Apparatus and method for the punctiform application of adhesives made of coagulable aqueous polymer dispersions

Abstract

The invention relates to an apparatus for the punctiform application of adhesives made of coagulable aqueous polymer dispersions, comprising: a nozzle device having a nozzle needle and a nozzle body, an actuator device, and a heating device which is designed to heat the nozzle device to a defined temperature required for coagulating the aqueous polymer dispersion. The invention further relates to methods for the punctiform application of adhesives made of coagulable aqueous polymer dispersions, preferably by means of an apparatus as described above, comprising the punctiform application of an application amount of a coagulated aqueous polymer dispersion onto a substrate.

Description

[0001] Device and method for the point-like application of adhesives made from coagulable aqueous polymer dispersions

[0002] Technical field

[0003] The invention relates to a device for the spot application of adhesives made from coagulable aqueous polymer dispersions, comprising: a nozzle assembly with a nozzle needle and a nozzle body, an actuator assembly, and a heating device configured to heat the nozzle assembly to a defined temperature required for the coagulation of the aqueous polymer dispersion. The invention further relates to methods for the spot application of adhesives made from coagulable aqueous polymer dispersions, preferably using the aforementioned device according to the invention, comprising the spot application of an application quantity of a coagulated aqueous polymer dispersion onto a substrate.

[0004] Background of the invention

[0005] Folding cartons and boxes, as well as bags made of paper and / or film composites, are versatile packaging types used in all areas of goods transport and presentation. The gluing steps required to manufacture the packaging, using different systems (dispersion and hot-melt adhesives) with varying advantages and disadvantages, take place at different points in the supply chain.

[0006] The packaging manufacturer produces corrugated board (testliner, kraftliner) from various paper and cardboard grades. This raw material is then used to create the packaging blank through printing, laminating, coating, and die-cutting processes. While the packaging manufacturer's work is complete for tray applications (tray erection), folding and slipcase boxes require pre-gluing of the longitudinal seam. This is predominantly achieved using dispersion adhesives. The finished packaging is delivered to the packer, who fills or packs the goods to be transported (marketed) into the packaging and then seals it with adhesive. To ensure high throughput and productivity, hot-melt adhesives based on ethylene vinyl acetate (EVA) and polyolefins (PO) are most commonly used for sealing cardboard and folding boxes.Since the adhesives based on these raw materials have setting times of less than one to three seconds, they are ideally suited to quickly absorb the restoring forces of the packaging after compression. A dispersion adhesive typically cannot achieve this. The performance of the adhesives increases from EVA to PO.

[0007] While EVA-based commodity products exhibit lower melt stability, reduced adhesion to various surfaces, a tendency to develop odors, and low transparency, PO-based products largely avoid these disadvantages. However, the greater benefits also come at a higher price.

[0008] Disadvantages of both systems mentioned include, for example, a lower heat resistance compared to dispersions (max. 70 °C), a weakening of the bond due to migrating components of the contents (tea packaging), or lower mechanical strength (blown-in filling). Therefore, in the area of ​​packaging bags, a so-called combination bond is preferred, in which a hot melt is applied alongside a dispersion. The hot melt provides initial cohesion of the packaging during the manufacturing or filling process, while long-term stability and durability are ensured by the dispersion.

[0009] The use of hot melts also has disadvantages in terms of processing. The hot melt must be melted before use and kept at a processing temperature for a certain period of time. Hoses and nozzle application systems are also heated. This results in considerable energy consumption. Although developments by application equipment manufacturers have already reduced this energy consumption (Nordson Freedom® and Liberty® systems), there is still room for improvement, as, for example, materials prone to clogging cannot be dispensed by such systems.

[0010] WO 2011 / 072237 describes a thermally activatable adhesive composition of the plastisol type, which contains particles of a first polymer and particles of a second polymer dispersed in a liquid, organic carrier medium (e.g., vegetable oils, epoxidized vegetable oils, biodiesel, glycerin). Upon reaching a certain activation temperature, the particles of the second polymer either dissolve or plasticize within the carrier medium.

[0011] The disadvantages of the aforementioned dispersion and hot melt systems are no longer present in the coagulable aqueous polymer dispersions described in WO 2016 / 050838, which comprise (i) at least one polymer dispersed in the aqueous phase, (ii) thermoplastic microspheres containing a blowing agent, and (iii) at least one additive selected from the group consisting of polyols, polyamines, and thermoplastic polymers. These can be formulated, filled, and transported like a dispersion adhesive, but their properties (setting rate, strength development) can be modified by means of a trigger in an application device (e.g., temperature, shear, or pressure). They behave like a hot melt and, in addition, retain the properties of a dispersion after application (heat resistance, flexibility, resistance to migrating substances).However, the application of such coagulable dispersions to the substrates is problematic; conventional spray nozzles tend to clog the nozzle openings severely.

[0012] The aim of the invention was therefore to develop a spray nozzle with which the aforementioned coagulable aqueous dispersions can be processed and applied to a desired substrate without clogging or blockage of the nozzle device. This aim can be achieved by the device described below and the corresponding application methods.

[0013] Brief description of the invention

[0014] In a first aspect, the invention relates to a device for the point-like application of adhesives made from coagulable aqueous polymer dispersions, comprising: a nozzle assembly with a nozzle needle and a nozzle body, an actuator assembly, and a heating device configured to heat the nozzle assembly to a defined temperature required for the coagulation of the aqueous polymer dispersion; wherein a through-channel is formed in the nozzle body, extending along a longitudinal axis from a first end to an opposite second end, and wherein a discharge nozzle with an outlet opening for the coagulated aqueous polymer dispersion is formed at the second end; wherein the nozzle needle is translationally displaceable in the through-channel along the longitudinal axis and can be repeatedly moved from a first closed position to a second open position and vice versa by means of the actuator assembly;wherein a receiving chamber for the coagulable aqueous polymer dispersion is formed between the nozzle needle and the discharge nozzle, at least in the region of the discharge nozzle's cross-sectional area; wherein the nozzle assembly has at least one feed channel extending from the first end to the opposite second end and designed to feed the coagulable aqueous polymer dispersion into the receiving chamber, wherein the volume of the receiving chamber for receiving at least one application quantity of the coagulable aqueous polymer dispersion is larger in the open position than in the closed position, and in the closed position the discharge opening of the discharge nozzle is completely closed by a lower end of the nozzle needle.

[0015] In a second aspect, the invention relates to a method for the spot application of adhesives made from coagulable aqueous polymer dispersions to a substrate, comprising the spot application of an application quantity of a coagulated aqueous polymer dispersion to the substrate by means of a device according to the first aspect of the invention.

[0016] In a third aspect, the invention relates to a method for the spot application of adhesives made from coagulable aqueous polymer dispersions onto a substrate by means of a device, preferably by means of a device according to the first aspect of the invention, for the spot application of a suitable application quantity of a coagulated aqueous polymer dispersion onto a substrate, which comprises the process steps:

[0017] (a) Initial feeding and heating of at least one application quantity of the coagulable aqueous polymer dispersion into a receiving chamber to a temperature required for coagulation of the aqueous polymer dispersion between the nozzle needle and the discharge nozzle at least in the area of ​​a passage cross-section of a discharge nozzle during a first opening duration of the nozzle device when the nozzle needle is arranged in the open position;

[0018] (b) Arranging a first application point of a substrate onto which an application quantity of the coagulated aqueous dispersion / adhesive is to be applied at a defined distance and opposite the outlet opening of the dispensing nozzle;

[0019] (c) Moving the nozzle needle from the open position to the closed position, thereby reducing the volume of the receiving chamber, thereby ejecting an application quantity of the coagulated aqueous polymer dispersion through the nozzle opening during the movement of the nozzle needle to the closed position and applying it to a first application site on the substrate until the nozzle needle completely and preferably flush closes the outlet opening of the discharge nozzle;

[0020] (d) Moving the nozzle needle to the open position and re-feeding and heating an application quantity of the coagulable aqueous polymer dispersion into the receiving chamber during a second opening duration of the nozzle device when the nozzle needle is in the open position; and

[0021] (e) optional repetition of process steps b) to d) by any integer number of repetitions, the discharge nozzle being positioned opposite further application locations.

[0022] In preferred embodiments of the second and third aspects of the invention, the coagulable aqueous polymer dispersion comprises (i) at least one polymer dispersed in aqueous phase, (ii) thermoplastic microspheres containing a blowing agent, and (iii) at least one additive selected from the group consisting of polyols, polyamines and thermoplastic polymers.

[0023] In a fourth aspect, the invention relates to the use of a device for the point-like application of coagulable aqueous polymer dispersions, preferably a device according to the preceding first aspect of the invention, for carrying out the method according to the second or third aspect of the invention.

[0024] Brief description of the characters

[0025] Figure 1 is a schematic sectional view of an exemplary embodiment of a device according to the invention for point-like application.

[0026] Figure 2A is an enlarged sectional view of the device according to the invention in the area of ​​the discharge nozzle in the closed state.

[0027] Figure 2B is an enlarged sectional view of the device according to the invention in the area of ​​the discharge nozzle in the open state.

[0028] Detailed description of the invention

[0029] For the purposes of the present invention, the terms "coagulable aqueous polymer dispersion" and "coagulable aqueous dispersion" or "coagulated aqueous polymer dispersion" and "coagulated aqueous dispersion" have the same meaning and are used interchangeably in the following detailed description. Likewise, "adhesive made of coagulable aqueous polymer dispersion", "adhesive", "coagulated aqueous polymer dispersion", and "coagulate" have the same meaning.

[0030] For the purposes of this document, "point-shaped" in the application of the adhesive refers not only to circular shapes, but also to shapes that are not completely round or oval, and also to multiple superimposed points.

[0031] The device according to the invention

[0032] In the device according to the first aspect of the invention, the coagulable aqueous polymer dispersion is supplied to the flow channel under pressure via the first end. The coagulable aqueous polymer dispersion is supplied to the flow channel under pressure in an unheated state, for example, at ambient temperature, with the nozzle needle for supplying the coagulable aqueous polymer dispersion in the open position. The pressure forces the coagulable aqueous polymer dispersion into the receiving chamber along the longitudinal axis of the flow channel. As the coagulable aqueous polymer dispersion flows along the flow channel, it is continuously heated by the heating device until the temperature in the receiving chamber reaches the required range, at which point coagulation occurs.When at least the desired application quantity of coagulated aqueous polymer dispersion is present, the nozzle needle is rapidly, within fractions of a second, or instantaneously, moved from the open to the closed position. Simultaneously, the volume of the receiving chamber is abruptly reduced, causing the application quantity of the coagulated aqueous polymer dispersion to be dispensed at high speed and pressure from the dispensing nozzle through the outlet opening, or more precisely, sprayed out and applied to a substrate opposite the outlet opening or the dispensing nozzle. Simultaneously with the dispensing of the application quantity, the nozzle needle closes the outlet opening, so that once the application quantity of the coagulated aqueous dispersion is complete, the lower end of the nozzle needle completely seals the outlet opening of the dispensing nozzle.

[0033] The device according to the invention has the advantage that the sudden reduction of the intake volume and the expulsion of the application quantity via the relative movement between the nozzle needle and the nozzle body result in shearing of the coagulable aqueous dispersion between the surfaces of the nozzle needle and the nozzle body in the region of the discharge nozzle's outlet opening, leading to further coagulation within the dispersion. Due to the sudden dispensing of the application quantity, it is sprayed onto the substrate to be applied at high speed and high pressure. This allows application in any orientation of the nozzle relative to the substrate; for example, application onto the substrate from the discharge nozzle can even occur against gravity, "upside down".The application method according to the invention further has the advantage that the substrate onto which the application quantity is to be applied can be arranged at a distance from the discharge nozzle, thus preventing the adhesion of dispersion residues to the discharge nozzle. The application quantity is applied to the substrate in a dot-like form. To reapply a desired amount of the coagulated aqueous dispersion, the nozzle needle is returned to the open position for a specified period of time, namely until the desired application quantity has again been supplied to the receiving chamber. Simultaneously with the supply of the application quantity, the discharge nozzle is moved to the desired application location relative to the substrate. After the desired application quantity has been supplied, the nozzle needle is abruptly returned to the closed position. This process, or rather,The process is repeated continuously, resulting in repeated pinpoint application of the desired amount of product onto the substrate. The specified time required to move the nozzle needle from the open to the closed position can also be described as the pulse time for the pinpoint application of the desired quantity.

[0034] Preferably, the nozzle needle can taper in the region of the lower end facing the outlet opening and have a nozzle needle tip which is adapted to the diameter of the outlet opening of the discharge nozzle; and wherein, in the closed position, the nozzle needle tip fills and closes the outlet opening and, in the open position, rests inside the passage channel spaced apart from the outlet opening and releases the outlet opening.

[0035] It can be provided that the discharge nozzle has a passage cross-section which tapers conically in the area of ​​a nozzle tip and opens into the discharge opening, wherein the nozzle needle has an upper section which is adapted to the dimensions of the passage channel, and a lower section which tapers conically and is adapted to the area of ​​the conically tapered passage cross-section, wherein the nozzle needle tip is designed as the lower end of the nozzle needle and is adapted to the cross-section of the discharge opening of the discharge nozzle.

[0036] By forming a conically tapered lower end of the nozzle needle, with the nozzle tip also being conically tapered, the receiving chamber is formed as an annular gap between the nozzle needle and the conical nozzle tip in the open position. When the nozzle needle moves from the open to the closed position, the cone of the nozzle needle forces the applied quantity of the coagulated aqueous dispersion out of the discharge nozzle at high velocity until the cone of the nozzle needle rests against the inner cone of the discharge nozzle, at which point the nozzle needle tip closes the discharge nozzle.The intended combination ensures that the coagulated application quantity of the aqueous dispersion is completely squeezed out of the discharge nozzle, whereupon the nozzle opening is closed by means of the nozzle needle tip, thus preventing any residues of the coagulated aqueous dispersion from adhering to the nozzle and preventing the nozzle from clogging.

[0037] In the closed position of the nozzle needle, the nozzle needle tip can completely fill the outlet opening of the discharge nozzle, as well as seal it fluid-tight, and in the closed position a lower portion of the cone facing the nozzle needle tip comes into contact with the inner wall of the conically tapered nozzle tip.

[0038] The cone of the nozzle needle can be made more pointed than the inner cone of the nozzle tip. The angle between a longitudinal axis and the outer surface of the nozzle needle cone is smaller than the angle between a longitudinal axis of the discharge nozzle and the surface of the inner cone.

[0039] The nozzle needle and the through-channel can preferably be designed as circular cylinders. This makes it possible to manufacture both the nozzle body and the nozzle needle entirely as turned parts.

[0040] The dimensions of the through-channel and the nozzle needle can be designed in the region of an upper section such that a clearance fit, preferably an "H7 / g6" fit system, is formed between them. In the region of the upper section of the nozzle needle, at least one trapezoidal recess can be formed on the outer circumference, which forms at least one feed channel of the nozzle assembly, at least partially.

[0041] In the upper section of the nozzle needle, a four-start trapezoidal thread can be formed, with each thread serving as a capillary-shaped feed channel. These threads together form four feed channels for supplying the coagulable aqueous dispersion into the receiving chamber. Forming the feed channels as threads of the nozzle needle is advantageous because they are easy to manufacture. Furthermore, the curved shape of the threads increases the length of the feed channel from the first end to the receiving chamber, thus enabling the supplied dispersion to be heated more effectively to the desired temperature. The four channels ensure that a sufficient quantity of dispersion can be supplied to the receiving chamber via the feed channels within a short opening or pulse duration.The design of the four feed channels distributed around the circumference of the nozzle needle further ensures that the aqueous coagulable polymer dispersion is fed evenly distributed around the circumference of the nozzle needle into the receiving chamber and that the receiving chamber is completely filled with the polymer dispersion.

[0042] The actuator device can have at least one pneumatically operated valve, particularly preferably a differential pressure valve, which is designed for repeatedly moving the nozzle needle from the closed position to the open position and back.

[0043] The actuator device may include an electrically driven valve designed for repeatedly moving the nozzle needle from the closed position to the open position and back.

[0044] The actuator assembly can include a spring assembly designed to exert a spring force on the nozzle needle, at least in the open position. This spring force acts in the direction of the closed position and returns the nozzle needle to the closed position. The spring assembly ensures that the nozzle needle is reliably returned to the closed position even in the event of a malfunction of the actuator assembly, thus preventing uncontrolled flow of dispersion through the nozzle. Preferably, the actuator assembly can have a stroke adjustment mechanism by which the position of the nozzle needle relative to the nozzle body in both the closed and open positions can be adjusted along its longitudinal axis.

[0045] The device may further include a feed device for pressurized feeding of the coagulable aqueous polymer dispersion into a feed opening in the region of the first end of the at least one feed channel.

[0046] The heating device may include a heating sleeve that surrounds the nozzle body along the longitudinal axis, at least along a section of the at least one supply channel.

[0047] The device may further include at least one control device which is designed to control the heating device by means of a temperature sensor and / or wherein the control device is designed to control the actuator device for setting a dwell time of the nozzle needle in the open position and in the closed position.

[0048] The methods according to the invention

[0049] In preferred embodiments of the methods of the second and third aspects of the invention, coagulable aqueous polymer dispersions are used, comprising the following components:

[0050] (i) at least one polymer dispersed in aqueous phase,

[0051] (ii) thermoplastic microspheres containing a blowing agent, and

[0052] (iii) at least one additive selected from the group consisting of polyols, polyamines and thermoplastic polymers.

[0053] Suitable components of the coagulable aqueous polymer dispersion and process parameters are explained in more detail below.

[0054] polymer dispersed in aqueous phase

[0055] The polymer content in the aqueous dispersion is preferably 20 wt.% or more to 70 wt.% or less, in particular 50 wt.% or more to 65 wt.% or less.

[0056] The term "aqueous phase" means a phase that consists of at least 50% by weight of water, based on the total weight of the phase. Preferably, it consists of at least 70% by weight, more preferably at least 80% by weight, and most preferably at least 90% by weight, and particularly preferably at least 99% by weight, based on the total weight of the phase. In a preferred embodiment, the phase consists exclusively of water.

[0057] Suitable polymers for the dispersed polymer are polyurethane, copolymers of vinyl acetate and ethylene, polyvinyl acetate (PVAc), polyacrylate, polystyrene acrylate, styrene / butadiene copolymer (SBR), polychloroprene and polyepoxide.

[0058] In particular, the polymer dispersed in the aqueous dispersion is obtainable by polymerization of radically polymerizable compounds (monomers) or it is a polymer obtainable by polycondensation, such as polyurethanes. Preferably, the aqueous polymer dispersion is produced by emulsion polymerization. Therefore, the polymer dispersed in the aqueous dispersion is preferably an emulsion polymer.

[0059] In the following, the term "(Meth)acryl" and similar terms are an abbreviated spelling for "acrylic or methacrylic".

[0060] Preferably, the polymer consists of at least 40 wt.%, particularly preferably at least 60 wt.%, and most preferably at least 80 wt.% of so-called main monomers. The main monomers are selected from C1-C20 alkyl(meth)acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl aromatics with up to 20 carbon atoms, ethylene unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds, or mixtures of these monomers. Preferably, the dispersed polymer consists of more than 40 wt.% of C1-C20 alkyl(meth)acrylates.

[0061] Examples include (meth)acrylic acid alkyl esters with a Ci-Cio alkyl group, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate. Mixtures of (meth)acrylic acid alkyl esters are particularly suitable. Vinyl esters of carboxylic acids with 1 to 20 carbon atoms include, for example, vinyl laurate, vinyl stearate, vinyl propionate, versatic acid vinyl ester, and vinyl acetate. Vinylaromatic compounds include vinyltoluene, alpha- and para-methylstyrene, alpha-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile. Vinyl halides are ethylene-unsaturated compounds substituted with chlorine, fluorine, or bromine, preferably vinyl chloride and vinylidene chloride. Vinyl ethers include, for example, vinyl methyl ether and vinyl isobutyl ether. Vinyl ethers of alcohols containing 1 to 4 carbon atoms are preferred.Examples of hydrocarbons with 2 to 8 carbon atoms and one or two olefinic double bonds include butadiene, isoprene, chloroprene, ethylene, and propylene. Polymers or copolymers obtained from butadiene or isoprene can also be subsequently hydrogenated.

[0062] The main monomers preferred are vinyl esters, preferably vinyl acetate, especially also in combination with ethylene (hereinafter referred to as vinyl acetate / ethylene copolymers), butadiene, especially also in combination with styrene (hereinafter referred to as butadiene / styrene copolymers) and Ci- to Cio-alkyl(meth)acrylates, especially Ci- to C8-alkyl(meth)acrylates (hereinafter referred to as polyacrylates), wherein polyacrylates are particularly preferred.

[0063] Ci-Cio alkyl(meth)acrylates are particularly preferred as the main monomers; in particular, methyl acrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate, as well as mixtures of these monomers, are mentioned. The emulsion polymer preferably consists of more than 40 wt%, particularly more than 60 wt%, and most preferably more than 80 wt% of Ci-C2O alkyl(meth)acrylates.

[0064] In addition to the main monomers, the polymer can contain other monomers, such as monomers with carboxylic acid, sulfonic acid, or phosphonic acid groups. Carboxylic acid groups are preferred. Examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Other monomers include monomers containing hydroxyl groups, in particular C1-C10 hydroxyalkyl(meth)acrylates, (meth)acrylamide, and ureido groups, such as ureido(meth)acrylates. Further examples of monomers include phenyloxyethyl glycol mono(meth)acrylate, glycidyl acrylate, glycidyl methacrylate, and amino(meth)acrylates such as 2-aminoethyl(meth)acrylate. Monomers that carry additional functional groups besides the double bond, such as isocyanate, amino, hydroxy, amide, or glycidyl groups, can, for example, improve adhesion to substrates. Cyclic lactams such as N-vinylpyrrolidone or N-vinylcaprolactam are particularly suitable candidates.

[0065] Particularly suitable polymer dispersions according to the invention are the coagulable aqueous self-crosslinking styrene acrylate dispersion of the Acronal type, such as Acronal® 5044, Acronal® 5047, and Acronal® 5011. A further group of polymers dispersed in the aqueous polymer dispersion according to the invention are polyurethanes, particularly adhesive polyurethanes at room temperature (20 °C). Preferably, a polyurethane is considered that is predominantly composed of polyisocyanates, especially diisocyanates, and, as reactants, polyester diols, polyether diols, or mixtures thereof. Preferably, the polyurethane is composed of at least 40 wt.%, particularly preferably at least 60 wt.%, and most preferably at least 80 wt.% of diisocyanates, polyether diols, and / or polyester diols. Preferably, the polyurethane contains polyester diols in an amount of more than 10 wt.%, particularly preferably more than 30 wt.%, and particularly more than 40 wt.%.-% or greater than 50 wt%, most preferably greater than 60 wt%, based on the polyurethane. In particular, polyester diols are used as building components. If polyester diols are used in a mixture with polyether diols, preferably at least 50 mol%, more preferably at least 80 mol%, and most preferably 100 mol% of the mixture of polyester and polyether diols are polyester diols.

[0066] The polyurethane is preferably composed of: a) diisocyanates, b) diols, of which b) 10 to 100 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000 g / mol, b) 0 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol, c) monomers different from monomers (a) and (b) with at least one isocyanate group or at least one group reactive towards isocyanate groups, which in addition bear at least one hydrophilic group or a potentially hydrophilic group, thereby effecting the water dispersibility of the polyurethanes, d) optionally further polyhydric compounds different from monomers (a) to (c) with reactive groups, which are alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups, and e) optionally from the Monomers (a) to (d) different monovalent compounds with a reactive group,which is an alcoholic hydroxyl group, a primary or secondary amino group, or an isocyanate group. The aqueous polymer dispersion or aqueous binder is preferably an adhesive, particularly preferably a pressure-sensitive adhesive. The term pressure-sensitive adhesive is understood to mean an adhesive that is permanently tacky at room temperature (20 °C). A characteristic of a pressure-sensitive adhesive is sufficient adhesion (stickiness) combined with the necessary cohesion (internal strength in the adhesive layer).

[0067] The glass transition temperature (Tg) of the polymer is generally less than or equal to +15 °C for adhesives, and preferably less than or equal to 0 °C for pressure-sensitive adhesives. Preferably, the Tg is -65 °C to +10 °C, particularly preferably -65 °C to less than or equal to 0 °C, and most preferably -65 °C to -10 °C or -65 °C to -20 °C. The glass transition temperature can be determined by differential scanning calorimetry (ASTM D 3418-08, so-called "midpoint temperature").

[0068] thermoplastic microspheres containing propellant

[0069] Furthermore, the aqueous polymer dispersion contains blowing agent-containing thermoplastic microspheres. These microspheres, which comprise a thermoplastic polymer shell and an enclosed blowing agent, are commercially available, for example, under the brand name EXPANCEL®.

[0070] In such microspheres, the blowing agent is typically a liquid with a boiling point not higher than the softening temperature of the thermoplastic polymer shell. The softening temperature of the polymer shell, usually corresponding to its glass transition temperature Tg, is preferably in the range of 0 to 140 °C, most preferably from 30 to 100 °C. Upon heating, the blowing agent evaporates, increasing the internal pressure and simultaneously softening the shell, resulting in a significant expansion of the microspheres. The temperature at which expansion begins is called Tstart, while the temperature at which maximum expansion is reached is called Tmax. Tstart for the microspheres is preferably from 40 to 140 °C, most preferably from 50 to 100 °C. Tmax of the microspheres is higher than Tstart and preferably from 80 to 200 °C, most preferably from 100 to 170 °C.

[0071] Such microspheres are available in a variety of forms, for example as dry, free-flowing particles, as aqueous slurry, or as partially dehydrated moist cakes. Microspheres can be produced by polymerizing ethylene unsaturated monomers in the presence of a blowing agent. Detailed descriptions of various suitable microspheres and their preparation can be found, for example, in WO 2004 / 113613, WO 2007 / 142593, and in the literature cited therein.

[0072] The microsphere content in the aqueous dispersion is preferably 0.1 to 20 wt.%, in particular 0.5 to 10 wt.%.

[0073] The blowing agent content enclosed in the microspheres is preferably 5 to 50 wt.%, or 10 to 50 wt.%, 15 to 40 wt.%, and particularly preferably 20 to 35 wt.%, based on the mass of the microspheres. The blowing agent is generally a liquid with a boiling point not higher than the softening temperature of the thermoplastic polymer shell and may comprise hydrocarbons such as propane, n-pentane, isopentane, neopentane, butane, isobutane, hexane, isohexane, neohexane, heptane, isoheptane, getane, or isooctane, or mixtures thereof. Apart from that, other types of hydrocarbons can also be used, such as petroleum ether, or chlorinated or fluorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethane, dichloroethylene, trichloroethane, trichloroethylene, trichlorofluoromethane, perfluorinated hydrocarbons, etc. Preferred blowing agents include isobutane, alone or in mixture with one or more other hydrocarbons.The boiling point at normal pressure is preferably in the range of about -50 °C to about 100 °C, most preferably from about -20 °C to about 50 °C, and particularly from about -20 °C to about 30 °C.

[0074] The particle size of the microspheres, represented as volume median D(0.5), is preferably from 1 pm or more to 500 pm or less, preferably from 5 pm or more to 100 pm or less, or from 5 pm or more to 40 pm or less. The particle size can be determined, for example, by laser light scattering.

[0075] The microspheres can be added to the polymer dispersion in various application forms. For example, in dried form with a solids content preferably greater than 95 wt.%, or in not completely dried, moist form with a solids content preferably 55 wt.% or more up to 85 wt.% or less, or in the form of an aqueous slurry with a solids content preferably 5 to 55 wt.% or 35 to 50 wt.%.

[0076] The thermoplastic polymer shell of the microspheres can be formed from one or more homo- or copolymers obtained by polymerizing ethylene-unsaturated monomers. Suitable monomers include, for example, acrylic esters such as methyl acrylate or ethyl acrylate; methacrylic esters such as methyl methacrylate, isobornyl methacrylate, or ethyl methacrylate; monomers containing nitrile groups such as acrylonitrile, methacrylonitrile, alpha-chloroacrylonitrile, alpha-ethoxyacrylonitrile, fumaronitrile, or crotonitrile; vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate; vinylpyridine; vinylidene halides such as vinylidene chloride; styrenes such as styrene, halogenated styrenes, or alpha-methylstyrene; dienes such as butadiene, isoprene, or chloroprene; and vinyl ethers, especially those with only one C-C double bond. Examples of vinyl ethers include alkyl vinyl ethers, the alkyl group preferably with 1 to 10 carbon atoms, most preferably with 1 to 5 carbon atoms, e.g.Methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, sec-butyl vinyl ether, and mixtures thereof, of which methyl vinyl ether and ethyl vinyl ether are particularly preferred. One or more hydrogen atoms on the alkyl group may be substituted with a functional group such as a hydroxy, carboxylic acid, amine, ether, etc., e.g., ethylene glycol vinyl ether. Any mixtures of the above-mentioned monomers may also be used.

[0077] Preferably, the monomers comprise at least one (meth)acrylic acid ester monomer, most preferably at least one methacrylic acid ester such as methyl methacrylate. The amount of these in the polymer shell is preferably from about 0.1 wt.% or more to about 80 wt.% or less, most preferably from about 1 wt.% to about 25 wt.% of the total amount of monomers. Preferably, the monomers also comprise at least one vinylidene halide, most preferably vinylidene chloride. The amount of these in the polymer shell is preferably from about 1 wt.% to about 90 wt.%, most preferably from about 20 wt.% to about 80 wt.% of the total amount of monomers. Most preferably, the monomers comprise both at least one (meth)acrylic ester monomer and at least one vinylidene halide monomer. Preferably, the monomers comprise at least one nitrile-containing monomer, most preferably at least one selected from acrylonitrile and methacrylonitrile, in particular acrylonitrile.The amount of this in the polymer shell is preferably from about 1 to about 80 wt.%, most preferably from about 20 wt.% or more to about 70 wt.% or less of the total amount of monomers.

[0078] In an advantageous embodiment, the monomers comprise at least one acrylic ester monomer, at least one vinylidene halide, and at least one nitrile-containing monomer. The shell polymer can, for example, be a copolymer obtainable from monomers comprising methyl methacrylate in a preferred amount of about 0.1 wt.% or more to about 80 wt.% or less, most preferably about 1 wt.% or more to about 25 wt.% or less of the total amount of monomers; vinylidene chloride in a preferred amount of about 1 wt.% or more to about 90 wt.% or less, most preferably about 20 wt.% or more to about 80 wt.% or less of the total amount of monomers; and acrylonitrile in a preferred amount of about 1 to about 80 wt.%, most preferably about 20 to about 70 wt.% of the total amount of monomers. Copolymers of monomers comprising 20 to 80 wt.% acrylonitrile and 1 to 70 wt.% of nitrile are also suitable for the polymer shell.-% vinyl ether with only one C-C double bond, wherein the total amount of acrylonitrile and vinyl ether is 30 to 100 wt.%, preferably 50 to 100 wt.% or 65 to 100 wt.% of the ethylene unsaturated monomers. The ethylene unsaturated monomers preferably comprise 1 to 60 wt.%, 1 to 50 wt.%, 5 to 50 wt.% or 5 to 30 wt.% vinyl ether with only one C-C double bond, and preferably 40 to 80 wt.%, most preferably 50 to 70 wt.%.

[0079] Acrylonitrile, and preferably also methacrylonitrile, is preferably present in an amount of 1 to 50 wt.%, most preferably in an amount of 5 to 40 wt.%, and preferably also one or more esters of acrylic acid, esters of methacrylic acid and mixtures thereof, preferably in an amount of 1 to 50 wt.%, more preferably in an amount of 5 to 40 wt.%.

[0080] Preferably, the shell of the microspheres is formed from a copolymer of ethylene-unsaturated monomers comprising at least one monomer selected from (meth)acrylic acid ester monomers, vinylidene halide monomers, acrylonitrile, and vinyl ether monomers. Copolymers of monomers comprising alkyl(meth)acrylate (e.g., methyl acrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate, as well as mixtures of these monomers), vinylidene chloride, and acrylonitrile, or copolymers of monomers comprising at least one vinyl ether monomer and acrylonitrile, are particularly preferred.

[0081] The monomers for the polymer shell can also include crosslinking multifunctional monomers, such as divinylbenzene, ethylene glycol di(meth)acrylate, di(ethylene glycol) di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,10-decanediol (meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, triallyl formal tri(meth)acrylate, allyl (meth)acrylate, trimethylolpropane tri(meth)acrylate, and tributanediol di(meth)acrylate. PEG-200 di(meth)acrylate, PEG-400 di(meth)acrylate, PEG-600 di(meth)acrylate, 3-acryloyloxyglycol monoacrylate, triacryl formal,

[0082] Triallyl isocyanate, triallyl isocyanurate, divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, etc. Particularly preferred crosslinking monomers are at least trifunctional, e.g., pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, triallyl formal tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, triacryl formal, triallyl isocyanate, and triallyl isocyanurate. The amount of crosslinking functional monomers can be, e.g., from 0.1 wt% or more to 10 wt% or less, or 0.1 wt% or more to 1 wt% or less, or 0.2 to 0.5 wt%. or of 1 to 3 wt.% of the ethylene unsaturated monomers, wherein 0.1 to 1 wt.% is particularly preferred for at least trifunctional monomers and 1 to 3 wt.% is preferred for difunctional monomers.

[0083] Apart from the polymer shell and the blowing agent, the microspheres may comprise other substances added, for example, during their manufacture; generally in an amount of 0 wt.% or more to 20 wt.% or less, preferably from 1 wt.% or more to 10 wt.% or less. Examples of such substances are solid suspending agents, such as one or more substances selected from starch, cross-linked polymers, gum agar, derivatized cellulose, such as methylcellulose, hydroxypropyl methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose, silica, colloidal clays such as chalk and bentonite, and / or one or more salts, oxides, or hydroxides of metals such as Al, Ca, Mg, Ba, Fe, Zn, Ni, and Mn, for example, one or more substances selected from calcium phosphate, calcium carbonate, magnesium hydroxide, barium sulfate, calcium oxalate, and hydroxides of aluminum, iron, zinc, nickel, or manganese.If present, these solid suspending agents are usually located mainly on the outer surface of the polymer shell.

[0084] Preferably, the microspheres are characterized in that the microspheres have a shell made of thermoplastic polymer and a blowing agent, preferably isobutane, enclosed therein, wherein preferably 17 to 40 wt.% blowing agent is enclosed in the microspheres and the microspheres have a particle size (volume median D(0,5)) of 5 pm or more to 40 pm or less.

[0085] Polyols, polyamines and thermoplastic polymers

[0086] The aqueous polymer dispersion further comprises at least one additive selected from the group consisting of polyols, polyamines and thermoplastic polymers.

[0087] The weight fraction of the additive in the polymer dispersion is preferably 1 wt.% or more to 15 wt.% or less, 1 wt.% or more to 8 wt.% or less, or 1 wt.% or more to 5 wt.% or less.

[0088] Suitable polyols include, for example, (poly)propylene glycol, (poly)ethylene glycol, glycerin, and starch. Suitable polyamines include, for example, urea. The thermoplastic polymers are selected from the group consisting of ethylene vinyl acetate, polyamide, polyester, polyethylene, polypropylene, polystyrene, styrene-containing copolymers, and ethylene / propylene copolymers. Ethylene vinyl acetate (EVA) is preferred as an additive. The ethylene vinyl acetate can have a vinyl acetate content of up to 28% by weight, preferably at least 14% by weight.

[0089] The ethylene vinyl acetate (EVA) can contain up to 28% by weight of vinyl acetate. Urea, EVA (e.g., in the form of EVA powder), starch, and glycerin are particularly preferred.

[0090] The use of such additives significantly increases the tightening speed during bonding.

[0091] The use of these substances for the formulation of classic dispersion adhesives based on polyvinyl acetate (PVAc), vinyl acetate ethylene (VAE; also called "ethylene vinyl acetate" or "EVA") or acrylate is not new, however, water retardation and thus reduced drying and setting speed are usually observed in these systems.

[0092] In the system described here, however, the effect is exactly the opposite. On all tested substrate combinations, there is a significant increase in the draw-up speed. This is due to improved water removal from the dispersion strand. Surprisingly, it was also found that a proportion of tackifiers typically used in such systems, either in the dispersion or the formulation, can reduce the draw-up speed of the base dispersion, but this can be compensated for by the addition of polyols, polyamines, or EVA.

[0093] Surprisingly, it was also found that adding starch to the dispersion ideally improves strand quality during extrusion, but leads to a reduction in the drawing speed. This is surprising, since the process temperatures are above the gelatinization temperature of commercially available starches. Again, the drawing speed can be improved by using additives such as urea or similar substances.

[0094] Surprisingly, it was also found that the incorporation of powdered EVA (ethylene / vinyl acetate copolymer) into the dispersion also significantly increases the pull-in speed compared to the initial value.

[0095] In a preferred embodiment of the invention, the dispersed polymer (i) is selected from the group consisting of polyacrylate, polystyrene acrylate, and polyurethane, and the additive (iii) is ethylene vinyl acetate. It is further preferred that the aqueous dispersion comprises polyacrylate as the dispersed polymer (i) and ethylene vinyl acetate as the additive (iii). The above descriptions of the individual components and their proportions are also applicable to these preferred embodiments.

[0096] Additional additives

[0097] The aqueous polymer dispersion can consist exclusively of (i) the polymer dispersed in aqueous phase, (ii) the microspheres and (iii) polyols, polyamines or the thermoplastic polymer, preferably ethylene vinyl acrylate, but may also contain other additives different from the additives.

[0098] For pressure-sensitive adhesives, suitable additives include, for example, so-called tackifier resins. Tackifiers are, for example, natural resins such as rosin resins and their derivatives formed by disproportionation or isomerization, polymerization, dimerization, or hydrogenation. The acid groups of these resins can be present in their salt form (with, for example, mono- or polyvalent counterions) or, preferably, in their esterified form. Alcohols used for esterification can be mono- or polyvalent. Examples include methanol, ethanediol ("glycol"), diethylene glycol, triethylene glycol, 1,2,3-propanetriol, and pentaerythritol.

[0099] Preferred tackifiers are natural or chemically modified rosin resins. Rosin resins consist predominantly of abietic acid or abietic acid derivatives.

[0100] Further additives to increase stickiness (tackifiers) are low-molecular-weight polymers, such as acidic polyacrylates with glass transition temperatures in the range of -60 °C to -20 °C. The low-molecular-weight polymers suitable as tackifiers have a weight-average molecular weight of preferably 500,000 or less, preferably 1,500 or more to 45,000 or less, or 2,000 or more to 20,000 or less, and can be added to the polymer dispersion, for example, as a 100% system. The tackifiers are preferably present in the aqueous polymer dispersion in amounts of 1 wt.% or more to 40 wt.% or less, and in particular 5 wt.% or more to 30 wt.%.

[0101] Other additives that may be contained in the aqueous dispersion include, for example, antioxidants, fillers, dyes, leveling agents, plasticizers and wetting agents.

[0102] Suitable wetting agents include, for example, sulfosuccinates, in particular alkyl sulfosuccinic acid esters (methyl, ethyl, propyl, butyl, pentyl, hexyl, and isooctyl esters). These are used to reduce the surface tension of the dispersion and lead to better wetting of the substrates to be bonded.

[0103] Polymer dispersion

[0104] Preferred polymer dispersions are characterized in that the content of dispersed polymer in the polymer dispersion is 20 wt.% or more to 75 wt.% or less, preferably 40 wt.% or more to 70 wt.% or less; the content of microspheres in the polymer dispersion is 0.1 wt.% or more to 20 wt.% or less, preferably 0.5 wt.% or more to 10 wt.% or less; and the total solids content of the aqueous polymer dispersion is 30 wt.% or more to 80 wt.% or less, preferably 40.5 wt.% or more to 80 wt.% or less, or 45 wt.% or more to 75 wt.% or less. This corresponds to a water content of 20 wt.% or more to 70 wt.% or less, or of 20 wt.% or more to 59.5 wt.% or less, or of 25 wt.% or more to 55 wt.% or less.

[0105] The viscosity of the coating compound before coagulation is preferably 50 mPa·s or more up to 3000 mPa·s or less, and particularly preferably 100 mPa·s or more up to 2000 mPa·s or less. Viscosities are measured according to DIN EN ISO 3219 (23 °C, 250 1 / s).

[0106] Coagulation

[0107] To induce coagulation in the aqueous polymer dispersions described above, energy is introduced. This energy is introduced primarily thermally, although, depending on the configuration of the device described in the first aspect of the invention, mechanical energy input through shear may also play a role.

[0108] Simultaneous heating and shearing is particularly preferred. Heating is preferably carried out to a temperature of 50 °C or more up to 150 °C or less, preferably 60 °C or more up to 110 °C or less. The temperature is greater than or equal to the temperature at which the microspheres are heated. Heating is achieved by flowing through the heatable components of the device according to the invention.

[0109] In shearing applications, the shear rates are preferably in the range of 100 1 / s or more to 500,000 1 / s or less. Shearing can be achieved by passing the material through a microchannel with diameters preferably from 0.5 to 10 mm.

[0110] Bonding of substrates

[0111] With the method according to the invention, the adhesive made from the coagulable aqueous polymer dispersion can be used to bond substrates by coating them completely or partially with the coagulate or the adhesive in a spot-like manner.

[0112] The coated substrate is preferably selected from the group consisting of paper, cardboard, wood, stone, concrete, non-woven materials made of artificial and / or natural fibers, woven textiles made of artificial and / or natural fibers, open-cell or closed-cell polymer foams, in particular consisting of polyurethane, polyester, polyethylene, polypropylene and polystyrene, or composites of the aforementioned substrates. Natural materials and composites of these with plastics are also suitable substrates.

[0113] The polymer dispersion, in its coagulated form, is applied in dot form to at least one substrate using a process according to the invention. In the case of a web-like coating, the coating is preferably applied in a continuous process, while in the case of, for example, a carton closure, it is applied as a discontinuous process. The substrates or carrier materials are preferably paper, cardboard, or carton.

[0114] In the preferred method, the polymer dispersion is applied in coagulated form to a sealable area of ​​a cardboard packaging and the cardboard packaging is sealed by means of the applied, coagulated adhesive dispersion.

[0115] Detailed character description

[0116] Exemplary embodiments of the device according to the invention are described in more detail below with reference to the accompanying figures. The figures show:

[0117] Fig. 1 shows a schematic sectional view of an exemplary embodiment of a device according to the invention for point-like application;

[0118] Fig. 2A shows an enlarged sectional view of the device according to the invention in the area of ​​the discharge nozzle in the closed state;

[0119] Fig. 2B shows an enlarged sectional view of the device according to the invention in the area of ​​the discharge nozzle in the open state; as well as

[0120] Fig. 3 shows a view of the embodiment according to the invention from Fig. 1 integrated into a system for adhesive application.

[0121] Figure 1 shows a schematic sectional view of an exemplary embodiment of a device according to the invention for the point-like application of adhesives made from coagulable aqueous polymer dispersions.

[0122] The device comprises a nozzle assembly 100 with a nozzle needle 2 and a nozzle body 1, an actuator assembly 11, and a heating device 4 configured to heat the nozzle assembly 100 to a defined temperature required for the coagulation of the aqueous polymer dispersion. A through-channel 111 is formed in the nozzle body 1, extending along a longitudinal axis from a first end 13 to an opposite second end 14, and a discharge nozzle 3 with an outlet opening 30 for the coagulated aqueous polymer dispersion is formed at the second end 14. The nozzle needle 2 is translationally displaceable in the through-channel 111 along the longitudinal axis and can be repeatedly moved from a first closed position to a second open position and vice versa by means of the actuator assembly 11.wherein a receiving chamber 31 (see Figure 2B) for the coagulable aqueous polymer dispersion is formed between the nozzle needle 2 and the discharge nozzle 3, at least in the region of the through-cross-section of the discharge nozzle 3; wherein the nozzle assembly 100 has at least one feed channel 21, which extends from the first end 13 to the opposite second end 14 and is designed to feed the coagulable aqueous polymer dispersion into the region of the receiving chamber 31. The device further comprises a heating device 4, which is designed to heat the nozzle assembly 100 to a defined temperature required for the coagulation of the aqueous polymer dispersion. In the exemplary embodiment, the heating device 4 is designed as a heating sleeve, which surrounds the nozzle body 1 and includes a temperature sensor 5.

[0123] A comparison of Figures 2A and 2B shows that the volume of the receiving chamber 31, which is large enough to hold at least one application quantity of the coagulable aqueous polymer dispersion, is greater in the open position according to Figure 2B than in the closed position according to Figure 2A. In the closed position, as shown in Figure 2A, the outlet opening 30 of the dispensing nozzle 3 is completely closed by the lower end of the nozzle needle 2. The figures show that the nozzle needle 2 tapers in the region of its lower end facing the outlet opening 30 and has a nozzle needle tip 22 which is adapted to the diameter of the outlet opening 30 of the dispensing nozzle 3. As can be seen from Figures 2A and 2B, the nozzle needle tip 22 completely fills the outlet opening 30 in the closed position and rests inside the passage channel 111 spaced apart from the outlet opening 30 in the open position, thus releasing the outlet opening 30.In the exemplary embodiment, a four-start trapezoidal thread is formed in the area of ​​an upper section of the nozzle needle 2, wherein each thread is formed as a capillary-shaped supply channel 24 and wherein the threads form four supply channels 21 for supplying the coagulable aqueous adhesive into the area of ​​the receiving chamber 31.

[0124] In the exemplary embodiment shown, the actuator device 11 is designed as a pneumatically operated valve, the valve having two pressure ports 6 and 8 for pneumatically opening and closing the valve or correspondingly moving the nozzle needle 2, which is connected to the valve, to drive the nozzle needle 2 via the valve.

[0125] A spring assembly 10 is arranged on the actuator assembly 11, which is designed to exert a spring force on the nozzle needle 2, at least in the open position. This spring force acts in the direction of the closed position and returns the nozzle needle 2 to the closed position. The actuator assembly 11 also has a stroke adjustment 9, by means of which the position of the nozzle needle 2 in the closed and open positions relative to the nozzle body 1 can be adjusted along its longitudinal axis.

[0126] The coagulable aqueous polymer dispersion is fed under pressure via a feed device not shown in the figures through the feed opening 7 in the area of ​​the first end 13 to the at least one feed channel 21.

[0127] In the illustrated embodiment, the discharge nozzle 3 has a through-section that tapers conically in the region of a nozzle tip 32 and opens into the outlet opening 30. The nozzle needle 2 has an upper section adapted to the dimensions of the through-channel 111 and a lower section that tapers conically and is adapted to the region of the conically tapered through-section. The nozzle needle tip 22 is formed as the lower end of the nozzle needle 2 and is adapted to the cross-section of the outlet opening 30 of the discharge nozzle 3. In the closed position of the nozzle needle 2, the nozzle needle tip 22 completely fills the outlet opening 30 of the discharge nozzle 3 and seals it fluid-tight. In the closed position, a portion of the cone facing the nozzle needle tip 22 comes into contact with the inner wall of the conically tapered nozzle tip 32.

[0128] Figure 3 shows the integration of the exemplary embodiment of a device according to the invention for the point-like application of adhesives made from coagulable aqueous polymer dispersions, as already described with reference to Figure 1. Figure 3 shows that the two pressure ports 6 and 8 are connected to a control device 40, or more precisely a control valve, for the pneumatic opening and closing of the valve and corresponding displacement of the nozzle needle 2. This control valve, via a corresponding time control device 42, pressurizes the pressure ports 6 and 8 according to a timed sequence. Figure 3 also shows that the feed opening 7 is connected via a feed line 70 to a pressurized reservoir 90, in which the aqueous coagulable polymer dispersion is stored. Pressurizing the reservoir 90 causes the dispersion to be conveyed through the feed line 70 and supplied to the feed opening 7.The delivery pressure for the polymer dispersion, as well as the control pressure, which is applied to the pressure connections 6 and 8, can be set via appropriate pumps and pressure regulating devices 80.

[0129] The present invention will be explained in more detail with reference to the following examples.

[0130] Example 1

[0131] A coagulable aqueous self-crosslinking styrene acrylate dispersion, e.g., Acronal® 5044, modified with 1 to 5 wt.% blowing agent-containing thermoplastic microspheres and with 2 to 8 wt.% ethylene vinyl acetate as an additive, was conveyed from a storage vessel by means of a pressure vessel, fed into the inventive heatable nozzle assembly comprising a nozzle needle and a nozzle body, and heated to a temperature of 94 °C to 95 °C, and applied at the nozzle outlet (nozzle diameter 0.5 mm; nozzle needle pulse times 10 to 15 ms) to a paper or cardboard surface (predominantly white kraftliner, type BE 73W, 135 g / m²). 2 There was no sign of the nozzle outlet becoming clogged.

[0132] Example 2

[0133] A coagulable aqueous self-crosslinking acrylate-based dispersion Acronal® 5047, an acrylate / styrene copolymer (CAS number 25085-34-1), modified with thermoplastic microspheres containing 2 to 8 wt.% blowing agent and 1 to 8 wt.% polyamines, was conveyed from a storage vessel by means of a pressure vessel, fed into the inventive heated nozzle assembly comprising a nozzle needle and a nozzle body, and heated to a temperature of 94 °C to 95 °C, and applied at the nozzle outlet (nozzle diameter 0.5 mm; nozzle needle pulse times 10 to 15 ms) to a paper or cardboard surface (predominantly white kraftliner, type BE 73W, 135 g / m²). 2 There was no sign of the nozzle outlet becoming clogged.

[0134] Example 3

[0135] Analogous to Example 2, a self-crosslinking styrene-acrylate dispersion based on Acronal® 5011 was applied to a paper or cardboard surface using the heated nozzle device according to the invention. No clogging of the nozzle outlet was observed.

Claims

Patent claims 1. Device for the point-like application of adhesives made from coagulable aqueous polymer dispersions, comprising: a nozzle assembly (100) with a nozzle needle (2) and a nozzle body (1), an actuator assembly (11), a heating device (4) configured to heat the nozzle assembly (100) to a defined temperature required for the coagulation of the aqueous polymer dispersion; wherein a through-channel (111) is formed in the nozzle body (1), which extends along a longitudinal axis from a first end (13) to an opposite second end (14) and wherein a discharge nozzle (3) with an outlet opening (30) for the coagulated aqueous polymer dispersion is formed at the second end (14);wherein the nozzle needle (2) is received in the passage channel (111) so as to be translatably displaceable along the longitudinal axis and can be repeatedly moved from a first closed position to a second open position and vice versa by means of the actuator device (11); wherein a receiving space (31) for the coagulable aqueous polymer dispersion is formed between the nozzle needle (2) and the discharge nozzle (3) at least in the area of ​​the passage cross-section of the discharge nozzle (3);wherein the nozzle assembly (100) has at least one feed channel (21) which extends from the first end (13) to the opposite second end (14) and is designed to feed the coagulable aqueous polymer dispersion into the area of ​​the receiving chamber (31), wherein a volume of the receiving chamber (31) for receiving at least one application quantity of the coagulable aqueous polymer dispersion is larger in the open position than in the closed position and in the closed position the outlet opening (30) of the discharge nozzle (3) is completely closed by a lower end of the nozzle needle (2).

2. Device according to claim 1, wherein the nozzle needle (2) tapers in the region of the lower end facing the outlet opening (30) and has a nozzle needle tip (22) which is adapted to the diameter of the outlet opening (30) of the discharge nozzle (3); and wherein the nozzle needle tip (22) in the closed position fills and closes the outlet opening (30) and in the open position rests inside the passage channel (111) spaced apart from the outlet opening (30) and releases the outlet opening (30).

3. Device according to claim 1 or 2, wherein the discharge nozzle (3) has a passage cross-section which tapers conically in the region of a nozzle tip (32) and opens into the outlet opening (30), wherein the nozzle needle (2) has an upper section which is adapted to the dimensions of the passage channel (111) and a lower section which tapers conically and is adapted to the region of the conically tapered passage cross-section, wherein the nozzle needle tip (22) is designed as the lower end of the nozzle needle (2) and is adapted to the cross-section of the outlet opening (30) of the discharge nozzle (3).

4. Device according to claim 3, wherein in the closed position of the nozzle needle (2) the nozzle needle tip (22) completely fills the outlet opening (30) of the discharge nozzle (3) and seals it fluid-tight, and wherein in the closed position a portion of the cone facing the nozzle needle tip (22) comes into contact with the inner wall of the conically tapered nozzle tip (32).

5. Device according to one of the preceding claims, wherein the nozzle needle (2) and the through-channel (111) are circularly cylindrical.

6. Device according to one of the preceding claims, wherein the dimensions of the through-channel (111) and the nozzle needle (2) in the region of an upper section are designed such that a clearance fit, preferably an "H7 / g6" fit system, is formed between them.

7. Device according to one of the preceding claims, wherein at least one trapezoidal recess (24) is formed in the outer circumference in the area of ​​the upper section of the nozzle needle (2), which forms at least one feed channel (21) of the nozzle device (100) at least sectionally.

8. Device according to one of the preceding claims, wherein a four-start trapezoidal thread is formed in the area of ​​the upper section of the nozzle needle (2), wherein each thread is formed as a capillary-shaped supply channel (24) and wherein the threads form four supply channels (21) for supplying the coagulable aqueous adhesive into the area of ​​the receiving chamber (31).

9. Device according to one of the preceding claims, wherein the actuator device (11) (1) comprising at least one pneumatically operated valve, particularly preferably a differential pressure valve, which allows for repeated repositioning of the nozzle needle (2) is configured to move from the closed position to the open position and back; or (ii) has an electrically driven valve configured to repeatedly move the nozzle needle (2) from the closed position to the open position and back.

10. Device according to one of the preceding claims, wherein the actuator device (11) comprises a spring device (10) which is configured to exert a spring force on the nozzle needle (2) at least in the open position, which acts in the direction of the closing position and returns the nozzle needle (2) to the closed position.

11. Device according to one of the preceding claims, wherein the actuator device (11) has a stroke adjustment (9) by means of which the position of the nozzle needle (2) in the closing and opening positions relative to the nozzle body (1) can be adjusted along the longitudinal axis.

12. Device according to one of the preceding claims, wherein the device further comprises a feed device for pressurised feeding of the coagulable aqueous polymer dispersion into a feed opening (7) in the region of the first end (13) of the at least one feed channel (21).

13. Device according to one of the preceding claims, wherein the heating device (4) comprises a heating sleeve which surrounds the nozzle body (1) along the longitudinal axis at least along a partial section of the at least one feed channel (21).

14. Device according to one of the preceding claims, further comprising at least one control device which is designed to control the heating device (4) by means of a temperature sensor (5) and / or wherein the control device is designed to control the actuator device (11) for setting a dwell time of the nozzle needle (2) in the open position and in the closed position.

15. Method for the spot application of adhesives made from coagulable aqueous polymer dispersions to a substrate comprising the spot application of an application quantity of a coagulated aqueous polymer dispersion on the substrate by means of a device having the features according to one of claims 1 to 14.

16. Method for the spot application of adhesives made from coagulable aqueous polymer dispersions onto a substrate by means of a device, preferably by means of a device having the features according to one of claims 1 to 14, for the spot application of an application quantity of a coagulated aqueous polymer dispersion, comprising the process steps: (a) Initial supply of at least one application quantity of the coagulable aqueous polymer dispersion into the receiving space (31) between the nozzle needle (2) and the discharge nozzle (3) at least in the area of ​​a passage cross-section of a discharge nozzle (3) during a first opening duration of the nozzle device (100) when the nozzle needle (2) is arranged in the open position, and heating of the coagulable aqueous polymer dispersion during the supply to a temperature required for the coagulation of the aqueous polymer dispersion; (b) Arranging a first application point on a surface on which an application quantity of the coagulated polymer dispersion is to be applied at a defined distance and opposite the outlet opening (30) of the discharge nozzle (3); (c) Moving the nozzle needle (2) from the open position to the closed position, thereby reducing the volume of the receiving chamber (31), which causes an application quantity of the coagulated aqueous polymer dispersion to be ejected through the nozzle opening during the movement of the nozzle needle (2) to the closed position and applied to a first application site on a substrate until the nozzle needle (2) closes flush with the outlet opening (30) of the discharge nozzle (3); (d) Moving the nozzle needle (2) into the open position and re-feeding and heating an application quantity of the coagulable aqueous polymer dispersion into the receiving chamber (31) during a second opening period of the nozzle device (100) when the nozzle needle (2) is in the open position; and (e) optional repetition of process steps b) to d) by any integer number of repetitions, wherein the discharge nozzle (3) is positioned opposite further application locations on the substrate.

17. Method according to claim 15 or 16, wherein the coagulable aqueous polymer dispersion (i) at least one polymer dispersed in aqueous phase, (ii) thermoplastic microspheres containing a blowing agent, and (iii) comprising at least one additive selected from the group consisting of polyols, polyamines and thermoplastic polymers 18. The method of claim 17, wherein the polyol is selected from the group consisting of (poly-)propylene glycol, (poly-)ethylene glycol, glycerin and starch, the polyamine is urea and the thermoplastic polymers are selected from the group consisting of ethylene vinyl acetate, polyamide, polyester, polyethylene, polypropylene, polystyrene, styrene-containing copolymers and ethylene / propylene copolymers.

19. Method according to claim 17 or 18, wherein the aqueous dispersed polymer is selected from the group consisting of polyurethane, copolymers of vinyl acetate and ethylene, polyvinyl acetate (PVAc), polyacrylate, polystyrene acrylate, styrene / butadiene copolymer, polyisoprene copolymer, polychloroprene and polyepoxide.

20. A method according to one or more of claims 17 to 19, wherein the content of dispersed polymer in the polymer dispersion is 20 wt.% or more to 75 wt.% or less, the content of microspheres in the polymer dispersion is 0.1 wt.% or more to 20 wt.% or less, and the total solids content of the aqueous polymer dispersion is preferably 30 wt.% or more to 80 wt.% or less.

21. A method according to one or more of claims 17 to 20, wherein the additive content in the polymer dispersion is 1 wt.% or more to 15 wt.% or less, 1 wt.% or more to 8 wt.% or less, or 2 wt.% or more to 5 wt.% or less.

22. Method according to one or more of claims 17 to 21, wherein the microspheres have a shell of thermoplastic polymer and blowing agent enclosed therein, preferably one or more hydrocarbon(s) having one or more to eight or fewer carbons, wherein the microspheres in the unexpanded state have a particle size with a volume median D(0.5) of 5 pm or more to 40 pm or less.

23. A method according to one or more of claims 17 to 22, wherein the shell of the microspheres is formed from a copolymer of ethylene unsaturated monomers comprising at least one monomer selected from (meth)acrylic acid ester monomers, vinylidene halide monomers, acrylonitrile and vinyl ether monomers, in particular that the shell of the microspheres is formed from a copolymer of monomers comprising alkyl (meth)acrylate, vinylidene chloride and acrylonitrile or from monomers comprising at least one vinyl ether monomer and acrylonitrile.

24. Method according to one or more of claims 17 to 23, wherein the microspheres have an expansion start temperature (Tstart) of 40 °C or more to 140 °C or less and a maximum expansion temperature (Tmax) which is higher than Tstart and in the range of 80 °C or more to 200 °C or less.

25. Method according to one or more of claims 17 to 24, wherein the coagulation is carried out by heating in the receiving chamber to a temperature of 50 °C or more up to 150 °C or less, preferably 60 °C or more up to 110 °C or less, and / or by shearing with shear rates of 100 1 / s or more up to 500000 1 / s or less.

26. A method according to one or more of claims 17 to 25, wherein a coagulable self-crosslinking styrene acrylate dispersion with 1 to 5 wt.% blowing agent-containing thermoplastic microspheres and 2 to 8 wt.% ethylene vinyl acetate is used as an additive and is heated to a temperature of 90 °C to 100 °C, preferably 94 °C to 95 °C, for coagulation in the receiving chamber.

27. Method according to one or more of claims 15 to 24, wherein the coagulated aqueous polymer dispersion is applied wholly or partially to the surface of at least one substrate, and wherein the application can also be carried out overhead.

28. Use of a device for the spot application of adhesives made from coagulable aqueous polymer dispersions, having the features according to any one of claims 1 to 14, for carrying out the method according to any one of claims 16 to 27.

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