Derbigum is a world leader in the production and recycling of bitumen roofing membranes. The company - located in Perwez (Wallonia) - is known for the production of durable membranes with a longevity of more than 40 years.

The company also produces a circular NT membrane made of recycled roofing (± 30 %) without any toxic solvent, for the circular economy is a key element in their business model that is highlighted by the “No Roof To Waste” concept.

Derbigum is also active in the Bitumclean project, in collaboration with Centexbel and other partners. The aim of Bitumclean is to optimize the recycling of bituminous roof coverings by prior extraction of tar (PAH). The purpose is to boost the production of recycled based roofing. 

The challenge

Bitumen is a very complex material that is obtained by different kinds of processes of (crude or vegetal-based) oil treatment. Depending on the origin of crude oil and on the process applied, several kinds of bitumen can be obtained with different properties in terms of viscosity, penetrability, shelf life and softening point. 

A bitumen can also be modified by mixing it with a polymer to form a modified bitumen. The polymer and the bitumen have chemical interactions. The addition of a polymer to bitumen will lead to a phase inversion when the amount of the polymer will be sufficient to obtain the phase inversion corresponding to the formation of a polymeric matrix wherein bitumen is retained. When the inversion phase occurs, the bitumen having the behavior of a Newtonian liquid will have the properties of a viscoelastic fluid.

During the production of waterproofing bituminous membranes, at least one reinforcement is fed and is covered by bitumen on both sides and sometimes finally surfaced with mineral granules, flakes, sand and/or thin foils. The reinforcement can be made by a structure which is typically flat and thin of a material chosen in the group comprising polyester nonwoven, glass grid or fleece, combination reinforcements (glass and polyester), metal foils (e.g. copper, aluminum)) and their combination.

Consequently, the origin of the bitumen, the nature of the polymer or the nature of the oil residue, the manufacturing method to produce the bitumen and the subsequent treatment of the bitumen, creates a broad range of bitumen membranes with different nature and diversified composition with production waste that need to be recycled.

To recycle bituminous products such as membranes provided with at least one reinforcement layer, the existing unit and methods needed to be adapted, to completely deconstruct and remove the reinforcing fibers.

The solution

The invention provides a recycling process for a broad diversity of waste products containing bituminous products and optionally reinforcement layers, including, without being limited thereto, bituminous membrane production waste, bituminous membrane cutting waste, roofing waste products collected from demolition worksite having many different composition and contamination.

The process is also efficient and optimized to ensure enough profitability to the industrial player, while requiring a lower maintenance and at least less frequent maintenance operations and it provides a recycled bituminous product to be used in a large variety of new bituminous final products.

The process includes the following steps:

  1. Collecting waste (batches)
  2. Grinding step
  3. Recycling unit: a rotor and a stator and an micronization chamber. The fine ground batch being heated and melted by shear strength upon the operation of the stator, rotor and micronization chamber and collecting a melted product. Feeding said melted product in a mixing tank having a predetermined volume containing fresh carrier at a level comprised between 35 and 50% of the predetermined volume. At a residence temperature preferably around 180°C, the mixing tank being continuously agitated with horizontal or vertical screw having mixing blades, said melted product being fed in said mixing tank until the volume of the melted product is comprised between 50 and 65 % of the predetermined volume to provide a recycled bitumen having a predefined viscosity for pumpability comprised between 500 and 45000 cPS. The recycled bituminous product containing a bitumen content comprised between 25 and 75%, and a fiber content between 2 and 12%. 
  4. Dilution: in some case, the recycled bituminous product can be diluted with other carrier substances before being used in a final bituminous product. The recycled bitumen product can be pumped and filtered in line or even used immediately depending on its purity or can be stored in storage tanks having heating means to keep the temperature substantially constant to keep if under a pumpable form.

The process allows to produce a recycled bitumen product, containing already an amount of polymer, meaning that the amount to be added to reach the phase inversion is reduced, and sometimes drastically up to less than 50% of the normal required amount.

Finally, the quality of the bitumen obtained by the process according to the present invention is high enough to be reintroduced in a bituminous membrane at a level as high as more than 50 weight % or 75% even 100% with respect to the total bitumen weight in the final product.