Poly Acrylic Acid: Synthesis, aqueous Properties and

ELASTOMERE UND KUNSTSTOFFE ELASTOMERS AND PLASTICS

Poly(acrylicacid)  Free radical reaction  Mechanism  Scale inhibitor  Calcium Sulphate A study was conducted on synthesis of a series of acrylic acid homopolymer P(AA).The polymerization process was carried out via free radical polymerization using sodium persulphate as an initiator. The P(AA) was characterized using a Fourier Transform Infrared (FTIR) spectroscopy and Size Exclusion Chromatography (SEC). The physical properties of the P(AA) were evaluated and its application as eco-friendly phosphate-free scale inhibitor agent was investigated.

Polyacrylsäure: Synthese, wässrige Eigenschaften und ihre Anwendungen als Inhibitor für Abalgerungen Poly(acrylsäure)  Freie radikalische Reaktion  Mechanismen  Ablagerungs Inhibitor  Kalzium Sulfat Es ist Studie zur Synthese einer Serie von Acrylsäure-Homopolymeren (P(AA) ertellt worden. Der Polymerisationsprozess ist über den Weg der freien radikalischen Polymerisation unter Einsatz von Natriumpersulfat als Initiator durchgeführt worden. Die P(AA) wurden durch Fourier Transform Infrarot (FTIR) Spektroskopy und Gelpermeationschromatographie (GPC) characterisiert worden. Es wurden die physikalischen Eigenschaften der P(AA) und die Anwendung als ökologisch freundlicher phosphatfreier Umsatz-Inhibitor untersucht.

Figures and Tables: By a kind approval of the authors.

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Poly Acrylic Acid: Synthesis, aqueous Properties and their Applications as scale Inhibitor Introduction

Acrylic acid polymers and copolymers cover a very huge range of applications, such as hydrosoluble agents for dispersing agents, thickeners, flocculating and super-absorbent agents, detergent auxiliaries, organic synthesis, copolymer emulsion for paints, cosmetics, papers, varnishes and inks. In addition, dispersions for leather, textiles, non-woven fabrics, glues and adhesives, cleaning and waxing products. Besides, plastics, synthetic resins, synthetic rubbers and lattices [1-9]. Growing social awareness and concern for environmental, health reasons and the state of our natural waters have been the major driving force to search for detergent additives other than phosphates. Phosphorus was accused as being responsible for eutrophication[10-11]. It is clearly desirable to reduce the amount of mineral acid used in thermal desalination by using lower molar mass polymers containing carboxylate, sulfonate or phosphonate groups [12], the scaling phenomenon may cause technical problems such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes In industrial applications [13], The efficiency of scale inhibitors depends on their chemical properties (functionality, molar mass, polydispersity, and structure) and usage (concentration and method of application) [14] in addition to and the nature of the solids forming.) [15], Polymers containing carboxylic acids such as poly(acrylic acid) and poly(maleic acid) are the most common groups of polymeric scale inhibitors[16], in addition to Aqueous dispersions of poly acrylates have excellent weather ability, water and alkaline resistance[17-18]Vinyl acrylic polymers are synthesized by copolymerization of acrylates with other materials, either monomers via direct polymerization [19] or with natural materials via graft copolymerization [20-22] using different polymerization techniques. Many countries have passed legislation to reduce the phosphate content of their products without reducing the level of performance expected by the

customers. Thus the incentive to replace phosphates in the detergent industry led to the synthesis of polyacrylic acid (poly AA) with a high chelation capacity for calcium ions (Ca2+) instead of phosphates in the detergent industry [23-25] Poly (AA) is an anionic polyelectrolyte [26] besides its chelation ability [27], (poly AA) has also dispersion properties [28], poly AA with molecular weights (Mw) in the range of (50 000 – 90 000) are effective species in preventing scale deposition in desalination [29]. polyacrylic acid as antiscaling agent on heat exchangers, cooling water [30-33]. The aim of this study to prepare poly acrylic acid homopolymers with high performance scale inhibitor, specifically develope to prevent the precipitation of calcium sulfate and calcium carbonate from solution (for oil and gas production systems).

Experimental Study Materials

Acrylic acid was obtained from Elf Chem. Co.,ATOFINA, France. Inhibitor content MEHQ (180-220 ppm), Sodium persulfate and ammonium persulfate Product of NBM Chem. Company (England). carbonate from M.R.P. Inc. of Taxes. India. The clay sodium montmorillonite was obtained from RP Mineral (Egypt). All the chemicals were used as received.

Authors Magdy A. Zahran, Waseem A. Abd El-Mawgood, Moneer Moneer Basuni, Giza, Egypt Corresponding author: Dr. Moneer Moneer Basuni EBCA R&D Petroleum center (Egyptian British co.) 6th, October City, Giza, Egypt. E-Mail: [email protected] [email protected] KGK · 07-8 2016

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1

2

6

7

Solution viscosity (cp)

Viscosity (cp)

Viscosity (cp)

5 4 3 2

5 4 3 2

1 0


6

1 5

10

15

20

25

Monomer Concentration (%)

Fig. 1: Effect of Acrylic Acid concentration on solution viscosity.

Synthesis of homopolymer

The used apparatus consists of a threenecked flask equipped with a stirrer, reflux, and condenser with nitrogen inlet, thermometer and dropping funnel. The apparatus was immersed in a constant

0

1

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KGK · 07-8 2016

3

4

5

6

Initiator concentration weight gm/100 gm

Fig. 2: Effect of initiator concentration on solution viscosity of polymer obtained.

temperature water bath. All reactions were carried out in an aqueous solution, where a certain quantity of bidistilled water was introduced in the threenecked flask and heated at first a certain temperature. SCHEM.(1) suggested reaction mechanism of poly acrylic acid. The calculated amount of water soluble monomer Acrylic Acid (AA) was dropped within a certain period of time, and at the same time the calculated amount of initiator (sodium persulphate) in an NaOH aqueous solution of the same weight as the monomer, was added simultaneously upon stirring. Stirring of reaction mixture was continued for a definite period of time at the specified temperature. When a reaction was finished, the reaction mixture was then cooled, it,s solid content and viscosity were determined.

Preparation of Poly Acrylic Acid (P(AA))

Scheme 1. Reaction mechanism for poly acrylic acid P(AA).

2

Poly (AA) was synthesized in Three -necked flask that was partially submerged in controlled temperature water bath. the procedure consisted of a load of 688 g of double – distilled water, placed in the round - bottom flask fitted with an over- head stirrer and an 18- in. reflux condenser. The pot temperature was typically maintained at (60-98 °C). Glacial AA (213 g, 2.36 ml per minute ) and also 70 ml of the initiator aqueous solution (1.0 ml per minute )were introduced. The amount of acrylic acid monomer varied in the range of (5-30 %) by weight during the experimental-design work. The initiator, sodium persulphate, was prepared by dissolving 3 g of the solid substance in 70 g of water.the acrylic acid and initiator were metered simultaneously over a 90- min period. The heating with slow

1 Effect of Acrylic Acid concentration on solution viscosity Polymer Monomer Solution code concentration (%) viscosity (cp) JA1 JA2 JA3 JA4 JA5

5 10 15 20 25

1.30 2.10 3.00 4.30 5.20

2 Effect of initiator concentration on solution viscosity Polymer Initiator Solution code concentration viscosity weight gm/100 gm (cp) JI1 1 6.30 JI2 2 5.70 JI3 3 4.20 JI4 4 3.00 JI5 5 2.10 JI6 6 1.15

stirring was continued for another 90 min. Temperature readings were recorded every 10 min during the 3-h run. After the reactions were completed (3-h), the reactor was cooled and vented and the poly acrylic acid P(AA) solution was removed and cooled.

Result and discussion Effects of reaction condition on homopolymerization

The optimum conditions for preparing homopolymerization acrylic acid by studying the effect of different factors, such as dosages of hydrogen peroxide, reaction temperature, reaction time and concentration of monomer. The effect of each factor on the viscosity of the obtained polymer was studied separately www.kgk-rubberpoint.de


3

4

7

7


6

5 Viscosity (cp)

5 Viscosity (cp)


6

4 3

4 3

2

2

1

1 0

0 0.5

1

1.5

2

3

4

60

Reaction time (h)

Effect of monomer concentration

The results of the investigations on the variation of the viscosity of polymer solution with concentration of acrylic acid are shown in table (1) and figure (1). The data listed in table (1) and shown in figures (1) indicate that, the increasing dosage of acrylic acid, lead to the increasing viscosity of the polymer obtained, due to the increased molecular weight of the polymer [34].Following the increasing dosage of monomers in polymerization, the content of macromolecules in final products was also increased [35]. At higher monomer concentration for example 30%, the polymerization solution becomes very viscous, so the stirring becomes too difficult and the distribution of reactants may be insufficient and hence the conversion of monomer to polymer decreases.

Effect of initiator concentration

Table (2) and Figure (2) show variation of the viscosity of the obtained polymer solution with initiator concentration. The data given in table (2) and figure (2) show that the viscosity of the obtained polymer solution decreases with the concentration of the initiator, This may be due to increased free radicals formed leading to shorter molecules.which lead to decrease the molecular weight, the performance of PAA has been shown to bestrongly dependent upon the molecular weight[36].,selection of initiator concentration is very important to get the optimum polymerization ratio [22]. www.kgk-rubberpoint.de

80

90

98

Reaction temperature (°C)

Fig. 3: Influence of reaction time on viscosity of Products.

while the other factors being kept constant. Such that the optimum reaction conditions could be estimated on polymerization process.

70

Fig. 4: Effect of polymerization temperature on solution viscosity.

3 Effect of Effect of addition time on solution viscosity Polymer Reactiontime Solution code (h) viscosity (cp) JH1 0.5 6.30 JH2 1 5.70 JH3 1.5 4.20 JH4 2 3.00 JH5 3 2.10 JH6 4 2.10

4 Effect of Reactiontemperatureon solution viscosity Polymer Reaction Solution code temperature viscosity (º C) (cp) JC1 60 6.30

Effect of addition time

crease with increase of reaction temperature, due to chain transfer which takes place as a result of increasing the kinetic energy, shorter half life of initiator and reflected on the number of collisions between the molecules. On the other hand,when the reaction temperature was highy,the decomposition of initiator would be too fast and the possibility of radical transfer would be greatly enhanced [38].

The results on variation of the viscosity of the obtained polymer solution with reaction time are shown in Table (3) and Figure (3). The effect of reaction time on P(AA) were studied under predetermined condition, the polymerization was conducted for a variety of reaction time ranging from 1 to 4hr, Table (3) and Figure (3) represents the effect of reaction time on viscosity of the homo-polymer. Between the reaction times of 1 and 3 h, the viscosity decreased gradually which may be attributed to termination steps of the growing chains. When the reaction time exceeded 3 h, the viscosity became relatively constant. The reason may be attributed to the decline in the number of monomers and the initiator as time increase [37], low molleculerwighte are widlyused .

Effect of temperature

In table (4) and figure (4) the results of the graft-copolymerization are shown with variation of the viscosity of obtained polymer solutions with reaction temperature.The data given in table (4), Figure (4) show that with the same amount of monomers the viscosity de-

JC2

70

5.70

JC3

80

4.20

JC4

90

3.00

JC5

98

2.10

Estimation of unreacted monomers

Bromine water reacts with alkene by addition reaction where the red-brown color of bromine disappear CH2=CH2(g) + Br2(aq) + H2O → BrCH2CH2OH(aq) + HBr(aq) 1 g of reaction mixture was transferred to flask (250 ml) containing 100 ml distilled water and then titrated with bromine water (10%) where the color initially disappear, the solution color is converted to red-brown after all (C=C) bonds are consumed[39], 1g (concentration = 25%) of reaction mixture contain 0.00347 mole of AA. respectively, every 1 g of bromine solution contain 0.000625 mole of Br2. KGK · 07-8 2016

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5 Effect of the time of reaction on the conversion of monomers

5 6

No. of grams of bromine water ( conc. 1%) {percentage of unreacted monomer} (conversion of monomers)

Reactiontime (h) 0 1 2 3 4 5

5

P AA 5.6{100%} 2.24{40%} 0.65{30%} 00.69{15%} 0 0

The data given in table (5) and figure (5) shows that, the monomers (AA) was consumed completely after 4hrs. Where the color of bromine water remain constant. So conversion of AA are 4 hrs.

Application of poly acrylic acid P(AA)

The study was conducted to explore the use of this water-soluble poly acrylic acid as eco-friendly phosphate-free scale inhibitor agent and as disperse colloids and fine particles.developePoly acrylic acid with high performance scale inhibitor, specifically prevent calcium sulfate and calcium carbonate salt deposits in water systems was evaluated using NACE standard method [40]. The results are given in table (6). The experimental results showed that the scale inhibitor modified homopolymer had an excellent efficiency of scale inhibition for calcium sulfate CaSO4, nearly 95% of scale inhibition efficiency and moderate for calcium carbonate CaCO3, This product, Poly acrylic acid can replace phosphonates as scale control agents to prevent the formation of calcium sulfateand other scales scale formers such as calcium carbonate.and calcium oxalate [41].In these research the recommended dose of the modified scale inhibitor P(AA)for calcium sulfate CaSO4 could be in the range (50-100 ppm).

Fourier Transform Infrared (FTIR) spectroscopy

Bromine water

Polymer code JU1 JU2 JU3 JU4 JU5 JU6

conversion of monomers

4 3 2 1 0

0

1

2 3 Reaction time (h)

4

5

Fig. 5: Influence of reaction time on the conversion of monomers.

py was able to differentiate the chemical bonds in the molecular structure of P(AA). The P(AA) sample was analyzed using KBr pellet technique. In this technique, the film of the polymer was obtained by blending the solid samples with KBr to obtain transparent discs. It was then scanned by the Perkin Elmer system 2000 FT-IR spectrometer in the range from 4000 cm-1 – 400 cm-1 IR spectrum of polyacrylic acid P(AA) shows that characteristic γ- C = 0 stretching vibration at 1714.68 cm-1 and very broad band having a medium value at 3429.14 cm-1 characteristic for γ CH aliphatic of methylene and methine coupled with that of γ OH of carboxylic group and that of γ H2O [43], (water of crystallization) stretching vibrations with appearing a σ CH deformation at 1457.86 cm-1 and OH out of plan at 1097.23 cm-1 [44]

Size exclusion chromatography (SEC) analysis

SEC spectra of modified P(AA) homopolymer (the weight average (Mw), number average (Mn), and polydispersity are given in in table (7) and figure (7).

Conclusions

The optimum conditions for the polymerization of homopolymers from poly acrylic acid P(AA).such as the concentrations of monomer, concentration of initiator, time of addition of both monomers and initiator effect of time reaction on the conversion of monomers can conclude that viscosity of the polymer solutions and hence their molecular weight increases by increasing monomer concentration, but decreases with increasing initiator concentration, time of addition and reaction temperature after a certain degree. ■■ At higher monomer concentration for example more than 30% the polymerization solution becomes very viscous, so the stirring becomes too difficult, on the other hand lowering the viscosity can be attained by increasing the initiator percentage, time of addition and reaction temperature, which results in decreasing the viscosity and enhance decreasing molecular weight of the obtained hompolymer. ■■ The experimental results showed that modifiedpoly acrylic acid had an excel■■

Fig. 6: FT-IR spectra of polyacrylic acid homopolymers P(AA).

6

FTIR spectroscopy was used as an analytical technique for the estimation of the functional groups presented in polymers [42]. In this study, FT-IR spectrosco6 Scale Inhibition Results Scale inhibition has been tested using NACEstanderd method

Scale Inhibition Dose, ppm 50 100 200

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Scale Inhibition CaCO3 CaSO4 28 94 37 95 29 95

4000

3500

3000

2500 2000 1500 Wave number (cm-1)

1000

500



Fig. 7: Size exclusion chromatography (SEC) for P(AA).

7 1.25

W (log M)

1.00 0.75 0.50 0.25

5e 4

1e 5

5e 5

1e 6

Molar mass [D]

7 Gell Permeation chromatography Data for P(AA) Sample Mn(g/mol) Mw(g/mol) P(AA) 5.7911e4 9.0861e4

lent efficiency of scale inhibition for calcium sulfate, nearly 95% of scale inhibition efficiency. This product, Poly acrylic acid can replace phosphonates as scale control agents to prevent the formation of calcium sulfate and other scales such as calcium carbonate,The recommended dose couid be in the range (50-100ppm).

Acknowledgments

The authors are deeply grateful to the support from EBCA R&D Petroleum center and (Egyptian British co. for chemicaland auxiliaries), 6th October City, Giza, Egypt.

Reference

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Bild: Kraiburg

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