Abstract: The effects of cationic, anionic, amphoteric and nonionic surfactants on the stability of aqueous ink colloids were discussed. The results show that: (1) When cetyltrimethylammonium bromide (ctab) is added to the aqueous ink colloid solution at a concentration of 0.14 mmol / l, the zeta potential changes from an initial value of 37.9 mv to 12. 7 mv; when the ctab concentration is 0.86 mmol / l, the zeta potential rises to 34.1 mv. Ph has a greater influence on the effect of ctab. When the concentration of ctab is 0.5 mmol / l, the system pH is adjusted from the initial value of 3.3 to 11.7, and the zeta potential is reduced from 38.6 mv to 23 ．7 mv, the maximum increase of the average particle size of carbon black particles reaches 13 nm. (2) When the concentration of sodium dodecyl sulfonate (sds) was 1 mmol / l, the zeta potential reached 38.2 mv, and the average particle size of carbon black particles decreased by 2 nln. (3) When the concentration of cocamidopropylamine oxide (capo) is 0.01 mol / l, the zeta potential reaches the isoelectric point when the system ph is about 6.0; when the system ph is 3.2, zeta The potential reached a maximum of 28.5 mv, and the maximum increase in the average particle size of carbon black particles was 9 nm. (4) When the concentration of fatty alcohol polyoxyethylene (7) ether (aeo-7) is 0.1 mol / l, the zeta potential of the system changes from a 37.9 mv to a 16.3 mv, and the average carbon black particles The particle size increased from the initial 154 nm to 240 nm. Join aeo-9 to get the same influence trend as aeo-7.

CLC number: tq423.9 Document identification code: a Article number: 1003? 5214 (2007) 04? 0332? 04

Organic solvents and heavy metal elements in solvent-based inks seriously pollute the environment, and it is imperative to replace solvent-based inks with water-based inks. Water-based inks are made with specific polymer resins, pigments, water and additives. At present, some developed countries have used water-based inks to print newspapers and periodicals]. There are great difficulties in the reuse of waste paper printed with water-based ink. The main process of deinking includes: (1) The waste paper is broken under alkaline conditions to separate the ink from the fiber; (2) The ink is floated out in the flotation tank. The conventional deinking process is to add human fatty acid and calcium chloride. The calcium soap formed will promote the aggregation of carbon black particles, which will adhere to the bubbles and be floated out, but the aqueous ink is dispersed into very small under alkaline conditions. Carbon black particles, these fine carbon black particles do not flocculate under the action of the conventional deinking agent 2 j, can not be trapped by air bubbles in the flotation process, easy to deposit on the fiber surface or inside j The presence of paper will greatly reduce the whiteness of the deinking pulp.

Foreign scholars have conducted preliminary studies on the stability and removal process of water-based inks. Femandez et al. found that the colloidal stability of water-based inks is determined by the electrostatic repulsive force and space steric hindrance effect. Gecol et al.'s research on the removal of water-based ink on the surface of plastic film shows that the addition of different types of surfactants can effectively remove water-based ink, and the addition of cationic surfactant cetyltrimethylammonium bromide (ctab) can make The surface charge of carbon black particles is reversed. However, Gecol did not study the effect of surfactants on the average particle size of carbon black particles in water-based inks. The average particle size of carbon black particles in water-based inks is a key factor related to whether they can be effectively removed.

This work discusses the influence of cationic, anionic, amphoteric and nonionic surfactants on the stability of aqueous ink colloids. Taking the average particle size of carbon black particles and electrostatic repulsive force as the main indicators of investigation, the characteristics of aqueous ink colloid solutions have been further improved. Recognized and found a surfactant suitable for deinking of water-based ink waste paper.

1 Experimental part

1.1 Reagents and instruments

The water-based ink is provided by an ink company in Guangzhou. Its main chemical composition is shown in Table 1.

Surfactants: cationic surfactant cetyltrimethylammonium bromide (ctab), anionic surfactant sodium dodecyl sulfonate (sds), both are ar; amphoteric surfactant cocamidopropyl Amine oxide (capo) and non-ionic surfactant fatty alcohol polyoxyethylene ether (aeo-7, aeo-9) are both industrial products. System ph titration: c (hci) = 0.5 mol / l and c (naoh) = 0.5 mol / l aqueous solution. The particle size and zeta potential of the ink solution were measured simultaneously with a malvem nano? Zs instrument (malvern instrumentsltd., England).

1.2 Steps

Take 10 ml of the diluted aqueous ink solution in a special plastic bottle, fix it on the MPT-2 automatic titrator attached to nano? Zs, start the magnetic stirring, and then put the surfactant to be added into another plastic bottle In the sampler of mpt-2, the surfactant will be added according to the set concentration. When reaching each set value of nano? Zs, the zeta potential of the solution system and the average particle size of carbon black particles will be measured simultaneously. Ph titration to add ph electrode in a plastic bottle, the steps are the same as above. The initial water-based ink carbon black particles had a zeta potential of 37.9 mv and an average particle size of 154 nm. [next]

2 Results and discussion

2.1 Cationic surfactant cetyltrimethylammonium bromide

(ctab) Effect on the stability of water-based ink colloids. The surface of water-based ink carbon black particles is negatively charged. In this experiment, the effect of cationic surfactant ctab on the stability of water-based ink colloids was first studied. Figure 1 shows the effect of different concentrations of ctab on the average particle size and zeta potential of water-based ink carbon black particles.

The zeta potential curve shows that when the ctab concentration is only 0.14 mmol / l, the zeta potential of the carbon black particles can reach 12.7 mv, and when the ctab concentration is 0.86 mmol / l, the zeta potential reaches the maximum value of 34.1 mv, which indicates that ctab has a very strong characteristic adsorption on the surface of carbon black particles. The average particle size curve shows that the maximum increase in average particle size is 5 nm.

Figure 2 shows the effect of the system ph on the adsorption of ctab [c (ctab) = 0.5 mmol / l] on the surface of carbon black particles. The zeta potential curve shows that after adding ctab, zeta potential is greater than 20 mv under each pn condition, and as ph increases, zeta potential shows a gradual downward trend. This may be because under acidic conditions, not only the characteristic adsorption of ctab on the surface of the carbon black particles, but also the characteristic adsorption of h ions; and under alkaline conditions, oh will neutralize part of the positive charge of ctab, so it will cause The zeta potential of carbon black particles decreases. The average particle size curve shows that the maximum average particle size can reach 167 nm, and the maximum increase in average particle size is 13 nm.

Figures 1 and 2 show that the cationic surfactant ctab has a greater influence on the zeta potential of the aqueous ink carbon black particles, and the reduction of the zeta potential does not promote the increase in the average particle size of the corresponding carbon black particles, which shows the stability of the aqueous ink colloid solution The property is mainly determined by the interstitial steric effect between carbon black particles.

2.2 Anionic surfactant sodium dodecyl sulfonate (sds) pair

The influence of the stability of water-based ink colloids

The effect of sodium dodecyl sulfonate on the stability of aqueous ink colloids is shown in Figure 3.

The zeta potential curve shows that when the concentration of sds is 0.2 mmol / l, the zeta potential of the carbon black particles is 31.1 mv, and when the concentration of sds is 1 mmol / l, the zeta potential is 38.2 mv. This may be because when the concentration of sds is low, the na ion neutralizes part of the negative charge on the surface of the ink carbon black particles and reduces the absolute value of zeta potential. Chemical adsorption j makes the carbon black particles more negatively charged; the average particle size curve shows that as the surface of the carbon black particles is more negatively charged, the average particle size is 2 nm lower than the average particle size of the original carbon black particles, so sds The addition of will make the aqueous ink colloid solution more stable.

2.3 Amphoteric surfactant Cocamidopropylamine oxide

(capo) Effect on the stability of aqueous ink colloids Amine oxide is a multifunctional weak cationic surfactant. Because its performance has a strong dependence on the system pH, this experiment studied the effect of capo on the average particle size of carbon black particles and zeta potential under different pH conditions, as shown in Figure 4.

The zeta potential curve shows that when ph = 8.3, the zeta potential is 37.4 mv. As the ph decreases, the zeta potential changes toward the isoelectric point. When the ph is about 6.0, the zeta potential reaches the isoelectric potential Point, and when ph = 3.2, the zeta potential reaches the maximum value of 28.5mv, which is mainly because capo shows the nature of cationic surfactant under acidic conditions, and its principle of action is the same as that of ctab. The average particle size curve shows that when the zeta potential of the carbon black particles reaches the isoelectric point, the average particle size only increases by 8 nm compared to the average particle size of the original aqueous ink carbon black, which also shows the steric effect between the carbon black particles It is the main factor affecting the stability of water-based ink colloids; when ph = 4.4, the average particle size reaches a maximum of 163 nm, and the maximum increase in average particle size is 9 nm. [next]

2.4 Nonionic surfactant fatty alcohol polyoxyethylene ethers

(aeo) Effect on the stability of water-based ink colloids Because nonionic surfactants do not exist in ionic state in solution, they are not easily affected by strong electrolytes, and their applications are becoming more and more widespread. The effects of aeo-7 and aeo-9 on the stability of water-based ink colloids were discussed.

The effect of average particle size and o: 7 on the zeta potential of water-based ink carbon black particles.

The zeta potential curve shows that the aeo-7 concentration increases from 0 to 0. At i mol / l, the zeta potential changes from a 37.9 rnv to a 16.3mv. Since the nonionic surfactant has no charge, its adsorption on the surface of the carbon black particles will not cause changes in its charge, but the addition of aeo-7 reduces the negative charge on the surface of the carbon black particles. The reason may be aeo-1 7 After adsorbed on the surface of the carbon black particles, the position of the slip surface is moved or the adsorption characteristics of the ions that already exist in the solution are changed; the average particle size curve shows that as the concentration of aeo-7 increases, the average carbon black particles The particle size increases from the initial 154 nm to 240 nm, which shows that the addition of aeo-7 may also reduce the steric hindrance effect between the carbon black particles of the aqueous ink. It can also be seen from Figure 5 that aeo-7 not only has a greater impact on the zeta potential of the solution system, but also has a greater impact on the aggregation of carbon black particles than ctab, sds and capo.

Figure 6 shows the effect of different concentrations of aeo-9 on the average particle size and zeta potential of water-based ink carbon black particles.

After adding aeo-9, the change tendency of the zeta potential of the aqueous ink colloid solution and the average particle size of the carbon black particles is the same as that of adding aeo-7.

3. in conclusion

(1) Cationic surfactants (ctab, capo under acidic conditions) can reverse the charge on the surface of carbon black particles. However, the decrease in zeta potential does not promote the average particle size of carbon black particles. The colloidal stability of the aqueous ink solution is mainly determined by the spatial steric hindrance effect.

(2) Adding anionic surfactant sodium dodecyl sulfonate (sds) can make the surface of carbon black particles more negatively charged, which will make the aqueous ink colloid solution more stable.

(3) Non-ionic surfactant fatty alcohol polyoxyethylene ether (aeo-7, aeo-9) can greatly reduce the negative charge of water-based ink carbon black particles, and its effect on the average particle size of carbon black particles is more than that of ctab, Both sds and capo are significant, so aeo-7 or aeo-9 is suitable for flotation deinking of water-based ink waste paper.

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