КАОЛИН

Описание

Kaolin or china clay is a naturally occurring, almost white, hydrated aluminum silicate. This material does not exhibit a high degree of slip. Kaolin boasts good absorbency, is dense, and is sometimes used to reduce the bulk densities in loose powder products. It provides a matte surface effect, which can slightly reduce sheen left by some talc products.

Химические свойства

Kaolin occurs as a white to grayish-white colored, unctuous powder free from gritty particles. It has a characteristic earthy or claylike taste, and when moistened with water it becomes darker in color and develops a claylike odor.

Физические свойства

Sericite is a mineral similar to white mica in shape and composition. It has a very fine grain size and a silky shine. This material is soft and smooth and has a slippery feel on the skin. Sericite may be coated with silicone and other treatments for enhanced water repellency and skin adhesion.

Вхождение

Kaolin is a naturally occurring clay that is treated for impurities.

Использование

kaolin (China clay) is a mixture of various aluminum silicates. It is often used in powders and masks given its absorbent, abrasive, bulking, and opacifying properties. This white, soft powder has good coverage and absorption abilities for both water and oil, making it an appropriate absorber of the oil and sweat secreted by the skin. It adheres well to the skin’s surface, yet is easily removed with normal cleansing procedures. Kaolin is considered a non-comedogenic raw material.

Показания

Kaolin is a naturally occurring hydrated aluminum silicate that is prepared for medicinal use as a very finely divided powder. The rationale behind its use in acute nonspecific diarrhea stems from its ability to adsorb some of the bacterial toxins that often cause the condition.

Определение

A mixture of clays, quartz, and feldspar usually containing at least 25% alumina. Ball and china clays are ordinarily used. A slip or slurry is formed with water to form a plastic, moldable mass, which is then glazed and fired to a hard, smooth solid.

Методы производства

Kaolin is a hydrated aluminum silicate obtained by mining naturally occurring mineral deposits. Large deposits are found in Georgia, USA and in Cornwall, England.
Mined kaolin is powdered and freed of coarse, gritty particles either by elutriation or by screening. Impurities such as ferric oxide, calcium carbonate, and magnesium carbonate are removed with an electromagnet and by treatment with hydrochloric acid and/or sulfuric acids.

Подготовка

The extraction of KAOLIN (china clay) from its deposits is usually performed in three steps: open-pit mining, mineral processing and beneficiation, and drying.
Open-pit operations require the removal of ground overlying the clay (i.e., overburden). The exposed clay is then mined by a hydraulic mining process, that is, a high-pressure water jet from a water cannon called a monitor erodes the faces of the pit. This liberates from the quarry face the china clay, together with sand and mica. The slurry formed flows to the lowest part of the pit or sink, where it is pumped by centrifugal pumps to classifiers, where coarse silica sand is removed. The silica sand is later reused for landscape rehabilitation. The remaining suspension of clay is transported by underground pipeline to the mineral-processing and beneficiation plant, where a series of gravity separation techniques are used to remove particulate materials such as quartz, mica, and feldspars. Sometimes the purified clay slurry undergoes an additional chemical bleaching process that greatly improves its whiteness. The refined clay suspension is then filtrated, and the filtration cake with a moisture content of about 25 wt.% passes through a thermal drier fired by natural gas to yield a final product with 10 wt.% moisture. The end product is normally sold in pelletized form with a pellet size ranging from 6 to 12 mm.

Всемирная организация здравоохранения(ВОЗ)

Kaolin, a hydrated aluminium silicate, is an absorbent and has been used to treat diarrhoea because of its ability to bind and inactivate bacterial toxins. However, it has been shown to induce only a slight change in stool consistency and there is no evidence that it can reduce the duration or the severity of diarrhoeal disease. It does not reduce fluid and electrolyte losses. It cannot be recommended in the treatment of diarrhoea.

Общее описание

Odorless white to yellowish or grayish powder. Contains mainly the clay mineral KAOLINite (Al2O3 SiO2)2 H2O)2), a hydrous aluminosilicate. KAOLINite has mp 740-1785°C and density: 2.65 g cm-3. KAOLINe is insoluble in water but darkens and develops a earthy odor when wet.

Профиль реактивности

KAOLIN is stable and chemically unreactive under ordinary conditions.

Опасность

Respirable fraction; questionable carcinogen.

Фармацевтические приложения

Kaolin is a naturally occurring mineral used in oral and topical pharmaceutical formulations.
In oral medicines, kaolin has been used as a diluent in tablet and capsule formulations; it has also been used as a suspending vehicle. In topical preparations, sterilized kaolin has been used in poultices and as a dusting powder. Therapeutically, kaolin has been used in oral antidiarrheal preparations.

Промышленное использование

The name kaolin comes from the two Chinese words kao-ling, meaning high ridge, and was originally a local term used to describe the region from which the clay was obtained. Kaolin (Al₂O₃2SiO₂2 H₂O) usually contains less than 2% alkalies and smaller quantities of iron, lime, magnesia, and titanium. Because of its purity, kaolin has a high fusion point and is the most refractory of all clays. Lone kaolins are widely used in casting sanitaryware, ceramics, and refractories.
Georgia china clay is one of the most uniform kaolins to be found. Generally speaking, there are two types of Georgia-sourced kaolin, both of which are widely used for casting and other processes. One type imparts unusually high strength and plasticity, and is used for both casting and jiggering where a high degree of workability is required. The other type typically is a fractionated, controlled particle size clay that also behaves well in casting, dries uniformly, and reduces cracking of ware.

Побочные эффекты

It is almost harmless and is effective in many cases of diarrhea if taken in large enough doses (2–10 g initially, followed by the same amount after every bowel movement). The adsorbents are generally safe, but they may interfere with the absorption of some drugs from the GI tract.

Безопасность

Kaolin is used in oral and topical pharmaceutical formulations and is generally regarded as an essentially nontoxic and nonirritant material. Oral doses of about 2–6 g of kaolin every 4 hours have been administered in the treatment of diarrhea.

Источник

Premier-quality deposits of kaolin such as those mined in Cornwall in the United Kingdom, Georgia and the Carolinas in the southe astern United States, and the Amazon Basin of Brazil.
Other suppliers of quality kaolin include France, Germany, the Czech Republic, Malaysia, and Australia.

хранилище

Kaolin is a stable material. Since it is a naturally occurring material, kaolin is commonly contaminated with microorganisms such as Bacillus anthracis, Clostridium tetani, and Clostridium welchii. However, kaolin may be sterilized by heating at a temperature greater than 160°C for not less than 1 hour. When moistened with water, kaolin darkens and becomes plastic.
Kaolin should be stored in a well-closed container in a cool, dry place.

Несовместимости

The adsorbent properties of kaolin may influence the absorption of other orally administered drugs. Drugs reportedly affected by kaolin include amoxicillin; ampicillin;cimetidine; digoxin; lincomycin; phenytoin; and tetracycline. Warfarin absorption by rat intestine in vitro was reported not to be affected by kaolin. With clindamycin, the rate (but not the amount) of absorption was affected by kaolin.

Регуляторный статус

Accepted in Europe as a food additive in certain applications. Included in the FDA Inactive Ingredients Database (oral capsules, powders, syrups, and tablets; topical preparations). Included in nonparenteral medicines licensed in the UK.