Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-23
2002-04-30
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S156000, C524S157000, C524S158000, C524S575500
Reexamination Certificate
active
06380283
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to natural rubber latex (NRL) which has been deproteinized, relative to antigenic proteins, utilizing an enzyme treatment and to a method for accomplishing same utilizing a natural rubber latex stabilizer. In another embodiment, the invention features a combination of antioxidants what allow for chlorination processing of enzyme treated natural rubber latex.
BACKGROUND OF THE INVENTION
Natural rubber latex products are found almost everywhere in the world. Natural rubber latex is used in various industrial, commercial, medical and home applications. Medical products made of natural rubber latex include exam and surgical gloves, anesthesia masks and bags, catheters, injection ports, dental damns, condoms, diaphragms, balloons and blood pressure cuffs. Non-medical products made of NRL include toy balloons, household gloves, and foam mattresses and pillows. During the manufacturing process of many of these products, proteins, which occur naturally in natural rubber latex, can migrate to the surface of the latex film.
It has recently been reported that some humans appear to suffer an allergic reaction, of varying intensity, to natural rubber latex. It is believed that the allergic reaction is a result of the naturally-occurring proteins in natural rubber latex.
Accordingly, several attempts at removing proteins from products made of natural rubber latex have been developed. One such method includes a water leaching process. Although the water leaching process removes many of the surface proteins, measurable amounts of proteins still remain. Since antigenic proteins may be one source of allergens, manufacturers are continuing to modify the manufacturing process of rubber goods in such a way to attempt to reduce protein levels.
Another approach, aimed at reducing the allergenicity of latex antigenic proteins, is that of treating natural rubber latex with proteolytic enzymes to digest the proteins into smaller and potentially less allergenic pieces. Although this method is not meant to be a cure all to latex allergy, it may be a practical approach to reducing latex allergens to tolerable levels.
Proteolytic enzymes, also called proteases and proteinases, have found wide use in the food processing industry. Proteases are used to improve elasticity of dough in baked products; to break up barley proteins and improve product stability in the brewing industry; to aide in digesting milk proteins during the cheese manufacturing process; to tenderize meat; and are used in detergents to treat protein stains on clothing. Additional information concerning enzyme-treated natural rubber latex products and the method for doing same can be found in a report entitled “Enzyme-Treated Natural Rubber Latex: A Practical Approach” by Frank- W. Perrella, Ph.D., Jul. 21-22, 1998, and “Enzyme-Treated Natural Rubber Latex: Concept to Product” by Frank W. Perrella, Ph.D., Jul. 27-28, 1999, which is fully incorporated herein by reference.
In order for the enzyme action to work appropriately on the natural rubber latex, the natural rubber latex solution must be kept at a temperature which is defined by the enzyme being utilized to treat the natural rubber latex. As is well known in the rubber industry, one step in making latex products and specifically, latex medical products, foam mattresses and pillows, and toy balloons requires the addition of stabilizers during the manufacturing process. It has been discovered that the use of standard practices for stabilizing latex before enzyme treatment often results in an unstable material or unwanted coagulation or hardening of the natural rubber latex into a ball-like substance or other undesirable qualities in the finished product. Accordingly, it has been found that the use of various chemical stabilizers during the enzyme treatment of natural rubber latex product maintains the desirable qualities in the latex and the finished product.
Even after deproteinization of latex using such enzyme treatment methods, it has been found to be desirable in latex products to use a water extraction process to reduce the water extractable protein content both with and without enzyme or other deproteinization processes. One such method includes chlorinating the natural rubber latex products, such as medical or household gloves, catheters, and toy balloons made from deproteinized natural rubber latex. In addition, chlorination allows the ability to produce powder-free medical gloves, household gloves and catheters.
On some thicker products, such as catheters and household gloves, chlorination has minimal effects on the physical properties of the material due to the thick physical profile of these products. However, when chlorination is applied to medical gloves, balloon catheters, or toy balloons having a thickness of approximately 0.2 mm and below, chlorination often results in the gloves having poor physical properties particularly after high temperature aging. Poor physical properties for medical gloves results in gloves that have a very short shelf life and suboptimal barrier properties before being unusable due to the premature aging caused by the chemical reaction on rubber during the chlorination step. Accordingly, a method of preventing premature aging of natural rubber latex products caused by oxidation of the chlorination process is also desirable and a feature of the present invention.
SUMMARY OF THE INVENTION
The present invention features a novel method and process for manufacturing enzyme-treated natural rubber latex and products made from such treated natural rubber latex. One feature of the present invention is the use of a branched or isomeric chemical form of the stabilizer dodecyl benzene sulphonic acid either alone or in combination with one or two other stabilizers such as, sulfated fatty acids or a low viscosity grade (less than 100 centipoise) chemically modified cellulose such as hydroxypropyl- or hydroxyethyl-methylcellulose.
Another feature of the present invention is a treatment of enzyme-treated natural rubber latex with a combination of antioxidants to allow for chlorination of enzyme-treated latex products, such as gloves, catheters, and toy balloons. In this embodiment, satisfactory chlorinated natural rubber latex medical gloves can be made with enzyme-treated latex with the proper addition of one or two antioxidants that maintain the desired physical properties of the gloves, and improve aging and shelf life. The first antioxidant type is of the chemical composition of 4,4-Butylidenebis (6-T-butyl-M-cresol) or 4,4+-Butylidenebis (3-methyl-6-tert-butylphenol); while the second antioxidant is a polymeric hindered phenol or butylated reaction product of P-cresol and dicyclopentadiene.
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F.W. Perrella, Ph.D., Enzyme-Treated Natural Rubber Latex: Concept to Product, International Latex Conference, Jul. 27-28, 1999.
F.W. Perrella, Ph.D., Enzyme-Treated Natural Rubber Latex: A Practical Approach, International Latex Conference, Jul. 21-22, 1998.
Nor Aisah AB. Aziz, Formulations for Heat Resistant Chlorinated Medical Gloves, Workshop on “Latex Protein Allergy”, Jun. 9, 1994.
Perrella Frank W.
Pieroni Joseph K.
Tillotson Thomas N.
Bourque & Associates PA
Cain Edward J.
Tillotson Healthcare Corporation
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