Composition and raw materials of bottle glass

There are many ways to classify the composition of bottle glass. According to the different oxide content of bottle glass, it can be divided into soda-lime glass Components, high calcium glass components, high aluminum glass components, but this classification is not rigorous. For example, the content of Ca0 is high calcium component, and the content of Al2 O3 is high aluminum component. It is difficult to set a clear boundary. Here it is only for the convenience of research and explanation.
According to the different uses of bottle glass, the components of bottle glass can also be divided into beer bottle glass components, liquor bottle glass components, canned bottle glass components, medical bottle glass components, and reagent and chemical raw material bottle glass components. According to the requirements of glass performance for different uses, the glass components should be designed in a targeted manner to reduce costs.
The more common method in China is to divide the glass component types according to color. It is customary to divide it into high white material (Fe2 O3< 0.06%), bright material (ordinary white material), semi-white material (light blue material Fe2O3<0.5%), color material, and milky white material. Common high-white materials are generally used for high-end wine bottles and cosmetic bottles; semi-white materials are used for canned bottles, which contain a certain amount of Fe2 O3, mainly used to absorb ultraviolet rays, containing Fe2 O3 <0.5%, and the ultraviolet limit is below 320nm. Beer bottles are green or amber, and the absorption limit is about 450nm.

Soda-lime bottle glass composition is based on the SiO2-CaO-Na2O ternary system with Al2O3 and MgO added. The difference from flat glass is that the Al2O3 content in bottle glass is relatively high, the CaO content is also relatively high, and the MgO content is relatively low. Regardless of the type of molding equipment, whether it is beer bottles, liquor bottles, or canned bottles, this type of composition can be used, and only some fine-tuning needs to be done according to the actual situation. Its composition (mass fraction) ranges from: SiO270% to 73%, Al2O3 2% to 5%, Ca07.5% to 9.5%, MgO1.5% to 3%, R2O13.5% to 14.5%. This type of composition is characterized by moderate aluminum content. Silica sand containing Al2O3 can be used, or alkali metal oxides can be introduced using feldspar to save costs. The amount of Ca0+MgO is relatively high, and the hardening speed is relatively fast to adapt to higher machine speeds. A portion of MgO is used to replace CaO to prevent glass from crystallizing in the flow hole, material channel and feeder. Moderate Al2O3 can improve the mechanical strength and chemical stability of glass.

The ratio of MgO and CaO in soda-lime glass has a great influence on the melting rate and crystallization performance of the glass. Research has found that when the MgO/CaO ratio is 0.49~0.50, which is located at the low eutectic point of the MgO-CaO binary system phase diagram, the glass melting rate is the fastest, the upper limit temperature of the glass crystallization is the lowest, and the crystallization tendency is small. 

High calcium composition is the traditional bottle glass composition. In the 1970s, Japan improved the sodium calcium system composition to high calcium composition to meet the needs of high-speed molding. At present, high calcium glass composition is the main component system of bottle glass, and its composition (mass fraction) ranges from: SiO270%^~73%, CaO9.5%~11.6%, R2013.5%~15%.
The main characteristics of high calcium glass are as follows.
1. Reduce the variety of raw materials and simplify the raw material processing and batching process.
2. Introduce more CaO, and use granular limestone with a particle size of about 1.5mm as raw material, which reacts with silica sand at a lower temperature, which is conducive to melting; at high temperature, Ca0 can reduce viscosity, which is conducive to clarification.
The increase in the hardening speed of glass is conducive to increasing the machine speed and reducing various defects in the molding process.
No MgO is used to prevent glass from falling off.
High-calcium glass is easy to crystallize, and the main crystal phase is wollastonite. If the temperature of the material channel and feeder fluctuates, it is easy to approach the crystallization temperature and crystallize. In severe cases, the material bowl will be blocked, so the temperature must be strictly controlled.

High-aluminum is also a traditional component of bottle glass. It is difficult to formulate a clear composition range for high-aluminum glass. It is generally believed that the content of Al2O3 is more than 6%, and some people believe that the content of Al2O3 should be more than 9%. Compared with soda-lime and high-lime glass, it may be more reasonable to use 6% Al2O3 to distinguish high-aluminum glass. If it is to be divided more finely, high-aluminum glass is also divided into high-aluminum high-calcium low-sodium type and high-aluminum soda-lime type.
The characteristic of high-aluminum glass is that it can use aluminum-containing and alkali-containing rocks, tailings, and slag, such as nepheline, phonolite, perlite, granite tailings, tantalum-niobium tailings, etc., especially lithium and fluorine, which make the glass easy to melt and clarify. Generally, high-aluminum raw materials will bring more impurities such as Fe2 O3 and TiO2 to the glass composition, so it can only be used for semi-white and green materials.
The biggest impact of high-aluminum components on the properties of glass is to increase the viscosity of the glass, and at the same viscosity, the corresponding temperature is increased. The temperature change of glass viscosity when 1% Al2O3 replaces SiO2 is shown in Table 2-3. Some domestic enterprises adopt the method of increasing the content of CaO and Mg0 in high-aluminum glass to reduce the high-temperature viscosity and melting temperature of glass liquid. At the same time, it is beneficial to clarify the glass, increase the output, and also help to increase the machine speed.

The melting temperature, forming temperature, softening temperature and annealing temperature of high-aluminum glass have all increased, the hardening speed has increased, the glass surface is prone to wave ribs and stripes, the uniformity of the bottle wall is difficult to control, and the uniformity of the ring cutting has deteriorated. Therefore, it is best to add surfactants to the high-aluminum glass to reduce the surface tension of the glass, so that the stripes in the high-aluminum glass are easy to diffuse and homogenize, so as to obtain glass liquid with better quality. High-aluminum glass is easy to crystallize, especially high-aluminum glass with high CaO content and low R2O content. Some factories have experienced crystallization in the flow hole and blocked the flow hole and stopped production. When using high-aluminum formula, the material channel is also easy to crystallize. Therefore, the material channel should have better insulation measures and perfect heating means. In addition, the chemical stability of high-aluminum glass, such as water resistance and alkali resistance, is slightly reduced, and the compressive strength is slightly improved.
High-aluminum glass has high strength and strong water erosion resistance. However, the glass liquid containing high-aluminum formula is not conducive to clarification and homogenization due to its high viscosity, especially when the clarifier is used improperly, there will be adverse consequences. Due to some problems in the production control and quality of high-aluminum glass, some domestic factories that originally used high-aluminum components for the purpose of replacing alkali have switched to soda-lime or high-calcium glass components as the market supply of soda ash becomes sufficient. However, individual factories have already mastered the production conditions of high-aluminum glass and still use high-aluminum components.