Method and system for purifying monomers

1. A process for purifying at least one monomer, comprising evaporating at least a portion of the at least one monomer present in a starting composition and then condensing vapors resulting from the evaporation,

wherein

at least a portion of the starting composition is evaporated in a short-path evaporator,

the mass flow density of the vapors, m, is non-zero and selected according to formula (I)

m

.

≤

1800

⁢

kg

·

K

mbar

·

m

2

·

h

·

kg

kmol

·

p

i

·

(

M

~

T

)

0.5

(

I

)

wherein

{tilde over (M)} is the average molar mass of the vapors in the short-path evaporator in kg/kmol,

T is the temperature of the vapors in K,

p i is the pressure in the short-path evaporator in mbar,

m{dot over ( )} is the mass flow density of the vapors in kg/(m 2 ·h),

said starting composition comprises 1 to 200 ppm of at least one polymerization inhibitor, and

said short-path evaporator has a ratio of evaporator area to condenser area of 0.1 to 10.

2. The process of claim 1 , wherein the starting composition comprises at least 95% by weight of the at least one monomer.

3. The process of claim 1 , wherein the evaporation is at a temperature in the range from 15° C. to 150° C.

4. The process of claim 1 , wherein the starting composition comprises a high-boiling monomer.

5. The process of claim 4 , wherein the high-boiling monomer is methacrylic anhydride or a methacrylate.

6. The process of claim 5 , wherein the high-boiling monomer is the methacrylate, which is selected from the group consisting of hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, 1,4-butanediol dimethacrylate, glycol dimethacrylate, 2-hydroxyethyl methacrylate, 2-ethoxyethyl methacrylate, decyl methacrylate, tetrahydrofurfuryl methacrylate, octadecyl/stearyl methacrylate, tetraethylene glycol dimethacrylate, 2,2-bis(hydroxymethyl)-1,3-propanediol dimethacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 1,3-butanediol dimethacrylate, benzyl methacrylate, allyl methacrylate, 2-(2-butoxyethoxyl)ethyl methacrylate, trimethylolpropane trimethacrylate, N-3-dimethylaminopropylmethacrylamide, 2-dimethylaminoethyl methacrylate, triethylene glycol dimethacrylate, isobornyl methacrylate, polyethylene glycol methacrylates, isodecyl methacrylate, dodecyl methacrylate, 2-[2-(2-ethoxyethoxyl)ethoxy]ethyl methacrylate, 2,3-dihydroxypropyl methacrylate, (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate, 2-carbamoyloxyethyl methacrylate and 1,6-hexanediol dimethacrylate.

7. The process of claim 1 , wherein the at least one monomer is acrylic anhydride or an acrylate.

8. The process of claim 7 wherein the at least one monomer is the acrylate, which is at least one selected from the group consisting of hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, 1,4-butanediol diacrylate, glycol diacrylate, 2-hydroxyethyl acrylate, 2-ethoxyethyl acrylate, decyl acrylate, tetrahydrofurfuryl acrylate, octadecyl/stearyl acrylate, tetraethylene glycol diacrylate, 2,2-bis(hydroxymethyl)-1,3-propanediol diacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 1,3-butanediol diacrylate, benzyl acrylate, allyl acrylate, 2-(2-butoxyethoxyl)ethyl acrylate, trimethylolpropane triacrylate, N-3-dimethylaminopropylmethacrylamide, 2-dimethylaminoethyl acrylate, triethylene glycol diacrylate, isobornyl acrylate, polyethylene glycol acrylates, isodecyl acrylate, dodecyl acrylate, 2-[2-(2-ethoxyethoxyl)ethoxy]ethyl acrylate, pentaerythrityl tetraacrylate, pentaerythrityl triacrylate and 1,6-hexanediol diacrylate.

9. The process of claim 1 , wherein the residence time of the at least one monomer is in the range from 1 second to 5 minutes.

10. The process of claim 1 , wherein at least one component with a low boiling point is withdrawn from the starting composition before the at least one monomer present in the starting composition is evaporated and condensed.

11. The process of claim 10 , wherein at least one component with a low boiling point is withdrawn from the starting composition by evaporation in a short-path evaporator.

12. The process of claim 11 , wherein the evaporation to remove the at least one component with a low boiling point is at a temperature in the range from 40° C. to 150° C.

13. The process of claim 1 , wherein the residue obtained after the evaporation of the at least one monomer is subjected to a residue evaporation and condensation in a short-path evaporator.

14. The process of claim 13 , wherein the residue evaporation is at a temperature in the range from 15° C. to 150° C.

15. The process of claim 1 , wherein a purified product comprises at least 99% by weight of the at least one monomer.

16. A plant for performing the process of claim 1 , wherein

the plant comprises at least three short-path evaporators, and

the short-path evaporators are connected to one another such that a residue from a first short-path evaporator is passed into a second short-path evaporator and a residue from the second short-path evaporator is passed into a third short-path evaporator.

17. A plant for performing the process of claim 3 , wherein

the plant comprises at least three short-path evaporators, and

the short-path evaporators are connected to one another such that a residue from a first short-path evaporator is passed into a second short-path evaporator and a residue from the second short-path evaporator is passed into a third short-path evaporator.

18. A plant for performing the process of claim 11 , wherein

the plant comprises at least three short-path evaporators, and

the short-path evaporators are connected to one another such that a residue from a first short-path evaporator is passed into a second short-path evaporator and a residue from the second short-path evaporator is passed into a third short-path evaporator.