Stone wool

Rocks are one of the main components of raw materials for stone wool production, as a rule, these are igneous rocks of the gabbro-basalt group and metamorphic rocks similar to them in chemical composition, as well as marls .

The approximate chemical composition of the raw materials:

• SiO ₂ 45–65%
• Al ₂ O ₃ 10–20%
• CaO 5–15%
• MgO 5–10%
• Fe ₂ O ₃ + FeO 5–15%
• Na ₂ O + K ₂ O 1-3%

One of the main indicators of the quality of stone wool fiber is the acidity module - the ratio between acidic and basic oxides.

The best quality stone wool can be obtained from mountain gabbro-basalt rocks, with the addition of carbonate rocks to regulate the acidity modulus.

According to the value of the acidity modulus, stone wool can be classified according to GOST 4640-93 “Mineral wool. Specifications ", as follows (3 types):

• A - St. acidity module 1,6
• B - St. acidity module 1.4 to 1.6
• B - St. acidity module 1.2 to 1.4

Vata with a large acidity modulus is more water resistant and therefore more durable.

One of the components of stone wool insulation is a binder that holds the fibers together, thereby providing products with specified shape and density parameters. Types of binder:

1. Bituminous binders
2. Synthetic binders. As a rule, these are phenol alcohols, phenol-formaldehyde, urea resins.
3. Composite binders (binders consisting of several components).
4. Bentonite clay.

Currently, the most common use is a composite synthetic binder consisting of phenol-formaldehyde resins and water-repellent additives, as This type of binder provides the best thermal insulation performance. In the finished product, phenol and formaldehyde are less than 2% by weight, the substances are in a connected state, the binder is inert with respect to the environment.

The method of stone fiber production was "peeped" in nature: after volcanic eruptions in the Hawaiian Islands, the so-called "Pele Hair" was found - cotton wool made from thin filaments of volcanic rocks, which turned out to be the "predecessors" of modern material. For the first time, rock wool was obtained in the USA in 1897. The modern production of stone wool is based on the principle of operation similar to the operation of a volcano: In a furnace, where the temperature reaches about 1500 ºС, a fiery-liquid melt is obtained from rocks, which are then pulled into various fibers ways:

• Blowing method
• Centrifugal roll method
• Centrifugal Blowing Method
• Centrifugal spinneret-blasting method
• Other modified methods

Production of products: After the fiber formation process, a binder is introduced by spraying the binder onto the fibers, watering the stone wool carpet or preparing hydromasses. A stone wool carpet with a binder applied to the fibers goes through the stage of forming the structure of the product. Technologically, horizontally layered, vertically layered, spatial or corrugated structures can be defined, and combined density can be created, which increases the possibilities of using products in various designs.

After molding, stone wool is subjected to heat treatment, where a coolant with a temperature of 180-230 ° C provokes a polycondensation reaction of the binder. The content of organic substances in the finished product, as a rule, is 3-4% by weight. Then the products are cut to the required sizes, packaging and warehousing.

Besides stone slabs and mats, molded products (cylinders, segments) can be made of stone wool.

Stone wool is a non - combustible material. Stone wool fibers can withstand temperatures without melting up to 870 ºС. Stone wool does not burn, but at a temperature of 600-700 degrees it decomposes forming hot dust. ^{[ specify ]} Stone wool products have heat and sound insulating properties due to open porosity. The coefficient of thermal conductivity of stone wool is in the range of 0.035 - 0.039 W / m • K. The air enclosed in the pores of the cotton wool has a low thermal conductivity and is in a static state, which determines its excellent thermal insulation properties. Due to open porosity, rockwool is a vapor-permeable material, vapor permeability is approximately 0.25 - 0.35 mg / m² • h • Pa.

The density of stone wool can vary widely from about 30 kg / m³ to 220 kg / m³, therefore, the physical and mechanical characteristics differ. So, rigid plates are able to withstand a distributed load of 70 kPa (700 kg / m²!).

Products can be produced with a coating of aluminum foil, kraft paper, fiberglass, etc.

The positive aspects of stone wool are: environmental friendliness, biological resistance, durability, ease of installation, sufficient steam transmission, fire safety, good heat-insulating ability.

The use of stone wool as a heater has been widespread since the beginning of the 20th century due to the fact that this natural material (approximately 95% stone) is non-combustible and durable. Stone wool received the main distribution as a heater for building envelopes (facades, roofs). Due to its heat-insulating abilities, the material allows to prevent heat loss through surfaces in the cold season and to keep the room cool during the warm season. Currently, stone wool is widely used for the following structures:

• Walls. In ventilated facade systems, facades with a thin or thick plaster layer, lightweight external frame structures of three-layer brick walls, reinforced concrete wall panels, metal sandwich panels, element-wise assembly panels.
• Partitions. Indoors as sound insulation in partitions in office and residential premises.
• The floors. For insulation of floors along logs or floor slabs, with the possibility of screed installation. For sound insulation in the designs of the "floating" floor.
• Roofs (pitched, flat). It is possible to lay insulation on flat roofs on reinforced concrete slabs or profiled flooring with further waterproofing with bituminous materials or PVC membranes.
• Fire protection of steel supporting columns and beams, transit ducts, reinforced concrete floors, pipe and cable penetrations

Insulation of equipment and pipelines. Due to the incombustibility and high melting temperature of the fibers with stone wool, it is possible to isolate surfaces with temperatures up to +700 ºС.

Cylinders, segments or mats (for large radii) can be used to isolate curved surfaces.

• Yu. P. Gorlov "Technology of heat-insulating and acoustic materials and products."
• GOST R 52953-2008 (EN ISO 9229: 2004) Heat-insulating materials and products. Terms and Definitions.
• GOST 4640-93
• SNiP 41-03-2003 Thermal insulation of equipment and pipelines
• R.Z. Rakhimov, N.S. Shelikhov, T.V. Smirnova. Stone wool thermal insulation. Tutorial. 2010.