WATER TREATMENT
Experimental data & analysis
The original and continued primary purpose of these classes of sulfonated polymers is to stabilise Ca 3
( PO 4
) 2 in cooling water applications . This tends to involve more highly alkaline waters than were widely common when the technology was introduced . For these reasons , we chose a screening method with a high saturation ratio with respect to Ca 3
( PO 4
) 2
. In this method , a solution was treated at dosages of 12-30 ppm active polymer . The solution pH of the test samples was maintained at 8.8-9.0 throughout using a borate buffer . After 18 hours of incubation at 70 º C , the samples were filtered using a 0.45-micron membrane and subsequently analysed for residual phosphate and iron content .
Figure 1 shows data for commercial 75:25 and 60:40 AA : AMPS copolymers where percentage phosphate stabilisation ( Y-axis ) is compared to dosage of active polymer ( X-axis ). The 60:40 AA : AMPS shows better stabilisation at lower polymer dosages . The incorporation of hydrophobic monomers was also found to have a particular benefit in further reducing the dosage demand versus the AA : AMPS copolymers .
For our experimental work , the leading candidates all had high levels of sulfonated monomer . We then focused upon the optimisation of MW , the use of a non-ionic monomer and the potential benefits of incorporating a FPA . A series of polymers were synthesised , analysed and subjected to Ca 3
( PO 4
) 2 scale inhibition testing .
Using the projection statistical techniques principal components analysis and projection to latent structures ( PLS ), we 13 measured variables . The PLS regression model showed that scale inhibition is predominately affected by percentage FPA , hydrophobic A and sulfonate variables , which are strongly negatively correlated .
Percentage of hydrophobic C and the use of a chain transfer agent ( CTA ) are positively correlated to higher calcium phosphate stabilisation , while
Figure 4 - Calcium phosphate stabilisation : RPX-3546 vs . AA : AMPS copolymers ( top ) & commercial sulfonated polymers ( bottom )
there is no statistically significant evidence that percentage carboxylate or hydrophobic B are correlated to
Ca 3
( PO 4
) 2 stabilisation ( Figure 2 ).
Our work next focused on the impact of average MW . This is effectively also related to the use of the FPA and CTA which also impact regulation of MW . The materials grouped at < 5,000 Da showed relatively poor performance versus polymers of > 5,000 Da ( Figure 3 ).
The leading candidate material is RPX-3546 , which contains hydrophobic monomer C , a low level of FPA and a MW of > 10,000 Da . Compared to 60:40 and 75:25 AA : AMPS copolymers , it had improved efficacy at 15 ppm polymer dosage ( Figure 4 ). RPX-3546 also worked better than both AA : AMPS : SSS and AA : MMA : SMS : SPME and comparably to AA : AMPS : t-BAM for
Ca 3
( PO 4 ) 2 stabilisation .
Summary & future work
The work presented here has led to the development of a new polymer that demonstrates significant improvement of performance versus most commercial polymers and similar performance to industry-leading AA : AMPS : t-BAM copolymers . The concentration of sulfonated monomer , the incorporation of a specific hydrophobic monomer , polymer MW and the selective use of FPA can contribute to improved efficacy . Based upon several unique properties of the new polymer , we believe that more extensive evaluations will further differentiate this material from all existing materials . Future work will include pilot cooling evaluations , particulate dispersion , iron stabilisation testing , pKa comparison and evaluation of functionality for other mineral scales , such as CaCO 3 and calcium sulfate . ●
* - AMPS Monomer is a registered trademark of Lubrizol , Bayer and Union Carbide
References : 1 . M . L . Standish , 2015 AWT Annual Convention
J j
Chelsea Farmer
PRODUCT MANAGER
RADICAL POLYMERS cfarmer @ mfgchemical . com www . radicalpolymers . com
60 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981