CA2099272C

CA2099272C - Marking element

Info

Publication number: CA2099272C
Application number: CA002099272A
Authority: CA
Inventors: Terence Colley; Stephen Minter; John Carnie
Original assignee: Food Guardian Ltd
Current assignee: Food Guardian Ltd
Priority date: 1990-10-26
Filing date: 1991-10-28
Publication date: 2002-09-17
Anticipated expiration: 2011-10-28
Also published as: GB9310864D0; AU8750891A; AU660154B2; WO1992008113A1; CA2099272A1; JP3056786B2; GB9023393D0; JPH06504117A; ZA918573B; GB2266954B; GB2266954A

Abstract

A marking element for indicating whether a pre-defined temperature condition has been maintained. The marking element (1) comprises a first material (8) capable of flowing above a pre-determined temperature separated from a second absorbent ma-terial (b) by a barrier layer (7). The first and second materials are such that when the barrier layer (7) is punctured and the prede-termined temperature is exceeded the first material (8) flows along the second material (6) to produce a detectable change.

Description

25 JUN '93 14:33 MRRKS & CLERK htiC 061 834 1142 P.6i30 WO 92/08113 ~ ~ ~ (~ ~ ~ ~ FCT/Gg91%~I879 ' ' MARKING ~~LEMENT
w The present invention relates to a yanking element for use ,in conjunction.with a product which is reguixed' to be maintained under a particular temperature or temperature-time condition. ' There are many products which need to be stored under conditions such that a particular temperature limit~.is not exceeded,. or at least is not exceeded for longer' than a predetermined time. For convenience, ' both~v of these conditions are referred to generically herein as the pre-defined temperature condition. Generally the temperature limit will be a maximum .(rather than a minimum) tempe.~ature~. ~ . . ' . . '.
.Particular examples are certain types of food product that.~have been pre-cooked or processed by 'freezing, irradiation, partial cooking, freeze drying or steaming (or other food processing procedures). If such products are not-stored in accordance with the pre-defroad temperature conditions than there is ,the danger of contamination by organisms which are injurious to human health. This danger is not removed by subsequently storing the' product below the temperature maximum. Further examples of products which may need to be stored in accordance w~.th pre-defined temperature conditions are certain pharmaceuticals which would otherwise deteriorate.
Currently, the purchasers of such susceptible products are not able to determine whether the product has been stored in contravention of the pre-defined conditions. For example, frozen food purchased in, say,.a supermarket may be adequately frozen ~t the time of sale but the purchaser is unable to tell whether the food has previously been inCOrrectly stored. This has the potential health disadvantages mentioned above.
According to a first aspect o~ the present invention there is provided a marking element for indicating whether ;a pre-defined temperature condition has been maintained, 25 JUN '93 14:34 MARKS & CLERK MiC 061 834 1142 P.'7i30 WO 9~10$Il3 ~ ~ ~ ~ ~ 7 N PCT/G B9y/01$79 comprising a first material.capable of flowing above a predetermined temperature separated from a second absorbent material by a barrier layer (preferably impervious), the . f first and second materials being' such that when. the .barrier layer is punctured and the predeterminedvtemperature is exceeded the first material flow's::along the second.material ~to produce a detectable change. . ~ ~. ' Preferably" the marking element i.sw constructed such that .the first flowable material is provided::,:adjacent one end of an elongate channel and ( at that Enc. of .t~ie~ channel ) is separated by said barrier layer from the absorbent material which extends along the channel. Thus when the baxrier layer has been punctured and the predetermined temperature has been exceeded the first mater~ial.flows along the .channel producing said .detectable change. The ' extent to which the first material f lows, alo~~g the: channel ( and this extent of~ the detectable change a~lon~g ~ the channel) is an indication of the total time; at which the marking element .has been apove Cne preae~ermmeu temperature. , . .
', A particularly suitable~way of producing~the~~marking element as described in the previous paragraph is to.print a layer of an ink on to a carrier sheet such that the channel is formed in the ink. The absorbent material may be laid in positzon along the channel and then.overxaid by a film providing the barrier layer. The first material may then be provided in the region of the barrier layer above the absorbent material and the whole then overlaid by a further f film having a melting point higher than that of the barrier layer. In this way it~is possible to use a~ probe heater to a temperature above~,the melting point of the barrier layer but belaw that of the outer film ~.ayer whereby the barrier layer is selectively .punctured to "activate" the label..
Ideally the elongate channel is formed at one end with an enlarged"reservoir" region in which the first material is received.

25 JUN '93 14:34 MARKS & CLERK MiC 061 834 1142 - P.8i30 3 ~ . : ~ PGT/GB91%01879 2~~9~'~2 Preferably the detectable: change is a vcolaur change so' that any flow of the first material: as. a~. result of the ,predetermined temperature being exceeded::.i.s immediately visible. . ~ - ... .
The first material may ~comprise:a polymeric material which reversibly fuses above a desired t.emperature~, e.g., a thermo-reversible wax. It will of course~be appreciated that the material to be used will.be selected having:: regard to the desired temperature of fusion, and that for.any one . type of polymeric material it is~possible to~haye a range of fusion temperatures depending on the mole~cular~wW3ght of the material : Inorganic salts. ( a .'g = sodium or potassium chloride) can also be incorporated in .the polymeric material for providing variationwin temperature .of fusion.
The absorbent material, may fox example .be .paper or a part~.culate material (e. g. kieselguhr)~
The detectable change rnay be produced in a number of ways. For example, the first material may include a dye which (during f ldw of the first material) causes the .absorbent material to become dyed: and therefore coloured.
.Alternatively, the detectable change may be a colour change resulting from an irreversible chemical reaction. Thus the first and second materials ma,y incorporate ~x'espective chemical reagents which wheat in contact react together to produce a colour change.
According to a second aspect of the present invention there is provided a marking element f or indicating whether a pre-defined temperature condition has been maintained, the marking element comprising an elongate indicator track along which a detectable change (preferably a colour change) occurs when the marking element is above a pre-determined temperature, the length of the change being representative of the time fox which the marking element is above said. pre-determined temperature.
Preferably the marking element comprises a_ carrier layer on one face of which is laid a coating in which the indicator track is provided. To this end, the indicatoz 25 JUN '93 14:35 MARKS & CLERK MiC 061 834 1142 P.9i30 WO 92/08113 ~ ~y ~ ~ ~ ~ PCf/GB91/0'1879 track may include an'.absorbent mater~ialv:along which a colour is developed, as.described f or~the fiesta aspect of the invention. The reverse side of theca=Tier layer.may be adhesively coated for _fixing.~ the marking element to a product for which the temperature storefe.'cbnditions. are to be , monitored : ~ .. . . . .,. , .. ~ . .
The invention will be further describedvby~ way of example only with reference to' the accompanyi~rig 'drawings, in which : ~. ~ ~ . - ' Fig. 1 is an exploded perspective~,view of one embodiment of label in accordance with 'the invention; and ", . ~ ~ Fig. 2 shows the label after ' storage above the permitted temperature.
The construction of the~~habel 1 will bewdescribed by 'reference to ,its method of production.
' A carrier sheet 2°(which'~is adhesively coated on its reverse face) is printed 'with' an ink layer.3 (e.g. a - polymer ~ based ink ) which is ~ such that r ~'a layer 3 of predetermined thickness is'haid down. Layer 3 is shown as ?~eirig generally rectangular but doe's- '.include ~~a circular aperture 9 adjacent to one, end of a ~ longitudinally extending rectangular channel 5. A plurality of rectangular ink layers 3 may be printed on to the carrier sheet 2. The layer 3 may, f or example be white.
An absorbent paper wick b is then laid completely along the length of channel 5, the wick 6 being of sufficient length so as to extend over into the aperture 9 . where the~wick terminates (fee inset to drawing)'. Instead of a paper wick it is possible to use a powder wick, e.g.
of kieselguhr. Furthermore, ~a~lthough Fig. 1 shows the channel 5 opening ~.nto aperture 4, it is possible for there to be a barrier of the ink 3 between the end of channel 5 and the aperture 9. In such a case, the wick 6 may simply extend over the barrier.
In the°.next stage of manufacture, a clear layer 7 of a heat shrink film is laminated~on to the ink layer 3. for convenience,~the drawing shows layer 7 as being coterminous 25 JUN '93 14:36 MAR1<S & CLERK MiC 061 834 1142 P,10i30 WO 9?J08113 PGT/GB91I01879 ..
2~~~9?'~2 with layer 3 but in p~racti~ce a" singJ:e layer ? may be provided to overlie all of ~ the layers ~3 ~. v An amount .of a temperature 'condition indicator material 8 is then introduced°irito'~aperfure~~4vand "sits" on the layer 7 above the.wick~6.. This matexial is one wh~.ch is of a viscosity such that the::material does not flow (at least to any substantial. extent) below a 'predetermined temperature,.,but will be capable of flowih'y along the wick 6 above this temperature: Th'e predetermined aemperature is the temperature above which a prod~uc~t (with : which the finished label will be associated). should.not'~'be stored, or at least not stored above the temperature.f~or more than a predetermined time.
The material 8 will generally be coloured, a.g. by the incorporation of a dye therein. A red dye~is particularly ' suitable tar:use in conjunction with a~~white layer 3.
In the final stage of~~manufaeture, a ~ further clear layer 9 is applied. This'layer'.9.may of course be a single layer overlying all.of the layers 3.
Layer 9 is of a material which melts (or softens) only at a higher temperature thap does layer ?. This latter layer may for example be one which melts or softens at 100 to 120°C. furthermore, layer 9 may be printed with indicia, such as the scale 10 and' other information e.g. company name (not shown).
In use, the label is attached to the packaging of a product whose storage temperature is to be monitored. The label. is then activated by the application of a point source of heat. This can be achieved by using a flat pointed probe of 2-2.5 mm in diameter heated to at least 100°C but no higher then 120°C ~(a hand held soldering iron will suffice if it can be controlled to the desired temperature). The flat pointed probe is applied within the circular area of the label and should be held in position fox 0.5-1 mseaonds. As a 'result, layer ? is punctured so that material 8 is able to come into contact with the wiek 6.

25 JUN '93 14:36 MARKS & CLERK MiC 061 834 1142 P.ili30 WO 92J08113 2 ~ (~ ~ ~ ~ ~ ~ 1'GT/GB9'1 /01879 . Once activat.ed~,; the. label must be maintained: below the specified storage.~temperature for the '. product.
If the temperature at which~the~.product is stored . .
rises above the predeterminedwtemperature then the~material 8 will become less ,viscous ~ aid taiLl be~ capable of f lowing along the wick, 6 : .The- niateriah. .:8 will . continue to f low along the wick for ~so, long as they predetermined temperature is exceeded. This. will result in tfie. wick becoming indelibly coloured ~ over a part of its lerrgth~ extending f rvm ~.ts end adjacent aperture 4 (see. Fig. 2) .; zt wihl be appreciated that in the event of the product being stored above the permitted temperature and. then returned to below the permitted temperature, the material 8 increases in viscosity to prevent movement along the wick 6 although the indelible colouring of.the~,wick 6 is maintained. If the product should then once again bew,st~ored above the permitted, temperature, ;the viscosity.. ofmaterial 8 will decrease and the material.Carr advance further along the Wick. ' , ; , . , .
A measure ,of the length .of, time for which the temperature has been exceeded maybe obtained by reference to the scale 10, the graduations of which may be representative of the number of minutes,exposure above the predetermined time. ~It is obviously an~easy matter to inspect the scale visually to obtain .a representation of the total time that the product has been stored above the predetermined temperature. If this time is excessive then the product may be discarded.
It should be appreciated that the labels 1 may be used in a number of ways. ~'or example, the label may be attached to the packaging of individual products so that a purchaser of the product (e.g. in a supermarket) can determine the time for w~:ich the product has been stored above the permitted tempera3ture_ Alternatively, a label mar be attached to a carton in which the products are delivered to (say) -a supermarket. In this case, the sapez~ta~'ket persr~nnel are able to de;.ide whether the 25 JUN '93 14:37 MARKS & CLERK MiC 061 834 1142 P.12i30 Wn 9/08113 ~ ~ ~ ~ 2 ~ ~ ' PCT/GB9i701879 product has been stored above .the permitted temperature for too long . , _ .
The marking element according.to the invention may also take a number af'forms other than t hat illustrated in the accompanying drawings. ~~
For example, the marking element may comprise a backing paper, a .paper. ,strip f arming a Wick which is positioned on the.backing~paper, a heat sensitive laminate applied aver the, backing paper and. paper strip:, 'a paper pad positioned over one end of the paper strip and containing the indicator material, and a final laminate to seal the system.
Furthermore,. it is not essential that the marking element be used as.an: indicator of the time for which the product has been. stored, above a. particular temperature.
The marking element may be used, f or example, merely to indicate that.a particular storage temperature hay been exceeded. For example:, the marking element may comprise a circular paper pad j E.ixed to a~ support ) overlaid by a heat-sensitive polyrner.,layer between which an upper laminate layer is sandwiched to the indicator material. To use the marking elementr the ,heat sensitive polymez~ layer is punctured as described above. If the marking element is subjected to a temperature above that at which the indicator material will. flow, then this material flows into the paper pad and. provides an indiction that a predetermined temperature has been exceeded.

Claims

8

1. A marking element for indicating whether a pre-defined temperature condition has been maintained, comprising a first material capable of flowing above a predetermined temperature separated from a second absorbent material by a barrier layer, and an outer film layer having a melting point higher than the melting point of the barrier layer, the first and second materials being such that when the barrier layer is punctured and the predetermined temperature is exceeded the first material flows in the second material to produce a detectable change.

2. A marking element as claimed in claim 1, wherein the barrier layer is impervious.

3. A marking element as claimed in claim 1 or claim 2, wherein the first flowable material is provided adjacent one end of an elongate channel and at the said end of the elongate channel is separated by said barrier layer from the absorbent material which extends along the channel.

4. A marking element as claimed in claim 3, wherein the elongate channel is formed at one end with an enlarged region to provide a reservoir in which the first material is received.

5. A marking element as claimed in any preceding claim, wherein the detectable change is a colour change.

6. A marking element as claimed in any preceding claim, wherein the first material comprises a polymeric material which reversibly fuses above 3 desired temperature.

7. A marking element as claimed in claim 6, wherein the polymeric material is a thermo-reversible wax.

8. A marking element as claimed in claim 7, wherein the polymeric material incorporates an inorganic salt to provide a modification of its temperature of fusion.

9. A marking element as claimed in any preceding claim, wherein the absorbent material is paper.

10. A marking element as claimed in any one of claims 1 to 8, wherein the absorbent material is a particulate material.

11. A marking element as claimed in any preceding claim wherein the first material includes a dye which during flow of the first material produces the detectable change in the absorbent material.

12. A marking element as claimed in any one of claims 1 to 10, wherein the detectable change is a colour change resulting from an irreversible chemical reaction.

13. A method of producing of a marking element as claimed in claim 3 comprising printing a layer of ink on to a carrier sheet such that the channel is formed in the ink providing the absorbent material along the channel, and then overlying the absorbent material with a film providing the barrier layer.

14. A method as claimed in claim 13, wherein the first material is provided in the region of the barrier layer above the absorbent material and the whole is then overlaid by a further film having a melting point higher than that of the barrier layer.