SE534029C2 - Biodegradable adhesive film - Google Patents

Abstract

The present description provides a composition suitable for the preparation of an adhesive film comprising a) 75 to 99% by weight of a biodegradable, aliphatic-aromatic branched copolyester b) 1 to 20% by weight of a biodegradable, aliphatic non-branched polyester, c) an adhesion additive, and d) 0 - 5% by weight of polylactide. In addition, there is provided a method of making such a composition and a method of making an adhesive film.

Description

534 029 The following is a non-limiting, detailed list of embodiments of the present specification, which is presented for the purpose of providing various features and combinations provided by the invention in some of its aspects.

ITEMS 1. Composition suitable for the preparation of an adhesive film comprising a) 75 to 99% by weight of a biodegradable, aliphatic-aromatic branched copolyester b) 1-20% by weight of a biodegradable aliphatic non-branched polyester, c) an adhesive additive and d) 0 to 5% by weight of polylactide. A composition according to item 1, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises aliphatic and aromatic dicarboxylic acids and an aliphatic dihydroxy compound as monomeric building blocks. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises monomeric building blocks of a) an acid component of at least one aliphatic or cycloaliphatic dicarboxylic acid or its ester-forming derivative or mixture thereof and b) an acid component of at least one aromatic dicarboxylic acid or its ester-forming derivative or a mixture thereof and c) at least one dihydroxy compound or at least one amino alcohol or a mixture thereof and d) optionally isocyanurate. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises monomeric building blocks selected from the group consisting of 1A-butanediol, adipic acid and terephthalic acid. A composition according to any one of the preceding claims, wherein said biodegradable, aliphatic-aromatic branched copolyester is poly- (butylene adipate terephthalate). 534 029 6. A composition according to any one of the preceding claims, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises a monomeric building block selected from the group consisting of mononuclear isocyanurate, divalent isocyanurate, trinuclear isocyanurate and a mixture thereof. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises isocyanurate as a monomeric building block. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises monomeric building blocks of a) an adipic acid or ester-forming derivative thereof or a mixture thereof, and b) a terephthalic acid or ester-forming derivative thereof or a mixture thereof, c) a dihydroxy compound selected from the group consisting of C 8 -C 10 alkanediols and C 5 -C 18 cycloalkanediols or a mixture thereof, and d) optionally a compound containing sulfonate groups. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester comprises epoxide as a monomeric building block. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic-aromatic branched copolyester has a glass transition temperature from -35 to -25 ° C and a melting range of 105 to 115 ° C. A composition according to any one of the preceding items, wherein said composition comprises 78-96% by weight, such as 80-95% by weight, such as 85-92% by weight, such as 88-92% by weight, and as about 90% by weight of the biodegradable aliphatic - aromatic branched copolyestem. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic non-branched polyester is selected from the group consisting of polyalkylene succinate adipates and polyalkylene succinates. 534 029 13. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic non-branched polyester is selected from the group consisting of polybutylene succinate, polyethylene succinate, polybutylene succinate adipate and polyethylene succinate adipate. A composition according to any one of the preceding items, wherein said biodegradable, aliphatic non-branched polyester is polybutylene succinate. A composition according to any one of the preceding items, wherein said composition comprises 1 to 15% by weight, such as 2 to 13% by weight, such as 4 to 11% by weight, such as about 5 to about 10% by weight of the biodegradable, aliphatic non-branched polyester. A composition according to any one of the preceding claims, wherein said additive is selected from mono- and diglycerides. A composition according to any one of the preceding items, wherein said composition comprises 0.3 - 1.5% by weight, such as 0.5 - 1% by weight, and as less than 1 but more than 0.5% by weight of the additive. A composition according to any one of the preceding items, wherein said composition comprises 1 to 5% by weight, such as 1 to 3% by weight and as about 2% by weight of polylactide. Adhesive strip comprising the composition according to any one of the preceding paragraphs. Use of an adhesive film according to item 19 for enclosing food or foodstuffs arranged on a tray. Granules comprising the composition according to any one of items 1 to 18. Use of the granules according to item 21 for the preparation of an adhesive film. A process for the preparation of a composition suitable for forming an adhesive film, said process comprising mixing the following components a) 75-99% by weight of a biodegradable, aliphatic-aromatic branched copolyester 534 029 b) 0-20 weight percent of a biodegradable, aliphatic non-branched polyester, c) an adhesion additive and d) 0 to 5 weight percent polylactide, said components being subjected to a compression with a pressure of 70 to 200 bar during said mixing. Process according to item 23, wherein said composition is according to any one of items 1 to 18. 25. Process according to items 23 to 24, wherein the pressure amounts to 80 - 180 bar such as 100 - 150 bar. A method according to any one of items 23 to 25, wherein the composition is compressed in the pre-blowing step. A method according to any one of items 23 to 26, wherein the mixing and compaction is performed using at least one barrier screw. A method according to any one of items 23 to 27, wherein the granulate is formed from said composition or said mixture and compression. A process for producing an adhesive film, comprising blow extrusion of a composition comprising a) 80 to 99% by weight of a biodegradable, aliphatic-aromatic branched copolyester, b) 0 to 20% by weight of a biodegradable, aliphatic non branched polyester, c) an adhesive additive and d) 0 to 5% by weight of polylactide, the inflation ratio of the inflation extinction ratio being 3 to 8. 30. Process according to item 29, wherein said composition is according to any one of items 1 to 18. 534 029 31. Process according to any one of items 29 to 30, wherein said inflation ratio is 3 to 7 such as 4 to 6. 32. A method according to any one of items 29 to 31, wherein the film is stretched by at least 20% longitudinally after film blowing extrusion. 33. The method of item 32, wherein said film is stretched by at least 25%, such as at least 30%, such as at least 40%. A method according to any one of items 32 to 33, wherein the film is joined to a first and second roll, said first roll being arranged upstream of the second roll, and the second roll rotating at a speed at least 20% higher than the speed of the first roller to effect the stretching. The item of item 34, wherein said speed is at least 25% higher, such as at least 30% higher, such as at least 40% higher. A method according to any one of items 29 to 35, wherein the components of the composition are mixed and subjected to a compression with a pressure of 70 - 200 bar, such as 80 - 180 bar, such as 100 - 150 bar, before the film blowing extrusion. A method according to any one of claims 29 to 36, wherein the composition is provided in the form of granules produced according to item 28.

Detailed Description As a first aspect of the present disclosure, there is provided a composition suitable for the manufacture of an adhesive film comprising a) 75 to 99% by weight of a biodegradable, aliphatic-aromatic branched copolyester b) 1 to 20% by weight of a biodegradable degradable, aliphatic non-branched polyester, c) an adhesion additive and d) 0 to 5% by weight of polylactide.

The adhesive film can be a thin plastic film that can be used, for example, to enclose food items in containers to keep them fresh. Adhesive film sold, for example, on rolls in boxes with a cutting edge, adheres to many smooth surfaces and can thus remain tight over the opening of a container without the use of glue or other devices.

Attachment film is also known as attachment cover. The film can have a thickness in the interval 5 - 50 pm.

Biodegradability means chemical degradation of materials through a physiological environment. Biodegradable biological plastics are plastics that can be degraded aerobically in a natural environment (eg by composting) or anaerobically (eg by burying rubbish). Biological degradation of plastics can be achieved by enabling microorganisms in the environment to degrade the molecular structure of plastic films through their metabolism. The plastics can be made up of either biological plastics, which contain components derived from renewable raw materials, or of petroleum-based plastics.

Under the right conditions, biodegradable plastics can degrade to the point where microorganisms can take up and metabolize them. Degradation of oil-based biodegradable plastics can release previously stored carbon as carbon dioxide. In the context of the present description, "aliphatic" refers to a compound which is composed of carbon and hydrogen and which does not contain aromatic rings. An aliphatic compound may be cyclic, acyclic, saturated or unsaturated. The carbon atoms may be joined together in straight or branched chains or in non-aromatic rings (which in this case are called alicyclic rings).

"Polyester" refers to a polymer category in which the monomeric building blocks are joined together via ester bonds. In the context of the present description, a "copolyester" further refers to a polyester which contains more than one type of monomeric building blocks. Polyester thus becomes a copolyester by its comonomer content.

"Aliphatic-aromatic copolyester" means a compound, in this case a copolyester, which is a compound consisting of at least two parts, an aliphatic part containing no aromatic ring and an aromatic part containing an aromatic ring. Aliphatic-aromatic copolyesters usually combine the property of aliphatic polyesters to be biodegradable with the strength and performance properties of aromatic polyesters.

In the context of the present description, an adhesion additive refers to a product which improves the ability of an elm to adhere to even surfaces, such as glass, ceramic or plastic surfaces. For example, the adhesion additive can smooth the surface of the film, thereby improving the adhesion properties.

Polylactic acid or polylactide (PLA) is a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources such as corn starch or sugar cane. The composition of the present disclosure is based on the inventor's insight that a biodegradable composition suitable for making an adhesive film is produced by combining an aliphatic aromatic branched copolyester with an aliphatic non-branched polyester together with the addition of an adhesive additive. and optionally also PLA. The components of the composition have generally been considered immiscible, but the inventor has found that the components are miscible when certain amounts of them are used. In addition, the composition of the present disclosure can be used to produce a biodegradable film having satisfactory optical and mechanical properties.

Thus, a composition according to the present description is suitable for the production of a film, such as an adhesive film, which exhibits both high clarity and good cutability.

In the context of the present description, "cutability" refers to the ease with which an film can be torn or cut in its lateral direction.

In the context of the present description, "clarity" refers to the transparency towards the eye. "Clarity" is thus a visual impression. A clear film is often required to give the food covered by the film an appetizing impression. One embodiment of the first aspect comprises the biodegradable, aliphatic-aromatic branched copolyester aliphatic and aromatic dicarboxylic acids and an aliphatic dihydroxy compound as monomeric building blocks. The aliphatic-aromatic branched copolyester may, for example, contain 95 to 100 mole percent of these three building blocks, in one example the monomeric building blocks are selected from the group consisting of 1,4-butanediol, adipic acid and terephalic acid. The compound 1A-butanediol is an aliphatic dihydroxy compound, a diol of the formula HOCH 2 CH 2 CH 2 CH 2 OH. The adipic acid is an aliphatic dicarboxylic acid of the formula (CH2) 4 (CO2H) 2. Terezylic acid is an aromatic dicarboxylic acid with a benzene ring and has the formula C6H4 (CO2H) 2.

Copolymerization of aliphatic monomers with aromatic monomers such as terephthalic acid (or diester derivatives such as dimethyl terephthalate (DMT)) can be a way to improve the performance properties of aliphatic polyesters. A film containing aliphatic-aromatic branched copolyesters can provide satisfactory transparency, flexibility and counteracting performance. The aliphatic-aromatic branched copolyestrams are biodegradable.

In one example, the biodegradable, aliphatic-aromatic branched copolyester is poly (butylene adipate terephthalate).

An example of an aliphatic-aromatic branched copolyester is manufactured by BASF and marketed under the trade name Eco fl ex. Under this trade name, there are a number of different qualities. Each polymer grade has been developed with controlled branching and chain extension to be adapted to its specific application if possible. Eco fl ex is a copolyester comprising 1A-butanediol, adipic acid and dimethyl terealate (DMT). In some cases, a diiosocyanate is used as a chain extender.

Ecoflex has the following structure: O O O il ll ll C "" O * (CH2) 4 O ~ C "(CH2) 6" C Eco fl ex is transparent to transparent and has a semi-crystalline structure. The copolyester can be used for extrusion of films.

By using the new generation product Ecoflex FS BX 7500 (from BASF) instead of the product Eco fl ex 7011 (from BASF) in the composition according to the present description, a higher percentage of renewable material can be used. The product Eco fl ex 7011 is a 100% oil-based product, while the product Ecoflex FS BX 7500 consists of 38% renewable raw material.

Another aliphatic-aromatic branched copolyester that can be used is manufactured by Eastrnan Chemical Company and marketed under the trade name Eastar Bio. The copolyester produced by Eastman is a copolyester derived from 1,4-butanediol, adipic acid and dimethyl terealate (DMT). Under the trade name Eastar Bio there are a number of different qualities.

Each polymer quality has been developed with controlled branching and chain extension to be adapted to its special application if possible.

In one embodiment, the biodegradable, aliphatic-aromatic branched copolyester may comprise a monomeric building block selected from the group consisting of mono-mono-isocyanurate, dicamlic isocyanurate, tri-mono-isocyanurate and a mixture thereof. The concentration of such a building block in the polymer can, for example, amount to 0.5 - 5 mol%.

As an example, the biodegradable aliphatic-aromatic branched copolyester may comprise monomeric building blocks of a) an acid component of at least one aliphatic or cycloaliphatic dicarboxylic acid or its ester-forming derivative or a mixture thereof and b) an acid component of at least one dicarboxylic acid ester-forming derivative or a mixture thereof and c) at least one dihydroxy compound or at least one amino alcohol or a mixture thereof and d) optionally isocyanurate.

"Cycloaliphatic" means an aliphatic compound which contains a cyclic ring.

Aliphatic dicarboxylic acids which can be used in the present description generally comprise 2 to 10 carbon atoms, preferably 4 to 6 carbon atoms. They can be either linear or branched. The cycloaliphatic dicarboxylic acids which can be used in accordance with the present description are, for example, those which comprise 7 to 10 carbon atoms and in particular those which comprise 8 carbon atoms. Particular examples of aliphatic dicarboxylic acids are malonic acid, succinic acid, sebacic acid, fumaric acid, 2,2-methylglutaric acid, 1,3-cyclopentane dicarboxylic acid, adipic acid, glutaric acid, pimelic acid, azelaic acid, maleic acid and cork acid. It is also possible to use dicarboxylic acids with a higher number of carbon atoms, for example up to 30 carbon atoms.

Aromatic dicarboxylic acids that can be used in the present description are, for example, those comprising 8 to 12 carbon atoms and preferably those comprising 8 carbon atoms.

Examples of aromatic dicarboxylic acids are: terephthalic acid, isophthalic acid, Zβ-naphthalenedicarboxylic acid and 1,5-naphthalene dicarboxylic acid. The aromatic dicarboxylic acids or their ester-forming derivatives may be used singly or as a mixture of two or more of them.

It is in principle possible to use all diols or amino alcohols which can form esters with the dicarboxylic acids. Examples of suitable alkanediols are ethylene glycol, 1,2-propanediol, LS-pentanediol, 1,4-butanediol, cyclopentanediol.

In another embodiment, the biodegradable aliphatic-aromatic branched copolyester comprises monomeric building blocks of a) an adipic acid or ester-forming derivative thereof or a mixture thereof and b) a terephthalic acid or ester-forming derivative thereof or a mixture thereof, c) a dihydroxy compound from the group consisting of C 2 -C 6 alkanediols and C 5 -C 18 cycloalkanediols or a mixture thereof and d) optionally a compound containing sulfonate groups.

Thus, the aliphatic-aromatic branched copolyester may contain monomeric building blocks other than aliphatic and aromatic dicarboxylic acids and an aliphatic dihydroxy moiety. Examples of other components are epoxide, anhydrides, isocyanates and sulfonates. These other components can be used to extend the molecular chain.

In one embodiment, the biodegradable aliphatic-aromatic branched copolyester exhibits a glass transition temperature from -35 to -25 ° C and a melting range of 105 to 115 ° C. In one embodiment, the composition comprises 78 to 96 weight percent, such as 80 to 95 weight percent, such as 85 to 92 weight percent, such as 88 to 92 weight percent, and as about 90 weight percent biodegradable, aliphatic-aromatic branched copolyester. The biodegradable, aliphatic non-branched polyester of the present disclosure may be either a homopolymer or a copolymer.

In one embodiment of the first aspect, the biodegradable, aliphatic non-branched polyester is selected from the group consisting of polyalkylene succinate adipates and polyalkylene succinates. Examples of polyalkylene succinate adipates and polyalkylene succinates are polybutylene succinate (PBS), polyethylene succinate (PES), polybutylene succinate adipate (PBSA) and polyethylene succinate adipate. PBS, PES and PBSA are manufactured by Showa High Polymers, LTD, and marketed under the trade name Bionolle. Examples are Bionolle 3001 (PBSA), Bionolle 1001 (PBS) and Bionolle 6000 (PES).

Other examples are polyhydroxybutyrate, copolymers based on polyhydroxybutyrate and polyhydroxyvalerated, poly (hexamethylene glutarate), poly (hexamethylene adipate) and poly (hexamethylene succinate). Other examples of aliphatic non-branched polyesters are polyesters from EnPol and Eastman Chemical. Succinate-based aliphatic polyesters are also manufactured by Mitsui Toatsu, Nippon Shokubai, Cheil Synthetics, SK Polymers, Mitsubishi and Sunkyon Industries.

PBS is a biodegradable, synthetic, aliphatic non-branched polyester. PBS exhibits good mechanical properties and can be used for many different end uses via conventional melt treatment technology. PBS is biodegradable under the influence of water and begins to biodegrade via a hydrolysis mechanism. The hydrolysis takes place at the ester bonds, which leads to a reduction in the molecular weight of the polymer, which in turn enables further degradation, for example by microorganisms.

In one embodiment, the composition comprises 1 to 15 weight percent, such as 2 to 15 weight percent, such as 3 to 13 weight percent, such as 4 to 12 weight percent, and such as about 5 to about 10 weight percent of the biodegradable, aliphatic non-branched polyester. The inventor has produced films using both 5 and 10% of the biodegradable, aliphatic non-branched polyester with satisfactory results.

In one embodiment of the first aspect, the adhesion additive is selected from mono- and diglycerides. Glycerides, also known as acylglycerols, are esters formed from glycerol and fatty acids. Glycerol has three functional groups, which can be esterified with one, two or three fatty acids to form monoglycerides, diglycerides and triglycerides. The adhesion additive improves the tackiness of the film. By producing a film with a sufficiently high degree of tack, the film can be used, for example, to cover trays or containers with fruit and vegetables. In one example, the composition comprises 0.3 to 1.5% by weight, such as 0.5 to 1% by weight, and as less than 1% by weight but more than 0.5% by weight of the additive. If too much adhesion additive is added, the result of the addition may be a slippery film. The adhesion additive can thus become a "slip additive" if its concentration in the film is too high.

In one embodiment, the composition comprises 1 to 5% by weight, such as 1 to 3% by weight and as 2% by weight of the polylactide. The polylactide, polylactic acid (PLA) is a linear aliphatic polyester which is produced by polycondensation of naturally produced lactic acid or by catalytic ring opening of the lactide group. PLA tends to be strong but also stiff and brittle. Lactic acid can be produced as a co-product in wet grinding of maize. The ester bonds in PLA are sensitive both to chemical hydrolysis and to enzymatic chain cleavage. One company that produces PLA is Cargill.

A plastic adhesive, such as an adhesive adhesive (sometimes referred to as an adhesive wrap or plastic wrap), which comprises the composition is thus provided in the present description, as will be apparent from the foregoing. There is also provided a use of such a film for enclosing food or sealing containers containing food.

The film can thus be used for enclosing fruits or vegetables which are arranged on trays, which can also be biodegradable. Accordingly, a unit consisting of foodstuffs is arranged in a biodegradable container which is sealed with an föreliglm according to the present invention biodegradable in its entirety. Accordingly, if a piece of food in such a unit is to be disposed of, the various components of the unit need not be separated from each other prior to composting. A piece of funnel which is wrapped in an enligt lm according to the present description must thus not be separated from the film before it is composted.

Granules containing the composition can also be obtained according to the present description. Granules are particles of a substance. Granules comprising the composition of the present disclosure may be a convenient way of storing the composition. It is also advantageous to add the composition according to the present description in the form of a granulate in a film production process. As a second aspect of the present description, there is provided a process for preparing a composition suitable for forming an adhesive film, said process comprises blending the following components a) 75 to 99% by weight of a biodegradable aliphatic-aromatic branched copolyester b) 0 to 20% by weight of a biodegradable, aliphatic non-branched polyester, c) a adhesion additive and d) 0 - 5% by weight of polylactide, said components being subjected to a compression with a pressure of 70 to 200 bar during said mixing.

The composition used during the second aspect may be the composition according to any of the embodiments according to the first aspect. Thus, components a) to d) may be a) to d) according to any of the embodiments of the first aspect.

In embodiments of the second aspect, the pressure amounts to 80 - 180 bar. In other embodiments, the pressure amounts to 100 - 150 bar. The pressure can be measured in the extruder at the end of the bairy disc.

The composition obtained according to the above-mentioned method can be used to form a film, such as an adhesive film, and the film formation can be carried out by means of blown film extrusion.

The composition according to the second aspect thus comprises a biodegradable, aliphatic-aromatic branched copolyester and an adhesion additive. Additives of a biodegradable, aliphatic non-branched polyester and polylactide are optional.

The mixing and compaction is normally carried out before use in a film blow extruding process. The components of the second aspect have generally been considered immiscible, at least to the extent that clear films can be obtained. However, the inventor has found that a clear film can be obtained by using said degree of compaction. The components can, for example, be mixed and compressed in one place and then delivered e.g. in the form of granules, to another place where the blow-extruding is carried out.

Another possibility is to mix the components while compressing them in connection with the blow molding extrusion process. In such cases, the components may be added to a hopper, which is connected to an extruder containing a rotating barrier screw and in which the components are mixed. Extrudes may also include kneading elements. Inside the extrudate, the pressure is raised during mixing.

Accordingly, in the blow extrusion process of the present disclosure, a pre-compressed composition may be used or the process may comprise a step of mixing and compressing the components of the composition.

In a third aspect of the present disclosure, there is provided a method of forming an adhesive film comprising film blowing extrusion of a composition comprising a) 80-99% by weight of a biodegradable, aliphatic-aromatic branched copolyester, b) 0-20% by weight of a biodegradable aliphatic non-branched polyester, c) an adhesion additive and d) 0 - 5% by weight of polylactide, the inflation ratio in the mlmblowing extrusion being 3 - 8.

The composition according to the third aspect thus comprises a biodegradable, aliphatic-aromatic branched copolyester and an adhesion additive. Additives of a biodegradable, aliphatic non-branched polyester and polylactide are valñia.

The composition used in the third aspect may be the composition according to any of the embodiments of the first aspect. Components a) to d) may thus be a) to d) according to one of the embodiments of the first aspect.

The "inflation ratio" is the ratio between the diameter of the blown film and the diameter of the outlet of the tool that pumps out the molten plastic (ie the outlet diameter of the mold).

In an embodiment of the present description, the outlet diameter of the mold can amount to 100 - 500 mm.

The inventor has found that an inflation ratio of 3 or higher leads to an elm with satisfactory cutability. Without being limited to any particular theory, the inventor considers that such an inflation ratio orients the polymers of the film in such a way that an angle is formed between the direction of elongation of the polymers and the direction of elongation of the film, which in turn leads to increased cutability.

The inflation ratio can be, for example, higher than 3, such as higher than 4.

In the embodiments, the inflation ratio is 3 to 7. In other embodiments, the ratio is 3 to 6. In still other embodiments, the inflation ratio is 4 to 6.

In one embodiment of the present disclosure, the film is stretched by at least 20% after the blow extrusion. In another example, the film is stretched by at least 25%, such as at least 30%, such as at least 40%.

The route is also called "advance route". The stretching is performed in the Y-direction, which is the extension direction of the film. Sometimes this direction is also called the longitudinal direction or the machine direction. "Pre-stretching" in combination, but the composition and inflation ratio improve cutability and clarity.

To achieve such a stretching, the film can be combined with a first and a second roll, said first roll being arranged upstream of the second roll, and the second roll rotating at a speed at least 20% higher than the speed of the first roller. "Upstream" and "downstream" refer to relative positions along the film-making process.

In one example, the speed is at least 25% higher. In yet another example, the speed is at least 30% higher or at least 40% higher.

The film blowing extrusion is a process by which many commodity plastics and special plastics are manufactured for the packaging industry. The film blowing process basically consists of extruding a tube of molten thermoplastic and continuously inflating it beyond its original diameter, forming a thin tubular product which can be used directly (for example in the manufacture of plastic bags or sacks), or which can cut up to produce a flat fi ch. (for example for making a sheet).

The components of the tin plastic (here the components of the "composition") can be added to a filling funnel which is arranged on an extruder which may contain at least one barrier screw.

The mixing of the components can be performed under compression (see above).

Another possibility is to add a prepared composition, in which the components have already been mixed in during compaction, to the filling funnel. In such a case, the composition may, for example, be in the form of granules (see above).

In another example, a mixer / kneader may be used which acts in combination with at least one screw compounding extruder to improve mixing efficiency. During operation, the at least one, the kneading element, the tooth or the pin moves through the slots of the screw spiral in order to achieve an effective mixing effect in the melt which is pumped therebetween.

The mixture of the components is heated and transported by extruder to a furnace.

The mold is the component of the extruder through which the melt is pressed to form the desired profile. The shape may be a vertical cylinder with a circular opening. The diameter can be a few centimeters to more than three meters across. The gap of the foam is the width of the gap through which the molten thermoplastic is pressed to form a blown film. In embodiments of the present invention, the spacing of the molds may be 0.5 - 2.5 mm, such as 0.9 - 1.7 mm.

An air ring can be arranged around the mold. The air ring can cool the film as it travels upward. Grain-primed gas, usually lu fi, from an air outlet can also be forced into the center of the extruded circular product, forming a bubble. This can expand the extruded circular cross-section in any ratio (a multiple of the diameter of the mold) to a desired diameter. The pressure inside the bubble is normally such that the tube is stretched, its diameter increases and its wall thickness decreases to a desired thickness. The gas that can be enclosed within the bubble of the mold and a roller nip that is arranged downstream of Relative to the mold.

Such a nip, e.g. arranged high above the mold, can also pull the molten plastic upwards from the mold (for example 4 to 20 meters or more depending on the amount of cooling required). The roller nip can provide the force to pull the bubble away from the mold in the machine direction at a desired speed. By changing the speed of the roller nip, the thickness of the film (wall thickness) can be changed.

When the hot, extruded material is pulled up several lengths of the nip, the air inside the expanded tube nonnally fulfills three basic functions. First, the volume and pressure of the air blown into the tube cause the material to stretch, thereby determining the overall size of the bubble and the width of the finished sheet. Second, the same effect associated with the speed at which the bubble is drawn upwardly away from the mold determines the thickness of the finished film. Third, the bubble begins the air cooling process as it travels upward to the nip. The extrusion speed of the melt, the speed of the roller nip and the degree of inflation of the bubble can together determine the final thickness of the film.

In the next step, the roller nip can flatten the bubble into an elm double layer whose width (called "lay fl at") is equal to half the circumference of the bubble.

Between the form and the roller nip, the melt can cool and undergo a phase transformation to a crystalline state. A so-called "frost line" can be observed at the point on the bubble where the phase transformation takes place.

The film can thus be cooled down to its crystallization temperature range when it is produced. The film can be cooled on both sides, ie. both on the inside and outside of the tubular plastic film during the production of the blown film. The cooling work step can be performed with different temperatures on both sides of the plastic.

When the film is stretched, so-called "forehand stretching" (see above), the film can be pulled by rollers rotating at different rotational speeds in such a way that the film is stretched to a desired longitudinal (machine direction) pull ratio. The draw ratio can be determined by dividing the linear velocity of the film coming out of the stretching step by the linear velocity of the film entering the stretching step.

After stretching, the film can optionally be heat cured to stabilize the stretched film.

The film can also be cut open and in that case it goes into a cutting station. Either or both sides of the flat tubular film can be cut open. 534 029 17 The film can finally be rolled up on winding rollers. The film recording speed can be, for example, 15 - 60 m / minute. The film produced can have a width of 100-100 mm and can have a thickness of 8-20 μm.

The treatment of the composition on the extrusion lines may depend on the composition, the extrusion technology and the process conditions. With the guidance of the present description, the person skilled in the art can without undue effort optimize these parameters to achieve satisfactory quality of the final product.

The concept in the present description has several advantages, some of which are discussed below.

One advantage is the biodegradability. The composition can be biodegradable and only carbon dioxide, water and biomass are produced.

Another advantage is that the moisture permeability through an mlm comprising the composition according to the present description can be improved compared to that of other plastics or biological plastics. For example, the shelf life of fruits and vegetables can be improved when they are covered during storage by a film comprising a composition according to the present description, thanks to the moisture permeability properties of the film.

Another advantage is that it is possible to tear or tear the film according to the present description in the lateral direction. This is particularly advantageous in machines that cut off parts of the film and wrap food products in such parts. Accordingly, it is generally possible to use the film in conventional dry packing machines. These dry packing machines can be used to pack fruit and vegetables on trays or in containers. Major adjustments to the packaging machine need not be necessary when using this new adhesive tape which includes the composition of the present specification. The wear and tear properties are also advantageous in forming pieces of the film from a roll in a box with a cutting edge.

Yet another advantage is that the components of the composition usually do not need to be dried in advance before mixing.

Brief Description of the Drawings Fig. 1 shows a schematic representation of a film blowing extrusion process.

Detailed Description of Illustrative Embodiments A non-limiting embodiment of a method according to the present description is described in more detail below. 534 029 18 Example 1.

In this example, the blown film is prepared by mixing 93% by weight of Eco ex, 5% by weight of Bionolle and 2% by weight of an adhesive additive (a glyceride).

Eco fl ex is purchased from BASF and Binolle from Showa High Polymer. The components are mixed and compressed by the blow molding extrusion process.

The composition in the form of granules is added to the filling funnel 1 which is arranged at an extruder 2 which contains a barrier screw 3 with extrusion element 4. The barrier screw 3 has a smaller diameter at the end of the extruder 2 where the material is added via the filling funnel I than at the end where the thermoplastic leaves the extruder 2 As the diameter of the barrier screw 3 increases along the extruder 2, the pressure inside the extruder 2 increases. The barrier screw 3 rotates by means of the screw drive motor 5.

In this example, the components of the composition are added to the hopper 1. The material is successively compressed and melts to form a continuous viscous liquid. A pressure develops on the molten resin inside the extruder 2. The pressure is usually in the range of 70 - 200 bar. The molten thermoplastic has a temperature in the range 160 - 180 ° C before it leaves the extruder.

The molten material is pumped through a circular, rotating mold 6. The mold 6 is a component of an extruder 2 and fixed to the head 7 of the extruder, through which the melt is forced out.

The shape is a vertical cylinder with a circular opening. The diameter of the circular opening of the mold 6 is about 300 mm.

The gap 8 is 1.3 mm. In this example, the filmblowing extrusion was performed vertically upward.

A loop 9 is arranged around the mold. The ring 9 cools the film 10 as it travels upwards. The lu fi temperature is around 20 ° C. Compressed lu fl from an air outlet is also forced into the center of the extruded circular profile at the beginning of the process and the pressure causes the extruded melt to expand into a bubble. An even and constant pressure is maintained to ensure uniform flow thickness as the roll nip 12a and the mold 6 prevent leaks.

The extruded circular cross-section expands in a certain ratio to a desired diameter. This ratio is called the inflation ratio, which is the ratio between the diameter 11 of the blown film and the diameter of the circular opening of the mold. The inflation ratio can be 3 - 8: 1. The polymer angle after inflation can be about 45%. The pressure 534 029 19 is such that the pipe is stretched, whereby its diameter increases and its wall thickness decreases to the desired thickness.

The molten plastic is pulled upwards from the mold 6 by a roller nip 12a which is arranged above the mold. The gas is trapped in the bubble of the mold 6 and the roller nip 12a. The roller nip 12a provides the collar to pull the bubble away from the mold 6 at the desired speed. Changing the speed of the nip 12 can change the thickness of the film (wall thickness).

The volume and pressure of the air that is blown into the tube causes the material to stretch, whereby the overall thickness of the bubble and the thickness of the finished sheet are determined. The volume and pressure of the air blown into the tube and also the rate at which the bubble is drawn upwards away from the mold 6 determines the thickness of the finished film. The bubble begins the light cooling process as it travels up to the roller nip l2a. Between the mold 6 and the roller nip 12a, the melt can cool and undergo a phase transformation to the crystalline state.

The film 10 moves into the roll nip 12a which causes the bubble to collapse and flattens the bubble into a double film layer 13 whose width (called "lay") is equal to half the circumference of the bubble.

The film 13 passes through the non-driven rollers 14 during this process to ensure that the tension in the film 13 becomes uniform. When the film is stretched, so-called "pre-stretching", the film is drawn by a second roller nip l2b whose rollers rotate at a higher speed than the rollers in the first roller nip l2a, so that the sheet is stretched to the desired draw ratio in the longitudinal direction (machine direction). The draw ratio is determined by dividing the linear velocity of the elm coming out of the stretching step by the linear velocity of the elm entering the stretching step. For example, a roller "downstream" rotates at a higher speed than a roller "upstream" and consequently the elm is stretched. For example, the film can be stretched by 25%, which means that the roller "downstream" rotates at a speed which is 25% higher than the rotational speed of the "upstream" roller.

The stretching, or dry-stretching of the film, increases the clarity of the film. In connection with a high inflation ratio, the stretching improves both the mechanical and optical properties of the film, for example cutability and clarity.

Finally, the film is pulled up on winding rollers 15. The film recording speed is about 15 - 60 ni / minute. Between the roll nip 12b and the take-up rollers 15, the film 13 may pass through a processing center depending on its application. During this stage, the film in this example is divided to form two films.

The thickness of the film is in the range of 8 - 20 μm and its width is in the range of 1,100 - 1,500 mm.

Claims (15)

23 Claims

1. A composition suitable for forming a cling film comprising a) 75-99 % by weight of a biodegradable, aliphatic-aromatic branchedcopolyester, b) 1-20 % by weight of a biodegradable aliphatic non-branchedpolyester, c) a cling-additive and d) 0-5 % by weight of polylactide.

2. A composition according to claim 1, wherein said biodegradable,aliphatic-aromatic branched copolyester comprises aliphatic and aromaticdicarboxylic acids and an aliphatic dihydroxy compound as monomericbuilding blocks.

3. A composition according to anyone of the preceding claims, whereinsaid biodegradable aliphatic non-branched polyester is selected from a groupconsisting of polyalkylene succinate adipates and polyalkylene succinates.

4. A composition according anyone of the preceding claims, wherein saidcomposition is comprising 1-15% by weight, such as 2-13% by weight, suchas 4-11% by weight, and such as about 5% to about 10% by weight of thebiodegradable aliphatic non-branched polyester.

5. A composition according to anyone of the preceding claims, whereinsaid cling additive is selected from mono- and diglycerides.

6. A composition according to anyone of the preceding claims, whereinsaid composition comprises 0.3-1.5% by weight, such as 0.5-1% by weight, and such as less than 1% but more than 0.5% by weight of the cling-additive. 24

7. A composition according to anyone of the preceding claims, whereinsaid composition comprises 1-5% by weight, such as 1-3% by weight andsuch as about 2% by weight of polylactide.

8. Cling film comprising the composition according to any of the precedingclaims.

9. Use of a c|ing film according to claim 8 for sealing food or food arrangedin a tray.

10. Granules comprising the composition according to any one of claims 1-7.

11. Use of granules according to claim 10 for the preparation of a c|ing film.

12. A process for preparing a composition suitable for forming a c|ing film,wherein said process comprises mixing of the following components a) 75-99 % by weight of a biodegradable, aliphatic-aromatic branched copolyester, b) 0-20 % by weight of a biodegradable aliphatic non-branched polyester, c) a cling-additive and d) 0-5 % by weight of polylactidewherein, during said mixing, said components are subjected to compressionof a pressure of 70-200 bar.

13. A process according to claim 12, wherein granules are formed from saidcomposition after said mixing and compression.

14. A method for forming a c|ing film, comprising blown film extrusion of a composition comprisinga) 80-99 % by weight of a biodegradable, aliphatic-aromatic branchedcopolyester,b) 0-20 % by weight of a biodegradable aliphatic non-branchedpolyester, 5 c) a cling-additive andd) 0-5 % by weight of polylactide,wherein the blow-up ratio in the blown film extrusion is 3-8.

15. A method according to claim 14, wherein the film is stretched by at least20% in the Iongitudinai direction after the blown film extrusion.