MANUFACTURING PROCESS OF LATEX GLOVES
Making latex exam gloves is a multi-stage process to ensure quality, medical-grade gloves are produced. The quality of gloves will differ based on how the factories treat each manufacturing stage. The following pages illustrate what these stages are to make exam gloves from gathering the raw materials to making the final inspection.
Making latex exam gloves start from collecting the raw material needed which is natural rubber. After workers tap the rubber trees for latex sap, the materials are sent to the glove factories where they will be combined according to the glove specifications. At the glove factories, exam glove formers go through stages of dipping, powdering, rinsing, and drying until latex gloves are made. For detailed process, click the following to observe the different phases of manufacturing latex exam gloves.
Cleaning the Formers
Quality production of exam gloves include making sure the enviornment throughout the glove factory is clean. This also means formers must be cleaned to ensure there are no dirt or debris anywhere. Not cleaning the glove formers would cause the final product to possibly have defects like holes. Exam glove formers are molds in the shape of the hand made from ceramic material. To clean the glove formers, an acid bath is used by dipping the formers in them and then rinsing with clean water. The formers are then dipped into an alkaline bath to neutralize the acid, and again rinsed in clean water. Afterwards, the formers are brushed to ensure the surfaces of the formers are consistent. This is an important step. Factories brush the formers to eliminate pin holes on the latex gloves.
Glove factories have multiple production lines that produce batches of disposable gloves. A dirty former can result in the manufacturer being forced to trash the entire batch of exam gloves. For this reason, glove formers are regularly inspected and cleaned before the molds are dipped into coagulant tanks.
Once cleaned, the glove formers are dipped into a coagulant bath to help the latex mixture adhere to the formers and help ensure the latex is distributed evenly. The coagulant tank stage determines the thickness of the latex exam glove. The thicker the requirements for the disposable gloves are, the longer the formers will travel in the coagulant tank.
The formers are dipped into the latex mixture and will eventually travel through a series of ovens to dry the gloves. The latex mixture will have different formulations depending on the brand of exam gloves being made. This liquid concoction is comprised of latex sap and chemicals which determines the elasticity of the medical glove.
After drying the latex mixture, the gloves are put through a leaching line to remove residual chemicals and proteins from the surface of the gloves. A good leaching line should be long, so latex proteins can be more effectively washed out. The water should also be hot and fresh to dissolve proteins better. This step is crucial to minimize the occurence of latex sensitivity. The key to making a good medical glove is to have a good leaching line. Factories that have bad leaching lines will probably be dirty in addition to the leaching line being short.
The glove leaching stage is one area factories will vary depending on the quality of exam gloves that are produced. Implanting a long leaching stage is expensive because there is an opportunity cost in the number of disposable gloves the production line can produce. The best factories will constantly circulate fresh water adding to the cost of making exam gloves marginally more expensive.
The glove formers then go through a wet powder to ensure even powdering. This wet powder, also referred to as slurry, is cornstarch. Traditionally, powdered latex exam gloves were preferred compared to poweder-free versions. The powder on the gloves were beneficial in the preservation of the latex gloves and assisted in the donning process of the gloves.
In light of latex allergy concerns, research has shown that latex allergens were found in the powder particles of powdered latex gloves which can exasperate allergic reactions in the respiratory system of individuals victim to latex sensitivity. For this reason, the healthcare community has shifted to the use of powder-free medical exam gloves. Interestingly enough, the glove formers still go through the wet, even powdering stage to make powder-free latex gloves. Afterwards, the gloves will go through more ovens for further drying and additional rinsing cycles where the powder will be removed.
Next, the latex gloves are stripped off the formers. The workers will collect the latex exam gloves for the final drying phase of the latex glove manufacturing process.
A latex glove contains natural latex, cornstarch powder frequently (added to help the surgeon don the glove), and numerous chemicals, some of which will be discussed below. These are foreign matter, and the human immune system sometimes responds. There are 3 major types of reactions.
There are several groups of people known to be at increased risk for latex allergy: patients who have had multiple hospitalizations and been exposed numerous times to latex medical products (especially patients with spina bifida), health care workers, and workers in the rubber industry. Current estimates are that 8-17% of health care workers become sensitized. The recent emphasis on universal precautions, with a concomitant marked increase in glove usage, is largely blamed for the increase in allergy among health care workers. Atopic individuals (those with other allergies or asthma) are at significantly greater risk to develop latex allergy than the general population. It is estimated that as many as 25-30% of atopic health care workers may become sensitized.
Another major issue is the cornstarch powder that has long been used in latex gloves. Researchers have shown in several papers3,4 that cornstarch powder binds the latex protein in the surgical glove, which allows the antigen to reach both the wearer’s skin more easily (when the hand becomes moist during surgery) and the patient’s skin. Also, when the surgeon both dons and removes the glove, cornstarch powder is released into the air, and this becomes a significant source of aerosolized latex protein that can sensitize health care workers via inhalation. In a separate study done at the Mayo Clinic,19 latex aeroallergen concentrations varied from 10 to 208 ng/m3 in areas where powdered latex gloves were used compared to 0.3 to 1.8 ng/m3 in areas where powdered latex gloves were never or seldom used. Donald Beezhold has also written that body sweat inside latex gloves may make latex proteins soluble, allowing absorption through skin and sensitizing the wearer.4 He has reported that the amount of free latex protein that can be extracted from powdered latex gloves is consistently higher than the amount that is liberated from non-powdered gloves. 4,12 He has suggested that cornstarch powdered latex gloves should be eliminated.2
Here is another thing to remember: not all latex gloves are created equal. There are significant (sometimes astounding) differences between manufacturers and product lines in the amount of free latex protein that can be liberated from the glove and the number and types of chemicals used in glove production. Also, gloves can be soaked after production to try to leach out the protein and chemicals, and once more there will be differences between manufacturers in how effectively these are removed. There is literature that clearly shows that some brands of gloves are more allergenic than others.21
How are gloves made?
Now on to some material about rubber in general and how gloves are made.1,14,15,20 This will be brief - a more detailed review at a level that a physician or nurse can understand is the article by Truscott. 20 In order to make a surgical glove, in addition to latex, one needs water, vulcanizing agents, accelerators, activators, blockers, retarders, anti-oxidants, preservatives, odorants, colorants, stabilizers, and processing aids. In other words, you need a veritable chemical soup.
Latex is a natural product. Rubber trees (Hevea brasiliensis) produce the milky, viscous liquid. The tree bark can be shaved so that the latex bleeds, and it is then collected. Unless treated with chemicals soon after collection, the latex tends to harden into a gum. It was named rubber by the British chemist Joseph Priestly, who noticed that it could be used to rub away pencil marks.
Natural latex is a polymer - that is, it is a long molecule composed of many repeating smaller molecular units. The basic unit of the polymer is called isoprene (synthetic rubbers use different chemicals as the basis for creating the polymer). Charles Goodyear first discovered a process that made rubber commercially useful. The story is that he accidentally dropped a mixture of rubber and sulfur into a fire. This produced a material that was no longer sticky, and had many desirable physical characteristics. Goodyear named this process vulcanization, after Vulcan, the Roman god of fire and craftwork. Vulcanized rubber is stronger yet also more elastic than the starting material. The sulfur cross-links the polymer chains in the latex. You can stretch vulcanized latex, but the polymer chains then snap back so the product returns to its original shape.
Nowadays, latex gloves are not produced with sulfur and fire. But sulfur is still very important as the primary vulcanizing agent. Accelerators are chemicals that speed the cross-linking process, either by donating sulfur atoms or because they are soluble within the natural rubber and help to draw the sulfur into the rubber by binding with sulfur. The major accelerators (and these are very important because they all can cause type IV allergy) are: thiurams, mercaptobenzothaizoles (usually abbreviated MBTs), and carbamates.
A second group of chemical sensitizers is the anti-oxidants. These are added to decrease the rate of rubber degradation. A wide variety of chemicals are available - glove manufacturers primarily use substituted phenols.
It is important to realize that different gloves will have different chemicals in differing concentrations in the final product. Also, since latex is a natural product, there will be some variation in the protein content from one lot to the next.
One brief comment about the word hypoallergenic - ignore it. The FDA proposed regulations in the summer of 1996 (which are not yet finalized as of this writing) that manufacturers not be permitted to use this term, since there is no established safe level below which latex protein or glove chemicals might not be harmful.
Gloves are created by dipping forms (which look like hands) into vats of liquid latex and admixed chemicals. The latex glove then hardens on the mold - it is formed with what will ultimately be the inside of the glove (touching your skin) on the outside of the mold. Then the gloves, still on the mold, go through one or more rinses to leach out protein and residual chemical (better rinsing equals less residua). Finally, the finished product is stripped off the mold, packaged, and sterilized.
What about synthetic rubbers? Remember that most of the world’s natural rubber trees are found in tropical countries such as Malaysia. During World War II, the supply of natural rubber from the Far East was disrupted. This led to the development of synthetic rubbers.
Various types of synthetic rubber are in production around the world today - the properties of the end product depend on the chemical that is used as the building block to form the final polymer. Much of the world’s synthetic rubber is made from styrene and butadiene, which are found in petroleum. For our purposes, here is a list of synthetic rubbers used in making non-latex surgical gloves and some of the brand names:
Synthetic Alternative Gloves
|Synthetic Rubber||Glove name||Manufacturer|
|Styrene ethylene butadiene||Allergard||J and J|
Even with synthetic rubbers, there are still numerous chemicals (carbamates, etc.) involved in manufacture. Once more, there will be differences from one manufacturer to the next. It is still possible to have a serious type IV allergic reaction (contact dermatitis) to a synthetic rubber. However, type I natural latex allergy does not occur in response to synthetic rubber and these gloves are therefore required when treating a patient with known type I hypersensitivity, or for the health care worker who has either become type I sensitized or cannot find a suitable latex glove because of type IV allergy.