Before reading this patent, please be aware that PTC Organics developed PTC etherification technology using epichlorohydrin that is more selective than that reported here and in other PTC glycidyl etherification literature. PTC Organics maintains this technology under trade secret status. Contact Marc Halpern of PTC Organics to inquire about licensing PTC etherification technology using epichlorohydrin.
One of the largest scale early commercial applications of phase-transfer catalysis was the reaction of bisphenol A with epichlorohydrin to for the bisphenol A-diglycidyl ether (DGEBA), a monomer used in epoxy resins. The inventors note that isosorbide diglycidyl ether may be a suitable substitute for DGEBA which has raised concerns about carcinogenicity even though there are no data that support human carcinogenicity. This patent describes the use of PTC for the etherification of isosorbide (derived from a natural product) with epichlorohydrin.
The challenge is to selectively produce the diglycidyl ether while minimizing both residual monoglycidyl ether and higher oligomers that result from hydrolysis of the epoxide and subsequent oligomerization. The inventors found that using 1 wt% tetraethylammonium bromide or tetrabutylammonium iodide maximizes the desired digylcidyl ether.
The inventors used 5 equiv epichlorohydrin. This level of excess is common in reports of other glycidyl etherifications. The excess epichlorohydrin also provides extra fluidity since no additional solvent is used.
50% NaOH (2.0 equiv) was added over time with continuous azeotropic drying to minimize hydrolysis, to neutralize the 2 hydroxyls without excess hydroxide.
The reaction was performed at 80 C. This is also a common temperature used in the literature foe etherifications using epichlorohydrin.
The attention to detail in reporting by the writers and examiners of the patent is poor. In all the examples, the identity of the phase-transfer catalyst quat is referred to as triethylammonium instead of tetraethylammonium and the abbreviations for the quats in the table are amazingly: TBAI = triethylammonium iodide, TEAC = triethylammonium chloride and TEAB = triethylammonium bromide. Look it up if you have a hard time believing that such errors would make it through all the reviews. We know that the real catalysts are tetraalkyl quats based on the claims, which apparently were actually read before issuing the patent.
If your company has a commercial application that can greatly benefit from selective PTC etherification technology, especially using epichlorohydrin, now contact Marc Halpern of PTC Organics to explore business opportunity under secrecy agreement.
