Cure-On-Demand Liquid Sealant Composition, Process For The Preparation Thereof And Uses Thereof

Abstract

The present invention is directed to a liquid sealant composition based on polysulphide, capable of curing on demand, and the process for preparing same, the liquid sealant composition including: (i) a polysulphide comprising an —SH end group, (ii) a crosslinking agent chosen from ethylenically unsaturated or acetylenically unsaturated compounds, the unsaturated ethylenic or unsaturated acetylenic functions of the crosslinking agent being chemically blocked with a blocking agent, and (iii) optionally, a catalyst. The present invention also relates to a process for coating a substrate with a composition according to the invention, and also to the cured sealant materials formed from this composition. Finally, the invention relates to the use of a liquid sealant composition according to the invention for the construction and/or the maintenance, and more particularly for the adhesive bonding and/or the protection, of vehicles and machines.

1 . Liquid sealant composition comprising at least:
 (i) a polysulphide with an —SH end group,   (ii) a crosslinking agent chosen from ethylenically unsaturated or acetylenically unsaturated compounds, said unsaturated ethylenic or unsaturated acetylenic functions of the crosslinking agent being chemically blocked with a blocking agent,   (iii) optionally, a catalyst.   
     
     
         2 . Composition according to  claim 1 , wherein said unsaturated ethylenic or unsaturated acetylenic functions of the crosslinking agent are chemically blocked by Diels-Alder reaction with said blocking agent. 
     
     
         3 . Composition according to  claim 1  wherein said crosslinking agent has a functionality f≧2, and preferably 2≦f≦4. 
     
     
         4 . Composition according to  claim 1 , wherein said crosslinking agent is a compound or a mixture of several compounds bearing an allyl function, a maleimide function, or an ethylenically unsaturated or acetylenically unsaturated function bearing an electron-withdrawing group in the alpha position with respect to this double bond or this triple bond, it being possible for said function to be an aldehyde function, ketone function, ester function, hemiester function, amide function, hemiamide function, ester-amide function, nitrile function or imide function which is α,β-ethylenically unsaturated. 
     
     
         5 . Composition according to  claim 4 , wherein said crosslinking agent is an α,β-ethylenically unsaturated imide compound or a mixture of several α,β-ethylenically unsaturated imide compounds chosen from monomaleimide, bismaleimide or trismaleimide compounds of formula: 
       
         
           
           
               
               
           
         
       
       in which:
 R is chosen from linear or branched C 1 -C 30  alkyl chains, 
 R a , R b , R c , R d , R e  and R f , which may be identical or different, are chosen from H or linear or branched C 1 -C 30  alkyl chains, and 
 W is a polyether, polythioether, polyester, polyamide or polysulphide unit. 
 
     
     
         6 . Composition according to  claim 5 , wherein said crosslinking agent is a monomaleimide, bismaleimide or trismaleimide compound in which W is a polyethylene glycol (PEG) unit, a polypropylene glycol (PPG) unit, or a mixed PEG/PPG unit, and is chosen from the compounds of formula: 
       
         
           
           
               
               
           
         
       
       in which:
 R a , R b , R c , R d , R e  and R f , which may be identical or different, are chosen from H or linear or branched C 1 -C 30  alkyl chains, 
 A and B, which may be identical or different, are linear or branched C 1 -C 30  alkyl chains, which can comprise, in their chain, one or more heteroatoms chosen from O, S or N, 
 Y is chosen from —CH 2 —, —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, —CH 2 —CH(CH 3 )— and —CH 2 —CH 2 —CH 2 —CH 2 , 
 x, x′, x″, y, y′, y″, z, z′ and z″, which may be identical or different, range from 1 to 70, preferably from 1 to 40, and even more preferentially from 1 to 12, 
 the sums x+y+z, x′+y′+z′ and x″+y″+z″ are strictly greater than 1, and preferably between 1 and 15, 
 n ranges from 0 to 6, and preferably n=0 or 1, 
 R′ is H or a C 1 -C 6  alkyl radical, and preferably R′ is H, CH 3  or C 2 H 5 , 
 
       and in which the ethylenic bond of the monomaleimide ring or the ethylenic bonds of the bismaleimide or trismaleimide rings are blocked by Diels-Alder reaction with said blocking agent. 
     
     
         7 . Composition according to  claim 1 , wherein said blocking agent is a diene comprising at least one pentacyclic nucleus. 
     
     
         8 . Composition according to  claim 7 , wherein said blocking agent is a diene corresponding to the following formula: 
       
         
           
           
               
               
           
         
       
       in which:
 R 1 , R 2 , R 3  and R 4 , which may be identical or different, are chosen from H or C 1 -C 12  alkyl chains optionally functionalized with at least one ester, ether, ketone or amide function, 
 X═CH 2 , O, S, or N—R x , in which R x  is chosen from linear or branched C 1 -C 30  alkyl chains. 
 
     
     
         9 . Composition according to  claim 8 , in which X═O. 
     
     
         10 . Composition according to  claim 8 , in which:
 the R 1  radical and optionally the R 4  radical are identical C 1 -C 12  alkyl chains optionally functionalized with at least one ester, ether, ketone or amide function,   the R 2  radical, the R 3  radical and, optionally, the R 4  radical, if it is not a C 1 -C 12  alkyl chain, are hydrogen atoms.   
     
     
         11 . Composition according to  claim 10 , in which the R 1  radical and optionally the R 4  radical are chosen from the following groups:
   —R y —C(O)O—R z ,—R y —(O)CO—R z ,and R y —O—R z ,
   
       in which:
 R y  is a linear or branched C 1 -C 8 , preferably C 1 -C 4 , and even more preferentially C 1 -C 2 , alkyl chain, 
 R z  is a linear, branched or cyclic C 1 -C 12 , preferably C 1 -C 6 , alkyl chain, and even more preferentially a linear C 1 -C 2  alkyl chain, or an aryl group, and preferably a phenyl group. 
 
     
     
         12 . Composition according to  claim 1 , wherein said blocking agent is chosen from: furfuryl acetate, furfuryl benzyl, ethyl 3-(2-furyl)propanoate, furan-2-ylmethyl pivalate, furan-2-ylmethyl-3,5,5-trimethyl hexanoate and furan-2-ylmethylcyclohexanecarboxylate. 
     
     
         13 . Process for preparing a liquid sealant composition as defined according to  claim 1 , wherein the process comprises at least the following steps:
 i) synthesizing of a crosslinking agent chosen from ethylenically unsaturated or acetylenically unsaturated compounds, said unsaturated ethylenic or unsaturated acetylenic functions of the crosslinking agent being chemically blocked by Diels-Alder reaction with a blocking agent, optionally in the presence of a catalyst, then   ii) mixing of the chemically blocked crosslinking agent obtained at the end of step i) with a liquid polysulphide polymer comprising an —SH end group, optionally in the presence of a catalyst, the mixing temperature having to be controlled so as not to exceed the crosslinking agent deblocking temperature.   
     
     
         14 . Coating process comprising a step of applying a composition as defined according to  claim 1  to a substrate, followed by a step of deprotecting the crosslinking agent chemically blocked with a blocking agent, under the effect of external energy, which results in the initiation of the reaction between the polysulphide and the crosslinking agent, and therefore in the curing of the mass of the sealant material. 
     
     
         15 . Process according to  claim 14 , in which the crosslinking agent chemically blocked with a blocking agent is deprotected by retro-Diels-Alder. 
     
     
         16 . Process according to  claim 14 , in which the external energy is provided by conduction, by convection or by radiation. 
     
     
         17 . Process according to one of  claim 14 , in which the crosslinking agent chemically blocked with a blocking agent is deprotected by heating at a temperature in the range of from 60 to 120° C. 
     
     
         18 . Process according to  claim 17 , in which the crosslinking agent chemically blocked with a blocking agent is subjected to the action of heat for a period ranging from 15 minutes to 2 hours. 
     
     
         19 . Process according to  claim 14 , in which, after the step of deprotecting the crosslinking agent, the mass of sealant material is subjected to a curing step. 
     
     
         20 . Process according to  claim 19 , in which the curing step is carried out at a temperature ranging from 18 to 35° C., for a period ranging from 1 to 3 days. 
     
     
         21 . Cured sealant material prepared from the curing of a liquid sealant composition as defined according to  claim 1  and in that it exhibits, after complete curing, a tensile strength of at least 1 MPa, a tensile elongation at break of at least 100%, and a hardness of at least 40 shA. 
     
     
         22 . Use of a liquid sealant composition as defined according to  claim 1  for constructing and/or maintaining aircraft or spacecraft, motor vehicles, rail vehicles, ships, machines, appliances and furniture. 
     
     
         23 . Use of a liquid sealant composition as defined according to  claim 22  for adhesive bonding and/or protection against corrosion of aircraft or spacecraft, motor vehicles, rail vehicles, ships, machines, appliances and furniture.