Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether made from natural polymer material cellulose through a series of chemical processes. Hydroxypropylmethylcellulose (HPMC) is an odorless, tasteless, non-toxic white powder that can be dissolved in cold water to form a transparent viscous solution. It has the properties of thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface active, maintaining moisture and protecting colloid.
HPMC is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries. HPMC can be divided into construction grade, food grade and pharmaceutical grade according to the purpose. At present, most of the domestic products are construction grade. In construction grade, putty powder is used in a large amount, about 90% is used for putty powder, and the rest is used for cement mortar and glue.
Cellulose ether is a non-ionic semi-synthetic high molecular polymer, which is water-soluble and solvent-soluble.
The effects caused by different industries are different. For example, in chemical building materials, it has the following compound effects:
①Water retaining agent, ②Thickener, ③Leveling property, ④Film forming property, ⑤Binder
In the polyvinyl chloride industry, it is an emulsifier and dispersant; in the pharmaceutical industry, it is a binder and a slow and controlled release framework material, etc. Because cellulose has a variety of composite effects, its application The field is also the most extensive. Next, I will focus on the use and function of cellulose ether in various building materials.
Application in wall putty
In the putty powder, HPMC plays three roles of thickening, water retention and construction.
Thickening: Cellulose can be thickened to suspend and keep the solution uniform up and down, and resist sagging.
Construction: Cellulose has a lubricating effect, which can make the putty powder have good construction.
Application in concrete mortar
The mortar prepared without adding water-retaining thickener has high compressive strength, but poor water-retaining property, cohesiveness, softness, serious bleeding, poor operation feel, and basically cannot be used. Therefore, water-retaining thickening material is an essential component of ready-mixed mortar. In mortar concrete, hydroxypropyl methyl cellulose or methyl cellulose is generally selected, and the water retention rate can be increased to more than 85%. The method of use in mortar concrete is to add water after the dry powder is evenly mixed. High water retention can fully hydrate the cement. Significantly increased bond strength. At the same time, the tensile and shear strength can be appropriately improved. Greatly improve the construction effect and improve work efficiency.
Application in tile adhesive
1. Hydroxypropyl methylcellulose tile adhesive is specially used to save the need to pre-soak the tiles in water
2. Standardized paste and strong
3. The paste thickness is 2-5mm, saving materials and space, and increasing the decoration space
4. The posting technical requirements for the staff are not high
5. There is no need to fix it with cross plastic clips at all, the paste will not fall down, and the adhesion is firm.
6. There will be no excess slurry in the brick joints, which can avoid the pollution of the brick surface
7. Multiple pieces of ceramic tiles can be pasted together, unlike single-piece sizing of construction cement mortar.
8. The construction speed is fast, about 5 times faster than cement mortar posting, saving time and improving work efficiency.
Application in caulking agent
The addition of cellulose ether makes it have good edge adhesion, low shrinkage and high abrasion resistance, which protects the base material from mechanical damage and avoids the negative impact of water penetration on the entire building.
Application in self-leveling materials
Prevent bleeding:
Plays a good role in suspension, preventing slurry deposition and bleeding;
Maintain mobility and:
The product’s low viscosity does not affect the flow of the slurry and is easy to work with. It has a certain water retention and can produce a good surface effect after self-leveling to avoid cracks.
Application of exterior wall insulation mortar
In this material, cellulose ether mainly plays the role of bonding and increasing the strength, making the mortar easier to coat and improving work efficiency. At the same time, it has the ability to resist hanging. Crack resistance, improve surface quality, increase bond strength.
The addition of hydroxypropyl methylcellulose also had a significant slowing effect on the mortar mix. With the increase of the amount of HPMC, the setting time of the mortar is extended, and the amount of HPMC is also increased accordingly. The setting time of the mortar formed under water is longer than that formed in the air. This feature is great for pumping concrete underwater. Fresh cement mortar mixed with hydroxypropyl methylcellulose has good cohesive properties and almost no water seepage
Application in gypsum mortar
1. Improve the spreading rate of gypsum base: Compared with similar hydroxypropyl methylcellulose ether, the spreading rate is significantly increased.
2. Application fields and dosage: light bottom plastering gypsum, the recommended dosage is 2.5-3.5 kg/ton.
3. Excellent anti-sagging performance: no sag when one-pass construction is applied in thick layers, no sag when applied for more than two passes (more than 3cm), excellent plasticity.
4. Excellent constructability: easy and smooth when hanging, can be molded at one time, and has plasticity.
5. Excellent water retention rate: prolong the operation time of gypsum base, improve the weather resistance of gypsum base, increase the bonding strength between gypsum base and the base layer, excellent wet bonding performance, and reduce landing ash.
6. Strong compatibility: It is suitable for all kinds of gypsum base, reducing the sinking time of gypsum, reducing the drying shrinkage rate, and the wall surface is not easy to hollow and crack.
Application of interface agent
Hydroxypropylmethylcellulose (HPMC) and hydroxyethylmethylcellulose (HEMC) are widely used building materials,
When applied as an interface agent for interior and exterior walls, it has the following characteristics:
-Easy to mix without lumps:
By mixing with water, the friction during the drying process is greatly reduced, making mixing easier and saving mixing time;
- Good water retention:
Significantly reduces the moisture absorbed by the wall. Good water retention can ensure a long preparation time of cement, and on the other hand, it can also ensure that workers can scrape the wall putty many times;
- Good working stability:
Good water retention in high temperature environment, suitable for working in summer or hot areas.
- Increased water requirements:
Significantly increases the water demand of putty materials. It increases the service time of the putty on the wall, on the other hand, it can increase the coating area of the putty and make the formula more economical.
Application in gypsum
At present, the most common gypsum products are plastering gypsum, bonded gypsum, inlaid gypsum, and tile adhesive.
Gypsum plaster is a high-quality plastering material for interior walls and ceilings. The wall surface plastered with it is fine and smooth, does not lose powder, is firmly bonded to the base, has no cracking and falling off, and has a fireproof function;
Adhesive gypsum is a new type of adhesive for building light boards. It is made of gypsum as the base material and various additives.
It is suitable for the bonding between various inorganic building wall materials. It has the characteristics of non-toxic, tasteless, early strength and fast setting, and firm bonding. It is a supporting material for building boards and block construction;
Gypsum caulk is a gap filler between gypsum boards and a repair filler for walls and cracks.
These gypsum products have a series of different functions. In addition to the role of gypsum and related fillers, the key issue is that the added cellulose ether additives play a leading role. Because gypsum is divided into anhydrous gypsum and hemihydrate gypsum, different gypsum has different effects on the performance of the product, so thickening, water retention and retardation determine the quality of gypsum building materials. The common problem of these materials is hollowing and cracking, and the initial strength cannot be reached. To solve this problem, it is to choose the type of cellulose and the compound utilization method of the retarder. In this regard, methyl or hydroxypropyl methyl 30000 is generally selected. –60000cps, the added amount is between 1.5‰–2‰, the cellulose is mainly used for water retention and retarding lubrication.
However, it is impossible to rely on cellulose ether as a retarder, and it is necessary to add a citric acid retarder to mix and use without affecting the initial strength.
Water retention generally refers to how much water will be lost naturally without external water absorption. If the wall is too dry, water absorption and natural evaporation on the base surface will make the material lose water too quickly, and hollowing and cracking will also occur.
This method of use is mixed with dry powder. If you prepare a solution, please refer to the preparation method of the solution.
Application in latex paint
In the latex paint industry, hydroxyethyl cellulose should be selected. The general specification of medium viscosity is 30000-50000cps, which corresponds to the specification of HBR250. The reference dosage is generally about 1.5‰-2‰. The main function of hydroxyethyl in latex paint is to thicken, prevent the gelation of the pigment, help the dispersion of the pigment, the stability of the latex, and increase the viscosity of the components, which is helpful for the leveling performance of the construction.
Post time: Dec-13-2022