Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1991-08-23
1997-07-15
Geist, Gary L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C07C 6952
Patent
active
056485182
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the production of polyfunctional esters of acrylic acid and/or methacrylic acid--hereinafter referred to as (meth)acrylic acid esters or poly(meth)acrylic acid esters--with polyhydric alcohols by reaction of the reactants in the presence of acidic esterification catalysts with addition of polymerization inhibitors to the reaction mixture.
(Meth)acrylic acid esters of polyhydric alcohols, particularly from the group of dihydric to tetrahydric aliphatic saturated alcohols and their alkoxylation products, are being used to an increasing extent as highly reactive constituents in radiation-curing systems. Polyfunctional (meth)acrylic acid esters of the type in question may be used, for example, as paint constituents for hardening by electron beams or as a constituent of UV-hardening printing inks or corresponding paints, surfacing, molding or encapsulating compounds or even in adhesives, particularly anaerobic adhesives. However, their production is not without problems. The end products are required in particular to be colorless with a low acid value, high stability in storage and hardly any odor. (Meth)acrylic acid esters of the type in question generally cannot be purified by distillation on account of their high molecular weight and their high reactivity. Accordingly, the products are intended to accumulate directly as colorless products of the esterification reaction. The esterification reaction requires the presence of highly effective inhibitors which, in turn, should not initiate any unwanted secondary reactions, for example in the form of discoloration.
Extensive literature is available on the production of such polyfunctional (meth)acrylic acid esters of polyhydric alcohols, cf. in particular DE-OS 29 13 218 and the relevant literature cited therein. Thus, it is known from DE-AS 12 67 547 and from the Journal "Chem. and Ind." 18 (1970), 597, that polyfunctional (meth)acrylic acid esters can be produced by azeotropic esterification of (meth)acrylic acid with polyhydric alcohols in the presence of azeotropic entraining agents and also acidic catalysts and polymerization inhibitors, such as phenols, phenol derivatives, copper, copper compounds or phenothiazine. Organic or inorganic acids or acidic ion exchangers are used as the acidic catalysts, p-toluene sulfonic acid and sulfuric acid being preferred. The esterification reaction takes place in particular at temperatures in the range from 40.degree. to 120.degree. C. Suitable azeotropic entraining agents for removing the water of reaction are aliphatic or cycloaliphatic or aromatic hydrocarbons or mixtures thereof having boiling ranges within the stated temperature limits.
It is proposed in DE-OS 29 13 218 cited above to carry out the azeotropic esterification in the presence of at least one organic ester of phosphorous acid in addition to a phenol-based inhibitor. However, the reaction again has to be carried out in the presence of at least one aliphatic, cycloaliphatic and/or aromatic hydrocarbon boiling at 40.degree. to 120.degree. C. The water of reaction formed is said to be azeotropically removed from the reactor by this entraining agent. According to the Examples of this publication, the reaction time is put at 10 to 18 hours.
The problem addressed by the invention is to establish reaction conditions for the esterification reaction in question which, on the one hand, enable the reaction time to be considerably shortened but which, on the other hand, do not adversely affect the quality of the esterification products formed, particularly their high color quality. In addition, the invention seeks to eliminate the need for comparatively complex inhibitor systems of the type described in DE-OS 29 13 218 cited above. Another problem addressed by the invention is to enable the application inhibitor required in practice for the highly reactive systems in question to be used simultaneously as a reaction inhibitor in the synthesis of the polyfunctional (meth)acrylic acid esters.
The technical solution to the problems
REFERENCES:
patent: 4053504 (1977-10-01), Rosenkranz et al.
patent: 5053316 (1991-10-01), Suzuki et al.
patent: 5159106 (1992-10-01), Ritter et al.
Ritter Wolfgang
Sitz Hans-Dieter
Speitkamp Ludwig
Drach John E.
Geist Gary L.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Millson Jr. Henry E.
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