Waterproof and breathable polyolefin roofing film by extrusion lamination and sequential stretching

Abstract

A reinforced microporous polyolefin sheet is disclosed that includes one or more layers of a microporous polyolefin and a nonwoven fabric at least partially embedded in the microporous polyolefin. The reinforced microporous polyolefin sheet is made in an extrusion lamination process by which a polyolefin sheet and a nonwoven fabric are laminated followed by sequential cold and hot stretching steps to create micropores.

Description

Background of the Invention

[0002] FIELD OF THE INVENTION The present invention relates to breathable polymeric films and methods of making the same.

[0003] Description of Related Art. Breathable films are films that are permeable to water vapor and other gases but highly impermeable to liquids. These films find use in the construction industry, such as in the form of housewrap. Breathable housewrap acts as a weather barrier, preventing water from passing through the wall assembly while allowing water vapor to escape. Other uses include backing sheets for sanitary absorbent products such as diapers, medical filtration applications, medical dressings, medical packaging, and medical back table cover applications.

[0004] The air permeability is caused by micropores in the membrane. Micropores can be created in several ways. They are sometimes caused by interstitial spaces between the fibers that make up the membrane, such as in plexifilamentary membranes (such as PTFE from DuPont). Micropores can also be formed mechanically or by using laser methods.

[0005] Stretching methods can be used to produce micropores. For example, U.S. Patent Nos. 3,801,404 and 3,426,754 describe stretching semi-crystalline polymers to produce micropores. More recently, U.S. Published Patent Application No. 2021 / 0095110 describes certain polypropylene copolymer films that are sequentially cold stretched and hot stretched to produce micropores. Although this last document mentions roofing membranes as potential applications for the membrane, the fact is that microporous polypropylene copolymer membranes themselves generally lack the mechanical properties and other performance characteristics required for roofing membranes. Roofing membranes are generally thicker sheets, typically with a thickness of 1 mm or more, and must meet strength, elongation and other mechanical requirements in addition to having the necessary water barrier and air permeability requirements. In addition, roofing membranes are typically manufactured as roll products that must be joined along seams to produce a continuous, leak-free water barrier. The industry's preferred method for this manufacturing is heat welding, and therefore, in addition to these other required properties, roofing membranes also need to be easily weldable at reasonable welding temperatures.

[0006] US2021 / 0095110 mentions that laminates can be formed by bonding microporous polypropylene copolymer films to various fabrics using methods such as thermal calendering point bonding, adhesive lamination, and ultrasonic bonding. Summary of the invention

[0007] The present invention relates to a method for forming a reinforced microporous polyolefin sheet, comprising the following steps:

[0008] a) extrusion laminating a polyolefin non-porous sheet onto at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm, the non-porous laminate comprising a non-woven fabric at least partially embedded in a polyolefin, and then

[0009] b) subjecting the non-porous laminate to a series of stretching steps to produce microvoids in the polyolefin, the stretching steps comprising:

[0010] 1) at least one cold stretching step at a temperature in the range of -20°C to 50°C, and

[0011] 2) at least one hot stretching step at a temperature above 50° C. and up to 150° C.,

[0012] The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and

[0013] Wherein the polyolefin is a phase-separated polymer, the phase-separated polymer comprises a continuous phase comprising a polypropylene homopolymer and a dispersed phase comprising an ethylene-propylene copolymer having a glass transition temperature of -30°C or less, the dispersed phase further comprising inclusions of the polypropylene homopolymer.

[0014] In another aspect, the present invention is a method for forming a reinforced microporous polyolefin sheet comprising the steps of:

[0015] a) extrusion laminating a polyolefin non-porous sheet onto at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm, the non-porous laminate comprising a non-woven fabric at least partially embedded in a polyolefin, and then

[0016] b) subjecting the non-porous laminate to a series of stretching steps to produce microvoids in the polyolefin, the stretching steps comprising:

[0017] 1) at least one cold stretching step at a temperature in the range of -20°C to 50°C, and

[0018] 2) at least one hot stretching step at a temperature above 50° C. and up to 150° C.,

[0019] The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and

[0020] The polyolefins include:

[0021] (i) 50 to 95 weight percent of one or more polypropylene homopolymer segments based on the weight of the polyolefin, or 43 to 79 mole percent of the polypropylene homopolymer segments based on the molar content of polymerized units of polypropylene in the polypropylene homopolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin, and

[0022] (ii) 5 to 50 weight percent of ethylene-containing copolymer segments based on the weight of the polyolefin, or 21 to 57 mole percent of ethylene-containing segments based on the mole content of polymerized monomer units in the ethylene-containing copolymer segments as a percentage of the total mole content of polymerized monomer units in the polyolefin,

[0023] wherein at least a portion of the ethylene-containing copolymer segments comprises polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer segments, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer segments.

[0024] Very surprisingly, when stretched according to step b), the non-porous laminate formed in step a) has produced an enhanced microporous sheet showing excellent air permeability or an effective barrier to liquid water. Despite the presence of nonwoven fabric, the non-porous laminate produced in step a) can be stretched under each of cold stretching conditions and hot stretching conditions to produce micropores. Even more surprisingly, the formation of this micropore is completed without producing significant defects on the interface of nonwoven fabric fibers and polyolefins. During the stretching process, polyolefins will not be pulled apart significantly from the fabric fibers. The method of the present invention allows the production of thick microporous sheets, which have mechanical properties and other characteristics that make them useful as roofing membranes and for other purposes.

[0025] In another aspect, the invention relates to a reinforced microporous polymer sheet having a thickness of at least 1 mm, the reinforced microporous polymer sheet comprising a nonwoven fabric embedded in a microporous polyolefin,

[0026] The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and

[0027] The polyolefin is a phase-separated polymer comprising a continuous phase containing a polypropylene homopolymer and a dispersed polyolefin phase containing an ethylene-propylene copolymer having a glass transition temperature of -30°C or less, the dispersed phase further containing a polypropylene homopolymer content.

[0028] In yet another aspect, the present invention also relates to a reinforced microporous polymer sheet having a thickness of at least 1 mm, the reinforced microporous polymer sheet comprising a nonwoven fabric embedded in a microporous polyolefin

[0029] The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and

[0030] The polyolefins include:

[0031] (i) 50 to 95 weight percent of one or more polypropylene homopolymer segments based on the weight of the polyolefin, or 43 to 79 mole percent of the polypropylene homopolymer segments based on the molar content of polymerized units of polypropylene in the polypropylene homopolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin, and

[0032] (ii) 5 to 50 weight percent of ethylene-containing copolymer segments based on the weight of the polyolefin, or 21 to 57 mole percent of ethylene-containing segments based on the mole content of polymerized monomer units in the ethylene-containing copolymer segments as a percentage of the total mole content of polymerized monomer units in the polyolefin, and

[0033] wherein at least a portion of the ethylene-containing copolymer segments comprises polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer segments, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a TEM micrograph of a phase separated polyolefin suitable for use in the present invention wherein the dispersed phase contains inclusions of polypropylene homopolymer.

[0035] Figure 2 is a cross-sectional view of a non-porous laminate for cold stretching and hot stretching according to the present invention.

[0036] Figure 3 is a schematic diagram of the continuous process of the present invention. DETAILED DESCRIPTION

[0037] In some embodiments of the present invention, the polyolefin is a phase separation polymer, which comprises a continuous phase and a dispersed phase containing a polypropylene homopolymer. The dispersed phase is in the form of discrete domains that can be observed by a transmission electron microscope (TEM) according to the method described in paragraph

[0173] of US 2021 / 0095110A1 or an equivalent method. The dispersed phase comprises an ethylene-propylene copolymer having a glass transition temperature of -30°C or lower (without considering inclusions). The dispersed phase further contains polypropylene homopolymer inclusions. Such inclusions can also be observed by the TEM method mentioned above.

[0038] Figure 1 It is a TEM micrograph of a suitable phase-separated polyolefin. The copolymer comprises a continuous phase 1, wherein the dispersed phase exists in the form of domains 2. Domains 2 comprise ethylene-propylene copolymers 3 having a glass transition of -30°C or less (without regard to inclusions). The glass transition temperature is measured by differential scanning calorimetry (DSC). The sample is melted, quenched, and then heated at a heating rate of 10°C / min, wherein the sampling interval is 0.1 seconds, with the glass transition temperature as the midpoint of the step transition curve.

[0039] Domains 2 and 5 together may constitute, for example, 18% to 65% or 25% to 55% of the total mass of the phase separated polyolefin.The relative mass of the dispersed phase may be estimated using nuclear magnetic resonance (NMR) spectroscopy.

[0040] The ethylene-propylene copolymer 3 may constitute, for example, 35% to 90% of the total mass of the domain 2. As shown, the domain 2 mainly has a maximum size of 0.5 to 2 μm. The domain 2 further contains polypropylene homopolymer inclusions 4. The polypropylene homopolymer of the inclusions 4 may be the same polypropylene homopolymer as that contained in the continuous phase 1. The inclusions 4 may constitute, for example, 10% to 65% of the total mass of the domain 2. Figure 1 As shown in , a small portion of the mass of the dispersed phase (e.g., up to 25%, up to 10% or up to 5%) can be in the form of smaller domains 5 having a maximum dimension of less than 0.5 μm and a glass transition temperature of -30°C or lower, which smaller domains 5 may lack inclusions 4.

[0041] Preferably, at least 95% of the mass of the dispersed phase is in the form of domains having a longest dimension of 0.1 to 5 μm. In some embodiments, at least 95% or at least 98% of the dispersed phase is in the form of domains having a longest dimension of 0.1 to 2.5 μm, and in preferred embodiments, at least 95% or at least 98% of the dispersed phase is in the form of domains having a longest dimension of 0.25 to 2 μm.

[0042] The continuous phase 1 comprises a polypropylene homopolymer. The polypropylene homopolymer may constitute, for example, 80% to 100%, 90% to 100%, or 95% to 100% of the mass of the continuous phase.

[0043] The ethylene-propylene copolymer may constitute, for example, 80% to 100%, 90% to 100%, or 95% to 100% of the mass of domain 2 (excluding the mass of inclusions 4).

[0044] Inclusions 4 are or comprise polypropylene homopolymers, which may be the same polypropylene homopolymers forming the continuous polyolefin phase 1. The polypropylene homopolymers may constitute, for example, 80% to 100%, 90% to 100% or 95% to 100% of the mass of inclusions 4.

[0045] The polypropylene homopolymer forming the continuous phase 1 and / or the inclusions 4 and the ethylene-propylene copolymer in the domains 2 may be separate polymers. Alternatively, they may be partially or completely covalently bonded to each other, such as by grafting or other methods.

[0046] In other embodiments, the polyolefin comprises (i) 50 to 95 weight percent of one or more polypropylene homopolymer segments based on the weight of the polyolefin, or 43 to 79 mole percent of the polypropylene homopolymer segments based on the molar content of polymerized units of polypropylene in the polypropylene homopolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin. The polyolefin may comprise at least 55, at least 60, or at least 70 weight percent of the polypropylene homopolymer segments and up to 90, up to 88, up to 85, or up to 82 weight percent of the polypropylene homopolymer segments.

[0047] In some embodiments, the polyolefin comprises (ii) 5 to 50 weight percent of ethylene-containing copolymer segments based on the weight of the polyolefin, or 21 to 57 mole percent of ethylene-containing segments based on the molar content of polymerized monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin. The polyolefin may comprise at least 10, at least 12, at least 15, or at least 18 weight percent and up to 45, up to 40, or up to 30 weight percent of ethylene-containing copolymer segments.

[0048] In some embodiments, at least a portion of the ethylene-containing copolymer segments comprises polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer segments, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer segments. The ethylene-containing copolymer segments may contain at least 45, at least 50, at least 55, or at least 50 weight percent of polymerized units of ethylene, and may contain, for example, up to 80, up to 75, or up to 75 weight percent of polymerized units of ethylene.

[0049] The copolymer segments containing ethylene are copolymers of ethylene and at least one other copolymerizable monomer. The other copolymerizable monomer is preferably propylene. The copolymer segments containing ethylene can be, for example, block, random, pseudo-random and / or graft copolymers of ethylene and the at least one other copolymerizable monomer. In a specific embodiment, the copolymer segments containing ethylene are block copolymers of ethylene and propylene or block copolymers containing ethylene and propylene.

[0050] The content of polymerized ethylene units in the polyolefin may be, for example, at least 10, at least 12, or at least 15 weight percent and, for example, up to 30 or up to 25 weight percent, based on the total weight of the polyolefin.

[0051] Additional suitable polyolefins are described in US 2021 / 009511 A1 paragraphs

[0063] to

[0078] , which are incorporated herein by reference.

[0052] The polyolefin may constitute, for example, at least 80%, at least 90%, at least 95%, at least 98%, or at least 99% of the total weight of the starting non-porous polyolefin sheet.

[0053] The polyolefin may contain other components that may be useful or desirable. Examples of these other components include extrusion processing aids, such as lubricants, etc.; antioxidants, titanium dioxide, 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 various hydroxyphenylbenzotriols, such as those manufactured by BASF under the trade name 328 or 329; hindered amine stabilizers, such as those sold by BASF under 770 or Those sold in 2020. One or more UV stabilizers may be used in combination with one or more antioxidants.

[0054] Although the polyolefin may contain filler particles, such fillers are preferably absent, or if present, are present only in small amounts, such as up to 3%, up to 2%, up to 1%, or up to 0.5% of the combined weight of the filler particles and the polyolefin. Such fillers are particulate materials that are thermally stable (i.e., do not melt or thermally degrade) under the conditions of the extrusion lamination process. Fillers include both inorganic and organic types, including those described in paragraph

[0099] of US2021 / 0095110 A1.

[0055] The nonwoven fabric has a weight of 100 to 400 g / m2 as measured according to EN ISO 9864:2016. 2 The preferred area weight is at least 125 or at least 150 g / m 2 And up to 350 or up to 300g / m 2 . At 2kN / m 2 The fabric thickness is preferably 0.25 to 0.95 mm under a load of 1000 psi and may be, for example, at least 0.3 or at least 0.4 mm and up to 0.9 or up to 0.8 mm, as measured in accordance with EN ISO 9863-1:2005. The nonwoven fabric has an elongation at break of 30% to 200% in each of the machine direction and the cross direction as measured in accordance with EN ISO 10319:2015. The nonwoven fabric is preferably water permeable and may have a 5×10 -3 Up to 200×10 -3 , especially 10×10 -3 Up to 100×10 -3 , or 10×10 -3 Up to 50×10 -3 Permeability (VH50) of m / s.

[0056] In certain embodiments, nonwoven fabrics include fibers or filaments or are made up of fibers or filaments, which are entangled, spunbonded and / or melt-bonded to form fabrics. For example, nonwoven fabrics can be made with spunbond, air-laid, spunlace or melt-bonded processes.

[0057] The fabric is composed of a material that is thermally stable under the conditions of the extrusion lamination step, i.e., the material does not melt, thermally soften or degrade so that the fabric loses its integrity during the extrusion lamination step. The material may be or comprise an organic polymer, preferably an organic polymer having a crystalline melting temperature or Vicat softening temperature of at least 80° C., preferably at least 100° C. or at least 125° C. Examples of such polymers include polypropylene, polyesters such as poly(ethylene terephthalate), poly(butylene terephthalate), various polyamides (nylon), poly(lactide), cellulosic fibers such as pulped and extruded cellulose Cellulose acetate, cellulose diacetate, cellulose triacetate and cellulose acetate butyrate, various acrylate polymers, M5 fiber, polybenzimidazole, polyvinyl alcohol, polyphenylene sulfide, polyacrylonitrile and acrylonitrile copolymers. The fabric may also contain, for example, carbon, wool, metal, mineral wool, silk, jute or other natural fibers, provided that the fabric has the elongation at break and preferably also has the permeability as mentioned above.

[0058] Preferred fabrics are polypropylene fabrics, polyethylene terephthalate fabrics or polypropylene-polyethylene terephthalate fabrics. Polypropylene-polyethylene terephthalate fabrics can be composed of polypropylene-polyethylene bicomponent fibers, wherein the polypropylene forms at least a portion of the surface of these bicomponent fibers. Such bicomponent fibers can be, for example, of the sheath-and-core type with a polypropylene sheath, or side-by-side bicomponent fibers.

[0059] Non-porous laminates are produced by polyolefin and nonwoven fabric. In the extrusion lamination process, polyolefin is melted, and then the molten polyolefin is forced to pass through a die to form a non-porous polyolefin sheet. This step can be carried out using, for example, a single screw extruder or a twin screw extruder, an accumulation extruder or other suitable devices, which are equipped with suitable dies such as slit dies or dog bone dies. Polyolefin is heated to a temperature higher than the crystalline melt temperature of the polypropylene homopolymer of the continuous phase in an extrusion device, and forced through a die to form a sheet. Preferred temperatures are at least 180°C or at least 200°C and up to 240°C or up to 260°C.

[0060] The extruded polyolefin sheet preferably has a thickness of at least 250 μm, at least 400 μm or at least 500 μm, or at least 1000 μm, and up to 10 mm, up to 5 mm, up to 2,000 μm or up to 1,500 μm.

[0061] The extruded sheet is non-porous. It is preferred to omit blowing agents and / or gases during the extrusion process to avoid the creation of pores. For the purposes of the present invention, the sheet is non-porous if, after cooling, at 37.8° C., 100% relative humidity, the sheet exhibits a relative humidity of not more than 2 g / m 2 as measured in accordance with ASTM D1249. 2 -day water vapor transmission rate (WVTR), the sheet is considered "non-porous".

[0062] The non-porous polyolefin sheet of melting contacts the surface of the nonwoven fabric to produce a non-porous polyolefin layer on the surface. This step is carried out before the sheet is cooled to be lower than its Vicat softening temperature. The contacting step is preferably carried out within 30 seconds, more preferably within 10 seconds, within 5 seconds or within 2 seconds from the time the sheet leaves the extruder die.

[0063] The contacting step is carried out under mechanical (clamping) pressure so that the nonwoven fabric becomes at least partially embedded in the non-porous polyolefin layer. "Embedding" means that all or part of the polyolefin penetrates into the interstitial space in the nonwoven fabric, so that at least a portion of the nonwoven fabric becomes infused with polyolefin. Mechanical (clamping) pressure is conveniently applied by passing the nonwoven fabric and the applied polyolefin layer through one or more calendering rollers; however, other devices such as double-belt laminators are also suitable. In some embodiments, one or more of the calendering rollers can be cooled to simultaneously cool the polyolefin to a temperature below its Vicat softening temperature (such as cooling to 80°C to 120°C) and impregnate the fabric.

[0064] Extrusion lamination method can be carried out by applying the extruded polyolefin sheet to both sides of the nonwoven fabric. In such case, the opposite polyolefin sheet can be contacted with the nonwoven fabric simultaneously or sequentially.

[0065] like Figure 2 As shown in, the resulting non-porous laminate 20 comprises a nonwoven fabric 21 and (in the illustrated embodiment) two polyolefin layers 22 and 22A. As shown, the nonwoven fabric 21 is partially embedded in each of the polyolefin layers 22 and 22A, and the small center section 23 of the nonwoven fabric 21 is not penetrated. In an alternative embodiment, the whole nonwoven fabric 21 is infiltrated and embedded therein by any one or both of the polyolefin layers 22 and 22A. Also as shown, a part of each of the polyolefin layers 22 and 22A extends above and below the nonwoven fabric 21, respectively, to form non-enhanced surface layers 24 and 24A. In an alternative embodiment, there is not one or both of those non-enhanced surface layers 24 and 24A, in which case, the corresponding polyolefin layers 22 and / or 22A have been fully penetrated into the nonwoven fabric 21.

[0066] The total thickness of the non-porous laminate is at least 1 mm. It may be at least 1.2 mm, and may be up to, for example, 12.7 mm, up to 6.35 mm, up to 3 mm, up to 2 mm, or up to 1.8 mm.

[0067] The non-porous laminate thus formed is cooled to a temperature of 50°C or less before being subjected to a sequential cold and hot stretching process. Cold stretching is performed first, followed by hot stretching.

[0068] The stretching process can be carried out in the general manner and conditions described in US2021 / 095110 A1. The cold stretching step is carried out with a non-porous laminate at a temperature of -20°C to 50°C. The preferred lower temperature is 0°C, 10°C or 15°C, and the preferred upper temperature is up to 35°C, up to 30°C or up to 25°C. The cold stretching percentage can be, for example, at least 15%, at least 25%, at least 35% or at least 40% and up to 150%, up to 100% or up to 80%. Cold stretching can be carried out in a single step or in multiple increments. The stretching percentage is calculated as 100% × [(stretched film length-initial film length) ÷ initial film length)].

[0069] The cold-stretched laminate can be annealed before the subsequent hot stretching step. Such an annealing step is conveniently performed by heating the cold-stretched laminate to a temperature of 90°C to 150°C for at least one second, preferably at least 2 seconds. An annealing period greater than 30 seconds is generally not required. Annealing can fix the pore structure formed in the cold-stretching step and can also reduce shrinkage. The annealing step is preferably performed immediately after the cold stretching, while the cold-stretched laminate is kept under tension, so it does not shrink before the annealing step is performed. In a continuous process in which hot stretching is performed immediately after the cold stretching, annealing can be performed when the cold-stretched laminate is heated to the hot stretching temperature.

[0070] The heat stretching step is performed with the laminate at a temperature of greater than 50°C to 150°C. A preferred lower temperature limit is at least 90°C or at least 120°C, and a preferred upper temperature limit is 140°C. The heat stretching can be performed in a single step or in multiple increments. The heat stretching percentage can be, for example, at least 25%, at least 40%, or at least 50% and up to 400%, up to 300%, up to 200%, up to 150%, up to 100%, or up to 80%.

[0071] The hot stretched laminate may optionally be annealed in the same manner as described with respect to annealing the cold stretched laminate.

[0072] Each of the stretching steps can be carried out uniaxially or biaxially. Uniaxial stretching can be carried out in any direction. When the non-porous laminate is produced by passing the polyolefin sheet and the nonwoven fabric through the device, the laminate will have a machine direction corresponding to the direction of motion through the device, and a transverse or cross direction (in the plane of the sheet) perpendicular to the machine direction. Any one or both of the stretching steps can be carried out uniaxially in the machine direction or in the cross direction. For example, both the cold stretching step and the hot stretching step can be carried out uniaxially in the same direction (that is, the machine direction or the cross direction).

[0073] Alternatively, one of the stretching steps can be performed in the machine direction and the other in the cross direction. This has the benefit of better balancing physical properties such as tensile strength and elongation in the machine and cross directions. In an embodiment that lends itself well to continuous operation, the cold stretching step is performed in the cross direction and the hot stretching step is performed in the machine direction.

[0074] The laminate can be stretched by simultaneous biaxial stretching using a biaxial stretching apparatus such as sold by Iwamoto Seisakusho Co., Kyoto, Japan.

[0075] Another suitable stretching device comprises one or more groups of sequentially driven stretching rollers, and each group of stretching rollers is operated with successively greater speeds, as described in Fig. 8 and the accompanying text of US2011 / 095110 A1. Such a device can be mainly used for uniaxially stretching laminates in the machine direction. The sequentially driven stretching roller section can be an unwinding station before, and the laminate is fed into the stretching process and / or pre-stretching section and / or pre-cooling or pre-heating section by this unwinding station. The sequentially driven stretching roller section can be an annealing section and / or a rewinding station afterwards, where the stretched laminate is removed from the stretching process.

[0076] Another stretching device that allows continuous operation is a tenter frame, which includes a clamp for clamping the side of the laminate. The clamp is mounted on a pair of tracks that are separated in the direction of movement of the laminate through the device. The clamp travels along the track, carrying the laminate, gradually separating and thus stretching the laminate. The device is particularly suitable for stretching the laminate in the cross direction. As previously mentioned, the stretching section (that is, a section including gradually separated tracks, where the laminate is stretched) may be preceded by an unwinding station and / or a preheating station or a precooling station, followed by an annealing section and / or a rewinding section.

[0077] Another suitable stretching device is a grooved roller stretcher. Such a grooved roller stretcher is particularly useful for stretching laminates in a cross direction. The grooved roller stretcher includes a staggered tooth-and-groove structure through which the laminate passes. The tooth-and-groove structure can be a roller pair as described in, for example, U.S. Patent Nos. 4,368,565, 5,028,289 and 6,843,949, U.S. Patent Application No. 2006 / 0148354 and EP 927 096B1. As described in U.S. Patent No. 8,337,190, the toothed activation member and the moving belt with complementary tooth grooves. The grooved roller stretcher can include a plurality of tooth-and-groove structures in series. The laminate is fed into the grooved roller stretcher and conveyed through the tooth-and-groove structure, wherein the laminate is stretched transversely to its direction of motion. Thereafter, the laminate is removed from the device. The stretching operation performed in a grooved roll stretcher is conveniently performed in a continuous manner by continuously feeding a length of the laminate through a grooved structure.

[0078] In one embodiment of the present invention, a reinforced microporous polymer sheet is produced in a continuous process, which includes the following steps: a-1) continuously extruding a polyolefin into a non-porous sheet, a-2) before cooling the non-porous sheet to a temperature below its Vicat softening temperature, the non-porous sheet is continuously contacted with a nonwoven fabric to produce a non-porous laminate, b-1a) continuously cooling the non-porous laminate to a cold stretching temperature, then b-1b) cold stretching the non-porous laminate in the transverse direction, then b-2a) continuously heating the cold stretched laminate to a hot stretching temperature, and then b-2b) continuously hot stretching the cold stretched laminate in the machine direction to produce a reinforced microporous polymer sheet. Each of steps a-1), a-2), b-1a, b-1b), b-2a and b-2b) can be carried out in the manner described above. Such a continuous process may include optional steps such as continuously annealing the cold stretched laminate, continuously annealing the reinforced microporous polymer sheet, and / or continuously extruding a second layer of polypropylene copolymer and continuously contacting such second layer with the opposite side of the nonwoven fabric.

[0079] Such a continuous process can be carried out on an apparatus comprising the following stations connected in series:

[0080] I. An extrusion lamination station comprising 1a) an extruder equipped with a die suitable for producing a polyolefin sheet, 1b) a laminator suitable for continuously contacting the polyolefin sheet with a nonwoven fabric and continuously mechanically compressing the polyolefin sheet and the nonwoven fabric together to produce a non-porous laminate, and 1c) a feed device for supplying the nonwoven fabric to the laminator;

[0081] II. A cold stretching station adapted to continuously receive a non-porous laminate from an extrusion lamination device and continuously cold stretch the non-porous laminate in a cross direction;

[0082] III. a hot stretching station adapted to continuously receive the cold stretched laminate, continuously heat the cold stretched laminate to a hot stretching temperature, continuously hot stretch the laminate to form a microporous reinforced polyolefin sheet, and optionally continuously anneal the microporous reinforced polymer sheet, and

[0083] IV. A cooling station adapted to continuously receive the microporous reinforced polymer sheet and continuously cool it to a temperature below 50°C.

[0084] A preferred apparatus for continuously manufacturing microporous polymer sheets is schematically shown in Figure 3 The apparatus 30 includes an extrusion lamination section 70. The extrusion lamination section 70 includes a first extruder 31 and an accompanying die 32, which are suitable for continuously extruding a polyolefin sheet 51. The nonwoven fabric 33 is continuously fed from the feed device 50 and carried into the first laminator 60, which in this embodiment is in the form of a calendering roller 34. Wherein, the nonwoven fabric 33 is contacted with the polyolefin sheet 51 at the calendering roller 34 at such a point that the polyolefin sheet 51 is maintained at a temperature above its Vicat softening temperature. The calendering roller 34 preferably mechanically compresses the polyolefin sheet 51 and the nonwoven fabric 33 together to force at least a portion of the polyolefin sheet 51 into the gap space in the nonwoven fabric 33 to form a non-porous laminate 52. If necessary, the calendering roller 34 can be heated or cooled. If an optional second polyolefin sheet is to be applied, it is generally preferred to heat the calendering roller 34.

[0085] In the illustrated embodiment, lamination section 70 comprises optional second extruder 31A and associated second die 32A and optional second laminator 60A.As shown, second laminator 60A adopts the form of calendering roller 35, although equivalent device as above is also available.Second extruder 31A and second die 32A continuously produce optional polyolefin second sheet material, and this second sheet material continuously contacts with non-porous laminate 52 at the opposite side with polyolefin sheet 51 at second laminator 60A, to form sandwich structure.Non-porous laminate 52 and second polyolefin sheet are mechanically compressed together by second laminator 60A, and second polyolefin sheet remains on the temperature higher than its Vicat softening temperature simultaneously.Calendering roller 35 can be heated or cooled.

[0086] The non-porous laminate 52 is then continuously directed to a cold stretching station 36 where it is cold stretched in the cross (transverse) direction. Before reaching the cold stretching station 36, the non-porous laminate is brought to a cold stretching temperature as previously described. This can be accomplished, for example, by cooling the calendar rolls 34 and / or 35, and / or in a separate cooling station located upstream of the cold stretching section 36 (and after the last extrusion lamination station). Cooling can also be performed in the cold stretching section 36 itself, by, for example, cooling the staggered tooth-groove structure 37A / B.

[0087] The cold stretching station 36 includes one or more staggered tooth-groove structures 37A / B, and the non-porous laminate 52 is continuously passed through these structures at the cold stretching temperature and stretched in the cross direction to produce a cold-stretched laminate 61. As shown, the cold stretching section 36 includes two staggered tooth-groove structures 37A / B. Fewer or more tooth-groove structures can be provided as needed or desired.

[0088] The cold stretched laminate 61 is then continuously guided through a hot stretch section 62 where it is brought to the hot stretching temperature, continuously stretched in the machine direction, and optionally annealed. In the illustrated embodiment, the hot stretch section 62 comprises a preheating section comprising rollers 40, 41, and 42. The rollers 40, 41, and / or 42 are heated to raise the temperature of the cold stretched laminate to the hot stretching temperature. The number of preheating rollers 40, 41, and 42 is 1 / 40 / 42. Figure 3 arbitrarily shown as three in the figure; more or less may be provided as needed or desired. As shown, each preheating roller 40, 41 and 42 has an optional associated guide roller or drive roller 40A, 41A and 42A, which can be used to guide the cold-stretched laminate 61 against the associated heating roller and / or provide power to the associated heating roller, and thus help pull the cold-stretched laminate 61 into the hot stretch section 62 and / or pull it through the hot stretch section 62. The cold-stretched laminate 61 may wrinkle after passing through the staggered tooth groove structure 37A / B; the guide or drive roller 40A, 41A and / or 42A can be further used to firmly press the cold-stretched laminate 61 against the corresponding preheating roller, thereby flattening the cold-stretched laminate 61, removing wrinkles, and reducing or preventing shrinkage in the cross direction.

[0089] Annealing may occur in a preheating section of the hot stretching section 62 .

[0090] exist Figure 3 In the embodiment shown in FIG. 6 , the heat stretching section 62 includes stretching rollers 43 and 44. Figure 3; fewer or more stretching rollers may be provided. As shown, each stretching roller 43 and 44 has an optional associated guide or drive roller 43A and 44A, which can be used to guide the cold stretched laminate 61 against the associated stretching roller and / or rotate the associated stretching roller and thus help pull the cold stretched laminate 61 through the hot stretching section 62. The stretching rollers 43 and 44 can be heated.

[0091] Each successive stretching roller is operated at a greater peripheral speed than the previous stretching roller. The first stretching roller is operated at a greater peripheral speed than the immediately preceding upstream roller (as shown, the preheating roller 42). The rate at which the laminate travels through the hot stretching section 62 thus increases as it passes through each successive stretching roller, which causes the laminate to be stretched in the machine direction to produce a reinforced microporous copolymer sheet 75.

[0092] like Figure 3 As shown in the figure, the reinforced microporous polyolefin sheet 75 then continuously passes through the optional annealing section 47. As shown, the annealing section 47 includes annealing rollers 45 and 46, each of which is associated with an optional drive or guide roller 45A and 46A. As previously described, there may be more or fewer annealing rollers. The peripheral speed of rollers 45 and 46 is preferably at least as great as the peripheral speed of the last stretching roller 44, so as to maintain sufficient tension on the reinforced microporous copolymer sheet 75 so that it does not shrink in the machine direction. The temperature of the reinforced microporous copolymer sheet 75 in the annealing section 47 is maintained within the annealing temperature range as previously described.

[0093] The reinforced microporous copolymer sheet 75 exiting the hot stretching section 62 (or annealing section 47, if present) then passes through a cooling station 48, where it is cooled to a temperature below 50° C. In the embodiment shown, the cooling station 48 comprises a cooling roller 49 and an optional associated guide or drive roller 49A. There may be a plurality of cooling rollers 49. If the annealing section 47 is not present, the peripheral speed of the roller 49 is preferably at least as great as the peripheral speed of the last stretching roller, so as to maintain sufficient tension on the reinforced microporous copolymer sheet 75 so that it does not shrink in the machine direction.

[0094] The cooled reinforced microporous copolymer sheet 75 exiting the cooling station 48 is then continuously removed from the process, such as by being wound onto a roller 55 to produce a roll-stock.

[0095] The resulting reinforced microporous copolymer sheet has a thickness of at least 1 mm. The thickness may be at least 1.2 mm, and may be, for example, up to 12.7 mm, up to 6.35 mm, up to 3 mm, up to 2 mm, or up to 1.8 mm.

[0096] The reinforced microporous copolymer sheet preferably exhibits a microporous copolymer sheet weight of at least 50, at least 80, at least 100, at least 120, or at least 200 g / m 2 as measured according to ASTM E96 / E96M (ISO 12572:2001). 2 - day water vapor permeability. The water vapor permeability can be, for example, up to 1000, up to 500 or up to 350 g / m 2 -sky.

[0097] The reinforced microporous copolymer sheet preferably passes the water tightness test of EN 1928:2000 Method B under a pressure of 0.3 MPa for at least 30 minutes without leakage.

[0098] High vapor pressure permeability and excellent water tightness are important and unexpected advantages of the present invention. Surprisingly, the presence of the nonwoven fabric does not inhibit stretching and micropore formation, and also adheres strongly to the polypropylene copolymer so as to avoid tearing and forming more macro defects in the stretched material.

[0099] The reinforced microporous copolymer sheet preferably exhibits a tear strength in at least one direction as measured according to EN 12310-2: 2000 of at least 200 N, more preferably at least 250 N. More preferably, the tear strength is at least 200 N, more preferably at least 250 N in each of the machine and cross directions.

[0100] The reinforced microporous copolymer sheet preferably exhibits a tensile strength of at least 1250 N / 5 cm, more preferably at least 1500 or at least 1750 N / 5 cm, measured at a crosshead speed of 30 cm / min in at least one direction under peak load according to ASTM D5034-09. The reinforced microporous copolymer sheet may exhibit a tensile strength of at least 1250 N / cm, at least 1500 N / cm, or at least 1500 N / cm in one direction (typically the machine direction) and at least 500 N / cm in the orthogonal direction (typically the cross direction) under peak load. The elongation at maximum force measured in the same manner is preferably at least 15% in both the machine direction and the cross direction.

[0101] Another advantage of the reinforced microporous copolymer sheet is that it is easily and securely welded to itself despite the presence of an embedded nonwoven fabric. The bond strength is determined by bonding two reinforced microporous polyolefin sheets together using a hot air welder operating at a set temperature of 250°C and subsequently measuring the peel strength of the resulting bond according to EM12316-2:2000. The peel force at the weld is typically at least 2 N / mm.

[0102] The reinforced microporous copolymer sheet can be used as a waterproof membrane or as a component of a waterproof membrane in applications where air permeability, especially water vapor permeability, is required. Roof membranes represent an application for which the reinforced microporous copolymer sheet is particularly suitable. Specific examples of roof membranes for which the reinforced microporous copolymer sheet can be used include metal roof membranes, temporary roof membranes, and concrete roof membranes, especially lightweight concrete roof membranes.

[0103] The reinforced microporous copolymer sheets are also suitable for use as or as components of packaging, personal care items such as diapers and adult incontinence devices, protective wear such as medical drapes, medical gowns, surgical gowns, air masks, and the like.

[0104] Examples

[0105] The following examples are provided to illustrate the present invention, but these examples are not intended to limit the scope of the present invention. Unless otherwise indicated, all parts and percentages are by weight.

[0106] The polyolefin is a phase separated copolymer available from Braskem PP Americas as PP C7054-07NA. It contains 67.1% propylene homopolymer and 32.9% by weight of a 50 / 50 copolymer of ethylene and propylene (T g <-50℃). Figure 1 As shown in , upon TEM imaging, the polyolefin exhibits a continuous phase containing a polypropylene homopolymer and a dispersed phase containing an ethylene-propylene copolymer in the form of discrete domains having a longest dimension of primarily up to 2 μm. The polypropylene homopolymer inclusions are contained within the ethylene-propylene copolymer domains. The polyolefin has a molecular weight of 0.9 g / cm 3 and a melt index of 7 g / 10 min (230° C. / 2.16 kg) as reported by its manufacturer.

[0107] PP-PET is a nonwoven fabric made of core-shell polypropylene-poly (ethylene terephthalate) fibers. The fabric has a 157 g / m 2 The area density and at 2kN / m 2 The thickness is 0.762mm under a load of . Its tensile strength is 550N / 5cm in the machine direction and 434N / 5cm in the cross direction. Its elongation is 75% in the machine direction and 82% in the cross direction.

[0108] Examples 1-4

[0109] Polyolefin was blended with UV stabilizer masterbatch in a single screw extruder with a 158 cm die and extruded into non-porous sheets of 558 μm (22 mils) and 762 μm (30 mils) containing 0.315% of UV stabilizer. In each case, the extrudate was passed through three cooling rollers set at 119° C., 120° C. and 88° C. to produce a smooth, uniform surface. In each case, the PP-PET nonwoven fabric was fed from the unwinding station to the first cooling roller, where the extrudate and the PP-PET nonwoven contacted. The gap between successive cooling rollers was set to mechanically compress the extrudate and the PP-PET nonwoven, and force a portion of the extrudate to enter the gap space of the fabric. This produced an intermediate laminate with polyolefin on one side of the nonwoven fabric.

[0110] Polyolefin was then applied to the opposite side of the nonwoven fabric in the same manner, replacing the PP-PET nonwoven fabric with the intermediate laminate. This produced nonporous laminates 1 and 2 for subsequent stretching. Nonporous laminate 1 was made of two layers of 558 μm polyolefin sheets, and nonporous laminate 2 was made of two layers of 762 μm polyolefin sheets. Nonporous laminate 1 had a thickness of about 1.15 mm; the thickness of nonporous laminate 2 was about 1.6 mm.

[0111] A cold stretched laminate 1 is made by passing a non-porous laminate 1 through a series of eleven rollers while cold stretching it in the machine direction to 125% of its original length (25% stretch), as generally shown in FIG. 8 of US2021 / 0095110 A1. The stretching temperature is 20°C-23°C. The laminate turns white as it passes through the stretching step, indicating pore formation. The last three rollers are heated to 140°C to heat the stretched sheet and thermally anneal it, thereby fixing the pore structure and size.

[0112] Cold stretched laminate 2 was made in the same manner except that non-porous laminate 1 was stretched to 140% of its original length (40% stretch).

[0113] Cold-stretched laminates 3 and 4 were made in the same manner as cold-stretched laminates 1 and 2, respectively, using non-porous laminate 2 instead of non-porous laminate 1.

[0114] Each of the cold stretched laminates 1-4 was then hot stretched 50% in the machine direction on the same apparatus at a stretching temperature of 135°C to produce Examples 1-4, respectively. The properties were determined according to the test methods described previously and are reported in Table 1.

[0115] Table 1

[0116]

[0117] MD = Machine Direction. CD = Cross Direction. WVP is Water Vapor Permeability. A water tightness rating of "Pass" indicates no water leakage. Tensile strength and elongation are reported at yield.

[0118] These examples demonstrate that reinforced microporous polyolefin sheets can be successfully made in a sequential cold / hot stretching process despite the presence of an embedded nonwoven fabric. The samples maintained good tensile, elongation, and tear properties, were breathable (as indicated by the water vapor permeability values), yet remained a barrier to liquid water. These results demonstrate the excellent adhesion of the propylene copolymer to the fibers of the nonwoven fabric during the stretching process.

[0119] Example 5-7

[0120] Non-porous laminates 3-5 were made in the same general manner as non-porous laminates 1 and 2, except that the polyolefin sheet thickness was about 840 μm and the amount of UV stabilizer varied from 0% in non-porous laminate 3 to 1.5% and 2.5% in non-porous laminates 4 and 5. Non-porous laminates 3, 4 and 5 all had a thickness of about 1725 μm.

[0121] Examples 5-7 were made by sequentially cold and hot stretching non-porous laminates 3-5, respectively, in the same general manner as described for Examples 1-4. The laminates were cold stretched 50% at 20-23°C and hot stretched 50% at 135°C.

[0122] The porosity and average pore diameter were measured by mercury intrusion porosimetry according to ASTM D4404-10. Tensile strength, elongation at maximum force, and water vapor permeability were also measured using the methods described above. The results are shown in Table 2.

[0123] Table 2

[0124]

[0125] MD = Machine Direction. CD = Cross Direction. WVP is Water Vapor Permeability. A water tightness rating of "PASS" indicates no water leakage. Tensile strength and elongation are reported at yield. ND - Not Determined.

[0126] These thick reinforced laminates were successfully stretched to create porosity while maintaining desirable mechanical properties. All were breathable, and all passed the water tightness test.

[0127] Example 8-12

[0128] Non-porous laminates 3, 4 and 5 were cold stretched 40% in the general manner described in the previous examples. The resulting cold stretched laminates were then hot stretched in the transverse direction on a continuous Marshall & Williams Plastics transverse direction orientation (TDO) unit at a stretching temperature of 140°C to produce Examples 8-12. Non-porous laminate 3 was used to produce Example 8; non-porous laminate 4 was used to produce Example 9, and non-porous laminate 5 was used to produce Examples 10-12. The amount of transverse heat stretching is indicated in Table 3.

[0129] For comparison, a 1780 μm polyolefin sheet was extruded and then subjected to 40% cold stretching in the manner described previously, followed by 25%-50% hot stretching in the transverse direction as described for Examples 8-12. This sample is referred to as Comparative Sample A.

[0130] Tensile strength, elongation at maximum force and WVP were measured as described previously. The results are indicated in Table 3.

[0131] Table 3

[0132]

[0133] MD = Machine Direction. CD = Cross Direction. WVP is Water Vapor Permeability. Tensile strength and elongation are reported at yield.

[0134] As shown by the WVP results, the reinforced non-porous laminates, when stretched, produced microporous sheets with water vapor permeabilities comparable to those seen when stretching the non-reinforced sheet (Comparative A). In Examples 8-12, tensile strength was increased relative to Comparative A. As shown by the tensile data, biaxial stretching balances properties in the machine and cross directions.

[0135] Comparative sample B

[0136] Example 1 was repeated using a PET web (9 mm x 9 mm) from Zhejiang Minglong Jibu Co., Ltd. instead of the PP-PET fabric. The PET web had an elongation at break of 18% in the machine direction and 21.2% in the cross direction. The non-porous laminate produced using the PET web did not turn white during the MDO cold stretching step, indicating that no voids were formed. The laminate broke during the MDO hot stretching step.

[0137] Comparison of samples C and D

[0138] Sample C: The polyolefin was extruded into a 500 μm sheet. Using the general method described for Examples 1-4, the non-porous sheet was sequentially cold stretched 20% in the machine direction and then hot stretched 100% in the machine direction at 125°C. The sheet was treated with a corona discharge. The stretched sheet was bonded to a PP-PET nonwoven fabric with a polyurethane adhesive by a hot lamination process to form a 1.5 mm thick sandwich structure. The water vapor permeability was only 113 g / m 2 - days, and the microporous sheet adhered poorly to itself, exhibiting a peel strength of less than 2 N / mm.

[0139] Sample D: Sample C was repeated with a polyolefin hot melt adhesive replacing the polyurethane glue. This sample failed the heat aging test (116°C for 672 hours) due to the low melt temperature of the polyolefin adhesive.

[0140] Comparison of samples E and F

[0141] Sample E: The polyolefin was extruded into sheets of 635 μm and 752 μm. Using the general method described for Examples 1-4, the non-porous sheet was sequentially cold stretched 20% in the machine direction and then hot stretched 100% in the machine direction at 125°C. The stretched sheet was ultrasonically welded to a PP-PET nonwoven fabric with a polyurethane adhesive to form a 1.5 mm thick microporous sandwich structure. A large amount of ultrasonic energy was required to produce the weld, and large indentation points were produced in the weld area. These indentation points had very low mechanical strength.

[0142] Sample F: Sample E was repeated with the PET web described in Comparative Sample B instead of the PP-PET nonwoven fabric. The resulting microporous structure exhibited high water vapor permeability but failed the water tightness test. The peel strength was also very poor, less than 0.5 N / mm.

Claims

1. A method for forming a reinforced microporous polyolefin sheet comprising the following steps: a) extrusion laminating a polyolefin non-porous sheet onto at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm, said non-porous laminate comprising said non-woven fabric at least partially embedded in said polyolefin, and then b) subjecting the non-porous laminate to a sequential stretching step to produce micropores in the polyolefin, the stretching step comprising: 1) at least one cold stretching step at a temperature in the range of -20°C to 50°C, and 2) at least one hot stretching step at a temperature above 50° C. and up to 150° C., The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and The polyolefin is a phase-separated polymer comprising a continuous phase containing a polypropylene homopolymer and a dispersed phase containing an ethylene-propylene copolymer having a glass transition temperature of -30°C or less, the dispersed phase further containing a polypropylene homopolymer content.

2. A method for forming a reinforced microporous polyolefin sheet comprising the steps of: a) extrusion laminating a polyolefin non-porous sheet onto at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm, said non-porous laminate comprising said non-woven fabric at least partially embedded in said polyolefin, and then b) subjecting the non-porous laminate to a sequential stretching step to produce micropores in the polyolefin, the stretching step comprising: 1) at least one cold stretching step at a temperature in the range of -20°C to 50°C, and 2) at least one hot stretching step at a temperature above 50° C. and up to 150° C., The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 20% to 200% in each of the machine direction and the cross direction, and wherein the polyolefin comprises: (i) 50 to 95 weight percent of one or more polypropylene homopolymer segments based on the weight of the polyolefin, or 43 to 79 mole percent of the polypropylene homopolymer segments based on the molar content of polymerized units of polypropylene in the polypropylene homopolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin, and (ii) 5 to 50 weight percent of ethylene-containing copolymer segments based on the weight of the polyolefin, or 21 to 57 mole percent of the ethylene-containing segments based on the mole content of polymerized monomer units in the ethylene-containing copolymer segments as a percentage of the total mole content of polymerized monomer units in the polyolefin, wherein at least a portion of the ethylene-containing copolymer segments comprises polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer segments, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer segments.

3. The method according to claim 1 or 2, wherein: Step a) comprises the step of compressing the polyolefin non-porous sheet and the non-woven fabric together to penetrate the interstitial openings in the non-woven fabric with the polyolefin.

4. The method according to claim 1 or 2, wherein: Step a) includes step a-1) of extrusion laminating the first non-porous layer of polyolefin to the first side of the non-woven fabric and step a-2) of extrusion laminating the second non-porous layer of polyolefin to the second side of the non-woven fabric, steps a-1) and a-2) being performed simultaneously or sequentially.

5. The method according to any one of claims 1 to 4, wherein: The non-porous laminate was cold stretched in the transverse direction.

6. The method according to any one of claims 1 to 5, wherein: The nonporous laminate was cold stretched in the machine direction.

7. The method according to any one of claims 1 to 6, wherein: The cold stretched laminate is hot stretched in the transverse direction.

8. The method according to any one of claims 1 to 7, wherein: The cold stretched laminate is hot stretched in the machine direction.

9. The method according to any one of claims 1 to 8, wherein: Step a) comprises a-1) continuously extruding the polyolefin into a non-porous sheet, and a-2) before cooling the non-porous sheet to a temperature below its Vicat softening temperature, continuously contacting the non-porous sheet with the non-woven fabric to produce the non-porous laminate; Step b-1) comprises b-1a) continuously cooling the non-porous laminate to the cold stretching temperature, and then b-1b) continuously cold stretching the non-porous laminate in the transverse direction; and Step b-2) comprises b-2a) continuously heating the cold stretched laminate to the hot stretching temperature, and then b-2b) continuously hot-stretching the cold-stretched laminate to produce the reinforced microporous polymer sheet.

10. The method of claim 9, further comprising the steps of: Before step b-2) continuously annealing the cold-stretched laminate, and, After step b), The reinforced microporous polymer sheet is continuously annealed and / or a second sheet of polyolefin is continuously extruded and such second sheet is continuously contacted with the opposite side of the nonwoven fabric.

11. The method according to claim 9 or 10, wherein: Step b-1b) is performed by passing the non-porous laminate through a slotted stretching machine comprising a staggered tooth-and-groove structure.

12. The method according to claim 9 or 10, wherein: Step b-1b) is performed by mounting the non-porous laminate on a tenter frame comprising clamps for clamping the side edges of the non-porous laminate, the clamps being mounted on a pair of rails spaced apart in the machine direction.

13. A reinforced microporous polymer sheet having a thickness of at least 1 mm, the reinforced microporous polymer sheet comprising a nonwoven fabric embedded in a microporous polyolefin The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and The polyolefin is a phase-separated polymer comprising a continuous phase containing a polypropylene homopolymer and a dispersed phase containing an ethylene-propylene copolymer having a glass transition temperature of -30°C or less, the dispersed phase further containing a polypropylene homopolymer content.

14. A reinforced microporous polymer sheet having a thickness of at least 1 mm, the reinforced microporous polymer sheet comprising a nonwoven fabric embedded in a microporous polyolefin The nonwoven fabric has a weight of 100 to 400 g / m 2 Area weight, at 2kN / m 2 a thickness of 0.25 to 0.95 mm under a load of 1000 rpm and an elongation at break of 30% to 200% in each of the machine direction and the cross direction, and wherein the polyolefin comprises: (i) 50 to 95 weight percent of one or more polypropylene homopolymer segments based on the weight of the polyolefin, or 43 to 79 mole percent of the polypropylene homopolymer segments based on the molar content of polymerized units of polypropylene in the polypropylene homopolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin, and (ii) 5 to 50 weight percent of ethylene-containing copolymer segments based on the weight of the polyolefin, or 21 to 57 mole percent of the ethylene-containing segments based on the molar content of polymerized monomer units in the ethylene-containing copolymer segments as a percentage of the total molar content of polymerized monomer units in the polyolefin, and wherein at least a portion of the ethylene-containing copolymer segments comprises polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer segments, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing segments as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer segments.

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