Method for manufacturing a laminate containing cellulose nanofibers, and the laminate

Abstract

To provide a method for producing a laminate having a functional layer that is ideal for use in a variety of industrial applications.SOLUTION: The present invention provides a method for producing a laminate, the method including a step for applying a coating liquid containing an anionically modified cellulose nanofiber onto a support substrate by a pre-metering coating method to form a functional layer, wherein the coating liquid has a viscosity of 50-1000 mPa s at 60 rpm and the functional layer has a thickness of 30 μm or less. Preferably, the anionically modified cellulose nanofiber is an oxidized cellulose nanofiber having a carboxyl group and / or a carboxylate group; or a carboxyalkylated cellulose nanofiber, a phosphorylated cellulose nanofiber, or a sulphated cellulose nanofiber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a laminate containing cellulose nanofibers and to such a laminate.

Background Art

[0002] Cellulose nanofibers obtained by introducing anionic or cationic groups into cellulose and defibrating using the charge repulsive force of these introduced groups have a very fine fiber diameter, are generally highly homogeneous, and have various functionalities based on the introduced groups and high strength, etc., and are thus widely studied. For example, as anionic modified cellulose nanofibers obtained by introducing anionic groups into cellulose and defibrating, there are oxidized cellulose nanofibers obtained by oxidizing a part of the hydroxyl groups of cellulose to carboxyl groups using the surface oxidation reaction of cellulose with an N-oxyl compound and defibrating, and carboxymethylated cellulose nanofibers having a carboxymethyl substitution degree of 0.01 to 0.30 and an average fiber diameter of 3 to 500 nm have been reported (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such nanofibers are beginning to be reported to exhibit unique properties in various applications due to the effects of their nanostructures. However, cellulose nanofibers are commercially available in the form of aqueous dispersions or powdered solids, and require secondary processing for industrial use. In particular, there is a growing expectation that cellulose nanofiber coatings will be formed on substrates and used as functional layers.

[0005] Therefore, the object of the present invention is to provide a method for manufacturing a laminate having an optimal functional layer for application in various industrial uses. [Means for solving the problem]

[0006] As a result of diligent efforts, the applicants have found that the problem can be solved with the following configuration. [1] The process includes applying a coating liquid containing anionic modified cellulose nanofibers onto a support substrate by a pre-metering coating method to form a functional layer, The viscosity of the coating solution at 60 rpm is 50-1000 mPa·s. The thickness of the functional layer is 30 μm or less. A method for manufacturing laminates. [2] The method for producing cellulose nanofibers according to [1], wherein the anionically modified cellulose nanofibers are oxidized cellulose nanofibers having carboxyl groups and / or carboxylate groups. [3] The method for producing the anionic modified cellulose nanofiber according to [1], wherein the anionic modified cellulose nanofiber is a carboxyalkylated cellulose nanofiber. [4] The method for producing the anionic modified cellulose nanofiber according to [1], wherein the anionic modified cellulose nanofiber is a phosphate esterified cellulose nanofiber. [5] The method for producing the anionic modified cellulose nanofiber according to [1], wherein the anionic modified cellulose nanofiber is sulfated cellulose nanofiber. [6] The manufacturing method according to any one of the items [1] to [5], wherein the pre-measurement coating method is a die coating method. [7] The manufacturing method according to any one of the following items [1] to [5], wherein the preceding metering and coating method is a curtain coating method. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for manufacturing a laminate having an optimal functional layer for application in various industrial uses. [Modes for carrying out the invention]

[0008] <1. Laminate> The laminate comprises a functional layer containing anionic modified cellulose nanofibers on a support substrate.

[0009] <Anionic Modified Cellulose Nanofibers> The functional layer of the laminate contains anionic modified cellulose nanofibers.

[0010] -Nanofiber (NF)- In this invention, nanofibers (NF) refer to nanofibers having an average fiber diameter of less than 1 μm. Preferably, the average fiber diameter is about 3 nm to 500 nm, more preferably about 3 nm to 150 nm, and even more preferably about 3 nm to 20 nm. The aspect ratio is usually 30 or more, or 35 or more, preferably 40 or more, more preferably 50 or more, and even more preferably 100 or more. There is no upper limit to the aspect ratio, but it is about 500 or less. The average fiber diameter and average fiber length of NF can be measured by analyzing 200 randomly selected fibers using an atomic force microscope (AFM) if the diameter is less than 20 nm, or a field emission scanning electron microscope (FE-SEM) if the diameter is 20 nm or more, and calculating the average. The aspect ratio can also be calculated using the following formula: Aspect ratio = average fiber length / average fiber diameter.

[0011] Among nanofibers, the present invention uses anion-modified cellulose nanofibers (hereinafter also referred to as anion-modified CNF).

[0012] -Definition and properties of anionic modified CNF- Anion-modified CNF is cellulose fiber in which anionic groups are introduced into the molecular chains of cellulose. Anion-modified CNF can be obtained by introducing anionic groups into the pyranose rings of cellulose, and then defibrating the resulting anion-modified cellulose to an average fiber diameter of less than 1 μm.

[0013] Anion-modified CNF retains at least a portion of its fibrous structure even when dispersed in water, and does not completely dissolve in water. When an aqueous dispersion of anion-modified CNF is observed with an electron microscope, fibrous material can be seen. Functional layers containing anion-modified CNF can exhibit good physical strength because the fibrous structure of the anion-modified CNF is maintained within the layer.

[0014] -Cellulose raw material- The type of cellulose (cellulose raw material) used as the raw material for anionically modified cellulose is not particularly limited. For example, bleached or unbleached mechanical pulp (e.g., thermomechanical pulp (TMP), wood pulp) and chemical pulp (e.g., sulfite pulp, kraft pulp) made from coniferous trees, broad-leaved trees, cotton, straw, bamboo, hemp, jute, kenaf, etc., as well as dissolved pulp, regenerated cellulose, fine cellulose, and microcrystalline cellulose with the amorphous region removed can all be used as cellulose raw materials.

[0015] -Method for introducing anionic groups and defibrillating them- By introducing anionic groups into such cellulose raw materials, anionic modified cellulose can be produced. The method for introducing anionic groups is not particularly limited. For example, there are methods of directly oxidizing the hydroxyl groups of the pyranose ring of cellulose into carboxyl groups, and methods of introducing anionic groups through an esterification reaction at the hydroxyl group part of the pyranose ring. By defibrating the anionic modified cellulose obtained by introducing anionic groups so as to have an average fiber diameter of less than 1 μm, anionic modified CNF can be obtained. The defibrating method is not particularly limited. For example, there are methods using known defibrating devices such as high-speed rotation type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, etc. Among them, the method using a wet high-pressure or ultra-high pressure homogenizer is preferred.

[0016] -Examples of Anionic Modified CNF- (Oxidized CNF) As an example of anionic modified CNF, oxidized CNF having carboxyl groups and / or carboxylate groups can be mentioned. In this specification, the carboxyl group refers to -COOH (acid type) and -COOM (metal salt type) (where M is a metal ion), and the carboxylate group refers to -COO - is referred to. Oxidized CNF having carboxyl groups and / or carboxylate groups (also simply referred to as "oxidized CNF" in this specification) can be obtained by obtaining oxidized cellulose using a known method of oxidizing the hydroxyl groups of the pyranose ring of cellulose into carboxyl groups and then defibrating it. As a method for oxidizing cellulose, for example, a method of oxidizing cellulose in water using an oxidizing agent in the presence of an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and a bromide and / or an iodide, or a method of oxidizing cellulose by bringing a gas containing ozone into contact with a cellulose raw material as an oxidizing agent can be mentioned.

[0017] The total amount of carboxyl groups and carboxylate groups in the oxidized CNF is preferably 0.4 to 3.0 mmol / g, more preferably 0.6 to 2.0 mmol / g, still more preferably 1.0 to 2.0 mmol / g, and still more preferably 1.1 to 2.0 mmol / g, based on the absolute dry mass of the oxidized CNF. The amounts of carboxyl groups and carboxylate groups in the oxidized CNF can be adjusted by controlling reaction conditions such as the addition amount of the oxidizing agent and the reaction time. The amounts of carboxyl groups and carboxylate groups can be measured by the following method: Prepare 60 ml of a 0.5% by mass slurry (aqueous dispersion) of oxidized CNF, add an aqueous 0.1 M hydrochloric acid solution to adjust the pH to 2.5, then dropwise add an aqueous 0.05 N sodium hydroxide solution and measure the electrical conductivity until the pH reaches 11. Calculate using the following formula from the amount of sodium hydroxide (a) consumed in the stage of neutralizing the weak acid where the change in electrical conductivity is gentle: Amount of carboxyl and carboxylate groups [mmol / g oxidized CNF] = a [ml] × 0.05 / mass of oxidized CNF [g].

[0018] (Carboxyalkylated CNF) As an example of anionic modified CNF, carboxyalkylated CNF having a carboxyalkyl group can be mentioned. In this specification, the carboxyalkyl group refers to -RCOOH (acid type) and -RCOOM (metal salt type). Here, R is an alkylene group such as a methylene group or an ethylene group, and M is a metal ion (for example, alkali metals such as Li, Na, and K; alkaline earth metals such as Mg and Ca; metals such as Fe and Al, with Li, Na, and Ca being preferred and Na being more preferred) (the same applies hereinafter). As the carboxyalkylated CNF having a carboxyalkyl group, carboxymethylated CNF having a carboxymethyl group where R is a methylene group is most preferred (hereinafter, "carboxymethyl" is referred to as "CM"). The carboxyalkylated CNF can be obtained by treating a cellulose raw material with a mercerizing agent and then treating it with a carboxyalkylating agent to introduce a carboxyalkyl group using a known method to obtain carboxyalkylated cellulose, and then defibrating it.

[0019] CM-modified cellulose, the raw material for CM-modified CNF, maintains at least a portion of its fibrous structure even when dispersed in water, and is distinguished from carboxymethylcellulose, an example of a water-soluble polymer described later. When an aqueous dispersion of "carboxymethylated cellulose (CM-modified cellulose)" is observed with an electron microscope, fibrous material can be seen. On the other hand, when an aqueous dispersion of carboxymethylcellulose, a type of water-soluble polymer, is observed, no fibrous material is seen. Furthermore, when "carboxymethylated cellulose (CM-modified cellulose)" is measured by X-ray diffraction, a peak of cellulose type I crystals can be observed, but cellulose type I crystals are not seen in the water-soluble polymer carboxymethylcellulose.

[0020] The degree of carboxyalkyl substitution per anhydrous glucose unit of carboxyalkylated CNF is preferably less than 0.40. Furthermore, the lower limit of the degree of carboxyalkyl substitution is preferably 0.01 or higher. Considering operability, the degree of substitution is preferably 0.02 to 0.35, more preferably 0.10 to 0.35, even more preferably 0.15 to 0.35, and still more preferably 0.15 to 0.30. Note that anhydrous glucose units refer to individual anhydrous glucose (glucose residues) constituting cellulose, and the degree of carboxyalkyl substitution refers to the proportion of hydroxyl groups (-OH) in the glucose residues constituting cellulose that are substituted with carboxyalkyl groups (-ORCOOH or -ORCOOM) (the number of carboxyalkyl groups per glucose residue). The degree of carboxyalkyl substitution can be adjusted by controlling reaction conditions such as the amount of mercerizing agent and reaction time. The degree of CM substitution per glucose unit can be measured by the following method: Accurately weigh approximately 2.0 g of CM-modified CNF (dry) and place it in a 300 mL stoppered Erlenmeyer flask. Add 100 mL of a solution made by adding 100 mL of special grade concentrated nitric acid to 900 mL of methanol, and shake for 3 hours to convert the salt-type CM-modified CNF to hydrogen-type CM-modified CNF. Accurately weigh 1.5 g to 2.0 g of hydrogen-type CM-modified CNF (dry) and place it in a 300 mL stoppered Erlenmeyer flask. Wet the hydrogen-type CM-modified CNF with 15 mL of 80% by mass methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. Back titrate the excess NaOH with 0.1 N H2SO4 using phenolphthalein as an indicator. Calculate the degree of CM substitution (DS) using the following formula: A = [(100 × F' - (0.1N H2SO4) (mL) × F) × 0.1] / (Dry mass of hydrogen-type CMN (g)) DS = 0.162 × A / (1 - 0.058 × A) A: Amount of 1N NaOH required to neutralize 1g of hydrogen-type CMF (mL) Factor of H2SO4 with F:0.1N F': Factor of 0.1N NaOH The degree of carboxyalkyl group substitution other than CM groups can also be measured using the same method as described above.

[0021] (Crystallization degree of cellulose type I) The crystallinity of type I cellulose in CM-modified CNF is preferably 50% or higher, and more preferably 60% or higher. The crystallinity of type I cellulose in CM-modified CNF can be controlled by the concentration of the mercerizing agent used in the production of the raw material CM-modified cellulose, the temperature during processing, and the degree of carboxymethylation. In mercerization and carboxymethylation, high concentrations of alkali are used, which tends to convert type I cellulose crystals to type II. However, by adjusting the amount of alkali (mercerizing agent) used to control the degree of conversion, the desired crystallinity can be maintained. There is no particular upper limit to the crystallinity of type I cellulose. In practice, it is considered that the upper limit is around 90%. The crystallinity of type I cellulose in CM-modified cellulose and the crystallinity of type I cellulose in CM-modified CNF obtained by defibrating it are usually the same.

[0022] (Phosphate-esterified CNF) One example of anionically modified CNF is phosphate-esterified CNF. Phosphate-esterified CNF can be obtained by introducing phosphate groups derived from phosphate compounds into cellulose by mixing a powder or aqueous solution of a phosphate compound with the cellulose raw material mentioned above, or by adding an aqueous solution of a phosphate compound to a slurry of cellulose raw materials, thereby obtaining phosphate-esterified cellulose, which is then defibrated. Examples of phosphate compounds include phosphoric acid, polyphosphate, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, or esters or salts thereof. Specifically, examples, though not limited to these, include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite, potassium hypophosphite, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, etc. One or more of these can be used in combination to introduce phosphate groups derived from phosphate compounds into cellulose. In this specification, phosphate groups derived from phosphate compounds include phosphate groups, phosphite groups, hypophosphite groups, pyrophosphate groups, metaphosphate groups, polyphosphate groups, phosphonic acid groups, and polyphosphonic acid groups. Phosphate-esterified cellulose and phosphate-esterified CNF include those in which one or more of these phosphate groups are introduced into the molecular chain of cellulose. When reacting a cellulose raw material with a phosphate compound, it is desirable to use the phosphate compound as an aqueous solution in order to ensure uniform reaction and high efficiency in introducing the above groups, and in this case, the pH of the aqueous solution is preferably pH 3 to 7. Nitrogen-containing compounds such as urea may also be added. The amount of compound having a phosphate group added to the cellulose raw material is preferably 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass, and even more preferably 2 to 200 parts by mass in terms of phosphorus element, per 100 parts by mass of solid content of the cellulose raw material. This makes it possible to efficiently obtain a yield commensurate with the amount of compound having a phosphate group used.The reaction temperature is preferably 0 to 95°C, and more preferably 30 to 90°C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, and preferably 30 to 480 minutes. If the esterification reaction conditions are within any of these ranges, it is possible to suppress excessive esterification of cellulose and its increased solubility, thereby improving the yield of phosphate-esterified cellulose. When reacting compounds having a phosphate group, a basic compound (for example, a basic compound having an amino group such as urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, etc.) may be added to the reaction system. The suspension obtained after esterification is preferably dehydrated as needed, and then heat-treated. This suppresses hydrolysis of the cellulose raw material. The heating temperature is preferably 100 to 170°C, and it is more preferable to heat at 130°C or lower (preferably 110°C or lower) while water is present during the heat treatment, and then heat-treat at 100 to 170°C after removing the water. It is preferable to perform a washing treatment, such as washing with cold water after boiling, and / or a neutralization treatment. This allows for efficient defibrillation. Washing can be performed by adding water and then dehydrating (e.g., filtration), and may be repeated two or more times. It is preferable to continue washing until the electrical conductivity of the filtrate decreases. For example, it can be continued until the electrical conductivity is preferably 200 or lower, more preferably 150 or lower, and even more preferably 120 or lower. After washing, a neutralization treatment may be performed as needed. The neutralization treatment can be performed, for example, by adding alkali (e.g., sodium hydroxide). Washing may be performed again after neutralization.

[0023] The degree of phosphate group substitution per glucose unit in phosphate-esterified CNF (hereinafter simply referred to as "degree of phosphate group substitution") is preferably 0.001 or higher at the lower limit, preferably 3.0 or lower at the upper limit, and more preferably less than 0.40. The degree of phosphate group substitution per glucose unit can be measured by the following method: A slurry of phosphate-esterified CNF with a solid content of 0.2% by mass is prepared. A volume of 1 / 10 of a strongly acidic ion exchange resin (Amberjet 1024; Organo, conditioned) is added to the slurry, and after shaking for 1 hour, the slurry is poured onto a 90 μm mesh to separate the resin from the slurry, thereby obtaining hydrogen-type phosphate-esterified CNF. Next, 50 μL of 0.1 N sodium hydroxide aqueous solution is added to the slurry after treatment with the ion exchange resin, at intervals of 30 seconds, while measuring the change in the electrical conductivity of the slurry. The amount of alkali (mmol) required in the region where the electrical conductivity rapidly decreases is divided by the solid content (g) in the slurry being titrated to calculate the amount of phosphate groups per gram of hydrogen-type phosphate-esterified CNF (mmol / g). Furthermore, the degree of phosphate group substitution (DS) per glucose unit of phosphate-esterified CNF is calculated using the following formula: DS = 0.162 × A / (1 - 0.079 × A) A: Amount of phosphate groups per gram of hydrogen-type phosphate-esterified CNF (mmol / g).

[0024] - Phosphite-esterified CNF- A second example of a method for producing esterified cellulose fibers is phosphorylated cellulose fibers. Phosphorylated cellulose fibers typically have a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, a carbon atom with a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated.

[0025] The degree of phosphite group substitution per glucose unit in phosphite-esterified cellulose fibers (hereinafter simply referred to as "phosphite group substitution degree") is preferably 0.001 to 0.60. This facilitates electrical repulsion between cellulose cells, making nanofibrillation easier. The degree of phosphite group substitution can be measured using the same method as for measuring phosphate group substitution. The degree of phosphite group substitution can be adjusted by controlling reaction conditions such as the amount of phosphite or its salt added, and, if necessary, the amount of alkali metal ion-containing substances, urea or its derivatives added.

[0026] One method for esterifying phosphorous acid is to react unmodified cellulose fibers with phosphorous acid or its metal salt (preferably sodium hydrogen phosphite) to introduce an ester group of phosphorous acid.

[0027] Examples of phosphorous acid and its metal salts include phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid, and combinations of two or more selected from these, with sodium hydrogen phosphite being preferred. This also allows alkali metal ions to be introduced into the cellulose fibers. The amount of phosphorous acid or its metal salt added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and even more preferably 300 to 1,500 g per 1 kg of unmodified cellulose fiber. In addition to phosphorous acid and its metal salt, alkali metal ion-containing substances (e.g., hydroxides, metal sulfates, metal nitrates, metal chlorides, metal phosphates, metal carbonates) may be further added to the reaction system.

[0028] Furthermore, urea or its derivatives may be added to the reaction system. This allows carbamate groups to be introduced into the cellulose fibers. Examples of urea and urea derivatives include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and two or more combinations selected from these, with urea being preferred. The amount of urea and urea derivatives added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and even more preferably 0.5 to 10 mol per 1 mol of phosphorous acid or its metal salt.

[0029] The reaction temperature is preferably 100-200°C, more preferably 100-180°C, and even more preferably 100-170°C. During the heat treatment, it is preferable to heat at 130°C or below (preferably 110°C or below) while water is present, and then, after removing the water, to heat-treat at 100-170°C. The reaction time is usually about 10-180 minutes, more preferably 30-120 minutes. It is preferable to wash the phosphite-esterified cellulose fibers before defibration. The degree of substitution of phosphite groups per glucose unit is preferably 0.01 or more and less than 0.23.

[0030] (Sulfated CNF) One example of anionically modified CNF is sulfated CNF. Sulfated CNF can be obtained by reacting the aforementioned cellulose raw material with a sulfate-based compound to introduce sulfate-based groups derived from the sulfate-based compound into the cellulose, thereby producing sulfated cellulose, which is then defibrated. Examples of sulfate-based compounds include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, or esters or salts thereof. Among these, sulfamic acid is preferred because it has low cellulose solubility and low acidity.

[0031] For example, when sulfamic acid is used as the sulfate compound, the amount of sulfamic acid used can be appropriately adjusted considering the amount of anionic group introduced into the cellulose chain. For example, it can be used in an amount of preferably 0.01 to 50 moles per mole of glucose units in the cellulose molecule, and more preferably in an amount of 0.1 to 3.0 moles.

[0032] The amount of sulfate groups per glucose unit in sulfated CNF (hereinafter simply referred to as "amount of sulfate groups") is preferably 0.1 to 3.0 mmol / g. The amount of sulfate groups per glucose unit can be measured by the following method: An aqueous dispersion of sulfated CNF is subjected to solvent substitution with ethanol and then t-butanol, followed by lyophilization. 200 mg of the resulting sample is mixed with 15 ml of ethanol and 5 ml of water, and stirred for 30 minutes. Then, 10 ml of 0.5 N aqueous sodium hydroxide solution is added, and the mixture is stirred at 70°C for 30 minutes, followed by stirring at 30°C for 24 hours. Next, phenolphthalein is added as an indicator, and the mixture is titrated with hydrochloric acid. The result is calculated using the following formula: Sulfate group amount [mmol / g sample] = (5 - (0.1 × hydrochloric acid titration volume [ml] × 2)) / 0.2.

[0033] <Functional Layer> The functional layer is a layer containing anion-modified CNF. Preferably, the functional layer contains anion-modified CNF as its main component, with the anion-modified CNF content typically exceeding 50%, being 60% or more, 70% or more, 80% or more, or 90% or more. It may also consist solely of anion-modified CNF (100% content). By containing anion-modified CNF, the functional layer can exhibit functions such as dielectric and insulating properties.

[0034] The film thickness of the functional layer (after drying) is usually 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less, and particularly preferably 10 μm or less. There is no particular lower limit, but in order to allow the functional layer to exert appropriate effects in various applications, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and particularly preferably 1.3 μm or more, 1.5 μm or more, or 2 μm or more. The film thickness is preferably substantially uniform. This allows for a homogeneous functional layer with no bias in the distribution of anionic CNF.

[0035] The surface of the functional layer preferably has uniform smoothness. This suppresses the localization of the effect of the functional layer. In this invention, uniform smoothness means that there are no irregularities on the functional layer at a visual level.

[0036] The functional layer may contain anionic modified cellulose nanofibers, but may also contain other optional components. Examples of optional components include optional components of the subsequent coating solution.

[0037] <Supporting base material> The support substrate can be any substrate made of a material that can form a functional layer substantially uniformly on its surface, without any particular limitations. Examples of support substrates include resin substrates, paper substrates, and metal substrates, and among these, metal substrates are preferred because a metal species with desired properties can be selected according to various applications. Examples of metals that make up the metal substrate include aluminum, copper, iron, zinc, titanium, nickel, lead, silver, platinum, tungsten, bismuth, stainless steel, brass, chromium, and other metals or alloys thereof, and aluminum or copper are preferred due to their versatility. The shape and size of the support substrate are not particularly limited. Examples include sheet-shaped and film-shaped substrates.

[0038] <Other layers> The laminate may have other layers. Examples of other layers include a primer layer. By providing a primer layer, the applicability of the functional layer (coating liquid) can be improved. Examples of primers that make up the primer layer include polyaniline.

[0039] <2. Method for manufacturing laminates> The above-described laminate can be manufactured by forming a functional layer on a support substrate through a coating process in which a coating solution containing anionically modified cellulose nanofibers is applied.

[0040] <Coating Process> -Pre-measurement coating method- Coating in the coating process can be carried out using a pre-metering coating method. A pre-metering coating method refers to a coating method in wet coating technology that performs continuous wet coating, in which the wet film thickness is determined by specifying the flow rate per unit coating width and the substrate speed. Examples of pre-metering coating methods include die coating, curtain coating, gravure coating, forward rotation roll coating, reverse coating, doctor coating, kiss coating, dip coating, and tension web coating, which adjusts the coating amount on the die by applying tension to the substrate. Among these, die coating and curtain coating are preferred because they allow for stable control of the flow rate during continuous coating.

[0041] (Die coating method) Die coating can be performed by slot die coating. Slot die coating is a method of coating a substrate by pushing the coating liquid out from the die head. An example of a coating method using slot die coating is as follows: The coating liquid is supplied to the die cavity that constitutes the slot die coater. The liquid (coating liquid) is pushed out from the die tip (discharge hole) via the slit channel using a pump, pressurizer, etc., while adjusting the coating speed to ensure a stable and uniform flow rate in the width direction (for example, coating speed: 0.1~1.0 m / min, coating width: 0.1~1.0 m). The size of the die coater (slit width) and its position relative to the substrate (clearance) can be adjusted as appropriate (for example, slit width 50~500 μm, clearance 100~1000 μm). When the slot die is fixed, the substrate is run on a backup roll and continuously supplied to the vicinity of the die tip. The coating liquid extruded from the discharge hole is supplied to the substrate, forming liquid reservoirs called beads between the substrate and the coating, and allowing for coating to achieve a predetermined wet film thickness. On the other hand, when the slot die is movable, the slot die moves along the surface of the substrate (fixed) while discharging the coating agent, forming a uniform coating film on the surface of the substrate.

[0042] When employing a die coating method, the upstream side of the die tip may be depressurized. This allows for adjustment of the pressure in the coating gap between the substrate and the die tip, thereby stabilizing the bead on the substrate. The degree of depressurization is preferably in the range of 0.05 kPa to 1.00 kPa below atmospheric pressure, but this can be adjusted as appropriate depending on the substrate speed and the properties of the coating solution. Pressure adjustment can be performed by installing a vacuum chamber.

[0043] (Curtain coating method) Curtain coating is a method of coating a substrate by dropping the coating liquid in a curtain-like pattern and allowing the substrate to pass through the curtain. Curtain coating methods are classified according to how the curtain is formed, and examples include overflow type, orifice type, die-feed type, and slide-hopper type. The overflow type is a method in which the coating liquid overflows from the edge of the container that holds the coating liquid. The overflow type is a method in which the coating liquid flows out from an orifice at the bottom of the coating liquid reservoir. The large-feed type is a method in which the coating liquid is pushed out from the bottom of the die to form a curtain, and the slide-hopper type is a method in which the coating liquid flows down from a sliding surface to form a curtain. The orifice type, die-feed type, and slide-hopper type are preferred as curtain coating methods. With these methods, a constant flow pressure can be continuously applied, and changes in the liquid properties due to thixotropy caused by the action of anion-modified CNF in the coating liquid containing anion-modified CNF can be suppressed.

[0044] <Supply volume of coating solution> In the pre-metering coating method, the amount of coating liquid supplied onto the substrate (in the case of die coating, the amount of coating liquid discharged from the die coater) is usually 400 mL / min or less, preferably 300 mL / min or less, more preferably 250 mL / min or less, and even more preferably 200 mL / min or less. The lower limit is not particularly limited, but is usually 1 mL / min or more, preferably 50 mL / min or more, and more preferably 80 mL / min or more. In the case of die coating, the above speed can be adjusted by the movement speed of the die or the movement speed of the substrate (the movement speed of the belt that moves the substrate).

[0045] <Coating liquid> The coating solution contains anionically modified CNF and is usually a liquid.

[0046] The coating liquid preferably has a moderate viscosity. This results in good coating properties. The 60 rpm viscosity of the coating liquid is usually 30 mPa·s or more, or 50 mPa·s or more, preferably 52 mPa·s or more, more preferably 54 mPa·s or more, and even more preferably 55 mPa·s or more. The upper limit is usually 1000 mPa·s or less, 900 mPa·s or less, 800 mPa·s or less, preferably 700 mPa·s or less, 600 mPa·s or less, or 500 mPa·s or less, more preferably 450 mPa·s or less, or 400 mPa·s or less. The 6 rpm viscosity is usually 60 mPa·s or more, or 65 mPa·s or more, preferably 70 mPa·s or more, and more preferably 75 mPa·s or more. The upper limit is usually 6000 mPa·s or less, or 5000 mPa·s or less, preferably 4000 mPa·s or less, more preferably 3000 mPa·s or less, or 2500 mPa·s or less. The 6 rpm viscosity and 60 rpm viscosity vary depending on conditions such as the type of anionic group, the average fiber diameter of the CNF, the average fiber length, the aspect ratio, and the concentration of anion-modified CNF in the coating solution. The 6 rpm viscosity and 60 rpm viscosity can be measured using a B-type viscometer at 25°C under conditions of 6 rpm and 60 rpm rotation speeds, respectively.

[0047] The solid content of anion-modified CNF contained in the coating solution is preferably less than 5%, more preferably 4% or less, even more preferably 3% or less, and particularly preferably 2% or less. This suppresses an increase in the viscosity of the coating solution and excessive thixotropy. The lower limit is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more. When employing the die coating method, the uniformity of the flow rate of the coating solution in the slit channel is generally linked to the uniformity of the wet film thickness on the supporting substrate. By adjusting the solid content of the coating solution to the above range, the uniformity of the flow rate of the coating solution and the uniformity of the wet film thickness can be improved.

[0048] Examples of dispersion media for the coating solution include water and solvents (e.g., hydrophilic solvents such as alcohol), which can be selected as appropriate. The aqueous dispersion produced during the manufacturing of anionically modified CNF (e.g., after defibration) can be used directly as the coating solution. On the other hand, by using a solvent as the dispersion medium, or by mixing a solvent with water, the viscosity and volatility of the coating solution can be adjusted according to the coating conditions.

[0049] In addition to anionically modified CNF and a dispersion medium, the coating solution may contain other additives as long as they do not hinder the effects of the present invention. Examples of such additives include leveling agents, defoaming agents, dispersion stabilizers such as water-soluble polymers, preservatives, binders, and rheology control agents.

[0050] Examples of water-soluble polymers include cellulose derivatives (carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginates, pullulan, starch, potato starch, kudzu starch, modified starch (cationized starch, phosphorylated starch, phosphate cross-linked starch, phosphate monoesterified phosphate cross-linked starch, hydroxypropyl starch, hydroxypropylated phosphate cross-linked starch, acetylated adipate cross-linked starch, acetylated phosphate cross-linked starch, acetylated oxidized starch, sodium octenyl succinate starch, acetate starch, oxidized starch), corn starch, gum arabic, gellan gum, Examples include polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acids, polylactic acid, polymalic acid, polyglycerin, latex, rosin-based sizing agents, petroleum resin-based sizing agents, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethyleneimine, polyamine, plant gum, polyethylene oxide, hydrophilic crosslinked polymer, polyacrylate salt, starch-polyacrylic acid copolymer, tamarind gum, guar gum, and colloidal silica, as well as mixtures of one or more of these. Among these, cellulose derivatives are preferred because they have good affinity with CM-modified CNF.

[0051] The coating liquid may be applied directly to the surface of the support substrate, but if an optional primer layer is provided between the support substrate and the functional layer, the coating liquid for the primer layer can be applied and dried before the functional layer is applied.

[0052] <Drying process> After the coating process, a drying process is usually performed. The drying process is a process of drying the coating film formed in the coating process. Drying can be done using known drying methods such as air drying, reduced pressure, or infrared, and a dryer such as an explosion-proof dryer can be used. Drying is preferably performed under heated conditions. The drying temperature is preferably 75 to 150°C, more preferably 75 to 130°C, and even more preferably 80 to 120°C. The drying time is preferably 10 seconds or more, more preferably 30 seconds or more, and even more preferably 45 seconds or more. The upper limit is preferably 10 minutes or less, more preferably 9 minutes or less, and even more preferably 8 minutes or less. Therefore, it is preferably 10 seconds to 10 minutes, more preferably 10 seconds to 9 minutes, more preferably 10 seconds to 8 minutes, even more preferably 10 to 180 seconds, and even more preferably 30 to 120 seconds.

[0053] In the drying process, the drying rate of the solvent is preferably 0.1% by weight / sec or higher, more preferably 0.2% by weight / sec or higher, and even more preferably 0.22% by weight / sec or higher. The upper limit is preferably 5.0% by weight / sec or lower, more preferably 4.0% by weight / sec or lower or 3.0% by weight / sec or lower, even more preferably 2.0% by weight / sec or lower, 1.5% by weight / sec or lower, or 1.07% by weight / sec or lower. Therefore, 0.1 to 5.0% by weight / sec is preferred, and 0.22 to 1.07% by weight / sec is more preferred. Within the above range, localized drying of the surface is suppressed, and a decrease in the surface quality of the coating film can be suppressed. That is, the formation of a film due to the progression of localized drying can be suppressed, and the occurrence of wrinkles due to stress concentration caused by drying shrinkage can be suppressed. The drying rate of the solvent can be calculated by dividing the ratio (by weight) of the solvent in the entire coated sample by the time (sec) it took for the solvent to evaporate and the coating film to dry. The drying speed can be adjusted by controlling the drying temperature and airflow.

[0054] When drying is performed by air drying, the wind speed during drying is preferably 100 m / min or less, and more preferably 90 m / min or less, 80 m / min or less, 70 m / min or less, 60 m / min or less, 50 m / min or less, 40 m / min or less, or 30 m / min or less. This helps to suppress the impact on the coating surface. The lower limit is preferably 1 m / min or more, and more preferably 5 m / min or more or 10 m / min or more. This helps to prevent insufficient drying.

[0055] <3. Applications of laminates> Applications of the laminate of the present invention include, for example, various display device substrates, electronic device substrates, home appliance components, back protective sheets for solar cell modules, encapsulation of organic EL elements, packaging materials for electronic components, electrodes for batteries and energy storage devices, flexible printed circuit boards and other electronic components; interior components, exterior components, door side panels, hoods, roofs, lithium-ion battery (LIB) spacers, battery cases, LED headlamps and other automotive components; and packaging materials for pharmaceuticals and food products. However, the invention is not limited to these exemplary applications.

[0056] The laminate of the present invention is expected to have self-regenerating properties without causing defects in the functional layer, because even when wetting occurs, the anion-modified CNF in the wetted portion undergoes an electrical adsorption phenomenon through redispersion. Therefore, the laminate is preferably used as an electronic component. [Examples]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0058] (Manufacturing Example 1: Preparation of Oxidized CNF) 500g (absolutely dry) bleached, unbeaten kraft pulp (whiteness 85%) derived from coniferous trees was added to 500ml of an aqueous solution containing 780mg of TEMPO (Sigma Aldrich) and 75.5g of sodium bromide, and the mixture was stirred until the pulp was uniformly dispersed. Sodium hypochlorite aqueous solution was added to the reaction system to a concentration of 6.0 mmol / g to initiate the oxidation reaction. During the reaction, the pH of the system decreased, but 3M sodium hydroxide aqueous solution was added sequentially to adjust the pH to 10. The reaction was terminated when the sodium hypochlorite was consumed and the pH of the system no longer changed. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp. The pulp yield at this time was 90%, and the oxidation reaction took 90 minutes. The oxidized pulp obtained in the above process was adjusted with water to the concentrations shown in Table 1, and subjected to five defibration treatments in an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain dispersions A1 to A3 of oxidized CNF. The amount of carboxyl groups in the obtained oxidized CNF was 1.42 mmol / g, the average fiber diameter was 3.4 nm, and the average fiber length was 528 nm (Table 1).

[0059] (Manufacturing Example 2: Preparation of CM-processed CNF) In a twin-screw kneader adjusted to a rotation speed of 150 rpm, 130 parts water and a mixture of 20 parts sodium hydroxide dissolved in 10 parts water and 90 parts isopropanol (IPA) were added. 100 parts of hardwood pulp (manufactured by Nippon Paper Industries Co., Ltd., LBKP), based on its dry mass after drying at 100°C for 60 minutes, were then loaded. The mixture was stirred and mixed at 35°C for 80 minutes to perform merceleration. Further stirring was performed, along with a mixture of 23 parts water and 207 parts IPA, and 40 parts sodium monochloroacetate. After stirring for 30 minutes, the temperature was raised to 70°C and etherification was performed for 90 minutes.

[0060] After the reaction was complete, the mixture was neutralized with acetic acid until the pH reached 7, washed with aqueous methanol, dehydrated, dried, and pulverized to obtain the sodium salt of the CM-modified pulp. The degree of CM substitution in the obtained CM-modified pulp was 0.17. The CM-modified pulp obtained in the above steps was adjusted with water to the concentrations shown in Table 1, and subjected to three defibration treatments in an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain dispersions B1 and B2 of CM-modified CNF. The average fiber diameter of the CM-modified CNF was 3.7 nm, and the average fiber length was 425 nm (Table 1).

[0061] (Production Example 3: Preparation of Phosphate-Esterified CNF) 100 g of hardwood pulp (manufactured by Nippon Paper Industries Co., Ltd., LBKP) was immersed in 400 g of an aqueous solution containing 120 g of urea and 45 g of ammonium dihydrogen phosphate. The pulp was then dried in a 70°C oven for 24 hours and subsequently heated at 150°C for 10 minutes. Afterward, it was washed five times with deionized water to obtain phosphated pulp. The amount of phosphate groups in the phosphated pulp was measured using the method described above and found to be 0.87 mmol / g. The phosphated pulp obtained in the above process was adjusted to 0.4% (w / v) with water and subjected to three defibration treatments in an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain dispersion C of phosphated CNF. The degree of phosphate group substitution of the phosphated CNF was 0.89 mmol / g, the average fiber diameter was 3.4 nm, and the average fiber length was 625 nm (Table 1).

[0062] (Production Example 4: Preparation of Sulfate Esterified CNF) 100 g of hardwood pulp (manufactured by Nippon Paper Industries Co., Ltd., LBKP) was dried in an oven at 105°C for 24 hours, then 2000 g of 60% sulfuric acid aqueous solution was added and stirred at 50°C for 1 hour. After that, it was washed five times with deionized water to obtain sulfated esterified pulp. The amount of sulfate groups in the sulfated esterified pulp was measured by the method described above and was found to be 0.79 mmol / g. The sulfated esterified pulp obtained in the above process was adjusted to 0.4% (w / v) with water and subjected to defibration treatment three times in an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain dispersion D of sulfated esterified CNF. The amount of sulfate groups in the sulfated esterified CNF was 0.92 mmol / g, the average fiber diameter was 4.2, and the average fiber length was 354 (Table 1).

[0063] (Production Example 5: Preparation of Phosphite-Esterified CNF) Reagent A was prepared by mixing 130 g of sodium hydrogen phosphite pentahydrate, 108 g of urea, and 762 g of water. 1000 g of the prepared reagent A was mixed with 100 g of coniferous pulp (manufactured by Nippon Paper Industries Co., Ltd., NBKP) and dried at 105°C. The dried pulp was reacted at 130°C for 2 hours, and washed with water and filtered twice to obtain phosphorous esterified pulp. The phosphorous esterified pulp obtained in the above process was adjusted to 0.4% (w / v) with water and subjected to defibration treatment three times in an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain dispersion F of phosphorous esterified CNF. The degree of phosphorous group substitution of the phosphorous esterified CNF was 2.11 mmol / g, the average fiber diameter was 3.9 nm, and the average fiber length was 471 nm (Table 1).

[0064] (Manufacturing Example 6: Preparation of Oxidized CNF) 5 g (dry) of bleached coniferous wood-derived kraft pulp (DKP, manufactured by Buckeye) was added to 500 ml of an aqueous solution containing 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 755 mg (7.4 mmol) of sodium bromide, and the mixture was stirred until the pulp was uniformly dispersed. 16 ml of 2 M sodium hypochlorite aqueous solution was added to the reaction system, and the pH was adjusted to 10.3 with 0.5 N hydrochloric acid aqueous solution to initiate the oxidation reaction (oxidation treatment). During the reaction, the pH in the system decreased, but 0.5 N sodium hydroxide aqueous solution was added sequentially to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and thoroughly washed with water to obtain carboxylated cellulose. Carboxylated cellulose slurries G1 and G2 were prepared by diluting this with water to the concentrations shown in Table 1. Hydrogen peroxide was added to these slurries at 2% (w / w) relative to the carboxylated cellulose, and the pH was adjusted to 11.3 with 3 M sodium hydroxide. This slurry was left at 80°C for 2 hours to undergo hydrolysis. This was then adjusted with water to concentrations of 1.0(w / v)%, 2.0(w / v)%, 3.0(w / v)%, 4.0(w / v)%, or 5.0(w / v)%, and treated three times in an ultra-high pressure homogenizer (20°C, 140 MPa) to obtain dispersions G3, G1, G2, G4, and G5 of TEMPO-oxidized CNF. The obtained TEMPO-oxidized CNF had a carboxyl group content of 1.7 mmol / g, an average fiber diameter of 5.7 nm, and an average fiber length of 230 nm (Table 1).

[0065] (slip angle) A droplet of liquid was dropped onto a plate, and the angle at which the liquid dripped when the plate was lifted was measured. Specifically, 0.2g of CNF slurry was dropped onto an aluminum plate at a temperature of 25°C, left to stand for 1 minute, and then one side of the aluminum plate was lifted. The minimum angle at which the distance the droplet traveled after 1 minute was 1cm or more was measured. A sliding angle of 70° or less, and more preferably 60° or less, indicates good uniformity during coating. The lower limit is usually 5° or more, preferably 10° or more.

[0066] (B type viscosity) The B-type viscosity of each dispersion was measured using a TV-10 viscometer (Toki Sangyo Co., Ltd.) under conditions of 25°C and 6 rpm or 60 rpm.

[0067] (contact angle) The contact angle between the CNF slurry and the aluminum foil was measured under the following conditions. • Conditions for measuring contact angle Equipment: Dynamic contact angle tester 1100DAT, manufactured by Fibro Systems AB. Discharge volume: 5μl Time from dispensing until the droplet falls: 40 seconds Base material: Aluminum foil A contact angle of 70° or less, and especially 65° or less, indicates good wettability. The lower limit is usually 50° or more.

[0068] (Sensory evaluation of fluidity and sauce-like properties) The fluidity and sagging properties of the coating liquid when it was poured from the die described below were visually evaluated and assessed according to the following criteria. A good balance between fluidity and sagging properties makes coating from the die easier, minimizes liquid movement after coating, and allows for the maintenance of a uniform film thickness. <Evaluation Criteria> ◎: The slurry is fluid and does not drip easily. ○: The slurry is fluid and slightly prone to dripping. ×: The slurry is fluid but drips. Or, the slurry is not fluid and does not drip.

[0069] (Ti value) The Ti value is the ratio of the viscosity at 6 rpm to the viscosity at 60 rpm and is proportional to the thixotropy. Generally, if the thixotropy is too high, the coating liquid will gel, making it difficult to pump, and if the thixotropy is too low, the coating liquid will flow and drip easily. The Ti value is preferably 7.0 or less, and more preferably 6.8 or less. The lower limit is preferably 1.0 or more, and more preferably 1.2 or more.

[0070] [Table 1]

[0071] [Footnote to Table 1] Contact angle "unmeasurable": The liquid coming out of the discharge nozzle was in the form of a long, thin string and could not form droplets. "No drop" in the angle of descent: Even when exceeding 90°, the movement was limited to less than 1 cm.

[0072] Compared to dispersions A3, B2, and G3-G5, dispersions A1, A2, B1, C, D, F, G1, and G2 exhibited appropriate sliding angles and contact angles, and were evaluated as having good uniformity and wettability during coating. They also received good evaluations for fluidity and sagging properties.

[0073] (Examples 1-5) The coating process was performed using a lab coater equipped with a die coater and a belt for transferring the substrate to the die coater, under the following conditions: The die coater's slit width was set to 130 μm and the clearance to 500 μm. A vacuum pressure of 0.6 kPa was applied to the upstream side of the die lip, and the coating speed was set to 0.2 m / min and the coating width to 0.4 m. The aqueous dispersions of each anion-modified CNF listed in Table 2 were used as the coating solution and were uniformly spread on one side of an aluminum substrate (roll-shaped, 1 m wide x 18 μm thick) while adjusting the discharge rate to 80-120 mL / min to ensure stable coating.

[0074] Subsequently, the coated samples were removed from the lab coater, dried in an explosion-proof dryer at 100°C for 10 minutes, and then cooled at room temperature to obtain laminates fabricated by the die coating method (Table 2).

[0075] (Comparative Example 1) A laminate was obtained in the same manner as in Example 1, except that instead of using a die, the material was spray-coated onto an aluminum substrate to achieve a film thickness of approximately 6 μm after drying (Table 2).

[0076] <Evaluation Method> (Film thickness after drying) The thickness of the functional layer after drying was observed in cross-section using a scanning electron microscope manufactured by Keyence Corporation. I took the measurement.

[0077] (exterior) The appearance of the laminate was visually inspected after drying and evaluated according to the following criteria. ○: A smooth functional layer is formed, resulting in a well-structured laminate. ×: The unevenness of the functional layer is noticeable, making it unsuitable as a laminate.

[0078] [Table 2]

[0079] Compared to Comparative Example 1, which was applied by spray coating, the appearance of the coating film in Examples 1-5, which were applied by die coating, was better (Table 1).

[0080] (Examples 6-17 and Comparative Examples 2-6) Laminates were obtained by the die coating method in the same manner as in Example 1, except that a lab coater equipped with a slot die for applying the coating solution to the substrate, a dryer for drying the coating film after coating, and a belt and rolls for supplying the substrate in the order of slot die and dryer were used, coating and drying were performed continuously under the conditions shown in Table 3, each of the dispersions shown in Table 3 was used as the coating solution for the aqueous dispersion of anion-modified CNF, and the discharge rate was adjusted to 130-200 mL / min and the clearance to 100-500 μm to ensure stable coating (Table 3).

[0081] (exterior) The appearance of the laminate was visually inspected after drying and evaluated according to the following criteria. ○: A smooth functional layer is formed, resulting in a well-structured laminate. ×: The unevenness of the functional layer is noticeable, making it unsuitable as a laminate.

[0082] [Table 3]

[0083] [Footnote to Table 3] *The drying temperature indicated is the temperature of each sample. The drying temperature setting in the drying apparatus was 100°C.

[0084] In Comparative Examples 2-5, which used dispersions G3-G5, A3, and B2, film formation was either not possible or the surface evaluation of the functional layer was unsatisfactory, whereas in Examples 6-17, which used dispersions G1, G2, A1, A2, B1, C, D, and F, the same evaluation was good (Table 3).

[0085] (Examples 18-23) In Example 6, die coating was performed with a drying apparatus set to a temperature of 100°C and sheet temperatures of 85 / 83 / 84 / 85 / 86 / 81°C. The drying conditions were the same as shown in Table 4, except that the wind speed was 20 m / min. The degree of drying was confirmed (○: sufficiently dried; △: locally insufficiently dried; ×: insufficiently dried) (Table 4).

[0086] [Table 4]

[0087] Although the laminate could be dried regardless of the drying conditions, as is clear from the results of Examples 18-22, sufficient drying could be achieved with a drying time of 1 minute 30 seconds to 7 minutes 30 seconds and a coater speed of 1 to 5 m / min (Table 4).

[0088] These results demonstrate that, according to the present invention, a laminate can be efficiently obtained that includes a functional layer containing anion-modified CNF on a support substrate and can be used for various industrial applications.

Claims

1. The process includes a step of forming a functional layer by applying a coating liquid containing anion-modified cellulose nanofibers onto a support substrate using a pre-metering coating method at a coating speed of 5 m / min or less. The viscosity of the coating solution at 60 rpm is 50 to 1000 mPa·s. The ratio (Ti) of the viscosity of the coating liquid at 6 rpm to its viscosity at 60 rpm is between 1.0 and 7.

0. The thickness of the functional layer is 30 μm or less. A method for manufacturing laminates.

2. The manufacturing method according to claim 1, wherein the anionic modified cellulose nanofiber is an oxidized cellulose nanofiber having a carboxyl group and / or a carboxylate group.

3. The manufacturing method according to claim 1, wherein the anion-modified cellulose nanofiber is a carboxyalkylated cellulose nanofiber.

4. The manufacturing method according to claim 1, wherein the anionic modified cellulose nanofiber is a phosphate-esterified cellulose nanofiber.

5. The manufacturing method according to claim 1, wherein the anionic modified cellulose nanofiber is a sulfated cellulose nanofiber.

6. The manufacturing method according to any one of claims 1 to 5, wherein the pre-measurement coating method is a die coating method.

7. The manufacturing method according to any one of claims 1 to 5, wherein the aforementioned pre-measurement coating method is a curtain coating method.

Images