Elimination of Amine Emissionsfrom Polyurethane Foams:Challenges and OpportunitiesF.M. Casati, J.M. Sonney, H. Mispreuve, A. Fanget,R. Herrington, J. Tu

Reprinted from The API 2001 Proceedings with permission from the Alliance for the Polyurethanes Industry.

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Elimination of amine emissions from polyurethane foams:challenges and opportunities

F.M. CASATI, J.M. SONNEY,F.M. CASATI, J.M. SONNEY,F.M. CASATI, J.M. SONNEY,F.M. CASATI, J.M. SONNEY,H. MISPREUVE, A. FANGETH. MISPREUVE, A. FANGETH. MISPREUVE, A. FANGETH. MISPREUVE, A. FANGETDow Europe S.AInternational Development Center13, rue de Veyrot - P.O. 3CH-1217 Meyrin 2 (GE)

R. HERRINGTON, J. TUR. HERRINGTON, J. TUR. HERRINGTON, J. TUR. HERRINGTON, J. TUThe Dow Chemical Company2301 North BrazosportFreeport TX 77541U.S.A.

Switzerland

ABSTRACT

Polyurethanes are a unique class of plastic in the sense thatindependent manufacturers buy liquid polyols and isocya-nates and then react them in the presence of catalysts, sur-factants and other additives in widely varying processingschemes to make the final commercial product. In somemanufacturing scenarios, there is a growing concern aboutworker exposure to volatile organic chemicals (VOC) suchas the amine catalysts. Emissions from manufactured arti-cles that contain polyurethane components are also a con-cern.

The polyurethane industry is continuing its legacy of suc-cessfully reducing the amount of volatile organic chemicalsreleased from its operations. Examples of this include thetotal elimination of the classical chlorofluorocarbon blow-ing agent from flexible foams and the replacement of vola-tile antioxidants with less migratory ones. Today, many ofthe classes of ingredients commonly used in preparingpolyurethanes are available in low-fogging or low VOCgrades. The next big challenge being addressed by the in-dustry is the elimination of amine catalyst vapors. This isimportant for both VOC and odor concerns.

The catalyst suppliers have responded by introducing avariety of new, non-fugitive (sometimes called reactive)amine catalyst compositions. Their success at reducingamine emissions while providing catalytic activity is widelyreported in the literature. Difficulties associated with reac-tivity profile adjustment, higher usage levels and losses incertain foam physical properties suggest that an improvedlevel of technology is still needed. This paper will present areview of work The Dow Chemical Company is doing todevelop flexible foam grades of polyether

polyol that help reduce and in some cases eliminate cata-lysts while improving process. Comparative data will bepresented to illustrate the utility of these new polyols inhelping the polyurethane industry continue to reduce vola-tile emissions.

INTRODUCTION

Flexible polyurethane foams are well-established industrialproducts with important technical and economic advan-tages. These materials have found their way into our dailylives through their use in the endless array of consumerproducts. To complement this wide-ranging success, sig-nificant development efforts continue today to improvetargeted performance features like comfort, durability, re-sistance to moisture and temperature [1-3]. Improvementsin the environmental impact of these products are also be-ing gained through reductions in the amount of VOC’s re-leased during their manufacture. In some manufacturingscenarios, there is a concern about worker exposure to thevapors of traditional amine catalysts. Amine emissionsfrom manufactured articles containing polyurethane com-ponents is a growing debate due to potential fogging, PVC(PolyVinyl Chloride) staining and PC (Poly Carbonate)degradation [4-6].

The industrial hygiene and safety issues related to handlingand use of amine catalysts in polyurethane production arecomplex. It begins with the need to purchase one or moreof these additives in separate containers that must be off-loaded, warehoused, transported to the formulation roomand in many cases physically handled by workers assignedthe task of blending up a formulation. Most amine catalystshave exposure and odor properties such that personal pro-tective equipment is required [7]. Empty working andshipment vessels need to be properly handled and preparedfor disposal or shipment back to the vendor.

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Due to the exothermic nature of the reactions and the extraheat applied in some curing scenarios, freshly preparedpolyurethane products are always at an elevated tempera-ture. With the classical non-reactive type amines, odorousvapors are released and in the absence of proper ventila-tion, worker exposure can occur [8-10]. When captured byan exhaust system, these amine vapors can represent a sig-nificant contribution to the total VOC’s being released bythe manufacturing plant.

Even after cooling down and undergoing fabrication intofinished products, trace amine odors are sometimes stilldetectable. Amine catalyst vapors have been identified asone component of the new car smell [11].

The catalyst suppliers have responded by introducing avariety of new, non-fugitive (sometimes called reactive)amine catalyst compositions. Examples of their success atreducing emissions while providing catalytic activity arerecorded in the literature [12-18]. Difficulties associatedwith reactivity profile adjustment, higher usage levels andlosses in certain foam physical properties suggest that animproved level of technology is needed.

In this paper, we continue to report the previously an-nounced activities at Dow to develop active polyetherpolyols [19]. Comparative data will be presented to illus-trate the utility of these new polyols in helping the polyu-rethane industry continue to reduce volatile emissions.

BACKGROUND

Most commercially manufactured polyurethane foams aremade with the aid of at least one catalyst. Many classes ofcompounds have been investigated and the amines and theorgano-metallics have been found most useful. Variouscombinations of catalysts are used in order to establish abalance between the chain propagation or gelling (isocya-nate with polyol) reaction and the blowing reaction (iso-cyanate with water). Any given catalyst molecule willnormally have some activity for both reactions and it iscommon to find synergistic performance when using two ormore catalysts in a formulation. The polymer formationrate and the gas evolution rate must be balanced so that thegas is entrapped efficiently in the gelling polymer while thefoam cells develop sufficient strength to maintain theirstructure without collapse or shrinkage. Catalysts are alsoimportant for assuring completeness of reaction or “cure”in the finished foam. Some of the challenges to success indesigning a catalyst package for a polyurethane productionreaction are listed in Table 1.

Table 1. Challenges to catalyze polyurethane reactionsSolubility parameters (including water)Steric hindranceDifference of NCO reactivity between isomersAcidityViscosity build-upEffect of temperature on catalyst efficiency

The first requirement for good catalytic activity is that thecatalyst molecule be highly compatible with the mixture ofreaction raw materials. Molecular structure of the catalystand the resulting steric hindrance will impact how easilythe molecule can approach the reactants and facilitate thedesired reactions [20]. The catalyst package needs to beeffective when isocyanates of varying isomer content andreactivity are used. Trace acidity, common in some rawmaterials, impact the performance of the catalyst(s). Mo-lecular mobility of the catalyst should be high so that it cancontinue to exert its effect as the system reacts and buildsviscosity. Since the reactions are exothermic, the catalyticeffect should not be overly influenced by a rise in tem-perature.

All of these requirements are more easily met with the con-ventional, fugitive type amines rather than the newer reac-tive type amines. To address these challenges, the reactiveamines are normally used at significant higher concentra-tions, hence sometimes are not fully bound in the polymernetwork [21]. In addition, most of the reactive amines aremono-functional and can be considered as polymer chainterminators (which generally detracts from the ultimateproperties of the polymer). Dow active polyols are useful toovercome these challenges.

EXPERIMENTAL

A list of all raw materials used with this study is given inTables 2, 3 and 4 (SPECFLEX *, VORANOL *,VORANATE *, ISONATE * are trademarks of The DowChemical Company).

Table 2. List of raw materialsSPECFLEX NC 630 Polyether polyolSPECFLEX NC 632 “VORANOL CP 6001 “VORANOL CP 1421 “VORANOL 3137 A “SPECFLEX NC 700 SAN copolymer polyolSPECFLEX NE 150 MDI isocyanateVORANATE T-80 TDI isocyanate

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Table 3. List of catalystsTrademark SupplierDABCO NE-200 Air ProductsDABCO NE-1060 “DABCO 33 LV “DABCO BLV “DABCO VP 137 “DABCO T “TOYOCAT RX-20 TosohTOYOCAT RX-21 “PC-CAT HPI NitroilDMAMP-80 AngusNIAX A-1 CromptonJEFFCAT ZF-10 Huntsman

(DABCO* is a trademark of Air Products & Chemicals Inc;TOYOCAT * is a trademark of Tosoh Corporation; NIAX * isa trademark of Crompton Corporation; JEFFCAT * is atrademark of The Hunstman Corporation; PC-Cat * is atrademark of Nitroil Europe Handels GMBH; DMAMP-80* isa trademark of Angus Chemical Company)

Table 4. List of Dow Experimental Active PolyolsOH number Functionality EO capping

Polyol A 56 3 noAdditive A 56 <2 yesPolyol B 32 >3 yesPolyol C 32 >3 yes

Foam Preparation

Foam formulations are indicated with each section of thepaper. Bench scale molded foams were produced in a30x30x10 cm test block mold heated at 60°C using thestandard hand-mix procedure [22]. Free-rise foams werepoured in a card-board box.

Slabstock foams were either produced on a POLYMECHor on a VARIMAX machines. For MDI HR molding highpressure impingement mixing machines (KRAUSS-MAFFEI and CANNON) were used to pour foams in a40x40x10 cm standard test block mold and in a variety ofproduction seat molds.

Foams for the processability studies in low-density TDI-based HR molded foams were prepared in a Hi-Tech Engi-neering Model RCM-40 high pressure, impingement mix-ing foam machine. The machine was retrofitted with anAdmiral brand, L-type (10/14) mixing head. Two processstreams (isocyanate and polyol masterbatch) were used.Nominal throughput of the machine was 10 kg/min (22pounds/minute) at the component ratios necessary tomaintain a 105 isocyanate index for all foams made duringthis study.

Molded Foam Processing Tests

The protocol for testing foam processability factors havebeen described in detail [22] and will be further discussedbelow. A variety of heated aluminum molds of variousshapes were used to evaluate the processing characteristicsof both control and experimental foam formulations.

Foam Testing

Foam physical properties were determined in accordancewith ASTM, ISO, NF and major OEM’s (Original Equip-ment Manufacturers) testing procedures.

PVC Staining Tests

Accelerated aging tests at elevated temperature were car-ried out in closed containers in the presence of a PVC foil.A foam sample of 50x 50 x 25 mm was cut from the core ofthe foam part which had been isolated just after productionand was placed at the bottom of a 1 liter glass jar. A pieceof gray PVC skin, reference E 025 373A0175A, suppliedby Bennecke-Kaliko (Germany), was hung by the rim ofthe jar, which was then sealed. Aging was carried out at115°C for 72 hours. After cooling, the PVC sheet discol-oration was measured using a Minolta Chroma Meter CR210. The smaller the change in color, the lower the ∆ Emeasured in this test.

RESULTS AND DISCUSSION

Dow newly developed active polyols were tested in variousconditions with different technologies. The purpose of thiswork was to assess their performance and to define howthey can be formulated to reduce and in some cases elimi-nate amine catalyst use. Initial work had been concentratedon the performance of reactive amines offered by the vari-ous suppliers and on their combination with Dow’s activepolyols. In most cases it was found that these products gavegood compatibility with Dow active polyols and that, byallowing a reduction of their concentration in polyurethaneformulations, overall processing was improved.

Main results of this study are presented hereafter with vari-ous technical options. These are concentrated on flexiblefoams since these are the focus of this research program.Each foam technology will be reviewed and discussedseparately.

SLABSTOCK FOAM

Dow’s experience with slabstock foam has shown that mostcommon density range can be produced without the addi-tion of traditional amine catalyst. Experimental Polyol Acan be used alone to provide a smooth rise profile for lowdensity (16kg/m³) formulations using all-water blowing.Rise rate of such formulation is identical to that of tradi-tional amine catalyst blown formulations (Figure 1). Addi-

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tive A was used, together with Polyol A in formulations,especially those with low water level, where more blowingis necessary. Figure 2 illustrates rise rate comparison of 3.7PHP (parts per hundred parts of polyol) water formulationswith the new active Polyol A. With tuning of additive A, arise rate similar to that of traditional amine catalyst can bereached.

Figure 1. Rise profile of 6.5 water formulation

Figure 2. Rise profile of 3.7 water formulation

Foams made with these new experimental polyols haveidentical physical properties with that of traditional amineblown foams, as can be seen in Table 5.

Table 5. Slabstock foam: Formulation and foamphysical propertiesFoam formulations A B C DTDI INDEX 115 115 110 110

VORANOL 3137A 100 100

Exp.POLYOL A 100 99.3

Exp ADDITIVE A 0.7

WATER 6.5 6.5 3.7 3.7

DABCO DC-5160 1.2 1.2 1 1

DABCO BLV 0.12 0.15

DABCO T-9 0.15 0.15 0.21 0.21

ReactivityCream Time (sec) 13 13 12 12

Rise Time (sec) 90 91 101 103

Foam physical propertiesCORE DENSITY (kg/m3) 16.8 17.6 26.9 26.6

90% COMPRESSION SETS CD (%) 9.7 11.2 2.4 2.8

TEAR STRENGTH (N/m) 227 227 315 315

ELONGATION @ BREAK (%) 68 66 107 109

TENSILE STRENTH (Kpa) 85 91 90 92

IFD HARDNESS (N)

Mean Load at 25% Deflection 201 211 203 193

Mean Load at 65% Deflection 381 399 366 354

Mean Load at 25% Return 110 114 141 135

Mean Modulus 1.89 1.89 1.80 1.83

RESILIENCY (%) 21 32 41 42

Foams made with experimental Polyol A were tested forPVC staining after production in order to detect any amineemission. No staining was observed. In conclusion, it isfeasible to consider that a slabstock foamer may in the fu-ture produce foam by just mixing polyols, water, surfactantand isocyanate.

MDI HR MOLDING

An emphasis has recently been put on elimination of amineemission in MDI based HR molding while maintaininggood humid aging resistance. Severe tests, such as BMW’s,VW-Audi’s, Volvo’s, Opel-GM’s are already challengingwhen using conventional catalysis, as it has been describedin previous articles [1,23]. The situation becomes moredifficult when using reactive amine catalysts for the fol-lowing reasons:1) The catalyst level has to be increased in the formulationto maintain equivalent reactivity. Since these reactivecatalysts are tied up in the polymer, they tend to disrupt itsomewhat.2) The gellation profile is changed when strong, fugitivecatalysts such as TEDA (Triethylenediamine) are replacedwith reactive amines. Hence the polymer build-up isslowed down or at least made differently.3) With the high concentration of tertiary amines in thepolymer chain there is always a possibility of retro-reaction, or chemical degradation, upon foam exposure to acombination of heat and moisture. Indeed polymer mor-

6.5 Water Formulation

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0 20 40 60 80 100 120 140Second

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Rise Rate , 3.7 Water Formulation

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0 20 40 60 80 100 120 140

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ate Dabco BLV 0.15 pphp

Exp. Polyol A + Add. A 0.7 pphp

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phology changes induced by accelerated aging are alreadyreported with conventional foam systems [24].

The present work was focused onto the use of ActivePolyol B together with reduced amount of conventionalamines and/or reactive amines in order to meet VW-AUDI’s technical (T2524-03) and environmental (PVC staining)requirements. This program is still underway at the time ofwriting this paper. Initial results presented in Table 6 con-firm that HACS’s (Humid Aged Compression Set) valuesof < 15 % are easily met and PVC staining is minimized.More challenging is the HALL (Humid Aged Load Loss),or CFD (Compression Force Deflection) change at 40 %deflection after humid aging, specifications of (-25 <HALL % < + 10) when fugitive amines are removed. Foamdensity of the tested foams was purposely reduced vs the52 kg/m3 target to assess the limits.

Table 6. MDI HR moldingFormulation A A B B C C

VORANOL CP 6001 64 64 49 49 64 64SPECFLEX NC632 34 34 34 34VORANOL CP 1421 2 2 2 2 2 2Exp. Polyol B 49 49Water 3.7 3.7 3.7 3.7 3.7 3.7Niax A-1 0.12 0.12 0.06 0.06Dabco 33-LV 0.35 0.35 0.27 0.27Catalyst A 0.20 0.20Catalyst B 0.50 0.50Diethanolamine LF 0.60 0.60 0.60 0.60 0.60 0.60Tegostab B-8715 LF 0.50 0.50 0.50 0.50 0.50 0.50SPECFLEX NE-150Index 85 105 85 105 85 105

ReactivityGel time (s) 52 57 60 66 74 78

PropertiesMolded densitykg/m3

45.3 45.0 45.0 45.2 45.1 45.6

40 % CFD (Kpa) 3.3 6.6 3.8 7.8 3.7 6.8Airflow (cfm) 1.2 0.9 2.3 1.8 2.4 1.850 % CS (%) (CT) 3.2 4.6 5.4 8.0 6.4 7.4Humid aging50 % HACS (%) 7.5 11.9 7.5 10.7 8.9 9.5CFD change 4th

cycle (%)18.4 20.7 23.7 26 24.5 30.1

PVC staining

∆ E 5.5 1.2 0.3 2.9 0.3 0.7

TEGOSTAB* is a trademark of Goldschmidt A. G.

All foam physical properties were measured according toVW’s PV 3410 test methods. Catalyst A is N,N,N’-Trimethyl N’-Hydroxyethyl-bis-Amino Ethyl Ether andCatalyst B is 2-Hydroxypropyl Imidazole.

Dual-Hardness molded parts have been produced with ac-tive polyols and based on formulations similar to the onegiven in Table 6 without any difficulties. Square pads werealso made with 100 parts of Polyol B and no catalysts withdemolding times between 4 and 5 minutes, depending onthe isocyanate index. Foam properties were found similarto the ones shown in Table 6 with Formulation C.

T-80 HR MOLDING

For introduction to the TDI-based HR molded foam mar-ket, we targeted Active Polyol C that would allow foamproducers to lower their added catalysts levels by 50%. Wereasoned that this would significantly reduce worker expo-sure and lead to foam processes and products with muchless volatile emissions.

Improvement, or at least equivalence, in both foam proc-essing and physical properties is important for the commer-cial success of any new product. Data demonstrating theperformance of a molded foam grade of active polyol inthese areas will be presented using the formulations givenin Table 7. Note that for comparison purposes, we includeda formulation based on the control polyols but at 50% re-duced catalysts. At nominal packing levels, this formula-tion typically gives molded foams at a core density of 32kg/m3 (2.0 lb/ft3).

Table 7. Formulations for low-density TDI HR moldedfoams.

ComponentControlAt Full

Catalysts

ControlAt 50%

Catalysts

ActivePolyol CAt 50%

CatalystsSPECFLEX NC 630 62.5 62.5Exp. Polyol C 62.5SPECFLEX NC 700 37.5 37.5 37.5Niax Y-10184 1.2 1.2 1.2Diethanol Amine, pure 1.6 1.6 1.6Dabco 33-LV 0.35 0.17 0.17Niax A-1 0.08 0.04 0.04Water 4.2 4.2 4.2

VORANATE T-80 Index 105 105 105

Masterbatch Viscosity,mPa s at 25°C

3450 3700 3600

Also listed in Table 7 is the resultant masterbatch viscosityfor each formulation. The masterbatch is that premixture ofingredients that will be combined with isocyanate in themixing head in order to cause a foam producing reaction tobegin. High viscosity here makes it difficult for the foammachine to accurately meter, mix and dispense the foamproducing chemicals. A practical limit for many commer-cial foam machines is taken as 5000 mPa s. The formula-tion based on the new Active Polyol C is comparable to thetwo control formulations and well below the stated limit.

Foam Processing

The ability to benchmark important factors related to howwell a foam formulation will process on foam makingequipment is helpful in the development and commercialintroduction of new products. With Dow’s in-house facili-ties and testing capabilities, candidate products undergorigorous testing for the following list of processability fac-tors.

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Table 8. HR foam processability factorsMasterbatch ViscosityFree-Rise Bulk StabilityIn-Mold FlowabilityVent StabilityRise ProfileShrinkageForce-to-CrushCure

Foam Stability

The production of defect-free molded foam parts requiresthat the candidate foam system possess an adequate level ofstability through each stage of the foam reaction. The dif-ficulty of maintaining adequate stability has increased asfoam density has decreased and part designs have gottenthinner and more complex in shape.

Free-Rise Bucket Foams

An easy way to measure overall stability of the bulk foamis the free-rise bucket test illustrated in Figure 3.

Figure 3. Free-rise bucket test for bulk stability.

In this test, a 22.7-liter (five imperial gallons) plasticbucket receives a shot from the foam-dispensing machine.The shot size is sufficient to totally fill the bucket with anapproximate 10-centimeter (3.9-inch) crown of foam abovethe top of the bucket. Typical data recorded would includetime to reach the top of the bucket, maximum and finalfoam height and an internal foam stability rating.

The internal stability rating is obtained by cutting the curedfoam in half (parallel to the direction of rise) and rankingthe severity of voids on a 1 to 10 scale. A perfect foamwould receive a 10 rating while a collapsed foam would berated at 1. This grading is easily done by visual comparisonof the candidate foam to a series of similar foams with pre-

viously established ratings. The data in Figure 4 show thatall three foam formulations from Table 7 perform excellentin this test.

PassFail

ControlAt Full

Catalysts

ControlAt 50%

Catalysts

Polyol CAt 50%

Catalysts

0123456789

10 9.5 9.5 9.5

Free Rise Stability, Blair UnitsTypical

Figure 4. Comparative free-rise stability performance.

Figure 5. In-mold flowability test.

In this test, the mixture is dispensed into one end of a 38.1x 76.2 x 6.3 cm (15 x 15 x 2.4 in) heated mold and pur-posely forced to flow over three rounded humps on its wayto the vent holes at the opposite end of the mold. Thisstresses the growing foam and allows for comparison ofcandidate polyols on the basis of area percent voids on theshow surface of the foam pad. Data for the current studyare presented in Figure 6.

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Polyol CAt 50%

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Development Standard

0123456789

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4

40

1

Flowability, Area % Voids

Figure 6. Comparative flowability performance.

In this test, the control foam with the full level of addedcatalysts performs well below our internal developmentstandard of no more than 10 area percent voiding. Drop-ping the catalyst levels of the control foam by 50% resulted

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in the formation of voids over forty percent of the foam’sshow surface. Active Polyol C at a 50% reduced catalystsloading performed better than the fully catalyzed control.

Vent Stability

Another common location for voids in a molded foam padare those areas immediately below or adjacent to the ventdevices. The data in Figure 7 were obtained by inspectionand measurement of voids appearing below the vent holesin a simple 38.1 x 38.1 x 11.4 cm (15 x 15 x 4.5 in) heatedtest block mold. The vents for that mold were 1.6 millime-ters (1/16 inch) in diameter and were arranged in a tradi-tional five-hole pattern on the lid of the mold.

FailPass

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Polyol CAt 50%

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Development Standard

0123456789

1024 58 26

4.2

7.2

2.3

Vent Collapse, cm² per vent

Rise Time, sec.

Figure 7. Polyol C vent stability results.

The development standard we use is that no foam formula-tion should demonstrate more than 5 square centimeters ofvoid area per vent. Above this level, the voids become eas-ily detectable without cutting into the foam. For the presentstudy, the control foam at full catalysis just meets this crite-rion. At the 50 percent reduced catalysts level, the controlformulation is well into the unacceptable range of perform-ance. Active Polyol C shows an improved level of per-formance.

Also shown in this figure are the rise or mold fill times foreach formulation. This number was recorded as the time forthe first extrusion to be visible through the center vent hole.Twenty-four seconds is very typical for the fully catalyzedcontrol formulation and that is matched nicely by the for-mulation containing Active Polyol C. The practical concernhere is that any new formulation component not cause afaster rise time since most commercial foam plants havesome limitations on how fast a mold lid can be closed andlocked. Also, the rise time should not be so slow as for theother control formulation, so that the foam won’t still berising (and still be weak) as the molds go bumping alongdown the conveyor line.

Foam Tightness

The overall moldability of a foam is often said to be betterwith a tight formulation than a more open one. One conse-quence of running a tight formulation is the danger of foamshrinkage if the cell-walls are not adequately opened in afoam crushing event. The concern here is that the foamsurvive that crushing event without losing physical dimen-sions or bursting apart. If the foam is too tight, the internalstress forces during crushing may exceed the tensilestrength of the fresh foam resulting in a physical splittingapart of the foam pad as it goes through the crushing de-vice. This gross splitting results in a foam pad that must bescrapped. Comparison of relative shrinkage and force-to-crush performances are often useful in the development ofnew molded foam technologies.

Shrinkage

Our test scenario for measuring shrinkage in a standard testblock of molded foam is illustrated in Figure 8.

Figure 8. Shrinkage testing.

In this test, foams are prepared in the normal manner, care-fully removed from the mold and allowed to standuncrushed overnight. The foam pad is then cut through thearea of maximum vertical shrinkage, measured for mini-mum thickness and a percent shrinkage number calculated.Comparative data for the present work is presented in Fig-ure 9.

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Shrinkage, %

Figure 9. Comparative shrinkage performance.

At the full catalyst levels, the control formulation performsat a shrinkage level that we consider to be an upper limit.With numbers above 50%, we have found that some com-mercial foamers have trouble running thicker foam padsthrough their crushing equipment. Shrinkage performanceof experimental Active Polyol C is quite acceptable.

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Force-To-Crush

A useful laboratory test for comparing relative foam tight-ness is the so-called Force-to-Crush test. Our version ofthis test scenario is illustrated in Figure 10.

Figure 10. Force-to-crush test.

In this procedure, a foam is prepared in the normal manner,cured for the desired time and then removed from the mold(usually the standard test block mold) with care. Theuncrushed foam pad is then quickly placed in the forcemeasuring machine and deflected to 50% of its originalthickness. Initial peak load and load decay are the basicdata available. Figure 11 presents the initial peak load datafor the present study. Foam based on the Active Polyol Cfalls nicely between the two control foams and all foamstested were well below any level of concern.

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1,000

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467

Force-To-Crush, N/323 cm2

Figure 11. Comparative force-to-crush results.

Cure

For a new polyol to be commercially viable, it must con-tribute to an adequate level of foam cure at several criticalpoints in the manufacturing process. Table 9 presents somepractical examples of why foam cure is an important per-formance feature.

Table 9. Practical examples of foam cure.Judged At Affecting

Mold Fill Bulk Stability and FlashPart Demold Station Green Strength and FingerprintingCrusher Station Hot SetShipping Station Short Term Static Fatigue

The extent of cure at the moment of mold fill directly af-fects the amount of polymer that escapes the mold throughthe venting devices and parting line. If this is excessive,valuable material is wasted and additional pad trimmingand cleanup labor may be needed.

At the demold station, the foam must have enough greenstrength to resist tearing and fingerprinting due to humanhandling. These imperfections can usually be repaired off-line at some additional expense.

Another measure of cure comes after the foam leaves thecrushing device. A poorly cured foam may densify and losea few millimeters of its height dimension. Wrinkles mayalso appear on the exterior of the pad, further detractingfrom its cosmetic appearance. Similar events may occur atthe shipping station when multiple pads are compressedinto a shipping container for delivery to the seat assemblyplants. A foam with inferior cure may exhibit a permanentloss in physical dimensions when removed from such ship-ping containers. The cure testing scenario used for thiswork is shown in Figure 12.

Pour Cure Demold

Figure 12. The hot set cure test.

In this test, foam pads made in the normal way are dis-pensed into a 38.1 x 76.2 x 6.3 cm (15 x 30 x 2.5 in) heatedmold. After a 6 minute cure cycle, the foam pad was de-molded and immediately roller crushed at a gap setting of1.27 cm (1/2 in). The pad was then placed in the indenterjig where four indenter feet regionally deflect the foam tovarious residual thicknesses. Four replicate pads are testedat different deflection times and a final cumulative percent

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hot set calculated. Data for the present study are presentedin Figure 13.

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145

267 240

Cure, % Hot Set

Figure 13. Comparative cure performance.

The control foam based on the high-functionality polyol,SPECFLEX NC 630 at a full catalyst level shows its typi-cal outstanding cure performance. Lesser, but still veryadequate, levels of cure were seen with reduced catalystlevels in both the control and Active Polyol C based foams.

Foam Physical Properties

All foam pads were thoroughly tested for physical proper-ties according to G.M. test methods. Of particular interestare the load-bearing and compression set performances ofthe new Active Polyol C versus the control foams. Datacomparing the 65% IFD (indentation force deflection) per-formance are presented in Figure 14.

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Typical Performance

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327

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65% IFD, N/323 cm 2

342

Figure 14. Comparative loadbearing performance.

Foams of this density grade and copolymer polyol levelwill generally give a 65% IFD in the range of 300 New-tons. Reducing the catalyst levels in the control foam gavethe expected increase in loadbearing. Foams based on thenew Active Polyol C were approximately 5% harder thanthe fully catalyzed control foam.

Compression set data are presented in Figure 15. The fig-ure shows the results for testing both the regular and thehumid aged 50% Cd set. These foams fall within the Gen-eral Motors Class C foam group and the typical specifica-

tion values shown are taken from General MotorsEngineering Standards Document GM6293M.

Humid Aged Set

Regular Set

Typical Specfor Reg Set

Typical Spec forHumid Aged Set

Fail

Pass

Fail

Pass

ControlAt Full

Catalysts

ControlAt 50%

Catalysts

Polyol DAt 50%

Catalysts

0

10

20

30

40

50

15

1012

1713

16

50% Cd Compression Set, %

65 93 54Airflow, l/min

Figure 15. Compression set performance.

Historically, compression set specifications have been amongthe most difficult to meet. All three foam systems easily metthe requirements of both the regular and humid aged specifi-cations. Considering that compression sets usually respond toimprovements in airflow, it seems logical that even betterperformance for the Active Polyol C based foams will be pos-sible with formulation fine tuning.

The remaining foam physical properties were consistent withthose expected for a 32 kg/m3 (2.0 lb/ft3) core density moldedfoam based on TDI. Figure 16 presents a summary of foamphysical properties wherein the performance of the ActivePolyol C based foam is compared to that of the fully catalyzedcontrol foam.

LoadbearingRegular CS

Humid Aged CSTensile

TearElongationResiliency

Airflow

15-15 10-10 25-25 0 20-20 5

5

20

6

7*

8

17

-5

Foam Properties Worse BetterSame

Percent Change Relative To Control* Still 150%Above specification

Figure 16. Performance features of active polyol versusfully catalyzed control foam.

In this format, the data is intended to show, for example, thatboth compression sets are improved, as is the tear strength.The tensile strength of the experimental foam was 7% worsethan the control but both foam systems were at least 150%over the minimum specification requirement for foams ofthis density. Elongation and resiliency performances wereidentical. Airflow in the experimental foam was 17%lower indicating a need for further formulation fine tuning.This formulation work is underway and current developmentsare confirming that total elimination of bis- (2-Dimethylaminoethyl) ether, causing halovision (7),should be feasible.

10

CONCLUSION

The present paper has demonstrated that amine emissionscan be drastically reduced and even eliminated from flexi-ble polyurethane foams through the use of new Dow activepolyols combined or not with reactive catalysts.

Further development of active polyols and adjustment offormulations are underway at Dow with the aim to giveseveral options to the polyurethane industry to eliminateamine emissions. Volatile and odor tests, not reported here,are being carried out routinely to make sure these programsare giving the desired outcomes.

The next step is the reduction of other volatile and foggingcomponents in overall formulations in order to support thepolyurethane industry’s strive to very low emissions and tomeet new stringent OEM’s specifications.

ACKNOWDLEGEMENT

The authors wish to thank their many Dow colleagues whohad a role in generating the data presented in this paper.Special thanks are extended to Alain Bleton, Lance Coo-per, Richard Elwell, Olga Milovanovic, Chris Noakes,Olivia Renevey, Alan Schrock, Mark Sonnenschein, An-toine Storione, Ross Polk, Eve Taylor, Mary White, andthe Meyrin and Freeport foam testing laboratories person-nel.

BIBLIOGRAPHY

1. Broos R.; Casati F.M.; Herrington R.M.(1999), “En-durance of Polyurethane Automotive Seating Foamsunder Varying Temperature and Humidity Condi-tions”, Journal of Cellular Plastics, Volume 36 – May2000, 207-245

2. Casati F.M.; Broos R.; Herrington R.M. ; Miyazaki Y.(1997), “Tailoring the Performance of Molded Flexi-ble Polyurethane Foams for Car Seats”, Proceedings ofthe 1997 SPI Polyurethane World Congress”, Tech-nomics: Lancaster, PA., 402-420

3. Casati F.M.; Herrington R.M.; Broos R. ; Miyazaki Y.;Phan Thanh H and Cadolle D.; (1998) “AutomotiveSeating Foams: Improving their Comfort and Durabil-ity Performance”, “Proceeding of Polyurethane the1998 SPI Polyurethane conference”; Technomics:Lancaster, PA., 417-431

4. Williams K.P.; J. Gerrard, D.L. “The Degradation ofPoly(Vinyl Chloride) Studied using Fourier-TransformRamam Spectroscopy” (1990), Eur. Polym. J., 26 (12)-1355-8

5. Wilson A.S.; Gerrard D.L.; Bowley H.J. “Problems ofInteraction Between Plasticised PVC and PolyurethaneFoam” (1987). Presented at PVC’ 87, Brighton, UK.,April 1987

6. Christfreund A.; Huygens E.; Eling B. “Amine-FreeCatalyst Systems for Automotive Instrument Panels”(1991), Proceedings of Polyurethane World Congress,Technomics: Lancaster, PA., 272-277

7. Polyurethane Amine Catalysts: Guidelines for SafeHandling and Disposal; Technical Bulletin AX173,November 2000; Alliance for the Polyurethane Ind-stry: Arlington, VA.

8. Dernehl C.U. (1966), “Health Hazards Associated withPolyurethane Foams”, Journal of Occupational Medi-cine, 8/2, 59-62

9. Belin L.; Wass U.; Audunsson G. and Mathiasson L.(1983), “Amines: Possible Causative Agents in theDevelopment of Bronchial Hypperreactivity in Work-ers Manufacturing Polyurethanes from Polyisocya-nates”, British Journal of Industrial Medicine, 40, 251-257

10. Bugler J.; Maddison P.; Hope S.J.; Mills I.G.; NuttA.R. and Wright M.D. (1992) Tertiary Amine andEthanolamine Catalysts in the Polyurethane Foam In-dustry: New Methods of Detection and Results of Per-sonal Sampling in Nine UK Flexible Foam Factories”,Cellular Polymers, 11/3, 171-200

11. Reed D. (1999), “VW aims to cut amines”, UrethanesTechnology, 16/4, 3

12. Boinowitz T.; Burkhart G.; Schloens H.H. (1999)“Emanations from Flexible Slabstock Foams – Signifi-cant Reduction of Emissions is Now Possible”, Pro-ceeding of Polyurethanes Expo 99; Technomics:Lancaster, PA., 283-287

13. Zimmerman R.L.; Renken T.L. (1988): “Low OdorReactive Amine Catalysts for Polyurethane Foams”,Proceedings of the SPI-31st Annual Techni-cal/Marketing Conference, Technomics: Lancaster,PA., 36-40

14. Mercando L.A.; Kniss J.G.; Tobias J.D.; Plana A.;Listemann M.L.; Wendel S.; “Non-Fugitive Catalystsfor Flexible Polyurethane Foams”, (1999) Proceedingof Polyurethanes Expo 99; Technomics: Lancaster,PA., 103-134

15. Kometani H; Tamano Y.; Masuda T.; Van Maris R.;Gay K.; (2000) “The Investigation of Amine Emis-sions from Polyurethane Foam”; Proceeding of Polyu-rethanes Conference 2000; Technomics: Lancaster,PA., 11-21

16. Rothe J.; Cordelair H.; Wehman C.; (2000) “NewCatalysts for Low VOC in Flexible Slabstock Foam”,Proceeding of Polyurethanes Conference 2000; Tech-nomics: Lancaster, PA., 109-116

17. Sikorski M.; Wehman C.; Cordelair H. (1999) “NewAdditive Solutions for Low VOC in HR MoldedFoams”. Proceedings of Polyurethanes Expo 99;Technomics: Lancaster, PA., 135-144

18. Mapleston P; “Riding Comfort is a Focus of Automo-tive Foam Systems” (2001), Modern Plastics, March2001, 30-31

19. Broos R.; Sonney J.M.; Phan Thanh H.; Casati F.M.;(2000) “Polyurethane Foam Molding Technologies for

11

Improving Total Passenger Compartment Comfort”,Proceedings of the Polyurethane Conference 2000,Technomics: Lancaster, PA., 341-353

20. Malwitz N.; Manis A.; Wong S.W.; Frisch K.C.;(1986) “Amine Catalysis of Polyurethane Foams”,Proceedings of the 30th Annual Polyurethane Techni-cal/Marketing conference, 1986, Technomics: Lan-caster, PA., 338-353

21. Nutt A.R.; Skidmore D.W. (1987) “Recovery of Chlo-rofluorocarbon 11 by Activated Carbon Scrubbing ona Polyurethane Foam Slabstock Plant”, Cellular Poly-mers, Volume 6, 1987, 62-77

22. Herrington, R., De Genova, R., Casati, F. and M.Brown (1997), “Molded Foams, Chapter 11”, InFlexible Polyurethane Foams; Herrington, R. and K.Hock, eds., The Dow Chemical Company, Form No.109-01061, 11.1-11.41

23. Herrington R.M. and Klarfeld D.R. (1983) “HumidAged Compression Set Phenomena in All WaterBlown HR Molded Foams”, Proceedings of the 1983SPI Polyurethanes Conference, Technomics: Lancas-ter, PA., 177-182

24. Brasington R. and De Roeck H. (2000) “AcceleratedTesting for Durability Performance of AutomotiveSeating Foam”, Proceedings of the API 2000 confer-ence, Technomics: Lancaster, PA., 267-279

BIOGRAPHIES

François M. Casati

François M. Casati graduated from ICPI (F), now CPE-Lyon (Ecole Superieure de ChimiePhysique Electronique de Lyon), in1967. He has over 30 years ofexperience in Polyurethanes,Industrial Amines and Biocides, withS.N.P.E., Recticel, AbbottLaboratories, BP Chemicals and TheDow Chemical Company. Duringthat time he has held various

positions in Manufacturing, Marketing and Research &Development. He is currently a Product DevelopmentLeader, R&D, for the Flexible Foam business of Dow.

Ronald M. Herrington

Ron Herrington is a DevelopmentAssociate in the Polyurethane ProductsTechnical Service and DevelopmentLaboratory of The Dow ChemicalCompany in Texas. He received aBachelor’s Degree in Chemistry fromthe University of Houston in 1970. Hejoined Dow in that year and has sincegained wide experience in the fields ofslabstock and molded flexible foams.

Jean-Marie Sonney

Dr. Jean-Marie Sonney graduated from the Swiss Federal In-stitute of Technology in Lausanne (Switzerland) and receivedhis Ph.D. degree in physical organic chemistry from the same

institution in 1979. After a post-doctoral research fellowship at theUniversity of California, Santa Cruz,he joined the Geneva-based Researchand Development group of BPChemicals in 1981 and was transferredto the Dow Chemical Company in1989. During these years, he hadvarious responsibilities in the field ofAnalytical Chemistry, Quality

Assurance, EH&S and Quality Management. He is currently aproject engineer in the Development Group for MoldedFoams and Specialties with responsibilities for NVH applica-tions.

Johnson Tu

Johnson Tu is a Sr. DevelopmentSpecialist in the Research andDevelopment Group of The DowChemical Company in Freeport, Texas.He received a BS Science from theChengkun University in Taiwan in1983. He joined Dow in 1990 and hasheld several positions in R&D/TS&D

and new Business Development.

Henri Mispreuve

Dr. Henri Mispreuve graduated from theState University of Mons (Belgium) in1975 and received his Ph.D. in PhysicalOrganic Chemistry from the sameUniversity in 1979. In 1984, he joinedDow Europe S.A. in Horgen(Switzerland). He is currently responsiblefor Technical Service and Developmentof Polyurethane Slabstock Foams at thecompany’s International Development

Center in Meyrin/Geneva (Switzerland).

Alain Fanget

Alain Fanget joined the Geneva-basedPolyurethane Research andDevelopment group of Union CarbideEurope in 1978 and was thentransferred to BP Chemicals in 1979and to The Dow Chemical Company in1989 where he worked in various PUmoulding and ACES applications.

He is currently a Technical Service Specialist in the Automo-tive Thermosets R&D Group of the Meyrin International De-velopment Center, with specific responsibilities in seating andNVH moulding applications.

*

*Trademark of The Dow Chemical Company Form No. 109-01552-901QRP

For Additional Information:The Dow Chemical CompanyCustomer Information Group

P.O. Box 1206Midland, MI 48641-1206

Telephone (800) 441-4369Website: www.dow.com