Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1991-08-23
1993-05-11
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C07C 6748
Patent
active
052102815
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an improved process for the production of pure, substantially neutral, low-volatility organic components containing reactive olefinic double bonds which are susceptible to polymerization or gelation. More particularly, the invention seeks to provide an improved processed for the production of pure, low-volatility organic components of the type mentioned which are difficult or impossible to purify by distillation.
The problem addressed by the present invention is described hereinafter with reference by way of example to a selected class of compounds which may be produced with particular advantage using the measures proposed in accordance with the invention. However, the expert will readily appreciate that the invention is not limited in its scope to this particular class of compounds. The new measures proposed in accordance with the invention may be applied in any fields of application where comparable, technologically created or freely selected problems have to be solved.
It is known that low-volatility polyfunctional esters of acrylic acid and/or methacrylic acid with polyhydric alcohols -- hereinafter also referred to as (meth)acrylates or multifunctional (meth)acrylates -- can be produced by reaction of the reactants in the presence of acidic esterification catalysts with addition of polymerization inhibitors to the reaction mixture. (Meth)acrylates of this type are acquiring increasing significance as highly reactive constituents of, for example, radiation-curing systems. The polyfunctional alcohols on which these esters are based are, for example, dihydric to tetrahydric aliphatic, saturated alcohols and/or alkoxylation products thereof. Polyfunctional (meth)acrylates of the type mentioned may be used, for example, as paint resins for curing by electron beams or as a constituent of UV-curing printing inks or corresponding coating compositions, in surfacing compositions, molding or encapsulating compounds and in adhesives, particularly anaerobic adhesives. However, their production is not without problems. The products required should be, above all, substantially colorless and odorless with a low acid value and high stability in storage. (Meth)acrylates of the type in question here generally cannot be purified by distillation on account of their high molecular weight and their high reactivity. The solvent-containing or solvent-free mixtures obtained as the crude reaction products may contain the acidic catalyst and possibly even acid residues from the esterification reaction, i.e. have to be subjected to neutralization and purification to bring the non-distilled product to the required quality.
The present invention is based on the concept of carrying out this concluding neutralization and purification step as so-called dry neutralization. Dry neutralization is understood to be the procedure in which an at least substantially dry, basic neutralizing agent is added to the organic crude reaction product in the form of a fluid paste, at least in the substantial absence and preferably in the complete absence of water, to bind the acidic components (catalyst, residual acids and the like), after which the added solid phase is separated from the fluid organic phase after the desired residual acid value has been established.
However, during the development of an industrial process based on this concept, it was found that the requirements stipulated to satisfy because, where selected process conditions are specifically varied to optimize a desired product property, for example the low acid value, other product properties, for example the color and/or stability of the reaction product, are adversely affected. The various problems involved are illustrated by way of example in the following: highly reactive (meth)acrylate systems of the type in question tend to gel through anionic polymerization on the addition of finely divided, solid, basic neutralizing agents. The desired neutralization of the acidic components present in the reaction mixture becomes preferential reaction over the anio
REFERENCES:
patent: 4304925 (1981-12-01), Watanabe
Ritter Wolfgang
Sitz Hans-Dieter
Speitkamp Ludwig
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Killos Paul J.
Ortiz Daniel S.
Szoke Ernest G.
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