JP2020133026A - Sheet, and laminate - Google Patents

Abstract

To provide a sheet that contains a fine fibrous cellulose and an aqueous resin, and has a low affinity with water.SOLUTION: The present invention relates to a sheet, containing an acrylic polymer and a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group, or a substituent derived from a phosphite group, and in which the acrylic polymer is a polymer containing 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 acryl polyol, and the water absorption is 6 mass% or less when the sheet is immersed in water for 24 hours.SELECTED DRAWING: None

Description

The present invention relates to sheets and laminates.

In recent years, due to the substitution of petroleum resources and heightened environmental awareness, materials using reproducible natural fibers have been attracting attention. 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 paper products.

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, development of sheets containing fine fibrous cellulose, resin composites, and thickeners is underway.

For example, Patent Document 1 discloses a water-based coating composition containing fine fibrous cellulose, a water-based resin, and a colorant. Here, it is studied to form a coating film having excellent water resistance from a water-based coating composition. The coating film in Patent Document 1 is a film that covers the surface of the base material and is in close contact with the base material.

Japanese Unexamined Patent Publication No. 2016-69618

In general, fine fibrous cellulose is stably dispersed in an aqueous solvent. Therefore, when trying to form a resin composite containing fine fibrous cellulose, a highly hydrophilic resin may be used in order to enhance the uniform dispersibility between the resin to be used and the fine fibrous cellulose. However, the resin composite such as a sheet thus obtained has a high affinity for water, and its use may be limited.

Therefore, an object of the present invention is to provide a sheet containing fine fibrous cellulose and an aqueous resin, which has a low affinity for water.

As a result of diligent studies to solve the above problems, the present inventors have set the water absorption rate to a predetermined value or less in a sheet containing fine fibrous cellulose and an aqueous acrylic polymer having a predetermined crosslinked structure. By doing so, it was found that a sheet having a 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 and having a phosphite group or a substituent derived from a phosphite group.
The acrylic polymer is a polymer containing 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 rate 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 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.
[3] The sheet according to [1] or [2], which has a haze of 4.5% or less.
[4] The sheet according to any one of [1] to [3], which has a total light transmittance of 89% or more.
[5] The sheet according to any one of [1] to [4], which has a YI value of 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 elastic modulus of 1.8 GPa or more.
[8] The sheet according to any one of [1] to [7], which has a thickness of 10 μm or more.
[9] A laminate having 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 contains 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 for water can be obtained.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group. FIG. 2 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 based on typical embodiments or 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 a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from the phosphite group. Here, the acrylic polymer is a polymer containing 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. Further, when the sheet is immersed in water for 24 hours, the water absorption rate 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-mentioned structure, the affinity with water can be suppressed to be low even if the sheet contains fine fibrous cellulose and an aqueous resin. Specifically, it can be determined that the water affinity of the sheet is low because the water contact angle of the sheet surface is large. The water contact angle of 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 of the sheet surface is preferably 120 ° or less. Here, the water contact angle on the sheet surface is a value measured in accordance with JIS R 3257, and 4 μL of distilled water is dropped on the surface of the sheet, and a dynamic water contact angle tester (1100 DAT manufactured by Fibro) is used. It is a value measured 0.1 seconds after dropping using. As described above, it can be said that the sheet of the present invention has a low affinity for water and is excellent in water resistance. In the present invention, the water contact angle of either one surface of the sheet may satisfy the above range, but it is preferable that the water contact angle of both surfaces of the sheet satisfies the above range.

The sheet of the present invention can maintain the sheet shape by itself (without a base material), and is distinguished from, for example, a coating film covering at least one surface of a base material. Here, the coating film is a film that covers at least one surface of the base material, and the coating film cannot be peeled off from the base material to form a sheet shape by itself. The sheet of the present invention may be laminated on at least one surface of the base material layer, for example, but if the sheet shape can be maintained independently, the sheet is laminated on the base material layer. 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 even more preferably 15 μm or more. The thickness of the sheet is
It is preferably 1000 μm or less. As described above, the sheet of the present invention has a certain thickness, whereby the sheet shape can be maintained independently. When the sheet of the present invention is a sheet constituting a laminated body as described later, the thickness of the sheet may be thinner than the above range. Here, the thickness of the sheet can be measured with, for example, a constant pressure thickness measuring device (manufactured by Teflock, PG-02J).

When the sheet of the present invention is immersed in water for 24 hours, the water absorption rate 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 formula by measuring the weight of the sheet after cutting it into a predetermined size (for example, 5 cm square) and then immersing the sheet piece in ion-exchanged water for 24 hours. It is the value that was set.
Water absorption _{(wt%) = 100 × (W B} -W A) / W A ··· ( wherein 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.

By setting the water absorption rate of the sheet within the above range, a sheet having a low affinity for water can be obtained. That is, a sheet having a large water contact angle on the sheet surface can be obtained. Here, in order to keep the water absorption rate of the sheet within the above range, for example, the content of fine fibrous cellulose contained in the sheet may be adjusted, or the mixing method of the raw materials constituting the sheet may be controlled. Can be mentioned. That is, the present invention optimizes the content of fine fibrous cellulose even in a sheet composed mainly of components having a high affinity for water such as fine fibrous cellulose and an aqueous resin, and further, the sheet is made. By controlling the mixing order of the constituent raw materials, we succeeded in suppressing the water affinity as a sheet to a low level. When controlling the mixing order of the raw materials constituting the sheet, it is preferable to use the mixing order described in the item (sheet manufacturing method) described later.

The content of the fine fibrous cellulose contained in the sheet is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and 2 parts by mass with respect to 100 parts by mass of the acrylic polymer. The above is more preferable. The content of the 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 even more preferable. By setting the content of the fine fibrous cellulose with respect to 100 parts by mass of the acrylic polymer within the above range, even a sheet containing a component having a high affinity for water such as the fine fibrous cellulose and an aqueous resin as a main component. , The water affinity can be suppressed low. Thereby, the water resistance of the sheet 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, fine fibrous cellulose is extracted by treating with a solvent that selectively dissolves only the resin, and the obtained solid content is the mass of the fine fibrous cellulose.

The haze of the sheet is preferably 4.5% or less, more preferably 4.0% or less, further preferably 3.0% or less, still more preferably 2.0% or less. It is preferably 1.0% or less, and particularly 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, for example, 0%. Here, the haze of the sheet is a value measured, for example, in accordance with JIS K 7136 and using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute).

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, for example, 100%. Here, the total light transmittance of the sheet is a value measured using, for example, JIS K 7361 and a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute).

The yellowness (YI) of the sheet is preferably 0.3 or less, more preferably 0.25 or less, and even more preferably 0.2 or less. The lower limit of yellowness (YI) is not particularly limited and may be 0.0. The yellowness (YI) of the sheet is a value measured by using, for example, 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 even more preferably 24 MPa or more. The upper limit of the tensile strength of the sheet is not particularly limited, but can be, for example, 240 MPa. The tensile strength of the sheet (unit: MPa) 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 in accordance with JIS P 8113 except that the length of the sheet (test piece) is 80 mm and the distance between chucks is 50 mm. As the testing machine for measuring the tensile strength, for example, a tensile testing machine Tensilon (manufactured by A & D Co., Ltd.) can be used. When measuring the tensile strength, a sheet whose humidity is controlled 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. The upper limit of the tensile elastic modulus of the sheet is not particularly limited, but may be, for example, 50 GPa. The tensile elastic modulus of the sheet was measured in accordance with JIS P 8113 except that the length of the test piece was 80 mm and the distance between chucks was 50 mm, and was calculated from the maximum positive inclination value in the SS curve. is there. As a testing machine for measuring the tensile elastic modulus, for example, a tensile testing machine Tensilon (manufactured by A & D Co., Ltd.) can be used. When measuring the tensile elastic modulus, a sheet whose humidity is controlled 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.

(Fine fibrous cellulose)
The sheet of the present invention contains fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from the phosphite group. The fiber width of the fibrous cellulose can be measured, for example, by observation with an electron microscope.

The average fiber width of the fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Especially preferable. By setting the average fiber width of the fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fibrous cellulose as a cellulose molecule in water, and to make it easier to exhibit the effects of the fibrous cellulose on improving strength, rigidity and dimensional stability. it can. The fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid to be used as a sample for TEM observation. And. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber intersecting the straight line X and the straight line Y is visually read with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the 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, destruction of the crystal region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose in an appropriate range. The fiber length of the fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

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

The ratio of the type I crystal structure to the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The degree of crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing fine fibrous cellulose. By setting the axial ratio to the above upper limit value or less, for example, when fibrous cellulose is treated as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

The fibrous cellulose in the present embodiment has, for example, both a crystalline region and a non-crystalline region. In particular, fine fibrous cellulose having both a crystalline region and a non-crystalline 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 a phosphite group or a substituent derived from the phosphite group (also simply referred to as a phosphite group). In the present invention, the phosphite group or the substituent derived from the phosphite group is, for example, a substituent represented by the following formula (2).

In equation (2), b is a natural number, m is an arbitrary number, and b × m = 1. α is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain hydrocarbon group. , An unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. Above all, it is particularly preferable that α is a hydrogen atom. The α in the formula (2) does not include a group derived from the cellulose molecular chain.

Examples of the saturated-linear hydrocarbon group represented by α in the formula (2) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like, but are not particularly limited. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. 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 chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

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

Β ^{b +} in the formula (2) is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing β is heated and is easily industrially used, but is not particularly limited.

In addition, the fine fibrous cellulose may have a phosphate group or a group derived from the phosphoric acid group in addition to the substituent derived from the phosphite group or the phosphite group. The phosphate group or the group derived from the phosphoric acid group is, for example, a substituent represented by the following formula (1) or (3). The phosphoric acid group or the group derived from the phosphoric acid group may be a condensed phosphorus oxo acid group as represented by the following formula (3).

In the formula (1), a and b are natural numbers, and m is an arbitrary number (where a = b × m). a number of alpha and alpha 'are O ^- a and the remainder is OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (1) may be a group derived from a cellulose molecular chain.

In the formula (3), a and b are natural numbers, m is an arbitrary number, and n is a natural number of 2 or more (where a = b × m). ^{α 1, α 2, ···,} a number of alpha ⁿ and alpha 'is O ^- a and the remainder is either R or OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (3) may be a group derived from a cellulose molecular chain.

The specific examples of each group in the formulas (1) and (3) are the same as the specific examples of each group in the formula (2). Further, the formula (1) and specific examples beta ^{b +} a in (3) are the same as specific examples of beta ^{b +} in equation (2).

The fact that the fine fibrous cellulose has a phosphite group as a substituent means that the infrared absorption spectrum of the dispersion containing the fine fibrous cellulose was measured, and a tautomer of the phosphite group was measured around 1210 cm ^-1. This can be confirmed by observing the P = O-based absorption of a phosphonic acid group. In addition, the fact that the fibrous cellulose has a phosphoric acid group as a substituent means that the infrared absorption spectrum of the dispersion containing the fibrous cellulose is measured, and the absorption of the phosphoric acid group based on P = O is performed in the vicinity of 1230 cm ^-1. It can be confirmed by observing. Further, the fact that fibrous cellulose has a phosphite group or a phosphate group as a substituent can be confirmed by a method of confirming a chemical shift by using NMR or a method of combining titration with elemental analysis.

The amount of the phosphorous acid group introduced into the fibrous cellulose is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of the fibrous cellulose. It is more preferably / g or more, and particularly preferably 1.00 mmol / g or more. The amount of the phosphorous acid group 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 the fibrous cellulose. It is more preferably 0.00 mmol / g or less. By setting the amount of the phosphorous acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose.
Here, the unit mmol / g indicates the amount of substituents per 1 g of mass of fibrous cellulose when the counterion of the phosphite group is a hydrogen ion (H ⁺ ).

The amount of a phosphorous acid group (including a phosphorous acid group) introduced into the fibrous cellulose can be measured by, for example, a neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH 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 added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group. The amount of the phosphorus oxo acid group introduced into the fibrous cellulose is measured, for example, as follows.
First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. The titration curve shown in the upper part of FIG. 1 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 1 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, two points are confirmed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociating acid of the fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point. The amount is equal to the amount of the second dissociating acid of the fibrous cellulose contained in the slurry used for the titration, and the amount of alkali required from the start to the second end point of the titration is the fibrous cellulose contained in the slurry used for the titration. Is equal to the total amount of dissociated acid. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxo acid group introduced (mmol / g). The amount of phosphorus oxo acid group introduced (or the amount of phosphorus oxo acid group) simply means the amount of the first dissociated acid.
In FIG. 1, the region from the start of titration to the first end point is referred to as a first region, and the region from the first end point to the second end point is referred to as a second region. For example, when the phosphoric acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of weakly acidic groups in the phosphoric acid group (also referred to as the second dissociated acid amount in the present specification) is apparently It decreases, and the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in the present specification) is the same as the amount of phosphorus atoms regardless of the presence or absence of condensation. When the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so that the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, the titration curve has one point where the pH increment is maximized.

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

In the measurement of the amount of phosphorus oxo acid groups by the titration method, if the amount of one drop of the sodium hydroxide aqueous solution is too large or the titration interval is too short, the amount of phosphorus oxo acid groups will be lower than the original value. It may not be obtained. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, for example, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

In addition, which of phosphorous acid, phosphorous acid, and condensed phosphoric acid is the phosphorous acid detected when the phosphorous acid group, the condensed phosphoric acid group, or both is contained in addition to the phosphorous acid group? As a method for distinguishing between, for example, a method of performing a treatment for cutting the condensed structure such as acid hydrolysis and then performing the above-mentioned titration operation, or a treatment for converting a phosphite group into a phosphorous acid group such as an oxidation treatment. Examples thereof include a method of performing the above-mentioned titration operation after the execution.

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

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians and bacterial cellulose produced by acetobacter can be used. Further, instead of the fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan can also be used.

<Phosphorous acid group introduction process>
The process for producing fine fibrous cellulose includes a step of introducing a phosphite group. In the phosphite group introduction step, at least one compound (hereinafter, also referred to as “compound A”) selected from compounds capable of introducing a phosphorous acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose is introduced. , A step of acting on a fiber raw material containing cellulose. By this step, a phosphite group-introduced fiber can be obtained.

In the phosphorous acid group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and Compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “Compound B”). You may go. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.

As an example of the method of causing the compound A to act on the fiber raw material in the coexistence with the compound B, a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state can be mentioned. Of these, since the reaction uniformity is high, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction uniformity is high, it is preferable to add the solution in the form of a solution dissolved in a solvent, particularly in the state of an aqueous solution. Further, compound A and compound B may be added to the fiber raw material at the same time, separately, or as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, the required amounts of compound A and compound B may be added to the fiber raw material, or after the excess amounts of compound A and compound B are added to the fiber raw material, the surplus compound A and compound B are added by pressing or filtering. It may be removed.

The compound A used in this embodiment is at least one selected from a compound having a phosphorous acid group and a salt thereof. Examples of the compound having a phosphorous acid group include phosphorous acid, and examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of the compound having a phosphorous acid group include a lithium salt, a sodium salt, a potassium salt, and an ammonium salt of phosphorous acid, and these can have various neutralization degrees. Of these, phosphorous acid and phosphorous acid are highly efficient in introducing phosphorous acid groups, are more likely to improve defibration efficiency in the defibration step described later, are low in cost, and are easy to apply industrially. A sodium salt of acid, a potassium salt of phosphorous acid, or an ammonium salt of phosphorous acid is preferably used.

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

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

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

In the reaction between the fiber raw material containing cellulose and compound A, for example, amides or amines may be contained in the reaction system in addition to compound B. Examples of 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 act as a good reaction catalyst.

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

In the heat treatment according to the present embodiment, for example, a method of adding compound A to a thin sheet-shaped fiber raw material by a method such as impregnation and then heating, or a method of heating while kneading or stirring the fiber raw material and compound A with a kneader or the like. Can be adopted. This makes it possible to suppress uneven concentration of the compound A in the fiber raw material and more uniformly introduce the phosphorous acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules by the surface tension and also moves to the surface of the fiber raw material (that is, the concentration unevenness of the compound A is caused. It is considered that this is due to the fact that it can be suppressed.

Further, the heating device used for the heat treatment always keeps the water content retained by the slurry and the water content generated by the dehydration condensation (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 device can be discharged to the outside of the device system. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, in addition to being able to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphate esterification, it is also possible to suppress the acid hydrolysis of the sugar chain in the fiber. it can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

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

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

The amount of the phosphorous acid group introduced into the fiber raw material is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of fine fibrous cellulose. It is more preferably / g or more, and particularly preferably 1.00 mmol / g or more. Further, the amount of the phosphorous acid group introduced into the fiber raw material is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of fine fibrous cellulose, for example, 3 It is more preferably 0.00 mmol / g or less. By setting the amount of the phosphorous acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose.

<Washing process>
In the method for producing fine fibrous cellulose in the present embodiment, a washing step can be performed on the phosphorous acid group-introduced fiber, if necessary. The cleaning step is performed, for example, by cleaning the phosphite group-introduced fibers with water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.

<Alkaline treatment process>
When producing fine fibrous cellulose, an alkali treatment may be performed on the fiber raw material between the phosphorous acid group introduction step and the defibration treatment step described later. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the phosphorous acid group-introduced fiber in an alkaline solution.

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

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersion time of the phosphorous acid group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10000% by mass or less, based on the absolute dry mass of the phosphorous acid group-introduced fiber. The following is more preferable.

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

<Acid treatment process>
In the case of producing fine fibrous cellulose, the fiber raw material may be subjected to acid treatment between the step of introducing a phosphorous acid group and the defibration treatment step described later. For example, the phosphorous acid group introduction step, the acid treatment, the alkali treatment, and the defibration treatment may be performed in this order.

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

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1,000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the fiber raw material. Is more preferable.

<Fiber processing>
Fine fibrous cellulose can be obtained by defibrating the phosphite-introduced fiber in the defibration treatment step. In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibrating apparatus is not particularly limited, but for example, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical refiner, and a twin shaft. A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-mentioned defibration processing devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, and an ultra-high-pressure homogenizer, which are less affected by crushed media and less likely to cause contamination.

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

The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the phosphorous acid group-introduced fiber in a dispersion medium may contain a solid content other than the phosphorous acid group-introduced fiber such as urea having a hydrogen bond property.

(Acrylic polymer)
The sheet of the present invention contains an acrylic polymer as an aqueous resin. Here, the acrylic polymer is a polymer containing 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 an 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 containing a hydroxy group-containing (meth) acrylate and a vinyl compound as copolymerization components. In the present specification, the term (meth) acrylate means a general term for acrylate and methacrylate. Further, the aqueous acrylic polyol may contain a structure derived from a (meth) acrylate other than the hydroxy group-containing (meth) acrylate. Examples of the hydroxy group-containing (meth) acrylate include 2-hydroxy (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples of the (meth) acrylate other than the hydroxy group-containing (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Can be mentioned.

The 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, vinyltoluene, α-methylstyrene, acrylonitrile, and acrylamide. ..

The acrylic polymer contains a structure derived from at least one compound selected from an isocyanate compound, a carbodiimide compound and an oxazoline compound. Here, the above compound is a curing agent or a cross-linking agent. Among them, the acrylic polymer preferably contains a structure derived from an isocyanate compound, and the isocyanate compound also includes polyisocyanate having two or more isocyanate groups. For example, the isocyanate group forms a crosslinked structure by reacting with the hydroxy group of the aqueous acrylic polyol.

(Optional ingredient)
The sheet of the present invention may contain a water-soluble polymer in addition to the acrylic polymer and fine fibrous cellulose described above. Examples of the water-soluble polymer include carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate / acrylic acid copolymer, polyvinylpyrrolidone, sodium polyacrylate, polyethylene glycol, diethylene glycol, triethylene glycol, polyethylene oxide, propylene glycol and dipropylene glycol. Synthetic water-soluble polymers such as 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, purulan , Carrageenan, and thickening polysaccharides such as pectin; cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hirodoxyethyl cellulose; cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, etc. , And starches such as amylose; glycerins such as glycerin, diglycerin, and polyglycerin; hyaluronic acid, metal salts of hyaluronic acid, and the like.

Further, 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 the 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-based resin, thermoplastic polyimide-based resin, polyacetal-based resin, polysulfone-based resin, amorphous fluorine-based resin, rosin-based resin, nitrocellulose, vinyl chloride-based resin, rubber chloride-based resin, vinyl acetate resin, phenol resin, epoxy Resin and the like can be mentioned.

Further, the sheet of the present invention has, as optional components, for example, a surfactant, an organic ion, a coupling agent, an inorganic layered compound, an inorganic compound, a leveling agent, a preservative, an antifoaming agent, an organic particle, a lubricant, and an antistatic agent. It may contain an inhibitor, an ultraviolet protective agent, a dye, a pigment, a stabilizer, a magnetic powder, an orientation accelerator, a plasticizer, a dispersant, a cross-linking agent and the like. 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 more preferably 30% by mass or less, based on the total mass of the sheet. More preferred.

In addition, 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, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of hydrocarbons include n-hexane, toluene, xylene and the like. Examples of halogens include methylene chloride, trichlorethylene, 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 even more preferable.

(Sheet manufacturing method)
In the method for producing a sheet of the present invention, a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from a phosphite group, an aqueous acrylic polyol, an isocyanate compound, a carbodiimide compound and an oxazoline. A step of mixing at least one compound selected from the compounds to obtain a sheet-forming composition (hereinafter, also referred to as a slurry or a coating liquid) and coating the sheet-forming composition on a substrate. The coating step is included, or the paper making step of making the sheet-forming composition is included. As a result, the above-mentioned sheet can be obtained.

<Step of obtaining a sheet-forming composition>
In the step of obtaining the sheet-forming composition, a dispersion liquid containing fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from the phosphite group is diluted as necessary. In the step of obtaining the sheet-forming composition, it is preferable to include this step 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, and preferably 1% by mass or less, based on the total mass of the diluted dispersion. Is more preferable. The content of the fine fibrous cellulose contained in the diluted dispersion is preferably 0.001% by mass or more with respect to the total mass of the diluted dispersion. As described above, in the first step, it is preferable to prepare a dispersion having a low content of fine fibrous cellulose, whereby a sheet having a low water absorption rate can be obtained.

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

As a 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, the carbodiimide compound and the oxazoline compound added in the third step is a curing agent or a cross-linking agent.

When each raw material is added in the second step and the third step, it is preferable to stir using a stirrer. As a stirrer, for example, T.I. K. Homo Dispar (manufactured by Tokushu Kagaku Kogyo) can be used, and the stirring speed is preferably 500 to 5000 rpm. The stirring time is preferably 1 minute to 100 minutes.

As described above, in the step of obtaining the sheet-forming composition, it is preferable to include the first step to the third step in this order, but the content of the fine fibrous cellulose in the dispersion liquid containing the fine fibrous cellulose is low. In this case, the first step may be omitted and the third step may be included after the second step. It should be noted that another step may be included between the first step and the second step, and another step may be included between the second step and the third step. Further, 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.

Through the above steps, the sheet-forming composition is an acrylic-based composition containing 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 polymer will be included. The content of the acrylic polymer in the sheet-forming composition is preferably 83.5% by mass or more, more preferably 85% by mass or more, based on the total solid content mass in the composition. , 87.5% by mass or more is more preferable. 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 mass in the composition. It is more preferably 5% by mass or less.

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

<Coating process>
In the coating step, for example, a sheet-forming composition (slurry) containing fibrous cellulose can be applied onto a base material, and the sheet formed by drying the composition can be peeled off from the base material to obtain a sheet. it can. Further, by using a coating device and a long base material, sheets can be continuously produced.

The material of the base material used in the coating process is not particularly limited, but a material having high wettability to the sheet-forming composition (slurry) may suppress shrinkage of the sheet during drying, but drying It is preferable to select a sheet in which the sheet formed later can be easily peeled off. Of these, a resin film or plate or a metal film or plate is preferable, but is not particularly limited. For example, resin films and plates such as polypropylene, acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polycarbonate, and polyvinylidene chloride, metal films and plates of aluminum, zinc, copper, and iron plates, and their surfaces are oxidized. , Stainless film or plate, brass film or plate, etc. can be used.

In the coating process, if the viscosity of the slurry is low and it develops on the base material, a dammed frame is fixed on the base material to obtain a sheet with a predetermined thickness and basis weight. You may. The frame for damming is not particularly limited, but it is preferable to select, for example, a frame in which the end portion of the sheet that adheres after drying can be easily peeled off. From this point of view, a resin plate or a metal plate molded 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, 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 whose surfaces are oxidized, stainless steel plates, brass plates and the like can be used.
The coating machine for coating the slurry on the base material is not particularly limited, and for example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater, or the like 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 the slurry is applied to the substrate are not particularly limited, but are preferably, for example, 5 ° C. or higher and 80 ° C. or lower, more preferably 10 ° C. or higher and 60 ° C. or lower, and 15 ° C. It is more preferably 50 ° C. or lower, and particularly preferably 20 ° C. or higher and 40 ° C. or lower. When the coating temperature is equal to or higher than the above lower limit, the slurry can be coated more easily. When the coating temperature is not more than the above upper limit value, volatilization of the dispersion medium during coating can be suppressed.

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

As described above, the coating step includes a step of drying the slurry coated on the substrate. The step of drying the slurry is not particularly limited, but 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, and for example, a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heat drying method) or a method of vacuum drying (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. Drying with infrared rays, far infrared rays or near infrared rays is not particularly limited, but can be performed by using, for example, an infrared device, a far infrared device or a near infrared device.

The heating temperature in the heat-drying method is not particularly limited, but is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 25 ° C. or higher and 105 ° C. or lower. When the heating temperature is set to the above lower limit value or more, the dispersion medium can be rapidly volatilized. Further, when the heating temperature is not more than the above upper limit value, it is possible to suppress the cost required for heating and suppress the discoloration of the fibrous cellulose due to heat.

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

The papermaking process is performed by filtering and dehydrating the slurry with a wire to obtain a wet paper sheet, and then pressing and drying the sheet. The filter cloth used for filtering and dehydrating the slurry 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, or a porous membrane is preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE) are preferable. In the present embodiment, for example, a porous membrane of polytetrafluoroethylene having a pore size of 0.1 μm or more and 20 μm or less, polyethylene terephthalate having a pore size of 0.1 μm or more and 20 μm or less, a polyethylene woven fabric, or the like can be mentioned.

In the sheeting process, a method of producing a sheet from a slurry is, for example, a water-squeezed section in which a slurry containing fibrous cellulose is discharged onto the upper surface of an endless belt and a dispersion medium is squeezed from the discharged slurry to generate a web. This can be done using a manufacturing apparatus comprising a drying section that dries the web to produce a sheet. An endless belt is arranged from the watering section to the drying section, and the web generated in the watering 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 the production of paper. Among these, a method of dehydrating with a long net, a circular net, an inclined wire or the like and then further dehydrating with a roll press is preferable. The drying method used in the papermaking process is not particularly limited, and examples thereof include methods used in the production of paper. 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 having the above-mentioned sheet on at least one surface side of the base material layer. FIG. 2 is a cross-sectional view illustrating the structure of the laminated body 100. As shown in FIG. 2, the laminated body 100 has a sheet 10 laminated on the base material layer 20. Here, another layer may be provided between the base material layer 20 and the sheet 10, but it is preferable that the sheet 10 is laminated so as to be in direct contact with the base material layer 20. Although FIG. 2 shows a laminate 100 in which a sheet 10 is formed on one side of the base material layer 20, the laminate of the present invention has sheets formed on both sides of the base material layer 20. It may be a laminated body, a laminated body having a base material layer on both sides of the sheet, or a laminated body containing two or more layers of the base material layer and the sheet, respectively.

Examples of the base material layer include a resin layer and an inorganic layer. Further, the base material layer is 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 the fine fibrous cellulose is preferably 0.5% by mass or more and 95% by mass or less. When the base material layer is a layer containing fine fibrous cellulose, the fine fibrous cellulose preferably has a phosphoric acid group or a substituent derived from the phosphoric acid group. In addition, in this specification, a phosphoric acid group and a phosphite group are mentioned as a phosphorous acid group.

An adhesive layer may be provided between the above-mentioned sheet and the base material layer, or the sheet and the base material layer may be in direct contact with each other without the adhesive layer. When an adhesive layer is provided between the sheet and the base material layer, examples of the adhesive constituting the adhesive layer include acrylic resins. Examples of the adhesive other than the acrylic resin include vinyl chloride resin, (meth) acrylic acid ester resin, styrene / acrylic acid ester copolymer resin, vinyl acetate resin, and vinyl acetate / (meth) acrylic acid 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. Be 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. The thickness of the base material layer is preferably 10000 μm or less, more preferably 1000 μm or less.

When the base material layer is a resin layer or an inorganic layer, the resin layer or the inorganic layer may be, for example, the layers listed below.

<Resin layer>
The resin layer is a layer containing a natural resin or a synthetic resin as a main component. Here, the main component refers to a component contained in an amount of 50% by mass or more with respect to the total mass of the 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, based on the total mass of the resin layer. The above is particularly preferable. The resin content may be 100% by mass or 95% by mass or less.

Examples of the natural resin include rosin-based resins such as rosin, rosin ester, and hydrogenated rosin ester.

As the synthetic resin, for example, at least one selected from polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, polyurethane resin and acrylic resin is preferable. Among them, the synthetic resin is preferably at least one selected from the polycarbonate resin and the acrylic resin, and more preferably the 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 aromatic polycarbonate-based resins and aliphatic polycarbonate-based resins. These specific polycarbonate-based resins are known, and examples thereof include the polycarbonate-based resins described in JP-A-2010-023275.

As the resin constituting the resin layer, one kind may be used alone, or a copolymer obtained by copolymerizing or graft-polymerizing a plurality of resin components may be used. Further, a plurality of resin components may be used as a blend material mixed by a physical process.

An adhesive layer may be provided between the sheet and the resin layer, or the sheet and the resin layer may be in direct contact with each other without the adhesive layer. When an adhesive layer is provided between the sheet and the resin layer, for example, acrylic resin can be mentioned as the adhesive constituting the adhesive layer. Examples of the adhesive other than the acrylic resin include vinyl chloride resin, (meth) acrylic acid ester resin, styrene / acrylic acid ester copolymer resin, vinyl acetate resin, and vinyl acetate / (meth) acrylic acid ester co-weight. Examples thereof include coalesced resin, urethane resin, silicone resin, epoxy resin, ethylene / vinyl acetate copolymer resin, polyester resin, polyvinyl alcohol resin, ethylene vinyl alcohol copolymer resin, 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 aid, or the surface of the resin layer may be subjected to surface treatment such as hydrophilization treatment.
Examples of the adhesion aid 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 them, the adhesion aid is preferably at least one selected from a compound containing an isocyanate group (isocyanate compound) and an organosilicon compound. Examples of the organosilicon compound include a silane coupling agent condensate and a silane coupling agent.
Examples of the surface treatment method other than the hydrophilization treatment include corona treatment, plasma discharge treatment, UV irradiation treatment, electron beam irradiation treatment, and flame treatment.

<Inorganic layer>
The substance constituting the inorganic layer is not particularly limited, and is, for example, aluminum, silicon, magnesium, zinc, tin, nickel, titanium; these oxides, carbides, nitrides, oxide carbides, oxide nitrides, or oxide carbides. Things; or mixtures thereof. From the viewpoint that high moisture resistance can be stably maintained, silicon oxide, silicon nitride, silicon oxide carbide, silicon nitride, silicon oxide, aluminum oxide, aluminum nitride, aluminum oxide carbide, aluminum nitride, or any of these. The mixture is preferred.

The method for forming the inorganic layer is not particularly limited. Generally, the method for forming a thin film is roughly classified into a chemical vapor deposition (CVD) method and a physical vapor deposition method (PVD), and any method may be adopted. .. Specific examples of the CVD method include plasma CVD using plasma, catalytic chemical vapor deposition (Cat-CVD) in which a material gas is catalytically pyrolyzed using a heating catalyst, and the like. Specific examples of the PVD method include vacuum deposition, ion plating, sputtering and the like.

Further, as a method for forming the inorganic layer, an atomic layer deposition method (Atomic Layer Deposition, ALD) can also be adopted. The ALD method is a method of forming a thin film in atomic layer units by alternately supplying the raw material gas of each element constituting the film to be formed to the surface on which the layer is formed. Although it has the disadvantage of a slow film formation rate, it has the advantage of being able to cleanly cover even a surface having a complicated shape and forming a thin film with few defects, as compared with the plasma CVD method. Further, 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 process, and reduce the amount of unreacted gas by using plasma.

(Use)
The use of the sheet of the present invention is not particularly limited. For example, sheets are suitable for applications of light transmissive substrates such as optical films, various display devices, and various solar cells. It is also suitable for applications such as substrates for electronic devices, materials for home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, and packaging materials. Further, it is suitable for applications such as threads, filters, woven fabrics, cushioning materials, sponges, abrasives, and the sheet itself as a reinforcing material.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.
In the following examples, for convenience of explanation, a slurry treated with fine fibrous cellulose is referred to as a fine fibrous cellulose dispersion. A mixture of a fine fibrous cellulose dispersion, a resin, a curing agent, and the like is called a 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.

<Manufacturing of fine fibrous cellulose dispersion>
[Pulp subphosphorylation process]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheet, dissociated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) is 700 ml) It was used.

The raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to add 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. The amount was adjusted to be parts by mass, and a chemical-impregnated pulp was obtained. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphite group into the cellulose in the pulp to obtain a phosphite pulp.

Then, the obtained subphosphorylated pulp was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of subphosphorylated pulp is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. Was done by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

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

The infrared absorption spectrum of the obtained subphosphorylated pulp was measured using FT-IR. As a result, absorption based on P = O of the phosphonic acid group, which is a tautomer of the phosphite group, was observed around 1210 cm ^-1 , and the phosphite group (phosphonic acid group) was added to the pulp. Was confirmed. Further, when the obtained subphosphorylated pulp was tested and analyzed by an X-ray diffractometer, two positions were found: 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals. The amount of phosphite group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphite group amount] described later for the obtained phosphorous acid pulp was 1.51 mmol / g. It was. The total amount of dissociated acid was 1.54 mmol / g.

[Defibering process]
Ion-exchanged water was added to the obtained subphosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizer (Starburst, manufactured by Sugino Machine Limited) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (1) containing fine fibrous cellulose. By X-ray diffraction, it was confirmed that this fine fibrous cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm.

<Measurement of fiber width>
The fiber width of the fine fibrous cellulose was measured by the following method.
The supernatant of the fine fibrous cellulose dispersion (1) obtained by treating with a wet atomizing device is adjusted so that the concentration of the fine fibrous cellulose is 0.01% by mass or more and 0.1% by mass or less. It was diluted with water and added dropwise to the hydrophilized 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 phosphite group amount>
The amount of phosphite groups in the fine fibrous cellulose is a fiber prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The cellulose-like cellulose-containing slurry was treated with an ion exchange resin and then titrated with an alkali.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, which has been conditioned) with a volume of 1/10 is added to the fibrous cellulose-containing slurry, and the slurry is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
For titration using alkali, the change in pH value indicated by the slurry is measured while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry treated with an ion exchange resin every 5 seconds. I went by doing. The titration was carried out while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point was divided by the solid content (g) in the slurry to be titrated, and the value was defined as the amount of phosphite groups (mmol / g).

[Preparation of fine fibrous cellulose-containing sheet]
<Example 1>
Ion-exchanged 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 of 0.2% by mass.
Weigh 49.8 g of the obtained fine fibrous cellulose dispersion (A) in a beaker, and weigh 10.3 g of ion-exchanged water, an aqueous acrylic polyol (manufactured by DIC, product name: Barnock WD-551, solid content concentration 45.). 34.5 g (0% by mass) and 5.5 g of a curing agent (manufactured by DIC, product name: Burnock DNW-5500, polyisocyanate, solid content concentration 79.8% by mass) were added in this order. When adding each raw material, T.I. K. Stirring was performed at 1500 rpm with Homo Dispar (manufactured by Tokushu Kagaku Kogyo), and after all the raw materials were added, stirring was further performed for 5 minutes. Then, the defoaming treatment was performed with a defoaming device (manufactured by Shinky Co., Ltd., rotation / revolution mixer AR-250). In this way, 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 liquid having a concentration of 20% by mass was obtained.

<Example 2>
Weigh 69.3 g of the fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by mass in a beaker, and add 2.8 g of ion-exchanged water, 24.0 g of an aqueous acrylic polyol, and 3.8 g of a curing agent in this order. A coating liquid 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 total solid content concentration was 14% by mass.

<Example 3>
Ion-exchanged 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 of 0.5% by mass. Example 1 and Example 1 except that 38.1 g of the fine fibrous cellulose dispersion (B) was weighed in 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 added in this order. A coating liquid 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 concentration was 4% by mass.

<Example 4>
Ion-exchanged 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 of 1.0% by mass. 54.6 g of the fine fibrous cellulose dispersion (C) was weighed in 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 this order. A coating liquid 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 concentration was 6% by mass.

<Example 5>
Weigh 78.3 g of a fine fibrous cellulose dispersion (C) having a solid content concentration of 1.0% by mass in a beaker, and add 11.3 g of ion-exchanged water, 9.0 g of an aqueous acrylic polyol, and 1.4 g of a curing agent in this order. A coating liquid 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 total solid content concentration was 6% by mass.

<Comparative example 1>
The coating liquid was applied in the same manner as in Example 1 except that 34.7 g of the aqueous acrylic polyol, 59.8 g of ion-exchanged water, and 5.5 g of the curing agent were added in this order to the beaker without adding the fine fibrous cellulose dispersion liquid. 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 concentration was 20% by mass.

<Comparative example 2>
Weigh 10.0 g of the fine fibrous cellulose dispersion (A) having a solid content concentration of 0.2% by mass in a beaker, and add 49.9 g of ion-exchanged water, 34.6 g of an aqueous acrylic polyol, and 5.5 g of a curing agent in this order. A coating liquid 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 total solid content concentration was 20% by mass. It was.

<Comparative example 3>
Weigh 66.7 g of fine fibrous cellulose dispersion (C) with a solid content concentration of 1.0% by mass in a beaker, and add 26.6 g of ion-exchanged water, 5.8 g of aqueous acrylic polyol, and 0.9 g of curing agent in this order. A coating liquid 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 concentration was 4% by mass.

<Comparative example 4>
A coating liquid was obtained in the same manner as in Example 3 except that the paint was prepared by the following procedure.
First, 24.0 g of an aqueous acrylic polyol is weighed in a beaker, and 2.8 g of ion-exchanged 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 are placed therein. Were added in order. When adding each raw material, T.I. K. Stirring was performed at 1500 rpm with Homo Dispar (manufactured by Tokushu Kagaku Kogyo), and after all the raw materials were added, stirring was further performed for 5 minutes. Then, the defoaming treatment was performed with a defoaming device (manufactured by Shinky Co., Ltd., rotation / revolution mixer AR-250). In this way, 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. A coating liquid having a concentration of 14% by mass was obtained.

<Comparative example 5>
A coating liquid was obtained in the same manner as in Example 4 except that the paint was prepared by the following procedure.
First, 6.6 g of an aqueous acrylic polyol is 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 are placed therein. Were added in order. When adding each raw material, T.I. K. Stirring was performed at 1500 rpm with Homo Dispar (manufactured by Tokushu Kagaku Kogyo), and after all the raw materials were added, stirring was further performed for 5 minutes. Then, the defoaming treatment was performed with a defoaming device (manufactured by Shinky Co., Ltd., rotation / revolution mixer AR-250). In this way, 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. A coating liquid having a concentration of 4% by mass was obtained.

[Preparation of evaluation sheet]
Using a PP (polypropylene) film (manufactured by Toray Industries, Inc., product name: Trefan BO, thickness 60 μm) as a base material, the coating liquids obtained in Examples and Comparative Examples have a sheet thickness of 10 μm or more after being dried using an applicator. It was coated on the base material so as to be. Immediately after coating, the mixture was heated in a dryer at a temperature of 80 ° C. for 30 minutes to obtain a laminate having a sheet on a base material layer of a PP film. The thickness of the sheet was measured with a constant pressure thickness measuring device (manufactured by Teflock, PG-02J). Then, the dried sheet was peeled off from the PP film and used as a fine fibrous cellulose-containing sheet for various evaluations.

[Measurement]
For each sheet prepared as described above, the water absorption rate, the water contact angle, the haze, the total light transmittance, the yellowness (YI), the tensile strength and the tensile elastic modulus were measured by the following methods.

[Water absorption rate]
Sheets obtained from the coating liquids of Examples and Comparative Examples were cut out to form test pieces of 5 cm square. It was then weighed W _A of the test piece. Then, this test piece was immersed in ion-exchanged water and held 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. Weight W _A, from W _B, was calculated water absorption of the sheet in accordance with the formula a below.
Water absorption _{(wt%) = 100 × (W B} -W A) / W A ··· ( wherein 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 (1100 DAT manufactured by Fibro), and the water contact angle 0.1 seconds after the dropping was measured.

[Haze and total light transmittance]
The haze was measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute) in accordance with JIS K 7136. In addition, the total light transmittance was measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute) in accordance with JIS K 7361.

[Yellowness of sheet]
According to JIS K 7373, the yellowness (YI) of the sheet was measured using Color Cutei (manufactured by Suga Test Instruments Co., Ltd.).

[Tensile strength]
Tensile strength (unit: N / m) using a tensile tester Tensilon (manufactured by A & D Co., Ltd.) in accordance with JIS P 8113 except that the length of the test piece is 80 mm and the distance between chucks is 50 mm. Was measured. This tensile strength was divided by the thickness of the test piece to calculate the tensile strength (unit: MPa). When measuring the tensile strength, a test piece prepared at 23 ° C. and a relative humidity of 50% for 24 hours was used.

[Tensile modulus]
The tensile elastic modulus was measured using a tensile tester Tensilon (manufactured by A & D Co., Ltd.) in accordance with 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 elastic modulus, a test piece prepared at 23 ° C. and a relative humidity of 50% for 24 hours was used.

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

As is clear from the results in Table 1, from the coating liquid of the example containing the aqueous acrylic polyol and the polymer containing the structure derived from at least one compound selected from the isocyanate compound, the carbodiimide compound and the oxazoline compound. A sheet having a low water absorption rate was obtained, and when water droplets were dropped on this sheet, a large water contact angle was shown. As described above, the sheet obtained in the examples had a low affinity for water and was excellent in water resistance. Further, the sheet 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 water droplets were dropped on this sheet, a small water contact angle was shown. As described above, the sheet obtained in the comparative example has a high affinity with water, and there is a concern about a practical problem 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 the fine fibrous cellulose. In addition, the results of Comparative Examples 4 and 5 suggest that the water absorption rate of the obtained sheet can be controlled by the coating liquid adjusting procedure, and further, the uniformity of the dispersion of the coating liquid is suggested by the coating liquid preparation procedure. It was suggested that the transparency of the sheet could be increased.

10 Sheet 20 Base material layer 100 Laminated body

Claims (10)

A sheet containing an acrylic polymer and fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from a phosphite group.
The acrylic polymer is a polymer containing 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 rate of 6% by mass or less when the sheet is immersed in water for 24 hours. The sheet according to claim 1, wherein the 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, which has a tensile strength of 15 MPa or more. The sheet according to any one of claims 1 to 6, which has a tensile elastic modulus of 1.8 GPa or more. The sheet according to any one of claims 1 to 7, which 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 contains at least one selected from fibrous cellulose having a fiber width of 1000 nm or less and a water-soluble polymer.