Latex Glove Production
The Rubber Tree
Latex is a natural product that comes from
rubber trees. Though rubber trees can live for up to 100 years, the
prime time for latex rubber
production is when they are between the ages of 6 and 30 years. Rubber
trees are either native trees (that grow naturally) or hybrid trees
have been organized in a rubber plantation. Latex output is usually
much greater from hybrid rubber trees. Some companies cut down rubber
after they reach production maturity, replant new ones, and use the
wood to fuel the factories that produce many latex-based products or
wood to local furniture producers.
Harvesting the Latex
Latex is a white, milky liquid that flows
from the tree when the tree bark is scored (or shaved) and flows into a
device that is attached to the tree. During the rainy season the trees
are tapped every day after the rain has stopped. The rest of the year
trees are tapped every other day. On the average, the annual yield of
latex from a rubber tree will produce only the equivalent of two boxes
exam gloves. The best time for tapping the trees is at night. Most
latex farmers work at night, and sleep during the day (we pulled the
the picture out of bed at 8:30 am). Usually one side of the tree is
scored for four years, and then it’s switched to the other
Collection of the Latex
Since latex is a natural product, it can
spoil. Therefore it needs to be collected quickly and stabilized. The
the latex follow the farmers (kind of a second shift) usually between
6:00 a.m. and 8:00 a.m. and take the tapping cups, which are attached
the tree, and load the contents into larger, easy-to-carry containers.
The latex needs to be treated with chemicals quickly or it hardens into
This is where the fresh latex is processed.
The collection centers are owned either by local dealers that have
with the rubber factories, or are part of company-owned cooperatives.
At the collection center the latex is centrifuged to remove water,
and impurities. Ammonia is added to preserve the product for its trip
to the factory and storage.
Although it seems obvious, the quality of
the latex used has a direct impact on the quality of the glove
produced. In fact,
many of the early cases of latex protein allergy might be traced to
latex that hadn’t been properly centrifuged (as well as to
conditions). Today, improvements to latex quality such as pretreatment
and additional centrifuging are done to remove as many of the remaining
impurities and proteins as possible, ensuring a better quality of latex
for production. The latex then moves to quality control and then in to
Some manufacturers are experimenting with
the addition of proteolytic enzymes prior to centrifugation to break
in the mix, and reduce the amount of available proteins in the final
Centrifuging the latex concentrates the
rubber content up to about 60 percent, but also reduces the protein
centrifuging can reduce protein content even further.
At this stage, up to a dozen chemical are
added, including accelerators (which help control the later
and antioxidants (which prevent deterioration of the rubber molecules
in the final product by heat, moisture, and ozone).
Dipping and Coagulation
The hand-shaped formers are coated with
coagulant (eg. calcium nitrate) and dipped into the latex to coat them
with a thin
film of latex. The coagulant converts the liquid latex film into a
wet-gel on the former. Subsequent passage through a warm oven completes
Also known as "wet gel leaching", this is
the process of immersing the latex-coated formers into a bath or spray
to wash out excess additives from previous stages, such as coagulant.
Chemical and protein content can be reduced at this stage. The
effectiveness of the process is dependent on the temperature of the
water, the duration of the process, and the rate of water exchange.
Vulcanization was one of the key discoveries
in the manufacture of rubber products. In this stage, the latex film is
and the combination of sulfur, accelerator and heat cause cross-linking
of the rubber, giving strength and elasticity to the film.
This is the removal of the gloves from the
formers, where they are turned inside out.
Also called "dry-film" leaching, this
process is similar to the wet-film leaching above, except it is carried
out on the
dry/vulcanized latex film. The effectiveness of the process in reducing
water extractives is a function of time and temperature.
Hydrolyzed corn starch is added as a
lubricant, to enable easy donning of the glove by tumbling the gloves
in a slurry of
starch and biocide.
Some gloves, especially NRL, are
"chlorinated" during the process of stripping powder that was added
Chlorination makes the glove surface slippery, and therefore negates
the requirement to add a powedered lubricant.
Checking and Packaging
Though the manufacturing processes for latex
gloves vary greatly according to product, with many additional steps
for different products, most companies use a similar process. Liquid
latex and some chemical additives are put into a large vat. Forms that
shaped liked hands (in different sizes) are then dipped into the latex.
The latex hardens on the form, with the inside of the glove molded on
outside of the form. The gloves are then stripped from the form (some
may be leached again), checked (some 100% air checked) and packaged.