Mixtures

The photoinitiated polymerization of ethyl cyanoacrylate (ECA) by benzyl triphenylphosphonium hexafluoroantimonate (BP+) and (anthracen-9-ylmethyl)triphenylphosphonium hexafluoroantimonate (MAP+) was studied. Zwitterionic and free radical mechanisms which involved homolytic and heterolytic decomposition of the phosphonium salts are discussed. The anthracene-sensitized photopolymerization of ECA was also demonstrated.

Methyl α-cyanoacrylate, when suitably inhibited by Lewis acids against anionic polymerization, can be polymerized readily with free-radical initiators to form hard, clear, high molecular weight polymers. The ratio of kp2/kt is approximately 0.021 at 60°C. if 100% efficiency of initiation by azobisisobutyronitrile is assumed. Acceleration occurs at very low conversion to polymer during bulk polymerizations. The homopolymer is thermally unstable at temperatures only slightly above the glass temperature (estimated to be 165–170°C.).

The absolute rate constants of propagation kp and of termination kt of ethyl α-cyanoacrylate (ECNA) were determined in bulk at 30°C by means of the rotating sector method under conditions to suppress anionic polymerization; kp = 1 622 1 · mol−1 · s−1 and kt = 4,11 · 108 1 · mol−1 · s−1 for the polymerization in the presence of acetic acid, and kp = 1610 1 · mol−1 · s−1 and kt = 4,04 · 108 l · mol−1 · s−1 for the polymerization in the presence of 1,3-propanesultone. The magnitude of k/kt determined was 6,39 · 10−3 l · mol−1 · s−1.

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.

Adhesive composition of the cyanoacrylate type containing Phthalic anhydride as an additive to improve the resistance to moisture and/or heat of the resulting adhesive bonds.