Milled Submicron Chlorothalonil With Narrow Particle Size Distribution, and Uses Thereof

Abstract

A method of milling chlorothalonil to form a sub-micron product having a narrow particle size distribution is presented. The milling involves wet milling of the chlorothalonil with high density milling media having a diameter between 0.1 mm and 0.8 mm, preferably between 0.2 mm and 0.7 mm, and a density equal to or greater than 3.8 g/cc, preferably greater than 5.5 g/cc, in a ball mill using between about 40% and 80% loading of the mill volume with milling media, and having the chlorothalonil suspended in an aqueous milling liquid which comprises one or more surface active agents. The milling speed is preferably high, for example from about 1000 rpm to about 4000 rpm. The milled product can be used in foliar applications at a lower effective dosage than prior art formulations, can be used in improved antifouling paint formulations, and can be used in new applications such as the direct injection of solid chlorothalonil particulates in wood to act as a long lasting wood preservative.

1 . A method of preparing a submicron chlorothalonil product comprising the steps of:
 1) providing chlorothalonil, a liquid, and a milling media to a mill, wherein the milling media comprises an effect amount of milling beads having a density of 3.5 g/cm 3  or greater and a diameter between about 0.1 mm and about 0.8 mm; and   2) milling the material for a time sufficient to obtain a product having a mean volume particle diameter d 50  of about 1 micron or smaller.   
     
     
         2 . The method of  claim 1  wherein at least 5% of the milling media has a diameter between about 0.1 mm and about 0.8 mm, comprises zirconium, and have a density greater than about 5.5 g/cm 3 . 
     
     
         3 . The method of  claim 1  wherein 10% or more by weight of the milling media has a diameter between about 0.1 mm and about 0.8 mm, a density greater than about 3.8 g/cm 3  and a diameter between about 0.1 and about 0.7 mm, and wherein the liquid comprises at least one surface active agent. 
     
     
         4 . The method of  claim 3  wherein the time is between about 10 minutes and about 240 minutes, wherein at least 40% by weight of the milling media comprises milling beads comprising a zirconium oxide and having a diameter between about 0.1 mm and about 0.7 mm, and wherein the product has a mean volume particle diameter d 50  of less than about 0.7 microns. 
     
     
         5 . The method of  claim 4  wherein the product has a diameter d 90 , such that 90 volume percent of the product has a diameter of the d 90  or less, of less than 4 times the d 50 . 
     
     
         6 . The method of  claim 3  wherein the product has a mean volume particle diameter d 50  of less than about 0.4 microns. 
     
     
         7 . The method of  claim 6  wherein the product has a diameter d 90 , such that 90 volume percent of the product has a diameter of the d 90  or less, of less than 4 times the d 50 . 
     
     
         8 . The method of  claim 6  wherein the product has a diameter d 90 , such that 90 volume percent of the product has a diameter of the d 90  or less, of less than 3 times the d 50 . 
     
     
         9 . The method of  claim 3  wherein the product has a mean volume particle diameter d 50  of between about 0.1 microns and about 0.3 microns. 
     
     
         10 . The method of  claim 9  wherein the product has a diameter d 90 , such that 90 volume percent of the product has a diameter of the d 90  or less, of less than 3 times the d 50 . 
     
     
         11 . The method of  claim 3  wherein at least 25% by weight of the milling media consists of milling beads having a diameter between about 0.1 mm and about 0.8 mm which consist essentially of zirconium oxide, doped zirconium oxide, stabilized zirconium oxide, or mixture thereof. 
     
     
         12 . The method of  claim 1  wherein at least 25% by weight of the milling media consists of milling beads having a diameter between about 0.2 mm and about 0.7 mm has a density greater than about 5.5 grams per cubic centimeter. 
     
     
         13 . The method of  claim 1  wherein at least 40% by weight of the milling media consists of milling beads having a diameter between about 0.3 and about 0.6 mm. and a density greater than about 3.8 grams/cm 3 . 
     
     
         14 . The method of  claim 3  wherein at least 25% by weight of the milling media consists of milling beads having a diameter between about 0.4 and about 0.6 mm. 
     
     
         15 . The method of  claim 1  wherein at least 40% of the milling media has a diameter between about 0.3 and about 0.7 mm and a density of 5.5 g/cc or greater, and wherein the milling media occupies between about 40% and 80% of the mill volume. 
     
     
         16 . The method of  claim 3  wherein the milling media consists essentially of milling beads having a diameter between about 0.3 and about 0.7 mm and a density of 5.5 g/cc or greater, and wherein the milling media occupies between about 40 and 80 volume % of the mill. 
     
     
         17 . The method of  claim 16  wherein the mill speed is between about 1000 and about 4000 rpm. 
     
     
         18 . The method of  claim 1  wherein at least 25% by weight of the milling media consists of steel milling beads having a diameter between about 0.2 and about 0.7 mm and a density of 6 g/cc or greater. 
     
     
         19 . The method of  claim 18  wherein the liquid comprises surface active agents. 
     
     
         20 . The method of  claim 19  wherein the steel milling beads have a diameter between about 0.3 and about 0.6 mm. 
     
     
         21 . The method of  claim 1  wherein the milling media comprises steel. 
     
     
         22 . The method of  claim 1  wherein at least 25% of the milling media are metallic milling beads having a diameter between about 0.3 and about 0.7 mm and a density of 5.5 g/cc or greater, and wherein the milling material is between about 40% and 80% of the mill volume. 
     
     
         23 . The method of  claim 22  wherein the product chlorothalonil comprises between 2 and about 60% by weight of surface active agents, based on the weight of the chlorothalonil. 
     
     
         24 - 51 . (canceled) 
     
     
         52 . A method of preserving wood comprising the steps of:
 injecting the wood with an injectable slurry comprising water and a plurality of chlorothalonil particles, wherein the particle size d 98 , such that 98 volume percent of the chlorothalonil particles has a diameter of the d 98  or less, is about 0.5 microns or less; and   removing at least a portion of the water.   
     
     
         53 . A method of preserving wood comprising the steps of:
 milling chlorothalonil according to  claim 10 , wherein the milled organic biocide product further comprises the surface active agents, and wherein the particle size d 98 , such that 98 volume percent of the chlorothalonil particles has a diameter of the d 98  or less, is about 0.5 microns or less;   adding the milled organic biocide product to water to form an injectable slurry; and   injecting the injectable slurry into wood, thereby obtaining a wood product with the milled chlorothalonil particles dispersed therein   
     
     
         54 . The method of preserving wood of  claim 53 , wherein the injectable slurry further comprises dispersed, injectable sparingly soluble copper salt particles, wherein the injectable copper salt particles have been milled by placing in a ball mill the sparingly soluble copper salt, an aqueous liquid comprising a surface-active agent, and a milling media to a mill, wherein the milling media comprises an effective amount of milling beads having a density or about 3.8 grams/cm 3  or greater, and a diameter between about 0.1 mm and about 0.8 mm; and milling the sparingly soluble copper salts for a time sufficient to obtain a milled organic biocide product having a mean volume particle diameter d 50  of about 0.1 microns to 0.3 microns and a d 98  of less than 3 times the d 50 .