USE OF VEGETABLE-OIL BASED THERMOSETTING RESINS IN COMPOUND STONE TECHNOLOGY

Unsaturated orthopthalic polyester resins (hereafter indicated as UP resins), dissolved in styrene, are widely used as binders to aggregate stone and other inorganic raw materials in the production of compound stone slabs using vibratory compaction in a vacuum environment, patented worldwide as Bretonstone Technology.
The use of UP resins involves some technical inconveniences: both resin and styrene monomer are oil-based, hence they come from non-renewable sources and their cost mainly depends on the value of crude oil; due to its high volatility rate, styrene is a dangerous chemical, which involves the designing of complex and expensive intake and burning plants.
Many efforts are dedicated to the development of a new organic binder, having similar properties to those of UP resins, which may solve these difficulties.
We have found that chemically modified vegetable oil could be used as new renewable raw material: the epoxidation of vegetable oils with a high iodine number (such as soybean and linseed oil) forms epoxidated oils which are cured with aliphatic dicarboxilic anhydride, preferably in liquid state. The curing process must be accelerated using a basic catalyst.
The new resin contains more than 50% by weight of renewable raw materials and contains no volatile organic components.
The properties of both new thermosetting resin and compound stones produced in this way are even better than traditional ones. In fact, the mechanical properties (such as the flexural strength and the water absorption) and the aesthetic effect (valuated technically by the gloss value) of the industrial slab remain constant, but the resistance to weather conditions (evaluated by QUV panel) is increased. The latter feature permits the use of compound stone in many outdoor applications.