The production of latex gloves begins with the harvesting of raw latex, which is tapped from the Hevea brasiliensis tree. Stabilisers such as ammonia and other vulcanising chemicals are then added to the latex in a process known as compounding. Next the mixture is stored in holding tanks where it is allowed to mature. The compounded latex then undergoes a variety of tests prior to being released for dipping.
Continuous batch machines perform the dipping process. The procedure produces powdered, chlorinated, powder free or coated powder free gloves.
Powdered / powder free gloves: Comparison of manufacturing processes
Ansell production, powdered gloves
Manufacturing flow chart for powder-free-gloves
The manufacture of powder-free gloves involves optimization of the protein removal stage and a specific inside coating stage.
After being dipped and cleaned in sodium hypochlorite and nitric acid, coagulant is applied to the clean glove former. Coagulant induces latex to deposit on the former and is critical for even film formation.
The glove former, which is now coated with a thin layer of coagulant, is then dipped into chilled latex. The latex is chilled to delay any further pre-vulcanisation.
The former is then coated with a film of coagulated latex. Next the latex film undergoes the first series of leaching to remove any residual coagulant.
After leaching, the film is vulcanised in ovens at temperatures ranging from 120°C to 140°C. The vulcanisation process irreversibly cross-links the polymer chains with sulphur. The accelerators which were added during the compounding phase increase the speed and efficiency of the cross-linking process.
Latex proteins present in the glove are then reduced in a process exclusive to Ansell known as PEARL (Protein and Endogenous Allergen Reduction Leaching). This process involves washing the gloves in three cycles: a 20 minute hot water and detergent wash, followed by two 20 minute hot water rinses. This reduces effective residual protein levels from 150µg/dm² to less than 50µg/dm². Gloves are then tested further for quality control before packing.
Nitrile and Synthetic Gloves
Nitrile and other synthetic gloves are manufactured using the same procedure as natural rubber latex gloves but with different starting materials.
Source: Latex Allergy Management, Section 4 Glove Manufacture, Ansell Cares, p14 – 17