DESC:FIELD OF INVENTION
The present invention relates to an antimicrobial additive for water based paint comprising silver nonmaterial/ silver-nano dispersion, preferably in aqueous base, and a process of manufacture thereof, whose Ag concentration ranges include higher ranges ranging from 1000 ppm-90000 ppm, and yet is highly stable for more than 6 months free of any tendency towards agglomeration at such high concentrations.
BACKGROUND ART
Preparation of high concentration of nanoparticles in dispersed form is a challenge because of its high tendency to agglomerate with the reduction of particle size. The problem is exemplified when such high concentrated dispersions needs to prepared in bulk scale for industrial applications. On this reference is invited to the following prior arts:
NL2028643A discloses nano-silver dispersion and a preparation method thereof, and relates to the technical field of nano-silver preparation. The method for preparing a nano-silver dispersion, includes: mixing y-aminopropyltriethoxysilane, polyvinylpyrrolidone, sodium lauryl sulfate, silver nitrate and water, and conducting a chelation, to obtain a chelating dispersion, wherein before the mixing, the y-aminopropyltriethoxysilane is exposed to the air for less than 5 min, and dropwise adding a sodium borohydride solution into the chelating dispersion, to obtain a mixture, and subjecting the mixture to an oxidation-reduction reaction, to obtain the nano-silver dispersion. The nano-silver in the nano-silver dispersion prepared by the method provided of the present disclosure has a small particle size and good dispersibility.
CN103212720A is directed to a preparation method of nano-silver dispersion liquid. The preparation method comprises the following steps that thickening agents and dispersing agents are added into pure water or deionized water, then, soluble silver salt is dissolved in solution, and the silver salt solution is obtained; and under the stirring effect, silver complexing agents are firstly added into the silver salt solution, then, reducing agents are added, or silver complexing reduction agents are directly added, the reaction is carried out for at least 12 hours under the condition of room temperature to 90 DEG C, silver ions in the silver salt solution are reduced into metal silver, the nano-silver dispersion liquid is obtained, the silver complexing agents and the silver complexing reduction agents can form the chemical bonding with the nano-silver particle surface, and in addition, functional groups with the cross linking effect are reserved. The invention correspondingly provides the nano-silver dispersion liquid prepared by the method. The process of the preparation method is simple, the stability of the prepared nano-silver dispersion liquid is good, nano-silver particles are uniform, the application is convenient, and the bonding force of the nano-silver and substrates is high. In addition, the invention also provides a preparation method of a nano-silver antibacterial coating.
US20180168037A1 provides silver nano-particles that are excellent in stability and develop excellent conductivity by low-temperature calcining, a producing method for same, and a silver coating composition comprising the silver nano-particles. A method for producing silver nano-particles comprising: preparing an amine mixture liquid comprising: an aliphatic hydrocarbon monoamine (A) comprising an aliphatic hydrocarbon group and one amino group, said aliphatic hydrocarbon group having 6 or more carbon atoms in total; an aliphatic hydrocarbon monoamine (B) comprising an aliphatic hydrocarbon group and one amino group, said aliphatic hydrocarbon group having 5 or less carbon atoms in total; and an aliphatic hydrocarbon diamine (C) comprising an aliphatic hydrocarbon group and two amino groups, said aliphatic hydrocarbon group having 8 or less carbon atoms in total; mixing a silver compound and the amine mixture liquid to form a complex compound comprising the silver compound and the amines; and thermally decomposing the complex compound by heating to form silver nano-particles.

US9888691B2 relates to methods and compositions for antimicrobial silver compositions comprising silver nanoparticles and further comprises compositions for preparing silver nanoparticles comprising at least one stabilizing agent, one or more silver compounds, at least one reducing agent and a solvent. In one aspect, the stabilizing agent comprises a surfactant or a polymer. The polymer may comprise polymers such as polyacrylamides, polyurethanes, and polyamides. In one aspect, the silver compound comprises a salt comprising a silver cation and an anion. The anion may comprise saccharinate derivatives, long chain fatty acids, and alkyl dicarboxylates. The methods of the present invention comprise treating devices with the silver nanoparticle compositions, including, but not limited to, such devices as woven wound care materials, catheters, patient care devices, and collagen matrices. The present invention further comprises treatment of humans and animals wacr6ith the antimicrobial devices described herein.
JP 2010-265543A is directed to solving problem of: To provide a coated ultrafine particle of silver, which is used as an electroconductive-wire-forming material that can be sintered at a low temperature and can be used even for a flexible print substrate having low heat resistance, and to provide a production method therefor. SOLUTION: The coated ultrafine particle of silver has a particle diameter of 30 nm or less, is covered with a molecular amine for protection, has a weight loss ratio of 30% or more when measured with a thermogravimetry at 160°C, and forms a sintered film of a silver color by being sintered for one hour or shorter at 100°C or lower. The coated ultrafine particle of silver is prepared by preparing a complex compound by mixing a silver compound which decomposes by being heated and forms metallic silver, with an alkylamine and alkyl diamine, and heating the complex compound to pyrolyze the silver compound.
KR101298804B1 is based on a method for preparing an aqueous-based dispersion of metal nanoparticles comprising: (a) providing an aqueous suspension of a metal salt; (b) pre-reducing the metal salt suspension by a water soluble polymer capable of metal reduction to form metal nuclei; and (c) adding a chemical reducer to form metal nanoparticles in dispersion. This prior invention further relates to aqueous-based dispersions of metal nanoparticles, and to compositions such as ink comprising such dispersions.
US20100068409A1 teaches ink jet printable compositions that include nano metal powders in a liquid carrier. Para [0015] therein mentions useful liquid carriers include water, organic solvents, and combinations thereof. Useful additives include surfactants, wetting agents, stabilizers, humectants, rheology adjusting agents, adhesion promoters, and the like. Specific examples, many of which are commercially available, include the following: Organic solvents: DPM (di(propyleneglycol)methyl ether), PMA (1,2-propanediol monomethyl ether acetate), Dowanol DB (diethylene glycol monobutyl ether), BEA (butoxyethyl acetate), Dispersing agents and stabilizers for solvent-based dispersions: BYK-9077, Disperbyk-163, PVP K-15, Dispersing/wetting agents and stabilizers mentioned for water-based dispersions: BYK-154, BYK-162, BYK-180, BYK-181, BYK-190, BYK-192, BYK-333, BYK-348, Tamol T1124, SDS, AOT, Tween 20, Tween 80, L-77, Betaine, Sodium Laureth Sulfosuccianate and Sulfate, Tego 735W, Tego 740W, Tego 750W, Disperbyk, PDAC (poly(diallyldimethylammonium chloride)), Nonidet, CTAC, Daxad 17 and 19 (sodium salt of naphthalene sulfonate formaldehyde condensate), BASF 104, Solspers 43000, Solspers 44000, Atlox 4913, PVP K-30, PVP K-15, Joncryl 537, Joncryl 8003, Ufoxan, STPP, CMC, Morwet, LABS W-100A, Tamol 1124; Humectants for water-based dispersions: PMA, DPM, glycerol, Sulfolam, diethylene glycol, triethanolamine, Dowanol DB, ethanol, DMF (dimethyl formamide), isopropanol, n-propanol, PM (1-methoxy-2-propanol), Diglyme (di(ethylene glycol) diethyl ether), NMP (1-methyl pyrrolidinone).
Reference is also invited to Preparation of Ag nanoparticles with triethanolamine as reducing agent and their antibacterial property, in Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 419, 20 February 2013, Pages 174-179 teaching that hydroxide ions play a crucial role in the reduction of Ag+ ions with alcohol. Ag nanoparticles were thus prepared with triethanolamine (TEA) serving as reducing agent and alkali for the first time. The effects of stabilizer, mole ratio of AgNO3/TEA, temperature and AgNO3 concentration on the particles, as well as the antibacterial performance of the particles, were studied. The results showed that, PEG and PVP are effective for inhibiting the growth of particles, and Ag particles about 40 nm in size were obtained. The effects of TEA amount on the particles are negligible. On rising temperature, the particles size increase and the particles become more regular. With the increased AgNO3 concentration, the particles tend to large and poly-dispersed. The Ag nanoparticles show excellent antibacterial property.
Reference is further invited to Triethylamine induced synthesis of silver and bimetallic (Ag/Au) nanoparticles in glycerol and their antibacterial study, by Pradnya Nalawade, Poulomi Mukherjee & Sudhir Kapoor, in Journal of Nanostructure in Chemistry, Volume 4, article number 113, (2014) that teaches formation of Ag nanoplates in the presence of glycerol/triethylamine/polyvinylpyrrolidone without using any external reducing agent is shown for the first time. This approach is a unique and size-controlled synthetic method for the preparation of Ag nanoplates.
While there are several state of the arts that populate this technical field, the technical deficiency remains to address the attainment and facile synthesis of silver nanomaterial/ silver-nano dispersion in aqueous base at concentration ranges including in higher ranges ranging from 1000 ppm-90000 ppm that would be stable for months free of any tendency towards agglomeration, for preferred end use and application as antimicrobial additive in water based paint and coating system thereof and so that bulk scale industrial applications can be facilitated.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for an antimicrobial additive for water based paint and coating system thereof which in comprising silver-nano dispersion in aqueous base would be highly stable even at high concentration ranges free of any tendency of agglomeration.
It is another object of the present invention to provide for said antimicrobial additive for water based paint and coating system thereof comprising said silver-nano dispersion in aqueous base that would be highly stable based on the involvement of simple reducing agent that would also act as capping agent in the presence of select stabilizer taken in select levels.
It is still another object of the present invention to provide for said antimicrobial additive for water based paint and coating system thereof comprising said silver-nano dispersion that would be manufactured based on a select sequence based process involving said select reducing and capping agent together with select stabilizer taken at select levels enabling the stability of the dispersion for few months/ years even at much higher concentrations to facilitate manufacturing in bulk scale for industrial applications.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided antimicrobial additive comprising stable silver-nano dispersion with Ag concentration ranging from 1000 ppm-90000 ppm based on co-acting combination of silver ion, select Triethanol amine and polyether modified styrene maleic acid copolymer in aqueous base stable for more than 6 months free of any tendency towards agglomeration at such high concentrations.

Preferably in said antimicrobial additive said select Triethanol amine is adapted as reducing agent as well as capping agent and said styrene maleic acid copolymer (BYK 190) is adapted as stabilizing agent when present in select levels.

According to another preferred aspect of the present invention there is provided said antimicrobial additive wherein said silver-nano dispersion for stable Ag concentration ranging from 1000 ppm-90000 ppm in water base includes 1.50-1.66 wt.% AgNO3, 3.80-4.20 wt.% Styrene maleic acid copolymer (BYK), 1.90-2.12 wt.% Triethanol amine.

Preferably said antimicrobial additive is provided wherein silver-nano dispersion in aqueous base have silver nanoparticle size ranging from 5 nm-50 nm adapted to impart antimicrobial attributes to compatible water based paints when incorporated in the same.

More preferably said antimicrobial additive is provided wherein said copolymer is polyether-modified styrene-maleic anhydride copolymer.

According to another preferred aspect of the present invention there is provided said antimicrobial additive wherein said compatible water based paint includes acrylic based paints including pure acrylic, styrene acrylate.

According to another aspect of the present invention there is provided a process for the manufacture of antimicrobial additive comprising the steps of
Providing select sequence wise silver salt in pre-heated water followed by addition of polyether modified styrene maleic acid copolymer (BYK 190) and triethanolamine to obtain stable silver nano dispersion with Ag concentration ranging from 1000 ppm-90000 ppm.

Preferably said process for the manufacture of antimicrobial additive is provided wherein said select sequence wise addition of ingredients in said process includes adding silver nitrate in pre-heated water (60 deg C) followed by addition of polyether modified styrene maleic acid copolymer (BYK 190), thereafter mixing for 10 mins, followed by adding triethanolamine to obtain therefrom silver nano dispersion having silver nanoparticle size ranging from 5 nm-50 nm that is stable at room temperature (20-40 deg C) for more than 6 months adapted to impart antimicrobial attributes to compatible water based paints when added to the same.

More preferably in said process for the manufacture of antimicrobial additive wherein said antimicrobial additive is added to compatible water based paints at the point of sale for imparting sustained antimicrobial attributes.

BRIEF DESCRIPTION OF FIGURES
Figure 1: illustrates FESEM micrograph evidencing the nanomaterials obtained of less than 30 nm in size.
DETAILED DESCRIPTION OF THE INVENTION
As described hereinbefore, the present invention provides for an antimicrobial additive for water based paint comprising silver-nano dispersion preferably in aqueous base and a process of manufacture thereof whose Ag concentration ranges include higher ranges ranging from 1000 ppm-90000 ppm, and yet is highly stable for more than 6 months free of any tendency towards agglomeration at such high concentrations.
According to another aspect of the present invention a robust and facile route for the synthesis of silver-nano dispersion whose Ag concentration is 1000 ppm could be provided, together with silver-nano dispersion whose Ag concentration ranges from 1000 ppm-90000 ppm, which dispersion could be manufactured as highly stable dispersion stable for more than 6 months at such high concentration ranges suitable for incorporation in water based paints at the point of sale for imparting antimicrobial attributes.
According to another preferred aspect of the present invention said silver-nano dispersion could be provided by involving triethanolamine as both capping agent as well as a reducing agent, and from FESEM micrograph it could be evidenced that the nanomaterials obtained are less 30 nm which is in conformity with Zetasizer results.
The present invention overcomes a problem in the art on known current methods for synthesizing silver nanomaterial that involves reducing agent for reducing the silver salt and more than one stabilizing agent in aqueous media or solvent mixture, and many a times the dispersions are either not stable or are stable for only a short time.
EXAMPLES:
A highly stable silver nanomaterial/ silver-nano dispersion in aqueous base could be thus provided by reducing Ag+ ions based on involving Triethanol amine as reducing agent as well as capping agent, in presence of BYK 190 (styrene maleic acid copolymer) in select levels as stabilizing agent, in water at 60 ?C.
Advantages of the present highly stable silver nanomaterial/ silver-nano dispersion in aqueous base are:
(a) Composition comprising silver nitrate, triethanolamine, BYK190 and water;
(b) Specific sequence of addition of constituents resulted in the formation of stable high concentrated dispersion of nanosilver, with the sequence of addition being:-
Silver nitrate was added to pre-heated water (60 deg C) followed by the addition of BYK 190, after mixing for 10 mins, triethanolamine was added to get silver nano dispersion. Dispersion is stable at room temperature (20-40 deg C) over long period of time;
(c) The developed synthesis route is manufacturable;
(d) With above synthesis route, varying concentration of nanosilver dispersion can be achieved (1000 ppm to 90000 ppm);
(e) Particle size ranges from 5 nm-50 nm;
(f) No settling and particle agglomeration of silver dispersion in the concentration range of 1000 ppm to 90000 ppm
(g) The dispersion show antimicrobial property on incorporation in water based paint.
Table 1: Ag-nano dispersion obtained with TEA and BYK 190 at select workable dosage levels are found to co-act towards stabilizing Ag-nano dispersion at higher concentrations as given below.
RM Wt (g) Range
AgNO3 1.58 1.50 1.66
Polyether modified Styrene maleic acid copolymer (BYK) 4 3.80 4.20
TEA 2.02 1.92 2.12

Table 2: Comparatives illustrating that operating beyond the select dosage levels does not give the desired stability of higher concentration Ag-nano dispersion
RM Wt (g) Wt(g) Wt (g) Wt (g) Wt(g)
AgNO3 1.58 1.58 1.58 1.58 1.58
Polyether modified Styrene maleic acid copolymer (BYK) 4 4 0.00 4 3
TEA 2.02 1.01 2.02 0.5 2.02
Remark Particle size: 10-30 nm
Stability: >6 months Particle size: 30-80 nm
Stability: ??6 months Particle settles after few days Particle settles Particle size: 10-30 nm
Stability: near to 6 months

Prolonged stability of Ag nano dispersion without agglomeration was found to be feasible only because of BYK 190, and as shown in the above table without the addition of BYK, the silver nanoparticles settles after few days. When BYK 190 is added at select levels the nanoparticle stability could be achieved. Also, the nanoparticle stability could not be achieved by other known dispersing agents such as solution of either any modified urea (BYK 420), or any Fatty-acid-modified polyester (Ultra FA 4425).
When such stable silver nanodispersion is added to compatible varied water based paints, the same could provide for desired antimicrobial effect that is made possible only because of BYK 190, and is also compatible with variety of water based paints including acrylic paints thereby making it a more universal silver nano dispersion.
For testing the antimicrobial effect when silver nanodispersion containing BYK190 is added @ 50ppm to a water based paint, it shows antibacterial effect >99% giving reduced bacterial cell count after 2 hours and sustained >99.9% reduced bacterial cell count after 24 hours. The antibacterial effect though is inherent property of silver nanoparticles but such effect could be stably sustained in water based paints based on select stable silver nanodispersion added to such paints with the nanodispersion of the present invention stabilized by select co-acting combination TEA and BYK 190. Also, BYK 190 does not have any role in antimicrobial property.

,CLAIMS:We Claim:

1. Antimicrobial additive comprising stable silver-nano dispersion with Ag concentration ranging from 1000 ppm-90000 ppm based on co-acting combination of silver ion, select Triethanol amine and polyether modified styrene maleic acid copolymer in aqueous base stable for more than 6 months free of any tendency towards agglomeration at such high concentrations.

2. The antimicrobial additive as claimed in claim 1 wherein said select Triethanol amine is adapted as reducing agent as well as capping agent and said styrene maleic acid copolymer (BYK 190) is adapted as stabilizing agent when present in select levels.

3. The antimicrobial additive as claimed in claims 1 or 2 wherein said silver-nano dispersion for stable Ag concentration ranging from 1000 ppm-90000 ppm in water base includes 1.50-1.66 wt.% AgNO3, 3.80-4.20 wt.% Styrene maleic acid copolymer (BYK), 1.90-2.12 wt.% Triethanol amine.

4. The antimicrobial additive as claimed in claims 1-3 wherein silver-nano dispersion in aqueous base have silver nanoparticle size ranging from 5 nm-50 nm adapted to impart antimicrobial attributes to compatible water based paints when incorporated in the same.

5. The antimicrobial additive as claimed in claims 1-4 wherein said copolymer is polyether-modified styrene-maleic anhydride copolymer.

6. The antimicrobial additive as claimed in claims 1-6 wherein said compatible water based paint includes acrylic based paints including pure acrylic, styrene acrylate.

7. A process for the manufacture of antimicrobial additive as claimed in claims 1-6 comprising the steps of
Providing select sequence wise silver salt in pre-heated water followed by addition of polyether modified styrene maleic acid copolymer (BYK 190) and triethanolamine to obtain stable silver nano dispersion with Ag concentration ranging from 1000 ppm-90000 ppm.

8. The process for the manufacture of antimicrobial additive as claimed in claim 7 wherein said select sequence wise addition of ingredients in said process includes adding silver nitrate in pre-heated water (60 deg C) followed by addition of polyether modified styrene maleic acid copolymer (BYK 190), thereafter mixing for 10 mins, followed by adding triethanolamine to obtain therefrom silver nano dispersion having silver nanoparticle size ranging from 5 nm-50 nm that is stable at room temperature (20-40 deg C) for more than 6 months adapted to impart antimicrobial attributes to compatible water based paints when added to the same.

9. The process for the manufacture of antimicrobial additive as claimed in claims 7 or 8 wherein said antimicrobial additive is added to compatible water based paints at the point of sale for imparting sustained antimicrobial attributes.

Dated this the 31st day of January, 2025 Anjan Sen
(Applicants Agent & Advocate)
IN/PA-199