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The Theory of Float Glass for Mildew

2015.06.05   Source:

            The Theory Of Float Glass For Mildew


               Shenzhen BOST Technology Co.,Ltd    Zhang Liqiang,Ou Yajun

     Float glass during storage atmosphere by erosion, the surface mildew (commonly known as "weathering), annual losses caused countless And with the further development of glass deep processing, deep processing of increasingly demanding, corresponding to the original film surface increasingly high performance requirements, such losses may also further increase. And many people think, mildew work float glass production is the responsibility of just the cold end, this is actually a very one-sided point of view. mildew float glass should work throughout the entire production process, from initial design to final material side of the cold end packaging and Reservoir storage, transport the whole process should be highly valued. If we really want to reduce the glass mold phenomenon, should start from the overall perspective to fully understand its importance to the system theory to proceed with a glass mold work.
       First, from the glass frit square design should consider to minimize the probability of moldy:

      Usually we discuss the mechanism of glass corrosion, mainly carried out by the erosion of media research for physical and chemical effects of the glass, aggressive medium often encountered including water, air various acid, alkali, salt solution and, erosion of their glass First is the effect of water on the glass surface by. Usually encountered in the actual production of glass mold is mainly water vapor in the air to glass erosion, this process begins with water vapor in the H + and alkali metal ions in glass R + ion exchange, then hydration, in and reactions. The reaction can be expressed as:

        [O3Si] -O-Na + + H2O [O3Si] -OH + NaOH
        [O3Si] -OH + H2O Si (OH) 4

        Si (OH) 4 + NaOH [Si (OH) 3O] + H2O

     In the above process, if NaOH too much left in the glass surface, the performance of the base of the glass erosion. We all know that the glass is generally not alkali, because the alkali glass erosion is the destruction of the silicone skeleton by OH- ions, so that SiO2 dissolved in the solution of the basic structure of the glass causing fatal damage [1].
     In actual use, and related tests show that ultra-white glass than ordinary float glass easier to mold, the main reason is an alkali metal ion R + content was high, relatively ordinary float glass up about 8.8%.

General and ultra-white float, ultra-white rolled glass component [2]

Sample category









Ordinary Float









Ultra-white Float









Ultra-white Rolling









      So in the design of the glass when the recipe should be possible to reduce the amount of sodium and other alkali metal oxides. In addition, an appropriate increase in Al2O3 content (such as the introduction feldspar as raw material), can be formed [AlO4], thus greatly improving the chemical stability of the glass [3]. But we all know, Al2O3 is insoluble matter, from the melting point of view, this is very unfavorable. Thus, according to the characteristics and the market position of the company client base production lines, the design of appropriate and reasonable formula to the entire mold work has played a fundamental role.
     Second, the melting and annealing glass has a certain influence on the chemical stability: the more fully melted, the longer the annealing time, the higher the annealing temperature, the more dense and compact the glass surface, the corresponding chemical stability is high, the probability of natural moldy It is reduced. In actual production, thin glass more easily than the thick glass mold, is the truth.

     Third, the cold end of the mold measures: As above two measures are all hot end glass production, need to consider other factors, can not be adjusted in production, therefore, the cold end of mildew work becomes quite critical. First, select the appropriate mold medium, there are mainly ion exchange, mold lining paper clip method, spray mold powder (liquid) method three kinds of mold method. Wherein the ion exchange method due to cost and technology, in addition to domestic and foreign SYP AGC few foreign production line, there is no domestic wire manufacturers use; mildew lined paper clip method because of the history and habits, some manufacturers Midwest still in use, but because of the factors that influence cost and national industrial policy, has gradually be eliminated; mildew spray powder (liquid) method has become the mainstream of the development trend of float glass and mildew. In fact, one of the spray mildew liquid method, since the liquid can cover every small place across the glass surface, in theory, the effect should be better than the antifungal powder mildew by the market's positive, but it may be necessary to increase a set of equipment, and the effect of mold powder mildew meet most requirements of manufacturers, currently mostly powder method using the mold. (For poor environmental conditions, glass reservoir longer and higher quality requirements in some cases, recommended mold and mildew pink liquid dual protection measures). So choose the right mold powder is vital. Among the many performance indicators powder mildew, mold effect should first focus needs to be considered. In fact not the case, due to the impact of this indicator glass selling and not possible to quantify such factors when selecting mold powder manufacturers often do not focus off note. 

     In the "glass with anti-mold material," the industry standard which is such a requirement: clip pad glass samples moldy mold material time T2 must not be less than 2T1 (T1 refers to any material not cushion clip glass samples start Moldy time). Experimental Methods in humidity 85% (± 2%), temperature 60 ℃ (± 2 ℃) of constant temperature and humidity chamber compared under the same conditions. On the one hand, it should be said that this threshold is relatively low, most of the mold powder have to meet, on the other hand, a lot of float glass manufacturers do not have this test conditions. Therefore, most manufacturers first consideration is to compare the use of liquidity and other key indicators. It is only when the glass market downturn, stored for a long time when it can distinguish which one is better. Secondly, glass storage and transportation of moisture is also very important. Once the glass to get wet or damp, and in the rainy season, the probability of mold will be greatly enhanced. Storage time is also an important factor, it is known that any mold measures only delay and reduce the glass mold, the longer the storage time, the greater the likelihood of mold. Thus, sales in specific sales should adopt the principle of "first in first out", the first sale of the glass front of the production time. Finally, take appropriate measures in accordance with the specific requirements of downstream customers. In fact, from the microscopic point of view, the glass mold is inevitable, but the degree of severity is different, the key is used in any place. Such as general moldy glass used in windows and doors and other buildings on completely meet the requirements of a slight musty for ordinary steel, laminated and other processing will not constitute a significant impact. Most sensitive to mold is plated mirrors, coated glass and other high-end electronic client, even very slight mildew can not be accepted.

      Therefore, if we really want to reduce the losses caused by glass mold, each employee, from the general manager down to each worker for each section of the production sector, and even fleet drivers and downstream customers, should pay full attention and take appropriate measures can minimize losses.

[1]: The latest glass and glass products, production processes and quality inspection standard book
[2]: "Building Glass and Industrial Glass" 2010 5
[3]: The latest glass and glass products, production processes and quality inspection standard book