Decorative syntactic foam products

A mixture of vinyl plastisol, suspension grade resin and expanded perlite is prepared in a manner such that the particles of perlite are not significantly damaged. The mixture is placed on a substrate and fused, thereby producing a foam-like material which is usable as a decorative covering. Alternatively, the mixture can be cast on a release surface and allowed to stand until the majority of the perlite particles have migrated to the top surface, thus leaving a layer of material containing substantially no perlite along the lower surface which interfaces with the release surface. Upon fusing this stratified mixture and separating the release surface, the fused material is inverted. The layer of material which contains substantially no perlite becomes the protective surface and the remaining portion of the fused material, which is foam-like in nature, becomes the resilient support. Such syntactic foams may be used as replacements or substitutes for mechanically frothed or chemically blown foams.

The present invention relates to decorative coverings and more particularly 
to decorative syntactic foam products. 
BACKGROUND OF THE INVENTION 
Foamed products and processes for making them have been extensively 
investigated, resulting in the development of foamed products which are 
used as floor coverings, wall coverings and the like. These investigations 
have led to many highly technical production methods, such as methods 
utilizing chemical blowing agents. Such methods often involve multiple 
steps which tend to be time-consuming and expensive. Accordingly, the 
industry is constantly trying to find new yet simplifed methods of 
manufacturing these foamed products. 
THE PRIOR ART 
Most foamed flooring products are presently prepared either by mechanical 
means, such as by mechanically frothing a vinyl plastisol which is then 
placed on a backing material, or by chemical means, in which case a 
foamable plastisol is placed on a backing and foamed using chemical 
blowing agents which are well known in the art. However, the cost of 
preparing such foamed materials can be relatively high because of the 
number of steps involved. Furthermore, the application of wear layers can 
increase these costs even further. 
Accordingly, one object of the present invention is to provide a unitary 
low-density flooring which has the attributes of foamed vinyl flooring, 
but which does not possess the inherent disadvantages of foamed flooring. 
Yet another object of the present invention is to provide a single step 
process by which a foam-like flooring having an integrated wear layer can 
be produced. 
Still another object of the present invention is to provide syntactic foam 
products which will be useful as decorative coverings, such as wall 
coverings, which are adaptable to a variety of environments. 
These and other features of the present invention will become apparent from 
the disclosure of preferred embodiments which follow. 
SUMMARY OF THE INVENTION 
A mixture of vinyl plastisol, suspension grade resin and expanded perlite 
is prepared in a manner such that the particles of perlite are not 
significantly damaged. The mixture is placed on a substrate and fused, 
thereby producing a foam-like material which is usable as a decorative 
covering. Alternatively, the mixture can be cast on a release surface and 
allowed to stand until the majority of the perlite particles have migrated 
to the top surface, thus leaving a layer of material containing 
substantially no perlite along the lower surface which interfaces with the 
release surface. Upon fusing this stratified mixture and separating the 
release surface, the fused material is inverted. The layer of material 
which contains substantially no perlite becomes the protective surface and 
the remaining portion of the fused material, which is foam-like in nature, 
becomes the resilient support. Such syntactic foams may be used as 
replacements or substitutes for mechanically frothed or chemically blown 
foams. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In one embodiment, the present invention comprises a process for producing 
a syntactic foam structure, said process comprising the steps of preparing 
a mixture comprising from about 65 to about 99 percent by weight of vinyl 
plastisol, from 0 to about 30 percent by weight of suspension grade resin 
and from about 1 to about 10 percent by weight of expanded perlite 
comprised essentially of particles having a diameter of from about 50 to 
about 1000 microns. The mixture is spread to a desired thickness on a 
substrate and fused. 
In a second embodiment, the present invention comprises a process for 
producing a syntactic foam structure having an integrated protective 
layer, said process comprising the steps of preparing a mixture comprising 
from about 65 to about 99 percent by weight of vinyl plastisol, from 0 to 
about 30 percent by weight of suspension grade resin, and from about 1 to 
about 10 percent by weight of expanded perlite comprised essentially of 
particles having a diameter of from about 50 to about 1000 microns. The 
mixture is spread to a desired thickness on a release surface and the 
perlite is permitted to rise to the upper surface of the mixture, thereby 
leaving a layer of material comprising essentially no perlite at the lower 
surface thereof, said lower surface interfacing with said release surface. 
The stratified material is fused and separated from said release surface. 
In a third embodiment, the present invention comprises a syntactic foam 
structure obtained by fusing a mixture comprising from about 65 to about 
99 percent by weight of vinyl plastisol, from 0 to about 30 percent by 
weight of dry blend resin and from about 1 to about 10 percent by weight 
of expanded perlite comprised essentially of particles having a diameter 
of from about 50 to about 1000 microns. 
Syntactic foams are pseudo foams in which the bubbles responsible for the 
foam-like character are formed prior to inclusion in the matrix material. 
For example, if microspheres or hollow particles consisting of glass, 
ceramic, carbon or plastic are embedded in a matrix, the resulting product 
is a syntactic foam. Such foams have been known for many years to have 
utility in producing molded furniture, deep water plastic floats and other 
materials in which the cast foam would be subjected to stress. However, 
the spheres used to produce these materials have been of sturdy 
construction, phenolic resins and glass spheres being the main types of 
additives. 
Surprisingly, we have found that a low-density syntactic foam structure may 
be constructed using expanded perlite as the preformed bubbles. Expanded 
perlite is extremely light in weight, having a bulk density as low as 3 to 
5 pounds per cubic foot. Unlike the aforementioned materials, many 
expanded perlite particles have an open-celled structure with fairly 
irregular surface characteristics. Perlite is also a very fragile material 
which is easily crushed. Accordingly, it is unexpected and surprising to 
find that suitable structures comprising expanded perlite can be produced, 
and even more surpising to find that such structures are suitable as 
flooring materials. When used for this purpose, the syntactic foams of the 
present invention can be embossed, coated and subjected to temperature and 
pressure conditions which would cause frothed or chemically blown 
plastisol foams to collapse. 
To practice the present invention, a vinyl plastisol is prepared by means 
well known in the art. Plastisols conventionally comprise a dispersion 
grade resin, a blending resin and a plasticizer. Virtually any dispersion 
grade resin and blending resin can be employed although polyvinyl chloride 
homopolymers are preferred. Typically, dispersion grade resins have a 
particle size of from about 0.5 to about 2 microns, whereas blending 
resins have a particle size of from about 10 to about 250 microns. 
Virtually any plasticizer compatible with these resins may be used, 
although dioctyl phthalate is preferred. Typically, the plastisol will 
contain about 50 to 80 parts by weight of plasticizer for every 100 parts 
of resin, and it may also contain other additives, such as stabilizers, 
pigments, decorative chips and the like. 
Furthermore, the mixture may comprise from 0 to about 30 percent by weight 
of a suspension grade resin to enhance the cellular characteristics and 
workability of the resulting product. As used herein, the term suspension 
grade resin will include dry blended resins, which are resins that have 
been treated with a plasticizer. Virtually any suspension grade resin may 
be used although vinyl homopolymers are preferred. 
In preparing the perlite-containing mixture, it is preferable to mix all of 
the components except the perlite with the plastisol and then, as the last 
step, to mix in the expanded perlite; however, a low-shear blender should 
be used in mixing the perlite in order to avoid damaging the perlite 
cells. The perlite cells will be comprised essentially of particles having 
a diameter of from about 50 to about 1000 microns, but preferably the 
majority of the particles will be from about 100 to about 500 microns in 
diameter. From about 1 to about 10 percent by weight of perlite may be 
used to practice the present invention, although from about 2 to about 6 
percent is preferred. 
After mixing is complete, the present invention takes one of several 
alternative courses. In one alternative, the mixture may be cast upon a 
substrate and immediately fused, or it may be cast on a release surface 
and allowed to stand for several minutes until the light-weight perlite 
has migrated to the upper surface of the plastisol, at which point the 
mixture can be fused. In the former case, a product having a relatively 
uniform foam-like structure is obtained, and this material may be used in 
a variety of ways. For example, if the substrate is a conventional floor 
backing, the structure may be used as is, or it may be further provided 
with a wear layer or other protective covering. In addition, if the 
substrate is of a different type, such as fibrous, glass reinforcing, the 
product may be used as is as a decorative wall covering, or incorporated 
into a more complex structure. A good example of the latter is a 
reinforced syntactic foam flooring structure having a polyurethane foam 
backing and, optionally, an added wear layer. Of course, all such 
possibilities and variations thereof are contemplated by the present 
invention. 
When the perlite is migrated as set forth above, a product having a 
relatively stratified structure is obtained. When this latter material is 
inverted, the resulting flooring structure has a lower foam-like layer and 
an upper wear surface. Of course, by varying the amount of time allowed 
for migration, widely variable structural characteristics may be obtained. 
Other additives may also be migrated within the plastisol matrix. For 
example, if it is desired to have decorative chips in the wear surface, 
chips with a specific gravity perhaps 10 to 20 percent greater than that 
of the plastisol can be added. As the perlite migrates to the upper 
surface, the chips will sink to the lower surface, thereby giving a 
decorative effect to the fused product. Of course, when migration of 
perlite and a heavier additive is intended, care must be taken to avoid 
using excess amounts of these materials because each will tend to 
interfere with the migration of the other. 
It must also be noted that the viscosity of the plastisol may require 
consideration. This is particularly true where the perlite must migrate so 
as to stratify the mixture because, if the viscosity is too high, 
migration may be severly hindered or entirely prevented. When migration is 
not required, maintaining a low viscosity is not as critical and 
viscosities ranging from about 500 up to about 30,000 cps may be employed. 
Nevertheless, high viscosities are not desirable because they tend to 
cause non-uniform mixing of the ingredients and/or breaking of the fragile 
perlite particles. For these reasons, viscosities of from about 500 to 
about 10,000 cps are preferred when migration is not contemplated whereas, 
when migration is desired, viscosities of from about 500 to about 5000 cps 
are preferred. In the latter case, however, viscosities on the order of 
about 700 to about 2000 are most preferred. 
Depending on the purpose for which the aforementioned products are 
intended, they may be used without further modification, or they may be 
printed with a design, embossed, have a wear layer applied, or be 
otherwise modified by means well known in the art. 
The utility of the syntactic foams, particularly as floor coverings, may be 
seen from the following. One test of a flooring product is its resistance 
to damage when a heavy object is dragged across its surface. A convenient 
way to approximate this condition is by holding a key (e.g., a car key) 
with force against a protective surface which overlies a foam, and then 
pulling the key across the surface. When this key test was applied to a 
conventional foam and a uniform syntactic foam of the present invention, 
each protected with a 10-mil vinyl wear layer, very dissimilar results 
were obtained. The conventional foam underlayment puckered and gathered 
under the applied stress, and the composite structure, including the wear 
layer, eventually tore. Conversely, the syntactic foam did not pucker and 
gather, and the only damage noted was a scratching of the wear layer by 
the key. 
Another advantage of such syntactic foam products is that they can be made 
to a desired gauge and they tend to maintain that gauge, even after 
further processing. Conventional foams made using chemical blowing agents 
tend to lack uniformity because initial defects and surface variations are 
magnified when the chemical blowing agents expand. The syntactic foams of 
the present invention overcome this disadvantage because the product gauge 
can be closely controlled. 
The following examples are provided to illustrate but not to limit, the 
advantages which may be obtained through the use of the present invention.

EXAMPLES 
All of the examples illustrated herein were prepared using a plastisol 
having the following composition and having a viscosity of about 1000 cps. 
______________________________________ 
Ingredient Parts by Weight 
______________________________________ 
Dispersion grade resin (Firestone 6337) 
80 
Blending resin (Tenneco 501) 
20 
Dioctyl phthalate plasticizer 
60 
Stabilizer (Argus M-275) 2 
______________________________________ 
EXAMPLES I-IV 
Examples I-IV were prepared from the following components 
______________________________________ 
Example (parts by weight) 
Ingredient I II III IV 
______________________________________ 
Plastisol 100 100 100 100 
Perlite 2.5 5.0 2.5 2.5 
Plasticized suspension grade 
-- -- 5 -- 
resin (Firestone 9290) 
Colorquartz (3-M Company) 
-- -- -- 5 
______________________________________ 
The expanded perlite in each case had a bulk density of about 4.0.+-.0.5 
pounds per cubic foot and was comprised of small particles, approximately 
80 percent of which were between 700 and 200 microns in diameter. For 
Examples I and II, the perlite was carefully mixed with the plastisol and 
then each mixture was cast into two Teflon.RTM.-coated steel molds having 
dimensions of 6".times.6".times.0.125". One mold for each example (label 
Examples Ia and IIa, respectively) was immediately heated at 385.degree. 
F. for 20 minutes to fuse the material whereas the other two molds 
(Examples Ib and IIb) were allowed to stand at room temperature for two 
minutes and then similarly fused. Upon cooling, the samples were separated 
from the molds and examined microscopically. Examples Ia and IIa showed a 
fairly uniform distribution of perlite particles, whereas Example Ib 
showed a definite layer comprising substantially no perlite particles at 
the interface of the mold and the fused plastisol. Example IIb did not 
show the same definite, perlite-free layer, thus indicating that the 
increased level of perlite tends to cause interference with the migration. 
Examples III and IV were prepared by premixing the resin or the 
Colorquartz, respectively, with the plastisol and then carefully mixing in 
the perlite. The mixed samples were cast in molds, allowed to stand for 
two minutes and fused as described above. Microscopic examination of 
Example III showed that the perlite had migrated to the top surface, as 
expected, but that the suspension grade resin had shown no tendency to 
migrate. Example IV showed that the Colorquartz, a high-density material, 
had concentrated along the lower surface whereas the perlite had migrated 
to the top surface. Thus, under appropriate conditions, different types of 
particles may be migrated within the plastisol to give a decorative 
protective layer at one surface and a syntactic foam at another surface. 
EXAMPLE V 
This example illustrates the preparation of a flooring structure in which a 
perlite-containing plastisol is cast on a permanent flooring carrier. The 
composition of Example III, comprising 2.5 parts of perlite and 5.0 parts 
of plasticized suspension grade resin for every 100 parts of plastisol, 
was prepared as previously described, cast on a conventional permanent 
flooring carrier, allowed to stand for two minutes, and fused in an oven 
at 385.degree. F. for 3 minutes. When cool, a 20-mil layer of plastisol 
was coated onto the layered material and fused for 2 minutes at 
385.degree. F. The resulting fused structure comprised, in order, a 
backing, a vinyl layer comprising essentially no perlite, a layer of 
syntactic foam, and a superimposed vinyl wear layer. 
The present invention is not limited solely to the descriptions and 
illustrations provided above, but encompasses all modifications 
encompassed by the following claims.