Discussion on lightweight measures of the hottest

Discussion on lightweight measures of glass packaging since the 1980s, due to the rising production cost of glass containers and the heavy and fragile glass containers, some fields have been replaced by metal containers, plastic bottles, composite flexible packaging, etc., especially in recent years, all kinds of packaging materials are competing and replacing each other in the packaging field with their unique performance advantages, and the glass packaging market is facing a severe test. At present, in Europe, America and Japan, some beer packaging has been replaced by polyester bottles. In terms of pharmaceutical packaging, in addition to high-grade nutrient solution bottles and infusion bottles, conventional packaging has been replaced by plastic bottles, hoses and blister packaging. From the perspective of market economy, glass packaging must speed up the implementation of lightweight, reduce costs, improve performance, in order to regain and consolidate the market

at the same time, green packaging has become the trend of global packaging development. Traditional glass packaging production does not meet the requirements of green packaging because of backward production technology and equipment, poor formula, no enhanced treatment, and high energy consumption. The implementation of lightweight and strengthening the promotion of technology can make the bottle wall thinner, maintain or increase the strength, reduce the material consumption, and greatly reduce the energy consumption and cost through the improvement of equipment and process. Therefore, lightweight glass packaging is an urgent requirement of green packaging

1 lightweight overview

the lightweight of glass packaging is to reduce the weight volume ratio of glass bottles under the condition of ensuring a certain strength, in order to improve its greenness and economy. Weight volume ratio is a measure to evaluate the mass of glass bottles and cans with the same volume. According to different uses, the weight volume ratio of lightweight bottles is generally between 0.15 and 0.8. The weight volume ratio of lightweight bottles is small, the bottle wall is relatively thin, and the weight is light. The average wall thickness of lightweight bottles is 2 ~ 2.5mm

the main way to reduce the weight volume ratio of glass packaging containers is to reduce the wall thickness. However, it is very difficult to maintain a high compressive strength in the thin-walled state. We must start with all links of the whole process from design to production, and achieve the purpose of small wall thickness and high strength through strengthening treatment measures such as glass composition modification, reasonable structural design, correct process arrangement, effective production process index control, effective surface treatment and so on. These aspects will be discussed below

2 lightweight production process control

2.1 doing a good job in batching is the first step to realize lightweight production

formulation design of raw materials and batch preparation process, raw material composition, particle size, moisture, batch uniformity, broken glass quality and addition uniformity all have a direct impact on product quality. To do a good job in batching, we must implement a stable transmission and stable formula, formulate and strictly implement raw material standards, and institutionalize the batch preparation process. Domestic high-end lightweight bottle production pays special attention to this link. In terms of weighing and accuracy, the batching system adopts advanced computer-controlled electronic weighing equipment, and the dynamic accuracy should reach 1/500 to ensure the batching quality

2.2 the melting process is not only to ensure the quality of glass packaging, but also the key link of green glass packaging.

the glass melting process can be roughly divided into five stages: silicate formation, glass formation, clarification, homogenization and cooling. The melting process adopts continuous operation, and these five stages are carried out in different parts of the furnace, so as to control the accurate melting temperature by sections. The stability of kiln operation process index is very important. Generally, the melting temperature fluctuation is not more than 10 ℃, the liquid level fluctuation is not more than 0.5mm, and the kiln pressure fluctuation is not more than 2PA, so as to prevent the fire in the kiln space, so as to prevent quality problems such as stones, color, appearance, poor strength, etc. In the production of high-grade lightweight bottles, the requirements for the fluctuation accuracy of the distribution channel temperature and the glass level are very high, and some are controlled within ± 2 ℃ and ± 0.2mm respectively

of course, to ensure high-precision production process indicators, we must promote oil fired kilns, improve the kiln type, and use high-temperature, wide cross-section, large roller type horseshoe flame furnaces. A series of measures such as full heat preservation, bubbling at the bottom of the furnace, electric melting aid, furnace sill, and microcomputer control of thermal parameters have been taken to make the melting rate reach 1.5 ~ 2.0 (TM-1), and the melting quality has been significantly improved

2.3 effective molding control is the guarantee to obtain the expected molding effect and uniform wall thickness.

the process of liquid glass forming glass products can be divided into two stages: molding and finalization. Molding and shaping are continuous. During the molding process, it is necessary to control the viscosity and temperature of the glass and the heat transfer to the surrounding media through the mold. Glass containers are usually controlled by three characteristic temperature values: softening temperature, annealing temperature and strain point. For different products, the key is to determine reasonable parameters through experiments. Advanced bottle making, feeding and heating systems and the use of advanced molding technology are the fundamental guarantee to obtain uniform wall thickness and realize lightweight

2.4 effective annealing and elimination of harmful residues should meet the needs of operators

annealing of glass bottles and cans is a heat treatment process to eliminate or reduce the residual stress in the glass to the allowable value. Any glass product has residual thermal stress or permanent stress during processing. In order to eliminate these thermal stresses, the glass needs to be heated to the annealing point for heat preservation and soaking, so that the internal structure of the glass can be adjusted and the stress can be released

the annealing process of glass includes four stages: heating, heat preservation, slow cooling and rapid cooling. The holding time should be accurately controlled according to the wall thickness. In the slow cooling stage, the cooling speed should be strictly controlled to avoid new stress. In the fast cooling stage, different cooling speeds should be adopted according to the wall thickness to prevent the temporary stress generated during cooling from exceeding the strength limit of the glass and causing fracture

3 using surface treatment technology to improve the surface properties of glass containers

the surface state, composition and structure of glass are very different from its internal composition and structure. The surface properties of glass have a great influence on its main properties. The chemical stability of glass actually depends on the chemical stability of its surface, and the mechanical strength and impact resistance of glass also depend on the shape and structure of the glass surface to a considerable extent. Therefore, the surface treatment of glass is one of the important technical means to manufacture high-strength lightweight glass containers

the purpose of glass container surface treatment is to change the chemical stability of the container surface and eliminate the damage of the glass surface, so as to achieve the purpose of strengthening. Main methods 6. There are methods such as adding coating, physical strengthening, chemical strengthening, surface acid treatment, plastic coating when making bottles on the front, back, left and right mobile stage

3.1 bottle making coating

hot coating. Hot coating shall be carried out after bottle making and molding and before annealing. When the formed glass bottle is slowly cooled to 500 ~ 600 ℃, metal coating agents (such as tin oxide, titanium oxide, tin chloride, etc.) are sprayed on the surface of the container to form a protective film of a certain thickness, which enhances the surface strength by about 30%, and makes the bottle withstand long-term water washing and washing

the center of the fixture coincides with the center of the swing frame for cold coating. Cold coating is to spray monostearate, polyethylene, oleic acid, silane, silicone or other polymer lotion into a fog after annealing the glass bottle, and attach it to the surface of the glass bottle with a certain temperature (the bottle temperature depends on the spraying material, about 21 ~ 80 ° C), forming a protective layer with wear resistance and lubricity

frost. Frosting refers to the spraying of carbon tetrachloride during the cooling process of the glass bottle or the introduction of sulfur dioxide in the annealing furnace. Both of them can react with alkaline oxides on the surface of the bottle to precipitate sodium ions on the surface of the glass and form mirabilite particles (i.e. turbid white powdered na2s04). After washing with water, the chemical stability of the surface is enhanced due to the reduction of alkalinity

surface silicone coating treatment. Organopolysiloxane hydrophobic film and polymerization (Si02) can be formed on the surface of glass by using silicone evaporation coating or dipping with silicone. The silicon oxide film is connected with the glass surface through the common silicon oxygen bond. After heat treatment, the organic groups will volatilize and the remaining silica film can be filled in the crack. The hydrophobicity can avoid the diffusion of the active medium in the crack and make the surface crack heal (commonly known as heterogeneous healing). Not only the strength and chemical stability of the glass are greatly improved, but also the glass has special optical properties and impact resistance. Commonly used silicone solutions include methyl fluorosilane, dimethyl dichlorosilane, diphenyl difluorosilane and phenyl trichlorosilane

the thickness of the polymer film on the surface of the container is 0.005mm, and its compressive stress increases by 10 ~ 12Pa under the standard weight of the container. Under the same internal pressure, the weight of several non recyclable standard glass bottles can be reduced from 420g to about 300g. The weight of the glass bottle is reduced by 25% - 30%. At the same time, because the coated film is very thin, the return of this glass container will not cause any environmental problems. Therefore, the polymer coated container can be included in the standard recycling process

3.2 physical strengthening (tempering)

physical strengthening (tempering) is also called air-cooled strengthening, which aims to improve the mechanical strength and thermal stability of glass bottles and cans. The physical strengthening treatment method is as follows: after the bottles and cans are demoulded by the bottle making machine, they are immediately sent to the muffle type tempering furnace to be evenly heated to a softening temperature close to the glass (but the softening temperature cannot be reached), and then transferred to the tempering room. Cold air is sprayed on the inner and outer walls of the bottles and cans with the air grille of the porous nozzle to quickly cool the bottles and cans, or the bottles and cans are suddenly cooled with liquid as the cooling medium, resulting in a compressive stress layer formed by the sudden contraction of the product surface, Because the cooling inside the product lags behind the surface, it is a tensile stress layer. When these two kinds of stress distributions are reasonable, the internal pressure strength of the glass can be doubled. The air pressure of the injection bottle body is generally 15 ~ 21kpa, and the air pressure of the injection bottle bottom is generally 6 ~ 7kpa

3.3 chemical strengthening (tempering)

ion exchange treatment on the surface of glass is also called chemical strengthening. The common methods include molten salt method and spraying method

molten salt method. Exchange the ions with small radius in the glass with the ions with large radius in the solute, or replace the ions with large radius in the glass with the ions with small radius in the solute, so as to generate compressive stress on the surface of the glass, which can improve the internal pressure strength, and the hardness of the treated products is high. Wear resistance, the strength of the products will not be reduced due to long-term use

spraying method. Chemical tempering by spraying has the advantages of good reinforcement effect, safe production and use, high production efficiency and low production cost. From the perspective of comprehensive evaluation, it is an ideal reinforcement process at present

in order to improve the enhancement effect of chemical tempering by spraying and adapt to the process characteristics, the ideal chemical composition of basic glass should be selected after research. The chemical composition of basic glass is different, and the formula of spraying liquid and spraying liquid additives should also be adjusted accordingly

each process link of spray chemical tempering will have a decisive impact on its final enhancement effect. Therefore, it is necessary to grasp the process parameters of two stages: in the first stage, the formation of solid-phase reagent layer must control the parameters such as spray temperature, solution concentration, spray time, spray droplet size, thickness and density of solid-phase reagent layer; In the second stage, the temperature of heat treatment (ion diffusion and exchange) must be well controlled. This method can make the strength of glass containers reach about twice the original value, and the loss of reinforced products in the process of transportation and mechanical filling is reduced to about 1/3 of the original value. The glass products chemically toughened by spraying method have good gloss and quotient