Method for producing modified cellulose fiber cake

Abstract

To provide a novel process for producing modified cellulose fiber-containing resin composition, and a novel process for producing a modified cellulose fiber cake, a stapled fiber anionic modified cellulose fiber cake, a reformed cellulose fiber, or a fine cellulose fiber that can be used therefor.SOLUTION: Provided is a process for producing modified cellulose fiber cake that comprises a step (step A) of solid-liquid separating a fluid dispersion containing a modified cellulose fiber under the condition that the centrifugal force of the centrifuge is 50 G or more and 600 G or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a modified cellulose fiber cake. [Background technology]

[0002] Traditionally, plastic materials derived from petroleum, a finite resource, have been widely used, but in recent years, technologies with less environmental impact have come into the spotlight. Against this technological backdrop, materials made from cellulose fiber, a naturally occurring biomass, have been attracting attention.

[0003] Since cellulose fiber dispersions have high viscosity, mixing them with a resin-containing coating material results in a significant increase in viscosity, making coating difficult. Therefore, a known method is to reduce the viscosity of the cellulose fiber dispersion by shortening the fiber length of the cellulose fibers.

[0004] For example, Patent Document 1 discloses a method for shortening cellulose fibers, in which anion-modified cellulose fibers are thermally decomposed in a solvent containing water to cleave the sugar chains. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2019 / 235557 Summary of the Invention [Problem to be solved by the invention]

[0006] Since solvents containing water cannot be mixed uniformly with resins used in paints, etc., it is necessary to replace the medium for cellulose fibers with organic solvents, especially in the case of short cellulose fibers. Solvent replacement processes typically require multiple cycles, resulting in a large amount of solvent being used, which incurs costs not only for the solvent itself but also for the disposal of the solvent after use.

[0007] Therefore, the present invention relates to a new method for producing a resin composition containing modified cellulose fibers, and in particular to a new method for producing a modified cellulose fiber cake, a shortened anion-modified cellulose fiber cake, a modified cellulose fiber, or a fine cellulose fiber that can be used for the resin composition. [Means for solving the problem]

[0008] The present invention relates to the following [1] to [6]. [1] A method for producing a modified cellulose fiber cake, comprising a step (step A) of subjecting a dispersion containing modified cellulose fibers to solid-liquid separation under conditions in which the centrifugal force of a centrifuge is 50 G or more and 600 G or less. [2] A step of subjecting the anion-modified cellulose fiber to a thermal decomposition treatment at a temperature of 50°C or higher and 230°C or lower to obtain a shortened anion-modified cellulose fiber; and The dispersion containing the shortened anion-modified cellulose fibers is subjected to solid-liquid separation (step A) under conditions in which the centrifugal force of a centrifuge is 50 G or more and 600 G or less. A method for producing a shortened anionically modified cellulose fiber cake. [3] A method for producing modified cellulose fibers, comprising a step of introducing a modifying group into modified cellulose fibers in a cake produced by the production method described in [1] above, or into shortened anion-modified cellulose fibers in a cake produced by the production method described in [2] above. [4] A method for producing fine cellulose fibers having an average fiber length of 50 nm or more and 300 nm or less, comprising a step of subjecting a modified cellulose fiber cake produced by the production method described in [1] above, a shortened anion-modified cellulose fiber cake produced by the production method described in [2] above, or a modified cellulose fiber produced by the method described in [3] above to a micronization treatment. [5] A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by the production method described in [1] above, a shortened anion-modified cellulose fiber cake produced by the production method described in [2] above, a modified cellulose fiber produced by the method described in [3] above, or a fine cellulose fiber produced by the production method described in [4] above, with a resin. [6] A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by the production method described in [1] above or a shortened anion-modified cellulose fiber cake produced by the production method described in [2] above, a modifying compound, and a resin. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a new, more efficient method for producing a resin composition containing modified cellulose fibers, and in particular a new, more efficient method for producing a modified cellulose fiber cake, a shortened anion-modified cellulose fiber cake, a modified cellulose fiber, or a fine cellulose fiber that can be used for the resin composition. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a decanter centrifuge. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Method for producing modified cellulose fiber cake] The method for producing a modified cellulose fiber cake of the present invention includes a step (step A) of subjecting a dispersion containing modified cellulose fibers to solid-liquid separation under conditions where the centrifugal force of a centrifuge is 50 G or more and 600 G or less.

[0012] [Modified cellulose fiber] Modified cellulose fibers can be obtained by introducing a substituent, preferably anionic group, for modification into cellulose fibers using a known method, and then preferably shortening the fiber length. From an environmental perspective, natural cellulose fibers are preferred as the raw cellulose fibers, including wood pulps such as softwood pulp and hardwood pulp; cotton pulps such as cotton linter and cotton lint; non-wood pulps such as straw pulp and bagasse pulp; and bacterial cellulose. The substituent is preferably an anionic group, and from the viewpoint of sugar chain cleavage efficiency, carboxy groups, sulfonic acid groups, and phosphate groups are preferred, with carboxy groups being more preferred.

[0013] Alternatively, carboxymethylated pulp may be mechanically defibrated, beaten, or disintegrated to obtain a modified cellulose fiber with an average fiber diameter of 500 nm or greater. However, shortening the fibers is preferable from the viewpoint of dispersibility of the composition. Examples of processing methods include: first, increasing the concentration of an aqueous dispersion of the pulp by dehydration or the like to a high concentration (20% by weight or greater) and then beating the dispersion; reducing the concentration of the aqueous dispersion to a low concentration (less than 20% by weight) and then subjecting the dispersion to mechanical processing such as beating or disintegration; or dehydrating and drying the aqueous dispersion and then mechanically defibrating or beating the dispersion, or dry-pulverizing the dispersion.

[0014] One example of a method for producing known anion-modified cellulose fibers is a method using 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst, as described in WO 2019 / 235557. In this production method, natural cellulose fibers are preferably used as the starting cellulose fibers, and TEMPO is used as the catalyst to introduce carboxyl groups as anionic groups into the cellulose fibers.

[0015] [Short fiber] Anion-modified cellulose fibers can be shortened by cleaving the sugar chains of the cellulose fibers. As a method for cleaving sugar chains, anion-modified cellulose fibers can be obtained by subjecting the anion-modified cellulose fibers to a thermal decomposition treatment at a temperature of preferably 50° C. or higher, and preferably 230° C. or lower. From the viewpoint of productivity, the temperature is more preferably 70° C. or higher, and even more preferably 80° C. or higher, while from the viewpoint of preventing excessive decomposition, the temperature is more preferably 220° C. or lower, and even more preferably 200° C. or lower.

[0016] The modified cellulose fibers thus obtained and subjected to step A are in the form of pre-shortened modified cellulose fibers, preferably pre-shortened anion-modified cellulose fibers. From the viewpoint of productivity, the average fiber length of the pre-shortened modified cellulose fibers thus obtained is preferably 50 μm or more, more preferably 150 μm or more, while from the viewpoint of dispersibility of the modified cellulose fibers in the resin composition, it is preferably 500 μm or less, more preferably 300 μm or less.

[0017] Therefore, one preferred embodiment of the method for producing a modified cellulose fiber cake of the present invention comprises the steps of: subjecting anionically modified cellulose fibers to a thermal decomposition treatment at a temperature of 50°C or higher and 230°C or lower to obtain shortened anionically modified cellulose fibers; The dispersion containing the shortened anion-modified cellulose fibers is subjected to solid-liquid separation (step A) under conditions in which the centrifugal force of a centrifuge is 50 G or more and 600 G or less. A method for producing a shortened anionically modified cellulose fiber cake.

[0018] The thermal decomposition treatment is carried out in a state in which the anion-modified cellulose fiber is mixed or dispersed in a medium. Preferred media include water, N,N-dimethylformamide (DMF), ethanol, isopropanol (IPA), methyl ethyl ketone (MEK), ethyl acetate, toluene, cyclohexanone, etc., and one or more of these can be used in combination. Among these, a water-containing solvent is preferred from the viewpoints of ease of handling and cost. In the water-containing solvent, the proportion of water in the solvent is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass, from the viewpoints of ease of handling and cost.

[0019] [Process A] The dispersion of modified cellulose fibers thus obtained can be used in step A. The modified cellulose fibers provided in step A are preferably anionically modified cellulose fibers, more preferably anionically modified cellulose fibers that have been subjected to a TEMPO oxidation treatment, and even more preferably anionically modified cellulose fibers that have been subjected to a TEMPO oxidation treatment and have been shortened.

[0020] Preferred examples of the medium used in the dispersion include water, N,N-dimethylformamide (DMF), ethanol, isopropanol (IPA), methyl ethyl ketone (MEK), ethyl acetate, toluene, and cyclohexanone, and these can be used alone or in combination. Of these, solvents containing water are preferred from the viewpoints of ease of handling and cost. In the case of a water-containing solvent, the proportion of water in the solvent is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass, from the viewpoints of ease of handling and cost.

[0021] The content of modified cellulose fibers in the dispersion is determined as a solid content, which is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and even more preferably 5.0% by mass or more from the viewpoint of productivity, and while the upper limit is not particularly limited, it is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less from the viewpoint of handleability. The content of modified cellulose fibers in the dispersion may be measured by the method described in the Examples below.

[0022] In step A, a dispersion containing modified cellulose fibers is subjected to solid-liquid separation using a centrifuge. The centrifugal force of the centrifuge is 50 G or more, preferably 80 G or more, and more preferably 200 G or more, from the viewpoint of reducing the water concentration in the resin composition. On the other hand, from the viewpoint of discharging the cellulose fiber cake out of the centrifuge, the centrifugal force is 600 G or less, preferably 550 G or less, and more preferably 400 G or less. In this specification, the centrifugal force of the centrifuge can be set to a desired level by adjusting the rotation speed of the rotating cylinder.

[0023] Various known types of centrifuges can be used in step A. Furthermore, a batch-type centrifuge or a continuous centrifuge capable of continuous operation can also be used, but a continuous centrifuge is preferred from the viewpoint of work efficiency.

[0024] Specific examples of centrifuges that can be used in step A include batch-type centrifuges such as siphon-type, basket-type, and plate-type centrifuges. Continuous-type centrifuges include decanter-type, decone-type, multi-stage, and plate-type centrifuges. Of these, from the viewpoint of work efficiency, multi-stage centrifuges are preferred, decone-type and decanter-type centrifuges are more preferred, and decanter-type centrifuges are even more preferred.

[0025] FIG. 1 is a schematic cross-sectional view of a decanter centrifuge. For example, in the case of a dispersion containing shortened anion-modified cellulose fibers as modified cellulose fibers, it is supplied to a decanter centrifuge as feed slurry 1. In a decanter centrifuge, centrifugal force is applied to the dispersion by the rotation of the rotating cylinder 2, allowing solid and liquid in the dispersion to be separated. Furthermore, because the screw 3 rotates at a speed slightly slower than that of the rotating cylinder, the dispersion with an increased content of shortened anion-modified cellulose fibers is gradually transferred to the cake discharge port and recovered as cake 4. Meanwhile, the dispersion from which most of the fiber components have been removed is recovered as separated liquid 5.

[0026] The supply flow rate of the supply slurry 1 can be set to a desired level, for example, by connecting a supply pump (not shown) to the decanter centrifuge. For example, when using a decanter centrifuge, the supply flow rate of the supply slurry 1 is preferably 500 L / h or less, more preferably 300 L / h or less, and even more preferably 100 L / h or less, from the viewpoint of increasing the residence time of the supply slurry in the apparatus to improve separation and avoiding the outflow of cellulose fibers into the separation liquid. On the other hand, from the viewpoint of improving productivity, it is preferably 100 L / h or more, more preferably 300 L / h or more, and even more preferably 500 L / h or more. Furthermore, the above-mentioned suitable range can be appropriately changed depending on the size of the apparatus.

[0027] By using the above-mentioned centrifugal separator, solid-liquid separation of the dispersion can be achieved, and a modified cellulose fiber cake can be produced. In this specification, "solid-liquid separation" refers to removing the solvent component from a dispersion of modified cellulose fibers to increase the content of modified cellulose fibers. A higher solids content in the cake after solid-liquid separation is preferable because it allows for a higher concentration of modified cellulose fibers or modified cellulose fibers in the resin composition. Specifically, the solids content is preferably 5% by mass or more, more preferably 9% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of handleability, the solids content is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less.

[0028] [Degeneration] The modified cellulose fiber cake produced by the production method of the present invention has a sufficiently reduced moisture content, so it can be blended directly into a resin. The modified cellulose fiber cake can be modified using various substituents, preferably anionic groups. The modified cellulose fiber may also be subjected to a treatment to shorten the chain length in advance. Furthermore, modified cellulose fiber cakes that have been shortened and anionically modified can be further bonded with modifying groups to produce modified cellulose fibers. After such treatment, the cellulose fiber cakes can be blended into a resin. Furthermore, the shortened anionically modified cellulose fiber cake or modified cellulose fiber can be further refined before being blended into a resin.

[0029] On the other hand, in the production method of the present invention, carboxylated (oxidized) cellulose can also be used as the chemically modified cellulose. For example, cationically modified cellulose can be obtained by reacting a cellulose raw material with a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride, or its halohydrin form, and an alkali metal hydroxide catalyst (sodium hydroxide, potassium hydroxide, etc.) in the presence of water or an alcohol having 1 to 4 carbon atoms.

[0030] [Method for producing modified cellulose fibers] The modified cellulose fiber of the present invention can be produced by a known method. The modified cellulose fiber is a cellulose fiber derivative in which a modifying group is further bonded to a modified cellulose fiber. More specifically, modified cellulose fibers can be obtained by reacting a compound (modifying compound) having a desired modifying group with the modified cellulose fibers or the shortened anion-modified cellulose fibers in the cake obtained by the above-mentioned production method of the present invention, and introducing the modifying group into such cellulose fibers.

[0031] When the bond between the modified cellulose fiber and the modifying compound is an ionic bond, examples of the modifying compound include primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and phosphonium compounds. Various hydrocarbon groups, such as chain saturated hydrocarbon groups, chain unsaturated hydrocarbon groups, cyclic saturated hydrocarbon groups, and aromatic hydrocarbon groups, as well as copolymerization moieties, can be introduced into these compounds as modifying groups. These groups and moieties may be introduced alone or in combination of two or more.

[0032] When the bonding mode is a covalent bond, an appropriate modifying compound is used depending on whether an anionic group or a hydroxy group is to be modified. When modifying an anionic group, for example, via an amide bond, it is preferable to use, for example, a primary amine or a secondary amine as the modifying compound. When modifying via an ester bond, it is preferable to use, for example, an alcohol such as butanol, octanol, or dodecanol as the modifying compound. When modifying via a urethane bond, it is preferable to use, for example, an isocyanate compound as the modifying compound. Various hydrocarbon groups, such as chain saturated hydrocarbon groups, chain unsaturated hydrocarbon groups, cyclic saturated hydrocarbon groups, and aromatic hydrocarbon groups, as well as copolymerization moieties, can be introduced into these compounds as modifying groups. These groups or moieties may be introduced alone or in combination of two or more.

[0033] When modifying a hydroxy group, for example, via an ester bond, it is preferable to use an acid anhydride (e.g., acetic anhydride, propionic anhydride) or an acid halide (e.g., caprylic acid chloride, lauric acid chloride, and stearic acid chloride) as the modifying compound. When modifying via an ether bond, it is preferable to use an epoxy compound (e.g., alkylene oxide and alkyl glycidyl ether), an alkyl halide, or a derivative thereof (e.g., methyl chloride, ethyl chloride, and octadecyl chloride). When modifying via a urethane bond, it is preferable to use an isocyanate compound as the modifying compound. Various hydrocarbon groups, such as chain saturated hydrocarbon groups, chain unsaturated hydrocarbon groups, cyclic saturated hydrocarbon groups, and aromatic hydrocarbon groups, as well as copolymerization moieties, can be introduced into these compounds as modifying groups. These groups and moieties may be introduced alone or in combination of two or more.

[0034] [Method for producing fine cellulose fibers] The modified cellulose fiber cake, shortened anion-modified cellulose fiber cake, or modified cellulose fiber obtained by the production method of the present invention can be further refined as needed to be used as nanoscale fine cellulose fibers (nanofibers). Examples of further refinement include mechanical refinement using a disintegrator, beater, low-pressure homogenizer, high-pressure homogenizer, grinder, cutter mill, ball mill, jet mill, single-screw extruder, twin-screw extruder, ultrasonic agitator, household juicer mixer, etc.

[0035] By converting the modified cellulose fibers obtained by the production method of the present invention into nanofibers, it is possible to obtain fine cellulose fibers having an average fiber length of preferably 50 nm to 300 nm and an average fiber diameter of preferably 2 nm to 10 nm. The average fiber length, average fiber diameter, and average aspect ratio of such fine cellulose fibers can be measured using an atomic force microscope (AFM, Nanoscope III Tapping mode AFM, manufactured by Digital Instruments, Inc., using a Point Probe (NCH) manufactured by Nanosensors, Inc.)

[0036] [Method for producing resin composition] The cellulose fibers can be produced by mixing various cellulose fibers obtained by the above-mentioned methods (i.e., modified cellulose fiber cake, shortened anion-modified cellulose fiber cake, modified cellulose fiber, and fine cellulose fiber) with various resins, solvents, and optional components. From the viewpoint of improving the efficiency of the work process, the modification treatment of (preferably anionically) modified cellulose fibers, more preferably fiber-shortened modified cellulose fibers, and the blending thereof with a resin may be carried out simultaneously. In this case, a method for producing a resin composition is provided, which includes a step of mixing the modified cellulose fiber cake produced by the production method of the present invention described above, the fiber-shortened anionically modified cellulose fiber cake, a modifying compound, and a resin, and then the pulverization treatment may be carried out.

[0037] The content of cellulose fibers (equivalent amount) in the resin composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and even more preferably 3% by mass or more from the viewpoints of suppressing shrinkage during curing of the cellulose fiber-containing resin obtained by removing the solvent component from the resin composition and imparting mechanical strength. On the other hand, from the viewpoint of avoiding a decrease in handleability due to an increase in the viscosity of the resin composition, the content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 8% by mass or less.

[0038] The cellulose fiber (equivalent amount) refers to the mass of various cellulose fibers to which modifying groups are bonded (i.e., modified cellulose fibers and fine cellulose fibers) minus the mass of the modifying groups. The cellulose fiber (equivalent amount) of various cellulose fibers to which modifying groups are bonded can be measured by the method described in the Examples below.

[0039] The resin that can be used in the resin composition is not particularly limited as long as it is a resin that has been conventionally used as a base resin for non-aqueous paints, and various resins can be blended. Specific examples of resins include alkyd resins, acrylic resins, acrylic urethane resins, melamine resins, urethane resins, epoxy resins, coumarone resins, urea resins, phenolic resins, vinyl chloride resins, phenoxy resins, silicone resins, fluororesins, nylon resins, styrene butadiene resins, nitrile butadiene resins, petroleum resins, rosin, drying oil, boiled oil, acetyl cellulose, nitrocellulose, and the like. Among these, acrylic resins, acrylic urethane resins, melamine resins, urethane resins, epoxy resins, urea resins, and phenolic resins are preferred, as they provide resin compositions with excellent dispersibility for fine cellulose fibers, and epoxy resins and phenolic resins are more preferred.

[0040] From the viewpoint of production efficiency, the resin content in the resin composition is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 40% by mass or more, while from the viewpoint of low viscosity, it is preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 50% by mass or less.

[0041] The resin composition may further contain a solvent, if necessary. Examples of the solvent in the present invention include organic solvents and organic media containing reactive functional groups.

[0042] Examples of organic solvents include alcohols such as methanol, ethanol, isopropyl alcohol, 2-butanol, 1-pentanol, octyl alcohol, glycerin, ethylene glycol, and propylene glycol; carboxylic acids such as acetic acid; hydrocarbons such as hexane, heptane, octane, decane, and liquid paraffin; aromatic hydrocarbons such as toluene and xylene; amides such as dimethyl sulfoxide, N,N-dimethylformamide, dimethylacetamide, and acetanilide; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; halogens such as methylene chloride and chloroform; and ethylene Examples of the oil-soluble organic solvent include carbonates such as propylene carbonate, dimethyl carbonate, and diethyl carbonate; esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, and polyoxyethylene fatty acid esters; polyethers such as polyethylene glycol and polyoxyethylene alkyl ethers; silicone oils such as polydimethylsiloxane; acetonitrile, propionitrile, ester oils, salad oil, soybean oil, and castor oil. These oils may be used alone or in combination of two or more.

[0043] Examples of organic media containing reactive functional groups include acrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and phenyl glycidyl ether acrylate; urethane prepolymers such as hexamethylene diisocyanate urethane prepolymer and phenyl glycidyl ether acrylate toluene diisocyanate urethane prepolymer; glycidyl ethers such as n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, glycidyl ether of stearic acid, styrene oxide, phenyl glycidyl ether, nonylphenyl glycidyl ether, butylphenyl glycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, and diethylene glycol diglycidyl ether; chlorostyrene, methoxystyrene, butoxystyrene, and vinylbenzoic acid.

[0044] When a solvent is used, the amount of the solvent is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, per 100 parts by mass of the resin from the viewpoints of low viscosity and uniform mixing of the resin and the anion-modified cellulose fiber cake, whereas from the viewpoint of production efficiency, the amount of the solvent is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, per 100 parts by mass of the resin.

[0045] The resin composition may further contain additives commonly used in the coating field, such as inorganic pigments, organic pigments, dyes, curing agents, plasticizers, catalysts, mildew inhibitors, antifoaming agents, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, thickeners, matting agents, light stabilizers, and ultraviolet absorbers.

[0046] In relation to the above-described embodiments, the present invention further discloses the following methods for producing a cake, a method for producing modified cellulose fibers, a method for producing fine cellulose fibers, and a method for producing a resin composition. <1> A method for producing a modified cellulose fiber cake, comprising a step (Step A) of subjecting a dispersion containing modified cellulose fibers to solid-liquid separation under conditions where the centrifugal force of a centrifuge is 50 G or more and 600 G or less.

[0047] <2> The solid content of the modified cellulose fiber cake is 5% by mass or more. <1> The manufacturing method described in <3> The centrifuge is a continuous centrifuge. <1> or <2> The manufacturing method described in <4> The continuous centrifuge is a decanter centrifuge, <3> The manufacturing method described in <5> The flow rate of the modified cellulose fiber slurry fed to the decanter centrifuge is 100 L / h or more and 500 L / h or less. <4> The manufacturing method described in <6> The modified cellulose fiber is anion-modified. <1> from <5> 1. The manufacturing method according to any one of the preceding claims. <7> The modified cellulose fibers to be subjected to step A are in the form of modified cellulose fibers that have been previously shortened. <1> from <6> 1. The manufacturing method according to any one of the preceding claims. <8> The average fiber length of the modified cellulose fibers that have been shortened in advance is 50 μm or more and 500 μm or less. <7> The manufacturing method described in <9> The dispersion liquid in step A is a medium containing water. <1> from <8> 1. The manufacturing method according to any one of the preceding claims. <10> A step of subjecting the anion-modified cellulose fiber to a thermal decomposition treatment at a temperature of 50°C or higher and 230°C or lower to obtain a shortened anion-modified cellulose fiber; The method includes a step (step A) of subjecting the dispersion containing the shortened anion-modified cellulose fibers to solid-liquid separation under conditions of a centrifugal force of 50 G or more and 600 G or less in a centrifuge. A method for producing a shortened anionically modified cellulose fiber cake.

[0048] <11> The medium in the pyrolysis treatment is a medium containing water. <10> The manufacturing method described in <12> The dispersion liquid in step A is a medium containing water. <10> or <11> The manufacturing method described in <13> The aforementioned <1> from <9> A method for producing modified cellulose fibers, comprising a step of introducing a modifying group into the modified cellulose fibers in a cake produced by any one of the production methods described above. <14> The aforementioned <10> from <12> 2. A method for producing modified cellulose fibers, comprising the step of introducing a modifying group into shortened anionically modified cellulose fibers in a cake produced by the production method described in any one of claims 1 to 11. <15> The aforementioned <1> from <9> 1. A method for producing fine cellulose fibers having an average fiber length of 50 nm or more and 300 nm or less, comprising a step of subjecting a modified cellulose fiber cake produced by the method according to any one of the above items 1 to 3. <16> The aforementioned <10> from <12> 1. A method for producing fine cellulose fibers having an average fiber length of 50 nm or more and 300 nm or less, comprising a step of subjecting a shortened anion-modified cellulose fiber cake produced by the production method described in any one of 1 to 3. to a micronization treatment. <17> The aforementioned <13> or <14> A method for producing fine cellulose fibers having an average fiber length of 50 nm or more and 300 nm or less, comprising a step of subjecting modified cellulose fibers produced by the method described in 1 to a fine treatment. <18> The aforementioned <1> from <9> 10. A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by any one of the production methods described above with a resin. <19> The aforementioned <10> from <12> 10. A method for producing a resin composition, comprising a step of mixing a shortened anion-modified cellulose fiber cake produced by the production method according to any one of claims 1 to 9, with a resin. <20> The aforementioned <13> or <14> A method for producing a resin composition, comprising a step of mixing the modified cellulose fiber produced by the method described in 1. with a resin. <21> The aforementioned <15> from <17> 10. A method for producing a resin composition, comprising a step of mixing the fine cellulose fibers produced by the production method according to any one of the above items 1 to 9 with a resin. <22> The aforementioned <1> from <9> 10. A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by any one of the production methods described above, a modifying compound, and a resin. <23> The aforementioned <10> from <12> 1. A method for producing a resin composition, comprising a step of mixing a shortened anion-modified cellulose fiber cake produced by the production method described in any one of 1 to 3, a modifying compound, and a resin. <24> The content of cellulose fibers (equivalent amount) in the resin composition is 0.1 mass% or more and 20 mass% or less. <18> from <23> 10. A method for producing the resin composition according to any one of the preceding claims. <25> The resin is selected from one or more of acrylic resin, acrylic urethane resin, melamine resin, urethane resin, epoxy resin, urea resin, and phenol resin. <18> from <24> 10. A method for producing the resin composition according to any one of the preceding claims. <26> The resin composition further contains a solvent. <18> from <25> 10. A method for producing the resin composition according to any one of the preceding claims. [Example]

[0049] The present invention will be specifically explained below by showing examples. Note that these examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention in any way. Parts in the examples are parts by mass unless otherwise specified. Note that "normal pressure" refers to 101.3 kPa, and "normal temperature" refers to 25°C.

[0050] [Average fiber length of various cellulose fibers] Ion-exchanged water is added to the cellulose fibers to be measured to prepare a dispersion containing 0.01% by mass of cellulose. The dispersion is measured using a wet dispersion image analysis particle size distribution analyzer (manufactured by Jusco International, product name: IF-3200) under the following conditions: front lens: 2x, telecentric zoom lens: 0.75x, image resolution: 1.113 μm / pixel, syringe inner diameter: 6515 μm, spacer thickness: 1000 μm, image recognition mode: ghost, threshold: 6, analysis sample volume: 300 mL, and sampling: 3%. More than 10,000 cellulose fibers are measured, and the average ISO fiber length is calculated as the average fiber length.

[0051] [Anionic Group Content of Anion-Modified Cellulose Fiber and Shortened Anion-Modified Cellulose Fiber] A 100 mL beaker is charged with 0.5 g of cellulose fiber (dry mass) to be measured. Ion-exchanged water or a 2:1 methanol / water mixture is added to a total volume of 55 mL, and 5 mL of 0.01 M sodium chloride solution is added to prepare a dispersion. The dispersion is stirred until the cellulose fiber is fully dispersed. 0.1 M hydrochloric acid is added to the dispersion to adjust the pH to 2.5-3. Using an automatic titrator (DKK-TOA Corporation, product name: AUT-701), 0.05 M sodium hydroxide solution is added dropwise to the dispersion with a waiting time of 60 seconds, and the conductivity and pH are measured every minute. Measurements are continued until the pH reaches approximately 11, and a conductivity curve is obtained. The sodium hydroxide titration amount is determined from this conductivity curve, and the anionic group content of the cellulose fiber to be measured is calculated using the following formula: Anionic group content (mmol / g) = sodium hydroxide titration amount × sodium hydroxide aqueous solution concentration (0.05 M) / mass of cellulose fiber to be measured (0.5 g)

[0052] [Solid content in various suspensions and cakes after solid-liquid separation] This is done using a halogen moisture meter (Shimadzu Corporation, product name: MOC-120H). Specifically, measurements are taken every 30 seconds for 1 g of sample at a constant temperature of 150°C, and the value when the mass loss is 0.1% or less is taken as the solid content.

[0053] [Amount of cellulose fiber (equivalent amount) in various cellulose fibers to which modified groups are bonded] The cellulose fiber amount (equivalent amount) in various cellulose fibers to which modifying groups are bonded is the amount of cellulose fiber excluding the modifying groups in various cellulose fibers to which modifying groups are bonded. The amount of cellulose fiber (equivalent amount) in various cellulose fibers to which modifying groups are bonded is measured by the following method. (1) When one type of "modifying compound" is added The amount of cellulose fiber (equivalent amount) is calculated by the following formula E. <Formula E> Amount of cellulose fiber (equivalent amount) (g) = Mass of each type of cellulose fiber with a modified group (g) / [1 + modifying compound (g / mol) × amount of modified group bonded (mmol / g) × 0.001] (2) When two or more types of "modifying compounds" are added The amount of cellulose fiber (equivalent amount) is calculated taking into consideration the molar ratio of each compound (that is, the molar ratio when the total molar amount of the compounds added is taken as 1).

[0054] [Preparation of Anion-Modified Cellulose Fibers] Preparation Example 1 (Oxidized Hardwood Pulp) First, 100 g of natural cellulose fiber was thoroughly stirred with 9900 g of ion-exchanged water. Then, 1.6 g of TEMPO, 10 g of sodium bromide, and 28.4 g of sodium hypochlorite were added, in this order, to the pulp mass of 100 g. Using a pH-stat titration system (manufactured by DKK-TOA Corporation, product name: AUT-701), 0.5 M sodium hydroxide was added dropwise to maintain the pH at 10.5. After the reaction was allowed to proceed for 60 minutes (20°C), the addition was stopped, yielding anion-modified cellulose fiber. Dilute hydrochloric acid was added to the resulting anion-modified cellulose fiber to convert the counter ions from sodium ions to protons. The fiber was then thoroughly washed with ion-exchanged water and subsequently dehydrated to yield anion-modified cellulose fiber with a solids content of 30.1% by mass. The anion-modified cellulose fiber had an average fiber length of 1003 μm and a carboxyl group content of 1.3 mmol / g.

[0055] Details of the raw materials used in Preparation Example 1 are as follows. Natural cellulose fiber: Eucalyptus-derived hardwood bleached kraft pulp (manufactured by CENIBRA) TEMPO:ALDRICH, Free radical, 98% by mass Sodium hypochlorite: Wako Pure Chemical Industries, Ltd. Sodium bromide: Wako Pure Chemical Industries, Ltd.

[0056] Example 1 A reaction vessel equipped with anchor blades was charged with 4.15 kg (bone dry mass) of the anion-modified cellulose fiber obtained in Preparation Example 1, and ion-exchanged water was added until the mass of the treatment liquid reached 25 kg. The treatment liquid was stirred and reacted at 95°C under normal pressure for 12 hours to obtain an aqueous suspension of shortened anion-modified cellulose fibers. The average fiber length of the shortened anion-modified cellulose fibers was 157 μm.

[0057] The resulting aqueous suspension of shortened anionically modified cellulose fibers was fed to a decanter centrifuge and continuously operated at a centrifugal force of 300 G and a feed rate to the decanter of 500 L / h to separate the solid and liquid. When a steady state was reached, a cake with a solid content of 22.9% by mass was obtained. To 3.60 g of the resulting cake, 12.92 g of acetone and 0.56 g of polyether monoamine were added and stirred at room temperature for 30 minutes to obtain an acetone dispersion of modified cellulose fibers (hereinafter referred to as CNF) in which EOPO groups were bonded to the carboxy groups of the anionically shortened cellulose fibers via ionic bonds. The EOPO group refers to a group having a structure in which ethylene oxide (EO) and propylene oxide (PO) are polymerized randomly or in a block fashion. 12.92 g of bisphenol A liquid epoxy resin was added to the CNF dispersion and stirred at room temperature for 30 minutes to obtain a resin composition paint. The mass ratio of epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 6 mass%.

[0058] Details of the raw materials used in Example 1 are as follows. Polyether monoamine: Jeffamine M-2070 (manufactured by HUNTSMAN, EO / PO (molar ratio) 32 / 10, molecular weight 2000) Bisphenol A liquid epoxy resin: jER828 (Mitsubishi Chemical Corporation, molecular weight 370)

[0059] Example 2 A cake with a solid content of 17.3% by mass was obtained in the same manner as in Example 1, except that solid-liquid separation was carried out under conditions of a centrifugal force of 100 G and a supply flow rate to the decanter of 100 L / h. To 3.18 g of the resulting cake, 13.22 g of acetone and 0.37 g of the polyether monoamine were added to obtain a dispersion of the CNF. To the CNF dispersion, 13.22 g of the bisphenol A liquid epoxy resin was added and stirred at room temperature for 30 minutes to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 4 mass%.

[0060] Example 3 A cake with a solid content of 23.5% by mass was obtained in the same manner as in Example 2, except that solid-liquid separation was carried out under the condition of a centrifugal force of 400 G. To 3.52 g of the resulting cake, 12.96 g of acetone and 0.56 g of the polyether monoamine were added to obtain a dispersion of the CNF. 12.96 g of the bisphenol A liquid epoxy resin was added to the CNF dispersion and stirred at room temperature for 30 minutes to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 6 mass%.

[0061] Example 4 A cake with a solid content of 20.1% by mass was obtained in the same manner as in Example 2, except that solid-liquid separation was carried out at a centrifugal force of 500 G. To 3.42 g of the resulting cake, 13.06 g of acetone and 0.46 g of the polyether monoamine were added to obtain a dispersion of the CNF. 13.06 g of the bisphenol A liquid epoxy resin was added to the CNF dispersion and stirred to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 5 mass%.

[0062] Example 5 A cake with a solid content of 12.1% by mass was obtained in the same manner as in Example 1, except that solid-liquid separation was performed by changing the supply amounts of short-fibered anion-modified cellulose fibers with different average chain lengths and their aqueous suspension. To 3.37 g of the resulting cake, 13.18 g of acetone and 0.27 g of the polyether monoamine were added to obtain a dispersion of the CNF. To the CNF dispersion, 13.18 g of the bisphenol A liquid epoxy resin was added and stirred to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 3 mass%.

[0063] Example 6 A cake with a solid content of 13.1% by mass was obtained in the same manner as in Example 5, except that the solid content (% by mass) in the aqueous suspension of shortened anion-modified cellulose fibers was 2% by mass. To 3.14 g of the resulting cake, 13.29 g of acetone and 0.28 g of the polyether monoamine were added to obtain a dispersion of the CNF. 13.29 g of the bisphenol A liquid epoxy resin was added to the CNF dispersion and stirred to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 3 mass%.

[0064] Comparative Example 1 In the same manner as in Example 1, an aqueous suspension of short anion-modified cellulose fibers was obtained. Without performing solid-liquid separation of the aqueous suspension, 12.39 g of acetone and 0.17 g of the polyether monoamine were added to 5.06 g of an aqueous suspension of shortened anion-modified cellulose fibers (solid content 5.0% by mass) to obtain a dispersion of the CNF. 12.39 g of the bisphenol A liquid epoxy resin was added to the CNF dispersion and stirred at room temperature for 30 minutes to prepare a paint. The mass ratio of the epoxy resin to acetone in the paint was 1:1, and the CNF content in the paint was 2 mass%.

[0065] Comparative Example 2 Solid-liquid separation was attempted in the same manner as in Example 2, except that solid-liquid separation was carried out under conditions of a centrifugal force of 700 G. However, no cake was discharged from the decanter centrifuge.

[0066] Comparative Example 3 Solid-liquid separation was attempted in the same manner as in Example 2, except that solid-liquid separation was carried out under conditions of a centrifugal force of 3100 G. However, no cake was discharged from the decanter centrifuge.

[0067] The specifications of the decanter centrifuge used in the above examples and comparative examples are as follows, and the main configuration of the decanter centrifuge generally coincided with that shown in FIG. Equipment name: Decanter centrifuge Model: PTM006 (Tomoe Engineering Co., Ltd.) Main motor: 3.7kW, 200V, 13.8A, INV Differential motor: 1.5kW, 200V, 6.0A, INV Maximum centrifugal force: 3100G

[0068] The specifications of the supply pump used in the above Examples and Comparative Examples for supplying the aqueous suspension to the decanter centrifuge are as follows: Equipment name: Heishin Mono Pump Model: NHL15PUN (manufactured by Heishin Equipment Co., Ltd.) Electric motor: 0.2kW, 200V, 1.5A, INV Maximum supply flow rate: 800L / h

[0069] The cake dischargeability from the decanter centrifuge was evaluated according to the following criteria. Dischargeability ⊚: When the cake was continuously discharged from the cake discharge port, the dischargeability was evaluated as ⊚. Dischargeability: ◯: When the cake was intermittently discharged from the cake discharge port, the dischargeability was evaluated as ◯. Dischargeability x: When the cake was not discharged from the cake discharge port, the dischargeability was evaluated as x.

[0070] The uniformity of the coating was evaluated according to the following criteria. Uniformity: When visually confirmed that the resin was uniformly dissolved and the coating was transparent, the uniformity was evaluated as "good." Uniformity x: When the paint was found to be cloudy due to resin precipitates by visual inspection, the uniformity was evaluated as x.

[0071] Table 1 shows the main conditions and results of the examples and comparative examples.

[0072] [Table 1]

[0073] As shown in Table 1, in Examples 1 to 6, a cake was discharged from the decanter centrifuge, and the resulting cake was sufficiently concentrated, resulting in good paint uniformity even in formulations where CNF was blended at a high concentration relative to the resin. On the other hand, in Comparative Example 1, solid-liquid separation was not performed, and the paint lacked uniformity even when the CNF concentration in the paint was 2% by mass. In Comparative Examples 2 and 3, the high centrifugal force prevented the cake from being discharged from the decanter centrifuge, making it impossible to produce a paint in the first place. Furthermore, the upper limit of the CNF concentration in the coating material indicates the concentration at which the CNF can be uniformly blended into the epoxy resin, and the higher the concentration, the better the result. The Examples showed values ​​2 to 3 times better than the Comparative Examples, and it is believed that when the CNF is blended into the coating material, the solvent can be removed from the coating material to improve the resin properties (mechanical strength such as elastic modulus, and shrinkage suppression during curing) when the resin is cured. [Industrial Applicability]

[0074] The (preferably anionically) modified cellulose fibers, preferably shortened modified cellulose fibers, obtained by the production method of the present invention can be used as a reinforcing agent that imparts mechanical strength to various coating materials, etc., and as an agent for suppressing shrinkage during curing. [Explanation of symbols]

[0075] 1. Feed slurry 2 Rotating Cylinder 3 screws 4. Recovery cake 5. Recovered separated liquid

Claims

1. A method for producing a modified cellulose fiber cake, comprising a step (Step A) of subjecting a dispersion containing modified cellulose fibers previously shortened to a solid-liquid separation under conditions in which the centrifugal force of a centrifuge is 50 G or more and 500 G or less, The manufacturing method, wherein the centrifuge is a continuous centrifuge.

2. A manufacturing method as described in claim 1, wherein the content of modified cellulose fibers in the dispersion is 2 mass% or more in terms of solid content.

3. The method according to claim 1 or 2, wherein the solid content of the modified cellulose fiber cake is 5% by mass or more.

4. The method according to any one of claims 1 to 3, wherein the continuous centrifuge is a decanter centrifuge.

5. The method according to any one of claims 1 to 4, wherein the modified cellulose fibers are anionically modified.

6. The method according to claim 5, wherein the anion-modified cellulose fibers are subjected to a thermal decomposition treatment at a temperature of 50°C or higher and 230°C or lower to obtain anion-modified cellulose fibers that have been shortened in advance and have an average fiber length of 50 μm or higher and 500 μm or lower.

7. A method for producing modified cellulose fibers, comprising the step of introducing a modifying group into the modified cellulose fibers in a cake produced by the production method according to any one of claims 1 to 6.

8. A method for producing fine cellulose fibers having an average fiber length of 50 nm or more and 300 nm or less, comprising a step of subjecting a modified cellulose fiber cake produced by the production method according to any one of claims 1 to 6 or a modified cellulose fiber produced by the method according to claim 7 to a micronization treatment.

9. A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by the production method according to any one of claims 1 to 6, a modified cellulose fiber produced by the method according to claim 7, or a fine cellulose fiber produced by the production method according to claim 8 with a resin.

10. A method for producing a resin composition, comprising a step of mixing a modified cellulose fiber cake produced by the production method according to any one of claims 1 to 6, a modifying compound, and a resin.

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