Patent GB-1346308-A (GB)
Title: Process for crosslinking polymers containing mercaptan groups
IPC: C08K5/32
Filed: 1971-04-30
Abstract: 1346308 Crosslinking polymers containing mercaptan groups CIBA-GEIGY AG 30 April 1971 [1 May 1970 3 Aug 1970] 12514/71 Heading C3R A crosslinkable composition comprises (a) a polymer containing a plurality of mercaptan groups; and (b) either (i) 0À01-50% wt. of the polymer of a polyfunctional nitrile N-oxide or (ii) 0À05-50% by wt. of the polymer of a precursor to a polyfunctional nitrile N-oxide and an alkaline material in at least a stoichiometric amount based on the precursor which may be selected from tertiary amines, alkali metal and alkaline earth metal hydroxides and aldoxides. Alternatively a latent base, such as a metal oxide or a molecular sieve material containing an organic amine, which in the absence of heat and water is inert to the curing agent and which in the presence of moisture yields an alkaline material, may be used with the precursor (ii). The nitrile N-oxide (i) can have the following general formulae -(-C#N-O) 2 ; R-(-C#N-O) x ; -(CO-C#N-O) 2 ; R-(-CO-C#N-O) x ; R-(-OCO-C#N-O) x , where x is an integer greater than 1, and R is an organic radical inert to the crosslinking reaction e.g. alkylene, cycloalkylene, arylene, aralkylene, alkarylene, alkylene.diarylene, cycloalkylene-dialkylene, arylene-dialkylene. Examples of precursors (ii) are polyfunctional hydroxamoyl halides or nitrolic acids of general formulae (HO-N=CX) n -R, R-(-CO-CX=NOH) n , R-(-OCO-CX = N-OH) n  where X is halogen or NO 2  respectively, and n is preferably 2-10. Polymer (a) may be (1) a mercaptan containing polyester-polysulphide of unit formula -(-S-C n H 2n -CO 2 -R-S-) terminated with mercaptan groups, (2) hydroxyl containing mercaptan resin containing 2-3 terminal mercaptan groups per chain prepared by reacting a polypropylene oxide polyol with epichlorohydrin and sodium sulphydrate, (3) mercaptan terminated polypropylene oxide, (4) polysulphides of formula HS-(RSS) x RSH where R is alkylene, alkyleneoxyalkylene, alkylene thioalkylene, (5) mercaptan terminated polyester sulphide polymers, (6) polyethers with pendant mercaptan groups. The compositions may contain fillers such as carbon black, SiO 2 , UV stabilizers, antioxidants, pigments, e.g. TiO 2 , plasticizers and hydrogenated terphenyl. In the examples a liquid polymercaptan resin prepared by reacting a trifunctional polypropylene oxide with 3 equivalents of toluene diisocyanate and 1 equivalent of mercaptobutanol is crosslinked in Example 1 with terephthalobis(nitrile N-oxide), and in Example 2 with terephthaloyl bis(hydroxamoyl chloride) and triethylamine, and in Example 6 with isophthaloyl-bis(phenylhydrazide chloride) and triethylamine. In Example 3 a liquid mercaptancontaining polysulphide is mixed with SiO 2  and crosslinked with terephthaloyl bis(hydroxamoyl chloride) and Ca(OH) 2 . In Example 4 a liquid polysulphide resin prepared from bis(chloroethylformal), 1,2,3-trichloropropane and sodium polysulphide is mixed with SiO 2  and cross-linked with 2,4,6-trimethyl-isophthalo-dinitrile oxide. In Example 5 a liquid di- and tri-functional mercaptan-terminated polyether is cross-linked with 4,4<SP>1</SP>-oxybis(phenylglyoxylohydroxamoyl) chloride and triethylamine. In Examples 7, 11 and 12 a polysulphide of the formula is crosslinked on exposure to atmospheric moisture with terephthaloyl bis(hydroxamoyl chloride) and CaO (Example 7), or with 1,3,5- phenyl tris(glyoxylohydroxamoyl chloride) (Example 11), or with terephthaloyl bis(hydroxamoyl chloride) and a molecular sieve containing ethylene diamine. In Example 13 a mercaptan terminated polypropylene oxide prepared by reacting a trifunctional polypropylene oxide with epichlorohydrin and then with sodium hydrogen sulphide, and in Example 15 a liquid polyether of the formula are each crosslinked with terephthaloyl bis-(hydroxamoyl chloride) and CaO on exposure to atmospheric moisture. Uses.-Adhesives; sealants; coatings.