Hydroxypropyl methylcellulose is a naturally occurring cellulose ether, which is not harmful to the human body. However, the raw materials of cotton linters and HPMC used in the factory are all face, because this will have the effect of dust, and the others are not harmful.
Hydroxypropyl methylcellulose is non-toxic. Cellulose is considered suitable and is processed by using naturally occurring fibers through alkali fusion, grafting response, washing, drying, grinding and other processes. Will not endanger people’s health.
Hydroxypropyl methyl cellulose, also known as hypromellose and cellulose hydroxypropyl methyl ether, is made by using highly pure cotton cellulose as raw material and undergoing special etherification under alkaline conditions.
The synthesis of hydroxypropyl methylcellulose: the refined cotton cellulose is treated with lye at 35-40℃ for half an hour, squeezed, the cellulose is crushed, and the aging is carried out at 35℃ to make the obtained alkali fiber uniformly polymerized. Within the required range. Put the alkali fiber into the etherification kettle, add propylene oxide and methyl chloride in sequence, and etherify at 50-80℃ for 5h, and the upper pressure is about 1.8MPa. Then add the appropriate amount of hydrochloric acid and oxalic acid to wash the materials in hot water at 90°C to increase the size and volume. Dehydrate by centrifugation. Swash to neutral. When the water content in the material is less than 60%, dry it with a stream of hot air at 130°C to a content of less than 5%.
The HPMC produced by the solvent method uses toluene and isopropanol as the solvent. If it is washed very badly, it will have a little leftover smell. This is a problem of the washing process, which does not affect the use or any problem.
Hypromellose is a refined cotton that is rarely impregnated with liquid to obtain alkaline cellulose, and then participates in solvents, etherification agents, toluene and isopropanol for etherification reactions, and is neutralized, washed, dried, and crushed to obtain finished products. Very bad and smelly, so users can use it in a stable mood.
Hydroxypropyl methylcellulose should pay attention to the following items in the application:
In the effect of mud powder, hydroxypropyl methylcellulose only plays a supporting effect, and does not participate in any chemical reaction. The mud powder is added with water and put on the wall, which is a chemical reaction. Because of the formation of new things, the mud powder on the wall is removed from the wall and ground into powder to form new things. Hydroxypropyl methylcellulose only retains water and helps gray calcium to have a better response, but it does not participate in any response.
Hydroxypropyl Methyl Cellulose HPMC does not participate in any chemical reaction, but only helps. Add water to the mud powder and put it on the wall, it is a chemical reaction. Because of the formation of new things, the mud powder on the wall is removed from the wall and ground into powder, and then it is not possible, because new things have been formed NS. The main components of gray calcium powder are: Ca(OH)2, a mixture of CaO and a small amount of CaCO3, CaO
H2O=Ca（OH）2-Ca（OH）2 CO2=CaCO3↓ H2O
Gray calcium produces other things under the effect of water and CO2 in the air, while HPMC only retains water and helps gray calcium to have a better response. It does not participate in any response.
Hydroxypropyl methyl cellulose has a wide range of uses. In daily life, many products are inseparable from the manufacturing process. Then, in different industries, what is the effect of hydroxypropyl methylcellulose, I will explain it to you, so that you can prevent misuse of it while gaining knowledge.
First of all, in the construction industry, it can be regarded as a retarder and water-retaining agent. The mortar mortar is pumpable, so all the dry mortar we use has its participation. In addition, in construction materials such as raw gypsum, plaster, and mud powder, it can be used as a binder, which not only extends the time for operation, but also makes the paint more smearable. In marble, adhesive ceramic tiles, molecular compound plastic decorations, it can be used as an adhesion enhancer, etc. It can be said that hydroxypropyl methyl cellulose is the most famous for its versatility in building materials.
In other industries, such as porcelain and pottery manufacturing, it can be used as an adhesive for the manufacture of porcelain and pottery products; in the lacquer industry and ink printing, it can be used as a loose powder, thickener, stabilizer, and even because it can be combined with organic Solvent or water blends beautifully, and can be used as paint remover in the manufacture of molecular compound plastics, as well as softeners, mold release agents, lubricants, etc.; in the manufacture of polyvinyl chloride, it is regarded as a loose powder.
The products made of hydroxypropyl methylcellulose are widely used in the freshness of fruits and vegetables, medicine, animal skins and textile industries. It is safe and non-toxic, not very irritating to human body mucous membranes and skins, and can even be used as a food additive. However, in the real situation of the matter, its dust may cause air pollution, and it is not beneficial to the maintenance of the skin to isolate it from the fire to avoid explosion.
There is also the amount of hydroxypropyl methylcellulose HPMC used in practical applications, which is affected by the climatological background, temperature, local gray calcium quality, the prescription of mud powder and the “quality required by customers”. Each is different. Generally speaking, it is between 4 kg and 5 kg. For example, most of the mud powder in Beijing is 5 kg; most of Guizhou is 5 kg in summer and 4.5 kg in winter; Yunnan has a small amount, usually 3 kg-4 kg and so on. The amount of addition is slightly different everywhere, and the quality requirements for the mud powder are also different everywhere.
water retention
The special hydroxypropyl methylcellulose for construction avoids the excessive use of water by the substrate, and the water should be kept in the plaster as much as possible during the period when the gypsum is completely set. This special property is called water retention and is directly proportional to the viscosity of the hydroxypropyl methylcellulose solution used for construction in the plaster. The higher the solution viscosity, the higher the water retention experience.
Anti-sagging
The mortar with special properties of anti-sagging can be applied with a thicker coating without sagging, which also means that the mortar itself does not change its gender, otherwise it will slide down when the construction starts.
Reduce viscosity and facilitate construction
After adding various construction-specific hydroxypropyl methylcellulose products, green gypsum plaster with a mildly viscous attitude can be produced. When it is deemed appropriate and a lower-viscosity grade of construction-specific hydroxypropyl methylcellulose is used, The degree of viscosity is relatively reduced and construction becomes easier. However, the water retention of hydroxypropyl methylcellulose for low-viscosity construction is relatively weak, and it is necessary to increase the amount of addition.
Plastic compatibilization rate
For a fixed amount of dry mortar, it is more economical to produce a higher wet mortar size, which can be achieved by adding a little water and bubbles. However, if the amount of water and bubbles is too long, the strength is impaired.
Post time: Nov-11-2021