Patent Application
20140206534
The present invention relates to the use of AB diblock copolymer micelles dispersed in an apolar liquid medium as hydrophobic surface treatments. More specifically, the present invention relates to the novel use of AB diblock copolymer micelles dispersed in an apolar liquid medium and the use of compositions thereof which self assemble into aggregate structures in a suitable medium, and to a method suitable for preparing a surface treatment using the same which provides functional benefits associated with hydrophobic surface treatments such as oil and/or water repellence, anti-ice and dirt-repellence properties. The invention is equally applicable to both large surfaces and discrete objects. In addition, the treatment of surfaces with the AB diblock copolymers according to the present invention can yield supplementary benefits such as oleophobic, anti-bacterial or anti-fungal properties. In particular, the present invention relates to a process for coating a surface with micelles which comprise an AB block copolymer comprising the step of treating the surface with an apolar liquid containing the micelles; and to surfaces coated with such micelles.
The controlled wetting of surfaces has many potential applications such as the waterproofing of surfaces, fabrics, concrete, paints, windows and windshields. In addition, controlled solid-liquid interfacial properties can have benefits in producing low friction surfaces for use in areas such as swimsuits, diving gear, boats and ships, as well as micro-fluidic devices. Additionally, small objects such as seeds and organic crystals can benefit from such waterproofing/protective surface treatments. Controlled wetting can also have implications for controlling/preventing the build-up of ice, for example on aircrafts and refrigeration equipment.
Further applications in the area of “easy-to-clean” surfaces/coatings are also possible {Emma Dorey, Chemistry& industry, issue 18, 5 (September 2006); Ralf Blossey, Nature Materials, vol. 2, 301-306, (2003)}. Such surfaces are usually designed to facilitate cleaning by minimising the adhesion of dirt and promoting water repellence such that as water “rolls off” the surface it collects the poorly adhered dirt particles {Jon Evans, Chemistry& industry, issue 18, 16-17 (September 2006)}. Often, “self-cleaning surfaces” such as those described in WO 96/04123 are termed “Lotus-effect” surfaces or coatings, and the technology is termed “Lotus-Effect” technology. Such “self-cleaning surfaces” can be produced in different ways: by creating the surface structures directly from hydrophobic polymers during manufacture or by creating the surface structures after manufacture (specifically by imprinting or etching, or by the adhesion of a polymer made of hydrophobic polymers to the surfaces).
A variety of methods for controlling the wetting of surfaces have been reported, {Mathilde Callies, David Quéré, Soft matter, vol 1, 55-61, (2005); Taolei Sun, Wenlong Song, Lei Jiang, Chem. Comm., 1723-1725, (2005)} based on both the control of the surface chemistry and the surface morphology {S. Herminghaus, Europhys. Lett., 52, 165, (2000); J. Bico, U. Thiele, D. Quéré, Colloids Surf., A, 206, 41, (2002); H. Li, X. Wang, Y. Song, Y. Liu, Q. Li, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 40, 1743, (2001); L. Feng, S. Li, H. Li, J. Zhai, Y. Song, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 41, 1221, (2002); L. Feng, Y. Song, J. Zhai, B. Liu, J. Xu, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 42, 800, (2003); T. Onda, S. Shibuichi, N. Satoh, K. Tsujii, Langmuir, 12, 2125, (1996)}. More recently, combinations of these two approaches have been used {Jon Evans, Chemistry& industry, issue 18, 16-17 (September 2006); Igor Luzinov, Sergiy Minky, Vladimir V. Tsukruk, Prog. Polym. Sci., vol 29, 635-698, (2004)}. It is known for example from basic surface wetting theory that a low energy surface (with a concomitant large contact angle, greater than 100°) will tend to repel water. The result will be the formation of drops that roll off the surface easily.
US2002/0048679 (and related EP 1018531A1) describe surfaces from which water runs off easily as having to be either very hydrophilic or hydrophobic. Hydrophilic surfaces have low contact angles with water, and this brings about rapid distribution of the water on the surface and finally rapid run-off of the resultant film of water from the surface. In contrast, hydrophobic surfaces form droplets through large contact angles with water. These droplets can roll off rapidly from inclined surfaces.
Many materials are known to be capable of producing water repellence. In general the materials possess a very low dielectric constant and are uncharged organics. Amongst these are materials such as halogenated organic polymers, for example polytetrafluoroethylene (PTFE) and derivatives thereof {Anthony M. Granville, William J. Brittain, Macromol. Rapid. Comm., vol 25, 1298-1302, (2004; Lei That, Fevzi C. Cebeci, Robert E. Cohen, Michael F. Rubner, NanoLetters, vol 4, 7, 1349-1353, (2004; Motoshi Yamanaka, Kazuki Sada, Mikiji Miyata, Knji Hanabusa, Kazunori Nakano, Chem Comm, 2248-2250, (2006)}. One approach for manufacturing such surfaces is to apply a thin layer of a new material with the appropriate characteristics (for example appearance, durability, adhesion and application requirements) directly onto the surface of interest. Such surface coatings or surface treatments should be easily and uniformly applied; established within a reasonable amount of time and process constraints; have a minimal environmental impact with respect to their synthesis and application; resist the effects of environmental assault; and provide good economic value.
The main problems with such materials to date include;
(a) Determining the best method to deposit the materials onto a surface of interest since the materials are often soluble in a limited number of organic/volatile solvents. One possibility is for example a spin-casting method. However, this method usually requires the liberal use of solvents with the associated cost and environmental concerns.
(b) The durability of the coatings when applied and used in ‘real applications’ is an issue. Damage of the coatings through abrasion and the impact of harsh external conditions can compromise their efficiency. For example, re-coating can not only be difficult but also expensive and is still subject to the same environmental concerns.
(c) Photo degradation effects caused by sunlight can also compromise the surface integrity and lead to re-application needs.
(d) Application of such treatments can be costly and requires complex and difficult to scale procedures during the manufacturing process.
(e) The coating of small objects (nanometre to millimetre sized), especially effective coating of small particles such as organic crystals with a polymer is difficult to achieve. Many techniques have been applied to coat particles, such as those based on Wurster coating technologies for spray dry coatings wherein a fluidised bed of dry particles has a coating solution sprayed onto the fluidised bed and solidified on the particles by either evaporation of a volatile solvent in the coating solution or cooling to set the coating polymer (if applied in molten form). Such techniques are notoriously variable, in that it is difficult to avoid agglomeration of the particles into larger masses and the coating can be extremely ineffective in coating all surfaces and edges of a particle (especially a small crystalline particle with variable edges and sides of crystal). This limitation can be partially overcome by employing higher quantities of coating composition but this can significantly alter the properties of the organic particle being coated as well as having an impact on the economics of the process and product cost. Coating of particles in a liquid medium is highly attractive if a technique could be identified. Work with dispersions of organic pesticides in water (WO2006/015791) in the presence of reactive monomers produced “coated” particles as dispersions in water but these are matrix particles where the particle is engulfed in a polymer during the polymerisation process. Many similar techniques produce such matrix particles.
Random fluorinated copolymers prepared by radical copolymerisation of monomers in solution in a water-miscible organic solvent using peroxides or azo compounds as initiators have been described, together with their hydrophobic and oleophobic properties on various substrates (see, for example, EP542598, U.S. Pat. No. 1,106,630 and US2004026053).
U.S. Pat. No. 5,324,566 describes the use of hydrophobic fluorinated siloxane polymers for producing water repellent surfaces and it discloses that the water repelling properties of the fluorinated siloxane material can be improved by forming surface irregularities on the surface of such a material. It is for example mentioned that the surface is modified with irregularities of a height from about 0.1 micrometer up to the wavelength of visible light. Likewise, U.S. Pat. No. 5,599,489 and EP0933388A2 describe how the structured surface includes fluorine containing polymers or has been treated using alkylfluorosilanes.
US2002/0048679 describes surfaces having a smooth, extremely hydrophobic polymer film (for example, polytetrafluoroethylene) and surfaces having a smooth extremely hydrophilic polymer film as examples where water and dirt run off without forming droplets. US2002/0048679 further describes how a ‘long-term’ hydrophobic coating may be formed by applying certain silane derivatives underneath a hydrophobic coating on a surface. Other self-cleaning surfaces are described in US2002/0150723, US2002/0150724, US2002/0150725, US2002/0150726, US2003/0013795 and US2003/0147932.
U.S. Pat. No. 3,354,022 discloses water repellent surfaces having a rough micro structure with elevations and depressions and a hydrophobic material based on a fluorine containing polymer. According to one embodiment, a surface with a self-cleaning effect can be applied to ceramic, brick or glass by coating the substrate with a suspension comprising of glass beads (diameter of 3 to 12 micrometres) and a fluorocarbon wax which is a fluoroalkyl ethoxymethacrylate polymer. Unfortunately, such coatings have a disadvantage in that they possess a low abrasion resistance and only a moderate self-cleaning effect.
Further developments of surface coatings that are designed to produce strongly hydrophobic surfaces include the use of copolymers, polymer blends and mixtures of polymers and nanoparticles (such as titanium dioxide, as described in U.S. Pat. No. 6,800,354, US7112621B2, U.S. Pat. No. 7,196,043 and DE10016485.4). For example, coated surfaces have been produced using fluorocarbon polymers that can give contact angles of up to 120°. Titanium dioxide (TiO2) has also been used with such fluorinated surfaces. It is known that under UV irradiation the TiO2 is photocatalytically active and can produce super-wetting properties as a result of water hydrolysis effects {Akira Nakajima, Kazuhito Hashimoto, and Toshiya Watanabe, Langmuir, 16 (17), 7044-7047, (2000)}. However the addition of TiO2 present with (fluoroalkyl)silane does not affect the hydrophobicity of the overall material; that is, the modified (fluoroalkyl)silane remains hydrophobic.
The preparation of such surfaces using nanoparticles suffers from several drawbacks including the use of organic solvents (U.S. Pat. No. 3,354,022) and the use of a subsequent heat treatment (U.S. Pat. No. 6,800,354). Thus, there is a need for a simple for producing surfaces that are “easy-to-clean” with water and are optically transparent.
It has also been demonstrated recently that the control over surface wetting can be improved by producing surfaces with a well-controlled micron-sized roughness {Eiji Hosono, Shinobu Fujihara, Itaru Honma, Haoshen Zhou; JACS, vol 127, 13458-13459, (2005); Xi Yu, Zhiqiang Wang, Yugui Jiang, Feng Shi, Xi Zhang, Adv. Mater. Vol 17, 1289-1293, (2005); A. A. Abramzon, Khimia i Zhizu (1982), no. 11, 38 40}. These rough surface features assist in producing ‘ultrahydrophobic’ substrates by physical methods that include trapping air and reducing contact areas between the water drops and the surface. The basic underlying surface should itself be hydrophobic and when combined with the roughness effects, it results in surfaces with contact angles greater than 150° which are extremely hydrophobic. However, such surfaces tend to be difficult to manufacture, they are usually very fragile and easily damaged and the micron-scale features can cause diffraction effects with light, which can be therefore problematic for use in applications involving glass.
Whilst many commercial surface coatings based on solutions of polymers in organic solvents are produced by drop-casting or spin coating, alternatives that are based on chemical grafting of polymer films have recently been discussed. Using this approach, coatings that comprise of dense brush-like films of polymers which are chemically attached to a surface are produced. The polymers detailed herein can have controlled chemistry that produces the desired wettability characteristics. Furthermore, the inherent chemical variety available to the synthetic polymer chemist means that such layers can be produced with a wide variety of physical properties, as well as the opportunity for including a stimulus responsive surface.
Stimuli-responsive polymers {J. Rodriguez-Hernandez, F. Checot, Y. Gnanou, S. Lecommandoux, Prog. Polym. Sci., 30, 691-724, (2005)} are polymers that are able to respond to small changes in their environment with a corresponding large change in a specific physical property. Typical stimuli include: temperature, pH, ionic strength, light-, electric- and magnetic fields. Some polymers respond to a combination of two or more of these stimuli. For coatings or surface treatments, stimulus responsive polymers have the potential to be used in a wide variety of applications where controlled changes in properties such as adhesion, lubrication and wetting are required.
WO08071957 and WO10038046 describe the novel composition and/or novel use of AB block copolymers comprising both fluorinated and non-fluorinated portions that can form micelle structures and can be employed to surface coat structures such as fabrics, concrete structures, glass windscreens, glass structures to render then “stay-clean” by a combination of dust repellence and water sheeting effects. However, these compounds were used solely in a water based formulation or mainly organic polar solvents to produce hydrophilic surface treatments, as they offer water sheeting properties.
It has been demonstrated that although these surface treatments give some easy clean characteristics, they lack other important functions such as water repellence and anti-ice that may be beneficial on a wide variety of substrates. Hence, there is a need for an alternative surface treatment which is as convenient and demonstrates such easy clean properties.
Surfactants are recognised to adsorb uniquely to interfaces such as oil/water interfaces and solid/liquid interfaces and are employed as stabilisers to produce dispersions of particles in a liquid medium (such as water) that remain stable to agglomeration on storage. Because of this property of adsorbing as a monomolecular layer at an interface, surfactants in the form of polyelectrolytes have been employed to produce layers of surfactant on a substrate such as a solid particle. Such processes (for example, as in WO2000/077281) are slow to build-up oppositely charged single layers of polyelectrolyte (each layer being only the thickness of a surfactant monolayer and many layers being required to build up a coating thickness of utility). Surfactants can also aggregate into structures containing many surfactant molecules in a single aggregate. These aggregates are called micelles. They are commonly spherical in shape but can have a large range of shapes and structures. The number of molecules that compose such an aggregate can be very many, often in the order of hundreds of molecules. Micelles can be composed of relatively simple surfactant structures but can also be composed of high molecular weight block-copolymer surfactants. Moreover, even large complex block copolymers can form micelles. Such block copolymer micelles, when comprised of oppositely charged micelles, have been induced to adsorb in a layer by layer (LbL) manner onto spherical colloidal particles to produce coatings on particles such as a latex or a spherical silica particle (NSTI-Nanotech 2007, www.nsti.org, ISBN 1420061836 Vol. 2, 2007 pp 13-16 and Adv. Mater. 2007, 19, 247-250).
We have now unexpectedly and surprisingly found that the use of complex copolymer micelles dispersed in an apolar liquid medium as coating agents for flat surfaces of a wide range of substrates (and small materials such as crystalline particles) produces surface coatings with high loadings of copolymer in a single treatment (or very few treatments) and such products find utility in a range of applications, particularly but not limited to the agrochemical field.
In one aspect, the present invention provides an apolar liquid comprising micelles which themselves comprise a copolymer and in which the micellar cores are more hydrophilic than the micelle coronas.
In another aspect, the present invention provides a surface coated with micelles which comprise a copolymer; where the micellar cores are more hydrophilic than the micellar coronas.
In a further aspect, the present invention provides a process for coating a surface comprising the step of treating the surface with an apolar liquid in which micelles are dispersed.
Examples of such small materials are objects that need to be protected from their environment, for example water soluble organic crystals that may be otherwise incompatible in an aqueous formulation or particles which may react with the other ingredients of the formulation causing an increase of viscosity and decrease in the shelf life of the formulation. Other objects may be seeds, plant tissue such as foliage, leaves, flowers or seed heads, organic and inorganic crystals, solid particles (TiO2, CaCO3, SiO2, gold, latex particles etc). Objects that are of irregular shape and size are especially well suited to be coated by this technology as the micelles coat all edges and corners of objects uniformly although regular shapes such as spherical particles (latex particles, spherical silica for example) are equally well coated.
Products of utility may be an agrochemical, laundry chemicals, cosmetics, food additives, paint and coating additives, biocides for paints, pharmaceutical or other particles that find utility in various fields. The novel coating, produced by micelle-forming polymers, finds utility in a variety of ways. The coated particle can now be more effectively targeted for adhesion to a substrate by selection of the block copolymer, as in targeting a specific substrate in agriculture such as an insect cuticle, leaf surface or fungal pathogen or in pharma, for delivery to a specific target organ or protection of an agent for delivery through the mammalian stomach for selective and protected delivery later in the digestion system or in laundry for release of an agent at the appropriate point in the wash cycle. Moreover, the effectively coated particles confer greater colloidal stability on systems, allowing greater and improved stability when mixed with other components.
Further suitable applications include, without limitation:
Sustained release or controlled release usages, for example: pharma, for example acid resistant structures (oral delivery past low pH in the stomach), protection of labile actives, pseudo-zero order release through the micelle layer and Ostwald-ripening resistant formulations; cosmetics; perfumes, for example slowing down evaporation of top-notes or sustained release and minimising overpowering odours; particles having affinity for cellulose and trapped on textile surface during laundering; flavours, for example light-stabilised to prevent oxidation; self-healing coatings, for example particle induced to burst to release a resin that repairs damage; carbonless copy paper; novel, double taste and texture food, for example a particle which dissolves in the mouth and releases a new taste; pressure sensitive adhesives; sealants; nutrition (for example increased bioavailability of complex molecules and protection of sensitive molecules such as vitamins, probiotics and other food additives); toner inks with photosensitivity or thermal sensitivity; textile coatings, for example, for altering permeability properties; antifouling coatings; surface protective coatings, for example, for improving scratch or abrasion resistance; and construction materials, for example wall-boards, plasterboards and cements.
It is well known that chemical incompatibility between different components in liquid laundry formulations can cause instability in these formulations. In particular, laundry chemicals including bleaching chemicals and bleach activation agents such as, but not limited to, sodium percarbonate and tetraacetylethylenediamine (TAED) that are widely used in powder laundry formulations are incompatible with liquid laundry detergents. Bleach activation agents, precursors and catalysts tend to be unstable in many liquid formulations and although the surfactants in the liquid formulation are stable they can react with bleach or bleach activator chemicals or catalysts or derivatives of them. One solution is to add a solid form bleach activator as a separate dose to the liquid laundry detergent, but this is inconvenient for the consumer. The present invention provides a means of protecting the solid bleach activator form interaction with water and other liquid detergent components to enable a stable liquid detergent to be formulated.
It is desirable to be able to control pH during a laundry cycle and to this end it would be advantageous to be able to release sodium carbonate into the laundry medium at a given point in the cycle in response to increased dilution with water. Sodium carbonate coated with reverse micelles as described in this invention is an efficient means of achieving this.
The sustained release of biocides and anti-fouling agents is of commercial interest to the paints and coatings industry and in particular for marine applications. One example of a biocide that has been employed as an antifouling agent for marine use is DCOIT (4,5-dichloro-2-n-octyl-3(2H)-isothiazolone). This active has low solubility in sea water which is extremely desirable, however in solvents used in paint formulations such as xylene, it is extremely soluble. This means that it is likely to react with the paint binders within the formulation and may increase the paint viscosity or induce plasticizing of the paint.
Marine paint manufacturers will benefit from a biocide that improves in-can stability of the paint whilst incorporating sustained release of the active after application onto the marine vessel. The present invention provides a means of protecting the biocide from the other active ingredients in a paint formulation and provides a means of sustained release in sea water.
Safe delivery of active pharmaceutical ingredients (APIs) to the intended target site within a mammalian body is a major area of both commercial unmet need and scientific research. In many cases the API needs to be protected from interaction with its environment in order to prevent unwanted chemical reaction or biological use of the active at the wrong site within the body or at the wrong rate. One solution to this problem is to formulate the API into a tablet and to add a protective or enteric coating to the tablet. This can be sub-optimal for a number of reasons including patient preference for non-tablet formulation and the potential risk of over-dosing [if the enteric coating fails]. The present invention enables individual crystals of API to be coated enabling formulation into a capsule rather than a tablet and minimizing the risk of over-dosing [as the coating would need to fail multiple times on individually coated API crystals rather than only once on the tablet].
Non Steroidal Anti Inflammatory Drugs (NSAIDs) such as ibuprofen and diclofenac are limited in their administration because at higher doses, side effects (such as gastric erosion, thrombasthenia or thrombocytopenia, and fluid retention) may become severe.
Taste masking of APIs is a current target for the pharmaceutical industry as numerous actives in the preparations are bitter or undesirable in taste. Applying a polymer coating to the API is one approach to achieving taste masking by providing an inert coating to prevent its dissolution. Successful taste masking can be evaluated by determining the rate of release of the active from the coated particles.
Vitamin C is also known as ascorbic acid, ascorbate and ascorbate monoanion. It is the enolic form of an α-ketolactone. Vitamin C works physiologically as a water soluble antioxidant by virtue of its high reducing power. It acts as singlet oxygen quenchers, and it is capable of regenerating vitamin E. Vitamin C is called an antioxidant because of its ability of quenching or stabilizing free radicals that lead over time to degenerative diseases, including cancer, cardiovascular disease and cataracts.
Ascorbic acid properties are impaired by its high reactivity, and hence, poor stability in solution, which can result in heavy losses during food processing. It can be degraded rapidly in the presence of oxygen in free-radical mediated oxidative processes. The processes are strongly catalysed by transition metal ions, especially iron and cooper, leading to rapid destruction of the ascorbate. Oxidation is also accelerated at neutral pH and above.
Destruction can occur in the presence of enzymes such as ascorbate oxidase and ascorbate peroxidase.
The food industry may employ microencapsulation to produce foods which are more nutritionally complete. The properties of microencapsulated nutrients will allow the food processor greater flexibility and control in developing foods with high nutritional value. Ascorbic acid is added extensively to many types of food products for two quite different purposes: as a vitamin supplement to reinforce dietary intake of vitamin C, and as an antioxidant, to protect the sensory and nutritive quality of the food itself.
The present invention enables individual crystals of ascorbic acid or other food supplements to be coated for application in the food industry as fortification. Coated particles could be potentially incorporated in dry form into cake mixes, puddings, gelatine desserts, chewing gum, milk powder, jellies, pet foods, breakfast cereals, in short, into products with low water activity.
It is therefore an object of the present invention to provide compositions that can be deposited easily onto a substrate surface without the need for expensive processing and has versatility that it can be applied equally well on large flat surfaces as well as contiguously to coat objects such as seeds, plant material, inorganic or organic particles (including polymer particles) and crystalline material such as inorganic or organic crystals.
A polymer or polymeric composition prepared according to the present invention may be coated onto a preferred substrate by any established coating process, for example, but not limited to for example a spray process. Methods of exposing the substrate to the solution include for example any known technique for forming a coating from a solution such as spin coating, dip coating, roller coating, brush coating, curtain flow or spraying, roller coating, wire-bar coating, extrusion coating, air knife coating, curtain coating and slide coating. More preferably dipping and spraying ensures that every part of the surface has been wetted by the treatment composition. The treatment can be applied to both interior and exterior surfaces.
Various surfaces may be treated including for example metals, metal alloys, glasses, plastics, textiles, rubber, porcelain, ceramics, tile, enamelled appliances, polymers (for example polyurethanes, polyesters, polyacrylics and polycarbonates), resins (for example melamine/phenolic resins), painted surfaces, natural surfaces (like wood) and cellulose substrates.
1) The metal or metal alloy object or articles may comprise a metal or metal alloy selected from the group comprising: aluminum, magnesium, beryllium, iron, zinc, stainless steel, nickel, nickel-cobalt, chromium, titanium, tantalum, rare earth metal, silver, gold, platinum, tungsten, vanadium, copper, brass and bronze; and combinations or derivatives thereof; and plated articles thereof.
2) The plastic objects or articles may comprise a polymer selected from the group comprising: transparent or non-transparent polyurethane, polycarbonate, polyethers, polyesters such as polyethylene terephthalate, polyvinyl chloride, polystyrene, polyethylene, polyvinyl acetate, silicone rubbers, rubber latex, polycarbonate, cellulose esters polycarbonate, polyester-polyether copolymers, ethylene methacrylates, polyolefins, silicone, natural and synthetic rubbers, nylon and polyamide; and combinations thereof.
3) The glass objects or articles may comprise, at least partially, a material selected from the group comprising: glass, such as optical glasses, optical lenses, polarizing glasses, mirrors, optical mirrors, prisms, quartz glass and ceramics; and combinations thereof.
The substrate may include an exterior surface or article member, such as for example: a window sash, structural member or windowpane of a building; an exterior member or coating of a vehicle such as automobile, railway vehicle, aircraft and watercraft; an exterior member, dust cover or coating of a machine, apparatus or article; and an exterior member or coating of a traffic sign, various display devices and advertisement towers, that are made, for example, of metal, plastics or glass or a combination thereof.
Examples of substrates, include, but are not limited to: medical devices, protection shields, window sheets, windowpane, greenhouse walls, freezer doors, food packaging foils and printing paper.
1) The metal objects can include for example: freezer doors, mirrors, condenser pipes, ship hulls, underwater vehicles, underwater projectiles, airplanes and wind turbine blades.
2) The plastic objects can include for example: face shields, helmet shields, swim goggles, surgeon face shields, food packaging, plastic foil, greenhouse walls, greenhouse roofs, mirrors, wind shields, underwater moving objects, airplane windows and shields.
3) The glass objects can include for example: window glasses, greenhouse, glasses, glass sheets, face shields, optical glasses, optical, lenses, polarizing glasses, mirrors, optical mirrors, prisms, quartz glass, parabolic antennas, automobile head beam light glasses, automobile windshields, airplane control light glasses, solar panels and solar concentrator mirrors and runway lights.
The coating may also be applied to clear plastic or glass used for example as protective shields, windows, windshields, greenhouse panels, food packaging foils, goggles, optical glasses and contact lenses.
Likewise the coating may be applied for example: to an exterior surface of a telescope lens, especially a riflescope, a spotting scope, or a binocular to reduce the likelihood of fogging or distortion due to the collection of moisture on the lens without significantly reducing light transmission through the lens in the visible range. That is, scopes used by sportsmen, the military and the like.
Exterior or interior parts of a building may also benefit from the coating for example: windowpanes, toilets, baths, wash basins, lighting fixtures, kitchenware, tableware, sinks, cooking ranges, kitchen hoods and ventilation fans, which are made from metal, glass, ceramics, plastics, a combination thereof, a laminate thereof or other materials.
It is a further aim of the present invention to provide a novel surface treatment that promotes variable wetting properties on the surface, or in other words provides an “easy-to-clean” surface, meaning that an identifiable cleaning benefit (“easier-to-clean”, “cleaner-longer”, “stay-clean” etc.). Examples include micelles applied to surfaces of chemical reactors to make them easy to clean; micelles applied to the inside surfaces of pipes and tubes to make them easy to clean; micelles applied to the surfaces of road vehicles, trains and aeroplanes to make them easy to clean; and micelles applied to the surfaces of food packaging materials to prevent food build up on the packaging.
It is still a further aim of the present invention to provide novel compositions that are able to demonstrate a hydrophobic effect which is desirable for different application areas, such as water repellence, anti-ice and water barrier properties for small objects.
It is still a further aim of the present invention to provide novel compositions that are able to vary or reverse the water repellent properties when the local environmental conditions are changed (such as temperature, salt concentration or pH).
The surface treatment of the present invention is hydrophobic. In the present invention, the properties and associated benefits are achieved using simple processing and application techniques.
Indeed the present process, composition and use invention requires the use of an AB block copolymer composition as a surface coating wherein the composition comprises:
(a) an AB block copolymer; and
(b) a liquid medium and,
wherein the AB block copolymer comprises:
Therefore, the present invention relies upon an AB block copolymer comprising two blocks (A and B) which have different affinities for a liquid medium such that micelles form in the liquid medium.
Although the micelles are formed in a liquid medium, any eventual coated particles may be present not only in a liquid composition but alternatively in a dry, solid composition [for instance, due to an evaporation step or a drying step].
A preferred AB block copolymer comprises:
(i) a first hydrophobic block A, comprising a polymer selected from the group consisting of a homopolymer of an acrylate or alkylacrylate (preferably an acrylate or C1-4 alkylacrylate; more preferably an acrylate or methacrylate) monomer; a copolymer comprising two or three different monomers selected from acrylate or alkylacrylate (preferably an acrylate or C1-4 alkylacrylate; more preferably an acrylate or methacrylate) monomers; a homopolymer of a styrenic derivative monomer; a copolymer comprising two different monomers selected from styrenic derivative monomers; a homopolymer of an alkene or diene monomer; a copolymer comprising two different monomers selected from alkene and diene monomers; a homopolymer of a heterocyclic monomer; a copolymer comprising two different monomers selected from heterocyclic monomers; and a random, alternating, gradient or block copolymer comprising monomers selected from acrylate monomers, alkylacrylate (preferably C1-4 alkylacrylate; more preferably methacrylate) monomers, styrenic derivative monomers, alkene monomers, diene monomers and heterocyclic monomers; and
(ii) either a second hydrophobic block B or a hydrophilic block B having a different affinity than the block A for the liquid medium in which the AB copolymers are dispersed such that micelles are formed.
Throughout the discussion of the present invention, references to alkyl and alkylene groups and moieties, relate to both straight-chained and branched versions.
Preferably any acrylate or alkylacrylate monomer is, independently, of formula A′
Preferably any styrenic derivative monomer is, independently, of formula B′
Preferably any alkene or diene monomer is, independently, of formula Ca or Cb
Preferably any heterocyclic monomer is, independently, of formula Da, Db, Dc or Dd
The ratio of the monomers in each block of block copolymer AB is such that the weight fraction of the (hydrophobic) block A and the (hydrophobic or hydrophilic) block B agents leads to the formation of organised aggregates, such as micelles. The number of the monomers comprising the block copolymer AB is: preferably from 5 to 250 units of A; more preferably from 10 to 200 units of A; and most preferably from 15 to 150 units of A; and, likewise, preferably from 5 to 250 units of B; more preferably from 10 to 200 units of B; and most preferably from 15 to 150 units of B.
A suitable alkylacrylic or acrylate monomer of Formula A′ is when Z is O; and R′ is a C1 to C18 alkyl group (more preferably a C1 to C8 alkyl group); another suitable monomer of Formula A′ is provided by Formula 1:
where n is 1 to 17, more preferably 1 to 8.
A suitable fluorinated alkylacrylic or acrylate monomer of Formula A′ is when Z is O; and R′ is a fluorinated alkyl group; another suitable monomer of Formula A′ is provided by Formula 2:
where n is 1 to 6 and the chain is linear or non-linear, more preferably 1 or 2; m is 0 to 7 and the chain is linear or non-linear, x is 0 to 2 and y is 3-x.
A suitable alkylacrylic or acrylate monomer for Formula A′ is when Z is O; and R′ is an alkylaminoalkyl group containing up to eighteen carbon atoms. Another suitable monomer of Formula A′ is provided by Formula 3:
where R1 and R2 are each independently H, a C1 to C6 alkyl group; phenyl; benzyl or cyclohexyl; and n is from 1 to 17; more preferably, R1 and R2 are each methyl and n is from 1 to 5.
A suitable alkylacrylic or acrylate monomer for Formula A′ is when Z is O; and R′ is an hydroxyalkyl containing up to 18 carbon atoms. Another suitable monomer of Formula A′ is provided by Formula 4a or 4b:
where n is 1 to 18 and the chain is linear or non-linear (more preferably n is from 1 to 4) and x and y are each 0 to 16, more preferably 0 to 6. Suitably, for Formula 4b, x=0 to 16; y=0 to 16; and x+y≦16.
A suitable alkylacrylic or acrylate monomer for Formula A′ is when Z is O; and R′ comprises a dihydroxyalkyl group. Another suitable monomer of Formula A′ is provided by Formula 5a or 5b:
where x and y are each 0 to 17 in Formula 5a or 0 to 16 in Formula 5b; more preferably x and y are each 0 to 7 in Formula 5a or 0 to 6 in Formula 5b (and the chain can be linear or non-linear). Suitably, for Formula 5a, x=0 to 17; y=0 to 17; and x+y≦17. Suitably, for Formula 5b, x=0 to 16; y=0 to 16; and x+y≦16.
A suitable alkylacrylic or acrylate monomer for Formula A′ is when Z is O; and R′ is a C1 to C17 silylalkyl group. Another suitable monomer of Formula A′ is provided by Formula 6a or 6b:
where R1 is H or C1 to C4 alkyl and x and y are each from 0 to 16, preferably from 1 to 6. Suitably, for Formula 6b, x=0 to 16; y=0 to 16; and x+y≦16.
A suitable alkylacrylic or acrylate monomer for Formula A′ is when Z is O; and R′ is an epoxy alkyl group. Another suitable monomer of Formula A′ is provided by Formula 7a or 7b:
where x and y are each from 0 to 16, preferably from 0 to 6. Suitably, for Formula 7b, x=0 to 16; y=0 to 16; and x+y≦16.
A suitable monomer of Formula A′ is when Z is O; and R′ is a phosphoryl or phosphoryl alkyl group. Another suitable monomer of Formula A′ is provided by Formula 8a or 8b:
where each R1 is independently H or C1 to C6 alkyl, preferably H or methyl.
Suitable monomers of Formula B′ are independently selected from styrene, α-methylstyrene, 2-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, 4-isopropylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,6-difluorostyrene, 2,3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene and 2,6-dichlorostyrene and other vinyl substituted aromatics.
Suitable monomers of Formula Ca or Cb are independently selected from ethylene, propylene, butylene, butadiene and isoprene.
Suitable monomers of Formula Da or Db or Dc or Dd are independently selected from ethylene oxide, propylene oxide, butylene oxide and caprolactone type monomers (such as ε-caprolactone or γ-butyrolactone, lactide, oxiran-2-one, 1,3-dioxolane and caprolactam).
When the Block B is hydrophobic, it may comprise one or more monomers, independently selected from the monomers defined above. Block B is chosen to have a different affinity to the liquid medium to Block A. The structures outlined for Block A can be applied for Block B provided Block A and B are different to each other.
When the block B is hydrophilic, a number of chemicals may be employed for the hydrophilic component B, all of which need to be water-soluble; examples may be selected from the group comprising:
hydrophilic organic monomers, oligomers, prepolymers or copolymers derived from vinyl alcohol, N-vinylpyrrolidone, N-vinyl lactam, acrylamide, amide, styrenesulfonic acid, combinations of vinylbutyral and N-vinylpyrrolidone, methacrylic acid, acrylic acid, vinylmethyl ether, vinylpyridylium halide, melamine, maleic anhydride/methyl vinyl ether, vinylpyridine, ethyleneoxide, ethyleneoxide ethylene imine, glycol, vinyl acetate, vinyl acetate/crotonic acid, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl ethyl cellulose, hydroxypropylmethyl cellulose, cellulose acetate, cellulose nitrate, hydroxyalkyl (alkyl)acrylate such as hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, alkylaminoalkyl(alkyl)acrylate, 2-(dimethyl amino) ethyl methacrylate, 2-(diethyl amino) ethyl methacrylate, 2-(diisopropyl amino) ethyl methacrylate, 2-(N-morpholino)ethyl methacrylate, or a derivative thereof, ethylene glycol(meth)acrylates (for example triethylene glycol(meth)acrylate) and (meth)acrylamide), N-alkyl(meth)acrylamides (for example N-methyl(meth)acrylamide and N-hexyl(meth)acrylamide), N,N-dialkyl(meth)acrylamides (for example N,N-dimethyl(meth)acrylamide and poly-N,N-dipropyl(meth)acrylamide), N-hydroxyalkyl(meth)acrylamide polymers, such as poly-N-methylol(meth)acrylamide and poly-N-hydroxy ethyl(meth)acrylamide, and N,N-dihydroxyalkyl(meth)acrylamide polymers, such as poly-N,N-dihydroxyethyl(meth)acrylamide, ether polyols, polyethylene oxide, polypropylene oxide, and poly(vinyl ether), alkylvinyl sulfones, alkylvinylsulfone-acrylates, (alkyl)acrylate with a pendent phosphorus group such as vinylphosphonate, vinylphosphonic acid, vinylphosphine oxide and any (alkyl)acrylate with a ester function —COOR such as R is CxH2xPO3R2 wherein x is 2 to 10, most preferably x is 2, and R is a hydrogen or an alkyl group having 1 to 4 carbon atoms, preferably methyl; and related compounds or a combination thereof.
In accordance with the present invention the polymers comprising the AB block copolymer comprise monomers, and the ratio of the monomers comprising each polymer of the block copolymer AB is such that the weight ratio of the (hydrophobic) block A to the (hydrophobic or hydrophilic) block B leads to the formation of organised aggregates. In addition, the weight fraction of the (hydrophobic) block A and the (hydrophobic or hydrophilic) block B leads to the formation of micelles. Certain copolymers used in the present invention have been found to form complex and large micelles in solution. As stated above AB Block copolymers can comprise a hydrophobic (“water hating”) block A and a second hydrophilic (“water loving”) or two hydrophobic blocks A and B differentiated as having different solubility parameters for a same liquid medium. Variation in the copolymer properties can be obtained by varying the monomer types (different available chemistries), the molecular weights of the copolymer (at a fixed ratio of the two component block sizes) and the ratio of the molecular weights of the constituent blocks (at a fixed overall molecular weight for the copolymer).
Importantly, to form micelles (that is, aggregates formed by molecules of block copolymer) in an apolar liquid medium, the insoluble (or poorly soluble in the liquid medium) blocks drive the formation of aggregates of the molecules. The structures of the aggregates are dependent on the copolymer concentration and the exact nature of the copolymer molecules. Schematically, micelles may be seen, for example, as a spherical aggregate having two parts; one core composed of the copolymer block insoluble or less soluble in the liquid medium and one corona composed of a copolymer block having affinity for the liquid medium. Other micellar structures are possible and known to those skilled in the art.
In accordance with the present invention the polymers comprising the AB block copolymer are comprised of monomers, and the ratio of the monomers comprising each polymer of the block copolymer AB is such that the weight ratio of the hydrophobic block A and the more hydrophilic block B leads to the formation of organised aggregates. In addition, the weight fraction of the hydrophobic block A and the more hydrophilic block B leads to the formation of micelles. The copolymers according to the present invention have been found to form complex and large micelles in organic solution.
In the present invention, once the AB block copolymer comprises two hydrophobic blocks A and B differentiated as having different solubility parameters for a same liquid medium, such structures will form micelles with a corona composed of block A in a liquid medium where the blocks B are less soluble than the blocks A in the chosen liquid medium or micelles with a corona composed of block B in a liquid medium where the blocks A are less soluble than the blocks B in the chosen liquid medium.
The chemistry for the micellar aggregates should be such that the micelles will adsorb freely onto a wide variety of particle surfaces. Also, the composition may form micelles and the aggregate structures of the composition preferably have a maximum dimension [diameter in the case of spherical micelles] of from to 3 to 500 nm, preferably from 3 to 300 nm. The block-copolymer micelle structures most preferably have a maximum dimension [diameter in the case of spherical micelles] of from 10 to 100 nm.
In one aspect of the present invention, the micelles each comprise from 10 to 1000 copolymer molecules.
The AB block copolymer may take the form of: linear block copolymer (diblock, triblock or multiblock), miktoarm copolymer (star copolymer), ladder (H-shaped) copolymer, graft and comb (co)polymer; preferably a linear block copolymer.
Also, the distribution of component monomers within each copolymer block is in the form of homo, random, gradient, alternative, block, graft and comb (co)polymers, any type of copolymer structures which will lead to a segregation of copolymers in the liquid media as organised aggregates.
It is also preferred that the block copolymer is preferably selected from the group comprising: AB blocks, ABA blocks, ABC blocks copolymers.
In a preferred example, the polymers used in the composition are prepared by controlled living radical polymerisation reactions. Preferably, the block copolymers according to the first aspect of the present invention are prepared by means of controlled living radical polymerisation to obtain narrow molecular weight distribution copolymers. Suitable synthetic routes include but are not limited to: Reversible Addition—fragmentation chain transfer (RAFT), Group transfer polymerisation (GTP) and Atomic transfer radical polymerisation (ATRP), Activated regenerated by electron transfer (ARGET), nitroxide-mediated polymerization (NMP), ring-opening polymerization and ionic type of polymerization and combinations of techniques where appropriate.
In a further aspect, the micelles may be crosslinkable and are optionally crosslinked (before, during or after treating the surface with the apolar liquid containing the micelles) resulting in a more durable coating on the substrate. In the current invention, crosslinking can be described as the physical and/or chemical interaction between chains of the AB diblock copolymer. The crosslinking can take place either in the core of the micelles, in the corona of the micelles and/or between the coronas of two contiguous micelles and the crosslinking may or may not be reversible.
Chemical crosslinking requires the use of a molecule called a crosslinker or crosslinking reagent. Three preferred chemical crosslinking strategies are: (1) crosslinking with a multifunctional organic compound, for example via condensation or addition reactions such as carboxylic acids with amines, carboxylic acids with hydroxyls, hydroxyls with isocyanates etc; (2) ring-opening reactions such as epoxy groups with amines and (3) radical initiated crosslinking of vinyl or similar chemical functions such as those in divinyl benzene and/or di-methacrylates, which can be introduced to the AB di-block copolymers.
A multifunctional organic compound is defined as an organic compound containing two or more functional groups that may react with functional groups described for the AB di-block copolymers used in this invention to form crosslinks. The functional groups in the organic compound may be any that will react with functions described herein for the AB di-block copolymer including but not limited to: amine, hydroxyl, carbonyls such as ketones or aldehydes, carboxyls such as carboxylic acid, isocyanates and sulfhydryl.
Vinyl groups may be introduced to the AB di-block copolymer by using vinyl compounds that also contain a function that will react with functional groups described in this invention for the AB di-block copolymer. Examples of such chemistry include, but are not limited to, amine functionalised vinyl compounds such as amino alkyl methacrylates. Following the introduction of the vinyl chemistry, crosslinking is carried out by radical initiation via thermal or UV curing.
Chemical covalent crosslinks are stable mechanically and thermally, so once formed are difficult to break, whereas physical crosslinks are reversible and the physical crosslinking process may or may not require the use of crosslinking agents. Physical crosslinking occurs when there is the formation of a physical interaction between functional groups located either in the AB diblock copolymer alone or between functional groups located in the AB diblock copolymer and in the multifunctional crosslinker. Techniques include, but are not limited to, dehydrothermal treatment, plasma treatment, hydrogen bonding, ionic interactions and freeze thawing.
Crosslinking (physical and/or chemical) can bring many benefits including making the hydrophilic corona of micelles more hydrophobic and controlling the release rate of an active coated with crosslinked micelles.
In accordance with the present invention the block copolymer comprises at least one block that adsorbs to a target surface. The composition may further comprise an adhesion promoter. An adhesion promoter will generally consist of a polyelectrolyte of opposite potential (charge) to the potential (charge) of the crystal; in the case the block copolymer micelles coat which is targeted is of similar relative potential to that of the crystal to be coated.
Also in a composition used in accordance with the present invention the apolar liquid medium may comprise an organic solvent or mixtures of solvent, or an organic solvent free from water, and wherein the block copolymer is preferably completely dissolved in the liquid medium. To especially but not exclusively encourage reverse micellisation the liquid medium employed will consist of two solvents, one a good solvent for the block-copolymer and a second, less effective, solvent which will cause separation of the block co-polymer from solution and the formation of micelles.
Preferred apolar solvents, can be selected from but are not limited to: alkanes, preferably pentane and hexane; halogenated solvents, preferably dichloromethane, chloroform, chlorobenzene and fluoroalkanes; and aromatic solvents and combinations thereof. Any solvent used conventionally in agrochemical formulations may be suitable for use in the present invention. Preferred apolar solvents can be also selected from what are generally classified as oils, such as high molecular weight alkanes, for example paraffinic oil; such as Isopar V and Exxsol D140; alimentary oil such as olive oil, soy bean oil and castor oil and the like and combinations thereof. Conventional ester solvents are also suitable.
Preferably the ratio of the number of Block A units to the number of Block B units is from 1:0.1 to 1:10; more preferably from 1:0.2 to 1:5; even more preferably from 1:0.25 to 1:4; yet more preferably from 1:0.5 to 1:2.
When the composition of the present invention comprises a liquid, the ratio by weight of block copolymer to the liquid medium is preferably from 1:100,000 to 1:1; more preferably from 1:10,000 to 1:2; especially from 1:5,000 to 1:5; and most preferably from 1:5,000 to:1:10.
It will also be appreciated by one skilled in the art that the composition according to present invention may preferably further comprise additional components or auxiliary agents selected from for example but not limited to dispersants, perfumes, biocides, and stabilisers, surfactants or wetting agents, emulsifiers, colouring agents, dyes, pigments, UV absorbers, radical scavenger, antioxidant, anti-corrosion agent, optical brightener, fluorescers, bleaches, bleach activators, bleach catalysts, non-activated enzymes, enzyme stabilizing systems, chelants, coating aid, metal catalyst, metal oxide catalyst, organometallic catalyst, filmforming promoter, hardener, linking accelerator, flow agent, leveling agent, defoaming agent, lubricant, matte particle, rheological modifier, thickener, conductive or non-conductive metal oxide particle, magnetic particle, anti-static agent, pH control agents, perfumes, preservative, biocide, pesticide, anti-fouling agent, algicide, bactericide, germicides, disinfectant, fungicide, bio-effecting agent, vitamin, drug, therapeutic agent or a combination thereof.
We have now found that these micelle structures can be conveniently employed to coat small particulate materials such as organic crystals. The chemistry of these applications is thereby incorporated herein. Moreover, the technique is easy to employ and permits high coating weights to be applied over all a surface (including corners and edges of crystals if present). The micelle structures of this invention can produce a coating thickness typically up to 50 nm in a single pass treatment—very much higher than any other known technique—while maintaining complete stability and non-agglomeration of the coated particle. Multi-coats produce even higher coating weights and thicknesses.
The block copolymers of the invention form micellar aggregates typically 3-300 nm in size. Aggregation number is controlled by the chemistry of the block copolymer in terms of absolute chemistry, charge, molecular weight and the solution conditions under which the micelle is formed. Typical aggregation numbers for such a block copolymer micelle can be of the order of 100 molecules. Typical molecular weights of a block-copolymer of the invention are 3 000 to 100 000 Daltons but are specified within the chemistry.
Block copolymer micelles can be simply employed by adding to a dispersion of a particle in a carrier liquid and allowing to equilibrate. Confirmation of coating can be obtained by SEM observation and quantitative data by analysis of a sample for total active material content (where an active material is coated). Other techniques to induce micelle formation (such as pH shift, temperature, solvent exchange or dilution) can all be suitably employed. As an alternative process, a drying technique to remove either a solvent or to induce a chemical change-such as loss of ammonia in a drying process—can be employed.
In the present invention, the block copolymer comprises at least one block that adsorbs to a target surface. The composition may further comprise an adhesion promoter (AP). An AP will generally consist of a polyelectrolyte of opposite potential (charge) to the potential (charge) of the surface (crystal); in this case the block copolymer micelles coat the AP modified surface (crystal). This allows copolymer micelles of similar potential (charge) to the surface (crystal) to be deposited on the surface (through a surface-AP-block copolymer arrangement).
The products of the invention comprise a surface (for example a particulate material) covered with a coating of block copolymer micelles (including, uniquely, edges and corners as well as faces). A key aspect of the present invention is the ability to provide good coverage [and protection] for sharp features such as edges and, particularly, corners of crystals.
As further embodiments, micelles comprise a core and a corona that are chemically different. This difference can be exploited for further benefits. The micelle core can be selectively loaded with a component that dissolves or can be dissolved by a suitable solvent in the core chemistry. For example, the application of a photostabiliser by such a technique (by incorporating the photostabiliser into the micelle core which is then coated onto the crystal surface), will improve the ability to stabilise sensitive chemistry against photolytic degradation. Soil mobility of particles of a pesticide can be similarly enhanced by coating a stable polymer micelle onto the crystal surface (in combination with added specific surfactants that can promoted improve soil mobility). In some situations, pesticides can induce a phytotoxic response (in cotton for example) due to too rapid a photolytic degradation. Coating crystals in this manner with a polymer micelle containing a photostabiliser could reduce the rate of degradation.
In a further aspect, the ability to coat such block copolymer micelle systems onto a substrate provides an elegant procedure to prepare mixed products by coating a polymer micelle containing a first active onto a crystal surface of a second active (with the option of further actives being in a dissolved or other dispersed state). Further, such coated polymer systems could then be applied to relevant surfaces, these to include seeds or surfaces outwith of Crop Protection uses that could require protection against attack such as wood or on surfaces where a long lasting barrier might be required (such as to prevent ingress of termites, ants or spiders or to prevent fungal growth in sensitive situations—eg fungicides in/on wallboards).
Furthermore, the coated crystalline particle may be a biologically active compound [for example, an agrochemical] whilst the micelle core may be loaded with a second biologically active compound [for example, an agrochemical]. Alternatively two or more different biologically active compounds [for example, agrochemicals] may be mixed together as coated particles according to the present invention in such a manner that the micellar coatings overcome any potential incompatibility problems [for example, physical or chemical incompatibility].
A composition according to the present invention may suitably be an agrochemical formulation; the agrochemical formulation may comprise an agrochemical active ingredient (such as a fungicide, herbicide, insecticide or plant growth regulator) or it may comprise an adjuvant which is used to enhance the bioperformance of an agrochemical [either in the same formulation as the adjuvant or to be applied from a separate formulation]. The composition can be in the form of a concentrate which is diluted or dispersed in a spray tank prior to use, although ready-to-use compositions can also be made. The final dilution is usually made with water, but can be made instead of, or in addition to, water, with, for example, liquid fertilisers, micronutrients, biological organisms, oil or solvents. The compositions may be chosen from a number of formulation types, many of which are known from the Manual on Development and Use of FAO Specifications for Plant Protection Products, 5th Edition, 1999. These include dustable powders (DP), soluble powders (SP), water soluble granules (SG), water dispersible granules (WG), wettable powders (WP), granules (GR) (slow or fast release), dispersible concentrates (DC), suspension concentrates (SC), capsule suspensions (CS; in which case, the particle is a microcapsule) and seed treatment formulations. The agrochemical formulation may be used to control or combat a pest [examples of agricultural pests include unwanted plants (weeds), insects and fungi].
In one aspect of the present invention the cores of the micelles contain a chemical [which preferably may be a photoprotectant, a biologically active compound or an adjuvant].
In a further aspect, the ability to coat such block copolymer micelle systems onto a substrate provides an elegant procedure to prepare mixed products by coating a polymer micelle containing a first active onto a crystal surface of a second active (with the option of further actives being in a dissolved or other dispersed state). Further, such coated polymer systems could then be applied to relevant surfaces that could require protection against attack such as wood or on surfaces where a long lasting barrier might be required (such as to prevent ingress of termites, ants or spiders or to prevent fungal growth in sensitive situations—e.g. fungicides in/on wallboards).
Further, non-limiting crop protection applications include particle coating leading to: reduced antagonism by altering availability between two or more actives, triggered release potential-triggers can be pH, light, water, enzymes and alteration of release profile. These release rate alterations may be possible not only in the products of the invention but also when subsequently applied (for example to seeds—triggered release from seeds by coating technology-triggers can be pH, light, water, enzymes. The size range of particles to be coated can vary enormously. Where the particle is an organic crystal, the size range [largest dimension] can usefully be from 10 nm to 500 microns, preferably 500 nm to 100 microns (although technical material greater than 500 microns could be also coated and employed in some utilities (such as pharma) in a pre-granulation stage to protect a material). When the crystal size is small, the micelle size chosen to coat the particle has to be even smaller. Where the particle is a granule (or a spray-agglomerated granule), the size can vary from about 50 microns to a few millimetres.
The present invention is illustrated by the following examples.
The surface treatment of the present invention is hydrophobic. The copolymers described in this example are AB block copolymers comprising a substantially hydrophobic block A, and a substantially hydrophobic or hydrophilic block B which has a different affinity for or solubility parameter within the liquid medium where the copolymers are dispersed compared to block A, such that micelles form in the liquid medium.
Block A can comprise one or more monomers, for example; styrene (S) and styrene derivatives, methacrylate and derivatives such as 2-ethyl hexyl methacrylate (EHMA), lauryl methacrylate (LMA), octadecyl methacrylate (ODMA), glycidyl methacrylate (GMA) and propylene oxide (PO). Those skilled in the art will appreciate the synthesis described in this example is not limited to the monomers listed here.
In the current example, the hydrophobic or hydrophilic block B is composed of methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA) or 2-ethyl hexyl methacrylate but those skilled in the art will understand that other monomers leading to a hydrophilic block can also be used.
The copolymers used herein were produced by Reversible Addition-Fragmentation Chain Transfer (RAFT) according to the protocol described in the patent applications WO08071957 and WO10038046 or by nitroxide mediated polymerisation (NMP) according to the protocol described in the Arkema patent application WO2007/057620A1. Therefore the block copolymers may be prepared by means of controlled living polymerisation techniques, such as group transfer polymerisation (GTP), atomic transfer radical polymerisation (ATRP), and activated regenerated by electron transfer (ARGET) or activated generated by electron transfer (AGET) that can synthesize well-defined homopolymers and block copolymers.
In addition to controlled radical polymerization, in the case of an heterocyclic monomer such as propylene oxide, ring-opening polymerisation techniques can be used. Examples of the composition of new prepared copolymers are given in Table 1.2.
In this example, in addition to structures described in WO08071957 and WO10038046, new copolymers structures were produced by RAFT polymerization using the RAFT agent, 2-cyanoisopropyl dithiobenzoate (CPDB). Whilst the current example prepares the block copolymer CPDB, those skilled in the art will appreciate that other RAFT agents may be used.
a) Synthesis of the Block A: PEHMA.
b) Synthesis of Block B from Block A
Various block copolymers were synthesised. Block B was obtained from various methacrylated based monomers such as EHMA, LMA, ODMA and TFEMA. Block B was composed of hydrophilic units such as MAA and HEMA, or hydrophobic monomers such as EHMA. In this case, toluene was the solvent used for the synthesis instead of isopropanol.
The method described above for the synthesis of P(EHMAx-b-MAAy) was used, which led for example to the successful synthesis of P(LMAx-b-EHMAy) and P(ODMAx-b-MAAy). The conversion rates, block sizes and reaction time are given in Table 1.2.
For the synthesis of (PEHMA51-r-PGMA22)-b-PMAA47 the following protocol was used:
a) Synthesis of the Block A: PGMA and EHMA
b) Synthesis of Block B from Block A
In this example, according to the protocol described in WO2007/057620-A1, new copolymers structures were produced by NMP polymerization using the NMP agent Blocbuilder®. Whilst the current example prepares the block copolymer using Blocbuilder®, those skilled in the art will appreciate that other NMP agents may be used.
NMP Synthesis of PSx-b-(HEMAy-r-PSz)
In the first step, the following conditions were used for the synthesis of PS with a targeted polymerisation degree of 55. Styrene (15.00 g, 0.14 mol) and Blocbuilder® (1.00 g, 2.62 mmol) were added to a 100 ml round bottom flask equipped with a magnetic stirrer. The reaction flask was degassed by nitrogen bubbling for 20 minutes and then heated at 90° C. in a thermostatically controlled oil bath under a nitrogen atmosphere. After 78 hrs 40 min of polymerization, a sample was withdrawn and analysed by 1H NMR (CDCl3). A conversion of 76.9% was determined by 1H NMR in CDCl3, hence the resultant product was PSx homopolymer where x=42.
At the end of this step 15 g chloroform was added to solubilise PS. The reactive mixture was precipitated drop by drop in 300 ml cold methanol and then filtered on paper. The product was dried down in a vacuum oven.
In a second step, newly synthesised PS (1.00 g, 0.23 mmol), styrene (0.24 g, 2.32 mmol), HEMA (2.95 g, 22.7 mmol) and dimethylformamide (DMF, 4.02 g, 0.55 mmol) were added to a 50 ml round bottom flask equipped with a magnetic stirrer. PS was solubilised in DMF by using a sonic bath (20 min). The reaction flask was degassed by nitrogen bubbling for 20 minutes and then heated at 90° C. in a thermostatically controlled oil bath under a nitrogen atmosphere. After 18 hrs of polymerization, a sample was withdrawn and analysed by 1H NMR (DMSO). A conversion of 90.0% for HEMA and 8.0% for styrene was determined by 1H NMR in DMSO, hence the resultant product was PSx-b-(HEMAy-r-PSz) diblock copolymer, where x=42, y=90 and z=8.
At the end of this step, 7 ml DMF was added to solubilise the copolymer. The reactive mixture was precipitated drop by drop in 300 ml cold ether and then filtered on paper. The product was dried down in a vacuum oven.
Other PSx-b-(HEMAy-r-PSz) were prepared with x=86, y=57 and z=0 and with x=74, y=30 and z=10. The generic structure of the corresponding PSx-b-(HEMAy-r-PSz) copolymers is given below.
SEC was used to determine the number-average molar mass (Mn) and thus demonstrate the increase of molar mass due to the addition of the second block during the polymerisation. SEC was also used to determine the polydispersity index (PDI=Mw/Mn, where Mw is the weight-average molar mass) of the polymers and copolymers, a low PDI being necessary to achieve regular micelles.
The samples were injected in the SEC equipment (2 PL gel 5 Micron Mixed-c columns) and analysis was performed as described below
An example of SEC chromatogram is given in
1H NMR was performed with a 500 MHz apparatus (Bruker), in CDCl3 for the homopolymer, and in DMSO for the copolymer.
i) Synthesis performed using RAFT in IPA
ii) Synthesis performed using NMP in DMF
iii) Synthesis performed using RAFT in toluene
Micellar aggregates can be formed from the copolymers of Example 1. Size distribution measurements using a Malvern Nano Zetasizer were performed on solutions of in apolar solvents such as dodecane, hexane, Exxsol D140, Solvesso 200ND and Isopar V.
To ensure an accurate measurement by the Malvern Nano Zetasizer, concentrations of the copolymer solution were varied so the sample was in the optimum detection range of the instrument for the polymer being examined. The size distribution measurements shown in Table 2.1 shows that the copolymers form micelles, since the minimum diameter measured is 20 nm and if copolymers were present as unimers, the diameter would be less than 5 nm. In all cases a clear solution was formed following stage 1. The results in Table 2.1 demonstrate that in each case micelles were formed following stage 3.
Examples of hydrophobic copolymer micelles solutions which were prepared according to the general procedure are described in Table 2.1.
A polymer or polymeric composition prepared according to the present invention may be coated onto a preferred substrate, as described hereafter, by any established coating process, for example, but not limited to a spray process. Generally, the treatment process involves the following steps:
Step (1): Dissolution of the copolymer molecules in a suitable organic solvent under gentle agitation.
The copolymers chosen are usually not of a high molecular weight (the copolymers typically have a range of between 3000 to 100000 g/mol) and such molecules equilibrate rapidly when dissolved in a good solvent.
Solvents suitable for use in the composition of the present invention are preferably as previously described.
Step (2): Slow drop-by-drop addition of a second solvent, which is a poor solvent for one of the blocks and a good solvent for the other block, under gentle agitation.
Agitation of the copolymer systems was used during the process of dissolution and mixing, but it was not found to be critical and simply slowly stirring the copolymer system was found to be sufficient. The length of time for agitation depended on the solvent system.
Examples of hydrophobic copolymer micelle solutions which were prepared according to the precedent protocol are described in Table 3.1.
Step (3): Applying the solution of the copolymer to a desired substrate.
Whilst not wishing to be bound by any particular theory, evidence from the present invention implies that adsorption of the copolymer onto the substrate is complete after a few minutes. Methods of exposing the substrate to the solution include any known technique for forming a coating from a solution such as spin coating, dip coating, roller coating, brush coating, curtain flow or spraying, roller coating, wire-bar coating, extrusion coating, air knife coating, curtain coating or slide coating. More preferably, dipping and spraying ensures that every part of the surface has been wetted by the treatment composition.
The treatment can be applied to both interior and exterior surfaces.
Step (4): Drying the treated surface.
Preferably the treated surfaces need to be dried after applying the treatment composition. This can be achieved at room temperature or at higher temperatures, and/or at lower pressure. It should be noted that the drying temperature does not enhance the performance of the coating; rather it shortens the drying time of the treatment. Drying in ambient conditions will only lengthen the drying time.
A copolymer solution was prepared by dissolving the copolymer in a good solvent (toluene/THF) under gentle agitation. Once a homogeneous solution was obtained a second solvent (for example hexane/Isopar V) was added to the mixture using drop-by-drop addition. The final concentration of the copolymer in solution was 0.4 wt %. The second solvent was selected to be a poor solvent or non-solvent for one of the blocks and a good solvent for the other block. The mixture was gently stirred and left for more than 2 hours in order to allow the copolymers to equilibrate into micelles. When the micelle system had reached equilibrium, 1 g of TMX (thiamethoxam) air milled crystals were added to the mixture. The sample was then allowed to tumble for at least 2 hours in order to ensure complete mixing and thus allow time for the micelles to coat the individual TMX crystals. Table 3.2 shows possible but not limiting combinations of copolymers and organic solvents which form micelles and can be used to coat crystals.
The copolymer solutions in Table 3.2 were used to coat TMX particles using the methodology outlined previously.
Crosslinking is described as the physical and/or chemical interaction between chains of the AB diblock copolymer. The crosslinking can take place either in the core of the micelles, in the corona of the micelles and/or between the coronas of two contiguous micelles.
In this example, crosslinking of copolymer micelles was used to decrease the solubility of a coated crystalline material in water. Micelles comprising AB di-block copolymers were deposited on the surface of crystals of a crystalline material (for example a pharmaceutical or an agrochemical) in oil based liquid media. Addition of either linear or cyclic diamine molecules to this system led to the modification of the topology of the micellar coating. This also resulted in a decrease in the release rate of the crystalline material in water compared to crystalline material coated with un-crosslinked copolymer micelles.
TMX was coated by using the same protocol as example 3b.
A copolymer solution (10 g) was prepared by dissolving (PEHMA51-r-PGMA22)-b-PMAA47 copolymer in a good solvent (THF) under gentle agitation. Once a homogeneous solution was obtained a second solvent (hexane) was added to the mixture using drop-by-drop addition. The final concentration of the copolymer in solution was 0.4 wt %. The second solvent was selected to be a poor solvent or non-solvent for one of the blocks and a good solvent for the other block. The mixture was gently stirred and left for 24 hours in order to allow the copolymers to equilibrate into micelles. When the micelle system had reached equilibrium, 1 g of TMX air milled crystals were added to the mixture. The sample was then allowed to tumble for 24 hours in order to ensure complete mixing and thus allow time for the micelles to coat the individual TMX crystals.
Crosslinking was then performed.
To perform release rate analysis 45-55 mg of each sample was accurately weighted into a 60 ml powder jar and 50 ml of dispersant solution (0.1% w/w Aerosol OTB, 0.5% w/w Morwet D425 in DI water) added at time zero. The samples were then placed on a roller moving at 20 rpm. A time point measurement of TMX in solution was made by extracting 3 ml of solution and passing it through a 0.45 μm filter. The filtrate was then analysed by HPLC to determine the concentration of TMX. The analysis was carried out by High-performance liquid chromatography (HPLC) using an Agilent 1100 (equipped with an auto-injector), a 50×3.0 MM ACE 3 μM C18 COLUMN FROM ACE, PART NUMBER ACE-111-0503 and mobile phases of (A) Acetonitrile+0.1% Formic acid and (B) ASTM II Water+0.1% Formic acid. Analysis was carried out with an injection load of 5 μl and column temperature of 40° C. Data were collected at a range of time points
Total TMX content of the samples was determined by weighing 30-50 mg of each dry powder accurately weighted into an aluminium weighting boat. The weighing boat was then placed in a volumetric flask and 50 ml acetonitrile added. The flask was gentle swirled until a colourless solution was formed. This solution was analysed using the HPLC conditions described previously.
Table 4.2 shows the quantity of TMX released after 1 and 4 hours as a percentage of the total TMX concentration as measured by the method described previously.
The mixture containing the micelles formed from the copolymers PEHMA-b-PMAA in hexane (Table 5.1—row 1) was used to treat glass microscope slides and painted Q-panels by dip coating, as well as Poly(methyl methacrylate) (PMMA), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) sheets by flow coating. The treatment led to an increase of the overall hydrophobicity of the surface as indicated by the contact angle increase of the surface after treatment (Table 5.1)
The protocol described in example 3 was used to coat sodium percarbonate with a copolymer micellar solution of Poly(PS42-b-HEMA69) at 0.4 and 5 wt % in DMF/Solvesso 200—see
The protocol described in example 3 was used to coat sodium carbonate with a micellar solution of Poly(PS42-b-HEMA45) at 0.4 and 5 wt % in DMF/Solvesso 200—see
Bitrex was chosen as it is the bitterest chemical known to man, and has similar physical and chemical characteristics to many pharmaceuticals.
Denatonium benzoate (Bitrex) crystals were coated by adding a copolymer micellar solution of Poly(EHMA60-b-MAA55) at 0.4 and 5 wt % in DMF/Solvesso.
The protocol described in Example 3 was used to coat Bitrex—see
Release rate was monitored visually in order to compare the uncoated Bitrex with the 5 wt % coated Bitrex particles. 0.4 mg of sample was agitated in 10 ml of water and observed over 8 hours. After 15 minutes the uncoated Bitrex was fully dissolved but after 8 hours the coated particles were still present—see
100 mg in 40 ml water of uncoated bitrex and 5 wt % coated Bitrex were shaken for a period of 10 minutes and sampled at various time intervals. 2 ml of the mixture was removed at each time interval for analysis.
Total content of the samples was determined by accurately weighing 17.5 mg of 5 wt % coated Bitrex particles, sonicated until the coated particles had fully dissolved in 25 ml of water and analysed by UV/Vis. A total content measurement of 57.75% was obtained. See
| Number | Date | Country | Kind |
|---|---|---|---|
| 1111439.4 | Jul 2011 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP12/62943 | 7/3/2012 | WO | 00 | 3/27/2014 |
