Phenolic, non-staining antioxidants

Phenolic antioxidants – a historical background

At the early beginning of manufacturing rubber goods, the producers were faced with rapid deterioration. It resulted in either hardening, brittleness or in sickness of the rubber goods. Around 1910 the first type of antioxidants were discovered, mainly naturally existing materials like creosote, asphalt and coal tar pitch. These were used until roughly 1925 when phenol, cresol, hydroquinone and aniline were used as antioxidants. Between 1925 and 1940 a big number of patents on antioxidants were issued, most of them based on secondary aromatic amine derivatives.

It was not until after 1940 when an increasing worldwide production of synthetic rubber, and consequently the development of tires based on synthetic rubber, called for a more demanding type of antioxidant, not only protecting the rubber goods and tires against oxygen and heat, but also against the severe cracking caused by ozone. The result was the development of a new class of antioxidants, p-phenylen-diamine derivates, which was soon after called antiozonant, due to their ability to protect rubber goods against cracking.

After 1945 the existing large synthetic rubber production had to be diverted to civilian use. The known and common used antioxidants and antiozonants were up to this stage staining types of chemicals. With the new approach to civilian use, there was a demand for non-staining antioxidants because synthetic rubber for civilian use included natural, white or light colored rubber goods, for example:

• sports rubber goods;

• surgical rubber goods;

• latex products, including foam;

• white side-walls;

• footwear;

• sheetings;

• flooring tiles;

• sponge rubber;

only to name a few. With the development of non staining antioxidants, it was possible to protect rubber against deterioration, caused by oxygen, heat, light and certain metals like copper and manganese, and still maintain the, natural colour of the rubber.

Antioxidants economical background

Antioxidants are rubber chemicals added to the rubber in the range of 1 to 2 %. Although the price of these antioxidants is ranging from $5 to $10/kg, the cost of protecting the rubber is only a few cents. It is estimated that the lifetime of rubber goods is three to five times longer when protected with antioxidants and one can get some ideas on the indirect value of antioxidants. Adding to this indirect value, costs of failure like idle machinery, break down of cars, blown tires and so on, then it is easy to understand that the costs of antioxidants becomes insignificant compared to the value of the improved rubber goods.

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Дата добавления: 2014-10-17