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(11)EP 3 530 344A1
欧柏宁(12)
EUROPEAN PATENT APPLICATION (43)Date of publication: 28.08.2019Bulletin 2019/35
(21)Application number: 19159103.1
(22)Date of filing: 25.02.2019
(51)Int Cl.:
B01D 71/34(2006.01)
B01D 67/00(2006.01)B01D 69/06(2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB
浅水
洼里的
小鱼教学设计
GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO
PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN (30)Priority:26.02.2018IT 201800003038
(71)Applicant: GVS S.p.A.
40069 Zola Predosa (Bologna) (IT)(72)Inventors:
40068 San Lazzaro di Savena (BO) (IT)
•Gaeta, Soccorso Felice Antonio 40050 Monte San Pietro (BO) (IT)•Bojarska, Marta Ewa 00-082 Warsaw (PL)•Alexowsky, Clemens 45883 Gelsenkirchen (DE)•Ulbricht, Mathias 45143 Essen (DE)
(74)Representative: Ripamonti, Enrico et al Giambrocono & C. S.p.A. Via Rosolino Pilo, 19/B 20129 Milano (IT)
(54)
NEW MACROPOROUS POLYVINYLIDENE FLUORIDE (PVDF) MEMBRANES (57)The invention relates to macroporous, hydrophobic and isotropic polyvinylidene fluoride (PVDF) membranes having improved properties and to a new method for preparing the same.党内立法法
EP 3 530 344A12510152025303540455055
Description
[0001]The invention relates to macroporous hydrophobic isotropic polyvinylidene fluoride (PVDF) membranes having improved properties and a method for preparation of the same. In particular the 碧桂园ERP>ESM
method according to the invention is characterised by the use of dimethyl sulfoxide (DMSO) as a solvent for PVDF, in combination with a vapour induced phase separation (VIPS) stage, for the preparation of macroporous hydrophobic membranes. The method according to the invention makes it possible to obtain macroporous hydrophobic PVDF membranes having improved characteristics in comparison with the membranes currently available in the art. This method also has the advantage of using a non-toxic solvent to dissolve the PVDF and of requiring very short processing times.
[0002]PVDF membranes are used in various applications such as for example filtration or ultrafiltration, in particular of corrosive chemicals, or in biomedical field. High membrane porosity is greatly desired because it allows a high flow velocity for liquids and gases per unit area.
[0003]PVDF membranes are generally formed from PVDF dissolved in a solvent; the solutions obtained by dissolving PVDF are poured (cast) as films (moulded films or cast films) in a mould or on a support, then the cast films undergo phase separation to form a porous membrane. Various methods are available for the phase separation stage, such as for example thermally induced phase separation (TIPS), non-solvent induced phase separation (NIPS), vapour induced phase separation (VIPS) or evaporation induced phase separation (EIPS). Different membrane morphologies are ob-tained depending upon the phase separation method used; for example, isotropic membranes and a
nisotropic mem-branes having a porous or dense upper layer may be prepared using the abovementioned methods.
[0004]In the VIPS method the cast film is exposed to an atmosphere of a non-solvent vapour which gives rise to phase separation by penetrating the cast film. Using this method PVDF membranes having a porous morphology and having adjustable barrier pore sizes can be obtained in a fast production process that can easily be converted to an industrial scale.
[0005]In the preparation of membranes through NIPS or VIPS methods, solvents such as: dimethyl formamide (DMF),dimethyl acetamide (DMAc), N-methyl-2-pyrrolidone (NMP), hexamethyl phosphoramide, tetramethylurea, triethyl phos-phate, trimethyl phosphate, acetone and tetrahydrofuran are generally used to dissolve the polymer. Most of said solvents are toxic according to the GHS classification (Z. Cui et al., Prog. Polym. Sci., 2014). The present invention advantageously uses DMSO as a solvent for PVDF; DMSO is a non-toxic solvent which is not classified by the GHS.
[0006]In the state-of-the-art non-toxic solvents have already been used to prepare membranes (Figoli A. et al. Green Chem., 2014), but not in combination with the VIPS method for forming porous
PVDF membranes. For example, the most common use of DMSO as the solvent in the preparation of PVDF membranes is in association with a phase of the NIPS type, which has the consequence of forming an anisotropic membrane with pores having a finger-like structure and a dense upper layer (A. Bottino et al., J. Memb. Sci., 1991). Another hydrophilic polymer which results in delayed separation during phase separation and produces more spongy structures with a dense upper layer is very often also added to the solution (D. Lin et al., Eur. Polym. J., 2006; Q. Wang et al., Desalination, 2012), or a mixture of solvent and non-solvent is used as a coagulation bath (D. Lin et al., Eur. Polym. J., 2006; F. Liu et al., J. Memb. Sci., 2011; C. Kuo,et al., Desalination, 2008).
[0007]DMSO has also been used as a solvent for PVDF in association with the freezing method, a variant of the TIPS method, in which phase separation is brought about by cooling the cast film below the freezing temperature of DMSO and the frozen DMSO is exchanged with water. This gives rise to the formation of porous membranes having a dense upper layer (C. Mu et al., J. Memb. Sci., 2010; B. Wang et al., Nat. Commun., 2016).
[0008]It will be noted that the type of solvent used has a very strong influence on membrane formation. Where a number of polymers and/or solvents associated for example with the NIPS method form a functional membrane, the same group of reagents may not be effective when associa
ted with the VIPS method.
[0009]The use of DMSO followed by a stage of the VIPS type for membrane formation is described by Cardoso et al. (V. Cardoso et al. Soft Matter, 2015), in which however a poly(vinylidine fluoride-co-trifluoroethylene) copolymer,comprising PVDF together with trifluoroethylene, is dissolved in DMSO. Also, in the Cardoso method, after the film has been cast, the membranes are exposed to the air for 15 minutes without any control of relative humidity; low porosity membranes with a dense upper and lower layer are thus obtained.
[0010]Another example is the work of Li et al. (B. Li et al., J. Memb. Sci., 2016) where polyvinylidene fluoride/sodium allyl sulfonate (PVDF/SAS) in DMSO was used. Again, in this case the authors did not investigate the use of pure PVDF in combination with DMSO as solvent; furthermore, as a method for membrane preparation, Li et al. used the EIPS process in which a cast film is exposed to ambient air for between 30 minutes and 9 hours at 40°C, 60°C or 80°C without any control of humidity, followed by immersion in a coagulation bath in water. Membranes having a nodular structure and a dense upper layer are obtained as a consequence.
[0011]EP 1839730 cites the possibility of using DMSO to dissolve PVDF, but only in combination with
a non-solvent compound, followed by a NIPS stage to form the porous membrane. In addition to this, no working examples showing the characteristics of the membranes obtained after dissolution in DMSO are provided.
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