A New Protein Reduction System for Latex Glove Manufacturing – Bioblox™
MARGMA International Rubber Glove Conference, 12 – 14 September 2006
Rick Tabor, Research Associate; Stepan Company (USA) and Bill Howe,
PolyTech Synergies LLC. (USA)
The topic of protein reduction for latex gloves and other articles comprised of
NR latex is no stranger to manufacturers of these products. Research
continues in efforts to reduce protein levels by double centrifuging, or through
additives to the latex concentrate at the plantation level prior to shipment to
the manufacturing plant. In all cases known thus far, the cost of NR latex raw
material increases commensurately with the cost of the additional processes
and/or materials required to demonstrate benefit by these products for
manufacturers seeking lower protein levels.
In the 1990’s, a slip coating was first introduced to replace powder as a glove
donning agent. Today, the growth of powderfree gloves by polymer coating
method continues, along with the steady presence of powdered gloves. For
these products, manufacturers continue to welcome methods to further reduce
protein levels in latex gloves. Post process chlorinated gloves were not
targeted for this study, in that most of this product family benefits from
significant protein reduction afforded by the exposure to chlorination and
downstream post washing.
The standard method for lowering protein for the targeted product family of
this study (powdered gloves and polymer coated gloves) is that of longer
leaching times and/or higher leaching temperatures, sometimes as high as 70
degrees Celsius. That technique for continues today in many manufacturing
plants, and adds cost primarily through energy consumption and water
The intent of this study was to develop an on-line leach tank protein reduction
additive that would seamlessly be implemented within most existing glove
manufacturing plants for powdered latex gloves and polymer coated latex
gloves. The goal is to achieve the following:
1. Result in no compromise to physical properties of the latex film.
2. Be environmentally safe and be compatible with existing post water
3. Add no cost, or even possibly decrease manufacturing cost of the latex
article. To achieve this, the modest cost of the additive would need to be
offset by reduced leaching times, lower operating temperatures in the
leaching system, or other yet unidentified savings.
4. Add little or no cost to manufacturing lines in the way of additional
equipment and/or modification to existing lines.
5. Result in impressive reduction of extractable proteins of latex articles, in
tandem with objectives one through four above.
The PremiseThe PremiseThe PremiseThe Premise
The washing of articles, regardless of material composition, is a long standing
method of removing contaminants and restoring articles as close as possible to
their original state of cleanliness. To optimize the washing of clothing, for
example, one would employ the use of a detergent that contains certain
surfactants to assist in removal of stains caused by many outside factors. The
stains are effectively loosened and released from the fabric in tandem with
detergent washing followed by water rinsing to remove the stains along with
any residual cleaning agents. Residential laundry detergents are
environmentally safe, of course, posing no hazard to water treatment plants or
the community in general.
In turn, the objective of this study was to test introduction
of certain surfactants into the leaching process for latex
gloves that would in turn result in enhance or accelerate
removal of extractable proteins in latex films, especially
gloves. Unlike detergents used for washing clothes, the
combination of ingredients used for latex glove
manufacturing applications would need to keep foaming non-existent or kept
at least to minimum levels controllable by industry de-foaming aids.
Testing Parameters and ProtocolTesting Parameters and ProtocolTesting Parameters and ProtocolTesting Parameters and Protocol
Protocol used for testing was:
1. The Standard Malaysian Glove Program, which cites
targeted maximum allowable protein levels in
powdered gloves of 200 mg/dm2.
2. ASTM D3578, which cites targeted maximum
allowable protein levels in powdered gloves of 200
In turn, to ensure measurable and accurate detection, the “Control” target for
subsequent testing was determined to be 200 mg/g or approximately 300
mg/dm2 (Modified Lowry method).
Testing was conducted using the following independent laboratories and
associated testing regimen:
Testing MethodTesting MethodTesting MethodTesting Method Lab / LocationLab / LocationLab / LocationLab / Location
ASTM D5712-95 Modified Lowry Leap Testing Service, USA
ASTM D6499-03 Inhibition ELISA Leap Testing Service, USA
FITkit® Quattromed Ltd., Estonia
Product made for Protein Testing Purposes: Examination Glove
Latex Used: Pre-vulcanized Thai latex compounded by Killian Latex; Akron,
Coagulant: Water based with 20% calcium nitrate, wetting agents, and release
Leach water: Salem, Ohio City Water and de-ionized water by reverse osmosis.
Dip Machine: DipTech Systems Diplomat™ Computerized Pilot Plant
Diplomat Pilot Plant Finished Gloves before stripping
The initial repeatable glove manufacturing process employed was as follows:
1. Clean Mold with warm water
2. Coag Dip – 1 ips entry / 5 seconds dwell / 2 ips exit
3. Coag Dry – 1 minute with rotation and heated convection
4. Latex Dip – 1 ips entry / dwell 9 seconds / 2 ips exit
5. Air dry 60 seconds
6. Pre Oven Leach – 3 minutes @ 54 degrees C (time and
temperature later reduced)
7. Oven Dry – 1 minute at 80 degrees C
8. Bead roll by hand
9. Cure – 13 minutes at 100 degrees C / 2 minutes - 110 degrees C
10. Post leach – 2 minutes @ 54 degrees C (later reduced)
11. Oven Dry – 2 minutes at 70 degrees C.
12. Cool Down – 2 minutes ambient
13. Powder by hand
14. Strip (hand protection – disposable nitrile gloves)
Bioblox™ Concentration in Leach Water: 0.5% Active Ingredient finalized after
testing levels at 0.25%, 0.5%, and 1.0% Active Ingredient.
Testing HistoryTesting HistoryTesting HistoryTesting History
Round one of testing showed that “control” levels of protein in gloves, using
the Modified Lowry method were undetectable (less than 28 mg/g or less than
41 mg/dm2). It was determined that the use of Salem, Ohio city water for
leaching was introducing bias into the study model. This water had chlorine
present through addition at the city water treatment plant. Therefore,
subsequent iterations were switched to de-ionized water through reverse
osmosis process to remove ingredients influencing the study results.
Round two’s testing resulted in similar results of below detectable limits for
“control”; this after water temperature was reduced to 38 degrees Celsius for
this round of testing.
Round three focused on centering in on proper “control” standards against
which Bioblox™ treatment would be measured. Leach temperatures were set
to 38 degrees C. Results from the laboratory were as follows:
Lab Iteration Pre Leach Post Leach Protein
M 30 seconds 15 seconds 105 169
N 0 seconds 30 seconds 729 1052
O 30 seconds 30 seconds 237 366
P 180 seconds 30 seconds 33 52
Testing for Round 4 was established with pre-oven leach residence time as 30
seconds and post leach residence time of 15 seconds, in accordance with
Group M in the previous round (that closest to the SMG standard of 200
mg/dm2). Five different grades of Bioblox™ surfactant treatment were tested
against control. For Bioblox™ treatment, both pre-oven leaching and post-
oven leaching residence times of 30 seconds and 15 seconds respectively,
were subjected to 100% exposure to Bioblox™ additive at 0.5% active
ingredient to water. No residual rinse for either step was employed. Results
demonstrated that the process established for this round actually increased
protein content against “control”.
Round 4 ResultsRound 4 ResultsRound 4 ResultsRound 4 Results
Group ID Additive Lowry mg/g Lowry
Q Control 351 538 9.3
R Bioblox L 546 906 18.9
S Bioblox A 561 879 47.9
T Bioblox S 402 634 13.7
U Bioblox M 534 854 13.7
V Bioblox 460 360 568 10.9
Corrections instituted for Round 5:
• Increased post oven leaching residence time from 15 seconds to 45
seconds, and split post leaching to 20 seconds water only, followed by
25 seconds Bioblox treatment. Pre Oven leach of 30 seconds of Bioblox
treatment only continued.
Round 5 resulted in the first improvement in protein levels against the
“control” iteration. The best Bioblox bath resulted in a total overall protein
reduction of about 20% - effective, but not considered impressive enough to
warrant pursuit of production plant testing at that time. Rounds 6 and 7
focused on establishing the proper level of Bioblox concentration, testing
various routines at both 0.5% and 1.0% active ingredient to water. This test
overwhelmingly determined that the higher concentration of Bioblox™ did not
benefit protein reduction according to the laboratory data, and that the level of
0.5% active ingredient appeared effective against protein removal. This proved
to be a key statistic in the interest of keeping any material cost addition to the
Testing continued on various grades of Bioblox™ through testing rounds 8, 9
and 10, including adjusting the leach water pH to determine if this had an
impact on enhancing protein removal in tandem with Bioblox™. For all
iterations, it was determined that normal water pH levels of 6.5 to 7.0 was the
optimal level for Bioblox™ performance. When pH was raised (to
approximately 12) or lowered (to approximately 3.2), the protein levels
increased anywhere from 10% to 30%, from that of regular water pH levels.
Round 11 yielded the most compelling results for protein removal, with the
following major process change implemented for testing, which resulted in
compelling protein reduction for several Bioblox™ versions:
Many glove lines have 3 or more separate leach tanks for both pre oven and
post oven leaching. Earlier results showed that Bioblox performed at a higher
level by first exposing the glove to water only, before entering the Bioblox™
treatment stage. However, in no earlier testing was a residual water rinse
subjected to the glove after the Bioblox™ exposure.
For Round 11, the following leaching schedule was implemented, with all
water temperatures remaining at 38 degrees C.
Station Leach H20
Bioblox™ Leach H20
10 seconds 15 seconds 10 seconds 35 seconds
15 seconds 20 seconds 10 seconds 45 seconds
Testing for Round 11 yielded favorable protein reduction results as follows:
Group IDGroup IDGroup IDGroup ID AdditiveAdditiveAdditiveAdditive LowryLowryLowryLowry
QQQ Control 215 332 2.9 4.4
135 212 1.4 2.2
65656565 106106106106 0.50.50.50.5 0.70.70.70.7
TTT Bioblox F 95 150 1.6 2.4
All Bioblox treatments benefited and improved in lab results by employment
of a short residual water rinse after 0.5% concentration Bioblox™ treatment in
the prior leach tank, preceded by another “water only” tank.
It was perceived that the potential for Bioblox™ as a protein treatment was
commercially viable, meeting all of the project objectives established during
early testing in 2005.
To further validate protein reduction potential of Bioblox™, samples consistent
with the leaching process in Round 11 (water – Bioblox™ - water) were made
at the pilot plant, and sent for FITkit® analysisFITkit® analysisFITkit® analysisFITkit® analysis. These highly sensitive tests use
specific monoclonal antibodies developed against the four major latex
allergens (Hev b 1, Hev b 3, Hev b 5 & Hev b 6.02) known to be present in NRL
Group IDGroup IDGroup IDGroup ID AdditiveAdditiveAdditiveAdditive Hev b 1Hev b 1Hev b 1Hev b 1 Hev b 3Hev b 3Hev b 3Hev b 3 Hev b 5Hev b 5Hev b 5Hev b 5 Hev b 6.02Hev b 6.02Hev b 6.02Hev b 6.02
Undect. Undect. 0.09 0.15
Undect. Undect. 0.1 0.18
PPPP Control Undect. Undect. 0.24 0.48
QQQQ Bioblox L Undect. Undect. 0.04 0.08
Undect. Undect. 0.24 0.28
Further testing was conducted in 2006 at a few manufacturing locations in
Malaysia, yielding promising results. In one test, a “control” was implemented
using normal Malaysian leach water and process temperatures of 60 degrees
C. A total of 60 seconds of both Pre-oven leach and post oven leach was
employed for the test.
The Bioblox treatment, employed at 38 degrees C, demonstrated a reduction of
approximately 10% to 15% in protein levels compared against “water only
leaching” at typical elevated temperatures of 60 degrees C. This test
demonstrated potential to achieve protein reduction better than existing
methods, while conserving energy costs so vital to profitability.
Bioblox™ in concentrate form is a liquid. Any dipping lines containing
approximately 30 to 45 seconds pre-oven and post-oven leaching are
candidates for simple installation of equipment necessary to implement the
system on existing lines. The following is one suggested procedure:
For example, in the case of BiobloxBiobloxBiobloxBiobloxTMTMTMTM
LLLL, which is a 30% actives concentrate, the
dosage rate would be 0.005X1000/0.3 = 16.67 mls of Bioblox™ LBioblox™ LBioblox™ LBioblox™ L per liter of
This dosage level can be routinely controlled in leaching systems that drain
continuously, by addition of a metering pump connected to a Bioblox™Bioblox™Bioblox™Bioblox™
holding tank or shipping drum (See Figures 1 and 2 below), or by gravity feed
using a flexible feeding tube pinch system, metered via measured feed. Some
Bioblox™Bioblox™Bioblox™Bioblox™ grades are more viscous by nature, which may require a metering
pump system for best performance.
Figure 1: EXAMPLE OF METERING PUMP FOR BIOBLOX™ (reference:Figure 1: EXAMPLE OF METERING PUMP FOR BIOBLOX™ (reference:Figure 1: EXAMPLE OF METERING PUMP FOR BIOBLOX™ (reference:Figure 1: EXAMPLE OF METERING PUMP FOR BIOBLOX™ (reference:
Figure 2: INSTALLATION OF METERING PUMP WITH BYFigure 2: INSTALLATION OF METERING PUMP WITH BYFigure 2: INSTALLATION OF METERING PUMP WITH BYFigure 2: INSTALLATION OF METERING PUMP WITH BY----PASSPASSPASSPASS
Bioblox™Bioblox™Bioblox™Bioblox™ is best used when employed in both pre-cure oven leaching and
post-cure oven leaching systems. Best results are obtained by subjecting the
in-process latex article to the following leaching schedule for pre-oven and
post-oven leaching systems:
• First Stage Leaching – water only
• Second Stage Leaching – Bioblox™ treatment in water
• Third Stage Leaching – water only (residual rinse)
Residence times for each leaching stage may vary according to the
manufacturer’s process and formulation, but the following minimal guideline
may be used for initial trials and validation:
• First stage leaching in water only – 15 seconds or more
• Second stage leaching in water with Bioblox™ - 15 to 20 seconds or
• Third stage leaching in water only – 15 seconds or more
It is possible that overall leach tank residence time may reduce from current
manufacturer settings. Each manufacturer must make this determination
based upon his/her evaluation and merit.
If one pumps water from the last leach tank upstream to the first leach tank, it
is important to by pass the Bioblox™ treatment tank with this procedure. The
Bioblox™ tank is best planned as an isolated leach tank with its own incoming
water line, and any overflow going to drain, not another leach tank. This is a
necessary approach, as protein reduction will likely suffer if Bioblox overflow
migrates to any upstream leach tank.
Future TestingFuture TestingFuture TestingFuture Testing
The following studies are planned for Bioblox™ treatment in the upcoming
1. Potential to remove vulcanization residues for both NR latex and nitrile
2. Post process laundering benefits of Bioblox™ and impact on residual
removal and proteins.
3. More detailed study on protein removal of polymer coated latex gloves.
4. Extended wear testing.
5. Physical parameters testing.
6. Optimization of Bioblox™ using cost-benefit analysis through
concentration comparisons, saturated leach tank protein testing.