DRINKING CUPS MADE FROM CARDBOARD COATED WITH PRINTING LAYER AND CROSSLINKED POLYSILOXANE LAYER

The invention relates to drinking cups comprising a sidewall that is composed of a multilayer cardboard comprising one or more crosslinked polysiloxane layers [A]; a pigment coating or barrier coating layer [B]; a fiber based substrate layer [C]; optionally, a pigment coating layer [D]; a printed layer [E] comprising a printed image and/or decoration; and optionally, one or more crosslinked polysiloxane layers [F]. The multilayer cardboard preferably has a Cobb 600 value determined according to EN ISO 535 of at least 0.2 g·m2. Preferably, the multilayer cardboard has a total content of polyolefins of at most 5.0 wt.-%, relative to the total weight of the multilayer cardboard.

Priority is claimed of European patent application no. 22 156 846.2 that was filed on Feb. 2, 2022.

The invention relates to drinking cups comprising a sidewall that is composed of a multilayer cardboard comprising one or more crosslinked polysiloxane layers [A]; a pigment coating or barrier coating layer [B]; a fiber based substrate layer [C]; optionally, a pigment coating layer [D]; a printed layer [E] comprising a printed image and/or decoration; and optionally, one or more crosslinked polysiloxane layers [F]. The multilayer cardboard preferably has a Cobb 600 value determined according to EN ISO 535 of at least 0.2 g·m2. Preferably, the multilayer cardboard has a total content of polyolefins of at most 5.0 wt.-%, relative to the total weight of the multilayer cardboard.

Paperboard used for drinking cups is usually provided with barrier coatings on the inside (facing the beverage) and sometimes also on the outside (print-side). The barrier coating applied on the inside makes the material resistant against liquids and/or aroma and enables it to withstand the influence of the hot or cold beverage on the paperboard. The barrier coating should also be sealable, preferably heat-sealable. The barrier coating applied on the outside protects the packed item from the surrounding, especially from water vapor and condensation that is formed on the surface due to temperature fluctuations or temperature differences between drinking cup outside vs. beverage.

Barriers are normally created by coating the fiber based substrate with a composition which gives the substrate barrier properties. The most commonly used materials when forming a barrier on a fiber based product, are polyolefins, such as polyethylene (PE) or polypropylene (PP). Bio-based versions thereof have also been proposed. Currently, most of the barrier coatings are manufactured with extrusion coating techniques and hence made off-line in a separate coating unit. This increases the flexibility of the paper or board machine since different operation schedules can be used on the paper or board machine and the extrusion coating unit.

However, one disadvantage is that this is not cost efficient since it requires extra handling of the reels and an extra converting step. In addition, such coatings might not be biodegradable or recyclable. The extrusion coated polymers are hard to disintegrate and re-use as part of a broke handling in paper and paperboard making. Polyolefin coatings further put limitations on the printability of the surface and are not compatible with all kind of inks. Environmental concerns and increasing oil prices have further created a renewed interest in barriers from non-fossil-based materials.

Other commonly used barrier materials comprise pigments such as clay and calcium carbonate in combinations with binders. Typical binders include synthetic organic polymers such as styrene-acrylate (SA), styrene-butadiene-rubber (SBR), ethylene acrylic acid (EAA), polyvinyl acetate (PVAC), polyvinyl acrylic polyester dispersions, and the like. Barrier materials of this type are typically applied in considerably high amounts in order to provide satisfactory barrier properties, e.g. 15 to 30 g·m−2, thereby introducing considerably high amounts of synthetic organic polymers.

Another disadvantage of conventional barrier materials is that they are often not transparent. Thus, print images and the like which are located underneath these materials would not be visible through said barrier materials with the naked eye. In consequences, print images are conventionally applied onto the layers of the barrier materials and then overcoated with suitable transparent materials in order to maintain visibility of the print images and to provide protection against outer mechanical impact.

Such arrangements are disadvantageous not only because they require an additional overcoating step; an additional disadvantage is that the barrier material does not form the outer surface of the fiber based substrates. Thus, when the coated and overcoated fiber based substrates are exposed to water or humidity, the barrier layer can evolve its barrier function as an intermediate layer only, but not as an outer layer. In consequence, the overcoated layer is fully exposed to the water and humidity, respectively. The barrier function merely comes into play when the water or humidity has penetrated the overcoated layer thus reaching the barrier layer.

This problem is even more critical when the fiber based substrates are used for the manufacture of drinking cups that need to be transparent on their inside, e.g. because they carry a print image on their inside, i.e. on the surface that faces the beverage. Such print images have become popular not only for indicating a certain fill height corresponding to a certain volume of filled liquid, but also for other purposes such as esthetics, commercials or other information.

Under these circumstances, the layer that comes into direct contact with the beverage must have sufficient barrier property. Thus, in these cases, the outer layer of the coated fiber based substrate needs to be based upon a barrier material. When such barrier material is not transparent, however, a print image underneath said barrier material would not be visible. Applying instead the print image onto the barrier material and overcoating said barrier material with an overcoat (which in turn has no barrier properties itself) would hardly be possible in view of the massive contact with water when the drinking cup is filled—the overcoat would not withstand the liquid.

Thus, there is a demand for new paperboards that exhibit sufficient barrier function and thus can be used for the preparation of drinking cups and overcome the drawbacks of the prior art.

The sol-gel process is a known method for producing layers of solid materials from small molecules. The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network (or gel) of network polymers. In particular, the colloidal solution is formed that then gradually evolves towards the formation of a gel-like diphasic system containing both a liquid phase and solid phase. Removal of the solvent typically requires a drying process. Afterwards, a thermal treatment, or firing process, is often necessary in order to favor further polycondensation and enhance mechanical properties and structural stability. The precursor sol can be deposited on a substrate to form a film, e.g. by dip-coating or spin coating (see e.g. https: en.wikipedia.org/wiki/Sol-gel_process).

Atypical process involves the hydrolysis of alkoxysilanes to produce hydroxyl groups, followed by polycondensation among these groups and residual alkoxy groups to form a three-dimensional polymeric network (or gel). Coatings with a longer chain are found to decrease the wettability and absorption of base paper more efficiently than coatings with a shorter alkyl chain (see e.g. S. Yujun, Inorganic and Organic Thin Films: Fundamentals, Fabrication, and Applications, 1st ed., Wiley 2021, page 500).

Substituted silanes may serve as feedstocks for numerous industrial sol-gel processes, which yield coatings that are very thin, yet extremely durable. Several silanes that are suitable for preparing such coatings are commercially available (e.g. the products of the series Geniosil®, Silan M1, M2, M3, IO and P series, all of Wacker Chemie AG, Munich).

U.S. Pat. No. 5,510,147 relates to a relaxed sol-gel composition and a coated substrate article which is produced therefrom. A tetrafunctional alkoxide silicate is hydrolyzed in an aqueous solution together with a Lewis acid or metal chelate catalyst with optional protic acid until a viscosity of 2600-3200 cps is obtained to form a crosslinked sol-gel polymer composition. The polymer is relaxed by diluting it with water or water plus alcohol optionally containing a Lewis acid or metal chelate until a viscosity of about 1 cps is obtained while not depolymerizing the polymer. The relaxed polymer has substantially no visible polymer particles. The relaxed polymer composition is uniformly coating a substrate and dried without requiring an in-situ curing.

U.S. Pat. No. 5,776,565 relates to hybrid sol-gel barrier coatings that are produced by hydrolyzing a tetrafunctional alkoxide silicate and a silane having one or two pendant crosslinkable groups in water or water plus a water miscible organic solvent and a catalytic amount a protic acid, Lewis acid, or metal chelate, until a viscosity of from about 2,600 to about 3,200 cps is obtained. The product is then diluted water or water plus a water miscible organic solvent, optionally containing a protic acid, Lewis acid, or metal chelate, until a viscosity of about 0.5 to about 10 cps is obtained. The diluted product is blended with a photoinitiator, coated onto a substrate, dried and irradiated to obtain oxygen barrier films having a very low oxygen transmission rate.

U.S. Pat. No. 6,307,192 relates to an ovenable food tray and its manufacturing method. The paperboard or cardboard tray is provided with at least one layer of polymeric coating which is lying at least on the side of the tray coming into contact with the food and contains a polymerized crosslink structure which consists of an inorganic, chain or crosslinked polymeric backbone which contains alternating silicon and oxygen atoms and which comprises side chains and/or crosslinks formed by organic groups or chains.

US 2009 0022898 A1 provides a sol-gel composition which is dilutable with water in any proportion and is based on the reaction of at least the following components: (i) a glycidyloxypropyl-alkoxysilane, (ii) an aqueous silica sol having a solids content of >1% by weight, (iii) an organic acid as hydrolysis catalyst, and (iv) n-propyl zirconate, butyl titanate or titanium acetylacetonate as crosslinker, starting from a mass ratio of the solids mass of component (ii) to component (i) 0.75.

US 2011 0114276 A1 relates to a method of improving a strength property of a sheet-formed fibrous material formed from an aqueous slurry of cellulose fiber, including coating at least one face of the material with a coating formulation including a polysaccharide containing at least two carboxylic groups and low molecular weight organic mono-, di- or poly-carboxylic acid in an aqueous carrier, keeping the coated face at a temperature of 50° C. or more for a time sufficient to obtain the desired improvement including drying of the material.

US 2014 0342098 A1 relates to a process of fabricating the waterproof coating that may include selecting a substrate, utilizing a sol-gel comprising a silane or silane derivative and metal oxide precursor to coat the substrate, and optionally coating the substrate with a hydrophobic chemical agent and/or other chemical agents to create a surface with nanoscopic or microscopic features.

US 2019 329929 A1 relates to a paperboard structure including a paperboard substrate having a first major side and a second major side, a barrier coating layer on the first major side of the paperboard substrate, a top coat on the first major side of the paperboard substrate, wherein the barrier coating layer is positioned between the paperboard substrate and the top coat, and a heat-sealable barrier coating layer on the second major side of the paperboard substrate.

WO 2020 261198 A1 relates to the techniques for producing stirring spoons or sticks made of paper or cardboard and coated with a layer of material. The layer of material is adapted to make the stirring spoons or sticks waterproof, to make them usable with all types of beverages, including hot beverages.

WO 2021 019220 A1 relates to colloidal solutions (known as sols), the use of sols to impart desirable properties to products, products made using sols, and methods of using such sols.

M.-Ch. Brochier Salon et al., Colloids and Surfaces A: Physicochem. Eng. Aspects 366 (2010) 147-154 relates to the competition between hydrolysis and condensation reactions of trialkoxysilanes, as a function of the amount of water and the nature of the organic group.

T.-A. Nguyen et al., Journal of Sol-Gel Science and Technology volume 69, 237-249 (2014), report about effects of hydrophobic polyhedral oligomeric silsesquioxane coating on water vapor barrier and water resistance properties of paperboard.

V. M. Dias et al., World Journal of Nano Science and Engineering, 2015, 5, 126-139, relates to silica-based nanocoating doped by layered double hydroxides to enhance the paperboard barrier properties.

The coated paperboards of the prior art are not satisfactory in every respect and there is a demand for improved coated paperboards. There remains a need for a coated paperboard for drinking cups, which provides a barrier towards liquids and towards moisture arising from condensation and yet good optical and mechanical properties.

It is an object of the invention to provide coated paperboards that can be advantageously used for the manufacture of drinking cups. The content of polyolefins, preferably of synthetic organic polymers in drinking cups, preferably for hot beverages or cold beverages, should be reduced without compromising the other properties of the drinking cups, such as mechanical strength and deep-temperature properties. The drinking cups should have good recyclability with little rejection and should facilitate repulping. Further, the drinking cups should be easy to manufacture on large scale in a timely and cost-efficient manner. Still further, the drinking cups should be printable, on their outside, their inside, or both.

This object has been achieved by the subject-matter of the patent claims.

A first aspect of the invention relates to a drinking cup comprising an interior for receiving a beverage, a sidewall having a rim, and a bottom, wherein the sidewall has a first edge and a second edge which are arranged in an overlapping manner at side seam area; wherein the sidewall is composed of a multilayer cardboard comprising

The drinking cup according to the invention is suitable for hot and cold beverages, carbonated and uncarbonated beverages, alcoholic and non-alcoholic beverages. Drinking cups need to satisfy certain requirements, particularly with respect to resistance against liquids. However, such requirements for drinking cups are considerably less strict than the corresponding requirements for cups that are devoted for packaging purposes, e.g. for dairy products, frozen food, and the like. The reason is that packaging materials come into contact with the liquids for a much longer period of time and thus need to maintain their resistance against liquids for weeks, months and sometime even years. In contrast, drinking cups (beverage cups for drinks) need to be liquid-proof for at least two hours, but usually for not more than 24 hours.

Water resistance of drinking cups and packaging materials can be quantified by various parameters. A very common parameter is the Cobb value which expresses the capability of a material to absorb and retain moisture (EN ISO 535). Thus, a low Cobb value indicates good resistance against moisture. Different Cobb values are measured at different contact times, e.g. 60, 180, 600 and 1800 seconds; a Cobb 600 value is measured at a contact time of 600 seconds.

While materials that are devoted for packaging purposes, e.g. for dairy products, frozen food, and the like, need to exhibit extremely low to almost non-existent Cobb 600 values, for drinking cups Cobb 600 values of up to 5 g/m2 (EN ISO 535) are typically acceptable (when measured on the inside that comes into direct contact with the drink; values measured on the outer side of the drinking cup can be higher).

As measures for achieving such extremely low to almost non-existent Cobb 600 values can be laborious and expensive, for drinking cups Cobb 600 values do not need to be below 0.1 g/m2, preferably not below 0.2 g/m2 (EN ISO 535). Thus, the drinking cups according to the invention typically have Cobb 600 values within the range of from 0.1 to 5 g/m2, preferably 0.2 to 5 g/m2 (EN ISO 535), in each case measured on the inside that comes into direct contact with the drink.

The sidewall of the drinking cup according to the invention is composed of a specific multilayer cardboard according to the invention. Preferably, the bottom of the drinking cup according to the invention is also composed of the specific multilayer cardboard according to the invention, wherein the multilayer cardboard forming the sidewall of the drinking cup may be the same as of differ from the multilayer cardboard forming the bottom of the drinking cup.

The multilayer cardboard according to the invention comprises layers that can be prepared by means of products that are known to the skilled person and that are commercially available. Technologies for applying such layers are also known to the skilled person. In this regard reference is made e.g. to A. A. Tracton, Coatings Technology Handbook, 3rd ed., Taylor Francis, 2005; J. R. Wagner Jr., Multilayer Flexible Packaging: Technology and Applications, Elsevier, 2010; M. J. Kirwan, Handbook Of Paper And Paperboard Packaging Technology, 2nd ed., Wiley-Blackwell, 2013; G. Cirillo et al., Functional Polymers In Food Science, Volume 1, Food Packaging, Wiley, 2015; P. Bajpai, Biermann's Handbook Of Pulp And Paper: Paper And Board Making, 3rd ed., Elsevier, 2018; S. Farris et al., Functional Coatings For Food Packaging Applications, MDPI, 2020; A. Athanassiou, Sustainable Food Packaging Technology, Wiley, 2021; which are incorporated by reference.

Unless expressly stated otherwise, all percentages are expressed in wt.-% and are related to the total weight of the multilayer cardboard or the specified layer thereof, respectively.

The multilayer cardboard according to the invention comprises at least one cardboard layer, namely the fiber based substrate layer [C], and at least three additional layers, namely the one or more crosslinked polysiloxane layers [A], the pigment coating or barrier coating layer [B], and the printed layer [E].

Preferably, the multilayer cardboard according to the invention has a total area weight (grammage), determined according to EN ISO 536, within the range of from 100 to 500 g·m−2. The total area weight of the multilayer cardboard includes the area weight of all coatings and layers that may be present.

In preferred embodiments, the multilayer cardboard has a total area weight, determined according to EN ISO 536, within the range of from 50 to 900 g·m−2. In preferred embodiments, the multilayer cardboard has a total area weight, determined according to EN ISO 536, within the range of 200±50 g·m−2, or 225±50 g·m−2, or 250±50 g·m−2, or 275±50 g·m−2, or 300±50 g·m−2, or 325±50 g·m−2, or 350±50 g·m−2, or 375±50 g·m−2, or 400±50 g·m−2.

In preferred embodiments, the multilayer cardboard has a total thickness, determined according to EN ISO 534, within the range of from 100 to 750 μm. In preferred embodiments, the multilayer cardboard has a total thickness, determined according to EN ISO 534, within the range of 200±50 μm, or 225±50 μm, or 250±50 μm, or 275±50 μm, or 300±50 μm, or 325±50 μm, or 350±50 μm, or 375±50 μm, or 400±50 μm, or 425±50 μm, or 450±50 μm, or 475±50 μm, or 500±50 μm, or 525±50 μm, or 550±50 μm, or 575±50 μm, or 600±50 μm, or 625±50 μm, or 650±50 μm, or 675±50 μm, or 700±50 μm.

In preferred embodiments of the multilayer cardboard according to the invention, the layers [A], [B], [C], optionally [D], [E], and optionally [F] are arranged in alphabetical order.

Preferably, the one or more crosslinked polysiloxane layers [A] form an outer surface of the multilayer cardboard. As the one or more crosslinked polysiloxane layers [A] face the interior of the drinking cup according to the invention, they are preferably devoted for coming into direct contact with a beverage (drink) that is contained in the drinking cup when being used as a drinking cup.

The beverage may be any drink including cold beverages and hot beverages. Preferred hot beverages (hot drinks) include but are not limited to coffee, hot chocolate, tea, and herbal tea. Preferred cold beverages (cold drinks) include but are not limited to water, soft drinks, juice, plant drinks, and alcoholic drinks such as beer, cider, wine, and spirits.

Preferably, the printed layer [E] forms an outer surface of the multilayer cardboard.

Preferably, the optionally present one or more crosslinked polysiloxane layers [F] form an outer surface of the multilayer cardboard.

Preferably, the one or more crosslinked polysiloxane layers [A] are in direct contact with the pigment coating or barrier coating layer [B].

Preferably, the printed layer [E] is in direct contact with the fiber based substrate layer [C] or the optionally present pigment coating layer [D].

Preferably, the optionally present one or more crosslinked polysiloxane layers [F] are in direct contact with the printed layer [E].

When the multilayer cardboard according to the invention comprises one or more crosslinked polysiloxane layers [F], said one or more crosslinked polysiloxane layers [F] are preferably transparent so that the printed image and/or decoration of printed layer [E] is visible through said one or more crosslinked polysiloxane layers [F] with the naked eye.

In preferred embodiments, the multilayer cardboard according to the invention essentially consists of

Preferably, the multilayer cardboard according to the invention has a total content of polyolefins, preferably of synthetic organic polymers, of at most 5.0 wt.-%, preferably at most 4.0 wt.-%, more preferably at most 3.0 wt.-%, still more preferably at most 2.0 wt.-%, yet more preferably at most 1.0 wt.-%, even more preferably at most 0.5 wt.-%, most preferably at most 0.2 wt.-%, and in particular at most 0.1 wt.-%, relative to the total weight of the multilayer cardboard.

For the purpose of the specification, the total content of “synthetic organic polymers” includes all synthetic organic polymers that may be contained in any coating or layer of the multilayer cardboard but does not include the non-synthetic (i.e. natural) polymers that are contained in the fiber based substrate, e.g. the cellulosic materials of the multilayer cardboard such as cellulose, hemicellulose, lignin, and the like. For the purpose of the specification, crosslinked polysiloxanes are no “synthetic organic polymers” in the meaning of the invention, but are “synthetic inorganic polymers”, even if they carry organic functional groups and/or side chains such as methoxy groups, ethoxy groups, and the like. In case that in the course of the manufacture of the multilayer cardboard the cellulosic material has been treated with chemicals thereby converting the non-synthetic (natural) polymer fibers into chemically modified polymer fibers, such chemically modified polymer fibers are nonetheless no “synthetic organic polymers” in the meaning of the invention.

For the purpose of the specification, the distinction of “synthetic organic polymers” on the one hand and the other constituents of the multilayer cardboard including e.g. the fiber-based substrate on the other hand shall serve the purpose of quantifying the recyclability of the overall material forming the multilayer cardboard according to the invention. The lower the total content of synthetic organic polymers, the better the recyclability and sustainability of the multilayer cardboard according to the invention. Minor chemical modifications of cellulosic fibers that are conventionally performed in the course of manufacture of multilayer cardboard are not considered to alter the recyclability and therefore do not render the non-synthetic (natural) polymers to become “synthetic organic polymers” according to the invention.

Preferably, all “synthetic organic polymers” according to the invention were synthesized from monomers or comonomers but were not obtained by polymer analogous reactions of natural polymers with other substances reacting with functional groups and/or side chains of the polymer backbone of the natural polymers.

Preferably, “synthetic organic polymers” according to the invention are those that are rejected according to the regulations related to circular economy and sustainability. In this regard, reference is made to the most current version of European Parliament and Council Directive 94/62/EC of 20 Dec. 1994 on packaging and packaging waste; and the most current version Directive (EU) 2018/851 of the European Parliament and Council of 30 May 2018 amending Directive 2008/98/EC on waste.

The multilayer cardboard according to the invention comprises a fiber based substrate layer [C] having an area weight, determined according to EN ISO 536, within the range of from 50 to 750 g·m−2; preferably 150 to 500 g·m−2.

Preferably, the fiber based substrate layer [C] is based on paper, paperboard or cardboard.

Preferably, the fiber based substrate layer [C] is based on cellulose fibers.

The multilayer cardboard according to the invention comprises a pigment coating or barrier coating layer [B] having an area weight, determined according to EN ISO 536, within the range of from 0.1 to 50 g·m−2; preferably 5.0 to 20 g·m−2. Optionally, the multilayer cardboard according to the invention additionally comprises a pigment coating layer [D] having an area weight, determined according to EN ISO 536, within the range of from 0.1 to 50 g·m−2; preferably 5.0 to 20 g·m−2.

In preferred embodiments of the multilayer cardboard according to the invention, the pigment coating or barrier coating layer [B] is a pigment coating layer [B].

Preferably, the pigment coating or barrier coating layer [B] and the optionally present pigment coating layer [D] independently of one another are permeable for solvents; preferably for water and/or humidity.

Preferably, the pigment coating or barrier coating layer [B] and the optionally present pigment coating layer [D] independently of one another comprise a binder, preferably a latex.

Preferably, the content of the binder is within the range of from 5.0 to 20 wt.-%, and wherein the content of the pigment is within the range of from 80 to 95 wt.-%, in each case relative to the total weight of the pigment coating or barrier coating layer [B] and the optionally present pigment coating layer [D], respectively.

In preferred embodiments of the multilayer cardboard according to the invention, the pigment coating or barrier coating layer [B] and the optionally present pigment coating layer [D] independently of one another have an area weight, determined according to EN ISO 536, within the range of from 10.0±5.0 g·m−2, or 12.5±5.0 g·m−2, or 15.0±5.0 g·m−2; preferably 7.5±2.5 g·m−2, or 10.0±2.5 g·m−2, or 12.5±2.5 g·m−2, or 15.0±2.5 g·m−2, or 17.5±2.5 g·m−2.

In preferred embodiments of the multilayer cardboard according to the invention, the pigment coating or barrier coating layer [B] is a barrier coating layer [B].

While it is contemplated that the barrier coating layer [B] may be based upon polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), polyamide, and combinations thereof, the barrier coating layer [B] is preferably free of polyolefins; preferably free of synthetic organic polymers.

Preferably, the barrier coating layer [B] comprises metal oxides (e.g. Al2O3, SiO2, CaO, MgO), starch, starch derivatives, cellulose, cellulose derivatives, other polysaccharides, derivatives of other polysaccharides, or mixtures thereof, preferably at a content of at least 50 wt.-%, more preferably at least 70 wt.-%, relative to the total weight of the barrier coating layer [B]. Starches, starch derivatives, celluloses, cellulose derivatives, other polysaccharides, or derivatives of other polysaccharides that are suitable for preparing layers having satisfactory barrier properties, especially against water vapor, are principally known to the skilled person and commercially available.

Preferred cellulose derivatives can be cross-linked or not crosslinked. Preferred cellulose derivatives can be hydrophobically modified. Preferred cellulose derivatives include but are not limited to cellulose ethers and cellulose esters, such as methyl cellulose (MC), ethyl cellulose (EC), methylhydroxyethyl (MHEC), methylhydroxypropyl (MHPC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HPC), carboxymethyl cellulose (CMC), nitrocellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, and other cellulosics.

Preferred starches include but are not limited to wheat starch, corn starch, potato starch, maize starch, rice starch, and the like. The starches may be modified, e.g. oxidized, acid treated, alkaline treated, enzyme treated, and the like.

The starches may be derivatized. Preferred starch derivatives can be cross-linked or not crosslinked. Preferred starch derivatives can be hydrophobically modified. Preferred starch derivatives include but are not limited to starch acetate, hydroxypropyl starch, starch glycolate, and the like.

Preferred other polysaccharides include but are not limited to carrageenan and pectin.

The multilayer cardboard according to the invention comprises a printed layer [E] comprising a printed image and/or decoration.

In preferred embodiments of the multilayer cardboard according to the invention, the printed layer covers at least 40% of the area of the multilayer cardboard; preferably at least 50%, more preferably at least 60%, still more preferably at least 70%, yet more preferably at least 80%, even more preferably at least 90%, most preferably at least 95%, an in particular about 100%.

Preferably, the printed image and/or decoration is made from at least two different colors.

Preferably, the printed image and/or decoration has been applied by flexography, rotogravure of offset printing.

The multilayer cardboard according to the invention comprises one or more crosslinked polysiloxane layers [A] having a total area weight, determined according to EN ISO 536, within the range of from 0.1 to 50 g·m−2; preferably 5.0 to 20 g·m−2. Optionally, the multilayer cardboard according to the invention additionally comprises one or more crosslinked polysiloxane layers [F] having a total area weight, determined according to EN ISO 536, within the range of from 0.1 to 50 g·m−2; preferably 5.0 to 20 g·m−2.

Preferably, the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another do not contain a pigment selected from kaolin, feldspar, mica, calcined kaolin, clay, natural clay, delaminated clay, calcined clay, calcium carbonate, chalk, ground calcium carbonate, precipitated calcium carbonate, prespite calcium carbonate, talc, gypsum, aluminum trihydrates, titanium dioxide, zinc sulfide, zinc oxide, calcium sulfite, barium sulfate, magnesium hydroxide, amorphous silica, silicates, plastic pigments, and mixtures thereof. Preferably, the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another do not contain any pigment or mineral filler.

Preferably, the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another are derived from a sol-gel composition.

In preferred embodiments, the sol-gel composition comprises a non-functionalized silane of general formula (I)

wherein

Preferably, the non-functionalized silane of general formula (I) is selected from the group consisting of

In preferred embodiments, the sol-gel composition comprises a non-functionalized silane of general formula (II)

wherein R5 means —C1-18-alkyl-Si(O—C1-6-alkyl)3; preferably wherein the non-functionalized silane of general formula (II) is tris-[3-(trimethoxysilyl) propyl]-isocyanurate.

In preferred embodiments, the sol-gel composition comprises a non-functionalized alkyl trialkoxy silane oligomer of general formula (III)

wherein

In preferred embodiments, the sol-gel composition comprises a functionalized silane of general formula (IV)

wherein

Preferably, the functionalized silane of general formula (IV) is selected from the group consisting of

In preferred embodiments, the sol-gel composition comprises a metal alcoholate; preferably selected from the group consisting of Al(OC1-6-alkyl)3, Zr(OC1-6-alkyl)4, Ti(OC1-6-alkyl)4, or mixtures thereof.

In preferred embodiments, the sol-gel composition comprises a combination of

In preferred embodiments, the sol-gel composition comprises a combination of

In preferred embodiments, the sol-gel composition comprises a combination of

In preferred embodiments, the sol-gel composition comprises a combination of

In preferred embodiments, the sol-gel composition comprises a combination of

In preferred embodiments, the sol-gel composition comprises a solvent; preferably water; more preferably does not comprise an organic solvent.

Preferably, the content of crosslinked polysiloxane in the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another is at least 35 wt.-%, preferably at least 40 wt.-%, more preferably at least 45 wt.-%, still more preferably at least 50 wt.-%, yet more preferably at least 55 wt.-%, even more preferably at least 60 wt.-%, most preferably at least 65 wt.-%, and in particular at least 70 wt.-%; relative to the total weight of the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F].

In preferred embodiments of the multilayer cardboard according to the invention, the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another have a total area weight, determined according to EN ISO 536, of not more than 25 g·m−2, preferably not more than 22.5 g·m−2, more preferably not more than 20 g·m−2, still more preferably not more than 17.5 g·m−2, yet more preferably not more than 15 g·m−2, even more preferably not more than 12.5 g·m−2, most preferably not more than 10 g·m−2, and in particular not more than 7.5 g·m−2.

In preferred embodiments of the multilayer cardboard according to the invention, the one or more crosslinked polysiloxane layers [A] and the optionally present one or more crosslinked polysiloxane layers [F] independently of one another have a total area weight, determined according to EN ISO 536, within the range of from 10.0±5.0 g·m−2, or 12.5±5.0 g·m−2, or 15.0±5.0 g·m−2; preferably 7.5±2.5 g·m−2, or 10.0±2.5 g·m−2, or 12.5±2.5 g·m−2, or 15.0±2.5 g·m−2, or 17.5±2.5 g·m−2.

In particularly preferred embodiments according to the invention,

In further particularly preferred embodiments according to the invention,

In preferred embodiments, wherein the Cobb 600 value is preferably measured on the side that is intended to form the inside of the drinking cup, the multilayer cardboard according to the invention has a Cobb 600 value determined according to EN ISO 535

In preferred embodiments, wherein the Cobb 600 value is preferably measured on the side that is intended to form the outside of the drinking cup, the multilayer cardboard according to the invention has a Cobb 600 value determined according to EN ISO 535

The drinking cup according to the invention comprises an interior for receiving a beverage, a sidewall having a rim, and a bottom, wherein the sidewall has a first edge and a second edge which are arranged in an overlapping manner at side seam area. The sidewall of the drinking cup and preferably also the bottom of the drinking cup is composed of a multilayer cardboard according to the invention as described above, wherein the one or more crosslinked polysiloxane layers [A] face the interior of the drinking cup.

Preferably, the surface of the side seam area that faces the interior and/or the surface of the side seam area that is opposite the interior, i.e. that faces the exterior, is sealed with a primer, preferably a heat-sealable primer.

Preferably, the primer is an adhesive or a varnish, preferably a heat-sealable adhesive or a heat-sealable varnish. Such adhesives and varnishes are commercially available, e.g. hot-melt adhesives which may be based upon e.g. polyvinyl acetate resins, ethylene vinyl acetate resins, or blends thereof with polyethylenes, polyterpenes, or starches.

In preferred embodiments, the multilayer cardboard comprises layers [A], [B], [C] and [E]; wherein a strip of primer is arranged along side seam area that is formed in an overlapping manner by a section at the first edge and a section at the second edge of one and the same multilayer cardboard; wherein

In preferred embodiments, the multilayer cardboard comprises layers [A], [B], [C], optionally [D], [E] and [F]; wherein a strip of primer is arranged along side seam area that is formed in an overlapping manner by a section at the first edge and a section at the second edge of one and the same multilayer cardboard; wherein

Preferably, the bottom of the drinking cup according to the invention is also composed of a multilayer cardboard according to the invention as described above.

Another aspect of the invention relates to a process for the preparation of a drinking cup according to the invention as described above, the process comprising the steps of

Preferably, in step (b) the printed image and/or decoration is applied by flexography, rotogravure of offset printing. Preferably, in step (b) the printed image and/or decoration is applied by printing in patterns.

Preferably, the sol-gel composition that is applied in step (c) comprises a solvent; preferably water; more preferably does not comprise an organic solvent.

In step (f) of the process according to the invention, an element of appropriate size is obtained from the laminated cardboard obtained by performing the preceding steps, e.g. from a roll or a board made of the laminated cardboard, and the drinking cup is then formed from said element, especially the sidewall of the drinking cup. Preferably, the element has a first edge as well as a second edge, which are joined with one another thereby forming the sidewall of the drinking cup. Preferably, joining the two edges of the element with one another in step (f) is performed by sealing, preferably under the application of heat.

Preferably, the first edge and the second edge, which are joined with one another thereby forming the sidewall of the drinking cup, are arranged in an overlapping manner at side seam area (see FIG. 4).

In preferred embodiments, a strip of primer is arranged along side seam area that is formed in an overlapping manner by a section at the first edge and a section at the second edge of one and the same multilayer cardboard of the sidewall (see FIGS. 5A-D). In a preferred embodiment, the strip of primer along side seam area is applied on top of layer [E] at the first edge and on top of layer [A] at the second edge (See FIG. 5A). In another preferred embodiment, layer [E] only partially covers layer [C] along side seam area at the first edge so that the strip of primer along side seam area is applied on top of layer [C] at the first edge and on top of layer [A] at the second edge (see FIG. 5B). In still another embodiment, layer [A] only partially covers layer [B] along side seam area at the second edge so that the strip of primer along side seam area is applied on top of layer [E] at the first edge and on top of layer [B] at the second edge (see FIG. 5C). In yet another preferred embodiment, layer [E] only partially covers layer [C] along side seam area at the first edge and layer [A] only partially covers layer [B] along side seam area at the second edge so that the strip of primer along side seam area is applied on top of layer [C] at the first edge and on top of layer [B] at the second edge (see FIG. 5D).

In further preferred embodiments, a strip of primer is also arranged along side seam area that is formed in an overlapping manner by a section at the first edge and a section at the second edge of one and the same multilayer cardboard of the sidewall (see FIGS. 6A-D). In a preferred embodiment, the strip of primer along side seam area is applied on top of layer [F] at the first edge and on top of layer [A] at the second edge (FIG. 6A). In another preferred embodiment, layer [F] only partially covers layer [E] along side seam area at the first edge so that the strip of primer along side seam area is applied on top of layer [E] at the first edge and on top of layer [A] at the second edge (see FIG. 6B). In still another preferred embodiment, layer [A] only partially covers layer [B] along side seam area at the second edge so that the strip of primer along side seam area is applied on top of layer [F] at the first edge and on top of layer [B] at the second edge (see FIG. 6C). In yet another preferred embodiment, layer [F] only partially covers layer [E] along side seam area at the first edge and layer [A] only partially covers layer [B] along side seam area at the second edge so that the strip of primer along side seam area is applied on top of layer [E] at the first edge and on top of layer [B] at the second edge (see FIG. 6D).

In preferred embodiments, step (f) of the process according to the invention involves obtaining a further element of appropriate size from the laminated cardboard obtained by performing the preceding steps, e.g. from a roll or a board made of the laminated cardboard, and the bottom of the drinking cup is then formed from said further element. Preferably, the further element has a circumferential edge, which is joined with another edge of the element that forms the sidewall thereby forming the bottom of the drinking cup. Preferably, joining the circumferential edges of the further element with the another edge of the element is also performed by sealing, preferably under the application of heat.

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