Method for producing reinforced regenerated cellulose fiber

Abstract

Provided is a method for producing a reinforced regenerated cellulose fiber with which it is possible to obtain a woven fabric having excellent fibrillar properties, high rupture strength, and excellent wear resistance in a wet state, while suppressing shrinkage during washing with water or the like. A method for producing a reinforced regenerated cellulose fiber according to the present invention comprises: step A: a step for causticizing a regenerated cellulose fiber; and step B: a step for adsorbing the fine cellulose fibers to the regenerated cellulose fibers.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing reinforced regenerated cellulose fibers. Background Art

[0002] Regenerated cellulose fibers such as rayon, polynosic, cupra, and lyocell have unique drapability, the feel, luster, and smoothness peculiar to cellulose filaments. Therefore, in addition to being used for the whole of women's clothing materials, shawls, and linings for men's / women's clothing, they are also used for a wide range of applications such as curtains, craft silk, wrapping cloths, handbags, and footwear. In addition, due to the heat retention and moisture absorption properties exhibited by regenerated cellulose-based fibers, they are also widely used for close-fitting clothing applications. In recent years, their use as functional close-fitting clothing that utilizes the exothermic effect of moisture absorption generated when moisture is adsorbed on the fiber surface is expanding.

[0003] On the other hand, it is known that the above-mentioned regenerated cellulose fibers have the following characteristics: due to their high moisture absorption, they absorb water and swell when immersed in water during washing such as by water washing, and the fiber length shrinks during subsequent drying. Therefore, woven fabrics and knitted fabrics using regenerated cellulose fibers are usually difficult to wash with water and sometimes need to be washed by dry cleaning.

[0004] The swelling property exhibited by the above-mentioned regenerated cellulose fibers and the accompanying fiber length contraction phenomenon are considered to be due to the structure of the fiber caused by the process of manufacturing regenerated cellulose fibers from cellulose raw materials. That is, it is known that in the manufacture of regenerated cellulose fibers, since a substance obtained by dissolving natural cellulose raw materials in carbon disulfide, cuprammonium solution, N-methylmorpholine-N-oxide, etc. is spun, etc., the crystallinity of natural cellulose decreases during this process. It is considered that for this reason, moisture easily penetrates between cellulose molecules constituting the regenerated cellulose fibers, and thus swelling is exhibited. In addition, during swelling, rearrangement of cellulose molecules occurs within the fiber, and thus shrinkage occurs after drying.

[0005] To solve the above problems, various improvement measures have been proposed. For example, Patent Document 1 describes a method for suppressing damage to woven fabrics caused by washing, etc. by attaching long-chain hydrocarbon compounds to the surface of regenerated cellulose fibers. In addition, Patent Document 2 describes a method in which washing with water can be carried out by coating the surface of regenerated cellulose fibers with amino-modified silicone. On the other hand, Patent Document 3 describes the following method: by applying a specified crosslinking agent that reacts with the hydroxyl groups in cellulose molecules to form a crosslinked structure between and within cellulose molecules, rearrangement of cellulose molecules within the fiber is suppressed, thereby suppressing shrinkage, etc. caused by washing with water.

[0006] In addition, depending on the type of regenerated cellulose fiber, the molecules are sometimes highly oriented in the fiber longitudinal direction, and such fibers have the following problems: the fibers are prone to axial cracking and fibrillation, especially in the wet state.

[0007] To solve the problem of fibrillation, for example, Patent Document 4 describes crosslinking treatment of regenerated cellulose fibers using a specific compound and glyoxal resin.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-6808

[0011] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2012-1830

[0012] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-113333

[0013] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2015-74861 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] A countermeasure that is effective against the problems of the above-mentioned regenerated cellulose fibers, namely shrinkage and fibrillation after washing, is required.

[0016] Therefore, an object of the present invention is to provide a method for manufacturing reinforced regenerated cellulose fibers, which can obtain a fabric that can suppress shrinkage during washing and the like, has excellent anti-fibrillation properties, high burst strength, and excellent abrasion resistance in the wet state.

[0017] Means for Solving the Problems

[0018] The present inventors conducted in-depth research to achieve the above object, and as a result, found that it is extremely effective to adsorb microcrystalline cellulose fibers to regenerated cellulose fibers after subjecting them to a specific treatment process, thereby completing the present invention.

[0019] The present invention provides the following solutions.

[0020] (1) A method for manufacturing reinforced regenerated cellulose fibers, comprising the following steps:

[0021] Step A: A step of subjecting regenerated cellulose fibers to caustic treatment;

[0022] Step B: A step of adsorbing microcrystalline cellulose fibers to regenerated cellulose fibers.

[0023] (2) The manufacturing method of the reinforced regenerated cellulose fiber according to (1), wherein the above-mentioned step B is carried out after the above-mentioned step A.

[0024] (3) The manufacturing method of the reinforced regenerated cellulose fiber according to (1) or (2), wherein the above-mentioned microcrystalline cellulose fiber is oxidized microcrystalline cellulose fiber.

[0025] (4) The manufacturing method of the reinforced regenerated cellulose fiber according to (1) or (2), wherein the above-mentioned regenerated cellulose fiber is Lyocell.

[0026] Advantages of the Invention

[0027] According to the present invention, a method for manufacturing a reinforced regenerated cellulose fiber can be provided. The reinforced regenerated cellulose fiber can obtain a fabric that can inhibit shrinkage during washing such as water washing, has excellent fibrillation resistance, high burst strength, and excellent abrasion resistance in a wet state. Description of the Drawings

[0028] Figure 1 It is the observation result of the fabric surface after the friction fastness test (wet method) (JIS L0849) of the knitted fabric obtained in Example 1.

[0029] Figure 2 It is the result of the fabric surface after the friction fastness test (wet method) (JIS L0849) of the knitted fabric obtained in Comparative Example 1. Detailed Description of the Invention

[0030] Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, "~" includes the end values. That is, "X~Y" includes the two end values X and Y.

[0031] (Manufacturing Method of Reinforced Regenerated Cellulose Fiber)

[0032] The present invention is a manufacturing method of a reinforced regenerated cellulose fiber, which includes: Step A: a step of subjecting a regenerated cellulose fiber to caustic treatment; and Step B: a step of adsorbing microcrystalline cellulose fiber onto the regenerated cellulose fiber. The order of Step A and Step B is not limited, but it is preferably that Step B is carried out after Step A.

[0033] (Regenerated Cellulose Fiber)

[0034] The regenerated cellulose in the present invention refers to cellulose and cellulose derivatives that exhibit high hygroscopicity compared to natural cellulose, and also includes hydrated cellulose (cellulose II) formed by dissolving natural cellulose (cellulose I) in specified solvents such as carbon disulfide, cuprammonium solution, N-methylmorpholine-N-oxide, etc. and then reprecipitating it, and cellulose derivatives with certain chemical modifications during this process. Additionally, it includes substances that can be made into hydrated cellulose through alkali treatment or the like without dissolving natural cellulose.

[0035] Examples of the above-mentioned regenerated cellulose include rayon, polynosic, cuprammonium fiber, lyocell, Fortisan, mercerized cotton, etc. From the perspective of more easily exerting the effects of the present invention, lyocell is preferably used.

[0036] Lyocell is a general term for fibers obtained by dissolving natural cellulose raw materials in an organic solvent, preferably N-methylmorpholine-N-oxide (NMO), and performing wet spinning. Lyocell fibers have the following characteristics: high crystallinity and orientation, a clearer fibril structure and low adhesion between fibrils. Therefore, they are prone to splitting along the fiber axis and fibrillation.

[0037] In the present invention, regenerated cellulose fibers refer to fibrils obtained by spinning the above-mentioned regenerated cellulose raw materials, etc., and fibers obtained by only twisting the fibrils or blending them with fibers composed of other raw materials. Additionally, in the present invention, fabrics refer to woven fabrics, knitted fabrics, non-woven fabrics, etc. made into cloth-like substances, and shaped bodies formed by sewing the cloth, etc.

[0038] Fabrics using the reinforced regenerated cellulose fibers obtained by the manufacturing method of the present invention can inhibit shrinkage during washing with water, etc., and have excellent anti-fibrillation properties and high bursting strength. Additionally, they can also inhibit fibrillation caused by friction when wet.

[0039] It should be noted that in this specification, when referring to regenerated cellulose fibers, etc., it means the above-mentioned regenerated cellulose fibers and fabrics containing the regenerated cellulose fibers.

[0040] From the viewpoint of achieving the effects of the present invention, the regenerated cellulose fiber used in the present invention preferably contains a regenerated cellulose component in a proportion of 1% by weight or more based on the total fiber weight. Additionally, it is more preferably to contain 10% by weight or more of the regenerated cellulose component, even more preferably 30% by weight or more, even more preferably 50% by weight or more, and even more preferably 70% by weight or more. In particular, fibers and fabrics substantially composed of regenerated cellulose by containing 90% by weight or more of the regenerated cellulose component can, through the manufacturing method of the present invention, reduce the swelling of the regenerated cellulose fiber when containing water due to washing with water, etc., and thereby can effectively reduce the shrinkage during subsequent drying. In the case where the regenerated cellulose is a fiber such as lyocell that is prone to fibrillation, in addition to reducing the shrinkage during drying, fibrillation caused by friction during wetting can also be suppressed.

[0041] (Process A)

[0042] Process A is a process of subjecting the regenerated cellulose fiber to caustic treatment. It is usually referred to as mercerization or alkalization. Specifically, therefore, it is a process of immersing a fabric containing the regenerated cellulose fiber in an alkali solution of 5 - 30°Bé, preferably 8 - 30°Bé, at 10 - 60°C, preferably 10 - 40°C. Preferably, the fabric immersed in the alkali solution is squeezed by a padding machine, stretched in the warp direction while being stretched, and then subjected to hot water washing after 20 - 120 seconds, neutralized by introducing a neutralizing solution containing formic acid aqueous solution, and then subjected to hot water washing / water washing and drying. Examples of the alkali component include sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.

[0043] (Process B)

[0044] Process B is a process of adsorbing microfine cellulose fibers onto the regenerated cellulose fiber. Hereinafter, Process B will also be referred to as the "adsorption process".

[0045] (Microfine cellulose fiber)

[0046] The microfine cellulose fiber used in the present invention is a microfiber using cellulose as a raw material, and is a collective term for cellulose nanofibers (hereinafter sometimes referred to as "CNF") with an average fiber diameter of less than 500 nm and microfibrillated cellulose (hereinafter sometimes referred to as "MFC") with an average fiber diameter of 500 nm or more. This average fiber diameter is the length-weighted average fiber diameter. For example, it can be measured by observing the microfine cellulose fiber using a fractionator manufactured by VALMET Corporation and an atomic force microscope (AFM). The average fiber diameter of the microfine cellulose fiber is not particularly limited and can be about 1 nm to about 60 μm. The microfine cellulose fiber can be manufactured by defibrating cellulose.

[0047] (Cellulose nanofiber (CNF))

[0048] In the present invention, the average fiber diameter of the CNF that can be used is preferably 100 nm or less, more preferably 50 nm or less. The average fiber length is preferably 5 μm or less, more preferably 3 μm or less. The lower limit of the average fiber length is about 0.1 μm or more. The average fiber length can be measured as follows: When the diameter is less than 20 nm, an atomic force microscope (AFM) is used, and when the diameter is 20 nm or more, a field emission scanning electron microscope (FE-SEM) is used. 200 randomly selected fibers are analyzed, and the average is calculated to perform the measurement. The average aspect ratio of the CNF that can be used in the present invention is preferably 50 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula.

[0049] Aspect ratio = average fiber length / average fiber diameter

[0050] (Microfibrillated cellulose (MFC))

[0051] In the present invention, the average fiber length of the MFC that can be used is preferably 5 μm or more, more preferably 200 μm or more. The upper limit of the average fiber length is preferably 2.0 mm or less, more preferably about 1.5 mm or less. The average fiber length (length-weighted average fiber length) can be obtained by measurement using a fractionator manufactured by VALMET Corporation or the like.

[0052] The cellulose raw material only needs to contain cellulose and is not particularly limited. For example, plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, wood pulp (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled wood pulp, waste paper, etc.)), animals (e.g., ascidians), algae, microorganisms (e.g., Acetobacter), microbial products, etc.) can be cited. As the cellulose raw material, any one of them can be used, or a combination of two or more can be used. Preferably, it is a cellulose raw material (e.g., cellulose fiber) derived from plants or microorganisms, and more preferably a cellulose raw material (e.g., cellulose fiber) derived from plants.

[0053] The number-average fiber diameter of the cellulose raw material is not particularly limited. In the case of softwood kraft pulp, which is a common wood pulp, it is about 30 μm to about 60 μm, and in the case of hardwood kraft pulp, it is about 10 μm to about 30 μm. In the case of other wood pulps, the substance after ordinary refining is about 50 μm. For example, in the case of a substance obtained by refining raw materials such as scraps that are several centimeters in size, it is preferably mechanically treated with a refiner, beater, or other dissociator to adjust it to about 50 μm.

[0054] The microcrystalline cellulose fibers used in the present invention can be used without particular limitation as long as they can be dispersed in a dispersion medium such as water, regardless of the manufacturing method for obtaining the microcrystalline cellulose fibers from the cellulose raw material. For example, microcrystalline cellulose fibers manufactured by mechanically defibrating the cellulose raw material, microcrystalline cellulose fibers manufactured by acid hydrolysis or alkali treatment of the cellulose raw material, and microcrystalline cellulose fibers manufactured by defibrating chemically modified cellulose obtained by chemically modifying the hydroxyl groups contained in the cellulose can be used. In addition, microcrystalline cellulose fibers commercially available in powder form and microcrystalline cellulose fibers commercially available in the form of an aqueous dispersion can be appropriately adjusted to a desired concentration and then used.

[0055] When using microcrystalline cellulose fibers obtained by defibrating chemically modified cellulose as the microcrystalline cellulose fibers, from the viewpoint of promoting the progress of defibrillation, it is preferable to use anion-modified microcrystalline cellulose fibers manufactured by defibrating a cellulose raw material (anion-modified cellulose) obtained by anion modification in the chemical modification. It is also possible to use regenerated microcrystalline cellulose fibers obtained by defibrating a cellulose raw material obtained by chemical modification to produce chemically modified microcrystalline cellulose fibers and then subjecting them to a regeneration treatment.

[0056] (Anion modification)

[0057] In the present invention, anion modification refers to introducing an anionic group into cellulose. Specifically, it refers to introducing an anionic group onto the pyranose ring of cellulose through an oxidation or substitution reaction. In the present invention, the above oxidation reaction refers to a reaction in which the hydroxyl group of the pyranose ring is directly oxidized to a carboxyl group. In addition, in the present invention, the substitution reaction refers to a reaction in which an anionic group is introduced onto the pyranose ring through a substitution reaction other than this oxidation.

[0058] Examples of anion modification include oxidation (carboxylation), carboxymethylation, etherification, and esterification such as phosphoric acid esterification, phosphorous acid esterification, xanthate esterification, and sulfuric acid esterification. Among them, oxidation (carboxylation) and carboxymethylation are more preferable, and oxidation (carboxylation) is particularly preferable. It should be noted that xanthate esterified cellulose (xanthate cellulose) obtained by xanthate esterification can be easily restored to unmodified cellulose by performing a regeneration treatment.

[0059] (Oxidation)

[0060] As the anionic modified cellulose, cellulose subjected to oxidation (carboxylation) can be used. Oxidized cellulose (also referred to as "carboxylated cellulose") can be obtained by oxidizing (carboxylating) the above-mentioned cellulose raw material by a known method. Although not particularly limited, the amount of carboxyl groups is preferably 0.6 to 3.0 mmol / g, more preferably 1.0 to 2.0 mmol / g, relative to the dry weight of the anionic modified cellulose. As an example of the oxidation (carboxylation) method, a method of oxidizing the cellulose raw material in water using an oxidizing agent in the presence of an N-oxy compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof can be cited. By this oxidation reaction, the primary hydroxyl group at the C6 position of the pyranose ring on the cellulose surface is selectively oxidized, and cellulose fibers having aldehyde groups and carboxyl groups (-COOH) or carboxylic acid ester groups (-COO - ) can be obtained. The concentration of cellulose during the reaction is not particularly limited, and is preferably 5% by weight or less.

[0061] The N-oxy compound refers to a compound capable of generating a nitroxide radical. As the N-oxy compound, any compound can be used as long as it is a compound that promotes the target oxidation reaction. For example, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and its derivatives (for example, 4-hydroxy TEMPO) can be cited. The amount of the N-oxy compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing the cellulose raw material. For example, relative to 1 g of dry cellulose raw material, it is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and further preferably 0.01 to 0.5 mmol. In addition, relative to the reaction system, it can be about 0.1 mmol / L to about 4 mmol / L.

[0062] The bromide refers to a compound containing bromine, and examples thereof include alkali metal bromides that can dissociate and ionize in water. In addition, the iodide refers to a compound containing iodine, and examples thereof include alkali metal iodides. The amount of the bromide or iodide used can be selected within a range that can promote the oxidation reaction. The total amount of the bromide and the iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and further preferably 0.5 to 5 mmol relative to 1 g of dry cellulose raw material. This modification is a modification caused by the oxidation reaction.

[0063] As the oxidizing agent, known oxidizing agents can be used. For example, halogens, hypohalous acids, halous acids, perhalic acids or their salts, halogen oxides, peroxides, etc. can be used. Among them, sodium hypochlorite, which is inexpensive and has a small environmental load, is preferred. The appropriate amount of the oxidizing agent to be used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, and still more preferably 2.5 to 25 mmol relative to 1 g of the dry cellulose raw material. In addition, for example, it is preferably 1 to 40 mol relative to 1 mol of the N-oxy compound.

[0064] The oxidation step of the cellulose raw material can efficiently proceed with the reaction even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 °C, and can also be room temperature of about 15 °C to about 30 °C. As the reaction proceeds, carboxyl groups are generated in the cellulose, and thus the pH of the reaction solution decreases. In order to efficiently carry out the oxidation reaction, it is preferred to add an alkaline solution such as an aqueous sodium hydroxide solution to the reaction system at any time to maintain the pH of the reaction solution at about 9 to about 12, preferably about 10 to about 11. From the aspects of ease of operation and less likelihood of side reactions, the reaction medium is preferably water. The reaction time in the oxidation reaction can be appropriately set according to the degree of oxidation, and is usually about 0.5 hour to about 6 hours, for example, about 0.5 hour to about 4 hours.

[0065] In addition, the oxidation reaction can be carried out in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the reaction in the first stage again under the same or different reaction conditions, carboxyl groups can be efficiently introduced into the cellulose raw material without being hindered by the salts generated as by-products in the reaction in the first stage.

[0066] As another example of the oxidation (carboxylation) method, a method of oxidizing by ozone treatment can be cited. In the present invention, it is preferred to use TEMPO-oxidized cellulose microfibrils obtained by defibrating the oxidized cellulose obtained by the method of oxidizing using TEMPO (TEMPO oxidation).

[0067] The amount of carboxyl groups contained in the oxidized cellulose microfibrils obtained by modifying the cellulose raw material by oxidation, relative to the dry weight of the cellulose microfibrils, is preferably 0.6 mmol / g or more, more preferably 0.8 mmol / g or more, and still more preferably 1.0 mmol / g or more. The upper limit is preferably 2.2 mmol / g or less, more preferably 2.0 mmol / g or less, and still more preferably 1.8 mmol / g or less. Therefore, it is preferably 0.6 mmol / g to 2.2 mmol / g, more preferably 0.8 mmol / g to 2.0 mmol / g, and still more preferably 1.0 mmol / g to 1.8 mmol / g.

[0068] The amount of carboxyl groups in the oxidized cellulose can be adjusted by controlling reaction conditions such as the addition amount of the above-mentioned oxidant and the reaction time. The amount of carboxyl groups in the oxidized cellulose is usually the same as that in the case of making microfibrils.

[0069] In the present invention, in the oxidized cellulose obtained by the above process, the carboxyl groups introduced into the cellulose raw material are usually in the salt form, such as alkali metal salts like sodium salts. The alkali metal salt of the oxidized cellulose can be replaced with salts, imidazoline salts, ammonium salts, sulfonium salts and other cationic salts before the fibrillation process. The replacement can be carried out by a known method.

[0070] (Carboxymethylation)

[0071] As a preferred anionic group, carboxyalkyl groups such as carboxymethyl can be cited. Carboxyalkylated cellulose can be obtained by a known method or a commercially available product can be used. The degree of carboxyalkyl substitution per anhydroglucose unit of cellulose is preferably less than 0.60. Further, when the anionic group is carboxymethyl, the degree of carboxymethyl substitution is preferably less than 0.60. When the substitution degree is 0.60 or more, the crystallinity decreases and the proportion of the dissolved component increases, so that the function as microfibrils is lost. In addition, the lower limit value of the degree of carboxyalkyl substitution is preferably 0.01 or more. Considering the operability, the substitution degree is particularly preferably 0.02 to 0.50, and more preferably 0.10 to 0.30. As an example of a method for producing such carboxyalkylated cellulose, a method including the following steps can be cited. This modification is due to a substitution reaction. The carboxymethylated cellulose will be taken as an example for explanation.

[0072] i) A step of mixing a starting material with a solvent and a mercerizing agent and performing mercerization treatment under the conditions that the reaction temperature is 0 to 70 °C, preferably 10 to 60 °C, and the reaction time is 15 minutes to 8 hours, preferably 30 minutes to 7 hours;

[0073] ii) Then, a step of adding a carboxymethylating agent in an amount of 0.05 to 10.0 times the molar amount per glucose residue and performing an etherification reaction under the conditions that the reaction temperature is 30 to 90 °C, preferably 40 to 80 °C, and the reaction time is 30 minutes to 10 hours, preferably 1 hour to 4 hours.

[0074] As the starting material, the above-mentioned cellulose raw materials can be used. As the solvent, 3 to 20 times by weight of water or lower alcohols can be used. Specifically, water, methanol, ethanol, N-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, etc. can be used alone, or a mixed medium of two or more can be used. In the case of mixing lower alcohols, the mixing ratio is 60 to 95% by weight. As the mercerizing agent, an alkali metal hydroxide in an amount of 0.5 to 20 times the molar amount per anhydroglucose residue of the starting material can be used. Specifically, sodium hydroxide and potassium hydroxide can be used.

[0075] As described above, the degree of carboxymethyl substitution per glucose unit of cellulose is less than 0.06, preferably 0.01 or more and less than 0.60. By introducing a carboxymethyl substituent into cellulose, the celluloses repel each other electrostatically. Therefore, the cellulose into which the carboxymethyl substituent has been introduced can be easily defibrated. It should be noted that when the carboxymethyl substituent per glucose unit is less than 0.02, defibrillation may be insufficient. The degree of substitution of carboxymethylated cellulose is usually the same as the degree of substitution when making microfibrils.

[0076] In the present invention, in the carboxyalkylated cellulose obtained by the above process, the carboxyalkyl introduced into the cellulose raw material is usually in the salt form, such as an alkali metal salt such as sodium salt. The alkali metal salt of the carboxyalkylated cellulose can be replaced with salts, imidazoline salts, ammonium salts, sulfonium salts and other cationic salts before the defibrillation step. The replacement can be carried out by a known method.

[0077] (Esterification)

[0078] It is also possible to use esterified cellulose as the anionic modified cellulose. Examples of methods include a method of mixing a powder or aqueous solution of a phosphoric acid compound A in a cellulose raw material, a method of adding an aqueous solution of a phosphoric acid compound A to a slurry of a cellulose raw material, etc. Examples of the phosphoric acid compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, or their esters. They may also be in the form of salts. Among the above, for reasons such as low cost, easy operation, and improving fibrillation efficiency by introducing a phosphoric acid group into the cellulose of wood pulp fibers, compounds having a phosphoric acid group are preferred. Examples of compounds having a phosphoric acid group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite, potassium hypophosphite, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, etc. One of them or a combination of two or more can be used to introduce a phosphoric acid group. Among these, from the viewpoints of high efficiency of phosphoric acid group introduction, easy fibrillation in the following fibrillation process, and easy industrial application, phosphoric acid, sodium salts of phosphoric acid, potassium salts of phosphoric acid, and ammonium salts of phosphoric acid are preferred. Sodium dihydrogen phosphate and disodium hydrogen phosphate are particularly preferred. In addition, from the aspect of enabling the reaction to proceed uniformly and improving the efficiency of phosphoric acid group introduction, the above phosphoric acid compound A is preferably used in the form of an aqueous solution. From the aspect of improving the efficiency of phosphoric acid group introduction, the pH of the aqueous solution of the phosphoric acid compound A is preferably 7 or less, and from the viewpoint of suppressing hydrolysis of wood pulp fibers, the pH is preferably 3 to 7.

[0079] As an example of a method for producing phosphoric acid esterified cellulose, the following method can be cited. While stirring, a phosphoric acid compound A is added to a suspension of a cellulose raw material having a solid content concentration of 0.1 to 10% by weight to introduce a phosphoric acid group into the cellulose. When the cellulose raw material is 100 parts by weight, the addition amount of the phosphoric acid compound A is preferably 0.2 to 500 parts by weight, more preferably 1 to 400 parts by weight, in terms of the amount of phosphorus element. When the proportion of the phosphoric acid compound A is above the above lower limit value, the yield of cellulose microfibrils can be further increased. However, when it exceeds the above upper limit value, the effect of increasing the yield reaches its peak, so it is not preferred from the cost aspect.

[0080] In addition to the phosphoric acid compound A, a powder or an aqueous solution of compound B may also be mixed. Compound B is not particularly limited, and a nitrogen-containing compound showing basicity is preferred. The "basicity" herein is defined as the aqueous solution showing a peach to red color in the presence of a phenolphthalein indicator, or the pH of the aqueous solution being greater than 7. The nitrogen-containing compound showing basicity used in the present invention is not particularly limited as long as it exhibits the effects of the present invention, and a compound having an amino group is preferred. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, etc. may be mentioned. Among them, urea which is low-cost and easy to operate is preferred. Regarding the addition amount of compound B, it is preferably 2 to 1000 parts by weight, more preferably 100 to 700 parts by weight, relative to 100 parts by weight of the solid content of the cellulose raw material. The reaction temperature is preferably 0 to 95 °C, more preferably 30 to 90 °C. The reaction time is not particularly limited, and is about 1 minute to about 600 minutes, more preferably 30 to 480 minutes. When the conditions of the esterification reaction are within these ranges, it is possible to prevent the cellulose from being over-esterified and easily dissolved, and the yield of the phosphorylated cellulose becomes good. From the viewpoint of being able to suppress the hydrolysis of cellulose, it is preferred to dehydrate the obtained phosphorylated cellulose suspension and then perform a heat treatment at 100 to 170 °C. More preferably, during the period when water is contained during the heat treatment, heating is performed at 130 °C or lower, preferably 110 °C or lower, and after removing the water, a heat treatment is performed at 100 to 170 °C.

[0081] The degree of substitution of phosphate groups per glucose unit of the phosphorylated cellulose is preferably 0.001 or more and less than 0.40. By introducing a phosphate group substituent into cellulose, the celluloses are electrically repulsive from each other. Therefore, the cellulose into which the phosphate group has been introduced can be easily defibrated. When the degree of substitution of phosphate groups per glucose unit is less than 0.001, defibrillation cannot be sufficiently performed. On the other hand, when the degree of substitution of phosphate groups per glucose unit is greater than 0.40, it swells or dissolves, and thus, it may not be possible to obtain it in the form of microfibers. In order to efficiently perform defibrillation, it is preferred to perform a cleaning treatment such as washing with cold water after boiling the obtained phosphorylated cellulose raw material. These modifications caused by esterification are modifications caused by substitution reactions. The degree of substitution of the phosphorylated cellulose is usually the same as the degree of substitution when making microfibers.

[0082] In the present invention, in the phosphorylated cellulose obtained by the above process, the phosphate groups introduced into the cellulose raw material are usually in the salt form, and are alkali metal salts such as sodium salts. The alkali metal salt of the phosphorylated cellulose can be replaced with salts, imidazoline salts, ammonium salts, sulfonium salts and other cationic salts. The replacement can be carried out by a known method.

[0083] In the present invention, xanthated cellulose in which a xanthate group (-OCSS - ) is introduced by adding carbon disulfide to cellulose after alkali treatment can be used. The xanthated cellulose can be used as regenerated microfibrillated cellulose fibers by subjecting it to acid treatment and heat treatment after the fibrillation treatment described below to convert the xanthate group back to a hydroxyl group.

[0084] (Fibrillation)

[0085] In the present invention, the apparatus for fibrillating the cellulose raw material is not particularly limited. It is preferable to use an apparatus such as a high-speed rotary type, a colloid mill type, a high-pressure type, a roll mill type, or an ultrasonic type to apply a strong shearing force to the aqueous dispersion of the cellulose raw material.

[0086] It is considered that by the manufacturing method of the present invention, the microfibrillated cellulose fibers are adsorbed on the regenerated cellulose fibers. Thus, the microfibrillated cellulose fibers suppress the volume increase caused by water absorption of the regenerated cellulose fibers, thereby suppressing their swelling. By adsorbing a small amount of microfibrillated cellulose fibers on the regenerated cellulose fibers, the effects of the present invention can also be achieved. On the other hand, based on the regenerated cellulose fibers, when 0.01% by weight or more of the microfibrillated cellulose fibers are adsorbed and coated on the surface of the fibers, the interval between the microfibrillated cellulose fibers at the surface of the regenerated cellulose fibers becomes smaller, and the swelling of the regenerated cellulose fibers when they contain water can be effectively suppressed. In addition, by adsorbing and coating the regenerated cellulose fibers with the microfibrillated cellulose fibers at a ratio of 0.05% by weight or 0.1% by weight or more, the swelling property of the regenerated cellulose fibers can be significantly improved. Furthermore, by adsorbing 0.5% by weight or 1.0% by weight or more of the microfibrillated cellulose fibers with respect to the regenerated cellulose fibers, the entire surface of the regenerated cellulose fibers can be substantially coated with the microfibrillated cellulose fibers.

[0087] In addition, from the viewpoint of improving the swelling property of the regenerated cellulose fibers, there is no upper limit to the amount of the coated microfibrillated cellulose fibers. However, when an excessive amount of the microfibrillated cellulose fibers are adsorbed and coated on the regenerated cellulose fibers, a decrease in the softness of the fibers and a tendency of so-called "paperization" are observed. Therefore, from the viewpoint of maintaining the feel of the regenerated cellulose fibers coated with the microfibrillated cellulose fibers, it is preferable to set the amount of the adsorbed microfibrillated cellulose fibers to 5% by weight or less based on the regenerated cellulose fibers.

[0088] Considering that the diameter of the fibrils of the regenerated cellulose fibers commonly used is about 10 μm, for example, when the regenerated cellulose fibers are coated with CNF at about 0.1% by weight relative to the regenerated cellulose fibers, the average thickness of the coating layer of the CNF is estimated to be about 2.5 nm. This value is smaller than the diameter of the CNF that is commonly known, and thus, it is considered that this amount of CNF does not cover the entire surface of the regenerated cellulose fibers but is randomly adsorbed at a prescribed interval. That is, the surface of the reinforced regenerated cellulose fibers produced by the production method of the present invention does not necessarily need to be entirely covered with fine cellulose fibers such as CNF. When the regenerated cellulose fibers contain water, the fine cellulose fibers are adsorbed on the surface of the regenerated cellulose fibers to such an extent that the volume increase caused by swelling can be suppressed, and thereby the swelling property can be improved.

[0089] Specifically, from the viewpoint of having an effect on improving the swelling property of the regenerated cellulose fibers, it is preferable to adsorb and coat the fine cellulose fibers on an area of 10% or more of the surface of the regenerated cellulose fibers. From the viewpoint of achieving a remarkable improvement effect on the swelling property, it is preferable to adsorb and coat the fine cellulose fibers on an area of preferably 30% or more, more preferably 50% or more of the surface of the regenerated cellulose fibers. In addition, from the viewpoint of achieving a remarkable improvement effect on the swelling property, it is also preferable to form a state in which the entire surface of the regenerated cellulose fibers is substantially covered with the fine cellulose fibers and further the entire surface of the regenerated cellulose fibers is covered with multiple layers of the fine cellulose fibers. The fine cellulose fibers adsorbed on the surface of the regenerated cellulose fibers can be observed by, for example, a scanning electron microscope, and the coating rate of the regenerated cellulose fibers can be evaluated.

[0090] The adsorption treatment of the fine cellulose fibers with respect to the regenerated cellulose fibers and the like can be carried out as follows: after a fine cellulose fiber adsorption step in which the regenerated cellulose fibers and the like are immersed in a fine cellulose fiber dispersion liquid in which the fine cellulose fibers are dispersed in an appropriate ratio so that the fine cellulose fibers infiltrate and adsorb on the regenerated cellulose fibers and the like, a drying step of drying the regenerated cellulose fibers and the like is carried out. In addition, after this drying step, by performing a shaping treatment (shape stabilization treatment) at about 150°C to about 200°C while maintaining the regenerated cellulose fibers and the like in a prescribed shape, an initial shape can be imparted to the regenerated cellulose fibers and the like having the fine cellulose fibers adsorbed on the surface.

[0091] The treatment of adsorbing the fine cellulose fibers on the above-mentioned regenerated cellulose fibers and the like can, for example, adsorb the fine cellulose fibers on the single fibers of the regenerated cellulose fibers before spinning, the regenerated cellulose fibers that have been refined or bleached, or can also adsorb the fine cellulose fibers on the fabric obtained using the regenerated cellulose fibers.

[0092] In addition, the treatment method of the present invention is a method of impregnating regenerated cellulose fibers or the like in a dispersion liquid in which microcrystalline cellulose fibers are dispersed, so that the microcrystalline cellulose fibers are infiltrated / adsorbed on the regenerated cellulose fibers or the like. Since this is similar to the dyeing process of fiber products, it can be carried out as part of the process such as dyeing of fibrous materials or fabrics. That is, within the range that does not hinder the effects of the present invention, for fibrous materials or fabrics in the dyeing process, microcrystalline cellulose fibers can be adsorbed on the fibrous materials or fabrics before or after dyeing, or microcrystalline cellulose fibers can be mixed in dyes or the like so that the microcrystalline cellulose fibers are adsorbed on the regenerated cellulose fibers or the like while dyeing.

[0093] In addition, it is also possible to use in combination the processing using a resin for imparting various properties to regenerated cellulose fibers or the like and the treatment using the microcrystalline cellulose fibers of the present invention. That is, the following various combinations with the processing using a resin can be carried out: resin processing of the regenerated cellulose fibers or the like that have been subjected to the treatment with the microcrystalline cellulose fibers of the present invention, simultaneous microcrystalline cellulose fiber treatment and resin processing using a treatment liquid obtained by mixing a resin component or the like in a dispersion liquid containing microcrystalline cellulose fibers, and microcrystalline cellulose fiber treatment of the regenerated cellulose fibers or the like that have been subjected to resin processing.

[0094] As a means for adsorbing microcrystalline cellulose fibers on regenerated cellulose fibers or the like, for example, a means classified as so-called dipping processing, such as impregnating the fibers in a bath in which a dye is dissolved so that the fibers exhaust the dye, can be appropriately used. By using a dispersion liquid of microcrystalline cellulose fibers as the bath, it is possible to easily adsorb the microcrystalline cellulose fibers. For example, by the dipping high-pressure processing in which regenerated cellulose fibers or the like are impregnated in a dispersion liquid containing microcrystalline cellulose fibers, sealed in a container, heated to about 120 °C, and maintained under high temperature and high pressure, the microcrystalline cellulose fibers contained in the dispersion liquid can be efficiently adsorbed on the regenerated cellulose fibers or the like.

[0095] In addition, in a padding processing step or the like implemented as a finishing step after the dyeing of a fabric containing regenerated cellulose fibers, the fabric containing regenerated cellulose fibers can also be impregnated in a treatment liquid containing microcrystalline cellulose fibers to adsorb the microcrystalline cellulose fibers, and then the microcrystalline cellulose fibers are adsorbed on the regenerated cellulose fibers or the like by means of dehydration, drying, heat treatment (curing) steps using rollers.

[0096] In addition, by only impregnating regenerated cellulose fibers or the like in a microcrystalline cellulose fiber dispersion liquid so that the microcrystalline cellulose fibers are adsorbed on the surface of the fibers, and then performing drying and heat treatment, the microcrystalline cellulose fibers can also be adsorbed on the surface of the regenerated cellulose fibers, and a shrinkage prevention effect can be produced. In addition, the microcrystalline cellulose fibers can be adsorbed on the surface of the regenerated cellulose fibers by means of a spraying method, a coating method, a printing method, or the like.

[0097] In addition, particularly by subjecting a fabric containing regenerated cellulose fibers to an adsorption treatment with microfibrillated cellulose fibers, it is possible to adsorb microfibrillated cellulose fibers also at the interlacing portions of the fibers present in the fabric, and it can be expected that the shift generated between the fibers is suppressed, and a shrinkage prevention effect or the like can be more effectively produced.

[0098] In Step B of the present invention, the dispersion medium for dispersing the microfibrillated cellulose fibers can be an appropriate dispersion medium used within a range that does not particularly damage the regenerated cellulose fibers to be treated or the like. As a dispersion liquid of microfibrillated cellulose fibers, there is commercially available an aqueous solution containing microfibrillated cellulose fibers in which microfibrillated cellulose fibers are dispersed in an aqueous solution, and a water dispersion liquid of microfibrillated cellulose fibers obtained by appropriately diluting the like of the aqueous solution containing microfibrillated cellulose fibers can be used for the treatment of the present invention. On the other hand, for example, by using an organic solvent having a low aggressiveness to regenerated cellulose fibers or the like used in ordinary dry cleaning or the like, and using a dispersion liquid in which microfibrillated cellulose fibers are dispersed in the solvent for the treatment of the present invention, it is possible to prevent swelling caused by water content of the regenerated cellulose fibers or the like generated in the treatment, and this is preferable.

[0099] In the treatment method of the present invention, it is preferable to determine the amount (concentration) of the microfibrillated cellulose fibers in the microfibrillated cellulose fiber dispersion liquid in consideration of the amount of the microfibrillated cellulose fibers adsorbed on the treated regenerated cellulose fibers or the like.

[0100] In the case where the microfibrillated cellulose fibers are adsorbed on the regenerated cellulose fibers or the like by the above-described dipping process, almost all of the microfibrillated cellulose fibers in the microfibrillated cellulose fiber dispersion liquid can be adsorbed on the regenerated cellulose fibers or the like. Therefore, a treatment liquid in which an amount of microfibrillated cellulose fibers corresponding to the amount of the regenerated cellulose fibers or the like involved in the treatment and the target amount of microfibrillated cellulose fiber adsorption is dispersed can be used.

[0101] In addition, in the case where the microfibrillated cellulose fibers are adsorbed on the regenerated cellulose fibers or the like by a pad dyeing process or the like in which the regenerated cellulose fibers or the like are immersed in a treatment liquid containing microfibrillated cellulose fibers under specified conditions and then dehydrated or the like, it is preferable to determine the concentration of the microfibrillated cellulose fibers in the treatment liquid or the like so that a desired amount of microfibrillated cellulose fibers is adsorbed on the treated regenerated cellulose fibers or the like.

[0102] Exemplarily, by dipping the regenerated cellulose fibers or the like in a treatment liquid containing about 0.001% or more of microfibrillated cellulose fibers, or by performing a pad dyeing process using the treatment liquid, it is possible to reduce the swelling property of the regenerated cellulose fibers or the like and reduce the shrinkage amount after washing with water.

[0103] It is considered that by immersing regenerated cellulose fibers or the like in a dispersion liquid in which microcrystalline cellulose fibers are dispersed, the microcrystalline cellulose fibers or their fibrous aggregates that come into contact with the regenerated cellulose fibers or the like are wound and adhered to the surface of the fibers, and the microcrystalline cellulose fibers are well adsorbed on the surface of the regenerated cellulose fibers mainly because the two have the same molecular structure. Moreover, it is considered that by adsorbing the microcrystalline cellulose fibers, morphological changes caused by subsequent swelling of the regenerated cellulose fibers or the like are suppressed, and as a result, shrinkage or the like during washing with water is suppressed.

[0104] In the manufacturing method of the present invention, for the purpose of imparting a desired feel or imparting water repellency or the like to the regenerated cellulose fibers or the like, a suitable resin component may be further coated on the regenerated cellulose fibers or the like adsorbed with microcrystalline cellulose fibers. In addition, the regenerated cellulose fibers or the like may be coated with microcrystalline cellulose fibers that have been previously mixed with a resin component or the like. In particular, by coating with a resin component or the like on the basis of the adsorption of the microcrystalline cellulose fibers, the tear strength of the fabric containing the regenerated cellulose fibers can be improved. As the resin, crosslinkable cellulose reaction type resins such as urea formaldehyde resin, nylon resin, polyamide resin, melamine-formaldehyde resin, ethylene urea, triazine type resin, acrylamide urea, glyoxal urea resin, polycarboxylic acid, epoxy resin, etc., and resins effective in improving the elongation recovery of knitted fabrics such as silicone resin and polyurethane resin are preferred.

[0105] As the resin component used above, resin components mainly for the purpose of hydrophobizing the surface of the regenerated cellulose fibers include fluorine-based, paraffin-based, etc. In addition, by using glyoxal resin, which is usually used for anti-wrinkle and anti-shrink of cellulose-based fibers, it is possible to expect a crosslinking reaction between cellulose molecules contained in the fibers and the microcrystalline cellulose fibers, and further improve the effect of the treatment of the microcrystalline cellulose fibers of the present invention, which is preferred in this regard.

[0106] As the glyoxal resin, a low-formaldehyde resin or a non-formaldehyde resin can be used. In the case of using a low-formaldehyde resin or a non-formaldehyde resin, the amount of formaldehyde generated is small, which is preferred from the aspect of safety.

[0107] In addition, in the case of using the resin component as described above, in order to improve the reactivity of the resin component with cellulose and quickly carry out the crosslinking reaction, a catalyst can be added. The type of the catalyst can be appropriately selected according to the type of the resin component used.

[0108] In a microfibrillated cellulose fiber dispersion in which regenerated cellulose fibers or the like are impregnated for the purpose of adsorbing microfibrillated cellulose fibers, appropriate reagents or the like can be used in combination according to purposes such as facilitating the adsorption treatment using microfibrillated cellulose fibers. For example, for the purpose of well-dispersing microfibrillated cellulose fibers in the microfibrillated cellulose fiber dispersion, various dispersants can be used. As the dispersant, various polymers that function as surfactants, orange oil, etc. can be cited.

[0109] In addition, in the microfibrillated cellulose fiber dispersion, for the purpose of promoting the attachment of microfibrillated cellulose fibers to regenerated cellulose fibers, it is effective to adjust the acidity according to the type of the modified fiber and the like. As the reagent used for adjusting the acidity, sodium hydroxide, soda ash, etc. can be used for the purpose of alkalization, and oxalic acid, acetic acid, malic acid, etc. can be used for the purpose of acidification.

[0110] In addition, in the microfibrillated cellulose fiber dispersion, in addition to the above components, various additives such as blocked isocyanate crosslinking agents and other crosslinking agents, softeners for adjusting the hand feeling, formaldehyde scavengers for reducing the free formaldehyde concentration, surfactants as penetrants, inorganic compounds as anti-slip agents, processing agents (strength reduction preventers) for preventing the strength reduction of fibers caused by resin processing, etc. can be used as needed.

[0111] According to the method for manufacturing reinforced regenerated cellulose fibers of the present invention, since it adopts a configuration including both a step of subjecting regenerated cellulose fibers to caustic treatment (step A) and a step of adsorbing microfibrillated cellulose fibers to regenerated cellulose fibers (step B), even in the case of using Lyocell or the like in which "fibrillation" where the fibers split axially when rubbed when wet becomes a problem as the regenerated cellulose fiber, the fabric obtained by using the reinforced regenerated cellulose fibers obtained by the manufacturing method of the present invention not only has reduced shrinkage when dry, but also has excellent anti-fibrillability, high bursting strength, and excellent abrasion resistance in the wet state.

[0112] Examples

[0113] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. It should be noted that when there is no particular description of the measurement / calculation method of each value in each example, it is measured / calculated by the method described in the specification.

[0114] (Amount of fibrils after friction fastness test (wet method))

[0115] For the knitted fabrics obtained in Examples 1 to 4 and Comparative Examples 1 to 3, according to the rubbing fastness test (wet method) (JIS L0849), the rubbing fastness test (wet method) was carried out by the Gakushin type rubbing fastness test. Under a load condition of about 2 N (about 200 g), the fabric impregnated with the same amount of moisture as the fabric weight was reciprocated 150 times over a length of 100 mm. For the surface of the knitted fabric after the rubbing fastness test (wet method), the appearance was visually confirmed and the amount of fibrils was evaluated. The results are shown in Table 1.

[0116] (Pilling test)

[0117] For the knitted fabrics obtained in Examples 1 to 4 and Comparative Examples 1 to 3, the pilling test of JIS L 1076 Method I was carried out. The results are shown in Table 1 in the form of grades (1 to 5 grades). The larger the numerical value of the grade, the better the anti-fibrillation property. In addition, the observation results of the test pieces are also described.

[0118] (Bursting strength)

[0119] For the knitted fabrics obtained in Examples 1 to 4 and Comparative Examples 1 to 3, according to JIS L 1096 Method A (Mullen type method), the bursting strength (kPa) was determined. The results are shown in Table 1.

[0120] (Wet abrasion test)

[0121] For the woven fabrics obtained in Examples 5 to 8 and Comparative Examples 4 to 10, according to JIS L 1096 Method E (Martindale method), the abrasion test was carried out using test pieces in a wet state. The pressing load was set to 9 kPa. The end point was set to the moment when the appearance changed and filament breakage occurred, and the number of rubs until the end point was measured. The results are shown in Table 2. The more the number of rubs, the better the wear resistance in the wet state.

[0122] (Domestic washing test)

[0123] For the woven fabrics obtained in Examples 5 to 8 and Comparative Examples 4 to 10, according to JIS L 1930 C4N, the domestic washing test was carried out. For the cases where the number of repetitions was set to 5 times and 10 times, the lengths of the measurement intervals before and after the test were measured respectively, and the dimensional change rate was calculated. It should be noted that the drying method was set to Method A (hanging to dry). The results are shown in Table 2. In addition, when the numerical value of the dimensional change rate is negative, it indicates shrinkage.

[0124] (Production Example 1)

[0125] (Production of oxidized cellulose nanofibers)

[0126] 5.00 g (dry weight) of bleached and unbeat pulp (whiteness 85%) derived from coniferous trees was added to 500 mL of an aqueous solution containing 39 mg of TEMPO (Sigma Aldrich) (0.05 mmol relative to 1 g of cellulose on a dry basis) and 514 mg of sodium bromide (1.0 mmol relative to 1 g of cellulose on a dry basis), and stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system to bring the sodium hypochlorite to 6.0 mmol / g, and the oxidation reaction was started. During the reaction, the pH in the system decreased, but 3M aqueous sodium hydroxide solution was added successively to adjust it to pH 10. The sodium hypochlorite was consumed, and the reaction was terminated when the pH in the system no longer changed. After acid treatment of the reaction mixture with hydrochloric acid, the pulp was separated by filtration using a glass filter, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the carboxyl amount was 1.6 mmol / g. It was adjusted to 1.0% (w / v) with water, and the pH was adjusted to 7 by adding 3M sodium hydroxide solution. It was treated 3 times with an ultra-high pressure homogenizer (20 °C, 150 MPa) to obtain a dispersion of TEMPO-oxidized cellulose nanofibers (CNF). The average fiber diameter was 3 nm, and the average fiber length was 550 nm. The transparency was 88.9% (solid content 1.0%). In addition, the viscosity of the dispersion of oxidized CNF at a solid content concentration of 1 wt% at 60 rpm was 3260 mPa·s.

[0127] (Production Example 2)

[0128] (Production of Carboxymethylated Cellulose Nanofibers)

[0129] In a 5 L capacity twin-screw kneader with the rotational speed adjusted to 100 rpm, a substance obtained by dissolving 1089 parts of isopropyl alcohol (IPA) and 31 parts of sodium hydroxide in 121 parts of water was added, and 200 parts of broadleaf tree pulp (manufactured by Nippon Paper Industries Co., Ltd., LBKP) based on the dry mass after drying at 100 °C for 60 minutes was added. The mixture was stirred at 30 °C for 60 minutes to prepare mercerized cellulose. Further, 117 parts of sodium monochloroacetate was added while stirring, and after stirring at 30 °C for 30 minutes, the temperature was raised to 70 °C over 30 minutes, and a carboxymethylation reaction was carried out at 70 °C for 60 minutes. The proportion of water in the reaction medium during the mercerization reaction and the carboxymethylation reaction was 10% by mass. After the reaction was completed, neutralization was carried out, washing was performed with 65% water-containing methanol, and dewatering, drying, and pulverization were carried out to obtain a sodium salt of carboxymethylated cellulose with a carboxymethyl substitution degree of 0.27 and a crystallinity of cellulose I of 64%. The obtained sodium salt of carboxymethylated cellulose was dispersed in water to prepare a 1% (w / v) aqueous dispersion. This was treated 3 times with a high-pressure homogenizer at 150 MPa to obtain a dispersion of carboxymethylated cellulose nanofibers. The average fiber diameter of the obtained carboxymethylated cellulose nanofibers was 3.2 nm, and the average fiber length was 120 nm. The transparency was 81% (solid content 1.0%). In addition, the B-type viscosity of the dispersion of this CNF at 60 rpm when the solid content concentration was 1% by weight was 4500 mPa·s.

[0130] (Production Example 3)

[0131] (Production of phosphorylated cellulose nanofibers)

[0132] As the raw material pulp, bleached unbeatened softwood kraft pulp manufactured by Nippon Paper Industries Co., Ltd. was used, and the Canadian Standard Freeness (CSF) measured according to JIS P 8121 was 700 mL). An aqueous mixed solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (dry mass) of the above raw material pulp, and the adjustment was made such that ammonium dihydrogen phosphate was 45 parts by mass, urea was 120 parts by mass, and water was 150 parts by mass to obtain pulp impregnated with the reagent. Next, the obtained pulp impregnated with the reagent was heated with a hot air dryer at 165 °C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, obtaining phosphorylated pulp. Next, the obtained phosphorylated pulp was subjected to a washing treatment.

[0133] The cleaning treatment is carried out as follows: The pulp dispersion obtained by injecting 100 g (dry weight) of phosphorylated pulp into 10 L of ion-exchanged water is stirred to uniformly disperse the pulp, and then filtered and dehydrated, and the above operations are repeated. When the conductivity of the filtrate becomes 100 μS / cm or less, it is taken as the cleaning end point. Next, the alkali treatment is carried out on the cleaned phosphorylated pulp as described below. First, the cleaned phosphorylated pulp is diluted with 10 L of ion-exchanged water, and while stirring, 1N aqueous sodium hydroxide solution is added little by little to obtain a phosphorylated pulp slurry with a pH of 12 or more and 13 or less. Next, the phosphorylated pulp slurry is dehydrated to obtain the phosphorylated pulp subjected to the alkali treatment. Next, the alkali-treated phosphorylated pulp is subjected to the above cleaning treatment. Ion-exchanged water is added to the obtained phosphorylated pulp to prepare a slurry with a solid content concentration of 2% by mass, and it is treated 3 times with an ultra-high pressure homogenizer (20 °C, 150 MPa) to obtain a phosphorylated cellulose nanofiber dispersion. The average fiber diameter of the obtained cellulose nanofibers is 4 nm, and the average fiber length is 620 nm. The transparency is 86% (solid content 1.0%). In addition, the B-type viscosity of the dispersion of this CNF at 60 rpm when the solid content concentration is 1% by weight is 3100 mPa·s.

[0134] (Production Example 4)

[0135] (Production of regenerated cellulose nanofibers)

[0136] The bleached and unbeaten kraft pulp derived from coniferous trees (whiteness 85%, manufactured by Nippon Paper Industries Co., Ltd.) is immersed in an 18% aqueous sodium hydroxide solution, and alkali cellulose is prepared by pressing / crushing. After aging the alkali cellulose, carbon disulfide is reacted to prepare cellulose xanthate. After dispersing this cellulose xanthate in water so that the solid content reaches 1%, it is treated 3 times with an ultra-high pressure homogenizer (20 °C, 150 MPa) to obtain a cellulose xanthate cellulose nanofiber dispersion. An aqueous sulfuric acid solution is added to the cellulose xanthate cellulose nanofibers, and after stirring for a specified time, sodium hydroxide is added to prepare regenerated cellulose nanofibers. Furthermore, the regenerated cellulose nanofibers are dehydrated / cleaned and refined. After refining, it is dispersed again to prepare a regenerated cellulose nanofiber aqueous dispersion (1% concentration). The average fiber diameter of the obtained cellulose nanofibers is 6.2 nm, and the average fiber length is 520 nm. The transparency is 82% (solid content 1.0%). In addition, the B-type viscosity of the dispersion of this CNF at 60 rpm when the solid content concentration is 1% by weight is 2900 mPa·s.

[0137] (Example 1)

[0138] A knitted fabric made of lyocell (100% lyocell, knitting structure: plain weave, weight per unit area: 170 g / m 2 ) was heat-set at 170 °C for 1 minute using a five-chamber heat-setting machine, then immersed in a 5°Bé sodium hydroxide aqueous solution at 20 °C. After 20 seconds, it was squeezed with a padding machine, followed by hot water washing, neutralization treatment by passing it through a neutralizing solution, and then hot water washing / water washing / drying, thereby performing caustic treatment (Process A).

[0139] Next, for the knitted fabric that has undergone caustic treatment, reactive dyes were used, and after dyeing at 60 °C using a jet dyeing machine, an adsorption treatment of microfibrillated cellulose fibers was performed (Process B). Specifically, after adding a dispersant (manufactured by Meisei Chemical Industry Co., Ltd., Alcosol GL) in an amount equivalent to 2% by weight relative to the stock solution to the aqueous dispersion of TEMPO-oxidized cellulose nanofibers (TEMPO-oxidized CNF) (CNF solid content concentration: 1.0% by weight, hereinafter sometimes referred to as "stock solution") manufactured in Production Example 1, it was diluted with industrial water so that the weight ratio of the CNF solid content reached 0.02% to prepare a treatment solution.

[0140] Using a pad-dyeing treatment device, after immersing the knitted fabric that has undergone caustic treatment and dyeing in the above treatment solution, it was squeezed with a roller so that the wet coating amount reached 100% by weight, then dried, and then heat-set with hot air at 170 °C for about 60 seconds (morphological stabilization treatment), and subjected to a rubbing fastness test, a pilling test, and a bursting strength test.

[0141] (Example 2)

[0142] The oxidized cellulose nanofibers in Example 1 were changed to carboxymethylated cellulose nanofibers (CM-CNF) manufactured in Production Example 2, and a knitted fabric was manufactured in the same manner as in Example 1 and subjected to each test.

[0143] (Example 3)

[0144] The oxidized cellulose nanofibers in Example 1 were changed to phosphoric acid esterified cellulose nanofibers manufactured in Production Example 3, and a knitted fabric was manufactured in the same manner as in Example 1 and subjected to each test.

[0145] (Example 4)

[0146] The oxidized cellulose nanofibers in Example 1 were changed to regenerated cellulose nanofibers manufactured in Production Example 4, and a knitted fabric was manufactured in the same manner as in Example 1 and subjected to each test.

[0147] (Comparative Example 1)

[0148] For the knitted fabric made of lyocell used in Example 1, processes A and B were not performed, and it was supplied for each test.

[0149] (Comparative Example 2)

[0150] Except for not performing process B, the same operations as in Example 1 were carried out to obtain a knitted fabric that had been subjected to caustic treatment (process A) and dyeing, and it was supplied for each test.

[0151] (Comparative Example 3)

[0152] Except for not performing process A, the same operations as in Example 1 were carried out to obtain a knitted fabric that had been subjected to dyeing and adsorption of microfibrillated cellulose fibers (process B), and it was supplied for each test.

[0153]

[0154] As can be seen from Table 1, for the knitted fabrics of Examples 1 to 4 of the fibers manufactured by the method for manufacturing reinforced regenerated cellulose fibers of the present invention using a process A: a process of subjecting regenerated cellulose fibers to caustic treatment and a process B: a process of adsorbing microfibrillated cellulose fibers to regenerated cellulose fibers, fibrillation after the rubbing fastness test (wet method) was suppressed, the anti-fibrillation property was excellent, and it had a high burst strength.

[0155] For the knitted fabrics of Example 1 and Comparative Example 1, the surface of the fabric after the rubbing fastness test (wet method) was observed. For the specimen after the rubbing fastness test of the knitted fabric obtained in Example 1, the observation result photos are shown in Figure 1 In. The same applies to Comparative Example 1, and the observation result photos are shown in Figure 2 In.

[0156] From Figure 1 , 2 It can be seen that fibrillation of the knitted fabric of Example 1 was suppressed even after the rubbing fastness test (wet method), but fibrillation occurred in the knitted fabric of Comparative Example 1 after the rubbing fastness test (wet method), and the fuzzing increased.

[0157] (Example 5)

[0158] A woven fabric made of lyocell (100% lyocell, woven density: 106 warp threads / 2.54 cm, 96 weft threads / 2.54 cm) was heat-set at 170 °C for 1 minute using a five-chamber heat-setting machine, then immersed in a 5°Bé sodium hydroxide aqueous solution at 20 °C. After 20 seconds, it was squeezed with a padding machine, subjected to hot water washing, neutralized in a neutralizing solution, and then subjected to hot water washing / water washing / drying, thereby performing caustic treatment (process A).

[0159] Next, for the mercerized woven fabric, reactive dyes are used, and after dyeing with a jet dyeing machine at 60 °C, an adsorption treatment of microfibrillated cellulose fibers is carried out (Process B). Specifically, in industrial water, 10% of the liquid obtained by dispersing and diluting the aqueous dispersion of TEMPO-oxidized CNF (1% stock solution) produced in Production Example 1 (CNF solid content concentration: 0.1% by weight, hereinafter sometimes referred to as "mother liquor"), 5% of glyoxal resin 1 (urea / formaldehyde resin, non-volatile content 38-42%), 1% of glyoxal resin 2 (melamine / formaldehyde resin, non-volatile content 75-79%), 0.5% of an amine salt catalyst, 1% of a formaldehyde scavenger, 1% of a softener (reactive silicone type), 0.01% of a surfactant as a penetrant, and 0.01% of acetic acid are mixed to prepare a treatment liquid. It should be noted that the weight ratio of the CNF solid component in this treatment liquid is 0.01%.

[0160] Using a padding treatment device, the mercerized and dyed woven fabric is impregnated in the above treatment liquid for 5 to 6 seconds, then squeezed with a roller so that the wet coating amount reaches 100% by weight, and then dried, and then subjected to a heat setting (morphological stabilization treatment) with hot air at 170 °C for about 60 seconds. The obtained woven fabric is subjected to a wear test and a home laundering test.

[0161] (Example 6)

[0162] Respectively, the concentration of glyoxal resin 1 in the treatment liquid used in Process B is changed to 1%, the concentration of glyoxal resin 2 is changed to 0.5%, and further 1% of a blocked isocyanate-based aqueous crosslinking agent (solid content 55%) is used. Otherwise, the same operations as in Example 5 are carried out to obtain a woven fabric that has been subjected to mercerization (Process A), dyeing, and adsorption of microfibrillated cellulose fibers (Process B), and is subjected to each test.

[0163] (Example 7)

[0164] As the treatment liquid used in Step B, a substance obtained by further blending 20% of a mother liquid (CNF solid content concentration: 0.1% by weight) obtained by dispersing and diluting the aqueous dispersion (stock solution) of TEMPO-oxidized CNF produced in Production Example 1 in industrial water, 8% of glyoxal resin 1 (a non-formaldehyde amide resin, solid content of about 42%), 3% of a catalyst for non-formaldehyde resin (complex metal salt type), 3% of a polyethylene-based emulsion as a strength reduction inhibitor, 2% of a modified inorganic compound as an anti-slip agent, 1.2% of a softener (amino-modified silicone), 0.01% of a surfactant as a penetrant, and 0.01% of acetic acid is used. Otherwise, the same operations as in Example 5 are performed to obtain a woven fabric that has been subjected to caustic treatment (Step A), dyeing, and adsorption of microfibrillated cellulose fibers (Step B), and is subjected to each test. It should be noted that the weight ratio of the CNF solid component in the treatment liquid used in Step B is 0.02%.

[0165] (Example 8)

[0166] As the treatment liquid used in Step B, a substance further blended with 1% of a blocked isocyanate-based aqueous crosslinking agent (solid content 55%) is used. Otherwise, the same operations as in Example 7 are performed to obtain a woven fabric that has been subjected to caustic treatment (Step A), dyeing, and adsorption of microfibrillated cellulose fibers (Step B), and is subjected to each test.

[0167] (Comparative Example 4)

[0168] For a woven fabric made of lyocell (100% lyocell, weaving density: 106 warp threads / 2.54 cm, 96 weft threads / 2.54 cm), a reactive dye is used, and dyeing is performed at 60 °C using a jet dyeing machine. Then, it is roll-extruded so that the wet coating amount reaches 100% by weight. Next, after drying, a woven fabric that has been shaped (morphologically stabilized) with hot air at 170 °C for about 60 seconds is obtained and subjected to a wear test and a home laundering test.

[0169] (Comparative Example 5)

[0170] For the dyed woven fabric, before roll-extrusion, a step of immersing it in a treatment liquid obtained by blending 1% of a softener (reactive silicone type) in industrial water for 5 to 6 seconds is provided, and otherwise, the same operations as in Comparative Example 4 are performed to obtain a woven fabric and subjected to each test.

[0171] (Comparative Examples 6 - 9)

[0172] Except for not performing Step A, the same operations as in Examples 5 to 8 are respectively performed to obtain a woven fabric that has been dyed and adsorbed with microfibrillated cellulose fibers (Step B), and is subjected to each test.

[0173] (Comparative Example 10)

[0174] The operation was carried out in the same manner as in Example 5 except that Process B was not performed. Caustic treatment (Process A) and dyeing were carried out, and then roll extrusion was performed so that the wet coating amount reached 100% by weight. After drying, heat setting (morphological stabilization treatment) was carried out with hot air at 170 °C for about 60 seconds, and the obtained woven fabric was subjected to each test.

[0175]

[0176] As can be seen from Table 2, for the woven fabrics of Examples 5 to 8 of the fibers produced by the method for producing reinforced regenerated cellulose fibers of the present invention using a process comprising Process A: caustic treatment of regenerated cellulose fibers and Process B: adsorption of microcrystalline cellulose fibers onto regenerated cellulose fibers, the abrasion resistance in the wet state was excellent and the dimensional change caused by washing with water was small.

Claims

1. A manufacturing method of reinforced regenerated cellulose fiber, comprising the following steps: Step A: A step of subjecting the regenerated cellulose fiber to caustic treatment; Step B: A step of causing microcrystalline cellulose fiber to adsorb onto the regenerated cellulose fiber.

2. The manufacturing method of the reinforced regenerated cellulose fiber according to claim 1, wherein, Said Step B is carried out after said Step A.

3. The method for manufacturing the reinforced regenerated cellulose fiber according to claim 1 or 2, wherein, Said microcrystalline cellulose fiber is oxidized microcrystalline cellulose fiber.

4. The method for manufacturing the reinforced regenerated cellulose fiber according to claim 1 or 2, wherein, Said regenerated cellulose fiber is Lyocell.

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