U.S. patent number 3,765,971 [Application Number 05/082,241] was granted by the patent office on 1973-10-16 for process for the dry production of a fiber web.
Invention is credited to Heinz Fleissner.
United States Patent |
3,765,971 |
Fleissner |
October 16, 1973 |
PROCESS FOR THE DRY PRODUCTION OF A FIBER WEB
Abstract
A method and apparatus for producing a fiber web by a dry method
which comprises adding at least a portion of a bonding agent to the
loose fibers and forming the loose fibers into a web, the bonding
agent being uniformly distributed throughout the web.
Inventors: |
Fleissner; Heinz (Frankfurt am
Main, DT) |
Family
ID: |
5748667 |
Appl.
No.: |
05/082,241 |
Filed: |
October 20, 1970 |
Foreign Application Priority Data
|
|
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|
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Oct 20, 1969 [DT] |
|
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P 19 52 741.4 |
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Current U.S.
Class: |
156/62.2; 68/5R;
156/104; 156/62.4; 425/81.1 |
Current CPC
Class: |
D04H
1/60 (20130101); D04H 1/00 (20130101); D04H
1/645 (20130101); D04H 1/46 (20130101) |
Current International
Class: |
D04H
1/00 (20060101); B24t 005/00 () |
Field of
Search: |
;156/62.2,62.4,104
;425/80,81 ;117/21,1R ;68/5R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Whitby; Edward G.
Claims
What is claimed is:
1. A continuous method for producing a fiber web by a dry method
which comprises admixing at least a portion of a bonding agent
uniformly with loose fibers, forming the resulting uniform
admixture of the loose fibers and said bonding agent into a fiber
web, the bonding agent being uniformly distributed throughout the
formed web, and thereafter bonding the fiber web together by
drawing a heated gaseous processing medium uniformly through said
web.
2. The method of claim 1, wherein the bonding agent is mixed with
the loose fibers in a powdery, granular, fibrous or liquid
form.
3. The method of claim 1, wherein the loose fibers are
cross-plaited on a carrier fabric forming a plurality of
cross-plaited surface layer and additional portion of the bonding
agent is applied between the individual layers before or during the
cross-plaiting step.
4. The method of claim 1, wherein the web is pre-bonded by
utilizing needles and/or hot calenders before being thermally
bonded by drawing the heated gaseous processing medium through the
web, said web being thermally bonded while being conveyed on the
surface of at least one sieve drum means subjected to a suction
draft.
5. The method of claim 4, wherein an additional bonding agent is
applied after the pre-bonding step and before the step of drawing
the heated gaseous medium through the web.
6. A method for producing a fiber web by a dry method which
comprises mixing a powdery, granular, or fibrous bonding agent
uniformly with loose fibers, distributing the resulting uniform
admixture of fibers and the bonding agent by air pressure to pile
up the admixture of the fibers and the bonding agent between a pair
of rotating perforated drums, forming the admixture of the fibers
and the bonding agent into a fiber web on said perforated drums,
and bonding the resulting fiber web by conveying the web on the
surface of at least one sieve drum means subjected to a suction
draft and by drawing a heated gaseous processing medium uniformly
through said web on said sieve drum means.
7. The method of claim 6, wherein the bonding of the web is
effected by drawing hot air through the web.
8. A method for producing carpets by a dry method which comprises
mixing a granular, powdery, or fibrous bonding agent uniformly with
loose carpet fibers, forming the resulting uniform admixture of the
fibers and the bonding agent into an unbonded web layer, rendering
the web layer thicker by cross-plaiting the web layer, depositing
the thick resulting web layer crossways onto a carrier fabric,
mechanically uniting the carrier fabric and the still unbonded
fiber web layer, containing said bonding agent uniformly
distributed throughout, and thereafter thermally bonding the web by
conveying said web and said carrier fabric on the surface of at
least one sieve drum means subjected to a suction draft and by
drawing a heated gaseous treatment medium through the web and
through the carrier fabric on said sieve drum means.
9. The method of claim 8, wherein the composite is impregnated with
an additive to improve its tensile strength prior to thermal
bonding.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a process and apparatus for
producing a fiber web by a dry method, which web is bonded by means
of bonding agents.
Between the dry and the wet method of producing a fiber there is
the following difference: With the wet method there is, just as in
the production of paper, an emulsion produced which consists of a
liquor and fibers which are disposed crossways, from which emulsion
the liquor is removed by the force of gravity and by means of
suction pumps with subsequent drying units. With the dry method,
the fibers which are to form the web are laid in very thin layers
by means of web-forming units such as carding machines, and then a
certain number of these layers are piled up crossways. The wet web
producing method features high production speeds and a great
uniformity of the web, which consists of crossways lying fibers,
but on the other hand it necessitates very power consuming
subsequent drying processes and apparatus.
The dry method is advantageous in as far as there is no drying
needed. On the other hand, the fibers are oriented in one direction
only so that at least in this direction the tensile strength of the
web is rather low unless several layers of fibers are piled up,
crossways.
One problem with the dry production method is the application of
the bonding agents which are to improve the strength of the webs.
It is known to apply a bonding agent to the dry web by guiding the
web through a padder which is filled with a bonding agent liquor.
However, this results in a complete drying-out of the web which is
to be avoided in order to save expense. The fiber web can also be
coated with bonding agents. This coating can be done by means of a
foam application, by a spreading-on application, application with a
doctor blade or by spraying-on the bonding agent. The web can be
coated with the bonding agent on one side only or on both sides,
but nevertheless, the final strength of such a coated web is very
often insufficient.
It is also known to apply a powdery or granular bonding agent or a
melting film of binding agents to the web. These bonding agents are
then melted in a heating unit and subsequently re-hardened so that
the web fibers stick together. This method is advantageous because
the drying process can be omitted, but it has been found that
either the bonding powder or the like do not mingle thoroughly
enough with the fibers or that the gelling process with a bonding
agent film takes too long because the coated web are impermeable to
air.
It has also been suggested to heat the material to be coated before
applying the bonding agent, preferably nearly up to the processing
temperature, which usually prevails in the gelling duct. If
thermoplastic materials are used, it is advantageous to heat the
web to be coated up to the melting temperature of the said
thermoplastic substances. The same can be said for the use of
gelling, curing or vulcanizing agents. Thorough experiments have
shown that the last described method gives good results but also
has the shortcomings that mingling of bonding agents with fibers is
not always satisfactory, especially with thick fiber webs.
Another method of producing a dry web consists of adding the
so-called melting fibers to the blend of fibers. These melting
fibers have a lower melting point than the other fibers and
therefore cause all the fibers to stick together after having
passed the heating aggregates, wherein only the melting fibers are
rendered viscous. However, having solidified again, the melting
fibers can re-assume a fiber structure. However, this method could
not be made use of in the present invention because the so-called
melting fibers are genuine fibers which only feature a low melting
point and have to be added before the web is formed so that after
having melted, they can cause a sticking together of the web
components. This is different with true bonding agents which are
usually applied after the proper web formation. The bonding agents
mingle with the fibers after the heating-up process, although this
mingling is often insufficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to avoid the prior art
disadvantages in the dry production of a fiber web.
It is another object of the present invention to provide a process
and apparatus by which an absolutely uniform penetration of the
bonding agent through even the thickest web can be obtained without
any subsequent drying process, as is required when a liquid bonding
agent has been applied.
Other objects and further scope of applicability of the present
invention will become apparent from the detailed description given
hereinafter; it should be understood, however, that the detailed
description and specific examples, while indicating preferred
embodiments of the invention, are given by way of illustration
only, since various changes and modifications within the spirit and
scope of the invention will become apparent to those skilled in the
art from this detailed description.
According to the present invention it is suggested to add at least
a portion of the bonding agent to the fibers before the actual web
formation takes place.
The process according to the present invention can be characterized
by saying that the bonding agent is applied in the web mixing unit
or in the dosing unit in the form of a powdery, granular, fibrous
or possibly liquid substance. Subsequently, a web is formed in an
essentially known way i.e. by means of at least one carding or
blowing unit, followed by possibly a pre-bonding process utilizing
needling units and/or hot calenders and a subsequent heat-bonding
stage, the latter preferably being carried out in a perforated drum
or belt steamer in which a vaporous and/or gaseous processing
medium is guided, preferably drawn through the web.
It has already been suggested that the tensile strength of a web
which has been produced by the dry method is satisfactory in one
direction only, i.e. vertical to the web length. It is therefore
known to pile the individual layers of the web up crossways in
order to obtain a sufficient tensile strength in all directions of
the final web. It is also known to zig-zag plait the web, which
consists of high-quality fibers, onto a carrier fabric or inferior
quality, e.g. a twilled cotton fabric or a sacking material length.
For a textile material length produced in this way and having at
least one cross-plaited surface layer, the present invention
suggests applying the bonding agent before or during the plaiting
process, between the individual layers. It is advantageous to apply
a second bonding agent after the initial or pre-bonding process by
means of needling units and/or hot calenders.
An apparatus for the dry production of a web comprises a mixing
unit, a dosing unit, a web forming unit and a bonding unit.
According to the present invention the mixing unit and/or the
dosing unit or the cross-plaiter of a device for carrying through
any of the described processes can be equipped with a spraying,
pulverizing and/or straying assembly. In addition, the bonding unit
can be followed by an essentially known impregnating, slop padding
or coating unit or by another bonding unit, preferably a perforated
drum or belt dryer.
DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only and thus are
not limitative of the present invention and wherein:
FIG. 1 shows a device for the dry production of a web with a
subsequent thermic bonding unit; and
FIG. 2 shows a device for forming, needling, impregnating, bonding
and drying of a carpet length, for example.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a web fiber mixing machine marked 1. The fibers are
disorderly fed into the funnel-shaped mixing trough 2 by means of a
conveyor belt 3. In the funnel 2, the fibers are continuously mixed
with a powdery, granular or fibrous bonding agent 4. After having
been thoroughly mixed with the bonding agent 4, the fibers are
guided onto a conveyor belt 5 which transports them to the
pneumatic web layer 6. The fibers can also pass a squeezing unit 7
which can be installed immediately in front of the web layer and in
which a slight pre-bonding of the fiber blend can be obtained under
the influence of heat.
In this embodiment of the apparatus according to the present
invention, the web layer 6 consists of a pneumatic assembly in
which the fibers are separated by air pressure which is provided by
a fan 8, and guided to a pair of perforated drums on which they are
piled up and evenly transported to the conveyor 10. The web which
has already its final form is then bonded in a bonding unit marked
11 and, if necessary, dried. The bonding unit comprises several
perforated drums 12 which are arranged behind each other and on
which the fiber web is uniformly heated and adheres because of a
suction draft. The application of hot air to the fiber web causes
the rapid bonding of the web which is then wound up on a batching
device.
FIG. 2 shows a device for the production of carpets, for instance.
The web of high-quality fibers, which is to serve as a surface
layer, is produced in the above described way or in a machine
assembly 13. In the hopper feeder 14, the fibers which are mixed
with the bonding agent are guided onto a vibration chute 15 from
which they are then transferred into a known web layer 16. A
conveyor 17 transports the completely formed but still unbonded web
to the cross-plaiter 18 which comprises three conveyors and where
the web is rendered thicker before being put crossways onto the
carrier fabric which is supplied by the conveyor 19.
It is possible to put a bonding agent between the individual
layers. Without any pre-bonding having been effected, the
double-layer material length is then fed into the needle looms 20
and 21 where the carrier layer and the still unbonded fiber web, in
which the bonding agent is evenly distributed are mechanically
united. The final step of the carpet production is the thermic
bonding process which can take place either immediately afterwards
in the apparatus 22 or later, i.e., when the material has passed
another impregnating or coating unit 23, in which further additives
are applied to the material length in order to improve its tensile
strength.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be apparent to one skilled in
the art are intended to be included.
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