Literature

Proceedings of the Polyurethane Foam Association Technical Program October 14, 1999

Recent Developments in POSTech® Polymer Polyols, S. S. Chin, Mark M. H. A. Boelens and R. Aerts, Shell Chemical Co. Proceedings of The Polyurethane Foam Association, October 14, 1999.

The flexible polyurethane foam industry is constantly challenged to provide cost-effective solutions that provide improved foam performance. End use customers want higher load bearing foams for slabstock applications, and improved comfort and durability for high resilience foam applications. In molded foam, cost effective improvements are required for improved processing and durability at lower density. Additionally, foam aesthetics are important in certain applications.

Polymer polyols have played an important role as a cost effective, versatile raw material that improves various aspects of foam performance. Recently, Shell Chemical Co. introduced POSTech polyols which contain "all-polystyrene" dispersions, to provide an additional raw material option for foamers. Since their introduction, POSTech polymer polyols have been widely accepted and used in commercial flexible foam systems. This paper reviews the recent developments in the use of POSTech polymer polyols in conventional and HR slabstock foam. Included in the paper is a predictive program for POSTech polymer polyol based HR foam, which further extends the utility of this class of polymer polyols.

The author also reviews the development and properties of Caradol MD32-04 for molded foams. This unique POSTech polymer polyol is optimally designed for use in CCMTDI-based automotive seating. Caradol MD32-04 allows the production of intermediate hardness high resilience foams with a wide processing latitude, superior tear strengths, shorter demold times as well as excellent foam durability.

New FR Silicone Stabilizer For CO2 Technology, A. Melle, MC. Desnier, SA Meyrin, D. Dounis, L. Lawler S. Mc Vey, CK Witco Corp. Proceedings of The Polyurethane Foam Association, October 14, 1999.

The first process to use carbon dioxide as auxiliary blowing agent to replace more hazardous materials was introduced in 1992. In the seven years since that introduction at least three distinct continuous processes and at least one discontinuous process are competing for global market share. Likewise, flexible polyurethane foam (FPF) additive suppliers have competed for business in this new market segment. The FPF conventional silicone surfactant market in North America was dominated by Niax® silicone L-620, and later L-618 when these new processes were introduced. While these two silicone surfactants perform well for the manufacture of FPF using no auxiliary blowing agents (ABA), or blowing agents other than carbon dioxide, they result in poor performance when carbon dioxide is used.

Witco quickly identified which silicones in their product portfolio were adequate for the production of foams made with carbon dioxide as ABA. Where flame retardancy (FR) is not an issue, Niax silicone L-580 was found to be an excellent material where non-hydrolyzable products are preferred. Niax SC-155, a hydrolyzable, non-FR material has consistently demonstrated superior cell structure performance to any other material. Where FR performance is required either L-5770 or L-603 could be used, though neither product was optimum.

After considerable research, Witco was able to define a FR silicone surfactant for use with carbon dioxide systems. The new surfactant is called Niax silicone L-631. The performance characteristics of L-631 are described in detail in this paper.

Next Generation Fire Retardants, Non-Halogen-High Efficiency, L. Bradford, B. Williams, E. Pinzoni, Akzo Nobel Functional Chemicals, LLC, Proceedings of The Polyurethane Foam Association, October 14, 1999.

The need for new non-halogen flame retardants, with low fogging properties, and increased efficiency has been discussed often over recent years. Following a five-year study, Akzo Nobel will introduce three new products in the year 2000 to address these needs. The new products have high phosphorus levels to achieve very good FR efficiency.

Data, collected from a large database developed to determine the efficiency of a number of FR's in polyurethane foams at various densities, is shown in this paper. The new products are Fyrol® PNX, Fyrol® TNX and Fyrol® CLP. Fyrol PNX and Fyrol TNX are non-halogenated high efficiency fire retardants designed for use in flexible urethane foam. Fyrol CLP is a high efficiency FR containing chlorine, but at a reduced level. Fyrol PNX is the experimental product identified in earlier PFA and SPI papers on fogging as ONRI, an oligomeric non-reactive material containing 19 % phosphorous.

The purpose of this introductory paper is to provide guidance to identify where each product will be most cost effective. The addition of this next generation of phosphorous flame retardants gives foamers the choice of reducing or eliminating halogens from most of their products. This protects against all pending and anticipated restrictions worldwide.

 

The Physics of Flexible Slabstock Foam, Tyler Housel, Inolex Chemical Co., Proceedings of The Polyurethane Foam Association, October 14, 1999.

Polyurethane foam was developed in the 1950's by pioneering researchers who learned how to control an unwanted side reaction and turn it into a viable commercial process. Throughout the years, the art has been advanced by countless other scientists and engineers into an enterprise of global proportions. Intuition, experimentation, and serendipity have fueled the development of flexible polyurethane foam (FPF), but beneath it all lies a set of basic physical principles. The purpose of this paper is to outline the physics that describes how a mixture of liquid chemicals can develop into a matrix of solid polymer with uniform, flexible, cellular structure.

The foaming process is broken down into five stages: raw material conditioning, mixing, growth, cell opening and cure. Different physical principles describe the events in each stage, and these are defined as they come up. The description of the events that occur are not presented in a very formal or exhaustive manner, but are only meant to convey a sense of what is happening and why. The work presented in the paper is not original, and the author is indebted to all who have discussed the topic in the literature and in person to further his understanding. It is hoped that the extensive references provided will result in deeper study in areas of interest.

A New Silicone Surfactant for Use in Carbon Dioxide Technology, D. H. Ridgway, J. G. Kniss, and L. A. Mercando, Proceedings of The Polyurethane Foam Association, October 14, 1999.

The adaptation of the Montreal Protocol in 1987 and new restrictions on the use of methylene chloride by OSHA have meant the flexible polyurethane foam (FPF) industry has had to find new methods of producing low-density foams at the desired hardness level. Additional pending restrictions by the EPA has heightened the search for viable substitutes.

Alternative auxiliary blowing agents such as acetone and pentane and mechanical forced cooling technologies have helped to fill the gap left by the demise of the industry's traditional use of methylene chloride. To date, the most widely accepted of the new technologies is blowing foam with liquid carbon dioxide. At least three different machine configurations have been introduced into the FPF industry, and are being used to produce foam commercially. These liquid carbon dioxide technologies are the CO-2™ process by Beamech, the Cardio® process by Cannon, and the Novaflex™ process by Hennecke.

As is common with all new technologies, production problems have been encountered which prevent carbon dioxide blown foam technology from being universally accepted. Some of the most persistent and troublesome shortcomings of these technologies, such as poor cell structure and striations, can be remedied by the proper choice of surfactant.

A surfactant, which performs well with carbon dioxide technology, would have to provide good nucleation, a high degree of emulsification, excellent froth stability, and good bulk stability. This paper reports on recent work to develop surfactants that possess all of these desired properties. Evaluations on commercial carbon dioxide machines have been performed and the results indicate these new surfactants provide improved foam properties compared to current surfactants. The improved foam properties include excellent fine cell structure, elimination of striations, improved airflow, and enhanced sidewall integrity. All of these properties are discussed in detail, along with several other benefits.

Latest Developments in Carbon Dioxide Technologies for the 21st Century, T. Griffiths, Cannon Viking, Proceedings of The Polyurethane Foam Association, October 14,1999.

Cannon started research into carbon dioxide as an alternative blowing agent to CFC 11 more than ten years ago. Carbon dioxide was a very logical choice since it was already part of the foam reaction, and it was environmentally very acceptable. The one major problem that was encountered with carbon dioxide was the high pressure required to keep it dissolved in the foam reactants during mixing. A controlled method of reducing pressure was required to prevent the foam from collapsing or developing a lot of holes. The key area for development, therefore, was a device for controlling the pressure drop. By the early 1990's this had resulted in the principle of the CarDio gatebar which used a slot as the method of reducing pressure. This development was responsible for the sale of more than forty CarDio plants worldwide by 1999.

The pressure drop caused by the gatebar is determined by the slot height. Normally this dimension is fixed before starting the run and cannot be changed during the run. If only one grade of foam is produced, this is not a problem. However, if a large number of grades need to be produced on the same run, compromises may need to be made. A gatebar with a variable slot height would enable pressure and nucleation conditions to be optimized for each foam grade in the run. Cannon now has such a device.

The height of the slot is controlled up or down by hydraulic pressure, and can be quickly and precisely adjusted by turning a control knob. An adjustment range of around 150 micron / 0.006" can be obtained during running.

The advantages of having a gatebar with a variable slot height are: gatebar pressure independent of output, optimized run conditions for each grade, and even wider range of carbon dioxide levels.

Cannon has also developed a CarDio Airless system. This is achieved by the addition of a zone of "Controlled turbulence" + Velocity reduction, after the pressure drop zone. This new part of the gatebar design induces nucleation with 60 % less nucleating gas. The result is a uniform froth with no voids.

 

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