WO1990011943A1

WO1990011943A1 - Envelopes

Info

Publication number: WO1990011943A1
Application number: PCT/GB1990/000536
Authority: WO
Inventors: Leslie Phillip Martin
Original assignee: Swift Adhesives Limited
Priority date: 1989-04-06
Filing date: 1990-04-06
Publication date: 1990-10-18
Also published as: AU5403690A; GB8907809D0

Abstract

Self-sealing envelopes utilising pressure-sensitive adhesives possess an adhesive layer (7) and a release layer (8) to protect the adhesive layer, the release layer being applied to a portion of the envelope itself.

Description

ENVELOPES

This invention relates to self-sealing envelopes and in particular to self-sealing envelopes employing a pressure sensitive adhesive which enables the envelopes to be sealed by the application of gentle pressure.

Most conventional self-sealing envelopes are provided with two strips of a latex-based adhesive, one on the flap of the envelope and the other on a facing portion of the body of the envelope. When brought together, the latex strips adhere to each other to seal the envelope. The latex strips are not particularly tacky and do not cause a problem of adhesion to other surfaces such as the rollers of typewriters.

However, due to the increase in world demand for rubber, the cost of latex has recently risen sharply and moreover in envelope manufacture, after application of the water-based latex adhesive, an expensive drying step is required. In addition, self-sealing envelopes of this nature have a relatively short shelf-life as the latex gradually deteriorates and loses its adhesive properties.

Another type of known self-sealing envelope employs a pressure sensitive adhesive. Such an adhesive will adhere to the majority of surfaces when pressed against them and so in such envelopes the adhesive must be protected by an release tape (for example a silicone-coated tape) which has to be peeled off just before the envelope is sealed. This has the disadvantage of creating waste, and adding an additional expensive step in the manufacturing process. Moreover, if the tape is dislodged while the envelope is being handled before sealing, for example on insertion into a typewriter, the tacky pressure sensitive adhesive can adhere to other objects, for example the proposed contents for the envelope or components of a typewriter. Moreover, it is clear that re-use of such envelopes is inconvenient once the released tape has been discarded.

There is therefore a need for an improved self-sealing envelope.

Thus, according to one aspect of the present invention, there is provided an envelope the surface whereof comprises a first area coated with a pressure sensitive adhesive, a second area provided with a release surface and positionable in facing relationship with said first area permitting said envelope to be loaded, and a third area positionable in facing relationship with said first area on disengagement of said first and second areas whereby to seal said envelope.

In one particularly preferred embodiment of the present invention, one or more of the first, second and third surface areas of the envelope are located on flap or flange portions of the envelope so that the adhesive and release areas may be disengaged and the third.or sealing surface area may be brought into contact with the adhesive area simply by folding or unfolding envelope flap portions. In an especially preferred embodiment, the release area and the sealing area are located on first and second flap portions of the envelope and the adhesive area is located on the outer surface of the body of the envelope, the adhesive area being positioned to be contactable by the release or sealing areas on folding the first or second flap portions respectively.

In an alternative embodiment, the adhesive and sealing areas are located on first and second flap portions of the envelope and the release area is located on the outer surface of the body of the envelope, the adhesive area being positioned to be contactable by the release or sealing areas on folding of the first flap portion or on unfolding of the first flap portion and f lding of the second flap portion respectively.

In another particularly preferred embodiment, the sealing area is located on the outer surface of the body of the envelope and the adhesive and release areas are located on the same face of a flap portion of the envelope, said flap portion being foldable to bring the adhesive and release areas into contact.

The envelopes of the present invention do clearly overcome the disadvantages mentioned above for self-sealing envelopes employing latex-based adhesives. It will also be apparent that the envelopes of the present invention do not require a separate release tape since during pre-use storage the adhesive layer is protected by the release area of the envelope surface and, immediately prior to use, the adhesive can be exposed simply by disengaging the adhesive and release areas, for example by unfolding a flap portion of the envelope.

The flap portions of the envelopes of the invention may be provided with fold-lines or creases or with scores or other lines of weakness in order to facilitate folding.

In the manufacture of the envelopes of the invention, any convenient pressure sensitive adhesive may be used. Hot melt pressure sensitive adhesive (for example B946/91 available from Swift Adhesives Limited) are particularly advantageous as there is no need to dry such adhesives after application. However, water-based adhesives (such as for example C945/52 available from Swift Adhesives Limited) and solvent-based adhesives may alternatively be used. Many such pressure sensitive adhesives have much higher tack levels than the latex-based adhesives of the conventional self-sealing envelopes so that the quantity of adhesive required may be relatively small.

The adhesive can be applied to the envelope or the web from which the envelope is later formed as a continuous strip or in a discontinuous fashion, for example as a plurality of patches, strips or dots.

The release surface on the envelopes of the invention is generally a surface to which the adhesive adheres less firmly than it does to the basic material of the envelope. It will generally be applied as a coating layer and can be of any substance to which the particular adhesive chosen will adhere but from which the adhesive may be disengaged with reasonable ease. Conveniently, the bond between the adhesive and release layers will only just be sufficient to maintain the two in contact under normal handling. Preferably, the release layer will be formed from a silicone, such as for example a solventless silicone (e.g. Syl-Off Q2-7203), a solvent-based silicone (for example Syl-Off 7046) or an emulsion-based silicone (for example Syl-Off Q2-7198/Q2-7199) . The Syl-Off silicones are available from Dow-Corning. The application of silicones which are curable by ultra-violet radiation is particularly preferred as the silicone can then be printed onto a continuous web which may then be passed under UV-radiation curing lamps thereby speeding up production.

The area covered by the release layer should be sufficient to mask the entire area coated by adhesive and preferably the surface area of the release layer will be greater than that of the adhesive layer so as to allow for some error in positioning.

In a particularly preferred embodiment of the present invention, the envelope may be made re-usable by providing the sealing area with an adhesion- reducing layer, for example a plastic film. The envelope can then be sealed by adhering the adhesive to this adhesion -reducing layer rather than directly to the basic material of the envelope itself. In this embodiment, the envelope can be opened by peeling adhesive and sealing layers apart without damaging either the envelope or the adhesive layer. The envelope can then be re-used immediately or it may be refolded to bring the adhesive layer back into contact with the release layer whereafter the envelope may be stored ready for re-use. This embodiment is particularly useful where the envelope is formed from a cellulosic web and thus is prone to tear on being opened.

In general, the release layer and the adhesive layer can be in any convenient position on the envelope where they can be readily brought into contact with each other. Thus, for example, the envelope comprises a wallet portion with extending from one side of the mouth thereof a flap portion which can be folded over the mouth of the wallet to seal the envelope; the adhesive and release layers may conveniently be applied in the form of two adjacent strips either to the sealing flap or to the back of the wallet portion. The envelope can then be folded between the two strips to bring the adhesive into contact with the release layer.

The adhesive and release layers can be applied to any conventional form of envelope such as paper or stiffened card envelopes, padded and plastic envelopes and the term "envelope" as used herein also extends to other types of containers such as bags. The invention however is particularly suited to use with heavy duty envelopes, for example those having surface areas (of one major surface)

2 . 2 greater than 250 cm , and particularly greater than 500 cm .

In a further aspect, the present invention also provides a method of producing a self-sealing envelope which method comprises applying an elongate release layer and an elongate pressure sensitive adhesive layer to a web, folding said web to bring said pressure sensitive adhesive and release layers into adhering contact, optionally cutting said web into envelope blanks, and forming said web or a said blank into an envelope.

Thus, using the method of the invention, self-sealing envelopes may be produced by applying adhesive and release layers either to a continuous web which may then be cut into envelope blanks or to webs already in the form of pre-cut envelope blanks.

Preferred embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which :

Figures 1 and 2 are perspective drawings of two different embodiments of the envelope according to the invention.

Referring to Figure 1, there is shown a self-sealing envelope 1 comprising a wallet portion 2 and flaps 3 and 4. Flaps 3 and 4 may be folded about fold lines 5 and 6. A strip of hot melt pressure sensitive adhesive 7 and a silicone release layer 8 are applied to flap 4 and to the rear of the wallet portion 2 respectively.

Before the envelope is used, for example whilst it is in storage, flap 4 is folded down along fold line 6 so that adhesive strip 7 holds onto silicone release layer 8. To seal the envelope, flap 4 is unfolded back to detach adhesive strip 7 from release layer 8 and flap 3 is folded down along fold line 5 and pressed against the exposed adhesive strip 7.

In Figure 2 there is shown an alternative self-sealing envelope 1 having a flap 3 which may be folded along fold lines 5 and 9. An adhesive strip 7 and a silicone release layer 8 are applied, to flap 3 on either side of fold line 9. The rear of the wallet portion 2 of the envelope is provided with a plastic film 10.

During storage before use, flap 3 is folded down over along fold line 9 so that adhesive strip 7 adheres to silicone release layer 8. To seal the envelope, flap 3 is unfolded to detach adhesive strip 7 from release layer 8 and the entire flap is then folded down along fold line 5 to bring the adhesive strip 7 into contact with film 10. The envelope can opened by peeling back flap 3 to detach adhesive strip 7 from film 10. Flap 3 may then be folded- again along fold line 9 so that the envelope can be stored ready for re-use.

Claims

CLAIMS :

1. An envelope the surface whereof comprises a first area coated with a pressure sensitive adhesive, a second area provided with a release surface and positionable in facing relationship with said first area permitting said envelope to be loaded, and a third area positionable in facing relationship with said first area on disengagement of said first and second areas whereby to seal said envelope.

2. An envelope as claimed in claim 1 wherein one or more of the first, second and third surface areas of the envelope are located on flap or flange portions of the envelope.

3. An envelope as claimed in claim 2 wherein the release area and the sealing area are located on first and second flap portions of the envelope and the adhesive area is located on the outer surface of the body of the envelope, the adhesive area being positioned to be contactable by the release or sealing areas on folding the first or second flap portions respectively.

4. An envelope as claimed in claim 2 wherein the adhesive and sealing areas are located on first and second flap portions of the envelope and the release area is located on the outer surface of the body of the envelope, the adhesive area being positioned to be contactable by the release or sealing areas on folding of the first flap portion or on unfolding of the first flap portion and folding of the second flap portion respectively.

5. An envelope as claimed in claim 2 wherein the sealing area is located on the outer surface of the body of the envelope and the adhesive and release areas are located on the same face of a flap portion of the envelope, said flap portion being foldable to bring the adhesive and release areas into contact.

_ 6. An envelope as claimed in any preceding claim wherein the adhesive is a hot melt pressure sensitive adhesive.

7. An envelope as claimed in any preceding claim wherein the release surface is formed from a silicone.

8. An envelope as claimed in claim 7 wherein the silicone is curable by ultra-violet radiation.

9. An envelope as claimed in any preceding claim wherein the sealing area is provided with an adhesion- reducing layer.

10. A method of producing a self-sealing envelope which method comprises applying an elongate release layer and an elongate pressure sensitive adhesive layer to a web, folding said web to bring said pressure sensitive adhesive and release layers into adhering contact, optionally cutting said web into envelope blanks, and forming said web or a said blank into an envelope.