PEGUERO, Larissa, Marie (52 Harvard Avenue, Warwick, Rhode Island, 02889, US)
BOWER, Douglas, James (1145 Wordens Pond Road, Charlestown, Rhode Island, 02813, US)
PEGUERO, Larissa, Marie (52 Harvard Avenue, Warwick, Rhode Island, 02889, US)
| WO 2011/140317;d is PCT/US2011/035320 285 I . An article resistant to oxygen and moisture vapor transmission, the article comprising a reclaimed composition comprising metal particles uniformly dispersed in a polymeric matrix, in which the reclaimed composition is a blend of (a) a virgin polymer component free of metal particles and (b) a reclaimed polymer component comprising metal-containing polymer derived from a pre-existing metalized polymer film. 290 2. The article of claim 1 in which the pre-existing metalized polymer film has a layer of polyester and a metal layer in direct contact with the layer. 3. The article of claim 2 in which the polyester is polyethylene terephthalate. 4. The article of claim 2 which is a barrier film consisting essentially of a base layer of the reclaimed composition and in which the reclaimed composition comprises 295 about 0.1 wt% to about 95 wt% of the reclaimed polymer component. 5. The article of claim 4 in which the reclaimed composition comprises about 5 wt% to about 10 wt% of the reclai med polymer component. 6. The article of claim 4 in which the barrier film has a thickness of about 3 μηι ( 12 gauge) to about 16μηι (64 gauge). 300 7. The article of claim 4 further comprising a metal layer in direct contact with the base layer in which the metal layer comprises a transition metal or alloy containing a transition metal. 8. The article of claim 7 in which the metal layer consists essentially of aluminum and the barrier film has an optical density of about 1 to about 4. 305 9. The article of claim 7 further comprising a polymeric core layer in direct contact with the base layer and opposite the metal layer. 10. A method of making an article resist ant to oxygen and moisture vapor transmission comprising the steps of (A) providing a pre-existing metalized polymer film having a metal layer in direct 310 contact with a polymer layer, (B) forming the pre-existing metalized polymer film into particles, WO 2011/140317^ particles of the pre-existing metahzed polymer film PCT/US2011/035320 virgin polymer to form a mixture comprising about 0.1 wt% to about 95 wt% of the preexisting metahzed polymer and a complementary amount of virgin polymer, 315 (D) melt processing the mixture to form a reclaimed composition comprising metal particles uniformly dispersed in a polymeric matrix, and (E) forming the reclaimed composition into an article resistant to oxygen and moisture vapor transmission. 1 1 . The method of claim 10 in which the article is a barrier film having two sides 320 and a thickness of about 3 μηι ( 12 gauge) to about 16μηι (64 gauge), and which method further comprises depositing a metal layer on the article in direct contact with one side of the barrier film such that the barrier film has an optical density of about 1 to about 4. 12. The method of claim 1 1 in which polymer of the barrier film consists essentially of polyethylene tercphthalate and the metal of the barrier film consists 325 essentially of aluminum. 1 3. The method of claim 10 in which the pre-existing metahzed polymer film is waste material recovered from the production of metahzed polyester film. 14. A method of recovering metahzed polyester film comprises the steps of recovering waste material from the production of multilayer metahzed polyester film, the 330 waste material consisting essentially of film having a base layer of polymer and a metal layer in direct contact with the base layer, forming waste material into particles blending the particles from the metahzed PET with particles from non-metalized PET base film to form a mixture comprising about 0.1 wt% to about 95 wt% of the waste material and a complementary amount of virgin polymer, melt processing the mixture to form a 335 reclaimed composition comprising metal particles uniformly dispersed in a polymeric matrix, and forming the reclaimed composition into an article resistant to oxygen and moisture vapor transmission. 15. A method of microwave cooking comprising the steps of ( A) providing a microwave susccptor formed by the steps of (i) obtaining multilayer metahzed polyester 340 film having a base layer of polymer and a metal layer in direct contact with the base layer, (ii) forming the multilayer metahzed polyester film into particles, (iii) blending the particles from the metahzed polyester film with particles of a non-metalized virgi WO 2011/140317m a mixture comprising about 0.1 wt% to about 95 wt'PCT/US20 l 1/035320 metalized polyester film and a complementary amount of virgin polymer, (iv) melt 345 processing the mixture to form a reclaimed composition comprising metal particles uniformly dispersed in a polymeric matrix, (v) forming the reclaimed composition into the microwave susceptor, ( B) providing an article of food that browns when conventionally heated, (C) placing the article of food in proximity to the microwave susceptor within a microwave oven, and (D) utilizing the microwave oven to effectively 350 irradiate the article of food, thereby cooking and browning the food. |
METALIZED POLYESTER
FIELD OF THE INVENTION
This invention relates to metal-containing polymer film having barrier properties to resist transmission of chemicals through the film. More specifically it relates to composite film with oxygen and moisture barrier properties and having a layer of a blend that includes a component obtained from reclaimed metalized PET film.
BACKGROUND OF THE INVENTION
It is common in the polyester film industry to produce specialty high oxygen and moisture barrier films for use as protective overwrap materials on foods and other oxygen or moisture sensitive products. This can be done with a variety of technologies including, but not limited to coextrusion of barrier polymers such as poly(ethylene vinyl alcohol) "EVOH", poly(ethylene naphthalate) "PEN" and polyamides, or by subsequent coating of the film using barrier polymers such as EVOH or poly(vinylidene chloride) "PvDC".
Another common approach to creating a high moisture and oxygen barrier is to overcoat the surface of the film with a layer of metal, such as aluminum or other metals typically using vacuum deposition. The metal layer provides a nearly impenetrable and therefore excellent moisture and oxygen barrier as well as an economical cost for the applications. Representative techniques for depositing nanometer thickness metal onto barrier films are disclosed in such references as US patent nos. 5631066 and 6153276.
Typically, the process of making metal-overcoated polymer film, i.e., metalized film, generates waste of trim scrap. Trim scrap results from slitting rolls to custom product widths, or from recovered metalized polyethylene tereph thai ate "PET" film that has defects which cause rejection (e.g., wrinkles, creases, poor metalization). With non- metalized PET, it is industry practice to take trim scrap and defect material and shred it into a flake, pelletize the flake through a secondary extrusion process, crystallize those pellets so that they do not agglomerate during further processing, and use these pellets as part of the resin feed to form a layer, such as a core or skin of a multilayer PET film. component of usual ly a virgin PET to form the layer of the multilayer PET film.
However, metalized PET has not been recycled. The metal particles can potentially cause web breaks during film formation processing if metalized film reclaim material is fed in a similar manner to non-metalized PET reclaim material. The tendency for web breaks to occur is believed due to the difference in crystallinity Accordingly, trim scrap and defect-containing metalized PET waste has traditionally been discarded at cost of materials, processing cost, and disposal and environmental costs. An objective of this invention is to provide a process that overcomes this difficulty as well as adds benefits of improved properties of the resultant film.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides the use of metalized film that has been shredded, pelletized or densified and dried/crystallized as a component for either the core or skin layer in a PET film. By appropriate processing conditions in the pelletizing operation, sufficiently small particles of the aluminum layer can be formed and dispersed in the PET resin.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an elevation section view of an embodiment of this invention of a multilayer film with a metal layer positioned on a polymer base layer that includes metalized polymer film reclaim material.
Fig. 2 is an elevation section view of an embodiment of this invention of a multilayer film with a polymer substrate layer on which is positioned a film as depicted in Fig. 1 .
Fig. 3 is an elevation section view of an embodiment of this invention in which a polymeric core layer is sandwiched between a polymer substrate layer on one side and a film as depicted in Fig. 1 on the opposite side.
DETAILED DESCRIPTION OF THE INVENTION
Reclaimed material means a substance that has been at least once formed into an article by a shape-transforming process. Usually as applied to this invention, shape- transforming process includes thermoplastic processing such as film extrusion of a polymeric composition. Virgin material means a raw material synthesized or refined . . . .
reclaimed material can be recovered from manufactured articles and recycled for use as a raw material to make another product. The reclaimed material can be combined with a virgin material to form a part or a whole of the product or it can be incorporated by itself, i.e., without combining with a virgin material.
This invention particularly relates to reclaimed material that includes both polymer and metal components, and especially to reclaimed metalized polymer film, i.e., a composite film having a layer of polymer and a metal layer positioned thereon. The metalized reclaimed film contemplated for use according to this invention typically has a polymeric layer of about 1 -1000 μπι thickness, and preferably about 1 - 100 iim thickness.
The metal component of the reclaimed metalized film is usually a distinct layer of the composite. The typical purposes of the metal component layer are to provide a moisture and/or gas barrier or for aesthetic decoration of the film. Hence the metal layer can be any thickness consistent with these utilities. Although the metal layer could be as thick as foil in the range of about 1 -10 μηι, usually the metal layer of the film being reclaimed is ultra thin. Preferably the metal of the reclaimed film was applied by a type of deposit ion technique such as vapor, chemical or electrical deposition. The resulting metal layers are usually less than about 1 μιη thickness, and therefore, metal layers applied in these ways are determined by such analytical techniques as optical density. The preferred metal layers of reclaimed polymer film suitable for use with this invention have optical density in the range of about 1 -50, more preferably about 1 -20, and most preferably about 1-10. The metal content on a mass basis of metalized reclaimed film generally contemplated for use with this invention is about 0.05- 1 wt%, preferably about 0.1-0.5 wt% and more preferably about 0.2-0.4 wt%.
As will be explained in more detail in this disclosure, according to this invention, the reclaimed metalized polymer film is incorporated as a raw material for the polymeric component of a newly made article. It is contemplated that the composition of the newly made article can contain up to about 95wt% of a reclaimed metalized polymer film component, preferably 2-90 wt%, and more preferably 5-50 wt%. This invention is very useful for consuming waste material from the production of metalized polymeric fi lm. Sources of such waste material include scrap product generated during deviations from normal operation conditions, such as occur at ,
production it is typical to generate scrap product by trimming film product to
95 specification sizes. Still further, waste material can include finished product returned to the factory by distributors and customers, for example because of damage in shipment. The present invention can be used to recycle waste material that would otherwise be unreusable as raw material because of the metal coating on the polymer.
Fig. 1 illustrates a metalized film 10 according to the present invention in which a 100 polymeric base layer 2 is in direct contact with a layer of metal 1. The metal layer is usually very thin relative to layer 2 and is deposited onto the polymer layer by conventional methods such as vapor deposition. The polymeric base layer includes metalized polymer reclaimed material. The metalized polymer reclaimed material is a blend of polymer and metal particles. The composition of the polymeric base layer may 1 05 be exclusively metalized polymer reclaimed material. Usually, the polymeric base layer includes some metalized polymer reclaimed materia] and other polymer material. The other polymer material may be virgin material polymer, nonmetalized polymer reclaim material, metalized polymer reclaim material or a mixture of them.
Typically, the source of the metalized polymer reclaim material is a metalized 1 10 polymer film. The metalized polymer film is usually shreddedto a particulate form, sometimes referred to as " flake". The flake may be further processed to pellet form for ease of mat erial handling and crystallized to reduce agglomeration. The metalized polymer reclaim material can be fed into melt processing equipment to form end use products, such as films and articles, for example molded parts. Preferably the metalized 1 1 5 polymer reclaim material is extruded to form a polymeric base layer 2 which can then be coated with a layer of metal 1 to produce a composite film as illustrated in Fig. 1.
According to this invention, a two-layer metalized film structure as seen in Fig. 1 can be combined with a substrate layer 4 to form a composite film 20 as illustrated in Fig. 2. In the drawing figures, like parts have the same reference numbers. The substrate
120 layer is usually polymeric and free of metal. Preferably, the polymer is virgin material, nonmetalized polymer reclaim material or a mixture of them. The two-layer metalized film structure contributes enhanced barrier resistance to the composite film 20. The composite film can be formed by adding a preformed metalized film 10 onto a substrate layer 4 either as the substrate layer is formed, e.g., by film extrusion, or after the
125 substrate layer is formed. Alternatively, the composite film 20 can be formed in situ in a , the polymeric base layer 2 is coextruded onto the substrate layer, and finally the metal layer 1 is deposited onto the surface of the polymeric base layer.
In another embodiment of this invention there is a multilayer film structure 30 as 130 seen in Fig. 3. In this embodiment, there is a core layer 3 interposed between the
polymeric base layer 2 and the substrate layer 4. The polymeric base layer, which comprises metalized polymer reclaim material is sometimes referred to herein as a skin layer. In preferred utilities, the core layer provides unique qualities to the composite 30 such as strength, puncture resistance and the like. It is contemplated that the core layer is 135 greater thickness than the skin layer or the substrate layer.
Preferably, the polymer composition suitable for use with this invention is PET. It is contemplated that the novel use of metalized polymer reclaimation can also be used with other polymers such as oriented polypropylene "OPP", oriented high density polyethylene "OHDPE", and oriented polyamide (nylon). For example, it is
140 contemplated to shred and pelletize a film of OPP film metalized on one side by vapor deposition to an optical density ranging from 0.5-5.0. This pelletized material can then be used as a portion or the whole of the core and/or skin layer of a newly made OPP film. The reclaimed metalized OPP replaces at least a portion of the virgin
polypropylene resin in such a film for cost-reduction purposes.
1 45 In a preferred embodiment, metalized polymer reclaim material comprises
polymer of PET and metal of aluminum. When the pelletized or densified reclaimed material is a component in the skin layer 2 of a PET film, the aluminum particles are thought to have a beneficial effect upon subsequent aluminum metal ization of the skin. That is, the aluminum particles affect the film surface of the side to be metalized so as to
1 50 provide anchoring points for the aluminum vapor being deposited in a vacuum onto the film surface. This use of reclaimed metalized PET can thus improve the bond force and applied aluminum layer density compared to PET films that do not have the aluminum particles within the PET layer. Having increased bond strength and metal density, the aluminum layer provides remarkably higher barrier properties then traditionally prepared
155 metalized PET at the same aluminum layer thickness.
When pelletized or densified metalized reclaim materia] is a component in the core layer of a PET film, that is, a non-surface-metalized polymer film, the dispersed properties to the resultant PET film without subsequent metalization. A tortuous path for
160 migrating species to transfer across through the film that is created by higher levels of metal particles of the core layer improves moisture vapor transmission rate "MVTR" and oxygen transmission rate "OTR" relative to conventional PET film shown in Figure 1 . In addition, at sufficiently high concentrations of metalized reclaim, the film can act as a susceptor for microwave "MW" radiation. A susceptor is a material that absorbs
165 electromagnetic energy and converts it to heat. Typical susceptor uses are browning food products in MW ovens and it is a common use of very low optical density aluminum deposition (very thin layer) on PET films. The use of aluminum reclaim material in the core of PET film is contemplated to perform the same function as the very thin layer of aluminum in the MW field with the advantage that the PET film does not
170 need to be subsequently metallized for added expense.
Thus according to this invention a polyester film that has been evaporatively metalized can be reclaimed by shredding and densifying. The reclaimed material is subsequently used as a reclaim feed stream in production of biaxially oriented polyester film which can be metalized on the surface containing the metalized reclaim stream. The 175 resulting metalized polyester film including metalized polymer reclaim material in the polyester layer provides improved oxygen barrier, compared to an equivalent structure film of polyester that does not contain such reclaim stream.
EXAMPLES
This invention is now illustrated by examples of certain representative
180 embodiments thereof, wherein all parts, proportions and percentages are by weight
unless otherwise indicated. The term "gauge" in this disclosure means a measure of plastic sheet thickness and corresponds to 3.94 gauge units per μηη.
Comparative Example 1 : Moisture Resistance of Metalized PET Film
Polyethylene terephthalate PET film was continuously cast and stretched to form 185 an oriented PET film of 36 gauge (9.1 μηι) nominal thickness. The polymer contained no metalized reclaim. This oriented PET sheet was plasma treated on one side and then aluminum was placed by vapor deposition on the treated side to a nominal thickness of about 3.0 optical density ("O.D"). Ten randomly located sample swatches of the metalized film were obtained and subjected to analyses for moisture vapor transmission OD-1. Results are shown in Table I, below.
Example 2: Moisture Resistance of Metalized film with 10% Metalized Reclaim
Reclaimed metalized PET was obtained by trimming PET film on which had been deposited a layer of aluminum metal of about 3.0 nominal optical density. The PET
195 of this film contained no metalized reclaim material, i.e., there was no aluminum in the PET. This metalized film was shredded into a flake and densified to form pellets. The densified reclaimed metalized PET contained 0.33 wt% aluminum. The reclaimed metalized PET pellets were melt blended with non-metalized reclaimed PET film at a 1 :9 weight ratio. The melt blend was cast and stretched to form PET film containing 10 wt%
200 of metalized reclaimed PET. The plasma treatment and aluminum deposition procedure of Comp. Ex. 1 was repeated to place an aluminum layer on the this PET film to form an aluminum metal-coated film. Three randomly located sample swatches of the metalized film were obtained and sampled for MVTR and OD. Results are also shown in Table I.
Comparative Example 3 : Moisture Resistance of Metalized PET Film
205 The film preparation procedure of Comparati ve Example 1 was repeated except that the PET film was not plasma treated before aluminum layer deposition. Three randomly located sample swatches of the metalized film were obtained and subjected to analysis for MVTR and OD. Results are also shown in Table 1, below.
Example 4: Moisture Resistance of Metalized film with 5% Metalized Reclaim
210 Reclaimed metalized PET was obtained from trimmings of PET film containing no metalized reclaim material and coated with aluminum to a nominal optical density of about 3.0. This reclaimed metalized film was shredded and densified to form pellets as in Ex. 2. The reclaimed metalized PET pellets were melt blended with pellets formed from the non-plasma treated PET of Comp. Ex. 3 at a 1 : 19 weight ratio to produce 5 wt%
215 reclaimed metalized PET. The metalized film preparation procedure of Comp. Ex. 3 was repeated using the 5 wt% reclaimed metalized PET blend to form an aluminum metal - coated oriented PET film. Three randomly located sample swatches of the metalized film were obtained and sampled for MVTR and OD. Results are also shown in Table I. Comp. Ex. 1 Ex. 2 Comp. Ex. 3 Ex. 4
OD MVTR OD MVTR OD MVTR OD MVTR
(gm/100 (gm/100 (gm/100 (gm/100 in. 2 /day) in. 2 /day) in. 2 /day) in. 2 /day)
3.41 0.2995
2.83 0.2471
2.98 0.2418
3.20 0.2810
3.04 0.2978
3.09 0.2613
3.00 0.2485
2.72 0.2442 3.05 0.1 182 2.89 0.241 1 3.52 0.1094
2.82 0.2479 2.81 0.1082 2.98 0.2048 3.52 0.1094
2.79 0.3084 3.09 0.1582 2.85 0.2015 3.35 0.1885
Average
value: 0.2677 0.1282 0.2158 0.1357
220 Average MVTR values were calculated from each of the multiple sample
performance analyses for Comp. Exs. 1, and 3, and Exs. 2 and 4. As seen from Table I, the MVTR value for the treated PET film having 10% reclaimed metalized film dropped from 0.2677 of the metalized virgin PET film to 0.1281 (reduction of 52%). Similarly, for the untreated PET film, the MVTR reduction was from 0.2158 to 0.1357 (reduction
225 of 37%).
Comparative Example 5: O ygen Transmission of Metalized PET Film
A metalized treated virgin PET film was prepared similarly as in Comp. Ex. 1. Multiple random sample swatches were taken and analyzed for oxygen transmission rate ("OTR") by method ASTM D3985 and for OD. Data are shown in Table II.
230 Examples 6 and 7: Oxygen Transmission of Metalized PET film with 5% and 10%
Reclaim
Reclaimed metalized PET was obtained from trimmings of PET film coated to a nominal optical density of about 3.0 with aluminum metal. This metalized film was shredded into a flake and densified to form pellets having 0.33 % aluminum. The
235 reclaimed metalized PET pellets were melt blended with pellets of non-metalized PET film reclaim material of the cast and stretched PET film described in Comp. Ex . 5. The metalized film production procedure of Comp. Ex. 5 was repeated using the oriented PET film containing reclaimed metalized PET to form aluminum metal -coated films. For Ex. 6, the reclaimed metalized PET was blended with non-metalized PET at a 1 : 19 . . ,
produce a 10 wt% reclaimed metalized PET. Randomly located sample swatches of the metalized films were obtained and sampled for OTR and OD. Results are also shown in Table II.
TABLE II
Comp. Ex. 5 Ex. 6 Ex. 7
OD OTR OD OTR OD OTR
(cc/100 (cc/100 (cc/100
in. 2 /day) in. 2 /day) in. 2 /day)
3.02 0.077 2.99 0.039
2.91 0.080 2.96 0.036 3.07 0.032
2.93 0.082 3.10 0.050 3.01 0.037
3.02 0.075 3.10 0.043 2.98 0.041
2.92 0.094 3.12 0.006 3.03 0.040
Average 0.082 0.034 0.038
245 Results of Table II show that the virgin PET film metalized with aluminum to an optical density of about 3.0, had an oxygen transmission rate of 0.082 cc/100 in /day on average. The average oxygen transmisson rates for similarly metalized PET films that included 5 and 10 wt% reclaimed metalized PET in the polymeric layer were reduced to about half that value.
250 Comparative Example 8 xygen Transmission of Metalized PET Film
A metalized virgin PET film was prepared similarly as in Comp. Ex. 3. Multiple random sample swatches were taken and analyzed for OTR and OD. Data are shown in Table III.
Examples 9 and 10: Oxygen Transmission of Metalized PET film with 5% and 10% 255 Reclaim
Reclaimed metalized PET was obtained from trimmings of PET film of polymer containing no metalized reclaim material and with an aluminum coating of 3.0 nominal optical density. This metalized film was shredded into a flake and densified to form pellets containing 0.33 wt.% aluminum. The reclaimed metalized PET pellets were 260 blended with pellets of non-metalized PET film of the cast and stretched base film
described in Comp. Ex. 8 and melt blended therewith. The metalized film production procedure of Comp. Ex. 8 was repeated using the PET blends to form aluminum metal- coated films. For Ex. 9, the reclaimed metalized PET was blended with virgin PET at a .
265 1 :9 to produce a 10 wt% reclaimed metalized PET. Randomly located sample swatches of the metalized films were obtained and sampled for OTR and OD. Results are also shown in Table III.
TABLE III
Comp. Ex. 8 Ex. 9 Ex. 10
OD OTR OD OTR OD OTR
(cc/100 (cc/100 (cc/100
in. 2 /day) in. /day) in. 2 /day)
3.10 0.064 3.08 0.034
2.93 0.065 3.07 0.016
3.04 0.076 3.07 0.035
3.07 0.070 3.10 0.030
2.78 0.068 3.23 0.043 3.04 0.041
Average 0.069 0.043 0.031
270 Results of Table III show that the virgin PET film metalized with aluminum to an optical density of about 3.0 had an oxygen transmission rate of 0.069 cc/100 in 2 /day on average. The average oxygen transmisson rate for similarly metalized PET films that included 5% reclaimed metalized PET in the polymeric layer was reduced to about 62% of that value. Moreover, increasing the reclaimed metalized PET content of the
275 polymeric layer to 10% reduced the OTR value to 45% of the virgin PET metalized film OTR.
A lthough speci fic form s of the invention have been selected in the preceding disclosure for illustration in specific terms for the purpose of describing these forms of the invention fully and amply for one of average skill in the pertinent art, it should be 280 understood that various substitutions and modifications which bring about substantially equivalent or superior results and/or performance are deemed to be within the scope and spirit of the following claims. All U.S. Patents named in this disclosure are hereby fully incorporated by reference herein.