Sodium 2-Acrylamido-2-methylpropanesulfonic ... - ACS Publications

Chapter 15

Sodium 2-Acrylamido-2-methylpropanesulfonic Acid Polymers as Agents for Controlling Mist in Aqueous Fluids

Downloaded by UNIV MASSACHUSETTS AMHERST on September 7, 2012 | http://pubs.acs.org Publication Date: March 27, 2000 | doi: 10.1021/bk-2000-0755.ch015

Richard A. Denis, Sanjay Kalhan, and Steve R. Twining The Lubrizol Corporation, 29400 Lakeland Boulevard, Wickliffe, OH 44092-2298

This chapter will focus upon the use of polymers as mist suppressants and on the development of tests which can measure mist suppression. Based upon these results, these polymers were added to metalworking fluids and tested in industrial machining operations for their effectiveness as mist suppression agents.

Aqueous fluids are extensively used in many commercial industries as agents for: process efficiency, friction modification, extending tool life, carrying away debris from a work surface, cooling surfaces, carrying additives, and providing other performance properties. During the course of these applications, these aqueous fluids commonly encounter shearing forces; such as high and low pressure spraying, high speed mixing, pumping and mechanical shear. The severity of these shearing forces causes part of the fluid to breakup into undesirable airborne particulates. The overall result is a loss of fluid, a reduction in processing, additional maintenance expenses, and creation of an unsafe work environment. Reduction of mist could be accomplished via enclosures and/or upgrading existing ventilation systems at a considerable capital investment to these industries. Alternatively, mist suppression may be accomplished by use of chemical additives that are shear stable and capable of altering the size distribution of particles which are generated from the breakup of an aqueous fluid. The use of additives in aqueous emulsions for mist suppression has been only recently been explored (1,2,3). In particular, high molecular weight polyethylene oxide (PEO) polymers have received considerable testing and have shown to have some degree of success in reducing mist. However, these polymers have a finite lifetime in the fluid before they shear degrade. Thus, this has led to the development of novel shear stable polymers derived from a highly hydrophilic sodium-2acrylamido-2-methyl propane sulfonic acid (NaAMPS) monomer polymerized with hydrophobic monomers. (4)

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© 2000 American Chemical Society

In Specialty Monomers and Polymers; Havelka, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.

201 Experimental A) Materials:


Sodium-2-acrylamido-2-methyl propane sulfonic acid (NaAMPS) monomer was polymerized with a variety of hydrophobic alkylacrylate and alkylacrylamide monomers. The reactions were performed as solution polymerizations in methanol using the redox radical initiator of sodium persulfate and sodium metabisulfite. B) Instrumentation: The molecular weights were determined on a Waters 150 GPC using a set of Waters Ultrahydrogel 120,250,1000, and 2000 columns (7.8 χ 300 mm), Mobile Phase was 80:20 water.acetonitrile with 0.10 M sodium nitrate, Flow Rate: 0.8 ml/min. (nominal), Column Temperature:35°C, Sample concentration: 1.6 - 2.0 mg/ml, Injection Volume: 200 μΐ, Detection: Differential Refractive Index, Sensitivity: -128, Calibration: narrow PEO and PEG standards, M W = 963,000 to 620 (Polymer Laboratories, Amherst, M A ) . C) Spray Test: The conditions for the Spray Analysis Test were set with a spraying time (t) = 10 seconds, an air pressure of 30 psig and a distance (x) at 38 cm. The solutions were pumped to the nozzle at a rate of 32 ml/min by means of a Sage model 355 syringe pump using a 50 cc syringe. D) Grinder Test: The Grinder Test machined a 1 inch square by 5 inch steel bar stock on an industrial grinder using a 0.5 inch by 8 inch grinding wheel at a removal rate of 1/10,000 of an inch per pass. The fluid pressure of the metalworking fluid was at 80 psi and utilized a 5 gal sump for the test fluid with a pump rate of 1.5 gallons per minute. The enclosed machining operation generated a mist which was measured in concentrations of mg/m by a real time assessment monitor (DataRAM). The probes for aerosol measurement were located 14 inches and 24 inches from the grinding surface. 3

Results and Discussion Development of a Spray Analysis Test for Measuring Mist Reduction In metalworking operations, mist is the by-product from the atomization of a metalworking fluid which has been subjected to shear and extensional flow forces. A qualitative method to measure the reduction of aerosol mist was developed by incorporating the use of a spray nozzle as a source for continuous atomization of the



202 fluid. A fluid that is sprayed through a nozzle at a set psi and at a given air to liquid ratio for a specified time will produce characteristic droplets which are analogous to mist. By placing a screen at a distance (x) away from the nozzle, the aerosol droplets will impact on the screen and form a spray pattern (Figure 1). As the average aerosol droplet size decreases, the dispersion of the spray increases and the result is an increase in the size dimension of the spray pattern. A polymer which can alter the rheological properties of a solution such that it causes an increase in the average droplet size distribution produced by the nozzle will form a smaller spray pattern.

Figure 1. Snrav Analvsis Screen Test

screen

A qualitative method to determine the percentage of aerosol mist reduction can be easily obtained by measuring the diameter (D additive) of the spray pattern from an "additized" aqueous fluid and comparing it to the diameter (D water) of the spray pattern from the "water" baseline. The relative percentage of aerosol mist reduction can be calculated from these spray pattern as follows,

ADGeducuon) = D water- D additive χ 100 D water Using the spray pattern analysis test, the amount of aerosol mist reduction,

^(reduction) obtained for an aqueous solution containing 5000 ppm of a 1 million M W PEO polymer was calculated to be 20%, Figure 2. Similarly, the amount of aerosol mist reduction, AD(redUction) obtained for an aqueous solution containing 5000 ppm of a 2 million M W PEO polymer was calculated to be 40%. These polymeric solutions were sheared in a Waring blender at 25,000 rpm for 2 minutes in order to determine the effect that continuous shear has on the polymer's ability to suppress mist formation. The 1 million M W PEO solution was sprayed and the ADGeduction) value was calculated to be < 6%, representing a 70% drop in mist


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suppression performance as compared to its non-sheared polymeric solution. The solution containing the 2 million M W PEO polymer had a ADGeductioo) of

Sodium 2-Acrylamido-2-methylpropanesulfonic ... - ACS Publications

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