WO2015091087A1

WO2015091087A1 - High oxygen- and moisture-barrier compositions

Info

Publication number: WO2015091087A1
Application number: PCT/EP2014/076967
Authority: WO
Inventors: Alessandro Veneroni; Pierre-Emmanuel Dufils; Yves Vanderveken; Joseba JUARISTI; José M. ASUA
Original assignee: Solvay Sa
Priority date: 2013-12-20
Filing date: 2014-12-09
Publication date: 2015-06-25

Abstract

Compositions comprising a vinylidene chloride polymer and a chlorotrifluoroethylene polymer provided with high oxygen- and moisture-barrier properties.

Description

HIGH OXYGEN- AND MOISTURE-BARRIER COMPOSITIONS

Cross-reference to related application

This application claims priority to European application No. 13306798.3 filed on December 20, 2014, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

The present invention relates to compositions provided with high oxygen- and moisture-barrier properties and to a process for their preparation. In particular the present invention relates to compositions comprising a vinylidene chloride polymer and a chlorotrifluoroethylene polymer.

Background Art

Certain pharmaceutical products include active pharmaceutical ingredients that undergo chemical degradation and can become physically unstable in the presence of even very small amounts of oxygen or moisture. For these products, it is critical that they be shipped and stored in containers capable of achieving and maintaining extremely low oxygen and moisture levels.

Vinylidene chloride polymers are known for their very high barrier towards oxygen permeation and for the relative insensitivity of said oxygen barrier properties with respect to moisture levels.

On the other hand poly(chlorotrifluoroethylene) (PCTFE) is known for its extremely high barrier to moisture permeation.

It would be advantageous to combine the properties of vinylidene chloride polymers and poly(chlorotrifluorethylene) to obtain a material having at the same time high oxygen and moisture barrier properties suitable for pharmaceutical packaging applications.

Description of invention

A first object of the present invention is a composition comprising at least one vinylidene chloride polymer and at least one chlorotrifluoroethylene polymer.

The term “polymer” is to be understood as a homopolymer (polymer comprising the repetition of the same monomer) or a copolymer (comprising the repetition of at least two different monomers, such as two or more, three or more, four or more, five or more, and so on).

The expression “vinylidene chloride polymer” is used in the present specification to refer to polymers comprising recurring units deriving from vinylidene chloride and, optionally, from at least one ethylenically unsaturated monomer copolymerizable with vinylidene chloride.

Non-limiting examples of suitable ethylenically unsaturated monomers copolymerizable with vinylidene chloride are, for instance, vinyl chloride, vinyl esters such as for example vinyl acetate, vinyl ethers, acrylic acids, their esters and amides, methacrylic acids, their esters and amides, acrylonitrile, methacrylonitrile, styrene, styrene derivatives, such as styrene sulfonic acid and its salts, vinyl phosphonic acid and its salts, butadiene, olefins such as for example ethylene and propylene, itaconic acid, maleic anhydride, but also copolymerizable emulsifiers such as 2‑acrylamido‑2‑methylpropanesulphonic acid (AMPS) or one of its salts, e.g. the sodium salt, 2-sulphoethylmethacrylic acid (2-SEM) or one of its salts, e.g. the sodium salt, and the phosphate ester of methacrylate-terminated polypropylene glycol or one of its salts, e.g. the sodium salt, poly(ethylene oxide) methyl ether acrylate (PEOA), poly(ethylene oxide) methyl ether methacrylate (PEOMA).

The ethylenically unsaturated monomer copolymerizable with vinylidene is preferably selected from the group consisting of vinyl chloride, maleic anhydride, itaconic acid, styrene, styrene derivatives, and the acrylic or methacrylic monomers corresponding to general formula (I):

CH₂ = CR₁R₂ (I)
in which R₁ is selected from hydrogen and –CH₃ and R₂ is selected from –CN and –COR₃, wherein R₃ is selected from ‑OH, –OR₄, wherein R₄ is a C₁-C₁₈ linear or branched alkyl group optionally bearing one or more ‑OH groups, a C₂-C₁₀ epoxyalkyl group and a C₂-C₁₀ alkoxyalkyl group and wherein R₃ is also chosen from the –NR₅R₆ groups in which R₅and R₆, which are the same or different, are chosen from hydrogen and C₁-C₁₀ alkyl groups, optionally bearing one or more –OH groups; 2‑acrylamido‑2‑methylpropanesulphonic acid or one of its salts; 2-sulphoethylmethacrylic acid or one of its salts; the phosphate ester of methacrylate-terminated polypropylene glycol or one of its salts; poly(ethylene oxide) methyl ether acrylate (PEOA); and poly(ethylene oxide) methyl ether methacrylate (PEOMA).

More preferably, the ethylenically unsaturated monomer copolymerizable with vinylidene chloride is selected from the group consisting of vinyl chloride, maleic anhydride, itaconic acid, the acrylic or methacrylic monomers selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2‑ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2‑hydroxyethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, N-methylolacrylamide, N,N-di(alkyl)acrylamide, 2‑acrylamido‑2‑methylpropanesulphonic acid (AMPS) or one of its salts, 2-sulphoethylmethacrylic acid (2‑SEM) or one of its salts, and the phosphate ester of methacrylate-terminated polypropylene glycol or one of its salts, poly(ethylene oxide) methyl ether acrylate (PEOA), poly(ethylene oxide) methyl ether methacrylate (PEOMA).

Most preferably, the at least one ethylenically unsaturated monomer copolymerizable with vinylidene chloride is selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2‑ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2‑hydroxyethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, N‑methylolacrylamide, N,N-di(alkyl)acrylamide, poly(ethylene oxide) methyl ether acrylate (PEOA), poly(ethylene oxide) methyl ether methacrylate (PEOMA).

Typically, the at least one vinylidene chloride polymer used in the inventive composition comprises at least 50 wt% of recurring units deriving from vinylidene chloride. Typically, the amount of vinylidene chloride in the vinylidene chloride polymer varies from 50 to 99.5 wt%, preferably from 60 to 98 wt% and more preferably from 65 to 95 wt%.

When the vinylidene chloride polymer comprises the vinyl chloride then the the amount of vinyl chloride in the vinylidene chloride polymer typically varies from 0.1 to 50 wt%, preferably from 0.5 to 40 wt% and particularly preferably from 0.5 to 30 wt%.

When the vinylidene chloride polymer comprises itaconic acid and/or acrylic or methacrylic monomer(s) the amount of itaconic acid and/or acrylic or methacrylic monomer(s) in the vinylidene chloride polymer varies generally from 0.1 to 50 wt%, preferably from 0.5 to 40 wt%, more preferably from 1 to 30 wt% and particularly preferably from 2 to 20 wt%.

The expression “chlorotrifluoroethylene polymer” is used in the present specification to refer to polymers comprising recurring units deriving from chlorotrifluoroethylene and, optionally, from at least one ethylenically unsaturated monomer copolymerizable with chlorotrifluoroethylene .

Non-limiting examples of suitable ethylenically unsaturated monomers copolymerizable with chlorotrifluoroethylene that can be used in the process of the present invention, are for instance trifluoroethylene, hexafluoropropylene, vinylidene fluoride, fluoroalkylvinylethers of formula CF₂=CFOR_f1, wherein R_f1 is a C₁-C₆ fluoroalkyl group, ethylene, hexafluoroisobutylene, tetrafluoroethylene, fluorodioxoles such as notably described in

US

6,277,936

AUSIMONT S.P.A. 20010821

herein incorporated by reference in its entirety; for example 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, CH₂=CHCOOR₁, wherein R₁ is a linear or branched C₁-C₂₀ alkyl, or a cycloalkyl, optionally containing heteroatoms and/or chlorine atoms, preferably the heteroatoms are O or N.

Preferably, the at least one chlorotrifluoroethylene polymer used in the inventive composition comprises at least 50 wt% of recurring units deriving from chlorotrifluoroethylene. Typically, the amount of chlorotrifluoroethylene in the chlorotrifluoroethylene polymer varies from 50 to 100 wt%, preferably from 60 to 100 wt% and more preferably from 85 to 100 wt%. Most preferably the amount of chlorotrifluoroethylene in the chlorotrifluoroethylene polymer is 100 wt%.

The phrase “at least one polymer” is used herein with reference to both vinylidene chloride and chlorotrifluoroethylene polymers to indicate that one or more than one polymer of each type can be present in the inventive composition. Hereinafter the term “polymer” will be used to refer to one or more than one polymer of a given type.

In an aspect of the invention the composition comprises in general at least 40 wt%, preferably at least 50 wt%, preferably at least 70 wt%, even more preferably at least 80 wt% of the vinylidene chloride polymer, with respect to the total amount of the vinylidene chloride polymer and the chlorotrifluoroethylene polymer in the composition. The composition typically comprises at most 99 wt%, preferably at most 98 wt%, more preferably at most 95 wt% and even more preferably at most 90 wt% of the vinylidene chloride polymer, with respect to the total amount of the vinylidene chloride polymer and the chlorotrifluoroethylene polymer in the composition.

In addition to the vinylidene chloride polymer and the chlorotrifluoroethylene polymer other ingredients may be present in the inventive composition. Suitable other ingredients for the inventive composition are for instance wax emulsions, such as notably montan ester waxes or carnauba waxes, emulsified polymers.

The composition may be in any form. The composition may be solid, for instance in the form of powder, pellets or granules, or it may be in the form of a dispersion.

The term “dispersion” is hereby intended to denote a colloidal suspension of a polymer in a liquid medium, wherein particles of a polymer of average particle size of generally less than 500 nm are stably suspended in a liquid medium with no settlement phenomena when left in unperturbed state.

Typically, the liquid medium comprises water.

In a first embodiment of the invention, the composition comprises particles, granules, powders or pellets of the vinylidene chloride polymer and of the chlorotrifluorethylene polymer physically mixed together.

When in solid form, the composition may be prepared by direct mixing of the vinylidene chloride polymer and of the chlorotrifluorethylene polymer using common techniques, such as dry blending, melt blending, or extrusion.

When in the form of dispersion, the composition according to the first embodiment may be prepared by dispersing, in a suitable liquid medium, a solid composition as defined above.

Alternatively, the dispersion comprising the vinylidene chloride polymer and the chlorotrifluorethylene polymer may be prepared by mixing together a first dispersion comprising the vinylidene chloride polymer and a second dispersion comprising the chlorotrifluorethylene polymer, to provide the polymer ratios defined above.

Advantageously, the dispersion comprising the vinylidene chloride polymer and/or the dispersion comprising the chlorotrifluorethylene polymer may be directly obtained from the radical polymerization in a liquid medium of the vinylidene chloride and/or the chlorotrifluorethylene monomers, and their optional comonomers as defined above. The liquid medium typically comprises water. Preferably, the liquid medium is water.

Typically the dispersion comprising the inventive composition comprises at least 20 wt% of dry solids, preferably at least 25 wt% of dry solids, more preferably at least 30 wt% of dry solids with respect to the total weight of the composition. The amount of dry solids generally is at most 75 wt%, preferably at most 70 wt%, more preferably at most 65 wt% with respect to the total weight of the composition. It is to be understood that the ratio of the vinylidene chloride polymer to the chlorotrifluoroethylene polymer in the dispersion is as defined above.

In a second embodiment of the invention the composition comprises particles characterized by a core/shell structure. A core/shell particle comprises a core component and a shell component which differ in their chemical composition. The shell is at least partially capping the core. The expression “capping the core” is to be understood as creating an “envelop” of the core. The expression “at least partially capping the core” is to be understood that the shell may entirely cover the core, homogenously or inhomogeneously, or that the shell may cover only part of the core.

The core/shell particles may comprise a core of the vinylidene chloride polymer partially covered by a shell of the chlorotrifluoroethylene polymer,

Preferably, the core/shell particles of the invention comprise a core of the chlorotrifluorethylene polymer which is at least partially covered by a shell of the vinylidene chloride polymer.

Hereinafter the expression “core/shell particles” will refer to particles which have a core made of the chlorotrifluorethylene polymer and a shell made of the vinylidene chloride polymer as defined above.

The term core/shell particles may include, without being limited to, several structures. Thus, the core/shell particles may consist of one or several cores at least partially capped by a shell layer forming basically the outer wall of the particles.

Between the core and the shell there may be intermediate layers separating core and shell from direct contact but overall the shell envelops the core part at least partially including the intermediate layer. Such intermediate layer may form an intermediate phase between the core and the shell and can be of any composition. Preferably this intermediate layer, if present, may have an intermediate composition (intermediate between the core and the shell in composition) and can be uniform throughout the interphase or may form a composition gradient gradually changing from the composition of the core to the composition of the shell. Preferably, in the present invention, the core is partially covered by the shell.

The structure of the core/shell particles of the invention can be determined by suitable techniques, such as by Transmission Electron Microscopy (TEM).

The average particle size of the core/shell particles of the inventive composition, as measured by dynamic light scattering, is advantageously more than or equal to 90 nm, preferably more than or equal to 100 nm, more preferably more than or equal to 110 nm. The average particle size of the core/shell particles of the composition is typically less than or equal to 300 nm, preferably less than or equal to 250 nm, more preferably less than or equal to 200 nm, and even more preferably less than or equal to 150 nm. The average particle size of the core-shell particle has any values within these ranges.

Typically, the chlorotrifluoroethylene polymer core has an average particle size, measured by dynamic light scattering, of less than or equal to 135 nm, more preferably less than or equal to 120 nm, more preferably of less than or equal to 110 nm. The core average particle size is advantageously more than or equal to 30 nm, preferably more than or equal to 35 nm, more preferably more than or equal to 40 nm. The core average particle size is advantageously between 40 nm and 110 nm, preferably between 60 and 90 nm.

What is understood by average particle size, as determined by dynamic light scattering, is defined in the experimental section.

The relative ratio of the core and the shell in the inventive core/shell particles is such that the amount of the vinylidene chloride polymer and the chlorotrifluoroethylene polymer fall within the range defined for the composition. Thus, in the core/shell particle the amount of the vinylidene chloride polymer is in general at least 40 wt%, preferably at least 50 wt%, preferably at least 70 wt%, even more preferably at least 80 wt% of the vinylidene chloride polymer, with respect to the total weight of the particles. The amount of the vinylidene chloride polymer typically is at most 99 wt%, preferably at most 98 wt%, more preferably at most 95 wt% and even more preferably at most 90 wt% with respect to the total weight of the core/shell particles.

The particles may be isolated in solid form or they may be dispersed in a liquid medium. The core/shell particles are preferably dispersed in water.

A further object of the present invention is a process for the preparation of the core/shell particles as defined above.

The process comprises the steps of: providing particles of a chlorotrifluoroethylene polymer; and polymerizing vinylidene chloride and, optionally, at least one ethylenically unsaturated monomer copolymerizable with vinylidene chloride in the presence of said chlorotrifluoroethylene polymer particles.

The core/shell particles may advantageously be prepared by radical polymerization of vinylidene chloride and, optionally, at least one other monomer in the presence of chlorotrifluorethylene polymer particles dispersed in a liquid medium. Typically, the liquid medium comprises water.

Advantageously, the process comprises the step of preparing the at least one vinylidene chloride polymer by radical polymerization in aqueous emulsion of vinylidene chloride and optionally at least one monomer in the presence of a chlorotrifluoroethylene polymer particles.

Chlorotrifluorethylene polymer particles having an average particle size of at least 30 nm and of at most 135 nm may be prepared as dispersion in a liquid medium according to methods known in the art. A suitable method is for instance disclosed in

EP

1067146

A SOLVAY SOLEXIS SPA 20010110

.

The chlorotrifluoroethylene particles preferably have an average particle size of at least 35 nm, more preferably of at least 40 nm. The average particle size is preferably at most 110 nm, more preferably at most 90 nm.

Typically the amount of dry content of chlorotrifluoroethylene polymer particles in a dispersion suitable for the vinylidene chloride polymerization process, in particular a radical polymerization in aqueous emulsion, is at least 0.1 wt%, preferably at least 1 wt%, preferably at least 2 wt% relative to the total weight of the vinylidene chloride polymer latex.

For the purpose of the present invention, the term "vinylidene chloride polymer latex" is understood to denote an aqueous dispersion of the vinylidene chloride polymer and chlorotrifluoroethylene polymer particles in water obtained after radical polymerization in aqueous emulsion.

The amount of dry content of the chlorotrifluoroethylene polymer particles in the dispersion, expressed relative to the total weight of the vinylidene chloride polymer latex, is advantageously at most 40 wt%, preferably at most 30 wt% and more preferably at most 20 wt% relative to the total weight of the vinylidene chloride polymer latex.

The expression "in the presence" is understood to mean that the chlorotrifluoroethylene polymer particles are in the polymerization medium when the vinylidene chloride polymerization takes place. Although it is not excluded that a small amount of the chlorotrifluoroethylene polymer particles may be added at a later time, it is preferred that all of the particles are present when the contents of the reactor are reacted. Particularly preferably, all of the chlorotrifluoroethylene polymer particles are introduced at the start and are therefore present when the contents of the reactor are reacted.

The expression "at the start" is understood to mean with the initial charge. The expression "at a later time" is understood to mean that the introduction begins after the initial charge has been introduced and the polymerization reaction initiated.

The expression "radical polymerization in aqueous emulsion" is understood to mean any radical polymerization process performed in aqueous medium in the presence of at least one emulsifier and at least one radical generator as known in the art.

The radical generators are selected from the group consisting of thermal and redox radical generators. Suitable thermal radical generators are well known in the art and include, but are not limited to, inorganic peroxides, such as ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, and hydrogen peroxide; organic peroxides, including percarbonates, and azo initiators. Examples of redox radical generators may include, but are not limited to, inorganic and organic peroxides paired with a suitable reducing agent. Additionally, the radical generators can be used without any limitation regarding their water solubility. This being said the radical generators, can be water soluble, oil soluble or a mixture thereof. For example, redox radical generators in which water-soluble and oil-soluble components are combined can also be used. Water soluble radical generators are preferred.

According to the process for preparing the core/shell particles of the invention, vinylidene chloride and the optional other monomers may be introduced into the polymerization medium in several different ways and in a different form.

Thus, according to a first variant, some monomers are introduced at the start of the process in one batch and the others at a later time, either in one batch, or continuously.

According to a second variant, all the monomers are introduced at the start of the process in one batch.

According to a third variant, all the monomers are introduced continuously, at a later time.

According to a fourth variant, one fraction of all of the monomers is introduced at the start of the process and the balance is introduced at a later time, either in one batch, or continuously.

According to a fifth variant, one fraction of the monomers is introduced at the start of the process and the balance is introduced as a monomer composition gradient.

According to the sixth variant, all the monomers are introduced at a later time with a monomer concentration gradient.

The monomers may be introduced individually (in the pure state or in the form of an emulsion) or after having been blended (the blend being introduced as is or in the form of an emulsion).

After reacting the contents of the reactor, preferably by heating the contents of the reactor until the degree of conversion of the monomers is advantageously at least 82 % and preferably at most 100 %, a vinylidene chloride polymer latex is advantageously obtained.

The temperature at which the contents of the reactor are reacted is advantageously equal to at least 15°C, preferably equal to at least 20°C, more preferably equal to at least 30°C. In addition, it is advantageously equal to at most 100°C, preferably at most 90°C, more preferably at most 80°C. The temperature is advantageously between 15°C and 100°C, preferably between 30°C and 80°C.

The process for preparing the vinylidene chloride polymer latex is carried out at a pH between 3 and 7, such as any value within this range, such as about 3, about 4, about 5, about 6, about 7 (the word “about” is in this context to be understood as +/- 0.5 pH unit). The pH is advantageously equal to or below 7, more advantageously equal to or below 6.5. The pH is advantageously equal to or above 3, more advantageously equal to or above 4.

The pH can be adjusted by any known means. Advantageously, the pH is adjusted by addition of at least one water soluble base and/or water soluble buffer. Non limiting examples of suitable bases are for instance trisodium pyrophosphate, tetrasodium pyrophosphate and calcium carbonate. Preferably, the base is the tetrasodium pyrophosphate.

It is general known in the art that a dispersion of vinylidene polymers obtained after radical polymerization in aqueous emulsion of vinylidene chloride is generally subjected to stripping of the residual monomers before its subsequent use. Stripping may be carried out by stripping under vacuum or else by stripping under vacuum and simultaneously injecting steam into the latex and/or by chemical stripping. Preferably, stripping is carried out by stripping under vacuum and simultaneously injecting steam into the latex. This being said, the dispersion of the core/shell particles obtained is advantageously further subjected to such stripping, as detailed above, of the residual monomers before its subsequent use.

The dispersion of the core/shell particles of the invention obtainable by the process is advantageously characterized by a solids concentration of at least 20 wt%, preferably at least 25 wt%, more preferably at least 30 wt%. The dispersion of core/shell particles is advantageously characterized by a solids concentration of at most 75 wt%, preferably at most 70 wt%, more preferably at most 65 wt%, most preferably at most 60 wt%.

Core/shell particles in solid form may be obtained from the dispersion as above described using common polymer recovery techniques, such as coagulation followed by drying.

It is to be understood that the definitions and preferences defined previously within the context of the composition apply to the process for preparing the core/shell particles according to the invention.

The compositions of the invention provide high-quality films, having the barrier properties, in particular oxygen permeability and water vapour permeability, required for the intended applications.

Accordingly further objects of the present invention are the use of the compositions of the invention for the preparation of films, as well as the films comprising a composition as above defined.

The following examples are intended to illustrate the invention without however limiting the scope thereof.

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.

EXPERIMENTAL SECTION

CHARACTERIZATION

Particle size measurements

Average particle diameter (Dz) and the polydispersity of the latexes were measured by dynamic light scattering (DLS) at 20 °C with a Zetasizer NanoZS (Malvern).

Particles dispersed in a fluid undergo random collisions with the thermally excited molecules of the fluid resulting in Brownian motion. The average velocity of a large number of mono-sized particles over a long period approaches a functional form that is related to the particle size distribution. Samples of the dispersions for DLS experiments were diluted approximately 10 times in deionised water in order to avoid interferences between the particles that may happen at high concentrations.

Structure of core/shell particles by Transition Electron Microscopy (TEM)

Dispersions comprising core/shell particles were diluted as follows: 2 droplets in 100 mL of water. The solution was deposited on a copper grid covered by a layer of FORMAR (polyvinyl formal), then dried at room temperature and under air atmosphere and standard staining methods are used.

They were analysed using a Zeiss EM910 (80kV) microscope.

Example 1

835 g of PCTFE seed (solid content = 27 %, Dz = 98 nm), 4 cm³ of Dowfax 2A1 and 3 cm³ of Disponil LDBS 25 were introduced in a 2 liter reactor. The resulting mixture was purged with nitrogen for 20 minutes. 450 g of vinylidene chloride and 50 g of methyl acrylate were introduced in a premixing tank, previously purged with nitrogen. 10 % of the mixture of monomers, were introduced into the reactor, and the resulting mixture was stirred at 130 rpm for 30 minutes. The mixture in the reactor was then heated to 70 °C. When the temperature reached 69 °C, a solution of ammonium persulfate (24 cm³, 100 g/L) was introduced into the reactor. Then, the mixture of monomers still in the premixing tank was introduced in the reactor over a period of two hours. The mixture in the reactor was then heated to 70 °C for 4 hours. The residual monomers were stripped for 2 hours at 60 °C. The properties of the obtained latex were the following: the Solid Content (i.e. total amount of PVDC and PCTFE relative to the total amount of the latex) = 48.3 %; pH = 1.22; Dz = 125 nm and PDI = 0.095.

Claims

A composition comprising at least one vinylidene chloride polymer comprising at least 50 wt% of recurring units deriving from vinylidene chloride and at least one chlorotrifluoroethylene polymer comprising at least 50 wt% of recurring units deriving from chlorotrifluoroethylene.
The composition according to claim 1 wherein the amount of the at least one vinylidene chloride polymer is at least 40 wt% and at most 99 wt% with respect to the total amount of the vinylidene chloride polymer and the chlorotrifluoroethylene polymer in the composition.
The composition according to claim 1 or 2 which is in the form of a core/shell particle.
The core/shell particle according to claim 3 which comprises a core of the chlorotrifluorethylene polymer which is at least partially covered by a shell of the vinylidene chloride polymer.
The composition or core/shell particle of anyone of the preceding claims wherein the chlorotrifluoroethylene polymer comprises 85 to 100 wt% of recurring units deriving from chlorotrifluoroethylene.
Process for preparing the composition of claim 1 or 2 comprising the step of blending at least one vinylidene chloride polymer and at least one chlorotrifluoroethylene polymer.
Process for preparing a core/shell particle according to anyone of claims 3 to 5 said process comprising the steps of: providing particles of a chlorotrifluoroethylene polymer; and polymerizing vinylidene chloride and, optionally, at least one ethylenically unsaturated monomer copolymerizable with vinylidene chloride in the presence of said chlorotrifluoroethylene polymer particles.
The process of claim 7 wherein the chlorotrifluoroethylene polymer particles are dispersed in a liquid medium comprising water.
The process of claim 8 wherein the amount of dry content of chlorotrifluoroethylene polymer particles in the liquid medium is at least 0.1 wt% and at most 40 wt% by weight relative to the total weight of the vinylidene chloride polymer latex.
The process according to anyone of claims 7 to 9 which comprises the radical emulsion polymerization of vinylidene chloride and, optionally, at least one ethylenically unsaturated monomer copolymerizable with vinylidene chloride, in the presence of said chlorotrifluoroethylene polymer particles.
Use of the composition or core/shell particle of any one of claims 1 to 5 for the preparation of films and coatings.
Articles comprising the composition or core/shell particle of any one of claims 1 to 5.