WO2013037707A1

WO2013037707A1 - Polymerization process

Info

Publication number: WO2013037707A1
Application number: PCT/EP2012/067495
Authority: WO
Inventors: Bradley Lane Kent; Alessandro Veneroni; Valeriy KAPELYUSHKO
Original assignee: Solvay Specialty Polymers Italy S.P.A.
Priority date: 2011-09-14
Filing date: 2012-09-07
Publication date: 2013-03-21

Abstract

The invention pertains to a process for manufacturing a dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said process comprising polymerizing VDF in an aqueous phase comprising at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹ R_F ²P(0)O^-X_a ⁺ wherein R_F ¹ and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)], and to a vinylidene fluoride thermoplastic polymer dispersion therefrom.

Description

Polymerization process

Cross-reference to related application

This application claims priority to U.S. provisional application No. 61/534586 filed September 14, 2011, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

The present invention pertains to a novel polymerization process for efficiently manufacturing stable vinylidene fluoride (VDF) polymer aqueous dispersions, preferably having particles with an average diameter from 0.1 to 0.4 micrometers, which are suitable for the formulation of paints, e.g. for high performance external architectural coatings.

Background Art

PVDF-based paints have been used since more than four decades for the coil painting for architecture as they are capable to produce high performance coatings.

Generally, the PVDF-based painting compositions comprise pigments, resins, generally acrylic resins, and various additives and can be applied in a liquid form, when formulated in water or in particular solvents, or in powder form.

Known high performance paints used for coatings in architecture have been known for years as being based on PVDF polymers prepared by emulsion polymerization in the presence of a surfactant mixture of perfluoroalkanoic acids having a chain length between 7 and 13 carbon atoms and average molecular weight of about 480. The PVDF dispersion prepared by polymerization by using this fluorosurfactants mixture is generally coagulated, and the polymer is then washed, dried in a spray dryer and then formulated with other additives to obtain the paint.

Nevertheless, recently, perfluoroalkanoic acids, in particular those having 8 or more carbon atoms, have raised environmental concerns. For instance, perfluoroalkanoic acids have been found to show bioaccumulation. Accordingly, efforts are now devoted to phasing out from such compounds and methods have been developed to manufacture fluoropolymer products using alternative surfactants having a more favourable toxicological profile.

Several approaches have been recently pursued to this aim, typically involving either non fluorinated, partially fluorinated or even perfluorinated surfactants.

Nevertheless, surfactants suitable to this aim should possess suitable nucleating behaviour for providing VDF polymer particles having suitable sizes in addition to ensuring adequate stabilization of the VDF polymer dispersion. This combination of properties is sparely achieved with surfactants otherwise effective for polymerizing other fluoromonomers.

On the other side, bisfluoroalkyl phosphinic acid surfactants are known.

US

2010273921

MERCK PATENT GMBH 20101028

discloses the use of bisfluoroalkyl phosphinic acid surfactant for the suspension and emulsion polymerization of fluorine compounds, and/or for the wetting/stabilization of aqueous dispersions thereof. Among those fluorine compounds, mention is only specifically made of PTFE. The use of (C₄F₉)₂P(O)OH for dispersing in water PTFE particles is exemplified in the working embodiments provided therein.

EP

0070498

A HOECHST 19830126

discloses a process for polymerizing an acryl monomer, a vinyl monomer and a functional monomer in the presence of a fluorinated surfactant, which can be notably, inter alia, a perfluoroalkylphosphinic acid having C₂-C₂₀ perfluoroalkyl residues.

GB

1388924

HOECHST AG 19750323

discloses perfluoroalkyl-phosphorous compounds, including notably perfluoroalkylphosphinic acids of general formula: (R_f)₂P(O)OH, with C4-C24 linear perfluoroalkyl radical, useful as surface active agents or wetting agents, or useful in the manufacture of PTFE dispersions.

US

3047619

DUPONT DE NEMOURS 19620731

discloses beta-hydroperfluoroalkyl phosphinic acids, i.e. phosphinic acids bearing only one fluoroalkyl group on the phosphorous atom, and comprising an hydrogen atom in the beta position of said fluoroalkyl group. Surface tension in water of said compounds is provided, which make them suitable for being used as emulsifying agents for fluorocarbon-oil and fluorocarbon-water systems, as well as emulsifying agents for polymerization, in particular for polymerizations involving fluorinated olefins.

Summary of invention

The Applicant has now surprisingly found that certain fluoroalkylphosphinic surfactants, although designed for other fields of use, and differing from fluorosurfactants known in the prior art for VDF polymerization because of their ionic phosphorous-based functionality (prior art surfactant being principally carboxylates and sulfonates) are particularly useful for vinylidene fluoride emulsion polymerization.

Further in addition, upon decomposition, as possibly observed at the temperatures of processing of the VDF polymer dispersions, these molecules might break into smaller fluorinated units with few carbons each, giving the molecule a more favorable toxico-kinetic and environmental profile than traditionally used perfluoroalkyl carboxylates with greater than six fluorinated carbons.

It is thus an object of the present invention a process for manufacturing a dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said process comprising polymerizing VDF in an aqueous phase comprising at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹R_F ²P(O)O^-X_a ⁺
wherein R_F ¹and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)].

The Applicant has surprisingly found that in above mentioned process, the use of said surfactant (P) enables efficient nucleation and tuning of the average particle size of the polymer (F), while also ensuring efficient colloidal stabilization of the dispersion.

More particularly, the average particle size of the particles of polymer (F) can be efficiently tuned by appropriate adjustment of the concentration of of said surfactant (P).

The expression ‘thermoplastic’ is used herein to denote a semi-crystalline VDF polymer which can advantageously processed in the melt and which possesses typically a heat of fusion of more than 5 J/g, preferably more than 7 J/g, even more preferably 10 J/g, when measured according to ASTM D 3418.

The vinylidene fluoride thermoplastic polymer [polymer (F)] is preferably a polymer comprising :
(a’) at least 60 % by moles, preferably at least 75 % by moles, more preferably 85 % by moles of vinylidene fluoride (VDF);
(b’) optionally from 0.1 to 15%, preferably from 0.1 to 12%, more preferably from 0.1 to 10% by moles of a fluorinated monomer different from VDF; said fluorinated monomer being preferably selected in the group consisting of vinylfluoride (VF₁), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), perfluoromethylvinylether (MVE), trifluoroethylene (TrFE) and mixtures therefrom; and
(c’) optionally from 0.1 to 5 %, by moles, preferably 0.1 to 3 % by moles, more preferably 0.1 to 1% by moles, based on the total amount of monomers (a’) and (b’), of one or more hydrogenated comonomer(s).

The vinylidene fluoride polymer [polymer (F)] is more preferably a polymer consisting of :
(a’) at least 60 % by moles, preferably at least 75 % by moles, more preferably 85 % by moles of vinylidene fluoride (VDF);
(b’) optionally from 0.1 to 15%, preferably from 0.1 to 12%, more preferably from 0.1 to 10% by moles of a fluorinated monomer different from VDF; said fluorinate monomer being preferably selected in the group consisting of vinylfluoride (VF₁), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), perfluoromethylvinylether (MVE), trifluoroethylene (TrFE) and mixtures therefrom.

As non limitative examples of the VDF polymers of the present invention, mention can be notably made of homopolymer of VDF, VDF/TFE copolymer, VDF/TFE/HFP copolymer, VDF/TFE/CTFE copolymer, VDF/TFE/TrFE copolymer, VDF/CTFE copolymer, VDF/HFP copolymer, VDF/TFE/HFP/CTFE copolymer and the like.

The process of the invention is particularly suitable for manufacturing VDF homopolymers.

The melt viscosity of the polymer (F), measured at 232˚C and 100 sec^-1 of shear rate according to ASTM D3835, is advantageously of at least 5 kpoise, preferably at least 10 kpoise.

The melt viscosity of the polymer (F), measured at 232˚C and 100 sec^-1 of shear rate, is advantageously of at most 60 kpois, preferably at most 40 kpoise, more preferably at most 35 kpoise.

The melt viscosity of VDF polymer is measured in accordance with ASTM test No. D3835, run at 232°C, under a shear rate of 100 sec^-1.

The VDF polymer has a melting point of advantageously at least 120°C, preferably at least 125°C, more preferably at least 130°C.

The VDF polymer has a melting point advantageously of at most 190°C, preferably at most 185°C, more preferably at most 170°C.

The melting point (T_m2) can be determined by DSC, at a heating rate of 10°C/min, according to ASTM D 3418.

Surfactant (P) preferably complies with formula:
R_f* ¹R_f* ²P(O)O^-X_a ⁺
wherein R_f* ¹and R_f* ², equal to or different from each other, is independently a branched or unbranched alkyl chain of formula C_nF_2n-z+1H_z, wherein n = 2-16, preferably 2-6, z = 0-3, and X_a has the meaning as above defined.

Still more preferably, surfactant (P) complies with formula:
R_f# ¹R_f# ²P(O)O^-X_a ⁺
wherein R_f# ¹and R_f# ², equal to or different from each other, is independently a branched or unbranched alkyl chain of formula C_nF_2n-1, wherein n = 2-6, preferably n=4, and X_a has the meaning as above defined.

A surfactant (P) which has been found to provide particularly good result is the surfactant of formula:
(C₄F₉)₂P(O)O^-X_a ⁺
with X_a having the meaning as above defined.

According to certain embodiments, the polymerization process of the invention may be carried out in the presence of an additional phosphorous-containing surfactant different from surfactant (P) and used in combination thereto. Thus, in the process according to these embodiments, VDF is polymerized in an aqueous phase further comprising an additional phosphorous-containing surfactant different from surfactant (P).

In particular, said aqueous phase can comprise at least one fluorocarbonphosphonic acid surfactant of formula:
R_QP(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)
wherein R_Qis a fluorinated or perfluorinated C₁-C₂₀ group, and each of X_a’and X_a”, equal to or different from each other, is independently H, a alkali metal or a NR^H’ ₄ group, with R^H’ being H or a C₁-C₆ hydrocarbon group [surfactant (Q)].

Generally, manufacturing methods suited for providing surfactants (P) may provide mixtures comprising surfactant (P) and surfactant (Q), as above detailed. In these cases, it has been observed that no extensive separation procedure is required for removing surfactant (Q) from the mixture comprising surfactant (P), as this additional surfactant (Q) does not impair performances in the polymerization process of the invention, but rather can provide advantageous effects.

It is nevertheless understood that the weight percent of surfactant (P), over the overall weight amount of surfactant (P) and surfactant (Q) used in the polymerization process of the present invention will be generally of at least 50 %wt, preferably of at least 60 % wt, more preferably of at least 75 % wt, still more preferably of at least 80 %wt.

Surfactant (Q) preferably complies with formula:
R_Q*P(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)
wherein R_Q* is a branched or unbranched alkyl chain of formula C_nF_2n-z+1H_z, wherein n = 2-16, preferably 2-6, z = 0-3, and each of X_a’and X_a”has the meaning as above defined.

Still more preferably, surfactant (Q) complies with formula:
R_Q#P(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)
wherein R_Q#is a branched or unbranched alkyl chain of formula C_nF_2n-1, wherein n = 2-6, preferably n=4, and each of X_a’and X_a”has the meaning as above defined.

A surfactant (Q) which has been found to provide particularly good result is the surfactant of formula:
C₄F₉P(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)
with each of X_a’and X_a” having the meaning as above defined.

To the aim of manufacturing polymer (F) dispersions suitable for formulating architectural coating paints, i.e. dispersions with average particles size of 200 to 400 nm, the amount of surfactant (P) will be generally of at least 0.1 g/l, advantageously at least 0.5 g/l, preferably at least 0.75 g/l, and of typically at most 5 g/l, advantageously at most 4 g/l, preferably at most 3.5 g/l.

With the purpose of achieving, notably, higher molecular weight polymers (F), e.g. melt viscosities of 22 to 35 kpoise, when measured at 232°C and shear rate of 100/s, according to certain embodiments, the process of the invention advantageously comprises polymerizing VDF in an aqueous phase comprising surfactant (P), as above detailed, and at least one base, in such an amount that the pH at the beginning of the polymerization is above 7.

The Applicant has indeed found that the effectiveness of the surfactant (P) in terms of latex stability, total attainable monomer conversion, reaction kinetics, but more particularly minimization of chain transfer effects can be further enhanced by operating with an initial alkaline pH in the reactor by the addition of a base, as above detailed.

The choice of the base is not particularly critical; the skilled in the art will generally select bases which will not form water insoluble salts with the surfactant (P), as above detailed. Among suitable bases, mention can be made of alkaline metal hydroxides, in particular NaOH, KOH, alkaline-earth metal hydroxides, in particular Mg(OH)₂, Ca(OH)₂ and ammonium derivatives of formula NR_H ¹R_H ²R_H ³, wherein each of R_H ¹, R_H ², R_H ³, equal to or different from each other, is H or a C₁-C₆ hydrocarbon group, preferably ammonia.

In certain preferred embodiments wherein ammonia is used as a base, it is generally used in an amount of at least 0.01 g/l, preferably of at least 0.05 g/l, even more preferably of at least 0.1 g/l, in the aqueous phase of the process of the present invention. Upper limit for the concentration of ammonia is not particularly critical; nevertheless, its amount will be generally limited below 1 g/l, more particularly below 0.75 g/l, even more particularly below 0.5 g/l.

The polymerization process of the invention is typically started by an initiator. Suitable initiators include any of the initiators known for initiating a free radical polymerization of vinylidene fluoride.

Non-limitative examples of suitable initiators include, notably, inorganic initiators and peroxide initiators.
Representative examples of inorganic initiators include, notably, ammonium-, alkali- or earth alkali-salts of persulfates or (per)manganic acids. A persulfate initiator, e.g. ammonium persulfate, can be used on its own or may be used in combination with a reducing agent. Suitable reducing agents include bisulfites such as, e.g., ammonium bisulfite or sodium metabisulfite, thiosulfates such as, e.g., ammonium, potassium or sodium thiosulfate, hydrazines, azodicarboxylates and azodicarboxyldiamide. Further reducing agents which may be used include sodium formaldehyde sulfoxylate (Rongalite) or fluoroalkyl sulfinates as disclosed in

US

5285002

MINNESOTA MINING AND MANUFACTURING CO. 19940208

. The reducing agent typically reduces the half-life time of the persulfate initiator. Additionally, a metal salt catalyst such as, e.g., copper, iron or silver salts may be added.
Representative examples of peroxide initiators include, notably, hydrogen peroxide, sodium or barium peroxide, diacylperoxides such as, e.g., diacetylperoxide, disuccinyl peroxide, dipropionylperoxide, dibutyrylperoxide, dibenzoylperoxide, di-tert-butylperoxide, benzoylacetylperoxide, diglutaric acid peroxide and dilaurylperoxide, and further per-acids and salts thereof such as, e.g., ammonium, sodium or potassium salts. Specific examples of per-acids include, notably, peracetic acid. Esters of the peracid can be used as well and examples thereof include tert-butylperoxyacetate and tert-butylperoxypivalate.

The amount of initiator typically ranges between 0.01% and 1% by weight, preferably between 0.01 and 0.5% by weight with respect to the weight of the polymer (F) to be produced.

The polymerization process may be carried out in the presence of other materials such as, notably, chain-transfer agents. Non-limitative examples of chain transfer agents suitable for the purpose of the process of the invention include, notably, compounds of formula R_f(I)_x(Br)_y, wherein R_f is a C₁-C₈ (per)fluoro(chloro)alkyl group, x and y are independently integers between 0 and 2, the (x+y) sum being comprised between 1 and 2, such as, e.g., 1,4-diiodoperfluorobutane. Further chain-transfer agents which may be used include, notably, C₁-C₅ alkanes such as, e.g., ethane, propane and n-pentane, halogenated hydrocarbons such as, e.g., CCl₄, CHCl₃, CH₂Cl₂, hydrofluorocarbon compounds such as, e.g., CH₂F-CF₃ (R134a), ethers such as, e.g., dimethyl ether and methyl tert-butyl ether and esters such as, e.g., ethyl acetate and malonic esters.

The process of the invention generally comprises the following steps:
a) feeding an aqueous solution of the surfactant (P) into the polymerization reactor, possibly in combination with deionized water, so as to achieve the required concentration of surfactant (P) in the aqueous phase;
b) optionally adding into the aqueous medium chain transfer agent(s), stabilizer(s) and/or other polymerization additive(s);
d) adding vinylidene fluoride (VDF), possibly in combination with other copolymerizable monomers, if required;
d) adding the polymerization initiator and, optionally, during the polymerization, further adding additional amounts of VDF monomer and/or comonomers, initiators, transfer agents;
f) recovering from the reactor the polymer (F) dispersion.

Polymerization is generally carried out at a pressure of at least 350 psi, preferably of at least 400 psi, more preferably of at least 500 psi.

Polymerization can be carried out at a temperature of at least 50°C, preferably of at least 60°C, more preferably of at least 80°C.

Upper temperature is not particularly limited, provided that an aqueous phase is maintained in polymerization conditions. Generally temperature will not exceed 130°C, preferably 125°C.

The invention further pertains to an aqueous dispersion of polymer (F), as above described, said aqueous dispersion comprising at least one surfactant (P), as above detailed.

The aqueous dispersion of the invention is advantageously obtained from the process of the invention.

Still an object of the invention is the use of the dispersion, as above detailed, for the manufacture of paints.

With the aim of being used for formulating paints, the aqueous dispersions of polymer (F) as above detailed is generally coagulated so as to obtain a dry powder of polymer (F).

According to certain embodiments of the invention, the dry powder of polymer (F) as above detailed may comprise surfactant (P).

The amount of surfactant (P) comprised in the polymer (F) will be generally of below 2500 ppm, preferably below 1500 ppm, even more preferably below 1000 ppm, with respect to the weight of polymer (F).

It is nevertheless understood that according to other embodiments, the dry powder of polymer (F) may be substantially free from surfactant (P) as above detailed.

Said dry powder of polymer (F) is generally dispersed in a suitable organic dispersing medium, typically a latent or intermediate solvent of polymer (F).

An intermediate solvent for the polymer (F) is a solvent which does not dissolve or substantially swell the polymer (F) at 25°C, which solvates polymer (F) at its boiling point, and retains polymer (F) in solvated form, i.e. in solution, upon cooling.

A latent solvent for the polymer (F) is a solvent which does not dissolve or substantially swell polymer (F) at 25°C, which solvates polymer (F) at its boiling point, but on cooling, polymer (F) precipitates.

Latent solvents and intermediate solvents can be used alone or in admixture. Mixtures of one or more than one latent solvent with one or more than one intermediate solvent can be used .

Intermediate solvents suitable for polymer (F) paint formulations are notably butyrolactone, isophorone and carbitol acetate.

Latent solvents suitable for suitable for polymer (F) paint formulations are notably methyl isobutyl ketone, n-butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethyl acetoacetate, triethyl phosphate, propylene carbonate, triacetin (also known as 1,3-diacetyloxypropan-2-yl acetate), dimethyl phthalate, glycol ethers based on ethylene glycol, diethylene glycol and propylene glycol, and glycol ether acetates based on ethylene glycol, diethylene glycol and propylene glycol.

Non limitative examples of glycol ethers based on ethylene glycol, diethylene glycol and propylene glycol are notably ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, propylene glycol methyl ether, propylene glycol dimethyl ether, propylene glycol n-propyl ether.

Non limitative examples of glycol ether acetates based on ethylene glycol, diethylene glycol and propylene glycol are notably ethylene glycol methyl ether acetate, ethylene glycol monethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol methyl ether acetate.

Non-solvents for polymer (F) such as methanol, hexane, toluene, ethanol and xylene may also be used in combination with latent solvent and/or intermediate solvent for special purpose, e.g. for controlling paint rheology, in particular for spray coating.

As a result, the polymer (F) paint formulation might comprise surfactant (P), as above detailed, in amounts of below 2500 ppm, preferably below 1500 ppm, even more preferably below 1000 ppm, with respect to the weight of polymer (F).

Typically, the polymer (F) paint formulation will comprise additional ingredients, including notably, (meth)acrylic resins, pigments, fillers, stabilizers and the like.

The invention will be now described with reference to the following examples, whose purpose is merely illustrative and not limitative of the scope of the invention.

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.

EXAMPLES

RAW MATERIALS:
MAFS-010 fluorosurfactant commercially available from Merck KGaA (Darmstadt, Germany) based on a fluoroalkyl phosphinic acid with the general structure (CF₃-CF₂-CF₂-CF₂)₂-POOH.

EXAMPLE 1

A 7.5-liter stainless steel horizontal reactor, equipped with a paddle agitator, was charged with a total of 5.375 kg of deionized water and aqueous solution of a surfactant mixture containing MAFS-010 fluorosurfactant such that the concentration of MAFS-010 fluorosurfactant was 1.0 g/L in the aqueous phase of the reactor. In addition, 4 g of a hydrocarbon wax melting at 50 to 60 °C was added. The reactor was sealed and deaerated by heating with agitation to 100 °C, then venting steam and air from the reactor for two minutes. The reactor was then heated to 122.5 °C. Sufficient vinylidene fluoride monomer was introduced from a cylinder to bring the reactor pressure to 650 psig. Then 24.4 mL of di-tert-butyl peroxide (DTBP) was pumped into the reactor to initiate the polymerization reaction.
After an induction period of approximately 15 minutes, the reactor pressure decreased slightly, indicating initiation. Vinylidene fluoride then was continuously added as needed to maintain the reactor pressure at 650 psig while the reactor temperature was maintained at 122.5 °C by pumping water and ethylene glycol through the reactor jacket. After about 276 minutes, when a total of 2298 g of vinylidene fluoride had been fed to the reactor, the monomer feed was stopped. In order to maximize yield, the system was allowed to continue reacting until the reactor pressure was decreased to about 150 psig. At that point, the reactor was cooled, the unreacted vinylidene fluoride was vented, and the latex was drained from the reactor.
The resulting latex was screened through an 80 mesh screen to remove precoagulated large particles. In addition, the reactor wall was cleaned mechanically to remove any adhering precoagulated large particles. A coagulation loss (defined as the percentage of the original 2298 g of vinylidene fluoride monomer that was recovered as precoagulated large particles) of 15% was found. The screened latex was analyzed by laser light scattering and found to have an average latex particle size of 389 nm.
The polymer melt viscosity at 232°C was measured in a Kayeness Galaxy V capillary rheometer with an L/D ratio of 15:1 and found to be 21.9 kP at 100/s shear rate.

EXAMPLE 2

The polymerization procedure in Example 1 was followed except for an increase in MAFS-010 concentration to 2.0 g/L. After about 360 minutes, when a total of 1634 g of vinylidene fluoride had been fed to the reactor, the monomer feed was stopped and a similar react down procedure was followed. The resulting latex was found to have a coagulation loss of 6.5% and an average particle size of 288 nm. The polymer melt viscosity at 232°C, measured as above detailed, was found to be 9.3 kP at 100/s shear rate.

EXAMPLE 3

The polymerization procedure in Example 1 was followed except for an increase in MAFS-010 concentration to 2.0 g/L and the initial addition of ammonium hydroxide solution such that the ammonia concentration was 0.10 g/L. After about 204 minutes, when a total of 2298 g of vinylidene fluoride had been fed to the reactor, the monomer feed was stopped and a similar react down procedure was followed. The resulting latex was found to have a coagulation loss of 5.1% and an average particle size of 300 nm. The polymer melt viscosity, measured as above detailed, was found to be 33.9 kP at 100/s shear rate.

EXAMPLE 4

The polymerization procedure in Example 1 was followed except for an increase in MAFS-010 concentration to 3.0 g/L and the initial addition of ammonium hydroxide solution such that the ammonia concentration was 0.16 g/L. After about 214 minutes, when a total of 2298 g vinylidene fluoride had been fed to the reactor, the monomer feed was stopped and a similar react down procedure was followed. The resulting latex was found to have a coagulation loss of 3.2% and an average particle size of 303 nm. The polymer melt viscosity, measured as above detailed, was found to be 26.6 kP at 100/s shear rate.

Claims

A process for manufacturing a dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said process comprising polymerizing VDF in an aqueous phase comprising at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹R_F ²P(O)O^-X_a ⁺

wherein R_F ¹and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)].
The process of claim 1, wherein surfactant (P) complies with formula:

R_f* ¹R_f* ²P(O)O^-X_a ⁺

wherein R_f* ¹and R_f* ², equal to or different from each other, is independently a branched or unbranched alkyl chain of formula C_nF_2n-z+1H_z, wherein n = 2-16, preferably 2-6, z = 0-3, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group.
The process of claim 2, wherein surfactant (P) complies with formula:

R_f# ¹R_f# ²P(O)O^-X_a ⁺

wherein R_f# ¹and R_f# ², equal to or different from each other, is independently a branched or unbranched alkyl chain of formula C_nF_2n-1, wherein n = 2-6, preferably n=4, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group.
The process of claim 3, wherein surfactant is a surfactant of formula:

(C₄F₉)₂P(O)O^-X_a ⁺

with X_a being H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group.
The process according to anyone of the preceding claims, wherein said aqueous phase further comprises an additional phosphorous-containing surfactant different from surfactant (P).
The process according to claim 5, wherein said aqueous phase can comprises at least one fluorocarbonphosphonic acid surfactant of formula:

R_QP(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)

wherein R_Qis a fluorinated or perfluorinated C₁-C₂₀ group, and each of X_a’and X_a”, equal to or different from each other, is independently H, a alkali metal or a NR^H’ ₄ group, with R^H’ being H or a C₁-C₆ hydrocarbon group [surfactant (Q)].
The process of claim 6, wherein the weight percent of surfactant (P), over the overall weight amount of surfactant (P) and surfactant (Q) used in the polymerization process of the present invention will be generally of at least 50 %wt, preferably of at least 60 % wt, more preferably of at least 75 % wt, still more preferably of at least 80 %wt.
The process according to claim 6 or 7, wherein surfactant (Q) complies with formula:

R_Q*P(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)

wherein R_Q* is a branched or unbranched alkyl chain of formula C_nF_2n-z+1H_z, wherein n = 2-16, preferably 2-6, z = 0-3, and each of X_a’and X_a”is independently H, a alkali metal or a NR^H’ ₄ group, with R^H’ being H or a C₁-C₆ hydrocarbon group.
The process according to claim 8, wherein surfactant (Q) complies with formula:

R_Q#P(O)(O^-X_a’ ⁺)(O^-X_a” ⁺)

wherein R_Q#is a branched or unbranched alkyl chain of formula C_nF_2n-1, wherein n = 2-6, preferably n=4, and each of X_a’and X_a”is independently H, a alkali metal or a NR^H’ ₄ group, with R^H’ being H or a C₁-C₆ hydrocarbon group.
The process according to anyone of the preceding claims, comprising polymerizing VDF in an aqueous phase further comprising at least one base, in such an amount that the pH at the beginning of the polymerization is above 7.
The process of claim 10, wherein the base is selected from the group consisting of alkaline metal hydroxides, in particular NaOH, KOH, alkaline-earth metal hydroxides, in particular Mg(OH)₂, Ca(OH)₂ and ammonium derivatives of formula NR_H ¹R_H ²R_H ³, wherein each of R_H ¹, R_H ², R_H ³, equal to or different from each other, is H or a C₁-C₆ hydrocarbon group, preferably ammonia.
An aqueous dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said aqueous dispersion comprising at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹R_F ²P(O)O^-X_a ⁺

wherein R_F ¹and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)].
Method for manufacturing paints, comprising using the dispersion of claim 12.
A dry powder of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said dry powder comprising at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹R_F ²P(O)O^-X_a ⁺

wherein R_F ¹and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)].
The dry powder of claim 14, wherein the amount of surfactant (P) comprised in the polymer (F) is of below 2500 ppm, preferably below 1500 ppm, even more preferably below 1000 ppm, with respect to the weight of polymer (F).
A paint formulation comprising a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], and at least one bisfluorocarbonphosphinic surfactant of formula R_F ¹R_F ²P(O)O^-X_a ⁺

wherein R_F ¹and R_F ², equal to or different from each other, is independently a fluorinated or perfluorinated C₁-C₂₀ group, and X_a is H, a alkali metal or a NR^H ₄ group, with R^H being H or a C₁-C₆ hydrocarbon group [surfactant (P)], in amounts of below 2500 ppm, preferably below 1500 ppm, even more preferably below 1000 ppm, with respect to the weight of polymer (F).