Gas curing chamber for flat substrates

Disclosed is a chamber which defines a constant gas flow environment for passing objects therethrough carried by a conveyor. The chamber comprises an elongate housing having an inlet opening and an outlet opening in the longitudinal direction and a moving conveyor which runs the length of said housing for transporting object from said inlet opening through said housing and thereout through said outlet opening, the space below said conveyor being enclosed and connected to a source of exhaust for exhausting gaseous substances therein. The space above the conveyor comprises an inlet zone, a central gas zone, and an outlet zone. The inlet zone and the outlet zone both are of a bi-cameral containment arrangement comprising an outer adjustable gate for determining the inlet opening, a central adjustable baffle gate, and an inner deflector wall. The space between the outer gate and the baffle gate is connected to a source of exhaust. The space between the baffle gate and the deflector wall is a modulating gas cell which contains a gas knife connected to a source of inert gas and capable of injecting said inert gas at an adjustable angle onto the conveyor substantially its entire width. The central gas flow zone operates under external recycle of its atmosphere in a direction countercurrent to the direction of the conveyor belt which passes therethrough. The chamber is ideally suited for vapor permeation curing of flat substrates coated with a vapor permeation curable coating.

BACKGROUND OF THE INVENTION 
The present invention relates to vapor permeation curable coating 
compositions and more particularly to a curing chamber with constant gas 
flow environment which is designed especially to cure said coating 
compositions. 
Vapor permeation curable coatings are a class of coatings formulated from 
aromatic-hydroxyl functional polymers and multi-isocyanate cross-linking 
agents wherein an applied film thereof is cured by exposure to a vaporous 
tertiary amine catalyst. In order to contain and handle the vaporous 
tertiary amine catalyst economically and safely, curing chambers have been 
developed. Generally, such curing chambers are substantially empty, 
rectangular boxes through which a conveyor bearing the coated substrate 
passes. Provision is made for entrance and exit of vaporous tertiary 
amine, normally borne by an inert gas carrier such as nitrogen or carbon 
dioxide, for example, and means are provided at the inlet and outlet of 
the chamber to enhance containment of the vaporous tertiary amine catalyst 
within the chamber. The inlet and outlet containment means further 
restrict the entrance of oxygen into the chamber because oxygen can create 
an explosive condition with the vaporous tertiary amine catalyst. Cure of 
such coatings is so rapid that no external source of heat is required. 
Representative examples of past curing chambers are set forth in U.S. Pat. 
Nos. 3,851,402, 3,931,684, and 4,294,021. Of particular note in the 
patented curing chambers is the provision made at the inlet and outlet for 
containment of the vaporous tertiary amine curing gas within the chamber. 
For example, U.S. Pat. Nos. 3,851,402 and 3,931,684 provide moist air 
curtains at the inlet and outlet which moist air curtains along with a 
source of suction are designed to minimize escape of tertiary amine gas 
from within the chamber. Somewhat different is the design in U.S. Pat. No. 
4,294,021 which calls for the exhaust fan to create a slight negative 
pressure to induce gas flow within the chanber in the direction of the 
exhaust duct which is located near the exit of the chamber. It is noted by 
the patentees that air is dragged by the conveyor from the inlet and such 
flow of air along with the vaporous amine circulates from the entrance of 
the chamber to the exhaust duct where the gas is withdrawn for 
recirculation. The patentees further note that the negative pressure 
created at the exhaust duct near the outlet also creates a flow of air 
from the exhaust end of the chamber into the chamber itself. No provision 
in this patent is seen for minimizing air flow into the chamber and, to 
the contrary, the design appears to encourage the flow of air into the 
chamber. 
While prior curing chambers certainly have performed adequately in the 
marketplace, many problems exist with prior designs. One problem with 
prior designs is the loss of amine vapor. Another problem is the inability 
to prevent air from entering into the curing portion of the chamber. A 
further disadvantage is the inability to operate at rapid conveyor belt 
speeds. The present invention addresses these and other deficiencies in 
the prior art and provides a unique chamber as will be more fully 
appreciated by the description contained below. 
BROAD STATEMENT OF THE INVENTION 
The present invention is directed to a curing chamber which defines a 
constant gas flow environment for passing objects therethrough carried by 
transporting or conveyor means, such as a conveyor. The chamber is ideally 
suited for vapor permeation curing of flat substrates carried by the 
conveyor. The chamber comprises an elongate housing having an inlet 
opening and an outlet opening in the longitudinal direction and a moving 
conveyor, which preferably is an endless conveyor, which runs the length 
of the housing for transporting objects from the inlet opening through 
said housing and out of said chamber through said outlet opening. The 
space below the conveyor is enclosed and is connected to a source of 
exhaust for exhausting gaseous substances therein. The space above the 
conveyor comprises an inlet zone, a central gas flow zone, and an outlet 
zone. The inlet zone comprises an outer inlet adjustable gate for 
determining the inlet opening, a middle inlet adjustable baffle gate, and 
an inner inlet deflector wall. The space between the outer gate and the 
inlet baffle gate is connected to exhaust means. The space between the 
inlet baffle gate and the inner inlet deflector wall is a modulating gas 
cell which contains a gas knife connected to a source of inert gas. The 
gas knife is capable of injecting the inert gas at an adjustable angle 
onto the conveyor substantially the entire width of the conveyor. The 
outlet zone comprises an adjustable outer gate which determines the outlet 
opening, a middle outlet adjustable baffle gate, and an inner outlet 
deflector wall. The space between the outer outlet gate and the middle 
outlet baffle gate also is connected to exhaust means. Preferably, the 
enclosed space between each outer gate and each baffle gate is maintained 
at substantially the same pressure within the inlet zone and the outlet 
zone which pressure typically is slightly less than atmospheric pressure. 
The space between the inner outlet baffle gate and the inner outlet 
deflector wall in the outlet zone is a modulating gas cell which contains 
a gas knife. The outlet gas knife also is connected to a source of inert 
gas which is capable of injecting the inert gas at an adjustable angle 
onto the conveyor substantially the entire width of the conveyor. 
The central gas zone has withdrawal means located in proximity to the inlet 
deflector wall which withdrawal means are connected to recirculating means 
for passing gaseous flow back into said central gas zone. The 
recirculating flow is passed back into the central flow zone at a location 
in proximity to the inner outlet deflector wall. Both the inlet and outlet 
deflector walls are sloped downwardly and inwardly. Preferably, such 
sloped surfaces are smooth and curvilinear. 
Advantages of the present invention include the ability to maintain a gas 
composition substantially constant even at relatively high conveyor belt 
speeds. Another advantage is the ability to effectively exclude oxygen, 
i.e. air, from the interior of the curing chamber. A further advantage is 
the minimization of losses of gas, eg. a tertiary amine or the like in 
vapor permeation curing adaptations of the invention, which contributes to 
the efficiency and economy of the design of the curing chamber. A further 
advantage is the conservation of inert diluent gas advantageously used in 
connection with vapor permeation cure adaptations of the present 
invention. These and objects will be readily apparent to those skilled in 
the art based upon the disclosure contained herein.

DETAILED DESCRIPTION OF THE INVENTION 
The curing chamber of the present invention comprises several unique 
aspects which operate conjunctively to the overall efficiency and economy 
of the curing chamber for containment of a constant gas flow environment 
to the exclusion of the ambient atmosphere. These conditions are 
maintained while a conveyor is passed through the curing chamber at a 
relatively high speed. Unique design concepts implemented in the novel 
curing chamber of the present invention include the bicameral containment 
sections at the inlet and outlet, the use of fully adjustable gas knives, 
and the countercurrent flow circuit within the central gas zone. Such 
design concepts, while dominant in the process, are not limitative of the 
unique, and often subtle, features embodied within the curing chamber. 
Referring to FIG. 1, curing chamber 10 is seen fitted with conveyor 12 
driven by motor 16 at the outlet of chamber 10 with follower 14 at the 
inlet of chamber 10. Follower 14 rests upon frame 18 while motor 16 rests 
upon frame 20. Chamber 10 is designed for having flat substrates passed 
therethrough on conveyor 12 which rests upon slide plate 44. The curing 
chamber, as depicted in the drawings as noted above, is a prototype having 
endless conveyor belt 12 being 30.48 cm (1 foot) in width and an overall 
inside width of about 40.64 cm (16 inches). For present purposes, conveyor 
is used in a generic sense to mean any suitable means for conveying or 
transporting a coated substrate through the chamber for its curing. The 
entire length of chamber 10 is about 7.32 meters (24 feet) and its height 
is about 50.8 cm (20 inches). Chamber 10 is supported by a series of 
struts 22 which place the bottom of housing 8 of chamber 10 about 0.92 
meter (3 feet) above the level of floor 24. One of the safety features 
fitted onto chamber 10 is emergency vent 26 which is fitted with an 
internal blow out diaphragm in conventional fashion. Should undesirable 
pressures build up within chamber 10 or an explosive condition be created 
therein, the safety diaphragm would rupture and the contents of chamber 10 
would be immediately vented through line 26. Many other safety features 
are incorporated into the design of the prototype chamber depicted in the 
drawings and these features will be noted as the description of the 
drawings unfolds. The remaining piping depicted in FIG. 1 will be 
described in detail in connection with the description of the remaining 
drawings. 
Referring now to the unique bi-cameral containment arrangement of the 
curing chamber, it must be recognized that the essence of the bicameral 
containment arrangement is effectively identical for the inlet section as 
for the outlet section. While both bi-cameral inlet zone 30 and bi-cameral 
outlet zone 32 operate to exclude oxygen and retain a desired internal 
atmosphere, it should be recognized that conveyor 12, especially at higher 
belt speeds, will drag atmosphere from the outside to within chamber 10. 
Thus, the primary focus of inlet bi-cameral zone 30 is to prevent such 
entering atmosphere from passing into central gas zone 34 and the primary 
function of bi-cameral outlet zone 32 is to prevent the escape of the 
atmosphere within central gas zone 34 from being dragged by conveyor 12 to 
the outside. With respect to containment of the atmosphere within central 
gas zone 34, it should be noted that, depending upon the material of 
construction of endless conveyor 12, such conveyor may have a tendency to 
absorb or adsorb the particular gaseous environment maintained within 
central flow zone 34. Chamber 10 is fitted with extended, elongate hood 36 
which houses the return loop of endless conveyor 12. Hood 36 is formed by 
the lower half of housing 8 and conveyor slide plate 44. Hood 36 is 
connected to a source of exhaust which removes components contained within 
hood 36 through outlet pipes 38, 40, and 42. Should any leakage between 
central flow zone 34 and hood 36 develop, the withdrawal suction placed 
thereon would prevent such leakage from finding its way to the atmosphere. 
It is to be noted that when using a tertiary amine for vapor permeation 
curing purposes of chamber 10, often the exhaust lines such as lines 38, 
40, and 42, for example, would be passed through an appropriate scrubber, 
eg. an acid, for scrubbing the amine from such flow. Other gaseous 
components desirably utilized in chamber 10 similarly may require 
scrubbing so that the withdrawal lines can be piped directly to scrubbers, 
vented to the atmosphere, or utilized in a by-product process as is 
necessary, desirable, or convenient in conventional fashion. 
Returning to FIG. 2, inlet bi-cameral zone 30 is divided into outer cell 50 
and inner cell 52. Outer cell 50 is defined by adjustable outer footed 
gate 54 and centrally located bi-footed, stationary gate 56. Outer footed 
gate 54 is adjustable vertically to define the opening of the chamber so 
that substrates of varying heights can be accommodated. Outer cell 50 is 
connected to a source of suction through line 58 which is shown in FIG. 1 
to be connected to exhaust header 134 along with exhaust lines 38, 40, and 
42. Exhaust line 58 maintains cell 50 at a total pressure of slightly less 
than the prevailing environmental atmospheric pressure. Oxygen or air 
which enters into chamber 10 desirably will be withdrawn from cell 50 via 
line 58 in order to prevent its entrance into central gas zone 34. The 
footed arrangement on gates 54 and 56 again tend to suppress gaseous flow 
as part of the integrated containment design of the curing chamber of the 
present invention. Inner cell 52 is defined by central stationary 
bi-footed gate 56 and adjustable inner footed gate 60 which bears 
deflector wall 64. Gate 60 is adjustable vertically for accommodation of 
substrates of varying thicknesses as is outer gate 54. Central fixed 
bi-footed baffle gate 56, which also may be adjustable, and inner 
adjustable gate 60 define modulating gas cell 52. Cell 52 desirably 
functions as a modulating or compression zone to provide a desirable 
transition between outer exhaust cell 50 and interior central gas zone 34. 
Referring to FIG. 4, gas knife 70 is adjustable by handle 72 (see FIG. 3). 
From FIG. 3, it can be seen that gas knife 70 runs substantially the 
entire width of belt 12 and is connected to a source of inert gas from 
both sides through lines 74 and 76. Plates 78 and 80 have holes extending 
therethrough for permitting pipes 74 and 76, respectively, to pass 
therethrough to gas knife 70. Sealing of inert gas pipes 74 and 76 is 
accomplished via gaskets 82 and 84, respectively. Also, plate 78 bears a 
protractor for determining the angle at which gas knife 70 incidences upon 
conveyor belt 12. From FIG. 3 it can be seen that adjustable gate 60 is 
retained within guides 86 and 88 which are on both sides of gate 60 for 
providing a recessed track for gate 60 to follow. A flow of inert gas, eg. 
nitrogen, carbon dioxide, or the like (supplied from line 150), flows 
through gas knife 70 through the lower slit which measures about 0.0635 mm 
(0.0025 inch) or less and faces belt 12 at an angle as depicted by its 
position 90 in FIG. 4. The angle at which knife 70 contacts belt 12, while 
being adjustable between 0.degree. and 50.degree., has been found to 
advantageously range from about 10.degree. to about 20.degree. based upon 
several factors which will be elucidated in more detail below. Knife 70 is 
retained within gas knife housing 94 as shown in FIG. 4. Inner cell 52 
desirably predominates in an inert gas composition provided by gas knife 
70 and is the transition from oxygen-rich outer cell 50 and oxygen-starved 
central gas zone 34. The momentum of the inert gas flow through gas knife 
70 is adjusted (flow rate and angle) to balance the momentum of the air 
layer on belt 12 and, thus, control the oxygen level in central zone 34. 
Outlet bi-cameral zone 32 similarly is divided into outer cell 102 and 
inner cell 104. Outer cell 102 is connected to a source of suction via 
line 106 as is outer cell 50. Cell 102 is defined by outlet adjustable 
footed gate 108 and central stationary bi-footed baffle gate 110. The 
pressures within cells 50 and 102 desirably are maintained to be the same. 
Inner compression cell 104 is defined by baffle gate 110 and inner 
adjustable gate 112. The arrangement of inner adjustable gate 112 is 
identical to inner gate 60 as previously described for inlet bi-cameral 
zone 30, i.e. as described in FIGS. 3 and 4. In this instance, however, 
the gas knife (supplied via line 152) for bi-cameral outlet zone 32 is 
adjustable by handle 103 and faces conveyor 12 at an angle contra the 
direction of the conveyor (i.e. as position 92 in FIG. 4 assuming FIG. 4 
was a view of gate assembly 112 from the opposite side of chamber 10 as 
shown in FIG. 2). The angle of the outlet knife generally ranges from 
about 20.degree. to 45.degree. based upon several factors which will be 
set forth below. The construction of assembly 112 also is identical to the 
construction as described in FIG. 3 for gate assembly 60. Operation of 
bi-cameral outlet zone 32 again is identical to that as described in 
detail for inlet bi-cameral zone 30 and will not be dwelled upon further. 
It should be noted at this juncture of the discussion that the pressure 
and/or gas composition within any zone or cell of chamber 10 is determined 
by use of sampling ports 114a-114j. 
Central gas flow zone 34 has a gas flow contained therein which is in 
countercurrent relationship to the direction of movement of endless 
conveyor belt 12. Such gas flow movement is provided by gas flow 
withdrawal line 120 which is located in proximity to bi-cameral inlet zone 
30 and return line 122 which is located in proximity to bi-cameral outlet 
zone 32. The direction of movement of the gas through zone 34 is assisted 
by deflector walls 64 and 124 which are borne by inner gate assemblies 60 
and 112, respectively. The gas flow movement, velocity, and direction is 
determined by in-line fan or blower 126 (see FIG. 1). Additional make-up 
gas, eg. tertiary amine catalyst, is provided through line 128 which 
enters withdrawal line 120 as shown in FIG. 1. This arrangement permits 
intimate mixing of the flows through lines 120 and 128 by blower 126. Line 
122 immediately following blower 126 is heated by line 130 which desirably 
can be a steam line, heated tape, or any similar desirable conventional 
heating system. For use of a vaporous tertiary amine catalyst, for 
example, it is desirable to provide such heating in order to ensure the 
vaporous phase of the tertiary amine catalyst and to prevent condensation 
of such catalyst. For use of different gases in chamber 10, it may be 
desirable to provide a source of cooling rater than heating through line 
130. Similarly, line 128 may be heated for a vaporous tertiary amine 
catalyst or cooled for other gases in conventional fashion. Another 
feature of the chamber is that inert gas is provided through line 137 to 
the chamber to maintain a slightly higher pressure in central zone 34 than 
in inlet zone 30 and outlet zone 32 in order to minimize the infiltration 
of air (oxygen) into central zone 34. The oxygen conentration in zone 34 
also can be maintained at a desired level by supplying nitrogen through 
lines 137 and 122 to zone 34. As noted above, additional safety features 
included into the prototype curing chamber in the drawings include line 
132 (FIG. 1) extending from line 120. Line 132 is connected to the source 
of suction provided through exhaust header 134. Line 132 can be 
automatically activated for evacuation of the contents of central zone 34. 
Another safety feature is inert gas line 136 (FIG. 1) which flows into 
line 122. Line 136 can have a flow of inert gas immediately passed into 
line 122 and thence into central gas zone 34 should the level of oxygen, 
for example, become too high and a potentially explosive condition be 
imminent. 
Operationally, extensive testing and observation of the prototype curing 
chamber of the drawings has permitted qualitative analysis of variables 
determinative of efficient operation of the chamber and quantification of 
such variables. Optimization of such variables even has been determined to 
a large extent based upon the data accumulated. The prototype curing 
chamber was operated under vapor permeation cure conditions utilizing 
triethylamine (TEA) vapor catalyst borne by nitrogen as the carrier gas. 
Nitrogen flow also was utilized for the gas knives. The data generated is 
accurate for the chamber design substantially independent of the 
particular gas components evaluated. Data collected included the belt 
velocity, the recycle volume, the composition of TEA and oxygen in chamber 
34, the flow of inert gas through and incident angle of both the inlet and 
outlet gas knives, and the total consumption of TEA and nitrogen in the 
system. In addition to the data collected and tabulated, many of the 
variables were varied while others remained constant in order to assess 
their impact on the operation of the chamber. These variations will appear 
as observations following the tables below. All gas flows rates are 
standardized for a temperature of 15.6.degree. C. and 1 atmosphere. 
TABLE 1 
__________________________________________________________________________ 
TEA 
Inlet Knife 
Outlet Knife 
Consump- 
Run 
Belt Vel. 
Recycle 
Chamber (vol %) 
Flow Angle 
Flow Angle 
tion 
No. 
(m/min) 
(L/min) 
TEA O.sub.2 
(L/min) 
(deg) 
(L/min) 
(deg) 
(Kg/hr) 
__________________________________________________________________________ 
1 24.4 1500 1.60 
4.0 31.1 10 42.5 25 0.34 
2 82.4 1415 2.20 
5.7 31.1 10 53.8 45 0.69 
3 91.5 1500 2.86 
5.0 31.1 20 53.2 45 0.74 
4 91.5 1500 4.05 
5.6 31.1 20 53.2 45 1.34 
__________________________________________________________________________ 
Observations 
As a general trend, as the desired TEA concentration in the chamber is 
increased, so is the TEA consumption (loss) increased. On runs 3 and 4, an 
increase of the inlet knife (70) angle to 30.degree. or a decrease of the 
inlet knife (70) angle to 10.degree. resulted in an increase of oxygen 
concentration within zone 34. Also, with a lower volume of nitrogen 
flowing through the outlet knife, the oxygen concentration in its chamber 
increased. 
TABLE 2 
__________________________________________________________________________ 
TEA 
Inlet Knife 
Outlet Knife 
Consump- 
Run 
Belt Vel. 
Recycle 
Chamber (vol %) 
Flow Angle 
Flow Angle 
tion 
No. 
(m/min) 
(L/min) 
TEA O.sub.2 
(L/min) 
(deg) 
(L/min) 
(deg) 
(Kg/hr) 
__________________________________________________________________________ 
1 91.5 1500 4.60 
5.6 31.1 20 53.8 45 1.50 
2 91.5 1500 5.00 
5.6 31.1 20 53.8 45 1.68 
3 122.0 
1500 2.10 
6.1 31.1 20 58.0 45 0.72 
4 122.0 
1500 4.90 
6.2 31.1 20 58.0 45 1.67 
__________________________________________________________________________ 
Observations 
Runs 1 and 2 show that even at a constant belt speed, increasing TEA 
chamber concentrations resulted in increased TEA consumption. On run No. 
3, when the knife angle for the inlet knife was increased to 25.degree., 
the oxygen concentration in the chamber increased. At an inlet knife angle 
of 15.degree., the oxygen concentration in the chamber decreased only 
slightly. On run No. 4, when the exit knife was varied to an angle of 
50.degree. with an increased flow of 62.3 liters per minute, the oxygen 
concentration in the chamber did not vary. At the increased angle of 
50.degree. for the exit knife, at the same 53.8 liter per minute gas flow, 
the oxygen in the chamber increased. At the increased angle of the exit 
knife of 50.degree., an increase of the gas flow to 65.1 liters per minute 
resulted in no significant improvement of the oxygen concentration in the 
chamber. 
TABLE 3 
__________________________________________________________________________ 
TEA 
Inlet Knife 
Outlet Knife 
Consump- 
Run 
Belt Vel. 
Recycle 
Chamber (vol %) 
Flow Angle 
Flow Angle 
tion 
No. 
(m/min) 
(L/min) 
TEA O.sub.2 
(L/min) 
(deg) 
(L/min) 
(deg) 
(Kg/hr) 
__________________________________________________________________________ 
1 30.5 1557 1.90 
3.9 31.1 10 42.5 28 0.44 
2 30.5 1557 2.25 
3.5 31.1 10 42.5 27 0.62 
3 30.5 1557 3.90 
3.8 31.1 10 42.5 27 1.04 
4 61.0 1557 1.90 
4.0 31.1 10 42.5 45 0.54 
5 91.5 1557 1.58 
5.6 31.1 20 53.8 45 0.54 
6 91.5 1557 2.30 
5.0 31.1 20 53.8 45 0.82 
7 91.5 1557 3.05 
5.7 31.1 10 53.8 45 1.07 
8 91.5 1557 3.37 
5.7 31.1 20 53.8 45 1.14 
__________________________________________________________________________ 
Observations 
The results of runs 1 and 4 show that with a doubling of the belt velocity, 
the TEA and oxygen concentration in the chamber can be maintained 
substantially the same by merely increasing the angle of the outlet gas 
knife. 
TABLE 4 
__________________________________________________________________________ 
TEA 
Inlet Knife 
Outlet Knife 
Consump- 
Run 
Belt Vel. 
Recycle 
Chamber (vol %) 
Flow Angle 
Flow Angle 
tion 
No. 
(m/min) 
(L/min) 
TEA O.sub.2 
(L/min) 
(deg) 
(L/min) 
(deg) 
(Kg/hr) 
__________________________________________________________________________ 
1 24.4 1500 3.03 
4.3 31.1 10 42.5 25 0.62 
2 30.5 1557 3.30 
3.8 31.1 10 42.5 25 0.83 
3 61.0 1557 3.35 
4.8 31.1 10 42.5 25 0.93 
4 122.0 
1557 1.80 
6.0 31.1 20 59.5 45 0.62 
5 122.0 
1557 2.72 
5.6 31.1 20 58.0 45 0.92 
6 122.0 
1840 2.76 
5.5 31.1 20 58.0 45 0.92 
7 122.0 
1982 2.76 
5.5 31.1 20 58.0 45 0.92 
8 122.0 
2265 2.73 
6.0 31.1 20 58.0 45 0.92 
9 122.0 
1840 3.99 
5.8 31.1 20 59.5 45 1.36 
__________________________________________________________________________ 
Observations 
Runs 5, 6, 7, and 8 maintained all variables constant but the recycle. 
These results demonstrate that the recycle can be increased to a level 
whereby the oxygen concentration in the chamber increases. Apparently, 
there is an optimum recycle for the chamber which results in a 
minimization of oxygen concentration therein, provided that all other 
variables remain essentially unchanged. 
Based upon the data tabulated above and the experience garnered by 
operation of the prototype chamber, optimization of the inlet and outlet 
knife angles and flow rates have been determined based upon the conveyor 
speed. These optimized design variables assume the exhaust rate from cells 
50 and 102 each will be about 425 L/min (15 SCFM) and the recycle flow 
rate through lines 120 and 122 will be less than 2265 L/min. With these 
conditions, and based upon the conveyor speed, the angle and flow rate 
through the knives will permit the oxygen concentration in the chamber to 
be maintained at less than 6%, generally 3-6%, and a constant TEA 
concentration maintained ranging up to about 5%. 
TABLE 5 
______________________________________ 
OPTIMUM SETTINGS AT VARIOUS BELT SPEEDS 
Inlet Knife Outlet Knife 
Conveyor Speed 
Angle Flow Angle Flow 
(m/min) (.degree.) 
(L/min) (.degree.) 
(L/min) 
______________________________________ 
15.25 10 31.1 20 36.8 
24.40 10 31.1 25 42.5 
30.50 10 31.1 25 42.5 
61.00 10 31.1 40 42.5 
91.50 20 31.1 45 53.8 
122.00 20 31.1 45 58.8 
______________________________________ 
As will be noted, the N.sub.2 flow rate and knife angle of the outlet knife 
appears to be more important in maintaining the TEA and oxygen balance 
within the system. 
While the data tabulated in Tables 1-4 above provide an accurate operating 
history of the prototype chamber, such data can be assembled and 
correlated to provide interesting and valuable information concerning the 
total TEA consumption and total nitrogen consumption for the chamber. This 
information is presented as a function of the belt speed and as a function 
of chamber concentration of TEA. 
TABLE 6 
______________________________________ 
Total N.sub.2 Consumption (L/min) 
Belt Speed 
TEA Chamber Concentration (vol %) 
(m/min) 1 2 3 4 5 Avg. 
______________________________________ 
24.4 112.13 112.41 111.28 
110.43 
110.15 
111.27 
30.5 117.51 117.23 116.66 
115.81 
115.25 
116.49 
61.0 131.39 130.82 130.25 
128.84 
128.27 
129.91 
91.5 150.92 150.07 149.51 
148.09 
147.53 
149.23 
122.0 159.42 158.57 158.00 
156.59 
155.74 
157.66 
______________________________________ 
TABLE 7 
______________________________________ 
TEA Consumption (Kg/hr) 
TEA 
Chamber Conc. 
Belt Speed (m/min) 
(vol %) 24.4 30.5 61.0 91.5 122.0 
______________________________________ 
1.0 0.21 0.25 0.29 0.33 0.34 
1.6 0.34 -- -- 0.54 -- 
1.8 -- -- -- -- 0.62 
1.9 -- 0.44 0.54 -- -- 
2.0 0.41 0.51 0.57 0.67 0.68 
2.1 -- -- -- -- 0.72 
2.3 -- 0.62 -- 0.79 -- 
2.7 -- -- -- -- 0.92 
2.9 -- -- -- 0.98 -- 
3.0 0.62 0.77 0.85 1.01 1.12 
3.3 -- 0.83 -.93 -- -- 
3.4 -- -- -- 1.1 -- 
3.9 -- 1.04 -- -- 1.36 
4.0 0.83 1.03 1.13 1.34 -- 
4.6 -- -- -- 1.50 -- 
5.0 1.04 1.28 1.42 1.68 1.70 
______________________________________ 
The above-tabulated data also is depicted graphically in FIGS. 5-7. FIG. 5 
graphically depicts the nitrogen consumption as a function of belt speed 
at various constant TEA chamber concentrations. As can be seen from the 
data in Table 5, the nitrogen consumption primarily is a function of the 
belt speed and appears to be substantially independent of the TEA 
concentration in the chamber. It should be noted that the amount of 
nitrogen required to maintain central zone 34 at a desired oxygen 
concentration can be supplied manually through lines 137 and 122 into zone 
34. The overall consumption of nitrogen, though, remains substantially 
constant at the varying concentrations of TEA within the chamber. FIG. 6 
graphically depicts the consumption of TEA as a function of the belt speed 
at various constant TEA chamber concentrations. Quite clearly the 
increased TEA consumption at increased TEA chamber concentrations is seen. 
Also, the TEA consumption is increased at increased belt speeds and such 
TEA consumption increases at a greater rate at higher TEA chamber 
concentrations for increasing belt speeds. 
FIG. 8 graphically depicts the TEA consumption as a function of TEA chamber 
concentration at various constant line speeds. The TEA consumption is 
shown to be essentially linearly related to the chamber concentration and 
appears to asymptotically approach a maximum consumption based upon line 
speed. 
The foregoing data demonstrates the remarkable efficiency and economy of 
the design of the chamber of the present invention. Also, the apparent 
important variables in chamber design have been identified qualitatively 
and quantitatively. It will be appreciated that various modifications of 
the chamber can be implemented without departing from the philosophy and 
scope of the present invention. 
It will be appreciated that the nature of the gas environment through the 
central flow zone merely can be heated air or can be simply a carrier gas 
(eg. nitrogen, carbon dioxide, or the like). Appropriate insulation or 
lagging of the chamber may be required under such circumstances if heat 
transfer is of prime concern. Materials of construction are conventional 
for the type of opertion contemplated. Thus, stainless steel, galvanized 
steel, glass-lined steel or the like is used as is necessary, desirable, 
or convenient in conventional fashion. Where erosion or corrosion is 
inconsequential, mild steel, aluminum or the like may be used. 
Alternatively, the carrier gas can bear a catalyst such as a vaporous 
tertiary amine catalyst. For practice of vapor permeation cure with the 
chamber of the present invention, a good discussion on various types of 
vapor permeation curable coating compositions can be found in commonly 
assigned U.S. patent application Ser. No. 474,156, filed Mar. 10, 1983, 
the disclosure of which is expressly incorporated herein by reference. 
Such copending application describes and references a variety of polyols, 
multi-isocyanates, and optional solvents for formulating vapor permeation 
curable coatings. In this application, all percentages of gaseous 
components are volume percentage and all units are in the metric system, 
unless otherwise expressly indicated.