Commodity Economics
Polyoles and polyisocyanates are generated in crude oil production.
Polyurethane PUR soft foam manufacturing is divided into two production groups: Block and formed foam, and two product types: polyether and polyester soft foam.
For manufacturing formed foam parts, the formulated mixture is introduced into a metal or plastics mould that is closed right after filling, and the foaming process happens within seconds. When the form is opened, the finished part can be removed. This way, many different objects, even where they need complicated shapes, can be created in a single work step.
Materials Features
Due to their high elasticity and open cells, polyether-based polyurethane (PUR) soft foams are a great cushioning material. The material’s good heat insulation and high breathability are prerequisites for a special micro-climate that creates an extraordinary sitting or lying climate.
The materials features of PUR soft foams can be adjusted to match the requirements profile. Thus, the material can manufactured to be highly stable and supporting, provide pressure relief or even be very soft.
These manifold materials features are described and tested using physical measured values. The most important features for the manufacture of upholstered furniture are raw density and hardness adjustments. Additionally, the comfort features are defined by elasticity and resilience, while the characteristics for permanent use are measured as changes to the hardness grade, height loss and compression set.
A PUR soft foam’s raw density (measured in kg/m³) is specified according to its intended use. As a general rule, a higher raw density increases the usability feature.
Hardness is measured as compression hardness in kPa or as indentation hardness in N and may be set very low (soft) to very high (hard).
Considering current statistics aspects, the foam quality hardness settings have tolerances of up to 20%. For any other features, minimum and maximum values are determined.
Proper combination of PUR soft foams with different hardnesses and raw densities lead to a perfect cushion build regarding pressure relief and support or stability.
Usability
Usability of PUR polyether soft foams is measured as hardness value change. In a fatigue test, the cushion is subjected to 80,000 load changes without break. The material fatigue appearing in this test is reflected in the hardness value change. The lower this figure, the higher the cushion’s usability.
Highly elastic PUR soft foams have lower hardness value changes than other PUR soft foams at the same raw density.
Environmental / Living Hygiene Aspects
PUR soft foams are environmentally compatible products. They are also perfectly harmless physiologically and contain no toxic heavy metals. They do not contain any other materials considered harmful today, such as nitrosamine, formaldehyde, asbestos, PCB (polychlorinated biphenyls), PCP (pentachlorophenol), styrole or vinyl chloride. They ?comply with? REACH without being the object of the regulation. Many of our foam qualities are tested and certified according to the Ökotex Standard 100.
Since 1 January 1992, only water has been used as a blowing-agent-forming component for the manufacturing process in the Federal republic of Germany. Halogenated hydrocarbon-based blowing agents such as CFC and methylene chloride are not used.
Hygiene
PUR polyether foams are harmless from a hygiene point of view. Their high open-cell rate enables good air circulation and high moisture transport. Integration of vapour stops in the cushion design can be avoided. They generate no dust and are body-neutral.
Odour
PUR polyether foams have no odour when stored sufficiently after manufacture. Fresh foams may still have the slight smell typical for plastics. No impairments of health are connected to this.
Utilisation / Disposal
The foams can be disposed of in household waste dumps or modern household waste combustion systems for energy recovery. The Waste Act has no special requirements regarding disposal.
Depending on its quality, the product decays slowly or not at all. The “Abfallbestimmungsverordnung für besondere überwachungsbedürftige Abfälle” (TA-Waste, part 1) does not list PUR soft foam. According to the LAGA waste type catalogue, polyurethane wastes are listed under waste key 57 110.
Foam Recycling
There are currently more than ten different procedures for recycling PUR foams, which can be structured into three categories:
1. Materials utilisation / materials recycling
2. Raw materials utilisation / chemical recycling
3. Energy recovery / thermal recycling
1. Materials utilisation / materials recycling
PUR materials recycling has a long tradition and currently offers four different technologies
1.1 Composite foam production
PUR foam is shredded to flock-size, before materials-compatible binder systems are added to the source material for creating a material with separate product characteristics: composite foam.
These traditional utilisation method has reached a high quality standard through continuous production technique optimisation.
1.2 Adhesive pressing of polyurethane and PUR composites
These recycling methods are very flexible and offer some special advantages. Adhesive pressing can be performed with the tried and proven method known from chipboard production. Furthermore, interesting materials characteristics can be achieved and controlled exactly by using additives.
Using adhesive pressing, PUR composites can often be processed without separating materials first. This economic and usually also environmentally compatible advantage can be decisive in many recycling applications.
Products manufactured with these technologies have a very wide application range: car interior covers, rear shelves, limiting elements, standing bases, pallets, elements for sound absorption walls, roll cores and water-proof semi-finished sheet products are some examples for good use.
1.3 Grist Inclusion
With the development of new grinding technologies, grist processing of PUR soft foam has become a trendsetting and economic procedure. Precision grinding of the selected PUR remainders to sizes of less than 0.1 mm delivers a materials-compatible filling material with exactly defined grain sizes. This product can be used in original PUR production for targeted modification of the characteristics profile, e.g. for manufacturing energy-absorbing PUR systems.
2. Raw materials utilisation / chemical recycling
In the scope of raw materials utilisation, chemical procedures such as hydration, glykolysis and pyrolysis are the methods of choice. With processes that place high demands in regard of process-technique, polymer plastics such as polyurethane can be degraded to fragments with lower molecular weights.
Further development and optimisation of these methods is mainly performed by the raw materials manufacturers of the chemistry industry.
3. Energy recovery / thermal recycling
Materials and raw materials recycling make an important contribution to reusability and thus to the cycle of materials idea. The realisation that there is no material with which such recycling cycley can be gone through indeterminately led to the logical demand of discussing thermal utilisation with energy recovery. Only when ?life cycle assessments? are drawn up for all materials will we be able to see what contribution thermal recycling can make to saving fossil fuels and protecting resources.
Keyword Summary
Commodity economics
Foam cushions
Polyurethane (PUR) soft foam
PUR soft foam is a cushion material manufactured by conversion of polyether polyolene using isocyanates and water. The polyol/isocyanate reaction forms the cell structure for the resulting foam. Water is used as a blowing-agent-component.
Materials Features
Good permanent elasticity, high air permeability, high resistance to aging from moisture and heat; physiologically harmless; different raw densities and hardness settings available; good performance characteristics; low materials-specific height-loss of max. 5% at use (pursuant to DIN 53 574).
Environment/Living Hygiene/Disposal/Utilisation
PUR soft foams are physiologically harmless according to the state of science and technology. They have no odour and are easy to clean; They can be disposed of and utilised.
Deutsch