PD052697IN-SC
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: A SLURRY COMPOSITION AND PROCESSES THEREOF
2. Applicant(s)
NAME
NATIONALITY
ADDRESS
ASIAN PAINTS LTD.
Indian
Research & Technology Center, Asian Paints Limited, C3-B1, TTC MIDC, Pawane Village, Turbhe, Navi Mumbai – 400703, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it is to be performed.
1
FIELD OF INVENTION
[0001]
The present disclosure broadly relates to a paint composition. In particular, the present disclosure provides a slurry composition, a paint composition, and processes thereof.
5
BACKGROUND OF INVENTION
[0002]
The application of paint on the surface of an article helps in blocking the direct exposure to harsh conditions which lead to withering and tearing of the article. Moreover, paint compositions are applied for decorative purposes to add color, lustre and finishing to an object. Nowadays, the paint compositions have 10 explored various additional properties such as self-cleaning, antimicrobial activity, dust-free and odour-free properties by incorporating specific additives in the coating compositions.
[0003]
Currently, paint compositions focus on mitigating the challenges of microbial infection that can lead to foul odours, staining and material degradation. 15 In view of this, the demand for antimicrobial paint compositions has increased substantially. However, the antimicrobial actives which are commercially available are costly and cannot be economically feasible for use in large scale applications. A better approach identified to economically utilize antimicrobial actives in paint compositions is by synthesising antimicrobial actives in high concentrations. 20 However, the stability and commercial viability of such high concentration actives are still challenging. Additionally, the stable antimicrobial actives prepared using economical reagents and synthesis routes may still face the problem of ineffective incorporation into paint compositions.
[0004]
Thus, the interest in water-based paint compositions has grown due to high 25 durability, better adhesion, greater flexibility, lower toxicity, ease of processing and many more. Incorporating antimicrobial actives in high concentration into a water-based paint composition to achieve antimicrobial water-based paint compositions, is still more challenging in aspects of large-scale manufacture. This is due to the economic factors, and compatibility issues of processing aids which have to be 30 employed along with the incorporation of antimicrobial actives into water-based 2
paint composition
in order to maintain stability and still exhibit antimicrobial activity. Hence, there is a dire need in the art to develop a stable composition to facilitate the direct incorporation of the composition into a water-based paint composition without any processing aids.
5
SUMMARY OF THE INVENTION
[0005] In a first aspect of the present disclosure, there is provided a slurry composition comprising: (a) 35 to 45 % by weight of a metal nanoparticle dispersion; (b) 11 to 20% by weight of at least one additive; and (c) 40 to 50% by weight a pigment-extender mixture, wherein the metal nanoparticle dispersion 10 comprises 0.3 to 2% (w/w) a plurality of metal nanoparticles in a particle size range of 1 to 100nm.
[0006] In a second aspect of the present disclosure, there is provided a process of preparing the slurry composition as disclosed herein, said process comprising: (a) adding the first additive to the metal nanoparticle dispersion to obtain a first 15 mixture; (b) charging the pigment-extender mixture to the first mixture to obtain a second mixture; and (c) contacting the second additive with the second mixture and stabilizing to obtain the slurry composition.
[0007] In a third aspect of the present disclosure, there is provided a water-based paint composition comprising (a) the slurry composition as disclosed herein; and 20 (c) at least one third additive.
[0008] In a fourth aspect of the present disclosure, there is provided process of preparing the water-based paint composition as disclosed herein, said process comprising: contacting at least one third additive with the slurry composition to obtain the paint composition. 25
[0009] In a fifth aspect of the present disclosure, there is provided a coating composition comprising: the stable dispersion as disclosed herein; and at least one coating additive.
[00010] In a sixth aspect of the present disclosure, there is provided a method of forming multilayer coating film comprising: applying the water-based paint 30 3
composition as
disclosed herein on to a coating object optionally followed by water-based intermediate coating and top coating to obtain a coating film.
[00011] In a seventh aspect of the present disclosure, there is provided articles coated by the method as disclosed herein.
[00012]
These and other features, aspects, and advantages of the present subject 5 matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 10
DESCRIPTION OF THE INVENTION
[00013] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and 15 modifications. The disclosure also includes all such steps, features, compositions, and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features.
Definitions
[00014] For convenience, before further description of the present disclosure, 20 certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth 25 below.
[00015] The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.
[00016] The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be 30 construed as “consists of only”.
4
[00017] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. 5
[00018] The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.
[00019] The term “metal nanoparticle dispersion” refers to the dilute mixture of a plurality of metal nanoparticle dispersed in a medium or a solvent.
[00020] The term “stable dispersion” refers to the dilute mixture of a metal 10 nanoparticle capped with a stabilizer in high concentration dispersed in a solvent mixture of water and at least one polyol along with a reducing agent.
[00021] The term “metal nanoparticle” and “plurality of metal nanoparticle” are used interchangeably. In an aspect of the present disclosure, the metal nanoparticle is a silver nanoparticle having a particle size in a range of 1 to 100 nm. In an aspect 15 of the present disclosure, the metal nanoparticles have a size in a range of 1 to 100 nm, preferably 1 to 50 nm.
[00022] The term “additive” refers to an add-on component in a specific composition. in an aspect of the present disclosure, the comprises 7 to 12% by weight of a first additive and 4 to 8% by weight of a second additive. The terms 20 “first additive” and “second additive” refer to assortments of one or more chemical additives which are added to the slurry composition for obtaining a stable slurry composition. The term “third additive” refers to an assortment of chemical additives which are added to the water-based paint composition in order to enhance the properties of the composition for use as a coating composition. 25
[00023] The term “pH regulator” refers to a chemical reagent which regulates or maintains the pH of a reaction mixture or a system in a specific pH range; the term “defoamer” and “anti-foaming agent” are used interchangeably to refer to chemical additives that eliminate existing foam and prevent the formation of further foam production while industrially processing the liquids and dispersion; the term 30 “preservative” refers to the chemical additives that help in extending the life of the 5
active components of a composition while processing and/or after manufacturing
the composition; the term “thickener” refers to the chemical additive that adds to the bulk of a composition without affecting the chemical and physical properties of the constituents of the composition; the terms “dispersant”, refer to the chemical additive which reduces the surface tension of the individual components of a 5 solution and thereby increasing the dispersibility and wettability of the components; and the term “solvent” refers to the liquid component in a reaction mixture or a solution in which the other components are dispersed in order to facilitate the reaction or disperse multiple components in a single system. In an aspect of the present disclosure, the solvent is selected from a first solvent or a second solvent. 10
[00024] The term “rheology modifier” refers to the chemical additive or assortment which is added to a composition to impart better flowability and control the consistency or viscosity of the composition.
[00025] The term “pigment” refers to the colouring agent which imparts a particular color into the composition to which it is added; and the term “extender” refers to 15 the chemical additives added to a composition to modify the flow properties, glossiness, surface topography and the mechanical and permeability characteristics of the composition. In an aspect of the present disclosure,
[00026] The term “binder” refers to substance used in a composition to bind the components of said composition together; an “adhesive” refers to the substance 20 used to ensure the composition in which the adhesive is added to enhance the adhesion property of the constituents of said composition to a surface upon which the composition has been coated for a long time especially under harsh conditions; a “promoter” refers to a chemical composition which is added to a composition to enhance the properties of the substrate such as adhesion, cohesion, and blending of 25 the constituents of the composition; the term “filler” refers to the substance(s) incorporated into a composition to enhance the bulk of the composition without affecting the physical and chemical properties of the composition; a “solubilizer” refers to the substance is added to a composition in order to solubilize or disperse the specific components in a particular solvent; the term “anti-caking agent” refers 30 to the chemical additive added to a composition to and a “surfactant” refers to the
6
additive which reduces the surface tension of the individual components of a
solution and thereby increasing the dispersibility and wettability of the components.
[00027] The term “slurry composition” refers to the composition comprising at least one additive and an active component in the form of a slurry form so as to facilitate the efficient incorporation of the active components into a composition 5 without the usage of additional processing aid and can be stable for an appreciable period of time.
[00028] The term “inorganic pigment” refers to an inorganic chemical substance added to a composition to impart a specific color to the composition. In an aspect of the present disclosure, the inorganic pigment is titanium dioxide. 10
[00029] The term “extender” refers to the chemical additive incorporated into a composition to enhance the flowability, glossiness, surface topography, and the mechanical and permeability of the composition. In an aspect of the present disclosure, the extender is selected from calcium carbonate, aluminium silicate, or combinations thereof. 15
[00030]
The term “water-based paint composition” refers to the paint composition wherein the composition comprises water in a weight range of 25 to 40 % with respect to the total weight of the composition.
[00031]
The term “antimicrobial coating” refers to the coating composition which can be used to exhibit the antimicrobial property of inhibiting the growth or 20 existence of microorganisms on the surface of an article by coating the antimicrobial coating over the surface of the article.
[00032]
Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to 25 include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, 0.3 to 1.5% should be interpreted to include not only the explicitly recited limits of 0.3 to 1.5% but also to include sub-ranges, such as 0.5 to 1.2%, 1.1 to 30 1.5%, 0.99 to 1.11%, and so forth, as well as individual amounts, including 7
fractional amounts, within the specified ranges, such as
0.356%, 0.112%, and so on.
[00033] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or 5 equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.
[00034]
As discussed in the background, water-based paint compositions which possess anti-microbial activity are in high demand these days. However, there are 10 many challenges to developing such an antimicrobial surface coating composition in an economically and conveniently viable method. The major challenge which has to be addressed on this behalf is the economic viability of the antimicrobial additives. The commercially available antimicrobial additives used in surface coating compositions are highly expensive and inconvenient for use in 15 compositions. Hence, in search of alternatives for antimicrobial additives for use in surface coating applications, metal nanoparticles, particularly silver nanoparticles, were observed to exhibit high antimicrobial properties. However, though synthesis of a dispersion comprising silver nanoparticles in high concentration could be achieved, the stability of the dispersion was observed to be difficult to attain due to 20 the increasing agglomeration of silver nanoparticles with increasing concentration. Moreover, it was observed that the stable silver nanoparticle dispersion was strenuous to be employed in the paint composition while processing due to the presence of various reducing agents and stabilizers. In view of the above-mentioned challenges, there is a dire need in the art to develop a stable composition to 25 incorporate the silver nanoparticle dispersion into a water-based paint composition without harsh conditions or costly processing aids. Accordingly, the present disclosure provides a slurry composition comprising silver nanoparticles as an antimicrobial agent, which could be easily employed in a water-based paint composition without any additional processing aids. 30 8
[00035]
In an embodiment of the present disclosure, there is provided a slurry composition comprising: (a) a metal nanoparticle dispersion; (b) at least one additive; and (c) a pigment-extender mixture.
[00036]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the metal nanoparticle dispersion 5 comprises 0.3 to 2% (w/w) a plurality of metal nanoparticles in a particle size range of 1 to 100nm. In another embodiment of the present disclosure, a plurality of metal nanoparticles is in a particle size range of 1 to 50nm. In another embodiment of the present disclosure, the metal nanoparticle dispersion comprises 0.4 to 1.5% (w/w) of a plurality of metal nanoparticles. In yet another embodiment of the present 10 disclosure, the metal nanoparticle dispersion comprises 0.5 to 1% (w/w) a plurality of metal nanoparticles.
[00037]
In an embodiment of the present disclosure, there is provided a slurry composition comprising: (a) 35 to 45 % by weight of a metal nanoparticle dispersion; (b) 11 to 20% by weight of at least one additive; and (c) 40 to 50% by 15 weight a pigment-extender mixture, wherein the metal nanoparticle dispersion comprises 0.3 to 2% (w/w) a plurality of metal nanoparticles in a particle size range of 1 to 100nm.
[00038]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the metal nanoparticle is a silver 20 nanoparticle.
[00039]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the metal nanoparticle dispersion is in a weight range of 35 to 52 % with respect to the total weight of the slurry composition; the additive is in a weight range of 11 to 20%; and the pigment-25 extender mixture is in a weight range of 40 to 50%. In another embodiment of the present disclosure, the metal nanoparticle dispersion is in a weight range of 37 to 42 % with respect to the total weight of the slurry composition; the additive is in a weight range of 12 to 19%; and the pigment-extender mixture is in a weight range of 42 to 48%. In yet another embodiment, the metal nanoparticle dispersion is in a 30 9
weight range of
45 to 52 % with respect to the total weight of the slurry composition.
[00040]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the at least one additive comprises a first additive and a second additive. 5
[00041]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the at least one additive comprises 7 to 12% by weight of a first additive and 4 to 8% by weight of a second additive.
[00042]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the first additive is selected from a pH 10 regulator, a defoamer, a preservative, a thickener, a dispersant, a first solvent, or combinations thereof; and the second additive is selected from a second solvent, a rheology modifier, or combinations thereof.
[00043]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the pH regulator is selected from 15 substituted alcohols, amino alcohols, primary amines, secondary amines, tertiary amines, or combinations thereof; the defoamer is selected from hydrocarbon-oil based compounds, mineral oil-based compounds, silicone-based compounds, or combinations thereof; the preservative is selected from thiazolinones, carbamates, diuron, alkylene glycol, polyols, acrylate polymers, cellulose ethers, or 20 combinations thereof; the thickener is selected from hydrophobically modified polyether, hydrophobically ethoxylated urethane polymers, or combination thereof; the dispersant is selected from poly carboxylic acids, polyols, ethoxylates, maleic anhydride-diisobutylene copolymer, acrylic/methacrylate copolymer, or combinations thereof; the first solvent is an alcohol; the second solvent is water; the 25 rheology modifier is selected from polyurethane, ethylene glycol ether, or combinations thereof.
[00044]
In another embodiment of the present disclosure, the pH regulator is a substituted alcohol, particularly 2-amino-2-methyl-1-propanol; the defoamer is a hydrocarbon-oil based compound; the preservative is selected from thiazolinones, 30 carbamates, diuron, alkylene glycol, polyols, acrylate polymers, cellulose ethers, or
10
combinations thereof;
the thickener is a hydrophobically modified polyether; the dispersant is a poly carboxylic acid; the first solvent is an alcohol; the second solvent is water; and the rheology modifier is polyurethane in ethylene glycol ether or polyurethane in water. In yet another embodiment of the present disclosure, the first solvent is ethoxylated C3-15 primary alcohol. 5
[00045]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the pigment-extender mixture comprises an inorganic pigment, and an extender selected from calcium carbonate, aluminium silicate, or combinations thereof. In another embodiment of the present disclosure, the inorganic pigment is titanium dioxide, and the extender is a combination of 10 calcium carbonate, and aluminium silicate.
[00046]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the inorganic pigment is titanium dioxide.
[00047]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, comprising: (a) a metal nanoparticle dispersion 15 having 0.3 to 1.5% (w/w) a plurality of silver nanoparticles in a particle size range of 1 to 100nm; (b) at least one additive comprising a first additive selected from a pH regulator, a defoamer, a preservative, a thickener, a dispersant, a first solvent, or combinations thereof, and a second additive selected from a second solvent, a rheology modifier, or combinations thereof; and (c) a pigment-extender mixture 20 comprising titanium dioxide as an inorganic pigment, and a combination of calcium carbonate, and aluminium silicate, as extender.
[00048]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein, wherein the slurry composition has a viscosity in a range of 120-145 KU. 25
[00049]
In an embodiment of the present disclosure, there is provided a process of preparing the slurry composition as disclosed herein, said process comprising: (a) adding the first additive to the metal nanoparticle dispersion to obtain a first mixture; (b) charging the pigment-extender mixture to the first mixture to obtain a second mixture; and (c) contacting the second additive with the second mixture and 30 stabilizing to obtain the slurry composition.
11
[00050]
In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the metal nanoparticle dispersion is stirred at a speed in a range of 400 to 600 rpm for a time period in a range of 5 to 20 minutes, prior to addition of the first additive.
[00051]
In an embodiment of the present disclosure, there is provided a process as 5 disclosed herein, wherein step (a) is carried out while stirring in a closed high shear disperser, for a time period in a range of 10 to 30 minutes at a speed in a range of 500 to 1000 rpm.
[00052]
In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein step (b) is carried out while blending for a time period in 10 a range of 40 to 80 minutes at a speed in a range of 1400 to 2200 rpm.
[00053]
In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the stabilizing of step (c) is carried out for a time period in a range of 10 to 30 minutes at a speed in a range of 700 to 1100 rpm.
[00054]
In an embodiment of the present disclosure, there is provided a process of 15 preparing the slurry composition as disclosed herein, said process comprising: (a) stirring a metal nanoparticle dispersion at a speed in a range of 400 to 600 rpm for a time period in a range of 5 to 20 minutes; (b) adding the first additive to the stirred metal nanoparticle dispersion while stirring in a closed high shear disperser, for a time period in a range of 10 to 30 minutes at a speed in a range of 500 to 1000 rpm 20 to obtain a first mixture; (b) charging the pigment-extender mixture to the first mixture while blending for a time period in a range of 40 to 80 minutes at a speed in a range of 1400 to 2200 rpm to obtain a second mixture; and (c) contacting the second additive with the second mixture and stabilizing to obtain the slurry composition. 25
[00055]
In an embodiment of the present disclosure, there is provided a water-based paint composition comprising: (a) the slurry composition as disclosed herein; and (b) at least one third additive.
[00056]
In an embodiment of the present disclosure, there is provided a water-based paint composition as disclosed herein, wherein at least one third additive is 30 12
selected from binder, adhesive, solvent, promoter, surfactant, solubilizer, anti
-caking agent, filler, anti-foaming agent, biocide, or combinations thereof.
[00057]
In an embodiment of the present disclosure, there is provided a water-based paint composition as disclosed herein, wherein the slurry composition is in a weight range of 0.5 to 1.5% with respect to the total weight of the paint composition. 5 In another embodiment of the present disclosure, the slurry composition is in a weight range of 0.9 to 1.2% with respect to the total weight of the paint composition. In yet another embodiment of the present disclosure, the slurry composition is in a weight of 1% with respect to the total weight of the paint composition.
[00058]
In an embodiment of the present disclosure, there is provided a water-10 based paint composition as disclosed herein, wherein the paint composition has an antimicrobial property.
[00059]
In an embodiment of the present disclosure, there is provided a process of preparing the water-based paint composition as disclosed herein, said process comprising: (a) contacting at least one third additive with the slurry composition to 15 obtain the paint composition.
[00060]
In an embodiment of the present disclosure, there is provided a process of preparing the water-based paint composition as disclosed herein, wherein the contacting is carried out while mixing for a time period in a range of 40 to 80 minutes at a speed in a range of 1400 to 2200 rpm. 20
[00061]
In an embodiment of the present disclosure, there is provided a process of preparing the water-based paint composition as disclosed herein, said process comprising: (a) contacting at least one third additive with the slurry composition while mixing for a time period in a range of 40 to 80 minutes at a speed in a range of 1400 to 2200 rpm to obtain the paint composition. 25
[00062]
In an embodiment of the present disclosure, there is provided a slurry composition as disclosed herein or the water-based paint composition as disclosed herein, for use as an antimicrobial coating.
[00063] In an embodiment of the present disclosure, there is provided a method of forming multilayer coating film comprising: applying the water-based paint 30 13
composition as disclosed herein, on to a coating object optionally followed by water-based intermediate coating and top coating to obtain a coating film.
[00064] In an embodiment of the present disclosure, there is provided articles coated by the method as disclosed herein.
[00065]
Although the subject matter has been described in considerable detail with 5 reference to certain examples and implementations thereof, other implementations are possible.
EXAMPLES
[00066]
The disclosure will now be illustrated with working examples, which is 10 intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described 15 herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices, and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.
20
Example 1
Preparation of a stable dispersion
[00067]
About 8.91 g of dioctyl sulfosuccinate (DOSS, i.e., stabilizer) was added to a solvent containing 76 mL of water and 76 mL of propylene glycol (polyol) while stirring followed by heating to 60°C for complete dissolution of DOSS to 25 obtain a stabilizer solution. The whole of the stabilizer solution was divided into two equal parts, say the first part and the second part. To the first part of the stabilizer solution, 8.3 g of L-ascorbic acid (reducing agent) was added while continuously stirring and maintaining the temperature at 60°C to obtain a reducing solution. 30 14
[00068]
To the second part of the stabilizer solution, about 2.7 g of silver nitrate (metal salt) was added while stirring and maintaining temperature at 60°C to obtain an intermediate metal salt dispersion.
[00069]
The reducing solution was contacted to intermediate metal salt dispersion under stirring at a transfer rate of 10 mL/min while maintaining the temperature at 5 60°C. The dispersion was stirred further for 30 mins to obtain a dark greenish yellow coloured stable dispersion comprising silver nanoparticles.
[00070]
Theoretical calculations performed for the obtained stable dispersion resulted in about 1g/L concentration of silver nanoparticles in a whole of the dispersion. 10
Preparation of a slurry composition
[00071]
About 40% by weight of the stable dispersion obtained by the process as explained above was charged into a high-speed disperser and stirred for about 10 minutes at 500 rpm. To the dispersion, first additive was added. About 0.38 % by 15 weight of 2-amino-2-methyl-1-propanol (pH adjuster) was added to the dispersion followed by 0.9% by weight of hydrocarbon oil-based defoamer while stirring at 700rpm. Once the pH adjuster and defoamer was homogenised completely in the dispersion, 0.2% by weight of an aqueous solution of 2-n-octyl-4-isothizoline (preservative), 4.1% by weight of hydrophobically modified ether (thickener), 20 2.64% by weight of poly carboxylic acid-based compound (dispersant) and 0.98% by weight of ethoxylated C13-alcohol were added to the dispersion mixture in the provided sequence, one by one upon homogenisation of the previously added first additive while stirring. After the addition of the first additives as provided above into the dispersion, the dispersion with first additives was stirred for 15 minutes at 25 700rpm to obtain first mixture. Subsequently, the pigment-extender mixture comprising 20% by weight of titanium dioxide i.e., pigment, 10 % by weight of calcium carbonate and 15% by weight of dehydroxylated aluminium silicate were added to the first mixture sequentially under stirring at 1800rpm and stirring was continued for 1 hour at 1800rpmto obtain a second mixture. The second mixture 30 15
was then
contacted with an assortment of second additive comprising a 0.2% by weight of rheology modifier and about 5.75% by weight of water followed by stabilizing at 900rpm for 10 minutes to obtain the slurry composition in beige colour.
[00072]
When any one of the process parameters was varied from the above-5 mentioned values to a greater extent or the sequence of addition of the various additives was perturbed, the obtained slurry composition was not beige but grey-coloured. The grey colour of the obtained slurry composition indicated the non-uniform particle size of the silver nanoparticles and the instability of the particles in the slurry composition. The pH of the slurry composition obtained was recorded 10 to be 7.23 and the Brookfield viscosity of the slurry composition was recorded as 125KU. It was observed that when silver dispersion content was present outside the working range of 35 to 45% by weight, the slurry turned to grey color, and the paint made using these slurries failed in both antibacterial property (giving results < 90%, which is not acceptable) as well as anti-fungal results (< 7 rating). 15
Example 2
Preparation of composition B using a comparative process
[00073]
The present example explains the process of preparation for the composition wherein the sequence of charging the components are reversed. 20
[00074]
In another example, instead of adding the first additives to the metal nanoparticle dispersion to obtain a first mixture as disclosed in the process of Example 1, the metal nanoparticle dispersion was added to a mixture of first additives (comprising 0.9% by weight of hydrocarbon oil-based defoamer, 0.2% by weight of an aqueous solution of 2-n-octyl 4-isothizoline (preservative), 4.1% by 25 weight of hydrophobically modified ether (thickener), 2.64% by weight of poly carboxylic acid-based compound (dispersant) and 0.98% by weight of ethoxylated C13-alcohol) was added under same experimental conditions as explained in Example 1 to obtain a mixture. The mixture was then added with a pigment-extender mixture and second additives as mentioned in Example 1, under stirring 30 to obtain a composition which was found to be unstable. The composition turned to 16
grey colour indicating non
-uniform particle size of the silver nanoparticles and instability of the nanoparticles in the composition.
Example 3
Preparation of a composition C without the use of thickener and rheology 5 modifier
[00075]
In another example, a composition C was prepared by the process as explained in the Example 1, but without the use of thickener (first additive; hydrophobically modified ether) and a rheology modifier (second additive; polyurethane in ethylene glycol ether). The composition C was found to be grey in 10 colour pointing towards undesirable particle size of silver nanoparticles leading to instability of the composition C.
Example 4
Preparation of water-based paint composition 15
[00076]
The slurry composition prepared by the process as explained in Example 1 was incorporated into a water-based paint composition. A water-based paint composition was prepared by contacting 1% by weight of the slurry composition obtained the process as explained in Example 1 to a plurality of third additive which comprises binder, adhesive, solvent, promoter, surfactant, solubilizer, anti-caking 20 agent, filler, anti-foaming agent, and zinc pyrithione as biocide with grinding to obtain the paint composition. The slurry composition was incorporated into the water-based paint composition directly without any harsh reaction conditions or processing aids. Thus, the present disclosure provides a stable yet processable slurry composition comprising about 0.5% by weight of silver nanoparticles to incorporate 25 the antimicrobial active dispersion into a water-based paint composition.
[00077]
Similarly, paint compositions were prepared using the composition B obtained by the process as explained in Example 2 and composition C obtained by the process as explained in Example 3, in place of the slurry composition.
Preparation of a coated article 30 17
[00078]
The water-based paint composition obtained by the process as explained above was then applied onto a coating object followed by subjecting to curing to obtain a multilayer coating film over an article. The water-based intermediate coating is applied for imparting the advantages of a multilayer film with better resistance to chipping and moisture, enhanced adaptability with a top coating, good 5 adhesion, and cohesion properties with coated article surface and layers of the multilayer coating. Top coating is a finishing coating composition that is applied to an underlying primer paint, base coat paint or other coating for a decorative or protective finish.
10
Example 5
Characterization of the stable dispersion.
a. Stability analysis
[00079]
The stability of the slurry composition obtained by the process as explained in example 1, was analysed. The beige-coloured stable slurry 15 composition obtained by the process as explained in example 1 was transferred into a glass bottle, closed airtight, covered with aluminium foil, and kept in dark for observation after 15 days.
[00080]
To analyse the stability of a slurry composition in elevated temperature, the slurry composition obtained by the process as explained in example 1 was 20 transferred into a glass bottle, closed airtight, covered with aluminium foil, and kept in oven at 55°C for 15 days.
[00081]
The slurry composition was found to be stable for at least 15 days at room temperature with no change in colour; the Brookfield viscosity was observed to change from 125KU to 130KU; and the pH was observed to be 6.7. 25
[00082]
The slurry composition was found to be stable for at least 15 days at 55°C with no change in colour; the Brookfield viscosity was observed to change from 125KU to 140KU; and the pH was observed to be 6.2.
[00083]
It was concluded that the slurry composition showed variation in pH and viscosity to a very small extend at room temperature and at an elevated temperature 30 of 55°C. Therefore, the slurry composition was observed to be stable.
18
b. Analysis of antimicrobial property
[00084]
The antimicrobial property of the water-based paint composition comprising the slurry composition obtained by the process as explained in Example 1, was analysed. 5
[00085] The water-based paint composition was subjected to washability test and oven stability test for 15 days to analyze the stability of the composition against leaching out from the coating matrix when subjected to harsh environmental conditions. The antibacterial and antifungal activities of water-based paint composition; as such composition, composition after washability and oven stability 10 tests were evaluated by subjecting them to a bacterial culture derived from the standard method JIS Z 2801. The results are compared with a commercially available paint composition which employed costly biocides and antimicrobial additives instead of the slurry composition, as depicted in Table 1.
Table 1 15
Sr No.
Sample
Fresh paint
15 days oven stability
Post washability
2 Hrs
24 Hrs
2 Hrs
24 Hrs
2 Hrs
24 Hrs
1
Commercially available paint composition
>99%
Acceptable
>99%
Acceptable
>99.9%
Acceptable
>99.9%
Acceptable
>99%
Acceptable
>99.9%
Acceptable
2
Water-based paint composition of the present disclosure
>99%
Acceptable
>99%
Acceptable
>99.9%
Acceptable
>99.9%
Acceptable
>99%
Acceptable
>99.9%
Acceptable
[00086]
The antibacterial results as depicted in the Table 1 above provided the conclusion that the water-based paint composition of the present disclosure exhibited impressive antimicrobial activity in comparison to the commercially 20 available paint composition. Hence, despite the absence of costly biocides and antimicrobial actives, the water-based paint composition of the present disclosure 19
exhibited appreciable antimicrobial activity using a dispersion comprising higher
concentration (0.5% w/w) of silver nanoparticles as a commercially viable antibacterial active.
[00087]
The water-based paint compositions prepared using the slurry compositions B and C, did not exhibit desired antimicrobial activity. Hence, it was 5 derived that the antimicrobial activity of the paint compositions diminished when the process of preparation of slurry was not followed as provided in the present disclosure (as in the case of composition B) or when the additives were not employed as provided in the present disclosure (as in the case of composition C).
Antibacterial evaluation: 10
[00088]
The antibacterial results provided the conclusion that the water-based composition of the present disclosure exhibited impressive antimicrobial activity in comparison to the commercially available paint composition. Hence, the water-based paint composition of the present disclosure exhibited appreciable antimicrobial activity using a stable slurry composition with high concentration of 15 silver nanoparticles as a commercially viable antibacterial active in the form of a stable slurry composition for use in the preparation of paint.
Antifungal evaluation:
[00089] The water-based paint composition of the present disclosure and a 20 commercially available paint composition were parallelly exposed to fungal culture by a method derived from the standard method ASTM D3274-09 for about 30 days and the antifungal property of the compositions were evaluated.
[00090] Table 2 as shown below depicts the antifungal results.
Sr No.
Sample
Antifungal rating out of 10
30 days exposure
1
Commercially available paint composition
9
2
Water-based paint composition of the present disclosure
9
[00091]
Similar to the results obtained for the antibacterial property, the water-25 based paint composition of the present disclosure comprising silver nanoparticle as
20
an antimicrobial active
showed excellent antifungal results as shown in Table 2. Hence, the process as disclosed in the present disclosure example 1 provide a stable dispersion comprising high concentration (0.5% w/w) of silver nanoparticle to be employed in a water-based paint composition for imparting antimicrobial activity on the surface of the articles upon which the composition was coated. 5
[00092]
Similar to the results obtained for the antibacterial property, the water-based paint composition of the present disclosure comprising silver nanoparticle as an antimicrobial active showed excellent antifungal results similar to that shown by the commercially available paint composition. Hence, the stable slurry composition 10 comprising a dispersion of high concentration of silver nanoparticle was found to be a stable medium to be employed in a water-based paint composition for imparting antimicrobial activity on the surface of the articles upon which the composition was coated.
15
ADVANTAGES OF THE PRESENT DISCLOSURE
[00093]
The present disclosure provides a stable slurry composition to incorporate the dispersion of silver nanoparticles as an antimicrobial active into a water-based composition. The slurry composition is easy to synthesise and inert in nature. The present disclosure further provides a convenient yet economical process for 20 preparing the slurry composition. The slurry composition obtained by the process as disclosed herein is stable for at least 15 days and could be easily used in a coating composition for preparing the antimicrobial compositions. Furthermore, the present disclosure provides a water-based paint composition comprising the slurry composition with antimicrobial property. The stable dispersion obtained by the 25 process herein can be employed in a coating composition through a slurry composition without the usage of any harsh reaction conditions or any processing aids. Moreover, the slurry composition being stable for at least 15 days, it could be stored for use into the water-based paint composition in a larger scale.

I/We Claim:

1.
A slurry composition comprising:
a.
35 to 45 % by weight of a metal nanoparticle dispersion;
b.
11 to 20% by weight of at least one additive; and 5
c.
40 to 50% by weight a pigment-extender mixture.
wherein the metal nanoparticle dispersion comprises 0.3 to 2% (w/w) a plurality of metal nanoparticles in a particle size range of 1 to 100nm.
2.
The slurry composition as claimed in claim 1, wherein the metal nanoparticle is a silver nanoparticle. 10
3.
The slurry composition as claimed in claim 1, wherein the at least one additive comprises 7 to 12% by weight of a first additive and 4 to 8% by weight of a second additive.
4.
The slurry composition as claimed in claim 3, wherein the first additive is selected from a pH regulator, a defoamer, a preservative, a thickener, a 15 dispersant, a first solvent, or combinations thereof; and the second additive is selected from a second solvent, a rheology modifier, or combinations thereof.
5. The slurry composition as claimed in claim 4, wherein the pH regulator is selected from substituted alcohols, amino alcohols, primary amines, 20 secondary amines, tertiary amines, or combinations thereof; the defoamer is selected from hydrocarbon-oil based compounds, mineral oil-based compounds, silicone-based compounds, or combinations thereof; the preservative is selected from thiazolinones, carbamates, diuron, alkylene glycol, polyols, acrylate polymers, cellulose ethers, or combinations 25 thereof; the thickener is selected from hydrophobically modified polyether, hydrophobically ethoxylated urethane polymers, or combination thereof; the dispersant is selected from poly carboxylic acids, polyols, ethoxylates, maleic anhydride-diisobutylene copolymer, acrylic/methacrylate copolymer, or combinations thereof; the first solvent is an alcohol; the 30 22
second solvent is water; the rheology modifier is selected from
polyurethane, ethylene glycol ether, or combinations thereof.
6.
The slurry composition as claimed in claim 1, wherein the pigment-extender mixture comprises an inorganic pigment, and an extender selected from calcium carbonate, aluminium silicate, or combinations thereof. 5
7.
The slurry composition as claimed in claim 6, wherein the inorganic pigment is titanium dioxide.
8.
The slurry composition as claimed in claim 1, wherein the slurry composition has a viscosity in a range of 120 to 145 KU.
9.
A process of preparing the slurry composition as claimed in any one of the 10 claims 1 to 8, said process comprising:
a.
adding the first additive to the metal nanoparticle dispersion to obtain a first mixture;
b.
charging the pigment-extender mixture to the first mixture to obtain a second mixture; 15
c.
contacting the second additive with the second mixture and stabilizing to obtain the slurry composition.
10.
The process as claimed in claim 9, wherein the metal nanoparticle dispersion is stirred at a speed in a range of 400 to 600 rpm for a time period in a range of 5 to 20 minutes, prior to addition of the first additive. 20
11.
The process as claimed in claim 9, wherein step (a) is carried out while stirring in a closed high shear disperser, for a time period in a range of 10 to 30 minutes at a speed in a range of 500 to 1000 rpm.
12.
The process as claimed in claim 9, wherein step (b) is carried out while blending for a time period in a range of 40 to 80 minutes at a speed in a 25 range of 1400 to 2200 rpm.
13.
The process as claimed in claim 9, wherein the stabilizing of step (c) is carried out for a time period in a range of 10 to 30 minutes at a speed in a range of 700 to 1100 rpm.
14.
A water-based paint composition comprising: 30
(a) the slurry composition as claimed in any one of the claims 1 to 8; and
23
(b) at least one third additive.
15.
The water-based paint composition as claimed in claim 14, wherein at least one third additive is selected from binder, adhesive, solvent, promoter, surfactant, solubilizer, anti-caking agent, filler, anti-foaming agent, biocide or combinations thereof. 5
16.
The water-based paint composition as claimed in claim 14, wherein the slurry composition is in a weight range of 0.5 to 1.5% with respect to the total weight of the paint composition.
17.
The water-based paint composition as claimed in claim 14, wherein the paint composition has an antimicrobial property. 10
18.
A process of preparing the water-based paint composition as claimed in claim 15, said process comprising:
a.
contacting at least one third additive with the slurry composition to obtain the paint composition.
19.
The process as claimed in claim 19, wherein the contacting is carried out 15 while mixing for a time period in a range of 40 to 80 minutes at a speed in a range of 1400 to 2200 rpm.
20.
The slurry composition as claimed in claim 1 or the water-based paint composition as claimed in claim 14, for use as an antimicrobial coating.