Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02319319 2000-09-11
PROCESS AND APPARATUS FOR MANUFACTURING
UREA/FORMALDEHYDE FOAMS
FIELD OF THE INVENTION
This invention relates to cellular plastic foams, and particularly to process
and apparatus for manufacturing urea/formaldehyde foams. Such foams can be
used, for example, in industry as oil absorbents.
BACKGROUND OF THE INVENTION
Urea/formaldehyde foams have been used as building insulation for
decades. Different kinds fo OF foams, including modified OF foams, have been
introduced since 1926. To the best of our knowledge, all OF foams commercially
made in this world are resin coated or catalyst coated bubbles. According to
National Bureau of Standards Technical Note 1210 :"Three major ingredients are
used in the generation of foam : Urea-formaldehyde resin, a surtactant
(generally
called a foaming agent) which includes an acid catalyst or hardening agent,
and
air." "In the United States the foaming agent-catalyst mixture is in general
pumped into the gun where compressed air mixes with it and mechanically
expands it into foam consisting of small bubbles. The bubbles are then coated
in
the nozzle of the gun with the urea-formaldehyde resin which has been pumped
through a separate line into the gun. The foam, consisting of resin coated
bubbles, is forced out of the gun under pressure at which time it contains
about
75 percent water by weight." This is resin coated bubbles------Most of OF
foams
are made according to this method.
"The technique for foam generation in the U.S. has also been used in
Europe in other methods. As one example, both resin and foaming agent
solutions are mixed through the expansion chamber of the gun. In another, the
catalyst is added to the foam after initial expansion". This is catalyst
coated
bubbles.
We can say that there are other methods to make OF foams. Such as :"
Using materials that react with the acid catalyst to form C02 gas, like those
used
in phenolic foam generation" or "Low-boiling liquids have also been used as
expanding agents". These techniques are out of date and worthless.
Different kinds of apparatus have been introduced and commercially
used too. Different apparatus may have different spraying nozzles, or may have
different foaming chambers, but all of these apparatus have been designed and
used to manufacture resin coated or catalyst coated foams.
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There are several problems associated with these foams. One problem
relates to the mechanical properties. These finished OF foams are usually
brittle
structures with very low compressive strength. In some cases, the foam was so
poor that it collapsed after application or crumbled within weeks.
Another problem is shrinkage. There is shrinkage with these OF foams,
and the shrinkage of these OF foams normally is between 3% to 8%, sometimes
it can be 20% or even more.
Yet another problem associated with these foams is the density. The
density of these foams is NOT less than 0.62 pound per cubic foot. This
density
is high for OF foams.
These traditional foams can pick up some oil. But it is not good enough
to use them as oil absorbent.
SUMMARY OF THE INVENTION
The present invention has been provided to solve the aforesaid
problems, and it is an object of the present invention to provide a process
and
apparatus for manufacturing well mixed, well solidified and well made OF
foams.
It is another object of the present invention to provide a manufacturing
process in which the mixing process is simultaneous with foaming process.
It is still another object of the present invention to provide a
manufacturing process in which foaming process is also a very good mixing
process.
It is a further object of the present invention to provide a manufacturing
process in which the foaming process takes place at the same place where the
mixing process takes.
It is a further object of the present invention to provide a manufacturing
process in which expanding the mixture of urea-formaldehyde resin and foaming
agent-catalyst is the main foaming process in the whole manufacturing process.
It is a further object of the present invention to provide a manufacturing
process in which the solidifying process starts with the foaming and mixing
process.
It is a further object of the present invention to provide a manufacturing
process in which the solidifying process starts at the place where the foaming
and mixing processes take place.
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It is a further object of the present invention to provide an apparatus
that can start the foaming, mixing and solidifying process at the same time.
It is a further object of the present invention to provide an apparatus
that can start the foaming, mixing and solidifying process at the same place.
It is a further object of the present invention to provide an apparatus
that can expand the mixture of urea-formaldehyde resin, air and foaming agent-
catalyst into foam.
Three major ingredients are used in the generation of this novel foam
main composition which includes urea-formaldehyde resin and foaming agent, an
acid catalyst and gas. These ingredients can also be urea-formaldehyde resin,
a
surfactant which includes an acid catalyst and gas. But traditional
ingredients
must be modified for this invention. Because in this invention, in a short
time, the
mixture of urea-formaldehyde resin, foaming agent and acid catalyst is still
good
to be used in a foaming process.
Broadly speaking, water-insoluble gases are suitable for this foaming
purpose. It is economical to use compressed air, either from gas cylinders or
compressors.
This novel foam has been used with excellent results as absorbent.
One gram of this foam absorbs 63 gram diesel oil which is more than 70 ml.
This novel foam has many outstanding properties when compared to
traditional foams. For instance, its density is 30% less than traditional
foams, and
its mechanical properties has been improved. It is half-flexible. Traditional
foams
are usually brittle structures. This foam is very stable too. We have made
more
than 100 cubic meters of this foam and we have not observed any shrinkage.
The standards for shrinkage of traditional foams is usually 4%, and in fact it
can
be more than 20%.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the present invention be better understood, preferred
embodiments of it will now be described by way of examples, in reference of
the
following drawings in which:
FIGURE 1 is an elevational view of the first embodiment of this invention.
FIGURE 2 is an elevational view of the second embodiment of this invention. It
is an apparatus of the earlier patent modified according to this invention.
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FIGURE 3 is a perspective view of foaming chamber used in this invention.
FIGURE 4 is a perspective view of another foaming chamber used in this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGURE 1, the apparatus includes a first container 1
which contains compressed air. A second container 2 and a third container 3
hold main composition and dilute acid catalyst separately. Container 2 and 3
can
also hold urea-formaldehyde resin and surfactant which includes an acid
catalyst
too.
Container 3 communicates with container 1 through a conduit 5 and
further communicates with a meeting chamber 9 through a conduit 8. Conduit 4
connects container 1 and 2 which communicates with chamber 9 through a
conduit 7, and conduit 7 enter the chamber 9 through a spiral nozzle 12 which
sprays ingredients into the chamber to help mixing process.
Main composition, acid catalyst and air meet at the meeting chamber 9
through conduits 7,8 and 6. The apparatus is operated by compressed air. When
the ingredients enter the chamber 9, the pressure push them into foaming
chamber 10 immediately. At foaming chamber 10, main composition and acid
catalyst is mixed and foam is formed. Conduit 11 communicates with chamber 10
and discharges the foam.
Referring to FIGURE 2, the apparatus is modified from Bauer U.S.
Pat. No.2860856. This apparatus is operated by compressed air supplied from
the steel bottle 1, conduit 13 connects this bottle and container 14 which
holds
urea-formaldehyde resin, conduit 15 links bottle 1 to container 16 containing
surfacant which includes acid catalyst. The container 16 is connected by a
line
17 with a container 18 wherein the pre-foam is formed with the aid of
compressed air introduced through the line 19.
The pre-foam thus prepared is led to a meeting chamber 20. The
conduit 21 which leads the urea-formaldehyde resin from the container 14 to
the
meeting chanmber enters the meeting chamber through a spiral mixing nozzle
12. Spiral nozzle 12 sprays urea-formaldehyde resin into the meeting chamber
to
help mixing process. Urea-formaldehyde resin, air and pre-foam are forced into
foaming chamber 10 immediately by pressure. At foaming chamber 10, pre-foam
and urea-formaldehyde resin is mixed and foam is formed. Conduit 11
communicates with chamber 10 and discharges the foam.
FIGURE 3 shows one model of foaming chamber used in this
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invention. It is a stirred foaming chamber. 23 is a stirrer. Air, urea-
formaldehyde
resin and surfactant which includes acid catalyst enter this chamber at 22 and
foam exits at 24.
FIGURE 4 is another model of foaming chamber used in this
invention. It is a beads-packed foaming chamber. This chamber is filled with
glass beads 25. Main composition, air and acid catalyst enter this chamber at
26
and foam exits at 27.
(5)
