JP7828575B2 - Biodegradable nail tips, nail polish, and nail polish remover - Google Patents

Description

This invention relates to nail tips made using a biodegradable composite material in which strength and biodegradability are enhanced by incorporating cellulose nanofibers into a biodegradable resin. In other words, this invention provides biodegradable nail tips. It also provides biodegradable nail polish and nail polish remover for decorating biodegradable nail tips.

Nail art, which involves decorating one's own fingernails and toenails (natural nails), is currently trending. While it's possible to directly form artificial nails on natural nails using synthetic resins such as (meth)acrylic resins or urethane resins containing (meth)acrylic (chemically polymerizable resin compositions, or photopolymerizable resin compositions/gels), this requires advanced shaping techniques and places significant stress on the nails. In recent years, the technique of attaching resin-based artificial nails (nail tips) to natural nails and then decorating them with color, stones, glitter, and other embellishments has become common. Using nail tips has led to an increase in people doing their own nail art, rather than having it done professionally at a salon. Therefore, the demand for nail tips has been rising in recent years.

Since nail tips are made of synthetic resin (plastic), the increasing demand and the resulting increase in waste raise concerns about their environmental impact.

To prevent environmental pollution caused by plastic waste, the "3R movement" of Reduce, Reuse, and Recycle plastics is being promoted worldwide. Separate collection of plastics is carried out for reuse and recycling. The collected plastic waste was previously exported to China and Southeast Asia, but these countries have banned the import of plastic waste, resulting in a buildup of plastic waste within Japan. In recent years, there has been growing concern, particularly about marine debris. When plastic waste flows into the ocean, it not only drifts around but also breaks down into microplastics smaller than 1 mm as it floats over long distances and for long periods, creating a major problem of ecosystem destruction. Although collected plastic waste is disposed of in landfills, it can flow into rivers due to floods and reach the sea. In 2010, it was estimated that 20,000 to 60,000 tons of plastic waste flowed from land into the ocean in Japan per year (Non-Patent Literature 1).
Reducing plastic use is a powerful solution, but in modern society, it's impossible to eliminate it entirely, so it doesn't work out as ideally as it could.

Therefore, various biodegradable plastics have been developed. Biodegradable plastics have the property of being broken down by microorganisms and ultimately into carbon dioxide and water. Examples of biodegradable plastics include polylactic acid (PLA), polycaprolactone, polyhydroxyalkanoate (PHA), polybutylene succinate, copolymer of polybutylene adipate and terephthalate, polyglycolic acid, modified polyvinyl alcohol, and casein. Biodegradable plastics derived from starch have also been developed (see Non-Patent Literature 2, etc.).

Biodegradable plastics are expected to reduce environmental pollution, but they have the drawback of low strength. Therefore, research is underway on composite materials that incorporate plant-derived biomass to increase strength without compromising biodegradability (e.g., Patent Documents 1 and 2). Furthermore, attempts are being made to improve the compatibility of the different phases at the interface between biomass and biodegradable resins to enhance the strength of biomass/biodegradable resin composite materials (Patent Document 3).

Japanese Patent Publication No. 2000-160034 Japanese Patent Publication No. 2002-069303 Japanese Patent Publication No. 2018-100312 Japanese Patent Publication No. 2008-001728 Japanese Patent Publication No. 2010-235679

J. R. Jambeck et al., "Plastic waste inputs from land into the ocean; Science 13 Feb. 2015, p.768 Du, Yicheng et al., Fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites, Composite Pat B: Engineering, v.56, pp. 717-723

This invention aims to provide biodegradable nail tips that are primarily made of biodegradable plastic, taking environmental impact into consideration, and that are particularly excellent in terms of strength and comfort when worn on the fingertips. Furthermore, it also aims to provide nail polish and nail polish remover for decorating these biodegradable nail tips.

In this invention, a biodegradable resin composition is used to manufacture nail tips (artificial nails) primarily from biodegradable plastics such as polylactic acid (PLA), polyhydroxyalkanoate (PHA), starch, and cellulose acetate. This composition also includes cellulose nanofibers as a material to increase the strength of the biodegradable plastics without impairing their biodegradability.

The biodegradable resins mentioned above, such as polylactic acid (PLA), polyhydroxyalkanoate (PHA), and starch-based resins, are manufactured from edible biomass raw materials such as potatoes, grains, sugarcane, and corn.

Furthermore, cellulose acetate has long been known as a resin made from non-edible biomass raw materials. Cellulose acetate is a semi-synthetic polymer obtained by esterifying cellulose, a natural polymer, with acetic acid. Since cellulose acetate itself is not thermoplastic, it needs to be plasticized by adding a plasticizer in order to be used as a resin. Dioctyl phthalate (DOP) and triacetin, which have high compatibility, are mainly used as plasticizers for cellulose acetate.

Cellulose nanofiber (CNF) is attracting attention as a material for increasing the strength of biodegradable plastics without compromising their biodegradability. CNF possesses excellent physical properties such as high elasticity, light weight, low elongation, and high gas barrier properties. Furthermore, CNF, produced from cellulose, a biomass abundant in nature, is a so-called carbon-neutral material; even when burned, it does not increase carbon dioxide levels on Earth, resulting in a low environmental impact during production and disposal. A generally known method for producing CNF with these excellent properties involves chemically treating wood chips with oxidizing agents to produce cellulose fibers, followed by mechanical processing such as homomixing (Patent Documents 4 and 5).

However, CNF produced by these conventional methods had the problem of insufficient strength in composite materials obtained by adding it to resins, etc. The inventors of this invention have discovered that CNF obtained by directly hydrothermally treating cellulose raw materials such as wood chips, followed by chemical treatment, improves the properties of composite materials with resin materials. This method allows for the effective utilization of cellulose materials that were previously discarded, by using not only new wood but also waste wood, rice stalks, kudzu, grasses such as pampas grass, and waste paper as raw materials for producing CNF.

Therefore, in this invention, we have decided to use CNF already developed by the inventors. The CNF that can be used in this invention is produced by a method for producing CNF that includes the steps of: obtaining swollen cellulose raw materials by hydrothermal treatment of cellulose raw materials such as broad-leaved trees, coniferous trees, woody plants such as bamboo, rice ears, kudzu, pampas grass, and paper; obtaining pulp by crushing the swollen cellulose raw materials; and obtaining cellulose nanofibers by chemical treatment of the pulp with acid or alkali.

Nail tips manufactured using a biodegradable resin composition in which CNF developed by the inventors was added to the above-mentioned biodegradable plastic exhibited sufficient strength and did not feel bulky or heavy when attached to natural nails.

The nail tips according to the present invention are manufactured using a biodegradable resin composition, thus minimizing the environmental impact of disposal and making them highly practical.

In its first aspect, the present invention provides a nail tip comprising a biodegradable resin composition containing at least a biodegradable polymer selected from the group consisting of polylactic acid (PLA), starch-based biodegradable resin, polycaprolactone, polyhydroxyalkanoate (PHA), polybutylene succinate, a copolymer of polybutylene adipate and terephthalate, polyglycolic acid, modified polyvinyl alcohol, casein, and cellulose acetate, as well as cellulose nanofibers.

The cellulose nanofibers that can be used in the present invention are cellulose nanofibers produced by a manufacturing method that includes, in this order, the steps of: subjecting a cellulose raw material to hydrothermal treatment to obtain a swollen cellulose raw material; crushing the swollen cellulose raw material to obtain pulp; and chemically treating the pulp to obtain cellulose nanofibers (CNF). Examples of the above-mentioned cellulose raw material include any substance from which natural cellulose can be extracted, such as woody plants selected from the group consisting of conifers, broad-leaved trees and bamboo, or herbaceous plants selected from the group consisting of rice ears, kudzu, pampas grass, etc., and also paper. These cellulose raw materials do not have to be new materials, but may also be used waste materials of the aforementioned woody plants and herbs, or recycled paper. Such cellulose raw materials are cut to an appropriate size for handling before being subjected to the process. In this invention, the size of the cellulose raw material subjected to the process is preferably in the range of 0.5 × 0.5 cm to 2.0 × 2.0 cm, more preferably 0.7 × 0.7 cm to 1.5 × 1.5 cm, and most preferably 0.8 × 0.8 cm to 1.2 × 1.2 cm. If the raw material is larger than the above range, it is crushed into chips or powder.

In the hydrothermal treatment step of the CNF manufacturing method according to the present invention, the cellulose raw material is immersed directly in water and subjected to subcritical to supercritical conditions under high temperature and high pressure. More specifically, the hydrothermal treatment of the water-immersed chips, etc., is carried out for 60 to 180 minutes in a subcritical or supercritical state within the range of 150 to 250°C at 1 to 300 atmospheres and 400°C or lower, preferably 5 to 200°C at 2 to 250 atmospheres, more preferably 100 to 380°C at 25 to 100 atmospheres and 150 to 250°C. Through these hydrothermal treatments, the cellulose raw material becomes a soft, swollen pulverized material.

Conventional CNF manufacturing methods involve first chemically treating cellulose raw materials such as wood chips with sulfuric acid, followed by solvothermal treatment. However, the present invention's manufacturing method is characterized by first hydrothermal treatment of cellulose raw materials of a certain size, such as wood chips, followed by chemical treatment using acids or alkalis. CNF produced by this method enhances the properties of composite materials when mixed with resins.

Sorvothermal treatment is a process that uses an organic solvent instead of water in hydrothermal treatment. Examples of such organic solvents include methanol, ethanol, propanol, pyrrolidone solvents such as N-methylpyrrolidone, acetate solvents such as butyl acetate, glycol ether solvents such as diethylene glycol monomethyl ether, ketone solvents such as methyl ethyl ketone, aromatic solvents such as toluene and xylene, and hydrocarbon solvents such as paraffin.

Next, the obtained swollen cellulose raw material is subjected to a crushing process to loosen the fibers and produce pulp. Ball mills, disc mills, wet cutter mills, pressure homogenizers, etc., can be used for this crushing process. This crushing process results in fibrous pulp with a thickness of 0.05 to 0.5 mm.

Finally, the pulp obtained by crushing is chemically treated. Examples of chemical treatments include acid treatment, alkali treatment, or a combination thereof. Acids such as sulfuric acid, nitric acid, hydrochloric acid, and acetic acid can be used for acid treatment. Alkali treatments can use sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, and hypochlorous acid. Chemical treatment allows for the introduction of functional groups such as carboxyl groups, hydroxyl groups, ester groups, sulfo groups, ketone groups, and acetyl groups onto the cellulose surface, improving its dispersion in the resin.

Furthermore, lignin can be added to the cellulose raw material before hydrothermal treatment. Adding lignin makes the surface of the resulting CNF hydrophobic (hydrophobic CNF). Composite materials produced by mixing hydrophobic CNF with resin are preferable because they have higher tensile strength compared to composite materials made from non-hydrophobic CNF without added lignin. The mixing ratio of cellulose raw material to lignin (by weight) is preferably cellulose raw material/lignin = 0.5 to 2, more preferably 0.7 to 1.5, and more preferably 0.8 to 1.2.

In the first aspect of the present invention, various additives can be added to the resin composition for injection molding, provided that the objectives of the present invention are not impaired. The biodegradable resin composition of the present invention may contain additives such as lubricants, plasticizers, mold release agents, flow improvers, and combinations thereof.

Examples of lubricants that can be used in this invention include fatty acid esters such as sucrose fatty acid esters and glycerin fatty acid esters; hydrocarbons such as liquid paraffin, paraffin wax, and synthetic polyethylene wax; fatty acids and higher alcohols such as stearic acid and stearyl alcohol; fatty acid amides such as stearamide, oleamide, and erucamide, and alkylene fatty acid amides such as methylenebisstearamide and ethylenebisstearamide; metal soaps such as zinc stearate, calcium stearate, and magnesium stearate; and fatty acid esters of ester-based alcohols such as monoglyceride stearate and stearyl stearate. In particular, from the viewpoint of reducing environmental impact, naturally derived components such as sucrose fatty acid esters, glycerin fatty acid esters, stearic acid, stearyl alcohol, zinc stearate, calcium stearate, and magnesium stearate are recommended.

Examples of biodegradable polymer plasticizers that can be used in the present invention include: phthalate esters selected from dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, dibutyl phthalate, etc.; adipic acid esters selected from dioctyl adipic acid, diisononyl adipic acid, etc.; trimellitic acid esters selected from trioctyl trimellitic acid, etc.; polyesters of dibasic acids (such as adipic acid, sebatic acid, or phthalic acid) and glycols (such as 1,2-propanediol or butanediol); phosphate esters selected from tricresyl phosphate, etc.; citrate esters selected from tributyl acetyl citrate, triethyl citrate, tributyl citrate, etc.; epoxidized soybean oil, epoxidized This includes epoxidized vegetable oils selected from linseed oil, etc.; mono- or diesters of dicarboxylic acids selected from sebacate esters, azelaic acid esters, maleic acid esters, etc.; esters of aromatic carboxylic acids selected from benzoic acid esters, etc.; fatty acid methyl esters selected from methyl myristate, methyl palmitate, methyl stearate, methyl oleate, animal fatty acid methyl methyl tallow fatty acid methyl

In particular, when using cellulose acetate as a biodegradable polymer, it is preferable to use a plasticizer selected from the group consisting of rosin-based plasticizers such as rosin, rosin esters, and rosin glycerin esters; ester-based plasticizers of unsubstituted or substituted _C1-10 alcohols with acetic acid, lactic acid, phthalic acid, citric acid, or phosphoric acid; glycerin-based plasticizers such as triacetin, diacetin, glycerin, polyglycerin, glycerin fatty acid esters, and polyglycerin fatty acid esters; polyester-based plasticizers; and sugar alcohol-based plasticizers such as sorbitol, sucrose fatty acid esters, and sorbitan fatty acid esters.

Examples of release agents that can be used in this invention include glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, and higher alcohol fatty acid esters.

In addition, inorganic material fillers such as carbonates, sulfates, silicates, phosphates, borates, oxides, or powders of hydrates thereof, including calcium, magnesium, aluminum, titanium, and zinc, also have lubricant, mold release agent, and flowability improver effects. Specifically, examples include calcium carbonate, silica, clay, feldspar, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, kaolin clay, talc, mica, wollastonite, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, zeolite, diatomaceous earth, sericite, shirasu, calcium sulfite, potassium titanate, bentonite, graphite, and ferrite.

The biodegradable resin composition according to the present invention can be molded using molding techniques such as injection molding, and then cured to produce nail tips.

In a second aspect, the present invention provides a biodegradable nail color comprising a biomass-derived resin selected from the group consisting of shellac resin, rosin resin, and cellulose acetate.
The biodegradable nail color according to the present invention is useful for coloring nail tips according to the present invention. Dyes, pigments, etc., commonly used for coloring nail tips can be added, and glitter or holograms can also be added. Furthermore, if made clear without coloring with dyes or pigments, it can be used as a top coat.
Furthermore, the biodegradable nail color according to the present invention can also be used as a nail polish to color natural nails.

The biodegradable nail color according to the present invention may contain a biomass-derived solvent selected from the group consisting of bioethanol, biobutanol, ethyl lactate, and ethyl acetate.
In the biodegradable nail color according to the present invention, it is preferable that the bio-alcohol content of either bioethanol or biobutanol in the biomass-derived solvent is 60 to 80 (w/w%), from the viewpoint of facilitating application to natural nails or nail tips and eliminating uneven drying.

In a third aspect, the present invention provides a nail polish remover comprising a biomass-derived solvent selected from the group consisting of bioethanol, biobutanol, ethyl lactate, and ethyl acetate.
The nail polish remover according to the present invention is useful for removing the above-mentioned biodegradable nail polish.

In a fourth aspect, the present invention provides a biodegradable nail care set comprising a nail tip made of the biodegradable resin composition according to the present invention and a biodegradable nail color according to the present invention. The biodegradable nail care set of the present invention may further include the nail polish remover of the present invention.

Preparation Example 1
[Manufacturing of nail tips using polylactic acid]
1 kg of wood chips (1.0 x 1.0 cm) and 10 L of N-methylpyrrolidone were mixed and subjected to solvothermal treatment in an autoclave (200°C, 25 atm) for 2 hours. The resulting wood pulverized material was heat-treated in a 10% aqueous solution of hypochlorous acid at 90°C for 1 hour to prepare solvothermal/chemically treated CNF.
A biodegradable resin composition containing 2% by weight of CNF was prepared by mixing 40 g of the above-prepared CNF with 2000 g of polylactic acid (PLA; manufactured by Natureworks) using a twin-screw extruder.

The above biodegradable resin composition was used to injection-molde nail tips at 190°C using an injection molding machine with a clamping force of 50 t.
We were able to mold the material to thicknesses of 0.25 mm and 0.5 mm.

Preparation Example 2
[Manufacturing of nail tips using cellulose acetate]
A cellulosic thermoplastic resin was prepared by kneading 10 kg of cellulose acetate with 4 kg of triethyl citrate using a twin-screw extruder.
To 2000 g of the cellulose-based thermoplastic resin prepared above, 40 g of the CNF produced above was added and mixed using a twin-screw extruder to prepare a biodegradable resin composition containing 2% by weight of CNF.

The above biodegradable resin composition was used to injection-molde nail tips at 190°C using an injection molding machine with a clamping force of 50 t.
We were able to mold the material with thicknesses of 0.35 mm and 0.5 mm.

Preparation Example 3
[Preparing Nail Color]
180 g of titanium dioxide, 44 g of shellac, and 38 g of bioethanol were dispersed with 0.5 mm diameter zirconia beads using a bead mill disperser for 60 minutes to create a white natural biomass biodegradable nail color A.
Next, a white natural biomass biodegradable nail color B was prepared in the same manner as above, except that a mixed solvent was obtained by mixing 30.4 g of bioethanol and 7.6 g of ethyl lactate: 80/20 (w/w%).
Furthermore, a white natural biomass biodegradable nail color C was prepared in the same manner as above, except that a mixed solvent obtained by mixing 22.8 g of bioethanol and 15.2 g of ethyl lactate was used: 60/40 (w/w%).

Preparation Example 4
[Preparing nail polish remover]
Nail polish remover was prepared by mixing 80 g of bioethanol and 20 g of ethyl lactate.

Characterization (1) Processability of Nail Tips The biodegradable resin composition containing polylactic acid prepared in Preparation Example 1 had a high melt mass flow rate (MFR) (24-25 g/10 min), and thin nail tips with a thickness of 0.25 mm could be molded. The MFR was measured at 190°C under a load of 2.16 kg using an extrusion type plastometer as defined in JIS K6760, in accordance with the provisions of JIS K 7210.
Nail tips with a thickness of 0.25 mm tended to break easily when bent to conform to the shape of the natural nail. Nail tips with a thickness of 0.5 mm did not break.
On the other hand, the biodegradable resin composition containing cellulose acetate prepared in Preparation Example 2 had a low melt mass flow rate (MFR) (7-9 g/10 min), making it difficult to mold nail tips with a thickness of 0.25 mm, but it was possible to form nail tips with a thickness of 0.35 mm or more.
(2) Wearing comfort Compared to commercially available nail tips (made of ABS), the biodegradable resin composition containing polylactic acid prepared in Preparation Example 1 felt slightly harder and heavier, but could be worn without any problems. In addition, the biodegradable resin composition containing cellulose acetate prepared in Preparation Example 2 felt light and comfortable, without feeling bulky, and had good wearability.
(3) Decorative properties of nail tips (a) Decorative properties with commercially available nail polish When colored with commercially available nail polish, the decorative properties of the nail tips made from the biodegradable resin composition containing polylactic acid or cellulose acetate prepared in Preparation Example 1 or 2 were equivalent to those of commercially available nail tips (made of ABS).
It has been confirmed that the nail tips of the present invention can be colored using commercially available nail polish.
(b) Decorative properties of nail color according to the present invention When natural nails or commercially available nail tips (made of ABS) were colored using biodegradable nail color A (bioethanol 100 w/w%) prepared in Preparation Example 3, application was difficult and drying was very uneven. When natural nails or commercially available nail tips (made of ABS) were colored using biodegradable nail color B (bioethanol 80 w/w%) prepared in Preparation Example 3, application was easy, drying time was short, and there were no problems with uneven drying. When natural nails or commercially available nail tips (made of ABS) were colored using biodegradable nail color C (bioethanol 60 w/w%) prepared in Preparation Example 3, application was easy, and although the drying time was longer, there were no problems with uneven drying.
Regardless of whether biodegradable nail color B or C prepared in Preparation Example 3 was used for coloring, the nail tips made from the biodegradable resin composition containing polylactic acid or cellulose acetate prepared in Preparation Example 1 or 2 had comparable decorative properties to commercially available nail tips (made of ABS).
Therefore, it was confirmed that in the biodegradable nail color according to the present invention, if the bioalcohol content of either bioethanol or biobutanol in the biomass-derived solvent is 60 to 80% (w/w%), application to natural nails or nail tips becomes easier and uneven drying is eliminated.
(4) Removal of biodegradable nail color with nail polish remover Biodegradable nail colors B and C according to the present invention were applied to a nail tip made of cellulose acetate prepared in Preparation Example 2, and the dried film obtained by drying could be removed without any problems using the nail polish remover prepared in Preparation Example 4.

According to this invention, nail tips made entirely from naturally derived materials exhibited the same level of comfort as conventional nail tips. Furthermore, since the nail polish and nail polish remover are also composed of naturally derived ingredients, the environmental burden caused by plastic waste was significantly reduced.

Claims (5)

The nail tip is made of a biodegradable polymer that is cellulose acetate and a biodegradable resin composition containing cellulose nanofibers.
Furthermore, it contains plasticizers,
The plasticizer is at least one selected from tributyl acetyl citrate, triethyl citrate, and tributyl citrate, in a nail tip. Furthermore, the nail tip according to claim 1 , comprising an additive selected from the group consisting of lubricants, release agents, and fluidity improvers. The nail tip according to claim 1 or 2 , wherein the plasticizer is triethyl citrate. The nail tip according to any one of claims 1 to 3, wherein the biodegradable resin composition further contains calcium carbonate, silica, clay, feldspar, magnesium carbonate, zinc oxide, titanium dioxide, silica, alumina, kaolin clay, talc, mica, wollastonite, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, zeolite, diatomaceous earth, sericite, shirasu, calcium sulfite, potassium titanate, bentonite, graphite, ferrite , or a combination thereof. The mixture comprises a biomass-derived resin selected from the group consisting of shellac resin, rosin resin, and cellulose acetate, and a biomass-derived solvent selected from the group consisting of bioethanol, biobutanol, ethyl lactate, and ethyl acetate.
A biodegradable nail polish in which the biomass-derived solvent contains 60 to 80 w/w% bioethanol or biobutanol.