JPH0158165B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an external preparation containing allantoin as a main ingredient. The term "external preparations" as used herein refers to medical and cosmetic preparations that are used externally to protect the face, limbs, etc., and keep them in a healthy condition. Allantoin is listed in the Standards for Cosmetic Ingredients and is used to treat wounds, ulcers, burns, etc. and for dermatological diseases such as eczema, and is usually prescribed at 0.1 to 0.5%. Allantoin is easily hydrolyzed; for example, it is known to be decomposed into glyoxylic acid and urea in acidic conditions, and to allantoic acid in alkaline conditions, but as accurate quantification has not been carried out, the content decreases considerably over time. seems to have occurred. Therefore, the present inventor conducted extensive research in order to obtain a topical preparation containing allantoin in which the content reduction is within an acceptable range, and which has an excellent feeling of use without causing any off-odor, color change, or viscosity change over a long period of time. As a result, the present invention was completed. In other words, the present invention has allantoin as the main component, contains carboxyvinyl polymer and water, and has a pH control.
This is an external preparation adjusted to 5.5 or less. Carboxyvinyl polymer is also listed in the Cosmetic Raw Materials Standards, and is mainly made of acrylic acid, copolymerized with allyl sucrose, etc., and is known to have an excellent thickening effect when neutralized.
It is commercially available under names such as Carbopol, Jiyunron, and Hibiswako. Carboxyvinyl polymers are generally 0.1-10%
It is said that the best effects are obtained when the pH is adjusted to 5.5-11 by neutralizing with basic inorganic substances such as sodium hydroxide and potassium hydroxide, or basic organic substances such as ethanolamine. However, the inventor's research has shown that when allantoin is added to external preparations, if the pH exceeds 5.5 on the alkaline side, the allantoin content may drop below 90% due to long-term storage. Therefore, we further investigated the possibility of using it at a pH lower than this, and found that even when the pH was lowered to 5.5 or lower using carboxyvinyl polymer, a gel-like external preparation was obtained that was colloidally stable and also exhibited a pH buffering effect. It was confirmed that it would be done. In addition to allantoin, carboxyvinyl polymer, and water, the external preparation of the present invention may contain other ingredients that are generally included in external preparations, such as petrolatum, liquid paraffin, squalane, etc., as an oil component that has a skin protective effect. Examples include hydrocarbons, higher alcohols such as cetyl alcohol and stearyl alcohol, and higher fatty acids such as palmitic acid and stearic acid. In addition, moisturizing agents such as glycerin, sorbitol, and propylene glycol, preservatives such as phenol derivatives such as methyl hydroxybenzoate, antiseptics such as benzalkonium chloride, sorbic acid, dehydroacetic acid, and boric acid, as well as fragrances and pigments, etc. May be added. Furthermore, surfactants, especially synthetic surfactants, are often used as emulsifiers when preparing ointments, creams, etc., and these can also be added. Examples include nonionic surfactants such as sorbitan fatty acid esters (spans), polyoxyethylene sorbitan fatty acid esters (tweens), polyoxyethylene glycol alkyl ethers, polyoxyethylene glycol fatty acid esters, benzalkonium chloride, These include cationic activators such as benzethonium chloride, anionic activators such as sodium alkyl sulfate, and the like. However, although it is possible to obtain a colloidally chemically stable cream by using a surfactant, the use of a surfactant is not preferable because it causes skin irritation and toxicity. Although the use of these surfactants is possible in the external preparation of the present invention, it is not essential, and even when they are not incorporated, the preparation is characterized by excellent feeling on use and good stability over time. The manufacturing method may be a general manufacturing method for external preparations, for example, oil layer components such as paraffin and squalane and water layer components such as glycerin, propylene glycol, and water are heated separately to 50 to 80°C, and then both are heated. Mix while stirring. It is then cooled with continued stirring until it reaches room temperature. The carboxyvinyl polymer may be added to the oil layer component, or it can be uniformly dissolved even if it is added after being dispersed in the water layer component such as glycerin or propylene glycol. Examples and comparative examples will be shown below and explained in detail. Examples Allantoin 0.4 parts by weight Carbopol 934 1.0 Squalane 10.0 parts by weight 1,3-butylene glycol 5.0 Ethyl paraoxybenzoate 0.1 Sodium hydroxide Appropriate amount Purified water The total amount is 100 parts by weight. An oil layer component is prepared by uniformly dispersing and suspending Carbopol 934 (carboxyvinyl polymer manufactured by Gutudoritsu) in squalane. Meanwhile, warm purified water to about 50°C, add ethyl paraoxybenzoate, 1,3-butylene glycol, and allantoin while stirring, and after dissolving, add the oil layer components and stir for 10 minutes. Next, sodium hydroxide was added to adjust the pH to 4±0.2, 5±0.2, 6±0.2 or 7±0.2, and the mixture was cooled to room temperature while stirring. Comparative example 1 O/W type hydrophilic ointment (Japanese Pharmacopoeia 10th revision) Allantoin 0.4 parts by weight White petrolatum 25.0 〃 Stearyl alcohol 22.0 〃 Propylene glycol 12.0 parts by weight Sodium lauryl sulfate 1.5 〃 Ethyl paraoxybenzoate 0.025 〃 Propyl paraoxybenzoate 0.015 〃 Purified water The total amount is 100 parts by weight. White petrolatum and stearyl alcohol were dissolved on a water bath, stirred, and kept at about 75°C. To this was added a solution in which allantoin had been previously dissolved in purified water and heated to 75°C, and stirred until solidified. Comparative example 2 w/o type water-absorbing ointment (Japanese Pharmacopoeia 10th revision) Allantoin 0.4 parts by weight White petrolatum 40 Setanol 18 Sorbitan sesquioleate 5 Lauromacrogol 0.5 Ethyl paraoxybenzoate 0.1 Propyl paraoxybenzoate 0.1 〃 Purified water The total amount is 100 parts by weight. Take white petrolatum, cetanol, propyl paraoxybenzoate, lauromacrogol, and sorbitan sesquioleate, and dissolve by heating to 75°C on a water bath to obtain an oil layer component. Separately, add allantoin and ethyl paraoxybenzoate to purified water.
The solution heated to 80°C and dissolved was gradually added to the oil layer components and stirred, then the heating was stopped and the mixture was stirred until solidified. In Comparative Examples 1 and 2, allantoin was prescribed in a hydrophilic ointment and a water-absorbing ointment according to the 10th edition of the Japanese Pharmacopoeia. The above Examples and Comparative Examples were used by five panelists, and sensory evaluations of stickiness, spreadability, and refreshing sensation upon use were conducted. The results are shown in Table 1, and the external preparations of Examples were the most excellent in terms of sensory aspects such as stickiness, spreadability, and refreshing feeling during use.

【table】

[Table] The external preparation of the example was used for 3 months at room temperature and 3 months at 40℃.
The product was stored for several months, and the appearance (judgment with the naked eye), feeling of use, and allantoin content were measured, and the test results shown in Table 2 were obtained.

[Table] Allantoin content was determined by high performance liquid chromatography. As can be seen from Table 2, when the external preparation of the present invention was stored at room temperature for 3 months and at 40°C for 3 months, no change was observed in the appearance or feel of each sample prepared to have a pH in the range of 4 to 7. However, the allantoin content was the best at PH4 and PH5, and when the pH was increased to 6 to 7, a decrease in the allantoin content was observed. In addition, since it is not preferable for Hif to lower the pH of the external preparation to less than 4, it is appropriate to adjust the pH to 4 to 5.5.

Claims (1)

[Claims] 1. An external preparation containing allantoin as a main component, a carboxyvinyl polymer and water, and having a pH adjusted to 5.5 or less. 2. The external preparation according to claim 1, which does not contain a surfactant.