Multilayer porous membrane with incompatible resins
View Patent ↗A monolayer, bilayer, trilayer, or multilayer porous membrane having at least one layer that contains a thermoplastic resin and a polymer that is incompatible with the thermoplastic resin. One structure is a multilayer porous membrane where at least one internal layer of the multilayer porous membrane contains the thermoplastic resin and the polymer that is incompatible with the thermoplastic resin. Higher amounts of incompatible polymer may be used in an internal layer. This structure has improved properties, including improved puncture strength. Another structure includes at least one layer containing polyethylene and a polymer that is incompatible with polyethylene. The at least one layer containing polyethylene and a polymer that is incompatible with polyethylene may be an internal layer or an external layer. An internal layer may include more incompatible polymer than an external layer. The porous membranes may be used as battery separators. For example, they may be used as battery separators in secondary batteries such as lithium ion secondary batteries.
1 . A multilayer porous membrane comprising
at least one internal layer that comprises a first polymer blend composition comprising a first polyolefin thermoplastic resin and a first block copolymer that is incompatible with the first polyolefin thermoplastic resin, wherein the first block copolymer comprises a styrenic block copolymer or an ethylene-butene block copolymer and is present in the first polymer blend composition in an amount of between 1 wt. % and 20 wt %; and
at least one layer adjacent to the at least one internal layer, wherein the at least one adjacent layer comprises a second polyolefin thermoplastic resin, wherein the first polyolefin thermoplastic resin and the second polyolefin thermoplastic resin each independently comprises a polypropylene, a polyethylene, mixtures thereof, copolymers thereof, or terpolymers thereof, and wherein the second polyolefin thermoplastic resin is the same as or different than the first thermoplastic resin;
wherein the membrane has a puncture strength of 350 gf or more when normalized for thickness at 14 microns.
2 . The multilayer porous membrane of claim 1 , wherein the first polyolefin thermoplastic resin and the second polyolefin thermoplastic resin are the same.
3 . The multilayer porous membrane of claim 1 , wherein the block copolymer is a styrenic block copolymer.
4 . The multilayer porous membrane of claim 3 , wherein the block copolymer is a styrene-ethylene-butylene-styrene (SEBS), a styrene-ethylene-propylene-styrene (SEPS) block copolymer, a styrene-ethylene-ethylene-propylene-styrene (SEEPS) block co-polymer, or a styrene-ethylene-propylene (SEP) block co-polymer.
5 . The multilayer porous membrane of claim 1 , wherein the at least one adjacent layer is an internal layer and does not contain a block copolymer incompatible with the second polyolefin thermoplastic resin.
6 . The multilayer porous membrane of claim 1 , wherein the internal layer has a thickness from 0.1 to 10 microns.
7 . The multilayer porous membrane of claim 1 , wherein the at least one adjacent layer is an internal layer and contains a second block copolymer incompatible with the second polyolefin thermoplastic resin, the second block copolymer comprising a styrenic block copolymer or an ethylene-butene block copolymer, and being the same or different from the first block copolymer.
8 . The multilayer porous membrane of claim 1 , wherein the first polymer blend composition comprises the first block copolymer in an amount of 8 wt. %.
9 . The multilayer porous membrane of claim 1 , wherein the first polymer blend composition comprises the first block copolymer in an amount of 5 wt. %.
10 . The multilayer porous membrane of claim 1 , wherein the first polymer blend composition comprises the first block copolymer in an amount of 10 wt. %.
11 . The multilayer porous membrane of claim 1 , wherein the glass transition temperature (T g ) of the first block copolymer is lower than that of the polyolefin thermoplastic resin.
12 . The multilayer porous membrane of claim 1 , wherein the porous membrane is formed by a dry-process.
13 . The multilayer porous membrane of claim 1 , wherein the at least one adjacent layer is an external layer and does not contain a block copolymer incompatible with the second polyolefin thermoplastic resin.
14 . The multilayer porous membrane of claim 1 , wherein the membrane is free of a compatibilizer that compatibilizers the polyolefin thermoplastic resin and the first block copolymer.
15 . The multilayer porous membrane of claim 1 , wherein the at least one adjacent layer is an external layer and contains a second block copolymer incompatible with the second polyolefin thermoplastic resin, wherein the second block copolymer comprises a styrenic block copolymer or an ethylene-butene block copolymer, and wherein the second block copolymer is the same or different from the first block copolymer.
16 . The multilayer porous membrane of claim 15 , wherein an amount of the second block copolymer in the external layer is less than an amount of the first block copolymer in the internal layer.
17 . The multilayer porous membrane of claim 16 , wherein the external layer comprises less than 10 wt. % of the second block copolymer.
18 . A battery separator comprising the multilayer porous membrane of claim 1 .
19 . A secondary battery comprising the battery separator of claim 18 .
20 . A porous membrane comprising
at least one first internal layer that contains a first polymer blend composition comprising a polyethylene and optionally a polymer that is incompatible with polyethylene;
at least one second layer comprising a second polymer blend composition that contains polypropylene and an incompatible polymer in an amount of between 1 wt. % and 20 wt %, wherein the incompatible polymer is a styrene-ethylene-butylene-styrene (SEBS), a styrene-ethylene-propylene-styrene (SEPS) block copolymer, a styrene-ethylene-ethylene-propylene-styrene (SEEPS) block co-polymer, or a styrene-ethylene-propylene (SEP) block co-polymer.
21 . The porous membrane of claim 20 , further comprising at least one third layer comprising a third polymer blend composition that contains polypropylene and optionally a polymer that is incompatible with polypropylene.
22 . The porous membrane of claim 21 , wherein the second layer is an internal layer and the amount of incompatible polymer in the second polymer blend composition is between 5 wt. % and 20 wt. %.
23 . The porous membrane of claim 21 , wherein the third layer is an external layer and the amount of incompatible polymer in the third polymer blend composition is less than 5 wt. %.
24 . The porous membrane of claim 21 , wherein the porous membrane is a trilayer or multilayer membrane.
25 . A battery separator comprising the porous membrane of claim 21 .
26 . A secondary battery comprising the battery separator of claim 25 .
27 . A textile, filter, or material for personal protective equipment comprising the porous membrane of claim 1 .
28 . A textile, filter, or material for personal protective equipment comprising the porous membrane of claim 21 .