Water-soluble film and sheet-shaped cosmetic

Abstract

To provide a water-soluble film including silk fibroin, which is ultrathin and flexible, and a sheet-shaped cosmetic formed from the water-soluble film.SOLUTION: Provided is a water-soluble film containing alginic acid or a salt thereof as a main component, wherein the thickness is 8 μm or more and 20 μm or less, the water-soluble film further containing silk fibroin, and when the mass of the alginic acid or the salt thereof is defined as A and the mass of the silk fibroin is defined as B, A / B is 25 or more and 100 or less. A sheet-shaped cosmetic composed of the water-soluble film and dissolved in water on skin at the time of use is also provided.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-soluble film and a sheet-type cosmetic, and more specifically to a water-soluble film containing alginic acid or a salt thereof as a main component and further containing silk fibroin, and a sheet-type cosmetic comprising said water-soluble film. [Background technology]

[0002] Silk fibroin, a protein produced by silkworm larvae, is widely used as a raw material for cosmetics, pharmaceuticals, foods, and the like. Patent Document 1 discloses a molded product containing silk fibroin and atelocollagen, and a cosmetic product prepared just before use that comprises the molded product. Patent Document 2 discloses a method for producing a silk fibroin molded product, which includes a step of spreading a silk fibroin solution containing a fluorinated solvent on a substrate. Furthermore, Non-Patent Document 1 describes that silk fibroin is useful as a coating for preserving fresh foods such as fruit.

[0003] Alginates are widely used as gelling agents and thickeners. Water-soluble films using alginates as a base component are known. For example, Patent Document 3 discloses an edible film in which a base layer mainly made of alginate is provided with a coating layer mainly made of shellac. Generally, films using alginates as a base component have excellent water solubility and transparency, but it is not easy to stably produce films of a predetermined thickness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-80144 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-3092 [Patent Document 3] International Publication No. 2019 / 130959 [Non-patent literature]

[0005] [Non-Patent Document 1] B. Marelli, MA Brenckle, DL Kaplan & FG Omenetto, "Silk Fibroin as Edible Coating for Perishable Food Preservation", Scientific Reports, volume 6, Article number: 25263 (2016) Summary of the Invention [Problem to be solved by the invention]

[0006] An ultrathin, flexible film containing an effective amount of silk fibroin would be useful for a variety of applications. For example, it could be used as a film-type cosmetic to be applied to the skin or as a packaging material for preserving fresh food. However, even if silk fibroin can be formed into a film, it is generally brittle, making it difficult to form into an ultrathin, flexible film. Therefore, an object of the present invention is to provide a water-soluble film containing silk fibroin that is ultrathin and flexible. [Means for solving the problem]

[0007] The present inventors conducted repeated trials to produce an ultrathin film containing silk fibroin. However, many of the films they produced were brittle and easily cracked. They then further investigated the substrates to be combined with silk fibroin and their blending ratios. As a result, they discovered that an ultrathin, flexible silk fibroin-containing film could be produced by creating a hybrid film containing alginic acid or its salt and silk fibroin.

[0008] One aspect of the present invention is a water-soluble film containing alginic acid or a salt thereof as a main component, having a thickness of 8 μm or more and 20 μm or less, and further containing silk fibroin, wherein A / B is 25 or more and 100 or less, where A is the mass of the alginic acid or a salt thereof and B is the mass of the silk fibroin.

[0009] The water-soluble film of this aspect is an ultrathin film containing alginic acid or a salt thereof as a main component and further containing silk fibroin. The mass ratio of alginic acid or a salt thereof to silk fibroin in this aspect is within a specific range. The water-soluble film of this aspect is ultrathin and flexible, making it useful for a variety of applications.

[0010] Here, "contained as a main component" means that the content ratio relative to the entire water-soluble film is 50% by mass or more.

[0011] Preferably, the A / B is 40 or more and 65 or less.

[0012] Preferably, the alginic acid or salt thereof is potassium alginate.

[0013] Another aspect of the present invention is a sheet-form cosmetic comprising the above-mentioned water-soluble film, which is dissolved in water on the skin during use.

[0014] This aspect relates to a sheet-type cosmetic comprising the water-soluble film. By dissolving the sheet-type cosmetic of this aspect in water on the skin, silk fibroin can be easily applied to the skin. Furthermore, alginic acid or a salt thereof can also be applied at the same time.

[0015] Preferably, the sheet-type cosmetic does not contain any preservatives.

[0016] With this configuration, it is possible to provide a sheet-type cosmetic material that gives a greater sense of security.

[0017] Preferably, the sheet-shaped cosmetic material is in the shape of a disk with a diameter of 5 mm to 50 mm.

[0018] With this configuration, it is possible to provide a sheet-type cosmetic material that is particularly easy to handle. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an ultrathin and flexible water-soluble film containing silk fibroin. Furthermore, the sheet-like cosmetic material of the present invention allows silk fibroin to be easily applied to the skin. DETAILED DESCRIPTION OF THE INVENTION

[0020] The water-soluble film of the present invention contains alginic acid or a salt thereof as a main component, and further contains silk fibroin.

[0021] <Alginic acid or its salt> The water-soluble film of the present invention contains alginic acid or a salt thereof (hereinafter sometimes abbreviated as alginic acid (salt)) as a main component. Here, "contained as a main component" means that the content is 50% by mass or more. The content of alginic acid (salt) can be appropriately selected from the range of 50% by mass or more depending on the amount of silk fibroin to be combined and the amount of other components.

[0022] The type of alginate is not particularly limited, and examples include sodium alginate, potassium alginate, etc. Among these, potassium alginate is preferably used in terms of low cost and easy availability. Alginate can be extracted and purified from seaweed such as kelp. Sodium alginate and potassium alginate derived from kelp can be obtained, for example, from Kouhara Co., Ltd. of Maikon Co., Ltd.

[0023] <Silk fibroin> The silk fibroin used in the water-soluble film of the present invention is not particularly limited, and any silk fibroin may be used regardless of its origin, production method, molecular weight, etc., as long as it can be combined with alginic acid (salt) to form an ultrathin and flexible film and has the desired effect and functionality. Silk fibroin can be derived from, for example, Lepidoptera, Hymenoptera, or Araneae, preferably Lepidoptera, more preferably Bombycidae, and even more preferably the silkworm moth (scientific name: Bombyx mori). Examples of methods for producing silk fibroin include those described in Japanese Patent Application Laid-Open Nos. 7-67687 and 2009-292743. Silk fibroin is commercially available, and for example, "Nanofibroin" (registered trademark; Matsuda Sericulture Co., Ltd.), a water-soluble polymeric silk fibroin, can be used.

[0024] The content of silk fibroin in the water-soluble film of the present invention can be appropriately selected from a range that allows its action and functionality to be exerted. In one embodiment, when the mass of alginic acid or a salt thereof contained in the water-soluble film of the present invention is A and the mass of silk fibroin is B, A / B is 25 or more and 100 or less (25 to 100). In other words, A:B is in the range of 25:1 to 100:1. A / B is preferably 30 to 90, more preferably 30 to 80, even more preferably 35 to 70, and particularly preferably 40 to 65. If A / B is less than 25, the content of silk fibroin will be excessive, which may adversely affect the flexibility of the film. If A / B is more than 100, the content of silk fibroin will be insufficient, which may prevent the desired effect from being obtained.

[0025] <Thickness> The water-soluble film of the present invention has a small thickness, in the range of 8 μm to 20 μm (8 to 20 μm). Therefore, it is easier to handle than a thicker film. The film thickness is preferably 9 to 19 μm, more preferably 10 to 18 μm.

[0026] <Other ingredients> The water-soluble film of the present invention is basically composed of two components, alginic acid (salt) and silk fibroin, but other components may be included as long as they do not impair its performance, such as the effect of silk fibroin, the water solubility of the film, the flexibility of the film, etc. From the perspective of use as a film-type cosmetic, which will be described later, it is preferable that the water-soluble film of the present invention does not contain any preservatives.

[0027] <Film manufacturing method> The water-soluble film of the present invention can be produced by applying known methods. For example, an aqueous solution containing predetermined amounts of alginic acid (salt) and silk fibroin is prepared. The viscosity (20°C) of the aqueous solution is preferably approximately 1,000 to 15,000 mPa·s (cps), more preferably approximately 4,000 to 13,000 mPa·s, and even more preferably approximately 6,000 to 10,000 mPa·s. Next, the aqueous solution is applied to a film made of polyethylene terephthalate (PET) or the like to a desired thickness, and the film is heated and dried with hot air. This allows the water-soluble film of the present invention (silk fibroin-containing alginate film) to be formed. If necessary, the dried water-soluble film is sequentially wound up into a roll.

[0028] <Sheet-type cosmetics> The water-soluble film of the present invention can be used in the form of a sheet cosmetic (film cosmetic). That is, one embodiment of the water-soluble film of the present invention is used as a cosmetic, and is dissolved in water on the skin during use. The sheet cosmetic of the present invention dissolves rapidly on contact with water on the skin. As a result, silk fibroin can be applied to the skin, and alginic acid (salt) can also be applied to the skin. The face is a typical example of a body surface to which the sheet cosmetic is applied, but other areas may also be used. When applied to the face, for example, the sheet cosmetic can be placed on a wet face immediately after washing, and the film can be dissolved.

[0029] When the water-soluble film of the present invention is used as a sheet-type cosmetic, it is preferably free of preservatives. That is, while preservatives are generally included in liquid cosmetics, the sheet-type cosmetic of the present invention has a high shelf life and therefore does not need to include preservatives. This increases the sense of security of the user. Note that "free of preservatives" as used herein not only means that no preservatives are included, but also includes cases where the content is so small that it does not act as a preservative (for example, trace amounts of unintended impurities).

[0030] The shape of the water-soluble film when used as a sheet-type cosmetic is not particularly limited, but can be, for example, a disk shape (circular in plan view). When the film is disk-shaped, the size can be, for example, 5 mm or more and 50 mm or less (5 to 50 mm) in diameter. This results in a sheet-type cosmetic that is easy to handle. It is also highly portable, making it easy to use when out and about. Note that multiple disk-shaped sheet-type cosmetics may be arranged on a support film. This allows the required number of sheet-type cosmetics to be peeled off and used at the time of use. The shape of the sheet-type cosmetic may be a polygonal shape or a strip shape in plan view, in addition to a disk shape.

[0031] <Other uses> Other uses of the water-soluble film of the present invention include food packaging and covering materials, which are useful for preserving foods such as vegetables and fruits, because silk fibroin has the effect of inhibiting spoilage of fruits and the like (e.g., Non-Patent Document 1).

[0032] Other applications include wound dressings. For example, the water-soluble film of the present invention may be applied directly to the wound surface to promote wound healing. The water-soluble sheet of the present invention may also be provided on the pad portion of a cloth bandage. Other applications include medical applications such as artificial skin.

[0033] When used as a wound dressing, it can also be expected to protect non-wound areas adjacent to the wound. In other words, when bandages or tape are generally applied and removed multiple times on the same area, the application and removal of the tape can damage healthy skin other than the wound. Therefore, by applying the water-soluble film of the present invention to the wound and its surrounding area and then applying a bandage, the irritation to the non-wound area caused by the application and removal of the tape can be reduced. This allows the non-wound area to be protected.

[0034] In general, adhesive bandages tend to peel off easily on skin that is coated with oily ingredients such as hand cream or ointment, or on skin that contains a lot of moisture. In such cases, if the water-soluble film of the present invention is applied to the skin before applying the adhesive bandage, it quickly dissolves on the skin to form a coating, preventing the adhesive bandage from peeling off easily. This allows the wound area to enjoy a stable, long-term effect of promoting wound healing. At the same time, the skin of non-wounded areas can be protected from irritation caused by applying and removing the tape. [Example]

[0035] [Experimental Example 1] A formulation was prepared by dissolving 7 parts by mass of potassium alginate powder (Maikon Kohara Co., Ltd.) and 2.5 parts by mass of a 6% aqueous solution of silk fibroin ("Nanofibroin"; Matsuda Yosan Co., Ltd.) in 90.5 parts by mass of ion-exchanged water. This formulation was applied to a 75 μm-thick PET film and dried in a dryer to form a film with a thickness of 16–17 μm. The film was peeled off from the PET film to obtain a silk fibroin-containing alginate film. The potassium alginate content (A) in this film was 7 parts by mass, and the silk fibroin content (B) was 2.5 × 0.06 = 0.15 parts by mass, resulting in an A / B ratio of 46.7 (A:B = 46.7:1). The resulting film was water-soluble, dissolving rapidly in water (evaluation: A). The resulting film was also flexible and easily bendable (evaluation: A).

[0036] [Experimental Example 2] A preparation was prepared by dissolving 7 parts by mass of potassium alginate powder and 2.016 parts by mass of a 6% aqueous solution of silk fibroin in 90.984 parts by mass of ion-exchanged water. The same procedure as in Experimental Example 1 was then repeated to obtain a silk fibroin-containing alginate film with a thickness of 16-17 μm. The potassium alginate content A in this film was 7 parts by mass, and the silk fibroin content B was 2.016 × 0.06 = 0.12096 parts by mass, resulting in an A / B ratio of 57.9 (A:B = 57.9:1). The resulting film was water-soluble, dissolving rapidly in water (evaluation: A). The resulting film was also flexible and easily bendable (evaluation: A).

[0037] [Experimental Example 3] A preparation was prepared by dissolving 7 parts by mass of potassium alginate powder and 3.5 parts by mass of a 6% aqueous solution of silk fibroin in 89.5 parts by mass of ion-exchanged water. The same procedure as in Experimental Example 1 was then performed to obtain a silk fibroin-containing alginate film with a thickness of 16-17 μm. The potassium alginate content A in this film was 7 parts by mass, and the silk fibroin content B was 3.5 × 0.06 = 0.21 parts by mass, resulting in an A / B ratio of 33.3 (A:B = 33.3:1). The resulting film was water-soluble, dissolving rapidly in water (evaluation: A). Although the resulting film was slightly inferior to those in Experimental Examples 1 and 2, it still had the required flexibility and could be easily bent (evaluation: B).

[0038] [Experimental Example 4] A preparation was prepared by dissolving 7 parts by mass of potassium alginate powder and 7 parts by mass of a 6% aqueous solution of silk fibroin in 86 parts by mass of ion-exchanged water. The same procedure as in Experimental Example 1 was then carried out. However, the film formed was brittle and lacked flexibility, cracking when slightly bent (evaluation: C). The potassium alginate content A in this film was 7 parts by mass, and the silk fibroin content B was 7 x 0.06 = 0.42 parts by mass, resulting in a ratio of A / B = 16.7 (A:B = 16.7:1).

[0039] (Skin application) The films obtained in Examples 1 to 3 were cut into circles with a diameter of 15 mm to prepare sheet-type cosmetics. When these sheet-type cosmetics were placed on a wet face immediately after washing, they all dissolved quickly (evaluation: A). All of the sheet-type cosmetics were flexible and could be easily placed in the desired location (for example, around the eyes or mouth). Furthermore, all of the sheet-type cosmetics had a good feel when used as a cosmetic (evaluation: A).

[0040] Table 1 shows the formulations (unit: parts by mass), film properties, and evaluation results of Experimental Examples 1 to 4.

[0041] [Table 1]

Claims

1. A water-soluble film containing alginic acid or a salt thereof as a main component, The thickness is 8 μm or more and 20 μm or less, It also contains silk fibroin, A water-soluble film, wherein A / B is 25 or more and 100 or less, where A is the mass of the alginic acid or salt thereof and B is the mass of the silk fibroin.

2. 2. The water-soluble film according to claim 1, wherein the A / B ratio is 40 or more and 65 or less.

3. The water-soluble film according to claim 1 , wherein the alginic acid or a salt thereof is potassium alginate.

4. The water-soluble film according to claim 2 , wherein the alginic acid or a salt thereof is potassium alginate.

5. A sheet-form cosmetic comprising the water-soluble film according to any one of claims 1 to 4, which is dissolved in water on the skin during use.

6. 6. The sheet-form cosmetic according to claim 5, which does not contain any preservatives.

7. 6. The sheet-form cosmetic material according to claim 5, which is in the shape of a disk having a diameter of 5 mm to 50 mm.

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