SEPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-94/013 September 1994
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer
of Felt Tip Markers, Stamp Pads, and Rubber Cement
Richard J. Jendtucko*, Todd M. Thomas*,
and Gwen P. Looby**
Abstract
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at the
University of Tennessee performed an assessment at a plant
that manufactures felt tip markers, stamp pads, and rubber
cement. Plastic components for the markers are formed in
injection molding machines. A porous filler is inserted into the
marker case and ink is injected into it. The endplug, nib, and
cap are added to the marker, which is then labeled and pack-
aged. The first step in stamp pad production is the injection
molding of plastic double-hinged stamp pad cases. Three types
of stamp pads are manufactured: felt, foam, and self-inking.
The pads are prepared and inserted into the cases. Rubber
cement is manufactured by mixing synthetic rubber strips and
solvent. The team's report, detailing findings and recommenda-
tions, indicated that a large quantity of scrap plastic is gener-
ated by the injection molding of markers and stamp pad cases,
and that significant cost savings could be achieved by segre-
gating scrap plastic and reusing it in subsequent production
runs.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing research
* University of Tennessee, Department ol Engineering Science and Mechanics
" University City Science Center, Philadelphia, PA
project that is fully documented in a separate report of the
same title available from University City Science Center.
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the
problem of waste generation is to reduce or eliminate the
waste at its source.
University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
Risk Reduction Engineering Laboratory, the Science Center
has established three WMACs. This assessment was done by
engineering faculty and students at the University of Tennes-
see WMAC. The assessment teams have considerable direct
experience with process operations in manufacturing plants
and also have the knowledge and skills needed to minimize
waste generation.
The waste minimization assessments are done for small and
medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall
within Standard Industrial Classification Code 20-39, have gross
annual sales not exceeding $75 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, and
reduction of waste treatment and disposal costs for participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate_students who participate
Printed on Recycled Paper
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In the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manua/(EPA/625/7-88/003, July 1988). The WMAC
staff locate the sources of waste in the plant and identify the
current disposal or treatment methods and their associated
costs. They then identify and analyze a variety of ways to
reduce or eliminate the waste. Specific measures to achieve
that goal are recommended and the essential supporting tech-
nological and economic information is developed. Finally, a
confidential report that details the WMAC's findings and recom-
mendations (including cost savings, implementation costs, and
payback times) is prepared for each client.
Plant Background
The plant produces several varieties of felt tip markers, stamp
pads, and rubber cement. It operates 6,120 hr/yr to produce >
2x 10* Ib/yr of product.
Manufacturing Process
Polypropylene, polystyrene, and polyethylene pellets, liquid and
powdered dyes, and solvents for ink mixing are the principal
raw materials used for making markers and stamp pads. Rub-
ber strips and solvents are the major raw materials required for
rubber cement manufacture.
Felt Tip Marker Production
In order to manufacture felt tip markers, polypropylene and
polystyrene pellets are placed in a hopper and mixed with
colored pellets. The pellet mixtures are metered into injection
molding machines in which the three parts of the marker are
formed (the case, cap, and endplug).
The filler, a porous ink reservoir that is to be inserted into the
marker case, is produced in a parallel operation. Cellulose
acetate or polyester fiber is fed into a machine that stretches
and relaxes the material. Next, cellophane is wrapped around
the filler piece, and a long cylindrical form is automatically cut
into individual pieces.
In a third parallel operation, solvent or water is mixed with
appropriate dyes to make marker ink.
During final assembly of markers, the fillers are inserted into
the molded cases, the inks are needle-injected into the fillers,
and the molded endplugs are attached. The next step is the
attaching of nibs (small pieces of felt that wick the ink from the
filler) in the tip of the marker body. Molded caps are snapped
into place, labels are applied to the markers, and the finished
products are packaged.
An abbreviated process flow diagram for felt tip marker produc-
tion is shown in figure 1.
Stamp Pad Production
Three types of stamp pads are manufactured by the plant: felt,
foam, and self-inking. Polystyrene pellets and black and grey
dyes are mixed together and metered into injection molding
machines where double-hinged stamp pad cases are formed.
Felt pads are made by layering and cutting felt and asphalt
sheets. A cloth overwrap is added and then the entire pad is
inserted into a molded case. Water-based ink is injected into
the pad and the finished stamp pad is labeled, packaged in
cellophane, boxed, and shipped. For foam stamp pad produc-
tion, pre-cut foam pieces are dipped in water-based ink and
passed through a wringer machine to remove excess ink. The
pad is inserted into a molded case, which is labeled, packaged
in cellophane, boxed, and shipped. Self-inking stamp pads are
manufactured by first blending dimethyl phthalate, powdered
dyes, and PVC resins in a covered tank. The mixture is poured
into individual trays, which are conveyed through a natural gas-
fired oven for curing and then air-cooled. A pad base material
is placed in the bottom of a case and the ink-impregnated pad
is placed on top. The assembled pads are labeled, wrapped in
cellophane, boxed, and shipped.
An abbreviated process flow diagram for stamp pad production
is shown in figure 2,
Rubber Cement Production
To produce rubber cement, synthetic rubber strips and rubber
solvent are mixed together in a tank and stored in a storage
tank. The contents of the storage tank are pumped to a filler
machine where the rubber cement is pumped into individual
bottles traveling on a conveyor. The filled bottles are capped,
packaged, and shipped to customers.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes,
Waste cardboard is baled and sold to a recycler.
* Plastic waste from the injection molding machines is reground
and sold to an outside firm for reprocessing after which it is
returned to the plant for reuse.
* Hydraulic oil from the injection molding machines is filtered to
extend its useful life.
* Liquid hazardous waste streams are segregated by primary
component.
* Attempts have been made in the past to recycle dimethyl
phthalate. However, recycling has bean discontinued be-
cause of varying product quality and employee health con-
cerns.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the annual waste management cost for each
waste stream identified are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The minimization
opportunity, the type of waste, the possible waste reduction
and associated savings, and the implementation cost along
with the simple payback time are given in the table. The
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Polypropylene pellets
polystyrene pellets
- Color pellets
Mixing
Injection
molding
I
Cases
caps
endplugs
Nibs
Labels
Cellulose
acetate
polyester
Solvent, liquid dyes
powdered dyes
Resins
anti-foam agents
Cellophane
Stretching/relaxing
cellophane
overwrapping
Fillers
Assembly
T
Markers shipped
to customers
Mixing
Filtering
f
Ink
Figure 1. Abbreviated process Sow diagram tor feK Up marker production.
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Felt
asphalt
sheets
Cotton
cloth
Water-
based
ink
Layering
and
cutting
Over-
wrapping
T
Insertion of
pad into
case
Ink
infection
Labeling,
wrapping,
packaging
Felt stamp
pads shipped
to customers
Dyes
Injection
molding
I
Polystyrene
pellets
Molded
cases
Pre-cut water-
foam based
pieces ink
T I
Ink
Wringing
Insertion of
pad into
case
Mixing
Pouring
into
trays
D/methylphthalate
dyes
resins
Oven
curing
Air
cooing
Labeling,
wrapping,
packaging
Positioning
pad in
case
Foam stamp
pads shaped
to customers
Pad base
material
Labeling,
wrapping,
packaging
Sett-inking stamp pads
shipping to customers
Figure 2. Abbreviated process flow diagram for stamp pad production.
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TğUğ 1, Summary of Current Waste Generation
Waste Stream Generated
OH-spedfication filer overwrap
Empty dye containers
Evaporated n-propyl alcohol
Excess plastic runners
Unusable filler pieces
Hydraulic oil filters
Contaminated ink alters
Hydraulic oil/detergent solution
Synthetic oil
Oil-specification markers
Off-specification markers
Scrap packaging material
Plastic scrap
Color-streaked marker
components
Ink system wash water
Plastic pellets/hydraulic oil
Ink system wash solvent
Scrap self-inking stamp pads
Wash water
n-propyl alcohol wash-out
Evaporated n-propyl alcohol
Unused inking mixture
Empty solvent containers
Scrap cellophane overwrap
Off-specification plastic cases
Off-specification felt stamp pads
Contaminated plastic floor owaring
Resins and powder dyes
Wash wetter
Waste felt inserts
Waste foam inserts
ft/bfcar cement residue
Evaporated rubber solvent
_Wastewater treatment sludge
Source of Waste
Filler machine in felt tip
marifer production
Felt tip marker and
stamp pad production
Ink mixing in felt tip
marker production
Injection molding in felt
tip marker production
Filler machine in felt tip
marker production
Filtering of hydraulic oil from
injection molding machines
Ink mixing in felt tip marker
and stamp pad production
Cleanup in felt tip marker
and stamp pad production
Air compressors
Felt tip marker production
Felt tip marker production
Felt tip marker and stamp
pad production
Color changes in injection
molding in felt tip marker
and stamp pad production
Color consistency problems
in felt tip marker production
Cleanup in felt tip marker
production
Spills in felt tip marker and
stamp pad production
Cleanup in felt tip marker
production
Improper curing of self-
inking pads
Stamp pad production
Ink mixing in stamp pad
production
Washout of ink mixer in
stamp pad production
Self-inking stamp pad
production
Stamp pad production
Packaging of stamp pads
Injection molding of stamp
pad cases
Stamp pad production
Stamp pad production
Stamp pad production
Ink mixer in stamp pad
production
Improper cutting during
stamp pad production
Poor ink transfer during
stamp pad production
Rubber cement production
Mixing of rubber cement
Onsite WWTP
Waste Management Method
Shipped K> municipal landfill
Returned to vendor for reuse
Evaporates to plant air
Ground; returned to supplier
for reprocessing
Shipped to municipal landfill
Shipped off site for incineration
Shipped to municipal landfill
Shipped off site for disposal
as hazardous waste
Shipped off site for incineration
Donated to charitable organizations
Shipped to municipal landfill
Shipped to municipal landfill
Returned to supplier for reprocessing
Ground; returned to supplier
for reprocessing
Treated onsite; sewered
Shipped to municipal landfill
Reused in black ink production
Shipped off site for disposal as
hazardous waste
Treated onsite; sewered
Shipped off site for incineration
Evaporates to plant air
Shipped off site for incineration
Returned to vendor for reuse
Shipped off site to recyder
Returned to supplier for
reprocessing
Shipped to municipal landfill
Shipped off site for disposal
as hazardous waste
Shipped off site for incineration
Treated onsite; sewered
Shipped to municipal landfill
Shipped to municipal landfill
Shipped to municipal landfill
Evaporates to plant air
Accumulating onsite in drying pond
Annual Quantity
Generated (Ib)
4,730
3,800
41,470
18,600
2,020
170
2,350
3,400
2,410
56.250
506,250
560
5,500
T65,f40
106,240
8,830
210
21,830
11,950
1,530
380
1,100
900
790
2,030
10,160
SO
50
27,890
3,750
4,500
380
15,800
N/A'
Annual Waste .
Management Cost
$500
500
16,170
1,980
1,000
2,280
1,640
10,530
8,620
90
830
500
S60
19,690
50,630
1,640
0
SS.540
5,700
2,010
150
5,540
500
420
240
500
630
560
13,290
500
500
500
o.
0'
* includes waste treatment, disposal, and handling costs and applicable raw material costs.
waste is accumulating onsite; no waste was shipped off site during the past year.
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. Summary of Recommended Waste Minimization Opportunities
Annual Waste Reduction
Mmmizatton Opportunity
Segregate scrap plastic from
injection molding by color and
reuse in subsequent production
runs.
Waste Stream Reduced
Excess plastic runners
Plastic scrap
Color-streaked marker
components
Quantity (Us)
9,340
3,090
81,930
Per Cent
56
56
38
Savings
$5,100'
implementation
Cost
$0
Smp/a
Payback (yr)
Immediate
Modify the self-inking stamp
pad production process to re-
duos pad thickness by one-half
so thai individual pads with surface
defects can be combined to
produce one pad with an acceptable
visible top surface,
improve maintenance o! injection
molding machines to reduc
leaking of hydraulic oil.
Filter and reuse synttietic oil
removed from air compressors.
Scrap self-inking stamp pads
Hydraulic oil/detergent
Synthetic oil
19,650
90
2,380
2,170
70
90
20,050'
7,370
7,450'
17,400
Immediate
2.4
immediate
Total savings have been reduced by an annual operating cost required for implementation of this opportunity.
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quantities of waste currently generated by the plant and pos-
sible waste reduction depend on the production level of the
plant. All values should be considered in that context.
It should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with waste treatment and disposal. Other savings not
quantifiable by this study include a wide variety of possible
future costs related to changing emissions standards, liability,
and employee health. It also should be noted that the savings
given for each opportunity reflect the savings achievable when
implementing each waste minimization opportunity indepen-
dently and do not reflect duplication of savings that may result
when the opportunities are implemented in a package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, several additional measures were consid-
ered. These measures were not analyzed completely because
of insufficient data, minimal savings, implementation difficulty,
or a projected lengthy payback. Since one or more of these
approaches to waste reduction may, however, increase in
attractiveness with changing conditions in the plant, they were
brought to the plant's attention for future consideration.
Line the ink mixing tanks with Teflon inserts to minimize the
amount of residual ink adhering to tank walls after mixing and
draining in order to reduce the amount of washout waste
generated during clean-up.
Reduce the scrap rate in the automated felt tip marker
assembly line by improving the scheduling of production runs
and maintenance of the line.
Utilize reusable, washable ink filters to recover resins and
dye pigments collected during filtration following ink mixing
and use them in production of black ink.
Modify the solvent-based ink mixing tanks to minimize sol-
vent evaporative losses.
Purchase a sludge dryer to reduce the weight of the waste-
water treatment sludge in order to reduce disposal costs.
This research brief summarizes part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.
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United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
EPA/600/S-94/013
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
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