Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-29
2002-09-10
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S111000, C523S113000, C424S448000, C424S449000
Reexamination Certificate
active
06448303
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an adhesive composition. In particular, a hot melt pressure-sensitive adhesive for dermal applications.
BACKGROUND OF THE INVENTION
Adhesives for application to the skin are permanently tacky at room temperature, hold the adhered article to the skin with gentle pressure, and should be easily removed without causing pain or depositing adhesive residue. Useful adhesives need to adhere well to human skin during perspiration, when the weather is hot, or in an environment of draining wounds.
Painless removal of adhesive articles from hair-covered regions of skin is especially difficult. For such regions, a soft adhesive with minimal viscoelastic loss is required. Hydrogels have been used effectively for such purposes, but have their own disadvantages, including high price, special packaging and release layers to retain the moisture (typically about 40% of the total adhesive), as well as variations in properties during use in response to changes in humidity.
Commonly assigned U.S. Pat. No. 5,559,165 improved upon the state of the art by providing a hot melt pressure sensitive adhesive having the desirable characteristics of a hydrogel, but not the drawbacks associated with their use. While U.S. Pat. No. 5,559,165 represents a substantial contribution to the art, there continues to be a need for improvements and modifications in hot melt adhesives for use in dermal applications, in particular hot melt adhesives which leave no residue upon removal from the skin.
SUMMARY OF THE INVENTION
The invention provides a hot melt pressure sensitive adhesive especially suited for adhesive skin application, including transdermal drug delivery applications. The invention is based on the discovery that hot melt pressure sensitive adhesives formulated with higher mid-block Tg's and less liquid diluent, in particular less liquid tackifier, than conventional hot melt pressure sensitive adhesives heretofore known and used in the art give good skin adhesion and leaves less adhesive residue on the skin.
One aspect of the invention is directed to a pressure sensitive hot melt adhesive composition. The adhesive comprises high molecular weight rubber and less than about 60 parts by weight, more preferably from about 35 to about 55 parts by weight, based on the total weight of the composition, of a liquid diluent. Preferred adhesive compositions of the invention comprise from about 1 to about 20 parts by weight of a high molecular weight rubber triblock or radial block copolymer, from 0 to about 20 parts by weight of a high molecular weight diblock rubber, 0 to about 10 parts by weight of other compatible high molecular weight polymers, 0 to about 30 parts by weight of an end block resin, 0 to less that about 60 parts by weight oil or other liquid midblock diluent, 0 to about 60 parts by weight of a solid tackifier and 0 to about 3 parts by weight of an anti-oxidant.
Another aspect of the invention is directed to a transdermal drug delivery system comprising a pressure sensitive hot melt adhesive and a therapeutic agent. The agent, while physiologically active, may or may not be pharmaceutically active. In one embodiment, the adhesive serves as a carrier for the physiologically active agent.
Still another aspect of the invention is directed to a transdermal drug delivery system comprising an adhesive layer, a therapeutic agent and a backing layer. In one embodiment, the drug delivery system also comprises a release layer. In another embodiment of the drug delivery system the drug to be delivered is incorporated into the adhesive.
Yet another aspect of the invention is directed to a method of administering a therapeutic agent to a patient comprising applying to a body surface of the patient a transdermal drug delivery system comprising a pressure sensitive hot melt adhesive and a physiologically active agent.
DETAILED DESCRIPTION OF THE INVENTION
The disclosures of all documents cited herein are incorporated in their entireties by reference.
As used herein, the term “pressure-sensitive adhesive” refers to a viscoelastic material which adheres instantaneously to most substrates with the application of slight pressure and remains permanently tacky. A polymer is a pressure-sensitive adhesive within the meaning of the term as used herein if it has the properties of a pressure-sensitive adhesive per se or functions as a pressure-sensitive adhesive by admixture with tackifiers, plasticizers or other additives.
Preferred adhesives will generally have a midbock Tg of from about −30° C. to about room temperature, more preferable from about −30° C. to about 10° C. Useful adhesives will preferably have a G′ (storage modulus) less than about 15×10
4
dynes/cm
2
at 10 rad/s. (25° C.), preferably at least about 1×10
4
and most preferably from about 4 to 10×10
4
dynes/cm
2
. Low G′ provides a soft adhesive that easily wets at rough surfaces such as skin. The adhesives will also preferable have a G″ (loss modulus) of about 1 to 6×10
4
dynes/cm
2
. It has been found that maintaining G″ within this range ensures adequate hold while ensuring painless removal. A tensile strength greater than 10 psi is necessary to ensure that the adhesive does not fail cohesively upon removal.
As used herein the term “high molecular weight rubbers” are those having a viscosity at 25° C. of above 1,000 cP in toluene at a concentration of 20% by weight.
In the case of the high viscosity triblock copolymers employed herein, they may have the more general configuration A-B-A wherein the polymer blocks A are non-elastomeric polymer blocks which, as homopolymers have glass transition temperatures above 20° C., while the elastomeric polymer blocks B are isoprene, or butadiene which may be partially or substantially hydrogenated or mixtures thereof. Further, the copolymers may be linear or branched. Typical branched structures contain an elastomeric portion with at least three branches which can radiate out from a central hub or can be otherwise coupled together. The amount of the triblock component is preferably from about 1 to about 20 parts by weight, more preferably about 3 to about 8 parts by weight.
The non-elastomeric blocks may comprise homopolymers or copolymers of vinyl monomers such as vinyl arenes, vinyl pyridines, vinyl halides and vinyl carboxylates, as well as acrylic monomers such as acrylonitrile, methacrylonitrile, esters of acrylic acids, etc. Monovinyl aromatic hydrocarbons include particularly those of the benzene series such as styrene, vinyl toluene, vinyl xylene, ethyl vinyl benzene as well as dicyclic monovinyl compounds such as vinyl naphthalene and the like. Other non-elastomeric polymer blocks may be derived from alpha olefins, alkylene oxides, acetals, urethanes, etc. Styrene is preferred.
The elastomeric block component making up the remainder of the copolymer is isoprene or butadiene which may be hydrogenated as taught, for example, in U.S. Pat. No. 3,700,633. This hydrogenation of butadiene may be either partially or substantially complete. Selected conditions may be employed for example to hydrogenate the elastomeric butadiene block while not so modifying the vinyl arene polymer blocks. Other conditions may be chosen to hydrogenate substantially uniformly along the polymer chain, both the elastomeric and non-elastomeric blocks thereof being hydrogenated to practically the same extent, which may be either partial or substantially complete. Hydrogenated polymers are preferred to minimize degradation during processing, which is a more severe problem with higher molecular weight polymers.
The high viscosity triblock copolymer of the invention can have a broad range of non-elastomeric end block to elastomeric center block ratio of approximately about 5:95 or less to about 40:60 or higher. Examples of high viscosity triblock copolymers that can be utilized to achieve one or more of the novel properties of the present invention are styrene-ethylene-butylene-styrene block copolymers (SEBS) available from Shell Ch
Cain Edward J.
Foulke Cynthia L.
National Starch and Chemical Investment Holding Corporation
Yeh James T.
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