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INHIBITOR SOLUTIONS WITH LOW FREEZING POINT

IP.com Disclosure Number: IPCOM000240342D
Publication Date: 2015-Jan-23
Document File: 2 page(s) / 15K

Publishing Venue

The IP.com Prior Art Database

Abstract

Acrylic acid or other polymerizable liquid monomers are sometimes stored in large quantities, for example, in storage tanks or trailers. Precautions are typically taken to avoid undesirable polymerization during large-scale storage of liquid monomers, and an inhibitor material is sometimes added.

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INHIBITOR SOLUTIONS WITH LOW FREEZING POINT

    Acrylic acid or other polymerizable liquid monomers are sometimes stored in large quantities, for example, in storage tanks or trailers. Precautions are typically taken to avoid undesirable polymerization during large-scale storage of liquid monomers, and an inhibitor material is sometimes added. Various inhibitors are available for addition to stored monomers, for example, the mono methyl ether of hydroquinone (MEHQ), and phenothiazine (PTZ). PTZ can be preferred over MEHQ, since PTZ can be active in the absence of oxygen.

    For the introduction of PTZ to the liquid monomer, the PTZ is typically dissolved in a non- flammable, non-toxic, high boiling solvent, in a concentration that is as high as possible. The PTZ concentration solution should be as high as possible in order to fit into a very small (and if possible, portable) storage device. Such a solution of inhibitor is called a "shortstop" solution, useful to inject an inhibitor into a storage tank of monomer to stop unwanted polymerization.

    In a practical example, for protection of stored volume of acrylic acid monomer from unwanted polymerization, the final concentration of the PTZ in acrylic acid monomer should be greater than 500 ppm. This final concentration of PTZ in acrylic acid monomer, taken together with the solubility of the PTZ in the solvent(s) at its freezing point, will determine the amount of shortstop solution required for protection of the stored monomer of a full storage tank.

    The freezing point of the shortstop solution should be as low as possible, so it does not need to be freeze-protected. The viscosity of the solution at its minimal usage temperature should be low (for example, <1000 cps).

Several additional characteristics can be listed as desirable in solvent selection:
 Preferably, the solvent should be non-toxic, non-carcinogenic, and not mutagenic or repro-toxic;

 The solvent should not be flammable so it does not contribute in adding extra flammability;

 The solvent should not promote polymerization and be inert; (e.g., should not itself be a polymerizable monomer); and

 The solvent should have a boiling point preferably above the boiling point of the monomer (e.g., > 139°C for acrylic acid).

    Examples of solvents commonly used for dissolving PTZ include N-methylpyrrolidone (NMP), N,N-dim...