DIIOCYANATE-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 diisocyanate-scavenging layer and an adhesive-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 non-polymeric polyol which is not in direct contact with the polyurethane adhesive. With this approach, the nonpolymeric polyol reacts with any residual 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 diisocyanate-scavenging layer and an adhesive-contact layer; a polyurethane adhesive layer bonding the exterior film to the adhesive-contact layer of the multilayer interior film; wherein the diisocyanate-scavenging layer comprises a non-polymeric polyol.

2. The packaging laminate according to claim 1, wherein the non-polymeric polyol has at least three pendant hydroxyl groups.

3. The packaging laminate according to claim 1, wherein the non-polymeric polyol has at least four pendant hydroxyl groups.

4. The packaging laminate according to claim 1, wherein the non-polymeric polyol has a melting point of at least 200 C. (392 F.).

5. The packaging laminate according to claim 1, wherein the non-polymeric polyol is a monosaccharide, a disaccharide or an oligosaccharide.

6. The packaging laminate according to claim 1, wherein the non-polymeric polyol is a cyclodextrin.

7. The packaging laminate according to claim 1, wherein the non-polymeric polyol is defined by the generic chemical structure: ##STR00003##

8. The packaging laminate according to claim 7, wherein the non-polymeric polyol is (1R, 2R, 3S, 45, 5R, 6S)-cyclohexane-1, 2, 3 4, 5, 6-hexol.

9. (canceled)

10. The packaging laminate according to claim 1, wherein the diisocyanate-scavenging layer comprises a blend of a polyolefin and the non-polymeric 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 any of claim 1, wherein the diisocyanate-scavenging layer comprises between 1.0 wt.- % (10,000 ppm) and 5 wt.- % (50,000 ppm) of the non-polymeric polyol relative to the total weight of the diisocyanate-scavenging layer.

13. The packaging laminate according to any of claim 1, wherein the diisocyanate-scavenging layer comprises a urethane-type compound.

14. The packaging laminate according to claim 1, further comprising a separate product-contact layer in the multilayer interior film, wherein the diisocyanate-scavenging layer is disposed between the product-contact layer and the adhesive-contact layer.

15. The packaging laminate according to claim 14, wherein the diisocyanate-scavenging layer is in direct contact with the adhesive-contact layer.

16. The packaging laminate according to any of claim 1, further comprising a separate product-contact layer in the multilayer interior film, wherein the diisocyanate-scavenging layer is in direct contact with the product-contact layer and the adhesive-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 polyamides.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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:

[0033] FIG. 1 illustrates a schematic of one preferred embodiment of a packaging laminate according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0034] 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.

[0035] Preparation of Masterbatch of the Diisocyanate Scavenging Layer

[0036] 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 UD 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 non-polymeric 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 96 wt.- % of a butene linear low density polyethylene (LLDPE) (Westlake LF1040AA) having a melt index of 0.8 gram/10 min. and a density of 0.922 gram/cm.sup.3 supplied by Westlake Chemical Corporation (Houston, Tex.); about 4 wt.- % of a non-polymeric polyol, inositol (Hard Eight. Nutrition LLC, Henderson, Nev.). It is also contemplated that a masterbatch can be prepared without the use of any processing aids.

[0037] Preparation of Laminates

[0038] 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.

[0039] Preparation of Pouches

[0040] Test samples of different laminates were removed from their production roll after 24 hours, 48 hours and 72 hours curing times. A 50 in.sup.2 pouch was formed from the laminate samples using a conventional heat sealing apparatus, and then filled with 200 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.

[0041] Efficacy of the Diisocyanate-Scavenging Layer

[0042] 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), 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

[0043] 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 an adhesive-contact layer 301, a diisocyanate-scavenging layer 302 and a product-contact layer 303.

[0044] In the following Example 1, the thickness of the total exterior film 100 vary between 11.2 and 12.2 micron (0.44 and 0.48 mil), or had a total basis weight of 9.5 lbs./ream, the total thickness of the polyurethane adhesive 200 was between 1.27 and 12.7 micron (0.05 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 63.5 micron (2.5 mil) or had a total basis weight of 36.22 lbs./ream. This example is intended to be representative of a specific embodiment of the invention and is not intended to be limiting to the scope of the invention.

Example 1

[0045] The Example 1 had a structure and layer compositions as described below and as illustrated in FIG. 1. [0046] Exterior Film 100: 100 wt.-% of a 44 gauge biaxially oriented polyethylene terephthalate crystalline polyethylene terephthalate (OPET)-SARAfil TFCO (Polyplex Corporation, Uttar Pradesh, India). [0047] 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.). [0048] Adhesive-contact layer 301:90 wt.- % of a low density polyethylene (LOPE) having a melt index of 2.3 gram/10 min, a density of 0.929 gram/cm.sup.3 and a melting point of 11T C-ExxonMobil LOPE LD 129.24 (ExxonMobil Chemical Company, Houston, Tex.), and 10 wt.- % of a linear low density polyethylene (LLDPE) having a melt index of 0.9 gram/10 min, a density of 0.921 gram/cm.sup.3 and a melting point of 120 C-DOWLEX 2645G (The Doer Chemical Company, Midland, Mich.). [0049] Diisocyanate-Scavenging Layer 302: 50 wt.- % of an ethylene-based hexene elastomer, a metallocene polyethylene (ExxonMobil EXACT 3040) having a melt index of 17 gram/10 min., a density of 0.900 gram/cm.sup.3 and a melting point of 95 C supplied by ExxonMobil Company (Houston, Tex.) and 50 wt- % of the EXACT 3040 m-PE/Inositol masterbatch described herein above. Total amount of non-polymeric polyol was 2 wt.- % relative to the total weight of this layer.

[0050] Product-Contact Layer 303: 100 wt.- % of a low density polyethylene (LDPE) having a melt index of 2.3 gram/10 min, a density of 0.929 gramicm.sup.3 and a melting point of 117 C.-ExxonMobil LDPE LD 129.24 (ExxonMobil Chemical Company, Houston, Tex.).

Control Example

[0051] In the following Control Example, the thickness of the total exterior film 100 was 12.7 microns (0.5 mil), the total thickness of the polyurethane adhesive 200 was between 1.27 and 12.7 microns (0.05 and 0.5 mil), and the total thickness of monolayer interior film 300 was about 25.4 micron (1 mil). [0052] Exterior Film 100: 100 wt.- % of a 44 gauge biaxially oriented polyethylene terephthalate crystalline polyethylene terephthalate (OPET)-SARAfil TFCO (Polyplex Corporation, Uttar Pradesh, India). [0053] 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.) [0054] Exterior Film-300: 100 wt.- % of a ultra-low density polyethylene (ULDPE) having a melt index of 0.8 gram/10 min, a density of 0.914 gram/cm.sup.3 and a melting point of 101 C. (214 F.)-ATTANE NG 47010 (The Dow Chemical Company, Midland, Mich.),

[0055] Reported below are the primary aromatic amines (2,2-MDA; 2,4-MDA and 4,4-MDA) extraction results for Example 1 and Control Example by HPLC/MS spectroscopy taken after 24 hours post-lamination-TABLE 1; after 48 hours post-lamination-TABLE 2; and after 72 hours post-lamination-TABLE 3.

TABLE-US-00001 TABLE 1 Extractable Primary Aromatic Amines at 24 Hours 4,4-MDA 2,4-MDA 2,2-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) Control 4.88 107 41.97 153.85 Example 1 <0.41 10.35 36.5 47.25

TABLE-US-00002 TABLE 2 Extractable Primary Aromatic Amines at 48 Hours 4,4-MDA 2,4-MDA 2,2-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) Control <0.40 15.17 11.27 26.84 Example 1 <0.40 <0.40 7.09 7.89

TABLE-US-00003 TABLE 3 Extractable Primary Aromatic Amines at 72 Hours 4,4-MDA 2,4-MDA 2,2-MDA Total MDAs Cure Time (ppb) (ppb) (ppb) (ppb) Control <0.40 4.5 16.3 21.2 Example 1 <0.40 <0.40 10.1 10.9

[0056] 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.

[0057] 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.