DIISOCYANATE-SCAVENGING PACKAGING LAMINATES

Abstract

The present invention is directed to packaging laminates for containing a food or pharmaceutical/medical product which includes an exterior film, a multilayer interior film comprising a product-contact layer, a diisocyanate-scavenging layer and an exterior film-contact layer, and a polyurethane adhesive layer bonding the exterior film to the multilayer interior film. The present invention reduces the amount of any unreacted diisocyanate precursor and primary amines which can migrate to a product in packaging assemblies formed with a polyurethane adhesive. This is achieved when an interior film (commonly known as a sealant film) includes a layer comprising a polyether polyol which is not in direct contact with the polyurethane adhesive. With this approach, the polyether polyol reacts with any residua! diisocyanate and/or primary amines which migrates from the polyurethane adhesive through the laminated assembly and thus, neutralizes any potential undesirable effects of these compounds.

Claims

1. A packaging laminate comprising: an exterior film; a multilayer interior film comprising a product-contact layer, a diisocyanate-scavenging layer and an exterior film-contact layer; a polyurethane adhesive layer bonding the exterior film to the exterior film-contact layer of the multilayer interior film; wherein the diisocyanate-scavenging layer comprises a polyether polyol.

2. The packaging laminate according to claim 1, wherein the polyether polyol is defined by the chemical formula: ##STR00004##

3. The packaging laminate according to claim 1, wherein the polyether polyol is defined by the chemical formula: ##STR00005##

4. The packaging laminate according to claim 1, wherein the polyether polyol is defined by the chemical formula: ##STR00006##

5. The packaging laminate according to claim 1, wherein the polyether polyol is selected from the group consisting of poly(ethylene glycol), poly(propylene glycol), poly(butylene glycol), poly(tetramethylene oxide) and blends thereof.

6. The packaging laminate according to claim 1, wherein the polyether polyol is poly(ethylene glycol).

7. The packaging laminate according to claim 1, wherein the polyether polyol has a minimum weight average molecular weight of at least 600 gram/mole.

8. The packaging laminate according to claim 1, wherein the polyether polyol has a maximum weight average molecular weight of 8000 gram/mole.

9. The packaging laminate according to claim 1, wherein the polyether polyol is a food grade polyether polyol.

10. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer comprises a mixture of a polyolefin and a polyether polyol.

11. The packaging laminate according to claim 10, wherein the polyolefin comprises high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene/-olefin copolymer, ethylene vinyl acetate copolymer, polypropylene, polybutylene and blends thereof.

12. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer comprises between 1500 ppm and 7500 ppm of polyether polyol relative to the total weight of the multilayer interior film.

13. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer comprises polyurethane.

14. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer is disposed between the product-contact layer and the exterior film-contact layer.

15. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer is in direct contact with the exterior film-contact layer.

16. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer is in direct contact with the product-contact layer and the exterior film-contact layer.

17. The packaging laminate according to claim 1, wherein the polyurethane adhesive comprises a two-component polyurethane adhesive.

18. The packaging laminate according to claim 17, wherein the two-component polyurethane adhesive comprises a diisocyanate and a polyol.

19. The packaging laminate according to claim 17, wherein the two-component polyurethane adhesive comprises an aromatic diisocyanate and a polyol.

20. The packaging laminate according to claim 1, wherein the exterior film comprises an exterior film layer comprising oriented polyethylene terephthalate, oriented polypropylene or oriented polyamide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0026] FIG. 1 illustrates a schematic of one preferred embodiment of a packaging laminate according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

Preparation of Masterbatch of the Diisocyanate Scavenging Layer

[0028] Compounding of a masterbatch for the diisocyanate-scavenging layer was done in advance to make the multilayer interior film. The masterbatch was compounded using APV MP2050 co-rotating 50 mm twin-screw extruder with a dual segment barrel (10:1 and 15:1) 25:1 ID machine. The drive was a 38 HP motor with a maximum screw speed of 600 RPM. The extruder has several barrel-temperature zones, including the die, and was water cooled. The extruder was heated to a temperature from 82 F. (180 C.) to 193 C. (380 F.). The screw speed was kept at about 300 RPM's. The specific conditions of the extruder can vary depending upon the specific thermoplastic resin and polyether polyol used to form the diisocyanate scavenging layer and the relative ratio of these components. The specific conditions of operation can readily be determined by one skilled in the art. The extruder extruded the layer masterbatch composition as strands which were then cooled and cut into pellets for subsequent use. In one preferred embodiment, a masterbatch was formed under the conditions described above which included a composition of about 97 wt.-% of a linear low density polyethylene (Westlake LF 1040) having a melt index of 2.0 gram/10 min. and a density of 0.919 gram/cm.sup.3 supplied by Westlake Polymers LP (Houston, Tex.); about 2 wt.-% of a poly(ethylene glycol) (CARBOWAX SENTRY polyethylene glycol (PEG) 3350) having a weight average molecular weight of between 3015 and 3685, a density at 60 C. of 1.09 gram/cm.sup.3, and a range of average hydroxyl number of between 30 and 38 milligram KOH/gram supplied by The Dow Chemical Company, Inc. (Midland, Mich.); and about 1 wt.-% of a fluoropolymer elastomer processing aid (3M Dynamar FX9613) supplied by 3M Company, Inc. (St. Paul, Minn.). It is also contemplated that a masterbatch can be prepared without the use of any processing aids.

Preparation of Laminates

[0029] Any suitable method of making flexible laminates can be used to form the laminates of the present invention. One specific method for use with solventless polyurethane adhesives included combining the diisocyanate precursor and the polyol precursor of the adhesive and then immediately sending the mixed components onto the lamination gravure rollers of a conventional plastic film laminator. In one preferred embodiment, a 1:1 ratio of diisocyanate to polyol precursor was used. Useful coating temperatures range from 20 C. to 75 C. Lower temperatures are preferred during the process in order to extend the working life of the adhesive composition. The mixed adhesive was then applied to an in-line corona treated surface of the exterior film. The coating weight of the adhesive may vary broadly depending on the desired properties of the laminate. Useful adhesive coating weights include from 0.5 grams/meter.sup.2 to 3 grams/meter.sup.2 and preferably from 1.5 grams/meter.sup.2 to 2.5 grams/meter.sup.2. Once coated, the exterior film was mated to the multilayer interior film by pressing the exterior film/adhesive/interior film structure together by use of nip rollers. The laminate was then wound onto a production roll for curing of the adhesive.

Preparation of Pouches

[0030] Test samples of different laminates were removed from their production roll after 24 hours, 48 hours and 72 hours curing times. A 100 in.sup.2 pouch was formed from the laminate samples using a conventional heat sealing apparatus, and then filled with 750 mL of food simulant (3% acetic acid solution) so that there was minimal headspace within the pouch. Specific heat sealing conditions such as sealing temperature, sealing pressure and sealing time can vary depending upon the specific thermoplastic used for the food-contact layer and would be readily known to one skilled in the art. The food simulant was prepared by diluting 1.5 liters of glacial acetic acid to 50 liters using ultra purified water.

Efficacy of the Diisocyanate-Scavenging Layer

[0031] The approach taken to test the efficacy of the diisocyanate-scavenging layer was to make pouches after the three post-lamination times, fill the pouches with a suitable food simulant, and seal and store the pouches. After filling, the pouches were kept in an air circulated oven for 2 hours at 70 C., after which a 20 mL sample of food simulant within the pouch was retrieved. The amount of extractable primary aromatic amines in the food simulant was then measured. One method of determining the amount of migratory amines is with the use of HPLC/MS coupling which measures the amines directly. Because it was believed that the lamination adhesive used for this study (MOR-FREE 403A/MOR-FREE C-117) contained three structural isomers of methylene diphenyl diisocyanate (MDI), i.e., 2,2-methylene diphenyl diisocyanate, 2,4-methylene diphenyl diisocyanate and 4,4-methylene diphenyl diisocyanate, the corresponding primary aromatic amines of these diisocyanate isomers were detected via liquid chromatography/mass spectrometry. The specific aromatic amines detected were 2,2-methylenedianiline (2,2-MDA), 2,4-methylenedianiline (2,4-MDA) and 4,4-methylenedianiline (4,4-MDA). A API 4000 LC/MS/MS system manufactured by AB Sciex LLC (Framingham, Mass.) which combines high pressure liquid chromatography (HPLC) with a quadrupole mass spectrometry (MS) was used to determine the concentration of the three primary aromatic amine isomers in each sample of food simulant. The retention time and concentration for each primary aromatic amine isomer were calibrated using commercial available analytical standards for each primary aromatic amine isomer using a Phenomenex Luna C18(2) HPLC column manufactured by Phenomenex Inc. (Torrance, Calif.). A 1 mL aliquot of the 20 mL sample of food simulant within each pouch was placed into an injection vial which had a 2 L portion of analytical standards of each primary aromatic amine isomer.

Working Examples

[0032] FIG. 1 illustrates one preferred embodiment of a laminate according to the present invention. In this drawing, laminate 10 comprises an exterior film 100, a polyurethane adhesive layer 200, and a multilayer interior film 300 comprising a exterior film-contact layer 301, a diisocyanate-scavenging layer 302 and a product-contact layer 303.

[0033] In the following Control Example and Examples 1-4, there is described various embodiments of a laminate 10 as illustrated in FIG. 1. In all these examples, the thickness of the total exterior film 100 vary between 0.44 mil and 0.48 mil, or had a basis weight of 9.5 lbs./ream, the total thickness of the polyurethane adhesive 200 was between 0.05 mil and 0.5 mil, or had a basis weight of 1.2 lbs./ream, and the total thickness of multilayer interior film 300 was about 2.5 mil or had a basis weight of 36.22 lbs./ream. The layer compositions of the exterior film, polyurethane adhesive and multilayer interior film are described below along with the individual thicknesses (basis weight) of each layer of the interior film. Also reported are the primary aromatic amines (2,2-MDA; 2,4-MDA and 4,4-MDA) extraction results by HPLC/MS spectroscopy taken after 24 hours, 48 hours and 72 hours post-lamination. These examples are intended to be representative of specific embodiments of the invention and are not intended to be limiting to the scope of the invention.

Control Example

[0034] The Control Example had a structure and layer compositions as described below and as illustrated in FIG. 1. No polyether polyol was present in the diisocyanate-scavenging layer 302 of interior film 300 of the Control Example. The extraction results by HPLC/MS spectroscopy are reported in TABLE 1. [0035] Exterior Film 100: 100 wt.-% of a 44 gauge biaxially oriented polyethylene terephthalate crystalline polyethylene terephthalate (OPET)-SARAfil TFCO (Polyplex Corporation, Uttar Pradesh, India). [0036] Polyurethane Adhesive 200: 100 wt.-% of a solventless, two-component polyurethane adhesive-MOR-FREE 403A/MOR-FREE C-117 (The Dow Chemical Company, Midland, Mich.) [0037] Exterior Film-Contact layer 301: 100 wt.-% of a linear low density polyethylene (LLDPE) having a melt index of 1.0 gram/10 min and a density of 0.922 gram/cm.sup.3-DOWLEX 2045G (The Dow Chemical Company, Midland, Mich.). Total basis weight of 39.98. [0038] Diisocyanate-Scavenging Layer 302: 100 wt.-% of a linear low density polyethylene (LLDPE) having a melt index of 2.0 gram/10 min and a density of 0.918 gram/cm.sup.3-Mobil LLDPE LL 1002YB (ExxonMobil Chemical Company, Houston, Tex.). Total basis weight of 25.02. [0039] Product-Contact Layer 303: 100 wt.-% of a medium density polyethylene (MDPE) having a melt index of 2.3 gram/10 min and a density of 0.929 gram/cm.sup.3-ExxonMobil LDPE LD 129.24 (Exxon Mobil Chemical Company, Inc., Houston, Tex.). Total basis weight of 15.

TABLE-US-00001 TABLE 1 Extractable Primary Aromatic Amines 2,2-MDA 2,4-MDA 4,4-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) 24 Hours 33.83 98.73 5.77 138.33 48 Hours 19.13 19.83 0 38.96 72 Hours 16.6 9.82 0 28.42

Example 1

[0040] Example 1 had a structure and layer compositions as described above in the Control Example and as illustrated in FIG. 1, except for the composition of the diisocyanate-scavenging layer 302 of the interior film 300. In this example, the composition of layer 302 was a blend of 97 wt.-% of a linear low density polyethylene (LLDPE) having a melt index of 2.0 gram/10 min and a density of 0.919 gram/cm.sup.3-Westlake LF 1040 (Houston, Tex.); about 2 wt.-% of a poly(ethylene glycol)-CARBOWAX SENTRY polyethylene glycol (PEG) 3350 having a weight average molecular weight of between 3015 and 3685, a density at 60 C. of 1.09 gram/cm.sup.3, and a range of average hydroxyl number of between 30 and 38 milligram KOH/gram (The Dow Chemical Company, Inc., Midland, Mich.); and about 1 wt.-% of a fluoroelastomer processing aid-3M Dynamar FX9613 (3M Company, Inc., St. Paul, Minn.). The CARBOWAX SENTRY polyethylene glycol (PEG) 3350 is a food grade polyether polyol. This layer had a basis weight of 4.5 lbs./ream which corresponded to 2485 ppm of polyether polyol relative to the total weight of the interior film 300. The extraction results by HPLC/MS spectroscopy are reported in TABLE 2.

TABLE-US-00002 TABLE 2 Extractable Primary Aromatic Amines 2,2-MDA 2,4-MDA 4,4-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) 24 Hours 19.07 32.13 26.87 78.07 48 Hours 10.71 2.64 15.03 28.38 72 Hours 5.83 0.71 8.21 14.75

Example 2

[0041] Example 2 had a structure and layer compositions as described above in the Example 1 and as illustrated in FIG. 1, except that the diisocyanate-scavenging layer 302 had a basis weight of 6.8 lbs./ream which corresponded to 3750 ppm of polyether polyol relative to the total weight of the interior film 300. The extraction results by HPLC/MS spectroscopy are reported in TABLE 3.

TABLE-US-00003 TABLE 3 Extractable Primary Aromatic Amines 2,2-MDA 2,4-MDA 4,4-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) 24 Hours 20.5 6.95 0 27.45 48 Hours 9.5 0.79 0 10.29 72 Hours 7.78 0.7 0 8.48

Example 3

[0042] Example 3 had a structure and layer compositions as described above in the Example 1 and as illustrated in FIG. 1, except that the diisocyanate-scavenging layer 302 had a basis weight of 7.0 lbs./ream which corresponded to 3865 ppm of polyether polyol relative to the total weight of the interior film 300. The extraction results by HPLC/MS spectroscopy are reported in TABLE 4.

TABLE-US-00004 TABLE 4 Extractable Primary Aromatic Amines 2,2-MDA 2,4-MDA 4,4-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) 24 Hours 19.07 10.29 0 29.36 48 Hours 10.71 1.3 0 12.01 72 Hours 5.83 0.6 0 6.43

Example 4

[0043] Example 4 had a structure and layer compositions as described above in the Example 1 and as illustrated in FIG. 1, except that the diisocyanate-scavenging layer 302 comprised 67 wt.-% of an ultra-low density polyethylene having a melt index of 0.80 gram/10 min and a density of 0.914 gram/cm.sup.3-ATTANE NG 4701G (The Dow Chemical Company, Inc., Midland, Mich.), 31.51 wt.-% of an ethylene vinyl acetate copolymer having a vinyl acetate content of 5.0 wt.-%, a melt index of 1.5 gram/10 min and a density of 0.927 gram/cm.sup.3-Petrothene NA442 (LyondellBasell Industries, Houston, Tex.) and 1.49 wt.-% of a poly(tetramethylene oxide) having a weight average molecular weight of between 1950 and 2050 gram/mole-PolyTHF 2000 Polyether (BASF Corporation, Florham Park, N.J.). The PolyTHF 2000 Polyether is a food grade polyether polyol. This layer had a basis weight of 9.0 lbs./ream which corresponded to 1640 ppm of polyether polyol relative to the total weight of the interior film 300. The extraction results by HPLC/MS spectroscopy are reported in TABLE 5.

TABLE-US-00005 TABLE 5 Extractable Primary Aromatic Amines 2,2-MDA 2,4-MDA 4.4-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) 24 Hours 25.07 41.4 0.73 67.2 48 Hours 15.37 6.27 0 21.64 72 Hours 9.77 1.57 0 11.34

[0044] The above-described data demonstrate the efficiency of the packaging laminates of the present invention in reducing the level of primary aromatic amines to acceptably low levels, within a short period of time, to eliminate long storage times.

[0045] The above description and examples illustrate certain embodiments of the present invention and are not to be interpreted as limiting. Selection of particular embodiments, combinations thereof, modifications, and adaptations of the various embodiments, conditions and parameters normally encountered in the art will be apparent to those skilled in the art and are deemed to be within the spirit and scope of the present invention.