Methylidene malonate process

1. A method of making a methylene malonate monomer said method comprising the steps of:

a) reacting a malonic acid ester or malonic acid ester precursor with a source of formaldehyde, in the presence of a catalyst, alone or in further combination with an acid, a solvent or both an acid and a solvent,

wherein a reaction phase polymerization inhibitor is added to the reaction mix prior to, concurrent with, or following the initial reaction of the malonic acid ester or its precursor, as applicable, with the formaldehyde source, said reaction phase stabilizer comprising at least one liquid phase primary anionic polymerization inhibitor, alone or in combination with at least one free radical polymerization inhibitor, and

b) subjecting the reaction product of (a) to flash distillation to create a vapor phase containing the methylene malonate monomer and recovering the methylene malonate from the vapor phase wherein (i) the flash distillation is carried out in the presence of a separation phase polymerization inhibitor or (ii) the recovery vessel for the methylidene malonate end product contains a separation phase polymerization inhibitor or both (i) and (ii), said separation phase polymerization inhibitor comprising at least one liquid phase anionic polymerization inhibitor, alone or in combination with a free radical polymerization inhibitor.

2. The process of claim 1 wherein the flash distillation is conducted in a still pot or vessel and at least a portion of separation phase polymerization inhibitor is added pot or vessel prior to initiating flash distillation.

3. The process of claim 2 wherein at least a portion of the same or a different separation phase polymerization inhibitor is also added to the collection vessel for the methylidene malonate prior to initiating flash distillation.

4. The process of claim 3 wherein additional separation phase stabilizer is added to the methylidene malonate recovered from the flash distillation process.

5. The process of claim 2 wherein the anionic polymerization inhibitor of the separation phase polymerization inhibitor comprises at least one primary anionic polymerization inhibitor, at least one secondary anionic polymerization inhibitor or a combination thereof.

6. The process of claim 1 wherein the methylene malonate is recovered from the vapor phase in a collection vessel and at least a portion of a separation phase polymerization inhibitor is added to the collection vessel prior to initiating flash distillation.

7. The process of claim 6 wherein additional separation phase stabilizer is added to the methylidene malonate recovered from the flash distillation process.

8. The process of claim 6 wherein the anionic polymerization inhibitor of the separation phase polymerization inhibitor comprises at least one primary anionic polymerization inhibitor, at least one secondary anionic polymerization inhibitor or a combination thereof.

9. The process of claim 1 wherein each primary anionic polymerization inhibitor is a strong acid.

10. The process of claim 1 wherein each primary anionic polymerization inhibitor is independently selected from trifluoroacetic acid, sulfuric acid, maleic acid, perchloric acid and chlorosulfonic acid.

11. The process of claim 1 wherein the catalyst is a metal salt of a lower monocarboxylic acid.

12. The process of claim 1 wherein the catalyst is selected from copper(II) acetate, cupric acetate monohydrate, potassium acetate, zinc acetate, zinc chloracetate, magnesium chloracetate, magnesium acetate, and combinations of any two or more thereof.

13. The process of claim 1 wherein a combination of a catalyst and an acid is present and the acid is acetic acid, acetic acid anhydride, or glacial acetic acid.

14. The process of claim 1 wherein a solvent is present.

15. The process of claim 1 wherein the temperature of the reactants is elevated until an exotherm occurs.

16. The process of claim 15 wherein the reaction (a) is conducted at a temperature of about 105° C.

17. The process of claim 1 wherein the flash distillation is conducted at a temperature of from 170° C. to 210° C.

18. The process of claim 1 wherein the collected methylene malonate is subjected to a subsequent purification process.

19. The process of claim 18 wherein the subsequent purification process is selected from fractional distillation, solvent stripping, crystallization, precipitation, extraction, gel filtration, electrophoresis, foam fractionation, electromagnetic separation, thin film evaporation, press extraction, and chromatography as well as combinations of the foregoing.

20. The process of claim 1 wherein a combination of a catalyst and an acid is present.

21. The process of claim 1 wherein the malonate ester is employed.

22. The process of claim 21 wherein the malonate ester is of the general structure:

wherein R 1 and R 2 may be the same or different and represent H or a C 1 to C 18 hydrocarbon group or heterohydrocarbon group having one or more nitrogen, halogen, or oxygen atoms; provided that R 1 and R 2 are not both H.

23. The process of claim 22 wherein R 1 and R 2 are each independently a C 1 to C 10 linear or branched alkyl group; a C 3 to C 6 alicyclic group; a C 2 to C 6 alkenyl group; or a C 2 to C 6 alkynyl group; any of which may optionally be substituted with an ether, epoxide, halo, ester, cyano, aldehyde, ketone or aryl group.

24. The process of claim 22 one or both of R 1 and R 2 , which may be the same or different, are of the formula:

—(CH 2 ) n —COOR 8   (IV)

wherein R 8 is a C 1 to C 6 , lower alkyl and n is an integer of from 1 to 5.

25. The process of claim 1 wherein the separation phase polymerization inhibitor is added to the crude product prior to conducting the flash distillation.

26. The process of claim 1 wherein the reaction phase stabilizer and the separation phase polymerization inhibitor are the same.

27. The process of claim 1 wherein the reaction phase stabilizer and the separation phase polymerization inhibitor are different.