Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/20—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C49/00—Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
  • C07C49/587—Unsaturated compounds containing a keto groups being part of a ring
  • C07C49/603—Unsaturated compounds containing a keto groups being part of a ring of a six-membered ring, e.g. quinone methides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
  • C08F2/40—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation using retarding agents

Definitions

• This invention relates to compositions of matter containing quinone methides and quinone diimides, and methods of using them to inhibit unwanted polymerization.
• quinone methides are used to inhibit the polymerization of vinyl aromatic monomers. Owing to their high reactivity, many of these monomers can undesirably polymerize at various stages of their manufacture, processing, handling, storage, and use. Undesirable polymerization reactions result in a loss in production efficiency because they consume valuable monomer and because they require additional purification steps to remove the undesired polymers from the process equipment and from the monomer product During the purification process, undesired polymerization reactions are particularly problematic for vinyl aromatic monomers as they form unwanted polymer. The purification process is performed at elevated temperatures. Even in the absence of contaminants that promote polymerization, vinyl monomers, particularly aromatic vinyl monomers like styrene undergo self-initiated
• the resultant polystyrene is linear, soluble in the styrene monomer and, therefore, can contaminate the monomer product It is imperative to prevent unwanted polymerization.
• inhibitors and retarders Two categories of compounds have been developed, viz. inhibitors and retarders. Inhibitors effectively prevent polymerization reactions from occurring as long as they are continuously added to the process stream. Inhibitors however are consumed rapidly unless they are continuously replenished. In cases of emergency shutdowns when, for mechanical or other operational reasons, more inhibitor cannot be added, previously added inhibitor will be rapidly consumed. Upon the complete consumption of.
• Inhibitor the unwanted polymerization reactions will occur unabated thereafter.
• retarders slow down the rate of polymerization reactions even though they are not as effective as inhibitors. Whereas inhibitors are consumed rapidly, retarders however are not consumed as quickly but effectively keep polymer content low, therefore they are more reliable In eases of emergency shutdown conditions In which inhibitor replenishment is not possible.
• DNP sulfur and dinitrophenol
• DNP and sulfur retarders however release ⁇ and SOx emissions, respectively. Furthermore, DNP-based retarders are highly toxic, so there is a significant need for a non-toxic replacement tor them.
• One class of compounds that is hoped to function as safer substitute retarders for DNP is based on quinone methide architectures, Quinone methides slow the rate of polymer formation under static conditions and do not need to be frequently re-fed into the process stream. Examples of quinone methide compounds are in US Patent Number 4,003,800. As a consequence of the alky! substituents on position 7 of the quinone methide, these compounds, however, are not stable enough for sustained use in industrial settings. Other applications of more stable quinone methides are found in US Patent Numbers 5,583,247, and 7,045,647.
• inhibitors are typically not to be used alone but are often combined with retarders.
• Compound A is a quinone methide compound with the formula:
• R 1 and R 2 are independently H, C 4 to C 18 alkyl; C 5 to C 12 cycloalkyl; C 7 to C 15 phenylalkyl, and any combination thereof.
• R 1 and Ra are tert-butyl, tert-amyl, tert- octyl, cyclohexyl, a-methylbenzyl or ⁇ , ⁇ -dimethylbenzyl; with tert-butyl,tert-amyl or tert-octyl most preferred, and, R 3 is preferably aryl, or aryl substituted with C 1 to C 6 alkyl, alkoxy, nitro, amino and carboxy, and R3 is also preferably nitrite, methoxy, 4-hydroxy-3,5-di-tert-butylphenyl, an acetylenic group, or phenyl-substituted acetyleno preferably substituted with C 1 to C 6 alky
• Compound B is a quinone diimide compound of the formula:
• substituents R 1 and R 2 are the same or different and are alkyl, aryl, alkaryl, aralkyl group, and any combination thereof, wherein the weight ratio of Compound A to Compound B is about 9: 1 to about 1 :9 and Compound A may be a stable quinone methide.
• quinone methides are 7-cyano quinone methide (2-(3 5 5-di-_3 ⁇ 4 /-butyl-4-oxocyclohexa-2,5- dienyHdeae)acetonitrile, a 7-substituted-quinone methide also called 2,6-di-1 ⁇ 2rr-butyl-7-cyano quinone methide), 4-Benzylidene-2,6-di-tert-butyI-cyclohexa-2,5-dienone also called 7-phenyl quinone methide, 2,6 ⁇ i-1 ⁇ 2r ⁇ buty -(methoxymethylene)cyclohexa-2,5-dienone also called 7- methoxy quinone methide, and 2»6-di-teri-butyl-4-(3,5-di-/erf-butyl-4- hydroxybenzylidene)cyclohexa-2,5-dienone
• Compound B may be a quinone diimide.
• the quinone diimide may be benzoqiiinonediimide compound N, T-(cyclohexa-2,5 ⁇ iene-l,4-diylidene)dibutan-l-ainine, benzoquinonediimide compound (E)-N- ⁇ (E)-4-(4-methylpentan-2-ylimino)cyclohexa-2,5- dienylidene)aniline, and any combination thereof.
• the monomer may be a vinylic monomer. The amount of said composition added to the monomer may vary from 1 to 10,000 parts per million of said monomer.
• the weight proportion of Compound A to Compound B may be between about 9:1 and about 1:9 to about 1:1 and or from 4:6 to 6:4.
• the polymerization may be substantially inhibited.
• the polymerization may be inhibited within an anaerobic environment.
• the inhibition may be more effective than the linear combination of the effectiveness of an inhibitor consisting essentially of Compound B plus the effectiveness of an inhibitor consisting essentially of Compound A.
• Compound A may be a quinone methide compound with the formula
• Ri and R2 are independently H, C to Cm alkyl; Cs to C12 cycloaJkyl; or C ? to Cis phenylalkyl.
• R t and R2 are tetf-butyl, tewf-amyL tetf-octyl, cyclohexyl, a- methylbenzyl or ⁇ , ⁇ -dimethylbenzyl ; with tert-butyl, ter/-amyl or tert-octyl most preferred, and, R 3 is also preferably nitrite, aryl, methoxy, 4-hydroxy-3,5-di-fe?-/-butylphenyl, an acetylenic group, or p enyl-substituted acetyleno preferably substituted with Ci to C « alkyl, alkoxy, nitro, amino and arboxy, and (B) a quinone di
• substituents R t and R are the same or different and are alkyl, aryl, alkaryl, or aralkyl groups wherein the weight ratio of Compound A to Compound B is about 9: 1 to about 1 :9.
• the quinone methide compounds may be (2-(3,5-di-te ⁇ butyM-oxocyclohexa- 2,5-dienylidene)acetonitrile (also called 7-cyano quinone methide), 2,6-di-/e /-butyl-4- (methoxymethylene)cyclohexa-2,5-dienone (also called 7-methoxy quinone methide), 2,6-di-tert- butyl-4-(3,5-di-ie ⁇ buryl-4-hydroxy ⁇ (also called 7-(4- hydroxy-3,5-di-ier/-butylphenyl) quinone met ide) and 4-benzylidene-2,6-di-ier/-butyl- cyclohexa-2.5-dienone (also called 7-phenyl quinone methide).
• the quinone diimide compound may be N,N ⁇ cyclohexa-2,5-diene-l,4- diytidene)dibutan-l -amine, (E)-N-((E)-4 ⁇ 4-methylpentan-2-ylimino)cyclohexa-2 1 5- dienylidene)aniline.
• the weight ratio of Compound ⁇ and Compound B may be between about 9: 1 to about 1:9 or about 4:6 to 6:4.
• FIG. 1 illustrates a graph demonstrating the synergistic inhibition effect of the invention.
• Alkoxy means an alkyl group, as defined herein, attached to the parent molecular moiety through an oxygen atom.
• Representative alkoxy groups include methoxy, ethoxy, propoxy, butoxy, and the like.
• AUcyl means a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom.
• Representative alkyl groups include methyl, ethyl, n- and so-propyl, see-, iso- and fert-butyl, n-octyl, and the like.
• Combination means the combined usage of two or more compounds to yield a composition that inhibits undesirable polymerization.
• Effective Inhibiting Amount means that amount of inhibitor composition which is effective at inhibiting vinyl aromatic monomer polymerization.
• Induction time means the period of time in which in an ideal closed system a composition of matter completely prevents the formation of a particular polymer during a given reaction.
• “Inhibitor” means a composition of matter that inhibits the formation of the particular polymer during an induction time but after the induction time has lapsed, the particular polymer's formation occurs at substantially the same rate mat it would form at in the absence of the composition of matter.
• Retarder means a composition of matter, which does not have an induction time- but instead once added to the given reaction the composition of matter reduces the rate at which the formation of the particular polymer occurs relative to the rate at which it would have formed in the absence of the composition of matter.
• invention is directed to compositions which comprise a quinone methide derivative and a quinone diimide. These compositions inhibit the unwanted polymerization of vinyl monomers.
• the quinone methide derivatives of the present invention commonly have the chemical structure:
• R i and R 2 are independently H, C 4 to C n alkyl; C 5 to C 12 cycloalkyl; or C 7 to C is phenylalkyl.
• and 2 are terf-butyl, terf-amyl, ter/-octyl, cyclohexyl, ⁇ x- methylbenzyl or ⁇ , ⁇ -dimethylbenzyl; with feri-butyl, lerf-amyl or iert-octyl most preferred.
• R3 is preferably aryl, or aryl substituted with C 1 to C « alkyl, aikoxy, nitro, amino, carboxy, or nitrite, or acetylenic group, or acetyleno substituted with a phenyl or substituted phenyl group, or acetyleno substituted with Cj to C « alkyl, aikoxy, nitro, amino, carboxy group.
• the quinone methide derivative is 2 J,5 H-f ⁇ butyl-4-oxocyclohexa-
• 2,5-dienone also called 7-phenyl quinone methide, 2,6-di-1 ⁇ 2r -butyl-4-
• the quinone diimide compound of the present invention comprises a benzoquinonediimide compound which typically has the general formula:
• R i and R 2 are the same or different and are alkyl, aryl, alkaryl, or aralkyl groups.
• the preferable benzoquinonediimide compound is selected from the group consisting of ⁇ , ⁇ '-dialkyl-p-benzoquinonediimides and N-phenyl-N'-alkyl-p-benzoquinonediimides.
• the benzoquinonediimide compound may also be selected from the group consisting of N » N'-di-iSt?c- butyl- ?-benzoquinonediimide,N-pheny1-N'-m
• benzoquinonediimide N-phenyl-N'-( l-methylhexyl ⁇ -benzoquinonediimide,, N-phenyl-N'-(l ,3- dimethylhexyl)- benzoquinonediimide, N,N * -bis( l,4-dimethylpentyl)-p-benzoquinonediimide, N-phcnyl-N'-( l,4-dimethylpentyl)- 7-benzoquinonediimide and N-phenyl-N'-(l ,4-dimethylbutyl)- jj-benzoquinonediimide.
• Preferred benzoquinonediimide compounds comprise N,N'- ⁇ cyclohexa-2 ) 5-diene- 1 ,4-diylidene)dibutan-l -amine and (E)-N- ⁇ (E)-4-(4-methylpentan-2-ylimino)cyclohexa-2,5- dienylidene)aniline.
• unwanted polymerization within a target liquid environment is inhibited by the addition of a quinone methide bearing composition into the monomer solution.
• the composition comprises at least one form of quinone methide and at least one form of phenylenediamine oxidized to quinone diimide.
• the phenylenediamines Prior to making the composition, the phenylenediamines are initially oxidized into quinone diimides. Alternatively, commercially available quinone diimide compounds can be used. The quinone diimide is then combined with a quinone methide and in this form it effectively inhibits polymerization.
• the combination occurs in a manner similar to the methods and procedures described in US Patent 5,955,643 whereby a combination of a stable nitroxide radical and non-toxic phenylenediamine is used to inhibit undesirable polymerization of styrene under anaerobic conditions.
• a significant difference is the fact that in this current invention, in the quinone diimide and quinone methide combination, the phenylenediamine is already oxidized to a quinone diimide and the combination relies upon a quinone diimide in the place of a nitroxide.
• the phenylenediamine is oxidized prior to the injection into the process stream.
• the combination consists of a quinone methide and a quinone diimide.
• the composition may comprise other materials as well as the combination.
• HTEMPO has been combined with other inhibitors to address technical and economic deficiencies with using HTEMPO alone. These combinations, however, did not result in t e combination having an overall inhibiting capability greater than the linear sum of their constituents. Moreover it is often the case that inhibitor combinations produce worse rather than better results than their constituents do alone. Thus it is quite unexpected that mis quinone diimide-quinone methide combination displays such a strong synergistic effect displaying stronger antipolymerant activity than would be expected from the linear combination of the effectiveness of quinone diimide with the effectiveness of quinone methide.
• the quinone diimide need not be generated in situ.
• the use of quinone diimide is taught in US Patents 6,184,276 and 6,376,728. In US Patents 6,184,276 and 6,376,728.
• compositions of the present invention efficaciously inhibit undesirable polymerization of vinyl aromatic monomers under processing conditions.
• processing conditions include but are not restricted to preparation,
• compositions of the present invention are effective at inhibiting the polymerization of styrene over this temperature range.
• the compositions are particularly efficient at inhibiting the polymerization of styrene monomer.
• the total amount of quinone methide derivative and quinone diimide compound used in the methods of the present invention is that amount which is sufficient to inhibit polymerization of vinyl aromatic monomers.
• the conditions, such as presence of contaminants in the system and the process temperature, of the system under which the vinyl aromatic monomer is being processed will determine the amount of the composition used. Accordingly, larger amounts of the inhibiting composition are required at higher processing temperatures and monomer with higher concentrations of contaminants.
• the preferred amount of quinone methide derivative and quinone diimide composition ranges from about 1 part to about 10,000 parts per 1 million parts of monomer. Most preferably, this amount wilt range from about 1 part total to about 1000 parts per million parts monomer.
• the resultant composition By combining a quinone methide compound and a quinone diim ide compound, it is possible for the resultant composition to produce a more effective vinyl aromatic monomer polymerization inhibiting treatment than is obtained by the use of either compound by itself when measured at comparable treatment levels.
• the subsequent synergy or enhanced activity between components allows for the concentration of each of the components to be lowered such that the total quantity of the polymerization inhibitor required is concomitantly lowered while achieving a commensurate level of polymerization inhibition.
• the mole percent of quinone methide compound to quinone diimide compound m the composition will generally vary from about 1:99 to about 99:1, with a mole percent ratio of about from about 30:70 to about 90:10 preferred. Most preferably, the mole percent ratio is about 50:50.
• the uninhibited solution was prepared and tested for unwanted polymer as follows: A solution containing 5.25 g of styrene, 5 ml of n-octane and 6 ml of xylene was prepared in a glass container (Petrotest, ef. 13-0533). Toluene was then added to the solution up to a total mass of 20.882 g. A glass lid (Petrotest, Ref. 13-0514) was fitted to the container, it was placed inside a closed reaction vessel known as a bomb (Petrotest, Ref. 13-1141) and the lid of the bomb was closed. An 8 bar, high-purity nitrogen supply (containing ⁇ 10 ppb oxygen) was used to purge the bomb six times.
• Example 2 The treated solutions were prepared and tested for unwanted polymer according to the procedure in Example 1. As the inhibitors all have different molecular weights, molar concentration was used for this investigation instead of milligrams of inhibitor per 1 kilogram of solution (ppm).
• the two components were in molar concentrations but the total concentration was kept constant at 0.145 mM.
• the mole percent of quinone methide relative to the mole percent of quinone diimide ranged from 0: 100 to 100:0.
• the mole percent of quinone methide relative to the mole percent of quinone diimide ranged from 10:90 to 90:10; more preferably from 30:90 to 90:1 ; more preferably about 50:50.
• a series of samples of inhibitor combinations were prepared.
• the combinations comprised various proportions of quinone methides (in particular 7- c ano quinone methide (Q -CN)) and oxidized (E)-N-((E)-4- ⁇ 4-methylpentan-2- ylimino)cyclohexa-2,5-dienylidene)aniline.
• the effectiveness of the various samples at inhibiting polymerization of vinyl monomers was compared to a linear representation of the "gap" between the effectiveness QM-CN and (E)-N-((EH-(4-methylpentan-2-ylimino)cycIohexa-2,5- dienylidene)aniline by themselves.

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