POLYMERIZATION INHIBITORS

Abstract

The present invention relates to a mixture comprising at least one substituted hydroquinone monoether and at least one polymerizable compound.

Claims

1-15. (canceled)

16. A mixture comprising at least one compound of formula (I), ##STR00002## wherein R is C.sub.1- to C.sub.4-alkyl R.sup.1 is C.sub.1- or C.sub.2-alkyl and R.sup.2 to R.sup.4 are independently of one another H, C.sub.1- or C.sub.2-alkyl, and at least one polymerizable compound.

17. The mixture according to claim 16, wherein R and R.sup.1 are independently of one another C.sub.1- or C.sub.2-alkyl and R.sup.2 to R.sup.4 are independently of one another H, C.sub.1- or C.sub.2-alkyl.

18. The mixture according to claim 16, wherein R is C.sub.1- to C.sub.4-alkyl, R.sup.1 and R.sup.2 are independently of one another C.sub.1- or C.sub.2-alkyl and R.sup.3 and R.sup.4 are independently of one another H, C.sub.1- or C.sub.2-alkyl.

19. The mixture according to claim 16, wherein R, R.sup.1 and R.sup.2 are independently of one another C.sub.1- or C.sub.2-alkyl and R.sup.3 and R.sup.4 are independently of one another H, C.sub.1- or C.sub.2-alkyl.

20. The mixture according to claim 16, wherein the compound of formula (I) is 2,3,6-trimethyl-4-methoxyphenol.

21. The mixture according to claim 16, wherein the total amount of the compounds of formula (I) in the mixture is from 0.0001% to 0.1000% by weight based on the total amount of polymerizable compounds.

22. The mixture according to claim 16, wherein the total amount of the polymerizable compounds is at least 5% by weight based on the total weight of the mixture.

23. The mixture according to claim 16, wherein the polymerizable compound is acrylic acid.

24. The mixture according to claim 23, wherein the total amount of the compounds of formula (I) in the mixture is from 0.0050% to 0.1000% by weight based on the total amount of acrylic acid.

25. The mixture according to claim 16, wherein the polymerizable compound is methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and/or 2-ethylhexyl acrylate.

26. The mixture according to claim 25, wherein the total amount of the compounds of formula (I) in the mixture is from 0.0001% to 0.0100% by weight based on the total amount of methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and/or 2-ethylhexyl acrylate.

27. A method comprising providing the at least one compound of formula (I) as defined in claim 16 and inhibiting polymerization of at least one polymerizable compound.

28. A process comprising storing and/or transporting the mixture according to claim 16.

29. The process according to claim 28, wherein the mixture is stored and/or transported in an oxygen-containing atmosphere.

30. The process according to claim 28, wherein the mixture is stored in a vessel in an oxygen-containing atmosphere having an oxygen proportion of 5 to 10 vol% and the mixture is regularly recirculated in the vessel.

Description

EXAMPLES

[0039] The employed monomer was distilled twice to remove the polymerization inhibitor MEHQ. The obtained monomer was in each case admixed with the reported amount of the specified polymerization inhibitor.

[0040] 0.5 ml of each mixture was transferred into a 1.8 ml ampoule and stored at the reported temperature in a recirculating air oven.

[0041] In each test series three ampoules of each mixture were filled and tested, wherein the average time for complete polymerization was determined by visual inspection.

[0042] Relative efficacy is calculated from the quotient of the time until polymerization of the sample with the polymerization inhibitor being tested and the time until polymerization of the sample with MEHQ. The efficacy of MEHQ itself is thus 100%.

[0043] The results are summarized in tables 1 to 6:

TABLE-US-00001 Mixtures with acrylic acid Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.004% by wt. 80° C. 21.3 h 100% TMMP 0.004% by wt. 80° C. 39.5 h 185% TMEP 0.004% by wt. 80° C. 37.1 h 172% TMPP 0.004% by wt. 80° C. 41.0 h 190% MEHQ 0.004% by wt. 90° C. 6.1 h 100% TMMP 0.004% by wt. 90° C. 10.3 h 170% MEHQ 0.006% by wt. 90° C. 10.1 h 100% TMMP 0.006% by wt. 90° C. 25.1 h 250% MEHQ 0.006% by wt. 80° C. 27.4 h 100% DMMP 0.006% by wt. 80° C. 40.1 h 146% MEHQ: hydroquinone monomethyl ether TMMP: 2,3,6-trimethyl-4-methoxyphenol TMEP: 2,3,6-trimethyl-4-ethoxyphenol TMPP: 2,3,6-trimethyl-4-propoxyphenol DMMP: 2,6-dimethyl-4-methoxyphenol

[0044] The polymerization inhibitors according to the invention exhibit improved efficacy compared to MEHQ. The polymerization inhibitors according to the invention simultaneously exhibit sufficient solubility in aqueous solutions, thus making acrylic acid stabilized with the polymerization inhibitors according to the invention suitable for producing aqueous polymer solutions. No cloudiness is observed.

TABLE-US-00002 Mixtures with methacrylic acid Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.003% by wt. 80° C. 36.8 h 100% TMMP 0.003% by wt. 80° C. 40.3 h 110%

TABLE-US-00003 Mixtures with methyl acrylate Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.0005% by wt. 80° C. 18.9 h 100% TMMP 0.0005% by wt. 80° C. >70 h >370%

TABLE-US-00004 Mixtures with ethyl acrylate Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.0005% by wt. 80° C. 15.5 h 100% TMMP 0.0005% by wt. 80° C. >70 h >450%

TABLE-US-00005 Mixtures with n-butyl acrylate Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.0005% by wt. 90° C. 7.4 h 100% TMMP 0.0005% by wt. 90° C. >70 h >940%

TABLE-US-00006 Mixtures with 2-ethylhexyl acrylate Polymerization inhibitor Amount Temperature Time until polymerization Efficacy MEHQ 0.0005% by wt. 90° C. 6.0 h 100% TMMP 0.0005% by wt. 90° C. 27.2 h 460%