JPS6260101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet-shaped hydrogel that is applied to the skin and the like.

A hydrogel obtained by adding an aqueous solution or suspension of an aluminum compound to an aqueous solution of a methoxyethylene/maleic anhydride copolymer or its salts and reacting in a pH range of 3 to 7 has the following properties. It has

(1) Self-shape retention This gel can contain a large amount of water inside, has low fluidity, and exhibits strong elasticity.
Does not disintegrate easily even under pressure. However, it is easily cut under tension and is an elastic gel with almost no malleability.

(2) Water-holding property Even if the material contains more than 80% of its volume of water and is compressed, no water will be expelled. Also, when you touch its surface, you only feel a slight dampness, and your hand does not get wet.

(3) Thermal stability Even after this gel was sealed in an aluminum foil bag and placed in a constant temperature bath at 50°C for two weeks, it retained its original shape, and the gel retained its original shape except for evaporation. No leaching of water as a result of the so-called syneresis phenomenon is observed.

(4) Transparency When producing a gel, if reaction conditions are selected such that no precipitation of insoluble aluminum compounds is present in the system, the resulting gel will be extremely transparent and homogeneous. .

(5) Water absorption Even when it contains a large amount of water, it swells when it comes into contact with water and absorbs even more water. Also, if you put the gel in water,
Expands approximately 3 times in volume.

(6) Moisture release (endotherm) When the gel is left indoors, water gradually evaporates from its surface. At this time, the latent heat of vaporization is taken away, so the gel is always kept at a temperature lower than room temperature.

The present invention has been made with the object of providing a sheet-shaped hydrogel having the above-mentioned characteristics, which can be easily used for applications such as prescription medicines. That is, the sheet-shaped hydrogel of the present invention has the above-mentioned high hydrogel layer,
It is constructed by enclosing a water-permeable sheet-like material, such as a sheet-like mesh, and eliminates the drawbacks of gel, such as being weak against tension and having poor spreadability. Therefore, this sheet-shaped hydrous gel can be used as a base for medicines, medical supplies, cosmetics, daily necessities, etc., as a base for medicines, cooling supplies for fever-affected areas, cushions and pack bases for preventing pressure sores, and cooling headbands. can be used to advantage.

Many gel-like pastes have been used in sheet form for these purposes. For example, in the case of a drug base, the paste is applied or spread on a support such as flannel. This paste is obtained by adding powder components such as kaolin and bentonite to a highly viscous paste that is mainly composed of natural or synthetic thickeners, natural or synthetic water-soluble polymer compounds, natural or synthetic water-retaining agents, and water. It consists of a viscous sol with moderate viscoelasticity, can be applied or spread, shows shape retention on a support,
Does not show fluidity at room temperature. However, quality deterioration cannot be avoided due to long-term storage, heating, or water absorption.

On the other hand, the high water content gel used in this invention has self-shape retention, water retention, thermal stability, water absorption,
Although it has the excellent properties mentioned above in terms of moisture dissipation, it does not have enough viscosity to be made into a sheet, and it easily tears when subjected to tension, and even if it can be formed into a sheet, it However, during use, it has the disadvantage that it easily tears due to tension or twisting at the place where it is applied, and it is also difficult to apply and spread it on a support such as flannel.

The present inventor took advantage of the advantages of this high water content gel,
As a result of conducting research to compensate for the lack of spreadability, we succeeded in solving this problem by encapsulating a water-permeable sheet material in a high water content gel layer. Encapsulation of a sheet-like material into a gel layer involves pouring a certain amount of the ungelled composition into a dish-shaped container, covering it with a sheet-like material, and allowing the sheet-like material to absorb the composition by its own weight. This can be carried out by submerging the composition into a substance, preferably to half the depth of the composition, and allowing the composition to gel in this state. As is clear from this, it is necessary to control the gelation rate of the composition in order to obtain the desired settling of the sheet-like material, and this control is achieved by using methoxyethylene/maleic anhydride copolymer or its gelling rate. This can be done by adjusting the PH value of a composition in which an aqueous solution or suspension of an aluminum compound is added to an aqueous solution of a salt. When controlling in the PH range of 3 to 7, the higher the PH value, the slower the gelation rate becomes, and in the PH range of 4.5 to 5.5, the gelation time can be delayed up to about 4 hours. .

It is also possible to pour the composition into a dish-shaped container to about half its depth, allow it to gel, place a sheet on top of it, and pour the composition from above to gel it. , a sheet-like material can be encapsulated in a hydrogel layer. Although it is preferable that the sheet-like material be completely encapsulated in the hydrogel layer, there is no problem even if a part of the sheet-like material is exposed on the surface of the hydrogel layer.

The water permeable sheet material used in this invention is:
A sheet-like material having water permeability that allows the non-gelled composition to exude or pass through, and a water-impermeable sheet material having through holes provided therein, may also be used, but a sheet-like mesh material is particularly preferred. Examples of such sheet-like mesh bodies include gauze, cheesecloth, coarse woven or nonwoven fabrics, nylon nets, coarse natural or synthetic fiber layers, and the like. However, it must be insoluble in water.
Moreover, the enclosure is not limited to one sheet, but a plurality of sheets may be enclosed, for example, in a scrambled manner.

Next, embodiments of the invention will be described.

Dissolve 50 g of methoxyethylene/maleic anhydride copolymer in 500 ml of water. Caustic soda 17 to this
Add g and 100 ml of 2M lactic acid to adjust the pH to 4.5-5, and then add 2.5% aluminum hydroxide suspension 190
ml, then add water to make a total volume of 1000g. The composition obtained here was poured into a dish-shaped container 1 shown in FIG. 1 to a desired depth, and a sheet-shaped mesh 2 was placed on the surface thereof. This sheet-like mesh 2 gradually sank due to its own weight, and after several minutes sank to about half the depth of the composition. The composition lost its fluidity after about 1 hour, after which the surface was covered with tissue paper 4.

The obtained sheet-shaped hydrogel has a sheet-shaped mesh 2 approximately in the center of the gel 3, as shown in FIG.
is enclosed, and its surface is covered with thin paper 4.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a sheet-shaped hydrogel obtained according to an embodiment of the present invention, and FIG. 2 is a partially cutaway perspective view of the same sheet-shaped hydrogel. 1... Container, 2... Sheet mesh, 3...
Hydrogel, 4...Thin paper.

Claims (1)

[Claims] 1. A sheet-like hydrogel formed by enclosing a water-permeable sheet-like material in a sheet-like high-water-containing gel layer mainly composed of a methoxyethylene/maleic anhydride copolymer or its salts and an aluminum compound.