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PLASTICS TECHNOLOGY SEPTEMBER 1991 5 7

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I I tions are on tap a t this year's polyurethanes meeting.

So far, glycolysis and the chopping and rebonding of scrap foam for carpet underlay have been the only commer- cially realized methods for recycling foam waste. Glycolysis has been limit- ed mostly to in-plant scrap where pro- duction wastes are placed in a batch reactor and transformed into a poly01 that is then used directly in the produc- tion of rigid foam. But as government and industry begin requiring the re- covery of CFC-blown insulation foams from old refrigerators and other dis- carded products, a process to either re- cover or totally destroy the CFCs in the foam will have to be developed.

One process that has shown promise in recovering blowing agents from PUR foams has been developed by Du Pont Canada. Du Pont will present results from pilot programs in Canada where appliances were dismantled, the polyurethane foam removed and crushed in a solvent system, and the CFC blowing agent recovered.

New equipment to degas PUR in- sulation panels and recover CFC-11 from old refrigerators and freezers will be discussed by Adelmann GmbH of Germany. The CFC recovery unit shreds foam waste in a gas-tight system, and the shredded parts are then spiral- fed into a high-pressure chamber. There, the foam waste is compressed, and the condensed water and pure CFC- 11 produced are drained and recovered. A condenser liquifies the absorbed gas and the residual air is purified by acti- vated charcoal filters, regenerated and released into the atmosphere. Adel- mann says the system is 99% efficient.

Dr. Gunter Bauer of Aalen, Ger- many, is among a group of industry lead- ers who think alcoholysis, a process that degrades polyurethanes to simple, low- molecular-weight products, could pro- vide an efficient answer to both polyurethane recycling and CFC re- covery. Bauer has used an experimen- tal alcoholysis process and continuous pilot plant in Germany to produce 2.2 lb/hr of polyol. Employing this system and waste from molding auto seats and RRIM parts at Ford AG in Cologne, Bauer was able to produce a poly01 that was later combined with fresh poly01 to produce rigid PU foams and RRIM ma- terial. According to Bauer, the recy- cled poly01 had a water content of 0.1% and 0.5% aromatic amine content. Dr. Bauer says he made discontinuous slab-

58 PLASTICS TECHNOLOGY 0 SEPTEMBER 1

stock with good properties, using a 50/50 combination of fresh primary poly01 and recycled poly01 and also with 100% recycled poly01 at an isocyanate in- dex of 200.

A technique that uses hot stamping or thermoforming to process recycled auto interior foams, is slated to be dis- cussed by Phoenix AG of Hamburg, Germany. After the urethanecontaining parts are dismantled and the foam is sep arated from the other components, it is

The 1991 session is no exception, plac- ing a major emphasis on this and close- ly related topics.

HCFCs appear to be the most promising replacements for CFCs in rigid PURfoams. Yet it is acknowledged by industry insiders that these present only a stopgap measure and, because of their chlorine content and pending re- strictions limiting their use, do not offer a long-term remedy to the depletion of the ozone layer. In an effort to develop

more than a temporary solution, a number of different chemistries have been tried as alternatives to chlorine- based blowing agents.

BASF AG in Ludwigshafen, Ger- many, has developed a procedure to emulsify perfluoroalkanes such as per- fluoro-pentane and perfluoro-hexane in polyols and produce foams by vaporiz- ing the emulsified droplets. BASF says the foams have reaction kinetics similar to conventionally blown foams, very fine

cells and low thermal conductivity. Investigation into fluorine chem-

istry is also reflected in work done by the Polyurethane Div. of Bayer AG (parent of Mobay) in Leverkusen, Germany. Bayer has developed a chlorine-free hex- afluorobutane blowing agent and insu- lation gas that is claimed to be non-ozone-depleting. The product re- portedly has a short atmospheric life- time, is nonflammable, has low gas-phase thermal conductivity, and is compatible with appliance inner-liner plastics.

THE COMPATIBILITY ISSUE The last point is an important one,

as finding a CFC-free foam/therino- plastic combination that works well in refrigerator liners is proving more than a bit difficult. This is a much-discussed topic at the 1991 Congress, with suppli- ers telling about their efforts to devel- op materials compatible with the new crop of alternative blowing agents.

HCFC-123 and HCFC-141b are con- sidered by most industry insiders to be the closest “dropin” substitutes for CFC- 11 in refrigeration foams. Carbon diox- ide (water-blown) has also been thought to be a possible CFC alternative. But all three have been found to be more ag- gressive than standard CFCs against thermoplastics like ABS and HIPS used in refrigerator liners. At their facilities in Belgium, Monsanto Europe and IC1 Polyurethanes have teamed up to find materials compatible with HCFC-123 and HCFC-l4lb, both known to cause stress-cracking of refrigerator liners.

Testing foams blown with HCFCs and with COz in contact with HIPS, ABS and a high-acrylonitrile barrier resin, the companies found ABS to offer between three and four times better resistance to COz than HIPS.

Using Monsanto’s Lustran 723 ABS with HCFC-l4lb, researchers found the material’s tensile properties remained unchanged after exposure to foam and thermocycling. Adding a coextruded layer of Lustran 732 ABS on the foam side of the liner offered even better

The trend in Detroit is toward larger exterior auto parts made with polyurea RIM systems. Additives such as ketimines and secondary polyether amines can increase these systems’ flowability while giving processors greater control over reactivity and product properties. (Photo: Mobay)

protection from systems blown with 141b, the team says. HCFC-123, which has been found to cause more severe cracking in liners than HCFC-l4lb, was tested against a liner made from a co- extruded blend of 70% Lustran 723 and 30% Lustran 732, resulting in good stress-crack resistance and good foam adhesion, IC1 and Monsanto report.

In similar work, Dow Europe in the Netherlands and Dow Plastics USA have found that either using a propri- etary polyolefin film barrier laminated to the ABS liner material, or a foam made with the company’s experimen- tal X2-88061.0 polyol, completely elimi- nates cracking of the liner by contact

A joint effort between the Polyurethane and Polystyrene Divs. of Enichem Polimeri, Marghera, Italy, has devised a method that seems to over- come the problem of HCFCs 22 and 123 chemically attacking refrigerator liners. The process combines HIPS and poly- olefins laminated or coextruded onto a polyethylene film barrier layer. Good ad- hesion of the materials to the foam in- sulation is accomplished by corona treatment, Enichem says.

Also discussing “promising” barri- e r materials for refrigerators at the conference is BASF, though details were unavailable at press time.

Other nagging issues in refrigera- tion foams are thermal conductivity and foam physical properties. While many suppliers see C02 as the alternative that will ultimately receive the most widespread use in rigid foams, some feel it’s probably not suited for use in re- frigeration because of its detrimental ef- fect on a foam’s K-factor. But HCFCs 123 and 141b can also have a negative affect on K-value because they have higher vapor-phase thermal conductiv- ities and increased solvent properties, leading to reduced thermal insulation capability and poorer strength and d e molding characteristics than are pro- vided by all-CFC systems.

In one approach to the problem, Air Products and Chemicals has developed a new, modified silicone surfactant for HCFC-123 and HCFC-141b blown rigid foam systems that reportedly enables the production of finer-celled foams with significantly improved K-values. Like- wise, Union Carbide says it has identi- fied selected silicone copolymer surfactants that yield finer foam cell structure to balance the higher thermal conductivity and plasticizing effect of

with HCFC-123.

PLASTICS TECHNOLOGY 0 SEPTEMBER 1991 59

’ HCFC-123. ~ Alternatively Mitsui Toatsu Chem-

icals of Japan tells of a new polyol that reportedly results in HCFC-blown re- frigeration foam with thermal insulation and physical properties equivalent to those blown with CFC-11. Mitsui says the key is introduction of an aromatic ring ester group or amide group into the polyol. The result is a rigid polyurethane that is virtually incompatible with CFC substitutes and does not allow any pen- etration by the blowing agents. This for- mulation results in foams with higher compressive strength and elimination of the negative effect HCFCs have on thermal insulation properties and low- temperature dimensional stability.

Both Mobay and Dow Mitsubishi Kasei Ltd. of Japan say they have de- veloped microcellular HCFGblown ap- pliance foams that reportedly provide demolding characteristics and thermal insulation properties equal to or better than those of commercial CFC-11 blown foams. Similar foams were introduced by Mobay at last year’s urethanes con- ference in Orlando, Fla. Those foams suffered from high densities and ex- tremely long demolding times due to their reduced strength caused by few- er urea groups and the HCFC’s soften- ing effect on the polymer. Newer foams from Mobay and Dow reportedly over- come those problems by combining new, proprietary polyols with tertiary amine catalysts and silicone surfactants, resulting in foams with low thermal con- ductivity and good demold properties.

NEW INSULATION SYSTEMS A CFGfree technology for produc-

ing insulation panels has been devel- oped by foam processor, Recticel NV of Wetteren, Belgium. The company’s new foam is blown with what Recticel calls LBL 2, based on 2-chloropropane. LBL2 has thermal conductivity 15 times higher than CFC-11 and 20 times high- e r than COa. Its main advantage, though, is environmental-it reported- ly has an atmospheric lifetime of only nine months, vs. 60 years for CFC-11, and its global warming potential is just 1% that of CFC-11, Recticel says. Exten- sive reformulation is required to sub- stitute LBL 2 for CFC-11, the company says, but with LBL 2,40% less blowing agent is required.

Seven low-viscosity, low-hydroxyl- value polyols for use in high-water, re- duced-CFC rigid insulation foams are new from Rhone-Poulenc Canada. The

60 PLASTICS TECHNOLOGY 0 SEPTEMBER 1

new polyols-four neutral sucrose types, a sucrose amine, a 700-M.W. glyc- erine propoxylate and a propoxylated mannich adduct-were tested on three non-CFC formulations and compared to a 100% CFC-blown system. In each for- mulation, properties were almost iden- tical to t he all-CFC formulation, Rhone-Poulenc says. Adding a portion of the propoxylated mannich adduct to the formulation in place of 40% of the usual CFC reportedly contributed finer cell structure and improved surface quality. Addition of 30 pbw of the adduct plus a 3000-M.W. triol to the COz-blown formulation increased cell formation in the foam’s softer segments and mini- mized demold time. This system also had 25% poorer thermal insulating per- formance than the all-CFC system.

Still-developmental polyols are also the key behind technology from Shell Chemical Co.’s Research Center in Bel- gium, designed to produce pipe insula- tion foams blown with systems combining water with HCFCs 141b and 142b. The developmental polyols provide slightly improved thermal conductivity over water-blown systems, Shell says.

DETROIT PUTS BRAKES ON CFCs Ford Motor Co.’s recently an-

nounced plan to eliminate 90% of CFC use from its seating and interior-trim production by the end of next year, and 100% elimination in 1993, is just one sign of the active development of non-CFC technologies for automotive use (see

Urethane suppliers are finding that systems blown with HCFCs or water

can achieve nearly the same thermal insulation values as CFC-blown foams.

-0 I 21 P l l

PT, June ’91, p. 186). A new way of producing low-densi-

ty, MDI-based seating foams without CFC-11 has been devised by Dow Eu- rope in the Netherlands. Density re- duction was achieved by increasing water levels to 3.7 pbw and modifying the MDI component so the foams meet or exceed most automotive specifica- tions for all-MDI foams. The substitu- tion of water for CFC, however, affects the foam’s reaction kinetics, morpholo- gy development and mechanical prop- erties because water continues to react with the other components after the foam’s cells open and the foam gels. By increasing the amount of 2,4MMDI in the formulation, Dow has been able to delay cell opening, resulting in slower viscosity build-up and improved flowa- bility around the mold, resulting in all- MDI foams that meet automotive standards requiring a molded density between 2.5 and 3.7 pcf, demold time of 3-4 min., elongation of 110140??, and load-bearing potential of 0.3-1.45 psi. However, Dow warns, the higher 2,4- MMDI content also leads to a reduction in hardness.

Bayer in Germany discovered that

adding small amounts of an inorganic salt to standard polyether polyol, to- gether with a special TDI-based iso- cyanate, can reduce the hardness of hot-cure, all-water-blown seating foams to a level the company says could p r e viously only be achieved in “supersoft” foams blown with a combination of CFG 11 and carbon dioxide.

In an attempt to overcome the prob lem of water-blown systems resulting in poor skin and inferior foam properties, Olin Corp., Stamford, Conn., has devel- oped a series of polyether polyols with carboxylic acid groups directly grafted onto their chemical backbones. These polyols reportedly have a built-in blow- ing capability. The acid reacts slowly with the isocyanate, causing the center of the foam to become hotter than the outside, Olin says.Therefore, less blowing occurs on the surface, resulting in the formation of a skin that, because of a cold mold and

Source: Phoenix AG

higher stream temperature, is of better quality than skins produced from water- blown systems. Initial applications for this technology have been in shoe soles, but Olin says it hopes to extend the technology to other integral-skin foam applications such a s auto steering wheels, headrests and armrests.

More than one paper at the confer- ence deals with innovations for steering- wheel production. One from Dow Italia presents technology for water-blown foams with strong physical properties, despite not having an integral skin.

Meanwhile, researchers at Eni- chem’s Polyurethane Div. in Italy have found an unusual way to achieve eco- nomical demolding and cycle times for integral-skin foams blown without CFCs. Using rotational molding tech- nology, Enichem has produced all-wa- ter-blown, low-density foams that would be suitable for complicated parts such as headrests and crashpads.

A non-CFC foam-in-fabric technol- ogy originally designed for seats has now been found to work well in head- rests and armrests. Hyperlite foam is based on a polymer poly01 from AC West Virginia Poly01 Co., a new sub- sidiary of Arc0 Chemical Co. resulting from the company’s acquisition of Union Carbide’s urethane business. Hyperlite isTDI-based foam that reportedly offers advantages in potential density reduc- tion and ability to produce parts with a wide firmness range. The foam-in-fabric system gels quickly to minimize pene- tration of foam into the fabric backing and allows rapid demolding.

NEW MATERIALS FOR RIM As plastic auto exterior body pan-

els get larger, suppliers of PUR RIM ma- terials have been working to increase the dimensional stability of their mate- rials through the use of reinforcing fillers. A critical factor for these large parts is using a filler that does not ad- versely affect surface quality or “dis- tinctness of image” (DOI). Sumitomo Bayer Urethane Co., Ltd. of Japan, a sub- sidiary of Bayer AG, reports that milled glass and classified mineral fibers 30-40 microns in length and less than 5 mi- crons in diameter give outstanding sur- face quality while supplying sufficient reinforcement.

Research by BASF AG has shown that incorporating secondary polyether amines in a polyurea RIM system con- taining ketimines results in increased flowability of the system compared with

PLASTICS TECHNOLOGY 0 SEPTEMBER 1991 61

polyurea/amide RIM and conventional polyurea systems. For automotive mold- ers this means greater control over re- activity and product properties and the ability to mold larger exterior parts. BASF says these systems result in bet- ter elastomeric properties and tear re- sistance than polyurea/amide RIM materials, but still provide the superior heat resistance of the polyurea/amide RIM.

CFCs AND FLAME RETARDANCY Reducing CFC levels in rigid foam

insulation reportedly has caused man- ufacturers some difficulty in meeting flammability requirements, and only the most efficient flame retardants seem to work well enough to be considered. One such flame retardant i s dimethyl- methylphosphonate (DMMP), says Al- bright &Wilson. However, as long as even a small portion of CFC is retained in the formulation, questions have arisen regarding the side reactions be- tween DMMP and CFCs.

Albright & Wilson will discuss the benefits of its new Amgard V490, an 18.6%-phosphorus, halogen-free liquid said to provide the same properties as DMMP, and which is mixable with poly- ols, MDI and organic solvents. The com- pany says the new flame retardant is nonreactive with CFC and remains sta- ble when used in both one and twocom- ponent systems, eliminating formation of undesirable methylated byproducts. In reduced-CFC systems, Amgard V490 reportedly provides a marked viscosity reduction.

Standards regulating flammability of flexible furniture foams have become more stringent over the past few years, leading to more complex formulations with, in some cases, attendant process- ing complications. In Nice, Olin Corp. will report on what’s said to be a novel, easier-to-process polyol system for flame-resistant flexible foams. The sys- tem is based on an undisclosed, con- ventional poly01 of 3000 M.W. The new system, which reportedly meets the

most stringent fire standards, can be used with as little as 20 phr of melamine along with a liquid chlorinated monophosphate or diphosphate ester, Olin says. Conventional silicone surfac- tants and other catalysts can be used, and Olin says physical properties of the resulting foams are improved. Com- pression sets reportedly are lower and tensile and tear strengths higher than in other flame-resistant HR foams.

Halogenated phosphate esters and aromatic hydrocarbons such as pentabromodiphenyloxide are probably the most widely used flame retardants in flexible polyurethane foam, experts say. But these products are not without their faults, frequently having negative effects on processing and the final phys- ical properties of the foams produced. Hardness is reduced, compression set soars, and in many cases high fogging occurs.Th. Goldschmidt AG in Ger- many has developed a proprietary flame retardant additive for flexible foams said to limit the adverse affects on process-

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ing, mechanical properties and fogging that can be observed with common FR agents such as phosphate esters and halogenated aromatics like pentabro- modiphenyloxide. The new additive, which Goldschmidt will not identify, reportedly allows 15-35% reduction in the use of these other additives in con- ventional foam systems with little or no other adjustments to the formulation.

Reduced levels of FR additives in flexible polyester slabstock are said to be possible with a new generation of sil- icone surfactants from Union Carbide. The surfactants reportedly provide im- proved foam processability, reduced emission of volatile compounds during manufacturing and fine, open foam with- out pinholes and with minimum prop erty gradients in flat and round block operation.

NEW CATALYSTS FOR FLEXIBLES In the same presentation, Car-

bide is expected to talk about new low- odor amine catalvsts with Drocessing

characteristics as good as the current crop of highly volatile compounds. They are highly catalytic, so they can be used at low levels, and have low va- por pressure.

A separate research effort at Union Carbide has produced a new blocked amine catalyst that reportedly has a high

degree of delayed activity in free-rise and molded flexible foams. The propri- etary blocker used in the catalyst is de- signed to react into the foam matrix, eliminating any volatility. The catalyst is reportedly noncorrosive in most a p plications, further limiting its volatility, the company says. o n

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64 PLASTICS TECHNOLOGY 0 SEPTEMBER 1991