WO2006122923A1

WO2006122923A1 - Aromatic heterocycles as stabilizers of polymerizable compounds

Info

Publication number: WO2006122923A1
Application number: PCT/EP2006/062318
Authority: WO
Inventors: Sylke Haremza; Gerhard Wagenblast; Frank HÖFER
Original assignee: Basf Aktiengesellschaft
Priority date: 2005-05-18
Filing date: 2006-05-15
Publication date: 2006-11-23
Also published as: DE102005023607A1

Abstract

Disclosed is a method for stabilizing polymerizable compounds against polymerization. According to said method, at least one aromatic heterocycle of general formula (I) is used, wherein X can represent a heteroatom, C-R1, C-NR1R2, or C-OR3, R1 and R2 having the meaning indicated below and R3 optionally also representing hydrogen, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle, or a halogen atom; Y represents hydrogen, NR1R2, O-R3, P-R4, SR5, C1-C20 alkyl, C2-C20 alkenyl, aryl, or a halogen atom, R1 and R2 having the meaning indicated below and R3 to R5 optionally also representing hydrogen, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle, or a halogen atom; Z can represent hydrogen, NR1R2, O-R3, P-R4, SR5, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, or a heterocycle, R1 and R 2 having the meaning indicated below and R3 to R5 optionally also representing hydrogen, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle, or a halogen atom; and R1 and R2 can independently represent hydrogen, NR4R5, O-R3, P-R4, SR5, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle, or a halogen atom, R3 to R5 optionally also representing hydrogen, C1-C20 alkyl, C1-C20 alkylcarbonyl, C1-C20 alkoxycarbonyl, C2-C20 alkenyl, C2-C20 alkenylcarbonyl, C2-C20 alkinyl, C2-C20 alkinylcarbonyl, C3-C15 cycloalkyl, C5-C15 cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle, or a halogen atom.

Description

Aromatic heterocycles as stabilizers of polymerizable compounds

description

The present invention describes a process for stabilizing polymerizable compounds against polymerization by the use of aromatic heterocycles. It further relates to a stabilizer mixture containing at least one aromatic heterocycle and at least one further stabilizer or co-stabilizer. Furthermore, the invention relates to a mixture of substances comprising such a stabilizer mixture and at least one polymerizable compound.

For the purposes of the present invention, polymerizable compounds are understood as meaning compounds which have one or more ethylenically unsaturated groups.

Chemical compounds which have one or more ethylenically unsaturated groups have a pronounced tendency to radical polymerization. Such compounds are used as monomers for the controlled production of polymers, eg. B. by radical polymerization. At the same time, however, the pronounced tendency for free-radical polymerization is disadvantageous in that it occurs both during storage and during chemical and / or physical processing, for. Example by distillation or rectification, the ethylenically unsaturated compounds, in particular under the action of energy, for. As heat and / or light, can come to unwanted, spontaneous radical polymerization. Such uncontrolled polymerizations can be used for the gradual formation of polymer coatings z. B. lead to heated surfaces or even run explosively.

It is therefore common to add ethylenically unsaturated compounds or mixtures containing such compounds, both during storage and during chemical and / or physical processing substances that prevent or slow a spontaneous polymerization. They are generally referred to as inhibitors or retarders and summarized under the term "stabilizers".

A large number of stabilizers are known for polymerizable compounds, in particular for acrylic acid and methacrylic acid, hereinafter called (meth) acrylic acid, and their esters, hereinafter called (meth) acrylic esters.

Valgimigli et al. in Chem. Eur. J. 2003, 9, 4997-5010 describe the ability of pyrimidin-5-ols as radical scavengers. The influence of these antioxidants and polymerization inhibitors in radical chain reactions is investigated. In particular, the importance of such substances in medical use against atherosclerosis, Alzheimer's, Parkinson's and also against cancer is described. In J. Am. Chem. Soc. 2001, 123, 4625-4626 disclose Valgimigli et al. also pyrimidin-5-ols as antioxidants, which are responsible for the radical chain termination in human blood plasma as well as in lipoproteins.

In Angew. Chem. Int. Ed. 2003, 42, 4370-4373 describes 6-aminopyridin-3-ols as antioxidants, the use of which in the treatment of various degenerative diseases is under discussion.

WO 02/00683 A1 discloses pyrimidine-5-ols and also pyridine-2-ols which, as antioxidants, are very reactive towards peroxyl radicals. In addition to one

Use in chemotherapy are also oxidation-inhibiting uses u.a. described as additives for fuels, coating agents and polymers.

In all cited references, high reaction rates with radicals are described. However, the stabilizing effect of the heterocycles, for example on polymerizable compounds is not disclosed.

The object of the present invention was therefore to provide an alternative method for stabilizing polymerizable compounds against polymerization.

The object has been achieved with a method for stabilizing polymerizable compounds against polymerization, wherein at least one aromatic heterocycle of the general formula (I)

starts.

In detail can be:

X can be a heteroatom, CR ¹ , C-NR ¹ R ² or C-OR ³ , wherein R ¹ and R ^{2 have} the meanings mentioned below, and R ^{3 is} also hydrogen, C ₁ -C 20 -alkyl, C ₁ -C 20 - alkylcarbonyl, CrC ₂ o-alkoxycarbonyl, _{C2-C2o-alkenyl,} C2-C ₂ o-alkenylcarbonyl, C ₂ -C ₂₀ - alkynyl, C ₂ -C ₂ o-AIkinylcarbonyl, C3-Ci ₅ cycloalkyl, Cs -Cis-cycloalkylcarbonyl, aryl, aryl carbonyl, a heterocycle or a halogen atom.

Y can be hydrogen, NR ¹ R ² , OR ³ , PR ⁴ , SR ⁵ , C _r C ₂ o-alkyl, C ₂ -C ₂₀ alkenyl, aryl or αrTHälogenätcTrh seih, wherein R ¹ and R ^{2 the} lunteTi ^ härmte ^{^} BeaeΗtürTg ^{^} häb ^ iVünd R ^{3 "} to R ⁵ is also hydrogen, _{Ci-C2o-alkyl,} d Co-alkylcarbonyl, CrC ₂₀ - alkoxycarbonyl, C2-C2o-alkenyl, C2-C2o-alkenylcarbonyl, _C2-C2o alkynyl, C ₂ -C ₂₀ - alkynylcarbonyl , C ₃ -C ₅ -cycloalkyl, C ₅ -C ₅ -cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom.

Z can be hydrogen, NR ¹ R ² , OR ³ , PR ⁴ , SR ⁵ , C 1 -C ₂₀ -alkyl, C 1 -C ₂₀ -alkylcarbonyl, C ₁ -C ₂ -alkoxycarbonyl, C ₂ -C ₂₀ -alkenyl, C ₂ -C ₂₀ -alkenylcarbonyl , C ₂ -C ₂ o-alkynyl, C ₂ -C ₂₀ -alkynylcarbonyl, C ₃ -Cis -cycloalkyl, Cs-Cis-cycloalkylcarbonyl, aryl, arylcarbonyl or a heterocycle, wherein R ¹ and R ^{2 have} the meanings mentioned below and R ³ to R ⁵ is also hydrogen, Ci-C ₂₀ alkyl, -C ₂ o-alkylcarbonyl, CrC ₂₀ -

Alkoxycarbonyl, C ₂ -C2o-alkenyl, _C2 -C2o-alkenylcarbonyl, _C2-C2o alkynyl, C ₂ -C ₂₀ - alkynylcarbonyl, C3-Ci ₅ cycloalkyl, C ₅ -Ci5-cycloalkylcarbonyl, aryl, arylcarbonyl, may be a heterocycle or a halogen atom.

The radicals R ¹ and R ² may in detail have the following meaning:

R ¹ and R ² can independently represent hydrogen, NR ⁴ R ^5, OR ^3, PR ⁴ SR ^5, C ₂ o alkyl, Ci-C ₂ o-d- AIkylcarbonyl, -C ₂ o-alkoxycarbonyl, C ₂ -C ₂ o-alkenyl, C ₂ -C ₂₀ - alkenylcarbonyl, C2-C ₂₀ alkynyl, CΣ-CΣo-alkynylcarbonyl, C ₃ -C ₅ cycloalkyl, C ₅ -C ₅ - cycloalkylcarbonyl, aryl, arylcarbonyl, a be heterocycle or a halogen atom, wherein R ³ to R ⁵ is also hydrogen, _{Ci-C2o-alkyl,} -C ₂ o-alkylcarbonyl, CrC ₂₀ - alkoxycarbonyl, C ₂ -C ₂₀ -alkyl keny I, C ₂ -C ₂₀ - alkenylcarbonyl, C ₂ -C ₂₀ alkynyl, C ₂ -C ₂₀ - alkynylcarbonyl, C3-Ci5-cycloalkyl, C ₅ -C ₅ cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom may be,

in which

a) when X has the meaning of CR ³ , in the case of said aliphatic substituents, the radicals R ¹ and R ³ or R ² and R ^{3 may} also be joined together and thus together a three- to eight-membered, preferably a five- to seven-membered and particularly preferably form a five- to six-membered ring,

b) in the case of said aliphatic substituents, the radicals Y and Z may also be linked to one another and thus together form a three- to eight-membered, preferably a five- to seven-membered and particularly preferably a five- to six-membered ring,

c) the abovementioned aliphatic substituents can be straight-chain or branched, d) the substituents may each be interrupted at any position by one or more heteroatoms, the number of these heteroatoms being not more than 10, preferably not more than 8, more preferably not more than 5 and in particular not more than 3, and /or

e) the substituents are in any desired position, but not more than five times, preferably not more than four times and more preferably not more than three times by alkyl, alkyloxy, alkyloxycarbonyl, aryl, aryloxy, aryloxycarbonyl, hydroxycarbonyl, aminocarbonyl, heterocycles, heteroatoms or halogen atoms. ■ me may be substituted, which may also be substituted at most twice, preferably at most once with said groups.

In detail, the collective terms given for the various radicals R have the following meaning:

C ₁ -C 20 -alkyl: straight-chain or branched hydrocarbon radicals having up to 20 carbon atoms, preferably C ₁ -C 10 -alkyl, such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, 1, 1 Dimethylethyl, pentyl, 2-methylbutyl, 1, 1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 2-methylpentyl, 3-methylpentyl, 1, 1-dimethylbutyl, 1, 2 Dimethylbutyl, 1, 3-dimethylbutyl, 2,2-

Dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-i-methylpropyl, 1-ethyl-2-methylpropyl, Heptyl, octyl, 2-ethylhexyl, 2,4,4-trimethylpentyl, 1,1,3,3-tetramethylbutyl, nonyl and decyl and their isomers.

C 1 -C 20 -alkylcarbonyl: a straight-chain or branched alkyl group having 1 to 20 carbon atoms (as mentioned above) which is attached via a carbonyl group (-CO-), preferably C 1 -C 10 -alkylcarbonyl, such as, for example, formyl, acetyl, n- or iso-propionyl , n-, iso-, sec- or tert-butanoyl, n-, iso-, sec- or tert-pentanoyl, n- or iso-nonanoyl, n-dodecanoyl.

C ₂ -C 20 alkenyl: unsaturated, straight-chain or branched hydrocarbon radicals having 2 to 20 carbon atoms and one double bond in any position, preferably C ₂ -C 10 -alkenyl, such as ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl , 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3 Pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2-methyl-1-butenyl, 3-methyl-1-butenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl, 3-methyl 2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2-propenyl, 1, 2-dimethyl-1-propenyl, 1 , 2-dimethyl-2-propenyl, 1-ethyl-1-propenyl, 1-ethyl-2-propenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1 -pentenyl, 2-methyl-1-pentenyl, 3-methyl-1-pentenyl, 4-methyl-1-pentenyl, 1-methyl-2-pentenyl, 2-methyl-2-pentenyl, 3-methyl-2-pentenyl , 4-methyl-2- pentenyl, 1-methyl-3-pentenyl, 2-methyl-3-pentenyl, 3-methyl-3-pentenyl, 4-methyl-3-pentenyl, 1-methyl-4-pentenyl, 2-methyl-4-pentenyl , 3-methyl-4-pentenyl, 4-methyl-4-pentenyl, 1,1-dimethyl-2-butenyl, 1,1-dimethyl-3-butenyl, 1,2-dimethyl-i-butenyl, 1,2 - Dimethyl-2-butenyl, 1, 2-dimethyl-3-butenyl, 1, 3-dimethyl-1-butenyl, 1, 3-dimethyl-2-butenyl, 1, 3-dimethyl-3-butenyl, 2.2 Dimethyl 3-butenyl, 2,3-dimethyl-1-butenyl, 2,3-dimethyl-2-butenyl, 2,3-dimethyl-3-butenyl, 3,3-dimethyl-1-butenyl, 3,3 -Dimethyl-2-butenyl, 1-ethyl-1-butenyl, 1-ethyl-2-butenyl, 1-ethyl-3-butenyl, 2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl 3-butenyl, 1, 1,2-trimethyl-2-propenyl, 1-ethyl-1-methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl and 1-ethyl-2-methyl-2 Propenyl, as well as the isomers of heptenyl, octenyl, nonenyl and decenyl.

C 2 -C 20 -alkenylcarbonyl: unsaturated, straight-chain or branched hydrocarbon radicals having 2 to 20 carbon atoms and a double bond in any position (as mentioned above) which are attached via a carbonyl group (-CO-), preferably C 2 -C 10 -alkylcarbonyl such as, for example Ethenyl, propenoyl, butenoyl, pentenoyl, nonenoyl and their isomers.

C ₂ -C 20 -alkynyl: straight-chain or branched hydrocarbon groups having 2 to 20 carbon atoms and a triple bond in any position, preferably C ₂ -C 10 -alkynyl, such as ethynyl 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3 Butinyl, 1-methyl-2-propynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, i-methyl-2-butynyl, 1-methyl-3-butynyl, 2-methyl-3-butynyl, 3-methyl-1-butynyl, 1,1-dimethyl-2-propynyl, 1-ethyl-2-propynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, 1-methyl 2-pentynyl, 1-methyl-3-pentynyl, 1-methyl-4-pentynyl, 2-methyl-3-pentynyl, 2-methyl-4-pentynyl, 3-methyl-1-pentynyl, 3-methyl-4 pentynyl, 4-methyl-1-pentynyl, 4-methyl-2-pentynyl, 1,1-dimethyl-2-butynyl, 1, 1-dimethyl-3-butynyl, 1, 2-dimethyl-3-butynyl, 2, 2-dimethyl-3-butynyl, 3,3-dimethyl-1-butynyl, 1-ethyl-2-butynyl, 1-ethyl-3-butynyl, 2-ethyl-3-butynyl and 1-ethyl-1-methyl 2-propynyl and the isomers of heptynyl, octynyl, nomenyl, decynyl.

C ₂ -C ₂ o-alkynylcarbonyl: unsaturated, straight-chain or branched hydrocarbon radicals having 2 to 20 carbon atoms and a triple bond in any position (as mentioned above) which are attached via a carbonyl group (-CO-), preferably C ₂ -C 10 -alkyl Alkynylcarbonyl such as propinoyl, butino, pentinoyl, noninoyl, decinoyl and their isomers.

C ₃ -C ₅ -cycloalkyl: monocyclic, saturated hydrocarbon groups having 3 to 15 carbon ring members, preferably C ₃ -C 8 -cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl, and a saturated or unsaturated cyclic system, such as, for example, , B. norbornyl or norbenyl. C ₃ -C 15 -cycloalkylcarbonyl: monocyclic, saturated hydrocarbon groups having 3 to 15 carbon ring members (as mentioned above) which are attached via a carbonyl group (-CO-), preferably C ₃ -C 8 -cycloalkylcarbonyl.

Aryl: a mono- to trinuclear aromatic ring system containing 6 to 14 carbon ring members, e.g. As phenyl, naphthyl and anthracenyl, preferably a mononuclear to dinuclear, more preferably a mononuclear aromatic ring system.

Arylcarbonyl: preferably a mono- to trinuclear aromatic ring system (as mentioned above) which is attached via a carbonyl group (-CO-), such as. B. benzoyl, preferably a mono- to binuclear, more preferably a mononuclear aromatic ring system.

Heterocycles: five- to twelve-membered, preferably five- to nine-membered, particularly preferably five- to six-membered oxygen, nitrogen and / or sulfur atoms, optionally having a plurality of rings ring systems such as furyl, thiophenyl, pyrryl, pyridyl, indolyl, benzoxazolyl, dioxolyl , Dioxy, benzimidazolyl, benzthiazolyl, dimethylpyridyl, methylquinolyl, dimethylpyrryl, methoxyfuryl, dimethoxypyridyl, difluoropyridyl, methylthiophenyl, isopropylthiophenyl or tert-butylthiophenyl.

The substituents listed in detail may each be interrupted at any position by one or more heteroatoms as described above, the number of these heteroatoms being not more than 10, preferably not more than 8, very particularly preferably not more than 5 and in particular not more is 3, and / or in any position, but not more than five times, preferably not more than four times and more preferably not more than three times, by alkyl, alkyloxy, alkyloxycarbonyl, aryl, aryloxy, aryloxycarbonyl, hydroxycarbonyl, aminocarbonyl, Heterocycles, heteroatoms or halogen atoms may be substituted, which may also be substituted at most twice, preferably at most once with said groups.

The classes of alkyl, aryl and heterocycles mentioned in this group have the abovementioned meaning.

Heteroatoms are oxygen, nitrogen, sulfur or phosphorus.

Alkyloxy denotes a straight-chain or branched alkyl group having 1 to 20 carbon atoms (as mentioned above), which are attached via an oxygen atom (-O-), preferably C 1 -C 10 -alkyloxy, such as, for example, methoxy, ethoxy, propoxy. Alkoxycarbonyl is an alkoxy group having 1 to 20 carbon atoms (as mentioned above) which is attached via a carbonyl group (-CO-), preferably C1-C ₁ 0- Aikyloxycarbonyl.

Aryloxy is a mono- to trinuclear aromatic ring system (as mentioned above) which is attached via an oxygen atom (-O-), preferably a mono- to binuclear, particularly preferably a mononuclear aromatic ring system.

Aryloxycarbonyl is a mono- to trinuclear aryloxy group (as mentioned above) which is bonded via a carbonyl group (-CO-), preferably a mono- to binuclear, particularly preferably a mononuclear aryloxycarbonyl.

Halogen atoms are fluorine, chlorine, bromine and iodine.

Preferably X is nitrogen or CR ^1, wherein R ¹ is preferably hydrogen or -C ₂ -alkyl, particularly preferably hydrogen or Ci-Cio-alkyl and very particularly preferably hydrogen or Ci-Ce alkyl.

Preferably Y is hydrogen, NR ¹ R ^2, OR ^3, C ₂ -alkyl, C ₂ -C ₂₀ -alkyl genatom keny I, or a halo-, wherein in the case of NR ¹ R ^2, the substituents R ¹ and R ² preferably are identical and are hydrogen or -C ₂ -alkyl, particularly preferably hydrogen or CRDO-alkyl, very particularly preferably hydrogen or Ci-Cδ-alkyl, and in the case of oR ³ R ³ is preferably hydrogen or CrC2o-alkyl, particularly preferably hydrogen or C 1 -C 10 -alkyl and very particularly preferably hydrogen or C 1 -C 6 -alkyl.

Z is preferably hydrogen, OR ³ , C 1 -C ₂₀ -alkyl, C 1 -C ₂₀ -alkylcarbonyl or C ₁ -C -alkoxy carbonyl, particularly preferably hydrogen, OR ³ , C 1 -C 10 -alkyl, C 1 -C 10 -alkylcarbonyl or C 1 -C 4 -alkylcarbonyl or Cio-alkoxycarbonyl, very particularly preferably hydrogen, R ³ O-, d-Ce-alkyl, Ci-C6-alkylcarbonyl or Ci-C ₆ alkoxycarbonyl, wherein R ³ is preferably hydrogen or Ci-C2o-alkyl preferably hydrogen or CRCI _θ Alkyl and particularly preferably hydrogen or Ci-Cβ-alkyl.

The radicals R ¹ and R ² are preferably identical and are hydrogen, C 1 -C 6 -alkyl, C 1 -C ₂₀ -alkylcarbonyl or C 1 -C 6 -alkoxycarbonyl, particularly preferably hydrogen, C ₁ -C ₀ -alkyl, C ₁ -C 10 -alkylcarbonyl or C 1 -C 10 -alkyl Alkoxycarbonyl, very particularly preferably hydrogen, C ₁ -C ₆ -alkyl, C ₁ -C ₆ -alkylcarbonyl or C ₁ -C ₆ -alkoxycarbonyl.

The radicals R ^3, R ⁴ and R ⁵ are preferably hydrogen or dCΣo-alkyl, particularly preferably hydrogen or d-C _θ alkyl and most preferably hydrogen or d-Ce-alkyl. In a preferred embodiment of the process according to the invention, the abovementioned aromatic heterocycles are used in an oxygen-containing environment. The oxygen content of the environment is between 0.001 ppm and 99.999%, based on the total volume of the environment. The aromatic heterocycles are preferably used in air or in air / nitrogen mixtures.

Typically, the aromatic heterocycles are used individually or as a mixture, wherein preferably not more than five, more preferably not more than four and most preferably not more than three of the aforementioned aromatic heterocycles are used.

The amount in which the aromatic heterocycles according to the invention are used in order to exert a stabilizing effect on the polymerizable compound is to be determined in the course of customary experiments.

For example, from 0.1 to 1000 ppm of an aromatic heterocycle or of a mixture of aromatic heterocycles based on the polymerizable compound is used, preferably 1 to 900 ppm, more preferably 10 to 800 ppm, most preferably 50 to 700 ppm and especially 100 to 500 ppm.

In a preferred embodiment of the process according to the invention, the aromatic heterocycles are advantageously used together with at least one other compound known as stabilizer and / or costabilizer. These are z. In DE-A 102 49 507 and in DE-A 102 58 329, DE-A 198 56 565 and in EP-A 765 856. As a result, existing deficiencies of the known stabilizers, for example, the color structure during the action or the processing of the polymerizable compound and the insufficient effect of the stabilizers during the workup of the polymerizable compound, compensated.

Suitable costabilizers are oxygen-containing gases, phenolic compounds, quinones and hydroquinones, N-oxyl compounds, aromatic amines and phenylenediamines, imines, sulfonamides, oximes, hydroxylamines, urea derivatives, phosphorus-containing compounds, sulfur-containing compounds, complexing agents based on tetraazannulenes (US Pat. TAA) and / or metal salts, and optionally mixtures thereof.

Oxygen-containing gases may, for example, be those gases which have an oxygen content of between 0.1 and 100% by volume, preferably of 0.5 to 50% by volume and more preferably of 1 to 25% by volume. For example, these may be nitrogen monoxide, nitrogen dioxide, oxygen or dinitrogen trioxide or air. These can be mixed individually, in any mixtures with each other or with another gas be, for example, nitrogen, noble gases, water vapor, carbon monoxide, carbon dioxide or lower alkanes, preferred are air or air-nitrogen mixtures.

Phenolic compounds are for. B: phenol, alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 2,6-diol tert-butyl-4-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert. Butyl-2,6-dimethylphenol, or 2,2'-methylenebis (6-tert-butyl-4-methylphenol), 4,4'-oxydiphenyl, 3,4-methylenedioxydiphenol (sesamol), 3,4 Dimethylphenol, catechol (1,2-dihydroxybenzene), 2- (1'-methylcyclohex-1'-yl) -4,6-dimethylphenol, 2- or 4- (1 '-

Phenyleth-1'-yl) phenol, 2-tert-butyl-6-methylphenol, 2,4,6-tris-tert-butylphenol, 2,6-di-tert-butylphenol, nonylphenol [CAS-No. 11066-49-2], octylphenol [CAS-No. 140-66-9], 2,6-dimethylphenol, bisphenol A, bisphenol B, bisphenol C, bisphenol F, bisphenol S, 3,3 ', 5,5'-tetrabromobisphenol A, 2,6-di-tert. butyl-p-cresol, Koresin® from the BASF Aktiengesellschaft, methyl 3,5-di-tert-butyl-4-hydroxybenzoate, 4-tert-butylcatechol, 2-hydroxybenzyl alcohol, 2-methoxy-4-methylphenol, 2, 3,6-trimethylphenol, 2,4,5-trimethylphenol, 2,4,6-trimethylphenol, 2-isopropylphenol, 4-isopropylphenol, 6-isopropyl-m-cresol, n-octadecyl-'K- (3,5- di-tert-butyl-4-hydroxyphenyl) propionate, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1, 3,5-trimethyl-2,4 , 6-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1 ₁ 3,5, -Tris- (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1, 3,5, -Tris- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl isocyanurate, 1,3,5-tris- (2,6-dimethyl-3-hydroxy-4- tert -butylbenzyl) isocyanurate or pentaerythritol tetrakis [i! im- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,6-di-tert-butyl-4-dimethylaminomethylpheno l, 1222 and 1425 from Ciba 6-sec-butyl-2,4-dinitrophenol, Irganox ^® 565, 1010, 1076, 1141, 1192 Specialty Chemicals, 3- (3 ', 5'-di-tert-butyl 4'-hydroxyphenyl) octadecyl propionate, hexadecyl 3- (3 ', 5'-di-tert-butyl-4 ¹ -hydroxyphenyl) propionate, 3- (3', 5'-di-tert-butyl-4'- hydroxyphenyl) octyl propionate, 3-thia-1,5-pentanediol bis - [(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecanediol -bis - [(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecanediol-bis - [(3'-tert-butyl) 4'-hydroxy-5'-methylphenyl) propionate], 1, 9-nonanediol bis - [(3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], 1,7-heptanediamine bis [3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionic acid amide], 1,1-methanediamine bis [3- (3', 5'-di-tert-butyl 4'-hydroxyphenyl) propionic acid amide], 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionic acid hydrazide, 3- (3', 5'-dimethyl-4'-hydroxyphenyl) propionic acid hydrazide, Bis (3-tert-butyl-5-ethyl-2-hydroxyphen-1-yl) methane, bis (3,5-di-tert-butyl-4-hydroxyphen-1-yl) methane, bis [3- (1'-methylcyclohex-1'-yl) -5-methyl-2-hydroxyphene 1-yl] methane, bis (3-tert-butyl-2-hydroxy-5-methylphen-1-yl) methane, 1,1-bis (5-tert-butyl-4-hydroxy-2 -methylphen-1-yl) ethane, bis (5-tert-butyl-4-hydroxy-2-methylphen-1-yl) sulfide, bis (3-tert-butyl-2-hydroxy-5-methylphen -1-yl) sulfide, 1, 1-bis (3,4-dimethyl-2-hydroxyphen-1-yl) -2-methylpropane, 1, 1-bis (5-tert. Butyl-3-methyl-2-hydroxyphen-1-yl) butane, 1,3,5-tris [1 '- (3 ", 5" -di-tert-butyl-4 "-hydroxyphen-1" - yl) meth-1'-yl] -2, 4,6-trimethylbenzene, 1,1,4-tris (5'-tert-butyl-4'-hydroxy-2'-methylphen-1'-yl) butane and tert-butylcatechol, and aminophenols, such as. B. p-aminophenol, nitrosophenols, such as. For example, p-nitrosophenol, p-nitroso-o-cresol, alkoxyphenols, for example 2-methoxyphenol (guaiacol, catechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di- tert-butyl-4-methoxyphenol, 3,5-di-tert-butyl-4-hydroxyanisole, 3-hydroxy-4-methoxybenzyl alcohol, 2,5-dimethoxy-4-hydroxybenzyl alcohol (syringa alcohol), 4-hydroxy-3 -methoxybenzaldehyde (vanillin), A-hydroxy-3-ethoxybenzaldehyde (ethylvanillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin), 1- (4-hydroxy-3-methoxyphenyl) ethanone (acetovanillon), eugenol, dihydroeugenol, Isoeugenol, tocopherols, such as. Tt, fä-, & .-, tt- and $> tocopherol, tocol, fit tocopherol hydroquinone, and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7- hydroxycoumaran).

Suitable quinones and hydroquinones are, for example, hydroquinone or hydroquinone monomethyl ether (4-methoxyphenol), methylhydroquinone, 2,5-di-tert-butylhydroquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 4- Methyl catechol, tert-butylhydroquinone, 3-methylcatechol, benzoquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, tert-butylhydroquinone, 4-ethoxyphenol, 4-butoxyphenol, hydroquinone monobenzyl ether, p-phenoxyphenol, 2- Methylhydroquinone, tetramethyl-p-benzoquinone, diethyl-1,4-cyclohexanedione-2,5-dicarboxylate, phenyl-p-benzoquinone, 2,5-dimethyl-3-benzyl-p-benzoquinone, 2-isopropyl-5-methyl- p-benzoquinone (thymoquinone), 2,6-diisopropyl-p-benzoquinone, 2,5-dimethyl-3-hydroxy-p-benzoquinone, 2,5-dihydroxy-p-benzoquinone, embeline, tetrahydroxy-p-benzoquinone, 2 , 5-Dimethoxy-1, 4-benzoquinone, 2-amino-5-methyl-p-benzoquinone, 2,5-bis-phenylamino-1,4-benzoquinone, 5,8-dihydroxy-1, 4-naphthoquinone, 2-anilino -1,4-naphth hochinone, anthraquinone, N, N-dimethylindoaniline, N, N-diphenyl-p-benzoquinone diimine, 1,4-benzoquinone dioxime, coerulignone, 3,3'-di-tert-butyl-5,5'-dimethyldiphenoquinone, p-rosolic acid (aurin ), 2,6-di-tert-butyl-4-benzylidene-benzoquinone, 2,5-di-tert-amylhydroquinone.

As N-oxyls (nitroxyl or N-oxyl radicals, compounds which have at least one> N-O group) are z. B. suitable 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-methoxy-2,2 , 6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 2,2,6,6-tetramethylpiperidine-N-oxyl, Uvinul ^® 4040P from BASF Aktiengesellschaft, 4.4 ¹ _> 4 "tris (2,2,6,6-tetramethyl-piperidine-N-oxyl) phosphite, 3-oxo-2,2,5,5-tetramethyl-pyrrolidine -N-oxyl, 1-oxyl-2,2,6,6-tetramethyl-4-methoxypiperidine, 1-oxyl-2,2,6,6-tetramethyl-4-trimethylsilyloxypiperidine, 1-oxyl-2,2,6 , 6-tetramethylpiperidin-4-yl-2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl sebacate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate, 1 -Oxyl-2,2,6,6-tetramethylpiperidiri-4-yl-benzoate, 1 -Oxyl-2,2,6,6- tetramethylpiperidin-4-yl- (4-tert-butyl) benzoate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate, bis (1-oxyl-2,2,6 , 6-tetramethylpipericiin-4-yl) adipate, 1,1-O-decanedioic acid bis (1-oxyl-2,2,6,6-tetraethylpiperidin-4-yl) ester, bis (1-oxyl-2, 2,6,6-tetramethylpiperidin-4-yl) n-butylmalonate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate, bis (1-oxyl-2,2, 6,6-tetrannethylpiperidin-4-yl) isophthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) terephthalate, bis (1-oxyl-2,2,6,6- tetramethylpiperidin-4-yl) hexahydroterephthalate, N, N ^l-bis (1-oxyl-2,2,6 _l 6-tetramethylpiperidin-4-yl) adipamide _I N-CI-oxyl ^^. ^ ee-tetramethylpiperidine -yOcaprolactam , N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecylsuccinimide, 2,4,6-tris [N-butyl-N- (1-oxyl-2,2,6, 6-tetramethylpiperidin-4-yl] tria2in ₁ N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6- diaminohexane, 4 _{l of} 4'-ethylene-bis- (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one).

Suitable aromatic amines or phenylenediamines are, for example, N ₁ N-diphenylamine, N-nitroso-diphenylamine, nitrosodiethylaniline, p-phenylenediamine, N ₁ N'-dialkyl-p-phenylenediamine, where the alkyl radicals may be identical or different and each independently is 1 to 4 carbon atoms and may be straight-chained or branched, for example N, N'-di-iso-butyl-p-phenylenediamine, N, N'-di-iso-propyl-p-phenylenediamine, Irganox ^® 5057 of the firm Ciba Specialty Chemicals, N-phenyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-isopropyl-N-phenyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine ( Kerobit® BPD from BASF Aktiengesellschaft), N-phenyl-N'-isopropyl-p-phenylenediamine (Vulka- nox ^® 4010 from Bayer AG), N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N-phenyl-2-naphthylamine, iminodibenzyl, N, N'-diphenylbenzidine, N-phenyltetraaniline, acridone, 3-hydroxydiphenylamine, 4-hydroxydiphenylamine.

Imines are z. Methyl ethylimine, (2-hydroxyphenyl) benzoquinoneimine, (2-hydroxyphenyl) benzophenone imine, N, N-dimethylindoaniline, thionine (7-amino-3-imino-3H-phenothiazine), methylene violet (7-dimethylamino-3-phenothiazinone) ,

Suitable sulfonamides as stabilizer are, for example, N-methyl-4-toluenesulfonamide, N-tert-butyl-4-toluenesulfonamide, N-tert-butyl-N-oxyl-4-toluenesulfonamide, N, N'-bis (4-sulfanilamide ) piperidine, 3 - {[5- (4-aminobenzoyl) -2,4-dimethylbenzenesulfonyl] ethylamino} -4-methylbenzenesulfonic acid, as in DE-A 102 58 329.

Oximes can be, for example, aldoximes, ketoximes or amidoximes, as described, for example, in DE-A 101 39 767, preferably diethylketoxime, acetoneoxime, methylethylketoxime, cyclohexanone oxime, benzaldehyde oxime, benzil dioxime, dimethylglyoxime, 2-pyridinaldoxime, salicylaldoxime, phenyl-2-pyridylketoxime, 1,4-

Benzoquinone dioxime, 2,3-butanedione dioxime, 2,3-butanedione monooxime, 9-fluorenone oxime, tert-butylcyclohexanone oxime, N-ethoxy-acetimidic acid ethyl ester. 2,4-Djmethyl-3- pentanone oxime, cyclododecanone oxime, 4-heptanone oxime and di-2-furanyl ethanedione dioxime or other aliphatic or aromatic oximes or their reaction products with alkyl transfer agents such. Alkyl halides, triflates, sulfonates, tosylates, carbonates, sulfates, phosphates or the like.

Hydroxylamines are z. N, N-diethylhydroxylamine and those disclosed in international application WO 03/099757.

Suitable urea derivatives are, for example, urea or thiourea.

Phosphorus compounds are z. B. triphenylphosphine, triphenyl phosphite, hypophosphorous acid, trinonyl phosphite, triethyl phosphite or Diphenylisopro- pylphosphin.

Examples of suitable sulfur-containing compounds are diphenyl sulfide, phenothiazine and sulfur-containing natural substances such as cysteine.

Complexing agents based on tetraazaannulenes (TAA) are e.g. Dibenzotetraza [14] annulenes and porphyrins as described in Chem. Soc. Rev. 1998, 27, 105-115.

Metal salts are z. As copper, manganese, cerium, nickel, chromium, carbonate, chloride, - dithiocarbamate, sulfate, salicylate or acetate, stearate, ethylhexanoate.

Preferred costabilizers are oxygen-containing gases, phenothiazine, o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert Butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, catechol (1,2-dihydroxybenzene), 2,6-di-tert-butylphenol, 4-tert-butyl-2, 6-dimethylphenol, octylphenol [140-66-9], nonylphenol [11066-49-2], 2,6-dimethylphenol, 2,6-di-tert-butyl-p-cresol, bisphenol A, tert. Butylcatechol, hydroquinone, hydroquinone monomethyl ether or methylhydroquinone, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2 , 2,6,6-tetramethyl-piperidine-N-oxyl and manganese (II) acetate, cerium (III) carbonate, cerium (III) acetate or cerium (III) ethylhexanoate, cerium (III) stearate and mixtures thereof different composition.

Particularly preferred are air, air-nitrogen mixtures, phenothiazine, o-, m- or p-cresol (methylphenol), 2,6-di-tert-butyl-4-methylphenol, 4-tert-butylphenol, 4-tert .- butyl-2,6-dimethylphenol, octylphenol [140-66-9], nonylphenol [11066-49-2], 2,6-dimethylphenol, 2,6-di-tert-butyl-p-cresol, tert Butylcatechol, hydroquinone, hydroquinone monomethyl ether or methyl hydroquinone, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo -2,2,6,6-tetramethyl-piperidine-N- oxyl and cerium (III) acetate or cerium (III) ethylhexanoate and mixtures of at least two of said components.

Particularly preferred are air, air-nitrogen mixtures, phenothiazine, hydroquinone and hydroquinone monomethyl ether and 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl , 4-Oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, N, N'-di-sec-butyl-p-phenylenediamine, cerium (III) acetate or cerium (III) ethylhexanoate, and mixtures from that.

The manner of adding the stabilizer of the present invention and the costabilizers to be used is not limited. The added stabilizer according to the invention can be added individually or as a mixture with further stabilizers according to the invention and / or with the aforementioned costabilizers, in liquid or in dissolved form in a suitable solvent, this Lösungsmittelgmittels itself may be a stabilizer such. B. in DE-A 102 00 583 described.

When using the stabilizers in the preparation of polymerizable compounds are suitable as solvent further the material streams from the preparation of the polymerizable compound. This may be, for example, the pure products, i. H. the polymerizable compounds, in a purity of usually 95% or more, preferably 98% or more and particularly preferably 99% or more, but also the educts used for the preparation of the polymerizable compounds, in a purity of 95% or more, preferably 98% or more and more preferably 99% or more, or such streams, the starting materials and / or products and / or intermediates and / or by-products.

The concentration of the solutions used is limited only by the solubility of the stabilizer / stabilizer mixture in the solvent, for example, it may be 0.1-50 wt.%, Preferably 0.2-25 wt.%, Particularly preferably 0.3. 10 wt .-% and most preferably 0.5 to 5 wt .-%.

Of course, the aromatic heterocycles or mixtures of aromatic heterocycles according to the invention can also be used as a melt, for example if the melting point below 120 ⁰ C _1, preferably below 100 ⁰ C _{1, more} preferably below 80 ⁰ C and especially below 60 ⁰ C.

In a further preferred form, the aromatic heterocycles or mixtures of aromatic heterocycles according to the invention as melt with a phenol having a melting point below 120 ⁰ C, preferably below 100 ⁰ C _{1 are more} preferably below 80 ⁰ C and in particular below 60 ⁰ C as Costabilizer used. The phenol is particularly preferably selected from p-aminophenol, p-nitrosophenol, 24-tert-butylphenol.A-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-1-tert-butylphenol. Butylphenol, 4-tert-butyl-2,6-dimethylphenol, hydroquinone and hydroquinone monomethyl ether.

As described above, 0.1 to 1000 ppm of the aromatic heterocycle of the invention or mixtures of aromatic heterocycles are used based on the polymerizable compound. If a mixture of at least one aromatic heterocycle is used with costabilizers, then 0.1 to 5000 ppm, preferably 1 to 4000 ppm, more preferably 5 to 2500 ppm, particularly preferably 10 to 1000 ppm and in particular 50 to 750 ppm, based on the polymerizable Connection used.

If a mixture of several stabilizers or costabilizers is used, they can be fed to one another independently of one another at different or identical metering points and can also be dissolved independently of one another in different solvents.

In the preparation of polymerizable compounds according to the invention, the stabilizers / stabilizer mixtures are preferably used in those places where the polymerizable compound, for example by high purity, high residence time and / or high temperature, is exposed to a polymerization.

These may be, for example, absorption units, desorption units, rectification units, for example distillation apparatus or rectification columns, evaporators, for example natural or forced circulation evaporators, condensers or vacuum units.

For example, the stabilizers can be metered at the top of a rectification unit, z. B. in the head of the rectification unit, removal fixtures or on the separating internals such. Soils, packs, breakwaters or Schüt- tions, sprayed or sprayed or metered together with the return, in a condenser, z. B. sprayed, so that the condenser head and / or the cooling surfaces are wetted, or in a vacuum unit, as described in EP-A 1 057 804 or as a barrier liquid in a liquid ring pump, as described in DE-A 101 43 565.

The erfindungemäß to be used aromatic heterocycles can be used both as a storage and as a transport stabilizer, d. H. for stabilizing the pure polymerizable compounds.

Furthermore, the invention relates to stabilizer mixtures containing

i) at least one aromatic heterocycle of the general formula (I) ii) at least one further stabilizer or costabilizer.

Combinations of all components mentioned above are possible.

Stabilizers or costabilizers are the abovementioned oxygen-containing gases, phenolic compounds, quinones and hydroquinones, N-oxyl compounds, aromatic amines and phenylenediamines, imines, sulfonamides, oximes, hydroxylamines, urea derivatives, phosphorus-containing and / or sulfur-containing compounds, complexing agents based on TAA and / or metal salts.

Preference is given to stabilizer mixtures of at least one aromatic heterocycle and phenothiazine, at least one aromatic heterocycle / hydroquinone, at least one aromatic heterocycle / hydroquinone monomethyl ether, at least one aromatic heterocycle / 4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxyl, at least one aromatic heterocycle / 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, at least one aromatic heterocycle / 2,2,6,6-tetramethyl-piperidine-N-oxyl, at least one aromatic heterocycle / phenothiazine / hydroquinone monomethyl ether, at least one aromatic heterocycle / phenothiazine / 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl or at least one aromatic heterocycle / hydroquinone monomethyl ether M- hydroxy .θ-tetramethyl-piperidine-N-oxyl and optionally in each case at least one of said cerium salts, in each case in the presence or absence of an oxygen-containing gas, preferably in the presence.

The stabilizer mixtures according to the invention comprise components i) and ii) in weight ratios i): ii) between 1: 100 to 100: 1, preferably 1:50 to 50: 1, more preferably 1:10 to 10: 1 and in particular 1: 5 to 5: 1.

The invention furthermore relates to substance mixtures which contain the abovementioned stabilizer mixtures according to the invention and at least one polymerizable compound. All combinations of stabilizer mixtures according to the invention with polymerizable compounds are possible.

The use of the substance mixtures which contain the abovementioned stabilizer mixtures for stabilizing polymerizable compounds against polymerization is likewise part of the invention.

Chemical compounds containing one or more ethylenically unsaturated groups are also referred to as polymerizable compounds. These are selected from mono-, di- or triethylenisch unsaturated C3-Ce-carboxylic acids,

this mono-, di- or triethylenisch unsaturated C ₃ -C 8 -carboxylic acids, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl ethers of alcohols containing from 1 to 10 carbon atoms, vinylaromatics and heteroaromatics having up to 20 carbon atoms, vinyllactams having from 3 to 10C In the ring, open-chain N-vinyl amide compounds and N-vinylamine compounds, vinyl halides, aliphatic optionally halogenated hydrocarbons having 2 to 8 C atoms and 1 or 2 double bonds, vinylidenes or mixtures of these monomers.

Preferred mono-, di- or triethylenisch unsaturated C3-C6-carboxylic acids are z. Example, (meth) acrylic acid, dimethylacrylic acid, ethacrylic acid, citraconic acid, methylenemalonic acid, crotonic acid, fumaric acid, mesaconic acid, itaconic acid, maleic acid and their Ci-C ₂ o-alkyl esters, amides, nitriles, aldehydes and -Anhydride such. Methyl (meth) acrylate, (meth) acrylic acid ethyl ester, (meth) acrylic acid n-butyl ester, (meth) acrylic acid n-propyl ester, (meth) acrylic acid iso-propyl ester, (meth) acrylic acid 2-ethylhexyl ester, (meth acrylate, maleic acid monomethyl ester, dimethyl maleate, maleic acid monoethyl ester, maleic acid diethyl ester, alkylene glycol (meth) acrylates, (meth) acrylamide, N-dimethyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, (meth) acrylonitrile, ( Meth) acrolein, (meth) acrylic anhydride, itaconic anhydride, maleic anhydride and its half esters. Cationic monomers of this group are, for example, dialkylaminoalkyl (meth) acrylates and dialkylaminoalkyl (meth) acrylamides, such as dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the salts of the last-mentioned monomers with carboxylic acids or mineral acids and the qauternated products.

Other monomers of this group are z. As well as hydroxyl-containing monomers, in particular Ci-Cio-hydroxyalkyl (meth) acrylates such as hydroxy ethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyisobutyl (meth) acrylate.

Further monomers of this group are phenyloxyethylglycol mono- (meth) acrylate, glycidyl (meth) acrylate, trimethylolpropane triacrylate, ureidomethyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate.

Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for. As vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate.

As vinyl ethers of 1 to 10 carbon atoms containing alcohols are z. For example, methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, 4-hydroxybutyl vinyl ether, vinyl isobutyl ether or dodecyl vinyl ether. Suitable vinylaromatic and heteroaromatic compounds are, for example, vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, styrene, divinylbenzene, 2-vinylpryridine, N-vinylimidazole, N-vinylpiperidone, N Vinyl-2-methylimidazole and N-vinyl-4-methylimidazole into consideration.

Vinyllactams having 3 to 10 carbon atoms in the ring are, for example, N-vinylcaprolactam, N-vinylpyrrolidone, laurolactam, oxygenated purines such as xanthine or its derivatives such as 3-methylxanthine, hypoxanthine, guanine, theophylline, caffeine, adenine or theobromine.

Furthermore, open-chain N-vinylamide compounds and N-vinylamine compounds such as N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide, N-vinyl Vinyl-N-methylpropionamide and N-vinylbutyramide and N-vinyl-N-dimethylamine, N-vinyl-N-methylethylamine, N-vinyl-N-diethylamine are stabilized by the novel process.

The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds such as vinyl chloride, vinyl fluoride and vinylidene chloride.

Aliphatic optionally halogenated hydrocarbons having 2 to 8 carbon atoms and 1 or 2 olefinic double bonds are, for example, ethylene, propene, 1-butene, 2-butene, isobutene, butadiene, isoprene and chloroprene.

Vinylidene, for example, is called vinylidene cyanide.

Other polymerizable compounds are N-vinylcaprolactam, vinylphosphoric acids, vinylacetic acid, allylacetic acid, N-vinylcarbazole, hydroxymethylvinylketone, N, N-divinylethyleneurea, vinylene carbonate, tetrafluoroethylene, hexafluoropropene, nitroethylene, allylacetic acid, .alpha.-chloroacrylic ester, .alpha.-cyanoacrylic ester, methylene malonate, α-Cyansorbinsäureester, cyclopentadiene, cyclopentene, cyclohexene and cyclododecene.

In a preferred embodiment of the process according to the invention, the aromatic heterocycles are used for stabilizing mono-, di- or triethylenically unsaturated C 3 -C ₈ -carboxylic acids, and their C 1 -C 20 -alkyl esters or N-vinylcaprolactam, N-vinylformamide, N-vinylimidazole, N Vinylpyrrolidone, vinylphosphoric acids, N-vinylcarbazole, N, N-divinylethyleneurea, trimethylolpropane acrylate, ureidomethyl methacrylate, styrene, butadiene or isoprene. Examples of preferred unsaturated C ₃ -C ₈ -carboxylic acids are acrylic acid and methacrylic acid and also their C ₁ -C ₈ -alkyl esters, such as, for example, For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate.

In a preferred embodiment, the aromatic heterocycles of the invention are used in a process as described in DE-A 100 64 642. For this purpose, in a process for the processing of (meth) acrylic acid in the presence of at least one stabilizer, a substance mixture originating from the workup and essentially containing (meth) acrylic acid, stabilizer-containing mixture is fed into a distillation apparatus and a light stabilizer obtained therefrom - Siederstrom returned to the workup.

Such aromatic heterocycles according to the invention are particularly suitable for such a process whose vapor pressures at 141 ^° C. (boiling point of acrylic acid) at normal pressure are at least 15 hPa, preferably between 20 and 800 hPa, more preferably between 25 and 500 hPa, very particularly preferably between 25 and 250 hPa and especially between 25 and 160 hPa, and mixtures thereof.

In a further preferred embodiment, the aromatic heterocycles according to the invention are used in a process for working up N-vinyl monomers such as the stated vinyl esters, vinyl ethers, vinylaromatics and heteroaromatics and the open-chain N-vinylamide compounds and N-vinylamine compounds.

Of course, the field of application of the method according to the invention also relates to storage and transport of these polymerizable compounds.

Ppm and percentages used in this specification, unless otherwise indicated, are by weight percent and ppm.

The following examples are intended to illustrate but not to limit the invention.

example 1

0.5 ml of freshly thawed and twice distilled to remove the storage stabilizer acrylic acid were filled under air atmosphere in 1.8 ml ampoules.

The samples were all stored in a convection oven at 120 ⁰ C.

In each test series, 3 ampoules of each acrylic acid sample were filled and tested, the mean of the time until complete polymerization was visually recorded. The mean standard deviation within a series of experiments was approximately 2 ft 4%.

Unless otherwise stated, concentrations were 25 ppm aromatic heterocycle plus 10 ppm phenothiazine (PTZ).

The relative effectiveness is calculated from the quotient of the time to polymerization of the sample of aromatic heterocycle and PTZ and the time to polymerization of the reference sample. As a reference sample, pure PTZ was used, the relative effectiveness of the reference sample is therefore 1, 0.

The results are summarized in Table 1.

Table 1

Claims

claims

1. A method for stabilizing polymerizable compounds against polymerization, characterized in that at least one aromatic heterocycle of the general formula (I)

wherein

X may be a heteroatom, CR ¹ , C-NR ¹ R ² or C-OR ³ , and wherein R ¹ and R ² are as defined below, and R ^{3 is} also hydrogen, C ₁ -C 20 -alkyl, C _r C ₂ o-alkylcarbonyl, C1-C20- alkoxycarbonyl, _{C2-C2o-alkenyl,} C ₂ -C ₂ o-alkenylcarbonyl, C ₂ -C ₂ o-alkynyl, C2-C2o-alkynylcarbonyl, C3-Ci5-cycloalkyl, Cs-cis-cycloalkylcarbonyl,

Aryl, arylcarbonyl, a heterocycle or a halogen atom,

Y is hydrogen, NR ¹ R ^2, OR ^3, PR ⁴ SR ^5, C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl may be, A- ryl or a halogen atom, and wherein R ¹ and R ^2, the bottom and R ³ to

R ⁵ is also hydrogen, Ci-C ₂ o--alkyl, -C ₂ o-alkylcarbonyl, C1-C20 alkoxycarbonyl, C ₂ -C ₂ -alkenyl, C ₂ -C ₂ o-alkenylcarbonyl, C2-C2o alkynyl, C C ₂ -C ₂ -alkynylcarbonyl, C ₃ -C ₅ -cycloalkyl, C ₃ -C 6 -cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom,

Z can be hydrogen, NR ¹ R ² , OR ³ , PR ⁴ , SR ⁵ , C ₁ -C ₂₀ -alkyl, CrC ₂₀ -

Alkylcarbonyl, C ₁ -C 20 -alkoxycarbonyl, C ₂ -C 20 -alkenyl, C ₂ -C 20 -alkenylcarbonyl, C ₂ -C ₂ -alkynyl, C ₂ -C ₂ -alkynylcarbonyl, C ₃ -C 15 -cycloalkyl, C ₅ -C ₅ -cycloalkylcarbonyl be, aryl, arylcarbonyl or heterocycle, and wherein R ¹ and R ² have the meanings stated below, and R ³ to R ⁵ is also hydrogen, CrC ₂ O-alkyl, _{Ci-C2o-alkylcarbonyl,} Ci-C ₂₀ - Alkoxycarbonyl, C ₂ -C ₂₀ alkenyl, C ₂ -C ₂ o-alkenylcarbonyl, C ₂ -C ₂ o-alkynyl, C ₂ -C ₂ o-alkynylcarbonyl, C ₃ -C ₅ -cycloalkyl, C ₅ -C ₅ cycloalkylcarbonyl,

Aryl, arylcarbonyl, heterocycle or halogen, and R ¹ and R ² can independently represent hydrogen, NR ⁴ R ^5, OR ^3, PR ⁴ SR ^5, C ₂ o alkyl, Ci-Cao-alkylcarbonyl, _{Ci-C2o-alkoxycarbonyl,} C ₂ - C ₂ o-alkenyl, C ₂ -C ₂ o-alkenylcarbonyl, C ₂ -C ₂ o-alkynyl, C ₂ -C ₂₀ alkynylcarbonyl, C ₃ -C 15 cycloalkyl, Cs-Cis cycloalkylcarbonyl, aryl, arylcarbonyl be heterocycle or a halogen atom, and wherein R ³ to R ⁵ is also hydrogen, CrC ₂ O-alkyl, -C ₂₀ - alkylcarbonyl, dC ₂ o-alkoxycarbonyl, C ₂ -C ₂₀ -alkyl keny I ₁ C ₂ -C ₂₀ - alkenylcarbonyl , _C2-C20 alkynyl, C2-C, C ₃ -C ₅ alkynylcarbonyl ₂₀ - cycloalkyl, C ₅ -C ₅ may be cycloalkylcarbonyl, aryl, arylcarbonyl, hetero a cyclus or a halogen atom,

starts.

2. The method according to claim 1, characterized in that X is nitrogen or C-R ¹ , wherein R ^{1 is} hydrogen or Ci-C ₂₀ alkyl.

3. A method according to any one of claims 1 or 2, characterized in that Y is hydrogen, NR ¹ R ^2, OR ^3, -C ₂₀ alkyl, C ₂ -C ₂₀ -alkenyl-Al or a halogen atom, wherein in the case of NR ¹ R ² R ¹ and R ^{2 are the} same and are hydrogen or C 1 -C ₂₀ alkyl, and in the case of OR ³ R ^{3 is} hydrogen or C 1 -C ₂₀ alkyl.

4. The method according to any one of claims 1 to 3, characterized in that Z is hydrogen, OR ³ , CrC ₂₀ alkyl, CrC ₂₀ alkylcarbonyl or CrC ₂₀ - alkoxycarbonyl, wherein in the case of OR ³ R ^{3 is} hydrogen or CrC ₂₀ - Is alkyl.

5. The method according to any one of claims 1 to 4, characterized in that R ¹ and R ² are the same and are hydrogen, -C ₂ o alkyl, -C ₂₀ alkylcarbonyl or d-C ₂₀ -alkoxycarbonyl.

6. The method according to any one of claims 1 to 5, characterized in that the at least one aromatic heterocycle is used in an oxygen-containing environment.

7. The method according to claim 6, characterized in that it is in the oxygen-containing environment to air or air-nitrogen mixtures.

8. The method according to claims 1 to 7, characterized in that one uses 0.1 to 1000 ppm of the aromatic heterocycle 'or a mixture of aromatic heterocycles based on the polymerizable compound sets.

9. Process according to claims 1 to 8, characterized in that at least one costabilizer is used.

10. The method according to claim 9, characterized in that the costabilizer is selected from the group of oxygen-containing gases, phenolic compounds, quinones and hydroquinones, N-oxyl compounds, aromatic A mine, phenylenediamines, imines, sulfonamides, oximes, hydroxylamines, urea derivatives, phosphorus-containing compounds, sulfur-containing compounds, complexing agents based on tetraazaannulen and metal salts, and optionally mixtures thereof.

11. The method according to claim 8 or 9, characterized in that as a costabilizer phenothiazine, hydroquinone, hydroquinone monomethyl ether, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-hydroxy-2,2,6,6- tetramethyl-piperidine-N-oxyl, _4-oxo-2,2) 6,6-tetramethyl-piperidine-N-oxyl, N, N'-di-sec-butyl-p-phenylenediamine, cerium (III) acetate, Cerium (III) ethylhexanoate, oxygen-containing gases and / or mixtures thereof.

12. The method according to any one of the preceding claims, characterized in that the polymerizable compound contains at least one ethylenically unsaturated group.

13. The method according to claim 12, characterized in that the polymerizable compound is selected from the group of mono-, di- or triethylenisch unsaturated C ₃ -C ₈ carboxylic acids, CrC ₂ o-esters, amides, nitriles and -Anhydride these mono-, di- or triethylenisch unsaturated C3-C8 carboxylic acids, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl ethers of alcohols containing 1 to 10 carbon atoms, vinyl aromatics and - heteroaromatic compounds having up to 20 carbon atoms, vinyl lactams with 3 to 10 C atoms in the ring, open-chain N-vinylamide compounds and N-vinylamine compounds, vinyl halides, aliphatic optionally halogenated hydrocarbons having 2 to 8 C atoms and 1 or 2 double bonds, vinylidenes or mixtures of these monomers.

14. The method according to claim 12 or 13, characterized in that as a polymerizable compound mono-, di- or triethylenisch unsaturated C ₃ - Cs-carboxylic acids, Ci-C ₂ o-esters of these mono-, di- or triethylenisch unsaturated C _3rd Cs-carboxylic acids, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl ethers of alcohols containing from 1 to 10 carbon atoms, vinyl aromatics and heteroaromatics having up to 20 carbon atoms, vinyl lactams having from 3 to 10

C atoms in the ring, open-chain N-vinyl amide compounds or N-Vjnylaminverbindungen uses.

15. The method according to claims 12 to 14, characterized in that as a polymerizable compound (meth) acrylic acid, (meth) acrylic acid esters, N-vinylcaprolactam, N-vinylformamide, N-vinylimidazole, N-vinylpyrrolidone, vinyl phosphoric acids, N-vinylcarbazole , N, N-divinylethyleneurea, trimethylolpropane triacrylate, ureidomethyl methacrylate, styrene, butadiene or isoprene.

16. containing stabilizer mixture

i) at least one general formula (I)

wherein

X may be a heteroatom, CR ¹ , C-NR ¹ R ² or C-OR ³ , and wherein R ¹ and R ² are as defined below, and R ^{3 is} also hydrogen, C ₁ -C ₂₀ -alkyl, CrC ₂₀ - alkylcarbonyl, d-C2o-alkoxycarbonyl, C ₂ -C ₂ -alkenyl, C ₂ -C ₂₀ - alkenylcarbonyl, C ₂ -C ₂ o-alkynyl, C2-C2o-alkynylcarbonyl, C ₃ - Ci5-cycloalkyl, Cs Cis-cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom,

Y is hydrogen, NR ¹ R ² , OR ³ , PR ⁴ , SR ⁵ , C _r C ₂ o-alkyl, C ₂ -C ₂₀ -

Alkenyl, aryl or a halogen atom, and wherein R ¹ and R ^{2 have} the meanings mentioned below, and R ³ to R ^{5 are} also hydrogen, C ₁ -C ₂₀ _-alkyl, CrC ₂₀ -

Alkylcarbonyl, -C ₂₀ alkoxycarbonyl, C ₂ -C2o-alkenyl, C ₂ -C ₂₀ - alkenylcarbonyl, C ₂ -C ₂₀ alkynyl, C ₂ -C ₂₀ alkynylcarbonyl, C ₃ - Ci5-cycloalkyl, Cs-Cis-cycloalkylcarbonyl , Aryl, arylcarbonyl, a heterocycle or a halogen atom,

Z can be hydrogen, NR ¹ R ² , OR ³ , PR ⁴ , SR ⁵ , C 1 -C ₂₀ -alkyl, d-

C ₂₀ alkylcarbonyl, CrC ₂ o-alkoxycarbonyl, C ₂ -C 2 ₀ alkenyl, C ₂ - C ₂₀ alkenylcarbonyl, C ₂ -C ₂₀ alkynyl, C ₂ -C ₂₀ alkynylcarbonyl, C ₃ -Ci5 cycloalkyl, be Cs-cis-cycloalkylcarbonyl, aryl, Arylcarbo- nyl or a heterocycle, and wherein R ¹ and R ² have the meanings stated below, and R ³ to R ⁵ is also hydrogen, -C ₂₀ alkyl, -C ₂₀ - alkylcarbonyl, CrC ₂ o alkoxycarbonyl, C ₂ -C ₂₀ alkenyl, C ₂ -C ₂₀ - alk ^ hylca7bönyirC ₂ -C ₂₀ -ÄlkiήyirC ₂ -C ₂₀ -AlkinylcaTböhyl, C ₃ - Cis-cycloalkyl, C ₅ -C ₅ -cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom, and

R ¹ and R ² can independently represent hydrogen, NR ⁴ R ^5, OR ^3, PR ⁴ SR ^5, -C ₂ o alkyl, dC ^ alkylcarbonyl, Ci-C ₂₀ -

Alkoxycarbonyl, C ₂ -C2o-alkenyl, C2-C2o-alkenyl-carbonyl, C ₂ - C ₂ o-alkynyl, C ₂ -C ₂ o-alkynylcarbonyl, C3-Ci5-cycloalkyl, C ₅ -C ₅ - cycloalkylcarbonyl, aryl, arylcarbonyl , a heterocycle or a halogen atom, and in which R ³ to R ^{5 are} also hydrogen, C 1 -C ₂₀ -alkyl, d-

C ₂ o-alkylcarbonyl, Ci-C ₂ o-AJkoxycarbonyl, C ₂ -C2o-alkenyl, C ₂ - C ₂ o-alkenylcarbonyl, C ₂ -C ₂ o-alkynyl, C2-C2o-alkynylcarbonyl, C3-Cis cycloalkyl , Cs-Cis-cycloalkylcarbonyl, aryl, arylcarbonyl, a heterocycle or a halogen atom,

and

ii) at least one further stabilizer or costabilizer.

17. A mixture comprising a stabilizer mixture according to claim 16 and at least one polymerizable compound.

18. Use of a stabilizer mixture according to claim 16 for stabilizing polymerizable compounds against polymerization.