GB2234974A - Adhesives - Google Patents

Abstract

An adhesive assembly comprises at least two component parts (1, 2), with two surfaces of matching surface contour or of conformable surface material adhered permanently, re-positionably or minimally by a continuous or discontinuous expanse of adhesive (3) mixed with or positionally associated with a material capable of a desired ascertainable physicochemical or chemical change over a period of time and/or in response to change of surrounding circumstances. <IMAGE>

Description

ADHESIVE ASSEMBLY This invention relates to adhesive assemblies.

By 1adhesive assembly' is meant an assembly of at least two component parts, with two surfaces of matching surface contour or of conformable surface material, adhered by a continuous or discontinuous expanse of adhesive material between the two surfaces. Usually (but not invariably) in the context of this invention the adhesive assembly comprises at least a first leaf of foil. cellulosic material or synthetic polymer adhered to a second leaf of one or the other of those materials. The adhesive material can for example be a continuous lay over all of the contacting surface areas or can be discontinuous e.g. dotted or striped or can be partial e.g. located around the margins only of the contacting areas.

The term "adhesive" as used herein is intended to cover permanent adhesion, where it is not intended or possible to separate the surfaces; temporary, or imperfect adhesion, where the surfaces are intended to be separable and can be separated without the potential however for repeated re-use; re-positionable adhesion, e.g. as of a so-called "POST-IT" (Registered Trade Mark) memorandum slip, where the adhesive surface cannot only be separated, but is capable of repeated re-use and re-separation; and nominal or minimal adhesion, e.g. of a temporary release paper over an adhesive surface, to be removed and discarded before the surface is used.

One area of use for adhesives is in the formulation of packages, advertisements, display material, or promotional material of all types. Sometimes with such products (for example) the need arises to incorporate a material capable of physicochemical or chemical change, over a period of time or in response to change of ambient circumstances. Fxamples of physicochemical change are diffusion out of odoriferous or other molecules, or of reaction with ultraviolet light.

Examples of chemical change are reaction with ambient air or moisture o in more specialised contexts, with contacting acid or alkalis e.g. litmus paper or universal indicator.

Without prejudice to the generality of the above, it can be seen that there are problems if for example cellulosic or polymer materials (the usual substrates) ace to be combined with odoriferous chemicals. (which can be exemplified by animal-repellent chemicals) or with oxidative colour pigments.

Odoriferous chemicals to repel animals are often also unpleasant to humans. A particular area of application for them is to protect filled rubbish bags, placed for collection, from the depredations of cats, dogs or even foxes. Usually the chemicals are provided as a dusting powder. which is one more operation to remember and which is susceptible to personal variations in use. We have investigated therefore whether the odoriferous chemical can be incorporated into a cellulosic e.g card substrate, for controlled diffusion through the card, and whether it can be similarly incorporated into the synthetic polymeric material of a rubbish disposal bag.

In neither case, however, did the experiment prove successful. In card, the compound starts to diffuse out immediately and is nearly all gone by the time such a card could be placed around or near the dustbin. On polymer, diffusion is much slower, but the odoriferous compound, being chemically complex, was in any case largely destroyed at the polymer melt temperatures needed to produce the thin-walled bag. Similar considerations applied to the oxygen-reactive colour-change pigment.

We have now realised that additive materials capable of physiochemical or chemical change over a period of time or in response to changed circumstances can be advantageously incorporated into or associated with the adhesive layer itself.

Adhesives are available with a wide variation of chemical composition (wider, for example, than garbage-bag polymers) so that it is not difficult to find a compatible adhesive for a proposed additive.

Also, they tend to be made up at or near ambient temperatures, so that the additive is not degraded during incorporation. Also, when applied, the zones of adhesive can be separate from the applied zones of chemical additive. Moreover, the adhesive layer can be designed of a thickness or type such as to control diffusion, colour-change, etc, of any contained additive.

In one aspect the invention consists in an adhesive assembly of at least two component parts, with two surfaces of matching surface contour or of conformable surface material adhered permanently, re-positionably or minimally by a continuous or discontimlous expanse of adhesive mixed with or positionally associated with a material capable of a desired ascertainable physicochemical or chemical change over a period of time and/or in response to change of surrounding circumstances.

The component parts could be solid elements such as a container and stopper glued together, e.g. on a temporary or imperfect basis so as to be separable with exertion of suitable force, and leaving one or other component with a surface of changed environment (e.g changed access to sunlight, oxygen, or moisture) to initiate or accelerate, for example odor-production or colour-change. The component parts could also be resilient elements, pressed into adherent conformity, for similar use.

Most preferably, however, each component part is a single or composite leaf or area including cellulosic and/or synthetic polymer materials. Generally speaking, cellulosic materials unless specially coated will be gas-permeable i.e. permeable to oxygen, water-vapour or odoriferous molecules at a rate adjustable by thickness, coatings, or loading of other components. Polymer materials are impermeable, or at least much less gas-permeable, and can be selective i.e. permitting oxygen but not large molecules to pass. These considerations, together with the permanently adhered, intermittently adhered or completely separated state of the units in use, or in end use as distinct from storage and transit, give to the man in the art a wide range of possible constructions and end uses for the assembly. Thus, those listed below are by way of example only.

The adhesive can be permanent. If covered by a single leaf or composite leaf or area, such foil or area must allow either gas molecules or light to transfer accross the barrier so constructed or must allow partial tearing away of the leaf or area, without breaking the adhesive bond, so expose e.g. an accessible pocket or the like to environmental change.

More usually, the adhesive will be intentionally peelable, to leave adhesive material, including or associated with the additive, on one or both separated surfaces, for the purposes discussed above. A special case of this is the adhesive coated peelable and repositionable leaf, using low-tack non-cured adhesives, such as is commonly available under the Registered Trade Mark of 'POST - IT; this has the advantage over a singly peelable but not repositionable leaf that the physicochemical or chemical change can be intermittent depending on periods of separation and re-unification of the two leaves.

Often, moreover, one leaf is only minimally or nominally adhered as a release layer, (comprising for example siliconised paper) and is capable of casual or incidental removal to expose the adhesive1 but not replacement.

The man skilled in the art will appreciate that double-sided tape, i.e having a central substrate with two adhesive coated faces, one in accordance with the proposals of the present invention and both covered by a release layer, is of value in the practice of the present invention.

It is commonplace, if two areas are to be adhered, for the interposed adhesive to be applied discontinuously as dots, stripes or a marginal application or some combination of these. The present invention includes such an arrangement within its scope, and includes moreover the possibilities either (a) of mixing the additive with adhesive or (b) of separately adhering the additive (in a form adhesive or non-adhesive) to available free spaces between the adhered surfaces, or (c) of both (a) and (b). Such separate application of additive, within the same general area as adhesive and between the same two surfaces is referred to herein as being "positionally associated with" the adhesive.

As indicated above, the additive can be odoriferous, either positively as an attractive scent or negatively as animal or insect repellent. In such a case, the physicochemical change is diffusion into the atmosphere, without chemical change.

The additive can be susceptible to heat above a given spoilage temperature: in such a case removal of a covering foil is not usually necessary and permanent adhesive will suffice. The change could be physicochemical or chemical.

The additive can be susceptible to various forms of radiation, e.g. nuclear, microwave, infra-red, ultra-violet and so on. In such a case the covering foil might have a partial or complete shielding effect until removed. Again, this is a physicochemical change.

One example of chemical change is reaction with oxygen.

Suitable materials can be utilised to give a progressive darkening (or lightening) of colour with oxygen access, either by diffusion through a cellulosic backing or by direct access to additive when a foil is separated from the assembly. Other examples could be with water vapour S0z, etc. They can give a simple chemical clock, discernable by colour change after leaf separation, and useful in assessing "sell by" or "use by" dates on merchandise or opened packets.

In general, it will be appreciated that the discernable change in the additive can be gradual, e.g. a slow change visible or through the assembly showing elapsed time since delivery, or can be relatively rapid e.g. a "use by" term of 24 or 48 hours, after a container has been opened and an expanse of additive thus revealed.

Similarly, with animal repellent one can achieve with slow release by suitable configuration of permeable and impermeable layers on a permanently adhered structure or maximum short-term effect by removing a cover foil from the assembly to expose the adhesive zone.

With the general nature of the invention as described above certain artefacts are particularly valuable.

Thus, the invention extends to (a) a garbage bag of polymer sheet having an area (preferably a strip) of adhesive located on an outer surface thereof, the adhesive being mixed or associated positionally with an animal-repellent odoriferous additive and being covered by a release layer. impervious to the vapour of the additive, for removal as the filled bag is dumped for collection.

(b) a label for a garbage bag in the form of a central layer covered on both faces with adhesive, in each case protected by an area of material : wherein the adhesive on one face at least is mixed with or positionally associated with an animal-repellent odoriferous additive.

(c) a label. or portion of a closure, for a package, wherein two leaves are adhered by peelable adhesive mixed with or positionally associated with a material capable of progressive colour change on exposure to atmosphere for a period after the leaves are peeled apart, as a measure of elapse of time since the package was opened.

The invention will be further described with reference to the accompanying drawings in which: fig 1 shows a section through an adhesive assembly; fig 2 shows an adhesive face including an additive in accordance with the invention fig 3 shows an alternative embodiment to fig 2: fig 4 shows a further alternative embodiment to fig 2 fig 5 shows the composition of an adhesive assembly in strip form, and fig 6 shows a garbage bag including an adhesive assembly in accordance with the invention.

Fig 1. shows a first leaf 1 of material, which can be for example singlelayer or multilayer, impermeable or slowly permeable to gases and vapour1 or optically transparent, translucent or opaque. It can be an area of defined shape, or part of a larger area.

Figure 1 also shows a second leaf 2 of the same potential range of characteristics. For convenience; and since the assembly is often part of a package structure. leaf 1. will be taken to be the wall of a carton or side of a polymer bag (when relevant to the context) and leaf 2 a layerapplied thereto.

The two leaves are adhered by a continuous or discontinuous layer of adhesive 3.

The adhesion can be permanent, peelable. re-positionable or minimal, as of a release layer. There is an additive. discussed further below, mixed with, or positionally associated with, the adhesive.

Fig 2 shows the adhesive layer 3, in the form of a pattern of adhesive dots 4 and additive dots 5 interspersed therewith. Fig 3 shows lines 6 of adhesive and lines 7 of additive. Fig 4 shows a discrete label shape with a peripheral strip of adhesive at 8 and additive printed on in lines at 9. Fig 5 shows a strip of material 10 with side edges printed with adhesive at 11 and centre coated with additive at 13, beneath a cover foil 2' adapted by end units 12 to be pulled away centrally but retained by adhesive 11. However, the easiest expedient is physically to mix adhesive and to coat them together (continuously or discontinuously) to achieve the configuration of Fig. 1.

The utility and advantages of the arrangement shown in Fig 1. can be emphasised with reference to the incorporation of an odoriferous compound as the additive, in either an attractive mode (a perfume) or an unattractive, animal-repellent, mode.

Suppose leaf 1 is slowly vapour permeable, e.g. is the cellulosic wall of a carton of haberdashery articles or of a lace handkerchief, and leaf 2 is impermeable, and the additive is a scent. The scent slowly permeates through leaf 1 to scent the box and contents, but takes a reasonable shelf-life period to do this. If leaf 2 is permanently adhered. this will be the only effect : but if leaf 2 is peelable, or a release layer, it can be, for example, linked to the opening of the box to give a stronger waft of perfume at that time, as the free surface at 3 then becomes exposed. If leaf 2 is re-positionable the effect can be repeated each time an article (already slightly perfumed) is removed.

If leaf 1 were non-permeable, the only effect would be the waft of perfume as the carton was opened. For some goods this might be preferable. If leaf 2 were permeable, however, there would be a general continuing loss of perfume to atmosphere through shelf life. which is not normally desirable.

If the additive were an unattractive scent e.g. or animal repellent, the desiderata are reversed. Leaf 1 should typically be impermeable, since the contained good would otherwise be tainted. For example, leaf 1 could be the side wall of a dustbin liner bag, or the underside of an impermeable fast food tray. No untoward smell or vapour permeates inwardly or if leaf 2 is impermeable, permeates outwardly, until such time (e.g as the filled bag is placed for collection, or the emptied tray disposed of in a litterbin) as the leaf 2 is peeled off. There is little point in such a case in using repositionable adhesive. The specific embodiment of a rubbish bag in accordance with the invention is described in more detail below.

Further understanding of the utility and advantages of the invention can be explained with reference to the incorporation of an oxygen-sensitive compound as the additive, the principles of construction being similar whether. the compounds goes darker or becomes lighter on exposure to oxygen.

The purpose of such an embodiment can be considered as providing a visible approximate record of elapsed time for a container, either before or after opening date.

There are three convenient variables to take into account, assuming for convenience that the adhesive layer 3 is affixed to the outside of a carton and covered with top layer 2. These are: (a) whether layer 1. or 2 is impermeable or is slowly permeable to oxygen (e.g. as a treated cellulosic layer).

(b) whether layer 1. or 2 is on the one hand transparent or translucent or on the other hand opaque.

(c) whether layer 2 is removable.

These give rise to three visible effects which can be used for timing e.g. shelf life or opened life. The effects are: 1. For impermeable layers on both sides the discoloration at the margins caused by diffusion of oxygen between the layers. This could be enhanced by cutting holes in one or more layers e.g. to provide more effective marginal regions.

For an impermeable layer on one side only, the slow discoloration effected by oxygen diffusion through the other layer, which can be specially treated for such a characteristic, and thus give a long time period of colour change.

3. For an exposed layer of adhesive, rapid colour change e.g. over 48 hours, suitable for a "use-by" or "safe-until" instruction.

These effects can be hybridized: for instance, a composite could be made up of impermeable foil adhesive + additive : impermeable transparent foil with holes cut therein : and top impermeable removable layers. This, once the top layer is removed would rapidly discolour inside the holes in the perforate layer, and the colored areas would then gradually grow e.g. until they met some time later depending upon oxygen diffusion. However. the basic three effects listed above give a variety of use possibilities, taking into account progressive color appearance from outside the carton (shopper), from inside the carton (retailers check-up) and after removal of leaf 2 e.g. after opening.

The combined effects will be as follows: 1. If both leaves are oxygen-impermeable there will be "margin" effects only unless and until the top leaf 2 is removed, at which time the "fast" effect will take over. From outside, the progress of both will be visible if leaf 2 is opaque. From inside. if leaf 1. is transparent the progress of either or both will be visible, but if not, neither will show.

2. If either the outer leaf 2 or the inner leaf 1 but not both are oxygen permeable the slow" effect will take place unless and until the top leaf 2 is removed at which time the fast effect will take over. From outside, the progress of both will be visible if leaf 2 is transparent but only the subsequent progress of the "fast" effect will be visible if leaf 2 is opaque from inside, and as above, the progress of either or both will be visible if the leaf 1 is transparent, but if not neither will show.

3. If both leaves 1 and 2 are oxygen permeable then essentially the same effect takes place as in the immediately preceding paragraph, except that the "s low" effect may be somewhat faster due to the increased oxygen supply.

The man skilled in the art will realise that there are limitless assemblies which can be made up, to show for example the "slow" progress and "fast" process separately on a two part assembly, or to create or obscure printed instruction indicia as the colour changes, in every case using the adhesive layer as the carrier and/or site of application of the active additive chemicals.

Analyses similar to the foregoing can be made for heat-changeable o radiation-changeable additives, which give the possibility of for instance a simple label indication for the progress of microwave or conventional cooking.

Figure 6 shows one practical embodiment of the invention as applied to a garbage bag, to confer animal-repellent properties without the difficulties of incorporation of materials into the hot melt and without unpleasant characteristics for the user.

A bag 20, made up continuously, with top and bottom seaming by travelling in the direction of the arrow A has a strip of adhesive material 21 applied continuously to one face in the lay-flat condition, and covered by a strip of siliconised release paper 22. The adhesive is admixed with a known animal repellent chemical, but the strip 22 prevents the unpleasant smell of this from reaching the user as the bag is filled with kitchen waste. When the bag is full the release strip is pulled off. The bag is then pulled shut with a conventional draw-tape 23, for storage outside until collected. This removal of the strip permits animal repellent vapour to be given off in adequate concentration to last until the bag is collected.

In a variant, the release strip 22 may be much that the ruching of the bag when the draw-string is pulled is sufficient to force the strip off, at least to a sufficient extent.

Claims (22)

CLAIMS:

1. An adhesive assembly comprising at least two component parts, with two surfaces of matching surface contour or of conformable surface material adhered permanently, re-positionably or minimally by a continuous or discontinuous expanse of adhesive mixed with or positionally associated with a material capable of a desired ascertainable physicochemical or chemical change over a period of time and/or in response to change of surrounding circumstances.

2. An assembly as claimed in claim 1, wherein each component part is a single or composite leaf or area including cellulosic and/or synthetic polymer materials.

3. An assembly as claimed in claims 1 or 2 wherein the adhesive is permanent.

4. An assembly as claimed in claims 1 or 2 wherein the adhesive is intentionally peelable, to leave adhesive, including or associated with the material, on one or both separated surfaces.

5. An assembly as claimed in claims 1 or 2 wherein the component parts are adhesive coated peelable and repositionable leaf, using low-tack non-cured adhesives.

6. An assembly as claimed in claim 2 wherein one leaf is minimally or nominally adhered as a release layer.

7. An assembly as claimed in any one of the preceding claims wherein the adhesive is double-sided tape, i.e having a central substrate with two adhesive coated faces, both covered by a release layer.

8. An assembly as claimed in any one of the preceding claims wherein the material is odoriferous, either positively as an attractive scent or negatively as animal or insect repellent.

9. An assembly as claimed in any one of the preceding claims wherein the material is such as to undergo said change gradually.

10. An assembly as claimed in any one of the preceding claims wherein the material is such as to undergo said change rapidly.

11. An assembly as claimed in any one of the preceding claims wherein the material is susceptible to heat above a given spoilage temperature.

12. An assembly as claimed in any one of the preceding claims wherein the material is susceptible to at least one form of radiation.

13. An assembly as claimed in any one of the preceding claims wherein the material undergoes a chemical change on reaction with oxygen.

14. An assembly as claimed in any one of the preceding claims wherein the material undergoes a chemical change on reaction with water vapour.

15. An assembly as claimed in any one of the preceding claims wherein the material undergoes a chemical change on reaction with sulphur dioxide.

16. An assembly as claimed in any one of the preceding claims wherein the adhesive is mixed with an additive.

17. An assembly as claimed in claim 16 wherein the additive is adhered (in a form adhesive or non-adhesive) to the available free spaces between the adhered surfaces.

18. An assembly as claimed in claim 16 or 17 wherein the adhesive is mixed with the additive and adhered (in a form.adhesive or non-adhesive) to the available free spaces between the adhered surfaces.

19. A garbage bag of polymer sheet having an area (preferably a strip) of adhesive located on an outer surface thereof, the adhesive being mixed or associated positionally with an animal-repellent odoriferous additive and being covered by a release layer, impervious to the vapour of the additive, for removal as the filled bag is dumped for collection.

20. A label for a garbage bag in the form of a central layer covered on both faces with adhesive, in each case protected by an area of material: wherein the adhesive on one face at least is mixed with or positionally associated with an animal-repellent odoriferous additive.

21. A label, or portion of a closure, for a package, wherein two leaves are adhered by peel able adhesive mixed with or positionally associated with a material capable of progressive colour change on exposure to atmosphere for a period after the leaves are peeled apart, as a measure of elapse of time since the package was opened.

22. An assembly substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.