Note: Descriptions are shown in the official language in which they were submitted.
CA 02145953 2002-03-11
CELLULOSIC FIBER INSULATING MATERIAL
TECHNICAL FIELD
The present invention relates to an insulating material
which is comprised of loose fill short cellulosic
fibers retained in a matrix formed by bondable
synthetic fibers which are heat-fused together at
crossing contact points to form pockets in the matrix
in which the cellulosic fibers are trapped without the
use of any adhesive binder.
BACKGROUND OF THE INVENTION
Fiberglass batts are well known in the art of
insulation and are commonly produced with glass fibers
and an aqueous thermosetting resin. The aqueous
thermosetting resin is applied on the glass fibers and
dried and cured in a forced air oven whereby to bind
the fibers together in a batt. Facings such as kraft
paper, aluminum foil, etc., are sometimes bonded with a
suitable adhesive to the batt after the oven.
One of the disadvantages of this process is that since
large volume of air are required to form and cure the
bait, it is difficult to control the emission by the
binder of toxic gases and aerosols in the air.
Furthermore, the heat required to evaporate the water
and cure the binder on the batt constitute an expensive
means of fabrication.
It is known in the art that cellulosic fibers can
provide good insulating properties. To this end, ground
recycled paper or virgin pulp are readily available.
However, a disadvantage of the use of these products
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has been the fact that the fibers or bundles of fibers
are very short, normally 1 to 10 mm as compared to
fiberglass fibers which are in the range of about from
25 to 75 mm. As a result of this short length, a large
quantity of liquid binder would be required to bind the
fibers together in order to make a cellulosic batt with
adequate integrity and this would not be economically
feasible. Furthermore, the water used with the binder
is undesirable due to the great affinity that the
cellulose fibers have to water as compared to
fiberglass. This would lead to an increase in the
drying time and therefore an increase in the cost.
There is therefore a need to find a means to fabricate
a batt of cellulosic pulp using an appropriate binder
and which could eliminate the problems associated with
a liquid binder.
The use of dry binders, such as thermosetting or
thermoplastic powders would eliminate the use of water
and problems associated therewith. However, these
powders must be utilized in large quantities in order
to permit the fabrication of batts having an adequate
integrity. Such large quantities of binder would not
again be economically feasible.
Thermal bonding techniques can be used to bond fibers
in a wide variety of nonwoven products such as filters,
absorbents and clothing. This process utilizes
thermoplastic fibers that bind together with heat. Such
fibers will become tacky while preserving their shape
at a predetermined temperature. Examples of such fibers
are copolymers of vinyl acetate and vinyl chloride
which is known under the trade mark WALKER MP FASER and
also bicomponents fibers which are known under the
trade mark CELBOND. ~~CELBOND~~ fibers are fibers
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manufactured with a high melting point (approximately
240° C.) polyester core and a lower melting
point polyester or polyolefin sheath. Several grades
are available with sheath melting points in as range of
110° to 200° C.
SUMMARY OF THE INVENTION
We have discovered that a cellulosic batt can be
fabricated by utilizing these fibers instead of
conventional binders. These thermoplastics fibers can
be mixed with the cellulose fibers in desirable
proportional and then bound together by heat. The bonds
will form a tridimensional structure (matrix) with
cells, which will trap the short cellulosic fibers
therein without the use of binder. Experimentation has
shown that this technique offers many advantages and
necessitates only a small quantity of these binding
fibers. By fabricating such a product no adhesive
binder is necessary and therefore there is no emission
of aerosols or other chemicals which pollute the air.
It is also more economical to fabricate insulation in
this manner and it results in a new use for recycled
pulp, particularly ONP cellulose which is fabricated
from recycled newsprint. The insulation can be used for
thermal and acoustical applications.
According to the above features of the present
invention there is provided, from a broad aspect, an
insulating material which is comprised of loose fill
short cellulosic fibers and bonding synthetic fibers.
The synthetic fibers are of longer length than the
short cellulosic fibers and heat-fused with the outer
sheath of other synthetic fibers have an outer sheath
which is at crossing contact points thereof to form a
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matrix having pockets which retains the loose fill
cellulose fibers throughout a body formed by the matrix
and thereby eliminates the need of adhesively binding
the cellulose fibers.
According to another broad aspect of the present
invention there is provided an insulating batt formed
from this composition of loose fill short cellulosic
fibers and bonding longer synthetic fibers treated as
above-mentioned.
BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention will
now be described with reference to the accompanying
drawings in which:
FIG. 1 is a magnification view of fiberglass bonded
together by an adhesive binder to form a fiber glass
insulating batt, as is known in the prior art;
FIG. 2 is a magnification view showing the insulating
material of the present invention comprised of loose
fill short cellulosic fibers and a matrix of bonding
synthetic fibers which form pockets to retain the short
cellulosic fibers to form an insulating cellulosic
fiber batt;
FIG. 3 is an extra magnification view showing two
synthetic fibers bonded together at crossing contact
points,
FIG. 4 is a cross-section view of a synthetic fiber as
used to form the binding matrix,
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FIG. 5 is a crass-view of an unfaced insulating batt
wherein the exterior surfaces thereof have been coated
to reduce the release of dust particles, and
FIG. 6 is a cross-section view of a faced insulating
batt wherein the extension surfaces thereof have been
coated to reduce the release of dust particles.
DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in FIG. 1, long fiberglass fibers 10, in the
range of 25 to 75 mm, are treated with a liquid binder
whereby to form batts by subjecting the fibers and
binders to a drying and curing process in a forced air
oven. As previously mentioned this is a costly process
and it produces the emission of aerosol in the air
which pollutes the environment. The resin is typically
a thermosetting water-based phenol formaldehyde resin.
The fiberglass fibers have a diameter of approximately
3 to 10 microns.
FIGS. 2 and 3 illustrate the fabrication of the
insulating material of the present invention which
comprises loose fill short cellulosic fibers 11 trapped
in a binding matrix formed by longer synthetic fibers
13 which bind together at their crossing contact points
such as 14 to form pockets 12 which trap the short
cellulosic fibers. The short cellulosic fibers 11 have
a length of from about 1 mm to about 4 mm, and a
diameter of between 15 to 40 microns. The long bonding
synthetic fibers are much longer and have a length
which is more than 4 mm and preferably, but not
exclusively, longer than 25 mm. These synthetic fibers
are of the type that become tacky without loosing their
shape at a predetermined temperature. FIG. 4 shows a
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cross section of a bicomponent fiber with a core 17
which has a higher melting point than its outer sheath.
The synthetic fibers are mixed with the short
cellulosic fibers 11 at a level by weight of 3% to 20%
and preferably 5% to 8%, and subjected to a heating
process wherein the outer sheath 18, and not the core
17, become tacky, with minimum shrinkage. An example of
such fibers would comprise bicomponents thereof which
are sold by Hoechst Celanese Corp. under the trade mark
CELBOND.
The longer synthetic bonding fibers 13 also have a
diameter which is approximately the same as the
fiberglass fibers of the prior art, above described.
The synthetic fibers 13 may also be of another type
than bicomponents provided that they become tacky
without loosing their shape at a predetermined
temperature. An example is vinyl chloride-vinyl acetate
copolymer fiber sold under the trade name WALKER MP
FASER. It is therefore important that during the
bonding process, to fabricate the insulating material
of the present invention, that the mixture of the
synthetic fibers and cellulose fibers be subjected to a
predetermined temperature whereby the strength and
length of the synthetic fibers is not effected but only
sufficient to soften the polyester sheathing 18 to
cause it to soften and bond at crossing contact points
to form a matrix body of interconnected synthetic
fibers which forms pockets to trap the loose short
cellulosic fibers and thereby retain them in a body or
batt having a specific shape.
It is also desirable when providing thermal or
acoustical insulation batts formed with this insulating
pulp to add a fire retardant chemical such as borax,
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boric acid, ammonium sulphate or aluminum sulfate or
any other suitable chemical. Levels of fire retardant
are typically 10 to 30% and preferentially 15% to 25%.
As shown in FIG. 5, suitable coatings can be used to
reduce the level of dust released in the handling of
the batts. The preferred coatings are greases and can
be formulated from a broad range of chemicals such as
hydrocarbons, fatty acids and silicones. The product
can also be provided in sheet, thin mats or roll form
and may be faced with a suitable facing sheet 21 which
is well known in the art to meet specific construction
practice. The facing sheet may be comprised of aluminum
foil, kraft paper, cellulosic scrim, polyethylene film
or any other material, as required. The batt, can of
course, be an unfaced insulating batt of rectangular
cross-section.
The cellulose fibers may be short virgin fibers or else
recycled paper such as ONP cellulose fibers fabricated
from old newsprint. It can also be long cellulose
fibers such as cotton, wood fibers, jute or linen. The
wood fibers are produced by coarse refining of wood
chips. Still further the cellulose fibers may be
derived from "so-called" urban wood which comprise
recycled pallets, wood cuttings from construction
sites, etc.
A mix of two or more cellulose fibers can also be used
to optimize the desired characteristics of a product.
For instance, jute can be used to reduce the density of
an ONP batt. In one experiment, a level of 15% of jute
reduced the density of a 2 lb/cu.ft batt to a value of
1.5 lb/cu.ft. A lower density is economically
beneficial.
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It is within the of the present invention to provide
any other obvious modifications of the preferred
embodiment described herein, provide such modifications
fall within the scope of the appended claims.
