WO2012127121A2

WO2012127121A2 - Label facestock film

Info

Publication number: WO2012127121A2
Application number: PCT/FI2012/050298
Authority: WO
Inventors: Noel Mitchell; Martti Vähälä; Tom Saxberg
Original assignee: Upm Raflatac Oy
Priority date: 2011-03-23
Filing date: 2012-03-23
Publication date: 2012-09-27
Also published as: WO2012127121A3

Abstract

The invention relates to a facestock of a label, and to a label having a facestock, wherein the facestock layer comprises at least linear low density polyethylene or high density polyethylene, and an additive comprising hydrocarbon resin. The invention also relates to a method for manufacturing such labels. The invention further relates to a combination of an item and a label, wherein the label has been attached to a surface of the item.

Description

Label facestock film Field of the Invention The present invention relates to labels, and more specifically to a facestock film of the label.

Background of the Invention It is general practice to apply a label to a surface of an item to provide decoration, and/or to display information about the product being sold, such as content of the item, a trade name or logo. A label typically comprises a face material and an adhesive layer to attach the face material to an item. Label face materials may be either paper or plastic film or combination of these. Plastic labels, in contrast to paper labels, are increasingly preferred. The plastic labels available include films made, for example, from polyvinyl chloride) (PVC), polypropylene (PP) and polyethylene (PE). Different grades of PE have been synthesized and various ethylene polymers may be used in films. Polyethylene grades include for example, high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

Since environmental and economical aspects plays an increasing role, there is a demand for more environmentally friendly labels and films used in labels.

Summary of the Invention

It is an object to provide plastic films for labels. It is an object of the present invention to provide a plastic film composition which is environmentally friendly and provides adequate properties for labelling applications. It is an object to provide a method for producing a laminated structure and labels thereof.

According to a first aspect, a label including a facestock layer and an adhesive layer against one side of the facestock layer is provided. The facestock layer consists of a plastic film comprising at least linear low density polyethylene (LLDPE) or high density polyethylene (HDPE), and an additive comprising hydrocarbon resin (HC).

According to a second aspect, a use of a label for labelling of an item in order to provide decoration, and or to display information about the content of the item is provided.

According to a third aspect, a method for producing a label is provided. The method includes at least forming a facestock layer consisting of a plastic film including linear low density polyethylene or high density polyethylene and an additive comprising hydrocarbon resin, combining an adhesive layer to a release liner and to one side of a facestock layer so as to form a laminated structure and cutting the laminated structure so as to form individual labels . According to a fourth aspect, a combination of an item and a label is provided. The combination consists of a label adhered to a surface of the item, the label comprising a facestock layer and an adhesive layer against one side of the facestock layer. The facestock layer consists of a plastic film comprising at least linear low density polyethylene (LLDPE) or high density polyethylene (HDPE) , and an additive comprising hydrocarbon resin (HC).

According to a fifth aspect, a facestock comprising a plastic film is provided. The plastic film comprises at least linear low density polyethylene or high density polyethylene, and an additive comprising hydrocarbon resin.

Further embodiments are presented in the dependent claims.

The plastic film of the facestock layer may comprise hydrocarbon resin between 5 and 40 wt-%, preferably between 10 and 30 wt-%, most preferably between 5 and 25 wt-% or between 10 and 25 wt-%. The facestock layer is preferably non-oriented. The haze of the facestock layer is is less than 60%, preferably less than 50, and most preferably less than 30%. The facestock layer is non-oriented. The label may be a pressure sensitive label. Description of the Drawings

The invention will be explained in the following with reference to the appending drawings, where

Fig. 1 presents, in a cross sectional view, a laminate structure for labels,

Fig. 2 presents, in a cross sectional view, a laminate comprising die- cut labels,

Fig. 3 presents, in a cross-sectional view individual labels released from the liner.

Detailed Description of the Invention

A label consists of a label film, also called as a carrier, substrate or facestock layer, and an adhesive layer to affix the label film to an article. The label film is commonly coated on one side with the adhesive and usually printed at least on the other side. Label film can be attached to an item by heat activated adhesive, wet glue adhesive, or pressure sensitive adhesive (PSA). The pressure sensitive labels, also called self-adhesive labels, consisting of a pressure sensitive adhesive, can be adhered to most surfaces through an adhesive layer without the use of a secondary agent such as solvents or heat to strengthen the bond. The pressure sensitive adhesive forms a bond when pressure is applied on the label at room temperature, adhering the label with the item to be labelled.

Referring to Fig. 1 , a pressure sensitive label laminate structure consists of a release liner 6 coated with a release agent, such as silicone, and a facestock 2 which are laminated together with a pressure sensitive adhesive layer 4 (PSA) in between. The release liner protects the adhesive and is removed prior to application of the label to a surface of an item.

The facestock 2 may be based on a single-layer (monolayer) or multilayer polymer film having two or more film layers. The facestock comprising multilayer structure may be coextruded or laminated. The multilayer structure may comprise polymeric films having same or different film composition. The thickness of individual films in a multilayer structure may also vary. The polymer film may be coextruded and produced through blown film extrusion technology. Alternatively film(s) may be casted, i.e. produced by cast extrusion technology.

The label structure may also comprise other layers in order to improve features, such as label functionality, conformability, printability, die-cutting, mechanical properties, or visual appearance. For example, tie layer, top coat or over-laminate may be applied to the facestock for protection or to enhance the adhesion of ink and/or adhesive. Alternatively, facestock layer(s) i.e. adhesive and/or print receiving layer(s) may be surface treated by known methods in the art, such as flame treatment, corona treatment, plasma treatment in order to enhance for example adhesion. According to the current invention, a facestok layer comprises a bio-derived polyethylene, also called as green PE or renewable polyethylene. The bio- derived polyethylene may be based on ethanol derived from renewable resources, such as sugarcane, sugar beet and wheat grain. By using non-oil based polymers for label films, the environmental burden may be reduced i.e. the C0₂ foot print is reduced.

The plastic film of a facestock layer comprises at least 25 % of green PE. Different grades of green PE may be used, for example HDPE or LLDPE. In HDPE the content of bio-based monomers may be about 95 % and in LLDPE about 87%. The melt flow rate of HDPE may be 7.2 (g/10min) and density 0.959 g/cm³. LLDPE may be copolymer of 1 -butene having melt flow rate 2.7 (g/1 Omin) and density 0.918 g/cm³.

In addition to bio-derived raw materials, also fossil based raw materials, either biodegradable or non-biodegradable, may be included in plastic film. The bio-level of the facestock, which means the level of bio-derived materials of the facestock, may be from 45 to 95%, preferably from 80 to 95% or even more.

According to an embodiment of the invention, a polymer film of the facestock comprises a polymer blend. The HDPE content of the blend may be at least 25%. Alternatively, the HDPE content may be 50-75%. Total content of PE based polymers of the polymer film may be from 25 to 100 %.

According to another embodiment of the invention, a polymer film comprises a blend including thermoplastic starch. Starch may be either pure or blended with other polymers, such as poly(caprolactone) (PCL). The amount of starch based thermoplastics may be up to 75%.

According to a further embodiment of the invention, a polymer film may further include additives, such as wood based rosin esters or hydrocarbon resins or mixtures thereof. The amount of additives may be up to 30%. Blending with additives typically increases the stiffness of the facestock layer and thus improves e.g. the die-cuttability of the label. According to another embodiment of the invention, a polymer film may also include biodegradable polymers, such as poly(lactide) (PLA).

According to another embodiment of the invention, a polymer film may also include hemicellulose. Hemicellulose may be modified through esterification i.e. acetylation. The film may further include plasticizers.

According to another embodiment of the invention, a polymer film may also include cellulose or starch modifications. There are various requirements for the labels, e.g. no-label look, clarity, conformability, surface smoothness, moisture resistance, rigidity, ease of die- cutting, suitability for printing etc. A high density polyethylene (HDPE) has low degree of branching and thus stronger intermolecular forces. Thus films consisting of HDPE have good mechanical properties, such as stiffness and tensile strength. A low density polyethylene (LDPE) is branched, a semicrystalline thermoplastic material. Linear low density polyethylene (LLDPE) is substantially linear polymer with short branches. It forms large crystallites that result in surface irregularities and films having poor optical properties. Although PE is recyclable, it is not considered as a biodegradable polymer. For allowing processing in usual labelling devices, the facestock layer should have sufficient mechanical properties. For example, facestock layer should have sufficient modulus and stiffness values in order to provide die-cuttability for the label. From the economical point of view, the smallest possible thickness of the facestock is preferred.

According to one embodiment of the invention, the facestock layer has an overall thickness of 60-100 microns, preferably 70-75 microns. The thickness of individual layers in multilayer facestock structure may vary. According to one embodiment of the invention, the facestock layer has a modulus value in machine direction of around 450 MPa. The elongation in machine direction (MD) may be at the maximum 1400%, preferably not more than 400%. The elongation in transverse direction (TD) may be around 200%. High elongation rates will reduce the die-cut performance of the facestock. From the optical point of view, the high transparency of the facestock layer is preferred. The haze level should be less than 35%, preferably equal or less than 25%.

Example 1 .

A multilayer structure of facestock layer comprising three films was produced by co-extrusion. All the films had substantially equal compositions and included at least LLDPE and HDPE. Additionally, the composition included additives.

Alternatively, in the multilayer structure, e.g. three layer structure, composition of different layers may be varied and more tailored facestock may be achieved. Thanks to the optimized multilayer structure, for example, performance or handling of the label during subsequent converting, e.g. printing, may be improved. A method for manufacturing a laminate web structure 1 for labels comprises at least the following steps: manufacturing a plastic film (polymer film) for facestock layer 2 by extrusion or casting from raw materials including at least HDPE and/or LLDPE and hydrocarbon resin, coating a release liner with a releasing agent, e.g. silicone, coating a facestock layer 2 with an adhesive layer 4, laminating the facestock layer 2 and the release liner 6 together with the adhesive layer 4 in between. Alternatively adhesive layer may be coated on top of the release agent layer of the release liner prior to laminating step. The facestock layer may be printed in order to provide a visual effect or provide information. The facestock may be printed on the reverse side so that the print layer is between the facestock layer 4 and the adhesive layer 2. Thanks to the reverse side printing of the facestock there will be no need for an additional over-lamination layer to protect the printing. Alternatively, the printing and adhesive layers may be provided on opposite surfaces of the facestock, i.e. the printing may be on the exterior side of the facestock. The facestock layer may also be surface treated prior to printing or coating with an adhesive layer.

The adhesive layer may consist of a pressure-sensitive adhesive. The adhesive layer may also consist of an adhesive that can be activated by some energy source, such as heat, IR or laser.

It is also possible that the label does not comprise a laminated structure containing a release liner, i.e. the label may only consists of the facestock layer 2 and the adhesive layer 4.

Referring to Fig. 2, individual labels 3 of desired shape and size may be die- cut from the laminate structure 1 . After cutting, a number of individual labels 3 may be attached to a liner 6, which remains uncut and continuous. Referring to Fig. 3, the individual labels 3 may be completely separate, i.e. also the liner 6 may be cut. After cutting and separating the label from the liner a surface of an adhesive layer 4 of the label is exposed so that the label can be attached to the surface of an item through the adhesive layer. The label may be used for labelling of items of different shapes and materials, such as glass or plastic bottles or other containers. Labels may be used in wide variety of labelling applications, such as food, home and personal care products, and products of industrial applications. According to an embodiment, the facestock layer 2 has a plastic film, also called to a polymer film, formulation comprising a base polymer of LLDPE or HDPE. The base polymer may also be called a main component. The total content of PE based polymers of the polymer film may be from 25 to 98%. Alternatively, it is possible to use blends of LLDPE and HDPE. The total content of PE based polymers of the polymer film may be from 25 to 98%. Additionally, the film includes additive(s), also called plastic modifier(s) or a minor component. Additives may include at least one of the following a wood based rosin ester, a hydrocarbon resin, polystyrene (PS), polypropylene (PP) or a compound of hydrocarbon resin. Preferably the plastic modifier comprises at least hydrocarbon resin. The melt flow rate of the HDPE and LLDPE may be from 0.5 g/10 min up to 7 g/10 min, when measured using temperature of 190 °C and 2.16 kg polymer.

The amount of additive is at least 1 or 2 wt-%, preferably at least 3 or 5 wt-%, most preferably at least 10 or 20 wt-%. In addition, the amount of additives is not greater than 40 wt-%, preferably not greater than 30 wt-%. For example, the amount of additives is between 5 and 40 wt-%, preferably between 10 and 30 wt-%, most preferably between 5 and 25 wt-% or between 10 and 25 wt-%. Blending with additives typically increases the stiffness of the facestock layer and thus improves e.g. the dispensing performance of the label. Also die-cuttability of the label may be improved. The additive may also decrease the haze of the film.

The hydrocarbon resin compound includes at least one hydrocarbon resin (HC). Hydrocarbon resin compound may also include other additives, such as wood based rosin esters, polystyrene (PS), polypropylene (PP) or mixtures thereof. The hydrocarbon resins are low molecular weight compounds consisting only of hydrogen and carbon. Hydrocarbon resin may have amorphous structure and may be derived from synthetic or natural monomers. Saturated hydrocarbons are composed entirely of single bonds and are saturated with hydrogen (fully hydrogenated). Hydrocarbon resin may be aromatic, i.e. having at least one aromatic ring. Alternatively it may be acyclic or cyclic aliphatic resin. The number average molecular weight (M_n) of HC may be below 2000 g/mol. For example, M_n may be between 400 and 500 g/mol and M_w (weight average molecular weight) between 600 and 700 g/mol, when measured via gel permeation chromatography using PS standards. Softening point according to ASTM E 28 may be below 140 °C, preferably between 90 and 1 10 °C. Hydrocarbon resin compound may also include LLDPE comprising bio-based monomers. Alternatively, LLDPE may be petroleum based.

An amount of hydrocarbon resin compound may be from 10 to 60 wt-%, preferably from 30 to 60 wt-% based on the total weight of the plastic film composition. An amount of HC is at least 5 or 10 wt-%, preferably at least 20 or 30 wt-%, most preferably at least 40 or 70 wt-%. For example, the amount of HC is between 10 and 30 wt-%, preferably between 20 and 40 wt-%, most preferably between 40 and 70 wt-% based on the total weight of the hydrocarbon compound. In addition to hydrocarbon resin, the hydrocarbon resin compound includes polyethylene, such as LLDPE comprising bio-based ethylene monomers. Alternatively, LLDPE of the compound may be petroleum based. Also other grades of polyethylene may be used. The polyethylene of the HC resin compound may also be petroleum based. An amount of PE may be between 70 and 90 wt-%, preferably between 60 and 80 wt-%, most preferable between 30 and 60 wt-%. For example, the amount of PE is at least 40 wt-% based on the total weight of the HC resin compound.

The base polymer (main component) of the plastic film may be petroleum based or bio-derived polyethylene, such as HDPE, LLDPE or a mixture thereof. Alternatively, it may include a mixture of petroleum based and bio- derived polyethylene. Thanks to the bio-derived PE the label poses less of an environmental burden when compared to petroleum based polyethylenes. An amount of main component of the plastic film may be at least 40 wt-%, preferably at least 50 or 60 wt-%. For example, the amount of main component is from 40 to 98 wt-%, preferably from 50 to 85 wt-%, and most preferably from 60 to 80 wt-% based on the total weight of the plastic film composition.. The amount of hydrocarbon resinas a minor component is not greater than 40 wt-%, preferably not greater than 30 wt-%. For example, the amount of HC is between 5 and 40 wt-%, preferably between 10 and 30 wt- %, most preferably between 5 and 25 wt-% or between 10 and 25 wt-%. The amount of bio-derived raw material of the plastic film may be, for example, up to 25 wt-% or even more. Thus, the bio-level of the facestock may be from 2 to 98%, preferably from 45 to 95% or from 80 to 95%. For example, in the plastic film an amount of LLDPE having bio-based ethylene monomer may be at least 5 wt-% or at least 10 wt-%, preferably from 15 to 20 wt-%. Alternatively, all PE of the plastic film may be bio-based polyethylene, such as LLDPE.

The plastic films of the facestock layer are preferably non-oriented, i.e. the molecule chains of the polymer are not aligned in a specific direction(s). Thus the films are not oriented by drawing or stretching after the film manufacturing, such as extrusion. Thanks to the non-oriented structure a good conformability of the plastic film for label applications is achieved. Conformability defines the capability of the label to conform smoothly to the contour of the item even when this is curved in two-dimensions. Thus label material should be flexible enough to conform with the surface of the item, i.e. with the underlying contour, without wrinkles.

Thanks to the additive comprising hydrocarbon resin, the properties of the plastic film containing polyethylene may be varied. For example, by the HC addition the stiffness of the polyethylene film can be increased thus causing decrease of the film flexibility. Thanks to the increased stiffness the film thickness may be down gauged, i.e. thinner facestock layer for label can be provided. Thanks to the film properties also better die-cutting performance of the label can be achieved. Also dispensing performance of the may be improved. The addition of HC also gives better optical properties for the film. It renders the PE films more transparent and the haze of the film can be reduced. From the optical point of view, the high transparency of the facestock layer is preferred. The haze of the film may be less than 60%, preferably less than 50% or less than 30%, and most preferably equal or less than 25%, when measured according to the standard ASTM D1003. In addition, the haze is at least 5 or 10%, preferably at least 12 or 15%. For example, the haze is between 10 and 30%, or preferably between 15 and 25% or between 10 and 20%.

In order to optimize the facestock properties, plastic films of a multilayer facestock structure, e.g. a three layer structure, may have different formulations. For example, skin layers may have less base polymer and increased additive amount when compared to a core layer. The properties of facestock layer having polyethylene plastic film are to be illustrated in the following example. Example 2.

The facestock layer has a plastic film formulation comprising: p.b.w (parts by weight)

Base polymer (main component)

of LLDPE or HDPE

Hydrocarbon resin compound

(minor component)

total

, wherein the hydrocarbon resin compound had a composition of p.b.w (parts by weight)

LLDPE (having bio-based monomers) 40

Hydrocarbon resin 60

total 100

In this film formulation the base polymer, HDPE, was polyethylene from petroleum resources. The LLDPE was bio-based SLL318 from Braskem. The LLDPE of hydrocarbon compound was also bio-based polyethylene LLDPE SLL318 from Braskem. The hydrocarbon resin was fully hydrogenated, such as Regalite R1090 from Eastman. Also other HC resins, such as Escorez 5300 from ExxonMobil Chemical, could have been used.

The monolayer plastic films having the above described formulation were produced by a cast extrusion process and tested in order to evaluate their properties.

The test results of the films are shown below in Table 1 , wherein the MD means machine direction of the tested film and Adj L&W bending resistance of the film when adjusted to the to the same film thickness of 83 μιτι. Adj L&W bending resistance test was performed for the film sample in machine direction and having following test parameters: test sample width 38 mm; bending distance 5 mm, bending angle of 15°, and wherein the figure gives the force (in mN) needed to bend the sample of 15 degree angle. Table 1 .

The embodiments described above are only example embodiments of the invention and a person skilled in the art recognizes readily that they may be combined in various ways to generate further embodiments without deviating from the basic underlying invention.

Claims

Claims:

1 . A label including a facestock layer and an adhesive layer against one side of the facestock layer, wherein the facestock layer comprises a plastic film comprising at least linear low density polyethylene or high density polyethylene, and an additive comprising hydrocarbon resin.

2. The label according to claim 1 , wherein an amount of hydrocarbon resin is between 5 and 40 wt-%, preferably between 10 and 30 wt-%, most preferably between 5 and 25 wt-% or between 10 and 25 wt-%.

3. The label according to claim 1 or 2, wherein the facestock layer is non- oriented.

4. The label according to any of the preceding claims, wherein the haze of the facestock layer is less than 60%, preferably less than 50, and most preferably less than 30%.

5. The label according to any of the preceding claims, wherein the label is a pressure sensitive label.

6. A use of the label according to any of the claims 1 - 5 for labelling of an item.

7. A facestock of a label, wherein the facestock comprises a plastic film comprising at least linear low density polyethylene or high density polyethylene, and an additive comprising hydrocarbon resin.

8. The facestock according to claim 7, wherein an amount of hydrocarbon resin is between 5 and 40 wt-%, preferably between 10 and 30 wt-%, most preferably between 5 and 25 wt-% or between 10 and 25 wt-%.

9. The facestock according to claim 7 or 8, wherein the facestock layer is non-oriented.

10. The facestock according to any of the preceding claims, wherein the haze of the facestock layer is less than 60%, preferably less than 50, and most preferably less than 30%.

1 1 . A method for producing a label, the method comprising:

providing a facestock layer comprising a plastic film including linear low density polyethylene or high density polyethylene and an additive comprising hydrocarbon resin;

combining an adhesive layer to a release liner and to one side of a facestock layer so as to form a laminated structure;

cutting the laminated structure so as to form individual labels.

12. A combination of an item and a label, wherein the label has been attached to a surface of the item, the label comprising a facestock layer and an adhesive layer against one side of the facestock layer, wherein the facestock layer comprises a plastic film comprising at least linear low density polyethylene or high density polyethylene), and an additive comprising hydrocarbon resin .