Melt blown nonwovens having high volume resistivity and articles thereof

Abstract

Melt-blown nonwovens and articles thereof are provided. The melt-blown nonwovens can be formed from a composition comprising an ethylene / αα-olefin interpolymer and specific additives. The melt-blown nonwovens according to the embodiments disclosed herein exhibit high volume resistivity and can be used in filtration applications.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to meltblown nonwovens, and more specifically to meltblown nonwovens formed from compositions having high volume resistivity. Background Technology

[0002] Electrical properties, such as volume resistivity and charge retention capacity, are crucial for filtration because they can help improve resistance to electrochemical degradation and reduce charge decay. Articles used for filtration purposes include meltblown nonwovens. Meltblown nonwovens made of polypropylene, rather than polyethylene, are widely used in filtration applications because polypropylene exhibits better electrical properties for filtration than polyethylene. For example, typical meltblown nonwoven fabrics formed from polypropylene compositions can be charged to obtain a static charge for dust collection. Although polypropylene is the most commonly used polyolefin matrix for filtration applications, it has several disadvantages compared to polyethylene. For example, polypropylene is rigid, cannot be sterilized by radiation, and can degrade and become odorous. Therefore, meltblown nonwovens made of polyethylene remain in demand, as polyethylene can be flexible and less odorous, and can exhibit good electrical properties (such as high volume resistivity) in use (e.g., filtration applications). Summary of the Invention

[0003] The embodiments disclosed herein meet the aforementioned needs by providing meltblown nonwovens comprising ethylene / α-olefin interpolymers and specific additives or combinations thereof.

[0004] This article discloses a meltblown nonwoven fabric. The meltblown nonwoven fabric is formed from a composition. The composition comprises: an ethylene / α-olefin interpolymer having a density of 0.911 g / cc to 0.939 g / cc, a Brookfield viscosity of less than or equal to 50,000 cP, and a molecular weight distribution of 1.8 to 3.5 (M). w，cc / M n，cc ); and an additive selected from the group consisting of titanium dioxide, bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, talc, halloysite, foliosilicates of organophilic substances, or combinations thereof; and wherein the composition has a volume resistivity greater than 7.0E+16 ohm·cm at room temperature.

[0005] This document also discloses air filters. Air filters include meltblown nonwoven fabrics according to embodiments disclosed herein. In one embodiment, the air filter comprises a meltblown nonwoven fabric formed from a composition comprising: an ethylene / α-olefin interpolymer having a density of 0.911 g / cc to 0.939 g / cc, a Brookfield viscosity less than or equal to 50,000 cP, and a molecular weight distribution (M) of 1.8 to 3.5.w，cc / M n，cc ); and an additive selected from the group consisting of titanium dioxide, bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, talc, halloysite, foliosilicates of organophilic substances, or combinations thereof; and wherein the composition has a volume resistivity greater than 7.0E+16 ohm·cm at room temperature.

[0006] These and other implementation schemes are described in more detail in the specific embodiments. Detailed Implementation

[0007] The disclosed aspects of the meltblown nonwoven fabric are described in more detail below. Meltblown nonwoven fabrics have a wide range of applications and can be used to produce a variety of articles, including, for example, air filters, insulating materials, face masks, surgical gowns, bandages, and wound dressings. However, it should be noted that this is merely an illustrative implementation of the embodiments disclosed herein. These embodiments are applicable to other technologies susceptible to similar problems described above.

[0008] As used herein, the term "interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. The general term "interpolymer" includes the term "copolymer" (typically used to refer to a polymer prepared from two different monomers) and the term "terpolymer" (typically used to refer to a polymer prepared from three different types of monomers). It also encompasses polymers prepared by polymerizing four or more types of monomers.

[0009] The terms “comprising,” “including,” “having,” and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not such components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated otherwise, all compositions claimed using the term “comprising” may include any additional additives, adjuvants, or compounds, whether polymerized or otherwise. In contrast, the term “substantially constitutes…” excludes any other components, steps, or procedures from any subsequently listed scope, except those that are not essential for operability. The term “consisting of…” excludes any ingredients, steps, or procedures not specifically described or listed.

[0010] Meltblown nonwovens are formed from a composition. This composition contains an ethylene / α-olefin interpolymer and additives.

[0011] Ethylene / α-olefin interpolymer of the composition

[0012] In embodiments, the composition comprises 90 wt% to 99.95 wt% of ethylene / α-olefin interpolymer based on the total weight of the composition. All individual values ​​and sub-ranges of 90 wt% to 99.95 wt% are disclosed and included herein. For example, based on the total weight of the composition, the composition may comprise 90 wt% to 99.95 wt%, 92 wt% to 99.95 wt%, 94 wt% to 99.95 wt%, 96 wt% to 99.95 wt%, 98 wt% to 99.95 wt%, or 99 wt% to 99.95 wt% of ethylene / α-olefin interpolymer.

[0013] Ethylene / α-olefin interpolymers generally refer to polymers comprising ethylene and α-olefins having three or more carbon atoms. In embodiments herein, ethylene / α-olefin interpolymers comprise greater than 50% by weight of ethylene-derived units and less than 30% by weight of units derived from one or more α-olefin comonomers (based on the total amount of polymerizable monomers). This document includes and discloses all individual values ​​and subranges of the greater than 50% by weight of ethylene-derived units and less than 30% by weight of units derived from one or more α-olefin comonomers.For example, in some embodiments, the ethylene / α-olefin interpolymer comprises (a) by weight, greater than or equal to 55%, such as greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 92%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, from greater than 50% to 99%, from greater than 50% to 97%, from greater than 50% to 94%, from greater than 50% to 90%, From 70% to 99.5%, from 70% to 99%, from 70% to 97%, from 70% to 94%, from 80% to 99.5%, from 80% to 99%, from 80% to 97%, from 80% to 94%, from 80% to 90%, from 85% to 99.5%, from 85% to 99%, from 85% to 97%, from 88% to 99.9%, from 88% to 99.7%, from 88% to 99.5%, from 88% to 99%, from 88% to 98%, from 88% to 97%, from 88% to 95%, from 88% to 94%, from 90% to 99.9%, from 90% to (a) 99.5%, from 90% to 99%, from 90% to 97%, from 90% to 95%, from 93% to 99.9%, from 93% to 99.5%, from 93% to 99%, or from 93% to 97% of ethylene-derived units; and (b) less than 30% by weight, for example less than 25%, or less than 20%, less than 18%, less than 15%, less than 12%, less than 10%, less than 8%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, from 0.1% to 20%, from 0.1% to 15%, 0.1% to 12%, 0.1% to 10%, 0. 1% to 8%, 0.1% to 5%, 0.1% to 3%, 0.1% to 2%, 0.5% to 12%, 0.5% to 10%, 0.5% to 8%, 0.5% to 5%, 0.5% to 3%, 0.5% to 2.5%, 1% to 10%, 1% to 8%, 1% to 5%, 1% to 3%, 2% to 10%, 2% to 8%, 2% to 5%, 3.5% to 12%, 3.5% to 10%, 3.5% to 8%, 3.5% to 7%, or 4% to 12%, 4% to 10%, 4% to 8%, or 4% to 7% of units derived from one or more α-olefin comonomers. The content of comonomers can be measured using any suitable technique, such as techniques based on nuclear magnetic resonance (“NMR”) spectroscopy, for example, by 13C NMR analysis as described in U.S. Patent No. 7,498,282 (which is incorporated herein by reference).

[0014] Suitable α-olefin comonomers typically have no more than 20 carbon atoms. One or more α-olefins may be selected from the group consisting of C3-C20 acetylene unsaturated monomers and C4-C18 dienes. For example, α-olefin comonomers may have 3 to 10 carbon atoms or 3 to 8 carbon atoms. Exemplary α-olefin comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4-methyl-1-pentene. One or more α-olefin comonomers may, for example, be selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene; or, alternatively, from the group consisting of 1-butene, 1-hexene, and 1-octene; or, alternatively, from the group consisting of 1-hexene and 1-octene. In some embodiments, the ethylene / α-olefin interpolymer comprises greater than 0% by weight and less than 30% by weight of units derived from one or more of the comonomers of 1-octene, 1-hexene, or 1-butene.

[0015] In the embodiments described herein, the ethylene / α-olefin interpolymer has a density of 0.911 g / cm³ to 0.939 g / cm³. This document includes and discloses all individual values ​​and sub-ranges of 0.911 g / cc to 0.939 g / cc. For example, in some embodiments, the ethylene / α-olefin interpolymer has a density of 0.911 g / cc to 0.935 g / cc. In other embodiments, the ethylene / α-olefin interpolymer has a density of 0.913 g / cc to 0.939 g / cc. In still other embodiments, the ethylene / α-olefin interpolymer has a density of 0.913 g / cc to 0.935 g / cc. The density can be measured according to ASTM D792.

[0016] In addition to density, the ethylene / α-olefin interpolymer has a Brookfield viscosity of less than or equal to 50,000 centipoise (cP). This document includes and discloses all individual values ​​and sub-ranges of less than or equal to 50,000 cP. For example, in some embodiments, the ethylene / α-olefin interpolymer has a Brookfield viscosity of less than or equal to 45,000 cP, less than or equal to 40,000 cP, or less than or equal to 35,000 cP. In other embodiments, the ethylene / α-olefin interpolymer has a Brookfield viscosity ranging from 5,000 cP to 50,000 cP, from 5,000 cP to 45,000 cP, or from 5,000 cP to 40,000 cP.

[0017] Besides density and Brookfield viscosity, ethylene / α-olefin interpolymers have a molecular weight distribution from 1.8 to 3.5 (M w，cc / M n，cc The molecular weight distribution can be described as the weight-average molecular weight (M). w，cc ) and number-average molecular weight (Mn，cc The ratio of (i.e., M) w，cc / M n，cc ), and can be measured by gel permeation chromatography (GPC). This document includes and discloses all individual values ​​and sub-ranges from 1.8 to 3.5. For example, in some embodiments, the ethylene / α-olefin interpolymer has a molecular weight distribution (M) from 1.9 to 3.5 or 2.0 to 3.5. w，cc / M n，cc In other embodiments, the ethylene / α-olefin interpolymer has a molecular weight distribution (M0.05) from 1.8 to 3.0, 1.9 to 3.0, or 2.0 to 3.0. w，cc / M n，cc In other embodiments, the ethylene / α-olefin interpolymer has a molecular weight distribution (M) from 1.8 to 2.8, 1.9 to 2.8, or 2.0 to 2.8. w，cc / M n，cc ).

[0018] Besides density, Brookfield viscosity, and molecular weight distribution, ethylene / α-olefin interpolymers can have an M value of less than 5.25. z，cc / M n，cc M z，cc This can be described as the z-average molecular weight. This document includes and discloses all individual values ​​and sub-ranges less than 5.25. For example, in some embodiments, the ethylene / α-olefin interpolymer has an Mz of less than 5.0, 4.5, 4.0, 3.8, or 3.5. z，cc / M n，cc In other embodiments, the ethylene / α-olefin interpolymer has an M of 2.5 to 5.25, 2.5 to 5.0, 2.5 to 4.5, 2.5 to 4.0, 2.5 to 3.8, or 2.5 to 3.5. z，cc / M n，cc .

[0019] Besides density, Brinell viscosity, molecular weight distribution, and M z，cc / M n，cc In addition, based on the total weight of the ethylene / α-olefin interpolymer, the ethylene / α-olefin interpolymer can have less than 2.5% of molecules with a molecular weight greater than 10. 5 The weight fraction (w) in g / mol, as determined by conventional gel permeation chromatography. This document includes and discloses all individual values ​​and subranges less than 2.5%. For example, in some embodiments, based on the total weight of the ethylene / α-olefin interpolymer, the ethylene / α-olefin interpolymer has less than 1.0% of a molecular weight greater than 10. 5 The weight fraction (w) in g / mol, as determined by conventional gel permeation chromatography.

[0020] Besides density, Brinell viscosity, molecular weight distribution, Mz，cc / M n，cc and molecular weight greater than 10 5 In addition to the weight fraction (w) in g / mol, ethylene / α-olefin interpolymers may have a comonomer distribution width index (CDBI) greater than or equal to 50%. This document includes and discloses all individual values ​​and sub-ranges greater than or equal to 50%. For example, in some embodiments, the ethylene / α-olefin interpolymer has a CDBI greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, or greater than or equal to 75%. In other embodiments, the ethylene / α-olefin interpolymer has a CDBI range from 50% to 98%, 50% to 97%, 55% to 98%, 55% to 97%, 60% to 98%, 60% to 97%, 70% to 98%, 70% to 97%, 75% to 98%, or 75% to 97%. In other embodiments, the ethylene / α-olefin interpolymer has a CDBI range of 50% to 85%, 55% to 85%, 60% to 85%, 60% to 80%, 65% to 80%, or 70% to 80%.

[0021] Besides density, Brinell viscosity, molecular weight distribution, M z，cc / M n，cc Molecular weight greater than 10 5 In addition to the g / mol weight fraction (w) and CDBI, ethylene / α-olefin interpolymers can have a highest DSC temperature crystallization peak Tc ranging from 80 °C to 110 °C. All individual values ​​and sub-ranges from 80 °C to 110 °C are included and disclosed herein. For example, in some embodiments, the ethylene / α-olefin interpolymer has a Tc ranging from 80 °C to 105 °C, 85 °C to 105 °C, or 90 °C to 105 °C. In other embodiments, the ethylene / α-olefin interpolymer has a Tc ranging from 95 °C to 105 °C. The highest DSC temperature crystallization peak is determined using the differential scanning calorimetry (DSC) method outlined below.

[0022] Besides density, Brinell viscosity, molecular weight distribution, M z，cc / M n，cc Molecular weight greater than 10 5In addition to the g / mol weight fraction (w), CDBI, and Tc, ethylene / α-olefin interpolymers can have a temperature difference ΔTm-Tc between the highest DSC melting temperature (Tm) and the highest DSC crystallization temperature (Tc) of less than 16 °C. This document includes and discloses all individual values ​​and sub-ranges below 16 °C. For example, in some embodiments, ethylene / α-olefin interpolymers can have a ΔTm-Tc of less than 15 °C. In other embodiments, ethylene / α-olefin interpolymers can have a ΔTm-Tc of less than 12 °C. The highest DSC melting temperature (Tm) is determined using the differential scanning calorimetry (DSC) method outlined below.

[0023] In the embodiments described herein, ethylene / α-olefin interpolymers can be prepared in solution polymerization using one or more conventional reactors, such as circulating reactors, isothermal reactors, plug flow reactors, and / or stirred tank reactors in parallel, series, and / or any combination thereof, in continuous or batch mode, to produce olefin-based polymers, such as ethylene polymers or propylene polymers. Solution-phase polymerization can occur in one or more well-mixed reactors (such as one or more circulating reactors and / or one or more isothermal reactors) at temperatures ranging from 100°C to 300°C (e.g., from 120°C to 190°C) and pressures ranging from 300 psi to 1,000 psi (e.g., from 400 psi to 750 psi). Residence times in solution-phase polymerization are typically from 2 minutes to 30 minutes; for example, from 5 minutes to 20 minutes. Ethylene, solvent, hydrogen, one or more catalyst systems, and one or more comonomers are continuously fed into the reactor. Exemplary solvents include, but are not limited to, isoalkanes and cycloalkanes. For example, such solvents can be commercially available under the name ISOPAR E from ExxonMobil Chemical Co., Houston, Texas, or under the name SBP100 / 140 from Shell Chemicals Europe. The effluent from the polymerization reactor (containing solvent, monomer, comonomer, hydrogen, catalyst components, and molten polymer) exits the reactor and enters a zone where it is contacted with a passivating agent and optional acid scavenging agent (such as calcium stearate and accompanying water hydrate) to stop the reaction and remove hydrogen chloride. Additionally, various additives, such as antioxidants, can be added at this point. The stream then passes through another set of static mixing elements (such as Kenics spiral static mixing elements) to uniformly disperse the catalyst, activator, and additives. The effluent (containing solvent, monomer, comonomer, hydrogen, catalyst components, and molten polymer) passes through a heat exchanger to increase the stream temperature, thereby preparing the polymer for separation from other lower-boiling-point reactive components. The feed stream then passes through a pressure-reducing control valve, which maintains the reactor pressure at a specified target. The stream then enters a multi-stage separation and de-volatiles system, where polymer is removed from the solvent, hydrogen, and unreacted monomers and comonomers. Impurities are removed from the recycled lower-boiling-point reactants, which then re-enter the reactor. The separated and de-volatiles polymer melt is pumped through a heat exchanger to reduce the stream temperature to less than 200°C, for example, less than 170°C or a temperature in the range of 50°C to 110°C; thus producing a cooled polymer melt. The cooled polymer melt is then pumped through a specially designed die for underwater granulation, cutting it into uniform solid beads, which are then dried and transferred to a hopper. After verifying the initial polymer properties, the solid polymer beads are transferred to a storage device.The portion removed in the devolatileization step can be recycled or destroyed. For example, most of the solvent is recycled back to the reactor after passing through the purification bed. This recycled solvent may still contain unreacted comonomers, which are then enhanced with fresh comonomers before re-entering the reactor. The recycled solvent may also contain some hydrogen, which is then enhanced with fresh hydrogen.

[0024] In some embodiments, ethylene / α-olefin interpolymers can be prepared in a circulating reactor via solution-phase polymerization using a catalyst composition according to the following procedure: All feedstocks (ethylene and one or more α-olefin comonomers, such as ethylene or octene) and process solvents (isoalkane solvents, such as ISOPAR E) are purified with molecular sieves before being introduced into the reaction environment. Hydrogen is supplied at a high purity level without further purification. The reactor monomer feed (ethylene) stream is pressurized to a pressure above the reaction pressure, e.g., 750 psig, via a mechanical positive displacement pump. The solvent and comonomer (one or more α-olefin comonomers, such as hexene or octene) feed streams are pressurized to a pressure above the reaction pressure, e.g., 750 psig, via a mechanical positive displacement pump. Individual catalyst components can be manually diluted batchwise to specified component concentrations using the purified solvent (ISOPAR E) and pressurized to a pressure above the reaction pressure, e.g., 750 psig. All reaction feed streams can be measured using mass flow meters and independently controlled using a computer-automated valve control system.

[0025] Continuous solution polymerization reactors can consist of a liquid-filled, non-adiabatic, isothermal, circulating loop. All fresh solvent, monomer, comonomer, hydrogen, and catalyst components can be fed independently. The combined solvent, monomer, comonomer, and hydrogen feed temperatures are controlled to any temperature between 5°C and 50°C, typically 40°C, by passing the feed stream through a heat exchanger. The fresh comonomer feed to the polymerization reactor is aligned to add the comonomer to the circulating solvent. The total fresh feed to the polymerization reactor is injected into the reactor at, for example, two locations, where the reactor volume is approximately equal between each injection location. The fresh feed is typically controlled using, for example, each injector receiving half the total fresh feed mass flow rate. The catalyst components are injected into the polymerization reactor through, for example, specially designed injection inlet devices, and combined into a mixed main catalyst / co-catalyst feed stream before injection into the reactor. The main catalyst component feed is computer-controlled to maintain the reactor monomer concentration at a specified target. The co-catalyst component is fed based on a calculated specified molar ratio to the main catalyst component. Immediately after each fresh injection point (feed or catalyst), the feed stream is mixed with the contents of the circulating polymerization reactor using a static mixing element (such as a Kernis spiral static mixing element). The reactor contents are continuously circulated through a heat exchanger responsible for removing a significant amount of heat of reaction, and the temperature on the coolant side is responsible for maintaining the isothermal reaction environment at the specified temperature. Circulation around the reactor loop can be provided by a screw pump. The effluent from the polymerization reactor (containing solvent, monomer, comonomer, hydrogen, catalyst components, and molten polymer) exits the reactor and enters a zone where it comes into contact with a passivating agent and optional acid scavenger (e.g., calcium stearate and accompanying hydrate) to stop the reaction and remove hydrogen chloride. Additionally, various additives, such as antioxidants, can be added at this point. The feed stream then passes through another set of static mixing elements (such as Kernis spiral static mixing elements) to uniformly disperse the catalyst, deactivator, and additives. The effluent (containing solvent, monomers, comonomers, hydrogen, catalyst components, and molten polymer) passes through a heat exchanger to raise the feed temperature, thus preparing the polymer for separation from other lower-boiling-point reactive components. The feed then passes through a pressure-reducing control valve, which maintains the reactor pressure at a specified target. Subsequently, the feed enters a secondary separation and de-volatiles system, where the polymer is removed from the solvent, hydrogen, and unreacted monomers and comonomers. Impurities are removed from the recycled low-boiling-point reactive components, which then re-enter the reactor. The separated and de-volatiles polymer melt is pumped through a heat exchanger to lower the feed temperature to less than 200°C, for example, less than 170°C or a temperature in the range of 50°C to 110°C; thereby producing a cooled polymer melt. The cooled polymer melt is then pumped through a die specially designed for underwater granulation, cut into uniform solid beads, dried, and transferred to a hopper.After verifying the initial polymer properties, the solid polymer beads are transferred to a storage device. The portion removed in the de-volatile step can be recycled or destroyed. For example, most of the solvent is recycled back to the reactor after passing through a purification bed. This recycled solvent may still contain unreacted comonomers, which are then reinforced with fresh comonomers before re-entering the reactor. The recycled solvent may also still contain some hydrogen, which is then reinforced with fresh hydrogen.

[0026] In other embodiments, ethylene / α-olefin interpolymers can be prepared using one or more catalyst systems suitable for polymerizing ethylene and one or more α-olefin comonomers via solution-phase polymerization in two adiabatic stirred tank reactors connected in series, according to the following procedure. Ethylene monomers and one or more α-olefin comonomers, along with hydrogen, are combined with a solvent (e.g., an isoparaffin solvent, such as ISOPAR E). Impurities (such as water, carbon dioxide, sulfur-containing compounds) are removed from the feed stream, and the feed stream is cooled to a temperature in the range of 5°C to 60°C, for example, about 13°C, before entering the reactor. Most (approximately 85% to 90%) of the reaction can occur in the first adiabatic stirred tank reactor. Mixing can be achieved by circulating the polymer / main catalyst / co-catalyst / solvent / ethylene / one or more α-olefin comonomers / hydrogen solution using one or more agitators equipped with mixing blades. The feed (ethylene / one or more α-olefin comonomers / solvent / hydrogen) can enter the reactor, for example, from the bottom, and the main catalyst / co-catalyst can, for example, be separate from the feed and also enter the reactor from the bottom. The temperature of the first reactor is in the range of 120°C to 190°C, for example, about 175°C, and the reactor pressure is in the range of 400 psig to 1,000 psig, for example, about 500 psig. The temperature of the second reactor, connected in series with the first reactor, is increased to a temperature in the range of 175°C to 210°C, for example, about 202°C, where about 10% to 15% of the remaining reaction occurs, and no additional catalyst or monomer is added. The average reactor residence time is in the range of 2 to 30 minutes; for example, the fluid specifically designed for this purpose resides in each adiabatic stirred tank reactor for about 8 minutes before termination.

[0027] The effluent from the polymerization reactor (containing solvent, monomers, comonomers, hydrogen, catalyst components, and molten polymer) leaves the reactor and enters a zone where it is contacted with a passivating agent and optional acid scavenging agent (e.g., calcium stearate and accompanying hydrate) to stop the reaction and remove hydrogen chloride. Additionally, various additives, such as antioxidants, can be added at this point. The stream then passes through another set of static mixing elements (such as a Kenneth spiral static mixing element) to uniformly disperse the catalyst, deactivator, and additives. The effluent (containing solvent, monomers, comonomers, hydrogen, catalyst components, and molten polymer) passes through a heat exchanger to raise the stream temperature, thus preparing the polymer for separation from other lower-boiling-point reactants. The stream then passes through a pressure-reducing control valve responsible for maintaining the reactor pressure at a specified target. Subsequently, the stream enters a secondary separation and devolatilization system, where the polymer is removed from the solvent, hydrogen, and unreacted monomers and comonomers. Impurities are removed from the recycled lower-boiling-point reactants, which then re-enter the reactor. The separated and devolatiled polymer melt is pumped through a heat exchanger to reduce the flow temperature to less than 200°C, for example, less than 170°C or a temperature in the range of 50°C to 110°C; thus producing a cooled polymer melt. The cooled polymer melt is then pumped through a die specially designed for underwater granulation, cut into uniform solid beads, dried, and transferred to a hopper. After verifying the initial polymer properties, the solid polymer beads are transferred to a storage device. The portion removed in the devolatileization step can be recycled or destroyed. For example, most of the solvent is recycled back to the reactor after passing through a purification bed. This recycled solvent may still contain unreacted comonomers, which are then reinforced with fresh comonomers before re-entering the reactor. The recycled solvent may also still contain some hydrogen, which is then reinforced with fresh hydrogen.

[0028] One or more additives in the composition

[0029] The composition also comprises one or more additives. The additives are selected from the group consisting of titanium dioxide, bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, talc, halloysite, organophilic pisilicates, or combinations thereof. In embodiments, the additives are selected from a more limited group. For example, in an embodiment, the additives are selected from the group consisting of bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, titanium dioxide, or combinations thereof. In another embodiment, the additive is bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate.

[0030] In embodiments, the composition comprises 0.05 wt% to 10.00 wt% of additives based on the total weight of the composition. All individual values ​​and sub-ranges from 0.05 wt% to 10.00 wt% are disclosed and included herein. For example, the composition may comprise additives from the lower limit of 0.05 wt%, 0.07 wt%, 0.09 wt%, 0.10 wt%, 0.50 wt%, 1.00 wt%, 1.50 wt%, 2.00 wt%, 3.00 wt%, 4.00 wt%, 5.00 wt% to the upper limit of 10.00 wt%, 9.00 wt%, 8.00 wt%, 7.00 wt%, 6.00 wt%, 5.00 wt%, 4.00 wt%, 3.00 wt%, 2.00 wt%, 1.00 wt%, 0.50 wt%, where the weight percentage is based on the total weight of the composition.

[0031] In embodiments, the additive is either melted during the formation of the meltblown nonwoven fabric or is a solid with a median particle size (D50) of less than 1 micrometer. For example, in one embodiment, a combination of titanium dioxide (wherein the titanium dioxide has a median particle size (D50) of less than 1 micrometer) and bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate (wherein the bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate has a melt-to-liquid temperature of about 100°C and melts during the formation of the meltblown nonwoven fabric (a formation process requiring temperatures greater than 100°C) is selected as the additive. In embodiments where the additive is a solid after the meltblown nonwoven fabric is formed, the additive may have a median particle size (D50) of less than 1 micrometer, less than 0.5 micrometer, or less than 0.25 micrometer. Without being theoretically constrained, smaller particle sizes (e.g., less than 1 micrometer) can reduce the likelihood of fiber breakage and reduce the likelihood of the spinneret clogging the die during the formation of the meltblown nonwoven fabric.

[0032] The composition can be formed by any suitable means known in the art, including, for example, dry blending or melt blending. Additives may be untreated or treated with a surface-treating agent (e.g., silanes, stearates, or surfactants) before being added to the composition, or treated in situ during the manufacture of the composition. One or more specific additives may be added to the ethylene / α-olefin interpolymer to increase the volume resistivity of the composition, and the composition may have an increased volume resistivity, making it suitable for filtration applications. Without being bound by theory, the addition of specific additives to the ethylene / α-olefin interpolymer during the formation of the composition and the meltblown nonwoven fabric alters the morphology of the composition or the meltblown nonwoven fabric, thereby increasing the volume resistivity of the composition or the meltblown nonwoven fabric and making them suitable for filtration applications.

[0033] In embodiments, the composition may have the following properties according to the methods disclosed herein or similar methods, wherein the volume resistivity is at room temperature. In some embodiments, the composition has a volume resistivity greater than 7.0E+16 ohm·cm at room temperature. All individual values ​​and sub-ranges greater than 7.0E+16 ohm·cm are disclosed and included herein. For example, the composition may have a volume resistivity greater than 7.0E+16 ohm·cm, greater than 8.0E+16 ohm·cm, greater than 9.0E+16 ohm·cm, greater than 1.0E+17 ohm·cm, greater than 2.0E+17 ohm·cm, greater than 3.0E+17 ohm·cm, greater than 4.0E+17 ohm·cm, or greater than 5.0E+17 ohm·cm, wherein the volume resistivity at room temperature can be measured according to the test methods described below.

[0034] In some embodiments, the composition has a volume resistivity greater than 7.0E+16 ohm·cm to 1.0E+19 ohm·cm, greater than 7.0E+16 ohm·cm to 5.0E+18 ohm·cm, greater than 7.0E+16 ohm·cm to 1.0E+18 ohm·cm, greater than 1.0E+17 ohm·cm to 1.0E+19 ohm·cm, greater than 1.0E+17 ohm·cm to 5.0E+18 ohm·cm, or greater than 1.0E+17 ohm·cm to 1.0E+18 ohm·cm, wherein the volume resistivity at room temperature can be measured according to the test methods described below.

[0035] The volume resistivity can also be measured at 60°C according to the test methods described below. In an embodiment, the composition has a volume resistivity greater than 5.0E+14 ohm·cm at 60°C. All individual values ​​and sub-ranges greater than 5.0E+14 ohm·cm are disclosed and included herein. For example, the composition may have a volume resistivity greater than 5.0E+14 ohm·cm, greater than 6.0E+14 ohm·cm, greater than 7.0E+14 ohm·cm, greater than 8.0E+14 ohm·cm, greater than 9.0E+14 ohm·cm, or greater than 1.0E+15 ohm·cm, wherein the volume resistivity at 60°C can be measured according to the test methods described below.

[0036] meltblown nonwovens

[0037] The composition can be used to form sheets, fibers, and / or nonwovens, such as meltblown nonwovens. As used herein, “meltblown” refers to fibers formed by extruding a molten thermoplastic polymer composition as molten yarns or filaments through multiple fine, typically circular, die capillary tubes into a converging high-speed airflow (e.g., air), the airflow acting to thin the yarns or filaments to reduce their diameter. The filaments or yarns are then carried by the high-speed airflow and deposited onto a collecting surface to form a nonwoven web of randomly dispersed meltblown fibers with an average diameter typically less than 10 micrometers. The terms “nonwoven,” “nonwoven web,” and “nonwoven fabric” are used interchangeably herein. “Nonwoven” refers to a web or fabric having a structure of individual fibers or threads that are randomly inserted rather than in a identifiable manner as in knitted fabrics.

[0038] In embodiments, meltblown nonwovens formed from the composition according to the methods disclosed herein or similar methods can have the following properties, wherein the volume resistivity is at room temperature. In some embodiments, the meltblown nonwovens formed from the composition have a volume resistivity greater than 7.0E+16 ohm·cm. This document discloses and includes all individual values ​​and sub-ranges greater than 7.0E+16 ohm·cm. For example, meltblown nonwovens formed from the composition can have volume resistivity greater than 7.0E+16 ohm·cm, greater than 8.0E+16 ohm·cm, greater than 9.0E+16 ohm·cm, greater than 1.0E+17 ohm·cm, greater than 2.0E+17 ohm·cm, greater than 3.0E+17 ohm·cm, greater than 4.0E+17 ohm·cm, or greater than 5.0E+17 ohm·cm, wherein the volume resistivity at room temperature can be measured according to the test methods described below.

[0039] In some embodiments, the meltblown nonwoven fabric formed from the composition has a volume resistivity greater than 7.0E+16 ohm.cm to 1.0E+19 ohm.cm, greater than 7.0E+16 ohm.cm to 5.0E+18 ohm.cm, greater than 7.0E+16 ohm.cm to 1.0E+18 ohm.cm, greater than 1.0E+17 ohm.cm to 1.0E+19 ohm.cm, greater than 1.0E+17 ohm.cm to 5.0E+18 ohm.cm, or greater than 1.0E+17 ohm.cm to 1.0E+18 ohm.cm, wherein the volume resistivity at room temperature can be measured according to the test methods described below.

[0040] In embodiments, the meltblown nonwoven fabric formed from the composition comprises fibers with a diameter of less than 10 micrometers. This document discloses and includes all individual values ​​and sub-ranges of less than 10 micrometers. For example, in embodiments, the meltblown nonwoven fabric described herein may comprise fibers having a diameter of less than 10 micrometers, less than 8 micrometers, less than 6 micrometers, less than 4 micrometers, less than 2 micrometers, or less than 1 micrometer, or may comprise fibers having a diameter in the range of 0.1 micrometers to 10 micrometers, 0.1 to 8 micrometers, 0.1 to 6 micrometers, 0.1 to 4 micrometers, 0.1 to 2 micrometers, or 0.1 to 1 micrometer.

[0041] Meltblown nonwovens can be used in composite structures. Composite structures may also include one or more spunbond nonwovens. As used herein, "spunbond" refers to fibers formed by extruding a molten thermoplastic polymer composition as filaments through multiple fine (typically circular) die capillaries of a spinneret. The diameter of the extruded filaments is then rapidly reduced, and the filaments are deposited on a collecting surface to form a web or fabric with randomly dispersed spunbond fibers, typically with an average diameter between about 7 micrometers and about 30 micrometers. Spunbond fibers can be bicomponent or monocomponent fibers. Monocomponent fibers may include polyethylene. Bicomponent fibers may have a sheath / core structure, wherein the sheath comprises polyethylene and the core comprises polypropylene. Of course, other configurations of bicomponent fibers can be used, such as side-by-side arrangement, disc arrangement, or "island" arrangement.

[0042] In some implementations, the composite structure has S a M b S c The configuration is defined as follows: S is a spunbond nonwoven fabric, M is a meltblown nonwoven fabric formed from the composition as described herein, and a, b, and c are the number of layers and are independent integers in the range of 1 to 5. For example, the composite structure may have SMS (where a = 1, b = 1, and c = 1), SMMS (where a = 1, b = 2, and c = 1), SSMSS (where a = 2, b = 1, and c = 2), SMMMS (where a = 1, b = 3, and c = 1), SMMSS (where a = 1, b = 2, and c = 2), or other configurations, since “a”, “b”, and “c” are independent of each other.

[0043] Products

[0044] Embodiments of the present invention also provide articles formed from the meltblown nonwovens described herein. Examples of such articles may include air filters, insulating materials, face masks, surgical gowns, bandages, and wound dressings. In view of the teachings herein, articles of the present invention can be formed from the meltblown nonwovens disclosed herein using techniques known to those skilled in the art.

[0045] Test methods

[0046] density

[0047] Density is measured according to ASTM D-792 and is expressed in grams per cubic centimeter (g / cc).

[0048] Brinell viscosity

[0049] Brinell viscosity was measured using a DV-II Pro Extra viscometer. This instrument uses Rheocalc V3.3 software, which provides excellent control and accuracy for the viscometer. An 8-gram sample was used with an SC4-31 rotor. The test temperature was 350°F. Sufficient spindle speed was applied so that the torque was between 40% and 70%. Viscosity data were recorded after 20 minutes once a stable viscosity reading was obtained.

[0050] Regular GPC

[0051] Conventional GPC was obtained using a high-temperature gel permeation chromatography (GPC) instrument (PolymerChar, Spain). An IR5 detector (“measurement channel”) was used as the concentration detector. GPCOne software (PolymerChar, Spain) was used to calculate the z-average molecular weight (Mz), weight-average molecular weight (Mw), and number-average molecular weight (Mn) of the polymer and to determine the MWD (=Mw / Mn). The method used either three 10-micron PL gel-mixed B columns (Agilent Technologies, column size 100 mm × 7.6 mm) or four 20-micron PL gel-mixed A columns (Agilent Technologies, column size 100 mm × 7.6 mm) operating at a system temperature of 150 °C. Samples at a concentration of 2 mg / mL were prepared via an autosampler (PolymerChar, Spain) in 1,2,4-trichlorobenzene solvent containing 200 million parts per million of the antioxidant butylated hydroxytoluene (BHT) at 160 °C with gentle shaking for 3 hours. The flow rate was 1.0 mL / min, and the injection volume was 200 μL. GPCOne software was used to calculate the plate count. The chromatographic system must have at least 22,000 plates.

[0052] GPC column sets were calibrated by running at least 20 polystyrene standards with narrow molecular weight distributions. Calibration used a third-order fit for systems with three 10-micron PL gel-mixed B columns, or a fifth-order fit for systems with four 20-micron PL gel-mixed A columns. The standards ranged in molecular weight (MW) from 580 g / mol to 8,400,000 g / mol and were contained in six “cocktail” mixtures. Each standard mixture had approximately ten resolutions across its molecular weights. These standard mixtures were purchased from Agilent Technologies. The polystyrene standards were prepared as follows: for molecular weights equal to or greater than 1,000,000 g / mol, 0.025 g in 50 mL of solvent was used, and for molecular weights less than 1,000,000 g / mol, 0.05 g in 50 mL of solvent was used. The polystyrene standards were dissolved at 80°C for 30 minutes with gentle stirring. First, operate the narrow standard mixture, following the order of decreasing molecular weight components to minimize degradation. Use equation (1) to convert the peak molecular weight of the polystyrene standards to the molecular weight of polyethylene (as described by Williams and Ward, *Journal of Polymer Science, Polymer Letters*, 6, 621 (1968)).

[0053] MW PE =A×(MW) PS ) B (Equation 1)

[0054] Where MW is the molecular weight of the labeled polyethylene (PE) or polystyrene (PS), and B equals 1.0. Those skilled in the art know that A can range from about 0.38 to about 0.44, such that an A value yields 52,000 MWPE for Standard Reference Material (SRM) 1475a. The molecular weight values ​​(e.g., molecular weight distribution (MWD or Mw / Mn)) and related statistics obtained using this polyethylene calibration method are defined herein as the modified Williams and Ward method. Number-average molecular weight, weight-average molecular weight, and z-average molecular weight are calculated by the following equations.

[0055] M n，cc =∑w i / ∑(w i / M cc，i (Equation 2)

[0056] M w，cc =∑w i M cc，i (Equation 3)

[0057]

[0058] Where Mn，cc M w，cc and M z，cc (In g / mol) represent the number-average molecular weight, weight-average molecular weight, and z-average molecular weight obtained from routine calibration. W i In the retention volume V i The weight fraction of polyethylene molecules eluted. M cc，i The value obtained using standard calibration is in the retention volume V. i The molecular weight (in g / mol) of the polyethylene molecules eluted below (see equation (1)).

[0059] When viewing the chromatogram at a 20% peak height, the chromatographic peaks should be set to include the marked region that deviates significantly from the baseline. The baseline integral should not be less than 100 polyethylene equivalent molecular weight, and mismatches between the antioxidant and the prepared sample and chromatographic mobile phase must be carefully handled. Referring to Figure 1, an appropriate set of baselines and integral limits for the sample is depicted, showing clear, independent antioxidant peaks.

[0060] The use of decane flow rate markers can be shown in the IR5 chromatogram. The difference in baseline (response) Y-values ​​between the baseline start and endpoint should never exceed 3% of the chromatogram integrated peak height. In such cases, the chromatographic sample must be properly treated by ensuring proper matching between the sample and the mobile phase antioxidant. An appropriate set of baselines and integration limits for the sample should exhibit continuity toward 100 polyethylene equivalent molecular weight. The final integration limit should never be set below 100 polyethylene equivalent molecular weight.

[0061] W (greater than 10) 5 According to equation (5), the weight fraction in g / mol is calculated based on the MWD curve (wi and logM) obtained from GPCOne software. cc，i )calculate

[0062]

[0063] Differential scanning calorimetry (DSC)

[0064] DSC is used to measure the melt and crystallization properties of polymers over a wide temperature range. For example, this analysis is performed using a TA instrument Q1000DSC equipped with a refrigerated cooling system (RCS) and an autosampler. During testing, a nitrogen purge gas flow of 50 ml / min is used. Each sample is melt-pressed into a thin film at approximately 175 °C; the molten sample is then cooled to room temperature (approximately 25 °C). Film samples are formed by pressing 0.1 g to 0.2 g of sample at 1,500 psi for 30 seconds to create a film of 0.1 mil to 0.2 mil thickness. A 6 mm diameter sample of 3 mg to 10 mg is drawn from the cooled polymer, weighed, placed in a light aluminum pan (approximately 50 mg), and rolled up. Analysis is then performed to determine its thermal properties.

[0065] The thermal properties of a sample were determined by generating a heat flow versus temperature curve through steep inclines and declines in sample temperature. First, the sample was rapidly heated to 180°C and held isothermally for five minutes to remove its thermal history. Next, the sample was cooled to -40°C at a cooling rate of 10°C / min and held isothermally at -40°C for five minutes. Then, the sample was heated to 150°C at a heating rate of 10°C / min (this is the "second heating" homogenization). The cooling and heating curves were recorded. The cooling curve was analyzed by setting a baseline endpoint from the start of crystallization to -20°C. The heating curve was analyzed by setting a baseline endpoint from -20°C to the end of melting. The measured value is the peak melting temperature (T0). m ), highest peak crystallization temperature (T) c ), heat of fusion (H) f (in joules / gram) and the crystallinity % of the polyethylene sample calculated using the following formula: Crystallinity % = ((H f (292 J / g) × 100. The heat of fusion (H₂) is reported from the second thermal curve. f The maximum peak melting temperature is determined from the cooling curve.

[0066] Crystallization Elution Fraction (CEF) Method

[0067] Comonomer distribution analysis (often also known as short-chain branching distribution (SCBD)) was performed using an IR-4 detector (PolymerChar, Spain) and a dual-angle light scattering detector, model 2040 (Precision Detectors, now Agilent Technologies). Crystallization elution fractionation (CEF) was performed using Polymocha Technologies (Monrabal et al., Proceedings of the Macromol Symposium, 257, 71-79 (2007), which is incorporated herein by reference). An IR-4 or IR-5 detector was used. A 10- or 20-micron guard column (PolymerLab, now Agilent Technologies) measuring 50 mm × 4.6 mm was mounted just before the IR-4 or IR-5 detector in the detector oven. o-Dichlorobenzene (ODCB, 99% anhydrous) and 2,5-di-tert-butyl-4-methylphenol (“BHT”, catalog number B1378-500G, lot number 098K0686) were obtained from Sigma-Aldrich. The ODCB was distilled before use. Also obtained from EMD... Chemicals obtains silica gel 40 (particle size 0.2 mm to 0.5 mm, catalog number 10181-3). Before use, the silica gel is dried in a vacuum oven at 160°C for approximately two hours. 800 mg BHT and 5 g silica gel are added to two liters of ODCB. ODCB can also be dried by passing it through one or more columns packed with silica gel. For CEF instruments equipped with an autosampler with N2 purging capability, silica gel 40 is packed into two 300 mm × 7.5 mm GPC-sized stainless steel columns, and the silica gel 40 columns are installed at the inlet of the CEF instrument's pump to dry the ODCB. BHT is not added to the mobile phase. This "ODCB containing BHT and silica gel" or ODCB dried with silica gel 40 is now referred to as "ODCB". ODCB is bubbled with dry nitrogen (N2) for one hour before use. The dry nitrogen is obtained by passing nitrogen at <90 psig through CaCO3 and... Molecular sieves were used. The resulting nitrogen gas should have a dew point of approximately -73°C. Samples were prepared at 160°C with shaking at a concentration of 4 mg / mL (unless otherwise specified) using an autosampler for 2 hours. The injection volume was 300 μL. The temperature profile for CEF was as follows: crystallization from 110°C to 30°C at 3°C / min; thermal equilibration at 30°C for 5 min (including a 2 min elution time for the soluble fraction); and elution from 30°C to 140°C at 3°C / min. The flow rate during crystallization was 0.052 mL / min. The flow rate during the cooling step was 0.052 mL / min. The flow rate during elution was 0.50 mL / min. Data were collected at a rate of one data point per second. According to U.S. Patent 8,372,931, the CEF column was filled with 125 μm ± 6% glass beads (MO-SCI specialty product) through 1 / 8-inch stainless steel tubing, which is incorporated herein by reference. The column outer diameter (OD) is 1 / 8 inch. Key parameters required to repeat this method include the column inner diameter (ID) and column length (L). The selection of ID and L must ensure that the internal liquid volume is between 2.1 mL and 2.3 mL when filled with glass beads of 125 μm diameter. If L is 152 cm, then ID must be 0.206 cm and the wall thickness must be 0.056 cm. Different L and ID values ​​can be used as long as the glass bead diameter is 125 μm and the internal liquid volume is between 2.1 mL and 2.3 mL. Column temperature calibration was performed using a mixture of NIST standard reference material linear polyethylene 1475a (1.0 mg / mL) and eicosane (2 mg / mL) in ODCB. CEF temperature calibration consisted of the following four steps: (1) calculating the delayed volume defined as the measured peak eicosane elution temperature minus the temperature offset between 30.00 °C; (2) subtracting the temperature offset of the elution temperature from the raw CEF temperature data. It should be noted that this temperature bias is a function of experimental conditions, such as elution temperature, elution flow rate, etc.; (3) A linear calibration line for switching elution temperatures in the range of 30.00 °C and 140.00 °C is established such that NIST linear polyethylene 1475a has a peak temperature at 101.0 °C and eicosane has a peak temperature at 30.0 °C; (4) For soluble fractions measured isothermally at 30 °C, the elution temperature is linearly extrapolated by using an elution heating rate of 3 °C / min. The reported elution peak temperatures are obtained such that the observed comonomer content calibration curves are the same as those previously reported in U.S. Patent 8,372,931, which is incorporated herein by reference. CEF data are processed using GPCOne software (Perimocha, Spain).

[0068] Volume resistivity

[0069] Volume resistivity was determined using the following method based on ASTM D257. Volume resistivity was measured using a Keithley 6517B electrometer in conjunction with a Keithley 8009 test fixture. The Keithley 8009 test chamber was located within a forced-ventilation oven capable of operating at high temperatures (maximum 80°C). Leakage current was recorded from the instrument using software, and volume resistivity (VR) was calculated using the following equation (Equation 6):

[0070]

[0071] Where ρ is the volume resistivity in ohms·cm, V is the applied voltage in volts, and A is the volume resistivity in cm⁻¹. 2 I is the electrode contact area in units, I is the leakage current in amperes recorded after 10 minutes of voltage application, and t is the sample thickness. The thickness of the compression molded plate was measured before testing. Five points on the plate were measured to obtain the average thickness, which was used in the calculations. Tests were conducted at 1000 volts at room temperature, where the room temperature ranged from 20°C to 25°C, and at 1000 volts at 60°C, where the Keithley 8009 test chamber was first stabilized at 60°C for 1 hour before VR measurement. Two compression molded plates were tested for both room temperature and 60°C conditions, and the recorded VR was the average of the two tests. Results are expressed in ohms-cm (ohm·cm).

[0072] Example

[0073] The following examples illustrate the features of this disclosure, but are not intended to limit the scope of this disclosure.

[0074] Material

[0075] The following materials are included in the embodiments.

[0076] The experimental fiber resin (hereinafter referred to as "Polymer 1") was used as an ethylene / α-olefin interpolymer of the compositions of the examples. Polymer 1 corresponds to "Invention 4" of PCT Publication WO 2018 / 169738, the entire contents of which are incorporated herein by reference. Polymer 1 has the properties as provided in PCT Publication WO 2018 / 169738, including those provided in Table 1.

[0077] Table 1 :

[0078]

[0079] Ti-Pure TMR-104, titanium dioxide, with a median particle size (D50) of 0.24 micrometers, is commercially available from The Chemours Company (Wilmington, DE).

[0080] Bis-TEMPO, bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, has a melt-to-liquid temperature of approximately 100°C and is commercially available from Suqian Unitech Co., Ltd. (Jiangsu, China). The formation temperature of meltblown nonwovens exceeds 180°C, therefore bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate becomes liquid during the formation of the meltblown nonwoven.

[0081] SD-900, talc, with a median particle size (D50) of 2.6 micrometers, is commercially available from Liaoning Xinda Talc Group (China).

[0082] DRAGONITE TM HP, halloysite, with a median particle size (D50) of approximately 50 nanometers, is commercially available from Applied Minerals, Inc. (New York, USA).

[0083] Cloisite 20A, an organophilic phyllosilicate with a median particle size (D50) of approximately 10 micrometers, is commercially available from BYK (Germany).

[0084] Barium titanate, with a median particle size (D50) of approximately less than 100 nanometers, is commercially available from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

[0085] Magnesium stearate has a melt-to-liquid temperature of approximately 150 degrees Celsius and is commercially available from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The formation temperature of meltblown nonwovens exceeds 180 degrees Celsius, therefore magnesium stearate becomes liquid during the formation of meltblown nonwovens.

[0086] Calcium stearate has a melt-to-liquid temperature of approximately 150 degrees Celsius and is commercially available from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The formation temperature of meltblown nonwovens exceeds 180 degrees Celsius, therefore calcium stearate becomes liquid during the formation of meltblown nonwovens.

[0087] Sample preparation

[0088] Polymer 1 was fed into a Brabender mixer set at 120°C and a rotor speed of 30 rpm. The resin was heated and melted, and then any one or more additives (at the concentrations listed in the table below) were added to the mixer. Mixing continued for seven minutes at 50 rpm to disperse any one or more additives. The composition was collected and pressed into a sheet in a 160 mm × 160 mm × 1.0 mm mold. The sheet was preheated at 150°C for 5 minutes, then degassed, followed by another 3-minute pressing process at 150°C. The volume resistivity (VR) of the sheet was then tested according to the test method described above.

[0089] Meltblown nonwovens are formed using the same composition used to form the sheets. Additive masterbatch pellets are dry-blended with ethylene / α-olefin interpolymer pellets and fed into the meltblown line extruder. 25 gsm meltblown nonwovens are manufactured on conventional meltblown lines via air-jet spinning, which refines the fibers to a diameter of less than 10 micrometers. Examples of conventional meltblown lines include, but are not limited to, the RF4 / RF5 single-row meltblown line (manufactured by Reicofil) and the biaxial meltblown line (manufactured by Biax-Fiberfilm).

[0090] Table 2 below shows the concentrations of polymer 1 and any additives, as well as VR measurements of the present invention and comparative examples at room temperature ("@RT") and at 60°C ("@60°C"), based on plates formed as described above.

[0091] As seen in the embodiments of the present invention (IE1 to IE8), the compositions of this disclosure surprisingly and unexpectedly exhibit a significant amount (e.g., up to an order of magnitude in some cases) of VR increase. Conversely, as seen in the comparative examples (CE1 to CE4), the absence of additives or the addition of certain other additives did not increase VR. Without being bound by any theory, the results surprisingly demonstrate the synergistic effect of the components in the embodiments of the present invention in enhancing VR.

[0092] Table 2 :

[0093]

[0094]

[0095] *Bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate

[0096] **NM = Not measured

[0097] Unless expressly excluded or otherwise limited, every document cited herein (if any), including any cross-referenced or related patent or application and any patent application or patent claiming priority or benefit to this application, is hereby incorporated in its entirety by reference. No reference to any document acknowledges it as prior art to any invention disclosed or claimed herein, or as teaching, indicating, or disclosing any such invention, alone or in combination with any other referenced document. Furthermore, in the event of any conflict between the meaning or definition of any term in this document and the meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to the term in this document shall prevail.

[0098] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be covered in the appended claims.

Claims

1. A meltblown nonwoven fabric formed from a composition comprising: (i) 94% to 99.95% by weight of an ethylene / α-olefin interpolymer, said ethylene / α-olefin interpolymer having a density of 0.911 g / cc to 0.939 g / cc, a Brookfield viscosity of less than or equal to 50,000 cP, and a molecular weight distribution of 1.8 to 3.5 Mw,cc / Mn,cc, wherein said α-olefin is selected from 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4-methyl-1-pentene; and (ii) 0.05% to 6% by weight of an additive, said additive being selected from the group consisting of titanium dioxide, bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, halloysite, organophilic folinic silicates, or combinations thereof; and The composition described herein has a volume resistivity greater than 7.0E+16 ohm·cm at room temperature.

2. The meltblown nonwoven fabric according to claim 1, wherein the additive is melted into a liquid during the formation of the meltblown nonwoven fabric, or is a solid with a median particle size D50 of less than 1 micrometer.

3. The meltblown nonwoven of claim 1 or 2, wherein the ethylene / alpha-olefin interpolymer has an Mw / Mn less than 5.25 z,cc / M n,cc .

4. The meltblown nonwoven of claim 1 or 2, wherein the ethylene / alpha-olefin interpolymer has a weight fraction w of less than 2.5% of the total weight of the interpolymer having a molecular weight greater than 10 5 g / mol as determined by conventional gel permeation chromatography.

5. The meltblown nonwoven fabric according to claim 1 or 2, wherein the additive is selected from the group consisting of bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate, titanium dioxide, or combinations thereof.

6. The meltblown nonwoven fabric according to claim 1 or 2, wherein the additive is bis(2,2,6,6-tetramethyl-1-piperidinoxy-4-yl) sebacate.

7. The meltblown nonwoven fabric according to claim 1 or 2, wherein the meltblown nonwoven fabric comprises fibers having a diameter of less than 10 micrometers.

8. The meltblown nonwoven fabric according to claim 1 or 2, wherein the composition has a volume resistivity greater than 5.0E+14 ohm·cm at 60°C.

9. The meltblown nonwoven of claim 1 or 2, wherein the ethylene / alpha-olefin interpolymer has an Mw / Mn less than 4.

0. z,cc / M n,cc .

10. The meltblown nonwoven fabric according to claim 1 or 2, wherein the ethylene / α-olefin interpolymer has an M value of less than 3.

5. z,cc / M n,cc .

11. The meltblown nonwoven fabric according to claim 1 or 2, wherein, based on the total weight of the interpolymer, the ethylene / α-olefin interpolymer has less than 1.0% of molecules with a molecular weight greater than 10. 5 The weight fraction w in g / mol was determined by conventional gel permeation chromatography.

12. An air filter comprising the meltblown nonwoven fabric according to any one of claims 1-11.

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