ENTRE-DEUX NATUREL FAIT DE MOUSSE DE POLYURETHANE A REVETEMENT INTEGRES

NATURAL SANDWICH OF FILLED POLYURETHANE FOAM

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
A molding composition is disclosed for forming
in a single step a natural sandwich foam product having a
cellular core and a thick, densified outer layer. A hard,
particulate filler material such as fly ash is admixed with
an unreacted, rigid polyurethane foam system, together with
density distribution control agent such as carbon tetra-
chloride which lowers the viscosity of the admixture. In
molding, the mold cavity is charged with the admixture and
the foam reaction is permitted to occur with the mold closed.
The resultant, filled foam product has a thick outer layer
formed adjacent the mold surface of substantially greater
density than its core. In the densified layer, both the
polyurethane ant filler material components of the resultant
product are concentrated to provide over three times the
density of the core structure. Formulations are set forth
which provide substantial layer thickness and an outer sur-
face having a durometer hardness value of 50 or greater over
the entire surface area. If desired, one or more barrier
members may be provided in the mold cavity in order to cause
the generation of a densified region in the resultant product
at the pressure barrier during the foam reaction, thereby
reinforcing the core to increase the structural strength of
the product.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A molded, rigid polyurethane foam product having
a cellular core and an integral, thick, densified outer portion of
essentially the same chemical composition and which presents the
outer surface of the product, said product having been made by
charging a closable mold with a foamable molding composition, clos-
ing the mold, and then allowing the composition to foam within the
closed mold and form said densified outer portion by self-generation,
said molding composition comprising the admixture of: a liquid,
foam-producing system having initially unreacted elements of a
rigid polyurethane foam and a blowing agent which is active at
system temperatures under 40° C., said elements being poly-
isocyanate and a polyol and characterized by the property of
reacting chemically to form an expanded, cellular, polyurethane
structure under the action of said blowing agent; a hard, parti-
culate inorganic filler material substantially uniformly dispersed
throughout said elements and inert to the liquid foam-producing
system; and a density distribution control agent having a low
viscosity relative to the viscosity of the mixture of said system
and said filler material, and capable of assisting the formation of
said densified outer portion during reaction of said elements in
said closed mold, said control agent being selected from the group
consisting of the halocarbons and ethyl acetate and characterized by
the properties of being liquid at room temperature, chemically un-
reactive with said elements and soluble therein, having a boiling
point of at least approximately 40° C. in order to prevent an
excessive increase in the pressure within said mold over that
provided by said blowing agent, and not significantly accelerating
or decelerating the reaction of said elements, and being present in
sufficient quantity to reduce the viscosity of the mixture of said
29

system and filler material, the particles of said filler material
being of a size sufficient to, in conjunction with the action of
said control agent, prevent the viscosity of the total admixture
from increasing to the point that the admixture becomes unworkable,
said system, filler material and control agent being present in
said admixture in the following relative proportions expressed in
parts by weight:
<IMG>
2. The composition as claimed in Claim 1, wherein the
major portion by weight of said filler material has a particle
size of at least approximately 10 microns.
3. The composition as claimed in Claim 1, wherein said
filler material is a fire retardant comprising one or more members
of the group consisting of raw volcanic ash, hydrated calcium
sulfate, and hydrated aluminum oxide.
4. The composition as claimed in Claim 3, wherein said
density distribution control agent is a halocarbon.
5. The composition as claimed in Claim 1, wherein said
filler material is fly ash.
6. The composition as claimed in Claim 1, wherein
said filler material is calcium carbonate.
7. The composition as claimed in Claim 1, wherein said
filler material is silicon dioxide.
8. The composition as claimed in Claim 1, wherein said
filler material is a glass composition.
9. The composition as claimed in Claim 1, wherein said
control agent is carbon tetrachloride.

10. The composition as claimed in Claim 1, wherein said
control agent is trichloroethylene.
11. The composition as claimed in Claim 1, wherein said
control agent is methylene chloride.
12. The composition as claimed in Claim 1, wherein said
control agent is chloroform.
13. The composition as claimed in Claim 1, wherein said
control agent is methylchloroform.
14. A method of molding a filled, rigid polyurethane
foam product having a cellular core and a greatly densified,
integral, thick in situ generated outer layer, said method
comprising the steps of: charging a mold cavity with a liquid,
foam-producing system having initially unreacted elements of a
rigid polyurethane foam composition and a blowing agent which is
active at system temperatures under 40° C., said elements being
capable of reacting chemically to form an expanded, cellular,
polyurethane structure under the action of said blowing agent,
and a hard, particulate inorganic filler material substantially
uniformly dispersed throughout said elements; causing the foam
reaction to occur with said cavity closed by a surrounding mold
surface; and providing a density distribution control agent in
said cavity capable of assisting the formation of said densified
outer layer adjacent said mold surface during said foam reaction,
said control agent characterized by the properties of being liquid
at room temperature, chemically unreactive with said elements and
soluble therein, having a boiling point of at least approximately
40° C. in order to prevent an excessive increase in the pressure
within the mold over that provided by said blowing agent, and not
significantly accelerating or decelerating the reaction of said
elements, and being present in sufficient quantity to reduce the
31

viscosity of the mixture of said system and filler material to
prevent the viscosity of the total admixture from increasing to
the point that the admixture becomes unworkable, said system,
filler material and control agent being present in said admixture
in the following relative proportions expressed in parts by weight:
<IMG>
15. The method as claimed in Claim 14, wherein said
filler material in the resultant molded product is distributed
substantially throughout the same.
16. The method as claimed in Claim 15, wherein the
percent by weight of said filler material in said resultant
product is substantially the same in both the outer layer and
the core thereof.
17. The method as claimed in Claim 14, wherein suf-
ficient amounts of said filler material and said control agent
are provided to cause the density of the outer layer of the
resultant molded product to be at least three times as great as
the density of the core.
18. The method as claimed in Claim 14, wherein said
elements are mixed with one another to provide a foamable liquid
having said filler material admixed therewith, the ratio of the
weight of said filler material to the weight of said system being
at least approximately 1:3.
19. The method as claimed in Claim 14, wherein is
included the additional step of inverting said mold cavity during
said foam reaction.
32

20. The method as claimed in Claim 14, wherein is
included the additional step of providing a pressure barrier
member in said cavity to cause the generation of an internal,
densified region in the resultant molded product at said barrier
during said foam reaction.
21. A molded, integral, filled foam product comprising:
a rigid, integral structure formed of cellular polyurethane material
which has essentially the same chemical composition throughout sub-
stantially the entirety thereof; and an inorganic, particulate
filler material dispersed throughout said structure, said struc-
ture presenting a cellular core and a densified, cellular outer
portion surrounding said core, said core having a first density,
a first average cell size, a first concentration of the polyurethane
material in the core, and a first concentration of the filler
material in the core, said outer portion having a second density
greater than said first density of the core, a second average cell
size less than said first average cell size, a second concentra-
tion of the polyurethane material in the outer layer which is sub-
stantially greater than said first concentration of the poly-
urethane material in the core, and a second concentration of the
filler material in the outer layer which is substantially greater
than said first concentration of the filler material in the core.
22. The product as set forth in Claim 21, wherein the
major proportion by weight of said filler material has a diameter
of at least about 10 microns.
23. The product as set forth in Claim 21, wherein the
weight ratio of said filler material to said polyurethane material
is at least about 1:3.
24. The product as set forth in Claim 23, wherein said
ratio by weight of filler material to polyurethane is in the range
of approximately 1:3 to 4:1.
33

25. The product as set forth in Claim 21, wherein the
percent by weight of said filler material in said product is sub-
stantially the same in both the outer portion and the core thereof.
26. The product as set forth in Claim 21, wherein the
density of said outer portion is at least three times as great as
the density of said core.
27. The product as set forth in Claim 21, wherein the
outer surface of said outer portion is rigid and essentially void-
free.
28. The product as set forth in Claim 27, wherein said
outer surface has a durometer hardness value of at least approxi-
mately 50 throughout its area.
29. The product as set forth in Claim 21, wherein said
outer portion includes a pair of opposed major layers with said
core interposed therebetween to present a natural sandwich member,
the ratio of the thickness of the core to the combined thickness
of said opposed major layers being in the range of approximately
10:1 to 1:2.
30. The product as set forth in Claim 21, including a
barrier member within said core having an internal densified layer
formed adjacent thereto which is integral with the core, said
internal layer being of greater density than said core.
34

Description

105~049
This invention relates to improvements in poly-
urethane foams and processes for molding foams of this type
and, in particular, to improvements in rigid polyurethane
foams subject to environments in which resistance to struc-
tural loads and hard, durable outer surfaces are desirable.
Polyurethane foams are commonly prepared by
reacting a.l isocyanate with a hydrogen-containing compound
having a reactive hydroxyl group, such as a polyether polyol.
The reaction occurs in the presence of a catalyst, and a
blowing agent is provided in order to produce an expanded,
cellular product. The blowing agent may be produced chemi-
cally by the interation of the isocyanate with water to pro-
duce C02 gas, but preferably in low density, highly expanding
systems a blowing agent such as trichlorofluoromethane is
added which vaporizes at the outset of the reaction. Low
density systems are commercially available having a core
density of two pounds per cubic foot and four pounds per
cubic foot, when free blown by the trichlorofluoromethane
agent. Such systems are commonly supplied in two components,
the isocyanate component being maintained separate from the
polyol-catalyst-blowing agent component until the time of use.
The employment of low density systems as a casting
resin for rigid type polyurethane foams is advantageous in
that the amount of polyurethane reactants required for a
given mold volume is reduced, with a corresponding reduction
in the cost of the molded product. However, the inherent
reduction in density, although tolerable and even desirable
in the core, creates a problem at the surface of the product
since such surface is much less resistant to impact and abra-
sion. Accordingly, utilization of rigid, low density poly-
urethane foams in structural applications has been limited in
some instances by this inherent surface defect.
--2--

105~049
In an effort to improve the physical character-
istics of the surface, numerous approaches have been devised
for forming a tough skin on a polyurethane foam integral with
the low density core. These prior approaches include the
self-generation of an integral skin during molding by cool-
ing the mold surface, overfilling or overpacking the mold,
or employing centrifugal force through continuous mold rota-
tion to obtain a skin effect. However, it is believed that
all of these prior techniques have inherent disadvantages,
such as excessive cost of the product due to the increase in
the amount of polyurethane material in the case of overfill
molding, or the necessity of providing special equipment in
the case of mold surface cooling or mold rotation.
It is, therefore, an important object of the pre-
sent invention to provide a rigid polyurethane foam product
having substantially increased density with a reduced quantity
of polyurethane, and wherein the density of the product is
concentrated adjacent the outer surface thereof to increase
surface hardness and form a greatly densified outer layer of
significant thickness.
It is another important object of the present
invention to provide a molding composition and a molding
process for polyurethane foams which both minimize the poly-
urethane content of the molded product and produce in situ a
thick, greatly densified outer layer.
As a corollary to the foregoing object, it is an
important aim of this invention to provide a composition and
process as aforesaid in which the in situ generation of the
densified outer layer is caused solely by the employment of
additives in the foam system, and wherein no special mechani-
cal means is required in connection with the molding apparatus
in order to obtain the improved product.
--3--

105~0~
Still another important object of this invention
is to achieve a thick, densified outer layer as set forth
above, while at the same time decreasing the quantity of
reactive elements of the foam system required to mold a pro-
duct of a given size and weight.
In this latter connection, it is a further
important object of the invention to provide a molding compo-
sition and process as aforesaid wherein a filler material
is employed to significantly reduce the cost of the molded
product, increase its density, and enhance the density and
hardness of the in situ generated outer layer.
Accordingly, it is yet another important object
of the present invention to provide a natural sandwich from
a filled, rigid polyurethane foam having both structural and
cost advantages, and wherein the polyurethane and filler
components of the product are concentrated adjacent the outer
surface thereof, yet wit'n such filler being distributed in
the core of the product as well as the densified outer layer.
Additionally, it is an important object of this
invention to provide a foam product as aforesaid having one
or more internal regions of increased density in order to
reinforce the core portion thereof, and it is a further
objective to provide a method of formlng such internal
regions as the foam reaction occurs during the molding pro-
cess.
Furthermore, it is an important object of this
invention to provide a method of forming a densified outer
layer as above with uniformity throughout the surface area,
both in thickness and in hardness or resistance of the sur-
face to impact or abrasion.

10520~L~
In the drawing:
Fig. 1 is a fragmentary, cross-sectional view of
a molded polyurethane foam wall panel made in accordance with
the present invention;
Fig. 2 is a cross-sectional view of an ornamental
molding made in accordance with the present invention;
Fig. 3 is a fragmentary view of the exterior sur-
face of the molding of Fig, 2, showing a wood-grain surface
effect; and
Fig. 4 is a diagrammatic view showing the outline
of the cross section of molded test pieces discussed in the
detailed specification to follow.
THE FOAM PRODUCT
Two examples of molded polyurethane products made
in accordance with the teachings of the present invention
are illustrated in Figs. 1-3. A wall panel is shown in Fig.
1 and may be suitably dimensioned for wall construction pur-
poses. The cross section reveals the thickness of the article
and a portion of its width. For example, suitable dimensions
are eight feet in length (height when installed), four feet
in width, and a thickness of three inches. This would pro-
vide a panel suitable for home and building construction
having high structural strength in compression and the
excellent insulating properties characteristic of expanded
polyurethane. The article in Fig. 2 is a decorative molding
as may be appreciated from the irregular surface contour.
Referring first in detail to Fig. 2, it may be
seen that the molding has a relatively low density core 10
and a high density outer layer 12. The core 10 is charac-
teristic of expanded polyurethane foam products, in that it
comprises a substantially closed-cell, rigid structure in
-5-

105;~0'~
which the closed cells are formed b~ the blowing agent during
molding. The layer 1~ completely surrounds the core 10 and
is integrally formed therewith, tl~ere being a rather pro-
nounced line of demarcation 14 between the low density core
10 and the densified layer 12. The thickness ofthe layer is
relatively uniform except for the re-entrants 16 formed by
the grooves of the molding design, and the outwardly curving
protuberances 18 which are particularly pronounced at the
lower corners of the cross-sectional configuration.
The layer 12 has a closed-cell, rigid polyure-
thane structure like the core 10, but the cell size and spacing
is less than in the core 10 in order to provide a density in
the outer layer of from three to ten times the density of the
core. An exception to the cellular structure of the layer 12
is the outer surface thereof which is smooth and void free.
A hard, particulate filler material is distributed
throughout the core and outer layer structures by virtue of
having been previously admixed with the reactive elements of
the foam system prior to molding. This will be discussed fully
in succeeding portions of the present specification. At this
juncture, however, it is sufficient to appreciate that the
filler content by weight percent is the same in the core 10
as in the layer 12. Accordingly, both the polyurethane and
the filler components of ~he foam structure have substantially
greater concentration in the layer 12. The significance of
this is that the filler material contributes to the formation
of the layer, and also increases the hardness of the outer
surface thereof.
As is illustrated in Fig. 3, the hardouter sur-
face may be provided with a wood grain effect in the moldingof the article, or any other desired ornamental surface tex-
ture or appearance may be provided as is conventional in the
--6--

0~
plastic molding art. It is important to note in this respect
that, although the core 10 is cellular and of relatively low
density, the outer surface depicted in Fig. 3 has sufficient
hardness to permit desired decorative surface effects to be
imparted during molding. As will be fully discussed herein-
below, the outer surface of the products of the present inven-
tion may be formed with a durometer hardness value of well
over 50 throughout the surface area (65 to 80 is readily
obtainable).
Referring to Fig. 1, it may be seen that the panel
has a low density core 20 and a densified, natural outer
portion 22 analogous to the core 10 and layer 12 of the
decorative molding of Fig. 2 discussed above. The panel has
the same structural characteristics, in that the core 20 and
outer portion 22 comprise an expanded polyurethane formed in
a closed mold cavity. Thus, the panel is a sandwich member,
the core 20 being interposed between the major layers of the
outer portion 22 that present the opposed faces of the panel.
A hard, particulate filler material is admixed with the reac-
tive elements of the foam system prior to the molding opera-
tion, and a rather pronouced line of demarcation 24 is
produced indicating that the cellular structure undergoes a
rapid increase in density at the boundary between the core 20
and the outer portion 22.
Other than its ultimate use and external appear-
ance, the panel construction is also essentially the same as
that of the decorative molding illustrated in Figs. 2 and 3,
except for internal reinforcement of the core 20 provided by
two densified regions 26. Each of the densified regions 26
is formed around a barrier member 28 in the nature of a thin
strip of metal, cardboard or other barrier-forming material
extending the length of the panel. The two strips 28 are

105Z049
placed in the mold cavity and positioned in accordance with
the desired locations of the regions 26 in the finished,
molded product. In the present example assuming that the
wall panel has a width of four feet, the two strips 28 could
be located on sixteen inch centers with the longitudinal
edges 30 of the panel, thereby providing reinforcement for
the panel core 20 at intervals sixteen inches apart from one
longitudinal edge to the other (the minor stretches of outer
portion 22 at the longitudinal edges 30 also serve as rein-
forcement). As foaming occurs during the molding process,each of the strips 28 provides a pressure barrier in a manner
analogous to the mold surfaces defining the closed mold
cavity. Accordingly, the region 26 formed on the strip 28
is in the nature of an internal, densified layer bridging
the opposed major layers of the outer portion 22 that present
the major surfaces of the panel. In effect, therefore, the
core 20 is divided into three sections, the center section
being bounded by the two regions 26 and each end section being
bounded by one of the regions 26 and the corresponding longi-
tudinal edge 30. The thickness of the internal skin formedon one surface or side of the associated strip 28 in the
article depicted in Fig. 1 is on the order of 1/8 inch,
whereas the thickness of each of the major layers presented
by outer portion 22 is somewhat over 1/4 inch. It should
be understood, however, that a foraminous material such as
strips of wire screen could also be employed as the barrier
members 28, with the result that the densified regions 26
would be appreciably thicker (although of lesser density)
and would be the result of a gradual densification without
the observable lines of demarcation. Accordingly, the
internal densified layers of the present invention have a

lOS'~O~9
density and delineation to the extent that the members 28
provide an effective barrier to the expanding foam.
It should be understood that the thickness of
the outer portion 22 of the natural sandwich member will
vary depending on the thickness of the member and the particu-
lar molding composition utilized (formulations are set forth
hereinafter). The wall panel of Fig. 1 is a typical example,
being three inches in total thickness and assuming a layer
thickness of 3/8 inch. Thus, the thickness of the core 20
between the opposed major surfaces is 2 1/4 inches, and the
combined thickness of the outer layers is 3/4 inch. This
is a ratio of core thickness to layer thickness between the
surfaces of 3:1. The thickness of the densified outer layer
increases with panel thickness and/or filler content. How-
ever, core thickness will normally increase in greater pro-
portion, thus thicker sandwich panels may have a core to
layer thickness ratio up to approximately 10:1. On the other
extreme, very thin panels (on the order of one inch from sur-
face to surface) may be produced with very thick densified
surface layers relative to the core, resulting in low core
to layer thickness ratios on the order of 1:2.
THE PROCESS AND MOLDING CO~OSITIONS
In the present invention, a molding composition
is employed comprising a foam-producing system plus additives
that cause the system to produce a natural sandwich product
during the molding operation. Conventional two-pound and
four-pound systems are preferred, but the teachings of the
present invention are also applicable to higher density sys-
tems which utilize greater amounts of the unreacted, poly-
urethane-forming elements in relation to the blowing agent.

lOS'~049
The additives comprise a hard, particulate filler material
and a density distribution control agent to be discussed in
detail.
It should be understood that a "two-pound system"
as used herein refers to a foam-producing system which will
produce an expanded, rigid polyurethane product having a
density of two pounds per cubic foot when free blown (free
rise density). In a four-pound system, a lesser relative
quantity of blowing agent is utilized, thus the nomenclature
refers to a foam product having a free rise density of four
pounds per cubic foot. Systems of this type are commonly
supplied in two components which are not mixed until just
prior to charging the mold. One component is the isocyanate,
and the other component is the polyol together with a cata-
lyst and a suitable blowing agent, Such systems are
employed as casting resins for rigid type polyurethane foams
and, particularly in the lower density systems, the blowing
agent is commonly trichlorofluoromethane which vaporizes at
well below the temperature reached during the reaction of
the isocyanate and polyol occurring after they are admixed.
The reactîon is exothermic and thus supplies the heat for
vaporization of the blowing agent necessary to form the
expanded foam product.
The filler material should not be chemically
reactive with the isocyanate or polyol to any significant
degree, and thus an inorganic material is preferred which
does not cause an inordinate increase in the viscosity of the
component (or admixed components) to which it is added. In
this latter regard, it should be understood that the compo-
nents of the foam-producing composition are liquids prior to
mixing, thus substantial increases in the viscosity of either
component or the admixed components caused by the filler
-10-

lO~Z049
material are ideally avoided. In general, the smaller the
particle, the higher the viscosity of a liquid in which is
dispersed a given quantity by weight of the filler material.
Accordingly, larger particle sizes are preferred so long as
the particle is not so large as to interfere significantly
with the formation of the cellular polyurethane structure.
Small particle sizes tend to increase the viscosity of the
foamable liquid when the filler additive is admixed there-
with in significant quantities, thus a filler having a small
particle size may increase the viscosity of the admixture
to such an extent that it can no longer be readily handled
and becomes unsuitable as a molding composition.
Examples of materials suitable as the filler in
the present invention include a number of inorganic materials
such as fly ash and various glass compositions, and specific
compounds such as calcium carbonate (CaCO3), silicon dioxide
(SiO2), and the oxides of iron. Calcium carbonate may be in
the form of ground calcite, silicon dioxide may be ground
quartz or sand, and iron oxides may be obtained from natur-
ally occurring hematite (Fe203) and magnetite (Fe304). Other
suitable natural minerals include feldspar, dolomite, barite
and anhydrite. The filler material should be nonflammable.
Furthermore, for fire retardancy, materials preferred for
this quality include raw volcanic ash, hydrated calcium sul-
fate, and hydrated aluminum oxide. A particle size of from
40 to 200 microns or somewhat larger is preferred, with
particle sizes in excess of 200 microns being usable as long
as the filler does not substantially impede the formation of
the cellular polyurethane structure.
The density distribution control agent is an
organic liquid at room temperature which is chemically
unreactive with the polyurethane-forming elements of the
-11-

10~ 49
foam system. Examples of suitable agents include carbon
tetrachloride (CC14) wh~ch has a boiling point of approxi-
mately 77 C., trichloroethylene (CHCl:CC12) which has a
boiling point of approximately 87 C., methylene chloride
(dichloromethane) whichh~s a boiling pointfapproximately
40C., chloroform (CHC13~ having a boiling point of 61 C.,
methylchloroform (l,l,l-trichloroethane) which boils at
approximately 74C., perchloroethylene (tetrachloroethene)
which boils at approximately 121C., and ethyl acetate which
boils at approximately 77C. The halocarbons are preferred
due to their natural fire retardancy and self-extinguishing
characteristics, particularly carbon tetrachloride.
The characterizing parameters of the control agent,
besides being liquid at room temperature, are that it must be
chemically unreactive with the isocyanate and polyol elements
of the foam system and soluble therein, with a boiling point
of approximately 40C. or greater. Furthermore, the control
agent must not influence the catalyst so as to significantly
accelerate or decelerate the reaction of the polyurethane-
forming elements, and should have a low viscosity in orderto render it capable of reducing the viscosity of the mixture
of the foam system and filler material. It is believed that
the viscosity reduction obtained through use of the control
agent is instrumental in the formation of the thick, densi-
fied outer layer during the foam reaction. The use of more
volatile agents (boiling points significantly under 40C.)
causes an undue increase in the pressure within the mold,
with the attendant possibility that the resultant product
could have dimensional instability under ambient temperature
extremes that would result in damage to the product through
warpage or fracture.
-12-

lOSZ049
Both the filler material and the control agent
reduce the temperature of the foam reaction within the mold
as compared with molding compositions not employing the addi-
tives of the present invention (heavily loaded formulations
may not reach 200F. during the exothermic foaming reaction).
Furthermore, the presence of the filler also reduces the
pressure reached during the foam reaction. These are bene-
ficial by-products of the invention. Since the filler
effects a pressllre reduction, the addition of a volatile con-
trol agent is possible without creating an extreme pressurecondition, so long as its volatility is restricted as dis-
cussed above and a minor proportion by weight of the agent
is used in the molding composition (specific examples are
set forth hereinafter).
It should also be noted in the examples to follow
that the amount of filler material in the molding composi-
tion is substantial, on the order of one-half of the composi-
tion by weight as will be discussed, which would in many
instances make the composition too viscous to handle in the
absence of the density distribution control agent. The
cooperative action of the agent and the relatively large
quantity of filler material results in the formation of a
very hard outer surface and a thick, densified outer layer.
In this respect, it is important that the filler material
have a sufficient particle size to eliminate problems of
viscosity increase discussed above so that the requisite
quantity of filler may be employed in the formulation. The
predominant particle size of the filler should ideally be at
least approximately 40 microns, size large amounts of smaller
particles (generally under 10 microns) will raise the vis-
cosity to the point that the desired filler content may be
difficult to maintain. As an example, it has been found that

lOSZ0~9
gypsum plaster (hydrous calcium sulphate) having the follow-
ing range of particle sizes is a usable filler:
Particle Size Percent by Weight
In Microns Of Total Material
Less Than 149 99.5%
Less Than 105 98.7
Less Than 74 95.4
Less Than 44 86.6
Less Than 37 77.2
10Less Than 30 70.8
Less Than 20 54.0
Less Than 10 32.2
Gypsum filler material having this range of particle sizes
may be admixed with the unreacted polyurethane foam compo-
nents in a ratio of 1:1 although a more viscous composition
is produced than is preferred, but the greater viscosity does
not preclude use of the admixture as a practical molding
composition.
To prepare the molding composition of the present
invention, mechanical impeller-type mixers may be employed
in a two-step mixing operation. The two components of the
foam system and the control agent are mixed first, and then
the filler material is added. This may be accomplished in
an in-line mixing operation with the first mixer being employed
for the foam system and control agent. The second mixer
receives the admixed system and agent and adds the filler
which may be metered intG the mixer by an auger or other
suitable means. It is important that the filler be thor-
oughly admixed with the isocyanate and polyol elements of
the foam system so that the filler will be uniformly dis-
persed throughout the foamable liquid composition. Such
-14-

105Z049
admixture is transferred directly from the second mixer to
the mold in order to charge the latter before the reaction
commences.
A number of exemplary molding formulations follow.
Component A is the isocyanate, and component B is the polyol
with blowing agent and catalyst. All of the examples are
expressed in terms of parts by weight with component A and
component B normally being mixed in approximately a l:l ratio.
EXAMPLE I
Components A and B 50 parts
Filler 50 parts
Control Agent 5 parts
Example I is a preferred formulation utilizing a
four to eight-pound polyurethane foam system in order to pro-
vide a superior natural sandwich product for structural
applications, such as entrance doors and structural as well
as decorative wall panels. The ratio of the weight of the
filler to the weight of the foam system is 1:1, and the
admixed composition has sufficiently low viscosity to be
readily handled in molding operations.
EXAMPLE II
Components A and B 60 parts
Filler 40 parts
Control Agent 5 parts
Example II is a formulation utilizing a two-pound,
highly expanding foam system with a lesser filler loading
to achieve a product of relatively light weight. Although
the densified outer layer of the product may be thinner than
in more heavily loaded formulations, a durable, high-density
outer layer is nonPtheless formed. The formulation would
-15-

~ O 5'~ O 49
find particular use, for example, in the mo]ding of decora-
tive appliques and non-structural furniture parts.
EXAMPLE III
Components A and B 30 parts
Filler 60 parts
Control Agent 5 parts
Example III employs a two-pound foam system as in
Example II, but a heavy filler loading (2:1 ratio of filler
to foam system) is utilized to enhance certain structural
characteristics of the molded part. The product has a
highly insulating core with great contrast between surface
density and core density and is characterized by a very
thick, durable outer layer. This formulation is useful in
such applications as the molding of non-structural wall
panels where superior insulating properties and a durable
outer surface are desired.
EXAMPLE IV
Components A andB 50 parts
Filler 50 parts
Although the formulation of Example IV is not as
desirable due to the omission of the density distribution
control agent, it does represent a cost saving factor of
50% as compared with utilizing unloaded polyurethane to
achieve the same part weight. The filler must be selected
so as to not increase the viscosity of the admixture to the
point that it is unworkable. Accordingly, a two-pound den-
sity foam system is preferred. Fillers such as banding sand
and fly ash, for example, are suitable. Generally speaking,
the selected filler should have particle sizes conforming
to the preferred range set forth above (approximately 40
microns or greater).
-16-

105;~0~9
With respect to all of the foregoing examples, the
quantity of the molding composition utilized may be equal to
approximately 40% of the volume of the mold cavity into which
the composition is to be charged, but this can be varied
greatly from application to application depending on the
desired overall product density. As will be discussed sub-
sequently when experimental results are set forth, enhance-
ment of the densified outer layer by way of both uniformity
in thickness and surface hardness may be obtained by invert-
ing the mold during the foam reaction.
A general formulation for the molding compositionof the present invention comprises an admixture of a foam
system as defined above present in from approximately 20 to
75 parts by weight, a filler material as previously defined
present in from approximately 25 to 80 parts by weight, and
a density distribution control agent present in from approxi-
mately 3 to 12 parts by weight. This provides a ratio by
weight of filler material to polyurethane in the range of
approximately 1:3 to 4:1. Fillers having large particle
sizes (on the order of 200 microns or greater) may be advan-
tageously employed for the very heavy loadings over 2:1 due
to the decreased viscosity.
As the foam reaction occurs within the mold cavity,
the expanded, cellular polyurethane structure is formed in
the usual manner by the action of the blowing agent of the
foam system. The closed mold cavity is, of course, defined
by a surrounding mold surface that serves as a barrier to
the expanding polyurethane during the foam reaction. It is
believed that the reduced viscosity of the admixture attained
through use of the control agent assists the greatly densi-
fied layer effect of the present invention since the cell

105;~049
walls of the polyure~hane structure are thinner just prior
to gelation, resulting in greater expansion in the core with
corresponding concentration of the density of the product
adjacent the surrounding mold surface. Due to the action
of the filler and control agent additives of the present
invention, the net result is to form a natural sandwich pro-
duct as previously described with reference to Figs. 1-3
wherein the core of the product has a relatively low density
as would be e~pected, but with the addition of a thick and
greatly desnified outer layer formed adjacent the mold sur-
face. Both the polyurethane and the filler components of
the foam structure are more greatly concentrated in the
outer layer than in the core, as evidenced by the fact that
the filler content by weight percent is the same throughout
both the core and the outer layer of the molded product.
Accordingly, not only the cellular polyurethane structure,
but also the particulate filler is concentrated in the outer
region. It has been found that this contributes to the for-
mation of the densified layer and also increases the hardness
of its outer surface.
PHYSICAL PROPERTIES OF THE PRODUCT
Table I sets forth the formulations employed in
twenty-two tests of molded products of the present invention,
which were run to determine the physical properties of the
outer layer in terms of thickness, durometer hardness values,
and uniformity of the results obtained. The physical para-
meters of the test pieces are set forth in Table II, and such
pieces are correlated with the formulations of Table I by the
test numbers appearing in the left-hand columns of both tables.

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iO5Z0~9
TABLE II
PHYSICAL PARAMETERS OF TEST PIECES
Densified
Hardness Values Weig_t of Outer Layer
Test No. Top Side Rottom Piece, gms. Thlckness, mm.
1 25 46 59 126.8 1 - 3
2 29 45 71 133.3 1 - 4
3 37 54 57 192.5 1 - 4
4 38 63 72 203.9 1 - 4
39 64 71 204.3 1 - 4
6 30 45 53 134.3 1 - 3
7 43 56 58 143.2 1 - 3
8 46 53 56 147.2 1 - 3
9 34 43 80 122.4 1 - 3
49 57 72 187.1 1 - 4
11 59 64 71 281.3 1 - 5
12 60 65 69 - 1 - 4
13 28 61 72 203.0 1 - 9
14 22 34 37 269.5 0 - 1
36 62 64 211.5 1 - 5
16 49 73 81 232.6 1 - 9
17 70 78 78 393.5 1 - 10
18 58 68 70 326.0 2 - 6
19 57 74 74 485.4 2.5 - 8
49 59 59 587.8 2.5 - 13
21 31 61 65 207.3 1 - 6
22 69 77 79 697.3 2 - 19
Each of the test pieces had a longitudinal cross-
sectional configuration illustrated in Fig. 4 (the figure
shows the outline of the cross section). The volume of the
mold cavity was 48.5 cubic inches, and the resultant molded
piece had a length of approximately 6 1/2 inches and a width
-20-

~ O S ZO 49
of 3 1/4 inches, as represented by "L" and '~" in Fig. 4.
The thickness of each piece was approximately 2 1/4 inches.
Tests 1-13, 15 and 21 utilized a four-pound foam
system; component A thereof is a crude diphenylmethane
diisocyanate and component B is a polyether polyol, plus
trichlorofluoromethane (blowing agent) and a catalyst. The
two-pound foam system used in tests 16-20 and 22 employed
tolylene diisocyanate as component A and a polyether polyol
as component B with a catalyst and a greater quantity of the
trichlorofluoromethane blowing agent. The ten-pound foam
system utilized in test 14 employed a modified diphenylmethane
diisocyanate as component A, and a component B comprising
essentially a polyether polyol with some water present, plus `
^ a catalyst. The ten-pound system is of the C02-blown type;
the water present in component B enters into the reaction
of the isocyanate and OH groups to liberate the C02 blowing
agent.
The fly ash ("Ash" in Table I) in the test formu-
lations was analyzed by x-ray diffraction to determine the
compounds present. The major component was an amorphous
(noncrystalline) mixture of silicon-aluminum-calcium-potassium-
oxide, i.e. glass. Fe304 and alpha-SiO2 (quartz) were also
present. A spectrographic analysis of the fly ash is set
forth in Table III.

105Z049
TABLE III
Spectro~raphic Analysis ~Semi-Quantitative2
Element Weight_Percent
Aluminum 8.0
Barium 0.02
Calcium 3.0
Copper 0.006
Iron 10.
Lead 0.05
lQ Manganese 0.03
Nickel 0.01
Potassium 2.
Rubidium 0.005
Silicon 25.
Strontium 0.03
Sulfur 0.3
Titanium 0.5
Vanadium 0.02
Yttrium 0.005
Zinc 0-3
Zirconium 0.01
As indicated in Table I and as will be discussed,
calcium carbonate (CaCO3) was substituted for fly ash in
several of the tests. The column headed "CaCO3 pptd" refers
to precipitated calcium carbonate, while the column headed
"CaCO3 200 mesh" refers to calcium carbonate ground from cal-
cite to minus 200 mesh (less than 74 microns). -~
The colllmns in Table I indicating quantities of CC14
or CHCl:CC12 represent the type and amount of density distri-
bution control agent utilized in the various tests. The right-
hand column indicates the quantity of diesel fuel added in some
tests to determine if this additive had any measurable effect
on surface hardness.
In all tests, the additives were combined with
component A of the foam system and thoroughly mixed with a
high speed hand drill mixer blade. The B component was then
metered into the plus additives mixture in amounts equal to
the A component weight and thoroughly mixed.
-22-

~ O SZ O 49
The total mixture was immediately poured (the
reaction commences in approximately one minute after the A
and B components are combined) into the top end of a two-piece
RTV (room temperature vulcanizing) rubber mold, the surface
of which had been treated with a light coating of a release
agent. The mold was closed with a top containing an air vent
hole. After expulsion of the air from the mold cavity,
indicated by ejection of the foaming polyurethane through
~ the vent, the vent hole was closed, In tests 20 and 22 the
; 10 mold cavity was filled approximately two-thirds full with
the molding composition; in tests 17 and 18 the mold cavity
was approximately half full. In the tests such as 1 through
15 employing less amounts of components A and B, the mold was
under half full. (In some of the heavier formulations of the
later tests, the mold cavity was not charged with the entire
quantity of prepared molding composition, thus some of the
variation in the weights of the finished pieces are attribu-
table to this.)
Time in the mold varied from fifteen to thirty min-
utes, depending on the quantity of additives in the mixture.The larger the quantity of fly ash, the longer the mold time
required.
After demold, each test piece was permitted to cool
and weighed, and was then cut in half parallel to the longi-
tudinal dimension and examined for external and internal
appearance. Hardness of the external surface was determined
by a maximum reading durometer (the instrument utilized con-
forms to ASTM D2240 and was a Shore durometer, Type D, made
by the Shore Instrument and Manufacturing Company of Jamaica,
New York). The distribution of outer layer thickness varia-
tions within each piece was determined. In all tests, the
-23-

1052049
appearance of the pieces was excellent; the other physical
parameters are set forth in Table II.
The results of the tests ~o now be discussed are
based on the data compiled in Tables I and II. Examination
of the hardness values presented in Table II shows that
differential hardness exists over different surface~ of a
number of the test pieces. In general, the top surface of
each piece was found to have the lowest hardness value as a
result of conventional molding practice. Since the foamable
liquid admixture is poured into the mold from the top, the
initially reacted polyurethane, together with entrapped gas
rises to the top of the mold while the balance of the liquid
admixture is compressed downward. This downward compression
of the as yet unreacted liquid results in a densification of
the surfaces in the lower portion of the piece. However,
attention is directed to tests 18-20 and 22 where the mold
was reversed 180 (inverted) during the foam reaction. As
compared with most of the other tests where the mold remained
in the same position, the difference between the three hardness
values is significantly less. Accordingly, inverting the mold
resulted in greater uniformity of the hardness values of the
outer surface.
The outer surfaces referred to in Table II may be
identified with reference to Fig. 4. The top surface is
identified by the reference numeral 32, the side surfaces are
identified by 34, and the bottom surface is 36. Note the
re-entrants 38 and the outwardly curving protuberances 40
formed by the mold configuration.
Further examination of the data in Table II per-
taining to the thickness of the densified outer layer revealsthat a certain degree of nonuniformity exists in all tests.
-24-

lOSZO~9
In those tests where the mold was not inverted, it was
observed that the thicker layer tended to develop on the
bottom surface of the piece as would be expected from the
previous discussion of surface hardness variation. Further-
more, the outer layer tended to thicken in areas associated
with the protuberances 40 and development of the densified
layer in the area of the sharply pointed re-entrants 38 was
noticeably reduced. However, inverting the mold immediately
after expulsion of the air therefrom (tests 18-20) materially
decreased the variation in thickness from the minimum at the
re-entrants 38 to the maximum at the protuberances 40, result-
ing in a more uniform thickness having an average value
approximately midway in the range for each test set forth in
Table II. This may be seen by comparing tests 17 and 18 in -
which the same formulations were employed, but without invert-
ing the mold in test 17. The layer thickness variation was
reduced from 1 to 10 mm. (test 17) to 2 to 6 mm. (test 18).
The layers present on the top and bottom of the piece in test -.
18 were nearly equal in thickness (2 mm.), with the thickest
layer being associated with the protuberances 40 near the top
and bottom of the p.iece.
The effect of the additives may be observed from a
number of comparisons. First, the isolated effect of the
CC14 ~ontrol agent is shown by comparing tests l.and 2. It
is evident that CC14 has to some extent increased the hardness
of the blank polyurethane (test 1). It is believed that the
CC14 is retained in the closed cells of the foam structure
and absorbed as is the case with the blowing agent provided
in component B, trichlorofluoromethane (CC13F). The effect of
the addition of fly ash to the blank polyurethane may be seen
by a comparison of tests 1 and 3. The weight of the piece has

lOSZ049
increased, a slightly thicker outer layer has been obtained,
and the differential hardness of the three surfaces i8
reduced.
The combined effect of the fly ash and CC14 addi- -
tives is shown by comparing these previous tests with test 4.
It is evident that the use of both additives has brought about
a dramatic improvement in the hardness values, resulting in
the formation of a useful outer layer. In tests 5, 8 and 11-
15, diesel fuel was also employed as an additive but without
significant improvement in the surface hardness of the test
pieces.
It should also be noted in Table I that calcium `
carbonate was substituted for fly ash in several of the tests
as mentioned above. Neither fly ash nor calcium carbonate
are believed to enter directly into the isocyanate-polyol
reaction. It was found from the teæts as may be observed in
Table II that the calcium carbonate is as effective as fly
ash in developing the integral layer.
Calcium carbonate in the ground calcite form (200
mesh) i8 preferred over the precipitated calcium carbonate
since the viscosity of the liquid admixture becomes quite
high in the case of the precipitated CaCO3. As discussed
previously in this specification, the particle size of the
filler material should not be so small as to create a vis-
cosity problem as in the case of the small particles con-
stituting CaCO3 in precipitate form, It may be noted that
the quantity of precipitated CaCO3 in tests 6-8 is h~lf that
of the fly ash in comparable formulations, such reduction
being necessitated by the high viscosity problem encountered
when an attempt was made to substitute the precipitated CaCO3
for fly ash on an equal quantity basis~
-26-

105Z049
The effect of substituting trichloroethylene
(CHCl:CC12) for carbon tetrachloride (CC14) is evident from
a comparison of tests 2 and 9, and 4 and 10. Examination
of Table I indicates that tests 9 and 10 are compositional
equivalents of tests 2 and 4 respectively with the exception
that trichloroethylene has been substituted for CC14. Other
nonreactive organic liquids having the properties set forth
earlier in this specification, particularly the halocarbons,
may also be substituted for CC14.
Insofar as the effect of changing the foam system
is concerned, the data indicates that both two-pound and four-
pound systems are quite satisfactory. As previously dis-
cussed, these systems are blown by an agent such as trichloro-
fluoromethane present in component B. The less expansive,
ten-pound system (test 14) is a CO2-blown polyurethane system
with significantly reduced expansion capabilities, thus 18
grams of CC14 in this test failed to produce a significant
outer layer. However, satisfactory outer layers may be
readily produced with higher density systems including those
that are CO2 blown. Due to the higher density core produced
by such systems, the lines of demarcation 24 and 14 shown in
Figs. 1 and 2 are not as pronounced.
With reference to test A, the resultant piece was
examined to determine the percent by weight of fly ash in the
core and in the outer layer, and the relative densities of
the core and outer layer. A core sample taken from the cen-
ter of the piece was found to have a density of 13.13 pounds
per cubic foot, while a sample of the outer layer taken from
the side of the piece had a density of 47.45 pounds per cubic
foot. In the core sample, the percentage of fly ash by
weight was 31.98%; in the side layer samples, 31.31%; and in
-27-

1052049
a sample of the outer layer taken from the bottom of the
piece, 32.91%. Accordingly, the density of the side layer
was approximately 3.6 times that of the core, and fly ash
content was essentially constant throughout the piece.
As is apparent from examination of the data for
individual tests in both Table I and Table II, the thic~er
outer layers formed in accordance with the teachings of the
present invention are associated with those formulations
which contain the higher fly ash content (test 17-20 and 22).
It is also apparent that an adequate amount of the control
agent should be added to the formulation to compensate for
the extra weight of the filler added to the isocyanate-polyol
mixture. The benefit of an adequate amount of CC14 is illus-
trated by a comparison of the hardness values for tests 20 and
22. In the test formulations, the weight percent of control
agent varies from approximately 3% to 6% of the total weight
of the admixture.
It should be understood that the temperature of
the A and B components of 85F. in tests 1-13 is not pre-
ferred, since this is above the boiling point of the tri-
chlorofluoromethane present in component B. This could
cause some loss of the blowing agent before the mold is charged
with the admixture, thus cool room temperature conditions are
preferred (or conditions recommended by the polyurethane
component supplier).
-28-
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