US20230382618A1

US20230382618A1 - Multilayer functional paper

Info

Publication number: US20230382618A1
Application number: US18/195,510
Authority: US
Inventors: Scott William Huffer; Mary Kate MIRMOW
Original assignee: Sonoco Development Inc
Current assignee: Sonoco Development Inc
Priority date: 2022-05-26
Filing date: 2023-05-10
Publication date: 2023-11-30
Also published as: WO2023229845A1

Abstract

A paper packaging structure is provided herein. The paper packaging structure comprises a paper structure having an inner surface and an outer surface. The structure further includes a barrier layer disposed adjacent the inner surface of the paper structure. The barrier layer comprises a water-based oxygen barrier and a solvent based sealant layer, wherein the oxygen barrier is positioned adjacent the inner surface of the paper structure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application 63/346,117, filed on May 26, 2022, the contents of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to paper products, and more particularly, paper products with effective moisture and oxygen barrier properties.

BACKGROUND

Flexible packaging structures are generally made from multiple polymeric components, often comprising layers of different polymeric films laminated together to achieve desired properties. The layered, laminated films provide desired barrier properties, however, are generally not recyclable in a standard recycling stream due to the multiple different polymers contained therein.
Paper products are being developed as an alternative to plastic packaging, however paper is a porous material, and thus lacks the barrier properties exhibited by plastic flexible packaging. There is a need to further improve the barrier properties for maintaining the safety and quality of packaged foods, while being recyclable in the standard recycling stream.
Through ingenuity and hard work, the inventors have developed a recyclable, repulpable paper product for use in packaging, a method for making the same, wherein the product exhibits acceptable moisture and oxygen barrier properties.

BRIEF SUMMARY

In an embodiment, the invention comprises a paper packaging structure that delivers barrier properties comparable to a laminate film. Generally speaking, the present invention comprises a paper layer and a barrier layer applied to the paper layer.
In another embodiment, the invention comprises a method of forming the multilayer functional paper from the modified paper layer, and barrier materials.
In an embodiment of the present invention a paper packaging structure is provided. The paper packaging structure comprises a paper structure having an inner surface and an outer surface. The paper packaging structure further comprises a barrier layer disposed adjacent the inner surface of the paper structure. The barrier layer comprises a water-based oxygen barrier and a solvent-based sealant layer. The oxygen barrier is positioned adjacent the inner surface of the paper structure.
In some embodiments, the inner surface of the paper structure may be surface treated. In some embodiments, the paper structure may comprise metalized paper. In some embodiments, the paper structure may comprise a topcoat applied to the metalized surface of the paper structure. In some embodiments, the paper structure may comprise a metal layer. In some embodiments, the paper structure may comprise a topcoat applied to the metal layer. In some embodiments, the topcoat may be configured to facilitate a bond between the paper structure and the barrier layer. In some embodiments, the metal layer may be a primer layer.
In some embodiments, the sealant layer may be a heat seal coating. In some embodiments, the oxygen barrier may be a PVA solution. In some embodiments, the PVA solution may be crosslinked. In some embodiments, the barrier layer may be a uniform thickness. In some embodiments, the sealant layer may be a cold seal coating. In some embodiments, the paper packaging structure may further comprise a moisture barrier.
In another embodiment a method for making a paper structure is provided. The method comprises applying a surface treatment to a paper structure. The method further comprises coating a water-based oxygen onto the surface treated surface of the paper structure. The method further comprises at least partially drying the water-based oxygen barrier and coating a solvent-based sealant layer onto the water-based oxygen barrier.
In some embodiments, the paper structure may comprise a moisture barrier. In some embodiments, the paper structure may be metalized and form a metalized surface. In some embodiments, the method may further comprise applying a topcoat to the metalized surface of the paper structure. In some embodiments, the method may additionally comprise applying a primer to the paper structure. In some embodiments, the surface treatment may be a corona treatment. In some embodiments, the oxygen barrier may be applied to the paper structure at a ratio of between 0.25-1 pound per ream. In some embodiments, the oxygen barrier may be applied to the paper structure at a ratio between 0.5-0.7 pounds per ream. In some embodiments, the sealant layer may be applied at a weight ration between 1-4 pounds per ream. In some embodiments, the sealant layer may be applied at a weight ratio between 2-3 pounds per ream.
In yet another embodiment a package is provided. The package comprises a paper packaging structure comprising a paper structure having an inner surface and an outer surface. A barrier layer is disposed adjacent the inner surface of the paper structure. The barrier layer comprises a water-based oxygen barrier and a solvent-based sealant layer. The oxygen barrier is positioned adjacent the inner surface of the paper structure. The paper packaging structure is sealed about a product to form a package.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 illustrates a cross-sectional view of an example paper packaging structure, in accordance with some embodiments discussed herein; and

FIG. 2 illustrates a process diagram for forming an example paper packaging structure, in accordance with some embodiments discussed herein.

DETAILED DESCRIPTION

Example embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout.
A paper packaging structure is provided herein. Paper packaging products may require added barrier properties to preserve the condition of the contents of the packaging, as paper is porous and transmits oxygen and moisture easily.
FIG. 1 illustrates an example paper packaging structure 100. In an embodiment, the paper packaging structure may comprise a paper structure 110, and a barrier layer 130. In some embodiments, a surface treatment 120 may be utilized to promote adhesion between the paper structure 110 and the barrier layer 130.
In some embodiments, the paper structure 110 may define at least one paper layer 115. In some embodiments, the paper structure 110 may comprise a plurality of paper layers 115. In some embodiments, the paper layer 115 may be a modified metalized paper. In some embodiments, the paper layer 115 may comprise only virgin paper, while in other embodiments, the paper layer 115 may comprise only recycled paper (post-consumer or post-industrial). In some embodiments, the paper layer 115 may comprise a combination of recycled paper and virgin paper. In some embodiments, the paper layer 115 may be a densified paper. In some embodiments, the paper layer 115 may have a density between 30-100 g/m², between 40-80 g/m², or 50-70 g/m². In some embodiments, the density of the paper may contribute to barrier properties, as the paper layer 115 may exhibit less porosity at higher densities as the cellulous fibers are closer together.
In some embodiments, the paper layer 115 may be treated to improve the smoothness of the paper layer 115 to ensure even coatings and layers, thereby improving the barrier properties of the paper layer 115. In some embodiments, a primer layer 117 may be applied to an inner surface 115 b (with respect to a packaging structure that may be formed) of the paper layer 115. In some embodiments, the primer layer 117 may smooth the inner surface 115 b of the paper layer 115. For example, in an embodiment the primer layer 117 may comprise inert clay particles configured to fill voids between the paper fibers of the paper layer 115. Thus, in some embodiments, the primer layer 117 may be used to change the porosity of the paper layer 115 by densifying the paper and smoothing the surface. In some embodiments, the primer layer 117 may provide an even surface for metallization. In an embodiment, the primer 115 may comprise a coating.
In some embodiments, a metalized layer 111 may be applied directly to the paper layer 115 or to the primer layer 117. In some embodiments, the metalized layer 111 may be vacuum deposited. In some embodiments, rather than a metallized layer, a barrier coating (e.g., AlOx, or SiOx) may be vacuum deposited onto the paper layer 115 or the primer layer 117. In other embodiments the metalized layer 111 may be substituted with a coating, film, or any other application known in the art.
In some embodiments, a topcoat 113 may be applied to the metalized layer 111 opposite the primer layer 117. The topcoat 113 may be a protective layer configured to increase flexibility and serve as a protective surface to keep the metalized layer 111 from being compromised. Thus, the topcoat 113 may decrease cracking or voids in the metalized layer 111, and general wear and tear from handling. In some embodiments, the topcoat 113 may prevent other degradation, and in some embodiments may prevent oxidation to the metalized layer 111. In an embodiment, the topcoat 113 may be a coating.
The paper structure 110 may define a first surface 110 a and a second surface 110 b. The first surface 110 a may form the exterior of the structure (e.g., the exterior of the packaging 100) and the second surface 110 b may bond with other structures. In some embodiments, the first surface 110 a may be printed or may include an ink layer to provide labeling, graphics, logos, product information, or the like. The printed matter or ink layer may be printed using any known printing process.
In some embodiments, a surface treatment 120 may be applied to the second side 110 b of the paper structure 110. The surface treatment 120 may be configured to promote adhesion between the paper layer and a barrier layer and/or increase the surface energy of the paper structure 110 (and in some cases the topcoat 113), to improve wettability and adhesion of inks, coatings and adhesives. In some embodiments, the surface treatment 120 may be a corona treatment, a flame treatment, a plasma treatment, or similar surface treatment.
In some embodiments, the barrier layer 130 may be applied to the paper structure 110, and in some embodiments, to the primer 117, metal layer 111, or surface treated topcoat 113, whichever is the innermost layer of the paper structure 110. The barrier layer 130 may include multiple layers including an oxygen barrier 133 and sealant layer 135. In some embodiments, the oxygen barrier 133 may be a printable coating. The oxygen barrier 133 may be printed or applied to the paper structure 110 with a pilot press in some embodiments. In some embodiments, the oxygen barrier 133 may be water-based. In some embodiments, the oxygen barrier 133 may be a polyvinyl alcohol (PVA) solution. In some embodiments, the oxygen barrier 133 may be produced by Siegwerk. In some embodiments, the barrier layer 133 may be filtered out of the recycling stream, while in other embodiments the barrier layer 133 may dissolve in a standard paper recycling stream, thus allowing the paper fibers within paper structure 110 to be recyclable.
The oxygen barrier 133 may be applied to the paper structure 110 at a ratio of up to 1 pound of oxygen barrier per ream, up to 0.8 pounds of oxygen barrier per ream, or up to 0.6 pounds of oxygen barrier 133 per ream. In some embodiments, the oxygen barrier may be applied in a ratio of between 0.4 pounds per ream to 1.0 pounds per ream, or between 0.5 pounds per ream to 0.7 pounds per ream.
In some embodiments, the barrier layer 130 may provide a barrier for migratory components between the product and the paper layer 115. In some embodiments, the barrier layer 130 may prevent any grease, mineral oil or similar from transferring from the product to the paper layer 115 thereby preventing grease stains or creases within the paper layer 115.
Crosslinking may also improve barrier properties of the coating and, in turn, the resulting sheet or container. Any other cross-linking methods could be utilized to crosslink the PVOH, which may include, but is not limited to chemical, physical, or mechanical cross-linking. For example, electron beam crosslinking methodologies could be applied to crosslink the PVOH within the coating material, optionally after the coating has been applied and dried.
In some embodiments, the barrier layer 130 may include a heat seal coating 135. The heat seal coating 135 may be applied to or coated onto the oxygen barrier 133 opposite the paper structure 110 in some embodiments. In some embodiments, the heat seal coating 135 may be a heat seal coating, while in other embodiments the heat seal coating 135 may be a cold seal. The heat seal coating 135 may be solvent-based, in some embodiments, while the heat seal coating 135 may be water-based in others. In some embodiments, the heat seal coating 135 has the same chemistry as the oxygen barrier 133, while in other embodiments the barrier layer 130 defines alternating chemistries. For example, in an embodiment the oxygen barrier 133 may be water-based and the heat seal coating 135 may be solvent-based. While not wishing to be bound by theory, it is believed that alternating the chemistries between water-based and solvent-based layers in the barrier layer 130, the barrier layer 130 may maintain distinct layers that do not dissolve into each other during printing or coating. In other embodiments, both the oxygen barrier 133 and the heat seal coating 135 may be water based.
In some embodiments, the oxygen barrier 133 is dried completely before application of the heat seal coating 135. In some embodiments, the heat seal coating 135 may be sprayed, coated, extruded, or printed onto the oxygen barrier 133. In some embodiments, the heat seal coating 135 may comprise PET based chemistry, for example ACTEseal®, produced by Actega, or similar.
In some embodiments, the heat seal coating 135 may applied be to the oxygen barrier 133 at a ratio between 1-4 pounds of heat seal coating per ream, between 2-3 pounds of heat seal coating per ream, or even between 2.25-2.75 pounds of heat seal coating per ream.
In some embodiments, the heat seal coating 135 may be a cold seal structure. In such embodiments, the cold seal may be coated with a release overlacquer.
In some embodiments, the barrier layer 130 may define a barrier layer thickness of less than 10 microns, in some embodiments less than 8 microns and in some embodiments less than 6 microns. The barrier layer 130 thickness may be correlated to the thickness of the paper structure 110. For example, a thicker barrier layer 130, may be utilized with a thicker paper structure 110. Further, a thinner barrier layer 130, may allow a thinner paper structure 110.
In some embodiments, the packaging structure 100 may be formed into a container for dry products including seasoning, mixes, cookies, crackers, nuts and the like. In some embodiments, the barrier layer 130 may comprise the product-facing side of a food package, and the paper structure 110, specifically the paper layer 115 in some embodiments, may be the outer or exterior layer. In some embodiments, the barrier layer 130 may further act as a barrier between the ink contained in or on the paper layer 115 and the product contained within the package. In some embodiments, the packaging structure 100 may be formed into a flow wrap package, a bar wrap, a slug wrap, a pouch, and pillow package, and in some embodiments, may be configured into a stand-up package.

Method of Manufacture

In the method of manufacture, referring to FIG. 2 , a paper structure 210 may be advanced from a first structure supply roll 211. In an embodiment, a paper layer may be coated with or otherwise adhered to a primer, a metal, and/or a topcoat (not shown). One or both surfaces of the paper structure 210 may be treated with a surface treatment, at station 220. In some embodiments, the surface treatment may be corona discharge or a flame treatment to render the surface more receptive to inks and/or more readily bondable to the barrier layer that is subsequently applied to the surface. The paper structure 210 may be optionally pre-printed as a part of the presently described manufacturing process. In other embodiments, the paper layer 210 may be advanced to a printing station 235 during manufacture. The inks and printing may be applied to the first side 110 a (i.e., exterior surface) of the paper structure 110 in an embodiment.
In an embodiment, an oxygen barrier 133 is applied to the second side 110 b (i.e., interior surface) paper structure 210 adjacent the surface treatment at a barrier coating station 233. In an embodiment, the oxygen barrier is at least partially dried and advances to a heat seal coating station 235, where the heat seal coating 135 may be applied.
In an embodiment, the paper packaging structure may be formed into packages or may be cut and stacked and/or rolled to be transported to a separate facility for packaging, at station 255.

Examples

Example 1. In this experiment, the inventors compared the oxygen and moisture transmission rates of a paper structure with a surface treatment as outlined herein versus a paper structure without the surface treatment. In the experiment the paper structure 110 was a metalized densified paper including a primer layer and a topcoat layer. In each trial, the barrier layer 130, including oxygen barrier 133 and heat coating layer 135, was applied to the paper structure 110 at the same ratio. The oxygen transmission rate (OTR) for each sample was measured as cc/100 in²/day at approximately 23° C., and 0% relative humidity in 100% O₂. The water vapor transmission rate (WVTR) for each sample was measured at g/100 in²/day at about 37.8° C., and 90% relative humidity. The results of the testing without a barrier coating are shown in Table 1, and the results of the testing with the barrier coating are shown in Table 2.

	TABLE 1

	OTR (cc/100 in²/day @ ~23°	WVTR (g/100 in²/day)
	C./0% RH) with 100% O₂	at 37.8° C./90% RH

Replicate #	Barrier Paper without Oxygen Barrier Coating

1	>12.9	0.298
2	>12.9	0.202
Mean	>12.9	0.250
Std. Dev.	N/A	0.048

	TABLE 2

	OTR (cc/100 in²/day @ ~23°	WVTR (g/100 in²/day)
	C./0% RH) with 100% O²	at 37.8° C./90% RH

Replicate #	Barrier Paper with Oxygen Barrier Coating

1	.69	0.17
2	.29	0.17
3	.06	0.16
Mean	.35	0.17
Std. Dev.	.28	0.005

As can be seen, the surface treatment leads to a significantly lower WVTR and lower OTR. The goal for WVTR is to be below 0.5 g/100 in²/day. Thus, in an embodiment, the structure 100 of the present invention has an WVTR of less than or equal to 0.5 g/in²/day. The goal for oxygen transmission is to be below Thus, in an embodiment, the structure 100 of the present invention has an oxygen transmission of less than or equal to 0.1 cc/100 in²/day.
As illustrated in Table 1 and Table 2, the OTR decreased by over 95% when compared to the paper layer without a barrier coating, while the WVTR decreased by over 30%.
In general paper will absorb coatings positioned on the paper layer. However, in utilizing a densified paper layer, the additional coatings were not absorbed by the paper layer. Rather the paper layer stayed intact and the barrier coating 130 provide exemplary barrier coatings as illustrated below.
The oxygen transmission rate was tested with an Ox-Tran 702 with 100% O₂and at 23 C and 0% RH. The oxygen transmission rates were compensated to a barometric pressure of 760 mmHg. For the tests the metallized surface was positioned towards the carrier gas for testing, in accordance with ASTM 3985.
The water vapor transmission rate was tested on the Permatran 3/31 at 90% A RH and 37.8 C. The samples were tested with the metallized layer 111 towards the moisture, in accordance with ASTM F1249.

Claims

That which is claimed:

1. A paper packaging structure comprising:

a paper structure having an inner surface and an outer surface;

a barrier layer disposed adjacent the inner surface of the paper structure, wherein the barrier layer comprises a water-based oxygen barrier and a solvent-based sealant layer, wherein the oxygen barrier is positioned adjacent the inner surface of the paper structure.

2. The paper packaging structure of claim 1, wherein the inner surface of the paper structure is surface treated.

3. The paper packaging structure of claim 1, wherein the paper structure comprises a vacuum deposited barrier coating.

4. The paper packaging structure of claim 3, wherein the vacuum deposited barrier coating is AlOx, or SiOx.

5. The paper packaging structure of claim 1, wherein the paper structure comprises a metalized paper.

6. The paper packaging structure of claim 5, wherein the paper structure comprises a topcoat applied to the metalized surface of the paper structure.

7. The paper packaging structure of claim 1, wherein the paper structure comprises a metal layer.

8. The paper packaging structure of claim 7, wherein the paper structure comprises a topcoat applied to the metal layer.

9. The paper packaging structure of claim 8, wherein the topcoat is configured to facilitate a bond between the paper structure and the barrier layer.

10. The paper packaging structure of claim 7, wherein the metal layer is applied to a primer layer.

11. The paper packaging structure of claim 1, wherein the sealant layer is a heat seal coating.

12. The paper packaging structure of claim 1, wherein the oxygen barrier is a PVA solution.

13. The paper packaging structure of claim 10, wherein the PVA solution is cross linked.

14. The paper packaging structure of claim 1, wherein the sealant layer is a cold seal coating.

15. The paper packaging structure of claim 1, wherein the barrier layer defines a uniform thickness.

16. The paper packaging structure of claim 1, wherein the paper structure comprises a moisture barrier.

17. A method of making a paper structure, the method comprising:

applying a surface treatment to a paper structure;

coating a water-based oxygen barrier onto the surface treated surface of the paper structure;

at least partially drying the water-based oxygen barrier; and

coating a solvent-based sealant layer onto the water-based oxygen barrier.

18. The method of claim 17, wherein the paper structure comprises a moisture barrier.

19. The method of claim 17, wherein the paper structure is metalized and forms a metalized surface.

20. The method of claim 17, additionally comprising applying a topcoat to the metalized surface of the paper structure.

21. The method of claim 17, additionally comprising applying a primer to the paper structure.

22. The method of claim 17, wherein the surface treatment is a corona treatment.

23. The method of claim 17, wherein the oxygen barrier is applied to the paper structure at a ratio of between 0.25-1 pound per ream.

24. The method of claim 17, wherein the oxygen barrier is applied to the paper structure at a ratio of between 0.5-0.7 pounds per ream.

25. The method of claim 17, wherein the sealant layer is applied at a weight ratio between 1-4 pounds per ream.

26. The method of claim 17, wherein the sealant layer is applied at a weight ratio between 2-3 pounds per ream.

27. The method of claim 17, wherein the paper structure comprises a vacuum deposited barrier coating.

28. A package comprising:

a paper packaging structure, wherein the paper packaging structure comprises:

paper structure having an inner surface and an outer surface; and

a barrier layer disposed adjacent the inner surface of the paper structure, wherein the barrier layer comprises a water-based oxygen barrier and a solvent-based sealant layer, wherein the oxygen barrier is positioned adjacent the inner surface of the paper structure,

and wherein the paper packaging structure is sealed about a product to form a package.