Kezadol GR is a soft 81.5 % calcium oxide granule coated with special dispersing agents, for use as a desiccant in rubber compounds which are cured on micro-wave systems, LCM or hot air. Moisture which is present in all rubber chemicals, especially fillers, will be absorbed and the calcium oxide will change to calcium hydroxide after reaction with the moisture. This reaction will happen while storing the uncured rubber compounds.

It is also possible to use Kezadol GR as acid absorber e g. in systems containing chlorine. By reaction of HCl (hydrochloric acid) with CaO, CaCl2 is formed. Therefore the corrosive effect of HCl on metal parts (e. g. vulcanization molds) can be diminished. Kezadol GR helps to decrease the formation of nitrosamines.

Kezadol GR has a delayed action but a fast reaction. If calcium oxide powder preparations are used they react during the mixing process, and so a higher dosage is required, which has a negative effect on the physical properties of the vulcanizate. Kezadol GR is inactive during mixing but then reacts quicker than other calcium oxide preparations, permitting shorter standing time between mixing and extrusion. After mixing, the storage time of the compound should be at least six hours.

In comparison to CaO-preparations in powder form, which react already during mixing process, Kezadol GR shows clear advantages due to its desensitized form. The most important point is, that the dosage may be reduced significantly; therefore the influence of CaO on physical properties of the compound is reduced.

CaO-preparations in pasty form often get very hard after some time of storing these materials. This causes dispersion problems which will not occur if Kezadol GR is used.

Kezadol GR granules are very soft so that the use and dispersion even in very soft rubber compounds, e. g. sponge rubber, and on open mills will be fast without any problems.

One of the reasons for the softness of Kezadol GR is the fact that the dispersing agents used to produce the granules have no melting or softening point. Easy dispersion will take place immediately after addition to the compound.

The quality of the calcium oxide is important. Kezadol GR contains an extremely fine calcium oxide. Screen residue of the untreated CaO:
> 45 µm max. 0,1 %
> 150 µm max. 10 ppm

Recommended use

Kezadol GR should be used in order to prevent blisters and porosity in the following rubber processes.
- Pressureless continuous curing systems like micro-wave, LCM, fluid beds or hot air
- Low pressure curing in the cable industry
- In compounds cured in heat transfer fluids