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Methods and compositions for inhibiting vinyl aromatic monomer polymerization

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Methods and compositions for inhibiting vinyl aromatic monomer polymerization

Methods and compositions are provided for inhibiting the polymerization of a vinyl aromatic monomer, such as styrene monomer, during elevated temperature processing thereof or during storage or shipment of polymer containing product. The compositions comprise a combination of a quinone methide derivative A) and a phenol compound B). The methods comprise adding from about 1-10,000 ppm of the combination to the monomer containing medium, per one million parts of the monomer.
Related Terms: Phenol Polymer Monomer Quinone

USPTO Applicaton #: #20130030225 - Class: 585 5 (USPTO) - 01/31/13 - Class 585 
Chemistry Of Hydrocarbon Compounds > Product Blend, E.g., Composition, Etc., Or Blending Process Per Se >O Containing >And N Containing >Additive(s) Aromatic

Inventors: Vinod Kumar Rai, Sherif Eldin, Mary King, John Link, Alagarsamy A. Subbiah, H. Kelly Herrington

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The Patent Description & Claims data below is from USPTO Patent Application 20130030225, Methods and compositions for inhibiting vinyl aromatic monomer polymerization.

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The present application is a divisional of allowed U.S. patent application Ser. No. 12/793,226 filed Jun. 3, 2010.


The invention pertains to methods and compositions for inhibiting the undesired polymerization of vinyl aromatic monomers, such as styrene monomer, during processes such as monomer preparation, and purification, and during storage and shipment of products containing such monomers.


Polystyrene is a thermoplastic with many desirable characteristics. It is clear, transparent, readily colored and easily fabricated. The family of styrene polymers includes polystyrene itself, copolymers of styrene with other vinyl monomers, polymers of derivatives of styrene and mixtures of polystyrene and styrene-containing copolymers with elastomers.

ABS (acrylonitrile, butadiene-styrene) resins have enjoyed tremendous commercial popularity for many years as durable, temperature and solvent resistant elastomers. On the other hand, styrene plastics are commonly used for packaging, including foams and films, coatings, in appliance fabrication, for housewares and toys, lighting fixtures and in construction materials.

It is well known that styrene monomer readily polymerizes when heated or exposed to light. Heat polymerization is rapid. In fact, polymerization increases with increasing temperature. This polymerization is undesirable during many stages of the manufacturing, processing, handling, storage and use of styrene monomers.

Common industrial methods for producing styrene include a variety of purification processes, including distillation, to remove impurities. Unfortunately, purification operations carried out at elevated temperatures result in an increased rate of undesired polymerization. Polymerization, such as thermal polymerization, during the monomer purification process, results not only in loss of desired monomer end- product, but also in loss of production efficiency caused by polymer formation or agglomeration on process equipment. In heat requiring operations, such agglomeration adversely affects heat transfer efficiency.



In accordance with aspect of the invention, a method is provided for inhibiting the polymerization of a vinyl aromatic monomer such as styrene monomer, i.e., ethylbenzene. The method comprises adding an effective polymerization inhibiting amount of a combined treatment to the monomer medium. The combined treatment comprises (A) a quinone methide derivative and (B) a phenol compound. From about 1-10,000 ppm of (A) and (B) collectively is brought into contact with the requisite vinyl aromatic monomer based on 1 million parts of the monomer. The method may, in other aspects of the invention, comprise the step of heating the monomer and, in another aspect of the invention, the monomer may be distilled to remove impurities therefrom.

In another aspect of the invention, a vinyl aromatic monomer anti-polymerization composition is provided which comprises a liquid carrier and dissolved or dispersed therein (A) a quinone methide derivative and (B) a phenol compound.

In another embodiment, the quinone methide derivative is 2,6-di-tert- butyl-4-benzylidene-cyclohexa-2,5-dienone.

In another aspect of the invention, the phenol compound (B) is 2,6-di-t-butylphenol.

In another exemplary embodiment, a liquid carrier such as a non-polar organic solvent is provided with the combined treatment (A) and (B) dissolved or dispersed therein.



In accordance with the invention, both a quinone methide derivative A) and a phenol compound B) are conjointly utilized to inhibit polymerization of a vinyl aromatic monomer such as styrene.

The quinone methide derivatives generally have the formula:


R1 and R2 are independently H, C4 to C18 alkyl; C5 to C12 cycloalkyl; or C7 to C15 phenylalkyl.

Preferably, R1 and R2 are tert-butyl, tert-amyl, tert-octyl, cyclohexyl, α-methylbenzyl or α,α-dimethylbenzyl; with tert-butyl, tert-amyl or tert-octyl most preferred.

R3 is preferably aryl, or aryl substituted with C1 to C6 alkyl, alkoxy, hydroxy, nitro, amino, carboxy, or mixtures thereof.

Means for preparing these compounds may be found in U.S. Pat. No. 4,032,547, the contents of which are wholly incorporated by reference to herein.

Preferably, the quinone methide derivative is 2,6-di-tert-butyl-4- benzylidene-cyclohexa-2,5-dienone.

The phenol compounds B) that may be utilized generally have the formula:

wherein R4 and R5 may be the same or different and are chosen from C1-C20 alkyl, C1-C30 alkaryl and substituted C1-C30 alkaryl, R6, when present, is selected from C1-C20 alkyl, thiophenol, substituted thiophenol, C1-C40 alkanoic acid ester, C1-C30 alkaryl, substituted C1-C30 alkaryl, C1-C6 alkylamino, C1-C6 alkoxy, amine, polynuclear aryl and substituted polynuclear aryl.

At present, the preferred phenol B) compound is 2,6-di-t-butylphenol. Exemplary phenols include 2,6-dipropylphenol, 2,6-diethylphenol and 2,6-dimethylphenol. Also mentioned as exemplary are the hindered phenols in accord with the above formula wherein R4, R5 and R6 are all present. These include: 2,6-di-t-butyl-4-methylphenol 4,4′-thiobis-(6-t-butyl-2-methylphenol) octadecyl 3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate 4,4′-methylenebis(2,6-di-t-butylphenol) 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene 2,6-di-t-butyl-α-dimethylamino-p-cresol 2,6-di-t-butyl-4-secbutylphenol 2,2′-methylenebis(4-ethyl-6-t-butylphenol) 2,2′-methylenebis(4-methyl-6-t-butylphenol) 2,2′-methylenebis(6-(1-methylcyclohexyl)-p-cresol; and 2,2′-methylenebis(4-methyl-6-cyclohexylphenol)

The compositions of the present invention are effective at inhibiting polymerization of vinyl aromatic monomers under processing conditions. These processing conditions include but are not limited to preparation, purification, distillation and vacuum distillation processes.

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Application #
US 20130030225 A1
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Other USPTO Classes
585/3, 252404
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