Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1995-03-29
1996-10-08
Mullis, Jeffrey C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
525 541, C08H 100
Patent
active
055631916
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a phase-separated membrane which is used as a permeation membrane for drugs and other chemical substances, and the like.
TECHNICAL BACKGROUND
As a drug-releasing controlling membrane (a drug permeation membrane) used in a plaster preparation for a transdermal administration, a polymer membrane of an ethylene vinyl acetate copolymer, an acrylic resin, a polyethylene, ethyl cellulose, etc., and a porous membrane thereof, or a membrane of gelatin which is a natural material have been known hitherto. The gelatin membrane includes a porous membrane which is prepared by adding a crosslinking agent to an aqueous solution of gelatin and an aqueous solution of dextran to form a membrane and, after drying, soaking the membrane into water to remove dextran; a membrane prepared by adding glycerin and a crosslinking agent to an aqueous solution of gelatin to form a membrane, followed by drying; and the like. These gelatin membranes are not irritative to the skin and do not cause inflammation and, from this standpoint, are considered to be superior to the above-described polymer membrane.
However, with respect to these gelatin membranes, it is difficult to control the rate of transfer of a minute amount of a certain type of drugs in the membrane and to control its amount to be permeated. With respect to the above-described polymer membrane, these controls have been found more difficult.
Since some of the drugs for transdermal administration are required to be absorbed gradually into the skin in a minute amount over a long period of time. In this case, it is necessary to strictly control the amount absorbed into the skin. Accordingly, the membrane which is unable to strictly control the rate and the permeating amount of a minute amount of the drug, such as the conventional gelatin membrane and polymer membrane, has a problem that it cannot be used as a releasing controlling membrane (a permeation membrane) for the drug which requires the above-described controls.
The present invention has been achieved in the light of the above-described problems, and an object thereof is to provide a phase-separated membrane which is capable of easily controlling a permeation rate and the permeation amount of a minute amount of drugs or other chemical substances.
DISCLOSURE OF THE INVENTION
The present invention relates to a phase-separated membrane wherein a crosslinked gelatin phase and an uncrosslinked segmented polyurethane phase are present as a mixture.
The membrane having separated phases (hereinafter simply referred to as "a phase-separated membrane") means a membrane in a state where two or more different phases are present in the membrane as a mixture. An interface of the phases is physically weak, and permeation is considered to occur from the boundary.
Polymer alloys which are multi-component polymer systems comprising a combination of chemically different polymers are classified into a group having a micro-phase-separated structure of a block or graft copolymer in which heterogeneous polymers are linked through a covalent bond, and a group of a polymer blend having a phase-separated structure in which heterogeneous polymers are present as a mixture in a macro-phase. The phase transition when these polymer alloys are cooled from their molten state proceeds over a broad temperature range, and the polymer having a higher crystallization temperature (Tc) tends to cause the phase-separation earlier.
The phase-separated membrane of the present invention belongs to the latter polymer blend. The membrane can be obtained by the solution-cast blends method in which the membrane is made by casting of a solution in water which is a solvent for both of the gelatin and the segmented polyurethane.
Generally, in an amorphous polymer blend system, a phase separation showing the phase pattern of LCST type (a lower critical solution temperature) and UCST type (an upper critical solution temperature) occurs. In this case, the phase pattern of a two-component system of a liquid/liquid phase separ
REFERENCES:
patent: 4762899 (1988-08-01), Shikinami
patent: 4997656 (1991-03-01), Shikinami et al.
patent: 5080292 (1992-01-01), Nishibori
patent: 5225536 (1993-07-01), Nishibori
Mullis Jeffrey C.
Takiron Co., Ltd.
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