A plant for coating films with water-based or hot-melt adhesive

Abstract

 A plant for coating films with adhesive is disclosed, comprising a linear oven of a length suitable for the drying of applicable water-based substances, at least a first front-end coating station and at least a first tail-end rewinding station, and further comprising a second tail-end coating station for the spreading of hot-melt adhesive and a corresponding second rewinding station.

Description

BACKGROUND ART

Field of the invention

[0001] The present invention relates to a spreading line or plant for adhesive films.

[0002] As known, spreading plants for adhesive film are laid out in various ways according to use requirements and to the nature of the adhesives and of the release agents used.

[0003] Figs. 1 and 2, which represent diagrammatic elevation side views of prior art plants, illustrate two of such exemplary spreading plants.

[0004] Fig. 1 shows a spreading line for films with a solvent-based release agent and "hot-melt" adhesive.

[0005] A film P, supplied on reels, is unwound on the right hand-side of the line and initially goes through a station A1 where the solvent-based release agent is delivered. After the release agent has been spread on one side of the film, the film is guided towards the top part of the line, where it continues its journey inside a horizontal linear oven F.

[0006] During the journey inside the oven F, the solvent-based release agent is dried to the required degree.

[0007] At the exit from the oven F, the film is guided downwards and then into the spreading station A2, where the film is coated with a thin layer of hot-melt adhesive, on the opposite side to that of the release agent.

[0008] Finally, the film is conditioned (cooled) and rewound on a reel in a terminal station A3.

[0009] Fig. 2 illustrates instead a plant for spreading an acrylic-based or water-based adhesive on a polypropylene film. In this case the adhesive, which is applied at the beginning of the line, is water-based and the drying journey hence is necessarily longer (the film travelling speed being equal) than the one for the drying of a solvent-based release agent.

[0010] As can be realised from the drawing, a plastic film of polypropylene P is unwound off a reel, made to pass through a station where the water-based adhesive A4 is applied, and then into a horizontal linear oven F.

[0011] At the exit from the oven, the film P passes through a rewinding station A5 where it is rewound on a reel in the terminal station A6.

[0012] It must be noted that, compared to the plant employing a solvent-based release agent and hot-melt adhesive, this latter plant has a remarkably longer oven, because longer are the drying times of water-based solutions.

[0013] This consideration immediately leads to the guessing that plants employing water-based release agents or adhesives have the disadvantage of considerable linear dimensions. Although the oven is located in the top part of the plant, exploitation of the bottom part of the plant - as can be seen in fig. 2 - is not fully achieved.

[0014] Both these plants are substantially designed for a single use and dedicated to a specific function: as such, they are consequently little flexible.

[0015] Therefrom derives the fact that, should a user need to produce an adhesive film with a water-based adhesive or a solvent-based release agent and hot-melt adhesive, he is presently forced to purchase both plants, although the one for water-based adhesive (typically for polypropylene films) has a useful oven length which is theoretically suitable for a solvent-based release agent, too.

[0016] Furthermore, a plant designed exclusively for a solvent-based release agent and hot-melt adhesive, such as the one shown in fig. 1, is intended to be more and more limited or to face high manufacturing and maintenance costs, due to the strict environmental requirements which must be observed during solvent treatment. Consequently, resorting to plants with a long linear oven will be more and more unavoidable in order to treat water-based substances, unless the film travelling speed is drastically reduced with detriment of its throughput.

[0017] However, as already said above, due to the oven linear length, use of ground space in these plants is a reason for dissatisfaction, especially in users who - up until now - were used to achieving similar results with a more compact plant (the one in fig. 1 for solvent-based release agents and hot-melt adhesives), especially if employing vertical ovens of the rotogravure type.

[0018] Finally, it must be noted that in some individual cases, for example in the masking-tape treatment, the film to be coated with the adhesive does not even require prior treatment with a release agent, because it arrives already treated by the manufacturer. In this case, a large part of the plant - at least all the length occupied by the oven - is substantially not used, although it occupies productive space inside the treatment premises.

[0019] It would hence be desirable to provide a plant which exploits more effectively the linear dimensions typical of the manufacturing area.

[0020] It is hence an object of the present invention to provide a spreading plant to coat the film with adhesive, which plant is equipped with a substantially linear and horizontal drying oven, which is more flexible and allows a better exploitation of ground space than those offered by the prior art.

[0021] Such objects are achieved through a spreading plant as described in its essential features in the attached main claim.

[0022] Other inventive aspects of the apparatus are described in the depending claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Further features and advantages of the plant according to the invention will in any case be clearer from the following detailed description, given by way of example and illustrated in the accompanying drawings, wherein:

fig. 1, as already mentioned, is an elevation side view of a prior art plant for a solvent-based release agent and hot-melt adhesive;

fig. 2, as already mentioned, is an elevation side view of a prior art plant for water-based adhesive;

fig. 3A is a diagrammatic elevation side view of a plant according to the invention;

fig. 3B is a top plan view of the plant of fig. 3A; and

fig. 3C is an elevation front view of the plant of fig. 3A.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0024] A spreading plant comprises, in a manner known per se, a bridge-like structure 1, above which are mounted a series of oven modules 2a-2d (four in the drawings), mutually linearly adjacent. In the present description the oven module - which is well-visible also in fig. 3C both in its open and closed position - will not be described in further detail, since it is well-known to a skilled person in the field.

[0025] Below the bridge-like structure 1 a series of processing stations is housed.

[0026] At the plant entrance (for example, the right-hand end in fig. 3A), an unwinding and coating station 3 is provided which also delivers water-based substances. A film P is unwound off a reel and made to pass through such station in different ways, which will be illustrated further on.

[0027] Typically, this station consists of an unwinding unit 3a of film reels to be treated, a calender stabilising unit 3b, and a proper spreading or coating head 3c.

[0028] It should be noted that the plant of the invention is designed to be able to treat in this front-end station at least one plastic film with a water-based substance: therefore, the length of the linear oven described above must be such as to be capable of completing the drying of this substance in a way adequate to the work speed to which it is destined.

[0029] According to the invention, at the opposite exit of the plant (the left hand-side one in fig. 3A) at least one spreading station applying the hot-melt adhesive, and one rewinding station are provided.

[0030] In particular, it is provided a winding device 4 - capable of rewinding a polypropylene film P, which arrives coated with water-based adhesive - and a spreading device 5 for hot-melt adhesive.

[0031] The plant is completed by a second rewinding station 6, arranged between the front-end station 3 and the hot-melt spreading device 5, where a winder is mounted to form a reel of film which is fully treated with release agent and hot-melt adhesive.

[0032] Advantageously, upstream of the spreading device 5 a further unwinding unit 7 is provided specifically for masking tape or for the unwinding of other films to be coupled, whose usefulness will be shown later on.

[0033] The general layout of each individual station is known per se and will hence not be described in further detail here.

[0034] Now the possible ways of use of the plant according to the invention will be described, so as to highlight the flexibility and the advantages which it carries.

[0035] In the front-end station 3, a reel of polypropylene plastic film can be loaded, which is treated in the stabilising station 3b and onto which a water-based adhesive is applied in the head 3c.

[0036] This film P is then dried in the oven 2 and finally rewound in the rewinder 4 at the opposite end of the plant.

[0037] Alternatively, in the front-end station 3, a plastic film can be loaded, onto which hot-melt adhesive is to be applied. In such case, through the same head 3c, a water-based or solvent-based release agent is initially applied, which is then suitably dried in the oven 2. In this case the film P, after having passed onto cooling calenders 8, is deviated towards the station 5, where it is coated with adhesive. Finally, the film is rewound in the rewinder 6.

[0038] In these two ways, the plant of the invention is exploited fully.

[0039] Advantageously, moreover, in case it is necessary to coat a masking tape with hot-melt adhesive, it is possible to mount the corresponding reel on the additional unwinder 7, have the tape travel through the hot-melt adhesive spreading head 5, and then rewind it in the rewinder 6.

[0040] For this last specific operation, as can be well understood, only a small portion of the plant is occupied. It is hence possible to perform simultaneously, exploiting the same plant, the coating of polypropylene with masking tape and with water-based adhesive: this further increases productivity and versatility of the plant according to the invention, fully achieving the objects set forth in the preliminary remarks.

[0041] Thanks to the layout of the plant according to the invention, good flexibility of use can be achieved at the same time for various processes requiring an oven for drying water-based solutions - be they a release agent for subsequent spreading of hot-melt adhesive, or directly a water-based adhesive - as well as an efficient exploitation of the ground space, in the case that two mutually compatible processed are performed simultaneously (specifically, coating polypropylene with a water-based adhesive and coating masking tape with a hot-melt adhesive).

[0042] It is understood, however, that the scope of the invention described above is not limited to the particular embodiment illustrated, but extends to any other construction variant which is comprised in the object of the attached claims.

Claims

1. Spreading plant for adhesive films, of the type comprising a linear oven of a length suitable for drying applicable water-based substances, at least a first front-end coating station, and at least a first tail-end rewinding station, characterised in that it further comprises a second tail-end coating station for spreading hot-melt adhesive and a corresponding second rewinding station.

2. Spreading plant as claimed in claim 1), wherein upstream of said second tail-end coating station and downstream of said linear oven, an auxiliary unwinding station is further provided.

3. Spreading plant as claimed in claims 1) or 2), wherein said first rewinding station is arranged beyond the tail-end of said linear oven, while said auxiliary unwinding station, said second coating station and said second rewinding station are arranged in this order below said linear oven suspended on a corresponding bridge-like structure.

4. Spreading plant as claimed in claims 1), 2) or 3), wherein said front-end coating station is alternatively suitable to the application of a water-based adhesive or of a release agent.

5. Spreading plant as claimed in claim 4), wherein said front-end coating station is suitable for the application of a water-based release agent.

6. Spreading plant as claimed in any one of the claims 2) to 5), wherein between the first coating station and the first rewinding station a first treatment path can be defined, and between said auxiliary unwinding station, the second coating station and the second rewinding station a second treatment path can be defined, the two spreading paths being available simultaneously.

Drawing