With the country's attention to energy issues, energy conservation has become a basic national policy, the country has formulated a corresponding policy to promote the external wall insulation system. And within the external wall thermal insulation is compared, external wall thermal insulation energy-saving structure is more reasonable, the use of the same size, the same performance of insulation material, thermal insulation than the thermal energy-saving effect is better. External wall thermal insulation technology can be used not only for new construction is also suitable for the energy-saving reconstruction of existing buildings; external thermal insulation material coated on the outside of the main structure, can effectively protect the construction to the main structure, prolong the service life of the building; can effectively reduce the thermal bridge of building structure, increase the construction of the effective use of space and improve the indoor living environment of comfort. In the current external wall insulation decoration surface layer, the use of most of the building paint (including high-grade paint and low-grade paint), the choice of the correct or not, directly affect the effect of external insulation and service life.
1 exterior insulation system in the presence of coating problems
At present, the vast majority of the external thermal insulation project has different degrees of coating problems, which is a prominent problem is the bubbling spalling, cracking seepage. It is mainly caused by the following reasons
First, the implementation of building insulation easily in the insulation layer below the dew and liquid water. Plus outside the insulation system if the construction is not strict or material itself, it is easy to absorb rainwater;
Second, the sun directly in the location of the sun, the wall temperature rises, the liquid water is heated into water vapor, water vapor volume expansion, it will spread around. The polystyrene board with poor permeability of condensation water generated only from the most vulnerable parts of the polyphenyl plate slit escape;
Third, paint is not breathable, the bubble is first appeared in the joints of the polystyrene board, and then through the freezing and thawing cycle, it will produce peeling off. Obviously, the poor permeability of the paint is the main cause of the blister, peeling and peeling off of the external thermal insulation coating.
Such as in exterior wall external insulation system, the low cost of the paint, the main problem is water seepage, efflorescence, fahua such, but it is not easy to appear on skin, flake, main reasons are as follows:
First, the low grade paint due to the low amount of emulsion, high porosity, good permeability, so there will not be peeling, peeling phenomenon;
Second, cheap coating of poor water resistance, easily efflorescence, poor weather resistance, for a long time, easy to fade and fly and its durability is poor.
2. Characteristics of high performance flexible coatings
According to the above analysis, it is required that the exterior insulation system should not only be breathable and waterproof, but also have good durability. Elastic paint is a synthetic resin emulsion as the base material, and pigments and fillers and additives formulated from the application of a certain thickness, can cover the base material to produce a small crack of the elastic functional coating.
Characteristics of high performance elastic coatings:
(1) maintain elasticity, flexibility and elongation is higher in a certain temperature range, good anti cracking leakage resistance;
(2) the fine water vapor permeability, which is not caused by the stress caused by the penetration of the moisture, which causes the film to bubble or peel off;
(3) in the process of ultraviolet radiation, has a good ability to resist carbon dioxide diffusion, so that the steel is not easy to rust;
3 factors affecting the performance of high performance flexible coatings

3.1 influence factors of elasticity
Factors affecting the elasticity of the emulsion, PVC (pigment volume concentration), the thickness of the film, the use of time, etc.. As time goes by, the elasticity will also decline. The ability of elastic coating to cover crack and waterproof mainly depends on the elasticity of the elastic coating and the thickness of dry film. The dry film thickness had no effect on the tensile strength, and had great influence on the elongation. With the increase of dry film thickness, the elongation rate increased slightly. The dry film thickness is proportional to the width of the cover crack. General average elastic coating dry film thickness is 150~250 mu m thick; 250~350 m; 250~450 m thickness of galling pattern. In order to obtain thick film, coating has high requirements not volatile (solid content 65%), viscosity to 75 000~85 000 mPa - S.
3.2 influencing factors of adhesion
Elastic emulsion paint film can sometimes be a piece of film peeling off, the reason is that the tensile strength of the elastic latex paint is higher than the bond strength of the elastic latex paint. In order to improve the elastic emulsion paint adhesion, through improve the formulation of PVC, water vapor permeability or using a closed primer to close a base, also can try to add a certain amount of silica sol in some elastic styrene acrylate emulsion, made of inorganic organic composite primer, permeability and adhesion are unified to. It is a good practice to use solvent based primer or cationic primer elastic topcoat.
3.3 factors affecting the stain resistance
Soon some buildings painted exterior elastic paint, it is dark and dirty greasy. This is because the water film is hydrophilic, elastic coating and soft clay, dirt and dust attached on the film surface will in the role of the coated capillary Mike Conley, using water as medium is adsorbed in coating surface, caused by contamination, it is difficult to wash clean.
The film elasticity and stain resistance is a contradiction. To improve the elastic paint stain resistance, through to improve the coating density, reduce dust adsorption; increase the hardness of the coating, slow coating to soften. There are mainly the following methods:
(1) particle size is fine, water resistance and good stain resistance, self crosslinked elastic emulsion, such as 2848M, 9389M, RC41-216; available to ordinary emulsion and elastic emulsion (such as 2438, 4800) equipped with; in coating added with a certain volume covering emulsion (such as OP-62), also can improve the coating deposition resistance dust resistance and compressive viscosity;