Polyolefin-based microporous films via sequential cold and hot stretching of unannealed polypropylene copolymer films

Abstract

To provide an improved breathable film.SOLUTION: Microporous polymer films and methods of making the same are disclosed. The microporous polymer film comprises: (a) 50-95 wt.% of a polypropylene copolymer comprising (i) polypropylene homopolymer chain segments in a total amount of 50-82 wt.% and (ii) ethylene-containing copolymer chain segments in a total amount of 18-50 wt.%, wherein at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 wt.% of the ethylene-containing copolymer chain segments; and (b) 5-50 wt.% of an ethylene-propylene elastomer, wherein at least 45 wt.% of the polymerized units in the ethylene-propylene elastomer are ethylene units.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to microporous films and their applications in a variety of end uses, such as house wraps, roof membranes, active and medical packaging, and hygiene and medical articles.

[0002] The present invention provides microporous polymer films derived from specific polypropylene (PP) copolymers containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments. The PP copolymer microporous films disclosed herein are produced without conventional means for achieving porosity, i.e., without the use of inorganic fillers, perforation, or extensive pre-annealing to create the favorable crystalline morphology practiced with homopolymer polyolefins, which can cause voiding. Instead, film porosity is achieved by using specific types of PP copolymers to produce non-porous films, followed by a sequential cold / hot stretching process that results in microphase separation-induced pore formation in the polyolefin-based films disclosed herein. One advantageous feature of the method disclosed herein is that the non-porous films do not require an annealing step prior to the cold / hot stretching process, and do not require a heat setting or annealing step after the cold / hot stretching process.

[0003] This specification describes process steps and methods for producing and using PP copolymer compositions and microporous films thereof. In particular, these microporous films can be manufactured to provide moisture vapor permeability while maintaining an effective barrier against liquid water, and these permeabilities can be tailored. The balance of properties of the microporous films disclosed herein suggests that these films may find use in applications such as house wraps, roof membranes, and hygiene and medical articles, packaging (including active packaging and medical packaging), and filtration. [Background technology]

[0004] Microporous films, methods for producing them, and their uses are described herein. The present invention provides a cost-effective and environmentally friendly way to create microporous structures in polyolefin-based films through extrusion film casting / blowing and dry-stretching processes. The pore size and porosity of these microporous films can be tailored to achieve optimized performance in various end-use applications (e.g., for house wrap applications, films can be manufactured to have porosity and permeability properties comparable to commercially available products such as Tyvek® house wrap from DuPont de Nemours, Inc., Wilmington, DE, USA). Alternatively, smaller pore sizes can provide a barrier to air migrating through walls. According to the U.S. Department of Energy, up to 40% of the energy consumed to heat or cool a building is lost due to air leakage.

[0005] A variety of end-use applications require, or at least benefit from, the use of breathable films, which may be described as films that are relatively permeable to water vapor and relatively impermeable to liquids.

[0006] Housewrap functions as a weatherproof barrier, preventing rain from entering the wall assembly while allowing water vapor to pass to the outside. Therefore, to be effective, housewrap must be water-repellent and have a high water vapor transmission rate (permeability). Currently, housewrap can be categorized into two categories: woven and perforated, and nonwoven and nonperforated. Perforated wrap, which is generally less expensive, is made from polyethylene or polypropylene that has been microscopically perforated to make it permeable, while nonperforated wrap consists of a polyolefin layer that allows water vapor to pass through its nonwoven fibrous mesh. Current technology generally involves multiple steps for the manufacturing process.

[0007] In addition, the present invention provides a polyolefin-based microporous film for roof membrane applications. There is a significant market need for breathable roof membranes. Current non-permeable roof membranes made from polyvinyl chloride (PVC), thermoplastic polyolefins (TPO), or polymerized ethylene propylene diene monomer (EPDM) cannot meet this need, and polyolefin-based microporous films offer an opportunity to provide a low-cost alternative with higher water vapor permeability compared to such current membranes. The low / low water vapor permeability of current roof membranes leads to moisture accumulation under the roof membrane, which over time causes delamination of the roof membrane from the roof (e.g., lightweight concrete structures) and subsequent failure of the roof structure. The higher water vapor permeability of thick polyolefin-based microporous films satisfies important requirements for roof membranes, such as high moisture vapor permeability (permeability), e.g., 10 perm or more; and good water repellency (weather-resistant barrier). The weatherability of polyolefin-based microporous films can be further enhanced by applying UV-resistant agents.

[0008] Polyethylene films are widely used in sanitary absorbent products, such as diaper backsheets. Diaper backsheets can be classified as breathable or non-breathable. Breathable backsheets typically use films filled with more than 50% by weight of CaCO (or other inorganic fillers) and / or microvoided. However, due to vigorous competition in the sanitary absorbent product market, film manufacturers are being prompted to pursue differentiation technologies that enable enhanced product performance, such as improved mechanical property performance, while also enabling cost reductions, preferably through further downgauging (thinner films). Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, in many end-use markets, there is a need for improved breathable films that have a very thin gauge and high porosity that allows for high water vapor transmission while preventing liquid water leakage and ensuring good processability and mechanical properties. The non-interconnected micropores of the microporous films disclosed herein provide better barrier performance against air, water, bacteria, and blood, which is essential for applications such as house wraps, roofing membranes, air filtration, medical packaging, and medical back table covers. The relatively high melting temperature of PP copolymers allows their application in steam sterilization related to medical packaging. The wide range of adjustable breathability also suggests that these microporous films may be suitable for active packaging (sachets) applications.

[0010] Furthermore, microporous films comprising PP copolymers having a lower tensile modulus are believed to be particularly desirable for some applications because the tensile modulus of the film is related to the flexibility of the film, and such lower tensile modulus films have the potential for improved toughness, hot air welding installation, and low temperature durability.

[0011] Thus, there exists a need for compositions containing the polypropylene copolymer compositions described herein, microporous films made therefrom, methods for preparing them, and methods for using them. The invention disclosed herein addresses these and other important objectives and provides a solution to these market needs. [Means for solving the problem]

[0012] In certain embodiments, the invention described herein comprises, consists of, or consists essentially of one or more polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments, wherein the microporous polymer film comprises: (i) polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the microporous polymer film, or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the microporous polymer film; and (ii) ethylene-containing copolymer chain segments. and ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt % based on the weight of the microporous polymer film, or 21 to 57 mol % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the microporous polymer film, wherein at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segments, or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segments.

[0013] In one embodiment, a method for forming a microporous polymeric film, the method steps comprising: (a) selecting one or more polypropylene copolymers, (i) one or more polypropylene homopolymer chain segments in a total amount of from 50 to 82 wt. % based on the weight of the polypropylene copolymer, or from 43 to 79 mol. % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; and (ii) one or more ethylene-containing copolymer chain segments in a total amount of from 18 to 50 wt. % based on the weight of the polypropylene copolymer, or from 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer. % total amount of one or more ethylene-containing copolymer chain segments, wherein at least a portion of the ethylene-containing copolymer chain segments contain polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) forming a non-porous film from the polypropylene copolymer; and (c) subjecting the non-porous film to successive cold-stretching and hot-stretching steps, including (i) at least one cold-stretching step at a temperature in the range of -20°C to 50°C, and (ii) at least one hot-stretching step at a temperature in the range of 50°C to 150°C, thereby producing a microporous polymer film. Disclosed is a method comprising, consisting of, or consisting essentially of:

[0014] In some embodiments, the method is a continuous process for producing a microporous polymer film. In particular, in some embodiments, the method proceeds without any annealing step after the formation of the non-porous film, and without any annealing or heat-setting step after the formation of the microporous polymer film, and is a continuous process for producing a microporous polymer film.

[0015] In another embodiment, the present invention relates to a microporous polymeric film comprising: (a) 50 to 95 weight percent, based on the total weight of the film, of one or more polypropylene copolymers, the polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments; the microporous polymer film comprising: (i) polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt. % based on the weight of the polypropylene copolymer or 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the film; and (b) at least 45 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units.

[0016] In yet another alternative embodiment, the present invention further relates to a method of forming a microporous polymeric film, said method steps comprising: A) providing a mixture, the mixture comprising: (a) 50 to 95 weight percent, based on the total weight of the blend, of one or more polypropylene copolymers: (i) one or more polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) one or more ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt. % based on the weight of the polypropylene copolymer or 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the mixture; providing a mixture, wherein at least 45 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units; B) forming a non-porous film from the mixture; and C) A non-porous film. (i) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and (ii) at least one hot drawing step at a temperature in the range of 50°C to 140°C and subjecting the sheet to successive cold and hot drawing steps, thereby producing a microporous polymer film.

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0018] [Figure 1A] 1 shows mercury intrusion porosimetry data for Tyvek® house wrap. [Figure 1B] 1 shows mercury intrusion porosimetry data for PP C7054-07NA microporous films after varying a range of hot stretch conditions. [Figure 2A] 1 shows an SEM image of a film cross section of unstretched PP C7054-07NA film, indicated by the 20 micron scale bar. [Figure 2B] 1 shows an SEM image of the film cross section of stretched PP C7054-07NA film after 25% cold stretching at 100 mm / sec (room temperature) and 50% hot stretching at 5 mm / sec (100° C.), as indicated by the 20 micron scale bar. [Figure 2C] 1 shows an SEM image of the film cross section of stretched PP C7054-07NA film after 25% cold stretching at 100 mm / sec (room temperature) and 50% hot stretching at 5 mm / sec (100° C.), as indicated by the 5 micron scale bar. [Figure 3A]1 shows an SEM image of the film surface of unstretched PP C7054-07NA film, indicated by the 20 micron scale bar. [Figure 3B] 1 shows an SEM image of the film surface of unstretched PP C7054-07NA film, indicated by the 10 micron scale bar. [Figure 3C] FIG. 1 shows an SEM image of the film surface of stretched PP C7054-07NA film after 25% cold stretch at 100 mm / s (room temperature) and 50% hot stretch at 5 mm / s (100° C.), as indicated by the 20 micron scale bar. [Figure 3D] 1 shows an SEM image of the film surface of stretched PP C7054-07NA film after 25% cold stretch at 100 mm / sec (room temperature) and 50% hot stretch at 5 mm / sec (100° C.), indicated by the 10 micron scale bar. [Figure 4A] FIG. 1 shows a TEM image of PP C7054-07NA film before stretching, indicated by a 1 micron scale bar. [Figure 4B] 1 shows a TEM image of PP C7054-07NA film after 25% cold stretching at 100 mm / sec (room temperature) and 100% hot stretching at 5 mm / sec (100° C.), indicated by the 1 micron scale bar. [Figure 4C] 1 shows a TEM image of PP INSPIRE® 114 film before stretching, indicated by the 0.2 micron scale bar. [Figure 4D] 1 shows a TEM image of PP INSPIRE® 114 film after 25% cold stretching at 100 mm / sec (room temperature) and 100% hot stretching at 5 mm / sec (100° C.), as indicated by the 0.2 micron scale bar. [Figure 5A] 1 shows wide-angle X-ray scattering (WAXS) data for PP C7054-07NA film before stretching. [Figure 5B] 1 shows wide angle X-ray scattering (WAXS) data for PP C7054-07NA microporous film after 25% cold stretching (room temperature) at 100 mm / s followed by 100% hot stretching (100° C.) at 5 mm / s. [Figure 5C]1 shows wide-angle X-ray scattering (WAXS) data of PP TI4020N film before stretching. [Figure 5D] 1 shows wide angle X-ray scattering (WAXS) data for PP TI4020N microporous film after 25% cold stretching at 100 mm / s (room temperature) followed by 100% hot stretching at 5 mm / s (100° C.). [Figure 6A] FIG. 1 shows a TEM image of a film from a 20 / 80 blend of homopolymers PP H314 (20%) and PP C7054-07NA (80%) before stretching, indicated by the 1 micron scale bar. [Figure 6B] FIG. 1 shows a TEM image of a film from a 20 / 80 blend of homopolymer PP H314 (20%) and PP C7054-07NA (80%) after a 25% cold stretch at 100 mm / s (room temperature) and a 100% hot stretch at 5 mm / s (100° C.), indicated by the 0.5 micron scale bar. [Figure 7A] 1 shows mercury intrusion porosimetry data for a 762 μm (30 mil) thick film of PP C7054-07NA after 25% cold stretching at 100 mm / sec (room temperature) and 100% hot stretching at 5 mm / sec (100° C.). [Figure 7B] Mercury intrusion porosimetry data for a 762 μm (30 mil) thick film of PP C7054-07NA after a 25% cold stretch (room temperature) at 100 mm / sec, followed by a 150% hot stretch (100° C.) at 5 mm / sec is shown. [Figure 8] One suitable multi-stage drawing process for either cold or hot machine direction orientation (MDO) of film using rolls is shown. [Figure 9] One suitable multi-stage stretching process for transverse direction orientation (TDO) of a film using an oven is shown. [Figure 10] 1 is a TEM image of a cast film made from a polypropylene copolymer comprising polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments before any stretching. [Figure 11]TEM images of a cast film made from (a) 90 weight percent polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments and (b) 10 weight percent ethylene-propylene elastomer before any stretching. [Figure 12] TEM images of a cast film made from (a) 70 weight percent polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments and (b) 30 weight percent ethylene-propylene elastomer before any stretching. [Figure 13] Photographs of the appearance of two welded samples of microporous film made from (a) 70 weight percent polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments and (b) 30 weight percent ethylene-propylene elastomer; specifically, the R30-20 mil film sample. [Figure 14] (a) Photograph of the appearance of two welded samples of microporous film made from a polypropylene copolymer comprising polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments; specifically, a PP-22 mil film sample. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention may be more readily understood by reference to the following detailed description, examples, drawings, and claims, as well as their preceding and following explanations. It should be understood, however, that the present invention is not limited to the specific compositions, articles, devices, systems, and / or methods disclosed, unless expressly stated otherwise, as such may, of course, vary. Although aspects of the invention may be described and claimed in particular statutory classes, such as composition statutory classes, this is for convenience only, and one of ordinary skill in the art will understand that each aspect of the invention may be described and claimed in any statutory class.

[0020] The following detailed description of the present invention is also provided as an enabling teaching of the best currently known mode of the present invention. To this end, those skilled in the art will recognize and appreciate that changes and modifications to the various aspects of the present invention described herein may be made while still obtaining the beneficial results of the present invention. It will also be understood that some of the benefits of the present invention can be obtained by selecting some of the features of the present invention without using other features. Thus, those skilled in the art will recognize that many modifications and adaptations to the present invention are possible and that such modifications and adaptations may even be desirable in certain circumstances and, therefore, are also part of the present invention.

[0021] While the present invention may be embodied in various forms, the following description of some embodiments is made with the understanding that this disclosure is to be considered an example of the invention and is not intended to limit the invention to the particular embodiments illustrated. Headings are provided for convenience only and should not be construed as limiting the invention in any way. Embodiments illustrated under any heading or in any portion of this disclosure may be combined with embodiments illustrated under the same or any other heading or portion of this disclosure.

[0022] Any combination of the elements described herein in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[0023] Unless expressly stated otherwise, it is in no way intended that any method or aspect described herein be construed as requiring that its steps be performed in a particular order. Accordingly, if a method claim does not specifically recite in the claim or description that the steps are limited to a particular order, no order is intended to be inferred in any sense. This applies to all possible non-expressive bases for interpretation, including logical matters regarding the arrangement or operational flow of steps, simple meaning derived from grammatical construction or punctuation, or the number or type of embodiments described herein. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and not restrictive.

[0024] All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited.

[0025] It should be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In this specification and in the claims that follow, reference will be made to a number of terms defined herein.

[0026] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0027] As used herein, the term "and / or" means "and or alternatively."

[0028] As used herein, the term "optional" or "optionally" means that a described event, condition, component, or circumstance may or may not occur, and that the description includes instances in which said event, condition, component, or circumstance occurs and instances in which said event, condition, component, or circumstance does not occur.

[0029] As used herein, any disclosure using the term "comprises" or "comprising" includes similar disclosures, and "comprises" or "comprising" may alternatively be replaced by "consisting of" or "consisting of," or alternatively by "consisting essentially of" or "consisting essentially of."

[0030] As used herein, the phrase "sufficient" (e.g., "conditions sufficient to") refers to a value or condition sufficient to perform the function or property for which such value or condition is manifested. As noted below, the exact values ​​or specific conditions required may vary from embodiment to embodiment depending on recognized variables such as the materials used and / or processing conditions.

[0031] The term "by weight," when used in connection with a component, is based on the total weight of the formulation or composition in which the component is included, unless otherwise specified. For example, when a particular element or component in a composition or article is said to be present in an amount of 8 weight percent (also written as 8 wt.%), this percentage is understood to relate to an overall composition percentage of 100%. The weight percent of component A in a composition is the weight of component A expressed as a percentage of the total weight of the composition, and is conventionally described as "weight percent of A based on the total weight of the composition." In some examples, the weight percent of a component is based on the total weight of the composition on a "dry basis," which refers to the weight of the composition without water (e.g., less than about 1 wt.%, less than about 0.5 wt.%, less than about 0.1 wt.%, less than about 0.05 wt.%, or about 0 wt.% water, based on the total weight of the composition).

[0032] When a numerical value, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., is disclosed herein, the following sentence typically follows such a numerical value: "The foregoing numerical values ​​can each be used in conjunction with the terms 'about,' 'at least about,' or 'less than about,' and any of the foregoing numerical values ​​can be used alone to describe an open-ended range or in combination with a limiting range description." This sentence means that each of the foregoing numerical values ​​can be used alone (e.g., 4), preceded by the word 'about' (e.g., about 8), prefixed with the phrase 'at least about' (e.g., at least about 2), prefixed with the phrase 'less than about' (e.g., less than about 7), or used in any combination with or without any of the preceding words or phrases used to define a range (e.g., 2 to 9, about 1 to 4, 8 to about 9, about 1 to about 10, etc.). Furthermore, when a range is described as "less than or equal to about X," this phrase is instead equivalent to the range that is a combination of 'about X' and 'less than about X.' For example, "about 10 or less" is the same as "about 10 or less than about 10." Such interchangeable range descriptions are contemplated herein. While other range formats are disclosed herein, differences in format should not be construed to imply differences in substance.

[0033] As used herein, "continuous" refers to a process that is continuous in duration or that is interrupted, halted, or stopped only momentarily compared to the duration of the process. A process is "continuous" if starting materials or reactants are supplied to an apparatus without or substantially without interruption, or if the processing of said starting materials or reactants is not carried out in a batch process.

[0034] As used herein, the term "substantially free" means a composition having less than about 1% by weight, e.g., less than about 0.5% by weight, less than about 0.1% by weight, less than about 0.05% by weight, or less than about 0.01% by weight of the indicated substance, based on the total weight of the composition.

[0035] As used herein, the term "substantially," when used in reference to a composition, means at least about 60% by weight, e.g., at least about 65% by weight, at least about 70% by weight, at least about 75% by weight, at least about 80% by weight, at least about 85% by weight, at least about 90% by weight, at least about 91% by weight, at least about 92% by weight, at least about 93% by weight, at least about 94% by weight, at least about 95% by weight, at least about 96% by weight, at least about 97% by weight, at least about 98% by weight, at least about 99% by weight, or about 100% by weight of a particular feature or component, based on the total weight of the composition.

[0036] All molecular weights and other values ​​related to molecular weight (such as polydispersity index) disclosed herein are determined by gel permeation chromatography (GPC).

[0037] As used herein, the terms "molar mass distribution," "MMD," and "molecular weight distribution" are used interchangeably and refer to the number of moles of each polymer species or number of polymer chains (N i ) and the molar mass of the species (M i ) or describes the relationship between polymer chains. The molar mass distribution of a polymer may vary depending on the polymer fraction. Depending on the statistical method applied, different mean values ​​may be defined and are described herein.

[0038] As used herein, "number average molecular weight" (M n , or

number

number

[0039] As used herein, "weight average molecular weight" (Mw, or

number

number

[0040] As used herein, gel permeation chromatography (GPC) refers to a chromatographic separation method in which molecules in a solution are separated by their size. Separation is achieved by differential exclusion of sample molecules as they pass through a bed of porous particles known as a separation column. GPC can be used to determine substantially accurate molar mass distributions of polymer molecules. For example, a constant volume of the liquid fraction (eluent) that passes through the column is collected. As the polymer elutes through the column, molecules too large to pass through the pores of the column are excluded from the packed pore volume and elute at earlier retention times, while smaller molecules enter the pores of the column and elute at later retention times. The concentration of the eluted polymer can be measured by spectroscopic techniques, such as refractive index (RI) and ultraviolet (UV). The eluent stream can also be continuously analyzed by RI, low-angle laser light scattering (LALLS), multi-angle laser light scattering (MALLS), UV, and / or viscosity measurements.

[0041] The use of numerical values ​​in the various quantitative values ​​set forth in this application, unless expressly indicated otherwise, is described as approximations, as if both the minimum and maximum values ​​within the stated range were preceded by the word "about." In this manner, slight variations from the stated values ​​may be used to achieve substantially the same results as the stated values. The disclosure of ranges also contemplates continuous ranges, including every value between the recited minimum and maximum values, and any ranges that may be formed by such values. Also disclosed herein are any and all ratios (and any such ratio ranges) that may be formed by dividing a recited numerical value into any other recited numerical value. Accordingly, those skilled in the art will understand that many such ratios, ranges, and ratio ranges may be explicitly derived from the numerical values ​​presented herein, and that in all instances, such ratios, ranges, and ratio ranges represent various embodiments of the present invention.

[0042] As used herein, "average pore size" refers to the "average pore size" measured by mercury intrusion porosimetry (4 V / A by UOP method 578-11 described below), which is known to those skilled in the art or known in the field of mercury intrusion porosimetry. The UOP method is available from ASTM International, West Conshohocken, PA, USA (or at www.astm.org). Since the average is the median average, the term may be referred to herein as "median pore size."

[0043] As used herein, the term "polypropylene copolymer" refers to a copolymer comprising a polymer backbone, side chains, or chain segments of polypropylene; in particular, such backbone, side chains, or chain segments comprise 15 or more consecutive polymerized units of propylene. As disclosed herein, preferred PP copolymers comprise polypropylene homopolymer chain segments (e.g., isotactic PP) and ethylene-containing copolymer chain segments. In some embodiments, the ethylene-containing copolymer chain segments are ethylene-propylene (EP) copolymer chain segments, and such polypropylene copolymers are sometimes described herein as PP-EP copolymers.

[0044] In some embodiments, the present invention relates to a microporous polymeric film comprising one or more polypropylene copolymers (PP copolymers), which may comprise one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments.

[0045] In some embodiments, the PP copolymer comprises polypropylene homopolymer chain segments in an amount of at least about 50% by weight, based on the total weight of the PP copolymer, and the maximum amount of polypropylene homopolymer chain segments is not particularly limited. In the same or other embodiments, the PP copolymer comprises polypropylene homopolymer chain segments in an amount of up to about 95% by weight, based on the total weight of the PP copolymer, and the minimum amount of polypropylene homopolymer chain segments is not particularly limited. For example, the PP copolymer may comprise polypropylene homopolymer chain segments in an amount of 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 65, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, or 95% (in weight percent based on the weight of the PP copolymer). Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of polypropylene homopolymer chain segments in the PP copolymer can be at least about 50 wt%, about 50 wt% to about 82 wt%, or about 60 wt% to about 82 wt%, by weight based on the total weight of the PP copolymer. In terms of mole %, the PP copolymer can comprise polypropylene homopolymer chain segments in an amount of 40, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 54, 55, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 79, 80, 82, or 85% (in mole % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the PP copolymer). Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range, or in combination to describe a limited range.For example, without limitation, the amount of polypropylene homopolymer chain segments in the PP copolymer can be at least about 43 mol %, about 43 mol % to about 79 mol %, or about 50 mol % to about 79 mol %, based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the PP copolymer.

[0046] In some embodiments, the PP copolymer comprises ethylene-containing copolymer chain segments in an amount of at least about 5 wt% based on the total weight of the PP copolymer, and the maximum amount of ethylene-containing copolymer chain segments is not particularly limited. In the same or other embodiments, the PP copolymer comprises ethylene-containing copolymer chain segments in an amount of up to about 50 wt% based on the total weight of the PP copolymer, and the minimum amount of ethylene-containing copolymer chain segments is not particularly limited. For example, the PP copolymer may comprise 5, 10, 15, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, or 55% (in wt% based on the weight of the PP copolymer) of ethylene-containing copolymer chain segments. Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of ethylene-containing copolymer chain segments in the PP copolymer may be at least about 10 wt.%, about 18 wt.% to about 50 wt.%, or about 25 wt.% to about 40 wt.%, by weight based on the total weight of the PP copolymer. Preferably, the ethylene-containing copolymer chain segments in the PP copolymer are ethylene-propylene (EP) copolymer chain segments. In terms of mole %, the PP copolymer may comprise 10, 15, 17, 18, 19, 20, 21, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55%, 57, or 60% of the ethylene-containing copolymer chain segments (in mole % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the PP copolymer). Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range.For example, but not limited to, the amount of ethylene-containing copolymer chain segments in the PP copolymer can be at least about 15 mol%, about 21 mol% to about 57 mol%, or about 21 mol% to about 45 mol%, based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the PP copolymer.

[0047] In some embodiments, the ethylene-containing copolymer chain segment in the PP copolymer contains at least 45% by weight of polymerized ethylene units based on the total weight of the ethylene-containing copolymer chain segment, and the maximum amount of ethylene in the ethylene-containing copolymer chain segment is not particularly limited. For example, the ethylene unit content in the ethylene-containing copolymer chain segment in the PP copolymer can be 40, 42, 44, 45, 46, 47, 48, 49, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 75, or 80% (in weight % based on the weight of the ethylene-containing copolymer chain segment). Each of the above numbers can be preceded by the words "about," "at least about," or "less than about," and any of the above numbers can be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of ethylene units in the ethylene-containing copolymer chain segment in the PP copolymer can be at least about 45 wt%, about 45 wt% to about 80 wt%, or about 45 wt% to about 60 wt%, based on the total weight of the ethylene-containing copolymer chain segment. In terms of mole percent, the ethylene unit content in the ethylene-containing copolymer chain segment in the PP copolymer can be an amount of 50, 52, 54, 55, 56, 57, 58, 59, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 85, or 90% (in mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment). Each of the foregoing numbers can be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers can be used alone to describe an open-ended range or in combination to describe a limited range. For example, but not limited to, the amount of ethylene units in the ethylene-containing copolymer chain segment in the PP copolymer can be at least about 55 mol %, about 55 mol % to about 80 mol %, or about 55 mol % to about 69 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.Preferably, the ethylene-containing copolymer chain segment in the PP copolymer is an ethylene-propylene (EP) copolymer chain segment, in which case the above percentages refer to the % ethylene unit content (either by weight or by mole, as above) in the EP copolymer chain segment.

[0048] The total ethylene content in polymerized form in the PP copolymer is at least 10 wt. %, such as from 10 to 30 wt. % or even from 15 to 25 wt. %, based on the weight of the PP copolymer, or at least 14 mol. %, such as from 14 to 39 mol. % or from 15 to 25 mol. %, based on the molar content of polymerized units of ethylene in the PP copolymer, as a percentage of the total molar content of polymerized monomer units in the PP copolymer.

[0049] The microporous polymer film can consist essentially of one or more polypropylene copolymers (PP copolymers) comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments. Thus, in at least some embodiments, the same amounts and ranges outlined above for the polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments in the PP copolymer are also appropriate for the amounts and ranges of the polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments in the microporous polymer film.

[0050] In some embodiments, the microporous polymer film comprises at least about 50% by weight of polypropylene homopolymer chain segments based on the total weight of the microporous polymer film, and the maximum amount of polypropylene homopolymer chain segments is not particularly limited. In the same or other embodiments, the microporous polymer film comprises up to about 95% by weight of polypropylene homopolymer chain segments based on the total weight of the microporous polymer film, and the minimum amount of polypropylene homopolymer chain segments is not particularly limited. For example, the microporous polymer film may comprise 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, or 95% of the polypropylene homopolymer chain segments (by weight based on the weight of the microporous polymer film). Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of polypropylene homopolymer chain segments in the microporous polymer film may be at least about 50 wt.%, about 50 wt.% to about 82 wt.%, or about 60 wt.% to about 82 wt.%, based on the total weight of the microporous polymer film. In terms of mole percent, the microporous polymer film can comprise polypropylene homopolymer chain segments in an amount of 40, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 54, 55, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 79, 80, 82, or 85% (in mole percent based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the microporous polymer film). Each of the foregoing numbers can be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers can be used alone to describe an open-ended range or in combination to describe a limited range.For example, but not limited to, the amount of polypropylene homopolymer chain segments in the microporous polymer film can be at least about 43 mol%, about 43 mol% to about 79 mol%, or about 50 mol% to about 80 mol%, based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the microporous polymer film.

[0051] The polypropylene homopolymer chain segments present in the microporous polymer film may be derived solely from the PP copolymer component, or may be a combination of polypropylene homopolymer chain segments derived from the PP copolymer component and one or more other polymer components (PP homopolymer or other copolymers containing polypropylene homopolymer chain segments) that contain polypropylene homopolymer chain segments. Preferably, the polypropylene homopolymer chain segments present in the microporous polymer film are derived solely from the PP copolymer component.

[0052] In some embodiments, the microporous polymer film comprises an ethylene-containing copolymer chain segment in an amount of at least about 5 wt% based on the total weight of the microporous polymer film, and the maximum amount of the ethylene-containing copolymer chain segment is not particularly limited. In the same or other embodiments, the microporous polymer film comprises an ethylene-containing copolymer chain segment in an amount of up to about 60 wt% based on the total weight of the microporous polymer film, and the minimum amount of the ethylene-containing copolymer chain segment is not particularly limited. For example, the microporous polymer film may comprise an ethylene-containing copolymer chain segment in an amount of 5, 10, 15, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 56, 58, or 60% (in wt% based on the weight of the microporous polymer film). Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of ethylene-containing copolymer chain segments in the microporous polymer film may be at least about 10 wt.%, about 18 wt.% to about 50 wt.%, or about 25 wt.% to about 40 wt.%, based on the total weight of the microporous polymer film. In terms of mole percent, the microporous polymer film may comprise 10, 15, 17, 18, 19, 20, 21, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 57, or 60% of the ethylene-containing copolymer chain segment (in mole percent based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units in the microporous polymer film). Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range.For example, but not limited to, the amount of ethylene-containing copolymer chain segments in the microporous polymer film can be at least about 15 mol%, about 21 mol% to about 57 mol%, or about 20 mol% to about 45 mol%, based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the microporous polymer film.

[0053] The ethylene-containing copolymer chain segments present in the microporous polymer film may be derived solely from the PP copolymer component, or may be a combination of ethylene-containing copolymer chain segments derived from the PP copolymer component and one or more other polymer components (e.g., EP copolymers) containing ethylene-containing copolymer chain segments. Preferably, the ethylene-containing copolymer chain segments present in the microporous polymer film are derived solely from the PP copolymer component. Preferably, the ethylene-containing copolymer chain segments are ethylene-propylene (EP) copolymer chain segments.

[0054] In some embodiments, the ethylene-containing copolymer chain segment in the microporous polymer film contains at least 45% by weight of ethylene polymerized units based on the total weight of the ethylene-containing copolymer chain segment, and the maximum amount of ethylene in the ethylene-containing copolymer chain segment is not particularly limited. For example, the ethylene unit content in the ethylene-containing copolymer chain segment in the microporous polymer film can be 40, 42, 44, 45, 46, 47, 48, 49, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 75, or 80% (in weight % based on the weight of the ethylene-containing copolymer chain segment). Each of the above numbers can be preceded by the words "about," "at least about," or "less than about," and any of the above numbers can be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the amount of ethylene units in the ethylene-containing copolymer chain segment in the microporous polymer film can be at least about 45 wt%, about 45 wt% to about 80 wt%, or about 45 wt% to about 60 wt%, based on the total weight of the ethylene-containing copolymer chain segment. In terms of mole %, the ethylene unit content in the ethylene-containing copolymer chain segment in the microporous polymer film can be in an amount of 50, 52, 54, 55, 56, 57, 58, 59, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 85, or 90% (in mole % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment). Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range, or in combination to describe a limited range.For example, but not limited to, the amount of ethylene units in the ethylene-containing copolymer chain segment in the microporous polymer film can be at least about 55 mol%, about 55 mol% to about 80 mol%, or about 55 mol% to about 69 mol%, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment. Preferably, the ethylene-containing copolymer chain segment in the PP copolymer is an ethylene-propylene (EP) copolymer chain segment, and in that case, the above percentages refer to the % ethylene unit content (either weight % or mole %, as described above) in the EP copolymer chain segment.

[0055] The total ethylene content in polymerized form in the microporous polymer film is at least 10 wt. %, such as from 10 to 30 wt. %, or even from 15 to 25 wt. %, based on the weight of the microporous polymer film, or at least 14 mol. %, such as from 14 to 39 mol. %, or from 15 to 25 mol. %, or from 21 to 33 mol. %, based on the molar content of polymerized units of ethylene in the microporous polymer film as a percentage of the total molar content of polymerized monomer units in the microporous polymer film.

[0056] In certain embodiments, these PP copolymers can be produced in a reactor from one or more PP homopolymers and one or more ethylene-containing copolymers. Preferably, the ethylene-containing copolymer is an ethylene-propylene (EP) copolymer. Thus, the present invention provides a microporous polymer film comprising a polypropylene copolymer produced from the reaction product of a polypropylene homopolymer and an ethylene-propylene copolymer.

[0057] In certain embodiments where the ethylene-containing copolymer is an ethylene-propylene (EP) copolymer, the microporous film can consist essentially of a PP-EP copolymer comprising one or more polypropylene homopolymer chain segments and one or more ethylene-propylene copolymer chain segments. In certain such embodiments, the weight ratio of the PP component to the EP component can be 50:50, 55:45, 60:40, 65:35, 67:33, 70:30, 72:28, 74:26, 76:24, 78:22, 79:21, 80:20, 81:19, 82:18, 84:16, 86:14, 88:12, 90:10, or 95:5. Each of the foregoing numbers can be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers can be used alone to describe an open-ended range or in combination to describe a limited range. For example, the weight ratio can be at least about 60:40, from about 65:35 to about 85:15, or less than about 90:10.

[0058] The ethylene-containing copolymer can be a random copolymer, an alternating copolymer, or a block copolymer, and the ethylene-propylene copolymer can be a random EP copolymer, an alternating EP copolymer, or an EP block copolymer. For example, a PP copolymer containing an EP copolymer main chain or chain segment can contain a random EP copolymer main chain or chain segment, an alternating EP copolymer main chain or chain segment, or a diblock copolymer main chain or chain segment. For example, a diblock copolymer can contain a polypropylene block and a polyethylene block, or a polypropylene block and an EP copolymer block, or a polyethylene block and an EP copolymer block. Other ethylene-containing copolymers can also be used.

[0059] Films can be made from PP copolymers or polymer blends thereof by any method known in the art, most conveniently by heating to a temperature sufficient to obtain the PP copolymer (or blends thereof) in molten form, followed by extrusion or blown film molding. In some embodiments, the film can be a multilayer film. The multilayer film can be coextruded, whereby a first layer is coextruded with a second layer.

[0060] Prior to stretching, the nonporous polymer film may have a morphology characterized by a majority polypropylene phase (or matrix) in the polymer film, minor polymer domains of an ethylene-containing copolymer, such as an ethylene-propylene copolymer domain, and an inclusion phase of the major polypropylene phase in the minor polymer domain. This allows for efficient transmission of stretching forces from the major phase to the minor domains, dividing the minor domains, and then initiating and developing micropores upon stretching. Thus, the nonporous films disclosed herein may be subjected to a stretching process (described herein) to produce a microporous film.

[0061] In one embodiment, the microporous film described herein is oriented in the machine direction. The microporous film can be oriented by cold stretching in the machine direction and hot stretching in the machine direction after cold stretching. Alternatively or in addition, one or more cold stretches and / or one or more hot stretches can be performed in any other direction, such as the transverse direction (crossing the machine direction). The cold stretch percentage can be 25% to 150% and is represented by Formula I:

number

number

[0062] In some embodiments, a method for making a microporous film includes providing a microporous film as described herein and cold stretching the film in the machine direction to a cold stretch percentage of 25% to 200% at a temperature ranging from -20°C to 50°C, preferably 10°C to 50°C. The cold stretch percentage is determined using Equation I above. After cold stretching, the film is subjected to hot stretching in the machine direction to a hot stretch ratio of 50% to 500% at a temperature ranging from 50°C to 150°C, preferably 90°C to 140°C or 100°C to 140°C. The hot stretch percentage is determined using Equation II above.

[0063] In one embodiment, the stretching process includes one or more cold stretching steps, optionally with one or more heat setting steps, followed by one or more hot stretching steps. The process may optionally include a post-annealing step. Film uniformity is important, so it is preferred to keep the temperature below 150°C.

[0064] In one embodiment, the stretching process can be carried out as the film moves along a production line, which can include a series of rollers. The degree of stretching in the machine direction can be controlled by using different speed rollers or different diameters of the rollers. Optionally, the degree of stretching in the transverse direction can be carried out by gripping the edges of the web and stretching the film in the transverse (cross) direction between a series of clips that grip a pair of adjustable diverging rails. While a polymer film at the front end of the production line (before stretching) may appear colorless and transparent, as it moves along the production line, such as along the region where the stretching process is carried out, it may appear to change to an increasing opacity, developing a white haze, and then the film will turn white due to the formation of pores (and the associated light scattering effect from the void spaces).

[0065] Processes for stretching nonporous films to produce microporous films have been previously reported (see, for example, U.S. Pat. No. 3,801,404 to Druin et al. and U.S. Pat. No. 3,426,754 to Bierenbaum et al.), but these reported processes using polyethylene or polypropylene films require an annealing step before the stretching process (or at an intermediate point between separate film stretching stages), sometimes with a separate heat-setting step after the stretching process. However, extended annealing times are problematic from the perspective of the desired goal of implementing a continuous production line for producing microporous films. Ideally, a continuous extrusion and pore-forming process in one continuous production line would be preferred, without the need for a holding period for the extended annealing step. Advantageously, films made from the PP copolymers (and blends thereof) described herein do not require any annealing or heat-setting steps to produce microporous films from the stretching process (in this case, the mechanism of pore formation is different from that of previously reported polyethylene and polypropylene films). Thus, the PP copolymers described herein can be heated and extruded to form non-porous films that can be stretched in a continuous manufacturing line to produce microporous films.

[0066] In certain embodiments, the invention described herein comprises one or more polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments, wherein the microporous polymer film comprises: (i) polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the microporous polymer film or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the microporous polymer film; and (ii) ethylene-containing copolymer chain segments, and a total amount of ethylene-containing copolymer chain segments of 18 to 50 wt % based on the weight of the microporous polymer film or 21 to 57 mol % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the microporous polymer film, and at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segments or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segments.

[0067] In one embodiment, a method for forming a microporous polymeric film, the method steps comprising: (a) dissolving one or more polypropylene copolymers comprising: (i) one or more polypropylene homopolymer chain segments in a total amount of from 50 to 82 wt % based on the weight of the polypropylene copolymer or from 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; and (ii) one or more ethylene-containing copolymer chain segments in a total amount of from 18 to 50 wt % based on the weight of the polypropylene copolymer or from 21 to 57 mol % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer. and at least one ethylene-containing copolymer chain segment, wherein at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) forming a non-porous film from the polypropylene copolymer; and (c) subjecting the non-porous film to successive cold-stretching and hot-stretching steps, including (i) at least one cold-stretching step at a temperature in the range of -20°C to 50°C, and (ii) at least one hot-stretching step at a temperature in the range of 50°C to 150°C, thereby producing a microporous polymer film.

[0068] In some embodiments, the method is a continuous process for producing a microporous polymer film. In particular, in some embodiments, the method proceeds without any annealing step after the formation of the non-porous film, and without any annealing or heat-setting step after the formation of the microporous polymer film, and is a continuous process for producing a microporous polymer film.

[0069] The present invention relates to the microporous films produced by the methods described herein, and further relates to articles produced from the microporous films described herein.

[0070] The total thickness of the microporous film is not particularly limited and can be less than 100 mils in some embodiments. Different end uses may require different film thicknesses, or conversely, different film thicknesses may be more appropriate for some end uses. For example, a microporous film suitable for use as a house wrap may have a thickness of 2 to 10 mils, preferably 4 to 7 mils. A microporous film suitable for use as a roof membrane in Europe may have a thickness of 4 to 20 mils, preferably 5 to 10 mils, or a microporous film suitable for use as a roof membrane in North America may have a thickness of 20 to 80 mils, preferably 40 to 60 mils. Also, microporous films suitable for medical applications such as packaging wrap for surgical packs may have a thickness ranging from 2 to 20 mils (51 to 508 μm), for example, 5 to 10 mils (127 to 254 μm) thick.

[0071] The thickness of the film may depend on the end use of the microporous film discussed herein, and all thicknesses and thickness ranges are considered suitable for the microporous film of the present invention. Accordingly, all individual values ​​and subranges less than 2540 μm (100 mils) are included and disclosed herein. For example, in some embodiments, the total thickness of the microporous film (in μm) may be 2540, 2032, 1524, 1270, 1016, 762, 508, 381, 254, 203, 178, 152, 127, 102, 51, 38, 25, 13, or 2.5 μm. Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. In further embodiments, the total thickness of the microporous film can be 2.5 to 152.4 μm (0.1 to 6 mils), 2.5 to 102 μm (0.1 to 4 mils), 2.5 to 50.8 μm (0.1 to 2 mils), hi further embodiments, the total thickness of the film can be 2.5 to 38.1 μm (0.1 to 1.5 mils).

[0072] The films described herein are microporous, with specific pore sizes and porosities that can be varied to control the desired and useful barrier properties for a selected end use. For housewrap films and roof membranes, the same types of barrier properties are important, such as water vapor transmission rate (WVTR) and permeability. Water vapor transmission rate is dependent on film thickness. Permeability is essentially the normalized water vapor transmission rate (assuming a constant pressure difference across the film when comparing different film samples), and WVTR is recorded adjusted for film thickness; all "perms" herein are US perms. 1 US perm = 5.72 x 10 -8 g / Pa·s·m 2 For architectural wrap applications, a suitable average pore size (nm) may be 30-300 nm, and a suitable film porosity may be 25-55% to achieve a water vapor transmission rate of 10-100 per m (and a WVTR of 70-700 g / 24 h m). 2Also, for roof membranes, a suitable median average pore size (nm) may be 30-250 nm, and a suitable film porosity may be 25-45% to achieve a permeability of 10-70 perm (and a WVTR of 70-500 g / 24 h m). 2 In the medical packaging field, the same barrier properties are important, but the focus on permeability is usually on air (or gas sterilant) permeability measured as Gurley air permeability and maximum penetration (calculated %P) in the ASTM F2638 test (for porous packaging as a surrogate microbial barrier). max For medical packaging, suitable mean pore size (nm) may be 300-1,000 nm and 1-100 sec / 100 cm. 3 Useful range of Gurley permeability and calculated %P less than 10 max The appropriate film porosity to achieve this value may be 55-75% (P max (For , the smaller the better).

[0073] In some embodiments, the microporous polymer film has a porosity of at least about 20%, and the maximum porosity is not particularly limited. In the same or other embodiments, the microporous polymer film has a porosity of up to about 75%, and the minimum porosity is not particularly limited. For example, the microporous polymer film may have a porosity (%) of 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80%. Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the microporous polymer film may have a porosity of at least about 20%, between about 20% and about 75%, or between about 25% and about 70%.

[0074] In some embodiments, the microporous polymer film has a median average pore size (by volume) of at least about 20 nm, and the maximum median pore size is not particularly limited. In the same or other embodiments, the microporous polymer film has a median pore size of up to about 2000 nm, and the minimum median pore size is not particularly limited. For example, the microporous polymer film may have a median pore size (nm) of 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 1500, or 2000 nm. Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the microporous polymer film may have a median pore size of at least about 20 nm, from about 20 nm to about 1000 nm, or from about 25 nm to about 1000 nm.

[0075] In some embodiments, the microporous polymer film has a permeability of at least about 1 perm, and the maximum permeability is not particularly limited. In the same or other embodiments, the microporous polymer film has a permeability of up to about 150 perm, and the minimum permeability is not particularly limited. For example, the microporous polymer film may have a permeability of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, or 150 perm. Each of the foregoing numbers may be preceded by the word "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, without limitation, the microporous polymer film can have a permeability of at least about 10 perm, from about 10 perm to about 100 perm, or from about 20 perm to about 100 perm.

[0076] In some embodiments, the microporous polymer film has a flow rate of at least about 1 sec / 100 cm 3 In the same or another embodiment, the microporous polymer film has a Gurley-Hill porosity (herein referred to as "Gurley air permeability") of about 35,000 sec / 100 cm, and the maximum Gurley air permeability is not particularly limited. 3 For example, the microporous polymer film may have a Gurley air permeability of 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, or 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 15000, 20000, 25000, 30000, or 35000 seconds / 100 cm. 3 Gurley air permeability (sec / 100cm 3 Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, but not limited to, a microporous polymer film may have a viscosity of at least about 1 sec / 100 cm. 3 , about 1 second / 100cm 3 ~About 10000 seconds / 100cm 3 , or about 10 seconds / 100cm 3 ~About 5000 seconds / 100cm 3 , or about 10 seconds / 100cm 3 ~About 1000 seconds / 100cm 3 , or about 10 seconds / 100cm 3 ~About 100 seconds / 100cm 3 The fabric may have a Gurley air permeability of 1000 psi or less.

[0077] In some embodiments, the microporous polymer film has a % Maximum Penetration (%P) calculated by ASTM F2638-18 testing of less than about 10. max ) and has a barrier to microorganisms as measured bymax For example, the microporous polymer film has a calculated %P of less than 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, 0.03, 0.02, 0.015, 0.010, or 0.005. max Each of the foregoing numbers may be preceded by the words "about," "at least about," or "less than about," and any of the foregoing numbers may be used alone to describe an open-ended range or in combination to describe a limited range. For example, but not limited to, a microporous polymer film may have a calculated %P of less than about 10, from about 0 to about 10, or from about 0 to about 1. max Ideally, the calculated %P max The value is zero, but the limit for detection cannot be zero. Calculated %P max can be from about 0.005 or less to about 10, or from about 0.005 or less to about 5, or from about 0.005 or less to about 1.

[0078] The films described herein do not use added fillers, such as calcium carbonate or CaCO3, to produce water vapor-breathable films with high water vapor transmission rates. Accordingly, the films described herein contain less than 5 wt. % filler, based on the total weight of the polymers present in the film. Exemplary fillers may include, but are not limited to, CaCO3, clay, silica, alumina, titania, zirconia, ceria, talc, magnesium carbonate, calcium sulfate, barium sulfate, porous glass beads, porous polymer beads, ceramic beads, aluminum trihydroxide, magnesium trihydroxide, wollastonite whiskers, wood flour, lignin, starch, clay, carbon black, graphite, graphene, carbon nanotubes, carbon fibers, carbon nanofibers, or combinations thereof. In further embodiments, the films described herein contain less than 3 wt. %, less than 2 wt. %, less than 1 wt. %, or less than 0.5 wt. % filler, based on the total weight of the polymers present in the film. In some embodiments, the films described herein contain no filler (0 wt. %). In many pharmaceutical applications, 0 wt % filler is preferred to minimize the possibility of such film particulate contamination and particle fragmentation of the film.

[0079] The films described herein may incorporate UV stabilizers, particularly if the intended use may include outdoor applications. Representative UV stabilizer additives include ultraviolet light absorbers such as Tinuvin® 329 (BASF, Ludwigshafen, Germany) and hindered amine light stabilizers such as Tinuvin® 770 or Chimassorb® 2020 (both BASF). For example, an effective UV stabilizer package for a microporous film of polypropylene copolymer PP C7054-07NA may include a combination of 0.75 wt.% Chimassorb® 2020, 0.25 wt.% Tinuvin® 770, 0.25 wt.% Tinuvin® 329, and 0.15 wt.% Irganox® B215 (antioxidant, BASF). The PP C7054-07NA microporous film without UV additives turned to powder after 8 weeks of UV aging at 50° C. In contrast, the PP C7054-07NA microporous film with the above UV additive package did not show any visual defects such as cracks, yellowing or deformation after 8 weeks of UV aging at 50° C.

[0080] The films described herein may incorporate other additives, such as antioxidants (e.g., hindered phenolic resins such as IRGANOX® 1010 or IRGANOX® 1076 (supplied by Ciba Geigy)), phosphates (e.g., IRGAFOS® 168 (supplied by Ciba Geigy)), processing aids, UV light stabilizers, heat stabilizers, pigments, colorants, antistatic additives, flame retardants, slip agents, antiblock additives, biocides, antibiotic agents, and cleaning / nucleation promoters (e.g., HYPERFORM® HPN-20E, MILLAD® 3988, MILLAD® NX 8000 (available from Milliken Chemical)). Other additives may be included in the films at concentrations typically used in the art to achieve their desired purpose. In some examples, the one or more additives are included in an amount ranging from 0 to 10 wt % based on the total polymer weight of the film, or from 0 to 5 wt %, 0.001 to 5 wt %, 0.001 to 3 wt %, 0.05 to 3 wt %, or 0.05 to 2 wt % based on the total polymer weight of the film. In embodiments herein where the fillers have other uses, such as colorants or pigments, they are present in a total amount of less than 5 wt %.

[0081] Laminates are also described herein. The laminate comprises the microporous film described hereinabove and a nonwoven substrate at least partially adhered to the film. As used herein, "nonwoven substrate" includes nonwoven webs, nonwoven fabrics, and any nonwoven structure in which fibers or threads are interleaved in a non-regular or repeating pattern. The nonwoven substrates described herein can be formed by various processes, such as air-laying, melt-blowing, spunbonding, and carding processes, including bonded-carded web processes. Nonwoven webs can include single webs such as spunbonded, carded, air-laid, spunlaced, or melt-blown webs. However, due to the relative strengths and weaknesses associated with the various processes and materials used to manufacture nonwoven fabrics, composite structures of two or more layers can be used to achieve a better balance of properties. Such structures are often identified by letters designating the various layers, such as SM for a two-layer structure consisting of a spunbond layer and a meltblown layer, SMS for a three-layer structure, or more commonly, an SXnS structure where S is the spunbond layer, and X can independently be a spunbond, carded, airlaid, spunlaced, or meltblown layer, and n can be any number, but in practice is generally less than 5. To maintain the structural integrity of such composite structures, the layers must be bonded together. Common bonding methods include thermal calendar point bonding, adhesive lamination, ultrasonic bonding, and other methods known to those skilled in the art. All of these structures can be used in the present invention, especially when incorporated with a microporous film in the form of a laminate.

[0082] The microporous films described herein should find use in housing and construction, for example, as barrier layers for architectural envelopes such as house wraps and roofing membranes.

[0083] Also described herein are articles. The articles include the films or laminates described hereinabove. In some embodiments, the breathable backsheet includes the microporous films described hereinabove. In other embodiments, the breathable backsheet includes a laminate. The articles can be used in a variety of hygiene and medical applications. In some embodiments, the articles can include diapers, training pants, and adult incontinence articles or other similar absorbent garments. In other embodiments, the articles can include air masks, medical drapes, gowns, surgical gowns, and protective garments or other fabric (knit or nonwoven) articles.

[0084] The present embodiment is applicable to other technologies susceptible to problems similar to those described above. For example, the film can be used to manufacture cloth-like backsheets and operating room medical back table (or end table) covers, as well as medical packaging (e.g., medical sterilization pouches and sterilization pouches for containing sterilized surgical equipment) and active packaging (e.g., sachets for containing desiccants in pharmaceutical tablet bottles). These are all within the scope of the present embodiment. The interstitial spaces between the pores of the microporous polymer films described herein contain thin solid segments of PP homopolymer or PP homopolymer and E / P copolymer, unlike other breathable textile candidates in which the interstitial spaces contain fibers that may or may not be bonded (typically by thermal bonding at the contact points where they meet). An advantage of the microporous polymer films of the present invention is that the inventive drawing process allows for better control of pore size and pore size distribution, so that pores are formed by overlapping fibers, and the pore size and distribution are controlled at a number density (fibers / cm). 3This results in a narrower pore size distribution than other (fibrous) porous structures, which depends on the number of fibers (number of micropores) and the distribution of fiber diameters. Furthermore, the microporous polymer films of the present invention have smaller pores with diameters in the nanometer range, compared to fibrous materials, which have much larger pore sizes in the range of several micrometers. While fibrous structures can be manufactured from similar hydrophobic materials, the smaller pore size of PP-copolymer microporous polymer films can provide higher resistance to blood and body fluids, thereby enabling their use as breathable covers for operating room end tables. Another advantage of the microporous polymer films described herein compared to fibrous breathable films is that the likelihood of debris generated by handling, cutting, converting, and using the microporous polymer film is much less than that associated with fibrous structures. This makes the microporous polymer films suitable for use in ultra-clean spaces, such as those in electronic processing, filtration, and sterile medical and pharmaceutical environments.

[0085] Microporous films may also find use in regular packaging (such as outer packaging, fruit packaging, powder packaging, packaging for sensitive electronic components, etc.) and as filtration media (for gas or liquid separation). The film may be a monolayer film or a multilayer membrane. As used herein, "multilayer membrane" refers to a film having two or more layers that are at least partially adjacent, preferably but optionally coextensive.

[0086] PP copolymer film further comprising an ethylene-propylene elastomer Furthermore, microporous films having a lower tensile modulus, comprising 18-50 wt. % total of PP copolymer and ethylene-containing copolymer chain segments, are believed to be particularly desirable for some applications. The tensile modulus of a film is related to the flexibility of the film; furthermore, films with a lower tensile modulus have the potential for improved toughness, hot air welding installation, and low temperature durability.

[0087] However, it has been found that even when the PP copolymer has ethylene-containing copolymer chain segments, the polypropylene breathable membrane can still be relatively stiff. Furthermore, it has been found that the addition of ethylene-propylene rubber can further modify the microporous film to reduce its tensile modulus.

[0088] Thus, in some embodiments, the present invention relates to a microporous polymeric film comprising: (a) 50 to 95 weight percent, based on the total weight of the film, of one or more polypropylene copolymers, the polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments; the microporous polymer film comprising: (i) polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt. % based on the weight of the polypropylene copolymer or 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the film; and (b) at least 45 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units.

[0089] It is understood that all details, options, variations, manufacturing details and processes, and uses described hereinabove with respect to inventions containing only (a) or including (a), i.e., combinations of (i) and (ii) to the exclusion of (b), are intended to be equally applicable to or suitable for all inventions comprising or consisting of (a) and (b), unless otherwise expressly stated herein.

[0090] In some preferred embodiments, the (b) ethylene-propylene elastomer has an ethylene content very similar to or identical to the ethylene content in the ethylene-containing copolymer chain segment in the polypropylene copolymer. In this way, the additional incorporation of ethylene-propylene rubber into the PP breathable membrane does not affect the pore-forming ability of the PP copolymer. As a result, the ethylene-propylene rubber is believed to offer the potential for PP breathable membranes with additional properties, such as improved toughness. Other potentially improved properties include better flexibility at lower temperatures, such as those experienced in roofing applications during frigid winter weather. Along with the potential for increased porosity and breathability of the PP breathable membrane, other property improvements, such as improved heat welding and / or improved tear strength, are also believed possible.

[0091] In some embodiments, the one or more ethylene-propylene elastomers (b) are present in the film in an amount of 5 to 30 weight percent, based on the total of (a) one or more polypropylene copolymers and (b) one or more ethylene-propylene elastomers in the film. In some other embodiments, the one or more ethylene-propylene elastomers (b) are present in the film in an amount of 5 to 20 weight percent, based on the total of (a) one or more polypropylene copolymers and (b) one or more ethylene-propylene elastomers in the film.

[0092] In the (b) one or more ethylene-propylene elastomers, at least 45 weight percent of the polymerized units are ethylene units. In some embodiments, 45 to 80 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units. In some other embodiments, 45 to 60 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units.

[0093] Ethylene-propylene elastomer means any elastomer or rubber having ethylene-propylene segments. Elastomers are polymers that are viscoelastic (i.e., both viscous and elastic), and generally have weak intermolecular forces with a low Young's modulus and a high strain at break compared to other materials, as evidenced by extensible and elastic polymers.

[0094] Preferably, the (b) one or more ethylene-propylene elastomers are a single type of ethylene-propylene elastomer. When the (b) one or more ethylene-propylene elastomers are a mixture of ethylene-propylene elastomers, preferably, all of these elastomers each have the above-mentioned amount of polymerized ethylene units; i.e., in the (b) ethylene-propylene elastomers, all of the elastomers have at least 45 weight percent of polymerized units that are ethylene units; or in some embodiments, all have 45 to 80 weight percent of polymerized units that are ethylene units; or in some other embodiments, 45 to 60 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units.

[0095] In many embodiments, (b) one or more ethylene-propylene elastomers preferably comprise ethylene-propylene rubber; however, in some embodiments, ethylene propylene diene monomer (EPDM) rubber may be desirable. Mixtures of these rubbers are also possible. Preferably, (b) one or more ethylene-propylene elastomers are exclusively ethylene propylene rubber or exclusively ethylene propylene diene monomer (EPDM) rubber. Other suitable ethylene-propylene elastomers include Vistalon™ from ExxonMobil Chemical Company, Buna® from Lanxess, and Mitsui EPT™ from Mitsui Chemicals. Any ethylene-propylene elastomer having the aforementioned amount of polymerized ethylene units would be suitable in (b).

[0096] (b) The one or more ethylene-propylene elastomers preferably have a Mooney viscosity of 10 to 40 Mu, as measured under ASTM D1646-07. If a blend of elastomers is used, each elastomer has a Mooney viscosity of 10 to 40 Mu, as measured under ASTM D1646-07.

[0097] The microporous polymer film comprises (a) and (b) as described above. In some embodiments, the microporous polymer film consists of (a) and (b) as described above. In some embodiments, the microporous polymer film comprising or consisting of (a) and (b) has a tensile modulus that is lower than the tensile modulus of a film made from only (a). In some other embodiments, the microporous polymer film comprising or consisting of (a) and (b) has a water vapor transmission rate that is lower than the water vapor transmission rate of a film made from only (a).

[0098] In the microporous film, (a) in the one or more polypropylene copolymers, at least a portion of the ethylene-containing copolymer chain segments contain polymerized units of ethylene in an amount of 45% by weight to 80% by weight based on the weight of the ethylene-containing copolymer chain segment, or 55 mol % to 86 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.

[0099] In some embodiments of the microporous polymeric film comprising or consisting of (a) and (b), (a) the ethylene-containing copolymer chain segments in the one or more polypropylene copolymers are ethylene-propylene copolymer chain segments.

[0100] In some embodiments of the microporous polymer film comprising or consisting of (a) and (b), (a) the ethylene-containing copolymer chain segments in the one or more polypropylene copolymers comprise ethylene-propylene copolymer chain segments, and at least some of the ethylene-propylene copolymer chain segments in (a) comprise polymerized units of ethylene in an amount of 45% to 80% by weight based on the weight of the ethylene-propylene copolymer chain segment, or 55% to 86% by mole based on the molar content of polymerized ethylene units in the ethylene-propylene copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-propylene copolymer chain segment.

[0101] In some further embodiments, (a) the ethylene-propylene copolymer chain segments in the one or more polypropylene copolymers are ethylene-propylene diblock copolymer chain segments comprising a polypropylene block and a polyethylene block, or are diblock copolymer chain segments comprising a polypropylene block and an ethylene-propylene copolymer block.

[0102] In some embodiments, the microporous polymer film comprising or consisting of (a) and (b) has a porosity of at least 25% and a median pore size of at least 25 nm (4 V / A, per UOP method 578-11), both characteristics measured by mercury intrusion porosimetry.

[0103] In some embodiments, the microporous polymer film comprising or consisting of (a) and (b) is a nonporous polymer film having domains of (a) and domains of (b), wherein the domains of (a) further have a morphology characterized by a majority polymer phase of polypropylene, a plurality of minor polymer domains of an ethylene-containing copolymer within the majority polymer phase, and an inclusion phase of a primary polypropylene phase within the minor polymer domains.

[0104] Microporous polymer films comprising or consisting of (a) and (b) have been found to have multiple uses, and for many applications, non-porous microporous polymer films having a thickness of at least 100 μm to 2.5 mm are particularly suitable.

[0105] For example, a microporous polymer film comprising or consisting of (a) and (b) is suitable for use as a roof membrane or a component of a roof membrane. The low / low permeability of current roof membranes made of PVC, TPO, or EPDM leads to moisture accumulation under the roof membrane (e.g., on metal roofs and / or lightweight concrete structures), causing delamination of the roof membrane from the roof over time and subsequent failure of the roof structure. A microporous polymer film comprising or consisting of (a) and (b) offers the opportunity to provide a liquid-tight product with high water vapor permeability.

[0106] Microporous films comprising or consisting of (a) and (b) are also suitable for use in medical packaging or active packaging articles, or medical covers, including back table covers. When used in medical packaging or active packaging articles, or medical back table covers, microporous polymeric films comprising or consisting of (a) and (b) preferably have a barrier to microorganisms corresponding to a calculated maximum penetration %Pmax of less than 10%, as defined by ASTM F2638-18. Similarly, when used in medical packaging or active packaging articles, or medical back table covers, microporous polymeric films comprising or consisting of (a) and (b) preferably have a barrier to microorganisms corresponding to a calculated maximum penetration %Pmax of less than 10%, as defined by ASTM F2638-18. Similarly, when used in medical packaging or active packaging articles, or medical back table covers, microporous polymeric films comprising or consisting of (a) and (b) preferably have a barrier to microorganisms corresponding to a calculated maximum penetration %Pmax of less than 10%. 3 Preferably, the microporous polymeric film has a Gurley air permeability of 100 psi or less, which controls the inflow or outflow of air or one or more gases into or out of the package. Microporous polymeric films comprising or consisting of (a) and (b) are thermoformable and heat sealable, and are particularly useful for medical packaging or active packaging articles, or medical back table covers, and many other different applications.

[0107] Method for forming a PP copolymer film further comprising an ethylene-propylene elastomer In yet another alternative embodiment, the present invention further relates to a method of forming a microporous polymeric film, said method steps comprising: A) providing a mixture, the mixture comprising: (a) 50 to 95 weight percent, based on the total weight of the blend, of one or more polypropylene copolymers: (i) one or more polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) one or more ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt. % based on the weight of the polypropylene copolymer or 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment or at least 55 mol % based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the mixture; providing a mixture, wherein at least 45 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units; B) forming a non-porous film from the mixture; and C) A non-porous film. (i) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and (ii) at least one hot drawing step at a temperature in the range of 50°C to 140°C and subjecting the sheet to successive cold and hot drawing steps, thereby producing a microporous polymer film.

[0108] It is understood that all details, options, variations, manufacturing details and processes, and applications, including equipment, described herein above for inventions described for combinations of (i) and (ii) containing only (a) or including (a), i.e., excluding (b), are intended to be equally applicable to or suitable for all inventions comprising or consisting of (a) and (b), unless otherwise specified herein. Specifically, all details and equipment described herein above for machine direction and transverse direction stretching of films are suitable for processing films comprising or consisting of (a) and (b), unless other specific differences are indicated. Providing a mixture comprising or consisting of (a) and (b) can be achieved, without limitation, by compounding the components in a screw extruder, preferably a twin-screw extruder. Forming a non-porous film can be achieved, without limitation, by casting the film directly from the extruder after mixing. Subjecting the cast film to cold and hot stretching steps can be achieved by the methods discussed and exemplified herein.

[0109] In some preferred embodiments for forming microporous polymer films, the (b) ethylene-propylene elastomer has an ethylene content very similar to or identical to the ethylene content in the ethylene-containing copolymer chain segments in the polypropylene copolymer. In this way, the incorporation of the ethylene-propylene rubber into the PP breathable membrane does not affect the pore-forming ability of the PP copolymer. As a result, the ethylene-propylene rubber is believed to offer the potential for PP breathable membranes with additional properties, such as improved toughness. Other potentially improved properties include better flexibility at lower temperatures, such as those experienced in roofing applications during frigid winter weather. Along with the potential for increased porosity and breathability of the PP breathable membrane, other property improvements, such as improved heat welding and / or improved tear strength, are also believed possible.

[0110] In some embodiments of the method for forming a microporous polymer film, the (b) one or more ethylene-propylene elastomers are present in the mixture in an amount of 5 to 30 weight percent, based on the total weight of the (a) one or more polypropylene copolymers and (b) one or more ethylene-propylene elastomers in the mixture. In some other embodiments, the (b) one or more ethylene-propylene elastomers are present in the mixture in an amount of 5 to 20 weight percent, based on the total weight of the (a) one or more polypropylene copolymers and (b) one or more ethylene-propylene elastomers in the mixture. In the (b) one or more ethylene-propylene elastomers, at least 45 weight percent of the polymerized units are ethylene units. In some embodiments, 45 to 80 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units. In some other embodiments, 45 to 60 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units. Preferably, the (b) one or more ethylene-propylene elastomers are a single type of ethylene-propylene elastomer. When the (b) one or more ethylene-propylene elastomers are a mixture of ethylene-propylene elastomers, preferably, all of these elastomers each have the above-mentioned amount of polymerized ethylene units; i.e., in the (b) ethylene-propylene elastomers, all of the elastomers have at least 45 weight percent of polymerized units that are ethylene units; or in some embodiments, all have 45 to 80 weight percent of polymerized units that are ethylene units; or in some other embodiments, 45 to 60 weight percent of the polymerized units in the (b) ethylene-propylene elastomer are ethylene units.

[0111] In some embodiments forming a microporous polymer film, (b) one or more ethylene-propylene elastomers preferably comprise ethylene-propylene rubber; however, in some embodiments, ethylene propylene diene monomer (EPDM) rubber may be desirable. Mixtures of these rubbers are also possible. Preferably, (b) one or more ethylene-propylene elastomers are exclusively ethylene propylene rubber or exclusively ethylene propylene diene monomer (EPDM) rubber. Other suitable ethylene-propylene elastomers include Vistalon™ from ExxonMobil Chemical Company, Buna® from Lanxess, and Mitsui EPT™ from Mitsui Chemicals. Any ethylene-propylene elastomer having the aforementioned amount of polymerized ethylene units would be suitable in (b).

[0112] In some embodiments of the method of forming a microporous polymeric film, (b) the one or more ethylene-propylene elastomers preferably have a Mooney viscosity of 10 to 40 Mu, as measured under ASTM D1646-07. If a blend of elastomers is used, each elastomer has a Mooney viscosity of 10 to 40 Mu, as measured under ASTM D1646-07.

[0113] In some embodiments of the method for forming a microporous polymer film, the mixture used to make the microporous polymer film comprises (a) and (b) as described above. In some embodiments of the method for forming a microporous polymer film, the mixture used to make the microporous polymer film consists of (a) and (b) as described above. In some embodiments of the method for forming a microporous polymer film, the microporous polymer film made from the mixture comprising or consisting of (a) and (b) has a tensile modulus that is less than the tensile modulus of a film made from (a) alone. In some embodiments of the method for forming a microporous polymer film, the microporous polymer film made from the mixture comprising or consisting of (a) and (b) has a water vapor transmission rate that is less than the water vapor transmission rate of a film made from (a) alone.

[0114] In some embodiments of the method of forming a microporous polymer film, (a) in the one or more polypropylene copolymers, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of 45% to 80% by weight based on the weight of the ethylene-containing copolymer chain segment, or in an amount of 55% to 86% by mole based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.

[0115] In some embodiments of the method for forming a microporous polymeric film made from a mixture comprising or consisting of (a) and (b), (a) the ethylene-containing copolymer chain segments in the one or more polypropylene copolymers are ethylene-propylene copolymer chain segments.

[0116] In some embodiments of the method for forming a microporous polymer film made from a mixture comprising or consisting of (a) and (b), (a) the ethylene-containing copolymer chain segments in the one or more polypropylene copolymers comprise ethylene-propylene copolymer chain segments, and at least some of the ethylene-propylene copolymer chain segments in (a) comprise polymerized units of ethylene in an amount of 45% to 80% by weight based on the weight of the ethylene-propylene copolymer chain segment, or 55% to 86% by mole based on the molar content of polymerized ethylene units in the ethylene-propylene copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-propylene copolymer chain segment.

[0117] In some further embodiments, (a) the ethylene-propylene copolymer chain segments in the one or more polypropylene copolymers are ethylene-propylene diblock copolymer chain segments comprising a polypropylene block and a polyethylene block, or are diblock copolymer chain segments comprising a polypropylene block and an ethylene-propylene copolymer block.

[0118] In some embodiments of the method of forming a microporous polymer film made from a mixture comprising or consisting of (a) and (b), the resulting film has a porosity of at least 25% and a median pore size of at least 25 nm (4 V / A, per UOP method 578-11), both characteristics measured by mercury intrusion porosimetry.

[0119] In some embodiments of the method for forming a microporous polymer film made from a mixture comprising or consisting of (a) and (b), the film is a nonporous polymer film having domains of (a) and domains of (b), wherein the domains of (a) further have a morphology characterized by a majority polymer phase of polypropylene, a plurality of minor polymer domains of an ethylene-containing copolymer within the majority polymer phase, and an encompassing phase of a predominant polypropylene phase within the minor polymer domains.

[0120] The present invention will be further clarified in the following examples, in which all parts and percentages are by weight unless otherwise specified. It should be understood that these examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and should not be construed as limiting in any way. From the foregoing discussion and these examples, one skilled in the art will be able to ascertain the essential characteristics of the present invention, and will be able to make various changes and modifications to the present invention to adapt it to various uses and conditions without departing from the spirit and scope thereof. [Example]

[0121] material Homopolymer polyethylene is referred to herein as PE. Homopolymer-PE as used herein is HDPE 6400, a resin available from Dow Chemical Company, Midland, MI, USA.

[0122] Homopolymer polypropylene is referred to herein as PP. The homopolymer PP used herein is PP H314, a resin available from Braskem, USA (Philadelphia, PA, USA).

[0123] Ethylene-propylene copolymers are referred to herein as EP. Numerous EP and PP-EP copolymers and homopolymer-PP blends with EP or PP-EP copolymers are described herein, for example, as detailed in Examples 2 and 6.

[0124] The polypropylene copolymer resin used in this study is PP C7054-07NA, a PP-EP copolymer containing PP chain segments and ethylene-propylene random copolymer chain segments, purchased from Braskem USA. PP C7054-07NA resin contains 32.9 wt% ethylene-propylene copolymer (and 100-32.9=67.1% PP), but the ethylene content in the ethylene-propylene copolymer chain segments is 49.7 wt%. It has a tensile strength of 0.9 g / cm. 3 and a melt index of 7 g / 10 min at 230° C. and 2.16 kg. Other PP copolymer resins are listed in Table 2.

[0125] The term "Tyvek®" by itself refers to Tyvek® housewrap (approximately 32% porous; 37 nm average pore size), and the term "Tyvek® 1073B" refers to a special grade of Tyvek® nonwoven used as a medical packaging layer (approximately 65% ​​porous; 2500 nm average pore size).

[0126] Cast film PP C7054-07NA resin cast films were produced on a film cast line consisting of a 1.25 inch Killion single screw extruder and a 30 inch wide cast die with a die gap of approximately 30 mils. A typical temperature profile (for extruder zones 1-8) of a pilot scale extrusion line using a 30 inch die used to produce the (co)polymer cast films described herein can be as follows (e.g., for PP copolymer films): 180, 200, 210, 210, 210, 210, 210, 210°C.

[0127] Uniaxial and biaxial stretching of film on an Iwamoto biaxial stretcher Uniaxial stretching (machine direction orientation, MDO) procedure: The film was cut to a predetermined dimension. Adhesive tape was attached to both ends of the film (in the cross direction), which was then fitted into a specially designed sample holder. The sample holder plates were fastened together with five bolts. The legs of the sample holder were then attached onto the back of the grip of an Iwamoto biaxial stretcher (BIX-703, Iwamoto Seisakusho). The film was subjected to uniaxial cold stretching in the machine direction. Afterwards, the sample chamber door was closed, and the sample chamber was heated to 100°C and subsequently held at this temperature for 1 minute. The film was then subjected to uniaxial hot stretching in the machine direction. The cold stretching degree was

number

number

[0128] After stretching, the film turned white due to the formation of a microporous structure.

[0129] For biaxial stretching, PP-based films were cut to predetermined dimensions (70 mm x 70 mm) and then loaded onto the grips of an Iwamoto biaxial stretcher. The films were simultaneously biaxially stretched in both directions at room temperature and then heated to 100°C. After holding at 100°C for 1 minute, the films were simultaneously biaxially stretched in both directions at elevated temperature. The degree of stretching for biaxial stretching is defined similarly to that for uniaxial stretching.

[0130] Differential Scanning Calorimetry (DSC) A portion of the sample was weighed and placed into an aluminum hermetically sealed DSC pan (P / N 900793.901 pan and lid 900794.901) and sealed. Sample weights were approximately 1-4 mg for each sample. Samples were scanned in a TA Instruments Q2000 DSC (differential scanning calorimeter) (P / N 970001.901) (s / N 2000.0877) equipped with an autosampler, a 50 ml / min nitrogen purge, and a mechanical cooling accessory. Run parameters for the heat-cool heating cycle were -20°C to 200°C at 10°C / min with a sampling interval of 0.1 s / pt. Scans were analyzed using Universal Analysis V4.7A TA Instruments software. Melting points obtained from the DSC scans are shown as output from the instrument software and correspond to a plot of the peak temperature in the heat flow versus the temperature in the second heating cycle.

[0131] Mercury intrusion porosimetry Mercury intrusion porosimetry analysis was performed according to ASTM D4404-10 on a Micromeritics Autopore IV 9520. Prior to mercury analysis, the samples were mechanically degassed at room temperature under vacuum to remove any physisorbed species (i.e., water) from the sample surface.

[0132] The test conditions were Hg filling pressure 0.50 psia, Hg contact angle 130°, Hg surface tension 485 dynes / cm, Hg density 13.53 g / mL, evacuation time 30 minutes, 5 cm 3The test included a small-bore hardness tester with a bulb (solid type: 0.392 stem volume), a 30-second equilibration time, a 92-point pressure table (75 indentation plus 17 extrusion pressure points), and a mechanical exhaust <50 μm Hg. The low-high pressure crossover point was collected at approximately 46 psia (3.8 μm). The pressure table used was constructed to allow for a logarithmic pressure distribution from 0.5 to 60,000 psia, and was used to detect pore sizes (pore diameters) from 0.003 to 400 μm in diameter. As the pressure was increased stepwise from vacuum to a maximum of approximately 60,000 psia, mercury was forced into the smaller pores. According to UOP Method 578-11, the average pore diameter (4V / A) was calculated based on the assumption that all pores are right circular cylinders with length (l) and diameter (d). The total pore volume (V = πd 2 When the average pore diameter (d) is divided by the total pore area (=πdl), the average pore diameter (d) is 4V / A.

[0133] To confirm that the instrument was functioning properly, a silica-alumina reference material, lot A-501-46, was analyzed. The reported median pore size (by volume) of the reference sample is 0.0072 ± 0.0005 μm. Autopore reported a median pore size (by volume) of 0.0072 μm.

[0134] Scanning Electron Microscopy (SEM) The samples were freeze-fractured, mounted on SEM stubs with carbon tape, and then coated with 30 nm of gold to mitigate charging. The top and fractured surfaces of each sample were imaged at specific locations and at various magnifications ranging from 5,000x to 10,000x using an FEI Nova NanoSEM Model 600 in secondary electron (TLD) imaging mode. To prevent beam damage to the sample, the accelerating voltage was set between 3 and 5 kV with a spot diameter of 3–4 (scale of the spot diameter knob) at a working distance of approximately 5 mm (the distance from the last pole piece of the lens to the sample when the image is in focus).

[0135] Transmission Electron Microscopy (TEM) The PP copolymer film was cut into small trapezoidal sections so that sections could be collected. Approximately 100-nanometer-thick sections were collected at ambient temperature using a diamond knife on a Leica EM UC7 microtome and placed on a 400-mesh virgin TEM grid for observation. The microtomed films were stained with the vapor phase of a 0.5 M (mol / L) aqueous solution of osmium tetroxide for 3–5 minutes at ambient temperature. TEM images were collected on an FEI Tecnai 12 operated at an accelerating voltage of 120 kV using a Gatan MultiScan CCD camera.

[0136] X-ray diffraction technology Small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) studies were performed at the Advanced Photon Source (Argonne National Laboratory) using the DND-CAT (5-ID-D beamline). A standard APS Undulator A was used as the X-ray source, with an X-ray energy setting of 17 keV (λ = 0.7923 Å). All samples were analyzed in normal beam transmission mode. Detector calibration was performed using silver behenate and lanthanum hexaboride standard reference materials. Two-dimensional scattering patterns were reduced to one-dimensional data sets of scattering intensity versus scattering vector by radial integration of the two-dimensional images. One-dimensional pattern reduction and analysis were performed using the commercially available software package JADE.

[0137] Water Vapor Transmission Rate (WVTR) Measurement (ASTM F1249) A Mocon 3 / 33 model MG module was used to evaluate the WVTR for this study. Test conditions were 37.8°C / 100% RH per ASTM method F1249. 2Film samples were prepared using a 76.2 μm (3 mil) aluminum foil / acrylic adhesive mask to focus the test area to approximately 2 inches in diameter. The film sample divided the test cell into two halves. The ends of the test cell were securely sealed to prevent outside air from leaking into the cell. This was achieved using silicone grease to aid in sealing the film to the cell (carrier gas side), and a rubber O-ring was used to seal the outer cell cover or water vapor side. The standard sample area was 50 cm. 2 During a typical test, water vapor (test gas) continuously entered the outer half of the test cell. This gas could be at 100% relative humidity (wet sponge) or generated by the instrument at 30-90% relative humidity. The water vapor permeated the film sample and was then transported in a carrier gas (dry nitrogen) to the IR sensor, which generated a current directly proportional to the amount of water vapor passing through the film. A computer collected the data from the IR sensor and calculated a final value describing the water vapor transmission rate of the test material. WVTR data was expressed in grams / 24 h m 2 The normalized WVTR takes into account the film thickness and is reported in units of g cm / 24h m 2 It is reported as

[0138] Water vapor permeability (ASTM E96 / E96M-16) Water vapor transmission rates were determined according to ASTM E96 / E96M-16, Standard Test Method for Water Vapor Transmission of Materials, Desiccant Method. Test specimens were cut into circular disks with a diameter of 90.3 mm. The pocket in the dish was filled with calcium chloride to within 6.4 mm (1 / 4 inch) of the specimen. The specimen was then fitted onto the dish directly above the pocket, with a metal plate extending 76.1 mm from the specimen's diameter, where it was exposed to the environment. The specimens were prepared with the outer surface of the product facing the desiccant. The assembly was then placed in a controlled chamber operated at a temperature and relative humidity (RH) of 23 ± 2°C and 50 ± 5%, respectively. The assembly was then periodically weighed. Water vapor transmission rate data are reported in units of "perm," and it is possible to convert the transmission to water vapor transmission in units of grams / 24 h m². Any use of the unit "perm" herein refers to US perm. 1 US perm = 5.72 x 10 -8 g / (Pa·s·m 2 ).

[0139] Gurley Hill Porosity (Gurley Air Permeability) To measure the Gurley flow values ​​of the microporous films, a Genuine Gurley Instruments Densometer and a Lorentzen & Wettre L&W Model 121D Densometer were used. The densometer measures the flow rate of gas (e.g., 100 cm), which is conventionally used in this test. 3 The time required for a given volume of air (of which there is air) to pass through a 1-inch diameter area of ​​the film (and with a specific pressure gradient, conventionally about 4.9 inches of water) is recorded. The test procedure conformed to the TAPPI T-460 OM-11 method. Prior to testing, a confirmation test was performed by using a calibration plate with a known value of Gurley air permeability (19.2 seconds). The calibration plate was sized to fit a 100 cm 3 of air passed through within 19.2 seconds. Once the validation was complete, the microporous film samples were tested. Even though permeability is dependent on the area and pressure of the test sample, these values ​​are normalized for the instrument, so the results are conventionally reported in s / 100cm. 3reported in units of 100 cm of air 3 (Because the sample is also standardized, it is reported simply as seconds, s). Herein, Gurley Hill porosity is described as Gurley air permeability, and as is common in the art, seconds / 100 cm. 3 It is reported in.

[0140] Grab tensile test Grab tensile tests were performed on an Instron Tester. The test procedure followed ASTM D 5034-09(2013) test method. The grab specimens were gripped at the center of the specimen width to ensure equal unequal gripping of the top and bottom sections. The crosshead speed was 12 inches / minute for all experiments. The Instron reports the tensile strength (Newtons per unit width) and elongation (%) at peak load.

[0141] Nuclear magnetic resonance (NMR) spectroscopy Approximately 0.25 g of sample was cut into small pieces and inserted into a 10 mm NMR tube. 2.6 ml of tetrachloroethane-d2 (TCEd2) containing 10 mM relaxation agent was added. The sample was then heated at 115 °C. The following parameters were used on a Bruker 600 MHz spectrometer equipped with a 10 mm cryogenic probe: 13 C NMR and diffusion measurements (translational diffusion) (to confirm homopolymer or blend) were performed. Repeat time: 15 seconds Number of scans: 1536 90° pulse: 12 ms Spectral width: 240 ppm Temperature: 115℃ Spectral center: 90 ppm

[0142] Gel Permeation Chromatography (GPC) Samples were dissolved in the carrier liquid at a concentration of 1 mg / ml by shaking in 1,2,4-trichlorobenzene (TCB) containing 200 ppm butylhydroxytoluene (BHT) at 160 °C for 2 hours. GPC was performed on a PolymerChar high-temperature LC system operated in GPC mode. The injection volume was 300 μl. The flow rate was 1 ml / min. The eluent was TCB containing 200 ppm BHT. Separation was performed on two 7.5 x 300 mm PL-Gel mixed-B columns (Agilent). An integrated IR5 detector was used for detection in the PolymerChar HTLC (high-temperature liquid chromatography). A series of 16 polystyrene (PS) narrow molecular weight distribution standards (Agilent Corporation) was used for molecular weight calibration. The calibration range was 0.58 to 3750 kg / mol, and the calibration curve was a least-squares fit to a third-order polynomial. Therefore, the reported molecular weights are PS-equivalent values. Once the validation was completed, the microporous film samples were tested.

[0143] Microbial Barrier Test (ASTM F2638-18) The Microbial Barrier Test (ASTM F2638-18) uses aerosol filtration to measure the performance of porous packaging materials as a surrogate microbial barrier and is applicable to porous materials used to package devices for terminally sterilized medical use. The aerosol filtration performance of porous packaging materials is measured by generating a defined aerosol of 1.0 μm particles and evaluating the filtration efficiency of the material using a single or dual particle counter. Test results are reported as a calculated %P max P is recorded as the highest percent concentration of particles in the filtrate aerosol (particles that remain aerosolized after passage of the specimen) when the specimen is tested over a range of pressure differentials or air velocities. max A lower value means a better barrier to particulate matter or microorganisms.

[0144] Mooney Viscosity Mooney viscosity (ML 1+4 at 125°C) was measured on an Alpha MV 2000 Mooney Viscometer according to the ASTM D1646-07 standard method. Here, L indicates the use of a large (i.e., standard) rotor, 1 is the warm-up time in minutes, 4 is the reading time in minutes, and 125°C is the test temperature. Mooney viscosity is commonly used to measure the viscosity of raw rubber / elastomers and characterize the quality of both natural and synthetic rubbers. The Mooney viscometer consists of rotating a serrated rotor embedded in a rubber specimen housed within a sealed, pressurized cavity. From that constant speed, the rotor experiences a given resistance to rotation, which is recorded as torque in Nm. ASTM D1646 describes the algorithm used to convert this torque to Mooney Units (MU). Mooney viscosity is affected by the rubber / elastomer preparation method and storage conditions prior to testing. The test specimen consists of two elastomeric disks, each 50 mm in diameter and approximately 6 mm thick, sufficient to completely fill the viscometer cavity. The specimen should be air-free and free of pockets that could trap air in the rotor and die surfaces. A hole is drilled through the center of one disk for insertion of the rotor stem. The specimen should rest at standard laboratory temperature for at least 30 minutes before testing and be tested within 24 hours after homogenization. For Mooney viscosity testing, a larger rotor should be used unless the Mooney viscosity exceeds the instrument's torque capacity. The closed die with the rotor in place is adjusted to the test temperature. The temperatures of the two dies should be within 0.5°C of each other. While the viscometer is running with the rotor in place and unloaded, the torque indicator is adjusted to a zero reading. The disks are then stopped from rotating. This adjustment should be performed with the die open for machines with a rotor release spring. For a properly adjusted cavity, remove the hot rotor, quickly insert a stem through the center of one of the specimens, and replace the rotor in the viscometer. The second specimen is placed in the center of the rotor, the die is immediately closed, and the timer is started. The sample is allowed to warm in the closed Mooney viscometer cavity for exactly one minute, and then the motor driving the rotor is started. Viscosity readings should be recorded continuously. The run time should never be less than two minutes.

[0145] Example 1 This example investigates the effect of annealing before stretching on homopolymer PP films. Table 1 shows the stretching conditions and corresponding porosity and pore size (median pore size) of homopolymer polypropylene, PP H314, after stretching both with and without annealing (before stretching). The designation CSXX-HSYY means that the film was subjected to XX% cold stretching followed by YY% hot stretching.

[0146] [Table 1]

[0147] Table 1 shows that annealing at temperatures near the melting point of PP for an extended period of time is required to achieve the desired pore size and porosity. Unannealed PP H314 samples did not turn white after stretching, and correspondingly, the films exhibited very low porosity (2-4%), as shown in Table 1. In contrast, when annealed at 150°C for 24 hours, the films immediately turned white and exhibited porosity of 20-24% after the same stretching conditions. Similar results were obtained for films of homopolymer PE (HDPE 6400).

[0148] Additionally, blends of homopolymer PE (HDPE 6400) and homopolymer PP (PP H314) were investigated to determine whether polymer incompatibility aided pore formation without prior annealing of the films. Blends of homopolymer polypropylene and homopolymer polyethylene were prepared in a twin-screw extruder and extruded into films. Extruded films with blend ratios (homopolymer polyethylene to homopolymer polypropylene) of 100:0, 90:10, 80:20, 70:30, 50:50, 30:70, 20:80, 10:90, and 0:100 were prepared as described above without an annealing step and then subjected to sequential cold (CS) and hot (HS) uniaxial stretching (25% cold stretch at 100 mm / s at room temperature, followed by 100% hot stretch at 5 mm / s at 100 °C). Again, no pore formation was observed for films of these PP / PE homopolymer blends if no annealing was performed.

[0149] The long annealing time is problematic from the perspective of the desired goal of producing microporous films running on a continuous production line. Ideally, a continuous extrusion and pore formation process on one continuous production line would be preferred, without the need for a hold period for the extended annealing step.

[0150] Example 2 One of the objectives of the present invention is to produce a film capable of pore formation during film stretching without the need for any thermal annealing step before or after film stretching. Eliminating the annealing step of the prior art process allows for a continuous manufacturing process. In this example, microphase separation-induced pore formation in homopolymer polypropylene was investigated to reduce the required annealing time or, preferably, completely eliminate the annealing step from similar manufacturing processes for polyethylene or polypropylene homopolymers. For this reason, a PP copolymer composed of homopolymer polypropylene (PP) chain segments and ethylene-propylene (EP) copolymer chain segments was prepared and extruded into a film.

[0151] To define the effective parameters and ranges of the present invention, four different reactor grade PP copolymers were evaluated. The characteristics of the various PP copolymers are shown in Table 2 (melt flow rate, EP copolymer content (isotactic PP content is 100-EP content), and ethylene and propylene content in the EP copolymer chain segments).

[0152] [Table 2]

[0153] Films of these PP copolymers were prepared as described above and then subjected to sequential cold (CS) and hot (HS) uniaxial stretching (25% CS at 100 mm / s, followed by 100% HS at 100°C and 5 mm / s). The film characteristics (average pore size, porosity, and WVTR) are shown in Table 3.

[0154] [Table 3]

[0155] The comparative PP TI4020N and PP INSPIRE® Film 114 films were found to have very low average pore sizes (8-12 nm) and very low film porosities (7-10%), and these film characteristics corresponded to very low water vapor transmission rates and very low water vapor transmission rates. Both samples were found to be unsuitable for their intended purpose as breathable films. On the other hand, the inventive PP C700-35N and PP C7054-07NA films had average pore sizes and film porosities in the target ranges similar to those of commercially available Tyvek® films, and film characteristics such as water vapor transmission rates and water vapor transmission rates, suggesting that both of these samples were suitable as breathable films.

[0156] Example 3 PP C7054-07NA resin, a PP copolymer containing homopolymer polypropylene chain segments and ethylene-propylene copolymer chain segments, was selected for further study to optimize stretching conditions to explore the range of microporous film characteristics accessible by this approach. The initial thickness of the PP C7054-07NA resin film before stretching was 203 μm.

[0157] As described above, films were prepared from PP C7054-07NA and subjected to successive cold and hot uniaxial stretching under various process conditions as listed in Table 4. Film characteristics (pore size and porosity) were then evaluated to confirm practical process parameters.

[0158] [Table 4]

[0159] [Table 5]

[0160] Table 4 shows that stretching conditions can be optimized to adjust the desired porosity and average pore size. Multiple comparisons can be performed for a particular stretching variable (cold stretch percentage (%), hot stretch percentage (%), and hot stretch temperature (°C)) by controlling two of the three variables constant while varying the third. For example, one such series is illustrated by Samples 1-4, which show the effect of hot stretch temperature (°C) when the range of room temperature cold stretch and the range of hot stretch are held constant (25% and 50%, respectively). Increasing the hot stretch temperature over the temperature range of 60-120°C increases porosity and pore size (median pore size). Another such series is illustrated by Samples 11-16, which show the effect of hot stretch percentage at 100°C after a 25% room temperature cold stretch. Again, increasing hot stretch in the 25-100% hot stretch range increases porosity and pore size (median pore size), but the trend recedes at higher hot stretches (200 or 300%).

[0161] Example 4 This example investigates the performance of uniaxially stretched microporous PP copolymer films. Example 3 demonstrated the effect of film stretching conditions on pore formation (in terms of porosity (%) and average pore size (nm)). In Table 4 above, the degree of hot stretching clearly has a significant effect on porosity and average pore size, so this series (Samples 11-14) was selected for further study, including physical properties and performance data.

[0162] The PP C7054-07NA resin microporous films were subjected to the same cold stretching degree (25%) at 25°C, but the hot stretching degree ranged from 25% to 100% at 100°C. The initial thickness of the PP C7054-07NA resin film before stretching was 203 μm, and the final film thickness after stretching under various stretching conditions is listed in Table 5.

[0163] Mercury porosimetry was used to measure the average pore size and porosity of the stretched PP C7054-07NA films in this series, and the results are summarized in Tables 4 and 5. The pore distribution of the PP C7054-07NA microporous films for this series is illustrated in Figure 1B and compared to that of Tyvek® in Figure 1A. Note that the y-axis scale is different in Figure 1A compared to that shown in Figure 1B.

[0164] [Table 6]

[0165] Table 5 and Figures 1A and 1B show that under appropriate stretching conditions, PP C7054-07NA microporous film can exhibit larger pore size and porosity than Tyvek® housewrap.

[0166] [Table 7]

[0167] As shown above (Table 4, Example 3), increasing the hot stretch range from 25 to 100% increases both porosity and pore size (average pore size). It is also expected that an increase in both porosity and average pore size will lead to an increase in water vapor transmission rate ("perm") (Table 6). As shown in Table 6, by adjusting the pore size of the PP C7054-07NA microporous film, the water vapor transmission rate can vary from 14 perm to 82 perm (ASTM E96). It should be noted that the water vapor transmission rate for Tyvek® housewrap with a similar thickness is approximately 60 perm. Table 6 also shows the Gurley air permeability of PP C7054-07NA microporous films, which indicates that C7054-07NA microporous films may have a better barrier to airflow and therefore may be a better choice for improving the energy efficiency of a home than, for example, Tyvek®.

[0168] Example 5 This example considers the morphology of PP copolymer films. Prior art blends of homopolymer polypropylene and minority homopolymer polyethylene produce films with microphase separation resulting in incompatible domains of polyethylene within the polypropylene matrix (PP / PE). The polypropylene copolymers disclosed herein were cast as films and investigated with the aim of producing microphase separation within the incompatible EP domains within the polymer film. Such microphase separation results in inclusion phases within the incompatible domains. The morphology of these films before and after stretching was investigated by SEM and TEM.

[0169] Figure 2 shows SEM images of film cross sections. Figure 2A shows the cross section of an unstretched PP C7054-07NA film (indicated by the 20-micron scale bar), while Figures 2B and 2C show PP C7054-07NA films stretched by 25% cold stretch and 50% hot stretch (100°C). The 20-micron scale bar in Figure 2B is compared to the 5-micron scale bar in Figure 2C. Microphase separation and associated domain formation are evident in the unstretched PP C7054-07NA film in Figure 2A, with domain diameters ranging from several hundred nanometers to approximately 3 microns. In Figures 2B and 2C, the PP C7054-07NA film was not annealed and was directly subjected to cold stretching (25%) at a stretching rate of 100 mm / s, followed by hot stretching at a stretching rate of 5 mm / s and a temperature of 100°C. As can be seen from the SEM images of the film cross section in Figures 2B and 2C, many pores are formed by 25% cold stretching and 50% hot stretching.

[0170] Figure 3 shows SEM images of the film surface. Figures 3A and 3B show unstretched PP C7054-07NA films, indicated by a 20-micron scale bar in Figure 3A compared to a 10-micron scale bar in Figure 3B. Figures 3C and 3D show PP C7054-07NA films stretched by 25% cold stretching at a stretching rate of 100 mm / s followed by 50% hot stretching (100°C) at a stretching rate of 5 mm / s, indicated by a 20-micron scale bar in Figure 3C compared to a 10-micron scale bar in Figure 3D. Before stretching, the film surface is very smooth (Figures 3A and 3B). In contrast, pores can be clearly observed on the surface of the stretched PP C7054-07NA film (Figures 3C and 3D).

[0171] Figure 4 shows TEM images of the film before and after stretching. Figures 4A and 4B show the PP C7054-07NA film before and after stretching, respectively (25% CS; 50% HS, as above), with the scale bar at 1 micron in both Figures 4A and 4B. Figures 4C and 4D show the PP INSPIRE® 114 film before and after stretching, respectively (25% CS; 50% HS, as above), with the scale bar at 0.2 microns in Figures 4C and 4D.

[0172] In the unstretched PP C7054-07NA film in Figure 4A, microphase separation and associated domain formation are readily visible, with domain diameters ranging from several hundred nanometers to approximately 3 microns. The TEM images in Figures 4A and 4B suggest that the cavitation process nucleates in the ethylene-propylene (EP) domains for the PP C7054-07NA film. While not wishing to be bound by theory, it is believed that the inclusion morphology of the PP microphase in the EP domains within the PP matrix allows the stretching force to be effectively transferred to the microphase domains, which then break up into small fragments and initiate pore formation and growth. In contrast, after stretching the PP INSPIRE® 114 film, the EP domains of the PP INSPIRE® 114 film only showed elongation along the stretching direction (Figures 4E and 4F). No pore formation occurred.

[0173] Further evidence of the different response to stretching between films of PP C7054-07NA or PP C700-35N compared to PP TI4020N or PP INSPIRE® 114 was observed in wide-angle X-ray scattering (WAXS) studies. The WAXS pattern correlates with the Bragg diffraction of X-rays by the polypropylene crystalline lattice and provides information on the crystalline composition, crystalline orientation, and relative amount of crystallinity.

[0174] Figure 5 shows the WAXS patterns of films of two different PP copolymers, PP C7054-07NA and PP TI4020N. Samples for each copolymer included unstretched films and samples stretched by 25% cold stretching at room temperature and 100% hot stretching at 100°C. No significant changes in the crystalline structure of the PP C7054-07NA resin film were observed before and after stretching (Figures 5A and 5B, respectively). The same observations were also made for the PP C700-35N resin film (not shown). As shown in Figures 5C and 5D, significant orientation was observed for the PP TI4020N resin film due to rotation and reorganization of the crystalline structure into a fibrillar structure, as indicated by strong diffraction intensity emissions in the (110), (040), (130), and (131) planes. Similar observations were also made for the PP INSPIRE® 114 resin film (not shown). From the above WAXS results, it was inferred that the stretching force was applied to the crystalline polypropylene structure of the PP TI4020N resin film and the PP INSPIRE® 114 resin film, but that the stretching force was transferred to the EP phase to initiate and grow pores during the stretching process of the PP C7054-07NA resin and the PP C700-35N resin film. This discrepancy results in high porosity for both the PP C7054-07NA resin and the PP C700-35N resin microporous films, but low porosity for both the PP TI4020N resin film and the PP INSPIRE® 114 resin microporous film.

[0175] Example 6 Pore ​​formation via stretching of unannealed films has been previously demonstrated using a PP copolymer (see PP C7054-07NA microporous film above) (Examples 2-4 above). Blends of this PP copolymer as the major component with the homopolymer PP, PP H314 (as a minor component) were also investigated (Table 7). Films were prepared as described above and stretched under the following stretching conditions: 25% cold stretch (room temperature) at a stretch rate of 100 mm / s, followed by 100% hot stretch (100°C) at a stretch rate of 5 mm / s.

[0176] [Table 8]

[0177] Blending increasing amounts of homopolymer-PP with PP C7054-07NA copolymer followed by cold and hot stretching processes resulted in progressively lower porosity and lower average pore size in the stretched microporous films until no pore formation was obtained with 40% additional homopolymer-PP.

[0178] Similarly, pore formation via stretching of unannealed films was previously demonstrated using another PP copolymer (see PP C700-35N microporous film, Table 3) (Example 2). Further blending of this PP copolymer as the major component with the homopolymer PP, PP H314 (as a minor component) was also investigated (Table 8).

[0179] [Table 9]

[0180] Blending 20 wt% of the homopolymer PP H314 with PP C7054-07NA using a twin-screw extruder followed by film production also reduced the inclusion morphology, such that upon stretching, the majority of the microphase domains extended only along the stretch direction (see, e.g., TEM images in Figures 6A and 6B).

[0181] The results for films from blends of PP C700-35N with homopolymer-PP were similar to those for films from blends of PP C7054-07NA with homopolymer-PP.

[0182] As noted above, pore formation via stretching of unannealed films has been demonstrated for a PP copolymer (see PPC7054-07NA microporous film above). Further blending of this copolymer as a major component with a PP copolymer, PP TI4020N (as a minor component), to form pores via stretching of unannealed films has also been demonstrated (Table 9).

[0183] [Table 10]

[0184] Blends of PP C700-35N and PP TI4020N can also form films that can be stretched (without pre-annealing) to produce microporous films.

[0185] Other polymer blends were evaluated as follows: VERSIFY® 2000 resin (melt flow rate = 2 g / 10 min at 230°C and 2.16 kg) is an ethylene-propylene random copolymer with a composition of 94% P / 6% E (propylene-rich). VERSIFY® 2400 resin (melt flow rate = 2 g / 10 min at 230°C and 2.16 kg) is also an ethylene-propylene random copolymer with a composition of 86 wt% P / 14 wt% E (propylene-rich). In each case, two blend ratios (85:15 and 70:30) with homopolymer PP (PP H314) were prepared. PP H314 was the major component in all blends. Unannealed films of these blends were subjected to the CS25-HS100 stretching conditions (described above). None of these PP / EP blends formed pores after the stretching process. This may be due to the high content of propylene segments in VERSIFY® 2000 and VERSIFY® 2400 resins, which have good compatibility with the PP matrix and therefore cannot induce sufficient phase separation in the PP H314 resin.

[0186] The 13C04R21 experimental resin (melt flow rate = 18 g / 10 min at 230 °C and 2.16 kg) is an isotactic PP diblock block copolymer with a 50:50 ratio of PP:EP components in the copolymer, with the EP copolymer block containing 14 wt% E and 86 wt% P (total ethylene content of the resin is 7 wt%). Blends of this diblock copolymer with homopolymer PP (PP H314) were prepared in ratios of 85:15, 80:20, 70:30, and 60:40 (predominant PP), and unannealed films were subjected to the CS25-HS100 stretching conditions (described above). None of these PP / EP blends formed pores after the stretching process. The EP block in this experimental-grade resin contains only 14 wt% ethylene, producing a PP-rich EP block. As a result, it is believed that the EP and iPP blocks have good compatibility with the homopolymer PP resin, and therefore the EP blocks are unable to initiate significant phase separation in the film.

[0187] INTUNE® D5545.00 (melt flow rate = 9.5 g / 10 min at 230°C and 2.16 kg) is another isotactic PP diblock block copolymer with a 50:50 ratio of PP:EP copolymer, but the EP copolymer block is ethylene-rich, containing 92 wt% E and 8 wt% P (total ethylene content of the resin is 46 wt%). Stretching the unannealed film (CS25-HS100 stretching conditions in Example 6 above) achieves only minimal pore formation: 13.6% porosity and an average pore size of 14.1 nm. The diblock copolymer film is not suitable for its intended purpose as a housewrap material. Blends of this diblock copolymer with homopolymer PP (PP H314) were prepared in ratios of 85:15, 80:20, 70:30, and 60:40 (predominant PP), and unannealed films were subjected to the CS25-HS100 stretching conditions (described above) of Example 6. None of these PP / EP copolymer blends formed pores after the stretching process.

[0188] NORDEL® 3722P is an EPDM (ethylene-propylene diene monomer) copolymer with a composition of 28.5 wt% propylene, 71 wt% ethylene, and 0.5 wt% ENB (ethylidene norbornene). Blends of the primary homopolymer PP with NORDEL® 3722P were investigated, including blend ratios of 90:10, 80:20, and 70:30 (polypropylene-rich), PP-H314:NORDEL® 3722P. Unannealed films were subjected to the CS25-HS100 stretching conditions (described above). None of these PP / EP copolymer blends formed pores after the stretching process.

[0189] Additionally, ethylene acrylic acid (PRIMACOR® 1410 resin: 90.3 wt. % E, 9.7 wt. % acrylic acid) was evaluated (melt flow rate = 1.5 g / 10 min at 230°C and 2.16 kg). The blend was 85 wt. % PP H314 resin and 15 wt. % PRIMACOR® 1410 resin. Under the same stretching conditions, this blend failed to exhibit pore formation. PRIMACOR® 1410 resin was incompatible with PP H314 resin, thus forming a completely separate interface between the two phases.

[0190] Example 7 This example examines the aging performance of non-thermoset microporous films. Many prior art microporous films have been observed to suffer from property degradation after heat aging (see, for example, Table 1 of U.S. Pat. No. 3,801,404, which shows the progressive loss of nitrogen flux of polypropylene microporous films from 1 to 281 hours at 65°C; and Table 2 of U.S. Pat. No. 3,843,761, which shows the air flow loss rate of polypropylene microporous films after 1 hour at 90°C). Heat setting (annealing at high temperatures after stretching polyolefin films) has often been used in the prior art (e.g., U.S. Pat. No. 3,679,538) to prevent loss of water vapor permeability during aging (e.g., at 65°C). Non-thermoset PP C7054-07NA MDO microporous films (uniaxially stretched, machine-oriented) were aged at 65°C for various times ranging from 1 hour to 168 hours (Table 10).

[0191] [Table 11]

[0192] As shown in Table 10, the water vapor transmission rate data did not change significantly over time. In the present invention, the stretching force was dissipated to shift to the microphase rubber-like (ethylene-propylene copolymer) region and create the microporous structure, as indicated by the slight change in the wide-angle X-ray (WAXS) data of the uniaxially oriented (MDO) PP C7054-07NA microporous film before and after stretching (Figures 5A and 5B). In contrast, for comparative films, such as the PP TI4020N resin film, the crystalline structure rotated and reorganized into a fibrillar structure, and significant orientation was observed in the WAXS data after stretching, as indicated by the emission of strong diffraction intensity in the (110), (040), (130), and (131) planes (Figure 5C before stretching vs. Figure 5D after stretching). This aging performance of the breathable film disclosed herein distinguishes it from other homopolymer polyolefin microporous films reported in the prior art, which always require heat curing.

[0193] Other than from the perspective of air permeability, the same phenomenon of performance degradation after a heat-setting step was investigated in U.S. Patent No. 3,843,761. In U.S. Patent No. 3,843,761, films resulting from the heat-setting step were compared to control films that did not undergo the heat-setting step. This reference concluded that the flow rate loss due to the heat-setting step ranged from 44 to 88% loss for the prior art cold-stretch / single hot-stretch process, and that the flow rate loss due to the heat-setting step ranged from 24 to 37% loss for their novel cold-stretch / multiple consecutive hot-stretch process.

[0194] To compare with the heat-setting results disclosed in U.S. Patent No. 3,843,761, PP C7054-07NA microporous films were prepared with the same stretching degrees as those disclosed in U.S. Patent No. 3,843,761 (see Table 11). Specifically, the first sample, PP C7054-07NA-CS20-HS95, was stretched by 20% cold stretching at 100 mm / s, followed by 95% hot stretching at 5 mm / s and 100°C. The second sample, PP C7054-07NA-CS40-HS75, was stretched by 40% cold stretching at 100 mm / s, followed by 75% hot stretching at 5 mm / s and 100°C.

[0195] [Table 12]

[0196] These microporous films were then subjected to the same heat curing step (1 hour at 90°C) as in the reference patent. The relative air permeability is calculated by the following formula:

number

[0197] Table 12 shows the relative air permeability (as defined above) of microporous films comparing the Gurley air permeability before and after heat setting for 1 hour at 90°C (for each film type, four samples at four locations for each sample; each relative air permeability entry in the table is the average of four ratios determined from four measurements at four locations before and after heat setting).

[0198] [Table 13]

[0199] From Table 12, it can be seen that the average relative air permeability is about 1.5 for both stretched films, indicating that for the films of the present invention, the (normal) air permeability increases by about 50% after heat setting, unlike the 24-88% flow loss disclosed in U.S. Pat. No. 3,843,761. The porous structure of the polyolefin-based microporous films disclosed in the present invention can withstand the heat setting process.

[0200] The breathable films of the present invention can be prepared without an annealing step before stretching to produce a microporous film, and further do not require any heat setting step after pore formation. Furthermore, if a heat setting step is desired for any reason, the films of the present invention do not suffer any loss in permeability compared to films that do not undergo a heat setting step.

[0201] Example 8 This example demonstrates the performance of PP copolymer biaxially stretched microporous films.

[0202] PP C7054-07NA copolymer film was subjected to simultaneous biaxial stretching, specifically, 25% cold stretching at room temperature at a speed of 100 mm / s and 50% hot stretching at 100°C at 5 mm / s. As shown in Table 13, the PP C7054-07NA biaxially stretched microporous film has a porosity of 34.7% and an average pore size of 44 nm. Correspondingly, the water vapor transmission rate for this microporous film is about 42 perm (Table 14), and after aging at 65°C for 168 hours, the water vapor transmission rate increases to 60 perm (Table 14).

[0203] [Table 14]

[0204] [Table 15]

[0205] This example demonstrates that biaxial orientation can also be used to produce microporous films.

[0206] Example 9 To conduct a proof-of-concept study for roof membranes, 762 μm (30 mil) thick PP C7054-07NA films were subjected to a 25% cold stretch (CS) at 100 mm / s at room temperature, followed by a 100% (150% for the second film) hot stretch (HS) at 5 mm / s at 100°C. Pore size distribution data ranging from tens of nanometers to several microns is shown in Figure 7. Table 15 shows that PP C7054-07NA-CS25-HS100, approximately 660 μm (25.5 mil) thick, has a porosity of 42.5%, resulting in a water vapor transmission rate of 58 perm, while PP C7054-07NA-CS25-HS150, approximately 533 μm (20.6 mil) thick, has a higher porosity of 55%, resulting in a water vapor transmission rate of 62 perm.

[0207] [Table 16]

[0208] Useful porosity (e.g., greater than 25%) and permeability values ​​(e.g., greater than 10 perm) are also obtained from thicker 762 μm (30 mil) films, suggesting that the films of the present invention may find utility in breathable roof membranes.

[0209] Example 10 Stretched microporous PP copolymer films were evaluated for medical packaging films and active packaging, where various combinations or degrees of air or water vapor permeability or microbial barrier may be required for each end use. Table 16 shows the film thickness, basis weight, porosity, and pore size (average pore size) for microporous films obtained from various stretching conditions.

[0210] [Table 17]

[0211] The same series of films was further investigated for permeability properties (Table 17), physical properties (Table 18) and gas fill / empty rates (Table 19) when used as medical packaging.

[0212] Table 17 shows the key barrier properties (Gurley air permeability, water vapor transmission rate and F2638 barrier to microorganisms) obtained for the same microporous films shown in Table 16.

[0213] [Table 18]

[0214] Table 17 shows data for uniaxially stretched PP copolymer films, demonstrating that permeability properties can be modified and controlled by changing the stretching conditions. Target ranges for various properties can be estimated by comparison with existing commercial products for these applications (e.g., Tyvek® 1073B or medical-grade paper), but these are not strict targets, as there are various end uses for films with different balances of properties (and any one or more of the properties of the commercial product may significantly exceed the minimum target range required for that property). At optimized stretching conditions or by using biaxially stretched films (F2638 P max The microbial barrier (as indicated by the pore size) should already be in a commercially viable target range, and a target for Gurley air permeability (probably about 10-100 seconds for some applications) should also be available. Some applications may require a specific hydrohead value (resistance to water pressure). As shown in Table 16, porosity and average pore size were measured for Films 4-9; porosity did not vary significantly (43%-53%), and pore size ranged from 70 nm to 108 nm. Although not shown in the table, Films 1-9 had hydrohead values ​​greater than 500 cmwc (cm of water column), easily exceeding the hydrohead value of Tyvek® 1073B (about 150 cmwc).

[0215] In addition to permeability properties, breathable films for medical films and active packaging also require adequate physical properties related to film strength, such as tensile strength, tear strength, and % elongation. Table 18 summarizes such properties for the same series of breathable PP copolymer microporous films.

[0216] [Table 19]

[0217] The stretching process conditions can be varied to control the film's thickness / basis weight and other physical properties (e.g., tensile strength, tear strength, and elongation) that are important for maintaining package integrity during shipping, sterilization, and storage, and for ensuring that the packaging structure does not tear when the package is peeled open.

[0218] Compared to current technology, at least, the tensile strength of these films appears to be sufficient for most medical and active packaging applications.

[0219] Medical packaging currently finds use as container packaging that can be filled with a sterilant gas (such as steam or ethylene oxide) to sterilize the package contents (such as a medical device or instrument). The package is filled with the sterilant, the contents then remain with the sterilant gas for a residence time for the sterilization process, and then the gas is vented and the package is sealed with the sterilized device inside. The packaging material provides a barrier against bacteria, microorganisms, and particulate matter so as to maintain the sterility of the medical device within the package after sterilization until such device is ready for use.

[0220] Table 19 explores how the stretching process conditions can affect the fill / empty time of PP copolymer films.

[0221] [Table 20]

[0222] In Table 19 above, the improvement in Gurley Air Permeability between the comparative film (immediately after cold stretching) and the inventive film ranges from 45,200 to 860 seconds, which already represents a 20% improvement in the time to fill (or empty) the medical package with gas. To demonstrate that a relatively modest improvement in Gurley Air Permeability, even if it does not match the Gurley Air Permeability of Tyvek® 1073B, corresponds to a significant % improvement in the time to fill (or empty) the medical package with gas, which can translate into significant cost savings when such medical packages are used for sterilization of medical instruments and devices, Table 19 also includes hypothetical films, Breathable Film (1) and Breathable Film (2), having Gurley Air Permeabilities of 300 seconds and 100 seconds, respectively.

[0223] The PP copolymer microporous films described herein are well suited for medical packaging. Compared to current polyethylene technology, sterilization processes can be carried out at higher temperatures due to the higher melting temperature of PP copolymer films compared to polyethylene films (e.g., the typical melting temperature of high-density polyethylene is about 125-130°C by DSC, whereas the typical melting temperature of the inventive PP-EP copolymers disclosed herein is about 168°C by DSC). Furthermore, PP copolymer films are easily thermoformable (enabling easily customizable packaging for a variety of medical devices and instruments) and heat-sealable (to easily seal sterilized packs).

[0224] When ranges are used herein with respect to physical properties, such as temperature ranges and pressure ranges, or chemical properties, such as monomer or copolymer content, all combinations and subcombinations of ranges and specific embodiments therein are intended to be included.

[0225] The disclosures of each patent, patent application and publication cited or described herein are hereby incorporated by reference in their entirety.

[0226] Those skilled in the art will recognize that many changes and modifications to the preferred embodiments of the present invention may be made without departing from the spirit of the present invention, and it is therefore intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the present invention.

[0227] Reference Example Numerous PP copolymer films of various thicknesses were extrusion cast onto a chill roll set at a temperature of 80°C using a 2.5-inch single-screw extruder and a 24-inch wide casting die manufactured by Davis-Standard, LLC to produce films with a smooth surface. The base resin was PP C7054-07NA, a polypropylene copolymer available from Braskem American, Inc. (product code C7054-07NA). The extruder was maintained at a constant temperature profile of 460°F (238°C), and the chill roll temperature was heated by heated oil. The resulting film thicknesses are summarized in Table 20.

[0228] [Table 21]

[0229] Example 11 The individual film samples in Table 20 were then stretched in the machine direction (MDO - machine direction orientation) using a multi-stage cold stretching process as shown in Figure 8. Each sample of PP copolymer film from Table 20 was attached to unwinder section 20, guided by 11 stretching rollers (1-11), including pre-stretch section 23, stretch section 24, and annealing section 25, and rewound onto winder section 21. Pressure was then applied to the film to prevent slippage during stretching, and the nip rollers were closed. The roller speeds of rollers 3-7 were slowly increased, stretching the film 50% or 100% at 25°C. During the stretching process, the film changed color from translucent to white, indicating initial pore formation. In annealing section 25, the cold-stretched film was then heated at 140°C on rollers 9-11 to fix the pore structure induced by the cold stretching step. The film was then cooled and rewound onto the winder. The measured properties of the final film are summarized in Table 21. The cold stretch degree is defined as (total roller speed ratio - 1) x 100%, and the total roll speed ratio is the result of multiplying all roller speed ratios together (from roller 2 / roller 1 to roller 8 / roller 7).

[0230] [Table 22]

[0231] The MDO cold-stretched films were then further hot-stretched in the machine direction (MDO) using the same multi-step process as shown in Figure 8; however, for hot-stretching, the process included a pre-hot-stretch section 23, a hot-stretch section 24, and an annealing section 25. Each MDO cold-stretched film was attached to an unwinder section, guided by 11 stretching rollers, and rewound onto another winder section 21. In this process, the first eight rollers were set to a hot-stretching temperature of 135°C. To apply pressure to the film to prevent slippage during stretching, the nip rollers were closed, and the roller speed of rollers 5-8 was then slowly increased to stretch the film by 50% or 100% at 135°C. After the hot-stretching step was completed, the film was annealed on rollers 9-11 at 140°C to reduce film shrinkage. The film was then cooled in winder section 22 and rewound into a roll. The hot stretch degree is defined as (total roller speed ratio - 1) x 100%, and the total roll speed ratio is the result of multiplying all roller speed ratios together (from roller 5 / roller 4 to roller 8 / roller 7). It can be seen from Table 22 that upon completion of MDO hot stretching, the porosity and average pore size of the PP film increased, which resulted in a higher water vapor transmission rate and a lower Gurley air permeability.

[0232] [Table 23]

[0233] Example 12 To illustrate the potential adverse effects of hot stretching on pore formation and air and water vapor permeability, the above cold and hot stretching processes were applied to a sample of Film 1 that was cold stretched 122% in the machine direction at 25°C and subsequently hot stretched 103% to 405% in the machine direction. As shown in Table 23, the porosity and permeability of the film worsened with stretching at higher temperatures. Consequently, biaxial stretching was proposed to further increase the porosity and pore size, thereby resulting in higher water vapor permeability and lower Gurley air permeability.

[0234] [Table 24]

[0235] Example 13 A selection of MDO cold- and hot-stretched films from Example 11 were then further hot-stretched in the transverse direction using a process as shown in Figure 9, including an unwinding section 41, a multi-zone oven 50 with a preheating section 43, a TDO (transverse direction orientation) stretching section 44, an annealing section 45, and a cooling section 46. The TDO line had a feed width ranging from 127 mm to 1,016 mm between clips and an exit width ranging from 203 mm to 2,184 mm between clips to stretch the film in the transverse direction. The TDO clips were capable of holding a wide range of material, with film thicknesses ranging from 25 μm to 2.54 mm. Following the heated sections (43, 44, and 45) was a 1.5 m-long cooling section 46 with circulating ambient air. After the TDO oven was preheated to the target temperature (135°C), the MDO stretched film was attached to the unwinder and guided through the feed section of the TDO line. The film was gradually gripped with clips and pulled at the same width through the preheating zone. The film was then stretched in the transverse direction until the TDO target stretch degree was reached. Upon completion of stretching, the film was passed through an annealing section 45 at 140°C and subsequently quenched with circulating ambient air in a cooling zone 46. The stretched film was then guided through a stack of rolls and rewound onto the winder section 42. To simplify the testing, the line speed was fixed at 2 m / min. The TDO stretch degree varied from 50% to 400%. Table 24 shows the stretching conditions and properties of biaxially oriented PP breathable films prepared by MDO cold stretching, MDO hot stretching, and TDO hot stretching. All samples had a hydrohead greater than 300. These experiments demonstrated that biaxial stretching is highly effective in opening additional pores in the film. It can be seen from Table 24 that many of the biaxially oriented films have porosities approaching 70% and average pore sizes greater than 200 nm. Correspondingly, most samples have Gurley air permeabilities of less than 100 sec / 100 cc, with some in the 20-30 sec / 100 cc range, but many have water vapor transmission rates greater than 100 per m. At the same time, although not shown in the table, all of the films have hydroheads greater than 300 cm, indicating good water resistance.Furthermore, the microbial barrier (%Pmax) measured by F2638 shows very good results (well within the target range).

[0236] [Table 25]

[0237] Example 14 Table 25 shows the stretching conditions and properties of biaxially oriented PP breathable films prepared by MDO cold stretching followed by TDO hot stretching. Even without MDO hot stretching, very high porosity can be achieved. Furthermore, porosity and average pore size continued to increase with increasing TDO stretching. Correspondingly, these PP breathable films exhibit comparable water vapor transmission rates, Gurley air permeability, and microbial barrier properties.

[0238] [Table 26]

[0239] Example 15 An important characteristic for a waterproof and breathable roof membrane is that it must pass the Hydrohead test, which requires it to resist 30 meters of water for at least 30 minutes. A selection of stretched films for use as roof membranes was made and tested. As can be seen from Table 26, all samples produced by cold and hot stretching passed the Hydrohead test. These MDO samples had film thicknesses ranging from 0.19 mm to 0.53 mm and exhibited water vapor transmission rates (WVTRs) ranging from 29.1 per m to 76.7 per m. Biaxially stretched samples produced by cold MDO stretching followed by hot TDO stretching did not pass the Hydrohead test due to the more interconnected pores created by the biaxial stretching process.

[0240] [Table 27]

[0241] Example 16 Polypropylene (PP) film samples were produced by cold and hot MDO stretching and tested for use as roof underlayment. All samples shown in Table 27 passed the water resistance (W1), durability after aging (EN 1297 & EN 1296), flexibility at low temperatures (≦-20°C), and side-drop test (TU Berlin). However, Table 27 shows that samples 16a and 16b had poor nail tear strength properties due to low film thickness after stretching. Samples 16c and 16d demonstrate that acceptable nail tear strength can be achieved by increasing film thickness. Samples 16e, 16f, and 16g demonstrate another possible solution: laminating thinner films with grids or nonwoven films. 16e was laminated to a D&L grid, 16f was laminated with Thermanet®, and 16g was laminated to a spunbond PP nonwoven. The property data for these laminates are shown in Table 27. These laminated films demonstrated significant improvement in nail tear strength.

[0242] [Table 28]

[0243] Example 17 Microbial barrier tests were collected on a selection of films from Examples 13 and 14 according to ASTM F2638, with additional particulate barrier testing on a TSI-8130 automated filter tester. The resulting data are shown in Table 28. Biaxial orientation allows for an increase in porosity and average pore size, thus increasing the 100 sec / 100 cm 3 This led to lower Gurley air permeabilities down to less than 0.25%. All biaxially oriented samples showed very good microbial barrier (<0.25% Pmax) within the target range. Furthermore, burst pressures, as measured by the Hydrohead test, were higher than 5 meters for all biaxially oriented PP breathable films.

[0244] [Table 29]

[0245] Example 18 This is an example of the preparation of a PP copolymer film further comprising an ethylene-propylene elastomer.

[0246] The (a) polypropylene copolymer used was a reactor grade PP copolymer purchased from Braskem known as C7054-07 NA polypropylene (PP C7054-07 NA). It contained 32.9 wt. % ethylene-propylene copolymer, with an ethylene content of 49.7 wt. % in the ethylene-propylene copolymer. It had a mass fraction of 0.9 g / cm. 3 and a melt index of 7 g / 10 min at 230°C under a load of 2.16 kg. PP C7054-07NA has a number average molecular weight (Mn) of 58,000 and a weight average molecular weight (Mw) of 295,000.

[0247] The (b) ethylene-propylene elastomer used was Vistalon™ 785, an ethylene-propylene copolymer rubber (EPR) obtained from ExxonMobil Chemical. It is an amorphous copolymer of ethylene and propylene with low Mooney viscosity, low ethylene content, and narrow molecular weight distribution. It contains 49% by weight ethylene content (per ASTM D3900A) and has a Mooney viscosity of 30 MU (per ASTM D1646). The PP copolymer was compounded with the EP elastomer to produce a modified compounded mixture for subsequent processing by successive cold and hot drawing.

[0248] The PP copolymer and EPR were compounded together using a 43 mm co-rotating twin-screw extruder. The PP copolymer was fed into the first barrel of the extruder, operating at 250 rpm, and pre-melted by the co-rotating screws before contacting the EPR. To aid processing and allow for metering of the EPR, a 4-inch (101.6 mm) Bonnot extruder was used to pulverize and preheat the EPR, then metered into the twin-screw extruder via a gear pump and spliced ​​into the PP melt at barrel 3. The EPR was measured at 112°C just before the gear pump. This PP / EPR mixture was then conveyed through a series of mixing elements, with the barrel temperature maintained at 200°C. The actual melt temperature was monitored during operation and increased from 170°C in barrel 5 to a peak temperature of just under 245°C in barrel 10. A water ring vacuum of -27 inHg was applied to barrel 11 to remove volatiles before pumping through barrel 12 to the die. The resulting product was collected from an underwater palletization system operating at 450-550 psig with a die heated to 220° C. The compositions, compounding conditions, EPR rubber concentration, and DSC results are summarized in Table 29.

[0249] [Table 30]

[0250] PP copolymer films were then produced on a film casting line consisting of a Davis-Standard 1-inch single-screw extruder and a 6-inch-wide casting die. Cast films were produced from the above materials (see Table 1) in a range of thicknesses by controlling the single-screw speed, and therefore throughput, and adjusting roller speed for overall line speeds ranging from 1 to 10 ft / min. A melt filter pack with a stack of 150 / 200 / 150 mesh screens was used in-line to remove gel from the melt stream before cooling to 200°C at the die. Films from the die were cast onto a chill roll, temperature-controlled at 50°C to ensure good film quality before winding onto a 3-inch core at the winding station. 10-mil films were cast from the R10, and 20-mil films were cast from the R30.

[0251] TEM was used to investigate the film morphology. Figure 10 shows a TEM image of (a) a cast film made from a polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments, and (b) without an ethylene-propylene elastomer, before any stretching. This image shows the encapsulation morphology in which the matrix PP material is contained inside the EP microphase domains. This unique morphology allows the transmission of stretching forces to disrupt the microphase domains, thus initiating and propagating pore formation during stretching. Figure 11 shows a TEM image of an R10 cast film made from (a) 90 weight percent polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments, and (b) 10 weight percent ethylene-propylene elastomer, before any stretching. The encapsulation morphology remained intact, and the domain size increased slightly. Figure 12 shows a TEM image of an R30 cast film made from (a) 70 weight percent polypropylene copolymer containing polypropylene homopolymer chain segments and ethylene-containing copolymer chain segments and (b) 30 weight percent ethylene-propylene elastomer before any stretching. Further increasing the EPR content for this film significantly increased the domain size, but the encapsulated morphology still persisted.

[0252] The cast film samples were then stretched in the machine direction (MDO - machine direction orientation) using a multi-stage cold stretching process. Each PP / EPR film sample was mounted on an unwinder and guided through 11 stretching rollers (1-11), which included a pre-stretching section, a stretching section, and an annealing section, before being rewound onto the take-up section. Pressure was then applied to the film, and the nip rollers were closed to prevent slippage during stretching. The roller speed of rollers 3-7 was slowly increased, stretching the film 50% at 25°C. During the stretching process, the film changed color from translucent to white, indicating initial pore formation. In annealing section 25, the cold-stretched film was then heated at 135°C on rollers 9-11 to fix the pore structure induced by the cold stretching step. The film was then cooled and rewound onto the winder. The cold stretch degree is defined as (total roller speed ratio - 1) x 100%, and the total roll speed ratio is the result of multiplying all roller speed ratios together (from roller 2 / roller 1 to roller 8 / roller 7).

[0253] The MDO cold-stretched films were then further hot-stretched in the machine direction (MDO) using the same multi-step process; however, as for hot-stretching, the process included a pre-hot-stretch section, a hot-stretch section, and an annealing section. Each MDO cold-stretched film was attached to an unwinder section, guided by 11 stretching rollers, and rewound onto another winder section. In this process, the first eight rollers were set to a hot-stretching temperature of 130°C. To apply pressure to the film to prevent slippage during stretching, the nip rollers were closed, and the roller speed of rollers 5-8 was then slowly increased to stretch the film 50% at 130°C. After the hot-stretching step was completed, the film was annealed on rollers 9-11 at 135°C to reduce film shrinkage. The film was then cooled in the winder section and rewound into a roll. The hot stretch degree is defined as (total roller speed ratio - 1) x 100%, and the total roll speed ratio is the result of multiplying all roller speed ratios together (from roller 5 / roller 4 to roller 8 / roller 7).

[0254] Table 30 shows the stretching conditions, water vapor transmission rate, air permeability, porosity, and average pore size of the PP / EPR films compared with those of the PP films. All of these films have the same degree of cold stretching (50%) and hot stretching (50%). The water vapor transmission rate of the PP-22 mil film is 52 ppm, while the water vapor transmission rates of the R10-10 mil and R30-20 mil films are 48.2 ppm and 27.5 ppm, respectively. This confirms that good water vapor transmission rates can be maintained even after incorporating EPR rubber into the PP film. The Gurley permeability of the R10-10 mil film is lower than that of the PP-22 mil film, which may be due to the fact that the R10-10 mil film has a thinner thickness. The high concentration of EPR in the R30-20 mil film results in a very high Gurley permeability.

[0255] [Table 31]

[0256] Table 31 summarizes the hydrohead, tensile strength, elongation at break, modulus, and trapezoid tear data for PP / EPR films compared to PP films. Both the R10-10 mil and R30-20 mil films, made by adding EPR to PP, had lower moduli than the PP-20 mil film. The addition of EPR to PP films also improved the film's tear strength. The trapezoid tear (maximum load) of the R30-20 mil film was more than twice that of the PP-22 mil film.

[0257] The addition of EPR also did not significantly adversely affect other film properties, such as tensile strength. The elongation at break of the R30-20 mil film was twice that of the PP-20 mil film, and the elongation at break of the R10-10 mil film was slightly lower than that of the PP-20 mil film, which may be related to the smaller film thickness of the R10-10 mil film (greater data scatter). All of these films also exhibited excellent water retention (hydrohead > 300 cm).

[0258] In other words, by incorporating EPR into PP films, the toughness and tear strength of PP breathable films can be significantly improved while maintaining water vapor permeability and water retention.

[0259] [Table 32]

[0260] Example 19 The thermal welding ability of the microporous film of Example 18 without adhesive coating was investigated. The edges of two samples of R30-20 mil microporous film were overlapped and welded by applying hot air (welding temperature 250°C). Similarly, the edges of two samples of PP-22 mil microporous film were overlapped and welded by applying hot air. The overall appearance of the two welded samples indicated that the R30-20 mil film sample shown in Figure 13 exhibited better visual sealing performance than the PP-22 mil film sample shown in Figure 14. While the PP film without EPR rubber was brittle and cracked after welding, incorporating EPR rubber into the PP breathable film (R30-20 mil film) made welding easier and the welded area stronger than the PP microporous film without EPR rubber.

[0261] Example 20 The machine direction (MDO) cold stretched and thereafter hot stretched film of Example 18 was then further hot stretched using a process and equipment similar to that described in Example 13 and shown in FIG. 9 , including an unwind section 41; a multi-zone oven 50 having a preheating section 43, a TDO (transverse direction orientation) stretching section 44, an annealing section 45, and a cooling zone 46; and a rewind section 42; except that the TDO oven was preheated to 130° C. and the annealing section 45 was set to 135° C.

[0262] The general properties of the biaxially stretched films (including increased porosity) and the extent of the difference in properties between machine direction only (MDO) films and films produced by biaxial stretching are similar to those in Examples 13 to 15 and Example 17. The following lists embodiments of the present invention. [Aspect 1] A microporous polymer film, (a) 50 to 95 weight percent, based on the total weight of the film, of one or more polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments. said microporous polymer film comprising: (i) polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer, or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) ethylene-containing copolymer chain segments in a total amount of 18 to 50 wt. % based on the weight of the polypropylene copolymer, or 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the film; Includes; A microporous polymer film, wherein at least 45 weight percent of the polymerized units in said ethylene-propylene elastomer are ethylene units. [Aspect 2] 2. The microporous film of claim 1, wherein in (b), the one or more ethylene-propylene elastomers are 5 to 30 weight percent, based on the total of (a) and (b) in the film. [Aspect 3] 3. The microporous film of claim 2, wherein in (b), the one or more ethylene-propylene elastomers are 5 to 20 weight percent, based on the total of (a) and (b) in the film. [Aspect 4] The microporous film according to any one of Aspects 1 to 3, wherein in (b), 45 to 80 weight percent of the polymerization units in the ethylene-propylene elastomer are ethylene units. [Aspect 5] A microporous film according to aspect 4, wherein in (b), 45 to 60 weight percent of the polymerization units in the ethylene-propylene elastomer are ethylene units. [Aspect 6] In (b), the ethylene-propylene elastomer is ethylene-propylene rubber (EPR), ethylene propylene diene monomer (EPDM) rubber, or a mixture thereof, the microporous film of any one of aspects 1 to 5. [Aspect 7] The microporous film according to any one of aspects 1 to 6, wherein in (b), the ethylene-propylene elastomer has a Mooney viscosity of 10 to 40 Mu. [Aspect 8] The microporous film according to any one of aspects 1 to 7, which consists of (a) and (b). [Aspect 9] The microporous film of any one of aspects 1 to 8, wherein the tensile modulus of the microporous polymer film comprising (a) and (b) is less than the tensile modulus of the film made from only (a). [Aspect 10] 10. The microporous film of any one of aspects 1 to 9, wherein the water vapor permeability of the microporous polymer film comprising (a) and (b) is less than the water vapor permeability of a film made of only (a). [Aspect 11] 11. The microporous polymer film of any one of aspects 1 to 10, wherein in (a), the ethylene-containing copolymer chain segment is an ethylene-propylene copolymer chain segment. [Aspect 12] 12. The microporous polymer film of claim 11, wherein in (a), the ethylene-propylene copolymer chain segment is an ethylene-propylene diblock copolymer chain segment comprising a polypropylene block and a polyethylene block, or a diblock copolymer chain segment comprising a polypropylene block and an ethylene-propylene copolymer block. [Aspect 13] 13. The microporous polymer film of any one of the preceding embodiments, having a porosity of at least 25% by UOP method 578-11, 4V / A, and a median pore size of at least 25 nm, both characteristics measured by mercury intrusion porosimetry. [Aspect 14] 14. The microporous polymer film of any one of claims 1-13, wherein the nonporous polymer film has a domain of (a) and a domain of (b), wherein the domain of (a) further has a morphology characterized by a majority polymer phase of polypropylene, a plurality of minor polymer domains of an ethylene-containing copolymer within the majority polymer phase, and an inclusion phase of a major polypropylene phase within the minor polymer domains. [Aspect 15] 15. The microporous polymer film of any one of embodiments 1 to 14, which is a roof membrane or a component thereof. [Aspect 16] 16. The microporous polymer film of any one of embodiments 1 to 15, having a thickness of at least 100 μm to 2.5 mm. [Aspect 17] A medical packaging or active packaging article or a medical back table cover comprising the microporous polymeric film of any one of embodiments 1 to 16. [Aspect 18] 18. The medical packaging or active packaging article or medical back table cover of aspect 17, wherein the microporous polymeric film has a barrier to microorganisms that is equivalent to the maximum penetration, calculated %Pmax, as defined by ASTM F2638-18, of less than 10%. [Aspect 19] 18. The medical packaging or active packaging article or medical back table cover of claim 17, wherein the microporous polymeric film has a Gurley Gauge air permeability of 1 to 35,000 seconds / 100 cm3 and controls the inflow or outflow of air or one or more gases into or out of the package. [Aspect 20] 18. The medical packaging or active packaging article or medical back table cover of claim 17, wherein the microporous polymeric film is thermoformable and heat sealable. [Aspect 21] 1. A method of forming a microporous polymer film, the method steps comprising: A) providing a mixture, said mixture comprising: (a) 50 to 95 weight percent, based on the total weight of the mixture, of one or more polypropylene copolymers: (i) one or more polypropylene homopolymer chain segments in a total amount of 50 to 82 wt % based on the weight of the polypropylene copolymer, or 43 to 79 mol % based on the molar content of polymerized units of propylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) one or more ethylene-containing copolymer chain segments in a total amount of from 18 to 50 wt. % based on the weight of the polypropylene copolymer, or from 21 to 57 mol. % based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the mixture; providing a mixture wherein at least 45 weight percent of polymerized units in said ethylene-propylene elastomer are ethylene units; B) forming a non-porous film from the mixture; and C) The non-porous film (i) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and (ii) at least one hot drawing step at a temperature in the range of 50°C to 140°C and subjecting the sheet to successive cold and hot drawing steps, thereby producing a microporous polymer film. [Aspect 22] 22. The method of claim 21, wherein in (b), 45 to 80 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units. [Aspect 23] 23. The method of claim 22, wherein in (b), 45 to 60 weight percent of the polymerized units in the ethylene-propylene elastomer are ethylene units. [Aspect 24] 24. The method of any one of aspects 21 to 23, wherein in (b), the ethylene-propylene elastomer is an ethylene-propylene rubber (EPR), an ethylene propylene diene monomer (EPDM) rubber, or some mixture thereof. [Aspect 25] 25. The method of any one of aspects 21 to 24, wherein in (b), the ethylene-propylene elastomer has a Mooney viscosity of 10 to 40 Mu. [Aspect 26] A method according to any one of aspects 21 to 25, wherein the mixture consists of (a) and (b). [Aspect 27] 27. The method of any one of aspects 21 to 26, wherein in (a), the ethylene-containing copolymer chain segment is an ethylene-propylene copolymer chain segment. [Aspect 28] The method of any one of aspects 21 to 27, wherein the polypropylene copolymer of (a) is blended with the ethylene-containing copolymer of (a) to form a polymer blend prior to forming the mixture with the one or more ethylene-propylene elastomers (b). [Aspect 29] 29. The method of any one of aspects 21-28, wherein the at least one cold-stretching step stretches the film at least 10% in at least one direction, and the at least one hot-stretching step stretches the film at least 20% in at least one direction. [Aspect 30]

[0033] Aspect 30. The method of any one of aspects 21-29, wherein the microporous polymer film has a porosity of at least 25% by 4V / A, UOP method 578-11, and a median pore size of at least 25 nm, both characteristics measured by mercury intrusion porosimetry. [Aspect 31] 31. The method of any one of aspects 21-30, wherein the microporous polymeric film has a permeability according to ASTM E96 / E96M-16 in the range of 10 to 150 perm.

Claims

1. A microporous polymer film, (a) 50 to 95 weight percent, based on the total weight of the film, of one or more polypropylene copolymers comprising one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments. wherein the polypropylene copolymer comprises (i) 50 to 82 weight percent polypropylene homopolymer chain segments based on the weight of said polypropylene copolymer, or 43 to 79 mole percent polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in said polypropylene copolymer; (ii) 18 to 50 wt. % ethylene-containing copolymer chain segments, based on the weight of the polypropylene copolymer, or 21 to 57 mol. % ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent, based on the total weight of the film, of one or more ethylene-propylene elastomers; Including; A microporous polymer film, wherein at least 45 weight percent of the polymerized units in said ethylene-propylene elastomer are ethylene units.

2. 10. The microporous polymeric film of claim 1, which is or is a component of a roof membrane.

3. A medical packaging or active packaging article or medical back table cover comprising the microporous polymeric film of claim 1 or 2.

4. 1. A method of forming a microporous polymeric film, the method steps comprising: A) providing a mixture, said mixture comprising: (a) 50 to 95 weight percent, based on the total weight of the blend, of one or more polypropylene copolymers: (i) one or more polypropylene homopolymer chain segments, the one or more polypropylene homopolymer chain segments being in an amount of 50 to 82 wt % based on the weight of the polypropylene copolymer, or 43 to 79 mol % as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; (ii) one or more ethylene-containing copolymer chain segments, the one or more ethylene-containing copolymer chain segments being 18 to 50 wt % based on the weight of the polypropylene copolymer, or 21 to 57 mol % as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; one or more polypropylene copolymers comprising: at least a portion of the ethylene-containing copolymer chain segments comprising polymerized units of ethylene in an amount of at least 45 wt %, based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol %, based on the molar content of polymerized units of ethylene in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units of the ethylene-containing copolymer chain segment; (b) 5 to 50 weight percent of one or more ethylene-propylene elastomers, based on the total weight of the mixture; providing a mixture wherein at least 45 weight percent of polymerized units in said ethylene-propylene elastomer are ethylene units; B) forming a non-porous film from the mixture; and C) the non-porous film, (i) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and (ii) at least one hot stretching step at a temperature in the range of 50°C to 140°C and subjecting the sheet to successive cold and hot drawing steps, thereby producing a microporous polymer film.

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