EPA-600/2-76-011
January 1976
Environmental Protection Technology Series
THOR V SOLVENTLESS METAL DECORATING
FOR THREE-PIECE CANS
Background
Industrial Environmental Research Laloratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research-and Development,
U.S. Environmental Protection "Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed
to develop and demonstrate instrumentation, equipment and
methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the U. S. Environmental Protection
Agency, and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the Agency, nor
does mention of trade names or commercial ^products constitute endorse-
ment or recommendation for use.
This document is available to the public through the National
Technical Information Service, Springfield, Virginia 22161.
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EPA-600/2-76-011
THOR V SOLVENTLESS METAL DECORATING
FOR THREE-PIECE CANS
BACKGROUND
by
J. W. Caprori and R. C. Heininger
Continental Can Corporation
1350 West 76th Street
Chicago, niinois 60620
ROAPNo. 21AFA-016
Program Element No. 1AB015
EPA Project Officer: Kenneth Baker
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
January 1976
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Table of Contents
I. ABSTRACT 1
II. INTRODUCTION 2
A. Conventional Coating Methods 2
B. Energy and Environmental Impact of Conventional
Coating Methods 2
C. Environmental Control Alternatives 5
D. Energy and Economic Impact of Environmental Control
Alternatives 7
E. The Ultraviolet System Alterative 7
III. PROJECT OBJECTIVES 10
IV. RESEARCH AND DEVELOPMENT TO DATE 11
A. Laboratory 11
B. Pilot 13
C. In-plant 13
V. FUTURE RESEARCH AND DEVELOPMENT 16
iii
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List of Illustrations
Fig. No. Title Page
1 Conventional Base Coat Line--2 Color 3
1A Left Side View of Complete DEF Oven 4
2 Thor 5. --UV White Base Coat--2 Color,
Single Pass 9
3 PERT Chart--Thor V Program 12
iv
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I. ABSTRACT
This is the first report of the Demonstration Project undertaken by
Continental Can Company Metal Operations in agreement with the Environ-
mental Protection Agency for the development and commercialization of a
process to apply and cure an outside protective/decorative UV white base
coating on flat sheets for the bodies of 3-piece cans. The Continental
project is designated as Thor V.
The Thor V process is a single pass line wherein the UV white coating is
applied, UV cured to a printable condition, two conventional inks and a
trailing varnish are applied followed by baking in a gas-fired wicket
oven. The conventional process is a 2-line operation. The first line
applies the white coating followed by the oven bake. The second line
then applies the two inks and varnish, again followed by an oven bake.
The Thor V process reduces total line length by 215 feet (65M) and total
solvent emissions by approximately 66% as compared to the conventional
process. Elimination of an oven and afterburner will also reduce new
equipment costs by over $400,000, and save approximately 8,000,000
BTU/hour (2,000,000 Cal/hour) in gas consumption.
Along with background information, this report reviews the development
work to date, describes the Continental Thor V line at our plant in
Weirton, West Virginia, and describes the work needed to complete the
project.
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II. INTRODUCTION
A. Conventional Methods
At the present time, external protective and decorative conventional
solvent coatings for flat metal sheets used for the bodies of 3-piece
cans are applied by direct roll coating followed by baking in gas-fired
wicket ovens at temperatures up to 430°F (221°C) for periods of six to
ten minutes.
The outside can body coatings, usually white, are referred to as base
coats since they most often become the background color and an integral
part of the design which is completed by lithograph decoration (inks and
varnish) on top of the base coating.
A schematic of the sequence of operations is shown in Figure 1.
B. Energy and Environmental Impact of
Conventional Coating Methods
The conventional outside white coatings are applied in film weights in
the range of 10 to 14 mgs/square inch (1.5 to 2.2 mgs/square cm). The
wet coated sheets, approximately 35 inches x 41 inches (86 cm x 104 cm)
are then transported on wickets through the baking oven at a rate of 85-
95 sheets per minute. The decorative inks and trailing varnish are then
applied and baked on a second line. A schematic of a direct externally
fired (DEF) wicket oven for baking flat sheets is shown in Figure 1A.
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CONVENTIONAL BASE COAT LINE-2 COLOR
Roller Conveyor Feeder
K
Bake Wicket Oven 10'at 385'F Stack & Turn Roller Conveyor
Roller Conveyor Feeder Print 2-Conv. ' Bake Wicket Oven 8'at340'F Stack & Turn Roller Conveyor
225' (70M)
FOIPF 1.
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LEFT SIDE VIEW OF COMPLETE DEF OVEN
21
1
2
3
4
5
6
7
8
9
10
11
Rear
Cooling Exhaust
Cooling Intake
No. 3 Burner Box
No. 3 circulating Fan
No. 2 Burner Box
No. 2 circulating Fan
Combustion Air Blower
Conveyor Preheat Circulating Fans
No. 1 Burner Box
No. 1 Circulating Fan
FIGURE 1A
12 Main Exhaust
13 Front
14 Zone 1
15 Zone 2
16 Zone 3
17 Maintaining Section
18 Heating Section
19 Baking Section
20 Cooling Section
21 To Oven Unloader
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For the system described (white base coat, two colored inks, varnish),
the typical oven solvent emissions are as follows:
Material
Solvent
Lbs
118
2.5
59
per hour
Kgms
53.6
1.1
26.8
% of total
emissions
66
1
33
White base coat
Two inks
Varnish
It is evident from the above figures that two-thirds of the solvent
emissions in the conventional system come from the high film weight
white base coating, approximately one-third from the varnish, and only a
trace from the inks.
Oven operation for baking the white coating will typically consume 4.2MM
BTU/hour (1.0 MM Cal/hour) of natural gas energy. An afterburner, if
one is needed, will consume an additional 3.8 MM BTU/hour (0.95 MM
Cal/hour).
C. Environmental Control Alternatives
In Priority I Air Quality Regions, as designated by the Environmental
Protection Agency, conventional coating materials cannot be run on
existing coating lines beyond mid-1975.
Dependent upon control regulations promulgated by the states, counties,
and municipalities, several, but not consistently applicable, hydro-
carbon control techniques can be used. The principle techniques per-
mitted include the following:
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a) The formulation of conventional coatings with "exempt sol-
vents," i.e., solvents generally considered to have no or low
photochemical reactivity.
b) The use of low solvent concentration high solids or water
based coatings.
c) The use of afterburners.
Dependent upon the applicable state, county, and municipal regulations,
the use of these types of coatings may also require substantial modif-
ication of existing ovens to provide no contact of the air-solvent
mixture with oven burners. This particular provision can add up to 30
or.40% increase, in the natural gas requirement to heat the oven. The
technical validity of this energy intensive requirement is highly ques-
tionable when the actual air flow characteristics of the direct fired
flat sheet metal decorating ovens are understood.
In many state, county, and municipal regulations the use of afterburners
is mandatory if the above mentioned alternatives are not available or
have not been developed and fully tested by mid-1975. This alternative
for oven exhaust controls can be characterized as follows:
a) The capital cost of the afterburner can range from 50% to
125% of the capital cost of the oven to be controlled.
b) The additional gas consumption for the afterburner can be
equivalent to the amount of natural gas to operate the oven.
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D. Energy and Economic Impact of
Environmental Control Alternative
Each of the environmental control alternatives are characterized for
their economic and energy impact in the following table.
TABLE 1
Type of control
Afterburner
Exempt solvent
Low solvent
Capital
cost $
+ 100%
0
0
Operating
cost $
+ 100%
+ 15%
+ 25-40%
Energy
requirement
+ 100% natural gas
No change
No change
These data show that a long term solution must be directed toward a
reduction in energy usage and solvent concentration in the coating
material.
E. The Ultraviolet System Alternative
For the past decade, Continental Can's Research and Development depart-
ments have explored many alternate processes and materials which would
minimize or eliminate the solvents in the coating materials. Additionally,
discreet energy input processes were investigated with the objectives of
energy reduction and potential increase in overall productivity through'
elimination of the requirements for wicket ovens.
In the course of those exploratory studies, experimental and analytical
evaluations of electron beam, X-ray, gamma ray, ultraviolet, fused
powder, and infrared, as examples, were undertaken.
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From these evaluations, ultraviolet light combined with coating mater-
ials sensitive to "curing" by UV evolved as the system with the preferred
techno-economic potential resulting in an approved, specific research
project in October 1972.
Concurrent with this coating system research, Continental developed and
commercialized the first UV litho ink flat metal sheet decorating system
which gave further credence for focusing its research and development on
UV coating systems.
By October 1973 sufficient development data had been derived to initiate
a project for installation of a full scale experimental system in a
manufacturing facility (see Figure 2). The Continental Mark I UV dryer
shown in Figure 2 contains nine medium pressure mercury vapor UV lamps
rated at 200 watts/ inch (78.7 watts/cm).
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THOR 5. - UV WHITE BASE COAT- 2 COLOR SINGLE PASS
O
Coat
Roller Conveyor Feeder "v Set Pass MARK 1(9)
Base
Varnish
Conv. Bake Wicket Oven
Print 2
Conv. Inks Trailing 8'at 340'F
Stack & Turn Roller Conveyor
260'(79M)
FIGURE 2.
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10
III. PROJECT OBJECTIVES
The purpose of this project is the development of a system for 3-piece
can decoration to apply a UV white base coat, one or two conventional
inks and a trailing varnish, in a single pass operation.
Commercialization of this system will eliminate the following:
a) One oven and afterburner (where needed) for curing the
white coating
b) 4 to 8 million BTU/hour (1 to 2 million Cal/hour) of
natural gas energy
c) 30% of the conventional system electrical demand
d) White, coating solvent
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11
IV. RESEARCH AND DEVELOPMENT TO DATE
A Pert Chart listing the major tasks in the complete Thor V program is
shown in Figure 3. Work to date has essentially covered the tasks up to
container fabrication evaluation. None of the materials tested to date
has warranted a customer performance evaluation.
A. Laboratory
In laboratory testing, the test coatings are applied to various metal
substrates, including tinplate, TFS (tin free steel), and QAR (quality
as rolled) plate, using a laboratory Wagner roll coater. The white
coating is set on a Continental designed laboratory UV dryer using one
medium pressure mercury vapor UV lamp rated at 200 watts per inch.
Conveyor speed can be adjusted from approximately 5 feet (1.5 m) per
minute to over 100 feet (30.5 m) per minute. The coated panels are then
baked in a laboratory gas fired oven to complete the cure of the white
coating.
The Thor V process, by definition, uses conventional inks and a trailing
varnish. A normal varnish bake is 8 minutes at 340°F (171°C). Conse-
quently, most tests were conducted at this bake. The normal laboratory
application and curing sequence is, therefore, as follows:
1) Apply UV white coating at a film weight of 10 to 12 mgs/square
inch (1.5-1.9 mgs/square cm)
2) UV set white coating at speeds of 20 to 60 feet per minute
(6.1 to 18.3 meters per minute) which is equivalent to a full
size sheet speed of approximately 10 sheets per minute.
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PERT CHART - THOR V PROGRAM
Customer
Performance
Evaluation
Updated
Techno-
Economic
Evaluation
EPA
Testing of
Pertinent
Process
Parameters
Decorated
Sheet
Evaluation
Container
Fabrication
Evaluation
Completed
*"* Project I,
FIGURE 3
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13
3) Apply Conventional ink
4) Apply conventional varnish over wet ink
5) Bake panels for 8 minutes at 340°F (171°C)
The coated and cured panels are then subjected to standard litho evalua-
tion which includes tests for the following properties:
1) Flow 6) Adhesion
2) Gloss 7) Fabrication
3) Color 8) Blocking
4) Hiding 9) Mobility
5) Odor 10) Pasteurization resistance
B. Pilot
The pilot scale testing has been done on a UV pilot line for flat sheet
coating located at the Chicago Technical Center. The line has over ten
UV lamps available for curing the UV test coatings, and can handle sheet
sizes up to approximately 24 inches (61 cm) long by 30 inches (76 cm)
wide at speeds up to over 100 sheets per minute. Evaluation of the
coated sheets is the same as described above in the standard litho
evaluation procedure.
C. In-Plant
Following promising test results at the Chicago Technical Center and
encouraged by the success of our commercial UV ink operations, it was
decided to install a full scale experimental line in a Metal Operations
plant and, consequently, the Thor V line was installed at our Plant 446
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14
in Weirton, West Virginia. The line (No. PC-7) was completed and initial
testing began in March of 1974. The line layout is described in Section
II of this report and is shown in Figure 2.
Since March 1974, a number of coating tests have been conducted on the
Thor V line at Weirton with experimental UV white coatings. A normal
testing sequence consists, essentially, of the following (assuming
satisfactory results at each operation:
1) Adjust entire line to run at 85 sheets per minute (feeder-
coater-press-oven-conveying equipment).
2) Using inside enameled plate, apply outside UV white base coat
on standard 15-inch Wagner roll coater.
3) Feed plate directly into Continental Mark I UV dryer to cure
white coating sufficiently to accept inks in next operation.
4) Apply one or two conventional inks on Hoe Y press and apply a
wet roll coated conventional trailing varnish.
5) Bake decorated plate in standard wicket oven.
None of the UV white coatings run on the line to date (August 1975) have
been fully acceptable. The primary problem common to all materials
tested thus far is coating rheology—ability to achieve a smooth film
comparable to that obtained with conventional solvent base white coat-
ings. Poor adhesion and discoloration of the white coating after baking
have also been problems.
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15
Work is also currently being done to improve flow through possible en-
gineering modifications to the standard commercial roll coater. If,
however, the coating formulation changes and/or coater modifications
do not result in satisfactory flow conditions, it may be necessary to
go to a different, more costly, application method.
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T6
V. FUTURE RESEARCH AND DEVELOPMENT PROGRAM
Referring to the Pert Chart in Figure 3, once a satisfactory UV white
coating is developed from the standpoint of application properties and
decorated sheet evaluation, the next phase of testing will be container
fabrication. For this, the decorated plate will be shipped to a can
manufacturing plant since only enameling and decorating is done at
Weirton.
The plate will be slit to body blank size and then fabricated into
necked-in Conoweld cans. During can manufacture, the test litho will be
carefully watched for scratching, adhesion, fabrication, and can mobil-
ity through the assembly operations.
If all prior test results are satisfactory, the next step will be to
submit cans to a customer, or customers, for their evaluation. While
litho appearance will be of primary concern, customer testing will also
include mobility, double seaming of the end on the body, pasteurizing
and product flavor testing. During this phase of the program, we will
also update our technical data and economics based on the then current
manning, energy, equipment, and coating material costs. If these
analyses are favorable, a large scale run will be made during which the
Federal Environmental Protection Agency and Continental will measure the
pertinent process parameters affecting energy usage and environmental
control.
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.17
Finally, we will begin XP production (commercial production on an ex-
perimental basis) leading to standardization of the UV white coating and
the Thor V process.
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18
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REP.ORT NO.
EPA-600/2-76-011
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Thor V Solventless Metal Decorating for
Three-Piece Cans--Background
5. REPORT DATE
January 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J. W. Capron and R. C. Heininger
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Continental Can Corporation
1350 West 76th Street
Chicago, Illinois 60620
10. PROGRAM ELEMENT NO.
1AB015; ROAP 21AFA-016
11. CONTRACT/GRANT NO.
No cost agreement
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERlOp C
Background; 1/75-10/75
COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES Project officer Baker is no longer with EPA; for details,
contact E. J. Wooldridge, Mail Drop 62, 919/549-8411, Ext 2547.
16 ABSTRACTThe report gives the background of a demonstration project to develop and
commercialize the Thor V process to apply and cure an outside, protective/decor-
ative, UV-cured white base coating on flat sheets used for the bodies of three-piece
cans. The Thor V process is a single-pass line: the UV white coating is applied and
UV-cured to a printable condition; and two conventional inks and a trailing varnish
are applied, followed by baking in a gas-fired wicket oven. The conventional process
is a two-line operation: one line applies the white coating, followed by the oven bake;
the other applies the two inks and varnish, again followed by an oven bake. The Thor
V process reduces total line length by 215 ft (65M) and total solvent emissions by
about 66%, compared to the conventional process. Elimination of an oven and after-
burner also reduces new equipment costs by over $400,000 and saves about 8 million
Btu/hr (2 million Cal/hr) in gas consumption. The report also reviews development
work to date, describes the Thor V line at a plant in Weirton, West Virginia, and
describes work needed to complete the project.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Metal Finishing
Cans
Metal Protection
Coating Processes
Coatings
Solvents
Photochemical
Reactivity
Ultraviolet Equipment
Air Pollution Control
Stationary Sources
Thor V Process
Metal Decorating
13B 11K
13H
13D 07E
11C 14B
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
Unlimited
21. NO. OF PAGES
22
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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