Process for Recycling A Formaldehyde Source During A Polymerization Process
A process for recovering volatile components from an oxymethylene polymer process is disclosed. The volatile components are removed from the process and the formaldehyde collected is converted to a cyclic acetal. The formaldehyde is converted to a cyclic acetal by contacting the formaldehyde with a catalyst in the presence of an aprotic solvent.
1 . A process for producing oxymethylene homo- or copolymers comprising:
a) polymerizing at least one monomer to form an oxymethylene polymer in the presence of an initiator;
b) deactivating the polymerization;
c) removing residual monomers containing formaldehyde;
d) contacting the formaldehyde with an aprotic compound and a catalyst; and
e) at least partly converting the formaldehyde to a cyclic acetal.
2 . (canceled)
3 . (canceled)
4 . A process according to claim 1 wherein at least 50 wt.-%, of the monomer is converted to the oxymethylene homo- or copolymer prior to removing the residual monomers containing formaldehyde and wherein the wt.-% refers to the total weight of the monomers.
5 . A process according to claim 1 , wherein the polymerization is deactivated prior to the removal of the residual monomers containing formaldehyde.
6 . A process according to claim 1 wherein the formaldehyde is removed as a gaseous mixture together with residual monomers.
7 . A process according to claim 1 wherein the polymerization process uses trioxane and/or tetroxane as a monomer; and optionally includes a comonomer.
8 . (canceled)
9 . (canceled)
10 . (canceled)
11 . A process according to claim 1 wherein the aprotic compound has a boiling point of 120° C. or higher, determined at 1 bar.
12 . A process according to claim 1 wherein the formaldehyde, the aprotic compound and the catalyst form a reaction mixture and wherein the reaction mixture comprises at least 60 wt.-%, of the aprotic compound, wherein the weight is based on the total weight of the reaction mixture.
13 . A process according to claim 1 wherein the aprotic compound comprises a sulfur containing organic compound.
14 . A process according to claim 1 wherein the aprotic compound comprises a dipolar nitro-group free compound.
15 . A process according to claim 1 wherein the aprotic compound is represented by formula (I):
wherein
n is an integer ranging from 1 to 6, and
wherein the ring carbon atoms may optionally be substituted by one or more substituents; selected from C 1 -C 8 -alkyl which may be branched or unbranched.
16 . A process according to claim 1 wherein the aprotic compound is sulfolane.
17 . A process according to claim 1 wherein the aprotic compound is represented by formula (II):
wherein R 1 and R 2 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched.
18 . A process according to claim 1 wherein the aprotic compound is represented by formula (III):
wherein
n is an integer ranging from 1 to 6, and
wherein the ring carbon atoms may optionally be substituted by one or more substituents, selected from C 1 -C 8 -alkyl which may be branched or unbranched; or
the aprotic compound is represented by formula (IV):
wherein R 3 and R 4 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched.
19 . (canceled)
20 . A process according to claim 1 wherein the conversion to the cyclic acetal is carried out at a temperature ranging from 20° C. to 150° C., and is carried out at a pressure of from 10 millibars to 10 bars.
21 . A process according to claim 1 wherein the removed formaldehyde has a water content of less than 10000 ppm.
22 . A process according to claim 1 wherein the residual monomers removed comprise formaldehyde and trioxane.
23 . A process according to claim 1 wherein the initiator comprises boron trifluoride, a heteropoly acid, an isopoly acid, or trifluoromethanesulfonic acid and the catalyst is trifluoromethanesulfonic acid.
24 . A process according to claim 1 , wherein the formaldehyde removed during the process is gaseous formaldehyde and is directly contacted with the aprotic compound and the catalyst.
25 . A process according to claim 1 , wherein the removed formaldehyde comprises an aqueous formaldehyde solution when contacted with the aprotic compound and the catalyst.
26 . An oxymethylene homo- or copolymer made according to claim 1 .
27 . A process according to claim 1 , wherein higher than 50 percent of the formaldehyde is converted into the cyclic acetal.
28 . A process according to claim 1 , wherein the polymerization process that forms the oxymethylene polymer comprises a heterogeneous process.
29 . A process according to claim 1 , wherein the polymerization process that forms the oxymethylene polymer comprises a homogeneous process.
30 . A process for recovering formaldehyde from an oxymethylene homo- or copolymer production process comprising;
a) at least partly removing formaldehyde during or after the polymerization process,
b) contacting said formaldehyde with an aprotic compound and a catalyst; and
c) at least partly converting the formaldehyde to a cyclic acetal.