EP3030494A1

EP3030494A1 - Process for manufacturing a release liner by plasma deposition

Info

Publication number: EP3030494A1
Application number: EP14749982.6A
Authority: EP
Inventors: Simon Read
Original assignee: Innovia Films Ltd
Current assignee: Innovia Films Ltd
Priority date: 2013-08-09
Filing date: 2014-07-31
Publication date: 2016-06-15
Also published as: WO2015019063A1; GB2516978B; GB2534080B; GB2516978A; GB2534080A; GB201314334D0

Abstract

There is provided a process for manufacturing a release liner, comprising the steps of providing a web of film; subjecting at least a first surface of the film web to a first plasma discharge treatment in the presence of a gas which effectively functionalises the first surface of the film web to provide thereon functional groups which are capable of actively binding to a release compound and/or a precursor thereof; and subsequently depositing a coating of a release compound onto the functionalised first surface of the film web by contacting a vapour comprising the release compound and/or a precursor thereof with the functionalised first surface during a second plasma discharge treatment.

Description

PROCESS FOR MANUFACTURING A RELEASE LINER BY PLASMA

DEPOSITION

The present invention relates to a process for manufacturing a release liner. More specifically, it relates to a process for manufacturing a release liner using plasma discharge treatment.

Release liners are used in a variety of applications. In particular, release liners are used with adhesive labels, for example pressure sensitive adhesive labels, and with packaging films. Release liners are generally made up of a substrate and a release coating. Typical release coatings are formed from waxes, silicones or fluoropolymers. The release coating aids the removal of the release liner from the adhesive surface to which it is attached.

It is known in the art to manufacture release liners by applying a release coating to a substrate using wet-chemical coating processes, for example solvent-based wet- chemical coating or aqueous-based wet-chemical coating. However, solvent-based wet-chemical coating involves the use of volatile organic compounds which are expensive and harmful to the environment. Furthermore, it is often difficult to form a release coating of even thickness using wet-chemical coating methods.

As an alternative to wet-chemical coating processes, release liners have been manufactured using plasma discharge treatment to deposit a release coating onto a substrate. This avoids the use of harmful volatile organic compounds and can be run as a continuous process. Plasma discharge treatment tends to be carried out in the presence of an inert gas, for example a noble gas such as argon, or nitrogen. EP 1 978 067 describes a release liner for use in a pressure-sensitive adhesive sheet comprising a release layer on a substrate, wherein the release liner is obtainable by a process comprising the steps of: providing a substrate; producing an atmospheric pressure plasma discharge in the presence of a gas; exposing the substrate to said atmospheric pressure plasma discharge; introducing a liquid aerosol comprising a precursor into said atmospheric pressure plasma discharge, thereby forming a release layer on the substrate; and curing the release layer on the substrate.

EP 1 816 231 describes a process for producing a fluorocarbon film chemically bonded to a substrate surface, comprising (a) applying a plasma to a substrate surface in a continuous or pulse manner to form active points on the substrate surface; and (b) applying plasma to the substrate surface in a continuous or pulse manner in the presence of a gas of a fluorocompound represented by the formula CxFy and/or CxFyOz under such a condition that active species impinge on the substrate surface at a relatively lower collision energy than in (a).

US 2008/0063811 describes a method of adjusting a surface characteristic of a substrate comprising: providing a substrate; and performing an atmosphere pressure plasma process on the surface of the substrate to form a film layer on the surface of the substrate, so as to adjust the surface energy of the substrate, wherein a process gas of the atmosphere pressure plasma process comprises a surface modifying precursor, a carrier gas and a plasma ignition gas, wherein the surface modifying

2 precursor is selected from fluorosilane, potysiloxane and a combination thereof, and the ratio of fluorosilane to polysiloxane is between 0 and 1.

However, there are numerous problems associated with the prior art processes, for example, the release coating tends to be weakly bonded to the substrate. Further to this, the release coating includes low molecular weight species which migrate to the opposite surface of the substrate. This is particularly problematic when the release liner is wound into a roll since it can result in the contamination of the material attached to the release liner, for example a label facestock film, which may cause printing issues. Additionally, the release liner will tend to have a release force which is insufficient for most high speed applications.

Thus, there is a need for a process for manufacturing a release liner which does not suffer from the problems of the prior art. From the description that is to follow, it will become apparent how the present invention addresses the deficiencies associated with the prior art processes, while presenting numerous additional advantages.

According to a first aspect of the present invention, there is provided a process for manufacturing a release liner, comprising the steps of:

a. providing a web of film;

b. subjecting at least a first surface of the film web to a first plasma discharge treatment in the presence of a gas which effectively functionalises the first surface of the film web to provide thereon functional groups which are capable of actively binding to a release compound and/or a precursor thereof; and

3 c. subsequently depositing a coating of a release compound onto the functionalised first surface of the film web by contacting a vapour comprising the release compound and/or a precursor thereof with the functionalised first surface during a second plasma discharge treatment.

'Release liner" is a well-known term of art in the pressure sensitive adhesive label industry. A 'release liner^* typically comprises a substrate and a coating of a release compound which provides a release effect against an adhesive surface to which it is attached, thus aiding the removal of the release liner from the adhesive surface.

The inventors of the present invention have surprisingly found that the process of the present invention results in the coating of release compound being more strongly bonded to the surface of the film web. Without wishing to be bound by any such theory, the inventors of the present invention believe that the first plasma treatment functionalises the surface of the film web to provide reactive functional groups thereon. These functional groups then covalently bond to the release compound and/or precursor thereof during the second plasma discharge treatment. Thus, producing a release liner in which the coating of release compound is strongly bonded to the surface of the film web.

Due to the strong bond between the coating of release compound and the surface of the film web, the tendency of the release compound to migrate to the opposite surface of the release liner is significantly reduced, if not eliminated. Further to this, the release force of the release liner has been found to increase.

4 Step b. and step c. may be carried out within the same reactor. For example, a single reactor with a first and a second plasma treatment zone which the film web sequentially passes through. Alternatively, step b. and step c. may be carried out in different reactors.

The first and second plasma discharge treatments may be atmospheric pressure plasma discharge treatments. Preferably, the atmospheric pressure plasma discharge treatment is a dielectric barrier discharge (DBD) treatment.

The first and second plasma discharge treatments may be carried out in the presence of an inert carrier gas, for example a noble gas such as argon, and/or nitrogen. The gas in step b. may comprise at least one functional agent Preferably, the functional agent is selected from ammonia, 1 ,2-butadiene, 1 ,3-butadiene, 1 ,3- hexafluorobutadiene, 1-butene, 1-butyne, 2,2-dimethylpropane, c/s-2-butene, trans- 2-butene, acetylene, nitrous oxide, dimethylamine, ethylamine, methyl vinyl ether, methylamine, trimethylamine, carbon dioxide, carbon monoxide and hydrogen.

The functional agent may be present in an amount of from about 10 ppm to about 20000 ppm. Preferably, the functional agent is present in an amount of from about 200 ppm to about 5000 ppm.

S The functional agent effectively functionallses the first surface of the film web to provide thereon functional groups which are capable of actively binding to a release compound and/or precursor thereof. The functional groups may include ketones, aldehydes, glyoxyls, amides, amines, hydroxides, nitrides and/or vinyls.

It has unexpectedly been found by the inventors of the present invention that the presence of a functional agent in the first plasma discharge treatment results in the grafting of functional groups on the surface of the film web which form strong covalent bonds with the release compound during the second plasma discharge treatment. Thus, forming a release compound coating which is strongly bonded to the surface of the film web.

The gas in step b. may comprise at least one oxidising agent such as oxygen, ozone, carbon dioxide, carbon monoxide, nitric and nitrous oxides or sulphur oxide, dioxide or trioxide. The oxidising agent may be present in an amount of from about 10 ppm to about 20000 ppm. Preferably, the oxidising agent is present in an amount of from about 200 ppm to about 5000 ppm.

The gas in step b. may comprise at least one cross-linker, for example, an unsaturated hydrocarbon such as ethylene or propylene. This is particularly advantageous when the release compound comprises an organosilicone since the cross-linker stabilises the organosilicone release compound. The cross-linker may be present in an amount of from about 10 ppm to about 1000 ppm. Preferably, the cross-linker is present in an amount of from about 50 ppm to 200 ppm.

6 In step c. a coating of a release compound is deposited onto the functionalised first surface of the film web by contacting a vapour comprising the release compound and/or a precursor thereof with the functionalised first surface during a second plasma discharge treatment.

The release compound precursor may comprise an organosilicone. The organosilicone may comprise at least one of a silane, a silanol, a silicide and a siloxane. Preferably, the release compound precursor comprises hexamethyl disiloxane (HMDSO), tetramethyl disiloxane (T DSO) and/or 3-glycldyloxyethyl trimethoxysilane.

The release compound itself may comprise a polymer resulting from polymerisation of the release compound precursor. For example, the release compound may comprise poly(dimethyl siloxane), poly(dimethyl dichloro silane), poly(dh inyl silane), poly(diphenyl siloxane), poly(phenylmethyl siloxane), 1 ,3-tetraphenyl 1 ,3-dimethyl disiloxane, and/or 1,3-diphenyl 1 ,2-tetramethyl disiloxane. Preferably, the release compound comprises poly(dimethyl siloxane). Preferably, the release compound and/or the precursor thereof is substantially or entirely non-fluorinated. Where the release compound and/or precursor thereof comprises a fluorinated component, preferably this is present in the vapour in a low quantity, for example less than about 10000 ppm, less than about 5000 ppm, less than about 1000 ppm, less than about 100 ppm, less than about 50 ppm or less than about 10 ppm.

7 The inventors of the present invention have surprisingly found that it is beneficial to reduce or eliminate the amount of fluorinated components in the vapour, since fluorinated components tend to have poor release properties.

The release compound and/or the precursor thereof may be present in the vapour in an amount of from about 10 ppm to about 20000 ppm. For example, the release compound and/or the precursor thereof may be present in the vapour in an amount of from about 10 ppm, about 50 ppm, about 100 ppm, about 200 ppm, about 300 ppm, about 400 ppm, about 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm, about 900 ppm or about 1000 ppm; to about 2000 ppm, about 3000 ppm, about 4000 ppm, about 5000 ppm, about 6000 ppm, about 7000 ppm, about 8000 ppm, about 9000 ppm, about 10000 ppm, about 15000 ppm or about 20000 ppm. Preferably, the release compound is present in the vapour in an amount of from about 200 ppm to about 5000 ppm.

The inventors of the present invention have found that it may be advantageous to use a vapour comprising the release compound and/or the precursor thereof in an amount of from about 10 ppm to about 20000 ppm, since in doing so, a nano-coating of the release compound may be deposited on the first surface of the film web. More specifically, it has been found that it may be possible to deposit a nano-coating of release compound with a thickness that is much less than that formed using prior art techniques, for example using a liquid aerosol.

8 The above ranges with respect to the quantity of release compound and/or precursor thereof, or the quantity of the fluorinated component, apply optionally to the vapour as comprised alone or together with the plasma gas. The coating of release compound may be a nano-coating. In this context, the term 'nano-coating' may mean a coating with a thickness up to about 100nm, for example up to about 75nm, about 50nm or about 25nm, or with a thickness of from about 1nm to about 100nm, for example from about 1nm to about 75nm, from about 1nm to about 50nm or from about 1nm to about 25nm. The nano-coating may have a thickness of from about 1nm to about 20 nm, from about 1 nm to about 15 nm, from about 1 nm to about 10 nm, or from about 1 nm to about 5 nm.

The film web may be formed by any process known in the art, including, but not limited to, cast sheet, cast film, or blown film.

The film web may comprise a substrate layer.

The substrate layer may comprise a polyolefin, for example polyethylene, polypropylene, polybutylene, mixtures, blends or copolymers thereof; a polyester, for example polyethylene terephthalate; a polyamide, for example nylon; a polyurethane; a polyvinyl halkJe, for example polyvinyl chloride; an acetate and/or a biopolymer, for example cellulose and/or its derivatives, polylactic acid or potyhydroxyalkanoate.

9 Preferably, the substrate layer comprises polypropylene, for example biaxially oriented polypropylene (BOPP). The BOPP may be prepared as a balanced film using substantially equal machine direction and transverse direction stretch ratios, or can be unbalanced, where the film is significantly more orientated in one direction (MD or TD). Sequential stretching can be used, in which heated rollers effect stretching of the film in the machine direction and a stenter oven is thereafter used to effect stretching in the transverse direction. Alternatively, simultaneous stretching, for example, using the so-called bubble process, or simultaneous draw stenter stretching may be used.

The substrate layer may have a modulus in the range of from about 0.1 GPa to about 10 GPa. More specifically, the substrate layer may have a modulus in the range of from about 0.5 GPa to about 5 GPa. Even more specifically, the substrate layer may have a modulus in the range of from about 1 GPa to about 3 GPa.

Modulus is defined as the ratio of tensile stress to tensile strain as measured using a Tensometer. Young's modulus (E) describes tensile elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis. It is often referred to simply as elastic modulus.

The film web may comprise at least one skin layer. The skin layer is preferably the outermost layer of the film web. The skin layer may be coextruded or laminated onto the substrate layer. Alternatively, the skin layer may be applied by coating techniques, including extrusion coating. The skin layer may comprise a polyolefln for example polyethylene, polypropylene, polybutylene, mixtures, blends or copolymers thereof; a polyester, for example polyethylene terephthalate; a polyamide, for example nylon; a polyurethane; a polyvinyl halide, for example polyvinyl chloride; an acetate and/or a biopolymer, for example cellulose and/or its derivatives, polylactic acid or polyhydroxyalkanoate.

Additionally or alternatively, the skin layer may comprise an ethylene-propylene copolymer (EPM), an ethylene propylene-diene monomer copolymer (EPD ), polybutadiene, polyisoprene, a styrene-butadiene copolymer, a styrene-isoprene copolymer, a urethane, a polyester and/or mixtures or blends thereof.

Preferably, the skin layer comprises an ethylene-propylene copolymer, an ethylene propylene diene monomer copolymer or amorphous polyester.

The substrate layer and/or the skin layer may be biodegradable and/or compostable. This is advantageous as the release liner will have a low carbon footprint.

The substrate layer and/or the skin layer may be recyclable. Advantageously, the entire release liner may be recyclable. Current release liners are often non- recyclable due to the presence of an unacceptably high amount of release compound in/on the liner. However, the release liner formed from the process of the present invention may comprise a nano-coating of release compound which results in a low dilution factor of the release compound. This may allow the entire release liner to be recycled. The substrate layer and/or the skin layer may have a radio carbon content i.e. the substrate layer and/or skin layer may be formed, at least in part, from a renewable material. The substrate layer and/or the skin layer may have a radio carbon content of at least about 10pMC, or at least about 20pMC, or at least about 30pMC, or at least about 40pMC, or at least about 50pMC, or at least about 60pMC, or at least about 70pMC, or at least about 80pMC, or at least about 90p C, or at least about 100pMC.

'pMC in this connection means 'per cent modem carbon". Advantageously, where the substrate layer and/or the skin layer has a radio carbon content, the release liner may have a low carbon footprint.

The skin layer may have a thickness of from about 0.01 μm to about 10μm. Preferably, the skin layer has a thickness of from about 0.1 μm, about 0.2μm, about 0.3μm, about 0.4μm, about Ο.5μm, about 0.55μm, about Ο.βμm, about 0.65μΓΤΐ, about 0.7μm, about 0.75μm, about 0.8μm, about 0.85μm, about 0.9μm or about 0.95μm; to about 1μm, about 1.5μm, about 2μm, about 2.5μm, about 3μm, about 3.5μm, about 4μm, about 4.5μm or about 5μm. For example, the skin layer may have a thickness of from about 0.1μm to about 5μm, from about 0.5μm to about 3μm, from about 0.7μm to about 2μm or from about 0.8μm to about 1.5μm. The skin layer may have a modulus of at least about 1% less than the modulus of the substrate layer. More preferably, the skin layer has a modulus of at least about 5% less than the modulus of the substrate layer. More preferably still, the skin layer has a modulus of at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80% or at least about 90% less than the modulus of the substrate layer.

The ratio of the modulus of the substrate layer to the modulus of the skin layer may be from 10-30:1 ; from 10-29:1; from 12-28:1; from 13-27:1; from 14-26:1; from 15- 25:1 ; or from 10-25:1.

It has been found that by altering the modulus of the skin layer with respect to the modulus of the substrate layer, the release force of the release liner can be manipulated. Thus, it is possible to manufacture a release liner with a release force tailored to its application.

The release force required to remove the release liner from an adhesive surface to which it is attached may be from about 0.01 g/cm to about 50 g/cm. Preferably, the release force is from about 0.1 g/cm, about 0.2 g/cm, about 0.3 g/cm, about 0.4 g cm, about 0.5 g/cm, about 0.6 g/cm, about 0.7 g/cm, about 0.8 g/cm or about 0.9 g/cm; to about 1 g/cm, about 2 g/cm, about 3 g cm, about 4 g/cm, about 5 g/cm, about 6 g/cm, about 7 g/cm, about 8 g/cm, about 9 g/cm or about 10 g/cm. For example, the release force may be from about 0.1 g/cm to about 3 g/cm, from about 0.1 g/cm to about 2 g/cm or from about 0.1 g/cm to about 1 g/cm. The release liner manufactured by the process of the present invention can be of a variety of thicknesses depending on the application requirements. The release liner may be from about 5μm, about 10μm, about 15μm, about 20μm, about 25μm, about 30μm to about 40μm, about 50μm, about 75μm, about 100μm, about 125μm, about 150μm, about 200μm or about 250μm.

Release liners manufactured by the process of the present invention may be particularly useful in applications such as pressure sensitive adhesive labels/tapes/packaging/vehicle decal films.

According to a second aspect of the present invention, there is provided a release liner obtained or obtainable by the process as hereinbefore described.

According to a third aspect of the present invention, there is provided a release liner comprising a film functionalised at its surface by one or more functional groups selected from ketone, aldehyde, glyoxyl, amide, amine, hydroxide, nitride and vinyl, and a release compound bonded thereto by means of a chemical bond with the functional group. It should be noted that all features of the first aspect of the invention also relate to the second and third aspects of the invention.

The present invention is more specifically described with reference to the following figures: is a schematic representation of a web of film passing though two sequential plasma discharge treatments wherein the functional agent is injected prior to the electrode Figure 2: is a schematic representation of a web of film passing through two sequential plasma discharge treatments wherein the functional agent is injected through the electrode

In Figure 1 , a web of film 11 is fed into a plasma discharge reactor with the aid of roller 12. Fluid injector 13 injects a functional agent in liquid form. The functional agent is vaporised and carried by an inert carrier gas to the first discharge gap 15. The first discharge gap 15 is defined as the space between the electrode 14 and roller 12. The surface of the web of film 11 positioned within the first discharge gap 15 is functionalised such that functional groups are grafted thereto.

Fluid injector 16 injects a vapour comprising a release compound precursor. The vapour comprising the release compound precursor is carried by the inert carrier gas to second discharge gap 18. The second discharge gap 18 is defined as the space between electrode 17 and roller 12. The web of film 11 is fed from the first discharge gap 15 into the second discharge gap 18 where the release compound precursor is covalently bonded to the functional groups on the surface of the web of film 1 . Thus, a coating of release compound is deposited and securely bonded to the surface of web of film 11. In Figure 2, a web of film 21 is fed into a plasma discharge reactor with the aid of roller 22. An inert carrier is passed between the first discharge gap 25, which is defined as the space between the electrode 24 and roller 22. Fluid injector 23 injects a functional agent in liquid form through electrode 24 and into the plasma discharge gap 25 where it is vaporised. The surface of the web of film 21 positioned within the first discharge gap 25 is functionalised such that functional groups are grafted thereto.

Fluid injector 26 injects a vapour comprising a release compound precursor through electrode 27 and into the second plasma discharge gap 28. The second discharge gap 28 is defined as the space between electrode 27 and roller 22. The web of film 21 is fed from the first discharge gap 25 into the second discharge gap 28 where the release compound precursor is covalently bonded to the functional groups on the surface of the web of film 21. Thus, a coating of release compound is deposited and securely bonded to the surface of the web of film 21.

Example 1

A web of film having a substrate layer of propylene homopolymer and coextruded skin layers of ethylene propylene copolymer (EPM) each having a thickness of approximately 1 μm is manufactured by means of a bubble process. The three-layer film web has an overall thickness of 30μm.

The film web is subjected to a first dielectric barrier discharge treatment in the presence of 500 ppm ammonia in a nitrogen carrier gas. The power used is 65 w.min/m² and the speed is 50m min. The film web is then subjected to a second dielectric barrier discharge treatment in the presence of 500 ppm hexamethyl disiloxane in nitrogen. Again, the power used is 65 w.min/m² and the speed is 275m/min. The first and second dielectric barrier discharge treatments are carried out in the same reactor.

A nano-coating of poiy(dimethyi siloxane) is deposited on the surface of the film web, having a thickness of 50nm as measured by cross-sectioning the film and putting it under a scanning electron microscope (SEM) in EDX mode.

Claims

CLAIMS process for manufacturing a release liner, comprising the steps of:

a. providing a web of film;

c. subsequently depositing a coating of a release compound onto the functionalised first surface of the film web by contacting a vapour comprising the release compound and/or a precursor thereof with the functionalised first surface during a second plasma discharge treatment. A process according to Claim 1 , wherein step b. and step c. are carried out within the same reactor. A process according to Claim 1 , wherein step b. and step c. are carried out in different reactors. A process according to any one of claims 1 to 3 wherein the first and second plasma discharge treatments are atmospheric pressure plasma discharge treatments. A process according to Claim 4, wherein the atmospheric pressure plasma discharge treatment is a dielectric barrier discharge treatment. A process according to any one of claims 1 to 5, wherein the first and second plasma discharge treatments are carried out in the presence of an inert carrier gas. A process according to Claim 6, wherein the inert carrier gas comprises a noble gas such as argon, and/or nitrogen. A process according to any one of claims 1 to 7, wherein the gas in step b. comprises at least one functional agent. A process according Claim 8, wherein the functional agent is selected from ammonia, 1 ,2-butadiene, 1 ,3-butadiene, 1 ,3-hexafluorobutadiene, 1-butene, 1-butyne, 2,2-dimethylpropane, c/s-2-butene, irans-2-butene, acetylene, nitrous oxide, dimethylamine, ethylamine, methyl vinyl ether, methylamine, trimethylamine, carbon dioxide, carbon monoxide and hydrogen. . A process according to any one of claims 1 to 9, wherein the release compound precursor comprises an organosilicone. . A process according to Claim 10, wherein the organosilicone comprises at least one of a silane, a silanol, a silicide and a siloxane. A process according to any one of clains 1 to 11 , wherein the release compound precursor comprises hexamethyl disiloxane (HMDSO) and/or tetramethyl disiloxane (TMDSO). A process according to any one of claims 1 to 12, wherein the release compound comprises poly{dimethyl siloxane). A process according to any one of claims 1 to 13, wherein the release compound and/or the precursor thereof is substantially or entirely non- fluorinated. A process according to any one of claims 1 to 14, wherein the release compound and/or the precursor thereof is present in the vapour in an amount of from about 10 ppm, about 50 ppm, about 100 ppm, about 200 ppm, about 300 ppm, about 400 ppm, about 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm, about 900 ppm or about 1000 ppm; to about 2000 ppm, about 3000 ppm, about 4000 ppm, about 5000 ppm, about 6000 ppm, about 7000 ppm, about 8000 ppm, about 9000 ppm, about 10000 ppm, about 15000 ppm or about 20000 ppm. A process according to Claim 15, wherein the release compound and/or the precursor thereof is present in the vapour in an amount of from about 200 ppm to about 5000 ppm. . A process according to any one of claims 1 to 16, wherein the coating of the release compound is a nano-coating. A process according to Claim 17, wherein the nano-coating has a thickness of: a. From about 1 nm to about 10Onm;

b. From about 1 nm to about 75nm

c. From about 1 nm to about 50nm

d. From about 1 nm to about 25nm;

e. from about 1 nm to about 20nm;

f. from about 1nm to about 10nm; or

g. from about 1 nm to about 5nm. A process according to any one of claims 1 to 18, wherein the film web comprises a substrate layer. A process according to Claim 19, wherein the substrate layer comprises a polyolefin, for example polyethylene, polypropylene, polybutylene, mixtures, blends or copolymers thereof; a polyester, for example polyethylene terephthalate; a polyamide, for example nylon; a polyurethane; a polyvinyl halide, for example polyvinyl chloride; an acetate and/or a biopolymer, for example cellulose and/or its derivatives, potylactic acid or polyhydroxyalkanoate. . A process according to Claim 20, wherein the substrate layer comprises polypropylene. A process according to any one of claims 1 to 21 , wherein the film web comprises at least one skin layer. A process according to Claim 22, wherein the skin layer comprises a polyolefin for example polyethylene, polypropylene, polybutylene, mixtures, blends or copolymers thereof; a polyester, for example polyethylene terephthalate; a polyamide, for example nylon; a polyurethane; a polyvinyl halide, for example polyvinyl chloride; an acetate and/or a biopolymer, for example cellulose and/or its derivatives, polylactic acid or polyhydroxyalkanoate. A process according to Claim 22, wherein the skin layer comprises ethylene- propylene copolymer, ethylene propylene-diene monomer copolymer, polybutadiene, polyisoprene, a styrene-butadiene copolymer, a styrene- isoprene copolymer, a urethane, a polyester and/or mixtures or blends thereof. A process according to any one of claims 19 to 24, wherein the substrate layer and/or the skin layer has a radio carbon content. A process according to Claim 25, wherein the substrate and/or skin layer has a radio carbon content of at least about 10pMC, or at least about 20 pMC, or at least about 30 pMC, or at least about 40 pMC, or at least about 50 pMC, or at least about 60 pMC, or at least about 70 pMC, or at least about 80 pMC, or at least about 90 pMC, or at least about 100 pMC.

22 A process according to any one of claims 19 to 26, wherein the substrate layer and/or the skin layer is recyclable. A process according to any one of claims 1 to 27, wherein the release liner is recyclable. A release liner obtained or obtainable by the process of any one of claims 1 to 28. A release liner comprising a film functionalised at its surface by one or more functional groups selected from ketone, aldehyde, glyoxyl, amide, amine, hydroxide, nitride and vinyl, and a release compound bonded thereto by means of a chemical bond with the functional group.

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