JP7699351B2 - Cosmetic gel composition - Google Patents

Description

The present invention relates to a gel composition for cosmetics containing cellulose nanofibers.

Gel compositions containing polyhydric alcohols are used in cosmetics to improve moisturizing properties. As a gelling agent for such compositions, a new material called cellulose nanofiber (hereinafter sometimes abbreviated as "CNF"), which is made by breaking down the fibers that make up plant-derived cellulose materials, has been attracting attention.

For example, there is a skin topical agent that contains CNF (see, for example, Patent Document 1). Patent Document 1 describes that CNF is not sticky, and therefore provides a good feel when applied to the skin.

There have also been biomaterials that use CNF (see, for example, Patent Document 2). Cosmetics that have a transparent appearance are preferred by consumers, but if the fiber diameter of the CNF is large or if the CNF aggregates together, the light scattering by the CNF increases, and the transparency decreases when the gel composition is made. Therefore, Patent Document 2 describes that the fiber diameter of the CNF should be 100 nm or less in order to obtain a transparent aqueous dispersion.

By the way, to produce CNF, the raw material cellulose must be defibrated into small pieces. Even if you try to defibrate cellulose as is, the fibers are bound together by strong hydrogen bonds, so defibration requires a huge amount of energy and it is difficult to obtain CNF of the appropriate size.

Therefore, in Patent Documents 1 and 2, carboxyl groups or carboxymethyl groups are introduced into cellulose, which causes electrical repulsion between cellulose fibers, making defibration easier, and nanofibers with anionic functional groups are obtained.

JP 2017-109946 A JP 2015-977 A

CNF with anionic functional groups can be easily miniaturized to improve transparency, but because it is made by modifying cellulose to give it ionic properties, it is prone to discoloration over time when used in cosmetics, and there is also a risk of its physical properties changing when it coexists with various additives.

However, because it is difficult to remove the functional groups from oxidized cellulose or carboxymethyl cellulose and return it to nonionic cellulose, the topical skin preparation in Patent Document 1 and the biomedical material in Patent Document 2 contain CNF with anionic functional groups and are not suitable for use as cosmetics.

The present invention was made in consideration of the above problems, and aims to provide a highly transparent gel-like cosmetic composition suitable for use on the face, etc.

The feature of the configuration of the cosmetic gel composition according to the present invention for solving the above problems is:
The composition contains nonionic cellulose nanofibers having an average fiber diameter of 2 to 30 nm, a diol, and water.

The cosmetic gel composition of this configuration contains nonionic cellulose nanofibers with an average fiber diameter of 2 to 30 nm, a diol, and water, and is easy to use and not sticky. In addition, the cosmetic gel composition of this configuration has cellulose nanofibers with an average fiber diameter of 2 to 30 nm uniformly dispersed in the composition, suppressing light scattering and providing high light transmittance, thereby improving the transparency required when used on the face, etc. Furthermore, since the nonionic cellulose nanofibers are chemically stable, the cosmetic gel composition of this configuration does not discolor over time and does not react with various additives even when coexisting with them, making it a cosmetic suitable for use on the face, etc.

In the cosmetic gel composition according to the present invention,
The content of the cellulose nanofiber is 0.1 to 5% by mass,
The content of the diol is 1 to 20% by mass,
It is preferable that the mass ratio (A:B) of the content of the cellulose nanofibers (A) to the content of the diol (B) is 1:2 to 1:40.

In the cosmetic gel composition of this configuration, the cellulose nanofiber content is 0.1-5 mass%, the diol content is 1-20 mass%, and the mass ratio (A:B) is 1:2-1:40, which suppresses aggregation of the cellulose nanofibers and stabilizes the viscosity of the gel composition.

In the cosmetic gel composition according to the present invention,
The diol is preferably at least one selected from the group consisting of 1,3-butylene glycol, pentylene glycol, propylene glycol, and dipropylene glycol.

In the cosmetic gel composition of this configuration, the diol is at least one selected from the group consisting of 1,3-butylene glycol, pentylene glycol, propylene glycol, and dipropylene glycol, which improves wettability and increases the viscosity appropriately, resulting in a cosmetic gel composition that is easy to handle when applied to the skin and has good skin affinity.

In the cosmetic gel composition according to the present invention,
It is preferable that the transmittance of light with a wavelength of 700 nm is 75% or more with an optical path length of 10 mm.

The cosmetic gel composition of this configuration has high light transmittance, which can further improve the transparency required when used on the face, etc.

In the cosmetic gel composition according to the present invention,
It is preferable that the viscosity is adjusted to be 10% or more higher than that of a cellulose nanofiber aqueous dispersion containing the same amount of cellulose nanofibers.

According to the cosmetic gel composition of this configuration, the viscosity is 10% or more higher than that of an aqueous dispersion of cellulose nanofiber containing the same amount of cellulose nanofiber, and therefore the viscosity is moderately higher than that of an aqueous dispersion of cellulose nanofiber, resulting in a product that is easy to use while maintaining good compatibility with the skin.

The cosmetic gel composition of the present invention will be described in detail below. However, the present invention is not intended to be limited to the embodiments and examples described below.

[Cosmetic gel composition]
The cosmetic gel composition of the present invention can be used as a cosmetic for use on the face or the like, or as a raw material for cosmetics, and contains CNF, a diol, and water. The main components of the cosmetic gel composition of the present invention, CNF and diol, will be described below. Although a detailed description of water will be omitted, water with few impurities, such as purified water or ion-exchanged water, can be used.

<CNF>
CNF is a main material that serves as a gelling agent in the cosmetic gel composition of the present invention. Nonionic CNF with an average fiber diameter of 2 to 30 nm is used. Since the fiber diameter of microfibrils, which are the constituent units of natural cellulose, is 2 to 3 nm in higher plants, in order to make the average fiber diameter of CNF less than 2 nm, it is necessary to use a large amount of energy to make it finer than that, which increases the production cost. On the other hand, if the average fiber diameter of CNF is made larger than 30 nm, there is a risk that light scattering will increase when it is made into a gel composition, and transparency will decrease. If the transparency of the gel composition decreases, there is a risk that white cast will occur when it is applied to cosmetics to be used on the face, etc. The crystal type of cellulose may be either type I or type II, but type I is stable in a solvent such as water, and can impart better shape retention when incorporated into cosmetics, etc. Nonionic CNF can be produced by suspending natural cellulose in water and finely pulverizing it by physical means. In addition, since the cellulose material is easily converted into a nanofiber state by electrostatic repulsion between fibers by introducing ionic functional groups through chemical modification rather than defibrating the cellulose material as it is, it is preferable to first chemically modify the cellulose material and then regenerate the material by removing the introduced functional groups. An example of such chemically modified cellulose is xanthated cellulose, which is obtained by adding carbon disulfide to alkali-treated cellulose to introduce xanthate groups (-OCSS ^- M ⁺ ).

Xanthated cellulose can be easily converted back to hydroxyl groups by a regeneration process such as acid treatment or heat treatment to remove the xanthate groups. By undergoing a process such as regeneration of xanthated cellulose, the amount of impurities in the CNF can be reduced. It is desirable that all of the xanthate groups introduced by chemical modification have been converted back to hydroxyl groups in the CNF used in the cosmetic gel composition of the present invention, but some xanthate groups may remain as long as it does not interfere with the production or use of the composition. The content of xanthate groups in xanthated cellulose is evaluated by the average degree of xanthate substitution, which is the average number of hydroxyl groups substituted with xanthate groups per glucose unit of cellulose. In the cosmetic gel composition of the present invention, the CNF preferably has an average degree of xanthate substitution of 0.01 or less, more preferably 0.005 or less. If the average degree of xanthate substitution is 0.01 or less, it exhibits the same reactivity as unmodified CNF and can be suitably used as nonionic CNF in cosmetics for use on the face, etc.

The CNF content in the cosmetic gel composition is preferably 0.1 to 5% by mass. If the CNF content is within the above range, the gel composition will have excellent viscosity stability. If the CNF content is less than 0.1% by mass, there is a risk that sufficient viscosity will not be obtained or that the viscosity will vary. If the CNF content exceeds 5% by mass, the composition will not become gel-like but will become paste-like, and there is a risk that free water that is not hydrogen-bonded to the CNF will escape if external pressure is applied during storage.

<Diol>
A diol is a type of alcohol having a structure in which one hydroxyl group is bonded to each of two carbon atoms, and in the cosmetic gel composition of the present invention, the diol is blended as a component that increases viscosity in order to maintain a uniform dispersion state of CNF in the gel composition and to improve the handleability when applied to the skin when the gel composition is used as a cosmetic or a raw material for a cosmetic. Examples of such diols include 1,3-butylene glycol, pentylene glycol, propylene glycol, and dipropylene glycol, and in particular, 1,3-butylene glycol and pentylene glycol are preferred from the viewpoint of thickening the cosmetic gel composition, although details will be described in the Examples below.

The diol content in the cosmetic gel composition is preferably 1 to 20% by mass. The mass ratio (A:B) of the CNF content (A) to the diol content (B) in the cosmetic gel composition is preferably in the range of 1:2 to 1:40 by mass. If the diol content and mass ratio (A:B) are within the above ranges, the dispersibility of the CNF in the cosmetic gel composition will be excellent. If the diol content and mass ratio (A:B) are outside the above ranges, the CNF may be more likely to aggregate in the cosmetic gel composition, or the transparency of the gel composition may decrease.

[Light transmittance]
It is desirable for a gel composition for cosmetic preparations to have high light transmittance. When the optical path length is 10 mm, the gel composition of the present invention preferably has a transmittance of 75% or more for light with a wavelength of 700 nm. If the transmittance of light with a wavelength of 700 nm is 75% or more, the high light transmittance can improve the sense of transparency required when used on the face, etc. The light transmittance can be measured by filling a measurement cell with the gel composition having an optical path length of 10 mm and using an ultraviolet-visible spectrophotometer (V-730, manufactured by JASCO Corporation).

〔viscosity〕
When the cosmetic gel composition is used as a cosmetic or a cosmetic raw material, it is desired to increase the viscosity in order to improve the handling when applied to the skin. The cosmetic gel composition of the present invention is preferably prepared so that its viscosity is 10% or more higher than that of a CNF aqueous dispersion containing the same amount of CNF. Specifically, when the viscosity of the cosmetic gel composition of the present invention is V1 and the viscosity of an aqueous dispersion of CNF prepared so that the CNF content is the same as that of the cosmetic gel composition is V2, the viscosity of the cosmetic gel composition of the present invention is expressed by the following formula (1):
Viscosity ratio = 100 × (V1-V2)/V2 ... (1)
is preferably 10% or more. If the viscosity ratio is 10% or more, the viscosity is appropriately increased compared to the aqueous dispersion of CNF, and the composition is easy to use while maintaining good compatibility with the skin. The viscosity of the cosmetic gel composition and the aqueous dispersion is measured at 25°C using an M3 rotor of a B-type viscometer (TVB-10H, manufactured by Toki Sangyo Co., Ltd.) at 30 rpm.

[Production of CNF]
CNF derived from xanthated cellulose, which is suitable as CNF for use in the cosmetic gel composition of the present invention, can be produced by carrying out the following steps (I) to (V) in order.

(I) Alkali treatment of cellulose materials Examples of cellulose materials include wood pulp such as kraft pulp and sulfite pulp, biomass-derived materials such as wood flour and rice straw, paper-derived materials such as waste paper, filter paper, and paper powder, and cellulose processed products that retain crystallinity such as powdered cellulose and microcrystalline cellulose of micrometer size. However, the cellulose materials are not limited to these examples. Among these cellulose materials, it is preferable to use wood pulp because it is easy to obtain and inexpensive.

In the alkali treatment of cellulose materials, the cellulose materials are treated with an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to obtain alkali cellulose. The concentration of the aqueous solution of an alkali metal hydroxide is preferably 4% by mass or more. If the concentration of the aqueous solution of an alkali metal hydroxide is less than 4% by mass, the mercerization of cellulose does not proceed sufficiently, and the amount of by-products generated during the subsequent xanthate conversion becomes significant, resulting in a low yield.

(II) Xanthate treatment In the xanthate treatment, carbon disulfide (CS ₂ ) is reacted with alkali cellulose to convert the (-O ^- M ⁺ ) group into a (-OCSS ^- M ⁺ ) group to obtain xanthate cellulose. The average degree of xanthate substitution of xanthate cellulose can be determined using the Breedee method. The procedure of the Breedee method is to weigh 1.5 g of xanthate cellulose as a solid content and add 40 mL of saturated ammonium chloride solution (5 ° C.). After mixing well with a glass rod, filter and thoroughly wash with saturated ammonium chloride solution. Next, 50 mL of 0.5 mol/L sodium hydroxide solution (5 ° C.) is added and stirred, and then neutralized with 1.5 mol/L acetic acid. Then, 250 mL of ion-exchanged water is added and stirred well, and 10 mL of 1.5 mol/L acetic acid and 10 mL of 0.05 mol/L iodine solution are added. This solution is titrated with 0.05 mol/L sodium thiosulfate solution using a 1% by mass starch aqueous solution as an indicator. Using the titration amount of sodium thiosulfate in the above procedure and the amount of cellulose (g) of the sample, the following formula (2):
Average degree of xanthate substitution = (0.05 × 10 × 2 - 0.05 × sodium thiosulfate titration (mL)) / {1000 × (amount of cellulose in sample (g) / 162.1)} ... (2)
The average degree of xanthate substitution is calculated by the above formula. The cellulose content in the xanthated cellulose is measured as follows. First, the xanthated cellulose is dispersed in water, and hydrochloric acid is added to perform a regeneration treatment. Next, the cellulose after the regeneration treatment is filtered, thoroughly washed, and then completely dried to measure the mass of only the cellulose, and the cellulose content in the xanthated cellulose is calculated.

When producing CNF for use in the cosmetic gel composition of the present invention, it is preferable that the average degree of xanthate substitution in the xanthate formation process is 0.1 or more and 0.4 or less. If the average degree of xanthate substitution is less than 0.1, the subsequent defibration process may not be performed sufficiently. If the average degree of xanthate substitution exceeds 0.4, the hydrophilicity becomes too high and there is a risk of dissolving during the defibration process.

(III) Defibration treatment The defibration treatment is preferably carried out after dispersing the xanthate cellulose in water. A general method can be used as the defibration treatment method. For example, a method of defibrating using a rotary homogenizer, a bead mill, an ultrasonic disperser, a high-pressure homogenizer, a disc refiner, etc. can be mentioned.

Cellulose materials require a large amount of energy to defibrate as is, but with xanthate cellulose, the electrostatic repulsion between the fibers due to the xanthate group improves dispersibility, so the energy required for defibration is extremely small and it can be defibrated under relatively mild conditions.

(IV) Regeneration Treatment Regenerated CNF can be obtained by regenerating the xanthated CNF. In this regeneration treatment, the xanthate group (-OCSS ^- M ⁺ ) is eliminated and converted to a hydroxyl group (-OH), thereby regenerating the xanthated cellulose into cellulose.

As an example of a regeneration treatment, a method of treatment using an acid can be used. The acid can easily promote a reaction that removes the xanthate group and converts it to a hydroxyl group. Examples of the acid used here include mineral acids and organic acids, and in particular, mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid are preferred.

As another regeneration method, the xanthate CNF can be heated to dissociate carbon disulfide from the xanthate CNF molecules and regenerate it into cellulose, thereby obtaining CNF.

(V) Redispersion treatment The CNF after the regeneration treatment has the xanthate groups removed compared to the xanthated CNF before regeneration, and is in a partially aggregated state due to hydrogen bonds and entanglement between the fibers. Therefore, the aqueous dispersion of the CNF after the regeneration treatment is subjected to a dispersion treatment again to obtain a CNF dispersion. Hereinafter, this dispersion treatment performed after the regeneration treatment is referred to as "redispersion treatment". For the redispersion treatment, general devices and methods used for dispersion treatment such as a rotary homogenizer, a high-pressure homogenizer, and an ultrasonic disperser can be used.

As described above, by carrying out steps (I) to (V) in order, the average fiber diameter of the obtained CNF derived from xanthated cellulose can be adjusted to 2 nm or more and 30 nm or less. The average fiber diameter of the CNF is measured by the following procedure. Ion-exchanged water is added to the obtained CNF to prepare an aqueous dispersion with a solid content concentration of 0.1% by mass, and the dispersion is centrifuged (12,000 G, 10 minutes) using a centrifuge (Avanti J-251, manufactured by Beckman Coulter) to settle the undefibrated material. The supernatant is further diluted with ion-exchanged water, applied to a support film, stained with uranyl acetate, and dried on the support film to obtain a dried specimen. The specimen is observed using a transmission electron microscope (TEM: JEM-1400, manufactured by JEOL Ltd.) at an accelerating voltage of 120 kV, and 50 nanofibers are selected from the 50,000x image, and the fiber diameters of each are measured to obtain the average value, which is the average fiber diameter.

[Production Example 1 of Nonionic CNF]
Bleached kraft pulp (NBKP) of softwood was weighed out so that the pulp solid content was 100 g, and 2500 g of 8.5 mass % sodium hydroxide aqueous solution was added and stirred at room temperature for 3 hours to carry out an alkali treatment. The pulp after this alkali treatment was subjected to solid-liquid separation to obtain a dehydrated alkali cellulose.

The dehydrated alkali cellulose prepared above was weighed to have a pulp solid content of 100 g, and 35 g of carbon disulfide (35% by mass of the pulp solid content) was added to proceed with the sulfurization reaction to perform a xanthate treatment, thereby obtaining xanthated cellulose.

The xanthated cellulose was weighed out so that the pulp solid content was 10 g, dispersed by adding ion-exchanged water, and subjected to solid-liquid separation and thoroughly washed with ion-exchanged water. After washing, all of the xanthated cellulose was collected, and ion-exchanged water was added to make 2 kg of an aqueous suspension with a cellulose concentration of 0.5% by mass. This aqueous suspension was defibrated by passing it three times through a high-pressure homogenizer at a pressure of 80 MPa to obtain xanthated CNF. The average degree of xanthate substitution of the obtained xanthated CNF was 0.263, the fiber diameter was in the range of 3.0 nm to 7.4 nm, and the average fiber diameter was 6.1 nm.

33 mL of 1 mol/L sulfuric acid was added to 1.5 kg of the aqueous suspension of xanthated CNF obtained by the above procedure (cellulose concentration 0.5% by mass) and a regeneration process was carried out. After completion of the process, the mixture was neutralized to pH 7 with 1 mol/L sodium hydroxide solution to obtain an aqueous suspension of regenerated CNF. When the average degree of xanthate substitution was measured, it was found to be less than the lower limit of measurement, 0.001, confirming that the xanthate groups had almost completely been released by the acid treatment and had returned to hydroxyl groups.

The aqueous suspension of regenerated CNF obtained above was thoroughly washed by adding ion-exchanged water while being centrifuged and dehydrated using a centrifugal dehydrator. After washing, all of the regenerated CNF was collected, and ion-exchanged water was added to make 1 kg of an aqueous dispersion with a CNF solid content concentration of 1.0 mass %, which was then redispersed at a pressure of 80 MPa using a high-pressure homogenizer to obtain non-ionic CNF as a manufacturing example. After the redispersion process, the average fiber diameter of the redispersed regenerated CNF was calculated to be 3.0 to 7.4 nm, with an average fiber diameter of 6.0 nm.

[Production Example 2 of Nonionic CNF]
The redispersion of the regenerated CNF (average fiber diameter 6.0 nm) obtained in Production Example 1 above was diluted to a solid content concentration of 0.5% by mass, centrifuged (75,000 G, 10 minutes) using a centrifuge (Avanti J-251, manufactured by Beckman Coulter), the centrifugal supernatant was recovered, and concentrated to a solid content concentration of 1.0% by mass using an evaporator. The average fiber diameter of the regenerated CNF in the centrifugal supernatant was calculated to be 2.0 to 3.1 nm, and the average fiber diameter was 2.6 nm.

[Production Example 3 of Nonionic CNF]
In the same manner as above, except that the aqueous suspension of xanthated cellulose of Production Example 1 was passed through the high-pressure homogenizer twice and defibrated, the average degree of xanthate substitution was 0.264, the fiber diameter was 2.0 to 51.4 nm, and the average fiber diameter was 28.1 nm. Xanthated CNF was obtained.

This xanthated CNF was treated in the same manner as in Production Example 1 to obtain a redispersion of nonionic CNF with fiber diameters of 2.0 to 50.7 nm and an average fiber diameter of 28.0 nm.

<Preparation and Evaluation of Cosmetic Gel Composition>
A cosmetic gel composition of the present invention (Example 1) was prepared, and the viscosity was measured and the feeling of use was evaluated. For comparison, cosmetic gel compositions outside the scope of the present invention (Comparative Examples 1 and 2) were prepared, and the same measurements and evaluations were performed.

Example 1
Ion-exchanged water and 1,3-butylene glycol (BG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and the final concentration was adjusted so that the CNF content was 0.5 mass% and the 1,3-butylene glycol content was 5 mass%, and then the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). The mixture was degassed to obtain a cosmetic gel composition. In the cosmetic gel composition of Example 1, the mass ratio (A:B) of the CNF content (A) to the diol content (B) was 1:10.

Comparative Example 1
Xanthan gum (KELTROL CG-T, manufactured by Sansho Co., Ltd.) was used in place of CNF. A gel composition for cosmetic preparations was obtained in the same manner as in Example 1 except for the above.

Comparative Example 2
An aqueous dispersion of CNF from the same lot as in Example 1 was diluted with ion-exchanged water so that the final concentration (solid content) of CNF was adjusted to 0.5 mass %. A gel composition for cosmetics was obtained in the same manner as in Example 1 except for the above.

<Viscosity>
The viscosity of the cosmetic gel composition was measured using an M3 rotor of a Brookfield type viscometer (TVB-10H, manufactured by Toki Sangyo Co., Ltd.) at 30 rpm.

<Feeling of use>
Five monitors applied the cosmetic gel composition to the upper arm and evaluated the feel after application according to the following criteria. When the average of the ratings by the five monitors was 5, the feel was rated as "○", when it was 3 or more but less than 5, the feel was rated as "△", and when it was less than 3, the feel was rated as "×".
5: Not sticky or slimy.
4: Feels slightly sticky and slimy.
3: Slightly sticky and slimy.
2: Sticky and slimy.
1: Very sticky and slimy.

The manufacturing conditions, viscosity, and usability of the cosmetic gel compositions of Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

The cosmetic gel composition of Example 1 had a higher viscosity and was easier to handle when applied to the skin than the cosmetic gel composition of Comparative Example 1, which used xanthan gum as the water-soluble polymer, and the cosmetic gel composition of Comparative Example 2, which did not contain a diol.

The cosmetic gel composition of Example 1 had neither the stickiness characteristic of water-soluble polymers nor the sliminess caused by diols, and was excellent in feel when used. On the other hand, the cosmetic gel composition of Comparative Example 1, which used xanthan gum as the water-soluble polymer, had the stickiness characteristic of water-soluble polymers and the sliminess caused by diols, and was inferior in feel when used, even though the content of the water-soluble polymer and diol was the same as that of the cosmetic gel composition of Example 1.

Example 2
Ion-exchanged water and 1,3-butylene glycol (BG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and the final concentrations were adjusted to 0.5% by mass for the CNF content and 1,3-butylene glycol content of 1% by mass (the mass ratio (A:B) of the CNF content (A) to the diol content (B) was 1:2), 5% by mass (the mass ratio (A:B) was 1:10), 10% by mass (the mass ratio (A:B) was 1:20), 20% by mass (the mass ratio (A:B) was 1:40), and 30% by mass (the mass ratio (A:B) was 1:60), and each was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). This was deaerated to obtain a gel composition for cosmetics.

Example 3
Ion-exchanged water and 1,3-butylene glycol (BG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 2.6 nm) of Production Example 2, and the final concentration was adjusted to 0.5% by mass for the CNF content and 10% by mass for the 1,3-butylene glycol content (mass ratio (A:B) of 1:20), and the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). The mixture was degassed to obtain a gel composition for cosmetics.

Example 4
Ion-exchanged water and 1,3-butylene glycol (BG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 28.0 nm) of Production Example 3, and the final concentration was adjusted to 0.5% by mass for the CNF content and 10% by mass for the 1,3-butylene glycol content (mass ratio (A:B) of 1:20), and the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). The mixture was degassed to obtain a gel composition for cosmetics.

Example 5
Ion-exchanged water and pentylene glycol (PeG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and the final concentration was adjusted to 0.5% by mass for the CNF content and 10% by mass for the pentylene glycol content (mass ratio (A:B) of 1:20), and the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). The mixture was degassed to obtain a gel composition for cosmetics.

Example 6
Ion-exchanged water and propylene glycol (PG) as a diol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and the final concentration was adjusted to 0.5% by mass for the CNF content and 10% by mass for the propylene glycol content (mass ratio (A:B) of 1:20), and the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation). The mixture was degassed to obtain a gel composition for cosmetics.

Comparative Example 3
A gel-like composition for a cosmetic preparation was obtained in the same manner as in Example 2, except that mechanically defibrated CNF (BiNFi-sWMa-10002, fiber diameter 24.1 to 53.2 nm, average fiber diameter 31 nm, manufactured by Sugino Machine Co., Ltd.) was used instead of the CNF used in the production example.

Comparative Example 4
A gel composition for cosmetics was obtained in the same manner as in Example 5 except that glycerin (GLY) was used instead of pentylene glycol in Example 5.

Example 7
A 1:1 mixture of 1,3-butylene glycol (BG) and glycerin (GLY) was used instead of the pentylene glycol in Example 5. A cosmetic gel composition was obtained in the same manner as in Example 5 except for the above.

<Light transparency>
The light transmittance [700 nm transmittance (T%)] of the cosmetic gel compositions of the present invention (Examples 2 to 7) was measured by measuring the transmittance (light transmittance) of light with a wavelength of 700 nm when the optical path length was set to 10 mm using an ultraviolet-visible spectrophotometer (V-730, manufactured by JASCO Corporation). The light transmittance was also measured in the same manner for cosmetic gel compositions outside the scope of the present invention (Comparative Examples 3 and 4).

The light transmittance of the cosmetic gel compositions of Examples 2 to 7 and Comparative Examples 3 and 4 is shown in Table 2. Table 2 also shows the light transmittance when the polyhydric alcohol content is 0% by mass.

As shown in Table 2, the cosmetic gel compositions of Examples 2 to 4 containing 1,3-butylene glycol as a diol, the cosmetic gel composition of Example 5 containing pentylene glycol as a diol, and the cosmetic gel composition of Example 6 containing propylene glycol as a diol had higher transmittance for visible light with a wavelength of 700 nm compared to Comparative Example 3 which used mechanically defibrated CNF (average fiber diameter 31 nm). In particular, in the cosmetic gel composition of Example 2, when the diol content was in the range of 1 to 20% by mass and the mass ratio (A:B) of the CNF content (A) to the diol content (B) was in the range of 1:2 to 1:40, there was a tendency that the greater the diol content, the higher the transmittance for visible light with a wavelength of 700 nm.

From the above, it is believed that in the cosmetic gel composition of the present invention, when 1,3-butylene glycol, pentylene glycol, or propylene glycol is used as the diol and its content is adjusted to 1 to 20 mass %, the light transmittance is particularly improved.

<Viscosity ratio>
For the cosmetic gel compositions of Examples 2 to 7 described above, the viscosity of the cosmetic gel compositions was measured at 30 rpm at 25°C using an M3 rotor of a Brookfield viscometer (TVB-10H, manufactured by Toki Sangyo Co., Ltd.), and the rate of increase in viscosity when the diol content was 10% by mass relative to the viscosity when the diol was added in an amount of 0% by mass, i.e., the viscosity ratio, was calculated using the above-mentioned formula (1). For comparison, in addition to the above-mentioned Comparative Example 4, cosmetic gel compositions outside the scope of the present invention (Comparative Examples 5 and 6) were prepared, and the viscosity was measured in the same manner, and the viscosity ratio was calculated.

Comparative Example 5
Xanthan gum (KELTROL CG-T, manufactured by Sansho Corporation) was used instead of CNF. Ion-exchanged water and 1,3-butylene glycol (BG) as a diol were added to the xanthan gum, and the final concentrations were adjusted to 0.5% by mass for the xanthan gum content, 5% by mass for the 1,3-butylene glycol content (mass ratio (A:B) of 1:10), and 10% by mass (mass ratio (A:B) of 1:20), and each was then stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5, manufactured by Primix Corporation). This was degassed to obtain a gel composition for cosmetic preparations.

Comparative Example 6
Ion-exchanged water and ethanol (EtOH), a monohydric alcohol, were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and the final concentration was adjusted to 0.5% by mass for the CNF content and 10% by mass for the ethanol content (mass ratio (A:B) of 1:20), and the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation).The mixture was degassed to obtain a gel composition for cosmetics.

The viscosities of the cosmetic gel compositions of Examples 2 to 7 and Comparative Examples 4 to 6 are shown in Table 3. Table 3 also shows the viscosities when the diol content is 0% by mass.

As shown in Table 3, the cosmetic gel compositions of Examples 2 to 4 containing 1,3-butylene glycol as a diol, the cosmetic gel composition of Example 5 containing pentylene glycol as a diol, and the cosmetic gel composition of Example 6 containing propylene glycol as a diol had higher viscosities than the composition without diol (addition amount 0 mass%). When the diol content was adjusted to 10 mass%, the viscosity ratio was 12.9% in Example 2, 13.1% in Example 3, and 13.3% in Example 4, in which 1,3-butylene glycol was used as the diol, 11.2% in Example 5, in which pentylene glycol was used as the diol, and 10.2% in Example 6, in which propylene glycol was used as the diol.

On the other hand, the viscosity ratio of the cosmetic gel composition of Comparative Example 4, which contains glycerin, a polyhydric alcohol, instead of diol, was -7.7%, the viscosity ratio of the cosmetic gel composition of Comparative Example 5, which does not contain CNF, was 3.0%, the viscosity ratio of the cosmetic gel composition of Comparative Example 6, which contains ethanol, a monohydric alcohol, was -3.0%, and the viscosity ratio of the cosmetic gel composition of Example 7, which contains glycerin, a polyhydric alcohol, in addition to diol, was -9.5%, and none of the viscosities were sufficiently high compared to the CNF aqueous dispersion containing the same amount of CNF.

In view of the above, it is considered preferable to use 1,3-butylene glycol, pentylene glycol, or propylene glycol as the diol in the cosmetic gel composition of the present invention from the viewpoint of increasing the viscosity to improve the ease of handling when applied to the skin, and it is particularly considered more preferable that the composition does not contain any polyhydric alcohol such as glycerin other than these diols.

The cosmetic gel composition of the present invention can be used as a raw material for cosmetics to be used on the face, etc.

Claims (4)

The present invention comprises a nonionic cellulose nanofiber having an average fiber diameter of 2 to 30 nm, a diol, and water,
The content of the cellulose nanofiber is 0.1 to 5% by mass,
The content of the diol is 1 to 20% by mass,
A cosmetic gel composition , wherein the mass ratio (A:B) of the content (A) of the cellulose nanofibers to the content (B) of the diol is 1:2 to 1:40 . 2. The cosmetic gel composition according to claim 1 , wherein the diol is at least one selected from the group consisting of 1,3-butylene glycol, pentylene glycol, propylene glycol, and dipropylene glycol. 3. The cosmetic gel composition according to claim 1 , wherein the transmittance of light having a wavelength of 700 nm is 75% or more at an optical path length of 10 mm. The cosmetic gel composition according to any one of claims 1 to 3, which has been prepared so as to have a viscosity 10% or more higher than that of an aqueous dispersion of cellulose nanofibers containing the same amount of cellulose nanofibers.