WO2008093333A2

WO2008093333A2 - Heat-shrinking removable label

Info

Publication number: WO2008093333A2
Application number: PCT/IL2008/000122
Authority: WO
Inventors: Ori Carmel; Ophir Ron
Original assignee: Nirotek Coated Paper Mfg. K. Nir-David Israel
Priority date: 2007-01-31
Filing date: 2008-01-28
Publication date: 2008-08-07
Also published as: IL181092A0; WO2008093333A3; IL181092A; RU2007128873A; RU2445714C2

Abstract

A self-removable label is disclosed comprising a face heat-shrink material, adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature. The measure of shrinkage is controlled by the chemical or orientational nature of the material. A method of manufacturing and attaching the abovementioned self-removable label is disclosed. The method comprises obtaining a face heat-shrink material adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature. The method further comprises steps of orienting the face-stock in a casting; (ii) producing a label-stock (iii) die cutting the label-; (iv) sticking the label to the substrate; (v) releasing the labeled item; (vi) collecting the labeled items; (vii) subjecting of the labeled item to a predetermined temperature, (viii) releasing the item to its intended reuse and (ix) collecting the delaminated label from the solution.

Description

Heat-Shrinking Removable Label

FIELD OF THE INVENTION

[001] The present invention generally relates to a label with heat-shrinking properties that renders it easily self-removable upon application of heat.

BACKGROUND OF THE INVENTION

[002] The invention relates to a label with heat-shrinking properties that renders it easily self-removable upon application of heat. Heat-shrinkable materials have been used in industry for a variety of purposes. In connection with the recycling of metal, glass or plastic containers, an easily removable label is advantageous insofar as it allows for easy separation of the label material and any ink printed upon it from the bulk of the container. In this way, high-purity bulk material may be reclaimed for recycling, refilling or other use. In connection with product repurposing, it may be found advantageous to have an easily removed label that allows for reuse of the same product under a changed label. Obviously it is desirable that the label does not detach under ordinary use, but when subjected to some particular condition such as a temperature of 70⁰C, it is easily removed. Thermoplastic polymers, particularly polyethylene terephthalate (PET) bottles, have taken a major share of the bottle market. In general such bottles may be fitted with various labels such as stretch labels made from polyolefins, heat- shrinkable labels made of polyesters, polystyrene, polyvinyl chloride, or other polymers, and tack labels made of polypropylene or other polymers. Such bottles are usually collected from customers without removal of the self adhesive labels and then brought to a recycling concern. There they are washed and the labels removed by crushing, wherein the crushed polymer material may still include labels in great quantity. Thus the subsequent conversion of PET bottles into recycled polymer material requires many subsequent steps of purification, such as secondary crushing, specific gravity separation of labels in liquid, dehydration and drying, specific gravity separation of labels by air blowing, and pelletization. Even after such steps, the final product may be deleteriously affected for example by discoloration caused by ink from a relatively small amount of label material entering the recycling stream. Thus in order to achieve the effective recycling of bottles, the incorporation of labels and label ink should be prevented, so as to increase the purity of recycled thermoplastic polymers. When it comes to glass bottles, reusing the bottles without recycling by means of removing the label in the washing process is highly beneficial. Large mineral water plastic bottles undergo tens of washing-refilling cycles in their life time, the label has to be manually replaced several times due to hauling and human handling. Many improvements have been made so far in the thermoplastic polymers used as label materials, and there have been labels made of polymers (e.g., polystyrene, polyolefins such as polyethylene and polypropylene) that can easily be separated by specific gravity and may have lower specific gravity than PET. The formation of ink layers cancels the advantage of low specific gravity, making it impossible to carry out complete separation.

[003] There have also been labels made of the same polyesters as used in PET bottles, which cause no problem even when incorporated into the PET bottles; however, no separation of ink layers can be made from the labels and the problem of how to prevent the coloring of recycled polymer pellets has not yet been solved.

[004] European patent application 0924678 A2 discloses a label with easily removable ink layers, bottles fitted with these labels, processes for removing ink layers from these labels, processes for removing ink layers from these labels on the bottles, and processes for recycling the ink-removed labels and bottles, as well as recycled polymer pellets. The label of the present invention has a thermoplastic polymer film and an ink layer formed on at least one surface thereof, and the ink layer is removable in alkaline hot water. Another label of the present invention has a thermoplastic polymer film and an ink layer, between which an intermediate layer removable in alkaline hot water is formed. The process for ink removal from the labels or bottles as described above according to the present invention involves immersing the labels or bottles in alkaline hot water to remove the ink layers from the labels. The removed ink may be dried, pulverized, and separated from the labels by air blowing. However in all these cases the label still adheres to the bottle, with provision being made for the easy removal of ink from said label. If the material of the bottle is different from that of the label, which is often the case, then the label must be separated from the bottle in order that profitable recycling may be performed.

[005] Hence, a system for easy self-removal of labels in their entirety from a given substrate, requiring only heat to perform and not reducing the adherence of the label before such heat is applied, is still a long felt need. BRIEF DESCRIPTION OF THE DRAWINGS

[006] In order to understand the invention and to see how it may be implemented in practice, a plurality of embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which Fig. 1 schematically presents a plot of percent shrinkage as a function of temperature.

SUMMARY OF THE INVENTION

[007] It is thus in the scope of the invention wherein a label comprising a heat-shrink material is disclosed. The label is adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature; said measure of shrinkage is controlled by the chemical or orientational nature of the material.

[008] The profile of the measure of shrinkage is possibly characterized by an asymptote in the shrinkage as it depends upon temperature, thus allowing for error and variation in the heating process yet providing a relatively exact amount of shrinkage despite these process variations. More specifically, a measure of shrinkage is e.g., about 60% upon application of about 70°C for a period of about 3 minutes is obtained.

[009] It is also in the scope of the invention wherein the heat-shrinking material is made of at least one thermoplastic polymer. More specifically, the polymer is possibly selected from a group consisting of polyolefins, polyesters, polystyrenes, polyvinyl chlorides, polypropylenes or mixtures thereof. The label is possibly adapted to be attached to a glass, metal or polymeric substrate, especially a bottle or a container.

[0010] It is also in the scope of the invention, wherein a method of manufacturing and attaching a label is provided. The label preferably comprises a heat-shrink material, adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature, said measure of shrinkage is controlled by the chemical or orientational nature of the material. The aforesaid method comprises steps of producing said label in a coating and laminating, casting, calendaring, providing a continuous-web, and attaching said label to its intended substrate by a suitable means, such as use of an adhesive interlayer, stretching the label onto the substrate, or other means.

[0011] It is still in the scope of the invention, wherein the method as defined in any of the above additionally comprises step or steps of applying of heat to the label and substrate or to the label alone, causing delamination of said label from its substrate thus facilitating easy removal thereof, said applying of heat consisting of subjecting of the substrate and label or label alone to a certain predetermined temperature for a certain predetermined amount of time, and subsequent separating of the now-delaminated label from the substrate.

[0012] It is further in the scope of the invention wherein the step of applying of heat as defied above is achieved by operations selected from a group consisting of (/) immersing in hot liquid, (H) exposing to heated gas such as air or argon, (Ui) exposing to radiant energy such as ultraviolet, infrared, or x-ray radiation, (iv) placing the label in contact with a heated body or any combination thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0013] The following description is provided, alongside all chapters of the present invention, so as to enable any person skilled in the art to make use of said invention and sets forth the best modes contemplated by the inventor of carrying out this invention. Various modifications, however, will remain apparent to those skilled in the art, since the generic principles of the present invention have been defined specifically to provide an easily-removed heat-shrinking label.

[0014] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. However, those skilled in the art will understand that such embodiments may be practiced without these specific details. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment or invention. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Lastly, the terms "comprising", "including", "having", and the like, as used in the present application, are intended to be synonymous.

[0015] The invention provides a method for easily removing labels from the substrate to which they are attached, without reducing the adhesion of the label to the substrate prior to the removal step. Removal is accomplished easily and cost-effectively by raising the label and substrate together to a predetermined temperature, at which point the label undergoes a predetermined amount of shrinkage, causing delamination of the label from the substrate.

[0016] In broad terms, the apparatus is comprised of the following elements: a label composed of heat-shrink face material, which undergoes a predetermined measure of shrinkage at a given temperature. This amount may be substantially varied by changing the chemical composition of the label, allowing the manufacturer to tailor the shrinkage profile of the label as desired.

[0017] In broad terms, the method comprises: (/) producing and orienting the face-stock in a casting or otherwise calendaring; (if) producing a label-stock especially by coating an adhesive interlayer between the face-stock and a release liner; printing the label-stock and lacquering or overlaminating; (Uf) die cutting the label-stock to its desired label shape; (iv) sticking the label to the desired substrate; (v) releasing the labeled item to its intended end-use; (vf) collecting of the labeled items; (yii) subjecting of the labeled item to a certain predetermined temperature, especially by means of hot water with alkali solution for a certain predetermined amount of time; (viif) releasing the no longer substrate item to its intended reuse and (ix) collecting the now-delaminated label from the solution.

[0018] It is within the core of the present invention that the label be composed of thermoplastic polymers. The thermoplastic polymers are selected in a non-limiting manner from PET, polyolefϊns, polyesters, polystyrene, polyvinyl chloride, polypropylene, or other polymers and any mixture thereof. Furthermore it is within the core of the present invention that the label composition has a well-defined and consistently reproducible shrinkage profile such as that presented in Fig. 1, allowing for instance for a shrinkage of 60% upon application of 70°C for a period of about 3 minutes. It is also within the scope of the present invention that the shrinkage profile be tailored such that an asymptote is reached at a certain temperature such as occurs in Fig. 1, thus preventing further shrinkage upon application of higher temperature, allowing for variations in the heat applied and yet still producing the same amount of shrinkage.

[0019] According to a preferred embodiment of the present invention, a label is provided that is composed of heat-shrink material, which undergoes a known amount of shrinkage at a given temperature, which amount may be substantially controlled by changing the chemical composition of the label thus allowing the manufacturer to tailor in some degree the shrinkage profile of the label as desired. [0020] According to another specific embodiment of the present invention, tailoring of the heat-shrink material is provided by switching a portion of the stretched alkali chains to randomly organized structures.

[0021] The term 'thermoplastic polymers' generally relates Acrylonitrile butadiene styrene (ABS); Acrylic; Celluloid; Cellulose acetate; Ethylene- Vinyl Acetate (EVA); Ethylene vinyl alcohol (EVAL); Fluoroplastics (PTFEs, including FEP, PFA, CTFE, ECTFE, ETFE); Ionomers; Kydex, a trademarked acrylic/PVC alloy; Liquid Crystal Polymer (LCP); Polyacetal (POM or Acetal); Polyacrylates (Acrylic); Polyacrylonitrile (PAN or Acrylonitrile); Polyamide (PA or Nylon); Polyamide-imide (PAI); Polyaryletherketone (PAEK or Ketone); Polybutadiene (PBD); Polybutylene (PB); Polybutylene terephthalate (PBT); Polyethylene terephthalate (PET); Polycyclohexylene dimethylene terephthalate (PCT); Polycarbonate (PC); Polyhydroxyalkanoates (PHAs); Polyketone (PK); Polyester; Polyethylene (PE); Polyetheretherketone (PEEK); Polyetherimide (PEI); Polyethersulfone (PES); Polyethylenechlorinates (PEC); Polyimide (PI); Polylactic acid (PLA); Polymethylpentene (PMP); Polyphenylene oxide (PPO); Polyphenylene sulfide (PPS); Polyphthalamide (PPA); Polypropylene (PP); Polystyrene (PS); Polysulfone (PSU); Polyvinyl chloride (PVC); Spectralon; its derivatives or any combination thereof. More specifically and in a non-limiting manner the term 'polyester' relates inter alia to a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain. The term 'PET' relates inter alia to homopolymers- and copolymers- polyesters, e.g., PETG by Eastman Chemical and SK Chemicals; modified PET etc. The term 'polyolefϊn' generally relates to any polymer produced from a simple olefin, e.g., polyethylene, polypropylene, or alkene as a monomer; such as a poly-alpha-olefin. The term 'polystyrene' generally relates to a polymer made from any monomer styrene, homopolymers, copolymers or derivatives thereof. The term polyvinyl chloride generally relates any polychloroethene.

[0022] In another preferred embodiment, the label is removed by application of heat to the label and substrate or to the label alone, causing delamination of the label from its substrate thus facilitating easy removal thereof. The label may be produced by any number of means such as will be obvious to those skilled in the art, including producing the label in a casting, calendaring, or other process. The label may be attached to its intended substrate by any number of suitable means such as use of an adhesive interlayer, stretching the label onto the substrate, or other means as will also be obvious to those skilled in the art. Removal of the label requires only the application of heat, specifically subjecting of the substrate and label to a certain predetermined temperature for a certain predetermined amount of time.

[0023] In another embodiment of the present invention, the label may be composed of thermoplastic polymers such as PET, polyolefins, polyesters, polystyterene, polyvinyl chloride, polypropylene, or other polymers. In the preferred embodiment, the label composition has a well-defined and consistently reproducible shrinkage profile such as that presented in Fig. 1, allowing for instance for a shrinkage of 60% upon application of 70°C for a period of 3 minutes. It is preferable that the shrinkage profile be tailored such that an asymptote is reached at a certain temperature such as occurs in Fig. 1, thus preventing further shrinkage upon application of higher temperature, and thereby allowing for variations in the heat applied and yet still producing the same amount of shrinkage in the label.

[0024] In the aforementioned embodiments we note that the label may be printed upon with indelible or otherwise hard-to-remove ink, but that this does not deleteriously impact the removal of the label or the quality of the separated substrate, since the label is removed from the substrate in nearly every case. Thus the amount of remaining label material in a recycling stream after the steps of heating and label separation is negligibly small, allowing for high- purity recycling without further separation steps.

Claims

1. A self-removable label comprising a face heat-shrink material, adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature, said measure of shrinkage is controlled by the chemical or orientational nature of the material.

2. The label of claim 1 , wherein the profile of said measure of shrinkage is characterized by an asymptote in the shrinkage as it depends upon temperature, thus allowing for error and variation in the heating process yet providing a relatively exact amount of shrinkage despite these process variations.

3. The label of claim 1, wherein a measure of shrinkage is about 60% upon application of about 70⁰C for a period of about 3 minutes.

4. The label of claim 1, wherein said heat-shrinking material is made of at least one thermoplastic polymer.

5. The label of claim 4, wherein the thermoplastic polymer is selected from a group consisting of polyolefins, polyesters, polystyterenes, polyvinyl chlorides, polypropylenes or mixtures thereof.

6. The label as defined in claim 1 or in any of its dependent claims, wherein said label is adapted to attach a glass, metal or polymeric substrate, especially a bottle or a container.

7. A method of manufacturing and attaching a self-removable label comprising a face heat- shrink material adapted to undergo a consistent and reproducible measure of shrinkage at a given temperature; said method comprising steps (z) producing and orienting the face- stock in a casting or otherwise calendaring; (if) producing a label-stock especially by coating an adhesive interlayer between the face-stock and a release liner; printing the label- stock and lacquering or overlaminating; (Hi) die cutting the label-stock to its desired label shape; (zv) sticking the label to the desired substrate; (v) releasing the labeled item to its intended end-use; (vi) collecting of the labeled items; (vif) subjecting of the labeled item to a certain predetermined temperature, especially by means of hot water with alkali solution for a certain predetermined amount of time; (viif) releasing the no longer substrate item to its intended reuse and (zx) collecting the now-delaminated label from the solution.

8. The method according to claim 7, comprising applying of heat to said label and substrate or to the label alone, causing delamination of said label from its substrate thus facilitating easy removal thereof, said applying of heat consisting of subjecting of the substrate and label or label alone to a certain predetermined temperature for a certain predetermined amount of time, and subsequent separating of the now-delaminated label from the substrate.

9. The method according to claim 8, wherein said applying of heat is achieved by operations selected from a group consisting of (/) immersing in hot liquid, (//) exposing to heated gas such as air or argon, (Ui) exposing to radiant energy such as ultraviolet, infrared, or x-ray radiation, (zv) placing the label in contact with a heated body or any combination thereof.