Nano aerogel materials have been found as early as 70 years ago, in 1931, the Pacific university of California kistlers using supercritical drying method to remove water from the hydrogel, obtained the first non-shrink nano aerogel insulation felt, but the early aerogel is very fragile, and very expensive, so it is mainly used in the laboratory. It was not until 10 years ago that NASA became interested in the material and made it more practical to use that it finally walked out of the lab.
In recent years, the development of thermal insulation materials abroad has been accelerated obviously. due to the development of the whole nano - technology, people pay more attention to the nano-thermal insulation materials. the research in the United States and Europe is very active, and Japan and Korea have also carried out more development. Aspen has studied the thermal insulation mechanism of nano aerogels earlier, especially the development and application of flexible nano aerogels thermal insulation felt. However, the u s nano aerogel insulation blanket is completely banned for China.
Tongji university, Xiamen university and Beijing university of science and technology in China also have research on nano aerogel insulation felt, but they are limited to basic research fields. Shaoxing nuogaoke co., ltd. of Zhejiang province took the lead in industrialization of nano aerogel insulation felt, but the company needs expensive silicone as raw material in the production process, at the same time also need to apply the investment of supercritical technology, so the generated nano aerogel insulation felt is very expensive ( as high as 2000 ~ 3000 yuan / kg ), limits its scope of use.
At present, how to optimize and improve the production process of nano aerogel insulation felt and reduce the production cost is the key to the successful application of nano aerogel insulation felt in building materials. Based on the above research objectives, Beijing building materials science research institute co., ltd., which has been committed to the development of high efficiency, energy saving, fire safety building insulation system, in recent years through technical cooperation with internationally renowned aerogel insulation felt manufacturers, using water glass as raw material, abandon the complex process such as supercritical drying and choose normal temperature and pressure drying technology to prepare nano aerogel insulation felt, greatly reduce the manufacturing cost of nano aerogel insulation felt ( 30 ~ 50 yuan / kg ), make the nano aerogel insulation felt in the field of building materials has become possible for large-scale application. The nano aerogel thermal insulation felt will be the best solid thermal insulation material after being compounded by heat-resistant fiber skeleton such as glass fiber.
The supercritical drying technology and normal temperature and pressure drying technology are compared below. The shortcomings and shortcomings of supercritical drying technology are mainly manifested in the following aspects: the existing production technology uses ion exchange resin and supercritical production technology equipment, which has high temperature and high pressure hazards, high production equipment cost, high initial investment ( equipment, raw materials ) cost, can not be produced continuously, and the production period is long. the supercritical drying technology is shown in fig. 2.
The normal temperature and normal pressure drying technology process does not use any ion exchange resin, dehydration / waterproof technology into a stage ( i.e., dehydration and hydrophobic in the drying process at the same time ), improve the efficiency, the project schedule time is shortened a lot, the normal temperature and normal pressure production time is 4 ~ 5 h ( the original process needs more than 100 h ), has the ability of continuous mass production; Reduce the use of waterproof materials, reduce the cost of the program; Sodium silicate is used as a raw material, the cost is low, and the finished product has the price competition advantage, which is only 1 / 10 to 1 / 8 of the original price. Normal temperature and pressure drying technology process as shown in figure 3.
The two processes are quite different, but the properties of the nano aerogel insulation felt prepared by the two processes are basically the same, and the technical indexes of the nano aerogel insulation felt prepared by the two processes are compared as shown in table 2. It can be seen that the drying technology at room temperature has good innovation, the product performance can meet the needs, and has high cost performance.