WO2014108519A1

WO2014108519A1 - Polycarbonates

Info

Publication number: WO2014108519A1
Application number: PCT/EP2014/050421
Authority: WO
Inventors: Irene Helland; Asbjørn HOLT; Harry ØYSAED; Siw Bodil Fredriksen
Original assignee: Norner Ip As
Current assignee: Norner Ip As
Priority date: 2013-01-11
Filing date: 2014-01-10
Publication date: 2014-07-17
Anticipated expiration: 2015-07-11
Also published as: GB201300539D0

Abstract

A film comprising a blend of at least one polycarbonate and at least one fluoropolymer.

Description

Polycarbonates

This invention relates to polycarbonate films. These films may be coated onto or may coat a substrate such as a paper substrate or be free of a substrate. The films of the invention show excellent transparency as well as good oxygen barrier properties and very low water vapour transmission properties. Moreover, they are biodegradable and recyclable. Most importantly, through the addition of a fluoroelastomer as an anti-blocking agent we prevent the blocking that typically may occur in these rather sticky films e.g. between two film surfaces or between film surfaces and an object in contact with said film.

Polymer films are now ubiquitous in the packaging industry. Whether as free films or coatings on another substrate such as paper, these films have wide utility in packaging everything from food and beverages to medical supplies and household goods. The vast majority of these films are however based on polyolefins.

It is well known in the art therefore to prepare polyolefin films or to coat paper with a wide range of polyethylene polymers such as low density polyethylene (LDPE) and high density polyethylene (HDPE). The use of polypropylenes for extrusion coating applications is also well known. These polymers can be mixed with fillers like talc or titanium dioxide to improve the properties of the extrusion coated material.

With the increasing oil price and environmental concerns however, the use of fossil fuel based polyolefins is becoming less attractive. Moreover, the human population is increasingly under pressure to recycle packaging materials as far as possible. Whilst packaging such as glass can now be recycled readily, polyolefins and in particular coated packaging with multiple layers of widely different materials such as Tetra Pak type cartons remains one area where recycling poses a challenge. It would be very useful to provide polymer films and in particular, a film coated paper substrate which is readily recyclable.

A further issue with polyolefins films is the fact that these films are not biodegradable. Providing packaging that is more biodegradable would be advantageous. The present inventors therefore propose the use of polycarbonates and in particular, poly(alkylene carbonates), in polymer films and as coatings for substrates such as paper.

There are two main types of polycarbonates. Those based on bisphenol A type monomers have found wide utility in applications such as data storage, construction and electrical components. However, bisphenol A is not a monomer which is desired for use in household applications and in particular for food contact. For food contact, poly(alkylene carbonates) would be preferred. Until recently, poly(alkylene carbonates) have had limited commercial application. They have been used as sacrifice materials in the electronics industry. Other applications of these polymers have been limited by their relative thermal instability and high costs of production.

The present inventors have realised that polycarbonates offer

environmentally friendly potential. The use of carbon dioxide in the formation of polycarbonates provides a useful sink for carbon dioxide and therefore these carbon capture polymers offer an environmentally friendly alternative to fossil based materials such as a polyethylene and polypropylene. There are therefore significant benefits to using polyalkylene carbonates industrially.

We have surprisingly determined that polycarbonates act as barrier layers, especially on paper substrates, in particular with an advantageous low sensitivity to water, offering excellent water vapour transmission and oxygen barrier properties. We have also shown that poly(alkylene carbonates) may be safely combined with food as their migration is low. Moreover, the inventors have determined that polycarbonates are easily recyclable and biodegradable. This makes them ideal for use as polymer films, e.g. as layers on paper substrates and on other substrates like glass and metal.

The use of polycarbonates as coatings on paper is only very generically known. In EP-0803532, polyethylene carbonate with a low ether linkage content is suggested as an oxygen barrier layer in a food packaging material. The inventors teach that low ether content improves oxygen barrier properties and the option of using that layer on its own or in a multilayer structure is mentioned. US4851507 describes polyalkylene carbonate terpolymers which are melt processable without thermal degradation. These can be used in packaging.

WO2011/005664 describes structurally precise poly(propylene carbonate) compositions or blends with alleged improved properties. These structurally precise polymers are suggested for use in essentially all possible applications of a polymer from film formation to moulded articles. Processing by any of injection moulding, extrusion, melt processing, blowing, thermoforming, foaming, and casting are all generically suggested (p. 29 1. 1-12). The major benefit of these materials is allegedly better thermal stability hence less degradation during processing (p. 39 1 18-19) compared to less structurally precise poly(alkylene carbonates) like for example the commercially available QPAC40 poly(propylene carbonate). The use of these materials in extrusion or coextrusion coatings onto plastics, metals, textiles or paper webs (p. 32 1. 16-18) is just one among the multitude of options mentioned.

These precisely controlled polymers with chain architecture with > 80 % head to tail linkages are costly to produce however and can only be prepared with certain costly catalysts.

The present inventors are the first to substantively research the use of poly(alkylene carbonates) in general, and polypropylene carbonates specifically, as barrier layers in conjunction with paper substrates for applications in packaging and as polymer films in general.

The inventors have found that the polycarbonates provide excellent haze (i.e. low haze, excellent transparency and a minimum of light diffraction) and gloss properties. Compared to polyolefms, the use of PACs provides an environmentally benign solution by the use of C0₂ as raw material.

Most importantly, the films and coated substrates of this invention can be recycled. The inventors have realised that polycarbonate coatings are susceptible to hydrolysis thus enabling separation and recovery from the cellulose substrate.

Recovery and possible reuse of low molecular weight compounds which are formed during a hydrolysis reaction, for example, propylene carbonate and/or propylene glycol is also possible. It is very difficult to separate polyolefms from a paper substrate. Alternatively, when PACs are subjected to high temperature the PAC may convert into a cyclic alkylene carbonate type molecule. This therefore forms an alternative process for separating the substrate and the PAC. The cyclic alkylene carbonate can find application as such or may be converted back to a reusable monomer.

The inventors have found however, that a problem with the polycarbonate films is their stickiness. If a film is too sticky it is unacceptable to the consumer and is also difficult to produce, handle and store. Also, sticky films have a tendency to stick to surfaces and a tendency to stick together, a phenomenon called blocking. The addition of anti-blocking agents to reduce stickiness is therefore needed. There are many conventional anti-blocking agents known in the field of polyolefins. Silica is frequently employed. Other mineral anti-blocking agents include talc, clay and calcium carbonate.

There are also many organic anti-blocking agents such as fatty acid amides or polyglycerol ester type agents. However, the addition of conventional mineral and organic anti-blocking agents is less successful with polycarbonates.

The present inventors have therefore devised a specific additive package which offers anti-blocking properties in the context of polycarbonates. This antiblocking property can be achieved without loss of transparency. In particular, the inventors teach the use of fluoroelastomers as very effective anti-blocking agents for polycarbonates.

Fluoroelastomers are well known commercial polymers and they are widely used in the processing of polyolefins. They are added therefore as polymer processing aids (PPA). They are added to help the extrusion process in polyolefin formulation where very high molecular weights are a problem for extrusion.

Fluoroelastomers are used for polyolefins of very high melt viscosity to reduce pressure in extrusion head at given extrusion rate. The generally accepted explanation for this is that the fluoroelastomer changes the surface properties of die through coating the metal of die with a thin layer of fluoroelastomer, and thus do not act through any modification of the polyolefin surface. There is no reason however, to add such compounds to polycarbonates as the molecular weights encountered may be much less and the extrusion of these polymers much easier.

There is no suggestion that these fluoropolymers might have utility, generally at much higher concentrations than are used as polymer processing aids anyway, as anti-blocking and anti-sticking agents for polycarbonates.

Summary of Invention Viewed from one aspect the invention provides a film comprising a blend of at least one polycarbonate and at least one fluoropolymer such as a fluoroelastomer.

Viewed from another aspect the invention provides a substrate having a film applied thereon, wherein said film comprises at least one polycarbonate and at least one fluoropolymer.

Viewed from another aspect the invention provides the use of a film as hereinbefore defined in packaging, such as for food, beverages, pharmaceuticals or medical supplies.

Viewed from another aspect the invention provides a process for the preparation of a film as hereinbefore described comprising blending at least one fluoropolymer with at least one polycarbonate and forming the mixture into a film.

Viewed from another aspect the invention provides a process for the preparation of a film as hereinbefore described comprising blending at least one fluoropolymer with at least one polycarbonate and extruding the mixture to form a film.

Viewed from another aspect the invention provides a composition comprising a blend of at least one poly(alkylene)carbonate and at least one fluoropolymer, such as an extruded article, e.g. a moulded article or thermoformed article.

Detailed Description of the Invention

Polycarbonate This invention relates to polycarbonate films having fluoropolymer antiblocking agents added thereto.

The polycarbonates of the invention can be any known polycarbonate well known in the art such as those based on bisphenol A. Polycarbonates of the invention therefore contain repeating carbonate groups (-0-(C=0)-0-) in the backbone. Well known commercial polycarbonates can be formed by the copolymerisation of bisphenol A and phosgene. Such polycarbonates therefore comprise also a repeating bi-phenyl linker in the backbone of the polycarbonate. This bisphenol linker can be adapted to carry a variety of substituents such as alkyl substituents. Preferably, polycarbonates which contain an aromatic repeating unit in the backbone of the molecule are formed from bisphenol A as a monomer along with phosgene.

However, polycarbonates of this invention are preferably not based on an aromatic group in the backbone of the molecule and are preferably synthesised in the absence of phosgene. These polycarbonates will be called poly(alkylene carbonates) herein. The term poly(alkylene carbonate) (PAC) is used to indicate that the polycarbonates of this invention are free of aromatic groups in the main backbone of the polymer. They can however, contain cyclic, non aromatic groups in the backbone. These cyclic groups can be saturated or unsaturated. The

poly(alkylene carbonates) called PACs herein, of the invention are not therefore based on bisphenol-A type products and they are produced in a phosgene-free way. The PAC's are otherwise broadly defined.

The backbone of the PACs of the invention contains 0-C(=0)-0 linkages along with non aromatic links between those linkages.

The backbone of the polymer can however, carry a wide variety of substituents (side chains) including aromatic side groups and various functional groups.

The PAC is preferably one formed from the polymerisation of carbon dioxide with a cyclic ether or perhaps from the ring opening of a cyclic carbonate. . The term cyclic ether is used here to cover not only epoxides (3-membered cyclic ethers) but also larger cyclic ethers such as those based on 4-6 membered rings or more. Preferably, the cyclic ether is an epoxide such as alkylene based epoxide. For example, the reaction of the four membered ring ether oxirane with carbon dioxide gives polytrimethylene carbonate (Darensbourg, D. J. Inorg. Chem. 2010, 49, 10765-10780).

Suitable (non epoxide) cyclic ether monomers are therefore of formula (II)

where a is 0-2 and R₅ is the same as Ri below. The number of R₅ groups which may be present may be the same as the number of carbon atoms in the ring of the cyclic ether (e.g. up to 5). Preferably however, only 1 such group is present, if at all.

Alternatively, PACs can be formed during the ring opening of a cyclic carbonate with a variety of catalysts as described in e.g. Suriano Polym. Chem., 201 1 , 2, 528-533; Endo et al. Journal of Polymer Science Part A: Polymer

Chemistry 2002, 40(13), 2190-2198.

As long as the backbone of the PAC does not contain an aromatic group within the backbone then any method can be used to form the PACs of the invention.

It is most preferred however if the PACs are obtained through the

polymerisation of a cyclic ether with carbon dioxide and especially through the polymerisation of carbon dioxide and an epoxide. Preferably, the epoxide which forms the poly (alkylene carbonates) of the invention is of formula (I):

wherein Ri to R4 are each independently hydrogen; Ci_io alkyl optionally interrupted by one or more heteroatoms selected from O or N; C2_io-alkenyl optionally interrupted by one or more heteroatoms selected from O and N; C6-10- aryl; or

R₂ and R₃ taken together can form a non aromatic, cyclic group having 4 to 8 atoms in the ring, said ring optionally comprising one or more heteroatoms selected from O or N;

said non aromatic cyclic group or any of Ri to R₄ being optionally substituted by one or more Ci_₆ alkyl groups, C₂_io-alkenyl groups, C6-10-aryl groups, -OCi_6 alkyl groups or OH.

It is preferred if at least one, preferably at least two of Ri to R₄ are hydrogen. Ideally, the carbon atoms attached to the epoxide ring should also be bonded directly to a hydrogen atom. In a highly preferred embodiment, three of Ri to R₄ are hydrogen, and one is an alkyl group, preferably a methyl group, thus forming propylene oxide, or all four are hydrogen (thus forming ethylene oxide).

When not hydrogen, it is preferred if substituents Ri to R₄ are Ci_6-alkyl or C₂_6-alkenyl groups. If an alkenyl group is present, the double bond should preferably not conjugate the epoxide. Any alkenyl group should preferably contain at least 3 carbon atoms and the double bond should be at least beta to the epoxide carbon. Alternatively, it is also preferred that one of the substituents is an alkoxy group (thus forming for example glycidyl ethers).

If R₂ and R₃ are taken together, they preferably form a 5 or 6 membered ring with the carbon atoms to which they are attached, especially a carbocyclic ring. That ring can be saturated or monounsaturated, preferably saturated. A 6-membered ring is in particular preferred.

In formula (I), it is preferred if no heteroatoms other than the oxygen of the epoxide are present. A preferred monomer is therefore of formula (II)

where R₂> and R₃> are independently hydrogen, CI -6 alkyl, phenyl or R₂> and R_3' taken together form a 5 or 6 saturated or monounsaturated carbocyclic ring, preferably where one or both of R₂> and R₃> are hydrogen, R_2' is hydrogen and R₃> is methyl. Preferred epoxide monomers include limonene oxide, styrene oxide, propylene oxide, ethylene oxide or cyclohexene oxide, i.e. the compound

The use of propylene oxide is especially preferred.

It will be appreciated that the polymerisation reaction takes place in the presence of carbon dioxide. In an ideal scenario, the PAC of the invention is one such as

where n is 0 to 4 and R is a side chain such as defined above for Ri to R4. In articular the PAC of the invention may be:

It will be appreciated, however, that when the epoxide and the carbon dioxide are polymerised, the structure of the polymer which forms may not be a perfectly alternating ABABA type polymer as depicted here. The invention encompasses the polymer which forms when these two monomers are polymerised. The polymer regioregularity may be described by the "head to tail" ratio as used in the conventional sense for polyalkylene carbonates and determined as described e.g. in Lednor et al. J. Chem. Soc. Chem. Commun. 1985, 598-599. Further, it is very common for ether linkages to be present in PACs. It is preferred if the content of polymer chains containing ether linkages is less than 15 wt%, preferably less than 10 wt%. The ether content can be determined by 1H NMR e. g. as described in Luinstra, G. Polymer Reviews, 48: 192-219, 2008.

It is of course possible for a mixture of cyclic ether monomers to be used to produce the poly(alkylene carbonate) used in the invention.

It is also possible for other monomers to be present in the PACs of the invention. For example, a difunctional or poly functional epoxide can be present during the polymerisation reaction in addition to the monomers described above. Typically this will be added in small amounts, e.g. less than 50 wt% of the total amount of epoxide monomers in the reaction mixture as a whole, preferably less than 10 wt% of the total amount of epoxide monomers.

Multifunctional epoxides of interest include 4-vinylcyclohexene dioxide and other epoxides carrying an epoxide (CH₂CH₂0) side chain. Such monomers introduce an epoxide group into side chain of the PAC (Cyriac et al. Polym. Chem. 2011, 2, 950-956). This may allow further increases in Mw and allows the Mw/Mn to be broadened during the polymerisation reaction, and allows a crosslinking reaction involving the pendant group carrying an epoxide group.

It is also within the scope of the invention for other monomers to be used in the manufacture of the PAC. For example, the use of lactone monomers is envisaged. Lactone monomers of interest include β-propiolactone, γ-butyrolactone, δ-valero lactone, ε-caprolactone. The use of lactones typically results in the formation of block polymers (see Huiser et al Macromolecules, 2011, 44 (5), pp 1132-1139, Lu and Huang, Journal of Polymer Science Part A: Polymer Chemistry, Volume 43 (12) 2468-2475, 2005; Hwang et al. Macromolecules 2003, 36, 8210- 8212).

Other alternative monomers include anhydrides such as maleic anhydride (Liu et al. Polymer 2006, 47(26), 8453-8461). Some monomers can therefore provide cross-linkable units into the backbone/side chains of the polymer. In addition the side chains of the PAC can contain groups such as alkenyl groups which can be crosslinked. Preferably however, the PAC is formed from the polymerisation of carbon dioxide and epoxide(s) of formula (I) only. In particular the PAC is poly(propylene carbonate) (PPC), poly(ethylene carbonate) (PEC) or poly(cyclohexene carbonate) (PCHC), most especially polypropylene carbonate. Preferably, the PAC can also be a polymer formed by the polymerisation of C0₂ and at least two different epoxide monomers carrying no substituents or only alkyl substituents, e.g. of formula (I), in particular by the polymerisation of C0₂ and at least two of the monomers propylene oxide, ethylene oxide and cyclohexene oxide. A further option is polycyclohexene- propylene carbonate PCHC-PPC formed from carbon dioxide, propylene oxide and cyclohexene oxide.

The PACs of the invention can be amorphous or potentially semicrystalline. Typically they are amorphous. Preferably they will have a glass transition temperature (Tg) of at least 0°C, preferably at least 10 °C, such as at least 15°C, such as at least 20° C. It will be appreciated that the Tg will depend heavily on the nature of the PAC in question. The higher glass transition temperature is preferred as coatings containing polymers with lower glass transition temperatures are likely to soften and go sticky. By using polymers with a glass transition temperature of 15°C or more, the present inventors seek to minimise stickiness of the coating surface.

The number average molecular weight Mn of the PAC may be at least 1500 g/mol, preferably at least 2000 g/mol. The use of higher Mn PACs is preferred in this invention. Values of at least 10,000, preferably at least 20,000 are therefore preferred. Mn can be measured by gel permeation chromatography.

The Mw/Mn of the PAC is preferably at least 1.1, such as at least 2, preferably at least 3. Mw/Mn is the same as polydispersity index herein. Broader Mw/Mn values are believed to enhance the processability of the materials of the invention.

The Mw of the poly(alkylene carbonates) of the invention may be at least 50,000, preferably at least 100,000, more preferably at least 150,000, especially at least 200,000. The high Mw gives significantly improved melt strength and increased glass transition temperature (Tg).

The skilled man will appreciate that PACs can be end capped. That means that a different group (i.e. formed during or after a polymerisation reaction) can be attached to the end of the polymer chain, for example an ester group. The presence of reactive end-capping groups (i.e. those capable of undergoing a cross-linking reaction such as those containing an alkenyl group) could be valuable in improving the mechanical properties of the film. The invention therefore encompasses PACs that are end-capped with reactive groups or which are not end capped at all or are end capped with non reactive groups.

It will be appreciated that the formation of the PAC may give rise to a well known cyclic carbonate by-product. For example, during the formation of polypropylene carbonate, propylene carbonate is formed as a by-product. That is the compound

It is common to try to remove this by-product but the present inventors have realised that it acts as a plasticiser and can offer some beneficial properties.

Preferably, the amount of carbonate impurity in the PAC of the invention (i.e.

relative to the weight of the PAC) is less than 10 wt%, preferably less than 7 wt%, e.g. 6 wt% or less. In some embodiments, its content can be reduced to less than 2 wt%, especially less than 1 wt%, e.g. 0.5 wt% or less. In some polymers the amounts of carbonate by product are too low to be detected.

As the carbonate by product has a low softening temperature, there is a risk that it contributes to stickiness in the blend. Maintaining a low content of the carbonate by product is therefore favourable.

It is an option however, if there is at least 1 wt% of the carbonate impurity in the PAC, e.g. at least 2 wt%. The carbonate impurity is preferably propylene carbonate but obviously the nature of the impurity depends on the nature of the PAC being formed. Further, it is an option to add other components well known in the art that act as plastizisers.

Catalysts Several catalyst systems are known that catalyze the copolymerisation reaction of epoxides and C0₂. The polymerisation can be catalysed by known catalysts, especially Zn based catalysts, Mg based catalysts or Co based catalysts such as cobalt salen catalysts. The use of zinc and magnesium catalysis, e.g.

heterogeneous or homogeneous mono- or multinuclear Zn catalysis is preferred. Most preferably these carboxylates are zinc glutarates, e. g. as described in

US4789727 and in Ree et al. J. Pol. Sci. Part A.: Polymer Chemistry Vol. 37, 1873- 1876 (1999) or other zinc based catalysts e. g. such as macrocyclic zinc complexes as described in WO2009/130470. Magnesium catalysts are typically macrocyclic magnesium catalysts such as described in WO2009/ 130470. Cobalt based catalysts are typically cobalt salen catalysts as described in WO2010/028362 and in Cyriac et al. Macromol. 2010, 7398-7801. Catalysts may need a cocatalyst as is well known in the art, e. g. as described in WO2010/028362.

Other well known catalysts for PAC formation are based on homogeneous reaction systems and include porphyrin systems such as DMAP. The use of phenoxide catalysts is also a possibility as well as the use of β-diiminate catalysts. As noted above, Co based salen systems are also of interest. A comprehensive discussion of available catalysts can be found in Coord Chem Rev (2011), Klaus et al. and in Kember et al. Chem. Commun. 2011, 47, 141-163. The skilled man is capable of choosing an appropriate catalyst. The catalyst will preferably contain a metal.

The procedures required to polymerise the monomers to form PACs are well known and are described in the literature. PACs are also commercially available products e.g. from Empower Materials. PACs suitable for use in the invention can be purchased commercially, e.g. under the trade name QPAC.

It is not uncommon that residues of other small molecules are also present in the PAC used in the inventions, for example epoxide monomer residues or solvent residues. Typically, such volatiles are present in concentrations lower than 1 wt% percent.

It is most preferred if the PAC used in the invention is a PPC

(poly(propylene carbonate)). Ideally this will contain between 40 and 50% of links derived from carbon dioxide, such as 43 %. This polymer possesses excellent adhesion in laminated paper compositions, high gloss, excellent barrier properties and is very well suited for separation and recycling of paper and polymer.

It is a further preferred feature of the invention that the PAC used is biodegradable and compostable, for example according to EN 13432 and ASTM 6400. Most importantly, it is important for the PAC to be recyclable.

Anti-blocking agent This invention relies on the use of a fluoropolymer, ideally fluoroelastomer antiblocking agent to prevent blocking in polycarbonate films. Fluoroelastomers are fluorocarbon-based synthetic rubbers. Preferred fluoropolymers may be based on atoms of F and C only.

The fluoropolymer useful in the compositions of this invention include amorphous fluoropolymers and thermoplastic fluoropolymers (i.e. semi-crystalline fluoropolymers). Fluoropolymers useful in this invention are fluoropolymers that are normally in the fluid state at room temperature, i.e. 25°C and above, i.e.

fluoropolymers which have Tg values below room temperature and which exhibit little or no crystallinity at room temperature. It is preferred, but not essential, to employ fluoropolymers having a fluorine to hydrogen ratio of at least 1 : 1. The fluorine content of the most preferred fluoropolymers varies between 50 and 80 wt%.

Fluorinated monomers which may be copolymerized to yield suitable fluoropolymers include vinylidene fluoride, hexafluoropropylene,

chlorotrifluoroethylene, tetrafluoroethylene and perfluoroalkyl perfluorovinyl ethers (such as perfluoromethylvinylether). Specific examples of the fluoroelastomers which may be employed include copolymers of vinylidene fluoride and a comonomer selected from hexafluoropropylene, chlorotrifluoroethylene, 1- hydropentafluoropropylene, and 2-hydropentafluoropropylene; copolymers of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene or 1- or 2- hydropentafluoropropylene; and copolymers of tetrafluoroethylene, propylene and, optionally, vinylidene fluoride, all of which are known in the art. In some cases these copolymers may also include bromine-containing comonomers as taught in Apotheker and Krusic, U.S. Pat. No. 4,035,565, or terminal iodo-groups, as taught in U.S. Pat. No. 4,243,770. The latter patent also discloses the use of iodo group-containing fluoroolefin comonomers. When fluorinated monomers are present in these copolymers in certain molar ratios, the glass transition temperature of the polymer is near or below 0°C, and the

compositions are useful elastomers that are readily available articles of commerce.

Semi- crystalline fluoropolymers which may be used in the invention include, but are not limited to poly(vinylidene fluoride), homopolymers and copolymers of tetrafluoroethylene (such as Teflon(R) FEP fluorocarbon resin, and copolymers of tetrafluoroethylene, propylene and, optionally, vinylidene fluoride).

Multimodal fluoropolymers, such as those disclosed in International Patent Publication WO 00/69967, may also be employed as the fluoropolymer in the compositions of this invention. By "multimodal" is meant that the fluoropolymer has at least two components of discrete and different molecular weights. Both components may be amorphous or semi-crystalline, or one component may be amorphous and another component semi-crystalline.

These polymers are commercial products and are available under the trade name Viton free flow from DuPont. Of particular interest are dipolymers of vinylidene fluoride and hexafluoropropylene (sold as Viton A and Tecnoflon), terpolymers of vinylidene fluoride and hexafluoropropylene and tetrafluoroethylene (sold as Viton B, Viton F and Tecnoflon). It will be appreciated that these commercial products may contain adjuvants in addition to the fluoroelastomer, in particular glycols such as polyethylene glycol.

In order to minimise the possibility of causing transparency issues, it is preferred if no more than 2 wt% of the fluoropolymer particles are retained on a 16 mesh screen. It is preferred if at least 75% of the fluoropolymer particles pass through an 80 mesh screen. In some embodiments, 90% or more of the

fluoropolymer particles are 200 microns or less, such as 200 to 10 microns.

The bulk density of the fluoropolymer may be in the range of 0.2 to 1.0 gr/cc, such as 0.25 to 0.50 gr/cc (ASTM D1895). The amount of fluoropolymer present may range from 0.01 to 5 wt% of the blend or polymer film, such as 0.1 to 4.5 wt%, preferably 0.25 to 4 wt% of the blend or polymer film in question. If necessary, the fiuoroelastomer may be added as a masterbatch as is well known in the art. Thus a higher percentage of fiuroelastomer may be added to a small amount of polycarbonate which is then blended with polycarbonate which is fiuoroelastomer free and results in a fiuoroelastomer content in the range above.

The polycarbonate/fluoropolymer blend may form at least 30 wt%, such as at least 40 wt%, more preferably at least 50 wt% of any film. In another embodiment, the polycarbonate/ fluoropolymer blend may form at least 60 wt%, such as at least 70 wt%, preferably at least 80 wt%, more preferably at least 90 wt% of any film, such as at least 93 wt% of any film in which it is present.

It is preferred if the invention allows blocking forces of less than 28 N to be achieved, such as less than 10 N.

Whilst the invention has primarily been described with reference to fluoropolymers, such as fluorocarbons, it is also envisaged that poly(siloxanes) might be used as the antiblocking agent either instead of or in combination with fluoropolymers. Polysiloxane additives are highly effective internal and external lubricants and offer a number of significant processing advantages and surface improvements such as improved processing and flow and better mould filling, scratch and abrasion resistance while reducing friction.

The polysiloxanes could be polydimethyl silicone oils and other silicon containing polymers that are well known to the man skilled in the art. Typically, they would have the formula -(-Si(R)2-0)_n- where R is CI -6 alkyl and n is an integer of more than 2. Preferred compound have R as methyl. Preferably, they are ultra-high molecular weight siloxanes, e.g. having a Mw of at least 100,000. They may be organically modified siloxanes. Polysiloxanes are commercially available in the form of the polymer or in masterbatches from Dow Corning and Ciba.

Viewed from another aspect the invention provides a film comprising a blend of at least one polycarbonate and at least one polysiloxane.

We have noted that both fluoropolymers and polysiloxanes provide a low surface energy to the films. Viewed from another aspect the invention provides a film comprising a blend of at least one polycarbonate and at least one thermoplastic polymer, e.g. a fluoropolymer or polysiloxane, with surface energy at 20°C of less than 25 mN/m, e.g. less than 23 mN/m. Surface energy can be measured by

IS08296 (ink method). The unit of measurement of Surface Energy is Dyne/cm² this can also be expressed in mN/m.

Fluoropolymers may be good in preventing adhesion because they are polymers that are not crosslinked. Instead they are thermoplastic, so their chains may diffuse within the polyalkylene carbonate material. Additionally the fluorocarbon polymers and polysiloxanes have a surface energy less than 25 mN/m, much lower than for polycarbonates which have about 46 mN/m. Polyethylene and polypropylene, while having relatively low surface energies, 35 and 31 mN/m respectively, are not so useful as the fluorocarbon polymers.

Whilst it is within the scope of the invention for other anti-blocking agents to be present as well as the fluoroelastomer, it is preferred if the fluoroelastomer is the only anti-blocking agent present in the films of the invention.

Other additives

The polycarbonates and in particular PACs of the invention are susceptible to degradation, e.g. via break down of the carbonate linkages in the backbone of the polymer. In order to prevent degradation of the polycarbonate, the present inventors have added anti-oxidants and/or UV stabilisers to the coating composition. Thus, either or both of these additives can be present, preferably both.

The anti-oxidant concentration may be in the range of 0.05 - 1.5 wt% in the film.

The UV stabiliser concentration may be present in the range of 0.05 to 1.5 wt% in the film.

The total concentration of UV stabiliser and anti-oxidants within the film is preferably 3 wt% or less. More preferably, the total content of all additives present is 3 wt% of less (i.e. including the fluoroelastomer).

It has surprisingly been observed that effective degradation protection can be achieved even at very low levels of UV additive. In particular prevention against degradation can be achieved at levels of 0.5 wt% or less, such as 0.25 wt% or less, especially 0.2 wt% or less. The addition of more additive has not been found to markedly improve degradation resistance. Even levels of 0.05 to 0.15 wt% have been shown to be sufficient.

The anti-oxidant is preferably a phenolic antioxidant. Preferred phenolic antioxidants are [Octadecyl 3-(3',5'-di-tert. butyl-4-hydroxyphenyl)propionate] (e.g. Irganox 1076) or [Pentaerythrityl-tetrakis(3-(3',5'-di-tert. butyl-4-hydroxyphenyl)- propionate] (e.g. Irganox 1010). It is more preferred if the anti-oxidant is a tocopherol or derivative thereof, in particular vitamin E. A further option is the use of organic phosphite or phosphonite antioxidants preferably [Bis(2-methyl-4,6- bis(l,l-dimethylethyl)phenyl)phosphorous acid ethylester] (e.g. Irgafos 38),

[Tris(2,4-di-t-butylphenyl)phosphite] (e.g. Irgafos 168), tris-nonylphenyl phosphate, [Tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylen-di-phosphonite] (e.g. Irgafos P- EPQ) or [Phosphorous acid- cyclic butylethyl propandiol, 2,4,6-tri-t-butylphenyl ester] (e.g. Ultranox 641).

It may be possible to use a mixture of anti-oxidants.

It is also preferred if a UV stabiliser is used instead of or preferably as well as the anti-oxidant. The at least one UV-stabiliser may be selected from [1,6- Hexanediamine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-, polymer with 2,4,6- trichloro- 1 ,3 ,5-triazine, reaction products with, N-butyl- 1 -butanamine and N-butyl- 2,2,6, 6-tetramethyl-4-piperidinamine] (e.g. Chimassorb 2020), [Poly((6-morpholino- s-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4 piperidyl)imino)hexamethylene (2,2,6,6- tetramethyl-4-piperidyl)imino))] (e.g. Cyasorb UV 3346); [Poly((6-((l,l,3,3- tetramethylbutyl)amino)-l,3,5-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4- piperidyl)imino)- 1 ,6-hexanediyl((2,2,6,6-tetramethyl-4-piperidyl)imino))] (e.g. Chimassorb 944); or 2-hydroxy-4-n-octoxy-benzophenone.

Films of the invention might also contain fillers. The presence of fillers can tailor the properties of the PAC further, in particular by improving thermal stability and glass transition temperature of the film. They may also modify mechanical properties, rheology, barrier properties, and importantly, the electrical conductivity of the polymer. In the present invention fillers which do not affect the transparency of the film are favoured such as some grades of calcium carbonate, nanoclays and silica. Ideally therefore the presence of a filler does not increase the haze value of the film by more than 10 %, such as no more than 5%.

Film Properties

It is an important feature of the invention that the transparency of the film is maintained even in the presence of additives. Thus, the haze value of the film is preferably less than 20%, especially less than 10%. It is believed that the addition of clarifiers might assist in forming transparent coatings.

Gloss values are preferably high. Gloss values of at least 50%>, preferably at least 80%) are possible.

The films of the invention can be in the range of 1 to 200 microns, such as 10 to 100 microns, e.g. 20 to 50 microns in thickness. When the films act as a coating on a substrate, however films tend to be thinner as discussed below.

The presence of the fluoroelastomer means that the films of the invention exhibit low blocking force. The blocking force is preferably less than 10 N. This means that the force to separate two films based on the test method below is less than 50 N. Blocking forces measured in the absence of the fluoroelastomers of the invention or in the presence of other anti-blocking agents have exceeded 50 N. Such films are essentially inseparable.

At a temperature of 38°C, and 90% relative humidity, WVTR for a film of the invention can be less than 10 g mm/m² day, even more preferably less than 5 g Omm/m² day, and even more preferably less than 1 g mm/m² day. For example, the value could be 0,2 g mm/m² day or less.

Oxygen transmission rate (OTR) for the films of the invention is preferably less than 4.0 cm³ mm/m² day at 23°C and 50% relative humidity which is comparable to PET ( poly(ethylene terephtalate). When compared with a

biodegradable polymer as PLA (poly(lactic acid) both OTR and in particular, the WVTR are significantly lower.

The films of the invention also possess low migration. It is vital, if a material is coming into contact with food, that material from the packaging does not migrate from the packaging into the product being packed. The maximum limit for such migration is typically 10 mg/day and the present films have migration levels well below that threshold.

The films of the invention are also printable.

The mechanical properties of the films are also important. The films of the invention may possess excellent mechanical properties such as impact strength, tensile properties and tear strength.

Substrate

The films of the invention might be present on a variety of substrates such as metal, glass or other plastic substrates. It is preferred if the films are laminated or extruded onto a substrate such as paper. The nature of the paper substrate is not important. The term paper substrate is intended to cover a cellulosic substrate such as carton board. Any conventionally used paper substrate can be employed. Paper is for instance made up of mechanical pulp and paperboard of bleached or unbleached chemical pulp. The chemical pulp is stronger. Typically, the paper used is in the form of paperboard. Paperboard is generally considered thicker and hence represents the paper material needed for packaging. The paper will typically be at least 0.05 mm, such as at least 0.1 mm in thickness.

Paperboard used in the invention is preferably paper with a basis weight above 224 g/m². Paperboard can be single or multi-ply.

The film of the invention may cover the whole of the substrate, i.e. both sides thereof and its ends so that the whole of the substrate is coated. It is also possible, for a coating to be placed only on one side of the substrate, in particular the side which will be exposed to any goods packaged using that coated substrate. It is also possible for a coating to be placed on an outer surface in order to create an appealing glossy and transparent surface suitable for printing.

The coated paper substrate exhibits a number of valuable properties. The coating polycarbonate layer is generally sufficiently transparent that any advertising or information presented on the paper substrate is clearly visible. The haze therefore of the polycarbonate film on the substrate may be <20%, such as less than 10%. The coated paper substrate also exhibits high gloss. Gloss values of >80% are possible.

Even without an adhesive layer described later, the adhesion between the paper substrate and coating layer is strong. Delamination forces are for example ca. 20-30 N. These values are obtained in a welding test.

The oxygen barrier and water vapour transmission properties of the films of the invention are excellent. The polycarbonate provides an excellent barrier to both oxygen and to water vapour. This makes the materials suitable for use in food packaging or the packaging of any substance susceptible to degradation in the presence of oxygen or water vapour.

At a temperature of 38°C, and 90% relative humidity, WVTR for a coated substrate of the invention can be less than 10 g mm/m² day, even more preferably less than 5 g mm/m² day, and even more preferably less than 1 g mm/m² day. For example, the value could be 0,2 g mm/m² day which is at the same level as LDPE (low density polyethylene).

Oxygen transmission rate (OTR) for the coated substrates of the invention is preferably less than 4.0 cm³ mm/m² day at 23°C and 50% relative humidity which is comparable to PET ( poly(ethylene terephtalate)). When compared with a biodegradable polymer as PLA (poly(lactic acid)) both OTR and in particular, the WVTR are significantly lower.

Adhesive

In order to ensure adhesion between the polycarbonate film and the paper substrate, it is possible to employ an adhesive layer between the two in addition to the conventional treatment like corona or flame treatment of the paper substrate. In a preferred embodiment, an adhesive layer is not used and the polycarbonate bonds directly to the paper substrate in the absence of an adhesive layer. However, as the use of an adhesive layer does further strengthen the bonding between the paper and polycarbonate layers, it is also a feature of the invention to use an adhesive layer. The adhesive layer used can be vary widely as long as the material is capable of providing the desired adhesion with desirable end properties. It should also be compatible with food.

Adhesives of interest are primarily based on ester, anhydride, hydroxyl and amide compounds, especially ester, anhydride, hydroxyl and amide polymers. Such adhesives are well known in the art and are commercially available from e.g.

DuPont and others.

Preferred polyamides will comprise the amide linkage within the backbone of the polymer or grafted on the backbone thus constituting a side chain. Preferably, polyamides will contain the amide group in the backbone of a polymer. Polyester adhesives can comprise the ester group within the backbone or as a side chain.

The use of acrylate polymers is also possible as adhesives. Also of interest are maleic anhydride modified polyolefins such as maleic anhydride grafted polypropylene. The use of maleic anhydride modified polyolefins is not favoured due to the use of peroxides in the grafting process for the maleic anhydride onto the adhesive polymer backbone.

Suitable acrylates include those formed using alkyl (meth)acrylate monomers in which the alkyl group has 1 to 6 carbon atoms. Such a monomer is preferably used with non acrylate comonomers. Non acrylates comonomers are preferably alpha olefins or styrene.

Preferably the acrylate polymer may be an ethylene methyl (meth)acrylate, ethylene ethyl (meth)acrylate or ethylene butyl (meth)acrylate resin, especially ethylene methyl acrylate, ethylene ethyl acrylate or ethylene butyl acrylate resin (EMA, EEA and EBA respectively). These polymers are commercially available materials and can be purchased from various suppliers, e.g. under the trade name Elvaloy™.

It will be appreciated that a mix of adhesives could be used.

Polyolefin layer

Although it is generally desirable to avoid the use of a polyolefin layer in the invention, it may be necessary for some applications. The inventors have found that due to the low glass transition temperature of some polycarbonates, such

polycarbonates may soften in higher temperatures making the surface sticky. In order to avoid this problem, the films of the invention can be provided with a polyolefm top layer.

Moreover, the top layer is able to provide good mechanical properties to the structure, e.g. in terms of tensile strength, sealing, stiffness, puncture resistance, tear resistance, abrasion resistance and slip resistance. The top layer is preferably formed from a polyethylene or a polypropylene polymer, especially a polyethylene. Suitable polyethylenes are well known polymers such as low density polyethylene (LDPE), high density polyethylene (of density 940 kg/m³ or more), or linear low density polyethylene (LLDPE). These polymers are well known and can be purchased from numerous suppliers and today they can obtained as green polymers produced from sugar canes and made by Braskem in Brasil.

Whilst the resulting article is harder to recycle having a polyolefm top layer, the multilayer structure still incorporates an environmental polymer and offers a reduced carbon footprint. Such a top layer may be a film (e.g. of thickness < 250 micron), a foil (e.g. of 250 - 1500 micron) or a plate ( e.g. > 1500 micron).

Manufacture

The films of the invention can be manufactured using known techniques of film casting or film blowing. The film can be formed before combination with a substrate (via lamination) or can be formed on the substrate (via extrusion coating). The term film as used herein also refers to a layer which can be present on a substrate.

Any additives will be added before or as the film is formed. Coated articles of the invention can be manufactured using known techniques such as extrusion coating, lamination, thermoforming or extrusion lamination. It is especially preferred if the polycarbonate layer is adjacent to a layer comprising cellulose, i.e. a paper layer.

In an extrusion coating process, the polycarbonate material with additives is extruded onto a paper substrate to thus form an extrusion coated substrate. The thickness of the extrusion coating i.e. the polycarbonate layer can be of the order of 0.1 to 0.3 mm in thickness. In the preferred extrusion coating process, molten polymer is continuously applied onto the solid substrate material. The molten polymer exits from a slit (flat) die down onto the substrate and solidifies while cooling. The substrate (with the coating polymer) is continually moving over rollers. This well known process is the most preferred coating method herein.

In a lamination procedure, a polymer film is initially produced. That can be achieved using well known film blowing, film casting or compression moulding techniques. Thermo forming may also be used. These films are typically of the order of 0.02 to 0.3 mm in thickness.

The film is then combined with a paper substrate to form the laminated article. The lamination can be effected using compression moulding or

thermo forming. It may be necessary, of course, to employ an adhesive between the two layers here. That adhesive will typically be extruded onto one of the layers and after that the other layer is pressed against the adhesive containing substrate layer. This is called extrusion lamination.

It is preferred if lamination is effected using a continuous process such as using rollers. This can be achieved hot or cold (i.e. at room temperature) although the use of heat is preferred.

All three techniques are suitable for use in the present case.

It is also envisaged that spin coating, dip coating or powder coating could be employed here. Spin coating is a procedure used to apply uniform thin films to flat substrates. In short, an excess amount of a solution is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force.

In dip coating, uniform films can be applied onto flat or cylindrical substrates simply by dipping the substrate in a solution of the coating material.

The formation of polymer coated paper substrates is generally well known and the techniques well known in the industry can be used in this invention.

It is preferred if the polycarbonates of the invention have a high molecular weight and broad molecular weight distribution. This benefits processability.

Polycarbonate can possess good drawdown due to the high Mw fraction within the polycarbonate. By good drawdown is meant that the melt can be stretched to thin film quickly without breaking.

The polycarbonates can also have good extrudability (low pressure build-up, high output rate, low amperage and torque at given rpm) due to presence of low Mw fraction in the PAC.

Moreover, the flow onto and into the surface of a coarse or fibrous surface such as paper is good.

One further advantage of the use of polycarbonate is that there is no need for surface treatment to be effected before joining the polycarbonate layer and substrate layer. The process of joining these layers can also be effected at comparatively low temperature at least in comparison to the use of polyolefms.

There is therefore no need to oxidise the substrate surface to achieve adhesion/wetting. That is typically essential when coating on polar surfaces like cellulose. For polyolefms, the polyolefin is often heated to about 300°C in order that the necessary oxidation of the polyolefin surface to give a sufficiently polar surface to give good adhesion to a polar surface like cellulose. In addition, the polyolefin surface is often treated with ozone. These methods tend to give unhealthy atmosphere in the room where this is done. In addition, heating the polymer to such high temperature wastes a lot of energy. Use of polycarbonate simplifies the process, uses less energy, and does not give the unhealthy oxidation products.

Recycling

The inventors have found that polycarbonates can be readily recycled. In particular PAC's of the invention can be easily removed from paper in a recycling process. That process is based upon the separation of cellulose and polymer in an aqueous process or thermally. In the aqueous process, the PAC coating is preferably hydrolysed to leave hydrolysis products such as a diol and carbon dioxide. This enables easy recycling of the paper substrate with low impact on the cellulose fibre recovery. Moreover, the diol can itself be used industrially or undergo chemical reactions to reform a monomer for polymerisation. In particular, when the poly(alkylene carbonate) is polypropylene carbonate then the formed diol is 1,2- propanediol.

The hydrolysis reaction can be catalysed by acids or bases, preferably base. Suitable bases include those containing hydroxy groups. The temperature of the hydrolysis reaction may be at least 100°C up to the decomposition temperature of the PAC, e.g. around 200°C. Pressure may also be used. It is important that the conditions used do not damage the paper substrate. The reaction can take up to 1 hr, e.g. up to 30 mins.

The hydrolysis process can be effected with aqueous acids or bases for example as described by Jung et al. Catalysis Today (2006), 115(1-4), 283-287, or Ma et al. Acta Polymerica Sinica 2010, 2, 217-221.

It is especially true that fiber recovery in paper recycling is made easier due to easy separation of the cellulose and poly(alkylene carbonate) coating in aqueous environment.

In an alternative process the recycling reaction involving cellulose can involve thermal degradation of the PAC. Heating the PAC to temperatures above 200°C, even in the presence of the claimed additives causes the PAC layer to convert to the corresponding cyclic alkylene carbonate. In this way, the substrate and PAC layer can be easily separated.

Applications

The films and coated paper substrates of the invention can be used in any packaging field. Preferably, they are used for the packaging of food or beverages or the packaging of medical products such as pharmaceuticals. A particular area of interest is liquid packaging but the films and coated substrates of the invention can be used for packaging meat, baking products such as cakes, cheese, and frozen food as well as non food related items such as photographic paper.

In general, the coated paper materials of the invention are suitable for packaging wet or greasy foods or foods which degrade easily. They are also heat sealable. The paper substrates can be formed into packaging articles such as cartons, pouches, boxes and so on. Films and coated paper substrates of the invention could be used in flexible packaging. Flexible packaging applications include MAP/CAP packaging for meat and cheese, sachets and pouches for soups and sugar, pet food bags, medical packaging, wrappers, e.g. for fresh food, crackers and snacks, bags and sacks, industrial packaging, including mill and industrial wrappings, transport packaging, sack linings, building, envelopes, medical/hygiene packaging and release base papers.

Rigid packaging applications include folding cartons such as frozen food, detergent and pet food packages, sleeves & tray, cup and plate boards for conventional and microwave oven use, bakery products, grease, moisture & temperature resistance.

It is a feature of the invention that the films coated substrates can be printed upon. Printing techniques such as flexography can be used. Flexography is a form of continuous printing process which utilizes a flexible relief surface on a roller. Moreover, the PAC layer is directly printable without any corona or ozone treatment. Such treatment is essential for printing on polyolefm coatings.

Extrusion coated substrates are the preferred application herein, e.g. for liquid packaging for milk, juice, wine or other liquids. Extrusion coatings are also of interest in flexible packaging for meat, cheese, pet food or medical products. Extrusion coatings are also of interest in rigid packaging for frozen food and detergent cartons, cup and plate boards for oven or microwave use. Extrusion coatings are also of interest in sterilisable food packaging.

Whilst the invention has been described primarily in relation to films, viewed from another aspect the invention provides a composition comprising a blend of at least one poly(alkylene)carbonate and at least one fluoropolymer. That composition may take the form of an extruded article, e.g. a moulded article or thermoformed article.

The invention will now be further defined with reference to the following examples.

GPC (Molecular weight and molecular weight distribution, Mw and MWD): The molecular- weight distribution was determined by size-exclusion

chromatography (SEC) in an Agilent PL-GPC 50 equipped with a refractive index detector and calibrated with narrow polystyrene standards. The determinations were performed in THF as the eluent at 40 °C. It was used a sample preparation system PL-SP260VS with 1μ glass fiber filter to remove the particles in suspension from composite samples.

Blocking force:

The blocking force was tested according to the conditions detailed in ISO 11502. The specimen consists of strips 150*76mm that are stacked, the stack is placed in an oven and a load of 5,4 kg is applied. The oven temp, is maintained at 50±2 °C for 24 hrs. The stack is taken from oven and kept at room temp, for minimum 2 hrs (maximum 24 hrs). The two layers are separated in a tension machine with a speed of separation of 25±2,5 mm/s, and the blocking resistance is obtained from the force-extension curve.

Tensile properties:

Tensile properties were measured on compression moulded or injection moulded specimens (ISO 293-1986, 1872-2-1997, 1873-2-1997, 150°C, pressure intervals of 25-90-165-165-165 bar) according to IS0527-1/2.

Water Vapour Transmission rate (WVTR):

Water vapour transmission rate (WVT) was measured at the specified temperature and relative humidity (Table below) on a Mocon PermaTran W3/33 MG Systems instrument according to ASTM 1249.05. The results are normalised with respect to thickness. Method: ASTM F 1249-05.

Oxygen Barrier properties (OTR):

Measurement of oxygen transmission rate (OTR) was performed in a Mocon Ox- Tran Model 2/21 SH instrument. Method: ASTM D 3985-05.

Food Compatibility: Migration test: The compatibility of the claimed structures of PPC coated on carton board with food was determined by measuring migration. The following standard test methods were employed:

EN 1186-5: Test method for overall migration into aqueous food simulants by cell. This method involves the use of acetic acid.

EN 1186-14: Test method for "substitute test" for overall migration from plastics intended to come into contact with fatty foodstuffs using test media iso-octane and 95 % ethanol (Cell method). The overall migration limit in either test is 10 mg/dm².

Haze is measured according to ASTM D1003.

Gloss is measured according to ASTM D523.

Dipping test was also performed were the sample was completely covered with stimulant solution. As a reference was non-coated carton board used. Conditions: 10 days at 40°C.

Examples: Polypropylene Carbonate

Polypropylene carbonate (PPC) is used in the examples of the invention and is purchased under the trade name QPAC40: The main characteristics of the PPC are given in table 1.

Table 1: Main characteristics of the PPC

*PC = propylene carbonate

The PPC was blended with 0.1 % vitamin E in all blends.

The paper substrate was carton board from Korsnas Frovi, with ca 70 % porosity.

Anti-blocking agents

The fluoroelastomer grade was added at a level of 2 wt%, giving a concentration of fluoroelastomer of at least 0.36 wt%.

Example 1 and 2 (with PPC1 and PPC2 respectively):

Blends of PPC and the antiblocking agents were prepared as shown in table

1 :

QPAC40 Stabilizer Stabilizer Modifier Modifier Type Modifier cone. Cone.

[wt%] [wt%]

Ex la Vitamin E 0,1 - - 0

Ex lb Vitamin E 0,1 Gasil AB725 Silica 10

Ex lc Vitamin E 0,1 Nan-O-Sil Nano size silica 5

Ex Id Vitamin E 0,1 PGE1010 Polyglycerol 5

ester

Ex le Vitamin 0,1 Viton Free Fluoroelastomer 2

E flow RC

Ex 2a Vitamin E 0,5 Licowax E Montanic acid 0,5

wax

Ex 2b Vitamin E 0,5 Polywax 655 Polyethylene 0,5

wax

Ex 2c Poly(ethylene- Ionomer 3

co-acetylene

(Zn)) Ex 2d Vitamin E 1,0 Boltorn H30 Dendrimer 3

Test specimens were prepared by compression moulding a 1 mm thick film at 150°C.

The recipes in table 1 were tested according to the conditions detailed in ISO 11502. Two layers of each film has been stored in contact for 24 hours at 50 °C under a 5 kg load before the two layers are separated in a tension machine, and blocking force measured.

The results from this test were that only the sample containing

fluoroelastomer was separable.. Blocking force for sample with 2 wt% Viton Free flow RC was between 0.2 and 2 N. All other samples had blocking forces greater than 28 N.

Example 2 The following further recipes were prepared to test a wider variety of fluoroelastomers. The following recipes was compounded at 140°C, under N₂ flush in the Prism 16 extruder:

1. QPAC40 - PPC 1 (95.9 wt%), Vitamin E (0.1 wt%), Viton Freeflow RC (4 wt% = at least 0.72 wt% fluoroelastomer)

2. QPAC40- PPC 1 (97.9 wt%), Vitamin E (0.1 wt%), Dynamar FX5922x (2 wt%)

3. QPAC40 - PPC 1 (97.9 wt%), Vitamin E (0.1 wt%), Kynar Flex PPA 5300 (2 wt%)

Films were produced by compression moulding a 1 mm thick film at 150°C. The blocking force was measured after exposing the samples to standard blocking conditions (ISO11502 ; 50°C/24h/5 kg load). Results:

Sample 1 : Separating layers was possible - Blocking force in that area around 27 N Sample 2: Separating layers was possible - Blocking force in that area around 2.7 N Sample 3: Separating layers was possible - Blocking force in that area around 1.6 N

Claims

1. A film comprising a blend of at least one polycarbonate and at least one fluoropolymer and/or polysiloxane.

2. A film comprising a blend of at least one polycarbonate and at least one fluoropolymer.

3. A film as claimed in any preceding claim wherein the polycarbonate is a poly(alkylene carbonate).

4. A film as claimed in any preceding claim wherein the polycarbonate is polypropylene carbonate, polyethylene carbonate, polycyclohexene carbonate or polycyclohexene-propylene carbonate (PCHC-PPC).

5. A film as claimed in any preceding claim wherein the polycarbonate has a Mw of at least 50,000.

6. A film as claimed in any preceding claim the polycarbonate has a molecular weight distribution (Mw/Mn) of more than 2.

7. A film as claimed in any preceding claim wherein the fluoropolymer is a dipolymer of vinylidene fluoride and hexafluoropropylene or a terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene.

8. A film as claimed in any preceding claim wherein the glass transition temperature (Tg) of the fluoropolymer is greater than 10°C.

9. A film as claimed in any preceding claim wherein there is between 0.1 and 5 wt% of fluoropolymer in said blend.

10. A film as claimed in any preceding claim wherein there is at least 50 wt% of the blend in said film.

11. A substrate having a film applied thereon, wherein said film is as claimed in any preceding claim.

12. A substrate as claimed in claim 11 being paper.

13. Use of a film as claimed in any one of claims 1 to 10 in packaging, such as for food, beverages, pharmaceuticals or medical supplies.

14. A process for the preparation of a film as hereinbefore described comprising blending at least one fluoropolymer with at least one polycarbonate and forming the mixture to form a film.

15. A process for the preparation of a substrate as claimed in claim 11 comprising blending at least one fluoropolymer with at least one polycarbonate and extrusion coating or laminating the blend onto a substrate.

16. A composition comprising a blend of at least one poly(alkylene)carbonate and at least one fluoropolymer.

17. A composition as claimed in claim 16 in the form of an extruded article such as a moulded article or thermo formed article.

18. A film comprising a blend of at least one polycarbonate and at least one thermoplastic polymer with surface energy at 20°C of less than 25 mN/m, e.g. less than 23 mN/m.