Dimensional stability, wipe-on, semi-crystalline polyester-based adhesive compound

Abstract

The present invention relates to a dimensionally stable adhesive compound that is formulated to be largely water- and solvent-free and that can be wiped on in the form of a thin adhesive film to contact the substrate to be bonded, and is particularly suitable for adhesive materials obtained from plant fibers. The organic component of the adhesive compound according to the invention is based on a polyester polyurethane, at least a portion of which is based on a semicrystalline polyester polyol. The present invention also relates to a method for applying a tacky film to a flat substrate, preferably paper, by wiping the adhesive compound onto the point of contact with the substrate.

Description

Technical Field

[0001] The present invention relates to a dimensionally stable adhesive compound that is formulated to be mostly water and solvent-free and can be brought into contact with a substrate that is joined by being wiped on (folded, wiped on) in the form of a thin adhesive film, and is particularly suitable for adhesive materials obtained from plant fibers. The organic component of the adhesive compound according to the present invention mainly consists of a polyester polyurethane based on at least a partially semi-crystalline polyester polyol. The present invention also relates to a method of applying an adhesive film to a flat substrate, preferably paper, by wiping the adhesive compound at the point of contact with the substrate.

Background Art

[0002] Dimensionally stable adhesive compounds that are used such that a thin film of the adhesive compound is wiped on at the point of contact and transferred to the substrate are known in the prior art and have been practiced for a long time, for example, in adhesive paper glue sticks. WO99 / 51699A1 describes a glue stick consisting of an aqueous preparation of starch ether and sucrose as an adhesive component, and a soap gel as a shaping builder substance, and optionally further auxiliaries, which can be wiped on smoothly but is dimensionally stable. After the thin film is wiped on, such an adhesive compound cures only by loss of water, thus purely by a physical method. In order to ensure the long-term applicability (coating property) of such an adhesive compound, it is necessary to prevent the adhesive compound from drying, which is made possible by the selection of appropriate, mainly steam-impermeable packaging means. The packaging means is often at the same time a dimensionally stable applicator as a rigid structure filled with the adhesive compound, and as a result, there is also more freedom in the preparation of dimensionally stable adhesive compounds. DE10047069A1 describes such an applicator for water-based dimensionally stable glue sticks.

[0003] In contrast, dimensionally stable adhesive compounds that do not contain water are also known and are formulated to be similarly wipe-on. WO96 / 37566A1 describes semi-crystalline and dimensionally stable adhesive compounds based on polyesters and / or polyurethanes, the semi-crystalline structure of which is destroyed by the heat released by friction on the substrate surface, as a result of which a thin adhesive film can be applied. After a while, the semi-crystalline regions are formed again, and in this way the substrates can be set and bonded. In said document, various additives that change the crystallinity or increase the tackiness, or are pigments, fillers, plasticizers, dyes, antioxidants and preservatives, are added to such adhesive compounds to improve the property profile. In principle, the adhesive compounds disclosed in WO publications are already suitable for being marketed mainly without packaging and for being applied manually to substrates, in particular paper, without a special applicator.

[0004] However, such mostly water- and solvent-free, dimensionally stable adhesive compounds need to meet a complex requirements profile that includes aspects specific to the application, the consumer, and environmental hygiene. For this purpose, the property profile of dimensionally stable adhesive compounds that can be activated by friction has to be further improved in order to enable the establishment of sales units without packaging in the consumer market. In this context, it is important to find a preparation that can be easily wiped on in the form of an adhesive film on a flat substrate and has sufficient initial tack so that the flat substrates can be fixed in relative positions to each other via the adhesive film, and that cures in a precisely arranged manner in a short time and forms a cohesive bond that lasts as long as possible in the process. Ideally, the adhesive compound is suitable for the adhesion of materials obtained from plant fibers. This property profile is also intended to be retained even after the adhesive compound has been stored in a customary and common manner of use in trade.

[0005] On the consumer side, a dimensionally stable adhesive compound that can be wiped directly onto the substrate by hand without an applicator is expected to be non-tacky, not stain the skin with the adhesive compound, and ensure skin compatibility. Consumers also expect that such an adhesive compound in the form of a stick can be guided over the substrate like a wax crayon during use, and a continuous adhesive film can be applied in the process. The adhesive compound on a flat substrate needs to be wipe-on with little effort. This prevents flexible thin substrates such as paper from being distorted or torn when the adhesive is applied.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] Accordingly, overall, the present invention addresses the problem of providing a dimensionally stable wipe-on adhesive compound that does not contain water and solvents, can be formulated to be skin-friendly, and can be easily applied without a separate applicator. This object is particularly aimed at low wiping resistance, the adhesive compound being permanently non-tacky at 30°C, and ideally being translucent. Temperature stability up to 70°C is also required for storage and transportation. In particular, the adhesive compound is intended to have a high adhesive strength to materials obtained from plant fibers, especially paper and cardboard. Furthermore, since the adhesive film wiped on with the adhesive is intended to generate sufficient initial adhesion, the user does not need to press and adhere the substrate until it cures to achieve sufficient adhesion. [Means for solving the problem]

[0008] Surprisingly, this range of problems is solved by formulating an adhesive compound whose organic component comprises a polyester polyurethane, at least a portion of which is based on a semi-crystalline polyester polyol.

[0009] The present invention therefore relates to a dimensionally stable adhesive compound whose organic component consists mainly of a polyester polyurethane, at least in part of which is based on a semicrystalline polyester polyol. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The semi-crystalline polyester polyol referred to in the present invention is one that can be obtained by polycondensation of a reaction mixture containing one or more dicarboxylic acids selected from saturated linear, aliphatic terminal dicarboxylic acids having at least eight even-numbered methylene groups (hereinafter referred to as "Component A") and one or more diols selected from saturated linear, aliphatic terminal diols containing at least one ether functional group (hereinafter referred to as "Component B").

[0011] In the context of semi-crystalline polyester polyols, a dicarboxylic acid or diol is considered aliphatic if, apart from the oxygen atoms, it consists only 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.

[0012] Aliphatic compounds are straight-chained, containing no tertiary or quaternary carbon atoms, and are quaternary if one carbon atom is covalently bonded to four other carbon atoms, and tertiary if a carbon atom is covalently bonded to three other carbon atoms.

[0013] The polyester polyurethane necessarily included according to the invention based on a semi-crystalline polyester polyol has a crystalline phase lower than its Vicat softening point measured according to DIN EN 1238:2011, and this phase is detected by differential scanning calorimetry (DSC) at a heating rate of 10 Kelvin per minute or less as an endothermic melting peak before reaching the softening point.

[0014] In certain embodiments, a polyester polyurethane is incorporated which is based on a semi-crystalline polyester polyol that recrystallizes upon melting and 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 acid is selected from terminal dicarboxylic acids having at least 8 even methylene groups which are saturated linear aliphatic (hereinafter "Component A"); and b) At least 40 mol%, preferably at least 60 mol%, particularly preferably at least 70 mol% of the diol is selected from terminal diols which are saturated linear aliphatic and have at least one ether functional group (hereinafter "Component B").

[0015] Such semi-crystalline polyester polyols that recrystallize upon melting are distinguished by an exothermic recrystallization occurring during the endothermic melting process before reaching the softening point, 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 10 Kelvin per minute or less before reaching the softening point. The corresponding semi-crystalline polyester polyols that recrystallize upon melting are described in detail in WO2019 / 011529A1. In the context of the present invention, as a component of the adhesive compound according to the invention, the polyester polyurethane produced based on these semi-crystalline polyester polyols that recrystallize upon melting provides excellent wiping behavior along with high-temperature stability. Thus, without a significant decrease in the softening point of the adhesive, the application of the adhesive film to the substrate to be adhered becomes easier, and a dimensionally stable adhesive without packaging is recognized as sticky for use by the end consumer.

[0016] In order not to use semi-crystalline polyester polyols that give a polyester polyurethane a softening point exceeding 60 °C and thus require the addition of additives to improve the wiping of the adhesive, the dicarboxylic acids from component A preferably do not have more than 24 methylene groups, particularly preferably not more than 18 methylene groups, and even more preferably not more than 16 methylene groups. Independently of this, the dicarboxylic acids from component A preferably need to contain at least 10 methylene groups in order to provide those semi-crystalline polyester polyols that give excellent wiping properties as a basis for the polyester polyurethane of the adhesive compound due to their pronounced tendency to recrystallize. Thus, preferred representative examples of the dicarboxylic acids from component A are 1,10-decamethylenedicarboxylic acid, 1,12-dodecamethylenedicarboxylic acid, 1,14-tetradecamethylenedicarboxylic acid and 1,16-hexadecamethylenedicarboxylic acid.

[0017] In order to improve the tack (adhesiveness) of the adhesive compound, it can be advantageous if they include polyester polyurethanes based on polyester polyols obtained from the polycondensation of aromatic dicarboxylic acids or unsaturated dicarboxylic acids having less than 9 carbon atoms and, preferably, aliphatic diols having at least one ether functional group but no tertiary and quaternary carbon atoms. Examples of aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, orthophthalic acid, furandicarboxylic acid, particularly 2,5-furandicarboxylic acid, and examples of unsaturated dicarboxylic acids having less than 9 carbon atoms include itaconic acid, fumaric acid and / or maleic acid, which may also be included in the adhesive compound as a polyester polyol component of the polyester polyurethane.

[0018] However, overall, when the proportion of polyester polyurethane based on semi-crystalline polyester polyol is dominant based on the whole of the polyester polyurethane, it is advantageous for the wiping behavior and temperature stability of the adhesive compound according to the present invention. According to the present invention, based on the polyester polyol ratio of all the polyester polyurethanes contained in the adhesive compound according to the present invention, the proportion of the dicarboxylic acid that can be formally separated from the polyester polyurethane by hydrolysis of the ester functional group according to component A and the diol that can be separated according to component B is at least 60% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight.

[0019] In any case, per gram of the reaction mixture comprising components A and B, preferably having an acid value of less than 50 mg KOH / g, particularly preferably less than 10 mg KOH / g, more particularly preferably less than 5 mg KOH / g, very particularly preferably less than 2 mg KOH / g, and the semi-crystalline polyester polyol obtained from the reaction mixture of components A and B (wherein the diol is contained in a molar excess based on the dicarboxylic acid but does not exceed a molar excess of 1.2:1) has been proven to be ideal in terms of the recrystallization behavior of the adhesive compound according to the present invention as a starting material for the above polyester polyurethane.

[0020] According to the present invention, the acid value is an experimentally determinable measurement variable and is, for example, an index for the number of free acid groups in a defined reference amount per gram of the reaction mixture. The acid value is determined by dissolving a weighed sample of the reference amount in a mixed solvent with a volume ratio of methanol to distilled water of 3:1 and potentiometrically titrating the sample with 0.05 mol / l KOH in methanol. The potentiometric measurement is carried out using a combined electrode (LL-Solvotrode (registered trademark) manufactured by Methrom, reference electrolyte: tetraethylammonium bromide in 0.4 mol / l ethylene glycol). In this case, the acid value corresponds to the amount of KOH added per gram of the reference amount at the inflection point of the potentiometric titration curve.

[0021] In order to provide a polyester polyurethane through the addition of a monofunctional or polyfunctional isocyanate to such a semi-crystalline polyester polyol, the hydroxyl value of the polyester polyol is in each case at least 30 mg / g KOH, particularly preferably at least 60 mg / g KOH, more particularly preferably at least 80 mg / g KOH, per gram of the reaction mixture comprising components A and B, but preferably less than 200 mg / g KOH, particularly preferably less than 140 mg / g KOH, more particularly preferably less than 120 mg / g KOH, which is preferred.

[0022] Similar to the acid value, the hydroxyl value can be determined experimentally by potentiometric titration, for example, as a measure of the number of free hydroxyl groups in a defined reference amount per gram of the reaction mixture. For this purpose, a weighed sample of the reference amount 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 amount of a reaction solution of deionized water (κ < 1 μS cm -1 ). The amount of phthalic acid released in this mixture is titrated with 1 M sodium hydroxide solution. Potentiometric measurements are carried out using a combined electrode (LL-Solvotrode (registered trademark) manufactured by Methrom; reference electrolyte: tetraethylammonium bromide in 0.4 mol / l ethylene glycol). The hydroxyl value 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.

[0023] The semi-crystalline polyester polyol obtainable from the reaction mixture containing components A and B as defined above preferably has a number average molar mass of less than 5,000 g / mol, particularly preferably less than 2,000 g / mol, but more preferably at least 500 g / mol, and a polydispersity of preferably less than 2.5. In this molar mass range, the polyester polyurethane having a preferred polydispersity can easily be wiped on the adhesive compound according to the invention which consists of at least 50% by weight of such a polyester polyurethane, and can impart sufficient temperature stability together with good tackiness to the said compound. The number average molar mass can be measured by gel permeation chromatography after calibration with polystyrene standard substances using a sample of the reaction mixture. For this purpose, chromatography eluting with tetrahydrofuran is carried out at a column oven temperature of 40 °C, and the distribution curve is likewise recorded at a temperature of 40 °C by a concentration-dependent RI detector which continuously measures the refractive index in the eluate.

[0024] The polyester polyurethane of the adhesive compound according to the present invention is an addition product of a monofunctional or polyfunctional isocyanate with a polyester polyol, and the addition product is end-capped and thus has no free isocyanate groups. According to the present invention, the addition is preferably 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-capping is preferably carried out with a monohydric alcohol. In the context of the present invention, a polyester polyurethane contains no free isocyanate groups if it contains less than 0.1% by weight of NCO, based on the total amount of the polyester polyurethane. To determine the proportion of free isocyanate groups, 4 millilitres of a 0.5 M dibutylamine solution in xylene are added to 1 gram of polyester polyurethane, then mixed with 50 millilitres of xylene and stirred at a temperature of 20 °C until completely homogenized. After adding 3 drops of bromophenol blue and 50 millilitres of isopropanol, titration is carried out with 0.5 M hydrochloric acid until the colour changes from blue to yellow. The difference in the consumption of hydrochloric acid for the titration of the blank value solution, i.e., when no polyester polyurethane is added, multiplied by the value 2.1 and divided by the exact weight of the polyester polyurethane gives the weight percentage of isocyanate groups.

[0025] According to the present invention, the polyester polyurethane is preferably obtained by adding at least trifunctional, especially aliphatic isocyanates, particularly preferably trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate, to a polyester polyol, preferably a semi-crystalline polyester. The free isocyanate groups formed by the addition reaction preferably react with at least one monohydric alcohol, particularly preferably with at least one aliphatic alcohol, and more particularly preferably with at least one linear aliphatic alcohol (hereinafter "end-capping"), each preferably having 24 or fewer carbon atoms in the main chain, but preferably having at least 4 carbon atoms in the main chain. To enhance adhesiveness, it is advantageous to perform end-capping with a monohydric aliphatic alcohol having at least 4 but less than 8 carbon atoms in the main chain. On the other hand, performing end-capping with a monohydric, preferably linear aliphatic alcohol having at least 12 but less than 24 carbon atoms in the main chain increases the temperature stability of the adhesive compound. The relative ratio of the long-chain and short-chain end-capped polyester polyurethanes can set the adhesiveness and temperature stability required for a particular application, depending on and due to the presence of specific further additives. In a preferred embodiment of the adhesive compound according to the present invention, the polyester polyurethane is end-capped with both a monohydric aliphatic, preferably linear aliphatic alcohol having at least 4 but less than 10, preferably 8 or fewer carbon atoms, and a monohydric aliphatic, preferably linear aliphatic alcohol having at least 10, preferably at least 12, particularly preferably at least 14 but 24 or fewer carbon atoms.

[0026] Also, polyester polyurethanes having a dynamic Brookfield viscosity at 80 °C (spindle 27) of at least 2,000 mPas, particularly preferably at least 3,000 mPas, more particularly preferably at least 5,000 mPas, but preferably less than 140,000 mPas, particularly preferably less than 60,000 mPas, are also preferably used. Polyester polyurethanes having a lower preferred range of dynamic viscosities are usually achieved by at least partially end-capping with a long-chain monohydric alcohol or by at least partially adding a diisocyanate to a semi-crystalline polyester polyol.

[0027] And the organic component of the adhesive compound according to the present invention mainly consists of polyester polyurethane if its proportion is more than 50% by weight based on the organic component of the adhesive compound. The adhesive compound usually shows particularly excellent temperature stability with good wiping behavior when the proportion of the polyester polyurethane as described above is at least 60% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, based on the organic component of the adhesive compound. Therefore, such an adhesive compound is preferred according to the present invention.

[0028] The excellent wiping behavior imparted to the adhesive compound according to the invention via the polyester polyurethane, as well as the temperature stability and good curing behavior, mean that a wide range of additives are hardly necessary. Nevertheless, the temperature stability can be further improved without significantly impairing the initial tack of the wiped-on film. For this purpose, at least a trifunctional isocyanate is preferably added to a polyester polyol, particularly preferably polytetramethylene ether glycol, and then at least one monohydric alcohol, preferably at least one aliphatic alcohol, particularly preferably at least one linear aliphatic monohydric alcohol, each having 24 or fewer carbon atoms in the main chain but preferably having at least 4 carbon atoms in the main chain, and the polyester polyurethane obtained by end-capping can be treated with additives. In certain embodiments, the at least trifunctional isocyanate can be added to a mixture of the above semi-crystalline polyester polyols, which mixture further contains a polyether polyol. As a result, if the proportion of the polyester polyol is more than 50% by weight based on the polyol proportion of the reaction mixture of the addition reaction, the required profile of the adhesive compound according to the invention is also met, and a mixed polyester-polyether polyurethane is obtained which imparts good wiping properties together with excellent temperature stability.

[0029] In a preferred adhesive compound according to the invention, the proportion of the polyether polyurethane based on the organic components of the adhesive compound is 40% by weight or less, particularly preferably 30% by weight or less, more preferably 20% by weight or less, very particularly preferably 15% by weight or less, but preferably at least 2% by weight, particularly preferably at least 5% by weight, in order to be able to obtain a colorless and translucent adhesive compound.

[0030] Enumerated below are additional additives and their associated functional groups that can be advantageously added to the adhesive compound according to the present invention in order to provide an adhesive compound that meets certain required profiles further defined below. One advantage of the adhesive compound according to the present invention is that, accordingly, it is easy to add additives to the adhesive compound mainly composed of polyester polyurethane.

[0031] In order to enhance the initial adhesiveness of the wipe-on film of the adhesive compound, for example, based on the adhesive compound according to the present invention, it may be advantageous to additionally contain an adhesive other than polyester polyurethane or polyether polyurethane up to 5% by weight. In order to significantly improve the initial adhesion, based on the adhesive compound, an adhesive in a proportion of at least 1% by weight is preferred. Such an adhesive is preferably an organic compound having a sum of hydroxyl value and acid value exceeding 100 mg KOH per 1 g of the organic compound. The adhesive is preferably a resin, is continuously available, and is substantially harmless with respect to environmental hygiene, so it is preferably a natural resin that can be chemically modified. According to the present invention, the natural resin according to DIN 55958 comprises excretions secreted by animals and plants. This type of resin is known to those skilled in the art as, for example, turpentine, balsam, gum lacquer, rosin, sandarac or mastic. According to the present invention, the natural resin also includes modified natural resins obtained from the natural resin, for example, by hydrogenation, graft addition reaction or esterification. The natural resin as component a) of the adhesive compound according to the present invention is preferably selected, in order, from resin acids and / or resin esters, particularly preferably resin acids and / or resin esters based on di- and / or triterpenes, which are preferably hydrogenated and / or present as inherent adducts. According to the present invention, the resin ester refers to a resin acid that has been modified one or several times by a condensation reaction via the carboxyl group of the resin acid to form an ester group. Preferred representatives of diterpene-based resin acids and / or resin esters are, as appropriate, abietic acid, neoabietic acid, levopimaric acid, pimaric acid, palustric acid, agathic acid, iridic acid and podocarpic acid, and triterpene-based resin acids are elemic acid, sumaresinol acid and its mono- or polyesters, and in each case it is desirable that the alkyl group of the ester group has 6 or fewer carbon atoms. By using the adhesive, the initial adhesiveness of the adhesive compound is increased after being coated on the paper surface with a thin film. For example, when adhering the opposite sides of a paper fold, the paper surface connected by the adhesive film remains connected without applying contact pressure until the adhesive hardens.

[0032] A small amount of polyolefin wax, since most of it is non-polar, may have a positive effect on the initial adhesion of the adhesive compound. Furthermore, polyolefin wax provides better long-term stability of the bond. Thus, according to the present invention, in each case based on the adhesive compound, it can contain polyolefin wax preferably up to 20% by weight, particularly preferably up to 10% by weight. In each case based on the adhesive compound, a proportion of at least 1% by weight, particularly at least 2% by weight, is preferred for achieving a great effect. In a preferred embodiment of the adhesive compound according to the present invention further comprising polyolefin wax, these are selected from copolymer waxes consisting of propylene and ethylene and / or at least one branched or unbranched 1-alkene having 4 to 20 carbon atoms, and can be further modified with carboxyl groups to improve compatibility with the adhesive compound, and the acid value is preferably less than 20 mg KOH per gram of the polyolefin wax. It is also an advantage that the additive-treated polyolefin wax is amorphous and thus has no crystallinity in the range from 20 °C to the softening point. In addition to the initial adhesiveness, polyolefin wax increases the elasticity of the adhesive compound. For example, a glue stick based on the corresponding additive-treated adhesive compound according to the present invention can provide one that is not easily damaged, which is particularly advantageous in the case of the administration and application forms of the adhesive compound according to the present invention without packaging.

[0033] In the case of the adhesive compound according to the present invention where the stickiness is felt to be too unpleasant when the adhesive compound is applied without packaging and the adhesive film is wiped on by hand, it may be suitable to add pyrogenic silica up to an amount of 15% by weight based on the adhesive compound. However, in order to reduce the stickiness of the dimensionally stable dosage form while maintaining other parameters such as initial adhesiveness, wipeability and curing behavior, at least 1% by weight of pyrogenic silica for a significant reduction in stickiness is preferably necessary to be treated with an additive.

[0034] To improve the wiping of the adhesive compound onto a flat substrate, the adhesive compound preferably has an HLB value in the range of 12 to 18, particularly preferably from polyalkoxylated C12 - C22 fatty alcohols, and very particularly preferably is selected from polyethoxylated C12 - C22 fatty alcohols having preferably more than 20 EO units, and may further advantageously contain up to 5% by weight of a nonionic surfactant. To significantly improve the wiping, it is preferred that the nonionic surfactant is present in a proportion of at least 0.5% by weight, based on the adhesive compound.

[0035] The adhesive compound according to the invention can be formulated to be solvent - free and anhydrous, and is distinguished in that upon setting of the adhesive compound, the bonded connection does not require physical loss of solvent or water. In a preferred embodiment, therefore, the adhesive compound according to the invention contains less than 5% by weight, preferably less than 1% by weight of water, based on the adhesive compound. The proportion of water in the adhesive compound can be measured by the Karl Fischer method using solvent xylene. Such a substantially water - free adhesive compound formulation according to the invention has the advantage that after wiping on an adhesive film onto a thin and flat substrate of a water - absorbent material such as paper, the material does not warp and maintains its flat shape even after the adhesive compound has cured. 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, of an organic compound having a boiling point of less than 100 °C at 1013 mbar, in each case based on the adhesive compound.

[0036] In a particularly preferred embodiment, the adhesive compound according to the invention a) At least 50% by weight, preferably at least 60% by weight, particularly preferably at least 70% by weight, more particularly preferably at least 80% by weight of a polyester polyurethane, at least a part of which is derived from a semi-crystalline polyester polyol, and is selected from one or more dicarboxylic acids which are saturated linear and aliphatic and have an even number of at least 8 methylene groups, and one or more diols selected from terminal diols which are saturated linear and aliphatic and contain at least one ether functional group, and can be obtained by polycondensation of a reaction mixture containing them. b) Up to 50% by weight, preferably 5 - 30% by weight of a polyether polyurethane; c) Up to 20% by weight, preferably 1 - 10% by weight of a polyolefin wax; d) Up to 5% by weight of an adhesive; and e) Up to 5% by weight of a polyalkoxylated C12 - C22 fatty alcohol, comprising, in each case based on the organic components, the proportion of the organic components does not exceed at least 80% by weight based on the adhesive compound, and the proportion of the inorganic components selected from pigments, fillers and salts does not exceed 20% by weight, preferably 15% by weight based on the adhesive compound, and contains less than 5% by weight, preferably less than 1% by weight of water based on the adhesive compound.

[0037] In relation to this particularly preferred embodiment, the specific constitution of the above-mentioned components a) - e) and further additives is analogized.

[0038] According to the present invention, the inorganic component is pyrolyzed in a reactor while supplying a CO-free oxygen stream at 900 °C without mixing a catalyst or other additives, and an infrared sensor measures CO at the outlet of the reactor. 2 while supplying a CO-free oxygen stream at 900 °C without mixing a catalyst or other additives, and an infrared sensor measures CO at the outlet of the reactor. 2It corresponds to the solid content of the adhesive compound remaining after pyrolysis until a signal (blank value) identical to the free carrier gas is given. Correspondingly, the organic component of the adhesive compound is obtained by subtracting from the adhesive compound the amount of water measured by the Karl Fischer method in solvent xylene and further subtracting the inorganic component defined above.

[0039] In the present invention, the adhesive compound is shaped to form a cylinder, and when a force continuously increasing to the mass acts perpendicularly to the bottom surface of the cylinder on a mass (10 g) of a preparation having a bottom surface of 2 cm 2 at 30 °C and 50% relative humidity, it irreversibly deforms only at a pressure exceeding 20 N / cm 2 and is dimensionally stable in principle. The measurement of the action of the force and the occurrence of deformation can be monitored by a force measuring device, for example, a Texture Analyzer TA-XT HiR (Stable Micro Systems Ltd.). The concept of dimensional stability is closely related to the required temperature stability of the adhesive compound according to the present invention. Specifically, an adhesive compound having a ring and ball softening point measured according to DIN EN ISO 4625-1:2006-04 is preferably at least 40 °C, particularly preferably at least 60 °C, but preferably less than 150 °C, particularly preferably less than 100 °C, and is considered to be temperature stable to the extent that it can provide an adhesive compound that is dimensionally stable at 30 °C. Ideally, at least 80% by weight of the organic component of the adhesive compound according to the present invention has a ring and ball softening point measured according to DIN EN ISO 4625-1:2006-04, preferably at least 40 °C, particularly preferably at least 60 °C, in order to provide an adhesive compound with as high dimensional stability and temperature stability as possible.

[0040] The dimensionally stable adhesive compound provided by the present invention has low tackiness at 30 °C and can be easily wiped onto a substrate. The movement of the material by wiping is carried out so as to form a thin adhesive film of the adhesive compound on a flat substrate, and since this film cures in a short time, the substrate can be sufficiently adhered to the adhesive compound and bonded to each other.

[0041] Accordingly, in a further aspect, the present invention relates to a method of applying an adhesive film to a planar substrate, preferably paper, by pressing a dimensionally stable adhesive compound according to the invention onto the planar substrate and then changing the relative position while maintaining a contact pressure perpendicular to the surface normal of the substrate. A suitable substrate is preferably one obtained from plant fibers, is planar and flexible, and is particularly preferably paper.

Examples

[0042] Practical example: First, the preparation of a mixture of semi-crystalline polyester polyols is outlined below, then it is converted to the corresponding polyester polyurethane, and thus cast to form a cylindrical dimensionally stable adhesive compound according to the invention, and the properties were evaluated with respect to the wiping behavior and adhesion to paper.

[0043] Preparation of a mixture of polyester polyols: 0.369 kg of isophthalic acid, 1.876 kg of dodecanedioic acid, and 1.421 kg of diethylene glycol as raw materials were placed in a 5-liter four-necked flask equipped with a nitrogen inlet, a thermostat, a paddle stirrer, and a distillation arm. The reaction mixture was heated and stirred at a temperature of 220 °C for several hours in a nitrogen stream, and then the pressure in the reaction flask was gradually reduced to 30 mbar. The acid value was continuously controlled as will be described in detail in the description of the present invention. As soon as the acid value of the reaction mixture dropped below a value of 3 mg KOH / g, the reaction mixture was first cooled to 80 °C, and then cooled, and then the reaction mixture was further cooled to room temperature. Thereafter, the acid value and the hydroxyl value were finally measured at 20 °C, and the mixture was characterized by chromatography. The hydroxyl value was 102 mg KOH / g; the acid value was 0.3 mg KOH / g, and the dynamic viscosity at 50 °C was 1,900 mPas.

[0044] Preparation of a mixture A of polyester polyurethane: 51.8 g of n-octanol and 170 g of isocyanate trimer Desmodur® N3300 (Covestro AG) were placed in a three-necked flask, heated to 80 °C and stirred for 30 minutes. Then, 165 g of polyester polyol mixture and 48.7 g of hexadecanol were added, and the reaction mixture was stirred first at 100 °C for 1 hour, then at 110 °C for about 1.5 hours, and finally at a reduced pressure of 300 mbar for an additional 10 minutes.

[0045] For chromatographic property evaluation by gel permeation chromatography (GPC), a sample of the reaction mixture was dissolved in tetrahydrofuran and applied to the column, and then eluted with tetrahydrofuran as well. After calibration with polystyrene standard samples, gel permeation chromatography (GPC) using an RI detector was carried out under the conditions of a column oven temperature of 40 °C and a detector internal temperature of 40 °C. Relative number-average molar mass values and weight-average molar mass values were determined from the molar mass distribution curve, and the polydispersity was determined therefrom.

[0046] Mixture A of polyester polyurethane had a number-average molar mass of about 3,700 g / mol and a polydispersity of 3.6.

[0047] Preparation of mixture B of polyester polyurethane: 51.8 g of n-octanol, 170 g of isocyanate trimer Desmodur® N3300 and 165 g of polyester polyol mixture were placed in a three-necked flask, heated to 100 °C and stirred for 30 minutes. Then, 48.7 g of hexadecanol was added, and the reaction mixture was stirred at 110 °C for 2 hours. Mixture B of polyester polyurethane had a number-average molar mass of about 3700 g / mol and a polydispersity of 8.4.

[0048] Mixtures A and B of polyester polyurethane were melted at 110 °C, cast into cylindrical stick shapes (2 cm in diameter, 6 - 8 cm in length), stored at 20 °C for 24 hours, and then the handling behavior of the stick-shaped adhesive compound and the properties of the wiped-on adhesive film were measured.

[0049] The cylindrical stick was cut at 10°, and through the cut surface, the basis weight was 80 g / m 2 , and the surface pressure was 5 N / cm 2 . After wiping on paper, for the wiping of mixture A, the value was "4", and for mixture B, the value was "3" (scale 1: hard wiping like eraser, 5: Henkel Pritt (registered trademark) original stick-like).

[0050] The number of grams of the paper sheet with an adhesive film provided by the wiping test was 80 g / m 2 . After joining the paper sheets, folding for adhesion, and then pulling them apart again after 1 hour at 20°C, the paper breakage obtained was "5" for both mixtures (1: no paper breakage, 2: less than 30%, 3: less than 60%, 4: less than 90%, 5: paper breakage is seen at the adhesive part exceeding 90%).

[0051] The softening points of the adhesive compound, or mixtures A and B of polyester polyurethane, measured using the ball method in accordance with DIN EN ISO 4625-1:2006-04, were 66°C (mixture A) and 64°C (mixture B). Thus, the adhesive compound had sufficient temperature stability and could be provided without packaging. Preferred embodiments of the present invention include the following. 〔1〕An adhesive compound having dimensional stability, wherein the organic component mainly consists of polyester polyurethane, and at least a part of the polyester polyurethane is based on a semi-crystalline polyester polyol, and the polyester polyurethane is obtained by polycondensation of a reaction mixture containing one or more dicarboxylic acids selected from terminal dicarboxylic acids having at least 8 even-numbered methylene groups that are saturated linear aliphatic, and one or more diols selected from terminal diols that are saturated linear aliphatic and contain at least one ether functional group. 〔2〕The polyester polyurethane can be obtained by adding at least a trifunctional isocyanate to a polyester polyol, preferably a semi-crystalline polyester polyol, and end-capping with at least one monohydric alcohol, preferably at least one aliphatic alcohol, particularly preferably at least one linear aliphatic alcohol, each of which preferably has 24 or fewer carbon atoms in the main chain, but preferably has at least 4 carbon atoms in the main chain. The adhesive compound according to 〔1〕. 〔3〕The end-capping is carried out with both a monohydric aliphatic, preferably linear aliphatic alcohol having at least 4 but less than 10 carbon atoms, and a monohydric aliphatic, preferably linear aliphatic alcohol having at least 10, preferably 12, particularly preferably at least 14 but 24 or fewer carbon atoms. The adhesive compound according to 〔2〕. 〔4〕The at least trifunctional isocyanate is aliphatic and is preferably selected from trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate. The adhesive compound according to any one of 〔2〕 and 〔3〕. 〔5〕The semi-crystalline polyester polyol, preferably all polyester polyols from which the polyester polyurethane is derived, has a number average molar mass of less than 5,000 g / mol, preferably less than 2,000 g / mol, but at least 500 g / mol. The adhesive compound according to any one of 〔1〕 to 〔4〕. 〔6〕All polyester polyols derived from a semi-crystalline polyester polyol, preferably a polyester polyurethane, in each case have a hydroxyl value of at least 30 mg / g KOH, preferably at least 60 mg / g KOH, particularly preferably at least 80 mg / g KOH, based on the amount of each polyester polyol, but preferably less than 200 mg / KOH, particularly preferably less than 140 mg / g KOH, and more particularly preferably less than 120 mg / g KOH, of the adhesive compound according to any one of 〔1〕to 〔5〕. 〔7〕The polyester polyurethane 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, and is characterized by the adhesive compound according to any one of 〔1〕to 〔6〕. 〔8〕The proportion of the polyester polyurethane obtained from the semi-crystalline polyester polyol is at least 60% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight, based on the total proportion of the polyester polyurethane, and is characterized by the adhesive compound according to any one of 〔1〕to 〔7〕. 〔9〕The proportion of the polyester polyurethane based on the organic components of the adhesive is at least 60% by weight, preferably at least 70% by weight, particularly preferably at least 80% by weight, and is characterized by the adhesive compound according to any one of 〔1〕to 〔8〕. 〔10〕Contains an additional polyester polyurethane preferably obtained by adding at least a trifunctional isocyanate to a polyester polyol, preferably polytetramethylene ether glycol, and then end-capping with at least one monohydric alcohol, preferably at least one aliphatic monohydric alcohol, particularly preferably at least one linear aliphatic alcohol, each of which preferably has 24 or fewer carbon atoms in the main chain, but preferably has at least 4 carbon atoms in the main chain, of the adhesive compound according to any one of 〔1〕to 〔9〕. 〔11〕Based on the organic component of the adhesive compound, the proportion of polyether polyurethane is 40% by weight or less, preferably 30% by weight or less, particularly preferably 20% by weight or less, and extremely particularly preferably 15% by weight or less, but preferably 2% by weight or more, particularly preferably 5% by weight or more. The adhesive compound according to any one of 〔1〕~〔10〕. 〔12〕The proportion of the organic component is at least 70% by weight, preferably at least 80% by weight, based on the adhesive compound. The adhesive compound according to any one of 〔1〕~〔11〕. 〔13〕Containing less than 5% by weight, preferably less than 1% by weight of water. The adhesive compound according to any one of 〔1〕~〔12〕. 〔14〕a) At least 50% by weight of polyester polyurethane, at least a part of which is derived from a semi-crystalline polyester polyol. This polyester polyurethane can be obtained by polycondensation of a reaction mixture containing one or more dicarboxylic acids selected from saturated linear aliphatic terminal dicarboxylic acids having at least 8 even methylene groups and one or more diols selected from linear aliphatic terminal diols containing at least one ether functional group; b) Up to 50% by weight, preferably 5 - 30% by weight of polyether polyurethane; c) Up to 20% by weight, preferably 1 - 10% by weight of polyolefin wax; d) Up to 5% by weight of an adhesive; and e) Up to 5% by weight of polyalkoxylated C12 - C22 fatty alcohol, containing, in each case, based on the organic component, and the proportion of the organic component does not exceed at least 80% by weight based on the adhesive compound. The proportion of inorganic components selected from pigments, fillers and salts does not exceed 20% by weight, preferably does not exceed 15% by weight, based on the adhesive compound, and here, based on the adhesive compound, less than 5% by weight, preferably less than 1% by weight of water is contained. The adhesive compound according to any one of 〔1〕~〔13〕. 〔15〕A method of applying an adhesive film to a planar substrate, preferably to paper, by pressing the dimensionally stable adhesive compound according to any one of 〔1〕~〔14〕 against the planar substrate and then changing the relative position while maintaining a contact pressure perpendicular to the surface normal of the substrate.

Claims

1. An adhesive compound having an organic component mainly composed of polyester polyurethane, at least a part of the polyester polyurethane being a dimensionally stable adhesive compound based on a semi-crystalline polyester polyol, wherein the polyester polyurethane is obtained by adding at least a trifunctional isocyanate to a polyester polyol and end-capping with at least one monohydric alcohol, and the polyester polyurethane can be obtained by polycondensation of a reaction mixture containing one or more dicarboxylic acids selected from terminal dicarboxylic acids having at least 8 even-numbered methylene groups which are saturated linear aliphatic, and one or more diols selected from terminal diols which are saturated linear aliphatic and contain at least one ether functional group.

2. The adhesive compound according to claim 1, wherein each of the at least one monohydric alcohol for end-capping has 24 or fewer carbon atoms in the main chain, but at least one aliphatic alcohol having at least 4 carbon atoms in the main chain.

3. The end-capping is carried out with both a monohydric linear aliphatic alcohol having at least 4 but less than 10 carbon atoms and a monohydric linear aliphatic alcohol having at least 10 but 24 or fewer carbon atoms, the adhesive compound according to any one of claims 1 and 2.

4. The adhesive compound according to any one of claims 1 to 3, wherein the at least trifunctional isocyanate is aliphatic.

5. The adhesive compound according to claim 4, wherein the at least trifunctional isocyanate is selected from trimers of hexamethylene diisocyanate and / or pentamethylene diisocyanate.

6. All polyester polyols from which the semi-crystalline polyester polyol is derived have a number average molar mass of less than 5,000 g / mol but at least 500 g / mol, the adhesive compound according to any one of claims 1 to 5.

7. All polyester polyols from which the semi-crystalline polyester polyol is derived have a hydroxyl value of at least 30 mg / g KOH based on the amount of the polyester polyol, the adhesive compound according to any one of claims 1 to 6.

8. The adhesive compound according to any one of claims 1 to 7, wherein the polyester polyurethane has a dynamic Brookfield viscosity (spindle 27) at 80 °C of at least 2,000 mPa·s.

9. The adhesive compound according to claim 8, wherein the polyester polyurethane has a dynamic Brookfield viscosity (spindle 27) at 80 °C of less than 140,000 mPa·s.

10. The adhesive compound according to any one of claims 1 to 9, wherein the proportion of the polyester polyurethane obtained from the semi-crystalline polyester polyol is at least 60% by weight based on the total proportion of the polyester polyurethane.

11. The adhesive compound according to any one of claims 1 to 10, wherein the proportion of the polyester polyurethane based on the organic components of the adhesive is at least 60% by weight.

12. The adhesive compound according to any one of claims 1 to 11, containing an additional polyether polyurethane obtainable by adding at least a trifunctional isocyanate to the polyester polyol and then end-capping with at least one monohydric alcohol.

13. The adhesive compound according to claim 12, wherein the polyester polyol is polytetramethylene ether glycol.

14. The adhesive compound according to any one of claims 1 to 13, wherein the proportion of the polyether polyurethane based on the organic components of the adhesive compound is 40% by weight or less.

15. The adhesive compound according to any one of claims 1 to 14, wherein the proportion of the organic components is at least 70% by weight based on the adhesive compound.

16. The adhesive compound according to any one of claims 1 to 15, containing less than 5% by weight of water.

17. a) at least 50% by weight of a polyester polyurethane, at least a part of which is derived from a semi-crystalline polyester polyol, and this polyester polyurethane can be obtained by polycondensation of a reaction mixture comprising one or more dicarboxylic acids selected from saturated linear aliphatic terminal dicarboxylic acids having at least 8 even methylene groups and one or more diols selected from linear aliphatic terminal diols containing at least one ether functional group; b) up to 50% by weight of a polyether polyurethane; c) up to 20% by weight of a polyolefin wax; d) up to 5% by weight of an adhesive; and e) up to 5% by weight of a polyalkoxylated C12 - C22 fatty alcohol, containing, in each case based on the organic components, the proportion of the organic components not exceeding at least 80% by weight based on the adhesive compound, the proportion of the inorganic components selected from pigments, fillers and salts not exceeding 20% by weight based on the adhesive compound, and wherein, based on the adhesive compound, less than 5% by weight of water is contained, the adhesive compound according to any one of claims 1 to 16. **Claim 18** A method of applying an adhesive film to a planar substrate by pressing an adhesive compound with dimensional stability according to any one of claims 1 to 17 against the planar substrate and then changing the relative position while maintaining a contact pressure perpendicular to the surface normal of the substrate.