When producing engineered or agglomerated stone, there are two different production methods, the discontinuous block process and the semi-continuous slabs process.

The so-called block process is executed at ambient temperature. After the cure the blocks are sawn into sheets, which are calibrated and polished.  The second process, to which we may refer as the slabs process, is a direct production of slabs and  done at elevated temperature (curing in ovens between 80°C and 100°C) and for this process temperature activated peroxides are used.

The slabs are mainly used in high-end sanitary applications such as kitchen tops and floor tiles and wall claddings.

The continuous slabs production process

This is a casting process where the cure is done at a higher temperature and the polymerization is started by temperature activated peroxides, mainly so-called peroxyesters, like Trigonox® 93 and Trigonox 42PR. The mold is a rubber sheet with upstanding sides. The highly-filled resin formulation is casted in the mold, pressed and put under under vacuum and transported into the oven. The oven time is around 20 minutes and the oven temperature is mostly 80°C, but higher temperatures are possible as well. After curing and cooling down, the slab is calibrated to the desired thickness and polished and cut to the right size. Quartz filler is mainly used for the slabs process, which results in an end product with a very high hardness and scratch resistance, especially for kitchen tops.

AkzoNobel curing agents for continuous slabs production

The curing is done in an oven with temperatures between 80°C and 120°C which allows the use of temperature activated peroxides. This results in a fully cured slab, with very low residual styrene values.  This is important to prevent post cure deformation. The peroxyesters also allow for a sufficiently long potlife of the resin, which is needed to have enough time to fill the molds. Promoted peroxyesters are used in combination with a metal accelerator. The most used peroxide is Trigonox 93, this however is an aromatic product and one of the decomposition products is benzene (in small amounts). To avoid formation of benzene, we recommend to use Trigonox 42PR which is an aliphatic peroxide. Both products have the same reactivity and efficiency.

Slabs manufacturing process equipment

A slabs production line consists of a high tech mixing unit, a vibrating table including press and vacuum possibility, an oven at least having a temperature of 80°C and 20 minutes oven time. The line is provided with a calibrating, polishing table and a sizing circuit. 

The discontinuous blocks process

This is a casting process with highly-filled formulations using approximately 90% filler such as for instance, calcium carbonate and marble. The mold is a large wooden cast mold having a size of 3 x 1.2 x 1.5 m. An automatic filler/resin mixing unit is mostly used to fill the mold. The formulation contains besides the necessary wetting and rheology additives an accelerator to activate the peroxide which mostly is added as the last component. The peak exotherm in the block is normally around 65°C. The block is kept in the mold for several weeks to fully cure which is needed to prevent post-shrinkage cracks.

AkzoNobel curing agents for the blocks process

The block casting process is done with standard MEKP, like Butanox® M-50. However, to obtain the right peak exotherm and a sufficient hardening also blends of MEKP and AAP, are used such as Trigonox 61 (during summer period) and Trigonox 63 (during winter period).

Blocks manufacturing process equipment

A mixing unit is needed which can handle highly filled resins and it should have with the possibility for deaeration under vacuum. The mold is a large plywood box shaped mold. The cured blocks are cut to sheets, which are calibrated to the desired thickness and polished, then cut to the desired final dimensions.

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