Waterproof coatings used in construction projects are called building waterproof coatings, or simply waterproof coatings. They are the general name for a waterproof film material that has a waterproof property through coating construction, and are functional building coatings with waterproof as the main purpose. Waterproof coatings are waterproof materials that are self-contained, that is, they are not capable of bearing structural forces on their own, and are in contrast to structural waterproofing. Waterproof coating is mainly used for certain structural parts or structural components of buildings that may be eroded by water, such as roofing, basements, bath and toilet rooms, water towers, pools, water storage tanks and other structures that are waterproof, moisture-proof and seepage-proof.
These structural parts have large temperature changes, and their base layers are generally cement materials. Cracks caused by various reasons are more common. Therefore, the resistance to high and low temperature performance of waterproof coatings and the adaptability to structural changes also have certain requirements. . Therefore, waterproof coating generally requires good low temperature flexibility, elongation, tensile strength and a certain degree of adhesion to the base layer (usually referred to as bonding strength in waterproof coatings). Therefore, the PVC of the coating must be lower than its critical PVC, so the proportion of the pigments (including fillers) used in the water-repellent coating is generally very small, and some do not contain pigment at all (for example, some waterproof coatings called waterproof glues) to ensure that the coating film is dense impermeable.
The amount of waterproof coating used is very large, and it has a great influence on the function of the building. Compared with other functional architectural coatings, it has a closer relationship with the function of the building and is therefore highly valued. This is also an important aspect of waterproof coatings that are different from other functional architectural coatings. Compared with waterproof membranes, waterproof coatings are easy to construct, especially for complex bases with irregular shapes, which can also form a dense, seamless continuous coating. Even for large-sized regular roofs suitable for use with waterproofing membranes, waterproof coatings are used as a supplement to construction materials and can be used for local areas such as exhaust outlets, gutter outlets, and parasol walls.
2 Classification of Waterproof Coatings In the two classification methods of paints specified in “Classification and Nomenclature of Coating Productsâ€, water-repellent coatings are classified as separate types of architectural coatings and divided into: 1 solvent-based resin waterproof coating; 2 polymer emulsion waterproof coating; 3 other waterproof coating 3 categories. In fact, there are many types of waterproof coatings. This is only rough and does not reflect the outline of waterproof coatings. In the waterproof material industry, there are more detailed methods for classification based on the composition of materials. According to this classification method, the main types of waterproof coatings are shown in Table 1. 3 Application and Development of Waterproof Coatings 3.1 Basics of Waterproof Coatings Status 3.1.1 Application Status After more than 40 years of development, China's waterproof coatings have formed multiple types with different properties, such as reaction-curable, volatile-drying, solvent-based, and water-based, single-component and two-component. Variety of patterns. At present, there are more than 200 waterproof coating manufacturers in China with a certain production scale. The total annual production volume exceeds 200,000 tons. It is mainly used in the waterproofing of industrial and civil building roofs, basements, bathroom rooms, and external walls. The production and development forecast of China's architectural waterproofing coatings for the last 10 years is shown in Table 2. 2006.07 Modern coatings and coatings Table 1 Classification and main categories of waterproof coatings Main categories Coating types Product examples Synthetic resin single-component 1 Solvent type: PVC 2Waterborne: Acrylate, styrene-acrylate and other two-component polysulfide epoxy resin (solvent type); neoprene rubber bituminous rubber single component 1 solvent type: chlorosulfonated polyethylene rubber, ethylene propylene rubber; Polyurethane; 2 Water-based: Silicone Rubber, Butadiene Benzene (Butadiene-Styrene: Rubber, Carbonyl Butadiene Rubber, Chloroprene (Vinyl Chloride-Butadiene) Rubber Two-Component Solvent Type: Tar Polyurethane Cool, Pitch Polyurethane Cool, polysulfide rubber, bituminous, one-component, solvent-based, bituminous waterproof coating; Waterborne: bentonite emulsified bituminous waterproof coating rubber and modified bituminous one-component solvent type: neoprene asphalt, recycled rubber asphalt, SBS modified asphalt , butyl rubber asphalt; 2 water: neoprene asphalt, carbonyl chloroprene rubber asphalt, recycled rubber asphalt coating covered inorganic type crystalline penetrating steady water (VANDEX, Germany), Cypress ( XYPEX, Canada), KRYST0L (Canada), Fangshui (F0RMDEX, Singapore), Penetra (PENETRON, USA), DIPSE; (France), RYSTAL (Australia), PANDEX (Japan), and various domestic types The cement-based penetrating crystalline waterproof coating and other organic composite two-component polymer cement composite waterproof coating; acrylate emulsion-silica sol composite waterproof coating, etc. Table 2 Waterproof Coatings in the Last 10 Years Production and Development Forecast Year Production/Ton 3.1.2 State of Technology Research Since the late 1970s, with the advancement of China’s science and technology and the development of the chemical building materials industry, China’s waterproof coatings have developed rapidly. So far, there are more than 120 invention patents on waterproof coatings. Items, mainly related to two-component and one-component polyurethane waterproof coatings, waterborne (modified) polyacrylate waterproof coatings, used material modified waterproof coatings, neoprene waterproof coatings, polymer cement waterproof coatings, and high polymer Asphalt waterproof coatings and inorganic waterproof coatings, etc. form a chemical reaction to cure and dispersion medium (solvent and water) volatilization Different properties like dryness, different forms of various types and variety of patterns.
3.2 The development and existing problems of waterproof coating 3.2.1 Pitch-based and modified asphalt-based waterproof coatings Pitch-based waterproof coatings are divided into solvent-based and water-based emulsions. Both coatings contain both modified and unmodified products. Since the emulsified asphalt that has not been modified has poor bonding strength and water resistance, it has basically been eliminated. The vast majority of emulsified asphalt used today is modified with synthetic resins. According to the different modification methods, it can be divided into two types: cold blending modification with synthetic resin emulsion and first modifying the asphalt and then emulsifying the modified asphalt. The former, such as neoprene modified emulsified asphalt, acrylic modified emulsified asphalt, styrene butadiene rubber modern coating and coating modified emulsified asphalt, etc.; the latter such as SBS modified emulsified asphalt, APP modified emulsified asphalt. The polymer modified emulsified asphalt waterproof coating currently has the following three problems: First, the solvent-based polymer modified asphalt waterproof coating has large environmental pollution, and the quality and performance of the water emulsion polymer modified asphalt waterproof coating. Both are unstable; Second, some polymer modified bituminous waterproof coatings can not fully meet the requirements for use in terms of mechanical properties, waterproof performance and durability, etc. Third, the polymer raw material market will have a significant impact on product quality and price.
3.2.2 Polyurethane Waterproof Coating After more than 20 years of development, China has gradually formed a series of polyurethane waterproof coatings with complete varieties and diversified properties, which occupies an important position in building waterproof coatings.
The coal tar polyurethane waterproof coating uses coal tar instead of some of the higher-priced polyether polyols to reduce costs, and has long dominated polyurethane waterproof coatings. However, such waterproof coatings have been eliminated and will gradually fade out of the waterproof coating market.
Compared with developed countries, China's polyurethane waterproof coating has few varieties, its overall quality is low, and its adaptation surface is narrow. There are 75 Japan-made polyurethane waterproof coatings and 346 types of waterproof coating products, including walking, non-walking, roofing, playground, flame retardant, weather resistant, primer coating, and waterproof coating; Quick-drying waterproof coatings developed in the UK are resistant to light rain within a few minutes of construction. China's polyurethane waterproof coating is usually based on TDI, MDI and polyether as the basic raw materials, the weather resistance of the product is poor, easily oxidized under the action of ultraviolet rays, the coating film yellowing, powdering, although by adding UV absorbers and resistance Oxidizers improve their weatherability but do not fundamentally change performance. Therefore, such a polyurethane waterproof coating cannot be used alone as outdoor waterproof, and it needs to use a protective layer when it is used on the roof.
On the other hand, the application of polyurethane waterproof coating requires a relatively high degree of dryness of the base layer. Although China has developed epoxy resin-based wet-based adhesives, it basically solves the problem of difficult construction of polyurethane waterproof coatings on wet substrates, but due to the high price of epoxy-based adhesives, The actual use of fashion is limited. Polyurethane waterproofing coatings that can be applied on wet substrates without primers are still in the research and development stage. In the field of surface protection of materials, the domestic market is still blank.
Polyurethane waterproof coating free isocyanate monomer toxicity, the International Health Organization strictly regulates the free monomer content of isocyanate polymer must be controlled at 0.56 or less, and the current domestic use of traditional distillation process, the product of free monomer content Very high, the content of some products may be above 26, affecting the health of construction workers and causing pollution to the environment.
3.2.3 Polymer Cement Waterproof Coatings Polymer cement waterproof coatings are commonly referred to as JS waterproof coatings and consist of polymer emulsions, inorganic gelling materials, skeleton reinforcements (eg quartz sand) and various coating additives. This type of waterproof coating has both the extensibility and water-resistance of the polymer waterproof coating, as well as the advantages of high strength of the hydraulic binder and easy adhesion to the moisture base. In practical applications, the proportion of polymer emulsion and cement can be adjusted to meet the requirements for different softness, strength, and water resistance of the project. The construction of this type of coating is simple and does not adversely affect the health and environment of construction workers. . In recent years, this type of paint has been used in a large number of applications with the trade name of "elastic cement." The main problem is that the quality of domestic acrylate emulsions is far from that of foreign products. Some domestic emulsions have unstable performance, and they tend to agglomerate in the process of mixing with the powder components and affect the coating performance and coating. Membrane mechanical properties. At present, high-quality emulsions used in polymer cement waterproof coatings mainly rely on imports, and domestically produced high-quality acrylic emulsions are also used for introducing foreign technologies.
3.2.4 Polymer emulsion waterproof coating Polymer waterproof coating consists of polymer emulsion (such as acrylate emulsion, styrene-acrylate copolymer emulsion, ethylene-vinyl acetate copolymer emulsion, etc.), skeleton reinforcement (such as heavy calcium carbonate, talc Powder, etc.) and various paint additives. The main performance characteristics of this type of waterproof coating are the elasticity of the coating film, high elongation, proper adhesion to the base layer, strong adaptability to the deformation of the base layer, and a wide range of adaptation to changes in temperature. Some products are available - 35 ~ 45 +, and has good resistance to aging (such as heat aging, UV aging and acid and alkali aging, etc.). At the same time, this type of paint is non-toxic, non-flammable (with water as the dispersion medium, no solvent pollution), the construction is simple, the coating can be formulated into the desired color, and has a very good decorative effect. The main products of this type of coating are roofing waterproof coating, exterior waterproof decorative coating, and kitchen interior decoration waterproof coating. 3.2.5 Silicone Rubber Waterproof Coatings Silicone rubber waterproof coatings also belong to emulsion type waterproof coatings. Silicone rubber emulsions are used as film-forming substances, and inorganic fillers and various additives are added. It has the advantages of both polymer emulsion waterproof coating and penetrating waterproof coating. It has good comprehensive performances such as waterproof, anti-infiltration, high elasticity, heat resistance and weather resistance. The Ministry of Construction once listed it as an "Eighth Five-Year" scientific and technological achievement for promotion.
3.2.6 Inorganic waterproof coatings There are two types of inorganic waterproof coatings: coating-type waterproof coatings and permeation-type waterproof coatings. ! Coating Covered Waterproof Coatings Coatings Covered waterproof coatings are generally powdered cement based waterproof coatings with hydraulic properties. Typical products include COPROX, Waterproof, M1500, HM1500, and TM1500. At the time of ensuring (COPROX) and waterproofing, the waterproof mechanism is based on cement as the main adhesive material. The film-forming, hydrophobic components, etc., under the action of the catalyst, together with the cement form a dense film on the surface of the base layer, and the closed surface The cracks, pores, and thus plug the water seepage channel. At the same time, the hydrophobic properties of the material itself can greatly increase the surface tension of the new surface, reduce the wetting ability of the water, and thus improve the water resistance. Such materials can be cold-applied and have low requirements for the construction surface, as long as the surface is free from oil, dust and loose materials. The base surface is fully wetted during construction, otherwise the coating may fall off after drying. This material is non-toxic and has a certain alkali resistance and aging resistance.
Silicate is a carrier (usually water glass), a colorless translucent liquid compounded with an appropriate amount of a catalyst, a dispersant, an additive, and water, and has a high permeability, and is directly sprayed on cement mortar and concrete. The surface can quickly infiltrate into the interior and react with Ca(OH)2 produced by cement hydration to produce silicate that is insoluble in water and has a certain strength, thereby blocking the internal pores, closing the capillary pore channels, and improving the impermeability of the concrete and mortar ability. This type of material is characterized by a one-time waterproof impervious effect, but it does not have self-healing properties. Once the concrete or mortar cracks again, there is the possibility of leakage.
(2) Permeable Crystalline Waterproof Coating Permeable Crystalline Waterproof Coating is a new type of waterproof material that has been developed on the basis of the idea of ​​infiltration and reaction in foreign countries. It is made of Portland cement, quartz sand and other basic materials, and is made of active chemical substances. , can be used as a paint, can also be directly incorporated into concrete or mortar as a structural waterproof. It is similar to the M1500, HM1500 and TM1500 in that it blocks the internal pores through chemical reactions and closes the capillary channels to improve the impermeability of concrete and mortar. However, the improvement is the use of catalytic substances in the composition. It can be activated to promote the hydration of cement to regenerate new crystals. When new fine cracks occur in concrete or mortar, once water infiltrates, new crystals will be formed to block the cracks, that is, they will be self-healing.
Cement-based osmotic crystalline waterproofing coatings have developed rapidly in foreign countries, extending from the early German brand of VANDEX to XYPEX and KRYSTOL in Canada, FORDEX in Singapore and the United States. Dozens of brands, such as PENETRON, France's DIPSEC, Australia's CRYSTAL, and Japan's PANDEX, have all improved to varying degrees and formed a series of products. The cement-based penetrating crystalline waterproof coating was originally used for waterproofing the inner surface of the structure in the process of exploiting engineering applications. It is particularly ideal for applications such as sewage treatment tanks and ground water storage tanks. As an effective method for the waterproof treatment of concrete structures (internal waterproof method), it gradually expands the variety and continues to expand into new areas of construction application. At present, through the research of product introduction, technology development and construction application technology, China has applied penetrating crystalline waterproof coating to basements, underground railways, bridges, roads, drinking water plants, sewage treatment plants, hydropower stations, nuclear power plants in industrial and civil buildings. Water conservancy projects and other fields.
4 Development Outlook 4.1 The development and application of high-performance waterproof coatings will receive attention Traditional asphalt waterproof coatings will be gradually modified due to poor performance. 2006.07 Modern coatings and coating asphalt waterproof coatings, especially polyurethane waterproof coatings, polymer emulsions Cement waterproof coating is replaced; polyurethane waterproof coating, acrylic waterproof coating and rubber modified thick asphalt waterproof coating will be the focus of development.
Polyurethane waterproof coating will gradually change from coal tar type to non-tar type and pure urethane type, and eventually eliminate tar-type polyurethane waterproof coating completely.
In underground waterproofing projects, coating-coated and osmotic-infiltrated inorganic waterproof coatings will be used more; waterproof solutions incorporating waterproof self-contained concrete and flexible waterproof coatings (such as polyurethane waterproof coatings) will also receive attention. application.
As the waterproofing of exterior walls, especially the demand for wall waterproofing in wet areas, grows, the application of elastic paints with good decorative effect will gradually increase; the varieties will use water-based acrylic paints or water-based acrylic-cement composite coatings as primers. Low-PVC outer wall elastic latex paint is mainly used as a top coat for composite coating.
4.2 Principle of environment-friendly waterproof coating, foreign waterproof coatings are developing towards water-based and environment-friendly, such as the development of high-performance waterborne polymer modified bituminous waterproof coatings, waterborne polyurethane waterproof coatings, etc. However, the market share of waterborne polymer modified asphalt waterproof coatings in China is still very low, and the production technology of waterborne polyurethane waterproof coatings is not yet mature. China's relatively mature water-based waterproof coating is polymer emulsion waterproof coating and polymer emulsion cement waterproof coating. With the introduction of foreign products and the increasing demand in China's waterproof coating market, waterborne polymer modified asphalt waterproof coatings and waterborne polyurethane waterproof coatings will receive further attention and development.
In recent years, foreign countries have been devoting themselves to the development of high-performance waterproof coatings made of cement as a carrier, incorporating active chemical catalysts, and other modifications. The most outstanding advantage of this kind of coating is that it will not emit any substances that pollute the environment during production, construction and application, and it will meet the environmental protection requirements. For example, in Japan, a waterproof coating named “Paratex†uses organic emulsions (Vinylon, polyvinyl acetate, etc.) and inorganic hybrid materials (special high-alumina cement, quartz sand, and various Additives) Composite two-component waterproof coating. It not only has the advantages of high elasticity of organic materials, but also has the advantage of durability of inorganic materials. In particular, its unique crack self-closing function fills the gap of waterproof coatings.
4.3 Development of multifunctional water-repellent coating emulsions, cement waterproof coatings and high-solids-modified rubber-modified asphalt waterproof coatings. In the coming period, the development direction of new waterproof coating products in China will be high-performance and multi-functional waterproof coatings. Industrial advanced countries have begun to develop in the direction of multifunctional waterproof coatings. China's current production of waterproof coatings can only play a role in waterproof, functional waterproof coatings, such as heat-insulating, reflective heat-type waterproof coating development will be due to the increase in the function of waterproof coatings and attention and welcome. With the development of modern coating and coating of nanotechnology and its penetration into various fields, research on the use of nano-materials to improve the performance (such as elasticity and durability) of waterproof coatings will be gradually applied to the production and application of waterproof coatings. Research has been conducted on the use of nano-Ti2, nano-Si2-x and nano-ZnO to improve the anti-aging properties of polymer emulsion waterproof coatings; the use of nano-CaC3 to improve the performance of two-component polyurethane waterproof coatings; Sub-polyurethane waterproof coating strength and elongation at break, etc.
4.4 The new construction tool materials, polymer emulsion cement coatings, etc. need to be mixed evenly at the time of construction. For a two-component waterproof coating with a combination of liquid material and powder, the powder must be fully dispersed and cannot be dispersed or pelletized. Otherwise, the coating performance will be affected, which raises higher requirements for on-site mixing. The two-component coating mixing equipment and the construction equipment that ensure that the coating has a uniform thickness are of great significance to ensure the quality of the coating film and the waterproof effect.
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