Glass

Glass

Glass

Glass is an ancient and at the same time modern material, it  is very diverse in terms of applications in both everyday life and in high-tech products.

Plate glass and container glass are produced mainly as so-called soda lime glass from silica sand, soda and limestone and/or dolomite. The oxides from these raw materials are responsible for the chemical and physical properties as well as for the glass melting process.

Glass is 100% recyclable. Alongside the primary raw materials, processed pieces of recovered glass also play an important role in glass production.

Soda lime glass makes up by far the greatest quantity of all industrially produced glass. As the name suggests, soda and lime, alongside sand, play an essential role as components. A typical soda lime glass consists of 10 to 15% CaO or CaO + MgO. In practice, soda lime glass is used in the production of drinks bottles, food jars, simple drinking glasses and plate glass. For the most part, limestone and dolomite provide the necessary CaO und MgO portions of the glass. In particular, dolomite ( MgO ) has a positive effect both on the melting process and the properties of the glass.

Lhoist supplies the glass industry with pure dolomite and limestone products of consistent chemical composition and particle size under the VISUCAL® brand.

Also, our SORBACAL® products based on lime hydrate are tried-and-tested additives effective for the treatment of flue gas for glass melting tanks for separating out SO2 und HF amongst other things.

Float glass

Nowadays, plate glass is mostly produced using float glass technology where the glass melt is passed over a molten tin bath. This produces a very high-quality plate glass which has a range of applications in the construction and automotive industries. In particular, colourless / low-iron plate glass is used amongst other things for the production of solar modules and therefore for generating solar electricity. Plate glass is an important design material in modern architecture.

In addition to limestone, up to 5% MgO from dolomite is used in the mix for plate glass. This provides a high level of process stability, improves the viscosity of the glass melt and increases the scratch resistance and chemical resistance of the glass. The lower calcination temperature of MgCO3 in the dolomite and the formation of low-melting mixture phases also result in a reduction in energy when dolomite is used.

Container glass

The use of glass is absolutely essential in food containers, drinks bottles and containers for pharmaceutical and cosmetic products. It is gas-tight, inert and tasteless, thus offering ideal conditions for such containers. The individual shape and colouring of glass containers offer additional marketing advantages.

In spite of, or owing to, the fact that large amounts of recycled glass are used in the production of container glass, low-iron, natural raw materials which are of a consistently high quality are required in glass production. In addition to limestone as a CaO carrier, it has also proven to be beneficial in the production of container glass to use 1.8 - 3.4% MgO from dolomite. The tendency of glass to crystalise is suppressed and soda and refining agents can be reduced. For containers which are heavy and have a complex shape, improved cooling properties are achieved with MgO.

Continuous glass fiber filaments

Textile glass fibres are used mainly for producing glass fibre-reinforced plastics (GRP). These plastics are used in industries ranging from transport (automotive, aircraft construction, shipbuilding) to wind power, electronics and sports equipment.

The production of E-glass and ECR (E-Glass Chemical Resistant) glass for continuous glass fibres requires very fine and high-quality raw materials. Fine-milled limestone and dolomite products as well as fine white lime and dolomite lime are used. Calcinated lime and dolomite products - which are burnt specifically for the production of E-glass, C-glass or ECR-glass - increase the performance and capacity of glass melting tanks for glass fibres. In fully electric cold-top glass melting tanks, the use of burnt lime and dolomite lime products prevents the formation of undesired CO2 foam layers and hot breakthrough in the batch blanket. Lhoist also offers kaolin products as an aluminium carrier for glass fibre melts.

Glass fibers for insulation

Glass, mineral and stone wool have been established for over 60 years as a material for insulating against heat, cold and noise. Mineral wool is based on natural and local raw materials such as silica sand or basalt and the environmentally-friendly use of recycled glass. It is the preferred insulating material in construction and industry. The glass or stone wool fibres are produced by blowing compressed air through a stream of glass or in a spinning process. Adding limestone and dolomite products to the mix serves to adjust and influence the desired properties of the melt and fibres. Depending on the composition, lime and dolomite products act as fluxing and stabilising agents for the glass.

Technical glass

The field of technical glass encompasses products such as glass for TV screens and computer monitors, lighting glass (tubes and bulbs), optical glass, laboratory and technical glassware, borosilicate glass and ceramic glass (hotplates and high-temperature domestic applications) and glass for the electronics industry (LCD panels). CaO and MgO play a small but important role as other glass-forming oxides are generally used (boron, aluminium, etc.). Our high-quality and homogeneous Visucal® limestone and dolomite products can be used to produce the highest quality technical glass (e.g. for smart phones, TVs, tablets, etc.).