Methylidene malonate process

Abstract

An improved process for the production of methylidene malonates is attained by use of select iminium salt reactants.

Description

RELATED APPLICATION[0001]This patent application claims the benefit of prior U.S. Provisional Patent Application No. 61 / 591,884 filed Jan. 28, 2012, entitled Improved Methylidene Malonate Process, Gondi et. al., the contents of which are hereby incorporated herein in their entirety.FIELD OF THE INVENTION[0002]The present invention relates to an improved process for the production of methylidene malonates as well as the methylidene malonates produced thereby and the use thereof.BACKGROUND[0003]Methylidene malonates are compounds having the general formula (I):wherein R1 and R2 may be the same or different and represent a C1 to C18 hydrocarbon group or heterohydrocarbon group having one or more nitrogen, halogen, or oxygen atoms. Such compounds have been known for well over half a century and their use, or potential use, in both organic synthesis and polymer chemistry is well known. Similarly, the use of these compounds as is or as a component of adhesives, including skin bonding adhe...

AI Technical Summary

Benefits of technology

The present invention describes a way to make methylidene malonates faster, more efficiently, in high yield and purity, and at a lower cost than previous methods. This makes them easier to produce and use for various applications.

Problems solved by technology

Yet, despite all the promise, these compounds have found limited, If any, commercial success owing to the difficulty of their production; the poor, though improving, yet still erratic, yields; and the general instability of these compounds.

The former was unsatisfactory due to very low yield and expensive starting materials.

The latter, though periodically giving better yields than the iodide process, gave relatively poor yields and, more critically, was widely inconsistent from batch to batch, even under the same conditions.

D'Alelio (U.S. Pat. No. 2,330,033), on the other hand, alleged that such processes were erratic and more often produced yields that averaged 10 to 12 per cent.

The resultant mass was then subjected to vacuum distillation at low temperature to separate an allegedly high purity methylidene malonate, though with a low yield.

In discussing the critical need for high purity materials, Coover at al. draw particular attention to the extreme sensitivity of their monomers to the presence of even small amounts of acidic and basic impurities, the former inhibiting polymerization leading to sluggish and ineffective adhesive activity and the latter accelerating polymerization leading to unstable and useless products.

Unfortunately, other than discussing its limitations with respect to the acidic and basic impurities, and despite its contention of high purity materials, Coover at al. never provide any data pertaining to the purity of their materials.

Despite the efforts that had been made in advancing the production of methylidene malonates, still no viable method was found.

Instability, poor yields, low purity, inconsistency in production, etc. continued to plague this technology.

These efforts, despite their gains in yield and / or purity, still failed to achieve commercial success.

Citing numerous disadvantages of the foregoing processes, which disadvantages were said to make them difficult, if not impossible, to adapt to industrial scale, Bru-Magniez et al.

Though the Bru-Magniez technology showed promise, instability and inconsistency continued to plague their effort to commercialize these materials.

Indeed, owing to the high instability of the overall production process and final products, they reported a high failure rate and of those batches that actually survived through crude distillation, the resultant products had to be stored in a freezer even after stabilizing with upwards of 50,000 ppm SO2 due to their high instability and spontaneous polymerization,

Although the stabilizer systems and stabilization techniques of Malofsky et. al. markedly improved the adduct processes, providing greater stability and consistency to the process as well as the final products thereot these processes still require harsh conditions, including temperatures up to 180° C.; prolonged isolation and purification processes, requiring at least two distillations (three if one employs distillation to remove the crude liquid product from the solids of the reaction mix) to achieve suitable purity; and high costs: the anthracene adduct route is comparatively expensive and while high purities are attained, the repeated purification steps results in overall loss in yield.

However, replacement of the ethyl cyanoacetate with dimethyl malonate resulted in yields of only 30% after an hour, with no indication as to purity.

duct. Additionally, these processes require specific amines to form the iminium salts: amines that are oftentimes expensive and whose reaction byproducts can be difficult to r

nt with. However, from the perspective of the formation of methylidene malonates, these factors are of considerable concern, particularly inasmuch as the yields and purity of the methylidene malonates so produced, as shown by McArdle et. al., are

In summary, processes for the direct preparation of methylidene malonates from formaldehyde give low yields and inconsistent results.

Adduct processes improve yields and purity, but still suffer from instability, inconsistency and high costs.

Processes in which select stabilizer systems are employed improves on the instability and inconsistency issues but still suffer from high costs, not just in materials costs and processing time but in terms of the overall yield and purity perspective, especially in view of the need for multiple purification steps which improve purity but lower yield.

McArdle and then Bigi provide an alternative direction which may address some of the issues but still suffer from high materials and processing costs and questionable, if not low, yields and purities.

In this respect, it is to be appreciated that the use of starting materials wherein the diester of malonic acid contains another functional group, which may be a heteroatom containing functional group, particularly the ester functional group, can adversely affect the production of the corresponding methylidene malonates, making it especially difficult to do so.

Similarly, difficulty is encountered where one intends to add or modify such functionality in-situ in-process.

Additionally, these additional functional groups may promote undesired and competitive reactions to the formation of the methylidene malonate.

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