Hydroxypropyl methylcellulose HPMC is a nonionic cellulose alkyl or hydroxyalkyl mixed ether obtained by a process of alkalizing, etherification, neutralization and water washing. Hydroxypropyl methylcellulose HPMC has good dispersing, emulsifying, thickening, bonding, water retention and gel retention properties, as well as adhesion, thickening and film forming properties. It can be widely used in petrochemical, construction, ceramics, textile, food, daily chemical, synthetic resin, pharmaceutical, paint and electronics industries due to its thickening, dispersing and emulsifying film forming properties.
Generally, hydroxypropyl methylcellulose can be produced, which can be refined cotton or wood pulp. It is necessary to pulverize it before alkalization or alkalization. The pulverization is to destroy the aggregate structure of the cellulose raw material by mechanical energy. In order to reduce crystallinity and degree of polymerization, increase the surface area thereof, thereby increasing the accessibility and chemical reaction ability of the reagent to the three hydroxyl groups on the cellulose macromolecular glucose ring group.
HPMC has three main grades: 75, 65 and 60: The 75 grade is mainly suitable for the construction industry.
Hydroxypropyl methylcellulose is one of the more and more celluloses used in the modern construction industry. Hydroxypropyl methylcellulose is widely used. Hydroxypropyl methylcellulose is alkalized by refined cotton. A nonionic cellulose mixed ether prepared by a series of reactions using propylene oxide and methyl chloride as an etherifying agent. The degree of substitution is generally 1.2 to 2.0. Its properties are different depending on the ratio of methoxyl content and hydroxypropyl content. High water retention with high hydroxypropyl content is better than major quality.
- Hydroxypropyl methylcellulose HPMC is easily soluble in cold water and dissolves rapidly in cold water. The dissolution in cold water is also much better than that of methyl cellulose. However, it is difficult to dissolve in hot water, and the gelation temperature in hot water is significantly higher than that of methyl cellulose.
The viscosity of hydroxypropyl methylcellulose HPMC is related to its molecular weight, and the molecular weight is high. The temperature also affects the viscosity of the hydroxypropyl methylcellulose, the temperature rises, and the viscosity decreases. The solution of hydroxypropylmethylcellulose HPMC is very stable at room temperature, but its viscosity is lower than that of methylcellulose by high temperature.
Hydroxypropyl methylcellulose HPMC is mixed with a water-soluble polymer compound to form a uniform, higher viscosity solution. Such as polyvinyl alcohol, starch ether and the like. Hydroxypropyl methylcellulose HPMC has better resistance to enzymatic, acid and alkali resistance than methylcellulose, and its solution is less likely to be enzymatically degraded than methylcellulose, hydroxypropylmethylcellulose The adhesion of mortar construction is higher than that of methyl cellulose, and the water retention is much better.
Hydroxypropyl methylcellulose is stable to acids and bases, and its aqueous solution is very stable in the range of pH=2~12. Hydroxypropyl methylcellulose has stability to general salts, but when the concentration of the salt solution is high, the viscosity of the HPMC solution tends to increase.
The choice of hydroxypropyl methylcellulose HPMC for construction mainly considers viscosity and light transmittance. Hydroxypropyl methylcellulose HPMC mainly has three kinds of viscosity, namely HPMC-100000, HPMC-150000, HPMC-200000 viscosity, doolchem Is a professional manufacturer of cellulose, also has low viscosity cellulose; hydroxypropyl methylcellulose HPMC light transmittance can reflect the quality and transparency of cellulose, so we have to affect the viscosity of hydroxypropyl methylcellulose and The factors of light transmittance are known.
- Factors affecting the viscosity of hydroxypropyl methylcellulose HPMC
Hydroxypropyl methylcellulose HPMC is produced by a series of etherification reactions in production, but only by vacuum and nitrogen replacement is the production of cellulose with a very high viscosity. Generally, the production of high-viscosity cellulose in China is uncontrollable, but if a trace oxygen meter is installed in the kettle, the viscosity of the cellulose production can be artificially controlled. In addition, considering the replacement rate of nitrogen, it is very easy to produce a high-viscosity product at the same time as the system is airtight. Of course, the degree of polymerization of refined cotton is also crucial. If it doesn’t work, use a hydrophobic association to do it. The choice of what kind of associative agent has a great influence on the performance of the final product. The residual oxygen in the reactor causes degradation of the cellulose, and the molecular weight is lowered, but the residual oxygen is limited, and it is not difficult to make the high viscosity by reconnecting the broken molecules. However, the water saturation rate is also closely related to the content of hydroxypropyl groups. The hydroxypropyl group content is high, and the water retention effect of the product is good. The water retention rate of the product is closely related to the hydroxypropyl group, but it also determines its water retention rate, the effect of alkalization, the ratio of methyl chloride to propylene oxide, the concentration of alkali and water for the entire reaction process. The ratio to refined cotton determines the performance of the product. Therefore, the water retention and hydroxypropyl content of hydroxypropyl methylcellulose have a great relationship with the specific gravity of the molecular weight. Therefore, we should use a product with a high specific gravity and a high hydroxypropyl content when selecting a cellulose product.
Second, factors affecting the transmittance of hydroxypropyl methyl cellulose
1, Quality of raw materials: selection of raw materials such as refined cotton, propylene oxide and methyl chloride.
2, The effect of alkalization.
3,The process ratio: the axe production, dissolution quickly, after washing three times in addition to the sewage washing process.
4, the ratio of solvent: raw materials and aqueous solution reasonable blending experiments.
5, the effect of neutralization: After the dissolution test of hydroxypropyl methylcellulose, some products are very turbid like milk after dissolution, some are milky white, some are yellow, some are clear and transparent… sometimes acetic acid can Severely affect the light transmittance, acetic acid is best used after dilution, the maximum effect is whether the stirring of the reaction is uniform, whether the system ratio is stable (some materials have moisture, the content is unstable, such as the solvent used for recycling), in fact, many factors are affecting. The equipment should be stable if the equipment is stable and the operator is skilled. The light transmittance does not exceed ±2%, and the substitution uniformity of the substituent group is controlled. Instead of uniformity, the light transmittance is definitely good. The light transmittance is good, and the aqueous solution of hydroxypropyl methylcellulose is very transparent and the transmittance is very good.
We supply different types of HPMC acted as building raw material for different application,
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