WO2014095299A1

WO2014095299A1 - Composition for hydrophobic coating

Info

Publication number: WO2014095299A1
Application number: PCT/EP2013/075027
Authority: WO
Inventors: Yi Zhou; Qingsheng Tao
Original assignee: Unilever N.V.; Unilever Plc; Conopco, Inc., D/B/A Unilever
Priority date: 2012-12-21
Filing date: 2013-11-29
Publication date: 2014-06-26
Also published as: BR112015011838A2; AR094152A1; EP2935488A1

Abstract

Disclosed is a composition capable of yielding a hydrophobic coating. The composition comprises: (a) colloidal particle which is both partially hydrophobic and partially hydrophilic; (b) a hydrolyzed quaternary silane having at least two hydroxyl ligands and/or its oligomer; and (c) solvent.

Description

COMPOSITION FOR HYDROPHOBIC COATING

FIELD OF THE INVENTION

The present invention relates to a composition for applying to surfaces to create a hydrophobic coating thereon. In particular, the present invention relates to a composition comprising colloidal particle which is both partially hydrophobic and partially hydrophilic, a first hydrolyzed quaternary silane and solvent.

BACKGROUND OF THE INVENTION

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.e., articles with hydrophobic surfaces, are therefore desirable since they possess self-cleaning properties when water is present at low volumes. Moreover, such coatings, subsequent to being applied, yield surfaces that make cleaning easier and faster for the consumer.

While hydrophobic, and especially superhydrophobic surfaces are desirable, compositions that result in such surfaces can be difficult to manufacture and can result in surfaces that display inferior self cleaning, a direct result, for example, of their characteristic contact angles that are too low. Moreover, reliable methods for generating superhydrophobic coatings that do not alter the look of treated surfaces are not a given.

There is an increasing interest to develop hydrophobic coatings that result in surfaces displaying high contact angles against water. For example, WO 2007/102960 A2 (ASHLAND LICENSING AND

INTELLECTUAL PROPERTY LLC) discloses a coating composition comprising a hydrophobic fumed silica ranging in size from 1000 to 4,000 nanometers, a solvent or solvent mixture selected from straight or branched, linear or cyclic aliphatic, or aromatic hydrocarbons with 2 to 14 carbon atoms, monovalent linear or branched alcohols with 1 to 6 carbon atoms, ketones or aldehydes with 1 to 6 carbon atoms, ethers or esters with 2 to 8 carbon atoms, or linear or cyclic polydimethylsiloxanes with 2 to 10 dimethylsiloxy units, in an effective amount of up to 50 percent by weight based on the total weight of the composition. The coating composition is said to be capable of rendering a superhydrophobic coating.

However, quite a lot of consumer products are formulated with relatively high concentrations of water. Therefore, the present inventors have recognized that there is a need for compositions for generating such a coating and that can be formulated into composition with high concentrations of water. In addition, the present inventors have recognized a need to generate coatings that do not alter the look of surfaces they are applied on and a need to improve the durability of the coating. This invention, therefore, is directed to a composition for yielding a hydrophobic coating comprising colloidal particle which is partially hydrophobic and partially hydrophilic, a first hydrolyzed quaternary silane and solvent. Such a composition may comprise large amount of water and is typically capable of curing to yield a coating that is at least translucent and often transparent and/or which is durable.

DEFINITIONS

Hydrophobicity

"Hydrophobic" for the purposes of the present invention is used to describe a molecule or portion of a molecule that is attracted to, and tends to be dissolved by oil (in preference to water), or a surface that has a contact angle against water of greater than 90°. "Ultrahydrophobic" as used herein means having a contact angle of at least 120° against water. "Superhydrophobic" as used herein means having a contact angle of at least 140° against water. Contact angle, as used herein, means the angle at which a water/vapor interface meets a solid surface at a temperature of 25 °C. Such an angle may be measured with a goniometer or other water droplet shape analysis systems. Sliding angle, as used herein, means the tilt angle of a surface at which a 5 μΐ droplet of water slides at 25 °C. Oligomer

"Oligomer" for the purposes of the present invention means a molecule that consists of several monomer units, for example, from 2 to 100, more preferably, from 2 to 60 monomer units. Hydrolysis

"Hydrolysis" for the purposes of the present invention refers to a reaction with water. "Hydrolyzable" herein means the compound may react with water. "Hydrolyzed" means the compound is the reaction product of another compound (a precursor) with water.

For sake of clarity, the weight of hydrolyzed silane as used herein refers to the weight of the hydrolyzed silane and its oligomers) (if have). pH

pH values referred to herein are measured at a temperature of 25 °C. Transmittance

Values of transmittance quoted herein are determined at a wavelength of 550 nm and are measured as follows:

An uncoated glass slide having a transmittance of 89.0% is taken as substrate. Composition is spread on to one side of the slide to give an even coating of about 2.86 x

10 -4 mg/mm 2.

The coating is cured for 10 minutes or until it forms a cohesive film.

- The coated slide is placed in a UV-vis spectrometer (e.g. Perkin-Elmer Lambda 650S) and the transmittance measured at 25 °C.

Transmittance is used herein as a measure of transparency and so should be determined in the absence of any chromophores with appreciable absorbance at 550 nm.

Particle Size

Particle size as used herein refers to particle diameter unless otherwise stated. For polydisperse samples having particulate with diameter no greater than 1 μητ, diameter means the z-average particle size measured, for example, using dynamic light scattering (see international standard ISO 13321) with an instrument such as a Zetasizer Nano™ (Malvern Instruments Ltd, UK). For polydisperse samples having particulate with diameter greater than 1 um, diameter means the apparent volume median diameter (D50, also known as x50 or sometimes d(0.5)) of the particles measurable for example, by laser diffraction using a system (such as a Mastersizer™ 2000 available from Malvern Instruments Ltd) meeting the requirements set out in ISO 13320.

"Primary particle size" refers to the diameter of particles in an unaggregated state.

Refractive Index

Refractive index is quoted at a temperature of 25 °C and a wavelength of 589 nm. Miscellaneous

Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use may optionally be understood as modified by the word ' 'about' '.

All amounts are by weight of the total composition, unless otherwise specified.

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.

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 invention), such disclosure is also to be considered to apply to any other aspect of the invention (for example a method of the invention) mutatis mutandis.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a composition comprising: a) colloidal particle;

b) a first hydrolyzed quaternary silane having at least two hydroxyl ligands and/or its oligomer; and

c) solvent,

wherein the colloidal particle is both partially hydrophobic and partially hydrophilic, and the composition is capable of yielding a hydrophobic coating on a substrate.

In a second aspect the present invention provides a method for forming a hydrophobic coating on a surface, the method comprising applying the composition of any embodiment of the first aspect to the surface and drying the composition to yield the hydrophobic coating.

In a third aspect the present invention provides a hydrophobic coating obtained and/or obtainable by any embodiment of the method of the second aspect.

In a fourth aspect the present invention provides a process for the preparation of the composition of any embodiment of the first aspect, wherein the process comprises the steps of:

i. forming a reaction mixture comprising water and a first quaternary silane precursor; ii. hydrolyzing the first quaternary silane precursor in the reaction mixture to provide a first hydrolyzed quaternary silane and/or its oligomer; and

iii. combining the reaction mixture with colloidal particle, wherein the colloidal particle is both partially hydrophobic and partially hydrophilic.

All other aspects of the present invention will more readily become apparent upon considering the detailed description and examples which follow.

DETAILED DESCRIPTION

Colloidal particle often refers to single particle or aggregates of articles with primary particle size no greater than 1 micron. The colloidal particle suitable for use in the present invention is both partially hydrophobic and partially hydrophilic. The hydrophobicity or hydrophilicity of the colloidal particle may originate from the surface characteristics of the colloidal particle per se. However, it is preferred that the colloidal particle is both partially hydrophobically modified and partially hydrophilically modified. No matter how the both partially hydrophobic and partially hydrophilic colloidal particle is obtained, the colloidal particle preferably comprises at least one group selected from monovalent, linear or branched, saturated or unsaturated hydrocarbon radicals, monovalent fiuoro-substituted linear or branched, saturated or unsaturated hydrocarbon radicals, and at least one group selected from -OH, -SH, and -NH₂. More preferably, the colloidal particle comprises at least one group selected from -Cf¾ and -CF₃, and at least one group selected from -OH, -SH, and -NH₂. Even more preferably, the colloidal particle comprises -CT¾ and at least one group selected from -OH and -NH₂. The present inventors have found that even in the presence of over 50 wt% of water, the composition can still create a hydrophobic coating with inclusion of the colloidal particle of the present invention. Without wishing to be bound by any theory, the inventors believe the hydrophobicity of the coating may be due to the hydrophobicity of the particles, along with their structure afforded to the coating by the particles, and the capability of yielding hydrophobic coating even in present of over 50 wt% of water may be contributed from the hydrophilicity of the particles.

An indicator of the surface hydrophobicity of colloidal particle is its relative diameter in a isopropanol/water solvent compared with pure isopropanol solvent, preferably the colloidal particle in a dispersion of 0.6 wt% of colloidal particle, 15.7 wt% of isopropanol, and 83.7 wt% of water, has number average diameter of greater than 2 times, more preferably greater than 3 times, even more preferably greater than 5, and most preferably greater than 10 times of number average diameter of the colloidal particle in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol. The number average diameter of colloidal particle in dispersion of 0.6 wt% of colloidal particle, 15.7 wt% of isopropanol, and 83.7 wt% of water, is preferably less than 10000 times, more preferably less than 1000 times, and even more preferably less than 100 times of the number average diameter of the colloidal particle in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol. As an indicator of the surface hydrophilicity, when in a dispersion of 0.6 wt% of colloidal particle,

30.5 wt% of isopropanol, and 68.9 wt% of water, the colloidal particle preferably has number average diameter of less than 50 times, more preferably less than 30 times, even more preferably less than 15 times of number average diameter when the colloidal particle is in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol. The number average diameter of colloidal particle in dispersion of 0.6 wt% of colloidal particle, 30.5 wt% of isopropanol, and 68.9 wt% of water is preferably greater than 1.5 time, more preferably than 2.5 times, and even more preferably than 5 times of the number average diameter of colloidal particle in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol. when in a dispersion of 0.6 wt% of colloidal particle, 0.07 wt% of hydrochloric acid, 30.5 wt% of isopropanol, and 68.83 wt% of water, the colloidal particle preferably has number average diameter of less than 30 times, more preferably less than 20 times, even more preferably less than 10 times of number average diameter when the colloidal particle is in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol. The number average diameter of colloidal particle in dispersion of 0.6 wt% of colloidal particle, 0.07 wt% of hydrochloric acid, 30.5 wt% of isopropanol, and 68.83 wt% of water is preferably greater than 1.5 time, more preferably than 2.5 times, and even more preferably than 5 times of the number average diameter of colloidal particle in dispersion of 0.6 wt% of colloidal particle and 99.4 wt% of isopropanol.

Examples of suitable colloidal particles include, for example, colloidal particles of metal salts, especially metal oxides. Suitable metal oxides include, for example, silica (Si0₂), titanium dioxide (Ti0₂), alumina (Α1₂ ⁽¾), zirconium dioxide (Zr0₂), tin dioxide (Sn0₂), zinc oxide (ZnO), iron oxide (Fe₂0₃) and mixtures thereof. More preferred are metal oxides with both partially hydrophobically modified and partially hydrophilically modified surfaces. Especially preferred, owing to their good compatibility with silanes, are both partially hydrophobically modified and partially hydrophilically modified silica particles.

Illustrative silica-based particles suitable for use in this invention comprise at least 25% by weight silicon dioxide (i.e., silica), and preferably, at least 50% by weight silicon dioxide, and most preferably, at least 75%> to 100% by weight silicon dioxide, based on total weight of particle and including all ranges subsumed therein.

Exemplary hydrophobically and hydrophilically modified silicas include those comprising at least one of the following groups:

- 0 - Si (CH₃)₃ (I)

O— Si C ₈ H ₁₇

(HI)

o

or

and at least one group selected from -OH, -SH, and -NH₂, more preferably -OH and -NH₂, and most preferably -NH₂.

In an often preferred embodiment, the silica-based particle used is pyrogenically produced silica (i.e. fumed silica) which has been both partially hydrophobically and partially hydrophilically modified. Without wishing to be bound by theory, the present inventors believe that the hierarchical structure of fumed silica contributes to the composition's ability to produce a hydrophobic coating. Especially preferred are silicas comprising the group represented by formula (I), formula (II) or a combination thereof and -NH₂.

Such silicas are made, for example, commercially available from suppliers like Evonik Degussa GmbH under the names Aerosil^® R504 and NA 200 Y.

The size of the colloidal particles used in this invention has no particular limitation save that the particles are necessarily colloidal. It is preferred, however that the particles have a primary particle size of less than 500 nm to avoid the final coating from being too opaque. More preferably the particle size is from 1 to 250 nm. Additionally or alternatively, the particles will have a primary particle size in the range of 0.1 to 100 nm, more preferably 1 to 50 nm and most preferably 3 to 13 nm. The composition preferably comprises the colloidal particles in an amount of from 0.001 to 8%, more preferably from 0.01 to 4%, even more preferably from 0.02 to 2% and most preferably from 0.05 to 1% by weight based on total weight of composition and including all ranges subsumed therein.

The first hydrolyzed quatemary silane in this invention is a silane having at least two hydroxyl ligands. It is also possible that two or more silanol groups of the first hydrolyzed quatemary silane are condensed together to form oligomers. Silanol groups of the first hydrolyzed quatemary silane may additionally or alternatively be condensed with silanol groups of the second hydrolyzed quatemary silane to form mixed oligomers. However, this condensation should not lead to excessive polymerization, otherwise, the silanes may not be well dispersed and may even precipitate.

Besides the hydroxyl ligands, the first hydrolyzed quatemary silane may have hydrophobic ligand(s) and/or hydrophilic ligand(s). However, it is preferred that the first hydrolyzed quatemary silane is a silane having at least two hydroxyl ligands and at least one hydrophobic ligand.

The hydrophobic ligand(s) of the first hydrolyzed quatemary silane are preferably independently selected from alkyl, alkenyl, fluoroalkyl, fluoroalkenyl, aryl, fluoroaryl and combinations thereof. Thus the first hydrolyzed quatemary silane may be hydrolyzed from a first quatemary silane precursor having the formula (R 1 2

)4__m Si(R )_m , wherein:

each R¹ is independently selected from alkoxy and halogen;

R is selected from alkyl, alkenyl, fluoroalkyl, fluoroalkenyl, aryl, fluoroaryl and combinations thereof; and

- m= l or 2.

To provide for maximum hydrophobicity, it is preferred that R comprises at least 2 carbon atoms, more preferably at least 3 carbon atoms, more preferably still at least 4 carbon atoms, even more preferably at least 5 carbon atoms and most preferably at least 6 carbon atoms. Longer carbon chains may, however negatively affect the stability of the silane and/or may impair its ability to condense into a gel or film. Thus it is preferred that R comprises less than 30 carbon atoms, more preferably less than 25 and most preferably less than 20. For similar reasons it is additionally or altematively preferred that only one of the ligands on the first hydrolyzed silane is hydrophobic, i.e., m = 1.

In a most preferred embodiment R is alkyl, especially C5-C20 alkyl.

Examples of first quatemary silane precursor employed in this invention include those which comprise phenyltrimethoxysilane, phenyltriethoxysilane, phenyltrichlorosilane, benzyltrimethoxysilane, benzyltriethoxysilane, benzyltrichlorosilane, phenethyltrimethoxysilane, phenethyltriethoxysilane, phenethyltrichlorosilane, butyltrimethoxysilane, butyltriethoxysilane, butyltrichlorosilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, cyclohexyltrichlorosilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, hexadecyltrichlorosilane, (tridecafluoro- 1 , 1 ,2,2 etrahydro-octyl)trimethoxysilane, (tridecafluoro- 1 , 1 ,2,2-tetrahydro-octyl)triethoxysilane, (tridecafluoro- 1 , 1 ,2,2-tetrahydro-octyl)trichlorosilane, pentyltnmethoxysilane, pentyltriethoxysilane, trichloropentylsilane, hexyltrimethoxysilane, hexyltriethoxysilane, trichlorohexylsilane, heptyltrimethoxysilane, heptyltriethoxysilane, trichloroheptylsilane, octyltrimethoxysilane, octyltriethoxysilane, trichlorooctylsilane, decyltrimethoxysilane, decyltriethoxysilane, trichlorodecylsilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, trichlorododecylsilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, trichlorooctadecylsilane, or a mixture thereof.

More preferably, the first quatemary silane precursor is selected from pentyltnmethoxysilane, pentyltriethoxysilane, trichloropentylsilane, hexyltrimethoxysilane, hexyltriethoxysilane, trichlorohexylsilane, heptyltrimethoxysilane, heptyltriethoxysilane, trichloroheptylsilane, octyltrimethoxysilane, octyltriethoxysilane, trichlorooctylsilane, decyltrimethoxysilane, decyltriethoxysilane, trichlorodecylsilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, trichlorododecylsilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, hexadecyltrichlorosilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, trichlorooctadecylsilane, or a mixture thereof.

For example, the first quatemary silane precursors suitable for use in this invention include hexyltrimethoxysilane, dodecyltrimethoxysilane, trichlorododecylsilane, and/or octadecyltriethoxysilane, all of which are commercially available from Tokyo Chemical Industry Co., Ltd (Japan).

The composition preferably comprises the first hydrolyzed quatemary silane in an amount from 0.001 to 10%, more preferably from 0.05 to 5%, even more preferably from 0.1 to 2% and most preferably from 0.2 to 1% by weight based on total weight of composition and including all ranges subsumed therein.

Apart from the colloidal particles and silanes, the composition additionally comprises solvent. Solvent as used herein especially refers to a liquid substance capable of dissolving a solute (a chemically different solid or liquid) to form a uniformly dispersed solution at the molecular or ionic size level. Liquid or solid refers to the state at 25°C and atmospheric pressure. 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 99.9% by weight, more preferably from 70 to 99%, more preferably still from 80 to 98% by weight, and most preferably from 90 to 97% by weight.

Preferred are volatile solvents (i.e. solvents which have a measurable vapour pressure at 25 °C). More preferred are solvents which have a vapour pressure at least equal to that of pure water at 25 °C 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 first hydrolyzed silane. The silanes may polymerize during the drying process and undergo a so-called sol-gel transition. Without wishing to be bound by theory, the present inventors believe that polymerization of the silanes in the final coating composition may, in part, contribute to its excellent robustness.

Occasionally, 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 silanes. Thus it is preferred that the solvent has a refractive index in the range 1.2 to 1.6, more preferably 1.3 to 1.5. Particularly preferred solvents, owing to their relative safety and high volatility, are polar organic solvent, more preferably C₁-C₄ alcohol. Most preferably the solvent comprises methanol, ethanol, propanol, isopropanol or a mixture thereof. The solvent may additionally or alternatively comprise water, preferably in an amount of at least 5% by weight of the composition, more preferably at least 10%, more preferably still at least 20% and most preferably at least 30%. Due to the hydrophilic end of the colloidal particle with water, the amount of water in the composition may be up to 90% by weight of the composition. However, it is more preferred that water is present in the composition in amount of no greater than 80% by weight of the composition, even more preferably no greater than 70% for sake of easy formation of hydrophobic coating, coherency of the coating, and/or higher contact angle.

Advantageously polar organic solvent may be used for good compatibility with hydrophobic groups of the colloidal particles. Thus in one embodiment the solvent comprises polar organic solvent (especially C₁-C₄ alcohol) and water. More preferably the solvent comprises polar organic solvent and water in a weight ratio of polar organic solvent: water of from 50: 1 to 1 :20, even more preferably from 20:1 to 1:10, more preferably still from 10:1 to 1:5 and most preferably from 3:1 to 1:4.

The composition may further comprise a second hydrolyzed quatemary silane. The present inventors have found that inclusion of the second hydrolyzed silane in compositions of the invention can provide coatings with excellent robustness, for example in terms of scratch and/or rub resistance. The second hydrolyzed quatemary silane in this invention is a silane with four hydroxyl ligands. It is also possible that two or more silanol groups of the second hydrolyzed quatemary silane are condensed together to form oligomers. However, this condensation should not lead to excessive polymerization, otherwise the silane may not be well dispersed and may even precipitate.

Typically, the second hydrolyzed quatemary silane may be hydrolyzed from a second quatemary silane precursor having a formula (R¹)₄Si. R¹ represents a ligand which can be hydrolyzed to a hydroxyl group. R¹ may, for example, be selected from alkoxy, halogen, or the like.

Examples of the second quatemary silane precursor employed in this invention include those which comprise tetraethoxysilane (also called tetraethyl orthosilicate or TEOS), tetramethoxysilane (also called tetramethyl orthosilicate or TMOS), tetrapropoxysilane (also called tetrapropyl orthosilicate or TPOS), tetrabutoxysilane (also called tetrabutyl orthosilicate or TBOS), tetrabromosilane, tetrachlorosilane or a mixture thereof. In a more preferred embodiment, the second quaternary silane precursor comprises TEOS, TBOS or a mixture thereof.

For example, the second quaternary silane precursors suitable for use in this invention include TEOS from Shanghai Chemical Reagent Co. Ltd (China) and/or TBOS from Sigma-Aldrich (Germany).

The weight ratio of the first hydrolyzed silane to the second hydrolyzed silane in the composition may be at least 1:50, more preferably at least 1:30, more preferably still at least 1:20 and most preferably at least 1 : 10. To maximise hydrophobicity of the final coating, however, it is preferred that the weight ratio of the first hydrolyzed silane to the second hydrolyzed silane in the composition is no greater than 100:1, more preferably no greater than 20:1, more preferably still no greater than 5 : 1 and most preferably no greater than 1:1.

The present inventors have also found that relatively low total amounts of silane are required to provide compositions which are both hydrophobic and robust. Moreover, excessive amounts of silane in the composition may lead to premature condensation polymerization and/or precipitation of the silanes. For example, the composition may comprise the first hydrolyzed silane and the second hydrolyzed silane in a total amount of no more than 10% by weight of the composition, more preferably no more than 7%, more preferably still no more than 5%, even more preferably no more than 2%, even more preferably still no more than 1% and most preferably no more than 0.2%. The minimum amount of total silane (the amount of first hydrolyzed silane plus the amount of second hydrolyzed silane) is preferably at least 0.001% by weight of the composition, more preferably at least 0.005%, more preferably still at least 0.01 % and most preferably at least 0.02%.

In certain embodiments, and especially where the composition is employed as a hard surface cleaning composition, it is preferable to include a surfactant in the composition. Therefore preferably the composition comprises surfactant. The surfactant may be anionic, non-ionic, cationic, amphoteric, zwitterionic or a mixture thereof. However cationic surfactants in particular may be employed in the composition of the invention without interfering with the ability of the composition to form a hydrophobic coating. Thus preferably the surfactant comprises cationic surfactant, more preferably at least 50% by total weight of surfactant in the composition is cationic surfactant, more preferably still at least 75% by weight, most preferably from 80 to 100%.

Preferred cationic surfactants are quaternary ammonium salts. More preferably, the cationic surfactant has the formula JNTT^R^R⁶ wherein R³, R⁴, R⁵ and R⁶ are independently (Ci to C₃₀) alkyl or benzyl. Preferably, one, two or three of R³, R⁴, R⁵ and R⁶ are independently (C₄ to C₃₀) alkyl and the other R³, R⁴, R⁵ and R⁶ group or groups are (Ci-Ce) alkyl or benzyl.

The most preferred cationic surfactant is selected from cetyl-trimethylammonium bromide (CTAB), cetyl-trimethylammonium chloride (CTAC), behenyl-trimethylammonium chloride (BTAC), stearyl trimethyl ammonium chloride (STAC), benzyldimethyltetradecylammonium chloride (BDMTAC) and mixtures thereof.

Anionic surfactant can often disrupt the ability of the composition to form a hydrophobic coating. Thus it is preferred that surfactant (when present) is substantially free from anionic surfactant. More preferably less than 10% by total weight of surfactant in the composition is anionic surfactant, more preferably still less than 5% by weight, most preferably from 0 to 1% of the surfactant in the composition is anionic surfactant. Typically, the composition comprises surfactant in an amount of from 0.01 to 4% by weight.

However, even for cationic surfactants, high levels can, in some instances, interfere with the composition's ability to form hydrophobic coatings. Therefore it is preferred that the composition comprises less than 1%> surfactant by weight of the composition, more preferably less than 0.7%>, even more preferably less than 0.5% and most preferably from 0.05 to 0.3%.

In some embodiments the composition may be substantially free from surfactant. More preferably such compositions comprise less than 0.01% surfactant by weight of the composition, most preferably from 0 to 0.001%. The composition of the invention may have any suitable pH. However, it was surprisingly found that the stability of the compositions is best if they are slightly acidic. Thus it is preferred that the pH of the composition is in the range of 2 to 7, more preferably 3 to 5. The composition of the invention is used to prepare a hydrophobic coating.The method for making a hydrophobic coating on a surface preferably comprises the steps of applying the composition to a surface and allowing the composition to dry. The silanes may (further) polymerize during the drying process and undergo a so-called sol-gel transition. Without wishing to be bound by theory, the present inventors believe that polymerization of the silanes in the final coating composition may, in part, contribute to its excellent robustness.

Typically, after drying, the coating will comprise less than 30% solvent by weight of the coating, more preferably less than 20%, more preferably still less than 10% and most preferably from 0.001 to 5%.

The coating is hydrophobic. In some instances, for example, the coating may be ultrahydrophobic, or even superhydrophobic. More preferably, the coating may display a contact angle for water of at least 140 degrees or even from 150 to 160 degrees. Additionally or alternatively the coating may display a sliding angle for water of less than 15 degrees or even from 0.1 to 10 degrees.

The coating is typically at least translucent and often transparent. For example, the coating may display a transmittance value of at least 80%, more preferably at least 85% and most preferably from 87 to 95%.

The composition of the present invention is preferably suitable for treating a hard surface, especially to aid cleaning or soil-resistance of the hard surface. "Hard surface" for the purposes of the present invention means any surface comprising a hard material such as glass, glazed ceramics, metal, stone, plastics, lacquer, wood, or combination thereof. Typically, the hard surface is in a household including window, kitchen, bathroom, toilet, furniture, floor, or the like.

When treating a hard surface by the composition, any general way for treating a hard surface is acceptable. Typically, the way for treating a hard surface by the composition is spraying the composition onto the hard surface, or wiping the hard surface by wipe impregnated with the composition, or pouring the composition onto the hard surface, or combination thereof. Preferably, the way for treating a hard surface is spraying the composition onto a hard surface, and/or wiping a hard surface by wipe impregnated with the composition. When spraying is employed for treating a hard surface, there is no limitation how the composition is sprayed. Typically, a spraying bottle for hard surface cleaning product is favourable. When wiping is employed for treating a hard surface, wipe including woven or nonwoven cloth, natural or synthetic sponges or spongy sheets, "squeegee" materials, paper towel, or the like is suitable. The wipe may be impregnated dry, or more preferably in wet form.

Whilst not being bound by any particular theory or explanation, we believe that the composition exerts it effect by depositing hydrolyzed quaternary silane and/or its oligomer, and collodial particles onto a hard surface, forming a hydrophobic layer attached to the hard surface. The layer could enhance resistance to deposition of soil and/or stains or at least make such substances easier to remove.

Thus, after treating the surface with the composition, the method for treating a hard surface may optionally further comprises the steps of allowing soil and/or stains to deposit. Thus, the soil or stains will be easily removed when the hard surface is subsequently cleaned according to the method of this invention. Meanwhile, the composition of the invention is also preferably applied to the hard surface during the subsequent cleaning. Optionally, treating of a hard surface with the composition may be followed by a rinsing step, preferably with water.

Therefore a most preferred method for treating a hard surface comprises:

I. forming the hydrophobic coating on the surface;

Π. allowing soil and/or stains to deposit on the coating; and then

ΠΙ. cleaning the surface to remove the soil and/or stains.

The present invention may also deliver other benefits such as long last cleaning, less effort for cleaning, less surface corrosion, less noise during cleaning, and/or scratch resistance. Further aspects of the present invention comprise methods for obtaining one or more these other benefits in a hard surface cleaning operation and/or use the composition in the methods in the manufacture of products for delivering any one more such benefits mentioned in this invention. The soils and stains of present invention may comprise all kinds of soils and stains generally encountered in the household, either of organic or inorganic origin, whether visible or invisible to the naked eye, including soiling solid debris and/or with bacteria or other pathogens. Specifically the method and compositions according to the invention maybe used to treat surface susceptible to fatty or greasy soil and stains.

The composition of the invention may be made in any convenient way. Suitably, however, the composition is prepared by a process comprising the steps of:

i. foiming a reaction mixture comprising water and a first quatemary silane precursor; ii. hydrolyzing the first quatemary silane precursor in the reaction mixture to provide a first hydrolyzed quatemary silane and/or its oligomer; and

When foiming a reaction mixture comprising water and the first quatemary silane precursor, there is no limitation in respect to the sequence of mixing water and the first quatemary silane precursor. Either water is added into the first quatemary silane precursor, or the first quatemary silane precursor is added into water. Generally, stirring is used for making water and quatemary silane precursor well mixed.

Similarly, there is no limitation in respect to the sequence of combining the reaction mixture with the colloidal particles. However, in a preferred embodiment step (iii) occurs prior to or during step (ii) as in this way the colloidal particles may to a greater or lesser extent interact with the silanes during the hydrolysis process. Especially where the particles comprise silica, this may lead to some bonding of hydrolyzed silane with the particles as we have found that durability of the final coating is improved if compositions are prepared in this manner (although with a slight loss of transparency). Thus in an especially preferred embodiment the process comprises the following steps:

A) providing a reaction mixture comprising both partially hydrophobically-modified and partially hydrophilically-modified colloidal particle, a first quatemary silane precursor, and water; and then

B) hydrolyzing the first quatemary silane precursor in the reaction mixture to provide the first hydrolyzed quatemary silanes and/or its oligomer. In a more preferred embodiments step (iii) occurs prior to step (i) because in this case the colloidal particle may mix effectively in non-aqueous solvent and therefore this may lead to more robust coating. Thus in a more preferred embodiment the process comprises the steps of:

a) forming a pre-mixture comprising both partially hydrophobically-modified and partially hydrophilically-modified colloidal particle, first quatemary silane precursor, and nonaqueous solvent;

b) combining the pre-mixture with water to form a reaction mixture, and

c) hydrolyzing the first quatemary silane precursor in the reaction mixture to provide the first hydrolyzed quatemary silanes and/or its oligomer.

Preferably, second quatemary silane precursor may be hydrolyzed together with the first quatemary silane precursor to enhance the durability of the coating. The even more preferred process comprises the steps of:

I. forming a pre-mixture comprising colloidal particle, a first quatemary silane precursor, a second quatemary silane precursor, and non-aqueous solvent;

Π. combining the pre-mixture with water to form a reaction mixture; and

ΠΙ. hydrolyzing the first and second quatemary silane precursors to provide a first and second hydrolyzed quatemary silanes and/or their oligomers.

Excessive amounts of silane in the reaction mixture may lead to premature condensation polymerization and/or precipitation of the silanes. For example, the mixture may comprise the first quatemary silane precursor and the second quatemary silane precursor in a total amount of no more than 10% by weight of the mixture, more preferably no more than 7%, more preferably still no more than 5%, even more preferably no more than 2% and most preferably no more than 1%. The minimum amount of total silane (the amount of first quatemary silane precursor plus the amount of second quatemary silane precursor) is preferably at least 0.001% by weight of the mixture, more preferably at least 0.005%, more preferably still at least 0.01% and most preferably at least 0.02%. The weight ratio of the first quatemary silane precursor to the second quatemary silane precursor in the composition may be at least 1 :50, more preferably at least 1 :30, more preferably still at least 1 :20 and most preferably at least 1:10. To maximise hydrophobicity of the final coating, however, it is preferred that the weight ratio of the first quaternary silane precursor to the second quaternary silane precursor in the composition is no greater than 100:1, more preferably no greater than 20:1, more preferably still no greater than 5 : 1 and most preferably no greater than 1:1. Hydrolysis of the quaternary silane precursors could be carried out when the mixture is either acidic or alkali. To avoid excessive polymerization, the mixture is preferably acidic. More preferably, the pH value of the mixture is in the range of 2 to 7, most preferably 3 to 5. The lower the pH of the mixture is, the faster the hydrolysis of quaternary silane precursor will be. There is no limitation for the acid used to tune the pH of the mixture, for example, hydrochloric acid, sulphuric acid, citric acid, oxalic acid or combinations thereof may be used.

The reaction mixture may additionally comprise polar organic solvent.

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 following examples are provided to facilitate an understanding of the present invention. The examples are not provided to limit the scope of the claims.

EXAMPLES

Materials

Silica-1 refers to Aerosil^® R504, hexamethyldisilazane and aminosilane-modified silica particles (average primary particle size 12 nm) supplied by Evonic AG.

Silica-2 refers to Aerosil^® R812S, hexamethyldisilazane-modified silica particles (average primary particle size 7 nm) supplied by Evonic AG.

Silica-3 refers to Aerosil^® A200, hydrophilic fumed silica (average primary particle size 12 nm) supplied by Evonic AG.

HTMS was hexyltrimethoxysilane from Tokyo Chemical Industry Co., Ltd.

TEOS was tetraethylorthosilicate from Sinopharm Chemical Reagent Co.

All other materials were analytical grade unless otherwise stated.

Characterization of the particles

Three types of silicas were dispersed into different solutions according to Table 1.

Table 1

For dispersion I, it was prepared by mixing the silica powders and isopropanol under sonication for 30 min. For other dispersion, the silica powders were blended with isopropanol under sonication for 30 min. Then, water was added into the mixture with sonication for 5 min. When used, hydrochloric acid (36.5%) was added along with water.

The diameters were measured by Zetasizer Nano™ (Malvern Instruments Ltd, UK) for the aggregates with diameter no greater than Ιμιη and the apparent volume median diameters were measured by Mastersizer 2000 (Malvern Instruments Ltd, UK) for the aggregates with diameter of greater than 1 um. The number average diameters of silicas in different dispersion are shown in Table 2. In dispersion Π, the diameter of the aggregates by the colloidal particle of the present invention (silica-1) is about 2.45 times of diameter in dispersion I. In contrast, the hydrophobic colloidal particle without hydrophilic modification, silica-2 generated aggregates in dispersion Π of 50.7 times of diameter of aggregates in dispersion I. Similarly, in dispersion ΠΙ, silica-1 aggregated around 2.36 times of that in dispersion I, while in dispersion ΠΙ, silica-2 aggregated 33 times of that in dispersion I. Since dispersion Π and HI have more water than dispersion I, it is believed that the surface hydrophilicity of the colloidal particle of the present invention make it was better dispersed into dispersion with less water that the particle with only hydrophobic modification. When the colloidal particle was dispersed into dispersion with even less water, it was found that the colloidal particle of the present invention was easy to aggregate. In dispersion IV, the aggregates of colloidal particle of the present invention (silica-1) had about 5.15 times of diameter of aggregates in dispersion I. In comparison, the hydrophilic particle, Silica-3, only aggregated about 1.8 times in dispersion IV of that in dispersion I. Due to the less content of water, the colloidal particle of the present invention was more difficult to be dispersed than the hydrophilic particle without any hydrophobic modification.

Table 2

Preparation of Composition

The silicas were dispersed into isopropanol under stirring for 30 min at room temperature (25 °C). Then, the first quaternary silane precursor was added dropwise into the silica-silane mixture under stirring. If the composition comprises a second hydrolyzed silane, the second quaternary silane precursor was added dropwise along with the first quaternary silane precursor. After the addition of silane(s), the mixture was stirred for another 30 min. Hydrochloric acid (36.5 wt%) was diluted into water and then the diluted hydrochloric acid was added into the solution under stirring at room temperature for 3 hours to induce hydrolysis and condensation of the silane(s) and produce the compositions. Preparation of Coatings

Glass slides were chosen as model substrate. Pipette was used to drop the dispersions on the glass slide in a controlled amount. After the dispersion was dropped on the target surface, the tip of the pipette was used to spread the composition on the surface to ensure uniform coating. For spray coating, a trigger-sprayer which is widely used in home care or personal care products was used to apply the composition on surfaces. After the dispersion was sprayed towards the target surface, tissue or cloth was used to wipe the target surface in order to homogenize the coating and remove excess dispersion.

After application of the dispersion on the substrate, the solvent was allowed to evaporate (typical evaporation time was 10-15 min) at room temperature. It is expected that the silanes undergo further polycondensation on the substrate surface to form a durable coating during this drying and, at the same time, the silica particles are embedded in the resulting network.

Characterisation of Coatings

- Drop shape analysis system 100 (DSA 100, Kriiss) was used to measure contact angle and sliding angle. DSA 100 with the tilting table maximum utilization of field of view up to 90 degrees was used for sliding angle test using deionised water drops of around 5 uL applied to five different points of each film and the sliding angle averaged over all 5 drops.

The visible light transmittance of the coatings was measured by a UV-Vis spectrometer (Perkin- Elmer Lambda 650S).

Durability of the coating was characterized by comparing the contact angle (CA) and sliding angle (SA) before and after abrasion test. The abrasion test was conducted by a modified automatic film applicator (Model 1133-N, Sheen). The glass slide with coating was placed underneath a ballerina cloth which glued with weight perpendicular to the coating. The automatic film applicator pushed the ballerina cloth move forward to brush the coated glass slide once at a speed of 100 mm/s. The pressure of the abrasion test was calculated to divide the mass by surface contact area. The contact angles and sliding angles were tested by following the method described above.

Example 1

This example demonstrates the composition of the present invention can produce hydrophobic coating, and the incorporation of the second quatemary silane into the composition is capable of improving the durability of the obtained coating.

The compositions were prepared by combining the ingredient in amount as listed in Table 3 by following the procedure of preparation of particle-silane composition. Then, the compositions were used to produce a coating on glass slides by following the procedure of preparation of coatings. Abrasion tests were conducted on each coating. The contact angles of the coatings were measured both before and after the abrasion. The number of each sample matches the number of the coatings made from that sample.

Table 3

All the composition had water with amount of over 50 wt%. Even with such high concentration of water, the compositions of the present invention (sample 1 and 2) were capable of yielding a coating with a contact angle over 150° as can be seen in Table 4. Even after abrasion, the coatings were still hydrophobic, indicating that the durability of the coating is excellent.

By comparing the contact angles after abrasion of coating 1 and 2, it was found that the contact angle of the coating was increased around 30° by incorporating the second hydrolyzed quatemary silane into the composition. It was manifested that the inclusion of second hydrolyzed quatemary silane can improve the durability of the coatings. Table 4

The pressure of abrasion test is 3.2kPa.

Coating 3 was generated by composition comprising the second hydrolyzed quaternary but not the first hydrolyzed quaternary silane. As shown in Table 4, a hydrophilic coating was generated. The incorporation of the first hydrolyzed quaternary silane is necessary to yield a hydrophobic coating.

Example 2

This example demonstrates the composition comprising colloidal particle which is both partially hydrophobic and partially hydrophilic can yield more hydrophobic coatings both before and after abrasion than other particles.

The compositions were prepared according to Table 5 and other experiments were similar with that in Example 1. The number of each sample matches the number of the coatings made from that sample.

Table 5

Table 6 shows the contact angles of coatings before and after the abrasion test by compositions comprising colloidal particles of the present invention, hydrophobic particles, and hydrophilic particles respectively. It was unexpectedly found that the contact angles were highest both before and after abrasion generated by the composition of the present invention among these three compositions. The colloidal particle which is partially hydrophobic and partially hydrophilic in composition with high amount of water was capable of yielding most hydrophobic coating both before and after abrasion among the three types of particles.

Table 6

'he pressure of abrasion test is 3.2kPa.

Example 3

This example demonstrates the composition comprising water in different amount yielded hydrophobic coatings.

The compositions were prepared according to Table 7 and other experiments were similar with that in Example 1. The number of each sample matches the number of the coatings made from that sample. The transmittances of coated glass slides were measured. The coherency of coating was also evaluated. The coated glass slide was completely immersed in a beaker filled with water for 5s. The slide was then removed vertically from the beaker, and any water remained on the back side of the glass slide was wiped away using paper towel. A rating (1-5) was given based on the amount of water residue observed by naked eyes on the side with coating. The more the water droplets remained, the lower the rating would be. Table 7

Silica- 1 TEOS HTMS Water HC1 Isopropanol

Sample

(wt%) (wt%) (wt%) (wt%) (wt%) (wt%)

3 0.66 0.97 0.21 33.14 0.07 To 100

4 0.63 0.93 0.20 51.65 0.07 To 100

5 0.60 0.89 0.19 68.68 0.07 To 100

6 0.59 0.87 0.19 76.69 0.07 To 100 As can be seen in Table 8, the contact angles of coatings produced by compositions of present invention with 76 wt% of water (sample 6) had contact angles greater than 140°. All other compositions with less water than sample 6 yielded coatings having contact angles even greater than 160°. Even after abrasion, the contact angles of all coatings had contact angles over 110°, demonstrating the excellent durability.

Table 8

¾e pressure of abrasion test is 2kPa. The transparency of each coating was very good. The coating was almost invisible on glass slides to naked eyes. According to the transmittance results, coatings 6 were slightly better than other coatings in transparency. The coherency of coatings was also evaluated as shown in the last column of Table 8. The coherencies of coatings 3, 4 and 5 were extremely excellent without noticeable water droplet. The coherency of coatings 6 was slightly poorer than other three coatings, with a few water droplets, which may be caused by the high amount of water in the composition.

Claims

1. A composition comprising:

a) colloidal particle;

b) a first hydrolyzed quatemary silane having at least one hydrophobic ligand and/or its oligomer; and

c) solvent;

2. The composition according to claim 1 wherein the colloidal particle is silica particle, preferably fumed silica particle.

3. The composition according to claim 2 wherein the silica particle comprises at least one of the following groups

- 0 - Si (CH₃)₃ (I)

O— Si C ₈ H 17 (HI)

o or

and at least one group selected from -OH, -SH, and -NH₂.

4. The composition according to any one of the preceding claims wherein the colloidal particle is present in amount of from 0.001 to 8% by weight of the composition.

5. The composition according to any one of the preceding claims, wherein the first hydrolyzed quaternary silane is hydrolyzable from a first quaternary silane precursor having the formula (RVm SitR²^, wherein:

each R¹ is independently selected from alkoxy and halogen;

R is selected from alkyl, alkenyl, fluoroalkyl, fiuoroalkenyl, aryl, fluoroaryl and combinations thereof; and

m = 1 or 2. 6. The composition according to claim 5 wherein R comprises at least 2 carbon atoms, preferably R² is C₃-C₃₀. 7. The composition according to claim 5 or claim 6, wherein m = 1. 8. The composition according to any one of the preceding claims wherein the first hydrolyzed quaternary silane is present in amount of from 0.05 to 5% by weight of the composition. 9. The composition according to any one of the preceding claims wherein the weight ratio of the colloidal particle to the first hydrolyzed quaternary silane is from 10: 1 to 1 : 1.

The composition according to any one of the preceding claims wherein the solvent comprises a polar organic solvent, preferably wherein the polar organic solvent comprises C₁-C4 alcohol.

The composition according to any one of the preceding claims wherein the solvent comprises water, preferably in amount of from 30 to 90% by weight of the solvent.

12. The composition according to any one of the preceding claims wherein the composition comprises a second hydrolyzed quatemary silane having four hydroxyl ligands and/or its oligomer.

13. The composition according to claim 12, wherein the second hydrolyzed quatemary silane is hydrolyzable from a second quatemary silane precursor having the formula (R¹^ Si, wherein each R¹ is independently selected from alkoxy and halogen.

14. The composition according to claim 13, wherein the second quatemary silane precursor comprises tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrabromosilane, tetrachlorosilane, or a mixture thereof.

15. The composition according to any one of the preceding claims, wherein the weight ratio of the first hydrolyzed silane to the second hydrolyzed silane is from 1:30 to 1:1, preferably from 1:10 to 1:2.

16. The composition according to any one of the preceding claims wherein the first and second quatemary silanes are present in a total amount of from 0.01 to 10% by weight of the composition.

17. A method for forming a hydrophobic coating on a surface, the method comprising applying the composition of any one of the claims 1 to 16 to the surface and drying the composition to yield the hydrophobic coating.

18. A hydrophobic coating obtainable by the method of claim 17 wherein the coating displays a contact angle for water of at least 120 degrees.

19. A process for the preparation of a composition of any one of claims 1 to 16, wherein the process comprises the steps of:

i. forming a reaction mixture comprising water and a first quatemary silane precursor; ii. hydrolyzing the first quatemary silane precursor in the reaction mixture to provide a first hydrolyzed quatemary silane and/or its oligomer; and

iii. combining the reaction mixture with colloidal particle which is both partially hydrophobic and partially hydrophilic.

20. The process according to claim 19, wherein the process comprises the steps of:

I. forming a pre-mixture comprising colloidal particle, a first quatemary silane precursor, a second quatemary precursor, and non-aqueous solvent;

Π. combining the pre-mixture with water to form a reaction mixture; and