Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-11-06
2003-03-04
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S232000, C156S272800, C156S275500, C156S379600, C156S542000
Reexamination Certificate
active
06527897
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process and a device for manufacturing segmented pressure-sensitive adhesive layers and applying the same to a substrate, involving the use of a reaction medium containing radiation-induced monomers and/or prepolymers of olefinically unsaturated compounds, and optionally the addition of a photoinitiator.
DESCRIPTION OF THE PRIOR ART
Segmented pressure-sensitive adhesive layers are widely used in practice, for example, in such pressure-sensitive adhesives which are required to be water- or gas-permeable. Also, in some cases, reducing the consumption of pressure-sensitive adhesive is a reason for the segmentation of a pressure-sensitive adhesive layer.
Furthermore, segmentation is required if small areas are stuck to substrates. Here, it is only the area to be adhered which is to be provided with a segment of the pressure-sensitive adhesive layer.
The processes for segmentation, punching, knife application, and screen printing are known above all. Among these, punching has the disadvantage of entailing large amounts of waste. Knife application only permits production of limited layer thicknesses, which also applies to screen printing. The latter moreover requires a considerable expenditure in terms of the provision of contours.
U.S. Pat. No. 5,344,681 describes a process for segmentation wherein pressure-sensitive adhesive segments are produced in recesses of a carrier material. This involves particular difficulties in connection with the removal of the segments from the recesses.
SUMMARY OF THE INVENTION
Starting from the aforementioned prior art, it is the object of the invention to provide a process and a device which enable the manufacture of segmented pressure-sensitive adhesive layers of any desired thickness and contour in an economical manner as well as in a manner which can be readily realized in technical terms, and which are suitable for mechanization with high output using comparatively uncomplicated devices.
To achieve this object in a process for manufacturing segmented pressure-sensitive adhesive layers and for applying the same to a substrate, using a reaction medium containing radiation-inducible polymers and/or prepolymers of olefinically unsaturated compounds under addition of photoinitiators, the following sequence of operational steps is proposed with the present invention:
that the reaction medium is kept ready in a metering and filling station under absence of oxygen,
that the empty templates are conveyed, preferably intermittently one after another, with a lower covering of their segment-defining opening put against the said templates, to a filling station wherein they are filled with a dosable amount of the reaction medium,
that the filled templates are passed in continuous conveyance below a UV section, whereby the reaction medium is solidified by means of radiation-induced reaction involving at least partial polymerisation,
that after removal of the lower covering, the reaction medium, which is then exposed on the upper side and the bottom side, is, during the further transport between an upper and a lower UV section, fully cured from above and from below by continued radiation-induced polymerisation reaction to form the finished pressure-sensitive adhesive layer,
that the template, containing the finished pressure-sensitive adhesive layer, is conveyed to a transfer station wherein the pressure-sensitive adhesive layer is pushed out of the template and is combined with a substrate,
that, optionally, the substrate which has been equipped with the pressure-sensitive adhesive layer is conveyed by a conveyor belt to a final-manufacturing station (not shown).
The process is suitable for economically and continuously manufacturing segmented pressure-sensitive adhesive layers of any desired thickness and contour in a manner which is comparatively uncomplicated and can be readily realized in technical terms. More particularly, the process is suitable for use in a fully-mechanized device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of the process provides that the thickness of the segmented pressure-sensitive adhesive layer is defined by the thickness of the template.
Furthermore it is provided by the invention that the template and the lower covering are rendered anti-adhesive, with the template and lower covering being made of dehesive material or the inner walls of the opening and the covering preferably being provided with a dehesive coating.
A further embodiment of the process provides that the polymerization reaction is performed by irradiating the reaction medium with ultraviolet light or electron radiation, and that the ultraviolet light is preferably generated by a laser.
The process is further characterized in that to produce the pressure-sensitive adhesive layer, acrylate-based pressure-sensitive adhesives are selected with preference, and that the mixture of monomers is principally employed under addition of a photoinitiator.
Also, a prepolymer may be used for polymerization. Since during polymerization, the reaction medium is subjected to a volume shrinkage, a corresponding embodiment of the process provides for the addition to the reaction medium of an additive compensating the volume shrinkage occurring in the course of polymerization.
Since the reaction medium must be protected from access of oxygen during its handling up to the time of performing the polymerization reaction, it has proved advantageous to render the environment of the template inert by means of nitrogen, in order to increase the degree of reaction. Since in the case that the reaction medium is metered into an opening of the template it is not absolutely necessary that said opening be filled-up completely, the thickness of the pressure-sensitive adhesive can be adjusted in accordance with the filling amount to be metered, i.e. the thickness can be smaller than the thickness of the template. As a consequence, in the manufacture of the adhesive layer it is possible to vary the thickness within relatively broad limits without the need of making a new template for each thickness.
A device for manufacturing segmented pressure-sensitive adhesive layers and applying the same to a substrate, more particularly for realizing the process according to the invention, is characterized by the following structural features:
a continuous conveyor belt or chain for templates to be conveyed in circulation,
a base or support belt running synchronously within the said conveyor belt, under section-wise formation of a lower covering,
a first, upper UV section and a subsequent lower UV section,
a transfer station comprising a template-emptying device.
As a transfer station, a turnstile is suitable.
In the vertical axis, a turnstile is mounted above the template to be emptied. From below, the contoured adhesive tape is pushed upwards out of the template by means of a plunger or punch. The turnstile consists of 4 arms fitted at a distance of 90°, each arm having a suction foot and a pneumatic cylinder.
A cycle starts at 0° at the magazine (
4
), from which the suction device takes out the piece which is to be rendered self-adhesive. The arm is rotated through 90° counter-clockwise and reaches a station (
5
) where the surface is processed (e.g. corona discharge pre-treatment). After a rotation of altogether 180°, at the push-out and transfer station (
3
) the piece is placed onto the template in exact position. With the aid of the push-out plunger provided at the bottom side, the piece, which has been rendered self-adhesive, is then jointly removed from the template. The said piece, after a further rotation of altogether 270°, is placed on a dehesive conveyor-belt (
6
) and is subsequently subjected to final manufacturing processes. After the final 90° rotation, the cycle is repeated, respectively, started anew (360°=0°).
The device is comparatively uncomplicated and is suitable for mechanized, continuous production of segmented pressure-sensitive adhesive layers using uncomplicated technological means.
One embodiment of the device
Ecker Günther
Herrmann Fritz
Hoffend Bernd
Nittenwilm Ralf
Ball Michael W.
Haran John T.
Hochberg D. Peter
Lohmann GmbH & Co. KG
Mellino Sean
LandOfFree
Method and device for producing segmented contact adhesive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for producing segmented contact adhesive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for producing segmented contact adhesive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3022372