Environmental Protection of Polyurethane Foam (I)

With the almost complete switch to "cleaner" foaming agents, the current priority is to adjust the foaming formula for optimum performance and cost.
The polyurethane foaming industry has largely turned to the use of “cleaner” foaming agents and is currently focused on optimizing the formulation to make the resulting foam easier to process and at a lower cost. At this point in time, the industry has been hit by unprecedented material and energy price increases, making the latter goal particularly challenging. Alternative foaming agents also have their own performance problems to solve, such as system compatibility, fluidity, insulation values, and dimensional stability.

Oxid's new high-performance polyester polyols can fine-tune HFC-245fa hard-spray formulas to create dimensionally stable, first-rate fire-retardant foams for wall insulation.

"Eco-friendly" polyurethane (PUR) formulations have reduced costs while meeting market performance requirements. This is the focus of the Polyurethanes 2005 Technology Show recently held in Houston, which was initiated by the Polyurethane Industry Alliance.

Many reports deal with hard foam materials used in construction. The goal is to reduce foaming agent costs and foam density while maintaining performance. Speakers discussed new polyols and surfactants that are dedicated to these goals. Upgrading to a universal sheet laminator promises shorter maintenance downtime.

New developments in the automotive industry include the latest in-mold spray polyurethane skin technology, and new non-volatile additives that can significantly reduce volatile organic compounds in and out of car seats.

An innovative modular tooling system is also discussed, which allows refrigeration and refrigeration boxes to be produced at a lower cost and with greater flexibility.

The latest development of foaming agents
At present, almost all major foaming industries have completed the conversion of blowing agents with zero ozone depletion potential (ODP), and most of them rely on HCFC-141b as the main first-generation alternative to replace the currently banned total chlorine. Hydrocarbons (CFCs).

The current major blowing agents include hydrofluorocarbons—mainly HFC-245fa ($4/lb), and to a lesser extent HFC-134a ($2/lb). They are usually high in water and can co-expand with carbon dioxide. The second main class of blowing agents are the hydrocarbons - isopentane, n-pentane and cyclopentane (50 to 60 A/lb). There is also an updated formic acid methyl based Ecomate supplied by Foam Supplies, which can be supplied separately or supplied in a blend at prices in the same price range as pentane. It is said that the insulation of Ecomate is between high-performance HFC-245fa and pentane.

Studies at the Huntsman Advanced Materials Center show that the isopentane/n-pentane blends have higher compressive strength and lower cost compared to the widely used cyclopentane/isopentane blends.

HFC-245fa is marketed under the trade name Enovate 3000. The only manufacturer in North America is Honeywell International, which dominates in infusion product insulation (refrigerators and water heaters) in walls, roofs, containers and Spa baths are also leading in the use of hard-spray foam insulation.

Being more sensitive to costs, it is mainly used in the field of thermal insulation of polyisocyanate (PIR) sheets on the roof, and has turned to pentane.

An exception to the overall shift is the metal-faced foamed sheet, which still allows the use of HCFC 22 and 142b with lower ODP values. The federal Environmental Protection Agency (EPA) aims to terminate use by 2010. Industry statistics still maintain that although HFC-245fa is also a candidate material, pentane is basically used and this industry has undergone significant changes.

At the conference, Foam Supplies reported that its Ecomate product has been used in the thermal insulation of drinking fountains and large coolers for the past four years and has now developed new uses for the filling of areas such as door panels. The company worked with some large suppliers of polyols and surfactants to find potential applications in other rigid foam industries, such as replacement of pentane in plates; spray foaming for the cost of HFC-245fa; perhaps even In the more conservative electrical industry.

According to the company, Ecomate has high solubility, low molecular weight, high foaming efficiency, and low volatility, and can be used in lower amounts than HFC-245fa and HCFC-141b. For example, a system with 15% HCFC-141b may require only 5% to 6% of Ecomate to obtain the same density.

Regardless of which foaming agent is used, it is of interest to the foaming formulator to understand what changes have occurred in the process. “Finding how much of the blowing agent is in the polymer matrix, how much is retained in the cell is critical to the optimization of the formulation and is a decisive factor in the nature of the foam,” explained Mary Bogdan, Buffalo, NY ) Chief Scientist of the Honeywell Research Laboratory Enovate Technical Services and Applications Group.

Honeywell's researchers determined that there is currently no single analytical technique that can easily quantify the distribution of blowing agents in polyurethane foam. Therefore, they are investigating a practical and economical method to determine the content of blowing agent in polymer and cell gas, as well as the blowing agent emission during the foaming reaction.

Best roof plate
According to the results of the Huntsman Advanced Technology Center, PIR plate manufacturers have the opportunity to reduce costs while maintaining and enhancing performance by choosing to use pentane blowing agents. In the absence of HCFCs initially, many PIR plate producers chose the 80/20 cyclopentane/isopentane mixture. Huntsman researchers studied the effect of changing the pentane component on the key performance criteria for PIR sheeting, as defined in the 2001 edition of ASTM C1289, compared to the 1998 version, it has the lowest compressive strength in the thickness direction and the sheet The dimensional stability puts forward more stringent requirements.

Formulations were tested with seven blowing agent combinations: 80/20 cyclopentane/isopentane; 100% isopentane; 70/30 isopentane/n-pentane; 30/70 isopentane/n-pentane; 100% n-pentane; 64/28/8 isopentane/n-pentane/iso-butane; and 73/19/8 cyclopentane/isopentane/iso-butane.

The results show that either all isopentane or a mixture of isopentane and n-pentane rich have the greatest potential for cost savings while maintaining or enhancing performance (pictured). According to the researchers, since isopentane and n-pentane are much lower in price than cyclopentane, they can reduce costs. In addition, the data of compressive strength and dimensional stability indicate that isopentane or isopentane alone is used as a main component to be blended with n-pentane, and the produced sheet has more requirements for structure, heat insulation and fire resistance, and at the same time, Low foam density and lower cost.