Patent Application
20210363025
The present invention relates to surface modified layered double hydroxides, as well as to processes for making the surface modified layered double hydroxides, and their uses in composite materials.
Layered double hydroxides (LDHs) are a class of compounds which comprise two metal cations and have a layered structure. A review of LDHs is provided in Structure and Bonding; Vol 119, 2005 Layered Double Hydroxides ed. X Duan and D. G. Evans. The hydrotalcites, perhaps the most well-known examples of LDHs, have been studied for many years. LDHs can intercalate anions between the layers of the structure. WO 99/24139 discloses the use of LDHs to separate anions including aromatic and aliphatic anions.
Owing to the concentration of hydroxyl groups on their surface, conventionally-prepared LDHs are highly hydrophilic. As a consequence, conventionally-prepared LDHs often retain a considerable amount of water from the manufacturing process by which they were made.
The hydrophilicity of conventionally-prepared LDHs limits the extent to which they can be dispersed in organic solvents, thereby precluding their incorporation into a variety of materials wherein the interesting properties of LDH would be desirable. Attempts to address this by thermal treatment of the LDH to remove surface complexed water, may result in the formation of highly aggregated, “stone-like”, non-porous bodies with low specific surface areas of typically 5 to 15 m2/g.
A method of preparing LDHs with a specific surface area of at least 125 m2/g was reported (WO2015/144778), the method comprising slurrying a dispersion of a water-wet LDH in an aqueous-miscible organic (AMO) solvent, followed by recovery and drying of the so-called AMO-LDH. Nevertheless, such AMO-LDHs suffer from a high moisture uptake capacity compared with conventionally-prepared LDHs and as a result can be difficult to process and incorporate into composite materials.
The present invention was devised with the foregoing in mind.
According to a first aspect of the present invention there is provided a process for forming a modified layered double hydroxide comprising the steps of:
According to a further aspect of the present invention there is provided a modified layered double hydroxide obtainable, obtained or directly obtained by a process defined herein.
According to a further aspect of the present invention there is provided a composite material comprising a modified layered double hydroxide as defined herein dispersed throughout a polymer.
As discussed hereinbefore, the present invention provides a process for forming a modified layered double hydroxide comprising the steps of:
The inventors have determined that the surface modification of conventionally-prepared LDHs is hindered by a number of factors. Principally, the presence of large amounts of water in the conventionally-prepared LDH significantly reduces the efficiency of the reaction between the surface modifying agent and the hydroxyl functional groups located on the surface of the LDH. In particular, rather than reacting with the available hydroxyl groups on the LDH, the surface modifying agent may react preferentially with the complexed water. Moreover, the presence of water is likely to give rise to an increased number of unwanted side-reactions, thus generating undesirable by-products which results in the generation of impure materials. Attempts to address this by thermal treatment of the conventionally-prepared LDH to remove complexed water may result in the formation of highly aggregated, “stone-like”, non-porous bodies having low specific surface area of generally 5 to 15 m2/g, but even as low as 1 m2/g.
A method of preparing LDHs with a specific surface area of at least 125 m2/g has been reported (WO2015/144778); the method comprises slurrying a dispersion of a water-wet LDH in an aqueous-miscible organic (AMO) solvent, followed by recovery and drying of the so-called AMO-LDH. Nevertheless, such AMO-LDHs suffer from a high moisture uptake capacity compared with conventionally-prepared LDHs and as a result can be difficult to process and incorporate into composite materials. Similarly, although conventionally-prepared LDHs can be subjected to grinding, milling or similar particle size reduction methods in order to increase their surface area for modification, this typically increases their moisture uptake capacity and makes subsequent processing difficult.
The inventors have now devised a means of successfully and flexibly modifying the surface properties of LDHs, thereby extending their interesting functionality to a wide array of applications. In particular, it has been discovered that carrying out a thermal treatment on the LDHs, followed by a mixing process with modifier carried out in the absence or near-absence of solvent, leads to modified LDHs having both higher densities, increased hydrophobicity and significantly reduced moisture uptake capacity. The process according to this invention also offers benefits in terms of scalability and environmental impact due to the avoidance of solvents.
The surface modified LDHs of the invention can be used in a variety of applications, wherein conventionally-prepared hydrophilic LDHs would be unsuitable.
In an embodiment, the layered double hydroxide provided in step a) has a specific surface area of at least 15 m2/g, for example at least 20 m2/g, such as at least 32 m2/g, preferably at least 50 m2/g, most preferably at least 75 m2/g. In an embodiment, the layered double hydroxide provided in step a) has a specific surface area of greater than 125 m2/g.
In an embodiment, the layered double hydroxide provided in step a) has a specific surface area in a range of 10-105 m2/g, preferably 10-40 m2/g, most preferably 20-40 m2/g. In an embodiment, the layered double hydroxide provided in step a) has a particle size (when measured in a-b plane) in a range of 30 nm-5 μm, preferably 50 nm-1 μm, most preferably 100 nm-1 μm. In an embodiment, the layered double hydroxide provided in step a) has a bulk density in a range of 0.1-0.6 g/ml, preferably 0.2-0.4 g/ml, most preferably 0.2-0.3 g/ml. In an embodiment, the layered double hydroxide provided in step a) has a tap density in a range of 0.2-0.7 g/ml, preferably 0.3-0.6 g/ml, most preferably 0.4-0.5 g/ml. In an embodiment, the layered double hydroxide provided in step a) has a moisture content less than 10%, preferably less than 5%, most preferably less than 3% w/w. In an embodiment, the layered double hydroxide provided in step a) has no impurity such as Fe, ZnO and Na2O. In an embodiment, the primary particle of layered double hydroxide is platelet, which may agglomerate to form rosette shape. In an embodiment, the layered double hydroxide provided in step a) has a particle size distribution with D10 in a range of 0.1-2 μm, preferably 0.3-1.5 μm, most preferably 0.5-1 μm; D50 in a range of 1-5 μm, preferably 1-4 μm, most preferably 2-3 μm; and D90 in a range of 2-10 μm, preferably 2-7 μm, most preferably 3-5 μm.
In an embodiment, the layered double hydroxide provided in step a) is of formula (IA):
[Mz+1-xM′y+x(OH)2]a+(Xn−)m.bH2O (IA)
wherein
In an embodiment, the layered double hydroxide provided in step a) is of formula (IB):
[Mz+1-xM′y+x(OH)2]a+(Xn−)m.bH2O.c(L) (IB)
wherein
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein when z is 2, M is Mg, Zn, Fe, Ca, Sn, Ni, Cu, Co, Mn or Cd or a mixture of two or more of these, or when z is 1, M is Li. Suitably, z is 2 and M is Ca, Mg, Zn or Fe. More suitably, z is 2 and M is Ca, Mg or Zn.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein when y is 3, M′ is Al, Ga, Y, In, Fe, Co, Ni, Mn, Cr, Ti, V, La or a mixture thereof, or when y is 4, M′ is Sn, Ti or Zr or a mixture thereof. Suitably, y is 3. More suitably, y is 3 and M′ is Al. Suitably, M′ is Al.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein x has a value according to the expression 0.18<x<0.9. Suitably, x has a value according to the expression 0.18<x<0.5. More suitably, x has a value according to the expression 0.18<x<0.4.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Zn/Al, Mg/Al, ZnMg/Al, Ni/Ti, Mg/Fe, Ca/Al, Ni/AI or Cu/AI layered double hydroxide.
The anion(s) X in the LDH may be any appropriate organic or inorganic anion, for example halide (e.g., chloride), inorganic oxyanions (e.g. X′mOn(OH)pq−; m=1-5; n=2-10; p=0-4, q=1-5; X′=B, C, N, S, P: e.g. carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, phosphate, sulphate), anionic surfactants (such as sodium dodecyl sulfate, fatty acid salts or sodium stearate), anionic chromophores, and/or anionic UV absorbers, for example 4-hydroxy-3-methoxybenzoic acid, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMBA), 4-hydroxy-3-methoxy-cinnamic acid, p-aminobenzoic acid and/or urocanic acid. In an embodiment, the anion X is an inorganic oxyanion selected from carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, sulphate or phosphate or a mixture of two or more thereof. More suitably, the anion X is an inorganic oxyanion selected from carbonate, bicarbonate, phosphate, borate, nitrate or nitrite. More suitably, the anion X is an inorganic oxyanion selected from carbonate, bicarbonate, nitrate or nitrite. Most suitably, the anion X is carbonate.
In a particularly suitable embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein, M is Ca, Mg, Zn and/or Fe, M′ is Al, and X is carbonate, bicarbonate, phosphate, borate, nitrate or nitrite. Suitably, M is Ca, Mg and/or Zn, M′ is Al, and X is carbonate, bicarbonate, phosphate, borate, nitrate or nitrite. More suitably, M is Ca, Mg and/or Zn, M′ is Al, and X is carbonate, nitrate, phosphate or borate.
In a particularly suitable embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein, M is Ca, Mg, Zn or Fe, M′ is Al, and X is carbonate, bicarbonate, nitrate or nitrite. Suitably, M is Ca, Mg or Zn, M′ is Al, and X is carbonate, bicarbonate, nitrate or nitrite. More suitably, M is Ca, Mg or Zn, M′ is Al, and X is carbonate.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein M is Mg, M′ is Al and X is carbonate, nitrate, phosphate or borate.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate, nitrate, phosphate or borate.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein M is Mg, M′ is Al and X is carbonate.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided with the formula MgqAl—X, wherein X is carbonate, nitrate, phosphate or borate, and 1.8≤q≤5, preferably wherein 1.8≤q≤3.5.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided with the formula ZnpMgqAl—X, wherein X is carbonate, nitrate, phosphate or borate, and 0.5≤p≤2.5 and 0.5≤q≤2.5.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided with the formula MgqAl—CO3, wherein 1.8≤q≤5, and preferably wherein 1.8≤q≤3.5.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided with the formula ZnpMgqAl—CO3, wherein 0.5≤p≤2.5 and 0.5≤q≤2.5.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Zn2MgAl—CO3 layered double hydroxide.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Mg3Al—CO3 layered double hydroxide.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Mg2Al—CO3 layered double hydroxide.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Zn2Al—NO3 layered double hydroxide.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Zn2Al—PO4 layered double hydroxide.
In an embodiment, in step a), a layered double hydroxide of formula (IA) or formula (IB) is provided which is a Zn2Al—BO3 layered double hydroxide.
The organic solvent, L, present in formula (IB) may have any suitable hydrogen bond donor and/or acceptor groups, so that it is capable of hydrogen-bonding to water. Hydrogen bond donor groups include R—OH, R—NH2, R2NH, whereas hydrogen bond acceptor groups include ROR, R2C═O, RNO2, R2NO, R3N, ROH, RCF3. The term ‘AMO’ refers to aqueous-miscible organic solvents, such as ethanol, methanol and acetone. In the context of this application ‘AMO’ is used to refer to solvents which are capable of hydrogen-bonding to water and as such, other organic solvents with limited aqueous miscibility (such as ethyl acetate) are also envisaged within the scope of an ‘AMO’, for example when used in the term ‘AMO-LDH’.
In an embodiment, L is selected from acetone, acetonitrile, dimethylformamide, dimethyl sulphoxide, dioxane, ethanol, methanol, n-propanol, isopropanol, tetrahydrofuran, ethyl acetate, n-butanol, sec-butanol, n-pentanol, n-hexanol, cyclohexanol, diethyl ether, diisopropyl ether, di-n-butyl ether, methyl tert-butyl ether (MTBE), tert-amyl methyl ether, cyclopentyl methyl ether, cyclohexanone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methyl isoamyl ketone, methyl n-amyl ketone, furfural, methyl formate, methyl acetate, isopropyl acetate, n-propyl acetate, isobutyl acetate, n-butyl acetate, n-amyl acetate, n-hexyl acetate, methyl amyl acetate, methoxypropyl acetate, 2-ethoxyethyl acetate, nitromethane, and a mixture of two or more thereof.
Suitably, L is selected from acetone, ethanol, ethyl acetate, and a mixture of two or more thereof. In one embodiment L is ethanol.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Mg, M′ is Al, X is carbonate, nitrate, phosphate or borate and L is ethanol or acetone.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate, nitrate, phosphate or borate and L is ethanol.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate, nitrate, phosphate or borate and L is ethanol or acetone.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided which is a Zn2MgAl—X layered double hydroxide, wherein X is carbonate, nitrate, phosphate or borate, and wherein L is ethanol.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Mg, M′ is Al, X is carbonate and L is ethanol or acetone.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate and L is ethanol.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided wherein M is Zn and Mg, M′ is Al, X is carbonate and L is ethanol or acetone.
In an embodiment, in step a), a layered double hydroxide of formula (IB) is provided which is a Zn2MgAl—CO3 layered double hydroxide and L is ethanol.
In an embodiment, b has a value according to the expression 0<b≤7.5. Suitably, b has a value according to the expression 0<b≤5. More suitably, b has a value according to the expression 0<b≤3. Even more suitably, b has a value according to the expression 0<b≤1 (e.g. 0.2<b≤0.95).
In an embodiment, c has a value according to the expression 0<c≤7.5. Suitably, c has a value according to the expression 0<c≤5. More suitably, c has a value according to the expression 0<c≤1. Most suitably, c has a value according to the expression 0<c≤0.5.
In an embodiment, the layered double hydroxide of formula (IA) is prepared by a process comprising the step of
The wet precipitate may be isolated in step II) by means of filtration (e.g. vacuum filtration), centrifugation, or other separation means as will be apparent to one skilled in the art.
The drying of the precipitated LDH may be carried out by various means such as heating, drying under vacuum or a combination of both, for example at 50-150° C. under vacuum. In an embodiment the drying step comprises drying under vacuum at 100-120° C.
Step III) involves reducing the particle size and/or increasing the surface area of the dried LDH by a grinding step. Other suitable methods for carrying out this step will be apparent to the skilled person, such as ball milling, jet milling or centrifugal grinding.
In an embodiment, the layered double hydroxide of formula (IB) is prepared by a process comprising the steps of
When a layered double hydroxide of formula (IB) is prepared, the water-washed wet precipitate is not allowed to dry prior to it being contacted with the solvent according to step (IIA). The wet precipitate may have a moisture content of 15 to 60% relative to the total weight of the wet precipitate.
It will be understood that the water-washed wet precipitate of step (I) may be pre-formed. Alternatively, the water-washed wet precipitate of step I) may be prepared as part of step (I), in which case step (I) comprises the following steps:
The ammonia-releasing agent used in step (i) may increase the aspect ratio of the resulting LDH platelets. Suitable ammonia-releasing agents include hexamethylene tetraamine (HMT) and urea. Suitably, the ammonia-releasing agent is urea. The amount of ammonia-releasing agent used in step i) may be such that the molar ratio of ammonia-releasing agent to metal cations (M+M′) is 0.5:1 to 10:1 (e.g. 1:1 to 6:1 or 4:1 to 6:1).
In an embodiment, in step (i), the precipitate is formed by contacting aqueous solutions containing cations of the metals M and M′, the anion Xn−, and optionally an ammonia-releasing agent, in the presence of a base being a source of OH− (e.g. NaOH, NH4OH, or a precursor for OH− formation). Suitably the base is NaOH. In an embodiment, the quantity of base used is sufficient to control the pH of the solution above 6.5. Suitably, the quantity of base used is sufficient to control the pH of the solution at 6.5-13. More suitably, the quantity of base used is sufficient to control the pH of the solution at 7.5-13. Yet more suitably, the quantity of base used is sufficient to control the pH of the solution at 9-11.
In an embodiment, in step (ii), the layered double hydroxide precipitate obtained in step i) is aged in the reaction mixture of step (i) for a period of 5 minutes to 72 hours at a temperature of 15-180° C. In an embodiment, in step (ii), the layered double hydroxide precipitate obtained in step i) is aged in the reaction mixture of step (i) for a period of 3 to 15 hours at a temperature of 100-160° C.; preferably for 3 to 5 hours at a temperature of 130-160° C.; most preferably for 5 hours at a temperature of 150° C.
Suitably, in step (ii), the layered double hydroxide precipitate obtained in step (i) is aged in the reaction mixture of step (i) for a period of 1 to 72 hours. More suitably, in step (ii), the layered double hydroxide precipitate obtained in step (i) is aged in the reaction mixture of step (i) for a period of 2 to 12 hours. Most suitably, in step (ii), the layered double hydroxide precipitate obtained in step (i) is aged in the reaction mixture of step (i) for a period of 2 to 6 hours.
Suitably, in step (ii), the layered double hydroxide precipitate obtained in step (i) is aged in the reaction mixture of step (i) at a temperature of 15-180° C. More suitably, in step (ii), the layered double hydroxide precipitate obtained in step (i) is aged in the reaction mixture of step (i) at a temperature 100-160° C.; preferably at 130-160° C.; most preferably at 150° C.
Step (ii) may be performed in an autoclave.
In an embodiment, in step (iii), the aged precipitate resulting from step (ii) is collected, then washed with water until the filtrate has a pH in the range of 6.5-7.5. Suitably, step (iii) comprises washing the aged precipitate resulting from step (ii) with water at a temperature of 15-100° C. (e.g. 18-40° C.). Optionally the precipitate may be washed with a mixture of water and solvent. Suitably, the solvent is selected from ethyl acetate, ethanol and acetone. More suitably, the quantity of solvent in the washing mixture is 5-95% (v/v), preferably 30-70% (v/v).
In an embodiment, in step IIA) the water-washed wet precipitate is contacted with a solvent L by dispersing said precipitate in the solvent L to produce a slurry. In a further embodiment, the preparation process comprises a further step IIIA) of maintaining the slurry resulting from step IIA). In an embodiment, the slurry produced in step IIA) and then maintained in step IIIA) contains 1-100 g of water-washed wet precipitate per 1 litre of solvent L. Suitably, the slurry produced in step IIA) and maintained in step IIIA) contains 1-75 g of water-washed wet precipitate per 1 litre of solvent L. More suitably, the slurry produced in step IIA) and maintained in step IIIA) contains 1-50 g of water-washed wet precipitate per 1 litre of solvent L. Most suitably, the slurry produced in step IIA) and maintained in step IIIA) contains 1-30 g of water-washed wet precipitate per 1 litre of solvent L.
In step IIIA), the slurry produced in step IIA) is maintained for a period of time. Suitably, the slurry is stirred during step IIIA).
In an embodiment, in step IIIA), the slurry is maintained for a period of 0.5 to 120 hours (e.g. 0.5 to 96 hours). Suitably, in step IIIA), the slurry is maintained for a period of 0.5 to 72 hours. More suitably, in step IIIA), the slurry is maintained for a period of 0.5 to 48 hours. Even more suitably, in step IIIA), the slurry is maintained for a period of 0.5 to 24 hours. Yet more suitably, in step IIIA), the slurry is maintained for a period of 0.5 to 24 hours. Most suitably, in step IIIA), the slurry is maintained for a period of 1 to 2 hours. Alternatively, in step IIIA), the slurry is maintained for a period of 16 to 20 hours.
The LDH resulting from step IIIA) may be isolated by any suitable means, including filtering, filter pressing, spray drying, cycloning and centrifuging. The isolated AMO-LDH may then be dried to give a free-flowing powder. The drying may be performed under ambient conditions, in a vacuum, or by heating to a temperature below 60° C. (e.g. 20 to 60° C.). Suitably, the AMO-LDH resulting from step IIIA) is isolated and then heated to a temperature of 10-40° C. in a vacuum until a constant mass is reached. In an embodiment, the AMO-LDH may be dried by heating at 50° C.-200° C., such as 100° C.-200° C., for example 150° C.-200° C.
Step b) of the process for forming a modified LDH comprises heating the layered double hydroxide to 110-200° C. Layered double hydroxides (whether treated with an AMO solvent or untreated) have a propensity to absorb atmospheric moisture. Such materials can become difficult to modify and process and can exhibit reduced shelf-lives. To overcome these problems, it has been surprisingly found that the surface modification of step c) benefits from a preceding thermal treatment of the LDH being carried out.
It has been discovered to be advantageous to carry out a surface modification of the heat-treated layered double hydroxide (step c) by mixing it with modifier in the presence of less than or equal to 50% by weight of a solvent, relative to the total weight of the layered double hydroxide and the modifier. For the avoidance of doubt, and purely as an example, if 1 g of heat-treated LDH is mixed with 0.5 g of modifier, then 50% by weight of a solvent would be 0.75 g of solvent. In an embodiment, in step c) the mixing is conducted in the presence of less than or equal to 10% by weight of a solvent, relative to the total weight of the layered double hydroxide and the modifier. In an embodiment, the mixing in step c) is conducted with substantially no, or no solvent present.
Preferably, the mixing in step c) is carried out straight after the heat treatment of step b). In an embodiment, in between the thermal treatment of the layered double hydroxide in step b) and the mixing with modifier in step c), the layered double hydroxide is not allowed to cool down to ambient temperature. In an embodiment, in between the thermal treatment of the layered double hydroxide in step b) and the mixing with modifier in step c), the layered double hydroxide is not allowed to cool down to below 50° C., preferably to not below 80° C., most preferably to not below 110° C.
In an embodiment, step b) and step c) are carried out substantially simultaneously.
Preferably, the surface modification of step c) is carried out at elevated temperature. In an embodiment, in step c) the mixing takes place at 60-270° C. In an embodiment, in step c) the mixing takes place at 70-200° C. In an embodiment, in step c) the mixing takes place at 110-200° C. In an embodiment, in step c) the mixing takes place at 130-180° C. In an embodiment, in step c) the mixing takes place at 130-160° C. In an embodiment, in step c) the mixing takes place at 150° C.
In another embodiment, in step c) the mixing takes place at 60-200° C. Suitably, in step c) the mixing takes place at 60-180° C. More suitably, in step c) the mixing takes place at 60-160° C.
In an embodiment, in step c) the mixing takes place at a temperature above the melting point of the modifier. In an embodiment, in step c) the mixing takes place at a temperature above the melting point of the modifier, wherein the modifier is a salt of stearic acid. In an embodiment, in step c) the mixing takes place at a temperature 20-30° C. above the melting point of the modifier, preferably wherein the modifier is a salt of stearic acid, such as zinc stearate.
In an embodiment, in step c) the mixing is maintained for a period of 15 minutes-2 hours and suitably 30 minutes to 1 hour.
Step c) may be conducted in dry air (such as not more than 20% RH) or under an inert atmosphere (e.g. under a N2 blanket). In an embodiment, step c) is conducted under an inert atmosphere.
In an embodiment, the quantity of the modifier used in step c) is 1-25% by weight relative to the weight of the layered double hydroxide. In an embodiment, the quantity of the modifier used in step c) is 1-15% by weight relative to the weight of the layered double hydroxide. In an embodiment, the quantity of the modifier used in step c) is 3-15% by weight relative to the weight of the layered double hydroxide. In an embodiment, the quantity of the modifier used in step c) is 1-7% by weight relative to the weight of the layered double hydroxide. In an embodiment, the mixing in step c) is conducted using more than 5% by weight modifier, relative to the weight of layered double hydroxide. In an embodiment, the mixing in step c) is conducted using more than 10% by weight modifier, relative to the weight of layered double hydroxide. In an embodiment, the mixing in step c) is conducted using about 15% by weight modifier, relative to the weight of layered double hydroxide. In an embodiment, the mixing in step c) is conducted using 10-20% by weight modifier, relative to the weight of layered double hydroxide, when the layered double hydroxide has a surface area of 70-125 m2/g, preferably 15% wt modifier when the layered double hydroxide has a surface area of 80-100 m2/g. In an embodiment, the mixing in step c) is conducted using 1-10% by weight modifier, relative to the weight of layered double hydroxide, when the layered double hydroxide has a surface area of 10-70 m2/g, preferably 7% wt modifier when the layered double hydroxide has a surface area of 30-50 m2/g.
In a preferred embodiment, the modifier in step c) is selected from the group consisting of fatty acids, fatty acid salts, sulfate modifiers, phosphonate modifiers, phthalate modifiers and organosilane modifiers.
Fatty acids are typically long-chain carboxylic acids and may comprise one or more C═C double bonds. Examples of fatty acids include caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, maleic acid, erucic acid, oleic acid, arachidic acid and linoleic acid. Fatty acid salts are typical salts of the above-mentioned fatty acids. Metal salts of fatty acids include sodium salts, lithium salts, magnesium salts, calcium salts and zinc salts, such as zinc salts.
Sulfate modifiers are metal salts of long-chain (e.g. up to 20 carbon atoms) sulfuric acids, such as sodium dodecyl sulfate. Owing to its low flash point, sodium dodecyl sulfate may require the use of an inert atmosphere.
Phosphonate modifiers are metal salts of long-chain (e.g. up to 20 carbon atoms) phosphonic acids, such as sodium octadecyl phosphonate.
Phthalate modifiers are dialkyl esters of phthalic acid, such as dioctyl terephthalate (DOTP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), dioctyl phthalate (DOP) and dibutyl phthalate (DBP).
Organosilane modifiers may be a hydroxysilane, alkoxysilane, or siloxane compound. Siloxane modifiers include polysiloxanes such as polydimethylsiloxane. The term “alkoxy” as used herein refers to an —O-alkyl group (wherein alkyl is straight or branched chain and comprises 1 to 6 carbon atoms) such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, and hexoxy.
In an embodiment, the organosilane modifier is an alkoxysilane compound.
In an embodiment, the organosilane modifier is selected from the group consisting of 3-aminopropyltriethoxysilane, (3-glycidyloxypropyl)triethoxysilane, (3-glycidyloxypropyl)-trimethoxysilane, (3-mercaptopropyl)-triethoxysilane, triethoxyvinylsilane, triethoxyphenylsilane, trimethoxy(octadecyl)silane, vinyl-tris(2-methoxy-ethoxy)silane, g-methacryloxy-propyltrimethoxysilane, g-aminopropyl-trimethoxysilane, b(3,4-epxycryclohexyl)-ethyltrimethoxysilane, g-mercaptopropyltrimethoxysilane, (3-aminopropyl)triethoxysilane, N-(3-triethoxysilylpropyl)ethylenediamine, 3-aminopropyl-methyl-diethoxysilane, vinyltrimethoxy-silane, chlorotrimethylsilane, tert-butyldimethylsilyl chloride, trichlorovinylsilane, methyltrichlorosilane, 3-chloropropyl trimethoxysilane, chloromethyltrimethylsilane, diethoxy-dimethylsilane, trimethoxypropylsilane, trimethoxyoctylsilane, triethoxyoctylsilane, trichloro(octadecyl)silane and γ-piperazinylpropylmethyldimethoxysilane.
Suitably, the organosilane modifier is selected from the group consisting of trimethoxypropylsilane, trimethoxyoctylsilane, (3-glycidyloxypropyl)-trimethoxysilane and (3-aminopropyl)triethoxysilane.
In an embodiment, the modifier is selected from the group consisting of:
In an embodiment, the modifier is selected from the group consisting of:
In an embodiment, the modifier is selected from the group consisting of:
In an embodiment, the modifier is selected from the group consisting of:
In an embodiment, the modifier is lithium stearate, zinc stearate, magnesium stearate, calcium stearate or sodium stearate.
In an embodiment, the modifier is zinc stearate. In an embodiment, the mixing in step c) is conducted using 12-17% by weight of zinc stearate, relative to the weight of layered double hydroxide. In an embodiment, the modifier is zinc stearate. In an embodiment, the mixing in step c) is conducted using 13-16% by weight of zinc stearate, relative to the weight of layered double hydroxide. In an embodiment, the modifier is zinc stearate. In an embodiment, the mixing in step c) is conducted using 15% by weight of zinc stearate, relative to the weight of layered double hydroxide.
In an embodiment, the modifier is a fatty acid (such as maleic acid) and the mixing in step c) is carried out at 130-200° C., preferably at 150-180° C., more preferably at 170° C.
In an embodiment, the modifier is a fatty acid salt (such as zinc stearate) and the mixing in step c) is carried out at 110-200° C., preferably at 130-180° C., more preferably at 130-160° C., most preferably at 150° C.
In an embodiment, the modifier is zinc stearate and the mixing in step c) is carried out at 130-160° C. In an embodiment, the modifier is zinc stearate and the mixing in step c) is carried out at 150° C. In a preferred embodiment, the modifier is zinc stearate and the mixing in step c) is carried out at 130-160° C. for 15 minutes to 2 hours, such as for 30 minutes.
In an embodiment, the modifier is a sulfate (such as sodium dodecyl sulfate) and the mixing in step c) is carried out at 190-270° C., preferably at 210-250° C., more preferably at 230° C.
In an embodiment, the modifier is a phosphonate (such as sodium octadecyl phosphonate) and the mixing in step c) is carried out at 160-240° C., preferably at 180-220° C., more preferably at 200° C.
In an embodiment, the modifier is an organosilane (such as (3-glycidyloxypropyl)-trimethoxysilane) and the mixing in step c) is carried out at 60-140° C., preferably at 80-130° C., more preferably at 120° C.
In an embodiment the modifier is chosen from dioctyl terephthalate, diisodecyl phthalate, diisononyl phthalate, dioctyl phthalate and dibutyl phthalate.
In an embodiment, the modifier is chosen from dioctyl terephthalate, diisodecyl phthalate, diisononyl phthalate, dioctyl phthalate and dibutyl phthalate and the mixing in step c) is carried out at 70-120° C., preferably at 100° C.
The mixing in step c) can be carried out by a variety of means which can provide simultaneous heating and mechanical mixing to a batch of material to be mixed. Suitable means comprise a vortex mixer, fluidised bed mixer, internal mixer, Labo mixer or high-speed mixer. In an embodiment, the mixing in step c) is carried out by means of vapour treatment, a dry mixer, a vortex mixer, or by milling the layered double hydroxide in the presence of the modifier. In an embodiment, the mixing in step c) is carried out by means of a high-speed mixer.
In another aspect, the present invention provides a modified layered double hydroxide obtainable, obtained or directly obtained by a process defined herein.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a BET surface area (as determined by N2 adsorption) of at least 20 m2/g. Suitably, the modified layered double hydroxide has a BET surface area of at least 32 m2/g. More suitably, the modified layered double hydroxide has a BET surface area of at least 40 m2/g. Even more suitably, the modified layered double hydroxide has a BET surface area of at least 50 m2/g. In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a BET surface area of 10-55 m2/g, such as 10-30 m2/g.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a loose bulk density of greater than 0.3 g/mL. In an embodiment, the modified layered double hydroxide has a loose bulk density of greater than 0.4 g/mL. In an embodiment, the modified layered double hydroxide has a loose bulk density of greater than 0.5 g/mL. In an embodiment, the modified layered double hydroxide has a loose bulk density of greater than 0.6 g/mL. In an embodiment, the modified layered double hydroxide has a tapped density of greater than 0.5 g/mL. In an embodiment, the modified layered double hydroxide has a tapped density of greater than 0.6 g/mL In an embodiment, the modified layered double hydroxide has a tapped density of greater than 0.7 g/mL. In an embodiment, the modified layered double hydroxide has a tapped density of greater than 0.8 g/mL.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a moisture uptake level of less than 6 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours. Suitably, the modified layered double hydroxide has a moisture uptake level of less than 4 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours. More suitably, the modified layered double hydroxide has a moisture uptake level of less than 2 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours. Most suitably, the modified layered double hydroxide has a moisture uptake level of less than 1 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a contact angle greater than or equal to 100°. Suitably, the modified layered double hydroxide has a contact angle greater than or equal to 110°. More suitably, the modified layered double hydroxide has a contact angle greater than or equal to 120°.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has greater dispersion in an oil phase (such as 1-hexene), than in an aqueous phase, when the modified layered double hydroxide is allowed to partition between a mixture of the two phases.
In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a contact angle greater than or equal to 100° and a moisture uptake level of less than 6 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours. In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a contact angle greater than or equal to 110° and a moisture uptake level of less than 4 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours. In an embodiment, a modified layered double hydroxide obtained by a process according to the present invention has a contact angle greater than or equal to 120° and a moisture uptake level of less than 2 wt % of dry LDH, when measured at RH60 at 25° C. for 3 hours.
As described hereinbefore, the present invention also provides a composite material comprising a modified layered double hydroxide as defined herein dispersed throughout a polymer.
LDHs have a variety of interesting properties that make them attractive materials for use as fillers in polymeric composites. However, given that conventionally-prepared LDHs are only dispersible in aqueous solvents, the preparation of polymer-LDH composite materials using polymers that are soluble in organic solvents has been restricted.
Owing to their increased hydrophobicity and reduced water content, the modified LDHs of the invention have improved processability with polymers to produce composite materials. This allows the preparation of a homogenous mixture of modified LDH and polymer, which can be processed into a LDH-polymer composite material, wherein the modified LDH is uniformly dispersed throughout the polymeric matrix.
In an embodiment, the polymer is selected from polypropylene, polyethylene, polyvinyl chloride, polyvinylidene chloride, polylactic acid, polyvinyl acetate, ethylene vinyl alcohol, ethylene vinyl acetate, acrylonitrile butadiene styrene, polymethyl methacrylate, polycarbonate, polyamide, an elastomer, or mixtures of two or more of the aforementioned. In an embodiment, the polymer is a biopolymer.
In a preferred embodiment, the polymer is polyvinyl chloride. In an embodiment, there is provided a composite material comprising a Zn2MgAl—CO3 layered double hydroxide obtained by a process according to the present invention, dispersed in a polymer. In an embodiment, there is provided a composite material comprising a Zn2MgAl—CO3 layered double hydroxide obtained by a process according to the present invention, dispersed in polyvinyl chloride. Polymer composite materials containing a Zn2MgAl—CO3 layered double hydroxide have properties that make them useful as flame retardants. Therefore, the present invention also provides the use of a polymer composite material comprising a Zn2MgAl—CO3 layered double hydroxide obtained by a process according to the present invention, as a flame retardant. The present invention further provides the use of a polyvinyl chloride composite material comprising a Zn2MgAl—CO3 layered double hydroxide obtained by a process according to the present invention, as a flame retardant.
The low moisture content of the modified layered double hydroxides obtained by a process according to the present invention, not only improves the processability of the modified layered double hydroxides in polymeric composite materials, it also results in composite materials with low, or no void formation and improved colour stability.
As a void is a non-uniformity in a composite material, it can affect the mechanical properties and lifespan of the void-containing composite material. Accordingly, in an embodiment, the composite material comprising a modified layered double hydroxide as defined herein dispersed throughout a polymer, has no voids when subjected to SEM cross-sectional imaging.
Polymer-LDH composites may be subject to undesirable discolouration. Higher colour stability of a composite material is signified by high values of whiteness index (WI) and/or low values of yellowness index (YI). Accordingly, in an embodiment, the composite material comprising a modified layered double hydroxide as defined herein dispersed throughout a polymer, has a WI value greater than 10 and/or a YI value less than 25; preferably a WI value greater than 30 and/or a YI value less than 20; more preferably a WI value greater than 40 and/or a YI value less than 15.
The following numbered statements 1-55 are not claims, but instead describe various aspects and embodiments of the invention:
[Mz+1-xM′y+x(OH)2]a+(Xn−)m.bH2O (IA)
[Mz+1-xM′y+x(OH)2]a+(Xn−)m.bH2O.c(L) (IB)
Embodiments of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which:
The abbreviations used in the below examples and tables have the following meanings:
Mg3Al—CO3: [Mg0.75Al0.25(OH)2][CO3]0.125.bH2O;
Zn2MgAl—CO3: [(Mg0.33Zn0.66)0.75Al0.25(OH)2][CO3]0.125.bH2O.
Zn2Al—NO3: [Zn0.66Al0.33(OH)2][NO3]0.31.bH2O.
Zn2Al—PO4: [Zn0.66Al0.33(OH)2][PO4]0.10.bH2O.
Zn2Al—BO3: [Zn0.66Al0.33(OH)2][BO3]0.31.bH2O.
Mg(NO3)2.6H2O (11.535 kg) and Al(NO3)3.9H2O (5.624 kg) were dissolved in 42 L of deionized water (Solution A). A second solution was made containing Na2CO3 (3.18 kg) and NaOH (3.84 kg) dissolved in 42 L of deionized water (Solution B). Solutions A and B were added together through mixing machine at the speed of 2,900 rpm and transfer to aging tank under a stirring speed of 40 rpm at 100° C. for 4 hours. The pH was controlled at 10. After 4 hours of ageing, the resulting slurry was filtered by filter press technique, the filter cake was washed with deionized water the pH of the washings was 7, dried by vacuum oven at 110° C. for 18 hours and ground to a powder.
A metal precursor solution was prepared by dissolving the Mg(NO3)2.6H2O (4.904 kg) and Al(NO3)3.9H2O (2.391 kg) in 8.5 L of deionized water. The metal precursor solution was added drop-wise with a drop rate of 645 ml/minute into 8.5 L of a 1.5 M Na2CO3 solution under a stirring speed of 800 rpm at room temperature. The system was kept at a constant pH 10 by using a 12 M NaOH solution. After 4 hours of ageing, the resulting slurry was filtered under vacuum, and the filter cake was washed with deionized water the pH of the washings was 7. The solid was then dried in a vacuum oven at 110° C. for 18 hours and ground to a powder.
Zn(NO3)2.6H2O (8.919 kg), Mg(NO3)2.6H2O (3.845 kg) and Al(NO3)3.9H2O (5.624 kg) were dissolved in 42 L of deionized water (Solution A). A second solution was made containing Na2CO3 (3.18 kg) and NaOH (3.84 kg) dissolved in 42 L of deionized water (Solution B). Solutions A and B were added together through mixing machine at the speed of 2,900 rpm and transfer to aging tank under a stirring speed of 40 rpm at 100° C. for 4 hours. The pH was controlled at 10. After 4 hours of ageing, the resulting slurry was filtered by filter press technique, the filter cake was washed with deionized water the pH of the washings was 7, dried by vacuum oven at 110° C. for 18 hours and ground to a powder.
A metal precursor solution was prepared by dissolving Zn(NO3)2.6H2O (3.793 kg), Mg(NO3)2.6H2O (1.635 kg) and Al(NO3)3.9H2O (2.391 kg) in 8.5 L of deionized water. The metal precursor solution was added drop-wise with a drop rate of 645 ml/minute into 8.5 L of a 1.5 M Na2CO3 solution under a stirring speed of 800 rpm at room temperature. The system was kept at a constant pH 10 by using a 12 M NaOH solution. After 4 hours of ageing, the resulting slurry was filtered under vacuum, and the filter cake was washed with deionized water the pH of the washings was 7. The solid was then dried in a vacuum oven at 110° C. for 18 hours and ground to a powder.
LDHs were prepared according to the methods described in Example 1 or Example 2, with the exception that after water washing of the filter cake, and prior to vacuum oven drying, the water-wet LDH was re-dispersed in ethanol for 1 hour at a stirring speed of 40 rpm and then filtered by vacuum filtration technique.
LDHs or AMO-LDHs prepared according to the methods described in Examples 1 to 3, were heated at 150° C. for 4 hours and then mixed with zinc stearate (for amounts see Table 1) at a mixing speed of 600 rpm and a temperature of 150° C. for 30 minutes to obtain modified LDH.
LDHs or AMO-LDHs prepared according to the methods described in Examples 1 to 3, were heated at 150° C. for 4 hours and then mixed with stearic acid (for amounts see Table 1) at a mixing speed of 600 rpm and a temperature of 100° C. for 30 minutes to obtain modified LDH.
LDHs or AMO-LDHs prepared according to the methods described in Examples 1 to 3, were heated at 150° C. for 4 hours and then mixed with either dioctyl terephthalate—DOTP, diisodecyl phthalate—DIDP, diisononyl phthalate—DINP, dioctyl phthalate—DOP, or dibutyl phthalate—DBP (7% w/w loading; equivalent to 7 g of modifier per 100 g of LDH powder) at a mixing speed of 600 rpm and a temperature of 100° C. for 30 minutes to obtain modified LDH.
aMg2Al—CO3 obtained from commercial source
The modifications according to Examples 4 & 5 were carried out on a 5-15 g scale in round-bottomed flasks. The zinc stearate modifications of Zn2MgAl—CO3 were repeated on (i) a 1 kg scale using an internal mixer at a speed of 800 rpm at 150° C. for 30 min, and on (ii) a 5-10 kg scale in a Labo powder mixer at a speed of 1200 rpm at 150° C. for 30 min.
Samples were heated at 110° C. for at least 3 hr to remove any excess moisture and then stored in a desiccator prior to density measurement. Sample was added to a pre-weighed 100 ml measuring cylinder, to a volume of 100 ml and then the mass of the cylinder+sample was weighed. The mass of the sample was determined by subtracting the mass of the cylinder. Bulk density (g/ml) was calculated as:
Bulk density=mass of sample (g)/100 (ml).
The measuring cylinder containing sample was then placed in an AutoTap machine (Quantachrome, Model AT-6-220-50) and subjected to tapping to reduce the volume. The tapped density (g/ml) was calculated as:
Tapped density=mass of sample (g)/volume of sample after tapping (ml).
Pre-weighed samples were exposed at 60% (+/−5%) relative humidity, 20° C. The percentage weight change for samples after an exposure time T were calculated by:
% weight change=(wt after exposure (T mins)−wt pre-exposure)×100.
Samples were added into a mixture of 200 ml of water/20 ml of 1-hexene.
LDH samples were prepared as flat pellets with 2 cm diameter. A water droplet (10 μl) was injected by Teflon type syringe and dropped onto the LDH pellet surface. The contact angle of the water droplet on the pellet surface was measured by Contact Angle Meter DM-701 (FAMAS). Triplet measurements were made and the average of the three measurements taken.
For a given LDH, the data in Table 2 shows that surface modification was generally found to increase the bulk and tapped densities, reduce the surface area and increase the hydrophobicity as seen by improved oil phase compatibility and increased average contact angle.
PVC composite materials were prepared by mixing 100 parts by weight of PVC resin, 4 parts by weight of tribasic lead sulphate, 20 parts by weight of 1,2-benzenedicarboxylic acid diisodecyl ester, 10 parts by weight of tris(2-ethylhexyl) trimellitate, 5 parts by weight of chlorinated paraffin oil, 5 parts by weight of epoxidized soybean oil, 50 parts by weight of CaCO3, 0.2 parts by weight of epoxidized PE wax, 3 parts by weight of antimony trioxide, 2 parts by weight of silicon dioxide, 1 parts by weight of acrylic processing aid, and the LDH examples as prepared (see Table 3 for LDH amounts, expressed as parts per hundred resin (phr)—e.g. 7 phr=7 parts LDH per hundred parts PVC resin by weight) in a hot melt mixer, HAAKE™ PolyLab™ OS system HAAKE Model at 180° C. for 3 minutes under a mixing speed of 60 rpm.
Colour stability of prepared PVC composites were evaluated after extrusion by spectrophotometer CM-3600A (Konica Minolta). PVC composites were compression molded into 11×11 cm2 square plaques of uniform thickness (approximately 3 mm) for measurement of whiteness index (WI) and yellowness index (YI) by spectrophotometer.
Voids of prepared PVC composites were assessed by evaluating the number of voids on a 3 mm cross-section of the PVC composites sample formed as an extruded strand, using scanning electron microscope (SEM) imaging. The samples were scanned with an accelerating voltage capacity of 1-20 k eV, at a working distance of 10 mm and a magnification at 30× at 10 kV providing a resolution of 500 μm.
The number of voids was scored according to the following criteria:
The tensile strength and elongation at break of the PVC composites were tested according to the IEC60811-1-1 standard.
The properties of the prepared PVC composite materials are summarized in Table 3. The composites containing modified LDHs prepared according to the invention, provide higher color stability (high value of WI and low value of YI) and lower voids in comparison with the comparable composites containing unmodified LDHs.
Zn(NO3)2.6H2O (11.141 kg) and Al(NO3)3.9H2O (7.035 kg) were dissolved in 42 L of deionized water (Solution A). A second solution was made containing Na2NO3 (11.921 kg) and NaOH (3.38 kg) dissolved in 42 L of deionized water (Solution B). Solutions A and B were added together through mixing machine at the speed of 2,900 rpm and transfer to aging tank under a stirring speed of 40 rpm at 100° C. for 4 hours. The pH was controlled at 10. After 4 hours of ageing, the resulting slurry was filtered by filter press technique, the filter cake was washed with deionized water the pH of the washings was 7, dried by vacuum oven at 110° C. for 18 hours and ground to a powder.
Zn2Al—PO4 was obtained from a commercial source.
Zn(NO3)2.6H2O (5.942 kg) and Al(NO3)3.9H2O (3.752 kg) were dissolved in 40 L of deionized water (Solution A). A second solution was made containing Boric acid (4.55 kg) and NaOH (3.29 kg) dissolved in 57 L of deionized water (Solution B). Solutions A and B were added together through mixing machine at the speed of 2,900 rpm and transfer to aging tank under a stirring speed of 40 rpm at 100° C. for 4 hours. The pH was controlled at 9. After 4 hours of ageing, the resulting slurry was filtered by filter press technique, the filter cake was washed with deionized water the pH of the washings was 7, dried by vacuum oven at 110° C. for 18 hours and ground to a powder.
LDHs prepared according to the methods described in Example 2 (Method 2.1) or Example 71 were heated at 150° C. for 4 hours and then mixed with stearic acid (for amounts see Table 4) via physical mixing technique via mechanical force. Then, the mixed powder is transferred to round-bottom flask to mix at a speed of 700 rpm and a temperature of 100° C. for 30 min to obtain modified LDH.
LDHs prepared according to the methods described in Example 2 (Method 2.1) or Example 71 were heated at 150° C. for 4 hours and then mixed with lauric acid (for amounts see Table 4) via physical mixing technique via mechanical force. Then, the mixed powder is transferred to round-bottom flask to mix at a speed of 700 rpm and a temperature of 70° C. for 30 min to obtain modified LDH.
LDHs prepared according to the methods described in Example 2 (Method 2.1) were heated at 150° C. for 4 hours and then mixed with 3-Glycidyloxypropyltrimethoxysilane (for amounts see Table 4) via physical mixing technique via mechanical force. Then, the mixed powder is transferred to round-bottom flask to mix at a speed of 700 rpm and a temperature of 60° C. for 30 min to obtain modified LDH.
LDHs prepared according to the methods described in Example 2 (Method 2.1) were heated at 150° C. for 4 hours and then mixed with 3-Aminopropyltrimethoxysilane (for amounts see Table 4) via physical mixing technique via mechanical force. Then, the mixed powder is transferred to round-bottom flask to mix at a speed of 700 rpm and a temperature of 60° C. for 30 min to obtain modified LDH.
Samples were heated at 110° C. for at least 3 hr to remove any excess moisture and then stored in a desiccator prior to density measurement. Sample was added to a pre-weighed 100 ml measuring cylinder, to a volume of 100 ml and then the mass of the cylinder+sample was weighed. The mass of the sample was determined by subtracting the mass of the cylinder. Bulk density (g/ml) was calculated as:
Bulk density=mass of sample (g)/100 (ml).
The measuring cylinder containing sample was then placed in an AutoTap machine (Quantachrome, Model AT-6-220-50) and subjected to tapping to reduce the volume. The tapped density (g/ml) was calculated as:
Tapped density=mass of sample (g)/volume of sample after tapping (ml).
Pre-weighed samples were exposed at 60% (+/−5%) relative humidity, 20° C. The percentage weight change for samples after an exposure time T were calculated by:
% weight change=(wt after exposure (T mins)−wt pre-exposure)×100.
Samples were added into a mixture of 200 ml of water/20 ml of 1-hexene.
LDH samples were prepared as flat pellets with 2 cm diameter. A water droplet (10 μl) was injected by Teflon type syringe and dropped onto the LDH pellet surface. The contact angle of the water droplet on the pellet surface was measured by Contact Angle Meter DM-701 (FAMAS). Triplet measurements were made and the average of the three measurements taken.
Table 5 illustrates that the LDH modification process increases the hydrophobicity, bulk density and/or tapped density.
As seen in Table 6 below, the particle size distribution D10, D50, D90 of the inventive modified LDHs (Examples 82, 86 and 87) are in the acceptable range (D10=0.5-1 micron/D50=1-3 micron/D90=2.5-6 micron) for use as an additive in polymer formulations that are processed via an extrusion technique (i.e. to achieve a good dispersion and a smooth surface), and are similar to those of the unmodified LDHs (Example 81 and 85). Therefore, the LDH modification process does not lead to the formation of aggregates.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18172128.3 | May 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2019/051296 | 5/10/2019 | WO | 00 |
