Synthesis of methylene malonates substantially free of impurities

Abstract

The present invention provides improved methods for the chemical synthesis of methylene malonates using the Knovenagel synthesis reaction. The method of the invention provides for improved methylene malonates by significantly reducing or eliminating the formation of alternative and/or deleterious side products, significantly reducing or eliminating unwanted consumption of methylene malonates, and significantly reducing or eliminating the degradation of methylene malonates. These advantages result in methylene malonates, which upon recovery, are of higher quality, greater purity, improved yield and possess overall improved performance characteristics (e.g., improved cure speed, retention of cure speed, improved shelf-life and/or stability).

1 - 58 . (canceled) 
     
     
         59 . A method of making a methylene malonate monomer comprising:
 (a) reacting a malonic acid ester with a source of formaldehyde in the presence of an acidic or basic catalyst and optionally in the presence of an acidic or non-acidic solvent, to form a reaction complex;   (b) optionally, inactivating the catalyst; and   (c) recovering methylene malonate monomer from the reaction complex.   
     
     
         60 . The method according to  claim 59 , wherein inactivating the catalyst comprises forming an insoluble precipitate of the catalyst and removing the precipitate from the reaction mixture. 
     
     
         61 . The method according to  claim 60 , wherein the precipitate is formed by reducing the solubility of the catalyst in the reaction mixture. 
     
     
         62 . The method according to  claim 59  further comprising:
 (d) minimizing the recovery of volatile latent acid forming impurities from the reaction complex. 
 
     
     
         63 . The method according to  claim 62 , wherein the step of minimizing the recovery of volatile latent acid forming impurities comprises:
 (a) adding to the reaction mixture water and an acid having a pKa range of −8 to 5;   (b) adding to the reaction mixture a sterically hindered organic acid; or   (c) adding to the reaction mixture a non-volatile organic acid, or any combination of (a), (b) or (c).   
     
     
         64 . The method according to  claim 59  comprising the basic catalyst, wherein the basic catalyst is at least one member of the group consisting of potassium acetate, sodium acetate, zinc acetate, aluminum acetate, calcium acetate, magnesium acetate, magnesium oxide, copper acetate, lithium acetate, aluminum oxide and zinc oxide. 
     
     
         65 . The method according to  claim 59  comprising the acidic catalyst, wherein the acidic catalyst is at least one member of the group consisting of paratoluene sulfonic acid, dodecylbenzene sulfonic acid, boron trifluoride, zinc perchlorate, sulfated zirconium oxide, sulfated titanium oxide, lithium chloride, boron trifluoride etherate, ferric sulfate, zirconium oxychloride, cupric chloride, titanium tetrachloride and zinc chloride. 
     
     
         66 . The method according to  claim 59 , wherein the reacting step is conducted in the presence of a non-acidic solvent being at least one member of the group consisting of chloroform, dichloromethane, toluene, heptane, ethyl acetate, n-butyl acetate and hexane. 
     
     
         67 . The method according to  claim 59 , wherein the reacting step is conducted in the absence of a solvent. 
     
     
         68 . The method according to  claim 59 , wherein the recovering step comprises at least one process selected from the group consisting of condensation, simple distillation, fractional distillation, flash distillation, steam distillation, vacuum distillation, short path distillation, thin-film distillation, reactive distillation, pervaporation, extractive evaporation, flash evaporation, and rotary evaporation. 
     
     
         69 . The method according to  claim 59 , wherein the recovering step is performed at reduced pressure. 
     
     
         70 . The method according to  claim 59 , wherein the malonic acid ester has the formula:
   R—O—C(O)—CH2-C(O)—O—R′
   wherein R and R′ are independently C 1 -C 15  alkyl, C 2 -C 15  alkenyl, halo-(C 1 -C 15  alkyl), C 3 -C 6  cycloalkyl, halo-(C 3 -C 6  cycloalkyl), heterocyclyl, heterocyclyl-(C 1 -C 15  alkyl), aryl-(C 1 -C 15  alkyl), heteroaryl or heteroaryl-(C 1 -C 15  alkyl), or alkoxy-(C 1 -C 15  alkyl), each of which may be optionally substituted by C 1 -C 15  alkyl, halo-(C 1 -C 15  alkyl), C 3 -C 6  cycloalkyl, halo-(C 3 -C 6  cycloalkyl), heterocyclyl, heterocyclyl-(C 1 -C 15  alkyl), aryl, aryl-(C 1 -C 15  alkyl), heteroaryl, C 1 -C 15  alkoxy, C 1 -C 15  alkylthio, hydroxyl, nitro, azido, cyano, acyloxy, carbox, or ester; or   wherein R and R′ are taken together with the atoms to which they are bound to form a 5-7 membered heterocyclic ring which may be optionally substituted by C 1 -C 15  alkyl, halo-C 1 -C 15  alkyl), C 3 -C 6  cycloalkyl, halo-(C 3 -C 6  cycloalkyl), heterocyclyl, heterocyclyl-(C 1 -C 15  alkyl), aryl, aryl-(C 1 -C 15  alkyl), heteroaryl, C 1 -C 15  alkoxy, C 1 -C 15  alkylthio, hydroxyl, nitro, azido, cyano, acyloxy, carboxy, or ester.   
     
     
         71 . A methylene malonate monomer prepared according to the method of  claim 59 . 
     
     
         72 . A product comprising a methylene malonate monomer prepared according the method of  claim 59 . 
     
     
         73 . The product according to  72  comprising an adhesive, a coating, a sealant, a composite or a surfactant. 
     
     
         74 . The product according to  72  further comprising at least one additive selected from the group consisting of an acidic stabilizer, a free radical stabilizer, a sequestering agent, a cure accelerator, a rheology modifier, a plasticizing agent, a thixotropic agent, a natural rubber, a synthetic rubber, a filler agent, and a reinforcing agent. 
     
     
         75 . The product according to  claim 74  comprising the acid stabilizer, wherein the acid stabilizer has a pKa in the range of −15 to 5. 
     
     
         76 . The product according to  claim 74  comprising the acid stabilizer, wherein the acid stabilizer is a volatile acid stabilizer, and wherein the volatile acid stabilizer has a boiling point less than 200° C. 
     
     
         77 . The product according to  claim 74  comprising the acid stabilizer, wherein the acid stabilizer is an acidic gas. 
     
     
         78 . The product according to  claim 77  wherein the acidic gas is SO 2  or BF 3 . 
     
     
         79 . The product according to  claim 74  comprising the acid stabilizer, wherein the acidic stabilizer is present in a concentration of from 0.1 ppm to 100 ppm. 
     
     
         80 . The product according to  claim 74  comprising the free radical stabilizer, wherein the free radical stabilizer is a phenolic free radical stabilizer. 
     
     
         81 . The product according to  claim 74  comprising the free radical stabilizer, wherein the free radical stabilizer is present in a concentration of from 0.1 ppm to 10000 ppm. 
     
     
         82 . The product according to  claim 74  comprising the sequestering agent, wherein the sequestering agent is at least one member of the group consisting of a crown ether, a silyl crown, a calixarene, and a polyethylene glycol. 
     
     
         83 . The product according to  claim 74  comprising the cure accelerator, wherein the cure accelerator is at least one member of the group consisting of sodium acetate, potassium acetate, tetrabutyl ammonium fluoride and tetrabutyl ammonium hydroxide. 
     
     
         84 . The product according to  claim 74  comprising the rheology modifier, wherein the rheology modifier is at least one member of the group consisting of hydroxyethylcellulose, ethylhydroxyethylcellulose, methylcellulose, a polymeric thickener and a pyrogenic silica. 
     
     
         85 . A polymer comprising at least two repeat units derived from polymerization of the methylene malonate monomer according to  claim 71 . 
     
     
         86 . A polymer product comprising the polymer according to  claim 85 . 
     
     
         87 . The polymer product according to  claim 86  wherein the product is a sealant, a thermal barrier coating, a textile fabric, a water-treatment polymer, an ink carrier, a paint carrier, a packaging film, a medical polymer, a polymer film, a polymer fiber or a polymer sheet.