EP2719825A1 - Paper material and paper cup made therefrom - Google Patents

Abstract

The material comprises a paper substrate and a coating having: middle coating, which comprises 40-90 wt.% of pigment, 20-55 wt.% of a binder and 0-5 wt.% of additives; and barrier coating comprising 0-20 wt.% of pigment, 80-100 wt.% of binder and 0-5 wt.% of additives. A center line is located between the paper substrate and the barrier coating, where the pigments, binder, and the additives in each line are same or different. The coating is free of polyethylene and is applied on both sides of the paper substrate. The material comprises a paper substrate and a coating having: middle coating, which comprises 40-90 wt.% of pigment, 20-55 wt.% of a binder and 0-5 wt.% of additives; and barrier coating comprising 0-20 wt.% of pigment, 80-100 wt.% of binder and 0-5 wt.% of additives. A center line is located between the paper substrate and the barrier coating, where the pigments, binder, and the additives in each line are same or different. The coating is free of polyethylene and is applied on both sides of the paper substrate. The material further comprises a primer applied between the paper substrate and the center line, where the primer comprises 75-95 wt.% of pigment, 5-20 wt.% of binder and 0-5 wt.% of additives. The middle coating, the barrier coating and the primer occupies 2-25 g/m 2>, 2-22 g/m 2> and 2-20 g/m 2> of the entire coating respectively. The paper substrate comprises highly-glued paper having less than 10 wt.% of ash, 90-99 wt.% of pulp and 1-3 wt.% of sizing agent. The substrate further comprises 90-100 wt.% of short fiber, based on total weight of the pulp, and 40-60 wt.% alkyl ketene dimer and 40-60 wt.% of rosin based on the total weight of the sizing agent. The pigment of the middle coating comprises 50-100 wt.% of additional inorganic filler, and 0-50 wt. of clay. The glass transition temperature of the binder of the middle coating is -20[deg] c to 30[deg] C. The binder of the middle coating is a copolymer formed by reacting styrene and an ethylenically unsaturated monomer. The barrier coating is formed by coating the middle coating with an aqueous polymer or copolymer. The paper material is a heat sealable paper material. An independent claim is included for a method for making a paper material.

Description

The present invention relates to a paper material, a process for producing a paper material, and articles made therefrom, such as a paper cup.

Paper materials that have a barrier effect towards water, ie are water-impermeable, are of great importance both for the food industry and for the catering trade. Typically, known paper materials of this type are extrusion coated with polyethylene to impart the desired barrier properties to the paper material. In order to be able to produce shaped articles such as paper cups from such paper materials without additional adhesives, they must be heat-sealable. In this case, such paper cups, if they are to be used as drinking vessels for hot drinks, only on the inside have a barrier effect against water. For cold drinks, however, the coating is usually applied on both sides, since in this case water can condense on the outside of the drinking vessel.

Packaging materials or shaped articles of paper materials are typically discarded after a single use and supplied to the disposal system. Due to their commonly used polyethylene coating they are not recyclable, i. H. recyclable, and must be disposed of otherwise, which is economically disadvantageous and a burden on the environment.

The present invention is therefore based on the object, a novel paper material that is water-impermeable, polyethylene-free, recyclable and suitable for the production of molded articles such as paper cups, and a method for producing such a paper material, wherein molded articles of the novel paper material are also said to be water impermeable and recyclable.

This object is achieved by the embodiments characterized in the claims.

In particular, there is provided a paper material comprising a paper substrate and a coating, the coating having a middle line comprising, based on the total weight of the middle line, 40 to 90 weight percent (wt%), pigment, 20 to 55 wt% binder and 0 to 5 wt .-% of one or more additives, and a barrier screed comprising, based on the total weight of the barrier screed, 0 to 20 wt .-% pigment, 80 to 100 wt .-% binder and 0 to 5 wt .-% one or more additives, wherein the middle line is between the paper substrate and the barrier screed, wherein the pigments, binders and the one or more additives in each line may be the same or different, and wherein the coating is free of polyethylene.

In a preferred embodiment of the present invention, the coating is on both sides of the paper substrate so that the paper material has a water barrier effect on both sides. As already mentioned above, this is particularly advantageous for paper materials from which paper cups for cold drinks are to be produced, since due to condensation on the outer surface of the cup, the outside of the cup should also be water-impermeable. In this case, the top and bottom applied strokes may be the same or different from each other, for example with respect to the coating jobs, pigments, binders, additives and the presence of one or two precursors. In another embodiment, the paper material has a coating on only one side of the paper substrate. From such coated paper material paper cups can be made with water-impermeable inside for hot drinks, such as tea, coffee or cocoa. Preferably, the middle bar contains, based on the total weight of the middle bar, 45 to 85 wt .-%, particularly preferably 50 to 70 wt .-%, for example 66 wt .-% pigment. Other preferred ranges are 45 to 70 weight percent and 50 to 85 weight percent pigment. The areas mentioned in the present application can be combined with one another as desired.

According to the present invention, the pigment is not particularly limited and includes all pigments and mixtures thereof commonly used in the production of coated paper. Kaolin is used as the preferred pigment. The pigment may comprise an organic filler, for example starch or cellulose fibers, or an inorganic filler, for example calcium carbonate, titanium dioxide, talc and / or diatomaceous earth.

A preferred embodiment of the present invention is that the pigment of the middle bar, based on the total weight of the middle bar pigment, comprises 50 to 100% by weight of kaolin and 0 to 50% by weight of an inorganic filler, for example 50 to 75% by weight % Kaolin and 25 to 50% by weight of an inorganic filler or 75 to 100% by weight of kaolin and 0 to 25% by weight of an inorganic filler. A preferred inorganic filler for the middle bar is calcium carbonate, for example "Hydrocarb 60".

Preferably, the middle bar, based on the total weight of the middle bar, contains from 25 to 50% by weight, particularly preferably from 30 to 40% by weight, for example 33% by weight, of binder. Other preferred ranges are 25 to 40 weight percent and 30 to 50 weight percent binder.

The binder used according to the invention is not subject to any particular restriction and comprises all binders customary in the production of coated paper and mixtures thereof, with the proviso that the binder is free of polyethylene. Possible binders are acrylate polymers, copolymers of styrene and an ethylenically unsaturated monomer, for example styrene-acrylate copolymers or styrene-butadiene copolymers.

Preferred middle-line binders are copolymers formed by reacting styrene and an ethylenically unsaturated monomer, more preferably styrene-acrylate copolymers, particularly preferably styrene-butadiene copolymers. The use of such copolymers in the middle bar advantageously produces a closed surface as a base for the functional barrier screed.

The glass transition temperature of the binder of the middle bar (and, if present, the precoat) is preferably -20 to 30 ° C, more preferably -10 to 20 ° C. Other preferred ranges of the glass transition temperature of the middle stripe binder are -20 to 20 ° C or -10 to 30 ° C. The glass transition temperatures mentioned in the present application, unless otherwise stated, are measured by differential scanning calorimetry. If the glass transition temperature of the binder of the middle bar is in the above-mentioned range, a middle bar having sufficient flexibility properties for a later forming process (eg, folding, winding, rolling, knurling, etc.) can be obtained. The same applies analogously to the binder of the optional pre-coat.

Preferred binders of the barrier screed are heat-sealable binders, for example polystyrene, polymethyl methacrylate and polyurethane esters.

The inventive use of one of the abovementioned polymers or copolymers as a binder in the middle line, together with one of the abovementioned binders in the barrier screed (and optionally the precoat), a paper material having a water resistance value of less than 5 g / m ² , measured by means of a Cobb tests (normal conditions, water exposure for 30 minutes). For the water impermeability of the paper material, it is particularly advantageous if the mass ratio of pigment to binder of the middle line is greater than the corresponding mass ratio of the barrier screed and, if a precoat is present, the mass ratio Pigment / binder of the precursor is greater than the corresponding mass ratio of the middle bar. In addition, the inventive composition of the individual layers, in particular the fact that the coating is free of polyethylene, provides a paper material which is recyclable and thus can be recycled. In addition, the paper material on the coated side, and also on the optionally unpainted side, printable.

According to a preferred embodiment of the present invention, the barrier coat is formed by coating the middle coat with an aqueous polymer or copolymer emulsion, wherein the aqueous polymer or copolymer emulsion, based on the total weight of the aqueous polymer or copolymer emulsion, comprises from 30 to 70% by weight of water and 30 to 70% by weight of at least one polymer or copolymer selected from the group consisting of polystyrene, polymethyl methacrylate, polyurethane ester and a copolymer formed by reacting styrene and an ethylenically unsaturated monomer, for example, styrene-acrylate copolymer and styrene Butadiene copolymer. The aqueous polymer or copolymer emulsion particularly preferably contains 40 to 60% by weight of water. The proportion of the polymer in the aqueous polymer or copolymer emulsion is particularly preferably 40 to 60 wt .-%. Suitable polymer or copolymer emulsions are, for example, Acronal S940 (comprising a copolymer of acrylic ester and styrene) and Acronal A969 (comprising a copolymer of acrylic ester and methacrylic acid ester) from BASF and Michem Coat 95 ("MC95" comprising acrylic-styrene copolymer). the company Michelman. Coating is not particularly limited and may be accomplished in any manner, such as air knife coating, knife coating, gravure coating, bar coating, curtain coating, spray coating. The coating of the aqueous polymer or copolymer emulsion preferably takes place by knife coating, particularly preferably with a doctor blade.

According to the invention, the precoat, the middle bar and the barrier screed may each contain one or more additives. Examples of such additives are Thickeners, defoamers, antifoams, dispersants, caustic soda, etc. As antifoams, for example, the product "Nalco74101" from Nalco can be used, a suitable thickener is, for example, "Rheocat 66" from Coatex.

The middle bar contains preferably 1 to 5 wt .-%, particularly preferably 0.3 to 1.0 wt .-% of one or more additives.

The barrier screed preferably contains, based on the total weight of the barrier screed, from 90 to 100% by weight, particularly preferably from 95 to 100% by weight, for example 100% by weight, of binder. The content of pigment in the barrier screed is preferably 0 to 10 wt .-%, more preferably 0 to 5 wt .-%, for example 0 wt .-%. In addition, the barrier screed preferably contains 0 to 2.5 wt .-%, particularly preferably 0 to 1 wt .-%, for example 0 wt .-% of one or more additives.

According to a preferred embodiment of the present invention, there is a precoating between the paper substrate and the middle bar, the precoat, based on the total weight of the precoat, 75 to 95 wt .-%, preferably 85 to 90 wt .-% pigment, 5 to 20 Wt .-%, preferably 10 to 15 wt .-% binder and 0 to 5 wt .-% of one or more additives. For pigment, binder and additive (s) of the precursor, unless otherwise stated, the same conditions apply as for the components of the middle stroke.

A preferred embodiment of the present invention is that the pigment of the precoat, based on the total weight of the pigment of the precoat, comprises 50 to 100% by weight of kaolin and 0 to 50% by weight of another inorganic filler, for example 50 to 75 Wt .-% of kaolin and 25 to 50 wt .-% of another inorganic filler or 75 to 100 wt .-% kaolin and 0 to 25 wt .-% of a further inorganic filler. A preferred further inorganic filler for the precoat is calcium carbonate.

The paper substrate used in the present invention is not particularly limited and includes any common paper suitable for the production of coated paper. According to a preferred embodiment, the paper substrate is highly sized paper comprising, based on the total weight of the paper substrate, less than 10 wt% ash, 90 to 99 wt% pulp and 1 to 3 wt% sizing agent, the pulp, based on the total weight of the pulp, 90 to 100 wt .-% short fiber comprises. In this context, the term "short fiber" refers to pulp fibers having a maximum length of 800 microns. In this case, the sizing agent is not particularly limited and comprises, based on the total weight of the sizing agent, preferably 40 to 60 wt .-%, particularly preferably 45 to 55 wt .-% Alkylketen dimer and preferably 40 to 60 wt .-%, particularly preferably 45 to 55% by weight resin glue. In addition, the paper substrate used according to the invention preferably has a specific weight per unit area of 100 to 450 g / m ² , more preferably 200 to 350 g / m ² . Unless stated otherwise, the stated basis weights of the base paper or the paper material refer to the air-dry (lutro) base paper or paper material, ie with a residual paper moisture content of 3.5% by weight.

The pulp used is not subject to any particular restriction. The term "pulp" includes any cell or pulp suitable for papermaking. Preferably, eucalyptus or birch pulp is used. The ash used is subject to no particular restriction and can be chosen arbitrarily. Preference is given to using calcium carbonate, for example Hydrocarb 60GU from Omya.

According to a preferred embodiment of the present invention, the coating application of the precursor, if present, amounts to 2 to 20 g / m ² , more preferably 5 to 15 g / m ² , the coating application of the middle stroke 2 to 25 g / m ² , particularly preferably 5 to 20 g / m ² , and the coat application of the barrier screed 2 to 22 g / m ² , particularly preferably 5 to 18 g / m ² .

The specific basis weight of the paper material according to the invention is preferably 200 to 600 g / m ² , more preferably 300 to 500 g / m ² , particularly preferably 350 to 450 g / m ² .

According to another preferred embodiment, the paper material of the present invention is heat-sealable, preferably at a force of 100 to 1000 N and a temperature of 80 to 400 ° C. A bond formed by heat-sealing under the above conditions between two surfaces of the paper material of the present invention, for example, a molded article made of the paper material, is impermeable to water. In this context, the term "water-impermeable" means that in a Cobb test, no water penetrates through the compound formed by heat-sealing. Moreover, the term "water-impermeable" means that a paper cup according to the invention filled with coffee (13 g of coffee powder per 330 ml of water, 80 ° C.) has no dark discoloration half an hour after filling with coffee and no liquid through the compound, formed by heat sealing, has penetrated (visual evaluation).

1. (a) Bereitstellen eines Papiersubstrats,
2. (b) gegebenenfalls Auftragen einer Vorstrichzusammensetzung auf mindestens eine Oberfläche des Papiersubstrats, gefolgt von Trocknen,
3. (c) Auftragen einer Mittelstrichzusammensetzung auf das Papiersubstrat, oder, falls vorhanden, auf den Vorstrich, gefolgt von Trocknen,
4. (d) Auftragen einer Barrierestrichzusammensetzung auf den Mittelstrich, gefolgt von Trocknen,

umfasst.Another object of the present invention relates to a method for producing the paper material described above, wherein the method comprises the steps

1. (a) providing a paper substrate,
2. (b) optionally applying a pre-coat composition to at least one surface of the paper substrate, followed by drying,
3. (c) applying a middle-line composition to the paper substrate or, if present, the precoat, followed by drying,
4. (d) applying a barrier coating composition to the middle bar followed by drying,

includes.

The pre-, middle- and barrier-coating compositions used according to the invention are preferably aqueous mixtures comprising from 10 to 90% by weight, particularly preferably 20 to 80 wt .-%, water, and the above-described components of the respective stroke as a solids content.

The drying is not particularly limited and can be done in any way. For example, it can be dried by applying heated air. Preferably, the heated air has a temperature of 50 to 130 ° C, particularly preferably 60 to 120 ° C, on. According to a preferred embodiment, the drying takes place in several stages, for example using infrared radiators, hot-air suspended dryers and / or steam-heated drying cylinders. After drying, the paper material can be cooled and processed further.

Another object of the present invention relates to a molded article comprising the above-described paper material. Molded article manufacturing processes such as paper cups, yogurt cups, fast food packaging, and other foods are known in the art. According to a preferred embodiment of the present invention, the molded article is a recyclable paper cup for hot and / or cold drinks.

The present invention provides a paper material which, surprisingly, is simultaneously water-impermeable and recyclable due to its particular properties. In addition, a method for producing such a paper material as well as molded articles comprising the paper material are provided. Shaped articles comprising or consisting of the paper stock of the present invention, particularly paper cups, can be recycled, thus making such shaped articles economically advantageous and less environmentally harmful than conventional paper cups and packages.

The following examples serve as further explanation of the present invention, without being limited thereto.

Example 1: Preparation of coated paper material base paper

The base paper was made in a Langenscheid paper machine with hybrid former from Escher-Wyss from 94 wt .-% bleached pulp (95 wt .-% short fiber and 5 wt .-% uncoated Rückstoff), 3 wt .-% ash and sizing agent (50 wt. % Alkyl ketene dimer and 50% by weight resin size). 30 liters of sizing agent were used per ton of air-dry (lutro) base paper. This corresponds to a proportion of sizing agent, based on the total weight of the paper substrate, of 3 wt .-%. description specific basis weight base paper [g / m ² ] oven-dry (otro) lutro CF-BLE - BBB 317 328 CF-BLE - III / R 317 328 CF-BLE - BB 255 264

primer

On base papers CF-BLE - BBB and CF-BLE - BB were on both sides, on CF-BLE - III / R on one side, using roller applicator and smoothing scraper 10 g / m ^{2 of} the coating composition 3272, corresponding to a solid coating order of 8 g / m ² , applied and dried by applying heated air at a temperature of 120 ° C.

Coating Composition 3272:

component parts by weight Hydrocarb 90 GU 50 Miragloss 90 50 Topsperse GX-N 0.12 Acronal PR 8828 X. 14 Caustic soda (10%) 0,051 Rheocat 66 0.3 Mixing time: at least 10 minutes Gluing (parts by weight): 14.0 Solids content (%): 70.5 pH should be (+/- 0.1) 8.4 Density (calculated): 1,629 Binder ratio (%): Acronal PR 8828 X. 100 Pigment ratio (%): Hydrocarb 90 GU 50 Miragloss 90 50 Hydrocarb 90 GU - Pigment Calcium Carbonate Dispersion 90's fineness
Miragloss 90 - pigment (gloss) kaolin dispersion in fineness of 90
Topsperse GX-N - Dispersant Polycarboxylate in aqueous solution
Acronal PR 8828 X - binder styrene / acrylic ester
Rheocoat 66 - Rheology Auxiliaries (Acrylic Polymer)

middle coat

Thereafter, 10 g / m ^{2 of} the coating composition 3273, corresponding to a solid coat application of 8 g / m ² , were applied on both sides, in the case of CF-BLE III / R with precoat on one side of the precoat side, by means of a roller applicator and smoothing blade Air dried at a temperature of 120 ° C.

Coating Composition 3273:

component parts by weight Hydrocarb 90 GU 50 Miragloss 90 50 Topsperse GX-N 0.12 Acronal PR 8828 X. 50 Caustic soda (10%) 0,051 Rheocat 66 0.3 Mixing time: at least 10 minutes Gluing (parts by weight): 50.0 Solids content (%): 64.2 pH should be (+/- 0.1) 8.4 Density (calculated): 1,393 Binder ratio (%): Acronal PR 8828 X. 100 Pigment ratio (%): Hydrocarb 90 GU 50 Miragloss 90 50

barrier line

Then on both sides, in CF-BLE - III / R with first and middle line on one side on the top with pre- and middle line, by roller applicator and smoothing scraper on the top side (later inside of the paper cup) 10 g / m ² , according to a solid coating order of 8 g / m ² , and lower side (later outside of the paper cup) 6 g / m ² , corresponding to a solid coating coverage of 4 g / m ^{2 of} the coating composition 6000, or the coating composition 6001, applied and by applying heated air at a temperature of 60 ° C (recipe 6000) or dried at 120 ° C (recipe 6001).

Coating Composition 6000:

component parts by weight Acronal A 969 100 Miragloss 90 10 Caustic soda (10%) 0.1266 Rheocat 66 0.8 Nalco 74101 0.25 Mixing time: at least 10 minutes Gluing (parts by weight): 100.0 Solids content (%): 41.5 pH should be (+/- 0.1) 8.5 Density (calculated): 1,044 Binder ratio (%): Acronal A 969 100 Acronal A969 - Acrylic acid ester with methacrylic acid ester
Miragloss 90 - pigment (gloss) kaolin dispersion in fineness of 90
Rheocoat 66 - Rheology Auxiliaries (Acrylic Polymer)
Nalco 74101 - Defoamer

Coating Composition 6001:

component parts by weight Michelman MC 95 100 Nalco 74101 0.01 Mixing time: at least 10 minutes Gluing (parts by weight): 100.0 Solids content (%): 46 pH should be (+/- 0.1) 8.5 Density (calculated): 1.05 Binder ratio (%): Michelman MC95 100 Michelman MC 95 - acrylic styrene copolymer
Nalco 74101 - Defoamer

Endflächengewichte:

description specific basis weight paper material [g / m ² ] (lutro, target moisture of 6% by weight) CF-BLE - BBB 6000 400 CF-BLE - III / R 6000 380 CF-BLE - BB 6000 315 CF-BLE - BBB 6001 400 CF-BLE - III / R 6001 380 CF-BLE - BB 6001 315

Example 2: Coffee Test

Paper cups were made from the coated paper materials of Example 1 with a paper cup making apparatus (PMC 1000 from Paper Machine Corporation). The finished paper cups were filled up to 1 cm below the upper edge with freshly brewed coffee (temperature approx. 80 ° C). After half an hour no coffee had penetrated through the seal and the paper cup showed no discoloration due to penetrating liquid.

Claims (12)

A paper material comprising a paper substrate and a coating, wherein the coating
a middle bar comprising, based on the total weight of the middle bar, 40 to 90% by weight of pigment, 20 to 55% by weight of binder and 0 to 5% by weight of one or more additives, and
a barrier screed comprising, based on the total weight of the barrier screed, 0 to 20% by weight of pigment, 80 to 100% by weight of binder and 0 to 5% by weight of one or more additives,
includes,
with the middle bar between the paper substrate and the barrier screed,
wherein the pigments, binders and the one or more additives in each stroke may be the same or different, and
wherein the coating is free of polyethylene. The paper stock of claim 1, wherein the coating is on both sides of the paper substrate. The paper material of claim 1 or 2, wherein there is a precoat between the paper substrate and the middle bar, the precoat, based on the total weight of the precoat, 75 to 95 wt .-% pigment, 5 to 20 wt .-% binder and 0 to 5 wt .-% of one or more additives. Paper material according to one of the preceding claims, wherein the stroke application of the middle stroke is 2 to 25 g / m ² , the coating application of Barrierstrichs 2 to 22 g / m ² and the coat application of the precursor, if present, be 2 to 20 g / m ² . A paper material according to any one of the preceding claims, wherein the paper substrate is highly sized paper comprising, based on the total weight of the paper substrate, less than 10% by weight ash, from 90 to 99% by weight pulp and from 1 to 3% by weight sizing agent .
wherein the pulp, based on the total weight of the pulp, comprises 90 to 100% by weight short fiber
wherein the sizing agent comprises, based on the total weight of sizing agent, 40 to 60% by weight alkyl ketene dimer and 40 to 60% by weight resin size. A paper material according to any one of the preceding claims, wherein the pigment of the middle stroke, based on the total weight of the middle stripe pigment, comprises 50 to 100% by weight of kaolin and 0 to 50% by weight of another inorganic filler, and
wherein the glass transition temperature of the binder of the middle bar is from -20 ° C to 30 ° C. The paper material of claim 6, wherein the middle stripe binder comprises a copolymer formed by reacting styrene and at least one ethylenically unsaturated monomer. The paper stock of any one of the preceding claims, wherein the barrier coat is formed by coating the middle coat with an aqueous polymer or copolymer emulsion,
wherein the aqueous polymer or copolymer emulsion, based on the total weight of the aqueous polymer or copolymer emulsion, comprises 30 to 70% by weight of water and 30 to 70% by weight of at least one polymer or copolymer selected from the group consisting of polystyrene, Polymethyl methacrylate, polyurethane ester and a copolymer formed by the reaction of styrene and an ethylenically unsaturated monomer. A paper material according to any one of the preceding claims, wherein the paper material is heat-sealable. A method of producing a paper material according to any one of the preceding claims, wherein the method comprises the steps (a) providing a paper substrate, (b) optionally applying a pre-coat composition to at least one surface of the paper substrate, followed by drying, (c) applying a middle-line composition to the paper substrate or, if present, the precoat, followed by drying, (d) applying a barrier coating composition to the middle bar followed by drying,
includes. A molded article comprising the paper material of any one of claims 1 to 9. A shaped article according to claim 11, wherein the shaped article is a recyclable paper cup for hot and / or cold drinks.