Production Of Polyurethane Foams Research Articles

Mortality and cancer morbidity of production workers in the UK flexible polyurethane foam industry: updated findings, 1958–98

Aims: To describe cause specific mortality and site specific cancer morbidity among workers employed in factories that produce polyurethane foams, and to determine if any part of the experience may...

A Case of Occupational Asthma in Tunnel Workers Exposed to Isocyanates

Occupational asthma is one of the most prevalent occupational lung diseases in the developed countries. The proportion of the cases of asthma in adults due to occupational exposure is estimated to be 15%. Because occupational asthma may cause long disability, it is important to identify the causes and remove the workers as soon as possible from the causal exposure. One of the main causes of occupational asthma is isocyanates. Because isocyanates are used in the production of polyurethane foams, adhesives, varnishes, insulating materials and hardeners, many cases of occupational asthma due to isocyanates have been reported in many different kinds of occupations. Pneumoconiosis has been mainly recognized as the occupational lung disease in tunnel workers. There have been no reports of the occupational asthma due to isocyanates in tunnel workers in Japan, and so there has been less concern about asthma in tunnel workers than about pneumoconiosis. Here we report on a tunnel worker who has been exposed to isocyanate and developed asthma.

Biodegradable polyurethane foam from liquefied waste paper and its thermal stability, biodegradability, and genotoxicity

Liquefaction of waste paper (WP) was conducted in the presence of polyhydric alcohols to prepare biodegradable polyurethane foam. The liquefied-WP-based polyol had suitable characteristics such as apparent molecular weight, hydroxyl value, and viscosity for the preparation of rigid polyurethane foam and was successfully applied to produce polyurethane foam with the appropriate combinations of foaming agents. The obtained foams showed satisfactory densities and mechanical properties as good as those of foams obtained from liquefied wood- and starch-based polyols. The foams had almost the same thermal stability at initial weight loss and seemed to be potentially biodegradable because they were degraded to some extent in leaf mold. There were no mutagens or carcinogens in the water extracts of the foams. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1482–1489, 2002

Biodegradable polyurethane foam from liquefied waste paper and its thermal stability, biodegradability, and genotoxicity

AbstractLiquefaction of waste paper (WP) was conducted in the presence of polyhydric alcohols to prepare biodegradable polyurethane foam. The liquefied‐WP‐based polyol had suitable characteristics such as apparent molecular weight, hydroxyl value, and viscosity for the preparation of rigid polyurethane foam and was successfully applied to produce polyurethane foam with the appropriate combinations of foaming agents. The obtained foams showed satisfactory densities and mechanical properties as good as those of foams obtained from liquefied wood‐ and starch‐based polyols. The foams had almost the same thermal stability at initial weight loss and seemed to be potentially biodegradable because they were degraded to some extent in leaf mold. There were no mutagens or carcinogens in the water extracts of the foams. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1482–1489, 2002

2,4-Toluene diamines--their carcinogenicity, biodegradation, analytical techniques and an approach towards development of biosensors.

2,4-Toluene diamine (TDA), a class A carcinogen, is a major raw material for the production of toluene diisocyanate (TDI), which is one of the precursors for the production of polyurethane foams (PU). This review deals with 2,4-toluene diamine's (TDA) carcinogenicity, analytical techniques, biodegradation and use as a biosensor for biogenic and synthetic amines, emphasizing various carcinogenicity studies by 2,4-TDA on animals and humans. This review reports some publications of the analysis of body fluid samples of workers from a PU producing factory for presence of TDA and TDI, since TDI gets absorbed into the worker's body, getting metabolized into TDA. Biodegradations of 2,4-TDA by various researchers are reported and also our own research experience with biodegradation of 2,4-TDA using Aspergillus nidulans isolated from soil site at a polyurethane foam dumping site have been discussed in this review. Biosensors for various biogenic and synthetic amines are discussed.

Polybrominated diphenyl ether flame retardants in Virginia freshwater fishes (USA).

Polybrominated diphenyl ethers (PBDEs) were examined in fish fillets collected from two large Virginia watersheds. Emphasis was on the tetra- to hexabrominated congeners since these exhibit the greatest bioaccumulation and toxicological potentials. These congeners are dominant constituents of Penta-, a commercial PBDE product used to flame retard polyurethane foam. In 1999, North America accounted for98% of global Penta-demand. Concentrations of total tetra- to hexabrominated congeners in fillets ranged from <5 to 47,900 microg/kg (lipid basis). BDE-47, one of the two major constituents of Penta-, was detected in 89% of samples and contributed 40-70% of the total PBDEs observed. Concentrations of BDE-99, the second major constituent of the Penta- commercial mixture, were much lower in fish. While some differences in PBDE profiles between fish species were apparent, dominant congeners were consistent with those in surficial sediments from the Virginia sites and recently published data for U.S. air samples. PCB and PBDE concentrations in fish were generally associated. These factors point to exposure from nonpoint sources. Exceptions existed, likely due to inputs from local sources. The Virginia study area has historically served as a center for furniture and textile manufacturing, although polyurethane foam production here has been limited.

Carcinogenic Risk of Toluene Diisocyanate and 4,4′-Methylenediphenyl Diisocyanate: Epidemiological and Experimental Evidence

Diisocyanates are highly reactive compounds widely used, for example, in the production of polyure-thane foams, elastomers, paints, and adhesives. The high chemical reactivity of these compounds is also reflected in their toxicity: diisocyanates are one of the most important causes of occupational asthma but also other adverse effects, such as irritation and toxic reactions, have been described in exposed subjects. One of the open questions is whether occupational isocyanate exposure is a carcinogenic hazard. The few epidemiological studies available have been based on young cohorts and short follow-up and are not conclusive. Toluene diisocyanate (TDI) has been classified as carcinogenic in animals on the basis of gavage administration studies, but no conclusions are available on inhalation exposure. For 4,4′-methylene diphenyldiisocyanate (MDI) there is suggestive evidence for carcinoge-nicity in rats. The possible carcinogenic mechanism of TDI and MDI is not clear. Both chemicals have been positive in a number of short-term tests inducing gene mutations and chromosomal damage. The reactive form could be either the diisocyanate itself or may derive from the metabolic activation of the aromatic diamine derivatives formed by hydrolysis. TDI and MDI react with DNA in vivo and in vitro. However, the structure of the adducts has not been identified. Especially from the in vivo experiment it is not known if the adducts are a product from the reaction with the isocyanate or the corresponding amine. In conclusion, both TDI and MDI are highly reactive chemicals that bind to DNA and are probably genotoxic. The alleged animal carcinogenicity of TDI and MDI would suggest that occupational exposure to these compounds is a carcinogenic risk. The few epidemiological studies available have not, however, been able to clarify if TDI and MDI are occupational carcinogens.

Characterization of thermally generated aerosols from polyurethane foam.

Isocyanates constitute a group of highly reactive chemicals used on a large scale for the production of flexible polyurethane (PUR) foam. Exposure to isocyanates is known to produce irritation of the mucous membranes and the eyes. Isocyanates also have strong sensitizing properties and may cause occupational asthma. It is therefore important to monitor isocyanate emissions at workplaces. To obtain information for the improvement of isocyanate samplers and for health risk assessments of exposure, the emitted aerosol from two types of flexible PUR foam subjected to thermal degradation was characterized. Particle size distribution and toluene diisocyanate (TDI) concentration in the emitted aerosols were measured. Thermal degradation of flexible PUR foam at temperatures from 250 to 300 degrees C produced an aerosol with a geometric mean particle diameter of 30-50 nm. Between 5% and 9% of the PUR foam was emitted as TDI, and 2% to 6% of TDI monomers were found in the particle phase under the experimental conditions used. The 2,6-TDI isomer was more abundant in the gas phase than in the particle phase.

ENVIRONMENTALLY FRIENDLY PROCESSING OF POLYURETHANE FOAM FOR THERMAL INSULATION

An environmentally friendly processing method of polyurethane foam was proposed and evaluated for the application of thermal insulation. For the production of polyurethane foam, chlorofluorocarbon (CFC) gases were eliminated to minimize environmental destruction. Carbon dioxide gas was used as a blowing agent instead of the CFC gas. Ultrasonic excitation was also applied to the mixture of polyol and isocyanate to increase the rate of nucleation and decrease the thermal conductivity. Nucleation and growth of bubbles were studied theoretically and experimentally. Water was used as a chemical blowing agent and carbon dioxide gas as the physical blowing agent. Experiments were carried out with different saturation pressures, and experimental results were evaluated to determine the best foaming conditions. Rate of bubble nucleation, final bubble sizes, conversion during polymerization reaction, and other parameters were predicted theoretically with the assumption that negative pressure is generated by the ultrasonic field and the bubble growth is controlled by diffusion of the gas from the resin into the bubble. The best results such as low thermal conductivity and small size of bubbles were obtained when the polyol which has been mixed with water was saturated with carbon dioxide gas and the ultrasonic excitation was applied to the mixture of polyol and isocyanate right after the impingement mixing.

Significantly Reduced Catalyst Consumption in Rigid Foams

The use of Mannich base initiated polyether polyols for the production of rigid polyurethane foams has been employed for many years. The use of this class of polyols has primarily been directed toward sprayed polyurethane foam applications. The inherent properties of these polyols include aromatic character, increased compatibility and inherent catalytic capabilities. The use of this family of polyols has not widely spread to other rigid foam applications. During the transition to HCFC-141b as the primary blowing agent for rigid polyurethane foams, increased catalyst levels were required. This introduced additional cost and handling concerns. This paper presents 20 rigid foam formulations which show how the use of a variety of Mannich polyols can reduce catalyst consumption by more than 40% while maintaining compressive strength, flowability and maintaining or improving the insulation properties of the foam (K-factor) and dimensional stability.

Meeting report

Meeting report

Review of the STM range of pressure distribution products.

STM Healthcare is a division of the Recticel Group which has been actively involved in the production and use of polyurethane foams for the past 40 years, and is now one of Europe's leading manufacturers of polyurethane foam for insulation, packaging, filtration, aerospace, the automotive and furniture industries, domestic and specialist bedding and seating products. STM Healthcare is able to draw upon the wealth of experience and expertise of the manufacturing facilities, enabling products to be developed using the latest environmentally friendly specification foams best suited to the requirements of pressure-reduction technology. All STM Healthcare mattresses, cushions and Linknurse mattresses are manufactured with Safeguard combustion modified high resilience foams. (Linknurse is a licensed product name; products are manufactured by Recticel and distributed by STM).

Formic acid as a co-blowing agent in rigid polyurethane foams

A valid substitute for CFC-11 (trichlorofluoromethane) for the production of rigid polyurethane foams for thermal insulating materials, with blowing agents having low environmental impact, is not available yet. HCFC-141b and n-pentane, at present the most utilized physical blowing agents (PBAs), cannot definitely replace CFCs because of their environmental impact and flammability, respectively. The aim of the present work is to investigate the opportunity of employing HCOOH as a chemical blowing agent (CBA), other than water, which can in some applications replace physical blowing agents. Advantages and disadvantages have been highlighted after studying the isocyanate–formic acid reaction. Evidently, the introduction of new reactions into the polyurethane chemistry introduces a wide range of opportunities and challenges.

Glycols in polyurethane foam formulations with a starch–oil composite

A dry starch–oil composite was blended with each of three glycols; ethylene, polyethylene, and propylene, and then reacted with isocyanate to produce polyurethane foams. The liquid glycols permitted the dry composite to blend well with the other ingredients in the foam formulations. Infrared spectra confirmed the presence of urethane structures in the composite–glycol foams. Polyethylene glycol provided a slightly less dense foam than the other glycols in the composite–glycol products. Microscopy showed a greater number of larger cells in the composite–polyurethane glycol foams. Infrared spectra indicated essentially no qualitative differences in the composite–glycol foams with the three glycols. By prestaining starch with toluidene blue and oil with sudan red, the location of the starch and oil components of the milled composite were observed in the composite–propylene glycol foam. Intact flakes of the composite were observed in the foam. An apparent loss of mobility of oil in the composite–polyurethane foam, as evidenced by NMR analysis, is probably due to crosslinking by isocyanate diffusing into the flakes. Both the cell structure and uniformity of blending were improved by using these glycols rather than the polyester polyol described previously. J Appl Polym Sci 69: 957–964, 1998. Published 1998 John Wiley & Sons, Inc.

Glycols in polyurethane foam formulations with a starch-oil composite

A dry starch–oil composite was blended with each of three glycols; ethylene, polyethylene, and propylene, and then reacted with isocyanate to produce polyurethane foams. The liquid glycols permitted the dry composite to blend well with the other ingredients in the foam formulations. Infrared spectra confirmed the presence of urethane structures in the composite–glycol foams. Polyethylene glycol provided a slightly less dense foam than the other glycols in the composite–glycol products. Microscopy showed a greater number of larger cells in the composite–polyurethane glycol foams. Infrared spectra indicated essentially no qualitative differences in the composite–glycol foams with the three glycols. By prestaining starch with toluidene blue and oil with sudan red, the location of the starch and oil components of the milled composite were observed in the composite–propylene glycol foam. Intact flakes of the composite were observed in the foam. An apparent loss of mobility of oil in the composite–polyurethane foam, as evidenced by NMR analysis, is probably due to crosslinking by isocyanate diffusing into the flakes. Both the cell structure and uniformity of blending were improved by using these glycols rather than the polyester polyol described previously. J Appl Polym Sci 69: 957–964, 1998. Published 1998 John Wiley & Sons, Inc.

Development of a rigid polyurethane foam from palm oil

The reactions between polymeric diphenyl methane diisocyanate (polymeric MDI) and conventional polyols to produce foamed polyurethane products are well documented and published. Current polyurethane foams are predominantly produced from these reactions whereby the polyol components are usually obtained from petrochemical processes. This article describes a new development in polyurethane foam technology whereby a renewable source of polyol derived from refined–bleached–deodorized (RBD) palm oil is used to produce polyurethane foams. Using very basic foam formulation, rigid polyurethane foams were produced with carbon dioxide as the blowing agent generated from the reaction between excess polymeric MDI with water. The foams produced from this derivatized RBD palm oil have densities in excess of 200 kg/m3 and with compression strengths greater than 1 MPa. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 509–515, 1998

Factors Affecting the Solubility of Gaseous HCFC and HFC Blowing Agents

The majority of the current production of rigid polyurethane foams utilizes HCFC-141b (1,1-dichloro-1-fluoroethane) as either the blowing or co-blowing agent to expand the foam. With the phase-out of hydrochlorofluorocarbons (HCFCs) scheduled for the year 2003, the usage of HCFC-141b will need to be reduced or terminated at that time. The existing options for rigid polyurethane foam blowing agents after the phase-out will be hydrofluorocarbon (HFC), carbon dioxide, or hydrocarbon based compounds. One possible candidate for HFC blowing agents is HFC-134a (1,1,1,2-tetrafluoroethane). Reasons for its use include its commercial availability, zero ozone depletion potential, low toxicity, low foam k factors at low temperatures, better dimensional stability, and the lack of flammability limits in air [1,2]. The major challenge in the use of HFC-134a is the difficulty in foam processing due to its low boiling point and moderate solubility in rigid foam polyols. During foam production, the reacting mixture rapidly expands and froths. This expansion can lead to isolated large cells in a matrix of smaller cells (worm hole formation) and can adversely affect the k factor and quality of the foam. A slower expansion is desirable to achieve better processibility and the lowest k factor possible. One way to influence the expansion is to increase the intermolecular interactions between the blowing agent and the foaming mixture. It may be possible to increase these intermolecular forces through the judicious selection of polyols and additives. Moreover, if a good understanding of the intermolecular interactions is gained, an opportunity exists to design rigid foam polyols to meet processing difficulties.

Commercial Potential for Recycling of Finely Ground Foam in Flexible Polyurethane Foam: A Project of the Polyurethane Recycle and Recovery Council—SPI

Attempts to include ground foam by cryogenic grinding of scrap foams in the production of new flexible polyurethane foams started more than ten years ago. Current work, sponsored by PURRC (Polyurethane Recycle and Recovery Council-SPI), reports on pilot plant and full scale demonstration of the use of foams from a variety of sources, including plant fall off and post consumer foams. Ground foams were produced by cryogenic and mechanical grinding. New foams were produced at two densities and different loading levels while maintaining equal density and IFD to unfilled control foams. The study includes data on dispersion properties of the powders, foam performance and estimated economics.

Software to Manage a Continuous Production of Flexible Polyurethane Foams by Slabstock Technology

Software, for IBM or IBM Compatible, operating in MS DOS environment, has been developed to manage a Continuous Flexible Polyurethane Foam Production. It is subdivided into a Main Menu and into various Sub-Menus that, all together, manage a series of activities, starting from the purchase of all raw materials up to the sale of produced foams. A series of databases, interconnected among them, allows the production of any foam corresponding to the formulations, using either sophisticated machines as Foamax Type or more economical ones. In addition the software allows the calculation of Foam Cost, Raw Materials, and Produced Foam Stocks, while the Raw Materials are purchased and utilized, and the Foams are produced and sold. A Testing and a Print Menu complete its performance.

Immobilized cyanobacteria as a biofertilizer for rice crops; Intl. Conference on Applied Algology, Knysna, South Africa, April 1996.

N2-fixing cyanobacteria (Anabaena azollae, symbiont strains) were immobilized in polyurethane foam and ammonia production by the cyanobacteria was investigated in the laboratory and rice field. The cyanobacterial symbiont, A. azollae - MPK-SK-AM-24 showed the highest growth rate and biomass production amongst the 5 isolates examined while A. azollae-AS-DS showed the highest nitrogenase activity followed by A. variabilis - SA0 (wild type, non-symbiotic). Treatment of the foam-immobilized cyanobacteria with the systemic fungicide Bavistin stimulated nitrogenase activity while inhibiting glutamine synthetase (GS) activity. Free-living A. azollae-MPK-SK-AF-38, A. azollae - MPK-SK-AM-24 and A. azollae-MPK-SK-AM-27 excreted the highest amounts of ammonia into the growth medium; under foam - immobilized conditions the ammonia production increased further. Treatment of the foam - immobilized cyanobacteria with the fungicides Bavistin and Vitavax resulted in ammonia production at significantly higher rates. Rice seedlings (var. ADT 36) grown in the laboratory in conjunction with foam - immobilized A. azollae showed increased growth. A field experiment with paddy rice and foam - immobilized A. azollae strains indicated that the cyanobacteria excreted significant amounts of ammonia into the flood water in the rice fields resulting in increased chlorophyll content of the plants and increased the rice grain and straw yields. A combination of fertilizer nitrogen and inoculation with foam - immobilized cyanobacteria also significantly increased the rice grain and straw yield. Additionally, both A. azollae and A. variabilis were immobilized in sugarcane waste (bagasse), added to rice paddy and resulted in increased rice grain yield.