Patent Application
20180297338
This disclosure generally relates to substantially clear, non-polyvinylidene chloride (“PVDC”) structures having exceptional flavor and aroma barriers and little to no shelf-life deterioration.
Traditionally, films based on PVDC have been used as packaging for confections due to their clarity and high barrier properties. However, these films are becoming increasingly less acceptable for today's end users due to pollution concerns arising from the presence of halogens (i.e., Group VII elements and compounds thereof).
Non-PVDC barrier films exist; but these films have significant drawbacks compared to the traditional PVDC packaging. They may have poor machinability, lower aroma and flavor barrier properties, or exhibit visual defects such as puckering or dimpling when used on products having long shelf lives.
There is, therefore, a need for clear non-PVDC barrier films which are environmentally friendly but which reduce the drawbacks.
Disclosed are methods, applications, compositions, structures, labels, packages, tags, and so forth associated with at least substantially clear, non-polyvinylidene chloride (“PVDC”) structures having exceptional flavor and aroma barriers and little to no shelf-life deterioration, such as puckering or dimpling, from a visual perspective, alongside excellent machinability performance. Disclosed structures include one or more protective barrier layer(s) based cm vinyl alcohol chemistry, e.g., ethylene vinyl-alcohol copolymers (“EVOH”) or polyvinyl alcohol (“PVOH”) layer(s), which may be in-line or out-line coated and/or co-extruded. Additionally and alternatively, the barrier layer(s) may be top-coated with an acrylic coating, which may enhance the machinability, sealability and/or appearance of the structure(s), whether used, for example, directly or indirectly in labels, packages, tags, or otherwise.
Below, directional terms, such as “above,” “below,” “upper,” “lower,” “front,” “back,” “top,” “bottom,” etc., are used for convenience in referring to the accompanying drawings. In general, “above,” “upper,” “upward,” “top,” and similar terms refer to a direction away the earth's surface, and “below,” “lower,” “downward,” “bottom,” and similar terms refer to a direction toward the earth's surface, but is meant for illustrative purposes only, and the terms are not meant to limit the disclosure.
This disclosure generally relates to methods, applications, compositions, structures, labels, packages, tags, and so forth associated with at least substantially clear, non-polyvinylidene chloride (“PVDC”) structures having exceptional flavor and aroma barriers and little to no shelf-life deterioration, such as puckering or dimpling, from a visual perspective, alongside excellent machinability performance. Disclosed structures include a protective barrier layer based on vinyl alcohol chemistry, e.g., ethylene vinyl-alcohol copolymers (“EVOH”) or polyvinyl alcohol (“PVOH”) layer(s), which may be in-line or out-line coated and/or co-extruded. Additionally and alternatively, the barrier layer may be top-coated with an acrylic coating, which may enhance the machinability, sealability and/or appearance of the structure(s), whether used, for example, directly or indirectly in labels, packages, tags, or otherwise.
An example coated barrier film is illustrated in “Structure 1.” This barrier layer may have a PVDC coating on one side of the film. The other side of the film may be coated with an acrylic coating for improved coefficient of friction (“COF”), machinability, and seal performances.
PVDC-based structures may show clear high barrier properties and are used for packaging, such as for confectionaries. PVDC-based structures, however, are not acceptable for today's end-users because of the presence of halogens, i.e., Group VII elements and compounds thereof. As compared to PVDC-based structures, non-PVDC barrier structures may have lower aroma barriers, flavor barriers, and combinations thereof; additionally and alternatively, non-PVDC barrier structures may have a poorer visual appearance, such as puckering or dimpling, over time and/or poorer machinability. Accordingly, there is a desire to have at least a substantially clear barrier structure that is non-PVDC, and, thus, environmentally friendly.
A coating's barrier is determined by its chemical and physical properties, wherein each may impact on the other. Physical properties may include the crystal morphology and packing of the coating, i.e., the relative form and structure as well as packing, respectively, of the amorphous and crystalline regions of a polymer matrix that wholly or partially constitutes the disclosed coating. As just mentioned, the crystal structure may be influenced by the chemical nature and the interfacial interactions between a primer and a barrier topcoat where a primer is present. Localized crystal structure imperfections may arise due to a host of reasons, including, for example, incompatibility of the primer and barrier topcoat, wherein such incompatibility may be due to surface defects in the primer that are translated to the barrier coating. Consequently, localized defects may lead to inferior barrier performances of a coating.
The overall flavor and aroma barrier of a packaging film may be determined by the mass transfer phenomena of adsorption, diffusion, and desorption of the flavor and aroma molecules from the product through the film to the environment as shown in
In some instances, as reported by Nielsen, et al., the absorbed compounds may act as plasticizers and swell the polymer film resulting in changes to modulus of elasticity and tensile strength of the packaging film. Nielsen, Tim and Margaretha Jägerstad, “Flavour Scalping by Food Packaging,” Trends in Food Science & Technology, Vol. 5, November 1994. In another instance, Van Willige RWG, et al., has reported that polypropylene films show considerable absorption of selected flavor compounds resulting in changes to the crystal structure of the polymeric film due to the plasticizing effect of the flavor and aroma compounds. Van Willige RWG, et al., Food Addit and Contam, 19:303-313 (2002). The change in the crystal structure increases the free volume of the polymeric film and results in increased oxygen permeability of the films. Id. Low oxygen permeability through the packaging film is an important factor for the shelf life of many food products.
In this disclosure, the interaction of the aroma and flavor molecules within the film was studied by two types of visual distortion: (1) package looseness; and (2) puckering or dimpling as described in further detail below. Package looseness is mainly observed when the inner layer of the film facing the flavored product provides low barrier for the compounds across the entire surface area of the film. The flavor and the aroma molecules are adsorbed throughout the film surface and diffuse in the bulk of the packaging film. During the diffusion process, the compounds interact with the polymer film as a plasticizer, resulting in package swelling or looseness. The diffusion rate or resident time of the compounds in the film dictates the extent of looseness or deformation of the polymeric film. The diffusion rate or resident time of the compounds may be affected by the concentration gradient of the aroma compounds, the thickness of the polymer film, the crystal morphology, the free volume of the polymeric film, and the chemical nature of the film. In one instance, the diffusion and desorption of the compounds from the flavored product through the film to the environment may be relatively fast where the package swelling is minimal due to the short residence time of the compounds in the bulk of the film. In another instance, the diffusion and desorption of the compounds from the flavored product through the film to the environment may be relatively slow where the package swelling is considerably affected by the long residence time of the compounds in the bulk of the film. For instance, if the outer layer of the film provides an obstacle for desorption process, then the flavor compounds are trapped in the bulk of the polymeric film, resulting in heavy swelling. The concern of the second visual distortion, i.e., puckering or dimpling, arises when the internal barrier layer facing the flavored product has localized defects on its surface that provide channel(s) for the flavor compounds to adsorb and diffuse through the film. This localized diffusion and chemical interaction between the flavor molecules and the BOPP core results in a localized structural distortion, i.e., puckering or dimpling, of the BOPP film used, for example, in packaging, labeling and/or tagging applications.
Below are example embodiments of structures, used through this disclosure as commensurate with compositions and films, for use in packaging, labeling, tagging, and/or other applications that have improved machinability, sealability, and appearance as a result, at least partially, on coating barrier(s). In one example embodiment, as shown in Structure 2 a biaxially coextruded film having a polypropylene core with barrier skin is used as a base film. The barrier skin is a non-halogenated layer not limited to EVOH or nylon layer. The non-halogenated barrier skin provides the necessary flavor and aroma barrier. The coextruded base film thickness may be with a range between 8 micrometers to 100 micrometers, or in the range between 12 micrometers to 50 micrometers, or yet in the range of 15 micrometers to 25 micrometers. The EVOH skin thickness may be with a range between 0.2 micrometers to 10 micrometers, or in the range between 0.4 micrometers to 5 micrometers, or yet in the range of 0.8 micrometers to 2 micrometers. The coextruded base film is flanked by acrylic coatings, each having an inline or outline coating. The dry coating weight may be with a range between 0.07 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/m2, or yet in the range of 0.35 g/m2 to 1.55 g/m2.
In a specific example as illustrated below in Structure 3 the base film is biaxially coextruded film having a polypropylene core with EVOH Evalca G176B in the skin layer. The base film is 18 micrometers in thickness including the EVOH skin layer thickness of 1 micrometer. The base film is flanked by acrylic coatings, with thickness of 0.62 g/m2. Not depicted in the Structure 2 below a primer layer of polyethylenimine is applied underneath each acrylic coating to enhance the adhesion of the acrylic coating to the base film. The 1 micrometer
EVOH skin provides the necessary flavor and aroma barrier. The acrylic coating provides superior machinability such as low and consistent COF and excellent hot slip properties.
In another example embodiment, Structure 4 is a coextruded BOPP film coated on a first side with a non-halogenated barrier coating. The barrier coating is polymeric solution or dispersion containing at least ethylene vinyl alcohol (“EVOH”), polyvinyl alcohol (“PVOH”), polyamide or combinations thereof. The “EVOH/PVOH coating” provides the necessary flavor and aroma barrier. The coextruded BOPP base film thickness may be with a range between 8 micrometers to 100 micrometers, or in the range between 12 micrometers to 50 micrometers, or yet in the range of 15 micrometers to 25 micrometers. The “EVOH/PVOH coating” dry coating weight may be with a range between 0.07 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/m2, or yet in the range of 0.35 g/m2 to 1.55. The EVOH/PVOH coating(s) layer are further top coated now with an acrylic coating. The dry acrylic coating weight may be with a range between 0.07 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/m2, or yet in the range of 0.35 g/m2 to 1.55. The second side of the coextruded BOPP core has an acrylic coating. The dry coating weight may be with a range between 0.07 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/m2, or yet in the range of 0.35 g/m2 to 1.55.
In a specific example as illustrated in Structure 5, the coextruded BOPP film is 17 micrometers in thickness with the EVOH coating dry coating weight of 0.62 g/m2. Not depicted in Structure 4 is a primer layer of polyethylenimine applied underneath each acrylic coating to enhance the adhesion of the acrylic coating to the base film. Also not depicted in the Structure 5 is a primer layer of polyethylenimine, which may blended with an EVOH coating in appropriate ratio so as to result in a one-step manufacturing process of primer, which includes the EVOH coating at one laydown point, and then an acrylic top-coating at another laydown point so that the multiple coatings to the base film occur in the same nm. The EVOH coating in Structure 5 may provide a barrier and the polyethyleneimine may provide both anchorage to a BOPP film and adhesion to the top-coated acrylic coating. The EVOH-polyethyleneimine coating provides the necessary flavor and aroma barrier, which is further enhanced by the flavor and aroma barrier properties imparted by acrylics in any acrylic top coatings. The acrylic coating may provide enhanced machinability, such as low and consistent COF, and excellent hot slip properties.
In another example embodiment, illustrated below as Structure 6, a coextruded BOPP film is coated on a both sides side with a non-halogenated barrier coating. The barrier coating is polymeric solution or dispersion containing at least EVOH, PVOH, polyamide or combinations thereof. The coextruded BOPP base film thickness may be with a range between 8 μm to 100 μm, or in the range between 12 μm to 50 μm, or yet in the range of 15 μm to 25 μm. The “EVOH/PVOH coating” dry coating weights may be with a range between 0.04 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/rn2, or yet in the range of 035 g/m2 to 1.55. The EVOH/PVOH coating(s) layer(s) are further top coated with an acrylic coating. The dry acrylic coating weight may be with a range between 0.04 g/m2 to 8 g/m2, or in the range between 0.15 g/m2 to 3.75 g/m2, or yet in the range of 0.35 g/m2 to 1.55.
The chemical compositions of the EVOH and acrylic coatings that may be used in the structures and applications of this disclosure may vary, but example EVOH, acrylic coatings may optionally include one or more additives, for instance, to combat slip and blocking, control rheology, crosslinker to enhance the humidity resistance, defoamer to eliminate foams and surface defects. In one example table 1 illustrates the EVOH coating composition used to produce Structure 3.
EXCEVAL™ AQ-4104 was obtained as flakes from Kuraray America, Inc. and a 10% dispersion was prepared. Cymel 385 was obtained from Cytec Industries Inc., and Sylobloc 45 was obtained from Grace Davison
The chemical compositions of the acrylic coatings that may be used in the structures and applications of this disclosure may vary, but example acrylic coatings may optionally include one or more additives, for instance, to combat slip and blocking, control rheology, crosslinker to enhance the humidity resistance, defoamer to eliminate foams and surface defects. In one example Table 2 illustrates the acrylic coating composition used to produce Structure 3.
The acrylic coating may be, e.g., 13Q51AA from Valspar Corporation, HSL 701 from BASF, HSL 700 from BASF. Silica may be, e.g., Ludox TM-40 from Grace Davison, Nalco 1040 from Nalco Company. Wax may be Michelman Carnauba wax, Roger Reed Carnauba wax, Micro Powders Inc. wax additive AQUABEAD® 270E. Talc may be Mistron Monomix from Luzenac America, Inc.
Turning now to
Next, the packages were placed in an oven at 35° C. The appearance of the packages was monitored regularly over several weeks for defects, such as puckering and package looseness. The analysis of puckering defects is reported by using a “weighted method,” which is representative of a typical person's view of the package. That is, when the number is higher, then the visible puckers are more prominent, and, therefore, the worse the package appears. The number of dimples of each size is multiplied by weight factors, wherein higher weight factors are given to larger dimples as represented in Table 3. The point at which the package appearance starts to look noticeably puckered, i.e., “unacceptable,” is above or greater than 10 weighted average number. The pucker appearance response provided by a sample at the end of 4 weeks at 35° C. is a good indication for extrapolating if the sample will provide acceptable or unacceptable appearance.
In a study of the film structures in Table 4, each control or example was wrapped around a sugar-free peppermint gum pack and monitored for its pucker-resistance performance as described in the preceding paragraphs.
Control 1 in Table 4 is BOPP film, and, more specifically, is Structure 1 as previously described. One side of Control 1 BOPP core has a PVDC barrier coating with an epoxy primer and the other side has an acrylic coating. Control 2 is also Structure 1 with a BOPP core, but with one side having a PVDC barrier coating with a polyurethane primer and the other side having an acrylic coating. Example 1 is as described by Structure 3, and, more specifically, has a coextruded EVOH skin as a barrier layer and top-coated with acrylic coating and the other side has an acrylic coating. Example 2 is as described by Structure 5, but has one side that is coated with an EVOH barrier layer that is top-coated with acrylic coating and the other side has an acrylic coating. Example 3 is as described by Structure 4, but does not have any barrier layer and is top-coated with acrylic coating on either side.
Turning now to
During the pucker-resistance tests, it was observed that looseness of the overwrap film was affected considerably as a function of time based on presence of the barrier layer and the type of the barrier layer. The looseness of the overwrap film is also indicative of the shelf-life of the package. Table 5 is a visual ranking used to rank the looseness of the package.
Turning now to
The above two testing clearly illustrates that the non-PVDC films based on EVOH as the barrier layer shows improved pucker resistance and looseness resistance which is indicative of their better flavor and aroma barrier performance as described later.
While the foregoing discussion illustrates the importance of a barrier layer for acceptable pucker and looseness resistance for flavor and aroma integrity, it is also important to maintain an acceptable machinability of the film. An acrylic coating on top of the barrier layer may provide excellent slip behavior and machinability properties to the film. To better understand the importance of top coating the barrier layer with an acrylic coating to enhance the fit-for-use (“FFU”) properties, such as slip and machinability behavior, the following structures in Table 6 were compared.
Example 1 is Structure 3, as previously described, and on one side has a coextruded EVOH skin as a barrier layer and is top-coated with acrylic coating, and the other side has an acrylic coating. Example 2 is Structure 5, as previously described, and on one side has a coated EVOH barrier layer and is top-coated with an acrylic coating, and the other side has an acrylic coating. Example 4 is Structure 3, as previously described, and on one side has a coextruded EVOH skin as a barrier layer without an acrylic top coating on the barrier layer, and the other side has an acrylic coating. Example 5 is Structure 5, as previously described, and on one side has a coated EVOH barrier layer without the acrylic top coating on the barrier layer, and the other side has an acrylic coating.
Of these structures, Example 4's coextruded barrier layer without the acrylic top coating had a kinetic COF of 0.247. By comparison, the acrylic top-coated, coextruded barrier layer of Example 1 had an improved lower average kinetic COF of 0.175. Similarly, Example 5's coated barrier layer without the acrylic top coating had a kinetic COF of 0.268. By comparison, the acrylic top-coated, coated barrier layer of Example-2 had an improved lower average kinetic COF of 0.194. A similar trend is also observed for static COF.
In another instance, the Handle-0 Meter test, which provides the stiffness of a film, was performed on all four examples listed in Table 7. The Handle-O-Meter test combines the effect of surface friction and flexibility of a film to provide quantitative data on the stiffness of the film. Example 4's coextruded barrier layer without the acrylic top had a machine direction (“MD”) stiffness of 7.14 g/mm (7.25 g/4″) and a transverse direction (“TD”) stiffness of 11.9 g/mm (12.1 g/4″). By comparison, Example 1's acrylic top coated coextruded barrier layer had a lower MD stiffness of 5.86 g/mm (5.95 g/4″) and a TD stiffness of 9.3 g/mm (9.4 g/4″). Since both of these compared films are of similar base film type, then the lower stiffness value may be said to be mainly indicative of lower surface friction. Similarly, Example 5's coated barrier layer without the acrylic top coating has a MD stiffness of (7.4 g/4″) and a TD stiffness of (10.5 g/4″). By comparison, the acrylic top-coated, coated barrier layer of Example-2 has a lower MD stiffness of (5.0 g/4″) and a TD stiffness of (7.1 g/4″). Since both the films compared are of similar base film type, the lower stiffness value is mainly indicative of lower surface friction.
The presence of the acrylic top coating on the barrier layer also may provide bet ter surface characteristics at elevated temperatures. The hot-slip characteristic of a film is indicative of its coefficient of friction or slip properties at higher temperature. This test is similar to coefficient of friction performed at a higher specified temperature. Hot-slip is a unitless number, which represents the resistance to sliding of two surfaces in contact with each other at a higher specified temperature. These values are between 0 and 1. Higher values indicate more resistance to sliding. The hot-slip test is based on a modified ASTM D 1894 that uses a 6.1 Instrumentor's Slip/Pee Tester Model #SP 102B with heated platen assembly #SPA 06. The hot-slip properties of the films listed in Table 7 were measured to better understand the slip behavior at the higher temperature of 250° F. Example 4's coextruded barrier layer without the acrylic top coating had a hot-slip value of 0.59. By comparison, the acrylic top-coated coextruded barrier layer of Example 1 has an improved lower average hot-slip value of 037. Similarly, Example 5's coated harrier coated barrier layer without the acrylic top coating had a hot-slip value of 0.71. By comparison, the acrylic top coated, coated barrier layer of Example 2 had an improved lower average hot-slip value of 0.46.
The presence of the acrylic top coating over the barrier layer may provide better FFU properties due to enhanced surface characteristics. The surface roughness, Ra, properties of the films listed in Table 7 were measured using a M2 Perthometer from Mahr Corporation, equipped with a 150 stylus to better understand the surface roughness of the barrier side of the film. In one instance, Example-4's coextruded barrier layer without the acrylic top coating had Ra of 21.56. By comparison, the acrylic top-coated, coextruded barrier layer Example 1 had an improved lower Ra of 7.95. Similarly, Example-5's coated barrier layer without the acrylic top coating has Ra of 22.9. By comparison, the acrylic top coated, coated barrier layer of Example-2 had Ra of 5.62.
Based on the above studies, the discussion below illustrates the mechanism of the puckering phenomenon. Turning now to
Turning now to
Turning now to
Structure 1 features a barrier layer 205 co-extruded with the polypropylene core 203 to from a two-layer core 204. Surrounding this core 204 is primer layers 202, 206, as well as coating layers 201,207. The action of the barrier is shown as 209 sealing the product 208.
Structure 2 features primer layers 302, 304 surrounding core 303. Structure 2 additionally comprises top coat 301 and flavor barrier top coat 305 providing the sealing action
While the foregoing is directed to example embodiments of the disclosed invention, other and further embodiments may be devised without departing from the basic scope thereof, wherein the scope of the disclosed applications, compositions, structures, labels, and so forth are determined by one or more claims of at least one subsequently filed, non-provisional patent application.
REFERENCE TO RELATED APPLICATION This is a continuation that claims priority to Patent Cooperation Treaty application PCT/US17/24068 filed on Mar. 24, 2017 and having the same title, which claims priority to United States provisional patent application Ser. No. 62/312,945, filed Mar. 24, 2017, wherein the contents of both of the foregoing applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62312945 | Mar 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US17/24068 | Mar 2017 | US |
| Child | 16011690 | US |
