Simple and effective test of hydroxypropyl methylcellulose

We all know that there are a large number of hydroxypropyl methylcellulose manufacturers and different models of hydroxypropyl methylcellulose at different prices on the market. How can we distinguish the quality of these products? From the appearance, it is very difficult to find, because the color and shape of the products are almost the same. Here we introduce the filter paper method to test the quality of the products.

Filter paper method:

Filter paper method is to judge the water retention of cellulose ether by the water absorption of filter paper. It is composed of a certain height of metal ring test mold, filter paper and glass supporting plate. There are six layers of filter paper under the test mold, among which the first layer is fast filter paper, and the other five layers are slow filter paper. Use a precision balance to weigh the weight of the supporting plate and 5 layers of slow filter paper, pour the mortar into the test mold after mixing and leveling, and then place it for 15min, and then weigh the weight of the supporting plate and 5 layers of slow filter paper.

According to the following formula:

M=（m1-m2）/S

M --- water loss, g / mm2

M1 --- weight of supporting plate + 5 layers of slow filter paper; G

M2 --- the weight of the back support plate + 5 layers of slow filter paper in 15min; G

S is the area of the test mold, mm ~ 2

It can also directly observe the degree of water absorption of the filter paper. The lower the water absorption of the filter paper, the better the water retention. This method is easy to operate and suitable for most users of HPMC.

Another way to dissolve hydroxypropyl methylcellulose is introduced

Dissolution method:

(1) The required water is heated at 80-90 ℃ and mixed continuously to gradually join MC. The slurry is cooled to obtain uniform aqueous solution. Or 1 / 3 ~ 2 / 3 of the required amount of hot water, heating to 80 ~ 90 ℃, gradually adding MC under continuous mixing, after swelling, then adding the remaining cold water, after mixing and cooling.

(2) MC after surface treatment can be wetted with cold water first, then added with ammonia or alkali water to adjust pH to 8 ~ 10 to form viscosity solution. (the ability of the solution to dissolve after transmission)