U.S. patent number 3,766,003 [Application Number 05/231,341] was granted by the patent office on 1973-10-16 for process for manufacturing endless fiber webs from inorganic fiber suspensions.
This patent grant is currently assigned to Werner Hugo, Wilhelm Schuller. Invention is credited to Harald Hohlfeld, Wolfgang Schuller.
United States Patent |
3,766,003 |
Schuller , et al. |
October 16, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
PROCESS FOR MANUFACTURING ENDLESS FIBER WEBS FROM INORGANIC FIBER
SUSPENSIONS
Abstract
In the process of manufacturing flat fibrous structures from
suspensions of fibers by depositing a suspension of such fibers
onto a moving permeable surface such as an endless sieve or belt
wherein the fibrous suspension has been prepared from fibrous
structures formed of a plurality of fibers which have been obtained
by drawing a flowing glass melt, followed by chopping of the drawn
fibers to form the fiber structures of predetermined length, the
improvement in accordance with the invention of preparing the fiber
suspension from fiber structures obtained by directing jets of
liquid onto the glass fibers drawn from the glass melt and which
are being wound onto the periphery of a rotating drum in a parallel
arrangement and which after a certain layer thickness thereof has
been obtained are cut to a predetermined length with the fibers
still being in the moistened state.
Inventors: |
Schuller; Wolfgang (Wertheim,
DT), Hohlfeld; Harald (Wertheim, DT) |
Assignee: |
Hugo; Werner (Munich-Grunwald,
DT)
Schuller; Wilhelm (Munich-Grunwald, DT)
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Family
ID: |
5800628 |
Appl.
No.: |
05/231,341 |
Filed: |
March 2, 1972 |
Foreign Application Priority Data
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Mar 5, 1971 [DT] |
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P 21 10 599.7 |
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Current U.S.
Class: |
162/156; 65/479;
65/480 |
Current CPC
Class: |
D21B
1/061 (20130101); D21H 13/40 (20130101) |
Current International
Class: |
D21B
1/06 (20060101); D21H 13/40 (20060101); D21H
13/00 (20060101); D21B 1/00 (20060101); C03b
037/02 (); D21h 005/18 () |
Field of
Search: |
;65/1,2,3,11W
;162/156 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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471,000 |
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Jan 1951 |
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CA |
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568,425 |
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Jan 1959 |
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CA |
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Other References
Paper Trade Journal - The Most Useful Paper Oct. 1, 1956 pp. 26,
27..
|
Primary Examiner: Lindsay, Jr.; Robert L.
Claims
We claim:
1. A process of producing a continuous web of individual short
glass strands which comprises drawing onto the outer surface of a
rotating drum a single layer consisting of a plurality of parallel
strands of molten glass from a feeder provided with a plurality of
orifices, spooling the said drawn glass strands in successive
layers upon the said rotating drum while continuously applying a
liquid to the said outer surface of the said drum and to the layers
of parallel glass strands as they are being spooled upon the said
rotating drum and, after a preselected number of layers of parallel
wet glass strands have been spooled upon the said rotating drum,
cutting through the said plurality of layers along a line
transverse to the parallel strands and peeling the said plurality
of layers as a unit of cohering wet glass strands from the said
rotating drum, subsequently chopping the said unit of wet coherent
parallel glass strands into units of shorter strands having a
preselected length along lines transverse to the parallel strands,
distributing the thus-chopped units of wet cohering parallel glass
strands into a liquid to form a flowable suspension of individual
short glass strands in the liquid, and depositing the said flowable
suspension of individual glass strands upon a moving continuous
screen that is permeable to the liquid on which the short glass
strands are retained as a continuous web.
2. A process as defined in claim 1 in which the liquid that is
continuously applied to the outer surface of the rotating drum is
water.
3. A process as defined in claim 2 in which the liquid into which
the cut glass strands are distributed to form a flowable suspension
is water.
4. A process as defined in claim 1 in which the liquid that is
continuously applied to the outer surface of the rotating drum
contains a wetting agent.
5. A process as defined in claim 1 in which the liquid that is
continuously applied to the outer surface of the rotating drum is
the same as that into which the cut glass strands are subsequently
distributed to form the flowable suspension.
6. A process as defined in claim 1 in which the unit consisting of
successive layers of parallel glass strands that was peeled from
the rotating drum is chopped at such intervals as to produce a unit
consisting of successive layers of shorter strands having a length
between 10 and 30 millimeters.
Description
This invention relates to a process for preparing endless fibrous
webs from suspensions of inorganic fibers and more particularly
relates to an improved process of preparing fibrous suspensions for
use in the making of endless fibrous webs.
It is known that flat fibrous structures can be manufactured by the
procedures utilized in the manufacture of paper and in particular
by the so called wet process. The fibers are for this purpose
possibly in admixture with a binding agent, suspended in water to
form the fiber suspension. The fiber suspension is required to be
entirely uniform in nature as the quality of the resultant fibrous
structure or web is directly determined by the degree of
uniformity, i.e., homogeneity of the suspension. It is accordingly
necessary that the starting fiber material be dispersed in the
water so that there is obtained a suspension of the individual
single fibers. The resultant fiber suspension is then delivered
onto a moving perforated belt on which it is deposited out in a
uniform form. The thusly obtained layer of fibers is then withdrawn
while still moist and further worked up to form a coherent felted
fiber web.
Recently it has been observed that this technique which has been
associated with cellulosic and other natural fiber materials can be
satisfactorily adapted for use with glass fibers. As is known, as
raw fiber starting material, there are used bundles of fibres
chopped up to form staple. The requirement that the bundles of
fibers thereafter be decomposed into the individual fibers has
posed great difficulties in connection with the use of inorganic
materials such as glass fibers.
In the manufacture of glass cords or ropes there is in the known
manner provided a plurality of individual fibers of endless length
but without any rotation or twist having been imparted thereto so
as to provide a substantially parallel arrangement of closely
associated fibers joined so as to form the unitary cord or rope. In
order to ensure that the single untwisted fibers are sufficiently
adhered one to the other as to impart to the resultant cord or rope
a resistance to abrasion as required by the later working, the
fibers in the process of their manufacture have been adhered one to
the other by means of a binding agent. The fibers are thusly
combined one with the other to form the unified structure and this
structure is thereafter chopped up to form staple consisting of the
same units each of substantially equal length. However, these units
are thereafter only with considerable difficulty separated into the
single or individual fibers as is required in connection with the
production of the satisfactory webs.
In order to avoid the above difficulties, it has been proposed that
the binding agent be reduced in amount to a minimum, i.e., that in
order to improve the decomposition of the bundle of fibers forming
the staple into the single and individual fibers in the suspension
medium, such as water, the binding agent has been considerably
reduced in amount. The result has been that in the chopping process
considerable and unsatisfactory dust is evolved and more important
a preliminary splitting up of the bundle into the individual fibers
takes place which in no way enhances the distribution of the fibres
in the suspending medium but which rather only results in that the
fibers before their introduction into the suspending medium becomes
entangled and are thereafter disentangled only with great
difficulty, if at all.
The poor decomposition of the fiber bundles into the single fibers
has the disadvantageous effect that it results in the formation of
specks or spots. This speck formation and spotting not only gives
rise to a non-uniform fiber suspension but also produces an
impaired final product. In order to avoid the speck formation or
for extensively reducing the same, a number of precautionary
measures have been proposed. Such measures include regulating the
length of the staple so as to be as low as possible, for example, a
maximum length of 6 mm has been proposed and in addition to employ
in the fiber suspension an additional agent serving to segregate
the speck or spot forming material. Still further, it has been
proposed that to obtain a better and more uniform distribution of
the individual fibers in the suspension agent, there be employed
certain additives, such as for example, wetting agents. The
disadvantage of such additives includes not only the increased
costs for the additives but for the increased working time and
equipment required in order to achieve the same operating capacity
as when no additives are present. Still further, the use of
additives such as the wetting agent has the disadvantage that the
same brings about a formation of foam which result in the
production of finished webs chracterized as defective by virtue of
included flaws and by a cloudy or hazy appearance. The quality of
the finished web is particularly so adversely affected, when the
webs are very thin in nature, i.e., have a surface weight of about
45-55 g/m.sup.2.
Further the webs prepared on the basis of short length staples,
i.e., about 6 mm are characterized as noted above by their lack of
uniformity, impaired strength resistance and also by optically
negative effects. When glass fiber webs having a non-uniform fiber
distribution are used, for example, as surfacing felts in the
synthetics industry, for example as insulating and decorating
plates or as so-called painting felts, there results that in the
non-uniform areas of the web there is an uneven porosity resulting
in an unequal uptake of the dye, paint or other coating material
applied thereon, so that the final finished product presents an
uneven appearance characterized by so-called disturbing spots.
In addition to the use of glass fiber bundles or bundles of glass
fiber rovings, it has been proposed to use so-called fiber ribbons
or tapes. The ribbons or tapes are prior to suspension in the
suspension medium cut up to staple length and in this form
introduced into the suspension medium. It was believed by the art
that the staple segments formed from the glass fiber ribbon or tape
and which contain no binding agent would be decomposed and
distributed in the water or like suspension medium in the form of
the desired single fibers more readily than were the bundles of
glass fibers as previously described.
This has however not been the case. All of the deficiencies and
defects associated with the use of bundles of fibers containing the
decreased amount of binder are encountered when using the fiber
ribbon or tape staple. The disadvantages are already evident in the
chopping process in that different lengths of fiber have been used
in the production of the ribbon or tape, the chopping forther
contributing to the unevenness in resultant fiber length. Further
the fibers in the ribbon are not parallelly arranged with respect
to each other and are further entangled in the chopping or cutting
process. The entanglement is so marked that the necessary
separation into the individual fibers in the suspension medium is
no longer possible. As a result, a strong flock formation takes
place which is manifested in the finished product as an optically
disturbing flaw or defect and in untenable variations in the
surface weight, strength, porosity, etc. of the finished web.
It is an object of the invention to provide a method for
economically and simply producing fibrous webs characterized by
their uniformity in surface weight, strength and porosity
throughout.
It is another object of the invention to provide a process for
producing uniform fiber suspension for use in the preparation of
such endless webs.
Still another object of the invention is to provide a process for
producing uniform and homogeneous suspensions of glass fibers
making possible endless fibrous webs and felts characterized by the
uniformity of the fiber distribution therein.
These and other objects and advantages of the invention will be
apparent from the following description including the drawing
forming a part thereof and which diagrammatically illustrates the
process of the invention.
In accordance with the invention it has now been found that
substantially uniform and homogeneous suspensions of glass fibers
in a suspension medium intended for use in the production of
endless fiber webs can be obtained if the individual units each
composed of a plurality of glass fibers of uniform length are
introduced into the suspension medium in a moistened state, wherein
the moistness has been imparted to the fiber units in the process
of their manufacture and namely between the drawing of the glass
melt into endless fibers and the chopping thereof into staple.
The choice of the agent serving for moistening the drawn glass
fibers is from amoung the materials known to the art in connection
with the manufacture of fiber cords and ropes and includes those
liquids used for instance as finishes or lubricants. The particular
material selected depends on the choice of the material employed as
suspension medium. If the latter is water, then for the moistening,
water or a liquid soluble in water can be used.
In accordance with the invention there is now provided a process
for manufacturing flat fiber structures from fiber suspensions by
deposition of such suspensions on a moving permeable surface for
instance an endless sieve or belt, wherein the fiber suspension is
obtained by introducing unitary fiber structures each composed of a
plurality of parallelly arranged fine glass fibers prepared by
drawing a glass melt and while winding such fibers in a parallel
arrangement onto the periphery of a known type of rotating drum,
spraying the same with jets of a liquid material, the winding being
continued util a certain layer thickness has been reached.
Thereafter the movement of the drum is interrupted and the layers
are cut through while still in the moistened state to form the
units composed of the adhering parallelly arranged fibers all
having substantially the same predetermined length.
These units composed of the moistened fibers are then introduced
into the suspension medium with the result that the units of the
adhering fibers undergo rapid and complete decomposition and are
substantially completely uniformly distributed as individual fibers
in the suspension liquid. The parallel arrangement of the fibers,
absence of any binder and the assistance of the moistening agent
all contribute to the rapid decomposition of the structure of the
fiber units or bundles.
The distribution of the fibers in the suspension medium can be even
further improved upon if there is added to the fiber suspension any
of the known wetting agents. In accordance with a particularly
preferred embodiment of the invention the wetting agent can be
incorporated into the liquid, for instance water used for spraying
the fibers as they are being wound onto the drum. This has the
advantage that the wetting agent is incorporated directly as a part
of process of producing the fibers. Under the conditions of the
just-mentioned embodiment, the decomposition of the fiber bundles
into their component single fibers is considerably enhanced, this
being the case even where the fibers have undergone a considerable
drying out of the moisture on the surfaces thereof.
The process of the invention will be further illustrated by
reference to the accompanying drawing which is a flow sheet
representing the sequence of operations that are required to
produce the continuous webs of glass strands that are referred to
herein.
In FIG. 1 the molten glass is drawn in the form of strands onto a
rotating drum while a stream of liquid is applied to the drum.
In FIG. 2 the plurality of successive drawn and spooled layers of
parallel glass strands are cut into units and peeled from the
rotating drum.
In FIG. 3 the peeled unit is flattened.
In FIG. 4 the flattened unit is chopped into smaller units composed
of strands of shorter lengths, which are then placed into a liquid
where the unit is broken up into individual short strands and are
then passed along in the form of a suspension in a liquid through
various conduits and vessels to a webforming machine.
As can be seen from the drawing, the process is carried out by
forming in the conventional manner a plurality of single fibers by
extrusion of a flowing glass melt using therefor a plate provided
with a plurality of nozzles. The glass is delivered from a tank or
source 2 containing the molten glass and the fibers thus formed
applied onto a rapidly rotating drum 3 so that they are wound in a
parallel arrangement onto the periphery of the drum. An intensive
and thorough moistening of all of the individual fibers is carried
out in accordance with the invention by spraying over the entire
drum surface a liquid stream, for example water, using therefor a
fan-shaped spray device 4. There is thusly simultaneously obtained
a good adhesion of the first fiber layer on the drum surface and
moistening of all of the applied fibers.
The intense moistening of the individual fibers acts also to
further ensure the cohesion of the fibers to each other under
maintenance of the parallel arrangement. After a certain layer
thickness has been reached, the movement of the drum is halted and
the layers of fiber cut through along the longitudinal direction 5
of the drum. The cut layers of fibers are then separated off from
the drum surface. Advantageously the layers can also be cut in the
direction 6 of the drum circumference. This latter cutting serves
to form smaller packets or bundles 7 of the moist fibers.
It has been established by testing that the average moisture
content of the fiber material present on the drum surface amounts
to about 17 percent which in the time elapsed from their
manufacture to the chopping is reduced to about 12-15 percent.
A too marked decrease in the moisture content can be avoided by
taking appropriate measures self evident to the artisan.
It has been found to be particularly advantageous if the moist
fiber packets are delivered immediately following their formation
into a chopping apparatus 8 wherein the same are chopped up into
fiber structures 9 preferably having a length of between 10 and 30
mm. Another advantage of the process of the invention and in
particular stemming from the use of the moistened glass fibers
results therefrom that the brittleness of the fiber which is
manifested in their dry state and which for instance in the
conveying of the fibers leads to breakage and entanglements is
considerably lessened in accordance with the invention as is the
disadvantage of dust evolvement.
The still moist parallel fiber structures 9 are then continuously
conveyed for instance by means of a conveying belt 10 the movement
of which is preferably controlled by an intermediately arranged
apportioning apparatus provided for feeding the fiber structures at
regularly spaced distances, into a mixing tank 11 and therein
admixed with the suspension medium which preferably is water.
The condition of the fibers in the packet, that is, the existing
cohesion of the fibers in the structure by virtue of the moistening
agent particularly in the case where the same agent also serves as
the suspension medium and also where the moistening agent is
soluble in such suspension medium results in that there is quickly
and completely brought about a destruction of the cohesive bonds
between the fibers and the same are separated one from the
other.
The separation is a very extensive one resulting in a uniform
distribution of fibers in the suspension medium. The mixture of
fibers and suspension medium is then fed from the mixing tank 11 by
means of a pump 15 into the working tank 16 and from there by means
of a pump 17, possibly via an intermediately installed beater 14 of
the known construction, discharged into the conduit 22 of the
circulating suspension medium and while still in this highly dilute
form introduced into the material take-off tank 18. Following
separation of the liquid suspension medium from the fibers in
chamber 19, the suspension medium is delivered over a conduit 20
after passing through a conventional filter apparatus into a
storage container 21. By means of pump 23 the circulating
suspension medium is thereafter recycled via conduit 24 into the
mixing tank 11 where it is reused for suspending additional fibrous
material. The suspension of fibers still present in the take-off
tank 18 is then applied onto the moving perforated belt for forming
the web.
It is also possible in accordance with the invention in the case of
particularly difficulty suspendable glass fibers to continuously
circulate the suspension agent 12 from the mixing tank 11 through
the working tank 16 and the material take off 18 back into the
mixing tank 11 whereby if necessary there can be installed further
mixing and working tanks. In this way, instead of directly
delivering the material to the storage or take off tank, a further
working tank and mixing tank are installed prior to the take-off
tank and adequate and uniform distribution of the fibers in the
suspension medium thereby assured. It is to be understood that
there can be used in the working tank the conventional stirring
apparatus for ensuring the best possible decomposition of the fiber
packets and distribution of the individual fibers.
* * * * *