Bismuth isooctanoate
The organic bismuth catalyst is mainly bismuth carboxylate, especially bismuth isooctanoate.
Bismuth isooctanoate, also known as bismuth tris(2-ethylhexanoate).
English name: bismuth octote; bismuth tris (2-ethylhexanoate), etc.
The molecular formula of bismuth isooctanoate is C24H45BiO6, and the molecular weight is 638.6. The CAS number is 67874-71-9 and the EINECS number is 267-499-7.
Structural formula: Bi[OCOCH(C2H5)C4H9]3.
Physical and chemical properties
Brown-yellow viscous liquid, the relative density (25°C) is 1.28-1.34, the viscosity (25°C) is not more than 3Pa.s.
The Shepherd Chemical Company’s bismuth isooctanoate 28% product has a bismuth content of 27.7% to 28.3%, and a non-volatile matter (105°C, 3h)≧85%.
Organobismuth catalysts from leading US chemical companies are as follows.
Among them, BiCAT 8118 and BiCAT 8108 can be used in almost all kinds of polyurethane materials, BiCAT 8124 is recommended for PU adhesives and elastomers, BiCAT 8106 is recommended for adhesives and sealants, and BiCAT 8210 is recommended for coatings and adhesives.
The bismuth isooctanoate 72% concentration product produced by Strem Chemicals, Inc. with mineral oil as the solvent contains about 28% of Bi; the 70%-75% concentration product with xylene as the solvent, The Bi content is about 24%.
Bismuth isooctanoate from Shenyang Applied Technology Experimental Factory is a yellow-brown liquid with a bismuth content of 4%. Another domestic company’s bismuth isooctanoate is a yellow-brown liquid with solvent naphtha or xylene as the solvent, and the bismuth content is 4%.
Features and uses
It can be used in paint driers, lubricating oil additives and polyurethane room temperature catalysts. Organic bismuth catalyst is an environmentally friendly substitute for toxic heavy metal catalysts such as organic mercury and organic lead. Bismuth isooctanoate has very similar technical characteristics to organic lead and can be used as a substitute for lead drier. Better selectivity, avoiding NCO side reactions, and reducing CO2 generation; bismuth compounds have better hydrolytic stability than tin compounds, reducing the selectivity of reacting with water; in aqueous PU dispersions, reducing the interaction between water and NCO groups The side reaction can improve the drying performance of the coating under harsh weather conditions, especially the harsh conditions of high air humidity, and the mechanical properties of the final product are better; Reaction of NCO with water. However, the catalytic activity is low in some systems. The combination of bismuth and zinc has a synergistic effect, making formulation and production more flexible. It can be used alone or in combination with amines or other organometallic compounds.
The catalytic effect of bismuth carboxylate on the reaction between aliphatic isocyanate and polyether secondary hydroxyl group is even better than that of primary hydroxyl group. The reaction rate of the hydroxy group is faster than that of the unhindered hydroxyl group.
The high price of organic bismuth inhibits its wide application.
