Synthesis and Rheological Properties of Hydroxyethyl Cellulose Ether

In the presence of a self-made alkali catalyst, industrial hydroxyethyl cellulose was reacted with N-(2,3-epoxypropyl)trimethylammonium chloride (GTA) cationization reagent to prepare high-substitution quaternary ammonium by dry method Salt type Hydroxyethyl  cellulose ether (HEC). The effects of the ratio of GTA to hydroxyethyl cellulose (HEC), the ratio of NaOH to HEC, the reaction temperature, and the reaction time on the reaction efficiency were investigated with a uniform experimental plan, and the optimized process conditions were obtained through Monte Carlo simulation. And the reaction efficiency of the cationic etherification reagent reaches 95% through experimental verification. At the same time, its rheological properties were discussed. The results showed that the solution of HEC showed the characteristics of non-Newtonian fluid, and its apparent viscosity increased with the increase of the solution mass concentration; in a certain concentration of salt solution, the apparent viscosity of HEC decreased with the increase of the added salt concentration. Under the same shear rate, the apparent viscosity of HEC in CaCl2 solution system is higher than that of HEC in NaCl solution system.

Key words: Hydroxyethyl  cellulose ether; dry process; rheological properties

Cellulose has the characteristics of rich sources, biodegradability, biocompatibility and easy derivatization, and is a research hotspot in many fields. Cationic cellulose is one of the most important representatives of cellulose derivatives. Among the cationic polymers for personal protection products registered by CTFA of Fragrance Industry Association, its consumption is the first. It can be widely used in hair conditioner conditioning additives, softeners, drilling shale hydration inhibitors and blood anti-coagulation agents and other fields.

At present, the preparation method of quaternary ammonium cationic hydroxyethyl cellulose ether is a solvent method, which requires a large amount of expensive organic solvents, is costly, unsafe, and pollutes the environment. Compared with the solvent method, the dry method has the outstanding advantages of simple process, high reaction efficiency, and less environmental pollution. In this paper, cationic cellulose ether was synthesized by dry method and its rheological behavior was studied.

1. Experimental part

1.1 Materials and reagents

Hydroxyethyl cellulose (HEC industrial product, its molecular substitution degree DS is 1.8~2.0); cationization reagent N-(2,3-epoxypropyl)trimethylammonium chloride (GTA), prepared from epoxy chloride Propane and trimethylamine are self-made under certain conditions; self-made alkali catalyst; ethanol and glacial acetic acid are analytically pure; NaCl, KCl, CaCl2, and AlCl3 are chemically pure reagents.

1.2 Preparation of quaternary ammonium cationic cellulose

Add 5g of hydroxyethyl cellulose and an appropriate amount of homemade alkali catalyst into a cylindrical steel cylinder equipped with a stirrer, and stir for 20 minutes at room temperature; then add a certain amount of GTA, continue stirring for 30 minutes at room temperature, and react at a certain temperature and time , a solid crude product essentially based on was obtained. The crude product is soaked in an ethanol solution containing an appropriate amount of acetic acid, filtered, washed, and vacuum-dried to obtain powdered quaternary ammonium cationic cellulose.

1.3 Determination of nitrogen mass fraction of quaternary ammonium cationic hydroxyethyl cellulose

The mass fraction of nitrogen in the samples was determined by the Kjeldahl method.

2. Experimental design and optimization of dry synthesis process

The uniform design method was used to design the experiment, and the effects of the ratio of GTA to hydroxyethyl cellulose (HEC), the ratio of NaOH to HEC, the reaction temperature and the reaction time on the reaction efficiency were investigated.

3. Research on rheological properties

3.1 Influence of concentration and rotational speed

Taking the effect of shear rate on the apparent viscosity of HEC at different concentrations Ds=0.11 as an example, it can be seen that as the shear rate gradually increases from 0.05 to 0.5 s-1, the apparent viscosity of HEC solution decreases, especially at 0.05 ~0.5s-1 apparent viscosity dropped sharply from 160MPa·s to 40MPa·s, shear thinning, indicating that the HEC aqueous solution exhibited non-Newtonian rheological properties. The effect of the applied shear stress is to reduce the interaction force between the particles of the dispersed phase. Under certain conditions, the greater the force, the greater the apparent viscosity.

It can also be seen from the apparent viscosities of 3% and 4% HEC aqueous solutions that the mass concentration is respectively 3% and 4% at different shear rates. The apparent viscosity of the solution indicates that its viscosity-increasing ability increases with the concentration. The reason is that as the concentration increases in the solution system, the mutual repulsion between the molecules of the main chain of HEC and between the molecular chains increases, and the apparent viscosity increases.

3.2 Effect of different concentrations of added salt

The concentration of HEC was fixed at 3%, and the effect of adding salt NaCl on the viscosity properties of the solution was investigated at different shear rates.

It can be seen from the results that the apparent viscosity decreases with the increase of the added salt concentration, showing obvious polyelectrolyte phenomenon. This is because part of the Na+ in the salt solution is bound to the anion of the HEC side chain. The greater the concentration of the salt solution, the greater the degree of neutralization or shielding of the polyion by the counterion, and the reduction of the electrostatic repulsion, resulting in a decrease in the charge density of the polyion. , the polymer chain shrinks and curls, and the apparent concentration decreases.

3.3 Effect of different added salts on

It can be seen from the influence of two different added salts, Nacl and CaCl2, on the apparent viscosity of the HEC solution that the apparent viscosity decreases with the addition of the added salt, and at the same shear rate, the apparent viscosity of the HEC solution in the CaCl2 solution system The apparent viscosity is significantly higher than that of HEC solution in NaCl solution system. The reason is that calcium salt is a divalent ion, and it is easier to bind on the Cl- of the polyelectrolyte side chain. The combination of the quaternary ammonium group on HEC with Cl- is reduced, and the shielding is less, and the charge density of the polymer chain is higher, resulting in The electrostatic repulsion on the polymer chain is larger, and the polymer chain is stretched, so the apparent viscosity is higher.

4. Conclusion

Dry preparation of highly substituted cationic cellulose is an ideal preparation method with simple operation, high reaction efficiency, and less pollution, and can avoid high energy consumption, environmental pollution, and toxicity caused by the use of solvents.

The solution of cationic cellulose ether presents the characteristics of non-Newtonian fluid and has the characteristics of shear thinning; as the solution mass concentration increases, its apparent viscosity increases; in a certain concentration of salt solution, HEC apparent viscosity increases with increase and decrease. Under the same shear rate, the apparent viscosity of HEC in CaCl2 solution system is higher than that of HEC in NaCl solution system.