WO2019203239A1

WO2019203239A1 - Sheet and layered product

Info

Publication number: WO2019203239A1
Application number: PCT/JP2019/016350
Authority: WO
Inventors: 一輝小泉; 紅酒井
Original assignee: 王子ホールディングス株式会社
Priority date: 2018-04-17
Filing date: 2019-04-16
Publication date: 2019-10-24
Also published as: JPWO2019203239A1; TW201943770A

Abstract

The present invention addresses the problem of providing a sheet which comprises finely fibrous cellulose and a water-compatible resin and which has a low affinity for water. The present invention relates to a sheet which comprises an acrylic polymer and fibrous cellulose having a fiber width of 1,000 nm or less, wherein the acrylic polymer comprises a structure derived from at least one compound selected from among isocyanate compounds, carbodiimide compounds, and oxazoline compounds and a structure derived from an aqueous acrylic polyol. The sheet has a water absorption through 24-hr immersion in water of 6 mass% or less.

Description

Sheet and laminate

The present invention relates to a sheet and a laminate.

In recent years, materials that use reproducible natural fibers have attracted attention due to the substitution of petroleum resources and the growing environmental awareness. Among natural fibers, fibrous cellulose having a fiber diameter of 10 to 50 μm, particularly fibrous cellulose (pulp) derived from wood has been widely used mainly as a paper product so far.

As the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Fine fibrous cellulose is attracting attention as a new material, and its uses are diverse. For example, the development of sheets, resin composites, and thickeners containing fine fibrous cellulose is in progress.

For example, Patent Document 1 discloses a water-based coating composition containing fine fibrous cellulose, a water-based resin, and a colorant. Here, formation of a coating film excellent in water resistance from a water-based coating composition has been studied. In addition, the coating film in patent document 1 is a film | membrane which covers the surface of a base material, and is a film | membrane which contact | adhered to the base material.

JP 2016-69618 A

Generally, fine fibrous cellulose is stably dispersed in an aqueous solvent. For this reason, when it is going to form the resin composite containing fine fibrous cellulose, in order to improve the uniform dispersibility of resin to be used and fine fibrous cellulose, highly hydrophilic resin may be used. However, the resin composite such as a sheet obtained in this way has a high affinity with water, and its use may be limited.

Therefore, an object of the present invention is to provide a sheet having a low affinity with water among sheets containing fine fibrous cellulose and an aqueous resin.

As a result of intensive studies to solve the above problems, the present inventors, in a sheet containing fine fibrous cellulose and a water-based acrylic polymer having a predetermined cross-linked structure, the water absorption rate is a predetermined value or less As a result, it was found that a sheet having low affinity with water can be obtained.
Specifically, the present invention has the following configuration.

[1] A sheet containing an acrylic polymer and fibrous cellulose having a fiber width of 1000 nm or less,
The acrylic polymer is a polymer including a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound and an oxazoline compound, and a structure derived from an aqueous acrylic polyol.
A sheet having a water absorption of 6% by mass or less when the sheet is immersed in water for 24 hours.
[2] The sheet according to [1], wherein the content of fibrous cellulose is 0.5 parts by mass or more and 19 parts by mass or less with respect to 100 parts by mass of the acrylic polymer.
[3] The sheet according to [1] or [2], wherein the haze is 4.5% or less.
[4] The sheet according to any one of [1] to [3], wherein the total light transmittance is 89% or more.
[5] The sheet according to any one of [1] to [4], wherein the YI value is 0.3 or less.
[6] The sheet according to any one of [1] to [5], which has a tensile strength of 15 MPa or more.
[7] The sheet according to any one of [1] to [6], which has a tensile modulus of 1.8 GPa or more.
[8] The sheet according to any one of [1] to [7], having a thickness of 10 μm or more.
[9] A laminate comprising the sheet according to any one of [1] to [8] on at least one surface side of the base material layer.
[10] The laminate according to [9], wherein the base material layer includes at least one selected from fibrous cellulose having a fiber width of 1000 nm or less and a water-soluble polymer.

According to the present invention, a sheet having a low affinity with water can be obtained.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and electrical conductivity for a fiber material having a phosphate group. FIG. 2 is a graph showing the relationship between the amount of dropped NaOH and electrical conductivity for a fiber material having a carboxyl group. FIG. 3 is a cross-sectional view illustrating the structure of a laminate having a base material layer and a sheet.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

(Sheet)
The present invention relates to a sheet containing an acrylic polymer and fibrous cellulose having a fiber width of 1000 nm or less. Here, the acrylic polymer is a polymer including a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound, and a structure derived from an aqueous acrylic polyol. The water absorption when the sheet is immersed in water for 24 hours is 6% by mass or less. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose.

Since the sheet of the present invention has the above-described configuration, the affinity with water can be kept low even for a sheet containing fine fibrous cellulose and an aqueous resin. Specifically, it can be determined that the water affinity of the sheet is low due to the large water contact angle on the sheet surface. The water contact angle on the sheet surface is preferably 68.2 ° or more, more preferably 68.5 ° or more, and further preferably 69.0 ° or more. The water contact angle on the sheet surface is preferably 120 ° or less. Here, the water contact angle on the surface of the sheet is a value measured according to JIS R 3257, 4 μL of distilled water is dropped on the surface of the sheet, and a dynamic water contact angle tester (manufactured by Fibro, 1100DAT). Is a value measured 0.1 seconds after dropping. Thus, it can be said that the sheet of the present invention is a sheet having low water affinity and excellent water resistance. In the present invention, the water contact angle on either surface of the sheet may satisfy the above range, but the water contact angle on both surfaces of the sheet preferably satisfies the above range.

The sheet of the present invention can maintain the sheet shape alone (without a substrate), and is distinguished from, for example, a coating covering at least one surface of a substrate. Here, the coating film is a film that covers at least one surface of the substrate, and the coating film cannot peel from the substrate to form a sheet shape by itself. The sheet of the present invention may be laminated on, for example, at least one surface of the base material layer. However, the sheet of the present invention is laminated on the base material layer as long as the sheet shape can be maintained alone. Is also called a sheet.

The thickness of the sheet of the present invention is preferably 10 μm or more, more preferably 12 μm or more, and further preferably 15 μm or more. In addition, it is preferable that the thickness of a sheet | seat is 1000 micrometers or less. Thus, the sheet | seat of this invention has a certain amount of thickness, and can maintain a sheet | seat shape independently by this. In addition, when the sheet | seat of this invention is a sheet | seat which comprises a laminated body which is mentioned later, the thickness of a sheet | seat may become thinner than the said range. Here, the thickness of the sheet can be measured with, for example, a stylus type thickness meter (Milltron 1202D, manufactured by Marl).

The water absorption when the sheet of the present invention is immersed in water for 24 hours may be 6% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less, and 3.5% by mass. % Or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. The water absorption rate of the sheet may be 0% by mass. Here, the water absorption rate of the sheet is calculated by the following equation by measuring the weight before and after immersing the sheet piece in ion exchange water for 24 hours after cutting the sheet into a predetermined size (for example, 5 cm square). It is the value.
Water absorption (mass%) = 100 × (W _B −W _A ) / W _A (Formula a)
In the above formula, W _A is the weight before dipping the sheet piece in deionized water, W _B is the after immersion for 24 hours sheet pieces in deionized water, pulling the test piece from the deionized water, Kimwipe etc. It is the weight after wiping off the water adhering to the surface of the test piece.

A sheet having a low affinity with water can be obtained by setting the water absorption rate of the sheet within the above range. That is, a sheet having a large water contact angle on the sheet surface can be obtained. Here, in order to make the water absorption rate of the sheet within the above range, for example, adjusting the content of fine fibrous cellulose contained in the sheet, or controlling the mixing method of the raw materials constituting the sheet, etc. Can be mentioned. That is, the present invention optimizes the content of fine fibrous cellulose, even if the sheet is composed mainly of components having a high affinity for water such as fine fibrous cellulose and water-based resin. By controlling the mixing order of the constituent materials, the water affinity as a sheet was successfully suppressed to a low level. In addition, when controlling the mixing order of the raw materials which comprise a sheet | seat, it is preferable to set it as the mixing order demonstrated in the item of the (sheet manufacturing method) mentioned later.

The content of fine fibrous cellulose contained in the sheet is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, with respect to 100 parts by mass of the acrylic polymer. More preferably, it is the above. The content of fine fibrous cellulose is preferably 19 parts by mass or less, more preferably 17 parts by mass or less, and preferably 15 parts by mass or less with respect to 100 parts by mass of the acrylic polymer. Is more preferable. Even if the content of the fine fibrous cellulose with respect to 100 parts by mass of the acrylic polymer is within the above range, the sheet contains a component having a high affinity for water such as fine fibrous cellulose and water-based resin as a main component. , Its water affinity can be kept low. Thereby, the water resistance of a sheet | seat can be improved.
When measuring the content of fine fibrous cellulose in the sheet, first, the fine fibrous cellulose is extracted by an appropriate method. For example, the fine fibrous cellulose is extracted by treatment with a solvent that selectively dissolves only the resin, and the resulting solid content becomes the mass of the fine fibrous cellulose.

The haze of the sheet is preferably 4.5% or less, more preferably 4.0% or less, still more preferably 3.0% or less, and even more preferably 2.0% or less. It is preferably 1.0% or less. On the other hand, the lower limit of the haze of the sheet is not particularly limited, and may be 0%, for example. Here, the haze of the sheet is a value measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with, for example, JIS K 7136.

The total light transmittance of the sheet is preferably 89% or more, more preferably 90% or more, and further preferably 91% or more. On the other hand, the upper limit of the total light transmittance of the sheet is not particularly limited, and may be 100%, for example. Here, the total light transmittance of the sheet is a value measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with, for example, JIS K 7361.

The yellowness (YI) of the sheet is preferably 0.3 or less, more preferably 0.25 or less, and further preferably 0.2 or less. In addition, there is no restriction | limiting in particular in the lower limit of yellowness (YI), and 0.0 may be sufficient. The yellowness (YI) of the sheet is a value measured using Color Cute i (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7373.

The tensile strength of the sheet is preferably 15 MPa or more, more preferably 20 MPa or more, and further preferably 24 MPa or more. In addition, although the upper limit of the tensile strength of a sheet | seat is not specifically limited, For example, it can be 240 MPa. The tensile strength (unit: MPa) of the sheet is a value calculated by dividing the tensile strength (unit: N / m) by the thickness of the test piece. Here, the tensile strength of the sheet is a value measured according to JIS P 8113, except that the length of the sheet (test piece) is 80 mm and the distance between chucks is 50 mm. As a tester for measuring the tensile strength, for example, a tensile tester Tensilon (manufactured by A & D) can be used. When measuring the tensile strength, a sheet conditioned at 23 ° C. and 50% relative humidity for 24 hours is used as a test piece, and the measurement is performed under the conditions of 23 ° C. and 50% relative humidity.

The tensile elastic modulus of the sheet is preferably 1.8 GPa or more, more preferably 2.0 GPa or more, and further preferably 3.0 GPa or more. In addition, although the upper limit of the tensile elasticity modulus of a sheet | seat is not specifically limited, For example, it can be 50 GPa. The tensile modulus of the sheet is a value calculated from the maximum positive slope value in the SS curve, measured according to JIS P8113, except that the length of the test piece is 80 mm and the distance between chucks is 50 mm. is there. As a tester for measuring the tensile elastic modulus, for example, a tensile tester Tensilon (manufactured by A & D) can be used. When measuring the tensile modulus, a sheet conditioned for 24 hours at 23 ° C. and 50% relative humidity is used as a test piece, and measurement is performed under conditions of 23 ° C. and 50% relative humidity.

(Fine fibrous cellulose)
The sheet | seat of this invention contains the fibrous cellulose (fine fibrous cellulose) whose fiber width is 1000 nm or less. The fiber width of the fibrous cellulose can be measured, for example, by observation with an electron microscope.

The average fiber width of fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and more preferably 2 nm or more and 10 nm or less. Particularly preferred. By making the average fiber width of fibrous cellulose 2 nm or more, it is possible to suppress dissolution in water as cellulose molecules, and to more easily express the effects of improving strength, rigidity, and dimensional stability due to fibrous cellulose. it can. The fibrous cellulose is, for example, monofilamentous cellulose.

The average fiber width of fibrous cellulose is measured as follows using, for example, an electron microscope. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a carbon film-coated grid subjected to a hydrophilization treatment, and a sample for TEM observation. And When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Next, observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the fiber to be observed. However, the sample, observation conditions, and magnification are adjusted 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 observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thereby, at least 20 fibers × 2 × 3 = 120 fiber widths are read. And let the average value of the read fiber width be an average fiber width of fibrous cellulose.

The fiber length of the fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, the destruction of the crystalline region of fibrous cellulose can be suppressed. Moreover, it becomes possible to make the slurry viscosity of fibrous cellulose into an appropriate range. In addition, the fiber length of fibrous cellulose can be calculated | required by the image analysis by TEM, SEM, and AFM, for example.

The fibrous cellulose preferably has an I-type crystal structure. Here, it can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418Å) monochromatized with graphite that the fibrous cellulose has an I-type crystal structure. Specifically, it can be identified by having typical peaks at two positions of 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °.

The proportion of the type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. Thereby, further superior performance can be expected in terms of heat resistance and low coefficient of thermal expansion. The degree of crystallinity is obtained by measuring an X-ray diffraction profile and determining the crystallinity by a conventional method (Seagal et al., Textile Research Journal, 29, 786, 1959).

The axial ratio (fiber length / fiber width) of fibrous cellulose is not particularly limited, but is preferably 20 or more and 10,000 or less, and more preferably 50 or more and 1,000 or less. By setting the axial ratio to be equal to or more than the above lower limit value, it is easy to form a sheet containing fine fibrous cellulose. By setting the axial ratio to be equal to or less than the above upper limit value, for example, when handling fibrous cellulose as an aqueous dispersion, it is preferable in terms of easy handling such as dilution.

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

The fibrous cellulose in the present embodiment has, for example, at least one of an ionic substituent and a nonionic substituent. From the viewpoint of improving the dispersibility of the fibers in the dispersion medium and increasing the defibrating efficiency in the defibrating treatment, it is more preferable that the fibrous cellulose has an ionic substituent. As an ionic substituent, any one or both of an anionic group and a cationic group can be included, for example. Moreover, as a nonionic substituent, an alkyl group, an acyl group, etc. can be included, for example. In this embodiment, it is particularly preferable to have an anionic group as the ionic substituent. In addition, the process which introduce | transduces an ionic substituent does not need to be performed to fibrous cellulose.

Examples of the anionic group as the ionic substituent include a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxyl group or a substituent derived from a carboxyl group (simply referred to as a carboxyl group). And at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxyl group A seed is more preferable, and a phosphate group is particularly preferable.

The phosphoric acid group is a divalent functional group corresponding to, for example, phosphoric acid obtained by removing a hydroxyl group. Specifically, it is a group represented by —PO ₃ H ₂ . Substituents derived from phosphate groups include substituents such as phosphate group salts and phosphate ester groups. In addition, the substituent derived from the phosphate group may be contained in the fibrous cellulose as a group (for example, pyrophosphate group) in which the phosphate group is condensed.
The substituent derived from a phosphoric acid group or a phosphoric acid group is, for example, a substituent represented by the following formula (1).

In the formula (1), a, b and n are natural numbers (where a = b × m). Of α ¹ , α ² ,..., α ⁿ and α ′, a is O ⁻ and the rest is either R or OR. Note that all αn and α ′ may be O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative thereof.

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

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

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of the monovalent or higher cation made of an organic substance include aliphatic ammonium or aromatic ammonium. Examples of the monovalent or higher cation made of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, Examples include, but are not particularly limited to, a cation of a divalent metal such as calcium or magnesium, or a hydrogen ion. These can be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably a sodium ion or potassium ion which is not easily yellowed when heated to a fiber raw material containing β and is industrially useful, but is not particularly limited.

The amount of ionic substituent introduced into the fibrous cellulose is, for example, preferably 0.10 mmol / g or more per 1 g (mass) of fibrous cellulose, more preferably 0.20 mmol / g or more, and 0.50 mmol. / G or more is more preferable, and 1.00 mmol / g or more is particularly preferable. The amount of ionic substituents introduced into the fibrous cellulose is, for example, preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less per 1 g (mass) of fibrous cellulose. More preferably, it is 0.000 mmol / g or less. By making the introduction amount of the ionic substituent within the above range, the fiber raw material can be easily refined and the stability of the fibrous cellulose can be enhanced.
Here, unit mmol / g shows the amount of substituents per 1 g of fibrous cellulose when the counter ion of the anionic group is hydrogen ion (H ⁺ ).

The amount of the anionic group introduced into the fibrous cellulose can be measured by, for example, a conductivity titration method. In the measurement by the conductivity titration method, the introduction amount is measured by obtaining a change in conductivity while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fibrous cellulose.

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and electrical conductivity for fibrous cellulose having a phosphate group. The amount of phosphate groups introduced into the fibrous cellulose is measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, you may implement the fibrillation process similar to the fibrillation process mentioned later with respect to a measuring object before the process by strong acidic ion exchange resin as needed. Next, a change in electrical conductivity is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. As shown in FIG. 1, at first, the electric conductivity suddenly decreases (hereinafter referred to as “first region”). Thereafter, the conductivity starts to increase slightly (hereinafter referred to as “second region”). Thereafter, the conductivity increment increases (hereinafter referred to as “third region”). Note that the boundary point between the second region and the third region is defined as a point at which the amount of change in the twice differential value of conductivity, that is, the increment (inclination) of the conductivity is maximized. Thus, three regions appear in the titration curve. Of these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group undergoes condensation, apparently weakly acidic groups are lost, and the amount of alkali required in the second region is reduced compared to the amount of alkali required in the first region. On the other hand, the amount of strongly acidic groups coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. Therefore, simply referring to the phosphate group introduction amount (or phosphate group amount) or the substituent introduction amount (or substituent amount) represents a strongly acidic group amount. Therefore, the value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve obtained above by the solid content (g) in the titration target slurry is the phosphate group introduction amount (mmol / g).

FIG. 2 is a graph showing the relationship between the amount of NaOH dropped and the electrical conductivity with respect to fibrous cellulose having a carboxyl group. The amount of carboxyl groups introduced into the fibrous cellulose is measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, you may implement the fibrillation process similar to the fibrillation process mentioned later with respect to a measuring object before the process by strong acidic ion exchange resin as needed. Next, a change in electrical conductivity is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. As shown in FIG. 2, in the titration curve, after the electrical conductivity decreases, the first region until the conductivity increment (slope) becomes substantially constant, and then the conductivity increment (slope) increases. Divided into second regions. Note that the boundary point between the first region and the second region is defined as the point at which the amount of change in conductivity twice, that is, the increase (inclination) in conductivity is maximized. The value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated is the amount of carboxyl group introduced ( mmol / g).

The amount of carboxyl group introduced (mmol / g) is the amount of substituent per 1 g of fibrous cellulose when the counter ion of the carboxyl group is hydrogen ion (H ⁺ ) (hereinafter, the amount of carboxyl group (acid Type)). On the other hand, when the cation C is substituted with an arbitrary cation C so that the counter ion of the carboxyl group has a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is the counter ion. Thus, the amount of carboxyl groups (hereinafter, the amount of carboxyl groups (C type)) possessed by the fibrous cellulose whose cation C is a counter ion can be determined.
That is, the carboxyl group introduction amount is calculated by the following formula.
Amount of carboxyl group introduced (C type) = Amount of carboxyl group (acid type) / {1+ (W−1) × (Amount of carboxyl group (acid type)) / 1000}
W: Formula weight per cation C (for example, Na is 23, Al is 9)

<Production process of fine fibrous cellulose>
<Fiber raw material>
The fine fibrous cellulose is produced from a fiber raw material containing cellulose. Although it does not specifically limit as a fiber raw material containing a cellulose, It is preferable to use a pulp from the point of being easy to acquire and cheap. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Although it does not specifically limit as wood pulp, For example, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolution pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP) ) And oxygen bleached kraft pulp (OKP) and other chemical pulp, semichemical pulp (SCP) and semi-chemical pulp such as Chemigroundwood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) and the like Examples thereof include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton-based pulp such as cotton linter and cotton lint, and non-wood-based pulp such as hemp, straw and bagasse. Although it does not specifically limit as a deinking pulp, For example, the deinking pulp which uses a waste paper as a raw material is mentioned. The pulp of this embodiment may be used alone or in combination of two or more.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. In addition, among wood pulps, it is possible to obtain a fine fiber cellulose having a large cellulose ratio and a high yield of fine fibrous cellulose at the time of defibrating treatment, and a long fiber fine fibrous cellulose having a small degradation of cellulose in the pulp and a large axial ratio. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable.

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used. Moreover, it can replace with the fiber raw material containing cellulose, and the fiber which linear nitrogen-containing polysaccharide polymer | macromolecules, such as chitin and chitosan form, can also be used.

<Phosphate group introduction process>
When the fine fibrous cellulose has a phosphate group, the production process of the fine fibrous cellulose includes a phosphate group introduction step. In the phosphoric acid group introduction step, at least one compound selected from compounds capable of introducing a phosphate group by reacting with a hydroxyl group of a fiber raw material containing cellulose (hereinafter also referred to as “compound A”) is converted into cellulose. It is the process made to act on the fiber raw material containing. By this step, a phosphate group-introduced fiber is obtained.

In the phosphate group introduction step according to this embodiment, the reaction between the fiber raw material containing cellulose and compound A is performed in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as “compound B”). May be. On the other hand, in the state where compound B does not exist, the fiber raw material containing cellulose and compound A may be reacted.

An example of a method for causing compound A to act on the fiber raw material in the presence of compound B includes a method of mixing compound A and compound B with a dry, wet or slurry fiber raw material. Among these, since the uniformity of the reaction is high, it is preferable to use a fiber raw material in a dry state or a wet state. Although the form of a fiber raw material is not specifically limited, For example, it is preferable that it is a cotton form or a thin sheet form. The compound A and the compound B may be added to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or heated to a melting point or higher and melted. Among these, since the uniformity of the reaction is high, it is preferable to add in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution. Compound A and Compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method for adding compound A and compound B is not particularly limited, but when compound A and compound B are in solution, they may be taken out after dipping the fiber raw material in the solution and absorbing the fiber raw material. The solution may be added dropwise. In addition, a necessary amount of Compound A and Compound B may be added to the fiber raw material, or after adding an excessive amount of Compound A and Compound B to the fiber raw material, respectively, excess compound A and Compound B may be added by pressing or filtration. It may be removed.

Examples of the compound A used in this embodiment include phosphoric acid or a salt thereof, dehydrated condensed phosphoric acid or a salt thereof, and anhydrous phosphoric acid (phosphorus pentoxide), but are not particularly limited. As phosphoric acid, those of various purity can be used, for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of the phosphate and dehydrated condensed phosphate include phosphoric acid or lithium salt of dehydrated condensed phosphoric acid, sodium salt, potassium salt, ammonium salt, and the like, and these can have various degrees of neutralization. Among these, phosphoric acid and phosphoric acid are introduced efficiently from the viewpoint that the introduction efficiency of phosphate groups is high, the fibrillation efficiency is easily improved in the fibrillation process described later, the cost is low, and the industrial application is easy. Sodium salt, potassium salt of phosphoric acid, or ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.

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

Compound B used in this embodiment is at least one selected from urea and derivatives thereof as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea.
From the viewpoint of improving the uniformity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

The amount of compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, and more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100 mass% or more and 350 mass% or less.

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

In the phosphate group introduction step, it is preferable to add or mix compound A or the like to the fiber raw material and then heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which a phosphate group can be efficiently introduced while suppressing thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment. For example, a stirring and drying apparatus, a rotary drying apparatus, a disk drying apparatus, a roll type heating apparatus, a plate type heating apparatus, a fluidized bed drying apparatus, an air flow A drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, or a microwave heating device can be used.

In the heat treatment according to this embodiment, for example, compound A is added to a thin sheet-like fiber raw material by a method such as impregnation, and then heated while heating or kneading or stirring the fiber raw material and compound A with a kneader or the like. The method to do can be adopted. Thereby, it becomes possible to suppress the concentration unevenness of the compound A in the fiber raw material and introduce the phosphate group more uniformly onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the fiber raw material surface with drying, the dissolved compound A is attracted to the water molecules by the surface tension and similarly moves to the fiber raw material surface (that is, the concentration unevenness of the compound A is reduced). This can be attributed to the fact that it can be suppressed.

In addition, the heating device used for the heat treatment, for example, always retains the moisture retained by the slurry and the moisture generated in the dehydration condensation (phosphate esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the apparatus can be discharged out of the apparatus system. As such a heating device, for example, a blower type oven or the like can be cited. In addition to being able to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphate esterification, by constantly discharging the water in the apparatus system, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. it can. For this reason, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

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

The phosphate group introduction step may be performed at least once, but can be repeated twice or more. By performing the phosphate group introduction step twice or more, many phosphate groups can be introduced into the fiber raw material. In this embodiment, the case where a phosphate group introduction | transduction process is performed twice as an example of a preferable aspect is mentioned.

The amount of phosphate groups introduced into the fiber raw material is, for example, preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, and 0.50 mmol / It is more preferable that it is g or more, and it is especially preferable that it is 1.00 mmol / g or more. The amount of phosphate groups introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of fine fibrous cellulose. More preferably, it is 00 mmol / g or less. By making the introduction amount of the phosphoric acid group within the above range, the fiber raw material can be easily refined, and the stability of the fine fibrous cellulose can be enhanced.

<Carboxyl group introduction step>
When the fine fibrous cellulose has a carboxyl group, the production process of the fine fibrous cellulose includes a carboxyl group introduction step. The carboxyl group introduction step has a compound or derivative thereof having a carboxylic acid-derived group or a carboxylic acid-derived group, or an oxidation treatment such as ozone oxidation, Fenton method oxidation, TEMPO oxidation treatment, or the like, on a fiber raw material containing cellulose. It is carried out by treatment with an acid anhydride of a compound or a derivative thereof.

The compound having a carboxylic acid-derived group is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, citric acid, aconitic acid, and the like. A tricarboxylic acid compound is mentioned. The derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an acid anhydride imidized compound having a carboxyl group and an acid anhydride derivative of a compound having a carboxyl group. The acid anhydride imidized compound of the compound having a carboxyl group is not particularly limited, and examples thereof include imidized compounds of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

The acid anhydride of the compound having a carboxylic acid-derived group is not particularly limited. An acid anhydride is mentioned. In addition, the acid anhydride derivative of the compound having a carboxylic acid-derived group is not particularly limited, but examples of the compound having a carboxyl group such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, and diphenylmaleic acid anhydride An acid anhydride in which at least a part of hydrogen atoms is substituted with a substituent such as an alkyl group or a phenyl group is exemplified.

In the carboxyl group introduction step, when TEMPO oxidation treatment is performed, for example, the treatment is preferably performed under a condition where the pH is 6 or more and 8 or less. Such treatment is also referred to as neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Furthermore, by allowing sodium chlorite to coexist, the aldehyde generated during the oxidation process can be efficiently oxidized to the carboxyl group.

Further, the TEMPO oxidation treatment may be performed under the condition that the pH is 10 or more and 11 or less. Such a treatment is also called an alkali TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be performed, for example, by adding nitroxy radicals such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. .

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

<Washing process>
In the manufacturing method of the fine fibrous cellulose in this embodiment, a washing | cleaning process can be performed with respect to a phosphate group introduction | transduction fiber as needed. The washing step is performed, for example, by washing the phosphate group-introduced fiber with water or an organic solvent. In addition, the cleaning process may be performed after each process described later, and the number of times of cleaning performed in each cleaning process is not particularly limited.

<Alkali treatment process>
When manufacturing a fine fibrous cellulose, you may perform an alkali treatment with respect to a fiber raw material between an anionic group introduction | transduction process and the fibrillation process mentioned later. Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing a phosphate group introduction | transduction fiber in an alkaline solution is mentioned.

The alkali compound contained in the alkali solution is not particularly limited, and may be an inorganic alkali compound or an organic alkali compound. In this embodiment, since versatility is high, it is preferable to use sodium hydroxide or potassium hydroxide as an alkali compound, for example. Moreover, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. The alkaline solution is preferably a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution because of its high versatility.

The temperature of the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, for example, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersion time of the phosphate group-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably, for example, from 5 minutes to 30 minutes, and more preferably from 10 minutes to 20 minutes. The amount of the alkali solution used in the alkali treatment is not particularly limited. For example, it is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less with respect to the absolute dry mass of the phosphate group-introduced fiber. It is more preferable that

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

<Acid treatment process>
When manufacturing a fine fibrous cellulose, you may acid-treat with respect to a fiber raw material between the process of introduce | transducing an anionic group, and the fibrillation process mentioned later. For example, the phosphate group introduction step, acid treatment, alkali treatment, and defibration treatment may be performed in this order.

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

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. Although the immersion time in the acid solution in acid treatment is not specifically limited, For example, 5 minutes or more and 120 minutes or less are preferable, and 10 minutes or more and 60 minutes or less are more preferable. Although the usage-amount of the acid solution in an acid treatment is not specifically limited, For example, it is preferable that it is 100 mass% or more and 100,000 mass% or less with respect to the absolute dry mass of a fiber raw material, and it is 1000 mass% or more and 10000 mass% or less. Is more preferable.

<Defibration processing>
Fine fibrous cellulose is obtained by defibrating the anionic group-introduced fiber in the defibrating process. In the defibrating process, for example, a defibrating apparatus can be used. The defibrating apparatus is not particularly limited, but, for example, a high-speed defibrator, a grinder (stone mill type pulverizer), a high-pressure homogenizer or an ultrahigh-pressure homogenizer, a high-pressure collision type pulverizer, a ball mill, a bead mill, a disk type refiner, a conical refiner, biaxial A kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-described defibrating apparatuses, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultrahigh-pressure homogenizer that is less affected by the pulverizing media and has less risk of contamination.

In the defibrating process, for example, it is preferable to dilute the phosphate group-introduced fiber with a dispersion medium to form a slurry. As a dispersion medium, 1 type, or 2 or more types selected from water and organic solvents, such as a polar organic solvent, can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents, and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate and butyl acetate. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of fine fibrous cellulose at the time of defibrating treatment can be set as appropriate. The slurry obtained by dispersing the phosphate group-introduced fibers in the dispersion medium may contain solids other than phosphate group-introduced fibers such as urea having hydrogen bonding properties.

(Acrylic polymer)
The sheet of the present invention contains an acrylic polymer as a water-based resin. Here, the acrylic polymer is a polymer including a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound, and a structure derived from an aqueous acrylic polyol. In other words, the acrylic polymer is a crosslinked acrylic polymer in which the aqueous acrylic polyol is crosslinked with a structure (unit) derived from at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound.

The aqueous acrylic polyol is a polymer having a hydroxyl group-containing (meth) acrylate and a vinyl compound as a copolymerization component. In the present specification, the term “(meth) acrylate” means a general term for acrylate and methacrylate. The aqueous acrylic polyol may contain a structure derived from (meth) acrylate other than hydroxyl group-containing (meth) acrylate. Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxy (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and the like. Examples of (meth) acrylates other than hydroxyl group-containing (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Is mentioned.

A vinyl compound is a compound having a polymerizable vinyl group. Examples of the vinyl compound include vinyl acetate, vinylidene chloride, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, ethylene, propylene, styrene, vinyl toluene, α-methyl styrene, acrylonitrile, acrylamide, and the like. .

The acrylic polymer includes a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound. Here, the compound is a curing agent or a crosslinking agent. Especially, it is preferable that an acrylic polymer contains the structure derived from an isocyanate compound, and the polyisocyanate which has two or more isocyanate groups is also contained in an isocyanate compound. For example, an isocyanate group reacts with a hydroxyl group of an aqueous acrylic polyol to form a crosslinked structure.

(Optional component)
The sheet of the present invention may contain a water-soluble polymer in addition to the above-described acrylic polymer and fine fibrous cellulose. Examples of water-soluble polymers include carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate / acrylic acid copolymer, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene glycol, diethylene glycol, triethylene glycol, polyethylene oxide, propylene glycol, dipropylene glycol, Synthetic water-soluble polymers exemplified by polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, and polyacrylamide; xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, pullulan , Carrageenan, and thickening polysaccharides exemplified by pectin; carboxymethylcellulose Cellulose derivatives exemplified by methyl cellulose and hydroxyethyl cellulose; starches exemplified by cationized starch, raw starch, oxidized starch, etherified starch, esterified starch and amylose; glycerin, diglycerin, and poly Examples include glycerins exemplified by glycerin and the like; hyaluronic acid, hyaluronic acid metal salts, and the like.

The sheet of the present invention may further contain a resin such as a thermoplastic resin, a thermosetting resin, or a photocurable resin, in addition to the acrylic polymer and fine fibrous cellulose described above. Examples of the resin include styrene resin, aromatic polycarbonate resin, aliphatic polycarbonate resin, aromatic polyester resin, aliphatic polyester resin, aliphatic polyolefin resin, cyclic olefin resin, polyamide resin, and polyphenylene. Ether resin, thermoplastic polyimide resin, polyacetal resin, polysulfone resin, amorphous fluorine resin, rosin resin, nitrocellulose, vinyl chloride resin, chlorinated rubber resin, vinyl acetate resin, phenol resin, epoxy Examples thereof include resins.

Furthermore, the sheet of the present invention includes, as optional components, for example, surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, charging agents. An inhibitor, an ultraviolet protection agent, a dye, a pigment, a stabilizer, a magnetic powder, an alignment accelerator, a plasticizer, a dispersant, a crosslinking agent, and the like may be included. The sheet of the present invention may contain one or more of the above components.

The content of the optional component contained in the sheet is preferably 50% by mass or less, more preferably 40% by mass or less, and preferably 30% by mass or less with respect to the total mass of the sheet. Further preferred.

The sheet of the present invention may contain a solvent as an optional component. Examples of the solvent include one or both of water and an organic solvent, and the solvent is preferably water. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, esters, hydrocarbons, halogens, aprotic polar solvents, and the like. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate and butyl acetate. Examples of hydrocarbons include n-hexane, toluene, xylene and the like. Examples of halogens include methylene chloride, trichloroethylene, chloroform and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

In this case, the content of the solvent contained in the sheet is preferably 50% by mass or less, more preferably 40% by mass or less, and 30% by mass or less with respect to the total mass of the sheet. Is more preferable.

(Sheet manufacturing method)
In the sheet manufacturing method of the present invention, fibrous cellulose having a fiber width of 1000 nm or less, an aqueous acrylic polyol, and at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound are mixed to form a sheet. A process for obtaining a composition for a sheet (hereinafter also referred to as a slurry or a coating liquid), a coating process for coating the sheet-forming composition on a substrate, or a paper-making process for making the sheet-forming composition. Including. Thereby, the sheet | seat mentioned above will be obtained.

<The process of obtaining the composition for sheet formation>
In the step of obtaining the sheet-forming composition, a dispersion containing fibrous cellulose having a fiber width of 1000 nm or less is diluted as necessary. In the step of obtaining the composition for forming a sheet, this step is preferably included as the first step. At this time, the content of the fine fibrous cellulose contained in the diluted dispersion is preferably 2% by mass or less, preferably 1% by mass or less, based on the total mass of the diluted dispersion. Is more preferable. Moreover, it is preferable that content of the fine fibrous cellulose contained in the diluted dispersion is 0.001% by mass or more with respect to the total mass of the diluted dispersion. Thus, in the first step, it is preferable to prepare a dispersion liquid in which the content of fine fibrous cellulose is kept low, thereby obtaining a sheet having a low water absorption rate.

Next, it is preferable that the step of mixing the aqueous acrylic polyol with the dispersion containing the fibrous cellulose whose concentration is adjusted is included as the second step. The aqueous acrylic polyol added at this time is preferably a polymer emulsion containing a hydroxyl group-containing (meth) acrylate and a vinyl compound as a copolymerization component. Further, in the second step, it is preferable to add the aqueous acrylic polyol emulsion in a plurality of times and to stir each time. In the sheet manufacturing method of the present invention, it is preferable to add aqueous acrylic polyol little by little to a dispersion containing fibrous cellulose whose concentration has been adjusted, and this makes it easy to obtain a sheet having a low water absorption rate.

In the third step, at least one compound selected from an isocyanate compound, a carbodiimide compound and an oxazoline compound is mixed. At least one compound selected from the isocyanate compound, carbodiimide compound and oxazoline compound added in the third step is a curing agent or a crosslinking agent.

When adding each raw material in the second step and the third step, it is preferable to perform stirring using a stirrer. Examples of the stirrer include T.I. K. A homodisper (made by Tokushu Kika Kogyo Co., Ltd.) can be used, and the stirring speed is preferably 500 to 5000 rpm. The stirring time is preferably 1 to 100 minutes.

As described above, the step of obtaining the sheet-forming composition preferably includes the first to third steps in this order, but the content of fine fibrous cellulose in the dispersion containing fine fibrous cellulose is low. In some cases, the first step may be omitted, and the third step may be included after the second step. In addition, another process may be included between the first process and the second process, and another process may be included between the second process and the third process. In addition, other steps may be included before the first step and / or after the third step. In particular, after the third step, it is preferable to provide a defoaming treatment step in order to eliminate foaming due to stirring.

By passing through the above steps, the sheet-forming composition includes an acrylic system including a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound, and an oxazoline compound, and a structure derived from an aqueous acrylic polyol. A polymer will be included. The content of the acrylic polymer in the sheet forming composition is preferably 83.5% by mass or more, and more preferably 85% by mass or more, based on the total solid content in the composition. 87.5% by mass or more is more preferable. Further, the content of the acrylic polymer is preferably 99.95% by mass or less, more preferably 99.9% by mass or less, based on the total solid content in the composition. More preferably, it is 5 mass% or less.

Further, the content of the fine fibrous cellulose in the sheet forming composition is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more with respect to the total solid mass in the composition. It is more preferable that the content is 0.5% by mass or more. Further, the content of the fine fibrous cellulose is preferably 16.5% by mass or less, more preferably 15% by mass or less, and more preferably 12.5% by mass with respect to the total solid mass in the composition. More preferably, it is% or less.

<Coating process>
In the coating step, for example, a sheet can be obtained by coating a sheet-forming composition (slurry) containing fibrous cellulose on a substrate, and drying the formed sheet from the substrate. it can. Moreover, a sheet | seat can be continuously produced by using a coating device and a elongate base material.

The material of the base material used in the coating process is not particularly limited, but the one having higher wettability with respect to the composition for forming the sheet (slurry) may be able to suppress the shrinkage of the sheet at the time of drying. It is preferable to select a sheet that can be easily peeled off later. Among them, a resin film or plate or a metal film or plate is preferable, but is not particularly limited. For example, a film or plate of a resin such as polypropylene, acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polycarbonate, or polyvinylidene chloride, a metal film or plate of aluminum, zinc, copper, or iron plate, and the surface thereof oxidized Stainless steel films and plates, brass films and plates, and the like can be used.

In the coating process, when the slurry has a low viscosity and spreads on the base material, a damming frame is fixed on the base material to obtain a sheet having a predetermined thickness and basis weight. May be. The damming frame is not particularly limited, but for example, it is preferable to select one that can easily peel off the edge of the sheet attached after drying. From such a viewpoint, a molded resin plate or metal plate is more preferable. In the present embodiment, for example, a resin plate such as a polypropylene plate, an acrylic plate, a polyethylene terephthalate plate, a vinyl chloride plate, a polystyrene plate, a polycarbonate plate, or a polyvinylidene chloride plate, or a metal plate such as an aluminum plate, a zinc plate, a copper plate, or an iron plate And those obtained by oxidizing these surfaces, stainless steel plates, brass plates and the like can be used.
Although it does not specifically limit as a coating machine which coats a slurry on a base material, For example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater etc. can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the sheet can be made more uniform.

The slurry temperature and the atmospheric temperature when applying the slurry to the substrate are not particularly limited, but are preferably 5 ° C. or more and 80 ° C. or less, more preferably 10 ° C. or more and 60 ° C. or less, and more preferably 15 ° C. The temperature is more preferably 50 ° C. or lower and particularly preferably 20 ° C. or higher and 40 ° C. or lower. If the coating temperature is equal to or higher than the lower limit, the slurry can be applied more easily. If coating temperature is below the said upper limit, volatilization of the dispersion medium during coating can be suppressed.

In the coating step, the slurry is used so that the finished basis weight of the sheet is preferably 10 g / m ² or more and 100 g / m ² or less, more preferably 20 g / m ² or more and 60 g / m ² or less. It is preferable to apply to the material. By coating so that the basis weight is within the above range, a sheet having higher strength can be obtained.

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

The non-contact drying method is not particularly limited. For example, 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 is not specifically limited, For example, it can carry out using an infrared device, a far-infrared device, or a near-infrared device.

Although the heating temperature in the heat drying method is not particularly limited, for example, it is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 25 ° C. or higher and 105 ° C. or lower. If the heating temperature is at least the above lower limit, the dispersion medium can be volatilized quickly. Moreover, if heating temperature is below the said upper limit, the suppression of the cost required for a heating and the discoloration by the heat | fever of a fibrous cellulose are realizable.

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

The paper making process is performed by filtering and dewatering the slurry with a wire to obtain a wet paper sheet, and then pressing and drying the sheet. The filter cloth used when the slurry is filtered and dehydrated is not particularly limited, but it is more preferable that, for example, fibrous cellulose does not pass through and the filtration rate does not become too slow. Such a filter cloth is not particularly limited, but for example, a sheet made of an organic polymer, a woven fabric, and a porous film 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. In this embodiment, for example, a porous film of polytetrafluoroethylene having a pore diameter of 0.1 μm or more and 20 μm or less, a polyethylene terephthalate or polyethylene fabric having a pore diameter of 0.1 μm or more and 20 μm or less, and the like can be mentioned.

In the sheeting step, a method for producing a sheet from the slurry includes, for example, a squeezing section that discharges a slurry containing fibrous cellulose onto the upper surface of the endless belt and squeezes the dispersion medium from the discharged slurry to generate a web. And a drying section that dries the web to produce a sheet. An endless belt is disposed from the squeezing section to the drying section, and the web generated in the squeezing section is conveyed to the drying section while being placed on the endless belt.

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

(Laminate)
The present invention also relates to a laminate including the above-described sheet on at least one surface side of the base material layer. FIG. 3 is a cross-sectional view illustrating the structure of the stacked body 100. As shown in FIG. 3, the laminate 100 has a sheet 10 laminated on a base material layer 20. Here, although other layers may be provided between the base material layer 20 and the sheet 10, the sheet 10 is preferably laminated so as to be in direct contact with the base material layer 20. FIG. 3 illustrates a laminate 100 in which the sheet 10 is formed on one side of the base material layer 20, but the laminate of the present invention has a sheet formed on both sides of the base material layer. A laminated body may be sufficient, the laminated body provided with a base material layer on both surfaces of a sheet | seat may be sufficient, and the laminated body which contains two or more layers of a base material layer and a sheet | seat respectively may be sufficient.

Examples of the base material layer include a resin layer and an inorganic layer. The base material layer is also preferably a layer containing at least one selected from fine fibrous cellulose and a water-soluble polymer. When the base material layer is a layer containing fine fibrous cellulose, the content of fine fibrous cellulose is preferably 0.5% by mass or more and 95% by mass or less.

An adhesive layer may be provided between the above-described sheet and the base material layer, or no adhesive layer may be provided, and the sheet and the base material layer may be in direct contact with each other. In the case where an adhesive layer is provided between the sheet and the base material layer, for example, an acrylic resin can be used as an adhesive constituting the adhesive layer. Examples of adhesives other than acrylic resins include vinyl chloride resin, (meth) acrylate resin, styrene / acrylate copolymer resin, vinyl acetate resin, vinyl acetate / (meth) acrylate ester. Examples include polymer resins, urethane resins, silicone resins, epoxy resins, ethylene / vinyl acetate copolymer resins, polyester resins, polyvinyl alcohol resins, ethylene vinyl alcohol copolymer resins, and rubber emulsions such as SBR and NBR. It is done.

The thickness of the base material layer is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more. Moreover, it is preferable that the thickness of a base material layer is 10,000 micrometers or less, and it is more preferable that it is 1000 micrometers or less.

In addition, when a base material layer is a resin layer or an inorganic layer, as a resin layer or an inorganic layer, the layer mentioned below may be sufficient, for example.

<Resin layer>
The resin layer is a layer mainly composed of natural resin or synthetic resin. Here, a main component refers to the component contained 50 mass% or more with respect to the total mass of a resin layer. The content of the resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and 90% by mass with respect to the total mass of the resin layer. The above is particularly preferable. In addition, content of resin can also be 100 mass%, and may be 95 mass% or less.

Examples of natural resins include rosin resins such as rosin, rosin ester, and hydrogenated rosin ester.

The synthetic resin is preferably at least one selected from, for example, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, polyurethane resin, and acrylic resin. Among these, the synthetic resin is preferably at least one selected from polycarbonate resin and acrylic resin, and more preferably polycarbonate resin. The acrylic resin is preferably at least one selected from polyacrylonitrile and poly (meth) acrylate.

Examples of the polycarbonate resin constituting the resin layer include an aromatic polycarbonate resin and an aliphatic polycarbonate resin. These specific polycarbonate resins are known and include, for example, the polycarbonate resins described in JP 2010-023275 A.

As the resin constituting the resin layer, one kind may be used alone, or a copolymer obtained by copolymerization or graft polymerization of a plurality of resin components may be used. Moreover, you may use as a blend material which mixed the some resin component with the physical process.

The adhesive layer may be provided between the sheet and the resin layer, or the adhesive layer may not be provided, and the sheet and the resin layer may be in direct contact with each other. In the case where an adhesive layer is provided between the sheet and the resin layer, an acrylic resin can be exemplified as an adhesive constituting the adhesive layer. Examples of adhesives other than acrylic resin include vinyl chloride resin, (meth) acrylic ester resin, styrene / acrylic ester copolymer resin, vinyl acetate resin, vinyl acetate / (meth) acrylic ester copolymer Examples include coalesced resins, urethane resins, silicone resins, epoxy resins, ethylene / vinyl acetate copolymer resins, polyester resins, polyvinyl alcohol resins, ethylene vinyl alcohol copolymer resins, and rubber emulsions such as SBR and NBR. .

When the adhesive layer is not provided between the sheet and the resin layer, the resin layer may have an adhesion assistant, and surface treatment such as hydrophilic treatment may be performed on the surface of the resin layer.
Examples of the adhesion assistant include a compound containing at least one selected from an isocyanate group, a carbodiimide group, an epoxy group, an oxazoline group, an amino group, and a silanol group, and an organosilicon compound. Among these, the adhesion assistant is preferably at least one selected from a compound containing an isocyanate group (isocyanate compound) and an organosilicon compound. Examples of organosilicon compounds include silane coupling agent condensates and silane coupling agents.
Examples of surface treatment methods other than hydrophilization treatment include corona treatment, plasma discharge treatment, UV irradiation treatment, electron beam irradiation treatment, and flame treatment.

<Inorganic layer>
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 method for forming the inorganic layer is not particularly limited. In general, a method of forming a thin film is roughly classified into a chemical vapor deposition method (Chemical Vapor Deposition, CVD) and a physical film formation method (Physical Vapor Deposition, PVD), and either method may be adopted. . Specific examples of the CVD method include plasma CVD using plasma, and catalytic chemical vapor deposition (Cat-CVD) in which a material gas is contact pyrolyzed using a heating catalyst. Specific examples of the PVD method include vacuum deposition, ion plating, and sputtering.

Further, as a method for forming the inorganic layer, an atomic layer deposition method (ALD) can also be employed. The ALD method is a method of forming a thin film in units of atomic layers by alternately supplying source gases of respective elements constituting a film to be formed to a surface on which a layer is formed. Although there is a drawback that the film forming speed is slow, there is an advantage that it is possible to form a thin film with few defects because it can cleanly cover even a complicated surface more than the plasma CVD method. In addition, the ALD method has an advantage that the film thickness can be controlled on the nano order and it is relatively easy to cover a wide surface. Furthermore, the ALD method can be expected to improve the reaction rate, lower the temperature, and reduce the unreacted gas by using plasma.

(Use)
The use of the sheet of the present invention is not particularly limited. For example, the sheet is suitable for the use of a light transmissive substrate such as an optical film, various display devices, and various solar cells. It is also suitable for applications such as substrates for electronic devices, members of household appliances, various vehicles and building windows, interior materials, exterior materials, packaging materials, and the like. Furthermore, it is also suitable for applications in which the sheet itself is used as a reinforcing material in addition to threads, filters, fabrics, cushioning materials, sponges, abrasives, and the like.

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
In the following examples, for the convenience of explanation, a slurry obtained by treating fine fibrous cellulose is referred to as a fine fibrous cellulose dispersion. And what mix | blended the fine fibrous cellulose dispersion liquid, resin, the hardening | curing agent, etc. is called coating liquid. However, this does not limit the scope of the present invention. For example, a coating liquid containing fine fibrous cellulose, a specific component, and other components is also included in the scope of the coating liquid of the present invention.

<Production of fine fibrous cellulose dispersion>
[Pulp phosphorylation process]
As a raw material pulp, conifer kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93 mass%, basis weight 208 g / m ² sheet, disaggregated and measured in accordance with JIS P 811-2: 2012, Canadian standard freeness ( CSF) used 700 ml). The raw material pulp was phosphorylated as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolutely dry mass) of the above raw pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. Thus, a chemical solution impregnated pulp was obtained. Next, the obtained chemical solution-impregnated pulp was heated with a hot air dryer at 165 ° C. for 200 seconds to introduce phosphate groups into cellulose in the pulp to obtain phosphorylated pulp.

Next, the obtained phosphorylated pulp was washed. The washing treatment is performed by repeating the operation of filtering and dewatering after stirring the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g of phosphorylated pulp (absolute dry mass) so that the pulp is uniformly dispersed. went. When the electrical conductivity of the filtrate reached 100 μS / cm or less, the end point of washing was determined.

Next, the washed phosphorylated pulp was neutralized as follows. First, after the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, a 1N sodium hydroxide aqueous solution was added little by little with stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. . Subsequently, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp subjected to neutralization treatment.

Next, the washing treatment was performed on the phosphorylated pulp after the neutralization treatment.
The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on phosphate groups was observed in the vicinity of 1230 cm ⁻¹ , confirming that phosphate groups were added to the pulp.
Moreover, when the obtained phosphorylated pulp was tested and analyzed with an X-ray diffractometer, it was found at two positions of 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °. A typical peak was confirmed and confirmed to have cellulose type I crystals.

[Defibration processing]
Ion exchange water was added to the resulting phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizer (Sugino Machine, Starburst) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (1) containing fine fibrous cellulose. X-ray diffraction confirmed that the fine fibrous cellulose maintained the cellulose I-type crystals. Further, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. In addition, the phosphate group amount (strongly acidic group amount) measured by the measurement method described later was 1.45 mmol / g.

<Measurement of fiber width>
The fiber width of the fine fibrous cellulose was measured by the following method.
In the supernatant of the fine fibrous cellulose dispersion (1) obtained by the treatment with the wet atomizer, the fine fibrous cellulose has a concentration of 0.01% by mass to 0.1% by mass. Diluted with water and dropped onto a hydrophilic carbon grid membrane. This was dried, stained with uranyl acetate, and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

<Measurement of phosphate group amount>
The amount of phosphoric acid group of the fine fibrous cellulose is prepared by diluting the fine fibrous cellulose dispersion (1) containing the target fine fibrous cellulose with ion-exchanged water so that the content becomes 0.2% by mass. It measured by performing the titration using an alkali, after processing with the ion exchange resin with respect to the fibrous cellulose containing slurry.
In the treatment with the ion exchange resin, 1/10 by volume of the strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) is added to the fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. The mixture was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry.
In addition, titration using an alkali is performed by adding 50 μL of a 0.1 N aqueous sodium hydroxide solution to a fibrous cellulose-containing slurry after treatment with an ion exchange resin once every 30 seconds. This was done by measuring the change in the value of. The phosphate group amount (mmol / g) is obtained by dividing the alkali amount (mmol) required in the region corresponding to the first region shown in FIG. 1 by the solid content (g) in the slurry to be titrated. Calculated.

[Preparation of sheet containing fine fibrous cellulose]
<Example 1>
Ion exchange water was added to the fine fibrous cellulose dispersion (1) having a solid content concentration of 2.0% by mass to obtain a fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by mass.
49.8 g of the obtained fine fibrous cellulose dispersion (A) is weighed in a beaker, and there are 10.3 g of ion-exchanged water, an aqueous acrylic polyol (manufactured by DIC, product name: Burnock WD-551, solid content concentration 45. (0% by mass) 34.5 g, and a curing agent (manufactured by DIC, product name: Vernock DNW-5500, polyisocyanate, solid content concentration 79.8% by mass) 5.5 g were sequentially added. When adding each raw material, T.W. K. Stirring was performed at 1500 rpm with a homodisper (manufactured by Tokushu Kika Kogyo Co., Ltd.), and stirring was further performed for 5 minutes after all the raw materials were added. Thereafter, defoaming was performed using a defoaming device (Sinky Corp., rotation / revolution mixer AR-250). Thus, the solid content ratio (mass ratio) of the aqueous acrylic polyol, the curing agent, and the fine fibrous cellulose is 78: 22: 0.5 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid A coating solution having a concentration of 20% by mass was obtained.

<Example 2>
Weigh 69.3 g of fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by weight in a beaker, and in that order 2.8 g of ion-exchanged water, 24.0 g of aqueous acrylic polyol, and 3.8 g of curing agent in this order. A coating solution was obtained in the same manner as in Example 1 except that it was added. The solid content ratio (mass ratio) in the obtained coating liquid was 78: 22: 1 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the concentration of the total solid content was 14% by mass.

<Example 3>
Ion exchange water was added to the fine fibrous cellulose dispersion (1) having a solid content concentration of 2.0% by mass to obtain a fine fibrous cellulose dispersion (B) having a solid content concentration of 0.5% by mass. Except that 38.1 g of the fine fibrous cellulose dispersion (B) was weighed into a beaker, and 54.3 g of ion-exchanged water, 6.6 g of an aqueous acrylic polyol, and 1.1 g of a curing agent were sequentially added thereto. A coating solution was obtained in the same manner. The solid content ratio (mass ratio) in the obtained coating liquid was 78: 22: 5 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid content was 4% by mass.

<Example 4>
Ion exchange water was added to the fine fibrous cellulose dispersion (1) having a solid content concentration of 2.0% by mass to obtain a fine fibrous cellulose dispersion (C) having a solid content concentration of 1.0% by mass. Except that 54.6 g of the fine fibrous cellulose dispersion (C) was weighed into a beaker and 34.5 g of ion-exchanged water, 9.5 g of an aqueous acrylic polyol, and 1.5 g of a curing agent were added thereto in that order. A coating solution was obtained in the same manner. The solid content ratio (mass ratio) in the obtained coating liquid was 78:22:10 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid content was 6% by mass.

<Example 5>
78.3 g of fine fibrous cellulose dispersion (C) having a solid content concentration of 1.0% by mass is weighed in a beaker, and 11.3 g of ion-exchanged water, 9.0 g of an aqueous acrylic polyol, and 1.4 g of a curing agent are sequentially added thereto. A coating solution was obtained in the same manner as in Example 1 except that it was added. The solid content ratio (mass ratio) in the obtained coating liquid was 78:22:15 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the concentration of the total solid content was 6% by mass.

<Comparative Example 1>
A coating solution was prepared in the same manner as in Example 1 except that 34.7 g of an aqueous acrylic polyol, 59.8 g of ion-exchanged water, and 5.5 g of a curing agent were sequentially added to a beaker without adding the fine fibrous cellulose dispersion. Obtained. The solid content ratio (mass ratio) in the obtained coating liquid was 78:22 (aqueous acrylic polyol: curing agent), and the total solid content was 20% by mass.

<Comparative Example 2>
10.0 g of fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by mass is weighed in a beaker, and 49.9 g of ion-exchanged water, 34.6 g of an aqueous acrylic polyol, and 5.5 g of a curing agent are sequentially added thereto. A coating solution was obtained in the same manner as in Example 1 except that it was added. The solid content ratio (mass ratio) in the obtained coating liquid was 78: 22: 0.1 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the concentration of the total solid content was 20% by mass. It was.

<Comparative Example 3>
66.7 g of a fine fibrous cellulose dispersion (C) having a solid content concentration of 1.0 mass% is weighed in a beaker, and 26.6 g of ion-exchanged water, 5.8 g of an aqueous acrylic polyol, and 0.9 g of a curing agent are sequentially added thereto. A coating solution was obtained in the same manner as in Example 1 except that it was added. The solid content ratio (mass ratio) in the obtained coating liquid was 78:22:20 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid content was 4% by mass.

<Comparative example 4>
A coating solution was obtained in the same manner as in Example 3 except that the coating material was prepared by the following procedure.
First, 24.0 g of an aqueous acrylic polyol was weighed in a beaker, and 2.8 g of ion exchange water, 69.3 g of a fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by mass, and 3.8 g of a curing agent. Were added in order. When adding each raw material, T.W. K. Stirring was performed at 1500 rpm with a homodisper (manufactured by Tokushu Kika Kogyo Co., Ltd.), and stirring was further performed for 5 minutes after all the raw materials were added. Thereafter, defoaming was performed using a defoaming device (Sinky Corp., rotation / revolution mixer AR-250). Thus, the solid content ratio (mass ratio) of the aqueous acrylic polyol, the curing agent, and the fine fibrous cellulose is 78: 22: 5 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid content is A coating solution having a concentration of 14% by mass was obtained.

<Comparative Example 5>
A coating solution was obtained in the same manner as in Example 4 except that the coating material was prepared by the following procedure.
First, 6.6 g of an aqueous acrylic polyol was weighed in a beaker, and 54.3 g of ion-exchanged water, 38.1 g of a fine fibrous cellulose dispersion (B) having a solid content concentration of 0.5% by mass, and 1.1 g of a curing agent. Were added in order. When adding each raw material, T.W. K. Stirring was performed at 1500 rpm with a homodisper (manufactured by Tokushu Kika Kogyo Co., Ltd.), and stirring was further performed for 5 minutes after all the raw materials were added. Thereafter, defoaming was performed using a defoaming device (Sinky Corp., rotation / revolution mixer AR-250). Thus, the solid content ratio (mass ratio) of the aqueous acrylic polyol, the curing agent, and the fine fibrous cellulose is 78:22:10 (aqueous acrylic polyol: curing agent: fine fibrous cellulose), and the total solid content is A coating solution having a concentration of 4% by mass was obtained.

[Production of evaluation sheet]
PP (polypropylene) film (product of Toray Industries, Inc., product name: Treffan BO, thickness 60 μm) is used as a base material, and the coating thickness obtained in Examples and Comparative Examples is 10 μm or more after drying using an applicator. It coated on the base material so that it might become. Immediately after coating, the laminate was heated for 30 minutes with a drier at a temperature of 80 ° C. to obtain a laminate comprising a sheet on the base material layer of the PP film. In addition, the thickness of the sheet was measured with a constant pressure thickness measuring instrument (PG-02J, manufactured by Teflock). Thereafter, the dried sheet was peeled from the PP film, and used for various evaluations as a fine fibrous cellulose-containing sheet.

[Measurement]
About each sheet | seat produced as mentioned above, the water absorptivity, water contact angle, haze, total light transmittance, yellowness (YI), tensile strength, and tensile elasticity modulus were measured with the following method, respectively.

[Water absorption rate]
The sheet | seat obtained from the coating liquid of the Example and the comparative example was cut out so that it might become a 5-cm square test piece. It was then weighed W _A of the test piece. Then, this test piece was immersed in ion-exchange water and kept for 24 hours. Pulling the test piece from the deionized water, after wiping off the water attached to the test piece surface with Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) to measure the weight W _B of the test piece. From the weights W _A and W _B , the water absorption of the sheet was calculated according to the following formula a.
Water absorption (mass%) = 100 × (W _B −W _A ) / W _A (Formula a)

[Water contact angle]
In accordance with JIS R 3257, 4 μL of distilled water was dropped on the sheet surface using a dynamic water contact angle tester (Fibro, 1100DAT), and the water contact angle 0.1 seconds after dropping was measured.

[Haze and total light transmittance]
According to JIS K 7136, haze was measured using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150). Further, based on JIS K 7361, the total light transmittance was measured using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150).

[Yellowness of sheet]
In accordance with JIS K 7373, the yellowness (YI) of the sheet was measured using Color Cute i (manufactured by Suga Test Instruments Co., Ltd.).

[Tensile strength]
Tensile strength (unit: N / m) using a tensile tester Tensilon (manufactured by A & D) according to JIS P 8113, except that the length of the test piece is 80 mm and the distance between chucks is 50 mm. Was measured. The tensile strength was divided by the thickness of the test piece, and the tensile strength (unit: MPa) was calculated. In addition, when measuring tensile strength, what was conditioned for 24 hours at 23 degreeC and 50% of relative humidity was used as a test piece.

[Tensile modulus]
The tensile modulus was measured using a tensile tester Tensilon (manufactured by A & D Co.) according to JIS P 8113 except that the length of the test piece was 80 mm and the distance between chucks was 50 mm. The elastic modulus is a value calculated from the maximum positive slope value in the SS curve. When measuring the tensile modulus, a specimen conditioned at 23 ° C. and 50% relative humidity for 24 hours was used as a test piece.

In Table 1, “A” to “C” in the preparation procedure of the coating liquid are procedures as described in Table 2 below.

As is apparent from the results in Table 1, from the coating liquid of the Examples containing an aqueous acrylic polyol and a polymer containing a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound and an oxazoline compound. Obtained a sheet having a low water absorption, and when a water droplet was dropped on this sheet, a large water contact angle was shown. Thus, the sheet | seat obtained in the Example was low in affinity with water, and was excellent in water resistance. Furthermore, the sheets obtained in the examples had high transparency and high sheet strength.
On the other hand, in the comparative example, a sheet having a high water absorption rate was obtained, and when a water droplet was dropped on this sheet, a small water contact angle was shown. Thus, the sheet obtained in the comparative example has a high affinity with water, and there is a concern about practical problems from the viewpoint of water resistance. From the results of Comparative Examples 1 to 3, it was suggested that the water absorption rate of the obtained sheet could be controlled by adjusting the content of fine fibrous cellulose. Further, the results of Comparative Examples 4 and 5 suggest the possibility that the water absorption rate of the obtained sheet can be controlled by the procedure for adjusting the coating solution, and further the uniformity of coating solution dispersion by the procedure for preparing the coating solution. It was suggested that the transparency of the sheet can be improved.

10 Sheet 20 Base material layer 100 Laminate

Claims

A sheet containing an acrylic polymer and fibrous cellulose having a fiber width of 1000 nm or less,
The acrylic polymer is a polymer including a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound and an oxazoline compound, and a structure derived from an aqueous acrylic polyol,
A sheet having a water absorption of 6% by mass or less when the sheet is immersed in water for 24 hours.
The sheet according to claim 1, wherein a content of the fibrous cellulose is 0.5 parts by mass or more and 19 parts by mass or less with respect to 100 parts by mass of the acrylic polymer.
The sheet according to claim 1 or 2, wherein the haze is 4.5% or less.
The sheet according to any one of claims 1 to 3, wherein the total light transmittance is 89% or more.
The sheet according to any one of claims 1 to 4, wherein the YI value is 0.3 or less.
The sheet according to any one of claims 1 to 5, wherein the tensile strength is 15 MPa or more.
The sheet according to any one of claims 1 to 6, wherein the tensile elastic modulus is 1.8 GPa or more.
The sheet according to any one of claims 1 to 7, wherein the sheet has a thickness of 10 µm or more.
A laminate comprising the sheet according to any one of claims 1 to 8 on at least one surface side of the base material layer.
The laminate according to claim 9, wherein the base material layer includes at least one selected from fibrous cellulose having a fiber width of 1000 nm or less and a water-soluble polymer.