A New Generation of Latex Gloves

Most proteins that can trigger latex allergies can be removed.

More than 40,000 types of commercial products are made from natural rubber latex (NRL), an extract of the Pará rubber tree. Valued for its desirable properties, NRL is used in numerous products in the medical industry and elsewhere, including latex gloves. However, out of more than 200 proteins contained within NRL, 13 are known to be allergens. The American Latex Allergy Association estimates that up to 1 percent of the general population and 17 percent of health care workers exhibit some form of latex allergy, thus hindering their use of gloves made from this material.

Fortunately, a solution to the protein content of NRL exists. It involves the patent-protected addition of aluminum hydroxide, Al(OH)3, a well-known protein binding chemical, to latex while still in liquid form. This compound acts as a binding agent to the latex and produces protein complexes that can be removed using existing industry practices. The result is an ultra low-protein variant of NRL that retains the advantages of latex with most of the antigenic proteins removed. How is this patented aluminum hydroxide-modified NRL made, what advantages does it offer health care workers and others who wear latex gloves, and what makes it superior to standard NRL?

The treatment process for this type of modified NRL removes specific non-rubber impurities from NRL through the directed application of aluminum hydroxide. A commonly used absorbent, emulsifier, ion-exchanger, and antacid, aluminum hydroxide is commonly used in the process of water purification. It forms a jelly-like structure suspending unwanted materials in water, including bacteria.

Using traditional latex processing methods, a slurry of aluminum hydroxide can be strategically added to the harvested latex. The effective binding of protein and other non-rubber impurities from this latex emulsion to insoluble aluminum hydroxide occurs, with some of the non-rubber impurities adsorbed to the reactive surface of the aluminum hydroxide crystals.

With this patented processing step integrated into the manufacturing stage, there is no added expense of capital equipment. Reacted aluminum hydroxide complexes are removed by standard filtration and centrifugation. The remaining rubber particles retain the surrounding lipid layer, which, during subsequent maturation, improves the mechanical stability of the latex. Scientists have observed that this process yields products that exhibit greater clarity and significantly reduced odor, in addition to the removal of most of the antigenic proteins, without sacrificing the properties that give NRL advantages over synthetic alternatives. Prior industry efforts have produced reduced protein-source latex through the treatment of raw latex with enzymes, with little commercial success.

A New Latex Glove
The rise of the AIDS epidemic in the 1980s highlighted the widespread use of latex gloves to protect against infection. But for many health care professionals, the increased exposure to latex led to allergic reactions. Symptoms ranged from watery and itchy eyes to red and irritated skin, to breathing trouble and even life-threatening anaphylaxis. Some health care professionals developed dangerous latex allergies that, in some cases, limited or ended their care-providing careers. Latex gloves were also negatively perceived because of the powder associated with the gloves that left residue on users' hands and caused skin irritation.

It must be stressed that NRL gloves are known for their superior barrier properties and cost effectiveness. As such, they have been, and still are, widely used, particularly in health care settings where effective barrier protection is of great importance against viral transmission and infectious diseases. With the exception of vinyl or PVC gloves, which have been shown to provide lesser barrier protection, latex gloves are generally less expensive than many synthetic alternatives, such as polyisoprene, neoprene, and often nitrile.

There is thus an obvious market for this aluminum hydroxide-modified NRL in the surgical, examination, and industrial glove markets. Both surgical and examination gloves in manufacturer trials contained significantly fewer antigenic proteins than untreated control gloves. This indicates that glove manufacturers using the aluminum hydroxide-modified NRL as their raw material can adhere to ASTM glove protein compliance levels with only "pre-leaching" to remove residual compounding chemicals, thus conserving water and energy. While reducing the antigenic protein content, such gloves preserve the durability, comfort, fit, tactile sensitivity, and high resistance to puncture and tear for which NRL is known.

In August 2010, latex glove manufacturer Brightway Holdings SDN BHD Malaysia announced the successful culmination of material use evaluation trials of this aluminum hydroxide-modified NRL. Conducted at Biopro, one of Brightway's facilities in Malaysia, the results paved the way for the manufacture and market introduction of the first exam and cleanroom gloves made from this material.

The aluminum hydroxide-modified NRL not only contains significantly fewer antigenic and total proteins, but also results in a more stable, cleaner latex that requires fewer compounding additives during production. The reduction in certain non-rubber constituents that can break down over time contributes to its greater stability compared to standard NRL. Customer observations reflect the "clean" appearance and lack of odor in the expansive list of products made from this aluminum hydroxide-modified NRL.

Unlike most synthetic alternatives, aluminum hydroxide-modified NRL uses green chemistry to modify natural latex. The aluminum hydroxide-modified NRL derived from the rubber tree remains 100 percent natural. As proof, note that bacteria and fungi are capable of degrading NRL; one elegant experiment has demonstrated that latex balloons degrade equally, if not faster than, oak leaves. In contrast, many synthetic alternatives to latex, such as PVC vinyl, nitrile, neoprene, and polyurethane, which are made from petrochemical derivatives, are neither biodegradable nor compostable. The incineration of these synthetic products can lead to the liberation of toxins and carcinogens, such as dioxin, cyanide, vinyl chlorides, and hydrogen chloride. Unlike such synthetic alternatives, the aluminum hydroxide-modified NRL has minimal impact on the environment.

Another advantage to the use of this aluminum hydroxide-modified NRL is the decreased amount of water required for end-product manufacture. Within the latex-dipped goods industry, manufacturers have demonstrated increased efficiency by reducing processes such as excessive washing and leaching, typically used to reduce protein levels. This reduction can significantly lower water and energy consumption and simultaneously reduce the presence of harmful chemicals used in the manufacturing process, such as zinc in wastewater. The overall environmental impact is minimized, resulting in increased production cost savings. This aluminum hydroxide-modified NRL is slightly more expensive than traditional NRL but is priced comparably to nitrile and neoprene, other commodity-priced, albeit synthetic alternatives.

Raw, natural latex is a liquid. When dried and cured, the film dries semi-transparent yellow. Manufacturers can add whitening agents, such as titanium dioxide or calcium carbonate, to the latex to express whiteness in the finished product or to provide a white background for which color pigments can be used. A common alternative, the use of titanium dioxide, can be more expensive. Because the aluminum hydroxide-modified NRL is characteristically whiter in appearance, its use reduces the amount and cost of the whitening agents.

Collectively, these results suggest that manufacturers can achieve savings in energy and material costs when using aluminum hydroxide-modified NRL. Natural products that minimize environmental impact while maximizing economic, health, and safety benefits are critical to the sustainability of the latex industry. This need is addressed by commercializing the process of modifying NRL with aluminum hydroxide while enhancing its attributes and performance. The process of using aluminum hydroxide eliminates a significant portion of proteins and other non-rubber composition in latex, providing a cleaner, more stable raw material. In fact, the aluminum hydroxide-modified latex is the only NRL on the market today that meets the new ASTM D1076-10 Category 5 standard for a natural latex containing less than 0.5 percent non-rubber content.

The use of this aluminum hydroxide-modified latex is an option for manufacturers that are currently using standard latex across a broad scope of industries, including medical manufacturing. The performance benefits and attributes of this aluminum hydroxide-modified latex offer a unique value proposition to these manufacturers, allowing them to continue to capitalize on the green advantages of natural rubber latex. Production cost-saving opportunities using aluminum hydroxide-modified latex makes this a sensible material of choice for future generations. Balancing material acquisition and production costs, manufacturers can quantify the true cost savings of aluminum hydroxide-modified NRL.

It is clear that the development of aluminum hydroxide-modified NRL has the potential to pave the way for a new era in the use of latex gloves, both within and outside the health care arena. Caregivers prone to latex allergies may find a new class of products at their disposal. As production of aluminum hydroxide-modified NRL products ramps up in coming years, it is reasonable to expect that users and their organizations will find it a welcome alternative to standard NRL and petroleum-based synthetics.

This article originally appeared in the April 2011 issue of Occupational Health & Safety.

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