Laminated sheets, laminates, heat-worked articles, transparent components, and methods for manufacturing laminates and heat-worked articles.

Abstract

This invention provides laminates that are rigid and do not easily generate bubbles even when heat-processed, laminates having laminates, heat-processed articles formed by heat-processing the laminates, transparent components including the heat-processed articles, and methods for manufacturing the laminates and the heat-processed articles. The laminates of this invention are: (i) having an adhesive layer (1a) on one side of a layer containing microfibrillated cellulose with a fiber width of 1000 nm or less, and the content of an organic solvent meeting specific conditions; or (ii) having an adhesive layer (1a) on one side and an adhesive layer (1b) on the other side of a layer containing microfibrillated cellulose with a fiber width of 1000 nm or less, and the content of an organic solvent meeting specific conditions.

Description

Technical Field

[0001] This invention relates to laminated sheets, laminated bodies, heat-worked articles, transparent components, and methods for manufacturing laminated sheets and heat-worked articles. Background Technology

[0002] In recent years, materials utilizing renewable natural fibers have gained attention due to the substitution of petroleum resources and increased environmental awareness. Among natural fibers, fibrous cellulose with a fiber width of 10μm or more but less than 50μm, especially fibrous cellulose derived from wood (pulp), has been widely used primarily for paper products to date.

[0003] As fibrous cellulose, microfibrillated cellulose with a fiber width of less than 1,000 nm is also known. Furthermore, sheets composed of such microfibrillated cellulose, composite sheets containing microfibrillated cellulose and resin, and molded articles have been developed. It is known that in sheets and molded articles containing microfibrillated cellulose, the contact points between fibers are significantly increased, thus greatly improving tensile strength and other properties.

[0004] Patent document 1 discloses a polycarbonate resin / cellulose fiber laminate, which provides a composite material with a good balance of properties such as high transparency, high elasticity, low coefficient of linear expansion, and impact resistance, and also has good productivity by forming a laminate of polycarbonate resin layer and cellulose fiber layer. For this purpose, in the laminate having polycarbonate resin layer and cellulose fiber layer, the thickness of polycarbonate resin layer is more than 1.4 times that of cellulose fiber layer.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 4985573 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Cellulose sheets containing microfibrillated cellulose exhibit excellent mechanical strength, such as tensile strength, and also excellent transparency. Therefore, laminates formed by combining them with adhesive layers, resin films, etc., are expected to be used as optical components in various display devices, various solar cells, etc., as well as window materials for various vehicles and buildings. However, according to the research of the inventors, when a laminate obtained by forming an adhesive layer on microfibrillated cellulose sheets is combined with a resin film, etc., and then heated and processed into a desired shape, problems arise where air bubbles are generated in the resulting processed product, reducing the appearance and transparency of the heat-processed product. Furthermore, in the case of the above-mentioned applications, it is desirable to improve the rigidity of the laminate to further improve the quality of the product.

[0010] Therefore, the object of the present invention is to provide a laminated body composed of a resin film or the like, which has excellent rigidity and is not prone to bubble formation even when heat-processed, a laminated body having a laminated body, a heat-processed article formed by heat-processing the laminated body, a transparent component including the heat-processed article, and a method for manufacturing the laminated body and the heat-processed article.

[0011] Solution for solving the problem

[0012] That is, the present invention relates to the following <1> ~ <21> .

[0013] <1> A type of laminated sheet, wherein,

[0014] (i) An adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm, and at least one of conditions A and B is satisfied; or,

[0015] (ii) The layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm has an adhesive layer 1a on one side and an adhesive layer 1b on the other side, and satisfies at least one of the following conditions C and D.

[0016] Condition A: The total organic solvent content in the microfibrillated cellulose layer and adhesive layer 1a is 0.1 ppm or more and 40 ppm or less by mass.

[0017] Condition B: The content of organic solvents in adhesive layer 1a is 0.5 ppm or more and 200 ppm or less by mass.

[0018] Condition C: The total content of organic solvents in the microfibrillated cellulose layer, adhesive layer 1a, and adhesive layer 1b is 0.1 ppm or more and 60 ppm or less by mass.

[0019] Condition D: The total content of organic solvents in adhesive layers 1a and 1b is between 0.5 ppm and 300 ppm by mass.

[0020] <2> according to <1> In the aforementioned laminated sheet, the thicknesses of adhesive layer 1a and adhesive layer 1b are both greater than 1 μm and less than 50 μm.

[0021] <3> according to <1> or <2> The laminated sheet, wherein (i) has an adhesive layer 1a and a resin film or protective film sequentially on one side containing a microfibrillated cellulose layer, and (ii) has an adhesive layer 1a and a resin film or protective film sequentially on one side containing a microfibrillated cellulose layer.

[0022] <4> according to <1> ~ <3> The laminated sheet according to any one of the following methods, wherein the microfibrillated cellulose layer contains a hydrophilic polymer.

[0023] <5> according to <4> The laminated sheet wherein the hydrophilic polymer contains nonionic water-soluble cellulose ether and / or polyvinyl alcohol.

[0024] <6> according to <5> The laminated sheet, wherein the microfibrillated cellulose layer is a single layer, and the hydrophilic polymer contains nonionic water-soluble cellulose ether, wherein the content of nonionic water-soluble cellulose ether in the hydrophilic polymer is more than 80% by mass.

[0025] <7> according to <6> The laminated sheet, wherein in the microfibrillated cellulose layer, the mass ratio of nonionic water-soluble cellulose ether to microfibrillated cellulose (nonionic water-soluble cellulose ether / microfibrillated cellulose) is 10 / 90 or more and 90 / 10 or less.

[0026] <8> according to <5> The laminated sheet, wherein the microfibrillated cellulose layer is multilayered, and includes a microfibrillated cellulose layer 1a containing polyvinyl alcohol and a microfibrillated cellulose layer 1b containing nonionic water-soluble cellulose ether.

[0027] <9> according to <8> The laminated sheet, wherein in the microfibrillated cellulose layer 1a, the mass ratio of polyvinyl alcohol to microfibrillated cellulose (polyvinyl alcohol / microfibrillated cellulose) is 25 / 75 or more and 90 / 10 or less.

[0028] <10> according to <1> ~ <9> The laminated sheet according to any one of the following methods, wherein the microfibrillated cellulose has anionic groups.

[0029] <11> according to <10> The laminated sheet wherein the anionic group comprises a phosphorus oxyacid group or a group derived from a phosphorus oxyacid group.

[0030] <12> A laminate having at least one side of a core resin board <3> The laminate of (ii) has a resin film, the core resin board contains a polycarbonate resin, and the adhesive layer 1b of the laminate is in contact with the core resin board.

[0031] <13> according to <12> The aforementioned laminate has a haze of less than 5.0%.

[0032] <14> according to <12> or <13> The haze difference of the laminate before and after heating at 170°C for 10 minutes is less than 2.0%.

[0033] <15> A method for manufacturing heat-worked products, which has the function of... <12> ~ <14> The process of heat-processing the laminate as described in any one of the above.

[0034] <16> A heat-processed product, which is for <12> ~ <14> The laminate as described in any one of the above is produced by heat processing.

[0035] <17> A transparent component comprising <16> The aforementioned heat-processed products.

[0036] <18> A sort of <1> ~ <11> The method for manufacturing the laminated sheet according to any one of the following steps 1 and 2.

[0037] Step 1: A process of coating a layer containing microfibrillated cellulose fibers with a width of less than 1,000 nm with a coating solution and then drying it to obtain a layer containing microfibrillated cellulose fibers.

[0038] Step 2: A step in which an adhesive layer 1a or adhesive layer 1b is formed by coating one side of the microfibrillated cellulose layer obtained in Step 1 with an adhesive solution and drying.

[0039] <19> according to <18> The method for manufacturing the laminated sheet, wherein step 2 is as follows: after coating one side of the microfibrillated cellulose layer obtained in step 1 with an adhesive coating liquid, it is dried at 80°C or above for more than 5 minutes to form adhesive layer 1a or adhesive layer 1b.

[0040] <20> according to <18> or <19> The method for manufacturing the laminated sheet further includes step 3 after step 2.

[0041] Step 3: Applying an adhesive coating liquid to the side opposite to the side containing the microfibrillated cellulose layer and the side where adhesive layer 1a or adhesive layer 1b is formed, and then drying it to form adhesive layer 1b or adhesive layer 1a.

[0042] <21> according to <18> ~ <20> The method for manufacturing a laminate according to any one of the following methods further includes step 4 after step 2.

[0043] Step 4: Applying a resin film or protective film to adhesive layer 1a or adhesive layer 1b.

[0044] The effects of the invention

[0045] According to the present invention, a laminate composed of a resin film or the like is made, thereby providing a laminate sheet with excellent rigidity that is not prone to bubble formation even when heat-processed, a laminate having the laminate sheet, a heat-processed article formed by heat-processing the laminate, a transparent component including the heat-processed article, and a method for manufacturing the laminate sheet and the heat-processed article. Attached Figure Description

[0046] Figure 1 This is a graph showing the relationship between the amount of NaOH added and pH for a slurry containing fine fibrous cellulose with phosphorus oxyacid groups.

[0047] Figure 2 This is a graph showing the relationship between the amount of NaOH added and pH for a slurry containing microfibrillated cellulose with carboxyl groups. Detailed Implementation

[0048] The embodiments of the present invention will be described below. It should be noted that in this specification, "X~Y" indicating a range means "X or more and Y or less". Furthermore, in this specification, the upper and lower limits of the numerical range can be arbitrarily combined. Additionally, in this specification, the components contained in each layer constituting the laminate or laminate, and the components that may be contained therein, can be a single type or a combination of two or more types.

[0049] [Laminated film]

[0050] The laminated sheet of the present invention is as follows:

[0051] (i) An adhesive layer 1a is provided on one side of a layer (single or multiple layers) containing microfibrillated cellulose with a fiber width of less than 1,000 nm, and at least one of conditions A and B below is satisfied; or,

[0052] (ii) An adhesive layer 1a is provided on one side of a layer (single or multiple layers) containing microfibrillated cellulose with a fiber width of less than 1,000 nm and an adhesive layer 1b is provided on the other side, and at least one of the following conditions C and D is satisfied.

[0053] Condition A: The total content of organic solvents in the microfibrillary cellulose layer (single or multiple layers) and adhesive layer 1a is 0.1 ppm or more and 40 ppm or less by mass.

[0054] Condition B: The content of organic solvents in adhesive layer 1a is 0.5 ppm or more and 200 ppm or less by mass.

[0055] Condition C: The total organic solvent content in the microfibrillary cellulose layer (single or multiple layers), adhesive layer 1a, and adhesive layer 1b is 0.1 ppm or more and 60 ppm or less by mass.

[0056] Condition D: The total content of organic solvents in adhesive layers 1a and 1b is between 0.5 ppm and 300 ppm by mass.

[0057] Even when the laminate of the present invention is heat-processed in the form of having a resin film on the adhesive layer 1a in (i), having a resin film on the adhesive layer 1a in (ii), or a laminate having any of these forms, it is considered that bubbles are not easily generated because the content of organic solvents in the adhesive layers 1a and 1b is controlled within a specific range.

[0058] The laminate having the laminate of this embodiment has the additional effects of being less prone to yellowing, having low haze, high total light transmittance, and excellent rigidity and visibility.

[0059] In condition A, the total content of organic solvents in the microfibrillated cellulose layer and adhesive layer 1a can be more than 1 ppm, more than 3 ppm, more than 5 ppm, or less than 35 ppm, less than 30 ppm, or less than 20 ppm.

[0060] In condition B, the content of organic solvent in adhesive layer 1a can be above 10 ppm, above 30 ppm, or above 50 ppm. Alternatively, it can be below 185 ppm, below 170 ppm, or below 155 ppm.

[0061] In condition C, the total content of organic solvents in the microfibrillated cellulose layer, adhesive layer 1a and adhesive layer 1b can be 1 ppm or more, 3 ppm or more, 5 ppm or more, or less than 50 ppm, less than 40 ppm or less than 30 ppm.

[0062] In condition D, the total content of organic solvents in adhesive layer 1a and adhesive layer 1b can be above 10 ppm, above 30 ppm, above 50 ppm, or below 185 ppm, below 170 ppm, or below 155 ppm.

[0063] [Contains a layer of fine fibrous cellulose]

[0064] The laminated sheet of this embodiment is as follows: (i) an adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm; or, (ii) an adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm and an adhesive layer 1b is provided on the other side.

[0065] The cellulose layer containing fine fibrous cellulose can be a single layer or multiple layers. When the cellulose layer containing fine fibrous cellulose is multiple layers, it is preferably 2 or more layers and 5 or less layers, more preferably 4 or less layers, further preferably 3 or less layers, and even more preferably 2 layers.

[0066] <Fine fibrous cellulose>

[0067] Microfibrillary cellulose is fibrous cellulose with a fiber width of less than 1,000 nm. It should be noted that the fiber width of fibrous cellulose can be measured, for example, by observation using an electron microscope.

[0068] The fiber width of the microfibrillated cellulose is 1,000 nm or less. Preferably, the fiber width of the microfibrillated cellulose is 2 nm or more and 1,000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and even more preferably 2 nm or more and 10 nm or less. By making the fiber width of the microfibrillated cellulose 2 nm or more, its dissolution in water as cellulose molecules can be suppressed, making it easier to exhibit the improved strength and dimensional stability effects brought about by the microfibrillated cellulose.

[0069] The average fiber width of the microfibrillated cellulose is, for example, 1,000 nm or less. Preferably, the average fiber width of the microfibrillated cellulose is 2 nm or more and 1,000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and even more preferably 2 nm or more and 10 nm or less. By making the average fiber width of the microfibrillated cellulose 2 nm or more, its dissolution in water in the form of cellulose molecules can be suppressed, and the improved strength and dimensional stability effects brought about by the microfibrillated cellulose are more easily exhibited. It should be noted that the microfibrillated cellulose is, for example, monofibrous cellulose.

[0070] The number-average fiber width of the fine fibrous cellulose was measured, for example, using an electron microscope as follows. First, an aqueous suspension of fine fibrous cellulose with a concentration of 0.01% by mass or more and 0.1% by mass or less was prepared. This suspension was then cast onto a hydrophilically treated carbon film-coated mesh to create a transmission electron microscope (TEM) specimen. In the case of wide fibers, a scanning electron microscope (SEM) image of the surface cast on the glass could be observed. Next, observation based on the electron microscope image was performed at any magnification of 1,000x, 5,000x, 10,000x, or 50,000x, depending on the width of the fiber being observed. The specimen, observation conditions, and magnification were adjusted in a manner that satisfied the following conditions.

[0071] (1) Draw a straight line X at any point in the observed image, with more than 20 fibers intersecting the straight line X.

[0072] (2) Draw a straight line Y that intersects the line perpendicularly within the same image, with more than 20 fibers intersecting the line Y.

[0073] For the observation images that meet the above conditions, the widths of the fibers intersecting lines X and Y are visually read. This yields at least three sets of observation images showing at least non-overlapping surface portions. Next, for each image, the widths of the fibers intersecting lines X and Y are read. This results in at least 20 × 2 × 3 = 120 fiber widths being read. The average of the read fiber widths is then taken as the number-average fiber width of the fibrous cellulose.

[0074] The fiber length of the microfibrillated cellulose is not particularly limited, but is preferably 0.1 μm or more and 1,000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and even more preferably 0.1 μm or more and 600 μm or less. By setting the fiber length within the above range, the destruction of the crystalline regions of the microfibrillated cellulose can be suppressed. Additionally, the viscosity of the microfibrillated cellulose slurry can be set within an appropriate range. It should be noted that the fiber length of the microfibrillated cellulose can be determined, for example, by image analysis using TEM, SEM, or atomic force microscopy (AFM).

[0075] The fine fibrous cellulose preferably has a type I crystal structure. Here, the type I crystal structure of the fine fibrous cellulose can be identified in the diffraction pattern obtained by using a wide-angle X-ray diffraction photograph of CuKα (λ=1.5418Å) monochromated with graphite. Specifically, it can be identified by the presence of characteristic peaks at two positions: near 2θ=14° and below 17°, and near 2θ=22° and below 23°.

[0076] The proportion of type I crystal structure in the fine fibrous cellulose is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. This allows for the expectation of superior performance in exhibiting a low coefficient of linear thermal expansion. Regarding crystallinity, the X-ray diffraction pattern is measured, and the pattern is determined using conventional methods (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0077] The axial ratio (fiber length / fiber width) of the microfiber cellulose is not particularly limited, but is preferably 20 or more and 10,000 or less, more preferably 50 or more and 1,000 or less. By setting the axial ratio to the lower limit or above, it is easy to form sheets containing microfiber cellulose. By setting the axial ratio to the upper limit or below, for example, when processing the microfiber cellulose into an aqueous dispersion, it is preferable to facilitate operations such as dilution.

[0078] In this embodiment, the fine fibrous cellulose preferably has at least one of ionic and nonionic substituents. From the viewpoint of improving the dispersibility of fibers in the dispersion medium and increasing the defiberization efficiency in the defiberization process, it is more preferable that the fine fibrous cellulose has ionic substituents. As ionic substituents, for example, any one or both of anionic and cationic groups may be included. In addition, as nonionic substituents, for example, alkyl and acyl groups may be included. In this embodiment, it is particularly preferable to have anionic groups as ionic substituents. Furthermore, the ionic substituent is preferably a group introduced into the fine fibrous cellulose via an ester bond or an ether bond, more preferably a group introduced into the fine fibrous cellulose via an ester bond. In this case, the ester bond is preferably formed by the dehydration condensation of the fine fibrous cellulose with the compound that becomes the ionic substituent.

[0079] It should be noted that the fine fibrous cellulose does not need to be treated by introducing ionic substituents.

[0080] Examples of anionic substituents include phosphorus oxyacid groups or substituents derived from phosphorus oxyacid groups (sometimes simply referred to as phosphorus oxyacid groups), carboxyl groups or substituents derived from carboxyl groups (sometimes simply referred to as carboxyl groups), sulfur oxyacid groups or substituents derived from sulfur oxyacid groups (sometimes simply referred to as sulfur oxyacid groups), xanthate groups or substituents derived from xanthate groups (sometimes simply referred to as xanthate groups), phosphonic acid groups or substituents derived from phosphonic acid groups, hypophosphonic acid groups or substituents derived from hypophosphonic acid groups, sulfonic acid groups or substituents derived from sulfonic acid groups, and carboxylalkyl groups. The anionic group is preferably selected from at least one group chosen from the group consisting of phosphorus oxyacid group, substituents derived from phosphorus oxyacid group, carboxyl group, carboxymethyl group, carboxyethyl group, sulfur oxyacid group and substituents derived from sulfur oxyacid group, xanthate group, and substituents derived from sulfonic acid group. More preferably, it is selected from at least one group chosen from the group consisting of phosphorus oxyacid group, substituents derived from phosphorus oxyacid group, carboxyl group, sulfur oxyacid group, substituents derived from sulfur oxyacid group, and xanthate group. Even more preferably, it is selected from at least one group chosen from the group consisting of phosphorus oxyacid group, substituents derived from phosphorus oxyacid group, carboxyl group, sulfur oxyacid group, and substituents derived from sulfur oxyacid group. More preferably, it is a phosphorus oxyacid group. By introducing a phosphorus oxyacid group as an anionic group, for example, even under alkaline or acidic conditions, the dispersibility of fibrous cellulose can be further improved, resulting in a high-strength and highly transparent cellulose layer containing fine fibrous fibers. Examples of cationic substituents include ammonium, phosphonium, and sulfonium groups. Among these, the cationic group is preferably an ammonium group.

[0081] The phosphorus oxyacid group or a substituent derived from the phosphorus oxyacid group is, for example, the substituent shown in formula (1) below. Multiple substituents shown in formula (1) below may be introduced into each microfibrillary cellulose. In this case, the multiple introduced substituents shown in formula (1) below may be the same or different from each other.

[0082]

[0083] In equation (1), a, b, and n are natural numbers, and m is any number (where a = b × m). At least one of the n α and α' (preferably a) is O. - The rest are R or OR. It should be noted that all α and α' can also be O. - The n α values ​​can be all the same, or they can be different from each other. β b+ It is a cation with a valence of 1 or higher, composed of organic or inorganic matter.

[0084] R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a derivative thereof. It should be noted that α in formula (1) can be a group derived from the cellulose molecular chain. Furthermore, in formula (1), n ​​is preferably 1.

[0085] Examples of saturated linear hydrocarbon groups include methyl, ethyl, n-propyl, or n-butyl, without particular limitation. Examples of saturated branched hydrocarbon groups include isopropyl or tert-butyl, without particular limitation. Examples of saturated cyclic hydrocarbon groups include cyclopentyl or cyclohexyl, without particular limitation. Examples of unsaturated linear hydrocarbon groups include vinyl or allyl, without particular limitation. Examples of unsaturated branched hydrocarbon groups include isopropenyl or 3-butenyl, without particular limitation. Examples of unsaturated cyclic hydrocarbon groups include cyclopentenyl, cyclohexenyl, etc., without particular limitation. Examples of aromatic groups include phenyl or naphthyl, without particular limitation.

[0086] In addition, as a derivative group in R, examples of addition or substitution of the main chain or side chain of the above-mentioned hydrocarbon groups include carboxyl groups, carboxylate groups (-COO), etc. -The functional group is in the state of at least one of the functional groups such as hydroxyl and amino, and is not particularly limited. In addition, the number of carbon atoms in the main chain constituting R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms in the main chain constituting R within the above range, the molecular weight of the phosphorus oxyacid group can be set in an appropriate range, and the penetration into the fiber raw material can be made easier, thereby improving the yield of microfibrillary cellulose. It should be noted that when there are multiple Rs in formula (1) or when multiple substituents shown in formula (1) are introduced into microfibrillary cellulose, the multiple Rs may be the same or different from each other.

[0087] β b+ It is a cation with a valence of 1 or higher composed of organic or inorganic substances. Examples of cations with a valence of 1 or higher composed of organic substances include organonium ions. Examples of organonium ions include organoammonium ions and organophosphorus ions. Examples of organoammonium ions include aliphatic ammonium ions and aromatic ammonium ions. Examples of organophosphorus ions include aliphatic phosphorus ions and aromatic phosphorus ions. Examples of cations with a valence of 1 or higher composed of inorganic substances include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, and ammonium ions, without particular limitation. One type or two or more types can be used. It should be noted that multiple β-ions exist in formula (1). b+ In the case of introducing multiple substituents as shown in formula (1) into microfibrillary cellulose, there are multiple β-type substituents. b+ They can be the same or different. As a cation with a valence of 1 or higher composed of organic or inorganic matter, it is preferred to have a β-category. b+ The fiber raw materials do not easily turn yellow when heated, and the sodium or potassium ions are readily available for industrial use, without any particular restrictions.

[0088] More specifically, examples of substituents derived from or derived from phosphorus oxyacid groups include phosphate groups (-PO3H2), salts of phosphate groups, phosphite groups (phosphonite groups (-PO2H2), and salts of phosphite groups). Additionally, phosphorus oxyacid groups or substituents derived from or derived from phosphorus oxyacid groups can also be groups formed by the condensation of phosphate groups (e.g., pyrophosphate groups), groups formed by the condensation of phosphonic acids (e.g., polyphosphonic acid groups), phosphate ester groups (e.g., monomethyl phosphate groups, polyoxyethylene alkyl phosphate groups), alkyl phosphonic acid groups (e.g., methylphosphonic acid groups), etc.

[0089] Furthermore, the sulfur-oxygenated acid group (or a substituent derived from the sulfur-oxygenated acid group) is, for example, the substituent shown in formula (2) below. Various substituents shown in formula (2) below may be introduced into each fine fibrous cellulose. In this case, the multiple introduced substituents shown in formula (2) below may be the same or different from each other.

[0090]

[0091] In equation (2), b and n are natural numbers, p is 0 or 1, and m is any number (where 1 = b × m). It should be noted that when n is 2 or more, multiple ps can be the same number or different numbers. In equation (2), β b+ A cation with a valence of 1 or higher, composed of organic or inorganic matter. Examples of cations with a valence of 1 or higher composed of organic matter include organonium ions. Examples of organonium ions include organoammonium ions and / or organophosphorus ions. Examples of organoammonium ions include aliphatic ammonium ions and aromatic ammonium ions. Examples of organophosphorus ions include aliphatic phosphorus ions and aromatic phosphorus ions. Examples of cations with a valence of 1 or higher composed of inorganic matter include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, and ammonium ions. It should be noted that when multiple substituents shown in formula (2) are introduced into the microfibrillary cellulose, multiple β-type cations exist. b+ They can be the same or different. As a cation with a valence of 1 or higher composed of organic or inorganic matter, it is preferred to have a β-category. b+ The fiber raw materials do not easily turn yellow when heated, and the sodium or potassium ions are readily available for industrial use, without any particular restrictions.

[0092] The amount of ionic substituent introduced relative to the microfibrillated cellulose is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, further preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and even more preferably 1.00 mmol / g or more, relative to 1 g (mass) of microfibrillated cellulose. Furthermore, the amount of ionic substituent introduced relative to the microfibrillated cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, even more preferably 3.50 mmol / g or less, and even more preferably 3.00 mmol / g or less, relative to 1 g (mass) of cellulose. By setting the amount of ionic substituent (preferably anionic group) within the above range, the micronization of the fiber raw material becomes easier, and the stability of the microfibrillated cellulose can be improved.

[0093] Here, the denominator in the unit mmol / g indicates that the counter ion of the ionic substituent is the hydrogen ion (H+). + The quality of fine fibrous cellulose at that time.

[0094] Furthermore, from the viewpoint of the absorbency of the laminate, the amount of ionic substituent (preferably anionic group) introduced relative to the microfibrillated cellulose is preferably less than 0.50 mmol / g, more preferably less than 0.40 mmol / g, further preferably less than 0.30 mmol / g, even more preferably less than 0.25 mmol / g, and even more preferably less than 0.15 mmol / g, relative to 1 g (mass) of microfibrillated cellulose. From the viewpoint of the total light transmittance and haze of the laminate, it is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, and even more preferably 0.03 mmol / g or more. Such microfibrillated cellulose with low substituent amounts can be obtained, for example, by performing the treatment described later to remove the substituents from the microfibrillated cellulose.

[0095] The amount of ionic substituent introduced into microfibrillary cellulose can be determined, for example, by neutralization titration. In this determination, an alkali such as an aqueous solution of sodium hydroxide is added to the resulting slurry containing microfibrillary cellulose, and the change in pH is measured to determine the amount introduced.

[0096] Figure 1 This is a graph showing the relationship between the amount of NaOH added and pH for a slurry containing fibrous cellulose with phosphorus oxyacid groups. The amount of phosphorus oxyacid groups introduced relative to the fibrous cellulose was determined, for example, as follows.

[0097] First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. It should be noted that, if necessary, the sample may also undergo the same defiberization treatment as described later before treatment with the strongly acidic ion exchange resin.

[0098] Next, while adding sodium hydroxide solution, the pH change was observed, and the results were as follows: Figure 1 The titration curve is shown on the upper side. Figure 1 In the titration curve shown on the upper side, the pH value measured relative to the amount of alkali added is plotted. Figure 1In the titration curve shown on the lower side, the pH increment (differential value) (1 / mmol) relative to the amount of alkali added is plotted. In this neutralization titration, in the pH curve measured relative to the amount of alkali added, two points where the increment (differential value of pH relative to the amount of alkali added) is maximized are identified. The point where the increment is maximized first when alkali is added is called the first endpoint, and the point where the increment is maximized next is called the second endpoint. The amount of alkali required from the start of titration to the first endpoint is equal to the first dissociative acid amount of fibrous cellulose contained in the slurry used for titration, the amount of alkali required from the first endpoint to the second endpoint is equal to the second dissociative acid amount of fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second endpoint is equal to the total dissociative acid amount of fibrous cellulose contained in the slurry used for titration. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first endpoint by the solids content (g) in the slurry to be titrated is the phosphorus oxyacid group introduction amount (mmol / g). It should be noted that when referred only to the amount of phosphorus oxyacid group introduced (or the amount of phosphorus oxyacid group), it indicates the amount of the first dissociated acid.

[0099] It should be noted that, in Figure 1 In this titration, the region from the start of the titration to the first endpoint is called the first region, and the region from the first endpoint to the second endpoint is called the second region. For example, when the phosphorus oxyacid group is a phosphate group and this phosphate group undergoes condensation, the apparent amount of weak acidic groups in the phosphorus oxyacid group (also referred to as the amount of second dissociated acid in this specification) decreases, and the amount of base required in the second region is less than that required in the first region. On the other hand, the amount of strong acidic groups in the phosphorus oxyacid group (also referred to as the amount of first dissociated acid in this specification) is consistent with the amount of phosphorus atoms, regardless of whether condensation occurs. Furthermore, when the phosphorus oxyacid group is a phosphorous acid group, there are no weak acidic groups in the phosphorus oxyacid group, so sometimes the amount of base required in the second region is less, or the amount of base required in the second region is zero. In this case, the point where the pH increment is extremely large in the titration curve becomes a single point.

[0100] It should be noted that the above-mentioned phosphorus oxyacid group introduction amount (mmol / g) represents the amount of phosphorus oxyacid groups in the acidic fibrous cellulose since the denominator represents the mass of the acidic fibrous cellulose (hereinafter referred to as phosphorus oxyacid group amount (acidic)). On the other hand, when the counter ion of the phosphorus oxyacid group is replaced by any cation C in a charge equivalent manner, the amount of phosphorus oxyacid groups in the fibrous cellulose with cation C as the counter ion can be determined by converting the denominator to the mass of the fibrous cellulose with cation C as the counter ion (hereinafter referred to as phosphorus oxyacid group amount (C-type)).

[0101] That is, it can be calculated using the following formula.

[0102] Phosphorus oxyacid content (C type) = Phosphorus oxyacid content (acid type) / {1 + (W-1) × A / 1,000}

[0103] A [mmol / g]: The total amount of anions derived from phosphorus oxyacid groups in fibrous cellulose (the value obtained by adding the amount of strong acid groups and weak acid groups of phosphorus oxyacid groups).

[0104] W: The formula weight of each monovalent cation C (e.g., 23 for Na, 9 for Al).

[0105] Figure 2 A graph showing the relationship between the amount of NaOH added relative to the pH of fine fibrous cellulose with carboxyl groups.

[0106] The amount of carboxyl groups introduced relative to the fine fibrous cellulose was determined, for example, as follows.

[0107] First, the slurry containing fine fibrous cellulose was treated with a strongly acidic ion exchange resin. It should be noted that, if necessary, the sample can also undergo the same defiberization treatment as described later before the treatment with the strongly acidic ion exchange resin. Next, the pH change was observed while adding an aqueous sodium hydroxide solution to obtain the following results. Figure 2 The titration curve is shown. It should be noted that, if necessary, the same defibering treatment as described later can be performed on the analyte.

[0108] like Figure 2 As shown, in this neutralization titration, a point was observed where the pH increment (the differential value of pH relative to the amount of alkali added) was extremely large in the plotted pH curve relative to the amount of alkali added. This point of maximum increment is called the first endpoint. Here, we will... Figure 2 The region from the start of titration to the first endpoint is called the first region. The amount of alkali required for the first region is equal to the amount of carboxyl groups in the slurry used for titration. Then, the amount of alkali (mmol) required for the first region of the titration curve is divided by the solid content (g) in the slurry containing fine fibrous cellulose, thereby calculating the amount of carboxyl groups introduced (mmol / g).

[0109] It should be noted that the above carboxyl group introduction amount (mmol / g) indicates that the counter ion of the carboxyl group is the hydrogen ion (H+). + The amount of substituents per 1g mass of fibrous cellulose (hereinafter referred to as the amount of carboxyl groups (acid type)).

[0110] It should be noted that the above-mentioned carboxyl group introduction amount (mmol / g) represents the amount of carboxyl groups in the acidic fibrous cellulose since the denominator is the mass of the acidic fibrous cellulose (hereinafter referred to as carboxyl group amount (acidic type)). On the other hand, when the counter ion of the carboxyl group is replaced by any cation C in a charge equivalent manner, the amount of carboxyl groups in the fibrous cellulose with cation C as the counter ion (hereinafter, carboxyl group amount (C type)) (mmol / g) can be determined by converting the denominator to the mass of the fibrous cellulose with cation C as the counter ion.

[0111] That is, it can be calculated using the following formula.

[0112] Carboxyl group content (C type) = Carboxyl group content (acid type) / {1 + (W - 1) × (Carboxyl group content (acid type)) / 1,000}

[0113] W: The formula weight of each monovalent cation C (e.g., 23 for Na, 9 for Al).

[0114] It should be noted that in the determination of substituent amounts based on titration, if too much sodium hydroxide aqueous solution is added (1 drop) or the titration interval is too short, the amount of substituent may be lower than it should be, resulting in an inaccurate value. As appropriate addition amounts and titration intervals, for example, it is preferable to titrate 10-50 μL of 0.1N sodium hydroxide aqueous solution every 5-30 seconds. Furthermore, to eliminate the influence of dissolved carbon dioxide in slurries containing fibrous cellulose, it is preferable, for example, to perform the measurement while blowing an inactive gas such as nitrogen into the slurry from 15 minutes before the start of the titration until the end of the titration.

[0115] Furthermore, the amount of sulfur-containing oxyacid groups or sulfonic acid groups introduced relative to fibrous cellulose can be calculated by freeze-drying a slurry containing fibrous cellulose and then determining the sulfur content of the pulverized sample. Specifically, the slurry containing fibrous cellulose is freeze-dried, and the pulverized sample is then decomposed under pressure and heat with nitric acid in a sealed container. After appropriate dilution, the sulfur content is determined using ICP-OES. The value calculated by dividing by the absolute dry mass of the tested fibrous cellulose is taken as the sulfur-containing oxyacid group content or sulfonic acid group content of the fibrous cellulose (unit: mmol / g).

[0116] <<Methods for Manufacturing Microfibrillated Cellulose>>

[0117] (Fiber raw materials containing cellulose)

[0118] Fine fibrous cellulose is made from cellulose-containing fibrous raw materials.

[0119] As a cellulose-containing fiber raw material, there are no particular limitations, but pulp is preferred from the perspective of easy availability and low cost. Examples of pulp include wood pulp, non-wood pulp, and deinking pulp. Wood pulp is not particularly limited, but examples include chemical pulps such as broadleaf kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), alkaline pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP); semi-chemical pulps such as semi-chemical pulp (SCP) and chemical groundwood pulp (CGP); and mechanical pulps such as wood chip pulp (GP) and thermomechanical pulp (TMP, BCTMP). Non-wood pulp is not particularly limited, but examples include cotton pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, wheat straw, and bagasse. There are no particular limitations on the deinking pulp; for example, deinking pulp made from waste paper can be cited. The pulp in this embodiment can be one of the above-described types used alone, or two or more types can be used in combination.

[0120] Of the aforementioned pulps, wood pulp and deinked pulp are preferred from the viewpoint of easy availability. Furthermore, among wood pulps, from the viewpoint of a high cellulose ratio and a high yield of fine fibrous cellulose during defibrillation, and from the viewpoint of obtaining fine fibrous cellulose with low cellulose decomposition and high axial ratio in long fibers in the pulp, chemical pulp is preferred, and kraft pulp and sulfite pulp are even more preferred. It should be noted that when using fine fibrous cellulose with long fibers and a high axial ratio, there is a tendency for the viscosity to increase.

[0121] As a cellulose-containing fiber raw material, cellulose contained in sea tunicates or bacterial cellulose produced by acetic acid bacteria can also be utilized.

[0122] Alternatively, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can be used to replace cellulose-containing fiber raw materials.

[0123] To obtain fine fibrous cellulose with the ionic substituents described above, it is preferable to sequentially include an ionic substituent introduction step (introducing the ionic substituents into the cellulose-containing fiber raw material), a washing step, an alkali treatment step (neutralization step), and a defiberization step. Alternatively, an acid treatment step may be included instead of the washing step, or an acid treatment step may be included in addition to the washing step. Examples of ionic substituent introduction steps include phosphorus oxyacid group introduction, carboxyl group introduction, sulfur oxyacid group introduction, xanthic acid group introduction, phosphonic acid or hypophosphonic acid group introduction, sulfonic acid group introduction, and cationic group introduction. These will be described separately below.

[0124] (Ionic substituent introduction process)

[0125] -Phosphorus-containing oxyacid group introduction process-

[0126] The phosphorus oxyacid group introduction process is a process in which at least one compound (hereinafter also referred to as "compound A") selected from compounds that can introduce phosphorus oxyacid groups by reacting with hydroxyl groups present in a cellulose-containing fibrous raw material is applied to the cellulose-containing fibrous raw material. Through this process, phosphorus oxyacid group introduced fibers are obtained.

[0127] In the phosphorus oxyacid group introduction process of this embodiment, the reaction of the cellulose-containing fiber raw material with compound A can be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). On the other hand, the reaction of the cellulose-containing fiber raw material with compound A can also be carried out in the absence of compound B.

[0128] As an example of a method for applying compound A to a fiber raw material in the presence of compound B, a method of mixing compound A and compound B in a dry, wet, or slurry state of the fiber raw material can be cited. Since the reaction has high uniformity, it is preferable to use a dry or wet state of the fiber raw material, and particularly preferable to use a dry state of the fiber raw material. The form of the fiber raw material is not particularly limited; for example, cotton-like or sheet-like forms are preferred. A method of adding compound A and compound B to the fiber raw material in the form of powder, solution dissolved in a solvent, or melted by heating above their melting point can be cited. Since the reaction has high uniformity, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution. Furthermore, compound A and compound B can be added simultaneously with the fiber raw material, added separately, or added as a mixture. As for the method of adding compound A and compound B, there is no particular limitation; when compound A and compound B are in solution form, the fiber raw material can be immersed in the solution and removed after absorbing the liquid, or the solution can be added dropwise to the fiber raw material. Alternatively, the necessary amounts of compound A and compound B can be added to the fiber raw material, or excess compounds A and B can be removed by pressing and filtering after adding excess compounds A and B to the fiber raw material.

[0129] Compound A used in this embodiment can be any compound having a phosphorus atom and capable of forming an ester bond with cellulose. Examples include phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, and phosphoric anhydride (phosphorus pentoxide), etc., without particular limitation. Phosphoric acid can be of various purities, such as 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Phosphorous acid can be, for example, 99% phosphorous acid (phosphonic acid). Dehydrated condensed phosphoric acid is formed by the condensation of two or more molecules of phosphoric acid through a dehydration reaction; examples include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates can be lithium, sodium, potassium, or ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, and they can have various degrees of neutralization.

[0130] From the perspectives of high efficiency in introducing phosphorus oxyacid groups, easier improvement in defiberization efficiency in the defiberization process described later, low cost, and ease of industrial application, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, or ammonium salt of phosphoric acid are preferred, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate are more preferred.

[0131] The amount of compound A added relative to the fiber raw material is not particularly limited. For example, when converting the amount of compound A added to phosphorus atoms, the amount of phosphorus atoms added relative to 100 parts by mass (absolute dry mass) of fiber raw material is preferably 0.5 parts by mass or more and 100 parts by mass or less, more preferably 1 part by mass or more and 50 parts by mass or less, and even more preferably 2 parts by mass or more and 30 parts by mass or less. By keeping the amount of phosphorus atoms added relative to the fiber raw material within the above range, the yield of microfibrillated cellulose can be further improved. On the other hand, by keeping the amount of phosphorus atoms added relative to the fiber raw material below the above upper limit, a balance between yield improvement and cost can be achieved.

[0132] The compound B used in this embodiment is selected from at least one of urea and its derivatives, as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea.

[0133] From the viewpoint of improving the uniformity of the reaction, compound B is preferably used in the form of an aqueous solution. Furthermore, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution containing both compound A and compound B.

[0134] The amount of compound B added relative to 100 parts by weight (absolute dry weight) of fiber raw material is not particularly limited, but is preferably 1 part by weight or more and 500 parts by weight or less, more preferably 10 parts by weight or more and 400 parts by weight or less, and even more preferably 100 parts by weight or more and 350 parts by weight or less.

[0135] In the reaction of cellulose-containing fiber raw materials with compound A, the reaction system may also contain, in addition to compound B, amides or amines. Examples of amides include formamide, dimethylformamide, acetamide, and dimethylacetamide. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Triethylamine is known, in particular, to act as a good reaction catalyst.

[0136] In the process of introducing phosphorus-containing oxyacid groups, it is preferable to heat-treat the fiber raw material after adding or mixing compound A, etc. As the heat treatment temperature, it is preferable to select a temperature that can suppress the thermal decomposition and hydrolysis reaction of the fiber and efficiently introduce the phosphorus-containing oxyacid groups. The heat treatment temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower. Furthermore, in the heat treatment, equipment with various heat media can be used, such as stirred drying devices, rotary drying devices, disc drying devices, roller heating devices, plate heating devices, fluidized bed drying devices, belt drying devices, filter drying devices, vibrating fluidized bed drying devices, airflow drying devices, reduced pressure drying devices, infrared heating devices, far-infrared heating devices, microwave heating devices, and high-frequency drying devices.

[0137] In the heat treatment of this embodiment, for example, a method can be used to add compound A to the sheet-like fiber material by impregnation and then heat it, or a method can be used to mix or stir the fiber material and compound A using a kneader while heating. This suppresses uneven concentrations of compound A in the fiber material and allows for more uniform introduction of phosphoric oxyacid groups onto the surface of the cellulose fibers contained in the fiber material. This is believed to be because, as water molecules move towards the surface of the fiber material during drying, it prevents dissolved compound A from being pulled towards the fiber material surface by water molecules due to surface tension (i.e., preventing uneven concentrations of compound A).

[0138] Furthermore, the heating device used in the heat treatment is preferably one that can continuously remove the moisture held in the slurry and the moisture generated by the dehydration condensation (phosphorylation) reaction of the accompanying compound A with the hydroxyl groups contained in cellulose and other fiber raw materials to the outside of the device system. Examples of such heating devices include, for instance, an oven with a forced-airflow mechanism. By continuously removing the moisture from the device system, not only can the reverse reaction of phosphorylation, i.e., the hydrolysis of phosphate ester bonds, be suppressed, but also the acid hydrolysis of sugar chains in the fiber can be suppressed. Therefore, fine fibrous cellulose with a high axial ratio can be obtained.

[0139] The heat treatment time, calculated from the point at which the moisture in the fiber raw material is substantially removed, is preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1,000 seconds or less, and even more preferably 10 seconds or more and 800 seconds or less. In this embodiment, by setting the heating temperature and heating time to appropriate ranges, the amount of phosphorus oxyacid groups introduced can be set to a preferred range.

[0140] The amount of phosphorus oxyacid groups introduced relative to 1 g (mass) of microfibrillated cellulose is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, further preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and even more preferably 1.00 mmol / g or more. Furthermore, the amount of phosphorus oxyacid groups introduced relative to 1 g (mass) of microfibrillated cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and even more preferably 3.00 mmol / g or less. By setting the amount of phosphorus oxyacid groups introduced within the above range, it is easier to refine the fiber material and improve the stability of the microfibrillated cellulose.

[0141] -Carboxyl group introduction process-

[0142] The carboxyl introduction process involves oxidizing cellulose-containing fiber raw materials as follows: ozone oxidation, Fenton-based oxidation, TEMPO oxidation, etc.; or using compounds with groups derived from carboxylic acids or their derivatives, or using acid anhydrides of compounds with groups derived from carboxylic acids or their derivatives.

[0143] The term "compound having a group derived from a carboxylic acid" is not particularly limited, and examples include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid; and tricarboxylic acid compounds such as citric acid and aconitic acid. Furthermore, the term "derivative of a compound having a group derived from a carboxylic acid" is not particularly limited, and examples include imides of the anhydrides of compounds having a carboxyl group, and derivatives of the anhydrides of compounds having a carboxyl group. The term "imide of the anhydrides of compounds having a carboxyl group" is also not particularly limited, and examples include imides of dicarboxylic acid compounds such as maleimide, succinimidide, and phthalimide.

[0144] An anhydride, as a compound having a group derived from a carboxylic acid, is not particularly limited, and examples include anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Furthermore, derivatives of anhydrides of compounds having a group derived from a carboxylic acid are not particularly limited, and examples include compounds formed by substituting at least some hydrogen atoms of anhydrides of carboxyl compounds such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride, which are substituted with substituents such as alkyl or phenyl groups.

[0145] When TEMPO oxidation is performed in the carboxyl group introduction process, it is preferable to perform the treatment under conditions where the pH is between 6 and 8. Such a treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be performed, for example, by adding pulp as a fiber raw material, nitrogen-oxygen radicals such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxo radical) as a catalyst, and sodium hypochlorite as a sacrificial agent to a sodium phosphate buffer (pH=6.8). Furthermore, by coexisting with sodium chlorite, the aldehydes generated during the oxidation process can be efficiently oxidized to carboxyl groups.

[0146] Furthermore, TEMPO oxidation treatment can be carried out under conditions where the pH is above 10 and below 11. Such treatment is also known as alkaline TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be carried out, for example, by adding nitric oxide radicals such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidant to pulp, which is a fibrous raw material.

[0147] The amount of carboxyl group introduced relative to the cellulose raw material varies depending on the type of substituent. For example, when the carboxyl group is introduced via TEMPO oxidation, the amount is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, further preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and even more preferably 0.90 mmol / g or more, relative to 1 g (mass) of microfibrillated cellulose. Furthermore, it is preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less, further preferably 2.50 mmol / g or less, even more preferably 2.20 mmol / g or less, and even more preferably 2.00 mmol / g or less. Additionally, when the substituent is carboxymethyl, the amount can be 5.8 mmol / g or less, relative to 1 g (mass) of microfibrillated cellulose. By setting the amount of carboxyl group introduced within the above range, the microfibrillation of cellulose fibers in the microfibrillation process can be facilitated, and the stability of the microfibrillated cellulose can be improved.

[0148] -Sulfur-containing oxyacid group introduction process-

[0149] The manufacturing process of microfibrillated cellulose may include, for example, a sulfur-oxyacid group introduction process as an ionic substituent introduction process. The sulfur-oxyacid group introduction process reacts the hydroxyl groups of the cellulose fiber raw material with sulfur-oxyacids to obtain cellulose fibers with sulfur-oxyacid groups (sulfur-oxyacid group introduced fibers).

[0150] In the sulfur oxyacid group introduction step, instead of compound A in the above-described phosphorus oxyacid group introduction step, at least one compound selected from compounds capable of introducing sulfur oxyacid groups through reaction with hydroxyl groups present in cellulose-containing fiber raw materials (hereinafter also referred to as "compound C") is used. As compound C, any compound having a sulfur atom and capable of forming an ester bond with cellulose is acceptable; examples include sulfuric acid or its salts, sulfurous acid or its salts, sulfonamides, etc., without particular limitation. As sulfuric acid, sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. As sulfurous acid, 5% sulfurous acid water can be used. As sulfates or sulfites, lithium salts, sodium salts, potassium salts, ammonium salts, etc., of sulfates or sulfites can be used, and they can have various degrees of neutralization. As sulfonamides, aminosulfonic acid, etc., can be used. In the sulfur oxyacid group introduction step, compound B from the above-described phosphorus oxyacid group introduction step is preferably used in the same manner.

[0151] In the sulfur-containing oxyacid group introduction process, it is preferable to heat-treat the cellulose raw material after mixing it with an aqueous solution containing sulfur-containing oxyacids and urea and / or urea derivatives. The heat treatment temperature is preferably selected to suppress the thermal decomposition and hydrolysis of the fiber and to efficiently introduce the sulfur-containing oxyacid groups. The heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 150°C or higher. Furthermore, the heat treatment temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0152] In the heat treatment process, it is preferable to heat until substantially free of moisture. Therefore, the heat treatment time varies depending on the moisture content of the cellulose raw material and the amount of aqueous solution containing sulfur-containing oxyacids and urea and / or urea derivatives added, and is preferably set to 10 seconds or more and 10,000 seconds or less. Various heat media can be used in the heat treatment, such as stirred drying devices, rotary drying devices, disc drying devices, roller heating devices, plate heating devices, fluidized bed drying devices, belt drying devices, filter drying devices, vibrating fluidized bed drying devices, airflow drying devices, reduced pressure drying devices, infrared heating devices, far-infrared heating devices, microwave heating devices, and high-frequency drying devices.

[0153] The amount of sulfur-containing oxyacid groups introduced relative to the cellulose raw material is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, even more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and even more preferably 0.90 mmol / g or more. Furthermore, the amount of sulfur-containing oxyacid groups introduced relative to the cellulose raw material is preferably 5.00 mmol / g or less, more preferably 3.00 mmol / g or less. By setting the amount of sulfur-containing oxyacid groups within the above range, it is easier to refine the cellulose raw material and improve the stability of fibrous cellulose.

[0154] -Oxidation process using chlorine-based oxidants (second carboxyl group introduction process)-

[0155] As an ionic substituent introduction process, an oxidation process utilizing a chlorine-based oxidant may be included. In the oxidation process utilizing a chlorine-based oxidant, a carboxyl group is introduced into the fiber raw material by reacting the chlorine-based oxidant with a hydroxyl group in a wet or dry state.

[0156] Examples of chlorine-based oxidants include hypochlorous acid, hypochlorite, chlorite, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, and chlorine dioxide. Considering the efficiency of substituent introduction, fiber dissociation efficiency, cost, and ease of processing, sodium hypochlorite, sodium chlorite, and chlorine dioxide are preferred chlorine-based oxidants. When adding chlorine-based oxidants, they can be added directly to the fiber raw material in reagent form (solid or liquid), or they can be dissolved in a suitable solvent before addition.

[0157] In the oxidation process using a chlorine-based oxidant, the concentration of the chlorine-based oxidant solution, converted to an effective chlorine concentration, is preferably 1% by mass or more and 1,000% by mass or less, more preferably 5% by mass or more and 500% by mass or less, and even more preferably 10% by mass or more and 100% by mass or less. The amount of chlorine-based oxidant added relative to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 10 parts by mass or more and 10,000 parts by mass or less, and even more preferably 100 parts by mass or more and 5,000 parts by mass or less.

[0158] The reaction time with the chlorine-based oxidant in the oxidation process can vary depending on the reaction temperature, and is preferably 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. The pH during the reaction is preferably 5 or more and 15 or less, more preferably 7 or more and 14 or less, and even more preferably 9 or more and 13 or less. Furthermore, the pH at the start of the reaction and during the reaction is preferably kept constant (e.g., pH 11) while appropriately adding hydrochloric acid and sodium hydroxide. After the reaction, excess reaction reagents and byproducts can be removed by filtration or other methods of washing with water.

[0159] -Xanthate introduction process (xanthate esterification process)-

[0160] As an ionic substituent introduction process, it may include, for example, a xanthate group introduction process (hereinafter also referred to as a xanthate esterification process). In the xanthate esterification process, xanthate groups are introduced into the fiber raw material by reacting carbon disulfide and an alkali compound in a moist or dry state with hydroxyl groups. Specifically, carbon disulfide is added to the fiber raw material that has been alkali-cellulosed by the method described later for reaction.

[0161] ((Alkali cellulose))

[0162] When introducing ionic substituents into fiber raw materials, it is preferable to act an alkaline solution on the cellulose contained in the fiber raw material to alkali-celluloseize the cellulose. Through this treatment, some of the hydroxyl groups of the cellulose undergo ionic dissociation, which enhances nucleophilicity (reactivity). The alkaline compound contained in the alkaline solution is not particularly limited and can be either inorganic or organic. For versatility, sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide are preferred, for example. Alkali celluloseization can be carried out simultaneously with the introduction of ionic substituents, as a pre-treatment, or at both times.

[0163] The solution temperature at the start of alkali cellulose formation is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 10°C or higher and 30°C or lower.

[0164] The alkali concentration in the alkaline solution is preferably 0.01 mol / L or more and 4 mol / L or less, more preferably 0.1 mol / L or more and 3 mol / L or less, and even more preferably 1 mol / L or more and 2.5 mol / L or less. Particularly when the processing temperature in alkali cellulose formation is below 10°C, the alkali concentration is preferably 1 mol / L or more and 2 mol / L or less.

[0165] The alkali cellulose treatment time is preferably 1 minute or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. Furthermore, the alkali treatment time is preferably 6 hours or less, more preferably 5 hours or less, and even more preferably 4 hours or less.

[0166] By adjusting the type of alkaline solution, treatment temperature, concentration, and soaking time as described above, the penetration of the alkaline solution into the crystalline region of cellulose can be suppressed, making it easier to maintain the type I crystal structure of cellulose and improving the yield of fine fibrous cellulose.

[0167] When ionic substituent introduction and alkali celluloseation are not performed simultaneously, alkali celluloseation is preferably carried out before the ionic substituent introduction. In this case, the alkali cellulose obtained from the alkali celluloseation treatment is preferably subjected to solid-liquid separation by conventional dehydration methods such as centrifugation and filtration to remove moisture. This improves the reaction efficiency in the subsequent ionic substituent introduction step. The concentration of cellulose fibers after solid-liquid separation is preferably 5% or more and 50% or less, more preferably 10% or more and 40% or less, and even more preferably 15% or more and 35% or less.

[0168] - Phosphonic acid or phosphonoside introduction process (phosphonylation process) -

[0169] As an ionic substituent introduction process, it may include a phosphonic acid group or a phosphonoside group introduction process (phosphonylation process). In the phosphonylation process, a compound (compound E) having a reactive group and having a phosphonic acid group or a phosphonoside group as an essential component is introduced. A Compound B, selected from alkali compounds, urea and its derivatives, is added as an arbitrary component to a hydroxyl-containing fiber raw material in a moist or dry state to react and thereby introduce phosphonic acid groups or hypophosphonic acid groups into the fiber raw material.

[0170] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0171] As compound E A Examples include vinylphosphonic acid, phenylvinylphosphonic acid, and phenylvinylphosphonic acid. Considering the efficiency of substituent introduction, fiber debonding efficiency, cost, and ease of processing, compound E... A Vinylphosphonic acid is preferred.

[0172] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0173] Add compound E AThe reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0174] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0175] Compound E A The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0176] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents and byproducts can be removed by filtration or other methods of washing with water.

[0177] -Sulfonic acid group introduction process (sulfonylation process)-

[0178] As an ionic substituent introduction process, a sulfonic acid group introduction process (sulfonylation process) may be included. In sulfonylation, a compound (compound E) having reactive groups and sulfonic acid groups as essential components is introduced. B Compound B, selected from alkali compounds, urea and its derivatives, and as an arbitrary component, is added to a hydroxyl-containing fiber raw material in a wet or dry state to react and thereby introduce sulfonic acid groups into the fiber raw material.

[0179] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0180] As compound E B Examples include sodium 2-chloroethane sulfonate, sodium vinyl sulfonate, sodium p-styrene sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid. Among these, compound E... (The sentence is incomplete and requires further context to translate accurately.) B Sodium vinyl sulfonate is preferred.

[0181] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0182] Add compound E BThe reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0183] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0184] Compound E B The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0185] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 15 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents, byproducts, etc., can be removed by filtration or other methods of washing with water.

[0186] -Carboxylation process (third carboxyl group introduction process)-

[0187] As an ionic substituent introduction process, a carboxylation process may be included. This involves introducing a compound (compound E) with reactive groups and a carboxyl group as an essential component. C Compound B, selected from alkali compounds, urea and its derivatives, is added as an arbitrary component to a hydroxyl-containing fiber raw material in a moist or dry state to react and thereby introduce carboxyl groups into the fiber raw material.

[0188] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0189] As compound E C Based on the factors of substituent introduction efficiency, fiber debonding efficiency, cost, and ease of processing, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred.

[0190] Furthermore, as an optional component, it is also preferable to use compound B from the above-described <phosphorus oxyacid group introduction process>, and the amount added is also preferably as described above.

[0191] Add compound E CThe reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0192] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0193] Compound E C The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0194] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1,000 minutes or less, more preferably 3 minutes or more and 500 minutes or less, and even more preferably 5 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents, byproducts, etc., can be removed by filtration or other methods through washing with water.

[0195] -Catonic group introduction process (cationization process)-

[0196] By using compounds (compound E) that have reactive and cationic groups as essential components D Compound B, selected from alkali compounds, urea and its derivatives, is added as an arbitrary component to a hydroxyl-containing fiber raw material in a moist or dry state to react and thereby introduce cationic groups into the fiber raw material.

[0197] Examples of reactive groups include haloalkyl groups, vinyl groups, and epoxy groups (glycidyl groups).

[0198] Examples of cationic groups include ammonium, phosphonium, and sulfonium groups. Among these, the ammonium group is preferred.

[0199] As compound E D Based on the factors of substituent introduction efficiency, fiber desiccation efficiency, cost, and ease of processing, glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride are preferred.

[0200] Furthermore, as an optional component, compound B from the aforementioned <phosphorus oxyacid group introduction process> is also preferably used. The amount added is also preferably as described above.

[0201] Add compound E DThe reagent can be added directly to the fiber raw material in the form of a reagent (solid or liquid), or it can be dissolved in a suitable solvent before addition. Preferably, the fiber raw material is pre-treated with alkali cellulose, or alkali cellulose is applied simultaneously with the reaction. The method of alkali cellulose treatment is as described above.

[0202] The reaction temperature is preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0203] Compound E D The amount added relative to 100 parts by weight of fiber raw material is preferably 1 part by weight or more and 100,000 parts by weight or less, more preferably 2 parts by weight or more and 10,000 parts by weight or less, and even more preferably 5 parts by weight or more and 1,000 parts by weight or less.

[0204] The reaction time can vary depending on the reaction temperature, and is preferably 1 minute or more and 1,000 minutes or less, more preferably 5 minutes or more and 500 minutes or less, and even more preferably 10 minutes or more and 400 minutes or less. Furthermore, after the reaction, excess reaction reagents, byproducts, etc., can be removed by filtration or other methods by washing with water.

[0205] (Cleaning process)

[0206] In the method for manufacturing microfibrillated cellulose according to this embodiment, a cleaning step can be performed on the fibers to which ionic substituents have been introduced, as needed. The cleaning step can be performed, for example, by washing the fibers with water and / or an organic solvent. Alternatively, the cleaning step can be performed after the steps described later, and the number of cleaning cycles performed in each cleaning step is not particularly limited.

[0207] (Alkali treatment (neutralization) process)

[0208] In the manufacture of microfibrillated cellulose, the fiber raw material can be subjected to alkali treatment (neutralization treatment) between the ionic substituent introduction step and the defibrillation treatment step described later. There are no particular limitations on the method of alkali treatment; for example, impregnating the fibers with ionic substituents in an alkaline solution can be cited.

[0209] The alkaline compound contained in the alkaline solution is not particularly limited and can be either an inorganic or organic alkaline compound. In this embodiment, for the sake of versatility, sodium hydroxide or potassium hydroxide is preferably used as the alkaline compound. Furthermore, the solvent contained in the alkaline solution can be any of water or an organic solvent. Preferably, the solvent contained in the alkaline solution is a polar solvent containing water or a polar organic solvent, such as an alcohol, and more preferably an aqueous solvent containing at least water. For the sake of versatility, aqueous solutions of sodium hydroxide or potassium hydroxide are preferred, for example.

[0210] The temperature of the alkaline solution in the alkali treatment process is not particularly limited, but is preferably 5°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower. The immersion time of the ionic substituent-introduced fibers in the alkaline solution in the alkali treatment process is not particularly limited, but is preferably 5 minutes or higher and 30 minutes or lower, more preferably 10 minutes or higher and 20 minutes or lower. The amount of alkaline solution used in the alkali treatment is not particularly limited, but is preferably 100% by mass or higher and 100,000% by mass or lower relative to the absolute dry mass of the ionic substituent-introduced fibers, more preferably 1,000% by mass or higher and 10,000% by mass or lower.

[0211] To reduce the amount of alkaline solution used in the alkali treatment process, the ionicly substituent-introduced fibers can be washed with water and / or an organic solvent after the ionic substituent introduction process and before the alkali treatment process. From the viewpoint of improving processability, it is preferable to wash the alkali-treated ionicly substituent-introduced fibers with water and / or an organic solvent after the alkali treatment process and before the fiber disintegration process.

[0212] (Acid treatment process)

[0213] In the manufacture of microfibrillated cellulose, the cellulose raw material can be acid-treated between the step of introducing ionic substituents and the subsequent defibrillation process. For example, the steps of introducing ionic substituents, acid treatment, alkali treatment, and defibrillation can be performed sequentially.

[0214] The method of acid treatment is not particularly limited; for example, impregnating the fiber raw material in an acidic solution containing acid can be cited. The concentration of the acidic solution used is not particularly limited; for example, it is preferably 10% by mass or less, more preferably 5% by mass or less. Furthermore, the pH of the acidic solution used is not particularly limited; for example, it is preferably 0 or higher and 4 or lower, more preferably 1 or higher and 3 or lower. The acid contained in the acidic solution can be, for example, inorganic acids, sulfonic acids, carboxylic acids, etc. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorite, chloric acid, perchloric acid, phosphoric acid, boric acid, etc. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, etc. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid, etc. Of these, hydrochloric acid or sulfuric acid is particularly preferred.

[0215] The temperature of the acid solution used in the acid treatment is not particularly limited, but is preferably 5°C or higher and 100°C or lower, more preferably 20°C or higher and 90°C or lower. The immersion time in the acid solution during acid treatment is not particularly limited, but is preferably 5 minutes or higher and 120 minutes or lower, more preferably 10 minutes or higher and 60 minutes or lower. The amount of acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or higher and 100,000% by mass or lower, more preferably 1,000% by mass or higher and 10,000% by mass or lower, relative to the absolute dry mass of the fiber raw material.

[0216] (Fiber debonding process)

[0217] By introducing ionic substituents into the fiber and performing defiberization in the defiberization process, microfibrillated cellulose can be obtained.

[0218] In the fiber debonding process, for example, a fiber debonding device can be used. The fiber debonding device is not particularly limited; for example, a high-speed fiber debonder, a grinder (mortar-type pulverizer), a high-pressure homogenizer, an ultra-high-pressure homogenizer, a high-pressure impact pulverizer, a ball mill, a bead mill, a disc mill, a conical mill, a twin-shaft mixer, a vibratory mill, a high-speed rotating homogenizer, an ultrasonic disperser, or a pulper can be used. Among the above-mentioned fiber debonding devices, a high-speed fiber debonder, a high-pressure homogenizer, or an ultra-high-pressure homogenizer are more preferably used as they have less influence from the grinding media and less potential for contamination.

[0219] In the fiber desiccation process, for example, it is preferable to use a dispersion medium to introduce ionic substituents into the fiber and dilute it to form a slurry. As the dispersion medium, one or more organic solvents selected from water and polar organic solvents can be used. There are no particular limitations on the polar organic solvent; for example, alcohols, polyols, ketones, ethers, esters, and aprotic polar solvents are preferred. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutanol. Examples of polyols include ethylene glycol, propylene glycol, and glycerol. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether. Examples of esters include ethyl acetate and butyl acetate. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP).

[0220] The concentration of solid components in the fine fibrous cellulose during defibrillation can be set appropriately.

[0221] In addition, the slurry obtained by dispersing phosphorus oxyacid group-introducing fibers in a dispersion medium may also contain solid components other than phosphorus oxyacid group-introducing fibers, such as urea with hydrogen bonding.

[0222] (Nitrogen removal treatment)

[0223] The manufacturing process of microfibrillated cellulose may further include a process for reducing the nitrogen content (nitrogen removal treatment). By reducing the nitrogen content, microfibrillated cellulose that can further suppress coloration can be obtained. The nitrogen removal treatment is preferably performed before the defibrillation treatment.

[0224] In the nitrogen removal process, it is preferable to adjust the pH of the slurry containing the substituent-introduced fibers to 10 or higher before heat treatment. During heat treatment, it is preferable to set the slurry temperature to 50°C or higher and 100°C or lower, and the heating time to 15 minutes or higher and 180 minutes or lower. When adjusting the pH of the slurry containing the substituent-introduced fibers, it is preferable to add an alkaline compound that can be used in the aforementioned alkaline treatment process.

[0225] Following the nitrogen removal process, a cleaning process can be performed on the substituent-introduced fibers as needed. The cleaning process can be carried out, for example, by washing the ionicly substituent-introduced fibers with water and / or organic solvents. Furthermore, there is no particular limitation on the number of cleaning cycles performed in each cleaning process.

[0226] (Substituent removal treatment)

[0227] A method for manufacturing microfibrillary cellulose may include a step of removing at least some of the substituents from microfibrillary cellulose having substituents and a fiber width of less than 1,000 nm. By performing such a step, microfibrillary cellulose with a small fiber width can be obtained even with a low amount of substituent introduction. In this specification, the step of removing at least some of the substituents from microfibrillary cellulose is also referred to as a substituent removal treatment step.

[0228] Examples of substituent removal treatment steps include heat treatment, enzyme treatment, acid treatment, and alkali treatment of fine fibrous cellulose with substituents and a fiber width of 1,000 nm or less. These steps can be performed individually or in combination. Preferably, the substituent removal treatment step involves heat treatment or enzyme treatment. By performing these treatment steps, at least some substituents can be removed from the fine fibrous cellulose with substituents and a fiber width of 1,000 nm or less, resulting in fine fibrous cellulose with a substituent introduction amount of less than 0.5 mmol / g. By using such fine fibrous cellulose to form a layer containing fine fibrous cellulose, a laminate with superior water resistance can be easily obtained.

[0229] The substituent removal process is preferably performed in a slurry form. Specifically, the substituent removal process is preferably a process involving heat treatment, enzyme treatment, acid treatment, or alkali treatment of a slurry containing microfibrillated cellulose fibers with substituents and a fiber width of 1,000 nm or less. By performing the substituent removal process in a slurry form, it is possible to prevent the residue of coloring substances, added or generated acids, alkalis, salts, etc., caused by heating during the substituent removal process. This suppresses coloring of the microfibrillated cellulose layer. Furthermore, if a salt removal process originating from the removed substituents is performed after the substituent removal process, the salt removal efficiency can be improved.

[0230] When performing a substituent removal treatment on a slurry containing fine fibrous cellulose with substituents and a fiber width of 1,000 nm or less, the concentration of the fine fibrous cellulose in the slurry is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more. Furthermore, the concentration of the fine fibrous cellulose in the slurry is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. By maintaining the concentration of the fine fibrous cellulose in the slurry within the above range, the substituent removal treatment can be performed more efficiently. Furthermore, by maintaining the concentration of the fine fibrous cellulose in the slurry within the above range, the residues of coloring substances, added or generated acids, alkalis, salts, etc., caused by heating during the substituent removal treatment, can be prevented. This suppresses coloring of the layer containing the fine fibrous cellulose. Additionally, when a salt removal treatment originating from the removed substituents is performed after the substituent removal treatment, the salt removal efficiency can also be improved.

[0231] When the substituent removal treatment step involves heating microfibrillated cellulose having substituents and a fiber width of 1,000 nm or less, the heating temperature during the heating treatment step is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, the heating temperature during the heating treatment step is preferably 250°C or lower, more preferably 230°C or lower, and even more preferably 200°C or lower. Wherein, when the substituents in the microfibrillated cellulose supplied for the substituent removal treatment step are phosphorus oxyacid groups, the heating temperature during the heating treatment step is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher.

[0232] When the substituent removal process involves heating, the heating device that can be used in the heating process is not particularly limited. It can be a hot air heating device, a steam heating device, an electric heating device, a hydrothermal heating device, a fire-powered heating device, an infrared heating device, a far-infrared heating device, a microwave heating device, a high-frequency heating device, a stirring drying device, a rotary drying device, a disc drying device, a roller heating device, a plate heating device, a fluidized bed drying device, a belt drying device, a filter drying device, a vibrating fluidized bed drying device, an airflow drying device, or a reduced pressure drying device. From the viewpoint of preventing evaporation, heating is preferably carried out in a closed system; furthermore, from the viewpoint of increasing the heating temperature, it is preferably carried out in a pressure-resistant device or container. The heating process can be batch processing, batch-continuous processing, or continuous processing.

[0233] In the case where the substituent removal process is an enzymatic treatment of microfibrillated cellulose with substituents and a fiber width of 1,000 nm or less, the enzyme treatment process preferably uses phosphate hydrolase, sulfate hydrolase, or the like, depending on the type of substituent.

[0234] In the enzyme treatment process, the enzyme is preferably added with an enzyme activity of 0.1 kPa or higher relative to 1 g of microfibrillated cellulose, more preferably with an enzyme activity of 1.0 kPa or higher, and even more preferably with an enzyme activity of 10 kPa or higher. Furthermore, the enzyme is preferably added with an enzyme activity of 100,000 kPa or lower relative to 1 g of microfibrillated cellulose, more preferably with an enzyme activity of 50,000 kPa or lower, and even more preferably with an enzyme activity of 10,000 kPa or lower. After adding the enzyme to the microfibrillated cellulose dispersion (slurry), the treatment is preferably carried out at a temperature of 0°C or higher and below 50°C for at least 1 minute and at least 100 hours.

[0235] After the enzyme reaction, a step can be included to inactivate the enzyme. Examples of methods for inactivating the enzyme include adding an acidic or alkaline component to the enzyme-treated slurry, or raising the temperature of the enzyme-treated slurry to above 90°C.

[0236] In the case where the substituent removal process is an acid treatment of microfibrillated cellulose having substituents and a fiber width of 1,000 nm or less, it is preferable to add an acid compound that can be used in the above-mentioned acid treatment process to the slurry during the acid treatment process.

[0237] In the case where the substituent removal process is an alkali treatment of microfibrillated cellulose having substituents and a fiber width of 1,000 nm or less, it is preferable to add an alkali compound that can be used in the above-mentioned alkali treatment process to the slurry during the alkali treatment process.

[0238] In the substituent removal process, it is preferable to uniformly advance the substituent removal reaction. To uniformly advance the reaction, for example, the slurry containing fine fibrous cellulose can be stirred, or the specific surface area of ​​the slurry can be increased. As a method of stirring the slurry, mechanical shearing from an external source can be applied, or self-stirring can be promoted by increasing the feed rate of the slurry in the reaction.

[0239] In the substituent removal process, spacer molecules can be added. These spacer molecules enter between adjacent microfibrillary cellulose fibers, thereby acting as spacers to create microspaces between them. By adding such spacer molecules during the substituent removal process, the aggregation of the microfibrillary cellulose fibers after the substituent removal treatment can be inhibited. This allows for a more effective improvement in the transparency of the layer containing the microfibrillary cellulose fibers.

[0240] The spacer molecule is preferably a water-soluble organic compound. Examples of water-soluble organic compounds include sugars, water-soluble polymers, and ureas. Specifically, examples include trehalose, urea, polyethylene glycol (PEG), polyethylene oxide (PEO), carboxymethyl cellulose, and polyvinyl alcohol (PVA). Other water-soluble organic compounds that can be used include alkyl methacrylate-acrylic acid copolymers, polyvinylpyrrolidone, sodium polyacrylate, propylene glycol, dipropylene glycol, polypropylene glycol, isopentyl glycol, hexanediol, 1,3-butanediol, polyacrylamide, xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, pullulan, carrageenan, pectin, cationic starch, raw starch, oxidized starch, etherified starch, esterified starch, amylose, and other starches, as well as glycerol, diglycerol, polyglycerol, hyaluronic acid, and metal salts of hyaluronic acid.

[0241] In addition, known pigments can be used as spacer molecules. Examples include kaolin (including clay), calcium carbonate, titanium dioxide, zinc oxide, amorphous silica (including colloidal silica), alumina, zeolite, sepiolite, montmorillonite, synthetic montmorillonite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene-based plastic pigments, hydrotalcite, urea resin-based plastic pigments, and benzoguanamine-based plastic pigments.

[0242] (pH adjustment process)

[0243] When performing the above-mentioned substituent removal treatment step in a slurry form, a step of adjusting the pH of the slurry containing microfibrillated cellulose can be set before the substituent removal treatment step. For example, an ionic substituent is introduced into the cellulose fibers, and the counter ion of the ionic substituent is Na. + In this case, the pulp containing finely fibrous cellulose after defibrination exhibits a weakly alkaline pH. If heating is carried out under these conditions, monosaccharides, which are one of the coloring factors, may sometimes be produced due to the decomposition of cellulose; therefore, it is preferable to adjust the pH of the pulp to 8 or below. Furthermore, monosaccharides may also be produced under acidic conditions; therefore, it is preferable to adjust the pH of the pulp to 3 or above.

[0244] Furthermore, when the substituent-containing microfibrillary cellulose is phosphate-containing microfibrillary cellulose, from the viewpoint of improving the removal efficiency of the substituent, it is preferable that the phosphorus in the phosphate group is susceptible to nucleophilic attack. Cellulose-OP(=O)(-OH) is susceptible to nucleophilic attack. + (-O-Na) + To achieve a neutralization degree of 1, it is preferable to adjust the pH of the slurry to 3 or higher and 8 or lower, and more preferably to adjust the pH to 4 or higher and 6 or lower.

[0245] There are no particular limitations on the methods used to adjust pH. For example, acidic or alkaline components can be added to slurries containing fine fibrous cellulose. Acidic components can be any type of inorganic or organic acid. Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Examples of organic acids include formic acid, acetic acid, citric acid, malic acid, lactic acid, adipic acid, sebacic acid, stearic acid, maleic acid, succinic acid, tartaric acid, fumaric acid, and gluconic acid. Alkaline components can be either inorganic or organic alkali compounds. Examples of inorganic alkali compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. Examples of organic base compounds include ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, and N,N-dimethyl-4-aminopyridine.

[0246] In addition, ion exchange treatment can be performed in the pH adjustment process to adjust the pH. During ion exchange treatment, either a strong acid cation exchange resin or a weak acid ion exchange resin can be used. By treating with an appropriate amount of cation exchange resin for a sufficient time, a slurry containing fine fibrous cellulose with the target pH can be obtained. Furthermore, the addition of acidic or alkaline components can also be combined with ion exchange treatment in the pH adjustment process.

[0247] (Salt removal process)

[0248] Following the substituent removal process, it is preferable to perform a salt removal process from the removed substituents. By removing the salts from the substituents, fine fibrous cellulose with suppressed coloration can be readily obtained. The means of removing the salts from the substituents are not particularly limited; examples include washing and ion exchange treatments. Washing is performed, for example, by using water and / or an organic solvent to wash the fine fibrous cellulose that has agglomerated due to the substituent removal process. In ion exchange treatment, an ion exchange resin can be used.

[0249] (Uniform dispersion treatment)

[0250] Following the substituent removal treatment step, a step can be provided to uniformly disperse the fine fibrous cellulose obtained through the substituent removal treatment. By performing the substituent removal treatment on the fine fibrous cellulose, at least some of the fine fibrous cellulose aggregates. The uniform dispersion treatment step is a step that uniformly disperses the thus aggregated fine fibrous cellulose.

[0251] In the uniform dispersion process, for example, a high-speed defiber mill, a grinder (mortar and pestle type pulverizer), a high-pressure homogenizer, a high-pressure impact pulverizer, a ball mill, a bead mill, a disc mill, a conical mill, a twin-shaft mixer, a vibratory mill, a high-speed rotating homogenizer, an ultrasonic disperser, or a pulper can be used. Among the above-mentioned uniform dispersion processing apparatus, a high-speed defiber mill and a high-pressure homogenizer are more preferred.

[0252] The processing conditions in the uniform dispersion process are not particularly limited, but it is preferable to increase the maximum moving speed of the fine fibrous cellulose and the pressure during processing. In a high-speed defibrillator, the circumferential speed is preferably 20 m / s or more, more preferably 25 m / s or more, and even more preferably 30 m / s or more. Compared with a high-speed defibrillator, a high-pressure homogenizer has a higher maximum moving speed of the fine fibrous cellulose and a higher pressure during processing, and therefore can be used more preferably. In the high-pressure homogenizer processing, the processing pressure is preferably 1 MPa or more and 350 MPa or less, more preferably 10 MPa or more and 300 MPa or less, and even more preferably 50 MPa or more and 250 MPa or less.

[0253] Furthermore, the aforementioned spacer molecules can be added during the uniform dispersion process. By adding such spacer molecules during the uniform dispersion process, the uniform dispersion of fine fibrous cellulose can be achieved more smoothly. This, in turn, can more effectively improve the transparency of the layer containing fine fibrous cellulose.

[0254] In the microfibrillated cellulose layer of this embodiment, from the viewpoint of improving the rigidity of the laminate, the content of microfibrillated cellulose in the solid component of the microfibrillated cellulose layer is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, and even more preferably 25% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, further preferably 80% by mass or less, and even more preferably 75% by mass or less. When the microfibrillated cellulose layer in this embodiment is multilayered, the content of microfibrillated cellulose in the solid component of each layer is preferably within the above range.

[0255] As a type of microfibrillary cellulose, microfibrillary cellulose containing ionic groups and unmodified microfibrillary cellulose can be used in combination.

[0256] In this embodiment, as microfibrillary cellulose, microfibrillary cellulose containing ionic groups and unmodified microfibrillary cellulose can be used in combination.

[0257] In addition to fine fibrous cellulose, it may also contain coarse cellulose fibers with a fiber width exceeding 1 μm. In the following description, both fine fibrous cellulose and coarse cellulose fibers will be collectively referred to as "cellulose fibers".

[0258] The fiber width of coarse cellulose fibers is not particularly limited as long as it is 1 μm or more. For example, it is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more, further preferably 10 μm or more, and even more preferably 50 μm or less, and even more preferably 40 μm or less. It should be noted that the fiber width of coarse cellulose fibers can be determined by a fiber length distribution measuring device (e.g., Valmet FS5, ABB L&W Fiber Tester Plus).

[0259] From the viewpoint of improving dispersibility in layers containing microfibrillary cellulose, coarse cellulose fibers can have ionic substituents. The preferred manner of ionic substituents is the same as that of microfibrillary cellulose, and the preferred range of their types and amounts is also the same.

[0260] Coarse cellulose fibers are preferably obtained by slowly defibrating the fiber raw material after introducing ionic groups. Examples of defibrating machines used in the slow defibrating process include disc mills, conical mills, and other fine mills.

[0261] When the cellulose contains coarse cellulose fibers, the preferred content of the fine cellulose fibers in the above-mentioned layer containing fine cellulose fibers is a preferred range of the total content of cellulose fibers, that is, the total content of fine cellulose fibers and coarse cellulose fibers.

[0262] When coarse cellulose fibers are present, the content of coarse cellulose fibers is preferably 1 part by mass or more and 80 parts by mass or less, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of fibrous cellulose (the sum of fine fibrous cellulose and coarse cellulose fibers).

[0263] When the content of coarse cellulose fibers is within the above range, since coarse cellulose fibers can be manufactured at a lower cost than fine cellulose fibers, laminates can be manufactured at a lower cost.

[0264] <Hydrophilic polymers>

[0265] From the viewpoint of ease of manufacturing the cellulose layer containing microfibrils, the cellulose layer containing microfibrils in this embodiment preferably comprises a hydrophilic polymer. A hydrophilic polymer generally refers to a polymeric compound that readily dissolves, swells, or wets in water. Examples include polymeric compounds with ionic groups such as carboxyl, sulfonic acid, or amino groups in their molecular structure; and polymeric compounds with nonionic hydrophilic groups such as hydroxyl, amide, ether, or polyoxyethylene and polyoxypropylene groups.

[0266] Examples of hydrophilic polymers include carboxyvinyl polymers; polyvinyl alcohol; alkyl methacrylate-acrylic acid copolymers; polyvinylpyrrolidone; polyvinyl methyl ether; sodium polyacrylate and other polyacrylates; alkyl acrylate copolymers; urethane copolymers; modified polyesters; modified polyimides; polyethylene glycol, polyethylene oxide, polypropylene glycol and other polyalkylene glycols; polycationic polyacrylamide, polyethyleneimine and other polycationic; polyanionic; amphoteric polymers; xanthan gum, guar gum, tamarind gum, carrageenan gum, and prickly ash gum. Thickening polysaccharides such as locust bean gum, quince seeds, alginic acid, metal salts of alginic acid, pullulan, Suizenji cyanobacteria polysaccharide, and pectin; cellulose derivatives such as carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, and hydroxyethyl cellulose; starches such as cationic starch, raw starch, oxidized starch, etherified starch, esterified starch, dextrin, and amylose; glycerols such as polyglycerol; hyaluronic acid and metal salts of hyaluronic acid; and proteins such as casein. Additionally, copolymers of these hydrophilic polymers are also acceptable. Furthermore, "polyvinyl alcohol" includes modified forms of polyvinyl alcohol.

[0267] The hydrophilic polymer preferably contains polyvinyl alcohol, polyalkylene glycol, or cellulose derivatives, and more preferably contains polyvinyl alcohol or cellulose derivatives. As a cellulose derivative, nonionic water-soluble cellulose ethers such as methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxyethyl cellulose are preferred, and hydroxypropyl methylcellulose is more preferred.

[0268] When the microfibrillated cellulose layer is a single layer, the hydrophilic polymer preferably contains nonionic water-soluble cellulose ether and / or polyvinyl alcohol, more preferably nonionic water-soluble cellulose ether. It should be noted that "water-soluble" means that at least 1g can dissolve in 100g of water at any temperature between 0°C and 100°C. Furthermore, "polymer" means that the average molecular weight (weight-average molecular weight when a molecular weight distribution is present) is 1,000 or more, preferably 1,500 or more, and more preferably 2,000 or more.

[0269] In the case of containing nonionic water-soluble cellulose ether, the content of nonionic water-soluble cellulose ether in the hydrophilic polymer is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, even more preferably 95% by mass or less, and 100% by mass or less.

[0270] In this embodiment, when the layer containing microfibrillated cellulose is a single layer, from the viewpoint of improving the rigidity of the laminate, the mass ratio of hydrophilic polymer to microfibrillated cellulose (hydrophilic polymer / microfibrillated cellulose) is preferably 5 / 95 or more and 90 / 10 or less, more preferably 10 / 90 or more, further preferably 20 / 80 or more, even more preferably 25 / 75 or more, and more preferably 85 / 15 or less, further preferably 80 / 20 or less, and even more preferably 75 / 25 or less.

[0271] In this embodiment, when the layer containing microfibrillated cellulose is a single layer, from the viewpoint of improving the rigidity of the laminate, the mass ratio of nonionic water-soluble cellulose ether to microfibrillated cellulose (nonionic water-soluble cellulose ether / microfibrillated cellulose) is preferably 10 / 90 or more and 90 / 10 or less, more preferably 15 / 85 or more, further preferably 20 / 80 or more, even more preferably 25 / 75 or more, and more preferably 85 / 15 or less, further preferably 80 / 20 or less, and even more preferably 75 / 25 or less.

[0272] In this embodiment, when the microfibrillated cellulose layer is a single layer, from the viewpoint of improving the rigidity of the laminate, the sum of the content of microfibrillated cellulose and the content of hydrophilic polymer in the solid component containing the microfibrillated cellulose layer is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, even more preferably 95% by mass or more, and is 100% by mass or less.

[0273] When the layer containing microfibrillated cellulose is multilayered, it preferably includes a layer 1a containing polyvinyl alcohol and a layer 1b containing nonionic water-soluble cellulose ether. In the laminate described later, it is preferable that the layer 1b containing nonionic water-soluble cellulose ether is bonded to the core resin board.

[0274] In this embodiment, when the microfibrillated cellulose layer is multilayered, the mass ratio of hydrophilic polymer to microfibrillated cellulose (hydrophilic polymer / microfibrillated cellulose) in each layer constituting the microfibrillated cellulose layer is preferably 5 / 95 or more and 90 / 10 or less, more preferably 10 / 90 or more, further preferably 20 / 80 or more, and even more preferably 80 / 20 or less, further preferably 70 / 30 or less, and even more preferably 60 / 40 or less.

[0275] In the microfibrillated cellulose layer 1a of this embodiment, from the viewpoint of interlayer adhesion, the mass ratio of polyvinyl alcohol to microfibrillated cellulose (polyvinyl alcohol / microfibrillated cellulose) is preferably 25 / 75 or more and 90 / 10 or less, more preferably 75 / 25 or less, further preferably 60 / 40 or less, even more preferably 45 / 55 or less, and even more preferably 40 / 60 or less.

[0276] In the microfibrillated cellulose layer 1b of this embodiment, from the viewpoint of interlayer adhesion, the mass ratio of nonionic water-soluble cellulose ether to microfibrillated cellulose (nonionic water-soluble cellulose ether / microfibrillated cellulose) is preferably 5 / 95 or more and 90 / 10 or less, more preferably 10 / 90 or more, further preferably 20 / 80 or more, and even more preferably 70 / 30 or less, further preferably 60 / 40 or less, even more preferably 50 / 50 or less, and even more preferably 40 / 60 or less.

[0277] In this embodiment, when the layer containing microfibrillated cellulose is multilayered, from the viewpoint of improving the rigidity of the laminate, the sum of the content of microfibrillated cellulose and the content of hydrophilic polymer in the solid components of each layer constituting the layer containing microfibrillated cellulose is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, even more preferably 95% by mass or more, and is 100% by mass or less.

[0278] <Other Ingredients>

[0279] The microfibrillated cellulose layer in this embodiment may contain components other than microfibrillated cellulose with a fiber width of less than 1,000 nm and hydrophilic polymers (other components). Examples of other components include fibrous cellulose with a fiber width greater than 1,000 nm, hydrophilic low molecular weight polymers, paper strength enhancers, thermoplastic resins, surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, defoamers, organic particles, lubricants, antistatic agents, UV protectants, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, anti-coloring agents, polymerization inhibitors, pH adjusters, and crosslinking agents.

[0280] It should be noted that, in the microfibrillated cellulose layer of this embodiment, the total content of "other components" in the solid components of the microfibrillated cellulose layer can be, for example, set to 5% by mass or less, 3% by mass or less, 1% by mass or less, or even 0% by mass.

[0281] <Thickness>

[0282] In this embodiment, the thickness of the cellulose layer containing fine fibrous cellulose is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more, even more preferably 20 μm or more, and even more preferably 80 μm or less, even more preferably 60 μm or less. It should be noted that when the cellulose layer containing fine fibrous cellulose is multilayered, the total thickness is preferably within the above-mentioned range.

[0283] The thickness of the cellulose layer containing fine fibrous cellulose is preferably adjusted appropriately according to the intended use of the laminate or laminate.

[0284] <Base Weight>

[0285] In this embodiment, the preferred basis weight of the microfibrillated cellulose layer is 20 g / m³. 2 Above and 110g / m 2 The following, or more preferably, is 30g / m 2 The above, and more preferably 40g / m 2 The above, and more preferably 90g / m 2 The following, and more preferably, is 70g / m 2 The following should be noted: when the layer of fine fibrous cellulose is multi-layered, the total basis weight is preferably within the above-mentioned range.

[0286] The basis weight containing the microfibrillated cellulose layer is preferably adjusted appropriately according to the intended use of the laminate or laminate.

[0287] <Density>

[0288] In this embodiment, the density of the cellulose layer containing fine fibrous fibers is preferably 0.6 g / cm³.3 Above and 2.5g / cm 3 The following, or more preferably, is 0.8 g / cm³ 3 The above, and more preferably, is 1.0 g / cm³. 3 The above, and more preferably 2.2 g / cm³ 3 The following, and more preferably, is 1.9 g / cm³. 3 the following.

[0289] The density of the cellulose layer containing fine fibrous cellulose is calculated by dividing the basis weight of the cellulose layer containing fine fibrous cellulose by its thickness. When the cellulose layer containing fine fibrous cellulose is multilayered, it is calculated by dividing the total basis weight by the total thickness.

[0290] [Adhesive layers 1a, 1b]

[0291] The laminated sheet of this embodiment is as follows: (i) an adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm; or, (ii) an adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm and an adhesive layer 1b is provided on the other side.

[0292] The components contained in each layer of adhesive layer 1a and adhesive layer 1b may be the same or different, but are preferably the same. It should be noted that the components contained in each layer of adhesive layer 1a and adhesive layer 1b are preferably in the same form.

[0293] Hereinafter, adhesive layer 1a and adhesive layer 1b will be collectively referred to as "adhesive layer".

[0294] Examples of adhesives constituting the adhesive layer include polycarbonate resins, acrylic resins, polyester resins, vinyl chloride resins, vinyl acetate resins, polyurethane resins, silicone resins, epoxy resins, ethylene / vinyl acetate copolymer resins, polyvinyl alcohol resins, ethylene-vinyl alcohol copolymer resins, styrene-butadiene rubber (SBR), nitrile rubber (NBR), and other rubber-based emulsions. Preferably, one or more of the group consisting of polycarbonate resins, acrylic resins, and polyester resins are selected, and more preferably, polycarbonate resins are selected.

[0295] As a polycarbonate-based resin, for example, the polycarbonate copolymer described in Japanese Patent Application Publication No. 2008-24919 can be used.

[0296] The adhesive layer is preferably formed from an adhesive composition containing an adhesive additive (formed using an adhesive composition containing an adhesive additive). Examples of adhesive additives include compounds containing at least one group selected from isocyanate groups, carbodiimide groups, epoxy groups, oxazoline groups, amino groups, and silanol groups. From the viewpoint of excellent adhesion to a cellulose layer containing fine fibrous tissue, the adhesive additive is preferably a compound containing an isocyanate group (isocyanate compound).

[0297] The adhesive composition preferably contains an adhesive and an adhesive aid, more preferably contains one or more selected from the group consisting of polycarbonate resins, acrylic resins and polyester resins, and an isocyanate compound, and even more preferably contains a polycarbonate resin and an isocyanate compound.

[0298] In the adhesive composition, from the viewpoint of improving adhesion, the content of adhesive aid is preferably 5 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of adhesive, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, and even more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less.

[0299] The adhesive composition preferably contains an organic solvent, such as toluene, dichloromethane, tetrahydrofuran, tetraethylene glycol dimethyl ether, dimethyl carbonate, methyl ethyl ketone, ethyl acetate, dimethylacetamide, and styrene.

[0300] From the viewpoint of coating adaptability and solvent removal, the concentration of solid components in the adhesive composition is preferably 1% by mass or more and 25% by mass or less, more preferably 4% by mass or more, even more preferably 7% by mass or more, and even more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0301] <Thickness>

[0302] In this embodiment, the thickness of each adhesive layer is preferably 1 μm or more and 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, even more preferably 20 μm or less, and even more preferably 10 μm or less. The thicknesses of adhesive layer 1a and adhesive layer 1b may be the same or different.

[0303] The thickness of the adhesive layer should preferably be adjusted appropriately according to the intended use of the laminate or laminate.

[0304] <Resin film, protective film>

[0305] The laminated sheet of this embodiment preferably (i) has an adhesive layer 1a and a resin film or protective film sequentially on one side containing a microfibrillated cellulose layer, and (ii) has an adhesive layer 1a and a resin film or protective film sequentially on one side containing a microfibrillated cellulose layer, and an adhesive layer 1b on the other side.

[0306] The resin constituting the resin film can be selected according to the intended use of the laminate or laminate, preferably at least one of the group consisting of polyolefin resin, cyclic olefin resin, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyimide resin, polystyrene resin and acrylic resin, more preferably polycarbonate.

[0307] The protective film is preferably a polyethylene film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyimide film, or a fluoropolymer film. In this embodiment, the protective film can be peeled off during the manufacturing stage of the laminate, and the resin film can be laminated onto the adhesive layer 1a.

[0308] <Thickness>

[0309] In this embodiment, the thickness of each resin film layer is preferably 30 μm or more and 500 μm or less, more preferably 50 μm or more, even more preferably 70 μm or more, and even more preferably 400 μm or less, even more preferably 350 μm or less, even more preferably 300 μm or less, and even more preferably 250 μm or less.

[0310] The thickness of the resin film is preferably adjusted appropriately according to the intended use of the laminate or laminate.

[0311] In this embodiment, the thickness of each protective film is preferably 20 μm or more and 300 μm or less, more preferably 30 μm or more, even more preferably 40 μm or more, and even more preferably 250 μm or less, and even more preferably 200 μm or less.

[0312] [Layered Body]

[0313] In this embodiment, the laminate has a laminate (ii) on at least one side of the core resin board, the laminate having a resin film, the core resin board containing a polycarbonate resin, and the adhesive layer 1b of the laminate being in contact with the core resin board. In the case where the laminate in this embodiment has laminates on both sides of the core resin board, the components, possible components, thickness, density, and basis weight of the layers or films constituting the laminate on one side may be the same as, or different from, the components, possible components, thickness, density, and basis weight of the layers or films constituting the laminate on the other side.

[0314] [Core Material Resin Board]

[0315] The laminate of this embodiment has a core resin plate. The core resin plate contains a polycarbonate-based resin. "Polycarbonate-based resin" refers to a resin containing sites where structural units are repeatedly bonded via carbonate groups (-O-(C=O)-O-).

[0316] From the viewpoint of improving the rigidity of the laminate, the content of polycarbonate resin in the core resin board is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and is 100% by mass or less.

[0317] It should be noted that, in addition to polycarbonate resins, the core material resin board may also contain, for example, acrylonitrile butadiene styrene copolymer and polymethyl methacrylate resin.

[0318] <Thickness>

[0319] In this embodiment, the thickness of each core resin board is preferably 200 μm or more and 4,500 μm or less, more preferably 400 μm or more, further preferably 800 μm or more, and even more preferably 4,000 μm or less, and even more preferably 3,500 μm or less. The thickness of the core resin board is preferably adjusted appropriately according to the intended use of the laminate.

[0320] [Characteristics of laminates]

[0321] [Haze]

[0322] The haze of the laminate (the laminate before heating described later) in this embodiment is preferably 5.0% or less, more preferably 4.0% or less, further preferably 3.0% or less, and even more preferably 1.5% or less. On the other hand, the lower limit of the haze of the laminate can be, for example, 0%.

[0323] The haze difference (haze after heating - haze before heating) of the laminate before and after heating at 170°C for 10 minutes in this embodiment is preferably 2.0% or less, more preferably 1.6% or less, even more preferably 1.2% or less, even more preferably 0.8% or less, even more preferably 0.4% or less, even more preferably 0.3% or less, and can be 0%.

[0324] The haze of a laminate can be controlled by factors such as the fiber width of the microfibrillated cellulose, the type of ionic groups, the amount of ionic groups introduced, the type of hydrophilic polymer, the type of resin constituting the resin film, the content of microfibrillated cellulose and hydrophilic polymer in the microfibrillated cellulose layer, and the thickness of each layer constituting the laminate.

[0325] The haze of the laminate was measured according to JIS K 7136:2000.

[0326] [Yellow Index]

[0327] From the viewpoint of applicability to various applications, the yellowness index (YI value) of the laminate in this embodiment is preferably 4.50 or less, more preferably 3.00 or less, and even more preferably 2.50 or less; the lower limit is not particularly limited. If the YI value is within the above range, it is also possible to obtain a heat-processed product with suppressed yellowing, which is therefore preferred.

[0328] The YI value of the laminate can be controlled by factors such as the fiber width of the microfibrillated cellulose, the type of ionic groups, the amount of ionic groups introduced, the type of hydrophilic polymer, the type of resin constituting the resin film, the content of microfibrillated cellulose and hydrophilic polymer in the microfibrillated cellulose layer, and the thickness of each layer constituting the laminate.

[0329] The YI value of the laminate was determined according to JIS K 7373:2006.

[0330] Total light transmittance

[0331] The total light transmittance of the laminate in this embodiment is preferably 80% or more, more preferably 83% or more, and even more preferably 85% or more. On the other hand, the upper limit of the total light transmittance of the laminate can be, for example, 100%. The total light transmittance of the laminate can be controlled by factors such as the fiber width of the microfibrillary cellulose, the type of ionic groups, the amount of ionic groups introduced, the type of hydrophilic polymer, the type of resin constituting the resin film, the content of microfibrillary cellulose and hydrophilic polymer in the microfibrillary cellulose layer, and the thickness of each layer constituting the laminate.

[0332] The total transmittance of the laminate was measured according to JIS K 7361-1:1997.

[0333] [thickness]

[0334] The thickness of the laminate in this embodiment is preferably 500 μm or more and 5,000 μm or less, more preferably 700 μm or more, even more preferably 900 μm or more, and even more preferably 4,500 μm or less, even more preferably 4,000 μm or less, and even more preferably 3,500 μm or less. The thickness of the laminate is preferably adjusted appropriately according to the application.

[0335] [Manufacturing method of laminated wafers]

[0336] The following laminated sheet is obtained by the laminated sheet manufacturing method of this embodiment.

[0337] The laminate is, (i) having an adhesive layer 1a on one side of a cellulose-containing layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm, and satisfying at least one of conditions A and B below; or

[0338] (ii) The layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm has an adhesive layer 1a on one side and an adhesive layer 1b on the other side, and satisfies at least one of the following conditions C and D.

[0339] Condition A: The total organic solvent content in the microfibrillated cellulose layer and adhesive layer 1a is 0.1 ppm or more and 40 ppm or less by mass.

[0340] Condition B: The content of organic solvents in adhesive layer 1a is 0.5 ppm or more and 200 ppm or less by mass.

[0341] Condition C: The total content of organic solvents in the microfibrillated cellulose layer, adhesive layer 1a, and adhesive layer 1b is 0.1 ppm or more and 60 ppm or less by mass.

[0342] Condition D: The total content of organic solvents in adhesive layers 1a and 1b is between 0.5 ppm and 300 ppm by mass.

[0343] Hereinafter, methods 1 and 2 for manufacturing the laminated sheet according to this embodiment will be described. It should be noted that method 1 is preferred as the method for manufacturing the laminated sheet according to this embodiment.

[0344] The manufacturing method 1 of the laminated wafer includes the following steps 1 and 2.

[0345] Step 1: A process of coating a layer containing microfibrillated cellulose fibers with a width of less than 1,000 nm with a coating solution and then drying it to obtain a layer containing microfibrillated cellulose fibers.

[0346] Step 2: A step in which an adhesive layer 1a or adhesive layer 1b is formed by coating one side of the microfibrillated cellulose layer obtained in Step 1 with an adhesive solution and drying.

[0347] The coating solution for the microfibrillated cellulose layer used in the manufacturing method of the laminated sheet of this embodiment can be obtained by mixing microfibrillated cellulose, water, and a hydrophilic polymer as needed. For example, the coating solution for the microfibrillated cellulose layer can be obtained as follows: in the manufacturing of microfibrillated cellulose, microfibrillated cellulose is obtained in the form of an aqueous dispersion, and this aqueous dispersion is mixed with an aqueous solution of a hydrophilic polymer.

[0348] Furthermore, the adhesive coating liquid used in the manufacturing method of the laminated sheet in this embodiment can dissolve or disperse the components of the desired adhesive layer in an organic solvent, for example, the adhesive composition described above can be used.

[0349] [Process 1]

[0350] In step 1, a coating liquid containing a microfibrillated cellulose layer is applied to a substrate and then dried. The drying temperature is preferably 50°C or higher and 130°C or lower, more preferably 65°C or higher, even more preferably 80°C or higher, and even more preferably 120°C or lower, even more preferably 110°C or lower. The drying time is preferably 5 minutes or higher and 120 minutes or lower, more preferably 15 minutes or higher, even more preferably 30 minutes or higher, and even more preferably 105 minutes or lower, even more preferably 90 minutes or lower.

[0351] Drying can be carried out under atmospheric pressure or under reduced pressure. Furthermore, when performing multiple drying operations, it is preferable that the sum of the drying times at the aforementioned drying temperatures falls within the range described above. Additionally, each drying time is preferably within the range described above. The same applies to the following drying processes.

[0352] As a substrate, polyethylene terephthalate substrate, acrylic resin substrate, polycarbonate substrate, polyethylene substrate, and polyimide substrate can be used.

[0353] [Process 2]

[0354] In step 2, an adhesive layer coating liquid is applied to one side of the microfibrillated cellulose layer obtained in step 1 and dried to form adhesive layer 1a or adhesive layer 1b. The drying temperature is preferably 50°C or higher and 130°C or lower, more preferably 60°C or higher, further preferably 70°C or higher, even more preferably 80°C or higher, even more preferably 90°C or higher, and more preferably 120°C or lower, even more preferably 110°C or lower. The drying time is preferably 1 minute or higher and 120 minutes or lower, more preferably 3 minutes or higher, even more preferably 5 minutes or higher, even more preferably 7 minutes or higher, even more preferably 10 minutes or higher, and more preferably 90 minutes or lower, even more preferably 60 minutes or lower.

[0355] The method for manufacturing the laminated wafer 1 preferably includes the following step 3 after step 2.

[0356] In step 3, an adhesive coating liquid is applied to the other side of the microfibrillated cellulose layer (the side opposite to the side where adhesive layer 1a or adhesive layer 1b is formed) and dried to form adhesive layer 1b or adhesive layer 1a. The drying temperature is preferably 40°C or higher and 100°C or lower, more preferably 50°C or higher, even more preferably 60°C or higher, and even more preferably 90°C or lower, and even more preferably 80°C or lower. The drying time is preferably 1 minute or higher and 120 minutes or lower, more preferably 2 minutes or higher, even more preferably 3 minutes or higher, and even more preferably 90 minutes or lower, and even more preferably 60 minutes or lower.

[0357] In the manufacturing method 1 of the laminated sheet, after step 2 or step 3, an additional heat treatment may be performed to strengthen the adhesion between the adhesive layer and the layer containing microfibrillated cellulose. The heating temperature is preferably 50°C or higher and 120°C or lower, more preferably 70°C or higher and 100°C or lower. The heating time is preferably 5 hours or higher and 150 hours or lower, more preferably 15 hours or higher and 100 hours or lower.

[0358] The method for manufacturing laminates 1 may further include step 4 below after step 2.

[0359] Step 4: Applying a resin film or protective film to adhesive layer 1a or adhesive layer 1b.

[0360] It should be noted that step 4 can be performed after step 2, but it can be performed before or after step 3.

[0361] Method 2 for manufacturing laminated wafers comprises the following steps I and II in sequence.

[0362] Step I: The step of applying an adhesive coating solution onto a resin film and drying it to form adhesive layer 1a.

[0363] Step II: A step of coating the adhesive layer 1a obtained in Step 1 with a coating solution and drying to form a layer containing microfibrillated cellulose.

[0364] [Process I]

[0365] In step I, an adhesive layer coating liquid is applied to a resin film and dried to form adhesive layer 1a. The drying temperature is preferably 50°C or higher and 130°C or lower, more preferably 60°C or higher, further preferably 70°C or higher, and even more preferably 115°C or lower, and even more preferably 100°C or lower. The drying time is preferably 1 minute or higher and 30 minutes or lower, more preferably 3 minutes or higher, even more preferably 5 minutes or higher, and even more preferably 25 minutes or lower, and even more preferably 20 minutes or lower.

[0366] [Process II]

[0367] In step II, a coating solution containing a microfibrillated cellulose layer is applied to the adhesive layer 1a obtained in step I and dried to form a microfibrillated cellulose layer. The drying temperature is preferably 50°C or higher and 130°C or lower, more preferably 65°C or higher, even more preferably 80°C or higher, and even more preferably 120°C or lower, even more preferably 110°C or lower. The drying time is preferably 5 minutes or higher and 120 minutes or lower, more preferably 15 minutes or higher, even more preferably 30 minutes or higher, and even more preferably 105 minutes or lower, even more preferably 90 minutes or lower.

[0368] [Process III]

[0369] Method 2 for manufacturing laminated wafers can have step III after step II.

[0370] Step III: The process of coating an adhesive layer with a coating solution on the cellulose layer containing fine fibrous material obtained in Step 2 and drying it to form adhesive layer 1b.

[0371] The drying temperature in step III is preferably 50°C or higher and 130°C or lower, more preferably 55°C or higher, even more preferably 60°C or higher, and even more preferably 115°C or lower, and even more preferably 100°C or lower. The drying time is preferably 1 minute or higher and 30 minutes or lower, more preferably 3 minutes or higher, even more preferably 5 minutes or higher, and even more preferably 20 minutes or lower, and even more preferably 10 minutes or lower.

[0372] Furthermore, after step III, in order to make the adhesion between the adhesive layer and the cellulose layer containing fine fibers stronger, an additional heat treatment can be performed. The heating temperature is preferably 50°C or higher and 120°C or lower, more preferably 70°C or higher and 100°C or lower. The heating time is preferably 5 hours or higher and 150 hours or lower, more preferably 15 hours or higher and 100 hours or lower.

[0373] [Manufacturing method of laminated bodies]

[0374] The method for manufacturing a laminate in this embodiment (method 1 for manufacturing a laminate) includes any one of the following steps P to S.

[0375] Step P: A step in which a resin film is disposed on the surface of either adhesive layer 1a or adhesive layer 1b of the laminate (adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b) obtained in method 1 of manufacturing laminate, and a core resin board is disposed on the surface of the other adhesive layer and pressure is applied.

[0376] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0377] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0378] The pressurization time is preferably 15 seconds or more and 30 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and even more preferably 20 minutes or less, and even more preferably 10 minutes or less.

[0379] Step Q: A step of placing a core resin board on the adhesive layer 1b of the laminate (resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b) obtained in method 1 of manufacturing laminate and applying pressure.

[0380] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0381] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0382] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0383] Step R: This step involves preparing two laminated sheets (adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b), two resin films, and one core resin board obtained in manufacturing method 1. These are arranged and pressurized in the following order: "resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b - core resin board - adhesive layer 1b - microfibrillated cellulose layer - adhesive layer 1a - resin film" or "resin film - adhesive layer 1b - microfibrillated cellulose layer - adhesive layer 1a - core resin board - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b - resin film".

[0384] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0385] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0386] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0387] Step S: This step involves preparing two laminated sheets (resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b) and one core resin board obtained in manufacturing method 1, arranging them in the order of "resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b - core resin board - adhesive layer 1b - microfibrillated cellulose layer - adhesive layer 1a - resin film" and then applying pressure to them.

[0388] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0389] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0390] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0391] Another method for manufacturing a laminate in this embodiment (method 2 for manufacturing a laminate) includes the following steps T and U or V.

[0392] Process T: The process of applying an adhesive coating solution onto a resin film and drying it to form adhesive layer 1a.

[0393] The drying temperature is preferably 50°C or higher and 130°C or lower, more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably 115°C or lower, and even more preferably 100°C or lower. The drying time is preferably 1 minute or higher and 30 minutes or lower, more preferably 3 minutes or higher, even more preferably 5 minutes or higher, and even more preferably 25 minutes or lower, and even more preferably 20 minutes or lower.

[0394] Step U: The laminated sheet (containing a microfibrillated cellulose layer - adhesive layer 1b) obtained in step 1, the laminated sheet (resin film - adhesive layer 1a) obtained in step T, and the core resin board are arranged and pressurized in the order of "resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b - core resin board".

[0395] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0396] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0397] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0398] Step V: This step involves arranging and pressing together two laminated sheets (containing a microfibrillated cellulose layer and an adhesive layer 1b) obtained in step 1, two laminated sheets (containing a resin film and an adhesive layer 1a) obtained in step T, and one core resin board in the following order: "resin film - adhesive layer 1a - microfibrillated cellulose layer - adhesive layer 1b - core resin board - adhesive layer 1b - microfibrillated cellulose layer - adhesive layer 1a - resin film".

[0399] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0400] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0401] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0402] Another method for manufacturing a laminate in this embodiment (method 3 for manufacturing a laminate) includes the following steps W or X.

[0403] Step W: A step of placing a core resin board on the adhesive layer 1b of the laminate (resin film-adhesive layer 1a-microfibrillated cellulose layer-adhesive layer 1b) obtained in step 2 of manufacturing method 2, and then applying pressure.

[0404] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0405] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0406] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0407] Step X: A step in manufacturing method 2 involving the arrangement of two laminated sheets (resin film-adhesive layer 1a-microfibrillated cellulose layer-adhesive layer 1b) and one core resin board in the order of "resin film-adhesive layer 1b-microfibrillated cellulose layer-adhesive layer 1a-resin film" and pressing them together.

[0408] The pressure is preferably 0.1 MPa or more and 10 MPa or less, more preferably 0.3 MPa or more, even more preferably 0.5 MPa or more, and even more preferably 7.5 MPa or less, and even more preferably 5.0 MPa or less.

[0409] The temperature during pressurization is preferably 130°C or higher and 190°C or lower, more preferably 135°C or higher, even more preferably 140°C or higher, and even more preferably 185°C or lower, and even more preferably 180°C or lower.

[0410] The pressurization time is preferably 15 seconds or more and 60 minutes or less, more preferably 30 seconds or more, even more preferably 1 minute or more, and more preferably 40 minutes or less, even more preferably 20 minutes or less.

[0411] The laminate having the laminate of this embodiment is suitable for use in optical components of various display devices, various solar cells, etc. It is also suitable for use as substrates for electronic devices, separators for electrochemical components, components for home appliances, various vehicles, window materials for buildings, interior materials, exterior materials, packaging consumables, and other applications.

[0412] [Manufacturing method for heat-worked products]

[0413] The laminate having the laminate of this embodiment can be heat-processed to produce a heat-processed article of a desired shape. The method for manufacturing the heat-processed article of this embodiment includes a step of heat-processing the laminate. In the heat-processing step, for example, the laminate is heated and formed by stamping while pressed into a mold (hot pressing), or it is bent (hot bending), thereby obtaining a heat-processed article of a desired shape.

[0414] The heating temperature for hot working is preferably 140°C or higher and 200°C or lower, more preferably 150°C or higher, even more preferably 160°C or higher, and even more preferably 190°C or lower, and even more preferably 180°C or lower.

[0415] The heating time can be, for example, more than 1 minute and less than 30 minutes, more than 2 minutes or more than 3 minutes, and less than 20 minutes or less than 10 minutes.

[0416] In addition, the bending radius during hot working can be, for example, 10 mm or more and 4,000 mm or less, 30 mm or more, 50 mm or more, and 3,000 mm or less or 2,000 mm or less.

[0417] Examples of the aforementioned heat-processed products include transparent components or constituent elements of transparent components such as windows of various transport aircraft, display devices, lenses, transparent containers and light-transmitting substrates, windows of buildings, interior materials, and exterior materials.

[0418] Example

[0419] The following examples and comparative examples further illustrate the features of the present invention. The materials, amounts, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited by the specific examples shown below. It should be noted that, unless otherwise specified, the following operations are performed at room temperature (23°C) and a relative humidity of 50%.

[0420] <Preparation Example 1 (Preparation of Microfibrillated Cellulose Dispersion)>

[0421] (Phosphorylation)

[0422] As the raw material pulp, hardwood dissolving pulp (dry pulp flakes) manufactured by Oji Paper Co., Ltd. was used. This raw material pulp was then subjected to phosphorylation treatment as follows: First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by weight (absolute dry weight) of the above-mentioned raw material pulp, adjusting the composition to 45 parts by weight of ammonium dihydrogen phosphate, 120 parts by weight of urea, and 150 parts by weight of water, to obtain a solution-impregnated pulp. Next, the obtained solution-impregnated pulp was heated in a hot air dryer at 165°C for 250 seconds to introduce phosphate groups into the cellulose in the pulp, resulting in phosphoric acid pulp.

[0423] (Cleaning process)

[0424] Next, the obtained phosphorylated pulp was washed. The washing process was carried out as follows: a pulp dispersion obtained by adding 100g (absolute dry weight) of phosphorylated pulp to 10L of ion-exchanged water was stirred to ensure uniform dispersion of the pulp, and then the process of filtration and dewatering was repeated. The washing endpoint was defined as the point at which the conductivity of the filtrate reached below 100μS / cm.

[0425] (Neutralization treatment)

[0426] Next, the washed phosphoric acid pulp was neutralized as follows. First, the washed phosphoric acid pulp was diluted with 10L of deionized water, and then 1N sodium hydroxide aqueous solution was added little by little while stirring, thereby obtaining a phosphoric acid pulp with a pH of 12 or higher and 13 or lower. Next, the phosphoric acid pulp was dewatered to obtain the neutralized phosphoric acid pulp. Then, the neutralized phosphoric acid pulp was subjected to the washing process described above.

[0427] (Nitrogen removal treatment)

[0428] A 4% by mass solids concentration was prepared by adding ion-exchanged water to phosphorylated pulp. A 48% by mass sodium hydroxide aqueous solution was added to the pulp to adjust the pH to 13.4, and the mixture was heated at 85°C for 1 hour. The pulp was then dewatered, and 100g (absolute dry weight) of phosphorylated pulp was added to 10L of ion-exchanged water to obtain a pulp dispersion. This dispersion was stirred to ensure uniform pulp distribution, and then filtered for dewatering. This process was repeated to remove excess sodium hydroxide. The endpoint of sodium hydroxide removal was defined as the point at which the conductivity of the filtrate fell below 100 μS / cm. It should be noted that the amount of urea introduced, determined by the nitrogen content as described later, was 0.01 mmol / g.

[0429] The resulting phosphorus-containing oxygen-acidified pulp was subjected to infrared absorption spectroscopy using FT-IR. The results showed that the absorption spectrum was within the range of 1230 cm⁻¹. -1 Absorption at P=O based on phosphate groups was observed nearby, confirming the addition of phosphate groups to the pulp. Furthermore, the resulting phosphorylated pulp was analyzed using X-ray diffraction, and characteristic peaks were identified at two locations: approximately 2θ = 14° to 17° and 2θ = 22° to 23°, confirming the maintenance of cellulose type I crystals. It should be noted that the amount of phosphate groups (first dissociated acid content) measured by the method described later was 1.45 mmol / g. It should also be noted that the total dissociated acid content was 2.45 mmol / g.

[0430] (fiber disassembly treatment)

[0431] Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a pulp with a solids content of 2% by mass. The pulp was then treated six times with a wet micronization apparatus (SUGINO MACHINE LIMITED, Starburst) at a pressure of 200 MPa to obtain a microfibrillated cellulose dispersion containing microfibrillated cellulose.

[0432] (Substituent removal treatment (high-temperature heat treatment))

[0433] A 20% (w / w) aqueous solution of citric acid was added to the obtained fine fibrous cellulose dispersion to adjust the pH of the dispersion to 5.5. Subsequently, the fine fibrous cellulose dispersion was placed in a pressure-resistant container and heated at 160°C for 15 minutes until the phosphate content reached 0.08 mmol / g. This operation confirmed the formation of fine fibrous cellulose aggregates.

[0434] (Cleaning treatment of slurry after removal of substituents)

[0435] An equal volume of ion-exchanged water was added to the heated slurry to prepare a slurry with a solids concentration of approximately 1% by mass. After stirring, the slurry was filtered and dehydrated, and this process was repeated to wash the slurry. When the conductivity of the filtrate fell below 10 μS / cm, ion-exchanged water was added again to prepare a slurry with a solids concentration of approximately 1% by mass, and the slurry was allowed to stand for 24 hours. The filtration and dehydration process was then repeated until the conductivity of the filtrate fell below 10 μS / cm again, which was taken as the washing endpoint. Ion-exchanged water was added to the resulting fine fibrous cellulose aggregates to obtain a slurry with desubstituents removed. The solids concentration of this slurry was 1.7% by mass.

[0436] (Uniform dispersion of the slurry after removal of substituents)

[0437] After removing the substituents, ion-exchanged water was added to the resulting slurry to prepare a slurry with a solid content concentration of 1.0% by mass. This slurry was then treated three times using a wet micronization apparatus (SUGINO MACHINE LIMITED, Starburst) at a pressure of 200 MPa to obtain a dispersion of substituent-removed microfibrillary cellulose. The fiber width of the microfibrillary cellulose was measured using a transmission electron microscope, and the result was 3–5 nm. Furthermore, ion-exchanged water was added to the dispersion of substituent-removed microfibrillary cellulose to obtain a dispersion of microfibrillary cellulose with a solid content concentration of 0.5% by mass.

[0438] (Determination of phosphorus oxyacid content)

[0439] Regarding the phosphorus oxyacid content (equal to that of phosphorus oxyacid- ...

[0440] The treatment using ion exchange resin is carried out as follows: 1 / 10 by volume of a strong acid ion exchange resin (Amberjet 1024; manufactured and adjusted by Organo Corporation) is added to the above slurry containing fine fibrous cellulose. After shaking for 1 hour, the resin is poured onto a 90 μm mesh screen to separate the ion exchange resin from the slurry.

[0441] Additionally, the titration using alkali was performed as follows: In a slurry containing fine fibrous cellulose treated with ion exchange resin, 10 μL of a 0.1N sodium hydroxide aqueous solution was added every 5 seconds, while the change in pH value displayed by the slurry was measured. It should be noted that the titration was performed while nitrogen gas was blown into the slurry starting 15 minutes before the titration began. In this neutralization titration, in the pH curve plotted relative to the amount of alkali added, two points were observed where the increment (the differential value of pH relative to the amount of alkali added) was extremely large. The point where the increment was most large at the beginning of alkali addition is called the first endpoint, and the point where the increment was most large afterward is called the second endpoint. Figure 1 The amount of alkali required from the start of titration to the first endpoint is equal to the amount of the first dissociated acid in the slurry used for titration. Furthermore, the amount of alkali required from the start of titration to the second endpoint is equal to the total amount of dissociated acid in the slurry used for titration. It should be noted that the amount of alkali required from the start of titration to the first endpoint (mmol) is divided by the solid content (g) of the slurry being titrated, and the value obtained is taken as the amount of phosphorus oxyacid (mmol / g). Additionally, the amount of alkali required from the start of titration to the second endpoint (mmol) is divided by the solid content (g) of the slurry being titrated, and the value obtained is taken as the total amount of dissociated acid (mmol / g).

[0442] It should be noted that the phosphorus oxyacid group content (phosphorus oxyacid group introduction amount) (mmol / g) indicates that the counter ion of the phosphorus oxyacid group is the hydrogen ion (H). + The amount of substituents per 1g mass of fine fibrous cellulose at that time.

[0443] (Determination of urea content)

[0444] The urea content of the microfibrillated cellulose was determined by testing a freeze-dried and pulverized sample using a TN-110 trace total nitrogen analyzer manufactured by Mitsubishi Chemical Analytical Technology Co., Ltd. It should be noted that ionic nitrogen was removed during neutralization and washing processes. The amount of urea introduced per unit mass of microfibrillated cellulose (mmol / g) was calculated by dividing the nitrogen content per unit mass of microfibrillated cellulose (g / g) obtained from trace nitrogen analysis by the atomic weight of nitrogen.

[0445] <Preparation Example 2 (Preparation of Hydroxypropyl Methylcellulose Aqueous Solution)>

[0446] Hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Industry Co., Ltd., Metrolose 65SH-1500, weight average molecular weight: 2.2×10⁻⁶) was obtained. 5 (Degree of substitution (methoxy): 1.8, Number of moles of substitution (hydroxypropoxy): 0.15) was dissolved in ion-exchanged water to obtain an aqueous solution of hydroxypropyl methylcellulose (solid component concentration 0.5% by mass).

[0447] <Preparation Example 3 (Preparation of Polyvinyl Alcohol Aqueous Solution)>

[0448] Acetylacetyl-modified polyvinyl alcohol (manufactured by Mitsubishi Chemical Corporation, GOHSENX (registered trademark) Z-300) was added to ion-exchanged water at a concentration of 12% by mass, and the mixture was stirred at 95°C for 1 hour to obtain an aqueous solution of polyvinyl alcohol. The aqueous solution of polyvinyl alcohol was diluted with ion-exchanged water to a solids concentration of 0.5% by mass.

[0449] <Preparation Example 4 (Preparation of Mixture 1)>

[0450] Mixture 1 was prepared by mixing 70 parts by mass of a fine fibrous cellulose dispersion (solid component concentration 0.5 by mass) with 30 parts by mass of an aqueous solution of hydroxypropyl methylcellulose (solid component concentration 0.5 by mass).

[0451] <Preparation Example 5 (Preparation of Mixture 2)>

[0452] Mixture 2 was prepared by mixing 70 parts by mass of a fine fibrous cellulose dispersion (0.5% by mass of solids) with 15 parts by mass of an aqueous solution of hydroxypropyl methylcellulose (0.5% by mass of solids) and 15 parts by mass of an aqueous solution of polyvinyl alcohol (0.5% by mass of solids) to obtain mixture 2.

[0453] <Preparation Example 6 (Preparation of Mixture 3)>

[0454] A mixture 3 was prepared by mixing 70 parts by mass of a fine fibrous cellulose dispersion (0.5% by mass of solids) with 21 parts by mass of an aqueous solution of hydroxypropyl methylcellulose (0.5% by mass of solids) and 9 parts by mass of an aqueous solution of polyvinyl alcohol (0.5% by mass of solids) to obtain a mixture 3.

[0455] <Preparation Example 7 (Preparation of Mixture 4)>

[0456] Mixture 4 was prepared by mixing 70 parts by weight of a fine fibrous cellulose dispersion (solid component concentration 0.5 by weight) with 30 parts by weight of a polyvinyl alcohol aqueous solution (solid component concentration 0.5 by weight).

[0457] <Preparation Example 8 (Preparation of Mixture 5)>

[0458] Mixture 5 was prepared by mixing 50 parts by mass of a polyvinyl alcohol aqueous solution (0.5% by mass) with 50 parts by mass of a microfibrillated cellulose dispersion (0.5% by mass of solids) to obtain mixture 5.

[0459] <Preparation Example 9 (Preparation of Mixture 6)>

[0460] Mixture 6 was prepared by mixing 30 parts by mass of a fine fibrous cellulose dispersion (solid component concentration 0.5 by mass) with 70 parts by mass of an aqueous solution of hydroxypropyl methylcellulose (solid component concentration 0.5 by mass).

[0461] <Preparation Example 10 (Preparation of Coating Liquid for Adhesive Layer)>

[0462] 8.5 parts by weight of modified polycarbonate resin (Iupizeta FPC-2136, manufactured by Mitsubishi Gas Chemical Co., Ltd.), 60 parts by weight of toluene, and 30 parts by weight of methyl ethyl ketone were mixed. 1.5 parts by weight of isocyanate compound (DURANATE TPA-100, manufactured by Asahi Kasei Chemicals Co., Ltd.) as an adhesive additive were added to the resulting mixture and mixed to obtain a coating liquid for the adhesive layer.

[0463] <Example 1>

[0464] [Fabrication of laminated wafers]

[0465] (Including the preparation of microfibrillated cellulose sheets)

[0466] A frame for fencing (internal dimensions 250mm × 250mm) was installed on a commercially available acrylic sheet. The frame was peeled off from the acrylic sheet to obtain a single layer of microfibrillated cellulose sheet; the microfibril height was 5cm. The final basis weight was 50g / m³. 2 The mixture was developed using the following method. After development, it was dried in a dryer at 100°C for 1 hour, resulting in a fibrous cellulose sheet thickness of 34 μm.

[0467] (Formation of the adhesive layer)

[0468] Using a rod coater, an adhesive layer coating solution was applied to one side of the microfibrillated cellulose sheet (the side in contact with the acrylic sheet). Then, the coating solution was heated at 100°C for 30 minutes to cure, forming adhesive layer 1b. Next, the adhesive layer coating solution was also applied to the opposite side of the microfibrillated cellulose sheet using a rod coater, and then heated at 70°C for 30 minutes to cure, forming adhesive layer 1a, thus obtaining a laminated sheet. The thickness of both adhesive layer 1a and adhesive layer 1b is 3 μm.

[0469] [Manufacturing of laminates]

[0470] Cut a laminated sheet with adhesive layers 1a and 1b using a cutter to create a 50mm x 50mm laminated sheet. Next, prepare one 100mm x 100mm core resin board cut from a commercially available 1mm thick polycarbonate sheet, and two 50mm x 50mm resin films cut from a commercially available 0.2mm thick polycarbonate film. Overlap these sheets in the following order: resin film / adhesive layer 1a / microfibrillated cellulose layer / adhesive layer 1b / core resin board / adhesive layer 1b / microfibrillated cellulose layer / adhesive layer 1a / resin film. Align the center of the resin film and the laminated sheet with the center of the core resin board. Clamp it with a 1mm thick, 200mm x 200mm stainless steel plate and insert it into a small-scale testing press (MP-WCH, Toyo Seiki Co., Ltd.) set to room temperature. A small-scale testing press was used to heat the material to 150°C over 3 minutes at a pressing pressure of 1 MPa, held at this temperature for 5 minutes, and then cooled to 30°C over 5 minutes. It should be noted that the stainless steel sheet used was coated with a release agent (manufactured by Audec Corporation, TEFRELEASE) on the clamping surface. Through the above steps, a laminate was obtained.

[0471] Manufacturing of hot-bent products

[0472] The laminated body is placed in a dryer set to 170°C and left to stand for 5 minutes. Then, it is pressed and fixed in a frame with a specified radius of curvature (R=120mm) at 170°C. It is then cooled while pressed in the frame and removed from the frame to obtain a heat-bent product with curvature.

[0473] <Example 2>

[0474] In Example 1, [Formation of Adhesive Layer], after forming a laminate containing a microfibrillated cellulose layer having adhesive layer 1a and adhesive layer 1b, the laminate was placed in a dryer set to 80°C and left to stand for 40 hours for additional heat treatment. In Example 1, [Manufacturing of Laminated Body], instead of a core resin board (100mm × 100mm × 1mm), a 100mm × 100mm core resin board was cut from a commercially available polycarbonate board with a thickness of 3mm, and instead of a resin film (50mm × 50mm × 0.2mm), two 50mm × 50mm resin films were cut from a commercially available polycarbonate film with a thickness of 0.1mm. Otherwise, laminated sheets, laminated bodies, and heat-bent products with curvature were obtained in the same manner as in Example 1.

[0475] <Example 3>

[0476] In Example 1 (Preparation of microfibrillated cellulose sheets), mixture 2 was used instead of mixture 1. Otherwise, laminated sheets, laminates and heat-bent products with curvature were obtained in the same manner as in Example 1.

[0477] <Example 4>

[0478] In Example 1 (Preparation of microfibrillated cellulose sheets), mixture 3 was used instead of mixture 1. Otherwise, laminated sheets, laminated bodies, and heat-bent products with curvature were obtained in the same manner as in Example 1.

[0479] <Example 5>

[0480] A frame for fencing (internal dimensions 250mm x 250mm, height 5cm) is installed on a commercially available acrylic sheet, resulting in a final basis weight of 35g / m². 2 The mixture 1 was developed using the following method. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1b containing fine fibrous cellulose. A frame (internal dimensions 250mm × 250mm, height 5cm) was placed on the layer 1b containing fine fibrous cellulose for enclosure, with a basis weight of 15g / m³. 2 The mixture 4 was developed in a manner similar to that described in Example 1. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1a containing microfibrillated cellulose. The stacked layers 1a and 1b containing microfibrillated cellulose were peeled off from the acrylic sheet to obtain a two-layer microfibrillated cellulose sheet. In the [formation of the adhesive layer] of Example 1, after forming a two-layer microfibrillated cellulose sheet with adhesive layer 1a and adhesive layer 1b, the stacked sheet was placed in a dryer set to 80°C and left to stand for 40 hours for additional heat treatment. In the [manufacturing of the laminate] of Example 1, a two-layer microfibrillated cellulose sheet with additional heat treatment was used instead of a single-layer microfibrillated cellulose sheet. Otherwise, the stacked sheet, the laminated body, and the heat-bent product with curvature were obtained in the same manner as in Example 1.

[0481] <Example 6>

[0482] In Example 5, the drying conditions of adhesive layer 1a were changed from "70°C for 30 minutes" to "60°C for 5 minutes". Otherwise, the laminate, laminate and hot-bent product with curvature were obtained in the same manner as in Example 5.

[0483] <Example 7>

[0484] In Example 5, mixture 5 is used instead of mixture 4, and no additional heating treatment is performed on the laminated sheet. Otherwise, the laminated sheet, laminated body and hot-bent product with curvature are obtained in the same manner as in Example 5.

[0485] <Example 8>

[0486] In Example 1 (Preparation of microfibrillated cellulose sheets), the final basis weight was 50 g / m³. 2 Using mixture 6 instead of mixture 1, otherwise, the same as in Example 1, laminated sheets, laminated bodies and hot-bent products with curvature are obtained.

[0487] <Comparative Example 1>

[0488] In Example 1 (formation of the adhesive layer), the adhesive coating liquid was applied only to one side (the side not in contact with the acrylic sheet) of the single-layer microfibrillated cellulose sheet. The adhesive coating liquid was heated at 90°C for 3.3 minutes and at 80°C for 6.6 minutes to cure and form adhesive layer 1b. Adhesive layer 1a was not formed. Otherwise, the laminate was obtained in the same manner as in Example 1.

[0489] An adhesive coating liquid is applied to a resin film, and the film is heated at 70°C for 7.5 minutes to cure the adhesive coating liquid and form adhesive layer 1a. This process is repeated in the same manner as in [Manufacturing of the Laminate] of Example 1, resulting in a laminate consisting of a resin film, adhesive layer 1a, a layer containing microfibrillated cellulose, adhesive layer 1b, a core resin board, adhesive layer 1b, a layer containing microfibrillated cellulose, adhesive layer 1a, and a resin film. Furthermore, a laminate with curvature is obtained in the same manner as in [Manufacturing of a Hot-Bent Product] of Example 1.

[0490] <Comparative Example 2>

[0491] A frame for fencing (internal dimensions 250mm x 250mm, height 5cm) is installed on a commercially available acrylic sheet, with a final basis weight of 15g / m². 2 The mixture was developed using the following method: 4. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1a containing fine fibrous cellulose. A frame (internal dimensions 250mm × 250mm, height 5cm) was placed on the layer 1a containing fine fibrous cellulose for enclosure, with a basis weight of 35g / m³. 2 The mixture 1 was developed in a manner similar to that of Comparative Example 1. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1b containing microfibrillated cellulose. Using the two-layer microfibrillated cellulose sheet obtained in this step, a laminate consisting of a resin film / adhesive layer 1a / microfibrillated cellulose layer 1a / microfibrillated cellulose layer 1b / adhesive layer 1b / core resin board / adhesive layer 1b / microfibrillated cellulose layer 1b / microfibrillated cellulose layer 1a / adhesive layer 1a / resin film and a laminate with curvature were obtained.

[0492] <Comparative Example 3>

[0493] In Example 1 (Preparation of Microfibrillated Cellulose Sheets) and (Formation of Adhesive Layer), firstly, an adhesive layer coating liquid was applied to a 0.2 mm thick resin film using a rod coater. The coating liquid was heated at 90°C for 3.3 minutes and then at 80°C for 6.6 minutes to cure, forming adhesive layer 1a. The final basis weight of adhesive layer 1a was 50 g / m³. 2 The mixture 1 was developed using the following method. After development, it was dried in a dryer at 100°C for 1 hour to form a single layer containing microfibrillated cellulose. An adhesive coating liquid was then applied to the single layer containing microfibrillated cellulose using a rod coater. The mixture was heated at 70°C for 7.5 minutes to cure the adhesive coating liquid, forming adhesive layer 1b.

[0494] Using a core resin sheet (100mm × 100mm × 1mm) cut from a commercially available polycarbonate sheet, a laminate consisting of layers of resin film / adhesive layer 1a / fiber-containing cellulose sheet / adhesive layer 1b / core resin sheet / adhesive layer 1b / fiber-containing cellulose sheet / adhesive layer 1a / resin film was obtained in the same manner as in [manufacturing of laminate] of Example 1. Furthermore, a laminate with curvature was obtained in the same manner as in [manufacturing of hot-bent processed article] of Example 1.

[0495] <Comparative Example 4>

[0496] In Comparative Example 3, instead of "the final basis weight on adhesive layer 1a is 50 g / m", 2 The mixture 1” is prepared by spreading it in the manner of adhesive layer 1a, and the final basis weight is 15 g / m 2 The mixture was developed using the following method: 5. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1a containing fine fibrous cellulose. The final basis weight of the layer 1a containing fine fibrous cellulose was 35 g / m³. 2 The mixture 1 was developed using a specific method. After development, it was dried in a dryer at 100°C for 1 hour to form a layer 1b containing microfibrillated cellulose, resulting in a two-layer microfibrillated cellulose layer. An adhesive coating liquid was applied to the two-layer microfibrillated cellulose layer using a rod coater. The coating liquid was heated at 70°C for 7.5 minutes to cure, forming adhesive layer 1b. Otherwise, a laminate consisting of a resin film / adhesive layer 1a / microfibrillated cellulose layer 1a / microfibrillated cellulose layer 1b / adhesive layer 1b / core resin board / adhesive layer 1b / microfibrillated cellulose layer 1b / microfibrillated cellulose layer 1a / adhesive layer 1a / resin film and a laminate with curvature were obtained similarly to Comparative Example 3.

[0497] <Comparative Example 5>

[0498] In Comparative Example 4, a resin film with a thickness of 0.3 mm was used instead of a resin film with a thickness of 0.2 mm. Otherwise, a laminate and a hot-bent product with curvature were obtained in the same manner as in Comparative Example 4.

[0499] <Comparative Example 6>

[0500] Using only a 1.5 mm thick polycarbonate sheet, bending was performed under the same conditions as in Example 1 [Manufacturing of Hot Bending Products] to obtain a polycarbonate sheet with curvature.

[0501] <Comparative Example 7>

[0502] In the [manufacturing of the laminate] of Example 1, the process of (forming the adhesive layer) is omitted. In the [manufacturing of the laminate], the resin film, the core resin board, and the layer containing microfibrillated cellulose are not bonded after hot pressing, and a laminate cannot be obtained. Therefore, the [manufacturing of hot-bent articles] cannot be carried out.

[0503] <Measurement and Evaluation>

[0504] (Including the thickness of the microfibrillated cellulose layer)

[0505] In Examples 1-4, 8, and Comparative Example 1, the thickness of the cellulose sheet containing microfibrils before the adhesive layer was applied was measured using a stylus-type thickness gauge (Millitron 1202D, manufactured by Mahr GmbH). In Comparative Example 7, the thickness of the cellulose sheet containing microfibrils obtained during the preparation of the cellulose sheet containing microfibrils was measured.

[0506] In Examples 5-7 and Comparative Example 2, the thickness of the two-layer cellulose sheet containing fine fibrous material was measured before the adhesive layer was formed. Furthermore, the thickness of each layer was calculated considering the expected final basis weight ratio.

[0507] In Comparative Example 3, the thickness was measured during the stage of forming a resin film-adhesive layer 1a-fiber cellulose layer, and the thickness of the resin film and the thickness of adhesive layer 1a were subtracted from the thickness to calculate the thickness of the fiber cellulose layer.

[0508] In Comparative Examples 4 and 5, the thicknesses (1), (2), and (3) were measured at the stages of forming the resin film-adhesive layer 1a, forming the resin film-adhesive layer 1a-containing microfibrillated cellulose layer 1a, and forming the resin film-adhesive layer 1a-containing microfibrillated cellulose layer 1a-containing microfibrillated cellulose layer 1b. The thickness of the microfibrillated cellulose layer 1a was calculated by subtracting the thickness of (1) from (2). The thickness of the microfibrillated cellulose layer 1b was calculated by subtracting the thickness of (2) from (3).

[0509] (Thickness of the adhesive layer)

[0510] In all embodiments 1 to 8, firstly, the thickness of adhesive layer 1b is calculated by subtracting the thickness of the cellulose layer containing microfibrillary fibers, as measured by the above method, from the thickness of the laminate containing adhesive layer 1b. Secondly, the thickness of adhesive layer 1a is calculated by subtracting the sum of the thicknesses of adhesive layer 1b and the cellulose layer containing microfibrillary fibers from the thickness of the laminate containing adhesive layer 1a and adhesive layer 1b.

[0511] In Comparative Examples 1 and 2, the thickness of adhesive layer 1a was calculated by subtracting the thickness of the resin film from the thickness of the resin film to which adhesive layer 1a is provided. Furthermore, the thickness of adhesive layer 1b was calculated by subtracting the thickness of the microfibrillated cellulose layer, as measured by the above method, from the thickness of the laminate.

[0512] In Comparative Examples 3-5, the thicknesses (1), (2), and (3) of the resin film-adhesive layer 1a, the resin film-adhesive layer 1a-containing microfibrillated cellulose layer, and the resin film-adhesive layer 1a-containing microfibrillated cellulose layer-adhesive layer 1b were measured using a stylus-type thickness gauge (Millitron 1202D, Mahr GmbH). The thickness of adhesive layer 1a was calculated by subtracting the thickness of the resin film from (1). The thickness of adhesive layer 1b was calculated by subtracting (2) from (3).

[0513] (Amount of organic solvent)

[0514] In Examples 1-8, each test piece (40mm × 50mm) of a cellulose sheet containing microfibrillated fibers (laminated sheet) with adhesive layer 1a and adhesive layer 1b was further subdivided into 10mm × 50mm pieces. The subdivided samples from Examples 1-8 were placed in 20mL headspace vials and sealed, and analyzed using headspace gas chromatography. The sample was heated at 80°C for 20 minutes using a headspace sampler (manufactured by Agilent Technologies, Inc., 7697A), and the gas production was measured using a gas chromatograph (manufactured by Agilent Technologies, Inc., 7890A). The organic solvent detected by this method was quantified, and the amount of organic solvent (experimentally measured value) was calculated. The "Amount of Organic Solvent (converted to each adhesive layer)" in Table 1 was calculated using "[Amount of Organic Solvent (experimentally measured value) × Thickness of the laminate] / [Sum of the thicknesses of adhesive layer 1a and adhesive layer 1b]".

[0515] In Comparative Examples 1 and 2, the resin film with adhesive layer 1a and the cellulose sheet containing fine fibrous material with adhesive layer 1b were cut into 40mm × 50mm test pieces, which were then further subdivided into 10mm × 50mm pieces. Each subdivided piece from Comparative Examples 1 and 2 was placed in a 20mL headspace vial, and the organic solvent was detected and quantified using the same method as in Examples 1-8. The obtained value was recorded as A. Additionally, for the resin film without an adhesive layer, the same method was used for detection and quantification, and the resulting value was recorded as A'. The "Amount of Organic Solvent (Experimental Measured Value)" in Table 1 is a value calculated from "A-A'".

[0516] In addition, the "Amount of organic solvent (converted to each adhesive layer)" in Table 1 is calculated by "[Amount of organic solvent (experimental measured value) × (Sum of the thicknesses of adhesive layer 1a and adhesive layer 1b, including microfibrillated cellulose sheets)] / [Sum of the thicknesses of adhesive layer 1a and adhesive layer 1b]".

[0517] In Comparative Examples 3-5, each test piece consisting of a resin film, an adhesive layer 1a, a microfibrillated cellulose layer, and an adhesive layer 1b was cut into 40mm × 50mm pieces and further subdivided into 10mm × 50mm pieces. Each subdivided piece from Comparative Examples 3-5 was placed in a 20mL headspace vial, and the organic solvent was detected and quantified using the same method as in Examples 1-8. The obtained value was recorded as B. Additionally, for the resin film without an adhesive layer, the value obtained by detection and quantification using the same method was recorded as B'. The "Amount of Organic Solvent (Experimental Measured Value)" in Table 1 is a value calculated from "B - B'".

[0518] In addition, the "Amount of organic solvent (converted to each adhesive layer)" in Table 1 is calculated by "[Amount of organic solvent (experimental measured value) × (Sum of the thicknesses of adhesive layer 1a and adhesive layer 1b, including microfibrillated cellulose sheets)] / [Sum of the thicknesses of adhesive layer 1a and adhesive layer 1b]".

[0519] (Transparency of laminates)

[0520] The total transmittance of the laminate was measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute, Co., Ltd.) according to JIS K 7361-1:1997. Furthermore, the haze (%) of the laminate before and after heating was evaluated according to JIS K 7136:2000. It should be noted that the haze after heating is defined as the haze of the laminate heated at 170°C for 10 minutes. The difference in haze between the laminate before and after heating was calculated using the following method.

[0521] Difference in haze (%) between the laminates before and after heating = Haze of the laminate after heating (%) - Haze of the laminate before heating (%)

[0522] (Yellowness index (YI value) of laminates)

[0523] The yellowness of laminates was determined using a Colour Cute i (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7373:2006.

[0524] (Presence or absence of air bubbles in hot-bent products)

[0525] The number of air bubbles generated in hot-bent products is evaluated according to the following criteria. A is acceptable.

[0526] A: The number of bubbles generated in the hot bending process is 0.

[0527] B: The number of air bubbles generated in the hot-bent product is more than 1 and less than 10.

[0528] C: More than 10 air bubbles are generated in the hot-bent product.

[0529] (Visibility of hot-bent products)

[0530] The visibility of hot-bent products should be evaluated according to the following criteria.

[0531] A: The image seen through the hot-bent product shows no distortion whatsoever.

[0532] B: The image seen through the hot-bent workpiece shows almost no distortion.

[0533] C: Images seen through hot-bent products show less distortion.

[0534] D: Image distortion seen through a hot-bent workpiece.

[0535] E: Images seen through hot-bent workpieces show significant distortion.

[0536] (Rigidity of hot-bent products)

[0537] The rigidity of hot-bent products is evaluated according to the following criteria.

[0538] A: To deform a hot-bent product, a very large force is required.

[0539] B: A large force is required to deform a hot-bent product.

[0540] C: To deform a hot-bent product, less force is required.

[0541] D: Products processed by hot bending are prone to deformation.

[0542] [Table 1]

[0543]

[0544] [Table 2]

[0545]

[0546] (Table notes)

[0547] PC: Polycarbonate

[0548] CNF layer: Contains a layer of fine fibrous cellulose

[0549] HPMC: Hydroxypropyl Methylcellulose

[0550] PVA: Polyvinyl alcohol

[0551] Thickness of adhesive layer 1a: 3μm

[0552] Thickness of adhesive layer 1b: 3μm

[0553] As shown in Table 1, the heat-bent processed articles of the laminates having the laminates of the present invention are less prone to bubble formation (Examples 1-8). In contrast, according to Table 2, Comparative Examples 1-5, where conditions C and D specified in the present invention are not met, produce bubbles, and the haze also increases as a result. In addition, the polycarbonate sheet has poor rigidity (Comparative Example 6).

Claims

1. A laminated sheet, wherein, (i) An adhesive layer 1a is provided on one side of a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm, and at least one of conditions A and B is satisfied; or, (ii) The layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm has an adhesive layer 1a on one side and an adhesive layer 1b on the other side, and satisfies at least one of the following conditions C and D. Condition A: The total content of organic solvents in the microfibrillated cellulose layer and adhesive layer 1a is 0.1 ppm or more and 40 ppm or less by mass. Condition B: The content of organic solvents in adhesive layer 1a is 0.5 ppm or more and 200 ppm or less by mass. Condition C: The total content of organic solvents in the microfibrillated cellulose layer, adhesive layer 1a and adhesive layer 1b is more than 0.1 ppm and less than 60 ppm by mass. Condition D: The total content of organic solvents in adhesive layers 1a and 1b is 0.5 ppm or more and 300 ppm or less by mass.

2. The laminated sheet according to claim 1, wherein, The thicknesses of adhesive layer 1a and adhesive layer 1b are both greater than 1 μm and less than 50 μm.

3. The laminated sheet according to claim 1 or 2, wherein, (i) An adhesive layer 1a and a resin film or protective film are sequentially provided on one side of the microfibrillated cellulose layer, and (ii) An adhesive layer 1a and a resin film or protective film are sequentially provided on one side of the microfibrillated cellulose layer.

4. The laminated sheet according to claim 1 or 2, wherein, The cellulose layer containing fine fibrous fibers contains hydrophilic polymers.

5. The laminated sheet according to claim 4, wherein, The hydrophilic polymer contains nonionic water-soluble cellulose ethers and / or polyvinyl alcohol.

6. The laminated sheet according to claim 5, wherein, The microfibrillated cellulose layer is a single layer, and the hydrophilic polymer contains nonionic water-soluble cellulose ether, with the content of nonionic water-soluble cellulose ether in the hydrophilic polymer being more than 80% by mass.

7. The laminated sheet according to claim 6, wherein, In the microfibrillated cellulose layer, the mass ratio of nonionic water-soluble cellulose ether to microfibrillated cellulose, i.e., nonionic water-soluble cellulose ether / microfibrillated cellulose, is greater than 10 / 90 and less than 90 / 10.

8. The laminated sheet according to claim 5, wherein, The microfibrillated cellulose layer is multilayered, including a microfibrillated cellulose layer 1a containing polyvinyl alcohol and a microfibrillated cellulose layer 1b containing nonionic water-soluble cellulose ether.

9. The laminate according to claim 8, wherein, In the microfibrillated cellulose layer 1a, the mass ratio of polyvinyl alcohol to microfibrillated cellulose, i.e., polyvinyl alcohol / microfibrillated cellulose, is 25 / 75 or more and 90 / 10 or less.

10. The laminate according to claim 1 or 2, wherein, Fine fibrous cellulose has anionic groups.

11. The laminate according to claim 10, wherein, Anionic groups include phosphorus oxyacid groups or groups derived from phosphorus oxyacid groups.

12. A laminate having a laminate of claim 1 or 2 (ii) on at least one side of a core resin board, the laminate having a resin film, the core resin board containing a polycarbonate resin, and an adhesive layer 1b having the laminate in contact with the core resin board.

13. The laminate according to claim 12, wherein the haze is 5.0% or less.

14. The laminate according to claim 12, wherein the haze difference before and after heating at 170°C for 10 minutes is less than 2.0%.

15. A method for manufacturing a heat-processed article, comprising a step of heat-processing the laminated body according to claim 12.

16. A heat-processed article, which is formed by heat processing the laminate of claim 12.

17. A transparent component comprising the heat-worked article of claim 16.

18. A method for manufacturing a laminated sheet according to claim 1, comprising the following steps 1 and 2, Step 1: A process of coating a layer containing microfibrillated cellulose with a fiber width of less than 1,000 nm with a coating solution and drying it to obtain a layer containing microfibrillated cellulose. Step 2: A step of coating one side of the microfibrillated cellulose layer obtained in Step 1 with an adhesive layer coating liquid and drying it to form adhesive layer 1a or adhesive layer 1b.

19. The method for manufacturing a laminated sheet according to claim 18, wherein, Step 2 is as follows: After coating one side of the microfibrillated cellulose layer obtained in Step 1 with an adhesive coating liquid, it is dried at 80°C or above for more than 5 minutes to form adhesive layer 1a or adhesive layer 1b.

20. The method for manufacturing a laminated sheet according to claim 18 or 19, wherein, Following step 2 is the following step 3. Step 3: Applying an adhesive coating liquid to the side opposite to the side where adhesive layer 1a or adhesive layer 1b is formed, and drying it, thereby forming adhesive layer 1b or adhesive layer 1a.

21. The method for manufacturing a laminated sheet according to claim 18 or 19, wherein, Following step 2 is the following step 4. Step 4: The process of attaching a resin film or protective film to adhesive layer 1a or adhesive layer 1b.

Images