Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – Automatic and/or material-triggered control
Reexamination Certificate
1996-06-04
2001-04-03
Mayes, Curtis (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
Automatic and/or material-triggered control
C156S543000, C226S030000, C226S031000
Reexamination Certificate
active
06209606
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to tapes and is concerned with tapes suitable for use as teartapes.
2. Description of the Prior Art
Teartapes are known to provide a means of facilitating the opening of packages such as packs of cigarettes, confectionery and the like including overwrapping formed form filmic packaging materials. They are adhered to the surface of the packaging material in a manner such that, in use, an end of the teartape can be pulled so as to tear the packaging material underlying the teartape to allow access to the contents.
Traditionally such teartapes have been made from cellulose film or derivatives of cellulose which are coated with barrier resistant and/or heat seal coatings. Such tapes can be readily applied to packaging material formed from films of a similar materials by moistening the coating with a solvent, to soften the coating, and applying heat and pressure to give firm adhesion. The replacement of cellulose-based packaging material by stronger and more cost effective polyolefin film packaging materials, and especially by biaxially oriented polypropylene films, has similarly led to the substitution of polypropylene for cellulose in teartape manufacture.
Polypropylene teartapes often comprise two-ply laminates of similar polypropylene film to provide increased tear strength and, also, to protect any print applied to the surface of the lower layer. Two methods have been employed to apply these polypropylene tapes to polyolefin film packaging materials. In the case where the polyolefin packaging material is a lacquer coated film a solvent is used to activate the coating and ensure adhesion of the teartape. Alternatively, if the polyolefin packaging material is uncoated, the teartape is caused to adhere by applying a hot melt wax composition. A lacquer coating is not, usually, a packaging requirement, when using polyolefin packaging film, since these have superior barrier properties to cellulose films. Also, in the case of polyolefins there is the opportunity to co-extrude films in order to provide for any specially demanding barrier properties. Hence, the use of lacquer coated polyolefin packaging film simply to promote the adhesion of a teartape involves an unacceptable coat penalty. The use of hot melt wax compositions is, also, undesirable since this gives rise to:
1. the need for cleaning,
2. the need for close attention by the operator to recharge the baths with adhesive wax and to ensure temperatures are correct in order to promote satisfactory adhesion,
3. a safety hazard with high temperature wax baths,
4. distortion of the packaging film and/or tape as a consequence of the heat of application or stress on cooling which can cause an unsightly “cockling” effect, and
5. poor and inconsistent adhesion to film, especially, on starting and restarting the lamination process.
These disadvantages are particularly troublesome when stopping and starting the application of the teartape to the packaging film and the nature of the teartapes and their means of application are such that relatively small spools of tape containing no more than 2500-5000 meters have had to be used, thus, causing frequent stoppages on fast operating packaging lines. The present invention provides a teartape suitable for applying to polyolefin film packaging materials without the foregoing disadvantages.
SUMMARY OF THE INVENTION
The present invention, generally, provides an improved method of applying a tape to a film packaging material, as well as a novel means for applying a tape to film packaging material.
According to one aspect of the present invention there is provided a teartape for applying to film packaging materials, particularly to polyolefin film packaging materials, which teartape is formed from an oriented thermoplastic plastic material base film coated with a pressure sensitive adhesive composition.
The base film may, for example, have a thickness of from 20 to 100 microns and a width of from 1 to 10 mm. Preferably, the thickness is from 40 to 70 microns and the width is from 1.5 to 4 mm. The thermoplastic plastic material of the base film may be, for example a polyvinyl chloride or vinyl chloride copolymer, a linear polyester, or, preferably, a polyolefin, such as, polypropylene or a copolymer of propylene and ethylene. Preferably, the plastic material of the base film is monoaxially oriented since this provides improved cross tear resistance and enables a thinner tape to be produced than in the case where biaxially oriented or non-oriented material is used. Advantageously, the tensile strength of such polypropylene or ethylene/propylene copolymer tape is from 1500 to 3000 kg/cm
2
in the longitudinal direction and from 200 to 500 kg/cm
2
in the transverse direction. Also, in this preferred embodiment, the extension in the longitudinal direction is from about 30 percent to about 50 percent and the extension in the transverse direction is from about 800 percent to about 1000 percent.
Any suitable pressure sensitive adhesive composition may be used. Thus, it may, for example, be a natural or synthetic rubber of an acrylic compound and, normally, a primer coating will be provided between it and the surface of the base film so as to promote anchorage of the pressure sensitive adhesive composition. The surface of the base film which is not coated with the pressure sensitive adhesive composition will ordinarily be coated with a release agent.
In a particularly preferred embodiment, the base film is printed in a manner such that the printed matter is righted for reading when the teartape is adhered to the filmic packaging material. For example, the printed matter may be printed normally onto a surface of the base film and overcoated with a transparent pressure sensitive adhesive composition. Thus, when the teartape is adhered to the inner surface of the filmic packaging material, the printed matter is righted for reading when viewed through the filmic packaging material and the adhesive composition. In this way, the printed matter is protected from abrasion and from possible contact with the contents of the package. Alternatively, the printed matter may be printed in reverse on one surface of a transparent base film and overcoated with release agent, the other surface being coated with a transparent pressure sensitive adhesive composition. The printed matter will then be righted for reading when the teartape is adhered to the inner surface of the packaging material and viewed through he base film, the adhesive and the packaging material. The matter printed can be either decorative or informative. Thus the teartape can form a sales promotion aid and/or carry a health warning, for example, the case where it is used in cigarette packing.
The tape is such that it can be produced in the form of traverse wound reels containing a large quantity of tape (e.g. at least 30,000 meters).
In using the tape as a teartape it is applied to the surface of filmic packaging material and, particularly, polyolefin film packaging material and adhered thereto by means of the pressure sensitive adhesive composition.
According to another aspect of the present invention there is provided a method of applying a tape, such as the aforementioned pressure sensitive adhesive teartape, to the surface fo filmic packaging material, which comprises affixing an end portion of the tape to a portion of the surface, moving the surface so as to move the tape in a manner such that successive portions of the tape are drawn into contact with successive portions of the surface and become affixed thereto, and controlling the speed of movement of the surface, so as to reduce tension imbalance between the tape and the surface.
By reducing imbalance between the tension in those portions of the tape which are affixed to the surface and the tension in those portions of the surface to which tape is affixed, unsightly puckering is reduced. The method of the present invention is particularly useful in the case where the filmic packaging material surface is a polyolefin film
Davis Brian Frederick
May Geoffrey Bilson
Nowak Wladyslaw Lakiyan
Harness & Dickey & Pierce P.L.C.
Mayes Curtis
P. P. Payne Limited
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