Note: Descriptions are shown in the official language in which they were submitted.
B~CKGROUND_OI TIIE INVENTION
A process for the productlon of shee~ products with
fibrous surfaces has been known in the prior art in which the
sheet products are composed of a substrate which is covered
with a thermoplastlc fiber nap. The substrate acts as a
carrier. This process presses polymer foils on a heated drum
until they begin to melt. As the molten polymer foils adhere
to the drum and to the substrate, the substrate is drawn off
with a simultaneous cooling of the molten film. Following
this drawing process, a plurality of uniform fibers are formed
from ~the molten polymer. These fibers adhere to the substrate.
This process produces surfaces which have textures of velour,
plush or pelt (see, for e~ample, U.S. Patent No. 3,708,565).
-~ The prior art required a polymer-unrelated substrate made
.''! out of textile fabric, paper or fleece. However, many enterprises
required plastic webs or films with fibrous outer surfaces with
substrates which consisted totally of polymeric materials. It
is desirable that a substrate be produced out of fiber naps in
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which the fibers combine the positive properties of several
polymers which have been amalgamated within the fiber.
Alternatively, it ~s desirable that the fibers should consist of
another polymer, similar to the substrate.
SUMMARY OF THE INVENTION
An ob~ect of this invention is to provide a process for
the production oE a polymer substrate with a Eibrous surface.
In one particular aspect the present invention provides
a process for producing~polymeric substrates.having fibrous
sur~aces comprising the steps of: drawing a precursor polymeric
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~-`lm al~ng and i~ contact with a drawlng surEace having a
melting zone; ~leatlng th~ pr~cur~or polymeric film :in the
me:Lting zone to melt the surface adjacent the drawing surface
and yield an unmelted substrate covered with a film of molten
po:Lymerlc component; and deElec~ing the unme:Lted substratecovered
with the fllm of molten polymeric component from the drawing
surface while simultaneously cooling the molten component, whereby
fibers are formed which are strongly bound to the surface of the
substrate.
10Previous to this invention, processes which involved the
use of calendars or extrusion were known in the prior art,
but were characterized by the great difficulty or the impossibility
- of amalgamating or compounding polymers.
DETAILED DESCRIPTION OF THE INVENTION
; According to the process of this invention, a polymer
film with a thickness of at least 50 mlcrons, and preferably
. 150 microns, is applied to a heated drawing surface upon which
the film will cling until drawn away. Part of the film will
melt and cove~ the unmelted film or substrate. The unmelted
:.......................................................................... :
substrate may be half of the total film thickness. For example,
if a thickness of 50 microns is used, then not more than 2/3
of the polymer (30 microns) is to be melted. Otherwise there
is too great a risk of breaking or tearing the substrate as
it is being drawn away from the heated drawing surEace. Fo]lowing
melting, the nascen~ Elbers are drawn away Erom the drawlng
surface and stabilized under simultaneous cooling. As a result
the melted part of the film is detached from the heated surface
thus commensing formation of a fiber nap. The unmelted part of
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the film is the substrate for the newly formed fiber nap. This
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~iber nap adh~res very strong:Ly to the proxlmate surface oE the
substrate.
~ lso thls inventlon of.Eers a possihility of making the film
as a compos:ite with 2 or more diEferent polymers layered upon a
substrate cons:Lsting of another polymer~ These films are made
by using polymers with distinctive melting polnts and/or melting
viscosities. The total thickness of the combined polymers in
.` the film should be at least 50 microns, and preferably 100 microns.
The composite ilm is then applied to the heated drawing surface.
In the composite film, a polymer with the lowest melting point
and/or lowest melting viscosity is deposited so that it will be
~ closest to the heated drawing surface. This invention provides
.~ for a relatively uniform mixture of fibers by mixing of the
molten polymers. Following the melting of the desired portions
of the film, intimate mixing is assisted by the shearing stress
which is formed between the unmelted substrate and the heated
: drawing surface during drawing.
This.invention can be further modified such that two or more
,- . .
films of different polymers are applied successively on the
` 20 drawing surface, rather than simultaneously. Still further,
.:,. this invention makes it possible to draw one of two or more .. ~. -.
::` different layered polymers, which comprise the composite film,
upon the heated drawlng surface, and then to melt and pull the
~ layer away from the heated drawing surEace causing the formation
': `:'
` of homogeneous or heterogeneous fiber naps which adhere on the
~ unmelted film substrate.
This modification of the invention makes po~sible very simple
operations for the production of polymer substrates with fibrous
. surfaces. Of all the horizontal polymer layers present, the ~:.
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~ibers c~re ~ormed only out of the me:Lted polymer layer whicll
is, for exampIe, proximate ~o tlle heated drawing xurface.
Another mo~lfLcation provides for the addltion of
polymers ln the form of particulate matter, such as granules
or powder, upon the polymer substrate.
An essentlal characterlstic of the inventlon is that
~ the nascent fibers are cooled until they are hardened,
; stabili~ed an~ solidified. The invention provides for
cooling which operates within the drawing angle, which is
, .
between the unmelted film residue which forms the substrate
and the drawing surface. Air cooling is preferable. It may ~.
be advantageous to conduct secondary cooling of the substrate
on the back side which is opposite the side to which the
fibers adhere. Also with secondary cooling, one can prevent
single or combined films from completely melting through.
. ~, ,
The cooling may, indeed, take place along with all of the
steps of feeding the film, for example by means of back side
coolers, or it may take place only in a single zone.
Polymers which have in the molten state a low viscosity
are suitable as a meltable thermoplastic Eilm andlor as components
.: ,
of a`composite film and as the substrate include, inter alia:
polyethylene having a MFI 190/2 of 10-300 grams/10 minutes;
ethylene/vinyl acetate having a MFI 190/2 above 10 grams/10
minutes; polypropylene having a MFI 190/5 of 10-70 grams/10
;, .
minutes; polymethylmethacry:late havililg a MFI 2:lO/10 above 10
, grams/10 minutes, cellulose acetate, cellulose acetate-butyrate,
and cellulose propionate, CA, CAB, CP having a MiFI 190/2 about ~ `
;! 8; polyoxymethylene having a MFI 190/2 above 13 grams/10 minutes;
polyvinyl chloride/acetate having a K value below 60 and
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C taining ~It least 15% plasticizer, polyam:lde 6 h~vln~ a
relative vlscosLty between 2.1 ~n~l 3.~; polyamide 12 having a
relative viscosity between 1.7 and 21.:l; and polyethylenetere-
phthalate having a relative viscosity above 1.6; and soft
polyvinyl chlorlde.
Polyvinyl chloride is preferred as the molten component.
The following considerations, inter alia, govern the selection of
, .
'~ polymers.
~ ~ A low melt viscosity improves the adhesion so that much
.
~ 10 more fiber nuclei are formed than in the case of a high melt
, .
viscosity.
A molten material at a high temperature results in a lower
melt viscosity so that the f iber-drawing time is prolonged, and
., -, .
i this prolongation provides for a longer time in which measures
;~ to control the process can be carried into effect.
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~, The mechanism of the fiber forming process oE the lnvention
`~; is that the forces of cohesion in the polymer cause the solidified
' fibers to visibly constrict near their point of contact wlth the
heatable drawiLIg surface causing tearing and breaking apart at
a distance from the drawing surface. The distance traveled by
., ~ .
the substrate prior to deflection depends on the curvature of the
~ heatable drawing surface. Within the scope of the invention, the
;; , distance traveled may amount to between a few millimeters and some
~ centimeters, preferably between 5 and 50 millimeters and up to an
~. J
~, upper limit of about 100 millimeters. As a result oE the
~ .
deflection of the substrate, the root portion oE the fiber is
withdrawn from the intense action of the flowing molten fluid so
that this portion is extended to a smaller thickness and a
~ ~1 longitudinal malecular orientation is imparted to the fibers
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fore the t-ips of the fibers ars~ torn Erom the heated dr~wing
surface near thelr upper encls.
It has been found to be necessary to provide for a
- proportionality or approxlmate:ly proportionality between the
solidification ra~e of the polymer and the flbers' temperature.
Thus, if the solidificat:Lon ~s too rapid, the molten polymer is
torn apart only as coarse fibers so that flakes rather than the
desired fibers would be formed from molten material of high
viscosity, whereas only thin filaments having bulblike roots
could be pulled from molten polycondensates of low viscosity.
For this reason, the process of the invention is applied
-~ primarily to polymerization products which have a low molecular
weight and, correspondingly, a high melt index.
On the other hand, the use of highly crystalline high
` polymers, particularly of polycondensates of such polymers, is
rendered difficult by the high crystallization rate. It has
thus proved desirable to use such high polymers ln the form of
copolymers or in polyblends together with other polymers so that
the tendency to crystalli~e is reduced and the solidification
range is increased. For instance, pure polyoxymethylene ~POM)
when used alone results in thin and brittle Eibers but, in
admixture with 10% by weight low density polyethylene, it can be
.
used to produce a useful product having a catsklnlike feel or
hand. An admixture oE polyamides Erom POM also improves the
fiber-forming process. On the other hand, pure Polyamlde 6
(PA 63 when used alone results in thin fibers which look like
. . :
cotton-wool. If this material is copolymerized with Polyamide
66 (PA 66) or with ethylene or is mlxed with 12% by weight poly-
me~hylmethacrylate of low viscosity, a fabric-like textile plush
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n be produc~cl. ~lix~lrcs oE PolyaolLde 6 (PA 6) with Polyamlde
11 (PA 11) or PA 12 or P~ 6.10 exhlblt a wlder sol:Ldlflcatlon
range; in thcse cases, ~he .;econd component may be added in an
amount ~Ip to 30% by ~eight. Other mixtures which have given
favorable results comprlse saturated polyesters, such as poly-
ethyleneterephthalate or polybutyleneterephthalate, together wlth
Polyamlde 6, PA 11, PA 12 or copolyamides. The fiber-forming
process and the quality of the product can be improved if such
polyblends are addltionally cross-linked as they are processed.
; 10 The use of pure polypropylene (PP) having an MFI at 190/2 of
20 normally results in a fiber having a thickness of, e.g. 10
microns. The addition of Polyamide 12 reisult~ in increasingly
; thinner flbers until the proportlon of PA 12 is so large that a
structure like that of cotton-wool is obtained.
: , :
Inorganlc substances, such as flllers and dyestuffs or
additives have a high thermal conductivity, and when used in the
, polymer layer accelerate solidification during the formation of
fibers. In most cases, such fibers tear off sooner. In the `
process according to the invention, the use of such substances
in a concentration up to 50% by weight is facilitated by the use
., . :
-~ of polymers having a low melt viscosity.
;~ ~An important feature of the process of the invention is that
the polymer substrates are deflected by at least 5 and at most
90~ from their direction of travel along the drawing surface.
;~ :
The degree of deflection of the substrate is chosen mainly by
consideration of the nature of the polymer and of the desired
quality of the product. Where mainly linear polymers are used,
a larger angle of deflection is preferred than with branched
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polymers. Optimum results are to be expected if, in the
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rroce~sing of polyoleflns (otller than low densLty polyethylene),
the angles of deflection lie bctween 30 a~d 80 whereas ln the
processing of low densLty polyethylene they slloul~l lie in a range
between 10 and 60. Ill the process:Lng of saturat:ed linear
polyesters, the selected angles lle wlthin the range of 50 a~d
80 and in the processing of cellulose acetate and cellulose
acetate¦butyrate, this selected range if between 20 and 60.
Polyblends can be processed with good results if the angle of
deflection, also known as ~he drawing angle, i9 at least 80~.
The polymer film is supplied to the fiber-forming region
at a temperature which i.s above, and preferably considerably above
its melting point; i.e., at a temperature of 10-200~C above the
~` melting point. This temperature melts the polymers closest to
the melting zone.
Another feature is that, for example, a small soft mass of
,j polyamide in which there are wads o~ polyethylene or polyamide 6.6
~1 which is compressed with polymethylmethacrylate, can be used in
the invented process.
BRI~F DESCRIPTION OF THE DRAWING
Figure 1 is a magnified representation of the fiber drawing
- process in which a single film has been applied;
, Figure 2 shows the fiber drawing process with two films
each respectively representing one of the two polymer layers o~
thecomposite film; and
Figure 3 shows the fiber drawing process with the application
of three polymer layers.
DESCRIPTION OF PREFERRED EMBODIMENT
Figure 1 represents a heatable drum or drawing surface 10.
The drawing surface moves in the direction of the arrow 12. The
; 30
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~ ly~ner f :i~.m 11 runs first throu~h a meltlng zone 13 in whicll it
is mel~ed as is indlca~ed by ~lle arrows li~ and the dotLed line~
15. As was prcv;ously stated, no more than 2/3 of E:Llm 11 is
per~itted to be melted. The un~elted portion of Eilin 11 ls
substrate 16. The polymer passes througll thls ~one layerwise
in a molten condition. The drawlng surface 10 ls heated above
the melting po:Lnt of the polymer. The substrate 16 is not melted.
Next to the melting zone 13 ls the actual fiber formation ~one
17. At the beginning of this zone the fllm 11 shows a more solid
consistency on the substrate 16 as the substrate is drawn away
from the drawing surface 10 by the deflector 29 under simultaneous
cooling. In the preferred embodiment, secondary cooling is used
and is arranged as backside cooler 40, which acts to prevent the
substrate 16 from completely melting and consequently breaking
under the stress caused by drawing. By drawing away the substrate
16, the fibers 18 are formed on the proximate surface of substrate
16. These fibers are formed as a consequence of the temperature
drop which resulted,as the molten polymer was torn away from the
heat,ed drawing surface 10. By this means, individual torn points
of the fibers 18 are formed on the drawing surface 10. After
pulling away and deflecting the molten polymer and the substrate,
a residue film 19 adheres upon the drawing surface 10. The
deflector 29 is so constructed that it can simultaneou~ly provide
for cooling of the residue film. Also a cooling apparatus operates
in the directicn of arrow 39 directly inside ~h~ drawing angle
between the drawn film and the drawing surface. Through the
cooling as indicated by arrow 39, the nascent fibers 18 are
... .
', stabilized so that they form a continuing fiber coating on the
", substrate 16. The individual fibers 18 are firmly and durably
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- l~oun(l witll the substrate 16. The len~th and qucllity of ~he
fibers 18 can be a:Ltered by adjusting the intensity of the
coollngl by al~er:ing the def:Lecting angle, by challglllg the velocity
of the drawing surface and by controlling the temperature of the
drawing surface. Also c~ntributing to the quality and the length
of the fibers 18 are the coolln~ system and the drawing tension.
Similarly, the depth of melting can be controlled, for example,
by choosing the thickness of the layering. In order to obviate
the problem of completely melting both the substrate and molten
component, in practice one varies the depth of the layers which are
; passed through the melting æone.
Figure 2 shows two films, 20 and 21, which are present on the
drawing surface 10. Films 20 and 21 may be different polymers
~ or they may be polymer isomer which have different melting points
i or differerlt meltlng viscosities. As is shown by the dotted line
25 which illustrates the depth oE the melting, film 20 has com-
petely melted in the melting zone 23, while there is stlll an
~, ~
unmelted residue of film 21, which is substrate 26. The melted
; polymer components are, for example, mixed with each other
intensively through the influence of the shearing stress 22. In
the fiber formation zone 27, a good union of both film polymers is
achieved. Next, fibers 28 are formed. The properties of fibers
28 will be dependebt on how much of the lower film 21 is melted and,
therefore, mi~ed wlth the molten polymer of the upper film 20.
Figure 3 depicts a third modification. Figure 3 shows the
drawing surEace 10 with 3 polymer Eilms 30, 31 and 32, respe.ctively.
Three polymers, which could be different polymers, form miY~ed
~ibers because fllms 30 and 31 melt completely in the melting
' ~ zone while a part of the third fi.tm 32 is melted. The substrate
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is the unmeLted res-ldue of film 32. In the fiber formatlon
zone 37, the mixed fibers 38 are drawn. Tlle mixed fibers 38
consist of a mixture of the polymers of f il7ns 30 and 31. By
ad~usting the melting dep~h (see dotted line 35) one can achieve
inclusion of a definLte part of the third polymer fllm 32.
Similarly, adj-lstments can be made which will preclude inclusion
of any polymer of film 32 in the polymer mixture (of layers 30
and 31) which will form the fibers. Such a process makes it
possible to utilize special physical properties, such as adhesive
or binding properties, of the polymer of film 32, such special
qualities can be adjusted to meet the unique requirements of
utility for special cases of application. A cooler which is
used for the production of the fiber nap is indicated through
` the arrow 39. By using this cooler, immediate stabilization of
the nascent Eibers is assisted. The melting roller 10 can be
;`l replaced with another customary melting apparatus such as a
heatable conveyor belt installation.
With the invented process, one can produce thermoplastic
webs, substrates and sheets having fibrous surfaces; previously,
this was not feasible. According to what was well-known in the
prior art regarding the operation of processes of extrusions
or spreading vent nozzles, blending could only be produced with
difficulty if it could b~ produced at all.
The process of the invention is especially suitable Eor
the production of new artlcles which could not be produced
.. . .
feasibly by the prior art. Polymer webs, substrates or sheets -
have always had a smooth glossy finish which was maximized by
calenders which transformed the surfaces. According to the
present invention, these films, sheets and webs can be produced
~. ;. .
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economlcal:Ly with velour, plusll or pel~ ke surfaces. Further-
..lore, these r~sults can be procluccd o~tt of one and the same
meltable matcrlal :Ln ~n economical process wlthout the need of
either any mater:ial in addltLon to the molten polymer component
and the polymer snbstrate or more steps in ~he process.
Such a new mater:lal opens the previously-known film, sheets,
and web materials to completely new possibilities. For example,
this invention could be applied to decorated regions, pouched
articles, floor, wall or celling overlays, for packaging, for
outer clothing, for cars, power propelled vehicles, trailers,
boat building, shoes and stuffed animals. Furthermore, numerous
variations or after treatments can be made to the invented
:~ ,
process such as stamping, shearing, embossing, friezing or printing.
This economical process of production by a systematic
operation without the requirement of a non-polymeric material will
have, for the seller, lmportant favorable eEfects on the price
structure. This effect will, of course, be important for a great
volume of sales. A further important modification is the
independence of the products produced by the claimed invention
from the fiber market. Furthermore, another advantage is that
~` the quality in form of the produc~s of the present invention can
. ............. .
be determined by the operator ~f he makes simple adjustments.
EXAMPLE 1
Using the apparatus as shown in Figure 3, film 30 is
polyamide 6 with a melting viscosity oE 2.1 to 3 b~, film 31 is
polyethylene 190/2 from 10 to 300 g./10 minutes and Eilm 32 is
polyamide 6 with a melting viscosity of 2.1 to 3.4. The thickness
of each film is 50 microns. Films 30 and 31 are supported by film
' ,:j','
32 which acts as a substrate. Films 30 and 31 encircle the
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~awing surface 10 as f~lm 32 :i5 dra~/n. The me:Ltlng zone 17
is on the drawing surEace L0. Zone 17 :Lncludes the areas of the
drawing surface ln wh:lch the temperature i.5 about 240C - a
temperature wh:lch ls larger than the melting points of both
polyamlde 6 and polyethy:lene 190/2.
Film 30 is completely melted. The temperature is also in
excess of the meltlng point of polyethylene 190/2; film 31
completely melts. A part of the substrate - film 32 (Yolyamide 6)
is melted. Because of the use of a backside cooler 40, film 32
melts only to a depth indicated by arrows 35. No more than 2/3
of film 32 is melted; melting more than 2/3 would risk breakage of
the substrate because of drawing tension. ThereEore, at least a
20 micron thickness of film 32 must remain unmelted. The depth
of melting can be controlled for example by regulating the amount
of heat ~ransferred from the melting zone to the proximate solid
film. Molten polymer still covers film 32. The deflector 29
guides film 32 and its covered surface away from the heated
drawing surface. The nascent fibers are then stabilized by cooling
- air which is blown in the direction oE arrow 39 from a cooler. The ;
fibers are strongly attached to the polyamide ~ substrate.
-~. Finally, the fibrous product is removed from the apparatus.
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