JP7477848B2 - Compositions Having Upper Critical Solution Temperatures - Google Patents

Description

The present invention relates to uses of a composition having an upper critical solution temperature containing a copolymer of acrylamide and acrylonitrile, and more specifically, to the composition for use as a cosmetic or topical skin preparation.

Cosmetics are often required to have opposing properties, such as being smooth yet adherent, or lasting but easy to remove. For example, the polymers used in film mascara are required to respond to certain stimuli and exhibit their functions, such as not coming off in water but coming off in hot water.

In addition to temperature, pH, light, etc. are known as the above-mentioned stimuli. Poly(N-isopropylacrylamide) is well known as a temperature-responsive polymer that undergoes a structural change in response to temperature, and there have also been reports on poly(N-acryloylglycinamide) (see, for example, Non-Patent Document 1). Although the incorporation of such temperature-responsive polymers into cosmetics has been investigated, it is difficult to say that their application in cosmetics has progressed. One of the reasons for this is that the properties of the polymers change in response to temperature stimuli even in situations where their function is not desired. For example, it is said that there is a risk that the stability of the quality of products containing temperature-responsive polymers may be compromised due to the change in properties in a high-temperature environment.

On the other hand, since polyacrylamide dissolves in water, polyacrylonitrile dissolves only in polar solvents such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and DMSO-H ₂ O is freely miscible, the solubility of copolymers of acrylamide (AAm) and acrylonitrile (AN) has been studied, and copolymers have been synthesized over a range of AAm/AN composition ratios from 0/100 to 100/0, and the composition of the copolymers obtained has been analyzed by infrared and ultraviolet absorption spectroscopy and specific gravity methods, while the solubility in various solvents has been measured (see, for example, Non-Patent Document 2). It has also been reported that an aqueous solution of a copolymer of acrylamide (AAm) and acrylonitrile (AN) has an upper critical solution temperature, and that the upper critical solution temperature can be adjusted by changing the AAm/AN composition ratio (see, for example, Non-Patent Document 3).

On the other hand, when using cosmetics or topical skin preparations, it is often necessary to wash them off after a certain time, taking into consideration the duration of effect and the purpose of use, but there are various opinions about the appropriate water temperature for washing the face. For example, washing the face with hot water at about 40°C, which is slightly higher than the skin temperature, opens the pores and allows the cosmetics and other substances to be removed well, so it is said to be excellent in terms of removing dirt, but there is a risk of losing more sebum and moisture than necessary from the skin. In contrast, washing the face with cold water can tighten the pores, but there is also a risk of the cosmetics and other substances remaining clogged in the pores. In addition, there are cases where it is necessary to maintain or easily remove cosmetics and topical skin preparations even in special environments such as tropical regions, cold regions, and underwater, and compositions used as cosmetics and topical skin preparations are required to be able to withstand a wide range of temperatures.

Howard C. H., Norman W. S., Polymer letters vol.2 (1964) Takahashi et al., Journal of Industrial Chemistry, Vol. 70, No. 6 (1967), pp. 988-992 Seuring et al., Macromolecules 2012, 45, 3910-3918

The object of the present invention is to provide a composition having an upper critical solution temperature suitable for use as a cosmetic or topical skin preparation.

The present inventors used acrylamide (AAm) and acrylonitrile (AN) as monomers and synthesized six types of random copolymers of acrylamide and acrylonitrile ([poly(AAm-co-AN)]) by free radical polymerization by varying the monomer mass charge ratio ([(AAm):(AN)]). The six types of copolymers were dissolved in water, and the temperature of each copolymer-containing aqueous solution was lowered and raised. The upper critical solution temperature of each copolymer-containing aqueous solution was determined by measuring the change in light transmittance. It was confirmed that the upper critical solution temperature of the copolymer-containing aqueous solution increased as the ratio of AN in [(AAm):(AN)] increased. Next, it was found that the upper critical solution temperature of each copolymer-containing aqueous solution decreased when a surfactant was added to the six types of [poly(AAm-co-AN)]-containing aqueous solutions. Therefore, it was confirmed how much the upper critical solution temperature decreased when each copolymer was dissolved in a surfactant-containing aqueous solution compared to when it was dissolved in an aqueous solution.

Next, six types of [poly(AAm-co-AN)] were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, and the temperature of each copolymer-containing aqueous solution was lowered and raised by dissolving each copolymer in water, and the change in light transmittance was measured to determine the upper critical solution temperature of each copolymer-containing aqueous solution. It was found that the aqueous solution containing [poly(AAm-co-AN)] synthesized by RAFT polymerization had a larger change in transmittance per unit temperature in the aqueous solution compared to that synthesized by free radical polymerization, and it was confirmed that the aqueous solution had a higher sensitivity in temperature response, which led to the completion of the present invention.

That is, the present invention is specified by the following items.
[1] A composition containing a copolymer of acrylamide and acrylonitrile and having an upper critical solution temperature or a temperature at which the solubility increases rapidly, for use as a cosmetic or topical skin preparation.
[2] The composition according to [1] above, wherein the copolymer has a monomer mass ratio of acrylamide:acrylonitrile=77.5:22.5 to 85:15.
[3] The composition according to [1] or [2] above, wherein the copolymer has a weight average molecular weight of 8,000 to 200,000.
[4] The composition according to any one of [1] to [3] above, wherein the copolymer is a random copolymer.
[5] The composition according to the above [4], wherein the random copolymer is a random copolymer synthesized by free radical polymerization.
[6] The composition according to [4] above, wherein the random copolymer is a random copolymer synthesized by reversible addition-fragmentation chain transfer polymerization.
[7] The composition according to any one of [1] to [6] above, which has temperature sensitivity when 1 to 20 mM sodium dodecyl sulfate is added.
[8] The composition according to [6] or [7] above, wherein the maximum value of the differential curve of the light transmittance-temperature curve in a 1 w/v % aqueous solution containing no surfactant is 50 d%T/dT or more.
[9] A method for lowering an upper critical solution temperature or a temperature at which solubility increases rapidly, comprising contacting a surfactant with a cosmetic or topical skin preparation comprising a composition having an upper critical solution temperature or a temperature at which solubility increases rapidly, the composition containing a copolymer of acrylamide and acrylonitrile.
Other aspects of the present invention relate to: [10] a cosmetic or topical skin preparation containing a copolymer of acrylamide and acrylonitrile and having an upper critical solution temperature or a temperature at which solubility increases rapidly; [11] use of a composition containing a copolymer of acrylamide and acrylonitrile and having an upper critical solution temperature or a temperature at which solubility increases rapidly, for the production of a cosmetic or topical skin preparation; [12] a method for producing a cosmetic or topical skin preparation having an upper critical solution temperature or a temperature at which solubility increases rapidly, which comprises blending a copolymer of acrylamide and acrylonitrile into a cosmetic or topical skin preparation component; and [13] a composition containing a copolymer of acrylamide and acrylonitrile having an upper critical solution temperature or a temperature at which solubility increases rapidly, for use as a cosmetic or topical skin preparation.

The composition for use as a cosmetic or topical skin preparation of the present invention is a cosmetic or topical skin preparation that contains a polymer of acrylamide and acrylonitrile having an upper critical solution temperature and a cosmetic component or topical skin preparation component, and since it has an upper critical solution temperature or a temperature at which solubility increases rapidly, it does not come off (does not dissolve) with water or sweat, but can be easily removed (dissolved) with warm water. In addition, according to the composition of the present invention, the upper critical solution temperature or the temperature at which solubility increases rapidly can be lowered by adding a surfactant to an aqueous solution in which a copolymer of acrylamide and acrylonitrile is dissolved, so that a cosmetic or topical skin preparation with a high cleaning effect can be provided according to the application and the temperature environment of use. For example, when washed with water of a specific temperature, it does not show solubility, but when washing the face with water using a detergent containing a surfactant, the upper critical solution temperature or the temperature at which solubility increases rapidly becomes lower, so that the polymer in the composition easily dissolves even at the above specific temperature, and the face can be washed at a lower temperature than before, which reduces the burden on the skin.

In addition, according to the composition of the present invention, by adding a salt (e.g., NaCl) contained in sweat to an aqueous solution in which a copolymer of acrylamide and acrylonitrile is dissolved, the upper critical solution temperature or the temperature at which the solubility increases rapidly does not decrease, so cosmetics are not removed by sweat, and cosmetics and topical skin preparations can be effectively removed only when washing is desired.

Furthermore, when a random copolymer synthesized by RAFT polymerization instead of free radical polymerization is used as the copolymer of acrylamide and acrylonitrile in the composition of the present invention, the sensitivity of the temperature response of the composition solution becomes high, that is, the change in transmittance of the composition solution per unit temperature becomes large. Therefore, even when the concentration of the surfactant in the water used for washing is very low or no surfactant is contained, the cosmetic material, etc., is easily dissolved within a specific narrow range of temperatures, and the washing effect becomes significantly high.

The graph shows six types of random copolymers (poly(AAm-co-AN)) (hereinafter simply referred to as [poly(AAm-co-AN)]) (F1 to F6) synthesized by free radical polymerization, each of which has a different monomer mass charge ratio ([(AAm):(AN)]) of acrylamide and acrylonitrile, plotting the light transmittance (vertical axis) of a 1 w/v % aqueous solution of each of these [poly(AAm-co-AN)] and the solution temperature (horizontal axis). A graph is shown in which the light transmittance and the solution temperature are plotted for mixed solutions in which sodium dodecyl sulfate (SDS) was added to a final concentration of 100 mM in a 1 w/v % aqueous solution of each of F1 to F6. FIG. 1 shows a graph plotting the light transmittance and solution temperature of each mixed solution in which SDS was added to a final concentration of 5 mM, 10 mM, 15 mM, 20 mM, 30 mM, and 100 mM in a 1 w/v % aqueous solution of [Poly(AAm-co-AN)] [82.5:17.5] (F3) synthesized by free radical polymerization. The graph shows the light transmittance and solution temperature of a mixed solution in which cetyltrimethylammonium chloride (CTAC) was added to a final concentration of 100 mM in a 1 w/v % aqueous solution of each of F1 to F6. The graph shows the light transmittance and solution temperature of mixed solutions prepared by adding NaCl to a final concentration of 100 mM to each of 1 w/v % aqueous solutions of F1 to F6. The graphs (A) and (A1) show plots of transmittance versus solution temperature for a 1 w/v % aqueous solution and a 0.1 w/v % aqueous solution of the copolymer R1, which is [Poly(AAm-co-AN)] [82.5:17.5] synthesized by RAFT polymerization and has a Mw of 12400, and their differential curves (a) and (a1) show the same. The graphs (F) and (F1) show plots of transmittance versus solution temperature for a 1 w/v % aqueous solution and a 0.1 w/v % aqueous solution of the copolymer F1, and their differential curves (f) and (f1) show the same. Four types of [Poly(AAm-co-AN)] [82.5:17.5] (R1 to R4) with different weight-average molecular weights (Mw) synthesized by RAFT polymerization are shown in graphs (A) to (D) in which the light transmittance of a 1 w/v % aqueous solution of each of them and the temperature of the solution are plotted, and their differential curves are shown in graphs (a) to (d), respectively. The transmittance of aqueous solutions of the copolymers R5, R2, R6, and a 1:1 mixture of R5 and R6 versus solution temperature are plotted in graphs (E), (B), (G), and (H), and their differential curves are shown in graphs (e), (b), (g), and (h), respectively.

The composition of the present invention is not particularly limited as long as it is a composition containing a copolymer of acrylamide and acrylonitrile for use as a cosmetic or topical skin preparation and has an upper critical solution temperature or a temperature at which solubility increases rapidly, and the composition contains a cosmetic component and a topical skin preparation component in addition to the copolymer. In addition, the method for lowering the upper critical solution temperature or the temperature at which solubility increases rapidly of the cosmetic or topical skin preparation of the present invention is not particularly limited as long as it is a method of contacting a surfactant such as an anionic surfactant with a composition containing a copolymer of acrylamide and acrylonitrile and has an upper critical solution temperature. In the present invention, "a composition ... for use as a cosmetic or topical skin preparation" means an invention of a use of a composition whose use is limited to a cosmetic or topical skin preparation, and "a composition having an upper critical solution temperature or a temperature at which solubility increases rapidly" means a composition in which a solution containing the composition has an upper critical solution temperature or a temperature at which solubility increases rapidly under specific conditions.

The copolymer of acrylamide and acrylonitrile mentioned above can be a copolymer (poly(acrylamide-co-acrylonitrile)) (poly(AAm-co-AN)) synthesized by polymerizing the acrylamide represented by the following formula (1) and the acrylonitrile represented by the following formula (2) as monomers. The form of the copolymer can be either a random copolymer or a block copolymer, but from the viewpoint of uniform dispersion of functional groups, a random copolymer represented by the following formula (3) is preferred.

The above random copolymer (poly(AAm-co-AN)) can be synthesized by a radical reaction in which a polymer chain extends from a radical at the reaction center. Specifically, the synthesis method can be free radical polymerization, which can produce a polymer with a wide molecular weight distribution, or living radical polymerization, which allows control of the molecular structure while maintaining the simplicity and versatility of radical polymerization. Among these, the synthesis method can be RAFT polymerization, which can produce a copolymer with a smaller molecular weight distribution (Mw/Mn).

The above-mentioned synthesis method using free radical polymerization can be exemplified by a conventionally known method that uses a polymerization initiator that generates sufficient radicals at the polymerization temperature and a solvent suitable for the polymerization reaction to copolymerize acrylamide and acrylonitrile as monomers. Since the reaction solution of the synthesized copolymer contains impurities such as unreacted monomers, it is preferable to prepare [poly(AAm-co-AN)] by further carrying out a purification process.

As a synthesis method using the above-mentioned RAFT polymerization, there can be mentioned a conventionally known method that uses a polymerization initiator that generates sufficient radicals at the polymerization temperature to copolymerize acrylamide and acrylonitrile as monomers, a solvent suitable for the polymerization reaction, and a reversible addition-fragmentation chain transfer (RAFT) agent for controlling the reactivity of the terminal active radicals to cause the polymerization to proceed in a pseudo-living manner.

The monomer mass ratio of acrylamide to acrylonitrile in the copolymer [(AAm):(AN)] is preferably 1:99 to 99:1, more preferably 50:50 to 95:5, more preferably 70:30 to 90:10, and most preferably 77.5:22.5 to 85:15. Other monomer components may also be used as long as they achieve the effects of the present invention.

Examples of the polymerization initiator include azo-based polymerization initiators such as 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine); persulfates such as potassium persulfate and ammonium persulfate; and peroxide-based polymerization initiators such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide.

Suitable solvents for the above polymerization reaction include DMSO, water, DMF, etc.

Examples of the RAFT agent include dithiocarbonates such as O-ethyl-S-(1-phenylethyl)dithiocarbonate, O-ethyl-S-(2-propoxyethyl)dithiocarbonate, and O-ethyl-S-(1-cyano-1-methylethyl)dithiocarbonate; dithioesters such as cyanoethyl dithiopropionate, benzyl dithiopropionate, benzyl dithiobenzoate, and acetoxyethyl dithiobenzoate; dithiocarbamates such as S-benzyl-N,N-dimethyldithiocarbamate and benzyl-1-pyrrolecarbodithioate; and trithiocarbonates such as dibenzyl trithiocarbonate and cyanomethyl dodecyl trithiocarbonate (CMDT).

In RAFT polymerization, the number of moles of the RAFT agent blended, assuming that the total number of moles of monomers is 1, is preferably 0.0001 to 0.01, more preferably 0.0002 to 0.005, and even more preferably 0.0003 to 0.003.

Specific examples of the method for preparing the poly(AAm-co-AN) of the present invention by free radical polymerization include a method in which acrylonitrile is dissolved in DMSO, acrylamide is added, the solution is degassed to prepare an initiation solution, an initiator such as AIBN is added, and the reaction is carried out at 50 to 70° C. for 5 to 10 hours (see Non-Patent Document 1 above); and a method in which acrylonitrile and acrylamide in various proportions are added to deoxygenated water, an initiator such as potassium persulfate, potassium metabisulfite, and ferrous ammonium sulfate solution is added, and polymerization is carried out in a nitrogen stream at 40° C. for 10 minutes, and the polymerization reaction product is precipitated by dropping into methanol or water immediately after the reaction is stopped, and the resulting precipitate is washed and dried, dissolved in DMSO or water depending on the ratio of acrylonitrile and acrylamide, and reprecipitated in methanol for purification (see SEN-I GAKAISHI, Vol. 32, No. 1 (1976)). Also, a copolymer having a molar composition of AAm/AN=0/100-30/70 was prepared by feeding 0.25 mol of AN+AAm, 0.3%/monomer of K ₂ S ₂ O ₈ , 0.78%/monomer of NaHSO ₃ , 0.05 mL of acetic acid, and 203 mL of H ₂ O for a polymerization time of 1-3 hours at a polymerization temperature of 40° C., and a copolymer having a molar composition of AAm/AN=0/100-30/70 was prepared by feeding 0.146 mol of AN+AAm, 0.0485%/monomer of K ₂ S ₂ O ₈ , 88 mL of H _{2 O} for a polymerization time of 1-3 hours at a polymerization temperature of 40° C. and a method of synthesizing a copolymer having a molar composition of AAm/AN=70/30 to 100/0 using a feed composition of 0.25 mol of AN+AAm, 0.14%/monomer BPO, 50 mL of DMF, a polymerization time of 1 to 4 hours, and a polymerization temperature of 60° C., and purifying the copolymer using an appropriate purification solvent such as DMF, water, methanol, or ethanol (see Non-Patent Document 2 above).

A specific example of a method for preparing [poly(AAm-co-AN)] by RAFT polymerization in the present invention is to dissolve a monomer such as acrylamide or acrylonitrile in DMSO, add a RAFT agent such as CMDT, and degas to obtain an initiation solution. An initiator such as AIBN is added to the initiation solution, and the solution is reacted at 60 to 80°C for 2 to 7 hours, then cooled to room temperature. The cooled reaction solution is poured into methanol, and the precipitated copolymer is dried at 30 to 50°C for about 12 to 48 hours (Polym. Chem. 2016, 7, 1979-1986, etc.).

Acrylonitrile is highly volatile and may evaporate during degassing. For this reason, in order to obtain a copolymer with a composition ratio close to the amount charged, i.e., a copolymer with the desired upper critical solution temperature, it is desirable to add acrylonitrile using a gas-tight syringe or the like just before heating the reaction solution to start the polymerization reaction.

In the present invention, the weight average molecular weight (Mw) of the [poly(AAm-co-AN)] can be 8,000 to 200,000, preferably 25,000 to 175,000, more preferably 50,000 to 150,000, and even more preferably 85,000 to 120,000, in the case of a copolymer [poly(AAm-co-AN)] produced by free radical polymerization, and can be 8,000 to 200,000, preferably 8,500 to 100,000, and more preferably 9,000 to 90,000, in the case of a copolymer [poly(AAm-co-AN)] produced by RAFT polymerization. The weight average molecular weight can be calculated by measuring the molecular weight using gel permeation chromatography (GPC), creating a calibration curve using a standard substance, and then calculating the molecular weight.

In the present invention, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of poly(AAm-co-AN) is preferably 1.0 to 5.0, and more preferably 1.1 to 4.5. Furthermore, in the case of [poly(AAm-co-AN)] obtained by free radical polymerization, a suitable ratio is 1.5 to 3.0, and in the case of [poly(AAm-co-AN)] obtained by RAFT polymerization, a suitable ratio is 1.1 to 2.0.

The cosmetic or skin topical preparation components constituting the composition of the present invention together with the copolymer may include one or more of the components commonly used in cosmetics or skin topical preparations, such as alcohols, moisturizers, gelling agents, powders, UV absorbers, preservatives, antibacterial agents, antioxidants, pH adjusters, skin beautifying ingredients, fragrances, and water.

Examples of the alcohols include lower alcohols such as ethanol and isopropanol, polyhydric alcohols such as glycerin, diglycerin, polyglycerin, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-butylene glycol, and erythritol, sugar alcohols such as sorbitol, maltose, xylitol, and maltitol, and sterols such as cholesterol, sitosterol, phytosterol, and lanosterol. Examples of the moisturizing agents include urea, hyaluronic acid, chondroitin sulfate, and pyrrolidone carboxylate.

The gelling agent is not particularly limited as long as it is an aqueous gelling agent or an oil-based gelling agent that is generally used in skin external preparations or cosmetics. For example, aqueous gelling agents include plant-based polymers such as gum arabic, tragacanth gum, galactan, carob gum, guar gum, karaya gum, carrageenan, pectin, agar, quince seed (derived from quince, etc.), starch (derived from rice, corn, potato, wheat, etc.), algae colloid, trang gum, and locust bean gum; microbial polymers such as xanthan gum, dextran, succinoglucan, and pullulan; and collagen. Examples of the gelling agent include animal-based polymers such as casein, albumin, and gelatin; starch-based polymers such as carboxymethyl starch and methylhydroxypropyl starch; cellulose-based polymers such as methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, sodium cellulose sulfate, and sodium carboxymethyl cellulose; alginic acid-based polymers such as sodium alginate and propylene glycol alginate; vinyl-based polymers such as sodium polyacrylate, carboxyvinyl polymers, alkyl-modified carboxyvinyl polymers, polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone; and inorganic gelling agent thickeners such as polyethylene glycol, ethylene oxide-propylene oxide copolymers, bentonite, aluminum magnesium silicate, laponite, hectorite, and silicic anhydride. Examples of the oil-based gelling agent include metal soaps such as aluminum stearate, magnesium stearate, and zinc myristate; amino acid derivatives such as N-lauroyl-L-glutamic acid and α,γ-di-n-butylamine; dextrin derivatives such as dextrin palmitate, dextrin stearate, and dextrin 2-ethylhexanoate palmitate mixed ester; fatty acid esters, sucrose fatty acid esters such as sucrose palmitate and sucrose stearate; benzylidene derivatives of sorbitol such as monobenzylidene sorbitol and dibenzylidene sorbitol; and organically modified clay minerals such as dimethyl benzyldodecyl ammonium montmorillonite clay and dimethyl dioctadecyl ammonium montmorillonite clay.

Examples of the powders include inorganic powders, organic powders, metal soap powders, colored pigments, pearl pigments, metal powders, tar dyes, and natural dyes, and are not limited to any particular particle shape (spherical, needle-like, plate-like, etc.), particle size (aerobic, fine particles, pigment-grade, etc.), or particle structure (porous, nonporous, etc.). These powders may be used as they are, or may be composites of two or more types of powders, or may be surface-treated with oils, silicone compounds, fluorine compounds, etc.

Examples of the ultraviolet absorber include benzoic acid-based ultraviolet absorbers such as para-aminobenzoic acid, anthranilic acid-based ultraviolet absorbers such as methyl anthranilate, salicylic acid-based ultraviolet absorbers such as methyl salicylate, cinnamic acid-based ultraviolet absorbers such as octyl paramethoxycinnamate, benzophenone-based ultraviolet absorbers such as 2,4-dihydroxybenzophenone, and urocanic acid-based ultraviolet absorbers such as ethyl urocanate.

Examples of the preservatives and antibacterial agents include paraoxybenzoic acid esters, benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, phenoxyethanol, salicylic acid, carbolic acid, parachlormetacresol, hexachlorophene, benzalkonium chloride, chlorhexidine chloride, trichlorocarbanilide, photosensitizers, isopropylmethylphenol, etc. Examples of the antioxidants include tocopherol, butylhydroxyanisole, dibutylhydroxytoluene, etc.

Examples of the pH adjuster include lactic acid, lactate salts, citric acid, citrate salts, glycolic acid, succinic acid, tartaric acid, malic acid, potassium carbonate, sodium bicarbonate, and ammonium bicarbonate.

Examples of the skin-beautifying ingredients include whitening agents such as arbutin, glutathione, and saxifrage extract; cell activators and skin roughness improvers such as royal jelly, photosensitizers, and cholesterol derivatives; blood circulation promoters such as nonylic acid valenylamide, nicotinic acid benzyl ester, nicotinic acid β-butoxyethyl ester, capsaicin, zingerone, cantharides tincture, ichthammol, caffeine, tannic acid, α-borneol, tocopherol nicotinate, inositol hexanicotinate, cyclandelate, cinnarizine, tolazoline, acetylcholine, verapamil, cepharanthine, and γ-oryzanol; skin astringents such as zinc oxide and tannic acid; and antiseborrheic agents such as sulfur and thianthrol.

The composition for use as a cosmetic or topical skin preparation of the present invention contains a copolymer of acrylamide and acrylonitrile having an upper critical solution temperature, and therefore a solution containing the composition of the present invention (composition solution) has an upper critical solution temperature or a temperature at which the solubility increases rapidly. Examples of the solvent in the solution containing such a composition include a solvent for washing cosmetics or topical skin preparations applied to body hair such as hair, eyelashes, and eyebrows, skin, lips, nails, etc., and specifically, water and washing water can be mentioned. Examples of such washing water include washing water, which is a mixed solvent in which a surfactant that lowers the upper critical solution temperature is added to water. In addition, other washing components and the like can be further contained as long as the effects of the present invention are achieved. Solutions containing the composition of the present invention having an upper critical solution temperature or a temperature at which the solubility increases rapidly include clear solutions with a transmittance of 100% and suspensions with a light transmittance of 0%.

The water is not particularly limited as long as it is water that can be used to wash cosmetics and topical skin preparations, and examples include tap water, natural water, purified water, distilled water, ion-exchanged water, pure water, and ultrapure water such as Milli-Q water.

Examples of the above surfactants include anionic surfactants such as SDS and sodium deoxycholate; and cationic surfactants such as CTAC and benzalkonium chloride; however, anionic surfactants are preferred.

The concentration of the surfactant is not particularly limited as long as it is a normal concentration that can be contained in a cleaning agent or rinsing solution, and examples include more than 0 mM, 5 mM or more, 10 mM or more, 15 mM or more, 20 mM or more, 30 mM or more, and 100 mM or more, and preferably, for example, 1 to 20 mM.

In the present invention, the upper critical solution temperature of the composition or the temperature at which the solubility increases rapidly can be determined by, for example, cooling a composition solution in which the composition is dissolved in water at a rate of 1 w/v %, then increasing the temperature of the cooled composition solution at a rate of 0.3 to 2.0°C per minute, and measuring the light transmittance of the composition solution every 0.5°C. In this case, 1) in the obtained transmittance-temperature curve, the temperature at the intersection of the straight line portion where the transmittance changes and the horizontal line representing the transmittance (100%) of the clear aqueous solution is determined as the upper critical solution temperature, or 2) in the obtained transmittance-temperature curve, the temperature at which the transmittance increases rapidly is determined as the temperature at which the solubility increases rapidly. The rate of increase in the temperature of the cooled composition solution can be appropriately determined according to the magnitude of the change in the transmittance of the solution containing each composition.

The method for measuring the light transmittance is not particularly limited as long as it is a method that uses light of a wavelength suitable for measuring the change in light transmittance in the composition solution. The wavelength is preferably in the visible light range, specifically, 650 to 700 nm, preferably 660 to 680 nm. The temperature inside the cell holder during the measurement of the light transmittance can be maintained using a temperature control device such as a temperature controller.

The upper critical solution temperature of the composition of the present invention is not particularly limited as long as it is within a range suitable for the mode of use and cleaning conditions of the cosmetic or topical skin preparation, and the upper critical solution temperature of the composition can be 10 to 70°C, preferably 20 to 60°C, more preferably 30 to 50°C, and particularly preferably 35 to 45°C. In addition, it is preferable that the upper critical solution temperature of the composition of the present invention constituting such a cosmetic or topical skin preparation is lowered by, for example, 5 to 50°C, 10 to 30°C, 15 to 25°C, 10 to 15°C, or 5 to 10°C by adding a surfactant to water.

In addition, in a composition using [Poly(AAm-co-AN)] by RAFT polymerization, the differential curve of the light transmittance-temperature curve in a 1 w/v% aqueous solution when washed off with water containing no surfactant is 50 d% T/dT or more, preferably 85 d% T/dT or more, as a preferred embodiment. Such a composition is a composition in which the change in transmittance per unit temperature is large, and the solution shows a change in dissolution/aggregation in a narrow temperature range of 7°C or less, preferably 5°C or less, and more preferably 3°C or less. The reason why the change in transmittance per unit temperature is large in Poly(AAm-co-AN) by RAFT polymerization is thought to be that the unit ratio of each polymer chain is uniform, so that a slight change in temperature causes a large change in properties. Therefore, when two or more types of [Poly(AAm-co-AN)] by RAFT polymerization are mixed and used, the change in transmittance per unit temperature may be small.

The composition of the present invention can be used as a cosmetic or skin topical agent with a high cleaning effect according to various applications and temperature environments. For example, when the composition of the present invention, Poly(AAm-co-AN) [85:15] produced by free radical polymerization, is used as a cosmetic, it is difficult to wash off the cosmetic when washed with only water at 22°C because the upper critical solution temperature of the aqueous solution of the composition is 28°C. However, when washed with water at 22°C using a detergent containing a surfactant (SDS), the upper critical solution temperature is lowered, so Poly(AAm-co-AN) [85:15] dissolves and the cosmetic is removed very easily, which is advantageous when it is difficult to supply heated water.

In addition, when the composition of the present invention, which is Poly(AAm-co-AN) [85:15] by RAFT polymerization and contains a copolymer with Mw of about 28,300, is used as a cosmetic, the composition has a high change in transmittance per unit temperature in an aqueous solution, and the composition, which is insoluble in water at 35°C, which is close to the body surface temperature, dissolves completely in hot water at 40°C. Therefore, the cosmetic will not come off even if you sweat, but you can wash your face with just hot water, so it can be used as an excellent cosmetic that puts less strain on the skin.

The composition of the present invention contains one or more types of poly(AAm-co-AN) and is used as a cosmetic or topical skin preparation. Examples of the cosmetic in the present invention include basic cosmetics such as lotion, cream, milky lotion, and serum; hair cosmetics such as shampoo, rinse, and treatment; makeup cosmetics such as foundation, blush, eyeliner, eye shadow, mascara, eyebrow, and face powder; base cosmetics (including quasi-drugs) such as sunscreen cosmetics; and nail polish. Examples of topical skin preparations include topical medicines such as liniments, lotions, and ointments.

The blending ratio of the above poly(AAm-co-AN) in the cosmetic or topical skin preparation of the present invention is not particularly limited as long as the effects of the present invention are achieved, but is usually preferably 0.01 to 80% by mass, more preferably 0.1 to 50% by mass, and even more preferably 1 to 20% by mass, based on the total cosmetic or topical skin preparation. One or more types can also be blended in appropriate combination.

The cosmetic or topical skin preparation comprising the composition of the present invention may be in the form of a liquid, emulsion, cream, gel, or solid.

The present invention will be explained in more detail below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[Example 1]
(Synthesis of [Poly(AAm-co-AN)] by free radical polymerization)
Six types of random copolymers Poly(AAm-co-AN) having monomer mass ratios [acrylamide (AAm):acrylonitrile (AN)] of 77.5:22.5, 80:20, 82.5:17.5, 85:15, 87.5:12.5, and 90:10, respectively, were synthesized by free radical polymerization according to the following procedure with reference to the above Non-Patent Document 3.

Acrylamide and AIBN were dissolved in DMSO (12 mL), and dissolved oxygen was removed by blowing argon gas into the solution for 30 minutes. Acrylonitrile in a proportion corresponding to acrylamide was added using a gas-tight syringe to prepare a reaction solution, which was reacted at 60°C for 5.5 hours under an argon atmosphere and then cooled to room temperature. The cooled reaction solution was poured into 250 mL of methanol, and the precipitated copolymer was filtered off. The obtained copolymer was further washed with 150 mL of methanol and then dried overnight in a desiccator.

The unit ratio of AAm and AN in the copolymer was determined by comparing the ratio of the peak derived from the amino group of AAm (near 1659 ^cm-1 ) and the peak derived from the cyano group of AN (near 2242 cm ^-1 ) with that of a standard sample by IR measurement. The standard samples used were prepared by mixing AAm homopolymer and AN homopolymer at molar fractions of 80:20, 85:15, 90:10, and 95:5. The IR measurement was performed using a Nicolet iS10 Fourier transform infrared spectrometer (manufactured by Thermo Fisher Scientific) by the total reflection (ATR) method.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer were determined using gel permeation chromatography (GPC). A JASCO PU-2080 pump, a JASCO RI-2031 differential refractometer, a JASCO 2060 column oven (all manufactured by JASCO), and a Shodex GPC KD806-M column (manufactured by Showa Denko) were used for the measurements. A calibration curve was prepared using a pullulan standard sample (manufactured by Showa Denko), and DMSO was used as the mobile phase.

The properties of six types of Poly(AAm-co-AN) (F1 to F6) synthesized by free radical polymerization are shown in Table 1 below.

[Example 2]
[Measurement of upper critical solution temperature of aqueous solutions containing copolymers synthesized by free radical polymerization]
The copolymers F1 to F6 were dissolved in water as a solvent, and the temperature of a 1 w/v% aqueous solution was increased or decreased in 0.5°C increments, and the solubility of each copolymer was confirmed by measuring the change in transmittance at 670 nm. The rate of temperature increase or decrease was 1°C/min, and the measurement was started immediately after the measurement temperature was reached. Thereafter, the reproducibility of the temperature response was confirmed by repeating the temperature change (1stCooling-1stHeating-2ndCooling-2ndHeating) for the same sample. In addition, when the measurement temperature was 15°C or lower, the measurement was performed while flowing argon gas into the cell holder to prevent condensation of the cell. The light transmittance was measured using a JASCO-V650 ultraviolet-visible spectrophotometer (manufactured by JASCO), and the temperature inside the cell holder was adjusted using a JASCO ETC-717 temperature controller (manufactured by JASCO). The results are shown in Figures 1(a) to 1(f) as graphs plotting the light transmittance (vertical axis) and the temperature of each solution (horizontal axis). The upper critical solution temperature was determined as the intersection of the linear portion of the transmittance changing in the obtained transmittance-temperature curve and the horizontal line representing 100% transmittance.

(result)
1(a) to (f), the aqueous solutions containing the copolymers F1 to F6 all showed a light transmittance-temperature curve. Although there were differences in the upper critical solution temperature, the aqueous solutions containing all of the copolymers repeatedly underwent reversible dissolution and aggregation.

In FIG. 1, the upper critical solution temperatures during heating and cooling of the 1 w/v % aqueous solutions of the copolymers F1 to F6 were as follows:
The upper critical solution temperature of the above-mentioned F1 Poly(AAm-co-AN) [77.5:22.5] during heating was 68° C., and the upper critical solution temperature during cooling was 66° C. ( FIG. 1( a) );
The upper critical solution temperature of the above-mentioned F2 Poly(AAm-co-AN) [80:20] during heating was 58° C., and the upper critical solution temperature during cooling was 56° C. ( FIG. 1( b) );
The upper critical solution temperature of the above-mentioned F3 Poly(AAm-co-AN) [82.5:17.5] during heating was 45.5°C, and the upper critical solution temperature during cooling was 42.5°C (Figure 1(c));
The upper critical solution temperature of the above-mentioned F4 Poly(AAm-co-AN) [85:15] during heating was 31° C., and the upper critical solution temperature during cooling was 28° C. ( FIG. 1( d) );
The upper critical solution temperature of the above-mentioned F5 Poly(AAm-co-AN) [87.5:12.5] during heating was 19.5°C, and the upper critical solution temperature during cooling was 16.5°C (Figure 1(e));
The upper critical solution temperature of the above-mentioned F6 Poly(AAm-co-AN) [90:10] during heating was 9° C., and the upper critical solution temperature during cooling was 6.5° C. ( FIG. 1( f) );

It was confirmed that in each copolymer-containing aqueous solution in Table 1, as the acrylamide monomer charge ratio increases, both the upper critical solution temperature during heating and the upper critical solution temperature during cooling decrease.

[Example 3]
[Measurement of upper critical solution temperature of copolymer mixed solution]
As a model cleaning solution for cleaning cosmetics and topical skin preparations, a copolymer mixed solution was investigated using a mixed solvent in which SDS was added to an aqueous solution. The solubility of the copolymer mixed solutions in which SDS was added to a final concentration of 100 mM to 1 w/v % aqueous solutions of the above polymers F1 to F6 was confirmed in the same manner as in Example 2. The results are shown in Figure 2.

(result)
As is clear from FIG. 2, in the copolymer-containing mixed solutions F1 to F6, when the monomer charging ratios were [77.5:22.5] and [80:20], the mixed solutions drew a light transmittance-temperature curve and repeatedly underwent reversible dissolution/aggregation phenomena, although there was a difference in the upper critical solution temperature.

More specifically, the upper critical solution temperature of the Poly(AAm-co-AN) [77.5:22.5] + SDS 100 mM mixed solution of F1 was 70°C or higher when heating and 69°C when cooling, meaning there was no significant difference in the upper critical solution temperature compared to before the addition of SDS (Figure 2 (a)). The upper critical solution temperature of the Poly(AAm-co-AN) [80:20] + SDS 100 mM mixed solution of F2 was 53°C when heating and 47°C when cooling, meaning the slope of the light transmittance-temperature curve became gentler and the upper critical solution temperatures when heating and cooling were both lower (Figure 2 (b)). In the above F3 Poly(AAm-co-AN) [82.5:17.5] + SDS 100 mM mixed solution (Figure 2 (c)), F4 [Poly(AAm-co-AN)] [85:15] + SDS 100 mM mixed solution (Figure 2 (d)), F5 Poly(AAm-co-AN) [87.5:12.5] + SDS 100 mM mixed solution (Figure 2 (e)), and F6 Poly(AAm-co-AN) [90:10] + SDS 100 mM mixed solution (Figure 2 (f)), no light transmittance-temperature curve was drawn, and the mixed solution remained dissolved without showing any coagulation.

[Example 4]
Further investigation was carried out on the above F3, Poly(AAm-co-AN) [82.5:17.5].

The solubility of each mixed solution was confirmed in the same manner as in Example 2, by adding SDS to a 1 w/v % aqueous solution of Poly(AAm-co-AN) [82.5:17.5] (F3) to a final concentration of 5 mM, 10 mM, 15 mM, 20 mM, 30 mM, and 100 mM. The results are shown in Figures 3(a) to 3(f).

(result)
The upper critical solution temperature of the mixed solution in which SDS was added to a 1 w/v % aqueous solution of Poly(AAm-co-AN) [82.5:17.5] of F3 to a final concentration of 5 mM was 44.5° C. when heating and 41° C. when cooling (FIG. 3( a)). The upper critical solution temperature of the mixed solution in which SDS was added to a final concentration of 10 mM was 36° C. when heating and 29.5° C. when cooling. The upper critical solution temperatures during heating and cooling were both approximately 15° C. lower than those in the case where SDS was not added to the aqueous solution (FIG. 3( b)).
The upper critical solution temperature of the mixed solution to which SDS was added so as to give a final concentration of 15 mM was 27° C. when heating and 17° C. when cooling. The upper critical solution temperatures when heating and cooling were both approximately 20° C. lower than when SDS was not added to the aqueous solution ( FIG. 3( c)).
The upper critical solution temperature during cooling of the mixed solution to which SDS was added so that the final concentration was 20 mM was 9.5° C. No light transmittance-temperature curve was drawn during heating (FIG. 3(d)).
In the mixed solutions to which SDS was added so that the final concentrations were 30 mM and 100 mM, no light transmittance-temperature curve was drawn, and the mixed solutions remained dissolved without exhibiting aggregation (Figures 3(e) and (f)).

[Example 5]
Instead of SDS (final concentration 100 mM) as the surfactant, a cationic surfactant, CTAC (final concentration 100 mM), was used and the study was carried out in the same manner as in Example 3. The results are shown in Figures 4(a) to (f).

(result)
As is clear from Fig. 4, the light transmittance-temperature curves were drawn for the CTAC mixed solutions of the copolymers F1 to F6, in which the monomer charge ratios were F1 [77.5:22.5], F2 [80:20], F3 [82.5:17.5], F4 [85:15] and F5 [87.5:12.5], except for F6 [90:10]. In addition, although there were differences in the upper critical solution temperature in these five copolymer-containing mixed solutions, the phenomenon of reversible dissolution and aggregation was repeated.

The upper critical solution temperatures during heating and cooling of the mixed solutions of CTAC (final concentration 100 mM) containing the copolymers F1 to F6 were as follows:
The upper critical solution temperature of the CTAC mixed solution of F1 during heating was 66° C., and the upper critical solution temperature during cooling was 62.5° C. ( FIG. 4( a) );
The upper critical solution temperature of the CTAC mixed solution of F2 during heating is 54° C., and the upper critical solution temperature during cooling is 50° C. ( FIG. 4B );
The upper critical solution temperature of the CTAC mixed solution of F3 during heating was 42° C., and the upper critical solution temperature during cooling was 38° C. ( FIG. 4( c ));
The upper critical solution temperature of the CTAC mixed solution of F4 during heating was 27.5° C., and the upper critical solution temperature during cooling was 23.5° C. ( FIG. 4( d) );
The upper critical solution temperature of the CTAC mixed solution of F5 during heating was 17.5° C., and the upper critical solution temperature during cooling was 13° C. ( FIG. 4( e) );
The CTAC mixed solution of F6 did not show any coagulation property (FIG. 4(f)). In all of the CTAC mixed solutions of F1 to F5 except for the CTAC mixed solution of F6, the upper critical solution temperature shifted to the lower temperature side. However, the lowering effect was weaker than that of SDS.

[Comparative Example]
Sodium chloride (final concentration 100 mM) was used instead of SDS (final concentration 100 mM), and the study was carried out in the same manner as in Example 3. The results are shown in Figures 5(a) to (f).

(result)
As is clear from Figures 5(a) to (f), when sodium chloride was added to the aqueous solutions of these six copolymers F1 to F6, almost no change in the upper critical solution temperature was observed in any of the copolymer solutions.

[Example 6]
(Synthesis of [Poly(AAm-co-AN)] by RAFT polymerization)
Six random copolymers, Poly(AAm-co-AN) (R1 to R6 in Table 2), having monomer mass ratios [acrylamide (AAm):acrylonitrile (AN)] in the range of 80:20 to 85:15 and different CMDT contents were synthesized by the RAFT polymerization method according to the following procedure with reference to Polym. Chem. 2016, 7, 1979-1986.

Acrylamide and AIBN were dissolved in DMSO (6 mL), CMDT was added and further dissolved, and then argon gas was blown in for 30 minutes to remove dissolved oxygen. Acrylonitrile in a proportion corresponding to the acrylamide was added using a gas-tight syringe to form a reaction solution, which was reacted at 70°C for 3.5 hours under an argon atmosphere and then cooled to room temperature.
The cooled reaction solution was poured into 150 mL of methanol, and the precipitated copolymer was filtered out. The copolymer obtained was washed with 150 mL of methanol and then dried overnight in a desiccator.

The unit ratio of AAm to AN in the copolymer, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the copolymer were measured using the method described in [Synthesis of Poly(AAm-co-AN) Copolymer by Free Radical Polymerization] above.

The properties of six types of [Poly(AAm-co-AN)] (R1 to R6) synthesized by RAFT polymerization are shown in Table 2 below.

[Example 7]
[Measurement of upper critical solution temperature of aqueous solution containing copolymer synthesized by RAFT polymerization 1]
The copolymer R1 was dissolved in water as a solvent, and the temperature was raised and lowered at 0.5°C intervals for a 1 w/v% aqueous solution or a 0.1 w/v% aqueous solution to confirm the solubility of each copolymer. The copolymer synthesized by RAFT polymerization has a large change in transmittance per unit temperature, so the rate of temperature rise or fall was set to 0.5°C/min, respectively, and the measurement was performed by the method described in Example 2 [Measurement of upper critical solution temperature of an aqueous solution containing a copolymer synthesized by free radical polymerization]. The results are shown in Figures 6(A) and (A1) as graphs plotting the light transmittance (vertical axis) and the temperature of each solution (horizontal axis). In addition, the differential curves of the graph of the aqueous solution containing the copolymer R1 are shown in Figures 6(a) and (a1), respectively. For comparison, the results of a similar study on the 1 w/v% aqueous solution and 0.1 w/v% aqueous solution of the copolymer F3 synthesized by free radical polymerization are shown in Figures 6(F) and (F1), and the differential curves are shown in Figures 6(f) and (f1).

(result)
As is clear from Fig. 6, the upper critical solution temperature of a 1 w/v % aqueous solution of [Poly(AAm-co-AN)] [82.5:17.5] of R1 was 30°C when heating and 27.5°C when cooling (Fig. 6(A)), while the upper critical solution temperature of a 0.1 w/v % aqueous solution was 28°C when heating and 25.5°C when cooling (Fig. 6(A1)). On the other hand, the upper critical solution temperature of a 1 w/v % aqueous solution of [Poly(AAm-co-AN)] [82.5:17.5] of F3 was 45.5°C when heating and 42.5°C when cooling (Fig. 6(F)), while the upper critical solution temperature of a 0.1 w/v % aqueous solution was 39.5°C when heating and 37°C when cooling (Fig. 6(F1)).

In addition, the maximum values of the transmittance change per unit temperature of the upper critical solution temperature during cooling for the 1 w/v% aqueous solution (Figure 6(a)) and 0.1 w/v% aqueous solution (Figure 6(a1)) of [Poly(AAm-co-AN)] synthesized by RAFT polymerization were 190 d% T/dT and 90 d% T/dT, respectively. These were significantly larger changes in transmittance per unit temperature than the values of 27 d% T/dT and 6 d% T/dT for the 1 w/v% aqueous solution (Figure 6(f)) and 0.1 w/v% aqueous solution (Figure 6(f1)) of [Poly(AAm-co-AN)] synthesized by free radical polymerization.

[Example 8]
[Measurement of upper critical solution temperature of aqueous solution containing copolymer synthesized by RAFT polymerization 2]
Of the six types of copolymers Poly(AAm-co-AN) synthesized above, the copolymers R1 to R4, all of which have a unit ratio of [82.5:17.5] and different Mws, were cooled and heated at 0.5°C intervals for 1 w/v% aqueous solutions, and the solubility of each copolymer was confirmed by measuring the change in transmittance at 670 nm. The measurement was performed by the method described in Example 2 [Measurement of upper critical solution temperature of copolymer-containing aqueous solution synthesized by free radical polymerization], except that the rate of temperature increase or decrease was 0.5°C/min. The results are shown in Figures 7(A) to 7(D) as graphs plotting light transmittance (vertical axis) and the temperature of each solution (horizontal axis). The differential curves are also shown in Figures 7(a) to 7(d), respectively.

(result)
7(A) to (D), the aqueous solutions of the copolymers R1 to R4 all showed a light transmittance-temperature curve. Although there were differences in the upper critical solution temperature, the phenomenon of reversible dissolution and aggregation was repeated in all of the copolymer-containing solutions.

In FIG. 7, the upper critical solution temperatures during heating and cooling of 1 w/v % aqueous solutions of the copolymers R1 to R4 were as follows:
The upper critical solution temperature of the above-mentioned R1 Poly(AAm-co-AN) [82.5:17.5] (Mw: 9970) during heating is 30° C., and the upper critical solution temperature during cooling is 27.5° C. ( FIG. 7(A) );
The upper critical solution temperature of the above R2 Poly(AAm-co-AN) [82.5:17.5] (Mw: 26,400) during heating is 30° C., and the upper critical solution temperature during cooling is 28.5° C. ( FIG. 7B );
The upper critical solution temperature of the above R3 Poly(AAm-co-AN) [82.5:17.5] (Mw: 38700) during heating was 32.5° C., and the upper critical solution temperature during cooling was 29.5° C. ( FIG. 7C );
The upper critical solution temperature of the above R4 Poly(AAm-co-AN) [82.5:17.5] (Mw: 74,800) during heating was 30° C., and the upper critical solution temperature during cooling was 29° C. ( FIG. 7(D) );

As is clear from the results in Figures 7(A) to (D), the upper critical solution temperature during heating and cooling was not significantly different in each aqueous solution, including four types of [Poly(AAm-co-AN)] by RAFT polymerization, which have the same unit ratio but different Mw. However, as is clear from Figures 7(a) to (d), when examining the change in transmittance per unit temperature, the change in transmittance was larger in all cases than in the aqueous solution of F3 in Figure 6, confirming that the sensitivity of the temperature response in the aqueous solution of the copolymer is high. Specifically, the maximum value of d%T/dT during cooling was 190 for R1, 105 for R2, 100 for R3, and 115 for R4. In addition, the smaller the molecular weight, the greater the degree of change in transmittance tends to be, and the change in transmittance was particularly large in R1, which has the smallest molecular weight.

[Example 9]
[Measurement of upper critical solution temperature of aqueous solution containing copolymer synthesized by RAFT polymerization 3]
The above R5, R2, R6, and a mixture of R5 and R6 at 1:1 were dissolved in water as a solvent, and the temperature was raised and lowered at 0.5°C intervals for a 1 w/v% aqueous solution to confirm the solubility of each copolymer. The rate of temperature rise or fall was set to 0.5°C/min, but the measurement was performed according to the method described in Example 2 [Measurement of upper critical solution temperature of aqueous solution containing copolymer synthesized by free radical polymerization]. The results are shown in Figures 8(E), (B), (G), and (H) plotting the above R5, R2, R6, and the aqueous solution containing a copolymer of a mixture of R5 and R6 at 1:1 as a graph plotting the light transmittance (vertical axis) and the temperature (horizontal axis) of each solution. The differential curves are also shown in Figures 8(e), (b), (g), and (h), respectively.

(result)
8(E), (B), (G), and (H), the aqueous solutions of the copolymers R5, R2, R6, and a 1:1 mixture of R5 and R6 all showed light transmittance-temperature curves. In addition, although there were differences in the upper critical solution temperatures, the phenomenon of reversible dissolution and aggregation was repeated in all of the copolymer-containing solutions.

In FIG. 8 , the upper critical solution temperatures during heating and cooling of 1 w/v % aqueous solutions of the copolymers of R5, R2, R6, and a 1:1 mixture of R5 and R6 were as follows:
The upper critical solution temperature of the above-mentioned R5 Poly(AAm-co-AN) [85:15] during heating was 12.5°C, and the upper critical solution temperature during cooling was 10.5°C (Figure 8 (E));
The upper critical solution temperature of the above-mentioned R2 Poly(AAm-co-AN) [82.5:17.5] during heating is 30° C., and the upper critical solution temperature during cooling is 28.5° C. ( FIG. 8B );
The upper critical solution temperature of the above R6 Poly(AAm-co-AN) [85:15] during heating was 37°C, and the upper critical solution temperature during cooling was 36°C (Figure 8(G));
The upper critical solution temperature of the mixture of R5 and R6 at a ratio of 1:1 was 37.5° C. when the temperature was increased, and was 34° C. when the temperature was decreased (FIG. 8(H)).

From the results in Figure 8, in each of the aqueous solutions containing one type of [Poly(AAm-co-AN)] synthesized by RAFT polymerization such as (E), (B), and (G), the upper critical solution temperature during heating and cooling showed a larger change in transmittance than the aqueous solution F3 in Figure 6, confirming that the temperature response sensitivity of the copolymer aqueous solution is high. On the other hand, the transmittance change per unit temperature of the aqueous solution containing two types of [Poly(AAm-co-AN)] synthesized by RAFT polymerization (H) was very small, and the temperature response sensitivity was reduced. From this, it is believed that the increase in the transmittance change of [Poly(AAm-co-AN)] synthesized by RAFT polymerization is due to the fact that the unit ratio of each polymer chain is uniform in the copolymer synthesized by RAFT polymerization.

[Example 10]
A mascara was prepared according to the following formulation and manufacturing method.
(Components) (% by mass)
(1) Hydrogenated polyisobutene balance (2) Dextrin palmitate 2.0
(3) Beeswax 9.0
(4) Carnauba wax 5.0
(5) Polymethylsilsesquioxane 5.0
(6) Disteardimonium hectorite 1.0
(7) Talc 5.0
(8) Black iron oxide 5.0
(9) Silica anhydride 1.0
(10) Purified water 10.0
(11) F3 of Example 1; poly(AAm-co-AN) [85:15] 1.0

(Production method)
A. Heat and dissolve ingredients (1) to (5) at 100°C, then cool to 70°C.
B. Add ingredients (6) to (9) in A and mix evenly.
C. Components (10) and (11) were mixed and dissolved uniformly at 70°C, then added to B and emulsified at 70°C, followed by cooling to room temperature to obtain a mascara.

The mascara obtained in this manner cannot be removed by water or sweat, but can be easily removed by using 42°C hot water and soap. The soap contains sodium fatty acid as a surfactant component.

[Example 11]
An ointment was prepared according to the following recipe and manufacturing method.
(Components) (% by mass)
(1) Stearyl alcohol 18.0
(2) Rowlet 15.0
(3) Polyoxyethylene (20 mol) monooleate 0.3
(4) Tocopherol 0.1
(5) Vaseline 30.0
(6) Glycerin 10.0
(7) Purified water Remaining amount (8) R6 in Example 6; poly(AAm-co-AN) [80:20] 3.0

(Production method)
A: Components (1) to (5) are mixed uniformly at 70°C.
B: Components (7) and (8) are mixed and dissolved uniformly at 70°C, and then component (6) is added and mixed uniformly.
C: B was added to A and emulsified at 70°C, then cooled to room temperature to obtain an ointment.

The ointment obtained in this manner could not be removed by water or sweat, but could be easily removed by using hot water at 42°C.

This invention is extremely useful in the fields of cosmetics and topical skin preparations.

Claims (1)

A method for lowering an upper critical solution temperature, characterized by contacting a surfactant with a cosmetic composition or topical skin composition having an upper critical solution temperature and containing a copolymer of acrylamide and acrylonitrile.