Glass bottles and jars are packaging containers for food, beverages and many products. They are widely used. Glass is also a kind of packaging material with a long history. With many packaging materials pouring into the market, glass containers still occupy an important position in beverage packaging, which is inseparable from its packaging characteristics that other packaging materials cannot replace.
Glass packaging containers refer to hollow glass products that can be sealed with lids or stoppers and can hold various materials in a quantitative manner. It is widely used in beverage, alcohol, food, medicine, cosmetics and other fields. The glass jar itself has the advantages of transparency, easy cleaning, good chemical stability, no pollution to the contents, high air tightness, excellent storage performance, rich style decoration, can be recycled for multiple times, and abundant raw material sources, but at the same time, glass bottles The tank is easy to break, and the weight-to-volume ratio is large. These shortcomings are gradually being improved with the development of process technology.
From 2000 to 500 BC, humans could make hollow glassware. After the blowpipe began to be used in 200 BC, the oil and wine industries subsequently used hollow glass as containers. During the Roman Empire, the demand for glass containers increased, and most of the products were round-bottomed and must be supported by iron or wooden frames. Later, due to the development of molds used for blowing glass, flat-bottom bottles without brackets were produced. From the 5th to 15th centuries, the pressing, drawing and blowing technology has been greatly developed, laying the foundation for the mechanization of glass manufacturing. In 1867, the German Siemens brothers applied the continuous melting tank kiln of the regenerator to the glass industry, which made the mass production of glass bottles possible. From 1880 to 1890, the molding technology of press-blow method to make wide-mouth bottles and blow-blow method to make small mouth bottles was invented. The first bottle-making machine driven by an electric motor appeared in 1900. From 1904 to 1905, American M.J. Owens created a fully automatic vacuum suction bottle making machine. From 1910, the gob feeder began to develop. In 1914, the semi-automatic blowing-blowing process was mature. In 1925, the Hardford-Empel Company of the United States successfully developed an in-line bottle making machine, which was produced by the blowing-blowing method, and later developed to also be produced by the pressure-blowing method. This line-type bottle making machine is still the main model used so far, and is gradually developing in the direction of multiple units and multiple drops.
In the Tang and Song Dynasties, China has used blowpipes to blow hollow glass containers. The modern glass industry was formed from 1904 to 1908. The Shanghai Jinghua Glass Factory, established in 1931, was the first factory in China to continuously manufacture glass bottles and jars using horizontal flame and horseshoe flame regenerator tank kilns and automatic bottle making machines. After the 1950s, a number of large-scale modern bottle-making factories were built. In the 1980s, the biggest improvement in the production of glass bottles and cans was the lightweight of glass bottles, which could save raw materials and fuel, increase production speed, and reduce transportation costs.
Glass bottle and jar batch materials generally consist of 7-12 kinds of raw materials. There are mainly quartz sand, soda ash, limestone, dolomite, feldspar, borax, lead and barium compounds. In addition, there are auxiliary materials such as clarifying agent, coloring agent, decoloring agent, opacifying agent and so on. Coarse particles of quartz are difficult to melt completely; too fine particles will easily produce scum and dust during the melting process, which will affect the melting and easily block the regenerator of the melting furnace. The suitable particle size is 0.25～0.5mm. In order to use waste glass, cullet is usually added, and the amount is usually 20-60%.
The chemical composition of glass bottle glass varies according to its use requirements, molding method, molding speed, process characteristics and raw material varieties. Most bottles and cans use soda lime silicate glass. The main components of soda lime silicate glass are SiO2, Na2O and CaO. Introducing a proper amount of Al2O3 and MgO can reduce the tendency of glass to crystallize, enhance the chemical stability and mechanical strength of the glass, and improve the forming performance of the glass. The chemical composition of soda lime glass in most countries in the world is: SiO270～74%, CaO and MgO10～14%, Na2O and K2O13～16%, Al2O31.5～2.5%. When manufacturing colorless glass jars, the content of Fe2O3 in quartz sand is very low (usually about 0.03%). In ordinary soda lime glass, adding Cr2O3 and Fe2O3, the glass is emerald green, adding sulfur-carbon or MnO2 and Fe2O3, the glass is brown. Bottles and cans containing medicines require high chemical stability and are made of borosilicate glass. High-end cosmetic bottles are commonly made of crystalline glass containing lead, barium or zinc, and some are opalescent glass, and fluoride is generally used as an opacifier.
1. Glass bottles and cans should have certain performance and meet certain quality standards, the main indicators are as follows;
①Glass quality: pure and uniform, without defects such as sand, streaks, and bubbles. Colorless glass has high transparency; the color of colored glass is uniform and stable, and can absorb light energy of a certain wavelength.
②Physical and chemical properties: It has certain chemical stability and does not interact with the contents. It has a certain degree of shock resistance and mechanical strength, and can withstand heating and cooling processes such as washing and sterilization, as well as withstanding filling, storage and transportation, and can remain undamaged when encountering general internal and external stress, vibration, and impact.
③Forming quality: maintain a certain volume, weight and shape, uniform wall thickness, smooth and flat mouth to ensure convenient filling and good sealing. There are no defects such as distortion, uneven surface, unevenness and cracks.
2. The manufacturing of glass bottles and cans mainly includes batch preparation, melting, forming, annealing, surface treatment and processing, inspection and packaging.
①Batch preparation: including storage, weighing, mixing and conveying of batch materials. It is required that the batch materials are uniformly mixed and the chemical composition is stable.
②Melting: The melting of bottle glass is mostly carried out in a continuous operation flame tank kiln. The daily output of horizontal flame tank kilns generally exceeds 200t, and the large-scale ones reach 400～500t. The daily output of horseshoe-shaped flame tank kilns is mostly below 200t. The glass melting temperature is as high as 1580～1600℃. The energy consumption of melting accounts for about 70% of the total energy consumption in production. It can effectively save energy through measures such as comprehensive heat preservation of the kiln, increasing the capacity of checker bricks in the regenerator, improving the distribution of the piles, increasing the combustion efficiency and controlling the convection of the glass liquid.
③Molding: Molding is mainly used, using blow-blow method to form small mouth bottles, and press-blow method to form wide mouth bottles. Less use of control law. The production of modern glass bottles and cans widely adopts automatic bottle making machines for high-speed forming. This kind of bottle making machine has certain requirements on the weight, shape and uniformity of the gobs, so the temperature in the feed tank must be strictly controlled. There are many types of automatic bottle making machines, among which the row-type bottle making machine is the most commonly used. The line-type bottle making machine has a wide range of manufacturing bottles and cans, and has great flexibility. It has been developed into 12 groups, double drop or triple drop molding and computer control.
④ Annealing: Annealing of glass bottles and cans is to reduce the residual permanent stress of the glass to allowable values. Annealing is usually carried out in a mesh belt continuous annealing furnace, and the maximum annealing temperature is about 550-600°C. The mesh belt annealing furnace adopts forced air circulation heating to make the temperature distribution of the furnace chamber uniform and form an air curtain, which restricts the longitudinal air flow movement and ensures the uniform and stable temperature of each belt in the furnace.
⑤Surface treatment and processing: Generally, the surface treatment of glass bottles and cans is carried out by coating the hot and cold ends of the annealing furnace. The hot-end coating is to place the formed bottle in a hot state (500～600℃) in the atmosphere of vaporized tin tetrachloride, titanium tetrachloride or tin butyl tetrachloride to make these metal compounds in The surface of the hot bottle and can is decomposed and oxidized into an oxide film to fill the micro-cracks on the glass surface, prevent the generation of surface micro-cracks, and improve the mechanical strength of the glass bottle and can. The cold end coating is sprayed with monostearate, oleic acid, polyethylene emulsion, silicone or silane at the exit of the annealing furnace on the surface of the bottle and can at a temperature of about 100-150°C to form a lubricating film. In order to improve the wear resistance, lubricity and impact strength of the bottle surface. In production, cold-end coating and hot-end coating are often used in combination.
⑥Inspection: Detect defective products and ensure product quality. The defects of glass bottles and cans are divided into two categories: glass defects and bottle forming defects. The former includes bubbles, stones, streaks, and color irregularities; the latter includes cracks, uneven thickness, deformation, cold spots, and wrinkles. In addition, it is necessary to check the weight, capacity, dimensional tolerances of bottle mouth and body, internal stress resistance, thermal shock resistance and stress relief degree. Glass beer bottles, glass beverage bottles, glass food bottles, etc. Due to the high production speed and large batches, visual inspection can no longer adapt to them. There are automatic inspection equipment, such as preselectors (to check the outline and dimensional tolerances of bottles and cans), bottles Mouth checker, crack checker, wall thickness checker, squeeze tester, pressure tester, etc.
⑦Packaging: Conventional forms include corrugated cardboard box packaging and pallet container packaging. All have been automated. The corrugated cardboard box packaging starts from empty bottle packaging to filling and sales, using the same carton. Tray container packaging is to arrange the qualified bottles into a rectangular bottle array, move them to the pallet and stack them layer by layer, and then wrap them up to the specified number of layers. Generally, it is also covered with a plastic film sleeve, heated to shrink it, wrap it tightly into a strong whole, and then bundle it. This is also called thermoplastic packaging.