What factors affect the water retention of hpmc cellulose ?
Hydroxypropyl Methyl Cellulose (HPMC) is odorless, tasteless,non-toxic cellulose ethers produce from natural high molecular cellulose through series of chemical processing and chieved.It is white powder with good water solubility. It has thickening, adhesion ,dispersing, emulsifying, film, suspended, adsorption, gel, and protective colloid properties of surface activity and maintain moisture function properties ect.
It is well known that the main function of HPMC cellulose is water retention . What kind of HPMC cellulose has good water retention performance, which factors will affect the performance of HPMC?
First factor is the ash content
The hydroxypropyl methyl cellulose is made of fine cotton , the main factor affecting the water retention of HPMC cellulose is the purity, commonly known as ash.
The smaller the ash, the better the water retention . On the contrary, the greater the ash content, the worse the water retention.
Secend factor is the gel temperature
High quality HPMC cellulose gel has high temperature characteristics, not affected by high temperature weather.
The lower the water retention temperature of the gel, the worse the water retention effect at high temperature, and the complete loss of water retention ability.
Third factor is the viscosity
In general, the higher the viscosity, the better the water retention effect, but if the viscosity is too high, the higher the molecular weight of HPMC cellulose, this will cause negative effects such as scraping.
Fourth factory is the amount added
Low addition amount can also lead to poor water retention.
The above 5 factors will affect the water retention of HPMC cellulose.
Fifth factor is the HPMC manufacturing process:
A.Horizontal reactor drying process is an early developed production process.
The cotton fiber was knead in liquid alkali and alkalized, and then etherified with etherifying agent.
The drying process is not conducive to the diffusion and penetration of etherification agents, and the etherification reaction time is short and the efficiency is low.
The reaction is unstable, poor uniformity and many side effects.The product quality is relatively poor, but the output is high.
Because of its relatively low cost, it is adopted by many manufacturers.But the HPMC cellulose produced by this process has poor water retention and high viscosity.
B.The alkalization and etherification of cotton fiber are carried out in inert organic solution.
Therefore, it increases the diffusion and permeability rate of the reagent, which is conducive to the mass and heat transfer in the reaction process and makes the reaction stable.
Etherification is uniform, etherification agent dosage is low, etherification efficiency is high, product quality is high and stable.
The HPMC cellulose produced by this process has good water retention, but the cost is slightly higher and the yield is low.
As a result, many manufacturers no longer use this process to pursue low cost and high yield.
