Note: Descriptions are shown in the official language in which they were submitted.
(
D# 80,967-F
RRS
A PROCESS FOR REMOVING CURED RIGID POLYURETHANE FOAMS
FROM SUBSTRATES
(D# 80,~67_F)
Cross-Reference to_~lated Application
This application is related to co-pending U. S. Patent
Application Serial No. 07/610,635, filed November 8, 1990.
Background of the Invention
Field of the Invention
The invention relates to solvents for loosening or
removing cured rigid polyurethane foams from tools, processing
equipment and other substrates.
Description of Related Methods
A variety of solvents have been used to clean processing
equipment, metal parts and tools after a rigid polyurethane foam
has cured on them. Some of the solvents used include such
compounds as dimethyl formamide, 1,1,1-trichloroethans, methylene
chloride, chlorofluorocarbons, toluene, xylene, acetone, methyl
ethyl ketone, ethylene glycol ethers, tetrahydrofuran, and
~-butyrolactone. However, though these compounds are effective
solvents, the use of each presents a hazard or complication of one
type or another. For example, the chlorine-containing compounds
are now thought to contribute to ozone depletion in the atmosphere.
The other solvents are either toxic, suspected carcinogens, or very
volatile, and thus present health and safety problems. An
alternative solvent, n-methyl pyrrolidinone, is more easily handled
and presents fewer environmental problems, but is expensive. Thus,
^i 7 ~ ,~
it would be a substantial improvement in the art if a relatively
inexpensive yet effective solvent formulation were available to
remove cured rigid polyurethane foams, and that did not present the
environmental, health and safety problems of the prior art solvent
formulations.
Applicant has discovered, surprisingly, that cured rigid
polyurethane foam may be removed from a substrate by contacting the
rigid polyurethane foam with a co-solvent system comprising an
alkylene carbonate and one or more other solvents. The present
inventive process, by substituting alkylene carbonate for a portion
of the more hazardous prior art solvents, reduces many of the
health, safety and environmental hazards associated with the prior
art solvents, and is economically attractive as well.
Summary of the Invention
The invention concerns, in a process for removing a cured
rigid polyurethane foam from a substrate by contacting said rigid
polyurethane foam with a solvent in which said cured rigid
polyurethane foam is at least partially soluble, the improvement
comprising diluting said solvent with a co-solvent comprising
alkylene carbonate. In another of its aspects, the invention
concerns a process for removing cured rigid polyurethane foam from
a substrate, comprising contacting a cured rigid polyurethane foam
with a co-solvent system comprising a mixture of alkylene carbonate
and at least one non-alkylene carbonate solvent selected from the
group consisting of aromatic hydrocarbons, alcohols, ketones,
esters, ethers, glycol ethers, imidazoles, and ureas. The
.
invention also concerns a proces9 for dissolving cured rigid
polyurethane foam, comprising contacting a cured rigid polyurethane
foam with a co-solvent system comprising a mixture of (1) an
alkylene carbonate selected from the group consisting of ethylene
carbonate, propylene carbonate, and 1,2-butylene carbonate and (2)
at least one non-alkylene carbonate solvent in which said rigid
polyurethane foam is at least partially soluble, selected from the
group consisting of aromatic hydrocarbons, alcohols, ketones,
esters, ethers, glycol ethers, imidazoles, and ureas.
Descri~tion of the Preferred Embodiments
Alkylene carbonates useful in the present invention may
be represented by the following formula:
O
R R
where R is H or an alkyl group containing from 1 to about 20 carbon
atoms. It is preferred that R be H or a methyl group, i.e. that
the alkylene carbonate be ethylene carbonate, propylene carbonate,
or 1,2-butylene carbonate. Diethyl carbonate is another preferred
alkylene carbonate.~Ethylene carbonate and propylene carbonate are
commercially available from Texaco Chemical Co. as Texacar~ EC
Ethylene Carbonate and Texacar~ PC Propylene Carbonate,
respectively. Alternatively, a mixture of alkylene carbonates may
J ~ 3
be used. A mixture of ethylene carbonate and propylene carbonate
is commercially available as Texacar EC-50.
Solvents that may be diluted by alkylene carbonates in
the present invention include, but are not limited to, solvents
selected from the group consisting of aromatic hydrocarbons,
alcohols, ketones, esters, ethers, glycol ethers, imidazoles, and
ureas. For example, Applicant has demonstrated the removal of
rigid polyurethane foams from substrates using co-solvent
formulations containing an alkylene carbonate and one or more of
the following solvents: 2-ethyl-1-hexanol, ethylene glycol
diacetate, 2-ethylhexyl acetate, N-methyl pyrrolidinone,
tetrahydrofurfuryl alcohol, ethylene glycol butyl ether acetate,
tetramethyl urea, diethylene glycol butyl ether, ethylene glycol
butyl ether, methyl iso-amyl ketone, diethylene glycol methyl
ether, dipropylene glycol methyl ether, dibasic ester, methyl
isobutyl ketone, 1,2-dimethyl imidazole, N,N'-dimethyl ethylene
urea, propylene glycol methyl ether, cyclohexanone, diacetone
alcohol, furfuryl alcohol, and isobutyl isobutyrate. Pref~rably,
the non-alkylene carbonate solvent is selected from the group
consisting of 2-ethyl-1-hexanol, 2-ethylhexyl acetate, N-methyl
pyrrolidinone, tetrahydrofurfuryl alcohol, ethylene glycol butyl
ether acetate, tetramethyl,urea, diethylene glycol butyl ether,
ethylene glycol butyl ether, methyl iso-amyl ketone, diethylene
glycol methyl ether, dipropylene glycol methyl ether, methyl
isobutyl ketone, 1,2-dimethyl imidazole, N,N'-dimethyl ethylene
urea, propylene glycol methyl ether, cyclohexanone, diacetone
~ 3
alcohol, furfuryl alcohol, dimethyl ~ormamide, and isobutyl
isobutyrate. More preferably, the non-alkylene carbonate solvent
is selected from the group consisting of 2-ethyl-1-hexanol,
N-methyl pyrrolidinone, tetramethyl urea, 1,2-dimethyl imidazole,
N,N'-dimethyl ethylene urea, furfuryl alcohol, tetrahydrofurfuryl
alcohol, propylene glycol methyl ether, ethylene glycol butyl ether
acetate, and dimethyl formamide. Optionally, other solvents may be
added to the formulations of the present invention as well.
Preferably, the portion of conventional solvent replaced
with alkylene carbonate in a formulation containing one or more
conventional (non-alkylene carbonate) solvents will be such that
the alkylene carbonate and the conventional solvents in the
formulation are present in a weight ratio of alkylene carbonate to
total conventional solvent of about 4:1 to about 1:4. It is more
preferred that the alkylene carbonate and the conventional solvents
in the formulation be present in a weight ratio of alkylene
carbonate to total convéntional solvent of about 1:2 to about 1:3.
One skilled in the art may find other weight ratios to be optimum
and not depart from the scope of the present invention. Those
skilled in the art will appreciate that the portion of conventional
solvent(s) in a formulation which should be replaced with alkylene
carbonate for a given rigid polyurethane foam involves a balance of
possible reduction in dissolution power versus the reduction or
avoidance of additional expense and/or environmental, health and
safety risks associated with the conventional solvents. Applicant
~ 3i)~ s
has demonstrated the use o~ several different formulations in the
examples that follow.
Optionally, other additives may be employed in the
formulations of the present invention. For example, suitable
thickeners may be included, such as ethylcellulose, hydroxypropyl
cellulose, organic modified clay, hydrogenated castor oil, and the
like. Surfactants, to enhance the water washability of the
substrate, may be included as well. Suitable surfactants include
potassium oleate, the dioctyl ester of sodium sulfosuccinic acid,
sodium alkylnaphthalene sulfonate, sodium alkylbenzene sulfonate,
and the like.
Applicant's inventive process is effective at
temperatures of from about room temperature to about 100 C and at
pressures of from about atmospheric to several hundred psi.
Optionally, the process of the present invention may be performed
at an elevated temperature. While Applicant's invention works well
at room temperature, more effective dissolution may be obtained by
heating the alkylene carbonate-containing formulation to a
temperature of about 50 to about 100 C. The alkylene carbonate-
containing formulation may be applied to the rigid polyurethane
foam in any conventional manner. Typically, the rigid polyurethane
foam-coated substrate will be placed in a vat or sonic bath
containing the alkylene carbonate-containing formulation.
Alternatively, the alkylene carbonate-containing formulation could
be applied to the foam-coated substrate by brush or spray. The
period of time for which the alkylene carbonate-containing
formulation should be permitted to work undisturbed on the rigid
polyurethane foam to be removed will vary. After said period of
time, agitation of the surfaces to be cleaned of the foam via
wiping, brushing or scraping is preferred.
Rigid polyurethane foam formulations are well known in
the art and are commercially available. Rigid foams are more
highly cross-linked than either elastomers or flexible foams.
Other characteristics generally true of rigid polyurethane foams
include (1) a structure having a high percentage of closed cells;
(2) low thermal conductivity; (3) nonreversible deformability;
(4) good load-bearing ability; and (5) high dimensional stability.
Generally, rigid polyurethane foams are based on polyols having a
molecular weight less than 1000, and more often from about 400 to
about 800. Rigid polyurethane foams are usually based on a polyol
having a functionality of 2 to 8, and more typically from about 4
to about 8.
The invention will be further illustrated by the
following examples, which are given by way of illustration and not
as limitations on the scope of this invention.
Examples
In the examples recorded in the table below, the
following procedure was used. Previously coated stainless steel
3/4" screw stock rods were wire brushed and cleaned with a solvent.
Rods that had been coated with cured fiberglass were treated with
acetone to remove any fiberglass residue; those that had been
coated with cured flexible or rigid polyurethane foam were treated
with methylene chloride. The rods were then sand blasted with
micro beads. The rods were then coated with a polyether-based foam
formulation having the following components:
Component Parts bv Weiaht
Thanol~ R-350-X 36.9
DC-1931 tsilicon surfactant) 0.5
Rll (trichlorofluoromethane) 15.0
TEXACAT~ TD-33 0.3
Rubinate M2 (polymeric isocyanate) 49.6
lDow Corning; 2ICI.
The coatings were then allowed to cure for two days or more before
dissolution studies were begun. Each coated stock rod was then
suspended in a beaker from a ring stand. Each beaker contained one
of the alkylene carbonate-containing formulations to be tested. At
the bottom of each beaker was a stirring bar. After from about 16
to about 22 hours at room temperature the rods were observed and
the approximate percentage of rigid polyurethane foam removed by
each formulation was estimated and recorded.
3 i~
~ _ ,.___ __= ~.. _
Ex No Co-Solvent Systcm Components Weight Ratlo d Appro~mate % Rigid
Components Foam Removed
.___
1 PC/2-ethyl-1-hexanol/EGDA 45/90/45 All foam removed
2 PC¦2-ethyl-1-hexanol/EGDA 45/45/90 10 %
._
3 PC/2-elhyl-l hexanol/2-ethylhoxyl 60/60/60 All toam removed
4 PC/2-ethyl-1-hexanol/lBlB 60/60/60 All toam temoved
PC/2-ethyl-1-hexanol/DB 60/60/60 70 %
6 PC/2-ethyl-1-hexanol/DM 60/60/60 60 %
7 PC/2-ethyl-1-hexanol/DPM 60/60/60 50 %
8 PC/2-ethyl-1-hexanol!Cyclohexanone 60/60/60 50 %
9 PC/2-ethyl-1-hexanol/DBe 45/45/90 10 %
PC/NMP 100/100 99 %
11 NMP ALL All foam removed
.
12 PC/NNDMEU 70/110 95 %
13 PC/NNDMEU 110/70 2 %
14 NNDMEU ALL 80 %
PCITHPA/PM 60/60/60 90 %
16 PC/`IHPA/E13A 60/60/60 90 %
17 PC/THPA/MIAR 60/60/60 70 %
18 PC~rHPA/lB18 65/65/65 50 %
19 PC~rHPA 120/60 2 %
PC/THPA 100/80 2 %
21 PC~rHPA 80/100 2 %
I
22 PC/1,2~DMI 70/110 60 %
23 PC/I ~ DMI 90/90 50 %
24 PC/1,2-DMI 110/70 5 %
1,2-DMI ALL All toam removed l
PC ~ P~leK c~ te; EGDA - Ethylene dycol diacebte; IBIB - Isobutyl Yobutyr te; DB - Dietnylene glycol butyl ether,
DM - Diethylene ~col methyl ether; DPM - Diprop~1ene dycol methyl ether; DBE - Dibasic ester (Du Pont); NMP = N-methyl
pynol;dinoK; THPA ~ Tetr hydroturhryl da~hol; 1,2-DMI - 1,2-dimethylimidazole; NNDMEU - N,N~-~dimethyl ethylene urea;
PM ~ Propylene g~col methyl ether; EBA ~ Ethylene dycol butyl ether cet te; MIAIC - Methyl iso~myl Icetone
~"~ J~
.
_l ,. . ,.~,~",~,~. ~ , ~
No. Co-Sol~nl Syslem Compononts Wolght Ratio o~ Approximate % Rlgid
Componentc Poam Removed
l , . . ._ . .. ~ .. . __. _ .
26 PC~rMU 60/120 80 %
. ._ . . _ ~
¦ 27 PC/TMU 100/100 50 %
2~t PC~IMU 120/60 5 %
.
29 TMU ALL All foam removed
. _ _ - __
¦ 30 PC/Furfuryi alcohol 1/2 80 %
¦ 31 1,2-BC¦f~yclohexanone/DEt 1/l/l 75 %
¦ 32 PC/Cyclohexanone/DB 65/65/65 50 %
1 33 PC/eB 100/80 40 %
¦ 34 PC/DBE/DB 65/65/65 30 %
¦ 35 DBe ALL No change
36 pC/PM 1/l 20 %
l ~
37 PC/MIBR/DB 1/l/l 20 %
~ pC/Dbcetone alcohol/DB 1/l/l 20 %
¦ 39 DMB ALL All foam lemoved
¦ 40 PC ALL No change
41 EC 50 ALL No change
EC-50 - 50/50 by weight blend of Telacar EC and PC; PC ~ P~ lene c tbonate; TMU - Tetrametbyl urea; 1,2-BC = 1,2-butylene
ca bon te; DB ~ Diethylene dycol butyl ether, EB - Ethytene dycol butyt ether, PM - P~lene dycol methyt elher, DM = Diethytcne
dycol methyl ether, DBe - Dib~uic ecter (Du Pont); PM ~ P~pylene dycol methyt ether, MIBK = Methyl i~butyl l~etone;
DMP - Di~nethyl form~mide.
