EP2377765A2 - Adhesive packaging - Google Patents

Abstract

Packaging hot melt adhesive, preferably pressure-sensitive hot melt adhesive or adhesive substance as a material to be packaged in a plastic film at room temperature, comprises (a) melting the material to be packaged, (b) portion-wise dosing of the molten material on a cooling belt and cooling the material below its melting point to form material portions, (c) removing the material portions from the cooling belt and, (d) packaging the material portions in a plastic film. The cooling belt exhibits a textile carrier with threads, which forms at least a part of thermal conductors. Packaging hot melt adhesive, preferably pressure-sensitive hot melt adhesive or adhesive substance as a material to be packaged in a plastic film at room temperature, comprises (a) melting the material to be packaged, (b) portion-wise dosing of the molten material on a cooling belt and cooling the material below its melting point to form material portions, (c) removing the material portions from the cooling belt and, (d) packaging the material portions in a plastic film. The cooling belt exhibits a textile carrier with threads, which forms at least a part of thermal conductors, with which heat can be transferred from one flat side of the cooling belt on the opposite side of the carrier embedded in a polymer matrix so that the thermal conductors are covered largely at least on the side, which comes into contact with the material to be packaged.

Description

The present invention relates to a method for packaging hot melt adhesive, in particular pressure-sensitive hot melt adhesive or substances sticky at room temperature as a material to be packaged in a plastic film.

Hotmelt adhesives are solvent-free adhesives which, for use by the introduction of heat, are put into a liquid or viscous state in which they can readily wet the material surfaces to be bonded and on which they adhere firmly after cooling and solidification. Hot melt adhesives usually consist of a mixture of substances, which are melted together during manufacture and then formulated.

For use as labeling adhesives or as pressure-sensitive adhesives hot melt adhesives are used which have adhesive properties at room temperature or below. Such adhesives are also referred to as PSA adhesives, which stands for "Pressure Sensitive Adhesive". The preparation or portioning of such pressure-sensitive hot-melt adhesives causes difficulties due to the sticky surface of the adhesive portions.

Since it is often desired that the packaging of the portioned hot melt adhesive in use with should be melted to avoid additional operations by emptying the packaging, the film materials used must have a low melting point and also must not significantly deteriorate the adhesive properties of the hot melt adhesive. When using film packaging from polymers with a low melting point separates due to the high melting temperatures of the hot melt adhesive, for example, 120 or 140 ° C direct filling of the hot melt adhesive in the film packaging.

In the EP 0 649 718 a method is proposed, after which the hot melt adhesive is formulated and the resulting adhesive portions are surface-treated with an anti-stick substance, cooled in a cooling bath and then packaged in foil bags.

In the WO 00/34129 It is proposed to cool pressure-sensitive hot melt adhesives so much after portioning in a water bath that they lose their tackiness and pack in this state. In addition, fatty acid derivatives are added to the water bath as an antiblocking agent. A disadvantage of this method is that in this way only PSA hot melt adhesives can be packed, which already lose their tack at temperatures above the freezing point of the cooling bath, ie above 0 ° C. In both of the aforementioned methods, the anti-adherents used may also adversely affect the adhesive properties of the hot melt adhesive. Finally, water residues of the cooling bath must be removed from the hotmelt adhesive before packaging to prevent the presence of Prevent water from re-melting the hot melt adhesive before use.

Another method for packaging hot melt adhesive is in the DE 199 13 034 described, after which the hot melt adhesive is filled directly into a film tube, which is located during the filling process in a water bath. In this way, the outside of the film tube is sufficiently cooled to prevent immediate melting by the filled hot melt adhesive. The film bag is partially squeezed together by means of transport rollers to form individual portions and welded at these points. A disadvantage of this method is that the hot melt adhesive is available only in relatively large massive portions and that these portions must first be dried after removal from the water bath. Furthermore, this process can only be carried out with packaging films which have a relatively high melting point, so that they do not melt despite water cooling during filling.

The object underlying the present invention is to provide a method by which the disadvantages known from the prior art can be overcome. In particular, should be dispensed with the use of non-stick surface coatings in the packaging of pressure sensitive hot melt adhesives. Furthermore, elaborate drying steps are to be avoided and the production of different dosage forms and Serving sizes for hot melt adhesive portions are made possible.

1. (a) Aufschmelzen des zu verpackenden Materials;
2. (b) portionsweises Dosieren des geschmolzenen Materials auf ein Kühlband und Abkühlen des Materials unter seinen Schmelzpunkt zur Ausbildung von Materialportionen;
3. (c) Entfernen der Materialportionen vom Kühlband und
4. (d) Verpacken der Materialportionen in die Kunststofffolie,

wobei das Kühlband einen textilen Träger mit Fäden aufweist, von denen wenigstens ein Teil Wärmeleitfäden bilden, mit denen Wärme von der einen Flachseite des Kühlbandes auf die gegenüberliegende Seite übertragen werden kann und der Träger in eine Polymermatrix derart eingebettet ist, dass die Wärmeleitfäden zumindest auf der mit dem zu verpackenden Material in Berührung kommenden Seite weitestgehend abgedeckt sind.The present object is achieved by a method of the type mentioned, which comprises the following steps:

1. (a) melting the material to be packaged;
2. (b) portioning the molten material in portions onto a cooling belt and cooling the material below its melting point to form portions of material;
3. (c) removing the material portions from the cooling belt and
4. (d) packaging the material portions in the plastic film,

wherein the cooling belt comprises a textile carrier with threads, of which at least one part form thermal conductors, with which heat can be transferred from one flat side of the cooling belt to the opposite side and the carrier is embedded in a polymer matrix such that the heat conducting threads at least on the are covered as far as possible with the material to be packaged coming into contact side.

For melting the hotmelt adhesive it can be used in any desired form or the hotmelt adhesive can be mixed from its individual components, that is to say be prepared directly. The preparation of the individual components can be carried out before or during the melting. In this case, the melt is expediently mixed, for example, by stirring.

The method of the present invention can package a variety of materials, such as resins and the like, with packaging of hot melt adhesives being a preferred application.

In the context of the method according to the invention, the portionwise dosing can be carried out in different variants. The molten material can be applied, for example, in strand form, in the form of pillows or in pasted form on the cooling belt. This can be done for example via a heated extruder, via one or more nozzles, such as in a Pastilliervorrichtung. By portionwise dosing we understand both the dosing in defined portions, for example by weight, as well as the dosing in different portions. For unitary weight portions, these can be summarized by counting to a desired package size. Portions of different weights can be combined, for example, via belt weighers to desired pack sizes.

In the context of the present invention, it is provided that the heat conducting threads are largely covered at least on the side in contact with the material to be packaged. This is understood to mean that the heat conducting threads are practically completely covered by the polymer matrix and can only protrude from the polymer matrix at individual points, in particular the bending points, for example in plain weave of the textile support. The coverage of the thermal conduction through the polymer matrix is in such a case on the corresponding side of the cooling belt at least 75%, in particular at least 85 to 95%, preferably 95% until complete coverage. Most preferably, a complete coverage of the thermal conduction through the polymer matrix on at least one side of the cooling belt before.

Also cooling belts can be used, which have on both sides of the above-mentioned covers the heat conduction through the polymer matrix.

The Wärmeleitfäden the cooling belt allow rapid heat transfer to the opposite side of the cooling belt, so that cooling of the material or the hot melt adhesive through a cooling bath, such as a water bath, is not required. On the opposite side, the heat dissipated therefrom can be dissipated, for example, by direct contact with a cooling medium, such as by spraying or indirectly by contact with a cooled plate or roller.

Due to the almost complete covering of the heat conducting threads with the polymer matrix of the cooling belt, the heat conducting threads, which are usually formed at least in part from metal threads or carbon fibers, do not come into direct contact with the material or hotmelt adhesive. This is important insofar as the hot-melt adhesive, depending on the composition of the material of the cooling threads can have such a high adhesion, that a simple removal of the adhesive portions of the cooling belt would not be possible in this case.

The cooling belts which can be used according to the invention can be suitably produced in such a way that initially the textile carrier is created, for example by interweaving weft and warp threads in plain weave. This textile carrier is then passed through a V-shaped slot in which is the raw material of the polymer matrix, which impregnates the textile carrier. For example, solutions or dispersions of the polymers of the polymer matrix in water or organic solvents are used as the raw material for the polymer matrix.

Likewise, reactive prepolymers can be used to prepare the polymer matrix, which react after impregnation of the textile support to form the polymer matrix. In principle, all reaction types are suitable for the polymerization reaction taking place in this case, in particular the radical polymerization, polyaddition or polycondensation, the latter for example with elimination of water, methanol, ethanol, acetic acid or other typical leaving groups. The aforementioned substances are known to those skilled in the field of adhesives and jointing compounds. The polymerization reaction can also be accelerated by irradiation with UV or IR light and / or by heat.

For example, a polymer matrix according to the invention can be prepared by curing two-component silicone at elevated temperatures at about 200 ° C.

In the context of the method according to the invention, the removal of the material portions from the cooling belt before packaging is achieved, for example, by simply dropping it on a deflection roller. The throwing off can additionally be assisted by a scraper, which does not necessarily have to touch the cooling belt surface, but can. The polymer matrix of the cooling belt and the scraper should expediently consist of a material to which the material does not or hardly adheres.

The choice of material for the polymer matrix ultimately depends on the type of material or hot melt adhesive to be packed, so that the skilled person can determine suitable polymer matrix materials by means of simple adhesive tests. Silicone elastomers, fluoroelastomers and / or fluorosilicone elastomers are particularly preferred as the material for the polymer matrix because of their anti-adhesive properties. The scraper may also be made of these materials or may consist of a metal sheet, which may be provided with these polymers or with a Teflon layer.

Both the cooling belt and the scraper may be subjected to corona or plasma treatment to further reduce the adhesion of the material or hot melt adhesive.

In an advantageous embodiment of the method according to the invention, the heat conduction of the cooling belt at least partially made of metals or metal alloys, which are in particular selected from iron, steel, copper, aluminum, silver, brass, bronzes and the like. Also the use of carbon thermal conduction is possible. These materials give the cooling belt on the one hand sufficient mechanical strength and thus dimensional stability and on the other hand have a high thermal conductivity, with which the heat of the molten material from one side of the cooling belt can be dissipated quickly to the opposite side of the cooling belt.

In an advantageous embodiment of the method according to the invention, the textile carrier of the cooling belt comprises a woven fabric in plain weave, in which the heat conducting threads at least partially form warp threads. This is advantageous in that in a fabric in plain weave warp the warp threads to the weft yarns, so that the warp threads and thus the heat conduction define the upper and lower surfaces of the textile support. Despite the involvement in the polymer matrix, the Kröpfungsstellen the Wärmeleitfäden are thus in the immediate vicinity of the surfaces of the cooling belt, whereby a good heat conduction between the two flat sides of the cooling belt is achieved. Likewise, other forms of textile support are possible, such as twill weave or satin weave. The wearer can also consist of knitted or knitted fabrics.

According to a further embodiment of the method according to the invention, the textile carrier has weft threads or transverse threads made of a material which is selected from coated and / or uncoated polymer, carbon and / or metal fibers, multifilaments or monofilaments. As polymer fibers, for example Fibers of nylon, aramid, kevlar, polyesters and the like in question. Suitable metal fibers are, for example, iron, steel, copper, aluminum, silver, brass, bronzes or the like. For example, silicones, fluoro- and / or fluorosilicone elastomers can be used to cover the aforementioned fibers.

The warp or weft threads used in the context of the present invention may comprise core threads which are wound around at least one wire or a polymer fiber. Alternatively, wires or polymer fibers may be stranded or braided around the core filaments. The individual fibers of such threads may have a sheath of the above-mentioned substances. It is also possible to provide weft or warp threads of the abovementioned type after wrapping or stranding or braiding with a surface coating of the abovementioned substances.

In the context of the method according to the invention, it is possible to cool the cooling belt at least in sections and / or on both sides by means of a cooling device, preferably at least on the side opposite the side coming into contact with the material or the hotmelt adhesive. As a cooling device, for example, cooling rollers or a cooled plate come into consideration, over which the cooling belt is guided and which can be cooled by means of coolant. The opposite side can also be cooled by direct contact with a cooling medium, such as by spraying. For this purpose, a corresponding Spray device for the coolant provided. Combinations of these cooling devices are possible.

In an advantageous embodiment of the method according to the invention, the material or the hotmelt adhesive is tacky at room temperature, in particular at 10 ° C. or even at 0 ° C., and the material or adhesive portions are preferably removed from the cooling belt in the adhesive state and packaged in the plastic film. In the context of the method according to the invention, it is thus not necessary to cool the material or the hotmelt adhesive before packaging to such an extent that it loses its pressure-sensitively adhesive properties. For this reason, hot melt adhesives can be portioned and packaged with the method according to the invention, which even at temperatures below 0 ° C, such as at -5 ° C, still have pressure-sensitive adhesive properties. In this case, the individual adhesive portions can partially sinter together after packaging. As a result, on the one hand, the enlarged surface of the adhesive portions is retained, which allows a rapid melting. On the other hand remains in this way less air in the package or between the adhesive portions, so that a space-saving packaging is guaranteed.

In a further embodiment of the present invention, the material to be packaged is a hotmelt adhesive containing a polymer component which is selected from polyolefins, in particular polyethylene, ethylene-vinyl acetate copolymers, polyamides, polyesters or polyester elastomers, polyurethanes, polyacrylates and / or styrene copolymers or block copolymers or mixtures thereof.

The hotmelt adhesive may further comprise adjuvants selected from defoamers, wetting agents, dyes, stabilizers, plasticizers, preservatives and / or tackifying resins, in particular rosin resins and / or their derivatives.

According to a particularly preferred embodiment of the method according to the invention, the plastic film is suitable for simultaneous melting with the hotmelt adhesive. For this purpose, the plastic film in particular contains polymers which are selected from polyethylene, polyvinyl acetate, polyamides, polybutadiene, polyesters, polycarbonates, atactic polyalphaolefins, thermoplastic polyacrylamides, polyacrylonitriles, polymethylpentenes, polyphenylene sulfides, aromatic polyurethanes, polystyrene acrylonitriles, polyethylene terephthalates and their copolymers and terpolymers, in particular ethylene vinyl acetate ,

The plastic film used in the context of the method according to the invention preferably has a melting temperature of 25 to 100 ° C, in particular 30 to 70 ° C, preferably 35 to 65 ° C. The use of such films is particularly advantageous, since they quickly pass into the liquid form during the melting of the hot melt adhesive and thus release the hot melt adhesive packaged in the films for melting. Plastic films with such low melting points can not be used in part in the processes hitherto known from the prior art be because the hot melt adhesive during the packaging still at such a high temperature that the film material would be melted thereby.

According to a preferred embodiment, the plastic films used consist of at least 5 wt .-% of an ethylene-vinyl acetate copolymer, for example, more than 10 wt .-%, preferably more than 25 wt .-%, in particular 35 wt .-% or more. The remaining portion is preferably formed from polyethylene. Particularly suitable are mixed films of ethylene-vinyl acetate copolymer (EVA) and polyethylene (PE) having a mass ratio of ethylene-vinyl acetate to polyethylene of 5:95 to 50:50, in particular from 25:75 to 40:60, preferably from 35:65 ,

The content of vinyl acetate in the ethylene-vinyl acetate copolymer used is advantageously at least 30 mol%, preferably at least 40 mol%, preferably from 30 to 70 mol%, particularly preferably from 40 to 60 mol%, very particularly preferably 50 mol -%.

In addition to low melting points, these polymers or blends of ethylene-vinyl acetate and polyethylene are characterized in particular by the fact that they do not adversely affect the adhesive properties of the hot melt adhesive generally when the film material is melted together with the hot melt adhesive and used.

The packaging of the material or hot melt adhesive portions in the plastic film in the simplest case by

Wrapping or wrapping done. Preferably, however, the plastic films used in the context of the present invention are in the form of a bag or a film tube, it being possible for the individual bags to be produced by welding and separating after the packaging of the hotmelt adhesive.

When packaging the material portions of the plastic film is usually closed and the air if desired, as far as possible removed, which can be realized for example by sucking the air with simultaneous shaking. The sealing is preferably carried out by welding, since this no additional auxiliary materials such as clips and the like are needed, which would interfere with the (re-) melting.

The plastic films used in the context of the present invention may in principle have any useful for the packaging of hot melt adhesives film thickness, for example, a thickness of 5 to 200 .mu.m, in particular from 10 to 100 microns.

Advantageously, neither the plastic film nor the material portions have a surface treatment with non-stick substances, such as, for example, silicone oils, surfactants and the like. Neither is an adhesion-reducing surface treatment required, such as by a corona or plasma treatment.

Claims (15)

Process for packaging hot melt adhesive, in particular adhesive hot melt adhesive or substances sticky at room temperature as material to be packaged in a plastic film, comprising the steps: (a) melting the material to be packaged; (b) portioning the molten material portionwise onto a cooling belt and cooling the material below its melting point to form portions of material; (c) removing the material portions from the cooling belt and (d) packaging the material portions in the plastic film, wherein the cooling belt comprises a textile carrier with threads, of which at least one part form thermal conductors, with which heat can be transferred from one flat side of the cooling belt to the opposite side and the carrier is embedded in a polymer matrix such that the heat conducting threads at least on the are covered as far as possible with the material to be packaged coming into contact side. A method according to claim 1, characterized in that the Wärmeleitfäden the cooling belt at least partially Metals or metal alloys, in particular selected from carbon, iron, steel, copper, aluminum, silver, brass, bronzes and the like. A method according to claim 1 or 2, characterized in that the textile carrier comprises a plain weave fabric, in which form the heat conduction threads at least in part warp threads. Method according to one of the preceding claims, characterized in that the textile carrier weft threads or transverse threads of a material which is selected from coated and / or uncoated polymer, carbon and / or metal fibers, multi-filaments or monofilaments. Method according to one of the preceding claims, characterized in that the polymer matrix is selected from elastic polyacrylate, silicone, fluorine and / or fluorosilicone elastomers. Method according to one of the preceding claims, characterized in that the cooling belt is at least partially cooled on one side and / or on both sides by means of a cooling device, preferably at least on the side opposite to the side in contact with the material to be packaged. Method according to one of the preceding claims, characterized in that the material to be packaged at room temperature, in particular at 10 ° C or even at 0 ° C. is sticky and the material portions are preferably removed in the sticky state from the cooling belt and packaged in the plastic film. Method according to one of the preceding claims, characterized in that the material to be packaged is a hot melt adhesive containing a polymer component which is selected from polyolefins, in particular polyethylene, ethylene-vinyl acetate copolymers, polyamides, polyesters or polyester elastomers, polyurethanes, polyacrylates and / or styrene copolymers or block copolymers or mixtures thereof. Method according to one of the preceding claims, characterized in that the hot melt adhesive contains auxiliaries which are selected from defoamers, wetting agents, dyes, stabilizers, plasticizers, preservatives and / or tackifying resins, in particular rosin resins. Method according to one of the preceding claims, characterized in that the plastic film for simultaneous melting with the hot melt adhesive is suitable and / or the plastic film has a melting temperature of 25 to 100 ° C, in particular from 30 to 70 ° C, preferably 35 to 65 ° C. , Method according to one of the preceding claims, characterized in that the plastic film contains polymers which are selected from polyethylene, polyvinyl acetate, polyamides, polybutadiene, polyesters, polycarbonates, atactic polyalphaolefins, thermoplastic polyacrylamides, polyacrylonitriles, polymethylpentenes, polyphenylene sulfides, aromatic polyurethanes, polystyrene-acrylonitriles, polyethylene terephthalates and their copolymers and terpolymers, especially ethylene-vinyl acetate. Method according to one of the preceding claims, characterized in that the plastic film consists of at least 5 wt .-% of an ethylene-vinyl acetate copolymer, for example more than 10 wt .-%, preferably more than 25 wt .-%, in particular to 35% by weight or more. Method according to one of the preceding claims, characterized in that the plastic film is present as a bag or as a film tube and / or the plastic film has a thickness of 5 to 200 .mu.m, in particular from 10 to 100 microns. Method according to one of the preceding claims, characterized in that the plastic film sealed after packaging the material portions and, if desired, the air is largely removed, possibly with simultaneous shaking. Method according to one of the preceding claims, characterized in that the plastic film and / or the material portions have no surface treatment with anti-adhesion substances, such as silicone oils, surfactants and the like.