Waterproof and breathable polyolefin roofing membranes produced by extrusion lamination and sequential stretching.

Abstract

The reinforced microporous polyolefin sheet comprises one or more layers of microporous polyolefin and a nonwoven fabric at least partially embedded in the microporous polyolefin. The reinforced microporous polyolefin sheet is produced by an extrusion lamination process in which the polyolefin sheet and the nonwoven fabric are laminated together, followed by sequential cold and hot stretching steps to generate pores.

Description

[Technical field]

[0001] The present invention relates to a breathable polymeric membrane and a method for making the same. [Background technology]

[0002] Breathable membranes are films that are permeable to water vapor and other gases, but highly impermeable to liquids. They are used in the construction industry, such as in the form of house wraps. Breathable house wraps act as a weatherproof barrier, preventing water from passing through the wall assembly while allowing water vapor to escape. Other applications include backsheets for sanitary absorbent products such as diapers, medical filtration applications, medical dressings, medical packaging, and medical back table cover applications.

[0003] Breathability is achieved through micropores in the film. Micropores can be produced in several ways. They may result from gaps between the fibers that make up the film, as in the case of plexifilamentary films (such as DuPont's Tyvek® film). Micropores can also be formed mechanically or by using laser methods.

[0004] Stretching methods can also be used to create micropores. For example, US Pat. Nos. 3,801,404 and 3,426,754 describe stretching semicrystalline polymers to create micropores. More recently, US Patent Publication No. 2021 / 0095110 describes certain polypropylene copolymer films that have been sequentially cold-stretched and hot-stretched to create micropores. This last document mentions roofing membranes as a potential application for the film, but in practice, microporous polypropylene copolymer films themselves often lack the mechanical and other performance properties required for roofing membranes. Roofing membranes are generally thick sheets, typically having a thickness of 1 mm or more, which must meet strength, elongation, and other mechanical requirements in addition to having the necessary waterproofing and breathability requirements. In addition, roofing membranes are generally manufactured as roll products, which must be joined along seams to obtain continuous, leak-free waterproofing. The industry's preferred method for doing this is heat welding, so the roofing membrane needs to be easily weldable at the appropriate welding temperatures, in addition to these other required properties.

[0005] US 2021 / 0095110 mentions that laminates can be formed by bonding microporous polypropylene copolymer films to various fabrics using methods such as thermal calendar point bonding, adhesive lamination, and ultrasonic bonding. Summary of the Invention [Means for solving the problem]

[0006] The present invention relates to a) extrusion laminating a non-porous sheet of polyolefin to at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm comprising the non-woven fabric at least partially embedded in the polyolefin; b) for a non-porous laminate, 1) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and 2) at least one hot drawing step at a temperature above 50°C and up to 150°C; generating micropores in the polyolefin by carrying out successive stretching steps comprising: 1. A method for forming a reinforced microporous polyolefin sheet comprising: Nonwoven fabric: 100~400g / m 2 Weight: 2kN / m 2 The thickness of the sheet is 0.25 to 0.95 mm under a load of 0.5 to 1.0 mm, and the elongation at break is 30 to 200% in each of the longitudinal and transverse directions. The present invention relates to a method of making a polyolefin polymer, the method comprising the steps of: (a) providing a polypropylene homopolymer having a glass transition temperature of about 100° C. to about 150° C.; and (b) providing a polyolefin having a glass transition temperature of about 100° C. to about 150° C., the method comprising the steps of: (a) providing a polypropylene homopolymer having a glass transition temperature of about 100° C. to about 150° C.;

[0007] In another aspect, the present invention provides a method for producing a composition comprising: a) extrusion laminating a non-porous sheet of polyolefin to at least one side of a non-woven fabric to produce a non-porous laminate having a thickness of at least 1 mm comprising the non-woven fabric at least partially embedded in the polyolefin; b) for a non-porous laminate, 1) at least one cold drawing step at a temperature in the range of -20°C to 50°C; and 2) at least one hot drawing step at a temperature above 50°C and up to 150°C; generating micropores in the polyolefin by carrying out successive stretching steps comprising: 1. A method for forming a reinforced microporous polyolefin sheet comprising: Nonwoven fabric: 100~400g / m 2 Weight: 2kN / m 2 The thickness of the sheet is 0.25 to 0.95 mm under a load of 0.5 to 1.0 mm, and the elongation at break is 30 to 200% in each of the longitudinal and transverse directions. The polyolefin is (i) 50 to 95 weight percent of one or more polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent of polypropylene homopolymer chain segments based on the mold content of polymerized units of polypropylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polyolefin; (ii) from 5 to 50 weight percent of ethylene-containing copolymer chain segments, based on the weight of the polyolefin, or from 21 to 57 mole percent of ethylene-containing chain segments, based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin; Including, wherein at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing chain segment as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.

[0008] Very surprisingly, the non-porous laminate formed in step a) produces a reinforced microporous sheet when stretched according to step b) that exhibits excellent breathability while providing an effective barrier to liquid water. Despite the presence of the nonwoven, the non-porous laminate produced in step a) can be stretched under both cold and hot stretch conditions to produce micropores. Even more surprisingly, this micropore formation is achieved without significant defects at the interface between the nonwoven fibers and the polyolefin. The polyolefin does not significantly separate from the textile fibers during the stretching process. The method of the present invention allows the production of thick microporous sheets that have mechanical and other properties that make them useful as roofing membranes and for other purposes.

[0009] In another aspect, the present invention provides a reinforced microporous polymer sheet having a thickness of at least 1 mm comprising a nonwoven fabric embedded in a microporous polyolefin, Nonwoven fabric: 100~400g / m 2 Weight: 2kN / m 2 The thickness of the sheet is 0.25 to 0.95 mm under a load of 0.5 to 1.0 mm, and the elongation at break is 30 to 200% in each of the longitudinal and transverse directions. the polyolefin is a phase separated polymer comprising a continuous phase comprising a polypropylene homopolymer and a dispersed polyolefin phase comprising an ethylene-propylene copolymer having a glass transition temperature of -30°C or less, the dispersed phase further comprising polypropylene homopolymer inclusions; The present invention relates to a microporous polymer sheet.

[0010] In yet another aspect, the present invention provides a reinforced microporous polymer sheet having a thickness of at least 1 mm, comprising a nonwoven fabric embedded in a microporous polyolefin, Nonwoven fabric: 100~400g / m 2 Weight: 2kN / m 2 The thickness of the sheet is 0.25 to 0.95 mm under a load of 0.5 to 1.0 mm, and the elongation at break is 30 to 200% in each of the longitudinal and transverse directions. The polyolefin is (i) 50 to 95 weight percent of one or more polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent of polypropylene homopolymer chain segments based on the mold content of polymerized units of polypropylene in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polyolefin; (ii) from 5 to 50 weight percent of ethylene-containing copolymer chain segments, based on the weight of the polyolefin, or from 21 to 57 mole percent of ethylene-containing chain segments, based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin; Including, The present invention also relates to a microporous polymer sheet, wherein at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing chain segment as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment. [Brief description of the drawings]

[0011] [Figure 1] 1 is a TEM micrograph of a phase separated polyolefin suitable for use in the present invention, in which the dispersed phase contains polypropylene homopolymer inclusions. [Diagram 2] 1 is a cross-sectional view of a non-porous laminate for cold and hot stretching according to the present invention. [Diagram 3] FIG. 1 is a schematic diagram of a continuous process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The polyolefin in some embodiments of the present invention is a phase-separated polymer comprising a continuous phase comprising a polypropylene homopolymer and a dispersed phase. The dispersed phase is in the form of discrete domains observable by transmission electron microscopy (TEM) according to the method described in paragraph

[0173] of US Patent Application Publication No. 2021 / 0095110, or an equivalent method. The dispersed phase comprises an ethylene-propylene copolymer having a glass transition temperature of -30°C or less (no reference to inclusions). The dispersed phase further comprises polypropylene homopolymer inclusions. Such inclusions are also observable by the TEM method described above.

[0013] Figure 1 is a TEM micrograph of a suitable phase separated polyolefin. The copolymer comprises a continuous phase 1 within which a dispersed phase is present in the form of domains 2. Domains 2 comprise an ethylene-propylene copolymer 3 having a glass transition below -30°C (no reference to inclusions). The glass transition temperature is measured by differential scanning calorimetry (DSC). Samples are melted, quenched and then heated at a heating rate of 10°C / min with a sampling interval of 0.1 seconds and the glass transition temperature is taken as the midpoint of the step transition curve.

[0014] Domains 2 and 5 together can comprise, for example, 18-65% or 25-55% of the total mass of the phase separated polyolefin. The relative masses of the dispersed phases can be estimated using nuclear magnetic resonance (NMR) spectroscopy.

[0015] The ethylene-propylene copolymer 3 may, for example, comprise 35-90% of the total mass of the domains 2. The domains 2 shown have a maximum dimension mainly between 0.5 and 2 μm. The domains 2 further comprise 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, for example, comprise 10-65% of the total mass of the domains 2. As shown in FIG. 1, a small portion of the mass of the dispersed phase (such as up to 25%, up to 10%, or up to 5%) may be in the form of smaller domains 5 having a maximum dimension less than 0.5 μm and a glass transition temperature below −30° C., and these smaller domains 5 may not comprise inclusions 4.

[0016] Preferably, at least 95% by mass of the dispersed phase is in the form of domains having a longest dimension between 0.1 and 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 between 0.1 and 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 between 0.25 and 2 μm.

[0017] The continuous phase 1 includes a polypropylene homopolymer. The polypropylene homopolymer can account for, for example, 80 to 100%, 90 to 100%, or 95 to 100% of the mass of the continuous phase.

[0018] The ethylene-propylene copolymer can account for, for example, 80 to 100%, 90 to 100%, or 95 to 100% of the mass of the domain 2 (not including the mass of the inclusions 4).

[0019] The inclusions 4 are or include a polypropylene homopolymer, which may be the same as the polypropylene homopolymer that forms the continuous polyolefin phase 1. The polypropylene homopolymer may account for, for example, 80-100%, 90-100%, or 95-100% of the mass of the inclusions 4.

[0020] 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, or they may be partially or fully covalently bonded to one another, such as by grafting or other methods.

[0021] In another embodiment, the polyolefin comprises (i) 50 to 95 weight percent of one or more polypropylene homopolymer chain segments, based on the weight of the polyolefin, or 43 to 79 mole percent of polypropylene homopolymer chain segments, based on the mold content of polymerized units of polypropylene in the polypropylene homopolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin. The polyolefin may comprise at least 55 weight percent, at least 60 weight percent, or at least 70 weight percent polypropylene homopolymer chain segments, and up to 90 weight percent, up to 88 weight percent, up to 85 weight percent, or up to 82 weight percent polypropylene homopolymer chain segments.

[0022] In some embodiments, the polyolefin comprises (ii) 5 to 50 weight percent ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing chain segments based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polyolefin. The polyolefin may comprise at least 10 percent, at least 12 percent, at least 15 percent, or at least 18 percent, and up to 45 percent, up to 40 percent, or up to 30 percent ethylene-containing copolymer segments.

[0023] In some embodiments, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized units of ethylene in an amount of at least 45 weight percent based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mole percent based on the molar content of polymerized units of ethylene in the ethylene-containing chain segment as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment. The ethylene-containing copolymer chain segment may comprise at least 45 weight percent, at least 50 weight percent, at least 55 weight percent, or at least weight percent polymerized units of ethylene, for example up to 80 weight percent, up to 75 weight percent, or up to 75 weight percent polymerized units of ethylene.

[0024] The ethylene-containing copolymer chain segment is a copolymer of ethylene and at least one other copolymerizable monomer. The other copolymerizable monomer is preferably propylene. The ethylene-containing copolymer chain segment may be, for example, a block, random, pseudorandom, and / or graft copolymer of ethylene and at least one other copolymerizable monomer. In certain embodiments, the ethylene-containing copolymer chain segment is or comprises a block copolymer of ethylene and propylene.

[0025] The content of polymerized ethylene units in the polyolefin may be, for example, at least 10 weight percent, at least 12 weight percent, or at least 15 weight percent, and for example up to 30 weight percent or up to 25 weight percent, based on the total weight of the polyolefin.

[0026] Further suitable polyolefins are described in paragraphs

[0063] to

[0078] of U.S. Patent Application Publication No. 2021 / 009511, which are incorporated herein by reference.

[0027] The polyolefin can, for example, comprise at least 80%, at least 90%, at least 95%, at least 98%, or at least 99% of the total weight of the starting nonporous polyolefin sheet.

[0028] The polyolefin may contain other ingredients that are deemed useful or desirable. Examples of these include extrusion aids such as lubricants, antioxidants, titanium dioxide, UV stabilizers, light stabilizers, heat stabilizers, pigments or other colorants, antistatic agents, flame retardants, antiblocking additives, biocides, and the like. UV stabilizers are preferred additives. Examples of these include various hydroxyphenyl benzotriols such as those sold by BASF as Tinuvin® 328 or Tinuvin® 329; 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.

[0029] The polyolefin may contain filler particles, but such fillers are preferably absent or, if present, 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 decompose) under the conditions of the extrusion lamination process. Fillers include both inorganic and organic types, such as those described in paragraph

[0099] of US Patent Application Publication No. 2021 / 0095110.

[0030] Nonwoven fabrics are 100-400g / m2 measured according to EN ISO9864:2016 2 The preferred basis weight is at least 125 or at least 150 g / m 2 And up to 350 or up to 300 g / m 2 The thickness of the fabric is preferably less than 2 kN / m 2 The nonwoven fabric preferably has a breaking elongation of 30-200% in each of the machine and cross directions when measured according to EN ISO10319:2015. The nonwoven fabric is preferably water permeable and has a water permeability of 5×10 to 10×10, for example at least 0.3 or at least 0.4 mm and at most 0.9 or at most 0.8 mm when measured according to EN ISO9863-1:2005. The nonwoven fabric preferably has a breaking elongation of 30-200% in each of the machine and cross directions when measured according to EN ISO10319:2015. The nonwoven fabric is preferably water permeable and has a water permeability of 5×10 to 10×10, for example at least 0.3 or at least 0.4 mm and at most 0.9 or at most 0.8 mm when measured according to EN ISO10319:2015. -3 ~200×10 -3 , especially 10x10 -3 ~100×10 -3 , or 10 x 10 -3 ~50×10 -3 It may have a permeability (VH50) of 10 ...

[0031] Nonwoven fabrics in some embodiments comprise or consist of entangled, spunbonded, and / or meltbonded fibers or filaments to form a fabric. Nonwoven fabrics can be made, for example, by a spunbond process, an airlaid process, a spunlace process, or a meltbond process.

[0032] The fabric is constructed from materials that are thermally stable under the conditions of the extrusion lamination process, i.e., materials that do not melt, heat soften, or degrade such that the integrity of the fabric is lost during the extrusion lamination process. The material may be or include 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 (nylons), poly(lactides), cellulose fibers such as pulped and extruded cellulose (Lyocell®), cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, various acrylate polymers, M5 fibers, polybenzimidazole, polyvinyl alcohol, polyphenylene sulfide, polyacrylonitrile, and acrylonitrile copolymers. The fabric may also comprise, for example, carbon fibers, wool fibers, metal fibers, mineral wool fibers, silk fibers, jute fibers, or other natural fibers, provided that the fabric has an elongation at break and preferably also has the permeability as described above.

[0033] Preferred fabrics are polypropylene fabrics, polyethylene terephthalate fabrics, or polypropylene-polyethylene terephthalate fabrics. Polypropylene-polyethylene terephthalate fabrics may be comprised of polypropylene-polyethylene bicomponent fibers, with the polypropylene forming at least a portion of the surface of the bicomponent fibers. Such bicomponent fibers may be sheath-core, for example with a polypropylene sheath, or may be side-by-side bicomponent fibers.

[0034] The non-porous laminate is made from polyolefin and nonwoven fabric. In the extrusion lamination process, the polyolefin is melted and then the molten polyolefin is forced through a die to form a non-porous polyolefin sheet. This can be done using a single or twin screw extruder with a suitable die, such as a slit or dog-bone die, an accumulating extruder, or other suitable equipment. The polyolefin is heated in the extrusion equipment to a temperature above the crystalline melting temperature of the continuous phase polypropylene homopolymer and forced through the die to form a sheet. The preferred temperature is at least 180°C or at least 200°C and up to 240°C or up to 260°C.

[0035] The extruded polyolefin sheet preferably has a thickness of at least 250 μm, at least 400 μm, 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.

[0036] The extruded sheet is non-porous. It is preferred that no blowing agents and / or gases are added during the extrusion process to avoid the creation of pores. For the purposes of this invention, the sheet, after cooling, has a density of 2 g / m2 at 37.8° C. and 100% relative humidity as measured according to ASTM D1249. 2 A sheet is considered to be "nonporous" if it exhibits a water vapor transmission rate (WVTR) of less than 1.5 MPa.

[0037] A molten non-porous polyolefin sheet is contacted with the nonwoven surface to produce a non-porous polyolefin layer on the surface. This step is performed before the sheet is cooled below its Vicat softening temperature. The contacting step is preferably performed within 30 seconds, more preferably within 10 seconds, 5 seconds, or 2 seconds after the sheet exits the extruder die.

[0038] The contacting step is carried out under mechanical (sandwiching) pressure so that the nonwoven is at least partially embedded in the nonporous polyolefin layer. By "embedded" it is meant that all or part of the polyolefin penetrates the interstices of the nonwoven, so that at least a portion of the nonwoven is polyolefin. The mechanical (sandwiching) pressure is conveniently applied by passing the nonwoven and applied polyolefin layer through one or more calendar rollers, although other devices such as double belt laminators are also suitable. In some embodiments, one or more calendar rollers can be cooled to cool the polyolefin to a temperature below its Vicat softening temperature (such as 80-120°C) and simultaneously impregnate the fabric.

[0039] The extrusion lamination process may be carried out by applying an extruded polyolefin sheet to both sides of the nonwoven fabric. In such a case, the polyolefin sheets on both sides can be contacted with the nonwoven fabric simultaneously or sequentially.

[0040] As shown in Figure 2, the resulting non-porous laminate 20 includes a nonwoven fabric 21 and (in the embodiment shown) two polyolefin layers 22 and 22A. As shown, the nonwoven fabric 21 is partially embedded in each of the polyolefin layers 22 and 22A, with no infiltration into a small central portion 23 of the nonwoven fabric 21. In an alternative embodiment, the entire nonwoven fabric 21 is infiltrated by and embedded within one or both of the polyolefin layers 22 and 22A. Also as shown, portions of each of the polyolefin layers 22 and 22A extend above and below the nonwoven fabric 21 to form non-reinforced surface layers 24 and 24A, respectively. In an alternative embodiment, one or both of these non-reinforced surface layers 24 and 24A are absent, in which case the respective polyolefin layers 22 and / or 22A completely infiltrate the nonwoven fabric 21.

[0041] The total thickness of the non-porous laminate is at least 1 mm. This may be at least 1.2 mm, for example at most 12.7 mm, at most 6.35 mm, at most 3 mm, at most 2 mm, or at most 1.8 mm.

[0042] The non-porous laminate thus formed is cooled to a temperature below 50° C. and then sequentially subjected to cold and hot stretching steps, with the cold stretching being carried out first, followed by the hot stretching.

[0043] The stretching process can be carried out in the general manner and under the conditions described in US Patent Application Publication No. 2021 / 095110. The cold stretching step is carried out at a temperature of -20°C to 50°C using a non-porous laminate. The preferred lower limit temperature is 0°C, 10°C, or 15°C, and the preferred upper limit temperature is up to 35°C, up to 30°C, or up to 25°C. The cold stretching ratio may 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 may be carried out in one step or gradually in multiple steps. The stretching ratio is calculated as 100% x [(length of stretched film - length of initial film) ÷ length of initial film)].

[0044] The cold stretched laminate may be annealed prior to carrying out a subsequent hot stretching step. Such an annealing step is conveniently carried out by heating the cold stretched laminate to a temperature of 90-150°C for at least 1 second, preferably at least 2 seconds. Annealing times of more than 30 seconds are usually unnecessary. Annealing can fix the pore structure formed in the cold stretching step and can also reduce shrinkage. The annealing step is preferably carried out immediately after cold stretching while keeping the cold stretched laminate under tension, so that there is no shrinkage before the annealing step is carried out. In a continuous process where hot stretching is carried out immediately after cold stretching, annealing may be carried out as the cold stretched laminate is heated to the hot stretching temperature.

[0045] The hot stretching step is carried out with the laminate at a temperature of more than 50° C. to 150° C. The preferred lower temperature limit is at least 90° C. or at least 120° C., and the preferred upper temperature limit is 140° C. The hot stretching may be carried out in one step or gradually in multiple steps. The hot stretching ratio may 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%.

[0046] The hot stretched laminate may be annealed in the same manner as described for annealing the cold stretched laminate.

[0047] Each stretching step can be performed uniaxially or biaxially. Uniaxial stretching can be performed in any direction. When a nonporous laminate is produced by passing a polyolefin sheet and a nonwoven through an apparatus, the laminate has a machine direction corresponding to the direction of movement through the apparatus and a transverse or transverse direction (in the plane of the sheet) perpendicular to the machine direction. Either or both of the stretching steps can be performed uniaxially in the machine direction or transverse direction. For example, both the cold stretching step and the hot stretching step can be performed uniaxially in the same direction, i.e., either the machine direction or the transverse direction.

[0048] Alternatively, one stretching step can be performed in the machine direction and the other in the transverse direction, which has the advantage of providing a better balance of physical properties such as tensile strength and elongation in the machine and transverse directions. In one embodiment suitable for continuous operation, the cold stretching step is performed in the transverse direction and the hot stretching step is performed in the machine direction.

[0049] The laminate may be stretched by simultaneous biaxial stretching using a biaxial stretching apparatus such as that available from Iwamoto Seisakusho Co., Ltd. of Kyoto, Japan.

[0050] Another suitable stretching apparatus includes one or more sets of continuously driven stretching rollers, each operating at a high speed in a sequential manner, as described in FIG. 8 of US2011 / 095110 and the accompanying text. Such an apparatus is useful primarily for uniaxially stretching laminates in the machine direction. The sequentially operating stretching roller section may be preceded by an unwinding station, where the laminate is fed into the stretching process, and / or a pre-stretching section, and / or a pre-cooling or pre-heating section. The sequentially operating stretching roller section may be followed by an annealing section and / or a winding station, where the stretched laminate is removed from the stretching process.

[0051] Another stretching device that allows for continuous operation is a tenter frame that includes clips for gripping both sides of the laminate. The clips are attached to a pair of rails that diverge in the direction of movement of the laminate through the device. The clips move along the rails, carrying and spreading the laminate, thereby stretching it. This device is particularly suitable for stretching the laminate in the transverse direction. As mentioned above, the stretching section (i.e. the section containing the extending rails along which the laminate is stretched) may be preceded by an unwinding station and / or a preheating or precooling station, followed by an annealing section and / or a winding section.

[0052] Yet another suitable stretching device is a grooved roller stretcher. Such a grooved roller stretcher is particularly useful for stretching the laminate in the transverse direction. The grooved roller stretcher is provided with an intermeshing tooth-groove structure through which the laminate is passed. The tooth-groove structure may be a roller pair, for example, as described in U.S. Pat. Nos. 4,368,565, 5,028,289, and 6,843,949, U.S. Published Patent Application No. 2006 / 0148354, and European Patent No. 927096. A moving belt with a toothed working member and a complementary tooth groove, as described in U.S. Pat. No. 8,337,190. The grooved roller stretcher may include multiple tooth-groove structures in series. The laminate is fed into the grooved roller stretcher and conveyed through the tooth-groove structure, where the laminate is stretched in the transverse direction to the moving direction. The laminate is then removed from the apparatus. The stretching operation carried out in a grooved roller stretcher is conveniently carried out continuously by passing the length of the laminate continuously through the tooth and groove structure.

[0053] In one embodiment of the present invention, the reinforced microporous polymer sheet is produced in a continuous process comprising a-1) continuously extruding a polyolefin into a nonporous sheet, a-2) continuously contacting the nonporous sheet with a nonwoven fabric before cooling the nonporous sheet to a temperature below its Vicat softening temperature to produce a nonporous laminate, b-1a) continuously cooling the nonporous laminate to a cold stretching temperature, then b-1b) cold stretching the nonporous laminate in the transverse direction, then b-2a) continuously heating the cold stretched laminate to a hot stretching temperature, then b-2b) continuously hot stretching the cold stretched laminate in the longitudinal 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 by the methods described herein above. Such a continuous process may include any of the steps of continuously annealing a cold stretched laminate, continuously annealing a reinforced microporous polymer sheet, and / or continuously extruding a second layer of a polypropylene copolymer and continuously contacting such second layer with the opposing side of the nonwoven fabric.

[0054] Such a continuous process can be carried out in an apparatus having in series: II-a) an extrusion lamination station including an extruder with a die configured to produce a polyolefin sheet, Ib) a laminator configured to continuously contact the polyolefin sheet with a nonwoven fabric and continuously mechanically compress the polyolefin sheet and the nonwoven fabric to produce a nonporous laminate, and Ic) a feeding device for feeding the nonwoven fabric to the laminator; II. a cold stretching station configured to continuously receive the nonporous laminate from the extrusion laminator and to continuously cold stretch the nonporous laminate in the transverse direction; III. a hot stretching station configured 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 IV. A cooling station which continuously receives the microporous reinforced polymer sheet and continuously cools it to a temperature below 50°C.

[0055] A preferred apparatus for continuously producing microporous polymer sheets is shown diagrammatically in FIG. 3. The apparatus 30 includes an extrusion lamination section 70. The extrusion lamination section 70 includes a first extruder 31 and associated die 32 configured to continuously extrude a polyolefin sheet 51. A nonwoven fabric 33 is continuously fed from a feeder 50 and conveyed to a first laminator 60, which in this embodiment takes the form of a calender roller 34. There, the nonwoven fabric 33 is brought into contact with the polyolefin sheet 51 at the calender roller 34 at a time when the polyolefin sheet 51 is maintained at a temperature above its Vicat softening temperature. The calender 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 interstices of the nonwoven fabric 33 to form the nonporous laminate 52. The calender roller 34 may be heated or cooled as required. When applying an optional second polyolefin sheet, it is often preferred to heat the calender roller 34.

[0056] In the illustrated embodiment, the laminating section 70 includes an optional second extruder 31A and associated second die 32A, as well as an optional second laminator 60A. The illustrated second laminator 60A takes the form of a calender roller 35, although equivalent devices to those described above are also useful. The second extruder 31A and second die 32A continuously produce a second sheet of optional polyolefin, which is continuously contacted with the nonporous laminate 52 at the second laminator 60A on the opposite side of the polyolefin sheet 51 to form a sandwich structure. The second laminator 60A mechanically compresses the nonporous laminate 52 and the second polyolefin sheet together while the second polyolefin sheet is held at a temperature above the Vicat softening temperature. The calender roller 35 may be heated or cooled.

[0057] The nonporous laminate 52 is then continuously conducted to the cold stretching station 36 where it is cold stretched in the transverse (cross) direction. Before reaching the cold stretching station 36, the nonporous laminate is brought to the cold stretching temperature mentioned above. This can be done, for example, by cooling the calender rollers 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 done in the cold stretching section 36 itself, for example, by cooling the intermeshing tooth and groove structures 37A / B.

[0058] The cold stretch station 36 includes one or more intermeshing tooth and space structures 37A / B through which the nonporous laminate 52 passes successively at a cold stretch temperature and is stretched in the transverse direction to produce a cold stretched laminate 61. As shown, the cold stretch section 36 includes two intermeshing tooth and space structures 37A / B. A fewer or greater number can be provided as needed or desired.

[0059] The cold stretched laminate 61 may then be continuously passed through a hot stretching section 62 where it is brought to the hot stretching temperature and continuously stretched in the machine direction and annealed. In the illustrated embodiment, the hot stretching section 62 includes a preheat section including rollers 40, 41, and 42. Rollers 40, 41, and / or 42 are heated to raise the temperature of the cold stretched laminate to the hot stretching temperature. In FIG. 3, the number of preheat rollers 40, 41, and 42 is shown arbitrarily as three, but more or less may be provided as needed or desired. As shown, each preheat roller 40, 41, and 42 has an optional associated guide or drive roller 40A, 41A, and 42A that may function to guide the cold stretched laminate 61 against and / or power the associated heated roller, thereby aiding in drawing the cold stretched laminate 61 into and / or through the hot stretching section 62. The cold stretched laminate 61 may be corrugated after passing through the intermeshing tooth and groove structures 37A / B. The guide or drive rollers 40A, 41A, and / or 42A further serve to press the cold stretched laminate 61 firmly against the corresponding preheat roller, thereby flattening the cold stretched laminate 61, removing wrinkles, and reducing or preventing lateral shrinkage.

[0060] In the preheat section of the hot stretching section 62, annealing may take place.

[0061] In the embodiment shown in Figure 3, hot stretching section 62 includes stretching rollers 43 and 44. Although two stretching rollers are shown in Figure 3, fewer or more may be provided. As shown, each stretching roller 43 and 44 has an optional associated guide or drive roller 43A and 44A that may function to guide the cold stretched laminate 61 relative to the associated stretching roller and / or to rotate the associated stretching roller, thereby aiding in drawing the cold stretched laminate 61 through hot stretching section 62. Stretching rollers 43 and 44 may be heated.

[0062] Each successive stretching roller operates at a greater peripheral speed than the previous stretching roller, which in turn operates at a greater peripheral speed than the immediately preceding upstream roller (preheat roller 42 as shown). Thus, the speed at which the laminate passes through hot stretching section 62 increases as it passes through each successive stretching roller, thereby longitudinally stretching the laminate to produce a reinforced microporous copolymer sheet 75.

[0063] As shown in FIG. 3, the reinforced microporous polyolefin sheet 75 is then passed continuously through an optional annealing section 47. As shown in the figure, the annealing section 47 includes annealing rollers 45 and 46 associated with optional drive or guide rollers 45A and 46A, respectively. As previously mentioned, there may be more or fewer annealing rollers. The peripheral speed of rollers 45 and 46 is preferably at least as fast as the peripheral speed of the final stretching roller 44 to maintain sufficient tension in 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 previously mentioned.

[0064] 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 includes a cooling roller 49 and any associated guide or drive rollers 49A. There may be multiple cooling rollers 49. If the annealing section 47 is not present, the peripheral speed of the roller 49 is preferably at least as fast as the peripheral speed of the last stretching roller to maintain sufficient tension in the reinforced microporous copolymer sheet 75 so that it does not shrink in the machine direction.

[0065] The cooled reinforced microporous copolymer sheet 75 exiting cooling station 48 is then continuously removed from the process, such as by winding on rollers 55 to produce roll stock.

[0066] The resulting reinforced microporous copolymer sheet has a thickness of at least 1 mm. The thickness may be at least 1.2 mm, such as at most 12.7 mm, at most 6.35 mm, at most 3 mm, at most 2 mm, or at most 1.8 mm.

[0067] The reinforced microporous copolymer sheet preferably has a modulus of at least 50, at least 80, at least 100, at least 120, or at least 200 g / m2 as measured according to ASTM E96 / E96M (ISO 12572:2001). 2 The water vapor permeability is, for example, up to 1000, up to 500, or up to 350 g / m 2 ·day may be used.

[0068] The reinforced microporous copolymer sheet preferably passes the watertight test of EN1928:2000 Method B, being leak-free under a pressure of 0.3 MPa for at least 30 minutes.

[0069] The high vapor pressure permeance and excellent water tightness are important and unexpected advantages of the present invention. Surprisingly, the presence of the nonwoven does not inhibit stretching and micropore formation, and also adheres strongly to the polypropylene copolymer, thereby preventing tearing and the formation of more macroscopic defects in the stretched material.

[0070] The reinforced microporous copolymer sheet preferably exhibits a tear strength in at least one direction of at least 200 N, more preferably at least 250 N, when measured according to EN12310-2:2000. More preferably, the tear strength is at least 200 N, more preferably at least 250 N, in each of the machine and cross directions.

[0071] The reinforced microporous copolymer sheet preferably exhibits a tensile strength at peak load of at least 1250 N / 5 cm in at least one direction, more preferably at least 1500 or at least 1750 N / 5 cm, when measured according to ASTM D5034-09 at a crosshead speed of 30 cm / min. The reinforced microporous copolymer sheet may exhibit a tensile strength at peak load 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). The elongation at maximum load, measured similarly, is preferably at least 15% in both the machine and cross directions.

[0072] Another advantage of the reinforced microporous copolymer sheet is that it is easily and securely welded to itself, despite the presence of the embedded nonwoven. Bond strength is determined by bonding two reinforced microporous polyolefin sheets together using a hot air welding machine operating at a set temperature of 250°C, and then measuring the peel strength of the resulting bond in accordance with EM12316-2:2000. The peel force of the weld is typically at least 2N / mm.

[0073] The reinforced microporous copolymer sheet is useful as a waterproofing membrane or as a component of a waterproofing membrane in applications requiring breathability, especially water vapor permeability. Roofing membranes are an application for which the reinforced microporous copolymer sheet is particularly suitable. Specific examples of roofing membranes for which the reinforced microporous copolymer sheet is useful include metal roofing membranes, temporary roofing membranes, and concrete roofing membranes, especially for lightweight concrete roofing membranes.

[0074] The reinforced microporous copolymer sheets are also suitable for use as or as components of packaging materials, personal care products such as diapers and adult incontinence products, protective clothing such as medical drapes, medical gowns, surgical garments, and air masks. EXAMPLES

[0075] The following examples are offered to illustrate the invention but are not intended to limit its scope. All parts and percentages are by weight unless otherwise specified.

[0076] The polyolefin is a phase separated copolymer available from Braskem PP Americas as PPC7054-07NA. It is composed of 67.1% propylene homopolymer and 50 / 50 by weight copolymer of ethylene and propylene (T g <-50°C). Under TEM imaging, the polyolefin exhibits a continuous phase comprising polypropylene homopolymer and a dispersed phase comprising ethylene-propylene copolymer primarily in the form of discrete domains having a longest dimension of up to 2 μm, as shown in Figure 1. The polypropylene homopolymer inclusions are contained within the ethylene-propylene copolymer domains. The manufacturer reports that the polyolefin has a melting point of 0.9 g / cm. 3 and a melt index of 7 g / 10 min (230°C / 2.16 kg).

[0077] PP-PET is a nonwoven fabric made from core-shell polypropylene-poly(ethylene terephthalate) fibers. The fabric has a weight of 157 g / m 2 areal density and 2kN / m 2 It has a thickness of 0.762 mm under a load of 0.5 mm. Its tensile strength is 550 N / 5 cm in the longitudinal direction and 434 N / 5 cm in the transverse direction. Its elongation is 75% in the longitudinal direction and 82% in the transverse direction.

[0078] Examples 1 to 4 In a single screw extruder with a 158 cm die, the polyolefin is blended with a UV stabilizer masterbatch and extruded into 558 μm (22 mil) and 762 μm (30 mil) nonporous sheets containing 0.315% UV stabilizer. In both cases, the extrudate is passed through three cooling rollers set at 119°C, 120°C, and 88°C to obtain a smooth and uniform surface. In both cases, the PP-PET nonwoven is fed from the unwinding station to the first cooling roll, where the extrudate and the PP-PET nonwoven are brought into contact. The gap between successive cooling rolls is set to mechanically compress the extrudate and the PP-PET nonwoven, forcing some of the extrudate into the interstices of the fabric. This produces an intermediate laminate with the polyolefin on one side of the nonwoven.

[0079] The PP-PET nonwoven is then replaced with the intermediate laminate and polyolefin is applied to the other side of the nonwoven in the same manner. This produces nonporous laminates 1 and 2 for subsequent stretching. Nonporous laminate 1 is produced from two layers of 558 μm polyolefin sheets and nonporous laminate 2 is produced from two layers of 762 μm polyolefin sheets. Nonporous laminate 1 is approximately 1.15 mm thick and nonporous laminate 2 is approximately 1.6 mm thick.

[0080] The cold stretched laminate 1 is produced by cold stretching the nonporous laminate 1 in the machine direction to 125% of its original length (25% stretch) by passing it through a series of 11 rollers, as shown diagrammatically in FIG. 8 of US 2021 / 0095110. The stretching temperature is 20-23°C. The laminate turns white as it passes through the stretching process, indicating the formation of pores. The final three rollers are heated to 140°C to heat and thermally anneal the stretched sheet, fixing the pore structure and dimensions.

[0081] Cold stretched laminate 2 is produced in a similar manner except that nonporous laminate 1 is stretched to 140% of its original length (40% stretch).

[0082] Cold stretched laminates 3 and 4 are produced in the same manner as cold stretched laminates 1 and 2, respectively, using non-porous laminate 2 in place of non-porous laminate 1.

[0083] Each of the cold stretched laminates 1-4 is then hot stretched 50% in the machine direction in the same equipment at a stretching temperature of 135° C. to produce Examples 1-4, respectively. Properties were determined according to the test methods previously described and are reported in Table 1.

[0084] [Table 1]

[0085] These examples demonstrate that, despite the presence of an embedded nonwoven fabric, reinforced microporous polyolefin sheets can be successfully produced by a sequential cold / hot stretching process. The samples retain excellent tensile, elongation, and tear properties, and are breathable (as indicated by water vapor transmission rate values) while retaining a barrier to liquid water. These results demonstrate that the propylene copolymer exhibits excellent adhesion to the nonwoven fabric fibers during the stretching process.

[0086] Examples 5 to 7 Nonporous Laminates 3-5 are manufactured in the same general manner as Nonporous Laminates 1 and 2, except that the polyolefin sheet is about 840 μm thick and the amount of UV stabilizer varies from 0% in Nonporous Laminate 3 to 1.5% and 2.5% in Nonporous Laminates 4 and 5. Nonporous Laminates 3, 4 and 5 are all about 1725 μm thick.

[0087] Examples 5-7 are made by sequentially cold stretching and hot stretching nonporous laminates 3-5, respectively, in the same general manner as described for Examples 1-4. The laminates are cold stretched 50% at 20-23°C and hot stretched 50% at 135°C.

[0088] The porosity and average pore size are measured by the mercury intrusion porosimetry method of ASTM D4404-10. The tensile, elongation at maximum load, and water vapor transmission rate are also measured using the aforementioned methods. The results are shown in Table 2.

[0089] [Table 2]

[0090] These thick, reinforced laminates are successfully stretched to form voids while retaining desirable mechanical properties. All are breathable and all pass watertight tests.

[0091] Examples 8 to 12 Nonporous Laminates 3, 4, and 5 are cold stretched 40% in the general manner described in the previous examples. The resulting cold stretched laminates are then hot stretched in the transverse direction at a stretch temperature of 140° C. in a Marshall & Williams Plastics continuous transverse orientation (TDO) apparatus to produce Examples 8-12. Nonporous Laminate 3 is used to produce Example 8, Nonporous Laminate 4 is used to produce Example 9, and Nonporous Laminate 5 is used to produce Examples 10-12. The amount of hot stretch in the transverse direction is shown in Table 3.

[0092] For comparison, a 1780 μm sheet of polyolefin was extruded and then cold stretched 40% as previously described and then hot stretched 25% to 50% in the transverse direction as described for Examples 8 to 12. This sample was designated Comparative Sample A.

[0093] Tensile strength, elongation at maximum load, and WVP are measured using the methods described above, and the results are shown in Table 3.

[0094] [Table 3]

[0095] As shown by the WVP results, the reinforced nonporous laminate can be stretched to produce a microporous sheet with water vapor transmission rates similar to those seen when the unreinforced sheet (Comparative A) is stretched. Tensile strength is increased for Examples 8-12 compared to Comparative A. As shown by the tensile data, biaxial stretching balances machine and cross direction properties.

[0096] Comparison sample B Example 1 was repeated, replacing the PP-PET fabric with PET mesh (9mm x 9mm) from Zhejiang Minglong Jibu Co., Ltd. The breaking elongation of the PET mesh is 18% in the longitudinal direction and 21.2% in the transverse direction. The non-porous laminate made using the PET mesh did not turn white during the MDO cold stretching process, suggesting that no pores were formed. The laminate broke during the MDO hot stretching process.

[0097] Comparative samples C and D Sample C: Polyolefin is extruded into a 500 μm sheet. The non-porous sheet is successively cold stretched 20% in the machine direction and then hot stretched 100% in the machine direction at 125 °C using the general method described in Examples 1-4. The sheet is treated with a corona discharge. The stretched sheet is bonded to a PP-PET nonwoven fabric with a polyurethane adhesive by a thermal lamination process to form a sandwich structure with a thickness of 1.5 mm. The water vapor transmission rate is only 113 g / m 2 ·day and the microporous sheet is poorly bonded to itself, exhibiting a peel strength of less than 2 N / mm.

[0098] Sample D: Repeat sample C, replacing the polyurethane adhesive with a polyolefin hot melt adhesive. This sample fails the heat aging test (116°C, 672 hours) due to the low melting temperature of the polyolefin adhesive.

[0099] Comparative samples E and F Sample E: Polyolefin is extruded into 635 μm and 752 μm sheets. The non-porous sheets are sequentially cold stretched 20% in the machine direction and then hot stretched 100% in the machine direction at 125° C. using the general method described in Examples 1-4. The stretched sheets are ultrasonically welded to a PP-PET nonwoven with a polyurethane adhesive to form a 1.5 mm thick microporous sandwich structure. A large amount of ultrasonic energy is required to create the weld, resulting in large recessed areas in the welded areas. The mechanical strength of these recessed areas is very low.

[0100] Sample F: Sample E is repeated, replacing the PP-PET nonwoven with the PET mesh described in Comparative Sample B. The resulting microporous structure exhibits high water vapor permeability, but fails to pass the watertightness test. The peel strength is also very poor, less than 0.5 N / mm.

Claims

1. a) A step of producing a non-porous laminate having a thickness of at least 1 mm, which includes the non-woven fabric at least partially embedded in the polyolefin, by extrusion lamination of a non-porous polyolefin sheet to at least one side of a nonwoven fabric, and then b) With respect to the non-porous laminate, 1) At least one cold stretching step at a temperature in the range of -20°C to 50°C, 2) At least one hot stretching step at a temperature between 50°C and 150°C. A step of generating micropores in the polyolefin by performing a sequential stretching process including the following: A method for forming a reinforced microporous polyolefin sheet, comprising: The aforementioned nonwoven fabric is 100 to 400 g / m² 2 Basis weight, 2 kN / m 2 It has a thickness of 0.25 to 0.95 mm under load, and a breaking elongation of 30 to 200% in both the longitudinal and transverse directions. The method wherein 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 lower, and the dispersed phase further comprises polypropylene homopolymer encapsulants.

2. a) A step of producing a non-porous laminate having a thickness of at least 1 mm, which includes the non-woven fabric at least partially embedded in the polyolefin, by extrusion lamination of a non-porous polyolefin sheet to at least one side of a nonwoven fabric, and then b) With respect to the non-porous laminate, 1) At least one cold stretching step at a temperature in the range of -20°C to 50°C, 2) At least one hot stretching step at a temperature between 50°C and 150°C. A step of generating micropores in the polyolefin by performing a sequential stretching process including the following: A method for forming a reinforced microporous polyolefin sheet, comprising: The aforementioned nonwoven fabric is 100 to 400 g / m² 2 Basis weight, 2 kN / m 2 It has a thickness of 0.25 to 0.95 mm under load, and a breaking elongation of 20 to 200% in both the longitudinal and transverse directions. The aforementioned polyolefin (i) 50 to 95 weight percent of one or more polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent of polypropylene homopolymer chain segments based on the molding content of polypropylene polymerization units in the polypropylene homopolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin. (ii) 5 to 50 weight percent of ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent of ethylene-containing chain segments based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin. Includes, A method wherein at least a portion of the ethylene-containing copolymer chain segment contains at least 45 weight percent of ethylene polymer units based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mole percent of ethylene polymer units based on the molar content of ethylene polymer units in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.

3. The method according to claim 1 or 2, wherein step a) includes a step of compressing the non-porous sheet of polyolefin and the nonwoven fabric together to impregnate the polyolefin into the gaps in the nonwoven fabric.

4. The method according to claim 1 or 2, wherein step a) includes step a-1) of extruding laminate a first non-porous layer of the polyolefin onto the first surface of the nonwoven fabric, and step a-2) of extruding laminate a second non-porous layer of the polyolefin onto the second surface of the nonwoven fabric, and steps a-1) and a-2) are performed simultaneously or sequentially.

5. The method according to claim 1 or 2, wherein the non-porous laminate is cold-stretched laterally.

6. The method according to claim 1 or 2, wherein the non-porous laminate is cold-stretched in the longitudinal direction.

7. The method according to claim 1 or 2, wherein the cold-stretched laminate is hot-stretched laterally.

8. The method according to claim 1 or 2, wherein the cold-stretched laminate is hot-stretched in the longitudinal direction.

9. Step a) is, a-1) A step of continuously extruding the polyolefin into a non-porous sheet, and a-2) Before manufacturing the non-porous laminate by cooling the non-porous sheet to a temperature below its Vicat softening temperature, the non-porous sheet is brought into continuous contact with the nonwoven fabric. Includes, Step b-1) is, b-1a) A step of continuously cooling the non-porous laminate to the cold stretching temperature, and thereafter b-1b) A step of continuously cold-stretching the non-porous laminate in the transverse direction, Includes, Step b-2) is, b-2a) A step of continuously heating the cold-stretched laminate to the hot-stretching temperature, and thereafter b-2b) A step of continuously hot-stretching the cold-stretched laminate to produce a reinforced microporous polymer sheet, The method according to claim 1 or 2, including the method described in claim 1 or 2.

10. Before step b-2), The process of continuously annealing the cold-stretched laminate. It further includes, After step b), The process further includes the steps of continuously annealing the reinforced microporous polymer sheet and / or continuously extruding a second sheet of polyolefin to continuously bring the second sheet into contact with the opposite side of the nonwoven fabric. The method according to claim 9.

11. The method according to claim 9, wherein step b-1b) is performed by passing the non-porous laminate through a grooved stretcher that includes a toothed structure with interlocking teeth.

12. The method according to claim 9, wherein step b-1b) is performed by attaching the non-porous laminate to a tenter frame including clips for gripping both sides of the non-porous laminate, the clips being attached to a pair of rails that extend in the longitudinal direction.

13. A reinforced microporous polymer sheet having a thickness of at least 1 mm, comprising a nonwoven fabric embedded in a microporous polyolefin, The aforementioned nonwoven fabric is 100 to 400 g / m² 2 Basis weight, 2 kN / m 2 It has a thickness of 0.25 to 0.95 mm under the load, and a breaking elongation of 30 to 200% in both the longitudinal and transverse directions. 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 lower, wherein the dispersed phase further comprises polypropylene homopolymer encapsulants. Microporous polymer sheet.

14. A reinforced microporous polymer sheet having a thickness of at least 1 mm, comprising a nonwoven fabric embedded in a microporous polyolefin, The aforementioned nonwoven fabric is 100 to 400 g / m² 2 Basis weight, 2 kN / m 2 It has a thickness of 0.25 to 0.95 mm under the load, and a breaking elongation of 30 to 200% in both the longitudinal and transverse directions. The aforementioned polyolefin (i) 50 to 95 weight percent of one or more polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent of polypropylene homopolymer chain segments based on the molding content of polypropylene polymerization units in the polypropylene homopolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin. (ii) 5 to 50 weight percent of ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent of ethylene-containing chain segments based on the molar content of polymerized monomer units in the ethylene-containing copolymer chain segments, as a percentage of the total molar content of polymerized monomer units in the polyolefin. Includes, A microporous polymer sheet in which at least a portion of the ethylene-containing copolymer chain segment contains at least 45 weight percent of ethylene polymer units based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mole percent of ethylene polymer units based on the molar content of ethylene polymer units in the ethylene-containing copolymer chain segment, as a percentage of the total molar content of polymerized monomer units in the ethylene-containing copolymer chain segment.

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