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Title:
THERMOPLASTIC COMPOSITION COMPRISING A BLEND OF ONE OR MORE VDF COPOLYMERS AND ONE OR MORE ACRYLIC OR METHACRYLIC ESTER POLYMERS.
Document Type and Number:
WIPO Patent Application WO/2020/157238
Kind Code:
A1
Abstract:
A thermoplastic polymeric composition comprising from 50 to 90% by weight of one or more thermoplastic VDF copolymers comprising 85%-99% by moles of VDF monomers and 1%-15% by moles of one or more fluorinated monomers different from VDF, and from 10 to 50% by weight of one or more thermoplastic acrylic or methacrylic ester polymers, said compositions having a viscosity from 100 to 10000 Pa·s when measured at 230°C and at an apparent wall shear rate of 10 s-1.

Inventors:
SANGUINETI ALDO (IT)
MIRENDA MARCO (IT)
KAPELYUSHKO VALERIY (IT)
Application Number:
PCT/EP2020/052359
Publication Date:
August 06, 2020
Filing Date:
January 30, 2020
Export Citation:
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Assignee:
SOLVAY SPECIALTY POLYMERS ITALY SPA (IT)
International Classes:
C08L27/16; C08L33/06
Domestic Patent References:
WO2018114608A12018-06-28
WO2000033975A22000-06-15
Foreign References:
EP0456018A11991-11-13
EP19155160A2019-02-01
Other References:
MOUSSAIF N ET AL: "Compatibilization of immiscible polymer blends (PC/PVDF) by the addition of a third polymer (PMMA): analysis of phase morphology and mechanical properties", POLYMER, ELSEVIER SCIENCE PUBLISHERS B.V, GB, vol. 40, no. 14, 1 June 1999 (1999-06-01), pages 3919 - 3932, XP004160536, ISSN: 0032-3861, DOI: 10.1016/S0032-3861(98)00620-X
JUNG GYU LEE ET AL: "Properties of PVDF and PMMA Blends Films Prepared by Thermal Casting", TEXTILE SCIENCE AND ENGINEERING, vol. 47, no. 5, 20 September 2010 (2010-09-20) - 2010, XP055595146, Retrieved from the Internet [retrieved on 20190606]
RUSSO S.BEHARI K.SHAN C. J., POLYMER, vol. 34, 1993, pages 4777 - 4781
PIANCA MBARCHIESI EESPOSTO GRADICE S, J FLUORINE CHEM., vol. 95, 1999, pages 71 - 84
Attorney, Agent or Firm:
BENVENUTI, Federica et al. (BE)
Download PDF:
Claims:
Claims

Claim 1

A thermoplastic polymeric composition comprising

- from 50 to 90% by weight of one or more thermoplastic VDF copolymers comprising 85%-99% by moles of VDF monomers and 1 %-15% by moles of one or more fluorinated monomers different from VDF, and

- from 10 to 50% by weight of one or more thermoplastic acrylic or methacrylic ester polymers, selected from polymers made of recurring units wherein at least 70% by moles of said recurring units are selected from methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate, methacrylate and acrylonitrile,

said compositions having a viscosity from 100 to 10000 Pa*s when measured at 230°C and at an apparent wall shear rate of 10 s 1.

Claim 2

A composition according to claim 1 wherein said other fluorinated monomers different from VDF is selected in the group consisting of vinyl fluoride (VFi); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1 ,2- difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl)vinyl ethers, such as perfluoro(methyl)vinyl ether (PMVE), perfluoro(ethyl) vinyl ether (PEVE) and perfluoro(propyl)vinyl ether

(PPVE); perfluoro(1 ,3-dioxole); perfluoro(2,2-dimethyl-1 ,3-dioxole) (PDD).

Claim 3

A composition according to any preceding claim wherein said one or more thermoplastic VDF copolymers are selected from VDF/TFE copolymers, VDF/TFE/HFP copolymers, VDF/TFE/CTFE copolymers, VDF/TFE/TrFE copolymers, VDF/CTFE copolymers, VDF/FIFP copolymers,

VDF/TFE/HFP/CTFE copolymers. Claim 4

A composition according to any preceding claim wherein said one or more thermoplastic VDF copolymers have a number average molecular weight of from 10000 to 1000000 dalton.

Claim 5

A composition according to any preceding claim wherein said one or more thermoplastic VDF copolymers have 4 to 20, more preferably 4.5 to 15, even more preferably 5 to 10 moles of molecular defects per 100 moles of VDF copolymer wherein said molecular defects are selected from head to head inversions, chain end groups and comonomers.

Claim 6

A composition according to any preceding claim wherein said one or more thermoplastic VDF copolymers are homogeneous copolymers.

Claim 7

A composition according to any preceding claim wherein said one or more acrylic or methacrylic ester polymers are selected from methyl

methacrylate polymers (“MMA polymers”) comprising at least 70% in moles of MMA recurring units and from 0% to 30% of other recurring units being derived from methyl acrylate, ethyl methacrylate, ethyl acrylate, n- propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate, methacrylate and acrylonitrile.

Claim 8

A composition according to any preceding claim having a viscosity from 100 to 6000 Pa*s, preferably from 500 to 3000 Pa*s when measured at 230°C and at a shear rate of 10 s 1.

Claim 9

An article made of the composition of any preceding claim said article being characterized by having a high aspect ratio. Claim 10

An article made of the composition of any preceding claim said article being a planar article, preferably being selected from a film, a sheet or a layer.

Claim 11

A method for manufacturing an article made of the composition of claims 1- 8 the method comprising the steps of:

i) providing a uniform melted polymeric composition wherein said uniform melted composition is a composition according to claims 1-9, at a temperature comprised from 120 °C to 250 °C,

ii) forming said composition into an article having a high aspect ratio at an apparent wall shear stress from 1 *102 Pa to 3*105 Pa.

Claim 12

A method according claim 11 wherein said article having a high aspect ratio is a planar article, preferably is a film, sheet or layer.

Claim 13

A method according to claims 11 or 12 wherein said article having a high aspect ratio has its smallest dimension of from dimension from 1 micro metre to 5 mm, preferably from 100 micro meters to 3 mm.

Claim 14

A method according to claims 11-13 wherein said composition is formed into an article having a high aspect ratio using an extruder, preferably a single screw extruder.

Claim 15

A method according to claims 11-14 wherein said article having a high aspect ratio has less than 8% haze and over 90% of total light

transmittance measured along the direction having the highest total light transmittance.

Description:
Description

Thermoplastic composition comprising a blend of one or more VDF copolymers and one or more acrylic or methacrylic ester polymers.

Technical Field

[0001] This application claims priority to EP Appl. No. 19155160.5 filed on 01 February 2019, the whole content of this application being incorporated herein by reference for all purposes. The present invention relates to thermoplastic polymeric compositions comprising one or more

thermoplastic VDF copolymers and one or more thermoplastic acrylic or methacrylic ester polymer.

[0002] The compositions of the invention have a low haze and high total light transmittance at relatively high concentration of VDF copolymer. These compositions can be used to manufacture transparent articles, in particular planar articles such as films, sheets or layers which exhibit high chemical resistance, good mechanical properties and can be easily manufactured using conventional forming techniques.

Background Art

[0003] Acrylic and methacrylic ester polymers are known for their transparency, polymethyl methacrylate in particular (PMMA) is widely used as glass replacement, however it is also known that such polymers are delicate and sensitive to the environment, for example humidity can cause layers or sheets of PMMA to warp and harsh chemicals and environmental factors can damage PMMA surface. Polymer blends with polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) have been described as being capable to form compositions which combine the resistance to chemical and environmental agents of VDF polymers with the clear transparency of acrylic or methacrylic ester polymers. These blends are typically thermoplastic and can be handled with conventional melt processing techniques and can form planar articles such as films, sheets or layers which are transparent and can find application wherever a transparent layer is required such as, for example, in coatings, as glass panel replacement, in architectural covers, in screens for TV and other electronic devices, smart devices, and the like. However many factors influence the light transmission properties of such planar articles. In planar articles comprising one or more vinylidene fluoride (VDF) copolymers and one or more acrylic or methacrylic ester polymers it is often desirable to incorporate high levels of VDF copolymers, such as higher than 50% by weight or, or higher than 65% by weight, in order to increase the durability of the article and to improve its resistance to environmental factors, such as humidity, UV light, or harsh chemicals which can be detrimental to the PMMA component.

[0004] However, at such high weight percentage of VDF copolymers, it is often difficult to obtain transparent articles. It is in fact well known that for PVDF/PMMA blends there is a sharp increase in haze when PVDF represents more than 50% by weight of the composition, in particular in the range from 50 to 80% by weight of PVDF polymer. The same holds true, in general for most blends of VDF copolymers and acrylic or methacrylic ester polymers.

[0005] Also the processing conditions appear to play a role in the transparency of articles obtained from a composition comprising one or more VDF copolymers and one or more acrylic or methacrylic ester polymers, in particular we found that elevated shear stress during forming of an article may increase the haze of the article thus formed.

[0006] Without being bound by theory we believe that the transparency of an article obtained by forming a polymeric composition comprising one or more VDF copolymers and one or more acrylic or methacrylic ester polymers depends by multiple factors among which homogeneity of the blend, degree of crystallinity, size of the crystals, and surface finishing play the biggest roles.

[0007] There is therefore a need to develop novel selected compositions

comprising one or more VDF copolymers and one or more acrylic or methacrylic ester polymers wherein such composition have a high level of VDF copolymers. There is also a need to develop a novel process for effectively manufacturing transparent articles from such polymeric compositions Such process should avoid using solvents and it should be possible to run such process at the highest possible speed for efficient industrial manufacturing of such articles.

[0008] The compositions and methods of the present invention address such a need by selecting appropriate polymers within the blend and appropriate processing equipment and settings.

Summary of invention

The present invention relates to a thermoplastic polymeric composition comprising

- from 50 to 90% by weight of one or more thermoplastic VDF copolymers comprising 85%-99% by moles of VDF monomers and 1 %-15% by moles of one or more fluorinated monomers different from VDF, and

- from 10 to 50% by weight of one or more thermoplastic acrylic or methacrylic ester polymers, selected from polymers made of recurring units wherein at least 70% by moles of said recurring units are selected from methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate, methacrylate and acrylonitrile,

said compositions having a viscosity from 100 to 10000 Pa * s when measured at 230°C and at an apparent wall shear rate of 10 s 1 .

Description of embodiments

[0009] An article having a“high aspect ratio” in the present invention refers to articles having a ratio between their largest dimension to their smallest dimension which is higher than 5. One example of“high aspect ratio” articles for which the method if the invention is particularly suitable are planar articles.“Planar articles” as used herein refers to articles such as films, sheets or layers. Planar articles according to the definition extend mainly along a flat, two dimensional surface and their thickness is at least 5 times smaller than the smallest other dimensions of the article. The term “planar articles” includes flexible articles which define a surface which can be bent and shaped in response to external stimuli such as a flexible film, and it also includes rigid shaped articles which can be obtained by shaping a sheet without changing its thickness such as for example a visor for a motorcycle helmet or a layer in a curved TV screen.

[0010] For the purpose of the present invention, the term“thermoplastic” is

intended to denote polymers and/or compositions which are solid at room or usage temperature, which become soft when heated and become rigid again when they are cooled, without there being an appreciable chemical and physical properties change. Such a definition may be found, for example, in the encyclopaedia called Polymer Science Dictionary. Edited by MARK S.M. ALGER. LONDON: ELSEVIER APPLIED SCIENCE, 1989. p.476.

[0011] The expressions“vinylidene fluoride copolymer” or“VDF copolymer” are equivalent and used within the frame of the present invention for designating polymers essentially made of recurring units, 85-99% by moles of said recurring units being derived from vinylidene fluoride (VDF) and 1-15% by moles of said recurring units being derived from other fluorinated monomers different from VDF.

[0012] Preferably said other fluorinated monomers different from VDF is selected in the group consisting of vinyl fluoride (VFi); trifluoroethylene (VF3);

chlorotrifluoroethylene (CTFE); 1 ,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl)vinyl ethers, such as perfluoro(methyl)vinyl ether (PMVE), peril uoro(ethyl) vinyl ether (PEVE) and perfluoro(propyl)vinyl ether (PPVE); perfluoro(1 ,3-dioxole);

perfluoro(2,2-dimethyl-1 ,3-dioxole) (PDD). More preferably, said other fluorinated monomer is selected from chlorotrifluoroethylene (CTFE), hexafluoroproylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE). [0013] Optionally a VDF copolymer suitable for the present invention may comprise from 0.1 to 5 %, by moles, preferably 0.1 to 3 % by moles, more preferably 0.1 to 1 % by moles of said recurring units derived from one or more hydrogenated comonomer(s), wherein for“hydrogenated

comonomer” it is intended a non-halogenated comonomer, the choice of the said hydrogenated comonomer(s) is not particularly limited; alpha- olefins, (meth)acrylic monomers, vinyl ether monomers, styrenic monomers may be used.

[0014] As non-limitative examples of VDF copolymers useful in the present

invention, mention can be notably made of VDF/TFE copolymers,

VDF/TFE/HFP copolymers, VDF/TFE/CTFE copolymers, VDF/TFE/TrFE copolymers, VDF/CTFE copolymers, VDF/FIFP copolymers,

VDF/TFE/HFP/CTFE copolymers and the like.

[0015] Preferably in the present invention the one or more VDF copolymers can be selected among VDF copolymers having 4 to 20, more preferably 4.5 to 15, even more preferably 5 to 10 moles of molecular defects per 100 moles of VDF copolymer. The expression“molecular defects” in the context of the present invention indicates all the structural anomalies with respect to the regular monomer sequence of a linear VDF homopolymer.

In particular in the context of the present invention are considered “molecular defects” head to head inversions, chain end groups and comonomers, these defects will be now described more in detail.

[0016] When the polymerization of VDF units is“ideal” this results in a linear chain of recurring units -(CF2-CFI2)- . One“head to head inversion” occurs when a unit -CF2-CFI2-CFI2-CF2- or -CFI2-CF2-CF2-CFI2- is formed.

Commonly“head to head inversions” occur in pairs forming a sequence

-CF2-CH2-CH2-CF2-CF2-CH2-CF2-CH2- in this case, since the second inversion appears to correct the first, are called“repaired inversions”. Each VDF copolymer has a certain amount of head to head inversions, their number mainly depends on the temperature of polymerization, increasing with increased temperature of polymerization. The amount of head to head inversions can be measured by NMR spectroscopy as described in the“Test Methods” section below.

[0017] Another class of molecular defects are the chain end groups. As

mentioned above, an ideal PVDF chain has 2 end groups. However a certain amount of chain branching points are often formed during polymerization of VDF monomers. In general the amount of chain branching is influenced by the temperature of polymerization (higher temperature of polymerization leads to a higher amount of chain

branching) and by the pressure of polymerization (higher pressure of polymerization leads to lower chain branching). Each chain branching point generates a new end group, therefore the amount of end groups is a correlated to the amount of chain branching. The amount of chain end groups can be measured by NMR spectroscopy as described in the“Test Methods” section below.

[0018] For the purpose of the present invention also co-monomers are

considered as molecular defects because co-monomers, beyond VDF, disrupt the“ideal” chain sequence of PVDF in a similar way than head to head inversions and chain branching points do.

It has been surprisingly found that the effect on the transparency of the planar objects obtained by the method of the invention is substantially the same irrespective from the nature of the defect, in particular the molar amount of co-monomers has an effect similar to the molar amount of head to head inversion and/or chain branching points.

[0019] VDF copolymers for use in the present invention preferably have a number average molecular weight of from 10000 to 1000000 dalton, preferably from 30000 to 200000 dalton.

[0020] The expression“acrylic or methacrylic ester polymers” refers to polymers made of recurring units wherein at least 70% by moles of said recurring units are selected from methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate, methacrylate and acrylonitrile. [0021] The expression“methyl methacrylate polymer” or“MMA polymer” are equivalent and used within the frame of the present invention for designating polymers made of recurring units, wherein more than 70 % by moles of said recurring units being derived from methyl methacrylate (MMA).

[0022] Preferred acrylic or methacrylic ester polymers for the present invention are MMA polymers. Among MMA polymers, preferred polymers are MMA polymers comprising at least 70% in moles of MMA recurring units and from 0% to 30% of other recurring units being derived from methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate, methacrylate and acrylonitrile.

The most preferred acrylic or methacrylic ester polymer is PMMA.

[0023] The present invention relates to a thermoplastic polymeric composition comprising from 50% to 90%, preferably from 60% to 85%, more preferably from 70% to 80% by weight of one or more thermoplastic VDF copolymers, said copolymers comprising from 85% to 99%, preferably from 88% to 97%, more preferably from 90% to 96% by moles of VDF monomers and from 1 % to 15%, preferably from 3% to 12%, more preferably from 4% to 10% by moles of one or more fluorinated monomers different from VDF, as described above.

The thermoplastic composition of the present invention also comprises - from 10 to 50%, preferably from 15% to 40%, more preferably from 20% to 30% by weight of one or more thermoplastic acrylic or methacrylic ester polymers as described above and has a viscosity from 100 to 10000 Pa * s, preferably from 100 to 6000 Pa * s, more preferably from 500 to 3000 Pa * s when measured at 230°C and at a shear rate of 10 s 1 .

[0024] It was surprisingly found that a thermoplastic composition according to the present invention has a reduced haze and a high total light transmittance. In general it is preferred that a thermoplastic polymeric composition according to the invention has a haze lower than 8%, preferably lower than 5%, even more preferably lower than 2%, and a total light transmittance higher than 85%, preferably higher than 90%, more preferably higher than 93% when measured across 1 mm thickness with the transparency test described herein. In general it is known that a given composition can be made more clear/less hazy by reducing the ratio between VDF copolymers and acrylic or methacrylic ester polymers.

Therefore also in this case a skilled person is able to provide such composition with the required degree of haze and transmittance by varying the ratio between its components.

[0025] As a result articles manufactured with a composition according to the

invention have an improved overall transparency as measured as a lower haze and a higher total light transmittance measured according to ASTM 1003-13 (procedure A).

[0026] It is particularly preferred that the VDF copolymer for the present invention is selected among homogenous copolymers. VDF copolymers, in particular VDF/FIFP copolymers are in fact typically classified in

“homogeneous copolymers” and“heterogeneous copolymers”. As reported in“Fluorinated Polymers: Applications Vol. 2, pag 131” (by Bruno Ameduri, Flideo Sawada, Royal Society of Chemistry Polymer Chemistry Series No. 24, 2017) homogenous VDF copolymers“contain randomly distributed comonomers along the polymer chain ... with melting points which are reduced when the comonomer levels are increased”. On the contrary “heterogeneous” VDF/HFP copolymers contain a mixture of PVDF homopolymer along with a VDF/HFP copolymer” and“retain a high melting point independent of comonomer levels”. Heterogeneous copolymers are also characterized by a lower elastic modulus than the corresponding homogenous copolymers. The polymerization conditions primarily influence the formation of a“homogeneous” copolymer or of a

“heterogeneous” copolymer. According to the cited reference“the addition of VDF alone and/or comonomers can be done at a consistent ratio or staged in differing ratios throughout the polymerization...” to produce either a homogeneous or a heterogeneous copolymer. [0027] In the present invention it is preferred that the VDF copolymer is selected among homogeneous VDF copolymers. It has in fact been found that the use of homogeneous copolymers leads to reduced haze and increased total light transmittance of the resulting composition with respect to the use of heterogeneous copolymers having the same composition.

[0028] The polymers for the polymeric composition of the invention must be

selected so that the resulting polymeric composition has a viscosity from 100 to 10000 Pa * s, preferably from 100 to 6000 Pa * s, more preferably from 500 to 3000 Pa * s when measured at 230°C and at a shear rate of 10 s 1 . As known to the skilled person, the viscosity for a given polymer is essentially proportional to its molecular weight, however the viscosity of a blend is influenced by the viscosity of all the components, so that the addition of a low viscosity/low molecular weight component will lower the viscosity of the whole composition and vice versa. Based on this a skilled person will be able to easily select the appropriate molecular weights for the polymers to be used in the present composition thereby obtaining a viscosity in the required range.

[0029] As mentioned above the thermoplastic composition of the invention can be used to manufacture solid articles, such as articles having a high aspect ratio, in particular planar articles such as sheets, films or layers. Articles being made with the compositions of the invention have an improved transparency. Articles according to the invention can be obtained with all conventional techniques for forming thermoplastic materials, such as, for example, extrusion (including slit extrusion, tube extrusion), film casting, calendering, film blowing, blow molding, injection molding, compression molding, thermoforming and the like.

[0030] The present invention also relates to a method for making an article having a high aspect ratio using the thermoplastic polymeric composition of the invention. [0031] Beyond the selection of the composition it was found that the method of manufacturing can impact the transparency properties of an article made using the composition of the invention.

[0032] Therefore, in one embodiment, the present invention relates to a method of manufacturing an article having a high aspect ratio said method comprising:

i) providing a uniform melted polymeric composition according to the invention, at a temperature comprised from 120 °C to 250 °C,

ii) forming said composition into an article having a high aspect ratio at an apparent wall shear stress from 1 * 10 2 Pa to 3 * 10 5 Pa, preferably from 2 * 10 3 Pa to 3 * 10 5 Pa, more preferably from 1 * 10 4 Pa to 1 * 10 5 Pa..

[0033] The expression“uniform melted polymeric composition” refers to a mixture of two or more melted polymers in a single phase. Such composition can be obtained with conventional techniques available to the skilled person, selecting appropriate polymers, melting them at a temperature above the highest melting point of all the polymers in the composition (or above the highest T g in case for some polymer T g is higher than its melting point) and thoroughly mixing the melted polymers so to form a single phase blend. The starting materials for obtaining the uniform melted polymeric composition can be selected from individual polymers or pre-prepared polymeric compositions in solid form, preferably in divided form such as pellets, granules or powders. In one embodiment the method of the invention comprises a step wherein the individual polymers making up the polymeric composition in divided form are loaded into a twin screw extruder, melted at a temperature above the highest melting temperature or T g , thoroughly mixed so to form a uniform melted polymeric

composition, extruded, preferably trough one or more capillary dies, cooled and preferably turned into a divided form such as pellets, granules of powders of the polymeric compositions. In order to perform the method of the invention such solid polymeric composition in divided form can be then introduced into an appropriate equipment such as a single screw extruder, the temperature within such equipment can be raised to an appropriate temperature from 120°C to 250°C, high enough so to completely melt the composition, thereby providing the uniform melted polymeric composition of the invention which can then be formed into a high aspect ratio article in step ii) of the method.

[0034] It is in general preferred to form a planar article using a single screw

extruder because this type of equipment is known to provide a better control on the extruded articles. On the other hand, a twin screw extruder is more efficient in mixing up a melted polymer mixture so to ensure uniformity of the resulting composition it is therefore preferred to pre-make such composition starting from the individual polymers into a twin screw extruder, and subsequently transfer said composition, preferably in solid pelletized form, into a single screw extruder so to form the final article having a high aspect ratio.

[0035] In step ii) of the method of the present invention the uniform melted

polymeric composition is formed into an article having a high aspect ratio using conventional techniques such as preferably extrusion, more preferably using a single screw extruder and a slit die, wherein the apparent wall shear stress is of from 1 * 10 2 Pa to 3 * 10 5 Pa, preferably from 2 * 10 3 Pa to 3 * 10 5 Pa, more preferably from 1 * 10 4 Pa to 1 * 10 5 Pa. The apparent wall shear stress can be easily calculated by measuring the composition viscosity at the forming conditions, the volumetric flow, and the geometry of the die using the formulas reported in (J.A. Brydson, Flow Properties of Polymer Melts, 2° edn., Chapter 2 and Appendix, published by George Godwin Ltd, London, 1981). In this step the uniform melted polymeric composition is typically pushed through a die, preferably a slit die. Process parameters such as pressure, viscosity of the uniform melted polymeric composition at the temperature of forming, speed of the screw if using a screw extruder, can be controlled so that the apparent wall shear stress is within the required range. [0036] A die used to form an article having a high aspect ratio has preferably the shape of a slit, wherein its thickness is least 5 times smaller than its length.

[0037] It has been surprisingly found that using the claimed combination of

composition, viscosity and shear stress it is possible to obtain articles with further reduced haze and improved total light transmittance , for example articles having less than 8% haze and over 90% of total light transmittance when measured along the direction having the highest total light transmittance.

[0038] One additional parameter which can further impact crystal formation,

crystal growth and, ultimately, haze and light transmittance is the cooling speed of the extruded article. In general it has been observed that using conventional extrusion techniques wherein the extruded material is cooled in a cold water bath or it is laid down on one or more cold calender rolls a satisfactory transparency is obtained. Preferably the water bath and the calender roll(s) are cooled at a Temperature below 15°C: this ensures quick solidification of articles having a relatively high thickness and can further improve the haze and light transmittance properties of the planar article.

[0039] As conventionally made during the extrusion of sheets and films, the

calender roll can move at a speed faster than the speed at which the sheet or film is extruded thereby stretching the film or sheet which results in a thinner film or sheet and typically in imparting directional optical and mechanical properties to the resulting object.

[0040] The extrusion method described above is a preferred execution of the

present invention, which however should not be intended to limit it to methods of extrusion. In fact according to the present invention the uniform melted polymeric composition can be transformed into the finished article of the invention using, alone or in combination, any of the

conventional technologies used in the plastic industry to form films, sheets or layers, such as slit extrusion, tube extrusion, film casting, calendering, film blowing, blow molding, injection molding, compression molding, thermoforming and the like.

[0041] Articles manufactured with the method of the present invention have

typically their smaller dimension from 1 micro metre to 5 mm, preferably from 100 micro meters to 3 mm.

[0042] Articles made using the method of the present invention can be used

wherever a transparent layer is required such as, for example, in coatings, as glass panel replacement, in architectural covers, in screens for TV and other electronic devices, smart devices, and the like.

[0043] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0044] The invention will be now described in more detail in connection with the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.

[0045] Raw materials

In all examples polymethyl methacrylate (PMMA) Acryrex CM 211 G from Chimei was used as thermoplastic methacrylic ester polymer.

Examples [0046] All examples shown in the table below were prepared starting from a mixture of VDF copolymer and PMMA each one in pellets. The mixture of pellets was introduced into a twin screw extruder, melted an thoroughly mixed at 230°C, and then extruded in pellet form. An assembly was prepared composed by, from bottom to top, a molding metal plate

(20x20x0.3 cm), a 12x12x0.02 cm film of aluminium, a 12x12x 0.02 cm film of Kapton, a 10 x 10 x 0.1 cm molding cavity.

20 grams of pellets from the polymeric composition were uniformly spread, in the molding cavity, then a second equal film of Kapton, a second equal film of Aluminum and a second equal metal plate were superimposed in this order. The assembly was put in the mold without applied force for 5 minutes, heating the mold up to 230°C and for 2 minutes under 16 tons compression. Then the assembly has been quickly transferred into a water-cooled press at a 150 bar pressure and cooled for 10 minutes. A 1 mm sheet was thereby obtained which was conditioned 24 hours at room T (25°C). The conditioned sheet was then measured for Haze and Total light transmittance according to ASTM 1003-13 (procedure A).

[0047] The results show how sheets obtained from blends 70% to 30% by weight of VDF copolymer and PMMA give articles have very low haze and high light transmittance when using VDF copolymers 1 , 2 and 3, which are preferred copolymers according to the invention. When using VDF copolymer 4 (Ex. 5), results are much poorer. VDF copolymer 4 has a comonomer content above the claimed limits. VDF copolymers 5 and 6 (Ex. 6 and 7) are instead heterogeneous copolymers and while the resulting composition is relatively transparent, give inferior results with respect to the corresponding homogeneous copolymers VDF copolymers

I , 2 and 3.

[0048] Test methods

Molecular defects: As mentioned above, the amount of molecular defects in a VDF polymer can be measured with NMR spectroscopy with

techniques which are known in the art.

[0049] The amount of“head to head inversions” and of“end groups” of the

polymers was measured by NMR analysis, by recording the NMR spectra at 60°C on a Varian VNMS 500 NMR spectrometer operating at 499.86 MFIz for 1 FI and 470.28 MFIz for 19 F using a Triple FIFCP-PFG probe with 5 mm 502-8 (Norell, Inc.) NMR sample tubes. The NMR experiments were carried out using 40 mg of sample solution in 0.75 ml of deuterated acetone (99.9% D, obtained from Sigma-Aldrich) with tetramethylsilane (TMS) used as an internal standard. 1 FI NMR was performed using 45 degree pulse length of 5.05 us, 5 s relaxation delay, 2.3 s acquisition time, 16 K complex points, 7 kFIz spectral width and 1500 repetitions.

19 F NMR was performed using 45 degree pulse length of 4.44 us, 5 s relaxation delay, 0.695 s acquisition time, 16 K complex points, 23.5 kFIz spectral width and 2000 repetitions.

[0050] The determination of the amount of“head to head inversions” (HH),

expressed in moles of“head to head inversions” for 100 moles of VDF monomers was obtained by the following expression:

HH = 100 x I HH / ITOT

where I HH are normalized integrated intensities of the corresponding“head to head inversions” signals, ITOT is the sum of all the normalized integrated intensities of HH and non inverted VDF units. The method is in accordance with the established procedure described in“Russo S.; Behari K.; Shan C.

J.; Polymer 1993, 34, 4777-4781”. [0051] The determination of the amount of the end groups (EG), expressed in moles of end groups for 100 moles of VDF monomers was obtained by the following expression:

EG = 100 x I EG / ITOT

where I EG are normalized integrated intensities of the corresponding endgroup signals, ITOT is the sum of all the normalized integrated intensities of EG and VDF units.

The method is in accordance with the established procedure described in “Pianca M, Barchiesi E, Esposto G, Radice S. J Fluorine Chem. 1999;95:71-84”.

[0052] Viscosity was measured according to ASTM D3835-02 using a Gottfert capillary rheometer equipped with 1 mm Hastelloy C die with a length-to- diameter ratio of 20, at 230 °C and 10 s 1 shear rate.

[0053] Haze and Total Light transmittance (ARTICLE) of an article was measured according to ASTM 1003-13 (procedure A) on the article resulting from the invention as is, after forming and conditioning 24 hours at room T (25°C) along the direction having the highest total light transmittance.

[0054] Haze and Total Light transmittance (COMPOSITION) for the transparency test of the polymeric composition (measured before forming the article) were measured with the following method:

an assembly was prepared composed by, from bottom to top, a molding metal plate (20x20x0.3 cm), a 12x12x0.02 cm film of aluminium, a 12x12x 0.02 cm film of Kapton, a 10 x 10 x 0.1 cm molding cavity.

20 grams of pellets from the polymeric composition were uniformly spread, in the molding cavity, then a second equal film of Kapton, a second equal film of Aluminum and a second equal metal plate were superimposed in this order. The assembly was put in the mold without applied force for 5 minutes, heating the mold up to 230°C and for 2 minutes under 16 tons compression. Then the assembly has been quickly transferred into a water-cooled press at a 150 bar pressure and cooled for 10 minutes. A 1 mm sheet was thereby obtained which was conditioned 24 hours at room T (25°C). The conditioned sheet was then measured for Haze and Total light transmittance according to ASTM 1003-13 (procedure A).