JPS63104909A - Skin protecting agent - Google Patents

Abstract

PURPOSE:To obtain a protecting agent forming a flexible, thin film having excellent water resistance and elongation, not providing the skin with a feeling of physical disorder, by dissolving specific amounts of a specific acrylic polymer and cellulose derivative in a hydrous alcohol. CONSTITUTION:(A) 2-10wt%, preferably 4-7wt% acrylic polymer (preferably 100,000-1,300,000 weight-average molecular weight) having a monomer weight ratio of ethyl acrylate and methacrylic acid of 75/25-95/5, preferably 80/20-90.10, <=50ppm residual monomers and substantially containing no surface active agent and (B) 0.3-2wt%, preferably 0.7-1.5wt% cellulose derivative, preferably ethyl cellulose are dissolved in a hydrous alcohol. The protecting agent has low irritation, a coating film formed protects a neutral detergent from permeating and can be readily removed with a weakly alkali solution of soap, etc., or an alcohol, etc., after use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a skin protective agent that is water resistant, alkali soluble, and contains little impurities, and is mainly comprised of an acrylic polymer.

[Prior Art] Protective coatings for protecting the skin from chemicals and other irritating substances are known. When applied to the skin surface, it forms a film to protect the skin.

In the past, cellulose derivatives dissolved in strong organic solvents such as acetone and ethyl acetate have been used, but organic solvents can irritate the skin and mucous membranes, and can remove the film formed from the skin. There were problems such as it was not easy.

Recently, a skin protective agent (hereinafter also referred to as the prior art protective agent) mainly composed of n-butyl polyester/maleic acid and plasticized ethyl cellulose has been developed in the United States.
Although it is commercially available, it has not been put into practical use in Japan because its safety has not yet been established and there are problems with its use.

This prior art protective agent creates a protective film between the skin and an extracorporeal catheter, fixation tape, cast, diaper, etc. Another proposed use is to help keep hands from getting dirty with grease.

In particular, the present inventors have conducted intensive studies on polymers that can coat the skin of housewives who use neutral detergents, and those who clean equipment in restaurants, hospitals, beauty salons, and the like. Acrylic polymers have long been used in medicine and are known to be highly safe. However, since all known acrylic polymers are manufactured by conventional polymerization methods such as solution polymerization and emulsion polymerization, the resulting polymers contain large amounts of anionic surfactants, chain transfer agents, residual monomers, etc. . Therefore, not only is it irritating to the skin and poses problems in terms of environmental protection, but the presence of surfactants also makes the film brittle and has poor water resistance, so the main purpose is to impermeate neutral detergents. This was not suitable for the present invention.

In addition, some research has been conducted on polymer emulsion synthesis that does not use surfactants or similar water-soluble substances, but for example, when this method is used to copolymerize ethyl acrylate and acrylic acid, The amount of
When the amount exceeds mol %, the resulting polymer emulsion becomes mechanically unstable and tends to gel (Matsumoto et al., Kobunshi Ronsen Vol. 32, No. 9, 1975).

Furthermore, known acrylic polymers known for pharmaceutical use, such as those manufactured by Rohm Pharma, West Germany (R6hm P
It has been found that Eudragid (Pharma) is unsuitable for the purpose of the present invention due to the elongation and tensile strength of the produced film.

[Problems to be Solved by the Invention] In order to achieve the purpose of the present invention, it is necessary to satisfy the following points in a well-balanced manner, but no polymer has been developed that satisfies them at the same time. 0 The required performance of the skin protective agent targeted by the present invention is 1) to be able to form a thin film, 2) to be water resistant and alkali soluble, and 3) to be able to form a stretchable and flexible film that does not adhere to the skin. 4) Low impurities such as residual monomers, no odor or irritation, 5) Impermeable to neutral detergents, 6) Soluble in alcohol or water-containing alcohol,
and 7) it has air permeability and moisture permeability, and does not get stuffy or sticky when covered.

[Means for Solving the Problems] In view of the above points, the present inventors added 75 to 95 parts by weight of ethyl acrylate (hereinafter also referred to as EA) and methacrylic acid (hereinafter referred to as MAA). 25 parts by weight to 5 parts by weight of the monomer in deionized water under heat,
The use of a persulfate as a polymerization initiator, optionally with further use of a redox catalyst system such as hydrogen peroxide, ferrous sulfate and L-ascorbic acid, alone or in combination, and post-treatment achieves the objectives of the present invention. We have now completed the present invention by discovering that a suitable polymer can be synthesized according to the present invention.The monomer units of the copolymer used in the skin protection agent of the present invention will be explained in more detail.

Ethyl acrylate is used in an amount of 75 to 95 parts by weight, preferably 80 to 90 parts by weight in the copolymer. EA was chosen because its use makes the synthetic copolymer more soluble in solvents such as alcohol or hydroalcohol.

Methacrylic acid is used in the copolymer in an amount of 25 to 5 parts by weight, preferably 20 to 10 parts by weight. If the composition ratio of MAA is below the above-mentioned lower limit, the alkali solubility will be insufficient, and if the composition ratio of MAA is above the above-mentioned upper limit, elongation and flexibility will decrease, which is undesirable.If the composition ratio of MAA exceeds 35 parts by weight, The water resistance of the films obtained from the compositions of the present invention was better than that of the prior art protectants.

The reason for choosing MAA instead of acrylic acid is that MAA is said to be safer and has been found to be superior in terms of water resistance and reduction of residual monomers. Furthermore, when making a copolymer with EA in the absence of an emulsifier, MAA was found to be more effective at using a higher proportion of unsaturated carboxylic acid monomers than when using acrylic acid as a copolymer. This is a strong reason for selection. As a result, a safer acrylic polymer with fewer impurities could be obtained. Compared to the known prior art protective agents, the skin protective agent of the present invention provides a protective film with a better feel without any discomfort or tightness.

The various performances required for the above-mentioned polymers for skin protection agents can also be adjusted by changing the monomer composition ratio of ethyl acrylate and methacrylic acid in the acrylic polymer. When desired, the MAA composition ratio may be lowered, and when a film with emphasis on alkali solubility is intended, the MAA composition ratio may be increased.

Deionized water is placed in a closed reactor purged with nitrogen and heated, showing a general method for producing the acrylic polymer of the present invention. A persulfate dissolved in deionized water in advance is added as a polymerization initiator, and then the respective monomers of EA and MAA are added over a predetermined period of time under stirring. The polymerization proceeds, and the polymerization is almost complete by the time the monomer addition is finished. ing. If it is desired to further reduce the monomer concentration, the reaction temperature is maintained as it is, or the temperature is raised further and stirring is continued (hereinafter, this step may be referred to as post-treatment). The reaction solution is cooled to obtain the desired polymer as a dispersion.

Examples of persulfates include ammonium persulfate, sodium persulfate, potassium persulfate, etc., and the total amount may be added at once, or may be added in portions or continuously.The amount of persulfate to be used depends on the final The optimum amount is selected depending on the polymer concentration, polymerization temperature, polymerization time, etc., but it is generally used in an amount of about 0.2 to 4 parts by weight, more preferably about 0.4 to 3 parts by weight, based on 100 parts by weight of the monomer. Below the lower limit, the stability of the polymer dispersion becomes poor and residual monomer increases, while above the upper limit, the water resistance of the coating decreases. If you want to reduce the time required for post-treatment, you can increase the post-treatment temperature, add persulfate during post-treatment, or use a combination of hydrogen peroxide, ferrous sulfate and L-ascorbic acid. It is sufficient to add a small amount of redox catalyst, etc. If the purpose is simply to complete the polymerization and reduce the residual monomer, polymerization initiators and redox catalysts other than those mentioned above may also be used, but they do not affect the skin that is the purpose of the present invention. This is not desirable considering the application of

As monomers, EA and MAA may be added separately, but
It is easier to mix and add. Although the rate of addition may vary, it is preferable to add at a constant rate because it prevents the formation of coarse particles and facilitates temperature control.

The polymerization temperature is about 45-98°C, more preferably 65-95°C.
Adjust to a range of ℃. Below the lower limit, coarse particles are likely to be generated.

Although the polymer concentration in the dispersion liquid should not be particularly limited, it is preferably 15 to 65%, more preferably 25 to 5%.
It is 5%. Below the lower limit, the amount of monomer persulfate required increases or the relative amount of residual monomer increases. Moreover, if it exceeds the upper limit, the polymer dispersion becomes unstable, and coarse particles and deposits on the vessel wall increase.

According to the above method, polymers with various degrees of polymerization can be obtained. Although it is not necessary to particularly limit the weight average molecular weight of the polymer, for the purpose of the present invention, a weight average molecular weight of about 100,000 to 2,000,000, more preferably about 100,000 to 1,300,000 is preferably used. By adjusting the amount of persulfate used, polymerization temperature, and polymer concentration, the molecular weight of the produced polymer can be freely selected.

Furthermore, if alcohol such as ethanol or isopropanol is used as a chain transfer agent, the molecular weight can be reduced.

The use of commonly used chain transfer agents such as organic sulfur compounds is not preferred in view of skin safety.

The skin protection agent of the present invention is prepared by dissolving the acrylic polymer and hydrophilic cellulose in a suitable medium. Alcohol-based solvents are preferred as the vehicle.Ethanol or aqueous ethanol is the most desirable dissolution medium for skin protection agents from the standpoint of safety, but high ethanol content evaporates quickly and may irritate the skin when there is a wound. There are problems such as

Conversely, too much water may reduce the solubility of the polymer,
Evaporation rate slows down. Isopropanol can also be used instead of ethanol. A preferred mixing ratio is 60/40 to 80/20 alcohol/water.

Approximately 2 to 10% of acrylic polymer in these solvents,
More preferably, it is dissolved at a concentration of about 4 to 7%; if the concentration is above the upper limit, a stiff feeling may be felt during use, and the adhesion to the skin may be reduced. Below the lower limit, only a thin film is formed and the film becomes brittle, which is not preferable.

Examples of cellulose derivatives used in the present invention include methylcellulose, ethylcellulose, and hydroxypropylcellulose. Among them, ethylcellulose is most preferably used. The amount of cellulose added is about 0.3% to 2%, more preferably about 0.3% to 2%.
It is 7-1°5%. Above the upper limit, the film formed becomes brittle, which is undesirable; below the lower limit, it becomes sticky during drying, which is also undesirable. The addition of these celluloses significantly increases the tackiness during application and the elasticity after drying. Improved.

If desired, the skin protective agent of the present invention may contain appropriate softeners, additives such as polyvinylpyrrolidone, preservatives, coloring agents, or pharmaceutically active ingredients. The skin protective agent of the present invention forms a colorless and transparent thin film, so
This is very desirable from a cosmetic point of view, but depending on the purpose of use, a suitable coloring agent may be added to the product so that the presence or absence of film formation can be confirmed.

In the present invention, the formulation packaging form of the skin protective agent should not be particularly limited. Since the protective agent is an alcohol solution, a closed container that can prevent the alcohol from volatilizing is preferable.For example, a glass or plastic bottle may be used, or a spray container may be used.

Advantages of the acrylic polymer used in the present invention,
The advantages for producing polymers and polymers are summarized below.

■ Forms a film that is virtually impermeable to neutral detergents and can be easily washed off with mildly alkaline stone noodles.

■ Forms a thin, highly flexible film with good elongation.

■ When the residual monomer is 50 ppm or less, there is almost no odor and no irritation. In normal emulsion polymerization, there is a lot of residual monomer, and therefore the odor is strong. To reduce this residual monomer, vacuum suction and shortening of the polymerization time are necessary. Post-processing such as extension takes a long time. However, in the polymerization method shown in the present invention, since there is little residual monomer, post-treatment is also easy.

■ Stable at room temperature and can be stored for long periods without using emulsifiers or suspending agents.

The present invention will be explained in more detail with reference to the following Examples, but these are not intended to limit the scope of the present invention in any way.

Reference example (manufacture of polymer) Reference example 1 Deionized water 2 was placed in a nitrogen-substituted closed reaction vessel equipped with a stirrer.
After charging 36.1 parts by weight and adjusting the inside of the reactor to 80°C, 1.2 parts by weight of ammonium persulfate was added, and then 85 parts by weight of the following monomer mixture EA and 15 parts by weight of MAA were added over 8 hours. While maintaining the inside of the reactor at 80° C., stirring was continued for an additional 8 hours to complete the reaction. The solid content of this dispersion was 30%, and analysis of residual monomers by gas chromatography revealed that EA was 37 ppm and M
AA was 10 ppm or less. Moreover, the weight average molecular weight of this copolymer was about 840,000.

Reference example 2 Deionized water 2 was added to a closed reaction vessel equipped with a stirrer and replaced with nitrogen.
After charging 37.3 parts by weight and 0.5 parts by weight of isopropanol and adjusting the temperature inside the reactor to 80°C, 1.7 parts by weight of ammonium persulfate was added, and then 85 parts by weight of the following monomer mixture EA and 15 parts by weight of MAA were added. The inside of the reactor was maintained at 85°C, and 0.1 parts by weight of hydrogen peroxide, ferrous sulfate and L-ascorbic acid were added and stirred for 5 hours to complete the reaction. . The solids content of this dispersion was 30%, and the residual monomer mixture by gas chromatography showed an EA of 12 pp.
MAA was below 10 ppm. Moreover, the weight average molecular weight of this copolymer was about 180,000.

Reference example 3 Deionized water 2.
After charging 37.3 parts by weight and 2.0 parts by weight of isopropanol and adjusting the temperature inside the reactor to 80°C, 1.7 parts by weight of ammonium persulfate was added, and then the following monomer mixture EA 80 parts by weight MAA 20 The inside of the reactor was maintained at 85°C, and 0.1 parts by weight of hydrogen peroxide, ferrous sulfate and L-ascorbic acid were added and stirred for 5 hours until the reaction was completed. Ta. The solid content of this dispersion was 30%, and as a result of analysis of residual monomers by gas chromatography, the EA was 20 pp.
MAA was below 10 ppm. Moreover, the weight average molecular weight of this copolymer was about 130,000.

Reference example 4 Deionized water 2.
After charging 38.0 parts by weight and 3.0 parts by weight of isopropanol and adjusting the temperature inside the reactor to 80°C, 2.0 parts by weight of ammonium persulfate was added, and then 75 parts by weight of the following monomer mixture EA and 25 parts by weight of MAA were added. The inside of the reactor was maintained at 85°C, and 0.1 parts by weight of hydrogen peroxide, ferrous sulfate and L-ascorbic acid were added and stirred for 5 hours to complete the reaction. . The solid content of this dispersion was 30%, and as a result of analysis of residual monomers by gas chromatography, the EA was 18 pp.
MAA was below 10 ppm. Moreover, the weight average molecular weight of this copolymer was about 110,000.

Reference example 5 Deionized water was poured into a sealed reaction vessel with a stirrer and replaced with nitrogen.
After charging 37.3 parts by weight and adjusting the inside of the reactor to 80°C, 1.7 parts by weight of potassium persulfate was added, and then 85 parts by weight of the following monomer mixture EA and 15 parts by weight of MAA were added over 8 hours. The inside of the reactor was maintained at 80° C., hydrogen peroxide, ferrous sulfate, and L-ascorbic acid were added in an amount of 0.1 part by weight, and the reaction was continued with stirring for 5 hours to complete the reaction. The solid content of this dispersion was 30%, and as a result of analysis of residual monomers by gas chromatography, the EA was 15 pp.
MAA was 10 ppm or less. Moreover, the weight average molecular weight of this copolymer was about 750,000.

Reference example 6. In a closed reaction vessel equipped with a stirrer and replaced with nitrogen, add 1 part of deionized water.
After charging 87.8 parts by weight and adjusting the temperature inside the reactor to 75°C, 1.1 parts by weight of ammonium persulfate was added, and then 80 parts by weight of the following monomer mixture EA and parts by weight of MAA at 20°C were added over 5 hours. The temperature inside the reactor was maintained at 88°C, and hydrogen peroxide, ferrous sulfate, and L-ascorbic acid were reduced to zero.
．． After adding 1 part by weight and stirring for 5 hours, the reaction was completed.

The solid content of this dispersion was 35%, and as a result of analysis of residual monomers by gas chromatography, the EA was 15 ppm.
The MAA was 10 ppm or less. Moreover, the weight average molecular weight of this copolymer was about 800,000.

Reference example 7 In a closed reaction vessel equipped with a stirrer and replaced with nitrogen, add 1 part of deionized water.
After charging 51.7 parts by weight and adjusting the temperature inside the reactor to 70°C, 1.1 parts by weight of ammonium persulfate was added, and then 85 parts by weight of the following monomer mixture EA and 15 parts by weight of MAA were added over 8 hours. While maintaining the inside of the reactor at GO'C, 0.1 parts by weight of hydrogen peroxide, ferrous sulfate and L-ascorbic acid were added and stirred for 5 hours to complete the reaction. The solid content of this dispersion was 40%, and as a result of gas chromatography analysis of residual sulfur, the EA was 20 pp.
MAA was less than 10 ppca at m. Moreover, the weight average molecular weight of this fupolymer was about 1,180,000.

Example 1 The dispersion prepared in Reference Example 1 was weighed as 50 g as a polymer into a suitable container. Add 658 g of isopropanol (hereinafter sometimes referred to as IF) and stir until the polymer is completely dissolved. Add 10 g of ethyl cellulose (hereinafter sometimes referred to as EC) to the polymer solution.
was gradually added to prepare a uniform dispersion, and water was added to make a total amount of 1 kg.This composition was prepared using Polymer 5. of Reference Example 1.
0% and EC 1,0% in the IP.

Example 2 Using the polymer prepared in Reference Example 2, according to the preparation method of Example 1, polymer 5.0% and EC 1.0
Prepare a water-containing IP bath solution containing %.

Example 3 Using the polymer prepared in Reference Example 3, according to the preparation method of Example 1, polymer 5.0% and EC 1.0
Prepare a water-containing IP bath solution containing %.

Example 4 Using the polymer prepared in Reference Example 4, according to the preparation method of Example 1, polymer 5.0% and EC 1.0
Prepare a water-containing IP bath solution containing %.

Example 5 Using the polymer prepared in Reference Example 1, according to the preparation method of Example 1, polymer 3.5% and EC 1.0
Prepare a hydrous IF solution containing %.

Example 6 Using the polymer prepared in Reference Example 1, according to the preparation method of Example 1, polymer 7.0% and EC 1.0
Prepare a water-containing IF bath solution containing %.

Example 7 Using the polymer prepared in Reference Example 1, according to the preparation method of Example 1, polymer 10.0% and EC1
, prepare a water-containing IF bath solution containing 0%.

Example 8 Using the polymer prepared in Reference Example 2, according to the preparation method of Example 1, polymer 7.0% and EC 1.0
Prepare a water-containing IF bath solution containing %.

Test Example 1 The following composition was applied to the back of a person's hand to examine the performance of the composition of the present invention. As a control, an EC-free composition of the polymer of the present invention, a composition of a known acrylic polymer,
and a commercially available liquid bandage. The results are shown in Table 1.

(Test composition) Composition of the present invention Examples 1-7 Control composition (prior art) Reference 1 The following components are contained in the hydrated IF.

Polymer of Reference Example 1 3.5% Reference 2 The following components are contained in the hydrated IF.

Polymer of Reference Example 1 5.0% Reference 3 The water-containing TP contains the following components.

Polymer of Reference Example 1 7.0% Reference 4 The following components are contained in the hydrated IF.

Polymer of Reference Example 1 10.0% Control l The hydrated IF contains the following components:

Eudragit E30D 5.0%EC1.0% Control 2 The following components are contained in the hydrated IF.

Eudragit E30D 10, 0% ECl, Q
% Control 3 Contains the following components in hydrated IF.

Eudragi y To L30D-5510, 0%EC1,0
% Control 4 Commercially available film forming agent (aerosol type) Control 5 Commercially available liquid adhesive bandage grade 3 The skin protective agent of the present invention is clearly more effective than skin protective agents using known acrylic polymers and commercially available liquid adhesive plasters. It showed high sensory properties. The addition of brown sugar and cellulose improved the tackiness during application and the elasticity after drying.

Test Example 2 A sensory test was conducted on 7 healthy adults while using the skin protectant. The test method is described below.

(Method of applying the specimen) Apply the reference specimen to the right hand and the test specimen to the left hand according to the following criteria.

1. Drop 5 drops (approximately 100 mg) of the reference specimen onto the back of your right hand.

2. Use the fingertips of your left hand to spread it evenly from the center of the back of your right hand to the second joints of all four fingers, excluding the thumb.

3. Drop 5 drops (approximately 100a+g) of the test specimen onto the back of your left hand.

4. Using the fingertips of your right hand, spread it evenly from the center of the back of your left hand to the second joints of all four fingers, excluding the thumb.

Evaluate after placing s and m.

6. Evaluate the specimen after drying 10 minutes after dropping.

7. Next, evaluate when using water.

8. Wipe the specimen with 70% ethanol.

9. The above items are considered to be one course, and evaluations are conducted three times a day. However, there should be at least 3 hours between each evaluation and the next evaluation.

(Evaluation items and evaluation criteria) [Evaluation items] 1 star Korei 1, ease of spreading 2, stickiness 3, ease of drying 4! ! ! Immediately after drying evaluation: Violet 5, gloss of film 6, smoothness of film 7, difficulty in peeling 8, skin tightness 9, overall evaluation after drying: 100%! 10, hard to peel 11, slimy feel 12, overall evaluation when using water 13, overall evaluation of the above [Evaluation criteria] The following evaluation was given for each of the above items, and the balanced incomplete block design An analysis of variance was performed based on the results.

Correct A Bad knee 2, slightly bad knee 1, same: 0, slightly good: +
1. Good: +2° The organoleptic properties of the following compositions were compared according to the test method described above. The results are shown in Table 2, and the evaluation values shown in the table below indicate that a value greater than 0 indicates a higher evaluation than the reference specimen, and a value smaller than 0 indicates a lower evaluation.

(Test composition) Skin protection agent of the present invention Examples 1 and 2 Prior art skin protectant Control composition 6 Water-containing ■P contains the following ingredients.

Eudragit E30D 3.5% EC1.5% Control composition 7 Water-containing IP contains the following ingredients.

Eudragit L30D-555.0% Propylene Glycol 1.0% Table 2 Liquid Balls The skin protectant of the present invention exhibited higher organoleptic properties compared to skin protectants using known acrylic polymers.

Test Example 3 According to the method described in Test Example 2, the preferred concentration of the polymer in the skin protective agent was investigated. Table 3 shows the results.

(Test composition) Example 2: Polymer 5.0% Example 8: Polymer 7.0% (Margin below) Table 3 1 0.458 0.167 2 0.025 -0.267 3 0.000 0.125 4 0.300 -0.117 5 1.000 0.292 60.20g -0,167 70,008-0,033 80,733-0,017 90,442-0,183 10-0,192-0,108 11-0,158-0,200 A suitable polymer concentration was 5%.

[Effects of the Invention] It was confirmed that the skin protection agent based on the acrylic polymer of the present invention is safer than any of the prior art skin protection agents and has a good feeling of use. The skin protective agent of the present invention forms an extremely thin film by applying a very small amount to the skin.

The formed film is sufficiently water resistant, stretchy and flexible, and adheres well to the skin without causing discomfort. Furthermore, since it does not contain a surfactant and the amount of residual dirt is kept to a minimum, it is less irritating and helps the permeation of neutral detergents, making it extremely safe for the skin. In addition, after use, it can be easily removed with a weak alkaline solution such as stone age or alcohol, so for example, housewives,
It can provide an excellent hand protection covering for professional equipment cleaners, chemical users, etc.

In addition, if a suitable external skin preparation is applied before applying the skin protection agent of the present invention, it can be used as a liquid bandage or a protective film for ODT therapy.For example, it can be used on the hands, knees, neck, face, etc. It is particularly suitable for areas subject to severe expansion and contraction.

Claims (4)

[Claims] (1) A skin protective agent consisting essentially of the following basic ingredients. a, an acrylic polymer in which the monomer ratio of ethyl acrylate and methacrylic acid is within the range of 75/25 to 95/5, the residual monomer is 50 ppm or less, and substantially does not contain a surfactant. ~10%, b. Approximately 0.2-2% of cellulose derivative, and c. Residual amount of hydroalcohol. (2) The weight average molecular weight of the acrylic polymer is about 1
The skin protective agent according to claim 1, which has a molecular weight of 0,000 to about 1,300,000. (3) The skin protective agent according to claim 1, wherein the cellulose derivative is ethylcellulose. (4) The skin protective agent according to claim 1, wherein the alcohol is ethanol or isopropanol.