Reactors and know-how for recycling of flexible PU residues

Chemical PU recycling is represented by several technologies which have their advantages and disadvantages.

As a result of years of research and experimentation, PU Engineering‘s specialists have succeeded in creating highly efficient and functional recycling systems for polyurethane waste.

The process developed by PU Engineering is based on reaction between dicarboxylic acids and the urethan chain. In contrast to other developments, the use of dicarboxylic acids does not lead to the formation of any primary aromatic amines such as toluene diamine (TDA) and methylene diamine (MDA) that are classified as carcinogenic.

Тechnological progress of the recycling process

In a reactor with a volume from 200 dm3 (laboratory installation) up to 10 m3 (fully automatic industrial plant) the raw materials are charged: – acids, catalysts, additives and flex foam waste. The duration of the chemical process is about 10 hours.

As a result of the chemical process, a recycling polyol is received as well as small amounts of condensed water originating from the humidity contained in the PU flakes.


Up to 45% of PU waste can be incorporated into recycling polyol, making the product very profitable.

The productioncosts of the recycling polyol is about 40% lower than the price of the original polyol.

Properties of the recycling polyol based on flex PU foam wastes:


4,000 -7,500 mPas

Hydroxyl value

40 – 58 mg KOH/g

Acid value

< 1 mg KOH/g

Amine value:

< 6 mg KOH/g

Hydroxil number is in the same level like the basic polyol and any change from Iso-Index is not necessary. This fact makes very easy the implementing of recycling polyol in already available existing polyurethane systems. Such good properties of the polyol enables high percentage of basic polyol replacement which makes 20%-25% for bedding and upholstery foams and even higher amount for technical foams like sponges or rollers.

The essential properties of a typical flexible PU block foam produced with 20% recycling polyol are following:


All parameters are in the range of the control samples.

The example is taken for conventional foams with density 25 kg/m3.

All parameters such as compression set, hardness, resilience, support factor, tensile strength and elongation at break remain in the range of the control samples. Even slight improvement of resilience can be observed.

The foams also do not contain any volatile organic compounds (VOC).

Recycling reactors for flexible PU foam

  • Planning, construction and installation of an industrial (or pilot) installation for the recycling of flexible PU foam wastes.
  • Transfer of know-how for the recycling of PU foam to recycling polyols suitable for the production of flexible PU foam
  • Training for the realization of the technology on a laboratory scale.
  • Training on chemical methods for analyzing recycling polyols
  • Training for working with the industrial reactor’s software.
  • Training on the maintenance of the equipment
  • Accompanying the production from our engineers to the full implementation