1. Ash content of hydroxypropyl methyl cellulose HPMC and its existing form
Hydroxypropyl methyl cellulose (HPMC) industrial quality standards called ash and pharmacopoeia called sulfate, namely burning residue, can simply be understood as the inorganic salt impurities in the product. Mainly by the production process of strong alkali (sodium hydroxide) through the reaction to the final adjustment of pH to neutral salt and raw material original inherent inorganic salt sum.

Method for determination of total ash; A certain amount of samples are burned in a high temperature furnace after carbonization, so that organic materials are oxidized and decomposed, escaping in the form of carbon dioxide, nitrogen oxides and water, while inorganic materials remain in the form of sulfate, phosphate, carbonate, chloride and other inorganic salts and metal oxides, these residues are ash. The total ash content of the sample can be calculated by weighing the residue.

According to the process in the use of different acid and will produce different salt: mainly sodium chloride (by the reaction of chloride ion in chloromethane and sodium hydroxide) and other acid neutralization can produce sodium acetate, sodium sulfide or sodium oxalate.

2. Ash content requirement of hydroxypropyl methyl cellulose HPMC
Hydroxypropyl methyl cellulose HPMC is mainly used for thickening, emulsifying, film forming, colloid protection, water retention, adhesion, enzyme resistance and metabolic inertia, etc. It is widely used in many fields of industry, which can be roughly divided into the following aspects:

(1) Construction: the main role is to retain water, thickening, viscosity, lubrication, flow to improve cement and gypsum workability, pumping. Architectural coatings, latex coatings are mainly used as protective colloid, film forming, thickening agent and pigment suspension aid.

(2) POLYvinyl chloride: mainly used as a dispersant in the polymerization reaction of suspension polymerization system.

(3) daily chemicals: mainly used as protective articles, it can improve the product emulsification, anti-enzyme, dispersion, bonding, surface activity, film forming, moisturizing, foaming, forming, release agent, softener, lubricant and other properties;

(4) pharmaceutical industry: in the pharmaceutical industry is mainly used for preparation production, as a solid preparation of coating agent, hollow capsule capsule material, binder, for the framework of sustained release agents, film forming, pore-causing agent, as a liquid, semi-solid preparation of thickening, emulsification, suspension, matrix application;

(5) ceramics: used as bonding forming agent of ceramic industrial blank, dispersant of glaze color;

(6) paper: dispersion, coloring, strengthening agent;

(7) Textile printing and dyeing: cloth pulp, color, color extension agent:

(8) in agricultural production: used in agriculture to treat crop seeds, can improve germination rate, can moisturize and prevent mildew, fruit preservation, sustained release of chemical fertilizers and pesticides.

From the feedback of the above long-term application experience and the summary of internal control standards of some foreign and domestic enterprises, it can be seen that only some products of PVC polymerization and daily chemical products require salt control < 0.010, and the pharmacopoeia of various countries requires salt control < 0.015. And other uses of salt control can be relatively wider, especially construction grade products in addition to the production of putty, coating salt has certain requirements outside the rest can control salt < 0.05 can basically meet the use.

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