阅读说明：本技术 具有聚丙烯骨架的接枝共聚物薄膜和纳米多孔聚丙烯膜 (Graft copolymer film having polypropylene skeleton and nanoporous polypropylene film ) 是由 A·洛扎恩斯基 L·甲辛斯卡-沃尔克 M·鲍雅伊 杨兰荑 R·杜查特奥 T·德菲泽 K· 于 2020-03-12 设计创作，主要内容包括：本发明涉及一种薄膜,其包含具有聚丙烯(PP)骨架和共价键合至所述骨架的3-8个聚酯片段的无规接枝共聚物,其中所述聚丙烯骨架的数均分子量(Mn)为10.000-100.000道尔顿(在150℃下在o-DCB中用HT-SEC测定),其中每个聚酯片段的Mn为5.000-25.000道尔顿,其中PP的量为45-80mol％,其中聚酯片段的量为55-20mol％,其中所述薄膜的厚度为0.01-10mm,其中所述聚丙烯和所述聚酯的区域独立地形成连续相,和其中所述mol％以相对于共聚物中存在的单体单元的总摩尔数进行计算。本发明还涉及纳米多孔PP膜及其应用。(The present invention relates to a film comprising a random graft copolymer having a polypropylene (PP) backbone and 3-8 polyester segments covalently bonded to said backbone, wherein the polypropylene backbone has a number average molecular weight (Mn) of 10.000-100.000 dalton (determined by HT-SEC in o-DCB at 150 ℃), wherein the Mn of each polyester segment is 5.000-25.000 dalton, wherein the amount of PP is 45-80 mol-%, wherein the amount of polyester segments is 55-20 mol-%, wherein the thickness of the film is 0.01-10mm, wherein the domains of the polypropylene and the polyester independently form a continuous phase, and wherein the mol-% is calculated with respect to the total number of moles of monomer units present in the copolymer. The invention also relates to a nanoporous PP film and its use.)

1. A film comprising a random graft copolymer having a polypropylene (PP) backbone and 3-8 polyester segments covalently bonded to the PP backbone,

wherein the number average molecular weight M of the PP skeleton_nIs 10-100kDa, preferably 20-100kDa,

wherein M of each polyester segment_nIs a mixture of 5-25kDa of alpha-amylase,

wherein the amount of PP is 45-80 mol%,

wherein the amount of polyester segments is from 55 to 20 mol%,

wherein the thickness of the film is 0.01-10mm,

wherein the domains of PP and polyester form a helical bicontinuous morphology,

wherein the mol% is calculated relative to the total number of moles of monomer units present in the copolymer,

wherein after the fragment sacrificial process, the polyester fragments self-align in a region suitable for forming porous channels through the membrane.

2. The film according to claim 1, wherein the PP backbone is preferably prepared from a PP-homopolymer or a copolymer of propylene and ethylene, wherein the amount of ethylene is less than 5 wt%, and wherein the PP is preferably isotactic or syndiotactic, most preferably isotactic.

3. The film according to claim 1 or 2, wherein the melting temperature of the PP in the copolymer backbone is at least 120 ℃, preferably at least 130 ℃, more preferably at least 135 ℃ or 140-160 ℃.

4. The film according to any one of claims 1 to 3, wherein said film has a Young's modulus of 300-1500MPa, preferably 350-1200 or 400-1000MPa, and a toughness of 1-150J/m³Preferably 2 to 120J/m³More preferably 4 to 100J/m³。

5. The film of any of claims 1-4, wherein the polyester segments comprise monomer units derived from caprolactone and/or valerolactone.

6. The film according to any of claims 1 to 5, wherein the amount of PP is from 50 to 75 mol% and the amount of polyester is from 50 to 25 mol%.

7. A nanoporous membrane comprising at least 90 wt% PP, preferably at least 95 or at least 98 wt% PP,

wherein the PP comprises-OX functional groups randomly distributed on the polymer chains,

in which press¹The number of functional groups per polymer chain is from 3 to 8, as determined by H NMR, and

wherein X is selected from Mg, Zn, Al, H, Li, Na or K.

8. The film of claim 7 wherein M of PP in the film_nFrom 10 to 100kDa, preferably from 20 to 100kDa, and isotactic or syndiotactic.

9. The film of claim 7 or 8, wherein the film has a thickness of 0.01 to 10mm,

wherein the membrane has a passage N according to the Barret-Joyner-Halenda model₂Desorption of pores measuring 10 to 50nm in size and determination of 50 to 200m according to the method of Brunauer-Emmet-Teller²BET surface area in g.

10. The film of any one of claims 7-9, wherein the film has a melting temperature T as measured by DSC_mAt a temperature of 120 ℃ to 160 ℃, preferably at a temperature of 130 ℃ to 159 ℃, and more preferably at a temperature of 140 ℃ to 158 ℃.

11. The membrane according to any one of claims 7 to 10, wherein the membrane has a Young's modulus of 50 to 400MPa, preferably 100 to 300MPa, and a toughness of 0.1 to 15J/m³Preferably 0.5 to 10J/m³。

12. Use of a film according to any one of claims 1 to 6 for the preparation of a membrane suitable for use as a water filter or battery separator.

13. A water filter system comprising a nanoporous membrane as defined in any one of claims 7 to 11.

14. A battery comprising a nanoporous membrane as defined in any one of claims 7 to 11.

A PP film unit which is a multilayer film or a plurality of films, wherein the layer or film is:

nanoporous membranes according to claims 7-11,

a microporous PP film and/or PP nonwoven.

Technical Field

The present invention relates to a film comprising a graft copolymer having a polypropylene (PP) backbone and polyester grafts attached to said backbone, a nanoporous PP membrane obtained from said film and uses thereof.

Background

Films comprising polyolefins coupled to polyesters are known in the art. In addition, nanoporous films of polyolefins are also known in the art.

Membrane technology is becoming increasingly important as a widely used separation technology. Water purification and industrial separation processes are good examples. Non-porous reverse osmosis membranes (i.e. water desalination, gas separation) and porous micro-/ultra-/nanofiltration membranes are applied. Polyvinylidene fluoride, poly (ethylene-co-chlorotrifluoroethylene), polysulfone, polyethersulfone, polyphenylsulfone and aramid are the most commonly used materials for producing membranes [1 ]. Although these particular polymers have excellent mechanical properties, the raw materials are very expensive at an average price of $10- $ 20/kg. In addition, the recycling or incineration of polyvinylidene fluoride or polysulfone and the like also poses risks in terms of contamination and release of toxic components.

Currently, most membranes used for microfiltration, ultrafiltration and nanofiltration are cracked by controlled opening (e.g., by chemical vapor deposition)Micro porous film [2]]) Track etching (e.g. ofNucleporeTM,[3]) Template leaching [4]Or by phase separation of block copolymers [5],[6]And (4) preparation.

Cracking is the initial fracture process that results in the development of certain fracture morphologies. When excessive tensile stress is applied to the polymer, cracking occurs, resulting in the formation of micropores in a plane perpendicular to the stress.

As precursor materials in film technology, block copolymers are receiving increasing attention because they can form films with the following properties: adjustable pore size and narrow pore size distribution, high flux, high selectivity, ability to be selectively functionalized, and good mechanical properties. The two main strategies for pore formation in block copolymer membranes are (1) self-assembly and phase separation as described above, and (2) membrane calendering and selective block sacrifice [5], [6 ].

Polyolefin-based nanoporous films.

Phase separation methods that require solvent casting, such as SNIPS, are not suitable for most polyolefin-based block copolymers due to poor solubility of polyolefins in environmentally friendly solvents [5 ]. Track etching is a rather expensive technique for producing nanoporous polycarbonate and polyethylene terephthalate films [3], and is also hardly applicable to polyolefins. Most commonly, polyolefin-derived microporous and nanoporous (>100nm) films are manufactured by a controlled cracking process [2 ]. Although this preparation technique is mature, the relatively large pore size and non-uniform pore size distribution of the membrane limits its application. Alternatively, a template leaching process has been developed in which a mixture of polyolefin and solvent, oil or other polymer is allowed to undergo Thermally Induced Phase Separation (TIPS), followed by removal of the solvent, oil or polymer by extraction to produce a polyolefin-based microporous membrane [4 ].

Selective segment sacrifice process

Starting from amphiphilic block copolymers, a similar strategy was applied to produce nanoporous membranes. By varying the volume fraction of each component forming the block copolymer, the phase separation induced morphology of such block copolymers can be finely tuned. When a cylindrical or helical bicontinuous morphology (also referred to as a bicontinuous phase) is formed, the degradable segments (such as polyester, polybutadiene, or polysiloxane) may be selectively removed by etching, leaving behind the nanoporous polymeric material. This selective fragment sacrificial technique was first reported for the production of polystyrene based nanoporous membranes [6], but recently also for the production of polyethylene based nanoporous membranes [7 ]. Hillmyer and his colleagues prepared PE-based block copolymers by catalytic ring-opening polymerization starting from hydroxy-functionalized hydrogenated polybutadiene as macroinitiator to produce the corresponding PE-PLA block copolymers [7b-c ]. The bottleneck of this process is a cumbersome and expensive three-step synthesis process for the production of OH-functionalized PE, involving ring-opening metathesis polymerization (ROMP) of cyclooctene, followed by air oxidation and a final hydrogenation step. In addition, it is limited to the production of PE-based films, which limits the thermal stability and, for example, cannot be sterilized. Coordination chain transfer polymerization followed by in situ air oxidation provides a rather simple and inexpensive synthesis method for obtaining chain end functionalized polyolefins [7a, e ]. However, this process must be carried out in high temperature solution, otherwise only low molecular weight (<5kDa) products can be obtained, since the chain process will be ineffective once the polymer starts to crystallize from solution. In addition, the effectiveness of the post-polymerization functionalization step is limited to 80%. Thus, the formation of chain-end functionalized polyolefin macroinitiators corresponding to block copolymer precursors is limited to PE-based products produced in a three-step process, or products having a functionality of up to 80% in a two-step process.

WO2011112897a1 describes nanoporous linear polyolefin films and block copolymer precursors for their use. The patent application mentions that the polyolefin may be Polyethylene (PE) or PP, but only linear PE is given as an example of a polyolefin block. The linear PE blocks are derived from a terminated hydrogenated polybutadiene polymer chain, which is then copolymerized with a cyclic ester to produce a polyester-polyolefin-polyester copolymer. The patent application does not explain how to prepare triblock copolymers from PP, which cannot be derived from polybutadiene.

Problems with PE-based nanoporous membranes are low operating temperatures, inability to sterilize, limited flux of the membrane, and susceptibility of the membrane to contamination, thus limiting the flux of the nanoporous membrane.

To date, there have been no reports of semi-crystalline film polyolefins that are not PE-based. One of the main drawbacks of PE or random polyethylene-cyclohexane based films is due to their melting point and glass transition point (T)_g) All are low and unable to sterilize [9]. By changing to high melting polyolefins such as isotactic or syndiotactic polypropylene, poly (4-methyl-1-pentene), polyethylene-cyclohexane, poly (3-methyl-1-butene), retortable films can be obtained.

The use of polyolefin-based graft copolymers for the production of nanoporous membranes has several advantages: the production of randomly functionalized polyolefin macroinitiators is a one-step process and can produce functionalized polyolefins having a variety of chemical structures, melting points, and molecular weights.

Typically, PE-polyester block copolymers are produced by ring-opening polymerization of lactones using hydroxyl chain end functionalized PE. Although this is an effective method on a laboratory scale, it requires dissolution of the PE macroinitiator, is difficult to scale up and is costly.

It is an object of the present invention to overcome at least some of these and other disadvantages.

Disclosure of Invention

The present invention relates to a film comprising:

a random graft copolymer having a polypropylene (PP) backbone and up to 3-8 polyester segments (also called grafts) covalently bonded to said backbone when all functional groups have reacted,

-wherein the number average molecular weight M of the PP skeleton_n(measured by HT-SEC in o-DCB at 150 ℃) of 10-100kDa, preferably 20-100kDa,

-wherein M of each polyester segment_nIs 5-25kDa (tetrachloroethane-d at 90 ℃ C.)₂Chinese character Zhongyuan¹H NMR measurement)，

-wherein the amount of PP in the backbone is 45-80 mol%,

-wherein the amount of polyester in the polyester segment is from 55 to 20 mol%,

-wherein the thickness of the film is 0.01-10mm,

-wherein domains of PP and polyester form a bicontinuous phase,

-wherein the mol% is calculated with respect to the total number of moles of propylene and ester present as monomer units in the copolymer.

The invention also relates to a nanoporous membrane comprising at least 90 wt% PP having 3-8 OX groups per polymer chain, wherein the membrane has a size of 20-50nm (N for Barret-Joyner-Halenda model₂Adsorption measurement) of 50 to 200m²(iv)/g, wherein for each-OX, X is selected from the group consisting of H, Li, Na and K.

The membrane of the invention can be used at high temperatures, making it possible to sterilize the membrane. Surprisingly, the membrane has a high flux of aqueous media, so that its flux is very high. In addition, it has been found that by choosing the right combination of PP and polyester, the size of the nanopores can be adjusted, thus enlarging the design freedom and the range of use of the membrane.

It has been found that the type of polyester used as sacrificial segment in the corresponding graft copolymer has a significant effect on the pore size. For example, changing the polyterelactone to polycaprolactone, while maintaining the same mole fraction, results in a 50% reduction in pore size.

Bicontinuous phases or bicontinuous helical morphologies are known crystalline phases. For polymers, it is between the lamellar and columnar phases.

In other words, the following features: when all functional groups are reacted, a random graft copolymer having a PP backbone and up to 3-8 polyester grafts covalently bonded to the backbone (wherein regions of PP and polyester form a bicontinuous phase) can also be described as "a random graft copolymer having a PP backbone and 3-8 polyester grafts, the graft copolymer being present in a nano-structured bicontinuous helical morphology comprising two continuous phases interpenetrating with one continuous phase comprising the PP portion of the graft copolymer and the other continuous phase comprising the polyester portion of the graft copolymer".

It is possible, however, that not all functional groups are reacted and therefore the number of polyester grafts may be from 1 to 8.

Such a multiple graft copolymer may have more than two functional groups per chain compared to the triblock copolymer described in prior art WO 2011/112897. The presence of the graft segment allows for higher reactivity due to sterically unhindered pendant OH groups rather than OH groups at the end of the PP chain.

The attached drawings are as follows:

FIG. 1: isotactic poly (propylene-co-undecenol) precursor for the synthesis of iPP-g-PVL and iPP-g-PVL copolymers¹H NMR spectrum, in which the methylene proton signal associated with the side chain OH groups is amplified for clarity, at 90 ℃ in tetrachloroethane-d₂Is measured.

FIG. 2: iPP-g-PVL copolymer (iPP)_53mol％-g-PVL_47mol％) Is/are as follows¹H NMR spectrum, in which the methylene proton signal associated with the side chain OH groups is amplified for clarity, at 90 ℃ in tetrachloroethane-d₂Is measured.

FIG. 3: iPP-g-PCL copolymer (iPP)_53mol％-g-PCL_47mol％)Is/are as follows¹H NMR spectrum, in which the methylene proton signal associated with the side chain OH groups is amplified for clarity, at 90 ℃ in tetrachloroethane-d₂Is measured.

FIG. 4: iPP-g-PVL after PVL chain degradation¹H NMR spectrum, tetrachloroethane-d at 90 deg.C₂Is measured.

FIG. 5: isotactic-poly (propylene-co-undecenol) precursor and iPP-g-PVL copolymer (iPP)_53mol％-g-PVL_47mol％) SEC trace of (c).

FIG. 6: iPP-g-PVL copolymer (iPP)_53mol％-g-PVL_47mol％) AFM of cross-sections of a) and b) before degradation and c) and d) after degradation.

FIG. 7: a) PVL degradationPre (solid line) and post degradation (dashed line) iPP-g-PVL copolymer (iPP_53mol％-g-PVL_47mol％) And b) iPP-g-PCL copolymer (iPP) before degradation of PCL (solid line) and after degradation (dotted line)_53mol％-g-PCL_47mol％) Stress-strain curve of tensile test (c).

FIG. 8: from a) degraded iPP-g-PVL copolymer (iPP)_53mol％-g-PVL_47mol％) B) degraded iPP-g-PCL copolymer (iPP)_53mol％-g-PCL_47mol％) FE-SEM of the formed porous membrane.

FIG. 9: a) nitrogen adsorption measurements on porous membranes measured at T ═ 77K, giving adsorption (solid squares) and desorption (empty squares) isotherms; b) and (3) calculating the pore size distribution of the porous membrane after the degradation of the PVL or PCL according to the isotherms of nitrogen adsorption (solid squares) and desorption (empty squares).

FIG. 10: and (4) a filtering device.

FIG. 11: DLS of silica nanoparticle dispersions before and after filtration.

FIG. 12: the 3D simulation of the embodiment shows: 12a, 12e and 12f are comparative examples, which are outside the scope of the present invention; 12b, 12c and 12d are embodiments of the present invention.

Reference documents:

[1](a)Baker,R.W.Membrane Technology and Applications,Wiley,West Sussex,2004.(b)Nunes,S.P.；Car,A.Ind.Eng.Chem.2013,52,993–1003.

[2](a)Bierenbaum,H.S.；Isaacson,R.B.；Druin,M.L.；Plovan,S.G.Ind.Eng.Chem.Proc.Res.Dev.1974,13,2–8.(b)Chen,R.T.；Saw,C.K.；Jamieson,M.G.；Aversa,T.R.；Callahan,R.W.J.Appl.Polym.Sci.1994,53,471–483.

[3](a)Fleisher,R.L.；Alter,H.W.；Furman,S.C.；Price,P.B.；Walker,R.M.Science 1972,172,225–263.(b)Awasthi,K.；Kulshrestha,V.；Acharya,N.K.；Singh,M.；Vijay,Y.K.Eur.Polym.J.2006,42,883–887.

[4](a)Ichikawa,T.；Takahara,K.；Shimoda,K.；Seita,Y.；Emi,M.US 4,708,800；Terumo Kabushiki Kaisha,1987.(b)Chau,C.C.；Im,J.-h.US 4,874,568；The DOW Chemical Company,1989.(c)Lopatin,G.；Yen,L.Y.；Rogers,R.R.US 4,874,567；Milipore Corporation,1989.

[5]For example see:(a)Zhang,Y.；Sargent,J.L.；Boudouris,B.W.；Phillip,W.A.J.Appl.Polym.Sci.2015,DOI:10.1002/APP.41683.(b)Nunes,S.P.Macromolecules 2016,49,2905–2916.

[6](a)Smith,D.R.；Meier,D.J.Polymer 1992,33,3777–3782.(b)Ndoni,S.；Vigild,M.E.；Berg,R.H.J.Am.Chem.Soc.2003,125,13366–13367.(c)Zalusky,A.S.；Olayo-Valles,R.；Wolf,J.H.；Hillmyer,M.A.J.Am.Chem.Soc.2002,124,12761–12773.

[7](a)Ring,J.O.；Thomann,R.；Müllhaupt,R.；Raquez,J.-M.；Degée,P.；Dubois,P.Macromol.Chem.Phys.2007,208，896–302.(b)Pitet,L.M.；Amendt,M.A.；Hillmyer,M.A.J.Am.Chem.Soc.2010,132,8230–8231.(c)Hillmyer,M.；Pitet,L.；Amendt,M.(University of Minnesota)US 9,051,421 B2,2015.(d)Kato,T.；Hillmyer,M.A.ACS Appl.Mater.Interfaces 2013,5,291-300.(e)Pillai,S.K.T.；Kretschmer,W.P.；Trebbin,M.；S.；Kempe,R.Chem.Eur.J.2012,18,13974–13978.

[8]The only example reported so far consist of nonporous poly(vinylidene fluoride)-graft-poly(meth)acrylate graft copolymers.For example see:Hester,J.F.；Banerjee,P.；Won,Y.-Y.；Akthakul,A.；Acar,M.H.；Mayes,A.M.Macromolecules 2002,35,7652–7661.

[9]Wolf,J.H.；Hillmyer,M.A.Langmuir 2003,19,6553–6560.

[10]Brunauer,S.；Deming,L.S.；Deming,W.E.；Teller,E.J.J.Am.Chem.Soc.1940,62,1723–1732.

[11]Barrett,E.P.；Joyner,L.G.；Halenda,P.P.J.Am.Chem.Soc.1951,73,373–380.

experimental part

Measuring method

Materials:

delta-valerolactone (VL; 98%, TCI) epsilon-caprolactone (CL; 97%, Si)gma-Aldrich) via CaH₂(95%, Sigma-Aldrich) and distilled under reduced pressure. The ether was used as such. Toluene (anhydrous, Sigma-Aldrich) was purified using a MBraun-SPS-800 purification column system and stored under an inert atmosphere in a chamber filled withMolecular sieve in glass bottles. 10-undecen-1-ol was purchased from Sigma-Aldrich and used under an inert atmosphereAnd (5) drying the molecular sieve. Methylaluminoxane (MAO) (30 wt% in toluene) was purchased from Chemtura. Diethyl zinc (DEZ) (1.0M in hexane), triisobutyl aluminum (TiBA) (1.0M in hexane), rac-Me₂Si(2-Me-4-Ph-Ind)₂ZrCl₂All from MCAT GmbH, Konstanz, Germany. Isotactic polypropylene (i-PP) (SABIC-PP520P, MFR 10.5g/10min (230 ℃/2.16kg)), tin (II) 2-ethylhexanoate (Sn (Oct))₂) (92-100%, Sigma-Aldrich), titanium (IV) n-butoxide (Ti (OBu))₄Sigma Aldrich), Irganox 1010 (antioxidant, BASF) were used as received.

Synthesis of isotactic poly (propylene-co-10-undecen-1-ol) (iPP-OH).

The copolymerization was carried out in a stainless steel Buchi reactor (300 mL). Before polymerization, the reactor was dried in vacuo and flushed with nitrogen. Toluene (100mL) was introduced into the reactor under a nitrogen atmosphere, followed by TiBA (1.0M in hexane, 5mL) and a functionalized comonomer (10-undecen-1-ol; 1mL, 2.5 mmol). The resulting solution was stirred for 15-20 min. MAO (30 wt% in toluene, 2.0mL) was then introduced into the reactor under a nitrogen atmosphere. The solution was saturated with propylene (5 bar). Preparation of rac-Me in a glove box under a Nitrogen atmosphere₂Si(2-Me-4-Ph-Ind)₂ZrCl₂(5mg, 8. mu. mol) of the starting material solution in toluene (10mL) and the catalyst solution (5mL) was transferred to the reactor. The propylene pressure was maintained constant for 30 min. At the end of the reaction, the propylene feed was stopped and residual propylene was released from the reactor. Acidifying the obtained mixtureMethanol (300mL, 2.5 wt% concentrated HCl) was quenched, filtered, and washed with desalted water. The resulting powder was dried in a vacuum oven at 60 ℃ under reduced pressure overnight.

Typical polymerization process of PP-graft-PCL by catalytic ring-opening polymerization.

Mixing iPP-OH (4g, M)_n＝27.8kDa，) Placed in a round bottom flask with magnetic stirrer and dried by Dean-Stark distillation in toluene (100mL) for 24 h. The solution was then cooled to 100 ℃ and the catalyst Sn (Oct) was added₂(180mg), ε -caprolactone (10.3g, 89.9 mmol). The reaction was carried out under an inert atmosphere for 24 h. By taking aliquots at set time intervals, from¹The H NMR spectrum tracks the copolymerization process. The synthesized copolymer was isolated by precipitation in diethyl ether and dried in a vacuum oven at 40 ℃ for 24 h.

Typical polymerization process of PP-graft-PVL by catalytic ring-opening polymerization.

Mixing iPP-OH (4g, M)_n＝27.8kDa，) Placed in a round bottom flask with magnetic stirrer and dried by Dean-Stark distillation in toluene (100mL) for 24 h. The solution was then cooled to 100 ℃ and the catalyst Sn (Oct) was added₂(180mg), delta-valerolactone (10.0g, 100 mmol). The reaction was carried out under an inert atmosphere for 24 h. By taking aliquots at set time intervals, from¹The H NMR spectrum tracks the copolymerization process. The synthesized copolymer was isolated by precipitation in diethyl ether and dried in a vacuum oven at 40 ℃ for 24 h.

Typical procedure for the synthesis of PP-grafted graft-PCL copolymer by transesterification.

iPP-OH(4g，M_n＝27.8kDa，) And PCL (6g, M)_n＝42.0kDa，) Premixed with the antioxidant Irganox 1010(2500ppm) for 5 minutes and fed into a co-rotating twin-screw micro-extruder at a screw rotation speed of 100rpm at 190 ℃. After this time, tin (II) 2-ethylhexanoate (0.09g, 0.22mmol) was added as a catalyst, and the mixture was stirred for another 5 minutes. The extruder chamber was then cooled and evacuated.

Compression moulding test. All films were prepared by compression molding on a LabEcon 600 high temperature press (Fontijne Presses, the Netherlands) using PP ISO equipment. The copolymer was introduced into a Teflon mold to prepare a sample having a thickness of 0.18 mm. The compression molding procedure included the following steps: heating to 200 deg.C under 5bar for 5min, and cooling to room temperature under 5bar for 10 min.

Film formation:

degradation of the polyester sequences of the copolymers was carried out by immersing the copolymer films in a 0.5M NaOH solution in a mixture of water and methanol (60: 40). The solution was held at 70 ℃ for 3 days, then the membrane was washed with slightly acidic MeOH (aq), then pure MeOH, and dried under vacuum for 24 h.

And (3) filtering:

the volumetric flux of the membrane was measured by the following procedure. The porous membrane was clamped to a glass filter unit, then a vacuum (20mbar) was applied and water was added on top of the filter unit.

Calculate the volumetric flux using equation 1, which equals 75L.m^-2.h^-1.

Formula 1: volumetric flux

Wherein J_VVolume flux, V volume (L), A membrane area (m)²) And t is time (h).

Then, a filtration experiment was performed using a 3% (w/v) dispersion of silica nanoparticles in ethanol (particle size less than 100 nm). The dispersion was filtered using the same filtration apparatus, and DLS experiments were performed on the solution before and after filtration. After filtration, no signal was detected by DLS, demonstrating that the porous membrane filters out the silica nanoparticles.

Characterization of

¹ H NMR：This was carried out at 90 ℃ using deuterated tetrachloroethane (TCE-d2) as solvent and recorded on a Bruker spectrometer operating at a frequency of 300MHz in a 5mm tube. Chemical shifts in ppm for TCE-d2 were determined by reference to the residual solvent signal.

HT-SEC：M_n、M_wAnd polydispersity index (PDI,) As determined by size exclusion chromatography: SEC measurement of the Polymer Char built around an Agilent GC oven model 7890 fitted with an autosampler and an integrated detector IR4 at 150 deg.CThe above process is carried out. 1, 2-dichlorobenzene (o-DCB) was used as eluent at a flow rate of 1 mL/min. Application calculation Software calls Software GPCThe SEC data is processed.

DSC：Melting (T) was measured by Differential Scanning Calorimetry (DSC) using DSC Q100 from TA Instruments_m) Temperature and crystallization (T)_c) Temperature and enthalpy of transition. At 10 ℃ min^-1The measurement is carried out at a heating and cooling rate of-60 ℃ to 230 ℃. The transition is inferred from the second heating and cooling curve.

Field emission scanning electron microscope (FE-SEM) imaging.The cross-sectional morphology of the degraded self-assembled copolymer films was characterized by FE-SEM imaging (JEOL JSM 7800-F) using an LED detector at 5kV operating voltage. To obtain a filmSufficient contrast of the nanopore morphology and avoidance of membrane cross-section disruption, the samples for FE-SEM imaging were first immersed in liquid nitrogen, fractured, and then sputtered with platinum/palladium (Pt/Pd).

Atomic Force Microscopy (AFM) analysis.

Sample preparation:for spin-on self-assembled copolymer films, AFM imaging was performed directly on the film surface under ambient conditions without further processing of the sample. For imaging the cross-section of the film before and after degradation, the specimens were cut into suitable samples and cryo-sectioned at-120 ℃ using a microtomy apparatus (LEICA EM UC 7). Sample sectioning was performed using a diamond knife (Diatom) mounted on a stainless steel holder. This cross-sectional fragment was used directly for AFM measurements without further processing.

AFM analysis:AFM imaging was performed on a Dimension FastScan AFM system from Bruker using a tap mode AFM tip (Model TESPA-V2, k:42N/m, f:320 kHz). Software Nanoscope Analysis 1.5 from Bruker was used as a computer interface to manipulate and analyze AFM measurements. All AFM measurements were performed at ambient conditions. Height and phase maps were recorded simultaneously at a scan rate of 1Hz and a resolution of 512x 512 pixels. Prior to AFM measurements, optical imaging integrated in an AFM apparatus is first applied to select the imaging region of interest.

And (3) pore size analysis:nitrogen adsorption-desorption isotherms were measured at-196 ℃ using a Micromeritics ASAP 2420 analyzer. Before the measurement, the sample was degassed at 30 ℃ overnight at high true capacity (133 Pa). The specific surface area of the membrane was calculated using the Brunauer-Emmet-Teller method [10 ]]And the Barret-Joyner-Halenda model was used to determine the pore size distribution [11]。

Dynamic mechanical thermal analysis: DMTA was performed using TA Instruments Q800 DMA measurements. The samples were tested by a strain controlled temperature ramp with a frequency of 1 Hz. The temperature profile was from-100 ℃ to the melting point of the polyolefin segment with a temperature rise rate of 3 ℃/min. The glass transition temperature is calculated as the peak of the tangent delta signal.

And (3) mechanical property analysis:applications ofThe micro tensile tester (Linkam, TST 350) characterizes the mechanical properties by performing the tensile test three times repeatedly. Both ends of a tensile specimen (length: 30mm, width: 2mm, thickness: 0.18mm) were clamped by jaws having a pitch of 15 mm. The applied force was measured using a load cell with a capacity of 200N. The tensile test was carried out at room temperature at a constant speed of 50 μm/s.

TABLE 1 copolymer composition (volume and mole fraction) (by¹H NMR measurement)

^aValerolactone units for PVL and caprolactone units for PCL.

TABLE 2A composition consisting of¹H NMR and SEC characterization of the copolymers

^aMolar mass (kDa) and polydispersity index (D)_M) Measured in o-DCB at 150 ℃ using HT-SEC (using PS standards and Mark-Houwink parameters).

^bThe amount of pendant OH groups per chain being determined by¹H NMR determination.

^cMolar mass of PVL in terms of¹H NMR measurement.

TABLE 3 thermal Properties

^aT measured by DSC_cAnd T_m。

TABLE 4 mechanical Properties

	Young's modulus (MPa)a	Tensile toughness (J/m)3)a	OH/chainb
				PP53mol％-g-PCL47mol％	660	35.1	6
PP53mol％-g-PVL47mol％	415	85.3	6
				PP56mol％-g-PVL44mol％	740	21.3	6
PP after degradation53mol％-g-PCL47mol％	225	5.6	6
				PP after degradation53mol％-g-PVL47mol％	145	1.9	6
PP after degradation56mol％-g-PVL44mol％	186	2.6	6
				PP52mol％-g-PCL48mol％	733	6930b	3
PP52mol％-g-PVL48mol％	780	4.7	3
				PP63mol％-g-PVL37mol％	787	32.1	3
PP66mol％-g-PVL34mol％	670	11.71	3
				PP after degradation52mol％-g-PCL48mol％	120	0.6	3
PP after degradation52mol％-g-PVL48mol％	106	0.7	3
				PP after degradation63mol％-g-PVL37mol％	115	0.4	3
PP after degradation66mol％-g-PVL34mol％	180	1.43	3

^aYoung's modulus and tensile toughness were determined by tensile testing.

^bVery ductile materials, deform to the maximum (500%) of the stretcher without breaking.

TABLE 5 porosity characteristics

^aPore size distribution as measured by the Barret-Joyner-Halenda model.

^bSurface area as determined by the Brunauer-Emmet-Teller method.

Detailed Description

The present invention relates to a film comprising:

a random graft copolymer having a polypropylene (PP) backbone and 3-8 polyester grafts (also called segments) covalently bonded to said backbone,

-wherein the number average molecular weight (M) of the PP skeleton_n) 10-100kDa (measured by HT-SEC in o-DCB at 150 ℃), preferably 20-100kDa,

-wherein M of each polyester segment_nIs 5-25kDa (tetrachloroethane-d at 90 ℃ C.)₂Chinese character Zhongyuan¹H NMR measurement),

-wherein the amount of PP in the backbone is 45-80 mol%,

-wherein the amount of polyester in the polyester segment is from 55 to 20 mol%,

-wherein the thickness of the film is 0.01-10mm,

-wherein the domains of PP and polyester form a bicontinuous phase,

-wherein the mol% is calculated with respect to the total number of moles of propylene and ester present as monomer units in the copolymer.

SEC-DV stands for size exclusion chromatography-differential viscometer. The measurements were carried out in o-dichlorobenzene (o-DCB). SEC instruments are equipped with infrared detectors and online viscometers. The Mark-Houwink plot gives the change in size (viscosity) with molar mass, which is generally linear for samples without Long Chain Branching (LCB), and shifts occur if LCB is present.

Mn (in kDa) was determined using standard high temperature size exclusion chromatography (HT-SEC) as follows:

polymer Char prepared at 150 ℃ in an Agilent GC oven model 7890 equipped with an autosampler and an integrated detector IR4The measurement is performed. 1, 2-dichlorobenzene (o-DCB) was used as eluent at a flow rate of 1 mL/min. Application calculation Software calls Software GPCAnd processing the data. The molecular weight was calculated according to polystyrene standards.

The film comprises a random graft copolymer having a PP backbone and polyester side chains covalently coupled to the backbone.

The PP backbone comprises functional groups, which are preferably prepared from PP homopolymer or copolymers of propylene and ethylene, wherein the amount of ethylene is less than 5 wt%.

The hydroxy-functionalized PP in the backbone of the copolymer preferably has a melting temperature of at least 120 ℃, preferably at least 130 ℃, more preferably at least 135 ℃ or 140-160 ℃. The PP is preferably isotactic or syndiotactic, most preferably isotactic. This high melting point allows the films of the invention to be sterilized, particularly steam sterilization at about 120 ℃, without losing their mechanical properties.

The films have good mechanical properties. The Young's modulus is usually 300-1500MPa, preferably 350-1200MPa or 400-1000 MPa. The toughness of the film is usually 1 to 150J/m³Preferably 2 to 120J/m³More preferably 4 to 100J/m³。

The PP is coupled to the polyester segment via an ester bond, whereby the original PP contains OH groups. The OH group is preferably part of the short side chain of the PP backbone. The short side chains are preferably obtained by copolymerization of propylene with alpha-olefins having OH groups. The OH groups are preferably randomly distributed along the PP polymer chain. Copolymers having randomly distributed OH groups are known in the art.

WO2017097570A1 and WO2017097571A1 disclose ethylene copolymers containing OH groups in the side chains.

EP1186619(Mitsui Chemicals Inc.) discloses olefin copolymers with polar groups.

WO2016097203 describes a number of examples of PP polymers having OH side chains wherein the OH group is coupled to polycaprolactone.

The number of OX groups, preferably the number of OH groups present in the PP (prior to preparation of the graft copolymer), is (on average) 3 to 8 OH groups per molecule. This can be done at 90 ℃ in tetrachloroethane-d₂Chinese character Zhongyuan¹H NMR measurement.

The molecular weight of the PP-skeleton is preferably between 10 and 100kDa (measured by HT-SEC in o-DCB at 150 ℃), more preferably between 20 and 100 kDa.

When all OX groups have reacted, the graft copolymer contains 3 to 8 polyester chains per molecule, which are coupled to the OX groups of the original PP, at 90 ℃¹HNMR tetrachloroethane-d₂And (6) measuring.

Thus, due to the large number of OX groups present in PP, when all OX groups have reacted, it allows to produce a multigraft copolymer comprising 4-9 segments (1 PP segment and 3-8 polyester segments).

It is possible, however, that not all functional groups are reacted, and therefore the number of polyester grafts may be from 1 to 8 polyester chains per molecule.

Coupling to give PP-graft-polyester copolymers can be effected by transesterification of at least one second polymer, for example a polyester, comprising at least one carboxylic or carbonic ester function and/or by ring-opening polymerization (ROP) of cyclic esters, examples being caprolactone, valerolactone, p-propiolactone, p-butyrolactone, 3-methyloxetan-2-one, ε -decalactone, 5-dimethyl-dihydrofuran-2-one, 1, 4-dioxepan-5-one, 1, 5-dioxepan-2-one, 3, 6-dimethylmorpholine-2, 5-dione, 1, 4-dioxepan-7-one, 4-methyl-1, 4-dioxepan-7-one, (S) -g-hydroxymethyl-g-butyrolactone, g-octanoic acid lactone, g-nonanoic acid lactone, 5-valerolactone, 5-caprolactone, 5-decalactone, 5-undecalactone, 5-dodecalactone, glycolide, lactide (L, D, meso), heptalactone, octalactone, nonalactone, decalactone, 11-undecalactone, 12-dodecalactone, 13-tridecanolide, 14-tetradecanolide, 15-pentadecanolide (or pentadecanolide), pentadecanolide, 16-hexadecanolide, pelargonide, 17-heptadecanode, 18-octadecanolide, 19-nonadecanolide, ethylene crotonate, butylene crotonate, cyclic butyl terephthalate, butyl terephthalate, Cyclic butyl adipate, cyclic butyl succinate, and cyclic butyl terephthalate oligomers.

The cyclic esters, particularly when they are lactones, may be in any isomeric form and may further comprise an organic substituent on the ring which does not prevent ROP.

Examples of such cyclic esters include 4-methylhexalactone, epsilon-decalactone, the lactone of ricinoleic acid or hydrogenated versions thereof, 13-hexyloxycyclotridecan-2-one, and the like.

It is also possible that the cyclic ester contains one or more unsaturations in the ring. Examples of such cyclic esters include 5-tetradecene-14-olide, 11-pentadecene-15-olide, 12-pentadecene-15-olide (also known as pentadecene lactone), 7-hexadecene-16-olide (also known as pelargonide), and 9-hexadecene-16-olide.

The cyclic ester may also have one or more heteroatoms in the ring, provided that the heteroatoms do not prevent ROP. Examples of such cyclic esters include 1, 4-dioxepan-5-one, 1, 5-dioxepan-2-one, 3, 6-dimethylmorpholine-2, 5-dione, 1, 4-oxepan-7-one, 4-methyl-1, 4-oxepan-7-one, 10-oxhexadecene lactone, 11-oxhexadecene lactone, 12-oxhexadecene-16-lactone.

The cyclic ester is preferably selected from caprolactone and valerolactone.

The polarity of the polyester segments can be adjusted, for example, by: adding a combination of a plurality of cyclic monomers of different polarities, adjusting the polarity of the second polymer fragment during pre-synthesis using a combination of monomers prior to attaching the second polymer fragment to the polyolefin fragment by nucleophilic substitution, adding a combination of a plurality of second polymers of different polarities, or adding a combination of a cyclic monomer and a second polymer by nucleophilic substitution. The melting temperature and/or glass transition temperature of the resulting graft copolymer grafts may also be adjusted by selecting the appropriate monomers for the second segment while maintaining the crystalline characteristics. In other words, the physical and mechanical properties can be adjusted using the present invention. In addition, the hydrolysis and degradation characteristics of the polar polymer segments can be adjusted without affecting the polyolefin segments.

M of each polyester segment_nIs 5-25kDa (tetrachloroethane-d at 90 ℃ C.)₂Chinese character Zhongyuan¹HNMR measurement).

The polyester segment (e.g., polycaprolactone or polypentanolactone segment) is incompatible with the linear PP backbone. This incompatibility results in phase separation of the graft copolymer from a point after synthesis in the initial homogeneous state and produces a multiphase composition having a bicontinuous microstructure of nanostructures, where one phase comprises polyester segments.

Depending on the composition of the PP/polyester, the copolymer forms a bicontinuous phase, which means that PP forms the continuous phase and the polyester also forms the continuous phase. The presence of the bicontinuous phase may be observed using different techniques, such as transmission electron spectroscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and/or small angle X-ray scattering (SAXS).

Within the limits of the film of the invention, the amount of polyester is from about 5 to 90 mol% (calculated as mol% relative to the amount of molar units present in the copolymer).

However, in order to make the film usable as the porous film of the present invention, the amount of PP is 45 to 80 mol% and the amount of the polyester segment is also 55 to 20 mol%. The amount of PP is preferably from 50 to 75 mol% and the amount of polyester segments from 50 to 25 mol% (mol% calculated with respect to the amount of molar units present in the copolymer). If this amount is not achieved, the film becomes a barrier because there is no pathway within the film and cannot be used as a porous film.

FIGS. 12a, b, c, d, e, f depict the self organization and morphology of graft copolymers depending on the number average molecular weight of the polyester and polypropylene.

FIG. 12a is a comparative example, which is not a graft copolymer but a block copolymer, wherein the number average molecular weight of the polyester and PP segments is within the scope of the present invention. It can be readily seen that the self organization and morphology of the block copolymer does not allow the formation of a nanoporous, helical bicontinuous phase when the polyester phase is removed.

Fig. 12b, c and d depict embodiments within the scope of the present invention wherein the number average molecular weight and the content of the polyester and PP of the graft copolymer are within the scope of the present invention.

It can be readily seen that the self organization and morphology of the graft copolymer allows for the creation of channels when the sacrificial segments are removed.

FIGS. 12e and 12f depict comparative embodiments outside the scope of the present invention wherein the number average molecular weight and the content of both the polyester and PP of the graft copolymer are within the scope of the present invention.

The comparative embodiment in fig. 12e contains less than 20 mol% polyester (mol% calculated relative to the amount of molar units present in the copolymer), the self organization and morphology of the graft copolymer is not bicontinuous after the selective fragment sacrificing process, and a porous membrane cannot be formed.

The comparative embodiment in FIG. 12f comprises polyester segments, each having a number average molecular weight of less than 5 kDa.

The self organization and morphology of the graft copolymer does not allow for the formation of a bicontinuous helical morphology.

The thin film of graft copolymer can be converted into a membrane with nanopores by selective dissolution or sacrifice of the polyester (the so-called segmental sacrifice process) while keeping the PP phase intact.

The polyester segments can be selectively removed, for example, by chemical etching using alkali or acid. Removal will result in a plurality of nanometer-sized pores. The pores are very small (e.g., pore diameters on the order of 1 to 500 nanometers, or 5 to 100 nanometers, preferably 10 to 50 nm). In addition, the pores are characterized by a relatively narrow size distribution and are substantially uniformly distributed throughout the film. These properties make nanoporous membranes particularly useful in applications such as separation membranes (e.g., battery separators). Generally, the thin films may be used in a variety of applications, including separation membranes (e.g., battery separator membranes), membranes for water purification, fuel cell membranes, catalytic reactors, nano-templates, and the like. The process described above produces a nano-scale bicontinuous structure comprising interpenetrating regions throughout the material. This bicontinuous nature allows one mechanically strong phase to support the entire structure, while the other permeable region imparts certain specific functions to the material. The nanoporous structure is generated by removing the functional regions (polyester segments) resulting in a material with a percolating pore structure. Due to the narrow pore size distribution and the pore structure penetrating the whole membrane, the membrane material can be used as a battery diaphragm and a separation membrane.

The invention therefore also relates to a nanoporous membrane. The nanoporous membrane comprises at least 90 wt% PP, preferably at least 95 or at least 98 wt% PP. The PP comprises-OX functional groups randomly distributed on the polymer chains. The amount of functional groups is from 3 to 8 per polymer chain (on average), this being done at 90 ℃ in tetrachloroethane-d₂Chinese character Zhongyuan¹H NMR measurement. For each-OX, X can be H, Li, Na, or K, which results in the-OX group being an-OH, -OLi, -ONa, or-OK group, respectively. In another embodiment, X may also be Mg, Zn, and Al.

M of PP in the film_nPreferably between 10 and 100kDa, more preferably between 20 and 100kDa, as determined by HT-SEC (in o-DCB at 150 ℃). The PP is preferably a propylene homopolymer or a copolymer of ethylene and propylene, wherein the amount of ethylene is less than 5 wt%.

The PP is preferably isotactic or syndiotactic, more preferably isotactic.

The thickness of the film may be 0.01 to 10 mm.

The membrane preferably has pores with a pore diameter of 1-500nm, preferably 5-100nm, more preferably 10-50nm (by N according to the model Barret-Joyner-Halenda₂Desorption measurement) and a BET surface area of from 50 to 200m²(measured by the Brunauer-Emmet-Teller method).

The film has preferred mechanical and thermal properties.

The film has high thermal stability and can be sterilized. Melting temperature (T) of the film_m) At a temperature of 120 ℃ to 160 ℃, preferably at a temperature of 130 ℃ to 159 ℃, and more preferably at a temperature of 140 ℃ to 158 ℃. T is_mMeasured by DSC (second heating curve, heating at a rate of 10K/min).

The Young's modulus of the film is 50-400MPa, preferably 100-300 MPa. The toughness of the film is 0.1-15J/m³Preferably 0.5 to 10J/m³。

It has been surprisingly found that the type of polyester segments affects the microstructure of the film, and thus the nanopore structure of the film, after the polyester segments are sacrificed. For example, when valerolactone is used as the polyester segment monomer, larger pores may be obtained than when caprolactone is used as the monomer.

It is believed that the presence of OX groups in PP membranes results in membranes with a unique structure, with the advantage of obtaining membranes with good mechanical properties and good flux properties. It has been found that the flux of water or aqueous solution through a membrane is higher compared to other membranes having similar pore sizes. This means that at a given membrane pressure difference, the amount of aqueous solution flowing through a membrane having a defined surface and thickness is greater.

The invention also relates to the use of the inventive film for producing a membrane suitable for use as a water filter or battery separator.

The present invention relates to a water filter system comprising the nanoporous membrane of the invention.

The invention also relates to a battery comprising the nanoporous membrane of the invention.

The invention also relates to a method for preparing the film defined by the invention.

The method comprises the following steps:

a) providing a hydroxy-functionalized PP having 3 to 8 hydroxyl groups,

b) the graft copolymer is prepared by any one of the following procedures:

a. ring Opening Polymerization (ROP) of cyclic esters, or

b. Polyester transesterification is carried out using a suitable transesterification catalyst,

c) and forming a film by:

a. extruding the copolymer at a temperature of at least 180 ℃ to produce a film of helical bicontinuous morphology through a film extrusion die, or

b. Films were prepared by compression molding.

The invention also relates to a PP film unit, which may be a multilayer film or a plurality of films, wherein said layer or film comprises

1. A nanoporous membrane as defined above which is,

2. a microporous PP film and/or a PP nonwoven.

The invention also relates to a polypropylene based film comprising the nanoporous film and the microporous polypropylene film and/or the polypropylene nonwoven material of the invention as defined above.

The invention also relates to the use of a nanoporous membrane for the preparation of an all-PP membrane for applications such as batteries, water filters or other applications. Some advantages of all-PP membranes are that they can be used at high temperatures, can be sterilized and can have high flux for efficient separation of components in e.g. aqueous media. They can also be easily recycled as part of a recycling economy.