CA1157756A - Process for producing multi-layer, tubular film - Google Patents
Process for producing multi-layer, tubular filmInfo
- Publication number
- CA1157756A CA1157756A CA000355152A CA355152A CA1157756A CA 1157756 A CA1157756 A CA 1157756A CA 000355152 A CA000355152 A CA 000355152A CA 355152 A CA355152 A CA 355152A CA 1157756 A CA1157756 A CA 1157756A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- film
- sheet
- layer
- tubing
- 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
Landscapes
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
PROCESS FOR PRODUCING MULTI-LAYER, TUBULAR FILM
Abstract of the Disclosure This invention is a process for producing a multi-layer thermoplastic tube by forming the substrate tube and inflating it sufficiently so that the inflation pressure alone supports the tube and no internal mandrel is needed as an additional layer or layers of film is wrapped around the tube and bonded thereto.
Abstract of the Disclosure This invention is a process for producing a multi-layer thermoplastic tube by forming the substrate tube and inflating it sufficiently so that the inflation pressure alone supports the tube and no internal mandrel is needed as an additional layer or layers of film is wrapped around the tube and bonded thereto.
Description
~ 157756 PROCES~ FOR PRODUCING ~ULTI-LAYER, ~UBULAR ~ILM
BACKGROUND
This invention relates to a process for producing a multi-layer, tubular, thermoplastic film. In particular, the invention relates to a thermoplastic, tubular film product which will serve as a casing for packaging food or which can be transversely sealed and severed to produce bags for packaging food products.
There are many ways to produce multi-layer thermoplastic films and among these are coextrusion processes in which the multiple layers are extruded simultaneously from an extrusion die, extrusion coating processes where a substrate layer is passed under an extrusion coating die which adds a layer to the substrate, and bonding processes where a preformed substrate is bonded, usually with an adhesive, to an additional layer or layers of thermoplastic film. In subsequent dev~lopments of this latter process with tubular substrates, it has been found advantageous to spirally wrap the additional layers around the tubular substrate for added strength and to balance out shrink properties and tear propagation resistance. In the prior art the wrapping of a tubular substrate is accomplished by passing the tube over a mandrel of approximately the ; same diameter as the substrate tube so that the mandrel acts as an internal support for the substrate. The use of a mandrel presents difficulties, particularly if a seamless tubing is to be wrapped.
Accordingly, it is a principal object of the present invention to eliminate the use of an internal mandrel or support means when wrapping a tubular film.
Another object of the present invention is to provide a novel process for producing a wrapped, particularly a spiral wrapped, thermo-plastic tubing which may be used in producing casings and bags.
~r, .~
~ 157756 Still another object of the present invention is to provide a continuous process for producing a multi-layer film product in which the directions of orientation of the various layers are neither parallel nor perpendicular to each other.
These and other objects of the present invention will be more readily understood by reference to the description of the invention and drawings set forth hereinafter.
DISCLOSURE STATEMENT
The following patents may be considered pertinent to the present application:
United States Patent No. 3,037,529 which issued June 5, 1963 to Albin M. Hancik and is entitled "Laminated Tube Structure and Method"
discloses a tube having a plurality of spirally wound layers of flexible resinous material.
United States Patent No. 3,294,609 which issued December 27, 1966 to W. A. Foll and is entitled "Method of Making a laminated Plastic Tube" discloses a method of making a heat sealable plastic tube by wrapping sheets around a mandrel.
20 United States Patent No. 3,519,518 which issued July 7, 1970 to R. A. Mathews et al and is entitled "Composite Tubing Product and Apparatus For Manufacturing Same" discloses a tubing in which one of the layers of the tubing wall is spirally wrapped.
BACKGROUND
This invention relates to a process for producing a multi-layer, tubular, thermoplastic film. In particular, the invention relates to a thermoplastic, tubular film product which will serve as a casing for packaging food or which can be transversely sealed and severed to produce bags for packaging food products.
There are many ways to produce multi-layer thermoplastic films and among these are coextrusion processes in which the multiple layers are extruded simultaneously from an extrusion die, extrusion coating processes where a substrate layer is passed under an extrusion coating die which adds a layer to the substrate, and bonding processes where a preformed substrate is bonded, usually with an adhesive, to an additional layer or layers of thermoplastic film. In subsequent dev~lopments of this latter process with tubular substrates, it has been found advantageous to spirally wrap the additional layers around the tubular substrate for added strength and to balance out shrink properties and tear propagation resistance. In the prior art the wrapping of a tubular substrate is accomplished by passing the tube over a mandrel of approximately the ; same diameter as the substrate tube so that the mandrel acts as an internal support for the substrate. The use of a mandrel presents difficulties, particularly if a seamless tubing is to be wrapped.
Accordingly, it is a principal object of the present invention to eliminate the use of an internal mandrel or support means when wrapping a tubular film.
Another object of the present invention is to provide a novel process for producing a wrapped, particularly a spiral wrapped, thermo-plastic tubing which may be used in producing casings and bags.
~r, .~
~ 157756 Still another object of the present invention is to provide a continuous process for producing a multi-layer film product in which the directions of orientation of the various layers are neither parallel nor perpendicular to each other.
These and other objects of the present invention will be more readily understood by reference to the description of the invention and drawings set forth hereinafter.
DISCLOSURE STATEMENT
The following patents may be considered pertinent to the present application:
United States Patent No. 3,037,529 which issued June 5, 1963 to Albin M. Hancik and is entitled "Laminated Tube Structure and Method"
discloses a tube having a plurality of spirally wound layers of flexible resinous material.
United States Patent No. 3,294,609 which issued December 27, 1966 to W. A. Foll and is entitled "Method of Making a laminated Plastic Tube" discloses a method of making a heat sealable plastic tube by wrapping sheets around a mandrel.
20 United States Patent No. 3,519,518 which issued July 7, 1970 to R. A. Mathews et al and is entitled "Composite Tubing Product and Apparatus For Manufacturing Same" discloses a tubing in which one of the layers of the tubing wall is spirally wrapped.
-2-~ 157756 SUMMARY OF THE INVENTION
The invention provides a continuous process for making a multi-layer, tubular, thermoplastic film product from flat sheets of film com-prising the steps of: forming a tube from a flat sheet of film by sealing the edges of the sheet together, said sheet comprising a substrate material selected from the group consisting of cross-linked and uncross-linked ethylene polymers and copolymers, propylene polymers or co-polymers, or nylon, said substrate having a heat-activatible coating selected from the group consisting of ethylene-vinyl acetate copolymers and ionomers, passing the tube through a first pair of nip rollers, inflating the tube and trapping an inflated portion of said tube between a second pair of nip rollers and said first pair, the resulting inflated tubing being supported between the pairs of nip rollers only by internal air pressure without any mechanical support, spirally wrapping sheet film around said inflated tube and heating the wrapped tube to bond the wrapped sheet film and tube together.
~ 1577~6 DESCRIPTION OF THE DRAWING
The drawing which is attached hereto and made a part of this disclosure consists of Figure l which is a schematic representation of the process of the present invention.
DETAILED DESCRIPTION
The process of the present invention can best be understood by reference to Figure 1 which is a schematic representation of the process as it is performed. In Figure 1, a sheet of roll stock film 1 is unwound from roll 2 and passes over guide roll 3 and under guide roll 4 as it approaches folder 5. Folder 5 can be any smooth folding mandrel which will take sheet film, overlap it, and put it in position to be sealed at a point 6 by a sealer such as a hot wire or heated roller which will seal the film in an overlap seam 7 to form an uninflated 1~ tube 10. As an alternative, a seamless tube can be used at this point which has been extruded as tubing. In either event, the tubing 10 is fed through the pair of nip rollers 8 and 9 and is inflated to become tubing 10' and this inflated segment of the tube 10' is trapped between the first set of pinch rolls 8 and 9 and the second set of pinch rolls 16 and 17. The technique for doing this is well known in the art and is sometimes referred to as the trapped bubble technique when used for heating and orienting film. However, in this instance, the inflated portion of the tubing is not heated but retains its tubular shape without stretching and the internal pressure provides sufficient rigidity so that film 11 from roll 13 and film 12 from roll 14 can be wrapped spirally therearound. Thus, the internal air pressure of tubing 10' acts as a mandrel which holds the tubing securely in place, i.e., the air pressure acts as a moving mandrel which allows the tubing to be continuously wrapped as it moves through rolls 8 and 9 to rolls 16 and 17.
~ 1577~6 Although the tubing 10' may be wrapped with a single sheet of film, it is desirable in a high speed process to use two sheets so that a greater quantity of material may be applied more rapidly. The angle at which the spiral is wound is not critical although it will generally be at a 45 angle from the direction of travel of the tube 10'. The film can be wound at Yirtually right angles to the direction of travel of the tube 10' but one of the objects of the present invention is to also provide a multi-layer film which is "cross-oriented" in that the axes of orientation of adjacent layers are neither parallel nor at right angles to each other. For example, in the instance where the material forming the tube 10' has been stretched longitudinally, the application of longitudinally stretched film 11 and 12 at approximately 45 from the ~; direction of travel of the tube lO' will provide a multi-layer film product 10 in tubular form where the axes of orientation of the adjacent layers are neither parallel nor perpendicular to each other.
After passing through pinch roll 16 the tubing is again re-inflated and passes through laminator 18 for treating. Preferably, laminator 18 is an oven which applies heat to heat bond the sheet wrapping material to the tube. The wrapping sheets 11 and 12 may be coated with a layer of a heat activatible adhesive such as ethylene-vinyl acetate copolymer which when heated above about 190F will tend to melt and form a bond between the wrapping sheets 11 and 12 and the tubing 10' to form the finished film product 20. Of course, the tubing could be coated with a heat activatible adhesive layer also so that the wrapping film 11 and 12 would not need to be so coated. Also, either the tubing material or wrapping material may be selected from polymers that readily seal one to the other. For example, the tubing material and both of the wrapping films may be constructed from oriented ethylene-vinyl acetate copolymer which will readily seal to itself.
~ 157756 As an alternate, the laminator 18, rather than being a radiant or convectively heated oven, can be a steam cabinet for more rapid transfer of heat. Infrared heating can be used as ~ell or laser beams can be focused upon the inflated tubing and scanned across the tubing surface. In some instances, it may even be desirable to irradiate the film if it is constructed from polymeric material which is readily cross-linkable by ionizing radiation.
After leaving the laminator 18, the finished film product 20 emerges from laminator 18 and passes through collapsing nip rollers 21 and 22 and is then wound up as roll 23.
In addition to the ethylene-vinyl acetate copolymers mentioned above, quite satisfactory and suitable materials for the tubing material can be selected from the polymers and copolymers of ethylene, propylene or nylon. In particular, these materials may be cross-linked or uncross-linked ethylene polymers and copolymers, polypropylene, ethylene-propylene copolymer and nylon 6 or nylon 66.
~hile the trapped "bubble" or "tube" technique described above is a commercially practical method of continuously producing a round cross-section tube, a similar result can be achieved by reducing the pressure on the outside of the tube as by passing it through a vacuum chamber and wraplping the tubing while therein. The object, of course, is to provide a sufficient pressure differential so that the tubing is relatively rigid and film layers can be wrapped therearound continuously without the use of an internal mandrel or supporting means.
~aving thus described my invention, I claim:
The invention provides a continuous process for making a multi-layer, tubular, thermoplastic film product from flat sheets of film com-prising the steps of: forming a tube from a flat sheet of film by sealing the edges of the sheet together, said sheet comprising a substrate material selected from the group consisting of cross-linked and uncross-linked ethylene polymers and copolymers, propylene polymers or co-polymers, or nylon, said substrate having a heat-activatible coating selected from the group consisting of ethylene-vinyl acetate copolymers and ionomers, passing the tube through a first pair of nip rollers, inflating the tube and trapping an inflated portion of said tube between a second pair of nip rollers and said first pair, the resulting inflated tubing being supported between the pairs of nip rollers only by internal air pressure without any mechanical support, spirally wrapping sheet film around said inflated tube and heating the wrapped tube to bond the wrapped sheet film and tube together.
~ 1577~6 DESCRIPTION OF THE DRAWING
The drawing which is attached hereto and made a part of this disclosure consists of Figure l which is a schematic representation of the process of the present invention.
DETAILED DESCRIPTION
The process of the present invention can best be understood by reference to Figure 1 which is a schematic representation of the process as it is performed. In Figure 1, a sheet of roll stock film 1 is unwound from roll 2 and passes over guide roll 3 and under guide roll 4 as it approaches folder 5. Folder 5 can be any smooth folding mandrel which will take sheet film, overlap it, and put it in position to be sealed at a point 6 by a sealer such as a hot wire or heated roller which will seal the film in an overlap seam 7 to form an uninflated 1~ tube 10. As an alternative, a seamless tube can be used at this point which has been extruded as tubing. In either event, the tubing 10 is fed through the pair of nip rollers 8 and 9 and is inflated to become tubing 10' and this inflated segment of the tube 10' is trapped between the first set of pinch rolls 8 and 9 and the second set of pinch rolls 16 and 17. The technique for doing this is well known in the art and is sometimes referred to as the trapped bubble technique when used for heating and orienting film. However, in this instance, the inflated portion of the tubing is not heated but retains its tubular shape without stretching and the internal pressure provides sufficient rigidity so that film 11 from roll 13 and film 12 from roll 14 can be wrapped spirally therearound. Thus, the internal air pressure of tubing 10' acts as a mandrel which holds the tubing securely in place, i.e., the air pressure acts as a moving mandrel which allows the tubing to be continuously wrapped as it moves through rolls 8 and 9 to rolls 16 and 17.
~ 1577~6 Although the tubing 10' may be wrapped with a single sheet of film, it is desirable in a high speed process to use two sheets so that a greater quantity of material may be applied more rapidly. The angle at which the spiral is wound is not critical although it will generally be at a 45 angle from the direction of travel of the tube 10'. The film can be wound at Yirtually right angles to the direction of travel of the tube 10' but one of the objects of the present invention is to also provide a multi-layer film which is "cross-oriented" in that the axes of orientation of adjacent layers are neither parallel nor at right angles to each other. For example, in the instance where the material forming the tube 10' has been stretched longitudinally, the application of longitudinally stretched film 11 and 12 at approximately 45 from the ~; direction of travel of the tube lO' will provide a multi-layer film product 10 in tubular form where the axes of orientation of the adjacent layers are neither parallel nor perpendicular to each other.
After passing through pinch roll 16 the tubing is again re-inflated and passes through laminator 18 for treating. Preferably, laminator 18 is an oven which applies heat to heat bond the sheet wrapping material to the tube. The wrapping sheets 11 and 12 may be coated with a layer of a heat activatible adhesive such as ethylene-vinyl acetate copolymer which when heated above about 190F will tend to melt and form a bond between the wrapping sheets 11 and 12 and the tubing 10' to form the finished film product 20. Of course, the tubing could be coated with a heat activatible adhesive layer also so that the wrapping film 11 and 12 would not need to be so coated. Also, either the tubing material or wrapping material may be selected from polymers that readily seal one to the other. For example, the tubing material and both of the wrapping films may be constructed from oriented ethylene-vinyl acetate copolymer which will readily seal to itself.
~ 157756 As an alternate, the laminator 18, rather than being a radiant or convectively heated oven, can be a steam cabinet for more rapid transfer of heat. Infrared heating can be used as ~ell or laser beams can be focused upon the inflated tubing and scanned across the tubing surface. In some instances, it may even be desirable to irradiate the film if it is constructed from polymeric material which is readily cross-linkable by ionizing radiation.
After leaving the laminator 18, the finished film product 20 emerges from laminator 18 and passes through collapsing nip rollers 21 and 22 and is then wound up as roll 23.
In addition to the ethylene-vinyl acetate copolymers mentioned above, quite satisfactory and suitable materials for the tubing material can be selected from the polymers and copolymers of ethylene, propylene or nylon. In particular, these materials may be cross-linked or uncross-linked ethylene polymers and copolymers, polypropylene, ethylene-propylene copolymer and nylon 6 or nylon 66.
~hile the trapped "bubble" or "tube" technique described above is a commercially practical method of continuously producing a round cross-section tube, a similar result can be achieved by reducing the pressure on the outside of the tube as by passing it through a vacuum chamber and wraplping the tubing while therein. The object, of course, is to provide a sufficient pressure differential so that the tubing is relatively rigid and film layers can be wrapped therearound continuously without the use of an internal mandrel or supporting means.
~aving thus described my invention, I claim:
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A continuous process for making a multi-layer, tubular, thermo-plastic film product from flat sheets of film comprising the steps of:
(a) forming a tube from a flat sheet of film by sealing the edges of the sheet together, said sheet comprising a substrate material selected from the group consisting of cross-linked and uncross-linked ethylene polymers and copolymers, propylene polymers or co-polymers, or nylon, said substrate having a heat-activatible coating selected from the group consisting of ethylene-vinyl acetate copolymers and ionomers, (b) passing the tube through a first pair of nip rollers, (c) inflating the tube and trapping an inflated portion of said tube between a second pair of nip rollers and said first pair, the resulting inflated tubing being supported between the pairs of nip rollers only by internal air pressure without any mechanical support, (d) spirally wrapping sheet film around said inflated tube, and (e) heating the wrapped tube to bond the wrapped sheet film and tube together.
(a) forming a tube from a flat sheet of film by sealing the edges of the sheet together, said sheet comprising a substrate material selected from the group consisting of cross-linked and uncross-linked ethylene polymers and copolymers, propylene polymers or co-polymers, or nylon, said substrate having a heat-activatible coating selected from the group consisting of ethylene-vinyl acetate copolymers and ionomers, (b) passing the tube through a first pair of nip rollers, (c) inflating the tube and trapping an inflated portion of said tube between a second pair of nip rollers and said first pair, the resulting inflated tubing being supported between the pairs of nip rollers only by internal air pressure without any mechanical support, (d) spirally wrapping sheet film around said inflated tube, and (e) heating the wrapped tube to bond the wrapped sheet film and tube together.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5573379A | 1979-07-09 | 1979-07-09 | |
| US55,733 | 1979-07-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157756A true CA1157756A (en) | 1983-11-29 |
Family
ID=21999798
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000355152A Expired CA1157756A (en) | 1979-07-09 | 1980-06-30 | Process for producing multi-layer, tubular film |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1157756A (en) |
-
1980
- 1980-06-30 CA CA000355152A patent/CA1157756A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |