Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND OF THE INV NTION
Field of the Invention:
This invention relates generally to polyester foam
materials and, more specifically, to resilient polyester
; foams.
20 Descrietion of the Prior Art:
' . :
Polyesters may be broadly defined as macro-
molecular compounds having a plurality of carboxylate
ester groups in their skele~al structures.
Polyesters, as so defined for use herein, are to be
distinguished from other ester-containing polymers (e.g.
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cellulose esters, polyvinyl esters, and polyacr~lates)
wherein carboxylate groups are present in substituent
entities pendant from the backbone of the polymer. Poly-
esters have been known to science for many years and have
been used in recent years in such diverse applications as
coatings, films, fibers, molding and casting compounds, and
as intermediates in chemical react:ions. Polyes~er foams
based on unsaturated acids and unsaturated monomeric cross-
-~ linking materials have also been known and used. Foams
made from polyesters whose polymeric structure is not
dependent for development on unsaturation within its
substituent monomers, however, have received scant if any
~- attention in the past. And the same is specifically true
of resilient foams made from such polyesters.
Most polyesters finding use today are linear
polymers as opposed to three dimensional polymers. Three
dimensional polymers are, of course, polymers having cross-
links between the essentially linear polymeric structures
forming the skeletal backbones of the molecules. There
~ 20 can be some branching within the skeletal backbones without
havlng a departure from essential linearity.
Polyesters have been synthesized in the past from'
a variety of reactants through the use of several reaction
schemes. The most direct synthesis is the esterification
'! of a dicarboxylic acid with a glycol. tDicarboxylic acids
and glycols are sometimes referred to,-respectively, as
dibasic acids and dihydroxy compounds). In this scheme,
the dicarboxylic acid/glycol mixture-is heated until
condensation occurs. The products of the condensation
reaction are polyester and water.
Polyesters can also be prepared by ester exchangè
reactions.
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A third general method of preparing polyesters,
and the one which is most useful in the practice of the
instant invention, is the polycondensation of polyols with
acyl halides such as diacid chlorides. The products of this
polycondensation reaction are, of course, the polyester and
a hydrogen halide such as hydrogen chloride. Depending upon
the physical properties of the reactants, the acyl halide-
polyol reaction is frequently conducted in the presence of
an inert solvent such as chlorobenzene or a chlorinated
biphenyl. A stream of an inert gas is frequently passed
through the reaction system to remove the gaseous hydrogen
halide. It is also possible to conduct the acyl halide
polyol reaction without the use of solvents if the reactants
are low melting compounds which can form a homogeneous
mixture. In either case, it is essential that all components
of the reaction system be free of moisture since water hydrolizes
the acyl halide thereby terminating the polYmerization reaction.
SUMMARY OF THE INVENTION
Stable, three dimensional polyester foams are
formed by rèacting together acyl halides, polyols, and
polyhydroxy cross-linking agents in the presence of alkali
metal carbonates under such conditions as to form foams. ~;
After formation, the polyester foams can be crushed so as
to rupture membranes between cells thereby producing inter-
.,
connected networks of cells and to aid in the release of
entraped gaseous hydrogen halide.
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Thus, one embodiment of the invention relates
to a stable, resilient polyester foam comprising
three-dimensional condensate of: at least one
polyol having at least two hydroxyl groups and an
eq~ivalent weight o at least about 1,000; at least
one propylene oxide-based polyhydroxy cross-linking
agent having at least three hydroxyl groups and an
equivalent weight of less than albout 250; and at
least one acyl halide having at least two -COX
radicals wherein X is a halogen atom.
A further embodiment relates to a process for
making a stable, resilient polyester foam comprising
reacting: at least one polyol having at least two
hydroxyl groups and an equivalent weight of at least
about 1,000; at least one propylene oxide-based
polyhydroxy cross-linking agent having at least
three hydroxyl groups and an equivalent weight of
` less than about 250; and at least one acyl halide
having at least two -COX radicals wherein X is a
halogen atom; in the presence of alkali metal
carbonate.
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DES~ OF THÆ PREFERRED EMBODIMENTS
While this specification concludes with claims particu-
larly pointing out and distinctly claiming the subject
matter regarded as the invention, it is believed that the
invention disclosed herein can be better understood from
the following detailed description.
As used herein, "stable" refers to materials which
retain their physical properties upon storage at ambient
and near-ambient conditions for at least several weeks.
As used herein, "resilient" refers to the ability of a
material to essentially return to its original configur-
ation after a deforming force is removed. As used herein,
"pharmacologically acceptable" refers to the ability of a
material to be used in intimate contact with portions of
- the human body, such as skin or mucous membrane, without
producing deleterious results. Unless otherwise indicated,
the terms "foam", "polyester foam", and "polyester foam
~- material" are used interchangeably herein and refer to
cellular structures the cell walls of which are formed '~
from solid polymeric material derived from polyesters.
. . .
- The polyester foam materials of the instant invention
are prepared from a reaction mixture comprising four
components: acyl halide, polyol, polyhydroxy cross-linking
agent, and alkali metal carbonate. i
While any suitable method of préparation can be used,
a preferred method for making polyester foams is similar
to that used in the well-known one-shot method of preparing
polyurethane foams. The various reaction components are
supplied at a temperature of from about 20 to about 65C
to a mixing head wherein they are violently agitated for
from about 0.005 to about 0.5 minute at a temperature of
from about 20C to about 65C and at a pressure of
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from about zero to about 7.03 kilograms per square centimeter
(about zero to about 100 pounds per square inch). The foamed
mixture is then discharged onto a moving belt. The foam is
allowed to cure for from about 5 to about 1,000 minutes at
a temperature of from about 20C to about 100C. Curing
can be accelerated through the addition of energy to the
foam. The cured foam is then ready for such further processing
as is dictated by the use to which the material will be put.
A very simple and effective batch method of
preparation comprises mixing the polyol and the polyhydroxy
cross-linking agent and heating the mixture to the desired
temperature. To the above mixture, in a suitable container,
is added the alkali metal carbonate with vigorous mixing.
Following a mixing period, the acyl halide is added with
mixing. The resulting mass, which can optionally be placed
in a suitable container, is allowed to cure at ambient
temperature. Infra-red radiation can optionally be used
"~,
to accelerate the curing of the surface of the foam mass.
AIternatively, any two or three of the reaction
components can be prereacted, in any desired proportions,
and the product of this prereac~ion then reacted with the
balance of the reaction components as indicated above.
Acyl halides (sometimes called polycarboxylic acid
; halides) useful in the present invention are organic
compounds containiny at least two -COX radicals wherein
X is a halogen atom. Preferably, the acyl halides are
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dicarboxylic chlorides having the general formula
ClOC-R-COCl wherein R is an aliphatic group defined as
(CH2)n wherein n is greater than or equal to three.
Examples of preferred dicarboxylic acid chlorides are
glutaryl chloride, adipyl chloride, pimelyl chloride,
- suberyl chloride, azelayl chloride and sebacyl chloride.
The most preferred acyl halide for use in making stable,
absorbent, resilient foams which can be used to absorb
body fluids is the diacid chloride of adipic acid, adipyl
chloride. Although in general a single acyl halide will
~- be ~sed, the use of mixtures of two or more acyl halides
is within the scope of this invention.
Polyols are organic compounds containing a plurality
;- of hydroxyl groups. Two different types of polyols
serving two different functions are used herein. For
convenience, one is referred to simply as "polyol" and
the other is referred to as "polyhydroxy cross-linking
agent". The distinction between the two will become
readily apparent from a reading of the following
paragraphs.
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As used herein, "polyol" refers to an organic molecule
having at least two hydroxyl groups and an equivalent
weight of at least about 1,000, preferably at least
1,500. Preferably, the polyol is aliphatic. These
polyols serve primarily to make up the basic skeletal ~ ;
structures oE the polyester of this invention.
~` Diols (polyol compounds containing two hydroxyl
groups) suitable for use in the instant invention are
the ethylene oxide-propylene oxide-propylene glycol
- 30 polymers such as Pluracol~ Polyol 686 made by BAS~
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Wyandotte of Wyandotte, Michigan. Pluracol Polyol 686 is an
ABA block copolymer containing about 80~ ethylene oxide (A)
and 20~ propylene oxide (B). It is a diol having a molecular
weight of approximately 5,000 and a hydroxyl number of 22.4.
(Hydxoxyl number is defined as the number of milligrams of
potassium hydroxide required to completely neutralize the
hydrolysis product of the fully acylated derivative prepared
from one gram of polyol. Mathematically, the hydroxyl number
of a compound is equal to 56,100 times the number of hydroxyl
groups in the compound divided by the molecular weight of
the compound.)
An example of a suitable triol (polyol compound
containing three hydroxyl groups) is the liquid ethoxylated-
propoxylated glycerin sold by The Dow Chemical Company of
Midland, Michigan-under the tradename XCl4?1. This material
has a molecular weight of about 5,000, is about 65% ethylene
oxide, and has a hydroxyl number of about 33.7.
Quadrafunctional polyols are preferred for use
in the instant invention. (As used herein, "quadrafunctional"
and "trifunctional" refer to compounds having, respectively,
four and three hydroxyl groups available for reaction.~ It
has been surprisingly discovered that quadrafunctional polyols
produce a polyester foam which is more resilient than that
produced from other polyols. Examples of quadrafunctional
~ polyols are ethylene oxide-propylene oxide block copolymers
;~ based on either ethylene diamine or on pentaerythritol. The
former are sold under the Tetronic tradename by BASF Wyandotte.
The latter, having a molecular weight from about 4,000 to
about 30,000,
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and an ethylene ox~de content of from about 5% to about
90~i, are preEerred for use in the instant invention in
making absorbent, resilient polyester foams useful in
catamenial tampons.
Polyols based on ethylene oxide without propylene oxide
present can be used, but such polyols generally have a
melting point too high for convenient processing. Ethylene
oxide contents greater than about 60% and less than about
90% are generally preferred.
Mixtures of polyols can be used in this invention.
As used herein, "polyhydroxy cross-linking agent"
refers to a propoxylated derivative tadduct) of a poly-
hydric alcohol. These polyhydroxy cross-linking agents
contain secondary available hydroxyl groups. These propy-
lene oxide,-based materials used in the instant invention ~-
must be at least trifunctionalt preferably quadrafunct- ''
ional. They should have an equivalent weight of less than
about 2500 Preferably, they should have a molecular ~,
weight of less than about 500. Especially preferred are
the propylene oxide adducts of trimethylol propane and ~,
pentaerythritol. Suitable materials are sold under the
Pluraco ~ trade mark as TP340, TP440~ PEP450 and PEP550~, '
by BASF Wyandotte. TP340 is the tripropoxylated derivative
of trimethylol propane while TP440 is the tetrapropoxylated
derivative. PEP450 and PEP550 are the tetrapropoxylated
and pentapropoxylated derivatives of,pentaerythritol.
Polyhydroxy cross-linking agents serve primarily to intro~
duce covalent cross-links between essentially linear
portions of the skeletal structure of the polyester foam
of this invention.
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' Mixtures oE polyhydroxy cross-linking agents as well
i as a single p~lyhydroxy cross-linking agent can be used to
produce the polyester of this invention.
The alkali metal carbonates useful in the instant
invention are well known inorganic compounds. Preferably,
reagent grade sodium carbonate i~3 used. It has been discovered
that some samples of technical grade sodium carbonate will not
function properly in this inventio~. However, heating these
samples to about 700C for several minutes has been found to
r' '` 10 convert them to properly functioning materials. Preferably,
the alkali metal carbonate is finely ground. Particularly
~; prPferred is reagent grade sodium carbonate ground so that
100% will pass through a 400 mesh screen.
Because of the aforementioned polymerization termina-
tion action of water, the level of moisture in the total
reaction system should be maintained below about 0.1~ by
weight.
-~ Further, it has been found that inorganic bases,
~; such as sodium hydroxide, do not function in the instant ~ -
invention in place of the alkali metal carbonates. Among
other reasons for this is the fact that they are hygroscopic
and tend to introduce excessive amounts of water into the
system.
As used herein, "reaction system" encompasses the
total quantity of reaction components used to make the
polyester foams of this invention.
~ Acid halide index is a measure of the amount of
- acid halide present in the reaction system. It is defined
; as 100 times the ratio of the number of acid halide
~ 30 equivalents present in the reaction system to the number of
:
equivalents of available hydroxyls present in the reaction
system. An acid halide index of 100 indicates the presence
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of stoichiometric quantities of acid halide and available
hydroxyls. An acid halide index greater than 100 indicates
the presence of an excess o~ acid halide while an acid halide
index smaller than 100 indicates the presence of an excess
of hydroxyls in the reaction system.
The acid halide index of the reaction system useful
~,
in the instant invention should be approximately 100. Systems
having an acid halide index greater than about 98 have been
, found suitable. A slight excess of acyl halide (acid halide
index greater than 100) is permissible and preferable. Thus
reaction systems having an acid halide index smaller than
about 108 but greater than about 100 are preferred. Acid
halide indicies between about 98 and about 108 represent
i systems having a substantially stoichiometric amount of
t.
acyl halide.
The amount of acyl halide present in the reaction
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system has a profound effect on the density of the polyester
foam produced. It has been demonstrated that when the acid
halide level increases from Dbout 19~ to about 21% by weight
of the~reaction system, while the number of equivalents of
hydroxyls present is adjusted to maintain a constant acid
halide index, the densiky of the polyester foam decreases
from about 10 pounds per cubic foot (0.16 gram per cubic
centimeter) to about 4 pounds per cubic foot (0.06 gram per
cubic centimeter). For use in catamenial tampons, as herein
after described, resilient foams of low density are preferred.
For other uses, of course, other densities can be more
.
suitable.
The amount of polyhydroxy cross-linking agent
-~ 30 present should be from about 15% to about 80% by weight
of the polyol present, preferably from about 20~ to about
40%.
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The amount of alkali metal carbonate presen-t should
be from about 2~ to about 150%, preferably from about 25
to about 67%, by weight of the total amount of polyol,
polyhydroxy cross-linking agent and acyl halide present.
Small quantities of alkali metal bicarbonate, such as sodium
- bicarbonate, are tolerated by the system Alkali metal
6, bicarbonate up to a level of about 5~ by weight of -the total
organic materials present can be added without adverse effect.
Mixtures of acyl halides, polyols, and polyhydroxy
, ~ lO cross-linking agents can be used to prepare polyester foams
7; if one follows the general reaction scheme described in this
specification. It has been discovered, however, that the
~ foams so prepared are unstable after curing; they tend to
s ~ liquify during storage at ambient conditions. It has been
surprisingly discovered that the addition of alkali metal
carbonate to the reaction system leads to the formation of
foa~ls having excellent stability even during prolonged
storageG It has also been discovered that low levels of
alkali metal bicarbonate in the absence of alkali metal
20 carbonate improve the stability of polyester foams over
that of foams made without the inclusion of either alkali
m~tal carbonate or bicarbonate in the reactio~ mixture,
but the improvement in polyester foam stability engendered
-
by alkali metal bicarbonate is significantly less than that
engendered by alkali metal carbonate.
Without advancing a specific theory as to the
function of the alkali metal carbonate, it can be stated
that this material neither appears to enter into the
; reaction as by becoming a part of the polymer structure
nor appears to function as a blowing agent. Essentially
all the alkali metal carbonate can be recovered after the
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polymerization reaction is complete.
The hydrophilic/hydrophobic character of thepolyester foams o~ this invention is determined in large
part by the nature of the reactants from which the polyester
is formed. For example, when propoxylated - ethoxylated
pentaerythritol having a molecular weight of more than
15rO00 and an ethylene oxide content greater than 70~ is
used as the polyol, the resulting polyester is hydrophilic
whereas that made with a similar polyol having a propylene
oxide content of about 90~ by weight is hydrophobic. Also,
increasing the length of the aliphatic chain in the acyl
halide, as by changing from glutaryl chloride to adipyl
chloride, decreases the hydrophilicity of the resulting
polyester foam. It is well within the ability of the
skilled artisan having before him the teachings of this
specification to select reactants that will yield a polyester
foam material with the hydrophilic/hydrophobic character
P~
'` best suited for the use at hand. ;~
In addition to the four required components of
the reaction mixture, additional materials can be present so
~ long as their presence does not interfere with the fundamental
- polycondensation reaction. Examples of optional materials
- include nonionic surfactants useful as uncured foam
.
stabilizers, catalytic surfactants, pigments,
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flame retardant chemicals, and the like. Pluronic L-92,
a nonionic surfactant having a molecular weight of about
3,600 and a hydroxyl number ol about 31, as made by BASF
Wyandotte, is particularly useful as a catalytic surfac-
tant. (Catalytic surfactants contribute to the structure
i of polyester, and polyurethane, foams by reducing foam
cell size and promoting uniform foam cell size.)
-~ In order to more fully describe the present invention,
and not by way of limitation, the following examples are
' 10 presented,
EXAMPLE I
A mixture consisting of 400 grams Pluraco ~ Polyol
- 686 (polyol) and 144 grams Pluraco ~ TP-340 (polyhydroxy
cross-linking agent) was heated in a stainless steel
vessel to a temperature of 40C. This mixture also
contained 0.1 gram Pluronic~ L-92 (catalytic surfactant).
The heated mixture was transferred to acylindrical paper
container 8.9 centimeters in diameter. To the mixture in
the cylindrical paper container was added 100 grams sodium
carbonate of which 100% would pass through an 80 mesh
screen and 50~ would pass through a 200 mesh screen. The
; resulting mixture was agitated Por 25 seconds with a 6.1
centimeter diameter turbine blade mixer. At the end of
the initial mixing, 151 grams adipyl chloride was added
and the total reaction composition was agitated for an
additional 10 seconds. The resulting resilient polyester
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foam was removed from the cylindrical paper container and
subjected to infra-red radiation to hasten the curing of
the surface. The resulting resilient polyester foam had
a density of 0.045 grams per cubic centimeter.
EX~M_LE II
A mixture consisting of 397.6 grams Dow XD 1~21~
(polyol) and 192.4 grams Pluracol~ TP-440 (polyhydroxy
- cross-linking agent~ was placed in a stainless steel
vessel. Four grams Pluroni ~ L-92 (catalytic surfactant)
;~ 10 were also added to the mixture. The procedure of Example
I was followed in making a resilient polyester ~oam except
that the initial mixture was heated to 45C. The quantity
of sodium carbonate used in this example was 200 grams
while 155 grams adipyl chloride was used. The resulting
resilient polyester foam had a density of 0.06 grams per
` cubic centimeter.
EXAMPLE III
` The absorbentr resilient polyester foam made in this
example was based on a polyol wllich was an ethylene oxide-
?'`: 20 propylene oxide block copolymer of pentaerythritol and
;~ which had an ethylene oxide content oE 73% and a hydroxyl
number of 14. A mixture consisting of l99o9 gra~s of the
-~ aforementioned polyoI and 73.1 grams Pluracol~ PEP-450
(polyhydroxy cross-linking agent) plus 2 grams Pluroni
L-92 tcatalytic surfactant) was placed in a stainless
steel vessel and heated to 50C. The warmed mixture was
.-:
transferred to a paper cylinder 8.9 centimeters in
diameter. To the mixture in the paper cylinder was
added 100 grams sodium carbonate as used in Example I
and the system was agitated for 20 seconds
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with a 7.6 cen-timeter diameter six-bladed mixer. Following
the initial mixing, 74 grams adipyl chloride was added
to the system and mixing was continued for 10 seconds. The
total reaction system was poured into a 15.2 centimeter by
22.9 centimeter rectangular container and allowed to set.
After the surface of the polyester foam had been subjected
to infrared radiation Eor five minutes to reduce surEace
tackiness, the foam mass was crushed between opposing rollers.
The resulting absorbent, resilient, open celled polyester
foam had a density of 0.06 gram per cubic centimeter. After
comminuting and washing with water, the absorbent, ~lexible
polyester foam of this example was eminently suitable for
use in the catamenial aggregate absorbent body described
by Schaefer in U.S. Patent 3,815,601.
For some applications, it is desirable that the
,.
polyester foam be open celled. As used herein, the term
~; "open celled" means that the individual cells of the foam
are interconnected by open channels. Cured polyester foam
can be converted to the open celled sta~e by subjecting it
-20 to sufficient compressive force to reduce its volume to
about 20% of its original value. This compression tends
to rupture the membrances making up the individual cell
walls. In addition to forming an interconnected network
' 'J of channels and cells, this compression and the resulting
membrane rupture facilitates the release of gaseous
.
~^ hydrogen halide Erom the cured foam mass.
; For use in catamenlal tampons, it is preferred
that the polyester foam be open celled and have from about
50 to about 400 cells per linear inch.
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For some applications, it is desirable that the
residual alkali metal carbonate and hydrogen halide be
washed from the polyester ~oam mass. This washing can
be readily accomplished by reclucing the foam mass to
convenient sized particles (as by chopping or cutting)
and agitating these particles in a suitable solvent such
as water. In most cases, the residual alkali metal car-
bonate is more than su~ficient to neutralize any residual
hydrogen halide present. Following washing, the polyester
foam can be dried in any convenient, known manner that
will be readily apparent to those skilled in the art.
The novel polyester foams of the instant invention
find application in numerous circumstances where soft~
resilient, absorbent foam materials are requiredO For
example, the comminuted and washed foam of the instant
invention can be used in the catamenial aggregate
absorbent body described by Schaefer in U.S. Patent
3,815,601 which was issued on June lI, 1974.
Futher, the novel polyester foams of the instant
invention can be used in applications where polyurethane
foams are now used. Such applications include use in
surgical bandages, household sponges, furniture pads,
and the like.
EXAMPLE IV
In this example, portions of two of the reaction
components are prereacted and the prereaction product
is used in the formation of a polyester foam o~ this
invention.
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` One hundred fifty grams Pluralcol~ PEP~450 ~polyhydroxy
cross-linking agent) was mixed with 35.7 grams adipyl
chloride (96% purity) for 20 seconds at room temperature
J and atmospheric presure in a 500 milliliter beaker with a
7.6 centimeter diameter turbine blade mixer. The resulting
. ~ product was allowed to degas for one hour at room tempera-
h - ture. A 105.7 gram aliquot of the reaction product was
. ~ mixed with 250 grams Pluraco ~ Polyol 747 and 2.5 grams
Pluroni ~ L-92. Pluraco ~ Polyol 747 is an ethylene
oxide-propylene oxide block copolymer of pentaerythritol,
;
, has an ethylene oxide content of 73~ and a hydroxyl number
of 14, and is manufactured by BASF Wyandotte. A 286.6
gram aliquot of this last described mixture, which had
' ~ been heated to 50C in a steel beaker, was mixed with 100
grams anhydrous, reagent grade sodium carbonate for 20
seconds in a 0.95 liter cylindrical paper can with the
hereinbefore described mixer. To the mixture in the
'~ cylindrical paper can, 57.9 grams adipyl chloride (96%
purity) was added and mixed for 10 seconds. The resulting
~ 20 product exhibited a cream time of 30 seconds and a rise
G time of 1 minute 50 seconds.
After being allowed to cure for 5 minutes at room
temperature, the resulting polyester foam was open celled
~- (i.e. required no reticulation to produce open cells~ and
had an exceedingly fine cell structure. It had a density
of approximately 0.19 grams per cubic centimeter (11.7
i~ pounds per cubic foot).
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