(Summary description)With the increase in beer production in my country, the demand for beer bottles has also increased year by year, so the quality of beer bottles has become a prominent problem. Among the many indicators that affect the quality of beer bottles, the impact resistance item is an important safety indicator for beer bottle products. The biggest weakness of glass bottles is their brittleness. In the production and packaging, beer filling, transportation and use of beer bottles, collisions between bottles or collisions with other hard objects often occur.
With the increase in beer production in my country, the demand for beer bottles has also increased year by year, so the quality of beer bottles has become a prominent problem. Among the many indicators that affect the quality of beer bottles, the impact resistance item is an important safety indicator for beer bottle products. The biggest weakness of glass bottles is their brittleness. In the production and packaging, beer filling, transportation and use of beer bottles, collisions between bottles or collisions with other hard objects often occur. This kind of collision will significantly reduce the mechanical strength of beer bottles. Due to current consumption habits and problems in the management of beer bottle reuse, the strength of beer bottles plummets. Some beer bottles with poor quality and frequent reuse are resistant to impact. The lowering of the index makes it difficult to withstand normal collisions, which creates hidden dangers for bottle bursts. Therefore, the production of beer bottles should meet the requirements of impact strength in the national standard GB4544-2020. The current standard stipulates: for V≤530ml disposable bottles and recyclable old bottles ≥0.2J, recyclable new bottles ≥0.4J; V＞530ml Disposable bottles and recyclable old bottles ≥ 0.3J, recyclable new bottles ≥ 0.6J. For the actual test method, please refer to the national standard GB/T 6552-2015 glass container anti-mechanical impact test method.
1. Affect the impact strength of beer bottles
The mechanical strength of beer bottles is not only related to bottle shape, bottle wall thickness and thickness distribution, but also closely related to glass uniformity, micro and macro defects and surface conditions. The theoretical strength of glass refers to the strength of its structural bonds. Different glass components have different strengths of structural bonds. As we all know, ≡Si-O-S≡ bond has very high strength, while ≡Si-O-R (alkali metal) has very low strength. In theory, to obtain high-strength glass, a large number of high-charge, small-volume cation glass network forming bodies must be added, but this will bring huge difficulties in melting and molding of the glass or increase the cost, which is actually impossible. . The theoretical strength of a beer bottle can be calculated from the structural keys. Its strength is very high and much stronger than steel. In fact, its theoretical strength is hundreds of times the actual strength. The reason why the actual strength is so low is due to lattice defects, streaks, cracks, etc., and another reason is its heterogeneity. Due to these factors, the actual impact resistance value of beer bottles is relatively low.
2. The impact of bottle shape and wall thickness against impact
The shape of the bottle has a great influence on the mechanical strength. The more complex the shape, the lower the strength. This is due to the stress concentration of the bottle with a complicated shape. At present, most glass factories in my country use the bottle shoulder to be relatively gentle, there are two bending points to buffer, and the stress distribution is uniform; there is a protruding ring above the bottle heel, which has better impact resistance. However, judging from the results of previous random inspections, the impact strength is not satisfactory. This is mainly because the actual process level, production conditions and technical level of my country’s glass industry have different degrees of problems, as well as the various micro and macro analysis above. The impact of surface defects on the mechanical strength of the beer bottle makes the actual impact resistance value of the beer bottle low.
Three, several factors to be considered to improve the impact strength
In the normal production process, if the product appearance and physical and chemical performance indexes of the glass bottle are relatively good, and the qualified rate of the finished product is relatively high, the only drawback is that the impact resistance index is not stable. Most of this situation is due to insufficient glass homogenization. Caused. Several factors need to be considered:
1. Fine-tune the glass composition, reduce the high temperature viscosity of the glass, and make the glass liquid easy to clarify and homogenize. (The data provided is for reference only)
(1) On the basis of not significantly increasing the cost, part of the quartz sand is used to replace part of the ordinary silica sand, and the content of the glass composition is reduced to 1.8-2.0% as much as possible.
(2) Intentionally increase the content of CaO in the glass composition so that the total amount of CaO + MgO is close to 12.3-12.5%. It can be directly increased and other components will naturally drop. During the adjustment process, if there are adverse reactions, stop immediately.
2. Check the particle size of ore raw materials, and the requirements for particle size (wt%): quartz sand + 20 mesh ≤ 0.1, -150 mesh ≤ 7; limestone (dolomite) + 10 mesh ≤ 0.5, -150 mesh ≤ 7; fluorite Stone+40 mesh=0, -200 mesh ≤5. This is to find the reason from the raw material itself to prevent it from being too coarse or too fine. The purpose is to ensure that the batch material can be mixed uniformly to accelerate the melting and clarification of the glass; at the same time, the storage of ore materials The limit should be guaranteed, and the test should be carried out in batches, clearly marked, and used in accordance with the principle of “first in, first out”.
3. Strengthen the quality management of cullet, try to reduce the content of heterogeneous glass, and control its entering the furnace; at the same time, strictly control the breaking link of cullet, so that the cullet is 20-25mm into the warehouse after processing, which promotes easy clarification and homogenization .
4. Strengthen the moisture control of quartz sand. Because the moisture content of quartz sand is large and unstable, the moisture content of quartz sand should be tested in time according to regulations. After testing, the wet base content of quartz sand should be carefully and timely based on the dry basis of quartz sand. The adjustment must not be wrong.
5. Control of the raw material weighing system. Weighing is the most important link in the batching process. The accuracy of the weighing of various raw materials directly affects the composition of the glass and the quality of the product. The batching scale is calibrated at full load with standard weights once a week, and the error is required to be ≤±0.1%. If the standard weights are not enough, the “physical calibration method” can be used to calibrate and correct in time.
6. Control of raw material preparation system
(1) Feeding sequence of raw materials: The sequence of raw materials discharged into the mixer after weighing should be: quartz sand→soda ash→limestone. At the same time, it is required that the three raw materials enter the mixer as much as possible simultaneously (the principle of Lantern Festival), which is an improvement. The key to batch uniformity.
(2) The uniformity and moisture of the batch: the mixing time of the mixer is divided into dry mixing time and wet mixing time. These two times determine the uniformity of the batch; the water addition time determines the moisture of the batch. Strive for the uniformity of the mixture to reach more than 98%, and the moisture content of the mixture is controlled within 4-5% (discharge port of the mixer).
7. The bottom temperature of the furnace is an important indicator, and its changes must be strictly controlled during normal production. The stability of the bottom temperature is the basis for stable production and the basis for us to adjust all process parameters.
8. The control of the glass liquid level: when automatically controlling the feeding, the glass liquid level is required to be stable within the standard height ±1.0mm; when manual operation is used, the glass liquid level is allowed to fluctuate within the standard height ±1.5mm. When a special situation causes the glass level to drop to catch up with the liquid level, it is required to execute at a speed of 0.5mm/hour (if the decrease is large, it depends on the situation). At the same time, the stock pile is required to not exceed 2/3 of the furnace length and is evenly distributed, and the bubble boundary is stable near the top of the kiln sill.
9. The control of the discharge capacity of the kiln: the change of the discharge volume of the kiln is stable within <2% during normal production, and the number of machines must be adjusted when changing the product to keep the increase and decrease of the discharge volume stable. If the weight of the products to be replaced is very different, some preparations and response plans need to be done in advance. Whether the bottle production is stopped or changed, it is necessary to communicate in advance. If you want to stop, stop and start, it is never allowed! There must also be a plan to increase or decrease the speed of the aircraft. You cannot increase or decrease as much as you want, and you cannot do it at will. It is very important to maintain the basic stability of the output of the kiln.
10. Kiln pressure control: When the system is under normal automatic control, it is required to control the kiln pressure change near the pressure measuring point within the range of ±3Pa (except during reversing). When using manual operation, the kiln pressure near the pressure measuring point is allowed to fluctuate within ±5Pa. Prevent the kiln pressure from fluctuating too much.
Fourth, the conclusion
The above adjustments and precautions are based on the author’s experience in practice when researching to improve the impact strength of beer bottles for process improvement for many years. They basically revolve around the clarification and homogenization of the glass liquid on the basis of the original process. Improvement, in summary, is to maintain “uniformity and stability” as a whole. One of its purposes is to improve the impact strength of beer bottles. In actual production, it is hoped to judge and adopt according to the circumstances. It can be regarded as a “throw a brick to attract jade”.