Coating with the VCM for Care with Care
By Tom Kerchiss, RK Print Coat Instruments
RK Print Coat Instruments Ltd have designed, manufactured and delivered their flagship VCM Coater to a number of companies engaged in the R & D, trialing and production of medical diagnostic and advanced wound care (dressings) products.
Bringing a product such as wound dressing or a medical diagnostic woven or a non-woven structure to market is a lengthy, complex and multi-step process that includes research and development, design, product verification, validation, regulatory compliance and market placement. Products must be manufactured to tight tolerances and to exact specification. Coating and coaters are important process tools as adhesive coated medical foams, PS fixation devices, diagnostic strips, grounding pads, breathable films rely upon coating systems to a large degree in the functionality and form of the finished product. Pilot coating systems, those that can monitor the process, enable comparison materials, formulae, etc., to be trialed or those coating systems that enable the research and development team and converting shop floor to bring a concept to realization, economically and to the satisfaction of regulatory agencies, health and safety executives and others is welcome.
The use of dressings in wound management can be traced back to the early Egyptians. A papyrus dated to somewhere between 3000 – 2500 BC indicates that wound dressings comprised of resins, honey, lint and even fresh meat were applied to wounds. Wounds were then covered with strips of linen secured with a sticky gum.
Fast forward a few thousand years or so to today, where there is an almost unlimited number of general and highly specialized wound care products and diagnostic aids available with many more products in the process of being developed. Though we might pride ourselves on the advances we’ve made in technology it’s a sobering thought that at least two of the natural products that the Egyptians used are still used today: Manuka honey and Aloe Vera.
Advances have bought us transparent dressings; film dressings consisting of a polymer membrane of varying thicknesses coated on one side with an adhesive. They are impermeable to water and other liquids and to bacteria but are permeable to moisture vapor and gases. Other options for dressings include the composites; essentially a single product that is comprised of multi-functional, multiple layers that incorporates a semi or non-adherent pad that covers a wound. Composite dressings often feature as part of their make up an adhesive border of a non-woven fabric tape or an adhesive coated transparent film.
Wound care and diagnostics also include the anti-microbial dressings, collagens, elastic bandages, the gauzes and non-woven; the amorphous and/or impregnated hydrogels; the impregnated dressings, absorptive dressings, and so on. Then there are the various structures used to hold systems temporarily in place: the drug or fluid delivery systems; the stoma, PIC line and other devices, many of which involve coating in tandem with another converting process.
The properties that make materials such as films, foils, adhesives, non-woven, silicone gel sheets and composite materials, the laminates and the agents and additives so indispensible in medical dressings, certain diagnostic products and other areas of health management often make them problematic when processing, coating and converting, etc. They have the potential to be dimensionally unstable, are prone to tear, are thin, or ultra-thin, require the careful deposition of coatings and require adhesive systems that are optimized to perform under the most difficult and challenging of conditions.
Care needs to be exercised when selecting coater applicator technology. Economic and product performance and viability over the time rests to some extent on the suitability of the coating technology to be used or decided upon. What are the characteristics of the web material and performance properties of the associated components? What is the web width, desired coating speed, thickness of the material? What is the nature of the coating fluid, its viscosity parameters and how is it going to be dried or cured? Once the various processing elements are known the decision as to whether or not to use a pre-metered or a post-metered method of coating can be decided upon.
Before looking at the high tech VCM supplied to sectors of the medical, diagnostic and care sectors lets consider the adhesives and requirements for not only these demanding sectors but also others. The VCM for instance is being used for aerospace components, the production of polymeric semi-conductors, solar reflective films, security, etc.
Advances in our understanding of acrylic, silicone and other adhesive systems and the way in which they work have resulted in the bringing to market of some very innovative products. An area of application is water -soluble pressure sensitive adhesive materials for surgical tapes and the fixing fastening and when desired the easy removal of electrodes. These adhesives are used for securing sterile sheets and instrument coveralls in operating theatres and day surgeries. The composition of water-soluble poly-acrylate adhesives enables these pressure sensitive adhesives to be applied even onto hydrophobic, low energy textile cloths and non-woven fabrics that have been coated with poly-fluorocarbon resins.
When it comes to wound care adhesives for direct skin attachment care is needed. For instance: adhesives can in some people cause inflammation and soreness. They can be difficult to remove and can be troublesome in geriatric and neo-natal wards. The challenge has been to provide medical grade PS-adhesives systems that bonded securely but at the same time were gentle to sensitive skin. Some work still needs to be done but on the whole new generation products are far superior to those on the market even a few years ago.
Pressure sensitive adhesive films and tapes and many other products now on the market or currently being developed provide a safe solution for many of the problems that health care professionals come up against. Natural and synthetic rubber, acrylic and synthetic adhesives with liners or supports of tissue, foam and film are available.
For direct skin or placement of devices in sensitive areas, catheters, etc., silicone gel adhesives have revolutionized sensitive skin care. These soft water resistant adhesives provide gentle adhesion, yet are removable without leaving any residue. Some of them offer a peel adhesion strength of just 20 to 50 grams per 2.85 cm. Altogether the range of materials on offer provides for a well rounded solution for many of dressing and diagnostic requirements that arise.
For the product developer and the converter a key requirement is to have the right processing devices, research and development and monitoring systems and equipment in place. In medical and many other demanding processing or product development areas including printable electronics, clean room conditions are a requirement. The VCM Coater is designed, configured and manufactured in order that it meets the specific requirements of the customer using the best available technology. These include high specification drives, tension and web control equipment. Rigid and stable framework is the foundation of the system facilitating the processing of wider and heavier substrates, while allowing considerable flexibility to expand or modify the machine as processing or product development needs change over time. Selectable coting technology may include gravure, offset-gravure, flexo, knife-over-roll, reverse roll and slot die, etc.
RK Print Coat Instruments Ltd
Litlington, Royston, Hertfordshire SG8 0QZ
www.rkprint.com sales@rkprint.com
Source: RK Print Coat Instruments Ltd
