Polyacrylamide Emulsions Handbook Publishing : Altavia Connexion - 11/2013 Introduction

1. General description Standard Inverse Emulsion Dewatered Emulsion zzStandard Emulsions These are dispersions or suspensions of a hydrogel (hydrated polymer) of water soluble polymer in a hydrocarbon. They are two-phase heterogeneous systems. The hydrogel is in the shape of microbeads of 1 micron average diameter, it can be considered as a soft solid, their consistency is similar to rubber. The water proportion varies from 20% to

40% of the final product, depending PolymerPolymer Dry Dry on the grade. Most of SNF’s standard HydrHyogeldrogel PolymerPolymer emulsions have a name starting by the ParticleParticle ParticleParticle two letters EM, and some others have a name starting by EMR or FB.

zzDewatered emulsions

Standard Inverse Emulsion Dewatered Emulsion d Inverse Emulsion Dewatered Emulsion Dewatered polyacrylamide emulsions Standar Oil Oil

differs from standard by the fact Oil Oil StabilizersStabilizers InverInvterserters

Inverters

Inverters Stabilizers Stabilizers

Oil that they contain less than 6% water, Oil Oil with the result that the hydrogel has StandarStandard Invd Inverseerse Emulsion Emulsion Oil DeDewawateredtered Emulsion Emulsion become almost the dry polymer itself. The consistency of the polymer is similar to plastic material. Most dewatered polyacrylamide emulsions from SNF

have names starting by DW.

Particle Particle

Particle rticle Polymer Pa

Hydrogel Hydrogel

Polymer olymer

EmulsionP

In summary, all emulsions are suspensions

Polymer Polymer

Dry Cationic Dry of solid particles. Emulsions have a liquid Polyacrylamide aspect but they are not pure liquids nor powders liquid blends. Nevertheless they can be Storage Anionic handled as liquids. But special care must Dewatered be taken in order to avoid difficulties inherent to the fact that they are not homogeneous isotropic liquids. for the emulsions than for powders. In general, emulsions outperform powders on a dry polymer basis and 2. Differences between some polymers, with specific chain polyacrylamide emulsions configurations, can only be prepared in and powders emulsion form. Handling of emulsions using pumps is simpler than powders and in many 3. Emulsions are complex cases, in-line injection can be used, avoiding the need for an aging tank. liquids Furthermore, dissolution times are much Polyacrylamide emulsions can be shorter and there are almost no solubility handled as liquid products, but they problems. are not simple liquids. So it is absolutely necessary for users, prior to any Unlike powders, emulsions are complex operation, to be informed of the specific multicomponent products which include recommendations that SNF provides polymer, surfactants, oil, and water. hereafter and which concern : Packaging and transport costs are zzhow to handle them greater for emulsions. Powders are very zzwhat care should be taken stable during storage whereas emulsions show some instabilities (physical settling, zzwhat are the problems inherent to skin formation etc.). The presence of oil the nature of emulsions and surfactants involve more regulations zzhow to overcome these problems

Polyacrylamide Emulsions Handbook 1 Storage and handling

4. Storage and handling of zzEffect of very cold or freezing temperature of 20°C in a warehouse, is emulsions : basic principles temperatures placed, for several hours outside where the temperature is 5°C. The water zzEmulsions must be stored inside a Most often this happens when an vapour contained in the free volume building at a constant temperature emulsion is stored outside and when the above the product condenses and between 5°C and 30°C. container is not closed. Emulsion has a drops of water formed on the roof of the tendency to dry-up especially when it zzDuring the storage and handling, the container fall down on the surface of the is a thin layer. This happens on surfaces emulsion must not be contaminated emulsion, creating local coagulations.» or walls which have been temporarily by water. Gel formed looks like white stringy lumps wetted by the emulsion. The upper floating on the surface or suspended to zzEmulsions must not be in a situation surface of the product in the container the cover of the drum or container. where the surface can dry-up by (drum, pail, etc...) will behave the ventilation. same way, especially if the container zzWater contamination zzEmulsions must be sheared as little is open to air. As polyacrylamide is as possible. Pumping, filtering, stirring very easily film-forming, when this layer There are also problems in the case etc. must be applied with maximum is submitted to freezing it become a of water contamination or if the care. skin. Polyacrylamides are film forming, components of the pump have not been dried properly after washing with zzIt is highly recommended to follow so when a layer is subject to freezing water, or with the involontary backwash SNF’s recommendations for equip- temperatures, a solid gel like skin is of dissolution water during shut off of the ment and conditions for storage and quickly formed. This skin can finally be system. Design of the make-up system handling. removed from the surface, fall in the product and contaminate the emulsion is critical and must be made in such a zz In the case of any doubt, it is highly with soft solid large lumps which cannot way that there is no possibility of water recommended to obtain the advice be re-homogenized. back-flow from the main water supply of a technician from SNF. into the emulsion piping. zzEffect of cycles of warm and Also any other contact between water Notes to readers : and emulsion (like rain for example) will - A common confusion is made by users of emulsions cold temperatures between the commercial form and the final solution generate white stringy lumps. of the polymer obtained from this emulsion. The observations are called raincycle. Too much shear applied when handling In the following paragraphs we call emulsion the A typical example of raincycle is pollution by foreign matters or dried commercial product described in page 2 as a described below : polymer. polymer suspension in oil. After its dilution in water, a container of emulsion initially at a this emulsion is destroyed and the result is a true solution of polymer in which are dispersed droplets of oil which give the solution it’s white color. - Technical details and information on all equipment described in the following paragraphs are found in the FLOQUIP brochure available on request from SNF or it can be downloaded from the www.snf- group.com website.

5. Storage and handling of emulsions : List of situations and operations Lumps, skins, gels etc. in the emulsion zzNormal emulsions The main causes for the formation of lumps, skins and gels are: zzemulsions are submitted to very cold or freezing temperatures. zzemulsions undergo cycles of warm and cold temperatures. zztoo much shear is applied zzwater contamination zzpollution by foreign matter or by dried polymer

2 Polyacrylamide Emulsions Handbook Storage and handling

how much an emulsion will settle. It depends on the grade, the batch, the temperature of storage and many other parameters. In most cases, the oil phase layer cannot be observed before 3-4 months. For dewatered emulsions, no settling can be observed during the first 12 months.

zzHow to avoid problems Emulsions which are going to be stored for long periods (more than 1 month) should be homogenized before use. Homogenization must be made by gentle agitation and short periods.

zzRecommendations concerning agitation Too strong or too long agitation can provide too much shear to the emulsions After the shelf life of an emulsion and destabilize them. Agitation by has been exceeded, free flow recirculation is not recommended, but gravity filtration from container in case where there is no other way, to container is recommended to avoid the use of pumps giving a strong recover the emulsion. shear and any device creating an increase in pressure drop in front of the pump (ex : check valves). Agitation by sparging with air (only dried air) is also possible but less area bag filter having a mesh size of 750 zzDewatered emulsions recommended. For dewatered emulsions, the situation microns and above (See “Filtering an is different. They are not concerned emulsion”, page 4). by raincycle. As the content of water FLOQUIP SE SS is very low there is no formation of skins For customers supplied in standard 1 and lumps during freezing or when they tonne containers (tote-bin, IBC), SNF are submitted to cycles of warm and recommends specifically designed cold temperatures. equipment called the Floquip SE for this Therefore the only caution to be operation. followed is that dewatered emulsions must be stored at temperatures above For bulk deliveries, filtration at reception 5°C. Below 5°C they become very thick is recommended between the truck and below 0°C they do not flow and and the storage tank. have a consistency of butter. zzImportant information Settling Therefore, even if the final user has zzMain observations appropriate storage facilities and follow After some time in storage a layer of oil strictly all SNF’s recommendations, (translucent, amber...) appears at the problems can still occur during transport top of the product and a thickened or during intermediate storages. layer of emulsion appears at the SNF invites its customers to be prepared bottom. to have to restore the product as it is The reason for this is that the internal described here. dispersed phase (the hydrogel of polymer) has a higher density than zzHow to restore the product the continuous oil phase, so they In such a situation, SNF recommends have a natural tendency to separate. to transfer by gravity, without previous Emulsions start to settle as soon as they agitation, in a free-flow mode to another are left without agitation. It is a normal container, while passing through a large behavior. It is very difficult to predict how fast and

Polyacrylamide Emulsions Handbook 3 Storage and handling

Manual Filtering Filtering an emulsion can also occur during the storage (due to temperature differences, UV zzGeneralities light etc.), and some pails may behave Emulsions are filtered at 300 microns differently within the same batch, quite after production and before at random. packaging. Filtering an emulsion is an It is absolutely impossible to predict or operation which apply shear on it, and control such limited color changes. This shear can destabilise the emulsion. So it parameter is not considered as a quality is recommended to avoid as much as issue. Performance studies versus color possible to do filtrations, and proceed changes have been made on different only when necessary. applications. They have concluded that color fluctuations have no impact zzWhen to filter on the performance. When the presence of lumps, gels, skins etc. is observed in the emulsion. See Pumping an emulsion paragraph “Lumps, skins, gel, etc… in Among the difficulties of pumping an Typical filter bags for filtering an emulsion the emulsion” page 2. emulsion are those generated by the following actions occurring during the zzHow to filter handling of the emulsions: SNF recommends to filter through a bag zzshearing with a large area. The recommended zzpinching or gripping mesh sizes are 750-1000 microns. The zzrubbing best process is to transfer the emulsion to Such actions happening repeatedly be filtered by gravity in a free-flow mode lead to the destabilization of to another similar empty container. For the emulsion. Polymer particles filtration of large quantities (e.g. transfer agglomerate, form lumps that stick on from tank-truck to a storage tank) in-line equipment. This mostly take place in the filtration can be made using a house pumps. filter equipped with the same kind of The importance of these difficulties bags. depends on the pumping conditions. Two critical parameters must be zzOther recommendations considered : pressure drop and Avoid filtration at mesh size below 750 cleanliness. microns. Avoid use of small diameter piping. In line filtration just before use is Pressure drop not recommended. Do not agitate the The pressure drop at the discharge of emulsion before filtration. Emulsions of different colors the pump is created by : zzimportant pipe length Color of the emulsions zzSmall pipe diameter Most of the emulsions are opaque, zzElbows on the lines some are slightly translucent. The most general shade is off-white, some zzEquipment on the lines (especially are creamy yellowish, some greenish mass flow meter) and dewatered emulsions (DW) are zzHydrostatic pressure milky white. As emulsions are multi- zzValves and check valves phase systems and are composed of The higher the pressure drop at the sometimes more than 10 components, discharge of the pump, the more slight color changes which are impossible shearing gripping and rubbing will take to control may occur. Variations can place in the pump. come from stabilizers, residues of the catalytic system, surfactants and oil which are never totally pure products, slight differences of raw material between suppliers etc. Furthermore, slight differences in statistical distribution of molecular weight of the polymer and size of the beads of polymer may generate changes in the refractive index of the components and lead to slight color variations. Color changes

4 Polyacrylamide Emulsions Handbook Storage and handling

Cleanliness Lower friction will limit fouling Peristaltic pump It is well known that emulsions left on a surface in open air conditions will dry- up. After a few hours appears a film/ skin that sticks to the surface. When this happens in an equipment which is used regularly but discontinuously and is never cleaned, several skins/films can be deposited always at the same place and a thick crusty layer develops. After a while, this layer will finally detach from where it has been formed and contaminate the product. Finally these particles may arrive in the pump and if they do not plug or block it immediately, they will nevertheless affect its running in a way which will generate shearing gripping and rubbing.

Result of a bad maintenance and of an inapropriate installation.

SNF has extensive experience on three kinds of metering pumps that work with emulsions

zzPiston/membrane pumps zzProgressive cavity pumps zzPeristaltic pumps

Pumping experience Standards emulsions Dewatered emulsions End-users use metering-pumps to feed When pumping standard Piston/membrane pumps and the emulsion in the water through polyacrylamide emulsions (EM, EMR, progressive cavity pumps are often used. various make up systems to prepare FB…) all three kinds of pumps can be SNF does not recommend this. In cases the polymer solutions. Every end user used. of high pressure drop at the discharge of polyacrylamide emulsions has its SNF recommends the progressive cavity of the pump or presence of particles of own specific operating conditions pumps for all normal and usual cases. polymer as described above, pinching, and equipment. In order to anticipate In case of high pressure drop at the gripping, and rubbing is increased and pumping difficulties it is necessary to discharge of the pump or if there is on dewatered emulsion generate hard know the behaviour of all kind of pumps a presence of polymer particles as particles which can block very quickly under various conditions, SNF has a long described above, a peristaltic pump the pump and even destroy it. experience on this subject. is recommended. When piston/ There are many kinds of metering- membrane pumps or progressive cavity When pumping dewatered pumps. Some have been tested in the pumps are used, pinching or gripping polyacrylamide emulsions (DW…), past and have been given up because and rubbing of the emulsion is increased peristaltic pumps are highly of very bad behaviour when used with and plugging after a long period of use recommended by SNF. any type of emulsions. These are, for can happen. example, gear pumps, lobular pumps, pallets pumps… and all pumps providing When there is a high pressure drop too much shearing, pinching, gripping, at the discharge of the pump, SNF and rubbing. The more sensitive part is recommends using peristaltic pumps for the mechanical seal. standard emulsions.

Polyacrylamide Emulsions Handbook 5 Storage and handling

Spills drying and exchange between outside Spills problems may occur. Oil absorbing and inside. They also must be filled powders, sawdust, paper can be used completely to have the minimum void to absorb the spills of emulsion on floor. space above the product. It is important to remove quickly the After a first opening and partial resulting thick mass, because it turns consumption the package must quickly to a hard crust stinking to the be closed tightly and complete floor which is very difficult to remove consumption must take place rapidly. even with high pressure water. In case (Because of the increasing void space of spills, SNF recommends also: above the product, the surface of the emulsion can start drying, coagulate zzfor small spills (i.e. few liters) : wipe and create a skin) the spill with large paper towels as well as possible, and then use high pressure zzStorage tank water to clean the ground. The tank has to be vertical with a conical zzfor important spills : wipe the pro- bottom to help unloading; it should also pumps need to be dried before duct in a corner with hand-scrapers be fitted with an inspection manhole to any contact with emulsion. For this and make a dam with planks and facilitate cleaning. reason a simple rinse with solvent is sand around to maintain the emulsion For anionic emulsions, stainless steel, recommended. and then pump it. After pumping, put Polyester Fiber Glass (FRP) or crosslinked Cleaning of items of equipment (pumps, sawdust or absorbers or directly wipe polyethylene are suitable. For cationics, valves, fittings, filter cartridges etc.) the ground with towels. Then use high FRP tanks or polyester glass coated steel which have contained emulsions follow pressure water to clean. tanks are preferable to avoid formation the same rules as the tanks. of rust at the interface between air and As described above, the complete In any case, avoid absolutly to add the product, which may occur with a washing of storage tanks takes time water directly on the spill because the stainless steel tank. and requires operations which are not amount of water necessary for a good Insulation and external electric heating easy. This can be done once a year dilution is very high. are necessary for outside tanks. or, preferably, once every three years, depending on the circumstances, Cleaning or when it is absolutely necessary for On the surface of any equipment which specific reasons. Complete washing has been in contact with an emulsion, a must be scheduled in advance and 20 - 50 rpm thin film remains which will dry (solvent takes at least two days. and water will evaporate) and become All contaminated cleaning solvents a skin of polymer. In general it is highly and solids must be incinerated. recommended to let this film/skin remain Contaminated water must be treated 600 as such, or just simply rinse. Before any by normal methods. rinse it is advised to drain the emulsion 2150 as much as possible and then rinse with Exposure to high and very solvents (kerosine, mineral spirits). low temperatures zzFull cleaning Emulsions which have been submitted 2950 to prolonged periods of storage 0 For the full cleaning of a tank, the 45 at temperatures far beyond those Inclined 1000 recommended procedure is as follows paddles recommended (5°C-30°C) can still be 80 : Remove as thoroughly as possible the used after restoration. Nevertheless, the remaining emulsion (dry or wet) on the loss of product during the restoration is different parts of the tank, by rinsing usually quite large. 1500 with solvent (same as above) or, when Ø 100 there are large deposits which cannot 300

Storage be removed by a simple rinse, it is 300 necessary to wipe manually. Emulsion must be stored inside a building Ø 100

Then fill the tank with hot water and at a constant temperature between 1500 add 2% of caustic. Let the polymer 5°C and 30°C.

swell and degrade as long as necessary Small packages recommended

80

paddles

(sometimes it may take more than one by SNF are plastic pails 1000 Inclined

day). Then rinse with water or preferably (polyethylene), full opening plastic 45 use high pressure water to finish the drums, one tonne containers 0

cleaning. (tote-bins, IBC). These packages must 2950 After any cleaning using water, all be closed tightly in order to avoid

the equipment, storage tank, pipe, 2150

6 Polyacrylamide Emulsions Handbook

600 20 - 50 rpm Storage and handling zzAgitation Compatibility of emulsions Polyethylene tubing During storage, emulsion can settle. with materials There are many situations where the motionless surface of the product can zzEmulsions contain or provide dry-up, for example when the product at the same time : is left in its original packaging partially zza solvent which reacts with certain empty, or left opened, or opened plastics and rubbers ; frequently. zza polymer which reacts with certain It is necessary to homogenize regularly metals ; an emulsion by agitation, especially when the time of storage of a tank is zza pH which varies with the type of higher than 10 days. product, neutral for anionics, acidic for Homogenization must be made by cationics ; gentle agitation for short periods. zzand in certain cases, chloride ions An agitation either too strong or to which enhance corrosion. prolonged may apply to much shear to an emulsion and destabilize it.. The general compatibilities are shown in the following tables : Typical examples of how to proceed: PLASTICS zzPails can be shaken 4-5 times by hand before use. ANIONICS CATIONICS Plastic good good zzDrums are not well adapted for long time storage, because it is not conve- Plasticised PVC (hoses) very poor very poor nient to provide agitation to them. Polyethylene high density medium medium For full opening drums it is possible to Polyethylene low density poor poor adapt a stirrer. But the preferred way is Crosslinked polyethylene good good to transfer to an adapted storage tank Fluorised polyethylene good good of 300-400 liters equipped with a stirrer. Polypropylene medium medium The stirring time recommended is 30 PTFE very good very good min. a week or 10 min. every 2/3 days PVDF very good very good and just before use. Fiberglass (FRP) good good zzFor containers (tote bins) it is possible Polycarbonate good good to adapt a stirrer to the hole but the Polyamide (nylon) good good best is to use the FLOQUIP SE system,. Plexiglass medium medium Stirring time recommended : 10 min. ABS medium medium every 2/3 days and just before use. zzStorage tanks must be equipped with a stirrer with large blades rotating at low speed (ex : 20 rpm with 1 meter METALS diameter blades for 30 tonnes). Stirring ANIONICS CATIONICS time recommended: 30 min. 2 times a Carbon steel very poor very poor week or 10 min. every 2 days. Galvanised iron very poor very poor Stainless steel 304 very good medium Stainless steel 316 very good medium (some rust) Hastelloy very good good Steel coated with polyester and glass flakes very good very good Aluminium poor very poor Copper poor very poor Zinc very poor very poor

Polyethylene is used for the transport results. The type of equipment and of emulsions, but the oil has tendency the materials used for the storage and to migrate in low density polyethylene handling of emulsions are very critical decreasing the drum strength. Treated due to the very high quality required by polyethylene (fluorinated microfibers) many applications. are sometimes used with very good

Polyacrylamide Emulsions Handbook 7 Dehydrated emulsions

RUBBERS This leads to the conclusion that only Viton (FPM) and Perbunan (NBR) are In the emulsions the solvent is the component which can affect the stability of rubbers. suitable for contact with the emulsions. The following table shows the behaviour of different rubbers after immersion in the solvent Jerricans, drums and containers during 4 weeks in polyethylene are often used for Abbrev. % increase of weight transport. If they are non-fluorinated, Viton (fluoro-elastomer of vinyldienne) FPM less than 0.1 it is necessary to use high density, Perbunan NBR 0.1 thick-walled equipment in order to (nitrile/rubber butadiene-acrylonitrile) reduce softening due to the plasticizing Hypalon CSM 0.3 effect. (chlorosulfonated polyethylene) Aflas 150 TFE/P 0.4 (tetrafluorethylene-propylene) Perbunan (food grade) NBRL 1.2 Therban (hydrogenated Perbunan) HNBR 2 Hypalon low density CSMh 8 Perbunan low density NBRh 11 Silicon Si 58 Ethylene propylene diene low density EPDMh 61 Silicon low density Sih more than 80 Ethylene propylene diene EPDM more than 80

Blends of emulsions 6. Dehydrated emulsions This improvement in stability affects : zzthe settlement which is negligible Sometimes situations arise when it SNF provides dehydrated emulsions over a period of more than one year; may be necessary to blend different (many of them have the prefix DW, zzno lumps or skin formations when the emulsions. Most often this happens eg DW 533, which is the dehydrated product is stored in cold conditions when there is a product change at a equivalent of EM 533). These products or submitted to cycles of warm and customer site. Maximum care must be are obtained from normal emulsion cold temperatures or left in conditions taken with blends of different emulsions. after removal of the water content. where the surface of the product Most of SNF’s emulsions are compatible This results in a more concentrated can dry. with each other, but so many different polymer content. These products blends are possible that it is highly can be considered to be dispersions recommended to check and get of polymer in oil. The advantage advice from SNF before proceeding. of this form is the improved stability compared to the normal emulsions. Two difficult cases : zzBlends between an emulsion from SNF and an emulsion from a competitor are to be avoided. Some components (particularly surfactants and oil) are different and can be incompatible. If there is no other way it is absolutely necessary to make compatibility tests. zzWhen a tank has been emptied but not washed and a small amount of the former product remains in the tank, loading the new product on top may very often lead to problems, espe- cially when the tank has no agitator. Generally what remains is thickened product. So it is better to completely clean the tank and then load the new product.

8 Polyacrylamide Emulsions Handbook Making the polymer solution

Inverse Emulsion Inverted Emulsion Dissolved Polymer

Polymer Polymer Polymer Hydrogel Hydrogel Hydrogel

Particle Particle Particle polymer polymer polymer polymer polymer polymer

Inverse Emulsion Inverted Emulsion Dissolved Polymer Inverse Emulsion Inverted Emulsion Inverse Emulsion Inverted Emulsion Dissolved Polymer Dissolved Polymer Water

Oil Inverters Water Water Water Water Water

StabilizersOil StabilizersOil StabilizersInverters Inverters Emulsified Oil Emulsified Oil Emulsified Oil Emulsified Oil Emulsified Oil Emulsified Oil

Emulsified Oil Emulsified Oil

Stabilizers Emulsified Oil Emulsified Oil

Emulsified Oil Emulsified Oil

Oil

Stabilizers

Stabilizers Inverters

Oil Oil

Inverters

Inverters Water

Water Water Water Water Water Inverse EmulsionInverse EmulsionInverse Emulsion Inverted EmulsioInvertedn InvEmulsioertedn Emulsion Dissolved DissolvPolymeredDissolv Polymered Polymer

7. Making the polymer Details on the main In cases of hard water, the ratio must be 5 g/liter of active polymer (10-15g/l

solution parameters commercial emulsion) in water and not

Particle

Particle

Particle polymer polymer

polymer polymer polymer polymer

Hydrogel

Hydrogel drogel

Hy zzWater quality below, to give a good inversion.

Polymer

Polymer olymer FundamentalsP Hardness of the water increases the Polyacrylamide emulsions are not zzShear during inversion simple concentrated solutions of time of aging and may make the polymer, so a simple dilution in water is solubilisation of the polymer incomplete To obtain a good inversion, it is necessary not possible. When preparing a polymer or impossible. Calcium and magnesium for each polymer particle to be dispersed solution from an emulsion, there are ions (mainly) reduce the efficiency of separately in water, otherwise the two physical phenomena (phase the surfactant. particles will agglomerate. To ensure inversion and dissolution) which take With alkaline buffered waters, the same efficient dispersion, it is necessary to place and need specific conditions to disturbances in the efficiency of the use high shear mixing at the point of be made properly. When the emulsion inversion can be observed and the emulsion-water contact. comes in contact with water the stability of the final solution is strongly inverting surfactant dissolves and affected. (See paragraph ‘Stability of zzMake-up systems the polymer solutions’, below.) emulsifies the oil in the water Many types of equipment are (inversion). Then the beads of hydrogel In hard water (above 300-400 ppm of CaCO or equivalent), the speed available on the market, made by come in contact with water and 3 several manufacturers. Some are dissolve (dissolution). of inversion is reduced. For very hard water such as sea water and brines, it more or less efficient depending The small oil droplets in the dissolved on the characteristics of the polymer solution diffract light and that is is necessary to adapt the formulation of the emulsion to make the inversion application. SNF provides advice and why the solution is opalescent white. help in any case based on the above The total time and the quality of possible. In such a case the product must be designed specifically and a recommendations. inversion/dissolution are dependent on In general, any equipment which the following fundamental rules: study should be made separately by SNF. does not provide enough shear zzEmulsion must be added to the water after the contact between and not the contrary. zzConcentration for inversion of emulsion and water will, in many zzVery high shear must take place at cases, not be efficient. the point of contact between water emulsions in water SNF recommends Floquip DE type and emulsion. Agitation which dis- To obtain a good inversion of the equipment for emulsion dissolution. perses the emulsion in the shape of emulsion, it is necessary for the unitary beads or agglomerates. surfactant to be present at its zzHigh ratios of emulsion vs. water are minimum effective concentration. preferred, (the higher the concentra- Ratios of 5g/liter of active polymer tion, the higher the dissolution speed). (10-15g/l commercial emulsion) in water are the most efficient. zzThe water must be as soft as possible At lower ratios, the time for aging and not alkaline buffered. will be higher or the solubilisation not zzThe water temperature must be complete. At higher ratios, the final below 30°C. solution may be too viscous.

Polyacrylamide Emulsions Handbook 9 Stability of the polymer solutions

8. Stability of the polymer Anionic emulsions solutions Anionic emulsions have good stability in the range of : Polymer in water solutions can be Anionic emulsions unstable and degradation can result in lower efficiency. Each case (based Active Content 1 g/liter 5 g/liter on the emulsion grade used, the kind Stability 8 hours 8 days of water used, the equipment make- up unit, times for aging of the solutions Cationics emulsions etc.) is different and must be studied specifically. Water polymer solutions obtained from cationics emulsions are much less stable than those from anionics emulsions. Hydrolysis Cationics emulsions The main reason for instability Alkalinity Low High Low High of the water polymer solution Active Content 1 g/liter 1 g/liter 5 g/liter 5 g/liter obtained from cationic emulsions Stability 1 hour 10 minutes 8 hours 30 minutes is the hydrolysis of the ester Acid Stabilised Emulsion 4 hours 1 hour 2 days 8 hours function of the cationic pendant group. Hydrolysis means that part of the cationic groups are transformed into anionic acrylate groups, giving an Assessing and limiting If the pH is above 6 (this is often the amphoteric polymer, thus reducing the hydrolysis case when underground source water cationicity. is used in papermills, refineries etc.), or In situations of short term continuous use Hydrolysis can occur especially if the when the solutions are prepared a long of solution made with rather soft water, water used to make the polymer time in advance, one or more of the there is in general no need for a special solution is alkaline buffered water. following actions should be taken : treatment, such as, for instance, the Under such circumtances the time for addition of an acid. using the solution can be very short and zztry to use soft water for dissolution ; For specific cases, acid addition to reach in some cases less than 10 mn. zzadd buffering acid to the solution to the emulsion during production or The solution becomes very thin, full of decrease the pH, directly in the solution can be made for white fine precipitates and very foamy stabilisation . zzincrease the concentration during (sometimes cream may appear at the The best pH for stability of solutions dissolution to maintain the pH under top of the solution). at 5g/l of emulsion is below 6, and 6, then dilute continuously just before The speed of hydrolysis depends on most preferred 5.5. The pH must be use ; many factors: dilution, water hardness, measured in the water which will be zzrequest a polymer from the produc- buffering effect, type of polymer, used industrially. tion plant containing a higher buffe- temperature, etc. Several cationic When the pH is below 6, ring acid content; polymers hydrolyze and especially normally the hydrolysis is slow, those made from Adam-Methyl zzincrease the cationicity of the poly- therefore it can be important to check chloride, which correspond to most of mer to be used ; if there will not be a risk of hydrolysis, the polymers produced by SNF. in particular when the solutions are The cationicity not only decreases prepared a long time in advance. proportionally to the degree of Cationic Polymer Hydrolysis hydrolysis but very often, depending on the pH and salinity of the water, it Cationic Polymer Hydrolysis may decrease at twice this speed due 500 to the interaction between the anionic groups formed through hydrolysis and 400 the unhydrolyzed cationic groups. This is known as the Zwitterion effect. 300

With water pH 5,5 200 With buffered water pH 8

100 Viscosity (centipoises)

0 0 5101520 Time (hours)

10 Polyacrylamide Emulsions Handbook Bench trials with emulsions

Free radical chain degradation Viscosity degradation due to Iron viscosity (cps) Polyacrylamides in solution are sensitive 55 to free-radical chain degradation. Free radicals are formed in water by a number of oxidizing and reducing 50 agents. Mostly they are formed from no iirroonn dissolved oxygen and iron. Degradation 45 occurs after about 2 hours at iron concentrations of 0.5 ppm. Some well 3 ppm Fe waters contain more than 5 ppm iron. 40 In such cases, degradation is high even during dissolution. 35 Iron sensitivity is very difficult to 6 ppm Fe overcome. Chelating agents, for instance, increase the degradation 30 when they are mixed in with the solution.

Treatment has to be on a case by case 25 basis using the following guidelines : 0510 15 20 25 30 35 40 45 50 55 60 2+ zzsince only Fe causes chain degra- Aging Time (days) dation, aerating the water oxidises it to Fe3+ and so reduces the effect ; zzadding a chelating agent before aeration (whenever possible) increases the speed of the oxidation of Fe2+ ; 9. Bench trials with emulsions Note : to check if the product is homogeneous, zzuse of an oxidizer such as perborate a sample must be taken from the top at 2 to 4% (based on the active polymer) General recommendations of the tank and a sample from the will rapidly oxidize the Fe2+ to Fe3+ ; bottom. Then measure the viscosity of both samples When preparing polymer solutions in and if zzincreasing the dissolution concen- the laboratory, all recommendations tration decreases the Fe2+ / polymer listed in the paragraph ‘Making the they are the same, the product can balance. This is the easiest solution for polymer solution’ above are also valid. be considered as homogeneous. If the Fe2+ level in the region of 1 to 2 ppm ; Cleaning of equipment which has viscosities are different, the product zzuse treated water (to be tested) ins- been in contact with emulsions is long must be stirred again. tead of well water. This water is more and not easy, so whenever possible, all When the viscosities are the same, aerated and normally more suitable equipment to be used for working with the value by itself is not particularly when the clarification is good ; emulsion in the lab must be disposable. important; it may differ from the zzuse potable water instead of well Among the items of equipment which value given from the technical water but this can considerably can be used, disposable plastic beakers information - normally up to -/+ 50% increase the cost of treatment. and syringes are highly recommended. is acceptable. These viscosities are called bulk viscosities. This bulk viscosity Based on European statistics, problems The bottle containing the emulsion is a parameter which is related to the due to hydrolysis and free radical must be homogenized by shaking it physical aspect and not related to the degradation are encountered with 30% each time prior to opening it to take a performance of the product. The value of all cationic polymers, especially in sample. For reliable tests use the same given on the technical information is an municipal water treatment plants and source of water than in the plant. average. It is only used to estimate the paper mills. Emulsions are normally used characteristics of the pumps that will with continuous dissolution equipment How to take a sample 2+ move the product. and are less sensitive to Fe than For accurate testing and analysis, it is powder polymers, where dissolution very important that samples be taken time is more than one hour. correctly. After a long time of storage, as the emulsions have a tendency to Note: Polymer solutions made up using distilled or potable water may not truly represent the industrial settle, samples taken from the top of a use. tank may be too thin, due to excessive oil, and samples taken from the bottom can be too thick. It is imperative to take the necessary actions (mainly agitation) to homogenenize the product before taking a sample.

Polyacrylamide Emulsions Handbook 11 Health, Safety, Environmental Information

Preparation of solutions 10. Health, Safety, Two major environmental risk To obtain a good inversion/dissolution, Environmental Information assessments on polyelectrolytes used the enough shear must be applied at the hydrolysis of ester-type polyacrylamides point of contact between the emulsion The polymer contained in the emulsions to conclude that they are not a risk for and water. has the same toxicity (very low) as the the environment. The preferred way is as follows : powders. zzprepare a beaker of the desired zzA Review of Polyelectrolytes to quantity of water and stir enough to The free acrylamide content of industrial Identify Priorities for EQS Development. have a wide vortex ; emulsions is lower than 1000 ppm United Kingdom Environmenal Agency, (0.1%) based on emulsion. For special 1996. zzweigh the required quantity of emul- uses it is possible to produce products sion in a disposable plastic syringe ; with less than 500 ppm (0.05%) of free zzAn investigation into the zzinject the content of the syringe by acrylamide. turning the jet toward the wall of the environmental impact of polyelectrolytes in waste water vortex. The oil is a dearomatised aliphatic treatment plants. STOWA (Stichting hydrocarbon. SNF inverse emulsions Toegepast Onderzoek Waterbeheer : do not flash and are, therefore, not The time for complete dissolution is 10 Netherlands Waste Water Authority), considered to be either flammable or min. on average 1995. combustible liquids. For agitation, the most preferred equipment is a mechanical agitator The surfactants used have very low with a variable speed motor fitted with toxicity, and are obtained from esters of a stainless steel shaft, equipped at the sorbitol and ethoxylated alcohols. end with approximately 2 cm radius long propeller type blades. In such a The degradation of ADAME-based situation the speed is at least 500 rpm. polyacrylamide is ecologically Use of a magnetic stirrer is possible but advantageous. Due to hydrolysis, the it is less recommended because the cationic charge, which represents a risk power of the agitation is often weak for aquatic organisms, is not persistent and, as the viscosity of the solution in the aqueous environment. At natural increases rapidly, it becomes impossible pHs (between 6 and 8), hydrolysis to agitate the solution properly. breaks the ester bond and the cationic group cleaves off to form an inoffensive, Typical application tests highly biodegradable substance known All standard applications tests can as choline chloride. On the polymer be made from solutions prepared as end, an acid group is formed which is above . immediately neutralized, forming an This includes flocculation tests (Jar anionic polyacrylamide of very low test, Laboratory test for centrifuges, aquatic toxicity. In this way, ester-type Laboratory test for belt press...) tests for polyacrylamide reduces the aquatic paper application, oilfield applications toxicity by a factor of 50 in just 12 hours. etc... Hydrolysis continues until no cationic All procedures for these tests are charge remains. Complete hydrolysis is available on request from SNF. achieved within 24 hours.

12 Polyacrylamide Emulsions Handbook SNF sas ZAC de Milieux 42163 Andrézieux Cedex FRANCE Tel : + 33 (0)477 36 86 00 Fax : + 33 (0)477 36 86 96 [email protected] www.snf-group.com Publishing : Altavia Connexion - 11/2013

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