WO2011110527A1

WO2011110527A1 - Microwave-activated adhesive compositions for producing collapsible box blanks

Info

Publication number: WO2011110527A1
Application number: PCT/EP2011/053393
Authority: WO
Inventors: Dieter Urban; Karl-Heinz Schumacher; Stefan Kirsch; Uta Holzenkamp
Original assignee: Basf Se
Priority date: 2010-03-08
Filing date: 2011-03-07
Publication date: 2011-09-15

Abstract

The invention relates to the use of a microwave-activated adhesive composition for producing collapsible box blanks for the microwave-activated production of collapsible boxes. Said adhesive composition has, preferably at a temperature of less than or equal to 25°C, an Ig G'-value of more than or equal to 6 and at a temperature of more than or equal to 120°C, an Ig G'-value of less than or equal to 4 and contains at least one polymer having a glass transition temperature of more than 30°C, the collapsible box blanks to which the adhesive composition is applied are block-resistant at 25°C prior to microwave activation

Description

Microwave activatable adhesive compositions for the manufacture of folding carton blanks

description

The invention relates to the use of microwave-activatable adhesive compositions for the production of folding carton blanks for the microwave-activated production of folding cartons and to a method for the production of folding cartons using the folding carton blanks.

Faltschachtelzuschnitte are industrially prefabricated blanks that are supplied in a compact, flat state from the manufacturer to the processing companies to save space in boxes, filled and sealed. In many cases, the upright, each opposing parts are connected to each other by gluing and / or the boxes are sealed by filling after filling. Conventionally, carton blanks to be bonded are unsealed, i. supplied without adhesive to the processing company, e.g. in the form of box type E according to the classification system of the European Carton Makers Association. The sections are then provided with a hotmelt adhesive immediately prior to introduction into the erecting device and glued after erection. There is a risk here that the erecting machines will be adversely affected by glue deposits on the nozzles and tools and that undesired, visible glue marks on the finished packaging may occur even with precise adhesive positioning. What is desired, therefore, is a technology in which it is possible to dispense with an adhesive application in the processing company immediately before the folding carton erection.

In DE 3246325 a process for the production of folding cartons is described, wherein on blanks a dispersion lacquer is applied and an adhesion is effected by the action of ultrasound. In WO 2004/076578 a reactivatable adhesive is described, which is reactivated by the action of a radiation energy having a wavelength of 400 nm to 100,000 nm. The radiation energy is generated in particular by NIR radiation, for example a halogen tungsten lamp, and the adhesive contains an NIR-absorbing ingredient. The non-specific, non-directional use of relatively high-energy NIR radiation can lead to an undesirable, large-scale heating of non-adhering packaging parts or the ingredients to be packaged, what the possibilities of filling the packaging with heat- or radiation-sensitive ingredients before or immediately after Irradiation impaired and also consumes more energy than is required for the actual bonding. The object of the present invention was to provide as far as possible energy-efficient as well as time-efficient technology for folding carton production in which it is possible to dispense with an adhesive application in the processing company immediately before the folding carton installation. Ideally, the technology should additionally allow the gluing or gluing closing of cartons already filled with heat- or radiation-sensitive ingredients or to be filled immediately after the gluing.

The invention relates to the use of a microwave-activatable adhesive composition for producing folded-carton blanks for the microwave-activated production of folding cartons.

The invention also provides a process for the production of folding cartons, wherein

(1) flat carton blanks are provided,

(2) a microwave-activatable adhesive composition is applied to at least parts of the flat folding carton blanks,

(3) the flat carton blanks are erected into a carton and

(4) before, during or after the erection of the carton blanks the adhesive composition is activated by microwave radiation and thereby a gluing of the carton is effected.

Microwave radiation in the context of the invention is electromagnetic radiation of a wavelength of 1 mm to 1 m.

The term adhesive composition includes the adhesive agents and optional additives and solvents. Unless otherwise stated, physical parameters and properties refer to ratios at room temperature (25 ° C) and for the range of conventional relative humidity (30-90%).

The adhesive composition has a temperature-dependent tack profile. At room temperature (25 ° C) the composition is not or only slightly adhesive. At temperatures above room temperature, the composition is adhesive.

The adhesive composition preferably has an IgG 'value of greater than or equal to 6.0, preferably of 6.0 to 8.0, at less than or equal to 25 ° C. and an IgG' at temperatures of greater than or equal to 120 ° C. Value of less than or equal to 4.0, preferably from 2.5 to 3.9, measured by means of a deformation-controlled rheometer with parallel-plate geometry (diameter 8 mm, sample thickness 0.9-1, 2 mm) or Torsion-Rectangular geometry (sample width 6 mm, sample length 21 mm, sample thickness 0.9-1, 2 mm). The dynamic shear modulus G ^' is measured at a measurement frequency of 1 Hz with the torsion-rectangular geometry at 25 ° C and with the parallel-plate geometry at 120 ° C. From the adhesives, films are cast for the measurements, which are dried to constant weight. The IgG 'values of the invention can be adjusted by the monomer composition of the adhesive polymers or by addition of plasticizer. If the adhesive composition does not already have the Ig G 'values due to the monomer composition of the polymers, the Ig G' values can be adjusted according to the invention by adding the plasticizers described in more detail below

The carton blanks with adhesive composition applied thereto are preferably block-resistant at 25 ° C prior to microwave activation. Block-proof within the meaning of the application means that when lifting a single blank from a stack of several blanks no further blank adheres. In the stack, a pressure of up to 2 g / mm ² can occur.

The adhesive composition may be a fusible solid composition, a polymer solution, or a polymer dispersion (before application to the blanks and optionally drying). Preference is given to aqueous polymer solutions and aqueous polymer dispersions. Preferably, at least one polymer is present which has a glass transition temperature Tg of greater than 30 ° C., preferably greater than 35 ° C. or particularly preferably greater than 40 ° C. The glass transition temperature can be determined by conventional methods such as differential scanning calorimetry (see, for example, ASTM 3418/82, so-called "midpoint temperature"). In the case of aqueous polymer dispersions, the dispersion preferably contains solids contents of 15 to 75% by weight. In one embodiment, the adhesive composition contains at least 40 weight percent, preferably from 40 to 75 weight percent dispersed polymer.

For the purposes of the invention, polymers are understood as meaning both homopolymers of a single monomer and copolymers of two or more different monomers. In the following, the term (meth) acrylate and similar terms are used as a shorthand notation for "acrylate or methacrylate".

Polymers preferably used in the adhesive composition are polyurethanes or polymers obtainable by radical polymerization of ethylenically unsaturated compounds (monomers). The polymer is preferably at least 40% by weight or at least 60% by weight, or at least 80% by weight, particularly preferably at least 90% by weight, of so-called main monomers. The main monomers are preferably selected from C ₁ -C 20 -alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics with bis to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols having 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers. Also preferred are vinyl acetate polymers and (meth) acrylate polymers. The vinyl acetate polymers are formed from at least one vinyl acetate monomer, which may be copolymerized with other monomers, for example ethylene / vinyl acetate copolymer. The (meth) acrylate polymers are formed from at least one (meth) acrylate monomer, which may be copolymerized with other monomers.

Examples of suitable monomers are (meth) acrylic acid alkyl esters with a C ₁ -C 10 -alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate. In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable. Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for example, vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate. Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile. The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride. Vinyl ethers include, for example, vinyl methyl ether or vinyl isobutyl ether. Preferred are vinyl ethers of alcohols containing 1 to 4 carbon atoms. Suitable hydrocarbons having 4 to 8 carbon atoms and two olefinic double bonds are, for example, butadiene, isoprene and chloroprene. Hydrocarbons having 2 to 4 carbon atoms are, for example, ethylene, propylene or butene.

Preferred main monomers are C ₁ -C 10 -alkyl acrylates and C ₁ -C 10 -alkyl methacrylates, in particular C 1 -C ₈ -alkyl acrylates and methacrylates and vinylaromatics, in particular styrene and mixtures thereof. Very particular preference is given to methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, styrene and mixtures of these monomers.

In addition to the major monomers, the polymer may contain other monomers, e.g. Monomers having carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called e.g. Acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. The content of acid monomers in the polymer in the case of aqueous dispersions z. B. 0 to 15 wt.%, In particular 0.05 to 5 wt.%, Based on the polymer. In the case of aqueous solutions, the content of acid monomers may be up to 40% by weight, e.g. from 25 to

40% by weight, based on the polymer. The acid groups may be in the form of their salts. Other monomers include, for example, hydroxyl-containing monomers, in particular Ci-Ci ₀ -Hydroxyalkyl (meth) acrylates or (meth) acrylamide. Phenyloxyethylglycol mono (meth) acrylate, in addition, may be mentioned as further monomers. Glycidyl (meth) acrylate, aminoalkyl (meth) acrylates such as called 2-aminoethyl (meth) acrylate. Alkyl groups preferably have from 1 to 20 carbon atoms. Other monomers which may also be mentioned are crosslinking monomers. The other monomers are generally used in minor amounts, their proportion is generally less than 10 wt.%, In particular less than 5 wt.%.

Preferred copolymers consist of at least 10% by weight or at least

20% by weight, or at least 40% by weight, more preferably at least

60% by weight of at least one first monomer and more than 3% by weight and up to 40% by weight of at least one second monomer. The first monomer is selected from alkyl (meth) acrylates and vinyl aromatics. The alkyl (meth) acrylate monomers are preferably selected from C ₁ -C 20 -alkyl (meth) acrylates, in particular C 1 -C 10 -alkyl acrylates and C 1 -C 10 -alkyl methacrylates, or C 1 -C ₈ -alkyl (meth) acrylates late. Suitable monomers are, for example, methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate. In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable. The vinylaromatics are preferably selected from vinylaromatics having up to 20 C atoms. Suitable vinylaromatics are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. In one embodiment, the copolymers according to the invention contain styrene in amounts of from 10 to 60% by weight, preferably 20-50% by weight.

The second monomer is selected from ethylenically unsaturated monomers having acid groups, hydroxyalkyl acrylates and hydroxyalkyl methacrylates. Monomers having acid groups are, in particular, ethylenically unsaturated compounds which have at least one carboxylic acid, sulfonic acid or phosphonic acid group. Preferred are carboxylic acid groups. Examples which may be mentioned are acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. The acid groups may be in the form of their salts. Preferred hydroxyalkyl (meth) acrylates are the C ₂ to C ₁₂ hydroxyalkyl (meth) acrylates and in particular the C ₂ to C ₆ or the C ₂ to C ₄ hydroxyalkyl (meth) acrylates. Very particular preference is given to hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate or hydroxybutyl methacrylate. The content of acid or hydroxy monomers in the copolymer can be, for example, 4 to 15% by weight in the case of aqueous dispersions, or in the case of aqueous solutions of up to 40% by weight, for example 24 to 40% by weight, based on the polymer be.

In particular, the polymer is at least 60% by weight, particularly preferably at least 80% by weight and very particularly preferably at least 90 or at least 95% by weight of C 1 to C ₂₀ alkyl (meth) acrylates or of C 1 to C 4 ₂₀ alkyl (meth) - acrylates in combination with styrene constructed. The ratio of the monomers to each other is preferably adjusted so that the glass transition temperature of the polymer is greater than 30 ° C, or greater than 35 ° C or greater than 40 ° C. The preparation of the radically polymerized polymers can be carried out by emulsion polymerization known per se. In the emulsion polymerization, ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are used as surface-active substances and also suitable initiators and optionally molecular weight regulators. The emulsion polymerization is generally carried out at 30 to 130 ° C, preferably at 50 to 90 ° C. The polymerization medium may consist of water only, as well as of mixtures of water and thus miscible liquids such as methanol. Preferably, only water is used. In the polymerization, for example, a polymer seed can be submitted for better adjustment of the particle size. In the emulsion polymerization, aqueous dispersions of the polymer are generally obtained with solids contents of 15 to 75 wt .-%, preferably from 40 to 75 wt .-%. Dispersions with the highest possible solids content are preferred. In one embodiment, the dispersion or adhesive composition contains at least 60% by weight of dispersed polymer. In order to achieve solids contents> 60 wt .-%, one should set a bimodal or polymodal particle size, otherwise the viscosity is too high and the dispersion is no longer manageable. The generation of a new generation of particles can be carried out, for example, by adding seed, by adding excess emulsifier amounts or by adding miniemulsions. The generation of one or more new particle generations can take place at any time. It depends on the particle size distribution desired for a low viscosity. The polymer thus prepared is used in the form of its aqueous dispersion. The size distribution of the dispersion particles may be monomodal, bimodal or multimodal. In the case of a monomodal particle size distribution, the average particle size of the polymer particles dispersed in the aqueous dispersion is preferably less than 400 nm, in particular less than 200 nm. More preferably, the average particle size is between 140 and

200 nm. By average particle size is meant here the d ₅₀ value of the particle size distribution, ie 50% by weight of the total mass of all particles have a smaller particle diameter than the d ₅₀ value. The particle size distribution can be determined in a known manner with the analytical ultracentrifuge (W. Mächtie, Makromolekulare Chemie 185 (1984), page 1025-1039). For bi- or multimodal particle size distribution, the particle size can be up to 1000 nm. The pH of the polymer dispersion is preferably adjusted to pH greater than 4.5, in particular to a pH of between 5 and 8. Further preferred polymers of the adhesive composition are polyurethanes, ethylene / vinyl acetate copolymers, polyamide resins, saturated polyesters, polyolefins, styrenes. rol / butadiene block copolymers, styrene / isoprene block copolymers, polyimides, PVC and polyvinylpyrrolidone.

Polyurethanes are preferably used in the form of aqueous polyurethane dispersions (PUD). Suitable polyurethanes are in principle obtainable by reacting at least one polyisocyanate with at least one compound which has at least two isocyanate-reactive groups. The polyurethane dispersion (PUD) according to the invention preferably comprises at least one polyurethane which contains at least one polyisocyanate and at least one polymeric polyol in copolymerized form. Suitable polymeric polyols are preferably selected from polyester diols, polyether diols, polycarbonate diols, and mixtures thereof. The polymeric polyol preferably has a number average molecular weight in the range of about 500 to 5000 g / mol. Preference is given to polymeric diols. The polyurethane dispersion (PUD) according to the invention preferably comprises at least one polyurethane which comprises in copolymerized form at least one polyisocyanate and one diol component, of which a) 10 to 100 mol%, based on the total amount of diols, has a molecular weight of 500 to 5000 g / mol and b) 0 - 90 mol% based on the total amount of the diols, have a molecular weight of 60 to 500 g / mol. Preferably, the polyurethane is at least 40 wt .-%, more preferably at least 60 wt .-% and most preferably at least 80 wt .-%, based on the total weight of the monomers used to prepare the polyurethane, from at least one diisocyanate and built up at least one polyether diol and / or polyester diol. Preferably, at least 95 mol% of the diols are polyesterdiols and / or polytetrahydrofuran. Particularly preferred diols used exclusively polyester diols and / or polytetrahydrofuran. Suitable further synthesis components ad 100% by weight are, for example, polyisocyanates having at least three NCO groups and compounds other than the polymeric polyols having at least two isocyanate-reactive groups. These include, for example, diols; diamines; polymers which are different from polymeric polyols and have at least two active hydrogen atoms per molecule; Compounds having two active hydrogen atoms and at least one ionic or ionic group per molecule; and mixtures thereof. Diisocyanates are, for example, those of the formula X (NCO) ₂ , where X is an aliphatic hydrocarbon radical having 4 to 15 C atoms, a cycloaliphatic or aromatic hydrocarbon radical having 6 to 15 C atoms or an araliphatic hydrocarbon radical having 7 to 15 C atoms , Examples of such diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,2-bis (4-isocyanatocyclohexyl) propane , Trimethylhexane diisocyanate, 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanate anato-diphenylmethane, 2,4'-diisocyanato-diphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), the isomers of bis (4-isocyanatocyclohexyl) methane (HMDI) such as the trans / trans, the cis / cis and the cis / trans isomers and mixtures consisting of these compounds.

As polyester diols are preferably used those obtained by reacting dihydric alcohols with dibasic carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof can be used to prepare the polyesterpolyols. The polycarboxylic acids may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and optionally, for. B. by halogen atoms, substituted and / or unsaturated. Examples which may be mentioned are: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene-tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dime fatty acids. Preferred are dicarboxylic acids of the general formula HOOC- (CH ₂ ) _y - COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, z. Succinic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid. As polyhydric alcohols come z. As ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane-1, 3-diol, butene-1, 4-diol, butyne-1, 4-diol, pentane-1, 5 diol, neopentyl glycol, bis (hydroxymethyl) cyclohexanes such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, furthermore diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, Dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycols into consideration. Alcohols of the general formula HO- (CH ₂ ) _x -OH, where x is a number from 1 to 20, preferably an even number from 2 to 20, are preferred. Examples of these are ethylene glycol, butane-1, 4-diol, hexane-1, 6-diol, octane-1, 8-diol and dodecane-1, 12-diol. Further preferred is neopentyl glycol. Suitable polyester diols are also those based on lactone. Preferred lactones are those which are derived from compounds of the general formula HO- (CH ₂ ) _z -COOH, where z is a number from 1 to 20 and an H atom of a methylene unit is also denoted by a C 1 to C ₄ Alkyl may be substituted. Examples are ε-caprolactone, β-propiolactone, γ-butyrolactone and / or methyl-γ-caprolactone and mixtures thereof. Suitable polyether diols are in particular by polymerization of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with itself, z. B. in the presence of BF ₃ or by addition of these compounds, optionally in admixture or in succession, to starting components with reactive hydrogen atoms, such as alcohols or amines, for. For example, water, ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, 2,2-bis (4-hydroxyphenyl) propane or aniline available. Particular preference is given to polyetherdiols having a molecular weight of from 500 to 5000, and especially from 600 to 4500. A particularly preferred polyetherdiol is polytetrahydrofuran. ran. Suitable compounds are also α, ω-diaminopolyethers which can be prepared by amination of polyalkylene oxides with ammonia.

In addition to the polymeric polyols as diols and low molecular weight diols having a molecular weight of about 60 to 500, preferably from 62 to 200 g / mol, be used, for example, short-chain alkane diols, wherein the unbranched diols having 2 to 12 carbon atoms and an even Number of carbon atoms and pentane-1, 5-diol and neopentyl glycol are preferred. As diols come z. As ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane-1, 3-diol, butene-1, 4-diol, butyne-1, 4-diol, pentane-1, 5- diol, neopentyl glycol, bis (hydroxymethyl) cyclohexanes such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, furthermore diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, Dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycols into consideration. Alcohols of the general formula HO- (CH ₂ ) _x -OH, where x is a number from 1 to 20, preferably an even number from 2 to 20, are preferred. Examples of these are ethylene glycol, butane-1, 4-diol, hexane-1, 6-diol, octane-1, 8-diol and dodecane-1, 12-diol. Further preferred is neopentyl glycol.

In order to improve the water-dispersibility of the polyurethanes, the polyurethanes preferably contain additional monomers which carry at least one isocyanate group or at least one isocyanate-reactive group and moreover at least one hydrophilic group or a group which can be converted into a hydrophilic group, as a synthesis component , In the following text, the term "hydrophilic groups or potentially hydrophilic groups" is abbreviated to "(potentially) hydrophilic groups". The (potentially) hydrophilic groups may be nonionic or, preferably, (potentially) ionic hydrophilic groups.

Suitable nonionic hydrophilic groups are, in particular, polyethylene glycol ethers of preferably 5 to 100, preferably 10 to 80, ethylene oxide repeat units. The content of polyethylene oxide units is generally 0 to 10, preferably 0 to 6 wt.%, Based on the weight amount of all monomers. Preferred monomers having nonionic hydrophilic groups are polyethylene oxide diols containing at least 20% by weight of ethylene oxide, polyethylene oxide monools and the reaction products of a polyethylene glycol and a diisocyanate which carry a terminally etherified polyethylene glycol radical.

Ionic hydrophilic groups are especially anionic groups such as the sulfonate, the carboxylate and the phosphate group in the form of their alkali metal or ammonium salts and cationic groups such as ammonium groups, in particular protonated tertiary amino groups or quaternary ammonium groups. Potentially ionic hydrophilic groups are especially those which can be converted by simple neutralization, hydrolysis or quaternization into the above-mentioned ionic hydrophilic groups, ie, for. As carboxylic acid groups or tertiary amino groups. examples Examples of (cationic) monomers are monomers having tertiary amino groups: tris- (hydroxyalkyl) -amines, N, N'-bis (hydroxyalkyl) -alkylamines, N-hydroxyalkyl-dialkylamines, tris (aminoalkyl) - amines, N, N'-bis (aminoalkyl) alkylamines, N-aminoalkyl-dialkylamines, wherein the alkyl radicals of these tertiary amines independently of one another consist of 1 to 6 carbon atoms, and tertiary nitrogen atoms containing polyethers having preferably two terminal hydroxyl groups. Suitable monomers with (potentially) anionic groups are usually aliphatic, cycloaliphatic, aliphatic or aromatic carboxylic acids and sulfonic acids which carry at least one alcoholic hydroxyl group or at least one primary or secondary amino group. Preference is given to dihydroxyalkylcarboxylic acids, especially those having 3 to 10 carbon atoms, for example dimethylolpropionic acid (DMPA). Also suitable are corresponding dihydroxysulfonic acids and dihydroxyphosphonic acids, such as 2,3-dihydroxypropanephosphonic acid. Also suitable are diaminocarboxylic acids and diaminosulfonic acids, for example N- (2-aminoethyl) -2-aminoethanecarboxylic acid, and N- (2-aminoethyl) -2-aminoethanesulfonic acid or the corresponding alkali metal salts, with Na being particularly preferred as the counterion.

Preferred polyurethanes are synthesized from aromatic or aliphatic diisocyanates, from polyether or preferably polyester diols, and from diamines or diols carrying sulfonate or carboxylate groups.

Preferred polymers of the adhesive composition are acrylate or methacrylate polymers which are formed from monomers having acid groups, apart from acrylic acid ester or methacrylic acid ester monomers. The monomers having acid groups are preferably more than 3% by weight and less than 35% by weight, based on the total amount of monomers. Monomers having acid groups are e.g. Monomers having carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called e.g. Acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. The acid groups may be present in the form of their salts. In a particularly preferred embodiment, the acrylate copolymers according to the invention contain styrene in amounts of from 10 to 60% by weight, preferably from 20 to 50% by weight.

The adhesive composition preferably contains at least one microwave radiation absorbing material. This substance is preferably non-adhesive or tacky by itself and is preferably contained in an amount of from 2 to 30, especially from 5 to 15,% by weight, based on the total composition.

Microwave radiation absorbing in the context of the invention is a substance when it absorbs radiation when irradiated with microwave energy, thereby heating and emits the absorbed energy as heat to the environment. The microwave radiation Sorbent material is for example selected from the group consisting of carbon black, graphite or organic color pigments and mixtures thereof.

The adhesive composition preferably contains at least one plasticizer. The plasticizers are preferably contained in an amount of from 5 to 50, in particular from 5 to 35,% by weight, based on the total composition. Examples of plasticizers are phthalic acid esters, trimellitic acid esters, acyclic dicarboxylic acid esters, polymeric plasticizers, phosphoric acid esters, fatty acid esters, hydroxycarboxylic acid esters, epoxy plasticizers, polyamide plasticizers and polyalkylene glycols. Phthalic acid esters and trimellitic acid esters are, for example, the esters of phthalic acid, isophthalic acid or mellitic acid with C 1 -C 10 -alkanols, for example di-n-octyl phthalate, di-n-nonyl phthalate, di-n-decyl phthalate, diisodecyl phthalate, di-n-octyl isophthalate, Di-n-nonyl isophthalate, diisononyl phthalate, di-n-decyl isophthalate, di- (2-ethylhexyl) phthalate, di-n-butyl phthalate, diisobutyl phthalate, dicyclohexyl phthalate, dimethyl phthalate, diethyl phthalate, tris (2-ethylhexyl) tri- laurate. mellitate. Acyclic dicarboxylic acid esters are, for example, the diesters of dicarboxylic acids with alkanols, in particular the diesters of C ₄ to C 10 dicarboxylic acids with C _{1 to} C ₁ alkanols, for example the diesters of adipic acid, decanedioic acid, glutaric acid, succinic acid, for example dimethyl adipate, diethyl adipate, adipic acid di -n-butyl ester, adipic acid diisobutyl ester, glutaric acid dimethyl ester, glutaric acid diethyl ester, glutaric acid di-n-butyl ester, glutaric acid diisobutyl ester, succinic acid diester, succinic acid diethyl ester, succinic di-n-butyl ester, succinic acid succinate and mixtures of the above-mentioned compounds. Polymeric plasticizers are, for example, the polyesters of dicarboxylic acids and alkanediols, in particular C ₄ to C _{1 0} dicarboxylic acids and C ₂ to C ₁ ₀ diols with molecular weights M r of from 1800 to 13 000, for example polyesters of adipic acid, decanedioic acid, azelaic acid or phthalic acid with diols, such as butane-1 , 3-diol, propane-1, 2-diol, butane-1, 4-diol, hexane-1, 6-diol and others. Phosphorus esters are, for example, phosphoric acid compounds which are at least monosubstituted by alkanol, for example C ₁ -C 10 -alkyl-di-C ₆ -C ₄ -aryl phosphates. Examples are isodecyldiphenyl phosphate, tricresyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, diphenylacetyl phosphate, tris (2-ethylhexyl) phosphate, tris (2-butoxyethyl phosphate, hydroxycarboxylic acid esters are, for example, citric acid esters such as tributyl O-acetyl citrate and corresponding tartaric and lactic acid esters, polyamide plasticizers are, for example, benzenesulfonamides and methylbenzenesulfonamides.

Particularly preferred plasticizers are polyalkylene glycols, especially polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, in particular the block copolymers, and polypropylene glycols etherified with two different alcohols. Suitable polyalkylene glycols are especially those with egg nem molecular weight of 100 to 2000. Suitable plasticizers are polyethylene glycols, which are commercially available under the brand name Puriol ^® E. Preferably, at least one polyethylene glycol is included, especially with one Molecular weight of 100 to 2000. The polyethylene glycols are preferably contained in an amount of 5 to 35, especially 10 to 30 wt.%, Based on the total composition. The adhesive composition may contain a tackifier (tackifying resins). Tackifiers are for example from Adhesive Age, July 1987, page 19-23 or Polym. Mater. Be. Closely. 61 (1989), pages 588-592. Tackifiers are, for example, natural resins, such as rosin resins and their derivatives formed by disproportionation or isomerization, polymerization, dimerization, hydrogenation. These may be in their salt form (with, for example, monovalent or polyvalent counterions (cations) or preferably in their esterified form.) Alcohols used for esterification may be monovalent or polyvalent, for example, methanol, ethanediol, diethylene glycol, triethylene glycol, 1 Furthermore, hydrocarbon resins, for example cumarone-indene resins, polyterpene resins, hydrocarbon resins based on unsaturated C-H compounds, such as butadiene, pentene, methylbutene, isoprene, piperylene, divinylmethane, pentadiene, are also found Cyclopentadiene, cyclopentadiene, cyclohexadiene, styrene, α-methylstyrene, vinyltoluene are also used as tackifiers, and polyacrylates which have a low molecular weight are preferably used, these polyacrylates preferably having a weight-average molecular weight M _{w of} less than 30 000. The polyacrylates are preferably added at least 60, in particular at least

80% by weight of C 1 -C ₈ -alkyl (meth) acrylates. Preferred tackifiers are natural or chemically modified rosin resins. Rosin resins consist predominantly of abietic acid or abietic acid derivatives. The tackifiers can be added in a simple manner to the polymer dispersion. The tackifiers are preferably themselves in the form of an aqueous dispersion. The amount by weight of the tackifiers is preferably from 5 to 50 parts by weight, more preferably from 10 to 30 parts by weight. based on 100 parts by weight of polymer (solid / solid).

The adhesive composition may consist solely of the polymer or of the aqueous dispersion of the polymer, but may also contain the abovementioned additives and further additives, for example fillers, dyes, leveling agents, thickeners, preferably associative thickeners, defoamers, pigments or wetting agents. For a better wetting of surfaces, the adhesive compositions may in particular wetting aids, for. For example, fatty alcohol ethoxylates, Alkylphenolethoxylate, Nonylphenolethoxylate, polyoxyethylene / -propylenes or sodium dodecylsulfonate included. The amount of additives is generally from 0.01 to 5 parts by weight, in particular 0.1 to 3 parts by weight per 100 parts by weight of polymer (solid). The carton blanks may be of a suitable material for producing cartons. Suitable materials are eg cardboard, cardboard, corrugated cardboard or plastic. The surface can be covered with paper, laminated with foil, with Plastic coated, printed with paint, primed or painted. The surface of the blanks can be coated eg with PP, OPP, PVC, PE or with waxes. The thickness of the blank material is preferably from 0.5 to 10 mm. The adhesive composition can be applied to the folding box blanks by conventional application or coating methods, for example by means of a size press, film press, blade coater, air brush, doctor blade, curtain coating or spray coater. In a preferred embodiment, the application is effected by means of a printing application technique, eg flexographic printing, offset printing or screen printing. Preferred is flexographic printing. After the printed adhesive coating has dried, it is so block-resistant that the printed flat folding-box blanks can be stacked without sticking to one another. In particular, the printed adhesive is blockable so that a stack of the printed with the adhesive sheet blanks, which are usually cartons, can be stored under a weight of 2 tm ^{2 for} up to one year without adhering to each other when separating the individual boxes.

In one embodiment, the adhesive composition is applied to the intended for the blanks, not yet cut raw material and then carried out the production of the blanks, for example by punching or cutting.

The blanks may be wholly or partially coated with the adhesive composition. Preferably, the adhesive composition is applied only in those limited areas that are actually bonded. The applied amount (wet) is preferably from 10 to 300 g / m ² . The layer thickness of the applied, dried adhesive is preferably from 5 to 200 μηη.

For the manufacture of folding cartons from the carton blanks provided with the adhesive composition known Aufrichtemaschinen can be used, which are preferably modified so that they have at least one built-microwave generator or that they allow the irradiation of the blanks with an external microwave generator. The irradiation with microwave radiation can be done before the surfaces to be bonded are brought into contact with each other, or preferably while the surfaces are brought into contact. In general, this is done with a suitable for a permanent fixed connection high contact pressure. The time of radiation activation of the adhesive layer in the straightening machine is preferably less than 2 seconds, less than 1 second or less than 0.5 seconds. The adhesive layer becomes so sticky within the activation time that secure bonding of the folding carton takes place in the erecting machine, optionally with subsequent or simultaneous application of a contact pressure. The bonding is considered sufficiently safe when in the In the case of bonded cartons, the bond can be released only with complete fiber breakage.

When bonded in the straightening machine, the adhesive layer applied to a first portion of the surface of the blank may be adhered either to an adhesive layer applied to a second portion of the surface of the blank or to an adhesive-free portion of the blank. The adhesive-free area can also be printed, primed or painted on the spot to be bonded.

The activation of the adhesive layer is preferably carried out with electromagnetic radiation (microwave radiation) having a wavelength in the range 1 mm to 1 m, preferably from 5 mm to 0.5 m. A preferred radiation source is a microwave concentrator with which microwaves can be focused, locally concentrated for local treatment of a workpiece and / or made usable for exciting plasma. An arrangement for concentrating microwave energy in a local area of action is described, for example, in DE 10 2006 034084. A further device for producing microwaves for the treatment of workpieces is described in US Pat

WO 00/75955. A portable microwave oven for local applications is described in JP 08-019620.

In one embodiment of the invention, the packages are filled with the ingredients to be packaged before, immediately after or simultaneously with the bonding activated by microwaves. It is particularly advantageous if the ingredients to be packaged are sensitive to heat or radiation and a microwave concentrator is used as the radiation source. The adhesive activation can then be carried out in a very short time and locally limited, without affecting heat- or radiation-sensitive ingredients of the packaging. Sensitive ingredients are e.g. Chocolate, ice cream, fat or waxy products, pharmaceuticals, cosmetics or similar products.

In one embodiment of the invention, the adhesive composition a) contains from 20 to 70% by weight, preferably from 30 to 50% by weight, of at least one micelle-cell-activatable polymer,

b) from 2 to 30 wt.%, Preferably from 5 to 15 wt.% Of at least one microwave radiation absorbing material and

c) from 5 to 40% by weight, preferably from 10 to 35% by weight, of at least one

Plasticizer. The use of microwave radiation for adhesive activation has the advantage over the use of other activation sources such as IR lamps that the contents are protected in the carton. When activated by microwave radiation, the cardboard located under the adhesive layer heats up only relatively slightly. In order to sufficiently activate the same adhesive with IR, so much IR

Radiation are irradiated that the under the adhesive box can be heated to temperatures of 100 ° C or more.

Examples of Microwave Activatable Adhesive Compositions

The following abbreviations are used:

MMA: methyl methacrylate

S: styrene

BA: butyl acrylate

AS: acrylic acid

MAS: methacrylic acid

E: ethylene

VAc: vinyl acetate

aMS: alpha-methylstyrene

Pluriol: polyethylene glycol (plasticizer)

The Ig G 'values were measured as described above.

In each case, 20 g / m ² adhesive were applied firmly to two cardboard strips and then the two strips of adhesive layer against adhesive layer under a pressure of

15 g / cm ^{2 placed} on each other and with the microwave so that the temperature in the adhesive layer for half a second, a temperature of 120 ° C resulted. Thereafter, the bond was allowed to cool to room temperature before the strength of the bond was evaluated.

The bonding properties were evaluated by separating the bonded cardboard test pieces at the bonding site by pulling by hand.

"+" Means: severe separation at the bonding site under cardboard fiber tear "-" means: Easy separation at the bonding site without fiber breakage

The blocking resistance was evaluated by a test in which, under a weight of 2 g / mm ² , the adhesive-coated and dried paperboard was stored against a second coated paperboard at 40 ° C for 3 days. The two adhesive layers were placed against each other. "+" Means: After storage, the boxes could be separated without blocking each other.

"-" means: Adherence of the adhesive layers (blocking) after storage.

The following polymers are used (amount in parts by weight):

MMA s BA AS MAS E VAc AMS Tg ° C

Polymer 1 31 26 33 - 10 - - - 45

Polymer 2 51 26 13 10 - - - - 78

Polymer 3 56 26 13 5 - - - - 77

Polymer 4 - 58 - - 34 - - 8 106

Polymer 5 - - - - 3 80 17 - 80

Comparative Examples

Polymer 6 10 52 28 10 - - - - 50

Polymer 7 10 40 40 10 - - - - 25

Adhesive compositions, dispersed or dissolved in water (in parts by weight):

contains 10 parts by weight tackifier (partially esterified abietic acid) Activation of the adhesive with microwave radiation leads to a comparatively low heating of the cardboard to only about 50 ° C with sufficient activation of the adhesive. In a comparative activation by IR radiation by means of IR lamps, however, the cardboard heats up to at least 100 ° C in order to ensure sufficient activation of the adhesive layer.

Claims

claims

Use of a microwave activatable adhesive composition for the production of folding carton blanks for the microwave-activated production of folding cartons.

Use according to claim 1, characterized in that at less than or equal to 25 ° C the adhesive composition has an Ig G 'value of greater than or equal to 6.0 and at greater than or equal to 120 ° C an Ig G' value of less than or equal to 4 , 0 and contains at least one polymer having a glass transition temperature greater than 30 ° C, and wherein the Faltschachtelzuschnitte with adhesive composition applied thereto at 25 ° C prior to microwave activation are block-resistant.

Use according to one of the preceding claims, characterized in that the adhesive composition contains at least one polymer which is selected from the group consisting of polyurethanes, vinyl acetate polymers, acrylate polymers and methacrylate polymers.

Use according to one of the preceding claims, characterized in that the adhesive composition comprises at least one copolymer which is formed from at least one first monomer and from more than 3% by weight and less than 40% by weight, based on the total amount of monomers, at least a second monomer other than the first monomer, wherein the first monomer is selected from the group consisting of alkyl acrylates, alkyl methacrylates and vinyl aromatics and the second monomer is selected from the group consisting of ethylenically unsaturated monomers having acid groups, hydroxyalkyl acrylates and hydroxyalkyl methacrylates.

Use according to one of the preceding claims, characterized in that the adhesive composition additionally contains at least one non-adhesive, microwave radiation absorbing substance.

Use according to the preceding claim, characterized in that the microwave radiation absorbing material is selected from the group consisting of carbon black, graphite, organic color pigments and mixtures thereof.

Use according to one of the preceding claims, characterized gekennzeich¬

net, that the adhesive composition additionally contains at least one plasticizer.

8. Use according to the preceding claim, characterized in that the plasticizer is a polyalkylene glycol.

9. Use according to one of the preceding claims, characterized marked, that the plasticizer is a polyethylene glycol.

10. Use according to one of the preceding claims, characterized in that the adhesive composition

a) from 20 to 70% by weight of at least one microwave-activatable polymer,

b) from 2 to 30% by weight of at least one microwave radiation absorbing substance and

c) contains from 5 to 35 wt.% Of at least one plasticizer.

1 1. Use according to one of the preceding claims, characterized in that the folding box blank has areas with a printed, microwave activatable adhesive composition of a layer thickness of 5 to 200 m.

12. Use according to one of the preceding claims, characterized in that the adhesive composition is printed on the Faltschachtelzuschnitt by flexographic printing, offset printing or screen printing.

13. Use according to one of the preceding claims, characterized in that the activation of the adhesive composition takes place in a period of less than 2 seconds by microwave radiation of a wavelength of 1 mm to 1 m.

14. Use according to one of the preceding claims, characterized in that the microwave activation takes place by means of a microwave concentrator. 15. A process for the production of folding cartons, wherein

(1) flat carton blanks are provided,

(2) a microwave activatable adhesive composition is applied to at least parts of the flat folding carton blanks,

(3) the flat carton blanks are erected into a carton and (4) before, during or after the erection of the carton blanks the adhesive composition is activated by microwave radiation and a gluing of the carton is effected. 16. The method according to any one of the preceding Verfahrensansprüche, characterized in that the adhesive composition at less than or equal to 25 ° C an Ig G 'value of greater than or equal to 6.0 and at greater than or equal to 120 ° C an Ig G' value of less than or equal to 4.0, after application to the Faltschachtelzuschnitte at 25 ° C prior to microwave activation is block-resistant and contains at least one polymer having a glass transition temperature greater than 30 ° C.

Method according to one of the preceding method claims, characterized in that the adhesive composition contains at least one polymer which is selected from the group consisting of polyurethanes, vinyl acetate polymers, acrylate polymers and methacrylate polymers.

18. The method according to any one of the preceding Verfahrensansprüche, characterized in that the adhesive composition contains at least one copolymer which is formed from at least a first monomer and from more than 3 wt.% And less than 40 wt.%, Based on the total amount of monomers at least one second monomer different from the first monomer, wherein the first monomer is selected from the group consisting of alkyl acrylates, alkyl methacrylates and vinyl aromatics and the second monomer is selected from the group consisting of ethylenically unsaturated monomers having acid groups, hydroxyalkyl acrylates and hydroxyalkyl methacrylates.

Method according to one of the preceding method claims, characterized in that the adhesive composition additionally contains at least one non-adhesive, microwave radiation absorbing substance.

20. The method according to any one of the preceding Verfahrensansprüche, characterized in that the adhesive composition

a) from 20 to 70% by weight of at least one microwave-activatable polymer,

c) from 5 to 35% by weight of at least one plasticizer

contains.

21. Method according to one of the preceding method claims, characterized in that the adhesive composition is printed on at least partial areas of the folding box blanks in a layer thickness of 5-200 μm.

22. The method according to any one of the preceding Verfahrensansprüche, characterized in that the activation takes place in a period of less than 2 seconds by microwave radiation having a wavelength of 1 mm to 1 m.

Method according to one of the preceding Verfahrensansprüche, characterized in that the microwave activation takes place by means of a Mikrowellenkonzen trators.

Method according to one of the preceding method claims, characterized in that the folding box is filled before or immediately after the microwave activation with ingredients to be packaged.