Microporous membranes exhibiting improved durability and methods of making the same

Abstract

A microporous membrane is provided comprising 1) an organic polymeric matrix and 2) a particulate filler distributed throughout the matrix. The matrix comprises: a polyolefin component comprising ultra-high molecular weight polyethylene present in the organic polymeric matrix in an amount of 1 to 80 wt%; and an aliphatic polyketone polymer present in the organic polymeric matrix in an amount of 1 to 80 wt%. The particulate filler exhibits a total particle size in the range of 5 to 40 microns, is distributed throughout the organic polymeric matrix, and is present in the microporous membrane in an amount of 10 to 90 wt% based on the total weight of the microporous membrane, as determined by use of a laser diffraction particle size instrument.

Description

Technical Field

[0001] This disclosure relates to microporous membranes exhibiting excellent durability and methods for preparing such microporous membranes. Background Technology

[0002] The manufacture of microporous polyolefin materials and membranes for a wide range of industrial and consumer applications is well-known. Filled microporous membranes are considered low-cost, efficient, and environmentally friendly materials. However, they are generally not UV stable and tend to disintegrate after prolonged exposure to ultraviolet radiation, such as during outdoor use. They also have end-use limitations related to high-temperature instability due to their low melting temperatures.

[0003] Methods to address the UV instability of these films have included adding UV absorbers and light stabilizers during manufacturing. However, these additives only improve UV stability by 5% to 10%; they are also expensive and may contain concerning substances. Microporous substrates can be coated to modify their surface and improve UV properties; however, such coatings tend to have short lifespans, and the fragility of the underlying substrate poses a risk of failure if the protective coating is broken, scratched, or degraded.

[0004] The aim is to provide microporous membranes that exhibit durability in terms of UV and high-temperature stability, while retaining the advantageous properties typically known for microporous polyolefin membranes, such as flexibility, high porosity, and excellent printability. Furthermore, it is desirable to use a process for preparing such membranes that employs current manufacturing steps and equipment without modification. Summary of the Invention

[0005] This disclosure relates to a microporous membrane comprising 1) an organic polymer matrix and 2) finely fragmented, particulate, substantially water-insoluble filler distributed throughout the organic polymer matrix. The organic polymer matrix 1) comprises: (a) a polyolefin component comprising ultra-high molecular weight (UHMW) polyethylene, wherein the polyolefin component is present in the organic polymer matrix in an amount of 20 to 99% by weight based on the total weight of the organic polymer matrix; and (b) an aliphatic polyketide polymer, which is present in the organic polymer matrix in an amount of 1 to 80% by weight based on the total weight of the organic polymer matrix. The filler 2) is present in the microporous membrane in an amount of 10% to 90% by weight based on the total weight of the microporous membrane. Detailed Implementation

[0006] Except in any operational instance, or where otherwise indicated, all figures used in the specification and claims to indicate, for example, the quantity of components, should be understood to be modified in all cases by the term “about.” Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that can vary depending on the desired properties to be obtained from the disclosed membrane. At least, and not in an attempt to limit the application of the doctrine of equivalence to the scope of the claims, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying ordinary rounding techniques.

[0007] Although the numerical ranges and parameters described in this disclosure are approximate, the numerical values ​​presented in specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard variation present in its corresponding test measurement results.

[0008] Furthermore, it should be understood that any numerical range described herein is intended to include all subranges thereof. For example, the range “1 to 10” is intended to include all subranges between the stated minimum value of 1 and the stated maximum value of 10, that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0009] In this application, unless otherwise specifically stated, the use of the singular includes the plural, and the plural encompasses the singular. Further, in this application, unless otherwise specifically stated, the use of “a” or “an” means “at least one / a.” For example, “an” additive, “an” silica, etc., refers to one or more of these items. Moreover, as used herein, the term “polymer” means both prepolymers, oligomers, and homopolymers and copolymers. The terms “resin” and “polymer” are used interchangeably.

[0010] This disclosure relates to a microporous membrane. As used herein, “microporous material”, “microporous membrane”, or “microporous sheet” refers to a material having an interconnected network of pores, wherein, without treatment, coating, printing ink, impregnation agent, and pre-bonding, the volume-average diameter of the pores is typically in the range of 0.001 to 1.0 micrometers, and can constitute at least 5% of the volume of the microporous material as described below.

[0011] The volume-average diameter of the pores in microporous materials can be determined using the Autopore III porosimeter (Micromeritics, Inc., Norcross, Georgia) according to the accompanying instruction manual, via the mercury porosimetry method. The volume-average pore radius for a single scan is automatically determined by the porosimeter. When operating the porosimeter, scans are performed in the high-pressure range (from 138 kPa to 227 MPa). If approximately 2% or less of the total infused mercury volume occurs at the lower end of the high-pressure range (138 to 250 kPa), the volume-average pore diameter is taken as twice the volume-average pore radius determined by the porosimeter. Otherwise, scans are performed in the low-pressure range (7 to 165 kPa), and the volume-average pore diameter is calculated using the following formula:

[0012]

[0013] Where d is the volume-average pore diameter, v1 is the total volume of mercury injected in the high-pressure range, v2 is the total volume of mercury injected in the low-pressure range, r1 is the volume-average pore radius determined by the high-pressure scan, r2 is the volume-average pore radius determined by the low-pressure scan, w1 is the sample weight after the high-pressure scan, and w2 is the sample weight after the low-pressure scan.

[0014] During the determination of the volume-average pore diameter in the above process, the maximum pore radius detected is sometimes recorded. This is taken from a low-pressure range scan (if running); otherwise, it is taken from a high-pressure range scan. The maximum pore diameter is twice the maximum pore radius. Due to some production or processing steps, such as coating, printing, impregnation, and / or bonding processes, at least some pores of the microporous material may be filled, and because some of these processes irreversibly compress the microporous material, parameters regarding porosity, volume-average pore diameter, and maximum pore diameter of the microporous material are determined before applying one or more of these production or processing steps.

[0015] The organic polymer matrix comprises (a) a polyolefin component, which in turn comprises ultra-high molecular weight (UHMW) polyethylene. Non-limiting examples of ultra-high molecular weight (UHMW) polyethylene may include substantially linear UHMW polyethylene (PE). Since UHMW polyolefins are not thermosetting polymers with an infinite molecular weight, they are technically classified as thermoplastic materials.

[0016] While there is no specific upper limit on the intrinsic viscosity of UHMW polyethylene, the intrinsic viscosity range can be, for example, at least 6 dL / g, or at least 7 dL / g, or at least 18 dL / g, up to at most 50 dL / g, or at most 45 dL / g, or at most 18 dL / g, or at most 16 dL / g. Therefore, the intrinsic viscosity of UHMW can be, for example, 6 to 50 dL / g, or 6 to 45 dL / g, or 6 to 18 dL / g, or 6 to 16 dL / g, or 7 to 50 dL / g, or 7 to 45 dL / g, or 7 to 18 dL / g, or 7 to 16 dL / g, or 18 to 50 dL / g, or 18 to 45 dL / g.

[0017] For the purposes of this disclosure, the intrinsic viscosity can be determined by extrapolating the specific viscosity or intrinsic viscosity of several diluted solutions of UHMW polyolefin to zero concentration, wherein the solvent is freshly distilled decahydronaphthalene with 0.2 wt% of neopentanetetraester of 3,5-di-tert-butyl-4-hydroxyhydrocinnamate [CAS Registry No. 6683-19-8]. The specific viscosity or intrinsic viscosity of UHMW polyolefin is determined according to the general procedure of ASTM D 4020-81 using an Ubbelohde viscometer at 135°C, except that several diluted solutions of different concentrations are used.

[0018] The nominal molecular weight of UHMW polyethylene is empirically related to the intrinsic viscosity of the polymer, according to the following formula:

[0019] M = 5.37 × 10 4 [η] 1.37

[0020] Where M is the nominal molecular weight and [η] is the intrinsic viscosity of UHMW polyethylene expressed in deciliters per gram. Similarly, the nominal molecular weight of UHMW polypropylene is empirically related to the intrinsic viscosity of the polymer according to the following formula:

[0021] M = 8.88 × 10 4 [η] 1.25

[0022] Where M is the nominal molecular weight and [η] is the intrinsic viscosity of UHMW polypropylene expressed in deciliters per gram.

[0023] Based on the total weight of the organic polymer matrix, UHMW polyethylene may be present in the organic polymer matrix in an amount of at least 18 wt%, or at least 25 wt%, or at least 40 wt% and at most 99 wt%, or at most 97 wt%, or at most 95 wt%. For example, UHMW polyethylene may be present in the organic polymer matrix in an amount of 18 wt% to 99 wt%, or 18 wt% to 97 wt%, or 18 wt% to 95 wt%, or 25 wt% to 99 wt%, or 25 wt% to 97 wt%, or 25 wt% to 95 wt%, or 40 wt% to 99 wt%, or 40 wt% to 97 wt%, or 40 wt% to 95 wt%.

[0024] Typically, the polyolefin component (a) further comprises high-density polyethylene (HDPE), which is present in an amount of up to 75% by weight based on the total weight of the polyolefin component (a). When used, HDPE may be present in the organic polymer matrix 1) in an amount of at least 0.1% by weight, or at least 1% by weight and up to 74.25% by weight, or up to 60% by weight, or up to 45% by weight based on the total weight of the organic polymer matrix. For example, HDPE may be present in the organic polymer matrix in an amount of 0.1 to 74.25% by weight, or 0.1 to 60% by weight, or 0.1 to 45% by weight, or 1 to 74.25% by weight, or 1 to 60% by weight, or 1 to 45% by weight based on the total weight of the organic polymer matrix.

[0025] In some instances, other thermoplastic organic polymers may also be present in the polyolefin component (a), provided that their presence does not adversely affect the properties of the microporous material substrate. The amount of other thermoplastic polymers that may be present depends on the properties of such polymers. Non-limiting examples of thermoplastic organic polymers that may optionally be present in the microporous material substrate include low-density polyethylene, poly(tetrafluoroethylene), polypropylene, copolymers of ethylene and propylene, copolymers of ethylene and butene, copolymers of ethylene and (meth)acrylic acid (i.e., acrylic acid and / or methacrylic acid), polyetherketone, polyvinylidene fluoride (PVDF), polysulfone, and / or polyethersulfone. If desired, all or part of the carboxyl groups of carboxyl-containing copolymers may be neutralized with sodium, zinc, etc. It should be noted that the phrase “and / or” when used in the list is intended to cover alternative examples that include each individual component in the list as well as any combination of components. For example, the list “A, B, and / or C” is intended to cover seven individual examples including A, or B, or C, or A+B, or A+C, or B+C, or A+B+C.

[0026] The organic polymer matrix 1) further comprises (b) an aliphatic polyketone polymer. Commercially available aliphatic polyketones are typically prepared from carbon monoxide and one or more olefin monomers, such as ethylene and propylene monomers. For the purposes of this disclosure, the polyketone has only carbon-carbon bonds along its backbone, in contrast to polyetherketones, which contain ether (-O-) bonds along their backbone. Suitable aliphatic polyketone polymers (b) comprise extrudable semi-crystalline thermoplastics having a melt range suitable for compounding with polyolefins in processes for constructing microporous substrates. Examples of suitable aliphatic polyketone polymers (b) include POKETONE™ resin, commercially available from Hyosung Chemical; unreinforced AKROTEK® PK resin, available from AKRO-PLASTIC GmbH; and unreinforced grades of Schulaketon®, available from LyondellBasell.

[0027] Aliphatic polyketone polymers (b) can exhibit melt indexes of 0.5 to 4 g / 10 min, typically 2 to 4 g / 10 min, or 3 g / 10 min as measured according to ASTM D1238-23. Suitable aliphatic polyketone polymers (b) typically exhibit melt temperatures of 190 to 220 °C as measured according to ASTM D3418-21.

[0028] Based on the total weight of the organic polymer matrix, the aliphatic polyketone polymer (b) may be present in the organic polymer matrix in an amount of at least 1% by weight, or at least 3% by weight, or at least 5% by weight and at most 80% by weight, or at most 75% by weight, or at most 60% by weight. For example, based on the total weight of the organic polymer matrix, the aliphatic polyketone polymer (b) may be present in the organic polymer matrix in an amount of 1 to 80% by weight, or 3 to 80% by weight, or 5 to 80% by weight, or 1 to 75% by weight, or 3 to 75% by weight, or 5 to 75% by weight, or 1 to 60% by weight, or 3 to 60% by weight, or 5 to 60% by weight.

[0029] The microporous membrane disclosed herein further comprises finely fragmented, particulate, substantially water-insoluble filler material distributed throughout the organic polymer matrix.

[0030] The filler may include any of a variety of fillers known in the art. The filler should be finely chopped and substantially insoluble in water to allow for uniform distribution throughout the organic polymer matrix during the fabrication of the microporous membrane. Generally, fillers include silica (such as precipitated silica), talc, carbon black, charcoal, graphite, titanium dioxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconium oxide, magnesium oxide, aluminum oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and / or magnesium carbonate. Typically, the filler comprises silica and / or calcium carbonate. For example, the filler may comprise silica and calcium carbonate, wherein the weight ratio of silica to calcium carbonate is in the range of 0.2:1 to 1:0.2.

[0031] Finely fragmented, substantially water-insoluble fillers can be in the form of final particles, aggregates of final particles, or a combination of both. "Finely fragmented" means that at least 90% by weight of the filler used to prepare the microporous membrane has a total particle size in the range of 5 to 40 micrometers, as determined by using a Beckman Coulter LS230 laser diffractometer capable of measuring particle diameters as small as 0.04 micrometers. Typically, at least 90% by weight of the filler has a total particle size in the range of 10 to 30 micrometers. During the processing of the components used to prepare the microporous membrane, the size of the filler aggregates can be reduced. Therefore, the total particle size distribution in the microporous membrane can be smaller than the total particle size distribution of the raw filler itself.

[0032] As mentioned earlier, the filler particles are substantially insoluble in water and also substantially insoluble in any organic processing liquid used to prepare microporous materials. "Substantially insoluble" means that, when dispersed in a liquid phase, less than 3% by weight or less than 1% by weight of the filler particles dissolves in the liquid phase at 25°C, based on the total weight of the filler particles. This promotes filler retention within the microporous material.

[0033] Packers typically possess a high surface area, allowing them to carry significant amounts of processing plasticizers used to form microporous membranes. High surface area packers are materials with extremely small particle sizes, high porosity, or exhibit both characteristics. The surface area of ​​the packer particles can range from at least 20 m² / g, or at least 25 m² / g, to at most 900 m² / g, or at most 850 m² / g; for example, 20 to 900 m² / g, or 20 to 850 m² / g, or 25 to 900 m² / g, or 25 to 850 m² / g, as determined according to ASTM C 819-77 by the Brunauer, Emmett, Teller (BET) method (using nitrogen as the adsorbate, but modified by degassing the system and sample at 130°C for one hour). Prior to nitrogen adsorption, the packing sample is dried by heating in flowing nitrogen (PS) to 160°C for one hour.

[0034] Inorganic fillers typically include silica, such as precipitated silica, silica gel, or fumed silica. Silica can exhibit a range of 125 to 700 μm as determined above. 2 / g of BET.

[0035] Commercially, silica gel is typically produced by acidifying an aqueous solution of a soluble metal silicate (such as sodium silicate) at a low pH. The acid used is usually a strong inorganic acid, such as sulfuric acid or hydrochloric acid, but carbon dioxide can also be used. Because there is essentially no density difference between the gel phase and the surrounding liquid phase, and due to its low viscosity, the gel phase does not settle; that is, it does not precipitate. Therefore, silica gel can be described as a non-precipitated, coherent, rigid three-dimensional network of continuous particles of colloidal amorphous silica. The subdivisions range from large solid masses to submicroscopic particles, and the degree of hydration ranges from nearly anhydrous silica to soft gel blocks, with approximately 100 parts by weight of water per part silica.

[0036] Commercially, precipitated silica is typically produced by mixing an aqueous solution of a soluble metal silicate (usually an alkali metal silicate, such as sodium silicate) with an acid, such that colloidal particles of silica grow in a weakly alkaline solution and are coagulated by the alkali metal ions of the resulting soluble alkali metal salt. A variety of acids can be used, including but not limited to inorganic acids. Non-limiting examples of acids that can be used include hydrochloric acid and sulfuric acid, but carbon dioxide can also be used to produce precipitated silica. Without a coagulant, silica will not precipitate from solution at any pH. The coagulant used to achieve silica precipitation can be a soluble alkali metal salt produced during the formation of colloidal silica particles, or it can be an added electrolyte, such as a soluble inorganic or organic salt, or a combination of both.

[0037] Precipitated silica can be described as precipitated aggregates of colloidal amorphous silica particles that do not exist in a macroscopic gel form at any point during preparation. The size and degree of hydration of these aggregates can vary considerably. Precipitated silica powder differs from pulverized silica in that it typically has a more open structure, i.e., a higher specific pore volume. However, the specific surface area of ​​precipitated silica, as measured by the Brunauer, Emmett, Teller (BET) method using nitrogen as the adsorbate, is generally lower than that of silica.

[0038] Many different precipitated silicas can be used as fillers for the fabrication of microporous membranes. Precipitated silica is a well-known commercial material, and its production methods are described in detail in numerous U.S. patents, including U.S. Patents 2,940,830 and 4,681,750. The average final particle size of the precipitated silica used (whether or not the final particles are agglomerated) is typically less than 0.1 micrometers, for example, less than 0.05 micrometers or less than 0.03 micrometers, as determined by transmission electron microscopy. Non-limiting examples of suitable precipitated silicas include those sold by PPG (Pittsburgh, Pennsylvania) under the trade name HI-SIL.

[0039] Based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler 2) may be present in the microporous membrane in an amount of at least 10% by weight, or at least 30% by weight, or at least 50% by weight and at most 90% by weight, or at most 80% by weight, or at most 75% by weight. For example, based on the total weight of the microporous membrane, filler 2) may be present in the microporous membrane in an amount of 10% to 90% by weight, or 10 to 80% by weight, or 10 to 75% by weight, or 30% to 90% by weight, or 30 to 80% by weight, or 30 to 75% by weight, or 50% to 90% by weight, or 50 to 80% by weight, or 50 to 75% by weight.

[0040] The microporous membrane disclosed herein further includes a network of interconnected pores throughout the microporous membrane.

[0041] Based on the absence of treatment, coating, or impregnation agents, such pores can account for at least 5% by volume, or at least 15% by volume, or at least 20% by volume, or at least 25% by volume, or at least 35% by volume, or at least 45% by volume, and up to 95% by volume, or up to 75% by volume. Therefore, such pores can account for 5 to 95% by volume, or 15 to 95% by volume, or 20 to 95% by volume, or 25 to 95% by volume, or 35 to 95% by volume, or 45 to 95% by volume, or 5 to 70% by volume, or 15 to 70% by volume, or 20 to 70% by volume, or 25 to 70% by volume, or 35 to 70% by volume, or 45 to 70% by volume. Typically, pores account for at least 35% by volume, or even at least 45% by volume, of the microporous membrane volume.

[0042] Porosity can be measured using a Model 4340 Gurley densitometer manufactured by GPI Gurley Precision Instruments (Troy, NY). The reported porosity value is a measurement of the rate at which airflow passes through the sample or its resistance to airflow through the sample. The unit of measurement for this method is the "Gurley second," which is the time (in seconds) required for 100 cc of air to pass through a 1 square inch area using a pressure difference of 4.88 inches of water column. Lower values ​​correspond to lower airflow resistance (allowing more air to pass freely). For the purposes of this disclosure, measurements were performed using the procedures outlined in the Model 4340 automatic densitometer manual. Typically, the membrane exhibits Gurley porosity of 10 to 5000 seconds, or 250 to 5000 seconds, or 500 to 5000 seconds, or 1000 to 5000 seconds, or 10 to 4500 seconds, or 250 to 4500 seconds, or 500 to 4500 seconds, or 1000 to 4500 seconds.

[0043] The microporous membrane may further comprise biodegradable accelerators, antioxidants, lubricants, UV absorbers, and / or UV light stabilizers distributed throughout the organic polymer matrix. Biodegradable accelerators are used to make the microporous membrane compostable and / or biodegradable. Examples include furanone compounds, glutaric acid, hexadecanoic acid compounds, sensory swelling agents (such as natural fibers, culture colloids, cyclodextrins, and polylactic acid), catalytic transition metal compounds, metal stearates, and / or metal chelates. Examples of suitable lubricants include calcium stearate, calcium-zinc stearate, zinc stearate, magnesium stearate, zinc phosphate, and magnesium phosphate. Antioxidants, such as those marketed by BASF under the names IRGANOX® and IRGAFOS®, and those marketed by Solvay under the name CYANOX®, are suitable for use. Non-limiting examples of suitable UV absorbers include UV absorbers available from BASF under the trade name TINUVIN® (such as TINUVIN® 1130) and UV absorbers available from Clariant under the trade name HOSTAVIN® PR-25. Examples of UV light stabilizers include benzophenone, benzotriazole, and hindered amine light stabilizers (HALS). Commercially available examples of UV stabilizers include HOSTAVIN® PR-31 available from Clariant, TINUVIN® 900 available from BASF, and CYANOX® M528 available from Solvay.

[0044] The aforementioned microporous membrane can be prepared by methods including the following:

[0045] (i) The organic polymer matrix, filler and processing plasticizer are mixed until a substantially homogeneous mixture is obtained, wherein the processing plasticizer is present in an amount of 30 to 80% by weight based on the total weight of the mixture;

[0046] (ii) Optionally, the mixture is introduced into the heated barrel of a screw extruder along with an additional processing plasticizer and the mixture is extruded through a tablet die to form a continuous sheet;

[0047] (iii) The continuous sheet formed by the die is conveyed to a pair of synergistic heated calendering rolls to form a continuous sheet with a smaller thickness than the continuous sheet leaving the die;

[0048] (iv) The sheet is conveyed to the first extraction zone, where the processing plasticizer is extracted from the sheet using an organic liquid;

[0049] (v) The continuous sheet is conveyed to a second extraction zone, where residual organic extract is extracted from the sheet by steam and / or water;

[0050] (vi) Pass the continuous sheet through a dryer to substantially remove residual water and remaining residual organic extract; and

[0051] (vii) Optionally, the continuous sheet is stretched above its elastic limit in at least one stretching direction, wherein stretching occurs during or immediately after step (ii) and / or step (iii), but before step (iv), to form a microporous membrane.

[0052] In an exemplary process, an organic polymer matrix (typically in solid form, such as powder or granules), fillers, processing plasticizers, and small amounts of lubricants and antioxidants are mixed until a substantially homogeneous mixture is obtained. The weight ratio of filler to polymer used to form the mixture is substantially the same as the weight ratio of filler to polymer for the microporous membrane to be produced. The mixture, along with additional processing plasticizers (if needed), is introduced into the heated barrel of a screw extruder. Connected to the extruder is a die, such as a tableting die, to form the desired final shape.

[0053] When material is formed into sheets or films, the continuous sheet or film formed by the die can be conveyed to a pair of synergistic heated calendering rolls to form a continuous sheet with a thinner thickness than the continuous sheet leaving the die. The final thickness may depend on the desired end use. Microporous membranes can have thicknesses ranging from 10 to 510 micrometers, such as 15 to 460 micrometers, or 15 to 390 micrometers, or 25 to 260 micrometers, or 125 to 250 micrometers.

[0054] Optionally, the sheet exiting the calendering rolls can then be stretched above its elastic limit in at least one stretching direction. Alternatively, stretching can be performed during or immediately after exiting the tableting die, or during calendering, or multiple times during the manufacturing process. Stretching can be performed before, after, or both of extraction. Additionally, stretching can be performed during the application of the pretreatment composition and / or the treatment composition, as described in more detail below. Stretched microporous material substrates can be prepared by stretching the intermediate product above its elastic limit in at least one stretching direction. Generally, the draw ratio is at least 1.2. In many cases, the draw ratio is at least 1.5. Often, it is at least 2. Typically, the draw ratio is in the range of 1.2 to 15. Often, the draw ratio is in the range of 1.5 to 10. Generally, the draw ratio is in the range of 2 to 6.

[0055] The temperature at which stretching is completed can vary considerably. Stretching can be performed at ambient room temperature, but is typically done at higher temperatures. Ambient temperatures are typically in the range of 60 to 90℉ (15.6 to 32.2°C), such as typical room temperature, 72℉ (22.2°C). The intermediate product can be heated before, during, and / or after stretching using any of a variety of techniques. Examples of these techniques include: radiant heating, such as heating provided by electric or gas-fired infrared heaters; convective heating, such as heating provided by recirculated hot air; and conductive heating, such as heating provided by contact with heated rollers. The temperature measured for temperature control purposes can vary depending on the equipment used and individual preferences. For example, temperature measuring devices can be placed to determine the surface temperature of the infrared heater, the internal temperature of the infrared heater, the air temperature at the point between the infrared heater and the intermediate product, the temperature of the circulating hot air at a point within the equipment, the temperature of the hot air entering or leaving the equipment, the surface temperature of the rollers used during stretching, the temperature of the heat transfer fluid entering or leaving such rollers, or the film surface temperature. Generally, one or more temperatures are controlled such that the intermediate product is stretched substantially uniformly, the variation (if any) in the film thickness of the stretched microporous material is within acceptable limits, and the amount of stretched microporous material outside these limits is acceptablely low. Obviously, the temperature used for control purposes may or may not be close to the temperature of the intermediate product itself, as these depend on the nature of the equipment used, the location of the temperature measuring device, and the characteristics of the substance or object being measured.

[0056] Considering the location of the heating device and the linear velocity typically used during stretching, a temperature gradient may or may not exist across the thickness of the intermediate product. Furthermore, due to such linear velocities, measuring these temperature gradients is impractical. When different temperature gradients occur, their presence makes referencing a single film temperature unreasonable. Therefore, measurable film surface temperatures are best suited for characterizing the thermal condition of the intermediate product.

[0057] The surface temperature of the film during stretching can vary considerably, but generally, it results in a roughly uniform stretching of the intermediate product, as described above. In most cases, the film surface temperature during stretching is in the range of 20°C to 220°C. Typically, such temperatures are in the range of 50°C to 200°C, such as 75°C to 180°C.

[0058] As needed, stretching can be performed in a single step or multiple steps. For example, when an intermediate product is to be stretched in a single direction (uniaxial stretching), stretching can be accomplished through a single stretching step or a series of stretching steps until the desired final stretch ratio is obtained. Similarly, when an intermediate product is to be stretched in two directions (biaxial stretching), stretching can be performed through a single biaxial stretching step or a series of biaxial stretching steps until the desired final stretch ratio is obtained. Biaxial stretching can also be achieved through a series of steps consisting of one or more uniaxial stretching steps in one direction and one or more uniaxial stretching steps in another direction. The biaxial stretching steps and uniaxial stretching steps in which the intermediate product is stretched simultaneously in two directions can be performed sequentially in any order. Stretching in more than two directions can be considered. It can be seen that there are quite a few possible arrangements of steps. Other steps, such as cooling, heating, sintering, annealing, winding, unwinding, etc., can be optionally included in the process as needed.

[0059] Various types of stretching equipment are well-known and can be used to complete the stretching of intermediate products. Uniaxial stretching is typically achieved by stretching between two rollers, where the second or downstream roller rotates at a greater circumferential speed than the first or upstream roller. Uniaxial stretching can also be performed on a standard tenter frame. Biaxial stretching can be achieved by stretching simultaneously in two different directions on a tenter frame. However, more commonly, biaxial stretching is achieved by first performing uniaxial stretching between two differentially rotating rollers as described above, and then performing uniaxial stretching in different directions using a tenter frame, or by performing biaxial stretching using a tenter frame. The most common type of biaxial stretching involves two stretching directions that are approximately right-angled with each other. In most cases where continuous sheets are stretched, one stretching direction is at least approximately parallel to the long axis of the sheet (machine direction), while the other stretching direction is at least approximately perpendicular to the machine direction and in the plane of the sheet (transverse).

[0060] Stretching the sheet prior to the extraction of the processing plasticizer can yield a thinner film with a larger pore size than conventionally processed microporous materials. It is also believed that stretching the sheet prior to the extraction of the processing plasticizer can minimize post-processing thermal shrinkage. It should also be noted that the stretching of the microporous membrane can be performed before, during, or after the application of the pretreatment composition (described below), and / or at any point before, during, or after the application of the treatment composition. During the processing, the stretching of the microporous membrane can occur once or multiple times.

[0061] The product enters a first extraction zone, where the processing plasticizer is extracted from the sheet using an organic liquid. This organic liquid is a good solvent for the processing plasticizer, a poor solvent for the organic polymer, and is more volatile than the processing plasticizer. Typically, but not always, both the processing plasticizer and the organic extract are substantially immiscible with water. The product then enters a second extraction zone, where residual organic extract is extracted from the sheet by steam and / or water. The product is then passed through a forced air dryer to substantially remove residual water and any remaining residual organic extract. When the microporous material is in sheet form, it can be conveyed from the dryer to a take-up roller.

[0062] Processing plasticizers exhibit almost no solvation effect on organic polymers at 60°C, moderate solvation at around 100°C, and significant solvation at around 200°C. They are liquids at room temperature and are typically processing oils, such as paraffin oils, naphthenic oils, or aromatic oils. Suitable processing oils include those meeting ASTM D2226-82, Type 103, and Type 104 requirements. Oils with pour points below 22°C or below 10°C according to ASTM D 97-66 (re-approved in 1978) are most commonly used. Examples of suitable oils include SHELLFLEX 412 and SHELLFLEX 371 oils (ShellOil Co. (Houston, TX)), which are solvent-refined and hydrogenated oils derived from naphthenic crude oils. Other materials, including phthalate plasticizers such as dibutyl phthalate, bis(2-ethylhexyl) phthalate, diisodecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, and ditridecyl phthalate, are expected to be satisfactorily used as processing plasticizers.

[0063] Many organic extractants can be used in the fabrication of microporous membranes. Examples of suitable organic extractants include, but are not limited to, 1,1,2-trichloroethylene; perchloroethylene; 1,2-dichloroethane; 1,1,1-trichloroethane; 1,1,2-trichloroethane; dichloromethane; chloroform; 1,1,2-trichloro-1,2,2-trifluoroethane; isopropanol; diethyl ether; acetone; hexane; heptane; and toluene. One or more azeotropes selected from trans-1,2-dichloroethylene, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, and / or 1,1,1,3,3-pentafluorobutane can also be used. These materials are commercially available as VERTREL MCA (a binary azeotrope of 1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropentane and trans-1,2-dichloroethylene: 62% / 38%) and VERTREL CCA (a ternary azeotrope of 1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropentane, 1,1,1,3,3-pentafluorobutane and trans-1,2-dichloroethylene: 33% / 28% / 39%); VERTREL SDG (80-83% trans-1,2-dichloroethylene, 17-20% hydrofluorocarbon mixture), all available from MicroCare Corporation (New Britain, Connecticut).

[0064] In the above-described method for manufacturing microporous membranes, extrusion and calendering are advantageous when the filler carries a large amount of processing plasticizer. The ability of the filler particles to absorb and retain processing plasticizer is a function of the filler surface area. Therefore, the filler typically has a high surface area as described above. Since it is desirable to retain the filler substantially within the microporous material substrate, the filler should be substantially insoluble in the processing plasticizer and substantially insoluble in the organic extractant when producing the microporous material substrate by the above method. The residual processing plasticizer content is typically less than 15% by weight of the resulting microporous material, and this content can be further reduced to levels such as less than 5% by weight through additional extraction using the same or different organic extractants. The resulting microporous membrane can be further processed according to the desired application.

[0065] The microporous membrane described above can be used to prepare multilayer membranes comprising two or more adjacent membrane layers. These layers may be the same as or different from each other, and at least one layer comprises the microporous membrane described above. For example, different embodiments of the microporous membrane described above can be used as independent layers, or these layers may be identical. Using different membrane layers allows the specific properties provided by each membrane to be incorporated into the final multilayer product.

[0066] In some instances, at least one layer of the multilayer membrane may comprise: a microporous polyolefin material, wherein the polyolefin material includes linear ultra-high molecular weight polyethylene, linear ultra-high molecular weight polypropylene, or mixtures thereof; and finely fragmented, particulate, substantially water-insoluble silica filler distributed throughout the microporous polyolefin material. Such polyolefin materials are available as TESLIN® from PPG.

[0067] Examples of other suitable materials that can be used as an additional layer include porous thermoplastic polymer sheets or films, porous thermosetting polymer sheets or films, porous elastomer sheets or films, and open-cell foams. Other examples include fabrics, such as woven fabrics, knitted fabrics, nonwoven fabrics, and loosely woven cloths. Still other examples include fiber mats, paper, synthetic paper, felt, etc. Further examples of suitable porous materials include microporous materials, such as the stretched microporous materials and precursor microporous materials described above, as well as other microporous materials. For fiber-based porous materials, the fibers can be natural, such as wood fibers, cotton fibers, wool fibers, silk fibers, etc.; or they can be any of the man-made fibers, such as polyester fibers, polyamide fibers, acrylic fibers, modified acrylic fibers, rayon fibers, etc.; or they can be combinations of different types of fibers. The fibers can be short fibers and / or they can be continuous. Metal fibers, carbon fibers, and glass fibers are also suitable.

[0068] Multilayer membranes can be constructed by bonding at least one layer of microporous material to at least one layer of porous material. A multilayer membrane may comprise one or more layers of microporous material and one or more layers of porous material. Optionally, the multilayer membrane may also be bonded to one or more layers of porous material. For example, the microporous material may be bonded to a sparse fabric, which in turn is bonded to a nonwoven fabric. In this case, the microporous material is typically also bonded to the nonwoven fabric through open areas of the sparse fabric. As another example, the microporous material is bonded to a nonwoven fabric, the other side of which is bonded to the sparse fabric. The possible combinations and arrangements of layers are quite numerous. Most commonly, but not always, at least one outer layer is a microporous material.

[0069] Bonding can be performed using conventional techniques, such as, for example, fusion bonding and adhesive bonding. Examples of fusion bonding include sealing using heated rollers, heated rods, heated plates, heated bands, heated wires, flame bonding, radio frequency (RF) sealing, and ultrasonic sealing. Thermal sealing is the most common. Solvent bonding can be used, where the porous material is soluble in the applied solvent to the point that the surface becomes tacky. After the microporous material has been brought into contact with the tacky surface, the solvent is removed to form a fusion bond.

[0070] Many well-known adhesives can be used to achieve bonding. Examples of suitable categories of adhesives include thermosetting adhesives, thermoplastic adhesives, adhesives that form a bond by solvent evaporation, adhesives that form a bond by the evaporation of a liquid non-solvent, and pressure-sensitive adhesives.

[0071] The foamable composition can be contacted with a microporous material to foam and form an adhesive between the porous foam and the microporous material.

[0072] Powder bonding is a particularly useful technique for bonding microporous materials to nonwoven webs of short and / or continuous fibers, as well as to woven or knitted fibers.

[0073] Depending on the bonding technique used, the adhesive used, and / or the nature of the porous material used, the porous material may be easily removable by hand from the microporous material (i.e., peelable), or it may not be (i.e., permanently bonded).

[0074] Microporous materials can be continuously bonded to porous materials, or they can be discontinuously bonded to porous materials. Examples of discontinuous bonding include bonded areas in the form of one or more dots, sheets, stripes, streaks, open curved stripes, closed curved stripes, irregular regions, etc. When it comes to the bonding pattern, they can be random, repetitive, or a combination of both.

[0075] Multilayer membranes can also be formed from a continuous, moisture-permeable coating of a hydrophobic polymer attached to one side of the aforementioned microporous membrane. Such coatings and methods of application are described, for example, in U.S. Patent No. 5,032,450, the entire contents of which are incorporated herein by reference. The coating is typically an elastomeric solid at ambient temperature and typically contains polysiloxanes. One surface of the coating may be interlocked with the surface of the microporous material, but the coating does not significantly penetrate into the interior of the microporous material. Therefore, the resulting membrane is considered a multilayer article.

[0076] As used herein, a polymer is considered "hydrophobic" if the contact angle between a water droplet and a flat surface of the polymer (on which the droplet rests) is greater than 90 degrees. The contact angle is discussed more fully in Sears and Zemansky, University Physics, 2nd ed., Addison-Wesley Publishing Company, Inc., (1955), pp. 231–235.

[0077] The microporous membrane disclosed herein is particularly useful for bonding to porous polyolefins (such as polyethylene and polypropylene materials) via heat sealing without the presence of an external adhesive. The resulting bond is typically quite strong, which is surprising, as laminating materials to polyolefins is usually difficult without the use of special adhesives.

[0078] The multilayer membranes disclosed herein have numerous and varied applications, including filters, wipes, gaskets, cushioning components, signage, printing substrates, pen and ink drawing substrates, maps (especially nautical charts), wall coverings, and breathable fabrics for clothing. They can also be used as bandages, sanitary napkins, incontinence products, diapers, and other components thereof. They can also be used as seams, joints, and seals in breathable packaging, breathable clothing, and the like.

[0079] This disclosure further relates to the following aspects:

[0080] 1. A microporous membrane comprising:

[0081] 1) An organic polymer matrix, comprising:

[0082] (a) A polyolefin component, present in the organic polymer matrix in an amount of 18 to 99% by weight, based on the total weight of the organic polymer matrix, wherein the polyolefin component comprises ultra-high molecular weight (UHMW) polyethylene; and

[0083] (b) An aliphatic polyketide polymer, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 1 to 80% by weight, based on the total weight of the organic polymer matrix; and

[0084] 2) Fine, particulate, substantially water-insoluble filler distributed throughout the organic polymer matrix, which is present in the microporous membrane in an amount of 10 to 90% by weight, based on the total weight of the microporous membrane.

[0085] 2. The microporous membrane according to aspect 1, wherein the polyolefin component is present in the organic polymer matrix in an amount of 18 to 97% by weight, based on the total weight of the organic polymer matrix.

[0086] 3. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 18 to 95% by weight, based on the total weight of the organic polymer matrix.

[0087] 4. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 25 to 99% by weight, based on the total weight of the organic polymer matrix.

[0088] 5. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 25 to 97% by weight, based on the total weight of the organic polymer matrix.

[0089] 6. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 25 to 95% by weight, based on the total weight of the organic polymer matrix.

[0090] 7. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 40 to 99% by weight, based on the total weight of the organic polymer matrix.

[0091] 8. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component is present in the organic polymer matrix in an amount of 40 to 97% by weight, based on the total weight of the organic polymer matrix.

[0092] 9. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 3 to 80% by weight, based on the total weight of the organic polymer matrix.

[0093] 10. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 5 to 80% by weight, based on the total weight of the organic polymer matrix.

[0094] 11. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 1 to 75% by weight, based on the total weight of the organic polymer matrix.

[0095] 12. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 3 to 75% by weight, based on the total weight of the organic polymer matrix.

[0096] 13. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 5 to 75% by weight, based on the total weight of the organic polymer matrix.

[0097] 14. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 1 to 60% by weight, based on the total weight of the organic polymer matrix.

[0098] 15. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 3 to 60% by weight, based on the total weight of the organic polymer matrix.

[0099] 16. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 5 to 60% by weight, based on the total weight of the organic polymer matrix.

[0100] 17. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 10 to 80% by weight.

[0101] 18. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 10 to 75% by weight.

[0102] 19. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 30 to 90% by weight.

[0103] 20. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 30 to 80% by weight.

[0104] 21. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 30 to 75% by weight.

[0105] 22. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely fragmented, particulate, substantially water-insoluble filler distributed throughout the organic polymer matrix is ​​present in the microporous membrane in an amount of 50 to 90% by weight.

[0106] 23. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 50 to 80% by weight.

[0107] 24. The microporous membrane according to any of the foregoing aspects, wherein, based on the total weight of the microporous membrane, finely broken, particulate, substantially water-insoluble filler is present in the microporous membrane in an amount of 50 to 75% by weight.

[0108] 25. The microporous membrane according to any of the foregoing aspects, wherein the polyolefin component further comprises high-density polyethylene (HDPE).

[0109] 26. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 0.1 to 74.25% by weight, based on the total weight of the organic polymer matrix.

[0110] 27. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 0.1 to 60% by weight, based on the total weight of the organic polymer matrix.

[0111] 28. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 0.1 to 45% by weight, based on the total weight of the organic polymer matrix.

[0112] 29. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 1 to 74.25% by weight, based on the total weight of the organic polymer matrix.

[0113] 30. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 1 to 60% by weight, based on the total weight of the organic polymer matrix.

[0114] 31. The microporous membrane according to any of the foregoing aspects, wherein HDPE is present in the organic polymer matrix in an amount of 1 to 45% by weight, based on the total weight of the organic polymer matrix.

[0115] 32. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer exhibits a melt index of 0.5 to 4 g / 10 min as measured according to ASTM D1238-23.

[0116] 33. The microporous membrane according to any of the foregoing aspects, wherein the aliphatic polyketide polymer exhibits a melting temperature of 190 to 220°C as measured according to ASTM D3418-21.

[0117] 34. The microporous membrane according to any of the foregoing aspects, wherein the filler comprises silica, talc, carbon black, charcoal, graphite, titanium dioxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconium oxide, magnesium oxide, aluminum oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate and / or magnesium carbonate.

[0118] 35. The microporous membrane according to any of the foregoing aspects, wherein the filler comprises silica and / or calcium carbonate.

[0119] 36. The microporous membrane according to any of the foregoing aspects, wherein the filler comprises precipitated silica.

[0120] 37. The microporous membrane according to any of the foregoing aspects, wherein the filler comprises silica and calcium carbonate, and the weight ratio of silica to calcium carbonate is in the range of 0.2:1 to 1:0.2.

[0121] 38. A microporous membrane according to any of the foregoing aspects, wherein the filler comprises silica, and wherein the silica exhibits a microporous density of 125 to 700 μm, as determined by the Brunauer, Emmett, Teller (BET) method according to ASTM C 819-77. 2 / g of BET.

[0122] 39. The microporous membrane according to any of the foregoing aspects, wherein the microporous membrane has a thickness in the range of 10 to 510 micrometers.

[0123] 40. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 10 to 5000 seconds.

[0124] 41. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 250 to 5000 seconds.

[0125] 42. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 500 to 5000 seconds.

[0126] 43. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 1,000 to 5,000 seconds.

[0127] 44. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 10 to 4500 seconds.

[0128] 45. The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 250 to 4500 seconds.

[0129] 46. ​​The microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 500 to 4500 seconds.

[0130] 47. A microporous membrane according to any of the foregoing aspects, wherein the membrane exhibits a Gurley porosity of 1,000 to 4,500 seconds.

[0131] 48. The microporous membrane according to any of the foregoing aspects, wherein the microporous membrane further comprises a biodegradation promoting material distributed throughout the organic polymer matrix, thereby making the microporous membrane compostable and / or biodegradable.

[0132] 49. The microporous membrane according to aspect 48, wherein the biodegradation promoting material includes furanone compounds, glutaric acid, hexadecanoic acid compounds, sensory swelling agents, catalytic transition metal compounds, metal stearates and / or metal chelates.

[0133] 50. The microporous membrane according to any of the foregoing aspects, wherein the microporous membrane further comprises an antioxidant, a lubricant, a UV absorber and / or a UV light stabilizer distributed throughout the organic polymer matrix.

[0134] 51. A multilayer membrane comprising two or more adjacent membrane layers, wherein the layers are identical or different from each other, and wherein at least one layer comprises a microporous membrane according to any of the preceding aspects.

[0135] 52. The multilayer membrane according to aspect 51, wherein at least one layer comprises: a microporous polyolefin material, wherein the polyolefin material comprises linear ultra-high molecular weight polyethylene, linear ultra-high molecular weight polypropylene, or mixtures thereof; and finely crushed, particulate, substantially water-insoluble silica filler distributed throughout the microporous polyolefin material.

[0136] The following examples are intended to illustrate various aspects of this disclosure and should not be construed as limiting this disclosure in any way. Components mentioned elsewhere in the specification as suitable alternatives but not shown in the working examples below are expected to provide results equivalent to their shown counterparts. Unless otherwise stated, all parts are by weight.

[0137] Example

[0138] Mixture preparation

[0139] Weigh the components listed in Tables 1 and 2 for each example and comparative example (adjusted proportionally to a total of 2230 g) and place them in a Littleford FT-130 Henschel horizontal mixer with a high-strength shredder-type mixing blade. Premix the mixture using only the plow blade for approximately 15 seconds. Pump heated process oil (TUFFLO® 6066 process oil, commercially available from PPC Lubricants) into the mixer over 40 to 60 seconds, with only the plow blade operating. Open the high-strength shredder blade along with the plow blade and mix the components for 30 seconds. Turn off the mixer and scrape the inside of the mixer to ensure all components are evenly mixed. Restart the mixer, opening both the high-strength shredder and the plow blade, and mix the mixture for an additional 30 seconds. Turn off the mixer and transfer the mixture to a storage container.

[0140] Extrusion, calendering and extraction

[0141] The sample mixtures were extruded and calendered into final sheet form using an extrusion system comprising the feeding, extrusion, and calendering systems described below. Each respective mixture was fed into a 27 mm twin-screw extruder, the Leistritz Micro-27gg, using a loss-in-weight feeding system (K-Tron model K2MLT35D5). The extruder barrel consisted of eight temperature zones and a heating adapter to the sheet die. The extruded mixture inlet was located just before the first temperature zone. The atmospheric vent was located in the third temperature zone. The vacuum exhaust vent was located in the seventh temperature zone.

[0142] The mixture is fed into the extruder at a rate of 90 g / min. Additional processing oil is also injected in the first temperature zone as needed to achieve a total amount of 60 to 100 parts by weight of the solids components as shown in Tables 2 and 3.

[0143] The extrudate is discharged from the barrel into a 15 cm wide Masterflex® die with a 1.5 mm discharge opening. The extrusion melt temperature is 203 to 210 °C and the output is 7.5 kg / hour.

[0144] The calendering process is completed using a three-roll vertical calender with one pressing point and one cooling roll. Each roll has a chrome-plated surface. The roll dimensions are approximately 41 cm in length and 14 cm in diameter. The top roll temperature is maintained between 135°C and 140°C. The middle roll temperature is maintained between 140°C and 145°C. The bottom roll is the cooling roll, where the temperature is maintained between 10°C and 21°C. The extrudate is calendered into sheet form and passes over the bottom water-cooled roll before being wound up.

[0145] Sheet samples, cut to approximately 18 cm wide and 150 cm long, were rolled into a cylindrical shape along with stainless steel wire mesh. The cylinders were placed in a container and exposed to room temperature liquid 1,1,2-trichloroethylene for approximately 1 hour to extract processing oil from the sheet samples. The residual oil content in the samples was 3 to 7% by weight. The extracted sheets were then air-dried and subjected to the test methods described below.

[0146] Table 1. Compositions containing only polyolefin components (UHMW polyethylene)

[0147]

[0148] 1. HI-SIL 135® precipitated silica, commercially available from PPG Industries, Inc.

[0149] 2. GUR® 4160 ultra-high molecular weight polyethylene (UHMWPE) is commercially available from Ticona Corp. and is reported to have a molecular weight of approximately 9.2 million g / mol.

[0150] 3. Aliphatic polyketone, with a reported melt flow rate of 3 g / 10 min at 220°C / 2.16 kg and a reported melt temperature of approximately 200°C, is available commercially from Hyosung Chemical under the trade name Poketone.

[0151] 4. TIPURE™ R-103 titanium dioxide, commercially available from EI du Pont de Nemours and Company.

[0152] 5. Antioxidants, commercially available from Cytec Industries, Inc.

[0153] 6. Technical grade.

[0154] 7. Cyasorb Synergy Solutions® M528 light stabilizer additive, commercially available from Solvay.

[0155] Table 2. Compositions further containing HDPE in the polyolefin component

[0156]

[0157] 8. FINA® 1288 high-density polyethylene (HDPE), commercially available from Total Petrochemicals.

[0158] All compositions except CE-2 produced smooth, continuous microporous sheets. CE-2 is not resistant to extrusion conditions and has not been tested.

[0159] Tests and Results

[0160] The physical properties measured on the extracted and dried films and the results obtained are listed in Table 3. Thickness was determined using an OnoSokki EG-225 thickness gauge. Two 4.5 x 5-inch (11.43 cm x 12.7 cm) samples were cut from each sample, and the thickness of each sample was measured at nine locations (at least ¾ inches (1.91 cm) from any edge). The arithmetic mean of the readings was recorded in mils.

[0161] According to ASTM D882-18, the maximum elongation or tensile modulus and maximum tensile strength, or the tensile energy that causes the sample to break, are tested using a modified sample crosshead speed of 5.08 cm / min until a linear travel speed of 0.508 cm is achieved, at which point the crosshead speed accelerates to 50.8 cm / s, and the sample width is approximately 1.2 cm and the sample gauge length is 5.08 cm. Measurements are obtained from both machine-oriented (MD) samples oriented along the length of the sheet and transverse-oriented (CD) samples oriented across the sheet.

[0162] Gurley porosity was determined using a Model 4340 Gurley densitometer manufactured by GPI Gurley Precision Instruments (Troy, NY). The reported airflow rate is a measurement of the rate at which airflow passes through the sample or its resistance to airflow through the sample. The unit of measurement is “Gurley second” and represents the time (in seconds) it takes for 100 cc of air to pass through a 1 square inch area using a pressure differential of 4.88 inches of water column. Lower values ​​correspond to lower airflow resistance (allowing more air to pass freely). Measurements were performed using the procedures listed in the manual (Model 4340 Automatic Densitometer and Smoothness Tester User Manual). As shown in Tables 3 and 4, highly porous sheets are produced when polyketone is used.

[0163] Table 3. Properties of the manufactured sheets (without HDPE)

[0164]

[0165] 9. CE-2, Organic polymer matrices containing 100% polyketone and free of polyolefins may not be processed by the methods listed.

[0166] Table 4. Properties of the manufactured sheets (including HPDE).

[0167]

[0168] As shown in Tables 3 and 4, compositions containing polyolefins and polyketides produce excellent sheets with good strength.

[0169] UV stability test

[0170] The samples were tested according to the universal UVA-340 test method for QUV accelerated aging, as per SAE J2020 (UVA). The samples were secured to a 6 x 3-inch aluminum Q panel, with tape applied only to the top and bottom (half an inch from the edge) to maintain sheet stability. The panels were exposed to approximately 0.72 W / m² of ultraviolet (UV) irradiance in an aging apparatus equipped with UVA-340 lamps. Cycles were performed using 8 hours of UV exposure at 70°C followed by 4 hours of conditioning at 50°C.

[0171] After the determined exposure duration (e.g., 336 hours), the panel was removed from the test cabinet and the sheet was carefully released from the aluminum panel by removing the retaining tape from the top and bottom portions of the panel. The 3 x 6-inch sheet was cut into three strips of the same size using a die-cutting machine, approximately 0.5 x 4.5 inches (1.2 x 5.08 cm) in length, where the length of the strip represents the MD. To test the CD properties, 0.5 x 4.5-inch (1.2 x 5.08 cm) strips were cut along an orientation corresponding to the CD orientation of the resulting microporous sheet. As previously described, each strip was independently tested according to ASTM D882-18 to give a total of three tensile readings from the three strips and an arithmetic mean calculated from the data to obtain their corresponding maximum tensile strength and maximum elongation.

[0172] As shown in Table 5, formulations containing aliphatic polyketides exhibited significantly enhanced UV stability. The microporous substrates according to this disclosure showed at least a twofold increase in UV stability, with some withstanding UV exposure times up to 1500 hours, while comparative examples disintegrated at or shortly after 336 hours under the same UV exposure conditions. Regardless of the tensile strength prior to testing, all examples containing polyketides according to this disclosure maintained significantly greater stability after UV exposure than those without polyketides. Furthermore, Example 11 shows that, compared to Example 10, no light stabilizer was required to significantly improve UV stability.

[0173] Table 5. UV stability.

[0174]

[0175] (10) A value of "0" indicates that the sheet is intact at the specified time interval but cannot be tested; for example, the sheet breaks before or at the start of the test.

[0176] (11) An empty cell indicates (unless otherwise specified) that the sheet has broken down at the specified time interval and is therefore not ready for testing.

[0177] Thermal stability properties were measured by the retention rate of tensile modulus of elasticity, as shown in Table 6. The thermoforming properties of the sheet were predictably superior to those of the comparison sheet. High-temperature tensile measurements showed that the microporous sheet was more stable at both low and high strain rates at 155°C, as shown in Comparative Example 10 of CE-7.

[0178] Table 6. Thermal stability

[0179]

[0180] The results in Table 6 show that the membranes according to this disclosure retained elongation at elevated temperatures, while Comparative Example CE-7 actually lost flexibility / elongation at elevated temperatures. Example 10 exhibited even higher elongation at higher strain rates (10 inches / min vs. 2 inches / min).

[0181] Although specific examples of this disclosure have been described above for illustrative purposes, it will be apparent to those skilled in the art that various changes may be made to the details of this disclosure without departing from the disclosure as defined in the appended claims.

Claims

1. A microporous membrane comprising: 1) An organic polymer matrix, comprising: (a) A polyolefin component, present in the organic polymer matrix in an amount of 18 to 99% by weight, based on the total weight of the organic polymer matrix, wherein the polyolefin component comprises ultra-high molecular weight (UHMW) polyethylene; and (b) An aliphatic polyketide polymer, wherein the aliphatic polyketide polymer is present in the organic polymer matrix in an amount of 1 to 80% by weight, based on the total weight of the organic polymer matrix; and 2) Fine, granular, substantially water-insoluble fillers, having a total particle size in the range of 5 to 40 micrometers as determined by laser diffraction particle size analyzer, wherein the fillers are distributed throughout the organic polymer matrix and are present in the microporous membrane in an amount of 10 to 90% by weight based on the total weight of the microporous membrane.

2. The microporous membrane according to claim 1, wherein the polyolefin component further comprises high-density polyethylene (HDPE).

3. The microporous membrane according to claim 1 or 2, wherein the HDPE is present in the organic polymer matrix in an amount of 0.1 to 74.25% by weight, based on the total weight of the organic polymer matrix.

4. The microporous membrane according to any one of claims 1 to 3, wherein the aliphatic polyketide polymer exhibits a melt index of 0.5 to 4 g / 10 min as measured according to ASTM D1238-23.

5. The microporous membrane of claim 4, wherein the aliphatic polyketide polymer exhibits a melting temperature of 190 to 220°C as measured according to ASTM D3418-21.

6. The microporous membrane according to any one of claims 1 to 5, wherein the filler comprises silica, talc, carbon black, charcoal, graphite, titanium dioxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconium oxide, magnesium oxide, aluminum oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate and / or magnesium carbonate.

7. The microporous membrane according to claim 6, wherein the filler comprises silica and / or calcium carbonate.

8. The microporous membrane according to claim 6 or 7, wherein the filler comprises precipitated silica.

9. The microporous membrane according to claim 7, wherein the filler comprises silica and calcium carbonate, and the weight ratio of silica to calcium carbonate is in the range of 0.2:1 to 1:0.

2.

10. The microporous membrane according to any one of claims 6 to 9, wherein the filler comprises silica, and wherein the silica exhibits a microporous density of 125 to 700 μm, as determined by the Brunauer, Emmett, Teller (BET) method according to ASTM C 819-77. 2 / g of BET.

11. The microporous membrane according to any one of claims 1 to 10, wherein the microporous membrane has a thickness in the range of 10 to 510 micrometers.

12. The microporous membrane according to any one of claims 1 to 11, wherein the membrane exhibits a Gurley porosity of 10 to 5000 seconds.

13. The microporous membrane according to any one of claims 1 to 12, wherein the microporous membrane further comprises a biodegradation promoting material distributed throughout the organic polymer matrix, thereby making the microporous membrane compostable and / or biodegradable.

14. The microporous membrane according to claim 13, wherein the biodegradation promoting material comprises furanone compounds, glutaric acid, hexadecanoic acid compounds, sensory swelling agents, catalytic transition metal compounds, metal stearates and / or metal chelates.

15. The microporous membrane according to any one of claims 1 to 14, wherein the microporous membrane further comprises an antioxidant, a lubricant, a UV absorber and / or a UV light stabilizer distributed throughout the organic polymer matrix.

16. A multilayer membrane comprising two or more adjacent membrane layers, wherein the layers are identical or different from each other, and wherein at least one layer comprises a microporous membrane according to any one of claims 1 to 15.

17. The multilayer membrane of claim 16, wherein at least one layer comprises: a microporous polyolefin material, wherein the polyolefin material comprises linear ultra-high molecular weight polyethylene, linear ultra-high molecular weight polypropylene, or a mixture thereof; and finely fragmented, particulate, substantially water-insoluble silica filler distributed throughout the microporous polyolefin material.

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