Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/911—Cooling
  • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
  • B29C48/914—Cooling drums
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/27—Cleaning; Purging; Avoiding contamination
  • B29C48/272—Cleaning; Purging; Avoiding contamination of dies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/911—Cooling
  • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means

Definitions

• This disclosure relates generally to an extrusion apparatus for producing an extrudate and to an apparatus and system for protecting same.
• Extrusion dies are used in manufacturing processes to make a variety of goods. Some dies, for example, are used to form thin films, sheets or other elongated shapes of plastic material. Techniques have been developed for melt laminating which involves joining two or more diverse materials (e.g., thermoplastic materials) from separate molten layers under pressure within a die to emerge as a single laminated material. Such processes make use of the laminar flow principle which enables two or more molten layers under proper operating conditions to join in a common flow channel without intermixing at the contacting interfaces. These multiple layer extrusion systems have come into use as a convenient way to provide for the formation of multiple layers of similar or dissimilar materials.
• materials e.g., thermoplastic materials
• a die assembly can be modular and is typically assembled from a plurality of parts and then set in a die station as an integral device.
• a die assembly can comprise a first die part and a second die part, which together form the components that allow a fluid to enter the assembly and be properly emitted therefrom.
• the first die part includes a first lip and the second die part includes a second lip, these lips defining a feed gap therebetween that determines the thickness of the fluid film emitted therefrom.
• center feed extrusion dies typically have a tear drop-shaped, flat manifold, which may be in a form known as a coat hanger manifold, a fish tail manifold, or a T- type manifold.
• this type of die may further include a flow pressure-compensating preland channel.
• a center feed extrusion die having a two stage, flow pressure-compensating, preland channel. This type of apparatus is exemplified in U.S. Patent No. 4,372,739 to Vetter et al. and U.S. Patent No. 5,256,052 to Cloeren.
• a die assembly can have a fixed feed gap or a flexible feed gap.
• the lips are not movable relative to each other, so that the thickness of the feed gap will always be the same dimension.
• a flexible feed gap one lip is movable relative to the other lip so as to enable adjustment of the feed gap along the width of the assembly.
• a flexible feed gap is typically accomplished by assembling the first die part so that it contains a flexible web between its rear portion and its front portion (to which the first lip is attached), as well as means for moving the front portion in localized areas. Movement of the front portion results in the adjustment of the position of the lip relative to the other lip and, thus, the thickness of the feed gap in the relevant localized area.
• Microporous polyolefin membranes are useful as separators for primary batteries and secondary batteries such as lithium ion secondary batteries, lithium-polymer secondary batteries, nickel-hydrogen secondary batteries, nickel- cadmium secondary batteries, nickel-zinc secondary batteries, silver-zinc secondary batteries, etc.
• the batteries it is desirable for the batteries to have a relatively low shutdown temperature and a relatively high meltdown temperature for improved battery safety, particularly for batteries exposed to high temperatures under operating conditions. Consistent dimensional properties, such as film thickness, are essential to high performing films. A separator with high mechanical strength is desirable for improved battery assembly and fabrication, and for improved durability.
• the optimization of material compositions, casting and stretching conditions, heat treatment conditions, etc. have been proposed to improve the properties of microporous polyolefin membranes.
• microporous polyolefin membranes consisting essentially of polyethylene (i.e., they contain polyethylene only with no significant presence of other species) have relatively low meltdown temperatures. Accordingly, proposals have been made to provide microporous polyolefin membranes made from mixed resins of polyethylene and polypropylene, and multi-layer, microporous polyolefin membranes having polyethylene layers and polypropylene layers in order to increase meltdown temperature. The use of these mixed resins and the production of multilayer films having layers of differing polyolefins can make the production of films having consistent dimensional properties, such as film thickness, all the more difficult.
• a solvent is mixed with the thermoplastic material, which may be a polyolefin, to form a solution.
• the thermoplastic material which may be a polyolefin
• heat is added to the system and gaseous fumes formed and emitted to the system's environment.
• These fumes which can contain solvent, liquid paraffin, and the like, can condense to form an oil-like substance under the cooler ambient conditions surrounding the extrusion die, particularly in the region of die outlet and the first chill roll. Further condensation can result at or near the first chill roll due to the cooling of the extrudate and the generally cooler ambient conditions in the region surrounding the first chill roll.
• the oily condensate can cause surface defects in the extrudate if it lands upon extrudate.
• JP7-2161 18A discloses a battery separator formed from a porous film comprising polyethylene and polypropylene as indispensable components and having at least two microporous layers each with different polyethylene content.
• the polyethylene content is 0 to 20% by weight in one microporous layer, 21 to 60% by weight in the other microporous layer, and 2 to 40% by weight in the overall film.
• the battery separator has relatively high shutdown- starting temperature and mechanical strength.
• WO 2004/089627 discloses a microporous polyolefin membrane made of polyethylene and polypropylene comprising two or more layers, the polypropylene content being more than 50% and 95% or less by mass in at least one surface layer, and the polyethylene content being 50 to 95% by mass in the entire membrane.
• WO 2005/113657 discloses a microporous polyolefin membrane having conventional shutdown properties, meltdown properties, dimensional stability and high- temperature strength. The membrane is made using a polyolefin composition comprising (a) composition comprising lower molecular weight polyethylene and higher molecular weight polyethylene, and (b) polypropylene.
• This microporous polyolefin membrane is produced by a so-called "wet process”.
• a system for producing an extrudate comprising polymer and diluent including an extrusion die having a die outlet that includes a first die lip and a second die lip through which a mixture of polymer and diluent is extruded, and a chill roll for cooling the extrudate, an apparatus for protecting a cooled extrudate, the apparatus including a plate having a leading edge, a first end and a second end, the plate having a width that increases from the first end to the second end, along the leading edge; and means for attaching the plate adjacent to the first die lip of the extrusion die.
• a process for producing an extrudate comprising a mixture of polymer and diluent, e.g., thermoplastic material.
• the process includes the steps of combining at least one polymer, e.g., a polyolefin composition, and a diluent (e.g., solvent) to prepare a mixture (e.g., a polyolefin solution), and extruding the mixture through an extrusion die, the extrusion die comprising a die outlet (which can be a slotted die outlet) through which the mixture is extruded, the die outlet comprising a first die lip and a second die lip, cooling the extrudate to form a cooled extrudate, protecting the cooled extrudate from condensate through the use of an apparatus that includes a plate having a leading edge, a first end and a second end, the plate having a width that increases from the first end to the second end, along the leading edge, and means for attaching
• a mixture e.g
• the apparatus for protecting a cooled extrudate from condensate includes a guide for directing accumulated condensate oil away from the cooled extrudate.
• the guide may further include an elongated member of a length sufficient to direct accumulated condensate oil to an oil collection device.
• the means for attaching the plate adjacent to the first die lip of the extrusion die includes a first bracket fastened to the first end of the plate and a second bracket fastened to the second end of the plate.
• the means for attaching the plate adjacent to the first die lip of the extrusion die further includes a longitudinal support member, the longitudinal support member fastened to the plate adjacent an edge opposing the leading edge.
• the process further includes the steps of exhausting process gases to minimize condensation, and, consistent with a wet orientation process, removing the solvent from the cooled extrudate to form a solvent-removed cooled extrudate, and drying the solvent-removed cooled extrudate to form the microporous membrane.
• FIG. 1 is a perspective view of an apparatus for protecting a cooled extrudate of thermoplastic material, in accordance herewith;
• FIG. 2 is another perspective view of the apparatus for protecting a cooled extrudate of thermoplastic material, in accordance herewith;
• FIG. 3 is yet another perspective view of the apparatus for protecting a cooled extrudate of thermoplastic material, which also shows a system for handling extrusion process air, in accordance herewith.
• FIGS. 1-3 wherein like numerals are used to designate like parts throughout.
• System 10 includes an extrusion die 12 having a die outlet (not shown) which includes a first die lip and a second die lip (also not shown), through which a polymer solution is extruded to form an extrudate 16.
• the heated melt stream is supplied to extrusion die 12 by heated hose 44, after filtering through filter 46.
• Extrudate 16 advances to a first chill roll 18 for cooling the extrudate 16 and may pass to a second chill roll 14 and other additional chill rolls (not shown) for further cooling.
• a diluent is mixed with at least one polymer, which may be a polyolefin or polyolefin composition, to form a mixture (e.g., a polyolef ⁇ n solution).
• a mixture e.g., a polyolef ⁇ n solution.
• heat is added to the system and gaseous fumes formed and emitted to the system's environment.
• fumes which can contain solvent, liquid paraffin, and the like, can condense to form an oil-like substance under the cooler ambient conditions surrounding die 12, particularly in the region of die outlet 14 and first chill roll 18.
• Apparatus 20 includes a plate 50 having a leading edge 52, a first end 54 and a second end 56. As shown, plate 50 has a width w that increases from first end 54 to second end 56, along leading edge 52.
• Apparatus 20 further includes means 60 for attaching plate 50 to a region adjacent the first die lip of die outlet 14 of extrusion die 12. [0031] As shown by reference to FIGS. 1-3, plate 50 of apparatus 20 may be positioned above chill roll 18 and cooled extrudate 16. When positioned in this manner, extrudate 16 is protected from condensate oil that may condense and land upon extrudate 16.
• apparatus 20 includes a guide 30 for directing accumulated condensate oil away from cooled extrudate 16.
• guide 30 may further include an elongated member 32, which may be selected to be of a length sufficient to direct accumulated condensate oil to an oil collection device 36 (see FIG. 3).
• Elongated member 32 may be a chain, a cord, a hollow tube, or the like and, in the form depicted in FIGS. 1-3, is a chain.
• guide 30 for directing accumulated oil away from the cooled extrudate 16 further includes a downwardly extending portion 38 of plate 20, formed at second end 56. As shown, elongated member 38 may be attached to downwardly extending portion 38 of plate 20.
• the means for attaching plate 50 adjacent to the first die lip of die outlet 14 of extrusion die 12 may be selected from any number of conventional means, including brackets extending from the die assembly or chill roll frame, welding directly to a portion of the die assembly frame or the like.
• means 60 for attaching plate 50 adjacent to the first die lip of die outlet 14 of extrusion die 12 may include a first bracket 22 fastened to first end 54 of plate 50 and a second bracket 22 fastened to second end 56 of plate 50.
• Means 60 for attaching plate 50 adjacent to the first die lip of die outlet 14 of extrusion die 12 may further include a longitudinal support member 24, longitudinal support member 24 fastened to plate 50 adjacent an edge 58 opposing leading edge 52.
• first bracket 22, second bracket 22 and longitudinal support member 24 are fastened to plate 50 with a plurality of bolts 26.
• welding or other fastening means may be utilized in the alternative, as those skilled in the art will plainly understand.
• Plate 50 of apparatus 20 may be formed from a variety of materials, so long as the material selected can withstand the extrusion environment, as those skilled in the art will recognize.
• plate 50 is a metal plate and may be steel, aluminum or a suitable alloy.
• Air handling system 40 for minimizing the impact of gaseous fumes formed and emitted to the extrusion system's environment is shown. As indicated above, these fumes, which can contain solvent, liquid paraffin, and the like, can condense to form an oil-like substance under the cooler ambient conditions surrounding die 12, particularly in the region of die outlet 14 and first chill roll 18. Air handling system 40 advantageously minimizes their impact. [0037] Air handling system 40 provides extrusion die 12 with a means for exhausting fumes generated during extrusion. Gaseous fumes generated by extrusion system 10 are evacuated at exhaust hood 46 and transferred away by exhaust hose 48. Additionally, and, as also shown in FIG.
• fumes generated by extrusion system 10 are evacuated in the region of the die outlet by one or more exhaust tubes 34.
• the potential for generating oily condensate that could be deposited on extrudate 16 may be greatly reduced.
• the apparatus and system disclosed herein overcome a difficulty when extruding a mixture of polymer and diluent, e.g., a polyolefin solution, through a die in a variety of processes, including a "wet" microporous membrane film or sheet process.
• a mixture of polymer and diluent e.g., a polyolefin solution
• diluent e.g., a polyolefin solution
• These films and sheets have at least one layer, e.g., single layer comprising polyethylene and/or polypropylene, but the number of layers is not critical. These films and sheets find particular utility in the critical field of battery separators.
• the invention is compatible with the production of multi-layer films described herein below, which can either be produced using a coextrusion die or be produced using a monolayer die to produce a monolayer film or sheet, with additional layers laminated thereto in a conventional manner.
• the invention is also compatible with the production of monolayer film.
• the multi-layer, microporous membrane comprises two layers.
• the first layer e.g., the skin, top or upper layer of the membrane
• the second layer e.g., the bottom or lower or core layer of the membrane
• the membrane can have a planar top layer when viewed from above on an axis approximately perpendicular to the transverse and longitudinal (machine) directions of the membrane, with the bottom planar layer hidden from view by the top layer.
• the extrusion dies described herein are also useful for producing monolayer microporous membranes, e.g., monolayer polyethylene microporous membranes and/or monolayer polyolefin membranes of the type disclosed in PCT Publication WO2007/132942, for example, which is incorporated by reference herein in its entirety.
• the multi-layer, microporous membrane comprises three or more layers, wherein the outer layers (also called the "surface” or “skin” layers) comprise the first microporous layer material and at least one core or intermediate layer comprises the second microporous layer material.
• the multilayer, microporous polyolefin membrane comprises two layers
• the first layer consists essentially of the first microporous layer material
• the second layer consists essentially of the second microporous layer material.
• the multilayer, microporous polyolefin membrane comprises three or more layers
• the outer layers consist essentially of the first microporous layer material and at least one intermediate layer consists essentially of (or consists of) the second microporous layer material.
• Such membranes are described in PCT Publication WO2008/016174, US2008/0057388, and US2008/0057389, which are incorporated by reference herein in their entirety.
• the first microporous layer material contains a first polyethylene (“PE-I”) having an Mw value of less than about 1 x 10 or a second polyethylene (“UHMWPE-I”) having an Mw value of at least about 1 x 10 6 .
• the first microporous layer material can contain a first polypropylene (“PP- 1").
• the first microporous layer material comprises one of (i) a polyethylene (PE), (ii) an ultra high molecular weight polyethylene (UHMWPE), (iii) PE-I and PP-I, or (iv) PE-I, UHMWPE-I, and PP-I .
• UHMWPE-I can preferably have an Mw in the range of from about 1 x 10 6 to about 15 x 10 6 or from about 1 x 10 6 to about 5 x 10 6 or from about 1 x 10 6 to about 3 x 10 6 , and preferably contain greater than about 1 wt.%, or about 15 wt.% to 40 wt.%, on the basis of total amount of PE-I and UHMWPE-I in order to obtain a microporous layer having a hybrid structure as described in WO2008/016174, and can be at least one of homopolymer or copolymer.
• PP-I can be at least one of a homopolymer or copolymer, or can preferably contain no more than about 25 wt.%, on the basis of total amount of the first layer microporous material.
• the Mw of polyolefin in the first microporous layer material can have about 1 x 10 6 or less, or in the range of from about 1 x 10 5 to about 1 x 10 6 or from about 2 x 10 5 to about 1 x 10 6 in order to obtain a microporous layer having a hybrid structure defined in the later section.
• PE-I can preferably have an Mw ranging from about 1 x 10 4 to about 5 x 10 5 , or from about 2 x 10 5 to about 4 x 10 5 , and can be one or more of a high-density polyethylene, a medium-density polyethylene, a branched low-density polyethylene, or a linear low- density polyethylene, and can be at least one of a homopolymer or copolymer.
• the second microporous layer material comprises one of: (i) a fourth polyethylene having an Mw of at least about 1 x 10 6 , (UHMWPE-2), (ii) a third polyethylene having an Mw that is less than 1 x 10 6 and UHMWPE-2 and the fourth polyethylene, wherein the fourth polyethylene is present in an amount of at least about 8% by mass based on the combined mass of the third and fourth polyethylene; (iii) UHMWPE-2 and PP-2, or (iv) PE-2, UHMWPE-2, and PP-2.
• UHMWPE-2 can contain at least about 8 wt.%, or at least about 20 wt.%, or at least about 25 wt.%, based on the total amount of UHMWPE-2, PE-2 and PP-2 in order to produce a relatively strong multi-layer, microporous polyolefin membrane.
• PP-2 can be at least one of a homopolymer or copolymer, and can contain 25 wt.% or less, or in the range of from about 2% to about 15%, or in the range of from about 3% to about 10%, based on the total amount of the second microporous layer material.
• preferable PE-2 can be the same as PE-I, but can be selected independently.
• preferable UHMWPE-2 can be the same as UHMWPE-I, but can be selected independently.
• each of the first and second layer materials can optionally contain one or more additional polyolefins, and/or a polyethylene wax, e.g., one having an Mw in the range of about 1 x 10 3 to about 1 x 10 4 , as described in US2008/0057388.
• a process for producing a two-layer microporous polyolefin membrane wherein an extrusion die and manifold system of the type disclosed herein is employed.
• the microporous polyolefin membrane has at least three layers and is produced through the use of an extrusion die and manifold system of the type disclosed herein. The production of the microporous polyolefin membrane will be mainly described in terms of two-layer and three-layer membrane.
• a three-layer microporous polyolefin membrane comprises first and third microporous layers constituting the outer layers of the microporous polyolefin membrane and a second (core) layer situated between (and optionally in planar contact with) the first and third layers.
• the first and third layers are produced from a first polyolefin solution and the second (core) layer is produced from a second polyolefin solution.
• a method for producing the multi-layer, microporous polyolefin membrane comprises the steps of (1) combining (e.g., by melt- blending) a first polyolefin composition and at least one diluent (e.g., a membrane- forming solvent) to prepare a first mixture of polyolefin and diluent, e.g., a first polyolefin solution, (2) combining a second polyolefin composition and at least a second diluent (e.g., a second membrane-forming solvent) to prepare a second mixture of polyolefin and diluent, e.g., a second polyolefin solution, (3) extruding the first and second polyolefin solutions through at least one die of the type disclosed herein to form a multi-layer extrudate, (4) optionally cooling the multi-layer extrudate to form a cooled extrudate, (5) removing at
• An optional stretching step (7), and an optional hot solvent treatment step (8) can be conducted between steps (4) and (5), if desired.
• an optional step (9) of stretching a multi-layer, microporous membrane, an optional heat treatment step (10), an optional cross-linking step with ionizing radiation (11), and an optional hydrophilic treatment step (12), etc. can be conducted.
• the first polyolefin composition comprises polyolefin resins as described above that can be combined, e.g., by dry mixing or melt blending with an appropriate membrane-forming solvent to produce the first polyolefin solution.
• the first polyolefin solution can contain various additives such as one or more antioxidant, fine silicate powder (pore-forming material), etc., as disclosed in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• the first and second diluents can be solvents that are liquid at room temperature. Suitable diluents include those described in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• the resins, etc., used to produce to the first polyolefin composition are melt-blended in, e.g., a double screw extruder or mixer.
• a conventional extruder or mixer or mixer-extruder
• a double-screw extruder can be used to combine the resins, etc., to form the first polyolefin composition.
• the diluent can be added to the polyolefin composition (or alternatively to the resins used to produce the polyolefin composition) at any convenient point in the process.
• the solvent can be added to the polyolefin composition (or its components) at any of (i) before starting melt-blending, (ii) during melt blending of the first polyolefin composition, or (iii) after melt-blending, e.g., by supplying the first membrane-forming solvent to the melt-blended or partially melt- blended polyolefin composition in a second extruder or extruder zone located downstream of the extruder zone used to melt-blend the polyolefin composition.
• the amount of the first polyolefin composition in the first polyolefin solution is not critical. In one form, the amount of first polyolefin composition in the first polyolefin solution can range from about 1 wt.% to about 75 wt.%, based on the weight of the polyolefin solution, for example from about 20 wt.% to about 70 wt.%. The remainder of the polyolefin solution can be the solvent.
• the polyolefin solution can be about 30 wt.% to about 80 wt.% solvent (or diluent) based on the weight of the polyolefin solution.
• the second polyolefin solution can be prepared by the same methods used to prepare the first polyolefin solution.
• the second polyolefin solution can be prepared by melt-blending a second polyolefin composition with a second membrane- forming solvent.
• the amount of the second polyolefin composition in the second polyolefin solution is not critical.
• the amount of second polyolefin composition in the second polyolefin solution can range from about 1 wt.% to about 75 wt.%, based on the weight of the second polyolefin solution, for example from about 20 wt.% to about 70 wt.%.
• the remainder of the polyolefin solution can be the solvent.
• the polyolefin solution can be about 30 wt.% to about 80 wt.% solvent (or diluent) based on the weight of the polyolefin solution.
• extrusion dies of the type disclosed herein are used for forming an extrudate that can be co-extruded or laminated.
• extrusion dies which can be adjacent or connected, are used to form the extrudates.
• the first and second sheet dies are connected to first and second extruders, respectively, where the first extruder contains the first polyolefin solution and the second extruder contains the second polyolefin solution.
• lamination if used is generally easier to accomplish when the extruded first and second polyolefin solution are still at approximately the extrusion temperature.
• first, second, and third dies are connected to first, second and third extruders, where the first and third dies contain the first polyolefin solutions, and the second die contains the second polyolefin solution.
• a laminated extrudate is formed constituting outer layers comprising the extruded first polyolefin solution and one intermediate comprising the extruded second polyolefin solution.
• the first, second, and third dies are connected to first, second, and third extruders, where the second die contains the first polyolefin solution, and the first and third dies contain the second polyolefin solution.
• a laminated extrudate is formed constituting outer layers comprising the extruded second polyolefin solution and one intermediate comprising extruded first polyolefin solution.
• the die gaps are generally not critical.
• extrusion dies of the type disclosed herein can have a die gap of about 0.1 mm to about 5 mm.
• Die temperature and extruding speed are also non-critical parameters.
• the dies can be heated to a die temperature ranging from about 140°C to about 250 0 C during extrusion.
• the extruding speed can range, for example, from about 0.2 m/minute to about 15 m/minute.
• the thickness of the layers of the layered extrudate can be independently selected.
• the resultant sheet can have relatively thick skin or surface layers compared to the thickness of an intermediate layer of the layered extrudate.
• the multi-layer extrudate can be cooled. Cooling rate and cooling temperature are not particularly critical. Suitable cooling methods are described in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• at least a portion of the first and second membrane-forming solvents are removed (or displaced) from the multi-layer extrudate in order to form the multi-layer, microporous membrane. Suitable methods for removing the solvents (diluents) are described in WO2008/016174, US2008/0057388, and US2008/0057389, for example. A washing solvent can be used, for example.
• any remaining volatile species in the membrane e.g., the washing solvent
• Suitable methods for removing the volatile species are disclosed in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• the extrudate Prior to the step for removing the membrane-forming solvents, the extrudate can be stretched in order to obtain an oriented extrudate. Suitable methods for stretching the extrudate or cooled extrudate are disclosed in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• the extrudate can be treated with a hot solvent as described in WO 2000/20493.
• the microporous membrane can be stretched at least monoaxially after removal of at least a portion of the diluent.
• the stretching method selected is not critical, and conventional stretching methods can be used such as by a tenter method, etc.
• the stretching of the dry microporous polyolef ⁇ n membrane can be called dry-stretching, re- stretching, or dry-orientation. Suitable stretching methods are disclosed in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• the stretching magnification is not critical.
• the stretching magnification of the microporous membrane can range from about 1.1 fold to about 2.5 or about 1.1 to 2.0 fold in at least one lateral (planar) direction. Biaxial stretching can be used, and the stretching magnification need not by symmetric.
• the microporous membrane can be heat-treated and/or annealed.
• the microporous membrane can also be cross-linked if desired [e.g., by ionizing radiation rays such as a-rays, (3-rays, 7-rays, electron beams, etc.)] or can be subjected to a hydrophilic treatment [i.e., a treatment which makes the microporous polyolefin membrane more hydrophilic (e.g., a monomer-grafting treatment, a surfactant treatment, a corona-discharging treatment, etc.)].
• a hydrophilic treatment i.e., a treatment which makes the microporous polyolefin membrane more hydrophilic (e.g., a monomer-grafting treatment, a surfactant treatment, a corona-discharging treatment, etc.)].
• Suitable methods for membrane heat treatment, annealing, crosslinking, etc. are described in WO2008/016174, US2008/0057388, and US2008/0057389, for example.
• methods for producing the microporous membrane such as those described in WO2008/016174 (for multi-layer membranes) and in WO2007/132942 (for monolayer membranes) can also be used.
• extrusion has been described in terms of producing two and three- layer extrudates, the extrusion step is not limited thereto.
• a plurality of dies and/or die assemblies can be used to produce multi-layer extrudates having four or more layers using the principles of the extrusion dies and methods disclosed herein.
• All patents, test procedures, and other documents cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent and for all jurisdictions in which such incorporation is permitted.
• the illustrative forms disclosed herein have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

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• 2008
  • 2008-09-30 WO PCT/JP2008/068129 patent/WO2009044906A1/en not_active Ceased
  • 2008-09-30 JP JP2010513511A patent/JP5162660B2/ja not_active Expired - Fee Related

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