Polymerization of vinylidene fluoride in water using a macromolecular suspending agent

Abstract

The present invention relates to a vinylidene fluoride polymer, a method for manufacturing the vinylidene fluoride polymer, and an article comprising the vinylidene fluoride polymer.

Description

Technical Field

[0001] This application claims priority to European Patent Application No. 20197702.2, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a vinylidene fluoride polymer, a method for manufacturing the vinylidene fluoride polymer, and an article comprising the vinylidene fluoride polymer. Background Technology

[0003] Vinylidene fluoride polymers are advantageously used in several different applications.

[0004] Poly(vinylidene fluoride) (PVDF) can be obtained by polymerization of vinylidene fluoride monomers (difluoro-1,1-ethylene, VF2, or VDF) through suspension polymerization or emulsion polymerization.

[0005] Compared to emulsion polymerization, the main advantage of suspension polymerization of VDF is that it can be carried out in the absence of surfactants, especially fluorinated surfactants.

[0006] However, during the suspension polymerization of VDF, in the absence of a suspending agent, reactor scaling (the accumulation of polymer deposits on the inner surfaces of the reactor and stirring equipment) was observed, which hindered the scaling of the method to industrial production.

[0007] The use of nonionic suspending agents in VDF suspension polymerization is known in the art. For example, WO 2016 / 041808 discloses the reduction of scaling in VDF polymerization by using a mixture of nonionic surfactants comprising an epoxy alkyl polymer (PAO) and nonionic hydroxyalkyl cellulose.

[0008] However, the purification step of the polymer may not be effective in removing non-ionic suspending agents, which is the step required to obtain high-quality VDF polymers suitable for a variety of applications.

[0009] The purification step includes washing the polymer particles with pure water. Therefore, the higher the solubility of the suspending agent in water, the higher the purification efficiency, and thus the purer the PVDF polymer obtained.

[0010] Among suspension concentrates, ionic suspension concentrates have the highest water solubility. However, the use of ionic suspension concentrates in VDF suspension polymerization can lead to unstable reactions in which reaction control may be insufficient, making it unsafe to scale up production to industrial levels.

[0011] Therefore, there remains a need in the field for a method to manufacture vinylidene fluoride polymers that produces purer PVDF and is feasible on an industrial scale. Summary of the Invention

[0012] It has now been unexpectedly discovered that the method of the present invention advantageously enables the easy acquisition of vinylidene fluoride polymers by means of a specific mixture that allows for the avoidance of reactor fouling while using a suspending agent that is easily washed away from the polymer at the end of polymerization.

[0013] In a first aspect, the present invention relates to a method for producing a vinylidene fluoride polymer [polymer (VDF)] in an aqueous suspension, the method comprising polymerizing vinylidene fluoride in the presence of:

[0014] A) at least one nonionic suspending agent; and

[0015] B) At least one ionic carboxyalkyl cellulose.

[0016] The inventors unexpectedly discovered that by using a mixture of at least one ionic suspending agent and at least one nonionic suspending agent, the amount of nonionic suspending agent can be significantly reduced, while controlled polymerization can be carried out without scaling.

[0017] Therefore, in a second aspect, the present invention relates to a vinylidene fluoride polymer [polymer (VDF)] obtainable by the method of the present invention.

[0018] Furthermore, it was unexpectedly discovered that the vinylidene fluoride polymer powder obtained by the method of the present invention is characterized by bead-like, substantially spherical particles with a size distribution D50 value higher than 150 micrometers, and advantageously exhibits excellent flowability.

[0019] In a third aspect, the present invention relates to a composition comprising at least one polymer (VDF) of the present invention [Composition (C)].

[0020] In a fourth aspect, the present invention relates to an article comprising the composition (C) of the present invention. Attached Figure Description

[0021] Figure 1 The SEM image of the polymer (VDF) particles of Example 1 at a magnification of 50x is shown.

[0022] Figure 2 SEM images of PVDF polymer particles manufactured according to standard processes are shown. These PVDF polymer particles are in granular form and subsequently ground to reduce particle size. Magnification: 2.55K x. Detailed Implementation

[0023] Unless otherwise specified, in the context of this invention, all percentages are ratios relative to the weight of a specific component of the mixture divided by the total weight of the mixture (expressed as wt / wt).

[0024] As used herein, the term “substantially circular” and related forms refer to particles that have a substantially circular appearance in both cross sections and do not have an elongated body.

[0025] As used herein, the term "vinylidene fluoride polymer" refers to a polymer comprising more than 50 mol%, preferably more than 80 mol%, of repeating units derived from the polymerization of vinylidene fluoride monomers (difluoro-1,1-ethylene, VF2, or VDF).

[0026] For the purposes of this invention, the vinylidene fluoride polymer is preferably a homopolymer containing only repeating units derived from VDF.

[0027] For the purposes of this invention, in addition to the VDF monomer, the vinylidene fluoride polymer may optionally contain repeating units different from the VDF repeating units, and these repeating units are derived from the polymerization of olefinically unsaturated monomers different from VDF (e.g., 0.1-20 mol%, preferably 0.5-10 mol%, relative to the total molar percentage of the composition). The olefinically unsaturated monomer may contain at least one fluorine atom and can therefore be designated as a fluorinated comonomer. Nevertheless, these olefinically unsaturated monomers may be fluorine-free; examples of these non-fluorinated comonomers are, in particular, hydrophilic (meth)acrylic acid monomers.

[0028] The hydrophilic (meth)acrylic acid monomer (MA) preferably conforms to the following formula:

[0029]

[0030] R1, R2, and R3 may be the same or different from each other, and each is independently a hydrogen atom or a C1-C3 hydrocarbon group, and R OH It is a hydrogen or C1-C5 hydrocarbon moiety containing at least one hydroxyl group. Non-limiting examples of hydrophilic (meth)acrylic acid monomers (MA) include, in particular, acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylic acid, hydroxypropyl (meth)acrylic acid, and hydroxyethylhexyl (meth)acrylic acid.

[0031] The monomer (MA) is more preferably selected from:

[0032] - Hydroxyethyl acrylate (HEA) of the following formula:

[0033]

[0034] - 2-Hydroxypropyl acrylate (HPA) of any of the following formulations:

[0035]

[0036] - Acrylic acid (AA) with the following formula:

[0037]

[0038] - and its mixtures.

[0039] Most preferably, the monomer (MA) is AA and / or HEA.

[0040] As detailed above, non-limiting examples of fluorinated comonomers other than VDF include, in particular, the following:

[0041] (i) C2-C8 fluoroolefins, such as trifluoroethylene (TrFE), tetrafluoroethylene (TFE) and hexafluoropropylene (HFP);

[0042] (ii) Equation CH2=CH-R f0 Perfluoroalkyl ethylene, wherein R f0 It is a C2-C6 perfluoroalkyl group;

[0043] (iii) Chlorinated and / or brominated and / or iodinated C2-C6 fluoroolefins, such as trifluorochloroethylene (CTFE);

[0044] (iv) Equation CF2 = CFOR f1 Perfluoroalkyl vinyl ethers, wherein R f1 It is a C1-C6 perfluoroalkyl group, such as perfluoromethyl vinyl ether (PMVE) and perfluoropropyl vinyl ether (PPVE);

[0045] (v) A (per)fluoroalkyl vinyl ether of formula CF2=CFOX0, wherein X0 is C1-C 12 oxyalkyl or C1-C having one or more ether groups 12 (per)fluoroalkyl groups, such as perfluoro-2-propoxy-propyl;

[0046] (vi) Equation CF2=CFOCF2OR f2 (Per)fluoroalkyl vinyl ethers, wherein R f2 It is a C1-C6 (per)fluoroalkyl group, such as -CF3, -C2F5, -C3F7, or a C1-C6 (per)fluorooxyalkyl group having one or more ether groups, such as -C2F5-O-CF3;

[0047] (vii) Functionalized (per)fluoroalkyl vinyl ethers of formula CF2=CFOY0, wherein Y0 is selected from C1-C 12 Alkyl or (per)fluoroalkyl, C1-C 12 oxyalkyl groups and C1-C groups having one or more ether groups 12 (All)fluoroalkyl, Y0 contains a carboxylic acid or sulfonic acid group (in the form of its acid, acyl halide or salt);

[0048] (viii) Fluorodioxole, especially perfluorodioxole;

[0049] (ix) Ethylene fluoride,

[0050] and its mixtures.

[0051] The preferred fluorinated comonomers are chlorotrifluoroethylene (CTFE), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoromethyl vinyl ether (PMVE).

[0052] In one embodiment of the present invention, the polymer (VDF) preferably comprises the following repeating units, and more preferably consists of the following repeating units:

[0053] -Derived from repeating units of vinylidene fluoride,

[0054] - Relative to the total molar amount of repeating units in the polymer (VDF), from 0.1% to 3% molar amounts of repeating units derived from at least one (meth)acrylic acid monomer [monomer (MA)], and

[0055] - Relative to the total molar amount of repeating units in the polymer (VDF), there are repeating units derived from hexafluoropropylene (HFP) of 0.1% to 10%, preferably 0.2% to 5% by molar.

[0056] The method of the present invention is polymerization carried out in an aqueous suspension.

[0057] For the purposes of this invention, polymerization in an aqueous suspension refers to a method in which the reaction medium is formed of an organic phase, to which water is added to promote thermal dispersion during the reaction process. The organic phase can be formed by the monomer itself without the addition of a solvent, or by the monomer dissolved in a suitable organic solvent in the presence of a suitable organic initiator and a water-soluble suspending agent having repeating molecular units in its structure.

[0058] Polymerization can be carried out under such temperature and pressure conditions, allowing for the existence of more abundant monomers (i.e., VDF) under subcritical or supercritical conditions.

[0059] The method of the present invention is carried out at a temperature typically at least 10°C, preferably at least 25°C, and more preferably at least 45°C.

[0060] The pressure is typically maintained at a value greater than 25 bar, preferably greater than 50 bar, and even more preferably greater than 75 bar.

[0061] For the purposes of this invention, the term "nonionic suspending agent" is intended to refer to polymers containing hydroxyl groups, selected from the group consisting of:

[0062] a) Polysaccharide derivatives;

[0063] b) Partially hydrolyzed polyvinyl alcohol (PVA); and

[0064] c) Epoxyalkane polymers (PAO).

[0065] The term "polysaccharide derivative" is intended herein to refer to a nonionic derivative of a polysaccharide polymer containing hydroxyl groups, comprising one or more glycosidic units linked together by glycosidic bonds as repeating units. A glycosidic unit is intended herein to represent a six-membered pyranoside ring or a five-membered furanoside ring.

[0066] Preferably, the nonionic polysaccharide derivative comprises repeating glycosidic units selected from D-glucopyranoside and furanoside, or mixtures thereof, linked together by glycosidic bonds.

[0067] More preferably, in the method of the present invention, the nonionic polysaccharide derivative a) is a repeating β-D-glucopyranoside unit of formula (I) connected to each other by β-glycosidic bonds:

[0068]

[0069] Each R' is the same or different from each other each time it appears, representing a hydrogen atom, a C1-C8 hydrocarbon group, or a C2-C8 hydroxyalkyl group.

[0070] More preferably, in the carbohydrate derivatives of formula (I), each R' is the same as or different from each other, representing a hydrogen atom, hydroxyethyl or 2-hydroxypropyl.

[0071] More preferably, in the method of the present invention, the carbohydrate derivative of formula (I) is hydroxyethyl methylcellulose or 2-hydroxypropyl methylcellulose, the latter being particularly preferred.

[0072] Non-limiting examples of nonionic polysaccharide derivatives (a) suitable for the methods of the present invention include, in particular, cellulose derivatives available under the following trade names: METHOCEL, having a dynamic viscosity of 80-120 mPa·s in aqueous solution at 2% wt% concentration at 20°C. TM K100, a METHOCEL with a dynamic viscosity of 11,250-21,000 mPa·s in aqueous solution at 2% wt% concentration at 20°C. TM K15M, a METHOCEL with a dynamic viscosity of 2.4 to 3.6 mPa·s in aqueous solution at 2% wt% concentration at 20°C. TM K3, METHOCEL, has a dynamic viscosity of 3000 to 6000 mPa·s in aqueous solution at 2% wt% concentration at 20°C. TMK4M, and a dynamic viscosity of 4 to 8 mPa x s in aqueous solution at 2% wt% concentration at 20°C. MHPC5.

[0073] Partially hydrolyzed polyvinyl alcohol (b) is intended herein as an aqueous composition comprising partially hydrolyzed polyvinyl acetate and polyvinyl alcohol.

[0074] Polyvinyl alcohol is commercially available and can be obtained within a certain range of molecular weight and degree of hydrolysis.

[0075] Typically, polyvinyl alcohol (PVA) is prepared by hydrolyzing the PVA precursor (polyvinyl acetate) obtained from the polymerization of vinyl acetate (CH3COOCHCH2), as shown in Scheme I below.

[0076] Option 1

[0077]

[0078] Furthermore, the degree of saponification is defined as the degree of hydrolysis (degree of saponification = l / (l+m)).

[0079] The degree of hydrolysis of PVA used in the aqueous composition of the present invention is preferably at least 80%.

[0080] The term “epoxide polymer (PAO)” here means a water-soluble nonionic suspension homopolymer or copolymer that is essentially composed of repeating units derived from one or more linear epoxy alkanes.

[0081] Suitable alkyl oxide homopolymers or copolymers for use in this invention are typically, but not exclusively, selected from homopolymers composed of repeating units derived from ethylene oxide (EO), such as polyethylene glycol (also referred to as PEG, POE, or PEO).

[0082] Typically, in the context of this invention, the average molecular weight (M) of the epoxy alkane polymer is... w The value is in the range of 50,000 to 10,000,000 g / mol, as measured by techniques known to those skilled in the art, such as by determining the viscosity of its solution in water.

[0083] According to a preferred embodiment, the epoxy alkane polymer (PAO) is a polyethylene oxide having formula (II):

[0084] R A O-(CH2CH2O) n -R B (II)

[0085] Where R A and R BEach is independently of H or C1-C5 alkyl, preferably H or CH3, and n is an integer from 1000 to 200000, preferably from 2000 to 100000, more preferably from 5000 to 70000.

[0086] Nevertheless, according to a more preferred embodiment, the epoxy alkane polymer (PAO) is a polyethylene glycol having formula (IIb):

[0087] HO-(CH2CH2O) n -H(IIb)

[0088] Where n is an integer from 1000 to 200000, preferably from 2000 to 100000, and more preferably from 5000 to 70000.

[0089] The at least one ionic carboxyalkyl cellulose (B) is of the formula [C6-H7-O5-R3]. n Cellulose derivatives, wherein R is H or a carboxyl alkyl salt, preferably of the formula -CH2-COO-M + The carboxymethyl salt, wherein M is a monovalent cation selected from ammonium or alkali metal cations, preferably selected from Na. + and Li + And n is an integer from 100 to 5000.

[0090] The at least one nonionic suspending agent A) is typically present in the polymerization reaction mixture in an amount of 0.01 to 2 g / kg VDF monomer, preferably 0.05 to 0.55 g / kg VDF monomer, more preferably 0.05 to 0.3 g / kg VDF monomer.

[0091] The at least one ionic carboxyalkyl cellulose (B) is typically present in the polymerization reaction mixture in an amount of 0.05 to 10 g / kg VDF monomer, preferably 0.3 to 5 g / kg VDF monomer, more preferably 0.5 to 5 g / kg VDF monomer.

[0092] In a preferred embodiment of the invention, the method is carried out in the presence of A) at least one nonionic suspending agent and B) at least one ionic carboxyalkyl cellulose, wherein the amount of the at least one ionic carboxyalkyl cellulose B) is higher than the amount of the nonionic suspending agent A).

[0093] More preferably, the amount of the at least one ionic carboxyalkyl cellulose (B) in the polymerization is higher than 0.5 g / kg VDF monomer and the amount of the at least one nonionic suspending agent (A) is lower than 0.3 g / kg VDF monomer.

[0094] The method of the present invention is typically carried out in an aqueous suspension medium in the presence of a free radical initiator. While the choice of free radical initiator is not particularly limited, it should be understood that those initiators suitable for the method according to the invention are selected from compounds capable of initiating and / or accelerating polymerization methods.

[0095] Among the free radical initiators that can be advantageously used in the methods of the present invention, organic free radical initiators may be mentioned. Non-limiting examples of suitable organic free radical initiators include, but are not limited to, the following: acetylcyclohexane persulfonic acid; diacetyl peroxydicarbonate; dialkyl peroxydicarbonate, such as diethyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate; tert-butyl peroxydidecanoate; 2,2'-azobis(4-methoxy-2,4-dimethylpentanolyl); tert-butyl peroxydidecanoate; tert-amyl peroxydidecanoate; dioctyl peroxide; dilauryl peroxide; 2,2'-azobis(2,4-dimethyl peroxydidecanoate); tert-butyl peroxydidecanoate; tert-amyl peroxydidecanoate; dioctyl peroxide; dilauryl peroxide; 2,2'-azobis(2,4-dimethyl peroxydidecanoate); dioctyl peroxide; dilauryl peroxide; 2,2'-azobis(2,4-dimethyl peroxydidecanoate); dioctyl peroxide; dilauryl peroxide; dioctyl ... (Valononitrile); tert-butylazo-2-cyanobutane; benzoyl peroxide; tert-butyl-per-2-ethylhexanoate; tert-butyl permaleate; 2,2'-azobis(isobutyronitrile); bis(tert-butylperoxy)cyclohexane; tert-butylperoxyisopropyl carbonate; tert-butyl peracetate; 2,2'-bis(tert-butylperoxy)butane; dicumyl peroxide; di-tert-pentyl peroxide; di-tert-butyl peroxide (DTBP); p-methane hydroperoxide; pinane hydroperoxide; cumene hydroperoxide; and tert-butyl hydroperoxide.

[0096] The VDF polymer of the present invention has an intrinsic viscosity of 0.05 to 0.75 l / g, preferably 0.10 to 0.55 l / g, and more preferably 0.13 to 0.45 l / g, as measured in N,N-dimethylformamide at 25°C.

[0097] The applicant has unexpectedly discovered that the method according to the invention allows for the production of polymers in particulate form (VDF) characterized by excellent flowability, a crucial feature in industrial processes where large quantities of VDF polymers in powder form must be handled.

[0098] Therefore, in a second aspect, the present invention relates to a vinylidene fluoride polymer [polymer (VDF)] that can be obtained by the method of the present invention.

[0099] In particular, the polymer (VDF) obtained by the method of the present invention is characterized by a size distribution with a D50 value greater than 150 micrometers and a very narrow particle size distribution (PSD).

[0100] Furthermore, the polymer powder obtained by the method of the present invention is characterized by having bead-shaped, substantially spherical particles.

[0101] Existing methods, which involve preparing polymer granules and then grinding the granules to obtain the desired particle size, allow for the production of particles with a size distribution having a D50 value greater than 150 micrometers. However, the ground particles are not spherical and have rough surfaces; therefore, the particles offer no advantage in terms of flowability.

[0102] The method of this invention allows for the production of bead-like, substantially spherical particles with a particle size distribution having a D50 value greater than 150 micrometers, which is significantly different from particles obtained by grinding granules according to prior art methods, such as... Figure 1 and Figure 2 As shown.

[0103] A particularly preferred embodiment of the present invention relates to a polymer (VDF) comprising more than 50 mol%, preferably more than 80 mol%, of repeating units derived from the polymerization of vinylidene fluoride monomers, said polymer (VDF) being characterized by a particle size distribution having a D50 value greater than 250 micrometers.

[0104] In a third aspect, the present invention relates to a composition comprising at least one polymer (VDF) of the present invention [Composition (C)].

[0105] The composition (C) of the present invention may further contain one or more additives.

[0106] Non-limiting examples of suitable additives include, for example, plasticizers such as dibutyl sebacate.

[0107] In a fourth aspect, the present invention relates to an article comprising a polymer (VDF) or composition (C) as defined above.

[0108] Articles of the present invention are typically obtained by processing polymers (VDFs) or compositions (C) as defined above using melt processing techniques such as injection molding or compression molding.

[0109] The articles of this invention are particularly suitable for use in a variety of applications, such as battery applications.

[0110] In particular, suitable articles comprising polymers (VDF) or compositions (C) as defined above are components of secondary batteries, such as electrodes and / or separators of secondary batteries, especially lithium-ion batteries.

[0111] The polymer (VDF) of the present invention or the composition (C) as defined above is particularly suitable as a binder in the electrodes of secondary batteries, especially lithium-ion batteries.

[0112] Furthermore, the polymer (VDF) of the present invention or the composition (C) as defined above is particularly suitable for separators in secondary batteries, especially lithium-ion batteries, such as composite separators comprising the following:

[0113] - At least one substrate layer comprising at least one polyolefin, preferably composed thereof, and

[0114] - At least one layer comprising at least one polymer (VDF) of the present invention, preferably composed thereof, is adhered to the substrate layer.

[0115] Another object of the present invention is the use of the polymer (VDF) or composition (C) as defined above for the manufacture of hydrophilic membranes.

[0116] Therefore, the present invention relates to a method for manufacturing a hydrophilic membrane comprising a polymer (VDF) or a composition (C), and a hydrophilic membrane comprising a polymer (VDF) or a composition (C) as defined above.

[0117] The uses, methods for manufacturing hydrophilic membranes and the membranes produced therefrom described above will be described in detail in conjunction with the polymer (VDF); however, it is understood that the composition (C) described above may be used in place of the polymer (VDF) in all the embodiments described below.

[0118] For the purposes of this invention, the term "membrane" has its usual meaning, that is, essentially refers to a discrete, generally thin interface that mitigates the penetration of chemicals in contact with it. This interface can be molecularly homogeneous, i.e., structurally completely homogeneous (dense membrane), or it can be chemically or physically non-homogeneous, for example containing voids, pores, or holes of finite size (porous membrane). The terms "pore," "void," and "hole" are used synonymously in the context of this invention.

[0119] The membrane of the present invention is preferably a porous membrane. Porous membranes typically have a void structure with interconnected pores.

[0120] Porous membranes are typically characterized by average pore size (d) and porosity (ε) (i.e., the fraction of the total porous membrane).

[0121] The porous membrane of the present invention has a porosity (ε) of advantageously at least 1%, preferably at least 2%, more preferably at least 3%, and advantageously at most 90%, preferably at most 80%. These pores generally have an average diameter (d) of advantageously at least 0.01 μm, preferably at least 0.05 μm, more preferably at least 0.1 μm, and advantageously at most 50 μm, preferably at most 25 μm, more preferably at most 10 μm.

[0122] The membrane can be in the form of a flat sheet or can be formed into thin tubes or fibers (hollow fiber membranes). Flat sheet membranes are generally preferred when high flux is required. Hollow fiber membranes are particularly advantageous when a dense module with a high surface area is required.

[0123] The membrane of the present invention can be used in various separation processes in the chemical processing industry, such as microfiltration and preferably ultrafiltration of aqueous media; and in biomedical applications, such as hemodialysis, controlled release of drugs, artificial organs, such as kidneys, lungs and pancreas; and in membrane bioreactors for municipal and industrial wastewater treatment.

[0124] If the film is a dense film, the method of the present invention advantageously includes casting and / or melt forming of the polymer (VDF) as defined above. Melt forming is commonly used to prepare dense films either by extruding them from a die into sheets or blown films.

[0125] If the membrane is a porous membrane, the method of the present invention advantageously includes at least one step, which includes one of irradiation technology, membrane expansion, template leaching technology, solution precipitation technology, and electrospinning technology.

[0126] If any patent, patent application, or disclosure incorporated herein by reference conflicts with the description of this application to the extent that it may lead to ambiguity in terminology, this specification shall take precedence.

[0127] The invention will now be described in more detail with reference to the following examples, which are merely illustrative and do not limit the scope of the invention.

[0128] raw material

[0129] (B-1): Sodium carboxymethyl cellulose with an average molecular weight of 250,000 g / mol is commercially available from Sigma-Aldrich.

[0130] (B-2): Sodium carboxymethyl cellulose with an average molecular weight of 90,000 g / mol, commercially available from Sigma-Aldrich.

[0131] (A-1): Hydroxypropyl methylcellulose ether, produced by Dow Chemical Company under the name... The K100GR is for sale, with a dynamic viscosity of 80-120 mPa·s in aqueous solution at 20°C and a concentration of 2% by weight.

[0132] (A-2): PVA is named after the product name 80 (Synthomer) is commercially available; it is a 80% hydrolyzed high molecular weight polyvinyl alcohol.

[0133] DCE: Vinylene carbonate purchased from Sigma-Aldrich.

[0134] Determination of intrinsic viscosity of polymers

[0135] Intrinsic viscosity (η) [dl / g] was measured using an Ubbelohde viscometer based on the drop time of a solution with a concentration of approximately 0.2 g / dl obtained by dissolving the polymer in N,N-dimethylformamide at 25°C, according to the following equation:

[0136]

[0137] Where c is the polymer concentration [g / dl], η r It is the relative viscosity, which is the ratio between the fall time of the sample solution and the fall time of the solvent, η. sp It is the specific viscosity, i.e., η. r -1, and Γ is the experimental factor, which corresponds to 3 for the polymer (VDF).

[0138] Example 1:

[0139] In a 4L reactor equipped with an impeller running at 650 rpm, the following components were sequentially introduced: 1,950 g of softened water and 0.08 g (A-1) / kg of total VDF monomer, 0.93 g (B-1) / kg of total VDF monomer, and 371.5 g of calcium hydroxide solution purchased from Sigma-Aldrich.

[0140] At a fixed temperature of 14°C, oxygen present in the reactor was removed by sequential vacuum and nitrogen purging. This sequence was repeated three times.

[0141] Then, 40g of softened water, 5.1g of hydrogen peroxide (purchased from Brenntag), 15.27g of DCE and 1.59g of ethyl chloroformate (purchased from Framochem) were introduced into the reactor.

[0142] After 15 minutes, 1,004 g of VDF was added to the mixture with stirring at 880 rpm. The reactor was then gradually heated until the set temperature of 41.5 °C was reached, corresponding to a reactor pressure of 83 bar. The pressure was kept constant at 83 bar by feeding 295 g of VDF. After this feed, no more monomer was fed and the pressure began to drop to 57 bar. The reactor was then gradually heated at 61 °C. At this point, the pressure began to drop. When the pressure dropped to 20 bar, the reaction was stopped by degassing the suspension until atmospheric pressure was reached. A total of 1,300 g of VDF was fed into the reactor. The polymer was then collected by filtration and suspended in clean water in a stirred tank. After washing, the polymer was dried in a fluidized bed dryer (Retsch) at 60 °C for 3 hours. 1,236 g of dried powder was collected.

[0143] Overall, a VDF conversion rate of greater than 90% was achieved in all working embodiments.

[0144] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0145] Example 2 (Comparison):

[0146] The same procedure as in Example 1 was followed, but only 0.46 g (A-1) / kg total VDF monomer was added to the reactor and (B-1) was not added.

[0147] 1,249 g of dried powder was collected.

[0148] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0149] Example 3:

[0150] The same procedure as in Example 1 was followed, but with 0.08 g (A-1) / kg total VDF monomer and 0.46 g (B-1) / kg total VDF monomer.

[0151] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0152] Example 4 (Comparison):

[0153] The same procedure as in Example 1 was followed, but only 0.09 g (A-1) / kg total VDF monomer was added to the reactor and (B-1) was not added.

[0154] The suspension was found to be highly unstable, and the reactor required degassing after 67 minutes, resulting in ineffective polymerization. This prevented the method from being scaled up for industrial production.

[0155] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0156] Example 5 (Comparison):

[0157] The same procedure as in Example 1 was followed, but only 1.19 g (B-1) / kg of total VDF monomer was added instead of (A-1).

[0158] The suspension was found to be highly unstable, and the reactor required degassing after 114 minutes, resulting in ineffective polymerization. This prevented the method from being scaled up for industrial production.

[0159] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0160] Example 6:

[0161] The procedure was the same as in Example 1, but with the addition of 0.08 g (A-1) / kg of initial VDF monomer and 0.93 g (B-2) / kg of total VDF monomer.

[0162] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0163] Example 7:

[0164] 2,239 g of softened water, 0.07 g (A-1) / kg total VDF monomer, and 0.80 g (B-1) / kg total VDF monomer were sequentially introduced into a 4 L reactor. The mixture was stirred using an impeller running at 880 rpm.

[0165] At a fixed temperature of 14°C, oxygen present in the reactor was removed by sequential vacuum and nitrogen purging. This sequence was repeated three times.

[0166] Then, 20 g of DCE and 1.47 g of a 75% solution of tert-amyl perpentyl ester initiator (purchased from United Initiators) in isododecane were added to the reactor.

[0167] 1,053 g of VDF was added to the mixture. The reactor was then gradually heated until the first set point temperature of 52°C was reached. At this temperature, the pressure in the reactor was kept constant at 120 bar.

[0168] The pressure was maintained constant at 120 bar by feeding 244 g of VDF. After this feed, no more monomer was fed and the pressure began to drop to 90 bar. The reactor was then gradually heated at 67°C. The pressure was maintained at 80 bar, and 281 g of VDF was fed into the reactor. The pressure was then reduced to 55 bar, and polymerization was stopped by degassing the suspension until atmospheric pressure was reached. A total of 1,580 g of VDF was fed into the reactor. The polymer was then collected by filtration and suspended in clean water in a stirred tank. After washing, the polymer was dried in a fluidized bed dryer (Retsch) at 60°C for 3 hours.

[0169] 1,414 g of dry powder was collected.

[0170] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0171] Example 8:

[0172] 2,542 g of softened water, 0.06 g (A-1) / kg total VDF monomer, and 0.68 g (B-1) / kg total VDF monomer were sequentially introduced into a 4 L reactor. The mixture was stirred using an impeller running at 880 rpm.

[0173] At a fixed temperature of 14°C, oxygen present in the reactor was removed by sequential vacuum and nitrogen purging. This sequence was repeated three times.

[0174] Then, a solution (75%) of 9.5 g of DCE and 1.33 g of initiator tert-amyl perpentyl ester (purchased from Uniter Initiator Company) in isododecane was added to the reactor.

[0175] Add 820g of VDF to the mixture. Then, gradually heat the reactor until the first set point temperature of 52°C is reached. At this temperature, the pressure of the reactor is fixed at 120 bar.

[0176] During polymerization, a total of 631 g of VDF was fed to maintain a constant pressure of 120 bar. After this feed, no more monomer was fed and the pressure began to drop to 95 bar. The reactor was then gradually heated at 65°C. At this point, the pressure began to decrease. When the pressure dropped to 46 bar, the reaction was stopped by degassing the suspension until atmospheric pressure was reached. A total of 1,450 g of VDF was then fed into the reactor. The polymer was then collected by filtration and suspended in clean water in a stirred tank. After washing, the polymer was dried in a fluidized bed dryer (Retsch) at 60°C for 3 hours.

[0177] 1,288 g of dried powder was collected.

[0178] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0179] Example 9:

[0180] 1,714 g of softened water, 0.1 g (A-1) / kg total monomer, and 1.2 g (B-1) / kg total monomer were sequentially introduced into a 4 L reactor. The mixture was stirred using an impeller running at 880 rpm.

[0181] At a fixed temperature of 14°C, oxygen present in the reactor was removed by a series of vacuum and nitrogen purging processes. This sequence was repeated three times.

[0182] Then, a solution (75%) of 0.55 g of acrylic acid (AA) and 4.94 g of tert-amyl perpentanoate (purchased from Uniter Initiators) in isododecane was added to the reactor. Immediately afterwards, 1,279 g of VDF was added to the mixture. The reactor was then gradually heated until a setpoint temperature of 55°C was reached, corresponding to a pressure of 120 bar.

[0183] Throughout the polymerization reaction, the pressure was maintained at a constant 120 bar by feeding an aqueous solution containing 14.91 g of AA per liter of solution. After 405 minutes, the polymerization reaction was stopped by degassing the suspension until atmospheric pressure was reached. A total of 909 g of AA solution was then fed into the reactor.

[0184] The polymer was then collected by filtration and suspended in clean water in a stirred tank. After washing, the polymer was dried in a fluidized bed dryer (Retsch) at 60°C for 3 hours. 974 g of dried powder was collected.

[0185] The polymerization time, particle characteristics, and flowability are shown in Table 1.

[0186] Liquidity test:

[0187] The flowability of the dried powder obtained in Examples 1 to 10 was evaluated according to the ASTM D 1895 standard for powders.

[0188] Weigh 50g of dry polymer powder on a precision balance. Then, manually shake the powder in a stainless steel cylindrical container (3.99 x 7.98cm) for 5 minutes. Next, place the resulting powder in a closed Inox funnel (11.4cm in size, with an opening diameter of 9.3cm) at a height of 12cm in the receiving cup. Release the powder and monitor the time required for powder flow using a stopwatch. If the powder flow is sluggish, tap the funnel gently until the sample flows completely. Weigh the powder collected in the cup again on the precision balance. Record the time and quantity of flowing powder, its appearance, and whether any assistance is needed to promote powder flow.

[0189] D50: Particle size analysis of powders using laser diffraction according to ISO 13320 standard. D50 specifies the particle size of half the total particles below this value and the other half above it.

[0190] The overall granularity distribution (PSD) is assessed by measuring SPAN.

[0191] SPAN is calculated according to the following formula:

[0192]

[0193] Where D90 is the diameter of 90% of the population below this value, and D10 is the diameter of 10% of the population below this value.

[0194] The results are shown in Table 1 below.

[0195] Table 1

[0196]

[0197]

[0198] As shown in Table 1, it has been found that the method of the present invention advantageously enables the acquisition of VDF polymers, particularly those obtained by the method according to any one of Examples 1, 3 and 6 to 9, having large polymer particles and simultaneously narrow PSD.

[0199] In particular, the VDF polymers of Examples 1 and 6 have exceptionally high particle sizes greater than 250 μm, exhibiting excellent flowability. On the other hand, the manufacturing methods of the polymers of Comparative Examples 2, 4, and 5, in which only nonionic or ionic suspending agents are used, produce dry polymers with lower particle sizes or lead to uncontrolled polymerization because the lack of a stable suspension causes polymer agglomeration in the reactor.

Claims

1. A method for producing vinylidene fluoride polymer (VDF) in an aqueous suspension, the method comprising polymerizing vinylidene fluoride in the presence of: A) At least one nonionic suspending agent, wherein... The nonionic suspending agent is a polymer containing hydroxyl groups, and the polymer is selected from the group consisting of: a) Polysaccharide derivatives; b) Partially hydrolyzed polyvinyl alcohol (PVA); and c) PAO (epoxide polymer); and B) At least one ionic carboxyl cellulose, wherein the ionic carboxyl cellulose is of the formula [C6-H7-O5-R3]. n Cellulose derivatives, wherein R is H or of the formula -CH2-COO-M + The carboxymethyl salt, wherein M is a monovalent cation selected from ammonium or alkali metal cations, and n is an integer from 100 to 5000.

2. The method as described in claim 1, wherein, The polysaccharide derivative is a carbohydrate comprising repeating units of formula (I) derived from β-D-glucopyranoside linked together by β-glycosidic bonds: Each R' is the same or different from each other each time it appears, representing a hydrogen atom, a C1-C8 hydrocarbon group, or a C2-C8 hydroxyalkyl group.

3. The method as described in claim 2, wherein, The carbohydrate of the repeating unit of β-D-glucopyranoside in formula (I) is hydroxyethyl methylcellulose or 2-hydroxypropyl methylcellulose.

4. The method of claim 1, wherein, The partially hydrolyzed polyvinyl alcohol (PVA) is an aqueous composition of partially hydrolyzed polyvinyl acetate and polyvinyl alcohol with a degree of hydrolysis of at least 80%.

5. The method of claim 1, wherein, The epoxy alkane polymer PAO is polyethylene glycol having formula (IIb): HO-(CH2CH2O) n -H (IIb) Where n is an integer from 1000 to 200000.

6. The method of claim 5, wherein, n is an integer from 2000 to 100000.

7. The method of claim 5, wherein, n is an integer from 5000 to 70000.

8. The method according to any one of claims 1-7, wherein, The nonionic suspending agent A) exists in the polymerization reaction mixture in an amount of 0.01 to 2 g / kg VDF monomer.

9. The method of claim 8, wherein, The nonionic suspending agent A) is present in the polymerization reaction mixture in an amount of 0.05 to 0.55 g / kg VDF monomer.

10. The method of claim 8, wherein, The nonionic suspending agent A) is present in the polymerization reaction mixture in an amount of 0.05 to 0.3 g / kg VDF monomer.

11. The method according to any one of claims 1-7, wherein, The ionic carboxyalkyl cellulose (B) is present in the polymerization reaction mixture in an amount of 0.05 to 10 g / kg VDF monomer.

12. The method of claim 11, wherein, The ionic carboxyalkyl cellulose (B) is present in the polymerization reaction mixture at an amount of 0.3 to 5 g / kg VDF monomer.

13. The method of claim 11, wherein, The ionic carboxyalkyl cellulose (B) is present in the polymerization reaction mixture at an amount of 0.5 to 5 g / kg VDF monomer.

14. The method according to any one of claims 1-7, wherein, The amount of at least one ionic carboxyalkyl cellulose (B) is higher than the amount of nonionic suspending agent (A).

15. The method according to any one of claims 1-7, wherein, In the polymerization, the amount of at least one ionic carboxyalkyl cellulose (B) is higher than 0.5 g / kg VDF monomer, and the amount of at least one nonionic suspending agent (A) is lower than 0.3 g / kg VDF monomer.

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