MULTI-LAYER FILM

Abstract

Described is a multilayer film comprising a layer (a) of a non-water-soluble polymer and a layer (b) of a swellable or water-soluble polymer, wherein layer (b) additionally contains either an odor-binding substance and / or a fragrance; and the use of the film in hygiene products such as diapers or sanitary napkins. The multilayer film can effectively and selectively suppress unwanted odors caused by fluids such as urine or menstrual fluid at the point of origin and is simultaneously simple and cost-effective to manufacture on an industrial scale.

Description

TECHNICAL AREA The present invention relates to a multi-layered film which can be used as an odor-reducing system for use in hygiene products such as diapers or sanitary napkins. BACKGROUND Hygiene products such as diapers or sanitary napkins, which collect bodily fluids like urine, blood, or menstrual fluids, typically develop an odor. Minimizing or even preventing this odor is therefore an important factor in the development of hygiene products that offer increased user comfort. One possible approach to this problem is to provide a water-soluble film filled with odor absorbers, perfumes, or oils. For example, EP 2 294 115 B1 discloses a film formed from a water-soluble polymer matrix containing at least one fragrance. The film is water-sensitive, so that upon contact with a sufficient amount of water, the polymer matrix gradually loses its integrity, and the fragrance is increasingly exposed to the environment, where it releases its odor. The ability to incorporate a fragrance into the polymer matrix is ​​achieved by controlling a variety of aspects of the film construction, including the type of fragrance, the type of water-soluble polymer, the way in which the polymer matrix and the fragrance are processed in the melt, and so on. For example, the fragrance can be injected directly into the extruder and mixed with the water-soluble polymer in the melt. EP 3 197 274 B1 discloses an extruded water-soluble article consisting of a homogeneous material containing a water-soluble polymer. The article also contains an active ingredient selected from isothiazolone, alkyldimethylammonium chloride, triazine, 2-thiocyanomethylthiobenzothiazole, methylene bisthiocyanate, acrolein, dodecylguanidine hydrochloride, chlorophenol, a quaternary ammonium salt, glutaraldehyde, dithiocarbamate, 2-mercaptobenzothiazole, parachlormeta-xylenol, silver compounds, chlorhexidine, polyhexamethylene biguanide, N-halamine, triclosan, phospholipid, an alpha hydroxy acid, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitro-1,3-propanediol, farnesol, iodine, bromine, hydrogen peroxide, chlorine dioxide, ozone, a vegetable oil, a plant extract, benzalkonium chloride, chlorine, sodium hypochlorite, and combinations thereof. The article may be in the form of a film and, in a possible use, may be placed in an absorbent article. Both of these revelations have in common that they contain their respective active ingredient in a water-soluble article, such as a film or foil. This has the disadvantage that the mechanical properties often do not meet the actual application requirements. Furthermore, such water-soluble articles are typically hygroscopic, which significantly complicates their processing according to industrial standards. Another possibility is disclosed in US 9,801,765 B2. This document describes an odor control material consisting of a water-insoluble particulate odor control agent and a thermoplastic, water-soluble carrier matrix that encapsulates the odor control agent. The carrier matrix dissolves upon contact with an aqueous solution, such as urine. The water-insoluble, particulate odor control agent is produced through a complex, multi-stage process that includes compounding, film extrusion, and die-cutting or slicing. Such a process is energy-intensive and costly on an industrial scale. Therefore, there is a need for a multi-layered film that is suitable for effectively reducing odor development when used in a hygiene product, also offers advantageous mechanical properties, and can be manufactured easily and cost-effectively on an industrial scale. SUMMARY The present invention solves this problem with the subject matter of the claims defined herein. The advantages of the present invention are explained in more detail in the following section, and further advantages will become clear to the person skilled in the art upon consideration of the disclosure of the invention. In general, the present invention provides in one aspect a multilayer film comprising a layer (a) comprising a non-water-soluble polymer, and a layer (b) comprising a swellable or water-soluble polymer, wherein the layer (b) additionally contains an odor-binding substance and / or a fragrance. In another aspect, the present invention provides for the use of the film in a hygiene product. BRIEF DESCRIPTION OF THE FIGURES Fig. 1: Schematic diagram of an exemplary film with a five-layer structure. Fig. 2: Schematic diagram of an exemplary film with a three-layer structure. DETAILED DESCRIPTION OF THE INVENTION For a better understanding of the present invention, reference is now made to the following description of exemplary embodiments: In a first aspect, the present invention relates to a multilayer film comprising a layer (a) comprising a non-water-soluble polymer, and a layer (b) comprising a swellable or water-soluble polymer, wherein layer (b) additionally contains an odor-binding substance or a fragrance or a combination thereof. The swellable or water-soluble polymer swells or dissolves upon contact with water or body fluids, thereby releasing the odor-binding substance or the fragrance, or increasing the diffusion rate of odor-causing substances to the odor-binding substance. The term "water-soluble" refers to a substance that can dissolve upon contact with water or an aqueous solution, such as urine or blood. In this context, it further means that the water-soluble polymer dissolves at least partially, thus releasing water-insoluble particles, such as odor-binding agents or fragrances, that are encapsulated in a water-soluble support matrix. A swellable polymer within the scope of this disclosure is a polymer into which water or an aqueous solution can penetrate, thereby causing an increase in the polymer's volume and releasing water-insoluble particles such as odor-binding agents or fragrances. Examples include, in particular, polyvinyl alcohol and polyethylene glycol, as well as water-soluble or water-swellable acrylic polymers. Suitable swellable polymers can also be cellulose esters and cellulose ethers, such as cellulose acetate, provided these materials swell sufficiently rapidly. In a preferred embodiment, the non-water-soluble (also referred to in this application as a water-insoluble polymer) polymer is a polystyrene, polyester, polyurethane, or polyolefin, or a biodegradable polymer. Examples of biodegradable polymers are polymers with ester linkages in the main chain that can be degraded by hydrolytic processes (but do not lose their integrity upon first contact with water or moisture, i.e., are water-insoluble within the meaning of the present invention), or cellulose-based polymers. Specific examples are cellulose esters and cellulose ethers, such as cellulose acetate; lactic acid-based polymers; polyglycolic acid; copolymers thereof, such as polylactide-co-glycolide; polyepsilon-caprolactone; poly(butylene adipate co-terephthalate); and polyhydroxyalkanoates.The use of such a polymer in layer (a) provides the multilayer film with advantageous mechanical properties and the necessary dimensional stability, for example for use in hygiene products. Preferably, layer (a) comprises polyethylene (PE) or polypropylene (PP) to ensure the desired mechanical properties. The biodegradable polymer is preferably poly(butylene adipate co-terephthalate) (PBAT) or a mixture of PBAT with other biodegradable polymers, in particular PLA. The thickness of layer (a) is, for example, 10 to 45 µm, preferably 10 to 40 µm, and particularly preferably 15 to 35 µm to obtain the desired mechanical properties. In one embodiment, layer (b) comprises polyvinyl alcohol (PVOH) as a swellable or water-soluble polymer to enable the effective release of the odor-binding agent and / or the fragrance. The fragrance is preferably selected from an oil or perfume with a boiling point above 165 °C; examples include long-chain essential oils. The odor-binding agent is preferably selected from at least one of the following: zeolite, cyclodextrin, activated carbon, ZnO, CaO, SiO₂, ZrO₂, inorganic or organic zinc salts, inorganic or organic zirconium salts, such as zinc ricinoleate, organosiloxanes, and chelating agents, such as citrate or EDTA, and preferably has a melting point or decomposition temperature above 200 °C. According to the invention, zeolites, ZnO, SiO₂, and cyclodextrins are preferred, optionally in combination with a fragrance.Zeolites are particularly preferred because their odor-binding properties are good and can be controlled by specifically adjusting the pore size of the respective zeolite material (since the size of the pores is relevant for the type of odorants that can be bound). The odor-binding substances and / or fragrances are selected to be able to bind or at least mask the "target substances" occurring in a given application. Depending on the application, these could be, for example, ammonia or other nitrogen-based unpleasant odors, fecal odors, or, if, for example, an application in the area of ​​waste packaging is planned, decomposition odors from plant waste, etc. The selection of the fragrance or odor-binding agent enables the effective reduction of unwanted odor development, for example, when using the multilayer film in a hygiene product. A fragrance described above can also have a cooling effect at the point of contact between the film and the skin. Preferably, the odor-binding agent or fragrance is present in layer (b) at a concentration of 0.50 to 25.0 wt.%, particularly preferably at a concentration of 0.50 to 10.0 wt.%, and even more preferably at a concentration of 1.00 to 8.00 wt.%. This allows for the effective reduction of unwanted odor development. Layer (b) can also contain a combination of one or more odor-binding agents and fragrances to generate a broader spectrum of effectiveness against unwanted odors.The thickness of layer (b) is, for example, 1 to 10 µm, preferably 1 to 6 µm and particularly preferably 2 to 4 µm to ensure the necessary dimensional stability and at the same time to enable effective exposure of the odor-binding substance or fragrance. In one embodiment, layer (b) can be modified, for example, by adding a foaming agent, to create a porous structure. The foaming agent is preferably sodium bicarbonate, which decomposes under heat during the manufacturing process, for example, an extrusion process, into CO2 and H2O, thus causing the polymer melt to expand after exiting the extrusion die. In another embodiment, the foaming can also be achieved physically by injecting gases such as CO2 into the extrusion cylinder. Foaming layer (b) increases its surface area, resulting in pores. This creates a porous, for example, open-pore structure, which allows for faster absorption of moisture, thus accelerating the odor-controlling effect. In another embodiment, the multilayer film additionally comprises a core layer (c) and an outer layer (d), wherein the individual layers are arranged in the sequence (a), (c), (b), (d). The core layer (c) has gas barrier properties and thus prevents volatile fragrances from migrating out of the film through the permeable layer (a). The core layer (c) also prevents the film from emitting an odor, depending on the fragrance used, even without contact with water or an aqueous solution. In one embodiment, the core layer (c) comprises an ethylene-vinyl alcohol copolymer (EVOH) or polyvinyl alcohol (PVOH), with an ethylene-vinyl alcohol copolymer (EVOH) being preferred for cost reasons. The thickness of the core layer (c) is, for example, 1 to 10 µm, preferably 1 to 6 µm, and particularly preferably 2 to 4 µm to effectively ensure the gas barrier properties. The outer layer (d) also serves as a barrier layer to prevent premature evaporation of the fragrance when a fragrance is used in layer (b). The outer layer (d) comprises a swellable, water-soluble polymer, for example, polyvinyl alcohol. This is necessary because the point of attack for the water or aqueous solution is located at the outer layer (d). The outer layer (d) swells or dissolves to release the odor-binding substance or fragrance from the underlying layer (b). The thickness of the outer layer (d) is, for example, 1 to 10 µm, preferably 1 to 6 µm, and particularly preferably 2 to 4 µm to ensure the necessary dimensional stability while simultaneously enabling effective release of the odor-binding substance or fragrance. In a further embodiment, the multilayer film additionally comprises a layer (e) comprising an adhesion promoter, wherein the layer (e) is arranged between the layers (a) and (c) or, if the film has no layer (c) and no layer (d), is arranged between the layers (a) and (b). Layer (e) serves to bond the nonpolar layer (a) to the next polar layer, either layer (c) or layer (b), thus ensuring the necessary stability of the multilayer structure of the film according to the invention. The adhesion promoter is preferably a maleic anhydride-grafted linear low-density polyethylene (LLDPE) to achieve sufficient adhesion between the nonpolar layer (a) and the nearest polar layer, even at low film thicknesses. The thickness of layer (e) is, for example, 1 to 10 µm, preferably 1 to 6 µm, and particularly preferably 2 to 4 µm, to guarantee the necessary adhesion and thus ensure the dimensional stability of the multilayer film. In one embodiment, the multilayer film can additionally contain water-soluble antibacterial compounds such as zinc chloride, copper salts, ammonium salts or complexing agents. The multilayer film of the embodiments described above is preferably produced by an extrusion process. The film's layer structure can comprise two, three, four, or five layers. In a five-layer structure (Fig. 1), the layers described above are arranged in the sequence (a), (e), (c), (b), (d). In a four-layer structure, the layers are arranged in the sequence (a), (c), (b), (d). Such a four-layer structure without layer (e) is preferred if layer (a) comprises a biodegradable polymer, since such a polymer can be co-extruded even without an adhesion promoter. In a three-layer structure (Fig. 2), the layers are arranged in the sequence (a), (e), (b). Such a three-layer structure without a core layer (c) and outer layer (d) is preferred if an odor-binding substance is used in layer (b) that is solid at standard conditions of 25 °C and 1 bar.In this case, the multilayer film can be constructed without a core layer (c) and an outer layer (d), since migration of the odor-binding substance from the film is not possible. In a two-layer structure, the layers are arranged in the order (a), (b). Such a structure is preferred if layer (a) comprises a biodegradable polymer and layer (b) comprises an odor-binding substance that is solid at standard conditions of 25 °C and 1 bar. The odor-binding agent or fragrance in layer (b) can be added to the film during extrusion or as a masterbatch during the manufacturing process. Selecting a fragrance with a boiling point above 165 °C allows for its direct incorporation into the extrusion process. Similarly, selecting an odor-binding agent with a melting point or decomposition temperature above 200 °C allows for its incorporation into the extrusion process. In one embodiment, the film is perforated during the manufacturing process. This is done, for example, by vacuum perforation, laser perforation, or mechanical perforation. This enables the film to be used in hygiene products such as diapers or sanitary napkins, where the film can be applied, for example, as a layer beneath the outermost layer that comes into contact with the skin, with the film oriented such that layer (a) abuts said outermost layer. Such a structure using a perforated film according to the present invention enables the hydrophilization of a layered composite with ADL fixation (ADL = acquisition distribution layer), thereby allowing water or an aqueous solution to penetrate the layered composite more quickly. In another embodiment, the film is used in a hygiene product and oriented such that layer (b) or, depending on the structure, the outer layer (d) faces the interior of the hygiene product and can thus come into contact with the liquid. In this case, the film is not perforated during the manufacturing process. Instead, a filler such as chalk can preferably be incorporated into layer (a), and the film can be made breathable or permeable to water vapor by subsequent stretching, as necessary to achieve the required properties (breathability, water vapor permeability, etc.). If layer (a) comprises a biodegradable polymer, no stretching is necessary, provided the required property profile (breathability, water vapor permeability, etc.) is achieved. If this is not the case, the desired breathability or water vapor permeability can again be achieved by stretching. Another aspect of the present invention describes the use of the multilayer film described above in a hygiene product such as a diaper or a sanitary napkin, according to the embodiments described above. Other possible applications include its use in the manufacture of packaging, such as pouches that can, for example, hold hygiene products after use, or garbage bags for collecting moist waste that releases unwanted odors. Use in the medical field is also possible, for example, in the form of stoma bags or bags for packaging medical waste. It is evident that the present invention can utilize any of the preferred features specified above in relation to the description of the individual embodiments, and that the preferred features can be combined in any combination except for combinations in which at least some of the features are mutually exclusive. EXAMPLES The present invention is described below by means of examples. Table 1 shows a film with a five-layer structure and a film with a three-layer structure according to the embodiment of the present invention described above. Table 1 Five-layer film polyolefin 20I95LD 151 BW5HD 6070 FA Adhesion promoter3100Admer NF518E EVOH3100DC 3203RB PVOH396Mowiflex C174ARX V 24 PVOH3100Mowiflex C17 Three-layer film PE2095LD 151 BW5HD 6070 FA Adhesion promoter3100Admer NF518E PVOH395Mowiflex C175KD 211 • LD 151 BW: ExxonMobil™ LDPE LD 151BW; low-density polyethylene resin, manufactured by ExxonMobil • Admer™ NF518E: maleic anhydride grafted linear low-density polyethylene (LLDPE), manufactured by Mitsui Chemicals • DC3203 RB: Soarnol™ DC3203RB, ethylene-vinyl alcohol copolymer with an ethylene content of 32 mol%, manufactured by Mitsubishi Chemical Group • Mowiflex™ C17: thermoplastic and water-soluble polyvinyl alcohol, manufactured by Kuraray; (MFI (190°C / 21.6 kg) 14 to 20 g / 10 min; melting point 170°C) • HD 6070 FA: Rigidex® HD6070FA, high-density polyethylene (HDPE), manufactured by INEOS Olefins & Polymers Europe • ARX V24: Masterbatch with a lemon fragrance in polyethylene from ARGUS Additive Plastics GmbH • KD 211: Inorganic material consisting mainly of zinc, manufactured by RASA Industries, Ltd. Both films shown in Table 1 were co-extruded (cast film extrusion; blown film extrusion can also be used as an alternative). As described above, films were obtained according to the embodiments described above. The resulting films only become active upon contact with liquid, e.g., urine or menstrual fluid, at which point they release their respective active ingredient and can thus effectively and precisely combat unwanted odors at their source. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature EP 2 294 115 B1

[0004] EP 3 197 274 B1

[0005] US 9 801 765 B2

[0007]

Claims

Multilayer film comprising a layer (a) comprising a non-water-soluble polymer, and a layer (b) comprising a swellable or water-soluble polymer, wherein layer (b) additionally contains either an odor-binding substance or a fragrance or a combination thereof. Multilayer film according to claim 1, wherein the non-water-soluble polymer is a polystyrene, polyester, polyurethane or polyolefin or a biodegradable polymer. Multilayer film according to claim 1 or 2, wherein the film additionally has a core layer (c) and an outer layer (d), wherein the individual layers are arranged in the sequence (a), (c), (b), (d). Multilayer film according to any one of claims 1 to 3, wherein the film additionally comprises a layer (e) comprising an adhesion promoter, wherein the layer (e) is arranged between layers (a) and (c) or, if the film does not have layer (c) and layer (d), is arranged between layers (a) and (b). Multilayer film according to one of claims 1 to 4, wherein the film is perforated. Multilayer film according to any one of claims 1 to 5, wherein the layer (a) has a thickness of 10 to 45 µm. Multilayer film according to any one of claims 1 to 6, wherein layer (b) has a thickness of 1 to 10 µm. Multilayer film according to any one of claims 3 to 7, wherein the core layer (c) has a thickness of 1 to 10 µm. Multilayer film according to any one of claims 3 to 8, wherein the outer layer (d) has a thickness of 1 to 10 µm. Multilayer film according to any one of claims 4 to 9, wherein the layer (e) has a thickness of 1 to 10 µm. Multilayer film according to any one of claims 1 to 10, wherein the odor-binding substance or the fragrance is present in layer (b) in a concentration of 0.50 to 25.00 wt.%. Multilayer film according to any one of claims 1 to 11, wherein the water-soluble polymer is polyvinyl alcohol. Multilayer film according to any one of claims 2 to 12, wherein the non-water-soluble polymer is polyethylene or polypropylene. Multilayer film according to any one of claims 2 to 13, wherein the biodegradable polymer contains poly(butylene adipate co-terephthalate). Multilayer film according to any one of claims 3 to 14, wherein the outer layer (d) comprises polyvinyl alcohol. Multilayer film according to any one of claims 3 to 15, wherein the core layer (c) comprises an ethylene-vinyl alcohol copolymer or polyvinyl alcohol. Multilayer film according to any one of claims 4 to 16, wherein the adhesion promoter is a linear low-density polyethylene (LLDPE) grafted with maleic anhydride. Multilayer film according to any one of claims 1 to 17, wherein the odor-binding substance has a solid state of matter at 25 °C and 1 bar. Multilayer film according to any one of claims 1 to 18, wherein the odor-binding substance is selected from at least one of zeolite, cyclodextrin, activated carbon, ZnO, CaO, SiO2, ZrO2, inorganic or organic zinc salts, inorganic or organic zirconium salts, such as zinc ricinoleate, organosiloxanes and chelating agents, such as citrate or EDTA. Multilayer film according to any one of claims 1 to 19, wherein the film contains further water-soluble or water-insoluble antibacterial compounds. Multilayer film according to any one of claims 1 to 20, wherein the water-soluble or water-swellable layer has a porous structure by the addition of a foaming agent or a gas. Use of the multilayer film according to any one of claims 1 to 21 in a hygiene article. Use of the multilayer film according to one of claims 1 to 21 in a hygiene article, wherein the film is permeable to water by perforation. Use of the multilayer film according to any one of claims 1 to 21 in a hygiene article in which the water-soluble or water-swellable layer faces away from the user's skin. Use of the multilayer film according to one of claims 1 to 21 in a hygiene article, wherein the film forms a barrier against liquid. Use of the multilayer film according to any one of claims 1 to 21 for the production of packaging material, preferably in bag form; for example, garbage bags, bags for packaging medical waste, stoma bags and bags for packaging moist waste.

Images