KR100879678B1 - Nitroaromatic solubilizer for nitroxyls in aromatic solvents - Google Patents

Abstract

Disclosed herein is a method of increasing the solubility of formula (I) in said solvent comprising adding a nitroaromatic compound having formula (II) to an aromatic hydrocarbon solvent:

Wherein, in formula (II), R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl, aryl, cycloalkyl, heterocyclic, substituted alkyl, substituted aryl, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , halogen, independently selected from the group consisting of, and / or any two proximity groups together To a 7-membered ring structure, provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ is NO ₂ , and R ₁₁ and R ₁₂ are hydrogen, alkyl, aryl , Benzyl, cyclic, heterocyclic and substituted alkyl or aryl whose substituents are C, O, N, S, or P, or R ₁₁ and R ₁₂ together represent a 5 to 7 membered ring Can form a structure,

In formula (I), R ₁ and R ₄ are independently selected from the group consisting of hydrogen, alkyl and heteroatom-substituted alkyl, and R ₂ and R ₃ are independent from the group consisting of alkyl and heteroatom-substituted alkyl Is selected; X ₁ and X ₂ are (1) halogen, cyano, COOR ₇ , -S-COR _7- , -OCOR ₇ where R ₇ is alkyl or aryl, amido, -SC ₆ H ₅ , carbonyl, Independently selected from the group consisting of alkenyl or alkyl having 1 to 15 carbon atoms, or (2) together with nitrogen to form a ring structure, preferably a 5, 6, or 7 membered ring structure.

Nitroaromatic, solubility, nitroxyl, polymerization inhibition

Description

Nitroaromatic solubilizer for nitroxyl in aromatic solvent {NITROAROMATIC SOLUBILIZER FOR NITROXYLS IN AROMATIC SOLVENTS}

The present invention relates to the use of at least one nitroaromatic compound to enhance the solubility of at least one nitroxyl compound in an aromatic hydrocarbon solvent.

Many ethylenically unsaturated monomers polymerize undesirably at various stages of their preparation, processing, handling, storage and use. Particularly intractable problems are the contamination of equipment by polymerization during the purification of these monomers. Polymerization reactions, such as thermal polymerization during their purification, result in the loss of monomers and the loss of production efficiency due to precipitation on or in the equipment used during the purification, which precipitation has to be removed from time to time. In addition, the formation of soluble polymers leads to loss of monomers, for example low yields and increased viscosity of any tar that can be produced. The treatment of tar then requires high temperatures and operation (energy costs) to remove residual monomers.

Nitroxyl is a very effective polymerization inhibitor for use in the purification of vinyl aromatic monomers. Many of these nitroxyls are solid under ambient conditions. It is difficult to administer the solid inhibitor to the monomer purification train in a continuous distillation process and the safety may be compromised by the easy closure of the closure of the solid dosage system. The solvents commonly used to add inhibitors to the distillation train for vinyl aromatics are vinyl aromatic monomers themselves or the corresponding saturated vinyl compounds, for example styrene or ethylbenzene or divinylbenzene or diethylbenzene. These solvents are highly flammable and are potential carcinogens. Therefore, in terms of safety (and economics), the solution needs to be made as concentrated as possible in these flammable solvents. Unfortunately, many nitroxyls have very limited solubility in these solvents.

US Pat. No. 3,163,677 describes N, N, O-trisubstituted hydroxylamines and N, N-disubstituted nitroxides of the formula:

Wherein R ₁ , R ₂ and R ₃ are each alkyl radicals having 1 to 15 carbon atoms. (NO * designations herein denote stable free radicals where * is an ancillary electron.) N, N, O-trisubstituted hydroxylamines can be used to make N, N-disubstituted nitroxides, which are stable It is a free radical and is known to be useful as a polymerization inhibitor.

U.S. Patent No. 3,334,103 discloses that nitroxides can be prepared from the corresponding heterocyclic amines where the nitrogen atom of the nitroxide group is attached in addition to the tertiary carbon of the aliphatic group (e.g., the nitrogen atom is a heterocyclic nucleus). Forms part of). These nitroxides are known to have useful properties similar to those described for the N, N-disubstituted nitroxides of US Pat. No. 3,163,677.

U.S. Patent No. 3,372,182 discloses a wide variety of N, N-disubstituted stable free radical nitroxides that are not readily readily available, with any hydroxylamine (e.g. tri-t- It is described that it can be prepared by a simple and convenient process comprising the step of substantially pyrolyzing butylhydroxyamine) in an inert reaction medium.

British Patent No. 1,127,127 describes that acrylic acid can be stabilized against polymerization by adding nitroxides having the necessary backbone structure as follows.

Wherein R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups and there is no hydrogen bonded to the remaining valence on the carbon atom bonded to nitrogen. Two remaining valences or nitrogens not satisfied by R ₁ to R ₄ may also form part of a ring (eg, 2,2,6,6-tetramethyl-4-hydroxy-piperi) Din-1-oxyl).

U.S. Patent No. 3,422,144 describes stable free radical nitroxides of the formula:

Wherein R is selected from tertiary alkyl, aryl, alkaryl, haloaryl, carboxyaryl, alkoxyaryl, alkylthioaryl, pyridyl and dialkylaminoaryl, and R 'is tertiary alkyl. These nitroxides are known to be useful as traps for reactive free radicals, both in free radical counting and for inhibiting oxidation and free radical polymerization.

U. S. Patent No. 3,494, 930 describes free radicals of the nitroxide type useful as initiators of free radical reactions, collectors of free radicals, polymerization inhibitors or antioxidants. These include nitrogen-containing bicyclic compounds, in which one of the bridges alone comprises nitroxide radical groups, in particular aza-9-bicyclo (3,3,1) nonanone-3-oxyl-9, and aza-9-bicyclo It is composed of (3,3,1) nonane oxyl-9.

U.S. Patent No. 3,873,564 discloses compounds and methods for the analysis of enzymes by adding a stable free radical compound having a stable free radical functionality that changes the environment of the free radical functionality when subjected to an enzymatic catalytic reaction. It is described. Depending on the electron spin resonance spectrum change as affected by changes in the environment, the type of enzyme and the activity of the enzyme can be determined. Compounds that have been found to be useful are generally stable nitroxide radicals having enzyme labile functionality. Other compounds include two cyclic nitroxides containing rings joined by chains with enzyme labile functionality.

U.S. Patent No. 3,966,711 discloses 2,2,7,7-tetraalkyl- and 2,7-disspiroalkylene-5-oxo-1,4-diaza substituted in the 4-position by a 1 or tetravalent radical. It is taught that cycloheptane is a powerful photo-stabilizer for organic polymers. They are known to have higher compatibility than their 4-unsubstituted moles, and they can be synthesized from molar animals by known N-alkylation reactions. Preferred substituents at the 4-position are alkyl, alkylene, alkenyl, aralkyl and esteralkyl groups. 1-nitroxyl derived from imidazolidine by oxidation to hydrogen peroxide or percarboxylic acid is also known as a good light stabilizer.

U. S. Patent No. 4,182, 658 describes a method for preventing the polymerization of vinyl aromatic compounds that can readily polymerize during distillation at elevated temperatures in a distillation apparatus in an emergency, for example in the event of a power interruption. The method comprises forcibly feeding each of the distillation vessels of a conventional distillation apparatus a sufficient amount of supplemental polymerization inhibitor with high solubility in vinyl aromatics and long term persistence of potency to prevent polymerization in the distillation vessel. do.

US Pat. No. 4,664,845 describes compositions comprising dinitrophenol in an aromatic hydrocarbon solvent that exhibits the desired low temperature stability that may not be expected and may be diluted with additional solvents used as polymerization inhibitors for vinyl aromatic compounds, The composition further comprises a sufficient amount of phenylenediamine so that when there is no phenylenediamine there is a greater amount of dinitrophenol in the solution than is present in the solution.

U.S. Pat. No. 4,665,185 describes the effective preparation of nitroxyls of sterically hindered amines by oxidation of amines using hydroperoxides at medium temperatures for short periods of time under small amounts of metal ion catalysts to obtain nitroxyls with high yields and purity. The method is described.

US 5,254,760 teaches that polymerization of vinyl aromatic compounds such as styrene is very effectively inhibited during distillation or purification by the presence of one or more stable nitroxyl compounds with one or more aromatic nitro compounds.

US Pat. Nos. 5,545,782 and 5,545,786 describe that nitroxyl inhibitors in combination with some oxygen reduce the immature polymerization of vinyl aromatic monomers during the manufacturing process of such monomers. Even small amounts of air used in combination with nitroxyl inhibitors are said to result in prolonged inhibition time for the monomers.

U.S. Patent 5,711,767 discloses that nitroxide compounds alone or in combination with aromatic amines or phenolic antioxidants such as substituted phenylenediamines provide an effective method of preventing oxidative degradation in gasoline and preventing gum formation. Is described.

US Pat. No. 5,910,232 teaches that the inhibition performance during styrene processing is improved through the addition of stable nitroxide free radicals in the styrene feed and to the reflux of one or more columns. Non-toxic emollients such as phenylenediamine may also optionally be added to the styrene feed and reflux.

EP 0 178 168 A2 describes a process for inhibiting the polymerization of α, β-ethylenically unsaturated monocarboxylic acids during their recovery by distillation using nitroxide free radicals.

European patent application 0 765 856 A1 describes stable acrylic acid compositions in which the polymerization of acrylic acid is inhibited during the distillation process for purification or separation of acrylic acid as well as during transportation and storage. The composition comprises three components: (a) acrylic acid, (b) a stable nitroxyl radical, and (c) a dihetero-substituted benzene compound having at least one transferable hydrogen (e.g., of hydroquinone Quinone derivatives such as monomethyl ether (MEHQ). During the distillation process, transportation and storage, components (b) and (c) are present in polymerization-inhibiting amounts. During the distillation process, oxygen (d) is preferably added together with components (b) and (c).

WO 97/46504 relates to a mixture comprising the following (A) and (B): (A) a monomer containing a vinyl group; And (B) inhibiting immature polymerization of the monomers containing vinyl groups during their purification or distillation, and (iii) a mixture of (B) one or more N-oxyl compounds of secondary amines having no hydrogen atoms at the α-C atoms. 0.05 to 4.5% by weight; And (ii) an effective amount of a mixture comprising 99.95 to 95.5% by weight of one or more nitro compounds relative to the entire mixture (B). The document also describes a method for inhibiting immature polymerization of monomers and the use of mixtures (B) for inhibiting immature polymerization of monomers.

WO 98/14416 states that the polymerization of vinyl aromatic monomers, for example styrene, is inhibited by the addition of stable hindered nitroxy radicals and compositions of oxime compounds.

WO 98/25872 relates to a mixture comprising the following (A) to (D): (A) a compound containing a vinyl group; An effective amount comprising (B) at least one N-oxyl compound of a secondary amine that inhibits premature polymerization of a compound containing a vinyl group and does not have a hydrogen atom on the α-carbon atom and (ii) at least one iron compound. Mixture of; (C) optionally a nitro compound; And (D) optionally a co-stabilizer. The document also discloses a method for inhibiting immature polymerization of a compound (A) containing a vinyl group, and a nitro compound (C) for inhibiting immature polymerization of radically polymerizable compounds and stabilizing organic materials against the deleterious effects of radicals. ) And / or the use of (B) optionally mixed with a co-stabilizing agent (D).

WO 99/20584 discloses that polymerization can be inhibited during the oxygen free production of styrene through the addition of a combination of stable nitroxide free radical compounds and nontoxic phenylenediamine compounds.

CS-260755 B1 relates to the preparation of 4-substituted-2,2,6,6-tetramethylpiperidine nitroxyl as olefin stabilizers.

SU-334845 A1 relates to the inhibition of radical polymerization of oligoester acrylates using imminoxyl radical inhibitors of a given formula.

SU-478838 relates to the inhibition of radical polymerization of oligoester acrylates and the prevention of oligomeric peroxides using binary polymerization inhibitors comprising quinones.

FR 2,761,060 relates to the injection of radical inhibitors based on oxyl-tetramethylpiperidine derivatives into the process effluent to inhibit their premature polymerization during the production of styrene by dehydrogenation of ethylbenzene.

These documents are incorporated herein by reference in their entirety.

As used herein, the abbreviation TEMPO means 2,2,6,6-tetramethyl-1-piperidinyloxy. Thus, 4-amino-TEMPO is 4-amino-2,2,6,6-tetramethyl-1-piperidinyloxy; 4-hydroxy-TEMPO is 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (or known in the art as HTEMPO); 4-oxo-TEMPO is 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy; And so on.

Nitroaromatics and niroxyls are known polymerization inhibitors. Since nitroxils are considered true inhibitors, they are used in combination with nitrophenol compounds (emollients) to provide protection against failure in the inhibitor supply system of the monomer manufacturing plant.

The inventors have found that the addition of nitroaromatics to nitroxyl compounds in aromatic hydrocarbon solvents increases the solubility of nitroxyls in aromatic solvents, which leads to the preparation and shipment of more concentrated solutions of niroxyl in aromatic solvents. It was found that this is possible. Nitroaromatics are also known polymerization inhibitors and, in addition, additives useful in the purification train. Thus, blends of nitroaromatic / nitroxyl / aromatic solvents can be added directly to the purification train of vinyl aromatic monomers or the blend can be further diluted to better control the dosage of the inhibition system.

More particularly, the present invention relates to a method of increasing the solubility of a compound having the following structural formula (I) in an aromatic hydrocarbon solvent, the method comprising adding to the solvent a nitro aromatic having the following structural formula (II). .

Structural formula Ι

Structural Formula II

Wherein R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ are hydrogen, alkyl having 1 to 8 carbon atoms, aryl having 5 to 7 carbon atoms, 5 to 7 carbon atoms Cycloalkyl having, heterocyclic having 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , Halogen (halogen as used herein is independently selected from the group consisting of fluorine, chlorine, bromine and iodine), and / or any two proximity groups may together form a 5-7 membered ring structure and Provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ is NO ₂ , and R ₁₁ and R ₁₂ are hydrogen, alkyl having 1 to 8 carbon atoms, 5 to 7 Aryl having a carbon atom, or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure. Nitroaromatic compounds useful in the practice of the present invention are described in US Pat. No. 5,254,760.

In formula (I), R ₁ and R ₄ have hydrogen, alkyl having 1 to 15 carbon atoms and having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl, R ₂ and R ₃ are alkyl having 1 to 15 carbon atoms and 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl having; X ₁ and X ₂ are independently selected from the group consisting of (1) halogen, cyano, amido, -SC ₆ H ₅ , carbonyl, or alkenyl or alkyl having up to 15 carbon atoms, or (2 ) Together with nitrogen form a ring structure, preferably a 5, 6, or 7 membered ring structure.

The present invention relates to a method of preferably increasing the solubility of a compound having the following structure in an aromatic hydrocarbon solvent:

delete

Wherein R ₁ and R ₄ are hydrogen, alkyl having 1 to 15 carbon atoms and alkyl having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from R ₂ and R ₃ are alkyl having 1 to 15 carbon atoms and alkyl having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of

The moiety represents the atoms necessary to form a 5-, 6- or 7-membered heterocyclic ring, the method comprising adding to the solvent a nitro aromatic having the structure (II):

Structural Formula II

Wherein R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl having 1 to 8 carbon atoms, aryl having 5 to 7 carbon atoms, having 5 to 7 carbon atoms Cycloalkyl, heterocyclic having 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , halogen (Halogen as used herein is independently selected from the group consisting of fluorine, chlorine, bromine and iodine), and / or any two proximity groups may together form a 5 to 7 membered ring structure, provided At least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ is NO ₂ , and R ₁₁ and R ₁₂ are hydrogen, alkyl having 1 to 8 carbon atoms, 5 to 7 carbon atoms Aryl, or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure.

The atoms necessary to complete the above-mentioned ring structure are preferably carbon atoms, but heteroatoms such as O, N, P or S may be present.

As stated above, in one preferred aspect, the present invention relates to a method of increasing the solubility of a compound having the following structural formula in an aromatic hydrocarbon solvent,

delete

Wherein R ₁ and R ₄ are hydrogen, alkyl having 1 to 15 carbon atoms and alkyl having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from R ₂ and R ₃ are alkyl having 1 to 15 carbon atoms and alkyl having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of

The moiety represents the atoms needed to form a 5-, 6- or 7-membered heterocyclic ring, the method comprising adding nitroaromatics having the structure (II) to the solvent:

Structural Formula II

Wherein R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl having 1 to 8 carbon atoms, aryl having 5 to 7 carbon atoms, having 5 to 7 carbon atoms Cycloalkyl, heterocyclic having 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , halogen (Halogen as used herein is independently selected from the group consisting of fluorine, chlorine, bromine and iodine), and / or any two proximity groups may together form a 5-7 membered ring structure, Provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ is NO ₂ , R ₁₁ and R ₁₂ are hydrogen, alkyl having 1 to 8 carbon atoms, 5 to 7 carbon atoms Or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure.

Thus, one of the various classes of cyclic nitroxides that can be used in the practice of the present invention can be represented by the following structural formula:

delete

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above and Z ₁ , Z ₂ and Z ₃ are oxygen, sulfur, secondary amines, tertiary amines, phosphorus in various oxidation states, and unsubstituted Carbon atom or C ₁ -C ₄ alkyl, C ₁ -C ₄ alkylene, halide, carboxy, hydroxyl, CN, amino, amido, carbo (C ₁ -C ₄ alkoxy), keto, oxo, oxyl, C ₁ -C ₄ alkanoloxy, carboxamido, oxymido, CNR ₅ R ₆ and CCONR ₅ R ₆ are selected from the group consisting of carbon atoms wherein R ₅ and R ₆ are hydrogen, alkyl, aryl and Independently selected from the group consisting of acyl. When R ₅ and / or R ₆ are alkyl, they are preferably lower alkyl (eg those having from 1 to 4 carbon atoms, specifically methyl, ethyl, propyl, butyl and isomers thereof).

When R ₅ and / or R ₆ are aryl, they are preferably aryl having 6 to 10 carbon atoms, for example phenyl or naphthyl, furthermore, non-interfering substituents such as lower alkyl groups , Halogen and the like.

When R ₅ and / or R ₆ are acyl, they are preferably acyl of the following structure,

delete

Wherein R ₁₉ is alkyl, aryl, OR ₂₀ , or NR ₂₀ R ₂₁ , wherein R ₂₀ and R ₂₁ are alkyl, aryl or the following structural formula:

delete

Wherein R ₂₂ is alkyl or aryl. When R ₁₉ , R ₂₀ , R ₂₁ or R ₂₂ are alkyl, they are preferably alkyl having 1 to 15 carbon atoms as described above, more preferably lower alkyl having 1 to 4 carbon atoms It is When R ₁₉ , R ₂₀ , R ₂₁ or R ₂₂ are aryl, they are preferably aryl having 6 to 10 carbon atoms as described above.

Various other classes of cyclic nitroxides that may be used in the practice of the present invention may be represented by the following structural formula:

delete

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above and Z ₁ and Z ₂ may be the same or different and are nitrogen or a substituted or unsubstituted carbon atom, for example = C (H) -, = C (CH ₃ )-, = C (COOH)-, = C (COOCH ₃ )-, = C (COOC ₂ H ₅ )-, = C (OH)-, = C (CN)-, = C (NR ₅ R ₆ )-, = C (CONR ₅ R ₆ )-, and the like, wherein Z ₃ , R ₅ , and R ₆ are as described above.

Cyclic nitroxides used in the practice of the invention may also be derived from 5-membered rings. These compounds have the following structure.

delete

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above, Z ₂ and Z ₃ may be the same or different, sulfur, oxygen, primary amine, secondary amine, phosphorus or non-oxidized in various oxidation states Cyclic carbon atoms or C ₁ -C ₄ alkyl, C ₁ -C ₄ alkylene, halide, carboxy, hydroxyl, CN, amino, amido, carbo (C ₁ -C ₄ alkoxy), keto, oxo, oxyl , C ₁ -C ₄ alkanoloxy, carboxamido, oxymido, CNR ₅ R ₆ and CCONR ₅ R ₆ may be selected from the group consisting of carbon atoms, wherein the various R groups are as described above.

The cyclic nitroxides used in the practice of the present invention may also have the following structure:

delete

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above and Z ₄ and Z ₅ may be the same or different and are nitrogen or a substituted or unsubstituted carbon atom, for example, = C ( H)-, = C (CH ₃ )-, = C (COOH)-, = C (COOCH ₃ )-, = C (COOC ₂ H ₅ )-, = C (OH)-, = C (CN)- , = C (NR ₅ R ₆ )-, = C (CONR ₅ R ₆ )-, and the like, wherein R ₅ and R ₆ are as described above.

Another class of cyclic nitroxides that may be used in the practice of the present invention is the following structural formula:

delete

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above, Z ₂ and Z ₃ may be the same or different, sulfur, oxygen, primary amine, secondary amine, and unsubstituted carbon atom or C ₁ -C ₄ alkyl, C ₁ -C ₄ alkylene, halide, carboxy, hydroxyl, CN, amino, amido, carbo (C ₁ -C ₄ alkoxy), keto, oxo, oxyl, C ₁ -C ₄ Alkanoloxy, carboxamido, oxymido, CNR ₅ R ₆ and CCONR ₅ R ₆ may be selected from the group consisting of carbon atoms, wherein R ₅ and R ₆ are as described above.

In addition, two or more nitroxy groups may be present in the same molecule, for example, by linking through one or more Z-type moieties by linking group E as described in US Pat. No. 5,254,760, which is incorporated herein by reference. Can be.

As mentioned above, R ₁ and R ₄ are independently selected from the group consisting of hydrogen, alkyl, and heteroatom-substituted alkyl, and R ₂ and R ₃ are in the group consisting of alkyl and heteroatom-substituted alkyl Selected independently. The alkyl (or heteroatom-substituted alkyl) groups R ₁ to R ₄ may be the same or different and preferably comprise 1 to 15 carbon atoms, for example methyl, ethyl, propyl, butyl, pentyl, hexyl , Heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and the like and isomers thereof, specifically t-butyl, 2-ethylhexyl, and the like. R ₁ to R ₄ are more preferably lower alkyl (or heteroatom-substituted lower alkyl) having independently selected 1 to 4 carbon atoms, for example methyl, ethyl, propyl, butyl and isomers thereof. If heteroatom substituents are present, they may include, for example, halogen, oxygen, sulfur, nitrogen and the like. Most preferably R ₁ to R ₄ are all methyl.

Examples of suitable nitroxide free radicals that can be used in combination with nitroaromatic compounds in the practice of the present invention include, but are not limited to:

N, N-di-tert-butylnitroxide;

N, N-di-tert-amylnitoxide;

N-tert-butyl-2-methyl-1-phenyl-propylnitroxide;

N-tert-butyl-1-diethylphosphono-2,2-dimethylpropylnitroxide;

2,2,6,6-tetramethyl-piperidinyloxy;

4-amino-2,2,6,6-tetramethyl-piperidinyloxy;

4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-oxo-2,2,6,6-tetramethyl-piperidinyloxy;

4-dimethylamino-2,2,6,6-tetramethyl-piperidinyloxy;

4-ethanoyloxy-2,2,6,6-tetramethyl-piperidinyloxy;

2,2,5,5-tetramethylpyrrolidinyloxy;

3-amino-2,2,5,5-tetramethylpyrrolidinyloxy;

2,2,4,4-tetramethyl-1-oxa-3-azacyclopentyl-3-oxy;

2,2,4,4-tetramethyl-1-oxa-3-pyrrolinyl-1-oxy-3-carboxylic acid;

2,2,3,3,5,5,6,6-octamethyl-1,4-diazacyclohexyl-1,4-dioxy;

4-bromo-2,2,6,6-tetramethyl-piperidinyloxy;                 

4-chloro-2,2,6,6-tetramethyl-piperidinyloxy;

4-iodo-2,2,6,6-tetramethyl-piperidinyloxy;

4-fluoro-2,2,6,6-tetramethyl-piperidinyloxy;

4-cyano-2,2,6,6-tetramethyl-piperidinyloxy;

4-carboxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-carbomethoxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-carbetoxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-cyano-4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-methyl-2,2,6,6-tetramethyl-piperidinyloxy;

4-carbetoxy-4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy;

4-hydroxy-4- (1-hydroxypropyl) -2,2,6,6-tetramethyl-piperidinyloxy;

4-methyl-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

4-carboxy-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

4-carbomethoxy-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

4-carbetoxy-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

4-amino-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

4-amido-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine-1-oxyl;

3,4-diketo-2,2,5,5-tetramethylpyrrolidinyloxy;

3-keto-4-oxymino-2,2,5,5-tetramethylpyrrolidinyloxy;

3-keto-4-benzylidene-2,2,5,5-tetramethylpyrrolidinyloxy;                 

3-keto-4,4-dibromo-2,2,5,5-tetramethylpyrrolidinyloxy;

2,2,3,3,5,5-hexamethylpyrrolidinyloxy;

3-carboxymido-2,2,5,5-tetramethylpyrrolidinyloxy;

3-oxymino-2,2,5,5-tetramethylpyrrolidinyloxy;

3-hydroxy-2,2,5,5-tetramethylpyrrolidinyloxy;

3-cyano-3-hydroxy-2,2,5,5-tetramethylpyrrolidinyloxy;

3-carbomethoxy-3-hydroxy-2,2,5,5-tetramethylpyrrolidinyloxy;

3-carbetoxy-3-hydroxy-2,2,5,5-tetramethylpyrrolidinyloxy;

2,2,5,5-tetramethyl-3-carboxamido-2,5-dihydropyrrole-1-oxyl;

2,2,5,5-tetramethyl-3-amino-2,5-dihydropyrrole-1-oxyl;

2,2,5,5-tetramethyl-3-carbetoxy-2,5-dihydropyrrole-1-oxyl;

2,2,5,5-tetramethyl-3-cyano-2,5-dihydropyrrole-1-oxyl;

Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate;

Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate;

Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;

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-tetramethylpiperidin-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'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipamide;

N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -caprolactam;

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)]-s-triazine;

4,4'-ethylenebis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one); And so on.

Nitroxyls used in the practice of the present invention are 4-amino-2,2,6,6-tetramethyl-piperidinyloxy (4-amino-TEMPO), 4-oxo-2,2,6,6-tetra Methylpiperidinyloxy (4-oxo-TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (4-hydroxy-TEMPO), and / or 2,2,6, Preference is given to 6-tetramethylpiperidinyloxy (TEMPO).

Such stable nitroxide free radical compounds can be prepared by known methods. (E.g., U.S. Patent Nos. 3,163,677; 3,334,103; 3,372,182; 3,422,144; 3,494,930; 3,502,692; 3,873,564; 3,966,711; and 4,665,185; It is included.)

Nitroaromatics that can be used are compounds having the following structural formula.
Structural Formula II

delete

Wherein R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl of 1 to 8 carbon atoms, aryl of 5 to 7 carbon atoms, cycloalkyl of 5 to 7 carbon atoms, Heterocyclic of 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , halogen (fluorine, chlorine , Bromine and iodine), and two adjacent groups among R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R _{30 may} together form a 5 to 7 membered ring structure, Provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ is NO ₂ , R ₁₁ and R ₁₂ are hydrogen, alkyl of 1 to 8 carbon atoms, 5 to 7 carbons Or are independently selected from the group consisting of aryl, or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure.

Preferably, the nitroaromatics comprise at least one alkyl group. Such alkyl groups contain from 1 to 8 carbon atoms, for example methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and their isomers, specifically secondary-butyl, tert-butyl, 2-ethylhexyl And the like. More preferably, the alkyl group is a lower alkyl group having 1 to 4 carbon atoms. Preferably, the nitroaromatics are 2,6-dinitro-4-methylphenol; 2,4-dinitro-6-methylphenol; 2,4-dinitrophenol; 2,4-dinitro-6-sec-butylphenol; 2,6-dinitro-4-sec-butylphenol, 2,4-dinitro-6-sec-butylphenol, 4,6-dinitro-2-sec-butylphenol; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-nitro-4-methylphenol; 2,4-dinitronaphthol; 2,4-dinitrochlorobenzene; And 4-cyano-2-nitrophenol; And the like.

The aromatic hydrocarbon solvent used in the practice of the present invention may be any liquid aromatic hydrocarbon in which the nitroaromatic compound is soluble or miscible. Examples of such solvents are benzene, toluene, xylene, ethylbenzene, diethylbenzene, styrene, vinyltoluene, divinylbenzene, alpha-methylstyrene and other alkylated styrene or alkyl-benzenes, all of which are commercially available. will be.

Although the most preferred solvent will depend on the particular application in which the nitroxyl composition can be used, the vinyl aromatic monomers and their hydrogenated precursors, which are typically stabilized, are the preferred solvents for such applications. Thus, for the stabilization of styrene, ethylbenzene and styrene itself are preferred solvents. Similarly, for the stabilization of alpha-methylstyrene, isopropylbenzene and alpha-methylstyrene are preferred solvents.

Typically, the weight ratio of nitroaromatic compound to aromatic hydrocarbon solvent is at least about 1:10. This ratio is preferably from about 1: 4 to about 2: 1, but as will be appreciated by those skilled in the art, the preferred ratio will depend on the particular component selected as well as the temperature and pressure applied.

The compositions of the present invention may be prepared by adding the required amounts of nitroaromatics and nitroxils in any order to the measured amounts of aromatic hydrocarbon solvents. Preferably this addition takes place under stirring.

The weight ratio of nitroaromatic compound to nitroxyl compound may be anywhere within the range of about 99: 1 to about 1:99. Preferably, the nitroaromatic: nitroxyl weight ratio is in the range of about 99: 1 to about 50: 1.

Solutions prepared by the process of the present invention are useful as polymerization inhibitors. When so used, they can be used in their concentrated state or by diluting them with an additional amount of solvent such that nitroxyl is present in the concentrate of about 5% by weight or less, and such dilute concentrates It is easily supplied to the vinyl aromatic reactor distillation column.

Among the vinyl aromatic monomers that can be polymerized-inhibited using the solution of the present invention are styrene, α-methylstyrene, styrene sulfonic acid, vinyltoluene, divinylbenzene, polyvinylbenzene, alkylated styrene, 2-vinylpyridine and the like. These monomers do not need to be reliably stabilized by the presence of the solution, but especially if the monomers are heated as in distillation, they should be considered to be stabilized as long as there is a measurable increase in the time that they can be heated before the initiation of their polymerization. Can be.

Those skilled in the art will appreciate that additional free radical scavengers may be included in the solution to be prepared by the process of the invention, if necessary. For example, as disclosed in US Pat. Nos. 5,545,782 and 5,545,786, air or O ₂ can be added, likewise diether-substituted benzenes having one or more transitionable hydrogens, such as European patent applications Quinone derivatives such as the mono-methyl-ether of hydroquinone disclosed in heading 0 765 856 A1, and other inhibitors known in the art can be added. The above disclosures are incorporated herein by reference in their entirety.

Example

As a control, 4-hydroxy TEMPO was dissolved in ethylbenzene at 25 ° C. to make a saturated solution. Thus the solution formed contained 7.0 wt% of 4-hydroxyTEMPO.

According to the invention, 4-hydroxyTEMPO was dissolved in a 1: 1 blend of 4,6-dinitro-2-sec-butylphenol and ethylbenzene at 25 ° C. to form a saturated solution. The solution thus formed contained 13.9% by weight of 4-hydroxyTEMPO.

2,6-dinitro-4-methylphenol; 2,4-dinitro-6-methylphenol; 2,4-dinitrophenol; 2,4-dinitro-6-sec-butylphenol; 2,6-dinitro-4-sec-butylphenol; Or substituted 2,4-dinitro-6-sec-butylphenol in place of 4,6-dinitro-2-sec-butylphenol and / or benzene, toluene, xylene, styrene, vinyltoluene, divinylbenzene, alpha- Equivalent results can be obtained by substituting methylstyrene or other alkylated styrenes or alkyl-benzenes in place of the ethylbenzenes used above.

In view of the many variations and modifications that may be made without departing from the principles of the invention, reference should be made to the appended claims for the understanding of the scope of protection provided by the invention.

Claims (13)

A method for increasing the solubility of the following structural formula (I) in an aromatic hydrocarbon solvent comprising adding a nitroaromatic compound having the following structural formula (II) to the aromatic hydrocarbon solvent: Structural formula Ι

Structural Formula II

Wherein, in formula (II), R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl of 1 to 8 carbon atoms, aryl of 5 to 7 carbon atoms, 5 to 7 Cycloalkyl of carbon atoms, heterocyclic of 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , Independently selected from the group consisting of halogens (including fluorine, chlorine, bromine and iodine), two proximal groups of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ together are a 5-7 membered ring Structure, provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ is NO ₂ , and R ₁₁ and R ₁₂ are hydrogen, alkyl of 1 to 8 carbon atoms May be independently selected from the group consisting of aryl of 5 to 7 carbon atoms, or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure, In formula (I), R ₁ and R ₄ have hydrogen, alkyl having 1 to 15 carbon atoms and having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl, R ₂ and R ₃ are alkyl having 1 to 15 carbon atoms and 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl having; X ₁ and X ₂ are independently selected from the group consisting of (1) halogen, cyano, amido, -SC ₆ H ₅ , carbonyl, or alkenyl or alkyl having up to 15 carbon atoms, or (2 ) Together with nitrogen to form a 5 to 7 membered ring structure. The method of claim 1, wherein the compound of formula (I) is a compound of formula III: Structural Formula Ⅲ

Ⅲ Wherein R ₁ and R ₄ are hydrogen, alkyl having 1 to 15 carbon atoms and alkyl having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Are independently selected from R ₂ and R ₃ having hydrogen, alkyl having 1 to 15 carbon atoms and having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl,

The moiety represents X ₁ and X ₂ of formula (I), which together with the nitrogen atom form a 5 to 7 membered ring structure. The compound of claim 1, wherein the nitroaromatic compound is selected from the group consisting of 2,6-dinitro-4-methylphenol; 2,4-dinitro-6-methylphenol; 2,4-dinitrophenol; 2,4-dinitro-6-sec-butylphenol; 2,6-dinitro-4-sec-butylphenol; 2,4-dinitro-6-sec-butylphenol; 4,6-dinitro-2-sec-butylphenol; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-nitro-4-methylphenol; 2,4-dinitronaphthol; 2,4-dinitrochlorobenzene and 4-cyano-2-nitrophenol. The compound of claim 2, wherein the nitroaromatic compound is selected from the group consisting of 2,6-dinitro-4-methylphenol; 2,4-dinitro-6-methylphenol; 2,4-dinitrophenol; 2,4-dinitro-6-sec-butylphenol; 2,6-dinitro-4-sec-butylphenol; 2,4-dinitro-6-sec-butylphenol; 4,6-dinitro-2-sec-butylphenol; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-nitro-4-methylphenol; 2,4-dinitronaphthol; 2,4-dinitrochlorobenzene and 4-cyano-2-nitrophenol. The process of claim 1 wherein the aromatic hydrocarbon solvent is selected from the group consisting of benzene, toluene, xylene, ethylbenzene, diethylbenzene, styrene, vinyltoluene, divinylbenzene and alpha-methylstyrene. The method of claim 2, wherein the aromatic hydrocarbon solvent is selected from the group consisting of benzene, toluene, xylene, ethylbenzene, diethylbenzene, styrene, vinyltoluene, divinylbenzene, and alpha-methylstyrene. The method of claim 4, wherein the compound of formula III is 4-amino-2,2,6,6-tetramethylpiperidinyloxy. The method of claim 4, wherein the compound of formula III is 4-oxo-2,2,6,6-tetramethylpiperidinyloxy. The method of claim 4, wherein the compound of formula III is 4-hydroxy-2,2,6,6-tetramethylpyridinyloxy. The method of claim 4, wherein the nitroaromatic compound is 2,4-dinitro-6-sec-butyl phenol. The method of claim 4, wherein the nitroaromatic compound is 2,6-dinitro-4-sec-butyl phenol. The method of claim 4, wherein the nitroaromatic compound is 4,6-dinitro-2-sec-butyl phenol. In a solution consisting essentially of a solvent system and a compound having the structure As a solvent system for the solution, a solution comprising using an aromatic hydrocarbon solvent and a nitroaromatic compound having the following structural formula (II): Structural formula Ι

Structural Formula II

Wherein, in formula (II), R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ are hydrogen, alkyl of 1 to 8 carbon atoms, aryl of 5 to 7 carbon atoms, 5 to 7 Cycloalkyl of carbon atoms, heterocyclic of 5 to 7 carbon atoms, OR ₁₁ , NR ₁₁ R ₁₂ , SR ₁₁ , NO ₂ , NO, CN, COR ₁₁ , COOR ₁₁ , CONR ₁₁ R ₁₂ , NR ₁₁ COR ₁₂ , Independently selected from the group consisting of halogens (including fluorine, chlorine, bromine and iodine), two proximal groups of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ and R ₃₀ together are a 5-7 membered ring Structure, provided that at least one of R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , and R ₃₀ is NO ₂ , and R ₁₁ and R ₁₂ are hydrogen, alkyl of 1 to 8 carbon atoms May be independently selected from the group consisting of aryl of 5 to 7 carbon atoms, or benzyl, or R ₁₁ and R ₁₂ may together form a 5 to 7 membered ring structure, In formula (I), R ₁ and R ₄ have hydrogen, alkyl having 1 to 15 carbon atoms and having 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl, R ₂ and R ₃ are alkyl having 1 to 15 carbon atoms and 1 to 15 carbon atoms substituted by heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen Independently selected from the group consisting of alkyl having; X ₁ and X ₂ are independently selected from the group consisting of (1) halogen, cyano, amido, -SC ₆ H ₅ , carbonyl, or alkenyl or alkyl having up to 15 carbon atoms, or (2 ) Together with nitrogen to form a 5 to 7 membered ring structure.