JP2020172035A - Laminate - Google Patents

Abstract

To provide a laminate having excellent strength and transparency and excellent flexibility.SOLUTION: There is provided a laminate having a fine fibrous cellulose-containing layer containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer, on at least one side of a cellophane sheet, in which a thickness of the fine fibrous cellulose-containing layer is 10 μm or more and 500 μm or less, and a thickness unevenness of the laminate is 50% or less.SELECTED DRAWING: None

Description

The present invention relates to a laminate.

Regenerated cellulose films are generally called cellophane, cellophane films, etc., and are used as packaging materials for various articles, base materials for sheets, and the like. However, at present, it is difficult to produce cellophane with a thick film thickness because cellophane contains conversion to cellulose in the production process. Usually, the thickness of cellophane is 10 μm to 50 μm. Although cellophane is excellent in transparency and moderate rigidity, its use is limited due to restrictions on film thickness.
The purpose of Patent Document 1 is to provide a manufacturing method for obtaining an antistatic laminated cellophane that can increase the thickness while maximizing the antistatic performance of cellophane and has improved biodegradation performance. , A plurality of cellophane films are impregnated to form a water-swelled cellophane paper, and a water-soluble adhesive is applied between the water-swelled cellophane papers to be laminated, and then dried. The method for producing cellophane is described.

Japanese Unexamined Patent Publication No. 2013-166362

In the method for producing laminated cellophane described in Patent Document 1, although thick laminated cellophane can be obtained, the haze tends to decrease because the cellophane films are laminated.
An object of the present invention is to provide a laminate having excellent strength and transparency and excellent flexibility. Furthermore, an object of the present invention is to provide a method for producing the laminated body having excellent productivity.

The present inventors have solved the above-mentioned problems by forming a laminate having a fine fibrous cellulose-containing layer containing fine fibrous cellulose and a water-soluble polymer on at least one surface of the cellophane sheet. I found it.
That is, the present invention relates to the following <1> to <6>.
<1> A laminate having a fine fibrous cellulose-containing layer containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer on at least one surface of the cellophane sheet, and the fine fibrous cellulose. A laminate in which the thickness of the containing layer is 10 μm or more and 500 μm or less, and the thickness unevenness of the laminate is 50% or less.
<2> The laminate according to <1>, wherein the content of the fine fibrous cellulose in the solid content of the fine fibrous cellulose-containing layer is 5% by mass or more and 95% by mass or less.
<3> A laminating step of laminating a cellophane sheet and a fine fibrous cellulose-containing sheet containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer to obtain a laminate, and the laminate. A method for producing a laminate, which comprises a drying step of drying the cells in this order, wherein at least one of the cellophane sheet and the fine fibrous cellulose-containing sheet is in a wet state in the laminate.
<4> The method for producing a laminate according to <3>, wherein the thickness of the fine fibrous cellulose-containing sheet is 10 μm or more and 500 μm or less.
<5> The method for producing a laminate according to <3> or <4>, further comprising a step of crimping the laminate after the lamination step and before the drying step.
<6> The method for producing a laminate according to any one of <3> to <5>, wherein the drying temperature in the drying step is 50 ° C. or higher.

According to the present invention, it is possible to provide a laminated body having excellent strength and transparency and excellent flexibility. Further, according to the present invention, it is possible to provide a method for producing the laminated body having excellent productivity.

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 graph showing the relationship between the amount of NaOH added dropwise to the fibrous cellulose-containing slurry having a carboxy group and the pH. FIG. 3 is a conceptual diagram of a test piece in the evaluation of folding cracks in the examples.

[Laminate and its manufacturing method]
The laminate of the present invention is a laminate having a fine fibrous cellulose-containing layer containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer on at least one surface of a cellophane sheet. The thickness of the fine fibrous cellulose-containing layer is 10 μm or more and 500 μm or less, and the thickness unevenness of the laminate is 50% or less. According to the laminate of the present invention, it is possible to provide a laminate having excellent strength and transparency and excellent flexibility. Further, the laminated body of the present invention suppresses uneven thickness.
Further, in the method for producing a laminate of the present invention, a cellophane sheet and a fine fibrous cellulose-containing sheet containing a fiber width of 1,000 nm or less and a water-soluble polymer are laminated and laminated. A laminating step of obtaining a product (hereinafter, also referred to as “step 1”) and a drying step of drying the laminating material (hereinafter, also referred to as “step 2”) are provided in this order. At least one of the cellophane sheet and the fine fibrous cellulose-containing sheet is in a wet state.
According to the method for producing a laminate of the present invention, a laminate having excellent strength and transparency and further excellent flexibility can be produced easily and with high productivity. Further, a laminated body in which the occurrence of thickness unevenness is suppressed is provided.
The detailed reason for obtaining the above-mentioned effects is unknown, but some of them are considered as follows. Fine fibrous cellulose is also used as a filler, has high strength, and is excellent in transparency. In the present invention, it is considered that a laminate having excellent transparency and strength is obtained by laminating a fine fibrous cellulose-containing layer containing fine fibrous cellulose and a water-soluble polymer with a cellophane sheet. Further, since the fine fibrous cellulose-containing layer contains a water-soluble polymer, the adhesiveness between the cellophane sheet and the fine fibrous cellulose-containing layer is improved, and a laminated body having excellent flexibility can be obtained. It is considered to be. Here, excellent flexibility means that no crease occurs when the bending test is performed. The test method is as described in the examples.
Further, in the method for producing a laminated body of the present invention in which a cellophane sheet and a fine fibrous cellulose-containing sheet are laminated, the fine fibrous cellulose-containing sheet having a constant thickness in advance and the cellophane sheet are laminated, and thus coated. It is considered that, unlike the case where the fine fibrous cellulose-containing layer is provided, the occurrence of thickness unevenness is suppressed, and as a result, the strength and flexibility are improved.
When a fine fibrous cellulose dispersion containing fine fibrous cellulose is applied to the cellophane sheet, the fine fibrous cellulose-containing layer on the cellophane sheet shrinks or cracks during drying, and the cellophane sheet is dried at room temperature. Unless it is dried under mild conditions, it is difficult to sufficiently suppress uneven thickness. However, when dried under mild conditions, productivity tends to decrease. According to the present invention, it is possible to produce a laminated body having excellent strength and flexibility with high productivity while suppressing thickness unevenness.
Hereinafter, the present invention will be described in more detail.

<Cellophane sheet>
The cellophane sheet is not particularly limited, and a commonly used cellophane sheet can be used. In general, cellophane is produced by the following method. That is, fibers (cellulose) obtained from cotton, pulp, waste paper, etc. are prepared into viscose by reaction with carbon disulfide in the presence of alkali, and the slurry-like viscose is coagulated containing sulfuric acid and sodium sulfate. It is released while forming a film with a hopper or the like in the bath. Here, viscose is converted to cellulose. In this way, a regenerated cellulose (cellophane) sheet is produced. After that, the cellophane sheet is completed by washing with water, desulfurization, bleaching, soft finishing, drying and the like. As can be seen from the series of processes, the cellophane sheet is excellent in biodegradability because natural cellulose is used as a raw material.

The thickness of the cellophane sheet is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and preferably 50 μm from the viewpoint of manufacturing and obtaining a laminated body having excellent strength. Hereinafter, it is more preferably 45 μm or less, still more preferably 40 μm or less. The film thickness is the thickness of the cellophane sheet in a dry state.

The basis weight of the cellophane sheet is not particularly limited, but is preferably 10 g / m ² or more, more preferably 20 g / m ² or more, still more preferably, from the viewpoint of manufacturing and obtaining a laminate having excellent strength and transparency. Is 40 g / m ² or more, and preferably 80 g / m ² or less, more preferably 70 g / m ² or less, still more preferably 60 g / m ² or less.

The haze of the cellophane sheet is preferably 0.4% or more, more preferably 0.8% or more, still more preferably 1.2% or more from the viewpoint of obtaining a laminated body having excellent transparency and from the viewpoint of availability. Yes, and preferably 2.5% or less, more preferably 2.0% or less, still more preferably 1.5% or less.
Haze is measured by the method described in the Examples.

<Fine fibrous cellulose-containing layer and fine fibrous cellulose-containing sheet>
The fine fibrous cellulose-containing layer contains fine fibrous cellulose and a water-soluble polymer. Further, the fine fibrous cellulose-containing sheet contains fine fibrous cellulose and a water-soluble polymer.
The fine fibrous cellulose and the water-soluble polymer contained in the fine fibrous cellulose-containing layer and the fine fibrous cellulose-containing sheet will be described below.

[Fine fibrous cellulose]
The fine fibrous cellulose is a fibrous cellulose having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose can be measured by, for example, observation with an electron microscope.
The fiber width of the fine fibrous cellulose is 1000 nm or less. The fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and preferably 2 nm or more and 10 nm or less. Especially preferable. By setting the fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to make it easier to exhibit the effects of the fine fibrous cellulose on improving strength, rigidity and dimensional stability. Can be done.

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

The average fiber width of the fine fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid to prepare 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 fine 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 0.1 μm or more and 600 μm or less. More preferred. By setting the fiber length within the above range, destruction of the crystal region of the fine fibrous cellulose can be suppressed. Further, it is possible to set the slurry viscosity of the fine fibrous cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine 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 = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The ratio of the type I crystal structure to the fine fibrous 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 crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

The axial ratio (fiber length / fiber width) of the fine fibrous 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. In addition, sufficient viscosity can be easily obtained when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when treating fine fibrous cellulose as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

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

Examples of the anionic group as an ionic group include a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxy group or a substituent derived from a carboxy group (simply referred to as a carboxy group). (Sometimes), and at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), preferably at least one selected from a phosphate group and a carboxy group. It is more preferably a seed, especially a phosphate group.

The substituent derived from the phosphoric acid group or the phosphoric acid group is, for example, a substituent represented by the following formula (1), and is generalized as a phosphoric acid group or a substituent derived from the phosphoric acid.
The phosphoric acid group is, for example, a divalent functional group obtained by removing a hydroxy group from phosphoric acid. Specifically, it is a group represented by −PO ₃ H ₂ . Substituents derived from phosphoric acid groups include substituents such as salts of phosphoric acid groups and phosphoric acid ester groups. The substituent derived from the phosphoric acid group may be contained in the fibrous cellulose as a group in which the phosphoric acid group is condensed (for example, a pyrophosphate group). Further, the phosphoric acid group may be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from the phosphorous acid group is a salt of the phosphorous acid group, a phosphorous acid ester group, or the like. May be good.

In the formula (1), a, b and n are natural numbers, and m is an arbitrary number (where a = b × m). Of α ¹ , α ² , ..., α ⁿ and α', a are O ⁻ , and the rest are either R or OR. It is also possible that all of each α ⁿ and α'are O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain hydrocarbon, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (1) may be a group derived from a cellulose molecular chain.

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

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

The amount of the ionic group introduced into the fine fibrous cellulose is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and more preferably 0.20 mmol / g or more per 1 g (mass) of the fine fibrous cellulose. It is more preferably 50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Further, the amount of the ionic group introduced into the fine fibrous cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the fibrous cellulose, for example, 3 It is more preferably .50 mmol / g or less, and even more preferably 3.00 mmol / g or less. By setting the amount of the ionic group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose. Further, by setting the amount of the ionic group introduced within the above range, good properties can be exhibited in various applications such as a thickener for fine fibrous cellulose.
Here, the denominator in the unit mmol / g indicates the mass of the fine fibrous cellulose when the counter ion of the ionic group is a hydrogen ion (H ⁺ ).

The amount of the ionic group introduced into the fine 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 fine fibrous cellulose.
FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise to fine fibrous cellulose having a phosphoric acid group and pH.

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 defibration treatment similar to 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 this 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. Further, 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 phosphoric acid group introduction amount (mmol / g) indicates the mass of the acid-type fibrous cellulose, the phosphoric acid group amount of the acid-type fibrous cellulose (hereinafter, the amount of phosphoric acid groups). (Called (acid type))). On the other hand, when the counterion of the phosphate group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is a counterion. This makes it possible to determine the amount of phosphate groups (hereinafter, the amount of phosphate groups (C type)) possessed by fibrous cellulose in which the cation C is a counter ion.
That is, it is calculated by the following formula.
Phosphate group amount (C type) = Phosphate group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total anion amount derived from phosphoric acid group of fibrous cellulose (value obtained by adding strongly acidic group amount and weakly acidic group amount of phosphoric acid group)
W: Formula amount per valence of cation C (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.

Which of phosphite, phosphoric acid, and condensed phosphoric acid is derived from the phosphoroxo acid detected when either or both of the phosphoric acid group and the condensed phosphoric acid group is contained in addition to the phosphite group. As a method for distinguishing, for example, a method of performing the above-mentioned titration operation after performing a treatment of cutting the condensed structure such as acid hydrolysis, or a treatment of converting a phosphite group into a phosphate group such as an oxidation treatment is performed. The method of performing the above-mentioned titration operation can be mentioned.

FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise to fine fibrous cellulose having a carboxy group and pH.
The amount of the carboxy group introduced into the fine fibrous cellulose is measured, for example, as follows.
First, the slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the defibration treatment similar to 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 to obtain a titration curve as shown in FIG. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target.
As shown in FIG. 2, in this neutralization titration, there is one point in which the increment (differential value of pH with respect to the amount of alkaline drop) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Observed. The maximum point of this increment is called the first end point. Here, the region from the start of titration to the first end point in FIG. 2 is referred to as a first region. The amount of alkali required in the first region is equal to the amount of carboxy groups in the slurry used for titration. Then, the amount of alkali (mmol) required in the first region of the titration curve is divided by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated, so that the amount of carboxy group introduced (mmol / g). ) Was calculated.
The above-mentioned amount of carboxy group introduced (mmol / g) is the amount of substituents per 1 g of mass of fibrous cellulose when the counterion of the carboxy group is hydrogen ion (H ⁺ ) (hereinafter, the amount of carboxy group (acid). Type)) is shown.

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

In the measurement of the amount of substituents by the titration method, if the titration interval of the aqueous sodium hydroxide solution is too short, the amount of substituents may be lower than the original amount. It is desirable to titrate 10 to 50 μL of the aqueous sodium solution every 5 to 30 seconds.

The content of the fine fibrous cellulose in the solid content of the fine fibrous cellulose-containing layer and the fine fibrous cellulose-containing sheet is preferably 3% by mass from the viewpoint of obtaining a laminate having excellent strength and transparency and excellent flexibility. % Or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less.

[Manufacturing method of fine fibrous cellulose]
(Fiber raw material containing cellulose)
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 is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp of 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. When long fiber fine fibrous cellulose having a large axial ratio is used, the viscosity tends to increase.
As the fiber raw material containing cellulose, for example, cellulose contained in ascidians 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.

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

(Ionic group introduction process)
-Phosphate group introduction process-
In the phosphate group introduction step, at least one compound (hereinafter, also referred to as “Compound A”) selected from compounds capable of introducing a phosphate group by reacting with a hydroxyl group of a fiber raw material containing cellulose is introduced into cellulose. It is a step of acting on a fiber raw material containing. By this step, a phosphoric acid group-introduced fiber can be obtained.
In the phosphoric 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. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.
As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, there is a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state. Of these, since the reaction uniformity is high, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction has high uniformity, it is preferable to add the mixture in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, 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, respectively, the excess Compound A and Compound B are added by pressing or filtering. It may be removed.

The compound A used in this embodiment may be a compound having a phosphorus atom and capable of forming an ester bond with cellulose, and may be phosphoric acid or a salt thereof, phosphoric acid or a salt thereof, dehydration-condensed phosphoric acid or a salt thereof. Examples thereof include salts and anhydrous phosphoric acid (diphosphorus pentoxide), but the present invention is not particularly limited. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of phosphates, phosphates, and dehydration-condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydration-condensed phosphoric acid, and these are among various types. It can be a sum.
Of these, from the viewpoints of high efficiency of introduction of phosphoric acid group, easy improvement of defibration efficiency in the defibration step described later, low cost, and easy industrial application, phosphoric acid and phosphoric acid A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.
The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the phosphorus atomic weight, the amount of phosphorus atom added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus 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 in particular is known to act as a good reaction catalyst.

In the phosphoric acid group introduction step, it is preferable to add or mix the compound A or the like to the fiber raw material and then heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which the phosphate group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized layer 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, compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and compound A are heated while kneading or stirring 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 phosphoric acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A 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. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, and also to suppress the acid hydrolysis of the sugar chain in the fiber. 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 phosphoric acid group introduced can be within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

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

The amount of the phosphoric 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 / 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. The amount of phosphoric acid group introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less per 1 g (mass) of fine fibrous cellulose, and more preferably 3.65 mmol / g or less. It is more preferably 00 mmol / g or less. By setting the amount of the phosphoric acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose.

-Carboxylic acid group introduction process-
The carboxy group introduction step has an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, TEMPO oxidation treatment, a compound having a group derived from carboxylic acid or a derivative thereof, or a group derived from carboxylic acid with respect to the fiber raw material containing cellulose. This is done by treating with an acid anhydride of the compound or a derivative thereof.
The compound having a group derived from a carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, itaconic acid, citric acid, aconitic acid and the like. Examples include tricarboxylic acid compounds. The derivative of the compound having a group derived from carboxylic acid is not particularly limited, and examples thereof include an imide of an acid anhydride of a compound having a carboxy group and a derivative of an acid anhydride of a compound having a carboxy group. The imide of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinateimide, and phthalateimide.

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

When the TEMPO oxidation treatment is carried out in the carboxy group introduction step, it is preferable to carry out the treatment under conditions of pH 6 or more and 8 or less, for example. Such a treatment is also referred to as a neutral TEMPO oxidation treatment. The neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) as a catalyst, and the like. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting sodium chlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group.
Further, the TEMPO oxidation treatment may be carried out under the condition that the pH is 10 or more and 11 or less. Such a treatment is also referred to as an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. ..
The amount of carboxy group introduced into the fiber raw material varies depending on the type of substituent, but for example, when introducing a carboxy group by TEMPO oxidation, it is preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose. , 0.20 mmol / g or more, more preferably 0.50 mmol / g or more, and particularly preferably 0.90 mmol / g or more. Further, it is preferably 2.5 mmol / g or less, more preferably 2.20 mmol / g or less, and further preferably 2.00 mmol / g or less. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol / g or less per 1 g (mass) of 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 ionic group-introduced fibers as needed. The washing step is performed by washing the ionic group-introduced fibers with, for example, water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.

(Alkaline treatment (neutralization treatment) process)
When producing fine fibrous cellulose, an alkali treatment (neutralization treatment) may be performed on the fiber raw material between the ionic 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 ionic group-introduced fiber in an alkaline solution.
The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In 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 ionic 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 10,000% by mass or less, for example, with respect to the absolute dry mass of the ionic group-introduced fiber. Is more preferable.

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

(Acid treatment process)
When producing fine fibrous cellulose, the fiber raw material may be subjected to acid treatment between the step of introducing an ionic group and the defibration treatment step described later. For example, the ionic group introduction step, the acid treatment step, the alkali treatment step, and the defibration treatment step may be performed in this order.
The acid treatment method is not particularly limited, and examples thereof include a method of immersing the fiber raw material in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably, for example, 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic 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.

(Defibration processing process)
Fine fibrous cellulose can be obtained by defibrating the ionic group-introduced fiber in the defibration treatment step.
In the defibration treatment step, for example, a defibration treatment apparatus can be used. The 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 ionic group-introduced fiber with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and an organic solvent such as a polar organic solvent can be used. The polar organic solvent is not particularly limited, but for example, alcohols, polyhydric alcohols, ketones, ethers, esters, 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 phosphate group-introduced fiber in a dispersion medium may contain a solid content other than the phosphate group-introduced fiber such as urea having a hydrogen bond property.

[Water-soluble polymer]
In the present invention, the fine fibrous cellulose-containing layer and the fine fibrous cellulose-containing sheet contain a water-soluble polymer.
Examples of the water-soluble polymer include carboxyvinyl polymer; polyvinyl alcohol; alkyl methacrylate / acrylic acid copolymer; polyvinylpyrrolidone; sodium polyacrylate; polyalkylene glycol such as polyethylene glycol and polypropylene glycol; polyacrylamide; xanthan gum, guar gum, tamarind. Thickening polymers such as gum, carrageenan, locust bean gum, quince seeds, alginic acid, metal salts of alginic acid, purulan, carrageenan, and starch; cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose; Examples of starches such as cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, and amylose; glycerins such as polyglycerin; hyaluronic acid, metal salts of hyaluronic acid, and the like can be mentioned.

Among these, the water-soluble polymer includes polyvinyl alcohol, polyalkylene glycol, polyacrylamide, and thickening polysaccharide from the viewpoint of improving the adhesiveness with the cellophane sheet and obtaining a laminate having excellent transparency and flexibility. , Cellulose derivatives, starches, glycerins are preferred, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, xanthan gum, guar gum, alginic acid and metal salts of alginic acid, carboxymethyl cellulose, hydroxyethyl cellulose, cationized starch, oxidized starch are more preferred, polyvinyl alcohol. , Polyethylene glycol, xanthan gum, metal salts of alginic acid and alginic acid, carboxymethyl cellulose and cationized starch are more preferred, and polyvinyl alcohol, metal salts of alginic acid and alginic acid, carboxymethyl cellulose and cationized starch are even more preferred.

The content of the water-soluble polymer in the solid content of the fine fibrous cellulose-containing layer and the fine fibrous cellulose-containing sheet is preferably 3% by mass from the viewpoint of obtaining a laminated body having excellent strength and transparency and excellent flexibility. % Or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less.

[Manufacturing method of fine fibrous cellulose-containing layer and fine fibrous cellulose-containing sheet]
The laminate of the present invention has a fine fibrous cellulose-containing layer, and the fine fibrous cellulose-containing layer is preferably formed by laminating a fine fibrous cellulose-containing sheet. It is possible to obtain the fine fibrous cellulose-containing layer by coating and drying, but in that case, it is difficult to reduce the thickness unevenness of the laminated body to 50% or less.
In the present embodiment, the fine fibrous cellulose-containing sheet (hereinafter, also simply referred to as “sheet”) is described later using, for example, a liquid composition containing the above-mentioned fine fibrous cellulose and a water-soluble polymer. It can be obtained by carrying out a sheeting step.

In addition to fine fibrous cellulose and water-soluble polymers, the sheet includes, for example, surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, etc. It may contain one or more selected from lubricants, antistatic agents, UV protective agents, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, and cross-linking agents.
The sheet may contain a solvent. As the solvent, for example, a solvent exemplified as a dispersion medium in the defibration treatment step can be used.

The content of the solvent in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 5% by mass or more, based on the total mass of the sheet. preferable. This makes it possible to impart flexibility to the sheet. On the other hand, the content of the solvent in the sheet is, for example, preferably 25% by mass or less, and more preferably 15% by mass or less, based on the total mass of the sheet. Thereby, a sheet having good flexibility can be obtained.

The water content (mass%) in the sheet can be calculated, for example, by the following procedure. First, a 100 mm square sheet is humidity-controlled for 24 hours under the conditions of a temperature of 23 ° C. and a relative humidity of 50%, and then the mass W0 of the sheet is measured. Next, the sheet is dried in a constant temperature dryer at 105 ° C. for 16 hours, and then the mass W1 of the sheet is measured. From the measured mass, the content of the solvent in the sheet is calculated according to the following formula 2.
(Equation 2) ... Water content in the sheet = (1-W1 / W0) x 100

The tensile elastic modulus of the sheet is, for example, preferably 2.5 GPa or more, more preferably 3.0 GPa or more, and further preferably 3.5 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 or less.
Here, the tensile elastic modulus of the sheet is, for example, a value measured using a tensile tester Tensilon (manufactured by A & D Co., Ltd.) in accordance with JIS P 8113. When measuring the tensile elastic modulus, a test piece prepared at 23 ° C. and 50% relative humidity for 24 hours is used as a test piece for measurement, and the measurement is performed under the conditions of 23 ° C. and 50% relative humidity.

The haze of the sheet is, for example, preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% 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, for example, a value measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136.
The total light transmittance of the sheet is, for example, preferably 85% 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 Co., Ltd.).

In the laminate of the present invention, the thickness of the fine fibrous cellulose-containing layer is 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and further, from the viewpoint of obtaining a laminate having excellent transparency, strength, and flexibility. It is preferably 40 μm or more, and is 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, still more preferably 150 μm or less.
The thickness of the fine fibrous cellulose-containing layer may be calculated from the difference between the thickness of the laminate and the thickness of the cellophane sheet, or may be obtained from the cross-sectional observation of the laminate, and is not particularly limited. The thickness of the laminate and the thickness of the cellophane sheet can be measured, for example, with a stylus type thickness gauge (Millitron 1202D manufactured by Marl Inc.).
Further, the thickness of the fine fibrous cellulose-containing layer is approximated by the thickness of the laminated fine fibrous cellulose-containing sheet, and the thickness of the desired fine fibrous cellulose-containing layer is adjusted by adjusting the thickness of the fine fibrous cellulose-containing sheet. Can be adjusted to.

The basis weight of the sheet is not particularly limited, but is preferably 10 g / m ² or more, more preferably 20 g / m ² or more, and further preferably 30 g / m ² or more. The basis weight of the sheet is not particularly limited, but is preferably 200 g / m ² or less, and more preferably 150 g / m ² or less. Here, the basis weight of the sheet can be calculated in accordance with, for example, JIS P 8124.
The density of the sheet is not particularly limited, but is preferably 0.1 g / cm ³ or more, more preferably 0.5 g / cm ³ or more, and further preferably 0.8 g / cm ³ or more. preferable. The density of the sheet is not particularly limited, but is preferably 5.0 g / cm ³ or less, more preferably 3.0 g / cm ³ or less, and 1.5 g / cm ³ or less, for example. Is even more preferable. Here, the density of the sheet can be calculated by measuring the thickness and mass of the sheet after adjusting the humidity of a 50 mm square sheet under the conditions of 23 ° C. and 50% RH for 24 hours.

<Manufacturing process of fine fibrous cellulose-containing sheet>
The sheet manufacturing step includes a coating step of coating a slurry containing fine fibrous cellulose and a water-soluble polymer on a substrate, or a papermaking step of making the slurry. As a result, a fine fibrous cellulose-containing sheet containing fine fibrous cellulose and a water-soluble polymer can be obtained.

(Coating process)
In the coating step, for example, a slurry containing fine fibrous cellulose and a water-soluble polymer is coated on a base material, and the sheet formed by drying the slurry is peeled off from the base material to obtain a sheet. .. 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 composition (slurry) may be able to suppress shrinkage of the sheet during drying, but is formed after drying. It is preferable to select a sheet that 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 acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polypropylene, 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, when 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 an acrylic plate, a polyethylene terephthalate plate, a vinyl chloride plate, a polystyrene plate, a polypropylene 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 (hereinafter, the slurry temperature and the atmospheric temperature are collectively referred to as “coating temperature”) when the slurry is coated on the base material are not particularly limited, but are, for example, 5 ° C. or higher and 80 ° C. or lower. It is more preferably 10 ° C. or higher and 60 ° C. or lower, further preferably 15 ° C. or higher and 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 step, it is preferable to coat the substrate with the slurry so that the finished basis weight of the sheet is within the above-mentioned preferable range. By coating so that the basis weight is within the above range, a sheet having more excellent transparency, strength and flexibility 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 fixing 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 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 at least the above lower limit value, 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 papermaking process, a method of producing a sheet from a slurry is, for example, to discharge a slurry containing fine fibrous cellulose and a water-soluble polymer onto the upper surface of an endless belt, and squeeze a dispersion medium from the discharged slurry to generate a web. This can be done using a manufacturing apparatus that includes a water squeezing section and 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. Further, the drying method used in the papermaking process is not particularly limited, and examples thereof include a method 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.

[Manufacturing method of laminate]
As described above, the laminate of the present invention has a lamination step (hereinafter, also referred to as “step 1”) of laminating a cellophane sheet and a fine fibrous cellulose-containing sheet to obtain a laminate, and the laminate. A drying step (hereinafter, also referred to as “step 2”) for drying is performed in this order, and at least one of the cellophane sheet and the fine fibrous cellulose-containing sheet is in a wet state in the laminate. Hereinafter, each step will be described.

(Step 1)
In step 1, the cellophane sheet and the fine fibrous cellulose-containing sheet described above are laminated to obtain a laminate. At this time, at least one of the cellophane sheet and the fine fibrous cellulose-containing sheet is in a wet state.
In step 1, a dry cellophane sheet and a fine fibrous cellulose-containing sheet may be laminated and then put into a wet state, but at least one of the cellophane sheet and the fine fibrous cellulose-containing sheet may be put into a wet state. It is preferable to obtain a laminate by laminating.
Among these, it is preferable that the cellophane sheet is in a wet state at the time of laminating, and it is more preferable that only the cellophane sheet is in a wet state.

The method of moistening the cellophane sheet and the fine fibrous cellulose-containing sheet is not particularly limited, and any method such as a method of spray coating with water or a method of immersing in a water bath may be used. Among these, the method of immersing in a water bath is preferable from the viewpoint of sufficiently evenly moistening the state.
The water to be used is not particularly limited, such as tap water, ion-exchanged water, distilled water, etc., but ion-exchanged water or distilled water is preferable from the viewpoint of obtaining a laminated body having more excellent transparency.

In step 1, it is preferable to laminate the cellophane sheet and the fine fibrous cellulose-containing sheet so as not to generate a gap such as air.
Further, it is preferable to have a step of crimping the laminated product after laminating in step 1 and before step 2 for the purpose of removing bubbles between layers and further improving adhesion.
At the time of crimping, it is preferable to superimpose another sheet, film or the like on both sides of the laminate in order to prevent scratches during crimping on the cellophane sheet and the fine fibrous cellulose-containing sheet.

As the crimping, either roll crimping or plate crimping may be used. Further, at the time of crimping, heating or cooling may be performed.
The pressure, temperature, and crimping temperature at the time of crimping may be appropriately selected so as to obtain the desired effect.

(Step 2)
The step 2 is a step of drying the laminate obtained in the step 1.
The drying temperature in step 2 is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, and further, from the viewpoint of suppressing shrinkage and cracking of the laminated body to obtain a laminated body having excellent flexibility and productivity. It is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, and preferably 200 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 125 ° C. or lower, still more preferably 110 ° C. or lower.
The drying time in step 2 is preferably 1 minute or longer, more preferably 3 minutes or longer, from the viewpoint of suppressing shrinkage and cracking of the laminated body, obtaining a laminated body having excellent flexibility, and productivity. It is more preferably 5 minutes or more, and preferably 6 hours or less, more preferably 3 hours or less, still more preferably 1 hour or less, still more preferably 0.5 hours or less.
The drying method is not particularly limited, and examples thereof include methods used in the production of paper, and for example, methods such as a cylinder dryer, a Yankee dryer, hot air drying, and an infrared heater are preferable.

[Characteristics of laminate]
The laminate of the present invention has a fine fibrous cellulose-containing layer on at least one surface of the cellophane sheet. The fine fibrous cellulose-containing layer may be provided on one side or both sides of the cellophane sheet, but it is preferable to have it on one side from the viewpoint of transparency.
Further, although another layer may be provided between the cellophane sheet and the fine fibrous cellulose-containing layer, it is preferable not to have the other layer from the viewpoint of transparency and flexibility. That is, it is preferably composed of only the cellophane sheet and the fine fibrous cellulose-containing layer, and more preferably it is composed of two types and two layers of the cellophane sheet and the fine fibrous cellulose-containing layer. In the present invention, since the fine fibrous cellulose-containing layer contains a water-soluble polymer, a laminated body having excellent flexibility can be obtained without providing another layer such as an adhesive layer, and the laminated body can be easily obtained. Can be manufactured.

The laminate of the present invention may have other layers in addition to the cellophane sheet and the fine fibrous cellulose-containing layer. For example, a dustproof layer, an antifouling layer, an antifogging layer, an antistatic layer, and ultraviolet rays are placed on the cellophane sheet side or the fine fibrous cellulose-containing layer side of a two-layer laminated structure in which a cellophane sheet and a fine fibrous cellulose-containing layer are laminated. By providing functional layers such as a preventive layer and a decorative layer and providing an adhesive layer on the surface opposite to the surface on which the functional layer of the laminated structure is provided, a laminated sheet that can be attached to various articles to be provided with a function is obtained. be able to. Further, a resin layer such as polyethylene terephthalate, polyethylene phthalate, or polycarbonate may be provided as a base material layer on the cellophane sheet side or the fine fibrous cellulose-containing layer side of the two-layer laminated structure. In this case, the cellophane sheet or the fine fibrous cellulose-containing layer itself may function as a functional layer such as an antistatic layer and an antifogging layer.

When the laminate is made of cellophane sheet and fine fibrous cellulose, the thickness of the laminate is preferably 55 μm or more, more preferably 60 μm or more, from the viewpoint of making the laminate excellent in strength, transparency and flexibility. It is more preferably 70 μm or more, and preferably 300 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less.
By providing the other layers (functional layer, adhesive layer, etc.) described above, the thickness of the laminated body as a whole is appropriately selected.

The thickness unevenness of the laminate is 50% or less, preferably 30% or less, more preferably 20% or less, still more preferably 10% or less from the viewpoint of obtaining a laminate having excellent strength and transparency and from the viewpoint of manufacturing. , And preferably 1% or more, more preferably 2% or more.
The thickness unevenness is measured by the method described in the examples, and is calculated by the following formula from the average value of the thickness measured at any 10 points or more and the maximum and minimum values of the thickness.
Thickness unevenness (%) = {(maximum value-minimum value) / average value} x 100

The laminate of the present invention preferably has excellent transparency, and the haze of the laminate is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 2.5% or less, and is produced. From the viewpoint of ease, it is preferably 0.3% or more, more preferably 0.5% or more.

The laminate of the present invention can be used for various purposes as a laminate of a cellophane sheet and a fine fibrous cellulose-containing layer, as a transparent sheet having excellent transparency and strength, and also having excellent flexibility. For example, packaging materials such as various cases are exemplified.
Further, by providing various functional layers, it is also used as an antifouling film, a dustproof film, an antifogging film, an ultraviolet ray prevention film, a decorative film and the like.

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 limited by the specific examples shown below.

[Manufacturing Example 1]
[Preparation of phosphorylated pulp 1]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g / m ² sheets, disintegrated and measured according to JIS P 8121 Canadian standard drainage degree (CSF)) 700 ml) was used. The raw material pulp was phosphorylated as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 200 seconds to introduce a phosphate group into the cellulose in the pulp to obtain phosphorylated pulp 1.

Next, the obtained phosphorylated pulp 1 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 phosphorylated pulp 1 is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. I went by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.
Next, the phosphorylated pulp 1 after washing was neutralized as follows. First, the washed phosphorylated pulp 1 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 phosphorylated pulp slurry 1 having a pH of 12 or more and 13 or less. Obtained. Next, the phosphorylated pulp slurry 1 was dehydrated to obtain a phosphorylated pulp 1 that had been neutralized.

Next, the phosphorylated pulp 1 after the neutralization treatment was subjected to the above washing treatment. The infrared absorption spectrum of the phosphorylated pulp 1 thus obtained was measured using FT-IR. As a result, absorption based on the phosphate group was observed around 1230 cm ^-1 , and it was confirmed that the phosphate group was added to the pulp.
Further, when the obtained phosphorylated pulp 1 was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

[Fiber processing]
Ion-exchanged water was added to the obtained phosphorylated pulp 1 to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) 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. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope as described below and found to be 3 to 5 nm. The amount of phosphoric acid group (first dissociated acid amount) measured by the measuring method described later was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[Manufacturing Example 2]
[Preparation of phosphorylated pulp 2]
The same procedure as in Production Example 1 was carried out except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate to obtain phosphorylated pulp 2.
The infrared absorption spectrum of the phosphorylated pulp 2 thus obtained 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 phosphorylated pulp 2 was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

[Fiber processing]
The phosphorylated pulp 2 was subjected to the same operation as in Production Example 1 to obtain a fine fibrous cellulose dispersion 2 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, fine fibrous cellulose having a diameter of 3 to 5 nm was observed. The amount of (sub) phosphorous acid group (first dissociated acid amount) measured by the measuring method described later was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[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 obtained by treatment with a wet atomizing device is mixed with water 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 added dropwise to the diluted and hydrophilized carbon grid film. This was dried, stained with uranyl acetate, and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

[Measurement of phosphate group amount]
The amount of phosphate groups in the fine fibrous cellulose is a fibrous form prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water so that the content is 0.2% by mass. The measurement was carried out by treating the cellulose-containing slurry with an ion exchange resin and then performing titration with an alkali.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Co., Ltd., conditioned) having 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 divided by the solid content (g) in the slurry to be titrated was defined as the amount of phosphate groups (mmol / g).

[Example 1]
[Preparation of fine fibrous cellulose-containing sheet]
The concentration of the fine fibrous cellulose dispersion 1 obtained in Production Example 1 was adjusted by adding ion-exchanged water so that the solid content concentration was 0.5% by mass.

Next, 15 parts by mass of a 0.5% by mass aqueous solution of carboxymethyl cellulose (Cerogen EP manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added to 85 parts by mass of this fine fibrous cellulose dispersion to obtain a coating liquid. It was.

Next, the coating liquid is weighed so that the finished basis weight of the obtained sheet (layer composed of the solid content of the coating liquid) is 50 g / m ² , and the coating liquid is applied to a commercially available acrylic plate at 50 ° C. It was dried in a constant temperature dryer. A metal frame for damming (a gold frame having an inner dimension of 180 mm × 180 mm and a height of 5 cm) was placed on the acrylic plate so as to have a predetermined basis weight. Next, the dried sheet was peeled off from the acrylic plate to obtain a fine fibrous cellulose-containing sheet.

[Preparation of laminate]
The obtained fine fibrous cellulose-containing sheet (180 mm × 180 mm) was placed on an acrylic plate. A cellophane sheet (PL # 500, manufactured by Futamura Chemical Co., Ltd.) was immersed in ion-exchanged water for 10 minutes to bring it into a wet state, and was layered on a fine fibrous cellulose-containing sheet so as not to form a gap between layers. Further, a commercially available polyester film was layered and rolled with a load of 2 kg while pressing a hand cleaner (manufactured by Audio-Technica Co., Ltd., HC-715 / 30) on the polyester film, and the fine fibrous cellulose-containing sheet and cellophane were pressure-bonded. Then, it was dried in a constant temperature dryer at 105 ° C. It took 10 minutes to dry. After controlling the humidity at 23 ° C. and 50% RH for 24 hours, the dried sheet was peeled off from the acrylic plate to obtain a laminate.
The physical properties of the cellophane used are shown in Table 1 below.

[Example 2]
In [Preparation of Fine Fibrous Cellulose-Containing Sheet], the mixture was laminated in the same manner as in Example 1 except that 50 parts by mass of a 0.5% by mass aqueous solution of carboxymethyl cellulose was added to 50 parts by mass of the fine fibrous cellulose dispersion. I got a body.

[Example 3]
In [Preparation of Fine Fibrous Cellulose-Containing Sheet], the mixture was laminated in the same manner as in Example 1 except that 90 parts by mass of a 0.5% by mass aqueous solution of carboxymethyl cellulose was added to 10 parts by mass of the fine fibrous cellulose dispersion. I got a body.

[Example 4]
In [Preparation of fine fibrous cellulose-containing sheet], the concentration of the fine fibrous cellulose dispersion 2 obtained in Production Example 2 was adjusted by adding ion-exchanged water so that the solid content concentration was 0.5% by mass. In the same manner as in Example 1 except that 15 parts by mass of a 0.5% by mass aqueous solution of starch (manufactured by Oji Corn Starch Co., Ltd., Ace K) was added to 85 parts by mass of this fine fibrous cellulose dispersion. A laminate was obtained.

[Example 5]
In [Preparation of Fine Fibrous Cellulose-Containing Sheet], the laminate was obtained in the same manner as in Example 4 except that 50 parts by mass of a 0.5% by mass aqueous solution of starch was added to 50 parts by mass of the fine fibrous cellulose dispersion. Got

[Example 6]
In [Preparation of Fine Fibrous Cellulose-Containing Sheet], a laminate was prepared in the same manner as in Example 4 except that 90 parts by mass of a 0.5% by mass aqueous solution of starch was added to 10 parts by mass of the fine fibrous cellulose dispersion. Got

[Example 7]
In [Preparation of fine fibrous cellulose-containing sheet], 15 parts by mass of a 0.5% by mass aqueous solution of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Poval 105) was added to 85 parts by mass of the fine fibrous cellulose dispersion. A laminate was obtained in the same manner as in Example 1 except that the finished basis weight of the fine fibrous cellulose-containing sheet was 120 g / m ² .

[Example 8]
In [Preparation of fine fibrous cellulose-containing sheet], 90 parts by mass of a 0.5% by mass aqueous solution of polyvinyl alcohol was added to 10 parts by mass of the fine fibrous cellulose dispersion to finish the fine fibrous cellulose-containing sheet. A laminate was obtained in the same manner as in Example 1 except that the amount was 120 g / m ² .

[Example 9]
In [Preparation of fine fibrous cellulose-containing sheet], 15 parts by mass of a 0.5% by mass aqueous solution of sodium alginate (manufactured by Kimika Co., Ltd., Algitex M) was added to 85 parts by mass of the fine fibrous cellulose dispersion. A laminate was obtained in the same manner as in Example 4 except that the finished basis weight of the fine fibrous cellulose-containing sheet was 120 g / m ² .

[Example 10]
In [Preparation of fine fibrous cellulose-containing sheet], 90 parts by mass of a 0.5% by mass aqueous solution of sodium alginate was added to 10 parts by mass of the fine fibrous cellulose dispersion to finish the fine fibrous cellulose-containing sheet. A laminate was obtained in the same manner as in Example 4 except that the amount was 120 g / m ² .

[Comparative Example 1]
The concentration of the fine fibrous cellulose dispersion 1 obtained in Production Example 1 was adjusted by adding ion-exchanged water so that the solid content concentration was 1% by mass. To 85 parts by mass of this fine fibrous cellulose dispersion, 15 parts by mass of a 1% by mass aqueous solution of carboxymethyl cellulose was added to obtain a coating liquid.
Next, the obtained coating liquid was applied to a cellophane sheet that had been moistened by immersing it in ion-exchanged water for 10 minutes with a wet film thickness of 5 mm, and dried in a constant temperature dryer at 105 ° C. It took 1.5 hours to dry. Humidity was adjusted for 24 hours under the conditions of 23 ° C. and 50% RH to obtain a laminate.

[Evaluation]
[Fold]
A 5 cm square test piece 10 was bent as shown in FIG. 3, and those that did not crack when bent until θ in FIG. 3 became 0 ° were evaluated as ◯, and others were evaluated as ×. The test piece was bent so that the fine cellulose-containing layer was on the outside. For the evaluation, a test piece whose humidity was adjusted for 24 hours under the condition of 23 ° C. and 50% RH was used. The results are shown in Table 2 below.

[Basis weight / thickness / thickness unevenness]
The laminate was cut into 10 cm × 10 cm, and the basis weight and thickness were measured. The thickness was taken as an average value measured at 16 points, and the thickness of the fine fibrous cellulose-containing layer was calculated by the following formula. The measurement was performed at 16 points, which are the intersections when lines are drawn vertically and horizontally with a width of 2 cm on the cut-out laminated body.
Thickness of fine fibrous cellulose-containing layer = Thickness of laminate-Thickness of cellophane The thickness unevenness was calculated by the following formula.
Thickness unevenness (%) = (maximum value-minimum value) / average value x 100
For the evaluation, a test piece whose humidity was adjusted for 24 hours under the condition of 23 ° C. and 50% RH was used. The results are shown in Table 2 below.

[Haze]
The haze was measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136. The results are shown in Table 2 below.

[Specific tensile strength]
The tensile strength 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 75 mm and the distance between chucks was 50 mm. The specific tensile strength was calculated by the following formula, and the geometric mean of the specific tensile strength in both the vertical and horizontal directions was taken. For the evaluation, a test piece whose humidity was adjusted for 24 hours under the condition of 23 ° C. and 50% RH was used. The results are shown in Table 2 below.
Specific tensile strength [Nm / g] = strength [kN / m] / basis weight [g / m ² ] x 1000

In the examples, by laminating the fine fibrous cellulose-containing sheet with the cellophane sheet, the drying time required for producing the laminate was short, and the laminate could be obtained while reducing the drying load on the cellophane. The laminate obtained in the examples had small thickness unevenness, did not crack, had good strength, and did not impair the transparency of the cellophane sheet.
On the other hand, in the comparative example, the cellophane sheet was directly coated with the fine fibrous cellulose dispersion, and a long drying time was required when producing the laminate. In addition, the thickness unevenness was large due to shrinkage during drying, and the creases and strength were inferior. In addition, cracks were also observed.

According to the present invention, a laminated body having excellent transparency and strength and further excellent flexibility, and a simple method for producing the laminated body can be obtained. The laminate of the present invention is expected to be useful as a functional sheet for various packaging materials and the like.

Claims (6)

A laminate having a fine fibrous cellulose-containing layer containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer on at least one surface of the cellophane sheet.
The thickness of the fine fibrous cellulose-containing layer is 10 μm or more and 500 μm or less.
The thickness unevenness of the laminated body is 50% or less.
Laminated body. The laminate according to claim 1, wherein the content of the fine fibrous cellulose in the solid content of the fine fibrous cellulose-containing layer is 5% by mass or more and 95% by mass or less. A laminating step of laminating a cellophane sheet and a fine fibrous cellulose-containing sheet containing fine fibrous cellulose having a fiber width of 1,000 nm or less and a water-soluble polymer to obtain a laminate, and drying the laminate. It has a drying process in this order,
A method for producing a laminate in which at least one of the cellophane sheet and the fine fibrous cellulose-containing sheet is in a wet state in the laminate. The method for producing a laminate according to claim 3, wherein the thickness of the fine fibrous cellulose-containing sheet is 10 μm or more and 500 μm or less. The method for producing a laminate according to claim 3 or 4, further comprising a step of crimping the laminate after the lamination step and before the drying step. The method for producing a laminate according to any one of claims 3 to 5, wherein the drying temperature in the drying step is 50 ° C. or higher.