Asymmetrical structure moisturizing mask pack

Abstract

The present invention relates to an asymmetric structure moisturizing mask pack comprising a polylactide. More specifically, the present invention relates to a porous membrane mask pack prepared from copolymers of polylactide and polyvinyl alcohol, wherein the skin contact surface of the mask pack is hydrophilic and the back surface thereof is hydrophobic.

Claims

1. An asymmetrically structured mask pack for nourishing facial skin comprising a porous membrane having one surface that is hydrophobic, and another surface that is hydrophilic, wherein the hydrophilic surface is hydrophilized by treatment with alkaline solution, wherein a material for the porous membrane is a copolymer of polylactide with polyvinyl alcohol, wherein porosity of the porous membrane is formed by salt-leaching phase transition so that the hydrophilic surface has a porosity (v/v) of 90 to 95% and the hydrophobic surface has a porosity (v/v) of 5 to 10% to suppress evaporation of moisture.

2. A method for producing an asymmetrically structured mask pack for nourishing facial skin, comprising: a first step of copolymerizing polylactide with polyvinyl alcohol; a second step of producing a microfiber sheet with copolymers of polylactide and polyvinyl alcohol by electrospinning; a third step of producing a porous membrane from the microfiber sheet by salt-leaching phase transition; and a fourth step of hydrophilizing one surface of the porous membrane by treatment with a 5 to 20% (w/v) NaOH solution for 5 to 20 minutes, wherein the one surface, which is hydrophilic, of the porous membrane has a porosity (v/v) of 90 to 95% and another surface, which is hydrophobic, has a porosity (v/v) of 5 to 10% to suppress evaporation of moisture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows polylactide which is a biocompatible material;

(2) FIG. 2 shows a surface structure and a cross-sectional structure of an asymmetrically structured moisturizing mask pack;

(3) FIG. 3 shows a conventional silicon hydrogel mask pack; and

(4) FIG. 4 shows an asymmetrically structured moisturizing mask pack containing polylactide.

BEST MODE

(5) The terms or words used in the present specification and claims should be construed, not as having ordinary or dictionary meanings, but as having meanings and concepts that are consistent with the technical ideas of the present invention, based on the principle that an inventor can appropriately define the concept of a term in order to describe the invention in the best way.

(6) Therefore, it should be understood that the configurations shown in the embodiments and drawings described in the present specification are suggested only as the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and various equivalents and modifications thereof that can replace them at the time of the present application are possible.

Example 1. Production of an Asymmetrically Structured Moisturizing Mask Pack Using Polylactide

1) First Step of Producing Sheet by Copolymerizing Polylactide with Polyvinyl Alcohol

(7) Polylactide, known as a biocompatible material, has been used as a plate, screw and suture for bone fractures for more than 30 years, and is known to be decomposed into water and carbon dioxide in the human body. In particular, since the injection of polylactide particles into the skin is known to promote collagen formation, polylactide has been developed as a medical device in the US and imported into Korea. However, polylactide has considerably different rates of decomposition depending on the molecular weight thereof, and enantiomers thereof are present, and among them, a commonly used polyisomer is poly-L-lactide having crystallinity.

(8) In the present example, a polylactide, which is a biocompatible material, is copolymerized with polyvinyl alcohol, which is hydrophilic, to prepare an asymmetrically structured moisturizing mask pack in the form of a porous membrane. A mask pack is produced, which can be mass-produced and has fine pores, using electrospinning and salt-leaching phase transition methods.

2) Second Step of Producing Copolymerized Polylactide and Polyvinyl Alcohol into Microfiber Sheet by Electrospinning

(9) Electrospinning is a process for producing ultrafine fibers on a nanometer scale. Unlike conventional methods that depend on physical forces, materials considered unsuitable for production into fibers can be produced into fibers because of the use of electrical repulsive forces in the fiber-forming process and a non-woven fabric can be produced even with a small amount of materials.

(10) In addition, factors affecting the thickness of the fibers by electrospinning include the concentration of the solution, the applied voltage, the distance between the electrodes (tip-to-collector distance, TCD), flow rate, temperature and humidity. In general, since the concentration of the solution is proportional to the viscosity thereof, as the concentration increases under a certain voltage, the bending and stretching forces decrease and thus the diameter of the fiber increases. In addition, as the applied voltage increases, whipping instability increases and the diameter of the fiber decreases, but the minimum diameter is obtained at a certain distance.

(11) Electrospinning is advantageously capable of producing very thin fibers, is applicable to a very wide range of polymers and can be realized by a simple device and a simple spinning process. Preferably, adhesion of the skin contact surface of the mask pack sheet is increased by controlling the thickness of the fiber through electrospinning.

(12) In order to further upgrade the performance of conventional cosmetic mask pack sheets, sheets are made with copolymers of polylactide and polyvinyl alcohol by electrospinning, thereby producing sheets from the microfiber fibers.

(13) Accordingly, it is possible to promote adhesion ability to the skin and moisture content, and improve the absorption rate of the essence into the skin. In addition, it is possible to adsorb fine dust and sebum on the fiber tissue due to excellent skin adhesion and thereby effectively remove waste matter.

3) Third Step of Producing Porous Membrane from Microfiber Sheet by Salt-Leaching Phase Transition Method

(14) In term of ‘phase transition’, ‘phase’ means a part of a substance in a certain state that exhibits the same physical and chemical properties. That is, a phase refers to a homogeneous part of a substance, which may be a single substance or a mixture. Even in case of a mixture, it is said that a single phase is formed if it is mixed completely and homogeneously. In term of ‘phase transition’, ‘transition’ means transferring or relocation from one place to another.

(15) In other words, phase transition means that any phase, which is a homogeneous part of a substance, changes to another phase due to a change in variables such as temperature, pressure, magnetic field, composition, and is also called “phase transformation”.

(16) In addition, when a substance is in one phase, it can undergo partial phase transition due to a change in variables and can thus be separated into two phases, which is called “phase separation”. That is, phase separation is a phenomenon caused by phase transition.

(17) Methods for producing membranes using phase transition, phase transformation or phase separation include non-solvent induced phase separation (NIPS), thermally induced phase separation (TIPS), solvent evaporation precipitation, vapor phase precipitation and evaporation control precipitation, depending on the phase separation principle.

(18) Non-solvent induced phase separation, which is also called immersion precipitation or solvent exchange, is a method that is suitable for mass production due to relatively simple and inexpensive production process. In the non-solvent induced phase separation process, a polymer to be used as a raw material is dissolved in a suitable solvent to prepare a thermodynamically stable polymer solution, cast into a flat-plate, tube or hollow fiber form, and then immersed in a non-solvent. This causes phase separation of the polymer, so that a portion of the region occupied by the solvent and the non-solvent becomes pores, thereby producing a porous membrane.

(19) The surface of the microfiber sheet is prepared by the salt-leaching phase transition method, and the surface in contact with the skin has a porosity of 90% or more and is hydrophilic, whereas the back surface a porosity of less than 10% and is hydrophobic. When the mask pack is attached to the skin, moisture is absorbed into the pores in the skin, so that skin moisturization is promoted and the composition penetrates well into the skin, thereby increasing efficacy thereof.

(20) FIG. 2 shows a surface structure and a cross-sectional structure of the asymmetrically structured moisturizing mask pack. FIG. 2 shows a hydrophobic surface and a hydrophilic cross-sectional surface in the asymmetric structure produced by the phase transition method.

(21) In particular, when the mask pack is attached to the skin, the temperature of the substance contained in the pack is increased and thus the composition of the mask pack promotes skin absorption, and evaporation to the atmosphere is suppressed due to the hydrophobic surface.

(22) Through the phase transition method, a porous membrane having a porosity (v/v) of 90 to 95% on a skin adhesion surface and a porosity (v/v) of about 5 to 10% on a back surface is produced to thus suppress evaporation of the mask pack composition into the atmosphere and promote absorption thereof into the skin.

4) Fourth Step of Hydrophilizing One Surface of Porous Membrane by Plasma Surface Treatment or Treatment with Alkaline Solution

(23) Most polymers, such as polyethylene and polypropylene, are hydrophobic due to the nonpolar molecular structure thereof. Therefore, these polymers can inhibit the absorption of the mask pack composition on the surface that is in contact with the skin.

(24) Accordingly, the present inventors hydrophilized one surface of the porous membrane through plasma treatment, so that the mask pack composition may be contained in the skin contact surface to thus enhance absorption in the skin.

(25) Preferably, the skin contact surface is hydrophilized through plasma surface treatment using plasma chemical vapor deposition. As a result, the hydrophilicity of the skin contact surface can be increased by plasma treatment, and the hydrophobicity of the back surface can suppress microbial growth and evaporation of the mask pack composition.

(26) In addition, treatment with alkaline solution can be performed in order to hydrophilize the porous membrane. Preferably, the porous membrane is hydrophilized with 10% (w/v) NaOH for 20 minutes.

Experimental Example 1. Hydrophilization of an Asymmetrically Structured Mask Pack Containing Polylactide

(27) Experimental Example 1 relates to a hydrophilization process of an asymmetrically structured mask pack containing polylactic acid (PLA) prepared in the above Example.

(28) 1) A PLA membrane and a PLGA (polylactic-co-glycolic acid) membrane (20 mm 30 mm) were prepared.

(29) 2) 5, 10, 20, 30, 40 and 50% (w/v) NaOH solutions were prepared.

(30) 3) 20 ml of each NaOH solution was added to a petri dish and a sheet cross-sectional surface was subjected to hydrophilization.

(31) 4) One surface of each of the PLA membrane and the PLGA membrane was immersed in the NaOH solution to make the membrane hydrophilic.

(32) 5) The membrane was measured for 1 hour at an interval of 10 minutes.

(33) As a result, it was found that the PLA membrane is preferably hydrophilized with 10% NaOH for 20 minutes and the PLGA membrane is preferably hydrophilized with 20% NaOH for 10 minutes.

Experimental Example 2. Preparation of Mask Pack Composition

(34) A mask pack composition was prepared from ingredients including a herbal extract, a solvent, a wetting agent, a viscosity modifier, a surfactant, a skin-conditioning agent, a preservative, a thickener, a pH adjuster, a flavoring agent and a chelating agent. The contents thereof are determined so that they can be easily utilized by those skilled in the art to prepare a pack composition.

(35) TABLE-US-00001 TABLE 1 Mask pack sheet Sample 1 Asymmetrically structured moisturizing mask pack containing polylactide produced in Example 1 Sample 2 PLA non-woven sheet Sample 3 PLGA membrane sheet Sample 4 Commercially available mask pack sheet

Example 3. Sensory Evaluation of Moisturizing Satisfaction and Skin Stability

(36) A sensory test based on a 9-point scale (1-9) was performed for moisturizing satisfaction, skin stability and texture according to the mask pack sheet produced from the same mask pack composition. The panel included 20 male adults and 20 female adults in 20s to 30s. The results of the test are shown in the following [Table 2]. The higher the number, the better the effect.

(37) TABLE-US-00002 TABLE 2 Moisturizing Skin Overall satisfaction stability Texture evaluation Sample 1 8.5 7.9 8.0 8.3 Sample 2 4.3 5.6 4.2 4.7 Sample 3 5.5 4.3 5.6 5.3 Sample 4 2.3 3.1 2.0 2.4

(38) As can be seen from [Table 2], the overall moisturizing effect of the asymmetrically structured moisturizing mask pack containing polylactide is the highest.

Experimental Example 4. Evaluation of Moisture Retention Capacity

(39) Five test subjects evaluated the moisture retention capacity of each sheet produced in Experiment Example 1 as follows. The moisture retention capacity was obtained by measuring the electrical conductivity of the skin surface using SKICON-200. After attaching the mask pack to the skin (16 cm.sup.2) for 30 minutes in a constant-temperature constant-humidity room maintained at 25° C. and 40% relative humidity, the mask pack was removed therefrom and the resistance value (moisture loss) was measured over time.

(40) TABLE-US-00003 TABLE 3 Sample Sample sample sample 1 2 3 4 Short-term One hour after 820 650 520 300 moisturizing removal Long-term Used once for 30 5.3 26 5.8 moisturizing five days

(41) As can be seen from the above [Table 3], the overall moisture retention capacity of the asymmetrically structured moisturizing mask pack containing polylactide is the highest.