Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
1999-07-26
2001-02-06
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
Reexamination Certificate
active
06184340
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to disposal methods and reduction of microbial contamination for a used or contaminated polyvinylalcohol (PVOH) item. An important class of PVOH items are items used in health care and other industries and woven or non-woven fabrics and articles that are contaminated in use and need to be sanitized before disposal. Further, the invention relates to an aqueous treatment that can render a pathogen population in a contaminated item, harmless and can also liquefy and promote the easy convenient disposal of polyvinylalcohol containing items.
BACKGROUND OF THE INVENTION
In the past, hospital and hospitality industries often used conventional cotton and woven fabric materials for a variety of hospital uses. Because of the time involved in collecting, laundering, sanitizing and reusing or recycling conventional fabric materials, replacements for such materials have been sought. One form of replacement including disposable, typically woven or non-woven, fabrics have found substantial use in hospitality and healthcare industries. Such non-woven materials are often made from or bonded with polyvinylalcohol materials. Polyvinylalcohol can be formed into fibers or can be formulated into adhesives which make up structural components of a non-woven fabric material. Non-wovens also can often contain a variety of other ingredients and components to make up fully functional gown, cap, shoe cover, drape, wipe, absorbent article or other component. However, in large part, the polyvinylalcohol materials can act either to maintain the integrity of the unit or can act as the main structural component of the non-woven fabric. Polyvinylalcohol resins have also been used in the manufacture of a variety of items that contain cast, extruded, molded or otherwise manufactured items (apart from woven or non-woven fabrics) that are made of polyvinylalcohol components. Such items can include adhesive materials, films, rigid and non-rigid containers, permeable and non-permeable tubing, permeable and non-permeable membranes, and a variety of other structures. Please note that such structures can contain both fabric and non-fabric components made from polyvinylalcohol resins.
Polyvinylalcohol typically comes in a variety of grades having varieties of water solubility. Partially hydrolyzed polyvinylalcohol, having a hydrolysis degree of about 87 to 88%, is typically an easily solubilized material using cold water. Fully hydrolyzed materials having a degree of hydrolysis of between about 90 and 95% have a reduced cold water solubility as the degree of hydrolyzing increases. Super-hydrolyzed polyvinylalcohol grades typically have a very low cold water solubility and are minimally soluble in aqueous solutions at ambient (room or typical indoor environmental temperature for employees, typically about 20 to 35° C.) temperatures. The water solubility of the polyvinylalcohol polymer can be reduced further by the presence of other typically hydrophobic monomers in the polymer backbone. Such monomers can include ethylene, propylene, vinyl chloride, vinyl alcohol esters, derivatized vinyl alcohol moieties such as those found in polyvinylbutyral, acrylic monomers and others well known to one of ordinary skill in the art. A small proportion of a co-monomer can substantially reduce aqueous solubility.
Non-woven items, woven items, molded sheet or film items made from or formed from polyvinylalcohol fibers or adhesive compositions can be substantially resistant to aqueous materials if the polyvinyl alcohol is selected from the more hydrolyzed or hydrophobic materials. The water solubility of these materials is unique since one would intuitively assume that materials with a high degree of hydrolysis (high proportion of hydroxyls from hydrolysis) would be more water soluble. However, the reverse is true since the reduced acetate content of the polyvinylalcohol results in polymer coiling due to intramolecular hydrogen bonding. These polymer properties result in substantially poorer water solubility as the hydrolysis content increases. Super-hydrolyzed (greater than about 99 wt. % hydrolyzed) polyvinylalcohol is very difficultly solubilized in cold water and when incorporated into a disposable item, can even be more resistant to the action of aqueous solutions because of the protective nature of the this overall structure.
Further, when used in hospitality and healthcare organizations, PVOH items, woven and non-woven materials can often come into contact with pathogenic materials. Non-wovens, in particular, can come into contact and can absorb a variety of biological fluids including whole blood, blood fractions; including red blood cells, white blood cells, platelets, serum, plasma; fecal material, urine, ascites, lymphatic fluids, hair, skin and other natural materials. Similarly, in the hospitality industry such non-woven materials can also come into contact with a more narrow range of biological materials. However, these materials can also be pathogenically hazardous. Because these materials are single use materials and because they are often are biohazards due to substantial pathogenic contamination, the disposal of these materials is a significant problem.
Currently we are aware of two approaches of promoting the disposal of woven and non-woven materials made using polyvinylalcohol. In one approach, the woven or non-woven materials are contacted with very high temperature water to maximize the rate of solubility of the materials, resulting in a disposable solution or dispersion of the components making up the disposable item or items. Our experience in using hot water for the purpose of dissolving and disposing polyvinylalcohol containing non-wovens has shown us that even in very hot water, water at 90° C. to 99° C. and higher, the dissolution rate for the certain polyvinylalcohol items is quite slow for efficient operations. Disposing of highly hydrolyzed polyvinylalcohol (99%+hydrolysis) containing non-woven items simply using very hot water can take in excess of one day, often up to three days for complete dissolution. We believe that any successful disposal method for treating polyvinylalcohol non-wovens will take less than 4 hours, typically less than 2 hours. Further, such hot water treatments often do not render the dissolved polymer free from biohazard pathogens. Examples of highly hydrolyzed polyvinylalcohol absorbent technology designed for hot water dissolution include: Honeycutt, U.S. Pat. Nos. 5,707,731 and 5,470,653, disclosing a mop head from highly hydrolyzed PVOH and its disposal soluble in hot water; Honeycutt, U.S. Pat. No. 5,650,219, disclosing a process for controlling PVOH solubilization temperature; Honeycutt, U.S. Pat. No. 5,661,217, disclosing manufacture of molded parts from highly hydrolyzed PVOH; Honeycutt, U.S. Pat. Nos. 5,628,222 and 5,207837, disclosing a composite highly hydrolyzed PVOH disposable fabric and its disposal in hot water; Honeycutt, U.S. Pat. No. 5,181,967, disclosing disposal of highly hydrolyzed PVOH utensils in hot water.
A second approach to disposing such materials includes the use of a chemically modified polyvinylalcohol polymer composition. The polymers are specially modified to make the polymers more suitable for alkaline digestion and subsequent dissolution. In our experiences using specially modified polyvinylalcohol polymers that are modified to be sensitive to alkaline dissolution can lead to relatively efficient disposal of non-woven materials. However, the costs of the specially modified polyvinylalcohol can be substantial while the use of the alkali digestion can often not achieve full decontamination and elimination of biohazard. Examples of PVOH items modified for disposal via alkaline dissolution include: Patenode in U.S. Pat. Nos. 5,630972, 5,567,510, 5,472,518, and 5,508,101, all disclosing a dispersible PVOH copolymer composition and a method of making the composition dispersible via alkaline digestion.
A substantial need exists for improved processes for disposing of used or contaminated polyvinylalcohol ite
Kennedy Shaun P.
Smith Kim R.
Boykin Terressa M.
Ecolab Inc.
Merchant & Gould P.C.
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