1. Putty is used as a material for pretreatment of the surface to be coated in architectural coatings

Putty is a thin layer of leveling mortar. Putty is scraped on the surface of rough substrates (such as concrete, leveling mortar, gypsum board, etc.) Make the exterior wall paint layer smooth and delicate, not easy to accumulate dust and easy to clean (this is more important for areas with more severe air pollution). Putty can be divided into one-component putty (paste putty paste and dry powder putty powder) and two-component putty (composed of putty powder and emulsion) according to the finished product form. With people’s attention to the construction technology of architectural coatings, putty as an important supporting material has also been developed accordingly. Various domestic manufacturers have successively developed putty with different purposes and various forms, such as powder putty, paste putty, interior wall putty Putty, exterior wall putty, elastic putty, etc.

Judging from the actual application of domestic architectural coatings, there are often disadvantages such as foaming and peeling, which seriously affect the protection and decoration performance of coatings on buildings. There are two main reasons for the damage of the coating film:

One is the quality of paint;

The second is improper handling of the substrate.

Practice has shown that more than 70% of coating failures are related to poor substrate handling. Putty for architectural coatings has been widely used as a raw material for surface pretreatment to be coated. It can not only smooth and repair the surface of buildings, but also high-quality putty can greatly enhance the protection and decoration performance of coatings on buildings. Extending the service life of the coating is an indispensable supporting product for high-performance architectural coatings, especially exterior wall coatings. The single-component dry powder putty has obvious economic, technical and environmental advantages in production, transportation, storage, construction and so on.

Note: Due to factors such as raw materials and cost, dispersible polymer powder is mainly used in anti-cracking putty powder for exterior walls, and also used in high-grade interior wall polishing putty.

2. The role of anti-cracking putty for exterior walls

External wall putty generally uses cement as the inorganic bonding material, and a small amount of ash calcium can be added to achieve a synergistic effect. The role of cement-based anti-cracking putty for exterior walls:
The surface layer putty provides a good base surface, which reduces the amount of paint and reduces the project cost;
Putty has strong adhesion and can be well attached to the base wall;
It has a certain toughness, can well buffer the effect of different expansion and contraction stresses of different base layers, and has good crack resistance;
Putty has good weather resistance, impermeability, moisture resistance and long service time;
Environmentally friendly, non-toxic and safe;
After the modification of functional additives, such as putty rubber powder and other materials, the exterior wall putty can also have the following additional functional advantages:
The function of direct scraping on old finishes (paint, tile, mosaic, stone and other smooth walls);
Good thixotropy, a nearly perfect smooth surface can be obtained by simply smearing, and the loss caused by multi-use coatings due to uneven base surface is reduced;
It is elastic, can resist micro-cracks, and can offset the damage of temperature stress;
Good water repellency and waterproof function.

3. The role of redispersible latex powder in exterior wall putty powder

(1) The effect of putty rubber powder on newly mixed putty:
Improve workability and improve putty batch scraping performance;
additional water retention;
increased workability;
Avoid early cracking.

(2) The effect of putty rubber powder on hardened putty:
Reduce the elastic modulus of putty and enhance the matching to the base layer;
Improve the micro-pore structure of cement, increase flexibility after adding putty rubber powder, and resist cracking;
Improve powder resistance;
Hydrophobic or reduce the water absorption of the putty layer;
Increase the adhesion of the putty to the base wall.

Fourth, the requirements of the external wall putty construction process

Putty construction process should pay attention to:
1. The influence of construction conditions:
The influence of construction conditions is mainly the temperature and humidity of the environment. In hot climates, the base layer should be properly sprayed with water, or kept wet, depending on the performance of the specific putty powder product. Since the exterior wall putty powder mainly uses cement as the cementitious material, the ambient temperature is required not to be lower than 5 degrees, and it will not be frozen before hardening after construction.

2. Preparation and precautions before scraping putty:
It is required that the main project has been completed, and the building and roof have been completed;
All embedded parts, doors, windows and pipes of the ash base should be installed;
To prevent contamination and damage to finished products in the batch scraping process, specific protection items and measures should be determined before batch scraping, and relevant parts should be covered and wrapped;
The installation of the window should be carried out after the putty batch is scraped.

3. Surface treatment:
The surface of the substrate should be firm, flat, dry and clean, free from grease, batik and other loose matters;
The surface of the new plastering should be cured for 12 days before the putty can be scraped, and the original plastering layer cannot be calendered with cement paste;
If the wall is too dry before construction, the wall should be wetted in advance.

4. Operation process:
Pour an appropriate amount of water into the container, then add dry putty powder, and then fully stir with a mixer until it is a uniform paste without powder particles and precipitation;
Use a batch scraping tool for batch scraping, and the second batch scraping can be carried out after the first layer of batch embedding is completed for about 4 hours;
Scrape the putty layer smoothly, and control the thickness to be about 1.5mm;
The cement-based putty can be painted with alkali-resistant primer only after the natural curing has been completed until the alkalinity and strength meet the requirements;

5. Notes:
The verticality and flatness of the substrate should be determined before construction;
The mixed putty mortar should be used up within 1~2h (depending on the formula);
Do not mix the putty mortar that has exceeded the use time with water before using it;
It should be polished within 1~2d;
When the base surface is calendered with cement mortar, it is recommended to use interface treatment agent or interface putty and elastic putty.

The dosage of redispersible polymer powder can refer to the dosage data in the formula of exterior wall putty powder. It is recommended that customers conduct several different small sample experiments before mass production to ensure the quality of putty powder.