No. 1031 - Miljøstyrelsen

38
Fate of the siloxanes
The siloxanes fluids used as softeners in the textiles will form a part of the final
textile product and will to some extent be washed out by laundry ending
up in the wastewater. In the technical data sheet for a new hydrophilic siloxane
textile softener, DOW Corning states that traditional hydrophobic aminofunctional
silicones lose their softening performance after 1-2 wash cycles
(http://www.dowcorning.com/DataFiles/090007b5801286cb.pdf). It is not
mentioned whether the silicones lose their softening performance because they
are washed out.
It has not been possible to identify studies on the fate of siloxanes in textiles.
2.2.8 Process control and plastic additives
Siloxanes are widely used for process control and as plastic additives:
• Surfactant (surface-active agent) in the manufacturing of polyurethane
(PUR) foams;
• Antifoaming agent in the manufacturing and processing of products in a
range of industries (food industry, pharmaceutical industry, chemical industry,
etc.);
• Plastic additive (e.g. flame retardant, smoke suppressant and for providing
a smooth surface);
• Release agent for plastics extrusion and moulding operations.
Silicone used as antifoams in textile industry is included in section 2.2.7.
The main application within this area is as surfactant used for manufacturing
of polyurethane foams. The silicones add stability to the liquid foaming mixture
so that collapse of bubbles is retarded, and flowability is increased.
Consumption
Based on Will et al. 2003 the total consumption as surfactants for PUR production
can be estimated at 290 t/year, whereas the consumption for other
applications can be estimated at 180 t/year. For processing aids, however, the
consumption in Denmark may deviate significantly from the general consumption
pattern in Europe.
According to the trade organisation Plastindustrien i Danmark, siloxane surfactants
are used for production of all PUR products. The siloxane content of
the products is approximately 0.75%. In total 35,000-40,000 tonnes PUR was
produced in Denmark in 1999, corresponding to 260-300 t siloxanes per year.
Based on the information above the total consumption as processing aid is
estimated at 470 t of which the main part is used for PUR production.
Siloxanes used
Siloxanes used as surfactants for PUR production are usually dimethylsiloxanes
copolymerised with polyesters. Fifteen compounds are registered in the
Product Register as used as surfactants. The most used is "Siloxanes and silicones,
di-methyl,3- hydroxypropyl methyl, ethers with polyethylenepolypolene
glycol methyl ether" (CAS 67762-85-0).