Note: Descriptions are shown in the official language in which they were submitted.
CA 02241039 1998-06-19
INSULATING CONSTRUCTION lrIATBRIAL
SCOPE OF THE INVENTION
The present invention relates to an insulating
material which may be used either as loose material or as
part of a panel construction, and more particularly to a
granular or chip-type insulating material having a sound
absorbing and sound isolating high density central core,
and a relatively less dense thermally insulating outer
coating.
BACKGROUND OF THE INVENTION
Granular-type insulating materials used in
providing thermal insulation are well known. Typically,
conventional granular insulating materials consist of
expanded or foamed light-weight polymers, such as
polystyrene. The polymers are formed into approximately
spherical granules which have an average diameter of about
1.5 millimetres.
It is known to use conventional polystyrene
granules in construction where, for example, the granules
are used as thermal insulation which is blown loose into
attics or cavities, or are compacted together to form
aggregate panels which range in thickness between 0.5 and
6 inches. While expanded polystyrene has low thermal
conductivity and provides good thermal insulation, the low
density of polystyrene makes conventional granules very
poorly suited to absorb sound energy and substantially
transparent to sound energy.
In another construction use, polystyrene granules
are admixed with cement to produce a light-weight concrete
slurry. In addition to producing set concrete having
enhanced thermal resistance, the lighter weight of the
CA 02241039 1998-06-19
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concrete mixture advantageously facilitates vertical
pumping, as for example, is required in the erection of
high-rise buildings. A disadvantage in using conventional
polystyrene granules in concrete slurries exists, however,
in that the granules have an overall density less than
about half of that of water and which typically ranges from
about 0.2 to 0.5 grams/cm3. As a result of their low
density, the polystyrene granules tend to float in the
slurry resulting in their uneven distribution in the set
concrete.
A further disadvantage with conventional
polystyrene insulating granules exists in that if the
granules are exposed to a flame, the polystyrene will
readily burn, producing noxious fumes and potentially
hazardous bi-products on combustion.
Conventional granular insulating materials also
suffer the disadvantage that they are highly susceptible to
damage by rodents and insects. In particular, mice and
rats may easily burrow through and nest in either loose
blown granules or aggregate panels made from such granules .
SUMMARY OF THE INVENTION
To overcome at least some of the disadvantages
associated with the prior art, the present invention
provides for an insulating particulate material which may
be used in construction and which has a sound absorbing
and/or sound isolating high density core which is
surrounded by a relatively less dense thermally insulating
outer coating. The insulating outer coating advantageously
prevents thermal conduction, while the higher density core
absorbs, reflects and/or refracts sound waves to reduce the
propagation of sound waves through the granules.
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Another object of the invention is to provide a
thermally insulating granule having a sound absorbing high
density core which may be easily and economically
manufactured.
Another object of the invention is to provide an
acoustical panel for use as a construction material which
is formed from a plurality of thermally insulating granules
having a high density core which incorporates rodent and/or
insect deterring compounds or compositions.
A further object of the invention is to provide
an insulating granule for use as a construction material
and which may safely incorporate flame retardant compounds
and/or compositions without concern of degradation of such
compounds over prolonged periods of time.
Another object of the invention is to provide a
light-weight concrete mixture incorporating a number of
insulating granules having an average density roughly equal
to or greater than that of water, and more preferably
ranging between 0.8 to 1.5 grams/cm3, and which may be
either cast or poured to form a rigid slab having improved
distribution of granules.
A further object of the invention is to provide
insulating granules which have an overall specific gravity
approximately equal to that of light concrete, and which
when added to a light concrete slurry will not tend to
float and/or sink in the slurry.
The applicant has appreciated that at least some
of the foregoing objects may be achieved by providing an
insulating granule which includes a sound absorptive
central core which has a density of at least 1.0 grams/cm3,
and an outer less dense thermally insulating coating
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provided at least partially about the core. The outer
coating preferably has an expanded cellular structure and
a density of less than 0.75 grams/cm3, with the core
comprising between about 5 to 80% of the granule by volume,
and more preferably about 10 to 40% by volume.
The granules may be either generally spherical or
have an amorphous shape and have an average diameter of
between about 0.5 to 30 mm. More preferably, the outer
coating is provided evenly about the core with the ratio of
average cross-sectional diameter of the core to that of the
overall granule diameter being selected at between about
5:6 and 1:6, and more preferably between about 1:2 to 1:4.
The high density core may be chosen from any
number of materials which absorb, reflect and/or diffract
sound waves, including metals as well as natural and
synthetic solid compositions and compounds. Particularly
suited materials may, for example, include recycled waste
material and metal scrap. Where the insulating granules
are to be admixed with concrete, as for example, as in
light cement used for high-rise construction, higher
density core materials such as molybdenum, iron, zinc, or
barium sulphate may be used to provide the granules with an
overall density between about 0.8 to 1.5 grams/cm3. In
other uses, however, silica sand or gravel may
advantageously be used as a core material as it is readily
available, inexpensive and may be found existing with the
preferred core diameter range of between about 0.1 and 25
mm.
The outer coating is selected to provide
thermally insulating properties and may have either an open
or closed foamed or expanded cellular structure. The outer
coating preferably consists of StyrofoamT" or other expanded
polystyrene. The polystyrene may be applied either as a
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continuous layer directly to the core material or as an
aggregate coating of expanded polystyrene particles, or
unexpanded polystyrene particles which are thereafter
expanded by steam contact. The polystyrene foam forms an
insulating layer having a thickness of between about 0.5 to
30 mm and preferably about 1 to 5 mm. While polystyrene is
readily available and provides a cost effective thermal
barrier, other low density materials are also possible,
including foamed or expanded plastics and polyurethanes,
vinyls, synthetic and natural rubbers, polypropylenes,
polyethylenes, styrenated polyesters and styrenated resins.
More preferably, one or more compounds which act
as a flame retardant, an insecticide and/or a rodenticide
are also provided within the outer coating. Fire
retardants, insecticides and/or rodenticides may form part
or all of the core itself, or may be provided as an initial
or pre-coating which is provided directly about the core
prior to the application of the outer coating. Where
polystyrene particles are used, the
retardant/insecticide/rodenticide compound may be provided
as part of an adhesive coating applied to the core and
which is used to adhere the unexpanded polystyrene
particles to the core during and following the expansion of
the particles.
Where a pre-coating is applied to the core to
provide enhanced anti-pest or fire resistant properties,
the thermally insulating outer coating is preferably
formed having a substantially closed cell structure. In
this manner, the outer coating completely encloses any fire
retardant coating, rodenticide or insecticide, sealing it
from the atmosphere. The applicant has appreciated that
sealing the fire retardant, insecticide, or rodenticide
from the atmosphere both reduces the potential for the
granules to give off any potentially hazardous or noxious
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fumes, and also permits the use of atmospherically unstable
compounds or pre-coatings without concern of their
breakdown to ineffective compounds by prolonged exposure to
the air.
The sound dampening insulation of the present
invention has numerous possible uses, including in thermal
and acoustical panels in railway cars, busses, trailers and
mobile homes, as well as for use in office dividers and
temporary partitions, as sound insulation for dish washers
and refrigerators, in doors for general use as well as
outside access and garage doors, in prefabricated
construction panels, as additives in self levelling light
concrete, and as infill material in buildings and houses to
fill cavities in partitions, crawl spaces, walls and
floors .
Accordingly, in one aspect the present invention
resides in a construction material comprising,
a plurality of insulating granules, each of said
granules having an average diameter of between about 0.5
and 30 mm and including,
a central core having a first density of at least
1.0 grams/cm3, and
a thermally insulating outer coating disposed at
least in part about said core, the outer coating having a
second density of less than 0.75 grams/cm3, and
wherein the core comprises between about 5 to 75%
of the granule by volume.
In another aspect, the present invention resides
in an insulation granule including,
a central core comprising silica sand, and
a thermally insulating outer coating disposed
about said central core, the outer coating having an
expanded closed cell structure and a density which is less
CA 02241039 1999-09-14
_'7_
than about 0.8 grams/cm3, the outer coating being selected
from the group consisting of polystryrene, polyethylene,
vinyl and rubber, and
wherein the core comprises between about 10 to
500 of the granule by volume.
In another aspect, the present invention resides in
a construction material comprising,
a plurality of insulating particles, each of said
particles having an average diameter of between more than 10
mm and 30 mm and including,
a central core having a first density of at least
1.O grams/cm3, and
a thermally insulating outer coating disposed at
least in part about said core, the outer coating having a
second density of Less than 0.75 grams/cm3, and
wherein v~he core comprises between 5 to 75~ of the
granule by volume.
In a further aspect, the present invention resides
in an insulating material including,
a pluraluty of insulating chips characterized by an
inner core having a. density of at least 1 grams/cm3, and
a thermally insulating outer coating disposed about
said core, the outer coating having an expanded closed cell
structure and a density which is less than about 0.6 grams/cm3,
CA 02241039 2002-I04-17
7a
the outer coating being selected from the group consisting of
polystyrene, polyethylene, polypropylene, polyvinyl acetate,
polyvinyl chloride and rubber, and
wherein the core comprises between about 10 to 500
of the particle by volume.
In another aspect, the present invention resides in
an insulation material including,
a plurality of particles, each particle comprising
a central core having a density of at least 1
gram/cm3 and comprising a core material selected from the group
consisting of rubber and heavy metals, and
a thermally insulating outer coating disposed about
said central core, the outer coating having an expanded closed
cell structure and a density which is less than 0.8 grams/cm3,
the outer coating being selected from the group consisting of
polystyrene, polyethylene, vinyl and rubber, and
wherein the core comprises between 10 to 50 0 of the
particle by volume.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will
appear from the following description taken together with the
accompanying drawings in which:
i
CA 02241039 2002-04-17
7b
Figure 1 is a cross-sectional view of an insulating
granule in accordance with a preferred embodiment of the
invention;
Figure 2 is a cross-section view of an insulating
granule in accordance with a second embodiment of the
invention;
Figure 3 is a cross-sectional view of an insulating
granule in accordance with a third embodiment of the
invention;
Figure 4 is a cross-sectional view of an acoustical
panel incorporating a plurality of the insulating granules
shown in Figure 1;
Figure 5 is a cross-sectional view of a cast
concrete slab incorporating a plurality of the insulating
granules shown in Figure 1;
Figure 6 schematically illustrates a preferred
apparatus for use in the manufacture of the insulating
granules of Figure 3;
CA 02241039 1998-06-19
r
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Figure 7 schematically illustrates an alternate
apparatus used for the manufacture of the insulating
granules of Figure 1.
Figure 8 shows a perspective view of an
insulating chip material in accordance with a fourth
embodiment of the invention;
Figure 9 shows schematically an insulating chip
material in accordance with a fifth embodiment of the
invention; and
Figure 10 shows a part cross-sectional view of a
panel incorporating a plurality of insulating chips shown
in Figure 8.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is first made to Figure 1 which shows
an insulating granule 10 in accordance with a first
embodiment of the invention. The granule 10 consists of an
inner core 12 and an outer coating 14 which is disposed
approximately evenly about the core 12. Figure 1 shows the
granule 10 as being generally spherical in cross-section
for clarity, however, it is to be appreciated that
typically, the granule 10 will have a more amorphous
overall shape.
In Figure l, the core 12 consists of a single
grain of silica sand and has an approximate density of
about 2.6 grams/cm3. The density of the silica core 12
advantageously acts to either reflect, diffract or absorb
sound waves which contact the core material. Silica sand
is a highly preferred material for use in the present
invention as, in addition to being readily available and
comparatively inexpensive, silica sand may easily be found
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existing having the preferred average core diameter size of
between about 0.5 and 2 mm. From a manufacturing
perspective, silica sand may therefore be used to form the
core 12 by selective screening, and without having to first
crush or pre-size the sand material.
The outer coating 14 comprises an expanded closed
cell polystyrene such as StyrofoamT", which completely
surrounds and encases the core 12. The outer coating
extends about the core 12 having a layer thickness of
between about 0.5 mm and 4 mm and an average density of
less than 0.6 grams/cm3, and more preferably less than 0.4
grams/cm3. It is to be appreciated that the closed cell
structure polystyrene coating 14 is thermally non-
conductive, making the granules 10 ideally suitable for use
as thermal insulation in a number of construction
applications.
The granule 10 is thus provided having an average
exterior diameter of up to about 10 mm, and preferably
between about 1 and 4 mm, with the core 12 comprising
between about 5% and 80% of the granule 10 by volume, and
more preferably between about 10% to 40%. The outer
coating 14 is applied over the core 12 such that the ratio
of the average core diameter D~ to the overall average
granule diameter D2 is selected at between about 1: 2 to 1: 4 ,
and more preferably at about 1:3. The granules 10 have a
range of uses, including as loose blown "chip-type"
insulation, as part of an aggregate use to form panel
boards and/or as additives in concretes, plasters, rubbers
or the like.
The applicant has appreciated that in use, the
plurality of granules 10 either as a loose insulating
material or compressed together as a sheet, form an
effective thermal and sound barrier. When a plurality of
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granules 10 are provided in proximity, the higher density
core 12 in each granule 10 locates a short distance from
cores 12 of the immediately adjacent granules 10. For
example, when an array of granules l0 is provided with a
number of granules 10 positioned so that the peripheral
surfaces of the respective outer coatings 14 are in
contact, the corresponding higher density cores 12 will be
separated relative to one another by a distance of between
about 1 mm and 4 mm.
By providing the granule with a higher density
core, the overall mass of the granule 10 is increased,
providing enhanced acoustical isolating and absorption
properties.
While silica sand is disclosed as a preferred
material for use in the present invention, it is to be
appreciated that larger pebble sized cores are also
possible. In addition, the core 12 could equally be formed
from any number of materials which have a sufficient
density to reflect or absorb sound waves. Preferably, the
compounds or compositions used provide the core 12 with an
average density of at least 2 grams/cm3. Table 1 provides
a non-limiting listing of possible materials suitable for
use in forming the core 12.
Table 1
Material Density (gms/cm3l
Tungsten and alloys 13.4-19.6
Molybdenum and alloys 10.0-13.7
Lead and alloys 10.7-11.3
Copper alloys 7.5-9.0
Iron 7-9
Barium Sulphate 5.0-6.0
Zinc and alloys 5.2-7.2
Magnesia, Mg0 3.5
Common rocks 2.2-3.0
Silica glass, SiOZ (quartz) 2.6
Soda glass 2.5
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Similarly, while expanded cellular polystyrene
may be a preferable coating, it is to be appreciated that
other low density materials may also be used for the
thermally insulating outer coating 14. Thermally
insulating materials suitable for use as the coating 14.
include foamed and expanded open or closed cell
polystyrenes, polyethylenes, polyurethanes, vinyls,
rubbers, styrene-butadiene rubbers, styrenated polyesters
and styrenated resins to name just a few.
Figure 2 shows a granule 10 in accordance with a
second embodiment of the invention in which like reference
numerals are used to identify like components. The granule
of Figure 2 includes a core 12 and outer coating 14
identical to that of Figure 1. An inner or pre-coating 16
is also provided applied directly to the core 12. The
inner coating 16 may, for example, comprise one or more of
an insecticide, a rodenticide or a fire retardant
composition. In this manner, the granule l0 may be
provided with rodent or insect repelling properties and/or
enhanced flame retardant capabilities.
The outer coating 14 is provided about the pre-
coating 16 in a closed cell configuration which
substantially isolates the pre-coating 16 from the
atmosphere. It is to be appreciated that the use of a
closed cell outer coating 14 permits insecticides,
rodenticides and/or flame retardants to be used which are
otherwise unstable when in prolonged contact with
atmospheric gases. As well, the use of a closed cell
coating 14 advantageously acts to trap large organic
molecule gases, effectively sealing the pre-coating 16, and
preventing the release of potentially noxious chemicals and
fumes which may be hazardous to human or animal health.
When an insecticide is provided as part or all of
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the pre-coating 16 and insects, such as carpenter ants or
termites, attempt to burrow through the granules 10, they
expose the insecticide containing pre-coating 16 on the
granule core 12. The present invention is advantageous in
that only minute amounts of insecticide are released at the
precise location of infestation, minimizing the potential
for health risks to humans when the insulating granules 10
are provided as part of building walls and foundations.
Similar advantages are also to be achieved where a
rodenticide is provided as part of the pre-coating 16.
A number of various insecticides or rodenticides
may be used to form part of the pre-coating 16, including
organic based compounds, borax, boric acid, or other
organo-chemical compounds. Organic based insecticides
could, for example, include those sold commercially under
the names DiazinonT" and Malathionr".
The presence of a closed cell coating 14 is
similarly advantageous when a fire retardant is provided as
part or all of the inner pre-coating 16. Flame retardants
which may be used in the present invention include aluminum
hydrate, bromides and/or borax hydrate which on combustion
of the polystyrene coating 14 release water or other
compounds to extinguish flames.
It is to be appreciated that although Figure 2
shows the granule 10 as including a pre-coating 16, solid
insecticides, rodenticides and/or the flame retardants may
also be used in place of silica sand to form part or all of
the high density core 12 itself.
Figure 3 shows a third embodiment of the granule
in accordance with the present invention and wherein
like reference numerals are used to identify like
components. The granule 10 of Figure 3 includes a core I2
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similar to the embodiments shown in Figures 1 and 2. The
outer insulating coating 14 is not formed as a uniform
layer, but rather consists of an aggregate of expanded
polystyrene particles 17 which envelope the core 12. The
polystyrene particles 17 which form the aggregate are
maintained in place surrounding the core 12 by an adhesive
matrix 18.
In manufacture of the granule 10 shown in Figure
3, the core material is coated with a liquid adhesive
composition used to form the matrix 18. Immediately
following coating by the adhesive 18, the core 12 and
adhesive 18 construct is then powdered with unexpanded
polystyrene particles. Preferably, the unexpanded
polystyrene particles range in average diameter of between
about 0.1 mm and 0.5 mm. To form a panel having a
predetermined shape as shown in Figure 4, following
powdering, the core 12 with its unexpanded coating is
placed into a mould and exposed to a dry steam environment,
resulting in the expansion of the polystyrene particles.
Alternately, to form individual granules for use as loose
insulation or in concrete, following powdering, the core
and unexpanded coating are immersed in boiling water or
placed in a wet steam environment to expand the
polystyrene.
The individual polystyrene particles 17
preferably are expanded to an averaged meter of between
about .25 mm and 2 mm. The applicant has appreciated that
as the polystyrene expands, the matrix 18 retains the
majority of the particles as an aggregate 17 about the core
12. This has been found to advantageously prevent the core
material from settling towards the bottom portion of the
mould cavity. Granules 10 having smaller sized cores 12
are formed in essentially the same manner. Where the
granules 10 are used to fill larger mould cavities,
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additional loose unexpanded polystyrene material may
optionally be added as intro-granular filler material prior
to exposure to the steam environment.
If desired, a flame retardant and/or insecticide
and/or rodenticide may be incorporated into the adhesive
matrix 18 so as to function in the same manner as the pre-
coating 16. Alternately, the pre-coating 16 of Figure 2
could be applied to the core 12 prior to the application of
the matrix 18 and particles 17.
The insulating granules 10 shown in Figures 1 to
3 may advantageously be used either alone or as part of
other materials used in construction. For example, the
insulating granules 10 may be provided either alone or
mixed with conventional cellulose as loose thermal
insulation which is blown into attics, crawl spaces or
between walis.
Alternately, the granules l0 may be fused
together to form rigid polystyrene-type panels for thermal
and sound insulation. Figure 4 shows a partial enlarged
cross-sectional view of an acoustical panel 20. The panel
20 consists of a number of insulating granules 10 which are
compressed together and heated to form an aggregate core
sheet 22, in a similar manner to that used in the
manufacture of existing expanded polystyrene board or bead
board. During heating, the outer surface of the low
density coatings 14 of the granules l0 partially melt and
deform, bonding granules l0 to each other.
Although not essential, the panel 20 is also
provided with a front and back layers of 1 to 2 mm
cardboard or other sheet material 24,26 which are glued to
each side of the aggregate core 22. In addition to
providing the panel 20 with an enhanced aesthetic
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appearance and increased structural rigidity, the covering
layers 24,26 minimize granule drop, whereby individual
granules 10 break loose from the outer surfaces of the
aggregate core 22. The panel 20 provides good thermal
insulating properties as well as acoustically insulating
and absorptive properties.
While Figure 4 illustrates a panel 20 in which
the granules 10 are formed into an aggregate core 22 by
partially melting the outer coating 14 of each granule 10,
the granules 10 could also be formed into a panel having a
looser structural arrangement by the use of glues or other
such binders used to adhere the various granules 10
together. Binders used in panel construction could
possibly include additives for enhanced fire preventative
properties and/or rodenticide and insecticidal compounds,
or even acoustically absorptive materials.
Figure 5 shows the granules 10 as used in a
construction material in accordance with a further
embodiment of the invention. In Figure 5, a number of
granules 10 are provided together with a cement matrix 28
to form a cement slurry 30. The cement matrix 28 consists
of light weight cement which, when wet, has an approximate
average density of between about 1.4 and 2.5 grams/cm3.
In the slurry 30 of Figure 5, the granules 10
have a core 12 size and material selected to provide the
granule with an overall density of between about 0.8 and
1.5 grams/cm3. Preferably, the granules 10 are provided in
the slurry 30 in a ratio with the concrete matrix at a
ratio of between about 1:1 to 1:20 by volume, and more
preferably between about 1:4 and 1:8 by volume.
The inclusion of the granules 10 lowers the
overall density of the cement slurry 30 making it easier to
CA 02241039 1998-06-19
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pump the wet slurry 30 under pressure through hoses. The
cement slurry 30 may therefore be advantageously used as a
construction material in the manufacture of high-rise
buildings and other structures where the pumping of cement
is required. As well, when the slurry 30 hardens to a set
concrete slab, the granules 10 advantageously provide both
enhanced thermal and sound insulation within the set
concrete.
When light cement is provided as the matrix 28,
the granules 10 advantageously have a reduced tendency to
float or sink in the cement matrix 28, as a result of their
density approaching that of the wet matrix 28. The
granules 10 therefore tend to remain statically in
suspension within the slurry 30 resulting in their more
even dispersion throughout the resulting concrete slab.
While the preferred embodiments disclose the use
of the granules 10 as part of aggregate panels 20 and
concrete slurry 30 mixtures, other uses are also possible
and will now become apparent. The loose insulating
granules 10 could, for example, be used for hydroponics or
as loose insulation to limit evaporation on water
reservoirs and the like. In particular, by forming the
granules 10 so that each has an overall density of about
0.8 grams per cc, the granules 10 may be floated on the
surface of the reservoir as a covering medium, without
concern that the granules 10 will be carried off by wind.
Figure 6 shows one possible apparatus 29 for use
in the manufacture of the granules 10 shown in Figure 3.
The apparatus includes a hopper 32 which opens downwardly
into an inclined cylindrical mixing chamber 33. The hopper
32 supplies pebbles 31 used to form the core 12 of the
completed granules 10 into an adhesive bath 34 at the
lowermost end of the chamber 33 where they are coated with
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the adhesive composition used to form the matrix 18. A
helical auger 35 is rotatably mounted within the chamber 33
driven in rotation by a motor (not shown). The rotation of
the auger 35 moves the pebbles 31 from the bath 34 and
beneath hopper 36. Unexpanded polystyrene particles are
fed from the hopper 36 into the cylindrical chamber 33.
The rotation of the auger 35 in the chamber 33 ensures the
even application of the unexpanded polystyrene particles.
It is to be understood that the configuration of the auger
35 and its flights may be modified to increase or decrease
the residence time of the core material in the chamber 33,
depending on the setting time of the adhesive composition
and the degree of mixing described. Preferably, the coated
particles are maintained in the chamber 33 until such time
as the adhesive sets, fully bonding the polystyrene
particles to the core 12.
Following the coating with the unexpanded
polystyrene particles, the coated pebbles are moved via the
auger 35 through a discharge opening 37 into a steam
sorting chamber 38. The coated pebbles entering the
sorting chamber 38 fall under gravity towards a blower 39
which blows a steam/hot air mixture towards a discharge
outlet 40. The chamber 38 is formed so that it narrows
towards its bottom and the blower 39, with the result that
air flow intensity increases towards the bottom of the
chamber 38 and decreases towards the top opening 40.
As the coated pebbles approach the bottom of the
chamber 38 the air flow from the blower 39 maintains them
in suspension. Simultaneously, the steam in the chamber 38
causes the polystyrene particles to expand to product the
thermally insulating coating 14. With the expansion of the
polystyrene coating, the surface area of the granule l0
increases whereby the granule 10 is carried by air current
outwardly from the chamber 38 via the outlet 40.
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If desired, a by-pass outlet 41 may also be
provided adjacent the discharge opening 37. The by-pass
outlet is positioned so that any pebbles which remain
uncoated following passage from the chamber 33 are carried
by the air flow therein to recovery hopper (not shown) for
re-use.
Figure 7 shows a second possible apparatus 42
used in the manufacture of granules 10 shown in Figure 1.
The apparatus 42 contains similar operational elements to
that shown in Figure 6 with like reference numerals
identifying like components. In the apparatus 42 as shown,
silica sand 43 which has been pre-sized by screening to
remove sand grains which are either larger or smaller than
the desired core size is fed into a hopper 32.
From the hopper 32, the sand 43 is slowly fed
onto a vibrating conveyor 44, with the vibrations evenly
dispersing the sand grains 43 across the surface of the
conveyor 44. The conveyor 44 next moves the dispersed sand
grains 43 through a spray chamber 46 where a foamable
liquid resin is sprayed from a liquid reservoir 48 onto the
sand grains 40. The use of a vibrating conveyor 44
advantageously ensures that during the spray coating
process in the chamber 46, each sand grain 43 is evenly
coated with the liquid resin.
The thickness of the coating 14 to be achieved
may be easily controlled by shortening or lengthening the
residence time of the sand grains 43 in the spray chamber
46; whereby a longer residence time in the chamber 46
produces a granule 10 having a thicker outer coating 14.
The expandable thermally insulating resin used to coat the
sand grains 43 is selected containing dissolved gases. It
is to be appreciated that the precise gas content of the
resin will vary depending on whether an open or closed cell
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coating 14 is to be provided about the core 12 of the
formed granule 10.
Once coated with the liquid resin, the sand
grains 43 are moved through an inlet 50 by the conveyor 44
into a steam/hot air sorting chamber 38 which is provided
with a top opening 40. Hot air or steam is blown upwardly
and outwardly through the top opening 40 via a steam/hot
air blower 39 positioned at the bottom of a chamber 38.
In the same manner as described with reference to
Figure 6, the coated sand grains 43 entering the chamber 38
tend to fall under gravity towards the blower 39. As the
sand grains 43 approach the bottom of the chamber 38, the
increasing intensity of the air flow entrains the sand
grains 40, maintaining them in suspension. While
entrained, steam and warm air from the air blower 39 causes
the simultaneous curing of the expandable resin while the
gases dissolved in the resin expand to produce the expanded
cellular coating 14 about the sand grain 43, which
functions as the granule core 12.
The coated sand grains/granule cores 12 remain
entrained by the upward gas flow until the resin coating 14
expands to a sufficient degree whereby, as a result of its
increased surface area, the gas flow carries the cured
granule 10 upwardly through the upper opening 40.
Following their movement through the opening 40,
the granules 10 are collected for later use as loose
insulation, or for incorporation into other construction
materials such as used in acoustical panels. When used in
panels, the granules 10 could be fused together by heating
to partially melt and fuse the foamed insulating layers
together. Alternately, the panels could be formed using a
binder to secure the granules together, such as elastomeric
CA 02241039 1998-06-19
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binders as, for example, neoprene.
While Figures 1 to 3 show generally spherical
granules l0 in which a low density coating 14 is provided
about the entire exterior surface of a core 12, the
invention is not so limited and other shapes will now
become apparent.
Figures 6 and 9 show two possible chip-type
insulating material construction. The insulating chip 60
of Figure 8 is characterized by a generally rectangular
construction in which a flattened high density core 62 is
sandwiched between two layers 64,66 of low density
thermally insulating material. The core 62 may be secured
to the layers 64,66 by adhesive. The chip 60
advantageously permits simplified construction as a
laminate which is formed in large sheets and then cut intc
squares or rectangles ranging in length up to 3 cm.
The chip 70 of Figure 9 has a cylindrical
construction in which a cylindrical high density core 72 is
positioned within a hollow sleeve 74 of thermally
insulating material. The chip 70 may advantageously be
formed as a single coextrusion which is then cut into
lengths of up to 3 cm.
Preferred materials for use as the high density
cores 62,72 would include rubbers such as from recycled
tires, as well as heavy metal such as lead and barium
sulphate, with or without binders and additives to function
as flame retardants, insecticides and rodenticides. In
addition to expanded polystyrene, suitable materials for
use as the thermally insulating layers would include PV
foam, PE foam, foam rubber, cork, and mixtures thereof.
Figure 10 shows the chip-type material of Figure
CA 02241039 1998-06-19
- 21 -
8 used to form part of a prefabricated panel 76 in which
the individual chips 60 are secured within a binder 78 such
as neoprene or silicone. It is to be appreciated, however,
that the chips 60,70 are equally suitable for use as a
loose insulation material.
Although the detailed description describes and
illustrates preferred embodiments, the invention is not so
limited. Modifications and variations will now become
apparent to a person skilled in this art. For a definition
of the invention, reference may be had to the appended
claims.
