PRE-VULCANIZATION OF NATURAL RUBBER LATEX USING UV TECHNIQUES: A NEW APPROACH FOR THE MANUFACTURE OF NON-ALLERGENIC LATEX GLOVES

The increasing demand of dipped natural rubber latex articles (e.g. gloves) has lead to a boom in the latex sector resulting in a recent emergence of latex allergies. Allergenic reactions ranging from mild contact dermatitis to eczema are caused by latex proteins as well as processing chemicals such as activators and accelerators used in conventional sulphur vulcanization processes. Alternative curing techniques (e.g. peroxide induced vulcanization and e-beam curing) are displaying other disadvantages such as high production costs and operational safety concerns.
The present work deals with a new pre-vulcanization process for natural rubber latex which is based upon an UV induced pre-curing of the latex emulsion. The new technology makes the manufacture of examination and surgical gloves feasible without using any sensitizing or allergenic processing agents. In the photochemical process, a selected photoinitiator and a poly-functional thiol are added to the natural rubber latex. Free radicals (bond cleavage of the photoinitiator) are generated due to UV irradiation and cross-linking of the latex particles is then achieved by a thiol-ene addition reaction. The photoreactions have been investigated using real time FTIR and Raman spectroscopy.
To provide a continuous irradiation of the liquid latex the pre-vulcanization is carried out in a falling-film photo-reactor. NR latex gloves (e.g. examination or surgical gloves) are then produced by a conventional dipping process. The dipped latex articles display excellent mechanical properties as well as good stability against ageing and gamma sterilization. Skin sensitization, irritation and cytotoxic tests prove the good skin compatibility of UV cross-linked NR latex gloves.