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Description  |
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This invention relates to an improvement connected with the generation of
polyurethane foam. More particularly, the invention relates to an improved
solvent system and to its use in cleaning polyurethane foam generating
equipment.
Polyurethane foam is prepared by mixing and reacting together, in the
presence of a foaming agent, an organic polyisocyanate with a polyol. For
the on-site generation of foam, a so-called portable foaming apparatus is
used. A variety of such portable apparatus have been disclosed in the
prior art. See for example U.S. Pat. Nos. 3,769,232 and 3,561,023.
Typically, a portable apparatus for the on-site generation of polyurethane
foam comprises at least two reactants supply tanks, a gun head including a
static mixer for mixing the reactants, and means for expelling the
reactants from their respective tanks, through the static mixer and onto a
surface or into a mold where the foaming reaction takes place.
In addition, the portable foaming apparatus usually includes, as an
essential or desirable component, a solvent supply tank. The solvent is
used in between or after repeated foaming operations, to clean the static
mixer and purge it of residual material that might otherwise accumulate
inside the mixed and interfere, chemically or physically, with subsequent
foaming operations. Thus, the outlet of the solvent supply tank is linked
to the static mixer via a valved conduit, and usually the same means that
is used to propel the reactants from their supply tanks is connected to
the solvent supply tanks for intermittently propelling the solvent through
and out of the static mixer.
Typical of the solvents that have been employed for this purpose are the
halogenated hydrocarbons, a commonly-used example of which is methylene
chloride. For conventional prior art applications, wherein the solvent is
used once and thereafter disposed of, the halogenated hydrocarbons are
usually satisfactory. However, they are generally unsatisfactory for
repeated use; for it has been found, according to the invention, that the
halogenated hydrocarbons do not retain their solvent properties after
being used once or a few times. For example, they usually form
precipitates or lose their homogeneity and therefore cannot be effectively
used again.
Now a select solvent composition has been found which is characterized by a
relatively low toxicity and a substantially improved capacity as a solvent
for polyurethane foam-forming chemicals. As such, it can be used
repeatedly to clean the apparatus for equipment utilized in processing
and/or foaming these chemicals. According to the invention, this
composition is comprised of (a) a halogenated hydrocarbon and (b) a
monhydric alcohol.
Further according to the invention, an improvement is provided in the prior
art method wherein an organic solvent is used to clean polyurethane-foam
generating equipment. The improvement resides in using, as the solvent,
the composition described above.
More in detail, the first component of the solvent composition of the
invention is a halogenated hydrocarbon. The desirability of this component
is predicated on the ready availability and relative low cost of various
halogenated hydrocarbons, and further on the fact that, by virtue of the
halogen therein, these materials have relatively low flammability.
The halogenated hydrocarbons used in the composition of the invention
include aromatic and aliphatic materials, although the aliphatic
halogenated hydrocarbons are generally preferred. Furthermore, the halogen
in this component can be chlorine, bromine, iodine, fluorine or a mixture
thereof.
Usually, the halogenated aliphatic hydrocarbons, which may be saturated or
unsaturated, cyclic or acyclic, have 1-12 carbon atoms, and, preferably,
they contain only carbon, hydrogen, and halogen atoms in the molecule.
Illustrative materials include the following:
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Methyl chloride
2-Chloropentane
Methylene chloride
3-Chloropentane
Chloroform 3-Bromopentane
Methyl iodide Isoamyl bromide
Bromoform Isoamyl iodide
Ethyl bromide Neopentyl bromide
Carbon tetrachloride
n-Hexyl bromide
n-Propyl chloride
3-Bromohexane
Trifluoromonochloro-
2-Chloro-2-methylhexane
methane
n-Propyl bromide
1-Iodo-2,4-dimethylpentane
Dichlorodifluoromethane
2-Bromooctane
n-Propyl iodide
2-Chloro-2-methylheptane
1,1,1-Trichloroethane
n-Nonyl chloride
Isopropyl bromide
n-Nonyl bromide
Isopropyl iodide
n-Decyl chloride
n-Butyl chloride
n-Dodecyl bromide
n-Butyl bromide
Cyclopentyl chloride
Isobutyl iodide
Cyclohexyl fluoride
n-Amyl fluoride
1-Chloro-2-methylcyclopentane
n-Amyl chloride
1-Chloro-1,3-dimethylcyclopentane
Methylene bromide
Allyl bromide
Methylene iodide
1,2-Dichloro-1-propene
Trifluoroiodomethane
1,1-Dibromo-1-pentene
Bromodichloromethane
Dichloroacetylene
Propylidene dichloride
1-Bromo-1-hexyne
Trimethylene bromide
______________________________________
The halogenated aromatic hydrocarbons, which include alkyl and
haloalkyl-substituted aromatic materials, again preferably contain only
carbon, hydrogen and halogen atoms in the molecule; and they usually have
from 6 to 12 carbon atoms. Illustrative of these are the following:
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Fluorobenzene m-Methylbenzyl chloride
Chlorobenzene Chloro-p-xylene
Bromobenzene 4-Phenylbutyl chloride
Iodobenzene m-Bromo-n-butylbenzene
Benzyl fluoride o-Chlorobiphenyl
Benzyl chloride Phenylchloroacetylene
o-Chlorotoluene 1-Phenyl-5-chloro-1-pentyne
.alpha.-Chloroethylbenzene
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As indicated earlier, the preferred halogenated hydrocarbons for use
according to the invention are aliphatic, such as illustrated above,
particularly those having 1-8, and still more preferably, 1-4 carbon
atoms. For reasons of low cost and ready availability, the most preferred
materials are the saturated, halogenated aliphatic hydrocarbons which
contain 2 or more halogens in the molecule. Those in which the halogen is
chlorine are especially preferred, such as methylene chloride and
1,1,1-trichloroethane.
The other component of the solvent composition of the invention is a
monohydric alcohol. According to the invention, the use of such a
material, in combination with the halogenated hydrocarbon, is critical.
This is because it has been found that the combination has a markedly
improved solvent capacity for polyurethane foam-forming chemicals than do
halogenated hydrocarbons alone. The criticality of using a monohydric
alcohol is further predicted on the additional discovery that similar
materials are less effective. For example, it has been found that
combinations of a halogenated hydrocarbon with other oxygen-containing
solvents, such as methyl ethyl ketone, has a substantially lower solvent
capacity for polyurethane foam forming chemicals than combinations of
halogenated hydrocarbons and monohydric alcohols.
The monohydric alcohol component can be a simple alcohol, a hydroxy ether
or a hydroxy polyether. Thus the term "monohydric alcohol", as used in the
specification and claims herein, is intended to encompass all these
materials.
As with the halogenated hydrocarbon component, the monohydric alcohol
component can be aliphatic or aromatic, although the aliphatic alcohols
are preferred. Furthermore, the monohydric alcohol preferably contains
only carbon, hydrogen, oxygen and optionally, halogen in the molecule.
Preferably, the oxygens in the molecule are limited to hydroxy and ether
oxygens. For reasons of economy, the use of monohydric alcohols which
contain only carbon, hydrogen and oxygen in the molecule, i.e.,
non-halogenated monohydric alcohols, is particularly preferred.
The aliphatic monohydric alcohols which are used in the composition of the
invention may be saturated or unsaturated, cyclic or acyclic, although the
saturated acyclic materials are generally preferred. And they may vary in
carbon atom content over a wide range, e.g., 1-20, depending for instance
on whether a long-chain monohydric polyether is used. Generally, in the
case of monohydric alcohols which are free of ether linkages, these should
preferably contain from 1 to 8, and more preferably 1-4, carbon atoms in
the molecule; whereas, in the case of the monohydric mono- and polyethers,
these should preferably contain 3-14 carbon atoms.
Illustrative of the aliphatic monohydric alcohols that may be used
according to the invention are the following:
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Methanol Dipropylene glycol monomethyl
ether
Ethanol Tripropylene glycol monomethyl
ether
Isopropanol Allyl alcohol
n-Butanol 3-Penten-1-ol
n-Pentanol Cyclobutanol
n-Hexanol Cyclohexanol
Ethylene glycol monomethyl
2-Octanol
ether
Ethylene glycol monoethyl
5-Nonanol (di-n-butyl-
ether carbinol)
Ethylene glycol monobutyl
2-Methoxy-1-propanol
ether
Diethylene glycol monomethyl
1-Methoxy-2-propanol
ether
Diethylene glycol monoethyl
4-Methoxy-1-butanol
ether
Diethylene glycol monobutyl
3-Methoxy-2-methyl-1-
ether propanol
Triethylene glycol monomethyl
1,3-Dimethoxy-2-propanol
ether
Triethylene glycol monoethyl
5-Methoxy-1-pentanol
ether
Triethylene glycol monobutyl
3-Methoxycyclohexanol
ether
Propylene glycol monomethyl
ether
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Aliphatic monohydric alcohols which are especially desirable for use
according to the invention include (1) the simple lower alcohols which
contain 1-4 carbon atoms and are free of ether linkages such as methanol,
ethanol, a propanol and a butanol and (2) the di- and tri- ether alcohols
containing 3-10 carbon atoms such as triethylene glycol monomethyl ether,
triethylene glycol monoethyl ether and triethylene glycol monobutyl ether.
The aromatic monohydric alcohols may be alkyl and/or haloalkyl substituted,
and the hydroxy group therein may be ring substituted or alkyl chain
substituted. They usually range in carbon atom content from 6 to 12 and
include, for example, phenol, the benzyl alcohols and their
alkyl-substituted derivatives, the phenyl alkanols and so forth.
The two essential components of the solvent composition of the invention
may be used in any suitable relative proportions. However, usually such
proportions are employed as to provide a weight ratio, of halogenated
hydrocarbon to monohydric alcohol ranging from about 1:1 to about 12:1 and
preferably from about 2:1 to about 10:1. From a practical standpoint, a
more desirable range is from about 3:1 to about 8:1, and in accordance
with the most preferred embodiments of the invention, such relative
proportions of halogenated hydrocarbon and monohydric alcohol are used as
to provide a weight ratio from about 3.5:1 to about 6:1, respectively.
The solvent composition of the invention is simply prepared by combining
and mixing together the halogenated hydrocarbon and the monohydric alcohol
in the desired or specified proportions. The mixture would then be ready
to use as a solvent for cleaning polyurethane foam generating equipment.
The mixture usually remains homogeneous and does not undergo phase
separation on prolonged storage.
In practicing the improved method of the invention, wherein the solvent
composition described herein is used as a solvent for cleaning a
polyurethane foam generating apparatus or a segment thereof, any suitable
prior art cleaning technique or method may be used. Thus, except for the
requirement of using the solvent composition specified herein, the method
of the invention is not limited to any particular cleaning process or mode
of operation. For example, the cleaning operation may be carried out by
rinsing or flushing the entire foaming apparatus, after the foam forming
chemicals have been exhausted, with the solvent; or, the solvent may be
periodically injected under pressure through the mixer portion of the
foaming apparatus in order to purge it of residual unreacted or partially
foam forming materials.
In accordance with a preferred embodiment of the invention, the solvent
composition described herein is used repeatedly in cleaning polyurethane
foam generating equipment. That is, after each individual use, the solvent
composition, rather than being disposed of and thus wasted, is retained in
a container and recycled for use again and again in subsequent cleaning
operations. To this end, a solvent recirculating system may be used such
as described in co-pending U.S. patent application Ser. No. 656,157, filed
by J. F. Zwirlein on Feb. 9, 1976. The entire disclosure of this
application is incorporated herein by reference. By virtue of its
stability and improved solvent capacity, the solvent composition of the
invention is particularly suited for use in this type of system. It is to
be realized, however, in connection with this embodiment of the invention
that the solvent composition described herein cannot be used over and over
again ad infinitum. Rather, after a great number of repeated uses, it may
eventually become contaminated with solid matter or its solvent capacity
may degrade to such a point that it cannot be effectively used again. When
this happens, the solvent composition must be replenished, purified or
replaced.
The following examples are provided to illustrate the invention. In these
examples all parts and percentages are by weight unless otherwise
specified. For testing the solvent capacity of the various solvent
compositions illustrated in the examples, a polyurethane foam forming
formulation is uniformly used. This formulation is supplied in two
separate components which had been pre-blended in separate containers. The
first component, referred to as the "A Component", consisted of a blend of
14.9 parts of trichloromonofluoromethane and 85.1 parts of an
isocyanate-terminated prepolymer. The latter was the product of mixing and
reacting together 97.7 parts of polymethylene polyphenylisocyanate and 2.3
parts of a polyether polyol having an average hydroxyl number of 365. This
polyether polyol is a product of reacting 4,4,4-trichloro-1,2-epoxybutane
with an equi-molar mixture of ethylene glycol and dextrose. As for the
polymethylene polyphenylisocyanate, this is a commercial product,
purchased under the trandemark "PAPI 135", which is characterized by an
amine equivalent of 134 and an average NCO functionability between 2.6 and
2.7.
The second component of the polyurethane foam forming formulation is
referred to as the "B Component". It consisted of a blend of the following
ingredients in the indicated relative proportions:
1. 57.24 parts of a polyether triol having a molecular weight of 5803 which
is the product of condensing glycerin first with 90.6 moles of propylene
oxide and then with 12.7 moles of ethylene oxide;
2. 6.78 parts of polyether diol having a molecular weight of 2000 which is
the product of condensing dipropylene glycol first with propylene oxide
and then with 20 moles of ethylene oxide;
3. 15.6 parts of trichloromonofluoromethane;
4. 12.05 parts of water;
5. 7.36 parts of dimethylethanolamine catalyst;
6. 1.51 parts of a silicone-glycol copolymer surfactant.
This is a commercial urethane foam surfactant, product of Union Carbide,
sold under the trademark or designation "L-540".
EXAMPLE 1
A solvent composition was prepared by mixing together 40 parts of
1,1,1-trichloroethane and 10 parts of methanol. The following procedure
was then used to test the capacity of this mixture as a solvent for
polyurethane foam forming chemicals.
A 50-gram sample of the mixture was placed in a small, stoppered bottle.
There was then added and admixed therewith 1 ml. of the polyurethane foam
forming composition described above, specifically 0.5 ml. of the A
Component and 0.5 ml. of the B Component. On visual examination, the
mixture was a homogeneous, clear solution. After storage at room
temperature for 3 days, the solution remained stable, exhibiting no
precipitation, gel-formation or viscosity increase.
At the end of the three day period, another 1 ml. dose of the polyurethane
foam forming formulation was added and mixed in. Again no change was
observed after the solution was allowed to stand for one day at room
temperature. This procedure was repeated two more times with no change
being observed. Rather, the solution remained stable with no
precipitation, gelling or noticeable change in viscosity.
EXAMPLE 2
A solvent composition was prepared, following the procedure of Example 1,
using 40 parts of methylene chloride and 10 parts of triethylene glycol
monoethyl ether, C.sub.2 H.sub.5 O(C.sub.2 H.sub.4 O).sub.3 H. A 50 gram
sample of this composition was mixed with 2 mls. of the polyurethane foam
forming composition described above, specifically 1 ml. of the A Component
and 1 ml. of the B Component. On visual examination, the mixture was a
homogeneous, clear solution which did not exhibit any precipitation,
gel-formation or viscosity increase on being stored overnight at room
temperature.
COMPARISONS 1-2
The procedure of Example 1 was repeated except that instead of 40 parts of
1,1,1-trichloroethane and 10 parts of methanol, 50 parts of
1,1,1-trichloromethane alone were used in Comparison 1 and 50 parts of
methylene chloride alone were used in Comparison 2.
In the case of each of the two comparisons, gellation and/or precipitate
formation were observed after the initial addition of the first dose of
polyurethane foam forming formulation. This demonstrates the improved
solvent capacity which obtains by using a solvent mixture of a halogenated
hydrocarbon and a monohydric alcohol, per Example 1, as compared with
using the same total amount of a halogenated hydrocarbon alone.
EXAMPLES 3-4
The procedurre of Example 1 was followed except that instead of 10 parts of
methanol, 10 parts of 1-butanol were used in Example 3 and 10 parts of
triethylene glycol monomethyl ether, CH.sub.3 O(C.sub.2 H.sub.4 O).sub.3
H, were used in Example 4. In both cases, the results were identical to
those of Example 1. That is, after the addition of 4 1-ml. does of the
polyurethane foam forming formation, the solution remained clear and
homogeneous with no evidence of any precipitation, gellation or viscosity
increased.
COMPARISONS 3-5
The procedure of Example 1 was followed except that instead of 10 parts of
methanol, equal amounts of perchloroethylene, methyl ethyl ketone and
cellulose acetate were used in Comparisons 3, 4 and 5, respectively. In
all three cases, the solution failed, as evidenced by precipitate
formation, at the end of the three days period following the first 1-ml.
dose addition of the polyurethane foam forming formulation. These
comparisons demonstrate the improvement which results from using a
monohydric alcohol, as the second component in the solvent composition, as
compared with using various other organic solvents.
EXAMPLE 5
Three solvent compositions, identified as 5-1, 5-2 and 5-3, were prepared
using 10%, 15% and 20%, respectively, of methanol in
1,1,1-trichloroethane. In the case of each of the three compositions, the
following procedure was employed to test solvent capacity for polyurethane
chemicals.
A 50-gram sample was placed in a small, stoppered bottle. To this, there
were added and mixed therewith, at specified intervals, three consecutive
doses of the polyurethane foam forming formulation described above. The
first dose was 3 mls. (1.5 mls. of Component A and 1.5 mls. of Component
B), and the other two doses were 2 mls. each. After each addition, and at
the end of each interval, the content of the bottle was visually examined.
If no precipitation or gelling was observed, the sample was given a "Pass"
rating; whereas if precipitation or gelling occurred, the sample was given
a "Fail" rating. Details of this test for each sample, including the
results, are provided in Table I below.
EXAMPLE 6
This example is a repetition of Example 5 except that in lieu of methanol,
triethylene glycol monoethyl ether, C.sub.2 H.sub.4 O(C.sub.2 H.sub.4
O).sub.3 H, was used. The results are provided in Table I wherein the
three illustrative solvent compositions corresponding to 5-1, 5-2 and 5-3
in Example 5 are identified as 6-1, 6-2 and 6-3.
EXAMPLE 7
Again the procedure of Example 5 was followed using, instead of methanol,
triethylene glycol monobutyl ether. The results are provided in Table I.
TABLE I
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%
Sample
Alcohol*
1st Dose
+ 16 Hrs.
2nd Dose
+ 6 Hrs.
3rd Dose
+ 4 Days
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5-1 10 PASS PASS PASS PASS FAIL FAIL
5-2 15 PASS PASS PASS PASS PASS PASS
5-3 20 PASS PASS PASS PASS PASS PASS
6-1 10 PASS FAIL FAIL FAIL FAIL FAIL
6-2 15 PASS PASS PASS PASS PASS FAIL
6-3 20 PASS PASS PASS PASS PASS PASS
7-1 10 PASS PASS FAIL FAIL FAIL FAIL
7-2 15 PASS PASS PASS PASS PASS FAIL
7-3 20 PASS PASS PASS PASS PASS PASS
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*The particular alcohols used were methanol in Samples No. 4, triethylene
glycol monoethyl ether in Samples No. 5 and triethylene glycol monobutyl
ether in Samples No. 6.
EXAMPLE 7
A solvent composition was prepared by mixing together 50 parts of
1,1,1-trichloroethane and 10 parts of triethylene glycol monoethyl ether.
This composition was successfully used, as a recirculating cleaning
solvent, in a portable polyurethane foam generating apparatus identical to
the one described in the above-noted Zwirlein patent application Ser. No.
656,157. The polyurethane foam forming formulation processed through the
apparatus was identical to that described above. Thirty foam shots were
made, with intermittent cleaning by running the above-described solvent
composition through the foaming head and back to its supply tank. The gun
head was then visually examined and found to be completely clean and free
of fouling or residual matter. After the last cleaning cycle, the solvent
composition itself was visually examined. It was still clear, homogeneous,
and free of any cloudiness or precipitation.
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