English

A process for producing a monomer comprising thermally cracking a pre-polymer in the presence of a stabiliser to form a monomer as a distillate , the stabiliser preventing the re-polymerisation of the monomer during cracking while not being carried over in the distillate in normally detectable amounts.

An adhesive composition based on 2-cyanoacrylate esters contains as an anionic polymerization inhibitor an acid chelate formed of boric acid or a derivative thereof and a selected polyhydroxy compound. The chelate is conveniently formed in situ in the 2-cyanoacrylate ester, but may also be prepared separately and added to the ester directly. An exemplary acid chelate used as stabilizer is prepared from boric acid and pyrogallol. The resulting stabilized adhesive compositions have a rapid cure rate and may be used on a wide variety of substrates.

An alpha-cyanoacrylate base adhesive composition comprising 0.0001 to 0.5 part by weight of borofluoric acid on a 100% basis per 100 parts by weight of an alpha-cyanoacrylate monomer, which composition has improved storage stability.

Cyanoacrylate adhesives contain one or several cyanoacrylic acid esters and stabilisers against anionic and radical polymerisation, as well as auxiliary substances common in such adhesives. The object of the invention is to find an anionic polymerisation inhibitor which counteracts setting time prolongation due to storage while retaining a reliable inhibitor effect. This object is attained by using 2-oxo-1,3,2-dioxathiolanes as inhibitors.

An adhesive composition based on 2-cyanoacrylate esters contains as an anionic polymerization inhibitor an acid chelate formed of boric acid or a derivative thereof and a selected polyhydroxy compound. The chelate is conveniently formed in situ in the 2-cyanoacrylate ester, but may also be prepared separately and added to the ester directly. An exemplary acid chelate used as stabilizer is prepared from boric acid and pyrogallol. The resulting stabilized adhesive compositions have a rapid cure rate and may be used on a wide variety of substrates.

Zirconocene is the key: A new synthetic method, which utilizes zirconocene-mediated coupling of alkynes, has been developed for the preparation of a new class of highly Lewis acidic boroles (see scheme). Such compounds hold potential for applications in catalysis and the field of electron-deficient organic materials.

Perfluorination: The fully fluorinated analogue of pentaphenylborole (see structure; B gray, C black, F green) has been prepared using successive transmetallation reactions involving Zr and Sn heterocycles. The highly moisture-sensitive borole is a new member of the perfluoroaryl borane family, a class of antiaromatic compounds of fundamental significance to concepts of aromaticity.

Under solvent free conditions between 40-50 °C, BF3.SiO2, a mild solid acid catalyst, is applied to regio-chemo and stereoselective Claisen-Schmidt condensation. The procedure is very simple and the products are isolated with an easy workup in good to excellent yields.

A cyanoacrylate-based adhesive composition comprises 55-92% by weight of a 2-cyanoacrylate ester, preferably the ethyl ester, from 40-30% by weight of a vinyl chloride/vinyl acetate copolymer and not more than 25% by weight of a plasticizer (the plasticizer may be omitted entirely). The copolymer is preferably a vinyl chloride/vinyl acetate/maleic acid terpolymer.

A cyanoacrylate-based adhesive composition comprises 55-92% by weight of a 2-cyanoacrylate ester, preferably the ethyl ester, from 40-30% by weight of a vinyl chloride/vinyl acetate copolymer and not more than 25% by weight of a plasticizer (the plasticizer may be omitted entirely). The copolymer is preferably a vinyl chloride/vinyl acetate/maleic acid terpolymer.