WO2024127189A1

WO2024127189A1 - Raw edge tape comprising mfc and polymeric outer layers for paperboard containers

Info

Publication number: WO2024127189A1
Application number: PCT/IB2023/062393
Authority: WO
Inventors: Sami-Seppo Ovaska
Original assignee: Stora Enso Oyj
Current assignee: Stora Enso Oyj
Priority date: 2022-12-13
Filing date: 2023-12-08
Publication date: 2024-06-20
Anticipated expiration: 2025-06-13
Also published as: SE546594C2; SE2230410A1

Abstract

The present invention relates to raw edge tape for paperboard containers, said raw edge tape comprising: a substrate layer having a first main surface and a second main surface, a first polymeric outer layer disposed at the first main surface of the substrate layer, and a second polymeric outer layer disposed at the second main surface of the substrate layer, wherein at least said first polymeric outer layer is heat sealable, characterized in that the substrate layer comprises at least 50 wt% of a highly refined cellulose composition having a Schopper-Riegler (SR) number in the range of 50-100 as determined by standard ISO 5267-1, based on the total dry weight of the substrate layer. The present invention relates to paperboard webs, blanks, and containers comprising such a raw edge tape attached thereto.

Description

RAW EDGE TAPE COMPRISING MFC AND POLYMERIC OUTER LAYERS FOR PAPERBOARD CONTAINERS

Technical field

The present disclosure relates to a raw edge tape for protecting exposed raw edges of paperboard used in containers, particularly food containers. The present invention further relates to paperboard webs, blanks, and containers comprising such a raw edge tape attached thereto.

Background

Effective gas, aroma, and/or moisture barriers are required in packaging industry for shielding sensitive products. The multilayer construction of food containers provides a resource efficient, lightweight and recyclable packaging solution that can be made from renewable resources. Sustainably sourced virgin cellulose fibers provide strength and stiffness while the plastic and/or metal foil layers provide barriers to liquid, water vapor, oil/grease, oxygen and light to protect the packed contents. The correct combination of materials ensures food transport and storage safety, while preventing food spoilage and waste by protecting the contents from deterioration.

A commonly used packaging material is paperboard which has been coated with plastic layers of for example polyethylene (PE) or polyethelene terephthalate (PET) on one or both of its main surfaces. When preparing blanks for paperboard container, sheets are cut from a coated paperboard web. The cut edges, referred to herein as “raw edges” will be uncoated and thus form a weak point in terms of resistance to penetration of liquid, water vapor, oil/grease and oxygen. These raw edges must therefore be sealed in order to provide sufficient impermeability for the containers. Commonly used methods for sealing the raw edges include taping, heat-sealing and skiving, i.e., milling of the edge to be thinner, and folding and sealing the thinned edge to seal the raw edge. Raw edge tapes are often used in hermetically sealed paperboard containers, such as noodle cups, soup cups, etc. A raw edge tape protecting the raw edge on the internal side of the cup wall helps to provide sufficient barrier for long-term storage for the packed dry food. Moreover, the raw edge tape on the internal side of the cup wall also provides protection against penetration of water into the raw edge of the paperboard when the food is prepared by adding hot water in the cup.

The raw edge tape is typically attached to the container blank in the blank manufacturing process and sealed when the blank is converted into a container, such as a cup. Typically, the raw edge tape will consist of three layers. A substrate layer of the tape is typically PET, which provides rigidity and stiffness to the tape, and ensures that the oxygen barrier is at required level also in the raw edge area. An outermost layer on each side of the substrate layer is typically based on a blend of PE and EVAc, which provides excellent heat-sealability to LDPE, the most common surface coating in the case of cup-stock board.

The current raw edge tape solutions work well form a permeability standpoint, but separation of the different polymer layers in the recycling process after use is very difficult. Moreover, the adhesion between the raw edge tape and the cup wall is usually so high that separation of the tape from the board is impossible.

Furthermore, the grammage of a typical raw edge tape is approximately 20-40 g/m² Having in mind the increasing demands on biodegradability of single use products, (according to current legislation/SUPD, only 5% of a product may be non-biodegradable), also the raw edge tape increases the plastic content of paperboard-based food containers.

Thus, there remains a need for further improved solutions for protecting exposed raw edges of paperboard used in containers, particularly food containers. Description of the invention

It is an object of the present disclosure to provide an improved raw edge tape for protecting exposed raw edges of paperboard used in containers, particularly food containers.

It is a further object of the present disclosure to provide an improved raw edge tape which can directly replace prior art raw edge tapes.

It is a further object of the present disclosure to provide a raw edge tape which facilitates recycling of containers comprising the raw edge tape.

It is a further object of the present disclosure to provide a raw edge tape which is based on biodegradable materials to a higher extent than prior art raw edge tapes.

The above-mentioned objects, as well as other objects as will be realized by the skilled person in the light of the present disclosure, are achieved by the various aspects of the present disclosure.

The present disclosure is based on the inventive realization that substrate layer based on a highly refined cellulose composition may replace the plastic substrate layer used in prior art raw edge tapes. The substrate layer based on a highly refined cellulose composition has been found to provide rigidity and stiffness to the tape comparable to that of a conventional PET substrate layer. Furthermore, the substrate layer based on a highly refined cellulose composition provides excellent oxygen and oil/grease barrier properties, in some cases even better than those of a conventional PET substrate layer.

According to a first aspect illustrated herein, there is provided a raw edge tape for paperboard containers, said raw edge tape comprising: a substrate layer having a first main surface and a second main surface, a first polymeric outer layer disposed at the first main surface of the substrate layer, and a second polymeric outer layer disposed at the second main surface of the substrate layer, wherein at least said first polymeric outer layer is heat sealable, characterized in that the substrate layer comprises at least 50 wt% of a highly refined cellulose composition having a Schopper-Riegler (SR) number in the range of 50-100 as determined by standard ISO 5267-1 , based on the total dry weight of the substrate layer.

The substrate layer is preferably in the form of a sheet or strip, having a first main surface and a second main surface.

The substrate layer of the inventive raw edge tape is obtained by providing a highly refined cellulose composition and forming the composition into a highly refined cellulose paper or film. The term film as used herein refers generally to a thin continuous sheet formed material. Depending on its composition, purpose and properties, the film can also be considered as a thin paper or even as a membrane.

Refining, or beating, of cellulose pulps refers to mechanical treatment and modification of the cellulose fibers in order to provide them with desired properties. The term “highly refined cellulose” used to herein generally refers to a cellulose pulp which has been subjected to refining to a Schopper-Riegler (SR) value in the range of 50-100, as determined by standard ISO 5267-1 .

The substrate layer comprises at least 50 wt% of the highly refined cellulose composition. Depending on the type of paper or film to be prepared, the highly refined cellulose composition may be used by itself or combined with other, components, such as polymers, fillers or less refined fibers.

Films and coatings made from highly refined cellulose compositions, such as m icrofibrillated cellulose (MFC) and other nanocellulosic materials, have emerged as an interesting alternative to conventional gas, oil and grease barrier films, such as aluminum and synthetic polymer films and various laminates thereof. Highly refined cellulose films have been developed, in which cellulosic fibrils have been dispersed and/or suspended in aqueous media and thereafter re-organized and rebonded together to form a dense film with high barrier properties.

In addition to providing excellent gas barrier properties, the highly refined cellulose films and coatings are also inherently transparent or translucent to visible light, making them especially useful in applications where transparency or translucency of the film in the visible light spectrum (typically in the range of 380 to 740 nm) is required. An MFC coating may for example be used as a varnish or overlay varnish.

Highly refined cellulose films can be made by applying a highly refined cellulose suspension on a porous substrate, for example a membrane or wire, forming a web followed by dewatering of the web by draining water through the substrate to form the film. This can be accomplished e.g. by use of a paper- or paperboard machine type of process. LIS2012298319A teaches a method of manufacturing of an MFC film by applying a furnish comprising MFC directly on porous substrate thus allowing the MFC to be dewatered and filtered.

Alternatively, the highly refined cellulose film can be made by use of casting technologies, including applying a highly refined cellulose dispersion onto a non- porous cast substrate, such as a polymeric or metal substrate, and drying said film by evaporation and/or wet pressing. Films made by casting technologies usually provide a more uniform thickness distribution and a smoother surface. The publication EP2771390 A4 describes preparation of MFC films, in which an aqueous cellulose nanofiber dispersion is coated on a paper or polymeric substrate, dried and finally peeled off as a nanofiber film sheet.

A problem with highly refined cellulose films is that they are typically sensitive to moisture, and that the barrier properties of the films typically deteriorate significantly when the films are exposed to moist or humid conditions.

Another problem with highly refined cellulose films is that they may be brittle and provide low strain ability and tear resistance since the fiber network formed from short fibers will not have the ability to stretch in the same way as longer fibers. When forming highly refined cellulose films of low grammage and thickness, the film may easily break during wet web forming, converting or handling. Also, the gas barrier properties of such highly refined cellulose films tend to deteriorate at high temperatures and high humidity. Moreover, highly refined cellulose is a relatively expensive material, making the cost of pure highly refined cellulose films high.

Various additives have been considered in order to address the problems associated with improving the mechanical properties of highly refined cellulose films. However, while the use of a given additive may solve one specific problem, it may not be able to solve or maintain other physical or mechanical requirements and may even cause new problems. As an example, the addition of longer cellulose fibers in the highly refined cellulose films may improve the mechanical properties of the films but will at the same time impair the gas barrier properties and transparency or translucency of the film. Other additives may adversely affect the re-use of the material such as in the form of broke or pre- or post-consumer reject.

In a raw edge tape according to the present invention the problems associated with highly refined cellulose films are effectively solved by the structural design of the tape, wherein the substrate layer comprising the highly refined cellulose is protected by polymeric outer layers disposed on both main surfaces of the substrate layer. The polymeric outer layers prevent liquid and moisture from coming into contact with the highly refined cellulose, thus preventing deterioration of the barrier properties of the substrate layer. The polymeric outer layers also provide improved strain ability and tear resistance to the substrate layer such that the mechanical and strength properties of the raw edge tape will be acceptable.

Replacing the conventional plastic substrate layer with a highly refined cellulose substrate layer also reduces the plastic content of the raw edge tape. Accordingly, the inventive raw edge tape can be used to help meet the increasing demands on biodegradability of paperboard containers. The highly refined cellulose composition may be produced from wood cellulose fibers, both from hardwood and softwood fibers and from mixtures thereof. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made from pulp including pulp from virgin fiber, e.g. mechanical, chemical and/or thermomechanical pulps. It can also be made from broke or recycled paper. In some embodiments, the highly refined cellulose composition is obtained from a chemical pulp, preferably a kraft pulp. The kraft pulp may be a bleached or unbleached kraft pulp, preferably a bleached kraft pulp. In preferred embodiments, the highly refined cellulose composition is obtained from a softwood pulp. In some embodiments, the highly refined cellulose composition is substantially free from lignin, preferably the highly refined cellulose composition has a lignin content below 10% by weight, based on the total dry weight of the highly refined cellulose composition. In some embodiments, the highly refined cellulose composition has a hemicellulose content in the range of 10-30% by weight, based on the total dry weight of the pulp highly refined cellulose composition.

The substrate layer should be thick enough to provide desired barrier and mechanical properties, but as thin as possible to minimize material consumption and effects of the raw edge tape on processes for converting paperboard to containers and the visual appearance of the finished container products. In some embodiments, the grammage of the substrate layer is in the range of 5-40 g/m², preferably in the range of 10-30 g/m², and more preferably in the range of 10-20 g/m².

The substrate layer comprises at least 50 wt% of highly refined cellulose composition. The substrate layer may be comprised solely of the highly refined cellulose composition or of a combination of the highly refined cellulose composition and one or more other components. In some embodiments, the substrate layer comprises at least 70 wt%, preferably at least 90 wt%, of the highly refined cellulose composition. In some embodiments, the substrate layer comprises in the range of 50-99 wt%, preferably in the range of 70-99 wt%, more preferably in the range of 80-99 wt%, and more preferably in the range of 90-99 wt% of the highly refined cellulose composition, based on the total dry weight of the substrate layer. The other components of the substrate layer may for example include a less refined cellulose pulp. The substrate layer may further comprise additives such as native starch or starch derivatives, cellulose derivatives such as sodium carboxymethyl cellulose, fillers, dispersing agents, drainage and/or retention additives, deflocculating additives, dry strength additives, softeners, cross-linking aids, sizing chemicals, dyes and colorants, wet strength resins, fixatives, de-foaming aids, microbe and slime control aids, or mixtures thereof. The substrate layer preferably comprises no more than 30 wt% of additives in total, based on the total dry weight of the substrate layer. More preferably the substrate layer comprises no more than 20 wt% or 10 wt% of additives in total, based on the total dry weight of the substrate layer.

The highly refined cellulose (HRC) is preferably produced from a cellulose pulp suspension by subjecting the pulp to refining. The highly refined cellulose comprises cellulose particles, fibers or fibrils.

The term highly refined cellulose pulp as used herein refers to a cellulose pulp which has been subjected to considerable refining, such that the highly refined cellulose composition exhibits a Schopper-Riegler (SR) value in the range of 50- 100, as determined by standard ISO 5267-1. In some embodiments, the highly refined cellulose composition has a Schopper-Riegler (SR) number in the range of 70-100, preferably in the range of 85-98, and more preferably in the range of GOGS, as determined by standard ISO 5267-1.

The size distribution of the particles in the highly refined cellulose composition may depend on the starting material and the refining processes used. In some embodiments, the highly refined cellulose composition has a content of fibers having a length >0.2 mm of at least 10 million fibers per gram based on dry weight, and preferably at least 15 million fibers per gram based on dry weight. In some embodiments, the highly refined cellulose fiber composition has a mean fibril area of fibers having a length >0.2 mm value of at least 14%, preferably at least 20%, more preferably at least 22%. The content of long fibrils and fibrillated fibers in a sample can be determined using the L&W Fiber tester Plus instrument (L&W/ABB). The L&W Fiber tester Plus instrument determines the content and mean fibril area of fibers having a length >0.2 mm (including long fibrils and fibrillated fibers having a length >0.2 mm). A known sample weight of 0.100 g is used for each sample and the content of fibers having a length >0.2 mm (million fibers per gram) is calculated using the following formula: Million fibers per gram = (No. fibers in sample) / (Sample weight) / 1 000 000 = (Property ID 3141) / property ID 3136) / 1 000 000.

In some embodiments, the highly refined cellulose composition is a m icrofibrillated cellulose (MFC) composition.

Microfibrillated cellulose (MFC) shall in the context of the patent application mean a cellulose particle, fiber or fibril having a width or diameter of from 20 nm to 1000 nm. Various methods exist to make MFC, such as single or multiple pass refining, pre-hydrolysis followed by refining or high shear disintegration or liberation of fibrils. One or several pre-treatment steps is usually required in order to make MFC manufacturing both energy efficient and sustainable. The cellulose fibers of the pulp used when producing MFC may thus be native or pre-treated enzymatically or chemically, for example to reduce the quantity of hemicellulose or lignin. The cellulose fibers may be chemically modified before fibrillation, wherein the cellulose molecules contain functional groups other (or more) than found in the original cellulose. Such groups include, among others, carboxymethyl (CM), aldehyde and/or carboxyl groups (cellulose obtained by N-oxyl mediated oxidation, for example "TEMPO"), or quaternary ammonium (cationic cellulose). After being modified or oxidized in one of the above-described methods, it is easier to disintegrate the fibers into MFC. MFC can be produced from wood cellulose fibers, both from hardwood and softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It can be made from pulp, including pulp from virgin fiber, e.g. mechanical, chemical and/or thermomechanical pulps. It can also be made from broke or recycled paper.

In some embodiments, the substrate layer further comprises fibers obtained from chemical pulp, CMP, CTMP, HT-CTMP, TMP, or broke. In some embodiments, the substrate layer further comprises in the range of 0.1 -20 wt%, preferably in the range of 1 -10 wt% of the fibers obtained from chemical pulp, CMP, CTMP, HT- CTMP, TMP, or broke. The fibers obtained from chemical pulp, CMP, CTMP, HT- CTMP, TMP, or broke may preferably be unrefined or only slightly refined fibers. In some embodiments the fibers obtained from chemical pulp, CMP, CTMP, HT- CTMP, TMP, or broke have a Schopper-Riegler (SR) number <50, preferably <35, as measured according to the standard ISO 5267-1 .

In some embodiments, the substrate layer further comprises in the range of 0.1 -20 wt%, preferably in the range of 1 -10 wt% of a water-soluble or water-dispersible polymer, based on the total dry weight of the substrate layer.

In some embodiments, the water-soluble or water-dispersible polymer is selected from the group consisting of a starch, a polyvinyl alcohol (PVOH), a cellulose derivative, a hemicellulose, a polyacrylamide, a polydiallyldimethylammonium chloride (PDADMAC), a polyvinylamine (PVAm), a polyethyleneimine (PEI), a protein or a combination thereof, preferably a PVOH.

In some preferred embodiments, the water-soluble polymer is a PVOH. The PVOH may be a single type of PVOH, or it can comprise a mixture of two or more types of PVOH, differing e.g. in degree of hydrolysis or viscosity or different functional groups. The PVOH may for example have a degree of hydrolysis in the range of 80-99 mol%, preferably in the range of 88-99 mol%. Furthermore, the PVOH may preferably have a viscosity above 5 mPaxs in a 4 % aqueous solution at 20 °C as measured according to the standard DIN 53015 / JIS K 6726.

In some embodiments, the substrate layer further comprises in the range of 0.1 -20 wt%, preferably in the range of 1 -10 wt% of a pigment, based on the total dry weight of the substrate layer.

In some embodiments, the pigment is a pigment that promotes oxygen barrier function of a barrier film, preferably a pigment selected from the group consisting of clays and nanoclays, talcum, silicates, carbonates, alkaline earth metal carbonates, ammonium carbonate, metal oxides, transition metal oxides, or a combination thereof. The content of highly refined cellulose in the substrate layer results in the substrate layer having a relatively high density. In some embodiments, the density of the substrate layer is in the range of 800-1800 kg/m³, preferably in the range of 850-1350 kg/m³.

The substrate layer is preferably in the form of a sheet or strip, having a first main surface and a second main surface. The raw edge tape further comprises two polymeric outer layers, one on each main surface of the substrate layer. The polymeric outer layers prevent liquid and moisture from coming into contact with the highly refined cellulose, thus preventing deterioration of the barrier properties of the substrate layer. The polymeric outer layers also provide improved strain ability and tear resistance to the substrate layer such that the mechanical and strength properties of the raw edge tape will be acceptable.

The polymeric outer layers are referred to herein as a first polymeric outer layer, disposed on a first main surface of the substrate layer, and a second polymeric outer layer, disposed on a second main surface of the substrate layer.

In some embodiments, the first polymeric outer layer comprises a polymer selected from the group consisting of polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polybutylene adipate terephthalate (PBAT), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc), polyamide (PA), and combinations thereof, preferably polyethylene (PE) or polyethylene terephthalate (PET).

In some embodiments, the first polymeric outer layer comprises a combination of polyethylene (PE) with ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc). It has been found that the combination of polyethylene (PE) and ethylene vinyl alcohol (EVOH) and the combination of polyethylene (PE) and ethylene vinyl acetate (EVAc) both improves the barrier properties and the recyclability of the raw edge tape. It has been found that the peelability of a raw edge tape comprising these mentioned polymer combinations is increased, meaning that it is easier to peel off the tape which improves the recyclability of the product where the tape is used.

At least said first polymeric outer layer is heat sealable. Heat sealable in the present context means that the polymeric outer layer is preferably thermoplastic and capable of being thermally fused with another polymeric or non-polymeric surface. More specifically, heat sealable in the present context means that the polymeric outer layer is capable of being thermally fused with a coated paperboard, preferably a paperboard coated with a polymer selected from the group consisting of polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc), polyamide (PA), and combinations thereof.

In some embodiments, the second polymeric outer layer comprises a polymer selected from the group consisting of polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polybutylene adipate terephthalate (PBAT), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc), polyamide (PA), and combinations thereof, preferably polyethylene (PE) or polyethylene terephthalate (PET).

In some embodiments, the second polymeric outer layer comprises a combination of polyethylene (PE) with ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc).

In some embodiments, the first and/or second outer polymeric layers comprises a combination of polyethylene (PE) with ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc).

In some embodiments, the second polymeric outer layer is also heat sealable.

In some embodiments, the first and/or second polymeric outer layer has a grammage in the range of 5-25 g/m², preferably in the range of 5-20 g/m². The polymeric outer layer(s) may be formed on, or attached to, the substrate layer using any suitable method. The polymeric outer layer(s) may for example be attached to the substrate layer by liquid coating, extrusion coating, extrusion coating lamination, heat lamination or lamination using an adhesive. A preferred method is extrusion coating.

The polymeric outer layer(s) may be formed directly on, or attached directly to, the substrate layer, or be separated from the substrate layer by one or more intermediate layers arranged between the substrate layer and the polymeric outer layer(s).

In some embodiments, the raw edge tape further comprises a polymeric tie layer arranged between said substrate layer and said first polymeric outer layer, between said substrate layer and said second polymeric outer layer, or both. The tie layer is a thin polymeric layer applied to improve compatibility and adhesion between the substrate layer and the polymeric outer layers.

In some embodiments, the polymeric tie layer comprises ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc), preferably ethylene vinyl acetate (EVAc).

The polymeric tie layer(s) have a lower grammage than the polymeric outer layers. In some embodiments, the polymeric tie layer has a grammage in the range of 1- 15 g/m², preferably in the range of 5-10 g/m².

It has been found that the barrier properties of highly refined cellulose films can be significantly improved by application of a vacuum coating layer on one or both of the main surfaces of the highly refined cellulose film. In some embodiments, the raw edge tape further comprises a vacuum coating layer arranged between said substrate layer and said first polymeric outer layer, between said substrate layer and said second polymeric outer layer, or both. The vacuum coating layer is preferably formed directly on the main surface(s) of the substrate layer. In some embodiments, the vacuum coating layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxides, magnesium oxides, silicon oxides, and combinations thereof, preferably aluminum or an aluminum oxide. Aluminum oxide vacuum coatings also known as AIOx coatings can provide similar barrier properties as aluminum metal coatings, but have the added advantage of thin AIOx coatings being transparent to visible light.

In some embodiments, the vacuum coating layer is formed by vapor deposition of a metal or metal oxide on the substrate layer, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

In some embodiments, the vacuum coating layer has a thickness in the range of 1 - 100 nm, preferably in the range of 10-100 nm, and more preferably in the range of 20-50 nm.

In a preferred embodiment, the raw edge tape comprises: a substrate layer having a first main surface and a second main surface, a first polymeric outer layer disposed at the first main surface of the substrate layer, wherein said first polymeric outer layer consists of EVAc, a second polymeric outer layer disposed at the second main surface of the substrate layer, wherein the second polymeric outer layer consists of PET, and a polymeric tie layer arranged between said substrate layer and said first polymeric outer layer, wherein said polymeric tie layer consists of EVAc, wherein at least said first polymeric outer layer is heat sealable, characterized in that the substrate layer comprises at least 50 wt% of a highly refined cellulose composition having a Schopper-Riegler (SR) number in the range of 50-100 as determined by standard ISO 5267-1 , based on the total dry weight of the substrate layer.

The EVAc provides excellent heat sealing, adhesion and water resistance properties, the PET provides rigidity and protects the surface of the tape, and the m icrofibrillated cellulose (MFC) substrate layer provides rigidity and oxygen barrier properties. The inventive raw edge tape preferably has an overall grammage similar to that of conventional tapes based on plastic substrates. In some embodiments, the inventive raw edge tape has an overall grammage in the range of 15-80 g/m², preferably in the range of 20-60 g/m², and more preferably in the range of 20-40 g/m².

The inventive raw edge tape preferably has low permeability for oxygen and water vapor.

In some embodiments, the raw edge tape has an oxygen transfer rate (OTR), as measured according to the standard ASTM F1927 - 20 at 50% relative humidity and 23 °C, of less than 10 cc/m²/24h/atm, and preferably less than 5 cc/m²/24h/atm.

In some embodiments, the raw edge tape has a water vapor transmission rate (WVTR), measured according to the standard ASTM F1249 - 20 at 50% relative humidity and 23 °C, of less than 10 g/m²/24h, preferably less than 5 g/m²/24h.

In some embodiments, the raw edge tape has a transparency of at least 75%, preferably at least 80%, as measured according to the standard DIN 53147.

The raw edge tape may preferably be manufactured in the form of a sheet or a strip. The strip may preferably have a width in the range of 2-20 mm.

The raw edge tape of the first aspect described above is useful in the preparation of paperboard webs and paperboard container blanks for use in the manufacture of paperboard containers. The raw edge tape is typically attached to a paperboard web or to a paperboard container blank, even before the web or blank is converted into a paperboard container.

According to a second aspect illustrated herein, there is provided a paperboard web comprising a raw edge tape as described above with reference to the first aspect attached thereto. According to a second aspect illustrated herein, there is provided a paperboard container blank comprising a raw edge tape as described above with reference to the first aspect attached thereto.

According to a third aspect illustrated herein, there is provided a paperboard container comprising a raw edge tape as described above with reference to the first aspect attached thereto.

Replacing the conventional plastic substrate layer with a highly refined cellulose substrate layer also reduces the plastic content of the raw edge tape. Accordingly, the inventive raw edge tape can be used to help meet the increasing demands on biodegradability of paperboard containers. Thus, in some embodiments, the paperboard container comprising a raw edge tape as described above with reference to the first aspect attached thereto has an overall content of non- biodegradable plastic of less than 5 wt%, based on the total dry weight of the paperboard container.

Unless otherwise stated, the term “wt%” as used herein refers to weight percent based on the total dry weight of the composition.

Generally, while the products, polymers, materials, layers and processes are described in terms of “comprising” various components or steps, the products, polymers, materials, layers and processes can also “consist essentially of” or “consist of” the various components and steps.

While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Brief description of the drawings

Fig. 1 is a diagram illustrating water vapor transmission rate for paper cups with different raw edge tapes.

Fig. 2 is a diagram illustrating oxygen transmission rate for paper cups with different raw edge tapes.

Examples

Example 1 - Preparation and analysis of OTR and WVTR of raw edge tapes

Preparation:

Raw edge tapes having three different substrate layers were prepared. The first substrate layer was regular copy paper having a grammage of 80 g/m² (essentially no barrier properties). The second substrate layer was MFC film formed from generation 1 MFC, having a grammage of 24 g/m² and a water vapor transmission rate (VWTR) of 14.5 g/m²/day. The third substrate layer was aluminum foil (commercial aluminum foil with a thickness of 17 pm, very good barrier properties). A PET/EVAc laminate film was used for the outer layers for all three substrate layers.

Raw edge tapes were prepared by laminating substrate layers with PET/EVAc laminate film on both main surfaces thereof. The EVAc layer of the PET/EVAc laminate films faced the substrate layer. Lamination was done using an office laminator. The obtained raw edge tapes had the following structures:

PET/EVAc/copy paper/EVAc/PET

PET/EVAc/MFC film/EVAc/PET

PET/EVAc/alu foil/EVAc/PET Analysis:

Oxygen transmission rate (OTR) was analyzed according to the standard ASTM F1927 - 20 at 23 °C and RH 50%. Water vapor transmission rate (WVTR) was analyzed according to the standard ASTM F1249 - 20 at 23 °C and RH 50%.

The results are presented in Table 1 . MFC film was found to significantly improve the barrier properties of the laminate material, albeit not as much as aluminum foil.

Table 1 .

Example 2 - WVTR of paperboard cups with tape

Preparation:

Commercial never-used soup cups made from Cupforma Special 270 + 15 g/m² polyethylene and experimental raw edge tapes prepared in Example 1 were used as starting materials.

The side seam was covered with the raw edge tape. The raw edge tape was attached to the cup wall using 2-sided tape. The raw edge tape was taped with 2- sided tape on the side seam so that the side seam area was not contaminated by the 2-sided tape. The bottom seam was filled with hot-melt adhesive to prevent possible leakage. The top of the cup was sealed with a high-barrier lidding film (Westlid 405 AMP). WVTR gas lines were attached to cup bottom and sealed carefully with hot-melt adhesive to prevent leakage. An H2 leakage sensor was used to confirm that the experimental cups really were gas tight.

Analysis:

The cups with the different raw edge tapes were stored in a constant climate chamber and WVTR was measured at 23°C and RH 50%. The results are presented in Figure 1. The MFC substrate layer improved the WVTR performance of the raw edge by 17% as compared to the copy paper substrate layer (where the barrier properties are essentially derived from the PET/EVAc layers). Adhesion between aluminum foil and EVAc was not perfect in the example, which may explain the high VWTR value of the aluminum foil tape compared to MFC tape.

Example 3 - Oxygen content of paperboard cups with raw edge tape

Preparation:

Experimental cups made from Cupforma Special 270 and having a 31 g/m² EnsoBarr coating on the internal side and a commercial raw edge tape (PE/EVAc/PET/EVAc) attached over the side seam, and experimental raw edge tape with MFC substrate layer prepared in Example 1 were used as starting materials.

Cups with the raw edge tape with MFC were prepared by first carefully removing the commercial tape and then attaching the raw edge tape with MFC raw edge tape on the side seam using 2-sided tape so that the side seam area was not contaminated by the 2-sided tape. Cups having the commercial raw edge tape (PE/EVAc/PET/EVAc) attached over the side seam were used as reference. The bottom seams of the cups were filled with hot-melt adhesive to prevent possible leakage. The top of the cup was sealed with a high-barrier lidding film (Westlid 405 AMP). An oxygen sensor was attached on the lidding film. An H2 leakage sensor was used to confirm that the cups really were gas tight.

Analysis:

The cups were stored in a constant climate chamber at 23°C/RH 50% and the oxygen content inside the cups was monitored for 14 days. The results are presented in Figure 2. The results showed that the experimental raw edge tape with an MFC substrate layer can provide a better barrier than a commercial raw edge tape. The commercial tape resulted in 2.3 times higher oxygen content after 14 days than the raw edge tape with an MFC substrate layer.

Claims

1 . A raw edge tape for paperboard containers, said raw edge tape comprising: a substrate layer having a first main surface and a second main surface, a first polymeric outer layer disposed at the first main surface of the substrate layer, and a second polymeric outer layer disposed at the second main surface of the substrate layer, wherein at least said first polymeric outer layer is heat sealable, characterized in that the substrate layer comprises at least 50 wt% of a highly refined cellulose composition having a Schopper-Riegler (SR) number in the range of 50-100 as determined by standard ISO 5267-1 , based on the total dry weight of the substrate layer.

2. The raw edge tape according to claim 1 , wherein the grammage of the substrate layer is in the range of 5-40 g/m², preferably in the range of 10-30 g/m², and more preferably in the range of 10-20 g/m².

3. The raw edge tape according to any one of the preceding claims, wherein said substrate layer comprises at least 70 wt%, preferably at least 90 wt%, of the highly refined cellulose composition.

4. The raw edge tape according to any one of the preceding claims, wherein the highly refined cellulose composition has a Schopper-Riegler (SR) number in the range of 70-100, preferably in the range of 85-98, and more preferably in the range of 90-98, as determined by standard ISO 5267-1.

5. The raw edge tape according to any one of the preceding claims, wherein the highly refined cellulose composition has a content of fibers having a length >0.2 mm of at least 10 million fibers per gram based on dry weight, and preferably at least 15 million fibers per gram based on dry weight.

6. The raw edge tape according to any one of the preceding claims, wherein the highly refined cellulose fiber composition has a mean fibril area of fibers having a length >0.2 mm value of at least 14%, preferably at least 20%, more preferably at least 22%.

7. The raw edge tape according to any one of the preceding claims, wherein the highly refined cellulose composition is a m icrofibrillated cellulose (MFC) composition.

8. The raw edge tape according to any one of the preceding claims, wherein said substrate layer further comprises fibers obtained from chemical pulp, CMP, CTMP, HT-CTMP, TMP, or broke.

9. The raw edge tape according to any one of the preceding claims, wherein said substrate layer further comprises in the range of 0.1 -20 wt%, preferably in the range of 1 -10 wt% of a water-soluble or water-dispersible polymer, based on the total dry weight of the substrate layer.

10. The raw edge tape according to claim 9, wherein said water-soluble or water-dispersible polymer is selected from the group consisting of a starch, a polyvinyl alcohol (PVOH), a cellulose derivative, a hemicellulose, a polyacrylamide, a polydiallyldimethylammonium chloride (PDADMAC), a polyvinylamine (PVAm), a polyethyleneimine (PEI), a protein or a combination thereof, preferably a PVOH.

11 . The raw edge tape according to any one of the preceding claims, wherein said substrate layer further comprises in the range of 0.1 -20 wt%, preferably in the range of 1-10 wt% of a pigment, based on the total dry weight of the substrate layer.

12. The raw edge tape according to claim 11 , wherein said pigment is a pigment that promotes oxygen barrier function of a barrier film, preferably a pigment selected from the group consisting of clays and nanoclays, talcum, silicates, carbonates, alkaline earth metal carbonates, ammonium carbonate, metal oxides, transition metal oxides, or a combination thereof.

13. The raw edge tape according to any one of the preceding claims, wherein the density of said substrate layer is in the range of 800-1800 kg/m³, preferably in the range of 850-1350 kg/m³.

14. The raw edge tape according to any one of the preceding claims, wherein said first polymeric outer layer comprises a polymer selected from the group consisting of polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polybutylene adipate terephthalate (PBAT), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc), polyamide (PA), and combinations thereof, preferably polyethylene (PE) or polyethylene terephthalate (PET).

15. The raw edge tape according to any one of the preceding claims, wherein said first polymeric outer layer comprises a combination of polyethylene (PE) with ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc).

16. The raw edge tape according to any one of the preceding claims, wherein said second polymeric outer layer is also heat sealable.

17. The raw edge tape according to any one of the preceding claims, wherein said second polymeric outer layer comprises a polymer selected from the group consisting of polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVAc), polyamide (PA), and combinations thereof, preferably polyethylene (PE) or polyethylene terephthalate (PET).

18. The raw edge tape according to any one of the preceding claims, wherein said second polymeric outer layer comprises a combination of polyethylene (PE) with ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc).

19. The raw edge tape according to any one of the preceding claims, wherein said first and/or second polymeric outer layer has a grammage in the range of 5- 25 g/m², preferably in the range of 5-20 g/m².

20. The raw edge tape according to any one of the preceding claims, further comprising a polymeric tie layer arranged between said substrate layer and said first polymeric outer layer, between said substrate layer and said second polymeric outer layer, or both.

21 . The raw edge tape according to claim 20, wherein said polymeric tie layer comprises ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVAc), preferably ethylene vinyl acetate (EVAc).

22. The raw edge tape according to claim 20 or 21 , wherein said polymeric tie layer has a grammage in the range of 1 -15 g/m², preferably in the range of 5-10 g/m².

23. The raw edge tape according to any one of the preceding claims, further comprising a vacuum coating layer arranged between said substrate layer and said first polymeric outer layer, between said substrate layer and said second polymeric outer layer, or both.

24. The raw edge tape according to claim 23, wherein the vacuum coating layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxides, magnesium oxides, silicon oxides, and combinations thereof, preferably aluminum or an aluminum oxide.

25. The raw edge tape according to claim 23 or 24, wherein the vacuum coating layer has a thickness in the range of 1-100 nm, preferably in the range of 10-100 nm, and more preferably in the range of 20-50 nm.

26. The raw edge tape according to any one of the preceding claims, wherein the raw edge tape has an overall grammage in the range of 15-80 g/m², preferably in the range of 20-60 g/m², and more preferably in the range of 20-40 g/m².

27. The raw edge tape according to any one of the preceding claims, wherein said raw edge tape has an oxygen transfer rate (OTR), as measured according to the standard ASTM F1927 - 20 at 50% relative humidity and 23 °C, of less than 10 cc/m²/24h/atm, and preferably less than 5 cc/m²/24h/atm.

28. The raw edge tape according to any one of the preceding claims, wherein said raw edge tape has a water vapor transmission rate (WVTR), measured according to the standard ASTM F1249 - 20 at 50% relative humidity and 23 °C, of less than 10 g/m²/24h, preferably less than 5 g/m²/24h.

29. The raw edge tape according to any one of the preceding claims, wherein said raw edge tape has a transparency of at least 75%, preferably at least 80%, as measured according to the standard DIN 53147.

30. A paperboard web comprising a raw edge tape according to any one of claims 1-29 attached thereto.

31 . A paperboard container blank comprising a raw edge tape according to any one of claims 1-29 attached thereto.

32. A paperboard container comprising a raw edge tape according to any one of claims 1-29 attached thereto.

33. The paperboard container according to claim 32, wherein the paperboard container has an overall content of non-biodegradable plastic of less than 5 wt%, based on the total dry weight of the paperboard container.