AF reactors for recycling of PU waste

 

AF - Engineering

AF Engineering is going to be a part from PU Engineering.

You will be redirected to our new home

www.pu-engineering.com

 

Recycling of flexible PU foam

 

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

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

The process developed by AF 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.

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

Up to 50% of PU waste can be incorporated into recycled polyol, making the product extremely economical.

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

Properties Value
Viscosity 4,000 -7,500 mPas
Hydroxyl value 40 - 58 mg KOH/g
Acid value < 1 mg KOH/g
Amine value: < 6 mg KOH/g
Appearance light to dark brown liquid depending on the colour of the waste foam
No primary aromatic amines !!!

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:

Foam density 25 kg/m3
Master sample

(foam without recovered polyol)

Foam with 20% recovered polyol
Resilience, % 44 43,6
Compression set (50%) 2,4 2,6
Hardness, [N] 153 150
Support factor 2,2 2,3
Elongation at break, %          239% 238 %
Tensile strength, [kPa] 158 154

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). All the tests were carried out by the independent institution.

Recycling of rigid /semi-rigid PU foam

Industrial and End of Life (EOL) waste from rigid PUs can be used in an efficient way for the production of recycling polyols to be used for the manufacturing of rigid PUs (panels, spray foam, etc.).

PU waste should be clean from impurities like paper and metal scraps.

Up to 60% of PU waste can be included in the recycling polyol formulation, making the product extremely economical.

 

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

Properties Value
Viscosity 3.000 -15.000 mPas
Hydroxyl value 200 - 340 mg KOH/g
Acid value < 1 mg KOH/g
Amine value: < 6 mg KOH/g
Appearance light to dark brown liquid
No primary aromatic amines

The hydroxyl number of the recycled polyol can be controlled and fixed at a certain value and any change from Iso-Index is not necessary.

The properties of the PU panels produced with 40 % recycled polyol were compared with the properties of PU panels made with original materials. The comparative data is presented in the following table:

T°C Reference 40 % Re-Polyol
CLOSED  CELLS [%]   95 93
STABILITY  at -20 °C    (%)   0,39 0,40
STABILITY  at + 90 °C    (%)   1,04 1,10
ISOTROPY  (EN 826)   2,70 2,75
TERMAL CONDUCTIVITY at different temperatures  [ƛ  = W  /  m*K   ]

(EN  12667  )

0 19,00 19,6
10 19,10 19,12
20 20,00 20,10

All parameters are in perfectly agreement.

The produced rigid PU foams show comparable properties such as traditional PU rigid foam using up to 40% recycling polyol.

Scope of delivery

  • Planning, construction and installation of an industrial (or pilot) installation for the recycling of PU foam wastes.
  • Transfer of know-how for the recycling of PU foam to recycling polyols suitable for the production of flexible/rigid 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 service of the industrial reactor.
  • Accompanying the production to the full implementation