Equipment Description:Ammonium Zirconium Carbonate (AZC)
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The main function of AZC is to improve the strength and printability of both starch and latex based coatings for paper and board. In the offset printing process, coatings can go through several cycles of being wetted and dried, and so can become weak. The addition of AZC renders coatings water resistant without being water repellent. |
Depending on which part of the world you are, materials like AZC can be known as an insolubiliser, a crosslinker or a hardener. An ammonia free version of AZC is also available, this is potassuim zirconium carbonate, (KZC). Competitive types of materials that also improve the strength properties of coatings are glyoxal, MF resin, and UF resin. |
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Unlike most other crosslinking agents incorporated in coating colour formulations, zirconium based crosslinkers are inorganic polymers. Other traditional materials, such as glyoxal, MF and UF resins, are organic materials. AZC is a clear, usually colourless solution, having an odour of ammonia and a pH of approximately 9.5. As a carbonate, it will react with acids, and so should not be used in coating systems below pH 7. In storage, it is stable for up to six months. Dosage rates are usually in the range of 0.1-2.0 parts on pigment. The mechanism of the reaction is that as the coating dries, the loss of water causes the AZC molecule becomes reactive towards functional groups such as carboxyl groups, and an irreversible covalent bond is formed. The function of the AZC is to make the coating stronger, so that the printing process will run more smoothly and with fewer faults, or will run faster with the same number of faults. The addition of AZC should improve coating properties such as wet pick resistance and dry pick resistance. |
Ammonium Zirconium Carbonate (AZC) was also mentioned in the following Fact Sheets (11): |
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