter, each will be described.

(Ionic substituent introduction step)
(Phosphate group introduction step)
The step of introducing a phosphate group into cellulose fibers (phosphate group introduction step) will be described below.
In the phosphate group introduction step, at least one compound selected from compounds capable of introducing a phosphate group (hereinafter, also referred to as “compound A”) by reacting with a hydroxyl group of a fiber material containing cellulose is converted into cellulose. This is a step of acting on the contained fiber raw material. By this step, a phosphate group-introduced fiber is obtained.

  In the phosphoric acid group introduction step according to the present embodiment, the reaction between the fiber 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”). You may. On the other hand, the reaction between the fiber raw material containing cellulose and the compound A may be performed in a state where the compound B is not present.

As an example of a method of causing the compound A to act on the fiber raw material in the presence of 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. Among them, it is preferable to use a fiber material in a dry state or a wet state because of high reaction uniformity, and it is particularly preferable to use a fiber material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably, for example, cotton or a thin sheet.
The compound A and the compound B may be added to the fiber material in the form of a powder, a solution dissolved in a solvent, or a state in which the compound A and the compound B are heated to a melting point or higher and melted. Among these, it is preferable to add in the form of a solution dissolved in a solvent, particularly an aqueous solution, because the reaction is highly uniform. Further, the compound A and the compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added 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 a solution state, the fiber raw material may be immersed in the solution, absorbed and then taken out. May be added dropwise to the solution. In addition, the necessary amount of compound A and compound B may be added to the fiber raw material, or the excessive amount of compound A and compound B may be added to the fiber raw material, respectively, and then the excess compound A and compound B may be squeezed or filtered. It may be removed.

Examples of the compound A used in the present embodiment include, but are not particularly limited to, phosphoric acid or a salt thereof, dehydrated condensed phosphoric acid or a salt thereof, and phosphoric anhydride (phosphorous pentoxide). As phosphoric acid, those having various purities can be used. For example, 100% phosphoric acid (normal phosphoric acid) and 85% phosphoric acid can be used. The dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of the phosphate and the dehydrated condensed phosphate include lithium salt, sodium salt, potassium salt, and ammonium salt of phosphoric acid or dehydrated condensed phosphoric acid, and these can have various degrees of neutralization.
Among these, phosphoric acid, phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of introduction of the phosphate group, easier to improve the defibration efficiency in the defibration step described later, low cost, and industrially applicable 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. For example, when the amount of the compound A added is converted into the atomic weight of phosphorus, phosphorus is added to the fiber raw material (absolute dry mass, hereinafter also referred to as “absolute dry mass”). The addition amount of atoms is preferably 0.5% by mass or more and 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 the 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 amount of phosphorus atoms added to the fiber raw material to be equal to or less than the above upper limit, the effect of improving the yield and the cost can be balanced. Here, the “absolute dry mass (absolute dry mass)” is the absolute dry mass that has been measured by the method described in ISO 638: 2008 and has reached a constant weight.

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Compound B includes, for example, 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 uniformity of the reaction, it is preferable to use an aqueous solution in which both the compound A and the compound B are dissolved.
The amount of the compound B to be added to the fiber raw material (absolute dry mass) is not particularly limited, but is, for example, 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 material containing cellulose and the compound A, for example, an amide or an amine may be included in the reaction system in addition to the compound B. Examples of the amide include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of the amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Among these, triethylamine is known to work as a good reaction catalyst.

  In the phosphoric acid group introduction step, it is preferable that after the compound A or the like is added to or mixed with the fiber raw material, the fiber raw material is subjected to a heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which a phosphate group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is, for example, preferably from 50 ° C. to 300 ° C., more preferably from 100 ° C. to 250 ° C., and even more preferably from 130 ° C. to 200 ° C. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying apparatus, a rotary drying apparatus, a disk drying apparatus, a roll heating apparatus, a plate heating apparatus, a fluidized bed drying apparatus, an air current A drying device, a reduced-pressure 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, compound A is added to a thin sheet-like fiber material by a method such as impregnation or the like, and then the fiber material and the compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. Thereby, it becomes possible to suppress the concentration unevenness of the compound A in the fiber raw material and more uniformly introduce the phosphate group to the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the fiber material surface with drying, the dissolved compound A is attracted to the water molecules by the surface tension and moves to the fiber material surface similarly (that is, the concentration unevenness of the compound A decreases). It can be considered that this is caused by the fact that it can be suppressed.
Further, the heating device used for the heat treatment always emits water generated by the dehydration condensation (phosphate esterification) reaction between the compound A and the hydroxyl group contained in cellulose or the like in the fiber raw material, for example, in the system system. It is preferable that the device can be discharged outside. As such a heating device, for example, an air-blowing oven or the like can be mentioned. By constantly discharging the water in the system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphorylation, and also to suppress the acid hydrolysis of the sugar chains in the fiber. it can. For this reason, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

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

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

  The amount of phosphate groups introduced into the fiber raw material is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and more preferably 0.50 mmol / g per 1 g (mass) of fine fibrous cellulose. g or more, more preferably 1.00 mmol / g or more. Further, the amount of the phosphate group introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, per 1 g (mass) of fine fibrous cellulose. More preferably, it is not more than 00 mmol / g. By setting the amount of the phosphoric acid group to be in the above range, the fineness of the fiber raw material can be easily made, and the stability of the fine fibrous cellulose can be increased.

(Carboxy group introduction step)
The carboxy group introduction step has a compound having a carboxylic acid-derived group or a derivative thereof, or a carboxylic acid-derived group, or a carboxylic acid-derived compound or a carboxylic acid-derived group, for a fiber raw material containing cellulose, such as ozone oxidation or oxidation by the Fenton method, or TEMPO oxidation treatment. It is carried out by treating with an acid anhydride of a compound or a derivative thereof.

Examples of the compound having a group derived from a carboxylic acid include, but are not limited to, 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. Tricarboxylic acid compounds. Examples of the derivative of the compound having a group derived from a carboxylic acid include, but are not particularly limited to, 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 imidized product of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include imidized products of dicarboxylic acid compounds such as maleimide, succinimide and phthalic imide.
Examples of the acid anhydride of the compound having a group derived from a carboxylic acid include, but are not limited to, maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and dicarboxylic acid compounds such as itaconic anhydride. Acid anhydrides. Examples of the acid anhydride derivative of the compound having a group derived from a carboxylic acid include, but are not particularly limited to, a compound having a carboxy group such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. An acid anhydride in which at least a part of hydrogen atoms are substituted with a substituent such as an alkyl group or a phenyl group is exemplified.

In the case where TEMPO oxidation treatment is performed in the carboxy group introduction step, it is preferable that the treatment be performed, for example, at a pH of 6 to 8. Such a process is also called a neutral TEMPO oxidation process. The neutral TEMPO oxidation treatment is performed, for example, by adding pulp as a fiber raw material to a sodium phosphate buffer (pH = 6.8) and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst. It can be performed by adding nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting sodium chlorite, aldehydes generated in the course of oxidation can be efficiently oxidized to carboxy groups.
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 alkali TEMPO oxidation treatment can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidizing agent 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. For example, when the carboxy group is introduced by TEMPO oxidation, the amount is preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose. , 0.20 mmol / g or more, more preferably 0.50 mmol / g or more, particularly preferably 0.90 mmol / g or more. Further, it is preferably at most 2.5 mmol / g, more preferably at most 2.20 mmol / g, even more preferably at most 2.00 mmol / g. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol / g or less per 1 g (mass) of fine fibrous cellulose.

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

(Alkali treatment step)
In the case of producing fine fibrous cellulose, the fiber raw material may be subjected to an alkali treatment between a step of introducing a substituent such as an ionic substituent and a defibrating step described below. The method of the alkali treatment is not particularly limited, and includes, for example, a method of immersing the substituent-introduced fiber in an alkaline solution.
The alkali compound contained in the alkali solution is not particularly limited, and may be an inorganic alkali compound or an organic alkali compound. In the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkali compound because of 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 a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkali solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of high versatility.

  The temperature of the alkali solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5 ° C or more and 80 ° C or less, and more preferably 10 ° C or more and 60 ° C or less. The immersion time of the substituent-introduced fibers in the alkali solution in the alkali treatment step is not particularly limited, but is, for example, preferably 5 minutes to 30 minutes, more preferably 10 minutes to 20 minutes. The amount of the alkali solution used in the alkali treatment is not particularly limited. For example, it is preferably 100% by mass or more and 100,000% by mass or less, and preferably 1,000% by mass or more and 10% by mass or less with respect to the absolute dry mass of the substituent-introduced fiber. It is more preferable that the content be 2,000 mass% or less.

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

(Acid treatment step)
In the case of producing fine fibrous cellulose, an acid treatment may be performed on the fiber raw material between the step of introducing a substituent such as an ionic substituent and the defibration step described below. For example, a substituent introduction step, an acid treatment, an alkali treatment, and a fibrillation treatment may be performed in this order.
The method of the acid treatment is not particularly limited, and includes, for example, a method of immersing the fiber raw material in an acid-containing acid solution. The concentration of the acidic solution used is not particularly limited, but is preferably, for example, 10% by mass or less, more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably, for example, 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 and 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, and trifluoromethanesulfonic acid. 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, for example, preferably from 5 ° C to 100 ° C, and more preferably from 20 ° C to 90 ° C. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably, for example, 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. For example, the amount is preferably from 100% by mass to 100,000% by mass, and more preferably from 1,000% by mass to 10,000% by mass, based on the absolute dry mass of the fiber raw material. Is more preferred.

(Fibrillation processing)
Fine fibrous cellulose can be obtained by defibrating a fiber having a substituent introduced therein, such as an ionic substituent, in a defibrating step.
In the defibrating process, for example, a defibrating device can be used. Examples of the defibrating apparatus include, but are not limited to, a high-speed defibrating machine, 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 disk-type refiner, a conical refiner, 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 apparatuses, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer, which is less affected by the pulverized media and is less likely to cause contamination.

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

(Desolvation step)
In the present invention, a solvent removal step may be further performed on the fine fibrous cellulose after the defibration treatment. The desolvation step includes a step of removing part or all of the dispersion medium from the slurry containing fibrous cellulose. In the present embodiment, fibrous cellulose or a solid or gel containing fibrous cellulose and a dispersion medium is obtained by, for example, removing part or all of the dispersion medium.
The desolvation step includes, for example, a concentration step of adding a concentrating agent to a slurry containing fibrous cellulose to perform gelation. By the concentration step, for example, a gel-like substance containing fibrous cellulose and a dispersion medium is obtained.
Examples of the concentrating agent include acids, alkalis, salts of polyvalent metals, cationic surfactants, anionic surfactants, cationic polymer flocculants, and anionic polymer flocculants. Among these, it is preferable to use a salt of a polyvalent metal as the concentrating agent. Examples of the salt of a polyvalent metal include aluminum sulfate (sulfuric acid band), polyaluminum chloride, calcium chloride, aluminum chloride, magnesium chloride, calcium sulfate, and magnesium sulfate.

When the dispersion medium of the slurry containing fibrous cellulose is water, the desolvation step may include, for example, a concentration step of performing gelation by treating the slurry containing fibrous cellulose with an organic solvent. . By the concentration step, for example, a gel-like substance containing fibrous cellulose and a dispersion medium is obtained. In the desolvation step, the slurry containing fibrous cellulose may be subjected to only one of the addition of a concentrating agent and the treatment with an organic solvent, or both of them may be performed. .
Examples of the organic solvent include, but are not limited to, the following: methanol, ethanol, 1-propanol (n-propanol), 1-butanol (n-butanol), 2-butanol, isobutyl alcohol , Isopropyl alcohol (isopropanol, 2-propanol), isopentyl alcohol (isoamyl alcohol), t-butyl alcohol (2-methyl-2-propanol), 1,2-dioxane, 1,3-dioxane, 1,4-dioxane , Tetrahydrofuran (THF), acetone, methyl isobutyl ketone, methyl ethyl ketone (MEK), methyl cyclohexanol, methyl cyclohexanone, methyl-normal-butyl ketone, ethyl ether (diethyl ether), ethylene glycol Monoethyl ether (cellosolve), ethylene glycol monoethyl ether acetate (cellosolve acetate), ethylene glycol mono-normal-butyl ether (butyl cellosolve), ethylene glycol monomethyl ether (methyl cellosolve), dimethyl sulfoxide (DMSO), dimethylformamide (DMF, N, N-dimethylformamide), dimethylacetamide (DMAc, DMA, N, N-dimethylacetamide), ortho-dichlorobenzene, xylene, cresol, chlorobenzene, isobutyl acetate, isopropyl acetate, isopentyl acetate (isoamyl acetate), acetic acid Ethyl, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate (normal-amyl acetate), methyl acetate, cycloalkyl Xanol, cyclohexanone, dichloromethane (methylene dichloride), styrene, tetrachloroethylene (perchlorethylene), 1,1,1-trichloroethane, toluene, normal hexane, chloroform, carbon tetrachloride, 1,2-dichloroethane (dichloride Ethylene), 1,2-dichloroethylene (acetylene dichloride), 1,1,2,2-tetrachloroethane (acetylene tetrachloride), trichlorethylene, carbon disulfide, gasoline, coal tar naphtha (including solvent naphtha) ), Petroleum ether, petroleum naphtha, petroleum benzine, turpentine oil, mineral spirits (including mineral thinner, petroleum spirit, white spirit and mineral terpenes)

The concentration step may further include a treatment with an acid. The treatment with an acid in the concentration step is preferably provided before and after the filtration step, and more preferably provided after the filtration step. When a treatment with an acid is provided after the filtration treatment step, the treatment may be an acid washing step for removing the concentrating agent.
The treatment with an acid in the concentration step includes, for example, inorganic acids exemplified by sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; formic acid, acetic acid, citric acid, malic acid, lactic acid, adipic acid, sebacic acid, stearic acid, maleic acid, It is preferable to use an organic acid such as succinic acid, tartaric acid, fumaric acid, and gluconic acid. In the present embodiment, for example, the treatment can be performed by immersing the obtained concentrate in an acidic solution. The concentration of the acidic solution used is not particularly limited, but is, for example, preferably 10% or less, more preferably 5% or less, and still more preferably 1% or less. By setting the concentration of the acidic liquid within the above range, degradation due to decomposition of cellulose can be suppressed.
In the concentration step, it is preferable to perform filtration after the treatment with the acid. In this filtration step, a compression step may be further performed.

The concentration step may further include a treatment with an alkaline solution. Thereby, when the obtained solid or gel is redispersed, the charge of the fine fibrous cellulose is increased and the redispersion becomes easy. Particularly, it is more preferable to add an alkaline solution in the presence of an organic solvent from the viewpoint of efficient concentration.
The desolvation step may include, for example, a drying step. By the drying step, for example, a solid containing fibrous cellulose is obtained. When the concentration step is performed, the drying step is performed, for example, after the concentration step. When the concentration step includes an acid treatment step, the drying step is preferably performed after the acid treatment step. The drying step is preferably an oven drying process. In this case, it is preferable to perform drying in an oven set at, for example, 30 to 70 ° C. for 1 to 60 minutes.
The desolvation step may include only the drying step without including the concentration step.

When the fibrous cellulose-containing material is a solid or a gel, the content of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material is, for example, 5% by mass relative to the total mass of the fine fibrous cellulose-containing material. % Or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and particularly preferably 20% by mass or more. When the fine fibrous cellulose-containing material is a solid or a gel, the upper limit of the content of fine fibrous cellulose contained in the fine fibrous cellulose-containing material is not particularly limited, but is, for example, 99.5. % By mass. By setting the content of the fine fibrous cellulose in the above range, a fine fibrous cellulose-containing material having more excellent handling properties can be obtained.
When the fibrous cellulose-containing material is a solid or a gel, the content of the solvent contained in the fibrous cellulose-containing material is, for example, 90% by mass or less based on the total mass of the fine fibrous cellulose-containing material. Is preferably 85% by mass or less, more preferably 80% by mass or less, and particularly preferably 70% by mass or less. By setting the upper limit of the content of the solvent in the above range, a fine fibrous cellulose-containing material having excellent handling properties can be obtained. On the other hand, the lower limit of the content of the solvent contained in the fibrous cellulose-containing material is not particularly limited, and may be, for example, 0% by mass. In the present embodiment, the content of the solvent contained in the fibrous cellulose-containing material can be, for example, 0.5% by mass or more based on the total mass of the fine fibrous cellulose-containing material.

When the fibrous cellulose-containing substance is a solid substance or a gel-like substance, the fibrous cellulose-containing substance may contain, for example, a concentrating agent used in the above-described concentration step. For example, when the concentrating agent is a metal component, the content of the metal component in the fibrous cellulose-containing material is preferably 1.0% by mass or less, more preferably 0.3% by mass or less, and 0% by mass or less. It is more preferably 0.15% by mass or less, particularly preferably 0.1% by mass or less. When the concentrating agent is a metal component, the lower limit of the content of the metal component in the fibrous cellulose-containing material is not particularly limited, but may be, for example, 0.0001% by mass. By setting the content of the metal component within the above range, a fibrous cellulose-containing material having excellent redispersibility in a predetermined dispersion medium such as water can be obtained.
When the fine fibrous cellulose-containing material is a granular material, the fine fibrous cellulose-containing material includes one or both of a powdery material and a granular material. Here, the powdery material is smaller than the granular material. Generally, the powdery material refers to fine particles having a particle diameter of 1 nm or more and less than 0.1 mm. Further, the granular material refers to particles having a particle diameter of 0.1 mm or more and 10 mm or less. The particle size of the powder can be measured and calculated using, for example, a laser diffraction method. The measurement by the laser diffraction method can be performed by using, for example, a laser diffraction scattering type particle size distribution measuring apparatus (Microtrac 3300EXII, Nikkiso Co., Ltd.).

  The fine fibrous cellulose-containing substance that is a solid substance or a gel substance can be used as a redispersion slurry redispersed in a solvent such as water. The type of solvent used to obtain such a redispersed slurry is not particularly limited, and examples thereof include water, an organic solvent, and a mixture of water and an organic solvent. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, esters, hydrocarbons, halogens, and aprotic polar solvents. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of the ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and propylene glycol monomethyl ether. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the hydrocarbons include n-hexane, toluene, xylene and the like. Examples of the halogens include methylene chloride, trichloroethylene, chloroform and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

<Glass ionomer cement>
The dental material composition of the present invention contains a glass ionomer cement, and the dental material of the present invention is obtained by curing a dental material composition containing a glass ionomer cement.
Glass ionomer cement is a cement containing polycarboxylic acid, fluoroaluminosilicate glass powder, and water as main components, and is preferably a conventional glass ionomer cement, but a polymerizable monomer was added to the conventional glass ionomer cement. It may be a resin-reinforced glass ionomer cement.
That is, the material is not particularly limited as long as it is a curable material containing at least a fluoroaluminosilicate glass powder, a polycarboxylic acid, and water.

As the fluoroaluminosilicate glass powder used in the present invention, those conventionally used in dental cement can be used. The fluoroaluminosilicate glass powder contains Al ³⁺ , Si ⁴⁺ , F ⁻ , and O ²⁻ as main components, and is preferably a fluoroaluminosilicate glass powder further containing Sr ²⁺ and / or Ca ^2+. Al ³⁺ : 10 to 21% by mass, Si ⁴⁺ : 9 to 21% by mass, F ⁻ : 1 to 20% by mass, and the total of Sr ²⁺ and Ca ²⁺ : 10 to 34% by mass with respect to the total mass of preferable. If zinc oxide is contained in the fluoroaluminosilicate glass powder, the transparency of the hardened cement is greatly reduced. Therefore, it is preferable that zinc oxide is not contained.

In a glass ionomer cement, a fluoroaluminosilicate glass powder and a polycarboxylic acid are hardened by a neutralization reaction. Therefore, in addition to the fluoroaluminosilicate glass powder, a polycarboxylic acid and water are required.
In general, the glass ionomer cement is supplied as a kit of a powder material containing at least a fluoroaluminosilicate glass powder and a liquid material containing at least water, and is used by mixing the powder material and the liquid material at the time of use.

The polycarboxylic acid may be contained in water and supplied to the fluoroaluminosilicate glass powder.
Examples of the polycarboxylic acid include polymer powders of a carboxy group-containing ethylenically unsaturated compound such as α, β-unsaturated monocarboxylic acid and α, β-unsaturated dicarboxylic acid. Specifically, homopolymers or copolymers of acrylic acid, methacrylic acid, 2-chloroacrylic acid, 3-chloroacrylic acid, aconitic acid, mesaconic acid, maleic acid, itaconic acid, fumaric acid, glutaconic acid, citraconic acid, etc. Polymers are exemplified. These copolymers may be copolymers of α, β-unsaturated carboxylic acids or copolymers of α, β-unsaturated carboxylic acids and components copolymerizable therewith. In this case, the ratio of the α, β-unsaturated carboxylic acid is preferably 50% or more. Examples of the copolymerizable component include acrylamide, acrylonitrile, acrylate, methacrylate, acrylates, vinyl chloride, allyl chloride, and vinyl acetate. Among the polymers of α, β-unsaturated carboxylic acids, particularly preferred are homopolymers or copolymers of acrylic acid or itaconic acid.
From the viewpoint of improving the mechanical strength of the obtained dental material, the polycarboxylic acid has a weight average molecular weight of preferably 3,000 or more, more preferably 4,000 or more, and still more preferably 5,000 or more, and , Preferably 100,000 or less, more preferably 50,000 or less, and still more preferably 30,000 or less.
When a powdery polycarboxylic acid is used, its amount is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less in the powder containing the fluoroaluminosilicate glass powder. .
When the polycarboxylic acid is blended in the liquid component, the blending amount of the polycarboxylic acid is preferably 20% by mass or more and 50% by mass or less in the liquid component. If the amount is less than 20% by mass, the strength of the dental material obtained by curing the dental material composition tends to be poor. If the amount exceeds 50% by mass, kneading tends to be difficult.

The neutralization reaction between the fluoroaluminosilicate glass powder and the polycarboxylic acid proceeds in the presence of water, so the presence of water is essential.
The water is not particularly limited, but preferably does not contain impurities such as hardening of the composition for dental materials, contact strength with teeth, etc., which adversely affect the mechanical strength of the dental material. Preferably, distilled water and ion-exchanged water are used.
The content of water is preferably at least 1 part by mass, more preferably at least 2 parts by mass, and preferably at least 2 parts by mass, based on 100 parts by mass of the powder material, from the viewpoint of the curability and the mechanical strength of the cured dental material. Is at most 40 parts by mass, more preferably at most 30 parts by mass, further preferably at most 25 parts by mass, particularly preferably at most 10 parts by mass.

  In the present invention, an acid can be added to the liquid material for pH adjustment as needed. As the acid used, phosphoric acid, citric acid, succinic acid, oxalic acid, fumaric acid, tartaric acid, malic acid, maleic acid, ethylenediaminetetraacetic acid, tricarballylic acid, levulinic acid, acidic amino acids, pyroglutamic acid, L-aspartic acid, L-arginine, citric acid, glycine, glycolic acid, DL-glyceric acid, gluconic acid, glucuronic acid, glutaric acid, acetone dicarboxylic acid, cyclopentanetetracarboxylic acid, diglycolic acid, diethylmalonic acid, L-cysteic acid, oxalic acid Acid, sulfosalicylic acid, tartronic acid, tricarballylic acid, tetrahydrofurantetracarboxylic acid, meso-butane-1,2,3,4-tetracarboxylic acid, trimellitic acid, lactic acid, benzenepentacarboxylic acid, malonic acid, DL-mandel Acid, benzenehexacarboxylic acid Malic acid. These acids may be used alone or in combination. The amount of the acid for pH adjustment in the liquid is preferably 20% by mass or less. When the content is within the above range, a dental material having high bending strength can be obtained.

The glass ionomer cement is not limited to the conventional glass ionomer cement, but may be a resin-reinforced glass ionomer cement to which a polymerizable monomer is added. In the present invention, a conventional glass ionomer cement is preferable as the glass ionomer cement in view of the fact that the pretreatment of the tooth surface is unnecessary, that the fluoride ion elution ability is excellent, and that it has excellent biocompatibility.
The resin-reinforced glass ionomer cement contains a polymerizable monomer and a polymerization initiator in addition to the above-mentioned fluoroaluminosilicate glass powder, polycarboxylic acid, and water.
The polymerizable monomer preferably contains an acrylate or methacrylate having at least one unsaturated double bond. Examples of the acrylate or methacrylate having at least one unsaturated double bond include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, hydroxyethyl (meth) acrylate, and n-butyl ( (Meth) acrylate, isobutyl (meth) acrylate, hydroxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2, 2-bis ((meth) acryloxyphenyl) propane, 2,2-bis [4- (2-hydroxy-3- (meth) acryloxypropoxy) phenyl] propane, 2,2-bis (4- (meth) Acryloxydi (Toxyphenyl) propane, 2,2-bis (4- (meth) acryloxypropoxyphenyl) propane, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, butylene glycol di (Meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, Trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylol methane tri (meth) acrylate, pentaerythritol tet (Meth) acrylate. Note that “(meth) acrylate” is a general term for methacrylate and acrylate, and the same applies to descriptions such as “(meth) acryloxy”.
Further, a (meth) acrylate having a urethane bond in the molecule is exemplified, and among those having a urethane bond, di-2- (meth) acryloxyethyl-2,2,4-trimethylhexamethylene dicarbamate, Compounds represented by the structural formula are preferred.

In the above formulas, R each independently represent a hydrogen atom or a methyl group, - (A) - is - (CH _{2) 6} -, represents a 1,4-phenylene group or a divalent group of the following.

It is also preferable to use a polymerizable monomer having an acidic group as the polymerizable monomer.
The polymerizable monomer having an acidic group contributes to further improving the adhesiveness to teeth and dental prostheses. Examples of the polymerizable monomer having an acidic group include, for example, at least one acidic group such as a phosphoric acid group, a phosphonic acid group, a pyrophosphoric acid group, a carboxylic acid group, a sulfonic acid group, a thiophosphoric acid group, and acryloyl. And a polymerizable monomer having a polymerizable unsaturated group such as a methacryloyl group, a vinyl group, and a styrene group.

  Examples of the phosphoric acid group-containing polymerizable monomer include 2- (meth) acryloyloxyethyl dihydrogen phosphate, 3- (meth) acryloyloxypropyl dihydrogen phosphate, and 4- (meth) acryloyloxybutyl dihydrogen phosphate 5- (meth) acryloyloxypentyl dihydrogen phosphate, 6- (meth) acryloyloxyhexyl dihydrogen phosphate, 7- (meth) acryloyloxyheptyl dihydrogen phosphate, 8- (meth) acryloyloxyoctyl dihydrogen Gen-phosphate, 9- (meth) acryloyloxynonyl dihydrogen phosphate, 10- (meth) acryloyloxydecyl dihydrogen phosphate, 11- (meth) Acryloyloxyundecyl dihydrogen phosphate, 12- (meth) acryloyl oxide decyl dihydrogen phosphate, 16- (meth) acryloyloxyhexadecyl dihydrogen phosphate, 20- (meth) acryloyloxy eicosyl dihydrogen phosphate Bis [2- (meth) acryloyloxyethyl] hydrogen phosphate, bis [4- (meth) acryloyloxybutyl] hydrogen phosphate, bis [6- (meth) acryloyloxyhexyl] hydrogen phosphate, bis [8- (Meth) acryloyloxyoctyl] hydrogen phosphate, bis [9- (meth) acryloyloxynonyl] hydrogen phosphate, bis [10- (meth) acrylic Yloxydecyl] hydrogen phosphate, 1,3-di (meth) acryloyloxypropyl-2-dihydrogen phosphate, 2- (meth) acryloyloxyethyl phenyl hydrogen phosphate, 2- (meth) acryloyloxyethyl-2 '-Bromoethyl hydrogen phosphate, 2-methacryloyloxyethyl (4-methoxyphenyl) hydrogen phosphate, 2-methacryloyloxypropyl (4-methoxyphenyl) hydrogen phosphate, glycerol phosphate di (meth) acrylate, dipentaerythritol phosphate Examples include polymerizable monomers such as penta (meth) acrylate, and acid chlorides thereof.

  Examples of the phosphonic acid group-containing polymerizable monomer include 2- (meth) acryloyloxyethylphenylphosphonate, 5- (meth) acryloyloxypentyl-3-phosphonopropionate, and 6- (meth) acryloyloxyhexyl-3-phospho. Nopropionate, 10- (meth) acryloyloxydecyl-3-phosphonopropionate, 6- (meth) acryloyloxyhexyl-3-phosphonoacetate, 10- (meth) acryloyloxydecyl-3-phosphono Examples thereof include polymerizable monomers such as acetate, and acid chlorides thereof.

Examples of the polymerizable monomer having a pyrophosphate group include bis [2- (meth) acryloyloxyethyl] pyrophosphate, bis [4- (meth) acryloyloxybutyl] pyrophosphate, and bis [6- (meth) acryloyl pyrophosphate Polymerizable monomers such as oxyhexyl], bis [8- (meth) acryloyloxyoctyl] pyrophosphate, bis [10- (meth) acryloyloxydecyl] pyrophosphate, and acid chlorides thereof.
Examples of the carboxylic acid group-containing polymerizable monomer include maleic acid, methacrylic acid, 4- (meth) acryloyloxyethoxycarbonylphthalic acid, 4- (meth) acryloyloxybutyloxycarbonylphthalic acid, and 4- (meth) acryloyloxy. Hexyloxycarbonylphthalic acid, 4- (meth) acryloyloxyoctyloxycarbonylphthalic acid, 4- (meth) acryloyloxydecyloxycarbonylphthalic acid, and anhydrides thereof; 5- (meth) acryloylaminopentylcarboxylic acid; 6- (meth) acryloyloxy-1,1-hexanedicarboxylic acid, 8- (meth) acryloyloxy-1,1-octanedicarboxylic acid, 10- (meth) acryloyloxy-1,1-decanedicarboxylic acid, 11- (Meta) acri Polymerizable monomers such as yloxy-1,1-undecane dicarboxylic acid, and chlorides, etc. These acids.

Examples of the sulfonic acid group-containing polymerizable monomer include polymerizable monomers such as 2- (meth) acrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, and 2-sulfoethyl (meth) acrylate, and acid chlorides thereof. Is mentioned.
Examples of the thiophosphate group-containing polymerizable monomer include polymerizable monomers such as 10- (meth) acryloyloxydecyldihydrogendithiophosphate and acid chlorides thereof.
Among these polymerizable monomers having an acidic group, it is preferable to use a polymerizable monomer having a phosphate group or a thiophosphate group because of its excellent adhesiveness to tooth material and dental prostheses. Among them, a divalent phosphoric acid group-containing polymerizable monomer having an alkyl group or an alkylene group having 6 to 20 carbon atoms in the main chain in the molecule is more preferable, and a 10-methacryloyloxydecyl dihydrogen phosphate or the like is preferable. Most preferred is a divalent phosphoric acid group-containing polymerizable monomer having an alkylene group having 8 to 12 carbon atoms in the main chain.

The polymerizable monomers may be used alone or in combination of two or more.
When using a polymerizable monomer having an acidic group, the amount thereof is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the fluoroaluminosilicate glass powder. The range is more preferably from 0.1 to 5 parts by mass.

  When it is a resin-reinforced glass ionomer cement, it contains a polymerization initiator. The polymerization initiator can be selected from known chemical polymerization initiators and / or photopolymerization initiators used in the general industry.

  Regarding the chemical polymerization initiator in the polymerization initiator, from the viewpoints of adhesion and storage stability, a ternary containing a peroxide, an aromatic secondary amine and / or an aromatic tertiary amine, and an aromatic sulfinic acid salt is used. Preferred specific examples include a chemical polymerization initiator.

  Examples of the peroxide used for the chemical polymerization initiator include inorganic peroxides such as peroxodisulfate, diacyl peroxides, peroxyesters, peroxycarbonates, dialkyl peroxides, and peroxyketals. And organic peroxides such as ketone peroxides and hydroperoxides. Specifically, examples of the peroxodisulfate include sodium peroxodisulfate, potassium peroxodisulfate, aluminum peroxodisulfate, and ammonium peroxodisulfate. Examples of diacyl peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-toluoyl peroxide, lauroyl peroxide and the like. Examples of peroxyesters include t-butylperoxybenzoate, bis-t-butylperoxyisophthalate, t-butylperoxy-2-ethylhexanoate, and the like. Examples of peroxycarbonates include, for example, t-butyl peroxyisopropyl carbonate. Examples of the dialkyl peroxides include dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, and the like. Examples of peroxyketals include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis ( (t-hexylperoxy) cyclohexane and the like. Examples of ketone peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl acetoacetate peroxide, and the like. Examples of the hydroperoxides include t-butyl hydroperoxide, cumene hydroperoxide, p-diisopropylbenzene peroxide and the like.

  Examples of the aromatic sulfinic acid salt used in the chemical polymerization initiator include, for example, benzenesulfinic acid, p-toluenesulfinic acid, o-trienesulfinic acid, ethylbenzenesulfinic acid, decylbenzenesulfinic acid, dodecylbenzenesulfinic acid, 2,4 Lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, magnesium salt, calcium salt of 2,6-trimethylbenzenesulfinic acid, 2,4,6-triisopropylbenzenesulfinic acid, chlorobenzenesulfinic acid, naphthalenesulfinic acid and the like , Strontium salts, iron salts, copper salts, zinc salts, ammonium salts, tetramethylammonium salts, tetraethylammonium salts and the like.

  As the aromatic secondary amine and / or aromatic tertiary amine used for the chemical polymerization initiator, for example, N-methylaniline, N-methyl-p-toluidine, N-methyl-m-toluidine, N- Methyl-o-toluidine, N-ethanol-p-toluidine, N-ethanol-m-toluidine, N-ethanol-o-toluidine, ethyl p-methylaminobenzoate, ethyl m-methylaminobenzoate, o-methylamino Ethyl benzoate, p-methylaminoanisole, m-methylaminoanisole, o-methylaminoanisole, 1-methylaminonaphthalene, 2-methylaminonaphthalene, N, N-dimethylaniline, N, N-dimethyl-p-toluidine N, N-dimethyl-m-toluidine, N, N-dimethyl-o-toluidine, N, N Diethanol-p-toluidine, N, N-diethanol-m-toluidine, N, N-diethanol-o-toluidine, ethyl p-dimethylaminobenzoate, ethyl m-dimethylaminobenzoate, ethyl o-dimethylaminobenzoate, Examples thereof include p-dimethylaminoanisole, m-dimethylaminoanisole, o-dimethylaminoanisole, 1-dimethylaminonaphthalene, and 2-dimethylaminonaphthalene.

Examples of the photopolymerization initiator in the polymerization initiator include α-diketones, ketals, thioxanthones, acylphosphine oxides, and α-aminoacetophenones. Specific examples of α-diketones include camphorquinone, benzyl, and 2,3-pentanedione. Specific examples of ketals include benzyl dimethyl ketal and benzyl diethyl ketal. Specific examples of thioxanthones include 2-chlorothioxanthone and 2,4-diethylthioxanthone. Specific examples of the acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, dibenzoylphenylphosphine oxide, bis (2,6-dimethoxy). Benzoyl) phenylphosphine oxide, tris (2,4-dimethylbenzoyl) phosphine oxide, tris (2-methoxybenzoyl) phosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2, 3,5,6-tetramethylbenzoyldiphenylphosphine oxide, benzoyl-bis (2,6-dimethylphenyl) phosphine oxide, 2,4,6- Water-soluble acylphosphine oxide compounds trimethyl benzoyl ethoxyphenyl phosphine oxide and KOKOKU 3-57916 Patent Publication discloses the like. Specific examples of α-aminoacetophenones include 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-benzyl-2-diethylamino-1- (4-morpholinophenyl ) -Butanone-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -propanone-1,2-benzyl-2-diethylamino-1- (4-morpholinophenyl) -propanone-1 , 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -pentanone-1, 2-benzyl-2-diethylamino-1- (4-morpholinophenyl) -pentanone-1.
One type of polymerization initiator may be used alone, or two or more types may be used in combination. The amount of the polymerization initiator (the total amount of the compounds contained as the polymerization initiator) is preferably 0.01 to 100 parts by mass of the polymerizable monomer from the viewpoint of curability and mechanical strength of the cured dental material. The range is preferably from 20 to 20 parts by mass, and from 0.1 to 10 parts by mass, more preferably from 0.5 to 5 parts by mass. In order to prepare a kit for producing the dental material composition of the present invention, it is preferable to appropriately pack components used as a polymerization initiator in consideration of storage stability.

  In the dental material composition of the present invention, aliphatic amines, aromatic amines, and aldehydes are further added in order to increase the polymerization initiation ability of the above-mentioned polymerization initiator (chemical polymerization initiator and / or photopolymerization initiator). And a polymerization accelerator such as a thiol compound.

The composition for dental materials of the present invention may contain an X-ray contrast agent as needed. This is because monitoring of the filling operation and changes after filling can be tracked. As the X-ray contrast agent, for example, one selected from barium sulfate, bismuth subcarbonate, bismuth oxide, zirconium oxide, ytterbium fluoride, iodoform, barium apatite, barium titanate, lanthanum glass, barium glass, strontium glass, etc. Or two or more.
The dental material composition of the present invention may further contain a filler for the purpose of improving fluidity and further improving the mechanical strength of the dental material as a cured product. The fillers may be used alone or in combination of two or more. As the filler, a silica-based mineral such as kaolin, clay, mica, mica; a silica-based mineral; Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , BaO, La ₂ O ₃ ; Ceramics and glasses containing SrO, ZnO, CaO, P ₂ O ₅ , Li ₂ O, Na ₂ O and the like are exemplified. As glasses, soda glass, lithium borosilicate glass, zinc glass, borosilicate glass, and bioglass are preferably used. Crystal quartz, alumina, titanium oxide, yttrium oxide, and aluminum hydroxide are also preferably used.

The dental material composition of the present invention may further contain a known water-soluble fluorinated compound in a range that does not adversely affect mechanical strength and adhesiveness, in order to enhance fluoride ion elution ability. . For example, lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, zinc fluoride, aluminum fluoride, Manganese fluoride, copper fluoride, lead fluoride, silver fluoride, antimony fluoride, cobalt fluoride, bismuth fluoride, tin fluoride, silver diammine fluoride, sodium monofluorophosphate, potassium titanium fluoride, fluoride Water-soluble metal fluorides such as stannates and fluorosilicates can be mentioned, and one or more of these can be used. At the time of compounding, it is preferable to use, for example, a method of forming fine particles of metal fluoride or a method of coating metal fluoride with polysiloxane.
Antibacterial agents, pigments, and the like that are usually used can be appropriately added to the dental material composition of the present invention, if necessary.

The composition for a dental material of the present invention can be a kit in which the components of the composition for a dental material are packaged as a product form. In order to make a kit in the form of a product, various forms are conceivable, and two-material forms such as powder / liquid, paste / liquid, and paste / paste are exemplified.
In any form, it is difficult to make the fluoroaluminosilicate glass powder, polycarboxylic acid and water coexist from the viewpoint of storage stability. From the viewpoint of storage stability, the following powder (powder material) / liquid (liquid material) or powder / powder divided forms are preferable.
(1) A powder-liquid type dental material composition kit which is divided into a powder material containing at least a fluoroaluminosilicate glass powder and a polycarboxylic acid, and a liquid material containing fine fibrous cellulose and water. (2) Dental material composition kit (3) packaged in a powder material containing at least a fluoroaluminosilicate glass powder and a polycarboxylic acid, and a liquid material containing fine fibrous cellulose and water, or a wet powder material (powder material) ) A dental material composition kit which is packaged in a powder material containing at least a fluoroaluminosilicate glass powder and a liquid material containing fine fibrous cellulose, polycarboxylic acid, and water, or a wet powder (powder material). The composition for dental material of the present invention is not limited to the above-described embodiment. There.

[Dental materials]
The dental material of the present invention is obtained by curing the composition for dental material of the present invention.
When the glass ionomer cement is a conventional glass ionomer cement, it hardens by a neutralization reaction between a fluoroaluminosilicate glass powder and a polycarboxylic acid. When the glass ionomer cement is a resin-reinforced glass ionomer cement, the resin is cured by a polymerization reaction of a polymerizable monomer in addition to the above reaction.
The dental material of the present invention can be used in various applications, and the required properties differ depending on the purpose of use. Fluidity and film thickness are important for luting and preventive filling, and strength is important for filling and backing layers. Therefore, the mechanical strength has a lower limit and an upper limit.

Since the dental material of the present invention contains fine fibrous cellulose, it has excellent mechanical strength, improves fluoride ion elution ability, or does not reduce fluoride ion elution ability.
The amount of fluoride ion eluted from the dental material of the present invention is preferably 50 μg / cm ² / week or more, more preferably 60 μg / cm ² / week or more, and still more preferably 70 μg, from the viewpoint of promoting remineralization of teeth. / Cm ² / week or more. Further, from the viewpoint of compatibility with mechanical strength, it is preferably at most 500 μg / cm ² / week, more preferably at most 400 μg / cm ² / week, even more preferably at most 300 μg / cm ² / week.
When a conventional glass ionomer cement is used as the glass ionomer cement, the fluoride ion elution amount of the dental material of the present invention is preferably 100 μg / cm ² / week or more, more preferably 120 μg / cm ² / week or more. And more preferably at least 150 μg / cm ² / week. Further, from the viewpoint of compatibility with mechanical strength, it is preferably at most 500 μg / cm ² / week, more preferably at most 400 μg / cm ² / week, even more preferably at most 300 μg / cm ² / week.
The fluoride ion eluting ability of the dental material is measured by the method described in Examples.

The dental material of the present invention is preferably excellent in mechanical strength, and has a three-point bending strength of preferably 7 MPa or more, more preferably 8 MPa or more, further preferably 9 MPa or more, particularly preferably 10 MPa or more. The upper limit is not particularly limited, but is preferably 150 MPa or less, more preferably 130 MPa or less, and still more preferably 100 MPa or less, from the viewpoint of design easiness.
When using a conventional glass ionomer cement as the glass ionomer cement, the upper limit of the three-point bending strength of the dental material of the present invention is preferably 50 MPa or less, more preferably 40 MPa or less, from the viewpoint of ease of design. Preferably it is 30 MPa or less.
The three-point bending strength of the dental material is measured by the method described in the examples.

The dental material of the present invention is preferably excellent in mechanical strength, and has a compressive strength of preferably 60 MPa or more, more preferably 65 MPa or more, further preferably 70 MPa or more, particularly preferably 75 MPa or more. The upper limit is not particularly limited, but is preferably 500 MPa or less, more preferably 400 MPa or less, and still more preferably 350 MPa or less, from the viewpoint of ease of design.
When using a conventional glass ionomer cement as the glass ionomer cement, the upper limit of the compressive strength of the dental material of the present invention is preferably 400 MPa or less, more preferably 300 MPa or less, further preferably from the viewpoint of ease of design. It is 200 MPa or less.
The compressive strength of a dental material is measured by the method described in the examples.

  The dental material composition and the dental material of the present invention are a filler for a defective portion of an affected tooth, a bonding material of a defective portion of the affected tooth and a prosthesis, a preventive material for dental caries and periodontal disease, a backing material, and the like. It can be suitably used for various applications.

[Fine fibrous cellulose]
The fine fibrous cellulose of the present invention is used for preparing a dental material by mixing with a glass ionomer cement, and has a fiber width of 1000 nm or less.
The fine fibrous cellulose may be in any state of a wet powder, a powder, and a slurry, and is not particularly limited. Further, it may be contained in a powder material or a liquid material, and may be mixed with a glass ionomer cement as a dry powder of fine fibrous cellulose or a water-containing powder (wet powder), and is not particularly limited.

  Hereinafter, features of the present invention will be described more specifically with reference to examples and comparative examples. 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 construed as being limited by the specific examples described below.

<Production Example 1>
As a raw material pulp, softwood kraft pulp manufactured by Oji Paper (solid content: 93% by mass, basis weight: 208 g / m ^2, sheet: Canadian standard freeness (CSF) measured by disintegration and measured according to JIS P 8121: 700 ml) It was used. This raw material pulp was subjected to a 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 with a hot air drier at 165 ° C. for 200 seconds to introduce a phosphate group into cellulose in the pulp to obtain a phosphorylated pulp.

Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment is performed by repeating the operation of pulverizing a pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g of phosphorylated pulp (absolute dry mass) so that the pulp is uniformly dispersed, and then filtering and dewatering. went. When the electric conductivity of the filtrate became 100 μS / cm or less, it was regarded as the washing end point.
The phosphorylated pulp after washing was further subjected to the above phosphorylation treatment and the above washing treatment once in this order.

  Next, the washed phosphorylated pulp was subjected to an alkali treatment (neutralization treatment) as follows. First, the phosphorylated pulp after washing 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 subjected to an alkali treatment (neutralization treatment).

Next, the above-mentioned 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 at around 1230 cm ⁻¹ , confirming that a phosphate group was added to the pulp. Further, the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer. As a result, it was found that two points, 2θ = around 14 ° to 17 ° and 2θ = around 22 ° to 23 °, were located at two positions. A typical peak was confirmed, and it was confirmed to have cellulose type I crystals.

(Fibrillation processing)
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content of 2% by mass. This slurry is treated four times at a pressure of 200 MPa by a wet atomizer (manufactured by Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion (A) containing fine fibrous cellulose (solid content: 2 mass%). %).

  250 g of an aqueous calcium chloride solution diluted to 0.5% by mass was added to 500 g of the fine fibrous cellulose dispersion (A) (solid content concentration: 2% by mass) to cause gelation. After filtering the obtained gel, it was squeezed with filter paper to obtain a fine fibrous cellulose-containing substance having a solid content of 20% by mass. This fine fibrous cellulose-containing substance (solid content concentration: 20% by mass) was immersed in 250 g of a 0.1N hydrochloric acid aqueous solution for 30 minutes, filtered, and squeezed with filter paper. Thus, a fine fibrous cellulose-containing material (concentrate) having a solid content of 25% by mass was obtained. Further, this fine fibrous cellulose-containing substance (concentrate) was pulverized using a mixer (Mircer 800DG, manufactured by Iwatani Corporation), and 100 parts by mass of a 0.35N aqueous sodium hydroxide solution was added to 100 parts by mass of the concentrate. Parts, a nonionic surfactant (manufactured by San Nopco Co., Ltd., SN wet PUR) is added by 1 part by mass, kneaded well with a spoon, and the concentration of the fine fibrous cellulose is 14.78%. A content (concentrate) was obtained.

X-ray diffraction confirmed that the fine fibrous cellulose maintained cellulose type I crystals.
Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. Furthermore, when the fiber length of the fine fibrous cellulose was measured by the method described later, it was 1,000 to 2,000 nm, and the axial ratio was 200 or more.
The amount of a phosphate group (the amount of a strongly acidic group) measured by a measurement method described later was 1.7 mmol / g.

(Measurement of phosphate group content)
The phosphate group content of the fine fibrous cellulose is obtained by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water so that the content becomes 0.2% by mass. After the treatment with the ion-exchange resin was performed on the cellulose-containing slurry, the measurement was performed by performing titration using an alkali.
In the treatment with the ion-exchange resin, 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; manufactured by Organo Co., Ltd., conditioned) was added to the fine fibrous cellulose-containing slurry, followed by shaking for 1 hour. Thereafter, the mixture was poured on a mesh having a mesh size of 90 μm to separate the resin and the slurry.
In addition, titration using an alkali is performed by adding 50 μL of a 0.1N aqueous sodium hydroxide solution once every 30 seconds to a slurry containing fine fibrous cellulose after treatment with an ion-exchange resin while the electric conductivity of the slurry is shown. This was done by measuring the change in the degree value. The amount of phosphoric acid groups (mmol / g) is obtained by dividing the amount of alkali (mmol) required in a region corresponding to the first region shown in FIG. 1 in the measurement results by the solid content (g) in the slurry to be titrated. Was calculated.

(Measurement of fiber width of fine fibrous cellulose)
The fiber width of the fine fibrous cellulose was measured by the following method.
The supernatant liquid of the fine fibrous cellulose dispersion obtained by the treatment with a wet atomizer is mixed with water so that the concentration of the fine fibrous cellulose becomes 0.01% by mass or more and 0.1% by mass or less. The diluted and hydrophilized carbon grid film was dropped. After drying, it was stained with uranyl acetate and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

(Measurement of fiber length of fine fibrous cellulose)
The fiber length of the fine fibrous cellulose was determined by observing a sample obtained by diluting a fine fibrous cellulose dispersion liquid (solid content concentration: 2% by mass) 100,000 times by AFM and performing image analysis.

<Example 1>
Ketac Cem Easymix (3M) powder material was used. The powder material contains a fluoroaluminosilicate glass and an acrylic acid-maleic acid copolymer as a polycarboxylic acid.
The above-mentioned powder material and the wet powder containing 14.78% by mass of fine fibrous cellulose obtained in Production Example 1 were mixed at the compounding amounts (parts by mass) shown in Table 1 to obtain a composition for a dental material. Was prepared.
The following evaluation was performed using the prepared composition for dental materials.

(Three-point bending test)
Using the above-mentioned composition for dental materials, a 2 × 2 × 25 mm rectangular parallelepiped dental material sample was prepared. The obtained sample was immersed in artificial saliva (Salibate, manufactured by Teijin Pharma Co., Ltd.) and stored in a thermostat at 37 ° C., 24 hours after the start of kneading (start of mixing of the powder material and the wet powder). Using a universal testing machine (AGS-X, manufactured by Shimadzu Corporation), a three-point bending test was performed at a crosshead speed of 0.5 mm / min and a fulcrum distance of 20 mm according to JIS T 6609-2: 2014. The bending strength was measured. A sample was prepared and measured at n = 5, and an average value was calculated.
The results are shown in FIG.

(Compression test)
Using the above-described composition for dental material, a cylindrical sample of dental material having a diameter of 4 mm and a height of 6 mm was prepared. The obtained sample was immersed in artificial saliva (Salibate, manufactured by Teijin Pharma Limited) and stored in a 37 ° C. constant temperature oven. Twenty-four hours after the start of kneading (starting mixing of the powder material and the wet powder), a crosshead speed of 1 was measured with an all-purpose testing machine (AGS-X, manufactured by Shimadzu Corporation) in accordance with ISO 9917-1. A compression test was performed at 0.0 mm, and the compression strength was measured. A sample was prepared and measured at n = 6, and the average value was calculated.
FIG. 4 shows the results.

(Measurement of elution amount of fluoride ion)
Using the composition for a dental material described above, a disk-shaped sample of a dental material having a diameter of 10 mm and a thickness of 2 mm was prepared. The obtained sample was immersed in 8 ml of deionized water and stored for 1 week in a thermostat at 37 ° C. One week later, the sample is washed with 2 ml of fresh deionized water, and the amount of fluoride ions contained in 10 ml of the immersion liquid including the washing liquid is attached to an ion meter (D-53, manufactured by HORIBA, Ltd.). It was measured with a fluoride ion selective electrode (6561-10C, manufactured by Horiba, Ltd.). The elution amount (ppm) obtained with the fluoride ion selective electrode was converted into the ion elution amount (μg / cm ² ) per sample surface area, and the fluoride ion elution amount (μg / cm ² / week) I asked. A sample was prepared and measured at n = 6, and the average value was calculated.
The results are shown in FIG.
In FIGS. 3 to 5, the statistical examination was performed by t-test (p <0.05).

<Comparative Example 1>
A dental material composition was prepared in the same manner as in Example 1 except that distilled water was used in place of the wet powder in Example 1, and the blending amount (parts by mass) shown in Table 1 was used. The same evaluation was performed.

From the results of the Examples and Comparative Examples, the dental material obtained from the composition for dental materials containing the fine fibrous cellulose of Example and the glass ionomer cement has the bending strength and the compressive strength of the fine fibers of Comparative Example. Compared with a dental material obtained from a glass ionomer cement containing no cellulose, it was significantly improved, and it was shown that the effect of improving mechanical strength was excellent.
Furthermore, surprisingly, in the Examples and Comparative Examples, it is shown that the fluoride ion elution amount after one week is significantly higher in the examples, and the fluoride ion elution amount is increased without decreasing. Was done.

  According to the present invention, by adding fine fibrous cellulose to the glass ionomer cement, without decreasing the fluoride ion elution amount, it is clarified that a dental material with significantly improved mechanical strength can be obtained. The material composition and the dental material are expected to be applied to a filling material for a defective portion of a tooth affected part, a bonding material for a defective part of a tooth affected part and a prosthesis, a preventive material, a back layer material, and the like.

Claims (9)

  A composition for a dental material, comprising a fine fibrous cellulose having a fiber width of 1,000 nm or less and a glass ionomer cement.   A dental material obtained by curing the composition for dental material according to claim 1. The dental material according to claim 2, wherein the amount of fluoride ion eluted is 50 µg / cm ² / week or more and 500 µg / cm ² / week or less.   The dental material according to claim 2 or 3, wherein the three-point bending strength is 7 MPa or more and 150 MPa or less.   The dental material according to any one of claims 2 to 4, having a compressive strength of 60 MPa or more and 500 MPa or less.   The dental material according to any one of claims 2 to 5, wherein the content of the fine fibrous cellulose is 0.1% by mass or more and 50% by mass or less based on the total solid content of the dental material.   The dental material according to any one of claims 2 to 6, wherein the fine fibrous cellulose has an axial ratio of 20 or more and 10,000 or less.   The dental material according to any one of claims 2 to 7, wherein the fine fibrous cellulose has an ionic substituent.   Fine fibrous cellulose having a fiber width of 1,000 nm or less, which is used for preparing a dental material by mixing with a glass ionomer cement.