WO1999058403A1

WO1999058403A1 - Method for packaging hot-melt adhesives

Info

Publication number: WO1999058403A1
Application number: PCT/EP1999/003001
Authority: WO
Inventors: Jan-Dirk Auris
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1998-05-13
Filing date: 1999-05-04
Publication date: 1999-11-18
Also published as: DE19913034A1; AU4137499A; BR9911777A; EP1077876A1; AR019290A1

Abstract

The invention relates to a method for packaging hot-melt adhesives in a film (3) which is suitable for fusing simultaneously with the hot-melt adhesive and presents no surface adhesion in the normal storage temperature range, especially at temperatures up to 50 °C. According to said method a defined portion of the molten hot-melt adhesive (1) is filled into the film, the filling process is interrupted so that a film area (8) following the portion remains free of adhesive, and the filling process is repeated. The film (3) is then heat-sealed in the adhesive-free area (8). According to the invention a film tube (3') filled with portions of hot-melt adhesive is produced, whereby areas (8) are situated between the portions which are adhesive-free across the full width of the film tube. The tube (3') is sealed by squeezing the hot-melt adhesive at the ends of the portions and is possibly allowed to cool. After squeezing, the film (3) is heat-sealed in the adhesive-free areas (8). This allows for especially high filling speeds and protects the portions enveloped by film (3) from running at elevated storage temperatures. The method also prevents air from being included in the film package.

Description

Process for packaging hot melt adhesive

The invention relates to a method for packaging hot melt adhesive, in particular pressure sensitive hot melt adhesive, in a film which is suitable for melting with the hot melt adhesive at the same time and has no surface tack in the range of normal storage temperatures, in particular at temperatures up to 50 ° C, a predetermined one Fills portion of the melted hot melt adhesive, interrupts the filling process so that a film area following the portion remains adhesive-free and repeats the filling process, and the film is sealed in the adhesive-free area.

Hot melt adhesives are solvent-free adhesives that can wet material surfaces well in the heat and in the liquid state and adhere firmly to them after cooling and solidification. They usually consist of a mixture of substances that form the adhesive, the cohesive and the additive component. During manufacture, the components are melted together and then assembled. The so-called pressure sensitive hot-melt adhesives cause particular difficulties in packaging. H. Hot melt adhesives with permanent stickiness, which are still sticky even at room temperature.

A method of the type mentioned above is known from German published patent application DE 24 13 575 A1. Here, the movement of the hose is first stopped and the hose is welded by a transverse double seam and thus closed. After the hose has moved into a water bath, the forward movement of the hose is stopped again, on the one hand air is pressed into the hose to compensate for the water pressure acting on the hose and on the other hand a certain amount of hot melt adhesive is introduced via a lance until it is perpendicular hanging hose is filled to a level that is below the water level. Above this portion of hot melt adhesive, the tube is then welded again by means of a transverse double-crimped seam and thus closed. At the same time, an overlying double pinch seam is attached by welding, which forms the lower end of the following portion.

The hose then continues to run through the water bath, in which the hot-melt adhesive cools, and is finally separated into the individual portions by a cutter.

It is advantageous to seal the individual portions by welding tubular film areas lying one on top of the other. If the hot melt adhesive, which has been separated into individual portions, is stored at a temperature above the softening temperature, the weld seams protect the adhesive from flowing out of the film. Such high storage temperatures occur again and again in practice, e.g. B. in hot summers on trucks or other uncooled storage, especially in subtropical or tropical areas. In these cases, temperatures up to 50 ° C and above are reached, so that the hot melt adhesive softens. Sealing the film by gluing with the hot melt adhesive is therefore not sufficient. Because if in such a case on the film z. B. is exerted by overlying packaging units, the adhesive opens and the adhesive flows out of the packaging, so that it is no longer usable on the one hand and on the other hand has a considerable cleaning effort.

A disadvantage in the known method mentioned above is the loss of time, which arises on the one hand from the frequent interruptions in the forward movement of the hose and on the other hand due to the interruption of the supply of adhesive during the welding, and the filling speed which is limited in this way. A uniform, uninterrupted movement of the film or the film tube is not possible with the system shown in DE 24 13 575 A1. The period of time required for welding cannot be shortened easily either, since a secure and complete closure requires a minimum time due to the thermal processes taking place during welding. On the other hand, shortly after filling the respective portion, a secure and complete closure is necessary so that the still liquid hot melt adhesive of the portion just filled from WO 99/58403 ^{"ό '} PCT / EP99 / 03001

hydrostatic pressure is not pressed into the hose area intended for the following portion.

Another disadvantage of the known method is the risk that the hot melt adhesive welded into the film contains air bubbles or air gaps. The air can be present within the adhesive mass or at the ends of the adhesive portions.

The invention is therefore based on the object of achieving a considerably higher filling speed in the process of the type mentioned at the outset, the portions covered with film being protected against outflow at elevated storage temperatures. In addition, the inclusion of air in the film packaging should be excluded.

This object is achieved according to the invention in the method mentioned at the outset by

that a film tube filled with the hot-melt adhesive portions is produced, areas being arranged between the portions which are free of adhesive over the entire width of the tube,

- That the tube is closed by squeezing the hot melt adhesive at the ends of the portions and, if necessary, allowed to cool and

- That, after squeezing, the film is welded in the adhesive-free areas and also cut through there if necessary.

It is essential in the invention to double-seal each portion, namely once by squeezing during the filling process and secondly by welding after the hot melt adhesive has cooled or solidified. The following advantages are achieved by these measures.

With the method according to the invention, an increased filling speed can be achieved, because the welding only needs later, e.g. B. to be made only after cooling of the film tube filled with hot melt adhesive. The filling of the hot-melt adhesive into the film tube or directly onto the film, as will be explained in more detail below, is only interrupted briefly in order to create the adhesive-free zone. There is nothing to increase the filling speed due to shorter cycle times WO 99/58403 ^" * ^" PCT / EP99 / 03001

Paths, because during the actual filling process there is no need to take thermal processes into account.

Nevertheless, there is no danger that the still hot melt adhesive of the portion just filled will flow into the adhesive-free area or into the tube area provided for the following portion, since the ends of the portions are at least provisionally closed by squeezing.

It is also avoided with certainty that the hot melt adhesive welded into the film contains air bubbles or air gaps, because any air that is present is squeezed out by the squeezing, the hot melt adhesive being simultaneously compressed.

The method according to the invention is suitable for the packaging of practically any type of hot-melt adhesive composition. It is particularly advantageous for hot melt adhesives with serious handling problems, e.g. B. for the above-mentioned, even at room temperature still tacky hot melt adhesives.

For example, the packaging process of the invention can be applied to hot melt adhesives made from polymers and copolymers of synthetic resins, rubbers, polyethylene, polypropylene, polyurethane, acrylic, vinyl acetate, ethylene vinyl acetate and polyvinyl alcohol.

Specific examples include hot melt adhesives made from the following components:

1) Elastic polymers such as block copolymers, e.g. B. styrene-butadiene, styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, styrene-ethylene-propylene-styrene;

2) ethylene vinyl acetate polymers, other ethylene esters and copolymers, e.g. B. ethylene methacrylate, ethylene n-butyl acrylate and ethylene acrylic acid;

3) polyolefins such as polyethylene and polypropylene;

4) polyvinyl acetate and copolymers with it;

5) polyacrylates;

6) polyamides;

7) polyester;

8) polyvinyl alcohols and copolymers therewith;

9) polyurethanes; WO 99/58403 ^" ° ^" PCT / EP99 / 03001

10) polystyrene;

11) polyepoxides;

12) copolymers of vinyl monomers and polyalkylene oxide polymers;

13) Aldehydes containing resins such as phenol aldehyde, urea aldehyde, melamine aldehyde and the like.

Components for strengthening the adhesion, diluents, stabilizers, antioxidants, dyes and fillers may also be present.

Examples of components for improving the adhesion are:

1) natural and modified resins,

2) polyterpene resins,

3) phenolic modified hydrocarbon resins,

4) aliphatic and aromatic hydrocarbon resins,

5) phthalate esters and

6) Hydrogenated hydrocarbons, hydrogenated resins and hydrogenated resin esters.

Liquid polybutene or polypropylene, petroleum waxes such as paraffin and microcrystalline waxes, semi-liquid polyethylene, hydrogenated animal, fish and vegetable fats, mineral oil and synthetic waxes and hydrocarbon oils may be mentioned as examples of diluents.

Examples of the other additives can be found in the literature.

Different variants of the method according to the invention are possible. As a preferred embodiment, it is proposed that, in order to produce the film tube filled with the hot-melt adhesive portions, the given portions are filled onto a band-shaped film and the band-shaped film containing the hot-melt adhesive portions is formed into a film tube, in particular by welding the longitudinal edges of the band-shaped film together.

Alternatively, it is also possible to fill the specified portions into a film tube that has already been formed. This variant offers other advantages.

It is of particular advantage with regard to a high filling speed if the process is carried out continuously, the film or the WO 99/58403 ^" ° ^" PCT / EP99 / 03001

Foil tube moves at a constant speed, but the filling of the hot melt adhesive is carried out discontinuously and intermittently.

A further improvement in the economy of the method according to the invention is achieved if the temperature of the melted hot-melt adhesive when filling the film or into the film tube is below the softening temperature of the film or the film tube. In this case, in contrast to the method according to DE 24 13 575 A1, subsequent cooling of the film or the hose with water is not necessary. It is also advantageous that, in this case, no measures are necessary to keep the hose area below the water surface exposed to the hydrostatic pressure.

Within the scope of the invention, however, it is also entirely possible to provide water cooling similar to that in DE 24 13 575 A1 if it is necessary that the temperature of the adhesive during filling is close to or even above the softening temperature of the film.

The speed and also the economy of the method according to the invention can be increased further if welding and cutting are carried out at the same time. This means that only one station, a combined welding and cutting station for the cooled film tube, is required. This proposal is possible since the hot melt adhesive - in contrast to the method according to DE 24 13 575 A1 - has already cooled down when the film tube is welded and the risk of the hot melt adhesive flowing out of the film tube no longer exists.

To save film, the adhesive-free area should only be as long as is technically necessary for welding and cutting. In practice, it has proven to be advantageous if the adhesive-free area between the individual portions has a length of 2 to 20 mm, in particular of about 10 mm.

It is also advantageous if the squeezed area has a length of 2 to 20 mm, in particular of about 10 mm, at the ends of the individual portions. WO 99/58403 ^" '^" PCT / EP99 / 03001

With regard to a high filling speed and economy, it is furthermore advantageous if the squeezing is carried out by means of two parallel and opposite rollers which are mutually variable in their spacing and between which the film tube is guided.

A quick work without hot melt dripping into the intended adhesive-free area and without stringing occurs if a nozzle is used to fill the portions, which can be closed by a valve, in particular a needle valve, at the nozzle outlet and through which the Hot melt adhesive can preferably be pressed out by means of compressed air.

The selection of the material for the film tubes used is based on the requirements that the film can be welded without problems and that the film can be mixed with the hot melt adhesive in the melting basin of the user without leaving any residue and the properties of the hot melt adhesive after the mixing are not negatively Way influenced.

Suitable film tubes include ethylene-based polymers such as ethylene / vinyl acetate, ethylene acrylate, ethylene methacrylate, ethylene methyl acrylate, ethylene methyl methacrylate, HD and LD polyethylene, polyethylene blends and chemically modified polyethylenes, copolymers of ethylene and mono- or di-unsaturated C 1- 6-monomers, polyamides, polybutadiene, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, etc .; thermoplastic polycarbonates, atactic polyalphaolefins including atactic polypropylene, thermoplastic polyacryiamides, polyacrylonitrile, copolymers of acrylonitrile and other monomers such as butadiene, styrene, etc., polymethylpentene, polyphenylene sulfide, aromatic polyurethanes,

Styrene acrylonitrile, acrylonitrile butadiene styrene, styrene butadiene rubber, acrylonitrile butadiene styrene elastomers.

Particularly preferred as the material for the film are LD polyethylene, where "LD" stands for "low density", or polyethylene vinyl acetate, which contains up to 10% by weight of vinyl acetate.

It is also advantageous if the mass of the film is 0.2 to 1.0% by weight of the hotmelt adhesive. It is also proposed that the film have a thickness of 2 to 150 μm, in particular 10 to 100 μm.

Exemplary embodiments of the invention are described in more detail below with reference to drawings. Show it

FIG. 1 shows a schematic representation of the filling area of a plant operating according to a first exemplary embodiment of the method according to the invention,

Figure 2 shows a section of part of the filled according to the invention

Foil tube before welding and cutting and

FIG. 3 shows a schematic illustration of the filling area of a plant operating according to a second exemplary embodiment of the method according to the invention.

In all drawings, the same reference symbols have the same meaning and are therefore only explained once, if appropriate.

In the system part shown schematically in FIG. 1, hotmelt adhesive 1 is filled at 60 to 130 ° C. The example relates in particular to filling temperatures between 100 and 130 ° C.

The liquid adhesive is fed to the film tube 3 'via a heated nozzle 2 which can be closed with a needle valve (not shown). The film tube 3 'runs continuously and without interruption at a uniform speed. The hot melt adhesive is filled into the hose 3 under pressure by means of compressed air in order to achieve a high filling speed.

The film consists of low density polyethylene (LD-PE) and is 30 μm thick. The nozzle 2 used is an application head of the type H200 ZC or H200 MC (product from Nordson Corp., USA) which is usually used to apply hot-melt adhesives to a substrate to be bonded, with a perforated nozzle and a needle valve which can be actuated by means of compressed air . The film tube 3 'is held by a guide basket 4 in the intended shape and in particular on the planned diameter, which here is 80 mm. In the area of the nozzle 2, a nozzle ring 5 is attached. This is designed as an annular distributor provided with nozzles, from which water is sprayed against the film tube 3 'in such a way that a closed water film flows down the film. Cooled drive and pinch rollers 6 transport the film and close the individual sausage-shaped portions by squeezing at both ends, so that pinch areas 7 are formed there (FIG. 2). An adhesive-free zone 8 is arranged between the squeezing areas 7 of successive portions, as can be seen most clearly from FIG. A cooling water tank 9 can be provided for further cooling of the packaged portions.

Alternatively, cooling can be dispensed with if the temperature of the melted hot-melt adhesive when the film tube is filled is below the softening temperature of the film tube. For example, the temperature of the hot melt adhesive can be around 80 ° C. and polyethylene can be used as the film tube so that cooling of the drive and pinch rollers 6 and subsequent cooling of the tube with water is not necessary.

After cooling the filled film tube 3 ', the adhesive-free area 8 is welded at points 10 and 11 by a transverse seam or a double transverse seam, and at the same time the tube 3' is cut at point 12 with a knife, so that individual, securely welded portions of hot melt adhesive packed in film are obtained.

In a second exemplary embodiment, the method according to the invention is carried out with a system which is shown schematically in part in FIG. 3. The details and data not expressly mentioned in this example correspond to those of the first example according to FIGS. 1 and 2.

A band-shaped film 3 is unwound evenly from a storage drum and moves smoothly and without interruptions in FIG. 3 to the right. An application head 13, as is known per se for the automatic application of hot melt adhesive to workpieces, has a slot nozzle 2 with a maximum gap width of 0.3 mm, the nozzle being able to be opened and closed by a nozzle valve which can be actuated by compressed air. In Figure 3 is only WO 99/58403 ^"1 ° ^" PCT / EP99 / 03001

a single application head 13 is drawn. However, it is also possible to provide a plurality of application heads 13 arranged one behind the other in order to further increase the filling speed.

600 g of hot melt adhesive are applied to the film in the form of portions 1 with the application head 13, the slot nozzle 2 being closed briefly after the application of each portion, so that 1 adhesive-free zones 8 are formed on the film 3 between the portions of hot melt adhesive .

In this example, the temperature of the melted adhesive is approximately 80 ° C. and thus below the softening temperature of the polyethylene film 3 used. Cooling is therefore not necessary and also not provided.

The film continues against deflection plates 14 or corresponding deflection rollers, which form a tube from the band-shaped film by bringing the opposite edges of the film 3 together and overlapping them. The longitudinal seam formed in this way is welded in a manner known per se. This method step and the subsequent steps are not shown in FIG. 3.

A squeezing station follows, which works similarly to the system according to FIG. 1. The movement of the rollers provided for this purpose is adjusted so that between the individual portions of adhesive melt adhesive 1 there is in each case an adhesive-free zone 8 with the desired length.

Finally, as in the first example, a transverse weld seam 10, 11 is applied to the ends of each portion 1, specifically in the respective adhesive-free area 8, and the portions 1 at the same time, likewise in the area of the adhesive-free zone 8 and between the adjacent cross-weld seams 10, 11 (see Figure 2), separated from each other with a knife. If desired, the hotmelt adhesive 1 can be cooled before welding and cutting or afterwards. Reference list

Adhesive melt adhesive, serving

jet

foil

Foil tube

Guide basket

Nozzle ring

Drive and pinch roller

Squeeze area adhesive-free zone

Cooling water tank

Sweat spot

Interface

Application head

Baffle plate

Claims

claims

1. Process for packaging hot melt adhesive, in particular pressure sensitive hot melt adhesive (1), into a film (3) which is suitable for simultaneous melting with the hot melt adhesive and has no surface tack in the range of normal storage temperatures, in particular at temperatures up to 50 ° C, whereby fills a predetermined portion of the melted hot melt adhesive (1), interrupts the filling process, so that a film area (8) following the portion remains adhesive-free and the filling process is repeated, and whereby the film (3) is welded in the adhesive-free area (8), thereby featured,

- That one produces a film tube (3 ¹ ) filled with the hot melt adhesive portions, areas (8) being arranged between the portions which are free of adhesive over the entire width of the tube,

- That the tube (3 ') is closed by squeezing the hot melt adhesive at the ends of the portions and, if necessary, is allowed to cool and

- That after the squeezing the film (3) in the adhesive-free areas (8) is welded and also cut through there if necessary.

2. The method according to claim 1, characterized in that for the manufacture of the film tube filled with the hot melt adhesive portions (3 ') the given portions are filled onto a band-shaped film (3) and the band-shaped film having the hot melt adhesive portions (3) to a film tube ( 3 ') forms, wherein in particular the longitudinal edges of the band-shaped film are welded together.

3. The method according to claim 1, characterized in that the predetermined portions are filled into an already formed film tube (3 ').

4. The method according to any one of the preceding claims, characterized in that the process is carried out continuously, the film (3) or the film tube (3 ') moving at a uniform speed, but the hot melt adhesive (1) is filled discontinuously and intermittently.

5. The method according to any one of the preceding claims, characterized in that the temperature of the melted hot melt adhesive (1) when filling on the film (3) or in the film tube (3 ') is below the softening temperature of the film or the film tube.

6. The method according to any one of the preceding claims, characterized in that is welded and cut simultaneously.

7. The method according to any one of the preceding claims, characterized in that the adhesive-free area (8) between the individual portions has a length of 2 to 20 mm, in particular of about 10 mm.

8. The method according to any one of the preceding claims, characterized in that the squeezed area (7) at the ends of the individual portions has a length of 2 to 20 mm, in particular of about 10 mm.

9. The method according to any one of the preceding claims, characterized in that the squeezing is carried out by means of two parallel and opposite, variable in their mutual distance rollers (6), between which the film tube (3) is guided.

10. The method according to any one of the preceding claims, characterized in that a nozzle (2) is used for filling the portions, which can be closed by a valve, in particular a needle valve, at the nozzle outlet and through which the hot melt adhesive (1) can preferably be pressed out by means of compressed air is.

11. The method according to any one of the preceding claims, characterized in that the film (3) is selected from a group consisting of polymers based on ethylene, polyamides, polybutadiene, polyester, polycarbonates, atactic polyalphaolefins, thermoplastic polyacrylamides, polyacrylonitrile and copolymers therewith Contains, polymethylpentene, polyphenylene sulfide, aromatic polyurethanes, styrene acrylonitrile, acrylonitrile butadiene styrene, styrene butadiene rubber, polyethylene terephthalate.

12. The method according to the preceding claim, characterized in that the material for the film (3) LD polyethylene or polyethylene vinyl acetate, which contains up to 10 wt .-% vinyl acetate, is used.

13. The method according to any one of the preceding claims, characterized in that the mass of the film (3) is 0.2 to 1.0 wt .-% of the hot melt adhesive (1).

14. The method according to any one of the preceding claims, characterized in that the film (3) has a thickness of 2 to 150 microns, in particular from 10 to 100 microns.