JP7140499B2 - Aqueous composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aqueous composition containing ceramides and cellulose nanofibers.

Ceramide is present in the stratum corneum of the skin and plays an important role in constructing a lipid barrier necessary for retaining moisture and maintaining moisture. Ceramide in the stratum corneum is produced by decomposing cerebroside with an enzyme called cerebrosidase. A part of ceramide is converted into phytosphingosine and sphingosine by an enzyme called ceramidase, and is known to be an important regulator of cell growth and differentiation. There are six different types of ceramides in human skin, each with different functions.

However, ceramide is a highly crystalline substance, has low solubility in other oil agents, and crystals precipitate at low temperatures. there were. Moreover, although it is possible to disperse the aqueous ceramide dispersion using a surfactant or the like, there is also the problem that crystal precipitation or precipitation occurs over time during storage.

On the other hand, as a technique for stably dispersing ceramides, it is known to incorporate specific thickening polysaccharides such as xanthan gum and guar gum. discloses a liquid skin care composition containing ceramide.

JP 2016-69323 A

However, in order to sufficiently stably disperse ceramides, it is necessary to increase the amount of the thickening polysaccharide, which may cause stickiness and impair the feeling of use.

An object of the present invention is to provide a ceramide-containing water-based composition in which ceramides are stably dispersed and sedimentation does not occur over time.

As a result of intensive studies in order to achieve this object, the present inventors have found that blending cellulose nanofibers (CNF) is extremely effective, and completed the present invention.

The present invention provides the following.
(1) A water-based composition containing ceramides and cellulose nanofibers.
(2) The water-based composition according to (1), which is a cosmetic additive.

According to the present invention, it is possible to provide an aqueous composition containing ceramides in which ceramides are stably dispersed and sedimentation does not occur over time.

The present invention will be described in detail below. In the present invention, "-" includes end values. That is, "X through Y" includes the values X and Y at both ends.

The aqueous composition of the present invention is characterized by containing ceramides and cellulose nanofibers.

<Ceramides>
The ceramides in the present invention include ceramides and their derivatives, regardless of origin such as synthetic products and extracts. The term "ceramides" as used in the present invention includes natural ceramides and compounds having this as a basic skeleton, as well as precursors from which these compounds can be derived, and sugar-modified ceramides such as natural ceramides and glycosphingolipids , ceramide analogues, sphingosine and phytosphingosine, and their derivatives. The ceramides in the present invention are described in detail below.

<Natural ceramide>
In the present invention, natural ceramide means ceramide having the same structure as that present in human stratum corneum. A more preferred embodiment of the natural ceramide is one that does not contain glycosphingolipids and has three or more hydroxyl groups in its molecular structure.
The natural ceramide that can be used in the present invention is described in detail below.

Examples of basic structural formulas of natural ceramides that can be suitably used in the present invention are shown in (1-1) to (1-9) below.
(1-1) is ceramide 1, (1-2) is ceramide 9, (1-3) is ceramide 4, (1-4) is ceramide 2, (1-5) is ceramide 3, (1-6) is known as ceramide 5, (1-7) as ceramide 6, (1-8) as ceramide 7, and (1-9) as ceramide 8.

The above structural formulas show examples of each ceramide, but since it is a natural product, ceramides actually derived from humans, animals, etc. have various variations in the length of the above alkyl chain. However, the alkyl chain may have any structure as long as it has the above skeleton.
In addition, the above ceramides are modified according to the purpose, such as by introducing a double bond into the molecule to impart solubility, or by introducing a hydrophobic group to impart permeability. can also be used.

Ceramides having a general structure, which are called natural types, include natural products (extracts) and those obtained by microbial fermentation, but may also include synthetic products and animal-derived ceramides.
For these ceramides, the natural (D(-) form) optically active form is used. Mixtures of natural forms may also be used. The relative configuration of the above compounds may be a natural configuration, a non-natural configuration, or a mixture thereof.
When the aqueous composition of the present invention is used for purposes such as a skin emollient, it is preferable to use a larger amount of the natural optically active substance from the viewpoint of the barrier effect.

Such natural ceramides are also available as commercial products. Takasago International Corporation), CERAMIDE II (manufactured by Quest International), DS-Ceramide VI, DS-CLA-Phytoceramide, C6-Phytoceramide, DS-ceramide Y3S (manufactured by DOOSAN), CERAMIDE2 (manufactured by Sederma) and the like. Further, the exemplary compound (1-5) is "Ceramide 3" [trade name, manufactured by Evonik (former Degussa)], and the exemplary compound (1-7) is "Ceramide 6" [trade name, Evonic (former Degussa)].

When natural ceramides are used as ceramides, they may be used alone or in combination of two or more. Ceramides generally have a high melting point and high crystallinity. It is preferable from the viewpoint of emulsion stability and handleability.

<Sugar modified ceramide>
A sugar-modified ceramide is a ceramide compound containing sugars in the molecule. Sugars contained in the molecule of the ceramide compound include, for example, monosaccharides such as glucose and galactose; disaccharides such as lactose and maltose; Saccharides, polysaccharides and the like can be mentioned. Moreover, the sugar may be a sugar derivative in which the hydroxyl group in the sugar unit is replaced with another group. Examples of such sugar derivatives include glucosamine, curcuronic acid, N-acetylglucosamine, and the like.
Among them, from the viewpoint of dispersion stability, saccharides having 1 to 5 sugar units are preferable, and specifically, glucose and lactose are preferable, and glucose is more preferable.
Specific examples of sugar-modified ceramides include the following.

Sugar-modified ceramides are available both synthetically and commercially. For example, the above-exemplified compound (4-1) is available from Okayasu Shoten as “Comesphingoglycolipid” (trade name).

<Ceramide analogue>
Ceramide analogues are synthesized to mimic the structure of ceramide. As such known compounds of ceramide analogues, for example, ceramide analogues represented by the following structural formulas can also be used.

When a ceramide analog is applied, for example, from the viewpoint of the feeling of use and moisturizing feeling of cosmetics containing the water-based composition of the present invention, it is preferably an analog of natural ceramide or sugar-modified ceramide. Analogues are more preferred.

<Sphingosine, Phytosphingosine>
As sphingosine and phytosphingosine, natural sphingosine and sphingosine analogues can be used regardless of whether they are synthetic products or natural products.

Specific examples of naturally occurring sphingosines include sphingosine, dihydrosphingosine, phytosphingosine, sphingadienine, dehydrosphingosine, dehydrophytosphingosine, and their N-alkyl (eg, N-methyl) and acetylated forms. is mentioned.
For these sphingosines, whether a natural (D(-) form) optically active form, a non-natural (L(+) form) optically active form, or a mixture of natural and non-natural forms is used. may be used. The relative configuration of the above compounds may be a natural configuration, a non-natural configuration, or a mixture thereof. Specific examples include PHYTOSPHINGOSINE (INCI name; 8th Edition) and exemplary compounds described below.

As phytosphingosine, either a natural extract or a synthetic product may be used. It is also available both synthetically and as a commercial product.
Commercially available natural sphingosines include, for example, D-Sphingosine (4-Sphingenine) (SIGMA-ALDRICH), DSphytosphingosine (DOOSAN), and phytosphingosine (Cosmo Pharm). 5-5) is available as “Phytosphingosine” (trade name) manufactured by Evonik (formerly Degussa).

In the present invention, the ceramides as described above may be used as they are added to the aqueous solvent, or may be used after being emulsified.

<Cellulose nanofiber>
In the present invention, cellulose nanofibers (CNF) are fine fibers with a fiber diameter of about 3 to 500 nm, which are obtained by miniaturizing pulp, which is a cellulose raw material, to the nanometer level. The average fiber diameter and average fiber length of cellulose nanofibers are obtained by averaging the fiber diameter and fiber length obtained from the results of observing each fiber using an atomic force microscope (AFM) or a transmission electron microscope (TEM). can be obtained by Cellulose nanofibers are obtained by applying a mechanical force to pulp to make it finer, or carboxylated cellulose (also called oxidized cellulose), carboxymethylated cellulose, cellulose with a phosphate ester group introduced, It can be obtained by defibrating modified cellulose obtained by chemical modification such as cationized cellulose. The average fiber length and average fiber diameter of fine fibers can be adjusted by oxidation treatment and fibrillation treatment.

The average aspect ratio of the cellulose nanofibers used in the present invention is usually 50 or more. Although the upper limit is not particularly limited, it is usually 1000 or less. Average aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length/average fiber diameter

<Cellulose raw material>
The origin of the cellulose raw material, which is the raw material of the cellulose nanofiber, is not particularly limited. , 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 pulp, waste paper, etc.), animals (for example, sea squirts), algae, microorganisms (for example, acetobacter), microbial products, etc. Cellulose raw materials include these Either one or a combination of two or more types may be used, preferably a plant- or microorganism-derived cellulose raw material (e.g., cellulose fiber), more preferably a plant-derived cellulose raw material (e.g., cellulose fiber).

Although the number average fiber diameter of the cellulose raw material is not particularly limited, it is about 30 to 60 μm for softwood kraft pulp and about 10 to 30 μm for hardwood kraft pulp, which are common pulps. In the case of other pulps, those that have undergone general refining are about 50 μm. For example, in the case of refining a chip or the like having a size of several cm, it is preferable to perform a mechanical treatment with a disaggregator such as a refiner or a beater to adjust the size to about 50 μm.

<Chemical denaturation>
[Carboxymethylation]
In the present invention, when carboxymethylated cellulose is used as the modified cellulose, the carboxymethylated cellulose may be obtained by carboxymethylating the above cellulose raw material by a known method, or may be obtained using a commercially available product. good too. In any case, the degree of carboxymethyl group substitution per anhydroglucose unit of cellulose is preferably 0.01 to 0.50. As an example of the method for producing such carboxymethylated cellulose, the following method can be mentioned. Using cellulose as a starting material, 3 to 20 times by weight of water and/or lower alcohol as a solvent, specifically water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary A single medium such as butanol or a mixed medium of two or more types is used. When the lower alcohol is mixed, the mixing ratio of the lower alcohol is 60 to 95% by mass. As the mercerizing agent, an alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, is used in an amount of 0.5 to 20 times the moles of the anhydroglucose residue of the starting material. The starting material, solvent, and mercerizing agent are mixed and mercerized at a reaction temperature of 0 to 70° C., preferably 10 to 60° C., for a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent is added at 0.05 to 10.0 mol per glucose residue, 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. The etherification reaction is carried out for ~4 hours.

In the present specification, "carboxymethylated cellulose", which is a type of modified cellulose used for preparing cellulose nanofibers, means that at least part of the fibrous shape is maintained even when dispersed in water. Say. Therefore, it is distinguished from carboxymethyl cellulose, which is a kind of water-soluble polymer. When an aqueous dispersion of "carboxymethylated cellulose" is observed with an electron microscope, a fibrous substance can be observed. On the other hand, no fibrous substance is observed in an aqueous dispersion of carboxymethyl cellulose, which is a type of water-soluble polymer. In addition, when "carboxymethylated cellulose" is measured by X-ray diffraction, a peak of cellulose type I crystals can be observed, but cellulose type I crystals are not observed in carboxymethyl cellulose, which is a water-soluble polymer.

[Carboxylation]
In the present invention, when carboxylated (oxidized) cellulose is used as modified cellulose, the carboxylated cellulose (also referred to as oxidized cellulose) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. . Although not particularly limited, during carboxylation, the amount of carboxyl groups should be adjusted to 0.6 to 2.0 mmol/g with respect to the absolute dry mass of anion-modified cellulose nanofibers. is preferable, and it is more preferable to adjust the concentration to be 1.0 mmol/g to 2.0 mmol/g.

As an example of a carboxylation (oxidation) method, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides or mixtures thereof. A method can be mentioned. This oxidation reaction selectively oxidizes the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface, resulting in a cellulose fiber having an aldehyde group and a carboxyl group (-COOH) or carboxylate group (-COO-) on the surface. can be obtained. Although the concentration of cellulose during the reaction is not particularly limited, it is preferably 5% by mass or less.

An N-oxyl compound means a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the desired oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (eg 4-hydroxy TEMPO).

The amount of the N-oxyl compound to be used is not particularly limited as long as it is a catalytic amount that can oxidize the raw material cellulose. For example, it is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, even more preferably 0.05 to 0.5 mmol, relative to 1 g of absolute dry cellulose. Also, it is preferably about 0.1 to 4 mmol/L with respect to the reaction system.

Bromides are compounds containing bromine, examples of which include alkali metal bromides that can be dissociated and ionized in water. Also, iodides are compounds containing iodine, examples of which include alkali metal iodides. The amount of bromide or iodide to be used can be selected within a range capable of promoting the oxidation reaction. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, even more preferably 0.5 to 5 mmol, relative to 1 g of absolute dry cellulose.

Known oxidizing agents can be used, for example, halogens, hypohalous acids, halogenous acids, perhalogenates or salts thereof, halogen oxides, peroxides and the like can be used. Among them, sodium hypochlorite is preferable because it is inexpensive and has less environmental load. The amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol, relative to 1 g of absolute dry cellulose. Further, for example, 1 to 40 mol is preferable per 1 mol of the N-oxyl compound.

Oxidation of cellulose allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, and may be room temperature of about 15 to 30°C. Since carboxyl groups are generated in the cellulose as the reaction progresses, the pH of the reaction solution decreases. In order to allow the oxidation reaction to proceed 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 about 8-12, preferably about 10-11. Water is preferable as the reaction medium because it is easy to handle and less likely to cause side reactions.

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

Moreover, the oxidation reaction may 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 step, again under the same or different reaction conditions, the reaction can be efficiently It can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a cellulose raw material with an ozone-containing gas. This oxidation reaction oxidizes at least the hydroxyl groups at the 2- and 6-positions of the glucopyranose ring and causes degradation of the cellulose chain. The ozone concentration in the ozone-containing gas is preferably 50-250 g/m ³ , more preferably 50-220 g/m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, 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, more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples include chlorine-based compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the additional oxidation treatment can be performed by dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

The amount of carboxyl groups in the oxidized cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidizing agent added and the reaction time.

[Cationization]
As the chemically modified cellulose, cellulose obtained by further cationizing the carboxylated cellulose can be used. The cation-modified cellulose is obtained by adding a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrate or its halohydrin type to the carboxylated cellulose raw material, and an alkali hydroxide as a catalyst. It can be obtained by reacting a metal (sodium hydroxide, potassium hydroxide, etc.) in the presence of water or an alcohol having 1 to 4 carbon atoms.

Preferably, the degree of cation substitution per glucose unit is between 0.02 and 0.50. By introducing cationic substituents into cellulose, the celluloses electrically repel each other. Therefore, cellulose into which cationic substituents have been introduced can be easily nano-fibrillated. If the degree of cation substitution per glucose unit is less than 0.02, sufficient nanofibrillation cannot be achieved. On the other hand, if the degree of cation substitution per glucose unit is greater than 0.50, the nanofibers may not be obtained due to swelling or dissolution. In order to defibrate efficiently, the cation-modified cellulose raw material obtained above is preferably washed. The degree of cation substitution can be adjusted by adjusting the amount of the cationizing agent to be reacted and the composition ratio of water or alcohol having 1 to 4 carbon atoms.

[Esterification]
Esterified cellulose can be used as the chemically modified cellulose. The cellulose can be obtained by a method of mixing a powder or an aqueous solution of the phosphoric acid compound A with the cellulose raw material described above, or a method of adding an aqueous solution of the phosphoric acid compound A to a slurry of the cellulose raw material.

Phosphoric acid compound A includes phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among these, compounds having a phosphate group are preferred because they are low in cost, easy to handle, and can improve defibration efficiency by introducing a phosphate group into the cellulose of pulp fibers. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate and the like. These can be used singly or in combination of two or more. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of introduction of phosphate group, easy fibrillation in the fibrillation process described below, and easy industrial application is more preferred. Sodium dihydrogen phosphate and disodium hydrogen phosphate are particularly preferred. Further, it is preferable to use the phosphoric acid-based compound A in the form of an aqueous solution, since the uniformity of the reaction is enhanced and the efficiency of introduction of the phosphoric acid group is enhanced. The pH of the aqueous solution of the phosphoric acid-based compound A is preferably 7 or less because the efficiency of introducing phosphate groups is high, but from the viewpoint of suppressing hydrolysis of pulp fibers, the pH is preferably 3 to 7.

The following method can be given as an example of the method for producing the phosphorylated cellulose. Phosphoric acid group is introduced into cellulose by adding phosphoric acid compound A to a dispersion liquid of cellulose raw material having a solid content concentration of 0.1 to 10% by mass while stirring. When the cellulose raw material is 100 parts by mass, the amount of phosphoric acid compound A to be added is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass, in terms of elemental amount of phosphorus. If the proportion of the phosphoric acid-based compound A is at least the lower limit, the yield of fine fibrous cellulose can be further improved. However, if the above upper limit is exceeded, the effect of improving the yield reaches a ceiling, which is not preferable from the viewpoint of cost.

At this time, in addition to the cellulose raw material and the phosphoric acid-based compound A, a powder or an aqueous solution of a compound B other than these may be mixed. The compound B is not particularly limited, but a basic nitrogen-containing compound is preferable. "Basic" herein is defined as the pink-red color of the aqueous solution in the presence of the phenolphthalein indicator or the pH of the aqueous solution being greater than 7. The basic nitrogen-containing compound used in the present invention is not particularly limited as long as the effect of the present invention is exhibited, but a compound having an amino group is preferable. Examples include, but are not limited to, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, urea is preferable because it is inexpensive and easy to handle. The amount of compound B added is preferably 2 to 1,000 parts by mass, more preferably 100 to 700 parts by mass, based on 100 parts by mass of the solid content of the cellulose raw material. The reaction temperature is preferably 0 to 95°C, more preferably 30 to 90°C. Although the reaction time is not particularly limited, it is about 1 to 600 minutes, more preferably 30 to 480 minutes. When the esterification reaction conditions are within these ranges, cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphate-esterified cellulose is improved. After dehydrating the obtained phosphate-esterified cellulose suspension, it is preferable to heat-treat at 100 to 170° C. from the viewpoint of suppressing hydrolysis of cellulose. Furthermore, it is preferable to heat at 130° C. or less, preferably 110° C. or less while water is contained in the heat treatment, and heat at 100 to 170° C. after removing the water.

The degree of phosphate group substitution per glucose unit of the phosphated cellulose is preferably 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses electrically repel each other. Therefore, cellulose into which a phosphate group has been introduced can be easily nano-fibrillated. If the degree of phosphate group substitution per glucose unit is less than 0.001, sufficient nano-fibrillation cannot be achieved. On the other hand, if the degree of phosphate group substitution per glucose unit is greater than 0.40, the nanofibers may not be obtained due to swelling or dissolution. In order to efficiently defibrate, it is preferable that the phosphate-esterified cellulose raw material obtained above is washed by washing with cold water after boiling.

<Fibrillation>
In the present invention, the defibrating device is not particularly limited, but a high-speed rotating device, a colloid mill device, a high pressure device, a roll mill device, an ultrasonic device, or the like may be used to apply a strong shearing force to the aqueous dispersion. is preferred. In particular, for efficient fibrillation, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer capable of applying a pressure of 50 MPa or more to the aqueous dispersion and applying a strong shearing force. The pressure is more preferably 100 MPa or higher, still more preferably 140 MPa or higher. In addition, prior to defibration and dispersion treatment with a high-pressure homogenizer, if necessary, the above CNF can be pretreated using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. is. The number of times of treatment (pass) in the fibrillation device may be one or two or more, preferably two or more.

In dispersion treatment, modified cellulose is usually dispersed in a solvent. The solvent is not particularly limited as long as it can disperse the modified cellulose, and examples thereof include water, organic solvents (eg, hydrophilic organic solvents such as methanol), and mixed solvents thereof. The solvent is preferably water because the cellulose raw material is hydrophilic.

The solid content concentration of the modified cellulose in the dispersion is usually 0.1% by mass or more, preferably 0.2% by mass or more, and more preferably 0.3% by mass or more. As a result, the amount of liquid becomes appropriate with respect to the amount of cellulose fiber raw material, which is efficient. The upper limit is usually 10% by mass or less, preferably 6% by mass or less. Thereby, fluidity can be maintained.

Prior to defibration treatment or dispersion treatment, a preliminary treatment may be performed as necessary. Pretreatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

When the modified cellulose nanofiber obtained through the fibrillation process is in a salt form, it may be used as it is, or it may be used as an acid form by an acid treatment using a mineral acid, a method using a cation exchange resin, or the like. Also good. Alternatively, hydrophobicity may be imparted by a method using a cationic additive.

<Aqueous composition>
The aqueous composition of the present invention is obtained by dispersing ceramides and cellulose nanofibers as essential components in an aqueous solvent. The aqueous solvent used in the present invention is preferably water, a water-soluble organic solvent, or a mixed solvent thereof. Considering the dispersibility of the chemically modified pulp and CNF, water or a mixed solvent of water and a water-soluble organic solvent is preferable as the aqueous solvent.

A water-soluble organic solvent is an organic solvent that dissolves in water. Examples 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, Dimethylsulfoxide, acetonitrile, and combinations thereof. Among them, lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol, and 2-propanol are preferred, and from the viewpoint of safety and availability, methanol and ethanol are more preferred, and ethanol is even more preferred. The amount of the water-soluble organic solvent in the mixed solvent is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. Although the upper limit of the amount is not limited, it is preferably 95% by mass or less, more preferably 90% by mass or less. Moreover, the water-based solvent may contain a water-insoluble organic solvent to the extent that the effect of the invention is not impaired.

In the water-based composition of the present invention, the blending ratio of each component is not particularly limited, but the content of ceramides in the water-based composition is 0.01 to 20% by mass, preferably 0.1 to 10%, from the viewpoint of moisturizing properties. % by mass, more preferably 1 to 7% by mass. In addition, the solid content concentration of cellulose nanofibers in the aqueous composition is 0.05 to 30% by mass, preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, from the viewpoint of dispersibility and tactile feel. %.

In addition, the water-based composition of the present invention can be blended with other commonly used cosmetic ingredients according to the purpose. The water-based composition of the present invention can be mixed by conventional devices and means, and temperature conditions and the like are not particularly limited.

<Method for producing water-based composition>
The method for producing the water-based composition of the present invention is not particularly limited, and any method may be used as long as the ceramides and cellulose nanofibers can be dispersed in the water-based solvent. For example, a method in which ceramides are mixed with an aqueous dispersion of cellulose nanofibers and stirred, or an aqueous dispersion of cellulose nanofibers in which ceramides are dissolved or dispersed in an aqueous solvent is mixed little by little and stirred. method.

Since the aqueous composition of the present invention contains cellulose nanofibers, ceramides are stably dispersed and sedimentation does not occur over time. Therefore, this water-based composition can be suitably used as an additive for cosmetics. In addition, the water-based composition of the present invention is not limited to cosmetic additives, and can be widely used.

<Cosmetic Additives>
The aqueous composition of the present invention can be used as a cosmetic additive.
The cosmetic additives of the present invention include, for example, basic cosmetics such as creams, milky lotions, lotions, and beauty essences; cleansing cosmetics such as soaps, facial cleansers, shampoos and rinses; hair cosmetics such as hair tonics and hair styling agents; It can be added to makeup cosmetics such as foundation, eyeliner, mascara and lipstick, oral cosmetics such as toothpaste, and bath cosmetics.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.

<Production Example 1>
5.00 g (bone dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood was mixed with 39 mg of TEMPO (Sigma Aldrich) (0.05 mmol per g of cellulose of bone dry) and 514 mg of sodium bromide (bone dry). 1.0 mmol for 1 g of cellulose) was added to 500 mL of an aqueous solution and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 6.0 mmol/g to initiate an oxidation reaction. The pH in the system decreased during the reaction, but was adjusted to pH 10 by successively adding 3M sodium hydroxide aqueous solution. The reaction was terminated when the sodium hypochlorite was consumed and the pH in the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). At this time, the pulp yield was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol/g. This was adjusted to 1.0% (w/v) with water and treated three times with an ultrahigh pressure homogenizer (20°C, 150 MPa) to obtain an aqueous oxidized cellulose nanofiber dispersion. The obtained oxidized cellulose nanofibers had an average fiber diameter of 3 nm and an aspect ratio of 250.

[Method for measuring carboxyl group content]
60 mL of a 0.5% by mass slurry (aqueous dispersion) of carboxylated cellulose was prepared, and 0.1 M aqueous hydrochloric acid solution was added to adjust the pH to 2.5. It was calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid, where the change in conductivity is gradual, using the following formula:
Carboxyl group amount [mmol/g carboxylated cellulose] = a [mL] x 0.05/carboxylated cellulose mass [g]

<Production Example 2>
200 g of dry mass of bleached kraft pulp (BKP, manufactured by Nippon Paper Industries Co., Ltd.) and 111 g of sodium hydroxide are added to a stirrer capable of mixing pulp, and water is added so that the solid content of the pulp becomes 20% by mass. was added. Then, after stirring at 30° C. for 30 minutes, 216 g of sodium monochloroacetate (converted to active ingredient) was added. After stirring for 30 minutes, the temperature was raised to 70° C. and the mixture was stirred for 1 hour. After that, the reactant was discharged, neutralized, and washed to obtain a carboxymethylated pulp having a degree of carboxymethyl substitution of 0.25 per glucose unit. Thereafter, the carboxymethylated pulp was adjusted to a solid content of 1% with water, and defibrated by a high-pressure homogenizer at 20° C. and a pressure of 150 MPa five times to obtain an aqueous dispersion of carboxymethylated cellulose nanofibers. The obtained carboxymethylated cellulose nanofibers had an average fiber diameter of 50 nm and an aspect ratio of 120.

[Method for measuring degree of carboxymethyl substitution per glucose unit]
About 2.0 g of carboxymethylated cellulose fiber (absolute dry) was precisely weighed and put into a 300 mL conical flask with a common stopper. 100 mL of a liquid prepared by adding 10 mL of special grade concentrated nitric acid to 90 mL of methanol was added and shaken for 3 hours to convert carboxymethylated cellulose salt (CM cellulose) into hydrogenated CM cellulose. 1.5 to 2.0 g of hydrogenated CM cellulose (absolute dry) was accurately weighed and put into a 300 mL conical flask equipped with a common stopper. Hydrogenated CM-cellulose was wetted with 15 mL of 80% methanol, 100 mL of 0.1N NaOH was added, and the mixture was shaken at room temperature for 3 hours. Excess NaOH was back _- titrated with 0.1N _H2SO4 using phenolphthalein as an indicator. The degree of carboxymethyl substitution (DS) was calculated by the following formula:
A=[(100×F′−(0.1N H ₂ SO ₄ ) (mL)×F)×0.1]/(absolute dry mass of hydrogen-type CM cellulose (g))
DS = 0.162 x A/(1 - 0.058 x A)
A: Amount of 1N NaOH (mL) required to neutralize 1 g of hydrogenated CM-cellulose
F: Factor of 0.1N H ₂ SO ₄ F': Factor of 0.1N NaOH

<Example 1>
The cellulose nanofiber aqueous dispersion obtained in Production Example 1 was adjusted to 0.5% by mass with water to obtain an aqueous suspension. Ceramide 3 was added to the obtained aqueous suspension so as to be 2% by mass to obtain an aqueous composition. Then, the mixture was stirred at 1000 rpm for 10 minutes, placed in a colorimetric tube and allowed to stand. After 24 hours, the degree of ceramide dispersibility was visually evaluated and evaluated according to the following criteria. Table 1 shows the results.
3: Ceramide is well dispersed.
2: Slight sedimentation of ceramide 1: Sedimentation due to poor dispersibility of ceramide.

<Example 2>
An aqueous composition was obtained in the same manner as in Example 1, except that the cellulose nanofiber aqueous dispersion obtained in Production Example 2 was used instead of the cellulose nanofiber aqueous dispersion obtained in Production Example 1. In addition, the dispersibility of ceramide in the resulting aqueous composition was evaluated in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 1>
An aqueous composition was obtained in the same manner as in Example 1, except that an aqueous suspension containing 0.5% by mass of xanthan gum was used. In addition, the dispersibility of ceramide in the resulting aqueous composition was evaluated in the same manner as in Example 1. Table 1 shows the results.

As shown in Table 1, in the aqueous compositions containing ceramides and cellulose nanofibers of Examples 1 and 2, ceramide was well dispersed even after 24 hours. On the other hand, in the aqueous composition of Comparative Example 1 using xanthan gum instead of cellulose nanofibers, ceramide had poor dispersibility and sedimentation occurred after 24 hours.

Claims (2)

An aqueous composition,
It contains ceramides and cellulose nanofibers,
The cellulose nanofiber is made from pulp-derived chemically modified cellulose that is at least one selected from the group consisting of carboxylated cellulose, carboxymethylated cellulose, phosphorylated cellulose, and cationized cellulose ,
The cellulose nanofiber is an aqueous composition having an average aspect ratio of 50 or more and 1000 or less . The water-based composition according to claim 1, which is a cosmetic additive.