Factors influencing the viscosity and light transmission of hydroxypropyl methylcellulose

Factors influencing the viscosity and light transmission of hydroxypropyl methylcellulose

The main points that affect the light transmission of hydroxypropyl methylcellulose are the following.

I. The quality of the raw material.

Second, the effect of alkalization.

Three, the process ratio

Four, the ratio of solvent

Five, the effect of neutralization

Some products are very cloudy after dissolution like adding milk, some are milky white, some are yellowish, some are clear and transparent …… To solve it, adjust from the following points. Sometimes acetic acid can seriously affect the transmittance, acetic acid is best diluted with, the biggest impact or the reaction of the stirring is uniform, the system ratio is stable (some material moisture, the content is not stable, such as recycling sets of solvents), in fact, many factors in the impact. If the equipment is stable and the operators are well trained, the production should be very stable. The light transmittance will not exceed ±2% range, and the uniformity of substitution of the substitution groups should be controlled. If the substitution is uniform, the transmittance will be good.

Factors affecting the viscosity of hydroxypropyl methyl cellulose

High-viscosity hydroxypropyl methyl cellulose in the production of vacuum and nitrogen replacement alone can not produce a very high cellulose. In general, the production of high viscosity cellulose is not controlled in China. However, if a micro oxygen meter can be installed in the kettle, the viscosity of the production can be controlled artificially. In addition, the speed of nitrogen replacement is taken into account, and the system is airtight again. Of course, the degree of polymerisation of the refined cotton is also crucial. If this is not possible, then hydrophobic bonding is the way to go. There are bonding agents available in China for this purpose. The choice of joining agent has a great influence on the performance of the final product. The residual oxygen in the reactor causes degradation of the cellulose and reduces the molecular weight, but the residual oxygen is limited and it is not difficult to make high viscosity as long as the broken molecules are reattached. However, the water saturation rate is related to the content of hydroxypropyl. Some factories only want to reduce the cost and price, and do not want to increase the content of hydroxypropyl, so the quality cannot reach the level of similar products abroad. The water retention rate of the product is very much related to hydroxypropyl, but for the whole reaction process also determines its water retention rate, the effect of alkalization, the ratio of chloromethane and propylene oxide, the concentration of alkali and the ratio of water to refined cotton all determine the performance of the product.

The higher the amount of cellulose ether HPMC added, the higher the water retention rate and the better the water retention effect. In the range of 0.25-0.6% addition, the water retention rate increases faster as the addition amount increases; when the addition amount increases further, the trend of increasing water retention rate becomes slower.