Barbara Pilch-Pitera

Urethane oligomers as raw materials and intermediates for polyurethane elastomers. Methods for synthesis, structural studies and analysis of chemical composition

Abstract Based on earlier models developed for polyaddition of diisocyanates and polyols, a non-stoichiometric process was provided for step-by-step polymerisation of 2,4- and 2,6-tolylene diisocyanate (TDI) with diols which had various molecule sizes and the nature of polyethers and polyesters. Said process yielded urethane oligomers which had –NCO or –OH groups as their chain end groups. After elimination of excess monomer, these compounds were—at subsequent stages (2–5)—subjected to further reaction with diisocyanate or with selected polyol. The process was operated in bulk and excess monomers were eliminated with the use of the selective extraction method. Linear products were obtained in that way which had well defined chain structures and narrow distribution of their molecular weights (MWD) PD = M w / M n =1.1–1.3. On the basis of IR and mass spectrometry (MS) (electrospray ionization (ESI) and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF)) structural analyses, the expected structures of oligomers were confirmed and the actual compositions of polyurethane mixtures formed at every stage of the polymerisation process could be verified against the data obtained from the model, from the balance calculations (based on determinations of free isocyanate groups) and from the findings of the gel-permeation chromatography (GPC) analysis. Applicability of the presented method was demonstrated and the general scheme was suggested for the process discussed.

Study on the synthesis of urethane oligomers as intermediate products for the production of linear polyurethanes

Abstract On the basis of kinetic scheme for step-growth polyaddition, a method was developed for the synthesis of urethane oligomers and linear polyurethanes with isocyanate and hydroxyl end groups arranged alternately 2,4-TDI, 2,6-TDI and 1,4-butanediol were used as the feedstock materials and the polymerisation process was carried out in a tetrahydrofuran solution at constant concentration. Complex mixtures of diisocyanate and hydroxyl compounds were obtained, which were then utilised as parent materials at further stages of the process. The mixtures of urethane oligomers were produced where the molecular weights were gradually higher and the molecular weight distribution was wider and wider. However, the chemical composition was pre-defined as resulted from the reaction stoichiometry. The products were subjected to structural investigation. The following analytical procedures were especially useful in the analysis of the linear polyurethanes obtained: gel-permeation chromatography and mass spectroscopy, which employed gentle excitation due to electro-spraying. These methods made it possible to identify oligomers, which were formed at the successive stages of step-growth polyaddition. The findings made a basis for the discussion of the technological aspects of the polymerisation method developed.

A study on the synthesis of urethane oligomers

Abstract A method of preparation of isocyanate- or hydroxy-terminated urethane oligomers of narrow molecular weight distribution was developed and the products used for preparation of polyurethane elastomers. The method consists of the controlled step-wise reaction of 2,4- and 2,6-toluene diisocyanate (TDI) with butan-1,4-diol (BD) (in the first step) or with polyoxyethylene glycols of molecular weight varying from 200 to 1000 (following steps). All reactions were carried out in bulk. The clue was that the isocyanate- or hydroxy-terminated oligourethanes obtained in a previous step were used as the substrates in the next preparation step where they reacted with an excess of appropriate glycol or TDI, respectively. The unreacted monomer excess was removed by extraction. The products of subsequent steps characterized by spectral analysis IR and NMR and their molecular weight were determined by matrix-assisted laser desorption ionization–time of flight and electrospray ionization mass spectroscopy and gel-permeation chromatography. The oligomers were cross-linked with trifunctional low-molecular chain extenders yielding polyurethane elastomers.

Polyurethane Blends for Powder Clear Coatings

This chapter discusses current development trends in the area of polyurethane powder clear coatings, including new contributions related to the use of various diisocyanates, blocked polyisocyanates, resins, and additives. The chapter also shows the relationship between properties of cured coatings and chemical structure of raw materials, and describes important technological parameters of raw materials in the manufacturing process of powder coatings such as functional groups content, glass transition temperature, melting point, and melt viscosity. Systems of the greatest commercial importance are characterized in terms of their chemical composition and applications. Special attention has been paid to ecological and economical aspects of powder systems.