CA1045323A - Apparatus and process for the production of pile surface articles - Google Patents
Apparatus and process for the production of pile surface articlesInfo
- Publication number
- CA1045323A CA1045323A CA283,692A CA283692A CA1045323A CA 1045323 A CA1045323 A CA 1045323A CA 283692 A CA283692 A CA 283692A CA 1045323 A CA1045323 A CA 1045323A
- Authority
- CA
- Canada
- Prior art keywords
- backing
- thermoplastic material
- heated surface
- pile
- roll
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for the production of pile-surface material which comprises the steps of interposing a thermo-plastic material between a backing and a substantially smooth heated surface, holding the backing against the thermoplastic material so that bonding of the backing to the thermoplastic material and adhesion of the material to the heated surface occurs, parting the thermoplastic material from the heated surface over a bar which provides a curved path having an initial radius of between 1 mm.
and 8 mm. so that fibrils are drawn out from the thermoplastic material between the heated surface and the backing and hardening the fibrils as they are drawn out by a stream of cooling fluid.
The present process seeks to improve both the uniformity of pile produced by this type of process, to allow uniform piles to be produced at higher speeds than before possible and to provide a versatile process which is readily adaptable to produce varying types of pile.
A process for the production of pile-surface material which comprises the steps of interposing a thermo-plastic material between a backing and a substantially smooth heated surface, holding the backing against the thermoplastic material so that bonding of the backing to the thermoplastic material and adhesion of the material to the heated surface occurs, parting the thermoplastic material from the heated surface over a bar which provides a curved path having an initial radius of between 1 mm.
and 8 mm. so that fibrils are drawn out from the thermoplastic material between the heated surface and the backing and hardening the fibrils as they are drawn out by a stream of cooling fluid.
The present process seeks to improve both the uniformity of pile produced by this type of process, to allow uniform piles to be produced at higher speeds than before possible and to provide a versatile process which is readily adaptable to produce varying types of pile.
Description
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The present invention relates to improvements in or relating to the production o~ pile sur~ace~ articles. This application is a divisional application of Canadian Application ;~ No. 186,864, filed November 28, 1973.
- 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 from the surface while cooling the material to below its soft-.
ening point. In this way fibrils are drawn out from the sur-face of the sheet and the cooling action ensures that the major `~ part of each fibril remains integral with the thermoplastic ; material. In the preerred mode of operation of this technique , cold air or another cooling medium is blown into the nip formed "r".,J between the heated roll and the thermoplastic material as the ~' thermoplastic material separates from the roll. It has also -~i been proposed to feed the thermoplastic material to the roll i` ' as a sheet and to feed a backing material with the thermoplastic ~ material in such a way that the thermoplastic material and the '', backing material bond together under the influence of the heated ~ 20 roll.
:,. .': ,. .
In some of the previous proposals a pile surface is ',, produced by forcing a thermoplastic material into cavities in :, 1 .
~, the surface of a roll and then separating the sheet from the roll so that the thermoplastic material that has been forced into the cavities is drawn into ~ibrils. This type of process suf- ,~
,i fers from the disadvantage that èxpensive equipment having ac-l curately machined rolls is required and that the techniques n~ cannot satisfactorily be used to produce short piles since the `' shallow cavities required for sihort pile would tend to be , 30 clogged with thèrmoplastic material. Furthermore, the nature : . . . .:
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~ of the pile (i.e. the fibril density and length) depends -~ upon the depth and size of the cavities so that only one ~,, type of pile may be obtained using one particular roller. ~' `
-, It has also been proposed that in techniques of this type the thermoplastic material which is drawn into fibrils is cold ~' : .:
, ,,;' drawn and oriented and it has been suggested that the material ...... .
~',, be stripped from the heated cavitied roll over a circular .. :.
, . . .
rod so that the polymer is pulled from the cavities in the ','' roll. However, in this technique using a cavitied roller the ' ''' 10 angle at which the material moves away from the roller makes ,~
~' little difference to the density of the pile. An object of ''~
~,',,,',, the present invention is to provide a wide range of pile'sur- -,.' ~ faces and the invention relates to a process in which a pile j"~; surface is produced by holding a thermoplastic material against ,''` a substantially smooth surface held at a temperature above the . .: ~ .::
melting point of the thermoplas-tic material. Under these cir- , cumstances the thermoplastic material melts and adheres weakly ,-' to the surface so that as the polymer is separated from the surface fibrils of the molten polymer are drawn out. Thus, ~....
~i 20 in our process fibrils are formed between the,surface and the ,~ ." .
; 1 thermoplastic material rather than within cavities formed in ;
', the surface of a roll. Such a process is already known but t;~': ` objects of the present invention are to improve both the uni-:$ ' . `.,.
'~ formity of pile produced by this type of process, to allow uni- '~
'';: ,, ,, form piles to be produced at higher speeds than has hitherto "' , been possible and to provide a versatile process which may '-`~
, . . .i .
`x~, readily be adapted to produce varying types of pile.
'~` The length of the individual fibrils produced by our ' ~;', process depends upon the length that can be drawn ou-t from the ~, sheet before the fibrils break and also the position at which .~:';"~ ' ~ . , i; _ 3 _ ~
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gL53'~3 the fibrils break. Both these factors depend on the path , . . .
the material takes as it separates from the roll and the rate ~ at which the material moves away from the surface of the heated ,..... :.......... , . :,:
r,~ roll and the cooling that is achieved. The lenyth of the fibrils that are produced depends upon the path the material takes as it moves away from the heated surface. The fibrils will begin to draw out at the point where the thermoplastic material first moves away from the heated surface and will :.: ....... : , . -.
break off at the point where the speed and direction of the , ~-material and the temperature of the fibril prevents further .:. ~ ., .
stretching. In addition since the surface of the roll is at , a temperature above the melting point of the polymer it is ;~' `` important that there be sufficient cooling in the area formed ;,~ between the surface and the sheet to prevent the fibrils be-,,; coming totally welded together under the influence of the .... . .
~' heated roll. For many applications it is important to have a short pile as this gives improved abrasion resistance. It has however hitherto proved difficult to obtain a short uniform pile since if a sheet takes its natural unimpeded direction ; 20 when moving away from a substantially smooth heated roll the distance between the sheet and the roll gradually increases and ,. ...
the point at which the two separate varies thus producing a non-uniform pile. Furthermore, the restriction of the extent ~``, of cooling reduces the speed at which the process can be operated.
The point at which the material separates from the -~
~ . ~ ;,.. .
heated surface and the path the material will naturally adopt ;
j' as lt moves away from a substantially smooth heated surface de- ~
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pends upon the position of the haul off. If it is situated some distance from the surface the material `~
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adopts its natural radius of curvature accordi~lg to the , .
position of the haul off and we have found that this natural radius of curvature is generally too large to allow the mat-, erial to move away from the h~ated surface sufficiently quickly , . ~
; i to obtain a satisfactory product. This is particularly so when the thermoplastic material is provided with a backing , . :
material, particularly a non-textile backing material such as paper which is one of our preferred backings as it allows easy handlability of the final product and is cheap. In addition ,: ., we have found that if the material is withdrawn by a haul off means situated some distance from the heated surface then the ,. . .
' exact position where the material leaves the surface tends `~ to wander which produces a non-uniform product.
The present invention is therefore concerned with a , :
l process for controlling and improving the texture and unifor-, mity of the pile which is produced by a process in which fib-. ~ . .
rils are drawn out from a thermoplastic material by pressing the thermoplastic material against a substantially smooth : ~ .
' surface held at a temperature which melts the thermoplastic material and withdrawing the thermoplastic material from the surface.
According to the present ivention we provide a pro-cess for the production of pile surfaced materials which com-;, prises the step of interposing a thermoplastic material be-,` tween a backing and a substantially smooth heated surface, holding the backing against the thermoplastic material so that `~
bonding of the backing to the thermoplastic material and ad-hesion of the material to the heated surface occur~, parting the thermoplastic material from the heated surface over a bar '1 30 which provides a curved path having an initial radius of be-.`.,, ' - 5 . . .
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tween 1 mm. and 8 mm. so that fibrils are drawn out from the ' thermoplastic material between the hea-ted surface and the backing - .
and hardening the fibrils as they are drawn out by a stream of . : , , cooling fluid, -Preferably, the substantially smooth heated surface is a roller which is heated internally to a temperature above the melt-`;, ing point of the thermoplastic material, It is to be understood '~ that within this specification the term substantially smooth includes -. .
,, surfaces which have a satin finish or have been sho-t or sand blasted `-,~ 10 but excludes surfaces in which definite cavities are formed into ~-.. :....................................................................... :
,~ which the polymer is forced to form fibrils since with cavitied rolls . .. :
- it is not possible to obtain the wide range of pile types that can be ' :;-. i',i '.' ' ,:
' achieved using the present invention, Examples of surfaces which :' fall within our definition include polished metal surf~ces such as :~ .
steel or chrome and satin finish metal rolls and sand blasted metal ` rolls and the rolls may be coated with non-stick materials such as ' ' polytetrafluoroethylene. The means which holds the thermoplastic ~ material against the heated surface may conveniently be a pressure ,:~ roll or a belt although whichever system is used we prefer that the ~,, 20 thermoplastic material be held against the roll by a resilient mat-,~' erial which allows a predetermined amount of compression as the ! material is held against the heated surface, Alternatively, if the thermoplastic material is i~ film form it may be pressed against the heated surface by the tension in the film it~elf, A further possi-~'1 bility is that the thermoplastic material may be held against the ',, heated surface by the tension in a backing material which bears ''~
, against the thermoplastic material to hold it against the heated ,,1 surface, In this type o~ process the backing may already be lami- , ~ -nated to the thermoplastic material or may become laminated ,' 30 thereto as the thermoplastic material melts during its contact ~ . . .
:;, with the heated surface. We do however prefer to use . .
~; ~L ' , :
3~3 '~ ancilliary means such as a roller or a belt, , ~ The material is co~led to ensure that the fibrils which " are drawn out from the sheet remain adhering to the thermoplastic material and do not sticX permanently to the heated surface, In ' addition it is important to have cooling to allow the process to '~, be operated at increased speeds, the greater t'he speed used the -,~- greatex the cooling needed for the production of any particular type "' of pile, Our preferred method of cooling is to us~ a jet of cold ., . ~ .
~'~ air whi~h flows into the nip formed between the heated surface and :
~'-; 10 the material as it moves away from the surface, cooling should be ,,.;~. iet ; uniform and thus the ~het should extend across the total width of this nip, We have found that the actual direction of the jet of cold air is important and it is also important to allow as free a -~ circulation o~ the air as possible in the space between the heated - surface and the material, We therefore prefer that the cooling air be directed from a narrow slit orifice of width less than 1 prefer-, ably less than ~ 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; this embodiment is described in ~opending patent Application ~o. 186,864, filed ~ovember ' 28, 1973. ~hus 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 thermoplastic ,,l material may also be cooled from the side furthest away from the ~!, heated surface and in one embodiment of the invention the radius of ''"~ .
curvature of the material is controlled by hauling it away from the , heated surface over a suitably . ,.
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shaped bar and this may be internally cooled.
The optimum path that the thermoplastic material should adopt as it leaves the heated surface depends upon the -~
thickness and nature of the thermoplastic material and the -type of product required. We find however that for most products the path may be curved and an initial radius of curvature between 1 1/2 millimetres and 8 millimetres is particularly suitable, if the radius is less than about 1 millimetre there is a danger that ... . . .
~ the product will be damaged; if however the radius is greater . , -, ~ 10 than about 8 millimetres the pile tends to be long and weak. We ;
have also found that the path of the material may best be con- -:.i . .
;, trolled by hauling the material off around a bar and in this way the path of the material may be controlled either by setting , the bar at a predetermined distance frorn the heated surface or , by posltioning the bar close to the surface and selecting thè -~
shape of the bar so that the material takes the required path as , . .: . , ;:
1 it is hauled off over the bar. Small variations in the path of :`~ . '' , .
,1 the material and thus a different pile structure may be achieved ;
by simply altqring the distance of the bar from the surface. It , is important that the bar be rigid to ensure uniform contact `-;~~ between the sheet and the heated roll. Accordingly, 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 r . ' ~'j rigidity. The bar is therefore not necessarily of circular ~
~ ~ :. . "
cross-section. This particular process 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 shape of the bar. In a further embodiment the bar '''r,~ 30 may act as an air knife which cools the thermoplastic material, ~ 8 ., - ~;~.
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~` in this embodiment the bar is provided with a slot or holes ~', through which cooling fluid such as cold air may be directed onto i.;.`:
,',;, the backing; this embodiment is described and claimed in our co-pending application No, 283,691 filed July 29, 1977, ~ We have found that the process of the present invention : is versatile because the texture of the pile obtained on the sur-face of the thermoplastic material may readily be altered by changing the path of the sheet of thermoplastic material as it , separates from the heated roll, which may be achieved either by :
~ 10 varying the actual radius of the means which controls the radius ,' of curvature of the thermoplastic material or by varying the ;~; distance between the means itself and the heated surface, ~', We have found that in a process in which the pile is ~: .
', formed against a substantially smooth surface there are several , , factors which effect the speed at which a satisfactory pile may ~' r"~,'',:, be obtained. The optimum conditions for the production of any one ,',,,1 type of pile depend upon the particular thermoplastic material.
.,.
However, for any given thermoplastic material faster speeds may be , obtained the higher the temperature of the surface provided that ~', 20 the pile may be well cooled as it is formed, Thus, subject to '~; other process variations we prefer that the material be drawn ,:"' ;; sharply away from the surface of the heated surface leaving as large ;,', a space as possible between the material and the surface so that ,' a cooling fluid such as cold air be blown into this large space ''''';lZ which allows for good circulation and escape of the fluid, The . ;Z ~,:
,'~', space between the material and the heated surface depends upon the ,~",Z path of the material and hence the provision of a means which con-;. ..,Z
",Z trols and reduces this radius of curvature and allows greater pro-,,1 duction speeds to be used. We also find that ,. .
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may ~e further in~re~s~d if th~ ~ack ~ the ~kir.~ -s cooled as it is parted from the heated surface. Accordingly, where the means which controls the radius of curvature of the sheet of thermoplastic material as it moves away rom the heated surface is a rod around which the material is withdrawn we prefer 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 backing. ~
.
` The preferred process of the present invention ~ 10 has the added advantage that the provision of the bar close --~ to the heated surface ensures that the matérial always leaves the surfaceat the same position and without this control the ,' ~ `
point of separation tends to wander which can result in non~
'.,'!' uniform pile.
. .
'; The present invention is illustrated by the accom-;~ panying drawings wherein Figure 1 shows a film of a thermo-. ~ . ! ' ,;,,~ plastic material and a backing material being fed to a `~
~, heated roll; Figures 2 and 3 illustrate how the radius of ,';,,, :
' curvature differs with and without, respectively a guiding means; Figure 4 is an enlarged illustration of the part of Figure 1 where the sheet leaves the heated surface; and ;
.,.. ; ~
'', Figure 5 is a further enlarged illustration of the part of ~. r~ ;.
Figure 1 where the sheet leaves the heated surface.
Referring now to Figure 1, there is shown a film of thermoplastic material 1 and a backing material 2 being ,-,............................. . ..
-~~ fed to a heated roll 3. The film is pressed against the ~' heated roll by means of the continuous resilient belt 4 ri which is driven by passage around rolls 5 and 6 both of , which are cold. The film and backing material remain close ~' 30 against roll 3 until they pass through the gap defined between ;i~. ;.
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':t, , -- 1 0 -- ,' .''` ' .
)9L5i3;~3 ~: the roll 3 and the guiding means 7. The backing material is then : .
;~ pulled sharply away from ~he roll 3 by the haul of~ rolls 8 and .~ .~.
.: : 9. In this way there is a wide angle between the web and the roll . . .
which allows good cooling due to the air jet 10 supplied from the nozzle 11.
.~ Figure 2 illustrates how the radius of curvature of the ~ web r' is controlled by the guiding means 7 compared with the - situation of Figure 3 when no guiding means is used.
Figure 4 is an enlarged illustration of the part of ; 10 Figure 1 where the sheet leaves the heated surface and is included :.,'.' : to show which angles are referred to herein as the take-off angle ~- and the haul off angle; angle ~ being the take-off angle and B
the haul off angle~
, .
. Figure 5 is a further enlarged illustration of the part : of Figure 1 where the sheet leaves the heated surface showing in .. , ": more detail the construction of the bar 7 and the nozzle 11 to-,, ~i gether with details of the direction of the air jet; the thermo-`''!'~ plastic material and backing material is omitted from this Figure to allow the other dimensions to be more clearly illustrated.
~; 20 Figure 5 of the accompanying drawings shows a heated roll 3 against which the thermoplastic material may be urged and a ;~, i bar 7 around which the backing material may be hauled away from i.,l the heated roll and 11 is a nozzle which directs a coolant between : ;.', .:~' the roll 3 and the har 7. The types of pile tha~ may be obtained .3 using this process depend upon the distance between the rod 7 and ::! the roll 3 (~ as shown in Figure 5), the distance between the cooling jet and the tangent to the roll (shown as X in Figure 5), ~ the height of the cooling jet 10 above the rod 7 (Y in Figure 5) ;;..!
'li., and the angle (e in Figure 5) at which the coolant is directed.
~`30 However, we prefer that these variables be within the following `j~ limits, ~ :
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X between 0.5 and 40 millimetres Y between -10 and 20 millimetres ~the negative value indicating that the jet is below the top of the rod 7.
between the thickness of the material passing ~ `
through the gap between the roll 3 and the rod 7 and ; 25 millimetres grea-ter than that -thickness~
e between -15 and 75 (the negative value indicating that the cooling jet is direct from below the level -of the rod 7).
~` 10 All these variables mentioned above may be varied inde-i ~ pendently or together to produce a desired type of pile surface ', from any particular thermoplastic material as i5 illustrated in , the accompanying examples.
;, In our preferred process the synthetic thermoplastic `
!;j',`'l;l material is in the form of a film and may be any of the well-known :,i,;: .~, film forming materials. Examples of suitable materials include i polyolefines, particularly high and low density polyethylene, polypropylene and olefine copolymers, polymers and copolymers of vinyl chloride, polymers and copolymers of styrene, polyesters and t~;l 20 the various nylons. The choice of material will of course depè~d on the particular type of product that is required and the uses ~, lJ; I to which it is to be put.
., The product is provided with a backing to improve the stiffness and the handlability of the product, The thermoplastic ~; .:
, material may be laminated to the backing before it is fed to the ;, heated surface or may be fed separately to the heated surface and laminated to the backing by the heat and pressures generated ~' during our process. Alternatively, the material may be applied as powder or granules to a backing web which carries the material 30 into contact with the heated surface where it is fused into a ~
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gl53~3 substantially continuous layer. The choice of backing material will depend upon the deslred nature o~ the product but we prefer for econo~ic reasons that the backlng be paper. 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 thermoplastic material and thus it is more difficult to achieve a good bond.
, Further~ore, when using an open mesh backing such as a fabric . i the material may be effectively cooled from the back which is not so with paper backingO Thus, when using paper as a backing . " . . .
; ~ the material must be cooled from the front as it separates from the surface and the more effective the cooling the higher the speeds that may be used. Oux preferred method of cooling is to blow cold air into the gap between the heated surface and the thermoplastic material and thus good circulation and escape of ,~ , .
~", the cooling air is important for high production rates and thus the techniques of the present invention are most useful when paper is used as a backing. Polyethylene and paper is a par-- ticularly suitable combination from which to produce backed pile surfaced products and the feedstock may be separate sheets ~ of papex and polyethylene or polyethylene coated paper. When ;'~ the backing material is paper we prefer that the sheet be with-'~ drawn from the heated surface over a bar having a radius of , curvature between 1 1/2 millimetres and 5 millimetres. In par- ,-ticular when using polythene of one thousandth inch thick lami- `
nated to Kraft paper of 50 gram/sq. metre we prefer that the i~
radius of curvature be about 2 millimetres. We have found that -the techniques of our invention are especially usefu] in the pro-duction of paper backed products and the product obtained has a ; ~ ;
30 uniform pile and the fibrils are of a lamella structure rather '~
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~; than being formed from individual fibrils.
.
~ As previously mentioned the heated surface is con- ~ -" .
; veniently a roller which may be polished, satin finished or sand blasted, the surface may also be coated with non-stick material such as polytetraEluorethylene. The cooling is ne-;~ :. . , cessary to ensure that the ~ibrils that are drawn out by the , heated surface remain integral with the thermoplastic material rather than sticking to the heated surface alld may readily be ~`
achieved by directing a blast of cooling fluid, particularly -.~ 10 cold air into the nip formed be~tween the heated surface and the - thermoplastic material as it leaves the surface~ However, we ` have found that in order to achieve the necessary cooling par-~' ticularly when producing a paper backed polyethylene pile sur-,.... , i .:
faced material the angle between the material and the tangent , to the heated surface at the point where the material lea~es the ~; roller (known as the take-off angle) should preferably be between ~ 10 and 70 preferably between 25 and 50 to allow the cooling `i`' air to reach the point where the material separates from the ~`
;, heated surface to achieve an acceptable pile at high production ~ 20 speeds and thus this is also dependent on suitable control of ,'~ the path of the material as it leaves the surface. In addition, ^
it is preferred that the haul off angle (angle B in Figure 4) : ~;
is sufficiently great to allow free flow of the cooling air thus preventing air becoming trapped which would lead to temperature !', fluctuations and a non-uniform product. In particular it is pre-~i ferred that the haul off angle be greater than 90~ espec:ially `';! when paper is used as the backing material.
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`''!,',1 The temperature at which the heated surface should be `
~;l held depends upon the nature of the thermoplastic material. How-ever, we have found that providing the temperature is not so high ., .. , . . ~ , .
a ~
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~ that the thermoplastic material is adversely affected the higher .~. .
- the temperature the higher the production rates may be used. We have found, for example, that roll surface temperatures between 7`
200C and 220~C are particularly suitable when processing low density polyethylene at speeds up to 3 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 effec-tively to ensure that they separate from the heated surface at the desired point to give the required pile length. In addition , :,:"
with processes operatiny at these temperatures we prefer to cool the back of the backing as it is withdrawn from the roll surface . ~ even when using a backing such as paper which has a low porosity.
We have found that this back cooling impr~ves the abrasion resis-` tance of the pile and we particularly prefer to draw the web : :: , :-~:, away from the roll over a suitably shaped internally cooled bar.
The thermoplastic material should be pressed against the heated surface and we have found that this may best be achieved using either a backing roll or a supporting belt. For `
,. ......................... . .
example, the thermoplastic material may be passed through the ~r 20 nip formed between two rolls one of which is heated. We prefer ~ that wha-tever backing is used it is resilient, and find that a ;
:f''j, rubber covered roll or a resilient belt is particularly useful. ~:
~ If desired, the backing material may be foamed, for example, poly-. :i~:, . . .urethane foam which will provide the necessary resilience during -processing. ;
~: It is important that the pile be cooled as it separates `
from the substantially smooth heated roll to ensure that once the fibrils have been drawn out from the bulk of the thermoplas- `-'t' ` ' tic materlal they remain integral therewith. We prefer to cool i by directing a jet of cold air in-to the nip between the roll and , .~, ~ . .
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~5323 : `
` -the thermQ~last;~ ~aterjal as i~ is separatin~ ~herefr~m- ~or high speed processing the cooling should be effective as possible and thus it is important that the coolant be as ~ree as possible to circulate in the gap between the roll and the backing. We ~ ~ have found that the most effective cooling is achieved if the ,:. `.` , jet itself is some distance away from the space and the coolant , deflected under high pressure into the space. In this way the physical presence of the jet does not impede the escaping coolant.
., .,. ~ ~
, In our preferred process the coolant is directed against the sur-face of the heated roll slightly beyond the position at which the backing separates from the roll so that the coolant is deflected :; into the space between the web and the surface and may then es-' cape. We also prefer that the coolant be directed under high pressure from a narrow slit orifice extending across the width ^~
of the web.
In our preferred process the heated surface is a sub-` stantially smooth surfaced roller heated to a temperature above thé melting point of the thermoplastic material from which the `"~ pile surface is to be produced and the material is withdrawn from the surface of the roll over a rod posltioned at a distance l between the thic~ness of the material being pressed (including ,p any backing) and 25 millimetres greater than that distance and , "~
a coolant is directed under pressure into the gap formed between ~' the roll and the thermoplastic from a jet positioned between 5 and 40 millimetres from the point on the roll and between 20 milli~
metres above that point and 10 millimetres below that point. The `,~, angle at which the jet is directed depending upon the position ;~, of the jet but being no greater than 75 to the horizontal.
According to the process of the present invention a device is provided which controls the path of the thermoplastic ;
- 16 _ ,~.
:, . :
3;~3 ,; ma-teria] as it leaves the heated surface. As mentioned the - device should be positioned close to the heated surface and the ,~ device preferably provides an edge ex-tending across the widt~l of -the roll so that the thermoplastic material may be hauled off along this edge. ~n -this way the position of the edge relative to the haul off may be adjusted to define the take off angle which gives a simple technique for altering the pile length and densi~y.
, .. ...
"~ We prefer that the guiding device be a rod, a square tube or an ... ;.` ~
anyle rod and that i-t may be internally cooled, the term "bar"
used herein comprehends these forms.
, ., The present invention is further illustrated but in no -~ way limited by the folloT~ing examples in which pile surfaced mate-~s~ rials were produced on apparatus substantially as illustrated in ~. ;.
1 , Figures 1, 2 and 4 of the accompanying drawings. The backing material 2 was Kraft paper and the thermoplastic material 1 was a 65 micron film of low density polyethylene. Several runs were ~'f ', carried out using various values for -the temperature of the roll 3 and the variables ~, X, ~ and e shown in Figure 5, to assess ,. , the efEect they have on the speed at which the process may be operated and the quality of the product.
~ The need to use the bar 7 was illustrated by two com-;,, parative experiments with all other variable kept constant but .~ ., .
~ one run used no bar as is illustrated in Figure 4 and in the other ~; ~
,, ; a bar of radius (r) 3 millimetres. It was found that a satis~
,' factory pile surfaced product could not be obtained without a bar ;
,'," whereas once the bar was present a satisfactory pile was obtained. ~-1 ~he following conditions were adopted to assess the '1 effect of cooling the bar 7 used above on production speeds.
:, ,, .
:,',,~
, :i,"' . :
/, . .
: ` :
45ii3i~3 ~; ¦ Web Speed ¦ Roll ¦ Peel sar ¦ Abrasion Resis- ¦
.~, M_tres/Min. Temperature _ ~ tance of Product ~ 1.50 216C 100C 85 i'~ 1.50 216C 20C 155
The present invention relates to improvements in or relating to the production o~ pile sur~ace~ articles. This application is a divisional application of Canadian Application ;~ No. 186,864, filed November 28, 1973.
- 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 from the surface while cooling the material to below its soft-.
ening point. In this way fibrils are drawn out from the sur-face of the sheet and the cooling action ensures that the major `~ part of each fibril remains integral with the thermoplastic ; material. In the preerred mode of operation of this technique , cold air or another cooling medium is blown into the nip formed "r".,J between the heated roll and the thermoplastic material as the ~' thermoplastic material separates from the roll. It has also -~i been proposed to feed the thermoplastic material to the roll i` ' as a sheet and to feed a backing material with the thermoplastic ~ material in such a way that the thermoplastic material and the '', backing material bond together under the influence of the heated ~ 20 roll.
:,. .': ,. .
In some of the previous proposals a pile surface is ',, produced by forcing a thermoplastic material into cavities in :, 1 .
~, the surface of a roll and then separating the sheet from the roll so that the thermoplastic material that has been forced into the cavities is drawn into ~ibrils. This type of process suf- ,~
,i fers from the disadvantage that èxpensive equipment having ac-l curately machined rolls is required and that the techniques n~ cannot satisfactorily be used to produce short piles since the `' shallow cavities required for sihort pile would tend to be , 30 clogged with thèrmoplastic material. Furthermore, the nature : . . . .:
~'., ~.. ': ' .
,, ' ' :.
~, , , f ~
~ of the pile (i.e. the fibril density and length) depends -~ upon the depth and size of the cavities so that only one ~,, type of pile may be obtained using one particular roller. ~' `
-, It has also been proposed that in techniques of this type the thermoplastic material which is drawn into fibrils is cold ~' : .:
, ,,;' drawn and oriented and it has been suggested that the material ...... .
~',, be stripped from the heated cavitied roll over a circular .. :.
, . . .
rod so that the polymer is pulled from the cavities in the ','' roll. However, in this technique using a cavitied roller the ' ''' 10 angle at which the material moves away from the roller makes ,~
~' little difference to the density of the pile. An object of ''~
~,',,,',, the present invention is to provide a wide range of pile'sur- -,.' ~ faces and the invention relates to a process in which a pile j"~; surface is produced by holding a thermoplastic material against ,''` a substantially smooth surface held at a temperature above the . .: ~ .::
melting point of the thermoplas-tic material. Under these cir- , cumstances the thermoplastic material melts and adheres weakly ,-' to the surface so that as the polymer is separated from the surface fibrils of the molten polymer are drawn out. Thus, ~....
~i 20 in our process fibrils are formed between the,surface and the ,~ ." .
; 1 thermoplastic material rather than within cavities formed in ;
', the surface of a roll. Such a process is already known but t;~': ` objects of the present invention are to improve both the uni-:$ ' . `.,.
'~ formity of pile produced by this type of process, to allow uni- '~
'';: ,, ,, form piles to be produced at higher speeds than has hitherto "' , been possible and to provide a versatile process which may '-`~
, . . .i .
`x~, readily be adapted to produce varying types of pile.
'~` The length of the individual fibrils produced by our ' ~;', process depends upon the length that can be drawn ou-t from the ~, sheet before the fibrils break and also the position at which .~:';"~ ' ~ . , i; _ 3 _ ~
':" ` ,;
: .
. ..
: ;"",, :
:: :
gL53'~3 the fibrils break. Both these factors depend on the path , . . .
the material takes as it separates from the roll and the rate ~ at which the material moves away from the surface of the heated ,..... :.......... , . :,:
r,~ roll and the cooling that is achieved. The lenyth of the fibrils that are produced depends upon the path the material takes as it moves away from the heated surface. The fibrils will begin to draw out at the point where the thermoplastic material first moves away from the heated surface and will :.: ....... : , . -.
break off at the point where the speed and direction of the , ~-material and the temperature of the fibril prevents further .:. ~ ., .
stretching. In addition since the surface of the roll is at , a temperature above the melting point of the polymer it is ;~' `` important that there be sufficient cooling in the area formed ;,~ between the surface and the sheet to prevent the fibrils be-,,; coming totally welded together under the influence of the .... . .
~' heated roll. For many applications it is important to have a short pile as this gives improved abrasion resistance. It has however hitherto proved difficult to obtain a short uniform pile since if a sheet takes its natural unimpeded direction ; 20 when moving away from a substantially smooth heated roll the distance between the sheet and the roll gradually increases and ,. ...
the point at which the two separate varies thus producing a non-uniform pile. Furthermore, the restriction of the extent ~``, of cooling reduces the speed at which the process can be operated.
The point at which the material separates from the -~
~ . ~ ;,.. .
heated surface and the path the material will naturally adopt ;
j' as lt moves away from a substantially smooth heated surface de- ~
.. . . . . .
pends upon the position of the haul off. If it is situated some distance from the surface the material `~
; ~. .' .
"'~' ~'. "
- 4 - ; ~
','' '' ' S3~3 .
adopts its natural radius of curvature accordi~lg to the , .
position of the haul off and we have found that this natural radius of curvature is generally too large to allow the mat-, erial to move away from the h~ated surface sufficiently quickly , . ~
; i to obtain a satisfactory product. This is particularly so when the thermoplastic material is provided with a backing , . :
material, particularly a non-textile backing material such as paper which is one of our preferred backings as it allows easy handlability of the final product and is cheap. In addition ,: ., we have found that if the material is withdrawn by a haul off means situated some distance from the heated surface then the ,. . .
' exact position where the material leaves the surface tends `~ to wander which produces a non-uniform product.
The present invention is therefore concerned with a , :
l process for controlling and improving the texture and unifor-, mity of the pile which is produced by a process in which fib-. ~ . .
rils are drawn out from a thermoplastic material by pressing the thermoplastic material against a substantially smooth : ~ .
' surface held at a temperature which melts the thermoplastic material and withdrawing the thermoplastic material from the surface.
According to the present ivention we provide a pro-cess for the production of pile surfaced materials which com-;, prises the step of interposing a thermoplastic material be-,` tween a backing and a substantially smooth heated surface, holding the backing against the thermoplastic material so that `~
bonding of the backing to the thermoplastic material and ad-hesion of the material to the heated surface occur~, parting the thermoplastic material from the heated surface over a bar '1 30 which provides a curved path having an initial radius of be-.`.,, ' - 5 . . .
,. :
", .. .
;;l .'.
tween 1 mm. and 8 mm. so that fibrils are drawn out from the ' thermoplastic material between the hea-ted surface and the backing - .
and hardening the fibrils as they are drawn out by a stream of . : , , cooling fluid, -Preferably, the substantially smooth heated surface is a roller which is heated internally to a temperature above the melt-`;, ing point of the thermoplastic material, It is to be understood '~ that within this specification the term substantially smooth includes -. .
,, surfaces which have a satin finish or have been sho-t or sand blasted `-,~ 10 but excludes surfaces in which definite cavities are formed into ~-.. :....................................................................... :
,~ which the polymer is forced to form fibrils since with cavitied rolls . .. :
- it is not possible to obtain the wide range of pile types that can be ' :;-. i',i '.' ' ,:
' achieved using the present invention, Examples of surfaces which :' fall within our definition include polished metal surf~ces such as :~ .
steel or chrome and satin finish metal rolls and sand blasted metal ` rolls and the rolls may be coated with non-stick materials such as ' ' polytetrafluoroethylene. The means which holds the thermoplastic ~ material against the heated surface may conveniently be a pressure ,:~ roll or a belt although whichever system is used we prefer that the ~,, 20 thermoplastic material be held against the roll by a resilient mat-,~' erial which allows a predetermined amount of compression as the ! material is held against the heated surface, Alternatively, if the thermoplastic material is i~ film form it may be pressed against the heated surface by the tension in the film it~elf, A further possi-~'1 bility is that the thermoplastic material may be held against the ',, heated surface by the tension in a backing material which bears ''~
, against the thermoplastic material to hold it against the heated ,,1 surface, In this type o~ process the backing may already be lami- , ~ -nated to the thermoplastic material or may become laminated ,' 30 thereto as the thermoplastic material melts during its contact ~ . . .
:;, with the heated surface. We do however prefer to use . .
~; ~L ' , :
3~3 '~ ancilliary means such as a roller or a belt, , ~ The material is co~led to ensure that the fibrils which " are drawn out from the sheet remain adhering to the thermoplastic material and do not sticX permanently to the heated surface, In ' addition it is important to have cooling to allow the process to '~, be operated at increased speeds, the greater t'he speed used the -,~- greatex the cooling needed for the production of any particular type "' of pile, Our preferred method of cooling is to us~ a jet of cold ., . ~ .
~'~ air whi~h flows into the nip formed between the heated surface and :
~'-; 10 the material as it moves away from the surface, cooling should be ,,.;~. iet ; uniform and thus the ~het should extend across the total width of this nip, We have found that the actual direction of the jet of cold air is important and it is also important to allow as free a -~ circulation o~ the air as possible in the space between the heated - surface and the material, We therefore prefer that the cooling air be directed from a narrow slit orifice of width less than 1 prefer-, ably less than ~ 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; this embodiment is described in ~opending patent Application ~o. 186,864, filed ~ovember ' 28, 1973. ~hus 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 thermoplastic ,,l material may also be cooled from the side furthest away from the ~!, heated surface and in one embodiment of the invention the radius of ''"~ .
curvature of the material is controlled by hauling it away from the , heated surface over a suitably . ,.
.: ' .:
~- -- 7 -- , ,. ,~, ~ .. ... . .
' : `"\
53~3 :-.,......... .. ~
shaped bar and this may be internally cooled.
The optimum path that the thermoplastic material should adopt as it leaves the heated surface depends upon the -~
thickness and nature of the thermoplastic material and the -type of product required. We find however that for most products the path may be curved and an initial radius of curvature between 1 1/2 millimetres and 8 millimetres is particularly suitable, if the radius is less than about 1 millimetre there is a danger that ... . . .
~ the product will be damaged; if however the radius is greater . , -, ~ 10 than about 8 millimetres the pile tends to be long and weak. We ;
have also found that the path of the material may best be con- -:.i . .
;, trolled by hauling the material off around a bar and in this way the path of the material may be controlled either by setting , the bar at a predetermined distance frorn the heated surface or , by posltioning the bar close to the surface and selecting thè -~
shape of the bar so that the material takes the required path as , . .: . , ;:
1 it is hauled off over the bar. Small variations in the path of :`~ . '' , .
,1 the material and thus a different pile structure may be achieved ;
by simply altqring the distance of the bar from the surface. It , is important that the bar be rigid to ensure uniform contact `-;~~ between the sheet and the heated roll. Accordingly, 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 r . ' ~'j rigidity. The bar is therefore not necessarily of circular ~
~ ~ :. . "
cross-section. This particular process 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 shape of the bar. In a further embodiment the bar '''r,~ 30 may act as an air knife which cools the thermoplastic material, ~ 8 ., - ~;~.
::`
5i3~3 ''':.
~` in this embodiment the bar is provided with a slot or holes ~', through which cooling fluid such as cold air may be directed onto i.;.`:
,',;, the backing; this embodiment is described and claimed in our co-pending application No, 283,691 filed July 29, 1977, ~ We have found that the process of the present invention : is versatile because the texture of the pile obtained on the sur-face of the thermoplastic material may readily be altered by changing the path of the sheet of thermoplastic material as it , separates from the heated roll, which may be achieved either by :
~ 10 varying the actual radius of the means which controls the radius ,' of curvature of the thermoplastic material or by varying the ;~; distance between the means itself and the heated surface, ~', We have found that in a process in which the pile is ~: .
', formed against a substantially smooth surface there are several , , factors which effect the speed at which a satisfactory pile may ~' r"~,'',:, be obtained. The optimum conditions for the production of any one ,',,,1 type of pile depend upon the particular thermoplastic material.
.,.
However, for any given thermoplastic material faster speeds may be , obtained the higher the temperature of the surface provided that ~', 20 the pile may be well cooled as it is formed, Thus, subject to '~; other process variations we prefer that the material be drawn ,:"' ;; sharply away from the surface of the heated surface leaving as large ;,', a space as possible between the material and the surface so that ,' a cooling fluid such as cold air be blown into this large space ''''';lZ which allows for good circulation and escape of the fluid, The . ;Z ~,:
,'~', space between the material and the heated surface depends upon the ,~",Z path of the material and hence the provision of a means which con-;. ..,Z
",Z trols and reduces this radius of curvature and allows greater pro-,,1 duction speeds to be used. We also find that ,. .
.. Z
~.. Z ,' .;,. .
'' . ,~ _ g _ 'i. ~ - ~
~ `
~
3;~3 ~:
, ~
may ~e further in~re~s~d if th~ ~ack ~ the ~kir.~ -s cooled as it is parted from the heated surface. Accordingly, where the means which controls the radius of curvature of the sheet of thermoplastic material as it moves away rom the heated surface is a rod around which the material is withdrawn we prefer 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 backing. ~
.
` The preferred process of the present invention ~ 10 has the added advantage that the provision of the bar close --~ to the heated surface ensures that the matérial always leaves the surfaceat the same position and without this control the ,' ~ `
point of separation tends to wander which can result in non~
'.,'!' uniform pile.
. .
'; The present invention is illustrated by the accom-;~ panying drawings wherein Figure 1 shows a film of a thermo-. ~ . ! ' ,;,,~ plastic material and a backing material being fed to a `~
~, heated roll; Figures 2 and 3 illustrate how the radius of ,';,,, :
' curvature differs with and without, respectively a guiding means; Figure 4 is an enlarged illustration of the part of Figure 1 where the sheet leaves the heated surface; and ;
.,.. ; ~
'', Figure 5 is a further enlarged illustration of the part of ~. r~ ;.
Figure 1 where the sheet leaves the heated surface.
Referring now to Figure 1, there is shown a film of thermoplastic material 1 and a backing material 2 being ,-,............................. . ..
-~~ fed to a heated roll 3. The film is pressed against the ~' heated roll by means of the continuous resilient belt 4 ri which is driven by passage around rolls 5 and 6 both of , which are cold. The film and backing material remain close ~' 30 against roll 3 until they pass through the gap defined between ;i~. ;.
.,; ~
':t, , -- 1 0 -- ,' .''` ' .
)9L5i3;~3 ~: the roll 3 and the guiding means 7. The backing material is then : .
;~ pulled sharply away from ~he roll 3 by the haul of~ rolls 8 and .~ .~.
.: : 9. In this way there is a wide angle between the web and the roll . . .
which allows good cooling due to the air jet 10 supplied from the nozzle 11.
.~ Figure 2 illustrates how the radius of curvature of the ~ web r' is controlled by the guiding means 7 compared with the - situation of Figure 3 when no guiding means is used.
Figure 4 is an enlarged illustration of the part of ; 10 Figure 1 where the sheet leaves the heated surface and is included :.,'.' : to show which angles are referred to herein as the take-off angle ~- and the haul off angle; angle ~ being the take-off angle and B
the haul off angle~
, .
. Figure 5 is a further enlarged illustration of the part : of Figure 1 where the sheet leaves the heated surface showing in .. , ": more detail the construction of the bar 7 and the nozzle 11 to-,, ~i gether with details of the direction of the air jet; the thermo-`''!'~ plastic material and backing material is omitted from this Figure to allow the other dimensions to be more clearly illustrated.
~; 20 Figure 5 of the accompanying drawings shows a heated roll 3 against which the thermoplastic material may be urged and a ;~, i bar 7 around which the backing material may be hauled away from i.,l the heated roll and 11 is a nozzle which directs a coolant between : ;.', .:~' the roll 3 and the har 7. The types of pile tha~ may be obtained .3 using this process depend upon the distance between the rod 7 and ::! the roll 3 (~ as shown in Figure 5), the distance between the cooling jet and the tangent to the roll (shown as X in Figure 5), ~ the height of the cooling jet 10 above the rod 7 (Y in Figure 5) ;;..!
'li., and the angle (e in Figure 5) at which the coolant is directed.
~`30 However, we prefer that these variables be within the following `j~ limits, ~ :
.i ! -11-J`' .~,,'.~, ..
. .'., .
"!~
:,;., ' . ' '~.i 4 . .
:'.' .
~: s~
S3;~3 `~ . . .
X between 0.5 and 40 millimetres Y between -10 and 20 millimetres ~the negative value indicating that the jet is below the top of the rod 7.
between the thickness of the material passing ~ `
through the gap between the roll 3 and the rod 7 and ; 25 millimetres grea-ter than that -thickness~
e between -15 and 75 (the negative value indicating that the cooling jet is direct from below the level -of the rod 7).
~` 10 All these variables mentioned above may be varied inde-i ~ pendently or together to produce a desired type of pile surface ', from any particular thermoplastic material as i5 illustrated in , the accompanying examples.
;, In our preferred process the synthetic thermoplastic `
!;j',`'l;l material is in the form of a film and may be any of the well-known :,i,;: .~, film forming materials. Examples of suitable materials include i polyolefines, particularly high and low density polyethylene, polypropylene and olefine copolymers, polymers and copolymers of vinyl chloride, polymers and copolymers of styrene, polyesters and t~;l 20 the various nylons. The choice of material will of course depè~d on the particular type of product that is required and the uses ~, lJ; I to which it is to be put.
., The product is provided with a backing to improve the stiffness and the handlability of the product, The thermoplastic ~; .:
, material may be laminated to the backing before it is fed to the ;, heated surface or may be fed separately to the heated surface and laminated to the backing by the heat and pressures generated ~' during our process. Alternatively, the material may be applied as powder or granules to a backing web which carries the material 30 into contact with the heated surface where it is fused into a ~
'''~ .. ::", i ,.l ~,," . ` , .:
..': :.:
: ' ` -~ ~
gl53~3 substantially continuous layer. The choice of backing material will depend upon the deslred nature o~ the product but we prefer for econo~ic reasons that the backlng be paper. 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 thermoplastic material and thus it is more difficult to achieve a good bond.
, Further~ore, when using an open mesh backing such as a fabric . i the material may be effectively cooled from the back which is not so with paper backingO Thus, when using paper as a backing . " . . .
; ~ the material must be cooled from the front as it separates from the surface and the more effective the cooling the higher the speeds that may be used. Oux preferred method of cooling is to blow cold air into the gap between the heated surface and the thermoplastic material and thus good circulation and escape of ,~ , .
~", the cooling air is important for high production rates and thus the techniques of the present invention are most useful when paper is used as a backing. Polyethylene and paper is a par-- ticularly suitable combination from which to produce backed pile surfaced products and the feedstock may be separate sheets ~ of papex and polyethylene or polyethylene coated paper. When ;'~ the backing material is paper we prefer that the sheet be with-'~ drawn from the heated surface over a bar having a radius of , curvature between 1 1/2 millimetres and 5 millimetres. In par- ,-ticular when using polythene of one thousandth inch thick lami- `
nated to Kraft paper of 50 gram/sq. metre we prefer that the i~
radius of curvature be about 2 millimetres. We have found that -the techniques of our invention are especially usefu] in the pro-duction of paper backed products and the product obtained has a ; ~ ;
30 uniform pile and the fibrils are of a lamella structure rather '~
, .. ..
;, - 13 - ' ~
',',,; ;,, ', j,'. ;:
532~
~; than being formed from individual fibrils.
.
~ As previously mentioned the heated surface is con- ~ -" .
; veniently a roller which may be polished, satin finished or sand blasted, the surface may also be coated with non-stick material such as polytetraEluorethylene. The cooling is ne-;~ :. . , cessary to ensure that the ~ibrils that are drawn out by the , heated surface remain integral with the thermoplastic material rather than sticking to the heated surface alld may readily be ~`
achieved by directing a blast of cooling fluid, particularly -.~ 10 cold air into the nip formed be~tween the heated surface and the - thermoplastic material as it leaves the surface~ However, we ` have found that in order to achieve the necessary cooling par-~' ticularly when producing a paper backed polyethylene pile sur-,.... , i .:
faced material the angle between the material and the tangent , to the heated surface at the point where the material lea~es the ~; roller (known as the take-off angle) should preferably be between ~ 10 and 70 preferably between 25 and 50 to allow the cooling `i`' air to reach the point where the material separates from the ~`
;, heated surface to achieve an acceptable pile at high production ~ 20 speeds and thus this is also dependent on suitable control of ,'~ the path of the material as it leaves the surface. In addition, ^
it is preferred that the haul off angle (angle B in Figure 4) : ~;
is sufficiently great to allow free flow of the cooling air thus preventing air becoming trapped which would lead to temperature !', fluctuations and a non-uniform product. In particular it is pre-~i ferred that the haul off angle be greater than 90~ espec:ially `';! when paper is used as the backing material.
~ :,.,1 :
`''!,',1 The temperature at which the heated surface should be `
~;l held depends upon the nature of the thermoplastic material. How-ever, we have found that providing the temperature is not so high ., .. , . . ~ , .
a ~
'`"' ' ~'' ."^~ ., ,,. 1~ ~ .
~: ' ';, ... . ~
Si3;2:3 .. :.
~ that the thermoplastic material is adversely affected the higher .~. .
- the temperature the higher the production rates may be used. We have found, for example, that roll surface temperatures between 7`
200C and 220~C are particularly suitable when processing low density polyethylene at speeds up to 3 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 effec-tively to ensure that they separate from the heated surface at the desired point to give the required pile length. In addition , :,:"
with processes operatiny at these temperatures we prefer to cool the back of the backing as it is withdrawn from the roll surface . ~ even when using a backing such as paper which has a low porosity.
We have found that this back cooling impr~ves the abrasion resis-` tance of the pile and we particularly prefer to draw the web : :: , :-~:, away from the roll over a suitably shaped internally cooled bar.
The thermoplastic material should be pressed against the heated surface and we have found that this may best be achieved using either a backing roll or a supporting belt. For `
,. ......................... . .
example, the thermoplastic material may be passed through the ~r 20 nip formed between two rolls one of which is heated. We prefer ~ that wha-tever backing is used it is resilient, and find that a ;
:f''j, rubber covered roll or a resilient belt is particularly useful. ~:
~ If desired, the backing material may be foamed, for example, poly-. :i~:, . . .urethane foam which will provide the necessary resilience during -processing. ;
~: It is important that the pile be cooled as it separates `
from the substantially smooth heated roll to ensure that once the fibrils have been drawn out from the bulk of the thermoplas- `-'t' ` ' tic materlal they remain integral therewith. We prefer to cool i by directing a jet of cold air in-to the nip between the roll and , .~, ~ . .
" ,.': ' `:, ' ''.:
, . ` .
~5323 : `
` -the thermQ~last;~ ~aterjal as i~ is separatin~ ~herefr~m- ~or high speed processing the cooling should be effective as possible and thus it is important that the coolant be as ~ree as possible to circulate in the gap between the roll and the backing. We ~ ~ have found that the most effective cooling is achieved if the ,:. `.` , jet itself is some distance away from the space and the coolant , deflected under high pressure into the space. In this way the physical presence of the jet does not impede the escaping coolant.
., .,. ~ ~
, In our preferred process the coolant is directed against the sur-face of the heated roll slightly beyond the position at which the backing separates from the roll so that the coolant is deflected :; into the space between the web and the surface and may then es-' cape. We also prefer that the coolant be directed under high pressure from a narrow slit orifice extending across the width ^~
of the web.
In our preferred process the heated surface is a sub-` stantially smooth surfaced roller heated to a temperature above thé melting point of the thermoplastic material from which the `"~ pile surface is to be produced and the material is withdrawn from the surface of the roll over a rod posltioned at a distance l between the thic~ness of the material being pressed (including ,p any backing) and 25 millimetres greater than that distance and , "~
a coolant is directed under pressure into the gap formed between ~' the roll and the thermoplastic from a jet positioned between 5 and 40 millimetres from the point on the roll and between 20 milli~
metres above that point and 10 millimetres below that point. The `,~, angle at which the jet is directed depending upon the position ;~, of the jet but being no greater than 75 to the horizontal.
According to the process of the present invention a device is provided which controls the path of the thermoplastic ;
- 16 _ ,~.
:, . :
3;~3 ,; ma-teria] as it leaves the heated surface. As mentioned the - device should be positioned close to the heated surface and the ,~ device preferably provides an edge ex-tending across the widt~l of -the roll so that the thermoplastic material may be hauled off along this edge. ~n -this way the position of the edge relative to the haul off may be adjusted to define the take off angle which gives a simple technique for altering the pile length and densi~y.
, .. ...
"~ We prefer that the guiding device be a rod, a square tube or an ... ;.` ~
anyle rod and that i-t may be internally cooled, the term "bar"
used herein comprehends these forms.
, ., The present invention is further illustrated but in no -~ way limited by the folloT~ing examples in which pile surfaced mate-~s~ rials were produced on apparatus substantially as illustrated in ~. ;.
1 , Figures 1, 2 and 4 of the accompanying drawings. The backing material 2 was Kraft paper and the thermoplastic material 1 was a 65 micron film of low density polyethylene. Several runs were ~'f ', carried out using various values for -the temperature of the roll 3 and the variables ~, X, ~ and e shown in Figure 5, to assess ,. , the efEect they have on the speed at which the process may be operated and the quality of the product.
~ The need to use the bar 7 was illustrated by two com-;,, parative experiments with all other variable kept constant but .~ ., .
~ one run used no bar as is illustrated in Figure 4 and in the other ~; ~
,, ; a bar of radius (r) 3 millimetres. It was found that a satis~
,' factory pile surfaced product could not be obtained without a bar ;
,'," whereas once the bar was present a satisfactory pile was obtained. ~-1 ~he following conditions were adopted to assess the '1 effect of cooling the bar 7 used above on production speeds.
:, ,, .
:,',,~
, :i,"' . :
/, . .
: ` :
45ii3i~3 ~; ¦ Web Speed ¦ Roll ¦ Peel sar ¦ Abrasion Resis- ¦
.~, M_tres/Min. Temperature _ ~ tance of Product ~ 1.50 216C 100C 85 i'~ 1.50 216C 20C 155
2~60 206C 100C 91 ~ 2.60 206C 20C 114 _ `i '`'~ :
~ Thus as may be seen cooling the peel bar .increases the ;
relative abrasion resistance to the product as measured by the .~ Frankhauser test. It was also found that the maximum speed at s l 10 which a satisfactory product could be obtained using a hot peel ~ ~ .
. bar was 2160 metres/minute but this could be increased with a ~-cooled bar. Similar results were obtained when using different :~l samples~of film but it was also found that the presence of a pig-~'; ment in the film and the quantity of pigment present also affects the maximum speed at which the process can be operated but with all samples the trend was the same as illustrated in the above table.
:l Example 2 ~;~ Polyethylene and paper were passed through an apparatus 20 of the type illustrated in Figure 5 at a speed of 2 metres per ;~
~;, minute. With reference to Figure 5 the operating conditions ~, were as follows.
.. ~, ~ , .
,~l X = 18 millimetres ~
, ................................. . .
Y = 18 millimetres S = 13 millimetres ~ e= 22 ~
. .~ .
, .
. . .
.. :.
. :
.~ - .
,. ' ,. .
:"
. . .
~C~45323 A product having a paper back with a pile length of about millim~tres w~s ~t~iine~ which ~æs f~un~ to be ~artic~l~rl~
suitable for the production of padded packaging materials such as those described in our canadian Patent No 988021, issued April 27, 1976.
Example 3 " , ~; The process as described in Example 2 was repeated ;.
altering the variables as follows:
X = 3.2 millimetres ~1 10 Y = 0,15 millimetres ~,~ ~ = 0.4 millimetres ;
A . ~ ; . .
~9 " ~ 38O ~
,( , . ::.
~he apparatus was opera~ed at 1.5 metres/minute. A very pleasing short pile fabric was obtained having a pile length j;: :
`,~ of about 1 millimetre which could readily be used as a velvet ;l replacement.
Exam~le 4 ~!1 'r The process used is similar to Example 5 with the ;~ following settings:
, 20 X - 2.0 millimetres ~ ;~
,~ Y - 5.0 millimetres ``
"'~'l ~ = 0.4 millimetres .. , e= 30 ~I Here again a most pleasing velvet like pile surfaced fabric ~ith a fibril length of about 1.5 millimetres was obtained.
, The above examples illustrate the versabilit~ o~ the ;l process and that providing the bar 7 is present different pile structures may be obtained by simple adjustment of the other process variables.
: 1 :
. , .
., , ",,~1: ' '-, - ' "" ;.
,: : ' .,j . .-, -.
~ Thus as may be seen cooling the peel bar .increases the ;
relative abrasion resistance to the product as measured by the .~ Frankhauser test. It was also found that the maximum speed at s l 10 which a satisfactory product could be obtained using a hot peel ~ ~ .
. bar was 2160 metres/minute but this could be increased with a ~-cooled bar. Similar results were obtained when using different :~l samples~of film but it was also found that the presence of a pig-~'; ment in the film and the quantity of pigment present also affects the maximum speed at which the process can be operated but with all samples the trend was the same as illustrated in the above table.
:l Example 2 ~;~ Polyethylene and paper were passed through an apparatus 20 of the type illustrated in Figure 5 at a speed of 2 metres per ;~
~;, minute. With reference to Figure 5 the operating conditions ~, were as follows.
.. ~, ~ , .
,~l X = 18 millimetres ~
, ................................. . .
Y = 18 millimetres S = 13 millimetres ~ e= 22 ~
. .~ .
, .
. . .
.. :.
. :
.~ - .
,. ' ,. .
:"
. . .
~C~45323 A product having a paper back with a pile length of about millim~tres w~s ~t~iine~ which ~æs f~un~ to be ~artic~l~rl~
suitable for the production of padded packaging materials such as those described in our canadian Patent No 988021, issued April 27, 1976.
Example 3 " , ~; The process as described in Example 2 was repeated ;.
altering the variables as follows:
X = 3.2 millimetres ~1 10 Y = 0,15 millimetres ~,~ ~ = 0.4 millimetres ;
A . ~ ; . .
~9 " ~ 38O ~
,( , . ::.
~he apparatus was opera~ed at 1.5 metres/minute. A very pleasing short pile fabric was obtained having a pile length j;: :
`,~ of about 1 millimetre which could readily be used as a velvet ;l replacement.
Exam~le 4 ~!1 'r The process used is similar to Example 5 with the ;~ following settings:
, 20 X - 2.0 millimetres ~ ;~
,~ Y - 5.0 millimetres ``
"'~'l ~ = 0.4 millimetres .. , e= 30 ~I Here again a most pleasing velvet like pile surfaced fabric ~ith a fibril length of about 1.5 millimetres was obtained.
, The above examples illustrate the versabilit~ o~ the ;l process and that providing the bar 7 is present different pile structures may be obtained by simple adjustment of the other process variables.
: 1 :
. , .
., , ",,~1: ' '-, - ' "" ;.
,: : ' .,j . .-, -.
Claims (8)
1. A process for the production of pile-surface material which comprises the steps of interposing an organic thermoplastic material between a backing and a substantially smooth heated surface, holding the backing against the thermoplastic material so that bonding of the backing to the thermoplastic material and adhesion of the material to the heated surface occurs, parting the thermoplastic material from the heated surface over a bar which provides a curved path having an initial radius of between 1mm. and 8 mm. so that fibrils are drawn out from the thermoplastic material between the heated surface and the backing and hardening the fibrils as they are drawn out by a stream of cooling fluid.
2. A process according to Claim 1 in which the initial radius is between 1.5 mm. and 8 mm.
3. A process according to Claim 1 in which the initial radius is between 1.5 mm. and 5 mm.
4. A process according to Claim 1, 2 or 3 in which the bar is positioned from the heated surface at a distance of between the thickness of thermoplastic material and the backing and 25 mm. greater than that thickness,
5. A process according to Claim 1, 2 or 3 in which the heated surface is the surface of a roller.
6. A process according to Claim 1, 2 or 3 in which the thermoplastic material is held against the heated surface by tension in the backing.
7. A process according to Claim 1, 2 or 3 in which the thermoplastic material is held against the heated surface by a resilient roller.
8. A process according to Claim 1, 2 or 3 in which the backing is paper.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB5583172A GB1451311A (en) | 1972-12-04 | 1972-12-04 | Apparatus and process for the production of pile surfaced materials |
| CA186,864A CA1043068A (en) | 1972-12-04 | 1973-11-28 | Apparatus and process for the production of pile surface articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1045323A true CA1045323A (en) | 1979-01-02 |
Family
ID=25667421
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA283,691A Expired CA1045322A (en) | 1972-12-04 | 1977-07-29 | Apparatus and process for the production of pile surface articles |
| CA283,692A Expired CA1045323A (en) | 1972-12-04 | 1977-07-29 | Apparatus and process for the production of pile surface articles |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA283,691A Expired CA1045322A (en) | 1972-12-04 | 1977-07-29 | Apparatus and process for the production of pile surface articles |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1045322A (en) |
-
1977
- 1977-07-29 CA CA283,691A patent/CA1045322A/en not_active Expired
- 1977-07-29 CA CA283,692A patent/CA1045323A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1045322A (en) | 1979-01-02 |
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