Note: Descriptions are shown in the official language in which they were submitted.
CA 02254499 1998-11-25
BREATHABLE TENT FABRIC
The present invention relates to a fabric material
and more particularly, relates to a fabric material suitable
for use in a tent.
BACKGROUND OF THE INVENTION
Tents are widely used in many applications and range
from the relatively small light weight tents used in many
recreational pursuits to the heavy duty tents such as are
used by the armed forces. The present invention is
concerned with the heavy duty type of tents which must
withstand various adverse conditions and in particular,
tents which are suitable for military use.
Initially, tent constructions were of a heavy cotton
cloth commonly known as canvas. This type of tentage
material was used for a number of years and was the only
available material until the decade of the 1960s. While the
saturated heavy cotton cloth provided the advantage of
breathability of vapor and carbon dioxide in conjunction
with low cost and good abrasion resistance, it only provided
a minimum of waterproofness. Although various spray-on
coatings were proposed for use on such tents, they were
still highly susceptible to leakage.
Subsequently, it was proposed that a PVC coated
polyester fiber be utilized as tentage material. This
material was advantageous in that it provided a waterproof
structure except at the seams. In order to overcome the
problem of seam leakage, the use of flies was proposed
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wherein the seams were covered with a piece of waterproof
material. This solved the water leakage problem and also
offered certain improved physical properties and increased
service life.
More recently, it has been proposed to use a PVC
blend coated onto polyester, which blend was more supple
than previous versions and offered the possibility of
manufacturing the tent using welded seams. This welded seam
technology was advantageous in that it prevented leakage of
the seams without requiring the use of the flies. However,
this material did not provide required breathability and
accordingly, the interior of the tent could still become wet
due to condensation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide
a fabric which is suitable for use in a tent, the fabric
having the desired physical properties associated with tents
and having improved breathability.
It is a further object of the present invention to
provide a tent which is resistant to abrasion while still
providing breathability.
According to one aspect of the present invention,
there is provided a tentage material comprising a polyester
base fabric having first and second opposed major faces,
the first major face having a first major face inner coating
and a first major face outer coating thereon, the second
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major face having a second major face inner coating and a
second major face outer coating thereon, each of the inner
and outer coatings being comprised of a mixture of a water
based low Tg styrene/acrylic copolymer dispersion, a fully
reacted aliphatic polyurethane dispersed in water, a water
based low Tg styrene/acrylic copolymer with an acrylonitrile
polymer, and diatomaceous silica.
According to a further aspect of the present
invention, there is provided a method of preparing a tentage
material comprising the steps of supplying a web of a woven
polyester fabric having a thickness of between 0.1 mm and
0.4 mm, coating a first face of the web with a layer of a
coating system, curing the coating system, coating an
opposed face of the web with a layer of the coating system,
curing the second face of the web, placing a second coating
on the first face of the web, curing the second coating on
the first face, placing a second coating on the second face
of the web, curing the second coating on the second face,
the method being characterized by the coatings being
comprised of a mixture of a water based low Tg
styrene/acrylic copolymer dispersion, a fully reacted
aliphatic polyurethane dispersed in water, a water based low
Tg styrene/acrylic copolymer with an acrylonitrile polymer,
and diatomaceous silica.
According to a still further aspect of the present
invention, there is provided in a tent, the improvement
wherein the tent includes a tentage material comprising a
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polyester base fabric having first and second opposed major
faces, the first major face having a first major face inner
coating and a first major face outer coating thereon, the
second major face having a second major face inner coating
and a second major face outer coating thereon, each of the
inner and outer coatings being comprised of a mixture of a
water based low Tg styrene/acrylic copolymer dispersion, a
fully reacted aliphatic polyurethane dispersed in water, a
water based low Tg styrene/acrylic copolymer with an
acrylonitrile polymer, and diatomaceous silica.
In greater detail, in one aspect of the present
invention, there is provided tentage material which has the
required breathability and other characteristics for use in
severe climatic conditions. In particular, tentage material
should have high durability which is closely related to
abrasion resistance. In addition, the tentage material must
be able to transmit moisture vapor to maintain the interior
of the tent comfortable while maintaining the waterproofness
of the material under severe climatic conditions.
Naturally, it will be recognized that the
transmission of the water vapor is a function of several
parameters including relative humidity, the total surface
area of the tent vis-a-vis the number of people occupying
the tent and the body vapor production rate. This in turn
is dependant upon the activities performed in the tent.
Since only light work is normally performed in a
tent, the evaporation rate does not need to be the same as,
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for example, breathable garments. Assuming that there is
provided a surface exchange area of 7.5 m2 per occupant, it
has been found that an evaporation rate of approximately
1,000 g/m2/day, using the test procedure ASTM E-96-E, is
suitable.
The tentage material of the present invention is
suitable for use in either desert or arctic climates with IR
and W camouflage protection which may be integrated in the
coated fabric itself. The use of suitable materials to
provide such capability is well known in the art. This
allows for extremely simple and rapid installation. There
is thus provided a single material which is capable of
providing protection against wind, sun, dust storms, IR
scanning, W scanning, visual detection, rain, moisture and
carbon dioxide build-up.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The base fabric of the present invention is
preferably formed of a woven polyester fabric material and
which woven polyester material preferably has a weight of
between 120 g/m2 and 160 g/m2. Preferably, the polyester
fabric has a thickness of between 0.1 mm and 0.4 mm and even
more preferably, has a thickness of between 0.17 mm and
0.23 mm.
As aforementioned, each of the inner and outer
coatings is formed of a mixture of different polymeric
materials along with suitable additives.
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The inner coatings, as outlined above, comprise a
water based low Tg styrene/acrylic copolymer dispersion, a
fully reacted aliphatic polyurethane dispersed in water, a
water based low Tg styrene/acrylic copolymer with
acrylonitrile polymer, and diatomaceous silica (diatomaceous
earth). As will be understood by those skilled in the art,
other materials may be added according to the properties
desired. Typical additives would include fire retardant
agents, UV agents, etc.
The inner coatings applied to the opposite faces of
the polyester base fabric are applied to preferably provide
a thickness of between 0.025 mm and 0.06 mm and even more
preferably, a thickness of between 0.033 mm and 0.043 mm.
These thicknesses will of course determine various
properties of the material including vapor transmission
rates.
The outer coatings are also applied to the
previously coated base fabric such that the outer coatings
will have a thickness of between 0.025 mm and 0.06 mm and
even more preferably, between about 0.033 mm and about
0.043 mm.
The outer coating, like the inner coating, is a
blend of different polymeric materials and additives
thereto. In a preferred embodiment, the outer coating
includes between about 8% and about 40% by weight of a
water based low Tg styrene/acrylic copolymer dispersion;
between about 5% and about 60% by weight of a fully reacted
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aliphatic polyurethane dispersed in water; between about 1%
and about 40% by weight of a water based low Tg
styrene/acrylic copolymer with acrylonitrile; and between
about 5% and about 30% by weight of diatomaceous silica.
Naturally, other components such as fire retardant agents
and the like can be added. The fire retardant agents may be
those such as antimony trioxide and aluminum oxide
trihydrate. In one particular embodiment, one may utilize a
polyurethane which is premixed with fire retardant agents.
The polyester fabric may be coated in any
conventional manner. Preferably, the coating process is a
two step process in which the inner and outer coatings are
spread onto the polyester base fabric. It may be coated in
a single doctor blading system wherein the base fabric is
put onto a feed reel situated near the doctor blade which is
placed over a coating roll. The coating roll supports the
fabric as it passes through the doctor blade apparatus. A
liquid delivery system allows the desired coating to be
spread on the fabric in front of the doctor blade apparatus
and then the adjustable doctor blade is positioned to the
desired height and spreads the compound onto the base fabric
when it passes under the blade.
Subsequently, the coated fabric will pass through a
curing oven wherein there are provided first and second
stages, the first curing stage driving off volatile
substances with the second stage providing the proper cure
of the coating. Optionally, the coated base fabric may be
CA 02254499 1998-11-25
pressed in a calander system and then wound onto a take-up
reel. The process is then repeated for the other side of
the fabric.
Having thus generally described the invention,
reference will be made to the following example illustrating
an embodiment thereof.
Example 1
The following coating compounds were prepared.
Inner Coating Outer Coating
Water based low Tg 18 32
styrene/acrylic copolymer
j dispersion
Fully reacted aliphatic 10 28
polyurethane dispersed
in water
Water based low Tg 29 3
styrene/acrylic copolymer
with acrylonitrile
Diatomaceous earth 18 15
Antimony trioxide 15.5 13.5
Aluminum oxide trihydrate 9.5 8.5
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A woven polyester fabric having a weight of 142 g/m2
and a thickness of 0.2 mm is put onto a feed reel and then
passed through a series of tension rollers to a single
doctor blading system. The doctor blade is placed over a
coating roll which supports the fabric as it passes
therethrough. A coating delivery system provides the inner
coating set forth above to the fabric in front of the doctor
blade. The doctor blade was set to provide a coating of
28 kg/100 m2. The inner coating is then cured at a
temperature of 170oC and the surface calandered with cold
pressure rolls. The fabric is then wound onto a take-up
reel. The take-up reel is brought to the front of the
machine and becomes the feed reel so that the opposite side
of the polyester fabric is coated. The second inner coat is
applied to the second side of the polyester fabric.
Subsequently, the process is repeated to provide an
outer coating on each side of the fabric. For the outer
coating, the doctor blade is set to a height sufficient to
provide 22 kg/100m2 of the outer coating compound set forth
above on the fabric. The outer coating is cured at a
temperature of 135oC.
The coated fabric is subjected to a visual
inspection which shows a smooth coating with an absence of
surface defects.
The coated material was tested as follows.
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Test Method Results
Breathability ASTM between 1 000 to
E96BW 1,300 g/m~/day
C02 vapor 100,000 cc/m2/day
transmission
Breaking Fed. std. 1,600 N (warp direction)
strength 191. 5100 1,100N (filler direction)
Tear strength ASTM 90 N (warp direction)
D1424 65 N (filling direction)
Flame resistance Fed. std. self extinguishing
191A
method 5903
There is thus provided a tentage material having the
required mechanical strength along with b>~eathability.
It will be understood that the above described
embodiment is for purposes of illustration only and that
changes and modifications may be made thereto without
departing from the spirit and scope of the invention.
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