Browse Prior Art Database

The Effectiveness of Various Food Acceptable Antioxidants for Controlling Leachable Total Organic Carbon (TOC) and Color Throw on Stored Strong Acid Gel Cation Resins.

IP.com Disclosure Number: IPCOM000125143D
Publication Date: 2005-May-20
Document File: 6 page(s) / 384K

Publishing Venue

The IP.com Prior Art Database

Abstract

This work has confirmed and measured the varied effectiveness of food acceptable antioxidants as additives for controlling TOC, color throw and cosmetic color shifts for strong acid gel cation resins in the H+ form. An unanticipated result of this work was that only one of the chemical preservatives, potassium metabisulfite, was suitable for meeting the varied color issues associated with H+ form cation resin and that was the potassium metabisulfite. The majority of the antioxidants evaluated actually showed an increase in TOC levels for the DOWEX gel cation resin in the H+ form as compared to none treated resin samples. Over all the potassium metabisulfite works as well as the 2,6-Di-tertiary-butyl-N,N,-dimethylamino-p-cresol for controlling color throw, TOC and cosmetic color changes as observed for gel type strong acid cation resins upon storage. The potassium metabisulfite would meet the requirements food and drinking water contacting.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 19% of the total text.

Short Communication

The Effectiveness of Various Food Acceptable Antioxidants for Controlling Leachable Total Organic Carbon (TOC) and Color Throw on Stored Strong Acid Gel Cation Resins.

Daryl J. Gisch

The Dow Chemical Company, Liquid Separations, Larkin Laboratory

1691 N. Swede Road

,

Midland

,

MI

48674

(dgisch@dow.com)

Key Words:

Cation Exchange Resins

Leachables

Color Throw

Antioxidants

1. Introduction

Strong acid cation resin in the H+ form have been cited as a source of leachable organics (1-4), that can effect the purity of water being processed.  The resulting leachable TOC’s can also reduce the capacity of a strong base anion resin when used in series with the cation resin.  Stored gel cation resins can impart color to liquids upon their initial exposure.  This is termed color throw and can generally be washed or diluted away by the contacting liquid.  Both color throw and TOC levels rise significantly upon resin storage. Previous work with strong acid gel cation resins in the H+ form has shown this resin type to release significant levels of organic leachables after a relatively short period of storage, 3-5 months (5) and to develop high levels of TOC (>20-200ppm) upon storage with-in the suggested two year shelf-life for the resin. TOC levels can not always be reduced to low levels (<20ppm) with just water rinsing, but may require either a cross regeneration or an acid/water rinse to assure their reduction back to low levels.

Another option would be the introduction of an antioxidant to the resin at the point of manufacture. Dow has applied an antioxidant, 2,6-Di-tertiary-butyl-N,N,-dimethylamino-p-cresol in the production of a select number of our gel cation resins (i.e. DOWEX Guardian 1).  This antioxidant has shown to maintain low TOC levels for stored resin and to reduce/control color throw (6).  The deficiency for applying 2,6-Di-tertiary-butyl-N,N,-dimethylamino-p-cresol in, as a general solution is that upon review with EH&S that this antioxidant is not a FDA regulated food additive, and as such would not be suitable for resins applied in for use with potable water or needing to meet the 21CFR173.25 food contacting regulations (7).

There are a number of varied food acceptable antioxidants, such as those that are listed under the 21CFR180 Subpart D (Chemical Preservatives) (8).  The focus of this effort was to evaluate over time the potential effectiveness of a variety of “generally recognized” chemical preservatives that could be applied to stabilize gel cation resins over time, and still meet the application needs of potable water and for food contacting applications. 

*Trademark of The Dow Chemical Company

The focus of this effort was to evaluate over time the potential effectiveness of a variety of “generally recognized” chemical preservatives that could be applied to stabilize gel cation resins over time, and still meet the application needs of potable water and for food contacting applications. 

2.  Ex...