Note: Descriptions are shown in the official language in which they were submitted.
~ ~fv'43~2
This invention relates to methods for the cleaning of
urethane foam dispensers and, more particularly, to such
methods which include the use of a cleaning composition
comprising heated water. In particular, the present
invention relates to methods for removing polyurethane
precursor components and foam from the interior of
polyurethane dispensing means.
Polyurethane foams have long been recognized for their
ability to act as an insulating material. These foams are
prized due to their low density and relatively high
insulating capability. As such, a number of products have
used polyurethane foam as their primary means of insulation.
One example of such a product is the refrigerator. During
the manufacturing process, a fixed volume of foam is
dispensed into the hollow refrigerator shell such that the
cavity of the shell becomes filled with the expanded
polyurethane foam, thereby creating an insulated food
compartment.
The polyurethane foam itself is comprised of the reaction
2G product of an isocyanate and a polyol, or blends thereof,
which, upon contact with water, reacts to foam the
polyurethane foam. Accordingly, these foam precursor
components, are preferably contacted
~ ~ ~; 3 J ~
and mixed just prior to the time of application. In this
way, foam is not formed from the precursor components
prematurely, ie prior to the time the precursor components
exit, or are on the verge of exiting, the dispenser.
As mentioned previously, the contact and mixing of the foam
precursor components, and the resulting formation of the
foam, should occur as close to the outlet of the dispenser as
possible. Despite taking precautions in this regard,
however, prematurely-formed foam can build up in the interior
of the dispenser, clogging control valves and passageways
such that the dispensing device is rendered inoperable.
As alluded to previously, one of the most difficult problems
associated with these polyurethane dispensers is not the
accurate metering of the various precursor components lnto a
cavity, but cleaning the device after use. Despite the best
efforts of designers to alleviate the problems of deposits
forming on the interior surfaces of these devices, there
remains troublesome solid deposits on valves, delivery lines,
and other elements on these dispensing devices after only a
relatively short period of use.
Various methods have been developed to remove these deposits
from the interior of dispensing
-- 2
2 2
devices. Organic solvents, such as methylene
chloride, have been used to clean polyurethane foam
dispensers ~or years, these solvents being circulated
through the interior of the dis~ensers arter use.
However, due to recent governmental regulations wnich
restrict the disposal of these solvents, the industry
has turned to other cleaners which do not contain
these restricted compqnents.
One example or a purportedly less
environmentally harmful cleaner is Neutra-~lush III
(~rulin & Company, Inc., Indianapolis, Indiana) which
contains 1-5 percent sodium metasilicate. ~owever,
this cleaner also contains what is classi~ied in the
art as a solvent. In addition, this material, li~e
other solvents, may cause irritation or the eyes and
skin o~ the user. Moreover, the resulting
polyurethane/solvent comDosition is also dif.icult to
dispose o~ in view os present state and Eederal
standards for waste disposal. ~owever, permits for
disposal of this cleaner are not as dif~icult to
obtain as the aforementioned methylene chloride-based
cleaners.
An alternative cleansing system is disclosed in
.S. Patent No. 4,485,840. This patent provides a
flushing system for a me~ered delivery apparatus,
said apparatus being adapted for the delivery of an
adhesive material. The adhesive material, which
J ~ 2
contains a water-dispersion polymer, such as a polyol, and
polyisocyanate, may be flushed from the dispensing device (or
gun) by use of this system. Generally, the system
contemplates that warm water, which may include additions
such as acids, bases or detergents, be circulated through
those areas of the dispensing gun which contact the adhesive.
optionally, air may be delivered in short bursts to provide
additional agitation for better cleaning action.
Further, a solvent cleaning fluid line is attached to the
isocyanate delivery line of the gun, this solvent preferably
being capable of solvating isocyanate. During cleaning, this
solvent flows through the isocyanate delivery line and acts
to remove the solid deposits derived from the isocyanate
during use of the metering delivery system described
previously.
In view of the limitations inherent in known polyurethane
foam dispenser cleaning methods, a need exists for a solvent-
free procedure which is non-toxic to humans, inexpensive, and
relatively easy to dispose of after use.
It is an object of the invention to provide an improved
method for removing polyurethane precursor components and
foam from the interior of a polyurethane dispensing means.
According to one aspect of the invention there is provided a
method for removing residual polyurethane precursor
components and foam from the interior of a polyurethane foam
dispensing means prior to the solidification of said
components, said means comprising a plurality of controllable
feed tubes, said tubes being adapted for transporting and
selectively introducing the precursor components into the
interior of said dispensing means, said method comprising
introducing a cleaning composition into the interior of said
h ~3 '~
dispensing means to remove s~lbstantially all of the
polyurethane foam precursor components and foam, said
cleaning composition being at a temperature of at least 80F
upon its introduction into said dispensing means and
comprising water free of other solvents.
Reference is now made to the accompanying drawings, in which:
FIG. 1 is a schematic representation of a typical foam
dispenser which may be cleaned using the method of the
present invention;
FIG. 2 is a top view of a foam dispensing apparatus in
accordance with an exemplary embodiment of the present
invention and illustrating the dispenser with the valves
being positioned so that
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?~t~
the cleaning composition is being admitted into the
dispenser;
FIG. 3 is a side e1evation view of the ~oam
dispenser of FIG. 2;
FIG. ~ is a side elevation view o~ the L^oam
dispenser cf FIG. 2, with the valves being positionec
so that the components or the foam are being aomitted
into the dispenser, and illustrates, in accordance
with another exemplary embodiment of the present
invention, the use of a plastic tube containing
mixing elements as the mixing chamber;
FIG. 5 is a cross-sectionaL view taken along
line 6---6 of FIG. 2, showing the position of the
valves when the cleanin~ composition is being
admltted to the dispenser;
PIG. 6 is a cross-sectional view similar to FIG.
5 showing the position or the valves when the foam
components are being admitted to the dispenser; and
~ IC- 7 is a cros~-section2l view taken alon~ the
line 7----7 of FIG. 4, which urther illustrates the
internal construction o~ the valves and passageways
in the preferred dispenser;
FIG. 8 is a cross-sectional view taken along
line 6----6 of FIG. 2, FIG. 2 being similar to FIG.
5, which further illustrates, in accordance with
another exemplary e~bodiment ot the present inventive
method, the attachment of a first pipe tee having a
t."'~ ~ ~ J ~ -.f
zert ~itting and a first check valve, a second pipe
te~ at.ached to a source of cleaning composition as
~ell as said first check valve, and a second check
valve beins to at~ached to said second piDe tee such
that air and the cleaning composition may selectivel-
~enter the dispenser; and
FIG. 9 is a schematic of an alternati~Je foam
dispensing system which may also be cleared of
polyurethane foam and its prec~rsor comronents by use
of the cleaning method oE the present invention.
While the invention will be desc-ibed and
disclosed in connection with certain preferred
em~odiments and procedures, it is not intended to
limit the inven~ion to those specific emoodiments.
Rather, it is intended to cover all such alternative
embodiments and modi~ications as all within the
spirit and scope o~ the invention. For exam~le,
although the present invention will be described as ,-
~method ~^r clear.ing particular types o~ dispensers
for polyurethane foam, the method of the present
invention is also useful for cleaning other types of
polyurethane foam dispensers, as will be readily
apparent to those skilled in the art.
DETAIBED DESC~IPTION OF THE P~EE~RED E~BaDIME~TS
The present invention provides a method for
removing residual polyurethane precursor components
2~ .S~J~J IJ
and ~oam from the interior of a ~olyurethane oam
dispens.ing means prior to the solidification of said
components, said means comprising a plurality of
controllable feed tubes, said tubes being adap~ed for
transporting and selectively introducing the
precursor components into the interior o~ said
dispensing means, said method comprising introducing
a cleaning composition into the interior of said
dispensing means to remove substantially all or the
polyurethane foam precursor components and foam, said
cleaning comoosition being at a temperature of at
least 80~F upon its introduction into said dispensing
means and comprising water free of other solvents.
Turning initially to FIG. l, an exemplary polyurethane
dispensing device is illustrated, for the purposes or
the present discussion, as a schematic diagram. The
device~ represented therein is adapted to provide a
polyurethane foam which is 'ormed from two precursor
compGnents. These components reside, until ready ~or
use, in holding tanks. 1 and 2. Typically, these
tanks will contain a polyisocyanate and a polyol,
respectively, which, upon activation of the dispenser
10w controllers 3 and 4, flow into the ~ixing
chamber 5 and are mixed and subsequently dispensed as
a polyurethane foam.
A propellant, e.g., nitrogen, which resides in a
storage tank 6, is used to dispense the precursor
2 ~ J ~J I~J
com~onents from their containers and into the
dispenser gun. A timer 7, is preferably connected to
the propellant storage tank 6 such that a consistent,
metered amount of polyurethane foam is delivered from
the dispenser. An air compressor 8 may be
advantageously used in combination with the water
cleaning solution of the present invention to ~rovide
more rapid cleaning of the dispenser, this method
being described in more detail infra.
The cleaning composition itself~ which comprises
water at a temperature of at least 80F, is supplied
from any suitable source, such as a ~ressurized tank
9. Preferably, said cleaning composition contains no
additional solvents other than water. Upon cleaning,
the cleaning composition flows ~rom the tank 9,
through a chec~ valve 10, and into the interior of
the dispenser such that the remaining ~recursor
components and Eoam are removed f rom the interior c
the dispen3er. The cl2anlng composltlon may then be
recirculated to the storage tank 9 or may be disposed
of in an environmentally safe manner.
More particlllarly, the cleaning com~osition
should be at least 80~, this being the temperature
at which adequate cleaning of the dispenser will
occur, i.e., the remaining prec~rsor components and
foam are removed from the interior of the
dispenser. Water at higher temperatures, including
_g_
5 ~
steam, may be advantageously employed as Lhe r~ater
cleaning component.
By using a cleaning solution at a higher
tem~erature, the use of solvents other than water,
e.g., methylene chloride, is avoided. A.
temperatures above 80F, the present composition was
Eound to remove substantially all of the residual
precursor components and foam, wherein composit~ons
below this temperature are less eEfec.ive and will
not remove substantially all of said residual
materials.
In addition to the water component, cleaning
enhancers may be used in the present composition,
e.g., detergents, surfactants, acids and bases,
although these should be distinguished ~rom the
previously mentioned solvents. The use of the
present cleaning composition which includes water,
and optionally a cleaning enhancer, is advantageous
o~er ~rior cleaners inasmuc~ as it is nQn-~o~ic to
humans, is inexpensive, and is not harmEul to the
environment.
As an example of those dispensers which ~ay be
cleaned by the present invention, a preEerred foam
dispenser will be described, which dispenser includes
a barrel having a plurality of passages which allow
communication between a center plug and the fluid
foam components and the cleaning component, warm
--10--
~ .~3 ~ rJ ~
waters. The center plug can have a central bore comprising a
mixing area as shown in FIG. 7, or can have discrete passages
for each of the foam components. A detachable mixing chamber
is connected to the center plug at the end of the barrel and
communicates therewith to provide a chamber for the various
foam components to meet and react to form the expanded foam.
A nozzle is connected to the end of the mixing chamber and
provides an opening for discharging the expanded foam from
the dispenser. A rotary valve structure for each principal
foam component is provided, each having a single passageway
formed therethrough to permit the introduction of either the
foam component or the cleaning composition through the vale
and into the center plug.
The passageway for each valve is in communications with a
passageway in the center plug and can move between a position
in which either a foam component or cleaning composition is
admitted into the gun. Each valve is provided with a tube
for carrying the foam component to the dispenser, each such
tube having a corresponding tube for carrying the cleaning
composition. The distance between the point where the supply
tubes are attached to the dispenser and the valves is short
so that, after the valves are rotated to flush the dispenser
with the cleaning composition, e.g., warm water, no
significant ~mount of film. components builds up in
-- 11 --
the dispenser during ~ormal usase. In a preferred
embodiment of the present method ~hich utilizes air
during cleaning, the cleaning composition tu~es
communicate with the rotary valve via a pipe tee.
The pipe tee has a zert ~itting and a chec~ valve,
the check valve being situated at the interface o~
the piDe tee and a com~ressed air eed tube.
In an alternative embodiment o~ the present
method, air and the cleaning composition may De
delivered to the interior o~ the dispenser in an
alternating manner such that short bursts of each
~luid are produced which act to clean tne interior.
Turning again to the drawings, FIGS. 2 and 3
show generally a hand-held foam dispenser 20, having
a handle 22 and a barrel 24. A mixing chamber 26 is
attached to the end of the barrel and has a nozzle
28, with a passageway ~or discharging the expanded
foam. Bosses 30 are affixed on opposite sides or the
barrel 24. Each boss 30 carries a rotary valve,
generally indicated by 52, as shown in FIGS. 5 and
6_ A rotary valve is provided for each different
fluid component required to make the expanded foam.
Although generally only two principal components are
required -- a polyol blend and an isocyanate blend --
thus necessitating only two valves 52, it is not
intended that this invention be limited to the use of
such components, or to an embodiment having only two
~alves. It should likewise be appreciated that
additionaL foam comoonents can be added to the pol~ol
and isocyanate constituents i~ desired by the user.
The foam comoonents and warm water sources are
connected to the dispenser by seDarate at.acnmen~
means. Thus, as shown, each boss 30 has two
internally threaded ports 34 and 36 as shown in FIGS.
S and 6. A conduit 38, which can be a flexible tube,
is affi~ed to each foam component port 34. ~ube 3
is removably secured to port 34 by a coupling ~0,
whose external threads cooperate with the internal
threads of the port. While the cleanins com~osi,ion
inlet port 36 may also be connected to a conduit 46
~y a coupling 44 (FIGS. 2 and 3), in a preferred
embodiment, the water inlet port 36 is actached a
pipe tee, which is attached to the port by a couplins
44. The coupling 44 has external threads which
cooperate with the internal threads of the port 36,
and internal threads that cocperate with the exte~n
threads of the pipe tee One end o the pipe tee is
connected to a conduit 46, w~ich can be a flexible
tube. Tube 46 communicates with the pipe tee via a
chec~ valve. A zert fitting, or other suitable one-
way valve for the introduction of a substance into
the system, is located at the end of the pipe tee
opposite the check valve. The zert fitting allows
the user to clean out foam components hydraulically
-13-
r~
~, t ~ ,, jJ
from the pathways of the dispenser. It also seals any trace
residue from the air, eliminating unwanted phenomenon such as
film formation in the interior of the dispenser. The check
valve is provided to prevent the foam components or purging
medium from entering the cleaning composition feed tube 46
during cleaning.
Tubes 38 and 46 lead to sources of pressurized fluid foam
components and cleaning compositions, respectively (not
shown). The admittance of the fluid foam components and the
cleaning composition from their respective supply sources
into the tubes may be regulated by a valve between the tube
and the supply source which is readily accessible to the
operator of the foam dispenser. Suitable supply sources for
the fluid foam components such as drums and the like are well
known and may be employed. Such sources of foam components
include 15 to 8,000 gallon cylinders pressurized by applying
pressurized nitrogen, supplied through a regulator, to the
top of each cylinder. Pressurized fluids can also be
supplied by a pumping device. Likewise, cleaning composition
and air may be provided via a pressurized tank.
Figs. 6 and 7 illustrate preferred valves 52, although those
skilled in the art will appreciate that other valves can also
be employed to implement the process described herein. Each
valve has a single L-shaped passageway 53 with an outlet 54,
which communicates through passage 56 to
- 14 -
~ ~I R ~
the center plug 60 which communicates with the mixing chamber
26 the center pug 60 and mixing chamber 26 are exemplified in
FIG. 4. Passageway 53 also has an inlet 62, which
alternatively rotates between communication with tube 38 when
foam is to be dispensed, and with a pipe tee (exemplified as
in 42 FIG. 8) when the apparatus is to be cleaned with the
previously described cleaning composition following the
completion of a foam-dispensing operation.
The mixing chamber 26 is preferably of a disposable type
which can be discarded after use or cleaned several times
without detachment via the use of the present method. Since
the mixing chamber 26 is located outside the barrel 24, it
can be removed from center plug 60 without the necessity of
disassembling the dispenser, thus facilitating easy removal
of the mixing chamber 26 for manual cleaning or replacement,
if desired. As shown in FIG. 4, the mixing chamber may be a
translucent p~astic tube which includes disposable mixing
elements. The length and diameter of this tube would vary
depending upon the desired use of the dispenser by the
operator.
As best shown in FIGS. 5, and 6, it is a feature of the
dispenser of this invention that when the valves 52 are in
position to emit either fluid components or a cleaning
composition, the inlets 62 are nearly coterminuous with the
ends of the couplings 40 and 44. Due to the single
passageway 53
- 15 -
on each valve, the cleaner travels in tne identical
path that the foam components travel while in the
dispenser. Pre~erably the distance between the point
where either the foam components or cleaning solution
are introduced into the dispenser and the point where
they enter the valves is short, so that a more
complete cleaning of the gun can be achieved.
In the illustrated form, the valves are grooved
to receive O-rings 68, as best seen in FIG. 7, on
which the va~lves are slidably mounted in a fluid-
sealed relation with bosses 30. ~he bosses also have
additional ports 70 (~IGS. S and 6), which are filled
with a lubricant, such as petroleum jelly or
dioctylphthlate (dop), and are plugged to allow the
lubrication of the valves 52. The valve seats should
desirably be made o a durable material so that the
requency of replacement can be minimized. Many
suitable materials arE known, with polytetrafluoro-
ethylene resins being pre~erred~
A urther feature of the dispenser o the
present invention is its ability to deliver a
predetermined amount of e~panded foam. This feature
is important when the foam is being introduced into a
conined region, such as a refrigerator shell, where
the operator wants to introduce neither too much nor
too little foam, but wants to precisely fill the
volume o~ the region. To this end, the valve inlets
-16-
2~J~ 2 2
52 are aligned with ports 54 for only the amount of
time suf~icient to allow the components needed to
make the required volume of foam into the mixing
chamber 26 via mi~ing area 61. Ar~er this time has
elapsed, the inlets 62 move out o~ alignmene with the
pGrts 54, and no additional components are allowea to
enter the mixing chamber 26 through the center plug
60. Thus, means are provided for moving all valves
in unison bPtween the position in which they
communicate with the foam companent carrying tubes
and the position in which they communicate with the
warm water carrying tubes.
In a preferred embodiment, each valve 52 has a
valve stem 71, best seen in FIG. 7, which extends out
~rom the boss 30 and is keyed to be held ~or rotation
by one end of a lever arm 72. The other end or each
lever arm 72 is connected by an extension 74 to the
rod 76 of a double-acting gas cylinder or piston 78
(FIG. 23 which is rigidly affixed to the roam
dispenser 20 through an L-shaped bracket 80. ~he
lever arms 72 are slotted to compensate for the
straight line movement of piston rod 76. The move-
ment of the piston rod 76 rotates the valves 52 in
unison between the position in which foam components
are allowed to enter the foam dispenser, when the
piston rod 76 is in its extended position (shown in
~IGS. 4 and 6), and the position ln which the warm
-17-
2 ~
water is admitted to the ~am disDenser, ~hen the
oiston rod 76 is in its retracted oosition (shown in
FIGS. 3 and 5).
The piston 78 provides timed actuating means for
the valve and is actuated by the manipulation of a
trigger switch 82 (~IG. 3), which is located in the
handle 22. When manipulated, the trigger 82 feeds
either a gas diverter valve or an eLectric control
circuit which emits gas to the left-hand side of the
piston, extending the piston rod 76 to move the valve
52 in unison into position to emit foam comoonents
(FIG. 4). After being in such a oosition for the
amount of time required to introduce the amoun~ of
oam components required to make the desired volume
o~ expanded foam, the piston rcd ~6 is automatically
retracted by introducing gas to the right-hand side
o~ the-piston to bring the valves 52 in unison into
position to admit. the warm water (FIG. 3) and thus
clean the foam dispenser of all foam components to
prevent the dispenser from becoming clogged.
In a preferred. embodimentr trigger 82 is
connected to a commercially available low voltage
switch cord. The switch cord is connected to a
commerciaLly available timer which has thumb wheels
on its front for varying the time of each dispensing
sequence between 0.1 and 99.9 seconds. The timer
also has an LED display which shows the time
-18-
~ 'J "'~ ~j ~ fJ .f
remaining before gas is admitted to right-hand side
o~ the piston to retract the piston rod 76 and, thus,
rotate the valves 52 so that no ~oam components are
introduced into the gun. 3y knowing the volume o~
the container to be filled, the Elow rate or^ tne foæm
components into the gun, and the expansion rate o~
the combined components, the operator can set the
timer so that the volume of the expanded foam
generated by the gun precisely fills the container.
After the timer is set, any number of identical size
containers can be ~illed to the desired level by
simply pulling the trigger 82 to initiate the timing
sequence.
As mentioned previously, an alternative
embodiment of the cleaning comoosition/comDressed air
delivery system, as illustrated in ~IG. 8 ~which
closely resembles ~IG~ 5) urt~er provides a second
~ipe tee 90 which is connected to the upstream end or
chec~ valve 48 in plac~ of the conduit 46. Pipe tee
90 communicates on one end wit~ a second check valve
91. This check valve 91 is in turn connected to
conduit 46, which connects the dispenser to a supply
of compressed air or other gas. The other opening in
the second pipe tee 90 is connected to the warm water
cleaning source.
The novel arrangement allows alternate short
bursts of cleaning composltion and compressed gas or
--19--
air to be circulated thr~ugh the dispenser until the
precursor components are removed from the dispenser.
For ourp~ses of exemoli~ying the operation of
this embodiment, the cleanin~ comoosition is supplied
to the dispenser by a pumo. During the uo st.oke of
the pump when the water pressure is at its minimum,
the air will rlow through conduit 46, check valve 91,
tee 90, check valve 48, and into the dispenser. A
short time later, when the pump is on its down stroke
and the water pressure is at its maximum, the cleaner
enters the pipe tee 90 at inlet 92 and oroc~eeds
through check valve 48, its passage into the air
conduit 46 being blocked by check valve 91. Thus,
alternating short bursts of cleaner and compressed
gas or air may be producPd, this resulting in
increased agitation of the cleaning fluids and,
accordingly, enhanced cleaning o~ the dispenser.
In polyurethane dispensing guns which use a
solvent to clean the residue ~rom their interiors,
such as those exemplified in ~.S. Patent No.
4,440,320 which is incorporated hy re~erence herein,
a supply line which carries the a~oresaid cleaner may
be placed in the position occupied by the solvent
line to efectuate cleaning according to the present
method. Other types of polymer foam dispensing
devices may also be cleaned by the present method,
-20-
2 ~ r~
including, e.g., dispensers available from the Olin
Corporation.
A ~urther example of a system in which the
method of the present invention may be used to remove
polyurethane precursors is schematically represented
in FIG. 9. In this diagram, the precursor components
are contained within storage tanks 100 and 102. A
supply of a compressed gas which resides in storage
tank 102 is used to provide streams of these
components which flow through hoses 111 and 112 to
the gun assembly 108. After entry into the assembly
108 these components are mixed in chamber lOg such
that a polyurethane faam is produced upon exit of the
mixture from the gun assembly 108. ~he com~ressed
gas 102 also provides ~or the 1OW of the cleaning
composition, e.g.., warm water, from tank 104 to the
gun assembly 108. The flow of cleaner in this system
is controlled by valve 105, which is opened when
cleaning o~ the gun i5 desired_ IE desired,
alternate bursts of the cleaner and air may also be
ef~ected to clean the dispensing assembly 108.
In regard to controlling the flow of precursor
components, valves 110 are provided which are adapted
for selectively allowing the components to flow into
the gun assembly 108. Further, flow valves 106 are
provided for each component feed line which regulate
the rate of flow of each component. In-line filters
-21-
107 are also provided for maintaining the ourit~ of
the precursor component feed.
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