Title:  Antimicrobial containing solventless hot melt adhesive composition

United States Patent:  6,503,531

Issued:  January 7, 2003

Inventors:  Cox; David D. (Woodbury, MN); Lund; Robert E. (Eagan, MN); Annett; Leland W. (Baytown, MN)

Assignee:  Medical Concepts Development, Inc. (St. Paul, MN)

Appl. No.:  836764

Filed:  April 17, 2001

An adhesive composition having dispersed therein a broad spectrum antimicrobial agent for use in medical applications, such as an adhesive for surgical drapes, wound dressings and tapes. The adhesive is composed of acrylic polymers, tackifiers and a preferred antimicrobial agent, diiodomethyl-p-tolylsulfone. The adhesive composition is essentially solventless and capable of application in a hot melt process while maintaining stability at elevated temperatures in the range of 275^o F. to 350^o F., which not only allows hot melt application, but allows for ethylene oxide sterilization under heat stress.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the present invention which may be embodied in various systems. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to variously practice the present invention.

The present invention is an adhesive compound which incorporates an adhesive component together with a broad spectrum antimicrobial agent dispersed therethrough. The antimicrobial agent is homogeneously dispersed throughout the adhesive layer 10. Active antimicrobial molecules of the present composition disassociate from the surface or leach out of the adhesive matrix over time, delivering biocidal activity at a distance from the adhesive surface 12. Applicants have conclusively demonstrated by zone of inhibition tests on a wide variety of infections organisms the efficacy of the present composition. These tests showed that microbes were inhibited and killed at a distance from the sample as detailed in the attached experimental examples.

The adhesive of the present invention is specifically suited for use in skin contact applications during and after medical procedures, for example; as an adhesive in surgical drapes 16, wound dressings and tapes. The adhesive composition is a hot melt adhesive. By hot melt adhesive, it is meant that the adhesive is essentially solventless or 100% solids and flowable at elevated temperatures for application to a substrate material 14, such as a surgical drape. The preferred adhesive composition incorporates acrylic polymers and added tackifiers to form a pressure-sensitive adhesive which is particularly suited for use in surgical procedures.

A preferred combination of acrylic polymers to form the adhesive composition includes the combination of a low molecular weight solid acrylic polymer and a medium molecular weight solid acrylic polymer in a ratio of about 1 to 4, respectively, to optimize the adhesion of the adhesive to skin, cohesion and resistance to cold flow. A low molecular acrylic polymer is a polymer having a molecular weight ranging from about 90,000 to about 120,000, while a medium molecular weight acrylic polymer has a molecular weight ranging from about 140,000 to about 160,000. Suitable low molecular weight solid acrylic polymers and medium molecular weight solid acrylic polymers are available from Schenectady International, Inc. under Product Nos. HRJ-4326 and HRJ-10127, respectively.

The adhesive component of the composition can also include tackifiers as are well known in the art. Tackifiers contemplated include SYLVATEC, ZONAREZ and FORAL which are available from Arizona Chemical and Hercules, Inc.

As previously stated, the adhesive compound is a hot melt adhesive. A preferred composition has a feasible temperature range for working with the hot melt adhesive in the range of about 275^o F. to 350^o F. The preferred temperature range for compounding and coating with the adhesive is 290^o F. to 320^o F.

Applicants have found that the addition of a heat stable antimicrobial agent to the above adhesive composition results in an effective antimicrobial adhesive composition. In particular, Applicants have found that the addition of diiodomethyl-p-tolylsulfone to the above adhesive composition results in an effective antimicrobial adhesive which retains desirable properties during use and application at 275^o F. to about 350^o F. A preferred loading of antimicrobial agent to the adhesive is in the range of about 0.1% to about 2% by weight. A preferred loading is about 0.2% by weight to about 0.6% by weight of diiodomethyl-p-tolylsulfone to adhesive. The resulting heat stable antimicrobial containing adhesive is 100% solids and eliminates the need for use of a solvent and the requisite evaporation of such solvent. The hot melt adhesive can also be ethylene oxide sterilized under heat stress or radiation sterilized without loss of effectiveness of the antimicrobial.

A preferred source of diiodomethyl-p-tolylsulfone is AMICAL 48, available from Angus Chemical Company.

The antimicrobial containing adhesive composition of the present invention is manufactured by mixing thoroughly at elevated temperature the acrylic polymers and tackifiers. A temperature of about 250^o F. to about 260^o F. has been found to be adequate. Once mixed, the polymers and tackifiers are heated to 310^o F. to 350^o F. with continued mixing until uniform, followed by cooling to 290^o F. to 295^o F. The diiodomethyl-p-tolylsulfone is then added to the polymer and mixed until uniform. The resultant composition is packaged and cooled for subsequent hot melt applications.

As detailed below, the antimicrobial adhesive of the present invention was shown to be effective against a wide variety of microorganisms. The antimicrobial activity was determined by using a series of zone of inhibition tests, as are well known in the art. The effective release of antimicrobial from the adhesive is estimated from the measurement of a zone of inhibition (an area of inoculated plate where organisms do not grow) surrounding the sample.

The adhesive utilized for the tests included 2% diiodomethyl-p-tolylsulfone homogeneously dispersed as detailed above in an adhesive composition. The adhesive composition included 17% low molecular weight acrylic polymer (HRJ-4326 from Schenectady International, Inc.) and 67% medium molecular weight polymer (HRJ- 10127 from Schenectady International, Inc.) along with 16% FLORAL 105 synthetic resin from Hercules, Inc. as a tackifier. The adhesive composition was prepared as detailed above. The adhesive composition was then melted and applied to a substrate layer 14 in a thin coating (approximately 0.05 mm in thickness). The substrate was a co-polyester surgical drape material available from DuPont under the tradename HYTREL. The coated substrate 14 was cut to 6.0 mm disks for use in testing.

Adhesive coated disks were then exposed to microorganisms using the following procedure:

1. A microbial suspension containing .apprxeq.1.0x10⁸ organisms per ml in TSB was compared to the turbidity of a 0.5 MacFarland Standard.

2. A sterile swab was dipped into the culture suspension. The swab was rotated several times, pressing firmly on the inside wall of the tube above the fluid level. This removed excess inoculum from the swab.

3. The surface of a Mueller Hinton agar plate was inoculated by streaking the swab over the entire sterile agar surface. This streaking procedure was repeated two more times, rotating the plate approximately 60^o each time to ensure an even distribution of inoculum.

4. The paper liner was removed from each 6 mm adhesive coated disc and the film was aseptically placed adhesive side down on the surface of the inoculated agar plate. Control samples were handled identically.

5. Immediately following the addition of the discs, the Mueller Hinton agar plates were placed in ambient air at 35-37^o for 18-24 hours. Following incubation, the zones of inhibition surrounding the discs were measured. When no zone was observed, the disc was aseptically removed and the area beneath the disc was evaluated for growth of the test organism. The tests were repeated two or three times, using relevant microorganisms. Experimental results are presented in the table below, reported as the average diameter zone of inhibition surrounding/under 6.0 mm samples. A 6.0 mm zone of inhibition indicates no growth of the test organism beneath the 6.0 mm test discs, while larger zones indicate effective antimicrobial activity at a distance from the disc.

 

These results indicate that the present adhesive is effective in inhibiting these eleven relevant organisms, even after hot melt processing and ethylene oxide sterilization.

New characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts, without exceeding the scope of the invention. The scope of the invention is, of course, defined in the language in which the appended claims are expressed.

Claim 1 of 4 Claims

What is claimed:

1. A hot melt adhesive composition having antimicrobial properties for skin contact applications, said composition comprising a matrix of an acrylic polymer in combination with an effective amount of diiodomethyl-p-tolysulfone dispersed therethrough, active antimicrobial molecules of said diiodomethyl-p-tolysulfone being disassociated from a surface of said matrix over time, said composition being stable at temperatures ranging from about 275^o F. to 350^o F. so as to permit ethylene oxide sterilization under heat stress, and applications as a hot melt.

 

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