Stretched microporous laminate

Abstract

A microporous laminate comprising a microporous polymeric surface coating comprising a polypropylene copolymer on a nonwoven substrate, the microporous polymeric surface coating having a matrix phase of polypropylene homopolymer segments and a plurality of domains of ethylene-containing copolymer segments within the matrix phase, the domains of ethylene-containing copolymer segments further comprising an interstitial phase of the polypropylene homopolymer segments, wherein the domains of ethylene-containing copolymer segments are fractured to form micropores in the microporous polymeric surface coating, wherein (a) the microporous polymeric surface coating has an average thickness of 0.4 to 3.9 mil (10 to 100 micrometers) and the microporous laminate has a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds force); or (b) the microporous polymeric surface coating has an average thickness of 0.5 to 3.0 mil (12.7 to 76.2 micrometers) and the microporous laminate has a Gurley air permeability of 20 to 150 seconds / 100 cubic centimeters air.

Description

Background Technology

[0001] Technical Field. This invention relates to tough, robust, and water-resistant microporous laminates, which are also permeable to water vapor. Such microporous laminates are suitable for a variety of applications in the construction industry, particularly cladding and roofing applications. Additionally, microporous laminates can also be used in healthcare and packaging applications.

[0002] Description of related technologies. U.S. Patent Application Publication US 2021 / 0095110 and US 2022 / 0298340, both issued to Huang et al., disclose microporous polymer membranes in which membrane porosity is achieved by first preparing a non-porous membrane with microphase separation having primary and secondary polymer domains using a specific type of polymer containing a PP copolymer, followed by a sequential cold / hot stretching process to induce micropore formation and form a microporous membrane through the fracture of secondary domains. The subsequent combination of the fully formed microporous membrane with a nonwoven substrate to form a laminate is also disclosed.

[0003] The microporous membranes described by Huang et al., or conventional polyolefin microporous membranes based on the use of calcium carbonate (CaCO3) as an additive to increase porosity, typically exhibit relatively low tensile strength and trapezoidal tear resistance (e.g., less than 3 lb for 5-mil membranes) due to the presence of their microporous structure. This presents challenges for the use of membranes in roofing and building construction applications, particularly for waterproof barrier (WRB) applications where installers need to peel the membrane from the laminate during installation.

[0004] Existing technologies laminate these fully formed microporous membranes to nonwovens, meshes, or other reinforcing substrates using adhesive lamination, hot-press bonding, or ultrasonic bonding. Adhesives are impermeable; therefore, if adhesive lamination is used, the permeability of the microporous membrane can be reduced due to the adhesive's penetration, and the presence of the adhesive also reduces the thermal aging performance of the laminate. If hot-press bonding or ultrasonic bonding is used, even with a large amount of nonwoven substrate, the microporous membrane is still prone to breaking off from or on the substrate, thus posing durability issues for roofing and construction applications (such as WRB applications).

[0005] Therefore, for roofing and construction applications, what is needed are these products that combine microporous membranes with nonwoven substrates, offering enhanced trapezoidal tear resistance and tensile strength; such products can also possess additional improved or unexpected properties related to water vapor permeability, resistance to liquid water or water pressure head, and Gurley air permeability. These products are not limited to roofing and construction applications but can also be used in medical and other applications. Summary of the Invention

[0006] The present invention relates to a microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate having a first surface and an opposite second surface;

[0007] The first microporous polymer surface coating comprises a polypropylene copolymer, the polypropylene copolymer comprising the following amounts of polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0008] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0009] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0010] At least a portion of these ethylene-containing copolymer segments contain at least 45% by weight of ethylene polymeric units based on the weight of these ethylene-containing copolymer segments; or at least 55% by weight of ethylene polymeric units as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0011] The first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segments, which further has multiple domains of the ethylene-containing copolymer segments within the matrix phase, and these domains of the ethylene-containing copolymer segments further contain an inclusion phase of the polypropylene homopolymer segments within the domains.

[0012] The domains of the ethylene-containing copolymer segments within the matrix phase break down to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating, having the broken domains of the ethylene-containing copolymer segments, has an average thickness of 0.4 to 3.9 mils (10 to 100 micrometers).

[0013] The nonwoven substrate includes a spunbond nonwoven fabric with a random network of continuous filaments of thermoplastic polymer, which are bonded together at the intersections in the random network.

[0014] The polypropylene copolymer of the first microporous polymer surface coating is fused to a continuous filament on the first surface of the nonwoven substrate; and

[0015] The microporous laminate has a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds of force).

[0016] The present invention also relates to a method for forming a microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate having a first surface and an opposite second surface, the method comprising the following steps:

[0017] A) A molten polymer layer is coated onto the first surface of the nonwoven substrate and subsequently cooled to form a nonporous laminate having a nonporous layer of the polymer on the first surface, the nonporous polymer layer having an areal loading of 22.9 to 114.3 gsm and a thickness of 1-5 mils (25 to 125 micrometers), wherein:

[0018] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising the following amounts of polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0019] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0020] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0021] At least a portion of these ethylene-containing copolymer segments comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of these ethylene-containing copolymer segments; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in these ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0022] The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, which further has multiple domains of the ethylene-containing copolymer segments within the matrix phase. These domains of the ethylene-containing copolymer segments further contain an inclusion phase of the polypropylene homopolymer segments within the domains.

[0023] b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer bonded together at the intersections in the random network; the nonwoven substrate has a basis weight of 30 to 100 gsm and less than 50% elongation at break at room temperature.

[0024] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0025] (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and

[0026] (ii) At least 20% to 50% of thermal stretching at a temperature above 100°C;

[0027] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break, thereby forming micropores in the non-porous polymer layer and producing a microporous laminate.

[0028] The present invention further relates to a method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate and a second microporous polymer surface coating on a second surface opposite to the nonwoven substrate, the method comprising the following steps:

[0029] A) A first molten polymer layer is coated on the upper surface of a first surface of the nonwoven substrate, and then cooled. A second molten polymer layer is then coated on the upper surface of the opposite second surface of the nonwoven substrate, and also cooled, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface.

[0030] Each non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0031] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising the following amounts of polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0032] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0033] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0034] At least a portion of these ethylene-containing copolymer segments comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of these ethylene-containing copolymer segments; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in these ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0035] Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, these domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and

[0036] b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer bonded together at the intersections in the random network; the nonwoven substrate has a basis weight of 30 to 100 gsm and less than 50% elongation at break at room temperature.

[0037] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0038] (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and

[0039] (ii) At least 20% to 50% of thermal stretching at a temperature above 100°C;

[0040] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in each non-porous polymer layer and producing a microporous laminate.

[0041] The present invention further relates to a microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate having a first surface and an opposite second surface; the first microporous polymer surface coating comprising a polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments in the following amounts:

[0042] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0043] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0044] At least a portion of these ethylene-containing copolymer segments contain at least 45% by weight of ethylene polymeric units based on the weight of these ethylene-containing copolymer segments; or at least 55% by weight of ethylene polymeric units as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0045] The first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segments, which further has multiple domains of the ethylene-containing copolymer segments within the matrix phase, and these domains of the ethylene-containing copolymer segments further contain an inclusion phase of the polypropylene homopolymer segments within the domains.

[0046] The domains of the ethylene-containing copolymer segments within the matrix phase break down to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating, having the broken domains of the ethylene-containing copolymer segments, has an average thickness of 0.5 to 3.0 mils (12.7 to 76.2 micrometers).

[0047] The nonwoven substrate is a spunbond nonwoven, a meltblown nonwoven, or a combination of spunbond and meltblown nonwoven layers; the nonwoven substrate comprises a random network of thermoplastic polymer filaments or fibers bonded together.

[0048] The polypropylene copolymer of the first microporous polymer surface coating is fused into the filaments or fibers on the first surface of the nonwoven substrate; and

[0049] The microporous laminate has a Gurley air permeability of 20 to 150 seconds per 100 cubic centimeters of air.

[0050] The present invention also relates to a method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate, the method comprising the following steps:

[0051] A) A molten polymer layer is coated onto the first surface of the nonwoven substrate, and then cooled to form a non-porous laminate having a non-porous layer of the polymer on the first surface.

[0052] The non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0053] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising the following amounts of polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0054] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0055] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0056] At least a portion of these ethylene-containing copolymer segments comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of these ethylene-containing copolymer segments; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in these ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0057] The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, which further has multiple domains of the ethylene-containing copolymer segments within the matrix phase. These domains of the ethylene-containing copolymer segments further contain an inclusion phase of the polypropylene homopolymer segments within the domains.

[0058] b) The nonwoven substrate comprises a random network of filaments or fibers of a thermoplastic polymer bonded together in the form of spunbond nonwovens, meltblown nonwovens, or some combination of spunbond and meltblown nonwoven layers; the nonwoven substrate has a basis weight of 30 to 100 gsm and an elongation at break of 50% or greater at room temperature.

[0059] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0060] (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and

[0061] (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C;

[0062] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break, thereby forming micropores in the non-porous polymer layer and producing the microporous laminate.

[0063] The present invention further relates to a method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate and a second microporous polymer surface coating on a second surface opposite to the nonwoven substrate, the method comprising the following steps:

[0064] A) A first molten polymer layer is coated onto the upper surface of a first surface of the nonwoven substrate, followed by cooling, and a second molten polymer layer is coated onto the upper surface of the opposite second surface of the nonwoven substrate, also followed by cooling, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface, each nonporous polymer layer having an areal loading of 22.9 to 114.3 gsm and a thickness of 1-5 mils (25 to 125 micrometers), wherein:

[0065] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising the following amounts of polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0066] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in these polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0067] ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in these ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer.

[0068] At least a portion of these ethylene-containing copolymer segments comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of these ethylene-containing copolymer segments; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in these ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomeric units in these ethylene-containing copolymer segments.

[0069] Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, these domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and

[0070] b) The nonwoven substrate comprises a spunbond nonwoven having a random network of filaments or fibers of thermoplastic polymer bonded together at the intersections in the random network; the nonwoven substrate has a basis weight of 30 to 100 gsm and an elongation at break of 50% or greater at room temperature.

[0071] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0072] (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and

[0073] (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C;

[0074] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break, thereby forming micropores in the non-porous polymer layer and producing a microporous laminate. Attached Figure Description

[0075] Figure 1 This is a representative TEM image of the non-porous polymer surface coating before stretching, shown on a 1-micron scale.

[0076] Figure 2 This is an optical microscope image of a representative cross section of an unstretched, non-porous monolithic sheet containing an opposite layer of a non-porous polymer surface coating on a polypropylene substrate, prior to stretching to produce a microporous laminate.

[0077] Figure 3 This is an illustration of a possible continuous method for manufacturing microporous laminates on an apparatus that includes an extrusion lamination unit 50, followed by a cold stretching unit 51, followed by a hot stretching unit 52, followed by a cooling unit 53, and finally a winding unit 54. Detailed Implementation

[0078] The present invention relates to a microporous laminate comprising a microporous polymer surface coating comprising a polypropylene copolymer on a nonwoven substrate, wherein the microporous polymer surface coating has a matrix phase of polypropylene homopolymer segments and a plurality of domains of ethylene-containing copolymer segments within the matrix phase, the domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments, wherein the domains of the ethylene-containing copolymer segments are broken to form micropores in the microporous polymer surface coating.

[0079] Additionally, the polypropylene copolymer of the microporous polymer surface coating is partially fused to filaments or fibers on the first surface of the nonwoven substrate to prevent the microporous polymer surface from peeling off from the nonwoven substrate. This is achieved by applying a surface coating of molten polypropylene copolymer to the nonwoven substrate to first form a nonporous monolithic sheet with excellent adhesion between the surface coating and the nonwoven substrate, followed by stretching the monolithic sheet in two steps to break the domains of the ethylene-containing copolymer segments (while simultaneously stretching the nonwoven substrate). The first stretching step stretches the laminate at a temperature below 30°C, preferably between 15°C and 28°C, while the second stretching step stretches the laminate at a temperature above 100°C.

[0080] In one embodiment, the microporous laminate is made by forming a non-porous monolithic sheet using a nonwoven substrate having an elongation at break of less than 50% (measured at room temperature), and stretching the monolithic sheet by 20% to 50% in both the first and second stretching steps. This preferably forms a microporous laminate with a microporous polymer surface coating having an average thickness of 0.4 to 3.9 mils (10 to 100 micrometers), and the microporous laminate has a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds of force). This embodiment is referred to herein as the “low elongation substrate embodiment” of the microporous laminate, and such microporous laminates are suitable for and desirable for roofing and other construction applications.

[0081] In another embodiment, the microporous laminate is made by forming a non-porous monolithic sheet using a nonwoven substrate having an elongation at break (measured at room temperature) of 50% or greater, stretching the monolithic sheet by 50% to 85% in a first stretching step, and further stretching the sheet by 100% to 150% in a second stretching step. This preferably forms a microporous laminate with a microporous polymer surface coating having an average thickness of 0.5 to 3.0 mils (12.7 to 76.2 micrometers), and the microporous laminate has a Gurley air permeability of 20 to 150 seconds per 100 cubic centimeters of air. This embodiment is referred to herein as a “high elongation substrate embodiment” of the microporous laminate, and such microporous laminates are suitable for and desirable for medical applications.

[0082] It is believed, as described herein, that the polypropylene copolymer composition and the method for manufacturing non-porous monolithic sheets and stretching them into microporous laminates in two stretching steps form a unique pore structure in the microporous laminates; providing, for example, uniform, smaller micropores with generally non-interconnected properties in coatings, producing breathable membranes that exhibit excellent barrier properties against liquid water and air while achieving the desired water vapor permeability. The micropores have an average pore size of about 100 nm to 1 micrometer, and in some embodiments preferably have an average pore size of 40 to 75 nm, as measured by mercury intrusion. Furthermore, these breathable polymer sheet materials are based on polypropylene, meaning they are naturally hydrophobic and thermally stable, as polypropylene has a melting temperature of about 165°C.

[0083] Specifically, the embodiment of the microporous laminate is made using a nonwoven substrate having a breakage elongation of less than 50% (measured at room temperature) (low elongation substrate embodiment) and preferably having a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds of force). The microporous laminate includes a first microporous polymer surface coating on the nonwoven substrate, the nonwoven substrate having a first surface and an opposite second surface; the first microporous polymer surface coating comprises a polypropylene copolymer, the polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0084] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0085] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0086] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment. Additionally, the first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segment, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segment within the matrix phase. The domains of the ethylene-containing copolymer segment further contain an inclusion phase of the polypropylene homopolymer segment within the domain; the domains of the ethylene-containing copolymer segment within the matrix phase are broken to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating having broken domains of the ethylene-containing copolymer segment has an average thickness of 0.4 to 3.9 mils (10 to 100 micrometers).

[0087] The nonwoven substrate comprises a random network spunbond nonwoven fabric with continuous filaments of a thermoplastic polymer bonded together at intersections in the random network, wherein a polypropylene copolymer of a first microporous polymer surface coating is fused to the continuous filaments on a first surface of the nonwoven substrate.

[0088] Examples of low elongation substrates for microporous laminates exhibit trapezoidal tearing of 40 to 225 Newtons (9 to 50 pounds of force), preferably 15 to 30 pounds of force.

[0089] Microporous laminates can possess other desired properties. Specifically, microporous laminates can have a density of 30 to 120 g / m³. 2 Preferably 45 g / m 2 Up to 100 g / m 2 The basis weight. The microporous laminate may also have a thickness of 3 to 15 mils (0.076 to 0.381 mm), preferably 6 to 12 mils. The microporous laminate may further have a hydrostatic head of 2 meters or more, preferably 2.5 meters or more, preferably 3 meters or more. The microporous laminate may also have a basis weight of 18 g / (24hr·m). 2 ) or greater, preferably 70 g / (24hr·m 2 The water vapor permeation rate can be 10 psi (87.6 N / 50 mm) or greater, preferably 20 psi or greater. The microporous laminate can further have a tensile strength of 10 psi (87.6 N / 50 mm) or greater, preferably 20 psi or greater.

[0090] In some embodiments, the microporous laminate has a first microporous polymer surface coating only on one surface of the low-elongation nonwoven substrate. In other embodiments, the microporous laminate has a first microporous polymer surface coating on a first surface of the nonwoven substrate and a second microporous polymer surface coating on a second, opposite surface of the low-elongation nonwoven substrate, thereby forming a sandwich structure in which the two microporous polymer surface coatings form the outer surface of the laminate. That is, in the sandwich structure, in some preferred embodiments, the nonwoven substrate forms the central layer of the microporous laminate.

[0091] Preferably, the second microporous polymer surface coating is the same as the first microporous polymer surface coating; that is, the two surface coatings have substantially the same composition, thickness and pore structure, or any difference in these parameters is very small, and the two surface coatings serve the same purpose in the desired application and both attach to the corresponding surfaces of the nonwoven fabric in the same manner.

[0092] Specifically, the low elongation substrate embodiment of the microporous laminate may further include a second microporous polymer surface coating, which is the same as the first microporous polymer surface coating, and wherein the polypropylene copolymer of the second microporous polymer surface coating is fused to a continuous filament on the opposite second surface of the nonwoven substrate.

[0093] Examples of low-elongation substrates for microporous laminates (referred to herein as "two-layer microporous laminates") comprising a first microporous polymer surface coating and a second microporous polymer surface coating on the opposite side of a nonwoven substrate exhibit trapezoidal tearing of 40 to 225 Newtons (9 to 50 pounds of force), preferably 15 to 30 pounds of force, similar to microporous laminates with only a first microporous polymer surface coating. However, two-layer microporous laminates can have other desired properties. Specifically, two-layer microporous laminates can have 40 to 150 g / m². 2 Preferably 60 to 125 g / m 2 The basis weight. The two-layer microporous laminate may also have a thickness of 4 to 19 mils (0.10 to 0.48 mm), preferably 8 to 15 mils. The two-layer microporous laminate may further have a hydrostatic head of 3 meters or more, preferably 3.5 meters or more. The two-layer microporous laminate may also have a basis weight of 25 g / (24hr·m). 2 ) or greater, preferably 95 g / (24hr·m 2 Water vapor permeation of 10 psi (87.6 N / 50 mm) or greater, preferably 20 psi or greater, can be achieved. The two-layer microporous laminate can further have a tensile strength of 10 psi (87.6 N / 50 mm) or greater, preferably 20 psi or greater.

[0094] All embodiments of microporous polymer surface coatings described herein include polypropylene copolymers comprising polypropylene homopolymer segments and ethylene-containing copolymer segments, as previously described herein.

[0095] As used herein, the term "polypropylene copolymer" means a copolymer comprising a polymer backbone, side chains, or segments of polypropylene, specifically, such backbone, side chains, or segments comprising 15 or more continuous polymeric units of propylene. Preferred polypropylene copolymers comprise polypropylene homopolymer segments (e.g., isotactic polypropylene) and ethylene-containing copolymer segments. In some embodiments, the ethylene-containing copolymer segments are ethylene-propylene copolymer segments. Microporous polymer surface coatings may comprise one or more polypropylene copolymers.

[0096] The polypropylene copolymer in the microporous polymer surface coating comprises at least about 50% by weight and up to about 95% by weight of polypropylene homopolymer segments based on the total weight of the microporous polymer surface coating. In some embodiments, the amount of polypropylene homopolymer segments in the microporous polymer surface coating may be from about 50% by weight to about 82% by weight, or from about 60% by weight to about 82% by weight, based on the total weight of the microporous polymer surface coating.

[0097] From a mol% perspective, the polypropylene copolymer in the microporous polymer surface coating comprises a polypropylene homopolymer segment in an amount of 43 mol% to 79 mol% based on the molar content of propylene polymeric units in the polypropylene homopolymer segment as a percentage of the total molar content of polymeric monomer units in the microporous polymer surface coating. In some embodiments, the amount of polypropylene homopolymer segment in the microporous polymer surface coating may be from about 43 mol% to about 79 mol%, or from about 50 mol% to about 80 mol%, based on the molar content of propylene polymeric units in the polypropylene homopolymer segment as a percentage of the total molar content of polymeric monomer units in the microporous polymer surface coating.

[0098] The polypropylene homopolymer segments present in the microporous polymer surface coating may be derived solely from the polypropylene copolymer component, or they may be a combination of polypropylene homopolymer segments derived from the polypropylene copolymer component and one or more other polymer components containing polypropylene homopolymer segments. Preferably, the polypropylene homopolymer segments present in the microporous polymer surface are derived solely from the polypropylene copolymer component.

[0099] The polypropylene copolymer in the microporous polymer surface coating comprises an amount of ethylene-containing copolymer segments of at least about 5% to 50% by weight based on the total weight of the microporous polymer surface coating. In some embodiments, the microporous polymer surface coating comprises an amount of ethylene-containing copolymer segments of about 18% to about 50% by weight, or about 25% to about 40% by weight based on the total weight of the microporous polymer surface coating.

[0100] From a mole % perspective, the microporous polymer surface coating contains ethylene-containing copolymer segments in an amount ranging from 21 mol% to 57 mol% of the total mole content of polymeric monomer units in the polypropylene copolymer of the microporous polymer surface coating, based on the mole content of polymeric monomer units in the ethylene-containing copolymer segments.

[0101] In some embodiments, the amount of ethylene-containing copolymer segments in the microporous polymer surface coating is based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer of the microporous polymer surface coating, from about 21 mol% to about 57 mol%, or from about 20 mol% to about 45 mol%.

[0102] The ethylene-containing copolymer segments present in the microporous polymer surface coating may be derived solely from the polypropylene copolymer component, or they may be a combination of ethylene-containing copolymer segments derived from the polypropylene copolymer component and one or more other polymer components containing ethylene-containing copolymer segments. Preferably, the ethylene-containing copolymer segments present in the microporous polymer surface coating are derived solely from the polypropylene copolymer component. Preferably, the ethylene-containing copolymer segments are ethylene-propylene copolymer segments.

[0103] The ethylene-containing copolymer segments in the microporous polymer surface coating comprise at least 45% by weight of ethylene polymeric units based on the total weight of the ethylene-containing copolymer segments. In some embodiments, the amount of ethylene units in the ethylene-containing copolymer segments in the microporous polymer surface coating may be from about 45% to about 80% by weight, or from about 45% to about 60% by weight, based on the total weight of the ethylene-containing copolymer segments.

[0104] From a mole % perspective, the ethylene unit content in the ethylene-containing copolymer segments of the microporous polymer surface coating is at least about 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the ethylene-containing copolymer segments. In some embodiments, the ethylene unit content in the ethylene-containing copolymer segments of the microporous polymer surface coating is about 55 mol% to about 80 mol%, or about 55 mol% to about 69 mol%, based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the ethylene-containing copolymer segments.

[0105] When the surface is coated onto a flexible substrate, the polypropylene copolymer provides a non-porous monolithic polymer sheet with a microphase separation / inclusion morphology. When stretched using the cold and hot stretching processes described herein, the non-porous monolithic polymer sheet can form a microporous laminate with a microporous polymer surface coating having non-interconnected pores.

[0106] The polypropylene copolymer in the microporous polymer surface coating may further comprise additives such as extrusion processing aids like lubricants; antioxidants, UV stabilizers, light stabilizers, heat stabilizers, pigments or other colorants, antistatic agents, flame retardants, anti-blocking additives, biocides, etc. UV stabilizers are preferred additives. Examples of these UV stabilizers include five different hydroxyphenylbenzotriols, such as those sold by BASF as Tinuvin® 328 or Tinuvin® 329; and hindered amine stabilizers, such as those sold by BASF as Tinuvin® 770 or Chimassorb® 2020. One or more UV stabilizers may be used in combination with one or more antioxidants. In some embodiments, the polypropylene copolymer in the microporous polymer surface coating does not contain any pore-forming additives that increase the porosity of the final microporous laminate.

[0107] Although polyolefins may contain filler particles, such fillers are preferably absent, or if present, only in small amounts, such as up to 3%, 2%, 1%, or 0.5% by weight of the combined filler particles and polyolefin. These fillers are thermally stable (i.e., do not melt or thermally degrade) particulate materials under the conditions of the extrusion lamination process. In some embodiments, the polypropylene copolymer in the microporous polymer surface coating does not contain any pore-forming fillers that increase the porosity of the final microporous laminate.

[0108] Figure 1 This is a representative TEM image of the unstretched, non-porous polymer surface coating, shown at a 1-micrometer scale bar. It illustrates the microphase separation and associated domain / inclusion formation as discussed earlier herein. A lighter gray matrix phase 1 containing polypropylene homopolymer segments is shown, and the matrix phase further comprises several darker gray domains 2 containing ethylene-containing copolymer segments. Additionally, the domains containing ethylene-containing copolymer segments further contain a lighter gray inclusion phase 3 of polypropylene homopolymer segments. (Not all domains / inclusion phases are identified by reference numerals.)

[0109] It is believed that within the polypropylene homopolymer segment matrix, the inclusion morphology of the polypropylene homopolymer segment microphase in the ethylene-containing copolymer segment domains enables the transfer of tensile forces to the microphase domains. This preferentially causes the microphase domains to break and induces unique micropore formation in the copolymer layer during sequential cold and hot stretching processes. Furthermore, it is believed that in the absence of polypropylene homopolymer segment inclusion morphology in the ethylene-containing copolymer segment domains, the ethylene-containing copolymer segment domains simply elongate upon stretching without the desired micropore formation; that is, until pores (large pores with diameters much larger than 1 micrometer) are uncontrollably torn into the polymer layer.

[0110] The microporous polymer surface coating having fractured domains of ethylene-containing copolymer segments has an average thickness of 0.4 to 3.9 mils (10 to 100 micrometers). In some embodiments, the microporous polymer surface coating having fractured domains has an average thickness of 1 to 3 mils.

[0111] In some embodiments, the nonwoven substrate of the microporous laminate is a spunbond nonwoven having a random network of continuous filaments of a thermoplastic polymer bonded together at their intersections. The terms "fiber" and "filament" are used interchangeably herein and refer to a relatively flexible unit of material having a high aspect ratio across its cross-section perpendicular to its length. The cross-section of the filaments described herein can be of any shape, but is typically a solid circle or round shape. Fibers and filaments can be discontinuous or continuous. Continuous fibers or filaments are typically filaments continuously extruded from a spinneret without undergoing additional intentional processing to discontinuity. Discontinuous fibers or filaments obviously undergo additional intentional processing to shorten them to a desired length, typically by cutting or shearing continuous filaments.

[0112] As used herein, the term "nonwoven fabric" is a network of filaments and / or fibers forming a flexible planar sheet material, which can be produced without weaving or knitting and held together by: (i) mechanical interlocking of at least some fibers or filaments, (ii) fusing at least some portions of some fibers or filaments, or (iii) bonding at least some fibers or filaments using an adhesive material. Nonwoven fabrics as used herein preferably include spunbond nonwoven fabrics, meltblown nonwoven fabrics, and combinations thereof.

[0113] Spunbond nonwovens are typically formed by extruding molten thermoplastic polymer material as continuous filaments from multiple fine capillaries of a spinneret, then stretching and randomly depositing them onto a screen; the filaments are then bonded together. Spunbond nonwovens are sometimes used as a general term to include any fibrous sheet containing fibrous material in sheet form, which is then heat-treated to melt some components of the sheet and bond the fibrous material together. Meltblown nonwovens are typically formed by extruding molten thermoplastic polymer as molten filaments through multiple fine, typically circular capillaries into a high-speed gas (e.g., air) stream. The high-speed gas stream thins the filaments of the molten thermoplastic polymer material to reduce their diameter to between approximately 0.5 and 10 micrometers. Meltblown fibers are typically discontinuous fibers. The meltblown fibers carried by the high-speed gas stream are typically deposited on a collecting surface to form a randomly dispersed fiber web. A common type of spunbond nonwoven fabric is the "SMS" nonwoven fabric, which combines a meltblown nonwoven (M) layer between two spunbond nonwoven (S) layers, which are combined on a spinning machine designed to manufacture nonwovens with different types of layers. Other spunbond combinations are possible.

[0114] In some embodiments, the thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof. In some preferred embodiments, the thermoplastic polymer includes polypropylene.

[0115] In the broadest sense, as used herein for thermoplastic polymers of polymer filaments for nonwoven substrates, the term "polypropylene" is intended to include not only homopolymers of propylene but also copolymers in which at least 85% of the repeating units are propylene units. Similarly, as used herein for thermoplastic polymers of polymer filaments, the term "polyester" as used herein is intended to include polymers in which at least 85% of the repeating units are condensation products of dicarboxylic acids and dihydroxy alcohols, wherein polymer bonding is achieved by forming ester units. This includes aromatic, aliphatic, saturated, and unsaturated diacids and diols. As used herein, "polyester" also includes copolymers (such as block, graft, random, and alternating copolymers), blends, and modifications thereof. A common example of polyester is poly(ethylene terephthalate), which is a condensation product of ethylene glycol and terephthalic acid. Additionally, as used herein for thermoplastic polymers of polymer filaments, the term "nylon" means including aliphatic polyamide polymers; and polyhexamethylene adipamide (nylon 66) is a preferred nylon polymer. Other nylons include polycaprolactam (nylon 6), polybutyrolactam (nylon 4), poly(9-aminononanoic acid) (nylon 9), polyheptyllactam (nylon 7), polyoctyllactam (nylon 8), and polyhexamethylene sebacate (nylon 6, 10).

[0116] In some embodiments, the polypropylene copolymer of the first microporous polymer surface coating is partially fused to a continuous filament located on a first surface of the nonwoven substrate. This allows the nonwoven substrate to be stretched, and that stretching to be transferred in a controlled manner to the very thin polymer surface coating without causing the filaments in the nonwoven substrate to stand up, which would otherwise potentially pierce the thin coating to reach the outer surface of the laminate.

[0117] Figure 2 Representative optical microscopic images are provided of a cross-section of an unstretched, non-porous monolithic sheet 5 containing a non-porous polymer surface coating and a polypropylene substrate before stretching to produce a microporous laminate. The non-porous monolithic sheet 5 has distinguishable filaments 6 and a combination 7 of polypropylene filaments fused together and a polypropylene copolymer polymer from the non-porous polymer surface coating. A thin non-porous polymer surface coating 8 is present on each side of the sheet. While a thin non-porous polymer surface coating is clearly shown on the upper side of the sheet, the thin non-porous polymer surface coating on the opposite side is blurred by dark lines at the bottom of the sheet (a microscopic artifact). Additionally, there are void regions 9 that do not contain polymer from the surface coating or filaments from the nonwoven substrate.

[0118] Low elongation embodiments of microporous laminates can be made using nonwoven substrates having an elongation at break (measured at room temperature) of less than 50%; the resulting microporous laminates preferably have a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds of force). Specifically, a method for forming a microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate having a first surface and an opposite second surface includes the following steps:

[0119] A) A molten polymer layer is coated onto the first surface of a nonwoven substrate, and then cooled to form a nonporous laminate having a nonporous layer of the polymer on the first surface.

[0120] The non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0121] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0122] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0123] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0124] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment.

[0125] The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, and the domains of the ethylene-containing copolymer segments further containing an inclusion phase of the polypropylene homopolymer segments within the domains.

[0126] b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer, the continuous filaments being bonded together at the intersections in the random network; the nonwoven substrate has

[0127] (i) Basis weight of 30 to 100 gsm, and

[0128] (ii) Elongation at break at room temperature less than 50%;

[0129] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0130] (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and

[0131] (ii) At least 20% to 50% of thermal stretching at a temperature above 100°C;

[0132] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in the non-porous polymer layer and producing a microporous laminate.

[0133] This method is particularly useful for manufacturing single-layer microporous laminates, i.e., microporous laminates comprising a single microporous polymer surface coating on a nonwoven substrate. Alternatively, the related method can be used to manufacture microporous laminates having a single microporous polymer surface coating on each opposite side of a nonwoven substrate (i.e., a two-layer microporous laminate). In this alternative method for forming a microporous laminate, the microporous laminate includes a first microporous polymer surface coating on a first surface of the nonwoven substrate and a second microporous polymer surface coating on an opposite second surface of the nonwoven substrate, and the method includes the following steps:

[0134] A) A first molten polymer layer is coated on the upper surface of a first surface of a nonwoven substrate, and then cooled; a second molten polymer layer is coated on the upper surface of the opposite second surface of the nonwoven substrate, and also cooled, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface.

[0135] Each non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0136] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0137] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0138] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0139] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment.

[0140] Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, and the domains of the ethylene-containing copolymer segments further containing an inclusion phase of the polypropylene homopolymer segments within the domains.

[0141] b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer, the continuous filaments being bonded together at the intersections in the random network; the nonwoven substrate has

[0142] (i) Basis weight of 30 to 100 gsm, and

[0143] (ii) Elongation at break at room temperature less than 50%;

[0144] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0145] (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and

[0146] (ii) At least 20% to 50% of thermal stretching at a temperature above 100°C;

[0147] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in each non-porous polymer layer and producing a microporous laminate.

[0148] As in the previous one-sided method, in some embodiments, the thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof; and in some preferred embodiments, the thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene.

[0149] The sequential cold and hot stretching steps of B) of a one- or two-layer microporous laminate can be performed in a variety of ways. In one embodiment, stretching steps (i) and (ii) stretch the non-porous laminate only in the machine direction. In another embodiment, stretching step (i) stretches the non-porous laminate in the machine direction, and stretching step (ii) stretches the non-porous laminate in the cross direction.

[0150] In some embodiments, the sequential cold and hot stretching steps of B) include a single cold stretching step and multiple hot stretching steps, and the multiple hot stretching steps may be performed sequentially only in the machine direction, or may be performed in alternating sequential machine direction and transverse direction steps.

[0151] In some embodiments, at least one cold stretching step (i) stretches the laminate by 20% to 40%. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about -20°C to below 30°C. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about 15°C to below 30°C. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about 15°C to about 25°C or 28°C.

[0152] In some embodiments, at least one hot stretching step (ii) stretches the laminate by 30% to 50%. In some embodiments, at least one hot stretching step (ii) stretches the laminate at a temperature above 100°C to about 150°C. In some embodiments, at least one hot stretching step (ii) stretches the laminate at a temperature above 130°C to about 150°C, and in some embodiments, at least one hot stretching step (ii) stretches the laminate at a temperature above 140°C to about 150°C.

[0153] In some embodiments, the extruded nonporous polymer layer preferably has a thickness of 2-4 mils (50.8 to 101.6 micrometers) on the base substrate (i.e., when applied to the substrate).

[0154] In some embodiments, the nonwoven substrate has a basis weight of 40 to 85 gsm. In some embodiments, the nonwoven substrate has an elongation at break of 40% or less at room temperature. In some embodiments, the nonwoven substrate has an elongation at break of 20%-50% at room temperature, and in some embodiments, the nonwoven substrate has an elongation at break of 20%-40% at room temperature.

[0155] In extrusion lamination methods, a polypropylene copolymer is melted and then forced through a die to form a non-porous polymer film or layer. This step can be performed using, for example, a single-screw or twin-screw extruder, a cumulative extruder, or other suitable equipment equipped with suitable dies such as slot dies or dog-bone dies. The polypropylene copolymer is heated in the extrusion equipment to a temperature above the crystallization melt temperature of the continuous phase polypropylene homopolymer and forced through a die to form a polymer layer. Preferred extrusion temperatures are at least 180°C or at least 200°C and up to 240°C or up to 260°C.

[0156] The molten non-porous polypropylene copolymer layer is brought into contact with the surface of the nonwoven substrate to form a non-porous polypropylene copolymer layer on that surface. This step is performed before the non-porous polypropylene copolymer layer is cooled below its Vicat softening temperature. The contact step is preferably performed within 30 seconds, more preferably within 10 seconds, 5 seconds, or 2 seconds from the time the sheet leaves the extruder die.

[0157] Ideally, the contacting step is performed under very low mechanical (clamping) pressure, such that the polypropylene copolymer layer is preferably surface-coated onto the nonwoven substrate, with limited penetration into the nonwoven substrate below the surface. "Surface-coated" means that the polypropylene copolymer layer is preferably primarily fused to continuous filaments on the surface of the nonwoven substrate. This means that the polypropylene copolymer layer is preferably embedded in the nonwoven substrate by no more than about 25% of the initial thickness of the nonwoven substrate, preferably no more than about 10% of the initial thickness of the nonwoven substrate, and most preferably no more than about 5% of the initial thickness of the nonwoven substrate. Sufficient mechanical (clamping) pressure is conveniently applied by passing the nonwoven substrate and the applied polypropylene copolymer layer through one or more calendering rolls; however, other equipment such as a two-belt laminator is also suitable. In some embodiments, one or more of the calendering rolls may be cooled to simultaneously cool the polyolefin to a temperature below its Vicat softening temperature (e.g., to 80°C to 120°C).

[0158] In some embodiments, the extrusion lamination method includes applying an extruded polypropylene copolymer layer to both sides of a nonwoven substrate. In such cases, opposing polypropylene copolymer layers may contact the nonwoven substrate simultaneously or sequentially.

[0159] Prior to any stretching, each extruded nonporous polypropylene copolymer layer preferably has a face load (i.e., basis weight) of about 22.9 to 114.3 gsm and a thickness of 1 to 5 mils (25 to 125 micrometers).

[0160] Prior to the stretching step, the extruded non-porous polypropylene copolymer layer on the substrate is non-porous. Preferably, foaming agents and / or gases are omitted during extrusion to avoid the formation of pores in the extruded non-porous polypropylene copolymer layer at this stage. For the purposes of this invention, if, after cooling, the sheet exhibits a value of no more than 2 g / m³ at 37.8°C and 100% relative humidity as measured according to ASTM D1249. 2 If the water vapor transmission rate (WVTR) is 1 day, the sheet material is considered "non-porous".

[0161] Preferably, the melt-extruded nonporous polypropylene copolymer layer is brought into contact with the surface of the nonwoven fabric and then cooled below its Vicat softening temperature to produce a coated nonporous polymer layer on the surface, thereby forming a nonporous monolithic sheet, which can then be further stretched to form the desired micropores.

[0162] The resulting non-porous laminate is preferably cooled to 50°C or lower before undergoing a sequential cold and hot stretching process. Cold stretching is first performed in the machine direction, followed by hot stretching in the transverse direction. The stretching process can be carried out in the general manner and conditions described in US 2021 / 095110 A1. Cold stretching can be performed in a single step or in multiple increments. The stretching percentage is calculated as 100% × [(stretched film length - initial film length) ÷ initial film length). As used herein, a “single step” is considered a single stretching process for stretching a sheet material by a certain amount in a specific direction at a specific temperature or temperature range. For example, a “single cold stretching step” may include multiple rollers working together to progressively stretch the sheet material with each roller, ultimately stretching the sheet material by a desired percentage in one direction.

[0163] If desired, the cold-drawn composite sheet can optionally be annealed before the subsequent hot-drawing step. This annealing step is conveniently performed by heating the cold-drawn composite sheet to a temperature of 90°C to 150°C for at least one second, preferably at least two seconds. An annealing period of no more than 30 seconds is typically required. Annealing can fix the pore structure formed during the cold-drawing step and can also reduce shrinkage. The annealing step is preferably performed immediately after cold drawing, while maintaining the cold-drawn composite sheet under the greatest possible tension necessary to prevent shrinkage before transverse drawing.

[0164] The hot stretching step is performed on the laminate at a temperature above 100°C in one or more steps in the machine direction, transverse direction, or both. When the laminate is stretched in the transverse direction, the transverse direction is preferably orthogonal to the cold machine direction. Hot stretching can be performed in a single step or in multiple increments. And similarly, the stretch percentage is calculated as 100% × [(stretched film length - initial film length) ÷ initial film length)] based on before and after hot stretching in one direction. The hot-stretched composite sheet may optionally be annealed in the same manner as described with respect to annealing cold-stretched composite sheets.

[0165] The transverse or cross direction is perpendicular (or orthogonal) to the machine direction (within the plane of the sheet). Either the cold or hot stretching step can be performed uniaxially in the machine direction or the cross direction; however, to produce a biaxially stretched microporous laminate, the cold and hot stretching steps should not be in the same direction, but preferably orthogonal. In a preferred embodiment, the cold stretching step is performed in the machine direction, and the hot stretching step is performed in the transverse or cross direction. When one stretching step is performed in the machine direction and the other in the cross direction, the resulting microporous laminate can have more relatively balanced physical properties, such as tensile strength and elongation in both the machine and cross directions.

[0166] Non-porous laminates can be biaxially stretched in a continuous operation involving a combination of various devices, such as a series of stretching rollers, that first stretch the non-porous laminate in a machine direction and then in a transverse or cross direction, as with a tenter frame including clamps for holding the sides of the laminate. The clamps are mounted on a pair of tracks that are separated in the direction in which the laminate moves through the equipment. The clamps travel along the tracks, carrying the laminate, separating the non-porous laminate and thus biaxially stretching it into a biaxially stretched microporous laminate. Tenter frames are particularly suitable for stretching sheet materials in cross directions. As previously described, the stretching section (i.e., the section including the separating tracks) may be preceded by a preheating section and followed by an annealing section and / or a rewinding section.

[0167] Another suitable stretching apparatus is a grooved roller stretching machine. Such a grooved roller stretching machine is particularly suitable for stretching non-porous membranes or composite sheets in intersecting directions. The grooved roller stretching machine includes an interlaced toothed structure through which the non-porous membrane or composite sheet passes. The toothed structure can be, for example, roller pairs as described in U.S. Patent Nos. 4,368,565, 5,028,289, and 6,843,949, U.S. Patent Application No. 2006 / 0148354, and EP 927 096 B1; or a toothed activating member and a moving belt with complementary toothed grooves as described in U.S. Patent No. 8,337,190.

[0168] A grooved roller stretching mill may include multiple toothed structures connected in series. A non-porous laminate is fed into the grooved roller stretching mill and conveyed through the toothed structures, where it is stretched transversely to its direction of movement. The resulting microporous laminate is then removed from the equipment.

[0169] Figure 3This is an illustration of a possible continuous method for manufacturing microporous laminates on an apparatus including an extrusion laminating unit 50, followed by a cold drawing unit 51, a hot drawing unit 52, a cooling unit 53, and a final winding unit 54. The extrusion laminating unit 50 may include, for example, an extruder equipped with a die suitable for producing a nonporous polymer layer, a feed device for supplying the nonwoven fabric to the laminator, and a laminator such as heated calendering rolls for contacting the polymer layer with the nonwoven fabric. The extrusion laminating unit may have heated or cooled calendering rolls as desired or required. The extrusion laminating unit may further include equipment for producing or providing a second polymer layer (i.e., a second extruder, casting die, laminating station, etc.) for contacting the second nonporous polymer layer on the opposite side of the nonwoven fabric in a similar manner to form a two-layer nonporous laminate with the nonwoven fabric located between the two polymer layers, thereby forming a sandwich structure.

[0170] The cold drawing apparatus 51 can receive non-porous laminates from the extrusion lamination apparatus and continuously cold draw the non-porous laminates, preferably in the machine direction. The cold drawing apparatus may include cooling rollers or other equipment (if desired) for cooling the non-porous laminates or bringing them to a specific drawing temperature, and one or more drawing rollers or tuck roller groups for drawing the non-porous laminates in a desired direction. This is considered herein as a single drawing step.

[0171] The hot stretching apparatus 52 can receive cold-stretched laminates from the cold stretching apparatus and continuously further hot stretch the laminates in the machine or transverse direction, and may include heating rollers or other equipment for heating the laminates or bringing them to a specific stretching temperature. In the case of transverse stretching, equipment for clamping and stretching the heated laminates in a direction transverse to the machine direction, such as transverse spreading rollers and / or tenter frames, can be used. The hot stretching apparatus may further include an optional annealing section after the stretching rollers for optionally annealing the microporous laminates at a desired temperature, for example, with additional temperature-controlled rollers. This is considered herein to be a single hot stretching step.

[0172] Cooling device 53 can receive the stretched microporous laminate from the hot stretching device and continuously cool the laminate; the cooling device may include cooling rollers or other equipment (if desired) to cool the biaxially stretched composite sheet to a desired final temperature for winding into a roll. Winding device 54 then preferably winds the final microporous laminate onto a core to form a roll of microporous laminate.

[0173] An alternative embodiment of the microporous laminate (i.e., the "higher elongation substrate embodiment") is made using a nonwoven substrate with an elongation at break of 50% or greater (measured at room temperature), and the microporous laminate preferably has a Gurley air permeability of 20 to 150 seconds / 100 cubic centimeters of air.

[0174] Specifically, the microporous laminate includes a first microporous polymer surface coating on a nonwoven substrate having a first surface and an opposite second surface;

[0175] The first microporous polymer surface coating comprises a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0176] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0177] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0178] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment. Additionally, the first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segment, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segment within the matrix phase. The domains of the ethylene-containing copolymer segment further contain an inclusion phase of the polypropylene homopolymer segment within the domain; the domains of the ethylene-containing copolymer segment within the matrix phase are broken to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating having broken domains of the ethylene-containing copolymer segment has an average thickness of 0.5 to 3.0 mils (12.7 to 76.2 micrometers).

[0179] The nonwoven substrate includes spunbond nonwovens, meltblown nonwovens, or some combination of spunbond and meltblown nonwoven layers; the nonwoven substrate comprises a random network of filaments or fibers of a thermoplastic polymer bonded together, wherein a polypropylene copolymer of a first microporous polymer surface coating is fused to the filaments or fibers on a first surface of the nonwoven substrate.

[0180] The microporous laminate has a Gurley air permeability of 20 to 150 seconds per 100 cubic centimeters of air, preferably 20 to 100 seconds per 100 cubic centimeters of air.

[0181] In some embodiments, the thermoplastic polymer of the polymer filament or fiber of the nonwoven substrate having an elongation at break (measured at room temperature) of 50% or greater includes polypropylene, polyester, nylon, or mixtures thereof. In some embodiments, the thermoplastic polymer of the polymer filament or fiber of the nonwoven substrate having an elongation at break (measured at room temperature) of 50% or greater includes polyester.

[0182] The high elongation substrate examples of microporous laminates can have other desired properties. Specifically, the microporous laminates can have an elongation of 30 to 100 g / m². 2 Preferably 45 to 85 g / m 2 The basis weight. The microporous laminate may also have a thickness of 3 to 15 mils (0.076 to 0.381 mm), preferably 6 to 12 mils. The microporous laminate may further have a hydrostatic head of 2.5 meters or more, preferably 3 meters or more. The microporous laminate may also have a basis weight of 200 g / (24hr·m). 2 ) or greater, preferably 400 g / (24hr·m 2 The water vapor permeation rate can be 10 psi (87.6 N / 50 mm) or greater, preferably 15 psi (131.4 N / 50 mm) or greater. The microporous laminate can further have a tensile strength of 10 psi (87.6 N / 50 mm) or greater, preferably 15 psi (131.4 N / 50 mm) or greater.

[0183] In some embodiments, the higher elongation substrate of the microporous laminate has a first microporous polymer surface coating only on one surface of the nonwoven substrate. In other embodiments, the microporous laminate has a first microporous polymer surface coating on a first surface of the nonwoven substrate and a second microporous polymer surface coating on a second, opposite surface of the nonwoven substrate, thereby forming a sandwich structure, wherein the two microporous polymer surface coatings form the outer surface of the laminate. That is, in the sandwich structure, in some preferred embodiments, the nonwoven substrate forms the central layer of the microporous laminate.

[0184] Preferably, the second microporous polymer surface coating is identical to the first microporous polymer surface coating; that is, the two surface coatings have substantially the same composition, thickness, and pore structure, or any difference in these parameters is minimal, and the two surface coatings serve the same function in the desired application and attach to the corresponding surfaces of the nonwoven fabric in the same manner. Preferably, the two high-elongation substrate embodiments of the microporous laminate have a Gurley air permeability of 20 to 150 seconds / 100 cubic centimeters of air, preferably 20 to 100 seconds / 100 cubic centimeters of air.

[0185] The two high-elongation substrates of the microporous laminate can have other desired properties. Specifically, the microporous laminate can have 30 g / m².2 Up to 100 g / m 2 Preferably 45 g / m 2 Up to 85 g / m 2 The basis weight. The microporous laminate may also have a thickness of 4 to 19 mils (0.10 to 0.48 mm), preferably 8 to 15 mils. The microporous laminate may further have a hydrostatic head of 3 meters or more, preferably 3.5 meters or more. The microporous laminate may also have a basis weight of 200 g / (24hr·m). 2 ) or greater, preferably 400 g / (24hr·m 2 The water vapor permeation rate can be 10 psi (87.6 N / 50 mm) or greater, preferably 15 psi (131.4 N / 50 mm) or greater. The microporous laminate can further have a tensile strength of 10 psi (87.6 N / 50 mm) or greater, preferably 15 psi (131.4 N / 50 mm) or greater.

[0186] The composition and morphology of the microporous polymer surface coating in this higher elongation substrate embodiment of the microporous laminate are the same as those of the polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments, as described herein with respect to the lower elongation substrate embodiment of the microporous laminate. Unless otherwise stated herein, all other elements described for the lower elongation substrate embodiment of the microporous laminate are also applicable to the higher elongation embodiment of the microporous laminate.

[0187] Similarly, unless otherwise stated herein, all the details and definitions of nonwoven substrates previously described herein can be applied to this higher elongation substrate embodiment.

[0188] Unless otherwise stated herein, the methods for manufacturing higher elongation substrates of microporous laminates (including methods for manufacturing both laminates having at least one polymer surface coating and laminates having two opposite polymer surface coatings) are similar to the methods previously disclosed herein for manufacturing lower elongation substrates.

[0189] Therefore, one embodiment of the method for manufacturing microporous laminates with higher elongation is to use a nonwoven substrate having an elongation at break (measured at room temperature) of 50% or greater, and the microporous laminate preferably having a Gurley air permeability of 20 to 150 seconds / 100 cubic centimeters of air.

[0190] Specifically, the embodiment is a method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate, the method comprising the following steps:

[0191] A) A molten polymer layer is coated onto the first surface of a nonwoven substrate, and then cooled to form a nonporous laminate having a nonporous layer of the polymer on the first surface.

[0192] The non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0193] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0194] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0195] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0196] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment.

[0197] The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, and the domains of the ethylene-containing copolymer segments further containing an inclusion phase of the polypropylene homopolymer segments within the domains.

[0198] b) The nonwoven substrate comprises a random network of thermoplastic polymer filaments or fibers bonded together in the form of spunbond nonwovens, meltblown nonwovens, or some combination of spunbond and meltblown nonwoven layers; the nonwoven substrate has

[0199] (i) Basis weight of 30 to 100 gsm, and

[0200] (ii) 50% or greater elongation at break at room temperature;

[0201] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0202] (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and

[0203] (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C;

[0204] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in the non-porous polymer layer and producing a microporous laminate.

[0205] Another embodiment of the method for manufacturing a microporous laminate made of a nonwoven substrate having a higher elongation ratio of 50% or greater (measured at room temperature) has two opposite polymer layers, and the microporous laminate preferably has a Gurley air permeability of 20 to 150 seconds / 100 cubic centimeters of air.

[0206] Specifically, this embodiment is a method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate and a second microporous polymer surface coating on a second surface opposite to the nonwoven substrate, the method comprising the following steps:

[0207] A) A first molten polymer layer is coated on the upper surface of a first surface of a nonwoven substrate, and then cooled; a second molten polymer layer is coated on the upper surface of the opposite second surface of the nonwoven substrate, and also cooled, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface.

[0208] Each non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein:

[0209] a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments:

[0210] i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and

[0211] ii) Based on the weight of the polypropylene copolymer, 5 to 50 wt% of ethylene-containing copolymer segments; or based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymeric monomer units in the polypropylene copolymer, 21 to 57 mol% of ethylene-containing copolymer segments.

[0212] At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of polymeric monomeric units in the ethylene-containing copolymer segment.

[0213] Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase, and the domains of the ethylene-containing copolymer segments further containing an inclusion phase of the polypropylene homopolymer segments within the domains.

[0214] b) Nonwoven substrates include spunbond nonwovens having a random network of thermoplastic polymer filaments or fibers bonded together at the intersections in the random network; the nonwoven substrate has

[0215] (i) Basis weight of 30 to 100 gsm, and

[0216] (ii) 50% or greater elongation at break at room temperature;

[0217] B) subjecting the non-porous laminate to sequential cold and hot stretching steps, including:

[0218] (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and

[0219] (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C;

[0220] This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in each non-porous polymer layer and producing a microporous laminate.

[0221] As in existing methods used for lower elongation substrate embodiments, in some embodiments of higher elongation substrate embodiments, the thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof; and in some preferred embodiments, the thermoplastic polymer of the polymer filament of the nonwoven substrate includes polyester.

[0222] The sequential cold and hot stretching steps of B) can be performed in a variety of ways. In one embodiment, stretching steps (i) and (ii) stretch the non-porous laminate only in the machine direction. In another embodiment, stretching step (i) stretches the non-porous laminate in the machine direction, and stretching step (ii) stretches the non-porous laminate in the cross direction.

[0223] In some embodiments, the sequential cold and hot stretching steps of B) include a single cold stretching step and multiple hot stretching steps, and the multiple hot stretching steps may be performed sequentially only in the machine direction, or may be performed in alternating sequential machine direction and transverse direction steps.

[0224] In some embodiments, at least one cold stretching step (i) stretches the laminate by 50% to 70%. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about -20°C to below 30°C. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about 15°C to below 30°C. In some embodiments, at least one cold stretching step (i) stretches the laminate at a temperature of about 15°C to about 25°C or 28°C.

[0225] In some embodiments, at least one hot stretching step (ii) stretches the laminate by 50% to 125%. In some embodiments, at least one hot stretching step (ii) stretches the laminate at a temperature above 100°C to about 150°C. In some embodiments, at least one hot stretching step (ii) stretches the laminate at a temperature above 130°C to about 150°C. In some embodiments, at least one hot stretching step (ii) stretches the laminate in at least two steps, wherein the first step has a lower temperature than the second step, and wherein the temperatures in both steps are above about 100°C and up to about 150°C. Additionally, the amount of stretching may be different in the two steps, wherein the first step begins with a low stretch percentage of 50% to 70%, and the second stretching step stretches to 100% to 150%; and each of the two hot stretching steps may be orthogonal to each other if desired.

[0226] In some embodiments, the extruded nonporous polymer layer preferably has a thickness of 2-4 mils (50.8 to 101.6 micrometers) on the base substrate (i.e., when applied to the substrate).

[0227] In some embodiments, the nonwoven substrate has a basis weight of 40 to 85 gsm. In some embodiments, the nonwoven substrate has an elongation at break of 40% or less at room temperature. In some embodiments, the nonwoven substrate has an elongation at break of 20%-50% at room temperature, and in some embodiments, the nonwoven substrate has an elongation at break of 20%-40% at room temperature.

[0228] Test methods

[0229] Melting temperature and glass transition temperature were determined by differential scanning calorimetry (DSC) as follows. The samples were weighed and sealed in an aluminum-sealed DSC apparatus (P / N 900793.901 apparatus and 900794.901 lid). The sample weight of each sample was approximately 1–4 mg. Fifteen samples were scanned in a TA Instruments Q2000 DSC (Differential Scanning Calorimeter) (P / N 970001.901) (S / N 2000.0877) equipped with an autosampler, 50 ml / min nitrogen purging, and mechanical cooling accessories. Operating parameters were -20°C to 200°C, with a sampling interval of 0.1 s / pt for the heating-cooling-heating cycle at 10°C / min. The scans were analyzed using Universal Analysis V4.7A TA 20 Instruments software. The melting temperature was obtained by DSC scanning, which was presented as an output of the instrument software and corresponded to the peak temperature in the heat flux versus temperature curve during the second heating cycle. The glass transition temperature was determined from the inflection point of the DSC curve during the second heating using a heating / cooling rate of 10-25°C / min.

[0230] Density is determined according to ASTM D792.

[0231] The softening point temperature is determined according to ASTM D36-06. The specific Vicat softening temperature is determined according to ASTM D1525.

[0232] Melt (mass) flow rate (MFR) is measured according to ASTM D-1238 at 230°C and 2.16 kg, according to condition L (at 230°C and 2.16 kg) or condition E (at 190°C and 2.16 kg) as indicated.

[0233] The average molecular weight was measured by gel permeation chromatography (GPC) as described in US 20210095110 A1.

[0234] The polymer composition was determined by nuclear magnetic resonance (NMR) spectroscopy as described in US 20210095110 A1.

[0235] Thickness and basis weight were determined according to ASTM D1777 and TAPPI T-410, respectively.

[0236] Trapezoidal tearing is defined according to ASTM D5587.

[0237] Breaking strength and elongation at break are determined according to ASTM D882. For the determination of elongation at break at room temperature, “room temperature” is assumed to be the ambient temperature, typically 22°C (+ / - 2.5°C).

[0238] Water vapor permeability was determined using a wet cup at a temperature of 23°C ± 0.6°C and an RH difference of 50% ± 2%.

[0239] The air permeability of the Grylloy was determined by TAPPI T-460, and the breaking strength and elongation at break were determined by ASTM D882.

[0240] Water resistance was determined by AATCC 127-1995 (dynamic 60 mbar / min to up to 1000 mbar or failure (3 pinholes)).

[0241] Example 1

[0242] This invention relates to the manufacture of microporous laminates comprising a microporous polymer surface coating on a nonwoven substrate, suitable for use as house wraps or roofing sheets. The microporous polymer surface coating is a reactor-grade polypropylene copolymer resin manufactured by Braskem, containing 67.1 wt% homopolymer segments and 32.9 wt% ethylene-propylene copolymer segments, wherein the ethylene content in the ethylene-propylene copolymer segments is 49.7 wt%. The polypropylene copolymer resin has a viscosity of 0.9 g / cm³. 3 The density and melt index at 230°C and 2.16 kg at 7 g / 10 min. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polypropylene copolymer resin are 58,000 and 295,000, respectively.

[0243] For each laminate in this example, a polypropylene copolymer is extruded and coated onto an 80 gsm Typar® polypropylene nonwoven fabric having a 40% elongation at break at room temperature. For Item 1.1, a layer of polypropylene copolymer is coated onto one side of the substrate to form a non-porous laminate. For Item 1.2, a layer of polypropylene copolymer is coated onto the opposite side of the substrate to form a non-porous laminate.

[0244] The non-porous laminates are then subjected to machine orientation (MDO) by cold stretching (20%-30%) at below 30°C (i.e., at room temperature without preheating), followed by transverse orientation (TDO) by hot stretching (30%-40%) at 148°C, as shown in Table 1, to form microporous laminates.

[0245] As shown in Table 2, both microporous laminates exhibit approximately 50 g / (24h·m) 2 It has low water vapor permeability (WVP) and high tear resistance of 30-45 lb in both the MD and CD directions. The breaking strength is also about 27-37 lb / in.

[0246] Table 1

[0247]

[0248] Table 2

[0249]

[0250] Example 2

[0251] Microporous laminates comprising a microporous polymer surface coating on a nonwoven substrate are manufactured, suitable as house wraps or roofing sheets. The reactor-grade polypropylene copolymer resin of Example 1 is used; however, the resin further contains 1.5% UV stabilizer.

[0252] For each laminate in this example, a polypropylene copolymer is extruded and coated onto a 45 gsm Typar® polypropylene nonwoven fabric with a 30% elongation at break at room temperature. Each individual layer of the polypropylene copolymer has a coating thickness of 2.5 mils before any stretching. For items 2.1 and 2.2, a layer of polypropylene copolymer is coated onto one side of the substrate using an extrusion temperature of 240°C and a roll gap pressure of 1 bar to form a non-porous laminate. For item 2.3, a layer of polypropylene copolymer is coated onto one side of the substrate using an extrusion temperature of 240°C and a roll gap pressure of 2.2 bar to form a non-porous laminate. For items 2.4 and 2.5, a layer of polypropylene copolymer is coated onto the opposite side of the substrate using an extrusion temperature of 240°C and a roll gap pressure of 2.2 bar to form a non-porous laminate.

[0253] As shown in Table 3, the non-porous laminates were then subjected to 30%–40% MDO cold stretching at below 30°C (i.e., at room temperature, without preheating), followed by 40%–50% TDO hot stretching at 143°C. The final basis weights of these microporous laminates ranged from approximately 65 gsm to 95 gsm.

[0254] All microporous laminates exhibited a s / 100 cm⁻¹ ratio much greater than 1000. 3 The air permeability of the microporous laminates was measured. As shown in Table 4, all microporous laminates exhibited water resistance (water head) greater than 450 mbar. The microporous laminates also exhibited a permeability of approximately 140 to 300 g / (24h·m). 2 Water vapor permeability (WVP) and high tear resistance exceeding approximately 9.5 pounds of force in both the MD and CD directions.

[0255] Table 3

[0256]

[0257] Table 4

[0258]

[0259] Example 3

[0260] Microporous laminates are manufactured, comprising a microporous polymer surface coating on a nonwoven substrate, suitable for certain medical applications such as table covers. The reactor-grade polypropylene copolymer resin of Example 1 is used; however, the resin further contains an FDA-approved blue colorant, as this color is preferred in medical applications.

[0261] For each laminate in this example, a polypropylene copolymer was extruded and coated onto a 50 gsm spunbond polypropylene (SBPP) nonwoven fabric with an elongation at break greater than 50% at room temperature, available from Acme Mills Company, 33 Bloomfield Hills Parkway #120, Bloomfield Hills, MI 48304. Upon inspection, the nonwoven substrate was found to be heat-fused with a small, localized cross-line pattern, each approximately 0.31 mm thick. 2 The fibers are spaced apart, such that approximately 15% of the fiber sheet surface area is fused. The areal density of the fused region is approximately 3 / cm². This SBPP has a higher elongation at break at room temperature than the polypropylene nonwovens of Examples 1 and 2; the nonwoven filaments in the SBPP nonwoven have a much smaller diameter than the filaments present in the nonwoven materials of Examples 1 and 2. For Item 3.1, a layer of polypropylene copolymer is coated on one side of the substrate to form a dark blue nonporous laminate. For Items 3.2 to 3.5, a layer of polypropylene copolymer is coated on the opposite side of the substrate to form a dark blue nonporous laminate.

[0262] As shown in Table 5, the non-porous laminates were subjected to 50%–70% MDO cold stretching at below 30°C (i.e., at room temperature, without preheating), followed by 50% MDO hot stretching at 130°C (except for item 3.2), and then a subsequent 100%–125% TDO hot stretching at 148°C. The basis weight of the final product was in the range of approximately 45 gsm to 80 gsm. As the laminates were stretched, the blue color of the coating lightened.

[0263] As shown in Table 6, most microporous laminates exhibit a porosity of less than 100 s / 100 cm. 3The air permeability of these samples is high, meaning they possess extremely high flux and surprisingly high water resistance (water head); microporous laminates made with a 3-mil coating exhibit at least 450 mbar water resistance, while those made with a 4-mil coating exhibit at least 840 mbar water resistance. These samples have an average water resistance of approximately 900 g / (24h·m). 2 Water vapor permeation (WVP).

[0264] Table 5

[0265]

[0266] Table 6

[0267] .

Claims

1. A microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate, the nonwoven substrate having a first surface and an opposite second surface; The first microporous polymer surface coating comprises a polypropylene copolymer, the polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments in the following amounts: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises an amount of ethylene polymeric units at least 45% by weight based on the weight of the ethylene-containing copolymer segment; or an amount of ethylene polymeric units at least 55% by weight based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. The first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase. The domain of the ethylene-containing copolymer segment is further contained within the inclusion phase of the polypropylene homopolymer segment. The domains of the ethylene-containing copolymer segments within the matrix phase break down to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating having the broken domains of the ethylene-containing copolymer segments has an average thickness of 0.4 to 3.9 mils (10 to 100 micrometers). The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer, wherein the continuous filaments are bonded together at the intersections in the random network. The polypropylene copolymer of the first microporous polymer surface coating is fused to a continuous filament on the first surface of the nonwoven substrate; and The microporous laminate described therein has a trapezoidal tear of 40 to 225 Newtons (9 to 50 pounds of force).

2. The microporous laminate as described in claim 1, wherein, The thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof.

3. The microporous laminate as described in claim 2, wherein, The thermoplastic polymer includes polypropylene.

4. The microporous laminate according to any one of claims 1 to 3, further comprising: (i) 30 g / m² to 120 g / m² 2 The base weight, (ii) A thickness of 3 to 15 mils (0.076 to 0.381 mm), (iii) A hydrostatic head of 2 meters or greater, (iv) 18 g / (24hr·m 2 ) or greater water vapor permeation, and (v) 10 psi (87.6 N / 50 mm) or greater tensile strength.

5. The microporous laminate as described in any one of claims 1 to 3, further comprising a second microporous polymer surface coating. The second microporous polymer surface coating is the same as the first microporous polymer surface coating, and The polypropylene copolymer of the second microporous polymer surface coating is fused to a continuous filament on the opposite second surface of the nonwoven substrate.

6. The microporous laminate as described in claim 6, further comprising: (i) 40 g / m 2 Up to 150 g / m 2 The base weight, (ii) A thickness of 4 to 19 mils (0.10 to 0.48 mm), (iii) A hydrostatic head of 3 meters or greater. (iv) 25 g / (24hr·m 2 ) or greater water vapor permeation, and (v) 10 psi (87.6 N / 50 mm) or greater tensile strength.

7. A method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate, the nonwoven substrate having a first surface and an opposite second surface, the method comprising the steps of: A) A molten polymer layer is coated onto the first surface of the nonwoven substrate, and then cooled to form a nonporous laminate having a nonporous layer of the polymer on the first surface. The non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein: a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segments within the matrix phase, the domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer, the continuous filaments being bonded together at their intersections in the random network; the nonwoven substrate has (i) Basis weight of 30 to 100 gsm, and (ii) Elongation at break at room temperature less than 50%; B) subjecting the non-porous laminate to sequential cold and hot stretching steps, these steps including: (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and (ii) At least 20% to 50% of thermal stretching is performed at a temperature above 100°C; This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in the non-porous polymer layer and producing a microporous laminate.

8. A method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate and a second microporous polymer surface coating on a second surface opposite to the nonwoven substrate, The method includes the following steps: A) A first molten polymer layer is coated on the upper surface of a first surface of the nonwoven substrate, and then cooled; a second molten polymer layer is coated on the upper surface of the opposite second surface of the nonwoven substrate, and also cooled, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface. Each non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein: a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segments within the matrix phase, the domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of continuous filaments of a thermoplastic polymer, the continuous filaments being bonded together at their intersections in the random network; the nonwoven substrate has (i) Basis weight of 30 to 100 gsm, and (ii) Elongation at break at room temperature less than 50%; B) subjecting the non-porous laminate to sequential cold and hot stretching steps, these steps including: (i) at least one cold stretching step of 20% to 50% at a temperature below 30°C; and (ii) At least 20% to 50% of thermal stretching is performed at a temperature above 100°C; This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in each non-porous polymer layer and producing a microporous laminate.

9. The method of claim 8 or 9, wherein, The stretching steps (i) and (ii) stretch the non-porous laminate only in the machine direction.

10. The method of claim 8 or 9, wherein, The stretching step (i) stretches the non-porous laminate in the machine direction, and the stretching step (ii) stretches the non-porous laminate in the cross direction.

11. The method of claim 8 or 9, wherein, The thermoplastic polymer of the polymer filament of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof.

12. The method of claim 12, wherein, The thermoplastic polymer includes polypropylene.

13. A microporous laminate comprising a first microporous polymer surface coating on a nonwoven substrate, the nonwoven substrate having a first surface and an opposite second surface; The first microporous polymer surface coating comprises a polypropylene copolymer, the polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments in the following amounts: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises an amount of ethylene polymeric units at least 45% by weight based on the weight of the ethylene-containing copolymer segment; or an amount of ethylene polymeric units at least 55% by weight based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. The first microporous polymer surface coating has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having multiple domains of the ethylene-containing copolymer segments within the matrix phase. The domain of the ethylene-containing copolymer segment is further contained within the inclusion phase of the polypropylene homopolymer segment. The domains of the ethylene-containing copolymer segments within the matrix phase break down to form micropores in the first microporous polymer surface coating. The first microporous polymer surface coating, having the broken domains of the ethylene-containing copolymer segments, has an average thickness of 0.5 to 3.0 mils (12.7 to 76.2 micrometers). The nonwoven substrate is a spunbond nonwoven, a meltblown nonwoven, or a combination of spunbond and meltblown nonwoven layers; the nonwoven substrate comprises a random network of thermoplastic polymer filaments or fibers bonded together. The polypropylene copolymer of the first microporous polymer surface coating is fused into the filaments or fibers on the first surface of the nonwoven substrate; and The microporous laminate described therein has a Gurley air permeability of 20 to 150 seconds per 100 cubic centimeters of air.

14. The microporous laminate of claim 14, wherein, The thermoplastic polymer of the polymer filaments or fibers of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof.

15. The microporous laminate of claim 15, wherein, The thermoplastic polymer includes polyester.

16. The microporous laminate according to any one of claims 14 to 16, further comprising: (i) 30 g / m 2 Up to 100 g / m 2 The base weight, (ii) A thickness of 3 to 15 mils (0.076 to 0.381 mm), (iii) A hydrostatic head of 2.5 meters or greater, (iv) 200 g / (24hr·m 2 ) or greater water vapor permeation, and (v) 10 psi (87.6 N / 50 mm) or greater tensile strength.

17. The microporous laminate of any one of claims 14 to 16, further comprising a second microporous polymer surface coating, The second microporous polymer surface coating is the same as the first microporous polymer surface coating, and The polypropylene copolymer of the second microporous polymer surface coating is fused into the surface filaments or fibers on the opposite second surface of the nonwoven substrate. The microporous laminate described therein has a Gurley air permeability of 20 to 150 seconds per 100 cubic centimeters of air.

18. The microporous laminate of claim 18, further comprising: (i) 30 g / m 2 Up to 100 g / m 2 The base weight, (ii) A thickness of 4 to 19 mils (0.10 to 0.48 mm), (iii) A hydrostatic head of 3 meters or greater. (iv) 200 g / (24hr·m 2 ) or greater water vapor permeation, and (v) 10 psi (87.6 N / 50 mm) or greater tensile strength.

19. A method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate, the method comprising the steps of: A) A molten polymer layer is coated onto the first surface of the nonwoven substrate, and then cooled to form a nonporous laminate having a nonporous layer of the polymer on the first surface. The non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein: a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. The non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segments within the matrix phase, the domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and b) The nonwoven substrate comprises a random network of thermoplastic polymer filaments or fibers bonded together in the form of spunbond nonwovens, meltblown nonwovens, or some combination of spunbond and meltblown nonwoven layers; the nonwoven substrate has (i) Basis weight of 30 to 100 gsm, and (ii) 50% or greater elongation at break at room temperature; B) subjecting the non-porous laminate to sequential cold and hot stretching steps, these steps including: (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C; This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in the non-porous polymer layer and producing the microporous laminate.

20. A method for forming a microporous laminate, the microporous laminate comprising a first microporous polymer surface coating on a first surface of a nonwoven substrate and a second microporous polymer surface coating on a second surface opposite to the nonwoven substrate, The method includes the following steps: A) A first molten polymer layer is coated on the upper surface of a first surface of the nonwoven substrate, and then cooled; a second molten polymer layer is coated on the upper surface of the opposite second surface of the nonwoven substrate, and also cooled, to form a nonporous laminate having a first nonporous layer of the polymer on the first surface and a second nonporous layer of the polymer on the second opposite surface. Each non-porous polymer layer has an areal loading of 22.9 to 114.3 gsm and a thickness of 1–5 mils (25 to 125 micrometers), wherein: a) The polymer is a composition comprising a polypropylene copolymer, said polypropylene copolymer comprising polypropylene homopolymer segments and ethylene-containing copolymer segments: i) 50 to 95 wt% polypropylene homopolymer segments based on the weight of the polypropylene copolymer; or 43 to 79 mol% polypropylene homopolymer segments based on the molar content of polypropylene polymeric units in the polypropylene homopolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer; and ii) 5 to 50 wt% of ethylene-containing copolymer segments based on the weight of the polypropylene copolymer; or 21 to 57 mol% of ethylene-containing copolymer segments based on the molar content of polymeric monomer units in the ethylene-containing copolymer segments as the percentage of the total molar content of polymeric monomer units in the polypropylene copolymer. At least a portion of the ethylene-containing copolymer segment comprises ethylene polymeric units in an amount of at least 45 wt% based on the weight of the ethylene-containing copolymer segment; or ethylene polymeric units in an amount of at least 55 mol% based on the molar content of the ethylene polymeric units in the ethylene-containing copolymer segment as a percentage of the total molar content of the polymeric monomer units in the ethylene-containing copolymer segment. Each non-porous polymer layer has a matrix phase of the polypropylene homopolymer segments, the matrix phase further having a plurality of domains of the ethylene-containing copolymer segments within the matrix phase, the domains of the ethylene-containing copolymer segments further comprising an inclusion phase of the polypropylene homopolymer segments within the domains, and b) The nonwoven substrate comprises a spunbond nonwoven fabric having a random network of thermoplastic polymer filaments or fibers, the filaments or fibers being bonded together at intersections in the random network; the nonwoven substrate has (i) Basis weight of 30 to 100 gsm, and (ii) 50% or greater elongation at break at room temperature; B) subjecting the non-porous laminate to sequential cold and hot stretching steps, these steps including: (i) at least one cold stretching step of 50% to 85% at a temperature below 30°C; and (ii) At least one 100% to 150% thermal stretching step at a temperature above 100°C; This causes the domains of the ethylene-containing copolymer segments within the matrix phase to break down, thereby forming micropores in each non-porous polymer layer and producing a microporous laminate.

21. The method of claim 20 or 21, wherein, The stretching steps (i) and (ii) stretch the non-porous laminate only in the machine direction.

22. The method of claim 20 or 21, wherein, The stretching step (i) stretches the non-porous laminate in the machine direction, and the stretching step (ii) stretches the non-porous laminate in the cross direction.

23. The method of claim 20 or 21, wherein, The thermoplastic polymer of the polymer filaments or fibers of the nonwoven substrate includes polypropylene, polyester, nylon, or mixtures thereof.

24. The method of claim 24, wherein, The thermoplastic polymer includes polyester.

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