Note: Descriptions are shown in the official language in which they were submitted.
:~7~
The present invention relates to improvements
in or relating to the productiorl of pile surfaced materials.
It has already been proposed to produce a pile on
the surface of a synthetic polymeric material by pressing
the material against the surface of a heated roll and
separating the material ~rom the surface while cooling the
material below its softening point. In this way fibrils
are drawn out from the surface of the sheet and the cooling
action ensures that the major part of each fibril remains
integral with the thermoplastic material. In the preferred
mode of operation of this technique cold air or another cooling
medium is blown into the nip formed between the heated roll
and the thermoplastic material as the thermoplastic separates
from the roll. It has also been proposed to feed the
thermoplastic to the roll as a sheek and to feed a backing
material with the thermoplastic in such a way that the
thermoplastic and the backing material bond together under
the influence of the heated roll. Another suggestion has
been to feed the material as a pre~ormed laminate with the
. . ~ . .
; 20 ~ polymer between the backing and the heated surface. Such
proposals and suggestions are described for example in UK
patent specifications 1378638, 1378639 and 1378640.
In some previous proposals such as UK patent
specification 1169621 a pile surface is produced by forcing
a thermoplastic into cavities in the surface of a roll and
then separating the sheet from ~he roll so that the thermo-
plastic that has been ~rced into the cavities is drawn lnto
fibxilso This type of process suffers from the disadvantage
~ ~ !
"' ' ' ' ' . . . ' :
.' '. ' . ' ~ ~ ',
. '
, . ': . . '~,;., ~ :
,
/,. ' ' ' ' '
~L0709~
--3--
that expensive equipment having accurately machined rolls
is required and that the techniques cannot satisfactorily
be used to produce short piles since the shallow cavities
required for short pile would tend to be clogged with
thermoplastic material. Furthermore, the nature of the pile
(ie. the fibril density and length~ depends upon the depth
and size of the cavities so that only ~ne type of pile
may be obtained using one particular roller.
The present invention is concerned with a process
i 10 in which fibrils are formed from a polymer between a
substantially smooth surface and a backing web by introducing
a polymer between the substantially smooth heated surface and
the backing so that it is softened and adheres to the heated
surface, and also bonds to the backing in the situation
where the polymer and backing are introduced separately other
than as a prelaminate. It is of course desirable that suGh
a process be able to operate as quickly as possible and
the present invention is aimed at speeding up such a process
~: and we have found that i~ the backing web is heated before
the polymer contacts the heated sur-face the process may
operate more quickly.
; The present invention thereore provides a
process for producing pile surfaced material in which a
polymer and a backing web are fed to a substantially smooth
- 25 sur~ace heated to above the softening point of the polymer, ~ .
the polymer being between the backing and the surface so
that it is softened and adheres to said substantially smooth
-: ~ '' ,,'
: . ' ' ,
'
. .
~C~7~
--4--
surface, withdrawing the backing web wi.th the polymer ?
adherent thereto from said surface so that ibrils or
tufts of said polymer are drawn out between said backing
and said surface, cooling said fibrils or tufts character-
ised in that the backing web is heated at a position prior ~
' . to contacting position where the polymer contacts the heated ,.
surface from which it is drawn into fibrils or tufts.
In a preferred process the substantially smooth
heated surface is a roller which is heated internally to . ,~
. lO a temperature above the melting point of the thermoplastic.
It is to be understood that within this specification the
term substantially smooth'includes surfaces which have a
satin finish'or have been shot or sand blasted but excludes
surfaces in whi'ch'definite cavities are formed into which
l~; 15 the polymer is forced to form fibrils since with cavited ~",
;~ , rolls it is not possible to obtain the wide range of pile
,~. types that can be achieved using the present invention.
i:. Examples of surfaces which fall within our definition '~
i,.. ' include polished metal surfaces such as steel or chrome
', 20 and satin finish metal rolls and sand blasted metal rolls :-
, and the rolls may be coated with materials such as
,.: , polytetrafluoroethylene which modify the adheslon properties :'
,'~ of the surface. The substantially smooth surface may however
.,
:~';,~ be a continuous belt~ It is preferred that the polymer
'~ 25 and backing web are pr~ssed into contact with each other
,' and into contact with the heated surface by a resilient
~', backing means, It has been found that this contributes
,' to the increasé in the speed at which the process may be
!"~ .;.'
,. . .
, . . . . .
:::'. . :. '
.~ . . . .
.' :'. ' :
:.,
:. ,
~97~ 9
-5-
operated which is thought to be because the resilient
means ensures good contact between the polymer and the
heated surface and the polymer and the backing web despite
irregularities in the roll surface. It has been found
that this may conveniently be achievecl by feeding the
materials to the heated sur~ace arouncl a resilient
co~ered lay-on roll.
It i5 also preferred that the thermoplastic
be held against the heated surface by a pressure roll or
; 10 a belt during its contact therewith as well as at the point
of initial contact. Whether a belt or roll be used it is
preferred that it is resilient material to allow a
predetermined amount of compression as the material is held
against the heated surface with the backing material between
the thermoplastic and the pressure roll or belt. A urther
possibility is that the thermoplastic may be held against
the heated surface by the tension in the backing material
which bears against the thermoplastic to hold it against
' the heated surface. It is however preferred to use ancilliary
means such as a roller or a belt particularly since the
roller or belt will pick up heat due to its proximity to
; the heated roll and the backing material may be preheated
by passi~g into con~act with the roller or belt.
The means which cools the fibrils is necessary
to ensure that the fibrils which are drawn out from the
sheet remain adhering to the thermoplastic and do not stick
permanently to the heated surface. In addition it is
important to have cooling to al~ow the process to be
,. .
, .,
: ' ' . . , ::
:. :
:~7~3~
--6--
operated at increased speeds, for the production of any
particular type of pile. A preferred method oE cooling
is to use a jet of cold fluid e.g. air particularly which flows
into the nip formed between the heated surace and the
material as it moves away from the surface, cooling should
be uniorm and thus the jet should extend across the total
width of this nip. It has been found that the actual
direction of the 3~et of cold air is important and it is
also important to allow as free a circulation of the air
as possible in the spacè between the heated surface and the
material. Therefore it is preferred that the cooling air
be directed from a narrow slit orifice of width less than
l,-preferably less than 0.5 millimetre under a comparatively
high pressure against the heated surface at a position just
beyond the point where the pile separates from the surface
;
in such a way that the jet is deflected by the surface into
this space. Thus the combination of the position and ;
direction of the cooling jet and the path the material takes
as it moves away from the roll to a large extent determine
the type of pile that can be obtained at any particular
operating speed. The fibrils or tufts may also be cooled
by directing a jet o coolant onto the side of the
backing furthest away Erom the heated surace. This
is particularly useful when the backing material is
porous and the cooling gas passes through the backing
material into the fibril forming area.
The path that the thermoplastic material
.. j , .. , ~ .
.~
-
:: :
' :~ ' ' ' '
. :: .. .
.: : . ~ ~ .
adopts as it leaves the heated surface is preferably con-trolled
by withdrawing the material over a bar situated close to the
heated surface as is described in British Patent Specifications
1378638, 137~639, 1378640 and Belgian Paten-t No. 807879. The
particular path chosen depends upon the thickness and nature
of the thermoplastic material and the type of product required.
It has been ~ound that small variations in the path of the
material and thus a different pile structure may be achieved
by simply altering the distance of the bar from the surace.
It is important that the bar be rigid to ensure uniform contact
~etween the sheet and the heated roll. Accordinglyr the shape
of the bar should be chosen to provide both the required path
of the sheet as it leaves the roll together with the necessary
rigidity. The bar is therefore not necessarily of circular
cross-section. This apparatus has the added advantage that it
is extremely versatile as not only may the pile be altered by
varying the distance of the bar from the roll but considerable
. .
variations in product may be achieved by altering the size and
x~ shape of the bar. In a further embodiment the bar may act as
20 an air knife which cools the thermoplastic, in this embodiment
the bar is provided with a slot or holes through which cooling
fluid such as cold air may be directed onto the web.
It has been found that in a process in which -khe pile is
;; formed against a substantially smoo~h sur~ace there are several
.,, . ~ .
~ fac~ors which effect the speed at which
J', ' `
. ~, . . .
.~' ' ' .
,~ - 7 -
... . . .
~, .
3~,
,:i .
1a~7~9~
a catisfactory pile may be obtained. The optimum condltions
for the production of any one type of pile depends upon
the particular thermoplastic material.
Thus subject to other process variations it is
preferred that the material be d~awn sharply away from the
heated surface leaving as large a space as possible betwe~n
the material and the surface so that a cooling fluid such
as cold air be blown into this large space which allows
for good circulation and escape of the fluid. The space
between the material and the heated sur~ace depends upon
the path or the material and hence the provision of a
means which controls and reduces this radius of curvature
and allows greater production speeds to be used. It has
also been found that production rates may be further
increased if the back of the web is cooled as it is parted
from the heated surface! Accordingly, where the means
which controls the radius of cur~ature of the sheet of
thermoplastic as it moves away from the heated surEace
is a rod around which the material is withdrawn it is
preferred that it be internally cooled and/or be of a
shape such that it can direct cooling gas such as cold
air onto the back of the web.
The techniques of the present invention allows
a further increase in the speed at which the process may
be operated by heating the backing material at a postion
before the polymer contacts the heated surface. The
:: '
techniques of the present invention are particularly useful
,,~ ,, . , ,
.~ '
! .' ' ' ' ' . : j
',' ' ' , '~ ' '` ' '`"' ' ' ' '
. ~ ' '~. ' ' .
. ' ~ ' ,, , ', ' . ' .
_9_
~hen the polymer and backing are fed separately to the
heated surface and are bonded together due to the heat
from the substantially smooth surface melting the polymer.
To this end the backing material may for example pass
around a heated roll such as the backing pressure roll if
one is used, or it may be indirectly heated by for example
passage under an infra-red heating lamp or through a
heated air tunnel. It has been found however that a
simple adjustment so that the backing passes around part
of the circumference of the pressure roll results in a
considerable in-crease in maximum speed at which an
aersthetically pleasing material is produced; the pressure
roll may be heated directly by internal heating or by
contact with another heated surface or roll, Eor example
the substantially smooth heated surface. The backing
material may be heated from the front, or back or both
and before and/or after being brought into contact with
the polymer. The temperature to which the backing material
should be heated depends upon the nature of the backing
and the thermoplastic. It has been found however that
providing the temperature is not so high that the thermo-
.
plastic or the backing is clamaged the higher the temperature
the faster the pro-cess may be operated.
In a preferred process the synthetic thermo-
plastic material is in the form of ia film and may be any
of thé well-known film forming materials. Examples of
,
suitable materials include polyolefines, particularly high
and low density polyethylene, polypropylene and olefine
`~ copolymers, polymers and copolymers of vinyl chloride polyrners
and copolymers of styrene, polyesters and the various nylons~.
, ~ 1 ~
;. ~: , . - ~:
~! ~
r
i~ ,
.
~ t7~39~ ~
- --10--
The choic~ oE material will of co~rse depend on the particular
type of product that is required and the uses to which it is to
be put. - ! ,
The cholce ol backing material will depend upon
the desired nature of the produc-t; The use of paper as a
backing presents problems as compared with meshed backings
such as fabrics and open-celled foams since the surface of
the paper has few points at which it can key to the thermo-
plastic and thus it is more difficult to achieve a good bond.
Furthermore, when using an open mesh backing such as a
fabric the fibrils may be mor0 eEfectively cooled from the
back by directing a cooling fluid through the backing into
the fibril forming arèa. Thus, when using paper as a
backing the material is pre~erably cooled from the front
as it separates from the surface and the more effective
the cooling the higher the speeds that may be used. A
preferred methbd of cooling is to blow cold fluid preferably
air into the gap between the heated surface and the
thermoplastic and thus good circulation and escape of the
cooling fluid is important for high production rates.
The techniques of the present invention are very useful
when paper is used as a backing. It is preferred to with-
draw the material rom the roll over a rod at a sharp angle
to provide a wide space for circulation of the cooling fluid.
Polyethylene and paper is a particularly suitable combination
from which to produca backed pile surfaced products and the
` feedstock may be separate sheets of paper and polyethylene
or polyethylene coated paper.
The temperature at which the heated surface
should be held depends upon the nature of the thermoplastic
j material. However, providing the temperature is not so
--/c,~ ~
.' ~ '
` ~L070~L9
high that the thermoplastic is adversely affected, the
higher the temperature the higher the production rates
-that may be used. For example, roll surEace temperatures
between 160C and 180C are particularly suitable when
processing low density polyethylene a-t speeds up to 5 metres/
minute, The higher the roll temperature and production
speed the greater -the need to control the path of the material
and cool the fibrils effectively to ensure that they separate
from the heated surface at the desired point to give the
required pile length. In addition with processes operating
at these temperatures it is preferred to cool the back of the
web as it is withdrawn from the roll surface even when using
a backing such as paper which has a low porosity.
This back cooling improves the abrasion resistance
of the pile and it is particularly preferred to draw the
web from the roll over a suitably shaped internally cooled
bar. In order that the invention may be more clearly under-
stood preferred embodiments are described with reference to
Figures 1 to 10 and the Examples, Figures 1 and 3 to lO are
diagrammatic representations of the arrangements of the rolls,
backing web and polymer in the various embodiments of the
invention. Figures 2 illustrates an apparatus which does not
fall within the scope o~ the present invention and is provided
by way of comparison,
Figure l illustrates a machine capable of operating
the present invention and shows a backing web (l) being fed
around a guide roll (2) into contact with a pressure roll ~3)
having a resilient surace (4) and bein~ heated by thq heat
picked up ~ pressure ro~ 3) from heated drum (8). The web
(l) passes from the pressure roll to a lay on roll (5) also
having a resilient surface (6); a film of thermoplastic (7)
is also fed to the lay on roll so that it contacts the backing
web and the two pass around the roll (5) to bring the thermo-
.
V~9
plastic (7) into contact with the satin finished surface of
,
the heated drum (8). Both the backing and the thermoplasticpass around the drum (8) wi-th -the -thermoplastic against the
surface of the drum, The hea-t from the drum melts the polymer
which bonds to the backing and adheres to the surface of :
the drum~ The backing with the polymex bondad thereto is ~ '.
then withdrawn from the surface of the drum over a rod (9
so that fibrils are drawn out between the backing and the
, drum, These fibrils are cooled by a stream of cold air
directed from nozzle (10) so that they break away from the
surface of the drum to yield the pile surface product (11)..
. The machines shown diagrammatically in Figures 2
J " to 4, 6 to 10, use numbers referring to the same features as
in Figure 1~ In Figures 2 to 4 and 6 roll (3) is similarly
, heated by contact with heated drum (8). The nomenclature used ~ ~ .
.` to describe the relative positions of the hot roll 3, guide
rod 9 and air jet 10 is illustrated in Figure 5~ Position 12
denotes the position of surface temperature measuring device.
~ In Figures 7 to 10 roll 13 is backing heating roll~
,; 20 EXAMæLE
~ A film of green pigmented low density polyethylene,
.~, ,
. ~ 6S microns thi.ck was continuously fed together with a backing
of blended sulphite/sulphate paper of substance 70 gram per
square metre into the apparatus as illustrated in Figure 3.
, The machine settings used according to Figure 5 were: :
X = 1,7 mm
.; ., .
= 2,0 mm
. d = 0,6 mm
~; r = 3,0 mm
a = 40
.. ~ . .
- 12
: .
,.
., ~ , .'
~ . .
..
.~ . ` .
1~70~9
The temperature of roll (8)i wcls rn~intained at 170C as
measured at p~sition 12. A constant air flow was supplied at
420 Nm3/h from the jet (10) througll a gap of width 0,2 mm over
a breadth of 740 mm. The speed at whicll the film and ~acking
were ed to the web and the speed of rotation of the hot roll
were gradually increased until the product ceased to exhibit a
visually attractive pile. This speed was found to be 3,5 m/min.
No lamination of the film to the backing appeared to have occured
due to the heat imparted to the backing by roll 3 because
in a sample of film/backing cut from the web around roll 5
before contact with roll 8, the film could be peeled from
the backing. For comparison, a film oE green pigmented low
density polyethylene 65 microns thick was fed together with
a backing of blended sulphite/sulphate paper of substance
70 grams per square metre into the apparatus illustrated
in Figure 2 wlth the same machlne settings. Machine speed
was gradually increased but the product ceased to exhibit
a visually attractive pile at a speed of only 2,5 m/min.
EXAMPLE 2
The low density polyethylene film and the blended sulfite/
sulfate p2per backing used in Example 1 were fed into the
apparatus illustrated in Figure 4, the machine settings were
the same as in Example 1.
The machine speed was gradually increased until the product
ceased to exhibit a visually attractive pile which was found
to occur at a speed of 5 m/min.
: ~ .
- ~/3 ~ ~
.
;3 '
.
~7~9~.~
EX~MPLE 3
A film of non-pigmented low density polye-thylene, 150 microns
thick was fed to~ether with a backing of bleached Kraftpaper
of weight 120 grams per square metre into the apparatus
illustrated in Figure 3.
The machine set-tings according to Figure 5 were:-
X = 6,1 mm
Y = 4,9 mm
d = 2,0 mm
r = 10 mm
a= 28
The temperature of r-ol~ (8)lwas maintained at 160C as
measured at position 12. A constant air flow of 360 Nm3jh
was supplied from nozzle 10 through a gap o~ width 0,2 mm
over a breadth of 800 mm. The speed of the machine was
gradually increased until the product ceased to e~hibit
a visually attractive pile. This speed was found to be
1,85 m/min. As in Example 1, no lamination of film to the
. . i . .
backing appeared to have occurred due to heat imparted by
roll 3.
-~ 20 For comparison, the low density polyethylene film and
bleached Kraftpaper backing were fed into an apparatus as
shown in Figure 2 using the same machine settin~s. The
machine speed was gradually increased until the product
ceased to exhibit a visually attractive pile. This speed
- 25 was found to be only, 1,4 m/min.
, ,. . -
" . : -
.. - . . . .
~'.: ' :
, . .
.
'~ ' ' ' ' .
i: _ J~f_
~tJ"~
7(~9~.~
15-
E~XAMPLE 4
The procedure of Example 3 which used apparatus illustrated\in
Figure 3 was repeated using the same c.onditions but using
apparatus illustrated in Figure 4. The maximum speed at
- S which an aesthetically pleasing ~ile surfaced ma-terial
could be produced was 2.7 m/min.
In the above Examples, the piIe-surfaced materials produced
on Apparatus illustrated in Figures 3 and 4 appeared to have ~ -
greater resistance to abrasion than that of comparative
materials produced on the Apparatus illustrated in Figure 2.
In Figures 1,3,4,6,7 and 9 the backing web ls heated from
the back, but in Figures 8 and 10 the backlng web is heated
from the front.
,~ ' . ' .
' ~ ' '
1 ' ;
., . -
~; '
~
.
. . .
,,,, _ / ,~
;,~
~. ~r~
