Tan Danjun, Wang Ying, Wang Pengqi, Zhao Jinping (Beixin Group Building Materials Co., Ltd., Beijing 102208) are highly valued by all walks of life. Rock wool has the outstanding advantages of low density, low thermal conductivity and non-combustion, and is an ideal inorganic thermal insulation material. This paper introduces the problems existing in the practical application of non-combustible thermal insulation materials for rock wool in China, and proposes ways to improve the acidity coefficient, optimize the melting and solidification process, and develop the deep discounting process to improve the performance of rock wool products and fill the rock wool products in China. The blank of the external insulation system.
At present, most of the urban residential building walls in China use expanded polystyrene foam (EPS) and extruded polystyrene foam clinker (XPS), and a small number of public buildings also use polyurethane foam. (PU). These organic insulation materials have the advantages of low cost, small thermal conductivity and good thermal insulation performance, and have the characteristics of convenient construction, good mechanical properties and anti-aging, and have formed mature construction techniques. These materials and their supporting construction techniques and relatively complete standards and norms have made tremendous contributions to China's building energy efficiency of 50%. It is the fund project “12th Five-Year†National Science and Technology Support Program (2011BA04B00). Not implemented, as polystyrene foam (PS) and polyurethane foam (PU) wall insulation materials have been widely used in public and civil construction, fire accidents have continued. The fire tragedy has increased year by year, resulting in huge loss of life and property. And caused a certain social panic and environmental pollution.
Rockwool is a high-quality and high-efficiency thermal insulation material. It has good thermal insulation, sound insulation and sound absorption performance. Compared with traditional thermal insulation materials, it has low density, low thermal conductivity, no combustion, no fire, no toxicity. With its wide range, stable chemical properties and long service life, it is an ideal thermal insulation material recognized at home and abroad. Rockwool products are widely used in foreign countries, especially in the construction market in Europe. The average consumption of Nordic people is above 20kg, and the average consumption of Americans is 5~10kg. Due to fire prevention, 70% of rock mineral wool in the United States exceeds in Germany. The 22m high building exterior insulation is almost entirely made of rock wool insulation material. However, in China, the use rate of rock wool as building insulation material is still low. It is mainly used for heat insulation and fire prevention of energy, petrochemical, shipbuilding and building light panels. Sound insulation and other aspects, but rarely used in civil buildings. In particular, the application of external thermal insulation for exterior walls is still blank. Analysis and summary of the application advantages, deficiencies and existing problems of rock wool will be beneficial to its better application and development.
1 The performance characteristics of rock wool insulation materials Compared with the organic insulation materials widely used in the domestic market (such as polystyrene foam, polyurethane foam, etc.), the performance advantages of rock wool mainly include the following aspects.
1.1 Outstanding fire performance The organic insulation materials (PS, PU) currently on the market have low fire rating.
For example, polystyrene foam (EPS) has a flash point of 346 ° C and a self-ignition point of 490 ° C. The external heat source passes through a 3 to 5 mm thick polymer plaster or a titanium zinc alloy plate to reach 490 C in just a few minutes. Initiates spontaneous combustion of the foam. The EPS can be burned in chain. The flame retardant foam melts quickly after burning. The droplet temperature is much higher than 490 °C. The droplets drop to the point where they cause spontaneous combustion of the foam and form a chain combustion. This kind of chain burning is the most terrible thing about foam.
Rockwool is the best material to meet Class A standards in exterior insulation materials. All metal oxides in rock wool are stable oxides, and no redox reaction occurs during fire, so it is an ideal non-combustible material. Admixtures such as organic binders added to the rock wool manufacturing process are the main factors affecting the combustion performance of rock wool products. By controlling the amount of organic matter added, the fireproof performance of rock wool products can fully meet the B1 or even Class A standards. Rockwool has good high temperature stability and is serviced below 300C. Its volume and strength properties remain stable for a long time. Short-term high temperature acts on the surface of the rock wool board, and its overall volume and shape do not change.
1.2 Material properties are stable Organic insulation materials are easy to age and have a short service life. The actual life is only 15 to 20 years. For ordinary buildings with a design life of 50 to 70 years, if organic insulation materials are used for external wall insulation, This means that the same building needs to be insulated several times, which will be a huge project, and the cost is incalculable. The rock wool component belongs to the CaO-Al23-Si2 system, and the chemical composition is stable, which can significantly improve the service life of the external wall insulation system and achieve the synchronization with the design life of the building structure.
1.3 Safety is good Organic insulation materials in the manufacturing process, there may be chemical leakage and cause poisoning, fire, explosion and other hazards. Rock wool is made of natural rock or blast furnace slag such as basalt. It is a non-toxic and non-polluting inorganic material. Its raw materials, production and construction applications will not adversely affect the environment.
2 Problems existing in the application of external thermal insulation for domestic rock wool exterior wall The existing rock wool in China cannot be used for external wall insulation, which is far from the requirements of foreign standards. Table 1 compares the technical specifications of EN 13500, which is the standard for rock wool products in China, GB/T19686-2005, rock wool and slag wool insulation products for construction and rock wool insulation board for European exterior walls.
Table 1 Comparison of existing rock wool product standards and European standard technical indicators in China. Acidity coefficient (MK) Mass moisture absorption rate/% tensile strength/kPa short-term water absorption/(kg/m) thermal conductivity/combustion performance Class A non-combustible Table 1 shows that the requirements of European rock wool product standards for acidity coefficient, mass moisture absorption rate, tensile strength, short-term water absorption and other performance are better than domestic existing product standards.
Most of China's rock wool is used for the insulation of steam pipes and furnace walls, and its quality is far from the requirements for large-scale wall insulation. The main reason is that the acidity coefficient is low due to the intravitretic silicon tetrahedron and The aluminum oxide tetrahedral structure has a high internal energy, resulting in low moisture resistance, elasticity, tensile strength and thermal stability. The silicon-oxygen-aluminum oxide backbone structure of domestic rockwool is unreasonable, and the automatic control of the equipment during the forming process is not high, resulting in the unsatisfactory three-dimensional distribution of the fibers in the sheet, which makes the compressive, tensile and shear strength of the sheet biased. Low, not good elasticity.
Therefore, only in the multi-links of charge ratio, furnace condition adjustment, melt temperature control, melt cooling process control, twisting process and process control, cotton collection, and process control, can we solve the large-scale use of rock wool. Key technical problems in high-grade fireproof exterior insulation.
3 Measures to be taken 3.1 Improving the acidity coefficient At present, the acidity coefficient of rock wool produced by almost all enterprises in China is below 1.6. The acidity coefficient of rock wool used abroad for external wall insulation is generally above 1.8. Changing the acidity coefficient can control the formation phase of rock wool, reduce the existence of C2S phase, avoid hydration reaction, and effectively improve its water resistance. At the same time, the high acidity coefficient means that the alkali content is small, the silicon-oxygen bond breakage in the fiber is reduced, and the strength is increased. In addition, the alkali metal ions are also easy to adsorb moisture in the air, so that the microcracks expand, and the reduction of the alkali content can reduce the adverse effect of the factor on the strength.
3.2 Research on the melting process If the acidity coefficient is to be increased, the content of Si2 and AI2O3 in the melt must be increased, so that the CaO and MgO contents are correspondingly reduced. In the case of low iron content, the viscosity of the melt is bound to be obtained. Increased, so that it is difficult to ensure the quality of rock wool fiber. A melt containing a lower iron oxide has a broad and stable viscosity range at an optimum fiber forming temperature when its acidity coefficient is about 1.2. In this case, even if the temperature of the stream fluctuates by 100 C, the fiber quality and fiber forming ratio are obtained. It is not affected much. However, as the acidity coefficient is gradually increased, the melt stability is deteriorated, and the sensitivity to temperature changes is also increased. As long as the temperature fluctuates slightly, the viscosity will change greatly, or even fiber, which is The change in acidity coefficient is the reason why the rock wool process has made 36 new building materials difficult.
After changing the formula, to increase the melting temperature, it is necessary to analyze the fiber forming effect and the phase change after the temperature is increased, so as to find a suitable melting temperature and temperature control method.
3.3 Adhesive and Curing Process Parameters The adhesive is closely related to the curing conditions. The purpose of using the adhesive is to form the fibers into a spatial three-dimensional interlacing point and fix the structure by a curing process.
Since the cracking of the material always starts at the weakest point, the uniformity of the curing agent has a great influence on the strength. Therefore, how to uniformly spray the adhesive in the case of high-speed fiber forming requires constant adjustment of the dispensing system. Increasing the amount of binder can increase the bonding strength between fibers, but the binder is an organic material. Excessive binder will make the burning performance of the material less than Class A. Therefore, it is necessary to further study the type of bonding agent and join the amount.
3.4 Development of deep discounting process Rockwool insulation material The purpose of pleating cotton sheet is to superimpose the surface of the cotton sheet to increase the tensile strength perpendicular to the board surface. From the current state of strength failure, the depth of pleating should be further improved. It is necessary to study the oscillating felting technique, optimize the oscillating mechanism, and ensure the formation of a continuous laminated cotton belt, including the determination of the process parameters of the oscillating felt, and the forming process of the laminated cotton belt.
3.5 Rockwool non-combustible external wall thermal insulation structural system and key technology research The research on the thermal insulation system structural form, interface connection method and supporting materials is carried out, and the mutual connection between the thermal insulation material and the wall, thermal insulation material and protective layer is improved. The connection capacity between the two sides to solve the problem of external wall insulation and wind pressure difference, easy to dislocate (on page 25) Li Beixing. Study on moisture sensitivity and modification of cement-based composites without macro defects. Wuhan: Wuhan University of Technology, 1998. Li Beixing, Wang Aimin. Study on structure and properties of MDF cement materials with fly ash. Journal of Building Materials, 2001, 4(1): 12-16. Li Beixing, Zhang Wensheng. High-strength non-macro-defective cement-based composites. Materials Herald, 1998, 12 (12): 65-68. Huang Congyun. New sulphoaluminate-based MDF cement and its coupling stabilization and toughening mechanism. Wuhan: Wuhan University of Technology, 1999. The problem of falling, the establishment of construction technical regulations, the realization of rock wool materials in the external thermal insulation project.
4 Conclusion Rockwool is a high-quality A-grade fire insulation material, whether it is cost-effective or industrial basis. By improving the formulation of raw materials, improving the acidity coefficient, optimizing the melting and solidification process, and developing deep discounting processes, etc., the existing rockwool products in China are improved in water resistance, tensile strength and low peel strength, so that they can meet the external wall. Application requirements for external insulation systems. The use of inorganic non-combustible insulation materials to replace the existing flammable organic insulation materials on the market can solve the problem of fire prevention of external thermal insulation systems of buildings, which is of great significance to urban safety.
(Finish)
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