Artificial nail application method and artificial nail removal method

Abstract

The present invention aims to provide a method for applying artificial nails that can reduce biological irritation during removal, and a method for easily and cleanly removing artificial nails with minimal biological irritation and without pain to the practitioner. [Solution] The present invention provides an artificial nail treatment method that involves performing an artificial nail formation treatment via a primer layer, characterized by comprising the step of applying an aqueous dispersion containing fine cellulose fibers to the surface of the nail to form a primer layer, and an artificial nail removal treatment method characterized by comprising the step of removing the artificial nail, which is a gel nail covering the nail surface via the primer layer, by underwater vibration treatment or steam treatment. The fine cellulose fibers are preferably chemically modified.

Description

[Technical Field]

[0001] The present invention relates to a method for performing artificial nail treatment, which involves applying an artificial nail formation treatment to the surface of a nail, and a method for removing the artificial nail. [Background technology]

[0002] Various types of artificial nails are used for the decoration and protection of the fingers, but in recent years, soft gels that can be dissolved with solvents have become popular due to their ease of use. Solvents such as toluene, butyl acetate, and ethyl acetate are commonly used in such soft gels, and since these solvents are skin irritants, direct application to the body poses health risks and is therefore undesirable.

[0003] Furthermore, when removing such artificial nails, it is common practice to soak cotton with a gel dissolving agent such as acetone to soften the gel nail, and then file off the softened gel nail with a metal pusher. However, gel dissolving agents also have skin irritant properties, and when filing off the gel nail, the surface of the natural nail is also filed away, which can thin the nail and cause pain, among other problems. For example, Patent Document 1 proposes a method to reduce pain for those undergoing such treatment by applying a cuticle remover to the surface of the nail and separating the base gel and color gel at the interface, thereby removing only the color gel and top gel. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-93966 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the method described in Patent Document 1 does not completely remove the base gel from the surface of the nail. While this is not a problem when reusing the base gel, there is a need for a method that can remove the base gel cleanly and painlessly along with the nail.

[0006] Therefore, the objective of this invention is to provide a method for applying artificial nails that causes minimal biological irritation during removal, and a method for easily and cleanly removing artificial nails with minimal biological irritation and without pain to the practitioner. [Means for solving the problem]

[0007] In other words, the present invention is as follows (1) to (8). (1) An artificial nail treatment method which involves performing an artificial nail formation treatment via a primer layer, A method for applying artificial nails, characterized by including the step of applying an aqueous dispersion containing fine cellulose fibers to the surface of the nail to form a primer layer. (2) The method for performing artificial nail treatment according to (1), characterized in that the fine cellulose fibers are chemically modified fine cellulose fibers. (3) The method for applying artificial nails according to (1) or (2), characterized in that the fine cellulose fibers have a transparency of 60% or more when dispersed in a 1.0% by mass aqueous solution. (4) A method for removing artificial nails, characterized by including a step of removing an artificial nail that covers the nail surface via a primer layer containing fine cellulose fibers by underwater vibration treatment or steam treatment. (5) The method for removing artificial nails according to (4), characterized in that the primer layer contains chemically modified fine cellulose fibers. (6) The method for removing artificial nails according to (4) or (5), characterized in that the removal is performed by underwater vibration treatment, and the vibration treatment is a vibration treatment of 1000 Hz or higher. (7) The artificial nail removal procedure described in (4) or (5), characterized in that the underwater vibration treatment is underwater ultrasonic treatment. (8) The method for removing artificial nails according to (4) or (5), characterized in that the removal is performed by steam treatment, and the steam treatment is a treatment in which the artificial nail is exposed to a steam atmosphere for 5 seconds or more. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for applying artificial nails that can reduce biological irritation during application and removal, and a method for easily and cleanly removing artificial nails with minimal biological irritation and without pain to the practitioner. [Modes for carrying out the invention]

[0009] The details of the present invention will be described below, but unless otherwise specified, any notation such as "AA~BB%" shall mean "AA% or more and BB% or less".

[0010] In other words, the present invention is an artificial nail treatment method (artificial nail formation method) that involves performing an artificial nail formation treatment via a primer layer, and is characterized by including a step of forming the primer layer, that is, a step of applying an aqueous dispersion containing fine cellulose fibers to the surface of the nail to form the primer layer.

[0011] Furthermore, the present invention is a method for removing artificial nails (artificial nail removal method) characterized by including a step of removing an artificial nail, which is a gel nail covering the nail surface via a primer layer, by underwater vibration treatment or steam treatment.

[0012] In this invention, the primer layer between the nail and the artificial nail contains fine cellulose fibers, thereby reducing biological irritation during the application and subsequent removal of the artificial nail. Specifically, by incorporating fine cellulose fibers, it is possible to use a primer agent that does not contain organic solvent-based components (e.g., volatile organic compounds (VOCs) such as acetone) like conventional primer materials. This suppresses the reduction in moisture retention of the skin and nails (dryness, rough hands) caused by these components, as well as the adverse environmental impact of VOC emissions. Furthermore, by forming a primer layer containing fine cellulose fibers, the removal of the artificial nail can be performed quickly and easily, significantly reducing the burden on the subject compared to the conventional artificial nail removal (filing off) process. In particular, it is possible to avoid nail damage that can sometimes be painful, such as thinning of the nail due to peeling of the nail surface or the nail itself peeling off, and dramatically shorten the treatment time.

[0013] <Fine Cellulose Fibers> In this specification, fine cellulose fibers refer to fine fibrous cellulose derived from cellulose raw materials. Fine fibrous cellulose refers to, for example, a dispersion of fine cellulose fibers (1 wt%) that exhibits a light transmittance in the range of 1 to 99% obtained using a visible light spectrometer (UV-1800, Shimadzu Corporation) with a path length of 1 cm / 660 nm. Methods for producing fine cellulose fibers include methods of defibration treatment of pulp, and, if necessary, methods of chemical modification treatment before or after defibration (usually before defibration). Fine cellulose fibers having a fiber diameter on the nano-order are called cellulose nanofibers, and fine cellulose fibers having a fiber diameter on the micron-order are called cellulose microfibrils. The size of fine cellulose fibers can be adjusted by conditions of micronization treatment, chemical modification treatment, etc.

[0014] [Cellulose nanofiber] In this specification, cellulose nanofiber (CNF) means cellulose fibers having a fiber diameter on the nanoscale, which are prepared through a micronization process.

[0015] The average fiber diameter (length-weighted average fiber diameter) of CNF is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less, and still more preferably 50 nm or less. The lower limit is not particularly limited, but is usually 1 nm or more, preferably 2 nm or more. Therefore, the average fiber diameter (length-weighted average fiber diameter) of CNF is usually 1 to 500 nm or 2 to 500 nm, preferably 2 to 300 nm or 2 to 100 nm, more preferably 2 to 50 nm or 3 to 30 nm. The average fiber length (length-weighted average fiber length) is usually 50 to 2000 nm, preferably 100 to 1000 nm. The aspect ratio of CNF is usually 10 or more, preferably 50 or more. The upper limit is not particularly limited, but is usually 1000 or less.

[0016] The average fiber diameter and average fiber length of microcrystalline cellulose fibers can be determined by a fractionator manufactured by Barmer Co., Ltd. When using a fractionator, they can be determined as length-weighted fiber width and length-weighted average fiber length, respectively. The average aspect ratio of microcrystalline cellulose fibers can be calculated by the formula: average aspect ratio = average fiber length / average fiber diameter.

[0017] [Cellulose microfibril] In this specification, cellulose microfibril (microfibrillated cellulose, MFC) means cellulose fibers having a micro-order fiber diameter prepared through a fibrillation process.

[0018] The average fiber diameter (average fiber width) of MFC is usually 500 nm or more, preferably 1 μm or more, and more preferably 3 μm or more. Thereby, it can exhibit higher water retention compared to unrefined cellulose fibers, and a high strength imparting effect and a yield improvement effect can be obtained even with a small amount compared to finely defibrated CNF. The upper limit of the average fiber diameter is preferably 60 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and even more preferably 20 μm or less, but there is no particular limitation. The average fiber length is usually 10 μm or more, 20 μm or more, or 40 μm or more, preferably 200 μm or more, 300 μm or more or 400 μm or more. More preferably, it is 500 μm or more or 550 μm or more, still more preferably 600 μm or more, 700 μm or more, 800 μm or more. The upper limit is not particularly limited, but is usually 3,000 μm or less, preferably 2,500 μm or less, more preferably 2,000 μm or less, still more preferably 1,500 μm or less, 1,400 μm or less or 1,300 μm or less. The aspect ratio of MFC is preferably 3 or more, more preferably 5 or more, still more preferably 7 or more, and may be 10 or more, 20 or more or 30 or more. The upper limit of the aspect ratio is not particularly limited, but is preferably 1000 or less, more preferably 100 or less, and still more preferably 80 or less.

[0019] Since the fine cellulose fibers are contained in the primer layer on the surface layer of the nail, from the viewpoint of design, CNF with higher transparency because it is finer fibers is more preferable. Transparency will be described later.

[0020] [Modified] The fine cellulose fibers may be modified or unmodified. Modified fine cellulose fibers refer to fine cellulose fibers (e.g., cellulose nanofibers, cellulose microfibrils) in which at least one of the three hydroxyl groups contained in the glucose unit has been chemically modified (hereinafter simply referred to as "modified"). Chemical modification treatment sufficiently refines the cellulose fibers, and defibrillation yields cellulose nanofibers with a uniform average fiber length and average fiber diameter. Therefore, when added to a dispersion medium such as water to form a dispersion, it is easier to obtain a stable viscosity, and the distribution of fiber length is suppressed, which reduces entanglement between fibers and thus suppresses clogging during spraying. For these reasons, modified cellulose fibers are preferred.

[0021] Modifications include, for example, oxidation, etherification, esterification such as phosphate esterification, silane coupling, fluorination, and cationization. Among these, oxidation (carboxylation), etherification, cationization, and esterification are preferred, with oxidation (carboxylation) being more preferred.

[0022] - Oxidation (carboxylation) - Oxidized fine cellulose fibers typically have a structure in which at least one carbon atom having a primary hydroxyl group in the glucopyranose unit constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at position C6) is oxidized. The amount of carboxyl groups in oxidized cellulose fibers and oxidized cellulose nanofibers is preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, and even more preferably 1.0 mmol / g or more, relative to the oven-dry mass. The upper limit of this amount is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and even more preferably 2.0 mmol / g or less. The amount of carboxyl groups is preferably 0.5 to 3.0 mmol / g, more preferably 0.8 to 2.5 mmol / g, and even more preferably 1.0 to 2.0 mmol / g. The amount of carboxyl groups can be adjusted by controlling the conditions when oxidizing the cellulose fibers (for example, the amount of oxidizing agent added, the reaction time). Furthermore, the amount of carboxyl groups and aldehyde groups can also be adjusted by controlling these conditions.

[0023] The amount of carboxyl groups can be calculated using the following procedure: Prepare 60 ml of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose. Add 0.1 M hydrochloric acid aqueous solution to the prepared slurry to adjust the pH to 2.5. Then, add 0.05 N sodium hydroxide aqueous solution dropwise and measure the electrical conductivity until the pH becomes 11. From the amount of sodium hydroxide consumed during the neutralization stage of the weak acid, where the change in electrical conductivity is gradual (a), calculate the amount of carboxyl groups using the following formula: Carboxylate group content [mmol / g cellulose oxide] = a [ml] × 0.05 / Mass of cellulose oxide [g]

[0024] The oxidation method is not particularly limited, but one example is the oxidation of a cellulose raw material in water using an oxidizing agent in the presence of an N-oxyl compound and bromide, iodide, or a mixture thereof. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, resulting in the formation of an aldehyde group, a carboxyl group (-COOH), and a carboxylate group (-COOH). -At least one group selected from the group consisting of ) is produced. The concentration of the cellulose raw material during the reaction is not particularly limited, but 5% by mass or less is preferred.

[0025] An N-oxyl compound is a compound capable of generating a nitroxyl radical. Examples of nitroxyl radicals include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives (e.g., 4-hydroxyTEMPO). Any compound that promotes the desired oxidation reaction can be used as the N-oxyl compound. The amount of N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize the cellulose raw material. For example, 0.01 mmol or more is preferred, and 0.02 mmol or more is more preferred, per 1 g of oven-dried cellulose raw material. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. The amount of N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.02 to 0.5 mmol, per 1 g of oven-dried cellulose raw material. The amount of N-oxyl compound used in the reaction system is usually 0.1 to 4 mmol / L.

[0026] Bromides are compounds containing bromine, such as alkali metal bromides that can dissociate and ionize in water. Iodides are compounds containing iodine, such as alkali metal iodides. The amount of bromide or iodide used can be selected within a range that promotes the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and even more preferably 0.5 to 5 mmol per 1 g of oven-dried cellulose raw material.

[0027] As an oxidizing agent, known substances can be used, such as halogens, hypohalous acids, halogenous acids, perhalous acids or their salts, halogen oxides, and peroxides. Among these, hypohalous acids or their salts are preferred because they are inexpensive and have a low environmental impact, hypochlorous acid or its salts are more preferred, and sodium hypochlorite is preferred. The appropriate amount of oxidizing agent to use is, for example, 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and even more preferably 3 to 10 mmol per 1 g of oven-dried cellulose raw material. Also, for example, 1 to 40 mol per 1 mol of N-oxyl compound is preferred.

[0028] The oxidation process of cellulose raw materials proceeds efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, and can also be around 15 to 30°C, i.e., room temperature. As the reaction progresses, carboxyl groups are formed in the cellulose, causing a decrease in the pH of the reaction solution. To ensure the oxidation reaction proceeds efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at around 8 to 12, or 10 to 11. Water is preferred as the reaction medium due to its ease of handling and the low likelihood of side reactions.

[0029] The reaction time in an oxidation reaction can be set appropriately according to the degree of oxidation, and is usually 0.5 to 6 hours, for example, 0.5 to 4 hours.

[0030] The oxidation reaction may be carried out in two stages. For example, by filtering out the oxidized cellulose after the first stage of the reaction and then oxidizing it again under the same or different reaction conditions, the oxidation can be carried out efficiently without being inhibited by the salt produced as a by-product in the first stage of the reaction.

[0031] Another example of a carboxylation (oxidation) method is oxidation by contacting a cellulose raw material with an ozone-containing gas (ozonation). This oxidation reaction oxidizes at least the hydroxyl groups at positions 2, 3, and 6 of the glucopyranose ring, and also causes decomposition of the cellulose chain. The ozone concentration in the ozone-containing gas is 50-250 g / m³. 3 Preferably, 50-220 g / m² 3 This is more preferable. The amount of ozone added is preferably 0.1 to 30 parts by mass, and more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50°C, and more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, it is possible to prevent the cellulose raw material from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

[0032] After ozone treatment, a follow-up oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the follow-up oxidation treatment is not particularly limited, but examples include chlorine compounds such as chlorine dioxide and sodium chlorite, as well as oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. The procedure for the follow-up oxidation treatment may involve, for example, dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and then immersing the oxidized cellulose in the solution.

[0033] The method for measuring the amount of carboxyl groups can be the same as described above.

[0034] - Acid-type oxidized cellulose and desalting - Oxidized cellulose contains carboxyl groups as a result of oxidation, but acidic carboxyl groups (-COOH) can be converted into salt-type carboxyl groups (e.g., -COOH). -It may contain more of ,-COONa) than salt-type carboxyl groups, and may contain more salt-type carboxyl groups than acid-type carboxyl groups. The amounts of salt-type carboxyl groups and acid-type carboxyl groups can be adjusted by desalting. Desalting can convert salt-type carboxyl groups to acid-type carboxyl groups. In this specification, oxidized cellulose (after desalting) is called acid-type oxidized cellulose, and oxidized cellulose (that has not undergone the desalting treatment described below) is called salt-type oxidized cellulose. Salt-type oxidized cellulose usually mainly contains salt-type carboxyl groups. On the other hand, acid-type oxidized cellulose has many acid-type carboxyl groups, and the proportion of acid-type carboxyl groups to carboxyl groups is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more. Acid-type oxidized cellulose can exhibit a better reinforcing effect together with component C. The proportion of acid-type carboxyl groups can be calculated by the following procedure.

[0035] 1) First, prepare 250 mL of an aqueous dispersion of acid-type oxidized cellulose with a solid content of 0.1% by mass before desalting. Add 0.1 M hydrochloric acid aqueous solution to the prepared aqueous dispersion to adjust the pH to 2.5, then add 0.1 N sodium hydroxide aqueous solution and measure the electrical conductivity until the pH becomes 11. From the amount of sodium hydroxide consumed during the neutralization stage of the weak acid, where the change in electrical conductivity is gradual (a), calculate the amount of acid-type carboxyl groups and salt-type carboxyl groups, i.e., the total amount of carboxyl groups, using the following formula: Total amount of carboxyl groups (mmol / g cellulose oxide (salt type)) = a (ml) × 0.1 / mass of cellulose oxide (salt type) (g) 2) Prepare 250 mL of a 0.1% by mass aqueous dispersion of desalted acid-type oxidized cellulose. Add a 0.1 N sodium hydroxide aqueous solution to the prepared aqueous dispersion and measure the electrical conductivity until the pH reaches 11. From the amount of sodium hydroxide consumed during the neutralization stage of the weak acid, where the change in electrical conductivity is gradual (b), calculate the amount of acid-type carboxyl groups using the following formula: Amount of acidic carboxyl groups (mmol / g acidic oxidized cellulose) = b (ml) × 0.1 / mass of acidic oxidized cellulose (g) 3) From the calculated total amount of carboxyl groups and the amount of acidic carboxyl groups, calculate the proportion of acidic carboxyl groups using the following formula: Percentage of acidic carboxyl groups (%) = (Amount of acidic carboxyl groups / Total amount of carboxyl groups) × 100

[0036] Desalting can be performed after oxidation, either before or after defibration (before or after step (2)), but is usually done after oxidation, preferably before step (2). Desalting is usually carried out by replacing the salt (e.g., sodium salt) contained in the salt-type oxidized cellulose with a proton. Methods of desalting include adjusting the system to be acidic and contacting the oxidized cellulose with a cation exchange resin. In the case of adjusting the system to be acidic, the pH of the system is preferably adjusted to 2-6, more preferably 2-5, and even more preferably 2.3-5. To adjust to be acidic, an acid is usually used (e.g., inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrite, and phosphoric acid; organic acids such as acetic acid, lactic acid, oxalic acid, citric acid, and formic acid). After adding the acid, a washing treatment may be performed as appropriate. The cation exchange resin has a counterion of H + As long as this condition is met, either a strongly acidic ion exchange resin or a weakly acidic ion exchange resin can be used. The ratio of oxidized cellulose to the cation exchange resin when contacting the cellulose is not particularly limited and can be appropriately set by those skilled in the art from the viewpoint of efficiently performing proton substitution. The cation exchange resin after contact can be recovered by conventional methods such as suction filtration.

[0037] -Aetherification- Examples of etherification include carboxyalkylation, methylation, ethylation, cyanoethylation, hydroxyethylation, hydroxypropylation, ethylhydroxyethylation, and hydroxypropylmethylation, with carboxyalkylation being preferred and carboxymethylation being more preferred.

[0038] Carboxyalkylated cellulose fibers typically have a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, a carbon atom with a primary hydroxyl group at the C6 position that constitutes a glucopyranose unit) is carboxymethylated.

[0039] The degree of carboxyalkyl substitution (DS, preferably carboxymethyl substitution) per anhydrous glucose unit of carboxyalkylated cellulose is preferably 0.01 or higher, 0.02 or higher, or 0.05 or higher, more preferably 0.10 or higher, even more preferably 0.15 or higher, even more preferably 0.20 or higher, and particularly preferably 0.25 or higher. This ensures a degree of substitution necessary to obtain the effects of chemical modification. The upper limit of this degree of substitution is preferably 0.50 or lower, more preferably 0.45 or lower, 0.40 or lower, or 0.35 or lower. This makes it difficult for cellulose fibers to dissolve in water, and allows the fiber form to be maintained in water. Therefore, the degree of carboxyalkyl substitution is preferably 0.01 to 0.50, more preferably 0.01 to 0.45, and even more preferably 0.02 to 0.40, 0.10 to 0.35, or 0.20 to 0.30.

[0040] The degree of substitution, for example, the degree of carboxymethyl substitution, can be measured by the following method. Approximately 2.0 g of carboxymethylated cellulose (dry) is accurately weighed and placed in a 300 mL stoppered Erlenmeyer flask. 100 mL of a solution of 1,000 mL of methanol and 100 mL of special grade concentrated nitric acid is added, and the mixture is shaken for 3 hours to convert the salt-type carboxymethylated cellulose (hereinafter also called "salt-type CM-cellulose") to the acid-type carboxymethylated cellulose (hereinafter also called "acid-type CM-cellulose"). 1.5 to 2.0 g of the acid-type CM-cellulose (dry) is accurately weighed and placed in a 300 mL stoppered Erlenmeyer flask. The acid-type CM-cellulose is moistened with 15 mL of 80% methanol, 100 mL of 0.1 N NaOH is added, and the mixture is shaken at room temperature for 3 hours. Using phenolphthalein as an indicator, the excess NaOH is back-titrated with 0.1 N H2SO4, and the degree of carboxymethyl substitution (DS) can be calculated by the following formula: A = [(100 × F - (0.1N H₂SO₄ (mL)) × F') × 0.1] / (Oven-dry mass of acid-type CM-modified cellulose (g)) DS = 0.162 × A / (1 - 0.058 × A) A: Amount of 1N NaOH required to neutralize 1g of acid-type C-mercured cellulose (mL) F': Factor of 0.1N H2SO4 F: Factor of 0.1N NaOH

[0041] The degree of carboxyalkyl substitution can be adjusted by controlling reaction conditions such as the amount of carboxyalkylating agent added, the amount of mercerizing agent, and the composition ratio of water to organic solvent.

[0042] One method of carboxyalkylation is to merce a cellulosic raw material (starting material) and then etherify it. The following explanation will use carboxymethylation as an example.

[0043] Carboxymethylated cellulose can be produced by using unmodified cellulose fibers (cellulose raw material: e.g., pulp) as a starting material, performing a mercerization treatment, and then carrying out an etherification reaction. This reaction is usually carried out in the presence of a solvent. As the solvent, for example, water, lower alcohols (e.g., methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tertiary butanol) can be used individually or as a mixture of two or more solvents. When lower alcohols are mixed, the mixing ratio of the lower alcohols is preferably 60 to 95% by mass. The amount of solvent is approximately 3 times the mass of the cellulose raw material. There is no particular upper limit to this amount, but it is 20 times or less. Preferably, the amount of solvent is 3 to 20 times the mass of the cellulose raw material.

[0044] Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of mercerizing agent used is preferably 0.5 times or more per anhydrous glucose residue of the starting material, more preferably 1.0 times or more, and even more preferably 1.5 times or more, on a molar basis. The upper limit of this amount is usually 20 times or less, preferably 10 times or less, and more preferably 5 times or less. The amount of mercerizing agent used is preferably 0.5 to 20 times, more preferably 1.0 to 10 times, and even more preferably 1.5 to 5 times, on a molar basis.

[0045] The reaction temperature for mercerization is usually above 0°C, preferably above 10°C. The upper limit is usually below 70°C, preferably below 60°C. The reaction temperature is usually between 0 and 70°C, preferably between 10 and 60°C. The reaction time for mercellation is usually 15 minutes or more, preferably 30 minutes or more. The upper limit is usually 8 hours or less, preferably 7 hours or less. The reaction time is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

[0046] The etherification reaction is usually carried out by adding a carboxymethylating agent to the reaction system after mercerization. Examples of carboxymethylating agents include sodium monochloroacetate. The amount of carboxymethylating agent added is preferably 0.05 times or more per glucose residue of the cellulose raw material, more preferably 0.5 times or more, and even more preferably 0.8 times or more, on a molar basis. The upper limit of this amount is usually 10.0 times or less, preferably 5 times or less, and more preferably 3 times or less. The amount of carboxymethylating agent added is preferably 0.05 to 10.0 times, more preferably 0.5 to 5 times, and even more preferably 0.8 to 3 times, on a molar basis.

[0047] The reaction temperature is usually 30°C or higher, preferably 40°C or higher. The upper limit is usually 90°C or lower, preferably 80°C or lower. The reaction temperature is usually 30 to 90°C, preferably 40 to 80°C. The reaction time is usually 30 minutes or more, preferably 1 hour or more. The upper limit is usually 10 hours or less, preferably 4 hours or less. The reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. During the carboxymethylation reaction, the reaction mixture may be stirred as needed.

[0048] -Differences from carboxymethylcellulose- It is preferable that carboxyalkylated cellulose fibers maintain at least a portion of their fibrous shape even when dispersed in water. Carboxyalkylated cellulose fibers are distinct from cellulose powders such as carboxymethylcellulose, which are a type of water-soluble polymer that dissolves in water and imparts viscosity. When an aqueous dispersion of carboxyalkylated cellulose fibers is observed with an electron microscope, fibrous material can be observed. On the other hand, when an aqueous dispersion of carboxymethylcellulose, a type of water-soluble polymer, is observed, no fibrous material is observed. Furthermore, when anionically modified cellulose fibers are measured by X-ray diffraction, peaks of at least one of cellulose type I and type II crystals can be observed, but when carboxymethylcellulose powder, a water-soluble polymer, is measured in the same way, such cellulose type I and type II crystals are usually not observed.

[0049] - Acid-type carboxyalkylated cellulose and desalting - Carboxyalkylated cellulose may contain more acidic carboxyl groups than saltic carboxyl groups, or vice versa. The amounts of saltic carboxyl groups and acidic carboxyl groups can be adjusted by desalting. Desalting can convert saltic carboxyl groups to acidic carboxyl groups. In this specification, carboxyalkylated cellulose (after desalting) is referred to as acidic carboxyalkylated cellulose, and carboxyalkylated cellulose (without undergoing the desalting treatment described later) is referred to as saltic carboxyalkylated cellulose. Saltic carboxyalkylated cellulose usually contains saltic carboxyl groups (-COO -) is the main component. On the other hand, acid-type carboxyalkylated cellulose has many acid-type carboxyl groups, and the ratio of the amount of acid-type carboxyl groups to the amount of carboxyl groups in acid-type carboxyalkylated cellulose is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more. Acid-type carboxyalkylated cellulose is presumed to have superior reinforcing effects with component C. The method for calculating the ratio of acid-type carboxyl groups is as described above.

[0050] The timing of desalting is usually after carboxyalkylation, preferably after etherification and before fibrillation. One method of desalting is to contact the carboxyalkylated cellulose with a cation exchange resin. The cation exchange resin has H counterions. + As long as this condition is met, either a strongly acidic ion exchange resin or a weakly acidic ion exchange resin can be used. The ratio of carboxyalkylated cellulose to the cation exchange resin when contacting the carboxyalkylated cellulose is not particularly limited and can be appropriately set by those skilled in the art from the viewpoint of efficiently performing proton substitution. For example, the ratio can be adjusted so that the pH of the aqueous dispersion after adding the cation exchange resin to the carboxyalkylated cellulose aqueous dispersion is preferably 2 to 6, more preferably 2 to 5. The cation exchange resin after contact can be recovered by conventional methods such as suction filtration.

[0051] - Esterification (Phosphate esterification) - One example of esterified cellulose fibers is phosphorylated cellulose. Phosphorylated cellulose typically has a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, the carbon atom with a primary hydroxyl group at position C6 that constitutes the glucopyranose unit) is phosphorylated.

[0052] The degree of substitution of phosphate groups per glucose unit in phosphate-esterified CNF (hereinafter simply referred to as "degree of phosphate group substitution") is preferably 0.001 or more and less than 0.40. The degree of phosphate group substitution can be measured by the following method. A slurry of phosphate-esterified CNF with a solid content of 0.2% by mass is prepared. A strongly acidic ion exchange resin is added to the slurry by volume at 1 / 10, and after shaking for 1 hour, the slurry is poured onto a mesh with a mesh opening of 90 μm to separate the resin from the slurry and obtain hydrogen-type phosphate-esterified CNF. Next, 0.1 N sodium hydroxide aqueous solution is added to the slurry after treatment with the ion exchange resin in 50 μL increments once every 30 seconds, and the change in the electrical conductivity value of the slurry is measured. The amount of alkali (mmol) required in the region where the electrical conductivity rapidly decreases is divided by the solid content (g) in the slurry to be titrated to calculate the amount of phosphate groups (mmol / g) per 1 g of hydrogen-type phosphate-esterified CNF. Furthermore, the degree of phosphate substitution (DS) per glucose unit of phosphate-esterified CNF is calculated using the following formula: DS = 0.162 × A / (1 - 0.079 × A) A: Amount of phosphate groups per gram of hydrogen-type phosphate-esterified CNF (mmol / g).

[0053] The degree of phosphate group substitution can be adjusted by controlling reaction conditions such as the amount of phosphate-containing compound added and, if necessary, the amount of basic compound added.

[0054] One method of phosphorylation is to react a compound having a phosphate group with unmodified cellulose fibers (phosphate esterification). Examples of phosphate esterification methods include mixing a powder or aqueous solution of a compound having a phosphate group with a cellulosic raw material (e.g., a suspension (solid content concentration of about 0.1 to 10% by mass)) or adding an aqueous solution of a compound having a phosphate group to an aqueous dispersion of a cellulosic raw material, with the latter being preferred. This improves the uniformity of the reaction and increases the esterification efficiency. The pH of the aqueous solution of the compound having a phosphate group is preferably 7 or less from the viewpoint of improving the efficiency of phosphate group introduction, and more preferably 3 to 7 from the viewpoint of suppressing hydrolysis.

[0055] Examples of compounds containing a phosphate group include phosphoric acid, polyphosphate, phosphorous acid, phosphonic acid, polyphosphonic acid, esters and salts thereof. These compounds are low-cost, easy to handle, and allow for the introduction of phosphate groups into cellulose, thereby improving the defibrillation efficiency. Specific examples of compounds containing a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, 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, and ammonium metaphosphate. One or more compounds containing a phosphate group can be used in combination. The amount of compound containing a phosphate group added to the cellulose raw material is preferably 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass, and even more preferably 2 to 200 parts by mass, in terms of phosphorus element, per 100 parts by mass of solid content of the cellulose raw material. This allows for the efficient acquisition of a yield commensurate with the amount of compound containing a phosphate group used. The reaction temperature is preferably 0 to 95°C, and more preferably 30 to 90°C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, and preferably 30 to 480 minutes. If the esterification reaction conditions are within any of these ranges, it is possible to suppress excessive esterification of cellulose and its increased solubility, thereby improving the yield of phosphate-esterified cellulose. When reacting compounds having a phosphate group, a basic compound (for example, a basic compound having an amino group such as urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, etc.) may be added to the reaction system. The suspension obtained after esterification is preferably dehydrated as needed, and then heat-treated. This suppresses hydrolysis of the cellulose raw material. The heating temperature is preferably 100 to 170°C, and it is more preferable to heat at 130°C or lower (preferably 110°C or lower) while water is present during the heat treatment, and then heat-treat at 100 to 170°C after removing the water. It is preferable to perform a washing treatment, such as boiling followed by washing with cold water. This allows for efficient defibration. Washing can be performed by adding water and then dehydrating (e.g., filtration), and may be repeated two or more times. It is preferable to continue washing until the electrical conductivity of the filtrate decreases. For example, it can be continued until the electrical conductivity is preferably 200 or lower, more preferably 150 or lower, and even more preferably 120 or lower. After washing, neutralization treatment may be performed as needed. Neutralization treatment can be performed, for example, by adding alkali (e.g., sodium hydroxide). Washing may be performed again after neutralization.

[0056] - Esterification (phosphorite esterification) - A second example of a method for producing esterified cellulose fibers is phosphorylated cellulose fibers. Phosphorylated cellulose fibers typically have a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, a carbon atom with a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated. The degree of phosphite group substitution per glucose unit in phosphite-esterified cellulose fibers (hereinafter simply referred to as "phosphite group substitution degree") is preferably 0.001 to 0.60. This facilitates electrical repulsion between cellulose cells, making nanofibrillation easier. The degree of phosphite group substitution can be measured using the same method as for measuring phosphate group substitution. The degree of phosphite group substitution can be adjusted by controlling reaction conditions such as the amount of phosphite or its salt added, and, if necessary, the amount of alkali metal ion-containing substances, urea or its derivatives added.

[0057] One method for esterifying phosphorous acid is to react unmodified cellulose fibers with phosphorous acid or its metal salt (preferably sodium hydrogen phosphite) to introduce an ester group of phosphorous acid.

[0058] Examples of phosphorous acid and its metal salts include phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid, and combinations of two or more selected from these, with sodium hydrogen phosphite being preferred. This also allows alkali metal ions to be introduced into the cellulose fibers. The amount of phosphorous acid or its metal salt added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and even more preferably 300 to 1,500 g per 1 kg of unmodified cellulose fiber. In addition to phosphorous acid and its metal salt, alkali metal ion-containing substances (e.g., hydroxides, metal sulfates, metal nitrates, metal chlorides, metal phosphates, metal carbonates) may be further added to the reaction system.

[0059] Furthermore, urea or its derivatives may be added to the reaction system. This allows carbamate groups to be introduced into the cellulose fibers. Examples of urea and urea derivatives include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and two or more combinations selected from these, with urea being preferred. The amount of urea and urea derivatives added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and even more preferably 0.5 to 10 mol per 1 mol of phosphorous acid or its metal salt.

[0060] The reaction temperature is preferably 100-200°C, more preferably 100-180°C, and even more preferably 100-170°C. During the heat treatment, it is preferable to heat at 130°C or below (preferably 110°C or below) while water is present, and then, after removing the water, to heat-treat at 100-170°C. The reaction time is usually about 10-180 minutes, more preferably 30-120 minutes. It is preferable to wash the phosphite-esterified cellulose fibers before defibration. The degree of substitution of phosphite groups per glucose unit is preferably 0.01 or more and less than 0.23.

[0061] - Esterification (Sulfuric acid esterification) - A third example of a method for producing esterified cellulose fibers is sulfated cellulose fibers. Sulfated cellulose typically has a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, a carbon atom with a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is sulfated.

[0062] The amount of sulfate groups per glucose unit in sulfated esterified cellulose fibers (hereinafter simply referred to as "amount of sulfate groups") is preferably 0.1 to 3.0 mmol / g. By introducing cationic substituents into the cellulose raw material, the cellulose molecules repel each other electrically. For this reason, cationized cellulose with introduced cationic substituents can be easily nanofibrillated. If the degree of cationic substitution per glucose unit is 0.02 or higher, sufficient nanofibrillation can be achieved due to the electrical repulsion between the cellulose molecules. On the other hand, if the degree of cationic substitution per glucose unit is 0.50 or lower, swelling or dissolution can be suppressed, preventing situations where nanofibers cannot be obtained. To efficiently perform fibrillation, it is preferable to wash the cationized cellulose obtained above.

[0063] The amount of sulfate groups per glucose unit can be measured by the following method: A aqueous dispersion of sulfated CNF is solvent-substituted with ethanol and then t-butanol, and then freeze-dried. 200 mg of the resulting sample is mixed with 15 ml of ethanol and 5 ml of water, and stirred for 30 minutes. Then, 10 ml of 0.5 N sodium hydroxide aqueous solution is added, and the mixture is stirred at 70°C for 30 minutes, followed by stirring at 30°C for 24 hours. Next, phenolphthalein is added as an indicator, and the mixture is titrated with hydrochloric acid. The amount of sulfate groups is then calculated using the following formula: Sulfate group amount [mmol / g sample] = (5 - (0.1 × hydrochloric acid titration volume [ml] × 2)) / 0.2.

[0064] The amount of sulfate groups can be adjusted by controlling reaction conditions such as the amount of sulfate-based compound added to the reaction.

[0065] One method of sulfuric acid esterification is to react unmodified cellulose fibers with a sulfuric acid compound, thereby introducing sulfuric acid groups derived from the sulfuric acid compound into the cellulose to produce sulfuric acid-esterified cellulose. Examples of sulfuric acid compounds include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, or esters or salts thereof. Among these, sulfamic acid is preferred because it has low cellulose solubility and low acidity.

[0066] For example, when sulfamic acid is used as the sulfate compound, the amount of sulfamic acid used can be appropriately adjusted considering the amount of anionic group introduced into the cellulose chain. For example, the amount is preferably 0.01 to 50 mol, more preferably 0.1 to 3.0 mol, per mol of glucose units in the cellulose molecule.

[0067] -Salt type / Acid type- Esterified cellulose may contain more acidic carboxyl groups than salt-type carboxyl groups, or vice versa. Esterified cellulose that has not undergone desalting treatment and that has undergone desalting treatment are called salt-type esterified cellulose and acid-type esterified cellulose, respectively. Salt-type esterified cellulose mainly contains salt-type carboxyl groups. Acid-type esterified cellulose is presumed to be superior due to its reinforcing effect with component C. The countercation of the salt-type carboxyl group and its preparation method are as described in the description of oxidized cellulose.

[0068] -Cationization- Cationized cellulose typically has a structure in which at least one carbon atom constituting the cellulose molecular chain (for example, the carbon atom with a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is cationized, and usually contains cations such as ammonium, phosphonium, sulfonium, or groups having such cations in the molecule. The degree of cation substitution per glucose unit in cationized cellulose is preferably 0.02 to 0.50. The degree of cation substitution per glucose unit can be measured by the following method: After drying the cationized cellulose fibers, the nitrogen content is measured using a total nitrogen analyzer (TN-10, manufactured by Mitsubishi Chemical Corporation), and the degree of cation substitution (average number of moles of substituents per mole of anhydrous glucose unit) is calculated using the following formula: Degree of cation substitution = (162 × N) / (1 - 151.6 × N) N: Nitrogen content.

[0069] The degree of cation substitution can be adjusted by reaction conditions such as the amount of cationizing agent added and the composition ratio of water or C1-C4 alcohols.

[0070] One method of cationization involves reacting unmodified cellulose fibers with a cationizing agent (e.g., glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrate, or its halohydrin form) and an alkali metal hydroxide catalyst (e.g., sodium hydroxide, potassium hydroxide) in the presence of water and / or an alcohol having 1 to 4 carbon atoms. By using any of the cationizing agents exemplified above, cationized cellulose having a quaternary ammonium group can be obtained. The cationization reaction is usually carried out in the presence of water or alcohol.

[0071] The amount of cationizing agent is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of cellulose raw material. The upper limit of this amount is usually 800 parts by mass or less, and preferably 500 parts by mass or less. Examples of catalysts used as needed during cationization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of catalyst is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of cellulose raw material. The upper limit of this amount is usually 7 parts by mass or less, and preferably 3 parts by mass or less.

[0072] -Basic-type cationized cellulose fiber- It is preferable to convert the cationized cellulose fibers, after cationization, into basic-type cationized cellulose or basic-type cationized cellulose nanofibers by desalting. Desalting allows the salts in the cationized cellulose to be converted into bases. In this specification, cationized cellulose (nanofibers) that have undergone desalting are referred to as basic-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (basic type). Furthermore, cationized cellulose and cationized cellulose nanofibers that have not undergone desalting are referred to as salt-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (salt type). Desalting may be performed at either the pre-fibrillation (cationized cellulose) or post-fibrillation (cationized cellulose nanofibers) stage described later. Desalting means replacing the salts (e.g., Cl-) contained in cationized cellulose (salt type) and cationized cellulose nanofibers (salt type) with bases to make them basic type. An example of a desalting method after cationization is to contact cationized cellulose or cationized cellulose nanofibers with an anion exchange resin. As long as the counterion is OH-, either a strongly basic ion exchange resin or a weakly basic ion exchange resin can be used. The ratio of modified cellulose to the anion exchange resin when contacting them is not particularly limited and can be appropriately set by those skilled in the art from the viewpoint of efficiently performing cation substitution. For example, the ratio can be adjusted so that the pH of the aqueous dispersion after adding the anion exchange resin to the cationized cellulose nanofiber aqueous dispersion is preferably 8 to 13, more preferably 9 to 13. The anion exchange resin after contact can be recovered by conventional methods such as suction filtration.

[0073] [Miniaturization (fibrillation, fibrillation)] Micronization is usually carried out by mechanical processes. These mechanical processes (preferably beating or disintegration) are usually carried out in a wet manner (i.e., in the form of an aqueous dispersion of cellulose fibers). Examples of equipment used for mechanical processing include refiners (e.g., disc type, conical type, cylinder type), high-speed defibrators, shear-type agitators, colloid mills, high-pressure jet dispersers, beaters, PFI mills, kneaders, dispersers, high-speed dissociators (top finers), high-pressure or ultra-high-pressure homogenizers, grinders (stone mill type grinders), ball mills, vibratory mills, bead mills, single-screw, twin-screw or multi-screw kneaders / extruders, homomixers under high-speed rotation, refiners, defibrators, friction grinders, high-shear defibrators, dispersers, homogenizers (e.g., microfluidizers), and other equipment capable of providing mechanical defibration. Equipment capable of providing defibration in a wet manner is preferred, and high-speed dissociators and refiners are more preferred, but are not particularly limited.

[0074] When defibration is performed by a wet process, an aqueous dispersion of cellulose fibers is usually prepared. The solid content concentration of modified cellulose in the aqueous dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. The upper limit of the concentration is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. During mechanical processing, pH adjustment (e.g., 7 or less, 6 or less, 5 or less) may be performed as needed.

[0075] Prior to the preparation of the aqueous dispersion, pretreatment such as dry grinding (e.g., grinding after drying) may be performed. Examples of the apparatus used for dry grinding include, but are not particularly limited to, impact mills such as hammer mills and pin mills, media mills such as ball mills and tower mills, and jet mills. Also, post-treatment may be performed after fibrillation. Examples of post-treatment include, but are not particularly limited to, drying (e.g., freeze-drying method, spray-drying method, shelf drying method, drum drying method, belt drying method, method of thinly spreading on a glass plate and drying, fluidized bed drying method, microwave drying method, heat-generating fan type vacuum drying method, vacuum (degassing) drying), redispersion in water (the dispersion apparatus is not limited), and grinding (e.g., grinding using equipment such as cutter mills, hammer mills, pin mills, and jet mills).

[0076] [Optional post-treatment] The microcrystalline cellulose fibers may be in the state of an aqueous dispersion obtained after production, or may be subjected to post-treatment as necessary. Examples of post-treatment include, but are not particularly limited to, drying (e.g., freeze-drying method, spray-drying method, shelf drying method, drum drying method, belt drying method, method of thinly spreading on a glass plate and drying, fluidized bed drying method, microwave drying method, heat-generating fan type vacuum drying method), redispersion in water (the dispersion apparatus is not limited), and grinding (e.g., grinding using equipment such as cutter mills, hammer mills, pin mills, and jet mills).

[0077] [Physical properties of microcrystalline cellulose fibers] The microcrystalline cellulose fibers preferably have the following physical properties. >

[0078] -Specific surface area- The BET specific surface area of the microcrystalline cellulose fibers is preferably 25 m 2 / g or more, more preferably 50 m 2 / g or more, and even more preferably 100 m 2The specific surface area is 1 / g or more. The BET specific surface area can be measured using a BET specific surface area meter after replacing the aqueous dispersion with t-BuOH and freeze-drying the sample according to the nitrogen gas adsorption method (JIS Z 8830). A specific surface area that meets this range is preferable because it increases the number of adhesion points between the gel nail layer and the primer layer, improving interlayer adhesion.

[0079] -Crystallization of Cellulose Type I- The crystallinity of type I cellulose in fine cellulose fibers is usually 10% or more, preferably 30% or more, and 50% or more. There is no particular upper limit, but in reality, it is considered to be around 90%. The crystallinity of cellulose can be controlled by the degree of chemical modification. The crystallinity of type I cellulose can be calculated by measuring and comparing the intensities of the (200) peak around 22.6° and the valley between (200) and (110) (around 18.5°) using X-ray diffraction. If the fine cellulose fibers contain type II crystals, it is preferable to separate the peaks based on type II crystals (around 12.3°, 20.2°, and 21.9°) before calculating the intensity of the type I crystals.

[0080] -viscosity- When fine cellulose fibers are used as an aqueous dispersion, a low viscosity of the aqueous dispersion is preferable. This allows for a material with good handling properties despite being fibrillated. For example, the B-type viscosity (25°C, 60 rpm) of an aqueous dispersion with 1% solids by mass is usually 5,000 mPa·s or less, preferably 4,500 mPa·s or less, and more preferably 4,000 mPa·s or less. The lower limit is preferably 10 mPa·s or more, more preferably 20 mPa·s or more, even more preferably 50 mPa·s or more, 100 mPa or more, 500 mPa or more, and 1,000 mPa or more. The B-type viscosity can be measured, for example, by the following method: After fibrillation (e.g., defibrillation), let it stand for at least one day, dilute as necessary, stir with a homodisperser (e.g., 3000 rpm, 5 min), and then measure the viscosity (measure the viscosity after 60 rpm, 3 minutes of rotation). By meeting this viscosity range, the workability of applying the primer layer is improved, allowing for easy application without requiring high skill levels from the applicator.

[0081] -Transparency- In this specification, the transparency of fine cellulose fibers refers to the transparency of a 1.0% by mass aqueous dispersion of fine cellulose fibers, and is measured using a UV-VIS spectrophotometer UV-265FS (manufactured by Shimadzu Corporation) at a wavelength of 660 nm. The transparency is preferably 60% or higher, more preferably 70% or higher, even more preferably 80% or higher, and particularly preferably 90% or higher and 95% or higher. A transparency within this range is preferable because it makes the primer layer clearer, thereby increasing the aesthetic appeal when forming artificial nails.

[0082] <Artificial Nail Application Method> The present invention's method for applying artificial nails includes the step of forming a primer layer on the surface of the nail.

[0083] [Primer layer] In this specification, the primer layer is a layer formed between the surface of the nail and the artificial nail (e.g., gel nail), and serves as a base layer for the artificial nail. The primer layer can be formed by applying the aforementioned aqueous dispersion containing fine cellulose fibers to the surface of the nail.

[0084] -solvent- For aqueous dispersions containing fine cellulose fibers, it is important that the solvent used is primarily water. In this specification, a primarily water-based solvent means an organic solvent-suppressing solvent.

[0085] Any hydrophilic organic solvent can be used as a solvent other than water in the aqueous dispersion. Examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, butanol, glycerin, acetone, methyl ethyl ketone, 1,4-dioxane, N-methyl-2-pyrrolidone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, and combinations thereof. Among these, lower alcohols with 1 to 4 carbon atoms, such as methanol, ethanol, and 2-propanol, are preferred, and methanol and ethanol are more preferred, with ethanol being even more preferred, from the viewpoint of safety and availability.

[0086] However, an objective of the present invention is to avoid using solvents that are highly irritating to the skin, even in small amounts. Preferably, the solvent is 60% or more, 70% or more, and more preferably 80% or more, 90% or more, 95% or more, 98% or more, 99% or more, or 100%.

[0087] -Concentration of fine cellulose fibers- The concentration of fine cellulose fibers in the aqueous dispersion containing fine cellulose fibers is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. The upper limit of the concentration is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, 5% by mass or less, 3% by mass or less, and 2% by mass or less.

[0088] -Additives other than fine cellulose fibers (such as adhesives)- Other additives to the aqueous dispersion besides fine cellulose fibers include, for example, adhesives such as polyvinyl alcohol, gelatin, and polysaccharide polymers, as well as other additives besides fine cellulose fibers (e.g., adhesives, preservatives (e.g., sorbic acid or its salts), thickeners, dispersants, antifungal agents, defoaming agents, cosmetic agents to enhance aesthetics, lubricants, etc.). Of these, it is preferable to add an adhesive because it can further improve the adhesion between the gel nail layer and the primer layer. It is also preferable to add a preservative because it can further improve shelf life.

[0089] Such an adhesive preferably contains 0.01 to 1000 parts by mass, more preferably 0.03 to 500 parts by mass, 0.05 to 300 parts by mass, 0.07 to 100 parts by mass, or 0.1 to 50 parts by mass per 100 parts by mass of fine cellulose fibers. By including the fine cellulose fibers and the adhesive in the aqueous dispersion within the above-mentioned ranges, sufficient adhesion to the gel nail layer is maintained, while the gel nail layer can be easily peeled off in the vibration treatment method described later.

[0090] -Application Method- The method for applying the aqueous dispersion to the nail surface is not particularly limited as long as it can cover the nail surface with the aqueous dispersion. Tools such as brushes and sprayers may be used as needed. The amount of aqueous dispersion applied (wet application amount per nail) is preferably 0.01 to 1 g, more preferably 0.05 to 0.5 g. After applying the aqueous dispersion to the nail, the solvent can be removed by drying methods such as natural drying or hot air drying to obtain a primer layer.

[0091] The term "nail surface" usually refers to the uncoated (i.e., exposed) surface of the nail, but it may also include cases where a small amount of a functional substance is coated on the nail, as long as it does not hinder the effects of the present invention.

[0092] -Artificial nails- In this specification, "artificial nail" refers to a nail that is artificially manufactured, rather than a nail that is a biological organ. Examples include gel nails, manicures, pedicures, and nail tips, with gel nails being preferred. Gel nails are typically artificial nails formed by sequentially layering a base gel layer, a color gel layer, (a clear gel layer if necessary), and a top gel layer through light curing treatment or the like (formed by so-called gel nail treatment).

[0093] The formation process for artificial nails can follow conventional treatment methods without any particular restrictions. For example, in the case of gel nail treatment, the raw material compositions (gel nail compositions) for each layer that make up the gel nail are sequentially layered. As the gel nail compositions that make up each layer, compositions can be used that mainly consist of acrylic resins or curable resins having functional groups such as urethane (meth)acrylate, and also include polymerizable monomer components (monofunctional or polyfunctional monomers) and polymerization initiators.

[0094] For the base gel layer, a highly transparent gel nail composition is used as is, or with a small amount of colorant added to create yellow, purple, or blue to prevent color changes due to deterioration over time.

[0095] For the colored gel layer, colorants and metallic powders (glitter) can be added to such gel nail compositions to create a variety of colors, including solid colors, glittery finishes, metallic finishes, dark colors, and light colors. For the clear gel layer, a colorless, transparent gel nail composition without added colorants can be used.

[0096] For the top gel layer, similar to the base gel layer, a highly transparent gel nail composition is used as is, or with a small amount of colorant added to create yellow, purple, or blue to prevent color changes due to deterioration over time.

[0097] [Formation of artificial nails] In the present invention, after forming a primer layer, an artificial nail can be formed by coating the surface of the primer layer. If the artificial nail is a gel nail, the gel nail composition may be applied to the surface of the primer layer using a brush or other tool as needed, and then cured with ultraviolet light, and the next layer may be formed on the surface in the same manner sequentially. Alternatively, an artificial nail (commercially available nail tips may also be used) that has been pre-coated, cured, and molded into a predetermined shape such as a nail in a sheet form may be coated and adhered to the surface of the primer layer. Furthermore, a coating film may be created on a base sheet in a predetermined shape such as a nail, and this may be layered on the primer layer, cured, and then the base sheet may be removed.

[0098] The nails targeted by the artificial nail treatment method of the present invention may be human fingernails, toenails, or even animal nails such as those of dogs or cats.

[0099] <Procedure for removing artificial nails> The present invention's method for removing artificial nails includes a step of removing an artificial nail, which is a gel nail covering the nail surface via a primer layer. The primer layer is preferably a primer layer containing the fine cellulose described above.

[0100] [Peeling process] Methods of removal include, for example, underwater vibration treatment and steam treatment. This method allows for the removal of artificial nails without causing biological irritation, as is done conventionally with solvents to soften the artificial nails.

[0101] -Underwater vibration processing- In this specification, underwater vibration treatment means a process of applying vibration to an artificial nail underwater. The vibration treatment preferably generates vibrations of 1000 Hz or higher from a vibration source, more preferably 2000 Hz or higher, even more preferably 3000 Hz or higher, and particularly preferably 5000 Hz or higher. There is no particular upper limit, but any vibration treatment that does not affect the human body is acceptable, preferably 60000 Hz or lower, more preferably 50000 Hz or lower, and even more preferably 45000 Hz or lower.

[0102] The processing time for vibration treatment can be set appropriately depending on the intensity of the vibration, but it is preferably between 1 second and 5 minutes, more preferably between 3 seconds and 3 minutes, even more preferably between 5 seconds and 2 minutes, and particularly preferably between 7 seconds and 1 minute. When the processing time for vibration treatment is within this range, it is possible to cleanly remove the artificial nail while ensuring work efficiency, which is preferable.

[0103] While there are no particular restrictions on the vibration source, and any known source can be used, considering that nail technicians typically operate small-scale shops and it is difficult to introduce specialized equipment, simpler devices such as an ultrasonic eyeglass cleaner (approximately 40,000 Hz vibration processing) or an electric toothbrush (approximately 6,000 Hz vibration processing) may be used.

[0104] Additionally, if necessary, light pressure may be applied with a pusher or similar device during or after the underwater vibration treatment to assist in the separation process.

[0105] [Steam treatment] The artificial nails applied using the present invention's artificial nail application method are groundbreaking because, unlike conventional methods that require solvent-based softening treatments for artificial nails, they can be easily and cleanly removed from the primer layer while minimizing biological irritation simply by, for example, steaming the artificial nail application area for a certain period of time.

[0106] The steam treatment can be any treatment that involves applying steam to the artificial nail. For example, the artificial nail treatment area is exposed to steam generated by heating water. The exposure time is usually 5 seconds or more, preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 25 seconds or more. This allows the steam to penetrate sufficiently into the primer layer and reduce the adhesive strength of the primer layer. There is no particular upper limit to the treatment time, but considering workability and the safety of the patient, it is preferably 20 minutes or less, more preferably 10 minutes or less, and even more preferably less than 5 minutes.

[0107] For steam treatment, commercially available steam-off machines can be used, such as the SHINYGEL professional steam-off machine (SOM-1) from Shinygel Professional. This can be done by generating water vapor instead of acetone vapor in the remover container of this device.

[0108] While conventional steam-off machines use acetone as a remover and detach artificial nails through acetone steam treatment, the present invention, by appropriately incorporating fine cellulose fibers into the primer layer, allows the primer layer to begin to deform through swelling and other means by steam treatment with water vapor alone, without the need for acetone, thus lifting the gel nail layer and making it easy to remove.

[0109] Furthermore, before steam treatment, it is preferable to lightly poke the end of the artificial nail with a pusher or similar tool to prepare a small gap that allows steam to penetrate.

[0110] Additionally, if necessary, light pressure may be applied with a pusher or similar tool after steam treatment to assist in the peeling process.

[0111] The reason why artificial nails can be cleanly removed in a short time using the method of the present invention is presumed to be that, as a result of the removal treatment such as vibration treatment and steam treatment, the fine cellulose fibers used in the primer layer resonate, allowing water to enter the countless gaps created between the primer layers, and the primer layers begin to deform due to swelling, etc., which allows the laminated artificial nails to be easily removed. [Examples]

[0112] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these. Unless otherwise specified, parts and % refer to parts by mass and mass%.

[0113] (Manufacturing Example 1: Preparation of Primer Agent) A water dispersion A (transparency 95%) was prepared using TEMPO-oxidized cellulose nanofibers (TC-01A, manufactured by Nippon Paper Industries Co., Ltd.) having a carboxyl group as a fine cellulose fiber, with a solid content of 1% by mass. In addition, a PVA aqueous solution B was prepared by dissolving polyvinyl alcohol (Gosenol® EG-05C, manufactured by Mitsubishi Chemical Corporation) to a solid content of 15% by mass.

[0114] 100 parts of the obtained aqueous dispersion A were placed in a stainless steel mixer equipped with stirring blades, and 2 parts of PVA aqueous solution B, 0.005 parts of potassium sorbate (manufactured by Yoneyama Pharmaceutical Co., Ltd.) as a preservative, and 10 parts of water were added. The mixture was then stirred at a rotation speed of 700 rpm for 5 minutes to obtain primer agent 1.

[0115] (Example 1: Artificial nail treatment) As described above, approximately 0.1g of the obtained primer agent 1 was applied to the subject's thumbnail with a brush and dried with a hairdryer for about 20 seconds. Then, the base gel, color gel, and top gel described later were applied in that order to the base layer with a brush, and cured by irradiation with ultraviolet light for 30 seconds, thereby obtaining artificial nail 1 in which the base gel layer, color gel layer, and top gel layer were applied in that order via the primer layer.

[0116] The thumb, to which artificial nail 1 had been applied, was left undisturbed in water for 5 minutes with the treated area submerged. After being removed from the water, pressure was applied to the artificial nail 1, but the artificial nail 1 remained firmly attached and did not peel off.

[0117] (Gel) Base gel: Manufactured by Inlet Co., Ltd. / Dorcus Base Gel Color Gel: Manufactured by MK Electric LLC / Rinogel Skin 305 Top gel: Clear Gel EX, manufactured by Nail Select Co., Ltd.

[0118] (Example 2: Artificial nail removal procedure 1 (underwater vibration treatment)) As described in Example 1, the thumb on which artificial nail 1 was applied was immersed in a water-filled ultrasonic spectacle cleaner so that the entire treated area was submerged, and then vibration treatment (approximately 40,000 Hz) was performed for about 30 seconds.

[0119] After the vibration treatment, the treated area was lifted out of the water. Since the artificial nail had not completely detached, light pressure was applied to the artificial nail using a pusher, and the artificial nail peeled off cleanly along with the base gel layer.

[0120] (Example 3: Artificial nail removal procedure 2 (steam treatment)) I placed water in the tray of the SHINYGEL professional steam-off machine (SOM-1) from Shinygel Professional, and started heating it. As in Example 1, the thumb, which had been treated with artificial nail 1, was gently pushed with a pusher at the edge of the artificial nail 1 to create a small gap. Then, the finger was placed in a sufficiently heated steam-off machine and treated with steam for 30 seconds. After the procedure, I removed my finger, and since the artificial nail hadn't completely detached, I applied light pressure to the artificial nail using a pusher, and the artificial nail peeled off cleanly along with the base gel layer.

[0121] (Comparative Example 1) Artificial nail 2 was obtained in the same manner as in Example 1, except that a commercially available primer 2 (ibd / Powerbond; containing ethyl acetate, isopropylidene diphenylbis(oxyhydroxypropyl methacrylate), and hydroxyethyl methacrylate (HEMA)) was used instead of primer 1. When the obtained artificial nail 2 was subjected to the same treatment as in Example 2, the artificial nail 2 did not peel off even when considerable pressure was applied with a pusher (which was stopped midway due to pain).

Claims

1. An artificial nail treatment method that involves performing an artificial nail formation treatment via a primer layer, The process includes a step of applying an aqueous dispersion containing fine cellulose fibers to the surface of the nail to form a primer layer. The artificial nail is a gel nail, The aforementioned fine cellulose fibers have an average fiber diameter of 1 to 500 nm and an average fiber length of 50 to 2000 nm. A method for applying artificial nails, characterized in that the solvent used in the aqueous dispersion is 100% water.

2. The method for performing artificial nail treatment according to claim 1, characterized in that the fine cellulose fibers are chemically modified fine cellulose fibers.

3. The method for applying artificial nails according to claim 1 or 2, characterized in that the fine cellulose fibers have a transparency of 60% or more when dispersed in a 1.0% by mass aqueous solution.