Note: Descriptions are shown in the official language in which they were submitted.
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1108
THERMAL AND MOISTURE RESISTANT INSULATIVE SHEET
FIELD OF THE INVENTION
This invention relates to bubble-pack thermal and moisture resistant
insulation
materials for use in the construction of buildings, roads, septic fields,
aircraft runways
and the like.
BACKGROUND TO THE INVENTION
It is well known to use separating sheets of materials to thermally separate
construction materials from underground soils. These materials are also used
to hold
and retain the different layers of sand and rocks used in the construction of
roads which
under the repetitive action of freeze and thaw leads to cracks and holes in
the exposed
external layer of the roads. These materials are also used as moisture
barriers in
buildings under construction, especially underneath the concrete floor of the
basement
that otherwise would be directly in contact with the soil and the moisture.
However, the aforesaid materials are generally formed as rigid or semi-rigid
insulating panels which have a strong tendency to crack and break apart under
heavy
loads which, thus decreases their eWcacy. Furthermore, they are difficult to
install and
are limited in size because of transportation problems.
Further, although, these materials are made in such a way that they do not
transfer heat by conduction or convection, they generally have a relatively
high
reflective surface material that still allows radiation heat transfer that is
fairly significant
for large surfaces.
Insulation materials are also know which comprise a clean, non-toxic, heat
barrier made of aluminum foil bonded to a single or double layer of
polyethylene-
formed bubbles spaced one bubble from another bubble in the so-called "bubble-
pack"
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arrangement. Non-foil bubble-packs are used extensively as packaging material,
whereas the metal foil bubble-pack sheet is used as thermal insulation in wood
frame
structures, walls, attics, crawl spaces, basements and the like and as
wrapping for hot
water heaters, hot and cold water pipes, air ducts and the like. The
reflective surface of
S the metal, particularly, aluminum foil enhances the thermal insulation of
the air-
containing bubble-pack
Generally, low density polyethylene films of 1 - 12 mil, optionally, with
various
amounts of linear low density polyethylene in admixture when additional
strength is
required, are used for the above applications. The insulating properties of
the bubble
pack primarily arise from the air in the voids. Typically, bubble diameters of
1.25 cm,
0.60 cm and 0.45 cm are selected.
In certain environments, the aluminum foil of the prior art assemblies are
vulnerable to chemical attack or delamination from the thermoplastic film by
reason of
being exposed to detrimental chemicals, acidic or alkaline vapours or the
like.
1 S Further, to reduce the risk of such undesired chemical attack and, also,
to utilize
the radiative insulative property of the aluminum surface, a space or gap is
left between
the prior art assembly and the wall, strut and the like adjacent the assembly.
This results
in a relatively larger combined unit than would otherwise be desired.
There is, therefore a need for a thermal and moisture resistant, insulation
pack
for use in road and building construction that is of a simple form, low cost
to
manufacture which is flexible, easy to carry and apply, provides reduced
radiative heat
transfer and provides reduced total unit construction volume.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an enhanced thermal and
moisture resistant insulation sheet for use in road and building construction
that is .
sufficiently flexible as to be readily adapted to be carried, installed and
enhanced weight
resistant.
It is a further object to provide a thermal and moisture insulation sheet
which is
environmentally more stable to attack on the metal and delamination.
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It is a further object to provide a thermal and moisture resistant insulative
sheet for use in abutement with an adjacent wall, strut and the like to
provide an
insulative barrier system of reduced thickness.
Accordingly, in one aspect, the invention provides a composite bubble-pack
assembly comprising (i) a first bubble-pack having a first thermoplastic film
having a
plurality of portions wherein each of said portions defines a cavity and a
second
thermoplastic film in sealed engagement with said first film to provide a
plurality of
closed said cavities; (ii) a second bubble-pack having a third thermoplastic
film having a
plurality of portions wherein each of said portions defines a cavity and a
fourth
thermoplastic film in sealed engagement with said third film to provide a
plurality of
closed said cavities; and (iii) a film selected from the group consisting of a
thin foil of
metal or a metallized thermoplastic film interposed between and bonded to said
first
bubble-pack and said second bubble-pack.
The terms "cavity" or "cavities" in this specification include voids, bubbles
or
other like closed spaces. The cavities may be formed of any desired suitable
shape,
such as, for example, of a semi-cylindrical, oblong or rectangular form.
However, a
generally hemi-spherical cavity is preferred.
The number, size and layout of the bubble in the pack according to the
invention
may be readily selected, determined and manufactured by the skilled artisan.
Typically,
in a single pack, the bubbles are arrayed in a coplanar ofd set arrangement.
Each of the
hemi-spherical bubbles may be of any suitable diameter and height protruding
out of the
plane of the bonded films. Typically, the bubble has a diameter selected from
0.5 cm -
5 cm, preferably 0.8 - 1.5 cm; and a height selected from 0.2 cm - 1 cm,
preferably 0.4
cm - 0.6 cm. A preferred bubble-pack has an array of about 400 bubble per 900
cm2.
The thermoplastic films may be formed of any suitable polymer or copolymer.
The first, second, third and fourth films may be formed of the same or
different material.
Most preferably, the assembly has each of the thermoplastic films formed of a
polyethylene or a nylon. A most preferred plastic is polyethylene,
particularly a low
density polyethylene, optionally, in admixture with a linear low density
polyethylene of
use as aforesaid first and second films.
The composite assembly of the invention further comprises one or more foils,
layers, films, laminates or the like of a suitable metal, for example,
aluminum or a
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metallized thermoplastic film within the assembly to enhance reflection of
infra-red
radiation.
Preferably, the aluminum foil forms part of the laminate having the foil heat
sealed between a pair of polyethylene films to provide a better seal to the
pair of bubble
arrays.
The composite bubble-pack assembly according to the invention is of particular
value when used in an environment that has a detrimental effect on the exposed
metal
when the latter is used as an outer film on bubble packs according to the
prior art.
Since, in the present invention, the metal is, in effect, embedded in a double
thermoplastic-air-filled void system, it is remote from metal-attaching
chemicals or an
environment which effects metal-thermoplastic film delamination.
Further, I have found that in order for the metal foil to be efficacious in
providing reflective heat reduction when bonded as an outer film, there needs
to be a
gap or space between the metal foil and adjacent wall, ground or like member.
This,
thus, often results in a thicker than desired insulative assembly. In
contrast, the
composite assembly according to the invention has an inherently built-in air
space
adjacent each side of the metal foil to provide the desired reflective
property. This, thus,
offers a more compact fully insulative package, sheet and the like than the
prior art.
Thus, the assembly according to the invention comprises an insulative sheet
that
provides air spaces on both sides of a metal or metallized foil which provides
thermal
and moisture insulation enhancement to the assembly and physical protection to
the foil,
in the rough and tough environment of placement adjacent to concrete, soil and
other
natural ground conditions, comprising particulate matter such as gravel and
lime.
The sheet according to the invention is flexible and easy to apply to cover
objects of a plurality of shapes.
The sheet effects useful reduction of heat transfer in each of the conduction,
convection and radiation modes, notwithstanding the relative thinness of the
sheet.
Further, the metal foil is protected from direct attack by most chemical
agents
that do not attack the thermoplastic layers.
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BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be better understood, preferred embodiments
S will now be described by way of example only, with reference to the
accompanying
drawings, wherein
Fig. 1 is an isometric view of an insulation panel comprising a bubble-pack
assembly
according to the prior art;
Fig. 2 is a diagrammatic top plan view of an embodiment insulation panel
comprising a
bubble-pack assembly according to the invention;
Fig. 3 is a diagrammatic enlarged sectional view taken along the line 3 - 3 of
Fig. 2;
Fig. 4 is a schematic sectional view of an alternative embodiment according to
the
invention; and wherein the same numerals denote like parts.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTs
With reference to Fig. 1, this show generally as 10, a double layer, bubble-
pack
with aluminum foil insulation assembly according to the prior art. The double
layer
consists of a pair of bubble arrays 12, 14 bonded together through an
intervening low
density polyethylene film 16. Arrays, 12, 14 are formed of a plurality of
bubble or
sealed cavities 18, 20, respectively, from a 5 mil polyethylene film 22, 24,
respectively.
Each of films 22, 24 at their outer surfaces is bonded to a reflective
aluminum foil 26,
28, respectively, to provide the whole assembly with external aluminum
surfaces..
Assembly 10 has approximately twenty, 1 cm diameter, 0.5 cm high bubbles per
cm length and breadth within each of films 22, 24.
The aforesaid assembly 10 is made by a double hot roller thermal and vacuum
forming process for cavity forming and lamination sealing techniques known in
the art.
With reference to Figs. 2 and 3, these show generally as 100 a composite
double
30 bubble-pack assembly according to the invention, having an aluminum foil
102 disposed
between and bonded to bubble arrays 112 and 114 formed as for prior art Fig. 1
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assembly. Bubbles 118 and 120 are encapsulated between polyethylene films
116 and 128.
Aluminum foil 102 has a low emissivity value of less than 5% on each surface
to
essentially eliminate heat transfer by radiation.
S Each of the single bubble-pack layers 112, 114 provides both thermal
conduction
and convection insulation, and, in combination with the aluminum surfaces,
excellent
radiation insulation.
The composite bubble-pack 100 offers significant resistance to heavy loading
whereby appreciative non-breakage of the air bubbles is often found.
Preferably, outer
layers 128 are made slightly thicker than inner layers 116 to better resist
abrasion.
Additional water resistance or abrasion resistant films may be bonded or
formed
laminated to layer 128. Such resultant composite bubble-pack assemblies are of
particular use in the construction of roads, septic fields, aircraft runways
and the like.
Further, in consequence that composite assemblies of the invention have better
I S thermal R-values than prior art assemblies, thinner or higher insulative
assemblies may
be provided. Thinner assemblies, say 0.2 cm - 0.8 cm thick facilitate the
manufacture,
transportation and handling of rolls of different desired sizes.
In alternative embodiments, but still illustrated by Figs. 2 and 3, metal foil
102 is
substituted with a strong and resistant plastics of a very thin, preferably a
few hundred
angstroms ( 1 angstrom equals 10-'° m), layer of metallic deposition on
each side to
provide the low emissivity surfaces.
Fig. 4 shows a similar embodiment to that of Fig. 3 wherein foil 102 is
laminated
by heat sealing between a pair of 2 mil polyethylene films 130 and 132 between
bubble
arrays 12, 14, at one of films 16.
Although this disclosure has described and illustrated certain preferred
embodiments of the invention, it is to be understood that the invention is not
restricted
to those particular embodiments. Rather, the invention includes all
embodiments which
are functional or mechanical equivalents of the specific embodiments and
features that
have been described and illustrated.
