Polypropylene copolymer biaxially stretched microporous film and composite sheet containing same

Abstract

a) 90 to 65 wt. % polypropylene copolymer, i) a polypropylene homopolymer chain segment; ii) an ethylene-containing copolymer chain segment; and a polypropylene copolymer comprising: b) 10-35 wt. % of a propylene-based elastomer having 5-25 wt. % of units derived from ethylene and having a melting point of less than 110°C; A biaxially stretched microporous film comprising: 50g / (24h m 2 ) or more, and liquid water cannot permeate the film for 30 minutes when subjected to a hydrohead test at 0.3 MPa; a biaxially stretched microporous film; a composite sheet containing the same; and a manufacturing method thereof.

Description

[Technical Field]

[0001] The present invention relates to biaxially oriented microporous films and composite sheets comprising biaxially oriented microporous films, and their use in a variety of applications where a moisture vapor permeable sheet structure with high liquid water retention is desired. Some preferred end uses are in various architectural applications in the construction industry, such as in breathable, water-resistant membranes for use in roofing applications. [Background technology]

[0002] Huang et al., U.S. Patent Application Publication No. 2021 / 0095110, discloses a microporous film by sequentially cold-stretching and hot-stretching an unannealed polypropylene copolymer film, where the polypropylene copolymer comprises one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments.

[0003] Huang et al., U.S. Patent Application Publication No. 2022 / 0298340, also discloses microporous films produced by sequentially cold-stretching and hot-stretching unannealed polymer films. Examples 1-17 of this reference utilize films in which the polymer comprises (a) a polypropylene copolymer containing one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments. As shown in Example 15 of this reference, film samples produced by both machine direction (MDO) cold-stretching and hot-stretching passed a very stringent hydrohead test in 30 meters of water for at least 30 minutes. However, biaxially stretched samples produced by only direct MDO cold-stretching followed by transverse direction (TDO) hot-stretching without an intervening MDO hot-stretching step failed this stringent hydrohead test. The cause of this test failure was the undesirably stretched and open pores created by the biaxial stretching process. Examples 18-20 of this document further disclose films in which the polymer comprises (a) a polypropylene copolymer containing one or more polypropylene homopolymer chain segments and one or more ethylene-containing copolymer chain segments, and (b) an ethylene-propylene elastomer. All of these films were produced by a process including cold stretching in the machine direction (MDO) and hot stretching. Example 20 discloses that the film of Example 18, which was cold stretched in the machine direction (MDO) and then hot stretched, was further hot stretched in the transverse direction. It is also disclosed that the general properties (including increased porosity) of the films produced by this biaxial stretching process and the degree of difference in properties between films produced by machine direction (MDO) only and films produced by biaxial stretching were similar to those shown in Examples 13-15 and Example 17. This includes a biaxially stretched sample that failed a rigorous hydrohead test when produced solely by the process of Example 15, in which a machine direction MDO cold stretching step was followed by a transverse direction (TDO) hot stretching step without an intervening MDO hot stretching step.

[0004] Water leakage is a significant challenge for the use of microporous films in roofing membranes. While some conventional microporous films are said to provide water vapor permeability while maintaining an effective barrier to liquid water, excessive machine direction stretching can result in the resulting film having an undesirable balance of machine and cross direction properties, sometimes improving certain machine direction properties at the expense of deteriorating cross direction properties. Additionally, because the act of stretching the film can damage it, it is desirable to manufacture such films using as simple a process as possible.

[0005] There is a need, of course, for microporous films that can be produced in a process with a minimum number of stretching steps and have a desirable balance of properties to avoid potential damage to the microporous membrane or to avoid potential damage due to undesirable pore connections in the membrane that would adversely affect liquid water retention. Specifically, there is a need for biaxially oriented microporous films and roofing membranes and other sheet structures that can pass this minimum liquid water retention test, preferably maintain liquid water retention at a water pressure of 0.3 MPa for at least 30 minutes, and ideally for 2 hours or more, and that can be produced in a two-step stretching process. Summary of the Invention [Means for solving the problem]

[0006] The present invention provides a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized 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 ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing copolymer 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, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of polymerized ethylene 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; Polypropylene copolymer and; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point of less than 110°C; A biaxially stretched microporous film comprising: the weight percentages of a) and b) are based on the combined weight of a) and b); 50g / (24h m 2 ) or more, and when subjected to a water head test at 0.3 MPa, liquid water does not permeate the film for 30 minutes. This relates to biaxially oriented microporous films.

[0007] The present invention provides a) 89 to 65 wt. % polypropylene copolymer, i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polypropylene copolymer, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized units in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; ii) 5 to 50 weight percent ethylene-containing copolymer chain segments based on the weight of the polypropylene copolymer, or 21 to 57 mole percent ethylene-containing copolymer 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 polypropylene copolymer; Including, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of polymerized ethylene 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; Polypropylene copolymer and; b) 10 to 34 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point of less than 110°C; c) 1 to 15 weight percent of a sealing additive; A biaxially stretched microporous film comprising: the weight percentages of a), b), and (c) are based on the combined weight of a), b), and c); It also relates to biaxially oriented microporous films.

[0008] The present invention provides a method for forming a biaxially stretched microporous film, comprising: A) a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized 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 ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing copolymer 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; at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of polymerized ethylene 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; Polypropylene copolymer and; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point of less than 110°C; 1. A film-forming composition comprising: forming a nonporous film from the composition, wherein the weight percentages of a) and b) are based on the combined weight of a) and b); B) For non-porous films, (i) cold-stretching in a first direction at a temperature in the range of −20° C. to 50° C.; and (ii) hot-stretching in a second direction at a temperature in the range of 50°C to 140°C; performing a sequential cold and hot biaxial stretching process consisting of 50g / (24h m 2 ) or more, and liquid water does not permeate the film for 30 minutes when subjected to a hydrohead test at 0.3 MPa; The present invention also relates to a method comprising:

[0009] The present invention further provides a method for forming a composite sheet comprising a biaxially oriented microporous film, comprising the steps of: A) a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized 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 ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing copolymer 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; at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of polymerized ethylene 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; Polypropylene copolymer and; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point of less than 110°C; A composition comprising: forming a polymeric nonporous film or layer from the composition, wherein the weight percentages of a) and b) are based on the combined weight of a) and b); B) combining a nonporous film or layer of polymer with a nonwoven fabric to form a composite sheet; and C) For composite sheets, (i) cold stretching at least once in a first direction at a temperature in the range of -20°C to 50°C; and (ii) hot-stretching at least once in a second direction at a temperature in the range of 50°C to 140°C; performing sequential cold and hot biaxial stretching steps including producing a composite sheet comprising a biaxially oriented microporous polymer film; The present invention also relates to a method comprising: [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a TEM micrograph of a nonporous polymer film sample comprising 80 wt. % polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and ethylene-containing copolymer, and 20 wt. % propylene-based elastomer. [Figure 2] 1 is a TEM micrograph of a "control" nonporous polymer film sample of a phase-separated polypropylene copolymer containing domains of polypropylene homopolymer (continuous phase) and ethylene-containing copolymer in a 70 / 30 weight ratio, but no propylene-based elastomer. [Figure 3] 1 is a TEM micrograph of a nonporous polymer film sample comprising 70% by weight of a polypropylene copolymer comprising a 70 / 30 weight ratio of a polypropylene homopolymer and an ethylene-containing copolymer, and 30% by weight of a propylene-based elastomer. [Figure 4] 1 is a TEM micrograph of a nonporous polymer film sample comprising 60% by weight of a polypropylene copolymer comprising a 70 / 30 weight ratio of a polypropylene homopolymer and an ethylene-containing copolymer, and 40% by weight of a propylene-based elastomer. [Figure 5] 1 is a TEM micrograph of a nonporous polymer film sample containing 75 wt. % polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and ethylene-containing copolymer, 10 wt. % propylene-based elastomer, 5 wt. % each of two different polyolefin elastomers, and a hydrocarbon-based tackifier. [Figure 6] TEM micrograph of a nonporous polymer film sample containing 65 wt. % polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and ethylene-containing copolymer, 20 wt. % propylene-based elastomer, 5 wt. % each of two different polyolefin elastomers, and a hydrocarbon-based tackifier. [Figure 7]FIG. 1 illustrates one embodiment of a cross-sectional view of a nonporous composite sheet formed by sandwiching a nonwoven fabric between two nonporous films, prior to biaxial stretching. [Figure 8] This is a cross-sectional photograph of a biaxially oriented composite sheet made from 73.5 wt% polypropylene copolymer containing a 70 / 30 weight ratio of polypropylene homopolymer and ethylene-containing copolymer, 25 wt% propylene-based elastomer, and 1.5 wt% UV stabilizer, in which a nonwoven fabric is symmetrically laminated within the composite sheet. [Figure 9] One possible continuous process for producing biaxially stretched microporous film or composite sheets containing microporous film in an apparatus including an extrusion laminator 50, followed by a longitudinal cold stretcher 51, followed by a transverse hot stretcher 52, followed by a cooling unit 53, and finally a winding unit 54. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a biaxially stretched polymeric microporous film, or a composite sheet comprising such a film, suitable for use in applications requiring a membrane that is resistant to liquid water but permeable to water vapor, such as roofing and other architectural applications. The polymeric microporous film is produced from a formulation that has a microphase-separated / inclusion morphology and can be further subjected to sequential cold stretching in one direction followed by hot stretching in a second, different direction to provide a microporous film in which pore formation can be induced. The polymeric microporous film, or a composite sheet comprising such a film, has mechanical properties suitable for the intended application.

[0012] The polymeric microporous film, or a composite sheet containing such a film, has a thermal conductivity of at least 50 g / (24 hr·m 2) or greater, while simultaneously preventing liquid water from permeating the microporous film (or composite sheet) for 30 minutes when subjected to a 0.3 MPa hydrohead test, and preferably preventing liquid water from permeating the microporous film (or composite sheet) for 2 hours when subjected to a 0.3 MPa hydrohead test. As used herein, the phrase "sheet material" is intended to include any type of film or composite sheet comprising a film. Additionally, the terms "composite sheet comprising a biaxially oriented microporous film" and "biaxially oriented composite sheet" are used interchangeably herein.

[0013] The formulation compositions and processes for stretching microporous films (or composite sheets) described herein are believed to create a unique pore structure in the biaxially oriented sheet material, providing, for example, uniform, smaller pores (100 nm to 1 micron in diameter) that are generally non-interconnected in nature, resulting in a breathable membrane that exhibits excellent liquid water and air barrier properties while still achieving desirable water vapor permeability. Additionally, these breathable polymeric sheet materials are based on polypropylene, which, due to its melting point of approximately 165°C, is inherently hydrophobic and heat stable.

[0014] The polymeric microporous film comprises a blend of a polypropylene copolymer and a propylene-based elastomer, and is preferably produced by casting a nonporous film of the desired composition and subsequently biaxially stretching the film to form a liquid-resistant, breathable, biaxially oriented microporous film structure.

[0015] Incorporating propylene-based elastomers with a high amount of propylene repeat units into the formulation changes the microphase morphology of the film, and the resulting pores formed in the film when stretched in two directions impart a water vapor transmission rate (through the film) that is sufficient for many applications, and even at least 100 grams / (24 hr m) for some construction applications. 2), which is much higher than certain industry standards. In fact, the water vapor transmission rate (through the film) is 50 grams / (24 hours m 2 ) or slightly below that, approximately 600 g / (24 h m 2 ) or even higher range (herein 587.6 g / (24 hr m 2 ) are specifically exemplified), and also provide excellent watertightness as evidenced by the lack of liquid water penetration through the film when subjected to a 0.3 MPa hydrohead test for a minimum of 30 minutes. This leak-free performance can last for as long as two hours or more of water exposure. The incorporation of a high propylene content polypropylene-based elastomer also significantly improved the flexibility of the film, as well as shortening the welding time for the seams while increasing the strength of the welded seams.

[0016] In some embodiments, the microporous film comprises 90-65 wt % polypropylene copolymer, wherein the polypropylene copolymer is i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized 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 ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing copolymer 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, At least a portion of the ethylene-containing copolymer chain segments contain polymerized ethylene units in an amount of at least 45% by weight based on the weight of the ethylene-containing copolymer chain segment, or at least 55% by mole based on the molar content of ethylene polymerized 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. One suitable polypropylene copolymer is reactor grade PP copolymer available from Braskem under product code PP C7054-07NA. It contains 32.9% by weight ethylene-propylene copolymer, and the ethylene content in the ethylene-propylene copolymer is 49.7% by weight. This provides a 0.9 g / cm 3 and a melt mass flow rate of 7 g / 10 min at 230°C and 2.16 kg. The number average molecular weight (Mn) and weight average molecular weight (Mw) of PP C7054-07NA are 58,000 and 295,000, respectively, which means that the copolymer has an Mw / Mn of about 5.1.

[0017] In some embodiments, the microporous film also includes 10 to 35 weight percent of a propylene-based elastomer, the propylene-based elastomer having 5 to 25 weight percent ethylene-derived units and a melting point below 110°C. The weight percent of the polypropylene copolymer and the weight percent of the propylene-based elastomer are based on the combined weight of the polypropylene copolymer and the propylene-based elastomer. One suitable propylene-based elastomer is Vistamaxx™ 6102 propylene-based elastomer manufactured by ExxonMobil. It is composed primarily of isotactic propylene repeat units (ethylene content 16 wt%) with randomly distributed ethylene. It has a melt mass-flow rate of 1.4 g / 10 min at 190°C and 2.16 kg and a melt flow rate of 0.862 g / cm. 3It is believed that for adequate biaxial orientation performance, the propylene-based elastomer should have an ethylene content of about 40% by weight or less, preferably about 25% by weight or less, and most preferably about 20% by weight or less, of the majority of the propylene repeat units.

[0018] In some embodiments, the microporous film (and / or composite sheet) further comprises up to 15% by weight of a sealing additive that promotes seaming between sheet materials. The sealing additive can be a single compound or a mixture of different compounds. The term "up to" in the phrase "up to 15% by weight" means that at least some sealing additive is present in the composition of the microporous film formulation, and therefore in the sheet material, preferably in an amount effective to enhance seam sealing of the microporous film. In some cases, this is believed to be at least 1% by weight, preferably at least 3% by weight, of the microporous film formulation. The weight percent of the sealing additive is based on the combined weight of the sealing additive, the polypropylene copolymer, and the propylene-based elastomer.

[0019] In some preferred embodiments, the sealing additive is a mixture of compounds such as one or more polyolefin elastomers, one or more polyolefin plastomers, one or more hydrocarbon-based tackifiers, and any mixture thereof. One preferred mixture includes two different polyolefin elastomers with different densities and a hydrocarbon-based tackifier, each present in equal parts by weight.

[0020] Polyolefin-based elastomers and plastomers are typically polymers, rubbers, or rubber-like compounds. In principle, the key difference between elastomers and plastomers is that elastomers exhibit elasticity, while plastomers exhibit both plasticity and elasticity. Elastomers also tend to be less crystalline than plastomers. However, these are general rules of thumb, not firm ones. A particular material used as a plastomer in one application may be used as an elastomer in another. Polyolefin elastomers and plastomers can be selected from suitable metallocene-catalyzed α-olefin copolymers, such as those described in Progress in Polymer Science, v. 33, pp. 797-819 (2008). Preferred polyolefin elastomers and plastomers are based on α-olefins, including 1-octene. A non-limiting example of a preferred polyolefin elastomer is ENGAGE™ 8402 polyolefin elastomer available from Dow, which has a melt mass flow rate (MFR) of 30 g / 10 min at 190° C. and 2.16 kg at 0.902 g / cm 3 ENGAGE™ 8402 elastomer has a glass transition temperature of -36°C and a melting point of 96°C. Plastomers have rubber-like elastic properties, but can be processed similarly to plastics and are generally tougher than elastomers. A non-limiting example of a preferred elastomer is AFFINITY™ GA 1900 elastomer, available from Dow, which has a density of 0.87 g / cm 3It is a polyolefin elastomer with a density of 100°C. It has a glass transition temperature of -57.8°C and a melting point of 67.8°C. Tackifiers are generally low molecular weight compounds commonly used to increase the tack of adhesives. One suitable tackifier is ESCOREZ™ 5400, available from ExxonMobil. It is an alicyclic hydrocarbon resin with a number average molecular weight (Mn) of 400 g / mol. It is designed to impart tack to a variety of adhesive polymers. It has a softening point of 103.4°C and a glass transition temperature of 52°C.

[0021] In some particular embodiments, the microporous film comprises 89-65 wt. % of a polypropylene copolymer as described herein above in combination with 10-34 wt. % of a propylene-based elastomer as described herein above and 1-15 wt. % of a sealing additive as described herein above.

[0022] In other words, in some embodiments, the microporous film comprises 89 to 65 weight percent polypropylene copolymer, wherein the polypropylene copolymer is i) 50 to 95 weight percent polypropylene homopolymer chain segments based on the weight of the polyolefin, or 43 to 79 mole percent polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized 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 ethylene-containing copolymer chain segments based on the weight of the polyolefin, or 21 to 57 mole percent ethylene-containing copolymer 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; Contains At least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of polymerized ethylene 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.

[0023] In this embodiment, the microporous film comprises 10-34 wt% of a propylene-based elastomer having 5-25 wt% ethylene-derived units and a melting point below 110°C, and 1-15 wt% of a sealing additive that promotes seaming between sheets. The wt% of each of the polypropylene copolymer, propylene-based elastomer, and sealing additive is based on the total weight of the polypropylene copolymer, propylene-based elastomer, and sealing additive. As described herein, the sealing additive is preferably a mixture of compounds, and one preferred mixture is equal parts by weight of a polyolefin elastomer, a polyolefin plastomer, and a hydrocarbon-based tackifier; or two different polyolefin elastomers and hydrocarbon-based tackifiers.

[0024] The microporous film, and preferably the composite sheet comprising the microporous film, has a surface roughness of 50 g / (24 hr m 2 ) or greater. In some embodiments, the water vapor transmission rate is 90 grams / (24 hours m 2 ) or greater is desirable. In some other embodiments, a water vapor transmission rate of 190 grams / (24 hr m 2 ) or higher water vapor permeability is desirable.

[0025] Additionally, the microporous film is impermeable to liquid water for 30 minutes when subjected to a 0.3 MPa hydrohead test. In some embodiments, the microporous film is impermeable to liquid water for 2 hours when subjected to a 0.3 MPa hydrohead test.

[0026] In some embodiments, the microporous film has a density of about 100 to 400 g / m2 In some other embodiments, the microporous film has a basis weight of about 200 to 300 g / m 2 The sheet has a basis weight of .

[0027] In some embodiments, nonporous films produced from the compositions described herein, as well as subsequent biaxially oriented microporous and nonporous films, comprise a phase-separated polymer comprising a continuous phase comprising a polypropylene homopolymer and a propylene-based elastomer, and a dispersed phase comprising domains of an ethylene-propylene copolymer. 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 U.S. Patent Application Publication No. 2021 / 0095110, or an equivalent method. The dispersed phase domains further comprise inclusions of at least the polypropylene homopolymer from the continuous phase. Such inclusions are also observable by the TEM method described above.

[0028] FIG. 1 is a TEM micrograph of a nonporous polymer film sample 10 comprising 80% by weight of a polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and an ethylene-containing copolymer, and 20% by weight of a propylene-based elastomer. Stated differently, the composition comprises approximately 67.1% by weight of polypropylene homopolymer (light-colored continuous phase 1), approximately 32.9% by weight of an ethylene-propylene copolymer (forming part of the darker dispersed phase domains 2), and 20% by weight of the propylene-based elastomer, with the propylene-based elastomer also forming part of the continuous phase 1. As shown, the domains 2 comprising the ethylene-propylene copolymer have a maximum dimension primarily between 0.5 and 2 micrometers (μm). The domains 2 further comprise inclusions 4 of at least polypropylene homopolymer present in the continuous phase 1. The inclusions 4 can comprise, for example, 10 to 65% of the total mass of the domains 2. A small portion of the mass of the dispersed phase (such as up to 25%, up to 10%, or up to 5%) may be ethylene-propylene copolymer in the form of smaller fragmented domains 5 having a largest dimension of less than 0.5 micrometers (μm). These smaller domains 5 may be free of inclusions 4. The relative mass of the dispersed phase can be estimated using nuclear magnetic resonance (NMR) spectroscopy.

[0029] The effect of adding a propylene-based elastomer on copolymer morphology is shown in Figure 2, which is a TEM micrograph of a "control" nonporous polymer film sample of a phase-separated polypropylene copolymer containing a 70 / 30 weight ratio of polypropylene homopolymer (continuous phase 11) and domains of an ethylene-containing copolymer 12, but no propylene-based elastomer. The ethylene-containing copolymer domains 12 further contain inclusions of polypropylene homopolymer 14. Comparing Figure 2 with Figure 1 suggests that the addition of a propylene-based elastomer reduces the size of the dispersed phase domains, as shown in Figure 1.

[0030] Thus, in the presence of the propylene-based elastomer, the domain size was reduced relative to the control sample. Preferably, at least 95% of the mass of the dispersed phase is in the form of domains having a longest dimension between 0.1 and 2 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 1.0 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 1.0 μm.

[0031] Figure 3 is a TEM micrograph of a nonporous polymer film sample containing 70 wt% polypropylene copolymer, comprising a 70 / 30 weight ratio of polypropylene homopolymer and an ethylene-containing copolymer, and 30 wt% propylene-based elastomer. Figure 4 is a TEM micrograph of a nonporous polymer film sample containing 60 wt% polypropylene copolymer, comprising a 70 / 30 weight ratio of polypropylene homopolymer and an ethylene-containing copolymer, and 40 wt% propylene-based elastomer. As shown, the dispersed phase domains become smaller with increasing amounts of propylene-based elastomer, and the desired morphology is no longer predominant at 40 wt% propylene-based elastomer.

[0032] Figure 5 is a TEM micrograph of a nonporous polymer film sample comprising 75 wt% polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and an ethylene-containing copolymer, 10 wt% propylene-based elastomer, 5 wt% each of two different polyolefin elastomers (having different densities), and 5 wt% hydrocarbon-based tackifier. Figure 6 is a TEM micrograph of a nonporous polymer film sample comprising 65 wt% polypropylene copolymer comprising a 70 / 30 weight ratio of polypropylene homopolymer and an ethylene-containing copolymer, 20 wt% propylene-based elastomer, 5 wt% each of two different polyolefin elastomers (having different densities), and 5 wt% hydrocarbon-based tackifier.

[0033] Additional polyolefin elastomer and tackifier (15 wt. % total) are believed to be present in the continuous phase, and as shown in the figure, as the amount of ethylene-containing copolymer in the overall formulation decreases, the dispersed phase domains become smaller, again indicating that a minimum amount of polypropylene copolymer of about 65 wt. % or more is required to achieve the desired morphology in the film.

[0034] The polypropylene copolymer comprises 50 to 95 wt% polypropylene homopolymer chain segments, based on the weight of the polypropylene copolymer. In some embodiments, the polypropylene copolymer can comprise at least 55 wt%, at least 60 wt%, or at least 70 wt% polypropylene homopolymer chain segments, and up to 90 wt%, up to 88 wt%, up to 85 wt%, or up to 82 wt% polypropylene homopolymer chain segments. The polypropylene copolymer also comprises 5 to 50 wt% ethylene-containing copolymer chain segments, based on the weight of the polypropylene copolymer. In some embodiments, the polypropylene copolymer can comprise at least 10 wt%, at least 12 wt%, at least 15 wt%, or at least 18 wt% ethylene-containing copolymer segments, and up to 45 wt%, up to 40 wt%, or up to 30 wt% ethylene-containing copolymer segments.

[0035] At least some 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. In some embodiments, at least some of the ethylene-containing copolymer chain segments can comprise 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.

[0036] 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, pseudo-random, and / or graft copolymer of ethylene and at least one other copolymerizable monomer. In certain embodiments, the ethylene-containing copolymer chain segment is or includes a block copolymer of ethylene and propylene. 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. Other suitable polyolefins include, for example, those described in paragraphs

[0063] to

[0078] of U.S. Patent Application Publication No. 2021 / 009511.

[0037] The propylene-based elastomer has at least about 60% by weight of units derived from propylene, preferably at least about 75% by weight, or at least about 80% by weight of units derived from propylene. The propylene-based elastomer is preferably a random propylene homopolymer or copolymer having crystalline regions interrupted by amorphous regions. The amorphous regions may result from regions of amorphous polypropylene segments and / or the inclusion of comonomer units, such as ethylene. In the presence of comonomers, the crystallinity and melting point of the propylene-based elastomer are reduced compared to highly isotactic polypropylene. Examples of commercially available propylene-based elastomers include ExxonMobil's Vistamaxx™ high-performance polymers and Dow Inc.'s VESIFY™ elastomers.

[0038] It has been discovered that the addition of a propylene-based elastomer with a high propylene content promotes adhesion between biaxially oriented microporous films and between composite sheets containing biaxially oriented microporous films, resulting in seam formation. Although polypropylene copolymers are used in microporous films, microporous films and composite sheets containing such films can stiffen at low temperatures, making roofing membrane installation difficult during the winter. It is desirable to seam-bond the edges of roofing membranes without adhesives by heating the edges of the sheets to a temperature above the melting point of the film polymer, thereby bonding the edges together. This sheet-bonding technique, known as thermal (hot air) welding, provides strong seams and reduces the overall time and cost involved in installing roofing membranes. It is believed that the addition of a sealing additive to the microporous film and composite sheet compositions containing such films can further improve heat-sealing (seaming) performance.

[0039] Compositions for producing biaxially oriented microporous films and composite sheets containing biaxially oriented microporous films can contain other ingredients, such as extrusion processing aids such as lubricants, antioxidants, titanium dioxide, UV stabilizers, light stabilizers, heat stabilizers, pigments or other colorants, antistatic agents, flame retardants, antiblocking agents, and biocides, to the extent that they do not adversely affect the desired performance of the sheet material. UV stabilizers are preferred additives. Examples of stabilizers include various hydroxyphenyl benzotriols, such as those sold by BASF under the generic brand name Tinuvin®, or hindered amine stabilizers, such as those sold by BASF under the Tinuvin® or Chimassorb® brands. One or more UV stabilizers may be used in combination with one or more antioxidants.

[0040] The polyolefin copolymer 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 copolymer. 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 can include both inorganic and organic types.

[0041] In some embodiments, the biaxially oriented composite sheet comprising the microporous film and the nonwoven fabric has a weight of about 500 to 2000 g / m 2 In some embodiments, the biaxially oriented composite sheet comprising the microporous film and the nonwoven fabric has a basis weight of about 300 to 1500 g / 2 The sheet has a basis weight of .

[0042] In some embodiments, the nonwoven fabric in the composite sheet has a density of about 100 to 400 g / cm2 measured according to EN 9864:2016. 2 Preferred basis weights are 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 nonwoven fabric is preferably 2 kN / m 2 The elongation at break of the nonwoven fabric is preferably 0.25 to 0.95 mm under a load of 1000 kJ / cm, for example, at least 0.3 mm or at least 0.4 mm and at most 0.9 mm or at most 0.8 mm, as measured in accordance with EN ISO 9863-1:2005. The nonwoven fabric may have an elongation at break of 30 to 200% in each of the machine and cross directions, as measured in accordance with EN ISO 10319:2015. The nonwoven fabric is preferably water permeable, and has a water permeability of 5 x 10 to 1000 kJ / cm, as measured in accordance with EN ISO 11058:2019. -3 ~200×10 -3 , especially 10x10 -3 ~100×10 -3 , or 10 x 10 -3 ~50×10 -3The nonwoven fabric may have a permeability (VH50) of 1000 m / s. In some embodiments, the nonwoven fabric comprises or consists of entangled, spunbonded, and / or meltbonded fibers or filaments to form the nonwoven fabric. The nonwoven fabric may be made, for example, by a spunbond process, an airlaid process, a spunlace process, or a meltbonded process, or may be a mesh.

[0043] The nonwoven fabric is preferably constructed from a material that is thermally stable under the conditions of the extrusion lamination process, i.e., that does not melt, unacceptably heat soften, or degrade during the extrusion lamination process to such an extent that the integrity of the nonwoven fabric is lost. 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, polybenzimidazole, aramid, polyvinyl alcohol, polyphenylene sulfide, polyacrylonitrile, and acrylonitrile copolymers. The nonwoven fabric may also contain, for example, carbon fibers, wool fibers, metal fibers, mineral wool fibers, silk fibers, jute fibers, or other natural fibers, provided that the nonwoven fabric has the breaking elongation and preferably also the permeability as described above.

[0044] Preferred nonwoven fabrics are polypropylene nonwoven fabrics, polyethylene terephthalate nonwoven fabrics, or polypropylene-polyethylene terephthalate nonwoven fabrics. Polypropylene-polyethylene terephthalate nonwoven fabrics may be composed 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, for example, sheath-core fibers with a polypropylene sheath, or side-by-side bicomponent fibers.

[0045] When biaxially oriented microporous films or biaxially oriented composite sheets containing microporous films are produced by an extrusion lamination process, the polypropylene copolymer blend is melted and then passed through a die to form a nonporous polymer film or layer. This process can be carried out using a single- or twin-screw extruder equipped with a suitable die, such as a slit die or dogbone die, an accumulating extruder, or other suitable equipment. The polyolefin copolymer blend is heated in the extrusion device to a temperature above the crystalline melting temperature of the continuous phase polypropylene homopolymer and passed through the die to form a polymer film or layer. Preferred temperatures are at least 180°C or at least 200°C and up to 240°C or up to 260°C.

[0046] The extruded polymeric non-porous film or layer preferably has a thickness of at least 250 μm, at least 400 μm, at least 500 μm, or at least 1000 μm, and at most 10 mm, at most 5 mm, at most 2,000 μm, or at most 1,500 μm.

[0047] The extruded polymer film or layer 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 at this stage. For purposes of this invention, a sheet is defined as having, after cooling, a foaming strength of 2 g / m² at 37.8°C and 100% relative humidity as measured according to ASTM D1249. 2A sheet is considered "non-porous" if it exhibits a water vapor transmission rate (WVTR) of 1.5 days or less.

[0048] Preferably, a nonporous film or layer of molten polymer contacts the surface of the nonwoven fabric to produce a nonporous polymer layer thereon. This step preferably occurs before the sheet is cooled below its Vicat softening temperature. The contacting step preferably occurs within 30 seconds, more preferably within 10 seconds, 5 seconds, or 2 seconds, of the sheet exiting the extruder die.

[0049] The contacting step is preferably carried out under mechanical (sandwiching) pressure so that the nonwoven fabric is at least partially embedded in the nonporous film or polymer layer. By "embedded," we mean that all or a portion of the polymer penetrates into some of the interstices between the fibers or filaments of the nonwoven fabric, resulting in the polymer permeating at least a portion of the nonwoven fabric. Mechanical (sandwiching) pressure is conveniently applied by passing the nonwoven fabric and applied polymer layer through one or more calendering rollers, although other devices, such as a double-belt laminator, are also suitable. In some embodiments, one or more calendering rollers may be cooled to simultaneously cool the polymer to a temperature below its Vicat softening temperature (e.g., 80-120°C) and impregnate the nonwoven fabric.

[0050] The extrusion lamination process can be carried out by providing extruded films or layers of polymer on both sides of the nonwoven fabric, in which case both polypropylene copolymer blend sheets can be contacted with the nonwoven fabric simultaneously or sequentially.

[0051] FIG. 7 illustrates one embodiment of a cross-sectional view of a nonporous composite sheet formed by sandwiching a nonwoven fabric between two nonporous films. As shown in FIG. 7, the resulting nonporous composite sheet 20 includes a nonwoven fabric 21 and (in the illustrated embodiment) two polyolefin copolymer layers 22 and 22A. As shown, the nonwoven fabric 21 is partially embedded in each of the polyolefin copolymer layers 22 and 22A, with no infiltration into a small central portion 23 of the nonwoven fabric 21. In an alternative embodiment of a nonporous composite sheet, more particularly a biaxially oriented composite sheet, the entire nonwoven fabric 21 is preferably infiltrated and embedded into one or both of the polypropylene copolymer layers 22 and 22A. As also shown, portions of each of the polypropylene copolymer 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, in a non-porous composite sheet, more particularly a biaxially oriented composite sheet, one or both of these non-reinforced surface layers 24 and 24A are absent, in which case the respective polypropylene copolymer layers 22 and / or 22A completely penetrate the nonwoven fabric 21.

[0052] In some embodiments, the composite sheet is in the form of an extrusion laminate sheet in which the nonwoven fabric is disposed within the composite sheet, hi some other embodiments, the nonwoven fabric is disposed symmetrically within the composite sheet in the center of the thickness of the composite sheet.

[0053] The non-porous composite sheet can have a total thickness of at least 1 mm. It can 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.

[0054] The nonporous composite sheet thus formed is preferably cooled to a temperature of 50°C or less, and then sequentially subjected to cold stretching and hot stretching. Cold stretching in the longitudinal direction is performed first, followed by hot stretching in the transverse direction. The stretching process can be performed using the general method and conditions described in U.S. Patent Application Publication No. 2021 / 095110. The cold stretching step is performed using the nonporous composite sheet at a temperature of -20°C to 50°C. A preferred lower temperature limit is 0°C, 10°C, or 15°C, and a preferred upper temperature limit is at most 35°C, at most 30°C, or at most 25°C. The cold stretching ratio may be, for example, at least 15%, at least 25%, at least 35%, or at least 40%, and at most 150%, at most 100%, or at most 80%. Cold stretching may be performed in one step or gradually over multiple steps. The stretching ratio is calculated as 100% × [(length of stretched film - length of initial film) / length of initial film]. As used herein, a "single step" is considered to be a single drawing process for stretching a sheet material a specific amount in a specific direction at a specific temperature or temperature range. For example, a "single cold drawing step" may include multiple rolls, each working together to gradually stretch the sheet material to ultimately stretch the sheet material a predetermined target percentage in one direction.

[0055] The cold-stretched composite sheet may be annealed, if necessary, before the subsequent hot-stretching step. Such an annealing step is conveniently carried out by heating the cold-stretched composite sheet 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 generally 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 maintaining the cold-stretched composite sheet under tension sufficient to prevent shrinkage before transverse stretching.

[0056] The transverse hot stretching step is carried out with the composite sheet at a temperature of from above 50°C to 150°C. Preferably, the transverse direction is perpendicular to the longitudinal cold stretching. A preferred lower temperature limit is at least 90°C or at least 120°C, and a preferred upper temperature limit is 140°C. 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%, at most 300%, at most 200%, at most 150%, at most 100%, or at most 80%. The hot stretched composite sheet may be annealed in the same manner as described for annealing the cold stretched composite sheet.

[0057] Figure 8 is a cross-sectional photograph (shown similarly to Figure 7) of an actual biaxially oriented composite sheet made from 73.5 wt% polypropylene copolymer containing a 70 / 30 weight ratio of polypropylene homopolymer and ethylene-containing copolymer, 25 wt% propylene-based elastomer, and 1.5 wt% UV stabilizer, in which a nonwoven fabric was symmetrically extrusion laminated into the composite sheet.

[0058] When a nonporous film or composite sheet is produced by film casting, extrusion lamination, or other equipment, the sheet material has a machine direction corresponding to the direction of travel through the equipment and a transverse or cross direction perpendicular (or orthogonal) to the machine direction (in the plane of the sheet). Either the cold-stretching step or the hot-stretching step can be performed uniaxially in the machine direction or the transverse direction, but to form a biaxially oriented microporous film or composite sheet, the cold-stretching step and the hot-stretching step should not be performed in the same direction, but preferably in orthogonal directions. In a preferred embodiment, the cold-stretching step is performed in the machine direction and the hot-stretching step is performed in the transverse or cross direction.

[0059] By performing one stretching step in the machine direction and the other in the cross direction, the resulting microporous film or composite sheet containing the microporous film will have a better balance of physical properties such as tensile strength and elongation in the machine and cross directions.

[0060] A nonporous film or composite sheet can be biaxially stretched in a continuous operation involving a combination of various apparatuses, such as by first stretching the nonporous film or composite sheet in the machine direction, e.g., with a series of stretching rollers, and then stretching the nonporous film or composite sheet in the transverse or cross direction, e.g., by using a tenter frame equipped with clips to grip both sides of the nonporous film or composite sheet. The clips are attached to a pair of rails that extend in the direction of travel of the nonporous film or composite sheet through the apparatus. The clips move along the rails, expanding as they carry the nonporous film or composite sheet, thereby biaxially stretching the nonporous film or composite sheet into a biaxially oriented microporous film or biaxially oriented composite sheet. A tenter frame is particularly well suited for stretching sheet material in the transverse direction. As previously mentioned, the stretching section (i.e., the section including the extension rails) may be preceded by a preheating section, followed by an annealing section and / or a rewinding section.

[0061] Yet another suitable stretching device is a grooved roller stretcher. Such a grooved roller stretcher is particularly useful for stretching nonporous films or composite sheets in the transverse direction. The grooved roller stretcher has an intermeshing tooth-groove structure through which the nonporous film or composite sheet passes. The tooth-groove structure may be a roller pair, as described, for example, in U.S. Pat. Nos. 4,368,565, 5,028,289, and 6,843,949, U.S. Patent Application Publication No. 2006 / 0148354, and EP 927096, or a moving belt having a toothed actuating member and a complementary tooth groove, as described in U.S. Pat. No. 8,337,190. The grooved roller stretcher may also include multiple tooth-groove structures in series. The nonporous film or composite sheet is fed into a grooved roller stretcher and conveyed through a tooth and groove structure, where the nonporous film or composite sheet is stretched transversely to the direction of travel. The resulting microporous film or composite sheet, including the microporous film, is then removed from the apparatus. The stretching operation carried out in a grooved roller stretcher is conveniently carried out continuously by continuously passing the length of the nonporous film or composite sheet through the tooth and groove structure.

[0062] In one embodiment, a composite sheet comprising a microporous film is produced by a continuous process comprising: i) continuously extruding a polypropylene copolymer composition into a nonporous polymeric film or layer; ii) contacting the nonporous polymeric film or layer with a first side of a nonwoven fabric, and then cooling the nonporous polymeric film or layer to a temperature below its Vicat softening temperature to produce a composite sheet; iii) cooling the composite sheet to a cold-stretching temperature; then iv) cold-stretching the composite sheet in a first direction, preferably the machine direction, followed by v) heating the cold-stretched composite sheet to a hot-stretching temperature, and then vi) hot-stretching the cold-stretched composite sheet in a second direction transverse to the first direction, preferably the transverse direction perpendicular to the machine direction, to produce a biaxially oriented composite sheet comprising a microporous film.

[0063] Optionally, a second nonporous film or layer of polymer can be attached to or contacted with the second, opposite surface of the nonwoven fabric before, after, or during step ii), thereby producing a composite sheet in which the nonwoven fabric is disposed within the composite sheet after biaxial orientation. In some preferred embodiments, the first and second nonporous films or layers of polymer have essentially equal weights, such that the nonwoven fabric is symmetrically disposed at or near the center of the thickness of the composite sheet.

[0064] As shown in FIG. 9, the continuous biaxial stretching process can be carried out in an apparatus including an extrusion laminator 50, followed by a longitudinal cold stretcher 51, followed by a transverse hot stretcher 52, followed by a cooling unit 53, and finally a winding unit 54.

[0065] The extrusion laminating apparatus 50 can include, for example, an extruder with a die adapted to produce a nonporous film or layer of polymer; a feeding device for feeding the nonwoven fabric to the laminator; and a laminator, such as a heated calender roll, for mechanically compressing the polymer film or layer in contact with the nonwoven fabric, preferably forcing at least a portion of the polymer from the polymer film or layer into the voids in the nonwoven fabric to produce a composite sheet. The extrusion laminating apparatus can have a heated or cooled calender roll, if desired or necessary. The extrusion laminating apparatus can further include a device (i.e., a second extruder, casting die, laminating station, etc.) for producing or feeding a second film or layer of polymer to contact the second nonporous film or layer of polymer on the opposite side of the nonwoven fabric in a similar manner, so as to form a composite sheet in which the nonwoven fabric is embedded between two films or layers of polymer, forming a sandwich structure with the polymer from the polymer film / layer in the voids between the fibrous components in the nonwoven fabric.

[0066] The longitudinal cold stretching device 51 can receive the composite sheet from the extrusion laminator and continuously cold stretch the composite sheet in the longitudinal direction, which may include, if necessary, chill rolls or other devices for cooling the composite sheet or bringing it to a particular stretching temperature, and one or more stretching rollers or a series of nip rollers for stretching the composite sheet in the longitudinal direction, which is considered herein as a single longitudinal stretching step.

[0067] The transverse hot stretching apparatus 52 can receive the cold-stretched composite sheet from the cold stretching apparatus and continuously further hot stretch the composite sheet in the machine direction, and can include heated rolls or other devices for heating or bringing the composite sheet to a specific stretching temperature, as well as devices such as transverse expansion rollers and / or a tenter frame for gripping and stretching the heated composite sheet in a direction transverse to the machine direction. The hot stretching apparatus can further include an optional annealing section after the stretching rollers for optionally annealing the stretched composite sheet at a desired temperature, for example, using additional temperature-controlled rollers. This is considered herein to be a single transverse stretching step.

[0068] A cooling device 53 receives the biaxially oriented composite sheet from the hot stretching device and can continuously cool the sheet, which can optionally include chill rolls or other devices to cool the biaxially oriented composite sheet to a desired final temperature for winding into a roll good. A winding device 54 then preferably winds the final biaxially oriented composite sheet onto a core to form a roll of composite sheet comprising a biaxially oriented microporous film.

[0069] Biaxially oriented microporous films can be made in a similar process to composite sheets containing biaxially oriented microporous films, by simply omitting the nonwoven fabric: one or more nonporous films or layers of polymer are cast in the same manner as described above without combining them with a nonwoven fabric, and only the nonporous films or layers of polymer are cold-stretched and hot-stretched to form the biaxially oriented microporous film.

[0070] The resulting biaxially oriented composite sheet has a thickness of at least 1 mm. The thickness can be at least 1.2 mm, e.g., at most 12.7 mm, at most 6.35 mm, at most 3 mm, at most 2 mm, or at most 1.8 mm. The biaxially oriented microporous film and biaxially oriented composite sheet preferably have a weight of at least 50, at least 90, at least 100, at least 120, or at least 190 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 is fine.

[0071] The biaxially oriented microporous film or composite sheet comprising the biaxially oriented microporous film is preferably leak-proof under a pressure of 0.3 MPa for at least 30 minutes and passes the watertightness test of EN1928:2000 Method B. Preferably, the biaxially oriented microporous film or composite sheet comprising the biaxially oriented microporous film is leak-proof under a pressure of 0.3 MPa for at least 2 hours.

[0072] Surprisingly, the presence of the nonwoven does not inhibit orientation and micropore formation in the film, and also adheres strongly to the polypropylene copolymer, thereby preventing tearing and the formation of more macroscopic defects in the oriented material. Thus, the biaxially oriented composite sheet preferably has high vapor pressure permeability and excellent watertightness.

[0073] The composite 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 EN 12310-2: 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.

[0074] The composite sheet preferably exhibits a tensile strength at peak load of at least 1250 N / 5 cm, more preferably at least 1500 or at least 1750 N / 5 cm, in at least one direction, when measured according to ASTM D5034-09 at a crosshead speed of 30 cm / min. The composite 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, similarly measured, is preferably at least 15% in both the machine and cross directions.

[0075] Another advantage of the composite sheet is that it is easily and securely welded to itself, despite the presence of the embedded nonwoven fabric. Bond strength is determined by bonding two composite 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 EM 12316-2:2000. The peel force of the weld is typically at least 2 N / mm.

[0076] Biaxially oriented microporous films or composite sheets comprising biaxially oriented microporous films are preferably useful as waterproof membranes or components of waterproof membranes in applications requiring breathability, particularly water vapor transmission, such as roofing applications. In some embodiments, biaxially oriented microporous films or composite sheets comprising biaxially oriented microporous films are or are used as roofing membranes. Specific examples of roofing membranes for which biaxially oriented microporous films or composite sheets comprising biaxially oriented microporous films are useful include metal roofing membranes, temporary roofing membranes, and concrete roofing membranes (especially for lightweight concrete roofing membranes). [Example]

[0077] Test Method Melting points and glass transition temperatures were determined by differential scanning calorimetry (DSC) as follows. Samples to be measured were weighed and sealed in aluminum hermetically sealed DSC pans (P / N 900793.901 pan and lid 900794.901). Sample weights were approximately 1-4 mg for each sample. Samples were scanned in a TA Instruments Q2000 DSC (differential scanning calorimeter) (P / N 970001.901) (S / N 2000.0877) equipped with an autosampler, a 50 ml / min nitrogen purge, and a mechanical cooling accessory. Run parameters for the heat-cool-heat cycle were -20°C to 200°C at 10°C / min with a sampling interval of 0.1 s / pt. Scans were analyzed using Universal Analysis V4.7A TA Instruments software. The melting points obtained from the DSC scans are shown as output from the instrument software and correspond to a plot of the peak temperature in the heat flow versus the temperature in the second heating cycle. The glass transition temperature was determined from the inflection point of the second heat of the DSC curve using a heating / cooling rate of 10 °C / min.

[0078] Density was determined according to ASTM D792.

[0079] Softening point temperatures were determined according to ASTM D36-06. Specific VICAT softening temperatures were determined according to ASTM D1525.

[0080] Melt (mass) flow rate (MFR) was measured at 230°C, 2.16 kg according to ASTM D-1238, either under condition L (230°C, 2.16 kg) or condition E (190°C, 2.16 kg) as described.

[0081] Peel strength was measured in accordance with GB / T328.21-2007 (Test Methods for Building Sheets for Waterproofing - Part 21: Plastic and Rubber Sheets for Waterproofing - Resistance to Peeling of Joints) test standard. Two 200mm x 350mm membranes were cut, then overlapped and welded using a hot air gun. The overlap width was 80mm. The welded sample was cut into five pieces, leaving at least 100mm of unoverlapped area. Each piece was 50mm wide. Each specimen was attached to an upper and lower clamp. The 180° peel force test was performed at a speed of 100±10mm / min, and the maximum peel force was recorded in N / 50mm. If the sample failed, either no peel force or only one peak peel force was recorded. A stress-strain curve was recorded, and the first and last quarter sections were removed. The average peel force was the average of the peel forces at 10 equally spaced points between the 1 / 4 and 3 / 4 areas. The average peel force was the average of five test specimens.

[0082] The average molecular weight was determined by gel permeation chromatography (GPC) as described in US Patent Application Publication No. 20210095110.

[0083] Polymer composition was determined by nuclear magnetic resonance (NMR) spectroscopy as described in US Patent Application Publication No. 20210095110.

[0084] Tensile and elongation tests were performed according to ASTM D882.

[0085] Trapezoid tear testing was performed according to ASTM D5587.

[0086] Example 1 The polypropylene copolymer oriented film was produced from a blend containing 80 wt% polypropylene copolymer and 20 wt% propylene-based elastomer. The polypropylene copolymer contained polypropylene homopolymer and ethylene-containing copolymer in a 70 / 30 weight ratio, meaning that the blend and polypropylene copolymer film contained 56 wt% polypropylene homopolymer, 24 wt% ethylene-containing copolymer, and 20 wt% propylene-based elastomer. The polypropylene copolymer was a reactor-grade resin from Braskem, which was a reactor blend of polypropylene homopolymer and ethylene-containing copolymer.

[0087] The propylene-based elastomer was composed primarily of isotactic propylene repeat units with random ethylene distribution and was produced using metallocene catalyst technology and was available from ExxonMobil as Vistamaxx™ 6102 elastomer.

[0088] Film casting was performed in a 2-inch diameter single-screw extruder equipped with a film-casting die. A loss-in-weight feeder was used to feed the copolymer blend into the extruder, which then melted the components and extruded a nonporous film or layer of the polymer. The extruded film was then passed through a roll stack containing three rolls set at 250°F (±10°C) to produce a nonporous film with a uniform, smooth surface.

[0089] Biaxially stretched films were produced by first stretching the film in the machine direction (MDO, parallel to the film production direction) on a roll at room temperature, and then preheating the film to a temperature of 120 °C and stretching the film in the transverse direction (TDO, perpendicular to the film production direction) using a tenter frame.

[0090] The degree of stretching of these films and the resulting properties are shown in Tables 1A and 1B. The final film thickness of all samples ranged from 18.8 to 19.8 mils. Water vapor transmission rate (WVP) was measured by wet cup at 23 (±0.6)°C and a relative humidity difference of 50 (±2)%. Hydrohead measurements were performed using a slotted plate at a pressure of 0.3 MPa for 2 hours. As shown in Table 1A, the films of the present invention passed the hydrohead test.

[0091] [Table 1]

[0092] [Table 2]

[0093] Example 2 A composite sheet containing a biaxially oriented film was produced using the same polypropylene copolymer blend containing 80 weight percent polypropylene copolymer and 20 weight percent propylene-based elastomer as in Example 1 and a polypropylene-polyester (PP-PET) nonwoven fabric. The PP-PET nonwoven fabric was a 157 gsm spunbond nonwoven fabric made using sheath / core PP / PET filaments purchased from Low & Bonar. The MD / CD tensile strength of this nonwoven fabric was 550 N / 5 cm and 434 N / 5 cm, respectively, and the MD / CD tensile elongation was 75% and 82%, respectively.

[0094] The composite sheet was fabricated by extrusion lamination by first extruding a nonporous film layer (or nonporous polymer layer) of a polypropylene copolymer blend and combining the film layer with a nonwoven fabric at the nip between a pair of rolls. The nip gap was set so that a portion of the surface of the first side of the nonwoven fabric was pressed into one side of the film or polymer layer. Another identical nonporous film layer (or nonporous polymer layer) was then extruded and brought into contact with the exposed second side of the nonwoven fabric, again sandwiched between the pair of rolls. The nip gap was set so that the second side of the nonwoven fabric was pressed into the extruded second film layer. Each extruded film layer had a thickness of approximately 762 micrometers. After cooling, the resulting structure formed a reinforced film having a sandwich structure of extruded polypropylene copolymer blend / nonwoven fabric / extruded polypropylene copolymer blend, with the voids between the fibrous material in the nonwoven fabric essentially completely impregnated or filled with the extruded copolymer blend.

[0095] The composite sheet was then biaxially stretched as in Example 1 by first stretching the film by 50% in the machine direction (MDO, parallel to the film production direction) on a roll at room temperature, and then stretching the film by 40% in the transverse direction (TDO, perpendicular to the film production direction) in a tenter frame at a temperature of 120° C. The peel strength of the inventive sample (5-1) is shown in Table 2.

[0096] For comparison, a composite sheet was prepared in the same manner as above, except that the extruded polymer film layer was made solely from a polypropylene copolymer rather than a polypropylene copolymer blend. That is, no propylene-based elastomer was present in the polymer film layer. The composite sheet was then biaxially oriented by first cold stretching 25 percent to MDO, followed by hot stretching 50 percent to TDO, both at the same temperatures. The peel strength of this comparative sample (5-A) is also shown in Table 2. The composite sheet of the present invention, which includes the additional propylene-based elastomer, has improved peel strength, as shown.

[0097] [Table 3]

[0098] Example 3 Biaxially oriented films were produced from two compositions of the polypropylene copolymer blend embodiment. This example included a mixture of polypropylene copolymer, a propylene-based elastomer, and a sealing additive. As in Example 1, the polypropylene copolymer included a polypropylene homopolymer and an ethylene-containing copolymer in a 70 / 30 weight ratio. The first composition included 75 wt% polypropylene copolymer, 10 wt% propylene-based elastomer, and 15 wt% sealant. The second composition included 65 wt% polypropylene copolymer, 20 wt% propylene-based elastomer, and 15 wt% sealant. As in Example 1, the polypropylene copolymer included a polypropylene homopolymer and an ethylene-containing copolymer in a 70 / 30 weight ratio.

[0099] The sealing additive contained equal parts by weight of two polyolefin elastomers of different densities and a hydrocarbon-based tackifier (5% by weight of the composition each). The two polyolefin elastomers were ENGAGE™ 8402 polyolefin elastomer and AFFINITY™ GA 1900 elastomer, both available from Dow. The hydrocarbon-based tackifier was ESCOREZ™ 5400, a cycloaliphatic hydrocarbon resin available from ExxonMobil. Figure 5 is a TEM micrograph of a nonporous film of the first composition before stretching, and Figure 6 is a TEM micrograph of a nonporous film of the second composition before stretching.

[0100] A nonporous film comprising the second composition (65% polypropylene copolymer / 20% propylene-based elastomer / 15% sealing additive) was then cold stretched 40% in the machine direction and then hot stretched 50% in the transverse direction to form a biaxial film as in Example 1. This biaxially stretched film passed a hydrohead test (slot plate) at 0.3 MPa for 2 hours.

Claims

1. a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 wt % polypropylene homopolymer chain segments based on the weight of the polypropylene copolymer, or 43 to 79 mol % polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized units in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; ii) 5 to 50 wt % ethylene-containing copolymer chain segments based on the weight of the polypropylene copolymer, or 21 to 57 mole % ethylene-containing copolymer 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 polypropylene copolymer; Including, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of ethylene polymerized 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; a polypropylene copolymer; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point less than 110°C; A biaxially stretched microporous film comprising: the weight percentages of a) and b) are based on the combined weight of a) and b); The biaxially stretched microporous film has a viscosity of 50 grams / (24 hours m 2 ) or more, and when subjected to a hydrohead test at 0.3 MPa, liquid water does not permeate the film for 30 minutes. Biaxially oriented microporous film.

2. 90 grams / (24 hours / m 2 2. The biaxially stretched microporous film of claim 1, having a water vapor permeability of at least 100%.

3. 190 grams / (24 hours / m 2 3. The biaxially stretched microporous film according to claim 2, having a water vapor permeability of at least 100%.

4. The biaxially stretched microporous film according to any one of claims 1 to 3, which does not allow liquid water to pass through the film for 2 hours when subjected to a 0.3 MPa hydrohead test.

5. A roof membrane comprising the biaxially oriented microporous film of any one of claims 1 to 4.

6. The nonwoven fabric further comprises a nonwoven fabric embedded therein, the nonwoven fabric having a weight of 100 to 400 g / m 2 A composite sheet comprising the biaxially oriented microporous film of any one of claims 1 to 4, having a basis weight of

7. The composite sheet of claim 6 , which is in the form of an extrusion laminate sheet in which the nonwoven fabric is disposed within the composite sheet.

8. 500~2000g / m 2 8. The composite sheet of claim 6 or 7, having a basis weight of

9. A roof membrane comprising the composite sheet of any one of claims 6 to 8.

10. a) 89 to 65 wt. % polypropylene copolymer, i) 50 to 95 wt % polypropylene homopolymer chain segments based on the weight of the polypropylene copolymer, or 43 to 79 mol % polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized units in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; ii) 5 to 50 wt % ethylene-containing copolymer chain segments based on the weight of the polypropylene copolymer, or 21 to 57 mole % ethylene-containing copolymer 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 polypropylene copolymer; Including, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of ethylene polymerized 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; a polypropylene copolymer; b) 10 to 34 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point less than 110°C; c) 1 to 15 weight percent of a sealing additive; A biaxially stretched microporous film comprising: the weight percentages of a), b), and c) are based on the combined weight of a), b), and c); Biaxially oriented microporous film.

11. 11. The biaxially oriented microporous film of claim 10, wherein the sealing additive is one or more polyolefin elastomers, one or more polyolefin plastomers, one or more hydrocarbon-based tackifiers, or any mixture thereof.

12. 12. The biaxially oriented microporous film of claim 11, wherein the sealing additive comprises a mixture of two different polyolefin elastomers.

13. A roof membrane comprising the biaxially oriented microporous film of any one of claims 10 to 12.

14. and a nonwoven fabric embedded therein, the nonwoven fabric having a weight of 100 to 400 g / m 2 A composite sheet comprising the biaxially oriented microporous film of any one of claims 10 to 12, having a basis weight of

15. 15. The composite sheet of claim 14, wherein the nonwoven fabric is in the form of an extrusion laminate sheet disposed within the composite sheet.

16. 500~2000g / m 2 16. The composite sheet of claim 14 or 15, having a basis weight of

17. A roof membrane comprising the composite sheet of any one of claims 14 to 16.

18. 1. A method for forming a biaxially stretched microporous film, comprising: A) a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 wt % polypropylene homopolymer chain segments based on the weight of the polypropylene copolymer, or 43 to 79 mol % polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized units in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; ii) 5 to 50 wt % ethylene-containing copolymer chain segments based on the weight of the polypropylene copolymer, or 21 to 57 mole % ethylene-containing copolymer 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 polypropylene copolymer; Including, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of ethylene polymerized 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; a polypropylene copolymer; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point less than 110°C; A composition comprising: forming a nonporous film from the composition, wherein the weight percentages of a) and b) are based on the combined weight of a) and b); B) the non-porous film, (i) cold stretching in a first direction at a temperature in the range of −20° C. to 50° C.; and (ii) hot stretching in a second direction at a temperature in the range of 50°C to 140°C; performing a sequential cold and hot biaxial stretching process consisting of 50 grams / (24 hours / m 2 a biaxially stretched microporous polymer film having a water vapor permeability of at least 1000 MPa and capable of preventing liquid water from permeating the film for 30 minutes when subjected to a hydrohead test at 0.3 MPa; A method comprising:

19. 20. The method of forming a biaxially oriented microporous film of claim 18, wherein the second direction is perpendicular to the first direction.

20. 190 grams / (24 hours / m 2 20. The method for forming a biaxially stretched microporous film according to claim 18 or 19, having a water vapor permeability of 100% or more.

21. The method for forming a biaxially stretched microporous film according to any one of claims 18 to 20, wherein liquid water does not permeate the biaxially stretched microporous film for 2 hours when subjected to a 0.3 MPa hydrohead test.

22. 22. The method of forming a biaxially oriented microporous film according to any one of claims 18 to 21, wherein the non-porous film is produced by extruding a polymer layer through a casting die.

23. 1. A method for forming a composite sheet comprising a biaxially oriented microporous film, comprising: A) a) 90 to 65 wt. % polypropylene copolymer, i) 50 to 95 wt % polypropylene homopolymer chain segments based on the weight of the polypropylene copolymer, or 43 to 79 mol % polypropylene homopolymer chain segments based on the molar content of polypropylene polymerized units in the polypropylene homopolymer chain segments as a percentage of the total molar content of polymerized monomer units in the polypropylene copolymer; ii) 5 to 50 wt % ethylene-containing copolymer chain segments based on the weight of the polypropylene copolymer, or 21 to 57 mole % ethylene-containing copolymer 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 polypropylene copolymer; Including, at least a portion of the ethylene-containing copolymer chain segments comprise polymerized ethylene units in an amount of at least 45 wt % based on the weight of the ethylene-containing copolymer chain segment, or at least 55 mol % based on the molar content of ethylene polymerized 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; a polypropylene copolymer; b) 10 to 35 wt. % of a propylene-based elastomer having 5 to 25 wt. % of units derived from ethylene and having a melting point less than 110°C; A composition comprising: forming a polymeric non-porous film or layer from the composition, wherein the weight percentages of a) and b) are based on the combined weight of a) and b); B) combining a non-porous film or layer of the polymer with a nonwoven fabric to form a composite sheet; and C) applying a coating of the composite sheet to the composite sheet; (i) cold stretching in a first direction at least once at a temperature in the range of −20° C. to 50° C.; and (ii) hot-stretching at least once in the second direction at a temperature in the range of 50°C to 140°C; performing sequential cold and hot biaxial stretching steps including producing a composite sheet comprising a biaxially oriented microporous polymeric film; A method comprising:

24. The sequential cold and hot biaxial stretching step of step C) comprises: (i) cold stretching in a first direction at a temperature in the range of −20° C. to 50° C.; and (ii) hot stretching in a second direction at a temperature in the range of 50°C to 140°C; 24. The method of forming a composite sheet of claim 23, comprising:

25. 25. The method of forming a composite sheet of claim 23 or 24, wherein the second direction is perpendicular to the first direction.

26. 26. The method for forming a composite sheet according to any one of claims 23 to 25, wherein the composite sheet is formed by combining the non-porous film or non-porous layer of polymer with a nonwoven fabric by extrusion lamination.

27. 27. The method of forming a composite sheet according to any one of claims 23 to 26, wherein the nonwoven fabric is disposed within the composite sheet between either two of the nonporous films or two layers of polymer.

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