Sheet, laminate, liquid-state composition, and method for producing sheet or laminate

Abstract

To provide a sheet containing fine cellulose fibers that can be easily produced using a general-purpose paper machine or coating machine and that exhibits an excellent visible light transmittance and / or gas barrier property.SOLUTION: There is provided a sheet, containing fine cellulose fibers and a cationic polymer, wherein the fine cellulose fibers and cationic polymer are aggregated in the sheet, a molecular weight of the cationic polymer is 100,000 to 1,000,000, and a content of the cationic polymer is 10 wt.% to 60 wt.% based on the fine cellulose.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sheet, a laminate, and a liquid composition containing fine cellulose fibers, and a method for producing the sheet or the laminate. [Background technology]

[0002] Microfibrillated cellulose fibers have attracted attention as a useful biomass raw material, and laminates, sheets, and the like that utilize microfibrillated cellulose fibers have been developed. Examples include a molded product in which a layer containing nanocellulose is formed on a layer made of a polyvalent cationic resin (see Patent Document 1), barrier paper having a paper substrate and a barrier layer containing cellulose fibers and a water-soluble polymer formed on the paper substrate, in which the cellulose fibers are crosslinked via oxazoline groups (see Patent Document 2), a method for producing a microfibrillated cellulose composite sheet that includes a preparation step in which a polymer emulsion such as cationic polyurethane is mixed with an aqueous suspension containing microfibrillated cellulose to produce a mixed solution, and a papermaking step in which the mixed solution is dehydrated by filtration on a porous substrate to form a moist sheet (see Patent Document 3), and a microfibrillated cellulose fiber sheet in which aggregates of blocked polyisocyanate into which cationic groups have been introduced chemically bonded to the microfibrillated cellulose fibers to form a crosslinked structure (see Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 212044 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-190541 [Patent Document 3] International Publication No. 2011 / 013567 [Patent Document 4] International Publication No. 2015 / 008868 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses an example in which a polyester resin layer and a polyethyleneimine layer are formed on a paper substrate, and then a nanocellulose dispersion is coated on top of them. The laminate obtained in this document is not one in which nanocellulose is directly coated on a paper substrate, and the manufacturing process is complicated.

[0005] Patent Document 2 discloses a coating solution containing cellulose fibers and a crosslinking agent, and states that the reaction between the cellulose fibers and the crosslinking agent must be carried out under acidic conditions (pH 3 to 7). Patent Document 3 adds aluminum sulfate as a cellulose coagulant to a suspension for producing a sheet. Therefore, the sheets and laminates obtained by the methods disclosed in these prior documents may have acidic properties, which can lead to the problem of being prone to deterioration.

[0006] Furthermore, Patent Documents 3 and 4 disclose the production of sheets by papermaking, but the dehydration of the liquid composition is carried out on a 508-mesh nylon sheet (Patent Document 3) or a plain-weave filter cloth made of a PET / nylon blend (Patent Document 4), and the mesh size of the nylon sheet or filter cloth is much smaller than the mesh size of the papermaking mesh used in general-purpose papermaking machines. The production methods disclosed in these documents have problems such as the need for special equipment for production and low production efficiency due to the difficulty of dehydrating the liquid composition.

[0007] In other words, the problem to be solved by the present invention is to provide a sheet containing fine cellulose fibers and / or a laminate of the sheet with a paper base material, which can be easily produced using a general-purpose papermaking machine or coating machine and exhibits excellent visible light transmittance and / or gas barrier properties. [Means for solving the problem]

[0008] That is, the present invention provides a sheet containing fine cellulose fibers and a cationic polymer. The fine cellulose fibers and the cationic polymer aggregate in the sheet. The molecular weight of the cationic polymer may be 100,000 to 1,000,000, and the content of the cationic polymer may be 10% by weight to 60% by weight of the fine cellulose.

[0009] In another aspect of the present invention, the cationic polymer in the sheet is one or more selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof.

[0010] In another aspect of the present invention, a basis weight of 40 g / m 2 In another aspect of the present invention, the sheet has a basis weight of 40 g / m2 and a visible light transmittance of 90% or more. 2 The oxygen permeability of the sheet is 1 cm 3 / (m 2 ·day·atm).

[0011] The present invention further provides a liquid composition containing fine cellulose fibers and a cationic polymer, in which the fine cellulose fibers and the cationic polymer aggregate in an aqueous solution, the molecular weight of the cationic polymer may be 100,000 to 1,000,000, the content of the cationic polymer may be 30% to 60% by weight relative to the fine cellulose fibers, and the zeta potential may be -15 mV to 20 mV.

[0012] In another aspect of the present invention, the cationic polymer is one or more selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof. In another aspect of the present invention, the fine cellulose fibers and the cationic polymer form aggregates having an average particle size of 300 μm to 800 μm in the liquid composition. In another aspect of the present invention, the liquid composition has a freeness of 100 mL to 600 mL when the solid content is 0.3 wt %.

[0013] The present invention further provides a method for producing a sheet, comprising: a supplying step of supplying the liquid composition onto a porous substrate having continuous openings; and a dehydrating or drying step of dehydrating or drying the sheet formed on the porous substrate, wherein the opening width of the openings is 50 μm to 300 μm.

[0014] Furthermore, the present invention provides a laminate comprising a paper substrate and a gas barrier layer adjacent to the paper substrate, the gas barrier layer comprising the sheet. In another aspect of the present invention, the content of the cationic polymer in the laminate may be 10% by weight to 30% by weight relative to the fine cellulose fibers. In another aspect of the present invention, the thickness of the gas barrier layer in the laminate may be 1 μm to 10 μm, and the oxygen permeability of the laminate may be 100 cm 3 / (m 2 ·day·atm).

[0015] The present invention further provides a method for producing a laminate, comprising a coating step of coating a paper substrate with a liquid composition, wherein the liquid composition coated in the coating step forms the gas barrier layer. The liquid composition comprises fine cellulose fibers and one or more cationic polymers selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof. The molecular weight of the cationic polymer may be 100,000 to 1,000,000, and the content of the cationic polymer may be 10% to 30% by weight based on the fine cellulose fibers.

[0016] In another aspect of the present invention, the coating amount of the liquid composition in the coating step may be 1 to 10 g per m2 of paper substrate, the liquid composition containing 1.25 wt% of the fine cellulose fibers may have a viscosity of 10,000 mPa·S or less when measured at a liquid temperature of 20°C and a rotation speed of 10 rpm, and the liquid composition having a solid content of 1.25 wt% may have a viscosity of 10,000 mPa·S or less when measured at a liquid temperature of 20°C and a rotation speed of 10 rpm.

[0017] Another aspect of the present invention may be a method for producing a laminate, wherein the fine cellulose fibers and the cationic polymer form aggregates having an average particle size of 100 μm to 300 μm in the liquid composition. Yet another aspect of the present invention may be a method for producing a laminate, comprising, before the coating step, a crushing step of crushing the aggregates formed by the fine cellulose fibers and the cationic polymer in the liquid composition to an average particle size of 100 μm to 300 μm. [Effects of the Invention]

[0018] According to the present invention, a sheet containing fine cellulose fibers and / or a laminate of the sheet and a paper substrate, which exhibits excellent visible light transmittance and / or gas barrier properties, can be obtained by a very simple method. The sheet and / or laminate of the present invention can be produced using a general-purpose papermaking machine or coating machine. Furthermore, the gas barrier layer of the sheet and / or laminate of the present invention does not need to be produced under acidic conditions, and therefore is characterized by being resistant to deterioration. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the measurement results of the tensile strength of the sheets of the examples. [Figure 2] FIG. 10 is a diagram showing the measurement results of light transmittance in the visible light region of the sheets of the examples. [Figure 3] 1 shows electron microscope images of the surface of the gas barrier layer of the laminate of the example (A) and a cross section of the laminate including the gas barrier layer and paper substrate (B). DETAILED DESCRIPTION OF THE INVENTION

[0020] The sheet of the present invention contains fine cellulose fibers and a cationic polymer. The present invention will be described in detail below based on embodiments, but the present invention is not limited to the following embodiments.

[0021] The fine cellulose fibers refer to fine fibers obtained by defibrating cellulose fibers. In one embodiment, the fine cellulose fibers are cellulose nanofibers, which may have a width of 100 nm or less.

[0022] Methods for obtaining fine cellulose fibers by defibrating cellulose fibers include those involving mechanical defibration treatment and chemical defibration treatment. Specific methods for obtaining fine cellulose fibers include modified pulp direct kneading, high-pressure homogenizer method, microfluidizer method, grinder method, ball mill crushing method, bead mill crushing method, freeze crushing method, biaxial kneading method, TEMPO oxidation method, phosphate esterification method, phosphite esterification method, xandation method, sulfonation method, enzyme hydrolysis method, acid hydrolysis method, and ionic liquid selective dissolution method. In the present invention, fine cellulose fibers obtained by any method can be used as long as they can form aggregates with a cationic polymer in the liquid composition described below.

[0023] The cationic polymer used is one that can aggregate with fine cellulose fibers to form aggregates in the liquid composition described below. In the present invention, by using a liquid composition containing aggregates of fine cellulose fibers and a cationic polymer, a sheet and / or laminate that exhibits high performance can be produced by a simple method.

[0024] In one embodiment, the cationic polymer forms aggregates with fine cellulose fibers in the liquid composition described below, having an average particle size of 10 μm to 2,000 μm, 50 μm to 1,500 μm, or 100 μm to 800 μm. The appropriate average particle size of the aggregates may vary depending on the production conditions of the sheet and / or laminate. If the particle size of the aggregates in the liquid composition is larger than the appropriate range, the liquid composition may be subjected to a crushing treatment using a homogenizer or the like to adjust the particle size of the aggregates to an appropriate particle size range. If the particle size of the aggregates is smaller than the appropriate range, the content of the cationic polymer may be increased to obtain aggregates with a larger average particle size. Here, the particle size of the aggregates in the liquid composition is determined by the average particle size measured using a particle size distribution analyzer.

[0025] In one embodiment, the molecular weight of the cationic polymer may be about 100,000 to about 8,000,000, about 100,000 to about 1,000,000, about 200,000 to about 500,000, or about 400,000 to about 500,000. If the molecular weight of the cationic polymer is too small, the particle size of the aggregates with the fine cellulose fibers in the liquid composition may become too small. On the other hand, if the molecular weight of the cationic polymer is too large, the viscosity of the liquid composition may become too high.

[0026] The cationic polymer is not limited as long as it forms aggregates with the fine cellulose fibers. In one embodiment, the cationic polymer may be one or more selected from the group consisting of polydiallyldimethylammonium chloride (hereinafter sometimes referred to as "Poly-DADMAC"), polyamide epichlorohydrin, cationic polyacrylamide, polyethyleneimine, and derivatives thereof.

[0027] The present invention provides a liquid composition containing at least fine cellulose fibers and a cationic polymer. The fine cellulose fibers and the cationic polymer form aggregates in the liquid composition, and a sheet and / or laminate can be obtained by a papermaking step and / or a coating step using the liquid composition.

[0028] In one embodiment, the liquid composition contains fine cellulose fibers and 1 wt % to 200 wt %, 3 wt % to 100 wt %, or 10 wt % to 60 wt % of a cationic polymer, based on the weight of the fine cellulose fibers. In another embodiment, the liquid composition does not contain any polymers other than the fine cellulose fibers and the cationic polymer. This is because, in the present invention, a sheet consisting of aggregates of the fine cellulose fibers and the cationic polymer can be formed, and therefore no other polymers are required. On the other hand, in another embodiment, the liquid composition may contain, among polymers other than the fine cellulose fibers and the cationic polymer, a polymer that is not intended to form aggregates with the fine cellulose fibers.

[0029] In one embodiment, the liquid composition may not contain a cellulose coagulant made of a water-soluble inorganic salt. This is because the presence of the aggregates makes it possible to produce a sheet and / or laminate without coagulating the fine cellulose fibers with an inorganic salt. Specific examples of water-soluble inorganic salts that are not contained in this embodiment include sodium chloride, calcium chloride, potassium chloride, ammonium chloride, magnesium chloride, aluminum chloride, sodium sulfate, potassium sulfate, aluminum sulfate, magnesium sulfate, sodium nitrate, calcium nitrate, sodium carbonate, potassium carbonate, ammonium carbonate, sodium phosphate, and ammonium phosphate. Here, "not containing a cellulose coagulant made of an inorganic salt" means that the inorganic salt is not intentionally added in the liquid composition, sheet, and / or laminate production process in order to achieve a coagulation effect. This does not include cases where these inorganic salts are unintentionally dissolved in the liquid composition or where these inorganic salts are contained in the liquid composition at a concentration that does not exert a coagulation effect.

[0030] In one embodiment, the zeta potential of the liquid composition is minus 15 mV or more. If the zeta potential is low, the formation of aggregates between the fine cellulose fibers and the cationic polymer may be insufficient. On the other hand, if the zeta potential is excessively high, the dispersion stability of the aggregates in the liquid composition may be reduced. In one embodiment, the zeta potential of the liquid composition may be minus 15 mV to 30 mV, minus 10 mV to 20 mV, or minus 8 mV to 12 mV.

[0031] The present invention provides a sheet manufacturing method using the liquid composition described above, and a sheet. In one embodiment, the manufacturing method includes a papermaking step of manufacturing a sheet from the liquid composition. Specifically, the papermaking step includes a supplying step of supplying the liquid composition onto a porous substrate, and a dehydrating or drying step of dehydrating or drying the sheet formed on the porous substrate.

[0032] Papermaking is a method in which a liquid composition containing paper stock such as pulp is supplied onto a papermaking net to obtain a sheet-like paper stock, which is then dehydrated and / or dried to obtain a sheet. Until now, when a liquid composition containing fine cellulose fibers was used for papermaking, it was not possible to obtain a sheet by papermaking because water did not drain from the papermaking net or the fine cellulose fibers did not remain on the papermaking net. On the other hand, the production method of the present invention uses a liquid composition containing aggregates formed by fine cellulose fibers, making it possible to form a sheet on the papermaking net on which paper stock such as pulp is made.

[0033] The solid content of the liquid composition may be adjusted to a level suitable for papermaking, and in one embodiment, the solid content of the liquid composition may be 0.01% by weight to 10% by weight, 0.1% by weight to 5% by weight, or 0.3% by weight to 1% by weight. The content of the cationic polymer in the liquid composition used for papermaking is preferably 30% by weight to 60% by weight relative to the weight of the fine cellulose fibers.

[0034] The liquid composition preferably exhibits a high degree of freeness sufficient to enable the formation of a sheet on a porous substrate such as a papermaking screen. In one embodiment, the lower limit of the freeness (Canadian Standard Freeness) of a liquid composition having a solid content of 0.3 wt% may be 10 mL, 50 mL, or 100 mL, and the upper limit may be 800 mL, 600 mL, or 400 mL. In one embodiment, the freeness (Canadian Standard Freeness) of a liquid composition having a solid content of 0.3 wt% may be 10 to 800 mL, 50 to 600 mL, or 100 to 400 mL.

[0035] In one embodiment, the porous substrate is a porous substrate having a large number of continuous openings. The shape of the openings in the porous substrate is not limited, and the openings may be rectangular, circular, elliptical, polygonal, or the like. The opening width of the openings is not limited as long as papermaking of the liquid composition is possible. In one embodiment, the openings may have an opening width of about 100 μm to about 500 μm.

[0036] In another embodiment, the porous substrate may be a wire mesh. When a wire mesh conforming to JIS-G-3555 (woven wire mesh) or JIS-G-3556 (industrial woven wire mesh) is used, the porous substrate may be a wire mesh with a mesh size of 40 mesh (opening size: about 350 μm to about 500 μm) to 150 mesh (opening size: about 100 μm to about 110 μm).

[0037] In another embodiment, the porous substrate may be a paper mesh. A paper mesh having approximately rectangular openings is generally used, and in such a case, the short sides of the openings may be about 100 μm to about 400 μm, and the long sides of the openings may be about 200 μm to about 600 μm. That is, a paper mesh having an opening width of at least 100 μm or more may be used.

[0038] In the supplying step, a sheet having a desired basis weight can be produced by controlling the amount of the liquid composition supplied onto the porous substrate. In one embodiment, the supplying step is carried out to produce a sheet having a basis weight of 5 to 300 g / m. 2 , 10~200g / m 2 , or 20 to 100 g / m 2This is a supplying step of supplying the liquid composition so that the liquid composition satisfies the following conditions.

[0039] The dehydration or drying step is a step in which moisture is removed from the sheet formed on the porous substrate, and methods used in known papermaking steps, such as dehydration by roll press, dehydration by pump suction, hot air drying, etc., can be used.

[0040] The sheet of the present invention is a sheet containing an aggregate of fine cellulose fibers and a cationic polymer. In one embodiment, the sheet is a sheet consisting of an aggregate of fine cellulose fibers and a cationic polymer, and is a sheet constituted by the aggregate. The sheet of the present invention can also be stacked. Therefore, another aspect of the present invention provides a multilayer sheet in which multiple sheets are stacked.

[0041] The sheet of the present invention has a basis weight of 40 g / m 2 In this case, the visible light transmittance is 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or approximately 90%. The visible light transmittance is specified as the average value of the transmittance at each wavelength when the transmittance is measured within the visible light region (measurement wavelength: 380 nm to 780 nm).

[0042] Another aspect of the present invention provides a laminate of a gas barrier layer made of the above-mentioned sheet and a paper substrate, and a method for producing the laminate, the method comprising a coating step of coating the above-mentioned liquid composition onto the paper substrate. Because the sheet has high gas barrier properties, by forming a laminate with the paper substrate, gas barrier properties can be imparted to the paper substrate.

[0043] The method for producing a laminate of the present invention includes a coating step in which a liquid composition is directly applied to a paper substrate. Generally, microfibrillated cellulose fibers have a high viscosity, making it difficult to directly coat the paper substrate. Furthermore, when microfibrillated cellulose fibers are applied to a paper substrate, there is a problem in that the microfibrillated cellulose fibers penetrate into the interior of the paper substrate, preventing the formation of a laminate. In contrast, the production method of the present invention uses a liquid composition containing aggregates formed by microfibrillated cellulose fibers, making it possible to directly coat the paper substrate with a liquid composition of appropriate viscosity, and the microfibrillated cellulose fibers form a gas barrier layer on the surface of the paper substrate, making it possible to obtain a laminate of the paper substrate and a sheet.

[0044] In one embodiment, the manufacturing method includes a crushing step in which the average particle size of aggregates formed by fine cellulose fibers and a cationic polymer is changed by crushing, and a coating step in which a liquid composition containing the crushed aggregates is applied to a paper substrate. In another embodiment, the manufacturing method does not include a dehydration step after the coating step, but includes a drying step. The drying step removes moisture contained in the liquid composition applied to the paper substrate, resulting in a laminate.

[0045] The liquid composition may be adjusted to have a solid content and viscosity suitable for coating. The liquid composition may be adjusted to contain 0.5% to 2% by weight of fine cellulose fibers and 10% to 30% by weight of cationic polymer relative to the fine cellulose fibers. The viscosity of the liquid composition may be 30,000 mPa·S or less, 20,000 mPa·S or less, or 10,000 mPa·S or less, measured using a rotational viscometer at a liquid temperature of 20°C and a rotation speed of 10 rpm.

[0046] The average particle size of the aggregates in the liquid composition used in the coating step is preferably 100 μm to 400 μm, more preferably 200 μm to 350 μm. If the average particle size is below this range, the content of the cationic polymer can be increased, and if it exceeds this range, the aggregates in the liquid composition can be crushed in a crushing step.

[0047] In the coating step, the liquid composition can be applied to the paper substrate by a known coating method, such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, or a die coater. The amount of the liquid composition applied in the coating step can be adjusted to achieve the desired gas barrier properties, and specifically, 1 g / m 2 ~20g / m 2 , 3g / m 2 ~15g / m 2 , or 4.5g / m 2 ~10g / m 2 It could be.

[0048] In one embodiment of the present invention, the laminate is a laminate comprising a gas barrier layer having a thickness of 1 μm to 10 μm and a paper substrate. Because the gas barrier layer is adjacent to the paper substrate, the laminate does not include any other layers between the gas barrier layer and the paper substrate. The gas barrier layer contains fine cellulose fibers, but because the fine cellulose fibers form aggregates with the cationic polymer, most of the fine cellulose fibers do not penetrate into the interior of the paper substrate, and a gas barrier layer made of the aggregates is formed on the surface of the paper substrate.

[0049] The laminate of the present invention has a coating weight of 5 to 10 g / m 2 When the coating is applied, the oxygen permeability is 100cm 3 / (m 2 ·day · atm) or less, 10cm 3 / (m 2 ·day·atm) or less, or 1cm 3 / (m 2 The oxygen permeability is specified as a value measured by the differential pressure gas chromatogram measurement method in accordance with JIS-K7126-1.

[0050] The sheet and / or laminate of the present invention is made from plant-derived cellulose and has high visible light transmittance and / or high gas barrier properties, and can therefore be used as packaging materials, containers, films, display materials, etc. for food, cosmetics, and / or pharmaceuticals. [Example]

[0051] The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0052] 1. Production of a sheet by a step of papermaking a liquid composition (1) The fine cellulose fibers used were TEMPO-oxidized cellulose nanofibers "LEOCRYSTA®" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) (hereinafter sometimes referred to as "TOCN"). 4 g of cationic polymer was added to 10 g (bone dry weight) of TOCN. The cationic polymers used were polydiallyldimethylammonium chloride (hereinafter sometimes referred to as "Poly-DADMAC") with molecular weights of approximately 100,000 or less, approximately 200,000 to 350,000, and approximately 400,000 to 500,000; cationic polyacrylamide "Aronfloc® E3590" (manufactured by MT Aquapolymer Co., Ltd.) with a molecular weight of approximately 1 million; cationic polyacrylamide "Aronfloc® E3130" (manufactured by MT Aquapolymer Co., Ltd.) with a molecular weight of approximately 8 million; and polyethyleneimine with a molecular weight of approximately 25,000.

[0053] Water was added to the TOCN and cationic polymer until the total weight reached 1500 g, and the mixture was stirred for 1 minute using a pulp disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.). After stirring, a liquid composition was produced with a solid content of 0.3 wt % and a liquid volume of 1 L. The freeness (Canadian Standard Freeness) of each liquid composition was measured using a Canadian type beating tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.).

[0054] Furthermore, each of the above liquid compositions was mixed with a sheet machine paper machine (Kumagaya Riki Kogyo Co., Ltd.) to form a sheet of paper with a basis weight of 60 g / m 2 In the sheet machine, a 120 mesh wire mesh corresponding to JIS-G-3555, with an opening of 125 μm and a wire diameter of 90 μm, was used as the papermaking screen.

[0055] The results of freeness and sheet formation are shown in Table 1. The freeness of liquid compositions containing at least a cationic polymer having a molecular weight of 100,000 to 500,000 was 100 mL or more, and the liquid composition containing a cationic polymer having a molecular weight of 400,000 to 500,000 (Experimental Example 13) showed a particularly high freeness of 300 mL. It was also confirmed that a sheet could be formed by papermaking from a liquid composition containing a cationic polymer having a molecular weight of 100,000 to 1,000,000.

[0056] [Table 1]

[0057] 2. Production of a sheet by papermaking a liquid composition (2) Liquid compositions were prepared by varying the content of cationic polymer relative to TOCN. The cationic polymers used were polydiallyldimethylammonium chloride with a molecular weight of 400,000 to 500,000 and polyamide epichlorohydrin WS4024 (Seiko PMC Corporation) with a molecular weight of 500,000 to 1,000,000. The zeta potential of the liquid compositions was measured using a zeta potential meter SZP-6 (Spectris Corporation). The average particle size of the aggregates of TOCN and polymer contained in the liquid compositions was measured using a particle size distribution analyzer (LMS5004, Seishin Enterprise Co., Ltd.). Furthermore, the freeness was measured using the same method as in (1), and whether or not a sheet could be formed by papermaking was confirmed.

[0058] The zeta potential and average particle size of each liquid composition, as well as the results of sheet formation using each liquid composition, are shown in Table 2. It was shown that sheet formation is possible with liquid compositions having a zeta potential of at least -15 mV or more. It was also considered preferable that the average particle size of aggregates in the liquid composition be 300 μm or more. However, discoloration was observed in the sheets of Examples 23 and 24, which contained a high polymer content. This discoloration was thought to be due to the excessive polymer content in the liquid composition.

[0059] [Table 2]

[0060] 4. Production of a sheet by papermaking the liquid composition (4) A liquid composition containing TOCN and 40% by weight of polydiallyldimethylammonium chloride (molecular weight: approximately 400,000 to 500,000) relative to TOCN was made into paper in the same manner as in (1) and (2), and paper was prepared at basis weights of 20, 60, and 80 g / m 2 The tensile strength of the sheets of each basis weight was measured using a tension-compression tester (manufactured by A&D Co., Ltd.). The results are shown in Figure 1. As the basis weight of the sheet increased, the tensile strength improved.

[0061] Next, using a spectrophotometer V-570 (manufactured by JASCO Corporation), the basis weight was measured at 20 to 40 g / m 2 The transmittance of the sheet in the visible light region was measured. As shown in Figure 2, the transmittance of the sheet of this example in the wavelength range of 380 to 800 nm, including visible light, was approximately 90%, and a highly transparent sheet was produced.

[0062] 5. Production of a sheet by papermaking the liquid composition (5) In the condition (4), TOCN was replaced with sulfonated cellulose nanofiber, phosphite-esterified cellulose nanofiber, dicarboxylated cellulose nanofiber, or mechanically defibrated cellulose nanofiber to produce a liquid composition, and papermaking was attempted. It was confirmed that a sheet could be formed using any of the liquid compositions.

[0063] 6. Production of a laminate by applying a liquid composition to a paper substrate (1) TOCN was mixed with 20-25 wt% polydiallyldimethylammonium chloride (molecular weight approximately 400,000-500,000) or 30 wt% polyamide epichlorohydrin (molecular weight approximately 1,000,000) based on the TOCN, and water was added to adjust the TOCN concentration to 1.1-1.3 wt%. The average particle size was measured and found to be 300 μm or greater. Therefore, the mixture was crushed at 20,000 rpm for 10 minutes using a homogenizer (Ultra Turrax T-25, IKA Japan Co., Ltd.). The average particle size of the aggregates in the crushed liquid composition was measured and found to be 200-300 μm. The resulting liquid composition was defoamed using a stirring defoamer SNB-350 (Ika Japan Co., Ltd.), and then coated at a coating weight of 5.5-8.0 g / m. 2 The paper base material (basis weight 58 g / m 2 The gas barrier layer was directly coated onto sized paper (manufactured by Miki Tokushu Paper Co., Ltd.). After coating, the paper was placed in a thermostatic oven set at 130°C and dried for approximately 10 minutes to obtain a laminate consisting of the paper substrate and the gas barrier layer adjacent to the paper substrate.

[0064] To evaluate the gas barrier properties of the laminates, the oxygen permeability was evaluated using a gas permeability tester (GTR-11AET, GTR Tech Co., Ltd.). The oxygen permeability of each laminate was 1 cm 3 / (m 2 The gas barrier properties of the laminate were less than 1000 kJ / day atm, and a laminate with high gas barrier properties was obtained. Furthermore, when the surface and cross section of the laminate of Experimental Example 32 were observed with an electron microscope JSM-IT300LA (manufactured by JEOL Ltd.), it was revealed that a gas barrier layer containing TOCN and having a thickness of about 3 μm was formed on the paper substrate, as shown in Figure 3.

[0065] [Table 3]

[0066] 7. Production of a laminate by applying a liquid composition to a paper substrate (2) Liquid compositions were prepared in the same manner as in Section 6, except that 10% to 40% by weight of polydiallyldimethylammonium chloride (molecular weight: approximately 400,000 to 500,000) or 25% or 30% by weight of polyamide epichlorohydrin (molecular weight: approximately 1,000,000) was added to TOCN. The average particle size of aggregates in the liquid compositions and the viscosity at a liquid temperature of 20°C and a rotation speed of 10 rpm were measured using a Brookfield viscometer (RVDV-1+). Furthermore, the liquid compositions were coated onto paper substrates to attempt the production of laminates. As shown in Table 3, the viscosity of the liquid compositions decreased as the content of the cationic polymer increased. Furthermore, laminates were formed in all of Experimental Examples 41 to 46.

[0067] [Table 4]

[0068] 8. Production of a laminate by applying a liquid composition to a paper substrate (3) Under the same conditions as in Example 6, a liquid composition was prepared using polydiallyldimethylammonium chloride (molecular weight 400,000 to 500,000) with a molecular weight of 100,000 or less, or a molecular weight of 200,000 to 350,000, a cationic polyacrylamide "Aronfloc (registered trademark) E3590" with a molecular weight of 1,000,000, or a polyethyleneimine with a molecular weight of 25,000. The liquid composition was then applied to a paper substrate to attempt the production of a laminate. When a liquid composition containing polydiallyldimethylammonium chloride with a molecular weight of 100,000 or less, or a molecular weight of 200,000 to 350,000, or a cationic polyacrylamide with a molecular weight of 1,000,000 was used, the formation of a laminate with the paper substrate was confirmed. On the other hand, when polyethyleneimine with a molecular weight of 25,000 was used, no laminate was formed.

Claims

1. A sheet containing fine cellulose fibers and a cationic polymer, the fine cellulose fibers and the cationic polymer are aggregated in the sheet, The molecular weight of the cationic polymer is 100,000 to 1,000,000; The content of the cationic polymer is 10% by weight to 60% by weight based on the fine cellulose. Sheet.

2. The cationic polymer is one or more selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof; The sheet according to claim 1.

3. Basis weight 40g / m ２ 3. The sheet according to claim 2, wherein the visible light transmittance of the sheet is 90% or more.

4. Basis weight 40g / m ２ The oxygen permeability of the sheet is 1 cm ３ / (m ２ 3. The sheet according to claim 2, wherein the sheet has a viscosity of 1000 psi (1000 psi).

5. A liquid composition containing fine cellulose fibers and a cationic polymer, the fine cellulose fibers and the cationic polymer are aggregated in the liquid composition in an aqueous solution, The molecular weight of the cationic polymer is 100,000 to 1,000,000; The content of the cationic polymer is 30% by weight to 60% by weight based on the fine cellulose fibers, The zeta potential is minus 15 mV to 20 mV. Liquid composition.

6. The cationic polymer is one or more selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof; The liquid composition according to claim 5.

7. The fine cellulose fibers and the cationic polymer form aggregates having an average particle size of 300 μm to 800 μm. The liquid composition according to claim 6.

8. The liquid composition according to claim 6, wherein the freeness is 100 mL to 600 mL when the solid content is 0.3 wt%.

9. A supplying step of supplying the liquid composition according to any one of claims 5 to 8 onto a porous substrate having continuous openings; a dehydration or drying step of dehydrating or drying the sheet formed on the porous substrate; Including, The opening width of the opening is 50 μm to 300 μm. A method for producing the sheet according to any one of claims 1 to 4.

10. A laminate comprising a paper substrate and a gas barrier layer adjacent to the paper substrate, The gas barrier layer is made of the sheet according to claim 2. Laminate.

11. The content of the cationic polymer is 10% by weight to 30% by weight based on the fine cellulose fibers. The laminate according to claim 10.

12. the thickness of the gas barrier layer is 1 μm to 10 μm, The oxygen permeability of the laminate is 100 cm ３ / (m ２ ・day・atm) or less, The laminate according to claim 11.

13. A coating step of coating a liquid composition onto a paper substrate, The liquid composition is Fine cellulose fibers, and one or more cationic polymers selected from the group consisting of polydiallyldimethylammonium chloride, polyamide epichlorohydrin, cationic polyacrylamide, and derivatives thereof; The molecular weight of the cationic polymer is 100,000 to 1,000,000; The content of the cationic polymer is 10% by weight to 30% by weight based on the fine cellulose fibers, The liquid composition applied in the application step forms the gas barrier layer. A method for producing the laminate according to any one of claims 10 to 12.

14. The coating amount of the liquid composition in the coating step is ２ 1 to 10 g per serving, The method of claim 13.

15. The liquid composition containing 1.25% by weight of the fine cellulose fibers has a viscosity of 10,000 mPa·S or less, measured at a liquid temperature of 20°C and a rotation speed of 10 rpm. The method of claim 13.

16. The liquid composition has a solid content of 1.25% by weight, and the viscosity measured at a liquid temperature of 20°C and a rotation speed of 10 rpm is 10,000 mPa·S or less. The method of claim 13.

17. In the liquid composition, the fine cellulose fibers and the cationic polymer form aggregates having an average particle size of 100 μm to 300 μm. The method of claim 13.

18. Prior to the coating step, A crushing step is included in which the average particle size of aggregates formed by the fine cellulose fibers and the cationic polymer in the liquid composition is 100 μm to 300 μm. The method of claim 13.

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