WO2025051753A1

WO2025051753A1 - Blown film, method of producing it, and articles comprising it

Info

Publication number: WO2025051753A1
Application number: PCT/EP2024/074633
Authority: WO
Inventors: Magnus KOKKO; David James; Martin Olofsson
Original assignee: Perstorp AB
Current assignee: Perstorp AB
Priority date: 2023-09-05
Filing date: 2024-09-04
Publication date: 2025-03-13
Anticipated expiration: 2026-03-05
Also published as: SE2330380A1

Abstract

The invention relates to a blown film comprising on a spiroglycol-based polyester, to a method of producing said blown film, and to articles comprising said blown film.

Description

Title: BLOWN FILM, METHOD OF PRODUCING IT, AND ARTICLES COMPRISING IT.

***

DESCRIPTION

FIELD OF THE INVENTION

The invention relates to a blown film comprising a spiroglycol-based polyester, to a method of producing said blown film, and to articles comprising said blown film.

BACKGROUND

Thermoplastic polyesters, such as polyethylene terephthalate) (commonly called also “PET”), are versatile and very useful polymers that are widely used for many different film applications, e.g., for industrial and consumer packaging, in construction, in agriculture, in medical applications, because they show in general many advantageous properties.

In fact, the versatility of thermoplastic polyesters allows for customization according to specific application requirements. At the same time, thermoplastic polyesters generally exhibit excellent mechanical properties, including high tensile strength and impact resistance. These characteristics make them ideally suitable for example for packaging films that need to withstand handling, transportation, and storage without compromising the integrity of the contents.

Additionally, polyesters like PET may have exceptional optical and barrier properties and can be also easily printed upon. Such properties are advantageous for example in packaging applications: good optical properties, offering high transparency and clarity, allow consumers to see the packaged goods, barrier properties against moisture, gases, and odours allow an effective control of its shelf-life, while the possibility of printing upon has enables informative packaging designs.

Moreover, recycling systems for thermoplastic polyesters like PET have been already established and their lightweight nature can also contribute to reduce transportation costs and carbon emissions, making them an effective environmentally friendly choice.

SUMMARY OF INVENTION

The Applicant noted that, despite the exceptional advantageous properties of thermoplastic polyesters like PET, nowadays films made of such polymers are mainly produced by the cast-f ilm/stretchi ng technique, even though such technique suffers from many technical and performance limitations.

For example, the cast-film/stretching technique is not cost-effective and limited in terms of productivity, because during the production of the cast film significant amounts of waste materials are produced from the edges of the film that are trimmed due to dimensional irregularities and/or poor layer distribution. The Applicant also noted that the costeffectiveness and the productivity of the process can be further negatively affected if such trimmed material is not efficiently recycled.

At the same time, the Applicant also noted that the precise control over film thickness and optical properties is a challenge in the cast-film/stretching technique and that this may affect also the applicability of such films for applications that require specific film thicknesses and optical properties as it is in packaging, where thin and transparent films are often requested.

The Applicant also noted that film blowing technique offers several advantages over the cast-film/stretching technique. In particular, the Applicant noted that film blowing technique is usually more efficient in terms of cost-effectiveness, reduction of material waste, lowering production costs and offering faster production speeds and continuous production of films, as well as in terms of thickness control, because film blowing enables precise, flexible, and versatile control over film thickness by adjusting process variables such as air pressure, die gap, and extrusion rate, as well as in terms of optical properties. The stretching and orientation of polymer molecules during the blowing process can also reduce haze and improve light transmission, making the films more visually appealing and suitable for applications where product visibility is important, such as packaging and display purposes.

At the same time, the Applicant noted that the attempts of applying this technique to currently known and used thermoplastic polyesters, such as PET, have been frustrated by the behaviour of such polymers during the film blowing process and that such attempts generally imposed the engineering of specific new polymer grades or the use of special machine equipment or settings, impacting negatively on the competitiveness with other materials more suitable for film blowing.

Therefore, the Applicant perceived the need in the art of developing a suitable thermoplastic polyester for film blowing technique. Surprisingly, the Applicant found out that such need can successfully be fulfilled by using a specific family of spiroglycol-based polyesters, that demonstrated to be suitable for film blowing technique.

Therefore, the present invention relates, in a first aspect, to a blown film comprising a spiroglycol-based polyester comprising a diol component and a dicarboxylic acid component, wherein said diol component comprises from 5 to 65 mol%, based on the total amount of the diol component, of residues of a diol having a spiroglycol structure represented by Formula (1 ):

wherein R¹ and R² each independently represent an organic group selected from the group consisting of aliphatic groups having 1 to 10 carbon atoms, alicyclic groups having 3 to 10 carbon atoms, and aromatic groups having 6 to 10 carbon atoms.

Surprisingly, the Applicant has found out that such spiroglycol-based polyester is suitable to be effectively processed for producing blown films, where such blown films show a combination of mechanical and optical properties rendering it suitable for many different film applications, e.g., for industrial and consumer packaging, in construction, in agriculture, in medical, and in healthcare applications.

In a further aspect, the present invention relates also to the use of such spiroglycol-based polyester as defined in the first aspect of the invention, for producing a blown film and to a method of producing a blown film, comprising the step of film blowing such spiroglycol-based polyester as above defined.

The applicant surprisingly noted indeed that the properties of the blown film so obtained renders it particularly useful for the production of many articles.

In a still further aspect, the present invention relates therefore also to an article selected from the group consisting of: selected from the group consisting of: a bag, a container, a package, a pouch, a shrink film, a tape, an agricultural film, a greenhouse cover, a mulch film a silage film, a vapor barrier film, a roofing membrane, a geomembrane, a laminated item, a surgical drape, a gown, a fabric, a protective cover, a liner, a window film for heat reduction, a protective film for a solar panel, and a wrap, comprising a blown film according to the first aspect of the invention.

The advantages of these further aspects according to the present invention have been disclosed in relation to the blown film according to the first aspect of the present invention and are not herewith repeated.

DETAILED DESCRIPTION OF INVENTION

The present invention relates, in a first aspect, to a blown film comprising a spiroglycol- based polyester comprising a diol component and a dicarboxylic acid component, wherein said diol component comprises from 5 to 65 mol%, based on the total amount of the diol component, of residues of a diol having a spiroglycol structure represented by Formula (1 ):

Surprisingly, the Applicant has indeed found out that such spiroglycol-based polyester is suitable to be effectively processed for producing blown films, where such blown films show a combination of mechanical and optical properties rendering it suitable for many different film applications, e.g., for industrial and consumer packaging, in construction, in agriculture, in medical, and in healthcare applications.

Within the framework of the present description and in the subsequent claims, except where otherwise indicated, all the numerical entities expressing amounts, parameters, percentages, and so forth, are to be understood as being preceded in all instances by the term "about". Also, all ranges of numerical entities include all the possible combinations of the maximum and minimum values and include all the possible intermediate ranges, in addition to those specifically indicated herein below.

Unless defined otherwise, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the articles “a” and “an” refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations of ±20% or ±10%, including ±5%, ±1 %, and ±0.1 % from the specified value, as such variations are appropriate to perform the disclosed methods.

The present invention may present in one or more of the its aspects one or more of the characteristics disclosed hereinafter.

The blown film according to the present invention comprises a spiroglycol-based polyester comprising a diol component and a dicarboxylic acid component. The diol component of the spiroglycol-based polyester comprises from 5 to 65 mol%, based on its total amount, of residues of a diol having a spiroglycol structure represented by Formula (1 ).

Preferably, in said spiroglycol-based polyester said diol component comprises from 20 to 55 mol%, more preferably from 30 to 45 mol%, based on the total amount of the diol component, of residues of said diol having a spiroglycol structure represented by Formula (1 ).

Preferably, said diol having a spiroglycol structure is 3,9-bis(1 ,1 -dimethyl-2-hydroxyethyl)- 2,4,8, 10-tetroxaspiro[5.5]undecane (|3, (3, [3', |3' - tetramethyl - 3, 9 - ( 2, 4, 8, 10 -tetraoxaspiro [5.5] undecane) diethanol).

The diol component of said spiroglycol-based polyester advantageously comprises at least one other diol. Preferably, said diol component comprises residues derived from at least one other diol selected from the group consisting of: ethylene glycol, trimethylene glycol, 1 ,4- butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol, a polyalkylene glycol such as polyethylene glycol, polypropylene glycol and polybutylene glycol; an alicyclic diol such as 1 ,3-cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 1 ,2- decahydronaphthalenedimethanol, 1 ,3-decahydronaphthalenedimethanol, 1 ,4- decahydronaphthalenedimethanol, 1 ,5-decahydronaphthalenedimethanol, 1 ,6- decahydronaphthalenedimethanol, 2,7-decahydronaphthalenedimethanol, tetralindimethanol, norbornanedimethanol, tricyclodecanedimethanol, 5-methylol-5-ethyl-2- (1 ,1 -dimehyl-2-hydroxyethyl)-1 ,3-dioxane and pentacylcododecanedimethanol; an alkylene oxide adduct of a bisphenol such as 4,4'-(1 -methylethylidene)bisphenol, methylenebisphenol (bisphenol F), 4,4'-cyclohexylidenebisphenol (bisphenol Z) and 4,4'- sulfonylbisphenol (bisphenol S); and an alkylene oxide adduct of an aromatic dihydroxy compound such as hydroquinone, resorcin, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether , 4,4'-dihydroxydiphenyl benzophenone, and a dioxane-diol represented by Formula (2)

wherein R³ and R⁴ each independently represent an organic group selected from the group consisting of aliphatic groups having 1 to 10 carbon atoms, alicyclic groups having 3 to 10 carbon atoms, and aromatic groups having 6 to 10 carbon atom.

In a preferred embodiment, said other diol is selected from the group consisting of: ethylene glycol, diethylene glycol, trimethylene glycol, 1 ,4-butanediol , 1 ,4-cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol; more preferably said other diol is ethylene glycol.

Preferably, in said spiroglycol-based polyester said diol component comprises from 35 to 95 mol%, more preferably from 45 to 80 mol %, even more preferably from 55 to 70 mol%, based on the total amount of the diol component, of residues derived from said at least one other diol.

In a preferred embodiment, in said spiroglycol-based polyester said diol component comprises from 20 to 55 mol%, more preferably from 30 to 45 mol%, of said diol having a spiroglycol structure which is 3,9-bis(1 ,1 -dimethyl-2-hydroxyethyl)-2,4,8,10- tetroxaspiro[5.5]undecane and from 45 to 80 mol%, more preferably from 55 to 70 mol% of at least one other diol selected from the group consisting of: ethylene glycol, diethylene glycol, trimethylene glycol, 1 ,4-butanediol and 1 ,4-cyclohexanedimethanol; more preferably said other diol being ethylene glycol.

The spiroglycol-based polyester according to the present invention comprises a dicarboxylic acid component. Preferably, said dicarboxylic acid component comprises from 80 to 100 mol%, based on the total amount of the dicarboxylic acid component, of residues derived from terephthalic acid. In an embodiment of the present invention, the dicarboxylic acid component of said spiroglycol-based polyester advantageously comprises at least one dicarboxylic acid other than terephthalic acid.

Preferably, said dicarboxylic acid component comprises 0 to 20 mol%; based on the total amount of the dicarboxylic acid component, of residues deriving from at least one dicarboxylic acid other than terephthalic acid selected from the group consisting of: isophthalic acid, phthalic acid, 2-methylterephthalic acid, 1 ,4-naphthalenedicarboxylic acid, 1 ,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2,7- naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetralindicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, norbornanediacarboxylic acid, tricyclodecanedicarboxylic acid, pentacylcododecanedicarboxylic acid, isophoronedicarboxylic acid, 3,9-bis(2-carboxyethyl)- 2,4,8,10-tetraoxaspiro[5.5]undecane, trimellitic acid, trimesic acid, pyromellitic acid, and tricarballylic acid.

The spiroglycol-based polyester according to the present invention may also advantageously comprise a polyglycol unit, for example a polyglycol unit comprising residues deriving from a three or more valent polyhydric alcohol such as glycerol, trimethylol propane and pentaerythritol.

The spiroglycol-based polyester according to the present invention may be produced by any suitable known method without particular limitations. For example, the spiroglycol-based polyester may be produced by transesterification or direct esterification which may be conducted in either a melt polymerization method or a solution polymerization method. As a transesterification catalyst, an esterification catalyst, an etherification inhibitor, a polymerization catalyst, various stabilizers such as a heat stabilizer and a light stabilizer and a polymerization modifier, those known in the polymer art are used. Examples of the transesterification catalyst include compounds of manganese, cobalt, zinc, titanium, and calcium. Examples of the esterification catalyst include compounds of manganese, cobalt, zinc, titanium, and calcium. Examples of the etherification inhibitor include amine compounds. Examples of the polycondensation catalyst include compounds of germanium, antimony, tin, and titanium. Examples of the heat stabilizer include various phosphorus compounds such as phosphoric acid, phosphorous acid and phenylphosphonic acid. In addition, various additives such as a light stabilizer, an antistatic agent, a lubricant, an antioxidant and a moldrelease agent may be used in the production of the polyester resin.

Suitable methods for producing a spiroglycol-based polyester according to the present invention may be also found e.g. in the patent references EP1 164155A1 and EP1535945A1 .

The diol having a spiroglycol structure represented by Formula (1 ) may be added at any stage of producing the spiroglycol-based polyester according to the present invention. For example, said diol having a spiroglycol structure may be added after completion of the esterification reaction or transesterification reaction. In the direct esterification method, water may be used to keep the slurry condition stable.

The spiroglycol-based polyester according to the present invention advantageously shows one or more properties rendering it particularly suitable for film blowing.

Preferably, the spiroglycol-based polyester shows an intrinsic viscosity from 0.40 to 1 .5 dL/g, more preferably from 0.50 to 1 .0 dL/g, even more preferably from 0.55 to 0.75 dL/g, when measured using an Ubbelohde viscometer at a constant temperature of 25°C in a 6:4 by mass mixed solvent of phenol and 1 ,1 ,2,2-tetrachloroethane.

Preferably, the spiroglycol-based polyester shows a glass transition temperature of 95- 1 10°C when measured according to ASTM D7426.

Preferably, the spiroglycol-based polyester shows a Melt Flow Index measured according to ISO 1 133 at 250 °C of from 5 to 25 g/10 min, more preferably from 7 to 18 g/10 min, even more preferably from 10 to 18 g/10 min, still even more preferably from 16 to 18 g/10 min.

Preferably, the spiroglycol-based polyester of the present invention has a molecular weight distribution of 1.5 to 12.0, more preferably of 2 to 10.0, still more preferably of 2.2 to 8.0. The molecular weight distribution can be regulated within the range of 2.5 to 12.0 by any technique known to the skilled person for that purpose, for example appropriately selecting the addition amount and addition timing of the diol having a spiroglycol structure represented by Formula (1 ), the molecular weight of the polyester, the polymerization temperature and the additives.

Spiroglycol-based polyesters according to the present invention are already known on the market; for example a type of spiroglycol-based polyester is marketed by Perstorp AB under the trademark Akestra™. Akestra™ exists in three different qualities: Akestra™ 90, Akestra™ 100 & Akestra™ 1 10.

The blown film according to the invention comprises at least one spiroglycol-based polyester as above defined.

Said blown film may advantageously have a single layer or a multi-layer film structure.

When the blown film according to the invention has a multi-layer film structure, preferably said spiroglycol-based polyester as above defined is comprised in at least one layer of said multi-layer structure.

In an embodiment of the present invention, the blown film according to the invention has a single layer film structure.

Preferably, according to said embodiment of the invention said blown film comprises, based on the total weight of the blown film, from 10 to 100 wt%, more preferably from 15 to 90 wt%, even more preferably from 20 to 60 wt% of said spiroglycol-based polyester.

Preferably, according to said embodiment of the invention said blown film comprises, based on the total weight of the blown film, from 0 to 90 wt%, more preferably from 10 to 85 wt%, even more preferably from 40 to 80 wt% of at least one other polymer, more preferably a polyester, even more preferably a polyethylene terephthalate).

In a preferred embodiment, the according to said embodiment of the invention said blown film comprises, based on the total weight of the blown film, from 10 to 90 wt%, more preferably from 20 to 60 wt%, of said spiroglycol-based polyester and from 90 to 10 wt%, more preferably from 40 to 80 wt%, of at least one other polymer which is a polyethylene terephthalate).

The blown film according to this embodiment of the invention shows a set of peculiar and advantageous mechanical and optical properties, rendering it particularly suitable for several applications, for industrial and consumer packaging, in construction, in agriculture, in medical, and in healthcare applications.

Among others, the blown film according to this embodiment of the invention advantageously shows a suitable combination of optical, tensile, impact and tear resistance properties.

In a further embodiment of the present invention, the blown film according to the invention has a multilayer film structure. Preferably, according to said embodiment of the invention said blown film comprises at least one layer comprising the spiroglycol-based polyester as above defined.

Preferably, said at least one layer comprises, based on the total weight of said one layer, from 10 to 100 wt%, more preferably from 10 to 90 wt%, even more preferably from 20 to 60 wt% of said spiroglycol-based polyester wt% of said spiroglycol-based polyester.

Preferably, said at least one layer comprises, based on the total weight of said one layer, from 0 to 90 wt%, more preferably from 10 to 90 wt%, more preferably from 40 to 80 wt%, of at least one other polymer, more preferably a polyester, even more preferably a polyethylene terephthalate).

In a preferred embodiment, the blown film according to the invention has a multi-layer film structure of a type selected from the group consisting of: A-B, A-B-A, B-A-B, wherein said layer A comprises, or consists of, said spiroglycol-based polyester as above defined, and said layer B comprises, or consists of, a polyethylene terephthalate).

The blown film according to this embodiment of the invention shows a set of peculiar and advantageous mechanical and optical properties, rendering it particularly suitable for several applications, such as for industrial and consumer packaging, in construction, in agriculture, in medical applications.

The polyethylene terephthalate) comprised in any embodiment of the blown film according to the present invention may be any grade known to the skilled person and is not particularly limited, thanks to its use in combination with the spiroglycol-based polyester according to this invention. This remarkably contributes to expand the range of applications for polyethylene terephthalate), overcoming the limitation to specific film grades and the use of a special equipment. Advantageously said polyethylene terephthalate) may also be totally or partially be a recycled polyethylene terephthalate) grade, for example.

Even if not strictly limited by them, said polyethylene terephthalate) may show one or more preferred properties.

Preferably, said polyethylene terephthalate) shows an intrinsic viscosity from 0.4 to 1 .2 dL/g, when measured according to ASTM D4603. The spiroglycol-based polyester and the blown film according to the present invention may advantageously also contain various additives such as light stabilizer, UV absorbent, antistatic agent, heat stabilizer, plasticizer, extender, delustering agent, drying regulator, antistatic agent, precipitation inhibitor, surfactant, antioxidant, etherification inhibitor, release agent, flow improver, drying oil, wax, filler, colorant, reinforcing agent, foaming agent, surface smoother, leveling agent, curing promoter, as long as the object of the present invention is not impaired.

Thanks to the properties and features of the spiroglycol-based polyester as above defined, the Applicant has found out that it is possible to effectively produce a blown film, where such blown film show a combination of mechanical and optical properties rendering it suitable for many different film applications, e.g., for industrial and consumer packaging, in construction, in agriculture, in medical, and in healthcare applications.

In a further aspect, the present invention relates therefore also to the use of a spiroglycol- based polyester as defined in the first aspect of the invention, for producing a blown film and also to a method of producing a blown film.

Notably, according to one of these further aspects of the present invention provided is a method of producing a blown film comprising the step of: film blowing at least one polymer feed comprising at least one spirogylcol-based polyester comprising a diol unit and a dicarboxylic acid unit, wherein said diol unit comprises from 5 to 65 mol%, based on the total amount of the diol unit, of a unit derived from a diol having a spiroglycol structure represented by Formula (1 ):

The advantages of the use and of the method according to these further aspects of the present invention have been disclosed in relation to the blown film according to the first aspect of the present invention and are not herewith repeated.

In the use and in the method according to these further aspects of the invention, a spiroglycol-based polyester as defined in the first aspect of the invention is used. Preferred features of this spiroglycol-based polyester have been therefore already defined above with respect to the same components in the other aspects of the invention, and are therefore not herewith repeated.

The use and the method according to these aspects of present invention advantageously involve the use of a film blowing machine or equipment, which may be any film blowing machine or equipment known to the skilled person for thermoplastic materials and is therefore not particularly limited, thanks to the processing properties of the spiroglycol-based polyester according to this invention. This remarkably contributes to render cost-competitive and sustainable the blown film according to the invention and also overcomes the current limitations of film blowing with thermoplastic polyesters like PET.

The method according to this further aspect of the invention comprises the step of film blowing at least one polymer feed.

Preferably, said polymer feed comprises at least one other polymer, more preferably a polyester, even more preferably a polyethylene terephthalate).

In a preferred embodiment of the method according to this further aspect of the invention, the blown film obtainable is a blown film according to the first aspect of the invention.

Notably, said blown film obtainable by the method according to the present invention may advantageously be a blown film with a single layer film structure or a multilayer firm structure as above defined for any embodiment of the blown film according to the first aspect of the invention.

Preferably, in said step of film blowing, said polymer feed is extruded or co-extruded to form a single or a multilayer film structure.

The properties of the blown film according to the present invention renders the same particularly useful for the production of a variety of articles.

In a still further aspect, the present invention relates therefore also to an article selected from the group consisting of: a bag, a container, a package, a pouch, a shrink film, a tape, an agricultural film, a greenhouse cover, a mulch film a silage film, a vapor barrier film, a roofing membrane, a geomembrane, a laminated item, a surgical drape, a gown, a fabric, a protective cover, a liner, a window film for heat reduction, a protective film for a solar panel, and a wrap, comprising a blown film according to the first aspect of the invention, or a blown film obtained through the method of producing a blown film according to the present invention. The advantages of the article according to this further aspect of the present invention have been disclosed in relation to the blown film according to the first aspect of the present invention and are not herewith repeated.

Further features and advantages of the invention will appear more clearly from the following description of some preferred embodiments thereof, made hereinafter by way of the following non-limiting examples.

EXPERIMENTAL PART

Methods

1 ) Intrinsic viscosity (IV): The intrinsic viscosity was measured using an Ubbelohde viscometer at a constant temperature of 25°C in a 6:4 by mass mixed solvent of phenol and 1 ,1 ,2,2-tetrachloroethane.

2) Melt viscosity: The melt viscosity was measured using Capirograph 1 C available from Toyo Seiki Co., Ltd. under the following conditions. Measuring temperature: 240°C; Preheating time: 1 min Nozzle diameter: 1 mm Nozzle length: 10 mm Shear rate: 100 s -1

3) Melt Flow Index (MFI): the melt flow index was measured according to ISO 1 133 at 250 °C with a weight of 2.16 kg using a CEAST Melt Flow Junior Instrument, the measure was taken on pellets of the polyester, prior dried at 143 ppm of moisture content (Karl Fischer titration method).

4) Tear Resistance: Elmendorf tear strength were done in Machine and Transverse direction of the films to determination of tear resistance and was measured according to ASTM D1922-15 (pendulum type: 200 grams). Specimens for all tests were conditioned for at least three days at 23 °C and 50% RH before measurements. The results are the average values obtained.

5) Impact resistance: The Impact was determined according to ASTM D 3420-14 and measured the puncture impact resistance of the plastic film . The fixture consisted of a probe mounted onto the end of the Elmendorf pendulum (type: 200 grams) and an air-operated clamp used to secure the film sample. The unit measured the resistance to impact/puncture as the probe penetrated a sheet of plastic film. Specimens for all tests were conditioned for at least three days at 23 °C and 50% RH before measurements. The results are the average values obtained. 6) Tensile properties: Tensile tests were done in Machine and Transverse direction of the films according to ISO 527-3 to measure stress at yield, tensile strength, elongation at yield, and elongation at break. The equipment used was a Zwick Z10 Tabletop machine with a 500 N load cell. A uniaxial extension rate of 20 mm/min has been used. Measurements were performed at 23°C and 50% RH on strip shaped sample specimens, ISO 527-3 type 2. Specimens for all tests were conditioned for at least three days at 23 °C and 50% RH before measurements. The tensile results are the average values of obtained.

Example 1 - preparation of a spiroglycol-based polyester

A mixture of 13,313 g (69 mol) of dimethyl terephthalate (“DMT”), 3,844 g (62 mol) of ethylene glycol and 18,871 g (62 mol) of 3,9-bis(1 ,1 -dimethyl-2-hydroxyethyl)-2,4,8,10- tetroxaspiro[5.5]undecane was heated to 200°C in nitrogen atmosphere in the presence of manganese acetate tetrahydrate in an amount of 0.03 mol based on 100 mol of DMT to conduct a transesterification reaction.

After the amount of methanol distilled reached 90% or higher the stoichiometric amount, 0.01 mol of antimony (III) oxide and 0.06 mol of triphenyl phosphate (hereinafter referred to merely as "TPP"), each based on 100 mol of DMT, were added to the reaction mixture. The temperature was gradually raised and the pressure was gradually reduced to finally reach 280°C and 0.1 kPa or lower to conduct a polymerization. The polymerization was terminated when the reaction product reached a predetermined melt viscosity of about 2500 Pa*s, thereby obtaining a polyester containing spiroglycol unit in an amount of about 50 mol%. The content of spiroglycol unit in the polymer was measured by ¹H-NMR (400 MHz).

The polyester was also characterized for determining its intrinsic viscosity (0.7 dl/g), its Tg (112 °C), its melt flow index (7.7 g/10 min).

Example 2 - preparation of a blown film comprising the spiroglycol-based polyester according to Example 1

Pellets of the spiroglycol-based polyester according to Example 1 were dried in Moretto compressed air dryer up to a moisture content of 206 ppm (Karl Fischer titration method).

The dried pellets were then mixed with 2wt % of a slip additive masterbatch (Crodamide VRX-BE-(HU)) and then fed to a Lab Tech LE20-30 film blowing machine, operating in the following operative conditions: - Screw speed: 36 rpm

- Barrel zones temperature: 255-260 °C

- Pressure control set value: 87 Bar

- Die temperature : 240 °C

- Blower speed: 1000 rpm

- Nip roll speed: 3.5 m/min

- Windup speed: 3.4 m/min

- Nip pressure: 0.4 Bar

The blown film so obtained had a thickness of about 30 microns and it appeared clear and transparent and without traces of defects. It was characterized in terms of its mechanical properties. The results are reported in Table 1 here below.

Table 1

Example 3 - preparation of a blown film comprising the spiroglycol-based polyester according to Example 1 and polyethylene terephthalate) in a weight ratio 60/40

Pellets of the spiroglycol-based polyester according to Example 1 were dried in Moretto compressed air dryer up to a moisture content of 1 11 ppm (Karl Fischer titration method).

60 weight parts of these dried pellets of the spiroglycol-based polyester were compounded with 40 weight parts of a polyethylene terephthalate) (“PET”, Papet Cool, Bottle grade, IV 0,8 dl/g) in presence of 0.8 wt% of a slip additive masterbatch (Crodamide VRX-BE-(HU)) in a Coperion twin-screw extruder operating in the following operative conditions:

- Screw speed (min ¹): 400

- Throughout (kg/h): 6

- Specific mechanical energy (kWh/kg): 0.338

- Barrel zones temperature profile (°C): 185-260-280x2-275x3-270-250-235 - Pressure (bar): 32

The compound so obtained was then fed to a Lab Tech LE20-30 film blowing machine, operating in the following operative conditions:

- Screw speed (rpm): 45

- Barrel zones temperature profile (°C): 260-270x2-255x2

- Pressure (Bar): 41

- Die temperature (°C): 250

- Blower speed (rpm): 1060

- Nip roll speed (m/min): 3

- Windup speed (m/min): 3.3

- Nip pressure (Bar): 0.4

The blown film so obtained had a thickness of about 60 microns and it appeared clear and transparent and without traces of defects. It was characterized in terms of its mechanical properties. The results are reported in Table 2 here below.

Example 4 - preparation of a blown film comprising the spiroglycol-based polyester according to Example 1 and polyethylene terephthalate) in a weight ratio 20/80

20 weight parts of these dried pellets of the spiroglycol-based polyester were compounded with 80 weight parts of a polyethylene terephthalate) (“PET”, Papet Cool, Bottle grade, IV 0,8 dl/g) in presence of 1.6 wt% of a slip additive masterbatch (Crodamide VRX-BE-(HU)) in a Coperion twin-screw extruder operating in the following operative conditions:

- Screw speed (min ¹): 400

- Throughout (kg/h): 72

- Specific mechanical energy (kWh/kg): 0.380

- Barrel zones temperature profile (°C): 185-260-280x2-275x3-270-250-235

- Pressure (bar): 32

- Screw speed (rpm): 45 - Barrel zones temperature profile (°C): 260-270x2-255x2

- Pressure (Bar): 55

- Die temperature (°C): 250

- Blower speed (rpm): 1060

- Nip roll speed (m/min): 3

- Windup speed (m/min): 3.3

- Nip pressure (Bar): 0.4

The blown film so obtained had a thickness of about 50 microns and it appeared clear and transparent and without traces of defects. It was characterized in terms of its mechanical properties. The results are reported in Table 2 here below.

Table 2

Claims

1 . A blown film comprising a spiroglycol-based polyester comprising a diol component and a dicarboxylic acid component, wherein said diol component comprises from 5 to 65 mol%, based on the total amount of the diol component, of residues of a diol having a spiroglycol structure represented by Formula (1 ):

2. The blown film according to claim 1 , wherein said diol component comprises from 20 to 55 mol%, based on the total amount of the diol component, of residues of said diol having a spiroglycol structure represented by Formula (1 ).

3. The blown film according to claim 1 or 2, wherein said diol having a spiroglycol structure is 3,9-bis(1 ,1 -dimethyl-2-hydroxyethyl)-2,4,8,10-tetroxaspiro[5.5]undecane.

4. The blown film according to any one of claims from 1 to 3, wherein the diol component comprises residues derived from at least one other diol selected from the group consisting of: ethylene glycol, diethylene glycol, trimethylene glycol, 1 ,4-butanediol, 1 ,4- cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1 ,3-cyclobutanedioL

5. The blown film according to claim 4, wherein said other diol is ethylene glycol.

6. The blown film according to claim 4 or 5, wherein the diol component comprises from 35 to 95 mol%, of residues derived from said at least one other diol.

7. The blown film according to any one of claims from 1 to 6, wherein the dicarboxylic acid component comprises from 80 to 100 mol%, based on the total amount of the dicarboxylic acid component, of residues derived from terephthalic acid.

8. The blown film according to any one of claims from 1 to 7, wherein said blown film has a single layer or a multi-layer film structure.

9. The blown film according to any one of claims from 1 to 8, wherein said blown film has a single layer film structure and said blown film comprises from 10 to 100 wt%, based on the total weight of the blown film, of said spiroglycol-based polyester.

10. The blown film according to any one of claims from 1 to wherein said blown film has a single layer film structure and said blown film comprises, based on the total weight of the blown film, from 20 to 60 wt% of said spiroglycol-based polyester and from 40 to 80 wt% of at least one other polymer which is a polyethylene terephthalate).

1 1 . Use of a spiroglycol-based polyester for producing a blown film, wherein said spiroglycol- based polyester comprises a diol component and a dicarboxylic acid component, and wherein said diol component comprises from 5 to 65 mol%, based on the total amount of the diol component, of residues of a diol having a spiroglycol structure represented by Formula (1 ):

12. A method of producing a blown film comprising the step of: film blowing at least one polymer feed comprising at least one spiroglycol-based polyester comprising a diol unit and a dicarboxylic acid unit, wherein said diol unit comprises from 5 to 65 mol%, based on the total amount of the diol unit, of a unit derived from a diol having a spiroglycol structure represented by Formula (1 ):

13. Use according to claim 11 or the method according to 12, wherein said spiroglycol-based polyester is a spiroglycol-based polyester according to any one of the claims from 1 to 10.

14. An article selected from the group consisting of: a bag, a container, a package, a pouch, a shrink film, a tape, an agricultural film, a greenhouse cover, a mulch film a silage film, a vapor barrier film, a roofing membrane, a geomembrane, a laminated item, a surgical drape, a gown, a fabric, a protective cover, a liner, a window film for heat reduction, a protective film for a solar panel, and a wrap, comprising a blown film according to any of claims from 1 to 10 or a blown film obtainable by a method according to claim 12.