Manufacture Of Polyurethanes Research Articles

Biological monitoring of exposure to toluene diisocyanate

Toluene diisocyanate (TDI) is used in the manufacture of polyurethane and is a potent inducer of diseases of the airways. In this study, 2,4- and 2,6-toluenediamine in hydrolyzed urine and plasma were evaluated as biomarkers of exposure to 2,4- and 2,6-TDI, respectively. For 81 exposed workers from nine different plants, the personal 8-hour time-weighted-average exposure to TDI was monitored by a filter method with 1-(2-methoxyphenyl)piperazine. In parallel, urinary samples (U1) were collected during the last 4 hours of the workshift. On a different occasion, blood samples and additional urinary samples (U2) were collected from the exposed workers, and also from a reference group consisting of 121 unexposed workers. The biomarker levels were determined in urine and plasma by the use of alkaline hydrolysis. There were strong associations between the personal air and biomarker levels, with correlation coefficients in the range of 0.75-0.88 for the U1 samples and in the range of 0.50-0.78 for the plasma samples. By weighted linear regression, the relations were calculated between the air and biomarker levels. The slopes of the obtained regression curves ranged from 1.8 to 2.7 m3/1 for air-urine and from 2.2 to 2.9 m3/1 for air-plasma, and the intercepts were all close to the origin of the coordinates. Through the extrapolation of these regression curves, biological exposure limits were calculated. The biological monitoring methods and strategies presented in this report are useful for assessing exposure to TDI in practice.

Treatment of Volatile Organic Compounds from Polyurethane and Epoxy Manufacture by a Trickle-Bed Air Biofilter

The objective of this study was to evaluate the performance of a trickle-bed air biofilter (TBAB) for the removal of volatile organic compound (VOC) produced during polyurethane (PU) and epoxy manufacture. The major VOCs emitted are ethyl acetate (EA) for PU and EA and xylene for epoxy production. For the treatment of VOCs emitted during PU production, the employed coal carbon appears to be efficient as a VOC concentration buffer in the biofiltration of waste gases. Based on the results of EA and total hydrocarbon (THC) removal, it was concluded that the TBAB is suitable for controlling VOC emission during PU manufacture. For the treatment of VOCs emitted during epoxy production, it was found that the performance of the TBAB is relatively poor due to the lack of VOC sources. However, this problem could be easily solved by mixing the VOCs emitted during PU and epoxy manufacture.

Treatment of volatile organic compounds from polyurethane and epoxy manufacture by a trickle-bed air biofilter

The objective of this study was to evaluate the performance of a trickle-bed air biofilter (TBAB) for the removal of volatile organic compound (VOC) produced during polyurethane (PU) and epoxy manufacture. The major VOCs emitted are ethyl acetate (EA) for PU and EA and xylene for epoxy production. For the treatment of VOCs emitted during PU production, the employed coal carbon appears to be efficient as a VOC concentration buffer in the biofiltration of waste gases. Based on the results of EA and total hydrocarbon (THC) removal, it was concluded that the TBAB is suitable for controlling VOC emission during PU manufacture. For the treatment of VOCs emitted during epoxy production, it was found that the performance of the TBAB is relatively poor due to the lack of VOC sources. However, this problem could be easily solved by mixing the VOCs emitted during PU and epoxy manufacture.

Multi-component reaction injection moulding (MC-RIM): A processing technology for the manufacturing of multi-component polyurethane mouldings

Multi-component injection moulding technologies are gaining constantly in importance for thermoplastics processing, in particular the gas-assisted injection moulding concepts could also offer a great potential of application to the manufacture of polyurethane (PU) parts. However, due to the significant differences between the material behaviour of thermoplastics and reactive PU systems with their coupled chemical and physical processes the transference of the experiences gathered in thermoplastics injection moulding has to be regarded critically. Therefore, focusing on the gas-assisted reaction injection moulding of hollow parts, designated as GRIM technique, numerous experimental investigations concerning the most significant process parameters gas delay time, mould temperature and gas pressure has been performed. The main resultats of these process investigations are reported.

Developmental toxicity of 1,6-hexamethylene diisocyanate (HDI) in the Sprague-Dawley rat.

1,6-Hexamethylene diisocyanate (HDI), a widely used chemical in commercial polyurethane manufacture, has been shown to affect the respiratory tract of experimental animals. However, its potential to affect neonatal development, particularly after inhalation exposure, is less well described. The present study was conducted to assess the developmental toxicity of HDI. Gravid Sprague-Dawley rats were exposed to concentrations of 0, 0. 005, 0.050, or 0.300 ppm HDI via inhalation (whole-body exposure) on days 0-19 of gestation. Maternal toxicity, as demonstrated by clinical signs and changes in body weight gain during gestation, was characterized. Dams were sacrificed on gestation day 20, at which time fetuses were removed by cesarean section, the uterus was examined, and a gross maternal necropsy was performed. Maternal evaluation also included lung weight and a detailed histopathologic assessment of the nasal turbinates, larynx, trachea, and lungs. All fetuses were evaluated for external anomalies. Approximately one-half of each litter was examined for visceral effects, the other half underwent a skeletal (bone and cartilage) examination. Maternal toxicity was demonstrated in the 0.300- and, to a lesser extent, in the 0.050-ppm exposure groups. No maternal effects were noted in the 0.005-ppm group. Test compound-related maternal effects were restricted to histopathological findings and included acanthosis, hyperkeratosis, inflammation of the nasal turbinates, and, more seriously, degeneration of the olfactory epithelium. No pathological alterations were noted in the larynx, trachea, or lungs in any dose group. No test compound-related effects were observed on any reproductive parameters, or any embryonic endpoints, including pre/postimplantation loss and resorption. There were no effects on litter size or the number of fetuses per implantation site and no effects on fetal or placental weights were observed. No test compound-related fetal external, visceral, or skeletal findings were observed. No effect on the fetal or litter incidence of total malformations or variations was observed, and there was no difference in the incidence of malformations between males and females. Administered as described in this study, 1, 6-HDI produced maternal effects (nasal turbinate histopathology) at concentrations of 0.050 and 0.300 ppm with no developmental toxicity observed at any concentration.

Micronuclei in peripheral lymphocytes and exfoliated urothelial cells of workers exposed to 4,4′-methylenebis-(2-chloroaniline) (MOCA)

4,4′-Methylenebis-(2-chloroaniline) (MOCA) is used in the manufacture of polyurethane. The IARC classifies MOCA as a probable human carcinogen. Suggested changes to guidelines for health surveillance of MOCA-exposed workers in Australia include a reduction in acceptable levels of urinary MOCA to below 15 μmol/mol creatinine. Twelve male workers aged 24 and 42 years were recruited into this study from four work locations where MOCA is used. Exfoliated urothelial cells from prework urine samples on a midweek work day were assessed for micronucleus (MN) frequencies. Postwork urine samples were analysed for total MOCA. Blood samples collected on the same day were cultured for 96 h and cytochalasin-B-blocked cells were scored for MN. Eighteen male control subjects (23–59 years) provided corresponding urine and blood samples. Median urinary MOCA concentrations were 6.5 μmol/mol creatinine (range 0.4–48.6 μmol/mol creatinine) in postwork samples of MOCA-exposed workers. MOCA was not detected in urine of control workers. Mean MN frequencies were higher in urothelial cells and lymphocytes of MOCA workers (14.27±0.56 and 13.25±0.48 MN/1000 cells) than in controls (6.90±0.18 and 9.24±0.29 MN/1000 cells). The mean number of micronucleate cells was also higher in both tissues of exposed workers (9.69±0.32 and 8.54±0.14 MN cells/1000 cells) than in controls (5.18±0.11 and 5.93±0.13 MN cells/1000). There was no correlation between postwork urinary MOCA concentrations and MN frequencies in either tissue. This study suggests that exposures to MOCA in South Australia are similar to those of a decade ago and are at levels similar to those currently acceptable in Australia. These are associated with genotoxic effects in urothelial cells and peripheral blood lymphocytes. It may be prudent to reduce MOCA exposures in line with proposed guidance values.

Toluene diisocyanate colocalizes with tubulin on cilia of differentiated human airway epithelial cells.

Toluene diisocyanate (TDI), a highly reactive industrial chemical with widespread use in the manufacture of polyurethane and plastics, is the leading cause of occupational asthma associated with chemical exposure. We report the effects of TDI vapor (20, 100, 500, 1000 ppb) in vitro on differentiated human bronchial epithelial cells. Increased mucus was observed by electron microscopy at all TDI concentrations. Cytotoxicity, as evidenced by cell pyknosis and DNA fragmentation, was detected following a 30-min exposure to TDI concentrations of 100 ppb or higher. At 1000 ppb, transepithelial resistance was lost. Using confocal microscopy and double staining, TDI was found colocalized with ciliary tubulin in cultures that had been exposed to 20 and 100 ppb. These findings are the first to identify TDI binding to human pulmonary epithelial cells and indicate extensive binding to the cilia of differentiated epithelial cells. The in vivo implications of these findings include decreased ciliary movement and longer retention of TDI and hence increased exposure. Altered cytoskeletal-derived signal transduction may be a consequence of tubulin involvement. The effects of such changes on respiratory sensitization remain to be explored.

Synthesis, Physicochemical Characterization, and Applications of Polyurethane Ionomers: A Review

1. INTRODUCTION In the increasingly changing scenario in which yesterday's luxuries have become today's necessities, polymers have played a very crucial role. From ships to aircraft, polymeric materials have found tremendous applications, often having many desirable properties compared to many conventional materials. Polyurethanes (PUs) belong to one such class of materials used for all-around applications. Polyurethanes are an important class of block copolymers for which the properties of the end product can be designed according to user needs. Due to the potential large volume of applications and the high versatility of properties, these materials require a thorough understanding of synthesis and properties, as well as updating of knowledge. The manufacture of polyurethanes involves a greater degree of control over chemical reactions than most other polymers do. Their properties range from liquid, soft, and rubbery solids to rigid thermoplastic and thermoset materials [1–8].

Mortality of workers exposed to toluene diisocyanate in the polyurethane foam industry.

To evaluate cancer mortality among United States workers exposed to toluene diisocyanate (TDI) in the manufacture of polyurethane foam. This cohort mortality study included 4611 men and women employed in four polyurethane foam plants for at least three months between the late 1950s and 1987. The mortality experience of the cohort was then compared with that of the general United States population. Current and past industrial hygiene data indicated that air concentrations in 1984-5 were below the current United States standard of 0.04 mg/m3 but exceeded the standard before 1980. Mortality ratio (SMR) 2.78, 95% confidence interval (95% CI) 0.57-8.13) and non-Hodgkin's lymphoma (SMR 1.54, 95% CI 0.42-3.95) were increased, but not significantly. There was one male breast cancer. However, breast cancer was not increased in women (SMR 0.74). No other cancer category had an increased number of deaths compared with the general population. Only non-Hodgkin's lymphoma and Hodgkin's disease showed a possible relation with time since first employment and no cancer death category showed a strong relation with duration of employment. Mortality from non-malignant respiratory disease was not increased (SMR 0.86). This young cohort has few deaths and short follow up. The findings are therefore not conclusive. Further years of follow up will enable better evaluation of mortality.

Synthesis and quantification of DNA adducts of 4,4'-methylenedianiline.

4,4'-Methylenedianiline (MDA) is used as a hardener in the manufacture of plastics and polyurethanes. MDA has been classified as a carcinogen in animals and is a suspected human carcinogen. Assuming that MDA would yield similar DNA adducts to other arylamines, we synthesized the following C-8 guanine adducts: N'-acetyl-N-(deoxyguanosin-8-yl)-MDA, N-(deoxyguanosin-8-yl)-MDA, N-(deoxyguanosin-8-yl)-4MA, and their corresponding 3'-monophosphate derivatives. We developed methods to identify these adducts of MDA in liver DNA using 32P-postlabeling, HPLC, and GC-MS techniques. Liver DNA was obtained from rats treated with radiolabeled MDA (1.11 and 116.5 mumol/kg body weight). The total radioactivity bound to the DNA corresponded to 0.06 and 2.7 adducts per 10(7) nucleotides [covalent binding index (CBI = (mumol of adduct per mol of nucleotide)/(mmol of compound per kg body weight)) of 1.05 and 2.3]. This DNA-binding potency is in the range of weakly genotoxic compounds. The liver DNA was analyzed for the presence of the synthesized adducts by the following methods: (I) HPLC analysis of nucleotides and purines after enzymatic and acid hydrolysis, and (II) 32P-postlabeling after enzymatic hydrolysis. The major adducts found in vivo did not correspond to the synthesized standards. Further work was carried out to determine the structure of the unidentified adducts. It was possible to release MDA and MDA-d4 from DNA of rats dosed with MDA and/or MDA-d4 and from the synthesized adducts using strong base hydrolysis. Liver of two female Wistar rats given 500 mumol/kg MDA-2HCl was hydrolyzed in 0.1 M NaOH overnight at 110 degrees C. GC-MS analysis of the heptafluorobutyric anhydride derivatized dichloromethane extracts detected 428 +/- 40 fmol of MDA/mg of DNA. In the control animals no MDA was found. The experiment was repeated with livers from animals dosed 500 mumol/kg MDA-d4.2DCl. In these rats 488 +/- 19 fmol MDA-d4 was found to be bound at liver DNA. Taking into account a 68% yield of the method, the CBI found in these cases was 0.82 and 1.0, respectively.

Basic kinetic model for the reaction yielding linear polyurethanes. II

AbstractOn the basis of the gradual polyaddition kinetic model developed earlier, an attempt was made to provide a generalized mathematical model for the set of reactions yielding linear polyurethanes. The model is a system of first‐order ordinary differential equations. It was assumed at the present stage of this model that the rate constants for the reaction considered do not change. The model developed was then solved numerically. Average molecular weight of the polymer and composition data for oligomers were calculated for a constant volume batch reactor and varied process parameters. The GPC method, which was tested for model urethane oligomers, was employed to verify the model developed. The reaction of 2,4‐TDI with 1,4‐butanediol proceeding in a solution was investigated. It was concluded that the model was applicable to a limited degree in describing the linear polyurethane manufacturing process which is more complex. However, it was suggested that the algorithms adopted could be utilized in developing further models which could assume changing rate constants for the polymer chain growth reactions. © 1995 John Wiley & Sons, Inc.

Pro-ecological syntheses of intermediates for the manufacture of polyurethanes. Part II. Addition of isocyanic acid to some alkenes and alkadienes

Pro-ecological syntheses of intermediates for the manufacture of polyurethanes. Part II. Addition of isocyanic acid to some alkenes and alkadienes

Albumin adducts, hemoglobin adducts and urinary metabolites in workers exposed to 4,4'-methylenediphenyl diisocyanate.

4,4'-Methylenediphenyl diisocyanate (MDI) is the most widely used isocyanate in the manufacture of polyurethanes. MDI has been implicated as one of the major causes of occupational asthma. Hydrolysis of MDI can yield 4,4'-methylenedianiline (MDA), which is a suspected human carcinogen. Thus the need to monitor occupational exposure to MDI is of great significance. The use of air monitors alone has been found to be insufficient and there is a need for sensitive markers of recent and long-term exposure. We obtained biological samples from a group of 20 workers exposed to MDI vapor during the manufacture of polyurethane products. The air levels of MDI in the factory were measured using personal, work room and work station monitors. In most cases the levels were below detection limits. The blood and urine samples were analyzed for the presence of adducts and metabolites using GC-MS methods. Urinary base-extractable metabolites were found above control levels in 15 of the 20 workers and ranged from 0.035 to 0.83 pmol MDA/ml. The level of the acetylated metabolite N'-acetyl-4,4'-methylenedianiline (AcMDA) ranged from 0.13 to 7.61 pmol/ml. The amount of MDA released after acid hydrolysis was on average 6.5 times higher than the amount of free MDA and AcMDA present in urine. MDA was detected as a hemoglobin (Hb) adduct in all of the 20 subjects. The level ranged from 70 to 710 fmol/g Hb. In one individual the Hb adduct of AcMDA was detected. This is the first time a Hb adduct of AcMDA has been detected after occupational exposure to MDI. This is a further piece of evidence for the biological availability of the suspected human carcinogen MDA from in vivo hydrolysis of MDI. Plasma albumin conjugates of MDI can cause the onset of respiratory disorders in both man and animal models. Thus we investigated the presence of plasma protein adducts. The plasma MDA levels ranged from 0.25 to 5.4 pmol/ml. Up to 120 fmol/mg were found to be covalently bound to albumin.

Pro-ecological syntheses of intermediates for the manufacture of polyurethanes. Part I. Preparation of organic diisocyanates by addition of isocyanic acid to a,b-unsaturated ethers and diethers

Pro-ecological syntheses of intermediates for the manufacture of polyurethanes. Part I. Preparation of organic diisocyanates by addition of isocyanic acid to a,b-unsaturated ethers and diethers

Pultruded fibre-reinforced polyurethane composites. III. Static mechanical, thermal, and dynamic mechanical properties

A proprietary process has been developed for the manufacture of polyurethane (PU) pultruded composites. The blocked isocyanate (NCO)-terminated PU prepolymer synthesized in this study was prepared from ϵ-caprolactam blocked blends of toluene diisocyanate and branched polyester. The static mechanical and thermal properties of various fibres (glass, carbon and Kevlar-49 aramid fibre) reinforced blocked PU composites have been studied. Results show that the static mechanical properties (i.e. tensile strength, specific tensile strength, flexural strength, specific flexural strength, flexural modulus and impact strength) and thermal properties (heat deflection temperature (HDT) increase with fibre content. Kevlar-fibre/blocked-PU composites possess the highest impact strength, specific tensile strength and HDT, whereas carbon-fibre/blocked-PU composites show the highest tensile strength, flexural strength, specific flexural strength and flexural modulus. Experimental results for tensile strength of all composites except carbon-fibre/blocked-PU composites follow the rule of mixtures. The deviation from the mixtures' rule of the properties of the carbon-fibre/blocked-PU composite is due to fibre breakage during processing. The glass-transition temperature (T g) increased slightly and the damping peak (tan δ) was broadened as a consequence of fibre reinforcement. The dynamic mechanical moduli (G', G“) of pultruded blocked PU composites are apparently higher than those of the matrices. The moduli (G', G“) increase with increasing fibre and filler content, and the damping peak becomes broad. The effect of postcuring on the degree of crosslinking, T g and dynamic modulus will be discussed.

Biological and biological-effect monitoring of workers exposed to 4,4'-methylene-bis(2-chloroaniline).

4,4'-Methylene-bis(2-chloroaniline) (MOCA), a curing agent used in polyurethane manufacture, is a genotoxic and carcinogenic amine. This study aimed to assess occupational exposure to MOCA using as indices: (1) the post-work urinary output of MOCA; (2) urinary thioethers, assuming that conjugation with glutathione might be a significant pathway for the elimination of putative electrophilic metabolites of MOCA; and (3) sister-chromatid exchange (SCE) frequency in peripheral lymphocytes as an indicator of genetic damage. Process workers at a polyurethane production unit were found to have up to 38 mumol MOCA mol-1 creatinine in their urine at the end of a work shift. Smaller quantities were found in the urine of laboratory and supervisory staff, but none was detected in the urine of a group of office and sales staff from an unrelated industry, who served as unexposed controls. There was no evidence of MOCA-related urinary thioether output. There was a graded increase in SCE frequency from controls to process workers, consistent with their apparent exposure to MOCA. Administration of MOCA to rats (5 daily i.p. injections of 125 or 250 mg kg-1 resulted in dose-related increases in MOCA excretion and in lymphocyte SCE frequency, but there was no change in thioether output. These results indicate that urinary thioether excretion is inappropriate for monitoring MOCA exposure, but that where MOCA exposure can be demonstrated, by the presence of MOCA in urine, this is associated with genetic damage in both man and in the rat.

Chemical recycling of polyurethanes and separation of the components by supercritical ammonia

AbstractChemical recycling of a polyurethane elastomer and a flexible foam based on methylenebis(phenyl isocyanate) (MDI) and a polyetherpolyol was performed by ammonolytic cleavage of urethane and urea bonds under supercritical conditions. Resulting products were the polyols, the amines corresponding to the isocyanates used, and unsubstituted urea. Under suitable conditions the polyetherpolyol was completely separated from the other ammonolysis products which in turn can be further separated and used for the manufacture of polyurethanes or for the synthesis of diisocyanates.

Nonisocyanate Exposures in Three Flexible Polyurethane Manufacturing Facilities

Abstract Although toluene diisocyanate (TDI) has been widely used for about 50 years, industrial hygiene characterizations of other chemical exposures used in conjunction with TDI have generally received much less attention. As part of a retrospective, cohort mortality study, industrial hygiene evaluations were performed in three facilities manufacturing flexible (TDI-based) foam. This report is concerned only with nonisocyanate exposures in that industry. In each facility, the concentrations of several air contaminants, other than TDI, were assessed, including aliphatic amines, nitrosamines, nitrogen dioxide, thermal degradation products, organic solvents, polyurethane dust, and flame retardants. Air samples were also collected for subsequent assay of mutagenic activity using Salmonella bacterial tester strains TA98 and TA100. Workers were found to have respiratory and probably dermal exposure to methylene chloride in each facility. Traces of nitrogen dioxide and some aliphatic amines were evident. Howev...

Air Concentrations of TDI and Total Reactive Isocyanate Group in Three Flexible Polyurethane Manufacturing Facilities

Abstract In-depth industrial hygiene surveys were conducted in two large facilities manufacturing molded flexible foam and one facility manufacturing and finishing flexible slab foam. These surveys were performed to support a retrospective, cohort, mortality study of workers that were potentially exposed to toluene diisocyanate (TDI). The air sample results show that isocyanate concentrations differed from plant to plant and were probably dependent on the operations performed, engineering controls, and the physical layout of the plant. In the two molded foam facilities, many of the personal exposures were above 35 μg/m3, as had been recommended by the National Institute for Occupational Safety and Health (NIOSH). As expected, pouring line workers were generally more exposed than finishing workers. However, thermal degradation of foam can release toxic substances, including TDI, into the air. This was found to occur in some of the finishing operations, resulting in elevated air concentrations of TDI. Throu...

Determination of residual aromatic amine hydrochlorides in process samples of di-isocyanate used in the manufacture of polyurethane: A comparison of electroanalytical methods

Aromatic diamine hydrochlorides have been determined in the presence of different amounts of hydrochloric acid by acid-base titration followed potentiometrically, by linear sweep voltammetry, by differential pulse voltammetry and also by direct DPV measurement. Tests on simulated and production samples have shown that the best results are obtained by using DPV at a mercury electrode, because of its good resolution, which makes it possible to achieve good accuracy (error < - 1 %) and good precision (rsd 1.5%) at 0.1 M levels. Moreover, it has the advantage that neither preliminary treatment of the sample nor a trial titration is required.