CA1221522A - Apertured elastic film of blend of polyurethane and an incompatible polymer - Google Patents
Apertured elastic film of blend of polyurethane and an incompatible polymerInfo
- Publication number
- CA1221522A CA1221522A CA000427711A CA427711A CA1221522A CA 1221522 A CA1221522 A CA 1221522A CA 000427711 A CA000427711 A CA 000427711A CA 427711 A CA427711 A CA 427711A CA 1221522 A CA1221522 A CA 1221522A
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- film
- roller
- polyurethane
- ribs
- stretching
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Abstract
A B S T R A C T
An apertured elastic film comprising a blend of polyurethane and an incompatible polymer which forms a discrete phase within the matrix of polyurethane.
a process for its preparation, and the use of the film in elastic articles for bodily contact.
An apertured elastic film comprising a blend of polyurethane and an incompatible polymer which forms a discrete phase within the matrix of polyurethane.
a process for its preparation, and the use of the film in elastic articles for bodily contact.
Description
PRODUCTS, PROCESSE5 AND USE
The present invention relates to elastomeric apertuled films, the proces6es for their preparat~on and their use, in particular in ela6eic articles for bodily contact.
British patent application no. 2081721A, publi6hed February 24, 1982, disclosed that voided moisture vapour permeable films could be prepared that were suitabla for uRe in the preparation of medical dre6sings. One of the virtue~ of ~uch films was tbat they could be u~ed to provide egress of moisture lC vapour from the skin without permitting ingress of bacte~ia. It has now been discovered that the material~ disclo~ed in said application can be provided in the form of elaRtic apertured films which, while they cannot be u6ed to prevent ingress of bacteria, can nevertheless be used for a wide variety of purposes including u6e in elastic bandage6, ela~tic garments and wound dressings.
The present invention provides elastic apertured films compri~ing a blend of polyurethane and an incompatible polymer which forms a discrete ehase within the matrix of polyurethane.
The present invention relates to elastomeric apertuled films, the proces6es for their preparat~on and their use, in particular in ela6eic articles for bodily contact.
British patent application no. 2081721A, publi6hed February 24, 1982, disclosed that voided moisture vapour permeable films could be prepared that were suitabla for uRe in the preparation of medical dre6sings. One of the virtue~ of ~uch films was tbat they could be u~ed to provide egress of moisture lC vapour from the skin without permitting ingress of bacte~ia. It has now been discovered that the material~ disclo~ed in said application can be provided in the form of elaRtic apertured films which, while they cannot be u6ed to prevent ingress of bacteria, can nevertheless be used for a wide variety of purposes including u6e in elastic bandage6, ela~tic garments and wound dressings.
The present invention provides elastic apertured films compri~ing a blend of polyurethane and an incompatible polymer which forms a discrete ehase within the matrix of polyurethane.
-2- i~21522 Suitable and prefecred blend~ of polymers for use in this invention are as desccibed in British patent application No.
~081721~.
In a first highly favoured aspect the elastic apertured film of this invention i8 in the form of a net. When used herein the term "net" mean~ a 6tructure having a set of ribs. Suitably the ribs of the set are parallel. Also suitably the rib~ of the set may be ~erpentine and touch or join each other ~ntecmittently.
More suitably the net~ of thi6 invention will have at least two o sets of parallel ribs which sets intersect or are ~kew to each other. Most ~uitably the nets of this invention w~ll have two sets of parallel ribs which sets are perpendicular to each other.
The net~ of this invention will fcequently contain membranes extending outwardly from the cibs to define the aperture. ~hether the apecture i8 defined by such membrane~ or by the ribs per se, it is believed that the area of aperture to the total area of the film i~ suitably 5 to 75%, more suitably 10 to 50~ and is preferably 20 to 40t.
. . ,
~081721~.
In a first highly favoured aspect the elastic apertured film of this invention i8 in the form of a net. When used herein the term "net" mean~ a 6tructure having a set of ribs. Suitably the ribs of the set are parallel. Also suitably the rib~ of the set may be ~erpentine and touch or join each other ~ntecmittently.
More suitably the net~ of thi6 invention will have at least two o sets of parallel ribs which sets intersect or are ~kew to each other. Most ~uitably the nets of this invention w~ll have two sets of parallel ribs which sets are perpendicular to each other.
The net~ of this invention will fcequently contain membranes extending outwardly from the cibs to define the aperture. ~hether the apecture i8 defined by such membrane~ or by the ribs per se, it is believed that the area of aperture to the total area of the film i~ suitably 5 to 75%, more suitably 10 to 50~ and is preferably 20 to 40t.
. . ,
3 ~221522 Nets of this invention will suitably contain at least one set of ribs which are from 0.05 to 2.5 mm thick, more suitably 0.1 to 1 mm and preferably from 0.2 mm to 0.5 mm thick in the direction of thickness of the film.
The nets of this invention may be prepared by forming a film having thicker and thinner areas and stretching that film until apertures arè formed. During stretching voiding of the film occurs (see afore mentioned sritish patent application) which is then followed by rupture of the thinner areas to form apertures.
Generally overall thickness of the embossed film will be from 0.15 to 7.5 mm thick, more suitably from 0.25 to 3.5 mm thick and preferably from 0.5 mm to 0.15 mm thick.
More suitably the thinner part of the film employed will be from 0.02 mm to 0.5 mm thick, more suitably from 0.010 mm to 0.075 mm thick and preferably from 0.005 mm to 0.1 mm thick.
The pattern of thicker and thinner areas provided on the film to be stretched will be chosen to ensure that undue propagation of the rupture will be prevented.
Suitable patterns thus include those set forth in British Patent Nos. 914489, 1055963, 1075487 and 1110051.
The nets of this invention may be prepared by forming a film having thicker and thinner areas and stretching that film until apertures arè formed. During stretching voiding of the film occurs (see afore mentioned sritish patent application) which is then followed by rupture of the thinner areas to form apertures.
Generally overall thickness of the embossed film will be from 0.15 to 7.5 mm thick, more suitably from 0.25 to 3.5 mm thick and preferably from 0.5 mm to 0.15 mm thick.
More suitably the thinner part of the film employed will be from 0.02 mm to 0.5 mm thick, more suitably from 0.010 mm to 0.075 mm thick and preferably from 0.005 mm to 0.1 mm thick.
The pattern of thicker and thinner areas provided on the film to be stretched will be chosen to ensure that undue propagation of the rupture will be prevented.
Suitable patterns thus include those set forth in British Patent Nos. 914489, 1055963, 1075487 and 1110051.
4 ~221522 The nets of this invention may be used as wound facing layers, elastic components in elastic bandages, elastic stockings or ladies' foun~ation garmen~s.
In a second highly favoured aspect the apertured film of this invention is in the form of an interrupted film.
When used herein the term "interrupted" means that the film contains a pattern of holes which holes have a maximum dimension of not more than 3 times the thickness of the film. Most aptly the holes have a maximum dimension of not more than the thickness of the f ilm and preferably not more than half the thickness of the film.
Aptly the area of the holes to that of the total area of the film is from 0.05 to 4.5~, more aptly from 0.1 to 2% and preferably from 0.5 to 1.5% for example 1%.
The interrupted films of this invention may be prepared by the same process as the nets of this invention.
The holes may suitably have an approximately elliptical shape (for a uniaxially stretched film) or an approximately circular shape (for a biaxially stretched film).
The interrupted films of this invention may be used ~22~5~:2 as backings in first aid dressings, for example by employing an adhesive as described in British Patent Application No. 2081721A.
The apertured films of this invention may be made by using methods known in the art to be suitable when emplo~ing non-elastomeric materials such as polyolefines, for example polyethylene. It is one of the surprising qualities of the polymer blends disclosed in British Patent Application No. 2081721A that they can be processed by such methods since it has herebefore been generally believed that elastomeric materials could not be processed in such manner.
The following Examples illustrate the invention.
6 122l5z2 Example 1 Extrusion Compound Preparation An extrusion feedstock was prepared as follows:
(i) 60 parts by weight of thermoplastic polyurethane .. ~ ~
(PU) polymer granules (Estane 58201, supplied by B.F.
Goodrich Ltd.), were combined with 40 parts by weight of High Impact polystyrene (HIPS) granules (Styron 485, manufactured by the Dow Chemical Co. Ltd., and supplied by R.H. Cole Ltd., reference 6MW), and the resultant mixture introduced into a rotary tumble blender, which was operated for ten minutes to ensure that a sufficiently even dispersion of one type of granule in the other had been obtained for the efficient operation of the next stage of the process.
(ii~ The mixture of granules from (i) was loaded into the hopper of a Reifenhauser S60 60mm extruder. This extruder was equipped with a multirod die which had 12 circular outlet channels, each 3 mm in diameter. The extruder was also cquipped with a polyolefin type screw which had a length to diameter ratio of 20:1 and a compression ratio of 3:1.
The extrusion was carried out using a die temperature of 185 deg. C and a screw speed of 38 rpm. The filaments :~ ~ rc.~
7 122ls~z produced were drawn through a water bath maintained at 20 deg. C at a speed sufficient to reduce their diameters to approximately 2 mm. After travelling a distance of 1 metre through this bath the filaments were passed through a chamber equipped with a hot air blower, to remove excess moisture before being cut into 3-5 mm lengths using a laboratory model granulator (Accrapak).
The granules were collected from the granulator and then dried for four hours at 90 deg. C in air circulating ovens in trays 2.5 cm deep.
Film Extrusion .
The dried compound prepared above was used to produce an embossed film as follows:
The compound was fed into the hopper of a Reifenhauser S60, 60 mm extruder equipped as above, with the exception of the die, which in this case was a 600 mm wide flat film flexible lip die set to a gap of 0.254 mm and maintained at a temperature of 185 deg. C. Using a screw speed of 36 rpm, a melt film was extruded vertically downwards and fed into the nip of a two roller chill casting unit located directly below the die at a distance of 13.75cm.
P4 ~k One roller of this chill casting unit ~9) was provided with one circumferential groove per transverse millimetre defined between flat topped roller ridyes with, in cross section, 45 deg. inwardly tapering sides. The flat tops of the ridges had a width of 0~203 mm. The film was taken off over this roller, which ~as maintained at a temperature of 40 deg. C. The other roller (8) was provided with one axial groove per circumferential millimetre, having the same geometry and dimensions as those provided in the roller (9). This roller was maintained at a temperature of 65C
At a nip casting speed of 1.4mJmin, the film produced was 465mm wide, had an overall thickness of 0.89mm and a weight of 470gsm. It had on one surface one longitudinal rib per 0.975mm (measured in the transverse direction), as a result of contact with the roller ~9).
The opposed surface had one transverse rib per 1.15mm (measured in the machine direction) as a result of contact with roller (8).
The continuous membranes remaining between the points of intersection of the two sets of ribs were approximately rectangular in shape, having dimensions of 0.23mm x 0.20mm, the smaller dimension being parallel to the 9 lZ;2lSZ2 machine direction and thickness of 0.052mm.
At the base of the ribs, i.e. where they formed the boundaries of the membranes, their widths were 0.78mm (longitudinal ribs) and 0.60mm (transverse ribs).
Film Stretching A sample of the above grooved sheet, lOOmm wide, was gripped in the jaws of a laboratory Hounsfield tensometer so as to have a gauge length of 80mm and with the longitudinal ribs parallel to the proposed direction of stretching.
The stretching operation was then carried out, at 20C with the jaws separating at a rate of approximately lOOmm per minute. In this manner the grooved sheet was stretched until a stretch ratio of 2.5:1 had been attained, by which stage the membranes had split and become apertured. The apertured sheet was then allowed to contract. A sample of the deformed portion was then stretched in a similar manner in the direction which was perpendicualr to the above stretch direction, until a strech ratio of 4:1 was achieved. The film was again allowed to contract.
The net produced by the above operations ws 0.79mm in 12215~2 overall thickness and had a weight per unit area of 280gsm.
The apertures in this net were essentially elliptical in shape, the larger axis being aligned in the direction S which was the transverse direction in the unstretched film. The maximum dimensions of the apertures were 0.73 and 0.31mm. The distance between centre points of the apertures was 1.36mm in the direction which had been the machine direction in the unstretched film and 1.22mm in the direction perpendicular to this.
Example 2 The extrusion compounding of the component materials (which were the same as in Example 1) extrusion of the film and the film produced were all as in Example 1.
The stretching procedure was the same as in Example 1, with the exception that the transverse stretching was carried out first. The draw ratios attained were 3:1 in both the transverse and machine directions.
The dimensions of the net obtained were as follows:
Overall thickness 0.81mm Weight 315 gsm 11 ~2Z~5~;~
Aperture dimensions:
Major Axis (transverse direction) 0.75mm Minor Axis (machine direction) 0.57mm Distance between centre points: 1.73mm Machine Direction 1.24mm Transverse Direction Example 3 The extrusion compounding of the component materials and the extrusion of the film were carried out as in Example 1 with the exception that roller (8) was provided with one axial groove per 0.635mm defined between flat topped roller ridges with, in cross section, 45 inwardly tapering sides. The flat tops of the ridges had a width of 0.125mm. This roller was maintained at a temperature of 65C.
At a casting nip speed of 2.Om/min the film produced was 465mm wide, had an overall thickness of 0.58mm and a weight of 305gsm. The film was of similar appearance to that produced in Examples 1 and 2. The longitudinal ribs had a frequency of one per l.Omm measured in the transverse direction, whilst the transverse ribs had a 12 122~S22 frequency of one per 0.706mm measured in the machine direction. The membrane dimensions were 0.28mm x 0.05mm thickness; the largest dimension being parallel to the transverse direction. At the base of the ribs their widths were 0.64mm (longitudinal ribs) and 0.48mm (transverse ribs).
The stretching procedure was the same as in Example 1, except that the temperature used was 60C and the draw ratios attained were 3:1 in the machine direction and 3.5:1 in the transverse direction.
The dimens--ions of-the net obtained were -as follows:
Overall thickness 0.46mm Weight 115 gsm Aperture dimensions:
Major Axis (transverse direction) 0.65mm Minor Axis (machine direction) 0.38mm Distance between centre point$: 1.32mm Machine Direction 1.31mm Transverse Direction Example 4 The extrusion compound was prepared as in Example 1 from the same constituent materials.
The compound was fed into the hopper of a Brabender Extrusiograph instrumented extruder, which was driven by a Brabender Plasticorder PLE 651 drive unit and which was equipped with a 150mm wide flat sheet die and a polyolefine-type screw with a length to diameter ratio of 25:1 and a compression ratio of 3:1. The die was maintained at a temperature of 185C and, using a screw speed of 60rpm, which gave registered torque and axial back pressure measurements of 68Nm and 3KN respectively, a melt film was extruded longitudinally and fed into the nip of a two roller chill casting unit located 5cm from the die face.
The roller of this chill casting unit (4) was provided with one conical projection per 0.725mm in both circumferential and axial roller directions. The height of these projections above the roller surface was 0.21mm and their diameter at the roller surface was 0.42mm.
The other roller in the chill casting unit (3) was a flat surfaced, rubber coated roller. the casting nip speed was 4.0 metres/minute. The film produced was 72mm wide, had a thickness of O.ll9mm and had a weight per unit area of 114gsm.
This film had a series of depressions in one surface, which were aproximately conical in nature. Where the depressions interrupted the surfce of the film, their diameter was 0.07mm. Their depth was such that the film was not perforated. Their centre to centre separation was 0.75mm measured in both machine and transverse directions.
A full width sample of this film was gripped in the jaws of a laboratory Hounsfield tensometer so as to have a gauge length of 80mm and with the machine direction parallel to the proposed direction of stretching.
The stretching conditions used were as in Example 1, and a stretch ratio of 3.25:1 was attained in the machi~ne direction after which the film was allowed to contract.
During this stretching procedure interruptions were formed, associated with the depressions in the film.
In the relaxed film these interruptions were elliptical in shape where they intersected the surface of the film, whch had been in contact with the embossing roller during casting, their dimensions being 0.19 x 0.069mm, with the larger dimension being aligned approximately parallel to the stretching direction.
The centre to centre separation of these .~
~2Z1522 interruptions, as measured in the plane of the surface which had been in contact with the embossing roller, was 1.24mm in what had been the machine direction during extrusion and 0.57mm in the direction perpendicular to this.
The film thickness was 0.107mm and the film weight per unit area was 81gsm.
Example 5 The extrusion compounding of the component materials and the film extrusion were carried out as in Example 4, except that the casting nip speed was 6.Om/min.
The film produced was 66mm wide, ahd a thickness of 0.082mm and a weight of 91gsm. The film had a series of depressions in one surface, which were approximately conical in shape. Where the depressions interrupted the surface of the film, they were elliptical in shape with dimensions of 0~062 x 0.087mm, the larger dimension being parallel to the machine direction. Their depth was such that the film was not interrupted. Their centre to centre separation was 0.080mm, measured in the machine direction and 0.70mm measured in the transverse direction.
.~
16 1~215~Z
The sample was stretched as in Example 4, except that a stretching ratio of only 3:1 was attained. During this stretching procedure, interruptions were formed associated with the depressions in the film.
In the relaxed film these interruptions were elliptical in shape, their dimensions being 0.06 x 0.16mm with the larger dimension being aligned approximately parallel to the stretching direction.
The centre to centre separation of these interruptions as measured in the plane of the surface which had been in contact with the embossing roller, was l.OOmm in what had been the machine direction during extrusion and 0.62mm in the direction perpendicular to this.
The film had a weight per unit area of 53gs, and a thickness of 0.063mm.
Example 6 Extrusion Compound Preparation An extrusion feedstock was prepared as follows:
(i) 60 parts by weight of thermoplastic polyurethane ~PU? polymer granules (Estane 58201, supplied by B.F.
17 122152~
Goodrich Ltd.), were combined with 40 parts by weight of low density polyethylene purge compound (British Petroleum Ltd.), and the resultant mixture introduced into a rotary tumble blender, which was operated for ten minutes to ensure that a sufficiently even dispersion of one type of granule in the other had been obtained for the efficient operation of the next stage of the process.
(ii) The mixture of granules from (i) was loaded into the hopper of a Reifenhauser S60 60mm extruder. This extruder was equipped with a multirod die which had 12 circular outlet channels, each 3mm in diameter. The extruder was also equipped with a polyolefin type screw which had a length to diameter ratio of 20:1 and a compression ratio of 3:1.
The extrusion was carried out using a die temperature of 185C and a screw speed of 38 rpm. The filaments produced were drawn through a water bath maintained at 20C at a speed sufficient to reduce their diameters to approximately 2mm. After travelling a distance of 1 metre through this bath the filaments were passed through a chamber equipped with a hot air blower, to remove excess moisture before being cut into 3-5mm lengths using an Accrapak laboratory granulator.
,, ~ .
122~522 The granules were collected from the granulator and then dried for four hours at 90c in air circulating ovens in trays 2.5cm deep.
_lm Extrusion The dried compound prepared above was used to produce an embossed film as follows:
The compound was fed into the hopper of a Reifenhauser S60 60mm extruder equipped as above, with the exception of the die, which in this case was a 300mm wide flat film flexible lip die set to a gap of 0.305mm and maintained at a temperature of190C. Using a screw speed of 18 rpm, a melt film was extruded vertically downwards and fed into the nip of a two roller chill casting unit located directly below the die at a distance of 14.6cm.
One roller of this chill casting unit (9) was provided with one circumferential groove per transverse millimetre defined between flat topped roller ridges with, in cross section, 45 inwardly tapering sides. The flat tops of the ridges had a width of 0.203mm. The film was taken off this roller, which was maintained at a temperatue of 60C. The other roller (8) was provided with one axial groove per circumferential millimetre, having the same geometry and dimensions as those provided in the other roller (9). This roller was maintained at a temperature of 70C.
At a nip casting speed of 1.8m/min, the film produced was 220mm wide, had an overall thickness of 0.355mm and a weight of 248gsm. It had on one surface one longitudinal rib per 0.98mm (measured in the transverse direction), as a result of contact with the roller (9).
The opposed surface had one transverse rib per 1.2mm (measured in the machine direction) as a result of contact with roller (8).
The continuous membranes remaining between the polnts of intersection of the two sets of ribs were approximately rectangular in shape, having dimensions of 0.76mm x 0.41mm, the smaller dimension being parallel to the machine direction and a thickness of O.Olmm.
At the base of the ribs, i.e. where they formed the boundaries of the membranes, their widths were 0.57mm (longitudinal ribs) and 0.44mm (transverse ribs).
Film Stretching A sample of the above grooved sheet, lOOmm wide, was gripped in the jaws of a laboratory Hounsfield tensometer 122~5Z~
so as to have a gauge length of 80mm and with the longitudinal ribs parallel to the proposed direction of stretching.
The stretching operation was then carried out, at 20C, with the jaws separating at a rate of approximately lOOmm per minute. In this manner the grooved sheet was stretched until a stretch ratio of 4:1 had been attained, by which stage the membranes had split and become perforated. The perforated sheet was then allowed to contract. A sample of the deformed portion was then stretched in a similar manner in the direction which was perpendicular to the above stretching direction, until a stretch ratio of 4.5:1 was achieved. The film was aga~n allowed to contract.
The net produced by the above operations was 0.228mm in overall thickness and had a weight of 99gsm, The apertures in this net were essentially elliptical in shape, the larger axis being aligned in the direction which was the transverse direction in the unstretched .0 film. The maximum dimensions of the apertures were 1.04mm and 0.81mm. The distance between centre points of the apertures was 1.83mm in the direction which had been the machine direction in the unstretched film and 1.59mm in the direction perpendicular to this.
Example 7 The extrusion compounding, of the component materials (which were the same as in Example 6), extrusion of the film and the film produced were all as in Example 6.
The stretching procedure was the same as in Example 6, with the exception that the transverse stretching was carried out first. The draw ratios attained were 3;1 in both the transverse and machine directions.
The dimensions of the net obtained were as follows:
Overall thickness 0.23mm Weight 115 gsm Aperture dimensions:
Major Axis (transverse direction~ 0.60mm 15 Minor Axis (machine direction) 0.43mm Distance betwen centre point: 1.72mm Machine Direction 1.27mm Transverse Direction ~ ~.~
In a second highly favoured aspect the apertured film of this invention is in the form of an interrupted film.
When used herein the term "interrupted" means that the film contains a pattern of holes which holes have a maximum dimension of not more than 3 times the thickness of the film. Most aptly the holes have a maximum dimension of not more than the thickness of the f ilm and preferably not more than half the thickness of the film.
Aptly the area of the holes to that of the total area of the film is from 0.05 to 4.5~, more aptly from 0.1 to 2% and preferably from 0.5 to 1.5% for example 1%.
The interrupted films of this invention may be prepared by the same process as the nets of this invention.
The holes may suitably have an approximately elliptical shape (for a uniaxially stretched film) or an approximately circular shape (for a biaxially stretched film).
The interrupted films of this invention may be used ~22~5~:2 as backings in first aid dressings, for example by employing an adhesive as described in British Patent Application No. 2081721A.
The apertured films of this invention may be made by using methods known in the art to be suitable when emplo~ing non-elastomeric materials such as polyolefines, for example polyethylene. It is one of the surprising qualities of the polymer blends disclosed in British Patent Application No. 2081721A that they can be processed by such methods since it has herebefore been generally believed that elastomeric materials could not be processed in such manner.
The following Examples illustrate the invention.
6 122l5z2 Example 1 Extrusion Compound Preparation An extrusion feedstock was prepared as follows:
(i) 60 parts by weight of thermoplastic polyurethane .. ~ ~
(PU) polymer granules (Estane 58201, supplied by B.F.
Goodrich Ltd.), were combined with 40 parts by weight of High Impact polystyrene (HIPS) granules (Styron 485, manufactured by the Dow Chemical Co. Ltd., and supplied by R.H. Cole Ltd., reference 6MW), and the resultant mixture introduced into a rotary tumble blender, which was operated for ten minutes to ensure that a sufficiently even dispersion of one type of granule in the other had been obtained for the efficient operation of the next stage of the process.
(ii~ The mixture of granules from (i) was loaded into the hopper of a Reifenhauser S60 60mm extruder. This extruder was equipped with a multirod die which had 12 circular outlet channels, each 3 mm in diameter. The extruder was also cquipped with a polyolefin type screw which had a length to diameter ratio of 20:1 and a compression ratio of 3:1.
The extrusion was carried out using a die temperature of 185 deg. C and a screw speed of 38 rpm. The filaments :~ ~ rc.~
7 122ls~z produced were drawn through a water bath maintained at 20 deg. C at a speed sufficient to reduce their diameters to approximately 2 mm. After travelling a distance of 1 metre through this bath the filaments were passed through a chamber equipped with a hot air blower, to remove excess moisture before being cut into 3-5 mm lengths using a laboratory model granulator (Accrapak).
The granules were collected from the granulator and then dried for four hours at 90 deg. C in air circulating ovens in trays 2.5 cm deep.
Film Extrusion .
The dried compound prepared above was used to produce an embossed film as follows:
The compound was fed into the hopper of a Reifenhauser S60, 60 mm extruder equipped as above, with the exception of the die, which in this case was a 600 mm wide flat film flexible lip die set to a gap of 0.254 mm and maintained at a temperature of 185 deg. C. Using a screw speed of 36 rpm, a melt film was extruded vertically downwards and fed into the nip of a two roller chill casting unit located directly below the die at a distance of 13.75cm.
P4 ~k One roller of this chill casting unit ~9) was provided with one circumferential groove per transverse millimetre defined between flat topped roller ridyes with, in cross section, 45 deg. inwardly tapering sides. The flat tops of the ridges had a width of 0~203 mm. The film was taken off over this roller, which ~as maintained at a temperature of 40 deg. C. The other roller (8) was provided with one axial groove per circumferential millimetre, having the same geometry and dimensions as those provided in the roller (9). This roller was maintained at a temperature of 65C
At a nip casting speed of 1.4mJmin, the film produced was 465mm wide, had an overall thickness of 0.89mm and a weight of 470gsm. It had on one surface one longitudinal rib per 0.975mm (measured in the transverse direction), as a result of contact with the roller ~9).
The opposed surface had one transverse rib per 1.15mm (measured in the machine direction) as a result of contact with roller (8).
The continuous membranes remaining between the points of intersection of the two sets of ribs were approximately rectangular in shape, having dimensions of 0.23mm x 0.20mm, the smaller dimension being parallel to the 9 lZ;2lSZ2 machine direction and thickness of 0.052mm.
At the base of the ribs, i.e. where they formed the boundaries of the membranes, their widths were 0.78mm (longitudinal ribs) and 0.60mm (transverse ribs).
Film Stretching A sample of the above grooved sheet, lOOmm wide, was gripped in the jaws of a laboratory Hounsfield tensometer so as to have a gauge length of 80mm and with the longitudinal ribs parallel to the proposed direction of stretching.
The stretching operation was then carried out, at 20C with the jaws separating at a rate of approximately lOOmm per minute. In this manner the grooved sheet was stretched until a stretch ratio of 2.5:1 had been attained, by which stage the membranes had split and become apertured. The apertured sheet was then allowed to contract. A sample of the deformed portion was then stretched in a similar manner in the direction which was perpendicualr to the above stretch direction, until a strech ratio of 4:1 was achieved. The film was again allowed to contract.
The net produced by the above operations ws 0.79mm in 12215~2 overall thickness and had a weight per unit area of 280gsm.
The apertures in this net were essentially elliptical in shape, the larger axis being aligned in the direction S which was the transverse direction in the unstretched film. The maximum dimensions of the apertures were 0.73 and 0.31mm. The distance between centre points of the apertures was 1.36mm in the direction which had been the machine direction in the unstretched film and 1.22mm in the direction perpendicular to this.
Example 2 The extrusion compounding of the component materials (which were the same as in Example 1) extrusion of the film and the film produced were all as in Example 1.
The stretching procedure was the same as in Example 1, with the exception that the transverse stretching was carried out first. The draw ratios attained were 3:1 in both the transverse and machine directions.
The dimensions of the net obtained were as follows:
Overall thickness 0.81mm Weight 315 gsm 11 ~2Z~5~;~
Aperture dimensions:
Major Axis (transverse direction) 0.75mm Minor Axis (machine direction) 0.57mm Distance between centre points: 1.73mm Machine Direction 1.24mm Transverse Direction Example 3 The extrusion compounding of the component materials and the extrusion of the film were carried out as in Example 1 with the exception that roller (8) was provided with one axial groove per 0.635mm defined between flat topped roller ridges with, in cross section, 45 inwardly tapering sides. The flat tops of the ridges had a width of 0.125mm. This roller was maintained at a temperature of 65C.
At a casting nip speed of 2.Om/min the film produced was 465mm wide, had an overall thickness of 0.58mm and a weight of 305gsm. The film was of similar appearance to that produced in Examples 1 and 2. The longitudinal ribs had a frequency of one per l.Omm measured in the transverse direction, whilst the transverse ribs had a 12 122~S22 frequency of one per 0.706mm measured in the machine direction. The membrane dimensions were 0.28mm x 0.05mm thickness; the largest dimension being parallel to the transverse direction. At the base of the ribs their widths were 0.64mm (longitudinal ribs) and 0.48mm (transverse ribs).
The stretching procedure was the same as in Example 1, except that the temperature used was 60C and the draw ratios attained were 3:1 in the machine direction and 3.5:1 in the transverse direction.
The dimens--ions of-the net obtained were -as follows:
Overall thickness 0.46mm Weight 115 gsm Aperture dimensions:
Major Axis (transverse direction) 0.65mm Minor Axis (machine direction) 0.38mm Distance between centre point$: 1.32mm Machine Direction 1.31mm Transverse Direction Example 4 The extrusion compound was prepared as in Example 1 from the same constituent materials.
The compound was fed into the hopper of a Brabender Extrusiograph instrumented extruder, which was driven by a Brabender Plasticorder PLE 651 drive unit and which was equipped with a 150mm wide flat sheet die and a polyolefine-type screw with a length to diameter ratio of 25:1 and a compression ratio of 3:1. The die was maintained at a temperature of 185C and, using a screw speed of 60rpm, which gave registered torque and axial back pressure measurements of 68Nm and 3KN respectively, a melt film was extruded longitudinally and fed into the nip of a two roller chill casting unit located 5cm from the die face.
The roller of this chill casting unit (4) was provided with one conical projection per 0.725mm in both circumferential and axial roller directions. The height of these projections above the roller surface was 0.21mm and their diameter at the roller surface was 0.42mm.
The other roller in the chill casting unit (3) was a flat surfaced, rubber coated roller. the casting nip speed was 4.0 metres/minute. The film produced was 72mm wide, had a thickness of O.ll9mm and had a weight per unit area of 114gsm.
This film had a series of depressions in one surface, which were aproximately conical in nature. Where the depressions interrupted the surfce of the film, their diameter was 0.07mm. Their depth was such that the film was not perforated. Their centre to centre separation was 0.75mm measured in both machine and transverse directions.
A full width sample of this film was gripped in the jaws of a laboratory Hounsfield tensometer so as to have a gauge length of 80mm and with the machine direction parallel to the proposed direction of stretching.
The stretching conditions used were as in Example 1, and a stretch ratio of 3.25:1 was attained in the machi~ne direction after which the film was allowed to contract.
During this stretching procedure interruptions were formed, associated with the depressions in the film.
In the relaxed film these interruptions were elliptical in shape where they intersected the surface of the film, whch had been in contact with the embossing roller during casting, their dimensions being 0.19 x 0.069mm, with the larger dimension being aligned approximately parallel to the stretching direction.
The centre to centre separation of these .~
~2Z1522 interruptions, as measured in the plane of the surface which had been in contact with the embossing roller, was 1.24mm in what had been the machine direction during extrusion and 0.57mm in the direction perpendicular to this.
The film thickness was 0.107mm and the film weight per unit area was 81gsm.
Example 5 The extrusion compounding of the component materials and the film extrusion were carried out as in Example 4, except that the casting nip speed was 6.Om/min.
The film produced was 66mm wide, ahd a thickness of 0.082mm and a weight of 91gsm. The film had a series of depressions in one surface, which were approximately conical in shape. Where the depressions interrupted the surface of the film, they were elliptical in shape with dimensions of 0~062 x 0.087mm, the larger dimension being parallel to the machine direction. Their depth was such that the film was not interrupted. Their centre to centre separation was 0.080mm, measured in the machine direction and 0.70mm measured in the transverse direction.
.~
16 1~215~Z
The sample was stretched as in Example 4, except that a stretching ratio of only 3:1 was attained. During this stretching procedure, interruptions were formed associated with the depressions in the film.
In the relaxed film these interruptions were elliptical in shape, their dimensions being 0.06 x 0.16mm with the larger dimension being aligned approximately parallel to the stretching direction.
The centre to centre separation of these interruptions as measured in the plane of the surface which had been in contact with the embossing roller, was l.OOmm in what had been the machine direction during extrusion and 0.62mm in the direction perpendicular to this.
The film had a weight per unit area of 53gs, and a thickness of 0.063mm.
Example 6 Extrusion Compound Preparation An extrusion feedstock was prepared as follows:
(i) 60 parts by weight of thermoplastic polyurethane ~PU? polymer granules (Estane 58201, supplied by B.F.
17 122152~
Goodrich Ltd.), were combined with 40 parts by weight of low density polyethylene purge compound (British Petroleum Ltd.), and the resultant mixture introduced into a rotary tumble blender, which was operated for ten minutes to ensure that a sufficiently even dispersion of one type of granule in the other had been obtained for the efficient operation of the next stage of the process.
(ii) The mixture of granules from (i) was loaded into the hopper of a Reifenhauser S60 60mm extruder. This extruder was equipped with a multirod die which had 12 circular outlet channels, each 3mm in diameter. The extruder was also equipped with a polyolefin type screw which had a length to diameter ratio of 20:1 and a compression ratio of 3:1.
The extrusion was carried out using a die temperature of 185C and a screw speed of 38 rpm. The filaments produced were drawn through a water bath maintained at 20C at a speed sufficient to reduce their diameters to approximately 2mm. After travelling a distance of 1 metre through this bath the filaments were passed through a chamber equipped with a hot air blower, to remove excess moisture before being cut into 3-5mm lengths using an Accrapak laboratory granulator.
,, ~ .
122~522 The granules were collected from the granulator and then dried for four hours at 90c in air circulating ovens in trays 2.5cm deep.
_lm Extrusion The dried compound prepared above was used to produce an embossed film as follows:
The compound was fed into the hopper of a Reifenhauser S60 60mm extruder equipped as above, with the exception of the die, which in this case was a 300mm wide flat film flexible lip die set to a gap of 0.305mm and maintained at a temperature of190C. Using a screw speed of 18 rpm, a melt film was extruded vertically downwards and fed into the nip of a two roller chill casting unit located directly below the die at a distance of 14.6cm.
One roller of this chill casting unit (9) was provided with one circumferential groove per transverse millimetre defined between flat topped roller ridges with, in cross section, 45 inwardly tapering sides. The flat tops of the ridges had a width of 0.203mm. The film was taken off this roller, which was maintained at a temperatue of 60C. The other roller (8) was provided with one axial groove per circumferential millimetre, having the same geometry and dimensions as those provided in the other roller (9). This roller was maintained at a temperature of 70C.
At a nip casting speed of 1.8m/min, the film produced was 220mm wide, had an overall thickness of 0.355mm and a weight of 248gsm. It had on one surface one longitudinal rib per 0.98mm (measured in the transverse direction), as a result of contact with the roller (9).
The opposed surface had one transverse rib per 1.2mm (measured in the machine direction) as a result of contact with roller (8).
The continuous membranes remaining between the polnts of intersection of the two sets of ribs were approximately rectangular in shape, having dimensions of 0.76mm x 0.41mm, the smaller dimension being parallel to the machine direction and a thickness of O.Olmm.
At the base of the ribs, i.e. where they formed the boundaries of the membranes, their widths were 0.57mm (longitudinal ribs) and 0.44mm (transverse ribs).
Film Stretching A sample of the above grooved sheet, lOOmm wide, was gripped in the jaws of a laboratory Hounsfield tensometer 122~5Z~
so as to have a gauge length of 80mm and with the longitudinal ribs parallel to the proposed direction of stretching.
The stretching operation was then carried out, at 20C, with the jaws separating at a rate of approximately lOOmm per minute. In this manner the grooved sheet was stretched until a stretch ratio of 4:1 had been attained, by which stage the membranes had split and become perforated. The perforated sheet was then allowed to contract. A sample of the deformed portion was then stretched in a similar manner in the direction which was perpendicular to the above stretching direction, until a stretch ratio of 4.5:1 was achieved. The film was aga~n allowed to contract.
The net produced by the above operations was 0.228mm in overall thickness and had a weight of 99gsm, The apertures in this net were essentially elliptical in shape, the larger axis being aligned in the direction which was the transverse direction in the unstretched .0 film. The maximum dimensions of the apertures were 1.04mm and 0.81mm. The distance between centre points of the apertures was 1.83mm in the direction which had been the machine direction in the unstretched film and 1.59mm in the direction perpendicular to this.
Example 7 The extrusion compounding, of the component materials (which were the same as in Example 6), extrusion of the film and the film produced were all as in Example 6.
The stretching procedure was the same as in Example 6, with the exception that the transverse stretching was carried out first. The draw ratios attained were 3;1 in both the transverse and machine directions.
The dimensions of the net obtained were as follows:
Overall thickness 0.23mm Weight 115 gsm Aperture dimensions:
Major Axis (transverse direction~ 0.60mm 15 Minor Axis (machine direction) 0.43mm Distance betwen centre point: 1.72mm Machine Direction 1.27mm Transverse Direction ~ ~.~
Claims (8)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An elastic film formed by stretching which contains voids and which comprises a blend of polyurethane and an incompatible polymer which forms a discrete phase within the matrix of polyurethane, characterized in that the film is apertured.
2. A film according to claim 1, characterized in that it is in the form of a net.
3. A film according to claim 2, characterized in that the area of the apertures is 20 to 40% of the total area of the film, and the film has at least one set of ribs 0.2 to 0.5mm thick.
4. A film according to claim 2, characterized in that the film has two sets of parallel ribs which sets are perpendicular to each other.
5. A film according to claim 1, characterized in that it is in the form of an interrupted film containing a pattern of holes.
6. A film according to claim 5, characterized in that the holes have a maximum dimension not more than half the thickness of the film and their area is 0.5 to 1.5% of the total area of the film.
7. An elastic article for bodily contact, characterized by comprising an elastic film according to claim 1.
8. An elastic article according to claim 7, characterized in that the elastic film is a wound facing layer.
22.
22.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000427711A CA1221522A (en) | 1983-05-09 | 1983-05-09 | Apertured elastic film of blend of polyurethane and an incompatible polymer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000427711A CA1221522A (en) | 1983-05-09 | 1983-05-09 | Apertured elastic film of blend of polyurethane and an incompatible polymer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1221522A true CA1221522A (en) | 1987-05-12 |
Family
ID=4125197
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000427711A Expired CA1221522A (en) | 1983-05-09 | 1983-05-09 | Apertured elastic film of blend of polyurethane and an incompatible polymer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1221522A (en) |
-
1983
- 1983-05-09 CA CA000427711A patent/CA1221522A/en not_active Expired
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