JP7005950B2 - Sheets and laminates - Google Patents

Description

The present invention relates to sheets and laminates. Specifically, the present invention relates to a sheet and a laminate containing fine fibrous cellulose.

In recent years, due to the substitution of petroleum resources and increasing environmental awareness, materials using reproducible natural fibers have been attracting attention. Among natural fibers, fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, particularly fibrous cellulose (pulp) derived from wood, has been widely used mainly as paper products.

As the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Further, a sheet composed of such fine fibrous cellulose and a composite sheet containing a fine fibrous cellulose-containing sheet and a resin have been developed. It is known that in a sheet or a composite sheet containing fine fibrous cellulose, the contact points between the fibers are remarkably increased, so that the tensile strength and the like are greatly improved. It is also known that the transparency is greatly improved by making the fiber width shorter than the wavelength of visible light.

For example, Patent Document 1 discloses fine fibrous cellulose obtained by subjecting a cellulose fiber having a cationic group to a defibration treatment, and a resin solution is applied onto a sheet containing the fine fibrous cellulose and cured. The composite sheet obtained by making it is disclosed. Further, Patent Document 2 discloses a composite sheet containing fine fibrous cellulose and a matrix resin. Here, the composite sheet has a portion containing fine fibrous cellulose and a portion not containing fine fibrous cellulose in the normal direction.

Japanese Unexamined Patent Publication No. 2015-071848 Japanese Unexamined Patent Publication No. 2015-017184

When producing a fine fibrous cellulose-containing sheet, a fine fibrous cellulose-containing slurry may be applied onto a substrate and then heat-dried. In such a process, there is a concern that the fine fibrous cellulose-containing sheet may be unintentionally peeled off from the base material, or wrinkles or cracks may occur, resulting in a decrease in the yield during the production of the fine fibrous cellulose-containing sheet. .. In addition, there is a concern that the produced fine fibrous cellulose-containing sheet may be curled and the dimensional stability of the sheet may be inferior.

Therefore, in order to solve the problems of the prior art, the present inventors have a fine fibrous form having a good yield at the time of producing a fine fibrous cellulose-containing sheet and excellent curl resistance and dimensional stability. We proceeded with the study for the purpose of providing a cellulose-containing sheet.

As a result of diligent studies to solve the above problems, the present inventors have found that a sheet having a first region containing fine fibrous cellulose and resin and a second region containing fine fibrous cellulose and resin has a sheet. By making the content of fibrous cellulose in the first region higher than the content of fibrous cellulose in the second region, the sheet has good yield during production and excellent curl resistance and dimensional stability. Was found to be obtained.
Specifically, the present invention has the following configurations.

[1] A first region containing fibrous cellulose having a fiber width of 1000 nm or less and a first resin, and a fibrous cellulose and a second resin having a fiber width of 1000 nm or less arranged on at least one surface side of the first region. When the content of the fibrous cellulose in the first region (% by mass) is C ₁ and the content of the fibrous cellulose in the second region (% by mass) is C ₂ . Sheet with C ₁ > C ₂ .
[2] The sheet according to [1], wherein the density of the fibrous cellulose in the first region is substantially uniform in at least a part of the thickness direction of the first region.
[3] The sheet according to [1] or [2], wherein the density of the fibrous cellulose in the second region is substantially uniform in at least a part of the thickness direction of the second region.
[4] The sheet according to any one of [1] to [3], wherein the first resin and the second resin are the same type of resin.
[5] The sheet according to any one of [1] to [3], wherein the first resin and the second resin are different resins.
[6] The sheet according to any one of [1] to [5], wherein the content of fibrous cellulose in the first region is 51% by mass or more with respect to the total mass of the first region.
[7] The sheet according to any one of [1] to [6], wherein the content of fibrous cellulose in the second region is 49% by mass or less with respect to the total mass of the second region.
[8] When the content of fibrous cellulose (% by mass) in the first region is C ₁ and the content of fibrous cellulose (% by mass) in the second region is C ₂ , C ₁ / C ₂ ≧ 1 .3 The sheet according to any one of [1] to [7].
[9] The sheet according to any one of [1] to [8], wherein the fibrous cellulose in the first region and the fibrous cellulose in the second region have an anionic group.
[10] A laminate having the sheet according to any one of [1] to [9] and a resin layer arranged on at least one surface side of the sheet.

According to the present invention, the yield at the time of manufacturing a sheet can be improved. Further, according to the present invention, it is possible to obtain a sheet having excellent curl resistance and dimensional stability.

FIG. 1 is a cross-sectional view illustrating the structure of the sheet. FIG. 2 is a diagram illustrating a method for evaluating the curl resistance of a sheet. FIG. 3 is a graph showing the relationship between the amount of NaOH dropped and the electrical conductivity with respect to the fiber raw material having a phosphoric acid group. FIG. 4 is a graph showing the relationship between the amount of NaOH dropped and the electrical conductivity with respect to the fiber raw material having a carboxyl group. FIG. 5 is a cross-sectional view illustrating the structure of the laminated body.

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

(Sheet)
The present invention is arranged on at least one surface side of a first region containing fibrous cellulose having a fiber width of 1000 nm or less and a first resin, and a fibrous cellulose having a fiber width of 1000 nm or less and a second resin. With respect to a second region comprising and a sheet having. Here, when the content rate (mass%) of the fibrous cellulose in the first region is C ₁ and the content rate (mass%) of the fibrous cellulose in the second region is C ₂ , then C ₁ > C ₂ . .. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose.

FIG. 1 is a diagram illustrating an example of the configuration of the sheet of the present invention. As shown in FIG. 1, the sheet 10 has a first region 10a and a second region 10b. Other layers may exist between the first region 10a and the second region 10b, but in the present embodiment, the first region 10a and the second region 10b are preferably adjacent layers. It is preferable that the second region 10b is directly laminated on the first region 10a. When the first region 10a and the second region 10b are adjacent layers, the boundary surface between the first region 10a and the second region 10b may or may not be clear. When the boundary surface between the first region 10a and the second region 10b is not clear, even if a part of the components constituting the first region 10a and a part of the components constituting the second region 10b are mixed in the vicinity of the boundary. good. In this case, even if there is an intermediate region between the first region 10a and the second region 10b in which a part of the components constituting the first region 10a and a part of the components constituting the second region 10b are mixed. good. In such a case, the first region 10a is a region from the end edge of the first region 10a to the center line in the thickness direction of the intermediate region, and the second region 10b is an intermediate region from the end edge of the second region 10b. The area up to the center line in the thickness direction of.

Since the sheet of the present invention has the above-mentioned structure, the yield at the time of producing the sheet can be improved. Further, the sheet of the present invention is excellent in curl resistance and dimensional stability. In the present specification, a good yield at the time of manufacturing a sheet means that the occurrence of wrinkles and cracks at the time of manufacturing a sheet is suppressed, and as a result, a sheet without defects can be produced without manufacturing loss. Further, the curl resistance can be evaluated by the degree of curl generated in the manufactured sheet, and the dimensional stability can be evaluated by measuring the linear thermal expansion coefficient in a high temperature region.

When evaluating the curl resistance, first, the sheet is cut into a test piece having a width of 5 mm and a length of 80 mm, and as shown in FIG. 2, the end including one short side of the test piece 50 has a width of 20 mm × a length. It is supported by two magnets (magnet 55) with a length of 30 mm and a height of 20 mm (a test piece 50 with a length of 50 mm is exposed from the magnet 55), and is placed on a horizontal table in an environment with a temperature of 23 ° C and a relative humidity of 50%. Place the test piece 50 on the table so that the length direction of the test piece 50 is perpendicular to the table. Then, the curl curvature at this time is measured. Specifically, the values of Δx and Δy in FIG. 2 are measured, and the curl curvature C is calculated according to the following equation (1).
Equation (1): C = 2Δy / (Δx ² + Δy ² )
The calculated curvature C is preferably less than 5 m ^-1 and more preferably less than 1 m ^-1 .

When evaluating dimensional stability, first, a sheet is cut into a width of 3 mm and a length of 30 mm, which is set in a thermomechanical analyzer, and is set in a thermomechanical analyzer with a chuck spacing of 20 mm, a load of 10 g, and a room temperature in a nitrogen atmosphere. From 180 ° C to 180 ° C at 5 ° C / min, from 180 ° C to 25 ° C at 5 ° C / min, and from 25 ° C to 180 ° C at 5 ° C / min. The coefficient of linear thermal expansion is obtained from the measured value at 150 ° C. As the thermomechanical analyzer, for example, TMA7100 manufactured by Hitachi High-Tech Co., Ltd. can be used. The calculated coefficient of linear thermal expansion is preferably less than 30 ppm / ° C, more preferably less than 20 ppm / ° C.

When the content of fine fibrous cellulose (% by mass) in the first region is C ₁ and the content of fine fibrous cellulose in the second region (% by mass) is C ₂ , then if C ₁ > C ₂ Well, that is, C ₁ / C ₂ > 1.0. Further, C ₁ / C ₂ ≧ 1.1 is preferable, C ₁ / C ₂ ≧ 1.3 is more preferable, and C ₁ / C ₂ ≧ 1.5 is further preferable. The content rate C ₁ of the fine fibrous cellulose in the first region is the ratio of the mass of the fine fibrous cellulose to the total mass of the first region, and the content rate C ₂ of the fine fibrous cellulose in the second region is. The ratio of the mass of the fine fibrous cellulose to the total mass of the second region.

The content of fine fibrous cellulose in each region is measured by the following method. That is, each region is cut from the surface of each region of the sheet with a device such as an ultramicrotome. At this time, cutting is performed so that the fragment obtained by cutting does not include the vicinity of the boundary between the first region and the second region. Then, after the cut fragment is sufficiently dried, the mass W0 of the cut fragment is measured. Then, the sheet is immersed in a cellulose solvent for 24 hours to dissolve the fine fibrous cellulose in the solvent. As the solvent for cellulose, for example, an acid such as hydrochloric acid and sulfuric acid, an alkali such as lithium hydroxide and sodium hydroxide, an organic solvent such as a mixture of pyridine / chloral and a mixture of dimethylformamide / dinitrogen tetraoxide can be used. Those that do not dissolve the resin in each region can be appropriately selected. After the sheet after immersion is pulled up and sufficiently dried, the mass W1 is measured, and the content of fine fibrous cellulose is calculated according to the following formula.
(Formula) Content of fine fibrous cellulose C = 100 × (W0-W1) / W0

The content rate C ₁ of the fine fibrous cellulose in the first region is the same as the ratio of the mass of the fine fibrous cellulose to the total solid content mass in the composition (slurry) used for forming the first region. The content rate C ₂ of the fine fibrous cellulose in the second region is the same as the ratio of the mass of the fine fibrous cellulose to the total solid content mass in the composition (slurry) used for forming the second region. In the present invention, by setting C ₁ / C ₂ in the above range, it is possible to improve the yield at the time of sheet production, and to obtain a sheet having excellent curl resistance and dimensional stability.

When the content rate (mass%) of the first resin in the first region is D ₁ and the content rate (mass%) of the second resin in the second region is D ₂ , it is preferable that D ₁ <D ₂ . That is, it is preferable that D ₁ / D ₂ <1.0. Further, D ₁ / D ₂ ≤ 0.9 is more preferable, D ₁ / D ₂ ≤ 0.8 is further preferable, and D ₁ / D ₂ ≤ 0.7 is particularly preferable. The content rate D ₁ of the first resin in the first region is the ratio of the mass of the first resin to the total mass of the first region, and the content rate D ₂ of the second resin in the second region is the second region. It is the ratio of the mass of the second resin to the total mass of.

The resin content of each region is measured by the following method. That is, each region is cut from the surface of each region of the sheet with a device such as an ultramicrotome. At this time, cutting is performed so that the fragment obtained by cutting does not include the vicinity of the boundary between the first region and the second region. Then, after the cut fragment is sufficiently dried, the mass W0 of the cut fragment is measured. Then, the sheet is immersed in the solvent of the resin for 24 hours to dissolve the resin in the solvent. Here, as the solvent of the resin, for example, when the resin is polyvinyl alcohol, ethylene glycol, glycerin, acetamide, dimethylamide, dimethylacetamide, dimethyl sulfoxide and the like can be used, and the fine fibrous cellulose in each region is not dissolved. Can be selected as appropriate. After the sheet after immersion is pulled up and sufficiently dried, the mass W2 is measured, and the resin content is calculated according to the following formula.
(Formula) Resin content D = 100 × (W0-W2) / W0

The content rate D ₁ of the first resin in the first region is the same as the ratio of the mass of the first resin to the total solid content mass in the composition (slurry) used for forming the first region, and the second The content rate D ₂ of the second resin in the region is the same as the ratio of the mass of the second resin to the mass of the total solid content in the composition (slurry) used for forming the second region. In the present invention, by setting D ₁ / D ₂ in the above range, it becomes easy to improve the yield at the time of manufacturing a sheet, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

The first region may be a region composed of fine fibrous cellulose and the first resin, and the second region may be a region composed of fine fibrous cellulose and the second resin. In this case, the content of fine fibrous cellulose in each region and the content of the resin (first resin or second resin) are calculated by the following formulas.
Content of fine fibrous cellulose (mass%) = mass of fine fibrous cellulose / (mass of fine fibrous cellulose + mass of resin) × 100
Resin content (mass%) = resin mass / (fine fibrous cellulose mass + resin mass) x 100

The content of the fine fibrous cellulose in the first region is preferably 51% by mass or more, more preferably 55% by mass or more, and more preferably 60% by mass or more, based on the total mass of the first region. It is more preferable, and it is particularly preferable that it is 70% by mass or more. The content of the fine fibrous cellulose in the first region is preferably 99% by mass or less, more preferably 95% by mass or less, and 90% by mass or less, based on the total mass of the first region. Is more preferable. By setting the content of the fine fibrous cellulose in the first region within the above range, it becomes easy to improve the yield at the time of sheet production, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

The content of the first resin in the first region is preferably 1% by mass or more, more preferably 5% by mass or more, and 10% by mass or more with respect to the total mass of the first region. Is more preferable. The content of the first resin in the first region is preferably 49% by mass or less, more preferably 45% by mass or less, and 40% by mass or less with respect to the total mass of the first region. It is more preferably present, and particularly preferably 30% by mass or less. By setting the content of the first resin in the first region within the above range, it becomes easy to improve the yield at the time of manufacturing the sheet, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

The content of the fine fibrous cellulose in the second region is preferably 49% by mass or less, more preferably 45% by mass or less, and more preferably 40% by mass or less, based on the total mass of the second region. It is more preferably 30% by mass or less, and particularly preferably 20% by mass or less. The content of the fine fibrous cellulose in the second region is preferably 1% by mass or more, more preferably 5% by mass or more, and 10% by mass or more with respect to the total mass of the second region. Is more preferable. By setting the content of the fine fibrous cellulose in the second region within the above range, it becomes easy to improve the yield at the time of sheet production, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

The content of the second resin in the second region is preferably 51% by mass or more, more preferably 55% by mass or more, and more preferably 60% by mass or more, based on the total mass of the second region. Is more preferable, 70% by mass or more is further preferable, and 80% by mass or more is particularly preferable. The content of the second resin in the second region is preferably 99% by mass or less, more preferably 95% by mass or less, and 90% by mass or less, based on the total mass of the second region. It is more preferable to have. By setting the content of the second resin in the second region within the above range, it becomes easy to improve the yield at the time of manufacturing the sheet, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

The content of the fine fibrous cellulose in the entire sheet is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more with respect to the total mass of the sheet. preferable. The content of the fine fibrous cellulose in the entire sheet is preferably 80% by mass or less, more preferably 70% by mass or less, and more preferably 60% by mass or less with respect to the total mass of the sheet. Is even more preferable.

The resin content (total content of the first resin and the second resin) in the entire sheet is preferably 20% by mass or more, more preferably 30% by mass or more, based on the total mass of the sheet. , 40% by mass or more is more preferable. The resin content in the entire sheet is preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less, based on the total mass of the sheet. .. By keeping the content of fine fibrous cellulose and the content of resin in the entire sheet within the above ranges, the sheet strength can be increased, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

In the present embodiment, the density of the fine fibrous cellulose in the first region is substantially uniform in at least a part of the thickness direction of the first region. Further, the density of the fine fibrous cellulose in the second region is substantially uniform in at least a part of the thickness direction of the second region. When the boundary surface between the first region 10a and the second region 10b is clear, the density of the fine fibrous cellulose in the first region is preferably substantially uniform in all regions in the thickness direction of the first region. The density of the fine fibrous cellulose in the second region is preferably substantially uniform in all regions in the thickness direction of the second region. Further, the boundary surface between the first region 10a and the second region 10b is not clear, and a part of the components constituting the first region 10a constitutes the second region 10b between the first region 10a and the second region 10b. When there is an intermediate region in which a part of the components is mixed, it is preferable that the density of the fine fibrous cellulose is substantially uniform in each region except the intermediate region.

Here, the state in which the density of the fine fibrous cellulose in each region is substantially uniform in at least a part in the thickness direction is the case where the concentration of the fine fibrous cellulose contained in the following regions (a) to (c) is measured. In addition, it means a state in which the fiber concentration ratio between the two regions is less than 2. That is, it means a state in which there is no difference of 2 times or more even if the concentrations of any of the two regions are compared. In the following, at least a part of each region in the thickness direction will be described as an X region.
(A) Region from one end face in the thickness direction in the X region to 10% of the total thickness of the X region (b) Region from the other end face in the thickness direction in the X region to 10% of the total thickness of the X region. (C) A region of ± 5% (total 10%) of the total thickness of the X region from the central surface in the thickness direction in the X region.

The thickness of the first region is preferably 20 μm or more, more preferably 30 μm or more, further preferably 40 μm or more, and particularly preferably 50 μm or more. The thickness of the first region is preferably 1000 μm or less.
The thickness of the second region is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and particularly preferably 20 μm or more. The thickness of the second region is preferably 500 μm or less.

When measuring the thickness of the first region and the thickness of the second region, cut out with an ultramicrotome UC-7 (manufactured by JEOL Ltd.) so that the cross section in the thickness direction of the sheet is exposed, and observe the cross section with an optical microscope. The measurement is performed by doing. In the present specification, the average value of the thickness of each region of 10 points existing in the cross section is taken as the thickness of each region.

When the thickness of the first region is P and the thickness of the second region is Q, P> Q is preferable, P> 1.5 × Q is more preferable, and P> 2.0 × Q. Is more preferable. By setting the thickness of the first region and the thickness of the second region as the above conditions, it becomes easy to improve the yield at the time of manufacturing the sheet, and it becomes easy to obtain a sheet having excellent curl resistance and dimensional stability.

(Fine fibrous cellulose)
In the sheet of the present invention, the first region and the second region each contain fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less.

The raw material for fibrous cellulose for obtaining fine fibrous cellulose is not particularly limited, but pulp is preferable because it is easily available and inexpensive. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen bleached craft. Examples thereof include chemical pulp such as pulp (OKP). Examples thereof include semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), mechanical pulp such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), but are not particularly limited. Examples of the non-wood pulp include cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweed, chitin, chitosan and the like, but are not particularly limited. .. Examples of the deinked pulp include deinked pulp made from recycled paper, but the pulp is not particularly limited. As the pulp of this embodiment, one of the above may be used alone, or two or more of them may be mixed and used. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferable in terms of availability. Among wood pulps, chemical pulp has a large cellulose ratio, so the yield of fine fibrous cellulose during fiber finening (defibration) is high, the decomposition of cellulose in the pulp is small, and the fineness of long fibers with a large axial ratio It is preferable in that fibrous cellulose can be obtained. Of these, kraft pulp and sulfite pulp are most preferably selected.

The average fiber width of the fine fibrous cellulose is 1000 nm or less as observed with an electron microscope. The average fiber width is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, more preferably 2 nm or more and 50 nm or less, and further preferably 2 nm or more and 10 nm or less, but is not particularly limited. When the average fiber width of the fine fibrous cellulose is less than 2 nm, it is dissolved in water as a cellulose molecule, so that the physical properties (strength, rigidity, dimensional stability) of the fine fibrous cellulose tend to be difficult to develop. .. The fine fibrous cellulose is, for example, a single fibrous cellulose having a fiber width of 1000 nm or less.

The fiber width is measured by observing the fine fibrous cellulose with an electron microscope as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared, and this suspension was cast on a hydrophilized carbon film-coated grid to form a sample for TEM observation. do. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the constituent fibers. 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 images of the non-overlapping surface portions are observed, and the widths of the fibers intersecting the straight lines X and Y are read for each image. In this way, at least 20 fibers × 2 × 3 = 120 fibers are read. The average fiber width of the fine fibrous cellulose is the average value of the fiber width read in this way.

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 particularly preferably 0.1 μm or more and 600 μm or less. By setting the fiber length within the above range, the destruction of the crystal region of the fine fibrous cellulose can be suppressed, and the slurry viscosity of the fine fibrous cellulose can be set within an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by 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 the 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 preferably 30% or more, more preferably 50% or more, still more preferably 70% or more. In this case, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion rate. 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 fine fibrous cellulose preferably has an ionic functional group, and the ionic functional group is preferably an anionic group. That is, the fine fibrous cellulose in the first region and the fine fibrous cellulose in the second region preferably have an anionic group. Examples of such anionic groups include a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxyl group or a substituent derived from a carboxyl group (simply referred to as a carboxyl group). Also, it is preferably at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxyl group. It is more preferably a seed, and particularly preferably a phosphate group.

The phosphoric acid group is a divalent functional group obtained by removing the hydroxyl group from phosphoric acid. Specifically, it is a group represented by -PO ₃ H ₂ . Substituents derived from a phosphoric acid group include substituents such as a group obtained by decomposing a phosphoric acid group, a salt of a phosphoric acid group, and a phosphoric acid ester group, and even if it is an ionic substituent, it is a nonionic substituent. It may be a group.

In the present invention, the phosphate group or the substituent derived from the phosphoric acid group may be a substituent represented by the following formula (1).

In equation (1), a, b, m and n each independently represent an integer of 1 or more (where a = b × m); α and α ′ independently represent R or OR, respectively. 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, an unsaturated-branched chain hydrocarbon group. , An aromatic group, or an inducing group thereof; β is a monovalent or higher cation consisting of an organic or inorganic substance.

<Phosphate group introduction process>
In the phosphorylation group introduction step, at least one selected from a compound having a phosphorylation group and a salt thereof (hereinafter referred to as "phosphorylation reagent" or "compound A") is reacted with a fiber raw material containing cellulose. Can be done by. Such phosphorylation reagents may be mixed with the dry or wet fiber raw material in the form of powder or aqueous solution. As another example, a powder or an aqueous solution of a phosphorylation reagent may be added to the slurry of the fiber raw material.

The phosphorylation group introduction step can be carried out by reacting a fiber raw material containing cellulose with at least one selected from a compound having a phosphorylation group and a salt thereof (phosphorylation reagent or compound A). This reaction may be carried out in the presence of at least one selected from urea and its derivatives (hereinafter referred to as "Compound B").

As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence of the compound B, there is a method of mixing the powder or the aqueous solution of the compound A and the compound B with the fiber raw material in a dry state or a wet state. Another example is a method of adding a powder or an aqueous solution of compound A and compound B to a slurry of a fiber raw material. Of these, since the reaction uniformity is high, a method of adding an aqueous solution of compound A and compound B to a dry fiber raw material, or adding a powder or aqueous solution of compound A and compound B to a wet fiber raw material. The method is preferred. Further, compound A and compound B may be added at the same time or separately. Further, the compound A and the compound B to be tested in the reaction may be added as an aqueous solution first, and the excess chemical solution may be removed by pressing. The form of the fiber raw material is preferably cotton-like or thin sheet-like, but is not particularly limited.

The compound A used in this embodiment is at least one selected from a compound having a phosphoric acid group and a salt thereof.
Examples of the compound having a phosphoric acid group include phosphoric acid, a lithium salt of phosphoric acid, a sodium salt of phosphoric acid, a potassium salt of phosphoric acid, an ammonium salt of phosphoric acid, and the like, but the compound is not particularly limited. Examples of the lithium salt of phosphoric acid include lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. Examples of the sodium salt of phosphoric acid include sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate. Examples of the potassium salt of phosphoric acid include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium polyphosphate and the like. Examples of the ammonium salt of phosphoric acid include ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate.

Of these, phosphoric acid and phosphoric acid are selected 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. A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable. Sodium dihydrogen phosphate or disodium hydrogen phosphate is more preferred.

Further, the compound A is preferably used as an aqueous solution because the uniformity of the reaction is enhanced and the efficiency of introducing the phosphoric acid group is increased. The pH of the aqueous solution of compound A is not particularly limited, but is preferably 7 or less because the efficiency of introducing a phosphoric acid group is high, and more preferably pH 3 or more and pH 7 or less from the viewpoint of suppressing hydrolysis of pulp fibers. The pH of the aqueous solution of the compound A may be adjusted, for example, by using a compound having a phosphoric acid group in combination with an acidic compound and an alkaline compound, and changing the amount ratio thereof. The pH of the aqueous solution of the compound A may be adjusted by adding an inorganic alkali or an organic alkali to the compound having a phosphoric acid group and showing acidity.

The amount of compound A added to the fiber raw material is not particularly limited, but 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 and 100% by mass. The following is preferable, 1% by mass or more and 50% by mass or less is more preferable, and 2% by mass or more and 30% by mass or less is most preferable. When the amount of phosphorus atom added to the fiber raw material is within the above range, the yield of fine fibrous cellulose can be further improved. When the amount of the phosphorus atom added to the fiber raw material exceeds 100% by mass, the effect of improving the yield reaches a plateau and the cost of the compound A used increases. On the other hand, the yield can be increased by setting the addition amount of the phosphorus atom to the fiber raw material to be equal to or higher than the above lower limit value.

Examples of compound B used in this embodiment include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.

Compound B is preferably used as an aqueous solution like compound A. Further, since the uniformity of the reaction is enhanced, 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 preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and 100% by mass or more and 350% by mass or less. It is more preferably 150% by mass or more, and particularly preferably 300% by mass or less.

In addition to compound A and compound B, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like. Among these, triethylamine in particular is known to act as a good reaction catalyst.

It is preferable to perform heat treatment in the phosphoric acid group introduction step. 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. Specifically, it is preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 150 ° C. or higher and 200 ° C. or lower. Further, a vacuum dryer, an infrared heating device, and a microwave heating device may be used for heating.

During the heat treatment, when the fiber raw material slurry containing the compound A contains water and the fiber raw material is allowed to stand for a long time, the water molecules and the dissolved compound A move to the surface of the fiber raw material as it dries. do. Therefore, the concentration of the compound A in the fiber raw material may be uneven, and the introduction of the phosphoric acid group to the fiber surface may not proceed uniformly. In order to suppress the occurrence of uneven concentration of compound A in the fiber raw material due to drying, a very thin sheet-shaped fiber raw material is used, or the fiber raw material and compound A are kneaded or stirred with a kneader or the like and dried by heating or under reduced pressure. You can take the method.

The heating device used for the heat treatment is preferably a device that can always discharge the water retained by the slurry and the water generated by the addition reaction of the fiber such as a phosphate group to the hydroxyl group to the outside of the device system. For example, a ventilation type oven. Etc. are preferable. If the water in the apparatus system is constantly discharged, the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, can be suppressed, and the acid hydrolysis of the sugar chain in the fiber can also be suppressed. , Fine fibers having a high axial ratio can be obtained.

Although the heat treatment time is affected by the heating temperature, it is preferably 1 second or more and 300 minutes or less after the water is substantially removed from the fiber raw material slurry, and more preferably 1 second or more and 1000 seconds or less. It is preferable, and it is more preferably 10 seconds or more and 800 seconds or less. In the present invention, 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 content of phosphoric acid group (introduction amount of phosphoric acid group) is preferably 0.10 mmol / g or more, and more preferably 0.20 mmol / g or more per 1 g (mass) of fine fibrous cellulose. , 0.50 mmol / g or more is more preferable. The content of the phosphoric acid group is preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less, and 3.00 mmol / g or less per 1 g (mass) of fine fibrous cellulose. Is more preferable. By setting the content of the phosphoric acid group 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. In the present specification, the content of the phosphoric acid group (the amount of the phosphoric acid group introduced) of the fine fibrous cellulose is equal to the amount of the strong acid group of the phosphoric acid group of the fine fibrous cellulose, as will be described later.

The amount of the phosphoric acid group introduced into the fiber raw material can be measured by the conductivity titration method. Specifically, it is refined by a defibration treatment step, the obtained fine fibrous cellulose-containing slurry is treated with an ion exchange resin, and then the change in electrical conductivity is obtained while adding an aqueous sodium hydroxide solution. The amount of introduction can be measured.

In the conductivity titration, the addition of alkali gives the curve shown in FIG. Initially, the electrical conductivity drops sharply (hereinafter referred to as the "first region"). After that, the conductivity begins to increase slightly (hereinafter referred to as "second region"). After that, the increment of conductivity increases (hereinafter referred to as "third region"). That is, three regions appear. The boundary point between the second region and the third region is defined by the point where the second derivative value of the conductivity, that is, the amount of change in the increment (slope) of the conductivity is maximized. Of these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group causes condensation, the weakly acidic group is apparently lost, 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, since the amount of strongly acidic group is the same as the amount of phosphorus atom regardless of the presence or absence of condensation, it is simply referred to as the amount of phosphoric acid group introduced (or the amount of phosphoric acid group) or the amount of substituent introduced (or the amount of substituent). When it is said, it means the amount of strongly acidic groups. That is, the amount of alkali (mmol) required in the first region of the curve shown in FIG. 3 is divided by the solid content (g) in the slurry to be titrated to obtain the amount of substituent introduced (mmol / g).

The phosphoric acid group introduction step may be performed at least once, but may be repeated a plurality of times. In this case, more phosphate groups are introduced, which is preferable.

<Carboxyl group introduction process>
In the present invention, when the fine fibrous cellulose has a carboxyl group, for example, the fiber raw material is subjected to an oxidation treatment such as a TEMPO oxidation treatment, a compound having a group derived from a carboxylic acid, a derivative thereof, or an acid thereof. Carboxyl groups can be introduced by treatment with anhydrides or derivatives thereof.

The compound having a carboxyl group is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. Be done.

The acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Be done.

The derivative of the compound having a carboxyl group is not particularly limited, and examples thereof include an acid anhydride derivative of the compound having a carboxyl group and an acid anhydride derivative of the compound having a carboxyl group. The imide of the acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinateimide, and phthalateimide.

The derivative of the acid anhydride of the compound having a carboxyl group is not particularly limited. For example, at least a part of the hydrogen atom of the acid anhydride of a compound having a carboxyl group, such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride, etc., is a substituent (for example, an alkyl group, a phenyl group, etc.). ) Is substituted.

The amount of the carboxyl group introduced is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g or more per 1 g (mass) of the fine fibrous cellulose. Is even more preferable. The content of the carboxyl group is preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less, and 3.00 mmol / g or less per 1 g (mass) of fine fibrous cellulose. It is more preferable to have.
The amount of the carboxyl group introduced into the fiber raw material can be measured by the conductivity titration method. In the conductivity titration, the addition of alkali gives the curve shown in FIG. The amount of alkali (mmol) required in the first region of the curve shown in FIG. 4 is divided by the solid content (g) in the slurry to be titrated to obtain the amount of substituent introduced (mmol / g).

<Alkaline treatment>
In the case of producing fine fibrous cellulose, an alkali treatment may be performed between the ionic substituent introduction step such as the phosphate group introduction step and the carboxyl 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 substituent-introduced fiber in an alkaline solution.
The alkaline compound contained in the alkaline solution is not particularly limited, but may be an inorganic alkaline compound or an organic alkaline compound. The solvent in the alkaline solution may be either water or an organic solvent. The solvent is preferably a polar solvent (water or a polar organic solvent such as alcohol), and more preferably an aqueous solvent containing at least water.
Further, among the alkaline solutions, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is particularly 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 in the alkaline solution in the alkaline 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 with respect to the absolute dry mass of the ionic substituent-introduced fiber. It is more preferable to have.

In order to reduce the amount of the alkaline solution used in the alkaline treatment step, the ionic substituent-introduced fiber may be washed with water or an organic solvent before the alkaline treatment step. After the alkali treatment, in order to improve the handleability, it is preferable to wash the alkali-treated ionic substituent-introduced fiber with water or an organic solvent before the defibration treatment step.

<Defibration processing process>
The ionic substituent-introduced fiber is defibrated in the defibration treatment step. In the defibration treatment step, the fibers are usually defibrated using a defibration treatment device to obtain a fine fibrous cellulose-containing slurry, but the treatment device and the treatment method are not particularly limited.
As the defibration processing device, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer, an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill and the like can be used. Alternatively, as the defibration processing device, a wet pulverizing device such as a disc type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater shall be used. You can also. The defibration processing apparatus is not limited to the above. Preferred defibration treatment methods include 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.

At the time of the defibration treatment, it is preferable to dilute the fiber raw material with water and an organic solvent alone or in combination to form a slurry, but the fiber raw material is not particularly limited. As the dispersion medium, a polar organic solvent can be used in addition to water. Preferred polar organic solvents include, but are not limited to, alcohols, ketones, ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol and the like. Examples of the ketone include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether and tetrahydrofuran (THF). The dispersion medium may be one kind or two or more kinds. Further, the dispersion medium may contain a solid content other than the fiber raw material, for example, urea having a hydrogen bond property.

In the present invention, the defibration treatment may be performed after the fine fibrous cellulose is concentrated and dried. In this case, the method of concentration and drying is not particularly limited, and examples thereof include a method of adding a concentrating agent to a slurry containing fine fibrous cellulose, a method of using a commonly used dehydrator, a press, and a dryer. Also known methods, such as those described in WO2014 / 024876, WO2012 / 107642, and WO2013 / 121086, can be used. Further, the concentrated fine fibrous cellulose may be made into a sheet. The sheet can also be crushed for defibration treatment.

Devices used for crushing fine fibrous cellulose include high-speed crushers, grinders (stone mill type crushers), high-pressure homogenizers, ultra-high pressure homogenizers, high-pressure collision type crushers, ball mills, bead mills, disc-type refiners, and conicals. Wet pulverizers such as refiners, twin-screw kneaders, vibration mills, homomixers under high-speed rotation, ultrasonic dispersers, beaters, etc. can also be used, but are not particularly limited.

(resin)
In the sheet of the present invention, the first region contains the first resin and the second region contains the second resin. The first resin and the second resin are preferably hydrophilic resins, respectively. Examples of the hydrophilic resin include polyethylene glycol, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.), casein, dextrin, starch, and modification. Examples thereof include starch, polyvinylpyrrolidone, polyvinylmethyl ether, polyacrylic acid salts, polyacrylamide, acrylic acid alkyl ester copolymer, and urethane-based copolymer. Among them, the hydrophilic resin is preferably at least one selected from polyethylene glycol (PEG), polyvinyl alcohol (PVA), modified polyvinyl alcohol (modified PVA) and polyethylene oxide (PEO), and polyvinyl alcohol (PVA). Is more preferable.

Examples of the first resin and the second resin include acrylic resin, olefin resin, polyester resin, styrene resin, urethane resin, phenol resin, fluororesin, epoxy resin, polyamide resin, polyimide resin and the like. Emulsions such as silicon-based resins; emulsions of copolymers of the monomers constituting the above-mentioned resins; and mixtures of the above-mentioned resin emulsions can also be used.

The weight average molecular weights of the first resin and the second resin are preferably 50,000 or more and 8 million or less, and more preferably 100,000 or more and 5 million or less.

In the present embodiment, the first resin and the second resin may be the same type of resin or different types of resin. When the first resin and the second resin are the same type of resin, the interlayer adhesion between the first region and the second region can be effectively enhanced. As a result, the strength of the entire sheet can be increased. On the other hand, when the first resin and the second resin are different resins, the physical characteristics of each surface of the sheet may be different.

(Optional ingredient)
In the sheet of the present invention, the first region may be a region composed of fine fibrous cellulose and the first resin, and the second region may be a region composed of fine fibrous cellulose and the second resin. The region may further contain an optional component in addition to the fine fibrous cellulose and the resin.

Examples of the optional component include organic ions. Examples of the organic ion include tetraalkylammonium ion and tetraalkylphosphonium ion. Examples of the tetraalkylammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion and lauryltrimethyl. Examples thereof include ammonium ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, octyldimethylethylammonium ion, lauryldimethylethylammonium ion, didecyldimethylammonium ion, lauryldimethylbenzylammonium ion and tributylbenzylammonium ion. Examples of the tetraalkylphosphonium ion include tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Further, examples of the organic ion include tetrapropyl onium ion and tetrabutyl onium ion, particularly tetra n-propyl onium ion and tetra n-butyl onium ion.

Further, each region has optional components such as a coupling agent, an inorganic layered compound, an inorganic compound, a leveling agent, a defoaming agent, an organic particle, a lubricant, an antistatic agent, an ultraviolet protective agent, a dye, a pigment, a stabilizer, and a magnetic substance. It may contain a powder, an orientation promoter, a plasticizing agent, a cross-linking agent and the like.

The content of the optional component contained in each region is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and 20 parts by mass with respect to 100 parts by mass of the fine fibrous cellulose contained in each region. It is more preferably less than or equal to parts by mass. By setting the content of the optional component within the above range, a sheet having high curl resistance and dimensional stability can be formed.

(Sheet manufacturing method)
The method for producing a sheet of the present invention includes a step of forming a second region containing fibrous cellulose having a fiber width of 1000 nm or less and a second resin, and a fiber width of 1000 nm or less on at least one surface side of the second region. Includes a step of forming a first region containing fibrous cellulose and a first resin. The step of forming the second region includes a step of coating the composition for forming the second region (hereinafter, also referred to as a composition or a slurry) on the substrate, or a step of making a paper for the composition for forming the second region. Is preferable. Above all, it is preferable that the step of forming the second region includes a step of applying the composition for forming the second region on the substrate. Further, in the step of forming the first region, a step of applying the composition for forming the first region (hereinafter, also referred to as a composition or a slurry) onto the second region, or a step of applying the composition for forming the first region to the second region. Includes the process of making paper on the area. Above all, it is preferable that the step of forming the first region includes a step of applying the composition for forming the first region on the second region. In the method for producing a sheet of the present invention, the sheet may be formed by forming the first region and then laminating the second region on the first region.

The content of fibrous cellulose (mass%) in the composition for forming the first region used in the method for producing the sheet of the present invention is _C11 , and the content of fibrous cellulose (mass) in the composition for forming the second region is defined as C11. %) Is C ₁₂ , and C ₁₁ > C ₁₂ may be satisfied, that is, C ₁₁ / C ₁₂ > 1.0. Further, C ₁₁ / C ₁₂ ≧ 1.1 is preferable, C ₁₁ / C ₁₂ ≧ 1.3 is more preferable, and C ₁₁ / C ₁₂ ≧ 1.5 is further preferable.

<Coating process>
The coating step is a step of applying a composition (slurry) on a base material and drying the composition to obtain a sheet (first region or second region). In the step of forming the second region, for example, the composition for forming the second region is applied onto the substrate. Further, in the step of forming the first region, for example, the composition for forming the first region is applied onto the second region provided on the base material. By using a coating device and a long base material, sheets can be continuously produced. The concentration of the slurry to be coated is not particularly limited, but is preferably 0.05% by mass or more and 5% by mass or less.

The material of the base material used in the coating process is not particularly limited, but a material having a high wettability to the composition (slurry) may 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, and polyvinylidene chloride, metal films and plates of aluminum, zinc, copper, and iron plates, and those whose surfaces are oxidized, stainless films. And boards, brass films and boards can be used.

In the coating process, when the viscosity of the composition (slurry) is low and it develops on the base material, a sheet containing fine fibrous cellulose having a predetermined thickness and basis weight can be obtained, so that it can be dammed on the base material. The frame may be fixed and used. The quality of the dammed frame is not particularly limited, but it is preferable to select one in which the end portion of the sheet to be attached after drying can be easily peeled off. Of these, a resin film or plate or a molded metal film or plate is preferable, but the present invention is not particularly limited. For example, resin films and plates such as acrylic, polyethylene terephthalate, vinyl chloride, polystyrene and polyvinylidene chloride, metal films and plates such as aluminum, zinc, copper and iron, and those whose surfaces are oxidized and stainless steel. Molded films, plates, brass films, plates, etc. can be used.

As the coating machine for coating the composition (slurry), for example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater and the like can be used. A die coater, a curtain coater, and a spray coater are preferable because the thickness can be made more uniform.

The coating temperature is not particularly limited, but is preferably 20 ° C. or higher and 45 ° C. or lower, more preferably 25 ° C. or higher and 40 ° C. or lower, and further preferably 27 ° C. or higher and 35 ° C. or lower. When the coating temperature is at least the above lower limit value, the composition (slurry) can be easily coated, and when it is at least 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 slurry so that the finished basis weight of the sheet is 10 g / m ² or more and 100 g / m ² or less. By coating so that the basis weight is within the above range, a sheet having excellent strength can be obtained.

The step of forming each region preferably includes a step of drying the composition (slurry) coated on the substrate. The drying method is not particularly limited, but may be either a non-contact drying method or a method of drying while restraining the sheet, and these may be combined.

The non-contact drying method is not particularly limited, but a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heat drying method) and a method of vacuum drying (vacuum drying method) are applied. Can be done. The heat drying method and the vacuum drying method may be combined, but usually, the heat drying method is applied. Drying with infrared rays, far-infrared rays or near-infrared rays can be performed using an infrared device, a far-infrared device or a near-infrared device, but is not particularly limited. The heating temperature in the heat drying method is not particularly limited, but is preferably 20 ° C. or higher and 120 ° 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, and when it is at least the above upper limit value, the cost required for heating can be suppressed and the discoloration of fine fibrous cellulose can be suppressed due to heat. ..

In the step of forming the first region, even if the first region obtained by coating the composition for forming the first region on the substrate by the same method as described above is laminated on the second region. good. In this case, the first region and the second region may be laminated before the drying step, and the regions may be joined by drying in the laminated state, and the first region and the second region may be bonded to each other by an adhesive layer or the like. It may be joined through. When an adhesive layer is provided between the first region and the second region, acrylic resin can be mentioned, for example, as the adhesive constituting the adhesive layer. Examples of the adhesive include vinyl chloride resin, (meth) acrylic acid ester resin, styrene / acrylic acid ester copolymer resin, vinyl acetate resin, vinyl acetate / (meth) acrylic acid ester copolymer resin, and urethane. Resins, silicone resins, epoxy resins, ethylene / vinyl acetate copolymer resins, polyester resins, polyvinyl alcohol resins, ethylene vinyl alcohol copolymer resins, rubber emulsions such as SBR and NBR can also be used.

The step of forming the first region preferably includes a step of applying the composition for forming the first region onto the second region. In this case, the composition for forming the first region is applied onto the sheet to be the second region and dried to form the sheet having the second region and the first region. When the viscosity of the composition for forming the first region is low and the composition is developed on the sheet as the second region, a dam is dammed on the sheet as the second region in order to obtain the first region having a predetermined thickness and basis weight. You may use it by fixing the frame for.

The sheet having the first region and the second region can be wound after being peeled from the base material. Alternatively, the sheet and the base material may be wound while being laminated, and the sheet may be peeled off from the base material immediately before the sheet is used. Further, a material containing a base material as a part of the laminated body may be used without peeling off the base material.

<Papermaking process>
The step of forming each region may include a step of making a paper of the composition (slurry). Examples of the paper machine in the paper making process 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, known papermaking such as hand papermaking may be performed.

In the papermaking process, the composition (slurry) is filtered on a wire and dehydrated to obtain a wet paper sheet, which is then pressed and dried to obtain a sheet. When the first region is formed on the second region by the papermaking process, the composition for forming the first region is filtered and dehydrated on the second region formed on the wire to obtain a wet paper state sheet. After that, a sheet is obtained by pressing and drying. The concentration of the slurry is not particularly limited, but is preferably 0.05% by mass or more and 5% by mass or less. When the slurry is filtered and dehydrated, the filter cloth at the time of filtration is not particularly limited, but it is important that the fine fibrous cellulose does not pass through and the filtration rate does not become too slow. The filter cloth is not particularly limited, but a sheet made of an organic polymer, a woven fabric, and a porous membrane are preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE) are preferable. Specific examples thereof include a porous membrane of polytetrafluoroethylene having a pore size of 0.1 μm or more and 20 μm or less, for example, 1 μm, polyethylene terephthalate having a pore diameter of 0.1 μm or more and 20 μm or less, for example, 1 μm, or a polyethylene woven fabric, but the present invention is not particularly limited.

The method for producing each region from the composition (slurry) is not particularly limited, and examples thereof include a method using the production apparatus described in WO2011 / 013567. This manufacturing device discharges a slurry containing fine fibrous cellulose onto the upper surface of an endless belt, and squeezes a dispersion medium from the discharged slurry to produce a web, and a water-squeezed section that dries the web to form a fiber sheet. It has a drying section to produce. An endless belt is disposed 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 that can be used in the present invention is not particularly limited, and examples thereof include a dehydration method that is normally used in the production of paper. Is preferable. Further, 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, a near infrared heater, and an infrared heater are preferable.

Further, in the present embodiment, after the first region and the second region are separately created, one of the first region and the second region may be laminated on the other. In this case, the first region and the second region are preferably laminated in a wet state, and the first region and the second region may be joined via an adhesive layer or the like. When the adhesive layer is provided between the first region and the second region, the adhesive constituting the adhesive layer may be the same as the above-mentioned adhesive.

(Laminated body)
The present invention also relates to a laminate having the above-mentioned sheet and a resin layer arranged on at least one surface side of the sheet. FIG. 5 is a cross-sectional view illustrating the structure of the laminated body 20. As shown in FIG. 5, the laminated body 20 has a sheet 10 having a first region 10a and a second region 10b, and a resin layer 22. The resin layer 22 may be provided only on one surface side of the sheet 10 or may be provided on both surface sides of the sheet 10.

The resin layer is a layer containing a natural resin or a synthetic resin as a main component. Here, the main component refers to a component contained in an amount of 50% by mass or more with respect to the total mass of the resin layer. The content of the resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and 90% by mass, based on the total mass of the resin layer. The above is particularly preferable. The content of the resin may be 100% by mass or 95% by mass or less.

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

The synthetic resin is selected from, for example, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, acrylic resin, epoxy resin, urethane resin, fluororesin, and silicon resin. It is preferably at least one kind. Above all, the synthetic resin is preferably a polycarbonate resin, an acrylic resin, or a silicon resin.

Further, as the synthetic resin, an adhesive constituting the adhesive layer can also be mentioned. Examples of such synthetic resins include acrylic resins, vinyl chloride resins, (meth) acrylic acid ester resins, styrene / acrylic acid ester copolymer resins, vinyl acetate resins, vinyl acetate / (meth) acrylic acid ester co-weights. Examples thereof include coalesced resin, urethane resin, silicone resin, epoxy resin, ethylene / vinyl acetate copolymer resin, polyester resin, polyvinyl alcohol resin, ethylene vinyl alcohol copolymer resin, and rubber emulsions such as SBR and NBR. ..

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

As the resin layer provided on each surface side of the sheet, a single resin layer may be provided, or a plurality of resin layers may be provided. As the resin layer when a plurality of resin layers are provided, a resin layer containing the adhesive constituting the above-mentioned adhesive layer and at least one selected from a polycarbonate resin, an acrylic resin, and a silicon resin may be formed.

When producing the laminate, it may be formed by applying a resin composition for forming a resin layer on a sheet. Further, the resin layer formed in advance may be laminated on the sheet. In this case, an adhesive layer may be provided between the resin layer and the sheet, and such an adhesive layer is also included in the resin layer. Further, when the base material at the time of sheet production is resin, the base material is not peeled off. In addition, it may be used as a part of the resin layer.

(Use)
The sheet of the present invention is suitable for applications of light-transmitting substrates such as various display devices and various solar cells. It is also suitable for applications such as substrates for electronic devices, materials for home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, and packaging materials. Further, it is suitable for applications such as threads, filters, woven fabrics, cushioning materials, sponges, abrasives, etc., as well as applications in which the sheet itself is used as a reinforcing material.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

[Example 1]
[Preparation of phosphate group-introduced cellulose fiber]
As coniferous kraft pulp, Oji Paper pulp (solid content 93% by mass, sheet shape with basis weight 208 g / m ² , separated and measured according to JIS P 8121, Canadian standard drainage degree (CSF) is 700 ml) Was used as a raw material. 100 parts by mass (absolute dry mass) of the above coniferous kraft pulp is impregnated into a mixed aqueous solution of ammonium dihydrogen phosphate and urea, squeezed to 49 parts by mass of ammonium dihydrogen phosphate and 130 parts by mass of urea, and impregnated with a chemical solution. Obtained pulp. The obtained chemical-impregnated pulp was dried in a dryer at 105 ° C. to evaporate the water content and pre-dried. Then, the pulp was heated in a blower dryer set at 140 ° C. for 10 minutes to introduce a phosphoric acid group into the cellulose in the pulp to obtain phosphorylated pulp.

100 g of the obtained phosphorylated pulp was taken out by the mass of the pulp, 10 L of ion-exchanged water was poured, the mixture was stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. The step of obtaining a dehydrated sheet was repeated twice. Next, the obtained dehydrated sheet was diluted with 10 L of ion-exchanged water, and 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a pulp slurry having a pH of 12 or more and 13 or less. Then, this pulp slurry was dehydrated to obtain a dehydrated sheet, and then 10 L of ion-exchanged water was added. After stirring and uniformly dispersing, the steps of filtering and dehydrating to obtain a dehydrated sheet were repeated twice.

With respect to the obtained dehydrated sheet, the steps of introducing a phosphate group and the step of filtering and dehydrating were repeated in the same manner as above to obtain a dehydrated sheet of phosphorylated cellulose twice. The infrared absorption spectrum of the obtained dehydrated sheet was measured by FT-IR. As a result, absorption based on the phosphate group was observed at 1230 cm ^-1 or more and 1290 cm ^-1 or less, and the addition of the phosphate group was confirmed.

[Defibration treatment]
Ion-exchanged water was added to the obtained dehydrated sheet of twice-phosphorylated cellulose to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated three times with a wet atomizer (Ultimizer manufactured by Sugino Machine Limited) at a pressure of 245 MPa to obtain a fine fibrous cellulose dispersion.

[Measurement of substituent amount]
The amount of the substituent introduced is the amount of the phosphoric acid group introduced into the fiber raw material, and the larger this value is, the more phosphoric acid groups are introduced. The amount of the substituent introduced was measured by diluting the target fine fibrous cellulose with ion-exchanged water so that the content was 0.2% by mass, treating with an ion-exchange resin, and titrating with an alkali. In the treatment with an ion exchange resin, a strongly acidic ion exchange resin (manufactured by Organo Corporation, Amber Jet 1024, conditioned) with a volume ratio of 1/10 is added to a slurry containing 0.2% by mass of fine fibrous cellulose, and 1 The time was shaken. Then, it was poured onto a mesh having an opening of 90 μm, and the resin and the slurry were separated. In the titration using alkali, the change in the electric conductivity value shown by the slurry was measured while adding a 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry after ion exchange. That is, the amount of alkali (mmol) required in the first region of the curve shown in FIG. 3 (phosphate group) is divided by the solid content (g) in the slurry to be titrated, and the amount of substituent introduced (mmol / mmol /). g). As a result of calculation, the amount of phosphoric acid group introduced was 0.98 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 was diluted with water so that the concentration was 0.01% by mass or more and 0.1% by mass or less, and dropped onto the hydrophilized carbon grid film. After drying, the cells were stained with uranyl acetate and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.). As a result, it was confirmed that the fine fibrous cellulose had an average fiber width of about 4 nm.

[Dissolution of polyvinyl alcohol]
Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Poval 105, degree of polymerization: 500, degree of saponification: 98-99 mol%) was added to ion-exchanged water so as to be 20% by mass, and the mixture was stirred at 95 ° C. for 1 hour to dissolve. .. An aqueous polyvinyl alcohol solution was obtained by the above procedure.

[Formation of the second region]
The fine fibrous cellulose dispersion and the above polyvinyl alcohol aqueous solution were each diluted with ion-exchanged water so that the solid content concentration was 0.6% by mass. Next, the diluted polyvinyl alcohol aqueous solution was mixed with 10 parts by mass of the diluted fine fibrous cellulose dispersion to 90 parts by mass to obtain a mixed solution (A). Further, the mixed liquid (A) was weighed so that the finished basis weight of the sheet was 37.5 g / m2, and developed on a commercially available transparent acrylic plate. A dammed frame (inner dimensions 180 mm × 180 mm, height 50 mm) was placed on the acrylic plate so as to have a predetermined basis weight. On the opposite surface of the acrylic plate, draw a 120 mm × 120 mm quadrangle with an oil-based pen in the area inside the dammed frame, and draw a straight line that divides the quadrangle into 36 equal parts, and draw a 20 mm square grid. I have drawn. After that, the mixed solution (A) was applied into the dammed frame so that the finished basis weight of the sheet was 37.5 g / m2, dried in a dryer at 70 ° C. for 24 hours, and later combined with the second region. Sheet (A) was obtained.

[Formation of the first region]
The fine fibrous cellulose dispersion and the above polyvinyl alcohol aqueous solution were each diluted with ion-exchanged water so that the solid content concentration was 0.6% by mass. Then, the diluted polyvinyl alcohol aqueous solution was mixed with 70 parts by mass of the diluted fine fibrous cellulose dispersion liquid so as to be 30 parts by mass to obtain a mixed liquid (B). Further, the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 105 g / m2, and developed on the sheet (A) formed on the commercially available acrylic plate as described above. A dammed frame (inner dimension 120 mm × 120 mm, height 5 cm) was arranged on the sheet (A) so as to overlap with the quadrangle described in [Formation of the second region] so as to have a predetermined basis weight. After that, it was dried in a dryer at 70 ° C. for 24 hours to form a sheet (B) as a first region on the sheet (A). By the above procedure, a sheet (C) composed of a first region composed of the sheet (B) and a second region composed of the sheet (A) was obtained.

[Formation of resin layer]
100 parts by mass of acrylic resin graft-polymerized with acryloyl group (Acryt 8KX-012C manufactured by Taisei Fine Chemical Co., Ltd .: acrylic resin component 39.0% by mass, 1-propanol 30.5% by mass, butyl acetate 30.5% by mass), poly A resin composition was obtained by mixing 38 parts by mass of an isocyanate compound (TPA-100 manufactured by Asahi Kasei Chemicals Co., Ltd.) and 2 parts by mass of a radical polymerization initiator (Irgacure 184 manufactured by BASF Co., Ltd.). Next, the resin composition is applied to the surface of the sheet (C) separated from the acrylic plate on the sheet (A) side with a bar coater, and then heated at 100 ° C. for 1 hour to cure the resin layer. Formed. The thickness of the resin layer was 10 μm. An evaluation sheet was obtained by the above procedure.

[Example 2]
In [Formation of the second region] of Example 1, the composition of the mixed liquid (A) was changed as follows. Specifically, 20 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 80 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (A). Further, the mixed liquid (A) was weighed so that the finished basis weight of the sheet was 39 g / m2, and developed on a commercially available acrylic plate.
Further, in [Formation of the first region], the composition of the mixed liquid (B) was changed as follows. Specifically, 80 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 20 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (B). Further, the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 108 g / m2, and developed on the sheet (A). Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Example 3]
In [Formation of the second region] of Example 1, the composition of the mixed liquid (A) was changed as follows. Specifically, 40 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 60 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (A). Further, the mixed liquid (A) was weighed so that the finished basis weight of the sheet was 41 g / m2, and developed on a commercially available acrylic plate.
Further, in [Formation of the first region], the composition of the mixed liquid (B) was changed as follows. Specifically, 60 parts by mass of the diluted polyvinyl alcohol aqueous solution was mixed with 60 parts by mass of the diluted fine fibrous cellulose dispersion liquid to obtain a mixed liquid (B). Further, the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 88 g / m2, and developed on the sheet (A). Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Example 4]
In Example 1, [formation of the resin layer] was not performed, and the sheet (C) was used as an evaluation sheet.

[Example 5]
In [Formation of the second region] and [Formation of the first region] of Example 1, a polyethylene oxide aqueous solution (manufactured by Sumitomo Seika Chemical Co., Ltd., PEO-18 was used with ion-exchanged water instead of the diluted polyvinyl alcohol aqueous solution. It was dissolved so as to have a concentration of 0.6% by mass). Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Example 6]
In [Formation of the first region] of Example 1, instead of the diluted polyvinyl alcohol aqueous solution, a polyethylene oxide aqueous solution (manufactured by Sumitomo Seika Co., Ltd., PEO-18 is used in ion-exchanged water to have a concentration of 0.6% by mass. (Soluble) was used. Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Comparative Example 1]
In Example 1, [formation of the second region] was not performed. Further, in [Formation of the first region], the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 150 g / m2, and developed on a commercially available acrylic plate. Then, the sheet (B) obtained by drying in a dryer at 70 ° C. for 24 hours was peeled off from the acrylic plate, and [formation of a resin layer] was performed on the surface in contact with the acrylic plate. Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Comparative Example 2]
In [Formation of the second region] of Example 1, the composition of the mixed liquid (A) was changed as follows. Specifically, 70 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 30 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (A). Further, the mixed liquid (A) was weighed so that the finished basis weight of the sheet was 45 g / m2, and developed on a commercially available acrylic plate. Other procedures were the same as in Example 1 to obtain an evaluation sheet.

[Comparative Example 3]
In the [formation of the first region] of Comparative Example 1, the composition of the mixed liquid (B) was changed as follows. Specifically, 10 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 90 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (B). Further, the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 125 g / m2, and developed on a commercially available acrylic plate. Other procedures were the same as in Comparative Example 1 to obtain an evaluation sheet.

[Comparative Example 4]
In [Formation of the first region] of Example 1, the composition of the mixed liquid (B) was changed as follows. Specifically, 10 parts by mass of the diluted fine fibrous cellulose dispersion was mixed with 90 parts by mass of the diluted polyvinyl alcohol aqueous solution to obtain a mixed liquid (B). Further, the mixed liquid (B) was weighed so that the finished basis weight of the sheet was 88 g / m2, and developed on the sheet (A). Other procedures were the same as in Example 1 to obtain an evaluation sheet.

<Measurement>
The evaluation sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were measured according to the following method.

[Thickness of each area]
The evaluation sheet was cut out by Ultra Microtome UC-7 (manufactured by JEOL Ltd.) so that the cross section in the thickness direction was exposed, and the cross section was observed with an optical microscope. The average value of the thickness of each region of 10 points existing in the cross section was taken as the thickness of each region.

<Evaluation>
The evaluation sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated according to the following methods.

[Interlayer adhesion]
In accordance with JIS K 5400, 100 1 mm ² crosscuts are placed on the surface of the evaluation sheet on the first region side, cellophane tape (manufactured by Nichiban Co., Ltd.) is attached on it, and a load of 1.5 kg / cm ² is applied. After pressing with, it was peeled off in the 90 ° direction. The adhesion between the first region and the second region was evaluated according to the following criteria based on the number of peeled squares. Since the evaluation sheet does not have a second region for Comparative Example 1 and Comparative Example 3, this evaluation was not performed.
⊚: The number of separated squares is less than 5.
◯: The number of separated squares is 5 or more and less than 10.
Δ: The number of separated squares is 10 or more and less than 20.
X: The number of separated squares is 20 or more.

[curl]
The evaluation sheet was cut into a test piece having a width of 5 mm and a length of 80 mm. As shown in FIG. 2, the end including one short side of the test piece 50 is supported by two magnets (magnet 55) having a width of 20 mm, a length of 30 mm, and a height of 20 mm (a test having a length of 50 mm from the magnet 55). The piece 50 was placed on a horizontal table in an environment where the temperature was 23 ° C. and the relative humidity was 50% so that the length direction of the test piece 50 was perpendicular to the table. Then, the curl curvature at this time was measured. Specifically, the values of Δx and Δy in FIG. 2 were measured, and the curl curvature C was calculated according to the following equation (1).
Equation (1): C = 2Δy / (Δx ² + Δy ² )
From the calculated curvature C, the curl resistance of the evaluation sheet was evaluated according to the following criteria.
⊚: Curvature C is less than 1 m ^-1 ○: Curvature C is 1 m ^-1 or more and less than 5 m ^-1 Δ: Curvature C is 5 m ^-1 or more and less than 20 m ^-1 ×: Curvature C is 20 m ^-1 or more

[Yield]
In Examples 1 to 6 and Comparative Examples 1 to 4, when each sheet was peeled off from the acrylic plate, the sheet was observed from above with the sheet stuck to the acrylic plate, and the mass in which wrinkles and cracks were generated on the sheet was counted. did. Further, after the sheet was peeled off from the acrylic plate, the number of squares remaining after the sheet was cracked on the acrylic plate was counted. The squares are squares obtained by dividing a 120 mm × 120 mm quadrangle drawn on the opposite surface of the acrylic plate into 36 equal parts. The yield was evaluated according to the following criteria from the total number of squares counted.
⊚: The total number of counted squares is less than 2.
◯: The total number of counted squares is 2 or more and less than 5.
Δ: The total number of counted squares is 5 or more and less than 10.
X: The total number of counted squares is 10 or more.

[Dimensional stability]
The evaluation sheet was cut out to a width of 3 mm and a length of 30 mm by a laser cutter. This is set in a thermomechanical analyzer (TMA7100 manufactured by Hitachi High-Tech), and the temperature is raised from room temperature to 180 ° C at 5 ° C / min under a tension mode with a chuck spacing of 20 mm, a load of 10 g, and a nitrogen atmosphere, from 180 ° C. The coefficient of linear thermal expansion was obtained from the measured values from 100 ° C. to 150 ° C. at the time of the second temperature rise when the temperature was lowered to 25 ° C. at 5 ° C./min and the temperature was raised from 25 ° C. to 180 ° C. at 5 ° C./min. From the results of the measured coefficient of linear thermal expansion, the dimensional stability was evaluated according to the following criteria.
⊚: Coefficient of linear thermal expansion is less than 20 ppm / ° C ○: Coefficient of linear thermal expansion is 20 ppm / ° C or more and less than 30 ppm / ° C Δ: Coefficient of linear thermal expansion is 30 ppm / ° C or more and less than 40 ppm / ° C ×: Coefficient of linear thermal expansion is 40 ppm / ℃ or higher

As is clear from Table 1, in Examples 1 to 6 provided with the first region having a large fine fibrous cellulose content and the second region having a low fine fibrous cellulose content, the curl resistance and the yield were high. Moreover, a sheet having excellent dimensional stability was obtained. Here, the interlayer adhesion is better when the resins contained in the first region and the second region are the same. In addition, the degree of curl was reduced by providing the resin layer.
On the other hand, Comparative Example 1 having only the first region having a large fine fibrous cellulose content, and Comparative Example 2 in which the content of fibrous cellulose in the first region and the content of fibrous cellulose in the second region are the same. Although a sheet having excellent dimensional stability was obtained, the results were inferior in the evaluation of curl resistance and yield, and there was a concern that productivity and handleability would be reduced. Further, Comparative Example 3 having only the first region having a small fine fibrous cellulose content, and Comparative Example 4 in which the content of the fibrous cellulose in the first region and the content of the fibrous cellulose in the second region are the same. In, good results were confirmed in curl resistance and yield, but the results were inferior in dimensional stability.

10 Sheet 10a 1st region 10b 2nd region 20 Laminated body 22 Resin layer 50 Test piece 55 Magnet

Claims (10)

A first region containing fibrous cellulose having a fiber width of 1000 nm or less and a first resin, and
It has a second region arranged on at least one surface side of the first region and containing a fibrous cellulose having a fiber width of 1000 nm or less and a second resin.
The first resin and the second resin are hydrophilic resins, respectively.
When the content (% by mass) of the fibrous cellulose in the first region is C ₁ and the content (% by mass) of the fibrous cellulose in the second region is C ₂ , C ₁ > C ₂ . Yes,
When the thickness of the first region is P and the thickness of the second region is Q, P> Q. The sheet according to claim 1, wherein the density of the fibrous cellulose in the first region is substantially uniform in at least a part of the thickness direction of the first region. The sheet according to claim 1 or 2, wherein the density of the fibrous cellulose in the second region is substantially uniform in at least a part of the thickness direction of the second region. The sheet according to any one of claims 1 to 3, wherein the first resin and the second resin are the same type of resin. The sheet according to any one of claims 1 to 3, wherein the first resin and the second resin are different kinds of resins. The sheet according to any one of claims 1 to 5, wherein the content of the fibrous cellulose in the first region is 51% by mass or more with respect to the total mass of the first region. The sheet according to any one of claims 1 to 6, wherein the content of the fibrous cellulose in the second region is 49% by mass or less with respect to the total mass of the second region. When the content (% by mass) of the fibrous cellulose in the first region is C ₁ and the content (% by mass) of the fibrous cellulose in the second region is C ₂ , C ₁ / C ₂ ≧ The sheet according to any one of claims 1 to 7, which is 1.3. The sheet according to any one of claims 1 to 8, wherein the fibrous cellulose in the first region and the fibrous cellulose in the second region have an anionic group. A laminate having the sheet according to any one of claims 1 to 9 and a resin layer arranged on at least one surface side of the sheet.

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