Nanosilicate plates

Abstract

The present invention relates to random form of nanoscale silicate plates produced by a process using an exfoliating agent. The exfoliating agent used in the present invention has the formula: where n=1 to 5 wherein n=1 to 5 and R is a polyoxypropylene group, poly(oxyethylene/oxypropylene) group, or polyoxyethylene group. In this invention, layered silicate clays are exfoliated into random silicate plates by acidifying AMO with inorganic acid, adding the acidified AMO to layered silicate clay with agitation, and adding sodium hydroxide or chloride of alkali metal or alkaline-earth metal, in ethanol, water and a hydrophobic organic solvent to the intermediate product and repeating phase separation procedures to isolate random silicate plates from water phase.

1 . A random form of nanosilicate plates produced by a process comprising the steps of:
 (a) preparing amine-terminating Mannich oligomers (AMO) from polyoxyalkylene diamine, p-cresol and formaldehyde to obtain a polymeric exfoliating agent having a general formula:   
     
       
         
         
             
             
         
       
       where n=1 to 5 
       wherein n is from 1 to 5; R represents an organic group selected from the group consisting of polyoxypropylene groups, poly(oxyethylene/oxypropylene) groups, and polyoxyethylene groups; wherein said formaldehyde is added at an appropriate addition rate by which the exothermic temperature is kept below 120° C.;
 (b) adding inorganic acid to said AMO to form an acidified AMO; 
 (c) mixing said acidified AMO with a swelled inorganic layered silicate clay so as to exfoliate said silicate clay directly through cationic exchange to form an exfoliated silicate clay; 
 (d) mixing an aqueous solution containing a hydroxide or a chloride of alkali metal or alkaline-earth metal, ethanol, water and an organic solvent with said exfoliated silicate clay obtained in step (c) to form a mixture; and 
 (e) keeping the mixture obtained in step (d) static to form an upper organic phase and a lower water phase containing nanosilicate plates. 
 
     
   
   
       2 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said polyoxyalkylene diamine used in said step (a) has molecular weight ranging from 400 to 4,000 g/mol. 
   
   
       3 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said polyoxyalkylene diamine used in said step (a) has molecular weight ranging from 1,000 to 2,000 g/mol. 
   
   
       4 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said polyoxyalkylene diamine used in said step (a) is selected from the group consisting of polyoxypropylene diamine, polyoxyethylene diamine, polyoxybutylene diamine and poly(oxyethylene-oxypropylene) diamine. 
   
   
       5 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said polyoxyalkylene diamine used in said step (a) is polyoxypropylene diamine. 
   
   
       6 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said polyoxyalkylene diamine, p-cresol and formaldehyde in said step (a) are added at a molar ratio (n+1):n:2n, wherein n is 1 to 5. 
   
   
       7 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said formaldehyde used in said step (a) is added at a reaction temperature in the range of 25° C. to 120° C. 
   
   
       8 . The random form of nanosilicate plates as claimed in  claim 1 , wherein 25˜100 wt % of said exfoliating agent obtained in said step (a) has molecular weight ranging from 9,000 to 20,000. 
   
   
       9 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said exfoliating agent and said inorganic acid are mixed in an equivalent ratio 2:1 in said step (b). 
   
   
       10 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said inorganic acid used in said step (b) is selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. 
   
   
       11 . The random form of nanosilicate plates as claimed in  claim 1 , wherein the molar ratio of amino groups in said exfoliating agent to cationic exchange capacity of said silicate clay ranges from 3:1 to 1:1 in said step (c). 
   
   
       12 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said silicate clay used in said step (c) is selected from the group consisting of montmorillonite, kaolin, mica and talc. 
   
   
       13 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said silicate clay used in said step (c) has a cationic exchange capacity ranging from 50 meq/100 g to 200 meq/100 g. 
   
   
       14 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said hydroxide or chloride of alkali metal or alkaline-earth metal used in said step (d) is sodium hydroxide. 
   
   
       15 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said hydroxide or chloride of alkali metal or alkaline-earth metal is added at the same equivalence in said step (d). 
   
   
       16 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said organic solvent used in said step (d) is selected from the group consisting of ether, ketone, ester, nitrile, saturated hydrocarbon, chlorinated hydrocarbon, saturated hydrocarbon and aromatic hydrocarbon. 
   
   
       17 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said organic solvent used in said step (d) is selected from the group consisting of tetrahydrofuran, isopropyl ether, methyl tert-butyl ether, methyl isobutyl ketone, ethylnitrile, ethyl acetate, pentane, hexane, heptane, cyclohexane, dichloromethane, benzene, toluene, dimethylbenzene, chlorobenzene and methoxybenzene. 
   
   
       18 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said hydroxide or chloride of alkali metal or alkaline-earth metal is added at 1 to 5 equivalences in step (d). 
   
   
       19 . The random form of nanosilicate plates as claimed in  claim 1 , wherein said organic phase formed in said step (e) comprises said exfoliating agent suitable for recycling. 
   
   
       20 . The random form of nanosilicate plates as claimed in  claim 1 , wherein solid content in the water phase formed in said step (e) is from 0.1 to 90 weight percent.