Water-responsive membrane and preparation method thereof

Abstract

The present disclosure relates to a film comprising a substantially crystalline water dispersible polymer and an aromatic thermoplastic polyurethane polymer. The film has a crystallinity of at least 25%. The membrane expands upon contact with water. The membrane may include one or more openings that may open / close in response to water. The membrane expands upon contact with water, but shrinks upon drying, allowing multiple infiltrations to trigger the expansion and shrinkage properties of the membrane.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 400,642, filed on August 24, 2022, which is hereby incorporated by reference in its entirety for all intents and purposes. Technical Field

[0003] The present disclosure generally relates to an expandable membrane and methods of making the expandable membrane. In particular, the present disclosure relates to a water-responsive membrane that expands when in contact with water. Background Art

[0004] Absorbent articles (such as diapers, incontinence garments, sanitary napkins and catamenial pads) are designed to absorb and retain liquids and other excretions from the human body to prevent soiling of the body and clothing. Absorbent articles should provide adequate leakage protection for healthy, dry skin. In order to prevent leakage, absorbent articles should be able to allow fluids (e.g., urine or menstruation) to quickly enter the absorbent structure of the absorbent article and retain the fluid therein. If the fluid is not adequately retained in the absorbent structure of the absorbent article, the pressure applied to the absorbent article may cause the fluid to flow from the inside of the absorbent article over the surface of the absorbent article. This will cause the fluid to come into direct contact with the user's skin, which may cause the skin to become overhydrated, making the skin susceptible to irritation and infection.

[0005] In order to absorb fluid quickly, the absorbent structure of the absorbent article needs to contain materials with sufficient permeability and wettability to facilitate the absorption of fluid. Although these properties of absorbent articles provide rapid absorption of fluid, the same properties also allow the fluid to easily flow back, that is, when pressure is applied to the absorbent article, the fluid flows out of the absorbent article and flows onto the user's skin. Therefore, there is a correlation between the fluid absorption rate of conventional absorbent articles and the return rate and volume, resulting in a phenomenon known as "easy in, easy out". Therefore, absorbent articles that can absorb fluid quickly usually have more fluid return, which may cause undesirable hydration of the skin. Conversely, absorbent articles that exhibit limited fluid return tend to have slower fluid absorption and more leakage.

[0006] There remains a need for an absorbent article that can substantially reduce the incidence of fluid leakage from the absorbent article while keeping the skin adequately dry. Summary of the invention

[0007] The embodiments covered by the present disclosure are defined by the claims rather than by this Summary. This Summary is a high-level overview of various aspects of the invention and introduces some concepts that will be further described in the Detailed Description section below. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the entire specification, some or all of the drawings, and appropriate portions of each claim.

[0008] In some embodiments, the present disclosure provides a water-responsive film, the water-responsive film comprising a water-soluble polymer and an aromatic thermoplastic polyurethane (TPU), wherein the film has a crystallinity of at least 25%. In some embodiments, the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid or a combination thereof. In some embodiments, the water-soluble polymer comprises polyethylene oxide. In some embodiments, polyethylene oxide has a molecular weight range of 50,000 g / mol to 500,000 g / mol. In some embodiments, the aromatic TPU comprises a polyester-based TPU. In some embodiments, the film has a crystallinity of 25% to 60%. In some embodiments, the film comprises a water-soluble polymer in an amount of 10% to 90% by weight based on the total weight of the film. In some embodiments, the film comprises an aromatic TPU in an amount of 10% to 90% by weight based on the total weight of the film. In some embodiments, the weight ratio of water-soluble polymer to aromatic TPU is at least 1: 1. In some embodiments, the film comprises a water-soluble polymer in an amount of 30% to 70% by weight based on the total weight of the film, a TPU in an amount of 30% to 70% by weight based on the total weight of the film, and a ratio of water-soluble polymer to aromatic TPU is at least 1.5: 1. In some embodiments, the film comprises one or more additives, the additives comprising surfactants, absorbents, antibiotics or skin benefit agents. In some embodiments, the additives comprise superabsorbents. In some embodiments, the film is cut or scored to include one or more openings. In some embodiments, the film has a tensile strength of 10MPa to 50MPa, and a tensile modulus of 1MPa to 5MPa.

[0009] In some embodiments, the present disclosure provides a water-responsive film, which comprises: 30 wt % to 70 wt % of a water-soluble polymer based on the total weight of the film, wherein the water-soluble polymer has a crystallinity greater than 50%; 30 wt % to 60 wt % of an aromatic thermoplastic polyurethane based on the total weight of the film; wherein the film has a crystallinity of 25% to 60%.

[0010] In some embodiments, the present disclosure provides a method for preparing a water-responsive expandable film, the method comprising: melt blending a composition comprising a water-soluble polymer and an aromatic TPU; and extruding the composition to prepare a film. In some embodiments, the film comprises a water-soluble polymer in an amount of 30% to 70% by weight based on the total weight of the film, and the film comprises an aromatic TPU in an amount of 30% to 60% by weight based on the total weight of the film. In some embodiments, the ratio of the water-soluble polymer to the aromatic TPU in the composition is 1:1 to 4:1. In some embodiments, the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid or a combination thereof, and the aromatic TPU comprises a polyester-based TPU. In some embodiments, the method further comprises cutting a pattern on the expandable film. In some embodiments, the method further comprises bonding the film to a base layer.

[0011] Other aspects, objects and advantages will become apparent through consideration of the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] According to some embodiments of the present invention, Figure 1 Schematic diagram of the microstructure of the expandable membrane in the contracted and expanded states.

[0013] According to some embodiments of the present invention, Figure 2 is a diagrammatic representation of an expandable membrane including open holes as it transitions between a contracted state and an expanded state.

[0014] According to some embodiments of the present invention, Figure 3 is a schematic diagram of a system for preparing expandable films using a single screw extruder.

[0015] According to some embodiments of the present invention, Figure 4 is a schematic diagram of a system for preparing expandable films using a twin-screw extruder.

[0016] According to some embodiments of the present invention, Figure 5 is a schematic diagram of a system for preparing expandable membranes by compounding and extruding polymer blends.

[0017] According to some embodiments of the present invention, Figure 6 is a flow chart of a method for preparing an expandable membrane.

[0018] According to some embodiments of the present invention, Fig. 7A is a schematic diagram of the shrinkage properties of a film comprising polyethylene oxide and a thermoplastic polyolefin, and Figure 7B is a schematic diagram of the expansion properties of films comprising polyethylene oxide and thermoplastic polyurethane polymers. DETAILED DESCRIPTION

[0019] introduce

[0020] The present disclosure relates to a water-responsive expandable film that allows rapid absorption of fluid and limits fluid backflow. The water-responsive expandable film described herein comprises a water-soluble polymer and an elastomeric thermoplastic polyurethane (TPU). Specifically, the water-responsive expandable film comprises a blend of two polymers: (1) a water-soluble polymer having a substantially crystalline morphology; and (2) an aromatic TPU. The film has elasticity and water sensitivity so that when the film is in contact with a fluid (e.g., urine, menstruation or other body fluids), it expands. When not expanded, the film allows the fluid to pass through the film quickly and optionally enter another material (e.g., the absorbent structure of an absorbent article). However, when the fluid flows through the film, the film also absorbs some of the fluid, causing the film to expand. In an embodiment of a film including one or more openings, sufficient expansion will close the openings that initially facilitate the rapid passage of the fluid. The closed openings will prevent the fluid from further flowing through the film, either along the original flow direction or backflow. After the film dries, that is, the fluid is desorbed, the film shrinks and can be used again. The dual properties of elasticity and water responsiveness are achieved by blending a synergistic combination of a water-soluble polymer and an aromatic TPU to prepare a film having a crystallinity of at least 25%. It was found that the combination of an aromatic TPU having appropriate strength and tensile modulus with a water-soluble polymer having an appropriate crystallinity can produce a film that swells upon contact with a fluid and then shrinks to its original size upon drying or desorption.

[0021] Conventional absorbent materials need to strike a balance between rapid fluid absorption and fluid retention. In order to rapidly absorb fluid, the absorbent structure of the absorbent article needs to contain materials that have sufficient permeability and wettability to facilitate absorption of the incoming fluid. Unfortunately, these properties also tend to cause the fluid to easily flow out of the absorbent article and onto the user's skin. Thus, known materials can either absorb fluid quickly but have poor fluid retention due to backflow, or absorb fluid slowly but have good retention.

[0022] The water-responsive expandable film described herein avoids the correlation between conventional fluid absorption rate and backflow volume, and is conducive to rapidly absorbing fluid into absorbent articles while limiting the backflow of fluid. This beneficial effect comes from the ability of the film to expand when in contact with the fluid. When a first volume of fluid enters the absorbent article through the film, the film expands and prevents other fluids from flowing through the film, including the backflow of the fluid that has entered the absorbent article. In some embodiments, the film can be scored or cut to include a pattern. For example, the film can be laser cut or embossed to provide one or more openings with various geometric shapes (e.g., circular, star-shaped, rectangular, square). In this way, the film can be used as a water-responsive one-way valve. The opening in the film can be opened in a first state and closed in a second state. The first state can represent a dry state of a film with the original size of the film. The second state can represent a film after contact with water. As discussed above, due to the polymer chemistry, the film can expand from a first state to a second state after contact with the fluid, and expansion can cause the opening to close. After the fluid dries or desorbs, the membrane may shrink to its original size (or substantially the original size) to open the pores and return to the first state.

[0023] Beneficially, the water-responsive expansion film allows fluid to quickly pass through the film and enter the article (e.g., absorbent article) and prevents the fluid from flowing back out of the absorbent article. Due to the water-responsive expansion and contraction properties of the film, the mechanism of the opening from the first open state to the second closed state does not require any action or input other than the fluid itself, that is, the valve automatically opens or closes to allow or prevent the fluid from passing through. Therefore, the opening acts as a valve, allowing or preventing the fluid from passing through by opening and closing. The state of the valve is determined by the amount of fluid absorbed by the film. In this way, the valve can alternate between a first state (e.g., a contracted size, an open opening) and a second state (expanded size, closed opening) to allow the fluid to quickly enter the absorbent article in the first state and to keep the fluid in the second state by preventing backflow. The ability of the film to expand when in contact with the fluid and to shrink to its original size when dry enables the film to responsively and repeatedly close and open the opening / valve, which is different from the known film that shrinks only when in contact with water.

[0024] Definition and Description:

[0025] The terms "invention", "this invention" and "the present invention" as used herein are intended to refer generally to all subject matter of this patent application and the following claims. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the following patent claims.

[0026] As used herein, the meaning of "a", "an" or "the" includes both singular and plural referents unless the context clearly indicates otherwise.

[0027] As used herein, the term "machine direction" or "MD" generally refers to the direction in which a material is produced. The term "cross direction" or "CD" refers to the direction perpendicular to the machine direction. The dimension measured in the cross direction is called the "width" dimension, while the dimension measured in the machine direction is called the "length" dimension.

[0028] As used herein, the term "bonded" refers herein to the joining, adhering, connecting, attaching, etc. of two elements. Two elements will be considered to be bonded together when they are joined, adhered, connected, attached, etc. directly to each other or indirectly to each other, such as when each element is directly bonded to an intermediate element. The bonding of one element to another element can be performed by continuous or intermittent bonding.

[0029] As used herein, the term "liquid impermeable" refers to a laminate or laminates wherein liquid body exudates (such as urine) do not pass through the layer or laminates under normal conditions of use.

[0030] As used herein, the term "liquid permeable" refers to any material that is not impermeable to liquids.

[0031] As used herein, the term "superabsorbent" refers herein to a water-swellable, water-insoluble organic or inorganic material that is capable of absorbing at least about 15 times its weight, and in some embodiments at least about 30 times its weight, in an aqueous solution containing 0.9 weight percent sodium chloride under most favorable conditions. Superabsorbent materials can be natural, synthetic, and modified natural polymers and materials. Additionally, superabsorbent materials can be inorganic materials such as silica gel or organic compounds such as cross-linked polymers.

[0032] As used herein, the term "thermoplastic" refers herein to a material that is softenable and shapeable when exposed to heat and substantially returns to a non-softened state when cooled.

[0033] As used herein, the terms "elastomeric" and "elastic" refer to a material that can stretch in at least one direction (such as the CD direction) upon application of a stretching force and contract / return to approximately its original dimensions upon release of the stretching force. For example, a stretched material may have a stretched length that is at least 50% greater than its relaxed, unstretched length and will return to within at least 50% of its stretched length upon release of the stretching force. A hypothetical example would be a one (1) inch sample of material that can be stretched to at least 1.50 inches and will return to a length of at least 1.25 inches upon release of the stretching force. Advantageously, the material contracts or recovers at least 50% of the stretched length, and even more advantageously at least 80%.

[0034] As used herein, the term "extensible" or "extensibility" generally refers to a material that stretches or extends at least about 50% of its relaxed length or width in the direction of an applied force. An extensible material does not necessarily have recovery. For example, an elastomeric material is an extensible material with recovery. A film may be extensible but have recovery and therefore are not an extensible non-elastic material.

[0035] All ranges disclosed herein should be understood to encompass any and all subranges contained therein. For example, the stated range "1 to 10" should be considered to include any and all subranges between a minimum value of 1 and a maximum value of 10 (including the end values); that is, all subranges start with a minimum value of 1 or greater (e.g., 1 to 6.1) and end with a maximum value of 10 or less (e.g., 5.5 to 10).

[0036] Membranes and membrane microstructures

[0037] In some embodiments, the water-responsive expandable film comprises a water-soluble polymer and an aromatic thermoplastic polyurethane (TPU). The specific combination of polymers, the morphology of the polymer, and the amount of the polymer in the film utilize the elastic energy of the film, allowing it to expand when in contact with water (e.g., body fluids). For example, a polymer can prepare a film with sufficient crystallinity so that the film can expand when in contact with a fluid and then shrink to its original state. In this regard, an aromatic TPU is used as an elastomeric material that entangles a water-soluble polymer to achieve expansion of the film. The water-soluble polymer contributes to the crystallization of the film so that when the film is dry, the water-soluble polymer recrystallizes and restores the film to its original size. It has been surprisingly and unexpectedly found that the combination of polymers described herein affects the ability and degree of water-responsive expansion and contraction.

[0038] According to some embodiments of the present invention, Figure 1 The microstructure of a water-responsive expandable membrane 105 is shown, which reversibly transitions between a contracted state 100 and an expanded state 125. Figure 1 As shown, the film 105 includes a water-soluble polymer 110, an aromatic TPU 115 and a superabsorbent powder 120. The water-soluble polymer 110 can be polyethylene oxide, but other water-soluble polymers can also be used as long as they have sufficient crystallinity. Polyethylene oxide ("PEO") generally has a high crystallinity (e.g., greater than 50%). The water-soluble polymer 110 is represented by an open circle, and the aromatic TPU 115 partially entangled with the water-soluble polymer 110 is represented by a dotted line. The solid circle represents the superabsorbent powder 120, which is an optional component in the film embodiment.

[0039] In the contracted state 100, the water-soluble polymer 110 is partially entangled with the aromatic TPU 115. The aromatic TPU 115 is a block copolymer comprising a hard segment and a soft segment. In some embodiments, the soft segment can be a polyester or a polyether, and the hard segment (e.g., a urethane bond) can be an aromatic segment or an aliphatic segment. It has been found that the chemical properties of the thermoplastic polyurethane control whether the film can expand after contact with the fluid. Without wishing to be bound by theory, it is believed that when the thermoplastic polyurethane chain is entangled with the water-soluble polymer, the aromatic segment (hydrophilicity) of the thermoplastic polyurethane interacts more extensively with the water-soluble polymer than the aliphatic segment.

[0040] like Figure 1 As shown, as fluid (e.g., water, blood, sweat, etc.) is absorbed, the film 105 changes from a contracted state 100 to an expanded state 125. As water is desorbed, the film 105 changes from an expanded state 125 to a contracted state 100. When the film 105 comes into contact with water, the crystalline portion of the water-soluble polymer 110 begins to change to a more amorphous state, and the polymer swells. However, the chemical attraction between the water-soluble polymer and the TPU prevents the water-soluble polymer from completely dissolving, but instead causes the film to swell. The morphological change of the water-soluble polymer 110 effectively releases the elastic energy of the aromatic TPU 115. Due to the entanglement of the aromatic TPU 115 chains with the water-soluble polymer 110 chains, the elastic expansion of the aromatic TPU 115 increases as the water-soluble polymer 110 swells, and the film swells.

[0041] For comparison, the more hydrophobic aliphatic thermoplastic polyurethanes have poorer chemical compatibility with water-soluble polymers, resulting in significantly less physical interaction (e.g., chain entanglement) with the thermoplastic polyurethane. Thus, when the water-soluble polymer absorbs water and its crystalline form changes to a more amorphous state, the polymer swells and eventually dissolves, but this change has little effect on the aliphatic TPU, and film expansion does not occur. In fact, in many cases the film shrinks.

[0042] Polymers are tailored to provide a combination of elasticity and rigidity. For example, in order to make the film have the elastomeric properties of expansion and recovery, water-soluble polymers and aromatic TPU are selected to prepare films with at least 25%, for example, at least 30%, at least 35%, at least 40%, at least 45%, at least 50% or at least 55% crystallinity. In some embodiments, the film can have a crystallinity of 25% to 60%, for example, 30% to 60%, 30% to 55%, 35% to 55%, 35% to 50%, 40% to 60%, 45% to 60%, 40% to 50% or any value between these ranges. Water-soluble polymers mainly contribute to the crystalline properties of the film.

[0043] In some embodiments, the water-responsive swellable film will continue to expand when in contact with the fluid until the growth of the film eventually reaches a maximum value. Thereafter, continued contact with the fluid will cause the film to begin to shrink. Without wishing to be bound by theory, it is believed that once a certain amount of water is absorbed, the water-soluble polymer will dissolve, chain entanglement will occur, and the expanded film will shrink due to dissolution. When the film is no longer in contact with the fluid, the remaining water-soluble polymer will recrystallize together with the TPU chains, and the film will shrink to its original size. The crystalline nature of the water-soluble polymer again utilizes the elastic energy of the elastomer, and if exposed to the fluid for a second time, the film can expand.

[0044] Thermoplastic polyurethane

[0045] The film may include one or more TPU polymers. In some embodiments, the TPU includes an aromatic TPU. The aromatic TPU is used as an elastomeric material to allow the film to expand. The combination of the aromatic TPU and the substantially crystalline water-soluble polymer in the film produces a surprising and unexpected result, that is, the film expands after contact with water, and then shrinks to its original size after drying or desorption. The film expands when in contact with water, and the ability to shrink to its original size enables the film to responsively and repeatedly close and open a valve (e.g., open a hole), while the film of the prior art only has the ability to shrink when in contact with water.

[0046] In some embodiments, the aromatic TPU polymer is hydrophilic. The TPU polymer can be present in the film in an amount of 10 wt % to 90 wt %, for example, 15 wt % to 85 wt %, 20 wt % to 80 wt %, 25 wt % to 75 wt %, 30 wt % to 70 wt %, 30 wt % to 65 wt %, 30 wt % to 70 wt %, 35 wt % to 65 wt % or 40 wt % to 60 wt %. In some embodiments, the film comprises at least 10 wt % of the TPU polymer, for example, at least 15 wt %, at least 20 wt %, at least 25 wt %, at least 30 wt %, at least 35 wt %, at least 40 wt %, at least 45 wt %, at least 50 wt %, at least 55 wt %, at least 60 wt %, at least 65 wt % or at least 70 wt % of the TPU polymer. In some embodiments, the film comprises 40 wt % to 60 wt % of the TPU.

[0047] The film includes the aforementioned amount of TPU to ensure that the elastic properties of the film allow expansion. It has been found that the chemical properties of the TPU contribute to the expansion properties of the film when it comes into contact with water. Without being bound by theory, it is believed that when the TPU chains are entangled with a water-soluble polymer (e.g., polyethylene oxide), the hydrophilic aromatic TPU chains interact more extensively with the water-soluble polymer than the hydrophobic aliphatic TPU chains. Therefore, when in contact with water, the crystalline regions of the water-soluble polymer begin to transform into a more amorphous state, resulting in polymer swelling. The morphological changes of the water-soluble polymer during swelling effectively release the elastic energy of the aromatic TPU.

[0048] TPU is usually synthesized by polyols, organic diisocyanates and optional chain extenders. Polyols are any high molecular weight products that usually have reactive active hydrogen components and contain substances with an average of about two or more hydroxyl groups per molecule. Long-chain polyols can be used, including advanced polymer polyols, such as polyester polyols and polyether polyols and polyols with active hydrogen components, such as polyhydroxy polyester amides, hydroxyl-containing polycaprolactones, hydroxyl-containing acrylic interpolymers, hydroxyl-containing epoxy resins and hydrophobic polyalkylene ether polyols. Typically, polyols are substantially linear and have two to three hydroxyl groups, and the number average molecular weight is 450 to 10,000, for example, 450 to about 6000, or 600 to 4500. Short-chain diols provide harder, more crystalline polymer segments, and long-chain diols provide softer, more amorphous polymer segments.

[0049] Suitable polyether diols can be prepared by, for example, reacting one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene residue with a starting molecule containing two or more active hydrogen atoms in a combined form. Exemplary alkylene oxides include ethylene oxide, 1,2-propylene oxide, epichlorohydrin, and 1,2-butylene oxide and 2,3-butylene oxide. Exemplary starting molecules include water; amino alcohols such as N-alkyl-diethanolamine (e.g., N-methyl-diethanolamine); and diols such as ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,6-hexanediol. In some embodiments, suitable polyester diols include ethylene glycol polyadipate, 1,4-butylene glycol polyadipate, ethylene glycol / 1,4-butylene glycol polyadipate, 1,6-hexanediol neopentyl glycol polyadipate, 1,6-hexanediol / 1,4-butylene glycol polyadipate, and polycaprolactone.

[0050] The organic diisocyanate may include aromatic diisocyanates such as 2,4-toluene diisocyanate or 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate; naphthalene-1,5-diisocyanate, xylene diisocyanate; methylene diphenyl isocyanate ("MDI"), hexamethylene diisocyanate ("HMDI"), mixtures thereof, and the like.

[0051] Chain extenders typically have a number average molecular weight of about 60 to 400 and contain amino, thiol, carboxyl and / or hydroxyl functional groups. In some embodiments, the chain extender contains two to three hydroxyl groups. As described above, one or more compounds selected from aliphatic diols containing 2 to 14 carbon atoms can be used as chain extenders. Such compounds include, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-dimethanol cyclohexane and neopentyl glycol. Diesters of terephthalic acid and diols having 2 to 4 carbon atoms can also be used. Some examples of such compounds include diethylene glycol terephthalate and bis-1,4-butylene glycol terephthalate, hydroxyalkyl ethers of hydroquinone (e.g., 1-4-bis(β-hydroxyethyl)hydroquinone), ethoxylated bisphenols (e.g., 1,4-bis(β-hydroxyethyl)bisphenol A), (cyclo)aliphatic diamines (e.g., isophoronediamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, N-methyl-1,3-propylenediamine, and N,N'-dimethylethylenediamine), and aromatic diamines (e.g., 2,4-toluenediamine, 2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, and 3,5-diethyl-2,6-toluenediamine, as well as primary mono-, di-, tri-, or tetra-alkyl-substituted 4,4'-diaminodiphenylmethane).

[0052] In addition to those mentioned above, other components can also be used to form TPU. For example, a catalyst can be used to promote the formation of polyurethane. Suitable catalysts include, for example, tertiary amines, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N, N'-dimethylpiperazine, 2-(dimethylaminoethoxy)-ethanol, diazabicyclo[2.2.2]octane, and metallic compounds, such as titanate, tin diacetate, tin dioctoate, tin dilaurate or dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate or dibutyltin dilaurate or other similar compounds. Other suitable additives that can also be used include light stabilizers (for example, hindered amines), chain terminators, slip agents and release agents (for example, fatty acid esters, their metal soaps, fatty acid amides, fatty acid ester amides and organosilicon compounds), plasticizers, anti-tack agents, inhibitors, stabilizers, dyes, pigments, inorganic fillers and / or organic fillers, fungistatic active substances and antibacterial active substances, fillers, etc.

[0053] In some embodiments, the TPU has a melting point of 75°C to 250°C, for example, 100°C to 240°C or 120°C to 220°C. The glass transition temperature (“T g ”) can be relatively low, e.g., -150°C to 0°C, e.g., -100°C to -10°C and -85°C to -20°C. The melting temperature and glass transition temperature can be determined using differential scanning calorimetry (“DSC”) in accordance with ASTM D-3417.

[0054] Examples of aromatic TPUs used in the films described herein include those sold under the name ESTANE TM 、PEARLSTICK TM AND PEARLBOND TM Obtained from The Lubrizol Co. and under the name Those obtained from Wanhua Chemical Group Co., Ltd. For example, ESTANE TM 58238、ESTANE TM EZ-44-61EXP and WHT-F170 is an aromatic polyester based polyurethane that can be used in the films described herein. For example, ESTANE TM MVT 75AT3 is an aromatic polyether based polyurethane that can be used in the films described herein.

[0055] Other physical properties of the TPU may affect the ability and degree of water-responsive expansion of the membranes described herein. Table 1 provides several grades of TPU and their chemical and physical properties. The tensile strength and tensile modulus of the TPU are important parameters for supporting the strong expansion of the membrane. For example, an aromatic TPU with poor tensile strength and low molecular weight may not be able to support the strong expansion of the membrane. On the other hand, if the tensile modulus is too high, the aromatic TPU may be too stiff to expand, and the TPU may not have enough elasticity to expand the membrane.

[0056] In some embodiments, the tensile modulus of the TPU at 100% elongation as measured according to ASTM D-412 (2022) may be in the range of 0.5 MPa to 8 MPa, e.g., 0.75 MPa to 7 MPa, 0.9 MPa to 6 MPa, 1 MPa to 5.5 MPa, 1 MPa to 5 MPa, 1.5 MPa to 4.5 MPa, or 2 MPa to 4 MPa. In some embodiments, the tensile modulus of the TPU at 100% elongation as measured according to ASTM D-412 (2022) may be in the range of 1 MPa to 5 MPa.

[0057] In some embodiments, the tensile strength of the TPU can be in the range of 5 MPa to 100 MPa, for example, in the range of 10 MPa to 80 MPa, 15 MPa to 60 MPa, 20 MPa to 50 MPa, 25 MPa to 50 MPa, 30 MPa to 60 MPa, or 30 MPa to 50 MPa. In some embodiments, the tensile strength of the TPU can be in the range of 20 MPa to 50 MPa.

[0058] In some embodiments, the Shore hardness value of the TPU can be in the range of 50 MPa to 90 MPa, for example, 55 MPa to 85 MPa, 60 MPa to 80 MPa, 60 MPa to 75 MPa, 65 MPa to 80 MPa, or 70 MPa to 80 MPa, as measured by ASTM D-2240 (2022). In some embodiments, the Shore hardness value of the TPU can be in the range of 60 to 80.

[0059] TPU-1 stands for thermoplastic polymer based on aromatic polyether. This product is sold under the name ESTANE TM Supplied by MVT 75AT3 (Lubrizol). The properties of this thermoplastic can be seen in Table 1 below.

[0060] TPU-2 stands for thermoplastic polymer based on aromatic polyester. WHT-F170 (Wanhua) was supplied. The properties of this thermoplastic can be seen in Table 1 below.

[0061] TPU-3 stands for thermoplastic polymer based on aromatic polyester. This product is sold under the name ESTANE TM 58238 (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0062] TPU-4 stands for thermoplastic polymer based on aromatic polyester. This product is sold under the name ESTANE TM EZ-44-61EXP (Pearlbond 405EXP) (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0063] TPU-5 stands for thermoplastic polymer based on aromatic polyester. 5702F3 (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0064] TPU-6 stands for thermoplastic polymer based on aromatic polyester. 302EXP (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0065] TPU-7 stands for thermoplastic polymer based on aromatic polyester. 305EXP (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0066] TPU-8 represents a thermoplastic polymer based on an aliphatic polyether. As used herein, this product can be used as a comparative example to compare aromatic-based thermoplastic polymers with aliphatic thermoplastic polymers. This product is marketed under the name ESTANE TM AG8451 (supplied by Lubrizol). The properties of this thermoplastic can be seen in Table 1 below.

[0067] TPU-9 represents a thermoplastic polymer based on an aliphatic polyether. As used herein, this product can be used as a comparative example to compare aromatic-based thermoplastic polymers with aliphatic thermoplastic polymers. This product is referred to by the name Supplied by LL1275A10 (BASF). The properties of this thermoplastic can be seen in Table 1 below.

[0068] TPU-10 represents an aliphatic polyester based thermoplastic polymer. As used herein, this product can be used as a comparative example to compare aromatic based thermoplastic polymers with aliphatic thermoplastic polymers. This product is marketed under the name ESTANE TM CLC93A-V (Lubrizol) was provided. The properties of this thermoplastic can be seen in Table 1 below.

[0069]

[0070] Table 1 highlights the importance of the chemical nature of the TPU, which can be clearly seen by comparing the aliphatic and aromatic characteristics of the TPU in the third column. Each of the TPUs in Table 1 was blended with a water-soluble polymer and extruded into a film to study the effect of the TPU on the properties of the film. Each of the films made from the aromatic TPU swells when in contact with water, while the films made from the aliphatic TPU (including both polyether-based aliphatic TPUs and polyester-based aliphatic TPUs) shrink when in contact with water. TPU-9 (aliphatic polyether-based TPU) has similar physical properties to TPU-1 (aromatic polyether-based TPU) and TPU-2 (aromatic polyester-based TPU). However, the film containing the aliphatic polyether TPU-9 shrinks, while the films containing the aromatic polyether TPU-1 and the aromatic polyester TPU-2 both swell.

[0071] TPU-8 (aliphatic polyether-based TPU) has similar physical properties to TPU-3 (aromatic polyester-based TPU). Again, the film made from the aromatic polyether-based TPU expands, while the film containing the aliphatic polyether-based TPU shrinks. All TPUs are examples of elastomers that can be used in the water-responsive, swellable films described herein. Other aromatic TPUs that are expected to have similar physical properties to those in Table 1 represent additional exemplary elastomeric components that can be used in the films described herein.

[0072] Water soluble polymer

[0073] Film also comprises one or more water-soluble polymers.Water-soluble polymers can be based on the gross weight of film, 10 % by weight to 90 % by weight, for example, 15 % by weight to 85 % by weight, 20 % by weight to 80 % by weight, 25 % by weight to 75 % by weight, 30 % by weight to 70 % by weight, 30 % by weight to 65 % by weight, 30 % by weight to 70 % by weight, 35 % by weight to 65 % by weight or 40 % by weight to 60 % by weight amount is present in film.In some embodiments, film comprises at least 10 % by weight, for example, at least 15 % by weight, at least 20 % by weight, at least 25 % by weight, at least 30 % by weight, at least 35 % by weight, at least 40 % by weight, at least 45 % by weight, at least 50 % by weight, at least 55 % by weight, at least 60 % by weight, at least 65 % by weight or at least 70 % by weight water-soluble polymers.In some embodiments, film comprises the water-soluble polymer of the amount of 40 % by weight to 60 % by weight based on the gross weight of film.

[0074] In some embodiments, the water-soluble polymer has a substantially crystalline (e.g., a crystallinity of at least 50%) morphology. The swelling and shrinking properties of the film depend in part on the morphology and molecular weight of the water-soluble polymer. For example, the crystalline morphology of the water-soluble polymer enables the water-soluble polymer to transform from a crystalline state to an amorphous state when in contact with water. When the film is no longer in contact with the fluid, the remaining water-soluble polymer recrystallizes along with the TPU chains, and the film shrinks to its original size after desorption or drying.

[0075] The crystalline nature of the water-soluble polymer "locks in" the elastic energy of the elastomer (eg, TPU).

[0076] The water-soluble polymer contributes to the crystallinity of the film. In some embodiments, the water-soluble polymer has a crystallinity greater than 50%. For example, the water-soluble polymer has a crystallinity greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or greater than 90%. In some embodiments, the water-soluble polymer has a crystallinity of 50% to 95%, for example, 55% to 95%, 60% to 95%, 65% to 90%, 70% to 90%, 75% to 90%, or 80% to 95%.

[0077] In some embodiments, the water-soluble polymers used in the films described herein generally have a high molecular weight. For example, the water-soluble polymers can have a weight average molecular weight (MW) greater than 25,000, greater than 50,000, greater than 75,000, greater than 100,000, greater than 125,000, greater than 150,000, greater than 175,000, greater than 200,000, greater than 225000, or greater than 250,000. w In some embodiments, the water-soluble polymer has a molecular weight of 25,000 to 500,000 g / mol, for example, 50,000 to 475,000 g / mol, 75,000 to 450,000 g / mol, 80,000 to 400,000 g / mol,

[0078] The weight average molecular weight (M) in the range of 90,000 to 350,000 g / mole, 100,000 to 300,000 g / mole, 100,000 to 250,000 g / mole, 100,000 to 200,000 g / mole, or 150,000 to 250,000 g / mole. wIn some embodiments, the water-soluble polymer is polyethylene oxide. In some embodiments, the polyethylene oxide has a weight average molecular weight (M) greater than 25,000, greater than 50,000, greater than 75,000, greater than 100,000, greater than 125,000, greater than 150,000, greater than 175,000, greater than 200,000, greater than 225000, or greater than 250,000. w ).

[0079] As described herein, the water-soluble polymer and aromatic TPU are specifically tailored to produce films having a crystallinity of 25% to 60%. The water-soluble polymer primarily contributes to the crystalline nature of the film. In some embodiments, the water-soluble polymer may include polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymers, polyacrylic acid, and mixtures thereof.

[0080] PEO-1 stands for water dispersible polyethylene oxide polymer. TM WSR N-80 is provided and available from DuPont, Inc.

[0081] PEO-2 stands for water dispersible polyethylene oxide polymer. TM WSR N-10 is provided and available from DuPont, Inc.

[0082] PVOH-1 means water dispersible polyvinyl alcohol polymer. This product is sold under the name NICHIGO G-POLYMER TM OKS-8035 is provided and available from Soarus, Inc.

[0083] In some embodiments, the water-soluble polymer can be polyethylene oxide (PEO). For example, a commercially available polyethylene oxide with high crystallinity is PEO-1. Table 2 provides a thermal analysis of a film comprising PEO-1 and TPU-2 (aromatic TPU). As measured by differential scanning calorimetry (DSC) thermal analysis, a film comprising 100% by weight polyethylene oxide exhibits a crystallinity of 77%. Each of the compositions comprising a blend of PEO-1 and TPU-2 exhibits a crystallinity sufficient to expand when in contact with water. According to DSC analysis, since the film comprising 100% by weight TPU has an amorphous morphology, no crystallinity is exhibited.

[0084]

[0085]

[0086] In some embodiments, the water-soluble polymer can be a homopolymer or an interpolymer (e.g., a copolymer, a terpolymer, etc.), and can be nonionic, anionic, cationic or amphoteric. In addition, the polymer can be a single type (i.e., homogeneous), or a mixture of different polymers can be used (i.e., heterogeneous). In a specific embodiment, the water-soluble polymer contains repeating units with functional hydroxyl groups, such as polyvinyl alcohol ("PVOH"), copolymers of polyvinyl alcohol (e.g., ethylene vinyl alcohol copolymers, methyl methacrylate vinyl alcohol copolymers, etc.). Vinyl alcohol polymers, for example, have at least two or more vinyl alcohol units in the molecule, and can be homopolymers of vinyl alcohol or copolymers comprising other monomer units. Vinyl alcohol homopolymers can be obtained by hydrolyzing vinyl ester polymers such as vinyl formate, vinyl acetate, vinyl propionate, etc. The vinyl alcohol copolymer can be obtained by hydrolyzing a copolymer of a vinyl ester and an olefin having 2 to 30 carbon atoms (such as ethylene, propylene, 1-butene, etc.), an unsaturated carboxylic acid having 3 to 30 carbon atoms (such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, etc.) or its ester, salt, anhydride or amide, an unsaturated nitrile having 3 to 30 carbon atoms (such as acrylonitrile, methacrylonitrile, etc.), a vinyl ether having 3 to 30 carbon atoms (such as methyl vinyl ether, ethyl vinyl ether, etc.), and the like.

[0087] The degree of hydrolysis can be selected to optimize the solubility of the water-soluble polymer, etc. For example, the degree of hydrolysis can be from 60 mol% to 95 mol%, for example, from 80 mol% to 90 mol% or from 85 mol% to 89 mol%. An example of a suitable partially hydrolyzed polyvinyl alcohol polymer can be named CELVOL TM 203, 205, 502, 504, 508, 513, 518, 523, 530 or 540 are available from Celanese Corp. Other suitable partially hydrolyzed polyvinyl alcohol polymers may be marketed under the name ELVANOL TM 50-14, 50-26, 50-42, 51-03, 51-04, 51-05, 51-08 and 52-22 were obtained from DuPont.

[0088] The relative amounts of the water-soluble polymer and TPU used in the film can also be selected to help further optimize the expansion and contraction properties of the film. In some embodiments, the weight ratio of the water-soluble polymer to the TPU is 0.5: 1 to 8: 1, for example, 1: 1 to 7: 1, 1.25: 1 to 6: 1, 1.5: 1 to 5: 1, 1.5: 1 to 4: 1, 1.5: 1 to 3: 1, 1.5: 1 to 2.5: 1, 1: 1 to 3: 1 or 1.25: 1 to 2: 1. TPU can account for 10% to 90% by weight based on the total weight of the film, for example, 15% to 60% by weight or about 20% to about 50% by weight. The water-soluble polymer can account for 10% to 90% by weight based on the total weight of the film, for example, 20% to 80% by weight or 40% to 70% by weight.

[0089] additive

[0090] In some embodiments, the film may optionally include one or more additives. In some embodiments, the additive may include a surfactant, an absorbent, a skin benefit agent, a plasticizer, a mineral, an antibiotic or any combination thereof. For example, the film may include a superabsorbent polymer. Superabsorbent polymers are generally used to increase the absorption capacity and expansibility of the film. In some embodiments, superabsorbent polymers are present in the film in the form of small particles. Superabsorbent polymer powders suitable for film include but are not limited to various anionic materials, cationic materials and nonionic materials. Suitable polymers include polyacrylamide, polyvinyl alcohol, ethylene maleic anhydride copolymer, polyvinyl ether, polyacrylic acid, polyvinyl pyrrolidone, polyethylene morpholine, polyamine, polyethyleneimine, polyquaternary ammonium, natural polysaccharide polymers (such as carboxymethyl cellulose, carboxymethyl starch, hydroxypropyl cellulose, alginic acid, alginate, carrageenan, acrylic acid grafted starch, acrylic acid grafted cellulose, chitin, chitosan) and synthetic polypeptides (such as polyaspartic acid, polyglutamic acid, polyasparagine, polyglutamine, polylysine and polyarginine) and any salt, copolymer and mixture of the aforementioned polymers.

[0091] In addition to the above components, other additives may also be incorporated into the film, such as slip additives (e.g., fatty acid salts, fatty acid amides, etc.), compatibilizers (e.g., functionalized polyolefins), dispersing aids, melt stabilizers, processing stabilizers, heat stabilizers, light stabilizers, antioxidants, heat aging stabilizers, brighteners, anti-blocking agents, adhesives, lubricants, fillers, etc.

[0092] In some embodiments, the film may include a filler. Fillers are microparticles or other forms of materials that can be added to the film polymer extrusion blend and do not chemically interfere with the film, but can be evenly dispersed throughout the film. Fillers can serve multiple purposes, including enhancing the opacity and / or breathability of the film (i.e., vapor permeable and substantially liquid impermeable). For example, the filled film can be made breathable by stretching, which causes the polymer to separate from the filler and form microporous channels. Breathable microporous elastic films are described, for example, in U.S. Patents 5,997,981, 6,015,764, and 6,111,163 to McCormack et al.; U.S. Patent 5,932,497 to Morman et al.; and U.S. Patent 6,461,457 to Taylor et al., all of which are incorporated by reference in their entirety for all intents and purposes. In addition, hindered phenols are commonly used as antioxidants in film manufacturing. Some suitable hindered phenols include those available under the trade name Such as The present invention also can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention. The present invention can be used to prepare the film of the present invention.

[0093] Membrane construction and valve design

[0094] In some embodiments, the film can be a monolayer film or a multilayer film. The multilayer film can be prepared by coextrusion of layers, extrusion coating or by any conventional layering process. In some embodiments, the multilayer film may include at least one base layer and at least one skin layer. In some embodiments, the multilayer film may include multiple layers. For example, the multilayer film may be formed by a base layer and one or more skin layers, wherein the base layer is formed by a blend of a water-soluble polymer and TPU. In some embodiments, the skin layer is also formed by a blend as described above. However, it should be understood that other polymers may also be used in the skin layer.

[0095] In some embodiments, film as described herein may include one or more perforations so that film can serve as a valve. Film may be attached to at least one substrate. For example, film may be adhesively bonded to at least one base layer. Film is combined with at least one substrate (top and / or bottom) to control lateral expansion and the closure of the perforation serving as a valve. This can be achieved by patterning an adhesive layer, which leaves a specific unbonded area near one or more perforations of film. The lateral expansion of unbonded film allows perforation to be closed when in contact with water. The amount of expansion (for example, lateral expansion) may be affected by the composition of film, the ratio of water-soluble polymer to TPU and the amount of fluid in contact with film.

[0096] For example, film as described herein can be bonded or attached on at least one base layer to regulate the amount of water flowing into and out of the base layer. In some embodiments, the base layer can be the absorbent structure of an absorbent article. The film can include one or more perforations to allow fluid to enter the absorbent structure. The fluid in contact with the film can enter the absorbent structure through the perforations. A part of the fluid can be absorbed by the film. The fluid absorbed by the film expands the film and closes the perforations, thereby acting as a valve of the absorbent structure.

[0097] Figure 2 An embodiment of a membrane described herein is shown that includes openings for fluid flow through the membrane. Figure 2 The film is shown transitioning between a contracted state 200 and an expanded state 250. The film 205 can be any of the films described herein. For example, the film 205 can include a substantially crystalline (e.g., greater than 50% crystallinity) water-soluble polymer and an aromatic TPU. The film 205 can include one or more openings 210. Figure 2 In the illustrated embodiment, the film 205 includes star-shaped openings 210. The film 205 can have a variety of different shapes to provide a desired flow rate of fluid passing through the openings. For example, the total area of ​​the film 205 occupied by the openings can be at least 25%, for example, at least 30%, at least 35%, at least 40%, at least 45%, at least 50% or at least 55%. Films with larger area openings can provide faster fluid absorption.

[0098] like Figure 2 As shown, the film 205 can be in a contracted state 200 or an expanded state 250. In the contracted state 200, the film 205 is dry. The contracted state 200 represents the initial state of the film, in which the pores 210 are open. In the contracted state 200, the film 205 provides openings for fluid absorption, i.e., the pores 210. As discussed herein, in the contracted state 200, the water-soluble polymer is entangled with the aromatic TPU and the elastic aromatic TPU is pulled to the contracted state due to the crystalline morphology of the water-soluble polymer.

[0099] Figure 2Also shown is the expanded state 250 of film 205 after absorbing water. In the expanded state 250, the expansion of film 205 will close the perforations 210, thereby preventing fluid from flowing back. When film 205 absorbs fluid (e.g., water), the water-soluble polymer begins to change from a crystalline state to an amorphous state. The morphological change of the water-soluble polymer from the contracted state 200 to the expanded state 250 causes the film 205 to swell, thereby effectively releasing the elastic energy of the aromatic TPU. In other words, due to the entanglement of the TPU chain with the hydrophilic water-soluble polymer chain, the film expands with the swelling of the water-soluble polymer. Therefore, film 205 absorbs water and the morphological change of the water-soluble polymer changes to an amorphous state to achieve film expansion.

[0100] Film preparation method

[0101] Any known technology can be used to form the film described herein, including blow molding, casting, flat die extrusion, etc. In some embodiments, the film can be formed by a blow molding process, in which a gas (e.g., air) is used to expand the bubbles of the extruded polymer blend through an annular die. The bubbles then collapse and are collected in the form of a flat film. The process for preparing a blown film is described in, for example, U.S. Patent Nos. 3,354,506, 3,650,649, 3,801,429, 2005 / 0245162, 2003 / 0068951, 2003 / 0068951, all of which are incorporated herein by reference for all intents and purposes. In another embodiment, the film is formed with a casting technique.

[0102] In some embodiments, each component can be blended together to form a film using various known techniques. In one embodiment, for example, the components can be provided individually or in combination. For example, the components can first be dry-mixed together to form a substantially uniform mixture, and they can also be supplied simultaneously or successively to a melt processing device (e.g., an extruder) that uniformly blends the materials.

[0103] In some embodiments, the preparation method of film can include batch and / or continuous melt processing technology.For example, mixer / kneader, Banbury mixer, Faro continuous mixer, single screw extruder, twin screw extruder, rolling mill etc. can be utilized to blend and melt process these materials.The example of suitable melt processing device can include co-rotating twin screw extruder (for example, derived from Thermo Electron Corporation, Stone, England's USALAB twin screw extruder or derived from Werner-Pfreiderer, Ramsey, NJ's extruder).Such extruder can include feed port and vent and provide high-intensity distributed and dispersed mixing.For example, component can be fed to the same or different feed port of twin screw extruder and melt blended to form substantially uniform molten mixture.If desired, other additives can also be injected into polymer melt and / or be fed to extruder respectively at different positions along extruder length.

[0104] According to some embodiments of the present invention, Figure 3 An exemplary system for preparing a film is shown. Raw materials (e.g., water-soluble polymers, TPU, superabsorbent polymers, optional additives, etc.) can be supplied to a melt blending device alone or as a blend. For example, each component can be supplied to a melt blending device, where they are uniformly blended in a manner such as described above. For example, an extruder including one or more feed ports and vents can be used. Figure 3 The system is a one-step process for preparing a film using an extruder 340 (e.g., a single screw extruder). In some embodiments, a water-soluble polymer 310 and a TPU 320 can be fed in large quantities into a feed port (e.g., a hopper) of the extruder 340. The polymer melt from the extruder 340 can be processed through a film die 350 to prepare a film 380.

[0105] The system 300 for preparing the film 380 may include an extruder 340, a film die 350, a cooling roll 360, and an optional winder 370. Figure 3 In the embodiment shown, the water-soluble polymer 310 is fed into the first feed port 330 and the TPU 320 is fed into the second feed port 335. In some embodiments, the TPU 320 may be first fed into the feed port of the extruder 340 and melted. Thereafter, the water-soluble polymer 310 and optional additives may be fed into the polymer melt. These materials are blended under high shear / pressure and heat to ensure adequate mixing in the extruder 340.

[0106] Extruder 340 can be a single screw extruder. Commercially available single screw extruders suitable for making films include, for example, the HAAKE TM Rheomex OS single screw extruder. In some embodiments, melt blending can be carried out at a temperature of 50°C to 300°C, e.g., 75°C to 250°C, 100°C to 225°C, 120°C to 215°C, or 120°C to 200°C. In some embodiments, the shear rate during melt blending can be 100 seconds to 250 seconds. -1 Up to 10,000 seconds -1 , for example, 500 seconds -1 Up to 5000 seconds -1 or 800 seconds -1 Up to 1200 seconds -1 The apparent shear rate is equal to 4Q / πR 3 , where Q is the volume flow rate of the polymer melt (“m 3 / s”), and R is the radius (“m”) of the capillary (e.g., extruder die) through which the molten polymer flows.

[0107] According to some embodiments of the present invention, Figure 4 Another exemplary system for preparing a film is shown. System 400 is a one-step process for preparing a film using a twin screw extruder 440. In some embodiments, the twin screw extruder 440 can be a co-rotating twin screw extruder. Particularly suitable co-rotating twin screw extruders include, for example, a ZSK-30 extruder available from Werner & Pfleiderer Corporation, Ramsey, NJ or a Thermo Prism available from Thermo Electron Corp., Stone, England. TMUSALAB 16 extruder. The water-soluble polymer 410 and the TPU 420 may be provided to the extruder 440 through a hopper 430. The water-soluble polymer 410 and the TPU 420 may be fed to the extruder 440 at a preset descending rate. The polymer blend may be coextruded into a film 480 at an extrusion temperature in the range of 50°C to 300°C, e.g., 75°C to 250°C, 100°C to 225°C, 120°C to 215°C, or 120°C to 200°C. In some embodiments, the extruder 440 may be operated at a set screw speed in the range of 110rpm to 280rpm, e.g., 120rpm to 270rpm, 130rpm to 250rpm, 140rpm to 225rpm, 150rpm to 210rpm, or 150rpm to 200rpm. The film from the extruder may be processed through a film die 450 and chill rolls 460 to produce a final film 480 which is pulled through the system and / or taken up by a winder 470 .

[0108] According to some embodiments of the present invention, Figure 5 Another exemplary system for preparing membranes is shown. Figure 5 A two-step process for preparing a film is shown, including a pelletizing system 500 and a film-forming system 550. In this embodiment, the polymer components are compounded into pellets 540 in the pelletizing system 500, and then the pellets 540 are extruded in the film-forming system 550 to prepare a film 580. In the pelletizing system 500, the water-soluble polymer 505 and the TPU 510 can be metered or bulk fed into a twin-screw extruder 515 at a specific ratio.

[0109] In some embodiments, the polymer blend can be melt blended at the extrusion temperature by a twin screw extruder 515 to form a homogeneous polymer blend. The molten polymer blend can then be extruded by a filament die 520. Thereafter, the extruded material can be cooled and cut into pellet form. In some embodiments, the extruded material can be air cooled on a conveyor 525 using a fan 530 and cut into pellets using a pelletizing system 535.

[0110] Then, the pellets 540 can be processed in a film forming system 550 in a second step to prepare a film. The compounded pellets 540 can be fed in large quantities into a single screw extruder or a twin screw extruder 555 having a casting film die 560. The pellets are melted at the extrusion temperature in the extruder 555 and extruded onto a cooling roller 565 through the film die 560. The film 580 can then be wound into a roll by a winder 570. If a multilayer film is to be prepared, multiple layers are coextruded together onto a casting roll. The casting roll can optionally have an embossing element to impart a pattern to the film.

[0111] According to some embodiments, Figure 6 A flow chart of a method for preparing a film is provided. In some embodiments, a method 600 for preparing a film is provided. Method 600 may include providing a water-soluble polymer 610. As described herein, the water-soluble polymer may be substantially crystalline. For example, the water-soluble polymer may have a crystallinity greater than 50%, for example, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or greater than 90%. In some embodiments, the water-soluble polymer may include polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymers, polyacrylic acid, and mixtures thereof.

[0112] Method 600 may include providing an aromatic TPU 620. As described herein, the aromatic TPU contributes to the expansion properties of the film when it comes into contact with water. The aromatic TPU may be provided in pellet or powder form. In some embodiments, the aromatic TPU may have a tensile strength in the range of 10 MPa to 50 MPa. In some embodiments, the aromatic TPU may have a tensile modulus in the range of 15 MPa to 30 MPa.

[0113] Method 600 can include melt blending of water-soluble polymer and aromatic TPU 630 to prepare polymer melt. In some embodiments, water-soluble polymer and aromatic TPU can be melt blended in an extruder. For example, water-soluble polymer, aromatic TPU and other additives can be melt blended in a single screw extruder or a twin screw extruder. In some embodiments, water-soluble polymer and aromatic TPU can be dry blended together to form a substantially uniform mixture, and they can be similarly supplied to a melt processing device (e.g., extruder) for uniformly blending materials simultaneously or successively. Water-soluble polymer and aromatic TPU are melt blended so that aromatic TPU is fully distributed in a water-soluble polymer matrix, so that the film is uniformly expanded, that is, the expansion percentages in the longitudinal direction (MD) and the transverse direction (CD) of the film are equal. In some embodiments, the method can include providing additional additives (e.g., plasticizers, surfactants, superabsorbent polymers, etc.) to the polymer blend.

[0114] Method 600 can include extruding the composition to prepare a membrane 640. In some embodiments, the membrane comprises a water-soluble polymer in an amount of 30 wt% to 70 wt% based on the total weight of the membrane, and an aromatic TPU in an amount of 30 wt% to 70 wt% based on the total weight of the membrane. The weight ratio of the water-soluble polymer to the aromatic TPU in the composition can be in the range of 1:1 to 4:1. In some embodiments, the method can include cutting a pattern into the expandable membrane. For example, a pattern can be embossed or cut into the membrane to prepare openings that can serve as a water-responsive valve. The pattern is any of the valve designs discussed herein, such as Figure 2 as shown in .

[0115] Example

[0116] The sample films were tested to determine the expansion properties of the films described herein. Comparative Examples 1-4 and Examples 1-16 were prepared according to the method described below. Examples 1-16 contained aromatic TPUs and Comparative Examples 1-3 contained aliphatic TPUs. Comparative Example 4 contained a water-soluble polymer with low crystallinity (e.g., less than 50%). Table 3 provides the film composition of each of Comparative Examples 1-4 and Examples 1-16.

[0117]

[0118]

[0119] Crystallinity measurements were measured for several samples. Crystallinity was measured by differential scanning calorimetry (DSC) using a DSC Q 200 from TA Instruments in a nitrogen atmosphere for a sample mass range of 4.9 mg to 5.8 mg. The method log for DSC is as follows:

[0120] 1. From room temperature to 0°C at 10.00°C / min, keep constant temperature for 2.0min;

[0121] 2. From 0℃ to 125℃ at 10.0℃ / min, keep constant temperature for 2.0min;

[0122] 3. 10.0°C / min from 125°C to -50°C, hold at constant temperature for 2.0 min; and

[0123] 4. Heat from -50°C to 125°C at 10.0°C / min and hold constant for 2.0 min.

[0124] Crystallinity (χ c ) can be measured according to the following formula (I):

[0125]

[0126] Where ΔH mis the enthalpy of fusion, and is the melting enthalpy of 100% pure PEO, which is 196 J / g. Crystallinity χ c Calculations are based on the 2nd heating cycle.

[0127] Example 1, Example 3 and Example 4 are Figure 3 The water-soluble polymer (in powder form) and TPU (in pellet form) were fed in large quantities to HAAKE TM Rheomex OS single screw extruder (Thermo Fisher Scientific, length to diameter ratio 25:1). HAAKE TM The Rheomex OS single screw extruder has a screw diameter of 0.75 inches. The polymers are melt blended in the extruder at the extrusion temperature to form a homogeneous polymer blend. A HAAKE TM The melt pump feeds the homogeneous polymer blend to the HAAKE TM 6-inch film die to produce the film. The film was collected in a HAAKE TM On the film take-up system.

[0128] Example 5, Example 6, Example 10, Examples 13-16 and Comparative Example 2 Figure 4 The process shown in the figure is prepared. The water-soluble polymer (powder form) and TPU (pellet form) are fed into a ZSK-30 twin-screw extruder (obtained from Werner & Pfleiderer Corporation, Ramsey, NJ, with a length of up to 1328 mm and a diameter of 30 mm) at a preset descending rate. The ZSK-30 twin-screw extruder has 14 barrels. The polymers are melt blended in the extruder at a temperature of 120° C. to 200° C. to form a uniform polymer blend and die cast to prepare a film. The screw speed of the extruder is 150 rpm to 200 rpm.

[0129] Example 2, Example 7, Example 8, Example 9, Example 11 and Example 12 and Comparative Example 1, Comparative Example 3 and Comparative Example 4 are Figure 5The process shown in the figure is prepared. Water-soluble polymer (powder form) and TPU (pellet form) are fed into a ZSK-30 twin-screw extruder (derived from Werner & Pfleiderer Corporation, Ramsey, NJ, with a length of up to 1328 mm and a diameter of 30 mm). Water-soluble polymer and TPU are metered into the extruder at a specific ratio to prepare thick filaments. The thick filaments are extruded onto an air-cooled conveyor including a fan. At the end of the conveyor, the filaments are collected on a tray for air cooling for 30 minutes to 1 hour. After cooling, the filaments are granulated to make small pellets. The pre-compounded pellets are fed into a co-rotating twin-screw extruder to cast the film. The film is extruded onto a cooling roller and finally wound on a roller.

[0130] Table 4 provides the results of the immersion test for each of Examples 1-16 and Comparative Examples 1-4. The membrane was evaluated using an aqueous solution immersion test to determine the expansion properties. At a fixed position in the transverse direction of the membrane, a film strip of 80 mm (MD) × 20 mm (CD) was cut from the substrate film along the MD. The film strip was weighed and the initial thickness was recorded. Then, the film strip was immersed in a 0.9 wt % NaCl saline solution bath. After one minute, the size of the film was recorded, and then after 15 minutes, the size was recorded again. Water-responsive membranes can change dynamically when immersed in an aqueous solution because they may curl and twist. Therefore, tweezers were used to straighten the membrane and accurate size measurements were made at one-minute intervals with the help of a ruler immersed in the bath. After 15 minutes, the membrane was removed from the saline and air cooled. After drying, the final mass was recorded. Three replicate films of each blend were tested.

[0131]

[0132]

[0133] The data of the immersion test in Table 4 show that, except for Example 6, all films containing aromatic TPU of Examples 1-16 expand in two dimensions (length and width) after being immersed in water for 1 minute. Whether the film is prepared using the different processes described above (e.g., single screw extruder, twin screw extruder or two-step process) will show expansion. For example, for the film measured after 15 minutes of immersion, the data show that the film size is recovering to its original size. Specifically, the length and width of the films of Example 1, Example 2, Example 5, Example 8, Example 9 and Examples 11-16 are reduced to their original size. Regardless of whether the film is prepared using a one-step process or a two-step process, Comparative Examples 1-3, each containing aliphatic TPU, shrinks in two dimensions (length and width) after being immersed in water for 1 minute.

[0134] Comparative Example 4 contains 60 wt % polyvinyl alcohol (as the water-soluble polymer) and 40 wt % TPU. According to DSC analysis, the crystallinity of the polyvinyl alcohol is 16.2%. Comparative Example 4 and Example 2 contain the same amount of water-soluble polymer and aromatic TPU and are prepared according to the same process. The data in Table 3 show that Comparative Example 4 containing polyvinyl alcohol does not swell despite containing the same aromatic TPU as Example 2. The crystallinity of the water-soluble polymer (polyvinyl alcohol) is significantly less than that of the water-soluble polymer (polyethylene oxide) used in Examples 1-7 (16% vs. 77%), which may contribute to the lack of any water-responsive swelling properties of the film of Comparative Example 4.

[0135] Example 2, Example 8, Example 9 and Example 10 are films containing different percentages of PEO-1 (water-soluble polymer) and TPU-2. Example 2 contains 60% by weight of water-soluble polymer, Example 8 contains 70% by weight of water-soluble polymer, Example 9 contains 80% by weight of water-soluble polymer, and Example 10 contains 53% by weight of water-soluble polymer. The films of Example 8 and Example 9 are prepared according to a different process from Example 10. The data show that the films of Example 2, Example 8, Example 9 and Example 10 are fully expanded in both length and width dimensions after being soaked in water for 1 minute. Example 9, which contains the least amount of TPU (20% by weight), shows the least expansion in length and width compared with Example 8 and Example 10.

[0136] Example 11 and Example 12 are films comprising 60 wt % and 70 wt % of PEO-2 (water-soluble polymer) and 40 wt % and 30 wt % of TPU-2, respectively. Both Example 11 and Example 12 were prepared according to the same process. In these examples, the polyethylene oxide water-soluble polymer has a molecular weight of 100,000 g / mol and a measured crystallinity of about 71.7%, while PEO-1 has a molecular weight of 200,000 g / mol and a crystallinity of 77%. Although the water-soluble polymers of Example 11 and Example 12 have lower molecular weights, they have sufficient crystallinity to support the expansion of the water-responsive membrane after immersion.

[0137] Example 13, Example 14, Example 15 and Example 16 are films comprising 60% by weight of PEO-1 (water-soluble polymer) and 40% by weight of TPU-5. The films of Example 13 and Example 14 were prepared by the process described above (one-step process using a single screw extruder), and the films of Example 15 and Example 16 were prepared according to a different process (two-step process using a twin screw extruder). The water responsive behavior of the exemplary films of different weights was tested using a water immersion test.

[0138] The results show that each of the films of Examples 13-14 expanded in both length and width after 1 minute soaking. Although the expanded area after 1 minute soaking does not seem to be sensitive to the preparation method, the expansion in both dimensions appears to be greater for the films prepared by the two-step process including compounding and extrusion ( Figure 5 ). This may be due to the better dispersion of TPU in the main water-soluble polymer phase in these runs. Therefore, how to evenly disperse TPU in water-soluble polymer or vice versa is one of the key factors in preparing expandable membranes.

[0139] Fig. 7A and Figure 7B The conventional membrane ( Fig. 7A ) and the membrane described herein ( Figure 7B ) have different responses to water. Specifically, Fig. 7A A schematic representation of the responsiveness of a comparative film comprising 60 wt% polyethylene oxide (a water soluble polymer) and 40 wt% VISTAMAXX (a polypropylene copolymer) (available from ExxonMobil Chemical Corporation) to water / saline is shown 700. The film was laminated to a spunbond-meltblown-spunbond (SMS) nonwoven. Figure 7B A schematic representation 750 of the responsiveness of an exemplary film comprising 70 wt % polyethylene oxide (a water soluble polymer) and 30 wt % aromatic TPU to water / saline is shown. The film was laminated to an SMS nonwoven. Figure 7B As shown, a film comprising polyethylene oxide (which is a substantially crystalline, water-soluble polymer) and an aromatic TPU swells when in contact with water. Specifically, when the exemplary film is immersed in water, it swells from its original length of about 4 inches to a length of about 6 inches. Although the measurements are not shown, it is clear from visual inspection that the film swells from its original length of about 4 inches to a length of about 6 inches. Figure 7B The width of the media has also increased. Fig. 7A As shown, the comparative film shrinks by as much as 80% upon contact with water.

[0140] All patents, publications and abstracts cited above are incorporated herein by reference in their entirety. Various embodiments of the present invention have been described to achieve the various purposes of the present invention. It should be appreciated that these embodiments are merely to demonstrate the principles of the present invention. It will be apparent to those skilled in the art that various modifications and adjustments of the present invention will be apparent without departing from the spirit and scope of the present invention as defined in the following claims.

[0141] Although the present invention has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art can easily conceive of modifications, variations and equivalents of these embodiments after obtaining an understanding of the foregoing. Therefore, the scope of the present invention should be assessed as the scope of the appended claims and any equivalents thereof and the following embodiments:

[0142] Embodiment 1: A water-responsive film comprising a water-soluble polymer and an aromatic thermoplastic polyurethane (aromatic TPU), wherein the film has a crystallinity of at least 25%.

[0143] Embodiment 2: A water-responsive membrane as described in any preceding or subsequent embodiment, wherein the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid, or a combination thereof.

[0144] Embodiment 3: The water-responsive membrane of any preceding or subsequent embodiment, wherein the water-soluble polymer comprises polyethylene oxide.

[0145] Embodiment 4: The water-responsive membrane of any preceding or subsequent embodiment, wherein the polyethylene oxide has a molecular weight in the range of 50,000 g / mol to 500,000 g / mol.

[0146] Embodiment 5: The water-responsive membrane of any preceding or subsequent embodiment, wherein the aromatic TPU comprises a polyester-based TPU.

[0147] Embodiment 6: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane has a crystallinity of 25% to 60%.

[0148] Embodiment 7: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane comprises the water-soluble polymer in an amount of 10 wt% to 90 wt% based on the total weight of the membrane.

[0149] Embodiment 8: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane comprises the aromatic TPU in an amount of 10 wt% to 90 wt%, based on the total weight of the membrane.

[0150] Embodiment 9: The water-responsive membrane of any preceding or subsequent embodiment, wherein the weight ratio of water-soluble polymer to the aromatic TPU is at least 1:1.

[0151] Embodiment 10: A water-responsive membrane as described in any of the preceding or subsequent embodiments, wherein the membrane comprises the water-soluble polymer in an amount of 30 wt% to 70 wt% based on the total weight of the membrane, TPU in an amount of 30 wt% to 70 wt% based on the total weight of the membrane, and the ratio of the water-soluble polymer to the aromatic TPU is at least 1.5:1.

[0152] Embodiment 11: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane comprises one or more additives comprising a surfactant, an absorbent, an antibiotic, or a skin benefit agent.

[0153] Embodiment 12: The water-responsive membrane of any preceding or subsequent embodiment, wherein the additive comprises a superabsorbent.

[0154] Embodiment 13: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane is cut or scored to include one or more openings.

[0155] Embodiment 14: The water-responsive membrane of any preceding or subsequent embodiment, wherein the membrane has a tensile strength of 10 MPa to 50 MPa, and a tensile modulus of 1 MPa to 5 MPa.

[0156] Embodiment 15: A water-responsive membrane, comprising: 30 wt% to 70 wt% of a water-soluble polymer based on the total weight of the membrane, wherein the water-soluble polymer has a crystallinity greater than 50%; 30 wt% to 60 wt% of an aromatic thermoplastic polyurethane based on the total weight of the membrane; wherein the membrane has a crystallinity of 25% to 60%.

[0157] Embodiment 16: A method of preparing a water-responsive swellable membrane, the method comprising: melt blending a composition comprising a water-soluble polymer and an aromatic TPU; and extruding the composition to prepare a membrane.

[0158] Embodiment 17: The method of any preceding or subsequent embodiment, wherein the film comprises the water-soluble polymer in an amount of 30 wt% to 70 wt% based on the total weight of the film, and the film comprises the aromatic TPU in an amount of 30 wt% to 60 wt% based on the total weight of the film.

[0159] Embodiment 18: The method of any preceding or subsequent embodiment, wherein the ratio of the water soluble polymer to the aromatic TPU in the composition is from 1:1 to 4:1.

[0160] Embodiment 19: A method as described in any of the preceding or subsequent embodiments, wherein the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid, or a combination thereof, and the aromatic TPU comprises a polyester-based TPU.

[0161] Embodiment 20: The method of any preceding or subsequent embodiment, further comprising cutting a pattern into the expandable membrane.

[0162] Embodiment 21: The method of any preceding or subsequent embodiment, wherein the method further comprises bonding the film to a substrate.

Claims

1. A water-responsive membrane, comprising: water soluble polymers; and Aromatic thermoplastic polyurethane (TPU); wherein the film has a crystallinity of at least 25%.

2. The water-responsive membrane of claim 1, wherein the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid, or a combination thereof. The water-responsive membrane of claim 1 , wherein the water-soluble polymer comprises polyethylene oxide. The water-responsive membrane of claim 3 , wherein the polyethylene oxide has a molecular weight in the range of 50,000 g / mol to 500,000 g / mol.

5. The water-responsive membrane of claim 1, wherein the aromatic TPU comprises a polyester-based TPU. The water-responsive film of claim 1 , wherein the film has a crystallinity of 25% to 60%. 7 . The water-responsive film of claim 1 , wherein the film comprises the water-soluble polymer in an amount of 10 wt % to 90 wt % based on the total weight of the film. 8 . The water-responsive film of claim 1 , wherein the film comprises the aromatic TPU in an amount of 10 wt % to 90 wt % based on the total weight of the film.

9. The water-responsive membrane of claim 1, wherein the weight ratio of the water-soluble polymer to the aromatic TPU is at least 1:

1.

10. The water-responsive film of claim 1, wherein the film comprises the water-soluble polymer in an amount of 30 to 70 wt % based on the total weight of the film, the TPU in an amount of 30 to 60 wt % based on the total weight of the film, and the ratio of the water-soluble polymer to the aromatic TPU is at least 1.5:

1.

11. The water-responsive membrane of claim 1, wherein the membrane comprises one or more additives, the additives comprising surfactants, absorbents, antibiotics, or skin benefit agents.

12. The water-responsive membrane of claim 11, wherein the one or more additives comprise a superabsorbent.

13. The water-responsive membrane of claim 1, wherein the membrane is cut or scored to include one or more openings. 14 . The water-responsive film of claim 1 , wherein the film has a tensile strength of 10 MPa to 50 MPa, and a tensile modulus of 1 MPa to 5 MPa.

15. A water-responsive membrane, comprising: 30 wt % to 70 wt % of a water-soluble polymer based on the total weight of the film, wherein the water-soluble polymer has a crystallinity greater than 50%; and 30 to 60 wt % of an aromatic thermoplastic polyurethane, based on the total weight of the film; The film has a crystallinity of 25% to 60%.

16. A method for preparing a water-responsive expandable membrane, the method comprising: melt blending a composition comprising a water-soluble polymer and an aromatic TPU; as well as The composition is extruded to prepare a film.

17. The method of claim 16, wherein the film comprises the water-soluble polymer in an amount of 30 wt% to 70 wt% based on the total weight of the film; wherein the film comprises the aromatic TPU in an amount of 30 wt % to 60 wt % based on the total weight of the film; and The ratio of the water-soluble polymer to the aromatic TPU in the composition is 1:1 to 4:

1.

18. The method of claim 16, wherein the water-soluble polymer comprises polyethylene oxide, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine, gelatinized starch, nylon copolymer, polyacrylic acid, or a combination thereof; and The aromatic TPU includes polyester-based TPU.

19. The method of claim 16, further comprising cutting a pattern into the film.

20. The method of claim 19, further comprising bonding the film to a substrate.

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