Polymers

Synhydrid® has found valuable applications in polymerization reactions. The most important is its use as an initiator in the anionic polymerization of lactams, especially 6-caprolactam, during production of polyamides. In the field of polyamide production, the use of Synhydrid® has reached industrial significance.

Synhydrid® could be also useful in the polymerization of unsaturated monomers, e.g. styrene during production of polystyrene. Other potential applications of Synhydrid® in polymer chemistry may be also catalysis of isocynates cyclotrimerization and cyclodimerization of butadiene. But in this rapidly developing segment of the industry, it is only a matter of time before Synhydrid® finds further practical applications.

Polyamides

A polyamide is a polymer that contains recurring amide groups (R―CO―NH―R′) as integral parts of the main polymer chain. Synthetic polyamides are commonly used in textiles, automotive industry, carpets, kitchen utensils and sportswear due to their high durability and strength. Polyamides are produced by a condensation reaction between monomers, in which the linkage of the molecules occurs through the formation of the amide groups. They may be produced by the interaction of a diamine and a dicarboxylic acid or they may be formed by the self-condensation of an amino acid or an amino-acid derivative. One of the important method for production of polyamides is an anionic polymerization of lactams, in which Synhydrid® can be successfully used as an effective initiator.

The anionic polymerization of lactams is catalyzed by strong bases which are capable for forming of lactam anion. In practice two-component initiator-activator catalytic systems are usually used for anionic polymerization of 6-caprolactam. As activators N-acetyl-6-caprolactam, N-aryl-6-caprolactams or isocyanates can be selected. The initiators are very often alkali metal salts of 6-caprolactam.

The suitable initiator, enabling better control of polymerization process, is possible to prepare by reaction between Synhydrid® and 6-caprolactam. By an inverse dosing procedure where Synhydrid® is added to 6-caprolactam, sodium bis(6-caprolactamo)bis(2-methoxyethoxo)aluminate is formed and simultaneously hydrogen is released. The obtained solution of sodium bis(6-caprolactamo)bis(2-methoxyethoxo)aluminate can be used either below melting temperature of the polymer for low temperature anionic polymerization of 6-caprolactam under adiabatic conditions or at temperatures above the melting point of polymer for isothermal continuous polymerization.

This initiator can be also usable for precipitation polymerization in 6-caprolactam solution suitable for preparation of polyamide powders. One of its main advantage is very high tolerance for 6-caprolactam impurities, including moisture. Sodium bis(6-caprolactamo)bis(2-methoxyethoxo) aluminate also serves as a drying agent and allows the use of technical 6-caprolactam as a raw material for the production of polyamide 6.