Patent Application
20080031832
The results obtained are shown in
These results clearly show the superiority of the doped TiO2 in reducing UVA transmission. The fact that the ratios of the values at time 0 and time 120 minutes are significantly different implies that a reduction in free radical load, from both reduced generation and scavenging, is present in the formulations where doped titania is used.
The third embodiment of the present invention relates to polymeric compositions for a variety of uses.
It is well known that many polymeric compositions are adversely affected by light, in particular UV light. This can result in a variety of physical properties of the composition being affected. Typically, solid plastics compositions have their strength adversely affected so that, over time, they become more brittle. Similar comments apply to coating compositions. Other properties which can be adversely affected include colour. It is well known, for example, that coating compositions such as paints are adversely affected by light so that fading or, in the case of white formulations, yellowing occurs.
Various attempts have been made to counteract these adverse effects. This has included incorporating light stabilisers into the composition, typically hindered amines. However, incorporation of such light stabilisers is relatively expensive and not always particularly effective.
The present invention resides in the discovery that the incorporation of particular types of titanium dioxide and zinc oxide can effectively counteract the adverse effect of exposure to light, typically sun light.
In our GB Application No. 0310365.2 we disclose that the degradation of polymeric compositions can be retarded if the compositions also have present either zinc oxide or titanium dioxide which has been doped with a second element or reduced zinc oxide. In other words by using these doped materials or reduced zinc oxide rather than ordinary titanium dioxide or zinc oxide it is, for example, possible either to provide a polymeric composition which gives better protection against UV light or a composition having the same resistance to degradation but containing a smaller quantity of light stabiliser. The application thus describes a polymeric composition which comprises an amount of one or more organic or inorganic components which are photosensitive and/or which are degraded by another ingredient of the composition, and an amount of either TiO2 and/or ZnO which has been doped with a second element or reduced ZnO, this composition having a rate of deterioration of a UV light-sensitive physical factor at least 5% less than that of a composition having the same formulation except that it does not contain the TiO2 and/or ZnO which has been doped with a second element or reduced ZnO.
By a “physical factor” is meant a measurable value of a physical property of the composition which is adversely affected by UV light. Examples of such physical factors include degradation and, in consequence, strength, colour change (e.g. for paints and textiles) and photographic stability (e.g. for photographic films).
Thus if the rate of deterioration of a physical factor is X then the amount of the component(s) which are photosensitive and/or which are degraded by another ingredient of the composition, possesses a said rate of deterioration of Y where Y is greater than X by at least 5%, and the amount of doped TiO2 and/or ZnO and/or reduced ZnO reduces the said rate of loss from Y to X. The present invention also provides the use of a doped TiO2/ZnO and/or reduced ZnO to reduce the concentration of one or more light stabilisers in a polymeric composition as well as to reduce the rate of deterioration of a physical factor of a polymeric composition. The present invention further provides a method of improving the stability of a physical factor of a composition which comprises one or more components which are photosensitive and/or which are degraded by another ingredient of the composition which comprises incorporating into the composition a doped TiO2/ZnO and/or reduced ZnO.
As mentioned in connection with the second embodiment, it is important that if the oxide is to be really effective there must be dopant on its surface which can interact with the component of the composition to be protected. Although existing methods for doping in the bulk will normally also result in some dopant in or on the surface of the particle, it is possible according to the present invention to use materials which are only surface doped i.e. where there is dopant only in or on the surface of the particle. In one embodiment such materials may be used in a single phase formulation
Accordingly the present invention provides (although not dependant on the above theory) a composition which comprises an amount of one or more organic or inorganic components which are photosensitive and/or which are degraded by another ingredient of the composition and an amount of TiO2 and/or ZnO which has been doped at least on or in a surface thereof with one or more other elements, typically with one i.e with only a second element.
The composition may be polymeric, which as used herein means that the composition may comprise one or more polymeric materials, typically constituting at least 1%, preferably 5% by weight of the composition. Also, the composition may be solid or liquid. Where a polymeric material is present it may comprise at least part of the organic component and/or it may comprise a binder and/or other component of the composition.
Where the particle has been bulk doped there will, in general, be dopant throughout the particle. On the other hand where the particle has been “surface doped” (i.e. the dopant is only in or on the surface) there will be a concentration gradient e.g. such that the ratio of dopant atoms to titanium or zinc atoms at the surface or outmost “skin” of the particle is greater than the ratio in the core or centre where it may be zero. In general, the composition has a formulation which has a rate of deterioration of a UV light-sensitive physical factor at least 5% less than that of a composition having the same formulation except that it does not contain the said TiO2 and/or ZnO which has been doped with a second element.
By “a polymeric composition” as used herein is meant a composition which comprises one or more polymeric materials. The composition can be solid or liquid.
In some instances, the composition of the present invention will contain TiO2 and/or ZnO which has not been doped. Typically such undoped TiO2/ZnO will be present as pigment, generally having a particle size of at least 100 nm.
Typical solid materials include polymeric solids including three dimensional objects, films and fibres as well as textiles and fabrics e.g. clothing and netting made from woven and non-woven fibres as well as foamed articles; solids which are not fibres are sometimes preferred. Three-dimensional objects include those made by melt-forming processes including extruded and moulded articles. Typical articles to which the present invention may be applied include generally external household and building materials including blinds and plastics curtains, trellis, pipes and guttering, cladding and facings such as soffit board and plastics roofing material which can be profiled as with corrugated sheeting, doors and windows frames. Other articles include advertising hoardings and the like e.g. advertising boards on vehicle sides as well as vehicle bodies and body parts including bumpers for cars, buses and trucks as well as roofs which can be used also for boats, as well as superstructures and hulls for boats and also bodies for lawnmowers and tractors and yachts, along with containers such as bottles, cans, drums, buckets and oil and water storage containers. Other objects include garden furniture. In one embodiment the solids are not transparent.
Films to which the present invention can be applied include self supporting as well as non-self supporting films such as coatings. Self-supporting films to which the present invention applies include photographic films, packaging film and plastics film bearing indicia, typically as advertising film, which can also be applied over advertising hoardings. Such films can contain one or more customary ingredients for such products. Thus photographic film will contain one or more dyes or dye couplers and, optionally, a silver halide.
In some instances the polymeric composition itself is not liable to degradation but the composition is intended to protect a substrate or, in the case of a container, something placed in it. Thus such compositions can contain the doped TiO2/ZnO. Examples include pigmented and non-pigmented containers, typically bottles.
Accordingly, the present invention also provides a self-supporting polymer composition, or a varnish composition, intended to protect a composition adjacent thereto from the adverse effects of light, and which comprises TiO2 and/or ZnO which has been surface doped with at least a second element. In one embodiment the composition is 3-dimensional and comprises a surface layer with the TiO2 and/or ZnO while the non-surface part is generally not wood or a reconstituted wood such as chipboard, plywood or fibreboard and is preferably synthetic.
Coating compositions are typically paints and varnishes which contain a polymer either as the active ingredient as in some varnishes or as a support as in paints along with furniture polishes, waxes and creams; they can be aqueous or non aqueous i.e. contain an organic solvent in which case they can be mono-phase or poly-phase, typically as an oil-in-water or water-in-oil emulsion. This coating composition can be in the form of a waterproofing agent. These coating compositions can contain one or more customary ingredients for such products. Some cosmetics compositions contain one or more polymers; such compositions are less preferred in the present invention.
The polymers which can be used in the compositions of the present invention include natural and synthetic polymers which may be thermoplastic or thermosetting.
The suitable polymers which may be homopolymers or copolymers which can be random, block or graft copolymers; the polymers can be crosslinked. Such polymers may be saturated or unsaturated. Typical polymers include alkylene polymers such as ethylene and propylene polymers, typically homopolymers, including polyethylene foams, siloxane and sulphide polymers, polyamides such as nylon, polyesters, such as PET, acrylate and methacrylate polymers e.g. poly(methyl methacrylate), polyurethanes, including foams, vinyl polymers such as styrene polymers e.g. ABS, including polystyrene foam, vinyl chloride polymers and polyvinyl alcohol as well as engineering thermoplastics including aromatic polymers, e.g. polymers such as linear aromatic semi-crystalline polymers such as PEEK and PES. Fluorinated polymers such as PTFE and polyvinylidene fluoride can be used. The polymers can be thermosetting as with epoxy resins as well as phenolic, urea, melamine and polyester resins
Natural polymers which can be used include cellulosic polymers, as in paper including starch, polysaccharides, lignins, and polyisoprenes such as natural rubbers.
It will be appreciated that some polymers can be regarded as photostable in that there is no, or no significant, change in physical characteristics on exposure to UV light. These polymers are, therefore, not photosensitive and their use does not fall within the scope of the present invention.
Typical polymers for different applications include the following: (a) polyester, polyamide e.g. nylon, acrylics for fibres and fabrics; (b) polyester, polyvinyl chloride, polyethylene, polypropylene for bottles and the like; (c) polyethylene, polypropylene, polyvinyl chloride for film (non active such as packaging).
The compositions can contain the usual additional ingredients characteristic for the composition in question including inorganic and organic pigments, including “ordinary” TiO2 and/or ZnO, fillers and extenders as well as light stabilisers, typically hindered amine stabilisers. The additional ingredients may themselves be susceptible to attack, with the degraded components potentially causing degradation of the polymer or other component of the composition.
The rate of colour change can be determined by illuminating a sample of the composition with and without the doped TiO2 or ZnO with sunlight or visible light and measuring the spectral response of the composition over a given period and determining the change in wavelength emitted. Accelerated ageing tests using, for example a Fadeometer, can be used for this purpose.
The rate of loss of strength of an article of the present invention can be determined in a similar manner by measuring tensile properties such as elongation at break or Young's modulus, using standard equipment such as an Instron tester; again an accelerated ageing procedure is beneficial.
While any reduction in the wavelength change or other physical factor is an advantage, it is generally desirable that the presence of the doped oxide should reduce the rate of change by an amount of at least 5%, preferably at least 10%, more preferably at least 15%, especially at least 20% and most preferably at least 40%.
It will be appreciated that although it will normally be the case that the bulk dopant will be the same element as the or each surface dopant (for simplicity of preparation), this need not necessarily be the case. (Of course with reduced zinc oxide there is no bulk dopant.) By this means it is possible, for example, to modify the colour of the particles. Suitable dopants for the oxide particles include manganese, which is especially preferred, e.g. Mn2+ but also Mn3+, vanadium, for example V3+ or V5+, chromium and iron but other metals which can be used include nickel, copper, tin, especially Sn4+, aluminium, lead, silver, zirconium, zinc, cobalt, especially Co2+, gallium, niobium, for example Nb5+, antimony, for example Sb3+, tantalum, for example Ta5+, strontium, calcium, magnesium, barium, molybdenum, for example Mo3+, Mo5+ or Mo6+ as well as silicon. These metals can be incorporated singly or in combinations of two or three or more. It will be appreciated that for effective bulk doping the size of the ion must be such as can readily be inserted into the crystal lattice of the particle. For this purpose Mn3+, vanadium, chromium and iron are generally the most effective; the ionic size of Mn2+ is much larger than that of Ti4+ and so there is little probability of ionic diffusion of Mn2+ into the TiO2 crystal lattice. On the other hand there is no such size limitation for the elements used in surface doping; preferred surface dopants include manganese, eg. as Mn2+, cerium, selenium, chromium and iron.
The optimum total amount of the second component on, and, if present, in, the particle may be determined by routine experimentation but it is preferably low enough so that the particles are minimally coloured. Amounts as low as 0.1 mole % or less, for example 0.05 mole %, or as high as 1 mole % or above, for example 5 mole % or 10 mole %, can generally be used. Typical concentrations are from 0.5 to 2 mole % by weight. The mole ratio of dopant to host metal on the surface is typically from 2-25:98-75, usually 5-20:95-80 and especially 8-15:92-85. The amount of dopant at the surface can be determined by, for example, X-ray Photoelectron Spectroscopy (XPS).
The surface-doped particles can be obtained by any one of the standard processes for preparing such doped oxides and salts. These include techniques such as those described below. It will be appreciated that the dopant need not necessarily be present as an oxide but as a salt such as a chloride or a salt of an oxygen-containing anion such as perchlorate or nitrate. However bulk doping techniques will generally result in some surface doping as well and these techniques can be used in the present invention. Such techniques include a baking technique by combining particles of a host lattice (TiO2/ZnO) with a second component in the form of a salt such as a chloride or an oxygen-containing anion such as a perchlorate or a nitrate, in solution or suspension, typically in solution in water, and then baking it, typically at a temperature of at least 300° C. Other routes which may be used to prepare the doped materials include a precipitation process of the type described in J. Mat. Sci. (1997) 36, 6001-6008 where solutions of the dopant salt and of an alkoxide of the host metal (Ti/Zn) are mixed, and the mixed solution is then heated to convert the alkoxide to the oxide. Heating is continued until a precipitate of the doped material is obtained. Further details of preparation can be found in WO 00/60994 and WO 01/40114.
It will be appreciated that such baking techniques and the like will result in dopant in the surface forming part of the crystal lattice, while in other techniques the dopant will merely be adsorbed, or remain as a separate layer, on the particle surface. It is thought likely that if the dopant is to quench internally generated free radicals then it needs to be in the crystal lattice.
The rutile form of titania is known to be less photoactive than the anatase form and is therefore preferred. Zinc oxide can be in the form of reduced zinc oxide particles (i.e. particles which possess an excess of zinc ions relative to the oxygen ions).
Doped TiO2 or doped ZnO may be obtained by flame pyrolysis or by plasma routes where mixed metal containing precursors at the appropriate dopant level are exposed to a flame or plasma to obtain the desired product.
Further details of such particles can be found in WO 99/60994.
The average primary particle size of the particles is generally from about 1 to 200 nm, for example about 1 to 150 nm, preferably from about 1 to 100 nm, more preferably from about 1 to 50 nm and most preferably from about 20 to 50 nm. Since the scavenging effect is believed to be essentially catalytic it is desirable that the particles are as small as possible to maximise their surface area and hence the area of doped material on the surface. This small size has the advantage that less dopant is needed, which has the consequential advantage that any colouring effect caused by the dopant is reduced.
Where particles are substantially spherical then particle size will be taken to represent the diameter. However, the invention also encompasses particles which are non-spherical and in such cases the particle size refers to the largest dimension.
The oxide particles used in the present invention may have an inorganic or organic coating. For example, the particles may be coated with oxides of elements such as aluminium, zirconium or silicon, especially silica or, for example, aluminium silicate. The particles of metal oxide may also be coated with one or more organic materials such as polyols, amines, alkanolamines, polymeric organic silicon compounds, for example, RSi[{OSi(Me)2}xOR1]3 where R is C1-C10 alkyl, R1 is methyl or ethyl and x is an integer of from 4 to 12, hydrophilic polymers such as polyacrylamide, polyacrylic acid, carboxymethyl cellulose and xanthan gum or surfactants such as, for example, TOPO. If desired the surface doping can be carried out by a coating technique either separately or in combination with the inorganic or organic coating agent. Thus for example the undoped oxide can be coated with, say, manganese oxide along with an organic or inorganic coating agent such as silica. It is generally unnecessary to coat the oxide particles to render them hydrophilic so that for the aqueous phase the particles can be uncoated. However if the particles are to be in the organic or oily phase their surface needs to be rendered hydrophobic or oil-dispersible. This can be achieved by the application directly of, for example, a suitable hydrophobic polymer or indirectly by the application of a coating, for example of an oxide such as silica (which imparts a hydrophilic property) to which a hydrophobic molecule such as a metal soap or long chain (e.g. C12-C22) carboxylic acid or a metal salt thereof such as stearic acid, a stearate, specifically aluminium stearate, aluminium laurate and zinc stearate.
It should be understood that the term “coating” is not to be construed as being limited to a complete covering. Indeed it is generally beneficial for the coating not to be complete since the coating can act as a barrier to the interaction of the free radicals with the dopant on or in the surface of the particle. Thus it is preferred that the coating should be discontinuous where maximum scavenging effect is desired. However it will be appreciated that dopant on the surface can still act to quench free radicals generated within the particle in which case the coating can be continuous. Since coatings of silanes and silicones which can be polymeric or short chain or monomeric silanes are generally continuous these are generally less preferred. Thus coating with an inorganic oxide is generally preferred since these generally do not result in a complete coating on the surface of the particles.
Typical coating procedures include the deposition of silica by mixing alkali such as ammonium hydroxide with an orthosilicate, such as tetraethylorthosilicate, in the presence of the particle. Alternatively the particle can first be coated with a silane such as (3-mercaptopropyl)trimethoxy silane (MPS) and then silicate e.g. sodium silicate is added. The silane attaches to the particle surface and acts as a substrate for the silicate which then polymerises to form silica. Similar techniques can be used for other inorganic oxides.
The compositions of the present invention can be single phase, either aqueous (or oily or generally hydrophobic) or multiphase. Typical two-phase compositions comprise oil-in-water or water-in-oil formulations. For single phase compositions the oxide particles must of course be dispersible in that phase. Thus the particles are desirably hydrophilic if the composition is aqueous or hydrophobic if the composition is oil-based. However it may be possible to disperse untreated TiO2 in the oily phase by appropriate mixing techniques. For two or multi-phase composition the particles must be present in the phase containing the ingredient (or one of those ingredients) to be protected. It can, though, be desirable for the particles to be present in both aqueous (or generally hydrophilic) and oily (or generally hydrophobic) phases even if no ingredients which are to be protected are present in one of those phases. Desirably, the weight ratio of the water-dispersible particles to the oil-dispersible particles is from 1:4 to 4:1, preferably from 1:2 to 2:1 and ideally about equal weight proportions.
In the compositions the metal oxides are preferably present at a concentration of about 0.5 to 20% by weight, preferably about 1 to 10% by weight and more preferably about 3 to 8% by weight.
The following Example, in addition to Example 1 given above in respect of the first embodiment, further illustrates the present invention.
Distilled water (170 cm3), conc. HCl (12 cm3) and propan-2-ol (12 cm3) were mixed together at room temperature with stirring. The appropriate metal salt at the calculated percentage loading was added to the solution (1% loading in this case). After thorough mixing, titanium isopropoxide (10.4 cm3) was gradually added using a pipette. A gelatinous precipitate was formed instantly. After the solution became clear it was heated in a water bath. The water bath temperature was slowly increased from room temperature to 328 K over a period of a few hours. The solutions were left overnight. The resulting precipitate was decanted and dried at 353 K and then placed in an oven for a few hours at 373 K. The samples were then calcined at either 873 K, initially, and then at 1273 K (to ensure formation of rutile crystals) in air for 3 h. (heating regime 298 Kelvin to the chosen temperature at 200 Kelvin/h, dwell time=3 h followed by cooling to 298 K at 200 K/h).
The appropriate metal salt (1% loading) was dissolved in methanol along with TiO2 powder Degussa P25 (0.05 moles ˜75% anatase and 25% rutile; surface area ˜50 m2/g; average particle size ˜30 nm). The solution was stirred for a few hours and then the solvent was evaporated to leave TiO2 powder. The powder was placed in an oven at 423 K for 2-3 h and later calcined in air at 873 K using the same heating regime as for the co-precipitation method.
EPR Electron paramagnetic resonance was carried out at low temperatures (100 K) at the EPSRC EPR facility at Cardiff University.
Mn(II)-doped TiO2 samples were prepared via both preparation methods and their EPR spectra obtained. The spectrum of 1% Mn(II)-doped TiO2, made by the coprecipitation route, shows Mn4+ occupying a substitutional site and Mn2+ occupying an interstitial site.
The spectrum of 1% Mn(II)-doped TiO2, made by the absorption method, shows substitutionally incorporated Mn4+ and Mn2+ substitutionally incorporated. Also there is evidence to suggest surfacial Mn2+.
V(IV)-doped TiO2 samples were prepared via both preparation methods and their EPR spectra obtained. The spectrum of 1% V(IV)-doped TiO2, made by the absorption route, shows a poorly resolved spectrum which is due to V4+ ions superimposed on a broad resonance which is probably due to Ti3+ ions. The spectrum of 1% V(IV)-doped TiO2, made by the coprecipitation method, shows a well-resolved spectrum of an eightfold hyperfine line resonances due to interaction between magnetic moments of the 51V nucleus with paramagnetic V4+ ions which is due to V4+ occupying substitutional sites in the TiO2 matrix.
V(V)-doped TiO2 samples were prepared via both methods and their EPR spectra obtained. V(V)-doped TiO2 samples prepared via the coprecipitation show that V4+ is occupying a substitutional site, whereas the V(V)-doped TiO2, produced by the absorption method, showed poorly resolved spectra reflecting the possibility that the vanadium ions are not substituting into the TiO2 lattice but exist on the surface.
Poly(vinyl chloride) (1 g) was dissolved in HPLC grade tetrahydrofuran (20 cm3) and the corresponding amount of modified TiO2 pigment added (4% loading in this case). The solution was then sonicated/stirred for approximately 1 h. Thin films (100-150 μm) were prepared by pouring the solution into disposable aluminium trays (area=8.55 cm2) and allowing the solvent to evaporate. The weight of the resulting disc was then obtained (four decimal point balance) and recorded. From these data the thickness could be obtained by using the known area, weight and density of the PVC film. The thickness was then verified by analysing the film under an Olympus BH2 scanning optical microscope. The IR spectra were recorded and samples chosen for size according to their relative absorbances at 2913 cm−1. The films were then irradiated in a QUV weatherometer (Q Panel Company) equipped with 8 UVB 300 W bulbs at a temperature of 318 K.
A Q Panel QUV accelerated weatherometer was used. The device is essentially an UV irradiation tank. 8 fluorescent bulbs (300 W), selected as UVB wavelength, are fitted inside the apparatus and a moisture bath can also be used to force harsh conditions. Thin film samples are mounted onto the plates and placed on the sides of the instrument. The light intensity delivered within the QUV weatherometer was determined using the potassium ferrioxalate system. The intensity at the side of the instrument was calculated to be 1.82×1017 quanta/s.
IR absorption spectra were recorded using a Perkin-Elmer 1000 spectrophotometer (range 3200 cm−1-400 cm−1). Resolution was predetermined at 4 cm−1. The appearance of a carbonyl peak at 1718 cm−1 was monitored and calculated. The appearance of this peak over time was recorded and normalised with respect to the CH band at 2913 cm−1 to produce the “carbonyl index”.
The results for the effect of addition of Mn and V to TiO2 upon the photodegradation of PVC film is shown in
In
This relates to compositions suitable for use in agriculture, horticulture and veterinary medicine.
It is well known that many of the active ingredients of veterinary, agricultural and horticultural compositions such as herbicides and insecticides are adversely affected by UV light. Such organic compounds have a tendency to degrade or decompose under the influence of UV light either to inactive compounds or compounds which have an adverse effect upon the area being treated. As a result it is necessary to store these products in special containers which do not allow the penetration of UV light. Otherwise the shelf life of the product is too short.
In our GB Application No. 0312703.2 referred to above, we disclose that the adverse effects of UV light on such organic compounds can be reduced and/or eliminated by incorporating in the composition titanium dioxide and/or zinc oxide which has been doped with a second element and/or reduced zinc oxide. In other words by incorporating this specific oxide in the formulation it is possible to dispense with the use of special containers and/or extend the life of the product. In addition its presence enables the user to use less of the product. The application thus describes a composition suitable for veterinary, agricultural or horticultural use which comprises at least one organic veterinarally, agriculturally and/or horticulturally active compound, and titanium dioxide and/or zinc oxide which has been doped with a second element and/or reduced zinc oxide as well as a method for treating a veterinary, agricultural or horticultural species at a locus which comprises treating the locus with such a composition.
While any reduction in the loss of TV absorption is an advantage, it is generally desirable that the presence of the oxide should reduce the rate of UV absorption by an amount of at least a 5%, preferably at least 10%, more preferably at least 15%, especially at least 20% and most preferably at least 40%.
It has now been found, according to the present invention, that the way in which the oxide is doped has a material effect on the efficacy of the oxide. Indeed it has now been appreciated that it is important that if the oxide is to be really effective there must be dopant on its surface which can interact with the component of the composition to be protected. For example if, in a two phase composition, the oxide is present in the aqueous phase and the component to be protected is in the organic phase there is little interaction because of the phase boundary. Thus the free radicals generated by degradation of the component cannot contact the dopant without moving from one phase to another. Although existing methods for doping in the bulk will normally also result in some dopant in or on the surface of the particle, it is possible according to the present invention to use materials which are only surface doped i.e. where there is dopant only in or on the surface of the particle. In one embodiment such materials may be used in a single phase aqueous formulation. Accordingly the present invention provides (although not dependent on the above theory) a composition suitable for veterinary, agricultural or horticultural use which comprises at least one organic veterinarally, agriculturally and/or horticulturally active compound, and titanium dioxide and/or zinc oxide which has been doped at least in or on a surface thereof with one or more other elements, typically with one i.e with only a second element. Where the particle has been bulk doped there will, in general, be dopant throughout the particle. On the other hand, where the particle has been “surface doped” (i.e. the dopant is only in or on the surface) there will be a concentration gradient such that the ratio of dopant atoms to titanium or zinc atoms at the surface or outmost “skin” of the particle is greater than the ratio in the core or centre where it may be zero.
It will be appreciated that although it will normally be the case that the bulk dopant will be the same element as the or each surface dopant (for simplicity of preparation), this need not necessarily be the case. (Of course with reduced zinc oxide there is no bulk dopant.) By this means it is possible, for example, to modify the colour of the particles. Suitable dopants for the oxide particles include manganese, which is especially preferred, e.g. Mn2+ but also Mn3+, vanadium, for example V3+ or V5+, chromium and iron but other metals which can be used include nickel, copper, tin, especially Sn4+, aluminium, lead, silver, zirconium, zinc, cobalt, especially Co2+, gallium, niobium, for example Nb5+, antimony, for example Sb3+, tantalum, for example Ta5+, strontium, calcium, magnesium, barium, molybdenum, for example Mo3+, Mo5+ or Mo6+ as well as silicon. These metals can be incorporated singly or in combinations of two or three or more. It will be appreciated that for effective bulk doping the size of the ion must be such as can readily be inserted into the crystal lattice of the particle. For this purpose Mn3+, vanadium, chromium and iron are generally the most effective; the ionic size of Mn2+ is much larger than that of Ti4+ and so there is little probability of ionic diffusion of Mn2+ into the TiO2 crystal lattice. On the other hand there is no such size limitation for the elements used in surface doping; preferred surface dopants include manganese, eg. as Mn2+, cerium, selenium, chromium, vanadium and iron.
The optimum total amount of the second component on, and, if present in, the particle may be determined by routine experimentation but it is preferably low enough so that the particles are minimally coloured. Amounts as low as 0.1 mole % or less, for example 0.05 mole %, or as high as 1 mole % or above, for example 5 mole % or 10 mole %, can generally be used. Typical concentrations are from 0.5 to 2 mole % by weight. The mole ratio of dopant to host metal on the surface is typically from 2-25:98-75, usually 5.20:95-80 and especially 8-15:92-85. The amount of dopant at the surface can be determined by, for example, X-ray Photoelectron Spectroscopy (XPS).
The surface-doped particles can be obtained by any one of the standard processes for preparing such doped oxides and salts. These include techniques such as those described below. It will be appreciated that the dopant need not necessarily be present as an oxide but as a salt such as a chloride or a salt of an oxygen-containing anion such as perchlorate or nitrate. However bulk doping techniques will generally result in some surface doping as well and these techniques can be used in the present invention. Such techniques include a baking technique by combining particles of a host lattice (TiO2/ZnO) with a second component in the form of a salt such as a chloride or an oxygen-containing anion such as a perchlorate or a nitrate, in solution or suspension, typically in solution in water, and then baking it, typically at a temperature of at least 300° C. Other routes which may be used to prepare the doped materials include a precipitation process of the type described in J. Mat. Sci. (1997) 36, 6001-6008 where solutions of the dopant salt and of an alkoxide of the host metal (Ti/Zn) are mixed, and the mixed solution is then heated to convert the alkoxide to the oxide. Heating is continued until a precipitate of the doped material is obtained. Further details of preparation can be found in WO 00/60994 and WO 01/40114.
It will be appreciated that such baking techniques and the like will result in dopant in the surface forming part of the crystal lattice while in other techniques the dopant will merely be adsorbed, or remain as a separate layer, on the particle surface. It is thought likely that if the dopant is to quench internally generated free radicals then it needs to be in the crystal lattice.
The rutile form of titania is known to be less photoactive than the anatase form and is therefore preferred. Zinc oxide can be in the form of reduced zinc oxide particles (i.e. particles which possess an excess of zinc ions relative to the oxygen ions).
Doped TiO2 or doped ZnO may be obtained by flame pyrolysis or by plasma routes where mixed metal containing precursors at the appropriate dopant level are exposed to a flame or plasma to obtain the desired product.
Further discussion details of such particles can be found in WO 99/60994.
The oxide particles used in the present invention may have an inorganic or organic coating. For example, the particles may be coated with oxides of elements such as aluminium, zirconium or silicon, especially silica or, for example, aluminium silicate. The particles of metal oxide may also be coated with one or more organic materials such as polyols, amines, alkanolamines, polymeric organic silicon compounds, for example, RSi[{OSi(Me)2}xOR1]3 where R is C1-C10 alkyl, R1 is methyl or ethyl and x is an integer of from 4 to 12, hydrophilic polymers such as polyacrylamide, polyacrylic acid, carboxymethyl cellulose and xanthan gum or surfactants such as, for example, TOPO. If desired the surface doping can be carried out by a coating technique either separately or in combination with the inorganic or organic coating agent. Thus for example the undoped oxide can be coated with, say, manganese oxide along with an organic or inorganic coating agent such as silica. It is generally unnecessary to coat the oxide particles to render them hydrophilic so that for the aqueous phase the particles can be uncoated. However if the particles are to be in the organic or oily phase their surface needs to be rendered hydrophobic or oil-dispersible. This can be achieved by the application directly of, for example, a suitable hydrophobic polymer or indirectly by the application of a coating, for example of an oxide such as silica (which imparts a hydrophilic property) to which a hydrophobic molecule such as a metal soap or long chain (e.g. C12-C22) carboxylic acid or a metal salt thereof such as stearic acid, a stearate, specifically aluminium stearate, aluminium laurate and zinc stearate.
It should be understood that the term “coating” is not to be construed as being limited to a complete covering. Indeed it is generally beneficial for the coating not to be complete since the coating can act as a barrier to the interaction of the free radicals with the dopant on or in the surface of the particle. Thus it is preferred that the coating should be discontinuous where maximum scavenging effect is desired. However it will be appreciated that dopant on the surface can still act to quench free radicals generated within the particle in which case the coating can be continuous. Since coatings of silanes and silicones which can be polymeric or short chain or monomeric silanes are generally continuous these are generally less preferred. Thus coating with an inorganic oxide is generally preferred since these generally do not result in a complete coating on the surface of the particles.
Typical coating procedures include the deposition of silica by mixing alkali such as ammonium hydroxide with an orthosilicate, such as tetraethylorthosilicate, in the presence of the particle. Alternatively the particle can first be coated with a silane such as (3-mercaptopropyl)trimethoxy silane (MPS) and then silicate e.g. sodium silicate is added. The silane attaches to the particle surface and acts as a substrate for the silicate which then polymerises to form silica. Similar techniques can be used for other inorganic oxides.
The average primary particle size of the particles is generally from about 1 to 200 nm, for example about 1 to 150 nm, preferably from about 1 to 100 nm, more preferably from about 1 to 50 nm and most preferably from about 20 to 50 nm. Since the scavenging effect is believed to be essentially catalytic it is desirable that the particles are as small as possible to maximise their surface area and hence the area of doped material on the surface. This small size has the advantage that less dopant is needed which has the consequential advantage that any colouring effect caused by the dopant is reduced.
Where particles are substantially spherical then particle size will be taken to represent the diameter. However, the invention also encompasses particles which are non-spherical and in such cases the particle size refers to the largest dimension.
The compositions of the present invention can be single phase, either aqueous or oily or multiphase. Typical two-phase compositions comprise oil-in-water or water-in-oil formulations. For single phase compositions the oxide particles must of course be dispersible in that phase. Thus the particles are desirably hydrophilic if the composition is aqueous or hydrophobic if the composition is oil-based. However it may be possible to disperse untreated TiO2 in the oily phase by appropriate mixing techniques. For two or multi-phase compositions the particles must be present in the phase containing the ingredient (or one of those ingredients) to be protected. It can, though, be desirable for the particles to be present in both aqueous and oily phases even if no ingredients which are to be protected are present in one of those phases. Desirably, the weight ratio of the water-dispersible particles to the oil-dispersible particles is from 1:4 to 4:1, preferably from 1:2 to 2:1 and ideally about equal weight proportions.
The present invention is applicable to any composition intended for agricultural or horticultural use which contains an organic active ingredient as well as to veterinary compositions containing an organic active ingredient, generally for topical application. Generally the active ingredient will be a biocide but it can be, for example, a plant growth promoter or regulator. Thus the compositions of the present invention are typically herbicides, fungicides, insecticides, bactericides, acaricides, molluscicides, miticides or rodenticides, which can be broad spectrum or selective. The present invention is particularly useful for fast knockdown insecticides which are badly affected by UV light. Veterinary compositions can take the form of, for example, antiseptic or wound healing preparations.
The compositions of the present invention can also be formulated for household use as with, for example, insecticides and rodenticides. Accordingly, the present invention also provides a composition suitable for household use which comprises at least one organic biocide and titanium dioxide and/or zinc oxide which has been doped with a second element and/or reduced zinc oxide.
The compositions of the present invention can contain any of the organic active ingredients currently employed for such compositions.
Suitable herbicides which can be used in the present invention include triazines, amides, in particular haloacetanilides, carbamates, toluidines (dinitroanilines), ureas, plant growth hormones, in particular phenoxy acids and diphenyl ethers. Thus herbicides which may be used include phenoxy alkanoic acids, bipyridiniums, benzonitriles with phthalic compounds, dinitroanilines, acid amides, carbamates, thiocarbamates, heterocyclic nitrogen compounds including triazines, pyridines, pyridazinones, sulfonylureas, imidazoles and substituted ureas as well as halogenated aliphatic carboxylic acids, some inorganic and organic materials and derivatives of biologically important amino acids. Specific herbicides which can be used in the present invention include 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Suitable triazines include 2-chloro-, 2-methylthio-, 2-methoxy-4,6-bis-(alkylamino)-s-triazines as well as some 2-azido-substituted triazines. Typical herbicidal ureas include monuron (3-p-chlorophenyl)-1,1-dimethylurea) as well as diuron, neburon, fenuron and chloroxuron. Suitable carbamates include N-phenylcarbamate and isopropyl carbanilate (propham) and substituted derivatives thereof including isopropyl m-chlorocarbanilate (chlorpropham) as well as barban, swep, dichlormate and terbutol. Suitable thiocarbamates include EPTC, metham, vernolate, CDEC, pebulate, diallate, triallate, butylate, molinate, cycloate, thiobencarb and ethiolate. Suitable amide herbicides include solan, dicryl, propanil, dipehamid, propachlor, alachlor, CDAA, naptalam, butachlor, prynachlor and napropamide. Suitable chlorinated aliphatic acids include triochloroacetic acid (TCA), dalapon and 2,2,3-trichloropropionic acid. Suitable chlorinated benzoic acids include chloramben, DCPA, dicamba, dichlobenil and 2,3,6-TBA. Phenolic herbicides which can be used include bromoxynil, ioxynil, DNOC and dinoseb. Suitable dinitroanilines which can be used include benefin, trifluralin, nitralin, oryzalin, isopropalin, dinitramine, fluchloralin, profluralin and butralin. Suitable bypyridinium herbicides include diquat and paraquat salts and derivatives thereof.
Suitable insecticides which can be used in the present invention include nicotinoids, rotenoids, derivatives of the seeds of sabadilla and the plant ryania speciosa and pyrethroids as well as organochlorine insecticides, organophosphorus insecticides, carbamate insecticides and various insect growth regulators.
Suitable nicotinoids include nicotine sulfate and imidocloprid. The pyrethroids constitute a large group of insecticides most of which are now synthetic including resmethrin, phenothrin, cyphenothrin, empenthrin, prallethrin, permethrin, cypermethrin, alpha cypermethrin, tetramethrin and delta tetramethrin, including their isomers, especially optical isomers along with derivatives of these. Suitable organochlorine insecticides include DDT (dichlorodiphenyltrichloroethane) along with methoxychlor and perthane, as well as lindane, toxaphene, chlordane, heptachlor, aldrin, dieldrin and endrin. Suitable organophosphorus insecticides include phosphoric acid and phosphorothioic acid anhydrides, aliphatic phosphorothioate esters along with phenyl phosphorothioate esters, phenyl phosphorodithioate esters, phosphonothioate esters of phenols, vinyl phosphates, phosphorothioate esters of heterocyclic enols and of s-methyl heterocycles. Of these specific mention can be made of parathion, methyl parathion, dicapthon, chlorthion, fenitrothion, fenthion and fensulfothion along with fenchlorphos, cyanophos, propafos and temephos. Suitable carbamate insecticides which can be used include carbaryl, carbofuran, propoxur, dioxacarb, bendiocarb, mexacarbate, isoprocarb and ethiofencarb. Suitable acaricides include chlorfenethol, chlorobenzilate, dicofol, tetradifon, sulphenone, ovex, propargite, cyhexatin and dienochlor.
Some of the insecticides given above are suitable for killing rodents but other rodenticides which can be used include acute rodenticides and chronic poisons include anticoagulants; these can be stomach poisons, contact poisons or fumigants. Such anticoagulants include dicoumarol, warfarin, coumatetraly, coumachlor, difenacoum, brodifacoum, bromadiolone, pindone, diphacinone and chlorophacinone.
Insecticides which can be used in the compositions of the present invention can also be in the form of microbial agents since insects are attacked by many pathogens. These include bacterial agents, in particular bacillus microorganisms, especially bacillus thuringiensis (b.t.) strains such as b.t. aizawa, israelensis, kurstaki and tenebrionis, fungal agents, protozoa and viruses.
Suitable fungicides which can be used in the compositions of the present invention include elements such as sulphur, copper, mercury and tin along with thiocarbamate and thiurame derivatives, phthalimides and trichloromethylthiocarboximides, aromatic hydrocarbons and dicarboximides. Specific examples include ferbam, ziram, thiram, zineb, maneb and mancozeb as well as dimethylthiocarbamates and ethylene bis-dithiocarbamates. Other useful fungicides include captan, folpet, captafol and dichlofluanid. Suitable aromatic hydrocarbons include quintozene, dinocap, chloroneb, dichloran, dichlone and chlorothalonil along with oxazolidinediones such as vinclozolin, chlozolinate, hydantoin such as iprodione and succinimide such as procymidone. Other fungicides which can be used include guanidine salts such as dodine, quinones such as dithianon, quinoxalines such as chinomethionat, pyridazines such as diclomezine, thiadiazoles such as etridiazole, pyrroles such as fenpiclonil, quinolines such as ethoxyquin and triazines such as anilazine. Other fungicides which can be used include mitochondrial respiration inhibitors which are generally carboxanilides including carbox, oxycarboxin, flutolanil, fenfuram, mepronil, methfuroxam and metsulfovax. Further fungicides which can be used include microtubuline polymerization inhibitors including thiabendazole, fuberidazole, carbendazim, benomyl and thiophanate methyl. Other suitable fungicides include inhibitors of sterol biosynthesis including C-14 demethylation inhibitors such as triazoles which have a 1,2,4-triazole group attached through the 1-nitrogen to a large lipophilic group, in particular triadimefon, propiconazole, tebuconazole, cyproconazole and tetraconazole along with flusilazole which incorporates a silicon atom, myclobutanil, flutriafol and imibenconazole. Other fungicides which can be used include RNA biosynthesis inhibitors, phospholipid biosynthesis inhibitors, melanin biosynthesis inhibitors, fungal protein biosynthesis inhibitors and cell wall biosynthesis inhibitors.
The compositions of the present invention can be in liquid or solid form. Liquid compositions can be aqueous or non aqueous while solid forms include powders or dusts, granules and tablets. For rodenticides, in particular, the compositions can take the form of a bait, especially a foodstuff, for example grain, which has been treated with the rodenticide and the special oxide.
The concentration of the active ingredient in the composition can vary within a wide range but is typically 0.5 to 95, for example 1 to 50, % by weight.
A composition according to the invention preferably contains from 0.5% to 95% by weight (w/w) of active ingredient.
The compositions for agricultural or horticultural use according to the invention generally contain a carrier to facilitate application to the locus to be treated, which may for example be a plant, seed or soil, or to facilitate storage, transport or handling. The carrier may be a solid, or a liquid, as well as material which is normally a gas but which has been compressed to form a liquid.
The compositions may be in the form of, for example, emulsion concentrates, solutions, oil in water emulsions, wettable powders, soluble powders, suspension concentrates, dusts, granules, water dispersible granules, micro-capsules and gels. Other substances, such as fillers, solvents, solid carriers, surface active compounds (surfactants), and optionally solid and/or liquid auxiliaries and/or adjuvants can be present. The composition can be formulated for dispersing by, for example, spraying, atomizing, dispersing or pouring.
Solvents which may be used include aromatic hydrocarbons, e.g. substituted naphthylenes, phthalic acid esters such as dibutyl or dioctyl phthalate, aliphatic hydrocarbons, e.g. cyclohexane or paraffins, alcohols and glycols as well as their ethers and esters, e.g. ethanol, ethyleneglycol mono- and dimethyl ether, ketones such as cyclohexanone, strongly polar solvents such as N-methyl-2-pyrrolidone or γ-butyrolactone, higher alkyl pyrrolidones, e.g. n-octylpyrrolidone or cyclohexylpyrrolidone, epoxidized plant oil esters, e.g. methylated coconut or soybean oil ester and water. Mixtures can also be used.
Solid carriers, which may be used for dusts, wettable powders, water dispersible or other granules, and granules or other particles that include mineral fillers, such as silicas, calcite, talc, kaolin, montmorillonite or attapulgite. The physical properties may be improved by addition of highly dispersed silica gel or polymers. Carriers for granules may be porous material, e.g. pumice, kaolin, sepiolite, bentonite; non-sorptive carriers may be calcite or sand.
The compositions can be formulated as concentrates which can subsequently be diluted by the user before application. The presence of small amounts of a carrier which is a surfactant facilitates this process of dilution. Thus, preferably the compositions according to the invention preferably contain a surfactant. For example, the composition may contain two or more carriers, at least one of which is a surfactant. Such surfactants may be nonionic, anionic, cationic or zwitterionic.
The compositions of the invention may for example be formulated as wettable powders, water dispersible granules, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 5 to 90% w/w of active ingredient and 3 to 10% w/w of dispersing and/or wetting agent and, where desirable, 0 to 10% w/w of stabilizer(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant. Water dispersible granules are usually prepared to have a size from 0.15 mm to 2.0 mm and contain 0.5 to 90% w/w active ingredient and 0 to 20% w/w of additives such as stabilizers, surfactants, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to a solvent or a mixture of solvents, 1 to 80% w/v active ingredient, 2 to 20% w/v emulsifiers and 0 to 20% w/v of other additives such as stabilizers, penetrants and corrosion inhibitors. Suspension concentrates usually contain 5 to 75% w/v active ingredient, 0.5 to 15% w/v of dispersing agents, 0.1 to 10% w/v of suspending agents such as protective colloids and thixotropic agents, 0 to 10% w/v of other additives such as defoamers, corrosion inhibitors, stabilizers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation and crystallization or as antifreeze agents for water.
The Example given above in connection with the first embodiment also illustrates this embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0401838.8 | Jan 2004 | GB | national |
| 0401840.4 | Jan 2004 | GB | national |
| 0401841.2 | Jan 2004 | GB | national |
| 0401846.1 | Jan 2004 | GB | national |
| 0405078.7 | Mar 2004 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB05/00257 | 1/26/2005 | WO | 00 | 5/7/2007 |
