Perfluoroelastomer gels

Abstract

Perfluoroelastomeric gel having the following properties: appearance: transparent gelatinous solid; water content between 10% and 90% by weight; density between 1.1 and 2.1 g/cm 3 ; said gel satisfies the following test: dried in a stove at 90° C. until a constant weight gives curable perfluoroelastomers.

1 . Perfluoroelastomeric gel having the following properties: 
 appearance: transparent gelatinous solid;    water content between 10% and 90% by weight;    density between 1.1 and 2.1 g/cm 3 ;    said gel satisfies the following test: the gel, subjected to drying in a stove at 90° C. until a constant weight, gives a curable perfluoroelastomer.    
   
   
       2 . Perfluoroelastomeric gel according to  claim 1 , containing TFE-based perfluoroelastomers with at least another (per) fluorinated comonomer having at least one unsaturation of ethylene type.  
   
   
       3 . Perfluoroelastomeric gel according to  claim 2 , wherein the comonomer in the perfluoroelastomers is selected from the following: 
 CF 2 ═CFOR f  (per)fluoroalkylvinyl ethers (PAVE), wherein R f  is a C 1 -C 6  (per)fluoroalkyl;    CF 2 ═CFOX (per)fluoro-oxyalkylvinylethers, wherein X    is a C 1 -C 12  (per)fluorooxyalkyl, containing one or more or    more ether groups;    perfluorodioxoles of formula                          wherein R′ Fn  is equal to R Fn  or OR Fn  wherein R Fn  is a linear or branched perfluoroalkyl radical with 1-5 carbon atoms, preferably R′ Fn ═OCF 3 ; X 1n  and X 2n , equal to or different from each other, are F, CF3; (per)fluorovinylethers (MOVE) of general formula CFX AI ═CX AI OCF 2 OR AI  (A-I) wherein R AI  is a C 2 -C 6 , linear, branched or C5-C6 cyclic perfluoroalkyl group, or a C2-C6 linear, branched perfluorooxyalkyl group containing from one to three oxygen atoms; R AI  can optionally contain from 1 to 2 atoms, equal or different, selected from the following: Cl, Br, I; X AI ═F; the compounds general formula: CFX AI ═CX AI OCF 2 OCF 2 CF 2 Y AI  (A-II) are preferred, wherein Y AI ═F, OCF 3 ; X AI  as above; the following: (MOVE  1 ) CF 2 ═CFOCF 2 OCF 2 CF 3  and (MOVE  2 ) CF 2 ═CFOCF 2 OCF 3  are more preferred;    C 3 -C 8  perfluoroolefins; preferably hexafluoropropene;    C2-C8 (per) fluoroolefins containing chlorine and/or    bromine and/or iodine atoms;    perfluorovinylethers containing hydrocyanic groups    
   
   
       4 . Perfluoroelastomeric gel according to  claim 2 , wherein the monomeric compositions of the perfluoroelastomers are the following, the sum of the comonomer percentages being 100%: 
 tetrafluoroethylene (TFE) 50-85%, perfluoroalkyl-vinylether (PAVE) and/or perfluorovinylethers (MOVE) 15-50%.    
   
   
       5 . Perfluoroelastomeric gel according to  claim 4 , wherein the monomeric compositions of the perfluoroelastomers are the following, the sum of the comonomer percentages being 100%: TFE 50-85%, PAVE 15-50%; TFE 50-85%, MOVE  1  15-50%; TFE 50-85%, MOVE  2  15-50%; TFE 50-85%, PAVE 1-40%, MOVE  1  1-40%; TFE 50-85%, PAVE 1-40%, MOVE  2  1-40%.  
   
   
       6 . Perfluoroelastomeric gel according to  claim 1 , wherein the perfluoroelastomers comprise also monomeric units deriving from a bisolefin of general formula:  
     
       
         
         
             
             
         
       
     
     wherein: 
 R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , equal to or different from each other, are H or C 1 -C 5  alkyls; Z is a C 1 -C 18  linear or branched alkylene or cycloalkylene radical, optionally containing oxygen atoms, preferably at least partially fluorinated, or a (per) fluoropolyoxyalkylene radical.  
 
   
   
       7 . Perfluoroelastomeric gel according to  claim 6 , wherein, in formula (I), Z is a C 4 -C 12 , preferably C 4 -C 8 , perfluoroalkylene radical; R1, R2, R3, R4, R5, R6 are hydrogen; when Z is a (per) fluoropolyoxyalkylene radical, it comprises units selected from the following: 
 —CF 2 CF 2 0—, —CF 2 CF(CF 3 )0—, CFX 1 0 wherein X 1 ═F, CF 3 , —CF 2 CF 2 CF 2 0—, —CF 2 —CH 2 CH 2 0—, —C 3 F 6 O—.    
   
   
       8 . Perfluoroelastomeric gel according to  claim 6 , wherein Z has formula:  
       -(Q)p-CF 2 0—(CF 2 CF 2 0) m (CF 2 O) n —CF 2 —(Q) p —  (II)  wherein: Q is a C 1 -C 10  alkylene or oxyalkylene radical; p is 0 or 1;  m  and  n  are numbers such that the m/n ratio is between 0.2 and 5 and the molecular weight of said (per) fluoropolyoxyalkylene radical is in the range 50010,000, preferably 700-2,000.    
   
   
       9 . Perfluoroelastomeric gel according to  claim 8 , wherein Q is selected from: —CH 2 OCH 2 —; —CH 2 0(CH 2 CH 2 0)sCH 2 —, s being=1-3.  
   
   
       10 . Perfluoroelastomeric gel according to  claim 6 , wherein the unit amount in the chain deriving from the bis-olefins of formula (I) is from 0.01 to 1.0 moles, preferably from 0.03 to 0.5 moles, still more preferably from 0.05 to 0.2 moles per 100 moles of the other monomeric units, constituting the basic perfluoroelastomer structure.  
   
   
       11 . Perfluoroelastomeric gel according to  claim 1  containing a semicrystalline (per) fluoropolymer, in an amount in per cent by weight referred to the total dry weight perfluoroelastomer+semicrystalline perfluoropolymer, from 0% to 70%, preferably from 0% to 50% by weight, still more preferably from 2% to 30% by weight.  
   
   
       12 . Perfluoroelastomeric gel according to  claim 11 , wherein the semicrystalline (per) fluoropolymer is constituted of tetrafluoroethylene (TFE) homopolymers, or TFE copolymers with one or more monomers containing at least one unsaturation of ethylene type, in an amount from 0.01% to 10% by moles, preferably from 0.050 to 7% by moles, on the total of the monomer moles.  
   
   
       13 . Perfluoroelastomeric gel according to  claim 12 , wherein the comonomers having an ethylene unsaturation of the semicrystalline (per)fluoropolymer are hydrogenated and fluorinated.  
   
   
       14 . Perfluoroelastomeric gel according to  claim 13 , wherein the hydrogenated comonomers having an ethylene unsaturation are selected from ethylene, propylene, acrylic monomers, selected from methylmethacrylate, (meth acrylic acid, butylacrylate, hydroxyethylhexylacrylate, styrene monomers.  
   
   
       15 . Perfluoroelastomeric gel according to  claim 13 , wherein the fluorinated comonomers having an ethylene unsaturation are selected from the following: 
 C 3 -C 8  perfluoroolefins, preferably hexafluoropropene    (HFP), hexafluoroisobutene;    C 2 -C 8 , hydrogenated fluoroolefins, preferably vinyl fluoride (VF), vinylidene fluoride (VDF), trifluoroethylene, CH 2 ═CH—R f  perfluoroalkylethylene, wherein R f  is a C 1 -C 6  perfluoroalkyl;    C 2 -C 8  chloro- and/or bromo- and/or iodo-fluoroole-fins, as chlorotrifluoroethylene (CTFE);    CF 2 ═CFOR f  (per) fluoroalkylvinylethers (PAVE), wherein R f  is a C 1 -C 6  (per) fluoroalkyl, preferably CF 3 , C 2 F 5 , C 3 F 7 ;    CF 2 ═CFOX (per) fluoro-oxyalkylvinylethers, wherein X is: a C 1 -C 12  alkyl, or a C 1 -C 12  oxyalkyl, or a C 1 -C 12  (per) fluoro-oxyalkyl having one or more ether groups;    (per) fluorodioxoles, preferably perfluorodioxoles.    
   
   
       16 . Perfluoroelastomeric gel according to  claim 12 , wherein the comonomers of the semicrystalline (per)fluoropolymer are selected from PAVE, preferably perfluoromethyl-, perfluoroethyl-, perfluoropropylvinylether and (per)fluorodioxoles, preferably perfluorodioxoles.  
   
   
       17 . Perfluoroelastomeric gel according to  claim 12 , wherein the semicrystalline (per)fluoropolymer is coated by a shell of a semicrystalline (per)fluoropolymer containing bromine and/or iodine atoms in the chain deriving from brominated and/or iodinated comonomers, in an amount from 0.1 s to 10% by moles referred to the total moles of the basic monomeric units of the semicrystalline (per) fluoropolymer core+shell, the semicrystalline (per) fluoropolymer in the core and in the shell can be of different composition.  
   
   
       18 . A process to form perfluoroelastomer gels according to  claim 1 , comprising the following steps, starting from a perfluoroelastomer polymerization latex: 
 Ao. optionally, mixing of the perfluoroelastomer latex with a semicrystalline (per)fluoropolymer latex, in an amount from 0% to 70% by weight, preferably from 0% to 50%, still more preferably from 2% to 30% by weight, referred to the total dry weight perfluoroelastomer+semicrystalline (per)fluoropolymer;    A. optionally, dilution with water of the polymerization latex of the perfluoroelastomer, or of the mixture Ao, until obtaining a perfluoroelastomer concentration, expressed in g polymer/kg latex, between 50 and 600;    B. optionally, mixing of the polymerization latex Ao, or of the diluted latex A, or of the starting latex, with one or more organic compounds soluble in the latex aqueous phase, capable to lower, the latex freezing point without causing the latex coagulation, said one or more organic compounds being such and/or in an amount such that the resulting mixture has the freezing point at a temperature lower than or equal to the glass transition temperature Tg (C) of the latex perfluoroelastomer;    C. preparation of an aqueous solution containing an electrolyte, optionally said solution being added of one or more organic compounds as defined in B, soluble in the latex aqueous phase, i.e. capable to lower the freezing point of the solution C, and such and/or in an amount such that the resulting solution C has a freezing point lower than or equal to the freezing point of the mixture prepared in B;    D. cooling of the polymerization latex, or of the mixture Ao, or of the diluted latex A, or of the mixture B, down to a temperature T 1  lower than or equal to the glass transition temperature of the latex perfluoroelastomer;    E. cooling of the aqueous solution C to a temperature T 2  lower than or equal to the glass transition temperature of the latex perfluoroelastomer, preferably T 2  being substantially equal to T 1 ;    F. formation of a gel by dripping of the mixture D into the solution E;    G. optionally, washing with water of the gel obtained in F;    H. optionally, gel drying and obtainment of the perfluoroelastomer.    
   
   
       19 . A process according to  claim 18 , wherein in step A the perfluoroelastomer concentration in the latex, expressed in g polymer/kg latex, is between 50 and 600, preferably between 100 and 250 g polymer/kg latex.  
   
   
       20 . A process according to  claim 18 , wherein step A is omitted if, after having carried out the optional step Ao, the perfluoroelastomer concentration is within the above limits.  
   
   
       21 . A process according to  claim 18 , wherein the optional step A can be carried out before the optional step Ao.  
   
   
       22 . A process according to  claim 18 , wherein step B is optional if the perfluoroelastomer has a glass transition temperature higher than 0° C.  
   
   
       23 . A process according to  claim 18 , wherein organic compounds are used lowering the freezing point of at least 1-2° C., more preferably of at least 3-6° C., with respect to the perfluoroelastomer Tg.  
   
   
       24 . A process according to  claim 18 , wherein the amount of the organic compounds as defined in B, in the mixtures prepared in B and in C, is from 5% to 70%, preferably from 10% to 50%, more preferably from 10% to 35%, referred to the total weight of the mixture.  
   
   
       25 . A process according to  claim 18 , wherein the organic compounds usable in steps B and C have a solubility in water higher than 1% to w/w and are liquid at room temperature (20-25° C.).  
   
   
       26 . A process according to  claim 25 , wherein the organic compounds are selected from C 1 -C 5  aliphatic alcohols, C 3 -C 4  ketones, diols selected from ethylene glycol and propylene glycol; preferably ethyl alcohol.  
   
   
       27 . A process according to  claim 18 , wherein the electrolytes used in C are selected from inorganic salts, inorganic bases, inorganic acids, preferably inorganic acids.  
   
   
       28 . A process according to  claim 18 , wherein in step G the gel washing is carried out at temperatures between that used in step F and 80° C., preferably between 10 C and 40° C. and at the place of water, neutral and/or acid aqueous solutions having pH from 1 to 7 are optionally used.  
   
   
       29 . A process according to  claim 18 , wherein at the end of step G the gel pH is brought to a value between 3 and 7.  
   
   
       30 . A process according to  claim 18 , wherein in step H the drying is carried out at temperatures in the range 60° C.-140° C.; preferably 90° C.-110° C., until a constant weight of the residue.  
   
   
       31 . A process according to  claim 18 , carried out batchwise or continuously.  
   
   
       32 . Crosslinkable perfluoroelastomers obtainable from the perfluoroelastomeric gel according to  claim 1 .  
   
   
       33 . Cured perfluoroelastomers obtainable by crosslinking the perfluoroelastomers according to  claim 32 .  
   
   
       34 . Manufactured articles comprising the cured perfluoroelastomers according to  claim 33 .  
   
   
       35 . Use of the gel according to  claim 1  to obtain coatings on manufactured articles.