Patent

The problem addressed by the invention was to find an anionic polymerization inhibitor for cyanoacrylate adhesives containing one or more cyanoacrylates, stabilizers against anionic and radical polymerization and auxiliaries typically used in such adhesive systems which, besides a reliable inhibiting effect, would counteract any increase in the setting time after storage. This problem was solved by using 2-oxo-1,3,2-dioxathiolanes as inhibitors.

An adhesive composition comprising 2-cyanoacrylate and at least one compound selected from the group consisting of R1-CH2OH,

pentafluorophenol, hexachloroacetone, hexachloroacetone hydrate, chloral and chloral hydrate as cationic-polymerization inhibitor. In the above formulas, R1 is a fluorinated alkyl or aryl group having up to 12 carbon atoms, and R2 and R3 are fluorinated or non-fluorinated alkyl or aryl groups having up to 12 carbon atoms. The above adhesive composition has an excellent storage stability and an improved bonding strength.

A method for producing a purified 2-cyanoacrylate is characterized in that distillation is conducted in the presence of a polymerization inhibitor whose boiling point is within ±12° C. of the boiling point of the 2-cyanoacrylate. With this method, polymerization of 2-cyanoacrylate can be continuously prevented in the distillate system during distillation of a crude 2-cyanoacrylate, so that a purified 2-cyanoacrylate can be obtained.

A curable cyanoacrylate adhesive composition intended for medical and/or veterinary uses is sterilized in liquid form by gamma irradiation. The composition comprises

a) a cyanoacrylate monomer

b) a combination of an anionic stabilizer in amounts effective to stabilize the composition during storage prior to cure, wherein the free radical stabilizer is a selected phenolic antioxidant (but not including hydroquinone).

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.

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.