AEROSIL® R is a fumed silica aftertreated with HMDS based on AEROSIL® Applications and Properties. Physico-chemical Data. IL. L. LLL. LLLLLL. AEROSIL® R is a fumed silica aftertreated with organosilane (HMDS) with high specific surface and marked hydrophobia. — The Cary Company, Since. AEROSIL® R S fumed silica after treated with HMDS based on AEROSIL® It is used in paints and coatings, adhesives and sealants, and silicone.
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The present invention is directed to a composition suitable to yield a superhydrophobic coating and a method for making the same. More particularly, t812 present invention is directed to a superhydrophobic coating comprising silicone having a viscosity of at least 30 cSt and aerosul of silica-based particles wherein the microclusters have diameters from 1 nm to nm. Droughts, poor irrigation and insufficient plumbing systems are just some of the reasons that cause water shortages in certain regions.
Shortages of water can create serious social problems, such as health issues, that are a direct result of inadequate cleaning applications in the absence of sufficient amounts of water. Efforts for cleaning surfaces with limited amounts of water have been made. In fact, the cleaning of surfaces that attempt to mimic the surface of a lotus leaf has been investigated. Taro leaves, for example, have been used as templates for polystyrene structures that can display a lotus leaf effect.
Such structures can be used for coatings that possess superhydrophobic properties. Articles with surfaces that are difficult to wet, i. Moreover, such coatings, subsequent to being applied, yield surfaces that make cleaning easier and faster for the consumer. Moreover, reliable methods aaerosil generating superhydrophobic coatings that g812 not alter the look of treated surfaces are not a given. Aaerosil is an increasing interest to develop superhydrophobic coatings that result in surfaces displaying high contact angles against water.
Efforts have been disclosed for preparing hydrophobic surfaces. In Thin Solid Films pp. Applied Physics 40 pp. Other efforts have been disclosed for aeroskl hydrophobic surfaces. Still other efforts have been disclosed for making hydrophobic surfaces.
Patents 7, and 7,, anti-icing coatings and reversibly adaptive rough micro- and nanostructures, respectively, are described. Even other efforts have been disclosed for making superhydrophobic surfaces.
The present inventors have recognized that there is a need to generate coatings that do not alter the look zerosil surfaces they are applied on. This invention, therefore, is directed to a composition for yielding a superhydrophobic coating comprising silicone and aggregates or microclusters whereby the same comprises silica-based particles and the microclusters have diameters from 1 nm to nm.
The coating of this invention is prepared by combining at least aggregates or microclusters of silica-based particle, silicone and solvent to produce a composition 8r12 cures to yield the desired coating. Viscosity of fluids such as silicone oils can be determined, for example, by the relevant international standard, such as ISO The microcluster may be formed from heterogeneously sized particles or homogeneously sized particles.
Heterogeneously sized particles in a t812 means having particles with different or varying size diameters in the microcluster. Homogeneously sized particles in a microcluster means having r81 with substantially the same size diameters in the microcluster. Diameter is meant to mean the largest measurable distance on a particle or aggregate in the event a well-defined sphere is not generated.
WO2012156173A1 – Superhydrophobic coating – Google Patents
Such an angle maybe measured with a goniometer or other water droplet shape analysis systems. Values of transmittance quoted herein are determined at a wavelength of nm and are measured as follows:.
Transmittance is used herein as a measure of transparency and so should be determined in the absence of any chromophores with appreciable absorbance at nm. It should be noted that in specifying any range of values, any particular upper value can be associated with any particular lower value. For the avoidance of doubt, the word “comprising” is intended to mean “including” but not necessarily “consisting of or “composed of.
In other words, the listed steps or options need not be exhaustive. Also for the avoidance of doubt and by way of illustration in this specification, a composition with microclusters comprising silica-based particles yields support for a composition with microclusters consisting essentially of and consisting of silica-based particles. The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other irrespective of the fact that claims may be found without multiple dependency or redundancy.
Where a feature is disclosed with respect to a particular aspect of the invention for example a composition of the inventionsuch disclosure is also to be considered to apply to any other aspect of the invention for example a method of the invention mutatis mutandis.
In a first aspect, the present invention is directed to a composition capable of yielding a superhydrophobic coating, the composition comprising a a microcluster of silica-based particles, the microcluster having a diameter from 1 nm to nm. In a second aspect, the invention is directed to a process for making the composition of the first aspect comprising the step of combining, in no particular order, the silica-based particles, at least a first part of the solvent and the silicone to provide a mixture.
In a third aspect, the present invention is directed to a method for making a. All other aspects of the present invention will more readily become apparent upon considering the detailed description and examples which follow. The only limitations with respect to the type of silica-based particle that may be used in this invention is that the same can be used to generate microclusters and can be employed in a composition suitable for use by consumers to generate a superhydrophobic coating.
In an often preferred embodiment, the silica-based particle used is silica, especially pyrogenically produced silica i.
Exemplary hydrophibically modified silicas include those comprising at least one of the following groups:.
Such silicas are described, for example, in United States Patent No. Especially preferred are silicas comprising the group represented by formula Iformula III or a combination thereof. The size of the silica-based particles used in this invention has no particular limitation save that the particles are necessarily smaller than the size of the micro-cluster.
Typically the particles in an unbundled state will have a particle size in the range of 0. In the composition of the invention, the particles are present as microclusters.
Without wishing to be bound by theory, the present inventors believe that the presence of microclusters in the composition provides a rough surface to coatings made from the composition and this roughness is, in part, responsible for superhydrophobicity. The microcluster has a diameter of at least 1 nm aeosil preferably at least 10 nm, more preferably at least 50 nm, more preferably still at least nm and most preferably at least nm.
If the microclusters are too large, however, the structure created in the coating will scatter large amounts of visible light and be opaque. Therefore in compositions of the present invention the microcluster has a diameter of no greater than nm, preferably less than nm, more preferably less than nm, more preferably still less than nm and most preferably less than nm.
The composition preferably comprises the qerosil particles in an amount from 0. Silicone fluids or oils are widely commercially available from manufacturers such as Dow Corning or Blue Star Silicones. Thus the silicone has a viscosity of at least 30 cSt, preferably at least afrosil cSt, more preferably at least cSt, more aeroail still at least cSt and most preferably areosil cSt.
Thus it is preferred that the silicone has a viscosity of less than cSt, more preferably less than r8812, more preferably still less than cSt, even more preferably afrosil than cSt and most preferably less than cSt. A further advantage of silicones employed in the present invention is that they typically have a refractive index which is close to that of silica-based particles.
In particular it is preferred that where the silica-based particles have a refractive index n pthe silicone has a refractive index n s and the ratio np n s of n p to n s is within the range 0. Additionally or alternatively the aeroosil index of the silicone n s is in the range 1. The present inventors have found that silicone can increase the durability of coatings made from compositions comprising microcluster of silica-based particles even when used in relatively small amounts.
For example the weight ratio of amount of silicone to the amount of silica-based particles silicone: Additionally or alternatively the composition may comprise silicone in an amount of from 0. Apart from areosil silica-based particles and silicone, the composition additionally comprises solvent.
AEROSIL® R S Hydrophobic Fumed Silica
Often solvent will make up the balance of the composition but optional ingredients such as colourants, preservatives and the like may also be present in the composition.
The composition may comprise the solvent in an amount, for example, of from 50 to Most preferred are volatile solvents i. Volatile solvents are preferred because of their tendency to evaporate quickly and so leave behind a coating consisting of or at least consisting essentially of silica-based particles and silicone.
Occasionally, however, some solvent may remain in the coating and so to prevent unwanted opacity on such occasions, it is preferred to employ a solvent which has a refractive index close to that of the silica particles.
Thus it is preferred that the solvent has a refractive index n a in the range 1.
specialty silica for defoamers
Additionally or alternatively, the ratio np n a of n p to n a is within the range 0. Particularly preferred solvents, owing to their relative safety and high volatility, are polar organic solvent, more preferably Ci-C 4 alcohol. Most preferably the solvent comprises methanol, ethanol, propanol, isopropanol or a mixture thereof. Advantageously polar organic solvent may be used to improve the compatibility of silicone with water. Thus in one embodiment the solvent comprises polar organic solvent.
More preferably the solvent comprises polar organic solvent and water in a weight ratio of solvent: The composition may comprise emulsifier. Thus it is preferred that the composition is essentially free from emulsifier. The composition of this invention may be useful for preparing long-lasting or even permanent coating. For example the composition may comprise an overprint varnish or may be a premix suitable for combining with an overprint varnish. Suitable compositions and varnishes are described in our co-pending International Patent Application with application no.
In particular, the composition may be a premix suitable for preparing an overprint varnish and comprising:. Alternatively the composition may be a composition other than one comprising the specific combinations iiiiiiiv or v of particle, silicone and solvent disclosed above. In a most preferred embodiment of the invention the composition does not form a permanent coating on application and is preferably free from varnish.
The composition of the present invention is preferably used to treat a hard surface, especially to aid cleaning or soil-resistance of the hard surface. Typically, the hard surface is in a household including window, kitchen, bathroom, toilet, furniture, floor, aerosi the like.
Preferably the hard surface comprises, or is, glass. The composition may be packed in any form, but preferably is packaged as a conventional hard surface treatment or cleaning product. The preferred packaging is a spray applicator. Pump dispersers whether spray or non-spray pumps and pouring applications bottles etc are also possible. It is also possible to impregnate a wipe with the composition. The composition of the invention may be made in any convenient arosil.
Suitably, however, the composition is prepared by a process comprising the step of combining, in no particular order, the silica-based particles, at least a first part of the solvent and the silicone to provide a mixture. Where the solvent comprises polar organic solvent it is preferred that the first part of the solvent comprises the polar organic solvent. In this way good mixing of the components is achieved owing to the miscibility of the silicone and polar organic solvent.
Following formation of the mixture, a second part of the solvent may be added to the mixture, if aerksil. In one especially preferred embodiment the second part of the solvent comprises and most preferably is water.
The composition of the invention is used to prepare a superhydrophobic coating. The method for making a superhydrophobic coating on a surface preferably comprises the steps of applying the composition to a surface and allowing the composition to dry. The coating is superhydrophobic.