Thermoformed article for food packaging

Abstract

The present invention relates to a biodegradable thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with at least three polymeric layers that possess oxygen and moisture barrier properties.

Description

[0001] THERMOFORMED ARTICLE FOR FOOD PACKAGING

[0002] The present invention relates to a biodegradable thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with at least three polymeric layers having oxygen and moisture barrier properties.

[0003] In the field of food packaging containers, or beverage dispensing capsules, there is an increasing demand for food containers that, to ensure preservation of the food, possess oxygen and moisture barrier properties and are biodegradable.

[0004] These containers (in the form of trays, jars, pots, capsules, etc.) are generally closed by welding a polymeric cover film along the edges of the container in order to seal the cavity containing the food.

[0005] Generally, the body of the article is made up of one or more layers, where the layer in contact with the top lid and therefore also with the food, must guarantee, by welding, a completely airtight seal with the top lid itself. At the same time, to facilitate use by the consumer, it is preferable that it can easily allow the top lid to be removed when the package is opened.

[0006] This ability to remove the top lid without leaving residues in the body close to the welded area, and without tearing, is called peelability (or ‘easy peel’).

[0007] In the sector art, many patents are known regarding multilayer films for food such as EP3328941, EP3328940, or WO2022195367 but in none of these patents is the issue of peelability raised.

[0008] Peelability is an extremely important property in commercial products such as food storage trays or microwave trays, but it is also useful in applications such as coffee capsules, where a very strong weld is generally required during coffee dispensing. After use, the fact that the top lid can be removed more easily means that the body can be separated from the tip lid, ensuring better disintegration in composting.

[0009] This peeling effect results from the combination of the properties of the top lid film with those of the material comprising the body. In other words, the peelable effect can be obtained by modulating the chemi cal -physical properties of the surface to be welded.

[0010] It has been found that a multilayer, compostable polymeric sheet (thick film for thermoforming) with oxygen and humidity barrier properties, which contains a specific quantity of mineral filler in the outermost layer (the one in contact with the food and in contact with the top lid) that has to be welded in order to close the package, surprisingly means that the top lid welded on to it can easily be peeled off the package. One object of the present invention is therefore a thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with at least three layers among which:

[0011] - a first polymeric layer A in contact with the food comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns;

[0012] - a second barrier layer B comprising a polymer selected from the list of a butanediol vinyl alcohol copolymer (BVOH), polyvinyl alcohol (PVOH) and a combination thereof;

[0013] - a third polymeric layer C comprising a biodegradable polymer chosen from an aromaticaliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv), a polylactic acid (v) and mixtures thereof.

[0014] Degradable polyesters (i) and (ii) can be the same or different for the two polymeric layers A and C.

[0015] In a preferred embodiment of the invention, the multilayer sheet comprises five layers, and in addition to layers A, B, and C, there are two additional tie layers D and E placed before and after the second barrier layer B; said tie layers D and E comprising a biodegradable aromaticaliphatic polyester functionalised by grafting.

[0016] A preferred embodiment of the invention therefore comprises a thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with five layers among which:

[0017] - A first polymeric layer A in contact with the food comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns; - a second binding (or tie) layer D comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;

[0018] - a third barrier layer B comprising a polymer selected from the list of a butanediol vinyl alcohol copolymer (BVOH), polyvinyl alcohol (PVOH) and a combination thereof;

[0019] - a fourth tie layer E comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;

[0020] - a fifth polymeric layer C comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv), a polylactic acid (v) and mixtures thereof.

[0021] In a further preferred embodiment of the invention, two further polymeric layers F and G can be added to the multilayer sheet of the invention; layer F between the first layer A in contact with the food and layer D, and layer G between layer E and the bottom layer C.

[0022] The two further polymeric layers F and G consist of a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof. Degradable polyesters (i) and (ii) may be the same or different for polymeric layers A, C, F and G.

[0023] As regards the polymeric layer A of the multilayer sheet of the invention, the aromatic-aliphatic polyester i) comprises: a) a dicarboxylic component comprising, in relation to the total dicarboxylic component: al) 30-70 mol%, preferably 40-60 mol%, of units derived from at least one aromatic dicarboxylic acid; a2) 70-30 mol%, preferably 60-40 mol%, of units derived from at least one saturated aliphatic dicarboxylic acid; a3) 0-5 mol% of units derived from at least one unsaturated aliphatic dicarboxylic acid; b) a diol component comprising, in relation to the total diol component: bl) 95-100 mol% of units derived from at least one saturated aliphatic diol; b2) 0-5 mol% of units derived from at least one unsaturated aliphatic diol.

[0024] The aromatic dicarboxylic acids in component al) are preferably selected from aromatic dicarboxylic acids of the phthalic acid type, preferably terephthalic acid or isophthalic acid, more preferably terephthalic acid, their esters, salts and mixtures. In a preferred embodiment, said aromatic dicarboxylic acids comprise: 1 to 99 mol%, preferably 5 to 95 mol% and more preferably 10 to 80 mol%, of terephthalic acid, its esters or salts.

[0025] The saturated aliphatic dicarboxylic acids in component a2) are preferably selected from saturated C2-C24, preferably C4-C13, more preferably C4-C11 dicarboxylic acids, their Cl- C24, preferably C1-C4 alkyl esters, their salts and mixtures thereof. Preferably, the saturated aliphatic dicarboxylic acids are selected from succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid and their Cl -24 alkyl esters. In a preferred embodiment of the present invention, the saturated aliphatic dicarboxylic acid comprises mixtures comprising at least 50 mol%, preferably more than 60 mol%, more preferably more than 65 mol%, of succinic acid, adipic acid, azelaic acid, sebacic acid, brassylic acid, their C1-C24, preferably C1-C4, esters, and mixtures thereof.

[0026] The unsaturated aliphatic dicarboxylic acids in the component a3) are preferably selected from itaconic acid, fumaric acid, 4-methylenepimelic acid, 3,4-bis(methylene)nonanedioic acid, 5- methylenenonanedioic acid, their C1-C24, preferably C1-C4 alkyl esters, their salts and mixtures thereof. In a preferred embodiment of the present invention, the unsaturated aliphatic dicarboxylic acids comprise mixtures comprising at least 50 mol%, preferably more than 60 mol%, more preferably more than 65 mol%, of itaconic acid and its C1-C24, preferably C1-C4 alkyl ester. More preferably, the unsaturated aliphatic dicarboxylic acids consist of itaconic acid.

[0027] As regards the saturated aliphatic diols in component bl), these are preferably selected from 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- hexanediol, 1,7-heptanediol, 1,8 -octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11- undecanediol, 1,12-dodecanediol, 1,13 -tridecanediol, 1,4-cyclohexanedimethanol, neopentylglycol, 2-methyl-l,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanemethanediol, dialkylene glycols and polyalkylene glycols with molecular weight 100-4000, such as polyethylene glycol, polypropylene glycol and mixtures thereof. Preferably, the diol component comprises at least 50% by moles of one or more diols selected from 1,2-ethanediol, 1,3-propanediol, 1,4- butanediol. More preferably, the diol component comprises or consists of 1,4-butanediol.

[0028] As for the unsaturated aliphatic diols in the component b2), these are preferably selected from cis 2-buten 1,4 diol, trans 2-buten 1,4 diol, 2-butine 1,4 diol, cis 2-penten 1,5 diol, trans 2- penten 1,5 diol, 2-penten 1,5 diol, cis 2-hexen 1,6 diol, trans 2-hexen 1,6 diol, 2-hexine 1,6 diol, cis 3hexen 1,6 diol, trans 3-hexen 1,6 diol, 3-hexine 1,6 diol. The molecular weight Mn of said aromatic-aliphatic polyester i) in the polymeric layer A is preferably higher than 20,000, more preferably higher than 40,000. As regards the poly dispersity index of the molecular weights, Mw / Mn, this is preferably between 1.5 and 10, more preferably between 1.6 and 5, and even more preferably between 1.8 and 2.7.

[0029] The molecular weights Mn and Mw can be measured by Gel Permeation Chromatography (GPC). The determination can be performed with the chromatographic system maintained at 40°C, using a set with two columns in series (particle diameter 5 pm and 3 pm with mixed porosity), a refractive index detector, chloroform as eluent (flow rate 0.5 ml / min) and using polystyrene as the reference standard.

[0030] Preferably, said aromatic-aliphatic polyester i) in the polymeric layer A has an intrinsic viscosity greater than 0.3 dl / g (measured using an Ubbelohde viscosity meter for solutions of concentration 0.2 g / dl in CHC13 at 25°C), preferably between 0.3 and 2 dl / g, more preferably between 0.4 and 1.2 dl / g.

[0031] The terminal acid groups content of said aromatic-aliphatic polyester i) in the polymeric layer A is preferably less than 100 meq / kg, preferably less than 60 meq / kg and even more preferably less than 40 meq / kg.

[0032] Terminal acid groups content can be measured as is known in the sector art, for example as described in W02017216150.

[0033] The said aromatic-aliphatic polyester (i) in the polymeric layer A is biodegradable. For the purposes of this invention, by biodegradable polymer is meant a biodegradable polymer according to EN 13432.

[0034] The said aromatic-aliphatic polyester (i) in the polymeric layer A can be synthesized according to any of the processes known in the state of the art. In particular, it can be advantageously obtained using a polycondensation reaction.

[0035] Advantageously, the synthesis process can be carried out in the presence of a suitable catalyst. Suitable catalysts include, for example, organometallic tin compounds, e.g. stannic acid derivatives, titanium compounds, e.g. orthobutyl titanate, aluminium compounds, e.g. triisopropyl aluminium, antimony and zinc and zirconium compounds and mixtures thereof.

[0036] The aliphatic polyester (ii) of the polymeric layer A is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) or a polylactic acid (v) and mixtures thereof.

[0037] Preferably the diol-diacid aliphatic polyester (iii) comprising: c) a dicarboxylic component comprising, in relation to the total dicarboxylic component: cl) 60-100 mol% of units derived from succinic acid; c2) 0-40 mol% of units derived from at least one saturated dicarboxylic acid with a number of carbon atoms greater than 4; d) a diol component comprising, in relation to the total diol component: dl) 95-100 mol% of units derived from at least one 1,4-butanediol; d2) 0-5 mol% of units derived from at least one aliphatic diol other than 1,4- butanediol;

[0038] The saturated aliphatic dicarboxylic acids other than succinic acid in component c2) are preferably selected from saturated dicarboxylic acids C5-C24, preferably C5-C13, more preferably C7-C11, their C1-C24, preferably C1-C4 alkyl esters, their salts and mixtures thereof. Preferably, the saturated aliphatic dicarboxylic acids are selected from: succinic acid (component cl), 2-ethyl succinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, and their Cl -24 alkyl esters. Preferably the aliphatic polyester (ii) comprises between 5% and 40% by moles of component c2) and 60% and 95% by moles of component cl), more preferably between 7% and 30% by moles of component c2) and 70% and 93% by moles of component cl).

[0039] In a particularly preferred embodiment of the invention, component c2) is azelaic acid.

[0040] As for the unsaturated aliphatic diols in component d2), these are preferably selected from cis 2-buten 1,4 diol, trans 2-buten 1,4 diol, 2-butyn 1,4 diol, cis 2-penten 1,5 diol, trans 2-penten 1,5 diol, 2-pentyn 1,5 diol, cis 2-hexen 1,6 diol, trans 2-hexen 1,6 diol, 2-hexyn 1,6 diol, cis 3hexen 1,6 diol, trans 3-hexen 1,6 diol, 3-hexyn 1,6 diol.

[0041] In a preferred embodiment of the invention, the aliphatic diol-diacid polyester (iii) of the polymeric layers A, C, F and G is selected from polybutylene succinate and polybutylene succinate copolymers, including polybutylene succinate-co-adipate, polybutylene succinate-co- azelate and polybutylene succinate-co-sebacate. In a more preferred embodiment of the invention, the aliphatic diol-diacid polyester (iii) of the polymeric layers A, C, F and G is selected from polybutylene succinate and polybutylene succinate-co-azelate.

[0042] The molecular weight Mn of said diol-diacid aliphatic polyester (iii) of the polymeric layer A is preferably higher than 20,000, more preferably higher than 40,000. As regards the poly dispersity index of the molecular weights Mw / Mn, this is preferably between 1.5 and 10, more preferably between 1.6 and 5 and even more preferably between 1.8 and 2.7.

[0043] The molecular weights Mn and Mw can be measured by Gel Permeation Chromatography (GPC). The determination can be carried out with the chromatographic system maintained at 40°C, using a set with two columns in series (particle diameter of 5 pm and 3 pm with mixed porosity), a refractive index detector, chloroform as eluent (flow rate 0.5 ml / min) and using polystyrene as the reference standard.

[0044] Preferably, said diol-diacid aliphatic polyester (iii) has an inherent viscosity (measured with an Ubbelhode viscometer for CHC13 solutions of concentration 0.2 g / dl at 25°C) greater than 0.3 dl / g, preferably between 0.3 and 2 dl / g, more preferably between 0.4 and 1.4 dl / g.

[0045] The terminal acid groups content of said diol-diacid aliphatic polyester (iii) is preferably between 30 and 160 meq / Kg.

[0046] Terminal acid groups content can be measured as is known in the sector art, for example as described in W02017216150.

[0047] Said diol-diacid aliphatic polyester (iii) can be synthesized according to any of the processes known in the state of the art. In particular, they can advantageously be obtained with a polycondensation reaction.

[0048] Advantageously, the synthesis process can be carried out in the presence of a suitable catalyst. Suitable catalysts include, by way of example, organometallic tin compounds, for example stannoic acid derivatives, titanium compounds, for example orthobutyl titanate, aluminium compounds, for example triisopropyl aluminium, antimony, zinc and zirconium compounds and mixtures thereof.

[0049] The said diol-diacid aliphatic polyester (iii) is biodegradable. For the purposes of this invention, by biodegradable polymer is meant a biodegradable polymer according to EN 13432.

[0050] In a preferred embodiment of the invention, said aliphatic polyester (ii) of the polymeric layer A comprises up to 50%, more preferably up to 37% by weight, with respect to the total polymeric component of the layer A, of a polyhydroxyalkanoate (iv) or a polylactic acid (v). Said polyhydroxyalkanoate (iv) is more preferably selected from the group consisting of poly- 8-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate, poly 3 -hydroxybutyrate 4-hydroxybutyrate.

[0051] In a particularly preferred embodiment, the polyhydroxyalkanoate (iv) is selected from polyhydroxybutyrate or polyhydroxybutyrate copolymers.

[0052] The polylactic acid (v) containing at least 95% by weight of repeating units derived from L- lactic or D-lactic acid or combinations thereof is preferred.

[0053] In the composition of the polymeric layer A, 5-45%, preferably 16-35% by weight with respect to the polymeric layer A is a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) of between 2 and 9 microns. Preferably the mineral filler (vi) can be chosen between talc and mica. In a particularly preferred embodiment of the invention, the mineral filler (vi) is talc.

[0054] In a preferred embodiment of the invention, the aromatic-aliphatic polyester (i) of the polymeric layer A, C, F and G is selected from poly(l,4-butylene adipate-co-l,4-butylene terephthalate), poly(l,4-butylene sebacate-co-l,4-butylene terephthalate. These polymers can also be mixed with polylactic acid (v).

[0055] In a preferred embodiment of the invention, the aliphatic diol-diacid polyester (iii) of the polymeric layers A, C, F and G is selected from polybutylene succinate and polybutylene succinate copolymers. These polymers can also be mixed with polylactic acid (v).

[0056] In a preferred embodiment of the invention, the layers A, C, F and G may contain up to 1% by weight, based on the sum of the layer’s components, of a cross-linking and / or chain-extending agent in order to improve stability to hydrolysis.

[0057] Said cross-linking and / or chain-extending agent is selected from di- and / or polyfunctional compounds bearing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxide, anhydride, divinylether groups and mixtures thereof. In a preferred embodiment of the invention, carbodilite is used.

[0058] Advantageously, the polymeric layers A, C, F and G can also contain pigments, for example titanium dioxide. These additives are preferably added up to 5% by weight.

[0059] The second polymeric layer B is a polymeric layer that provides oxygen barrier properties.

[0060] In particular, the polymeric layer B, which provides oxygen barrier properties, helps maintain the characteristics of the food product, the integrity of which could be altered during the product's shelf life.

[0061] The polymeric layer B can be suitably chosen from those known in the art for this purpose such as metallization layers, silicon and / or silicon oxide-based coatings, aluminium and / or aluminium oxide-based coatings, polyvinyl alcohol (PVOH) and / or butenediol vinyl alcohol copolymer (BVOH, “G polymer™”), polyglycolic acid and its copolymers, furandicarboxylic acid polymers and / or copolymers and combinations thereof.

[0062] To improve the adhesion between the oxygen barrier layer B and the materials of the adjacent layers, polymeric layers of a material having this property can be inserted, generally called “tie layers” (polymeric layers D and E).

[0063] As for the tie layers, these can be defined as polymeric layers that bond to both polar and nonpolar polymers typically used to produce sheets having at least five coextruded layers. Products known in the art can be used, such as, for example, aliphatic polyesters or biodegradable aromatic-aliphatic polyesters functionalised with a,P-unsaturated carboxylic acids (e.g. BTR8002P™).

[0064] A preferred embodiment of the invention relates to a multilayer sheet in which the following layers are included between the polymeric layer A and the final layer C: a first tie layer D comprising a biodegradable aliphatic polyester or aromatic-aliphatic polyester functionalised with a,P-unsaturated carboxylic acids; a polymeric layer B comprising a polymer selected from polyvinyl alcohol (PVOH) and butenediol vinyl alcohol copolymer (BVOH); a second tie layer E comprising a biodegradable aliphatic polyester or aromatic-aliphatic polyester functionalised with a,P-unsaturated carboxylic acids.

[0065] Regarding the technical characteristics of the layers, the polymeric layer A and the polymeric layer E preferably have a thickness between 30 and 600 pm, preferably between 100 and 300 pm, each tie layer D and E preferably has a thickness between 1 and 10 pm, while polymeric layer E preferably has a thickness between 1 and 20 pm.

[0066] Flat polymer sheet extrusion is an industrial process used to produce sheets or plates of plastic material with uniform thickness and a smooth surface.

[0067] The machine used for this operation is an extruder. From the hopper, the polymer flows into a cylinder; here it is melted, homogenized, and pushed forward by a screw. It is then passed through a die with a flat opening, which gives the material the shape of a sheet. Immediately after, the extruded sheet is transported through a series of rollers called calenders. These rollers have the task of gradually cooling the material and ensuring that the surface is smooth, with the precisely defined thickness. Finally, the cooled sheet can be wound into coils or cut into sheets according to the customer's needs.

[0068] The multilayer sheet with at least three polymeric layers A, B and C according to the invention is particularly suitable for the production of containers, capsules for dispensing drinks, and food containers.

[0069] The top lid of the article according to this invention comprises a film selected from poly(l,4- butylene adipate-co-l,4-butylene terephthalate) (PBTA), polylactic acid (PLA) and mixtures thereof.

[0070] Generally, the top lid is closed on the tray using welding machines into which the already filled tray is placed. The top lid film, generally supplied wound on a reel, is unwound, either automatically, using towing systems, or manually by an operator, and positioned over the tray. At this point, a heated plate, or a sonotrode in the case of ultrasonic welding, rests on the top lid for a specified time and at a specific pressure or power. The temperature, contact time and pressure are defined by the operator depending on the products to be welded based either on their own experience or on the data provided by the manufacturers of the tray and lid.

[0071] It has been found that, by carrying out the welding at a temperature between 100 and 135°C, preferably between 105 and 130°C, at a pressure between 2 and 4 bar and a time between 0.5 and 2 s, an easy manual opening of the weld is obtained with the article of this invention. Easy to open by hand means that its holding force is in the range of approximately 5 to 15 N. Said welding force is measured by a tensile test of the welds according to the ASTM F88 method (Technique C: 180° supported, 300mm / min).

[0072] Generally, the top lid must allow, through the welding, a complete hermetic seal but at the same time, in order to facilitate use by the consumer, easy removal when the package is opened.

[0073] Transformation of the sheet into containers by thermoforming takes place on machines that have an area equipped with heating systems (oven) where the sheet is heated, and a forming and cutting area where a male-female moulding system (mould) gives the desired shape, and a cutting system (shearing) that separates the various containers from each other and from the portions of unformed sheet.

[0074] Depending on the shape and size of the containers, the amount of unformed sheet, commonly referred to as waste, may be as much as 50% of the initial sheet, with a significant economic and environmental impact. This material can be ground (in-line or offline at a later stage) and reused during the production phase of a new sheet, fed into one or more of the layers that make up the multilayer sheet using appropriate dosing systems in a percentage that varies depending on the quantity of waste available and the desired technical characteristics.

[0075] Waste can also be generated during sheet production: for example, the side selvedges or the starting and regulation coils can be ground and reused in-line or offline for the production of new sheets.

[0076] The waste has a composition that is the weighted average of all the materials used in the multilayer sheet from which it was generated.

[0077] A further object of the present invention is therefore a thermoformed article for food packaging consisting of a body and a top lid, in which said body comprises a multilayer sheet with at least three layers among which:

[0078] - a first polymeric layer A in contact with the food comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) or a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns;

[0079] - a second barrier layer B comprising a polymer selected from the list of a butanediol vinyl alcohol copolymer (BVOH), polyvinyl alcohol (PVOH) or a combination thereof;

[0080] - a third polymeric layer C comprising a biodegradable polymer selected from an aromaticaliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) or a polylactic acid (v) and mixtures thereof, characterized in that the process waste (vii) is added from 1 to 50%, preferably from 10 to 30% with respect to the total sheet.

[0081] In a preferred embodiment of the invention, the waste (vii) is added to layers A and C of the multilayer sheet of the thermoformed article.

[0082] In a further preferred embodiment of the invention, the multilayer sheet of the thermoformed article of the invention may be made of:

[0083] - a first polymeric layer A in contact with the food comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv), a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns

[0084] - a second tie layer D comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;

[0085] - a third barrier layer B comprising a polymer selected from the list of a butanediol copolymer vinyl alcohol (BVOH), polyvinyl alcohol (PVOH) or a combination thereof;

[0086] - a fourth tie layer E comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;

[0087] - a fifth polymeric layer C comprising a biodegradable polymer selected from an aromaticaliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) or a polylactic acid (v) and mixtures thereof and further characterised in that the waste (vii) is added in a range of 1 to 50%, preferably 10 to 30%, with respect to the total sheet. The waste (vii) can also be advantageously added to the single polymeric layer of the sheet. It can be advantageously used in layers A, C of three-layer and five-layer sheets, and in layers A, C, F and G in a seven-layer sheet.

[0088] The invention is now illustrated with some embodiments intended to be illustrative and not restrictive of the scope of protection of this patent application.

[0089] Example 1

[0090] This example describes the methods that have been used to evaluate the ability of a polymer film to be peeled from a thermoformed container to which it has been welded.

[0091] The multilayered sheets used have layer A with a thickness between 300 and 350 pm.

[0092] The covering films that were welded onto the sheets are made of PBTA and PLA (Luminy LX 175™) in the welding layer, both with a thickness of 35 pm.

[0093] The welding was carried out with a Brugger tool, the Heat Sealing Machine HSG-CC model, setting a pressure of 3 bar for 1 second and using a single sealing bar (positioned on the top lid film side) measuring 1 cm x 15 cm. The welds were performed starting from 90°C and gradually increasing up to 140°C, in 10°C increments.

[0094] To measure the welding strength and evaluate the peelability of the top lid film from the sheet, a tensile test of the welds was performed according to the ASTM F88 method (Technique C: 180° supported, 300mm / min). The test was performed on 60 x 25 mm specimens to which TESA 04129 adhesive tape was applied to avoid traction of the top lid film during the test.

[0095] Example 2

[0096] The method described in example 1 was used for a Sheet 1 whose formulation is shown in table 1.

[0097] Poly(l,4-butylene succinate) (“PBS”, component (iii)) with an MFR (190°C, 2.16 kg) = 6 g / 10 minutes;

[0098] Commercial grade Luminy L175™ polylactic acid (“PLA” component (v)) from Total -Corbion with an MFR (190°C, 2.16Kg) =3 g / lOmin

[0099] Talc (component (vi)) having a mean diameter of 7 microns (particle distribution D50 measured by laser diffraction (ISO 13320)) commercial grade Edofill™ from Imifabi;

[0100] Additives:

[0101] • Nisshinbo Chemical Inc. carbodimide carbodilite HMV15CA™ (“carbodi mi de”, crosslinking and / or chain-extending agent).

[0102] • Masterbatch comprising 60% by weight of poly(l,4-butylene adipate-co-l,4-butylene terephthalate) and 40% by weight of titanium dioxide (“master TiO2”, pigment) Nippon Gohsei BTR8002P™ biodegradable aromatic-aliphatic polyester functionalised with a,P-unsaturated carboxylic acids (“Functionalised PBTA”)

[0103] Nichigo G-polymer™ BVE8049P butanediol vinyl alcohol copolymer from Nippon Gohsei (“BVOH”)

[0104] Table 1

[0105] Table 2 shows the results of the peelability test as described in Example 1 for Sheet 1. Table 2 shows only layer A of the sheet, which is the layer welding to the PLA top lid.

[0106] Table 2

[0107] Table 3 shows the results of the peelability test as described in example 1 for Sheet 1. Table 3 shows only layer A of the sheet, which is the layer welding to the PBTA top lid. Table 3

[0108] Example 3

[0109] The method described in example 1 was used for a Sheet 2 whose formulation is shown in table

[0110] 4.

[0111] Table 4

[0112] Table 5 shows the results of the peelability test as described in example 1 for Sheet 2. Table 5 shows only layer A of the sheet, which is the layer welding to the PBTA top lid.

[0113] Table 5

[0114] Example 4 (for comparison)

[0115] The method described in example 1 was used for a Sheet 3 whose formulation is shown in table

[0116] 6.

[0117] Table 6

[0118] Table 7 shows the results of the peelability test as described in example 1 for Sheet 3. Table 7 shows only layer A of the sheet, without talc, which is layer welding to the PLA top lid (top lid). Table 7

[0119] Table 8 shows the results of the peelability test as described in example 1 for Sheet 3. Table 8 shows only layer A of the sheet, without talc, which is the layer welding to the PBTA top lid.

[0120] Table 8

[0121] Example 5 (comparison)

[0122] The method reported in Example 1 was used to evaluate the peelability of a polymer film.

[0123] In particular, a sheet similar to Sheet 1 was tested, the only difference being that the talc used (Imerys Steal ene grade) as a mineral filler has a D50 value measured by laser refraction (ISO 13320) of 15 microns, which is outside the range of the invention (between 2 and 9 microns). The peelability test results are shown in Table 9. Table 9

Claims

CLAIMS1) Thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with at least three layers including: a first polymeric layer A in contact with the food comprising a biodegradable polymer selected from: an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns; a second barrier layer B comprising a polymer selected from the list of a butanediol vinyl alcohol copolymer (BVOH), polyvinyl alcohol (PVOH) and a combination thereof; a third polymeric layer C comprising a biodegradable polymer chosen from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), a polyhydroxyalkanoate (iv), a polylactic acid (v) and mixtures thereof.2) Thermoformed article for food packaging according to claim 1 wherein the aromaticaliphatic polyester (i) of the first layer A of the multilayer polymeric sheet comprises: a) a dicarboxylic component comprising, in relation to the total dicarboxylic component: al) 30-70 mol%, preferably 40-60 mol%, of units derived from at least one aromatic dicarboxylic acid; a2) 70-30 mol%, preferably 60-40 mol%, of units derived from at least one saturated aliphatic dicarboxylic acid; a3) 0-5 mol% of units derived from at least one unsaturated aliphatic dicarboxylic acid; b) a diol component comprising, in relation to the total diol component: bl) 95-100 mol% of units derived from at least one saturated aliphatic diol; b2) 0-5 mol% of units derived from at least one unsaturated aliphatic diol.3) Thermoformed article for food packaging according to claim 1 wherein the aliphatic polyester (ii) of the first layer A of the multilayer polymeric sheet is a diol-diacid polyester (iii) comprising:c) a dicarboxylic component comprising, in relation to the total dicarboxylic component: cl) 60-100 mol% of units derived from succinic acid; c2) 0-40 mol% of units derived from at least one saturated dicarboxylic acid with a number of carbon atoms greater than 4; d) a diol component comprising, in relation to the total diol component: dl) 95-100 mol% of units derived from at least one 1,4-butanediol; d2) 0-5 mol% of units derived from at least one aliphatic diol other than 1,4- butanediol;4) Thermoformed article for food packaging according to claim 1 wherein the polyhydroxyalkanoate (iv) is selected from polyhydroxybutyrate or copolymers of polyhy droxybutyrate .5) Thermoformed article for food packaging according to the previous claims wherein the polymeric layer A is a mixture of aromatic-aliphatic polyester (i), a diol-diacid aliphatic polyester (iii) and polylactic acid (v).6) Thermoformed article for food packaging according to claims 1 and 2 wherein the aromatic-aliphatic polyester (i) is selected from poly(l,4-butylene adipate-co-1,4- butylene terephthalate) and poly(l,4-butylene sebacate-co-l,4-butylene terephthalate).7) Thermoformed article for food packaging according to claims 1 and 2 wherein the diol- diacid aliphatic polyester (iii) is selected from polybutylene succinate and copolymers of polybutylene succinate.8) Thermoformed article for food packaging according to claim 1 wherein the top lid is selected from polylactic acid, poly(l,4-butylene adipate-co-l,4-butylene terephthalate) and mixtures thereof.9) Thermoformed article for food packaging according to the preceding claims wherein the layer A further contains up to 1% by weight of at least one cross-linking and / or chainextending agent.10) Thermoformed article for food packaging according to the preceding claims wherein the layer A contains 5-45%, preferably 16-35% by weight with respect to said polymeric layer A of a mineral filler (vi) having particles of an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns.11) Thermoformed article for food packaging according to claim 10 wherein the mineral filler is selected from talc and mica12) Thermoformed article for food packaging according to the previous claims wherein the multilayer sheet comprises the waste.13) Thermoformed article for food packaging according to claim 12 where the waste is contained in layers A and C14) Thermoformed article for food packaging consisting of a body and a top lid wherein said body comprises a multilayer sheet with five layers including:- a first polymeric layer A in contact with the food comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii), and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof and of between 5 and 45% by weight with respect to the total weight of said layer A of a mineral filler (vi) having particles with an average diameter D50 measured by laser diffraction (ISO 13320) between 2 and 9 microns;- a second tie layer D comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;- a third barrier layer B comprising a polymer selected from the list of a butanediol vinyl alcohol copolymer (BVOH), polyvinyl alcohol (PVOH) and a combination thereof;- a fourth tie layer E comprising a biodegradable aromatic-aliphatic polyester functionalised by grafting;- a fifth polymeric layer C comprising a biodegradable polymer selected from an aromatic-aliphatic polyester (i), an aliphatic polyester (ii) and a mixture thereof, wherein said aliphatic polyester (ii) is selected from a diol-diacid aliphatic polyester (iii), polyhydroxyalkanoate (iv) and a polylactic acid (v) and mixtures thereof.15) Thermoformed article for food packaging according to claim 14 wherein the waste is contained in layers A and C.

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