WO2022141430A1

WO2022141430A1 - Low voc and food grade resealable label

Info

Publication number: WO2022141430A1
Application number: PCT/CN2020/142230
Authority: WO
Inventors: Jianfeng Wu; Haiqiu Song; Chong Sen OOI
Original assignee: Upm Raflatac Oy
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2022-07-07
Also published as: CN116867863A

Abstract

An open-closure sealing label (311, 411, 511, 611) have a low content of volatile organic compounds. The open-closure sealing label (311, 411, 511, 611) comprises a face (101) and an adhesive layer (102) adjoined to the face. The face (101) comprises filmic material and the adhesive layer (102) comprises a removable pressure sensitive adhesive. The removable pressure sensitive adhesive comprises an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures. The filmic material and the removable pressure sensitive adhesive are food grade materials. A label laminate web (100) for providing the open-closure sealing label (311, 411, 511, 611) is disclosed. Also, a method for producing the label laminate web (100) is provided. Further, the specification relates to a package (310) comprising the open-closure sealing label (311, 411, 511, 611) having a low content of volatile organic compounds.

Description

Low VOC and food grade resealable label

Technical field

This specification relates to an open-closure sealing label having a low content of volatile organic compounds, as well as to a label laminate web for providing the same. Also, a method for producing the label laminate web is provided. Further, the specification relates to a package comprising the open-closure sealing label disclosed.

Background

It is often of importance to store consumables, such as food, candy or cigarettes, in an open-closure type package which allows the consumables to stay fresh but which can also be easily opened and closed per need. If cigarettes, for example, go dry, they will lose their taste and may burn too quickly, which makes cigarettes very unpleasant to smoke. Exposure to air, for one, may cause candies to lose moisture and harden, and also cause them to lose their flavour and other enjoyable properties. It is preferable to provide the consumable package of this kind with an open-closure sealing that helps to maintain the optimal conditions for the consumables despite of the fact that the package in use will be opened and closed for several times. Plastic labels, in contrast to paper labels, are preferred, for example due to their more appealing appearance (for example matte finishing with metallic colours) , better impermeability and better mechanical properties.

For edible consumables and also for cigarettes, it is important that the open-closure sealing label itself does not emit any significant amount of odour or smell affecting the taste or flavour of the consumable. It would also be preferable for the materials of the package to be food certified. Thus, also the materials of the open-closure sealing label and the package comprising the open-closure sealing label should be food certified.

Traditional approaches for producing resealable labels have shown to promote good user experience on resealable packaging as a whole. However, said approaches may still suffer from a nuisance of strong smell caused by the precursor components and potential risk on volatile organic compounds (VOC) content. Further, approaches using for example solvent based adhesives often are implemented in environmentally unfriendly manner involving solvent as the dispersion medium.

Thus, it is desired to produce resealable labels which have low VOC content and are food certified, and that at the same time possess excellent open-closure properties. A further desire is to develop environmentally friendlier methods for producing the labels. For edible or tobacco products where the flavour of the product itself is very important for the consumer, the low VOC content becomes a significant feature required from the open-closure sealing label.

Summary

This specification aims to provide an open-closure sealing label which has low VOC content, suitable for use at food applications, and at the same time possesses excellent open-closure properties even after repeatable open-closure actions.

According to an embodiment, an open-closure sealing label comprising a face and an adhesive layer adjoined to the face is provided. The face comprises filmic material and the adhesive layer comprises a removable pressure sensitive adhesive. The removable pressure sensitive adhesive comprises an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures. The filmic material and the removable pressure sensitive adhesive are food grade materials.

According to an embodiment, a package comprising an open-closure sealing label is provided. The open-closure sealing label comprises a face and an adhesive layer adjoined to the face. The face comprises filmic material and the adhesive layer comprises a removable pressure sensitive adhesive. The removable pressure sensitive adhesive comprises an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures. The filmic material and the removable pressure sensitive adhesive are food grade materials.

According to an embodiment, a label laminate web for providing an open-closure sealing label is provided. The label laminate web comprises a face stock, an adhesive layer and a release liner. The face stock is adjoined to the release liner via the adhesive layer. The face stock comprises filmic material and the adhesive layer comprises a removable pressure sensitive adhesive. The removable pressure sensitive adhesive comprises an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures. The release liner comprises a release agent arranged to build a releasable contact with the adhesive layer. The filmic material and the removable pressure sensitive adhesive are food grade materials.

According to an embodiment, a method for manufacturing a label laminate web is provided. The method comprises arranging a substrate with a release agent as a release liner, arranging a food grade filmic material as a face stock, coating the release liner with a removable pressure sensitive adhesive of food grade comprising an aqueous acrylate polymer dispersion so as to form a resealable adhesive layer, laminating the release liner together with the face stock comprising in such a way that the adhesive layer is arranged in between the face stock and the release liner so as to form the label laminate web, subsequently delaminating the label laminate, exposing the delaminated label laminate web to heat and ventilation in a de-odorization process, and re-laminating the release liner together with the face stock in such a way that the adhesive layer is arranged in between the face stock and the release liner.

Brief description of the drawings

Fig. 1a illustrates, by way of an example, a side view in the S _x, S _z-plane of a label laminate web 100 according to an embodiment,

Fig. 1b illustrates, by way of an example, a side view in the S _x, S _z-plane of a label laminate web 100 according to another embodiment,

Fig. 2 illustrates, by way of example, a process chart of a method for providing a label laminate web according to an embodiment,

Fig. 3a illustrates, by way of an example, a package comprising an open-closure sealing label according to an embodiment, and

Fig. 3b illustrates, by way of an example, a package comprising an open-closure sealing label according to another embodiment

Fig. 4 illustrates, by way of an example, packages comprising an open-closure sealing label disclosed herein,

Fig. 5 illustrates, by way of an example, packages comprising an open-closure sealing label disclosed herein, and

Fig. 6 illustrates, by way of an example, packages comprising an open-closure sealing label disclosed herein.

The figures are schematic. The figures are not in any particular scale.

Detailed description

The solution is described in the following in more detail with reference to some embodiments, which shall not be regarded as limiting.

In this description and claims, the percentage values relating to an amount of a material are percentages by weight (wt. %) unless otherwise indicated. Term “comprising” may be used as an open term, but it also comprises the closed term “consisting of” . Unit of thickness expressed as microns corresponds to μm. Unit of temperature expressed as degrees C corresponds to ℃. The following reference numbers and denotations are used in this application:

S _x, S _y, S _z 3D coordinates

PSA pressure sensitive adhesive

MD machine direction

CD cross (machine) direction

100 label laminate web

101 face stock

102 adhesive layer

103 release liner

310 package

311, 411, 511, 611 open-closure sealing label

A label is a piece of material to be applied onto articles of different shapes and materials. An article may be a package. A label comprises at least a face material also referred to as a face stock or a face. A typical way to adhere the label onto an article is by use of adhesive. The label comprising an adhesive layer is referred to as an adhesive label. The adhesive may comprise pressure sensitive adhesive (PSA) . A label comprising pressure sensitive adhesive may be referred to as a pressure sensitive adhesive label. Pressure sensitive adhesive labels may also be referred to as self-adhesive labels.

The labels comprising PSA can be adhered to most surfaces through an adhesive layer without the use of a secondary agent, such as a solvent, or heat to strengthen the bond. In that case the adhesive is pressure sensitive as such. Alternatively, the adhesive may be activatable in order to be pressure sensitive. The PSA forms a bond when pressure is applied onto the label at ambient temperature (e.g. between 15 and 35℃) or for cold applications even under freezing temperatures below 0℃, adhering the label to the item to be labelled. Examples of pressure sensitive adhesives include water-based (water-borne) PSAs, solvent based PSAs and hot-melt PSAs. A label may further comprise other adhesive (s) .

Term “face” refers to a top substrate of the label, also called as a face stock, a face material or in case of plastic, i.e. filmic material a face film. The face may have a monolayer structure or a multilayer structure comprising at least two layers. In case of a plastic material the multilayer filmic structure may be co-extruded or it may comprise several layers laminated together. The face is the layer that is adhered to the surface of an article during labelling through an adhesive layer. The face comprises an adhesive side and a print side. A combination comprising a face and adhesive may be referred to as an adhesive label. The face may comprise e.g. print in order to provide information and/or visual effect. Printable face is suitable for printing by any known printing methods, such as with gravure, flexographic process, offset, screen or letter-press. The print may exist on a top surface, reverse side or both top and reverse side of the face. Further, the label may contain additional layers, for example top coatings or overlaminates to protect the top surface and/or print of the label against rubbing or other external stress. Coating or additional layers, such as a primer, may enable enhancing compatibility of adjacent layers or parts of the label, for example adhesion between the layers. A label comprising a face, a print layer and an adhesive may be referred to as a printed label.

Term “release liner” refers to a structure comprising a substrate and a release layer on a surface of the substrate contacting the adhesive in a label laminate. The substrate may also be called a backing material. The release liner may comprise a release agent. The release agent is a chemical having low surface tension. The release agent may be used in order to prevent other materials from bonding to it and to provide a release effect. Release liners of the label laminates may serve one or more useful functions: they may be used as a carrier sheet onto which the adhesive is coated; they may protect the adhesive layer during storage and transportation; they may provide a support for labels during die-cutting and printing, and ultimately they may provide the release substrate carrying the labels for dispensing onto the items to be labelled.

Term “label laminate” , also referred to as an adhesive label laminate refers to a product comprising a face, adhesive and a release liner. In the label laminate the face is laminated together with the release liner having the adhesive in between. The label laminate may be a continuous structure from which the individual labels may be die-cut. The release liner of the label laminate is typically removed prior to labelling i.e. attaching the label onto the surface of an item to be labelled.

Individual labels may be cut from the label laminate structure. After cutting, the labels may remain to be attached to a common release liner (the release liner remains uncut) . Thus, a plurality of labels may remain to be attached to a common continuous release liner. This may be called a converted label web. Alternatively, the labels may be completely separate (i.e. also the release liner may be cut) . A label, including a face and adhesive, may be separated from the release liner e.g. by pulling the release liner in the direction -Sz with respect to the label. Thus, a surface of the adhesive layer is exposed so that said surface can be attached to an article.

Term “web” refers to a continuous sheet of material. The web is generally processed by moving over rollers. Between processing stages, webs may be stored and transported as rolls.

Term “machine direction” refers to manufacturing direction of a web. Machine direction may also refer to a circumferential direction of a roll. Term “cross machine direction” or “cross direction” refers to a direction that is transversal to the machine direction.

Term “laminate web” refers to a structure comprising two or more continuous sheets of material attached together into a web format. Typically, the laminate web comprises a face material attached (laminated) onto a release liner via a pressure sensitive adhesive.

Labels may be used in wide variety of labelling applications and end-use areas, such as labelling of food, home and personal care products, industrial products, pharmaceutical and health care products, beverage and wine bottles, other consumables etc. Labels enable providing information, like product specification, on the labelled product (s) . Information, e.g. print of a label, may comprise human-readable information, like image (s) , logo (s) , text, and/or machine-readable information, like bar code (s) , QR (Quick Response) code (s) . The surface of the labelled article may be for example plastics, glass, metal, or paper based. The labelled article may be for example a container, such as a bottle, jar, canister, can, tin or the like. The label may also be applied to semi-rigid or flexible packages used for e.g. packaging of food.

For reasons mentioned earlier in this application, certain consumables benefit from being packaged in a manner wherein an open-closure sealing label is hermetically or semi-hermetically capable of sealing the packages and protecting the products from the environment or from losing their moisture or other properties. In the applications, it may also be typical that the consumer will touch the label face film and/or unintentionally also the adhesive surface upon operating the sealing label. This may cause fingers to catch some of the odour and interfere with the consumer experience.

Packaging of cigarettes represents one such example. An open-closure sealing label may be used for sealing an inner sleeve of a cigarette box. Cigarette box refers to a container or a package for storing cigarettes. Cigarettes may refer to conventional tobacco products and to so-called smoke-free products. The materials of the inner sleeve of the cigarette box may comprise for example an uncoated film or acrylic coated film.

An outmost envelope of the cigarette box comprises a lid that is opened when extracting a cigarette from the box and closed afterwards. Inside the outmost envelope the cigarette box typically comprises an inner sleeve, into which the cigarettes are being placed. The inner sleeve comprises material that enables to maintain the cigarettes moist, not allowing them to dry. The inner sleeve may comprise for example acrylic or cellulosic materials, or polylactic acid film. It is of importance to seal the inner sleeve efficiently in between extracting the cigarettes and opening and closing of the lid.

Other examples represent resealable labels for containers for edible consumables, such as fruits, berries, salad, nuts, chips and raisins. Such container may be for example a plastic container having a plastic cover film including an open-closure sealing label for hermetically or semi-hermetically sealing the container.

Within context of this specification, open-closure sealing label is also referred to as resealable label. One common nominator for the open-closure sealing labels of this disclosure is that they are intended to tolerate and serve repeatable peeling, i.e. opening, and closing actions from and onto the labelled surface. Number of repeatable peeling and closing actions varies depending on the package and the contents of the package in question. For cigarette products, the number of peeling and subsequent closing actions may be at least 20 or equal to the number of cigarettes in a cigarette package. For edible consumables the number of open-closure actions of the sealing label may vary for example from a couple to tens of them.

Taste and freshness of the products is particular concern of the tobacco brand owners. Thus they provide their packages with a PSA sealing label. However, they have a growing concern on the materials of the PSA labels to be food certified and low in volatile organic compounds content. Especially the smell of the adhesive propagated via the smoker’s hand to the cigarette and its effect on the flavour of the cigarette is of concern. Similar kind of concern may be attributed with the producers of edible consumables in resealable packages. It may happen, that the odour or volatiles emitted by the sealing label materials diffuse into the sealed product package and, while in the package, the contained products catch the odour over time.

This specification aims to provide an open-closure sealing label which has low VOC content and is food certified, and at the same time possesses excellent open-closure properties even after repeatable open-closure actions.

Volatile organic compounds are organic chemicals that have a high vapour pressure at ordinary room temperature. Their high vapour pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. VOCs may be harmful to human health. The European Union defines a VOC as “any organic compound having an initial boiling point less than or equal to 250 ℃ (482 °F) measured at a standard atmospheric pressure of 101.3 kPa” . Within context of this specification, VOCs are referred to as volatile emissions.

As already mentioned, for edible consumables and also for cigarettes, it is preferable for the materials of the package to be food certified. Thus, also the materials of the open-closure sealing label and the package comprising the open-closure sealing label should be food certified. Food certified materials may also be referred to as food grade materials, food safe materials or food approved materials. Food certified materials may refer to materials that have been given by an accredited laboratory an approval for direct contact with dry and moist non-fatty foods. Food certified materials may refer to materials that are in compliance with at least one of the following EC regulations: EC 1935/2004, EC 2023/2006, EU 10/2011 or with the demands of the Code of Federal Regulations, Food and Drug Administration (FDA) , 21 CFR Ch. I (April 1, 2012 edition) § 175.105 and § 175.125.

The legal requirements in various nations for a material to be food safe may vary, but generally it is assured that a food safe container is free of any toxic contaminants which could be contacted from the manufacturing process and that the container material shall not potentially become a source of toxic contamination through usage (degeneration) . The latter is assured by estimating and regulating the migration limits of the material. According to EU regulation the overall migration is limited to 10 mg of substances/dm ² of the potential contact surface.

Face

Face (face stock) of the open-closure sealing label or resealable label disclosed herein comprises food grade filmic material. The face may comprise polyolefin, such as polyethylene or polypropylene. The face may comprise polyester, i.e. polyethylene terephthalate. The face may comprise renewable materials. Preferably the face emits as low amount of VOCs as possible at conventional operating temperatures, but this may depend on specific filmic material grade and even vary between production batches.

Requirements of a suitable face for label end use as an open-closure sealing label include compatibility of the face and the adhesive, which includes high enough adhesive anchorage to the face material. Adhesive anchorage ensures that the adhesive stays with the face during multiple opening and closing actions.

The face may be a multilayer structure. It may comprise a top coat layer for example in order to protect printing. The face may comprise a barrier layer, such as a metallized layer in order to prevent components of the adhesive layer from migrating into the face. The face may comprise a primer coating in order to improve adhesive anchorage to the face.

Preferably the face shows a certain degree of stiffness that enables the open-closure sealing label when in open position to tend to return to the closed position.

Adhesive

The adhesive according to this disclosure comprises a pressure sensitive adhesive of food grade comprising an aqueous acrylate polymer dispersion, i.e. an aqueous dispersion of acrylic polymer (s) . The adhesive is arranged to emit minimum volatile emissions at conventional operating temperatures. Conventional operating temperatures may refer to room temperature, i.e. ambient temperature, ± 10 degrees C.

The aqueous acrylate polymer dispersion is free from alkylphenol ethoxylates (APEs) . APE surfactants have traditionally been widely used in emulsion polymerization due to their cost-effectiveness and performance. However, concerns about APE ecotoxicity have been raised, thus leading to an effort to replace them with more environmentally friendly alternatives.

The aqueous acrylate polymer dispersion may be compliant with FDA regulation of adhesives in food packaging (21 CFR 175.105) . The aqueous acrylate polymer dispersion may be used safely for the reverse coating of labels for the labelling of food stored at room temperature. The adhesive composition may stand in direct contact with dry, moist, non-fatty food.

Most VOC emissions of a label are shown to originate from the adhesive. The VOC emissions may be caused for example by residual monomers, residual surfactant, left-over initiator from the polymerization process as well as impurities contained by the raw materials, such as impurities that are inactive in the polymerization process. Thus, care should be taken when selecting the adhesive raw materials. The adhesive raw materials should contain as low amount of VOC sources as possible. The pressure sensitive adhesive also needing to be in a certain amount “soft” to provide tackiness makes is more pronounced to emit VOC from its surface. Therefore, in practise to obtain a low VOC adhesive requires careful selection of the raw materials but also a separate step of removing odour from the exposed outer surface layer of the final adhesive coating.

The adhesive of the final label product is substantially free from residual components. Within context of this disclosure the residual components include, but are not limited to, unreacted monomers, volatile by-products for example from manufacturing of the monomers, residual artefacts from polymerizing process, such as 2-ethylhexanol.

Presence of unreacted monomers after the polymerizing process may be caused by impurity of the raw materials. Thus, for obtaining an adhesive substantially free from residual components, purity of the raw materials should be assured.

Amount of unreacted monomers in the adhesive may be less than about 50 ppm, more preferably less than about 40 ppm, more preferably less than about 30 ppm, more preferably less than about 25 ppm, more preferably less than about 20 ppm, more preferably less than about 15 ppm and even more preferably less than about 10 ppm or less than about 5 ppm.

The pressure sensitive adhesive may further comprise additive (s) with low level of volatile emissions or minimum volatile emissions. Such additives may be selected from a group comprising pH adjustors, surfactants, defoamers, softeners, rheology modifiers, biocides and preservatives. In case a softener is used, a non-phthalate type softener is preferred.

The pressure sensitive adhesive according to this disclosure has low level of volatile emissions or minimum volatile emissions at conventional operating temperatures.

According to an embodiment the pressure sensitive adhesive composition has minimum volatile emissions if the composition exhibits volatile emission values less than about 250 ppm, or less than about 200 ppm, or less than about 150 ppm, or less than about 100 ppm or even less than about 50 ppm when measured by a headspace gas chromatography/mass spectrometry (HS-GCMS) at about 70 degrees C or 120 degrees C.

In case the PSA composition comprises a colour pigment the composition may have a volatile emission factor of less than about 500 μg/m ²·hr as measured according to ASTM D-5116 after a four hour period. For a composition not comprising a colour pigment the volatile emission factor may be less than about 50 μg/m ²·hr as measured according to ASTM D-5116 after a twenty-four hour period.

Within context of this disclosure, the pressure sensitive adhesive is removable adhesive, i.e. it can be peeled manually after having been attached onto the surface to be labelled. For removable adhesive, it is characteristic that the peeling force does not grow to unacceptable levels even after longer period of having been adhered to a labelled surface. Further, it is characteristic to a removable adhesive that it can be clean peeled, i.e. leaving minor or negligible residues on the surface having been labelled onto.

A specific subcategory of removable adhesives is open-closure adhesives which have been designed for repeatable peeling and closing actions from and onto the labelled surface. For an open-closure adhesive, the peeling and tackiness properties remain substantially unchanged over several open-closure actions. To further have clean peeling, the open-closure adhesive needs to have proper anchorage to the face material as well as suitable release values from the surface onto which it has been labelled. This ensures that adhesive remains attached to the face material and at the same time can be easily enough opened from the labelled surface without leaving residues of the adhesive on that surface.

In order to ensure a repeatable clean peel behaviour, the face is arranged to properly anchor the adhesive layer to the face stock and to have certain peel adhesion properties. When the anchorage of the adhesive to the face material is correctly balanced with the peel properties of the adhesive from the labelled surfaces, then the adhesive layer remains securely attached to the face material even during repeatable open-closure actions.

The adhesive layer may have a peel adhesion value from 1.0 to 7.0, preferably from 1.0 to 3.0 or from 2.0 to 4.0 or from 4.0 to 7.0 N/25 mm when measured according to standard FTM 2 90°. Peel adhesion is defined as the force required to remove adhesive coated material, which has been applied to a standard test plate under specified conditions, from the plate at a specified angle and speed. Adhesion is measured 20 minutes and 24 hours after application, the latter being considered as the ultimate adhesion.

The adhesive anchorage refers to bonding of the adhesive layer to the face. The right adhesive anchorage is important for use of the open-closure sealing label for sealing a package. When the adhesive anchorage is desired, the adhesive layer remains with the face stock. The adhesive anchorage may be measured by a modified FINAT ink adhesion standard (FTM 21/22) . The measurement is performed at a temperature of 15 ℃ in a climatic chamber having a relative humidity of 70%. The measurement is performed four days after coating the adhesive. The adhesive anchorage is desired, whereupon after contact and release of the adhesive label with a counterpart material, the adhesive remains with the face stock and no spots of the adhesive transfer from the adhesive to the counterpart material. As counterpart materials, different types of tapes (TESA 4663, Scotch tape 810, TESA 4124) are used.

A proper balance between the peel adhesion values and the adhesive anchorage provides a label material that provides correct open-closure behaviour as well as clean peeling properties.

In order to obtain desired high level of adhesive anchorage, the face stock may comprise a primer coating. The primer coating may be arranged to anchor the adhesive layer to the face stock. The choice of the primer coating is dependent on the nature of the adhesive. The primer coating may be for example acrylic based or polyurethane based. Preferably the primer coating comprises or consists of food certified materials. In an example, the primer is polyurethane based and in compliance with FDA regulation of adhesives in food packaging (21 CFR 175.105) .

A coat weight of the adhesive layer may be from 15 to 25 g/m ². The adhesive layer may be fully cured. With fully cured adhesive the chemistry and performance of the adhesive layer over time are assured. Fully cured adhesive provides constant adhesive anchorage and T-peel force over time.

In an example, the adhesive has a tack from 2 to 6 N/25 mm on a glass surface when measured according to standard FTM 9, a peel adhesion (90°) value on glass from 1 to 3 N/25 mm when measured according to FTM 2, and a static shear from 300 to 1500 min when measured according to FTM 8.

Label laminate web

Typically a label laminate web is manufactured as a continuous web with the original width of the label laminate web corresponding to the width of the manufacturing/laminating machine. This manufacturing width may be, for example, 1-3 meters and corresponds therefore to the width of the so-called machine rolls that are created in the end of the lamination process. Then, the machine rolls are slit, i.e. cut lengthwise to so-called customer rolls with smaller widths ranging from a few centimetres typically to some tens of centimetres depending on the end use. The slitting involves typically unwinding the machine roll, then slitting the web and again winding the narrower webs into individual customer rolls. Alternatively, the slitting into customer rolls may be performed as a part of the label lamination process as an in-line process, or it may be even performed as a part of the label laminate converting process, where the label laminate is die-cut (kiss cut) to form individual labels carried by continuous release liner. Printing and other converting steps may be performed on suitable process phases, as known in the art.

A label laminate web 100 for providing open-closure sealing labels according to this disclosure comprises a face stock 101, an adhesive layer 102 and a release liner 103, as illustrated in Fig. 1a. The face stock 101 is adjoined to the release liner 103 via the adhesive layer 102. Thus, the release liner 103 is arranged on opposite side of the adhesive layer 102 with respect to the face stock 101. The label laminate web 100 is a continuous structure from which individual labels may be die-cut.

The label laminate web 100 comprises at least one label width. The label laminate web 100 may have been cut from a wider label laminate web having a manufacturing width.

According to an embodiment illustrated in Fig. 1 b a label laminate web 100 is arranged to comprise an adhesive area and at least one adhesion-free area on longitudinal edge of the face stock in machine direction, i.e. in the manufacturing direction of the web. The adhesion-free area is a continuous area arranged along the longitudinal edge of the face stock in machine direction of the label laminate web.

The adhesion-free area may be created leaving adhesive out from the adhesion-free area. Alternatively, the adhesion-free area may be created by locally treating the adhesive layer to lose its tack, for example, by varnishing the adhesive layer locally or by using some other appropriate chemical treatment.

The adhesion-free area may be obtained by pattern gumming. Pattern gumming is a manufacturing technique, wherein before lamination of the label laminate web the adhesive is only locally coated onto the release liner, or alternatively the adhesive is before lamination locally removed from certain areas of the release liner before drying/curing to become a pressure sensitive adhesive and lamination with the face material thereafter.

Typically, the adhesive is coated onto the release liner in fluidic phase and afterwards “solidified” into pressure sensitive adhesive layer. This “solidification” may be performed by heat treating the adhesive layer to remove water in case of water based adhesives, or by removing solvents in case of solvent based adhesives. Further, the solidification may include chemical cross-linking reactions to cure the adhesive layer into pressure sensitive adhesive. Within context of this disclosure, solidification is in general referred to as drying/curing if not otherwise specified.

The adhesive may be coated using a modified slot die coating method, wherein the slot die nozzle has been modified to comprise external adhesive flow blocking units to provide pattern gumming capability. The blocking units have been custom designed to correspond to the predetermined adhesion-free area widths and shaped to provide an adhesive flow that ensures even adhesive coating profile at adhesive coated areas. The modified slot die including the blocking units is designed by taking into account the speed of the web and the fluidic properties of the adhesive to be coated.

The release liner 103 comprises a release agent. The release agent is arranged to build a releasable contact with the adhesive layer. The release agent may comprise silicone. The release liner may comprise paper or polyester as a backing material.

The method for manufacturing a label laminate web may comprise a pre-selection step, wherein the filmic material of the face stock and/or one or more raw materials of the pressure sensitive adhesive are pre-selected based on showing minimum volatile emissions at conventional operating temperatures. The volatile emissions of the face stock and/or one or more raw materials may be measured or they may be provided by the raw material supplier.

The low VOC content of the label laminate and thus the labels manufactured therefrom is assured besides by selecting the suitable raw materials, also by exposing the label laminate to a de-odorization process. The de-odorization process comprises re-opening, i.e. delaminating, the label laminate and exposing the opened, i.e. delaminated, label laminate to heat and ventilation. The temperature of the de-odorization process may vary for example between 45 and 75 degrees C. In an example, the temperature of the de-odorization process is 60 degrees C. Web speed of the label laminate web may vary for example between 5 and 20 m/min. In an example, the web speed is 10 m/min. The ventilation air intake volume may be for example 15-35 %. The ventilation air outlet volume may be for example 90 %.

Time needed for the de-odorization process to take place effectively, i.e. the effective time of de-odorization process depends on the temperature and ventilation and is always longer than the time needed for adhesive drying/curing in the label laminate manufacturing process. In adhesive drying/curing the web speeds are approximately 5-10 times higher. By choosing raw materials that are capable of emitting high VOC concentrations, the effective time needed for the de-odorization may be longer. Long de-odorization times means higher manufacturing costs, and thus proper selection of raw materials is of importance. Raw materials, in particular their VOC content have an effect on the conditions and/or the measures needed in the de-odorization process. In other words, by selecting the raw materials in a clever way it is possible to minimize the measures needed to be performed to the label laminate before its final use as an open-closure sealing label. By a proper selection of the raw materials for example a lower temperature and/or higher web speed in the de-odorization process may be possible, thus leading to a more environmentally friendly and cost-efficient manufacturing process. In other words, an inventive and comprehensive approach how to design an open-closure label for a certain type of end use starting from careful selection of raw materials and components and then providing further de-odorization treatment to ensure a verified low level of VOC emissions suitable for such end uses is provided herein. Depending on the available raw materials and components, the de-odorization process can be further adjusted to ensure that the final objective of low VOC emissions under measurable limits is achieved. Without the combination of these steps the commercially viable production of such open-closure label products would not be possible. Being able to verify the level of VOC emissions via measurements and having acceptable levels defined to such measurements allows the use of these measurements as feedback in refinement of the overall process.

After exposing the delaminated label laminate to heat and ventilation the label laminate web is re-laminated. Thus, and the release agent of the release liner is arranged to rebuild a contact with the adhesive layer when re-laminating the label laminate web.

Volatile emissions measured or obtained either while pre-selecting the filmic material of the face stock and/or one or more raw materials of the pressure sensitive or volatile emissions measured from the re-laminated label laminate web after exposing the delaminated label laminate web to heat and ventilation may be used as process feedback in order to adjust the de-odorization process. The process feedback may be used for adjusting temperature, period, i.e. duration, or ventilation air volume of the de-odorization process.

Sometimes the manufacturing process of for example the pressure sensitive adhesive and/or the label laminate web may be such that raw materials that itself do not substantially emit volatile emissions react in a manner that produces substances that cause significant amount of volatiles to be emitted. Therefore the process feedback obtained by measuring the volatile emissions of the re-laminated label laminate web may be of particular importance in low VOC label manufacturing process.

Fig. 2 illustrates an exemplary process chart of a method for providing a label laminate web. The method comprises mixing an aqueous acrylic polymer dispersion with additive (s) so as to provide a food grade pressure sensitive adhesive. The method further comprises arranging a substrate as a release liner and coating the release liner with the food grade pressure sensitive adhesive, and subsequently laminating the release liner together with a food grade face stock in such a way that the pressure sensitive adhesive is arranged in between the face stock and the release liner so as to form a label laminate web. The method comprises exposing the label laminate web to de-odorizing, details of which were discussed above. After exposing the delaminated label laminate to heat and ventilation, i.e. de-odorization process, the label laminate web is re-laminated. A low VOC and food grade label laminate web product is obtained as a result of the method disclosed.

The label laminate web may be arranged to undergo certain conversion steps during or linked with the de-odorization process. Such conversion steps are such which would require opening and closing of the laminate. This provides a more time-efficient manufacturing process, as several manufacturing steps may take place simultaneously. For example, in a very specific end use of using as an automatic sealing label for tobacco packages (Fig. 3a) , the label laminate web during the de-odorization process may undergo a special conversion step wherein an area of the pressure sensitive adhesive layer is arranged to receive additional permanent adhesive layer. The permanent adhesive is applied onto the adhesive area of the face. In re-lamination the label laminate web is closed by adjoining the release liner and the label. Thus, in addition to the above presented features, the converted label web comprises permanent adhesive arranged in between the pressure sensitive adhesive layer and the release liner. Permanent adhesive may be for example hot melt adhesive.

The purpose of the aforementioned conversion is to prepare the label laminate web for its end use as an automatic open-closure sealing label, wherein the permanent adhesive arranged onto the pressure sensitive adhesive layer is configured to be permanently attached to a separated part of an inner sleeve of a package to be sealed with the open-closure sealing label. When used as a tobacco package automatic open-closure sealing label, this area of the label comprising a separated part of the inner sleeve of the tobacco package permanently attached to the sealing label is arranged to overlap the opening of the inner sleeve of the tobacco package holding the cigarettes. The separated part of the inner sleeve is essential to securely cover the pressure sensitive adhesive of the sealing label and to prevent the adhesive from adhering and contaminating the tobacco products.

The odour evaluation, i.e. the amount of volatile emissions of the final label laminate product or the label product manufactured therefrom may be implemented for example by smelling by human nose, by determining the VOC content of the label laminate or the label by HS-GCMS and/or by determining the residual monomer content and the VOC content of the adhesive layer by HS-GCMS or gas chromatography (GC) . As smelling by human nose is always subjective, the experiments relying on technical measurements are of course preferred.

Smelling by human nose may be responsible for detecting VOCs having shorter retention times in gas chromatography, such as toluene, dibutyl ether and butyl propionate. According to the measurements performed, the origin of these VOCs may mainly be the face material of the label. However, the measurements reveal that the adhesive is the main source of the VOCs emitted by the label. In any case, the de-odorization process is shown to reduce the VOCs emitted by the label laminate or the label.

In an exemplary HS-GCMS measurement, a bottle containing a label laminate sample is put into an headspace oven at 65 degrees C for 120 minutes in order to achieve smell evaporation. The gas content of the bottle is thereafter injected into a GC column for quantitative GC/MS analysis. A commercial MS library may be used for identifying the components. The amount of respective component is determined by the GC peak area. Total VOC content may be calculated by adding up all GC peak areas, i.e. the total integral area. Odorant component fraction may be calculated by subtracting the silicone oligomer area from the total integral area.

As already mentioned, according to this disclosure the adhesive of the label laminate should be substantially free from residual components including unreacted monomers. The content of the residual monomers, i.e. the unreacted monomers in the adhesive of a label sample may be determined by HS-GCMS as discussed above or by GC. In an exemplary GC method the adhesive is scraped from a label sample and dissolved in THF. The sample thus formed is the injected into GC for residual monomer and total VOC determination. The presence and content of at least the following components may be determined: methyl acrylate (MA) , methyl methacrylate (MMA) , butyl acrylate (BA) , styrene (St) , 2-hydroxyethyl acrylate (2-HEA) , acrylic acid (AA) , methacrylic acid (MAA) , 2-ethylhexyl acrylate (2-EHA) , acetone, tert-butyl alcohol, butyl acetate, dibutyl ether, butyl propionate, 2-ethyl-1-hexanol, 2-ethylhexyl acetate.

Label laminate web is configured to be converted before dispensing the individual labels. The conversion refers to processes such as printing, coating, die-cutting and slitting. During conversion the label laminate web is converted to an intermediate product, namely a converted label web. The converted label web refers to a product wherein individual labels remain to be attached onto a release liner, which is used as a carrier in later phases to help to carry and dispense the individual labels to their final use.

The label laminate web as presented above is die-cut in order to obtain individual labels attached on a continuous release liner. In die-cutting the labels are cut into a desired shape. Die-cutting is arranged to cut the face stock and the pressure sensitive adhesive layer adjoined to it. Waste material that does not belong to the labels is removed. Thus, a converted label web comprising a release liner with labels disclosed above attached onto it is provided. The release liner comprises a release agent arranged to build a releasable contact with the pressure sensitive adhesive layer. The converted label web comprises at least one label width.

Label structure

The label laminate web disclosed herein is used for providing an open-closure sealing label. The open-closure sealing label can be repeatably opened and closed with clean peel and recurring performance. The open-closure sealing label comprises a face and an adhesive layer adjoined to the face. The face comprises food grade filmic material and the adhesive layer comprises a food grade pressure sensitive adhesive as discussed above.

The face may comprise an adhesive area and at least one adhesion-free area. The at least one adhesion-free area may be arranged along length of at least one edge of the open-closure sealing label.

The adhesion-free area of the face provides an area via which the open-closure sealing label is permanently attachable to a package to be sealed with the label, if needed. The adhesion-free area is capable of receiving permanent adhesive. Spots of permanent adhesive may be applied onto the adhesion-free area of the face, and the label may be attached to the package to be sealed with the label. The permanent adhesive may be for example hotmelt adhesive or cold glue. However, not all open-closure sealing labels are arranged to be permanently attached to the package to be sealed, and thus do not comprise an adhesion-free area arranged to receive permanent adhesive. In such cases the entire open-closure sealing label is detachable from the package when opening and attachable back when closing again.

The open-closure sealing label may be used for sealing a package. Examples of packages and open-closure sealing labels within the scope of this disclosure are presented in Figs. 3a, 3b and 4-6. The open-closure sealing label may be used as a manual seal, that is a seal opened and closed by the user by hand. Alternatively, the open-closure sealing label may be arranged as an automatic seal that does not require to be touched by the user when opening and closing. Figs. 3a and 3b illustrate exemplary sealing labels for a cigarette/tobacco package. Fig. 4 illustrates exemplary packages suitable for example for so-called wet wipes and provided with open-closure sealing labels 411. Exemplary sealing label 511 for sealing a cover of a box type package is shown in Fig. 5. Fig. 6 illustrates an example wherein an open-closure sealing label 611 may be responsible for forming at most of the cover of the package.

The open-closure sealing label may comprise a grip surface, i.e. a finger tab for manually opening and closing the sealing label by user. The finger tab of the open-closure sealing label preferably comprises an adhesion-free area. The finger tab may be arranged in different shapes/sizes and/or positions on a label edge to be conveniently gripped by the user. The adhesion-free area of the grip surface may be implemented by killing or varnishing the pressure sensitive adhesive on the area.

As discussed, in a special end use the open-closure sealing label may be used for sealing an inner sleeve of a cigarette box. Cigarette box refers to a container or a package for storing cigarettes. Cigarettes may refer to conventional tobacco products and to so-called smoke-free products. The materials of the inner sleeve of the cigarette box may comprise for example an uncoated film or acrylic coated film.

As illustrated in Figs. 3a and 3b, an outmost envelope of the cigarette box comprises a lid that is opened when extracting a cigarette from the box and closed afterwards. Inside the outmost envelope the cigarette box typically comprises an inner sleeve, into which the cigarettes are being placed. The inner sleeve comprises material that enables to maintain the cigarettes moist, not allowing them to dry. The inner sleeve may comprise for example acrylic or cellulosic materials, or polylactic acid film. It is of importance to seal the inner sleeve efficiently in between extracting the cigarettes and opening and closing of the lid.

Fig. 3b illustrates an example of a specific end use of an open-closure sealing label 312 in sealing a cigarette inner sleeve. The manual open-closure sealing label 312 comprises an adhesion-free area along length of one edge of the sealing label. The manual open-closure sealing label 312 is permanently attached to the package 310 from this one edge of the label via permanent adhesive. The opposing edge of the sealing label is used as a grip surface, i.e. a finger tab for manually opening and closing the sealing label by the user.

The adhesive layer of the open-closure sealing label may be configured to adhere to a separated part of an inner sleeve of a package to be sealed with the open-closure sealing label. When used as a tobacco package manual open-closure sealing label, this area of the label adhered to a separated part of the inner sleeve of the tobacco package is arranged to overlap the opening of the inner sleeve of the tobacco package holding the cigarettes. The separated part of the inner sleeve is essential to securely cover the adhesive of the sealing label and to prevent the adhesive from adhering and contaminating the tobacco products.

The open-closure sealing label is releasably connectable via the adhesive layer to a counterpart material. Being releasably connectable means that the adhesive label may be attached to the counterpart material via the pressure sensitive adhesive and released from the counterpart material for several times without affecting the adherent properties of the label. In a case the open-closure sealing label is intended to be used in cigarette products several times refers to at least 20 times or equal to the number of cigarettes in a cigarette package. The counterpart material may comprise for example uncoated film or acrylic coated film. The counterpart material may comprise for example acrylic or cellulosic materials, or polylactic acid film.

Fig. 3a illustrates another example of a specific end use of an open-closure sealing label 311 in sealing a cigarette inner sleeve. The open-closure sealing label 311 is aimed to be used as an automatic seal. In addition to the above presented features for manual seal the open-closure sealing label 311 comprises permanent adhesive arranged onto the pressure sensitive adhesive layer. Also, the face of the open-closure sealing label comprises two adhesion-free areas along lengths of opposite edges of the open-closure sealing label. The opening and closure of the automatic open-closure sealing label 311 is integrated to the opening and closure of a lid of the package, as illustrated in Fig. 3a. The open-closure sealing label for automatic sealing is permanently attached to the package 310 via permanent adhesive applied on both two adhesion-free areas. One adhesion-free area provided with the permanent adhesive may be attached to an inner sleeve of a package. The other adhesion-free area provided with the permanent adhesive may be attached to the lid of the package. By this way, the open-closure sealing label 311 is arranged to seal the package 310 when closing the lid and to open the seal when opening the lid.

The permanent adhesive arranged onto the pressure sensitive adhesive layer is configured to be permanently attached to a separated part of an inner sleeve of a package to be sealed with the open-closure sealing label 311. When used as a tobacco package automatic open-closure sealing label, this area of the label comprising a separated part of the inner sleeve of the tobacco package permanently attached to the sealing label is arranged to overlap the opening of the inner sleeve of the tobacco package holding the cigarettes. The separated part of the inner sleeve is essential to securely cover the pressure sensitive adhesive of the sealing label and to prevent the adhesive from adhering and contaminating the tobacco products.

Claims

An open-closure sealing label (311, 411, 511, 611) comprising a face (101) and an adhesive layer (102) adjoined to the face, wherein

- the face (101) comprises filmic material,

- the adhesive layer (102) comprises a removable pressure sensitive adhesive comprising an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures,

and wherein the filmic material and the removable pressure sensitive adhesive are food grade materials.
The open-closure sealing label (311, 411, 511, 611) according to claim 1, wherein the removable pressure sensitive adhesive is arranged to emit volatile emissions less than 250 ppm when measured by a headspace gas chromatography/mass spectrometry at about 70 degrees C or 120 degrees C.
The open-closure sealing label (311, 411, 511, 611) according to claim 1 or 2, wherein the face (101) comprises a primer coating.
The open-closure sealing label (311, 411, 511, 611) according to any of the preceding claims, wherein the removable pressure sensitive adhesive comprises less than about 50 ppm unreacted monomers.
A package (310) comprising an open-closure sealing label (311, 411, 511, 611) according to any of the claims 1-4.
A label laminate web (100) for providing an open-closure sealing label (311, 411, 511, 611) according to any of the claims 1-4, comprising a face stock (101) , an adhesive layer (102) and a release liner (103) , the face stock (101) being adjoined to the release liner (103) via the adhesive layer (102) , wherein

- the face stock (101) comprises filmic material,

- the adhesive layer (102) comprises a removable pressure sensitive adhesive comprising an aqueous acrylate polymer dispersion and is arranged to emit minimum volatile emissions at conventional operating temperatures,

- the release liner (103) comprises a release agent arranged to build a releasable contact with the adhesive layer (102) ,

and wherein the filmic material and the removable pressure sensitive adhesive are food grade materials.
A method for manufacturing a label laminate web (100) , the method comprising

- arranging a substrate with a release agent as a release liner (103) ,

- arranging a food grade filmic material as a face stock (101) ,

- coating the release liner (103) with a removable pressure sensitive adhesive of food grade comprising an aqueous acrylate polymer dispersion so as to form a resealable adhesive layer (102) ,

- laminating the release liner (103) together with the face stock (101) in such a way that the adhesive layer (102) is arranged in between the face stock (101) and the release liner (103) so as to form the label laminate web (100) ,

- subsequently delaminating the label laminate web (100) ,

- exposing the delaminated label laminate web to heat and ventilation in a de-odorization process, and

- re-laminating the release liner (103) together with the face stock (101) in such a way that the adhesive layer (102) is arranged in between the face stock (101) and the release liner (103) .
The method according to claim 7, further comprising

- pre-selecting the filmic material of the face stock (101) and/or one or more raw materials of the pressure sensitive adhesive based on showing minimum volatile emissions at conventional operating temperatures.
The method according to claim 7 or 8, further comprising

- using i) volatile emissions measured or obtained either while pre-selecting the filmic material of the face stock and/or one or more raw materials of the pressure sensitive adhesive, or ii) volatile emissions measured from the re-laminated label laminate web after exposing the delaminated label laminate web to heat and ventilation as process feedback in order to adjust the de-odorization process.
The method according to claim 9, wherein the process feedback is used for adjusting temperature, period or ventilation air volume of the de-odorization process.
The method according to any of the claims 7-10, wherein the delaminated label laminate is exposed to a temperature of between 45 and 75 degrees C in the de-odorization process.
The method according to any of the claims 7-11, wherein a web speed of the delaminated label laminate in the de-odorization process is arranged to be between 5 and 20 m/min.