Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE ~ N'VENTION
1. Field of the ~nvention
This invention relates to the conversion of scrap
polyurethane to useful polyols and is more particularly
concerned with a process for the conversion of scrap
flexible polyurethane foam, derived from a polyether
polyol, to polyols which are reusable in the preparation
of cellular polyurethanes.
2. DescriPtion of the Prior Art
The amount of scrap polyurethane foam which is being
~~ generated as trim, dust and the like from foam cutting
operations, is a problem of increasing concern. The
disposal thereof in solid waste form represents an
environmental pollution problem as well as an economic
L5 one. The racGvely and reuOe of sc.3p r gid ~olyu-eth_ne
foam has recently become possible through the process
described in U. S. Patent 3,738,946. The latter process
involves heating the scrap foam with a mixture of aliphatic
diol and a minor amount of dialkanolamine to produce a
homogeneous polyol mixture capable of use, in its entirety
as a polyol component in the production of new polyurethane
foam. The prior attempts to solve the problem of recovery
of scrap foam are discussed in some detail in the above
cited patent and will not be reviewed here.
Unfortunately the process of the above cited patent,
which is entirely satisfactory for rigid foams, cannot be
applied successfully to the recovery of the major class of
flexible foams, namely, those derived from a polyether polyol.
Thus, the process of the above patent, when employed with
scrap from flexible, polyether-based foams, gives a product
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which separates into two layers, one of which is a polyol
and the other appears to be a polyamine. The latter
requires to be separated from the former and is not useful
in the preparation of further polyurethane foams, although
it has uses as a curing agent for epoxides and the like.
Substantially the same result is reported in U. S.
Patent 3,632 530 which describes the treatment of scrap
flexible polyether-based polyurethane foam by heating in
the presence of an aliphatic glycol and, optionally, a
tertiary amine. The product separates into two layers one
of which is polyol and the other is said to be polyamine.
; The latter is separated and shown to be useful as an amine
curative for epoxy resins and for isocyanate-terminated
prepolymers. As is evident from Example 9 of the above
cited patent, there is no such problem with a polyester-
based flexible foam. The latter gives rise to a homo-
- geneous product which shows no tendency to separate into
' two layers.
~- Unfortunately, however, the bulk of the flexible foams
currently produced commercially are derived from polyether
polyols, and scrap from such foams has not so far been
converted successfully to a homogeneous product which is
, -
usable in its entirety as a polyol cbmponent for the pre-
~aration of new polyurethane foam.
We have now found that, contrary to previously reported
experience, it i9 possible, by careful choice of reactants,
and of proportions thereof, and of reaction conditions, to
convert scrap, polyether-based flexible polyurethane foam
into a homogeneous mixture of polyols, which mixture does
not separate into different components but can be used in
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its entirety as part, or the whole, of the polyol component
employed in the preparation of new polyurethane foam.
SUMMARY OF THE INVENTION
The invention comprises a process of converting scrap
flexible polyurethane foam, which has been derived from a
polyether polyol, to a homogeneous mixture of polyols,
which process comprises heating, at a temperature in the
range of 180C to 250C, a mixture of (a) said scrap
flexible polyurethane foam, preferably in a comminuted form, and
10 (b) an aliphatic diol having the formula HO -A -OH wherein A is
selected from the class consisting of an alkylene radical
from 2 to 6 carbon atoms, inclusive, and an alkylene radical
from 2 to 6 carbon atoms wherein the chain thereof is
interrupted by an oxygen atom, both of which alkylene
radicals carry at least one lower-alkyl substituent on a
carbon atom in the chain thereof, said di.ol being present
in an amount by weight which does not exceed the total
weight of said scrap foam.
The invention also comprises the polyol recovered in
accordance with the above process.
The recovered polyol is useful, either alone or in
admixture with virgin polyol, in the preparation of new
polyurethane foam and, more particularly, in the preparation l -
of new rigid polyurethane foam.
DETAILED DESCRIPTION OF THE INV~NTION
The term "alkylene radical from 2 to 6 carbon atoms,
` inclusive" means (CH8)n wherein n is an integer
from 2 to 6, such as ethylene, propylene, butylene, pentylene, .
- hexylene. The term ~alkylene radical from 2 to 6 carbon-
atoms, inclusive, wherein the chain thereof is interrupted
;. ~ .
- ' ' ' " ~ ' ' `
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by an oxygen atom" means a radical of the formula
(CHa)X 0 - (CH2)y wherein x and y are each integers
and wherein the sum of x ~ y is a whole number from 2 to 6.
The term "lower-alkyl" means alkyl from l to 6 carbon
atoms, inclusive, such as methyl, ethyl, propyl, butyl~
pentyl, hexyl and isomeric forms thereof.
It will be apparent from the above definitions that
the aliphatic diols employed in the process of the invention
are those in which the alkylene group separating the two
hydroxyl groups must be branched, i.e. there is a lower-alkyl
- group present as a substituent on at least one of the
carbon atoms of the alkylene chain. In addition to this
alkyl substituent, there can, optionally, be an oxygen atom
(i.e. an ether linkage) in the alkylene chain separating
the two hydroxyl group.s~ Illustrative of aliphatic diols
which meet the above requirements are 1,2-propylene glycol~
- 1,2-butanediol, 1,2-hexanediol, di(l~2-propylene glycol),
~ di(L,2-butylene glycol), 3-methylpentane-1,5-diol, 2~2-
dimethyl-1,3-propanediol, 1,2-octanediol, and mixtures of
two or more of any of these diols.
It is to be noted that certain of .he above glycols
have been suggested previously as media in which to carry
out the heat degradation of scrap flexible foam, see
U. S. 3~632~530O However, the results reported in that
patent with these diols, and a series of other closely
related diols, always show the production of a product
which separates into two layers, one of which constitutes
polyol and the other amine. Although it is di~closed ln
general terms by the reference that proportions of scrap
; 30 foam to glycol as high as equal amounts by weight can be
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employed, the actual examples all use amounts of glycol
which are considerably in excess, by weight, of the
amount of scrap foam.
In contrast, we have found that, in the case of certain
glycols only, namely, those in which the alkylene chain
separating the hydroxyl groups is branched, it is possible
to obtain an entirely different result to that hitherto
described, provided that the proportion of scrap foam
introduced into the admixture with the glycol is markedly
increased over the proportion hitherto employed in the artO
Thus, by employing a glycol which meets the definition set
forth above, and, further, by substantially increasing the
proportion of scrap flexible polyether polyol-based foam to
a minimum of at least an equal amount by weight based on
glycol, and preferably in substantial excess of this
amount, it has been found~ very surprisingly, that it lS
possible to convert said scrap foam to a homogeneous
mixture of polyols. That is to say, the product shows no
tendency to separate into two layers, as in the case of the
prior art, and shows no indication of the presence of amine
therein. Further,the entire product, rather than a minor
proportion thereof, can be used as the polyol component,
or as a part thereof, in the preparation of virgin poly-
urethane foam.
As will be appreciated by one skilled in the art, this
- is a highly advantageous and clearly unexpected finding
particularly in view of the concentrated search which has
been made by the polyurethane foam industry in recent years
to find a commercially feasible and economic manner in which
to recover scrap from flexible foam.
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In carrying out the process of the invention, the
scrap flexible foam is advantageously chopped or ground to
particles of relatively small size in order to reduce the
volume of the scrap and to assist in reducing the time
necessary for the reaction to take place~ The scrap
foam and the appropriate diol defined above are then
brought together in a single operation, if desired, and
the resulting mixture is heated to a temperature in the
range of about 180~C to about 250C, advantageously with
agitation. Alternatively and preferably, the diol is
heated to a temperature in the above range and the
comminuted scrap foam is added thereto in increments with
agitation.
As set forth above, the proportions in which the scrap
foam and the aliphatic diol are employed in the process of
- the invention are such that the amount of scrap foam by
weight is at least equal to the amount by weight of
aliphatic diol. Preferably the scrap foam is employed in
a proportion corresponding to from about 1.5 times to about
} 20 2 times the amount by weight of diol which is employed~
Once the admixture of scrap foam and aliphatic diol
has been completed, preferably with agitation, the mixture
is maintained at a temperature within the above range at
least until all the scrap foam has dissolved and a homogeneous
solution has been obtained. The end point of the reaction,
namely, the point at which degradation of the scrap to a
- useful polyol has been completed9 can be detected by
routine techniques, for example, by infrared spectroscopic
analysis, or by observing the rate of change of viscosity.
In general, the period of heating necessary to recover the
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scrap foam as polyol will range from about 2 hours to about
12 hours depending upon thelnature of the scrap polyurethane
foam and diol which are employed. The most desirable reaction
time for any particular combination of scrap foam and diol can
be determined by a process of trial and error.
When the degradation of scrap foam is complete, as
determined by routine analytical tests such as those described
above, the reaction mixture is cooled, or allowed to cool, to
room temperature. Depending upon the origin of the scrap foam
it may be necessary to remove small quantities of particulate
matter (e.g. fibers, non-polyurethane dust, laminate foil and
the like) from the product by filtration or like techniques.
Subject to the necessity for such treatment the product derived
above is ready, without any further modification, for use as
the polyol component in the preparation of new polyurethane
foam.
The product generally has an hydroxyl equivalent
w~ight in the range of about 65 to about 120 and is accordingly
preferably used in the preparation of rigid polyurethane
foams or for any other purpose, e.g. as a minor component
in the preparation of polyisocyanurate foams, for which
polyols having equivalent weights within this range are
normally used. If desired, the polyol mixture obtained by
the process of the invention can be blended with virgin
polyol prior to conversion to polyurethane and the like foams.
Alternatively, the hydroxyl equivalent weight of the
polyol mixture obtained by the process of the invention can
- be modified, i.e. increased, if desired, by reacting the
recovered polyol with an alkylene oxide such as ethylene
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oxide, propylene oxide and the like. The alko~ylation can
be carried out by processes well-recognized in the art
optionally in the presence of a basic catalyst such as
potassium hydroxide, sodium hydroxide, and the like.
It has also been found surprisingly that substantial
amounts of scrap foam derived from semi-rigid (also some-
times known as semi-fle~ible) and/or rigid polyurethane or
polyisocyanurate foams can be combined with the scrap
flexible, polyether-based foams employed in the process of
the invention without detracting from the overall result,
- i.e. the production of a homogeneous mixture of polyols
suitable for re-use in the preparation of polyurethane and
like foams. Thus, it has been found that quantities of
.~ . .
- scrap semi-rigid and/or rigid polyurethane or polyisocyanurate
foam. Up to ahol~t 75 percent by weight, based on the scrap
flexible polyether based foam, can be incorporated into the
`- reaction mixture employed in the process of the invention.
Preferably, the various types of scrap foam are pre-blended
before being added to the aliphatic diol, but the different
types of scrap foam can be added separately to the aliphatic
diol if desired.
When the flexible foam is subjected to the process of
the invention in combination with scrap from other types of
foam as discussed above, it is necessary that the total
amount of scrap be such that the proportion of total scrap
foam to aliphatic diol be always within the limits discussed
above.
It is pertinent to note that, where the scrap flexible
foam is subjected to the process of the invention in combin-
ation with substantial quantities of scrap from the other
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sources described above, said scrap fle~ible foam can
be present in the reaction mixture in an amount which
represents less than an equal amount by weight compared
to the aliphatic diol present in said reaction mixture.
Yet, provided that the total weight of flexible and other
types of scrap foam present in the reaction is still at
least equal by weight to the amount of aliphatic diol
present therein, the overall desired result will still be
obtained, i.e. the reaction product will be a homogeneous
mi~ture of polyols. This finding is clearly contrary to
the result which would be achieved were the scrap flexible
foam to be employed alone in the same proportion by weight.
The viscosity of the reaction product obtained in
; accordance with the process of the invention is largely
governed by the particular diol and scrap foam used and
by the proportions in which they are used in the range
set forth above. Advantageously, the viscosity of the
, reaction product is within the range of about 300 centi-
stokes to about 4,500 centistokes measured at 25C. A
viscosity in this range can be attained readily in the
case of any particular diol and scrap polyurethane by
a process of trial and error.
While any of the branched chain aliphatic diols
falling within the definitions given above can be used in
the process of the invention, a particularly preferred
diol is 1,2-propylene glycol. It is to be noted in this
regard that closely related aliphatic diols such as
- ethylene glycol, diethylene glycol and butane-1,4-diol~
which differ only from the diols employed in the process
of the invention by the absence of branching in the alkylene
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~(~4~1~6
chain, do not give rise to a homogeneous mixture of polyols
when employed under exactly the same conditions. Thus, the
straight chain aliphatic diols such as those enumerated
above, when heated with scrap flexible polyether-based foam
5 at the temperatures and in the proportions corresponding to
those employed in the process of the invention, give rise to
products which separate into two layers of different
character, in contrast to the homogeneous mixturesobtained
in accordance with the invention.
As will be obvious to one skilled in the art, the
process of the invention can, if desired, be operated on
a continuous basis. For example, the scrap foam and the
aliphatic diol can be fed in separate streams, or after
preblending if desired, to a continuous tube reactor in
which the reactants are agitated and subjected to a
temperature within the range set forth above. The residence
time, or hold up time, in the reactor is adjusted so that
the conversion to homogeneous polyol is effected in a
single pass through the reactor. Alternatively, the
reaction mixture can be continuously recycled through
the reactor a plurality of times until the total residence
`, time in the reactor is such as to accomplish the desired
conversion. In a further alternative mode of operation on
a continuous basis, the preliminary step of comminuting the
scrap foam can be omitted and the scrap foam can be fed
to a continuous reactor which is provided with means for
crushing or comminuting the scrap foam in contact with the
aliphatic diol preferably at a temperature within the
; range set forth above. Other modes of operation on a
continuous basis will be readily apparent to one skilled in
3064
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the art.
The following examples describe the manner and pro-
cess of making and using the invention and set forth the
best mode contemplated by the inventors of carrying out
the invention but are not to be construed as limiting.
~xamDle 1
The scrap foam employed as starting material in the
process described in this Example was obtained from a
flexible foam which had been prepared using the following
reactantS in the proportions (parts by weight) set forth
below.
Toluene diisocyanate (80/20) u 49 parts
Propoxylated glycerol * : 100 parts
(eq. wt. = 1000; LG-56, Union Carbide)
Stannous octoate - : 0.22 part
N-ethylmorpholine u 0.25 part
Triethylenediamine ~ 0 3 part
Surfactant (L-520) . 1.0 parts
Water u 4,0 parts
~he foam was prepared by thoroughly admixing all the
components except the isocyanate and then adding the latter
to the preblend of the other components and subjecting the
resulting mixture to high speed mechanical stirring for
10 seconds. The resulting foam was cured at 25C for 7
days.
A batch ~25 9.) of scrap from the above foam was
comminuted in a Wiley laboratory mill and added in incre-
ments, over a period of 2 hour~ and 50 minutes, to 25 9.
of 1,2-propylene glycol maintained at 200C to 225C with
. .
stirring. After the addition was complete, the mixture was
heated with agitation for a further 6 hours ~approx.) until
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a clear homogeneous solution was obtained. The resulting
product was allowed to cool to room temperature (circa 20VC)
and was found to remain a homogeneous liquid even after standing
for several weeks. The product (48 g.) was dark brown and
mobile, and had a viscosity of 407 centistokes at 20C and a
hydroxyl equivalent weight of 81.5.
Example 2
A second batch of 40 g. of scrap from the flexible
foam described in Example 1 was comminuted and added in
10 increments over a period of 4 hours and 25 minutes to 25 g.
of propylene glycol maintained at 200 to 234C with agitation.
When the addition was complete, the mixture was maintained
for a further 6.5 hours within the same temperature range
- with agitation. At the end of this time, the mixture was
allowed to cool to room temperature (20C) to yield 60.6 g.
of a brown homogeneous mobile liquid which had a viscosity
of 607 centistokes at 20C and a hydroxyl equivalent weight
-- of 101.
Example 3
` 20 This example illustrates the different result obtained
using an aliphatic glycol other than those called for by the
process of the invention.
The experiment described in Example 2 was repeated
exactly as described, but the 1,2-propylene glycol was replaced
by an equal weight of ethylene glycol. The product so obtained
separated into two layers on being allowed to cool to room
temperature.
- Example 4
This example demonstrates the effect of using the
aliphatic diol in an amount greater than the amount by
3064
104~4~
weight of scrap foam.
A batch (23 g.) of comminuted scrap from the flexible
foam described in Example 1 was added incrementally, over
a period of 1 hour, to 48.7 g. of 1,2-propylene glycol
maintained at 200 - 230C with agitation. The resulting
mixture was maintained at a temperature within the above
range for a further 8 hours with agitation and was then
allowed to cool to room temperature (circa 20C). After
standing at the latter temperature for a very short period
the initially homogeneous product separated into two layers.
Example 5
A further batch (20 g.) of comminuted scrap from the
flexible foam described in Example 1 was added incrementally,
over a period of 3 hours and 25 minutes, to 20 g. of 1S2-
butanediol maintained at 200 to 223C with agitation. After
the addition was complete, the mixture was maintained at
a temperature in the above rang~ with agitation for a
further 3.5 hours and was then allowed to cool to room
temperature (20C). The product so obtained (39 g.) was
a brown mobile liquid which was homogeneous and showed no
tendency to separate into two layers on standing. The
product had a viscosity of 396 centisto~es at 20C and a
hydroxyl equivalent weight of 91.
Exam~le 6
A further batch (20 g.) of comminuted scrap from the
flexible foam described in Example 1 was added incrementally,
over a period of 2 hours, to 20 9. of 3-methylpentane-1,5
- diol maintained at 200 to 228C with agitation, The result-
; ing mi~ture was maintained at a temperature in the above
range for a further 5 hours with agitation before being
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allowed to cool to room temperature (20C). The resulting
brown liquid(39.2 g.) showed no tendency to separate into
two layers even after allowing to stand for several weeks.
The product had a viscosity of 2018 centistokes at 20C
and an hydroxyl equivalent weight of 120.
,Example 7
The scrap employed in this example was taken from a
commercially available polyether-based flexible foam
(2 pcf density) in the form of bunstock sold by the CPR
Division of The Upjohn Company as flexible foam "CPR
9700-2.0 WFR".
' An aliquot of 50 g. of scrap from the above foam
, was comminuted and then added incrementally, over a period
- of 3 hours, to 25 g. of 1,2-propylene glycol maintained at
- 15 200 to 234C with agitation. The resulting mixture was
maintained at a temperature in the above range for a
period of a further 5 hours with agitation and then was
allowed to cool to room temperature (20C). The result-
ing brown liquid (70.5 g.) was homogeneous and showed
no tendency to separate even upon standing for several
weeks. The product had a viscosity of 1271 centistokes
at 20C and an hydroxyl equivalent weight of 98.5.
ExamDle 8
A mixture was prepared of 20 g. of comminuted scrap
flexible foam from the commercially available flexible
foam described in Example 7 and 20 9. of comminuted scrap
' from a semi-flexible foam prepared using the following
reactants in the proportions (all parts by weight) set
-- forth below~
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Polymethylene polyphenyl polyisocyanatel : 64.2 parts
Polyether (propoxylated trimethylolpropane: 100 parts
eq. wt. - 2000)
Aromatic based polyol2 :10 parts
N,N',Nn-tris(dimethylaminopropyl)hexa- : 0.7 part
hydrotriazine [5~/O w/w solution in
aromatic based poLyol2]
Triethanolamine : 4 parts
Water : 2 parts
Dibutyltin dilaurate :0.5 part
Trichlorofluoromethane 10 parts
The foam was prepared by thoroughly admixing all the
components except the isocyanate and then adding the latter
- to the preblend of the other com'ponents and subjecting
the resulting mixture to high speed mechanical stirring
for 10 seconds. The resulting foam was cured at 25C
for 7 days.
The mixt~re of scrap foams was added in increments,
with stirring, over a period of 2 hours and 15 minutes
to 25 g. of 1,2-propylene glycol maintained at 200 to
230C. When the addition of scrap was complete, the
mixture was maintained at the above temperature with
stirring for a further 5.5 hrs. and then allowed to cool
to room temperature (circa 20C). There was thus obtained
60.9 g. o a mobile homogeneous mixture of polyols having
a viscosity of 1042 centistokes at 20C and an hydroxyl
1 Containing approximately 6~h methylenebis(phenyl
isocyanate) and having eq. wt. = 133.
2 Blend of N,N-di(2-hydroxypropyl)aniline and
Mannich base polyol derived from nonylphenol, diethanol-
amine and formaldehyde capped with propylene oxide
eq. wt. = 104.5.
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eguivalent weight of 91.
ExamPle 9
A mi~ture was prepared by blending 40 9. of comminuted
scrap flexible foam from the commercially available flexible
foam described in Example 7 and 20 g. of scrap from a
rigid polyurethane foam which had been prepared using the
following reactants in the proportions (all parts by weight)
set forth below:
(1) A blend of the following polyols:
60 parts of a blend (eq. wt = 151)
of (i) a polyol obtained by pro-
poxylating a polymethylene poly- -
phenyl polyamine containing approx-
imately 50 percent by weight of
methylenedianiline and (ii) a poLyol
of eq. wt = 89 obtained by propoxy-
lating glycerol;
30 parts of an adduct of phosphoric
acid and propylene oxide having an
equivalent weight of 148;
10 parts of trimethylolpropane.
(2) 2 parts of organosilicone surfactant (L-5410)
(3) 0.4 part of water
(4) 0.6 part of tetramethylguanidine
(5) 0.4 part of N,N,N',N'-tetramethylbutanediamine
(6) 33 parts of trichlorofluoromethane
(7) 140 parts of polymethylene polyphenyl polyisocyanate
of eguivalent weight 134.
~~ Ingredients (1) to (6) were blended by mechanical
mixing and the polyisocyanate (7) was added to the blend.
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The resulting mixture was subjected to high speed mechanical
stirring for 10 seconds and then was allowed to foam freely.
The foam so obtained, after being cured for 7 days at
circa 15C, was found to have a density of 2.03 pcf and
S a compressive strength of 48.5 psi parallel to rise and
17.3 psi perpendicular to rise.
The mixture of scrap foams was added in increments,
with stirring, over a period of 3 hours to 25 g. of
propylene glycol maintained at 200C to 228C with
agitation. After the addition was complete, the mixture
was maintained for a further 5 hours and 15 minutes at
the same temperature with stirring, and was then allowed
to cool to room temperature (cirFa 20C). There was thus
- obtained 80.5 9. of a mobile, homogeneous mixturè of
polyols havinq a viscosit~ of 4~14 centistoXes at 20C
and an hydro~yl equivalent weight of 92.5.
ExamDle 10 :`
A total of 3000 9. of scrap from the commercially
available flexible foam described in Example 7 was
comminuted and added in increments, over a period of
5 hours,to 1500 g. of 1,2-propylene glycol maintained at
180 to 195C with agitation in an 18 Liter reactor. When
the addition was complete the mixture was maintained
within the same temperature range with stirring for an
additional hour. Thereafter an additional 865 g. of
1,2-propylene glycol were added and the mixture was heated
for an additional 2 hours at 190C with stirring. The
resulting product was allowed to cool to room temperature
(circa 20C). There was thus obtained 4832 g. of a mobile,
homogeneous ~ixture of polyols having an hydroxyl equivalent
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weight of 68.
A rigid foam was prepared by blending 50 parts by
weight of the mixture of polyols obtained as described
above with 50 parts by weight of a polyol of equivalent
weight 151 which itself was a blend of (i) a polyol
obtained by ~ropoxylating a polymethylene polyphenyl
polyamine containing approximately 50 percent by weight
of methylenedianiline and (ii) a polyol of equivalent
weight 89 obtained by propoxylating glycerol.
The polyol mixture so obtained was blended with 2
parts by weight of triethylenediamine, 2 parts by weight
of organosilicone surfactant and 42 parts by weight of
trichlorofluoromethane, and to the resulting mixture
was added 175 parts of polymethylene polyphenyl poly-
isocyanate (equivaient weight i33;. ~he mixiure ~v obtdin~u
was subjected to high speed mechanical stirring for 10
seconds and then allowed to foam freely. The foam which
resulted was cured for 3 days at 20C and found to have
the following properties:
Density - : 1.96 pcf
Compressive strength:
- Perpendicular to rise: 18.1 psi
.
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