Method for treating a mineral filler with a polydialkylsiloxane and a fatty acid, resulting hydrophobic fillers thus obtained and the applications thereof in polymers for breathable films

Abstract

The invention relates to a method for treating a mineral filler by means of a polydialkylsiloxane and a fatty acid, the hydrophobic fillers thus obtained, and the application thereof in polymers for the manufacture of films and notably breathable films.

1 . A method for treating a mineral filler consisting of a filler selected from the group consisting of marble, calcite, precipitated calcium carbonate, and mixtures thereof to provide the filler with hydrophobic properties suitable for incorporation into a polymer for a breathable film, comprising a two-step surface treatment of the filler, wherein the first step (pretreatment) comprises treating the filler with at least one polydialkylsiloxane, and the second step comprises treating the polydialkylsiloxane treated filler with at least one fatty acid having more than 10 carbon atoms, and the two steps can be carried out simultaneously.  
   
   
       2 . The method according to  claim 1 , wherein the two treatments are carried out simultaneously, but the fatty acid never comes into contact first with the filler.  
   
   
       3 . The method according to  claim 2 , wherein the polydialkylsiloxane is added firstly and then the fatty acid is added immediately afterwards.  
   
   
       4 . The method according to  claim 1 , wherein the method is carried out in two distinct steps, so that the polydialkylsiloxane is added first to the filler, and then the fatty acid is added.  
   
   
       5 . The method according to  claim 1 , wherein the filler is marble or calcite or a mixture thereof.  
   
   
       6 . The method according to  claim 1 , wherein the filler is precipitated calcium carbonate.  
   
   
       7 . The method according to  claim 1 , wherein the polydialkylsiloxane is a polydialkylsiloxane of general formula (R) 3 —Si—O—[(R) 2 —Si—O] n —Si—(R) 3  and the alkyl group R is a C1-C4 alkyl group having a kinematic viscosity at 25° C. of between 50 and 100,000 centistokes.  
   
   
       8 . The method according to  claim 7 , wherein the alkyl group R is a methyl radical.  
   
   
       9 . The method according to  claim 1 , wherein the method further comprises: 
 placing the filler in a high-speed mixer,    adding the polydialkylsiloxane at a temperature of around 100° C., over 5 minutes, and, at the end of the 5 minutes,    adding the fatty acid.    
   
   
       10 . The method according to  claim 1 , wherein the filler is marble or calcite or a mixture thereof, the polydialkylsiloxane is polydimethylsiloxane, and the fatty acid is stearin.  
   
   
       11 . The method according to  claim 1 , wherein the polydialkylsiloxane is present in an amount of 100 to 2000 ppm of polydialkylsiloxane relative to the weight of dry filler.  
   
   
       12 . The method according to  claim 1 , wherein the fatty acid is present in an amount of 0.6% to 1.4% fatty acid relative to the weight of dry filler.  
   
   
       13 . A mineral filler treated by the method according to  claim 1 .  
   
   
       14 . The mineral filler according to  claim 13 , wherein the filler has a high flowability, determined by the pile method, of less than or equal to 0.98, a specific surface area of between 2 and 6 m 2 /g, and a granulometry top cut of less than 10 μm.  
   
   
       15 . The mineral filler according to  claim 13 , having a turbidity index of between 0.9 and 1 and a foam index of between 0.7 and 1, the two indices being determined by the whizzing method, and a moisture pickup of less than or equal to 0.42 mg/m 2  measured by the moisture pickup method.  
   
   
       16 . A breathable film comprising a filler according to  claim 15 .  
   
   
       17 . A method of manufacturing a breathable film comprising at least one polyolefin and at least one mineral filler according to  claim 15  wherein the method comprising mixing at least one polyolefin with the mineral filler, then forming a film from the mixture.  
   
   
       18 . The method according to  claim 17 , wherein the polyolefin comprises a polymer selected from the group consisting of low-density linear polyethylene, low-density polyethylene, high-density polyethylene, polypropylene and mixtures thereof.  
   
   
       19 . The method according to  claim 17 , further comprising forming a master-batch or compound comprising 20% to 80% by weight of treated filler with respect to the total weight of the master batch or compound.  
   
   
       20 . The method according to  claim 17 , further comprising subjecting the film to uni- or biaxial stretching (or orientation).  
   
   
       21 . A film prepared by the method according to  claim 17 , wherein the film is in the non-stretched state or is stretched uni- or biaxially.  
   
   
       22 . The film according to  claim 21 , having a mottling index below 10 measured according to the “mottling viewer” method.  
   
   
       23 . An article comprising at least one film according to  claim 22 .  
   
   
       24 . A master-batch or compound comprising one or more polyolefin(s) and one or more filler(s), wherein the filler is prepared by the method according to  claim 1 .  
   
   
       25 . The master-batch or compound of polyolefin(s) and filler(s) according to  claim 24 , wherein the master-batch or compound has a melt volume-flow rate greater than 9 cm 3 /10 min (temperature 190° C., load 5 kg, die diameter of 2.095 mm) measured in accordance with ISO 1133 and a thermal stability expressed, according to the strip method, by a length of non-discoloured strip greater than or equal to 20 cm.  
   
   
       26 . A breathable film prepared from a master-batch according to  claim 24 .  
   
   
       27 . A polyolefin article comprising at least one filler according to  claim 14 .  
   
   
       28 . The film of  claim 16 , wherein the breathable film is a polyolefin film.  
   
   
       29 . The method of  claim 8 , wherein the polydimethylsiloxane has a kinematic viscosity at 25° C. of between 300 and 5000.  
   
   
       30 . The method of  claim 8 , wherein the polydimethylsiloxane has a kinematic viscosity at 25° C. of around 1000.  
   
   
       31 . The method of  claim 1 , wherein the fatty acid is selected from the group consisting of stearic acid, palmitic acid, behenic acid, and mixtures thereof.  
   
   
       32 . The method of  claim 11 , wherein the polydialkylsiloxane is present in an amount of from 200 to 1000 ppm relative to the weight of dry filler.  
   
   
       33 . The method of  claim 11 , wherein the polydialkylsiloxane is present in an amount of around 500 ppm relative to the weight of dry filler.  
   
   
       34 . The method of  claim 12 , wherein the fatty acid is present in an amount of from 0.8 to 1.2% relative to the weight of dry filler.  
   
   
       35 . The mineral filler of  claim 13 , wherein the filler is selected from the group consisting of marble, calcite, and mixtures thereof.  
   
   
       36 . The mineral filler of  claim 14 , wherein the granulometry top cut is less than 8 μm.  
   
   
       37 . The method of  claim 19 , wherein the master-batch or compound comprises 45% to 60% by weight of treated filler.  
   
   
       38 . The method of  claim 19 , wherein the master-batch or compound comprises approximately 50% by weight of treated filler.  
   
   
       39 . The article of  claim 23 , wherein the article is a product for absorbing water.