Abstract:
A stabilized biocidal dispersion comprising a biocide coated or adsorbed onto stable sub-micron carrier particles and wherein sub-micronized particles are stabilized by additives having polar moieties, hydrophobic and hydrophilic segments. The sub-micron particles are selected from metal oxides like zinc oxide, titanium dioxide, cerium dioxide and silica, alumina, minerals, clays, stilbene and sub-micron carbons. Exemplary biocides include carbamates, isothiazolones, pyrithione chelates and/or trizoles. Also disclosed is a process for preparing stabilized sub-micronized carrier particles.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to biocides and more particularly to stabilized biocidal dispersions and the process for preparing the same. The biocidal dispersion disclosed herein is stabilized by stable sub-micronized carrier particles. 
       BACKGROUND OF THE INVENTION 
       [0002]    US Patent Publication No. 20040120884 discloses nanoparticulate titanium dioxide coating produced by reducing flocculates of titanium dioxide nanoparticles from a titanyl sulfate solution and dispersing the nanoparticles in a polar sol-forming medium to make a solution suitable as a coating usable to impart photocatalytic activity, U.V. screening properties, and fire retardency to particles and to surfaces. The photocatalytic material and activity is localized in dispersed concentrated nanoparticles. 
         [0003]    US Patent Publication No. 20040241206 discloses the use of nanoparticles of inorganic materials (e.g., synthetic smectite clays) in ophthalmic compositions. The nanoparticles are utilized as biologically inert carriers or depots for biocides. The nanoparticles are useful in preventing or reducing the uptake of biocides from ophthalmic compositions by contact lenses, when the compositions are applied to the lenses. 
         [0004]    US Patent No. 6905698 assigned to Ineos Silicas Limited discloses a particulate carrier material impregnated with a biocidal formulation serving as a vehicle for introduction of the biocide into a liquid-based media, such as a surface coating or surface cleaning compositions, in order to allow controlled release of the biocide to combat bacterial, fungal, algal or like growth for an extend period of time. 
         [0005]    U.S. Pat. No. 7,311,766 by Billdal &amp; Kullavik discloses a method for preventing marine biofouling that comprises applying a protective coating to a substrate that contains an imidazole containing compound bound to metal oxide sub-micron-particles and a product for preventing marine biofouling of a substrate comprising a paint that contains an imidazole compound bound to metal oxide sub-micron particles. US Patent Publication No. 20060201379 discloses that Medetomidine, an imidazole compound, is employed to produce antifouling paint and wherein said imidazole compound is bound to metal nanoparticles to develop an efficient antifouling surface and improved performance of antifouling paints. 
       SUMMARY OF THE INVENTION 
       [0006]    We have discovered that sub-micron particles of a carrier ingredient having a large surface area and small particle size provide an effective interface for coating a biocide and that the use of such sub-micron particles as a biocide carrier will assist in milling the biocide close to the sub-micron meter particle size range making it essentially a sub-micron sized biocide particle. Furthermore, the carrier sub-micron particles can act as a stabilizing interface for the biocide as well as providing enhanced UV-protection on exposure to sunlight. For example, it has been found that sub-micron particles, preferably sub-micron zinc oxide, provide such UV-protection even at a very low concentration while also improving the efficacy of the biocide. Such sub-micron particles, preferably ZnO, also can provide transparent to clear biocide-containing formations. In summary, the sub-micron based and preferably sub-micron ZnO-based biocidal compositions of the invention provide biocidal stabilization, UV-protection, protection from leaching of biocides and enhanced biocidal activity. These dispersions find particular utility in personal care and industrial compositions. Sub-micron particles can be introduced in the biocide compositions with built-in linking polymer species composites or as a sub-micron particle concentrate. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0007]    While this specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the invention, it is anticipated that the invention can be more readily understood through reading the following detailed description of the invention and study of the included examples. 
         [0008]    In accordance with this invention, there is provided a stable dispersion composition comprising a biocide coated and stabilized with sub-micron carrier particles. The sub-micron particles can be selected from sub-micron zinc oxide, sub-micron titanium dioxide, sub-micron cerium dioxide and sub-micron silica, sub-micron alumina, sub-micron stilbene, sub-micron carbon and clay particles. 
         [0009]    Biocides useful in the practice of the present invention include, but are not limited to, iodopropyny butyl carbamate (IPBC), benzisothiazolinone (BIT), zinc pyrithione, triazole, thiocarbamates and naturally occurring biocides. In a preferred embodiment, the biocide employed for the biocidal dispersion is selected from the group consisting of amine reaction products, 1,2-benzisothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol (bronopol), 3-iodo-2-propargyl butyl carbamate (IPBC), 5-chloro-2-methyl-4-isothiazolin-3-one (CMTT)/2-methyl-4-isothiazoli-3-one (MIT), bicyclic oxazolidines, glutaraldehyde, N-(trichloromethylthio)phthalimide biocides (Folpet), tetrachloroisophthalo-nitrile biocides, benzisothiazole (BIT), Zinc pyrithone, triazole and/or tetrahydro-3,5-dimethyl-2h-1,3,5-thiodiazine-2-thione. It is believed that the invention can be practiced in conjunction with a wide variety of biocides. 
         [0010]    The dispersion can be an aqueous or non-aqueous formulation and the biocide concentration can be present in an amount of 1-40 wt. % of the composition. The sub-micron particles are processed to re-disperse the agglomerated fraction. This is accomplished by using several polymeric compositions with other optional additives (see examples). The stabilized sub-micron particles can be present in an amount of 0.001-20 wt %, preferably from 0.001 to 5% of said composition. 
         [0011]    The carrier sub micron particles are processed using polar additives containing polar moieties and hydrophobic segments, capable of binding the sub-micron particles through the polar moieties and adsorbing on to the target biocide via the hydrophobic segments. Examples of such polar additives are compounds containing two or more hydroxyl groups, or carboxylate acids/esters/salts or chelating moieties like thio compounds, nitrogen containing moieties with at least one lone pair of electron per mole. The chelating moieties should be in close proximity separated by not more than ten carbon atoms. Example of such stabilizing compositions include a mixture of hydrophobic polymers along with hydrophilic surfactants preferably anionic and nonionic surfactants with HLB&gt;12 for aqueous dispersions and HLB&lt;12 for non aqueous dispersions. 
         [0012]    The dispersions find particular utility in personal care and industrial compositions. In addition to all types of personal care compositions, these biocidal compositions can be used to protect paints and coatings, building materials, stucco concrete, asphalt, caulks, sealants, leather, wood, inks, pigment dispersions, metal working fluids, drilling muds, clay slurries and the like. 
         [0013]    The invention will now be described in detail by reference to the following working examples: 
         [0014]    Method of Preparation: A typical method consists of mixing 0.1 to 50% weight of ZnO with 0.1-10 Weight % of an anionic wetting agent, 0.01 to 10% of a film forming polymeric deagglomerant/dispersant and water. The mixture is wet grinded in a basket mill using a 0.1 mm ZrO 2  grinding aid (1 to 20 times the weight of metal oxide) until the particle sizes are in the submicron to sub-micron particle size range. Advantage of using the above method is to obtain dispersion of high loading, low viscosity, the medium of dispersion can be either oil or water and it forms a good film. 
         [0015]    (Example 1-20). The stabilizing components for the sub-micron particles, as described could be present in the biocide composition for in-situ stabilization or can be provided as a sub-micron particle concentrate which can be added to the biocide formulation. 
         [0016]    Further, the present invention is illustrated in detail by way of the below given examples. The examples are given herein for illustration of the invention and are not intended to be limiting thereof. 
     
    
     STABILIZATION OF SUB-MICRON-PARTICLES IN AQUEOUS SYSTEM  
     Example 1 
       [0017]      
         [0000]                                                          Ingredient   Wt %                                        ZnO   40           Styleze 2000   2           Sodium dodecyl benzene sulfonate   4           Water   54                        
Viscosity 530; pH 8.25, Particle size distribution is D 10   -0.07  μ, D 25 =0.095 μ; Dd 50 =0.113 μ; D 75 0.26 μ and D 90 =0.33 μ
 
         [0018]    Commercially available ZnO from Unicore, Horse head and other suppliers were used to prepare the above dispersions. Styleze 2000 is anionic terpolymer of PVP and acrylic acid from ISP Inc. 
         [0019]    All dispersions are prepared by grinding the samples in a basket mill using zirconium bead as grinding aid. The pH of the formulation is 7.5 and the viscosity around 1000 CP. The dispersion is stable after heat aging at 50 C. for 1 month. Good for skin and sun care applications with less whitening. 
       STABILIZATION OF SUB-MICROPARTICLE IN NON AQUEOUS SYSTEM  
     Example 2 
       [0020]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Polyethylene glycol (PEG 400) 
                 89.80 
               
               
                   
                 Cyclohexane dimethanol 
                 0.200 
               
               
                   
                 Sub-micron ZnO 
                 10.00 
               
               
                   
                   
               
             
          
         
       
     
         [0021]    Grinding or milling sub-micron ZnO or TiO 2 (0-10%) in PEG 400, propane diol or other solvent mixture to form a non-aggregated, well-dispersed sub-micron particles of ZnO/TiO 2 /CeO 2 . Propanediol, Easyperse P20, PVP or Styleze 2000 is used to stabilize the sub-micron particles. The resultant dispersion is further diluted and mixed with the corresponding solvent to form transparent or translucent dispersions of required concentration (0.001 to 1%) based on needs. 
       COMPARATIVE EXAMPLES OF BIOCIDE (EXAMPLE 3, 4 AND 5) IN WATER USING CONVENTIONAL METAL OXIDE 
       [0022]    Method of Preparation: Typical method consists of mixing the ingredients mentioned below in a steel beaker. To the above sample 2 to 20 times the weight of Zirconium beads are added and grinded well in a basket or roller mill until a stable dispersion with particle size in the submicron to sub-micron range is obtained. 
       Example 3 
       [0023]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 72.96 
               
               
                   
                 Surfynol CT 111 
                 0.50 
               
               
                   
                 Pluronic L 101 
                 0.50 
               
               
                   
                 Easyperse P 20 
                 1.5 
               
               
                   
                 Regular ZnO 
                 4.00 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    Viscosity 7530; pH 8.25, Particle size distribution is D 10 =0.32 μ, D 25 =0.74 μ; Dd 50 =1.09 μ; D 75  3.4 and D 90 =7.2 μ 
       Example 4 
       [0025]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 71.26 
               
               
                   
                 Surfynol CT111 
                 0.70 
               
               
                   
                 Easyperse P 20 
                 2.50 
               
               
                   
                 Regular TiO2 
                 5.00 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
             
          
         
       
     
         [0026]    Viscosity 6200 CP, pH 5.5, Particle size distribution is D10=0.27 μ; D25=0.65 μ; D50 0.97 μ; D75=2.9 μ and D90=5.9 μ 
         [0027]    The stabilization of a 20% active IPBC based formulation requires at least 4% of a regular metal oxide compound. The stabilization with sub-micron metal requires only a very small concentration (e.g. 0.1%). Moreover, the viscosity of the formulation obtained with sub-micron metal oxide and sub-micron organic particles are low compared to one with regular metal oxide or organic particulates. 
       EXAMPLES OF BIOCIDE USING STABILIZED FORM OF SUB-MICRON  PARTICLES   
     Example 5 
       [0028]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 76.86 
               
               
                   
                 Surfynol CT 111 
                 0.005 
               
               
                   
                 Easy Sperse P20 
                 2.00 
               
               
                   
                 Sub-micron ZnO (composition from 
                 0.10 
               
               
                   
                 example 1 is added to obtain 0.1% ZnO) 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
             
          
         
       
     
         [0029]    The formulation was stable at RT and after heat-aged for one month at 50C. The viscosity was 2000-4500 CP; the pH was 7 to 8.5. The particle size distribution is D10=0.06 μ; D25=0.09 μ; D50=0.29 μ; D75=0.76 μ and D90=1.8 μ 
       EXAMPLE OF BIOCIDE DISPERSIONS USING INSITU GNERATED SUBMICRON UV-BLOCKERS (EXAMPLE 6-15) 
     Example 6 
       [0030]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 75.96 
               
               
                   
                 Surfynol CT111 
                 0.70 
               
               
                   
                 Easysperse P 20 
                 2.50 
               
               
                   
                 Sub-micron TiO 2   
                 0.30 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
             
          
         
       
     
         [0031]    Viscosity is around 2300-3200 CP, pH is between 5.3 and 6.0. The particle size distribution is D10=0.08; D25=0.103; D50=0.37; D75=0.84 and D90=1.96 
       Example 7 
       [0032]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 76.86 
               
               
                   
                 Surfynol CT111 
                 0.50 
               
               
                   
                 Easysperse P 20 
                 2.00 
               
               
                   
                 Sub-micron ZnO 
                 0.10 
               
               
                   
                 IPBC 
                 10.00 
               
               
                   
                 Folpet 
                 10.00 
               
               
                   
                 Kelzan 
                 0.50 
               
               
                   
                   
               
               
                   
                 Viscosity is 1500-3000 CP; its pH was 7.8-8.5. 
               
             
          
         
       
     
       Example 8 
       [0033]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 76.86 
               
               
                   
                 Surfynol CT111 
                 0.50 
               
               
                   
                 Pluronic L 101 
                 0.50 
               
               
                   
                 EasySperse P 20 
                 1.5 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Previously stabilized 
                 0.10 
               
               
                   
                 sub-micornized ZnO 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
               
                   
                 Viscosity 3000-3500 CP; 
               
               
                   
                 pH 7.7-8.3. 
               
             
          
         
       
     
       Example 9 
       [0034]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 77.4 
               
               
                   
                 Surfynol CT111 
                 0.50 
               
               
                   
                 Pluronic L 101 
                 1.50 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 sub-micronized ZnO 
                 0.10 
               
               
                   
                 Kelzan 
                 0.50 
               
               
                   
                   
               
               
                   
                 Viscosity is 2000-3000 CP; 
               
               
                   
                 pH 7.7-8.3. 
               
             
          
         
       
     
       Example 10 
       [0035]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 74.4 
               
               
                   
                 Surfynol CT111 
                 0.50 
               
               
                   
                 Pluronic L 101 
                 0.75 
               
               
                   
                 Pluronic L 103 
                 0.75 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Sub-micornized ZnO 
                 0.10 
               
               
                   
                 Kelzan 
                 0.50 
               
               
                   
                   
               
               
                   
                 Viscosity is 1500-2300 CP; 
               
               
                   
                 pH 7.8-8.2. 
               
             
          
         
       
     
       Example 11 
       [0036]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 70.9 
               
               
                   
                 Surfynol 104E 
                 0.50 
               
               
                   
                 Sub-micornized ZnO 
                 0.50 
               
               
                   
                 BIT 
                 26.4 
               
               
                   
                 Sag 30 
                 0.2 
               
               
                   
                 Kelzan 
                 0.50 
               
               
                   
                   
               
               
                   
                 Viscosity 2000-3500 CP, 
               
               
                   
                 pH 5.5-6.5 
               
             
          
         
       
     
       Example 12 
       [0037]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 55.6 
               
               
                   
                 Easysperse P20 
                 2.5 
               
               
                   
                 Surfynol CT111 
                 0.9 
               
               
                   
                 Sub-micron ZnO 
                 0.5 
               
               
                   
                 Zinc Pyrithione 
                 40.0 
               
               
                   
                 Kelzan 
                 0.5 
               
               
                   
                   
               
             
          
         
       
     
       Example 13 
       [0038]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 76.86 
               
               
                   
                 Easysperse P20 
                 2.0 
               
               
                   
                 Surfynol CT111 
                 0.005 
               
               
                   
                 Sub-micron ZnO 
                 0.10 
               
               
                   
                 Propoconazole 
                 20.00 
               
               
                   
                 Kelzan 
                 0.54 
               
               
                   
                   
               
             
          
         
       
     
       Example 14 
       [0039]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 72.8 
               
               
                   
                 Styleze W20 
                 3.5 
               
               
                   
                 Sub-micron TiO 2   
                 1.0 
               
               
                   
                 BIT 
                 22.7 
               
               
                   
                   
               
             
          
         
       
     
       Example 15 
       [0040]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Water 
                 20.0 
               
               
                   
                 Thyme 
                 10.0 
               
               
                   
                 Peppermint 
                 10.0 
               
               
                   
                 Balm mint 
                 10.0 
               
               
                   
                 Tea Tree Oil 
                 10.0 
               
               
                   
                 Sub-micron ZnO 
                 0.5 
               
               
                   
                 Tween 20 
                 1.5 
               
               
                   
                 Pluronic L 127 
                 1.0 
               
               
                   
                   
               
             
          
         
       
     
         [0041]    Thyme, peppermint and Balmint extracts were obtained from Ruger chemicals, Tea tree oil was obtained from Trekking company. 
       EXAMPLE OF BIOCIDE STABILIZED FROM YELLOWING IN PRESENCE OF SUB-MICRON METAL OXIDES (FROM EXAMPLE 2) 
     Example 16   
       [0042]    The formulation 11 is diluted with PEG and grinded using zirconium beads to get concentration of sub-micron ZnO in the range of 0.001 to 0.5%. To the sample prepared above, 20% biocides are added and mixed well to dissolve or disperse the biocides in the above solution. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 PEG 400 
                 79.999 
               
               
                   
                 IPBC 
                 20.0 
               
               
                   
                 Stabilized sub-micron ZnO 
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
       Example 17 
       [0043]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Texanol 
                 60 
               
               
                   
                 Tripropylene glycol ether 
                 9.999 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Stabilized ZnO 
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
       Example 18 
       [0044]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 PEG 400 
                 79.999 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Stabilized sub micron TiO 2   
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
       Example 19 
       [0045]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Texanol 
                 60.00 
               
               
                   
                 Tripropylene glycol ether 
                 9.999 
               
               
                   
                 IPBC 
                 30.00 
               
               
                   
                 Stabilized sub-micron TiO 2   
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
       Example 20 
       [0046]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 PEG400 
                 79.999 
               
               
                   
                 IPBC 
                 20.00 
               
               
                   
                 Stabilized Sub-micron CeO 2   
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
       Example 21 
       [0047]      
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ingredient 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Texanol 
                 60.00 
               
               
                   
                 Tripropylene glycol ether 
                 9.999 
               
               
                   
                 IPBC 
                 30.00 
               
               
                   
                 Stabilized sub-micron CeO 2   
                 0.001 
               
               
                   
                   
               
             
          
         
       
     
         [0048]    Yellowing of the above samples was measured (Gardner color) at room temperature, after heat aging for 1 month at 50C. or after exposing them to UV irradiation using a Xenon lamp continuously for 6 hours at a controlled humidity. Yellowing was compared to a control that contains no metal ion. Results showed that the presence of sub-micron ZnO, TiO 2 , CeO 2  particles were effective even at the 0.001% level to preclude yellowing of the biocide. The samples were clear to transparent at a concentration of 0.05% and below. The product was stable for 1 month at RT and/or heat-aged at 50°C. for the same period of time. 
       Example 22   
       [0049]    Various biocide formulations (Example 3 and Example 5) were added to standard polyvinyl acetate (PVA) to a final concentration of 500 ppm IPBC. 
         [0050]    Drawdown of the paint samples were prepared by casting a 3-mil film onto drawdown paperboard (Lanetta). The drawdown samples were allowed to dry at room temperature for 24 hrs. Strips were cut from each drawdown sample and leached with distilled water at a flow rate of six exchanges for 72 and 96 hrs, followed by drying at room temperature for 24 hrs. 
         [0051]    One inch squares were cut from each strip and placed painted-side-up on solidified malt agar. The plates were inoculated with 1.0 mL of a mixed fungal suspension consisting of  Aspergillus niger  (ATCC 6275) and  Penicillium funiculosum  (ATCC 11797), each with a concentration of about 10 7  spores/mL. 
         [0052]    The plates were incubated at 28° C. and 85% RH for 28 days. Fungal growth was rated on the surface of the painted sample as indicated in ASTM D5590 on a scale from 0-4 where “0” represents no growth; 1 represents traces of growth (&lt;10%); 2 represents light growth (10-30%); 3 represents moderate growth (30-60%) and 4 represents heavy growth (60% to complete coverage). As shown in Table I, the biocide formulation containing the submicron ZnO provided enhanced biocidal efficacy (less growth) on its surface as compared to the same formulation containing standard ZnO particles. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Efficacy data showing enhanced biocidal activity 
               
             
          
           
               
                   
                 IPBC 
                 0 hrs or 
                   
                   
               
               
                 Sample 
                 (in ppm) 
                 No leach 
                 72 hrs 
                 96 hrs 
               
               
                   
               
               
                 IPBC dispersion + ZnO 
                 500 
                 0 
                 2 
                 2 
               
               
                 (Example 3) 
               
               
                 IPBC dispersion + submicron 
                 500 
                 0 
                 1 
                 1 
               
               
                 ZnO (Example 5) 
               
               
                   
               
             
          
         
       
     
         [0053]    While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.