Study on Preparation and Application as Organic Particulate Retention

Agent of Chitosan-AM-DMDAAC Inverse Latex

Yongsheng Ma 1, a, Xianhui Sun2, b 1Chemistry and Chemical Engineering College, Weifang University, Weifang, Shandong, 261061,

China

2Weifang Vocation College, Weifang, Shandong, 261041, China

amysh@sdili.edu.cn,

bsxh1.319@163.com

Keywords: Chitosan, Acryamide, DMDAAC, Inverse Emulsion Polymerizing, Organic Microparticle Retention System.

Abstract. Graft copolymerization of acrylamide (AM) and diallyl dimethyl ammonium chloride

(DMDAAC) onto chitosan in inverse emulsion was studied. The effect on Zeta potential and average

granularity of synthetic inverse latex of the main reaction conditions such as the proportion of cationic

monomer in total monomers, concentration of potassium persulfate (KPS) used as initiating agent

were investigated in detail. It was shown that when the weight ratio of chitosan, AM and DMDAAC

was 1:6:2, KPS concentration was 4.0mmol/L, NaHSO3 concentration was 2.0mmol/L, stable inverse

latex which had optimal performance could be gained. Good retention effect was obtained when a

novel organic microparticle retention system composed of the above-mentioned

chitosan-AM-DMDAAC inverse latex and anicnic polyacryamide (APAM) was applied to the deink

pulp. First Pass Retention retention percentage of deink pulp was improved from 83.2% to 95.0%

with the organic microparticle retention system when the dosage of inverse latex was from 0 to 0.4%

of absolute dry pulp.

Introduction

Graft copolymerization of vinyl monomers onto chitosan using free radicals initiator was paid more

and more attention to in the last two decades. Inverse emulsion polymerization has become important

branch of emulsion polymerization. Inverse emulsion polymerization has become important branch of

emulsion polymerization. This technique enables the production of new polymer materials with

desired properties. Water-soluble monomers such as acrylic acid can be polymerized with high

molecular weight and high solid content in inverse emulsion[1]

.

Microparticle retention system that was an important multiple retention system was paid more and

more attention to, for example, Compozil system composed of Cationic starch and colloidal silica,

Hydrocol system composed of CPAM and modified bentonite. The particulate in these systems was

all anionic inorganic particles. Organic microparticle retention system which action mechanism was

different from the inorganic particles retention system was still in research stage.The cationic organic

microparticle was added in pulp first, consequently, cationic patches were formed on surface of fibers

and fillers, or flocculation body which had certain flexibility between fibers and fillers was formed.

The pulp was high sheared, then, the anionic polymer was added in. So the ideal "micro- flocculation

body" was formed through the bridge effect and the activity of electrostatic neutralisation. This novel

organic microparticle retention system was relative not sensitive to pH value or shear force, so it was

conducive that papermaking system was developed to the neutral-alkaline environment.

AM, DMDAAC and chitosan was graft copolymerized in inverse emulsion to prepare organic

microparticle in this experiment. A novel organic microparticle retention system composed of the

chitosan-AM-DMDAAC inverse latex synthesized in this study and anionic polyacryamide (APAM)

was used in deink pulp to experiment retention effect of the organic microparticle.

Advanced Materials Research Vols. 233-235 (2011) pp 1722-1725Online available since 2011/May/12 at www.scientific.net© (2011) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.233-235.1722

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Experimental

Materials. Industry grade chitosan was purchased which degree of deacetylation and viscosity was

92.5% and 400 mPa·s. Chemical pure acrylamide, DMDAAC, NaHSO3 and potassium

persulfate(KPS) were dissolved in distilled water. Chemical pure Span-80, and OP-10 were used as

emulsification agent. Deink pulp with the beating degree of 580SR was provided by one papermaking

factory in Shandong province.

Graft Copolymerization. Graft copolymerization was carried out under nitrogen atmosphere in a

four necked-flask equipped with reflux condenser, stirrer, thermometer, and nitrogen gas inlet. 70mL

of chitosan acetic acid solution containing 0.50g of chitosan and a chosen amount of KPS were added

into the flask. Then N2 was pressed into the flask for 15mins to take the place of oxygen atmosphere.

Then a chosen amount of liquid paraffine and quantitative emulsification agent were also added into

the flask. In order to control the reaction temperature, the flask was placed in thermostat water bath.

The mixture was heated to the desired temperature and stirred for 10 min before a chosen amount of

AM/DMDAAC dissolved in distilled water was added. Polymerization was started and continued for

a predetermined period. The reaction mixture was not stirred until the reaction was stopped by cooling

down the reactor rapidly.

Test of Inverse Emulsion Performance. The resultant emulsion was dropped respectively into

water and ethanol. Their dispersing style was observed to judge the style of emulsion. Average

granularity of emulsion was measured with a Mastersizer 2000 laser granularity tester. Zeta potential

was measured with JS94F Micro electrophoresis instrument.

Results and Discussion

Physical Chemistry Performance and Emulsion Style of Resultant Latex.Production appearance

was ivory-white latex, which was easily dispersed in water. Its pH value was 5.0~5.5. Its viscosity was

100mPa·s~250mPa·s. Resultant emulsion can be dissolved in liquid paraffine but cannot be dissolved

in water. Therefore, the resultant emulsion was W/O emulsion.

Reaction Conditions Effect on Latex Stability. Stability of inverse latex which was difficult and

key question in inverse emulsion polymerizing was reported in another paper.It was shown that when

the volume ratio of oil phase and water phase was 1:1, the weight ratio of chitosan and AM was 1:8,

the reaction temperature was 50℃, the reaction time was 4h, the dosage of emulsification agent was 8

% of the weight of oil phase, the weight ratio of Span-80 and OP-10 was 6:4, and the shearing rate was

1100 rpm, stable inverse latex could be gained.

In this study the impacts on Zeta potential and average granularity of stable inverse latex of the

main reaction conditions such as the proportion of cationic monomer in total monomers,

concentration of potassium persulfate (KPS) initiator were investigated in detail.

Effect of Proportion of DMDAAC Monomer in Total Monomer.Cationic monomer

DMDAAC was main source of cationic property of chitosan-AM-DMDAAC graft copolymer latex

synthesized, so DMDAAC dosage may have a significant effect on Zeta potential of latex. When the

other reaction conditions were unchanged, proportion of DMDAAC in total monomer was changed, a

series of stable cationic inverse latex was synthesized. Their Zeta potential, average granularity, were

measured and displayed in Table 1.

It was shown in Table 1 that when the other reaction conditions were unchanged, with the increase

of the proportion of DMDAAC monomer, the average granularity decreased gradually, and that the

increase trend of the Zeta potential was more apparent, gradual increase extent was great.

This trend may be due to that DMDAAC monomer has a strong hydrophilic amino group which as

far as possibly distributed in interface of particles and water. With the increase of the DMDAAC

content, the amount of cationic amino groups on the particles surface was gradually increased, so the

corresponding charge density was also increased, leading to larger Zeta potential and smaller particle

size.

Advanced Materials Research Vols. 233-235 1723

Effect of Initiator Concentration.Initiator concentration was an important factor that affected the

graft copolymerization. Initiator concentration is directly related to the amount of free radicals that

were active center of graft polymerization. So the molecular weight of product was affected by the

initiator concentration. The effect of potassium persulfate (KPS) concentration on the average particle

size and Zeta potential of latex was shown in Table 2.

It was found from Table 2 that the impact of KPS concentration on the properties of synthesized

latex was not as DMDAAC monomer dosage. Although change margin of not the average granularity

but the Zeta potential was not distinct, it can be seen that No.6 sample had the smallest average

particle size and the strongest Zeta potential.

Table 1 Effect of DMC proportion

Sample

number

DMC

proportion/

%

Average

granularity

/µm

Zeta

potential

/mV

1

2

3

4

0

8

16

25

1.26

1.17

1.08

1.03

2.4

6.2

16.0

33.1

Table 2 Effect of KPS concentration

Sample

number

KPS con-

centration

/mmol·L-1

Average

granularity

/µm

Zeta

potential

/mV

4

5

6

7

8

2

3

4

5

6

1.03

1.12

1.01

1.03

1.07

33.1

29.8

34.1

28.3

28.5

Effect of Sodium Bisulphite Concentration. It was shown from Table 3 that the average

granularity and Zeta potential of latex were also influenced by the concentration of sodium bisulphite,

but the effect was not as good as DMDAAC monomer on the performance of latex synthesized.

Considering not average particle size but Zeta potential, No.6 sample was still selected as the sample

which had optimal performance.

Table 3 Effect of sodium bisulphite concentration

Sample

number

NaHSO3concentration /

mmol·L-1

Average granularity

/µm

Zeta potential

/mV

9

10

6

11

12

0.5

1

2

3

4

1.07

1.02

1.01

1.12

1.15

32.5

32.8

34.1

33.5

32.6

Retention Effect of Cation Organic Microparticle Retention System in Deink Pulp.The cation

organic microparticle retention system composed of chitosan-AM-DMDAAC inverse latex

synthesized in this study and anionic polyacryamide purchased was applied to the deink pulp to

improve retention percentage.The cationic latex was added in the deink pulp firstly, cationic patches

was formed on surface of fibers and fillers, or flocculation body which had certain flexibility between

fibers and fillers was formed. The deink pulp was high sheared with dynamic drainage jar, and then

the anionic polymer was added in. So ideal "micro-flocculation body" was formed through the bridge

effect and the activity of electrostatic neutralisation to achieve the uniform retention of the tiny fiber

and filling.Among them, properties of invert cationic latex synthesized in this study such as particle

size, surface charge density, is an important factor of the impact of organic microparticle retention

system.Particle size of organic particles added in the deink pulp was smaller, the larger ratio surface

area, the stronger integrating action between surface area and the colloid, more likely colloid

aggregation sedimentation, the weaker colloid interference, so, the better coordination retention effect

of the organic particle system[2]

.

The cation organic microparticle retention system retention effect to the fillers and tinny fiber was

proportional to the surface charge density of cationic particles. The higher surface charge density,

more obvious the particle[3]

. In addition, retention effect was also influenced by the molecular weight

1724 Fundamental of Chemical Engineering

of polymer. The molecular weight was larger, the stronger its ability to form floccule retention effect,

the better retention effect of the organic particle system.

No. 6 sample which had the highest charge density and the smallest average granularity was

selected in this study to compose organic microparticle retention system with anionic polyacrylamide.

The influence of the dosage of above-mentioned inverse cationic latex to First Pass Retention of deink

pulp was shown in Fig 1.

75

80

85

90

95

100

0 0.1 0.2 0.3 0.4 0.5 0.8 1

Dosage of synthetic latex/%

First

Pass

R

ete

ntion

Fig 1 Synthetic latex dosage effect to FRP of deink pulp

It was shown in Figure 1 that good retention effect was obtained at proper application conditions

when the organic microparticle retention system composed of the inverse cationic latex synthesized in

this study and anionic polyacryamide (APAM) was used in the deink pulp. As the dosage of synthetic

latex was from 0 to 0.4%, First Pass Retention was increased from 83.2% to 95.0%.

The likely reason was that with the increase of additive dosage, there would be more

macromolecule polymer to participate in the formation of pulp stratum. Then the opportunity of

polymer and fibers/fillers to contact was increased, so that the organic cation microparticle retention

system was taken full advantage of. The result was that a high one-way retention percentage of pulp

was achieved.

When the dosage of cationic latex was from 0.4% to 1.0%, the First Pass Retention was still on an

upward trend, but the increase was at a lesser extent. Taking into the cost factor, 0.4% dosage was

selected as the appropriate dosage of cationic synthetic latex.

Conclusion

Graft copolymerization of AM and DMDAAC onto chitosan in inverse emulsion was studied. The

impacts on Zeta potential and average granularity of synthetic inverse latex of the main reaction

conditions such as the proportion of cationic monomer in total monomers, concentration of potassium

persulfate (KPS) used as initiating agent were investigated in detail.

When the weight ratio of chitosan, AM and DMDAAC was 1:6:2, KPS concentration was

4.0mmol/L, NaHSO3 concentration was 2.0mmol/L, stable inverse latex No. 6 sample which had

optimal performance could be gained. No. 6 sample which had the highest Zeta potential

(34.1mV)and the smallest average granularity(1.01µm) was selected to compose organic

microparticle retention system with anionic polyacrylamide. First Pass Retention of deink pulp was

improved distinctly. First Pass Retention of deink pulp was improved from 83.2% to 95.0% when the

dosage of chitosan-AM-DMDAAC inverse latex was from 0 to 0.4% of absolute dry pulp.

References

[1] Ming L, Shuchai L, Lin W. China Paper Industry, Vol. 11(2004), p. 43 In Chinese.

[2] Juntai L. Paper Technology, Vol.24 (2009), p. 41

[3] Cherize O, Huining X, Nicholas W. Tappi Journals, Vol.32(2000), p.80-84

Advanced Materials Research Vols. 233-235 1725

Fundamental of Chemical Engineering 10.4028/www.scientific.net/AMR.233-235 Study on Preparation and Application as Organic Particulate Retention Agent of Chitosan-AM-

DMDAAC Inverse Latex 10.4028/www.scientific.net/AMR.233-235.1722