DE19940261A1 - Process for the production of paper composites and moisturizing sticky materials - Google Patents

Abstract

The invention relates to a method for producing paper compound materials containing at least two layers. A water-soluble hot-melt-type adhesive is applied to a first layer of paper and at least a second layer of paper is laminated onto the adhesive side pertaining to the first layer of paper. The solubility of the hot-melt-type adhesive amounts to 3 wt. % in water at 20 DEG C.

Description

The invention relates to a method for producing at least two layers Using paper composites or dampening sticky materials water-soluble hot melt adhesives and the use of water-soluble high molecular polymer as a hot melt adhesive for gluing paper, in particular for gluing hygienic paper or for the production of moisturizing sticky materials.

As a rule, hygiene papers should be particularly skin-friendly, d. that is, they should use as little skin irritation as possible on sensitive parts of the body cause. In addition to checking the migratable ingredients of the To achieve this effect, hygiene paper plays a highly subjective role perceived "softness" or "gentleness" of the hygiene paper. A particularly soft and gentle impression is usually achieved by that the hygiene paper is composed of several thin layers. Between these individual layers, the User friendliness, however, there is a noticeable liability for the Hygiene papers do not immediately dissolve into individual layers when they are used their handling deteriorates significantly. Another trend in However, the area of hygiene papers goes to the number of layers that can be achieved of the softest possible effect are necessary to reduce as far as possible. Manufacturing and merging multiple layers is usually more expensive than the production of one, for example, reduced to only two layers Sanitary paper.  

In order to achieve the required, velvety surface effect, the The surface of the hygiene paper is usually embossed or otherwise Treatments, for example the alignment of the fibers on the paper affect surface, modified. Now try to glue the to individual layers of the hygienic paper using a water-soluble adhesive achieve this has several disadvantages. For example, water practices as Solvent for the adhesive on the paper surface has an adverse effect. This is expressed, for example, in the formation of wrinkles, shrinkage or smoothing Paper surface. All of these effects have an adverse impact on the Condition of the surface with regard to a "velvety" feeling when User.

Similar phenomena such as wrinkling or shrinkage also occur in the Manufacture of moisturizing sticky materials, for example stamps, Envelopes or labels, on.

Furthermore, the use of water-soluble adhesives requires in the course of Bonding process a drying stage in which water from the bonded Hygiene paper is removed. Such drying stages are usually energy intensive and lead to an increase in price and time delay of Production process.

Another disadvantage is the use of water-soluble adhesives also in the fact that it usually takes a long time until the Adhesion and cohesion values ensure sufficient individual adhesion Allow layers of paper. This has an adverse influence on the further Processing the bonded layers from, d. that is, the glued paper layers are in the Sufficiently mechanically loadable after drying.

Another requirement for adhesives used for bonding hygienic paper used is that the adhesives are as complete as possible should be water soluble. This requirement is based on the high recycling rate  in the manufacture of sanitary paper, d. H. that production waste if possible must be used again directly in the production of new paper layers. However, this requires that the bond between the individual Paper layers are completely removed from a recycled pulp. Water-insoluble or poorly water-soluble adhesive components, which during the production of a new paper layer from the recycled fiber material in the If the paper web gets stuck, it can lead to serious production downtimes. Such adhesive residues usually form in the recycled paper webs so-called "stickies", i.e. H. sticky spots that stick to the paper web can lead on rollers and similar guide elements for the paper web. This usually has a paper web tear-off and lengthy Production interruptions. It is therefore not only necessary that the Adhesion by water is releasable and thereby a dispersion of the Glue leads in water, but the glue itself is said to be completely in water be soluble. This prevents any adhesive residue that may have been removed from becoming fine distributed lead to sticky agglomerates (stickies).

EP-A 0 705 895 relates to a method for gluing tissue or Nonwovens using a hot melt adhesive composition that from up to 60% of a starch ester, up to 40% of a polar wax, up to 50% a plasticizer, up to 25% of a tackifier and up to 3% of one Contains antioxidant. While this adhesive composition does Basic requirements for an adhesive for bonding hygienic paper layers fulfilled, but not all components of the adhesive are completely water-soluble. This can add to the disadvantages of recycling such as described above Keep hygiene papers.

In the older application DE 198 21 769 a method for the production described at least two-layer paper composites, in which a water-soluble Hot melt adhesive applied to a first layer of paper and at least a second Paper layer is laminated on the adhesive side of the first paper layer, the Solubility of the hot melt adhesive in water at 20 ° C at least 3% by weight  is. This document addresses the problem of visual assessment of the Spray image without a dye appearing optically disturbing, not addressed and also not solved.

It was therefore the task of providing a hot melt adhesive for the bonding of hygienic paper layers, which can be applied as a melt, which allows a clean application even in the smallest application quantities (less than 0.1 g / m ² ), a firm, permanent and quick adhesive bond guaranteed after joining two paper webs to be glued and is also completely water-soluble, that is, is miscible with water in any amount. The application of the hot melt adhesive should be easy to control.

It has now been found that water soluble polymers have a water solubility of at least 3 wt .-% at 20 ° C do not have the disadvantages mentioned above.

The invention accordingly relates to a method for producing at least two-ply paper composites, in which a water-soluble hot melt adhesive on a first layer of paper applied and at least one second layer of paper on the Adhesive side of the first paper layer is laminated, the solubility of the Hot melt adhesive in water at 20 ° C is at least 3 wt .-% and Hot melt adhesive is a UV active fluorescent dye in a detectable Quantity contains.

The method according to the invention is particularly suitable for paper composites that to serve as hygiene paper. Under "hygiene paper" within the scope of the present invention predominantly in the household, in Community facilities and used for personal hygiene Types of paper, e.g. B. household towels (paper towels), paper towels, Paper handkerchiefs, paper napkins, toilet paper, children's diapers and understood the like. The method according to the invention is particularly suitable for the production of paper composites from tissue.  

"Tissue" means a particularly thin, soft, predominantly wood-free material, possibly with fine (dry) crepe. The material is very absorbent and in a single layer usually has a basis weight of <25 g / m ² (before the crepe). Such tissue composites, as can be obtained by the process according to the invention, are mainly used to produce toilet paper, paper tissues or facial tissues.

For the purposes of the present invention, “hot melt adhesives” means adhesives understood that solid at room temperature and at least largely water and are solvent-free. Hot melt adhesives are made from the melt towards the adhesive paper layers applied and bind when cooling Consolidation physically. Organic hot melt adhesives, for example Polymers such as polyesters, polyurethanes, polyamides, polyalkylene oxides or Polymers, for example polyacrylates, are suitable. The hot melt adhesives must however at least the above requirements regarding the Meet water solubility.

The terms "polyacrylate" as used in the context of the present text, in the following refers to both polymers or copolymers of acrylic acid or their derivatives as well as on polymers or copolymers of methacrylic acid or their derivatives.

Polyacrylates suitable as hot-melt adhesive in the context of the present invention can be prepared by using acrylic acid or methacrylic acid or derivatives of Acrylic acid or methacrylic acid, for example esters of acrylic or Methacrylic acid with mono- or polyfunctional alcohols, each alone (in the case acrylic acid or methacrylic acid) or as a mixture of two or more thereof, can be polymerized in a known manner, for example by radical or ionic means. The polymers or copolymers should definitely contain some free Acid groups or their salts with alkali, alkaline earth or ammonium ions have so high that the polymer has a water solubility of at least about 3 wt .-% at 20 ° C.  

For example, the present invention can be used as a hot melt adhesive Polyacrylates in the form of homopolymers or copolymers are used, the latter in addition to the acrylic or methacrylic acid components or a mixture thereof still styrene, styrene sulfonic acid, acrylonitrile, vinyl acetate, vinyl propionate, vinyl chloride, Have vinylidene chloride and / or butadiene.

If necessary, other acrylates or methacrylates or their Mixture with one or more functional groups during the polymerization to be present. For example, these are maleic acid, itaconic acid, butanediol diacrylate, hexanediol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, Neopentylglycol diacrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2- Hydroxyethyl methacrylate, hydroxypropyl acrylate, propylene glycol methacrylate, butane diol monoacrylate, ethyl diglycol acrylate and monomers bearing sulfonic acid groups, for example 2-acrylamido-2-methylpropanesulfonic acid.

In a preferred embodiment of the invention, the polyacrylates have Molecular weight from about 3,000 to about 50,000.

Also for use as a hot melt adhesive in the context of the present invention suitable are polyesters with a molecular weight of about 3,000 to about 50,000. For example, polyesters can be used that are converted low molecular weight alcohols, in particular ethylene glycol, Diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerin or Trimethylolpropane with corresponding at least difunctional acids are formed. Also suitable as polyfunctional alcohols for the production of polyesters 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, 1,2-butanetriol, Triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, Polypropylene glycol, dibutylene glycol and polybutylene glycol.

Suitable polyester polyols can be produced, for example, by polycondensation. So difunctional or trifunctional alcohols or a mixture of two  or more thereof, with dicarboxylic acids or tricarboxylic acids or a mixture from two or more thereof, or their reactive derivatives, to polyester polyols be condensed. Suitable dicarboxylic acids are, for example, succinic acid and their higher homologues with up to 16 carbon atoms, furthermore unsaturated Dicarboxylic acids such as maleic acid or fumaric acid and aromatic dicar bonic acids, especially the isomeric phthalic acids, such as phthalic acid, isophthal neck acid or terephthalic acid. As tricarboxylic acids are, for example Citric acid or trimellitic acid suitable. Particularly within the scope of the invention polyester polyols from at least one of the dicarboxylic acids mentioned are suitable and glycerin, which have a residual content of OH groups. Especially suitable alcohols are hexanediol, ethylene glycol, diethylene glycol or Neopentyl glycol or mixtures of two or more thereof. Particularly suitable Acids are isophthalic acid or adipic acid or a mixture thereof.

Polyols which can also be used as the polyol component for the production of the polyesters are, for example, diethylene glycol or higher polyethylene glycols with a molecular weight (M _n ) of about 100 to about 22,000, for example about 200 to about 15,000 or about 300 to about 10,000, in particular about 500 to about 2,000.

Polyesters which can be used in the context of the present invention as hot melt adhesive include in particular the reaction products of polyfunctional, preferably difunctional alcohols (optionally together with small Amounts of trifunctional alcohols) and polyfunctional, preferably difunctional carboxylic acids. Instead of free polycarboxylic acids (if existing) also the corresponding polycarboxylic anhydrides or corresponding Polycarboxylic acid esters with alcohols preferably having 1 to 8 carbon atoms become. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or be heterocyclic. They can be optionally substituted for example by alkyl groups, alkenyl groups, ether groups or halogens. Examples of polycarboxylic acids are succinic acid, adipic acid, suberic acid, Azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trime llithic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthal  acid anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthal acid anhydride, glutaric anhydride, maleic acid, maleic anhydride, Fumaric acid, dimer fatty acid or trimer fatty acid or mixtures of two or more of it suitable. If necessary, minor amounts of monofunctional fatty acids are present in the reaction mixture.

The polyesters can have, for example, carboxyl end groups. From lactones, for example ε-caprolactone or hydroxycarboxylic acids, for example ω- Hydroxycaproic acid, available polyesters, can also at least be used proportionately.

In any case, however, the polyesters must have a water solubility of at least 3% by weight at 20 ° C. Water solubility can be achieved, for example, by using suitable water-soluble comonomers in polyester production. To adjust the water solubility of the polyesters, it is advisable, for example, to use appropriate sulfonated polycarboxylic acids, for example sulfonated phthalic acid, isophthalic acid or terephthalic acid, or to use water-soluble polyether polyols such as polyethylene glycol with a molecular weight (M _n ) of at least about 100 in the case of polycondensation.

Also suitable as hot melt adhesive are, for example, polyalkylene glycols with a molecular weight (M _n ) of at least about 1,000, whose solubility in water at 20 ° C. is at least about 3% by weight.

Such polyalkylene glycols are usually supported by catalytic ones ring-opening polymerization of alkylene glycols.

Usually, polymerization is started from a so-called starter molecule. In principle, old compounds which, if appropriate, are suitable as starter molecules in the presence of a suitable catalyst, for ring opening of epoxy rings in are able. For example, these are primary, secondary or tertiary amines, primary, secondary or tertiary alcohols, thiols or carboxylic acids.  

The polymerization usually takes place under basic catalysis. In the context of the present invention, preference is given to using polyalkylene glycols such as those obtainable by polymerizing ethylene oxide, optionally in a mixture with C _3-12 alkylene. The proportion of higher alkylene oxides in the polyalkylene glycol may, however, be such that the solubility in water (in the context of the present text also: water solubility) at 20 ° C. is at least about 3% by weight. Suitable are, for example, polyethylene glycols with a proportion of C ₃ or C ₄ units, or both, as can be obtained by copolymerizing ethylene oxide with propylene oxide or butylene oxide or a mixture thereof. However, polyethylene oxide is preferably used in the context of the present invention, as can be obtained by polymerizing ethylene oxide.

In a preferred embodiment of the invention are used as hot melt adhesive Polyalkylene glycols used using primary, secondary or tertiary alcohols or mixtures of two or more of them as starting molecules were manufactured.

Basically, all mono- or polyfunctional alcohols or are their mixtures are suitable, preferably within the scope of the present However, the invention used polyalkylene glycols, which using a two- or trihydric alcohol, for example ethylene glycol, propylene glycol, Butylene glycol, pentanediol, hexanediol, heptanediol, octanediol and their higher Homologues, neopentylglycol, glycerin, trimethylolpropane, triethylolpropane, Pentaerythritol, glucose, sorbitol, mannitol or a mixture of two or more of which were produced as a starting molecule.

The lower limit of the molecular weight as a hot melt adhesive within the The present invention usable polyalkylene glycols is characterized by the adhesive technical properties of polyalkylene glycol determined. It is in everyone If necessary, the molecular weight is so high that sufficient adhesion and cohesion of the hot melt adhesive are given. Furthermore, that should  The molecular weight must be so high that the polyalkylene glycols are not pressure sensitive Have more properties.

The polyalkylene glycols which can be used as hot-melt adhesive in the process according to the invention therefore generally have a molecular weight (M _n ) of at least about 1,000, for example at least about 3,000 and in particular at least about 6,000.

The upper limit for the molecular weight is usually determined by the processing as a hot melt adhesive and determined by water solubility. This gives it that the upper limit of the molecular weight should be such that a easy rolling or spraying of the molten polyalkylene oxide is possible through conventional nozzles within the framework of customary application techniques. Farther the molecular weight of the polyalkylene oxide should only be so high that the required water solubility of about 3 wt .-% is maintained. The upper limit the molecular weight is therefore, for example, approximately 100,000, in particular at up to about 50,000.

The polyalkylene glycols can be individually, i.e. H. as a polyaddition product with usually in the case of base-catalyzed additions of alkylene oxides to water or other starter molecules resulting molecular weight distributions be used. However, it is also possible to mix different ones Polyalkylene glycols with different molecular weight distributions to use. It is also possible to use polyalkylene glycols which are characterized by Addition of only one alkylene oxide compound to a starter molecule. It is however, it is also possible to use polyalkylene glycols by addition various alkylene oxides are available. It can be both block Copolymers as well as statistical copolymers.

Polyurethanes with a molecular weight (M _n ) of at least about 2,000, for example about 5,000 or more, which have a water solubility at 20 ° C. of at least 3% by weight can also be used as the hot melt adhesive in the context of the present invention. Both ionic and nonionic, water-soluble polyurethanes are suitable as hot melt adhesives.

Polyurethanes as used in the context of the present invention as a hot melt adhesive can be used, are usually implemented by implementing at least one Polyisocyanate, preferably a diisocyanate, and a polyol component, the preferably consists predominantly of diols. The polyol component can contain only one polyol, but it can also be a mixture of two or more different polyols can be used as the polyol component. As Polyol component or at least as part of the polyol component for example polyalkylene oxides, especially polyethylene oxide, particularly suitable.

The term "ionic" means that the polyurethane is ionic or at least in As part of an acid-base reaction, ionizable groups act as solubilizers has, for example carboxylate, sulfonate, phosphonate or ammonium Groups.

The term "nonionic" means accordingly that the polyurethane has no ionic groups as emulsifying groups, that is to say no carboxylate, sulfonate, phosphonate or ammonium groups. Rather, the water solubility is based on the hydrophilic nonionic groups of polyoxyethylene - [CH ₂ -CH ₂ -O-] _n -. These structural units are derived in particular from the polyethylene oxide which is preferably used as the polyol component. However, polyethylene oxide is not only to be understood as polyaddition products of ethylene oxide with water or ethylene glycol as the starting molecule, but also polyadditions of ethylene oxide with other dihydric alcohols, e.g. B. butanediol, hexanediol or 4,4'-dihydroxy diphenylpropane. Mixtures of two or more different polyethylene oxides can also be used, which differ, for example, in the average molecular weight M _w or M _n or in both. Copolymers of ethylene oxide with higher alkylene oxides, e.g. B. with propylene oxide, can be used as poly ol component, provided that they are sufficiently water-soluble, ie, more than about 3 g remain dissolved in about 100 g of water at about 20 ° C for about 6 months.

The polyethylene oxide in the polyol component can be up to 10, preferably up to at most 5, in particular up to at most 2 wt .-% replaced by other diols be a hydrophobic residue with a water solubility of at most Contain 2 g / 100 g water. The hydrophobic residue is in particular aliphatic or alicyclic structures with 2 to 44, in particular 6 to 36 C- Atoms. The residues can also contain aromatic structures. Are preferred Diols with at least one primary OH group, in particular 1,2- or α, ω-diols. Diols with the vicinal position of the OH groups are also suitable.

The polyethylene oxide in the polyol component preferably has a molecular weight (M _n ) of about 200 to about 20,000, in particular about 1,000 to about 15,000, for example about 1,550, 3,000, 6,000 or 12,000.

Furthermore, up to 10, preferably 0.5 to 5% of the polyethylene glycol can pass through hydrophobic homopolymeric polyalkylene glycols are replaced, the Alkylene group has more than 2, preferably 3 or 4 carbon atoms. Your Molecular weights are in particular 150 to 10,000 g / mol.

Specific examples of the hydrophobic diols with pure CH residues and with ether groups are polypropylene glycol (PPG), polybutylene glycol, polytetrahydrofuran, polybutadiene diol, hydroxyl-terminated ethylene-butylene copolymers (e.g. KRATON LIQUID polymer L-2203), hydrogenated polybutadiene diol and alkane diol with 4 to 44 carbon atoms. Preferred hydrophobic diols are polypropylene glycol, polyetrahydrofuran with a molecular weight of 150 to 10,000, in particular 200 to 4,500, particularly preferably 250 to 1,000, and 1,10-decanediol, 1,12-dodecanediol, 1,12-octadecanediol, dimer fatty acid diol, 1,2 Octane diol, 1,2-dodecane diol, 1,2-hexadecane diol, 1,2-octadecane diol, 1,2-tetradecane diol, 4,4-isopropylidenedicyclohexanol and its isomer mixtures, 4,8-bis (hydroxymethyl) tricyclo [5.2, 1.0 ^2,6 ] decanes and their isomer mixtures, 1,4: 3,6-dianhydro-D-mannitol, 1,4: 3,6-dianhydro-D-sorbitol, 1,16-hexadecanediol, bisphenol-A and their prop- or ethoxylation products or their mixtures, in particular with up to 30 EO units, and finally monofatty acid esters of glycerol with fatty acids containing up to 22 carbon atoms, e.g. B. glycerol monoesters of behenic acid, oleic acid, stearic acid, myristic acid. Mixtures of two or more of the hydrophobic diols mentioned can of course also be used.

The polyethylene glycol can also be present in an amount of 0 to 5, in particular 0.2 up to 2% can be replaced by higher functional alcohols, especially by triols, e.g. B. by glycerol, trimethylolpropane, triethanolamine or their ethoxylated or propoxylated variants. Pentaerythritol is also useful. Are also possible ethoxylated or propoxylated variants of amines or amino alcohols, e.g. B. starting from ethylenediamine, diethylenetriamine, and their higher homologues, for example aminophenol, N-2-aminoethylpiperazine.

In order to obtain particularly high molecular weight polyurethanes, pure ones should be used Diols are used. For this purpose, the content of alkali and Alkaline earth metal ions below 500 ppm, in particular below 150 ppm and preferably are below 10 ppm. In addition, the water content should be below 0.5, in particular are below 0.1, preferably below 0.05% by weight according to K. Fischer.

In addition to the diols of the polyol component, diisocyanates are essential building blocks of the polyurethane that can be used as a hot melt adhesive. These are ver bonds of the general structure O = C = N-X-N = C = O, where X is an aliphatic, is alicyclic or aromatic, preferably an aliphatic or alicyclic radical with 4 to 18 C atoms.

Examples of suitable isocyanates are 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H ₁₂ -MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4,4'-diphenyldime, methyl methane diisocyanate, di- and tetraalkylene diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of tolylene diisocyanate (TDI), 1-methyl-2,4-diisocyanato-cyclohexane, 1,6-diisocyanato-2, 2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4 'Di-isocyanatophenylperfluoroethane, tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalic acid bis- isocyanato ethyl ester, also diisocyanates with reactive halogen atoms such as 1-chloro-methylphenyl-2,4-d called isocyanate, 1-bromomethylphenyl-2,6-diisocyanate or 3,3-bis-chloromethylether-4,4'-diphenyidiisocyanate. Sulfur-containing polyisocyanates are obtained, for example, by reacting 2 mol of hexamethylene diisocyanate with 1 mol of thiodiglycol or dihydroxydihexyl sulfide. Further usable diisocyanates are, for example, trimethylhexamethylene diisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimer fatty acid diisocyanate. Particularly suitable are: tetramethylene, hexamethylene, undecane, dodecamethylene, 2,2,4-trimethylhexane, 1,3-cyclohexane, 1,4-cyclohexane, 1,3- or 1,4-tetramethylxylene -, Isophorone, 4,4-dicyclohexylmethane and lysine ester di-isocyanate. Tetramethylxylylene diisocyanate (TMXDI) is very particularly preferred, in particular the m-TMXDI available from Cyanamid.

To further increase the molecular weight, for example, known ones Way a chain extension can be made. This will be done first Prepolymers made with excess diisocyanate, which then with short chain amino alcohols, diols, diamines or with water while increasing the Molecular weight can be extended.

To this end, prepolymers with excess diisocyanate are first produced, which are then subsequently extended with short-chain diols or diamines or with water. As chain extenders, the following are specifically mentioned:

• - Saturated and unsaturated glycols such as ethylene glycol or condensates Ethylene glycol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2-butyne-1,4-diol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, hexanediol, bis- hydroxymethylcyclohexane, dioxyethoxyhydroquinone, terephthalic acid bisgly kolester, succinic acid di-2-hydroxyethylamide, succinic acid di-N-methyl- (2- hydroxyethyl) amide, 1,4-di (2-hydroxymethylmercapto) -2,3,5,6-tetrachlorobenzene, 2-methylene-propanediol- (1,3), 2-methyl-propanediol- (1,3), 3-pyrrolidino-1,2- propanediol, 2-methylenepentanediol-2,4,3-alkoxy-1,2-propanediol, 2-ethylhexane 1,3-diol, 2,2-dimethylpropanediol-1,3, 1,5-pentanediol, 2,5-dimethyl-2,5-hexanediol, 3-phenoxy-1,2-propanediol, 3-benzyloxy-1,2-propanediol, 2,3-dimethyl-2,3- butanediol, 3- (4-methoxyphenoxy) -1,2-propanediol and Hydroxymethylbenzyl alcohol;
• Aliphatic, cycloaliphatic and aromatic diamines such as ethylenediamine, Hexamethylene diamine, 1,4-cyclohexylene diamine, piperazine, N-methyl propylene diamine, diaminodiphenyl sulfone, diaminodiphenyl ether, Diaminodiphenyldimethylmethane, 2,4-diamino-6-phenyltriazine, isophoronediamine, Dimer fatty acid diamine, diaminodiphenylmethane or the isomers of Phenylenediamine;
• - Also carbohydrazides or hydrazides of dicarboxylic acids;
• - Amino alcohols such as ethanolamine, propanolamine, butanolamine, N-methyl ethanolamine, N-methyl-isopropanolamine, diethanolamine, triethanolamine and higher di- or tri (alkanolamines);
• - Aliphatic, cycloaliphatic, aromatic and heterocyclic mono- and Diaminocarboxylic acids such as glycine, 1- and 2-alanine, 6-aminocaproic acid, 4- Aminobutyric acid, the isomeric mono- and diaminobenzoic acids and the isomeric mono- and diaminonaphthoic acids.

However, the polyurethane is preferably used in a one-step process manufactured. For example, all starting materials are initially present an organic solvent with a water content of less than 0.5% by weight mixed. The mixture is kept at 60 to 200 ° C. for about 1 to 30 hours, in particular heated to 80 to 180 ° C and preferably to 100 to 150 ° C.  

The reaction time can be shortened by the presence of catalysts.

In particular, tertiary amines are suitable, e.g. B. triethylamine, 1,4-diazabi cyclo [2,2,2] octane (= DABCO) dimethylbenzylamine, bis-dimethylaminoethyl ether and Bis-methylaminomethylphenol. 1-Methyl are particularly suitable imidazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1,2,4,5- Tetramethylimidazole, 1- (3-aminopropyl) imidazole, pyrimidazole, 4-dimethylamino pyridine, 4-pyrrolidinopyridine, 4-morpholino-pyridine, 4-methylpyridine.

Organotin compounds can also be used as catalysts. These are understood to mean compounds which contain both tin and an organic radical, in particular compounds which contain one or more Sn — C bonds. Organotin compounds in the broader sense include e.g. B. salts such as tin octoate and tin stearate. The tin compounds in the narrower sense include above all compounds of tetravalent tin of the general formula R _{n + 1} SnX _3-n , where n stands for a number from 0 to 2, R stands for an alkyl group or an aryl group or both and X finally for is an oxygen, sulfur or nitrogen compound or a mixture of two or more thereof. R expediently contains at least 4 carbon atoms, in particular at least 8. The upper limit is generally 12 carbon atoms. X is preferably an oxygen compound, that is to say an organotin oxide, hydroxide, carboxylate or an ester of an inorganic acid. X can also be a sulfur compound, that is, an organotin sulfide, thiolate or a thiosate. In the Sn-S compounds, especially thioglycolic acid esters are suitable, e.g. B. Compounds with the following residues:

-S-CH ₂ -CH ₂ -CO-O- (CH ₂ ) ₁₀ -CH ₃ or

-S-CH ₂ -CH ₂ -CO-O-CH ₂ -CH (C ₂ H ₅ ) -CH ₂ -CH ₂ -CH ₂ -CH ₃ .

Such compounds fulfill a further selection rule: the molecular weight in a preferred embodiment, the organotin compound is said to Invention over 250, especially over 600.

Another preferred class of compounds are the dialkyl tin (IV) carboxylates (X = O-CO-R ¹ ). The carboxylic acids have 2, preferably at least 10, in particular 14 to 32, carbon atoms. Dicarboxylic acids can also be used. Suitable acids are, for example, adipic acid, maleic acid, fumaric acid, terephthalic acid, phenylacetic acid, benzoic acid, acetic acid, propionic acid and in particular caprylic, capric, lauric, myristic, palmitic and stearic acid. For example, dibutyltin diacetate and dilaurate and dioctyltin diacetate and dilaurate are particularly suitable.

Tin oxides and sulfides as well as thiolates are also within the scope of the present Invention suitable. Specific compounds are: bis (tributyltin) oxide, Dibutyltin didodecyl thiolate, dioctyltin dioctyl hiolate, dibutyltin bis (thioglycolic acid 2- ethyl hexyl ester), octyltin tris (2-ethylhexyl thioglycolic acid), dioctyltin bis (thioethylene glycol 2-ethylhexoate), dibutyltin bis (thioethylene glycol laurate), Dibutyltin sulfide, dioctyltin sulfide, bis (tributyltin) sulfide, dibutyltin bis (2-ethylhexyl thioglycolate), dioctyltin bis (2-thioethylene glycol) ethylhexoate), trioctyltin thioethylene glycol 2-ethylhexoate and dioctyltin bis (2-ethyl-thiolatoacetic acid), bis (S, S-methoxycarbonyl ethyl) tin bis (2-ethylhexyl thiolatoacetate), bis (S, S-acetyl-ethyl) tin bis (2-ethyl-hexyl thiolatoacetate), tin (II) octyl hiolate and Tin (II) thioethylene glycol 2-ethylhexoate.

Also mentioned are: dibutyltin diethylate, dihexyltin diaminexylate, Dibutyltin diacetylacetonate, dibutyltin diethylacetylacetate, bis (butyldichlorotin) oxide, Bis (dibutylchlorotin) sulfide, tin (II) phenolate, tin (II) acetylacetonate, and other α- Dicarbonyl compounds such as acetylacetone, dibenzoylmethane, benzoylacetone, Ethyl acetoacetate, n-propyl acetoacetate, α, α'- Diphenylacetoacetic acid ethyl ester and dehydroacetoacetic acid.  

The catalyst is preferably added to the polyol. Its amount is judged according to its activity and the reaction conditions. It is preferably in the Range of 0.001 to 0.5% by weight based on the polyol.

However, preference is given to working without a catalyst. The solvent too conveniently omitted. Under "solvents" within the scope of In this text inert organic liquids with a boiling point of understood less than 200 ° C at normal pressure (1 bar).

The reaction is preferably carried out so that the ratio of OH Groups in the polyol component to NCO groups in the polyisocyanate about 1.0 to about 2.0, in particular about 1.05 to 1.8, for example about 1.1 to 1.7 or about 1.3 to 1.6.

One possibility for the introduction of ion-forming structural elements is the Reaction of OH-terminated polyurethane oligomers with dicarboxylic acid anhydrides. These can contain a total of 2 to 44, preferably 2 to 12 carbon atoms between the Contain bisacyl groups such as alkylene, alkenylene or arylene grouping. For example, succinic anhydride, glutaric anhydride, 1,2,3,6- Tetrahydrophthalic anhydride and its isomers, phthalic anhydride, Trimellitic anhydride, 7-oxabicyclo [2,2,1] hept-5-en-2,3-dicarboxylic anhydride, 5- Norbornene-2,3-dicarboxylic acid anhydride and its isomers, diglycolic acid anhydride, Maleic anhydride, dimethyl maleic anhydride, citraconic anhydride, Itaconic anhydride, alkenyl succinic anhydrides, preferably those thereof Alkenyl groups more than 2 carbon atoms, in particular more than 5, particularly preferred possess more than 7 C atoms. Specifically mentioned are: n- Octenylsuccinic anhydride, n-dodecenylsuccinic anhydride, tetra propenylsuccinic anhydride, n-hexadecenylsuccinic anhydride and n- Octadenyl succinic anhydride. The alkenyl radical can be linear or branched be constructed. Mixtures of alkenyl groups can also be used  different numbers of carbon atoms occur. Mixtures of several Anhydrides are possible, but cyclic anhydrides are preferred.

However, it is also possible to use a molar excess of isocyanates producing NCO-terminated oligomers.

In general, NCO groups are undesirable in the end product. You can however used to e.g. B. hydrophobic or ionic structural elements introduce.

Hydrophobic structural elements can, for example, by reaction of NCO terminated oligomers with monools or monofunctional amines with ≧ 2 C- Atoms, in particular ≧ 6, ≧ 10 or ≧ 16 C atoms can be obtained. Be specific called: poly-ethylene / butylene with 1 OH group, for. B. with an OH Equivalent weight of 3600 (Kraton L 1203) and 1-hexanol, 1-heptanol, 1- Octanol, 1-nonanol, 1-decanol, 1-undecanol, 10-undecen-1-ol, 1-dodecanol, 1- Tridecanol, 1-tetradecanol, 1-pentadecanol, 1-hexadecanol, 1-heptadecanol, 1- Octadecanol, 9-cis-octadecen-1-ol, 9-trans-octadecen-1-ol, 9-cis-octadecen-1,12- diol, all-cis-9,12-octadecadien-1-ol, all-cis-9,12,15-octadecatrien-1-ol, 1- Nonadecanol, 1-eicosanol, 9-cis-eicosen-1-ol, 5,8,11,14-eicosatetraen-1-ol, 1- Heneicosanol, 1-docosanol, 13-cis-docosen-1-ol, 13-trans-docosen-1-ol. Also the corresponding fatty amines are possible as hydrophobizing structural elements.

Finally, another possibility for introducing ion-forming structures is that Reaction of NCO-terminated oligomers with hydroxycarboxylic acids or Aminocarboxylic acids with alkylene, alkenylene or arylene groups as in the Dicarboxylic acid anhydrides. Examples include: glycolic acid, lactic acid, Caproic acid and mandelic acid and aminocaproic acid, aminododecanoic acid, Glycine, alanine and phenylalanine.  

In a preferred embodiment of the invention, a nonionic polyurethane with a molecular weight (M _n ) of at least about 2,000 is used as the hot melt adhesive, in particular a nonionic polyurethane which can be obtained by reacting at least one polyisocyanate with at least one polyalkylene glycol with a molecular weight of at least 1,000.

The hot melt adhesive can contain further additives, for example Plasticizers, rheological additives, antioxidants, UV stabilizers, dyes, Tackifier resins or pigments (filler).

For example, hydrocarbon resins are used as tackifiers, in particular C5 or C9 resins or C9 resins modified with C5 resins. Resins based on pure are also suitable for use as tackifiers Hydrocarbon monomers, for example resins such as those from the polymerization of mixtures of styrene, α-methylstyrene and vinyl toluene are available. The mentioned hydrocarbon resins can be partially hydrogenated or fully hydrogenated.

Natural resins such as balsamic resin such as it are also suitable for use as tackifiers For example, is obtained from trees or tall resin, which is used in the Papermaking is incurred. The natural resins can be used in the above form Tackifier can be used, but it is also possible to use the resins mentioned after esterification with appropriate polyfunctional alcohols as Pentaerythritol ester, glycerol ester, diethylene glycol ester, triethylene glycol ester or Use methyl ester.

The polyterpene resins are also suitable as tackifiers. Terpenes fall at the Separation of resin acids from their natural solvents and can be Polymerize polyterpene resins. Are also suitable for use as tackifiers those obtainable from polyterpene resins by phenol modification Terpene phenolic resins.  

The additives can be used individually or as a mixture of two or more of the mentioned substances are present in the hot melt adhesive. The amount of additives should not be about 20% by weight (based on the total hot melt adhesive) exceed. For example, amounts of about 0.1 to about 15% by weight are suitable, or about 1 to about 10% by weight in a preferred embodiment of the For example, about 2, 3, 4, 5, 7 or 9 wt .-% additives used.

To enable a visual assessment of the spray pattern, but without the Changing the glue optically is a UV-active fluorescent dye mixed with the hot melt adhesive. These are so-called optical Brightener of the following substance classes: benzoxazole, benzoxazole stilbene, stilbene, Biphenyl, coumarin, pyrazoline, pyrazine and benzimidazole derivatives. Be specific mentioned as examples: bis (5-tert-butyl-2-benzoxazolyl) thiophene * 2,5-, bis (2- benzoxazolyl) thiophene * 2,5-, bis (benzoxazolyl) stilbene * 4,4'-, diphenylstilbene derivative, [Bis- (2-methoxy-4-anilinocyanurato) 4,4'-diamino] stilbene-2,2'-disulfonic acid di- Sodium salt, bis [(4-anilino-6-methoxy-1,3,5-triazin-2-yl) amino] -2,2'- stilbene disulfonic acid di-sodium salt * 4,4'-, diphenyldistyryl derivative, distyrylbiphenyl Derivative anionic, stilbene disulfonic acid derivative, bis [(4,6-dianilino-s-triazine-2- yl) amino] -stilbene-2,2'-disulfonic acid disodium salt * 4,4'-, stilbene disulfonic acid Derivative, stilbene triazine derivative, bis (styryl) biphenyl derivative, bis (2-methylstyryl) biphenyl * 4,4'-, dibenzofuranylbiphenyl derivative, coumarin derivative dispersion in Benzyl butyl phthalate, 2 (4- (3- (4-chlorophenyl) -4,5- dihydropyrazolyl) phenylsulfonyl) ethyldimethylammonium hydrogenphosphonate, Chlorophenyl-3 (4-chlorophenyl) -4,5-dihydro-1H-pyrazole-1 (3-chlorophenyl-3-phenyl-4,5- dihydro-1H-pyrazole mixture * 1 (3-, sulfamidophenyl) -3 (4-chlorophenyl) pyrazoline- * 1 (4-, diphenylpyrazoline derivative * 1,3-non-ionic, diphenylpyrazoline derivative * 1,3-, Diphenylpyrazoline derivative ketone aldehyde condensation resin mixture * 1,3-, Sulfamidophenyl) -3 (4-chlorophenyl) pyrazoline * 1 (4-, chlorophenyl) -1 (4- amidosulfonylphenyl) pyrazoline * 3 (4-, N, N-dimethyl-2 (3- (4-chlorophenyl) -4,5- dihydropyrazol-1-ylphenylsulfonyl) ethylamine.  

Such products can e.g. B. from the Uvitex or Tinopal product lines from the company Ciba Geigy, blankophore from Bayer, leucophore from Sandoz, Hostalux der Hoechst or Eastobrite from Eastman. Specifically: Uvitex-OB, -ERN-P, -SOF, -EFT, -CBS, -3257, -CF, -CFkonz., -3692, -NFW-liquid, -CK, -SOP, -MST, -FP, -SWN-conc. and -4457, Tinopal-SOF, -CBS, -3257, -SOP, -DMSIX, -3859, -PLC, -SWN-conc., -FS, -CH-3566 and -LS, Eastobrite-OB-1, Blankophor-CA-4499, -CA-4601, -FBW, -MAR, -MAN, -K-2002-SK, FB-766 and -FB, Lenkophor-CRL-20/119, -EFR and Hostalux-VP-3481. Prefers Uvitex-OB is used.

The UV-active fluorescent dyes are used in an amount of up to 10. preferably up to 1 and in particular up to 0.05% by weight, based on on the total hot melt adhesive. The lower limit results from the Effectiveness of the specific dyes used and the desired ones Color intensity of UV light.

It is advisable to check the spray pattern in the following way:

A sample of the paper composite loaded with the hot melt adhesive is delaminated and preferably in a darkened room (e.g. Sample box) the light of a UV radiation source of a wavelength of z. B. Exposed 254 mm. It is important that the wavelength is capable of the dye to stimulate.

The qualitative assessment of the application picture of the adhesive is done visually. There is also the possibility of a quantitative assessment of the spray pattern, by the fluorescence light via suitable photoreceptors (photometer, Cameras) and recorded via connected image analysis methods is evaluated. In addition to an analysis of the adhesive distribution, there is also the Possibility of a statement about the amount of adhesive.

The polyalkylene glycol advantageously no longer has a melt viscosity than 20,000 mPas (Brookfield Thermosel, spindle 27, 180 ° C). In a preferred embodiment, however, the melt viscosity is below this value,  for example at about 1,000 mPas to about 10,000 mPas, for example about 2,000 to about 8,000 mPas. Good results can be found, for example, at 5,000 to 6,000 mPas at a melting temperature of about 150 ° C (Brookfield Thermosel, spindle 27) achieve.

Those used in the method according to the invention Hot melt adhesives should generally have a viscosity that allows them Use hot melt adhesives in the context of normal application processes. The hot melt adhesives therefore advantageously have a viscosity (Brookfield Thermosell, spindle 27), which are in a range of approximately 400 mPas at 100 ° C to about 20,000 mPas at about 180 ° C. In a preferred embodiment In the present invention, the hot melt adhesives have one of the above Viscosity in a range from about 120 ° C to about 150 ° C. Suitable viscosities are, for example, about 1,000 to about 15,000 mPas or about 3,000 to about 8,000 mPas.

The process according to the invention for producing at least two layers Paper composites usually include at least one process step in which Hot melt adhesive is applied to a first layer of paper and in one determined a second paper layer on the first one at a certain time and space Paper layer is laminated. So that there is sufficient liability between the first and the second layer of paper is formed, the hot melt adhesive must at the time of Laminating the second layer of paper is still sufficiently sticky, d. that is, he may not yet be physically hardened. The time after the order of the Hot melt adhesive in which the adhesive has sufficient tack to Laminating a second layer of paper, in the following "open time" called. “Sufficiently sticky” is understood to mean a stickiness that ver bond between the layers of paper creates a peeling force of more than 0 N / cm having.

At usual machine speeds of up to 600 m / min, for example it is generally sufficient if the hot melt adhesive has an open time of approximately  0.1 to about 1 second, for example about 0.2 to about 0.5 seconds. If the hot melt adhesive should only be used when the full one Machine speed is reached is an open time in the above The order of magnitude is usually sufficient. However, the hot melt adhesive should for example, during the start-up phase of the machine to a connection of at least two layers of paper, so the open time should be longer Include period than that specified above. Then, for example, are advantageous open times from about 1 to about 10 seconds, for example from about 2 to about 8 or about 4 to about 6 seconds.

In a preferred embodiment of the invention, the hot melt adhesive has no adhesive properties, d. that is, the surface of the hot melt adhesive no longer sticky after the end of the open time.

The melt to be used in the process according to the invention Adhesive is water-soluble so that at least an amount of about 3 % By weight completely dissolves in water. The training is called "complete loosening" a non-sticky dispersion in the subsequent recycling process, preferably but understood a molecularly disperse solution of the adhesive in water.

As already mentioned at the beginning, they serve in the context of the invention Process used hot melt adhesives, for example, to simplify the Return of already glued paper layers to the material cycle for production new layers of paper. For this, the paper days already glued are usually mixed with water, which dissolves the hot melt adhesive and at the same time further processing suitable pulp produced. This water points in the Usually a temperature of for example about 25 to about 80 ° C. In this context it can occur that certain polymers suitable as hot-melt adhesive with increased Temperature no longer have sufficient solubility in water. The Property of certain macromolecular compounds when heated The solution of the macromolecular compounds is called to precipitate out of the same  generally "upper critical solution temperature" temperature, UCST). This phenomenon usually shows up in that through the agglomeration of molecules that are no longer in solution visible turbidity is generated.

Similarly, certain macromolecular compounds can also have one "lower critical solution temperature" (LCST) demonstrate. This means that dissolved macromolecular compounds in a Reducing the temperature of the solution will fail. This will also causes the solution to become cloudy.

In the context of the present text, for better observability therefore spoken of the "cloud point", i.e. that is, from the point at which a measurable Turbidity of the aqueous solution of the hot melt adhesive can be observed. Under the “Upper cloud point” is understood to mean both the cloudiness that occurs which results from a UCST of the hot melt adhesive, under the "lower Cloud Point "is a cloud based on an LCST.

For example, if a hot melt adhesive is used, which consists of different Polymer exists, and at least one of the polymers has a UCST and at least one of the polymers has an LCST, so there is an aqueous solution of such a hot melt adhesive both causes a lower cloud point ( by the LCST) as well as an upper cloud point (caused by the UCST). The cloud points are given as the temperature at which a solution of the Hot melt adhesive shows a turbidity visible to the eye.

In a preferred embodiment, the water-soluble hot melt adhesive an upper cloud point of at least about 60 ° C at a 0.3 wt .-% Solution of the hot melt adhesive. The cloud point is preferably 60 ° C. for a 1% by weight and in particular for a 3% by weight solution.  

The lower cloud point should advantageously be less than about 20 ° C a 0.3 wt .-% solution of the hot melt adhesive. Preferably, the Cloud point at less than about 20 ° C for a 1 wt% and in particular for a 3% by weight solution. For example, the lower cloud point at about 10 ° C or below, about 5 ° C or about 3 ° C for the above Concentrations are.

In a preferred embodiment of the invention, hot melt adhesives used that are essentially infinitely miscible with water, d. that is, at a concentration of at least about 10% by weight or more, for example about 20 wt% or about 50 wt% or above, no miscibility gap exhibit.

The hot melt adhesives which can be used in the context of the present invention are in the Room temperature is generally solid and at least partially crystalline. The crystallisa degree of variation varies widely depending on the raw materials and the Crystallization conditions. For example, it is at least about 20 to about 100%, in particular at least about 30%, based on the crystallization degree, of polyethylene glycol 6,000 (measured with DSC). The melting point of the However, hot melt adhesive is at least about 60 ° C, for example about 70 to about 100 ° C, provided the required viscosity values of the Melt can be met at the processing temperature.

100% amorphous systems can also be used. Their glass over but transition temperature (Tg) should be at least about 30 ° C, preferably at least about 50 ° C.

The hot melt adhesive is usually processed by application of the Adhesive to the paper layers using conventional application methods in melted Status. Suitable application methods are, for example, the order through Rollers, slot nozzles or spray nozzles.  

If a roller is used, it can usually only be quite high Realize basis weights of adhesive. The roller application therefore serves usually a firm connection of the individual layers of paper. For the Roller application, for example, hot melt adhesives are suitable, which are around 120 to about 150 ° C a melt viscosity (Brookfield Thermosel, spindle 27) of about Have 1,000 to about 6,000, in particular about 2,000 to about 3,000 mPas. By means of roller application, for example, the production of moisturizing adhesives is possible Materials possible.

"Moisturizing sticky materials" are understood to mean materials which are caused by Humidification can be transferred into self-adhesive systems. These include in usually materials that have a layer on at least one side that is formed by Humidification made sticky with water and for example to a second one Material can be applied. After the water has evaporated, they stick Adhesive materials to each other. Examples of such materials are stamps, Envelopes, labels and the like.

If the hot melt adhesive is applied by means of a slot nozzle, then in the Usually a hot melt adhesive is used, which at about 120 to about 150 ° C. Melt viscosity (Brookfield Thermosel, spindle 27) from about 400 to about Has 20,000 mPas, in particular about 600 to about 5,000 mPas.

The application of the hot melt adhesive is preferably used to bond tissues by means of a spray nozzle, wherein no full-area application is generated. The Tissue bonding cannot be done either by atomizing or by means of perform atomizing spray nozzles, in the latter case also by Spinning spray spoken.

Atomizing spray nozzles usually require a hot melt adhesive, which about 120 to about 150 ° C a melt viscosity (Brookfield Thermosel, spindle 27) from about 400 to about 10,000, especially about 600 to about 5,000 mPas  having. Non-atomizing spray nozzles require hot melt adhesives with a slightly higher viscosity to achieve the required thread cohesion guarantee. For example, hot melt adhesives with a Melt viscosity (Brookfield Thermosel, spindle 27) from about 3,000 to about 10,000 mPas at a temperature from about 120 to about 150 ° C.

Another object of the invention is a method for manufacturing moisturizing sticky materials, where a hot melt adhesive with a solubility in water at about 20 ° C of at least about 3% by weight on a material, especially on paper. The order is made by spray or Rolling process, in particular by means of a roller.

Another object of the present invention is the use of Polyalkylene glycol with a molecular weight of at least 1000 and one Water solubility of at least 3% by weight at 20 ° C as a hot melt adhesive, in particular for the production of at least two-ply hygiene paper or moisturizing sticky materials.

Another object of the invention is the use of a nonionic polyurethane with a molecular weight (M _n ) of at least 2000 as a hot melt adhesive, in particular for the production of at least two-ply hygienic paper or moisturizing sticky materials.

The process according to the invention is explained in more detail below by examples.  

Examples Manufacture of hot melt adhesives Examples 1 to 4

97.3 parts by weight of polyethylene glycol with an OH number of 19 (PEG 6000) were dewatered for two hours at 90 ° C and a pressure of 1 mbar. After adding The reaction temperature was 2.7 parts by weight of TMXDI under nitrogen 140 ° C increased. After a reaction time of about 2 hours, the NCO value was 0%. The Substance had a melt viscosity of approximately 5,500 mPas at 150 ° C. There were 1, 01, 0.05 and 0.02% by weight of the UV-active fluorescent dye Uvitex OB, the finished hot melt adhesive mixed in the melt at 140 ° C.

Examples 5 to 11

Analogously to the procedure described in Example 1, the following were carried out Polyurethanes listed in Table 1 were prepared.

The following fluorescent dyes were used in a quantity in the hot melt adhesives of 0.05% by weight, based on the hot melt adhesive as a whole:

The above hot melt adhesives were used to make two-ply paper composites used, namely by melting the adhesive over nozzles at 150 ° C. was sprayed on.

The spray pattern was checked by taking a sample of the one with the Hot melt adhesive applied to delaminated paper composite in one darkened box was exposed to the light of a UV lamp (254 nm). The Distribution of the adhesive was assessed visually.  

Table 1

Claims (13)

1. A process for producing at least two-ply paper composites, in which a water-soluble hot melt adhesive applied to a first layer of paper and at least a second paper layer on the adhesive side of the first paper layer is laminated on, the solubility of the hot melt adhesive in water 20 ° C is at least 3% by weight and the hot melt adhesive has a UV contains active fluorescent dye in a detectable amount. 2. The method according to claim 1, characterized in that a 0.3 wt .-% Solution of the hot melt adhesive in water has an upper cloud point of has at least 60 ° C. 3. The method according to any one of claims 1 or 2, characterized in that the hot melt adhesive at a temperature of 100 to 180 ° C. Melt viscosity (Brookfield Thermosel, spindle 27) from 400 to 20,000 mPas having. 4. The method according to any one of claims 1 to 3, characterized in that the Hot melt adhesive has an open time of at least 0.2 seconds. 5. The method according to any one of claims 1 to 4, characterized in that the hot melt adhesive has a crystallinity (measured by means of DSC) of at least about 20% of the value measured for polyethylene glycol with a molecular weight (M _n ) of 6,000. 6. The method according to any one of claims 1 to 5, characterized in that a polyalkylene glycol with a molecular weight (M _n ) of 1,000 to 100,000 is used as the hot melt adhesive. 7. The method according to any one of claims 1 to 6, characterized in that at least one nonionic polyurethane with a molecular weight (M _n ) of at least 2,000 or a polyester with a molecular weight of at least about 3,000 is used as the hot melt adhesive. 8. The method according to claim 7, characterized in that the nonionic Polyurethane by reacting at least one polyisocyanate with at least a polyalkylene glycol with a molecular weight of at least 1,550 is available. 9. Use of polyalkylene glycol with a molecular weight of at least 1,000 and a water solubility of at least 3% by weight at 20 ° C as Hot melt adhesive. 10. Use of a nonionic polyurethane with a molecular weight (M _n ) of at least 2,000 as a hot melt adhesive. 11. Use according to claim 9 or 10, characterized in that the Hot melt adhesive in the manufacture of at least two layers Hygiene paper or in the manufacture of moisturizing sticky Materials is used. 12. The method according to claim 1, characterized by the concentration of the UV active fluorescent dye in a range from 0.0001 to 10, in particular 0.001 to 1.0 wt .-%, based on the hot melt adhesive all in all. 13. The method according to claim 1, characterized by at least one UV active fluorescent dye from the group of benzoxazole derivatives.