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Stabilized foam for medical PSA substrate

a technology of stabilizing foam and psa, applied in the direction of film/foil adhesives, bandages, drug compositions, etc., to achieve the effect of maintaining cleanliness of operation incision sites, and maintaining acceptable conformability properties

Inactive Publication Date: 2005-12-15
ETCHELLS MARC D
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention provides a stabilized foam that has softness and conformability properties approaching or even exceeding those of PVC. The foam can be used in both medical and skin contact applications. It exhibits improved stability and resistance to stretching during processing. The foam does not require the use of potentially hazardous plasticizers and does not have the disadvantages associated with PVC foams or non-stabilized polyolefin foams. The foam can be used to treat wounds, maintain cleanliness of operation incision sites, and monitor electrical impulses during EKG or deliver electrical impulses in a TENS or biofeedback therapy. It can also be used to soften scar tissue and collagen deposits in a scar and reduce the raised or keloid portion of the scar over time."

Problems solved by technology

An alternative unstabilized polyolefin foam material is presently in limited use.
There are several disadvantages to the use of PVC foams.
These plasticizers have been investigated for possible medical safety risk with a concern of migration from the foam into the skin.
Additionally, when bandages and tapes utilizing PVC foam are sterilized or simply aged, shrinkage of the foam is often observed.
This shrinkage can be minor and is generally considered to be only a visual problem.
But it can also be a more severe problem that can cause finished product rejections and / or can cause a visible exposed adhesive edge resulting from the PVC foam shrinking while the adhesive layer remains stable.
Shrinkage in the PVC foam can also cause curling or rolling of the finished product.
The plasticizer used in the PVC can also limit the selection of fillers and “actives” that could potentially be incorporated into or on the foam.
Additionally, via a process known as “plasticizer migration” the PVC plasticizer can flow to adjacent materials and effectively limits what materials and adhesives can be adjacent to it.
A typical problem is softening and expansion, even wrinkling, of an adjacent layer.
However, it also has several undesirable properties.
Polyolefin foams tend to be stiff and rigid when flexed and are easily torn or ripped.
It is believed that this cross-linking leads to the stiffness and tearing tendency.
In summary, if polyolefin foam is made to be thin and conformable, it is very weak and tears.
Conversely, if thickness or density is increased to decrease tearing, the foam is stiff and not conformable to the skin.
Stiffness is generally not a desired property for foam used in a skin contact application.
Thus, despite the presence of an adhesive layer, stiff foams do not remain attached during flexing and, as a result, tends to lift off the skin.
Although strong in the machine-direction, so is the tendency to tear.
For many potential end-use applications, this pronounced tear is a problem.
The physical apertures of the perforation imparted for breathability additionally weaken the foam and further promote tearing.
The low level of dimensional stability makes PO foams difficult to process through converting operations.
Tensions within the unwinding pull-roll and die cutting zones result in elongation often with delayed recovery or no recovery.
This tension and stretch imparted in the foam will often relax after processing and result in differential shrinkage of components and / or curling of the finished products.
As thinner grades of PO foam are converted, the stretch and curling problems become exaggerated.
However, there have been no suitable alternatives found to date that meet all the design criteria listed above.
The reasons for the absence of suitable alternatives include the following: (1) polyvinyl alcohol foams are difficult to manufacture and not readily commercially available; (2) polyurethane foams offer good physical properties but are very expensive; (3) silicone foams also offer good properties but are more costly than the polyurethanes; and (4) although polyolefin foams are relatively low cost, they have poor dimensional stability, exhibit stretching especially when thin and tend to rip or tear when stressed, particularly when a bandage is removed from a wound.
Thus, because of their stiffness, polyolefin foams generally have poor adhesion to the skin and are not conformable to the skin when flexed.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0104] A cross-linked closed cell polyolefin foam sourced from Voltek, a div. of Sekisui America Corporation. The foam is a 6-lb / cubic foot density foam that is extrusion coated with a linear low density polyolefin (LLDPE) stabilizing layer on one side. The color is a medium tan or “flesh” color and the total foam thickness is 0.023 inch. This extrusion coating is 0.002 inch thick and is corona treated to assist in firm anchorage of the adhesive layer. Following extrusion coating, the combined thickness is approximately 0.025 inch. The release liner is a 42-lb / ream bleached Kraft paper, available from SilTech division of Technicote, which has been coated with a silicone release coating on one side. The adhesive is a conventional block copolymer synthetic rubber hot melt from HB Fuller and is applied via a melter and gear pump that delivers the adhesive to a slot coating die. The die is from May Coating and it is set up for direct contact or proximity coating against the silicone lin...

example 2

[0107] Cross-linked PO foam is manufactured at 0.016 inches thick with a density of 8-lbs / cubic foot and is extrusion coated with an ultra low density polyolefin film layer at 0.0015 inch thickness. A 0.003 inch polyester film that has been coated with a fluorosilicone release coating for use with silicone adhesives is proximity coated with a Dow Corning hot melt adhesive formulated with silicone.

[0108] The stabilized foam, adhesive layer and silicone release liner are all brought together in a nip between two rollers and the adhesive transfers to the stabilized foam. The assembly is rotary die cut and is useful for EKG grounding pads.

[0109] If required for a grounding pad application, a conductive material such as carbon black, carbon film or carbon fibers can be added to the foam, stabilizing layer and / or adhesive layer. The stabilizing layer allows the production of a thin and soft foam pad with the integrity required for die cutting and converting.

[0110] If the silicone adhes...

example 3

[0111] Cross-linked PO foam is manufactured at 0.031 inches thick with a density of 6-lbs / cubic foot and is extrusion coated with a LLDPE film layer at 0.002 inch thickness. A liquid acrylic adhesive in a solvent, Gelva 2999 from Solutia, is reverse roll coated onto 53-lb Kraft release liner supplied by SilTech. The solvent is driven off as the coated liner travels through a heated oven. As the coated liner exits the oven, it is married to the stabilized foam with a set of rollers. Following slitting to width and perforation via the hot needle system, the laminate is converted into finger bandages and tape.

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Abstract

The present invention provides a stabilized foam having a crosslinked closed cell polyolefin foam having a top and a bottom surface; a stabilizing layer disposed onto at least one of the top and the bottom surfaces of the crosslinked closed cell polyolefin foam; and an adhesive layer disposed onto at least one of the top or the bottom surfaces. Also provided is a method of preparing the stabilized foam, a method of treating a wound, scrape, abrasion or skin puncture, a method of maintaining cleanliness of an operation incision site, suture site, catheter insertion site, or an intentional skin breach site, a method of monitoring electrical impulses during EKG or delivering electrical impulses in a TENS or biofeedback therapy, and a method of softening the collagen deposits on a scar and reducing the raised or keloid portion of the scar over time.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a stabilized foam. More particularly, the present invention relates to a stabilized foam suitable for use in medical and skin contact applications, having a crosslinked closed cell polyolefin foam, at least one stabilizing layer and at least one adhesive layer. [0003] 2. Description of the Related Art [0004] For a variety of medical and skin contact products including first-aid bandages, tapes, absorbent dressings, wound covers and closures, scar reduction therapy pads, electrode grounding pads and drug delivery patches, foam is used as the exterior layer away from the skin. A skin contact adhesive is applied to this foam to provide adhesion to the skin. Many adhesives are in use and include acrylics in hot melt, solvent solution or aqueous suspension, synthetic block copolymer and other hot melts, silicone gels and silicone from solvent or hot melt systems. Often such foam films are...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A61L15/42A61L15/58B32B3/00B32B3/26B32B5/18C08K3/00C09J7/26
CPCA61L15/425A61L15/58B32B5/18C08J2205/052C09J7/0289C09J2201/28C09J2483/003C09J2423/006C09J2431/003C09J2433/00C09J2475/003C09J2477/003C09J2483/00C09J2423/003C09J7/26Y10T428/249982Y10T428/249953Y10T428/249985Y10T428/249977Y10T428/249976Y10T428/249987A61P17/02C09J2301/204B32B2535/00B32B2266/08B32B2305/72B32B38/04B32B7/12B32B2266/025B32B2307/72
Inventor ETCHELLS, MARC D.
Owner ETCHELLS MARC D
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