Delamination of layered materials in polar solvents.

Abstract

To provide a synthetic layered material that easily exfoliates into single clay lamellae. The present invention relates to a composition Na x [Mg 3-z Li y ]SiO 10 For a material containing a layered material having (T)2, x is in the range of 0.4 to 0.8, and y is in the range of 0.0 to 0.8; wherein z is in the range of 0.2 to 0.8, T each independently in each occurrence represents F or OH, and x+(3-z)+y≦4, a powder X-ray diffraction pattern of the layered material has a 001 peak in the range of 8.00 to 5.88° 2-theta, said 001 peak having a full width at half maximum of the peak maximum of greater than 0.10°, and the layered material has a Z-average particle size of 500 nm or greater as determined by dynamic laser light scattering in an aqueous dispersion of the material containing up to 1.5 wt.% of the material.

Description

[Technical Field]

[0001] The present invention relates to a layered material, a method for preparing the material, a composition comprising the material and a binder, and the use of the material to improve the barrier properties of a coating layer. [Background technology]

[0002] Stoter et al., Langmuir 2013, 29 pp. 1280-1285, describe sodium hectorite nanoplatelets exhibiting an aspect ratio of 20,000 upon delamination. This material can spontaneously and completely decompose into single clay lamellae, each 1 nm thick. This synthetic clay offers potential as a functional filler in highly transparent nanocomposites with excellent gas barrier and mechanical properties. The material was obtained by melt synthesis followed by extended annealing. The extended annealing was performed at 1045°C in a molybdenum crucible for a period of 6 weeks. The extended annealing time at high temperatures has significant disadvantages, making this technology less attractive for commercial implementation.

[0003] US2011 / 0204286A1 relates to synthetic phyllosilicates for polymer / phyllosilicate nanocomposites. The synthetic phyllosilicates described in this document exist in the form of layer stacks and are also referred to as tactoids. Polymer nanocomposites containing these tactoids exhibit improved gas barrier properties. However, complete delamination into single clay plates is not observed. It is generally believed that complete delamination maximizes the path length for diffusion through the composite, thereby improving the barrier properties. Therefore, the full potential of the gas barrier properties is not achieved with the tactoids described in this document.

[0004] WO2019 / 154758A discloses a method for producing a fluoride-containing oxide of the composition Na by providing a mixture of fluorides and oxides of Na, Mg, Li and Si.0.5 Mg 2.5 Li 0.5 SiO 10 A method for preparing a layered material containing F2 is described. The mixture is heated to a temperature of 1750°C to form a homogeneous liquid. The mixture is then cooled to 1300°C at a rate of 55°C / min, and further cooled to 1050°C at a rate of 10°C / min. Finally, it is rapidly cooled by turning off the power. Summary of the Invention [Problem to be solved by the invention]

[0005] There is currently a need for synthetic layered materials that easily exfoliate into single clay platelets, that provide good barrier properties, and that can be prepared by an economically viable process. [Means for solving the problem]

[0006] The present invention is based on the composition Na x [Mg 3-z Li y ]SiO 10 providing a material comprising a layered material having (T)2, x is in the range of 0.4 to 0.8, y is in the range of 0.0 to 0.8, z is in the range of 0.2 to 0.8, T independently in each occurrence represents F or OH; and x+(3-z)+y≦4, the powder X-ray diffraction pattern of the layered material has a 001 peak in the range of 8.00 to 5.88° 2θ, the 001 peak having a full width at half maximum of the peak maximum of greater than 0.1°; and The layered material has a Z-average particle size of 500 nm or greater as determined by dynamic laser light scattering in an aqueous dispersion of the material containing up to 1.5% by weight of the material. DETAILED DESCRIPTION OF THE INVENTION

[0007] The materials of the present invention provide layered materials that readily, and often spontaneously, delaminate into single plates (single lamellae) that can be prepared by economically viable processes.

[0008] The layered materials are clay materials and can generally be classified as hectorites. Hectorites are magnesium-based smectite-type clays. The layered materials of the present invention are generally synthetic clays. Preparation methods are further described below.

[0009] The layered material has the composition Na x [Mg 3-z Li y ]SiO 10 (T)2, x is in the range of 0.4 to 0.8, y is in the range of 0.0 to 0.8, z is in the range of 0.2 to 0.8, T independently in each occurrence represents F or OH; and x+(3-z)+y≦4.

[0010] Preferably, at least 50%, more preferably at least 70%, and most preferably at least 90% of the occurrences of T are represented by F. In some embodiments, T represents F at 100% of the occurrences.

[0011] The ratio of Na, Mg, and Li can vary within the above ranges. In preferred embodiments, the material includes lithium. In these embodiments, y is generally in the range of 0.4 to 0.8. In more preferred embodiments, x is in the range of 0.4 to 0.6, y is in the range of 0.4 to 0.6, and z is in the range of 0.4 to 0.6.

[0012] The powder X-ray diffraction pattern of the layered material has a 001 peak in the range of 8.00° to 5.88° 2θ, with the 001 peak having a full width at half maximum of the peak maximum of greater than 0.10°. These features have been found to result in very easy delamination of the layered material into single thin plates.

[0013] Powder X-ray diffraction patterns are typically obtained on powder samples of the layered material that have been equilibrated for a period of at least 12 hours in ambient humidity at 43% relative humidity at 23° C. Copper K-alpha radiation with a wavelength of 1.541 Å is used to measure the X-ray diffraction patterns.

[0014] The position of the 001 peak is defined as the position of the peak maximum.

[0015] The full width at half the peak maximum is defined as the width of the 001 peak and is expressed in °. The width of the peak is measured at the height corresponding to half the maximum intensity value.

[0016] In preferred embodiments, the full width at half maximum of the peak maximum is at least 0.15°, more preferably at least 0.20°. Typically, the full width at half maximum of the peak maximum is at most 0.60°, preferably at most 0.50°. In typical embodiments, the full width at half maximum of the peak maximum is in the range of 0.15° to 0.60°, preferably 0.20° to 0.50°.

[0017] The layered material has a Z-average particle size of 500 nm or greater as determined by dynamic laser light scattering in an aqueous dispersion of the material containing up to 1.5 wt.% of the layered material. Typically, the aqueous dispersion contains 0.2 to 1.5 wt.% of the layered material.

[0018] Dynamic light scattering results are often expressed in terms of Z-average, which is obtained when dynamic light scattering data is analyzed by use of the cumulant technique.

[0019] The calculation of the Z-average is mathematically stable, making it insensitive to noise. The Z-average can be expressed as an intensity-based harmonic mean, given by the following equation:

[0020]

number

[0021] where S i is the scattering intensity from particle i, and D i is the diameter of particle i. The result is in the form of a harmonic mean. This mean is calculated from the intensity-weighted distribution, leading to the statement that the Z-average size is the intensity-weighted harmonic mean size.

[0022] Generally, the Z-average particle size is in the range of 500 nm to 25,000 nm. In preferred embodiments, the Z-average particle size is at least 1,000 nm, more preferably at least 1,500 nm, and most preferably at least 1,800 nm. In typical embodiments, the Z-average particle size is in the range of 1,500 to 25,000 nm.

[0023] Generally, the materials of the present invention, when present as solid particulate materials, contain 80-100% by weight of layered material, preferably 90-100% by weight, and most preferably 95-100% by weight of layered material. The materials may contain minor amounts of other layered silicates that do not meet the characteristics of the layered material described above.

[0024] The present invention further relates to a method for preparing the substance of the present invention, said method comprising the steps of: (i) providing a mixture comprising a Na compound, a Mg compound, a Li compound, and a Si compound, wherein these compounds are selected from carbonates, halides, and oxides, and the molar ratio of Na:Mg:Li:Si is in the range of 0.4-0.8:2.2-2.8:0.0-0.8:4.0; (ii) heating the mixture to a temperature above 1100°C to form a homogeneous liquid; (iii) cooling the mixture to a temperature of less than 1000°C over a period of at least 0.5 hours.

[0025] In the first step, a mixture of Na compounds, Mg compounds, Li compounds, and Si compounds is provided. These mixtures are provided in the form of oxides, halides, or carbonates. In a typical embodiment, alkali metal salts / alkaline earth metal salts, alkaline earth oxides, and silicon oxides are used, preferably binary alkali fluorides / alkaline earth fluorides, alkaline earth oxides, and silicon oxides, preferably LiF, NaF, MgF2, MgO, and quartz. In a further preferred embodiment, the material of the present invention is prepared from a mixture of sodium carbonate, lithium carbonate, magnesium oxide, magnesium fluoride, and silicon dioxide (quartz). The molar ratio of the starting compounds reflects the molar composition of the layered material to be prepared. Therefore, the molar ratio of the metal compounds used as starting materials is selected to achieve the above-mentioned molar composition of the layered material.

[0026] The relative proportions of the starting compounds are, for example, 0.4 to 0.6 moles of F in the form of alkali / alkaline earth fluorides per mole of silicon dioxide. - and 0.4 to 0.6 moles of alkaline earth oxide per mole of silicon dioxide, preferably 0.45 to 0.55 moles of F in the form of alkali / alkaline earth fluoride per mole of silicon dioxide. - and 0.45 to 0.55 moles of alkaline earth oxides per mole of silicon dioxide, particularly preferably 0.5 moles of F in the form of alkali / alkaline earth fluorides per mole of silicon dioxide. - and 0.5 moles of alkaline earth oxide per mole of silicon dioxide.

[0027] Preferably, the starting compounds have a high purity. In a preferred embodiment, each starting compound has a calcium oxide content of less than 0.05% by weight. More preferably, each starting compound has an iron oxide content of less than 0.05% by weight.

[0028] In a second step, the mixture of starting compounds is heated to a temperature above 1100° C. to form a homogeneous liquid. Heating is preferably carried out in an open or closed crucible.

[0029] Typically, a high melting crucible made of a chemically inert or slowly reactive metal, preferably molybdenum or platinum, is used.

[0030] Heating is typically performed in a high frequency induction furnace. If necessary, the crucible is protected from oxidation by a protective ambient atmosphere (e.g., argon), a vacuum, or a combination of these measures. For precious metals such as platinum, this is not necessary.

[0031] In the second step, the mixture is heated to a temperature above 1100°C. The temperature must be above the melting temperature of the reaction mixture so that a homogeneous liquid is obtained. Generally, the temperature range for the second step is 1100°C to 1700°C, preferably 1300°C to 1600°C. Generally, the duration of this step is 60 to 240 minutes, preferably 75 to 180 minutes.

[0032] In the third step, the mixture is cooled to a temperature below 1000° C. over a period of at least 2.0 hours, preferably over a period of at least 3.0 hours.

[0033] The third step is generally a controlled cooling step in which the temperature of the mixture is reduced to a specific target temperature over a specific period of time. At the end of the specific period, the temperature of the mixture reaches this specific temperature. In some embodiments, the temperature is reduced uniformly over the specific period of time.

[0034] Alternatively, the temperature may be decreased stepwise in three or more intervals. Generally, the duration of the third step is in the range of 2.0 to 36.0 hours, preferably in the range of 2.5 to 24 hours. In a highly preferred embodiment, the duration of the controlled cooling step is in the range of 2.5 to 18 hours, and even more preferably in the range of 4 to 15 hours.

[0035] During the controlled cooling step, the mixture is cooled to a temperature below 1000° C. Generally, the mixture is cooled from a temperature of 1100° C. or higher to a temperature below 1000° C. In a preferred embodiment, the mixture is cooled to a temperature below 800° C., even more preferably to a temperature below 600° C., and most preferably to a temperature below 400° C.

[0036] In a more preferred embodiment, the mixture is cooled from a temperature of 1100° C. or greater to a temperature of 600° C. or less over a period of 4 to 15 hours. In a further embodiment, the mixture is cooled from a temperature in the range of 1600-1400° C. to a temperature of 600-400° C. or less over a period of 4 to 12 hours.

[0037] After a controlled cooling step, the material is generally allowed to cool to ambient temperature.

[0038] In some embodiments, the method comprises a further step, which comprises dispersing the material obtained after step (iii) in an aqueous medium comprising water.

[0039] Generally, water is the main component of the aqueous medium. Therefore, the aqueous medium contains 65 to 100% by weight, preferably 80 to 100% by weight, of water. In addition to water, the aqueous medium may contain other additives and an organic polar solvent, preferably a water-miscible solvent, such as an alcohol having 1 to 4 carbon atoms.

[0040] Generally, the amount of substance dispersed in the aqueous medium ranges from 0.5 to 20.0% by weight, preferably from 1.0 to 18.0% by weight, and more preferably from 1.5 to 15.0% by weight, each calculated based on the total weight of the dispersion.

[0041] Under these conditions, the materials of the present invention often spontaneously delaminate into a single thin plate.

[0042] In some embodiments, delamination of the layered material into single sheets can be facilitated by heating the aqueous medium containing the dispersed material to a temperature in the range of 50 to 400° C. Very good results have been obtained by heating the aqueous medium to a temperature in the range of 50 to 120° C.

[0043] In a further embodiment, the dispersion may be heated in a pressure reactor to a temperature in the range of 180 to 500°C, preferably in the range of 250 to 400°C.

[0044] The dispersion is generally heated for a period of 0.5 to 48 hours.

[0045] The aqueous dispersion, with or without heat treatment, can be used for formulations that provide improved barrier properties. If desired, the lamellar dispersion can be separated from any non-delaminated impurities by a liquid-solid separation process, such as by centrifugation. If desired, the delaminated material can be dried by evaporation of the water.

[0046] In an alternative embodiment, step (iii) of the method is followed by a further step of grinding the material to a powder and heating this powder to a temperature in the range of 500° C. to 1100° C. for a period of at least 48 hours. To avoid unwanted loss of material by evaporation during this heating step, the material may be placed in a sealed container.

[0047] As mentioned above, the materials of the invention are highly suitable for improving the barrier properties of composite materials. The invention therefore also relates to compositions comprising at least one binder and a material of the invention.

[0048] A binder is generally a substance that can form a layer on a substrate.

[0049] Examples of binders include organic polymers and resins, prepolymers, and monomers capable of forming polymers. Binders can be of natural or synthetic origin, or natural materials that have been synthetically modified. Examples of binders include polyurethanes, polycarbonates, polyamides, polyacrylates, polyesters, polyolefins, rubbers, polysiloxanes, polyvinyl alcohols, polylactic acids, polysaccharides, polylysines, polystyrenes, polyalkylene oxides, and polyepoxides, as well as combinations thereof.

[0050] The binder preferably comprises at least one of an aqueous polymer solution or an aqueous polymer dispersion. Examples of binders in aqueous media include proteins, polysaccharides, polylysine, polyacrylates, polyvinyl esters, polyvinyl alcohols, polyethylene oxides, oxidized polyolefins, and maleated polyolefins, and combinations thereof.

[0051] In some embodiments, the composition is a liquid composition that can be applied to a substrate as a coating. If the liquid composition includes water or an organic solvent as a diluent, after application to the substrate, the composition is dried by evaporation of the water or solvent to form a coating layer.

[0052] The substrate to be coated may be any substrate suitable for receiving a coating layer. Examples of suitable substrate materials include polymers, such as polyester, polyacrylate, polyvinyl chloride, and polyolefin, as well as paper, cardboard, and metal. In some embodiments, the substrate is a polymer foil, such as a polymer foil suitable for food packaging. In other embodiments, the substrate may be in the form of a tray, container, or bottle suitable for packaging food or beverages. In further embodiments, the substrate may be a metal substrate to be protected against corrosion, such as an iron, steel, or copper, or aluminum substrate. The substrate may also be in the form of a laminate and may include two or more layers of different materials. Furthermore, the coating layer may itself form an inner or outer layer in a multi-layer material.

[0053] The weight ratio of binder to material according to the present invention in the composition is generally in the range of 3:97 to 97:3, preferably 7:93 to 93:7.

[0054] The incorporation of the materials of the invention into the binder may be carried out by conventional techniques, for example by mixing, stirring, extrusion, kneading processes, rotor-stator processes (Dispermat, Ultra-Turrax, etc.), grinding processes or jet dispersion, depending on the viscosity of the binder.

[0055] In a further embodiment, the present invention relates to the use of the substance according to the present invention for improving the barrier properties of a coating layer. When contained in a coating layer, the substance according to the present invention significantly improves the barrier properties of the coating layer. Relevant barrier properties include the permeability of gases and liquids through the coating layer. Improved barrier properties mean that the permeability of gases and liquids through the coating layer is reduced. Examples of gases that are reduced in permeability include oxygen, carbon dioxide, water vapor, and nitrogen. Reducing the permeability of these gases is particularly important in the field of food and beverage packaging. [Example]

[0056] Example 1 Process (a) A layered material of formula Na0.5[Mg2.5Li0.5]SiO10F2 was prepared from a mixture of sodium carbonate (68.8 g, 99.9% purity), lithium carbonate (47.8 g, 99.9% purity), magnesium oxide (159.8 g, 98.0% purity), magnesium fluoride (161.4 g, 99.9% purity), and silicon dioxide (623.0 g, 99.9% purity). This raw material mixture was heated to 1530°C in a platinum crucible to form a homogeneous melt and held at this temperature for 2 hours. The melt was then poured into a ceramic crucible. The ceramic crucible with the melt was placed in a furnace and cooled to a temperature of 400°C over a period of 6 hours.

[0057] Process (b) After cooling to room temperature, 3.0 g of the layered material prepared in step (a) was dispersed in 97.0 g of distilled water by stirring. The aqueous dispersion was heated to a temperature of 80° C. for a period of 45 minutes. Approximately 0.3 g of non-exfoliated material was then removed from the dispersion by centrifugation (5000 rpm for 10 minutes). The dispersion was dried by evaporation of water, and the residue was ground into a powder.

[0058] Example 2 After cooling to room temperature, 3.0 g of the layered material prepared in step (a) of Example 1 was dispersed in 97.0 g of distilled water by stirring. The aqueous dispersion was heated to a temperature of 80°C. The heated dispersion was processed in an IKA ULTRA-TURRAX™ T25 with an S25N 18G disperser at a speed of 5000 rpm for a period of 10 minutes. Approximately 0.3 g of non-delaminated material was then removed from the dispersion by centrifugation (5000 rpm for 10 minutes). The dispersion was dried by evaporation of water, and the residue was ground into a powder.

[0059] Example 3 After cooling to room temperature, 3.0 g of the layered material prepared in step (a) of Example 1 was dispersed in 97.0 g of distilled water by stirring. The aqueous dispersion was heated to a temperature of 80°C. The heated dispersion was processed in an IKA ULTRA-TURRAX™ T 25 with an S25N 18G disperser at a speed of 25,000 rpm for a period of 10 minutes. Approximately 0.3 g of non-delaminated material was then removed from the dispersion by centrifugation (5,000 rpm for 10 minutes). The dispersion was dried by evaporation of water, and the residue was ground into a powder.

[0060] Example 4 After cooling to room temperature, 10.0 g of the layered material prepared in step (a) of Example 1 was dispersed in 90.0 g of distilled water by stirring. The aqueous dispersion was then placed in a pressure vessel and heated to a temperature of 300° C. for a period of 48 hours. After cooling to room temperature, the dispersion was dried by evaporation of water, and the residue was ground to a powder.

[0061] Example 5 (comparison) After cooling to room temperature, 3.0 g of the layered material prepared in step (a) of Example 1 was exposed to 23°C and 43% relative humidity for 12 hours and crushed into a powder. The powder was loaded into an appropriately sized Si3N4 crucible and placed in a steel-type reactor 1.4841. The reactor was closed with a lid made of the same material as the reactor. To make the reactor gas-tight at high temperatures, the lid was covered with potassium silicate powder, which melts at 900°C. The reactor was then placed in a furnace. The furnace was heated from room temperature to 500°C within 3 hours and held for 12 hours. The furnace was then heated to 1023°C within 1 hour. The furnace temperature was held for 6 weeks. After 6 weeks, the furnace was cooled to room temperature and the powder was recovered from the reactor.

[0062] Example 6 (comparison) Example 1 was repeated, however, after holding the homogeneous melt at 1530°C for 2 hours, the material was cooled to 25°C over a 15 minute period.

[0063] Determination of X-ray diffraction patterns Prior to determination of the X-ray diffraction pattern, powders of the layered materials of the above examples were exposed to 43% relative humidity at 23°C for a period of 12 hours. X-ray diffraction patterns were determined on a Panalytical Empyrean X-ray instrument with a Pixcel detector. Samples were measured using the following measurement conditions and instrument settings:

[0064] [Table 1]

[0065] The full width at half maximum (FWHM) of the peak was determined using 001 Miller indices. The FWHM values ​​were viewed from the powder X-ray diffraction patterns using Panalytical data viewer software. The results are summarized in Table 1 below.

[0066] Z-average particle size determination The Z-average particle size of the layered material was determined by dynamic laser light scattering in an aqueous dispersion of the material containing 1.0 wt % of the layered material on a Malvern Zetasizer Nano ZS instrument.

[0067] The following measurement and instrument settings were used:

[0068] [Table 2]

[0069] The results are shown in Table 1 below.

[0070] Measurement of barrier properties The layered silicate powder was dispersed in deionized water under stirring until completely dispersed. A solution of polyvinyl alcohol (Mowiol® 20-98 Mw 125,000 g / mol) was gradually added to the silicate dispersion over a period of 1 hour with stirring. The total nonvolatile content was 3 wt%. The silicate:polyvinyl alcohol weight ratio was 10:90. The composite dispersion was coated onto a polyethylene terephthalate (PET) foil with a thickness of 36 μm. The dry thickness of the coating layer was 1 μm. The coating layer was dried at 80°C for 6 hours. The oxygen transmission rate (OTR) of the coated foil was measured at 75% relative humidity using a Mocon Ox-Tran (1 / 50) type. The water vapor transmission rate (WVTR) of the coated foil was measured at 75% relative humidity using a Mocon Permatran W (1 / 50G) type. The results are summarized in Table 1.

[0071] Determination of osmotic swelling and delamination of layered materials via small angle X-ray spectroscopy (SAXS) The layered materials of the above examples were measured with a small-angle diffraction system of the type Double Ganesha AIR (SAXSLAB). The X-ray source was a rotating anode (Cu, MicroMax 007HF, Rigaku Corporation) producing a microfocus beam. A spatially resolved detector PILATUS 300K (Dectris AG) was used. Measurements were carried out in a 1 mm diameter glass capillary (glass no. 50, Hilgenberg) at room temperature (23 °C) and with 5 wt % layered material in water. Radially averaged data were normalized to the main beam and measurement time, and the solvent was removed. Data analysis was performed according to: M. Stoter, B. Biersack, S. Rosenfeldt, M.J. Leitl, H. Kalo, R. Schobert, H. Yersin, G.A. Ozin, S. Forster, J. Breu, Angew. Chem. Int. Ed. 2015, 54, 4963-4967. The results are summarized in Table 1.

[0072] [Table 3] * indicates a comparative example. Laponite™ B is a synthetic layered fluorosilicate. It is insoluble in water but hydrates and swells to form a translucent, colorless colloidal dispersion. Laponite™ B is commercially available from BYK-Chemie.

[0073] From Table 1, it can be concluded that the examples according to the present invention, when coated onto PET foil, provide a significant improvement in oxygen and water vapor barrier properties. The barrier properties are at the same level as those obtained with the comparative layered material of Comparative Example 5. The layer distance value d001 indicates complete delamination of the material in water. However, the layered materials of Examples 1-4 according to the present invention were prepared by a method that is economically much more attractive than the process used to prepare the layered material of Comparative Example 5. Comparative Example 6 was prepared in a manner similar to Example 1. However, the cooling rate in Comparative Example 6 was significantly faster than in Example 1. The material of Comparative Example 6 provides inferior barrier properties. This indicates that the cooling rate of the homogeneous melt significantly determines the properties of the layered silicate. Laponite B is a commercially available layered material with a composition similar to Examples 1-5. This material has a small particle size. As a result, inferior gas barrier properties were observed.

Claims

1. Composition Na ｘ [Mg ３－ｚ Li ｙ ]Si ４ O １０ (T) ２ A material comprising a layered material having x is in the range of 0.4 to 0.8; y is in the range of 0.0 to 0.8; z is in the range of 0.2 to 0.8; T independently in each occurrence represents F or OH; and x+(3−z)+y≦4, the powder X-ray diffraction pattern of the layered material has a 001 peak in the range of 5.88° to 8.00° 2-theta, the 001 peak having a full width at half maximum of the peak maximum greater than 0.10°; and the layered material has a Z-average particle size of 500 nm or greater as determined by dynamic laser light scattering in an aqueous dispersion of the material containing up to 1.5 wt. % of the material; material.

2. 2. The substance of claim 1, wherein T represents F in at least 50% of its occurrences.

3. 3. The material of claim 1, wherein y is in the range of 0.4 to 0.

8.

4. 4. The material of any one of claims 1 to 3, wherein the layered material has a Z-average particle size in the range of 500 nm to 25,000 nm as determined by dynamic laser light scattering in an aqueous dispersion of the material containing up to 1.5 wt% of the material.

5. A material according to any one of claims 1 to 4, wherein the material comprises 80 to 100% by weight of the layered material.

6. The substance according to any one of claims 1 to 5, wherein the substance is obtained by a process comprising the steps of: (i) providing a mixture containing a Na compound, a Mg compound, a Li compound, and a Si compound, wherein these compounds are selected from carbonates, halides, and oxides, and the molar ratio of Na:Mg:Li:Si is in the range of 0.4-0.8:2.2-2.8:0.0-0.8:4.0; (ii) heating the mixture to a temperature above 1500°C to form a homogeneous liquid; (iii) cooling the mixture to a temperature below 500°C for a period of at least 0.5 hours.

7. A method for preparing a substance according to any one of claims 1 to 6, comprising the steps of: (i) providing a mixture containing a Na compound, a Mg compound, a Li compound, and a Si compound, wherein these compounds are selected from carbonates, halides, and oxides, and the molar ratio of Na:Mg:Li:Si is in the range of 0.4-0.8:2.2-2.8:0.0-0.8:4.0; (ii) heating the mixture to a temperature above 1100°C to form a homogeneous liquid; (iii) cooling the mixture to a temperature less than 1000°C for a period of at least 2.0 hours.

8. 8. The method of claim 7, wherein step (iii) is carried out for a period of at least 3.0 hours.

9. 9. The method of claim 7 or 8, wherein the method comprises the further step of dispersing the substance in an aqueous medium containing water.

10. 10. The method of claim 9, wherein the aqueous medium containing the dispersed material is heated to a temperature in the range of 50°C to 400°C.

11. 9. A method according to claim 7 or 8, wherein the method comprises the further step of grinding the material to a powder and heating the powder to a temperature in the range of 500°C to 1100°C for a period of at least 48 hours.

12. A composition comprising at least one binder and a substance according to any one of claims 1 to 6.

13. The composition of claim 12 , wherein the binder comprises at least one of an aqueous polymer solution or an aqueous polymer dispersion.

14. Use of a substance according to any one of claims 1 to 6 for improving the barrier properties of a coating layer.

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