Лако-красочные материалы — производство

An important factor in the initiation of anaerobic adhesive cure is the redox reaction between a hydroperoxide and transition metals with adjacent oxidation states [10].

Fe2+ + ROOH! Fe3+ + RO • + OH~

Fe3+ + ROOH! Fe2+ + ROO • + H+

In the reactions above, other transition metals will react similarly, and copper is particularly active. Where cumene hydroperoxide (CHP) is used, R = C6H5C(CH3)2.

B. Accelerators

The use of saccharin and N, N-dimethyl-p-toluidine (DMPT) results in a substantial accel­eration of the initiating reaction. Although each of these components itself is an accel­erator, their combination has a strong synergistic effect. It has been suggested that a charge-transfer complex is formed by these materials [11]. It is not clear whether this complex is itself an initiator or whether it acts on other components to generate initiating species.

This same study indicated that the rate of anaerobic polymerization was nearly independent of the concentration of CHP and proceeded at a significant but slower rate with no hydroperoxide. This does not indicate that the hydroperoxide is not essential to the anaerobic cure but that it does not participate in the rate-determining step.

The use of 1-acetyl-2-phenylhydrazine [APH (VI)] and saccharin resulted in a some­what slower reaction rate than with DMPT unless a catalytic amount of copper was added. In this study the concentration of CHP was found to be very important where the molar ratio of CHP/APH was less than 1. Where the ratio was greater than 1, the rate was independent of CHP [12]. These papers [11,12] have been reviewed [13]. The accel­erating effect of the salts of saccharin and 6-methyl-1,2,3,4-tetrahydroquinoline (VII), 1,2,3,4-tetrahydroquinoline (IV), or 1,2,3,4-tetrahydroquinaldine (VIII) on the anaerobic polymerization of methyl methacrylate were studied. No organic peroxides were required for these polymerizations [14].

The effect on initiation reactions of charge-transfer complexes of o-benzosulfanilide (IX) and tertiary aromatic amines with various substituents was studied. The rates increased with increasing electron donor and decreasing acceptor properties of the substituents on the amine [15]. Aromatic tertiary amines mixed with benzosulfimides formed charge-transfer complexes whose decay products were effective catalysts for poly­merization of polyethylene glycol dimethacrylate. The most effective catalyst system was DMPT with dibenzenesulfonamide (X). The effectiveness of the system was increased by the addition of CHP [16].

A study using a model reaction system consisting of cumene hydroperoxide (CHP), N, N-dimethyl-p-toluidine (DMPT), and o-benzoic sulfimide (saccharin) in toluene (with­out reactive acrylic monomer) showed conclusively that the DMPT was depleted signifi­cantly during the initiation step of an anaerobic reaction. The saccharin concentration was unchanged during this process. The initiating species may be radical anions derived from DMPT rather than reactive free radicals derived from the CHP [17].

A dilatometric study was carried out on the polymerization of an anaerobic system containing diethylene glycol dimethacrylate, DMPT, CHP, saccharin, and iron filings. DMPT was more effective than N, N-dimethylaniline (XI), triethylamine, or tributylamine. Saccharin was more effective than benzoyl cyanamide (XII), phthalimide (XIII), or succinimide (XIV) [18].