Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METALIZED FABRIC
TECHNICAL FIELD
This invention relates to the manufacture of
fabric, and more particularly to the manufacture of
plastic fabric having a metalized surface.
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BACKGROUND AND SUMMARY
Fabrics are utilized in numerous situations
requiring strength, flexibility and durability. For
example, fabrics are often used in the construction of
containers for storing and~or transporting granular or
powder materials, as well as in the construction of
shelter for goods, equipment, people, and the like.
Traditionally, fabrics have been constructed of natural
fibers; however, in recent years synthetic fibers
manufactured from polypropylene or other plastics have
come into extensive use since they are generally
stronger and more durable than fabrics made of natural
fiber.
Characteristics of fabrics in general make their
use undesirable in some circumstances. For example,
many granular and even liquid materials develop a
static-electric charge through friction as they are
poured into, discharged from or vibrated within a
receptacle. However, since fabrics are not
electrically conductive, discharge of static-
electricity from such materials contained by fabric
receptacles is difficult, if not impossible, posing the
danger of explosion or fire caused by an electrical spark.
Fabrics also cannot be used in applications
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requiring an air or moisture-tight barrier due to their
fiberous nature. Plastic fabrics, in particular, are
also highly susceptible to degradation caused by
ultraviolet light and therefore cannot be used in
direct sunlight, for example, without incurring a
substantial reduction in their flexibility and strength.
In an effort to eliminate the foregoing combination
of undesirable characteristics, fabrics manu~actured of
plastic fibers have been covered with a metallic
laminate such as foil made of aluminum or other
electrically conductive metal. This approach involves
securing the foil to one side of the synthetic fabric
by means of a suitable adhesive. The laminated fabric
may then be used to construct a receytacle, for
example, with the foil laminate comprising the interior
surface of the receptacle, thereby providing an
electrically conductive surface through which the
electrical charge can be discharged to an appropriate
ground. The foil laminate may also be applied to
portions of the synthetic fabric which will be e~posed
to ultraviolet light, thereby acting as a reflector to
substantially reduce the amount of ultraviolet light
contacting the fabric and the resultant degradation
thereof. Use of foil laminates has also proved to be
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initially effective in reducing the transmission of gas
and moisture through the underlying fabric.
Foil laminates in the past, however, have proven
susceptible to abrasion, tearing and separation from
the underlying abric over a period of time,
particularly along the edges of the foil laminate. For
example, foil laminates used to cover the interior
surface of fabric receptacle will often tear or
separate from the underlying fabric due to abrasion
from the contents of the receptacle as the receptacle
is filled, emptied or transported. The cumulative
effect of such abrasion quickly reduces the
effectiveness of the foil layer as a grounding surface
and often results in unwanted contamination of the
contents of the bag with foil particles or flakes. In
addition, damage to the foil laminates through normal
wear and tear or due to handling of materials reduces
the ability of the fabric to inhibit the passage of
moisture and air and the ability of the laminate to
protect the fabric against degradation from ultraviolet
light.
The present invention comprises a highly durable
metalized fahric which overcomes the foregoing
disadvantages associated with foil-laminated fabrics.
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The metalized fabric includes a supporting layer of plastic
fabric to which a layer of plastic film having an outer metalized
surface is secured. In one embodiment, the plastic film is
secured to the underlying fabric by extrusion lamination. The
resulting metalized surface of the fabric is electrically
conductive, resistant to degradation by ultraviolet light and is
substantially air and moisture tight.
In accordance with one aspect of the invention there is
provided a metalized fabric comprising: a lower layer of fabric;
an upper layer of material secured to the lower layer of fabric;
and at least a portion of the outer surface of the upper layer
of material being metalized by vapor deposition.
In accordance with another aspect of the invention there is
provided a method for manufacturing a metalized fabric
comprising: providing a length of fabric; providing a length of
film material having a lower surface and an upper surface, at
least a portion of which is metalized by vapor deposition; and
securing the lower surface of the length of film material to the
length of fabric material to provide a metalized surface.
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IN THE DRAWINGS
A more complete understanding of the invention may
be had by reference to the following Detailed
Description when taken in conjunction with the
accompanying FIGURE which schematically illustrates the
construction of fabric incorporating the invention.
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DETAILED DESCRIPTION
The FIGURE schematically illustrates the
construction of the present invention. A roll 10
comprises a length of plastic fabric 12, such as woven
polyethelene or polypropylene, having an upper surface
14 and an opposing lower surface 15. Supported above
the roll 10 of plastic fabric is a roll 16 comprising a
length of plastic film 18 having a metalized upper
surface 20 and a lower surface 21. The length of
fabric 12 and the length of film 18 are manufactured
from the same type of plastic. The film 18 is oriented
in two substantially perpendicular directions, thereby
strengthening the film against tearing or breaking.
The upp~r surface 20 of the length of film 18 is
metalized continuously along its entire length by
conventional methods to a level which is electrically
conductive. For example, one such method includes
vaporization of an electrically conductive metal within
a vacuum. The surface 20 of the length of film 18 is
exposed to the metallic vapors within the vacuum while
opposing electrical challes are imposed on the metal
vapor and the film 18. ;e opposing charge causes the
vapor to deposit or pl~e onto the film forming a
strong bond therebetween. Typically, a metallic layer
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no more than one or two molecules thick is required to
provide an electrically conductive surface. In the
embodiment shown, aluminum is deposited on the length
of-film 18 due to its relatively low melting point and
low cost. However, it will be apparent that other
electrically conductive metals, such as gold, silver,
chromium, and the like may be utilized, if desired.
The film 18 is extrusion laminated to the fabric 12
by drawing the fabric 12 and the film 18 from rolls 10
and 16, respectively, through the nip between two
compression rollers 22 and 24. Prior to passage of the
film la and ~abric 12 between the rollers 22 and 24, a
thin layer o molten plastic of the same type ~rom
which the fabric 12 and the film 18 are manufactured is
lS interposed between the lower, non-metalized surface of
the film 18 and the upper surface 14 of the fabric 12
by a nozzIe 25. Molten plastic is provided to the
nozzle 25 from a supply 26 through a tube 27. As the
fabric 12 and the metalized film 20 are compressed
together between the rollers 22 and 24, the molten
plastic partially melts both the non-metalized surface
of the film 18 and the upper surface 14 of the fabric
12, resulting in a homogeneous layer of molten plastic
which hardens when cooled to securely bond the film 18
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to the underlying fabric 12. The resulting metalized
fabric 28 exits from the compression rollers 22 and Z4
and is collected on a take-up roll 30.
The fabric 28 can be used in the construction of a
receptacle having an inner electrically conductive
surface, such as is disclosed by U.S. Patent No.
4,45?,456. The fabric 28 can also be used in the
construction o~ weather resistant tents, covers,
shelters and the like having a reflective outer surface
to shield against sunlight or other similar radiation.
The metalized surface will also protect the fabric 28
from the harmful effects of ultraviolet radiation.
Although preferred embodiments of the invention
have been illustrated in the accompanying Drawings and
described in the foregoing Detailed Description, it will
be understood that the invention is not limited to the
embodiments disclosed, but is capable of numerous
rearrangements,l modifications and substitutions of parts
and elements without departing from the spirit of the
invention.
