Polymer Multilayers

Abstract

The multilayer body comprises at least one first layer and at least one second layer. The first layer comprises a water-soluble polymer, and the first layer has an oxygen barrier. Furthermore, the first layer comprises a salt. The salt can act as a lubricant. The second layer has a water vapor barrier and / or a moisture barrier. The multilayer body can provide high barrier performance with respect to oxygen penetration and water / moisture penetration. This allows a wide range of applications of the multilayer body in various fields, such as, for example, packaging, especially food packaging, especially coffee packaging.

Description

[Technical field]

[0001] The present invention relates to the field of polymer multilayers. The present invention relates to a multilayer and a method for producing a multilayer as defined in the preamble of the independent claim. [Background technology]

[0002] Currently existing packaging materials suitable for perishable products such as coffee, cereals, cheese, meat, detergents, skin care products, and / or chocolate typically consist of multi-layer films or structures such as, for example, PET / Alu / PE or paper / PET / Alu / PE.

[0003] Each multi-layer material is known not to be recyclable in existing cost-effective recycling streams, which are also energetically or chemically complex. One reason for this is that the layers, which in most cases are made of very different materials, are irreversibly bonded to each other. As a result, available mechanical recycling processes are not able to separate the individual layers.

[0004] One disposal method for each multi-layer body is thermal treatment, i.e. incineration. In countries where there is no existing disposal system or where landfill disposal is common, these multi-layer structures may remain substantially unchanged for hundreds of years (see, for example, Non-Patent Document 1).

[0005] An important topic in the hot melt processing of vinyl alcohol-rich polymers is their susceptibility to heat-induced decomposition. This is due to the fact that the difference between their crystalline melting point and their decomposition temperature is often negative, i.e., decomposition occurs already before the complete melting of the crystalline polymer part. One approach to solve such problems is to use ethylene-vinyl alcohol copolymers (EVOH), or butenediol-vinyl alcohol copolymers (BVOH), or vinyl acetate-vinyl alcohol copolymers that contain a sufficient amount of vinyl acetate (VAc) comonomer (typically more than approximately 15% VAc). The incorporated comonomer reduces the melting point and results in the elimination or at least a significant reduction of thermal decomposition compared to PVOH homopolymer. However, PVOH with a high vinyl alcohol comonomer content is often preferred, since it provides the highest barrier performance or water solubility only at high temperatures.

[0006] Some approaches for hot melt processing PVOH with high vinyl alcohol content in the formulation try to solve such problems by special processing means or by specific additives. Examples include US Pat. No. 5,399,663 (special formulation applying phosphoric acid as plasticizer, which reduces polymer degradation when hot melt processed), US Pat. No. 5,499,636 (processing aid water during extrusion allows fast dissolution and addition of plasticizer. Water is removed during hot melt extrusion, leaving plasticized PVOH), and US Pat. No. 5,499,636 (addition of hygroscopic salts). Polymer multilayers are also known from US Pat. No. 5,499,623, US Pat. No. 5,499,635, US Pat. No. 5,499,647, and US Pat. No. 5,523,363. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 0415357 [Patent Document 2] U.S. Patent No. 10,316,210 [Patent Document 3] UK Patent Application Publication No. 2501607 [Patent Document 4] International Publication No. 2007 / 118280 [Patent Document 5] U.S. Patent No. 7,854,994 [Patent Document 6] U.S. Patent Application Publication No. 2020 / 384750 [Patent Document 7] International Publication No. 2019 / 049798 [Non-patent literature]

[0008] [Non-Patent Document 1] W. Feng et.al., Progress in Polymer Science, 117(2021), 101395 Summary of the Invention [Means for solving the problem]

[0009] It is therefore an object of the present invention to provide a multi-layer body which overcomes the shortcomings of the prior art.

[0010] These objects are achieved by a multi-layer body and a process for producing the multi-layer body, as well as the use of said body for packaging and a packaging material comprising said body.

[0011] The multi-layer body includes at least one first layer and at least one second layer, The first layer includes a water soluble polymer, said first layer having an oxygen permeability barrier.

[0012] Additionally, the first layer includes a salt, which can act as a lubricant.

[0013] In an embodiment, the first layer comprises at least 20% by weight, in particular at least 35% by weight, of a water-soluble polymer.

[0014] The water-soluble polymer can form a solution with water as a solvent.

[0015] The salt may be present as an essentially solid material. The solid salt may be embedded in the water-soluble polymer of the first layer. The salt may also be partially or completely soluble in the polymer.

[0016] The second layer comprises a water vapor barrier and / or a moisture barrier.

[0017] In an embodiment, the first layer does not include starch.

[0018] In selected embodiments, the water-soluble polymer is cold soluble, meaning that it is soluble in cold water. The water-soluble polymer may be soluble in water at a temperature of up to 40° C., in particular at most at most at 38° C., in particular at most at most at 35° C., in particular at most at most at 30° C. Such solubility in water allows the incorporation of the multilayer body, for example, in paper recycling circuits, in particular paper recycling according to DIN EN 13430 (as of the end of 2021).

[0019] The multilayer, especially the first layer, is subject to a maximum of 3 cm per day at room temperature (RT, room temperature = 23 ° C.) and a relative humidity of 50% (relative humidity = rh). 3 / m 2 and in particular the oxygen permeability may be up to 1 cm per day at room temperature and 50% relative humidity. 3 / m 2 , especially at room temperature (23°C) and relative humidity of 50%, up to 0.2 cm per day 3 / m 2 , especially at room temperature (23°C) and 50% relative humidity, up to 0.05 cm per day 3 / m 2 It could be.

[0020] Oxygen Transmission Rate (OTR) is the steady-state rate at which oxygen gas permeates through a film at specified conditions of temperature and relative humidity. Values ​​are given in metric (or SI) units, cc / m 2 / 24hr, cc is cm 3 is cubic centimeter, m 2 is square meters, 24hr is 24 hours and 1 day. The OTR in this specification is determined in accordance with ISO15105-2 (as of April 2022). The test gas is oxygen, the carrier gas is nitrogen, and water is added to the test gas to achieve a relative humidity of 50% at 23°C. A sample of the layered structure is cut out with a diameter of 105 mm and hermetically attached to a test area of ​​80 mm diameter. The sample is attached to a lid and fixed to the measurement device. Water vapor in nitrogen or oxygen is supplied to the sample through the lid. A measurement sensor is placed on the opposite side of the sample. The sample is mounted between the test chambers at ambient atmospheric pressure. One chamber contains oxygen and the other chamber is slowly purged by a flow of nitrogen. Due to the concentration difference between the two chambers, oxygen molecules penetrate through the sample to the nitrogen side and reach the sensor, where they generate a corresponding electrical signal. The oxygen permeability is then obtained by analysis and calculation of the above signals.

[0021] The multilayer, especially the second layer, is subject to a maximum of 15 g / m2 per day at 23°C and 85% relative humidity. 2 , especially up to 10 g / m per day at 23°C and 85% relative humidity 2 , especially at 7 g / m per day at 23°C and 85% relative humidity 2 , especially up to 3 g / m per day at 23°C and 85% relative humidity 2 , especially up to 1 g / m per day at 23°C and 85% relative humidity 2 , especially up to 0.5 g / m per day at 23°C and 85% relative humidity 2 , especially up to 0.1 g / m per day at 23°C and 85% relative humidity 2 The coating may have a water vapor barrier and / or moisture barrier of 100%.

[0022] The water vapor barrier and / or moisture barrier in this specification are determined in accordance with ISO 15106-2 (as of April 2022).

[0023] The multilayer body can provide high barrier performance with respect to oxygen permeation and water / moisture permeation, which allows for a wide range of applications of the multilayer body in various fields such as, for example, packaging, especially food packaging, especially coffee packaging.

[0024] The multi-layer body may have barrier properties with respect to oxygen permeation, CO2 permeation, nitrogen permeation, and / or water / moisture permeation, and thus the applied multi-layer body may achieve long-term storage of products, for example when used in packaging.

[0025] The strategy behind each multi-layer structure is to provide the inherent properties of two or more materials that cannot be achieved by the application of one single material alone, such as good oxygen permeation barrier, water barrier, CO2 barrier, and aroma barrier properties for packaged goods, etc.

[0026] The subject matter of the present invention will be explained in more detail in the following specification with reference to exemplary embodiments illustrated in the accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1] A multi-layer body is shown. [Diagram 2] 1 shows a multi-layer body including an additional tie layer. [Diagram 3] 1 shows a multi-layer body including a tie layer and a sealing layer. [Figure 4] 1 shows a multilayer with an incorporated tie layer. [Diagram 5] A multi-layer body is shown that includes a second layer as an intermediate layer. [Figure 6] 1 shows a multi-layer body including a first layer covered by two second layers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In embodiments, the multi-layer body may be at least one of a film-like article, a container-like article, a sheet-like article, or any other type of article. The multi-layer body may have two flat surfaces.

[0029] The water soluble polymer of the first layer may comprise a polymer having multiple vinyl alcohol [CH2CH(OH)] groups in the polymer chain, in particular the water soluble polymer is poly(vinyl alcohol) (PVOH).

[0030] The water soluble polymer can be at least one of the following: - poly(vinyl alcohol) (PVOH), - cellulose-ether polymers, butenediol-vinyl alcohol-copolymer (BVOH), and - Ethylene-vinyl alcohol-copolymer.

[0031] The water-soluble polymer may comprise at least one vinyl alcohol copolymer and / or a mixture and / or blend of two or more vinyl alcohol copolymers, which may differ in molar mass, molecular structure, e.g., branching, type and amount of comonomer (these are just a few examples of the parameters that may be varied).

[0032] The water-soluble polymer may further include polar comonomers. Examples include maleic acid and maleic anhydride, fumaric acid and itaconic acid.

[0033] PVOH can be vinyl alcohol-rich copolymers and / or vinyl alcohol homopolymers. Water-soluble polymers, especially polyvinyl alcohol (PVOH), can have a degree of hydrolysis of 70% to 99.9%. The degree of saponification can control the performance with respect to oxygen permeation barrier. Higher saponification can improve the performance of oxygen permeation barrier, for example.

[0034] The vinyl alcohol-containing polymer may comprise monomer units containing >75%, especially >90% OH units.

[0035] The first layer may include at least one of the following polymers: poly(vinyl alcohols), obtained for example by saponification of poly(vinyl ester) homopolymers or copolymers; - ethylene-vinyl alcohol-copolymer (EVOH), - Butenediol-vinyl alcohol-copolymer (BVOH) (These are just a few examples).

[0036] The first layer may comprise at least one vinyl alcohol copolymer and / or a mixture and / or blend of two or more vinyl alcohol-containing homopolymers or copolymers, which may differ in molar mass, molecular structure, e.g., branching, type and amount of comonomer (these are just some examples of parameters that may be varied).

[0037] The molar mass of the polymer can vary widely, for example to optimize the performance of the product, with respect to the thermal and mechanical performance of the final product or with respect to the manufacturing conditions. Typical values ​​can be from 10 kD (kilodaltons) to 150 kD, in particular from 15 kD to 100 kD, in particular from 20 kD to 75 kD. In many cases viscosity data, most often the viscosity data of a 4% aqueous solution of the polymer, can be used instead of the molar mass, for example for Mowiol 4-88 (degree of sonification 88%, viscosity of 4 mPa sec in aqueous solution at 20° C.) a molar mass of approximately 31 kD.

[0038] The water-soluble polymer may further include polar comonomers. Examples include maleic acid and maleic anhydride, fumaric acid and itaconic acid.

[0039] The salts may include alkali metals, alkaline earth metal salts, aluminum-containing salts, and / or mixtures thereof, in particular NaCl, Na citrate, and their respective potassium analogs, and / or mixtures thereof. The addition of such salts may increase the melt flow index (MFI) and thus improve the hot melt processability of the formulation. It may also improve the solubility, disintegration, and biodegradation rate (e.g., composting).

[0040] The first layer may comprise at least 1%, or at least 2%, or at least 3%, or at least 10%, or at least 15%, or even at least 20%, or at least 25%, with a maximum amount of 55%, or 40%, or 35% salt. All percentages herein refer to weight % unless otherwise specified. The first layer may comprise 1-40% by weight salt, in particular 2-30% by weight salt.

[0041] The first layer may include at least 15% by weight salt.

[0042] The salt content may improve the processability of the first layer.

[0043] The salt content of the first layer may also be specified in volume percent, which can be recalculated from weight percent using the densities of the salt and first layer components.

[0044] The first layer may comprise at least 1% by volume, or at least 2% by volume, or at least 3% by volume, or at least 10% by volume, or at least 15% by volume, or even at least 20% by volume, or at least 25% by volume of salt, with a maximum amount being 55% by volume, or 40% by volume, or 35% by volume.

[0045] The first layer may include a vinyl alcohol copolymer that includes 1 to 25 mole % of a comonomer that is not vinyl alcohol.

[0046] The first layer may include an inorganic filler. The inorganic filler may be a clay mineral, particularly bentonite, montmorillonite, to name just a few examples. The inorganic filler may be a single or mixed metal carbonate, particularly calcium carbonate, including precipitated calcium carbonate. The inorganic filler may be silica, particularly fumed silica.

[0047] The first layer may comprise an organic filler. The organic filler may be cellulose, cellulose derivatives such as cellulose esters, cellulose ethers, etc., lignocellulose, and / or mixtures thereof, in particular low molar mass oligomers thereof. The organic filler may be starch and starch derivatives, in particular low molar mass oligomers thereof. The organic filler may be chitin, chitosan, and derivatives thereof. The organic filler may be coffee silverskin.

[0048] In an embodiment, the first layer comprises a minimum of 35% by weight of one or more respective vinyl alcohol rich copolymers.

[0049] The first layer may include a comonomer that does not contain an OH unit. Such comonomers may be incorporated into the polymer in the form of blocks, or in a random manner, or in any statistical manner in between. A more stochastic distribution is typically preferred.

[0050] The molar mass of the water-soluble polymer may vary widely in order to optimize the performance of the product, for example with respect to the thermal and mechanical performance of the final product or with respect to the manufacturing conditions.

[0051] The first layer has a maximum moisture content of 10%, for example a moisture content of 5% or less, in particular 1% or less or 0.5% or less.

[0052] The first layer may include an additive, which may be at least one of a plasticizer, a stabilizer, and a processing aid.

[0053] The plasticizer may be liquid or solid. The plasticizer may be partially or completely soluble in the base polymer. The plasticizer may be hygroscopic. The plasticizer may be selected from the group consisting of polyols (oligo- and poly-hydroxy compounds), low molecular weight amides, in particular triols, diols, polymeric triols, polymeric diols, such as glycerin, ethylene glycol, propylene glycol, triethylene glycol, low molecular weight polyethylene glycols, and low molecular weight amides. In certain embodiments, the plasticizer may be selected from the group consisting of dipropylene glycol, higher oligomers of ethylene glycol or propylene glycol, butylene glycol, glycerol, pentaerythritol, sorbitol, 1,4-monoanhydrohexitol, 1,4-3,6-dianhydrohexitol, and esters thereof. Preferred plasticizers are glycerin and polypropylene glycol. Glycerin or other plasticizers may be present in an amount of 2% to 25%, in particular 5% to 18%.

[0054] The salt may be present in a higher weight percentage than the plasticizer. The ratio of salt to plasticizer may be from 1.25 to 12:1, particularly from 1.25 to 7:1, particularly from 1.4 to 5-5:1, particularly from 4 to 5:1.

[0055] The stabilizer may be a primary antioxidant, a secondary antioxidant, in particular a phosphite, a thioester, and / or a C radical scavenger. The stabilizer may be a UV stabilizer. It may be applied for stabilization during processing and / or storage and / or use.

[0056] The processing aid may be a long chain aliphatic acid, its metal salt, and / or its derivatives, such as esteramides or esters.

[0057] The second layer may include at least one of the following components: - Polyester - Aliphatic polyester - Poly(hydroxyalkanoates) (PHAs) - Polylactic acid (PLA) - Polybutylene succinate (PBS) - poly(hydroxybutyrate) (PHB), in particular poly(3-hydroxybutyrate), and - Copolymers containing 3-hydroxybutyrate as a comonomer.

[0058] The polyesters may be obtained by polycondensation of one or more diacids and one or more polyols, resulting in particular in poly(alkylene succinates) such as poly(ethylene succinate), poly(propylene succinate), poly(butylene succinate), poly(alkylene adipates), poly(ethylene furanoate), and cocondensates thereof. The polyesters obtained may contain <20% aromatic moieties. In particular, the polyesters are free of aromatic moieties.

[0059] The polyesters may be obtained by polycondensation of one or more hydroxy-carboxylic acids.

[0060] The polyesters may be obtained by ring-opening homopolymerization or ring-opening copolymerization of one or more cyclic lactones, in particular polyglycolide (K. Yamane et.al., "Development of an industrial production technology for high-molecular-weight polyglycolic acid", Polymer Journal (29014), 46, 769-775), poly(lactic acid), polycaprolactone, to name just a few examples. The polyesters may also be copolymers thereof.

[0061] The polyesters may be based on one or more poly(hydroxyalkanoates) (PHAs) obtained from biological sources by fermentation and, optionally, subsequent modification. See, for example, Biotech. Progr., 2018, Vol. 34, No. 1, “Polyhydroxyalkanoates: Properties and Chemical Modification Approaches for Their Functionalization”.

[0062] The polyesters may include short chain (sc) PHAs (typically containing up to 5 carbon atoms in the monomer unit), in particular poly(hydroxypropionate), poly(hydroxybutyrate) (PHB), and poly(hydroxyvalerate). Poly(hydroxyalkylate) may occur in one or more chemically distinct isomeric forms. In particular, poly(hydroxybutyrate) may be used in the form of poly(3-hydroxybutyrate) and / or poly(4-hydroxybutyrate).

[0063] The polyesters may include medium chain (mc) PHAs (containing 6 to 14 carbon atoms per monomer unit), in particular poly(3-hydroxyhexanoate), and may be applied in the form of their homopolymers or copolymers. Short chain alkanoates and medium chain alkanoates may be present in the respective copolymers.

[0064] They may contain specific amounts of copolymers or be blended together to adjust physical parameters such as the glass transition temperature (Tg), melting point (Tm), etc. of the polyesters. Examples include 3-hydroxybutyrate-rich copolymers, which may incorporate 4-hydroxybutyrate, or 3-hydroxyvalerate, or 3-hydroxyhexanoate (these are just a few options) as comonomers. Also, terpolymers and higher copolymers and blends of three or more polyesters can be used.

[0065] Typically, the melting point of a suitable polyester is well above the highest application temperature and must be able to withstand the application pressure at each temperature. Typically, the melting point of the bulk of the crystalline portion of the polymer is at least 5K above such application temperature, and more preferably more than 10K above such application temperature.

[0066] The homo- and / or copolyesters may contain as much as at least 80% by weight of aliphatic units.

[0067] The homo- and / or copolyesters may be made up to 90% by weight from aliphatic building blocks. In particular, the homo- and / or copolyesters may be made exclusively from aliphatic building blocks.

[0068] In addition to the ester moieties, the copolyesters may further include polar moieties, particularly polycarbonate units, polyurethane units, polyamide units, to name just a few examples.

[0069] The second layer may also be water soluble. The water solubility of the second layer may be less than the water solubility of the first layer.

[0070] The second layer may include an additive, which may be at least one of a plasticizer, a stabilizer, and a nucleating agent.

[0071] The plasticizer, like the plasticizer of the first layer, can be liquid or solid. The plasticizer can be partially or completely soluble in the base polymer. In particular, the plasticizer can be trialkyl citrates, such as triethyl citrate, and epoxidized soybean oil, to name just a few examples. Selected further examples are given, for example, in V. Jost et.al., European Polymer Journal, 68 (2015), 302-312.

[0072] The stabilizers may be primary antioxidants, secondary antioxidants, C radical scavengers and / or UV stabilizers. The stabilizers may be applied for stabilization during processing and / or storage and / or use.

[0073] Carbodiimides and poly(carbodiimides) can be applied as water scavengers. They can be used in combination with phosphite-based secondary antioxidants.

[0074] A nucleating agent may be applied. The nucleating agent may be selected from Handbook of Nucleating Agents, 2nd Ed. (ChemTec Publishing, Toronto, 2021).

[0075] In certain embodiments, at least one of the first layer and the second layer may be biodegradable, in particular the first layer is biodegradable.

[0076] The water-soluble polymer may be biodegradable, although this is not necessarily the case for all water-soluble polymers. The water-soluble polymer of the multi-layer may be biodegradable in addition to being water-soluble.

[0077] In this specification, "biodegradable" may mean biologically degradable according to European standard EN 13432 (as of the end of 2021). Additionally or alternatively, it may mean biologically degradable according to European standard EN 14995 (as of the end of 2021). Thus, "biodegradable" refers in particular to "biologically degradable according to EN 13432 and / or according to EN 14995".

[0078] In some embodiments, the first layer and / or the second layer can be biodegradable in at least one of soil, water, and wastewater.

[0079] Insofar as water-soluble polymers are mentioned in this specification, such water-soluble polymers may optionally be (biodegradable) in sewage treatment plants in accordance with EN ISO 9888 (as of the end of 2021) (aerobic biodegradable), determined in particular at 20°C according to the so-called Zahn-Wellens test.

[0080] This allows the body to provide sufficient barrier properties, for example for perishable food products, while at the same time being compatible with existing recycling streams: in areas where such streams do not exist or where landfilling is common, the body is environmentally neutral and decomposes within a short period of time into carbon dioxide (CO2), water (H2O), and biomass.

[0081] In addition, multi-layer bodies made from biodegradable plastics often contain a significant proportion of fossil raw materials (in most cases they contain 50-60%, and in selected cases up to 80% bio-based plastics).By using the present invention, biodegradable multi-layer bodies can be provided.

[0082] Multilayer bodies made from prior art biodegradable plastics can exhibit poor barrier performance, especially against oxygen and water vapor, as well as poor head deformation stability.

[0083] The multi-layer body may be compostable, in particular home compostable. At least one of the first layer and the second layer may be compostable, in particular home compostable.

[0084] Biodegradation in the context of this specification means the degradation of the polymers of the multilayer by microorganisms. Biodegradability means that the material must be broken down in the presence of microorganisms or fungi under specific defined temperature, oxygen and humidity conditions after a specified time to a degree of more than 90 percent into water, carbon dioxide (CO2) and biomass.

[0085] The term compostable refers to biodegradation under certain conditions.

[0086] For the multi-layer body, in particular the first layer and / or the second layer, to be compostable, at least the following conditions may be met: - At least 90% of the organic material must be verifiably biodegraded into CO2 within six months; - after 3 months of composting and subsequent screening through a 2 mm mesh sieve, no residue should remain that is more than 10% of the original mass; - There must be no adverse effects on the overall composting process; - the resulting compost has no adverse effects on plant growth (agronomic tests) and / or ecotoxicity tests; - Maximum concentrations of heavy metals (Cu, Zn, Ni, Cd, Pb, Hg, Cr, Mo, Se, As) and fluorines must not be exceeded.

[0087] During composting, the multi-layer body, particularly at least one of the first and second layers, can be decomposed. The multi-layer body, particularly at least one of the first and second layers, can be composted and / or decomposed into carbon dioxide (CO2), water (H2O), and biomass in a short period of time.

[0088] The multi-layer body, particularly at least one of the first and second layers, may be industrially and / or domestically compostable. Home compostability may not adversely affect industrial composting processes.

[0089] In this specification, "compostable" or "home compostable" means compostable or home compostable in accordance with European Standard EN 13432 (as of the end of 2021) for packaging materials and / or European Standard EN 14995 (as of the end of 2021) for plastic / synthetic materials.

[0090] In order for a multi-layer body, in particular the first layer and / or the second layer, to be home compostable, at least the following conditions must be met: - At least 90% of the material must decompose into water, carbon dioxide and biomass within 6 months in the compost pile (approximately 30°C); - Neither organic pollutants nor heavy metals should enter the soil; - The substance must not have any adverse effect on the quality of the compost; - The product can be disposed of in garden compost and organic waste bins.

[0091] The multi-layer body may include a sealing layer.

[0092] The sealing layer can be essentially the same as or similar to at least one of the second layer and the first layer.

[0093] The sealing layer may include at least one of the following components: - polyester; - polyurethane; - polycarbonate; - Aliphatic polyesters; - Poly(hydroxyalkanoates) (PHAs); - vinyl alcohol-rich copolymers and / or homopolymers, - Poly(vinyl alcohol) (PVOH), ethylene-vinyl alcohol (EVOH), and / or butenediol-vinyl alcohol (BVOH) in combination with one or more salts.

[0094] The sealing layer may have a chemical composition that is similar or identical to that of the water vapor barrier layer, ie, the second layer.

[0095] The multi-layer body may include a tie layer to promote adhesion between the first and second layers.

[0096] The tie layer may also be referred to as an adhesion promoting layer. The tie layer may enhance the adhesion between layers, which means that it enhances the adhesion between adjacent layers of a multi-layer body.

[0097] In certain applications, the adhesion between adjacent layers may be insufficient for the desired application and require improvement. Enhanced interlayer adhesion may be achieved by adding an adhesion promoting additive to one or both of the adjacent layers that do not exhibit sufficient interlayer adhesion, or by chemical modification of the base polymers used for the individual layers.

[0098] Examples of chemical modifications of the base polymers constituting the individual layers include at least one of the following: - Use of hydrophilic, e.g. acid-modified PHAs. One example is PHAs modified with maleic anhydride (MAA). Such PHA modifications typically enhance adhesion to more highly polar vinyl alcohol-containing copolymers (Non-Patent Document 1). Another example is a poly(vinyl alcohol) copolymer that is hydrophobically modified, for example by the incorporation of long aliphatic side chains. Such hydrophobic modification reduces the polarity of the vinyl alcohol-containing copolymer and typically enhances interlayer adhesion to the PHA layer.

[0099] To achieve the desired interlayer adhesion, one or both of the adjacent layers may be modified.

[0100] An example of an adhesion promoting additive to a tie layer is to blend the base polymer used in one of the layers into the adjacent second layer. The blend typically contains less than 50% of the base polymer of the adjacent layer in the first or second layer. One or both adjacent layers may each be modified.

[0101] Enhanced interlayer adhesion may also be achieved by the incorporation of a specific adhesive layer (also called a tie layer) between two adjacent layers that do not exhibit sufficient adhesion to each other. Examples of adhesion promoting layers (tie layers) may include at least one of the following: - a blend of base polymers used in each adjacent layer. The blend may use 5% to 95% by weight of the base polymer used in each adjacent layer. In particular, the blend may use 10% to 90% by weight of the base polymer used in each adjacent layer. In particular, the blend may use 20% to 80% by weight of the base polymer used in each adjacent layer. - Nippon Gosei's BTR-8002P biodegradable adhesion promoting layer or a similar material may be used as the adhesion promoting layer. Further options include cellulose alkyl esters and ethylene-vinyl alcohol copolymers with a degree of alkylation between 0.5 and 1.5.

[0102] Enhanced interlaminar adhesion may also be achieved by: - Hydrophobic treatment of PVOH, e.g. with long-chain aliphatic silanes (see, e.g., Markus Schmid et.al., Polymers, 2014, 6, 2764-2783, doi:10.3390 / polym6112764). - Hydrophilic treatment for PHA.

[0103] The layers of the multi-layer body may be at least partially separable from one another.

[0104] According to the prior art, layers of chemically similar materials are irreversibly bonded to one another. The resulting material may be called a monomaterial. Such monomaterials are difficult or impossible to recycle. In contrast, the layers of the multilayer body of the present invention can be separated from one another and recycled individually.

[0105] In an embodiment, the layers of the multi-layer body can be separated from each other under the conditions of the recycling process. In particular, said layers are separable in an aqueous environment at a maximum temperature of 40° C., in particular at most 38° C., in particular at most 35° C., in particular at most 30° C.

[0106] Examples of suitable polymer compositions for the first layer can be found, for example, in WO 2014 / 155059.

[0107] The multi-layer body may include a print layer, which may be a layer onto which ink may be applied.

[0108] The multilayer body may have a thickness of 30 to 3000 micrometers, in particular at least 30 micrometers, or at least 50, or at least 100 micrometers, or at least 150 micrometers, or even at least 300 micrometers. The maximum thickness of the multilayer body may be 100 micrometers, or 120 micrometers, or 150 micrometers, or 200 micrometers, or 300 micrometers, or 1000 micrometers, or 1500 micrometers, or at most 3000 micrometers. The first layer may have a thickness of 2 micrometers to 1500 micrometers. The first layer may have a thickness of at least 2 micrometers, or at least 3 micrometers, or at least 5 micrometers, or at least 10 micrometers, or at least 20 micrometers, or at least 500 micrometers, or at least 700 micrometers, or at least 1000 micrometers. The maximum thickness of the first layer may be 20 micrometers, or 40 micrometers, or 50 micrometers, or 70 micrometers, or 100 micrometers, or 200 micrometers, or 500 micrometers, or 1000 micrometers, or at most 1500 micrometers.

[0109] The second layer may have a thickness of 2 micrometers to 1500 micrometers. The second layer may have a thickness of at least 2 micrometers, or at least 3 micrometers, or at least 5 micrometers, or at least 10 micrometers, or at least 20 micrometers, or at least 500 micrometers, or at least 700 micrometers, or at least 1000 micrometers. The maximum thickness of the first layer may be 20 micrometers, or 40 micrometers, or 50 micrometers, or 70 micrometers, or 100 micrometers, or 200 micrometers, or 500 micrometers, or 1000 micrometers, or at most 1500 micrometers.

[0110] In one embodiment, the first layer can have a thickness of 12 to 15 micrometers and the second layer can have a thickness of 25 micrometers.

[0111] The multi-layer can provide a reliable bond to the paper substrate. The bond between the multi-layer and the paper substrate can have a reliable peel strength. The multi-layer and the paper substrate can comprise a paper composite.

[0112] Multi-layers can provide sealing strength that, when used in packaging applications, can allow for complex constructions and increased packaging line speeds.

[0113] The thickness of the first layer may be at most 40 to 50% of the total thickness of the multilayer body.

[0114] In an embodiment, the multilayer body includes three sublayers, two of which are first layers and one second layer. The two first layers cover both sides of the second layer. In other words, the second layer is disposed between the two first layers. The first layer may have a thickness of 12 to 15 micrometers, and the second layer may have a thickness of 25 micrometers.

[0115] In another embodiment, the multi-layer body includes three sub-layers, two of which are second layers and one of which is a first layer. The two second layers cover both sides of the first layer. In other words, the first layer is disposed between the two second layers.

[0116] The method for producing a multi-layer body is characterized in that the multi-layer body is produced as at least one of the following: - Blown film, - Cast film, and - By extrusion coating method.

[0117] This allows the interdigitated production of first and second layers in a multi-layer body.

[0118] In an embodiment, the multi-layer body is produced by at least one of the following: - coextrusion of the first layer and the second layer; - thermoforming; - Co-injection molding; - Compression Molded.

[0119] In the coextrusion, both single and multi-component layer structures can be produced.

[0120] In the co-injection molding described above, two or even three components can be used to produce multi-layer bodies.

[0121] Such a multi-layer body can be used for packaging, especially food packaging, especially coffee packaging.

[0122] In particular, bio-based plastics also have major advantages in terms of CO2 emissions: the use of compostable food containers with food residues on the inside, which can be recycled by composting, being all-natural, is suitable for the circular economy. Thus, for example, there is a need for food containers that contain dry powders or granules with functions such as coffee brewing, e.g. single-serving coffee capsules.

[0123] The packaging material may include multiple layers as described above.

[0124] Further preferred embodiments are evident from the dependent claims. Features of the method claims may be combined with features of the device claims and vice versa.

[0125] The reference signs used in the drawings and their meanings are listed in summary form in the list of reference signs. As a rule, identical parts are provided with the same reference signs in the figures.

[0126] Figure 1 shows a multi-layer body 5 comprising a first layer 1 and a second layer 2. The first layer 1 comprises a water-soluble polymer and a salt. The first layer 1 has an oxygen permeability barrier.

[0127] The multilayer body 5, in particular the first layer 1, can grow at a maximum of 3 cm per day at room temperature (RT, room temperature = 23 ° C.) and a relative humidity of 50% (rel.h.). 3 / m 2 In particular, the oxygen permeability is up to 1 cm per day at room temperature and 50% relative humidity. 3 / m 2 , especially at room temperature (23°C) and relative humidity of 50%, up to 0.2 cm per day 3 / m 2 It could be.

[0128] The second layer 2 comprises a water vapour barrier and / or a moisture barrier.

[0129] The multilayer, especially the second layer, is subject to a maximum of 15 g / m2 per day at 23°C and 85% relative humidity. 2 , especially up to 10 g / m per day at 23°C and 85% relative humidity 2 , especially up to 3 g / m per day at 23°C and 85% relative humidity 2 The coating has a water vapor barrier and / or moisture barrier.

[0130] 2 shows a similar multilayer body 5 including a first layer 1 and a second layer 2. In addition, a tie layer 4 is disposed between the first layer 1 and the second layer 2. The tie layer 4 may be designed as an additional layer. Furthermore, the tie layer 4 may be designed to be incorporated into the first layer 1 and / or the second layer 2, as shown in FIG.

[0131] 3 shows a multi-layer body 5 including an additional sealing layer 3 disposed adjacent to a second layer 2. The second layer 2 and the sealing layer 3 are joined by a tie layer 4. As noted above, the tie layer 4 may also be incorporated into the second layer 2 and / or the sealing layer 3.

[0132] The sealing layer 3 may be designed such that the multi-layer body 5 is sealable to a further multi-layer body 5 , in particular to the sealing layer 3 of the multi-layer body 5 .

[0133] In particular, the further multi-layer body 5 is identical to the first multi-layer body 5. This allows the multi-layer body 5 to be sealed to itself and a packaging bag to be produced from the continuous multi-layer body 5. In another embodiment, the first multi-layer body 5 and the further multi-layer body 5 are separate multi-layer bodies which can be sealed to each other as a packaging bag.

[0134] 5 shows a multi-layer body 5 in which two first layers 1 are arranged next to one second layer 2. The second layer 2 is arranged midway between the two first layers 1.

[0135] Figure 6 shows another multi-layer body 5 of at least wood layers, two layers being second layers 2 and one being a first layer 1. The two second layers 2 cover both sides of the first layer 1. The first layer 1 is disposed between the two second layers.

[0136] While the invention has been described in its presently preferred embodiments, it is to be clearly understood that the invention is not limited thereto and may be variously and otherwise embodied and practiced within the scope of the appended claims.

Claims

1. - At least one first layer (1) comprising at least 20% by weight of a water-soluble polymer, It has an oxygen permeable barrier, A first layer (1) containing salt, - At least one second layer (2), A second layer (2) having a water vapor barrier and / or moisture barrier, A multilayer structure including a multilayer body.

2. The multilayer according to claim 1, wherein the water-soluble polymer is at least one of poly(vinyl alcohol) (PVOH), cellulose-ether polymer, butenediol-vinyl alcohol copolymer (BVOH), and ethylene-vinyl alcohol copolymer (EVOH).

3. The first layer (1) is subject to the following conditions: - The first layer (1) comprises an alkali metal, an alkaline earth metal salt, an aluminum-containing salt, and / or a mixture of the alkali metal, the alkaline earth metal salt, and the aluminum-containing salt; - The first layer (1) contains at least 1% by weight of the salt; - The first layer (1) contains 1 to 55% by weight of the salt; - The first layer (1) comprises a vinyl alcohol copolymer containing 1 to 25 mol% of OH group-free comonomers; - The first layer (1) contains an inorganic filler; - The first layer (1) contains an organic filler; - The first layer (1) comprises at least 35% by weight of one or more vinyl alcohol-rich copolymers, A multilayer according to claim 2, satisfying at least one of the following conditions.

4. The multilayer according to claim 3, wherein the first layer (1) contains at least one of a plasticizer and a stabilizer as an additive.

5. The second layer (2) described above is subject to the following conditions: - The second layer (2) has the following components: 〇 Polyester 〇 Aliphatic polyester 〇 Poly(hydroxyalkanoate) (PHA) 〇 Polylactic acid (PLA) 〇 Polybutylene succinate (PBS) ○ Contains at least one of poly(hydroxybutyrate) (PHB), - The second layer (2) comprises homo and / or copolyester having at least 80% by weight of aliphatic units, - The second layer (2) contains, as an additive, at least one selected from plasticizers, stabilizers, and nucleating agents. A multilayer according to claim 1, satisfying at least one of the following conditions.

6. The second layer (2) is subject to the following conditions: - The second layer (2) has the following components: 〇 Polyester 〇 Aliphatic polyester 〇 Poly(hydroxyalkanoate) (PHA) 〇 Polylactic acid (PLA) 〇 Polybutylene succinate (PBS) 〇 Poly(hydroxybutyrate) (PHB) Including at least one of the following: - The second layer (2) comprises homo and / or copolyester having at least 80% by weight of aliphatic units, - The second layer (2) contains, as an additive, at least one selected from plasticizers, stabilizers, and nucleating agents. A multilayer according to claim 2, satisfying at least one of the following conditions.

7. The second layer (2) is subject to the following conditions: - The second layer (2) has the following components: 〇 Polyester 〇 Aliphatic polyester 〇 Poly(hydroxyalkanoate) (PHA) 〇 Polylactic acid (PLA) 〇 Polybutylene succinate (PBS) 〇 Poly(hydroxybutyrate) (PHB) Including at least one of the following: - The second layer (2) comprises homo and / or copolyester having at least 80% by weight of aliphatic units, - The second layer (2) contains, as an additive, at least one selected from plasticizers, stabilizers, and nucleating agents. A multilayer according to claim 3, satisfying at least one of the following conditions.

8. The second layer (2) is subject to the following conditions: - The second layer (2) has the following components: 〇 Polyester 〇 Aliphatic polyester 〇 Poly(hydroxyalkanoate) (PHA) 〇 Polylactic acid (PLA) 〇 Polybutylene succinate (PBS) 〇 Poly(hydroxybutyrate) (PHB) Including at least one of the following: - The second layer (2) comprises homo and / or copolyester having at least 80% by weight of aliphatic units, - The second layer (2) contains, as an additive, at least one selected from plasticizers, stabilizers, and nucleating agents. A multilayer according to claim 4, satisfying at least one of the following conditions.

9. The multilayer structure according to claim 1, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

10. The multilayer body according to claim 2, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

11. The multilayer body according to claim 3, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

12. The multilayer body according to claim 4, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

13. The multilayer body according to claim 5, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

14. The multilayer body according to claim 6, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

15. The multilayer body according to claim 7, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

16. The multilayer body according to claim 8, wherein at least one of the first layer (1) and the second layer (2) is biodegradable and / or compostable.

17. The multilayer according to any one of claims 1 to 16, wherein the multilayer may have a water vapor barrier and / or moisture barrier of up to 15 g / m² per day at 23°C and 85% relative humidity.

18. The multilayer body according to any one of claims 1 to 16, wherein the multilayer body includes a sealing layer.

19. The sealing layer comprises the following components: ○ Components essentially similar to those of the first layer (1) and / or the second layer (2) 〇 Polyester 〇 Polyurethane or 〇 Polycarbonate 〇 Aliphatic polyester 〇 Poly(hydroxyalkanoate) (PHA) ○ Copolymers and / or homopolymers rich in vinyl alcohol The multilayer according to claim 18, comprising at least one of the following.

20. The multilayer according to claim 18, further comprising a bonding layer for promoting adhesion between the first layer (1) and the second layer (2).

21. The multilayer according to claim 18, wherein the first layer (1), the second layer (2), and the sealing layer of the multilayer are separable from one another.

22. The multilayer according to claim 20, wherein the first layer (1), the second layer (2), the sealing layer, and the bonding layer of the multilayer are separable from one another.

23. The multilayer according to claim 18, wherein the salt in the first layer (1) exists as a solid material.

24. The multilayer according to claim 20, wherein the salt in the first layer (1) is present as a solid material.

25. The multilayer according to claim 21, wherein the salt in the first layer (1) is present as a solid material.

26. The multilayer according to claim 22, wherein the salt in the first layer (1) is present as a solid material.

27. The aforementioned multilayer body is manufactured by the following method: - Blow molding, - Cast molding, - Extrusion coating, - Co-extrusion of the first layer (1) and the second layer (2), - co-injection molding, - Compression molding, A multilayer body according to any one of claims 1 to 18, manufactured by at least one of the following.

28. The multilayer body is manufactured as follows: - Blow molding, - Cast molding, - Extrusion coating, - Co-extrusion of the first layer (1) and the second layer (2), - co-injection molding, - Compression molding, The multilayer body according to claim 20, manufactured by at least one of the following.

29. A multilayer body for food packaging, comprising the multilayer body described in any one of claims 1 to 16.

30. A multilayer material for food packaging, comprising the multilayer material described in Claim 17.

31. A multilayer body for food packaging, comprising the multilayer body described in Claim 18.

32. A multilayer material for food packaging, comprising the multilayer material described in Claim 20.

33. A multilayer body for food packaging, comprising the multilayer body described in Claim 21.

34. A multilayer material for food packaging, comprising the multilayer material described in Claim 22.

35. A packaging material comprising a multilayer body according to any one of claims 1 to 16.

36. A packaging material comprising the multilayer body described in Claim 17.

37. A packaging material comprising the multilayer body described in Claim 18.

38. A packaging material comprising the multilayer body described in Claim 20.

39. A packaging material comprising the multilayer body described in Claim 21.

40. A packaging material comprising the multilayer body described in Claim 22.

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