CA1198354A - Cold refining of extruded polymer film - Google Patents
Cold refining of extruded polymer filmInfo
- Publication number
- CA1198354A CA1198354A CA000402585A CA402585A CA1198354A CA 1198354 A CA1198354 A CA 1198354A CA 000402585 A CA000402585 A CA 000402585A CA 402585 A CA402585 A CA 402585A CA 1198354 A CA1198354 A CA 1198354A
- Authority
- CA
- Canada
- Prior art keywords
- film
- web
- roller
- composite
- station
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/023—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D24/00—Producing articles with hollow walls
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
- B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
- B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/0008—Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/04—Interconnection of layers
- B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
- B32B7/14—Interconnection of layers using interposed adhesives or interposed materials with bonding properties applied in spaced arrangements, e.g. in stripes
Abstract
Abstract of the Disclosure A method and apparatus for cold refining extruded plastic film, including advancing the film through a lateral stretching station while applying heat centrally of the film and gradually laterally from the central longitudinal axis of the film, then overstretching the film longitudinally and allowing the film to relax and taking up the film at a length greater than its original length and thinner than its original thickness, while maintaining the physical charac-teristics of the plastic film.
Description
~ ~?~35~
The presen-t invention relates to a method and apparatus for treating flexible plastic films, and more particularly, to increasing the yield of polymer films by stretching such films laterally and longitudinally.
Biaxial orientation of various polymers, such as polyethylene terephthalate, is now well known in the industry, particularly in the blow molding of such polymers, whereby the parison, in the case of blow molding, will be over-stretched in the longitudinal as well as in the circumfer-ential direction in order to obtain a biaxial re-orientation of the molecules, thereby increasing the strength of the parison w~ll while making the wall thinner.
Such processes as hereinabove described have mostly been carried out in the forming stage of the product either through blow molding, injection molding, casting or extruding, at the time when the polyrner material is .subject to high temperatures and is itself in a plastic, fonnable state.
It has now been found that an extruded film, for instance, can be more efficiently biaxially oriented in its cold state. In other words, rather than biaxially orienting the film in the extrusion process, one can take the ex-truded film after it is cooled and restretch it both laterally and longitudinally in order to reduce the thickness of the film and increase or at least maintain the strength characteristics of the film, and in the case of a stretchable film, maintain its elasticity and memory.
It has also been discovered that by reprocessiny or restretching the cold film, the yield can be greatly improved. In other words, by a multi-stage reprocessing of the cold film, the film can be reduced by thr~e or four times its original thickness, yet maintain the strength and other characteristics of the original extruded film.
~e~ !33S~
The term "cold ref.ining" as used in this speci-fication means the processing of an extruded polymer film by lateral and longitudinal stretching and by simultaneously applying heat to the film.
A method in accordance with the present invention includes the treating of an extruded film of flexible polymer plastics material in elongated web form having a longitudinal axis and a lateral extent, the method including the steps of advancing the web, heating a central portion of the web gradually from the central l.ongitudinal axis of the web outwardly, stretching the web laterally by stretchiny the lateral edges of the web while applying heat thereto, the application of heat being maintained below the temperature at which the polymer material would break down, overstretching the web in its longitudinal direction, relaxiny the overstretched web and taking up the web at a length greater than and a thic~ness less than the original web while maintaining physical characteristics similar to the original web.
The types of polymers to which the present inven-tion could apply are polyethylene, polypropylene, poly-l-butene, copolymers of these and other polyolefins', including polystyrene, expanded polystyrene foam film, polysulfon, polyvinyl alcohol, polyvinylchloride, vinyl chloride acetate and copolymer derivatives, polyurethane elastomer, rubber hydrochloride, vinyl nitrite, vinylidene, chloride vinyl chloride copolymer, polymide ethylene vinyl acetate copolymer, polyester (polyethyLene terphthalate) poly~
carbonate, polymethyl , methacrylate, ionomer, fluoroplastics, fluorochloroethylene copolymer, polytetrafluoroethylene and polyvinylfluoride.
The uses and advantages of films, which are much thinner or of smaller gauge than present extruded fllms yet include the same physical characteristlcs, are quite vast. For instance, an extruded film of 1 mil can be stretched to twice its length and reduced in thickness to .5 mil. Since the physical characteristics of t'he stretched film are the same as the original extruded film', a :Lamina-te of -two such stretched films would provide twice the strength as the original film. By the same reasonin~', three superimposed or laminated ~ilms would increase the strength of the composite film which is now 1.5 mils thic~ by three.
It has also been contemplated to use such thin strong films as a composite insulating web. For instance, it can be visualized that ten stretched thin films could ~e utilized with a spacer material in between each film', such as sawdust or other', with an adhesive such that air spaces would be present between the film and the composite web would have high insulating characteristics.
It is evident from t'he above that the s-tretched or cold refined films have a yield which is much greater than the original extruded film, and thus the cost per square meter of film can be grea-tly reduced with the same physical characteristics.
~aving t~us generally described the nature of the invention, re~erence will now be made to the accompanying drawings', showing by way of illustration, a preferred em-bodiment thereof, and in which:
Figure 1 is a side elevation of the apparatus in accordance with t-he present invention, Figure 2 is a top plan view of the apparatus sho~n in Figure 1, Figure 3 which is on the same sheet as Figure 1 is an enlarged fragmentary longitudinal cross-section of a portion of the apparatus taken along line 3-3 of Figure 2, Figure 4 whlch is on the same ~heet as Figure 7 is a fragmentary top plan view, partly in cross~ection, of a detail of the apparatus' ,.'.'`;
35~
Figure 5 i.s a vertical cross-3ection taken along line 5-5 of Figure 2, Figure 6 i5 a vertical aross-section taken along-line 6-6 of Figure 2; and Figure 7 is a vertical cross-section taken along line 7-7 of Figure 2.
Referring now to the drawings, there is shown a frame 10 which includes at one end a film supply station 12 from which a web of plastic material to be treated is iden-tified by the letter W and which passes through a preparatorystation 14 and then to a lateral stretching station 16 and subsequently to a longitu~; n~l stretching station 18. From the longitudinal stretching station, the web W is rolled in a wind-up roller station 22. The longitudinal stretching assembly and the wind-up rollers are all driven by means of a drive arrangement 20.
The film supply station 12 includes a pair of upstanding frame columns 24 and 26 which mount a pair of parallel rollers 34 and 36 adapted to receive a film supply roll 30 wrapped on a core 32.
The web W passes over the idler 38 before entering into the preparatory station 14. The preparatory station 14, which is downstream from the fil.m supply station 12, includes an overhead heated-air plenum 40 through which hot air is forced through nozzles 42 forming jets of hot air on the passing film W. The film W passes over a double conical roller 44 which is shaped such as to bring the central longi-tudinal portion of the web W closest to the heated air plenum 40 and to thereby allow a temperature gradient from the center of the web laterally outwardly.
At the exit of the preparatory station 14, the web W passes under an idler roller 46 into the lateral stretching ~9~33S~
station 16. Rn overhead heated air plenum 48, similar to plen~ 40, is mounted on the frame over the path of the web to be stretched. The hot air in the heated air plenum 48 is forced to pass throuyh the nozzles 50 onto the central por tion of the web being stretched, as shown in Figure 2. The edges of the web W are pulled laterally by means of a pair of diverging vacuum-type conveyor belts 52 and 52a. Only one of these conveyor belts will be described as they are identical.
Conveyor belt 52 passes over the rollers 54 and 56 at each end of the assembly, and the belts are of a rubber cloth composition provided with 1/4 inch diameter apertures 110, as shown in Figures 4 and 7, at every inch coordinate on the belt 52. A vacuum box 57 is provided hetween the two lengths of conveyor belt, and a series of slits or apertures 112 would be provided on the box (not shown) which would be in intermittent communication with the passing apertures 110 on the belt 52. Thus, the vacuum applied through the aper-tures 110 on the belt pulls the edges of the film web W to the surfaces of the conveyor belts which are running in a forward direction on the machine but divergently.
The conveyor belt assemblies 57 and 57a can have their angles varied about pivots 104 anywhere from 0 to the horizontal axis of the web up to 25 from the longitudinal axis of the web. ~he web is laterally stretched to about 25%
of the width of the original web.
The web W is released at the end of the conveyor belts 57 and 57a to be taken up by pressure roller 58 which in turn presses the web W against the soft surface of the driven roller 60. Roller 60 would include a cover made of elastomeric material, such as rubber, about 1/2 inch deep, on a steel cylinder base. The roller 58 presses the laterally -- 6 ~
stretched web against the roller 60 which is driven at approximately the speed of the infeed roller which, of course, is higher than the speed of the web as it comes from the laterally stretching station 14 since the longitudinal advance of the web has been reduced in the light o~ the lateral stretching.
The web then goes over an idler roller 62 and about the stretching driven roller 64 which is o~ a similar con~truc-tion to roller 60. Roller 64 is.driven at a speed approxi-mately three times thè speed of the previous rollers or185%. The roller 64 overstretches the web longitudinally and feeds i.t through a path around idler roller 66. Between idler roller 66 and the wind-up roller station 22, the web relaxes back ~o its more natural position being twice the length of the original film or 100% of the infeed length. The web then pas~es under roller 94 and onto a core 100 which i5 at the wind-up roller station 22~ A pair of rollers 94 and 96 are provided in the station to support the wind-up roller 100. Roller 96 is driven by a timing belt 98 from the drive shaft 76 as will be described later. A further pressure driven roller 102 is provided above the roller 100 in order to ensure that the web is being rolled at a con~tant pressure on the roller 100.
The motor 70 drives a variable speed reducing gear box 72 by means of the helt 71. A pulley 74 is provided on the gear box ~hich in turn, with the aid of belt 73, drives a pulley 74 fixed to a drive shaft 76. From the drive shaft 76, a timing belt 82 drives a pulley 80 on the one end of the roller 60 while a further timing belt 84, mounted about a pulley adjacent pulley 60, drives the pulley 86 on the roller 64~ A tension arm 88 is also provided to keep tension on the timing belt 84. The idler 66 is mounted on a pivoting a~3S~
compensating set of a~s which are maintained in the vertical position by springs and pivoted at pivot point 92. Finally, the web is taken up on the wind-up roller 100 after passing over or under roller 94. The roller 100 is nested between rollers 94 and 96, and roller 96 can be driven by the timing belt 98 coming from the drive shaft 76. ~ pressure roller 102 is also driven and ensured that the film is rolled on the wind-up roller 100 with a constant tension.
The speeds of the stretching rollers 60, 64, can be adjusted depending on the material being stretched.
Likewise, the angle of the conveyor belts 57 and 57a can also be adjusted. Depending on the various properties of the polymer film being stretched, various results can be obtained.
Example 1 A polyethylene stretch film was cold refined on the apparatus mentioned above. The film, prior to passing through the apparatus, was characterized by the following:
length 5,000 feet thickness ~001 inch (1 mil) width 20 inches breaking point 65 pounds elongation force 40 pounds maximum elongation factor 2.4 X
memory factor at 100% elongation 25%
memory factor at 40% elongation 18%
The stretch polyethylene film was passed through the apparatus and overstretched 185% longitudinally and 25%
laterally. In the longitudinal stretching station, the web shrunk 25% laterally, therefore returning to its initial width. The elongation of the web W at the wind-up roller 100 was 100% compared to the web at the supply roll 30. The temperatures were maintained in the preparatory station and ;3tj~
the lateral stretching stations as follows:
Near the central longitudinal axis 175 to 180F.
and towards the edges of the web W, the temperature was 155F. After the bia~ial stretching, the polyethylene stretch film had the following characteristics:
length 10,000 feet thickness .0005 inches (50 gauge) width 20 inches break point 80 pounds elongation force 65 to 75 pounds maximum elongation factor 2.3 X
memory factor at 100% elongation 20%
memory factor at 40% elongation 25%
The film can be reprocessed or re-cold refined any number of times. However, it must be laid up between stretching in order to allow equilibrlum of the tension forces within the web. It has been found that a lay-up time for stretch polyethylene is 72 hours. A film which is extruded at 1.5 mil thickness, 20 inches wide, and 5,000 feet long, could, after cold refining, be .75 mil thick at 20 inches wide and 10,000 feet long. After a second cold refining, the thickness would be .375 mil thick and 20 inches wide and 20,000 feet longO After a third cold refining, the same film would have a thickness of .1875 mil, 20 inches wide, and 40,000 feet long.
g
The presen-t invention relates to a method and apparatus for treating flexible plastic films, and more particularly, to increasing the yield of polymer films by stretching such films laterally and longitudinally.
Biaxial orientation of various polymers, such as polyethylene terephthalate, is now well known in the industry, particularly in the blow molding of such polymers, whereby the parison, in the case of blow molding, will be over-stretched in the longitudinal as well as in the circumfer-ential direction in order to obtain a biaxial re-orientation of the molecules, thereby increasing the strength of the parison w~ll while making the wall thinner.
Such processes as hereinabove described have mostly been carried out in the forming stage of the product either through blow molding, injection molding, casting or extruding, at the time when the polyrner material is .subject to high temperatures and is itself in a plastic, fonnable state.
It has now been found that an extruded film, for instance, can be more efficiently biaxially oriented in its cold state. In other words, rather than biaxially orienting the film in the extrusion process, one can take the ex-truded film after it is cooled and restretch it both laterally and longitudinally in order to reduce the thickness of the film and increase or at least maintain the strength characteristics of the film, and in the case of a stretchable film, maintain its elasticity and memory.
It has also been discovered that by reprocessiny or restretching the cold film, the yield can be greatly improved. In other words, by a multi-stage reprocessing of the cold film, the film can be reduced by thr~e or four times its original thickness, yet maintain the strength and other characteristics of the original extruded film.
~e~ !33S~
The term "cold ref.ining" as used in this speci-fication means the processing of an extruded polymer film by lateral and longitudinal stretching and by simultaneously applying heat to the film.
A method in accordance with the present invention includes the treating of an extruded film of flexible polymer plastics material in elongated web form having a longitudinal axis and a lateral extent, the method including the steps of advancing the web, heating a central portion of the web gradually from the central l.ongitudinal axis of the web outwardly, stretching the web laterally by stretchiny the lateral edges of the web while applying heat thereto, the application of heat being maintained below the temperature at which the polymer material would break down, overstretching the web in its longitudinal direction, relaxiny the overstretched web and taking up the web at a length greater than and a thic~ness less than the original web while maintaining physical characteristics similar to the original web.
The types of polymers to which the present inven-tion could apply are polyethylene, polypropylene, poly-l-butene, copolymers of these and other polyolefins', including polystyrene, expanded polystyrene foam film, polysulfon, polyvinyl alcohol, polyvinylchloride, vinyl chloride acetate and copolymer derivatives, polyurethane elastomer, rubber hydrochloride, vinyl nitrite, vinylidene, chloride vinyl chloride copolymer, polymide ethylene vinyl acetate copolymer, polyester (polyethyLene terphthalate) poly~
carbonate, polymethyl , methacrylate, ionomer, fluoroplastics, fluorochloroethylene copolymer, polytetrafluoroethylene and polyvinylfluoride.
The uses and advantages of films, which are much thinner or of smaller gauge than present extruded fllms yet include the same physical characteristlcs, are quite vast. For instance, an extruded film of 1 mil can be stretched to twice its length and reduced in thickness to .5 mil. Since the physical characteristics of t'he stretched film are the same as the original extruded film', a :Lamina-te of -two such stretched films would provide twice the strength as the original film. By the same reasonin~', three superimposed or laminated ~ilms would increase the strength of the composite film which is now 1.5 mils thic~ by three.
It has also been contemplated to use such thin strong films as a composite insulating web. For instance, it can be visualized that ten stretched thin films could ~e utilized with a spacer material in between each film', such as sawdust or other', with an adhesive such that air spaces would be present between the film and the composite web would have high insulating characteristics.
It is evident from t'he above that the s-tretched or cold refined films have a yield which is much greater than the original extruded film, and thus the cost per square meter of film can be grea-tly reduced with the same physical characteristics.
~aving t~us generally described the nature of the invention, re~erence will now be made to the accompanying drawings', showing by way of illustration, a preferred em-bodiment thereof, and in which:
Figure 1 is a side elevation of the apparatus in accordance with t-he present invention, Figure 2 is a top plan view of the apparatus sho~n in Figure 1, Figure 3 which is on the same sheet as Figure 1 is an enlarged fragmentary longitudinal cross-section of a portion of the apparatus taken along line 3-3 of Figure 2, Figure 4 whlch is on the same ~heet as Figure 7 is a fragmentary top plan view, partly in cross~ection, of a detail of the apparatus' ,.'.'`;
35~
Figure 5 i.s a vertical cross-3ection taken along line 5-5 of Figure 2, Figure 6 i5 a vertical aross-section taken along-line 6-6 of Figure 2; and Figure 7 is a vertical cross-section taken along line 7-7 of Figure 2.
Referring now to the drawings, there is shown a frame 10 which includes at one end a film supply station 12 from which a web of plastic material to be treated is iden-tified by the letter W and which passes through a preparatorystation 14 and then to a lateral stretching station 16 and subsequently to a longitu~; n~l stretching station 18. From the longitudinal stretching station, the web W is rolled in a wind-up roller station 22. The longitudinal stretching assembly and the wind-up rollers are all driven by means of a drive arrangement 20.
The film supply station 12 includes a pair of upstanding frame columns 24 and 26 which mount a pair of parallel rollers 34 and 36 adapted to receive a film supply roll 30 wrapped on a core 32.
The web W passes over the idler 38 before entering into the preparatory station 14. The preparatory station 14, which is downstream from the fil.m supply station 12, includes an overhead heated-air plenum 40 through which hot air is forced through nozzles 42 forming jets of hot air on the passing film W. The film W passes over a double conical roller 44 which is shaped such as to bring the central longi-tudinal portion of the web W closest to the heated air plenum 40 and to thereby allow a temperature gradient from the center of the web laterally outwardly.
At the exit of the preparatory station 14, the web W passes under an idler roller 46 into the lateral stretching ~9~33S~
station 16. Rn overhead heated air plenum 48, similar to plen~ 40, is mounted on the frame over the path of the web to be stretched. The hot air in the heated air plenum 48 is forced to pass throuyh the nozzles 50 onto the central por tion of the web being stretched, as shown in Figure 2. The edges of the web W are pulled laterally by means of a pair of diverging vacuum-type conveyor belts 52 and 52a. Only one of these conveyor belts will be described as they are identical.
Conveyor belt 52 passes over the rollers 54 and 56 at each end of the assembly, and the belts are of a rubber cloth composition provided with 1/4 inch diameter apertures 110, as shown in Figures 4 and 7, at every inch coordinate on the belt 52. A vacuum box 57 is provided hetween the two lengths of conveyor belt, and a series of slits or apertures 112 would be provided on the box (not shown) which would be in intermittent communication with the passing apertures 110 on the belt 52. Thus, the vacuum applied through the aper-tures 110 on the belt pulls the edges of the film web W to the surfaces of the conveyor belts which are running in a forward direction on the machine but divergently.
The conveyor belt assemblies 57 and 57a can have their angles varied about pivots 104 anywhere from 0 to the horizontal axis of the web up to 25 from the longitudinal axis of the web. ~he web is laterally stretched to about 25%
of the width of the original web.
The web W is released at the end of the conveyor belts 57 and 57a to be taken up by pressure roller 58 which in turn presses the web W against the soft surface of the driven roller 60. Roller 60 would include a cover made of elastomeric material, such as rubber, about 1/2 inch deep, on a steel cylinder base. The roller 58 presses the laterally -- 6 ~
stretched web against the roller 60 which is driven at approximately the speed of the infeed roller which, of course, is higher than the speed of the web as it comes from the laterally stretching station 14 since the longitudinal advance of the web has been reduced in the light o~ the lateral stretching.
The web then goes over an idler roller 62 and about the stretching driven roller 64 which is o~ a similar con~truc-tion to roller 60. Roller 64 is.driven at a speed approxi-mately three times thè speed of the previous rollers or185%. The roller 64 overstretches the web longitudinally and feeds i.t through a path around idler roller 66. Between idler roller 66 and the wind-up roller station 22, the web relaxes back ~o its more natural position being twice the length of the original film or 100% of the infeed length. The web then pas~es under roller 94 and onto a core 100 which i5 at the wind-up roller station 22~ A pair of rollers 94 and 96 are provided in the station to support the wind-up roller 100. Roller 96 is driven by a timing belt 98 from the drive shaft 76 as will be described later. A further pressure driven roller 102 is provided above the roller 100 in order to ensure that the web is being rolled at a con~tant pressure on the roller 100.
The motor 70 drives a variable speed reducing gear box 72 by means of the helt 71. A pulley 74 is provided on the gear box ~hich in turn, with the aid of belt 73, drives a pulley 74 fixed to a drive shaft 76. From the drive shaft 76, a timing belt 82 drives a pulley 80 on the one end of the roller 60 while a further timing belt 84, mounted about a pulley adjacent pulley 60, drives the pulley 86 on the roller 64~ A tension arm 88 is also provided to keep tension on the timing belt 84. The idler 66 is mounted on a pivoting a~3S~
compensating set of a~s which are maintained in the vertical position by springs and pivoted at pivot point 92. Finally, the web is taken up on the wind-up roller 100 after passing over or under roller 94. The roller 100 is nested between rollers 94 and 96, and roller 96 can be driven by the timing belt 98 coming from the drive shaft 76. ~ pressure roller 102 is also driven and ensured that the film is rolled on the wind-up roller 100 with a constant tension.
The speeds of the stretching rollers 60, 64, can be adjusted depending on the material being stretched.
Likewise, the angle of the conveyor belts 57 and 57a can also be adjusted. Depending on the various properties of the polymer film being stretched, various results can be obtained.
Example 1 A polyethylene stretch film was cold refined on the apparatus mentioned above. The film, prior to passing through the apparatus, was characterized by the following:
length 5,000 feet thickness ~001 inch (1 mil) width 20 inches breaking point 65 pounds elongation force 40 pounds maximum elongation factor 2.4 X
memory factor at 100% elongation 25%
memory factor at 40% elongation 18%
The stretch polyethylene film was passed through the apparatus and overstretched 185% longitudinally and 25%
laterally. In the longitudinal stretching station, the web shrunk 25% laterally, therefore returning to its initial width. The elongation of the web W at the wind-up roller 100 was 100% compared to the web at the supply roll 30. The temperatures were maintained in the preparatory station and ;3tj~
the lateral stretching stations as follows:
Near the central longitudinal axis 175 to 180F.
and towards the edges of the web W, the temperature was 155F. After the bia~ial stretching, the polyethylene stretch film had the following characteristics:
length 10,000 feet thickness .0005 inches (50 gauge) width 20 inches break point 80 pounds elongation force 65 to 75 pounds maximum elongation factor 2.3 X
memory factor at 100% elongation 20%
memory factor at 40% elongation 25%
The film can be reprocessed or re-cold refined any number of times. However, it must be laid up between stretching in order to allow equilibrlum of the tension forces within the web. It has been found that a lay-up time for stretch polyethylene is 72 hours. A film which is extruded at 1.5 mil thickness, 20 inches wide, and 5,000 feet long, could, after cold refining, be .75 mil thick at 20 inches wide and 10,000 feet long. After a second cold refining, the thickness would be .375 mil thick and 20 inches wide and 20,000 feet longO After a third cold refining, the same film would have a thickness of .1875 mil, 20 inches wide, and 40,000 feet long.
g
Claims (4)
1. A composite insulating web comprising a plurality of stretched thin films laminated together and spacer material between each film, adhesive means to adhere the films to each other thereby forming air pockets with the spacer material such as to provide a composite web with high insulating characteristics.
2. A composite insulating web as defined in claim 1 wherein the spacer material is a particulate material.
3. A composite insulating web as defined in claim 2 wherein the particulate material is sawdust.
4. An extruded laminated insulating web made up of a plurality of thin films of flexible polymer plastics material which has been heated by stretching laterally while applying heat thereto, application of heat being maintained below the temperature at which the polymer material would break down and also the film having been overstretched in the longitudinal direction and thereafter having been relaxed, the laminated web including a spacer material between each film and an adhesive between the film, such that air spaces are present to provide an insulating sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000402585A CA1198354A (en) | 1982-05-10 | 1982-05-10 | Cold refining of extruded polymer film |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000402585A CA1198354A (en) | 1982-05-10 | 1982-05-10 | Cold refining of extruded polymer film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1198354A true CA1198354A (en) | 1985-12-24 |
Family
ID=4122739
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402585A Expired CA1198354A (en) | 1982-05-10 | 1982-05-10 | Cold refining of extruded polymer film |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1198354A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114379070A (en) * | 2020-10-22 | 2022-04-22 | 布鲁克纳机械有限责任两合公司 | Longitudinal tensioning mechanism and method for replacing a structural unit subject to wear |
-
1982
- 1982-05-10 CA CA000402585A patent/CA1198354A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114379070A (en) * | 2020-10-22 | 2022-04-22 | 布鲁克纳机械有限责任两合公司 | Longitudinal tensioning mechanism and method for replacing a structural unit subject to wear |
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