Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-08-22
2004-03-23
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S022000, C524S045000, C524S054000, C524S055000, C524S474000, C428S497000, C428S532000
Reexamination Certificate
active
06710100
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of International application number PCT/GB00/03931, filed Oct. 13, 2000, which in turn claims priority of British application number 9924374.3, filed Oct. 14, 1999, and British application number 9924375.0, filed Oct. 14, 1999.
This invention relates to a fluid-absorbing, composite material that is pressure-sensitive and comprises a continuous phase formed from a pressure-sensitive adhesive matrix and a discontinuous phase substantially comprised of one or more natural or synthetically derived water soluble and/or water insoluble absorbents.
Pressure sensitive adhesive materials are used in many medical device fields and are made into products such as tapes, bandages, surgical drapes, IV dressings and the like. Hydrocolloid pressure sensitive adhesives are medically useful adhesives that have been known for about 30 years and were originally developed as bandages for the oral cavity to aid in delivery of drugs to the gingiva. Hydrocolloid adhesives have been hitherto unique in that they are inherently adhesive and inherently absorbent. They are useful as wound dressings because they can be applied directly to open wounds and secured on the surrounding intact skin, and as skin barriers because they protect the peristomal skin of ostomy patients. Many hydrocolloid skin barriers are known and are used for these purposes. The more modern of these adhesives are “integrated”. In this context, “integrated” means those compositions that substantially retain their dimensional stability and form when saturated with wound exudate and/or other body fluid. “Non-integrated” means those compositions which become soft gels and amorphous as they become saturated with fluid. The shear strength of both integrated and non-integrated compositions can be improved using the teachings of the present invention, and the integrity of non-integrated compositions will also generally be increased.
The first hydrocolloid compositions to be described were non-integrated. U.S. Pat. No. 3,339,546 discloses compositions which are inelastic, and which are non-integrated, i.e. which do not maintain their dimensional stability and become amorphous when imbibed with wound fluid or other body fluid. A typical formulation taught by this prior art is the composition formed from low molecular weight polyisobutylene (40% by wt), pectin (20% by wt), sodium carboxymethyl cellulose (20% by wt) and gelatin (20% by wt). This formulation was used as a dressing for the gingiva but is also believed to be the basis of commercially successful skin barrier and wound care products. Such compositions form a soft gel when in contact with an exuding wound, and the resultant gel remains in the wound when the dressing is removed. This lack of integrity is a drawback. The gel must be removed from the wound at the time the dressing is changed. This is usually done by irrigation, which is time consuming for the nurse and painful for the patient. Adhesives taught by this patent also normally have relatively low shear strength, which can be a drawback in some use situations, particularly those in ostomy care, where the adhesive must retain on the abdomen a pouch containing body waste.
The lack of integrity was a serious drawback in the use of these dressings and barriers and much development was completed in efforts to overcome the deficiency. Thus, British Patent 1,576,522 corresponding to U.S. Pat. No. 4,231,369, describes improved hydrocolloid compositions that are integrated. There is provided a sealing material for ostomy use consisting of a hydrocolloid dispersed in a continuous phase of styrene-isoprene-styrene copolymer, or other thermoplastic elastomer such as an ethylene-propylene copolymer. Also present is a hydrocarbon tackifier and optionally an oil extender and an antioxidant. This material is said to have the advantage of being elastomeric and flexible. However, the absorption rate is lower than hydrocolloids made in accord with U.S. Pat. No. 3,339,546.
The shortcomings of barriers and dressings based upon formulae such as are described in U.S. Pat. No. 3,339,546 are also recognised by both U.S. Pat. No. 4,477,325 and U.S. Pat. No. 4,738,257. These two later patents disclose barriers and dressings based on an integrated formulation containing a continuous phase composed of a blend of high vinyl acetate EVA copolymer (51% wt VA and 49% wt ethylene) and low molecular weight polyisobutylene, in which is dispersed a discontinuous phase containing a blend of a superabsorbent material, pectin and sodium carboxymethyl cellulose. The function of the EVA copolymer is to cross link in the presence of ionising radiation, such as gamma radiation at a dosage of, for example, 25 KGy, which would be used to sterilise dressings formed from the compositions of the invention. The cross-linked network is formed essentially from the EVA polymer by irradiation of the EVA containing elastomeric phase. If the composition is to be used as an ostomy barrier, the gamma radiation is an expensive process to achieve integration, because ostomy products are not normally sold sterile. If the adhesive composition is used non-sterile, its shear strength is low.
U.S. Pat. No. 4,551,490 describes integrated hydrocolloid adhesives modified by diluting the amount of styrene-isoprene-styrene block copolymer present in the composition. The patent provides a medical grade pressure sensitive adhesive composition comprising a heterogeneous mixture of one or more polyisobutylenes or blends of polyisobutylenes and butyl rubber, one or more styrene radial or block copolymers, a tackifier, mineral oil and one or more water soluble and/or swellable hydrocolloid gums. It is believed that the polyisobutylenes, butyl rubber, mineral oil and tackifier serve to modify and plasticise predominantly the isoprene segment of the block/radial copolymer. In particular, the mineral oil is said to provide increased extensibility and aggressiveness of the adhesive. It is believed that the teachings of this patent form the basis of the commercially available hydrocolloid dressing products DuoDerm and Signa Dress. However, it has been found that the rates of absorption of saline with these compositions is very slow, and not very reproducible, and moreover very much less than the absorption levels available with the compositions of U.S. Pat. No. 3,339,546.
Our co-pending Application WO99/14282 describes a pressure sensitive adhesive material made of a weakly elastic mixture comprising a continuous phase formed from a blend of a physically cross-linked solid rubbers such as a styrene-isoprene-styrene triblock copolymer with a styrene-isoprene diblock copolymer, a compatible tackifying resin and a low molecular weight polyisobutylene, optionally modified by inclusion within the continuous phase of a quantity of butyl rubber, and a discontinuous phase comprising one or more hydrocolloids that are soluble and/or swellable in water. Small quantities of additives such as stabilisers and fumed silica may be present. The adhesive layer can be combined with a non-adhesive, water impervious film and can be used in wound care, ostomy care and in other medical products.
Our co-pending Application WO99/11728 describes a pressure sensitive adhesive material made of an elastic mixture comprising a continuous phase formed from a physically cross-linked solid rubber such as a styrene-isoprene-styrene block copolymer, and a compatible liquid rubber, such as a liquid styrene-isoprene rubber, and a discontinuous phase comprised of one or more absorbents that are swellable or soluble in water. Resinous materials are preferably absent, but additives such as polybutenes, polyisobutylene, mineral oil, stabilisers, and other rubbers, may be present. The pressure sensitive adhesives have the advantage over the prior art that they are extremely well integrated and contain no materials known to irritate skin and mucous membranes.
The composition of the present invention is characterised in that it contains 0.1 to 50% by weight, based on the conti
Avery Dennison Corporation
Christie Parker & Hale LLP
Sanders Kriellion A.
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