English

Various alkyl2-bromoacrylates were synthesized in high purity and yield. They were characterized by spectroscopic techniques. The monomers were then formulated into aerobic adhesive compositions and their adhesive bond strengths between various surfaces were evaluated.

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.

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.