Patent Application
20180111359
The present application relates to multi-ply films, particularly multi-ply films that are suitable for use in sterilization or pasteurization processes.
Various types of multi-ply films are used for packaging of products such as food, medicines, and the like. The features and functionality of the multi-ply films may be varied depending on the desired application. For example, in some instances it is desirable to have multi-ply films suitable for use in packaging that undergoes sterilization processes, such as retort sterilization, microwave assisted thermal sterilization (MATS), ultra-high temperature sterilization, or pasteurization processes, that often are performed at high temperatures, and in certain instances, for prolonged periods of time.
The multi-ply films used in such applications must have good burst strength to survive the internal pressures generated during the sterilization or pasteurization process. In addition, it often is desirable that the package be “easy open” so that the consumer can readily access the contents within the package. These features generally require that there be a compromise between maximizing burst strength and minimizing seal strength. These multi-ply films also generally must have sufficient tear resistance and gas barrier properties.
Although there are some multi-ply films capable of providing some of the needed features and functionality, existing multi-ply films still suffer from numerous deficiencies. For example, most multi-ply films suitable for sterilization or pasteurization are at least three-ply and require use of adhesives, both of which increase cost, waste, and/or manufacturing complexity and processing time. Thus, there remains a need to provide improved multi-ply films.
In one aspect, multi-ply films are provided. In one embodiment, the multi-ply film includes a top layer affixed to a coextruded film, in which the coextruded film includes a first polyamide structural layer, a sealant layer, and a first tie layer that is disposed between the first polyamide structural layer and the sealant layer, and the coextruded film is substantially free of an adhesive. In a further embodiment, the coextruded film also includes an outer layer, in which the first polyamide structural layer is disposed between the sealant layer and the outer layer, and a second tie layer that is disposed between the first polyamide structural layer and the outer layer. In yet a further embodiment, the coextruded film also includes a second polyamide structural layer, in which the second polyamide structural layer is disposed between the second tie layer and the outer layer, and a third tie layer that is disposed between the second polyamide structural layer and the outer layer.
In another aspect, packages are provided. In one embodiment, the package includes a multi-ply film as described above.
In yet another aspect, methods for sterilization are provided. In one embodiment, the method includes feeding a package as described above into a sterilizing chamber, in which the package has product disposed therein, and preserving the product within the sterilizing chamber by thermal sterilization.
In another aspect, rolls of film for forming a package are provided. In one embodiment, the roll of film includes a multi-ply film as described above.
Additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.
The detailed description is set forth with reference to the accompanying drawings. The use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Elements and/or components in the figures are not necessarily drawn to scale.
Improved multi-ply films have been developed that are suitable for use in sterilization processes, such as retort sterilization, microwave assisted thermal sterilization (MATS), or ultra-high temperature sterilization, or pasteurization processes. Generally described, the present multi-ply films include a top layer affixed to a coextruded film, in which the coextruded film is substantially free of an adhesive.
As used here, the term “multi-ply film” refers to two or more films affixed together using any suitable method, non-limiting examples of which include laminating, extruding, coating, and combinations thereof. Desirably, the multi-ply film is a “2-ply” or “two-ply” film (e.g., formed from two films, with or without one or more adhesive layers disposed between the two films) or a “3-ply” or “three-ply” film (e.g., formed from three films, with or without one or more adhesive layers disposed between any of the films), in which the coextruded film is substantially free of adhesive. Although the multi-ply films provided herein are primarily described with reference to two-ply films, three-ply films also are contemplated herein (e.g., including a foil layer or other film layer).
As used herein, “substantially free” means that the total amount of adhesive present within the coextruded film is less than about 1% by weight of the multi-ply film. For example, in certain embodiment, there is no adhesive between the first polyamide structural layer and the sealant layer, and in some embodiments also between the second polyamide structural layer and the outer layer. In another embodiment, the coextruded film does not comprise an adhesive.
As used herein, the term “adhesive” when used in the context of “substantially free” is defined as a composition that is coated onto the surface of a preformed material, such as a film or layer, such that the preformed material adheres or connects to another material that is subsequently disposed over the coated surface of the preformed material. For example, such adhesives may include adhesives that are used in adhesive lamination processes, such as aqueous, water or solvent, adhesives or cold seal adhesives. In contrast, coextruded films are typically produced by extruding two or more films or layers simultaneously that bond to each other when in the soft or molten state and then cooled. For purposes of this disclosure, preformed materials do not include extruded materials that are in the soft or molten state.
Several embodiments of multi-ply films, packages made at least in part therefrom, and methods for sterilization are described herein. Parameters of different steps, components, and features of the embodiments are described separately, but may be combined consistently with this description of claims, to enable other embodiments as well to be understood by those skilled in the art. Various terms used herein are likewise defined in the description which follows. Unless otherwise specified, quantities referred to by percentages (%) are by weight (wt %).
Values or ranges may be expressed herein as “about”, from “about” one particular value, and/or to “about” another particular value. When such values or ranges are expressed, other embodiments disclosed include the specific value recited, from the one particular value, and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that there are a number of values disclosed therein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. In aspects, “about” can be used to mean within 10% of the recited value, within 5% of the recited value, or within 2% of the recited value.
The present multi-ply films include a top layer affixed to a coextruded film, in which the coextruded film is substantially free of an adhesive. It was discovered that by forming a film of the multi-ply film via co-extrusion, rather than using conventional adhesive, a greater adhesion among the layers of the film could be achieved, thereby reducing the amount of adhesive needed to bond the layers of the multi-ply film together. Decreasing the amount of adhesive advantageously results in reduced cost, waste, and/or manufacturing complexity and processing time of the multi-ply films compared to that of conventional multi-ply films. Moreover, given that every interface within a film is a potential failure point, by forming at least a portion of the multi-ply film via co-extrusion—i.e., the coextruded film—reduces the number of adhesive interfaces, which in turn beneficially reduces potential failure points of the overall multi-ply film.
An exemplary multi-ply film 100 is illustrated in
As used herein, “polypropylene” can be a homo-polymer, a co-polymer of propylene and other one or more monomers, such as ethylene, or a combination thereof.
As used herein, “polyethylene” can be a homo-polymer, a co-polymer of ethylene and other one or more monomers, or a combination thereof.
In some embodiments, the top layer may include a polyolefin, an oriented polyester, an oriented polyamide, or combinations thereof. In a preferred embodiment, the top layer is an oriented polyester having a thickness from about 40 to about 120 gauge.
In certain embodiments, the material forming the top layer includes a high barrier coating and/or is metallized. In one embodiment, the top layer includes a high barrier coating and a polyolefin, an oriented polyester, an oriented polyamide, or combinations thereof. In another embodiment, the top layer is metallized and includes a polyolefin, an oriented polyester, an oriented polyamide, or combinations thereof. In yet another embodiment, the top layer is metallized and includes a high barrier coating and a polyolefin, an oriented polyester, an oriented polyamide, or combinations thereof.
The coextruded film 106 includes a first polyamide structural layer 108, a sealant layer 112, and a first tie layer 110. The first tie layer 110 is disposed between the first polyamide structural layer 108 and the sealant layer 112. The first tie layer 110 aids in the bonding of the first polyamide structural layer 108 to the sealant layer 112. In some embodiments, an inner layer is disposed between the first tie layer 110 and the sealant layer 112.
In certain embodiments, the first polyamide structural layer includes nylon. In one embodiment, the first polyamide structural layer includes biaxially unoriented nylon. It has been discovered that employing biaxially unoriented nylon, rather than biaxially oriented nylon used in conventional multi-ply films, beneficially provides for greater elongation of the multi-ply film, thereby increasing the burst strength of the multi-ply film, while yet still maintaining suitable peel strength. Additionally, biaxially unoriented nylon provides the ability to utilize the coextrusion process, thereby producing a coextruded film with minimal, if any, conventional adhesive. As stated above, in certain embodiments, the coextruded film does not comprise an adhesive.
Non-limiting examples of suitable sealant materials of the sealant layer include polypropylene, polyethylene, polyester, polycarbonate, and the like, and combinations thereof. In certain embodiments, the sealant layer includes a blend of an easy-peel component and a polypropylene. The easy-peel component may be present in the sealant layer in an amount from about 16 to about 28% by weight of the sealant layer, whereas the polypropylene may be present in the sealant layer in an amount from about 72 to about 84% by weight of the sealant layer. The sealant layer advantageously allows for the multi-ply film to be heat-sealed to a container (i.e., as a lidding) or to itself (i.e., to form a pouch) with sufficient strength to withstand sterilization or pasteurization but weak enough to be separated by a consumer after sterilization or pasteurization. For example, in certain embodiments the easy-peel component comprises a blend of a polypropylene, a polyethylene, an antiblock agent (e.g., diatomaceous earth), and a slip agent (e.g., erucamide).
Non-limiting examples of suitable first tie layer materials include-anhydride-modified polyolefins (e.g., anhydride modified polypropylene), modified ethylene vinyl acetate, anhydride modified ethylene acrylate, acid/acrylate modified ethylene vinyl acetate, anhydride modified ethylene vinyl acetate, anhydride modified ethylene vinyl acetate, and combinations thereof, and any of the foregoing materials in combination with polyolefins, such as polypropylene.
The type of materials in the first tie layer is based, at least in part on the materials of the opposing layers being bonded via the first tie layer. For example, where the first tie layer is used to bond a first polyamide structural layer comprising nylon and a sealant layer comprising a blend of an easy-peel component and a polypropylene, the first tie layer may comprise anhydride modified polypropylene or a combination of anhydride modified polypropylene and polypropylene.
In embodiments, the coextruded film may include one or more additional layers, and/or one or more of the foregoing layers may be formed from two or more adjacent layers, and/or one or more additional layers of the foregoing layers.
For example, in one embodiment, a coextruded film, illustrated in a cross-sectional view, of the present multi-ply films is shown in
In embodiments, the outer layer of the coextruded film desirably comprises a polypropylene. The polypropylene may be blended with other polymers such as polyethylene to improve the bond between the outer layer of the coextruded film and the top layer. For example, the polypropylene may be present in the outer layer of the coextruded film in an amount from about 90 to about 100% by weight of the outer layer while the polyethylene may be present in the outer layer of the coextruded film in an amount from about 0 to about 10% by weight of the outer layer.
In certain embodiments, the coextruded film 206 may also include a second polyamide structural layer and a third tie layer, in which the second polyamide structural layer is disposed between the second tie layer 216 and the outer layer 214. In such embodiments, the third tie layer is disposed between the outer layer 214 and the second polyamide structural layer. In some embodiments, additional polyamide structural layers and additional tie layers may be included within the coextruded film, in which, for example, each polyamide structural layer is disposed between two separate tie layers.
Another exemplary coextruded film, illustrated in a cross-sectional view, of the present multi-ply films is shown in
Non-limiting examples of suitable second tie layer materials include anhydride modified polypropylene, modified ethylene vinyl acetate, anhydride modified ethylene acrylate, acid/acrylate modified ethylene vinyl acetate, anhydride modified ethylene vinyl acetate, anhydride modified ethylene vinyl acetate, combinations thereof, and any of the foregoing materials in combination with polypropylene. The type of materials in the second tie layer is based, at least in part on the materials of the opposing layers being bonded via the second tie layer. For example, where the second tie layer is used to bond a first polyamide structural layer comprising nylon and an outer layer comprising polypropylene the second tie layer may comprise anhydride modified polypropylene or a combination of anhydride modified polypropylene and polypropylene.
In embodiments, the inner layer may include a polypropylene, polyethylene, or a combination thereof. The inner layer provides additional structure and function to the multi-ply film, such that the sealant layer may be formed at a desirable thickness. The thickness of the sealant layer affects the ability to effectively separate the multi-ply film from another substrate, e.g., in instances where the multi-ply film is an easy-to-peel lid. That is, if the sealant layer is too thick, the multi-ply film, when being separated from another substrate, such as a body substrate of container, may not result in a clean peel. As used herein, a “clean peel” is defined as a peel that results in a clean appearance, with minimal, if any, or no obvious stringing, fuzziness, tearing, or delamination.
The multi-ply film using the coextruded film generally is of the same thickness as conventional multi-layer films. For example, the total thickness of the multi-ply film may range from about 2.0 mils to about 10.0 mils, more particularly from about 3 mils to about 7 mils, or from about 3.5 mils to about 6 mils. The top layer may have a thickness from about 0.4 to about 1.2 mils and the coextruded film may have a thickness from about 1.5 to about 5.0 mils.
In instances where the coextruded film further includes an outer layer, the outer layer of the coextruded film may have a thickness from about 0.2 to about 1.2 mils, the first polyamide structural layer and the optional second structural layer may each have a thickness from about 0.4 to about 1.4 mils, and the sealant layer (together with the optional inner layer) may have a thickness from about 0.5 to about 2.5 mils.
The multi-ply films provided herein advantageously have an improved ratio of peel strength to burst strength as compared to three-ply films in which the top layer, biaxially-oriented nylon layer, and sealant layer are laminated together by two adhesive layers. For example, exemplary multi-ply films may have a peel strength from about 1000 grams to about 2500 grams and a burst strength of greater than about 7 PSI. The peel strength may be measured using the ASTM-F2824-10 Standard Test Method for Mechanical Seal Strength testing for Round Cups and Bowl Containers with Flexible Peelable Lids (i.e., using a pull rate of 0.5 inch/min for peak values and 12 inch/min for peel values). The burst strength may be measured using the ASTM-F1140-07 Standard Test Methods for Internal Pressurization Failure Resistance of Unrestrained Packages.
The multi-ply films provided herein may be formed by any of the conventional processes for making multi-ply films, including adhesive lamination, extrusion, coextrusion, blown extrusion, cast extrusion, extrusion coating, and combinations thereof. The top layer and coextruded film may be affixed together in-line or off-line with the forming of the coextruded film.
The multi-ply films described herein may be used in a variety of packaging applications, such as in the formation of packages. In embodiments, the present multi-ply films may be formed in-line or off-line with the forming of a packaging. In certain embodiments, a roll of film comprising the multi-ply films described herein may be used to form a package.
In some embodiments, the multi-ply films described herein are used to form packages in which the multi-ply film is sealed to a container base, such as a rigid or semi-rigid tray or cup.
In another embodiment, the multi-ply films described herein may be sealed to itself or to another film to form a pouch by forming heat seals about the periphery of the pouch body. The other film may be the same or different than the multi-ply film. In certain embodiments, the packages further include one or more fitments.
The multi-ply films described herein are suitable for use in sterilization processes, particularly thermal sterilization of products, such as food, medicine, and the like. Non-limiting examples of thermal sterilization include retort sterilization, microwave assisted thermal sterilization (MATS), such as those described in U.S. Pat. Nos. 5,436,432, 5,750,966, 6,618,957, 7,230,217, 7,607,860, 8,878,109, 9,066,376, 9,179,505, and 9,271,338, all of which are incorporated herein by reference, ultra-high temperature sterilization, and the like, and combinations thereof.
In embodiments, the method for sterilization includes feeding a package as described herein into a sterilizing chamber, in which the package has product disposed therein; and preserving the product within the sterilizing chamber by thermal sterilization. In one embodiment, the coextruded film of the multi-ply film is substantially free of an adhesive and includes a first polyamide structural layer, a sealant layer, and a first tie layer that is disposed between the first polyamide structural layer and the sealant layer. In another embodiment, the coextruded film further includes an outer layer, in which the first polyamide structural layer is disposed between the sealant layer and the outer layer, and a second tie layer is disposed between the first polyamide structural layer and the outer layer. In yet another embodiment, the coextruded film further comprises a second polyamide structural layer, in which the second polyamide structural layer is disposed between the second tie layer and the outer layer, and a third tie layer is disposed between the second polyamide structural layer and the outer layer.
In some embodiments, the thermal sterilization includes exposing the package to a heat medium to heat the product within the package to a predetermined temperature and to maintain the product at the predetermined heating temperature for a predetermined time.
In other embodiments, the thermal sterilization includes exposing the package to a heat medium to heat the product within the package to a predetermined temperature and to maintain the product at the predetermined heating temperature for a predetermined time and also exposing the heat medium, the package, and the product to microwave energy.
In embodiments, the heat medium may be pressurized high temperature water or steam.
Embodiments of the present description are further illustrated by the following examples, which are not to be construed in any way as imparting limitations upon the scope thereof. On the contrary, it is to be clearly understood that sterilization and/or pasteurization processes may be conducted on various other embodiments, modifications, and equivalents thereof which, after reading the description therein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims.
A two-ply film was prepared including a seven-layer coextruded film and was compared to a conventional three-ply laminate (control), the structures of which are summarized below.
The burst strength and peel strength of the finished films were tested both in the form of a flat lidding-stock and after being heat-sealed to a container base (both pre- and post-retort) using the methods described above. The retort samples were test retorted at both 250° F./30 psi/60 min and at 265° F./35 psi/30 minutes. The results are shown in
Although the films had similar peel strengths, the two-ply film had a distinctive improvement in post-retort burst strengths. In addition, the two-ply films had less “fuzz” stringing and tearing as compared to the three-ply laminate.
The following numbered aspects, embodiments, and features of the disclosure are provided, with an emphasis on the ability to combine the various features which may disclosed only in certain embodiments, into other disclosed embodiments, as the context and technical reason allow.
While the invention has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, the scope of the present invention should be assessed as that of the appended claims and any equivalents thereof.
This application claims priority to U.S. Provisional Application No. 62/141,783, filed Apr. 1, 2015, which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2016/025642 | 4/1/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62141783 | Apr 2015 | US |
