ADHESIVE COMPOUND BASED ON MODIFIED POLYETHER POLYURETHANE, SWIPABLE APPLICABLE, DIMENSIONALLY STABLE

Abstract

The present invention relates to a dimensionally stable adhesive compound formulated to be largely solvent- and water-free, which can be applied to the substrate to be bonded by sweeping it onto the substrate in the form of a thin adhesive film, particularly suitable for bonding materials made from plant fibers. The organic constituent of the adhesive compound according to the invention consists predominantly of a mixture of polyether polyurethanes end-protected with at least two monohydric aliphatic alcohols of different chain lengths. The invention also relates to a method for applying a sticky film to a planar substrate, preferably paper, by sweeping the adhesive compound onto the point of contact with the substrate.

Description

ADHESIVE COMPOUND BASED ON MODIFIED POLYETHER POLYURETHANE, SWIPABLE APPLICABLE, DIMENSIONALLY STABLE [1] The present invention relates to a dimensionally stable adhesive compound formulated to be largely solvent- and water-free, which can be applied to the substrate to be bonded by sweeping it onto the substrate in the form of a thin adhesive film, particularly suitable for bonding materials made from vegetable fibers. The organic constituent of the adhesive compound according to the invention consists predominantly of a mixture of polyether polyurethanes end-protected with at least two monohydric aliphatic alcohols of different chain lengths. The invention also relates to a method for applying a sticky film to a planar substrate, preferably paper, by sweeping the adhesive compound onto the point of contact with the substrate. [2] Dimensionally stable adhesive compounds, which are used in such a way that a thin film of the adhesive compound is transferred to the substrate by being swept over the point of contact, are known in the prior art and have long been implemented, for example, in glue sticks for bonding paper. WO 99 / 51699 A1 describes glue sticks that can be applied by gently sweeping but are dimensionally stable, consisting of an aqueous preparation of starch ethers and sucrose as the adhesive component and a soap gel as the shaping building substance and, if desired, additional auxiliaries. After a thin film has been swept over, such adhesive compounds set only through the loss of water and thus in a purely physical manner.To ensure the applicability of such an adhesive compound over a longer period, it is necessary to prevent it from drying out. This is achieved by selecting a suitable packing medium, generally impermeable to water vapor. The packing medium often also serves as an applicator, which, as a rigid structure in which the adhesive compound is filled, is also dimensionally stabilizing, thus allowing greater freedom in the formulation of the dimensionally stable adhesive compound. DE 10047069 A1 describes such an applicator for a dimensionally stable, water-based glue stick. [3] In contrast, dimensionally stable, water-free adhesive compounds formulated for sweep application are also known. WO 96 / 37566 A1 describes dimensionally stable, semicrystalline adhesive compounds based on polyether polyurethanes, whose semicrystalline structure is broken by the heat released by friction on a substrate surface, such that MA / a / ¿U¿¿ / UU l ¿34 A thin adhesive film can be applied which, after a short time, forms semicrystalline regions again and thus sets and is able to bond the substrate. In said document, various additives that modify crystallinity or increase tackiness, or that are pigments, fillers, plasticizers, colorants, antioxidants, and preservatives, are added to such adhesive compounds to improve the property profile. In principle, the adhesive compounds disclosed in the WO publication are already suitable for being placed on the market mostly without packaging and for manual application to substrates, particularly paper, without a special applicator. [4] Such a dimensionally stable, mostly solvent- and water-free adhesive compound must, however, meet a complex set of requirements, including environmental hygiene, consumer-specific, and application-specific aspects. To this end, the property profile of friction-activated, dimensionally stable adhesive compounds must be further improved to enable the establishment of packaging-free sales units in the consumer market. In this context, it is important to find formulations that can be easily swept onto flat substrates as a sticky film, that have sufficient initial tack to allow the flat substrates to be fixed in their relative positions by the adhesive film, and that cure quickly in a precisely positioned manner, forming a cohesive bond that is as durable as possible.Ideally, the adhesive compound is suitable for bonding materials made from plant fibers. This property profile is also intended to be maintained even after the adhesive compound is stored in a manner that is common in the trade and typical for use. [5] From the consumer's perspective, a dimensionally stable adhesive compound that can be swept directly onto the substrate by hand without an applicator is also expected to be non-sticky, not to stain the skin, and to be skin-compatible. The consumer also expects that such an adhesive compound, in stick form, can be guided onto the substrate like a wax crayon during use, and that a continuous adhesive film can be applied in the process. Sweeping the adhesive compound onto a flat substrate should be possible with minimal effort, so that thin, flexible substrates, such as paper, do not warp or tear when the adhesive is applied. [6] In general, the present invention thus addresses the problem of providing a dimensionally stable, sweepable adhesive compound that can be formulated to be solvent-free, water-free, and skin-friendly, and ML / a / ZUZZ / UU l ZO4 should be easily applied without a separate applicator and, for this particular purpose, should have low sweep resistance. This means the adhesive compound should not be permanently tacky at 30°C and should ideally be translucent. Thermal stability up to 70°C is also required for storage and transport. Above all, the adhesive compound should have high bond strength for materials made from plant fibers, particularly paper and cardboard. Furthermore, a sweepable adhesive film should generate sufficient initial adhesion so that the user does not need to press the substrates to be bonded together until they set to achieve proper adhesion. [7] This range of problems is surprisingly solved by formulating an adhesive compound whose organic constituent consists predominantly of a mixture of polyether polyurethanes that are protected at the ends with two different monohydric aliphatic alcohols of different chain lengths. [8] The present invention consequently relates to a dimensionally stable adhesive compound whose organic constituent consists predominantly of a mixture of polyether polyurethanes that are end-protected with two different monohydric aliphatic alcohols, one of the at least two different monohydric aliphatic alcohols being selected from those having at least 4 but not more than 8 carbon atoms and the other of the at least two different monohydric aliphatic alcohols being selected from those having at least 16 but less than 22 carbon atoms. [9] The organic constituent of the adhesive compound according to the invention particularly preferably consists predominantly of a mixture of polyether polyurethanes, each of which is protected at the ends with the two different monohydric aliphatic alcohols mentioned above.

[10] With regard to the adhesive compound according to the invention, an organic compound or a constituent of an organic compound is considered to be aliphatic if said organic compound or constituent is, in addition to oxygen atoms, composed exclusively of carbon and hydrogen atoms.

[11] According to the invention, the polyether polyurethane blend, which is the essential constituent of the adhesive compound, is protected at the ends with primary monohydric aliphatic alcohols, which in turn are preferably linear, i.e., they have neither tertiary nor quaternary carbon atoms. A carbon atom is quaternary when it is covalently bonded to four additional carbon atoms, while a tertiary carbon atom is covalently bonded to three other carbon atoms.

[12] According to the invention, polyether polyurethanes are addition products of polyfunctional isocyanates with polyether polyols, the molar ratio of isocyanate groups to hydroxyl groups of the polyether polyols being greater than 1.0, preferably greater than 2.0, particularly preferably greater than 2.5, but preferably less than 4.0, particularly preferably less than 3.5, and the addition product is end-protected and thus has no free isocyanate group. Within the meaning of the present invention, a polyether polyurethane contains no free isocyanate group if it contains less than 0.1% NCO, based on the total amount of polyether polyurethane. To determine the amount of free isocyanate groups, 4 milliliters of a 0.1% dibutylamine solution were added.5 M xylene is added to 1 gram of polyether polyurethane, and the mixture is then combined with 50 milliliters of xylene and stirred at 20 °C until completely homogenized. After adding 3 drops of bromophenol blue and 50 milliliters of isopropanol, the titration is carried out with 0.5 M hydrochloric acid until the color changes from blue to yellow. The difference in hydrochloric acid consumption for the titration of a blank solution (i.e., without the addition of polyether polyurethane), multiplied by the value 2.1 and divided by the exact weight of the polyether polyurethane, gives the weight percent. MA / a / 4U44 / UU 1444 of the isocyanate groups.

[13] In a preferred embodiment for increasing the semicrystalline organic constituents of the adhesive compound, the polyether polyols that form the basis of the polyether polyurethanes are selected from those whose ether functional groups are linked together by aliphatic divalent groups, which in turn are preferably linear and unbranched, i.e., having neither tertiary nor quaternary carbon atoms. The divalent groups in turn preferably have at least 4 carbon atoms but preferably no more than 8 carbon atoms, particularly preferably no more than 6 carbon atoms, in the main chain, and most particularly preferably have 4 carbon atoms in the main chain. Adhesive compounds of this type are distinguished by very good thermal stability along with good sweeping properties.

[14] It is also preferred that the polyether polyols forming the basis of the polyether polyurethane blend of the adhesive compound according to the invention have a hydroxyl index of less than 200 mg KOH / g, particularly preferably less than 120 mg KOH / g, but preferably at least 30 mg KOH / g, particularly preferably at least 40 mg KOH / g, in each case based on the totality of the polyether polyols forming the basis for the polyether polyurethane blend.

[15] The hydroxyl number is a measure of the number of free hydroxyl groups in the relevant defined reference quantity, for example, per gram of the polyether polyols that make up the polyether polyurethane blend, and can be determined experimentally by potentiometric titration. For this purpose, a weighed sample of the reference quantity is heated in a reaction solution of 0.1 mol / L phthalic anhydride in pyridine at 130 °C for 45 minutes, and mixed with 1.5 times the volume of the pyridine reaction solution, and then mixed with 1.5 times the volume of deionized water (κ < 1 pScm-1) reaction solution. The amount of phthalic acid released is titrated in this mixture using 1 M sodium hydroxide solution. The potentiometric measurement is carried out using a combination electrode (LL-Solvotrode® from Methrom; reference electrolyte: 0.4 mol / 1 of tetraethylammonium bromide in ethylene glycol).The hydroxyl index in this case corresponds to the amount of NaOH added per gram of the reference amount at the inflection point of the potentiometric titration curve.

[16] To establish optimum thermal stability along with good sweeping properties when applying an adhesive film to paper, it is preferred if the molar ratio of the two different monohydric aliphatic alcohols to each other, defined ML / a / ZUZZ / UU l ¿04 as the molar amount of aliphatic alcohols having at least 4 but not more than 8 carbon atoms to the molar amount of aliphatic alcohols having at least 16 but less than 22 carbon atoms, is in the range from 1:2 to 3:1, particularly preferably in the range from 1:1 to 5:2.

[17] According to the invention, the polyether polyurethane blend is preferably obtained by adding at least trifunctional isocyanates, particularly preferably aliphatic, which are very preferably selected from trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate, to polyether polyols. As already explained, the free isocyanate groups formed in the addition reaction are reacted with the two monohydric aliphatic alcohols (hereafter end protection), one of the two monohydric aliphatic alcohols being selected from those having at least 4 but not more than 8 carbon atoms and the other of the two monohydric aliphatic alcohols being selected from those having at least 16 but less than 22 carbon atoms.

[18] Polyether polyurethanes having a dynamic Brookfield viscosity (spindle 27) at 80 °C of at least 2,000 mPas, particularly preferably at least 3,000 mPas, more particularly preferably at least 5,000 mPas, but preferably less, are also preferably used. ML / a / ZUZZ / UU l ¿34 of 140,000 mPas, particularly preferably less than 60,000 mPas. Polyether polyurethanes having a dynamic viscosity in the lower preferred range are usually achieved by end protection carried out predominantly with a long-chain monohydric aliphatic alcohol having a higher number of carbon atoms, or by an addition of divalent isocyanates to semicrystalline polyether polyols carried out at least in part.

[19] The polyether polyurethane mixture in the adhesive compound according to the invention preferably has a number-average molar mass of less than 6,000 g / mol, particularly preferably less than 5,000 g / mol, but preferably at least 1,000 g / mol, particularly preferably at least 2,000 g / mol, and a polydispersity that is preferably greater than 4.0, but preferably less than 20.0, particularly preferably less than 15.0. Within this molar mass range and with the preferred polydispersity, polyether polyurethanes can be obtained that allow the adhesive compounds according to the invention, consisting of more than 40% by weight of such polyether polyurethanes, to be easily swept on and that give such compounds good tackiness along with sufficient thermal stability.The number average molar mass can be determined using a sample of the reaction mixture, by gel permeation chromatography after calibration against standards. ML / a / ZUZZ / UU l ZÚ4 polystyrene. For this purpose, at a column oven temperature of 40 °C, chromatography is carried out by elution with tetrahydrofuran, with the distribution curve being recorded by means of a concentration-dependent RI detector that continuously determines the refractive index in the eluate at a temperature of also 40 °C.

[20] For the purposes of the present invention, it is preferred that the polyether polyurethane constituent of the adhesive compound consists predominantly of the above-described mixture of polyether polyurethanes. Correspondingly, adhesive compounds according to the invention are preferred in which the proportion of the polyether polyurethane mixture, end-protected with the two different monohydric aliphatic alcohols, based on the total polyether polyurethanes, is at least 80% by weight, preferably at least 90% by weight, and particularly preferably at least 95% by weight.

[21] The organic constituent of the adhesive compound according to the invention then consists predominantly of a mixture of polyether polyurethanes if its proportion is greater than 40% by weight, based on the organic constituent of the adhesive compound. The adhesive compounds usually exhibit particularly good thermal stability along with good sweeping behavior when the proportion of polyether polyurethanes, as described above, based on the organic constituent of the adhesive compound, is greater than 50% by weight, preferably greater than 70% by weight, or even more preferably greater than 80% by weight, so that such adhesive compounds are preferred according to the invention. Higher proportions of polyether polyurethanes in the mixture are also particularly advantageous for the translucency of the adhesive compound according to the invention, which consumers find particularly attractive.

[22] Due to the excellent sweeping behavior, along with the thermal stability and good setting behavior imparted to the adhesive compound according to the invention by the blending of the polyether polyurethanes, the extensive addition of additives can be largely dispensed with. However, the thermal stability can be further increased and the sweeping behavior can be further improved without having to accept significant losses in terms of the initial tack of the sweep-applied film.For this purpose, polyester polyurethanes can be treated with additives, at least some of which polyester polyurethanes are preferably based on semicrystalline polyester polyols, which in turn can be obtained by the polycondensation of a reaction mixture comprising one or more dicarboxylic acids selected from terminal dicarboxylic acids that are both linear saturated and aliphatic and have an even number of at least 8 methylene groups (hereafter, component A), and one or more diols selected from terminal diols that are both linear saturated and aliphatic and contain at least one ether function (hereafter, component B).

[23] With regard to semicrystalline polyester polyols, a dicarboxylic acid or diol is considered aliphatic if, in addition to oxygen atoms, it is composed exclusively of carbon and hydrogen atoms. The term dicarboxylic acid also includes the corresponding single or double methyl and / or ethyl esters, as well as the corresponding single or double acid chlorides. In this context, it also applies that, in the case of a terminal dicarboxylic acid or a terminal diol, the two carboxyl and hydroxyl groups, respectively, are at the end.

[24] The optionally contained polyester polyurethanes according to the invention based on semicrystalline polyester polypoles have crystalline phases below their ring and ball softening point, measured in accordance with DIN EN 1238:2011, whose phases can be detected by differential scanning calorimetry (DSC) at a heating rate of no more than 10 Kelvin per minute (10 °C per minute) as an endothermic melt peak before the softening point is reached.

[25] In one particular embodiment, polyester polyurethanes are incorporated that are based on semicrystalline polyester polyols that recrystallize upon melting and that can be obtained by polycondensation of a reaction mixture comprising one or more dicarboxylic acids and one or more diols, a) at least 50 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol%, of the dicarboxylic acids selected from terminal dicarboxylic acids having an even number of at least 8 methylene groups that are both linear saturated and aliphatic (hereafter referred to as component A); and b) at least 40 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol%, of the diols are selected from terminal diols that are both saturated linear and aliphatic and have at least one ether function (hereafter referred to as component B).

[26] Such semicrystalline polyester polyols that recrystallize during melting are distinguished by the fact that exothermic recrystallization occurs during the endothermic melting process before the softening point is reached, i.e., before the transition to the liquid phase. Thus, an exothermic crystallization peak superimposed on the endothermic melting peak can also be detected by differential scanning calorimetry (DSC) at a heating rate of no more than 10 Kelvin per minute (10 °C per minute) before the softening point is reached. Semicrystalline polyester polyols MA / a / ¿U¿¿ / UU l ¿04 corresponding recrystallizing upon melting are described in detail in WO 2019 / 011529 A1. In the context of the present invention, polyester polyurethanes produced based on these semicrystalline polyester polyols that recrystallize upon melting, as a constituent of the adhesive compound according to the invention, impart improved sweeping behavior along with high thermal stability and initial adhesion.

[27] The preferred representatives of dicarboxylic acids according to component A are therefore 1,1O-decamethylenedicarboxylic acid, 1,12-dodecamethylenedicarboxylic acid, 1,14-tetradecamethylenedicarboxylic acid and 1,16-hexadecamethylenedicarboxylic acid.

[28] To improve the stickiness of the adhesive compound, it may be advantageous if those polyester polyurethanes based on polyester polyols obtained from the polycondensation of aromatic dicarboxylic acids or unsaturated dicarboxylic acids having less than 9 carbon atoms with aliphatic diols, preferably having at least one ether function, but not having a tertiary or quaternary carbon atom, are additionally contained. Isophthalic acid, terephthalic acid, orthophthalic acid, and furandicarboxylic acid, in particular 2,5-furandicarboxylic acid, may be mentioned in particular as aromatic dicarboxylic acids, and itaconic acid, fumaric acid and / or maleic acid, which may also be contained in the adhesive compound as a constituent of polyester polyol of polyester polyurethanes, may be mentioned as unsaturated dicarboxylic acids having less than 9 carbon atoms.

[29] Semicrystalline polyester polyols having an acid value preferably less than 50 mg KOH / g, particularly preferably less than 10 mg KOH / g, more particularly preferably less than 5 mg KOH / g and very particularly preferably less than 2 mg KOH / g, in each case per gram of the reaction mixture comprising components A and B and obtainable from a reaction mixture of components A and B, the diols being contained in molar excess on the basis of the dicarboxylic acids, but not above a molar excess of 1.2:1, have proven, as starting materials for the polyester polyurethanes described above, to be ideal in terms of the recrystallization behavior of the polyester polyurethanes optionally contained in the adhesive compound according to the invention.

[30] The acid number, according to the invention, is an experimentally determinable variable that is a measure of the number of free acid groups in the relevant defined reference quantity, for example, per gram of the reaction mixture. The acid number is determined by dissolving a weighed sample of the reference quantity in a solvent mixture of methanol and distilled water in a 3:1 volume ratio, and then potentiometrically titrating said sample with 0.05 mol / L of KOH in methanol. The potentiometric measurement is carried out using a combination electrode (Methrom LL-Solvotrode®; reference electrolyte: 0.4 mol / L of tetraethylammonium bromide in ethylene glycol). The acid number in this case corresponds to the amount of KOH added per gram of the reference quantity at the inflection point of the potentiometric titration curve.

[31] For the provision of the optionally contained polyester polyurethanes in the adhesive compound according to the invention by means of the addition of monofunctional or polyfunctional isocyanates to such semicrystalline polyester polyols, it is preferred if the hydroxyl number of the polyester polyols is at least 30 mg / g of KOH, particularly preferably at least 60 mg / g of KOH, more particularly preferably at least 80 mg / g of KOH, but preferably has a hydroxyl number below 200 mg / g of KOH, particularly preferably below 140 mg / g of KOH, more particularly preferably below 120 mg / g of KOH, in each case per gram of the reaction mixture comprising components A and B.

[32] The polyester polyurethanes of the adhesive compound according to the invention, optionally contained in an adhesive compound according to the invention, are addition products of monofunctional or polyfunctional isocyanates with polyester polyols. The addition product is end-protected and thus has no free isocyanate groups. It is preferred according to the invention if the addition is carried out such that the molar ratio of isocyanate groups to hydroxyl groups of the polyester polyol is greater than 2, preferably greater than 2.5, but preferably less than 4, particularly preferably less than 3.5. The end protection is preferably carried out with monohydric alcohols. Within the meaning of the present invention, a polyester polyurethane contains no free isocyanate groups if it contains less than 0.1 wt% of NCO, based on the total amount of polyester polyurethanes.To determine the proportion of free isocyanate groups, 4 milliliters of a 0.5 M dibutylamine solution in xylene are added to approximately 1 gram of the polyurethane polyester and then mixed with 50 milliliters of xylene and stirred at 20 °C until thoroughly homogenized. After adding 3 drops of bromophenol blue and 50 milliliters of isopropanol, titration is carried out with 0.5 M hydrochloric acid until the color changes from blue to yellow. The difference in hydrochloric acid consumption for the titration of a blank solution (i.e., without the addition of the polyurethane polyester) multiplied by the value 2.1 and divided by the exact weight of the polyurethane polyester gives the weight percent of the isocyanate groups.

[33] According to the invention, the polyester polyurethanes are preferably obtained by adding at least trifunctional isocyanates, particularly preferably aliphatic, which are very preferably selected from trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate, to polyester polyols, preferably to semicrystalline polyester polyols, with free isocyanate groups formed in the addition reaction which are preferably reacted with at least one monohydric alcohol, particularly preferably with at least one aliphatic alcohol, more particularly preferably with at least one linear aliphatic alcohol, each of which preferably has no more than 24 carbon atoms in the main chain, but preferably has at least 4 carbon atoms in the main chain.

[34] The proportion of polyester polyurethanes based on the organic constituent of the adhesive compound in a preferred adhesive compound according to the invention is not greater than 50% by weight, particularly preferably not greater than 30% by weight, more particularly preferably not greater than 20% by weight, very particularly preferably not greater than 15% by weight, but preferably at least 2% by weight, ML / a / ZUZZ / UU l particularly preferably at least 5% by weight, in order to optimize paper sweep performance and thermal stability.

[35] The following are additional additives and their relevant functionality that can be advantageously added to the adhesive compound according to the invention in order to provide adhesive compounds that meet specific requirement profiles, as further set out below. One advantage of the adhesive compounds according to the invention is consequently that it is easy to add additives to the adhesive compound, which consists predominantly of a polyether polyurethane mixture.

[36] To increase the initial tack of a sweep-applied film of the adhesive compound, it may be advantageous, for example, to have the adhesive compound according to the invention additionally contain up to 5% by weight of tackifying agents other than polyether polyurethanes or polyester polyurethanes. For a significant increase in initial adhesion, a proportion of at least 1% by weight of tackifying agents, based on the adhesive compound, is preferred. Such tackifying agents are organic compounds that preferably have a sum of hydroxyl and acid values ​​above 100 mg of KOH per gram of the relevant organic compound. The tackifying agents are preferably resins, preferably, due to their sustainable availability and generally harmless nature with respect to environmental hygiene, natural resins that can be chemically modified.According to the invention, a natural resin as defined by DIN 55958 comprises excretions secreted by animals and plants. Resins of this type are known to a person skilled in the art, for example, as turpentine, balsam, gum lake, rosin, sandarac, or mastic. According to the invention, natural resins also include modified natural resins obtained from natural resins, for example, by hydrogenation, intrinsic addition reactions, or esterification. The natural resins as component a) of the adhesive compound according to the invention are in turn preferably selected from resin acids and / or resin esters, particularly preferably from resin acids and / or resin esters based on diterpenes and / or triterpenes, which are preferably hydrogenated and / or present as intrinsic addition products.According to the invention, the term resin ester describes resin acids that have been modified once or several times by means of the carboxyl groups of the resin acids in condensation reactions with the formation of ester groups. The preferred representatives of diterpene-based resin acids and / or resin esters are consequently abietic acid, neoabietic acid, levopimaric acid, and other acids. MA / a / ¿U¿¿ / UU l ¿34 Pimaric acid, palustric acid, agatenic acid, yluric acid, and podocarpic acid, and the triterpene-based resin acids are elemic acid, sumaresinoleic acid, and their monoesters or polyesters, which preferably have in each case no more than 6 carbon atoms in the alkyl group of the ester group. The use of tackifying agents gives the adhesive compound, after it has been swept in the form of a thin film onto a paper surface, increased initial adhesion, which, for example, when gluing opposite sides of a paper fold, ensures that the paper surfaces joined by the adhesive film remain connected without exerting contact pressure until the glue has set.

[37] Small amounts of polyolefin waxes can also have a positive effect on the initial adhesion of the adhesive compound due to their mostly non-polar nature. Furthermore, polyolefin waxes result in improved long-term bond stability, so that preferably up to 20% by weight, particularly preferably up to 10% by weight, in each case based on the adhesive compound, of polyolefin waxes may be contained according to the invention, with a proportion of at least 1% by weight, particularly at least 2% by weight, in each case based on the adhesive compound, being preferred for a significant effect.In a preferred embodiment of an adhesive compound according to the invention, further comprising polyolefin waxes, these waxes are selected from copolymer waxes composed of propylene and ethylene and / or at least one branched or unbranched 1-alkene having 4 to 20 carbon atoms, and may be further modified with carboxyl groups for improved compatibility with the adhesive compound. The acid value is preferably below 20 mg of KOH per gram of the polyolefin wax. It is also advantageous if the additive-treated polyolefin wax is amorphous and therefore has no crystallinity in the range from 20 °C to the softening point.In addition to the initial adhesion, the polyolefin waxes also increase the elasticity of the adhesive compound, so that, for example, glue sticks based on an adhesive compound correspondingly treated with additives according to the invention can be provided that are less susceptible to breakage, which is particularly advantageous in the case of packaging-free delivery and application forms of the adhesive compound according to the invention.

[38] For adhesive compounds according to the invention whose tackiness is perceived as too unpleasant when the adhesive compound is applied without packing and an adhesive film is applied by hand sweeping, the addition of pyrogenic silicic acids up to an amount of 15% by weight, based on the adhesive compound, may be suitable, while maintaining the other ML / a / ZUZZ / UU l ZÚ4 parameters such as initial adhesion, sweepability and setting behavior, to reduce the stickiness of the dimensionally stable delivery form, with at least 1% by weight of pyrogenic silicic acid preferably needing to be treated with additives for a noticeable reduction in stickiness.

[39] In order to improve the sweepability of the adhesive compound on a flat substrate, it may also be advantageous for the adhesive compound to additionally contain up to 5 wt% of nonionic surfactants, preferably having an HLB value in the range of 12–18, and selected particularly preferably from polyalkoxylated C12–C22 fatty alcohols, most preferably from polyethoxylated C12–C22 fatty alcohols having preferably more than 20 EO units. For a significant improvement in sweepability, a proportion of at least 0.5 wt% of nonionic surfactants, based on the adhesive compound, is preferred.

[40] The adhesive compound according to the invention is distinguished in that it can be formulated to be solvent-free and water-free, and the bonded connection, due to the setting of the adhesive compound, does not require any physical loss of solvent or water. In a preferred embodiment, the adhesive compound according to the invention therefore contains less than 5% by weight, preferably less than 1% by weight, of MA / a / ¿U¿¿ / UU l ¿04 water, based on the adhesive compound. The proportion of water in the adhesive compound can be determined by the Karl Fischer method in the solvent xylene. Such virtually water-free adhesive compound formulations according to the invention have the advantage that after an adhesive film has been swept onto a flat, thin substrate of a water-absorbent material, for example, paper, said material does not deform and retains its flat shape even after said adhesive compound has set. In a further preferred embodiment, the adhesive compound according to the invention contains less than 5% by weight, particularly preferably less than 1% by weight, based in each case on the adhesive compound, of organic compounds having a boiling point below 100 °C at 1013 mbar (101.3 kPa).

[41] For the sweeping properties and the breaking strength of the adhesive compound according to the invention, it is generally preferred if the proportion of organic constituents is at least 70% by weight, preferably at least 80% by weight, based on the adhesive compound.

[42] In a particularly preferred embodiment, the adhesive compound according to the invention contains: a) at least 40% by weight, preferably at least 60% by weight, particularly preferably at least 80% by weight, of a mixture of polyether polyurethanes protected at the ends with two different monohydric aliphatic alcohols, one of the two different monohydric aliphatic alcohols being selected from those having at least 4 but not more than 8 carbon atoms and the other of the two different monohydric aliphatic alcohols being selected from those having at least 16 but less than 22 carbon atoms; b) up to 50% by weight, preferably 5 to 30% by weight, of polyester polyurethanes; c) up to 20% by weight, preferably 1 to 10% by weight, of polyolefin waxes; d) up to 5% by weight of tackifying agents; and e) up to 5% by weight of polyalkoxylated C12-C22 fatty alcohols, in each case on an organic constituent basis, the proportion of organic constituents not exceeding at least 80% by weight on an adhesive compound basis, and the proportion of inorganic constituents selected from pigments, fillers and salts not exceeding 20% ​​by weight, preferably 15% by weight, on an adhesive compound basis, and containing less than 5% by weight, preferably less than 1% by weight, on an adhesive compound basis, of water.

[43] In relation to this particularly preferred modality, the specific configurations of the components ML / a / ZUZZ / UU l ¿34 a) ae) and additional additives listed above apply analogously.

[44] According to the invention, the inorganic constituent corresponds to the solids content of the adhesive compound remaining after pyrolysis in a reaction furnace with the supply of a CO2-free oxygen stream at 900 °C without the addition of catalysts or other additives, with the pyrolysis being carried out until an infrared sensor provides a signal identical to that of the CO2-free carrier gas (blank value) at the outlet of the reaction furnace. Correspondingly, the organic constituent of the adhesive compound is the adhesive compound less the amount of water determined by the Karl Fischer method in the solvent xylene and less the inorganic constituent as defined above.

[45] In the context of the present invention, an adhesive compound is dimensionally stable in principle when a mass of the preparation (10 grams) shaped to form a cylinder with a base of 2 cm² is irreversibly deformed when a constantly increasing force acts on said mass perpendicular to the base of the cylinder at 30 °C and 50% relative humidity, only above a pressure of 20 N / cm². The action of the force and the determination of the occurrence of deformation can be monitored by means of a force-measuring device. MA / a / ¿U¿¿ / UU l ¿04 for example, by means of the TA-XT HiR Texture Analyzer (Stable Micro Systems Ltd.). The concept of dimensional stability is closely related to the required thermal stability of the adhesive compounds according to the invention, specifically such that adhesive compounds with a ring and ball softening point measured according to DIN EN ISO 4 62 5-1:2 00 6-04 of preferably at least 40 °C, particularly preferably at least 60 °C, but preferably less than 150 °C, particularly preferably less than 100 °C, are considered to be thermoset to the point that dimensionally stable adhesive compounds can be provided at 30 °C.Ideally, at least 80% by weight of the organic constituents of the adhesive compound according to the invention have a ring and ball softening point, measured according to DIN EN ISO 4625-1:2006-04, of preferably at least 40 °C, particularly preferably at least 60 °C, in order to provide an adhesive compound that is as dimensionally stable and thermostable as possible.

[46] The dimensionally stable adhesive compound provided according to the present invention has low tack at 30°C and can be easily swept onto substrates. The material transfer caused by sweeping occurs in such a way that a thin, sticky film of the adhesive compound results on flat substrates, whose ML / a / ZUZZ / UU l ¿04 film sets after a short time so that the substrates can be bonded together with sufficient adhesion to the adhesive compound.

[47] In a further aspect, the present invention relates to a method for applying a sticky film to a planar substrate, preferably paper, by pressing a dimensionally stable adhesive compound according to the invention onto the planar substrate and subsequently changing its relative position while maintaining contact pressure perpendicular to the normal surface of the substrate. Suitable substrates are preferably obtained from vegetable fibers, are planar and flexible, particularly paper. Practical examples

[48] ​​In the following, the preparation of polyether polyurethane mixtures is first outlined, which as such were cast to form dimensionally stable, cylindrical adhesive compounds, according to the invention and were characterized with respect to sweeping behavior and paper bonding.

[49] First, 150 g of polytetrahydrofuran (PolyTHF 1000, BASF SE) were weighed into a three-necked flask and stirred for approximately 90 minutes at 80 °C and 30 mbar (3 kPa) under vacuum. 173.4 g of Desmodur® N3300 isocyanate trimer (Covestro AG) were then added to ensure an NCO / OH ratio of 3.0. The reaction mixture was heated to MA / a / ¿U¿¿ / UU l ¿04 80-100 °C and was stirred for approximately 30-45 minutes. Then, 53.4 g of n-octanol and 49.7 g of n-hexadecanol (mixture A) or 30.4 g of n-butanol (mixture B) and 49.7 g of n-hexadecanol were added for end protection and stirred for 2-3 hours at 80-120 °C before the batch was bottled.

[50] For the purpose of chromatographic characterization by gel permeation chromatography (GPC), a sample of the reaction mixture was dissolved with tetrahydrofuran and applied to the column, and subsequently eluted with tetrahydrofuran. Gel permeation chromatography (GPC) with an RI detector, after calibration using polystyrene standards, was performed at a column oven temperature of 40 °C and a detector temperature also of 40 °C. The number-average and relative weight-average molar mass values ​​were determined from the molar mass distribution curve, and the polydispersity was determined from the same. Polyether polyurethane mixture A had a number average molar mass of approximately 3,800 g / mol with a polydispersity of 5.2, while for mixture B a polydispersity of 7.0 and a number average molar mass of approximately 4,250 g / mol were determined.

[51] Polyester polyurethane blends A and B were melted at 110 °C and cast into a cylindrical rod shape MA / a / ¿U¿¿ / UU l ¿04 (diameter 2 cm, length 6-8 cm) and were stored for 24 hours at 20 °C before the handling behavior of the stick-shaped adhesive compounds and the property of the sweep-applied adhesive film were determined.

[52] The sweep, determined after the 10° incision of the cylindrical stick and the sweep by means of the cut surface on paper with a basis weight of 80 g / m2 and a contact pressure of 5 N / cm2, received the value 4 for mixture A and the value 3 for mixture B (scale from 1: rigid, sweep comparable to an eraser, to 5: like the original Pritt® stick from Henkel AG & Co. KGaA)

[53] Paper tearing, determined after gluing a sheet of paper with a basis weight of 80 g / m2, which was provided with an adhesive film according to the sweep test and then folded to stick and separated again after 1 hour at 20 °C, received the value 5 (1: no paper tearing, 2: less than 30%, 3: less than 60%, 4: less than 90%, 5: more than 90% of the glued area shows paper tearing) for both mixtures.

[54] The softening point of the adhesive compound or of polyether polyurethane blends A and B, measured using the ring and ball method in accordance with DIN EN ISO 46251:2006-04, was 64 °C (blend A) and 63 °C (blend B). The adhesive compounds were thus sufficiently thermostable to be offered free of packing.

Claims

CLAIMS 1. A dimensionally stable adhesive compound whose organic constituent consists predominantly of a mixture of polyether polyurethanes end-protected with two different monohydric aliphatic alcohols, wherein one of the two different monohydric aliphatic alcohols is selected from those having at least 4 but not more than 8 carbon atoms and the other of the two different monohydric aliphatic alcohols is selected from those having at least 16 but less than 22 carbon atoms.

2. The adhesive compound according to claim 1, characterized in that the polyether polyurethane mixture is protected at the ends with two different primary monohydric aliphatic alcohols, which are preferably linear.

3. The adhesive compound according to one or both of the preceding claims, characterized in that the polyether polyurethanes are based on polyether polyols whose ether functional groups are linked together by means of aliphatic divalent groups, which are preferably linear and unbranched, the divalent groups preferably having at least 4 carbon atoms but preferably not more than 8 carbon atoms in the main chain, and particularly preferably having 4 carbon atoms.

4. The adhesive compound according to claim 3, characterized in that the polyether polyols have a hydroxyl index of less than 200 mg KOH / g, preferably less than 120 mg KOH / g, but more preferably at least 30 mg KOH / g, particularly preferably at least 40 mg KOH / g, in each case based on the totality of the polyether polyols that are a constituent of the polyether polyurethanes.

5. The adhesive compound according to one or more of the preceding claims, characterized in that the molar ratio of the two different monohydric aliphatic alcohols to each other, defined as the molar amount of aliphatic alcohols having at least 4 but not more than 8 carbon atoms to the molar amount of aliphatic alcohols having at least 16 but less than 22 carbon atoms, is in the range from 1:2 to 3:1, preferably in the range from 1:1 to 5:

2.

6. The adhesive compound according to one or more of the preceding claims, characterized in that the polyether polyurethanes can be obtained by adding at least trifunctional isocyanates to polyether polyols and by end protection with the two monohydric aliphatic alcohols, the at least trifunctional isocyanates preferably being aliphatic and particularly preferably selected from trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate.

7. The adhesive compound according to one or more of the preceding claims, characterized in that the polyether polyurethane mixture has a dynamic Brookfield viscosity (spindle 27) at 80 °C of at least 2,000 mPas, preferably at least 3,000 mPas, particularly preferably at least 5,000 mPas, but preferably less than 140,000 mPas, particularly preferably less than 60,000 mPas.

8. The adhesive compound according to one or more of the preceding claims, characterized in that the proportion of the polyether polyurethane mixture that is protected at the ends with the two different monohydric aliphatic alcohols, based on the total polyether polyurethanes, is at least 80% by weight, preferably at least 90% by weight, particularly preferably at least 95% by weight.

9. The adhesive compound according to one or more of the preceding claims, characterized in that the proportion of the polyether polyurethane mixture that is protected at the ends with the two different monohydric aliphatic alcohols, based on the organic constituent of the adhesive compound, is greater than 50% by weight, preferably greater than 70% by weight, particularly preferably greater than 80% by weight.

10. The adhesive compound according to one or more of the preceding claims, characterized in that it additionally contains polyester polyurethanes, which are preferably based on semicrystalline polyester polyols, which in turn can preferably be obtained by the polycondensation of a reaction mixture comprising one or more dicarboxylic acids selected from terminal dicarboxylic acids that are both linear saturated and aliphatic and have an even number of at least 8 methylene groups, and one or more diols selected from terminal diols that are both linear saturated and aliphatic and contain at least one ether function.

11. The adhesive compound according to claim 10, characterized in that the polyester polyurethanes can be obtained by adding at least trifunctional isocyanates to polyester polyols, preferably to semicrystalline polyester polyols, and then protecting at the ends with at least one monohydric alcohol, preferably with at least one aliphatic alcohol, particularly preferably with at least one linear aliphatic alcohol, each of which preferably has no more than 24 carbon atoms in the main chain, but preferably has at least 4 carbon atoms in the main chain.

12. The adhesive compound according to one or more of the preceding claims, characterized in that the proportion of organic constituents is at least 70% by weight, preferably at least 80% by weight, based on the adhesive compound.

13. The adhesive compound according to one or more of the preceding claims, characterized in that it contains less than 5% by weight, preferably less than 1% by weight, of water.

14. The adhesive compound according to one or more of the preceding claims, comprising: a) at least 40% by weight of a mixture of polyether polyurethanes end-protected with two different monohydric aliphatic alcohols, wherein one of the two different monohydric aliphatic alcohols is selected from those having at least 4 but not more than 8 carbon atoms and the other of the two different monohydric aliphatic alcohols is selected from those having at least 16 but less than 22 carbon atoms; b) up to 50% by weight, preferably 5 to 30% by weight, of polyester polyurethanes; c) up to 20% by weight, preferably 1 to 10% by weight, of polyolefin waxes; d) up to 5% by weight of tackifiers;(e) up to 5% by weight of polyalkoxylated C12-C22 fatty alcohols, in each case on an organic constituent basis, wherein the proportion of the organic constituents does not exceed at least 80% by weight on a basis of the adhesive compound, and the proportion of inorganic constituents selected from pigments, fillers and salts does not exceed 20% by weight, preferably 15% by weight, on a basis of the adhesive compound, and wherein less than 5% by weight, preferably less than 1% by weight, on a basis of the adhesive compound, is contained in water.

15. A method for applying a sticky film to a planar substrate, preferably paper, by pressing the dimensionally stable adhesive compound according to one or more of the preceding claims onto the planar substrate and subsequently changing the relative position while maintaining a contact pressure perpendicular to the normal surface of the substrate.