NZ243109A - Self-welding packaging film having layers of a self-welding ionomer, ethylene vinyl acetate copolymer, a copolymer of vinylidene chloride and vinyl chloride or methyl acrylate, and a blend of hdpe and ethylene vinyl acetate copolymer - Google Patents
Self-welding packaging film having layers of a self-welding ionomer, ethylene vinyl acetate copolymer, a copolymer of vinylidene chloride and vinyl chloride or methyl acrylate, and a blend of hdpe and ethylene vinyl acetate copolymerInfo
- Publication number
- NZ243109A NZ243109A NZ243109A NZ24310992A NZ243109A NZ 243109 A NZ243109 A NZ 243109A NZ 243109 A NZ243109 A NZ 243109A NZ 24310992 A NZ24310992 A NZ 24310992A NZ 243109 A NZ243109 A NZ 243109A
- Authority
- NZ
- New Zealand
- Prior art keywords
- self
- welding
- vinyl acetate
- copolymer
- ethylene vinyl
- Prior art date
Links
- 238000003466 welding Methods 0.000 title claims description 33
- 239000005038 ethylene vinyl acetate Substances 0.000 title claims description 17
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 title claims description 17
- 229920006280 packaging film Polymers 0.000 title claims description 15
- 239000012785 packaging film Substances 0.000 title claims description 15
- 229920001577 copolymer Polymers 0.000 title claims description 13
- 229920000554 ionomer Polymers 0.000 title claims description 9
- 239000000203 mixture Substances 0.000 title claims description 8
- 229920001903 high density polyethylene Polymers 0.000 title claims description 7
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 title claims description 6
- OEPOKWHJYJXUGD-UHFFFAOYSA-N 2-(3-phenylmethoxyphenyl)-1,3-thiazole-4-carbaldehyde Chemical compound O=CC1=CSC(C=2C=C(OCC=3C=CC=CC=3)C=CC=2)=N1 OEPOKWHJYJXUGD-UHFFFAOYSA-N 0.000 title claims description 3
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 title claims description 3
- 239000000758 substrate Substances 0.000 claims description 7
- 239000004700 high-density polyethylene Substances 0.000 claims description 6
- DQXBYHZEEUGOBF-UHFFFAOYSA-N but-3-enoic acid;ethene Chemical compound C=C.OC(=O)CC=C DQXBYHZEEUGOBF-UHFFFAOYSA-N 0.000 claims description 5
- 229920000642 polymer Polymers 0.000 claims description 2
- 230000005855 radiation Effects 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 25
- 238000000034 method Methods 0.000 description 11
- 239000000463 material Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 238000010926 purge Methods 0.000 description 3
- 235000015278 beef Nutrition 0.000 description 2
- 238000007765 extrusion coating Methods 0.000 description 2
- 235000011389 fruit/vegetable juice Nutrition 0.000 description 2
- 235000013372 meat Nutrition 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 239000000565 sealant Substances 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 229920001169 thermoplastic Polymers 0.000 description 2
- 239000004416 thermosoftening plastic Substances 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- 229920003182 Surlyn® Polymers 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000012611 container material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011243 crosslinked material Substances 0.000 description 1
- 235000013365 dairy product Nutrition 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 244000144977 poultry Species 0.000 description 1
- 235000013594 poultry meat Nutrition 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000012815 thermoplastic material Substances 0.000 description 1
Landscapes
- Laminated Bodies (AREA)
- Wrappers (AREA)
Description
24 310 9
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I . e3,2_ez.-? (05 S2_
2 7 SEP m
NEW ZEALAND PATENTS ACT, 1953
No.:
Date:
COMPLETE SPECIFICATION SELF-WELDING FILM AND BAG MADE THEREFROM
We, W. R. GRACE & CO.-CONN., a corporation of the State of Connecticut, United States of America, 1114 Avenue of the Americas, New York, NY 10036, United States of America hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-
- 1 -(followed by page -la-)
24 3 1 0
Field of The"invention
This invention relates to a flexible, thermoplastic packaging film which will adhere to itself within certain temperature ranges and is referred to as being "self-welding". In particular, this invention relates to a self-welding thermoplastic film for packaging fresh meat, dairy products, and poultry.
Background of The Invention
In the prior art self-adhering packaging films which are heat shrinkable are well known? and, likewise, heat shrinkable abuse resistant films which are relatively impervious to the passage of gas or moisture are also well known. Accordingly, a prime object of the subject invention is to combine the best qualities of both of these types of films into a single film or film laminate.
In making a self-welding film, particularly a self-welding film which is to be made into receptacles such as bags, several key factors must be balanced, namely; process-ability, sealability and seal strength, and self-welding ability. Processability concerns the ease with which a bag or receptacle may be made from film free of wrinkles and creases and, after being made, the ease with which a bag or receptacle may be opened and filled. Sealability concerns the' relative speed of making bags and the strength of the heat seal which closes one end of the bag when the bag is la
24 3 1 0 9
made from flattened tubing. This primary closure seal is usually made with heated jaws under pressure. Self-welding ability concerns the ability of the material to adhere to itself at elevated temperatures. Therefore, it is another object of the present invention to provide a self-welding film which has an optimum combination of processability, sealability, and self-welding characteristics.
U. S. Patent No. 3,625,348 (Titchenal et al) discloses a self-welding film.
U. S. Patent No. 3,741,253 (Brax et al) discloses a packaging film having low oxygen permeability. This packaging film is a three layer laminate having an inner layer of cross-linked EVA copolymer, a middle layer of vinylidene chloride copolymer, and an outer layer of an EVA copolymer.
As mentioned in the foregoing paragraphs, self-welding packaging films are most often made into pouches, bags, containers, or receptacles. For packaging fresh meats it is desirable that the container not only be self-welding but that it have low gas and moisture permeability and be heat shrinkable and abuse resistant because current packaging techniques require that fresh beef, for example, remain out of contact with air if it is to be stored chilled and unfrozen for periods in excess of 10 days.. For such storage, beef products are preferably placed in a self-welding container, the container evacuated, and sealed with a heat seal or metal clip. After sealing, the bag is shrunk around the enclosed product by placing it in an elevated temperature medium such as a heat tunnel or hot water bath. In the self-welding bag or container the excess areas of the bag "weld" together after the bag has been shrunk. Self-welding provides a second seal should the clip or heat seal fail or the bag be punctured and the self-welding also will retard movement and seepage of blood and juices or "purge" within the package because the container material has welded to itself and there are no wrinkles or crevices in the material into which the
2
24 3 1 0
purge can seep. Thus, an advantage to the present invention is that there is less loss due to defective clips or seals and the packaged product has an improved appearance by preventing the seepage of the juices into the unshrunk and unsealed areas of the bag.
The term "self-welding" is not defined in precise, measurable parameters but is a subjective term, and a "self-welding" material is best defined as one which will adhere to itself in a contact seal and"will stay welded through normal commercial distribution without external force so that the self-welded areas remain impenetrable to purge. The expression "without external force" means that the self-adherence or contact weld is -maintained by the strength of the weld alone and is not due to any extraneous force pushing the film sheets or package walls together as would be the case when the interior of a bag is evacuated so that the bag walls collapse against themselves and are held in contact under the influence of atmospheric pressure.
As will be readily apparent to those skilled in the art the foregoing objects are accomplished by the present invention which is summarized below.
Summary of The Invention
In one aspect of the present invention, a self-welding packaging film comprises in order, a self-welding layer comprising an ionomer; a substrate layer comprising a copolymer of ethylene vinyl acetate; a layer comprising a copolymer of vinylidene chloride and vinyl chloride or methyl methacrylate; and an outer abuse-resistant layer comprising a blend of high density polyethylene and copolymer of ethylene vinyl acetate; said film being self-welding in its heat-shrinking temperature range.
In the preferred process it has been found that optimum self-welding and strength characteristics are
3
achieved when said blend has been cross-linked to the degree which is induced by a radiation dosage in the range from about 2.5 to 6.5 MR or greater depending upon the specific polymer ana its initial molecular weight.
The ionomer used as the sealing layer preferably has a relatively low softening point, and more preferably a softening point in the range of 190
F to 205
F. These temperatures represent those typically encountered in shrink baths operated at packaging facilities.
In the preferred embodiment of the process of the subject invention said resins are coextruded in tubular form ; and, after coextrusion, the tube is cooled, collapsed, and, if desired, irradiated to the optimum dosage level. The collapsed tubing is then heated to the orientation temperature range of one of the cross-linked materials in the tube; expanded to film thickness by the trapped bubble technique; rapidly cooled after expansion; and, again collapsed and wound up. Rapid cooling is necessary in order to bring the self-adhering surfaces below the temperature of self-adhesion before the bubble is collapsed.
Description of The Drawings
In the drawings which are appended hereto and made a part of this disclosure:
FIG. 1 is a schematic- representation of the preferred process of making the self-welding packaging film of the present invention;
FIG. 2 is a schematic representation of the process of stretching the film made in the process of FIG. 1; and,
FIG. 3 is a schematic representation of the cross-section of the packaging film of the present invention made according to the process shown in FIGS. 1 and 2.
4
3 1 0 fi'
Li ' 5 1 Best Mode of Carrying Out The Invention
Turning first to FIG. 1, the preferred process of the subject invention will be described. Extruders 2 and 4 are shown feeding coextrusion die 3 to produce a multi-walled, tubular unexpanded film laminate 1. As is known in the art, a suitable release agent is maintained within the laminated tube 1. This laminate is chilled by bath 5 and collapsed by pinch rolls 6 and leaves the bath 5 over guide rolls 7. Extruders for thermoplastic materials and coextrusion dies fed by two or more extruders are well known in the art and are available from a number of manufacturers.
Extruder 2 which, by way of example, feeds the inner melt stream for die 3 to form the innermost annular die stream in die 3 is fed by an ionomer. For the material for the outer or substrate layer of the two ply tube which emerges from coextrusion die 3, extruder 4 is fed by an ethylene vinyl acetate copolymer resin . ■ After the coextruded tubing leaves bath 5 over guide roll 7 it passes into shielded irradiation vault 8, through the beam from electron accelerator 9, over roll 11, and out of the vault to rollers 12. The electron beam produced by the accelerator is operated at an energy and current level such that the tube material receives a dosage of between about 2.5 MR and 6.5 MR.
Upon moving through pinch rolls 12 the previously flattened and collapsed tubing . is inflated to a round cross-section but not stretched beyond its originally extruded diameter. The inflated tubing next passes through vacuum chamber 14 and receives a layer on its outer surface as it passes through extrusion coating die 15 which is fed by extruder 13. The function of the vacuum chamber 14 is to remove air from around the tubing and to prevent any air bubbles from being trapped between the coating layer 16 and the tubing 14.
24 3 1
The extruder 13 is fed a vinylidene chloride copolymer.
After receiving the vinylidene chloride copolymer coating, the two ply tube is now three ply tube 10 which is fed through a second vacuum chamber 17 and through a second extrusion coating die 18 which is fed by extruder 19. Melt 16' is coated onto the tubing 10 to form four ply tubing 100. The extruder 19 is fed a blend of high density polyethylene and ethylene vinyl acetate copolymer. -*
In FIG. 2 the four ply tubing 100 from roll 20 is unwound and fed through hot water bath 21 which is maintained at approximately 170
F (94
C) which is within the orientation temperature range of the irradiated ethylene-vinyl acetate copolymer layer coextruded from extruder 4. As the collapsed tubing 100 leaves the water bath 21 and passes through pinch rollers 22, it is expanded into bubble 200 by inflating the tubing and trapping the inflated portion or bubble between pinch rollers 22 and 24. The inner layer of the laminated tubular film, which is the ionomer, has been raised to its melting temperature range by the hot water bath and the flattened tube walls are separable while hot so bubble 200 can be formed. However, this layer must be cooled below its self-adhering temperature before it is collapsed and wound up or it will completely adhere to itself in the wind up roll 25. Air rings 201, 300, and 301 surround the bubble 200 and chilled air is delivered to them. The chilled air impinges uniformly on the bubble surface to cool the inner layer below its self-adhering temperature range before the bubble is collapsed.
A cross-section of the expanded film 100' is represented by FIG. 3 where inner layer 101 comprises the ionomer, the substrate layer 102 comprises cross-linked ethylene vinyl acetate copolymer, the relatively gas impermeable layer 103 comprises vinylidene chloride copolymer, and the outer layer 104 comprises a blend of high density polyethylene and ethylene vinyl acetate copolymer. This four ply material has
6
243109
low gas and moisture permeability, has excellent abuse resistance and structural strength, heat shrinkability and self-weldability. The film 100' in its flattened tubular condition as it is wound up to roll 25 in FIG. 2 may be transversely sealed and severed to form bags which are heat shrinkable and self-weldable.
Embodiments of The Packaging Film
Preferred packaging films according to the subject invention are described in the examples set forth below. These examples were produced by the above-described process.
Example (1)
The self-welding sealant layer comprises an ionomer (Surlyn 1702-1 from DuPont); a substrate layer adjacent the sealant layer was ethylene vinyl acetate copolymer (EP 4062 -2 from DuPont) having 15% vinyl acetate ; the barrier layer was a vinylidene chloride methyl acrylate copolymer (MA 134 from Dow) having 8.5% methyl acrylate comonomer; and the outer, abuse-resistant layer was a blend of 16% high density polyethylene (Alathon 7850 from Oxychem) and 84% ethylene vinyl acetate copolymer (LD-318-92 from Exxon) having 9% vinyl acetate.
The ionomer/substrate were irradiated to a dosage equivalent of 3.5 megarads.
The four ply laminate of this Example was oriented from a hot water bath at 170
F to 212
F.
Example (2)
Another preferred film was prepared in the same way as Example 1, but having a substrate layer of ethylene vinyl acetate copolymer having a vinyl acetate content of 19% (LD 720.92 from Exxon).
7
2* A 9
Claims (6)
1. A self-welding packaging film comprising, in order:
(a) a self-welding layer comprising an ionomer;
(b) a substrate layer comprising a copolymer of ethylene vinyl acetate;
(c) a layer comprising a copolymer of vinylidene chloride and vinyl chloride or methyl acrylate; and
(d) an outer abuse-resistant layer comprising a blend of high density polyethylene and a copolymer of ethylene vinyl acetate;
said film being self-welding in its heat-shrinking temperature range.
2. The self-welding packaging film of claim 1
wherein the polymer in said self-welding layer has been cross-linked to a degree which is induced by a radiation dosage of 2.5 to 6.5 MR.
3. The self-welding packaging film of claim 1
wherein the outer abuse-resistant layer comprises a blend of 10% to 20% by weight high density polyethylene; and 80% to 90% by weight of a copolymer of ethylene vinyl acetate.
5. A self-welding packaging film substantially as hereinbefore described with reference to the accompanying examples and drawings.
with reference to the accompanying example ^ ^
4. A bag made from the film of claim 1.
6. A bag substantially as hereinbefore describedti
8
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73667291A | 1991-07-26 | 1991-07-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| NZ243109A true NZ243109A (en) | 1994-09-27 |
Family
ID=24960825
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| NZ243109A NZ243109A (en) | 1991-07-26 | 1992-06-11 | Self-welding packaging film having layers of a self-welding ionomer, ethylene vinyl acetate copolymer, a copolymer of vinylidene chloride and vinyl chloride or methyl acrylate, and a blend of hdpe and ethylene vinyl acetate copolymer |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH05220904A (en) |
| AU (1) | AU662533B2 (en) |
| CA (1) | CA2071234A1 (en) |
| MX (1) | MX9204215A (en) |
| NZ (1) | NZ243109A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0802044A3 (en) * | 1996-04-16 | 2000-03-22 | Danapak A/S | Method for the manufacture of a self-adhesive recloseable packing laminate |
| AR041232A1 (en) * | 2002-09-12 | 2005-05-11 | Danaflex Packaging Corp Ltd | SECONDARY SEALING BARRIER FILMS |
| CN102083624A (en) | 2008-05-28 | 2011-06-01 | 比密斯公司 | Innerliner with EVA copolymer |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4853265A (en) * | 1987-09-02 | 1989-08-01 | W. R. Grace & Co.-Conn. | Eva based multi-layer, heat-shrinkable, packaging film and bags made therefrom |
-
1992
- 1992-06-11 NZ NZ243109A patent/NZ243109A/en unknown
- 1992-06-15 CA CA002071234A patent/CA2071234A1/en not_active Abandoned
- 1992-06-18 AU AU18391/92A patent/AU662533B2/en not_active Ceased
- 1992-07-17 MX MX9204215A patent/MX9204215A/en unknown
- 1992-07-20 JP JP4213200A patent/JPH05220904A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU662533B2 (en) | 1995-09-07 |
| JPH05220904A (en) | 1993-08-31 |
| AU1839192A (en) | 1993-01-28 |
| CA2071234A1 (en) | 1993-01-27 |
| MX9204215A (en) | 1993-01-01 |
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