RU2444440C2 - Packing laminate - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to packing laminate, its fabrication and application, to package for foodstuffs or drinks. Retortable packing laminate comprises main layer of sized paper or cardboard, barrier layer for liquid and barrier layer for gas. Note here that said paper or cardboard comprises expanded or nonexpanded expanding thermoplastic microspheres.

EFFECT: higher resistance against water and gas penetration.

17 cl, 10 tbl, 8 ex

Description

The present invention relates to a packaging laminate, its manufacture and use, as well as to packaging for food products and its manufacture.

A packaging laminate comprising at least one layer of paper or paperboard is widely used for food packaging containers. Examples of such a laminate are described, for example, in WO 02/090206, WO 97/02140, WO 97/02181 and WO 98/18680.

Finished packaging containers can be made from packaging laminates using modern packaging and filling machines that form, fill and seal packages. In combination with forming and filling the package, the packaging laminate can be treated with a disinfectant, such as an aqueous solution of hydrogen peroxide. When a food product is packaged for long-term storage in packaged form, the package as a whole can be autoclaved at high temperature and pressure above atmospheric pressure, for example using hot steam, and then quickly cooled by direct contact with water. In any of these cases, liquid or moisture may penetrate the paper or cardboard layer on unprotected edges. Various attempts to solve this problem are described.

In the previously mentioned WO 02/090206 it is described that paper or paperboard can be made hydrophobic by sizing in bulk using an aqueous dispersion of an alkyl ketene dimer.

WO 03/021040 describes cardboard for packaging, consisting of one or more layers, with a top layer of bleached kraft pulp having a gloss value of 15-50%, a minimum gloss spread, a density in the range of 700 to 850 kg / m ³ and which is hydrophobic due to the sizing agent treatment of each layer.

WO 2005/003460 describes a packaging intended for heat treatment, comprising a fiber-based packaging material, treated with a hydrophobic sizing agent, and containing one or more layers with reduced permeability to water on the outside and / or inside of the fiber substrate. The fiber backing is treated with a combination of a sizing agent to impart moisture resistance to the hydrophobic sizing agent and the aluminum and / or calcium compound.

WO 03/106155 describes a method for forming a container from a packaging laminate in order to protect edges against moisture penetration.

WO 2004/056666 describes a specific heating cycle for packages to minimize moisture penetration at the edges.

Japanese Patent Application Laid-Open No. JP 2002-254532 describes containers of heat-insulating paper containing thermoplastic microspheres. It is described that the properties associated with the impregnation of the edges are improved by preventing the expansion of microspheres on the edges of the paper.

Other disclosures related to the use of thermoplastic microspheres in paper for various applications include US patents 3556934, 4133688, 5125996 and 6379497, Japanese patent JP 2689787, Japanese patent application laid open JP 2003-105693, WO 01/54988, WO 2004/099499 , WO2004 / 101888, WO 2004/113613 and WO 2006/068573, publication of patent application US 2001/0038893 and O. Soderberg, "World Pulp & Paper Technology 1995/96, The International Review for Pulp & Paper Industry" p. 143-145.

A variety of sizing compositions are described, for example, in patents US 4654386, 5969011, 6093217, 6165259, 6306255, 6444024, 6485555,6692560,6818100 and 6846384.

The aim of the present invention is to provide a packaging for food products made of a packaging laminate with a high resistance against penetration of liquid or moisture at the edges of the laminate.

An additional objective of the present invention is to provide a packaging laminate containing paper or cardboard, with properties suitable for such packaging.

It has been found that these goals can be achieved by incorporating expanded or unexpanded expandable thermoplastic microspheres into the paper or at least at the edges of the paper.

Thus, one aspect of the present invention relates to a packaging laminate comprising at least one base layer of paper or cardboard, at least one liquid barrier layer and at least one gas barrier layer, wherein said paper or cardboard, preferably contains at least at its edges expanded or non-expanded expandable thermoplastic microspheres.

Another aspect of the present invention relates to a method for manufacturing a packaging laminate, comprising the step of applying at least one liquid barrier layer and at least one gas barrier layer to a sheet or web of paper or paperboard, preferably containing at least edges, expanded or unexpanded expanding thermoplastic microspheres.

Another aspect of the present invention relates to the use of a packaging laminate as defined above for the manufacture of sealed packaging for food or drink.

An additional aspect of the present invention relates to a method for manufacturing sealed packages, comprising the steps of forming a container from a packaging laminate, filling the container with a food or drink, and sealing the container, said packaging laminate comprising at least one base layer of paper or paperboard and at least at least one liquid barrier layer and, preferably, at least one gas barrier layer, said paper or paperboard containing, preferably at least at their edges, expanded or non-expanded expanding thermoplastic microspheres.

Another additional aspect of the present invention relates to a sealed packaging for food or drinks made from a packaging laminate containing at least one base layer of paper or cardboard and at least one barrier layer for liquid and, preferably, at least one barrier a gas layer, said paper or cardboard containing, preferably at least at its edges, expanded or unexpanded expandable thermoplastic microspheres.

In one embodiment, the package is suitable for packaging food products or beverages that should not be heat treated after the package is filled and sealed. Typically, such packages are used for beverages such as milk, juice, and other non-alcoholic drinks, and the packaging laminate used for this will be referred to herein as a liquid packaging laminate or cardboard for packaging liquid. The desired properties of a liquid packaging laminate include the ability to withstand the liquid contents of the package as well as liquid disinfectants such as aqueous hydrogen peroxide solutions.

In another embodiment, the packaging is suitable for food or beverage, where the filled and sealed packaging is heat treated to increase the shelf life of the contents. Such packaging can be used for all types of food products, especially those that are traditionally packed in cans, and will be referred to here as sterilized packaging, and the material for them - as a sterilized packaging laminate or sterilized cardboard. The desired properties of the sterilizable packaging laminate include the ability to withstand saturated steam treatment at high temperature and pressure, for example, from about 110 to about 150 ° C, for a period of time from about 30 minutes to about 3 hours.

The packaging laminate of the present invention contains one or more base layers of paper or paperboard, typically containing cellulosic fibers. Preferably, the base layer of paper or paperboard has a grammage of from about 30 to about 2250 g / m ² or from about 50 to about 1500 g / m ³ , most preferably from about 65 to about 500 g / m ² or from about 100 to about 300 g / m ² . The density is preferably from about 100 to about 1200 kg / m ³ , most preferably from about 150 to about 1000 kg / m ^3, or from about 200 to about 900 kg / m ³ .

Paper or paperboard can be made from various types of pulp, such as bleached or unbleached pulps based on natural and / or recycled fibers. Pulp can be based on cellulose fibers such as sulphate cellulose, sulphite cellulose and organosolvent cellulose, wood pulp such as thermomechanical cellulose (TMP), chemo-thermomechanical cellulose (CTMP), refined wood pulp and wood pulp from chopped wood like wood hardwood, and from coniferous wood, and can also be based on recycled fibers, optionally from enriched cellulose (DIP) and mixtures thereof. Paper or paperboard may contain one or more layers of the same or different types of pulp. Examples of multilayer combinations include bleached cellulose top / middle of DIP, CTMP or wood pulp / bleached cellulose back; top of bleached pulp / middle of DIP, CTMP or wood pulp / back of wood pulp; top of bleached pulp / middle of DIP, CTMP or wood pulp / back of unbleached pulp; and a bleached pulp top / unbleached pulp back, an upper side optionally coated, and a reverse side optionally coated. The upper side refers to the side intended to be located outside the finished package. In multilayer paper or paperboard, at least one layer contains thermoplastic microspheres. In paper or paperboard with three or more layers, preferably at least one of the middle layers contains thermoplastic microspheres.

In single-layer paper or paperboard, the grammage is preferably from about 50 to about 1500 g / m ² , most preferably from about 100 to about 700 g / m ^2, or from about 150 to about 500 g / m ² . The density is preferably from about 100 to about 1200 kg / m ³ , most preferably from about 150 to about 1000 kg / m ³ or from about 200 to about 800 kg / m ³ .

In a two-ply paper or paperboard, the grammage per layer is preferably from about 25 to about 750 g / m ² , most preferably from about 50 to about 400 g / m ^2, or from about 100 to about 300 g / m ² . The total grammage is preferably from about 50 to about 1500 g / m ² , most preferably from about 100 to about 800, or from about 200 to about 600 g / m ² . The total density is preferably from about 300 to about 1200 kg / m ³ , most preferably from about 400 to about 1000 kg / m ³ or from about 450 to about 900 kg / m ³ .

In paper or paperboard of three or more layers, the outer layers preferably have a grammage of from about 10 to about 750 g / m ² , most preferably from about 20 to about 400 g / m ^2, or from about 30 to about 200 g / m ² . The density of the outer layers is preferably from about 300 to about 1200 kg / m ³ , most preferably from about 400 to about 1000 kg / m ³ or from about 450 to about 900 kg / m ³ . The central or non-outer layer or layers preferably have a grammage of from about 10 to about 750 g / m ² , most preferably from about 25 to about 400 g / m ^2, or from about 50 to about 200 g / m ² . The density of the central or non-outer layer or layers is preferably from about 10 to about 800 kg / m ³ , most preferably from about 50 to about 700 kg / m ^3, or from about 100 to about 600 kg / m ³ . The total grammage is preferably from about 30 to about 2250 g / m ² , most preferably from about 65 to about 800 g / m ^2, or from about 110 to about 600 g / m ² . The total density is preferably from about 100 to about 1000 kg / m ³ , most preferably from about 200 to about 900 kg / m ^3, or from about 400 to about 800 kg / m ³ .

An embodiment of a sterilizable packaging laminate comprises a base layer of bilayer paper or cardboard made from bleached and unbleached, respectively, softwood kraft pulp. However, other combinations of single or multilayer paper or paperboard with various compositions can also be used.

An embodiment of a liquid packaging laminate comprises a base layer of three-layer paper or paperboard, in which, preferably, at least the middle layer comprises thermoplastic microspheres. Examples of layer combinations include those discussed above.

The paper or paperboard is preferably sized, most preferably sized in bulk by a hydrophobic sizing agent. In multilayer paper or cardboard - this means that at least one layer is glued. Such a layer may or may not contain thermoplastic microspheres. Preferred sizing agents include cellulose-reactive sizing agents such as ketene dimers or multimers like alkyl or alkenyl ketene dimers (AKD), succinic anhydrides like alkyl or alkenyl succinic anhydrides (ASA), and mixtures thereof. Other suitable sizing agents include sizing agents that do not chemically react with cellulose, such as rosin, starch, and other polymer sizing agents, such as styrene-vinyl monomer copolymers such as maleic anhydride, acrylic acid, and their alkyl esters. acrylamide and the like. The same or different sizing agents can be used for different layers in paper or paperboard. For example, AKD or ASA in one or more layers and rosin in one or more other layers can be used. The amount of sizing agent used is preferably from about 0.1 to about 10 kg / ton of paper, more preferably from about 0.3 to about 5 kg / ton of paper, and most preferably from about 0.5 to about 4, 5 kg / ton of paper or from about 2 to about 4 kg / ton of paper.

Preferred ketene dimers have the general formula (I)

where R ¹ and R ² are the same or different saturated or unsaturated hydrocarbon groups, such as alkyl, alkenyl, cycloalkyl, aryl or aralkyl. Hydrocarbon groups may have a branched or straight chain and, preferably, have from 6 to 36 carbon atoms, most preferably from 12 to 20 carbon atoms. Examples of hydrocarbon groups include branched and straight chain octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, beta-naphthyl, cyclohexyl and hexadecyl groups. Suitable ketene dimers include those obtained from organic acids such as montanic acid, naphthenic acid, 9,10-decilenic acid, 9,10-dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, linoleic acid, stearic acid, isostearic acid, eleostearic acid, naturally occurring fatty acid mixtures found in coconut oil, in babassu oil, in palm kernel oil, in palm oil, in olive oil, in peanuts m oil, rape oil, beef fat in in lard, whale blubber, and to mixtures of any of the fatty acids with one another mentioned above. Depending on the hydrocarbon groups, ketene dimers can be solid or liquid at room temperature (25 ° C).

In most cases, a sizing agent is included in the preparation also containing a natural polymer, such as starch or a synthetic polymer. A suitable sizing preparation is preferably in an aqueous dispersion with a preferred dry product content of from about 5 to about 40 wt.%, Most preferably from about 15 to about 30 wt.%. Preferably, from about 50 to about 99% wt., Most preferably, from about 75 to about 95% wt. the dry content of the product consists of a sizing agent, as described above.

It has been found that unexpectedly good results are achieved if a sizing agent, in particular a ketene dimer or multimer, alkyl succinic anhydride, rosin, or a mixture thereof, is included in a sizing preparation also containing an acrylamide-based polymer, in particular a charged, and most preferably a polymer on based on cationic acrylamide. However, polymers based on anionic, amphoteric and nonionic acrylamide can also be used. The amount of acrylamide-based polymer is preferably from about 1 to about 50% by weight, most preferably from about 5 to about 30% by weight. or from about 10 to about 20% wt. in relation to the dry content of the sizing agent.

The sizing agent may also contain other commonly used additives, such as compounds acting as dispersants, emulsifiers or stabilizers, examples of which include organic compounds like naphthalenesulfonate, lignosulfonate, quaternary ammonium compounds and its salts, cellulose and derivatives thereof, and inorganic compounds similar to polyaluminium compounds, such as polyaluminium chloride, polyaluminium sulfate or polyaluminium silicate sulfate. Other additives include various types of biocides and anti-foaming agents. Suitable additives in sizing preparations are also described, for example, in US Pat. Nos. 6,165,259, 5,969,011, 6,306,255 and 6,846,384. The amount of organic compounds acting as dispersants, emulsifiers or stabilizers can be, for example, from about 0.1 to about 10% wt. . from the content of dry foods. The amount of polyaluminium compounds may, for example, be from about 0.1 to about 10% wt. from the content of dry foods. The amount of biocide may be, for example, from about 0.01 to about 2% wt. from the dry matter content.

Preferred acrylamide-based polymers have a weight average molecular weight of at least about 10,000 or at least about 50,000. In most cases, the molecular weight is preferably at least about 100,000 or at least about 500,000. In most cases, it is preferred so that the molecular weight is about no more than 50 million, or about no more than 20 million, or about no more than 5 million.

Suitable acrylamide-based polymers can be prepared by polymerizing acrylamide or acrylamide-based monomers, preferably in combination with one or more ethylenically unsaturated cationic, potentially cationic, anionic or potentially anionic monomers. The term “potentially cationic monomer,” as used herein, refers to a monomer carrying a potentially ionizable group that becomes cationic when incorporated into a polymer when added to a cellulosic suspension. The term “potentially anionic monomer,” as used herein, refers to a monomer carrying a potentially ionizable group that becomes anionic when incorporated into a polymer when introduced into a cellulosic suspension.

Examples of acrylamide monomers and acrylamide-based monomers include methacrylamide, N-alkyl (meth) acrylamides, such as N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-n-propyl (meth) acrylamide, N isopropyl (meth) acrylamide, N-n-butyl (meth) acrylamide, N-tert-butyl (meth) acrylamide and N-isobutyl (meth) acrylamide; N-alkoxyalkyl (meth) acrylamides, such as N-n-butoxymethyl (meth) acrylamide and N-isobutoxymethyl (meth) acrylamide; N, N-dialkyl (meth) acrylamides, such as N, N-dimethyl (meth) acrylamide; and dialkylamino-alkyl (meth) acrylamides.

Suitable ethylene unsaturated cationic and potentially cationic monomers are preferably water soluble. Examples of such monomers include diallyldialkylammonium halides, for example diallyldimethylammonium chloride, and cationic monomers represented by the general structural formula (II):

where R ₁ represents H or CH ₃ ; R ₂ and R ₃ represent, independently from each other, H or, preferably, a hydrocarbon group, respectively, alkyl having from 1 to 3 carbon atoms, preferably 1-2 carbon atoms; A represents O or NH; B represents an alkyl or alkylene group having from 2 to 8 carbon atoms, respectively, from 2 to 4 carbon atoms, or a hydroxypropylene group; R ₄ represents H or, preferably, a hydrocarbon group, respectively, an alkyl having 1-4 carbon atoms, preferably 1-2 carbon atoms, or a substituent containing an aromatic group, respectively, a phenyl or substituted phenyl group, which can be attached to nitrogen through an alkylene group, usually having 1-3 carbon atoms, respectively, 1-2 carbon atoms, optionally R ₄ includes a benzyl group (—CH ₂ —C ₆ H ₅ ); and X ^- is an anionic counterion, usually a chloride-like halide.

Examples of suitable monomers represented by the general structural formula (II) include quaternary monomers which can be obtained by treating dialkylaminoalkyl (meth) acrylates, for example dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and dimethylamino-hydroxypropyl (meth) ) acrylate or dialkylaminoalkyl (meth) acrylamides, for example dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and diethylaminopropyl (meth) acrylamide, methyl chloride or benzyl chloride. Preferred cationic monomers of the general formula (II) include dimethylaminoethyl acrylate quaternary methyl chloride salt, dimethylaminoethyl methacrylate quaternary methyl chloride salt, dimethylaminoethyl acrylate quaternary benzyl chloride salt and dimethylaminoethyl quaternary benzyl chloride salt.

Examples of suitable co-polymerizable anionic and potentially anionic monomers include ethylenically unsaturated carboxylic acids and their salts, such as (meth) acrylic acid and its salts; ethylenically unsaturated sulfonic acids and their salts, such as 2-acrylamido-2-methylpropanesulfonate, sulfoethyl (meth) acrylate, vinyl sulfonic acid and its salts, styrene sulfonate and paravinylphenol (hydroxy styrene) and their salts. Any salts, such as sodium or other alkali metal salts, may be used.

Amphoteric acrylamide-based polymers can be prepared by polymerizing a mixture containing one or more acrylamide-based monomers, one or more ethylenically unsaturated anionic or potentially anionic monomers and one or more water-soluble ethylenically unsaturated cationic or potentially cationic monomers. Examples of suitable anionic and potentially anionic monomers include those discussed above.

The acrylamide-based monomer mixture may also contain one or more polyfunctional crosslinking agents in addition to the ethylene unsaturated monomers discussed above. The presence of a multifunctional cross-linking agent in the monomer mixture improves the dispersibility of the polymer in water. The multifunctional crosslinking agents may be nonionic, cationic, anionic or amphoteric. Examples of suitable polyfunctional crosslinking agents include compounds having at least two ethylenically unsaturated bonds, for example N, N-methylene bis (meth) acrylamide, polyethylene glycol di (meth) acrylate, N-vinyl (meth) acrylamide, divinylbenzene, triallylammonium salts and N-methylallyl (meth) acrylamide; compounds having an ethylenically unsaturated bond and a chemically active group, for example glycidyl (meth) acrylate, acrolein and methylol (meth) acrylamide; and compounds having at least two chemically active groups, for example dialdehydes like glyoxal, diepoxy compounds and epichlorohydrin. Suitable water-dispersible polymers can be prepared using at least 4 molar parts per million of a multifunctional crosslinker with respect to the monomers present in the monomer mixture or with respect to the monomer units present in the polymer, preferably from about 4 to about 6000 molar parts per million, most preferably from 20 to 4000. Examples of suitable water-dispersible polymers include acrylamide-based polymers, described in patent US 5167766.

The ratio between acrylamide or acrylamide-based monomers and charged or potentially charged monomers is selected to produce an acrylamide-based polymer with an appropriate charge density. For an acrylamide-based cationic polymer, the charge density is preferably from about 0.1 to about 11 meq / g or from about 0.5 to about 10 meq / g, most preferably from about 0.6 to about 8 meq / g or from about 1 to about 5 meq / g. In some cases, the charge density of the cationic acrylamide-based polymer is preferably from about 3 to about 8 meq / g. For an acrylamide-based anionic polymer, the charge density is preferably from about 0.5 to about 10 meq / g, most preferably from about 2 to about 8 meq / g.

The paper or paperboard may further comprise a moisture resistant agent that is added to the stock before dehydration. Suitable moisture resistant agents include resins of polyamine epihalohydrin, polyamide epihalohydrin, polyamino amide epihalohydrin, urea / formaldehyde, urea / melamine / formaldehyde, phenol / formaldehyde, polyacrylamide amine polyamide, polyaminyl amine amide, polyamide polyamide particularly preferred. The amount of moisture resistant agent is preferably from about 0.1 to about 10 kg / ton of paper, most preferably from about 0.5 to about 5 kg / ton of paper.

It is particularly preferred that at least one agent of a sizing agent, preferably a ketene dimer, and a moisture resistant agent, preferably a polyaminoamidepihalogenhydrin, is added to the pulp upon receipt of paper or paperboard.

Paper or paperboard may also contain other additives commonly used in paper making and added to the stock before dewatering. Such additives may include one or more fillers, such as mineral fillers, such as kaolin, porcelain clay, titanium dioxide, gypsum, talc, chalk, ground marble or precipitated calcium carbonate. Other commonly used additives may include retention aids, aluminum compounds, dyes, optical brightness agents, and the like. Examples of aluminum compounds include alum, aluminates and polyaluminium compounds, for example, polyaluminium chlorides and sulfates. Examples of retention aids include cationic polymers, anionic inorganic materials in combination with organic polymers such as acrylamide-based polymers, for example bentonite in combination with cationic organic polymers or silica-based sols in combination with cationic organic polymers or cationic and anionic organic polymers.

Examples of cationic organic polymers suitable for use in retention aids include, for example, those described in WO 2006/068576 and WO 2006/123989. In one embodiment, the cationic organic polymer contains one or more aromatic groups of the same or different types. Aromatic groups may be present in the polymer backbone (backbone) or in a substituent group that is attached to the polymer backbone. Examples of suitable aromatic groups include aryl, aralkyl and alkaryl groups such as phenyl, phenylene, naphthyl, xylylene, benzyl and phenylethyl groups; nitrogen-containing aromatic (aryl) groups, such as pyridinium and quinolinium, as well as derivatives of these groups, such as benzyl. Examples of cationic charged groups that may be present in the cationic polymer, as well as in the monomers used to prepare the cationic polymer, include quaternary ammonium groups, tertiary amino groups and their acid addition salts.

The packaging laminate comprises at least one, preferably at least two liquid barrier layers on each side of the base layer (s) of paper or paperboard. The liquid barrier layer can be obtained from any material that shows little or no water permeability. Suitable materials include polyethylene polymers like high density polyethylene or linear low density polyethylene, polypropylene, PVC (polyvinyl chloride), polyesters like polyethylene terephthalate, and their physical or mechanical mixtures. Can also be used copolymers, such as copolymers of ethylene and propylene. The barrier layer (s) for the liquid can be applied by any known means, such as various lamination methods or the like.

The packaging laminate may further comprise a gas barrier layer, preferably between the base layer and the liquid impermeable layer, intended to be located inside the package. Any material that exhibits little or no molecular oxygen permeability can be used. Examples of materials include a metal foil similar to aluminum foil, a silica coating, for example, applied as a coating composition containing colloidal silicon oxide and optional various additives, as described in WO 2006/065196, or obtained by plasma deposition . Other possible materials include polymers like polyvinyl alcohol, or copolymers of ethylene and vinyl alcohol. The gas barrier layer may be applied by any known means, such as various lamination methods or the like.

Typically, there are separate layers for creating barriers to liquid and gas, respectively, but in one embodiment, the liquid barrier layer and the gas barrier layer are provided with a single layer of material having barrier properties for both liquid and gas.

The thermoplastic microspheres in paper or paperboard are preferably expanded and added to the pulp during paper or paperboard production, either as pre-expanded microspheres or as unexpanded thermally expandable microspheres, which are preferably expanded by heating during the paper or paperboard process, for example during the drying step when heat is applied, or in a separate process step, for example in a cylindrical heater or laminator. The microspheres can expand when the paper or paperboard is still wet or when the paper or paperboard is completely or almost completely dried. The microspheres are preferably added in the form of an aqueous suspension thereof, which optionally may contain other additives desired for incorporation into the mass. The amount of thermoplastic microspheres introduced is preferably from about 1 to about 100 kg / t of paper, most preferably from about 1 to about 50 kg / t of paper, or from about 4 to about 40 kg / t of paper.

Thermally expanding thermoplastic microspheres, as mentioned here, preferably comprise a thermoplastic polymer shell encapsulating the propellant. The propellant is preferably a liquid having a boiling point not higher than the softening temperature of the thermoplastic polymer shell. When heated, the propellant increases internal pressure at the same time that the shell softens, which leads to a significant expansion of the microspheres. Both expandable and pre-expanded thermoplastic microspheres are commercially available under the trade name Expancel® (Akzo Nobel) and are commercially available in a variety of forms, for example, as dry bulk particles, as an aqueous suspension, or as partially dehydrated wet sludge. They are also well described in the literature, for example, in US patents 3615972, 3945956, 4287308, 5536756, 6235800, 6235394 and 6509384, in the publication of patent application US 2005/0079352, in EP 486080 and EP 1288272, in WO 2004/072160, WO 2007 / 091960 and WO 2007/091961 and Japanese Patent Laid-open Publications JP 1987-286534, 2005-213379 and 2005-272633.

A shell of a thermoplastic polymer of thermoplastic microspheres is preferably made from a homo- or copolymer obtained by polymerization of ethylenically unsaturated monomers. These monomers may, for example, be nitrile-containing monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile or crotonitrile; acrylic esters such as methyl acrylate or ethyl acrylate; methacrylic esters such as methyl methacrylate, isobornyl methacrylate or ethyl methacrylate; vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate, vinyl ethers such as vinyl vinyl ethers like methyl vinyl ether or ethyl vinyl ether, other vinyl monomers such as vinyl pyridine; vinylidene halides such as vinylidene chloride; styrenes such as styrene, halogenated styrenes or α-methylstyrene; or dienes such as butadiene, isoprene and chloroprene. Any mixtures of the above monomers may also be used.

The propellant of thermoplastic microspheres may contain hydrocarbons such as propane, butane, isobutane, n-pentane, isopentane, neopentane, hexane, isohexane, neohexane, heptane, isoheptane, octane or isooctane, or mixtures thereof. In addition to them, other types of hydrocarbons, such as petroleum ether, or chlorinated or fluorinated hydrocarbons, such as methyl chloride, methylene chloride, dichloroethane, dichloroethylene, trichloroethane, trichlorethylene, trichlorofluoromethane, perfluorinated hydrocarbons, and the like, can also be used.

Expandable thermoplastic microspheres suitable for the present invention preferably have a volume median diameter of from about 1 to about 500 microns, more preferably from about 5 to about 100 microns, most preferably from about 10 to about 50 microns. The temperature at which expansion begins, referred to as T _start , is preferably from about 60 to about 150 ° C, most preferably from about 70 to about 100 ° C. The temperature at which maximum expansion is achieved, referred to as T _max , is preferably from about 90 to about 180 ° C, most preferably from about 115 to about 150 ° C.

Pre-expanded thermoplastic microspheres suitable for the present invention preferably have an average volume median diameter of from about 10 to about 120 microns, most preferably from about 20 to about 80 microns. The density is preferably from about 5 to about 150 g / dm ³ , most preferably from about 10 to about 100 g / dm ³ . Even if pre-expanded thermoplastic microspheres are commercially available as such, it is also possible to obtain them by in-situ thermal expansion from unexpanded expandable thermoplastic microspheres, for example, just before they are added to the mass, which is easier if the expanding microspheres have T _start lower approximately 100 ° C, so that steam can be used as a heating medium.

The present invention will be described further in connection with the following Examples, which, however, should not be interpreted as limiting the scope of the claims of the present invention. Unless otherwise stated, all shares and percentages relate to shares and percent by weight.

In the Examples, one or more of the following products were used:

ST 1: Biological polymer based on cationic starch modified with 2,3-hydroxypropyltrimethylammonium chloride, D.S. 0.042, a polymer having a cationic charge density of about 0.28 meq / g.

ST 2: Biological polymer based on cationic starch modified with 2,3-hydroxypropyltrimethylammonium chloride, D.S. 0.02, a polymer having a cationic charge density of about 0.14 meq / g.

ST 3: Biological polymer based on cationic starch modified with 2,3-hydroxypropyltrimethylammonium chloride, D.S. 0.035, a polymer having a cationic charge density of about 0.23 meq / g.

WS 1: Moisture resistant agent PAAE (Eka WS XO)

WS 2: Moisture resistant agent PAAE (Eka WS 320)

SA 1: Sizing preparation with AKD and 10% wt. with respect to AKD, a cationic polymer obtained by polymerization of 90% mole of acrylamide and 10% mole of dimethylaminoethyl acrylate quaternary methyl chloride, and having a weight average molecular weight of about 1 million and a cationic charge density of about 1.2 meq / g.

SA 2: Starch stabilized AKD sizing agent (Eka DR 28 HF).

SA 3: AKD sizing agent stabilized with starch (Eka DR C223).

MS 1: Expancel ™ Expandable Microspheres (461WU20) with an average particle size of 6-9 microns.

MS 2: Pre-expanded Expancel ™ Microspheres (461WE20) with an average particle size of 20-30 microns.

MS 3: Expancel ™ Expandable Microspheres (820SL40) with an average particle size of 10-16 microns.

MS 4: Expansl ™ Expandable Microspheres (551DUX12), fraction with an average particle size of 4-6 microns.

PL 1: A polymer based on cationic acrylamide obtained by polymerization of 90% mole of acrylamide and 10% mole of dimethylaminoethyl acrylate quaternary methyl chloride and having a weight average molecular weight of about 6 million and a cationic charge of about 1.2 meq / g.

PL 2: A polymer based on cationic acrylamide obtained by polymerization of 90% mole of acrylamide and 10% mole of the quaternary benzyl chloride salt of dimethylaminoethyl acrylate, and having a weight average molecular weight of about 6 million and a cationic charge of about 1.2 meq / g.

NP 1: An anionic inorganic condensation polymer of silicic acid in the form of a colloidal silica sol modified with aluminum having a value of S <35 and containing particles based on silica with a specific surface area of about 700 m ² / g.

Example 1: A central layer of liquid packaging board with a grammage of approximately 120 g / m ^{2 was} obtained in a Dynamic Sheet Former sheet forming apparatus (Formette Dynamic, supplied by Fibertech AB, Sweden) from a mass of 100% unbleached chemo-thermomechanical cellulose (CTMP) fibers ) with a mass consistency of 0.5% and a neutral pH.

Sheets of paper were formed in the Dynamic Sheet Former by pumping the pulp from the mixing basin through a feed nozzle into a rotating drum onto a film of water over the mesh, pressing the pulp to form a sheet, pressing and drying the sheet.

Additions to the mass were made at the following time points (in seconds) before injection:

90 sec, cationic starch

75 sec. Moisture resistant agent PAAE

60 sec. AKD sizing agent

45 sec. Expancel ™ Microspheres

30 sec, cationic polymer

15 sec, Anionic sol based on silicon oxide

0 sec, Pumping

Sheets of cardboard were pressed and dried in a cylindrical dryer at 140 ° C, causing heat treatment of the microspheres in either a wet or dry surrounding paper web and the expansion of at least unexpanded microspheres. Two different drying methods were used.

Wet heat treatment: pre-drying, 2 min 105 ° C (still wet) + final drying, 140 ° C.

Dry heat treatment: drying, 10 min 105 ° C (dry) + final drying, 140 ° C.

Samples were obtained by laminating cardboard and PVC material and cutting pieces of 75x25 mm.

The penetration into the raw edge (REP) of the samples was investigated in two ways:

1. REP, Water: Water 80 ° C, 3 hours 2. REP, H ₂ O ₂ : Aqueous 35% hydrogen peroxide solution, 70 ° C, 10 min.

The wet heat treatment results are shown in Table 1, while the dry heat treatment results are shown in Table 2. The levels of addition are calculated as the dry product relative to the dry weight of the system, with the exception of silica-based particles for which additives are calculated as SiO ₂ in relation to the dry weight system.

Table 1
(Wet heat treatment) Test number ST1
(kg / t) WS1
(kg / t) SA1
(kg / t) Ms
(kg / t) / type System
retention
PL1 / NP1 REP, H ₂ O ₂ (kg / m ² ) 1 (Comp.) 5 - 0.5 - 0.3 / 0.3 15.22 2 (Comp.) 5 - four - 0.3 / 0.3 2.08 3 5 - 0.5 4 / MS 1 0.3 / 0.3 13.05 four 5 one 0.5 4 / MS 1 0.3 / 0.3 9.10 5 5 - four 4 / MS 1 0.3 / 0.3 1.35 6 5 - four 40 / MS 1 0.3 / 0.3 1.42 7 5 - four 4 / MS 2 0.3 / 0.3 1.16 8 5 - four 40 / MS 2 0.3 / 0.3 1,63

table 2
(Dry heat treatment) Test number ST1
(kg / t) WS1
(kg / t) SA1
(kg / t) Ms
(kg / t) / type Retention system
PL1 / NP1 REP, water
(kg / m ² ) 1 (Comp.) 5 - 0.5 - 0.3 / 0.3 10.18 2 (Comp.) 5 - four - 0.3 / 0.3 4.00 3 5 - 0.5 4 / MS 1 0.3 / 0.3 9.93 four 5 one 0.5 4 / MS 1 0.3 / 0.3 9.54 5 5 - four 4 / MS 1 0.3 / 0.3 3.82 6 5 - four 40 / MS 1 0.3 / 0.3 3.25 7 5 - four 4 / MS 2 0.3 / 0.3 3.32 8 5 - four 40 / MS 2 0.3 / 0.3 3,55

Example 2: The center layer of liquid packaging paperboard was obtained on XPM (experimental paper machine) using the same pulp as used in Example 1, at pH 8.0.

Additions to the mass were made in the following order:

Cationic Starch 1.50%

Moisture resistant agent PAAE

Expancel ™ Microspheres

Cationic starch 2, 50%

Sizing Agent AKD

Cationic polymer

Anionic silica sol

The paper mesh was dried at a maximum of 100 ° C in XPM (maximum drying temperature of 100 ° C). The microspheres were subjected to dry heat treatment at 140 ° C in a cylindrical dryer. Samples were obtained and investigated as in Example 1, except that the aqueous hydrogen peroxide solution was only 30%. The results are shown in Table 3 with addition levels calculated as in Example 1.

Table 3 Test number ST 1
(kg / t) SA1
(kg / t) Ms
(kg / t) / type Retention System PL1 / NP1 REP, Water
(kg / m ² ) REP, H ₂ O ₂ (kg / m ² ) 1 (Comp.) 3 + 3 - - 0,15 / 3 13,99 21.31 2 (Comp.) 3 + 3 0.5 - 0,15 / 3 13.06 20.82 3
(Comp.) 3 + 3 one - 0,15 / 3 6.22 14.62 four
(Comp.) 3 + 3 four - 0,15 / 3 4.08 7.01 5 3 + 3 0.5 4 / MS 1 0,15 / 3 11.96 19.95 6 3 + 3 0.5 20 / MS 1 0,15 / 3 11.47 20.17 7 3 + 3 0.5 40 / MS 1 0,15 / 3 11.71 20,44 8 3 + 3 four 4 / MS 1 0,15 / 3 3,54 4.90 9 3 + 3 four 20 / MS 1 0,15 / 3 3.44 5.23 10 3 + 3 four 40 / MS 1 0,15 / 3 3.76 5.36 eleven 3 + 3 0.5 4 / MS 2 0,15 / 3 11.06 19.96 12 3 + 3 0.5 20 / MS 2 0,15 / 3 11.22 18.47 13 3 + 3 0.5 40 / MS 2 0,15 / 3 11.55 20.31 fourteen 3 + 3 four 4 / MS 2 0,15 / 3 3.64 5.54 fifteen 3 + 3 four 20 / MS 2 0,15 / 3 3.64 6.99 16 3 + 3 four 40 / MS 2 0,15 / 3 2.66 7.38 17 3 + 3 0.5 4 / MS 3 0,15 / 3 12.59 20.12 eighteen 3 + 3 0.5 20 / MS 3 0,15 / 3 12.37 19.65 19 3 + 3 0.5 40 / MS 3 0,15 / 3 12.83 23.14 twenty 3 + 3 four 4 / MS 3 0,15 / 3 3.53 5.00 21 3 + 3 four 20 / MS 3 0,15 / 3 4.23 5.01 22 3 + 3 four 40 / MS 3 0,15 / 3 4.10 6.16

Example 3: A central layer of liquid packaging board was prepared and tested for REP for water, as in Example 2. The results are shown in Table 4.

Table 4 Test No. ST 1 SA WS 2 Ms PL NP 1 REP, (kg /
t) (kg / t) / type (kg /
t) (kg / t) / type (kg / t) / type (kg / t) water (kg / m ² ) 1 (Comp.) 3 + 3 - - - 0.15 / PL 1 3 10.80 2
(Comp.) 3 + 3 2 / SA 2 - - 0.15 / PL 1 3 4.06 3
(Comp.) 3 + 3 2 / SA 1 - - 0.15 / PL 1 3 3.80 four
(Comp.) 3 + 3 2 / SA 1 one - 0.15 / PL 1 3 3.66 5 3 + 3 2 / SA 1 - 40 / MS 1 0.15 / PL 1 3 3.56 6 3 + 3 2 / SA 1 one 20 / MS 1 0.15 / PL 1 3 3.42 7 3 + 3 2 / SA 2 - 40 / MS 2 0.15 / PL 1 3 3.65 8 3 + 3 2 / SA 1 - 40 / MS 2 0.15 / PL 1 3 3.12 9 3 + 3 2 / SA 1 one 20 / MS 2 0.15 / PL 1 3 3.53 10 3 + 3 2 / SA 2 - 40 / MS 3 0.15 / PL 1 3 3.69 eleven 3 + 3 2 / SA 1 - 40 / MS 3 0.15 / PL 2 3 3.26 12 3 + 3 2 / SA 1 one 20 / MS 3 0.15 / PL 1 3 3.49 13 3 + 3 2 / SA 1 one 40 / MS 3 0.15 / PL 1 3 2.90

Example 4: A sterilizable cardboard with a grammage of approximately 250 g / m ^{2 was} obtained in a PFI sheet forming machine, supplied by Hamjern Maskin A / S, Norway, from a pulp based on 100% bleached softwood kraft fibers having a weight consistency of 1.88% . Mass additions were made at the following time points (in seconds) before dehydration:

75 sec. AKD sizing agent

60 sec. Expancel ™ Microspheres

45 sec, cationic starch

30 sec, cationic polymer

15 sec, Anionic silica sol

0 sec, dehydration

Sheets of cardboard were pressed and dried in a cylindrical dryer at 140 ° C, causing heat treatment of the microspheres in the wet surrounding paper web and the expansion of at least unexpanded microspheres. The following methods were used.

Wet heat treatment: cylindrical drum, 1 hour 85 ° C (still wet) + final drying, 140 ° C.

Samples were obtained as in Example 1, and examined for penetration into the raw edge (REP) by steam treatment in an autoclave for 60 min at 130 ° C and 2 bar. The autoclave was a Certoclav TT 121, supplied by Certoclav Sterilizer GmbH, Austria. The results are shown in Table 5 with addition levels calculated as in Example 1.

Table 5 Test number ST 1
(kg / t) SA1 (kg / t) Ms
(kg / t) / type Retention System PL1 / NP1 REP, Couples
(kg / m ² ) 1 (Comp.) 7 - 0.5 / 0.45 1.15 2 (Comp.) 7 0.75 - 0.5 / 0.45 0.55 3 7 0.75 5 / MS 2 0.5 / 0.45 0.44 four 7 0.75 40 / MS 2 0.5 / 0.45 0.28 5 7 0.75 5 / MS 1 0.5 / 0.45 0.40 6 7 0.75 10 / MS3 0.5 / 0.45 0.43 7 7 0.75 40 / MS 3 0.5 / 0.45 0.40 8 7 0.75 10 / MS 4 0.5 / 0.45 0.40

Example 5: A sterilized cardboard was obtained as in Example 4, but with a mass based on 100% unbleached softwood kraft fibers and with a consistency of 1.75%. Mass additions were made at the following time points (in seconds) before dehydration:

75 sec. AKD sizing agent

65 sec. Moisture resistant agent PAAE

55 sec. Expancel ™ Microspheres

45 sec, cationic starch

30 sec, cationic polymer

15 sec, Anionic silica sol

0 sec, dehydration

Sheets of cardboard were pressed and dried in a cylindrical dryer at 160 ° C, causing heat treatment of the microspheres in a dry or wet surrounding paper web and the expansion of at least unexpanded microspheres. The following methods were used.

Dry heat treatment: cylindrical drum, 3 hours, 85 ° C (dry) + final drying, 160 ° C.

Wet heat treatment: cylindrical drum, 1 hour, 85 ° C (dry) + final drying, 160 ° C.

Samples were obtained and investigated as in Example 1, and penetration into the untreated edge, REP, was investigated in two different ways.

1. REP, pairs: Steam autoclave, 130 ° C, 60 min, 2 bar

2. REP, H ₂ O ₂ : Aqueous solution, 35% hydrogen peroxide, 70 ° C, 10 min.

Dry heat treatment results are shown in Table 6, while wet heat treatment results are shown in Table 7 with addition levels calculated as in Example 1.

Table 6
(Dry heat treatment) Test number ST 2
(kg /
t) SA 1
(kg /
t) WS 1
(kg /
t) Ms 1
(kg / t) Retention system
PL1 / NP1
(kg / t) REP,
pairs (kg / m ² ) REP,
H ₂ O ₂ (kg / m ² ) 1 (Comp.) 7 - - - 0.5 / 0.45 2.14 7.64 2 (Comp.) 7 0.375 - - 0.5 / 0.45 0.60 2.04 3 (Comp.) 7 - 2 0.5 / 0.45 0.45 8.37 4 (Comp.) 7 - - 5 0.5 / 0.45 2.75 7.32 5 7 0.375 - 5 0.5 / 0.45 0.41 2.17 6 7 - 2 5 0.5 / 0.45 0.40 6.43 7 7 0.375 2 5 0.5 / 0.45 0.44 2,34 8 (Comp.) 7 0.75 - - 0.5 / 0.45 0.77 0.92 9 (Comp.) 7 0.75 2 - 0.5 / 0.45 0.49 1.30 10 7 0.75 - 5 0.5 / 0.45 0.47 0.85

Table 7
(Wet heat treatment) Test number ST 2
(kg / t) SA 1
(kg / t) WS 1
(kg / t) Ms 1
(kg / t) Retention system
PL1 / NP1
(kg / t) REP, H ₂ O ₂ (kg / m ² ) 1 (Comp.) 7 - - - 0.5 / 0.45 10.19 2 (Comp.) 7 0.375 - - 0.5 / 0.45 3.08 3 (Comp.) 7 - 2 - 0.5 / 0.45 5.30 4 (Comp.) 7 - - 5 0.5 / 0.45 8.93 5 7 0.375 - 5 0.5 / 0.45 2.77 6 7 - 2 5 0.5 / 0.45 4.13 7 7 0.375 2 5 0.5 / 0.45 2.42 8 (Comp.) 7 0.75 - - 0.5 / 0.45 1.29 9 (Comp.) 7 0.75 2 - 0.5 / 0.45 2.06 10 7 0.75 - 5 0.5 / 0.45 1.21

Example 6: Sterilizable cardboard was obtained as in Example 4, but with a mass consistency of 2.1%. Mass additions were made at the following time points (in seconds) before dehydration.

75 sec. AKD sizing agent

60 sec. Expancel ™ Microspheres

45 sec, cationic starch

30 sec, cationic polymer

15 sec, Anionic silica sol

0 sec, dehydration

Sheets of cardboard were pressed and dried in a cylindrical dryer, causing heat treatment of the microspheres in the wet mesh of the surrounding paper and the expansion of at least unexpanded microspheres. The following methods were used.

1. Cylindrical drum, 2 hours, 70 ° C (still wet) + final drying, 140 ° C.

2. Cylindrical drum, 2 hours, 70 ° C (still wet) + final drying, 160 ° C.

Samples were obtained as in Example 4, and penetration into the untreated edge, REP, was examined in two different ways.

1. REP, pairs: steam autoclave, 130 ° C, 60 min, 2 bar

2. REP, water: water, 80 ° C, 3 hours

REP for vapors was investigated for samples dried at 140 ° C, and REP for water, for samples dried at 160 ° C.

The results are shown in Table 8 with addition levels calculated as in Example 1.

Table 8 Test number ST 1
(kg / t) SA1
(kg / t) Ms
(kg / t) / Type Retention System PL1 / NP1 REP, pairs (kg / m ² ) REP, water (kg / m ² ) 1 (Comp.) 7 - - 0.5 / 0.45 2.21 9.21 2 (Comp.) 7 0.75 - 0.5 / 0.45 0.53 2,30 3 7 0.75 5 / MS 2 0.5 / 0.45 0.45 1,61 four 7 0.75 10 / MS 2 0.5 / 0.45 0.45 1.27 5 7 0.75 20 / MS 2 0.5 / 0.45 0.44 1,57 6 7 0.75 40 / MS 2 0.5 / 0.45 0.27 1.05 7 7 0.75 10 / MS 3 0.5 / 0.45 0.44 1.82

Example 7: Sterilized cardboard was obtained, as in Example 6. Additives to the mass were made at the following times (in seconds) before dehydration:

75 sec. AKD sizing agent

60 sec. Expancel ™ Microspheres

45 sec, cationic starch

30 sec, cationic polymer

15 sec, Anionic silica sol

0 sec, dehydration

Sheets of cardboard were pressed and dried in a cylindrical dryer, causing heat treatment of the microspheres in the moist surrounding paper web and the expansion of at least unexpanded microspheres. Used the following method.

Wet heat treatment: cylindrical drum, 2 hours 70 ° C (still wet) + final drying, 140 ° C.

Samples were obtained and investigated as in Example 1. The results are shown in Table 9 with the levels of addition calculated as in Example 1.

Table 9 No. Test ST 1 (kg / t) SA1 (kg / t) MS (kg / t) / type Retention System PL1 / NP1 REP, H ₂ O ₂ (kg / m ² ) 1 (Comp.) 7 - 0.5 / 0.45 23.17 2 (Comp.) 7 0.75 - 0.5 / 0.45 0.88 3 7 0.75 5 / MS 2 0.5 / 0.45 0.70 four 7 0.75 5 / MS 1 0.5 / 0.45 0.67 5 7 0.75 10 / MS 3 0.5 / 0.45 0.68 6 7 0.75 10 / MS 4 0.5 / 0.45 0.77

Example 8: A two-layer, sterilizable cardboard with a grammage of approximately 290 g / m ² was obtained from Dynamic Sheet Former (Formette Dynamic, supplied by Fibertech AB, Sweden) using 50% by weight based on 100% unbleached softwood kraft fibers and the consistency of the mass of 0.5% for molding the lower layer and using 50% of the mass on the basis of 100% bleached softwood kraft fibers and the consistency of the mass of 0.5% for forming the upper layer. For both masses, the conductivity is 1.5 mSim / cm and the pH is approximately neutral.

Sheets of paper were formed on a Dynamic Sheet Former by pumping the pulp from the mixing basin through a feed nozzle into a rotating drum onto a film of water over the mesh, pressing the pulp to form a sheet, pressing and drying the sheet. Masses were added sequentially to form two layers in a sterilized paperboard.

The additions of each of the masses were done at the following times (in seconds) before pumping:

90 sec, cationic starch

75 sec, Moisture resistant agent PAAE,

60 sec. AKD sizing agent

45 sec. Expancel ™ Microspheres

30 sec, cationic starch

15 sec, Anionic silica sol

0 sec, Pumping

Sheets of cardboard were pressed and dried in an oven, causing heat treatment of the microspheres in the moist surrounding paper web and the expansion of at least unexpanded microspheres. Used the following method.

Dry heat treatment: drying, 20 min 105 ° C (dry) + final drying, 10 min 105 ° C.

Samples were obtained as in Example 1, and penetration into the untreated edge, REP, was investigated using:

REP, vapors + water: steam autoclave 130 ° C, 60 min, 2 bar + water, 6 ° C, 10 min.

Bending resistance was measured in accordance with SCAN P 29:95 using the L&W Bending Resistance Tester, Type 16D supplied by Lorentzon & Wettre, Sweden. The bending resistance coefficient was calculated by dividing the bending resistance by a cube of grammage. The results are shown in Table 10 with addition levels calculated as in Example 1.

Table 10 No. Test ST 2
(kg /
t) WS 1
(kg /
t) SA
(kg /
t)
/type of Ms
(kg /
t /
Type ST 3
(kg /
t) NP1
(kg /
t) REP,
pairs (kg / m ² ) The coefficient of resistance to bending (Nm ⁶ / kg ³ ) 1 (Comp.) 7 - - - 3 - 4,57 15.9 2
(Comp.) 7 - 4 / SA 3 - 3 0.45 1.28 15.1 3
(Comp.) 7 - 4 / SA 1 - 3 0.45 1,07 15.4 four
(Comp.) 7 four - - 3 0.45 4.43 16.7 5
(Comp.) 7 four 4 / SA 1 - 3 0.45 1,08 15,5 6 7 - 4 / SA 1 4 / MS 3 3 0.45 0.84 16,0 7 7 - 4 / SA 1 10 / MS 3 3 0.45 0.92 16,4

From this it follows that it is possible to obtain both low penetration into the raw edge and high bending resistance.

Claims (17)

1. A sterilizable packaging laminate comprising at least one core layer of sizing paper or paperboard, at least one liquid barrier layer and at least one gas barrier layer, said paper or paperboard containing expanded or unexpanded expandable thermoplastic microspheres. 2. The laminate according to claim 1, having the ability to withstand treatment with saturated steam at a temperature of from about 110 to about 150 ° C for a time from about 30 minutes to about 3 hours 3. Laminate according to any one of claims 1 and 2, in which the paper or cardboard is made of pulp from coniferous wood. 4. The laminate according to claim 3, containing the main layer of two-layer paper or cardboard, made of bleached and unbleached, respectively, softwood kraft pulp. 5. The laminate according to any one of claims 1 and 2, in which the paper or cardboard is glued with a composition containing a sizing agent selected from the group consisting of ketene dimers and multimers, succinic anhydrides and rosins, and also containing an acrylamide-based polymer. 6. The laminate according to claim 5, in which the acrylamide-based polymer is cationic. 7. Laminate according to any one of claims 1 and 2, in which paper or cardboard contains a moisture-resistant resin. 8. The laminate according to claim 7, in which the moisture-resistant resin is selected from the group consisting of polyamine epigalogenhydrins, polyamide epigalogenhydrin and polyaminoamide epigalogenhydrin. 9. The laminate according to any one of claims 1 and 2, in which the thermoplastic microspheres are expanded. 10. The laminate according to claim 9, in which thermoplastic microspheres are added as pre-expanded thermoplastic microspheres. 11. The laminate according to claim 9, in which the thermoplastic microspheres are added as unexpanded, thermally expanding microspheres that expand during the manufacture of paper or paperboard, while said paper or paperboard is still wet during expansion. 12. The laminate according to claim 9, in which thermoplastic microspheres are added as unexpanded, thermally expanding microspheres during the manufacture of paper or paperboard, wherein said paper or paperboard is completely or almost completely dried during expansion. 13. A method of manufacturing a sterilizable packaging laminate according to any one of claims 1-12, comprising the step of applying at least one barrier layer for liquid and at least one barrier layer for gas on a sheet or sheet of sterilized paper or paperboard containing expanded or unexpanded expanding thermoplastic microspheres. 14. The use of a sterilized packaging laminate according to any one of claims 1 to 12 for the manufacture of sealed packages for food or beverages. 15. Sealed packaging for food or drinks made from a sterilized packaging laminate according to any one of claims 1 to 12. 16. A method of manufacturing a sealed package, comprising the steps of forming a container from a sterilized packaging laminate according to any one of claims 1-12, filling the container with a food or drink and sealing the container. 17. The method according to clause 16, further comprising heat treatment of the filled and sealed packaging.