Note: Descriptions are shown in the official language in which they were submitted.
CA 02683296 2009-10-22
1898
FIRE RETARDANT-IMPREGNATED CELLULOSE BOARD,
PROCESS OF MANUFACTURE THEREOF AND USES THEREOF
FIELD OF THE INVENTION
This invention relates to fire retardant-impregnated cellulose materials,
particularly in
the form of sponges, boards and blocks, to methods of manufacture and uses
thereof.
BACKGROUND OF THE INVENTION
Cellulose sponges are well-known in the art - see, for example, USP 1,142,619 -
G. Pum et al (1915) and USP 6,281,258 B1 - Hausdorf J. et al (August 28, 2001)
and
references cited therein.
A typical manufacturing process for a synthetic cellulose sponge is described
by the
following steps
1. The cellulose used for sponges arrives at the sponge factory in large,
stiff sheets.
Workers take the sheets and soak them in a vat of water mixed with certain
chemical
softeners. The cellulose becomes soft and jelly-like. Then workers load the
cellulose
into a revolving mixer, which is a large rotating metal drum. Workers add
sodium
sulphate crystals, cut hemp fibers, and dye, and close the mixer. The mixer is
set to
rotate, and it churns the ingredients so that they are thoroughly amalgamated.
2. From the mixer, workers pour the material into a large rectangular mold
that may be 2
ft (61 cm) high, 2 ft (61 cm) wide, and 6 ft (1.8 m) long. The mold is heated,
and the
cellulose mixture cooks. As it cooks, the sodium sulphate crystals melt, and
drain
away through openings in the bottom of the mold. It is their melting that
leaves the
characteristic pores in the finished sponge. The size of the pores is
determined by the
size of the sodium sulphate crystals. A rough sponge used for washing a car,
for
instance, is made with coarse crystals, while a fine sponge of the type used
for
applying makeup is made with very fine crystals. As the celluolose mix cooks,
then
cools, it becomes a hard, porous block.
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3. The sponge block is then soaked in a vat of bleach. This removes dirt and
impurities,
and also brightens the color. Next the sponge is cleaned in water. Additional
washings
alter the texture, making the sponge more pliable. The sponge is left to dry,
to prepare
it for cutting.
4. Some manufacturers make the sponge and cut and package it themselves.
Others
produce the raw blocks of sponge, and then sell them to a company known as a
converter. The converter cuts the sponges according to its customers needs,
and takes
care of the packaging and distribution. Whether at the first manufacturing
facility or at
the converter, workers cut the sponges on an automatic cutter. They load each
big
rectangle of sponge into a machine that slices it into the desired size.
Because the
sponge block is rectangular, it can be cut into many smaller rectangles with
little or no
waste.
5. Many household sponges have a textured plastic scouring pad attached to one
side.
This is attached in a process called laminating, after the sponge is cut. The
scouring
pad, which is cut to the same size as the sponge, is affixed to the sponge in
a
laminating.
Alternatively, softened cellulose is mixed with sodium sulphate crystals, cut
hemp
fibers, and dye in a large, revolving metal drum. Once blended, the material
is poured into a
large rectangulor mold, which may be 2 ft (61 cm) high, 2 ft (61 cm) wide, and
6 h (182.9
cm) long. As the mold cooks, the sodium sulphate crystals melt, and drain away
through
openings in the bottom of the mold. It is their melting that leaves the
characteristic pores in
the finished sponge machine that uses a specialized sponge glue made of
moisture-cured
polyurethane. Next, the sponges move to a packaging area where they are sealed
in plastic.
The packaged sponges are boxed, and the boxes sent to a warehouse for further
distribution.
SUMMARY OF THE INVENTION
The invention, in one aspect, provides a board comprising dried, fire
retardant-
impregnated cellulose material.
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In preferred embodiments, the boards are essentially rigid, and preferably
comprises
voids of an average particle size of less than 5mm and more preferably
selected from 0.05mm
to 3mm.
In alternative embodiments, the boards are constituted as cellulose sponges
comprising voids of an average particle size selected from 0.5cm to 5.0cm,
preferably 2.5cm
to 4.0cm.
The invention, in a further aspect, provides a method of making a board
comprising a
dried, fire retardant-impregnated cellulose material comprising
(a) mixing a particulate cellulose material in a salt-containing aqueous
solution;
(b) forming a salt-impregnated cellulose board from said particulate
cellulose material;
(c) washing said salt-impregnated cellulose board with an aqueous
solution to remove said impregnated salt to provide a reduced salt-containing
board;
(d) treating said reduced salt-containing board with a fire retardant-
containing aqueous solution to provide a fire retardant-impregnated board; and
(e) drying said fire retardant-impregnated board to provide said dried, fire
retardant-impregnated cellulose board.
Preferably, the salt is essentially eliminated.
We have found, surprisingly, that the average particle size of the salt of use
in the
practise of the invention has an effect on the size of the voids produced
resulting from the
removal of the salt crystals and also the physical property of degree of
flexibility and rigidity
in the resultant dried, fire retardant-impregnated cellulose board.
For example, we have found that salt having an average particle size of less
than
0.5cm and preferably selected from 0.05mm to 3mm produces an essentially rigid
board,
having some degree of bendable dependent on its thickness.
In contrast, an average particle size of at least 2.5cm, preferably 2.5cm to
5.0em, and
more preferably 2.5cm to 4.0 cm, provides an extremely flexible sponge.
Any suitable salt may be used to provide the desired void-size. Preferred
examples
are selected from alkali metal halides and sulphates, particularly sodium
sulphate.
Suitable fire retardants may be selected from compounds of small molecular
weights
containing phosphorus, antimony, or halogens. The most effective commercially
available
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fire retardant systems are based on halogen- containing compounds. However,
due to
concerns over the environmental effects of such halogenated compounds, there
is an
international demand to control the use of such halogenated additives.
Some of the most common halogenated agents are methyl bromide, methyl iodide,
bromochlorodifluoromethane, dibromotetrafluoroethane, dibromodifluoromethane
and
carbon tetrachloride. These halogenated fire retarding materials are usually
available
commercially in the form of gases or liquids. Unlike chlorine and bromine,
fluorine reduces
the toxicity of the material and imparts stability to the compound. However,
chlorine and
bromine have a higher degree of fire extinguishing effectiveness and,
accordingly, a
combination of fluorine and either chlorine or bromine is usually chosen to
obtain an
effective fire-retarding compounds.
Other commercially available fire retardant materials that do not include
halogens
include boric acid and borate based compounds, monoammonium phosphonate, and
urea-
potassium bicarbonate.
Intumescent compounds which limit the heat and mass transfer by creating an
insulating charred layer on the surface of the burning cellulose are also
considered fire
retardant materials. A typical intumescent additive is a mixture of ammonium
polyphosphate
and pentaerythritol.
In a further embodiment of the invention, steps (c) and (d) are combined.
In a further aspect, the invention provides a method of making a dried, fire
retardant-
impregnated cellulose board comprising
(a) mixing a particulate cellulose material with an aqueous solution of a fire
retardant;
(b) forming a fire retardant-impregnated cellulose board; and
(c) removing water from said fire retardant-impregnated cellulose board to
provide said dried, fire retardant-impregnated cellulose board.
Preferred embodiments of the boards according to the invention are essentially
rigid,
particularly if of a thickness greater than 2cm.
Further preferred embodiments are constituted as flexible sponge materials
produced
using salt having an average particle size of at least 0.5cm and preferably,
at least 2.5cm to
5.0cm and more preferably 2.5cm to 4.0cm.
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In a further aspect, the invention provides a dried, fire retardant
impregnated
cellulose board when made by a process as hereinabove defined.
In yet a further aspect, the invention provides a wallboard comprising
a dried, fire retardant-impregnated cellulose board, as hereinabove defined,
sandwiched between a first member and a second member.
The member may be formed, for example, of paper, plywood or like suitable
material,
optionally impregnated and/or coated with a fire retardant.
The boards produced according to the invention may be manufactured having any
suitable thickness, for example, having a thickness selected from 3mm to 2.5cm
and of a
desired width, typically, 1.5cm to 1.5m. The smaller widths can be utilized as
a wrap around
wires and pipes for fire protection and manufactured as rolls, optionally
bearing an adhesive
on one surface.
The selected, suitable boards, according to the invention, may be used as wall
structures in buildings, such as, for example, residences and commercial
establishments
having a thickness selected, for example, from 1cm to 80 cm. Such boards would
preferably
be sandwiched, for example, with paper, cardboard, plyboard or like material
sheets. When
the board has an average void size to provide a somewhat flexible sponge,
suitable additives,
such as a resin or glue, may be used to provide adequate stiffening.
The larger void cellulose "matting" can be used in rolls and sheets as well
for various
applications. For example the lining of an engine compartment or the hull on a
fiber glass
boat.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be better understood, preferred embodiments
will now
be described, by way of example only, with reference to the accompanying
drawings wherein
Fig. I is a diagrammatic cross section of a sheet of wall board according to
the
invention; and
Fig. 2 is a diagrammatic side view of a board according to the invention in
the form of
a wrapping roll.
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DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig. 1 shows generally as 10, a wallboard having a cellulose sponge core 12
sandwiched between paper sheets 14 and 16. Sponge 12, impregnated with boric
acid fire
retardant 18, has an average void size of 2cm. Wallboard 10 is a typical sized
2.4m x 1.2m x
1.2 cm sheet, used in home construction.
Fig. I also represents a more rigid ammonium polyphosphate/pentaerythritol
fire
retardant-impregnated cellulose core 20 having an average void size of 0.lmm.
Fig. 1 also represents a more flexible fire retardant-impregnated cellulose
sponge core
22 having an average void size of 3.5cm.
Fig. 2 shows generally as 24 a urea/potassium bicarbonate fire retardant-
impregnated
cellulose board in the form of a coil or tape for use as insulation wrapping
for pipes, wires
and the like. Coil 24 has an average void size of about 4.0cm.
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 equivalence of the specific embodiments and features that have been
described
and illustrated.
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