Claims:We Claim:
1. Water insoluble layered double hydroxides (LDHs) of Cu (II) comprising divalent and trivalent metal cation salts with MII/MIII molar ratio range of 2:1 to 4:1 including CuMg7Al4(OH)4(CO3)2. nH2O having copper ions infused in stacked hydroxide layers of LDH that are intercalated with inorganic anions.
2. The water insoluble layered double hydroxides (LDHs) of Cu (II) as claimed in claim 1 that are free of organic anions.
3. The water insoluble layered double hydroxides (LDHs) of Cu (II) as claimed in claims 1 or 2 wherein Cu to Mg in said LDH is in range of 1:1 to 1:7 and is preferably in the molar ratio of 1:7 that performs equivalently as an antialgal additive in standard paint formulations with respect to antialgal performance and is free of imparting any blue color to paint formulation in which it is incorporated or is free from impacting adversely the aesthetics of white paint formulation.
4. A process for preparation of water insoluble layered double hydroxides (LDHs) of Cu (II) as claimed in claims 1-3 comprising the steps of
(i) providing solution of guest molecule or anion to be intercalated of OH-/CO32-;
(ii) providing a solution of divalent and trivalent metal cation salts in an adequate proportion;
(iii) adding solution of said anion of step (i) into the solution of step (ii) and obtaining true LDH phases by precipitation when 0.2< x <0.33 resulting in MII /MIII molar ratio to be in the range of 2:1 to 4:1 said precipitation caused by increasing the pH of the mixture in the range of 9-10.5 to allow precipitation and obtaining water insoluble layered double hydroxides (LDHs) of Cu (II) therefrom.
5. The process for preparation of water insoluble layered double hydroxides (LDHs) of Cu (II) as claimed in claim 4 wherein after step (iii) the entire reaction mixture is aged at room temperature for 6-12 hours followed by washing with DM water to remove any kind of salt present in the filtered LDH and thereafter drying the filtered cake in hot air oven and crushed to powder for directly involving in paint formulations.

6. Water based coating formulations/ paints comprising
(i) Upto 70% of water insoluble layered double hydroxides (LDHs) of Cu as anti-algal additive as claimed in claims 1-3;
(ii) water based acrylic emulsion, that is free of any blue colour and stable from leaching throughout dry paint film durability as it is completely insoluble in water.

Dated this the 28th day of March, 2022 Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199

, Description:FIELD OF THE INVENTION
The present invention provides for layered double hydroxides (LDHs) of copper as potential inorganic antialgal additives for water based paint formulations that serve as a replacement to existing organic antimicrobial agent in water-based exterior paint, and also provides for paint formulations thereof.

BACKGROUND ART
Organic antimicrobial compounds are the most preferred biocidal agents used in paints and coatings. These materials provide protection to the paint against in can microbial growth as well as antifungal and antialgal growth on dried paint film. Most of these organic antimicrobial agents pose a threat of high rates of leaching in the environment and contaminate water bodies and ecosystem in general. Also available alternates to these organic antimicrobial agents are not as effective to combat microbial attack on paint films.
Copper based compounds are used as algaecide and herbicide [Current Medicinal Chemistry, 2005, 12, 2163-2175; US4324578; US2734028 A; US4098602 A; US6069113 A; US 3930834 A; US 4505734 A; US 4361435 A]. Their application in antifouling coatings is also reported [Surface Coating & Technology, 201, 2006, 3642-3652; Progress in Organic Coatings 50, 2004, 75-104].
Reference is made to WO2012164131 that teaches nanoclays and nanocomposite materials comprising said nanoclays as a support for metal oxide particles that confer multi-functional properties on the materials. The aforementioned properties are obtained by formulating a specific type of additives based on sheets of natural and/or synthetic clays which are intercalated with metal oxides having antimicrobial and/or oxygen scavenging and/or catalytic and/or self-cleaning and/or anti-abrasion capacities, and which can also optionally contain other organic, metal or inorganic compounds or a combination thereof, for compatibilization and/or dispersion and/or increasing the functionality of the metal oxides and/or providing new functions, including both passive physical reinforcement functions and active functions, with said nanoclays selected from the group consisting of montmorillonite-type clays, kaolinite, bentonite, smectite, hectorite, sepiolite, gibbsite, dickite, nacritita, saponite, halloysite, vermiculite, mica, and/ or mixtures thereof or with other phyllosilicates, mainly, with or without surface modification prior organic and/ or inorganic. Said nanoclay precursor expander are selected from the group consisting of DMSO, polyethylene oxide, metal salts, NMF, alcohols, acetates, hydrazine hydrate, water, anhydrous hydrazine, carboxymethyl starch, acetamide, starch, DMSO + methanol, hydroxyethylstarch, hexanoic acid, hydroxypropyl starch, acrylamides, adonitol, glucose, acrylamide, Salicylic acid, caprolactam, glycolic acid, tannic acid, maleic acid, maleic anhydride, lactic acid, adipic acetic acid, acetaldehyde, sorbitan, butyric acid, tetrafluoroethylene, chlorotrifluoroethylene, vinyl pyrrolidone, hexamethylene, vinyl versatate or any combination thereof; and metal salts selected from the group consisting of silver, copper, iron, titanium, cerium, zinc, nickel, palladium, calcium, manganese, manganese or cobalt. This prior art involves different nanomaterials and nanoclays like bentonite, cloysite, halloysite, kaolin, hectorite etc. including silicates however does not involve any layered structure formation.
US20110040006 reveals the dirt pickup resistance of substrates, in particular coatings, is improved by the incorporation of small amount (0.1-20%) of certain layered double hydroxide particles comprising at least two metals selected from Group II metals, Group III metals and transition metals, wherein at least one of the metals is a divalent cation. The preparation of effective, readily intercalated, layered double hydroxide particles containing cationically charged mineral layers, which make up the anionically charged interlayers and their incorporation into composition, such as architectural coatings, in particular water-based architectural coatings, are provided. This prior art however, teaches LDH particles that is partially or fully intercalated with certain organic anions like alkylolamino carboxylates which organic anions are known to improve dirt pickup resistance.
WO2010066642A1 relates to polymer-containing composition which comprises layered double hydroxide in a polymer matrix, wherein the layered double hydroxide, comprising stacks of individual platelets, comprises carbonate as charge-balancing anion and wherein the individual platelets have an average L/D value above (150), and the polymer comprises a thermoset polymer and/or a non-halogen-containing thermoplastic polymer. The invention further relates to the use of said layered double hydroxide for improving properties of the polymer-containing composition; the use of the polymer-containing composition in a coating, ink, cleaning, rubber or rubber formulation, drilling fluid, cement formulation, plaster formulation, or paper pulp,- a polymer formulation, a coating composition or article comprising the polymer-containing composition; and a process for preparing the polymer. This prior art teaches incorporating layered double hydroxides in polymer matrix preferably thermoset polymers based on solvothermal treatment. For the advancement the layered double hydroxides prepared by solvothermal process has been incorporated in polymer matrix-preferably thermoset polymers to make it suitable for dispersion in different formulations.

US9642919B2 relates to layered double hydroxide (LDH) materials and in particular to new methods of preparing improved LDH materials which have intercalated active anionic compounds (improved LDH-active anion materials). The improved LDH-active anion materials are characterized by their high degree of robustness, demonstrated by their high Particle Robustness Factor values, and by their ability to retain substantially all of the intercalated active anionic compound, in the absence of ion exchange conditions and/or at pH>4 wherein the treated layered double hydroxide-active anion material consists of mixed hydroxides of one or more trivalent metal cations and one or more divalent metal cations, having an excess positive charge that is balanced by one or more intercalated active anions, and
wherein the one or more divalent metal cations are selected from the group consisting of Co2+, Ni2+, Cu2+, Zn2+, Mn2+, Pd2+, Ti2+, Ca2+, Cd2+, and Mg2+. However this advancement use a solvothermal method for the preparation of LDH.
EP0987328(B1) (Choy and Kwak) describes an LDH/bio-inorganic hybrid composite prepared using three steps: a first step involving co-precipitation in which an alkaline material is added to an aqueous mixed metal solution comprising a bivalent metal (MII) (e.g. Mg(NO3)2) and a trivalent metal (MIII) (e.g. Al(NO3)3). A second step which isolates the reaction product from the first step; that is, a stable layered double hydroxide (LDH) intercalated with charge compensating anions (derived from the original bi- and trivalent metal starting materials (e.g. OH-, NO3 -)). And a third step is insertion of the biomolecule..
WO2010/089691A1 provides a method of producing a degradable polymeric material by preparing an intercalated double hydroxide of the general formula (I) in which MII represents a single metal ion or more than one metal ion selected from V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Sn and MIII represents a single metal ion or more than one metal ion selected from Al, V, Cr, Mn, Fe, Co, Ni, Nb, Mo, In, W and Ce. A is selected from C8 to C24 straight or branched chain carboxylic acids and mixtures thereof and, optionally, at least one further component selected from an anionic surfactant, a straight or branched chain C8 to C24 amine, a straight or branched chain C8 to C24 alcohol and a straight or branched chain C8 to C24 aldehyde. The intercalated double hydroxide is combined with at least one polymeric substrate and, optionally, at least one additional component selected from anti-oxidants and degradation susceptible polymers to produce a mixture which is compounded to produce the degradable polymeric material.
Very recent prior disclosures of Cu active sites confined in MgAl layered double hydroxide for hydrogenation of dimethyl oxalate to ethanol by JianzheShi YanHe KuiMa SiyangTang ChangjunLiu HairongYue BinLiang in Catalysis Today Volume 365, 1 April 2021, Pages 318-326; and; Facile synthesis of Cu-LDH with different Cu/Al molar ratios: application as antibacterial inhibitors by Hadja Alia Tabti, Mehdi Adjdir, Abdelkader Ammam, Baghdad Mdjahed, Brahim Guezzen, Amina Ramdani, Choukry Kamel Benddedouche, Noria Bouchikhi & Nadir Chami Research on Chemical Intermediates volume 46, pages 5377–5390 (2020)- teaches incorporation of Cu into inorganic layered structure but does not disclose any Cu leaching problems encountered in paint formulation based on the same.
However, all of these copper complexes have intense color, and their water solubility is extremely high. This inhibits them for applying them as anti-algal additive in water based paint formulation.
Hence there is a need in the art to provide for effective alternative to organic antimicrobial agent which displays acceptable antialgal performance along with environmental safety as water based exterior paints.

OBJECTS OF THE INVENTION
It is thus primary object of the present invention to provide for layered double hydroxides of copper as potential inorganic antialgal additives suitable for water based paint formulations that would serve as a replacement to existing organic antimicrobial agent in water-based coating formulation without impacting adversely the aesthetics of the white paint
It is another object of the present invention to provide for said water based coating formulation comprising layered double hydroxides of copper together with water based acrylics.
It is yet another object of the present invention to provide for layered double hydroxides of copper through co-precipitation method free of any intercalation of organic anions like alkylamino carboxylates and other organic anions known to improve dirt pickup resistance.
It is still another object of the present invention to provide for said antialgal water based coating formulation that would be leaching free and would not require addition of organic biocides as antialgal agents whereby due to its high leaching tendency, excess dosages needs incorporation posing environmental threat due to its harmful impact to the environment and ecological impact on the whole.

SUMMARY OF THE INVENTION
The primary aspect of the present invention is directed to provide water insoluble layered double hydroxides (LDHs) of Cu (II) comprising divalent and trivalent metal cation salts with MII/MIII molar ratio range of 2:1 to 4:1 including CuMg7Al4(OH)4(CO3)2. nH2O having copper ions infused in stacked hydroxide layers of LDH that are intercalated with inorganic anions.
Another aspect of the present invention is directed to provide said water insoluble layered double hydroxides (LDHs) of Cu (II) that are free of organic anions.
Yet another aspect of the present invention is directed to provide said water insoluble layered double hydroxides (LDHs) of Cu (II) wherein Cu to Mg in said LDH is in range of 1:1 to 1:7 and is preferably in the ratio of 1:7 that performs equivalently as an antialgal additive in standard paint formulations with respect to antialgal performance and is free of imparting any blue color to paint formulation in which it is incorporated or is free from impacting adversely the aesthetics of white paint formulation.
Another preferred aspect of the present invention is directed to provide a process for preparation of water insoluble layered double hydroxides (LDHs) of Cu (II) comprising the steps of
(i) providing solution of guest molecule or anion (to be intercalated);
(ii) providing a solution of divalent and trivalent metal cation salts in an adequate proportion;
(iii) adding solution of said anion of step (i) into the solution of step (ii) and obtaining true LDH phases by precipitation when 0.2< x <0.33 resulting in MII /MIII ratio to be in the range of 2:1 to 4:1 said precipitation caused by increasing the pH of the mixture in the range of 9-10.5 to allow precipitation and obtaining water insoluble layered double hydroxides (LDHs) of Cu (II) therefrom.
Further aspect of the present invention is directed to provide said process for preparation of water insoluble layered double hydroxides (LDHs) of Cu (II) wherein after step (iii) the entire reaction mixture is aged at room temperature for 6-12 hours followed by washing with DM water to remove any kind of salt present in the filtered LDH and thereafter drying the filtered cake in hot air oven and crushed to powder for directly involving in paint formulations.

Yet another aspect of the present invention is directed to provide said water based coating formulations/ paints comprising
(i) Upto 70% of water insoluble layered double hydroxides (LDHs) of Cu as anti-algal additive;
(ii) water based acrylic emulsion paint, that is free of any blue colour and stable from leaching throughout dry paint film durability as it is completely insoluble in water.

DETAILED DESCRIPTION OF THE INVENTION
As stated hereinbefore the present invention provides for inorganic copper compound (copper layered double hydroxide) free of any intercalated organic anions which when incorporated in water based acrylic coating formulations preferably exterior paints, exhibits antialgal performance. Advantageously, said copper-based layered double hydroxides are sparingly soluble in water as compared to copper complexes which have intense colour in being highly water soluble showing undesirable bluish colour when copper complexes are incorporated thus inhibiting their application as anti-algal additive in water based paint formulation. On the contrary, the coating formulation/paint of the present invention is white in color without impacting adversely the aesthetics of the white paint unlike other paints with incorporated copper, and yet shows strong antialgal performance.
Stoichiometric formula of the Water insoluble layered double hydroxides (LDHs) of the present invention is CuMg7Al4(OH)4(CO3)2. nH2O. Cu is infused in the hydroxide layers which are forming the LDH. When it is said that LDH is insoluble in water meaning its stacked hydroxide layers are insoluble in water. Therefore, reason behind insolubility of Cu is a special feature of LDH.
Generally, organic biocides are the preferred antialgal agents that are used in water based exterior paints. Due to its high leaching tendency, excess dosages need to be incorporated. This poses an environmental threat due to its harmful impact to environment and ecological impact on the whole, which could be overcome by the present advancement.
According to an embodiment copper based layered double hydroxide showing excellent antialgal performance in water based coating formulation preferably exterior paint could be attained. Thus the present advancement is made capable of potentially replacing completely the commercial organic biocide Diuron in paint.
According to another embodiment water based paint formulations by wt. to wt. replacement of Diuron could be provided with thus synthesized copper-layered double hydroxide compounds that were prepared and tested by chamber test method for their antialgal performance.
Although exact efficacy comparison of developed Cu-LDH against known commercially available Cu-LDH based compounds with organic anions was not done, however a paint formulation was processed containing only 70% of developed Cu-LDH compound. When antimicrobial performance of the same was evaluated against a standard paint formulation ie. 100% diuron based paint formulation it was found that antimicrobial performance of the paint containing 70% Cu-LDH was similar (with a rating of 7) as against that of 100% diuron based paint formulation
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed that should not be construed to limit the scope of the present invention. The advancement according to the present invention is discussed in further detail in relation to the following non-limiting exemplary illustrations.
BRIEF DESCRIPTION OF FIGURES
Fig.1: illustrates Cu-Mg/Al LDH powder as attained.

Preparation method of LDHs of Cu (II)
In this method, a solution of guest molecule or anion (to be intercalated) is added slowly into another solution containing divalent and trivalent metal cationic salts in an adequate proportion. True LDH phases are often only observed when 0.2< x <0.33 (x = MIII/ (MIII + MII), where MII and MIII are divalent and trivalent metal ions respectively which results in MII /MIII molar ratio to be in the range of 2:1 to 4:1. Then the pH of the mixture is slowly increased to an extent where precipitation of LDH occurs. Most pure form of LDH is obtained at pH range of 9-10.5. After adjusting the pH at a select pre-decided value of this range, the entire reaction mixture is aged at room temperature for 6-12 hours. After aging, this mixture is filtered and washed several times with DM water to remove any kind of salt present in the filtered LDH. The filtered cake can be dried in hot air oven and crushed to powder or used directly in a paint system.
Process for LDHs of Cu (II)
Adding slowly a solution of anion (OH-/CO32-) to be intercalated into another solution containing divalent and trivalent metal cation salts with MII /MIII ratio in the range of 2:1 to 4:1
Increasing slowly the pH of the mixture to preferably 9-10.5.
Aging the entire reaction mixture at room temperature for 6-12 hours followed by filtration, washing several times with DM water to remove any kind of salt to afford the filtered cake of desired LDH.
Said filtered cake obtained by filtering and washing of aged reaction mixture can be dried in hot air oven for 22 to 24 hrs at 80 Deg C. and crushed to powder or used directly in a paint system.

Example-1
The raw materials used were Cu(NO3)2.3H2O, Al(NO3)3.9H2O, Mg(NO3)2.6H2O, Na2CO3 and 5M solution of NaOH in De-mineralized water and all the materials used were of General grade. Also, De-mineralized water was used as a medium for the synthesis. 18.75 gm Cu(NO3)2.3H2O, 22.4 gm Mg(NO3)2.6H2O and 3 gm Al(NO3)3.9H2O were dissolved in 400 ml of De-mineralized water in a round bottom flask equipped with an overhead stirrer, condenser and heating source. A solution of 5.45 gm of Na2CO3 was prepared in 100 ml De-mineralized water and added dropwise to the Round bottom flask. The pH of the mixture was adjusted to 10-10.5 by dropwise addition of 5M NaOH solution. The precipitate obtained was aged at 65°C-70°C for 8-9 hr followed by filtration and drying in hot air oven at 80°C for 24 h. Entire reaction was carried out in N2 atmosphere. Dried LDH was crushed to extremely fine powder. This fine powder was filtered with nylon mesh. % Yield- of 80% to 95%.
Cu-LDH can also be prepared by an alternate method where steps such as filtration, washing, drying and grinding can be eliminated and Cu-LDH in slurry form incorporated in the paint composition.
For the present invention anions used are NO3-, CO3-2, and OH- along with Cu and Mg as the divalent and Al as the trivalent metal ion. In another embodiment apart from the ions already stated - Zn+2, Ni+ as divalent metal ion, Ga+3, Fe+3, and Mn+3 as trivalent metal ion and Cl-, SO4-2, and RCO2- as anions can also be used for the present invention in any combination. It is noteworthy that present invention does not require chemicals/reagents of special grade.
Different copper based LDH were prepared maintaining molar ratio of Cu to Mg in the composition in range of 1:1 to 1:7. Experiments with copper content of (1:1), although showed satisfactory microbial performance but this LDH imparted a bluish color to the white paint formulation.
Hence the ratio of Cu to Mg were selectively employed in LDH in such a way so as to resolve the color issue in the paint formulation without any compromise on the microbial performance. As already stated, LDHs intermediate ratios of Cu: Mg (1:2, 1:4 and 1:7) were prepared and evaluated for colour (Please see Table 1). Surprisingly and unexpectedly the LDH with a CU: Mg ratio of 1:7, performed equivalent to the standard paint with respect to antialgal performance without imparting any color to the final paint. This was of critical importance to the development given that it could adversely impact the aesthetics of the white paint if any discoloration (bluish tone) was seen. This was a challenge faced in the development to retain the antimicrobial performance even at the lowest concentration of copper in LDH so as to retain the whiteness and overall finish of the white paint. The special co-action of Cu and Mg at the selective level of 1:7 enables attaining the objective of the present invention. The appearance and colour of the Cu-LDH with a CU: Mg ratio of 1:7 can be seen in Figure 1.

Table 1: Properties of LDHs of Cu (II) having different Copper: Magnesium ratio:-
Parts of Copper Parts of Mg Color of developed LDH Color of paint incorporated with LDH Antimicrobial Performance
1 1 Dark Blue Pale blue tone Passes
1 2 Blue Pale blue tone Passes
1 4 Light Blue Slight bluish tone Passes
1 7 Pale Bluish White (Absence of Blue tone) Passes
*passes means similar performance (with rating of 7) to a std. paint i.e. 100% diuron based paint (having rating of 7).
In the process of selection for optimal ratios of Cu and Mg, there has been no use of any organic moiety like organic anions etc. for effective incorporation of the said LDH in the paint composition.
Stoichiometric formula of LDHs of Cu (II) is CuMg7Al4(OH)4(CO3)2. nH2O. Cu is infused in the hydroxide layers which are forming the LDH. One of the most significant attribute of the synthesized LDH of Cu (II) is insolubility in water. Generally copper based compounds showing antialgal performance are reported to be soluble in water. But present invention enabling water insoluble copper based compounds have been found to have excellent antialgal performance even in being insoluble in water based paint formulations. The image under Fig.1 shows the appearance of the Cu (II) LDH of the present invention.
It is well known in the literature to use intercalated LDH-active anion materials- a completely insoluble material in water, as a means to slow down the release of an active anionic compound and thereby to provide controlled release preparations. However, the present invention is not concerned with providing such preparations. Instead the present invention is concerned with developing copper containing LDH-capable to exert antialgal action and copper ion being an integral part of stacked hydroxide layers of LDH which are insoluble in water become non-leaching. Therefore, reason behind insolubility of Cu is a special feature of LDH.
Example-2
CHAMBER TEST METHODOLOGY FOR EVALUATION OF ANTI-ALGAL PERFORMANCE IS FOR TESTING PURPOSES ONLY AND THE PRESENT INVENTION DOES NOT INVOLVE ANY BIOLOGICAL RESOURCE MATERIALS IN EITHER ITS PRODUCT OR ITS PROCESS
First step of Algal chamber test is Algae inoculum preparation; two species of algae, Chlorella sp. and Oscillatoria sp. are cultured separately. Dehydrated media and distilled water are taken in a flask and sterilized in autoclave at 121 °C, 15 psi steam pressure for 15 - 20 minutes. To this, inoculum of the same species from the reserve flask is added. Flask is incubated under the light intensity of around 1000 µmol m-2 s-1. For Chlorella sp., which is a unicellular species, the culture is diluted to 0.5 OD750. For Oscillatoria sp., which is a multicellular species, the media is filtered and biomass is kept on petridish. It is left overnight at 30 °C for drying. Upon drying, biomass is crushed to fine powder, and added in the chamber.
Second step is application of paint. Paint samples are thinned as per instructions by manufacturer. Paint samples are applied on the FRCs with the help of 38 mm sable hair brush. Number of coats are applied as per the recommendation of the manufacturer. Panels are dried overnight after each coat and kept for 7 days curing after final coat application. Panels are prepared in triplicate for every sample.
Third step is charging of ATC (Algae test chamber). ATC is cleaned properly and bottom tank is filled with distilled or demineralized water. Chlorella sp. and Oscillatoria sp., prepared in the first step are charged to ATC.
Fourth step is Exposure of painted panels. Panels are exposed in the ATC. There are three rows with each row hosting 8 tiles. Every alternate day, three right most panels of the bottom row are shifted to the left most positions of the top row. As a result, each panel moves three places ahead of its earlier position to the right side in the top row, to the left side in the middle row and to the right side in the bottom row. During each test run, panels of standard sample along with the experimental samples are tested together. After completion of test, photograph of the panels are taken and procedure of Image analysis of algal panels is followed thereafter. Also, visual ratings of the panels are also recorded every Monday and Friday until completion of the experiment. The final ratings are given basis image analysis software.
Following the above test protocol- when synthesized LDHs of Cu (II) with Mg:Cu ratio 7:1 was used for painted panels it was observed that only 70% of Cu-LDH was enough to offer similar antialgal performance as that of 100% Diuron based coats. Thus, efficacy of said Cu based inorganic compound (Cu-LDH) was found to be higher than commercial organic biocide (eg. Diuron).
Various biocides are used in paints for antialgal performance and antifouling of paints. However, all these biocides are registered pesticides and pose harmful effects on human, aquatic life and environment in general. Till date there is no report of use of purely inorganic compounds, commercially available as antialgal biocides for use in water based paints.
Hence to tackle the problem of various regulations and restrictions posed on use of potent registered biocides in water-based paints, such inorganic Cu based (Cu-LDH) free of organic anions which exhibits antialgal performance in paint and can replace part or completely the existing organic antimicrobial agents currently used in water based exterior paints, was prepared.
Layered double hydroxides containing copper have not been reported to date for using in water based exterior paint compositions to exhibit antialgal performance. Moreover replacement of organic and potent antimicrobial agents with inorganic copper based layered double hydroxide in water based paints is not known, which is provided in accordance to the present invention to lessen or eliminate the harmful impact of leached, excess organic biocide to the environment. As copper-LDH shows minimal tendency of leaching, its dosage can be made selective (unlike organic antialgal agents where excess needs to be added due to high leaching rate) that thus favours a positive impact on environment.
It is thus possible for the present invention to provide for said water insoluble inorganic copper based LDHs, free of any organic anions, that exhibits strong antialgal performance in water based coating formulations/ paints thus having potential to replace existing organic biocides as antialgal agent conventionally used in water based exterior paints. The coating formulations/ paints of the present invention incorporating said inorganic Cu-LDH do not pose any blue color thus maximizing their potential use in white premium coating formulations/paints. Preferably the advantages provided by present invention are:
1. Anti-algal additive based on Copper (II) complexes;
2. Replacement of existing antialgal agent in paint formulation wherein copper compound is purely in inorganic form;
3. Copper compound, when incorporated in paint at a concentration sufficient for replacement of existing organic biocide, does not impart any blue color to paint;
4. Said copper based compound is not soluble in water thus can be used in water based paint formulations without the problem of leaching.