Patent

A process is described for preparing 2,2,6,6-tetramethylpiperidine-N-oxyl and its 4-position substituted derivatives by oxidation of 2,2,6,6-tetramethylpiperidine and its 4-position substituted derivatives in the presence of hydrogen peroxide and low concentrations of divalent metal salts.

A cyanoacrylate adhesive composition having an acrylic monomer toughening agent. Preferably, the acrylic monomers are selected from the group consisting of methyl methacrylate, butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, and combinations thereof. A useful amount of acrylic monomers is about 1.0% by weight to about 10.0% by weight, preferably about 1.0% by weight to about 5.0% by weight, and more preferably about 2.0% by weight to about 5.0% by weight.

A process for the preparation of esters, including non-distillable esters, of 2-cyanoacrylic acid comprises reacting 2-cyanoacrylic acid or an acid halide thereof with an alcohol, including a diol or polyol, or a phenol in the presence of an inert organic solvent under polymerisation inhibiting conditions and, additionally, in the presence of an acid catalyst when 2-cyanoacrylic acid is a reactant, continually removing the water or hydrohalic acid produced and recovering the ester.

A process for the preparation of 2-cyanoacryloyl chloride in pure form comprises reacting 2-cyanoacrylic acid with a chlorinating agent, said reaction being carried out under side-reaction and polymerisation inhibiting conditions. A preferred chlorinating agent is a volatile chlorinating agent which forms only volatile by-products during the course of the reaction. Suitable volatile chlorinating agents include oxalyl chloride, sulfur oxychloride, trifluoroacetyl chloride and phosgene.

Improved 2-cyanoacrylate adhesive compositions containing acetic acid exhibit greatly enhanced bond strength with no significant reduction in cure rate. Such compositions may be used on a wide variety of substrates and are particularly useful on metals.

Adhesive compositions having enhanced bond strength are obtained by mixing a monomeric ester of 2-cyanoacrylic acid with an anionic polymerization inhibitor and from 1 to 30 mmoles per kg. of adhesive of an adhesion promoter of the formula: wherein R' is hydrogen or an alkyl, aryl or cycloalkyl group having 1-10 carbon atoms. Such compositions may be used on a wide variety of substrates and are particularly useful on metals.

A rapid setting .alpha.-cyanoacrylate-based adhesive composition having an improved stabilizer therein. The stabilizer is a sulfamide derivative containing the group

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Stabilizing may be further improved by using the sulfamides in combination with phenolic anti-oxidants, particularly sterically hindered phenols, without reducing the curing rate of the composition.

An adhesive composition characterized in that the composition is prepared by subjecting finely divided hydrophobic silica surface-treated with hexamethyldisilazane to a heat treatment under a reduced pressure, subsequently treating the silica with an acid gas, and admixing the resulting silica with an alpha-cyanoacrylate.

Die erfindung betrifft eine Cyanoacrylate-Klebstoffzusammensetzung, die eine organische oder eine anorganische Säure mit einem pKa-Wert von etwa -12 bis etwa 7 in Kombination mit einem sauren Gas als Stabilisatoren enthält. Der synergistiches Effekt ergibt eine verbesserte Stabilität und Lagerstabilität, ohne daß die Klebstoffeingenschaften nachteilig beeinflußt werden.