Network carbon composite material

Abstract

The present invention discloses a reticulated film composite and a method for producing the reticulated film composite suitable as a three-dimensional porous and conductive matrix containing up to 80% porosity and exhibiting high recovery after compression. The reticulated film composite has a high yield stress (i.e., 50 dynes / cm). 2 and high MW resins dissolved in solvents (i.e., solution viscosity in 5% NMP at room temperature is greater than 100 cp) and high specific surface areas (i.e., 1 m 2 / g, preferably above 10m 2 / g) by casting and drying a slurry of dispersed nanoparticles of carbon (examples include, but are not limited to, conductive carbon, carbon nanotubes, graphene, activated carbon, or mixtures thereof).

Description

Technical Field

[0001] The present invention discloses a method for manufacturing a reticulated (porous, continuous bubble matrix structure) film composite material. Said composite material is suitable as a conductive composite material, as a gas diffusion layer of a fuel cell, or as a high-efficiency electrode of an electric double layer capacitor.

Background Art

[0002] A reticulated film composite material is a very porous low-density solid film. A reticulated form refers to a very continuous structure like a net. Similarly, a reticulated film composite material is also made of a very continuous bubble structure and exhibits novel physical properties compared to their bulk counterparts, such as a large specific surface area and high energy absorption upon impact. Due to its excellent strength-to-weight ratio, it is optimal for catalyst media, catalyst carriers, energy storage, damping, construction of components, and protective coatings. However, when a sufficient amount of carbon (>20%) is incorporated into the solid film, in order to impart conductivity, the film often exhibits insufficient mechanical and thermal stability. The elongation at break is much lower, which means it is brittle and easily broken and cannot be deformed into a foam or reticulated film.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Thin porous films are often made of melt-processable plastics, which form the film by solution casting or extrusion and then stretch it to create a porosity of 30 - 60% within the film. Today's common thin porous films (less than 100 μm thick) are generally based on polypropylene (melting point about 160 - 165 °C), polyethylene (melting point about 110 - 135 °C), or blends thereof. For example, U.S. Pat. Nos. 4,620,956 and 5,691,047 disclose melt extrusion and stretching processes for manufacturing polyolefin porous films or separators, and U.S. Pat. Nos. 8,064,194 and 8,012,799 disclose solution casting processes for manufacturing polyolefin porous films or separators. Porous separators made of polyvinylidene fluoride (PVDF) (melting temperature about 165 - 170 °C) disclosed in U.S. Patent Application Nos. 2009 / 0208832 and 2010 / 0183907 are also known. A significant drawback of such thin porous films is their low dimensional stability at high temperatures or lack of thermal robustness that can lead to shrinkage. Furthermore, to the author's knowledge, there is no thin porous conductive film (less than 100 μm thick) with a porosity exceeding 20% and a volume resistivity less than 10,000 Ω·cm.

[0004] PVDF has been found to be useful as a binder or coating for separators in non-aqueous electrolyte devices due to its excellent electrochemical resistance and good adhesion among fluoropolymers. The separator forms a barrier between the anode and cathode of the battery and prevents electronic short circuits while enabling high ion transport. Polyvinylidene fluoride (PVDF), and its copolymers, are used in many applications such as durable coatings, wire jackets, binders for lithium-ion batteries, chemical piping, continuous and closed-cell foams. However, due to its high insulation property, more than 30% carbon is required to make it conductive. With such a high carbon loading, it is almost impossible to create low-density foams or films from PVDF-carbon composites.

Brief Description of the Drawings

[0005]

Figure 1

DETAILED DESCRIPTION OF THE INVENTION

[0006] "Copolymer" is used to mean a polymer having two or more different monomer units. "Polymer" is used to include homopolymers and copolymers. Resin and polymer are used in the same meaning. The polymer can be homogeneous, heterogeneous, and can have a gradient distribution of comonomer units. All references cited are incorporated herein by reference. As used herein, unless otherwise specified, percent means weight percent. The crystallinity and melting temperature are measured by DSC at a heating rate of 10°C / min as described in ASTM D3418. The melt viscosity is measured at 232°C according to ASTM D3835 and is expressed in kPoise at 100 sec -1 and is expressed in kPoise. The dilute solution viscosity and reduced viscosity of the polymer are measured at room temperature as described in ASTM D2857.

[0007] A reticulated film or coating means a film or coating having a porous continuous cellular matrix structure. "Continuous cells" means that the pores are not surrounded. The fluid can move between the pores. The void ratio or porosity can be measured by compressing the continuous cellular matrix, measuring the density, or filling the voids with a liquid and measuring the change in density. Preferably, the voids are measured by density.

[0008] A nano-sized filler or nano-sized particle means that the size of the filler or particle is less than 1 μm, preferably less than 500 nm, more preferably less than 200 nm. The nano-sized particle can be less than 100 nm. The particle size is the volume average particle size measured by light scattering (such as equipment from Nicom or Microtech).

[0009] High specific surface area particles refer to particles with a surface area greater than 1 m 2 / g, preferably greater than 5 m 2 / g, more preferably greater than 10 m 2 / g. Preferably, it is 1 m 2 / g to 10000 m 2 / g, preferably 1 m 2 / g to 5000 m 2 / g, 1 m 2 / g to 1000 m 2 / g, more preferably 1 m 2 / g to 700 m 2 / g, even more preferably 10 m 2 / g to 500 m 2 / g. The surface area of the particle can be 5 m 2 / g to 700 m 2 / g. Some high specific surface area particles have a three-dimensional branched structure. This is sometimes called a fractal shape that can result in particles with a large aspect ratio. The fractal shape is an aggregate with three-dimensional branches. For example, the primary particles of a conductive carbon structure may aggregate into a three-dimensional branched structure. This is composed of many closely bound primary particles.

[0010] High molecular weight means that, using ASTM D2857, the solution viscosity measured at 5% in NMP at room temperature (25 °C) is at least 100 cp, preferably 100 cp to 10,000 cp, more preferably 100 cp to 5000 cp, or the viscosity is decreasing, and Rv is at least 0.2 dl / g and at most 2 dl / g.

[0011] The yield stress is the minimum shear stress required to initiate fluid flow. High yield stress is at least 50 dynes / cm 2 , preferably greater than 100 dynes / cm 2 , greater than 125 dynes / cm 2 . The yield stress is at most 5000 dynes / cm 2 , preferably at most 3000 dynes / cm 2 . Also, the slurry must be castable, which means that the solution viscosity of the slurry is less than 20,000 cP at room temperature, preferably less than 10,000 cP.

[0012] The recovery of volume or porosity after compression and heating is calculated by dividing the thickness of the coating or film after heating at 150 °C for 10 minutes after compression by the thickness before compression.

[0013] The present invention provides a network film composite material having nano-sized pores, and a method for producing a network film composite material having nano-sized pores. The nano-sized pores have an average pore size of less than 500 nm, preferably 2 nm to 500 nm. The present invention also provides a coating made from a network film composite material having nano-sized pores, wherein the porosity recovers to at least 30% of the porosity before compression after compression. The recovery of volume or porosity after compression and then heating can be at least 30%, preferably 50%, preferably 55%, preferably 60%, preferably 70% or the original thickness.

[0014] The network film composite material can be manufactured using different types of resins and a wide variety of carbon-based nano-sized particles.

[0015] The network film composite material is produced by combining high specific surface area particles and a polymer resin in a solvent at room temperature (25 °C), and has a high yield stress (50 dynes / cm 2results in a slurry (exceeding...). Casting the slurry and drying it at high temperature forms a network film composite material with nano-sized pores. When heated (30 - 180 °C, preferably 80 °C or higher, more preferably 110 °C or higher), the compressed film recovers its porosity to at least 30% (preferably at least 60%, preferably 50%, preferably 55%, even more preferably at least 70%) of the original porosity before compression.

[0016] Surprisingly, slurries (made in NMP) of high specific surface area particles (i.e., nano-sized carbon-based materials such as conductive carbon, carbon nanotubes, graphene, etc.) and polymer resins (e.g., high MW-PVDF with a 5% solution viscosity exceeding 100 cp at room temperature), or high MW-PMMA (with a reduced viscosity and Rv exceeding 0.5 dl / g) can exhibit a high yield stress (exceeding 50 dynes / cm 2 even at low solids content (i.e., total solids less than 30 wt%, preferably less than 20 wt%, more preferably less than 12%, even less than 10%). Due to the low dispersion viscosity (i.e., less than 10,000 cp at room temperature), casting is easy. Casting this high yield stress slurry and drying it at high temperature (i.e., 50 - 180 °C, preferably 80 - 180 °C, preferably 120 °C or higher) forms a network film composite material with nano-sized pores. The film showed recovery of porosity after compression when heated. Interestingly, these network film composite materials can be compressed to half their thickness using a room temperature calendar roll. This simply indicates that the composite material contains at least about 50% porosity. Even more unexpectedly, the compressed composite material can expand back to more than 50% of its original height when simple polymer relaxation occurs, such as placing it in an oven at 120 °C or exposing it to a potential solvent. This rebound indicates that these composite materials have a mechanically very durable continuous cellular structure. The ratio of carbon to polymer can vary greatly, and the higher the carbon content, the higher the porosity (lower density) of the composite material obtained.

[0017] The type of carbon filler can be, for example, conductive carbon, carbon nanotubes, graphene, or a combination thereof, thereby imparting high electron conductivity.

[0018] In one embodiment of the present invention, a semi-crystalline high molecular weight PVDF (having a solution viscosity of more than 100 cp measured at 5% in NMP at room temperature) functions in the present invention.

[0019] Using high molecular weight resins such as PMMA (reduced viscosity, Rv, exceeding 0.5 dl / g), and high MW PAA (having a solution viscosity of 100 to a maximum of 1000 cp, preferably a maximum of 5000, measured in water at pH 7 at room temperature), a high yield stress slurry (exceeding 50 dynes / cm 2 ) can be obtained, and finally, a reticulated film composite material with properties similar to a reticulated film made of PVDF can be manufactured.

[0020] The types of fillers useful in the present invention are carbon-based materials including, but not limited to, for example, conductive carbon, carbon nanotubes, activated carbon, graphene, or a combination thereof.

[0021] Small amounts of other fillers (0 to 15 wt%, preferably less than 10 wt%) may be present in the composition. Other fillers include, for example, alumina, silica, BaTiO 3 , CaO, ZnO, boehmite, TiO 2 , SiC, ZrO 2 , boron silicate, BaSO 4 , nanoclay, Pb(Zr,Ti)O 3 , Pb 1-x La x Zr y O 3 (0 < x < 1, 0 < y < 1), PBMg 3 Nb 2 / 3 ) 3 , PbTiO 3 , hafnia (HfO(HfO 2 ), SrTiO 3 , SnO2 , CeO 2 , MgO, NiO, Y 2 O 3 , Al 2 O 3 , SiO 2 , ceramic, or a mixture thereof is included. Also, other useful organic fillers include, but are not limited to, aramid fillers and fibers, polyetheretherketone fibers, polyetherketoneketone fibers, PTFE fibers, and nanofibers, carbon nanotubes, and mixtures thereof, which are chopped fibers.

[0022] The resin should have a high solution viscosity (i.e., higher than 100 cp measured at 5% in NMP at room temperature). Preferably, the solution viscosity is 100 - 10,000 cp, more preferably 100 - 5000 cp, at 5% solids measured in NMP at room temperature. In the case of water-soluble polymers, when measured at pH 7 at room temperature (25 °C) in 2% water, the solution viscosity is 100 cp - 10,000 cp, preferably 100 cp - 5000 cp. In this application, the pH varies in the range of 2 - 12 depending on the type and use of the polymer.

[0023] Polymers (resins) useful in the present invention include, but are not limited to, the following homopolymers and copolymers: polyvinylidene fluoride (PVDF), polyethylene tetrafluoride ethylene (PETFE), polyvinyl fluoride (PVF), poly(alkyl) acrylate, poly(alkyl) methacrylate, polystyrene, polyvinyl alcohol (PVOH), polyester, polyamide, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), polymethacrylic acid (PMAA). Other useful polymers include polyetherketoneketone, polyetheretherketone, and polyester.

[0024] Polyvinylidene fluoride In a preferred embodiment, the polymer is a polyvinylidene fluoride homopolymer or copolymer. As used herein, the term "vinylidene fluoride polymer" (PVDF) includes within its meaning, within the scope of its meaning, usually any of high molecular weight homopolymers, copolymers, and terpolymers. Copolymers of PVDF are particularly preferred because they are softer (having a lower Tm, melting point and reduced crystalline structure). Such copolymers include vinylidene fluoride copolymerized with at least one comonomer. The most preferred copolymers and terpolymers of the present invention are those in which the vinylidene fluoride units constitute at least 50 mol%, at least 70 mol%, preferably at least 75 mol%, more preferably at least 80 mol%, even more preferably at least 85 mol of the total weight of all monomer units in the polymer.

[0025] Copolymers, terpolymers, and higher polymers of vinylidene fluoride can be made by reacting vinylidene fluoride with one or more monomers from the following group: vinyl fluoride; trifluoroethylene; tetrafluoroethylene; one or more partially or fully fluorinated α-olefins such as 3,3,3-trifluoro-1-propene, 1,2,3,3,3-pentafluoropropene, 3,3,3,4,4-pentafluoro-1-butene, and hexafluoropropene; partially fluorinated olefin hexafluoroisobutylene; perfluorovinyl ethers such as perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, and perfluoro-2-propoxypropyl vinyl ether; fluorinated dioxoles such as perfluoro(1,3-dioxole) and perfluoro(2,2-dimethyl-1,3-dioxole); allyl, partially fluorinated allyl, or fluorinated allyl monomers (such as 2-hydroxyethyl allyl ether or 3-allyloxypropanediol); and ethene or propene. In some preferred embodiments, the comonomer is selected from the group consisting of tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene, vinyl fluoride, pentafluoropropene, tetrafluoropropene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether.

[0026] Particularly preferred are copolymers composed of at least about 75 to a maximum of 90 mole % vinylidene fluoride and correspondingly 10 to 25 mole % hexafluoropropene. Terpolymers of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene are also representative of the class of vinylidene fluoride copolymers embodied herein.

[0027] In one embodiment, the vinylidene fluoride polymer contains up to 50 wt%, preferably up to 20 wt%, more preferably up to 15 wt% of hexafluoropropene (HFP) units, and 50 wt%, preferably 80 wt%, more preferably 85 wt% or more of VDF units. To provide a PVDF-HFP copolymer with excellent dimensional stability in end-use environments such as batteries, it is desirable to disperse the HFP units as uniformly as possible.

[0028] The copolymer of PVDF for use in separator coating compositions preferably has a high molecular weight as measured by melt viscosity. High molecular weight means a PVDF having a melt viscosity exceeding 10 kilopoise, preferably exceeding 20 kilopoise, when measured at 232 °C for 100 sec -1 in accordance with ASTM method D-3835.

[0029] Fluoropolymers such as polyvinylidene-based polymers are produced by any process known in the art. Processes such as emulsion and suspension polymerization are preferred and are described in US6187885 and EP0120524.

[0030] Synthetic polyamide Polyamide is a polymer (a substance composed of long, multiple-unit molecules) in which the repeating units of the molecular chain are linked to each other by amide groups. The general chemical formula of the amide group is CO-NH. They may be formed by the interaction of an amine (NH 2 ) group and a carboxyl (CO 2 H) group, or may be formed by the polymerization of amino acids or amino acid derivatives (molecules containing both an amino group and a carboxyl group).

[0031] The synthesis of polyamides is well described in the art, for example, WO15 / 071604, WO14179034, EP0550308, EP0550315, US9637595.

[0032] The polyamide can be the following condensation or ring-opening product: - one or more amino acids such as 6-aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid, or one or more lactams such as caprolactam, enantholactam, and laurolactam; and - one or more salts or mixtures of a diamine such as hexamethylenediamine, dodecamethylenediamine, metaxylylenediamine, bis(p-aminocyclohexyl)methane, and trimethylhexamethylenediamine, and a diacid such as isophthalic acid, terephthalic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, and dodecanedicarboxylic acid.

[0033] Examples of polyamides can include PA6, PA7, PA8, PA9, PA10, PA11, and PA12, as well as copolyamides such as PA6,6.

[0034] Copolyamides are obtained from the condensation of at least two alpha, omega - aminocarboxylic acids or two lactams, or one lactam and one alpha, omega - aminocarboxylic acid. Copolyamides are obtained from the condensation of at least one alpha, omega - aminocarboxylic acid (or one lactam), at least one diamine, and at least one dicarboxylic acid. Examples of lactams include those having 3 to 12 carbon atoms on the main ring, and this lactam can be substituted. For example, there are β,β - dimethylpropiolactam, α,α - dimethylpropiolactam, amylolactam, caprolactam, capryllactam, and laurolactam.

[0035] Examples of alpha, omega - aminocarboxylic acids include aminoundecanoic acid and aminododecanoic acid. Examples of dicarboxylic acids include adipic acid, sebacic acid, isophthalic acid, butanedioic acid, 1,4 - cyclohexanedicarboxylic acid, terephthalic acid, sodium or lithium salts of sulfoisophthalic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated), and dodecanedioic acid, and HOOC-(CH2)10 - COOH.

[0036] The diamine can be an aliphatic diamine having 6 to 12 carbon atoms. It can be of the aryl and / or saturated cyclic type. Examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5 - diaminohexane, 2,2,4 - trimethyl - 1,6 - diaminohexane, diamine polyol, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), and bis(3 - methyl - 4 - aminocyclohexyl)methane (BMACM).

[0037] Examples of copolyamides include the following: copolymers of caprolactam and lauryllactam (PA6 / 12), copolymers of caprolactam, adipic acid, and hexamethylenediamine (PA6 / 6 - 6), copolymers of caprolactam, lauryllactam, adipic acid, and hexamethylenediamine (PA6 / 12 / 6 - 6), copolymers of caprolactam, lauryllactam, 11 - aminoundecanoic acid, azelaic acid, and hexamethylenediamine (PA6 / 6 - 9 / 11 / 12), copolymers of caprolactam, lauryllactam, 11 - aminoundecanoic acid, adipic acid, and hexamethylenediamine (PA6 / 6 - 6 / 11 / 12), and copolymers of lauryllactam, azelaic acid, and hexamethylenediamine (PA6 - 9 / 12).

[0038] Polyamides include polyamide block copolymers such as polyether-b-polyamide and polyester-b-polyamide.

[0039] Another polyamide is Arkema's ORGASOL® ultra-fine polyamide 6, 12, and 6 / 12 powders, which are microporous and have closed cells due to their manufacturing process. The particle size range of these powders is very narrow and can be 5 - 60 μm depending on the grade. A lower average particle size of 5 - 20 is preferred.

[0040] Acrylic As used herein, acrylic polymers mean polymers, copolymers, and terpolymers formed from methacrylate and acrylate monomers, and mixtures thereof. Methacrylate and acrylate monomers can constitute 51 - 100% of the monomer mixture, and 0 - 49% of other ethylenically unsaturated monomers including, but not limited to, styrene, alpha-methylstyrene, acrylonitrile may be present. Suitable acrylate and methacrylate monomers and comonomers include, but are not limited to: methyl acrylate, ethyl acrylate and ethyl methacrylate, butyl acrylate and butyl methacrylate, isooctyl methacrylate and acrylate, lauryl acrylate and lauryl methacrylate, stearyl acrylate and stearyl methacrylate, isobornyl acrylate and methacrylate, methoxyethyl acrylate and methacrylate, 2-ethoxyethyl acrylate and methacrylate, dimethylaminoethyl acrylate and methacrylate monomers. (Meth)acrylic acids such as methacrylic acid and acrylic acid can be comonomers. Acrylic polymers typically include multilayer acrylic polymers such as core-shell structures made by emulsion polymerization.

[0041] Styrene As used herein, styrenic polymers mean polymers, copolymers and terpolymers formed from styrene and alpha-methylstyrene monomers, and mixtures thereof. Styrene and alpha-methylstyrene monomers may constitute 50 to 100% of the monomer mixture, and 0 to 50% of other ethylenically unsaturated monomers including but not limited to acrylates, methacrylates, acrylonitrile may be present. Styrene polymers include, but are not limited to: polystyrene, acrylonitrile-styrene-acrylate (ASA) copolymer, styrene acrylonitrile (SAN) copolymer, styrene-butadiene copolymers such as styrene-butadiene rubber (SBR), methyl methacrylate-butadiene-styrene (MBS), and styrene-(meth)acrylate copolymers such as styrene-methyl methacrylate copolymer (S / MMA).

[0042] As used herein, polyolefins mean polyethylene, polypropylene, and copolymers of ethylene and propylene. Ethylene and propylene monomers may constitute 51 to 100% of the monomer mixture, and 0 to 49% of other ethylenically unsaturated monomers including but not limited to acrylates, methacrylates, acrylonitrile, anhydrides may be present. Examples of polyolefins include ethylene ethyl acetate copolymer (EVA), ethylene (meth)acrylate copolymer, ethylene anhydride copolymer and grafted polymers, propylene (meth)acrylate copolymer, propylene anhydride copolymer and grafted polymers.

[0043] Solvents useful in the present invention for preparing slurries include, but are not limited to, water, N-methyl-2-pyrrolidone (NMP), toluene, tetrahydrofuran (THF), acetone, and hydrocarbons. In a preferred embodiment, the solvent is NMP, water, or acetone. The solvent must be able to dissolve the polymer used to provide a visibly clear solution. For example, PVDF is soluble in NMP. Since PVDF is insoluble in water, water is not used for PVDF. Polyvinyl alcohol (PVOH), polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), and their copolymers are generally water-soluble.

[0044] Other additives The coating composition of the present invention may further comprise an effective amount of other additives (including, but not limited to, fillers, leveling agents, defoaming agents, pH buffers, and other auxiliary components commonly used in formulations) while meeting the desired requirements.

[0045] In the slurry coating composition of the present invention, optionally, a wetting agent, a thickening agent, or a rheology modifier can be further included.

[0046] The wetting agent can be present in the coating composition slurry in an amount of 0 to 5 parts (all in parts by weight), or 0.1 to 5 parts, preferably 0 to 3 parts, or 0.1 to 3 parts of one or more wetting agents per 100 parts of the solvent. Surfactants can function as wetting agents, but wetting agents can include non-surfactants. In some embodiments, the wetting agent can be an organic solvent. The presence of an optional wetting agent can uniformly disperse the powdery substance in the slurry. Useful wetting agents include, but are not limited to: TRITON® series (manufactured by Dow) and PLURONIC® series (manufactured by BASF), ionic and non-ionic surfactants such as BYK-346 (manufactured by BYK Additives), and organic liquids (NMP, DMSO, and acetone) compatible with the solvent.

[0047] The thickener and / or rheology modifier may be present in the coating composition in an amount of 0 to 10 parts (all parts by weight), preferably 0 to 5 parts, of one or more thickeners or rheology modifiers per 100 parts of water. When a thickener or rheology modifier is added to the above dispersion, it provides a slurry viscosity suitable for the casting process while preventing or slowing down the sedimentation of the powdery material. In addition to the organic rheology modifier, an inorganic rheology modifier can also be used alone or in combination.

[0048] The ratio of the resin to the total solids and the nanoparticle filler should be selected to produce a slurry with a high yield stress, i.e., higher than 50 dynes / cm 2 more preferably higher than 75 dynes / cm 2 even more preferably higher than 100 dynes / cm 2 or higher than 200 dynes / cm 2 even higher. The yield stress is up to 5000 dynes / cm 2 preferably up to 3000 dynes / cm 2 at most.

[0049] The solids content of the slurry can be 2 wt% to 30 wt% solids, preferably 2 to 20 wt%, even more preferably 2 to 12 wt%, or 2 to 10 wt% (based on the total weight of the polymer and the nanoparticles).

[0050] Carbon has a high specific surface area, good dispersibility in a solvent, and preferably a fractal-shaped structure.

[0051] Several factors can affect the porosity or density of the network film composite material. For example, reducing the solids in the slurry (i.e., from 10% to 6%) results in a few percent higher porosity, and a higher drying temperature (i.e., 180°C instead of 100°C) increases the porosity by a few percent. The higher the MW resin, the higher the porosity, and the larger the surface area of the filler, the higher the porosity. By applying all these adjustable properties, a network film composite material with the desired properties for a specific application can be manufactured.

[0052] Use: The network film composite material of the present invention can adjust the hot spots in the device by slowing down the current.

[0053] The network film composite material of the present invention is a very flexible and deformable conductive film for wearable electronics or biomedical sensors.

[0054] The network film composite material of the present invention can be used as a diffusion layer of a fuel cell.

[0055] The network film composite material of the present invention can be used as a host for an anode or a cathode of a lithium-ion battery or an electric double layer capacitor.

[0056] The network film composite material of the present invention can be used as an electromagnetic interference, EMI, or radio frequency interference, RFI, shield.

[0057] The network film composite material of the present invention can be used as a catalyst carrier.

[0058] The network film composite material not only does not shrink at high temperatures but can also be adjusted to expand at the hot spots in the device to slow down the current.

[0059] Another advantage of the network film composite material is that it can be cast on different surfaces and can function as a conductive network. The highly flexible and deformable conductive film is useful for wearable electronics and biomedical sensors.

[0060] As another example, a network film composite material of PVDF and conductive carbon with a porosity of 50% can be used in energy storage, for example, as a bipolar plate coating, or as a diffusion layer of a fuel cell, or as a host for an anode or cathode of a lithium-ion battery, and can provide a long cycle life (i.e., a lithium-sulfur battery). Since the composite material of the present invention has a very large surface area, it can also be used as a highly efficient electrode of an electric double layer capacitor.

[0061] As another example, a network film composite material of PVDF and conductive carbon with a porosity of 50% can be used as a gas diffusion layer, which is a main component of various types of fuel cells including proton exchange membrane (PEM), direct methanol (DMFC), and phosphoric acid (PAFC) stacks. The gas diffusion layer is disposed on both sides of the fuel cell membrane to allow reactants such as H2, air / oxygen, methanol, and product gas to flow uniformly.

[0062] The network film composite of the present invention, especially PVDF, has ultraviolet and radiation resistance, and thus can have other uses such as effective lightweight electromagnetic interference (EMI), or radio frequency interference (RFI) shielding or shielding gaskets used in electronics, especially in aeronautics.

[0063] The network film composite material can also provide a high surface medium for catalyst-driven reactions and can be used as a catalyst carrier to improve catalyst efficiency. The catalyst can be incorporated into the network film or deposited thereon.

[0064] Use: The response to temperature can be adjusted with the resin composition. For example, a network film composite material made of a resin with a higher HFP (i.e., 20% HFP) content may require a higher temperature to obtain the same swelling / expansion compared to one with a lower HFP (i.e., 8% HFP) content, so it swells / expands at a lower temperature. Thus, the amount of HFP comonomer in the PVDF resin is varied. The preferred weight percent of HFP in the copolymer of VDF is 1 to 25 weight percent, although higher weight percents (up to 50 weight percent) of HFP can be used.

[0065] The coating can be cast onto a substrate, removed from the substrate and placed onto another substrate, or cast in combination with another layer in a wet-on-wet process.

[0066] Another advantage of the network film composite material is that it can be cast simultaneously with another layer, i.e., using a double slot die casting machine, two slurry layers can be cast simultaneously using wet-on-wet technology. The integrated structure is then formed during the drying and calendaring steps. In the case of multilayer composite structures such as electrode separators for electrochemical devices or filter media, it can be cast wet-on-wet. Using wet-on-wet technology, the two layers are intertwined, there are no sharp interfaces, and the adhesion is improved. The network film or coating can be cast directly onto the substrate simultaneously with the substrate in one step of the wet-on-wet process.

[0067] Coating In one embodiment, the carbon-based nanoparticles or fibers can be surface-treated chemically (such as by etching or functionalization), mechanically, or by irradiation (such as by plasma treatment).

[0068] The particles are of nano size. Preferably, the fibers have a diameter of less than 1 μm.

[0069] The carbon-based nanoparticles are present in the coating composition at 20 to 95% by weight, preferably 20 to 90% by weight, based on the total of the polymer solid and the carbon-based nanoparticles. When the content of the carbon-based nanoparticles is less than 20% by weight, the binder polymer will be present in such a large amount as to reduce the interstitial volume formed between the particles.

[0070] In another example, a network film composite can be used as a protective coating, i.e., nano-sized ZnO or nano TiO 2 If included, it exhibits high UV blocking / protection.

[0071] The network film composite also provides a high surface medium for catalyst-driven reactions and can be used as a catalyst support to improve catalyst efficiency. The catalyst can be incorporated into the network film or deposited thereon.

[0072] Coating method The coating composition can be applied to at least one surface of the substrate by means known in the art such as brush, roller, inkjet, dip, knife, gravure, wire, squeegee, foam applicator, curtain coating, vacuum coating, slot die or spray. Next, the coating is dried on the substrate at room temperature or high temperature. The thickness of the final dry coating is 0.5 to 500 μm, preferably 1 to 100 μm, more preferably 2 to 50 μm.

[0073] In some aspects, the network film composite can be cast simultaneously with another layer.

[0074] Aspects of the present invention Aspect 1: a network coating or film comprising a) a resin and b) nanoparticles, The coating or film has a porous structure, the porous structure consists of 10% to 80% continuous pores, the solution viscosity of the resin is about 100 cp to 10,000 cp, preferably 100 cp to 5000 cp (5 wt% in NMP, 2% water in the case of aqueous polymer, measured at room temperature), the nanoparticles are carbon-based with a surface area of 1 to 10000 m 2 / g, preferably 1 to 5000 m 2 / g, preferably 1 to 1000 m 2 / g, and the film is a reticulated coating or film that exhibits a recovery of at least 30%, preferably 50%, preferably 55%, preferably 60%, preferably 70% in thickness or porosity after being compressed and then heated. Aspect 2: The reticulated coating or film according to Aspect 1, wherein the average pore size is less than 500 nm, preferably less than 100 nm, more preferably less than 50 nm. Aspect 3: The reticulated coating or film according to Aspect 1 or 2, wherein the resin is selected from the group consisting of: polyvinylidene fluoride (PVDF), PVDF copolymer, polyethylene tetrafluoride ethylene (PETFE), polyvinyl fluoride (PVF), polyacrylate, polymethacrylate, polystyrene, polyvinyl alcohol (PVOH), polyester, polyamide, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), polymethacrylic acid (PMAA), and their copolymers, and combinations thereof. Aspect 4: The reticulated coating or film according to any one of Aspects 1 to 3, wherein the resin comprises a homopolymer or copolymer of polyvinylidene fluoride. Aspect 5: The reticulated coating or film according to any one of Aspects 1 to 3, wherein the resin comprises polymethacrylate. Aspect 6: The reticulated coating or film according to any one of Aspects 1 to 3, wherein the resin comprises carboxymethyl cellulose. Aspect 7: The reticulated coating or film according to any one of Aspects 1 to 3, wherein the resin comprises polyacrylic acid and / or polymethacrylic acid. Aspect 8: The nanoparticle is the network coating or film according to any one of Aspects 1 to 7, which is selected from the group consisting of graphene, carbon nanotubes, conductive carbon, activated carbon, and mixtures thereof. Aspect 9: The nanoparticle contains conductive carbon, and is the network coating or film according to any one of Aspects 1 to 7. Aspect 10: The nanoparticle contains activated carbon, and is the network coating or film according to any one of Aspects 1 to 7. Aspect 11: The weight percentage ratio of the polymer to the nanoparticle is 80:20 to 10:90, preferably 70:30 to 20:80, and is the network coating or film according to any one of Aspects 1 to 10. Aspect 12: The surface area of the nanoparticle is 1 to 700 m 2 / g, more preferably 1 to 600 m 2 / g, and is the network coating or film according to any one of Aspects 1 to 11. Aspect 13: The coating has a thickness of 0.1 to 500 μm, preferably 0.5 to 100 μm, more preferably 0.5 to 50 μm, even more preferably 0.5 to 20 μm, and is the network coating or film according to any one of Aspects 1 to 12. Aspect 14: The size of the nanoparticle is less than 500 nm, preferably less than 200 nm, and is the network coating or film according to any one of Aspects 1 to 13. Aspect 15: The size of the nanoparticle is less than 100 nm, and is the network coating or film according to any one of Aspects 1 to 13. Aspect 16: A method for producing a network coating or film, the method comprising the following steps: Providing a resin dissolved in a solvent, wherein the polymer has a molecular weight such that the solution viscosity is about 100 cp to 10000 cp, preferably 100 cp to 5000 cp (5 wt% in NMP, 2 wt% water in the case of an aqueous polymer solution, measured at room temperature); Providing nanoparticles, wherein the surface area of the nanoparticles is 1 to 10000 m 2 / g; Combining the resin solution and the nanoparticles to produce a slurry (where the ratio of the weight percentage of the polymer to the weight percentage of the nanoparticles is from 80:20 to 5:95); Casting the slurry to form a coating or film; Drying the formed coating or film comprising, The dried coating or film has a porous structure, and the porous structure consists of 10% - 80% continuous pores, The slurry has a yield stress of 50 dyn / cm 2 to 5000 dyn / cm 2 , preferably 75 - 3000 dyn / cm 2 The solid content of the slurry is 2 - 30 wt% solids, preferably 2 - 20 wt% solids, and the film shows a recovery of at least 30%, preferably 50%, preferably 55%, preferably 60%, preferably 70% in thickness or porosity after being compressed and then heated. A method. Aspect 17: The method according to aspect 16, wherein the average pore size is less than 1000 nm. Aspect 18: The method according to aspect 16, wherein the average pore size is less than 100 nm, more preferably less than 10 nm. Aspect 19: The method according to any one of aspects 16 - 18, wherein the resin is selected from the group consisting of: polyvinylidene fluoride (PVDF), PVDF copolymer, polyethylene tetrafluoride ethylene (PETFE), polyvinyl fluoride (PVF), polyacrylate, polymethacrylate, polystyrene, polyvinyl alcohol (PVOH), polyester, polyamide, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), polymethacrylic acid (PMAA), and their copolymers, and combinations thereof. Aspect 20: The method according to any one of aspects 16 - 18, wherein the resin comprises a homopolymer or copolymer of polyvinylidene fluoride. Aspect 21: The method according to any one of aspects 16 to 18, wherein the resin contains polymethacrylate. Aspect 22: The method according to any one of aspects 16 to 18, wherein the resin contains carboxymethyl cellulose. Aspect 23: The method according to any one of aspects 16 to 18, wherein the resin contains polyacrylic acid and / or polymethacrylic acid. Aspect 24: The method according to any one of aspects 16 to 23, wherein the nanoparticles are selected from the group consisting of graphene, carbon nanotubes, conductive carbon, activated carbon, or mixtures thereof. Aspect 25: The method according to any one of aspects 16 to 23, wherein the nanoparticles contain conductive carbon or activated carbon. Aspect 26: The method according to any one of aspects 16 to 23, wherein the nanoparticles contain graphene or carbon nanotubes. Aspect 27: The method according to any one of aspects 16 to 26, wherein the solvent is selected from the group consisting of water, N-methyl-2-pyrrolidone (NMP), toluene, tetrahydrofuran (THF), acetone, and hydrocarbons. Aspect 28: The method according to any one of aspects 16 to 26, wherein the solvent is selected from the group consisting of NMP, water, acetone, and combinations thereof, preferably NMP. Aspect 29: The method according to any one of aspects 16 to 26, wherein the solvent contains water. Aspect 30: The method according to any one of aspects 16 to 26, wherein the solvent contains NMP. Aspect 31: The method according to any one of aspects 16 to 30, wherein the solid content of the formed slurry containing both the solvent and the nanoparticles is 2 to 15% by weight. Aspect 32: The method according to any one of aspects 16 to 30, wherein the solid content of the formed slurry containing both the solvent and the nanoparticles is 2 to 12% by weight. Aspect 33: The method according to any one of aspects 16 to 32, wherein the weight percentage ratio of the polymer to the nanoparticles is 80:20 to 10:90. Aspect 34: The method according to any one of aspects 16 to 32, wherein the weight percentage ratio of the polymer to the nanoparticles is from 70:30 to 20:80. Aspect 35: The surface area of the nanoparticles is from 1 to 700 m 2 / g, more preferably from 1 to 600 m 2 / g. The method according to any one of aspects 16 to 34. Aspect 36: The method according to any one of aspects 16 to 34, wherein the coating has a thickness of from 0.1 to 100 μm, preferably from 0.5 to 50 μm, more preferably from 0.5 to 20 μm. Aspect 37: The method according to any one of aspects 16 to 36, wherein the size of the nanoparticles is less than 500 nm, preferably less than 200 nanometers. Aspect 38: The method according to any one of aspects 16 to 36, wherein the size of the nanoparticles is less than 100 nm. Aspect 39: The method according to any one of aspects 16 to 36, wherein the film shows a recovery of at least 55%, preferably at least 60% of the thickness or porosity after being compressed and then heated. Aspect 40: The method according to any one of aspects 16 to 39, wherein the network film or coating is directly cast simultaneously with the substrate in one step of a wet-on-wet process. Aspect 41: A network coating or film produced by the method according to any one of aspects 16 to 40. Aspect 42: An article comprising the network coating or film according to any one of aspects 1 to 15 and 41, wherein the article is selected from the group consisting of a separator for wearable electronic devices or biomedical sensors, a diffusion layer of a fuel cell, an anode or cathode of a lithium-ion battery or an electric double layer capacitor, an electromagnetic interference, EMI, or radio frequency interference, RFI, shield, and a catalyst support, and the like of an electrochemical device. Aspect 42: An article comprising the network coating or film according to any one of aspects 1 to 15 and 41, wherein the article comprises an electrochemical device. Side 43: An article comprising the reticulated coating or film according to any one of sides 1 to 15 and 41, the article comprising a diffusion layer of a fuel cell. Side 44: An article comprising the reticulated coating or film according to any one of sides 1 to 15 and 41, the article comprising a diffusion layer of a catalyst carrier.

[0075] Test method The melt viscosity to be measured is measured at 232 °C for 100 sec according to ASTM method D-3835 -1 and is measured at.

[0076] The particle size of the nanoparticles can be measured using a Malvern Masturizer 2000 particle size analyzer. The data is shown as the weight average particle size (diameter).

[0077] The powder / latex average discrete particle size can be measured using a NICOMP TM 380 submicron particle size analyzer using laser light scattering. The data is shown as the weight average particle size (diameter).

[0078] The density of the composite material was calculated by dividing the weight of the composite material by the volume of a specific sample. First, the composite material was cast onto aluminum foil, and then a sample with a surface area of 1.33 cm 2 was created by stamp cutting the cast composite material. The thickness of the sample was measured with a micrometer having an accuracy of 0.1 μm. The weight of the composite material was measured using an analytical balance, and the weight of the aluminum foil was subtracted. The density of the solid material is based on published literature values. That is, PVDF polymer = 1.78 g / cm 3 , PMMA = 1.13 g / cm 3 , CMC = 1.6 g / cm 3 is.

[0079] The BET specific surface area, pore volume, and pore size distribution of the material can be determined using a QUANTACHROME NOVA-E gas sorption apparatus. The nitrogen adsorption and desorption isotherms are generated at 77K. The multipoint Brunauer-Emmett-Teller (BET) nitrogen adsorption method is used to specify the specific surface area. The nonlocal density functional theory (NLDFT, N2, 77k, slit pore model) is used to specify the pore volume and pore size distribution.

[0080] Solution viscosity: ASTM2857

[0081] Yield stress back-calculation: Brookfield viscometer DV-III Ultra, spindle CP52 calculation based on the Herschel-Bulkley model equation:

Number

[0082] τ is the shear stress. To obtain the viscosity, it is necessary to divide by the shear rate. The calculation is as follows.

Number

[0083] In the formula, since k is expressed in Centipoise, it needs to be divided by 100 to get D / cm 2 and this needs to be added to τ°. When calculating τ° inversely, the equation becomes as follows.

Number

[0084] Volume resistivity measurement: The slurry was cast onto an aluminum foil about 110 μm thick and placed in a convection oven at 120 °C for 30 minutes. Next, an Instron testing machine was used together with a gold-plated electrode of 3.09 cm 2 to obtain the resistivity under various compressive forces. The circular gold-coated contacts were adhered to the Instron fixture using 3M double-sided tape. The resistance was measured using a Yokogawa digital resistor meter (755601, 4-probe). The contact pressure was applied at a rate of 20 N / min using an Instron (500 N load cell). All data were recorded manually. The resistivity decreased with pressure and reached a plateau at about 100 N.

Number

Example

[0085] Example 1: Using different conductive carbons and fumed alumina as a control, recovery from compression after calendaring of a network film composite of PVDF / HFP and a PVDF (Kynar 1810) copolymer of 50 wt% HFP and PMMA (RV = 1.1 dl / g) resin.

[0086]

Table 1

[0087] This indicates that recovery is observed in carbon-based materials, but not in Al 2 O 3 . When heated, a recovery exceeding 30% of the original volume is observed.

[0088] Example 2: Influence of temperature on the network film composite material:

[0089]

Table 2

[0090] This indicates that a porosity exceeding 50% or the original porosity recovers upon heating.

[0091] Resistivity measurement: The slurry was composed of NMP (manufactured by Aldrich), conductive carbon Super-P (manufactured by Timcal), and three different PVDF resins including Kynar® HSV-900 (manufactured by Arkema), Solef-5130 (manufactured by Solvay), and Kynar® HSV-1810 (manufactured by Arkema). Three composite materials were cast onto aluminum foil and subsequently dried in a convection oven at 120 °C. The resulting composite materials showed the following volume resistivities.

[0092]

Table 3

[0093] The reproducibility of resistivity measurement seems to be relatively good, and a difference exceeding 100 (Ω·cm) should be regarded as significant.

Claims

1. a) A reticulated coating or film comprising a resin and b) nanoparticles, The net coating or film has a continuous porous structure, the porous structure has continuous pores of 10% to 80% by volume, the solution viscosity of the resin is 100 cp to 10,000 cp (5 wt% in NMP, 2 wt% in the case of a water-soluble polymer, measured at room temperature), the nanoparticles are carbon-based and have a surface area of 1 to 10,000 m 2 / g, and the film is a net coating or film that is compressed to half its thickness at room temperature and then heated at 150 °C for 10 minutes, and then shows a recovery to at least 60% of its original thickness or porosity.

2. The reticulated coating or film according to claim 1, wherein the resin is selected from the group consisting of the following homopolymers or copolymers: polyvinylidene fluoride (PVDF), polyethylene tetrafluoroethylene (PETFE), polyvinyl fluoride (PVF), poly(alkyl) acrylate, poly(alkyl) methacrylate, polystyrene, polyvinyl alcohol (PVA), polyester, polyamide, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), polymethacrylic acid (PMAA), and combinations thereof.

3. The reticulated coating or film according to claim 1 or 2, wherein the average pore size is less than 500 nm.

4. The reticulated coating or film according to any one of claims 1 to 3, wherein the resin comprises a homopolymer or copolymer of polyvinylidene fluoride.

5. The reticulated coating or film according to any one of claims 1 to 3, wherein the resin comprises polymethacrylate.

6. The reticulated coating or film according to any one of claims 1 to 3, wherein the resin comprises at least one of carboxymethyl cellulose, polyacrylic acid or polymethacrylic acid.

7. The reticulated coating or film according to any one of claims 1 to 6, wherein the nanoparticles are selected from the group consisting of graphene, carbon nanotubes, conductive carbon, activated carbon, and mixtures thereof.

8. The reticulated coating or film according to any one of claims 1 to 7, wherein the weight percentage ratio of polymer to nanoparticles is 80:20 to 10:

90.

9. A method for producing a reticulated coating or film, the method comprising the following steps: a) Providing a resin dissolved in a solvent, wherein the polymer has a solution viscosity of 100 cp to 10,000 cp (5 wt% in NMP, 2 wt% water for water-soluble polymers, at room temperature); b) providing nanoparticles, wherein the surface area of the nanoparticles is 1 to 10,000 m 2 / g); c) Combining the solution of the resin and the nanoparticles to produce a slurry, wherein the weight percentage ratio of the polymer to the nanoparticles is 80:20 to 10:90; d) casting the slurry to form a coating or film on a substrate; e) drying the formed coating or film comprising the dried coating or film has a porous structure, and the porous structure is composed of continuous pores of 10% to 80% by volume; The slurry has a yield stress of 50 dyn / cm 2 to 5000 dyn / cm 2 and the solid content of the slurry is 2 to 30% by weight, and the film is compressed to half its thickness at room temperature and then heated at 150 °C for 10 minutes and then shows a recovery to at least 60% of its original thickness or porosity, a method.

10. The method according to claim 9, wherein the resin is selected from the group consisting of the following homopolymers or copolymers: polyvinylidene fluoride (PVDF), polyethylene tetrafluoroethylene (PETFE), polyvinyl fluoride (PVF), poly(alkyl) acrylate, poly(alkyl) methacrylate, polystyrene, polyvinyl alcohol (PVA), polyester, polyamide, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose CMC, polyacrylic acid (PAA), polymethacrylic acid (PMAA), and combinations thereof.

11. The method according to claim 9, wherein the resin comprises a homopolymer or copolymer of polyvinylidene fluoride.

12. The method according to claim 9, wherein the resin comprises a homopolymer or copolymer of polymethacrylate.

13. The method according to claim 9, wherein the resin comprises at least one homopolymer or copolymer of carboxymethyl cellulose, polyacrylic acid, or polymethacrylic acid.

14. The method according to any one of claims 9 to 13, wherein the nanoparticles are selected from the group consisting of graphene, carbon nanotubes, conductive carbon, activated carbon, and mixtures thereof.

15. The method according to any one of claims 9 to 14, comprising both the solvent and the nanoparticles, and the solid content of the formed slurry is 2 to 30% by weight.

16. The method according to any one of claims 9 to 15, wherein the weight percentage ratio of the polymer to the nanoparticles is 80:20 to 10:

90.

17. The method according to any one of claims 9 to 16, wherein the size of the nanoparticles is less than 500 nm.

18. The method according to any one of claims 9 to 17, wherein the film is compressed to half its thickness at room temperature and then heated at 150 °C for 10 minutes, and then shows a recovery to at least 70% of its original thickness or porosity.

19. The method according to any one of claims 9 to 18, wherein the mesh coating or film is directly cast simultaneously with the substrate in one step of a wet-on-wet process.

20. An article comprising the mesh coating or film according to any one of claims 1 to 8, wherein the article is selected from the group consisting of a separator for a wearable electronic device or a biomedical sensor, a diffusion layer of a fuel cell, an anode or a cathode of a lithium ion battery or an electric double layer capacitor, an electromagnetic interference, EMI, or a radio frequency interference, RFI, shield, and a catalyst alone, etc., of an electrochemical device.

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