JP2017066556A - Sheet and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine fiber-containing sheet and a laminate which have high transparency, suppress the occurrence of wrinkles and cracks when forming into a sheet and have excellent strength.SOLUTION: There are provided: a sheet which contains a fine fiber having an ionic substituent and an organic ion which is a counter ion of the ionic substituent, wherein the content of the organic ion is 0.40 mmol/g or less; and a laminate which comprises the sheet and at least one of an inorganic layer and an organic layer formed on at least one side of the sheet.SELECTED DRAWING: None

Description

  The present invention relates to a sheet and a laminate including fine fibers.

  In recent years, materials using reproducible natural fibers have attracted attention due to the substitution of petroleum resources and the growing environmental awareness. Among natural fibers, cellulose fibers having a fiber diameter of 10 to 50 μm, especially wood-derived cellulose fibers (pulp) have been widely used as paper products so far.

  As the cellulose fiber, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Sheets and composites containing fine fibrous cellulose significantly increase the tensile strength because the contact points between fibers are remarkably increased. Moreover, transparency is greatly improved because the fiber width is shorter than the wavelength of visible light. As a method for producing fine fibers, there is known a method for introducing a substituent having electrostatic or steric functionality into a fiber raw material in order to easily refine the fiber raw material (defibration) (for example, Patent Documents 1 to 4).

  The fine fiber into which a functional substituent is introduced has been studied from various viewpoints. For example, in Patent Document 5, it is soluble in a wide range of organic solvents in view of the fact that the cellulose nanofibers having carboxylic acid groups are aggregated and precipitated when put into the same organic solvent as the material to be combined. Considered from the viewpoint of providing cellulose nanofibers. Specifically, an attempt has been made to disperse a carboxylate type group in an organic solvent after substituting the carboxylate type group of an amine having an organic group. Further, in Patent Document 6, it is possible to uniformly disperse in an organic solvent or resin, and to provide a dispersion containing fine cellulose fibers not containing metal ions in order to maintain water resistance and strength when formed into a sheet. Therefore, a fine cellulose fiber dispersion characterized by containing fine cellulose fibers and ammonia or organic alkali has been proposed. Furthermore, Patent Document 7 has been studied with the problem of being able to produce in a high yield, ensuring the stability of the slurry dispersion on the acidic side, and lowering the viscosity of the dispersion. Here, there has been proposed a fine fibrous cellulose into which two types of functional groups having a salt form with at least one selected from the group consisting of a cation, an ammonium ion, an aliphatic ammonium ion and an aromatic ammonium ion are introduced. .

JP 2008-308802 A JP 2010-254726 A Special table 2012-511596 gazette International Publication WO2013 / 073652 JP2012-21081A International Publication WO2011 / 111612 JP 2013-253200 A

  According to the study by the present inventors, when drying to form a fine fiber into which a hydrophilic functional group has been introduced, the fine fiber aggregates due to the formation of hydrogen bonds. There was a tendency for wrinkles and cracks to occur and the yield of the sheet to decrease. On the other hand, a study was made to give a counter ion to the introduced functional group so as to block a hydrogen bond. However, there was a concern that the mechanical properties of the sheet were lowered while the yield was improved. With respect to the fine fiber-containing sheet, it has been required to improve the strength while suppressing wrinkles and cracks. However, sufficient studies have not been made so far regarding techniques for achieving both.

  The inventors diligently studied to achieve both suppression of wrinkling and cracking of the sheet and improvement of strength. As a result, the inventors have newly found that the intended effect can be obtained by appropriately adjusting the content of counter ions in the sheet, thereby completing the present invention.

The present invention provides the following.
[1] a fine fiber having an ionic substituent;
An organic ion that is a counter ion of the ionic substituent;
Including
The sheet | seat whose content of the said organic ion is 0.40 mmol / g or less.
[2] The sheet according to 1, wherein the haze is 40% or less.
[3] The sheet according to 1 or 2, wherein the density is 1.0 g / cm ³ or more.
[4] The sheet according to any one of 1 to 3, wherein the organic ion has 4 or more carbon atoms.
[5] The sheet according to any one of 1 to 4, wherein the content of the ionic substituent is 0.5 mmol / g or less with respect to the fine fiber.
[6] The sheet according to any one of 1 to 5, wherein the tensile elastic modulus at a temperature of 23 ° C. and a relative humidity of 50% is 4.0 GPa or more.
[7] The sheet according to any one of 1 to 6,
A laminate comprising at least one of an inorganic layer and an organic layer laminated on at least one side of the sheet.

  The fine fibers having an ionic substituent obtained by the present invention are suppressed in wrinkling and cracking during sheet formation, and the resulting sheet has excellent mechanical strength.

FIG. 1 shows three regions in the substituent content measurement by the conductivity titration method.

  Values relating to the mass of fibers such as cellulose are based on the absolute dry mass (solid content), unless otherwise specified. The numerical range “X to Y” includes the values X and Y at both ends unless otherwise specified.

  The present invention relates to a sheet comprising fine fibers having an ionic substituent and an organic ion which is a counter ion of the ionic substituent, and the content of the organic ion is a predetermined value or less, and a laminate using the sheet , And methods for their manufacture.

1. Sheet containing fine fibers and organic ions [Fine fibers with ionic substituents]
<Fine fibers>
The sheet | seat of this invention contains the fine fiber which has an ionic substituent. The fine fiber having an ionic substituent can be obtained by introducing an ionic substituent into a fiber raw material and performing a fine treatment. In the present invention, the fine fiber is, for example, a fiber having a fiber width of 1000 nm or less, and is preferably a natural fiber. Natural fibers are preferably polysaccharides because they are available in abundance, and more preferably cellulose, chitin, or chitosan because strength can be expected when formed into a sheet. A cellulose fiber is mentioned as a particularly preferable example of the natural fiber. In the following, the present invention, its embodiments and examples may be described by taking the case of using fine fibrous cellulose as an example, but those skilled in the art will use other types of fibers as appropriate for the description. It can be understood by applying to cases.

  The average fiber width of the fine fibers contained in the sheet of the present invention is not particularly limited as long as it is 1000 nm or less, but can be, for example, 1 nm or more, preferably 2 to 1000 nm, more preferably 2 to 500 nm, and still more preferably. 3-100 nm. When the average fiber width of the fine fibers is 1000 nm or less, the features (high transparency, high elastic modulus, low linear expansion coefficient, flexibility) as fine fibers are easily exhibited. On the other hand, when the average fiber width is 1 nm or more, the dissolution of molecules in water is suppressed, so that physical properties (strength, rigidity, dimensional stability) as a fine fiber are sufficiently expressed.

  In applications where the sheet is required to have relatively high transparency, if the average fiber width is 30 nm or less, it approaches 1/10 of the wavelength of visible light, and in the case of a laminate, refraction and scattering of visible light at the interface. There is a tendency that a product with high transparency is obtained. Therefore, the average fiber width is not particularly limited, but is preferably 2 to 30 nm, and more preferably 2 to 20 nm. A laminate obtained from such fine fibers generally has a high strength because it becomes a dense structure, and has high transparency because it scatters less visible light.

The average fiber width is measured as follows. A fine fiber-containing slurry having a concentration of 0.05 to 0.1% by mass is prepared, and the slurry is cast on a carbon film-coated grid subjected to a hydrophilization treatment to obtain a sample for TEM observation. When wide fibers are included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, 20000 times, or 50000 times, depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location 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 with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight lines X and Y is read for each image. Thus, at least 20 × 2 × 3 = 120 fiber widths are read. The average fiber width is an average value of the fiber widths read in this way.

  Although the fiber length of a fine fiber is not specifically limited, 0.1 micrometer or more is preferable. If the fiber length is 0.1 μm or more, it is preferable in that the tear strength of the sheet is sufficient when a sheet described later is manufactured. The fiber length can be obtained by image analysis of TEM, SEM, or AFM. The said fiber length is a fiber length which occupies 30 mass% or more of a fine fiber.

  The axial ratio of fibers (fiber length / fiber width) is not particularly limited, but is preferably in the range of 20 to 10,000. An axial ratio of 20 or more is preferable in that a fine fiber-containing sheet is easily formed during production. When the axial ratio is 10,000 or less, it is preferable in that the slurry viscosity at the time of sheet production becomes low.

<Ionic substituent>
The fine fiber contained in the sheet of the present invention has an ionic substituent. The ionic substituent facilitates the refinement (defibration) of the fiber raw material in the production of the fine fiber-containing sheet. The ionic substituent may be anionic or cationic.

Examples of the anionic substituent include a phosphate group or a substituent derived from a phosphate group (hereinafter, a phosphate group and a substituent derived from a phosphate group are also referred to as a phosphate-derived group), a carboxy group, or Substituents derived from carboxy groups (hereinafter, carboxy groups and substituents derived from carboxy groups are also referred to as carboxylic acid-derived groups), sulfate groups or substituent groups derived from sulfate groups (hereinafter referred to as sulfate groups and sulfate groups). The substituent derived from the above is also referred to as a group derived from sulfuric acid), a sulfonic acid group or a substituent derived from a sulfonic acid group (hereinafter, the substituent derived from a sulfonic acid group and a sulfonic acid group is referred to as a group derived from a sulfonic acid Also called). The phosphoric acid group is a divalent functional group equivalent to the phosphoric acid obtained by removing the hydroxyl group. Specifically, it is a group represented by —PO ₃ H ₂ . The substituent derived from the phosphate group includes a substituent such as a group obtained by polycondensation of a phosphate group, a salt of a phosphate group, and a phosphate ester group. Moreover, the substituent derived from a phosphoric acid group or a phosphoric acid group may be represented by the following formula (1).

In formula (1), a, b, m and n each independently represent an integer (where a = b × m); α ⁿ (n = 1 to n) and α ′ are each independently R or OR is represented. R represents a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group. , An aromatic group, or a derivative group thereof; β is a monovalent or higher cation composed of an organic substance or an inorganic substance.

  The anionic substituent is at least one selected from the group consisting of a group derived from phosphoric acid, a group derived from carboxylic acid, and a group derived from sulfuric acid, from the viewpoint of ease of handling and reactivity with fibers during production. It is preferable. These groups preferably form an ester or ether with the fiber, but are not particularly limited.

  Examples of the cationic substituent include groups derived from onium salts such as ammonium salts, phosphonium salts, and sulfonium salts. Specific examples include groups containing ammonium, phosphonium and sulfonium such as primary ammonium salt, secondary ammonium salt, tertiary ammonium salt and quaternary ammonium salt. The cationic substituent is preferably at least one of a group derived from a quaternary ammonium salt and a group derived from a phosphonium salt in view of ease of handling and reactivity with fibers during production.

  In a preferred embodiment of the present invention, a method of desorbing the ionic substituent together with reducing the organic ions contained in the sheet as described later is employed. In this case, the content of ionic substituents in the sheet is not particularly limited as long as the sheet has the intended properties, but it is preferably 0.5 mmol / g or less with respect to the sheet or fine fiber, and 0.1 mmol / g. Or less, more preferably 0.05 mmol / g or less. This is because organic ions are sufficiently reduced when the concentration is 0.5 mmol / g or less. Although the lower limit of the content of the ionic substituent is not particularly limited, it is 0.001 mmol / g or more with respect to the sheet or fine fiber regardless of the upper limit. From the viewpoint that there are few organic ions that are concerned about the influence on the sheet strength, it is considered that the content of ionic substituents in the sheet is preferably as small as possible.

The content (mmol / g) of the ionic substituent in the sheet can be measured as follows using a fluorescent X-ray analysis method.
First, for preparing a calibration curve, a sheet having the same fine fiber as that used for the measurement target sheet and having a known ionic substituent content (mmol / g) is prepared, and this is determined by fluorescent X-ray analysis. The X-ray intensity of the sample is measured. The element to be measured is an element that is included in the ionic substituent but is not included in the fine fiber (for example, a phosphorus atom when the ionic substituent is a group derived from phosphoric acid), or a counter ion of the ionic substituent Is an element that is contained in but not in fine fibers. If necessary, the measurement object sheet can be used for measurement after exchanging the counter ion of the ionic substituent with another counter ion containing an element not included in the fine fiber. For example, when the ionic substituent is a group derived from a carboxylic acid, the counter ion can be exchanged for sodium ion and then used for measurement. In this case, the measurement element is sodium ion. Next, a calibration curve is prepared based on the X-ray intensity obtained thereby and the known ionic substituent content.
On the other hand, the X-ray intensity of the measurement target sheet is measured by fluorescent X-ray analysis. Next, the content (mmol / g) of the ionic substituent of the measurement target sheet is determined from the X-ray intensity obtained thereby and the calibration curve. The determined value can be expressed as the content of ionic substituents on the sheet or fine fiber.

  When adopting a method in which the ionic substituent is not eliminated when removing the counter ion, the content of the ionic substituent in the sheet corresponds to the amount of the ionic substituent introduced into the sheet during the production. When the introduced substituent is at least one selected from the group consisting of a phosphoric acid-derived group, a carboxylic acid-derived group and a sulfuric acid-derived group, the amount of substituent introduction is not particularly limited, but 0 0.001 to 5.0 mmol / g. It may be 0.05 to 4.0 mmol / g, or 0.1 to 2.0 mmol / g.

[Organic ions]
The sheet | seat of this invention contains an organic ion. An organic ion refers to an ion that can form an ion pair with an ionic substituent of a fiber and that has an organic group. An organic group refers to a group derived from an organic compound (compound containing a carbon atom). The organic ions can suppress the formation of wrinkles and cracks in the sheet by suppressing the formation of hydrogen bonds between the ionic substituents in the drying step in forming a sheet from fine fibers having an ionic substituent. Conventionally, the carboxy group on the fiber is an amine salt type (see Patent Document 5), the carboxy group on the fiber is an onium salt type (described in Patent Document 6), and the carboxy group and phosphate group on the fiber. Some of them have an ammonium salt type, and the purpose of each is to improve dispersibility in an organic solvent and to ensure compatibility with a resin to be composited. The present invention is the first to use organic ions in a fine fiber-containing sheet having an ionic substituent, paying attention to a novel problem of suppressing wrinkles and cracks when forming a fine fiber into a sheet.

<Types of organic ions>
The kind of organic ion when the fine fiber has an anionic substituent and the kind of organic ion when the fine fiber has a cationic substituent are not particularly limited as long as the desired effect is exhibited. In the case of an anionic substituent, the organic ion is preferably an organic onium ion represented by the following formula (2).

In the formula:
M is a nitrogen atom or a phosphorus atom;
At least one of R _{1 to} R ₄ is an organic group that may contain a hetero atom, and the remainder is a hydrogen atom. The number of carbons in the organic group (when having a plurality of organic groups, the total number of carbons) is 1 or more and is not particularly limited as long as the desired effect is exhibited, but is preferably 4 or more, and 8 or more. More preferably, it is more preferably 16 or more. This is because a large carbon number and a certain amount of bulk are effective. R _{1 to} R ₄ may be the same or different from each other, but are preferably the same or the same size group. This is because it is considered that the effect closer to the spherical shape is greater than the linear shape.

  Such an organic onium ion is preferably a tetraalkylonium ion, for example, and more preferably contains at least one of a tetraalkylammonium ion and a tetraalkylphosphonium ion. Examples of tetraalkylammonium ions include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion, lauryltrimethylammonium ion. Ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, octyldimethylethylammonium ion, lauryldimethylethylammonium ion, didecyldimethylammonium ion, lauryldimethylbenzylammonium ion, and tributylbenzylammonium ion. Examples of tetraalkylphosphonium ions include tetramethylphosphonium ions, tetraethylphosphonium ions, tetrapropylphosphonium ions, tetrabutylphosphonium ions, and lauryltrimethylphosphonium ions. In addition, as tetrapropyl onium ion and tetrabutyl onium ion, it is particularly preferable to use tetra n-propyl onium ion and tetra n-butyl onium ion, respectively.

<Content of organic ions>
Although the sheet | seat of this invention contains an organic ion, the content is 0.40 mmol / g or less with respect to a sheet | seat. The organic ion is added to the ionic substituent before sheeting, and then the content is reduced to 0.40 mmol / g or less after sheeting. By reducing the organic ion content, the mechanical strength of the sheet can be increased. From the viewpoint of further improving the mechanical strength, the content of organic ions in the sheet is preferably 0.20 mmol / g or less, more preferably 0.10 mmol / g or less, and still more preferably 0.00. 05 mmol / g or less. On the other hand, the lower limit of the content of organic ions in the sheet is not particularly limited, and can be 0 mmol / g, for example, 0.005 mmol / g with respect to the sheet. In addition, regarding the fiber or sheet in the present invention, when it is referred to as the organic ion content, the measurement described below is performed regardless of whether an ion pair is formed with the ionic substituent on the sheet, unless otherwise specified. The value measured by the method.

The content (mmol / g) of organic ions in the sheet can be measured using, for example, chemiluminescence, infrared spectroscopy, time-of-flight mass spectrometry, or fluorescent X-ray analysis.
When nitrogen is contained in the organic ions, the concentration of nitrogen atoms in the sheet can be measured by, for example, a trace nitrogen analyzer using a chemiluminescence method. At this time, the nitrogen atom concentration of the fine fiber-containing sheet not treated with organic ions is also measured, and the nitrogen atom concentration derived from organic ions is reduced by subtracting the value from the nitrogen atom concentration of the fine fiber-containing sheet to be measured. And the organic ion content can be calculated. In addition, for example, when a group derived from phosphoric acid is included as an ionic substituent, an organic ion is not imparted by performing a treatment for 2 hours at 180 ° C. using glycerin by a polyhydric alcohol boiling method described later. It is thought that it can be handled in the same manner as the fine fiber-containing sheet. In the case of containing an ionic substituent other than a phosphate-derived group, in the counter ion exchange described later, in the case of an anionic substituent, the pH 1 treatment liquid, and in the case of a cationic substituent, the pH 14 treatment liquid, respectively. It is thought that it can treat like the fine fiber containing sheet | seat which has not provided the organic ion by immersing for 2 hours.

  When a phosphorus atom is contained in the organic ion, it is possible to calculate the phosphorus atom concentration derived from the organic ion in the sheet using, for example, a fluorescent X-ray analysis method as follows. First, X-ray fluorescence analysis is performed on the measurement target sheet, and the phosphorus atom concentration in the measurement target sheet is calculated based on the characteristic X-ray intensity of phosphorus atoms and the calibration curve for the amount of phosphorus introduced. calculate. Next, the phosphorus atom concentration of the fine fiber-containing sheet that does not contain organic ions is also measured, and the phosphorus atom concentration derived from organic ions is obtained by subtracting the value from the phosphorus atom concentration of the fine fiber-containing sheet to be measured. The content can be calculated. The fine fiber-containing sheet not containing organic ions is, for example, a counter ion exchange described later with respect to the sheet to be measured, in a treatment solution having a pH of 1 in the case of an anionic substituent, and pH 14 in the case of a cationic substituent. It is thought that it can treat like the fine fiber containing sheet | seat which has not provided the organic ion by immersing in each processing liquid for 2 hours.

When the organic ions contain an element other than nitrogen and considered not to exist in the fine fiber-containing sheet, the content of organic ions in the sheet is as follows using a fluorescent X-ray analysis method: Can be measured.
First, to prepare a calibration curve, a sample having a composition and form similar to those of the measurement target sheet (for example, using filter paper) and having a known analytical element content (mmol / g) is prepared, and fluorescence is prepared. The X-ray intensity of the sample is measured by X-ray analysis. Here, an element that is included in the organic ions but is considered not to exist in the fine fiber-containing sheet is an analytical element. Then, a calibration curve is created based on the X-ray intensity obtained thereby and the known content of the analytical element. Next, the X-ray intensity of the measurement target sheet is measured by fluorescent X-ray analysis. And the content (mmol / g) of the analytical element in a measuring object sheet | seat is computed from the X-ray intensity obtained by this, and the said calibration curve.

[Sheet characteristics]
The sheet of the present invention has the following characteristics.

<Density>
The density of the sheet refers to a value (g / cm ³ ) obtained from the thickness and mass of the sheet after conditioning a 100 mm square sheet under conditions of 23 ° C. and 50% relative humidity for 24 hours. The density of the sheet of the present invention can be appropriately determined according to the use and the like, but can be 0.1 to 7.0 g / cm ³ from the viewpoint of strength and transparency, and 0.5 to 5 it is preferably .0g / cm ^3, more preferably 1.0 to 3.0 g / cm ^3.

<Wrinkles / cracks>
Wrinkles and cracks during sheet production can be evaluated by the following method. When forming a dispersion of fine fibers into a sheet, a total of 81 squares of 9 × 9 in width is written on the back surface of the acrylic plate in accordance with the size of each 180 mm damming metal frame. The fine fiber-containing sheet is observed from above with the acrylic plate attached to the acrylic plate, and the masses where wrinkles and cracks are generated are counted. Next, it is calculated what percentage of the total number of cells where wrinkles and cracks occur.
When the sheet of the present invention is evaluated by this method, the proportion of mass in which wrinkles and cracks are generated is less than 20%.

<Total light transmittance>
The total light transmittance of the sheet refers to a value measured using a haze meter in accordance with JIS standard K7361. The sheet of the present invention has high transparency, and the total light transmittance thereof is 80% or more, preferably 85% or more, and more preferably 88% or more.

<Haze value>
The haze value of the sheet refers to a value measured using a haze meter in accordance with JIS standard K7136. The sheet of the present invention has high transparency, and its haze value is 40.0% or less, preferably 35.0% or less, and more preferably 20.0% or less.

<Tensile strength, tensile modulus>
The tensile strength and tensile modulus of the sheet refer to values measured at a temperature of 23 ° C. and a relative humidity of 50% using a tensile tester in accordance with JIS K 7127. The sheet obtained according to the present invention has reduced wrinkles and cracks during production, and is excellent in tensile strength and tensile modulus as compared with a sheet that does not use organic ions for the ionic substituent. . Specifically, the tensile strength of the sheet of the present invention is 60.0 MPa or more, preferably 70.0 MPa or more, and more preferably 80.0 MPa or more. This is because if it exceeds this value, it can be used as an optical material. Although an upper limit is not specifically limited, For example, it is 400.0 MPa or less, or is 300.0 MPa or less.
The tensile modulus of the sheet of the present invention is 4.0 GPa or more, preferably 5.0 GPa or more, and more preferably 6.5 GPa or more. This is because if it exceeds this value, it can be used as an optical material. Although an upper limit is not specifically limited, For example, it is 25.0 GPa or less, or is 20.0 GPa or less.

Thus, in the sheet | seat of this invention, generation | occurrence | production of the wrinkles and a crack in the case of manufacture is suppressed, and it is thought that it is based on the following factors that it is excellent in the tensile characteristic. At the time of forming a sheet, an appropriate organic ion is applied as a counter ion to the ionic substituent (the aggregation of fine fibers due to the ionic substituent observed in the drying step during sheet formation can be prevented). After forming into a sheet, organic ions that have a concern of affecting the strength of the sheet are reduced to an appropriate level.
Further, according to the present inventors, the production conditions of the fine fiber, the type of ionic substituent on the fine fiber, in some cases, the amount thereof, the type of organic ions contained in the sheet, in some cases the amount thereof, etc. It is presumed that the proper selection also contributes to improving tensile properties while suppressing wrinkles and cracks. These are considered to affect the density, total light transmittance, haze, and yellowness change of the sheet.

<Yellowness change>
The yellowing degree change (ΔYI) of the sheet is expressed by the following formula: ΔYI = YI ₂ −YI ₁
However, YI ₁ indicates the yellowness before vacuum drying at 200 ° C. for 4 hours, and YI ₂ indicates the yellowness after vacuum drying at 200 ° C. for 4 hours. Yellowness refers to a value measured according to JIS standard K7373. In the sheet of the present invention, the yellowing degree change (ΔYI) is suppressed. The yellowing degree change (ΔYI) of the sheet of the present invention is, for example, 75.0 or less.

  In a preferred embodiment, as will be described later, a method of desorbing the ionic substituent together with reducing the organic ions contained in the sheet is employed. In this case, the yellowness change (ΔYI) is 50.0 or less, more preferably 7.0 or less, and even more preferably 5.0 or less. The reason why the change in yellowness is suppressed in the preferred embodiment is that yellowing due to heating of the sheet is further suppressed due to elimination of organic ions and ionic substituents. In addition, when the ionic substituent is a group derived from phosphoric acid, if reduction of organic ions is achieved by elimination together with the group derived from phosphoric acid, the formation of char at a high temperature by the group derived from phosphoric acid is reduced. Because.

2. Manufacturing method of sheet The manufacturing method of the sheet of the present invention,
(1) introducing an ionic substituent into the fiber raw material to obtain an ionic substituent-introduced fiber;
(2) a step of refining the ionic substituent-introduced fiber to obtain an ionic substituent-introduced fine fiber, and further before or after step (2),
A step of treating ionic substituents with organic ions, and (3) a step of preparing a sheet from ionic substituent-introduced fine fibers treated with organic ions;
(4) reducing the organic ions contained in the sheet.

[Step (1): Step of obtaining an ionic substituent-introduced fiber by introducing an ionic substituent into a fiber raw material]
<Fiber raw material>
The fine fiber having an ionic substituent can be obtained by introducing an ionic substituent into a fiber raw material and performing a fine treatment. The fiber raw material used in the step (1) is a natural fiber that can be obtained in abundance, preferably cellulose, chitin or chitosan, more preferably cellulose. As the fiber raw material, it is preferable to use pulp because it is easily available and inexpensive. Among the pulps, wood pulp containing cellulose is preferable in terms of availability. Among wood pulps, chemical pulp has a large cellulose ratio, so the yield of fine cellulose fibers is high when fibers are refined, and cellulose fibers in the pulp are small, and long fine fiber fibers with a large axial ratio are obtained. However, it is not particularly limited. Of these, kraft pulp and sulfite pulp are most preferably selected, but are not particularly limited.

<Introduction of ionic substituent>
An ionic substituent is introduced into the fiber raw material. A method for introducing a substituent into the fiber is not particularly limited, and examples thereof include an oxidation treatment and a treatment with a compound capable of forming a covalent bond with a functional group in the fiber. The oxidation treatment is a treatment for converting a hydroxy group in the fiber into an aldehyde group or a carboxy group, and examples thereof include a TEMPO oxidation treatment and treatment using various oxidizing agents (such as sodium chlorite and ozone).

  An example of the oxidation treatment is a method described in Biomacromolecules 8, 2485-2491, 2007 (Saito et al.), But is not particularly limited.

  Treatment with a compound capable of forming a covalent bond with a functional group in the fiber introduces the above substituents into the fiber raw material by mixing the fiber raw material in a dry or wet state with a compound that reacts with the fiber raw material. Can be implemented. In order to promote the reaction at the time of introduction, a heating method is particularly effective. The heat treatment temperature for introducing the substituent is not particularly limited, but is preferably a temperature range in which thermal decomposition or hydrolysis of the fiber raw material hardly occurs. For example, it is preferable that it is 250 degrees C or less from a viewpoint of the thermal decomposition temperature of a fiber, and it is preferable to heat-process at 100-170 degreeC from a viewpoint of suppressing hydrolysis of a fiber.

The compound that reacts with the fiber raw material is not particularly limited as long as fine fibers can be obtained and an ionic substituent is introduced.
When a compound having a phosphoric acid-derived group is used as the compound that reacts with the fiber raw material, it is not particularly limited, but is composed of phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, or a salt or ester thereof. It is at least one selected from the group. Among these, a compound having a phosphate-derived group is preferable because it is low-cost, easy to handle, and can further improve the refinement (defibration) efficiency by introducing a phosphate-derived group into the fiber raw material. There is no particular limitation.

The compound having a phosphoric acid-derived group is not particularly limited, but phosphoric acid, lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, lithium polyphosphate Can be mentioned. Furthermore, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate and sodium polyphosphate which are sodium salts of phosphoric acid are mentioned. Furthermore, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate which are potassium salts of phosphoric acid are mentioned. Further examples include ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate, which are ammonium salts of phosphoric acid.
Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, and ammonium salt of phosphoric acid are preferable from the viewpoint of high efficiency of introduction of a group derived from phosphoric acid and easy industrial application. Sodium dihydrogen and disodium hydrogen phosphate are more preferable, but not particularly limited.

In addition, the compound is preferably used as an aqueous solution because of the uniformity of the reaction and the introduction efficiency of the group derived from phosphoric acid, but it is not particularly limited. The pH of the aqueous solution of the compound is not particularly limited, but is preferably 7 or less because of the high efficiency of introducing a phosphoric acid-derived group. Although pH 3-7 is more preferable from a viewpoint of suppressing hydrolysis of a fiber, it is not specifically limited.
In the present embodiment, for example, the compound having a phosphate-derived group is selected from urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, benzoleinurea, and hydantoin. It is mentioned as a preferable aspect to make it react with a fiber raw material with at least 1 type.

  When a compound having a carboxylic acid-derived group is used as the compound that reacts with the fiber raw material, the compound having a carboxylic acid-derived group, an acid anhydride of the compound having a carboxylic acid-derived group, and the like are not particularly limited. At least one selected from the group consisting of

  The compound having a carboxylic acid-derived group is not particularly limited, but a dicarboxylic acid compound such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid or itaconic acid, or a tricarboxylic acid compound such as citric acid or aconitic acid. Is mentioned.

  The acid anhydride of the compound having a carboxylic acid-derived group is not particularly limited, but acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, etc. Things.

  The derivative of the compound having a carboxylic acid-derived group is not particularly limited, and examples thereof include an acid anhydride imidized compound having a carboxylic acid-derived group and an acid anhydride derivative of a compound having a carboxylic acid-derived group. . The acid anhydride imidized compound having a carboxylic acid-derived group is not particularly limited, and examples thereof include imidized dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

  The acid anhydride derivative of the compound having a carboxylic acid-derived group is not particularly limited. For example, at least some of the hydrogen atoms of the acid anhydride of the compound having a carboxylic acid-derived group, such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride, are substituted (for example, alkyl group, And those substituted with a phenyl group or the like.

  Among the compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are easily applied industrially and easily gasified, but are not particularly limited.

  When a compound having a group derived from sulfuric acid is used as the compound that reacts with the fiber raw material, it is not particularly limited, but it is at least one selected from the group consisting of sulfuric anhydride, sulfuric acid and salts and esters thereof. Among these, sulfuric acid is preferred, but is not particularly limited because it is low in cost and can further improve the refinement (defibration) efficiency by introducing a sulfate group into the fiber raw material.

  By introducing a substituent into the fiber raw material, the dispersibility of the fiber in the solution is improved, and the refinement (defibration) efficiency can be increased.

The amount of the ionic substituent introduced is not particularly limited as long as sufficient miniaturization can be performed, but can be determined in consideration of the amount of substituent introduced as a sheet, as will be described later. When the sheet | seat of this invention contains the fine fiber which has an anionic substituent, 0.005 (alpha) -0.11 (alpha) are preferable per 1g (mass) of fibers, and the introduction amount of a substituent is 0.00. 01α to 0.08α is more preferable. If the introduction amount of the substituent is 0.005α or more, the fiber raw material can be easily refined (defibration). If the introduction amount of the substituent is 0.11α or less, dissolution of the fiber can be suppressed. However, (alpha) is the quantity (unit: mmol / g) by which the functional group which the compound which reacts with a fiber material can react, for example, a hydroxyl group and an amino group, is contained per 1 g of fiber materials.
In addition, the measurement of the introduction amount (titration method) of substituents on the fiber surface can be performed by the following method, unless otherwise specified:
A fine fiber-containing slurry containing about 0.04 g of solid content in an absolutely dry mass is collected and diluted to about 50 g using ion-exchanged water. While stirring this solution, the change in the value of electrical conductivity when a 0.01N sodium hydroxide aqueous solution was added dropwise was measured, and the amount of 0.01N sodium hydroxide aqueous solution added when the value was minimized was measured. The amount dropped at the titration end point. The content X of the substituent on the cellulose surface is represented by X (mmol / g) = 0.01 (mol / l) × V (ml) / W (g). Here, V: A dripping amount (ml) of 0.01N sodium hydroxide aqueous solution, W: Solid content (g) contained in the slurry containing fine cellulose fibers.

  When the introduced substituent is at least one selected from the group consisting of a phosphoric acid-derived group, a carboxylic acid-derived group and a sulfuric acid-derived group, the amount of substituent introduction is not particularly limited, but 0 0.001 to 5.0 mmol / g. It may be 0.05 to 4.0 mmol / g, or 0.1 to 2.0 mmol / g.

The cationic substituent can be introduced into the fiber raw material, for example, by adding a cationizing agent and an alkali compound to the fiber raw material and reacting them. As the cationizing agent, one having a quaternary ammonium group and a group that reacts with a hydroxy group of cellulose can be used. Examples of the group that reacts with the hydroxy group of cellulose include an epoxy group, a functional group having a halohydrin structure, a vinyl group, and a halogen group.
Specific examples of the cationizing agent include glycidyltrialkylammonium halides such as glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride or halohydrin type compounds thereof.

  The alkali compound used in the cationization step contributes to the promotion of the cationization reaction. The alkali compound may be an inorganic alkali compound or an organic alkali compound.

Examples of inorganic alkali compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphoric acids. Salt.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the alkaline earth metal hydroxide include calcium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate.
Examples of the alkali metal phosphate include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

Examples of the organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums, aromatic ammoniums, heterocyclic compounds and their hydroxides, carbonates, and phosphates. For example, ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, etc. Can be mentioned.
The said alkali compound may be single 1 type, and may combine 2 or more types.

  Among the above alkali compounds, sodium hydroxide and potassium hydroxide are preferable because the cationization reaction is more likely to occur and the cost is low. Although the quantity of an alkali compound changes according to the kind of alkali compound, it shall be in the range of 1-10 mass% with respect to a pulp absolute dry mass, for example.

  Since the cationizing agent and the alkali compound can be easily added to the pulp, it is preferable to form a solution. The solvent used for the solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferable, and an aqueous solvent containing at least water is more preferable.

  In this production method, it is preferable that the solvent substance amount per 1 g of the pulp dry mass at the start of the cationization reaction is 5 to 150 mmol. The substance amount of the solvent is more preferably 5 to 80 mmol, and further preferably 5 to 60 mmol. In order to bring the pulp content during the cationization reaction into the above range, for example, a pulp having a high content (that is, having a low water content) may be used. Moreover, it is preferable to reduce the amount of solvent contained in the solution of the cationizing agent and the alkali compound.

  The reaction temperature in the cationization step is preferably in the range of 20 to 200 ° C, more preferably in the range of 40 to 100 ° C. If the reaction temperature is not less than the lower limit, sufficient reactivity can be obtained, and if the reaction temperature is not more than the upper limit, the reaction can be easily controlled. In addition, there is an effect of suppressing coloring of the pulp after the reaction. The time of the cationization reaction varies depending on the type of pulp and cationizing agent, pulp content, reaction temperature, etc., but is usually in the range of 0.5 to 3 hours.

  The cationization reaction may be performed in a closed system or an open system. Further, the solvent may be evaporated during the reaction, and the amount of the solvent substance per 1 g of the pulp dry mass at the end of the reaction may be lower than that at the start of the reaction.

  By introducing a substituent into the fiber raw material, the dispersibility of the fiber in the solution can be improved, and the fibrillation efficiency can be increased.

<Acid treatment or base treatment>
If necessary, after the step of introducing an ionic substituent into the fiber raw material to obtain an ionic substituent-introduced fiber, before the step of treating the ionic substituent with an organic ion, an anionic substituent An acid treatment can be performed on fibers having a base, and a base treatment can be performed on fibers having a cationic substituent. The acid used for the acid treatment is preferably an acid having an ionization degree equal to or higher than the introduced anionic substituent, but is not particularly limited. The acid treatment can be performed using, for example, one or more selected from the group consisting of hydrochloric acid, nitric acid and sulfuric acid. The base used for the base treatment is preferably a base having an ionization degree equal to or higher than the introduced cationic substituent, but is not particularly limited. The base treatment can be performed using, for example, one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, and calcium hydroxide. By such treatment, the introduced ionic substituent becomes sufficiently H-type or OH-type, and organic ions can be added to the ionic substituent more easily.

  The acid treatment or base treatment method can be carried out, for example, by immersing the ionic substituent-introduced fiber in an acid solution or a base solution. As the solvent in the acid solution or the base solution, at least one of water and an organic solvent can be used. A polar one (polar organic solvent such as water or alcohol) is preferable, and an aqueous solvent containing water is more preferable. A particularly preferred example of the acid solution is hydrochloric acid, and a particularly preferred example of the base solution is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.

  In the case of acid treatment, the pH of the acid solution at 25 ° C. can be appropriately determined, but is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. In the case of the base treatment, the pH of the base solution at 25 ° C. can be appropriately determined, but is preferably 9 or more, more preferably 10 or more, and further preferably 11 or more.

  In order to reduce the amount of acid or base used, the fibers having ionic substituents may be washed before the acid treatment or base treatment step. For washing, at least one of water and an organic solvent can be used. Further, after the acid treatment or the base treatment, the treated fiber having an ionic substituent may be washed with at least one of water and an organic solvent. In either case, the washing operation can be repeated.

[Step (2): Step of obtaining an ionic substituent-introduced fine fiber by refining the ionic substituent-introduced fiber]
During the refinement (defibration) process, the fibers are dispersed in a solvent. The type of the solvent is not particularly limited as long as it can be appropriately refined (sometimes referred to as defibration), but an aqueous solvent (water or a mixture of water and an organic solvent) can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and tbutyl alcohol. Further, ketones such as acetone and methyl ethyl ketone (MEK), ethers such as diethyl ether and tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like can be mentioned. Only one organic solvent may be used, or two or more organic solvents may be used.

  The dispersion concentration is preferably from 0.1 to 20% by mass, and more preferably from 0.5 to 10% by mass. This is because if the content is equal to or higher than the lower limit, the processing efficiency is improved, and if the content is equal to or lower than the upper limit, blockage in the defibrating apparatus can be prevented.

  The defibrating apparatus is not particularly limited. Examples include a high-speed defibrator, a grinder (stone mortar-type pulverizer), a high-pressure homogenizer, an ultra-high-pressure homogenizer, a CLEARMIX, a high-pressure collision-type pulverizer, a ball mill, a bead mill, a disk refiner, and a conical refiner. In addition, a wet pulverizing apparatus such as a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, and a beater can be used as appropriate.

  The refinement process is performed until fibers having a desired average fiber diameter are obtained. A fine fiber dispersion (slurry) is obtained by the refining treatment. The obtained fine fiber dispersion may contain fibers having a fiber width of more than 1000 nm, but preferably does not contain fibers having a fiber width of more than 1000 nm. The density | concentration of a fine fiber here is 0.1-20 mass%, for example, and may be 0.5-10 mass%.

[Process of treating ionic substituent with organic ion]
In the present invention, the ionic substituent is treated with an organic ion before the step (3).

  This step may be performed before the miniaturization treatment in step (2). Specifically, organic ions are introduced into the fiber dispersion before the micronization treatment. This aspect has an advantage that the washing load of organic ions is low, and surplus organic ions can be sufficiently removed by washing. In addition, since excess organic ions can be sufficiently removed, there is an advantage that the transparency of the obtained sheet becomes higher.

  This process can also be performed after the miniaturization process of a process (2). Specifically, organic ions are introduced into the fine fiber dispersion after the refinement treatment. According to this aspect, many kinds of fine organic ions can be introduced.

  The method of treatment with organic ions is not particularly limited as long as the ionic substituent of the fiber and the organic ions can form an ion pair. Typically, it is carried out by adding an aqueous solution of a compound that is an organic ion source to a fiber before dispersion or a dispersion of fine fibers. The concentration of the aqueous solution used depends on the solubility of the compound in water, but can be 0.1% by mass or more, preferably 1.0% by mass or more, and more preferably 5.0% by mass or more. It is more preferable. The upper limit value may be determined from an economical viewpoint, but is preferably 40% by mass or less, and more preferably 35% by mass or less from the viewpoint of ensuring the transparency of the sheet. The amount of organic ions used is preferably an amount capable of forming ion pairs with many of the ionic substituents introduced into the sheet. For example, at least 50% or more, preferably 60% or more, more preferably 70% or more, more preferably 80% or more, and more preferably 90% or more of the ionic substituents of the introduced substituent can form ion pairs. Can be used in any amount.

  After the treatment with organic ions, washing can be performed as necessary. Washing can be performed with water or an aqueous solvent, preferably water.

  By treatment with organic ions, it is considered that organic ions and ionic substituents on the fibers form ion pairs, and aggregation of fine fibers during sheet formation is suppressed. As a result, the occurrence of wrinkling and cracking of the sheet is considered to be suppressed. Furthermore, it is considered that the sheet can be dried at a higher temperature and in a shorter time.

[Step (3): Step of preparing a sheet from ionic substituent-introduced fine fibers treated with organic ions]
A sheet is prepared from a dispersion (slurry) of fine fibers obtained by the refinement treatment. The method for preparing the sheet is not particularly limited, but can typically be based on the following papermaking method, coating method, or the like.

<Papermaking method>
In addition to continuous paper machines such as long-mesh type, circular net type, and inclined type, which use fine fiber-containing slurry for ordinary paper making, multi-layered paper making machines combining these, and well-known paper making methods such as hand-making Paper is made and can be made into a sheet in the same manner as ordinary paper. That is, it is possible to obtain a sheet by filtering and dewatering the fine fiber-containing slurry on a wire to obtain a wet paper sheet, followed by pressing and drying. The concentration of the slurry is not particularly limited, but is preferably 0.05 to 5% by mass. If the concentration is too low, filtration takes a long time. Conversely, if the concentration is too high, a uniform sheet cannot be obtained, which is not preferable. When the slurry is filtered and dehydrated, the filter cloth at the time of filtration is not particularly limited, but it is important that the fine fibers do not pass and the filtration rate is not too slow. Although it does not specifically limit as such a filter cloth, The sheet | seat, fabric, and porous film which consist of organic polymers are preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) and the like are preferable. Specific examples include a porous film of polytetrafluoroethylene having a pore diameter of 0.1 to 20 μm, for example, 1 μm, and polyethylene terephthalate or polyethylene fabric having a pore diameter of 0.1 to 20 μm, for example, 1 μm, but are not particularly limited.

<Coating method>
The coating method is a method of obtaining a sheet by coating a fine fiber-containing slurry on a base material and drying the slurry to peel the fine fiber-containing layer formed from the base material. By using a coating apparatus and a long base material, sheets can be continuously produced. The quality of the base material is not particularly limited, but the one having higher wettability to the fine fiber-containing slurry may be able to suppress the shrinkage of the sheet during drying, but the sheet formed after drying is more easily peeled off It is preferable to select what can be done. Among them, a resin plate or a metal plate is preferable, but is not particularly limited. Among them, suitable ones are preferably used alone or laminated. For example, resin plates such as acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, polyvinylidene chloride plates, metal plates such as aluminum plates, zinc plates, copper plates, iron plates, etc., and those whose surfaces are oxidized, stainless steel Although a board, a brass board, etc. can be used, it is not specifically limited. In order to apply the fine fiber-containing slurry onto the base material, various coaters that can apply a predetermined amount of slurry to the base material may be used. Although not particularly limited, for example, a roll coater, a gravure coater, a die coater, a curtain coater, a spray coater, a blade coater, a rod coater, an air doctor coater, etc. can be used, among which a die coater, curtain coater, spray coater, air doctor coater can be used. A coating method such as the above is effective for uniform coating. As will be described later, when a sheet is used as a laminate, it may not be necessary to peel off the substrate.

<Sheet thickness>
The thickness of the sheet to be prepared is not particularly limited, and can be appropriately determined according to the application. Based on the finished basis weight or thickness of the sheet, the amount of slurry is measured, and papermaking or coating is performed. Can do.

<Dehydration and drying>
After papermaking or coating, if necessary, at least one of dehydration and drying is performed to form a sheet. In addition, since dehydration and drying are performed with a predetermined aqueous solution in order to reduce organic ions in the subsequent step (4), the dehydration and drying can be performed until moisture is removed to some extent. It is considered that it does not have to be performed completely as in the case of obtaining a sheet as a final product. Although it does not specifically limit as a dehydration method, The dehydration method normally used by manufacture of paper is mentioned, The method of dehydrating with a roll press after dehydrating with a long net, a circular net, an inclined wire, etc. is preferable. Further, the drying method is not particularly limited, and examples thereof include methods used in paper production. For example, methods such as a cylinder dryer, a Yankee dryer, hot air drying, and an infrared heater are preferable.

  Although it does not specifically limit as a drying method, Either a non-contact drying method or the method of drying while restraining a sheet | seat may be sufficient, and these may be combined.

  The non-contact drying method is not particularly limited, but a method of drying by heating with hot air, infrared rays, far infrared rays or near infrared rays (heating drying method) or a method of drying in vacuum (vacuum drying method) is applied. Can do. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Although drying by infrared rays, far infrared rays, or near infrared rays can be performed using an infrared device, a far infrared device, or a near infrared device, it is not particularly limited. Although the heating temperature in a heat drying method is not specifically limited, It is preferable to set it as 40-120 degreeC, and it is more preferable to set it as 40-105 degreeC. If the heating temperature is at least the lower limit value, the dispersion medium can be volatilized quickly, and if it is at most the upper limit value, the cost required for heating and the discoloration due to the heat of the fine fibers can be suppressed.

(Other fibers)
In preparing the sheet, although not particularly limited, the sheet can be prepared by mixing at least one kind of the fine fibers and fibers other than the fine fibers (hereinafter referred to as “additional fibers”). Examples of the additional fiber include inorganic fiber, organic fiber, synthetic fiber, semi-synthetic fiber, and recycled fiber, but are not particularly limited. Examples of inorganic fibers include, but are not limited to, glass fibers, rock fibers, and metal fibers. Examples of organic fibers include, but are not limited to, fibers derived from natural products such as cellulose, carbon fibers, pulp, chitin, and chitosan. Examples of synthetic fibers include, but are not limited to, nylon, vinylon, vinylidene, polyester, polyolefin (for example, polyethylene, polypropylene, etc.), polyurethane, acrylic, polyvinyl chloride, aramid, and the like. Semi-synthetic fibers include but are not limited to acetate, triacetate, promix and the like. Examples of the regenerated fiber include, but are not limited to, rayon, cupra, polynosic rayon, lyocell, and tencel. The additional fibers can be subjected to treatment such as chemical treatment and defibration treatment as necessary.

  Although mixing is not specifically limited, For example, before papermaking or coating, it can be performed by adding other fibers to the fine fiber-containing slurry. When the additional fiber is subjected to chemical treatment, defibrating treatment, etc., it can be mixed with fine fibers and then subjected to chemical treatment, defibrating treatment, etc., and the additional fiber can be chemically treated, defibrated. It can also be mixed with fine fibers after being treated. Mixing those having the same average fiber diameter is preferable in that it is easier to mix uniformly.

  When the additional fiber is mixed, the addition amount of the additional fiber in the total amount of the fine fiber and the additional fiber is not particularly limited, but is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30%. It is below mass%. Especially preferably, it is 20 mass% or less.

  Moreover, you may add a hydrophilic polymer in the case of preparation of a sheet | seat. Examples of hydrophilic polymers include polyethylene glycol, cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.), casein, dextrin, starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), Polyethylene oxide, polyvinyl pyrrolidone, polyvinyl methyl ether, polyacrylic acid salts, polyacrylamide, acrylic acid alkyl ester copolymer, urethane copolymer and the like can be mentioned, but are not particularly limited.

  A hydrophilic low molecular weight compound can also be used in place of the hydrophilic polymer. Examples of hydrophilic low molecular weight compounds include, but are not limited to, glycerin, erythritol, xylitol, sorbitol, galactitol, mannitol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and butylene glycol.

  The mixing of the hydrophilic polymer or the hydrophilic low molecular compound is not particularly limited. For example, the hydrophilic polymer or the hydrophilic low molecular compound is added to the fine fiber-containing slurry before papermaking or coating. Can be done. The addition amount in the case of adding a hydrophilic polymer or a hydrophilic low molecular weight compound is preferably 1 to 200 parts by mass, more preferably 1 to 150 parts by mass, further preferably 100 parts by mass of the solid content of the fine fiber. Is 2 to 120 parts by mass, particularly preferably 3 to 100 parts by mass, but is not particularly limited.

[Step (4): Step of reducing organic ions contained in sheet]
In this invention, the process of reducing the organic ion contained in a sheet | seat is included after a process (3). The method for reducing the organic ions is not particularly limited as long as the organic ions can be reduced to a desired level. For example, by desorbing the ionic substituent that forms an ion pair with the organic ion (desorption of the ionic substituent) or by replacing the organic ion with another ion (counter ion exchange), It can be carried out.

<Elimination of ionic substituent>
By removing all or part of the introduced ionic substituent, organic ions can be removed from the sheet. Desorption can be performed by treating the sheet obtained in step (3) with at least one of water and alcohol. Alcohols include polyhydric alcohols, and when polyhydric alcohols are used, desorption can be achieved by boiling the sheet with polyhydric alcohol and can also be accomplished by treating the sheet with polyhydric alcohol vapor. . When at least one of water and a low-boiling alcohol is used, desorption can be achieved by treating the sheet with polyhydric alcohol vapor.

(Polyhydric alcohol boiling method)
In one of the preferred embodiments of the present invention, when the substituent is eliminated in the step (4), the sheet is boiled with a polyhydric alcohol. A polyhydric alcohol means what has two or more OH groups among alcohol. When using a polyhydric alcohol, it is preferable to use a OH / C ratio of 0.15 or more. More preferably, 0.2 or more is used. “OH / C ratio” refers to the number of OH groups per carbon (C) atom contained in a molecule. For example, ethylene glycol (C ₂ H ₆ O ₂ ) has an OH / C ratio of 1, and diethylene glycol. The OH / C ratio of (C ₄ H ₁₀ O ₃ ) is 0.67.

  Examples of polyhydric alcohols having an OH / C ratio of 0.2 or more are ethylene glycol, diethylene glycol, propylene glycol (1,2-propanediol), glycerin (glycerol, 1,2,3-propanetriol) , Pentanediol, octanediol, decanediol, sugar alcohol (for example, sorbitol, lactitol, maltitol, mannitol, xylitol).

  The amount of polyhydric alcohol used in step (4) in the case of boiling with polyhydric alcohol is not particularly limited as long as it can sufficiently remove the substituent, but can be appropriately determined based on the sheet mass. it can. Also when using any alcohol, 1-100 mass parts of alcohol can be used with respect to 1 mass part of sheet | seats, for example. If the amount of alcohol used relative to 1 part by mass of the sheet is less than 1 part by mass, desorption may not be performed sufficiently.

  The temperature of the boiling treatment is not particularly limited as long as the substituent can be sufficiently eliminated, but it can be 140 ° C. or higher, preferably 160 ° C. or higher, and more preferably 170 ° C. or higher. However, it is preferable to select a temperature at which decomposition of the fiber raw material is suppressed, and the temperature is not particularly limited. Moreover, you may add additives, such as an acid or a base, in the case of a heating suitably.

  The time for the boiling treatment is not particularly limited as long as the elimination of the substituent can be sufficiently performed. For example, when glycerin, which is a polyhydric alcohol having an OH / C ratio of 1, is used as the alcohol, 10 to 120 minutes, preferably 15 to 90 minutes, and more preferably 15 to 60 minutes. The same applies when other alcohols are used.

(Steam method)
Vapor may be used when the substituent is eliminated in step (4). The type of the vapor is not particularly limited, and it is considered that the introduced substituent can be eliminated if the vapor is a substance having an OH group. From the viewpoint of high ability to remove a substituent, the vapor is preferably at least one of water vapor and alcohol vapor. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, and t-butanol, and the polyhydric alcohols described above. One particularly preferred example of steam is steam. Water vapor is lower alcohol such as water, methanol, ethanol, propanol, etc., preferably an alcohol having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms; 3 to 6 carbon atoms such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. The following ketones; linear or branched saturated hydrocarbons or unsaturated hydrocarbons having 1 to 6 carbon atoms; aromatic hydrocarbons such as benzene and toluene may be included.

  The treatment with steam in the step (4) is not particularly limited, but can be performed by bringing the sheet into contact with pressurized steam (pressurized saturated steam) or superheated steam.

  For the treatment with pressurized steam, for example, a conventional autoclave can be used. A typical autoclave has, for example, a cylindrical container and a lid that opens and closes the upper surface opening of the container. An exhaust port, a thermometer, and a pressure gauge are installed on the lid, and a drain valve is installed on the bottom of the container. Has been. When using this autoclave, first, with the drain valve closed, water is poured into the container, and a sheet is placed above the water in the container, and the lid is closed. After that, when the exhaust port is opened and the container is heated, the air in the container comes out from the exhaust port initially, but steam gradually begins to spout out. When the container is filled with water vapor, the exhaust port is closed, and then heating is continued while adjusting the temperature and pressure. When the predetermined time has elapsed, heating is stopped, and after cooling, the sheet in the container is taken out.

  The treatment with pressurized steam in the step (4) can be performed within a temperature range of 100 ° C. to 250 ° C., for example. From the viewpoint of processing efficiency, it can be set to 100 ° C. or higher, preferably 120 ° C. or higher, and more preferably 140 ° C. or higher. Moreover, from a viewpoint of coloring prevention of a sheet | seat, it can be 250 degrees C or less, Preferably it is 200 degrees C or less, More preferably, it is 180 degrees C or less.

  The treatment pressure with pressurized steam in the step (4) is preferably 0.1 MPa or more, more preferably 0.5 MPa or more, and further preferably 0.8 MPa or more. In any case, it is preferably 30 MPa or less, more preferably 25 MPa or less, further preferably 20 MPa or less, and further preferably 18 MPa or less.

  The treatment time with the pressurized steam in the step (4) depends on the temperature and pressure, but can be carried out until the desired desorption can be achieved. For example, it is 5 minutes or more, preferably 10 minutes or more, more preferably 30 minutes or more. In any case, the treatment time can be 24 hours or less, preferably 10 hours or less, and more preferably 3 hours or less. The processing time represents the time during which the heating temperature is maintained, with the time when the heating temperature is reached as 0 hours.

The treatment with superheated steam can be performed, for example, by spraying superheated steam on the sheet. Superheated steam, for example, the supply amount is sprayed from the nozzle to the sheet in the range of ^{500g / m 3 ~600g / m 3} . The temperature of the superheated steam can be controlled to 100 ° C. to 160 ° C. at 1 atmosphere, for example. In this case, the supply time of the superheated steam can be 4 seconds to 120 seconds.

<Counterion exchange>
Organic ions can be removed from the sheet by counter-ion exchange with other suitable ions. When the ionic substituent is anionic, the exchanged counter ion is not particularly limited, and is, for example, a hydrogen ion, an alkali metal ion, or an alkaline earth metal ion. More specifically, they are hydrogen ion, lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, calcium ion, strontium ion, barium ion, europium ion, thallium ion or guanidine ion. Preferred examples are sodium ion, potassium ion or calcium ion. When the ionic substituent is cationic, the exchanged counter ion is not particularly limited, but is, for example, a halide ion or an anionic polyatomic ion. More specifically, fluoride ions, chloride ions, bromide ions, iodide ions, hydroxide ions, cyanide ions, nitrate ions, nitrite ions, dihydrogen phosphate ions, and bicarbonate ions. Preferred examples are fluoride ion and chloride ion.

  Prior to the counter ion exchange, the fiber having an anionic substituent can be subjected to an acid treatment, and the fiber having a cationic substituent can be subjected to a base treatment. The acid used for the acid treatment is preferably an acid having an ionization degree equal to or higher than an anionic substituent, but is not particularly limited. The acid treatment can be performed using, for example, one or more selected from the group consisting of hydrochloric acid, nitric acid and sulfuric acid. The base used for the base treatment is preferably a base having an ionization degree equal to or higher than that of the cationic substituent, but is not particularly limited. The base treatment can be performed using, for example, one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, and calcium hydroxide. By such treatment, the ionic substituent becomes sufficiently H-type or OH-type, and a counter ion in place of the organic ion can be more easily added to the ionic substituent. For the method and conditions of acid treatment or base treatment, the acid treatment or base treatment in step (1) described above can be referred to.

<Sheet>
Step (4) can be performed until the organic ions are reduced to a desired level. After the treatment by ion exchange, if necessary, washing, dehydration and drying can be performed to obtain a final sheet. Washing can be performed with water or an aqueous solvent, preferably water. Dehydration and drying can be performed by the method and conditions described in the section of step (3).

  In the present invention, while maintaining the advantage of suppressing the occurrence of wrinkling and cracking of the sheet during sheet formation with organic ions, organic ions that can affect the strength of the sheet after sheet formation are reduced to an appropriate level. Therefore, a sheet excellent in strength can be produced. Moreover, coloring by high temperature processing is suppressed because organic ions are reduced.

3. Lamination of sheets, application, etc. The sheet of the present invention can be used as a single sheet, but at least one of an organic layer and an inorganic layer is formed on at least one surface and used as a laminate. You can also. By lamination, water resistance (water resistance, moisture resistance, water repellency) can be further imparted. When laminating the inorganic layer and the organic layer, the order is not particularly limited, but first laminating the organic layer on the surface of the base sheet smoothes the surface for forming the inorganic layer, and the formed inorganic layer Is preferable in that it can have fewer defects. In addition, other constituent layers other than the organic layer and the inorganic layer, for example, an easy adhesion layer for facilitating adhesion of the upper layer may be included. In the case of lamination, when used for applications in which transparency is particularly important, it is preferable not to include a heating step or a UV irradiation step that promotes yellowing of the sheet. It is preferable that the laminated body obtained by lamination includes at least one inorganic layer and at least one organic layer formed on at least one side of a base sheet layer made of a fine fiber-containing sheet. The number of layers such as an inorganic layer and an organic layer is not particularly limited. From the viewpoint of sufficient moisture resistance while maintaining flexibility and transparency, for example, it is preferable to laminate two to 15 layers of inorganic layers and organic layers alternately on one side, for example, 3 to 7 layers. More preferably, the layers are laminated.

  The material constituting the inorganic layer is not particularly limited, but for example, aluminum, silicon, magnesium, zinc, tin, nickel, titanium; these oxides, carbides, nitrides, oxycarbides, oxynitrides, or oxycarbonitrides Or a mixture thereof. From the viewpoint that high moisture resistance can be stably maintained, silicon oxide, silicon nitride, silicon oxide carbide, silicon oxynitride, silicon oxycarbonitride, aluminum oxide, aluminum nitride, aluminum oxide carbide, aluminum oxynitride, or these Mixtures are preferred.

  The resin used for the formation of the organic layer is not particularly limited, but epoxy resin, acrylic resin, oxetane resin, silsesquioxane resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, silicon resin, A polyurethane resin, a silsesquioxane resin, a diallyl phthalate resin, or the like can be given. In order to obtain a low water-absorbing laminate, the resin preferably has few hydrophilic functional groups such as a hydroxy group, a carboxyl group, or an amino group.

  Since the sheet and laminate of the present invention have excellent transparency and strength, they are suitable for use as packaging materials for foods, cosmetics, pharmaceuticals, personal computers, home appliances and the like by taking advantage of characteristics such as light weight.

  In addition, the sheet and the laminate provided by the preferred embodiment are suitable for use as a display element, a lighting element, a solar cell or window material, or a panel or substrate for these, because yellowing is suppressed and optical properties are excellent. ing. More specifically, the sheet and the laminate are suitable for use as a flexible display, a touch panel, a liquid crystal display, a plasma display, an organic EL display, a field emission display, a rear projection television, and the like, and an LED element.

  Furthermore, the sheet and the laminate are suitable for use as a substrate for solar cells such as silicon solar cells and dye-sensitized solar cells. For use as a substrate, it may be laminated with a barrier film, ITO, TFT or the like. It is also suitable for use as a window material for automobiles, railway vehicles, aircraft, houses, office buildings, factories and the like. As a window material, you may laminate | stack films | membranes, such as a fluorine film and a hard-coat film | membrane, and an impact-resistant and light-resistant material as needed.

  Sheets and laminates can be used as structural materials other than those for transparent materials, taking advantage of properties such as low linear expansion coefficient, high elasticity, high strength, and light weight. Especially suitable for automobiles such as glazing, interior materials, skins, bumpers, railway vehicles, aircraft materials, personal computer casings, home appliance parts, packaging materials, building materials, civil engineering materials, marine products, and other industrial materials. Can be used.

  Sheets and laminates can be used for various products. Examples of products include computers, tablet terminals, mobile phones using the above display elements or displays; light bulbs, lighting (lighting fixtures / lighting devices), lighting, liquid crystal panel backlights, pockets using lighting elements Electric lights, bicycle headlights, car interior lights and meter lamps, traffic lights, high altitude lighting inside and outside buildings, home lighting, school lighting, medical lighting, factory lighting, plant growing lights, video lighting lighting Lighting in 24 hours or late-night stores such as convenience stores, lighting in refrigeration / freezers; houses, buildings, automobiles, rail cars, aircraft, home appliances using windows and structural materials, etc. be able to.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, the scope of the present invention is not limited by an Example.

<Example 1>
[Manufacture of phosphorylated pulp]
As softwood kraft pulp, it was used Oji Paper Co., Ltd. Pulp (Canadian Standard Freeness of solids 93 wt% basis weight 208g / m ² by sheet maceration is measured according to JIS P8121 (CSF) 700ml). 100 parts by mass of the above-mentioned softwood kraft pulp is impregnated with a mixed aqueous solution of ammonium dihydrogen phosphate and urea, and compressed to 49 parts by mass of ammonium dihydrogen phosphate and 130 parts by mass of urea. Pulp was obtained. The obtained chemical solution-impregnated pulp was dried with a dryer at 105 ° C. to evaporate the moisture and pre-dried. Then, it heated for 10 minutes with the ventilation dryer set to 140 degreeC, the group derived from phosphoric acid was introduce | transduced into the cellulose in a pulp, and the phosphorylated pulp was obtained.

[Cleaning of phosphorylated pulp]
The step of pouring 10000 parts by mass of ion-exchanged water with respect to 100 parts by mass as the absolute dry mass of the obtained phosphorylated pulp, stirring and dispersing uniformly, and then performing filtration and dehydration to obtain a dehydrated sheet twice Repeatedly, a dehydrated sheet A of phosphorylated pulp was obtained.

[Multiple phosphorylation]
Using the obtained phosphorylated pulp dehydrated sheet A as a raw material, the process of introducing phosphoric acid-derived groups and the process of filtration and dehydration were repeated twice more in the same manner as above (the total number of phosphorylation and filtration dehydration was 3 times) to obtain a dehydrated sheet B of phosphorylated pulp.

[Content of introduced substituents]
In the dehydrated sheet B of the phosphorylated pulp, the amount of phosphoric acid-derived groups introduced by the following titration method was 1.4 mmol / g.

[Measurement of substituent introduction amount (introduction amount of phosphoric acid-derived group)]
The amount of substituent introduction is the amount of phosphoric acid-derived groups introduced into the fiber raw material. The larger the value, the more phosphoric acid-derived groups are introduced. The amount of substituent introduced was measured by diluting the target fine fibrous cellulose with ion-exchanged water so that the content was 0.2% by mass, and then treating with ion-exchange resin and titration with alkali. In the treatment with an ion exchange resin, 1/10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) is added to the 0.2 mass% cellulose fiber-containing slurry, and the mixture is shaken for 1 hour. It was. Thereafter, the mixture was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry. In titration using an alkali, a change in the value of electrical conductivity indicated by the slurry was measured while adding a 0.1N sodium hydroxide aqueous solution to the cellulose fiber-containing slurry after ion exchange. That is, the alkali amount (mmol) required in the first region of the curve shown in FIG. 1 was divided by the solid content (g) in the titration target slurry to obtain the substituent introduction amount (mmol / g).

[Counterion conversion of phosphorylated pulp (H type)]
As an absolutely dry mass of the dehydrated sheet B of phosphorylated pulp, 5000 parts by mass of ion-exchanged water was added to 100 parts by mass for dilution. Next, 1N hydrochloric acid was added little by little while stirring to obtain a pulp slurry having a pH of 2 to 3. Thereafter, the pulp slurry was dehydrated to obtain a dehydrated sheet, and then ion-exchanged water was poured again, and the mixture was stirred and dispersed uniformly. Subsequently, excess hydrochloric acid was sufficiently washed away by repeating the operation of filtration and dehydration to obtain a dehydrated sheet. By the above procedure, phosphorylated pulp (H type) was obtained in which the counter ion of the group derived from phosphoric acid was hydrogen (H) ion.

[Addition of organic counter ions to phosphorylated pulp]
As an absolutely dry mass of the phosphorylated pulp (H type), 5000 parts by mass of ion-exchanged water was added to 100 parts by mass to dilute. Next, a 10% by mass tetrabutylammonium hydroxide aqueous solution was added little by little with stirring to obtain a pulp slurry having a pH of 10 to 12. Thereafter, the pulp slurry was dehydrated to obtain a dehydrated sheet, and then ion-exchanged water was poured again, and the mixture was stirred and dispersed uniformly. Subsequently, the operation of obtaining a dehydrated sheet by filtration and dehydration was repeated to sufficiently wash away the excess aqueous solution of tetrabutylammonium hydroxide. By the above procedure, phosphorylated pulp (TBA type) was obtained in which the counter ion of the group derived from phosphoric acid was tetrabutylammonium (TBA) ion.

[Machine processing]
Ion exchange water was added to the phosphorylated pulp (TBA type) to obtain a 1.0% by mass pulp suspension. This pulp suspension was passed five times at a pressure of 245 MPa with a wet atomizer (Sugino Machine Co., Ltd .: Ultimateizer) to obtain a fine fibrous cellulose suspension (TBA type).

[Sheet]
The concentration was adjusted so that the solid content concentration of the fine fibrous cellulose suspension (TBA type) was 0.5% by mass. The suspension was weighed so that the finished basis weight of the sheet was 75 g / m ² , developed on a commercially available acrylic plate, and dried in a constant temperature and humidity chamber of 35 ° C. and 15% RH. A damming metal frame (180 mm square) was disposed on the acrylic plate so as to have a predetermined basis weight. By the above procedure, a fine fibrous cellulose sheet (TBA type) was obtained.

[Dephosphorylation (removal of phosphate-derived groups and counter ions)]
As a spacer, a heat-resistant rubber sheet (manufactured by Shin-Etsu Chemical Co., Ltd., X-30-4084-U) with a 150 mm square gap was placed as a spacer, and 50 mL of glycerin was developed in the hole. A fine fibrous cellulose sheet (TBA type) cut into 120 mm square was immersed in it, and a stainless steel plate was placed on top of it, and installed in a heat press machine (manufactured by Imoto Seisakusho: manual hydraulic vacuum heating press) heated to 180 ° C. did. The fine fibrous cellulose sheet (TBA type) was treated at 180 ° C. for 30 minutes, and then immersed in 500 mL of water for cleaning. Washing was repeated three times, and the fine fibrous cellulose sheet was attached to a glass plate and heated and dried at 100 ° C. for 15 minutes to obtain a fine fibrous cellulose sheet from which phosphoric acid-derived groups and counterions were removed.

<Example 2>
[Counterion conversion of phosphorylated pulp (Na type)]
In the counter ion conversion (TBA type) of the phosphorylated pulp of Example 1, a 1N NaOH aqueous solution was used instead of the 10 mass% tetrabutylammonium hydroxide aqueous solution, so that the counter ion of the group derived from phosphoric acid was sodium ( Phosphorylated pulp (Na type) became Na) ions.

[Machine processing]
Ion exchange water was added to the phosphorylated pulp (Na type) to make a 1.0 mass% pulp suspension. This pulp suspension was passed 5 times at a pressure of 245 MPa with a wet atomizer (Sugino Machine Co., Ltd .: Ultimateizer) to obtain a fine fibrous cellulose suspension (Na type).

[Counterion conversion of fine fibrous cellulose suspension (Na type) (H type)]
The fine fibrous cellulose suspension (Na type) was diluted to 0.5% by mass with ion-exchanged water, and 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; Organo Corporation, conditioned) In addition, the mixture was stirred for 1 hour. Thereafter, the mixture was poured onto a mesh having an opening of 51 μm and filtered under reduced pressure to separate the resin and the slurry. By the above procedure, a fine fibrous cellulose suspension (H type) in which the counter ion of the group derived from phosphoric acid was hydrogen (H) ion was obtained.

[Addition of organic counter ions to fine fibrous cellulose suspension (H type)]
A 10 mass% tetrabutylammonium hydroxide aqueous solution was weighed so that the content of phosphoric acid-derived groups (1.5 mmol / g) and tetrabutylammonium ions were equivalent, and the fine fibrous cellulose suspension (H Type). Thereafter, the mixture was stirred for 1 hour to obtain a fine fibrous cellulose suspension (TBA type) in which the counter ion of the phosphoric acid-derived group was tetrabutylammonium (TBA) ion.

  The subsequent procedure was the same as in Example 1 to obtain a fine fibrous cellulose sheet from which phosphoric acid-derived groups and organic counter ions were removed.

<Example 3>
[Counterion exchange (removal of organic counterion)]
By immersing the fine fibrous cellulose sheet (TBA type) obtained in Example 2 in hydrochloric acid adjusted to pH 2 for 30 minutes, tetrabutylammonium ions are removed from the fine fibrous cellulose sheet (TBA type). The counter ion of the phosphoric acid-derived group was a hydrogen (H) ion. Then, it was immersed for 5 minutes in the sodium hydroxide aqueous solution which adjusted pH to 12, and the counter ion of the group derived from phosphoric acid was made into sodium (Na) ion. The fine fibrous cellulose sheet was attached to a glass plate and dried by heating at 100 ° C. for 15 minutes. By the above procedure, a fine fibrous cellulose sheet from which organic counter ions were removed was obtained.

<Example 4>
Except for using 10 mass% tetraethylammonium hydroxide aqueous solution instead of 10 mass% tetrabutylammonium hydroxide aqueous solution when organic counter ions were applied to the fine fibrous cellulose suspension (H type) in Example 2. In the same manner as in Example 2, a fine fibrous cellulose sheet from which phosphoric acid-derived groups and organic counter ions were removed was obtained.

<Example 5>
In addition to using a 10% by mass tetrabutylammonium hydroxide aqueous solution in place of the 10% by mass tetrabutylammonium hydroxide aqueous solution in addition of the organic counter ion to the fine fibrous cellulose suspension (H type) in Example 2, Obtained a fine fibrous cellulose sheet from which phosphoric acid-derived groups and organic counter ions were removed in the same manner as in Example 2.

<Example 6>
When organic counter ions were added to the fine fibrous cellulose suspension (H type) in Example 2, a 30% by mass lauryltrimethylammonium chloride aqueous solution (Daiichi Kogyo Seiyaku) was used instead of the 10% by mass tetrabutylammonium hydroxide aqueous solution. A fine fibrous cellulose sheet from which phosphoric acid-derived groups and organic counter ions were removed was obtained in the same manner as in Example 2 except that “Kachiogen TML” manufactured by the company was used.

<Example 7>
[Production of TEMPO oxidized pulp (TEMPO oxidation reaction)]
Undried Oji Paper Co., Ltd. softwood bleached kraft pulp equivalent to a dry mass of 100 parts by mass, TEMPO 1.25 parts by mass, and sodium bromide 12.5 parts by mass were dispersed in 10000 parts by mass of water. Subsequently, 13 mass% sodium hypochlorite aqueous solution was added so that the quantity of sodium hypochlorite might be 8.0 mmol with respect to 1.0 g of pulp, and reaction was started. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was considered complete when no change in pH was observed.

[Cleaning of TEMPO oxidized pulp]
Thereafter, this pulp slurry is dehydrated to obtain a dehydrated sheet, and then the process of pouring 5000 parts by mass of ion exchange water, stirring and uniformly dispersing, and dehydrating by filtration to obtain a dehydrated sheet is repeated twice. It was. The amount of substituents (groups derived from carboxylic acid) introduced by the titration method was 1.5 mmol / g.

[Counterion exchange of TEMPO oxidized pulp]
Furthermore, 5000 mass parts of ion exchange water was added to the obtained dehydration sheet for dilution. Next, 1N hydrochloric acid was added little by little while stirring to obtain a pulp slurry having a pH of 2 to 3. Thereafter, the pulp slurry was dehydrated to obtain a dehydrated sheet, and then ion-exchanged water was poured again, and the mixture was stirred and dispersed uniformly. Subsequently, excess hydrochloric acid was sufficiently washed away by repeating the operation of filtration and dehydration to obtain a dehydrated sheet. By the above procedure, TEMPO oxidized pulp (H type) was obtained in which the counter ion of the group derived from carboxylic acid was hydrogen (H) ion.

[Addition of organic counter ions to TEMPO oxidized pulp]
As the absolutely dry mass of the obtained TEMPO oxidized pulp (H type), 5000 parts by mass of ion-exchanged water was added to 100 parts by mass for dilution. Next, a 10% tetrabutylammonium hydroxide aqueous solution was added little by little with stirring to obtain a pulp slurry having a pH of 10 to 12. Thereafter, the pulp slurry was dehydrated to obtain a dehydrated sheet, and then ion-exchanged water was poured again, and the mixture was stirred and dispersed uniformly. Subsequently, the operation of obtaining a dehydrated sheet by filtration and dehydration was repeated to sufficiently wash away the excess aqueous solution of tetrabutylammonium hydroxide. By the above procedure, TEMPO oxidized pulp (TBA type) was obtained in which the counter ion of the carboxylic acid-derived group was tetrabutylammonium (TBA) ion.

  The subsequent procedure was the same as in Example 3 except that the TEMPO oxidized pulp (TBA type) was used instead of the phosphorylated pulp (TBA type), and a fine fibrous cellulose sheet from which organic counter ions were removed was obtained. It was.

<Reference Example 1>
In Example 1, mechanical treatment and sheet formation were performed without applying organic counter ions to the phosphorylated pulp. In addition, the remarkable crack generate | occur | produced in the case of sheeting, and the fine fibrous cellulose sheet was not obtained.

<Reference Example 2>
A fine fibrous cellulose sheet provided with tetrabutylammonium ions as organic counterions was obtained in the same manner as in Example 1 except that the counterions were not removed (removal of phosphate-derived groups and counterions). .

<Reference Example 3>
A fine fibrous cellulose sheet provided with tetrabutylammonium ions as an organic counter ion was obtained in the same manner as in Example 2 except that the counter ion was not removed (removal of phosphate-derived group and counter ion). .

<Reference Example 4>
A fine fibrous cellulose sheet provided with tetraethylammonium ions as an organic counterion was obtained in the same manner as in Example 4 except that the counterion was not removed (removal of phosphate-derived group and counterion).

<Reference Example 5>
A fine fibrous cellulose sheet provided with tetrabutylphosphonium hydroxide as an organic counter ion is obtained in the same manner as in Example 5 except that the removal of the counter ion (the removal of the phosphate-derived group and the counter ion) is not performed. It was.

<Reference Example 6>
A fine fibrous cellulose sheet provided with lauryltrimethylammonium ion as an organic counterion was obtained in the same manner as in Example 6 except that counterion removal (removal of phosphate-derived groups and counterion) was not performed. .

<Reference Example 7>
A fine fibrous cellulose sheet provided with tetrabutylammonium ions as organic counterions was obtained in the same manner as in Example 7 except that the counterions were not removed.

<Evaluation>
[Method]
The fine fibrous cellulose sheets produced in Examples 1 to 7 and Reference Examples 2 to 7 were evaluated according to the following evaluation methods. In Reference Example 1, since a fine fibrous cellulose sheet was not obtained, evaluation was not performed.
(1) Content of ionic substituent in fine fibrous cellulose sheet Phosphorus and sodium atom concentrations in the fine fibrous cellulose sheet were measured with a fluorescent X-ray analyzer (Spectras "PW2404"). That is, when the fine fibrous cellulose sheet is irradiated with X-rays, the inner shell electrons of phosphorus or sodium atoms are excited, and the phosphorus or sodium atoms released when the outer shell electrons transition to the vacancies. By measuring the intensity of characteristic X-rays, the concentration of phosphorus or sodium atoms was obtained. In Example 7 and Reference Example 7 containing a carboxylic acid-derived group as an ionic substituent, hydroxylation in which the fine fibrous cellulose sheet was adjusted to pH 12 before analysis with a fluorescent X-ray analyzer. It was immersed in an aqueous sodium solution for 5 minutes, and the counter ion of the group derived from carboxylic acid was defined as sodium (Na) ion.

  In calculating the content of the ionic substituent from the atomic concentration, calculation was performed from a calibration curve prepared by the following method. After preparing a fine fibrous cellulose sheet with a known content of phosphoric acid-derived groups and conducting fluorescent X-ray analysis, create a calibration curve for the characteristic X-ray intensity of phosphorus atoms and the content of phosphoric acid-derived groups did. Similarly, in the case of a group derived from a carboxylic acid, a fine fibrous cellulose sheet having a known content of the group derived from the carboxylic acid and having a sodium salt type is prepared, and the characteristic X-ray intensity of the sodium atom and the group derived from the carboxylic acid are produced. A calibration curve for the content of was prepared.

In Example 5 and Reference Example 5, the content of phosphoric acid-derived groups in the fine fibrous cellulose sheet was determined by subtracting the phosphorus atom concentration derived from tetrabutylphosphonium hydroxide described later.
In Table 1, the content of phosphoric acid-derived groups or carboxylic acid-derived groups with respect to the fine fibrous cellulose thus calculated is shown.

(2) Content of organic counter ion For Examples 1-4, 6, and 7, and Reference Examples 2-4, 6, and 7, a trace nitrogen analyzer ("TN-110" manufactured by Mitsubishi Chemical Analytech Co., Ltd.) Thus, the nitrogen atom concentration in the sheet was measured. That is, from the nitrogen atom concentration of the fine fibrous cellulose sheet obtained in Examples 1 to 6 and Reference Examples 2 to 6, using the nitrogen atom concentration of the fine fibrous cellulose sheet not provided with the organic counter ion as a reference value. By reducing the reference value, the concentration of nitrogen atoms derived from organic counter ions was used, and the organic counter ion content was calculated.

For Example 5 and Reference Example 5, the phosphorus atom concentration in the sheet was measured with a fluorescent X-ray analyzer (Spectras "PW2404"). That is, the intensity of the characteristic X-rays of phosphorus atoms emitted when electrons in the outer shell transition to vacancies generated by the excitation of inner electrons of phosphorus atoms when the sheet is irradiated with X-rays is measured. Thus, the concentration of phosphorus atoms was obtained. A filter paper having a known phosphorus introduction amount was prepared and subjected to fluorescent X-ray analysis in the same manner as the fine fibrous cellulose sheet, and then a calibration curve for the characteristic X-ray intensity of phosphorus atoms and the phosphorus introduction amount was prepared. By subtracting the phosphorus atom concentration of the fine fibrous cellulose sheet that has not been given the organic counter ion as the reference value from the phosphorus atom concentration calculated from the calibration curve, the phosphorus atom concentration derived from the organic counter ion is obtained as the organic counter ion. The content was calculated.
In Table 1, the content of organic counter ions with respect to the sheet thus calculated is shown.

(3) Density 100 mm square sheets cut into 100 mm square fine fibers were conditioned for 24 hours under conditions of 23 ° C. and 50% relative humidity, and then weighed to calculate rice basis weight (g / m ² ). Then, the density of the fine fibrous cellulose sheet was calculated by dividing by the thickness of the fine fibrous cellulose sheet.

(4) Wrinkles / Cracks When forming a sheet of fine fibrous cellulose suspension, in accordance with the size of each 180 mm damming metal frame, a square of 2 cm square is arranged on the back of the acrylic plate in a total of 9 × 9 in the vertical direction. The mass was described. The fine fibrous cellulose sheet was observed from above with the acrylic plate attached to the acrylic plate, and the masses where wrinkles and cracks were generated in the fine fibrous cellulose sheet were counted. The mass where wrinkles and cracks occurred was evaluated as ○ when the mass was less than 20% of the total mass, and x when the mass was 20% or more.

(5) Total light transmittance Based on JIS standard K7361, the total light transmittance was measured using the haze meter ("HM-150" by Murakami Color Research Laboratory Co., Ltd.).

(6) Haze Based on JIS standard K7136, the haze was measured using a haze meter ("HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.).

(7) Tensile properties Based on JIS standard K7127, tensile strength and tensile modulus at a temperature of 23 ° C. and a relative humidity of 50% were measured using a tensile tester (“Tensilon” manufactured by A & D).

(8) Yellowness before and after heating Based on JIS standard K7373, yellowness (YI) before and after sheet heating was measured using a colorimeter (“Color Cute i” manufactured by Suga Test Instruments Co., Ltd.). Further, the difference in YI before and after heating was evaluated as ΔYI. The heating conditions were vacuum drying at 200 ° C. for 4 hours.

[result]
The evaluation results are shown in Table 1.

  As is clear from Table 1, in Examples 1 to 7 where organic counter ions were removed, the sheet density was improved as compared with the corresponding Reference Examples 2 to 7, and as a result, the tensile elastic modulus was improved. Also, the tensile strength was improved. Furthermore, in Examples 1 to 7 in which the organic counter ions were removed after being formed into sheets, the organic counter ions that caused the heating coloring were removed, so that YI after heating compared to the corresponding Reference Examples 2 to 7, ΔYI was also reduced.

<Example 8 (Manufacture example 1 of a laminated body)>
Using the sheet obtained in any of Examples 1 to 7, a laminate is obtained by the following procedure.
An aluminum oxide film is formed on the sheet with SUNALE R-100B (Picosun). As an aluminum raw material, trimethylaluminum (TMA) and H ₂ O are used for the oxidation of TMA. The chamber temperature is set to 150 ° C., the TMA pulse time is 0.1 seconds, the purge time is 4 seconds, the H ₂ O pulse time is 0.1 seconds, and the purge time is 4 seconds. By repeating this cycle for 405 cycles, a laminate in which an aluminum oxide film having a thickness of 30 nm is laminated on both sides of the sheet is obtained.

<Example 9 (Manufacture example 2 of a laminated body)>
Using the sheet obtained in any of Examples 1 to 7, a laminate is obtained by the following procedure.
Silsesquioxane resin (Arakawa Chemical Industries "Composeran SQ107") 10 parts by weight, curing agent (Arakawa Chemical Industries "HBSQ202") 30 parts by weight, isopropyl alcohol 60 parts by weight are mixed, coating liquid obtain. Next, the coating solution is applied to one side of the substrate with a Mayer bar. Thereafter, after drying at 100 ° C. for 3 minutes, UV coating of 300 mJ / cm ² was irradiated using a UV conveyor device (“ECS-4011GX” manufactured by Eye Graphics) to cure the coating solution, and the thickness was 5 μm. The resin layer is formed. Furthermore, a resin layer having a thickness of 5 μm is formed on the opposite surface in the same procedure.

<Example 10 (Manufacture example 3 of a laminated body)>
Using the sheet obtained in any of Examples 1 to 7 or the sheet obtained in Example 8, a laminate is obtained by the following procedure.
50 parts by weight of a urethane acrylate resin composition (“Beamset 575CB” manufactured by Arakawa Chemical Industries) and 50 parts by weight of methyl ethyl ketone are mixed to obtain a curable resin precursor solution. The curable resin precursor solution is applied onto the sheet using a Mayer bar. Next, after drying at 80 ° C. for 3 minutes, UV light of 300 mJ / cm 2 is irradiated using a UV conveyor device (“ECS-4011GX” manufactured by Eye Graphics Co., Ltd.) to cure the curable resin precursor solution. A 5 μm resin layer is formed. Further, by forming a resin layer having a thickness of 5 μm on the opposite surface in the same procedure, a sheet in which the resin layer is laminated on both surfaces on which the aluminum oxide film is laminated is obtained.

<Example 11 (Manufacturing Example 4 of laminate)>
Using the sheet obtained in any of Examples 1 to 7 or the sheet obtained in Example 9, a laminate is obtained by the following procedure.
A silicon oxynitride film is formed on the sheet using an ICP-CVD roll-to-roll apparatus (Celback). A resin laminated sheet is bonded to the upper surface of a carrier film (PET film) with a double-sided tape and placed in a vacuum chamber. The temperature in the vacuum chamber was set to 50 ° C., and the inflow gas was silane, ammonia, oxygen, and nitrogen. Plasma discharge is generated and film formation is performed for 45 minutes to obtain a sheet in which a silicon oxynitride film having a thickness of 500 nm is laminated on one surface of a resin laminated sheet. Furthermore, a sheet having a 500 nm-thick silicon oxynitride film laminated on both surfaces of the sheet is obtained by performing film formation on the opposite surface in the same procedure.

Claims (7)

Fine fibers having an ionic substituent;
An organic ion that is a counter ion of the ionic substituent;
Including
The sheet | seat whose content of the said organic ion is 0.40 mmol / g or less. The sheet according to claim 1, wherein the haze is 40% or less. The sheet according to claim 1 or 2, wherein the density is 1.0 g / cm ³ or more. The sheet according to any one of claims 1 to 3, wherein the organic ion has 4 or more carbon atoms. The sheet according to any one of claims 1 to 4, wherein a content of the ionic substituent is 0.5 mmol / g or less with respect to the fine fiber. The sheet according to any one of claims 1 to 5, wherein the tensile elastic modulus at a temperature of 23 ° C and a relative humidity of 50% is 4.0 GPa or more. A sheet according to any one of claims 1 to 6;
At least one of an inorganic layer and an organic layer formed on at least one side of the sheet;
A laminate comprising:

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