Use of a crosslinkable silicone invert emulsion for producing breathable coatings

Abstract

The invention relates to the general field of silicone coating on various pliable supports, for example textiles, made of synthetic polymers (polyamide, polyester, etc.). An aim of the invention is to propose an effective process for producing coatings that are waterproof and permeable to moisture vapour, on pliable supports, this process allowing an improvement in the moisture vapour-permeability of the silicones while at the same time conserving the waterproofness. The process according to the invention which achieves this aim consists essentially in coating one of the faces of the support with a film formed by a water-in-oil inverse silicone emulsion comprising a continuous oily silicone phase φs, which can be crosslinked into an elastomer and which comprises a polyorganosiloxane (POS) A that is crosslinkable by polyaddition, by polycondensation, by cationic means or by free-radical means; optionally a crosslinking organosilicic compound B; optionally at least one catalyst C, an aqueous phase φa, a stabilizer, and in seeing to it that the silicone phase φs crosslinks and that removal of water occurs. The invention also relates to pliable supports made of polyamide or polyester, that are waterproof and permeable to moisture vapour, obtained by using a water-in-oil inverse silicone emulsion.

1 . Process for producing coatings that are waterproof and permeable to moisture vapour, on pliable supports, comprising: 
 applying to at least one of the faces of the support, so as to form a film, a silicone-based water-in-oil inverse emulsion comprising: 
 a continuous oily silicone phase φs: 
 which can be crosslinked into an elastomer  
 and which comprises:  
 
 -A- at least one polyorganosiloxane (POS) that is crosslinkable by polyaddition, by polycondensation, by cationic means or by free-radical means;  
 -B- optionally at least one crosslinking organosilicic compound;  
 -C- optionally at least one catalyst for the crosslinking reaction;  
 an aqueous phase (pa comprising at least 20% by weight of water,  
 at least one stabilizer,  
   in seeing to it that the silicone phase φs crosslinks and that removal of water occurs.    
     
     
         2 . Process according to  claim 1 , wherein the silicone phase φs has a viscosity η at 25° C. of less than 2000 mPa·s.  
     
     
         3 . Process according to  claim 1 , wherein the aqueous phase φa comprises from 30 to 90% by weight of water.  
     
     
         4 . Process according to  claim 1 , wherein the continous oily phase the aqueous phase φa has a mean particle size defined by its mean diameter D50 (in μm) such that:  
         D50≦100.  
     
     
         5 . Process according to  claim 1 , having an amount of inverse silicone emulsion such that the thickness of the film forming the coating is less than or equal to 50 μm applied to the support.  
     
     
         6 . Process according to  claim 1 , wherein the stabilizer is selected from the group comprising: 
 non-ionic, anionic, cationic, or even zwitterionic surfactants;    silicone polyethers;    solid particles, preferably particles of silica optionally in combination with at least one co-stabilizer;    and mixtures thereof;    the solid particles optionally in combination with at least one co-stabilizer.    
     
     
         7 . Process according to  claim 1 , wherein the continuous oily silicone phase φs comprises: 
 -A- at least one POS carrying crosslinking functional groups, the latter being selected from groups comprising at least one ethylenically unsaturated function;    -B- optionally at least one silane and/or one POS carrying functional groups which may or may not be of the same nature as the crosslinking functional groups of POS A;    -C- at least one photoinitiator system selected from the onium salts of an element of groups 15 to 17 of the Periodic Table or of an organometallic complex of an element of groups 4 to 10 of the Periodic Table;    the crosslinking functional groups being selected from groups comprising at least one ethylenically unsaturated function and/or epoxide and/or oxethane.    
     
     
         8 . Process according to  claim 7 , wherein the POSs A are epoxysilicones and/or vinyl ether silicones which are: 
 either linear or substantially linear and comprise units of formula (I), ending with units of formula (II.1) and (II.2),    or cyclic and consists of units of formula (II.1):    in which formulae:    the symbols R 1  are similar or different and represent: 
 either a linear or branched C 1 -C 6  alkyl radical optionally substituted advantageously with one or more halogens,  
 or an optionally substituted C 5 -C 8  cycloalkyl radical,  
 or an aryl or aralkyl radical optionally substituted: 
 with halogens and/or alkoxyls,  
 the phenyl, xylyl, tolyl or dichlorophenyl radicals,  
 
   the symbols Z are similar or different and represent: 
 either the radical R 1 ,  
 or a crosslinking functional group corresponding to an epoxide or vinyl ether residue linked to the silicon by means of a divalent radical comprising from 2 to 20 carbon atoms optionally comprising a hetero atom, at least one of the symbols Z corresponding to a crosslinking functional group,  
 the POSs A most specially envisaged being epoxysilicones of formulae (A.I) and (A.II) below:  
                     
 with  
   X═CH 3 ; phenyl; cycloalkyl; alkyl; C 1 -C 18  alkyl; alkenyl;    —OH; H; CH 2 —CH 2 —CH 2 —OH; CH 2 —CH 2 —CF 3 ; —(CH 2 ) n —CF 3 , n=1 to 20; 
 and Y= 
                     
   a 1 , a 2  and b 1 , b 2  being defined as follows, in these formulae (A.I) and (A.II) 
 1≦a 1 , a 2  1≦b 1 , b 2    
   a 2 , b 2  being =0 in formula (A.II) to give the epoxidized disiloxane (A.III).    
     
     
         9 . Process according to  claim 1 , wherein the following products are selected as constituents of the silicone phase: 
 POS (A′): product having units of formula:                          in which:    W is an alkenyl group,    Z is a monovalent hydrocarbon-based group, free of unfavourable action on the activity of the catalyst and selected from alkyl groups containing from 1 to 8 carbon atoms inclusive, and also from aryl groups    a is 1 or 2, b is 0, 1 or 2 and a+b is between 1 and 3, optionally at least some of the other units are units of general formula:                          in which Z has the same meaning as above and c has a value of between 0 and 3;    dimethylpolysiloxanes with dimethylvinylsilyl ends, copolymers of methylvinyldimethylpolysiloxanes with trimethylsilyl ends, copolymers of methylvinyldimethylpolysiloxanes with dimethylvinylsilyl ends and cyclic methylvinylpolysiloxanes being more specially selected; 
 POS (B′): product having siloxyl units of formula:  
                     
 in which:  
 L is a monovalent hydrocarbon-based group free of unfavourable action on the activity of the catalyst and selected from alkyl groups comprising from 1 to 8 carbon atoms inclusive and  
 d is 1 or 2, c is 0, 1 or 2, d+c has a value of between 1 and 3,  
 optionally at least some of the other units being units of general formula:  
 in which L has the same meaning as above and g has a value of between 0 and 3, and (methylhydrosiloxy)(α,ω-dimethylhydro)-poly(dimethylsiloxane) being more specifically selected.  
   
     
     
         10 . A method for producing coatings that are waterproof and permeable to moisture vapor comprising a water-in-oil inverse silicone emulsion, comprising: 
 a continuous oily silicone phase φs: 
 which can be crosslinked into an elastomer  
 and which comprises: 
 -A- at least one polyorganosiloxane (POS) that is crosslinkable by polyaddition, by polycondensation, by cationic means or by free-radical means;  
 -B- optionally at least one crosslinking organosilicic compound;  
 -C- optionally at least one catalyst for the crosslinking reaction;  
 
   an aqueous phase φa,    at least one stabilizers.    
     
     
         11 . Film-forming water-in-oil inverse silicone emulsion, for producing coatings that are waterproof and permeable to moisture vapour, on pliable supports, which comprises: 
 a continuous oily silicone phase φs: 
 which can be crosslinked into an elastomer  
 and which comprises: 
 -A- at least one polyorganosiloxane (POS) that is crosslinkable by polyaddition, by polycondensation, by cationic means or by free-radical means;  
 -B- optionally at least one crosslinking organosilicic compound;  
 -C- optionally at least one catalyst for the crosslinking reaction;  
 
   an aquous phase φa comprising at least 20% by weight of water,    at least one stabilizer,    at least one additive which promotes adhesion of the coating to the support and/or an improvement in the waterproof and moisture vapour-permeability properties,    and/or at least one additive for optimizing the mechanical properties of the coating.    
     
     
         12 . Pliable support, optionally a textile support, which is coated on at least one of its faces with a coating that is waterproof and permeable to moisture vapour, obtained by implementing the process according to  claim 1.