Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – With nonhydrocarbon additive
Reexamination Certificate
2000-06-20
2002-04-23
Howard, Jacqueline V. (Department: 1764)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
With nonhydrocarbon additive
C585S024000, C252S403000, C252S404000
Reexamination Certificate
active
06376728
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and compositions for inhibiting monomer polymerization, particularly the polymerization of alkenyl monomers, such as vinyl monomers.
2. Background and Material Information
Alkenyl monomers such as styrene undergo polymerization if subjected to heat and/or initiators. Such polymerization presents a problem for manufacturers where the monomer polymerizes during manufacturing and purification processes. Patented technology exists for the use of combinations of oxygen with certain inhibitors to prevent premature polymerization of vinyl monomers during processing.
U.S. Pat. No. 4,466,905 discloses a composition for inhibiting polymerization of vinyl aromatic compounds at higher temperatures which comprises using an effective amount of 2,6-dinitro-p-cresol and an effective amount of a phenylenediamine having the formula:
wherein R
1
and R
2
are alkyl, aryl or hydrogen.
The vinyl aromatic compounds contemplated include styrene, substituted styrene, divinyl benzene, vinyl toluene, vinyl naphthalene and the polyvinylbenzenes. As noted at column 4, line 21, of the patent, oxygen must be added to the system in order for the phenylenediamine co-inhibitor to work properly. Oxygen is added separately into the system to achieve a greater concentration of oxygen in the required area. The oxygen employed may be in the form of oxygen or an oxygen containing gas. Air is listed as a useful and the least expensive source of oxygen, and is preferred for purposes of the patent. The amount of oxygen used depends on the number and spacing of oxygen inlets around the distillation column, and how efficiently oxygen and liquid hydrocarbon are mixed therein. The oxygen flow is increased as long as polymer yields are reduced, limited by the amount of oxygen which would yield an explosive mixture.
U.S. Pat. No. 5,959,126 acknowledges that quinones, such as, for example, the benzoquinones, napthoquinones, anthraquinones, phenanthraquinones, and the like can be prepared by oxidizing the appropriately disubstituted aromatic hydrocarbon derivatives, the substituents being hydroxyl or amino groups in the ortho or para positions. The patent notes that some of the prior art processes utilize a catalytic agent to achieve an acceptable reaction rate, while other processes proceed without catalysts. The patent uses activated carbon catalysts to convert phenylenediamine to quinonediamine in almost quantitive yield.
Kotulak, Ludovit et al., “The Effect of 1,4-phenylenediamine Antidegradants on the Photo-Oxidation of Selected Liquid Hydrocarbons”, Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, 162 06 Prague 6
, Collection Czechoslovak Chem. Commun
., Vol 48, pp. 3384-3395 (1983) discusses the antidegradation activity of phenylenediamines and 1,4-benzoquinonediamines. The article states at page 3388 that in the oxidation of both saturated and unsaturated hydrocarbons stabilized with N,N′-disubstituted 1,4-phenyldiamines Ia-If, the corresponding N,N′-disubstituted 1,4-benzoquinonediamines are formed first. Also at page 3388, the article states that “formation of 1,4-benzoquinone diamines II may involve the oxidation with ROO radicals or with oxygen.
U.S. Pat. No. 4,774,374 discloses stabilizing a vinyl aromatic composition with an effective amount of a stabilizer system in which the active member consists essentially of oxygenated species formed by reacting a compound of the formula:
wherein R is C
6
-C
10
aryl or C
7
-C
16
alkaryl; and R
1
is a C
1
-C
12
alkyl or C
3
-C
12
cycloalkyl, with oxygen. The patent states that the oxygenated species may be formed by reacting oxygen in gaseous form or in the form of an oxygen doner with the phenylenediamine compounds. The patent states that the oxygenated species may be formed in situ by the addition of oxygen to a composition comprising vinyl aromatic compound and the phenylenediamine compound.
U.S. Pat. No. 5,648,573 discloses inhibiting the polymerization of vinyl aromatic monomer by the addition of a composition of a benzoquinone derivative and a hydroxylamine compound, in the presence of oxygen or under oxygen-free processing conditions. The benzoquinone derivatives are represented as:
wherein X is N—R or O; R is H, phenyl aryl, nitrogen-containing aryl, or a C
1
to C
7
alkyl group; and R
1
is a C
1
to C
7
alkyl.
Hydroxylamine compounds useful in the patent have the formula:
wherein R
2
and R
3
are the same or different and are hydrogen, akyl, aryl, alkaryl, aralkyl or hydroxalkyl groups.
U.S. Pat. No. 3,674,651 to OTSUKI et al. is said to teach the use of benzoquinone for inhibiting the polymerization of acrylic acid.
Tamir, Lud{haeck over (e)}k et al., “Antioxidants and Stabilizers”, 111
*, Die Angewandte Mackromolekulare Chemie
, 175 (1990), pp. 169-180 (No. 2950) discusses the deactivation of alkyls in stabilizing polymers under conditions of relative oxygen deficiency. In this connection, reactions including N,N′-diphenyl-1,4-benzoquinonediimine (IIb) were studied and discussed (p. 170).
Raevskii, A. B. et al., “Inhibition of Oxidation of Isoprene Rubber with Quinone Imines”, UDC 678.762.3:678.048:541.124, 1968(?); Raevskii, A. B. et al., “Kauch, Rezina”, 1970, 29 (3), pp. 9-10, discloses the inhibition of oxidation of isoprene rubber with quinone imines. N,N-diphenyl-p-quinonediimine was said to inhibit oxidation of SKI-3 rubber. It has been hypothesized that in the inhibition of oxidation of the rubber by the quinonediimine, a high-molecular free radical is formed, whose existence is said to be established by the EPR method.
Taimr, L. et al., “Antioxidants and Stabilizers: Part XCV—A Cooperative Effect Between Antioxidants N-Iso-Proply-N′-Phenyl-1,4-Phenylene Diamine and 2,6-Di-tert-Butylphenol”,
Polymer Degradation and Stability
(1984), pp. 23-35 discusses the reactivity of N-iso-propyl-N′-phenyl-1,4-benzoquinonediimine.
Ignatz-Hoover, Fred et al., “6-QD1—A Review of a Multifunctional Chemical for the Rubber Industry”,
Rubber World
, May 1988, pp. 38-40, discloses the preparation of quinone diimines by the oxidation of p-phenylene diarnine antidegradants. The listed activities include “antioxidant” for polymers and hydrocarbon liquids.
SUMMARY OF THE INVENTION
The invention seeks to provide an improved method of inhibiting polymerization of alkenyl monomers comprising contacting the alkenyl monomers with:
wherein R
1
and R
2
independently of one another are alkyl, phenyl, aryl, alkoxy, or carboxy groups; and oxygen. More specifically, the invention can be directed to polymerization inhibition of vinyl aromatic monomers.
Generally, the ratio of (1) to oxygen is: about 1 to 1000 parts by weight. More preferably, the ratio of (1) to oxygen is about 5 to 500 parts by weight. Most preferably, the ratio of (1) to oxygen is about 10-200 parts by weight.
Generally, the ratio of oxygen and (1) to monomer is about 1 to 2000 per million parts of monomer. Preferably, the ratio of oxygen and (1) to monomer is about 1 to 1000 per million parts of monomer. Most preferably, the ratio of oxygen and (1) to monomer is about 1 to 500 per million parts of monomer.
In one embodiment, R
1
and R
2
independently of one another are: phenyl, alkyl, aryl or alkoxy. Specific compounds (1) include: one or more of [4-(1,3-dimethyl-butylimino)-cyclohexa-2,5-dienylidene]-phenyl-amine; 3,6-Bis-(phenylimino)-cyclohexa-1,4-diene; 3,6-Bis-sec-butylimino-cyclohexa-1,4-diene; 3,6-Bis-(1,3-dimethyl-butylimino)-cyclohexa-1,4-diene; 3,6-Bis-(1,4-dimethyl-pentylimino)-cyclohexa-1,4-diene; 3,6-Bis-isopropylimino-cyclohexa-1,4-diene; [4-(1,4-dimethyl-pentylimino)-cyclohexa-2,5-dienylidene]-phenyl-amine; (4-isopropylimino-cyclohexa-2,5-dienylidene)-phenyl-amine.
The vinyl aromatic monomers being inhibited may be one or more of: styrene, bromostyrene, divinylbenzene, substituted styrene divinylbenzene, &agr;-methylstyrene, vinyl toluene, vinyl naphthalene and polyvinylbenzene.
The oxygen may be present as pure o
Eldin Sherif
Link John
Hercules Incorporated
Howard Jacqueline V.
LandOfFree
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