Glass jar is a food and beverage and many products, packaging containers, the use of a wide range of glass is also a very historical packaging materials. In the case of many kinds of packaging materials into the market, the glass container in the beverage packaging still occupies an important position, which it has other packaging materials can not replace the packaging characteristics can not be separated
Raw materials and chemical composition Bottle glass Fittings are generally composed of 7 to 12 raw materials. Mainly quartz sand, soda ash, limestone, dolomite, feldspar, borax, lead and barium compounds. In addition, there are clarifying agents, colorants, bleaching agents, opacifiers and other auxiliary materials (see glass). Coarse particles of quartz is difficult to melt completely; particles too fine in the melting process and prone to scum and dust, affecting the melting, easy to plug the furnace regenerator. Suitable particle size is 0.25 ~ 0.5mm. For the use of waste glass, generally also added broken glass, the amount is usually 20 to 60%, up to 90%.
Glass chemical composition of the glass, according to its use requirements, molding methods, molding speed, process characteristics and varieties of raw materials and other differences. The vast majority of bottles are made of soda-lime silicate glass. The main components of soda-lime silicate glass are SiO2, Na2O and CaO. The introduction of proper amount of Al2O3 and MgO can reduce the crystallization tendency of glass, enhance the chemical stability and mechanical strength of glass, and improve the forming performance of glass. Most countries in the world of sodium and calcium glass chemical composition of glass: SiO270 ~ 74%, CaO and MgO10 ~ 14%, Na2O and K2O13 ~ 16%, Al2O31.5 ~ 2.5%. When manufacturing a colorless glass jar, the content of Fe2O3 in quartz sand is very low (usually about 0.03%). In the ordinary soda lime glass, add Cr2O3 and Fe2O3, glass was emerald green, add sulfur - carbon or MnO2 and Fe2O3, glass was brown. Containers of pharmaceuticals are required to have high chemical stability and are made of borosilicate glass. Advanced cosmetic bottles, commonly used lead, barium or zinc crystal glass manufacturing, and some for the opaque glass, generally with fluoride as opacifying agent.
Quality requirements Glass bottles should have a certain performance and meet certain quality standards.
① glass quality: pure uniform, no gravel, stripes, bubbles and other defects. Colorless glass of high transparency; color glass color uniformity and stability, can absorb a certain wavelength of light energy.
② physical and chemical properties: a certain degree of chemical stability, not with the stuffing effect. Has a certain degree of shock resistance and mechanical strength, can withstand washing, sterilization and other heating, cooling process and bear the filling, storage and transportation, encountered general internal and external stress, vibration, shock, can be maintained without damage.
③ molding quality: to maintain a certain capacity, weight and shape, uniform wall thickness, mouth smooth, smooth to ensure good filling and sealing good. No distortion, the surface is not smooth, uneven and cracks and other defects.
Manufacturing process Glass jar manufacturing mainly includes preparation, melting, molding, annealing, surface treatment and processing, inspection and packaging processes.
① preparation of ingredients: including the storage of raw materials, weighing, mixing and batching of the delivery. Requires the mix material to be homogeneous and the chemical composition is stable.
(2) Melting: The melting of the glass of the bottle is carried out in the continuous operation of the flame pool kiln (see the glass melting furnace). Horizontal flame pool kiln daily output is generally more than 200t, large up to 400 ~ 500t. Horseshoe-shaped fire pool kiln daily output of more than 200t. Glass melting temperature up to 1580 ~ 1600 ℃. Melt energy consumption accounts for about 70% of total energy consumption in production. Can be through the pool kiln full insulation, increase the capacity of the regenerator lattice brick, to improve the material pile distribution, improve the combustion efficiency and control of glass convection and other measures to effectively save energy. Bubble in the melting tank can improve the convection of glass, to strengthen the clarification process, increase the amount of material. In the flame kiln with electric heating, can not increase the furnace in the case of increased production, improve quality.
③ molding: the main use of molding method, the application of blowing - blowing method of forming small mouth, pressure - blowing method of forming jars (see glass). Less use of control. The production of modern glass bottles widely used automatic bottle machine high-speed molding. This bottle machine on the drop weight, shape and uniformity have a certain requirement, so to strictly control the temperature in the feed tank. Automatic bottle making machine type more, of which the most commonly used in the determinant bottle machine. This bottle is drained from the bottle making machine, not the bottle machine, and there is no rotating part, the operation is safe, and any part can be parked separately for maintenance without affecting other branch operations (Figure 1 ). Cylindrical Bottle Making Machine A wide range of bottles and bottlenecks has been developed for 12 groups, double drop or three drops of material and computer control.
④ Annealing: The annealing of the glass jar is to reduce the permanent stress of the glass to the permissible value. Annealing is usually carried out in a ribbon-type continuous annealing furnace with a maximum annealing temperature of about 550 to 600 ° C. The belt-type annealing furnace (Figure 2) uses the forced air circulation heating, so that the furnace cross-section temperature distribution and the formation of air curtain, limiting the vertical air movement to ensure that the furnace temperature uniformity and stability.
⑤ surface treatment and processing: generally through the hot end of the annealing furnace and cold side of the method of coating the glass cans surface treatment. The hot-end coating is placed in a hot state (500 to 600 ° C) in a heated state in the atmosphere of vaporized tin tetrachloride, titanium tetrachloride or tin tetrachloride, so that these metal compounds The surface of the hot cans is decomposed and oxidized into oxide films to fill the surface of the glass microcracks while preventing microcracks on the surface and improve the mechanical strength of the glass jars. Cold end coating is a monostearate, oleic acid, polyethylene emulsion, silicone or silane, etc., at the exit of the annealing furnace temperature of about 100 ~ 150 ℃ bottle surface spray to form a layer of lubricating film, To improve the anti-wear, lubricity and impact strength of the surface of the bottle. Production, the cold side coating and the hot side of the coating is often used in combination. For more than 1l large capacity bottles, and some in its surface plus foam polystyrene or polyethylene film jacket. Sheath has heat shrinkability, put on the heat tightened after the bottle, tough and flexible, shock and anti-friction, bottled broken pieces without flying into, to avoid personal injury.