EP0991733A1

EP0991733A1 - Mixture of substances containing compounds with vinyl groups and stabilizers

Info

Publication number: EP0991733A1
Application number: EP98934913A
Authority: EP
Inventors: Heinz Friedrich Sutoris; Konrad Mitulla; Jacques Dupuis; Claus Kaliba
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1997-06-17
Filing date: 1998-06-04
Publication date: 2000-04-12
Also published as: CA2293577A1; AU8435998A; KR20010013936A; US6475348B1; PL337673A1; JP2002504128A; WO1998058038A1; BR9810128A; CN1260822A; BG103970A; EA199901084A1; DE19725519A1; ID23525A

Abstract

The invention relates to a mixture of substances containing one or several compounds with vinyl groups as constituent (A) and a stabilizer (B) as another constituent containing one or several easily volatile nitroxyl compounds as constituent (b1), one or several non-easily volatile nitroxyl compounds as constituent (b2), optionally one or several aromatic nitro compounds as constituent (b3) and optionally one or several iron compounds as constituent (b4). The invention also relates to stabilizers (B) containing constituents (b1) and (b2), (b1) and (b2) and (b3), (b1) and (b2) and (b4), in addition to (b1), (b2), (b3) and (b4). The invention further relates to a method for inhibiting premature polymerization of compounds with vinyl groups during the cleaning thereof or distillation by adding a stabilizer (B), or by adding the constituents of stabilizer (B) as individual substances or in at least two groups of constituents.

Description

Mixture of substances containing compounds containing vinyl groups and stabilizers

description

The present invention relates to a mixture of substances which contains one or more compounds containing vinyl groups as component (A) and as a further component a stabilizer (B) which contains one or more volatile nitroxyl compounds of secondary amines as component (bi), one or more low-volatility nitroxyl compounds contains secondary amines as component (b ₂ ), optionally one or more aromatic nitro compounds as component (b ₃ ) and optionally one or more iron compounds as component (b).

The invention further relates to stabilizers (B) which contain the components (bi) and (b), (bi) and (b ₂ ) and (b ₃ ), (bi) and (b) and (b ₄ ) and (bi) , (b ₂ ), (b ₃ ) and (b ₄ ) contain, and a method for inhibiting the premature polymerization of vinyl group-containing compounds during their purification or distillation by adding a stabilizer (B) or by adding the components of Stabilizer (B) as individual substances or in at least two groups of the components.

It is known that many unsaturated compounds tend to polymerize when the temperature rises, generally as a result of free radicals. For example, vinyl aromatic compounds, such as styrene or α-methylstyrene, must be stabilized with suitable compounds in order to prevent premature polymerization during the purification of the industrially obtained raw products by distillation. These stabilizers or polymerization inhibitors are usually added to the raw products to be distilled before or during the purification step. Despite this measure, considerable proportions of polymers are still obtained. In individual cases, particularly in the event of operational malfunctions, a complete polymerization of the monomers or monomer mixtures present can take place during the purification or distillation. This results in high costs due to the enormous cleaning effort and the loss of production.

Soviet patents 1,027,150, 1,558,888 and 1,139,722 describe the stabilization of styrene by using nitroxyl or bisnitroxyl compounds. 4 -Acylaminopiperidine-N-oxyl derivatives are used in the older German patent application 19 510 184.7 for the stabilization of free-radically polymerizable monomers.

The older German patent application DE 19 609 312.0 describes compositions which contain vinyl group-containing monomers and at least one N-oxyl compound of a secondary amine, the latter having no hydrogen atoms on the N-bonded C atom.

Mixtures of vinyl aromatic compounds with sterically hindered nitroxyl compounds, which are activated by traces of oxygen, are listed in WO 96/16921.

Japanese hei 1-165 534 discloses I-piperidyloxy derivatives as polymerization inhibitors for styrene. US Pat. No. 3,733,326 describes the inhibition of the polymerization of vinyl monomers by using free radical precursor compounds.

Mixtures of nitroxyl and nitro compounds are described in US Pat. No. 5,254,760 and in the older German patent application 19 622 498.5 for stabilizing vinylaromatic compounds or monomers containing vinyl groups during the purification or distillation.

Mixtures which, in addition to compounds containing vinyl groups, also contain nitroxyl compounds and iron compounds and, if appropriate, nitro compounds and costabilizers, are described in the earlier German patent application 19 651 307.3.

The effectiveness of the stabilizers described in these documents and the stability of the additive monomer mixtures are good, although the higher proportion of nitro compounds described in the earlier German patent application 19 622 498.5 also achieves an improved retardation / effect and the presence of iron compounds increases the stabilizers described in the earlier German application 19 651 307.3 have a clearly positive effect on their effectiveness. Therefore, in the event of an interruption in the feed of monomers and stabilizing additive into the column, these stabilizers achieve a better time delay effect until massive polymerization reactions begin.

So far, the main focus of all stabilizers has been on stabilizing the column bottom, but neglecting the stabilization of the monomers present in the vapor phase. sigt. Common procedures here are spraying the stabilizer, also used in the sump, in a carrier solution, such as the monomer mixture to be distilled, and / or wetting the column walls with, for example, carrier solutions mixed with stabilizer. A uniform distribution of the stabilizer hase in the vapor and hence their effective stabilization during distillation / purification is not sufficiently ensured by such measures _^.

However, since even smaller proportions of polymers add up to large amounts of undesirable by-products in these large-scale industrial processes, there is a permanent need for even more effective polymerization inhibitors. A reduction in the proportion of nitro compounds is also desirable in view of improved handling by the operating personnel and a reduction in possible environmental pollution.

The object was therefore to provide mixtures of compounds containing vinyl groups which are more effectively stabilized against premature polymerization during purification or distillation in both the liquid and vapor phases.

It has been found that this can be brought about in an advantageous manner by mixtures which contain

(A) one or more compounds containing vinyl groups,

(B) containing a stabilizer

(bj_) a nitroxyl compound of a secondary A ins which has no hydrogen atoms on the α-C atoms and whose vapor pressure at the boiling point of the lowest boiling vinyl group-containing compound from (A) is 0.01 to 50% of the vapor pressure of the lowest boiling vinyl group-containing compounds from (A) is or

a mixture of nitroxyl compounds of secondary amines which carry no hydrogen atoms on the α-C atoms, in which the vapor pressure of the highest-boiling nitroxyl compound at the boiling point of the lowest-boiling vinyl group-containing compound from (A) 0.01 to 50% of the vapor pressure of the lowest-boiling vinyl group-containing compound (A) is (b ₂ ) a nitroxyl compound of a secondary amine which has no hydrogen atoms on the α-C atoms and whose vapor pressure at the boiling point of the compound with the highest boiling point from (A) is less than 0.01% of the vapor pressure of the compound with the highest boiling point vinyl group ( A) is or

a mixture of nitroxyl compounds of secondary amines which do not carry any hydrogen atoms on the α-C atoms, in which the vapor pressure of the lowest boiling

Nitroxyl compound at the boiling point of the high-boiling vinyl group-containing compound from (A) is less than 0.01% of the vapor pressure of the high-boiling vinyl group-containing compound from (A),

where (bi) and (b ₂ ) each refer to the vapor pressure of the nitroxyl pure compound in question and the vapor pressure of the pure vinyl aromatic compound in question at the boiling point of this pure vinyl aromatic compound,

(b ₃ ) optionally one or more aromatic nitro compounds,

(b ₄ ) optionally one or more iron compounds.

To simplify the use of language, component (b) or component (b) is also referred to below as a volatile or non-volatile component and the nitroxyl compound containing it as a volatile nitroxyl compound (or a

Mixture of volatile nitroxyl compounds) or as a non-volatile nitroxyl compound (or a mixture of non-volatile nitroxyl compounds).

A mixture of substances which contains, as component (A), vinyl compound-containing compounds of the formula Ia is preferred

in what mean

R ^{1 is} hydrogen, Cχ-C ₄ alkyl, C ₂ -C ₄ alkenyl, carboxy, formyl, sulfo, hydroxy, amino or nitro

R ² C ₂ -C ₄ alkenyl and / or compounds of the formula Ib containing vinyl groups

in what mean

R ^{3 is} hydrogen, -C ₄ alkyl

R ⁴ C ₂ -C ₄ alkenyl.

The C ¹ -C ₄ -alkyl groups of the radicals R ¹ and R ³ can be methyl, ethyl, propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl and t-butyl. Suitable C -C ₄ alkenyl groups of the radicals R ¹ , R ³ and R ⁴ are vinyl, 1-propenyl, 1-butenyl, 1-methyl-1-ethenyl, 1-methyl-1-propenyl, 2-methyl - 1-propenyl (isobutenyl) and 1-ethyl-l-ethenyl. Examples of compounds of the formula Ia which may be mentioned are styrene, α-methylstyrene, p-, m-, o-nitro-styrene, p-, m-, o-styrene sulfonic acid, p-, m-, o-vinyltoluene, p-, m -, o-divinylbenzene, p-, m-, o-vinylaniline and p-, m-, o-vinylphenol, with the isomeric vinyl aromatic compounds in practice the o-isomer - if at all - only in small amounts the usual large-scale production.

Compounds of the formula Ib are, for example:

2-, 3-, 4 -vinylpyridine or the various isomers of methylvinylpyridine, such as the technically important 2-methyl-5-vinylpyridine. Of the vinylpyridine isomers, the 2- and 4-vinylpyridine are particularly important industrial products.

Of course, mixtures of compounds of the formula Ia or of the formula Ib, or else mixtures of compounds of the formulas Ia and Ib, can also be present in the substance mixture according to the invention.

Another preferred substance mixture contains, as component (A), vinyl group-containing compounds of the formula II

CH ₂ ^: cz ⁴ QZ ¹ (Ib)

where mean

Q is a chemical single bond, oxygen or a group -NZ ² -, 0 Z ¹ 1 or - Z ³ ,

- C - Z ³

Z ² , Z ^{4 are} hydrogen, -CC ₄ alkyl,

Z ^{3 is} hydrogen, hydroxy, cyano, Ci-Cs-alkoxy, Ci-Cs-alkyl or a radical which, together with Z ² or Z ^{4, is} a saturated or unsaturated C ₃ -, C ₄ -, C ₅ - or C ₆ -alkylene- forms, in which up to two non-adjacent carbon atoms can be replaced by N, NH, N (-CC alkyl), N (C ₆ -C ₁₀ aryl) or oxygen.

Denoted in formula II Q a chemical single bond, the group Z ^{1 is} either a radical -CO-Z ³ or the group Z ³ alone. In the first case, especially hydroxyl and Ci-Cs-alkoxy, such as methoxy, ethoxy, propoxy, t-butoxy or n-butoxy, but also 2-ethylhexoxy, in the latter case cyano, are suitable as Z ³ radicals.

Z ⁴ denotes hydrogen or -CC ₄ alkyl groups, with hydrogen and methyl being preferred radicals. Acrylic acid, methacrylic acid, the corresponding methyl, ethyl, propyl, t-butyl, n-butyl and 2-ethylhexyl esters, as well as acrylonitrile and methacrylic acid nitrile, therefore result as preferred compounds (A) of the formula II in the substance mixture according to the invention .

Furthermore, the compounds (A) of the formula II which are contained in the mixture of substances according to the invention can contain oxygen as the variable Q. Among these compounds, preference is given to the vinyl esters in which the group Z ¹ corresponds to the radical -CO-Z ³ , and the vinyl ethers in which the group Z ^{1 is} identical to the group Z ³ and in which Z ^{3 is} preferably a Ci-Cs-alkyl - Group, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl or 2-ethylhexyl.

If the variable Q is a group -NZ ² -, then Z ^{1 is} preferably a group -CO-Z ³ .

In addition to those already mentioned, suitable radicals Z ³ are those which, for example, together with the group —NZ ² - form a saturated or unsaturated 5- to 7-membered ring. Examples of such ring systems are: especially the N-pyrrolidinonyl and the N-caprolactamyl radical.

The C ₆ -Cιo-aryls listed in the radicals N (C _δ- Cιo-aryl) of the group Z ³ preferably comprise phenyl groups which can be substituted by one or more Cι-C ₄ -alkyl. If two or more substituents are present, the sum of their carbon atoms should not be more than four. Exemplary substitution patterns on the benzene ring are about three methyl groups, one methyl and one propyl group or just one t-butyl group. Further examples of C 1 -C ₄ -alkyl radicals, which may also be present in the N (C 1 -C ₄ -alkyl) radicals of group Z ³ , have already been mentioned above. A naphthyl radical can also be used as the cio-aryl.

Further preferred compounds (A) in the mixture according to the invention are N-vinylformamide, N-vinyl-2-pyrrolidone and N-vinyl-ε-caprolactam.

To select suitable nitroxyl compounds as components (bi) and (b) of the stabilizer (B), it is advantageous to start from the vinyl group-containing compounds of component (A) which - as pure substance - have the lowest or highest boiling point (at the same reference pressure p) exhibit. These compounds identified in this way are designated a ± or α ₂ , their boiling points Tunkte (p) and T ₂ (p). Since boiling points are often available for normal pressure (1013 hPa), αi and α apply to the highly volatile compounds containing vinyl groups

p (αχ) = p (α ₂ ) = p = 1013 hPa and

Tι (p) <T ₂ (p),

Low or high boiling according to the language used. For a volatile nitroxyl compound as component (bi), referred to here as βi, the invention therefore generally results

0.0001 • p (α _x , Ti) <p (ßχ, Ti) <0.50 • (αι, T _x ) (1)

and for a non-volatile nitroxyl compound as component (b ₂ ), here referred to as β ₂ , can be written according to the invention in general form P (ß2, T ₂ ) <0, 0001 ^• p (α ₂ , T ₂ ) (2),

where p (αχ, i), p (α ₂ , T ₂ ), p (ßι, Ti) and p (ß ₂ , T ₂ ) the vapor pressures of the pure compounds αi, α _/ ßi and ß _2, respectively in the ent speaking temperatures Ti, T. If these vapor pressures correspond to the normal pressure ("reference pressure") of 1013 hPa, then the relationships (1) and (2) can be described as

0.0001 • 1013 hPa <p (ß _lf i) <0.50 • 1013 hPa (1 ')

and

P (β2, T ₂ ) <0.0001 ^• 1013 hPa (2 '). 1 2 3 Should several volatile nitroxyl compounds (ßi, ß _λ , ß _x ...) be used as component (b) and several non-volatile nitroxyl compounds (ßi, ß _!, Ss _! ...) as component (b ₂ ) of the stabilizer (B ) are used, these compounds must, according to the invention, individually and as pure substances satisfy the relationships (1) and (2), ie

0.0001 ^• p (αι, Ti) <p (ßj, _Tl ) <0.50 • p (α _χ , T _x ),

2 0.0001 ^• p ⁽ αι, Ti ⁾ <p ⁽ ßj_. I) <0.50 • p (c-ι, i), “3

0.0001 • p (αι, i) <p (ß _χ , _Tl) < _0f50 . _{p (θlf Tl) #}

and

P ⁽ ß2 'T ₂ ) <0.0001 ^• p (α ₂ , T ₂ ),

2

P ⁽ ß ₂ 'T ₂ ) <0.0001 ^• p (α ₂ , T ₂ ),

3

P ⁽ β2 'T ₂ ) <0.0001 ^• p (α ₂ , τ ₂ ).

in the case that p (αχ, i) = p (α ₂ , T) = 1013 hPa, of course, one can establish corresponding relationships to (1 ') and (2').

In the case of distillations, for example, there are (ideally) isothermal conditions, so that αi or α can be written for the lowest or highest-boiling compound containing vinyl groups p (αι, Ti) = p (αι, T) or p (α ₂ , T ₂ ) = p ( ₂ , T),

where still applies

p (αι, T) = p (αι) <p (α ₂ , T) = p (α ₂ )

with Ti = T ₂ = T.

For the considered (vapor phase) temperature T (= T _x = T ₂ ) one obtains according to the relationships (1) and (2) according to the invention

0.0001 • p (αι) <p (ßι, T) = p (ß _x ) <0.50 • p (ttχ)

and

p (ß _x , T) <0.0001 • p (α ₂ ),

where p (αχ), p (α ₂ ), p (ßι) and p (ß ₂ ) denote the vapor pressures of the pure substances concerned cti, α, ßi and ß at the temperature T considered.

The vapor pressure curves as well as the corresponding data for the vinyl group-containing compounds (A), which are to be stabilized in both the liquid and the vapor phase, serve as an orientation for the selection of suitable nitroxyl compounds as components (bi) and (b). The vapor pressure curves of the latter compounds are readily available from the relevant literature in most cases, but the data for the former compounds are usually not available. The determination of vapor pressures as a function of temperature is, however, easy and routine for most substances, so that these data can usually be obtained quickly by a person skilled in the art. For companies that deal with the distillation / purification of compounds containing vinyl groups, they represent the basis of work.

Are basic data such as the heat of vaporization and a boiling temperature with associated pressure for a connection, you can also perform an approximate extrapolation to other pressure / temperature pairs using the Clausius-Clapeyron equation.

Nitroxyl compounds which can be used either in the volatile component (b _x ) or the low volatile component (b ₂ ) can be used, for example, in the older ones German application 196 51 307.3. As a rule of thumb, the selection can be based on the molar mass of the nitroxyl compound. Thus, compounds with high molar masses are usually, for example also the nitroxyl compounds described in the earlier German application 196 51 307.3, which contain two or more 1-N-

Oxyl-2, 2, 6, 6 -tetramethylpiperidine units contained in the molecule, less volatile than compounds with low molecular weights, e.g. the nitroxyl compounds described in the above-mentioned older German document which have only one 1-N-oxyl-2, 2, 6, 6-tetraethylpiperidine unit or the N-oxyl compounds of the formula which are also mentioned in this document

R R

N

R R

but in the event that the radicals R mentioned in this older German document are aralkyl or aryl groups and not lower alkyl groups, more volatile nitroxyl compounds must be expected again.

As the volatility depends only partly on the molecular weight, but also to a large extent on the structural conditions of the compounds under consideration, such as the presence of polar groups, intermolecular and intramolecular interactions, etc., the molecular weight can, as already mentioned of the envisaged nitroxyl compounds serve only as a first indication. The suitability of a compound as a component of component (b _x ) or component (b ₂ ) can only be checked with regard to the vinyl group-containing compounds of component (A), which need to be stabilized. As a rule, the easy-to-determine boiling point of the nitroxyl compound provides a good indication of this, if this compound has a boiling point, if appropriate also under reduced pressure, compared to the boiling point or the boiling points of the vinyl group-containing compound or compounds. The Picet-Trouton rule and the Clausius-Clapeyron equation can then be used to estimate the pressure / temperature behavior deviating from the specific boiling point. The Pictet-Trouton rule (often just called the Trouton rule) states that the molar entropy of evaporation takes on a value of approximately 88 J • mol " ¹ • K" ¹ . This rule is usually well fulfilled by non-polar substances. However, there are deviations in strongly associative connections.

According to the invention, one or more compounds of the formula purple are preferably used as the volatile component (b _x )

purple,

in what mean

R ^{5 is} hydrogen,

R ^{6 is} hydrogen, hydroxy, C 1 -C ₄ -alkoxy, Ci-Cg-acyloxy,

Tri (-C-C ₄ alkyl) silyloxy or CR ⁵ R ⁶ together a carbonyl group and

as the non-volatile component (b ₂ ) preferably one or more compounds of the formula IIIb

Illb,

in what mean

X is oxygen or R ⁷ -N,

AC ₆ "-C ₂ alkylene, α, ω-bis (carbonyloxy) -C ₆ -C ₂ alkylene, α, ω-C ₆ -C ₂ diacyl, 1,2-, 1,3- or 1,4 -Phenylene, phthaloyl, isophthaloyl or terephthaloyl,

R ^{7 is} hydrogen, -CC ₄ alkyl or Cχ-C ₆ acyl.

The C 1 -C ₄ alkoxy groups of the radical R ⁶ of compound lilac include methoxy, ethoxy, propoxy, 2-propoxy, butoxy, 2-butoxy, 2-methylpropoxy (isobutoxy) and t-butoxy. The Ci-Cg-acyloxy groups of the radical R ⁶ are to be understood as formate, acetate, propionate, butanoate, pentanoate (valerate), hexanoate (capronate) and the isomeric groups such as 2-methylpropionate (isobutanoate), 3-methylbutanoate (isovalerate), 2-methylbuta- noat, neopentanoate or 2-, 3-, 4 -methylpentanoate (-valeriate). In the tri (C 1 -C ₄ alkyl) silyloxy groups of the radical R ⁶ , the silyloxy groups trisubstituted with the same C ₄ -C ₄ alkyl groups are preferably used. As _Cι-C4 alkyl groups are the alkyl ₄ alkoxy already contained in the above Cι-C in question. Examples of suitable silyloxy groups are, for example

(H ₃ C) ₃ Si-0-, (H ₅ C ₂ ) ₃ Si-0- or [(H ₃ C) ₃ C] ₃ Si-0-.

In individual cases, however, mixed substituted silyloxy radicals such as, for example

CH ₃ CH ₃ CH ₃ CH ₃

0 Si C CH ₃ or O Si CH

I I I I

CH ₃ CH ₃ CH ₃ CH ₃

Find use.

Examples of volatile nitroxyl compounds as a component of component (b _x ) are

₃₃

Examples of C 1 -C ₄ -alkyl groups which can appear under the R ⁷ radical in the compounds of the formula IIIb have already been mentioned under the R ⁶ radical of compounds of the formula purple. Correspondingly, the Ci-Ce acyl groups of the radical R ⁷ groups used in the above-mentioned acyloxy groups of the radical R ⁶ . In those mentioned in the verbrük- kenden Group A C ₆ -Cι ₂ alkylene, α, ω-bis (carbonyl-oxy) -C ₆ "Cι ₂ alkylene- and α, ω- -CG-Cι ₂ -Diacylgruppen the linear groupings - (CH) χ-, -OOC- (CH ₂ ) _m -COO- and - (CO) O- (CH ₂ ) _n -0 (CO) - (with 1, m and n as integers from 6 to 12, 4 to 10 and 6 to 12 respectively). However, branched bridges A are also possible.

Examples of suitable non-volatile nitroxyl compounds which can be used as a component of component (b ₂ ) are

The indices 1, m, n can assume the numerical values mentioned above.

The compounds bis (1N-oxyl-2,2,6,6-tetramethylpiperidine-4-yl) adipate, bis (IN-oxyl-2, 2,6, 6-tetramethylpiperidine-4-yl) sebacate are used in particular ,

N, N '-Bis (1N-oxyl-2, 2,6, 6-tetramethylpiperidin-4-yl) adipinamide, N, N' -Bis (1N-oxyl-2,2,6,6-tetramethylpiperidine-4 -yl) -sebacinamide, N, N'-bis (IN-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6-diaminohexane.

The compounds of the formulas lilac and Illb are preparatively easily accessible or in some cases commercially available, for example the compound

OH

("Tempol"),

0

which can be obtained from Hüls and can be used to prepare the corresponding dimeric compounds of the formula IIIb.

On the other hand, the piperidine derivatives on which the compounds purple and Illb are based can also be prepared and converted into the corresponding nitroxyl compounds in a final oxidation step, for example using hydrogen peroxide. Examples of such preparations can be found in the older German application 196 51 307.3 and the literature cited therein. The listed volatile or low-volatility compounds lilac or Illb are preferably used in a mixture which contains the above-mentioned vinyl group-containing compounds of the formulas Ia and / or Ib and of the formula II as component (A). However, the compounds of the formulas purple and IIIb can also be used for any other vinyl group-containing compounds whose boiling temperatures and vapor pressures in relation to the data of the nitroxyl compounds meet the criteria according to the invention.

In addition to constituent (A) and stabilizer (B), one or more aromatic nitro compounds and optionally one or more iron compounds may also be present in the mixture of substances according to the invention. Suitable nitro compounds are described, for example, in the earlier German patent application 196 51 307.3. In particular, these are compounds such as 1, 3-dinitrobenzene, 1,4-dinitrobenzene, 2, 6-dinitro-4-methylphenol, 2-nitro-4-methylphenol, 2, 4, 6-trinitrophenol, 2, 4- Dinitro-1-naphthol, 2, 4-dinitro-6-methylphenol, 2, 4-dinitrochlorobenzene, 2, 4-dinitrophenol, 2,4-dinitro-6-sec-butylphenol, 4-cyano-2- nitrophenol or 3-iodo-4-cyano-5-nitrophenol. Aromatic nitro compounds such as 2,6-dinitro-4-methylphenol, 2-nitro-4-methylphenol, 2,4-dinitro-6-sec-butylphenol or 2,4-dinitro-6-methylphenol are preferably used. det.

Iron compounds are also listed in the older German patent application 196 51 307.3. In particular, these are iron compounds from the groups of

a) iron carbonyls and carbonyl ferrates, b) organometallic iron carbonyl compounds, c) unsubstituted and substituted ferrocene compounds, d) iron compounds with ligands which act as donor atoms alone or in a mixture of oxygen, nitrogen, sulfur or

Contain phosphorus, e) iron halide and iron pseudohalide compounds.

Iron compounds from groups a) and b) are preferably used, particularly preferably from group d). In the latter

The iron complexes with heteroannulenes (eg azoannulene), such as eg iron dibenzo [b, i] -1, 4, 8, 11-tetraaza- (14) annulene (Fe (taa)), or the iron complexes with are particularly suitable (Substituted and / or benzannelated) phthalocyanines. The connections are shown again as formula pictures below:

and

In addition, the mixture of substances according to the invention can, if desired, e.g. contain one or more costabilizers from the group of aromatic nitroso compounds, phenothiazines, quinones, hydroquinones and their ethers, phenols and their ethers, hydroxylamines and phenylenediamines.

Aromatic nitroso compounds e.g. p-nitrosophenol, p-nitroso-o-cresol or p-nitroso-N, N '-diethylaniline.

Other costabilizers can also be substituted phenols or hydroquinones, for example the following:

4-tert-butyl catechol, methoxyhydroquinone, 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-ß- (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, 1,3,5-tris- (3,5-di-tert-butyl-4-hydroxy-benzyl) -isocyanurate, 1,3,5-tris- [ß- ( 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 [ß- (3, 5-di-tert-butyl-4-hydroxy-phenyl) propionate].

According to the invention, a stabilizer (B) is claimed which contains, as components (b _x ) and (b), one or more nitroxyl compounds of the formulas purple and IIIb. In addition, the invention claims a stabilizer (B) which, in addition to the compounds of the formulas lilac and Illb (as components (b _x ) and (b)), also contains one or more aromatic nitro compounds as component (b ₃ ).

According to the invention, a stabilizer is also claimed which, in addition to the nitroxyl compounds of the formulas purple and IIIb, additionally contains one or more iron compounds as component (b ₄ ).

According to the invention, a stabilizer is furthermore claimed which, in addition to the nitroxyl compounds of the formulas purple and IIIb, also contains one or more aromatic nitro compounds and one or more iron compounds as components (b ₃ ) and (b ₄ ). The nitroxyl compounds, aromatic nitro compounds and iron compounds have already been mentioned above as examples.

If desired, other additives can of course also be added to the stabilizers (B) according to the invention, such as the costabilizers also mentioned above.

The stabilizers (B) mentioned contain component (b _x ) or (b ₂ ) in a proportion of 1 to 99% by weight or 99 to 1% by weight, based on the total amount of components (b _x ) and (b). Component (b _x ) contains one or more nitroxyl compounds of the formula lilac, which are to be regarded as very volatile with regard to the compound (or compounds) containing vinyl groups, for example subjected to distillation, that is to say they have vapor pressures corresponding to the criterion described at the beginning, which have a boiling point If the lowest-boiling vinyl group-containing compound from component (A) has a few percent or a few ten percent of the vapor pressure of this vinyl group-containing compound, the proportion of component (b _x ) can be below 99% by weight and correspondingly the proportion of the component Set (b ₂ ) to values above 1% by weight.

If, on the other hand, component (bi) contains nitroxyl compounds with lower volatility in the abovementioned sense, their proportion in the total mixture of components (bi) and (b ₂ ) will preferably be set higher.

When aromatic nitro compounds are added as component (b ₃ ) to the stabilizer (B), the ratio between the amount of component (b ₃ ) and the amount of nitroxyl compounds (the sum of the amounts of components (b _x ) and (b ₂ ) ) vary as desired. There Nitroxyl compounds are usually relatively expensive, you will want to set their share in the stabilizer as small as possible.

Such mixtures usually then consist of 0.05 to 4.5% by weight of nitroxyl compounds (sum of components (b _x ) and (b ₂ )) and 95.5 to 99.95% by weight of aromatic nitro compounds, where the proportions are based on the total amount of components (b _x ), (b ₂ ) and (b ₃ ).

If iron compounds are added to the stabilizer (B) in addition to the components (b _x ) and (b) as component (b ₄ ), their proportion is usually from 1 ppm to 5% by weight, preferably from 10 ppm to 3% by weight. -%, based on the total amounts of components (bi), (b ₂ ) and (b ₄ ).

If, in addition to the nitroxyl compounds, both component (b ₃ ) and (b ₄ ) are also present, their proportions are calculated similarly as before for the stabilizers (B) which contain the nitroxyl compounds (as components (b _x ) and (b ₂ ) ) and aromatic see nitro compounds (as component (b ₃ )) or iron compounds (as component (b ₄ )). For a stabilizer (B) which contains the components (b _x ), (b ₂ ), (b ₃ ) and (b ₄ >), the proportion of component (b ₃ ) based on the sum of the components (b _x ), (b ₂ ) and (b ₃ ) can be set as desired, usually the proportion of (b ₃ ) based on the sum of (bi), (b ₂ ) and (b ₃ ) is 95.5 to 99.95% by weight The proportion of component (b ₄ ), based on the sum of components <bχ), (b) and (b ₄ ), is usually from 1 ppm to 5% by weight, preferably from 10 ppm to 3% by weight. %.

If, for example, costabilizers, such as those already listed above, are added to the stabilizers (B), their proportion is based on the total amount of components (b _x ), (b), optionally (b ₃ ) and / or optionally (b) and the co-stabilizer (the costabilizers) at 0.01 to 20% by weight.

The stabilizer (B) is usually present in the mixture according to the invention in a proportion of 0.0002 to 5% by weight, preferably in a proportion of 0.0005 to 0.5% by weight, based on the total amount of the mixture Component (A) and stabilizer (B).

Under inert conditions, such as, for example, under a nitrogen atmosphere, it is advantageous to use stabilizers (B) with at least one nitro compound as component (b ₃ ) and, if appropriate, an iron compound as component (b ₄ ). The suitable ratio of nitroxyl compounds to component (b ₃ ) is the individual boundary conditions such as the chemical nature of the compounds (A) to be stabilized, the temperature ranges to be observed during distillation, for example (important with regard to the volatility and thus distribution of components (bx) and (b ₃ ) between vapor and liquid phase) or the (residual) oxygen content in the unit used. However, it is possible for a person skilled in the art to determine an optimized ratio of these components by means of preliminary tests taking into account the respective circumstances. Usually, however, stabilizers (B) with a content of 95.5 to 99.95% by weight of the aromatic nitro compounds already mentioned above should develop a good activity.

If the compounds (A) to be stabilized are exposed to an atmosphere which still has proportions of (residual) oxygen, the proportion of nitro compounds can be reduced or their use can be dispensed with entirely. This is desirable particularly with regard to the safety when handling such inhibitors and also with regard to the reduction of possible harmful effects on the environment. For example, nitroxyl compounds alone (ie stabilizers (B) which contain only the components (b (> and (b ₂ )), but to an even greater extent iron stabilizers (B) without addition of nitro compounds at oxygen contents of about 0.5 ppm to some 10,000 ppm, as found, inter alia, in customary industrial distillation columns, very good stabilizing action on compound (A) against undesired premature polymerization.

The stabilizer (B) - if appropriate in a mixture with nitro compounds (b ₃ ) and / or iron compounds (b ₄ ) and / or if appropriate costabilizers - can be the vinyl group-containing compounds (A) before or during the purification or distillation in bulk, as Add suspension or as a solution using a suitable solvent or solvent mixture in an effective amount to prevent premature polymerization. In a special case, it may also be necessary to add components <bχ) and (b ₂ ) of the stabilizer (B), and optionally nitro compounds (b ₃ ) and / or iron compounds (b ₄ ) and / or one or more of the above-mentioned costabilizers, separated and then preferably added at different locations.

It may also be necessary to mix partial mixtures, ie groups of components, such as, if appropriate, a mixture of component (b) with nitro compounds (b ₃ ) and / or iron compounds (b ₄ ) and / or with other costabilizers on the one hand and Component (bx), on the other hand, separated and then preferably to add in spatially different places.

Suspensions or solutions of the stabilizers (B) are preferably made with water. Alkanols, such as methanol, ethanol, propanol and n-, i-, t-butanol, optionally in a mixture with water, are furthermore preferably used. These alcohols, or their mixtures with water, are preferably used in the case of the corresponding esters of acrylic acid and alkyl acrylic acid, i.e. used for compounds containing vinyl groups corresponding to formula II.

Furthermore, ketones such as, for example, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, diols such as glycol or propylene glycol and their alkyl mono- or diether, oligomeric or polymeric ethylene glycols can also be used as suspension or solvent, optionally in a mixture with alcohols and water ( Polyethylene glycols) and propylene glycols (polypropylene glycols) and their alkyl ethers, diamines such as ethylene diamine or propylene diamine and their alkyl mono- or diimino ethers, oligomeric or polymeric ethylene diamines (polyethylene imines) and their alkyl imino ethers are used. Of course, the compounds (A) used or their mixtures can also be used as solvents or suspending agents.

Raw product mixtures can also be used for this purpose. If, for example, so-called “oven δl”, a mixture resulting from the dehydrogenation of ethylbenzene and consisting predominantly of styrene, ethylbenzene, toluene and other substituted aromatics, is to be purified by distillation, this mixture can be used as a solvent and / or suspending agent . Of course, you can also use ethylbenzene or toluene in pure substance for the solution and / or suspension.

The stabilizers (B) according to the invention can also be used - in bulk or as a suspension or solution - in general to inhibit the premature polymerization of compounds which are preferably free-radically polymerizable and show their stabilizing effect in a wide temperature range. They are effective at any usual storage temperature from -50 to + 50 ° C. The pressure range of the stabilization process is not critical. The stabilizers work at normal pressure but also at reduced or increased pressure. The following explanations are intended to illustrate the inventive concept, but without restricting the scope of the invention.

Table 1 shows various compounds corresponding to the purple formula, with their boiling points dependent on the equilibrium pressure (own measurements).

The connections mentioned here mean: Tempo

0 O

•

and with the respective radicals R in the formula

0 - R

0

Ac-Tempol for R = acetyl, Tempol for R = H, Me-Tempol for

R = methyl, Et-Tempol for R = ethyl and TMS -Tempol for R = trimethylsilyl.

Table 1

At the pressures given in hPa, the compounds listed in Table 1 have the boiling temperature corresponding to the numerical value in ° C.

Table 2 shows a selection of compounds containing vinyl groups corresponding to formulas Ia and Ib, Table 3 shows a selection of compounds containing vinyl groups according to formula II with their respective boiling points. The numerical values (to be understood as hPa) of the corresponding vapor pressures at the boiling temperature mentioned are given in brackets, provided that the pressures deviate from normal pressure (1013 hPa).

Tables 2 and 3 also show the literature references for the boiling temperatures. If, in addition to the page number of the literature reference, the volume and the year are also given, the data are taken from the Römpp chemistry dictionary (Georg Thieme Verlag Stuttgart-New York). If only the page number is mentioned, the data come from the chemist's calendar (3rd edition, Springer-Verlag Berlin, Heidelberg, New York, Tokyo, (1983)).

Table 2

Connection boiling temperature in reference ° C

Styrene 145.8 volume 5, p. 4355/6, (1992) α-methylstyrene 165 volume 4, p. 2761, (1991)

Vinyltoluene 172 volume 6, p. 4927, (m: p = 60:40) * (1992)

Divinylbenzene 195 Volume 2, pp. 1018/9, (m: p = 75:25) * (1990)

2 -Vinylpyridin 49-51 (15) Volume 6, p. 4926, (1992)

4 -Vinylpyridine 62-65 (20) Volume 6, p. 4926, (1992)

2 -Methyl -4 -vinyl -py- 181 volume 4, p. 2763, ridin (1991)

* Proportions of the m and p isomers in a mixture with the stated boiling temperature Table 3

If, for example, styrene is to be stabilized in both the liquid and the vaporous form during the distillation and the distillation is carried out at normal pressure, then a volatile nitroxyl compound (bx) must be selected according to the invention, which at the boiling temperature of 145.8 ° C. which is then available for styrene , 01 to 50% of the vapor pressure of styrene (1013 hPa). According to Table 1 it can be seen immediately that the compound Tempol with a vapor pressure of 12.5 hPa at a temperature of 145 ° C ( ^" 145.8 ° C) meets this criterion (12.5 / 1013 = 1.2%).

The following can be used to estimate whether the Tempo connection is suitable:

According to Table 1, Tempo has a vapor pressure of 76.1 ° C

12.5 hPa. According to the Clausius-Clapeyron equation in their

Approximation form

L In p (T ₂ ) - In p (Tχ) = - (1 / Tχ - 1 / T ₂ ),

R where Tx and T ₂ different boiling temperatures, here Tx = 76.1 ° C and T ₂ = 145, 8 ° C, p (Tχ) and p (T ₂ ) the corresponding vapor pressures, here p (Tχ) = 12 , 5 hPa and p (T) as the desired vapor pressure, L the heat of vaporization, in the natural logarithm to the base e and R the gas constant (8.314 J-mol ^ K " ¹ ), the vapor pressure p (T ₂ ) of the nitroxyl compound can be The Pictet-Trouton rule gives an estimate of the heat of vaporization L at temperatures of 76.1 ° C and 145.8 ° C of

L (76.1 ° C) * 88 J-mol- ⁱ K ^"1 • (273.15 + 76.1) K = = 30734 J-mol" ¹

and

L (145.8 ° C) * 88 J-mol ^ K ^"1 • (273.15 + 145.8) K = = 36867.6 J-mol" ¹ .

If one uses these values for L in the approximate form of the Clausius-Clapeyron equation, the vapor pressure at 145.8 ° C results between 72.7 hPa (L (76.1 ° C )) and 103.3 hPa (L (145.8 ° C)). Both values met the criterion according to the invention (72.7 / 1013 = 7.2% or 103.3 / 1013 = 10.2%).

Tempo is therefore also an option for the stabilization of styrene in normal pressure distillation as component (bx) and thus also the other nitroxyl compounds listed in Table 1. If styrene is to be distilled under reduced pressure, which is usually also done, the pressure / temperature ratios then applicable for styrene can be determined using the equation applicable for this (taken from Ullmanns Encykl. D. Techn. Chem., Vol. 22, Verlag Chemie Weinheim, 4th ed., P. 294 (1982))

1457.3 lg p (T) = 7.0916

211.45 + T

determine where p (T) denotes the pressure in hPa at temperature T ° C and lg is the logarithm to base 10. The procedure for determining a suitable component (bx) is then analogous to that already described.

For other compounds containing vinyl groups, the vapor pressure data are often also available in the analytical form of a corresponding equation or can be easily determined. For example, if a mixture of compounds containing vinyl groups, such as a mixture of styrene and divinylbenzene, is to be stabilized in the vapor phase - the boiling points here are at normal pressure at 145, 8 ° C and 195 ° C respectively (the latter for a mixture of the m and p isomers in a ratio of 75:25) - the pressure / temperature data of the lower-boiling (lowest-boiling) compound, here styrene, serve as a reference for the selection of the volatile nitroxyl compound as component (bx) and the corresponding data of the isomer mixture of divinylbenzene, as a higher boiling "compound", as a reference for the selection of the low volatility nitroxyl compound as component (b ₂ ). If several volatile nitroxyl compounds are to be used, the one with the lowest vapor pressure (ie the highest-boiling nitroxyl compound) at the reference temperature must also meet the criterion according to the invention.

If compounds are used as component (bx) which have excessively high volatilities, there is a fear that these nitroxyl compounds (in part) will pass into the distillate and possibly there. for further reactions (e.g. polymerizations) of the purified compounds containing vinyl groups are a hindrance.

Without performing further detailed estimates or calculations as before, one can immediately see by comparing Tables 2 and 3 with Table 1 that to stabilize almost all vinyl-containing compounds in Tables 2 and 3 or their mixtures, all nitroxyl compounds in Table 1 or mixtures of these compounds as Component (bx) should be usable.

In the case of vinyl methyl ether, which has a boiling temperature of 5.5 ° C at normal pressure, the vapor pressure of the Tempol compound could already be too low at this temperature, ie the lower percentage limit of the selection criterion could be undershot. An estimate, as has already been carried out as an example above, provides vapor pressures for this nitroxyl compound which at 5.5 ° C between 0.083 and 0.17 hPa and thus based on the vapor pressure of the vinyl methyl ether (1013 hPa) with percentages of 0.0082 up to 0.017%. The proportion of this nitroxyl compound to stabilize the vinyl methyl ether in the vapor phase may already be too low. It would have to be decided on the basis of well-founded data and experiments, whereby, of course, the tendency towards radical polymerization is clearly reduced in this temperature range. Since the vapor pressure curves of the vinyl group-containing compounds and the volatile nitroxyl compounds suitable for their vapor phase stabilization generally run parallel or approximately parallel at least over wide pressure / temperature ranges, the potential suitability found at one or more pressure / temperature pairs should be one Nitroxyl compounds are also valid for different pressure / temperature ratios.

If the addition of aromatic nitro compounds and / or iron compounds as components (b ₃ ) and (b ₄ ) and, if appropriate, further costabilizers is considered, compounds are used here which are not very volatile or not at all volatile under the pressure / temperature conditions under consideration are. However, as with the nitroxyl compounds of components <bχ) and (b ₂ ), it may also be desirable to use combinations of corresponding readily volatile and low-volatility compounds. The selection criteria for this are then preferably to be applied completely analogously to the criteria for the selection of the nitroxyl compounds of components (bx) and (b ₂ ).

It should also be noted here that the partial pressures of the components (bx), optionally (b ₃ ) and / or optionally (b ₄ ) as well as any costabilizers that are actually present in the gas phase due to intermolecular interactions in the gas but also liquid phase are quite of the values to be expected from the Henry Dalton Law and thus from the composition of the liquid phase. Since the vapors of the components in the gas phase generally do not behave like ideal gases, it is often only possible to make rough estimates of the quantitative relationships between the components in the steam room. Here, however, you can usually get quick and easy information about the respective compositions via the analysis of the vapor phase (the condensed vapor) and the liquid phase and correlate this with the stabilizing effects.

Furthermore, reactions of the components with one another or with the compounds containing vinyl groups can give rise to more volatile derivatives or convert volatile compounds into less volatile ones. It should be noted here only the readiness of various iron compounds (as possible component (b ₄ )) to form π complexes with compounds containing vinyl groups or aromatic nitro compounds.

Claims

claims

1. Mixture containing

(A) one or more compounds containing vinyl groups,

(B) containing a stabilizer

(bx) a nitroxyl compound of a secondary amine which does not bear any hydrogen atoms on the α-C atoms, the vapor pressure at the boiling point of the lowest-boiling vinyl group-containing compound from (A) 0.01 to 50% of the vapor pressure of the lowest-boiling vinyl group-containing compounds from (A ) is or

a mixture of nitroxyl compounds of secondary amines which do not carry any hydrogen atoms on the α-C atoms, in which the vapor pressure of the highest boiling nitroxyl compound at the boiling point of the lowest boiling vinyl group-containing compound from (A) 0.01 to 50% of the vapor pressure of the lowest-boiling vinyl group-containing compound from (A),

(b ₂ ) a nitroxyl compound of a secondary amine which does not carry any hydrogen atoms on the α-C atoms, the vapor pressure of which at the boiling point of the high-boiling vinyl group-containing compound from (A) is less than 0.01% of the vapor pressure of the high-boiling vinyl group-containing compound from (A) is or

a mixture of nitroxyl compounds of secondary amines which do not carry any hydrogen atoms on the α-C atoms, in which the vapor pressure of the lowest-boiling nitroxyl compound at the boiling point of the highest-boiling vinyl group-containing compound from (A) is less than 0.01% of the vapor pressure of the high-boiling vinyl group-containing compound Connection from (A) is

where (bx) and (b) each refer to the vapor pressure of the pure nitroxyl compound in question and the vapor pressure of the pure vinyl aromatic compound at the boiling point of this pure vinyl aromatic compound, (b ₃ ) optionally one or more aromatic nitro compounds,

(b ₄ ) optionally one or more iron compounds.

2. Mixture of substances according to claim 1, containing as component (A) compounds of the formula Ia containing vinyl groups

in what mean

R ^{1 is} hydrogen, Cχ-C ₄ alkyl, C ₂ -C ₄ alkenyl, carboxy, formyl, sulfo, hydroxy, amino or nitro,

R ² C ₂ -C ₄ alkenyl and / or

compounds of the formula Ib containing vinyl groups

in what mean

R ^{3 is} hydrogen, Cχ-C ₄ alkyl,

R ⁴ C -C alkenyl.

3. Mixture of substances according to claim 1, containing as component (A) compounds of the formula II which contain vinyl groups

CH ₂ = CZ ⁴ Q z ¹ (Ib)

where mean

Q is a chemical single bond, oxygen or a group -NZ ² -,

0

Z ¹ || or - Z ³ ,

- CZ ³

Z ² , Z ⁴ hydrogen, C -C ₄ alkyl, Z ^{3 is} hydrogen, hydroxy, cyano, Ci-Cβ-alkoxy, Cx-C _ß -alkyl or a radical which together with Z ² or Z ^{4 is} a saturated or unsaturated C ₃ -, C ₄ -, C ₅ - or C ₆ Forms alkylene bridge in which up to two non-adjacent carbon atoms can be replaced by N, NH, N (Cχ-C-alkyl), N (C ₆ -Cχ ₀ -aryl) or oxygen.

Mixture of substances according to claims 2 or 3, containing as component (bχ> one or more compounds of the formula purple

purple,

in what mean

R ^{5 is} hydrogen,

R ^{6 is} hydrogen, hydroxy, Cχ-C ₄ alkoxy, Cχ-Cg acyloxy, tri (C ₁ -C ₄ alkyl) silyloxy or CR ⁵ R ⁶ together a carbonyl group and

as component (b ₂ ) one or more compounds of the formula Illb

Illb,

in what mean

X is oxygen or R ⁷ -N,

AC ₆ -C ₂ alkylene, α, ω-bis (carbonyloxy) -Cg-Cχ -alkylene, α, ω-C ₆ -Cχ ₂ -diacyl, 1,2-, 1,3- or 1,

4 -phenylene, phthaloyl, isophthaloyl or terephthaloyl,

R ^{7 is} hydrogen, Cχ -C alkyl or Cχ -C ₆ acyl.

5. Stabilizer (B) according to claim 1, containing as component (bx) one or more compounds of the formula purple and as component (b) one or more compounds of the formula IIIb.

5

6. Stabilizer (B) according to claim 5, containing as additional component (b ₃ ) one or more aromatic nitro compounds.

10 7. Stabilizer (B) according to claim 5, containing as additional component (b ₄ ) one or more iron compounds.

8. stabilizer (B) according to claim 5, containing as additional component (b) one or more aromatic nitro compounds and 15 as additional component (h ^) one or more iron compounds.

9. A method for inhibiting the premature polymerization of compounds containing vinyl groups according to claims 1 to 20 3, characterized in that the vinyl group-containing compounds (A) before or during their purification or distillation, a stabilizer (B) according to claims 1 or 5 to 8 in an effective amount.

25 10. A method for inhibiting the premature polymerization of compounds containing vinyl groups according to claims 1 to 3, characterized in that the components of the stabilizer (B) according to the vinyl group-containing compounds (A) before or during their purification or distillation

30 Claims 1 or 5 to 8 individually or in at least two groups of the components.

35

40

45