WO2007042101A1 - Method for removing packaging from melt adhesives - Google Patents

Abstract

The invention relates to a method for packaging, transporting and for unpacking permanently tacky melt adhesives, wherein the packaging is made of flexible paper and/or film materials or from dimensionally stable hollow bodies. Prior to unpacking, the melt adhesive is cooled to temperatures, on at least the surface thereof, such that the adhesiveness is lowered whilst the packaging materials are removed.

Description

 "Method for removing the packaging of hot melt adhesives"

The invention relates to a method for removing the packaging of permanently tacky hot melt adhesives, so-called hot melt adhesives. A process is described for quickly and easily separating such hot-melt pressure-sensitive adhesives from the packaging.

The packaging of conventional hot melt adhesives is known. On the one hand, they can be packed in solid containers. These containers are then heated at the user and the hot melt adhesive is melted out of the container (DE 40 09 686 A1). The handling of the container, the heating and emptying of the container is a complex process. The longer term heating to melt the adhesives, especially in large containers, can also damage the packaged adhesive in its properties.

Furthermore, it is known to encapsulate hot melt adhesives with non-stick coated films or papers. Such paper packaging or film wrappings, for example in the form of a bag are known. These bags can be cut or torn in conventional hot melt adhesives and are then separated from the adhesive, or they can be melted with (DE / EP 06 42 404 T1).

Hot melt pressure sensitive adhesives are known in the literature. WO 2004/013244 A1 describes hot-melt pressure-sensitive adhesives based on radiation-crosslinkable binders. A field of application for such hot-melt pressure-sensitive adhesives is described as applying to self-adhesive labels. Further, hot melt pressure sensitive adhesives are described in US 5,204,390 consisting of a thermoplastic resin together with a plasticizer and a tackifier resin. Furthermore, hot melt pressure sensitive adhesives are also disclosed in WO 01/98427 A1. As a use, the use as an adhesive for self-adhesive labels is described.

All these hotmelt adhesives have in common that they have a permanent stickiness at room temperature. Depending on the field of application and intended adhesion to the appropriate substrate, the tackiness must be very high.

In US 5333439 a package is described as a refastenable outer package for hot melt adhesives comprising a film coated with silicone, which film adheres to the surface a micronized powder which allows separation of film and adhesive. However, this approach has the disadvantage that these powders adhere to a large extent in the adhesive and thus are also contained in the melt of the adhesives. This can lead to abrasive effects in the applicator or it can have a detrimental effect on the composition and function of the hot melt adhesive. Furthermore, US Pat. No. 3,314,536 is known, in which hot melt adhesives are coated with a recyclable cellulose film. This cellulose film is exposed to cold water prior to removal, which film swells and can then be removed. This is difficult with highly adhesive pasty hot melt adhesives. Adherent film residues can interfere with the processing of the melt. In addition, water is not applicable to reactive hot melt adhesives. In addition, the unpackaged sticky hot melt adhesives must then be transferred to a melt tank.

These procedures are not suitable for hotmelt adhesives at room temperature. The pressure-sensitive hot melt pressure sensitive adhesives should not be removed from the packaging by simply peeling off a film. The adhesion is often so high that the packaging film or paper tears into irregular pieces and has to be laboriously removed from the surface. Thus, the complete removal of the packaging from the surface of the packaged hot melt pressure sensitive adhesive is very expensive. Working methods involving the cladding melt, lead to altered compositions of the adhesive and restrict the choice of packaging materials.

The object of the invention is therefore to provide a method to allow a cheap and simple packaging of strongly permanent adhesive hot melt adhesives and at the same time to allow easy and easy unpacking of the hot melt adhesives often present in block form.

The object is achieved by a method for unpacking hotmelt adhesives, in which the hotmelt PSA is present as a shaped body and these shaped bodies are enclosed with a packaging material, wherein the packaging material on the side facing the hotmelt adhesive adhesive has an adhesion-reducing surface, and the hot melt adhesive before removing the enveloping Packaging material is cooled to a temperature at which the hot melt adhesive with reduced pressure tack is present.

An embodiment of the present invention employs flexible packaging materials. These are intended to envelop the hot-melt pressure-sensitive adhesive, can adapt to the shape of the adhesive and can be removed from the hotmelt adhesive molding according to the method of the invention. Another embodiment of the invention works with solid containers. In this, the hotmelt adhesive can be filled. Such packages should have a shape that has an at least straight shape from an openable side, but preferably a slightly conical tapered shape. After the cooling according to the invention, the hot melt pressure-sensitive molded articles can be easily removed from the solid packaging.

The particularly flexible packaging materials which are suitable for a preferred procedure according to the invention are known to the person skilled in the art. It is usual paper, cardboard or foil material. This should be so flexible that they can assume the particular shape of the hot-melt pressure-sensitive adhesive to be packaged. For example, round or square shaped bodies are to be enveloped can. The packaging should also be able to adapt to a possibly uneven surface. Furthermore, the material should be removed during removal. The packaging material suitable according to the invention should be resistant to tearing, ie the tensile strength or tensile strength of the flexible material should be so great that it is higher than the force required to overcome the separation of flexible packaging material and hot-melt adhesive at a temperature corresponding to the process of the invention.

The tensile strength should be so high in practice that film or paper in large pieces or preferably in the whole can be deducted. Possibly. In the packaging material also predetermined breaking points may be predetermined, for example on edges, to allow a quick removal. For cardboard packaging, these should also be in pieces, eg. B. entire sides, can be removed. The tear strength must be present at the temperatures of the unpacking, for example from +10 ° C to -200 ° C, preferably from 0 ° C to -100 ° C. Suitable films may for example be made of polyethylene, polypropylene, polyamide or other commercially available polymer films. The polymer films may by themselves have a low adhesion to the hot-melt pressure-sensitive adhesive. They can also be treated on the side facing the adhesive to reduce adhesion to the surface or be provided with an anti-adhesive layer. Suitable paper materials are also known. These should be provided with an adhesion-reducing coating at least on the side facing the hot-melt adhesive.

Such films, paper, cardboard can consist of one layer, preferably they should be composed of at least two different layers. These are therefore two-layered or multi-layered materials, wherein the coating should contain adhesion-reducing substances. Examples of such substances are known to the person skilled in the art. The coatings may be silicone compounds or siliconized materials. However, it is also possible to apply perfluorinated coating materials. These coatings should adhere firmly to the packaging material, only the adhesion to the adhesive should be reduced. Preferably, the surfaces facing the hot melt adhesive are smooth, but it is also possible to use surfaces having an adhesion-reducing structure.

Examples of such papers are commercially available under the name Laufenberg, NSA 1350/56 BF from B. Laufenberg GmbH. Suitable coated paperboard materials are also known, e.g. B. under the name Packomelt 86946, silicon coated the company Pacomelt GmbH.

The shape of the hotmelt adhesive bodies to be packaged in this embodiment is variable. They should only have a sufficient size and shape, so that the removal of the packaging from the surface of the moldings is made possible cost. The shaped bodies can be cuboid, cubic, cylindrical or in the form of a strand or block, for example. There are also irregular shapes possible. In principle, strand-like or angular packaging forms are particularly favorable for dense storage. In order to be able to separate them from one another, these hot-melt adhesive moldings must be enveloped on the contacting sides with a packaging material suitable according to the invention. Possibly. it is expedient to wrap these coated adhesive moldings individually or in a plurality with another outer packaging.

It is possible to insert suitable films or paper first in an additional external form. These may be tubular structures or barrel-shaped or square outer packaging. These are designed on the inner surface with the packaging material suitable according to the invention, after which, if appropriate, the still flowable, hot melt adhesive can be introduced. In a further embodiment, however, it is also possible to allow the hotmelt adhesive to solidify into molds and then to coat it in the cold with a packaging material suitable according to the invention. In a further embodiment, the hot melt pressure sensitive adhesives are filled into solid containers. These are generally on the inside with an adhesion-reducing coating, for. B. a silicone coating or a plastic coating provided. Furthermore, it is necessary that the packages are open at least on one side. The opening must have a size that corresponds to the maximum cross section of the package Holhlkörpers. This can be, for example, the opening of a barrel lid. It is also possible for smaller containers to provide a tear line on the container on which a part of the container can be separated. The container itself may preferably be made of metal or plastic, but it is also possible to use dimensionally stable, preferably multi-layer cardboard packaging.

The inside of the solid packaging materials should be substantially smooth. There should be no protrusions, dents, beads or the like on the wall of the packaging body. The side surfaces should be smooth, so that a removal of the hot melt adhesive molded article is easily possible. The side walls with respect to the intended opening of the packaging means should be at least straight, cylindrical in rotationally symmetrical bodies. Preferably, however, it is also expedient that the side walls are slightly tapered away from the surface to be opened. This is si chergestellt that the molding can be removed without mechanical interference or entanglement of the packaging material.

Such packaging materials are already known. These may be conventional drums, barrels, hobbocks or canisters made of coated metal, plastic or cardboard materials, the side walls being smooth, cylindrical or slightly conical. Another possibility is, for example, an embodiment of pyramidally shaped round or rectangular shaped bodies, wherein the large bottom side is to be provided as the opening side. Typical hot melt pressure sensitive adhesives are composed of base polymers, tackifying resins, optionally plasticizers, waxes, oils and various additives. The adhesives should be solid at room temperature and melt at elevated temperatures, for example from 80 ⁰ C. However, they should have a high adhesion to the substrate at room temperature, ie a high surface tack.

Commonly used base polymers are elastomeric or thermoplastic polymers.

Examples of elastomers are acrylate, polyester urethane, ethylene acrylate, butyl rubber; Natural rubber; Ethylene-propylene copolymers; Ethylene-vinyl acetate copolymers or styrene copolymers such as styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), SEBS or SIBS block copolymers; Examples of thermoplastic binders are ethylene-vinyl acetate (EVA) polymers, amorphous poly-α-olefins (APAO), polyurethanes, polyether esters and polyether amides. Particularly suitable are also the thermoplastic elastomers.

The resin is said to increase the tackiness of the base polymer and to improve the compatibility of the hot melt adhesive components. These are, for example, hydroabietyl alcohol and its esters; modified natural resins of balsam resin, tall resin, root resin, partially hydrogenated rosin; Acrylic acid copolymers, preferably styrene-acrylic acid copolymers or resins based on functional hydrocarbon resins.

Waxes may also be included in the hot melt pressure sensitive adhesive. In this case, the wax used may be natural, chemically modified or synthetic origin. Vegetable waxes, animal waxes can be used as natural waxes, mineral waxes or petrochemical waxes as synthetic waxes. Also chemically modified waxes are known. Likewise, hotmelt adhesives often contain plasticizers. These may be, for example, monohydric or polyhydric alcohols, in particular Polyalkylene glycols, mineral oils or esters of organic carboxylic acids, such as liquid polyesters, glycerol esters or esters of aromatic dicarboxylic acids.

In addition, the hot melt adhesive customary auxiliaries and additives can be added. These are, for example, stabilizers, color pigments, fillers, adhesion promoters, catalysts or initiators.

The hot melt pressure sensitive adhesives used in the present invention have a glass transition temperature (Tg) of about -100 ⁰ C to about 50 ⁰ C (measured by DSC). The average molecular weight (M _N ) of the base polymers is about 5,000 to about 500,000 g / mol (as determined by GPC). The hot-melt pressure sensitive adhesives can build up the adhesion due to their melting behavior, but they can also be reactive hot melt pressure sensitive adhesives.

Hot-melt adhesives based on, for example, styrene-isoprene-styrene block copolymers are described in EP 0 451 920; those based on polyacrylate copolymers are described, for example, in WO 02/10307. Adhesives of the type mentioned are generally known to the person skilled in the art.

The hot melt pressure sensitive adhesives can be prepared by known methods. The components are melted individually or successively, homogenized and then discharged from the mixing unit. They can be discharged, for example in the form of strands on, for example, a cooled base, in the case of non-reactive hot melt adhesives, for example, in a cooling liquid. After the hot melt adhesives have solidified, they can be packaged and packaged. Furthermore, it is possible to pour the liquid hot melt pressure sensitive adhesives into molds. If necessary, the molds can be cooled from the outside in order to allow rapid solidification of the hot-melt adhesives.

The packaging according to the invention suitable flexible paper, cardboard or foil materials can be done in different ways. For example, it is possible to coat the discharged and solid adhesive moldings with a flexible material. This can be done at usual temperatures. However, it is also possible to cool the adhesive blocks in advance and pack in the cold with less surface adhesion in appropriate flexible packaging materials.

In a further embodiment of the invention, the molds in which the hotmelt adhesive is intended to solidify are lined with packaging materials suitable according to the invention before the hotmelt adhesive is introduced. Then it is possible to remove these packaged directly from the molds after solidification, in which case possibly the top is still covered and packaged.

According to a further embodiment, the adhesive is filled directly into stable packaging. This package may be provided on the inside with a suitable surface coating. It is in this way so the packaging later removed from the hot melt adhesive.

According to a further embodiment, the hotmelt adhesives are additionally packed in stable containers as outer packaging. Also in this case it is necessary to pack the hotmelt PSA in accordance with the invention suitable, non-adhesive, flexible tear-resistant materials. These shaped bodies can then remain in the outer packaging for transport and storage.

The hot-melt adhesive molded bodies packaged according to the invention can have any desired shape. They are provided on parts of the surface or on all surfaces with a paper, cardboard or foil packaging according to the invention and then do not adhere to each other. They can therefore be stacked or individually or packaged in several additional packaging. Hot melt adhesive tablets packaged in accordance with the invention can be transported and stored at normal temperatures to the user. This can be done at room temperature. However, it is also possible that the hot-melt pressure sensitive adhesives already transported cooled to the user at low temperature. At the latest at the user, the hot-melt adhesive moldings are cooled and brought to a low temperature, so that the pressure-sensitive adhesive is significantly reduced or no longer present. Depending on the property profile of the hotmelt PSA, temperatures below 10 ° C. are suitable for this, preferably below 0 ° C., more preferably at temperatures below -10 ° C. A lower limit of the temperature is given by the lowest possible energy consumption for cooling. Typically, the temperature above -200 ⁰ C should, preferably about - 100 ^° C, especially preferably above -35 ⁰ C.

Under reduced tacky is to understand that film materials can be easily removed from the surface, it should be below the existing at room temperature stickiness. The force can be measured by known test methods for release liners, for example according to Pritt K 7476 (Henkel KGaA). The force should be below 5 N / 20mm, in particular below 2 N / 20 mm.

The cooling can be done by immersion in liquid materials, for example, cooled organic liquids, cooled aqueous solutions or liquid gases, eg. As liquid nitrogen. It can be provided solid coolant, for. As solid CO ₂ , ice, or it is possible to store the hot melt adhesive blocks in refrigerators or cold rooms, at least in the short term. Also a flat contact with cooled, good heat conducting surfaces is possible. The cooling of the molding can be done continuously. However, it is sufficient and preferred according to the invention if only the surface of the moldings is cooled from all sides to a suitable temperature. The cooled layer on the surface can be up to 1 cm. But it is also sufficient if only the surface of the hot melt pressure sensitive adhesive up to 0.5 mm is cooled to such a temperature. This can also be achieved by only briefly applied coolant.

After cooling to the appropriate temperatures, the packaged hot-melt adhesive moldings can be unpacked. This should generally be done immediately after the cooling phase to prevent significant surface tack from being generated again by external heating.

In order to unpack the hot-melt adhesive molded bodies enveloped with flexible packaging materials, these claddings can be unfolded and removed at possible abutting edges or folds. Due to the tear-resistant design of the flexible packaging material can be easily deduct the packaging materials in large pieces of the hot melt adhesive. Adhesion on the surface of the hot-melt pressure-sensitive adhesive is reduced by the cold and possibly also by the surface coating. Possibly. it is possible, by cutting with knives, scissors and similar objects, to produce corresponding edges and cuts on the packaging in order to remove the flexible covering from there. Another embodiment of the invention uses pre-embossed tear edges or tearing lines on the flexible package, which are designed as predetermined break points to tear the package there and remove it from the packaged hot melt pressure sensitive adhesive. As a further preferred embodiment, in which the hotmelt adhesives are packed in stable containers, the corresponding container can have break lines or tear edges. For example, cylindrical containers can be made from spirally wound flexible materials that open when unpacked along this tear edge and can be removed in one piece.

If the hot-melt pressure-sensitive adhesive molded articles are packed in stable, solid packages with a smooth inner surface of the enveloping contact surfaces, the packages can be cooled with the hot-melt pressure-sensitive adhesive. In this case, before or after the openings for removing the hot melt pressure sensitive adhesive be exposed. After cooling, the containers are rotated so that the opening points downwards or diagonally downwards. Due to the reduced adhesion of the hot melt adhesive body, supported by its own weight and possibly by mechanical measures, the hot melt adhesive molded article can slide out of the container and be introduced directly into the melting device. Since the packaging material is inherently strong, there will be no contamination of the surface of the hot-melt pressure-sensitive adhesive, so that a further after-treatment is not necessary.

Immediately after unpacking, the hot-melt adhesive moldings are placed in the melting aggregates present for melting. In exceptional cases, however, it is also possible to store these unpackaged hot melt adhesives at low temperature, wherein the temperature is to be selected so that during the storage time no sticking or no sticking of the hotmelt PSA can occur with each other or each other.

Corresponding units for the further processing of hotmelt PSAs are known, such as melting units, mixing and pumping devices, application devices and require no further explanation for the person skilled in the art.

The inventive method for packaging and unpacking permanently tacky hot-melt pressure sensitive adhesives at low temperature, it is possible to store such adhesives in larger quantities and to unpack shortly before use. By reducing the tack, it is possible to remove the corresponding packaging materials over a large area. This also prevents, if necessary, that corresponding packaging residues, which are melted with, must be removed by filtration. Another advantage of the procedure according to the invention is that the removed packages generally have no residues of hotmelt adhesives and can be disposed of immediately or that they are reusable. Furthermore, a simplified procedure in the unpacking is possible.

Claims

claims 1. A method for removing the packaging of hot melt adhesives, characterized in that the hotmelt PSA is present as a shaped body and these moldings are enclosed with a packaging material, wherein a) the packaging material on the side facing the hotmelt adhesive side has an adhesion-reducing surface and b) the hot melt pressure sensitive adhesive before Removing the enveloping packaging material is cooled to temperatures that the hot melt pressure-sensitive adhesive is present. 2. The method according to claim 1, characterized in that the packaging material on the side facing the hot melt adhesive side has a surface coating based on silicones or perfluorinated compounds. 3. The method according to claim 1 or 2, characterized in that a flexible, tear-resistant material such as a film, a multi-layer film, multilayer cardboard or multilayer paper is used as packaging material. 4. The method according to claim 1 or 2, characterized in that a dimensionally stable hollow body is used as packaging material, which has a closable opening which corresponds to the largest diameter of the hollow body. 5. The method according to claim 4, characterized in that the side walls of the hollow body are formed smooth on the inside and, starting from the closable opening, are straight or conically tapered. 6. The method according to any one of claims 1 to 5, characterized in that the temperature of the hotmelt PSA when removing the packaging material between + 10 ⁰ C to -100 ° C, preferably between 0 ° C and -35 ° C. 7. The method according to any one of claims 1 to 6, characterized in that only the packaging and the surface of the hotmelt adhesive molding is cooled. 8. The method according to any one of claims 1 to 3, 6 and 7, characterized in that the flexible tear-resistant packaging is cooled to a temperature at which the tensile strength of the packaging is greater than the residual adhesion between the packaging and hot-melt adhesive. 9. The method according to any one of claims 1 to 8, characterized in that the hotmelt PSA molding for a period of less than 30 min. is cooled. 10. The method according to any one of claims 1 to 9, characterized in that the hotmelt PSA molding with liquids, such as aqueous solutions, liquid gases or organic solvents, is cooled. 11. The method according to any one of claims 1 to 9, characterized in that the hotmelt PSA molding is cooled with solid CO ₂ . 12. The method according to any one of claims 1 to 9, characterized in that the hotmelt PSA molding is cooled in a refrigerator. 13. The method according to any one of claims 1 to 9, characterized in that the hotmelt PSA molding is cooled with abutting surface of the molding surfaces. 14. The method according to any one of claims 1 to 13, characterized in that the packaged hot melt pressure sensitive adhesive is cooled to a temperature at which the hot melt adhesive shows only low pressure tack, then the packaging is removed and the hot melt adhesive is placed directly in the necessary melting device for application , 15. The method according to claim 14, characterized in that after cooling of the packaged hot melt pressure sensitive adhesive, the package is heated so that the tear strength of the packaging material is above the current adhesive force of the adhesive, the hot melt adhesive molded body but still shows a reduced pressure tack.