Process for manufacturing reduced water content (meth) acrylic acid

Abstract

A method is provided herein for purifying (meth)acrylic acid to provide a purified (meth)acrylic acid product having a low aldehyde concentration and not more than 0.2 wt % water. One embodiment of the method includes distilling (meth)acrylic acid in the presence of an aldehyde treating compound. Another embodiment of the method includes also distilling crude (meth)acrylic acid in the presence of a reactive drying agent. (Meth)acrylic acid produced in this manner is especially suitable for use in specialty (meth)acrylic acid polymers, such as for example superabsorbent polymers, binders, and ethylene-(M)AA copolymers.

1 - 14 . (canceled) 
   
   
       15 . A (meth)acrylic acid product comprising less than 1% impurities and less than 5 ppm furfural. 
   
   
       16 . The (meth)acrylic acid product of  claim 15 , further comprising not more than 0.2 wt % water based on the total weight of the (meth)acrylic acid product. 
   
   
       17 . The (meth)acrylic acid product of  claim 16 , further comprising not more than 5 ppm acrolein, not more than 5 ppm benzaldehyde, and not more than 5 ppm protoanemonin. 
   
   
       18 . A specialty polymer composition comprising units derived from at least the (meth)acrylic acid product of  claim 15 . 
   
   
       19 . A specialty polymer composition comprising units derived from at least a (meth)acrylic acid product produced by a method comprising
 a. directing a (meth)acrylic acid stream containing at least (meth)acrylic acid and water and at least one aldehyde compound to a distillation system;   b. adding at least one aldehyde treating compound capable of reacting with said at least one aldehyde compound to the (meth)acrylic acid stream, such that said at least one aldehyde compound reacts with said at least one aldehyde treating compound to produce a first product having a higher boiling point temperature than (meth)acrylic acid;   c. adding at least one reactive drying agent to the distillation system wherein said at least one reactive drying agent is capable of reacting with said water such that said at least one reactive drying agent reacts with said water to produce a second product having a higher boiling point temperature than (meth)acrylic acid, wherein said at least one reactive drying agent is selected from the group consisting of acetals, ketals, halogenated anhydrides, isocyanates, 1,3-phenylene diisocyanate, tetramethoxy-1,4-cyclohexadiene, trifluoroacetic anhydride, and combinations thereof; and   d. separating said first and said second products from said (meth)acrylic acid stream by distillation to produce a high purity (meth)acrylic acid stream comprising less than 1 wt % impurities, less than 5 ppm furfural, and not more than 0.2 wt % water, based on the total weight of the (meth)acrylic acid product.   
   
   
       20 . A method of purifying a (meth)acrylic acid stream using a distillation apparatus, comprising maintaining the temperature at the bottom of the distillation apparatus at not more than 110° C. 
   
   
       21 . The method of  claim 20 , wherein the production of methyl vinyl ketone within the distillation apparatus is minimized. 
   
   
       22 . The method of  claim 21 , further comprising producing a final product (meth)acrylic acid stream comprising no more than 25 ppm methyl vinyl ketone.