Literature

Abstracts

Proceedings of the Polyurethane Foam Association Technical Program, Arlington, VA, May 18, 2000

New Development in Low VOC Flexible Polyurethane Foams, Matthias Sikorski, Nitroil Performance Chemical Intl., Proceedings of the Polyurethane Foam Association, May 18, 2000.

Strong pressure is being exerted on foam suppliers to reduce the amount of volatile organic compounds (VOCs) in flexible foam used in automotive, furniture, bedding and carpet backing products. The main sources of VOCs are additives like silicone surfactants, and amine catalysts. Nitroil® Performance chemicals have evaluated a series of catalyst combinations in MDI as well as TDI based molded foam formulations to reduce the amount of amines in the VOC. Standard formulations containing triethylene-diamine and bismethylaminoethylether were used as controls.

It was found that by using only reactive amine catalysts, the amine emission could be eliminated, and the total VOC could be reduced by 50% for TDI, and 80% for MDI based molded foam formulations. For the MDI based formulations, most foam physical properties were similar to those obtained with the reference formulation. The humid aged compression set (HACS) properties were not as good as those obtained with the reference catalysts. Acceptable values were obtained, however, when combinations of PC CAT® HPI with selected other catalysts were used. PC CAT® NP146 gave the best overall performance. TDI based foam formulations showed good processing and properties with the exception of HACS. This property suffered from the use of reactive amines. Substitution of PC CAT® HPI as the base catalyst in combination with a non-reactive amine as "blow" catalyst, resulted in values for all physical foam properties, including HACS, which were quite acceptable. A VOC reduction of ca. 20% was also obtained. Compared to standard molded foams, slabstock foams show even higher volatile emissions. The VOCs of these foams can be reduced considerably by avoiding antioxidant containing polyols, using reactive amine catalysts like PC CAT® NP 145, low VOC silicone surfactants, and built-in flame retardants.

Challenges of Diagnosing Diisocyanate Allergic Disease, Pat Conner, MD, BASF Corp. & CMA Diiso Panel, Proceedings of the Polyurethane Foam Association, May 18, 2000.

This paper discusses the issues involved with diagnosing allergic sensitization due to diisocyanates. The formation of antigens, which can lead to allergic reactions, along with the immunology of diisocyanates is discussed.

Asthma and dermatitis, which can result from an allergic reaction to diisocyanates, and the benefits that result from early detection are shown. The diagnostic technologies, which are available for identifying those persons that are highly sensitive to diisocyanates, are presented.

The best treatment for persons displaying allergic symptoms is removal from the exposure area.

Manufacturing Routes for Polyurethanes Raw Materials, Brian Fogg, Huntsman Polyurethanes, Proceedings of the Polyurethane Foam Association, May 18, 2000.

The range of raw materials used for the manufacture of polyurethanes has grown enormously during the past fifty years. A wide range of products is now available, which allow the formulator to produce an infinite spectrum of products, collectively known as POLYURETHANES. This paper examines some of these raw materials from the viewpoint of their manufacture. The range of products is so large that only a brief introduction can be presented. The intention of the presentation is to benefit the less experienced polyurethane technologists, and those less involved in the technical aspects of the industry.

The paper begins with a discussion of the different types of polyurethanes, and a description of the raw materials used in their manufacture. It continues with a brief description of the production of polyether polyols, polyester polyols, diisocyanates (both TDI and MDI), metallic catalysts, surfactants, fire retardants and colorants.

The Use of Solid Particles in Flexible Polyurethane Foams Expanded by Carbon Dioxide as an Auxiliary Blowing Agent, Brian Blackwell, Beamech Group Ltd., Proceedings of the Polyurethane Foam Association, May 18, 2000.

Solid particles are added to a flexible polyurethane foam formulations principally to increase foam hardness, increase foam density, and improve flammability characteristics. Recent advances in the area of slabstock processing equipment have made processing formulations containing solid particles very difficult. These machines use carbon dioxide instead of halocarbons to expand the foam. The carbon dioxide is normally stored and metered in a liquid state at high pressure and low temperature. It is then added to the reactants and additives under high pressure and ambient temperature. To prevent violent expansion, which results in foam defects, the pressure is carefully reduced to atmospheric conditions over a very short period (about 0.004 seconds). The pressure reduction is accomplished by passing the reactants and carbon dioxide through micron sized passages where some of the velocity energy is used to produce a froth. Any solid particles in the formulation tend to clog these very small passages causing severe production problems.

The objective of this paper is to examine some of the parameters contributing to the use of solid particles in carbon dioxide blown slabstock formulations. Variables such as particle size, particle shape, particle nature, particle content and distribution, agglomeration and flocculation, and viscosity of the reactants are examined.

The authors found the following potential solutions to the problem of adding solids to carbon dioxide expanded foams:

  1. Filtration of large unwanted particles.
  2. Increasing opening size (effective area size) and increasing the passage length. Increasing the passage opening dimensions enable the use of polymeric polyols and calcium carbonate.
  3. Uniform pressure drop gives better quality foam. The reactants and carbon dioxide must be pressure reduced as uniformly as possible in order to obtain defect- free foam.
  4. The relationship of pressure reduction and pressure reduction dwell time is very important (passage size and length).

Slabstock Equipment Innovations for the New Millenium, Jack Ferrand, Bayer Corp., Proceedings of the Polyurethane Foam Association, May 18, 2000.

Recent advances in slabstock processing equipment have been focused primarily on modifications geared at processing carbon dioxide blown systems. Hennecke's Nova Flex technology is currently the most widely used process, using carbon dioxide, in this market segment. Hennecke recently introduced a new more versatile technology called Multi Flex, which provides foamers with the capability to process void free, striation free foam buns with a yield of over 96%. This new technology allows for the consistent production of absolutely square blocks across the complete range of polyether formulations. The hard and thick cover crust on useful foam is eliminated, and the density distribution is optimized throughout the bun. These improvements result in a yield increase of up to 10% as compared to conventional dome block produced foams.

Some of the other advantages offered by the Multi Flex technology are:

  1. Elimination of costly cleaning activities involved with trough systems.
  2. Easy processing of quick reacting polyols.
  3. Flexibility for a wide range of foam densities.
  4. Precisely adjustable side walls.
  5. Vibration free conveyer band.
  6. Improved operator safety as a result of direct removal of reaction fumes in the foaming zone.

State of the art controls provide process control and data management capabilities, not typically found in the industry. The control package also minimizes on-the-fly formulation changes, and allows for precise reproducibility of given formulations. Multi Flex plants can also be fitted with Nova Flex equipment, to produce critical grades of foam using carbon dioxide technology.

Recent Technical Advances in Recycling of Scrap Polyurethane Foam as Finely Ground Powder in Flexible Foam, H. Stone, Staff Consultant to Mobius Technologies, Inc., R. Villwock, B. Martel, Mobius Technologies, Inc. Proceedings of the Polyurethane Foam Association, May 18, 2000.

The feasibility of using finely ground foam as a filler in new foam has been previously demonstrated; however, the economics of the process have been poor because of high grinding costs. Recently commercialized advances in non-cryogenic grinding technology have provided a cost-effective method for producing fine powders from scrap polyurethane foam. Powder with a maximum particle size of 125 microns can now be obtained at low cost from production trim scrap, fabrication scrap, and changeover blocks. The details of this new grinding process and the subsequent methods used for mixing and handling of the powder/polyol slurries are the subject of this paper. Results from commercial scale trials of slabstock and molded flexible polyurethane foams, using up to 10% by weight of finely ground foam, are presented.

The formulations used in this study were adjusted to maintain foam density and hardness. Formulation adjustments were minor. The most significant change was a slight increase in water content and a corresponding change in isocyanate level to maintain foam density. Low viscosity foam powder/polyol slurries can be achieved. The Dougherty -Kreiger model can be used to determine the dependence of viscosity on foam powder concentration.

Evaluation of the physical properties of the filled foams indicated that the compression modulus is generally increased, and physical properties throughout the bun are more uniform.

It was concluded from these studies that technology to recycle scrap foam by means of pulverization has reached a commercialization stage. The process produces foam with good quality at reduced cost. Recycle content of 10% is commonly achieved and higher amounts are possible. Both slabstock and molded flexible polyurethane foams can be produced.

Real -World Economics of Polyurethane Foam Recycling, Jeff Jensen, Mobius Technologies, Inc., Proceedings of the Polyurethane Foam Association, May 18, 2000.

During the last ten years, the use of polyurethane scrap in the production of carpet padding has increased dramatically. As the available scrap from both manufacturing and post consumer sources continues to increase, foam manufacturers seek new applications for this material. The reintroduction of scrap foam as a filler in new foam, is one application which has received renewed attention. To be viable, this approach must not only be technically feasible, but economically beneficial as well.

During the last three years, Mobius Technologies has commercialized the process of grinding scrap polyurethane to a fine powder, and reintroducing it as an additive in new foam production. The key drivers to the economic viability of this process are the value of the scrap "raw material", the cost of the chemical ingredients for the foam, the process cost itself, and the required adjustments to the formulation when incorporating the recycled material. This paper examines the effect of these drivers with respect to the ultimate economics of this recycling process.

The author concludes that manufacturers who can incorporate low-cost scrap as an additive in the production of new foams will have a distinct cost advantage. The key variable in determining the profitability of polyurethane foam recycling is the difference between chemical price and scrap price. Current trends indicate that the scrap supply will increase relative to demand for bonded carpet cushion, creating downward pressure on scrap prices. This will tend to increase the profitability of the recycling process. Foam manufacturers can profit from this situation by utilizing recycled polyurethane in the production of new foam.

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