Carbomer's dispersion and thickening technology
Carbomer is a white loose powder with strong hygroscopicity and slight special smell. It has the functions of thickening, suspending and emulsifying. When we use it, we usually make it into a gel and use it. How to make carbomer achieve better results is inseparable from the role of dispersion and thickening. How to disperse and thicken is a technical life.
Before thickening, the resin powder must be fully dispersed in the liquid medium. Carbomer powder is very easy to absorb moisture and agglomerate, and the surface gelatinizes to form a protective layer to prevent rapid wetting inside the lumps. The following methods can be used to disperse:
① Sprinkle the fine powder evenly on the vortex surface of the solution to make it swell naturally.
②Add glycerin, propylene glycol or polyhexylene glycol into the drying container, sprinkle the powder on it, moisten and swell first, and then add water to dissolve it.
③ Use 0.05% anionic or non-ionic wetting agent such as polysorbate 80 to accelerate dispersion.
④ Dry mixed with other dry ingredients first.
⑤Carbomer resin is easy to disperse in the oil phase of most emulsions. After dispersion, add the water phase, and the neutralizer can still thicken normally.
⑥ It can be stirred properly to accelerate the mixing of resin and solvent.
Neutralization and thickening:
①The usual thickening method in water is to neutralize with a monovalent inorganic base such as NaOH, KOH, NaHCO3 or triethanolamine. The inorganic base should be added as a 10%-20% solution, because the soluble divalent cations make the carbomer resin Cross-linking causes a decrease in viscosity and precipitation, so it cannot be neutralized with a divalent base such as Ca(OH)2.
②In a weakly polar or non-polar organic solvent, neutralize with amine soluble in the solvent medium used to ensure that the salt is easily soluble in the solvent.
③ Excessive neutralization will cause viscosity loss. The amount of neutralizer can be estimated in advance, and the pH value should be measured after equilibrium. The pH value is generally controlled between 5.5 and 10. Some drugs need to choose a more suitable pH value due to drug stability.
④When carbomer is used as emulsifier, it can be neutralized by water-soluble alkali and oil-soluble amine. The part of carbomer that is neutralized by water-soluble alkali is soluble in water, and the part that is neutralized by oil-soluble amine is soluble in oil. Phase, this emulsion has excellent chemical and physical stability.
Another-the thickening method is hydrogen bonding:
Carbomer is a hydrogen bond proton donor (carboxyl donor), plus 10% to 20% of the hydroxyl donor (such as polyols, polyhydroxy and polyethoxy solvents, non-ionic surfactants), carboxyl donor The body and the hydroxyl donor combine to form a hydrogen bond, and the curled molecules are unwound and plasticized in the aqueous system without neutralization. The hydrogen bond bonding takes 5min to 3h.
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