CA1219106A - Cellular, molded polyurethane parts, process for their preparation by thermoforming of polyester- urethane foam and their use - Google Patents

Abstract

CELLULAR, MOLDED POLYURETHANE PARTS, PROCESS FOR THEIR PREPARATION BY THERMOFORMING
OF POLYESTER-URETHANE FOAM AND THEIR USE

Abstract of the Disclosure A cellular polyurethane having a density of from 15 Kg/m3 to 400 Kg/m3 obtained by means of thermoforming, in a forming tool, at a compression factor of from 1 to 10 and temperatures of from 140°C to 200°C, polyester-urethane foams having a density of from 15 Kg/m3 to 40 Kg/m3 which are based on aromatic polyisocyanates and polyester polyols. The resulting polyurethane shaped objects are suitable for use as self-supporting trim panels, headliners, engine compartment covers, or instrument panels in the automotive, aircraft or railway industries.

Description

Case 1417 CELLULAR, MOLDED POLYURETHANE PARTS, PROCESS FOR THEIR PREPARATION ~Y THERMOFORMING
OF POLYESTER-URETHANE FOAM AND THEIR USE
~ .. . _ Back~round of the Invention 1. Field of the Invention ~ .
The present invention relate~ to thermoformed cellular polyurethane. More particularly, the invention relates to the formation of shaped polyurethane part~, especially panel~, by the thermoforming compre~sion of polyester-urethane foam~. The re~ulting shape~ and panel3 are advantageously used in the railway, automotive, and aircraft indu~try a~ headliner~, trim panel~, engine compartment cover~, and the like.

2. Description of the Prior Art Formed ~heet~ ~uch as trim panels, headliners, and vehicle trim have exhibited great utility in the automotive, aircraft, and railway industries. A~ described in German Patent 2,602,839 (U. S. 4,059,660 and U. S. 4,11g,7493, such 4heets may be formed by laminating ~mooth sided corruga~ed paper with a foam layer, for example, a layer of poly-urethane foam. An adhe~ive i~ utilized to adhere the various layers followiny which the components are bonded together under pressure at room temperature and formed to the desired shape. The preparation of these sheet~ i9 highly labor-intensive and is unsuitable for large-scale production.

lZ1~6 Rever~ibly thermoformable fiber-reinforced rigid polyurethane plastics may be prepared according to German Patent 2,1~4,381 (Great Britain Patent 1,411,958) by incorporating inorganic or organic fiber~ in a partially reacted polyurethane ~ystem which is liquid up to 50C, containing primarily bifunctional polyol~ having hydroxyl numberq from 100 to 600, and modified polyisocyanates or polymeric diphenylmethane-diisocyanates. The disadvantage of this two-~tep process is that the fiber reinforcing material, whether woven or non-woven, muqt first be coated with a flowable polyurethane reac~ion mixture followed by curing in a clo~ed mold at temperature~ over 120C. The flat ~heets produced in this manner can then be thermoformed at temperature~ from 130C to 220C. However, this C09t-intensive proce~ also limits the rate at which molded parts may be produced to a low number of parts per unit time.
German Patent 2,607,3~0 (U. S. 4,129,697) des-cribes the preparation of thermoformable polyisocyanurate foams by reacting polyether polyol~, glycols, and diphenyl-methane diiRocyanate, which can contain up to 20 weightpercent closely related polyi~ocyanate~ of higher molecular weight. Expan~ion takes place in heated molds or on conveyors, whereby the foams are post cured or tempered for approximately 15 minutes at 80C. One of the disadvantage~
of thiq proce~ that the polyi~ocyanurate foams are a~

brittle, do not exhibit internal cu~hioning, and are poor 4ound abqorbers. Moresver, polyisocyanurate ~lab foams cannot generally be produced with Qlab thicknes es greater than 50 cm since otherwise foam core di~coloration can occur.
It is difficult or even impo~sible to uAe in-mold foaming to produce flat structures with wall thickne~es from 1 mm to 6 mm 4uitable for trim panels, headliners, engine compartment covers, since this would lead to very high gross den~ities. In addition, it i~ extremely diffi-cult to completely and uniformly fill moldQ having compli-cated 3hape~ with relatively high-vi~cosity polyurethane mixtures. If thi~ were possible at all, very high pressure would be required.
The object of this invention i~ to prepare cellular, qelf-supporting, polyurethane ~haped objects, having large 4urface area and low densitie~, whereby said objects may be produced economically at high volume. The polyurethane ~haped object~ should po~e~s a high degree of ~ound ab~orption, good thermal insulation properties, high flame re~istance and the ability to recover from compression loads. Polyurethane foams suitable for use a~ the initial component~ ought not to exhibit core di~coloration or scorching.

Summary of the Invention The subject invention relates to cellular poly-urethanes having a den~ity of from 15 ~9/m3 to 400 Kg/m3 which are produced by thermoforming polyurethane foams having a den~ity of from 15 Rg/m3 to 40 Kg~m3, and which are baqed on aromatic polyi ocyanates and predom-inately polyester polyols. The thermoforming process takes place in a forming tool at a compression factor of from l to 10 at temperatures from 140C to 200C.
The thermoforming of flexible, semi-rigid, and rigid polyurethane foams having densities up to 40 Rg/m3 repreqents a useful addition to in-mold foaming and can be used in many ca~es where conventional methods of producing ~haped parts are unavailabl2. This process can also be u~ed to produce self-supportiny shaped par~ with complicated ~hapes, large surface area, and low densitie~
which remain true to contour and which may be produced at high part rate~.
De~cription of the Preferred Embodiment~
In order to produce the ~ellular thermoformed polyurethane shaped objects of the invention, it is nece~-~ary that the selected startin~ polyol component comprise polyester polyols, possibly mixed with no more than 45 weight percent polyether polyols based on the total weight of the polyol component, and the isocyanate component ~Zl~)6 compri~e a mixture of diphenylmethane diisocyanates and polyphenyl-polymethylene polyisocyanates, subsequently referred to as polymeric MDI. This sy~tem can be u~ed to continuou~ly produce flexible, semi-rigid, or rigid poly-urethane ~lab foamA on conventional slab foam equipment, or di~continuously in open molds. The~e slab foams exhibit densities of 15 Kg~m3 to 40 Rg/m3, preferably 20 Kg/m3 to 38 Kg/m3, are thermoformable, and possess the desired mechanical propertie~, e.g., cu~hioning, recoverability, hydrolysis resistance, sound absorption capabilities, etc.
Suitably dimensioned foam, corresponding in size to the shaped object which is to be produced, are cut from the resulting polyurethane foam slabs. The initial slabs can have dimensions up to 1 m x 2 m x 60 m. The cut ~labs mu~t be as free as possible from scrap and du~t, must be able to be 3plit into foam sheets having a thickness of from 2 mm to 20 cm, preferably from ~ mm to 10 cm, and more preferably from 5 mm to 25 mm. Standard industrial split-ting equipment i~ suitable, while oscillating hot-wire slicer~ are preferred in actual practice. It mu~t be cautioned that the larger size foam ~heets must exhibit sufficiently high mechanical ~tability to be able to with~tand being transported without damage.
In order to produce the polyurethane ther~oformed objects of the invention, the foam sheet~ which, as already ~tated, have densitie~ of from 15 Kg/m3 to 40 Kg/m3, prefer-ably from 20 Kg/m3 to 38 Kg/m3, are thermoformed at tempera-tureq from 140C to 200C, preferably 150C to 180C, at a cOmpre~BiOn factor of from 1 to 10, preferably from 2 to 10, in forming or ~tamping tools. Relatively high degree~ of compression must be utilized if polyurethane shaped objects which have a cellular foam core and an outer margin of higher den~ity are to be produced. Compression factors of greater ehan 2, preferably from 3 to 8, are quitable.
According to the invention, the compre~sion factor is defined as for foam e~pansion in closed molds, a~ the quotient of the density of the produced eellular poly-urethane shaped object divided by the density of the initially utilized polyurethane foam. A compression factor of 6, for example, may be illustrated by compressing a foam sheet having a den~it~,~ of 20 Kg/m3 to form a shaped object having a density of 120 Kg/m3.
The thermoforming of the polyurethane foam sheets at from 140C to 200C can be accompli~hed in various ways. In one version, the polyurethane foam sheets are heated to their deformation temperature with the aid of infrared radiators, hot air ovens, contact hot plates or other heating means. The heated foam Yheets are then placed in the forming tool maintained either at room temperature or moderately heated, for example to 60C, and are formed therein without the application of pres~ure (compres~ion factor 1) or, preferably, with pressure. The advantage of this method i8 that the molding tools can be made of economical material~ ~uch a~ ceramics, gyp~um, wood, or plastic~/ e.g.l unsaturated polye~ter or epoxy re~ins, and the resulting shaped objects can be de~olded i~mediately.
In the preferred proces~, polyurethane foam sheets, preferably at room temperature, or moderately heated, are placed in a temperature controlled molding tool of metal, for example, steel or cast aluminum, heated to 140C to 200C, and are formed therein over a period of from 30 second~ to 300 seconds, preferably from 30 second~ ~o 120 ~econd~, without pres3ure or preferably, under pressure, following which the resulting cellular polyurethane shaped object i8 demolded.
Of courRe, it i8 also pos~ible to combine both methods to achieve extremely rapid thermoforming of foam sheets which have been preheated to 140C to 200C and have been placed in 140~C to 200C forminq tools. The poly-urethane shaped object~ of the invention, especially thocewith a cellular core of low den~ity and a skin of higher densityl can be used directly for indu~trial purpo~es such as ~ound insulation or as engine compart~ent covers.
If desired, the foam sheet~ can also be provided on one oe both sideq with reinforcing or decorative cover-ing~ at the qame time the thermoforming operation occurs inthe molding tools. To accomplish thi3, the~e optional materials are placed in the molding tool and are bonded to the polyurethane foam under pre~sure with the aid of ~pray, laminating, or hot-melt adhe~iveq. It is especially noteworthy that wood or qawdu~t-filled polypropylene exhibits a high bonding strength with the polye3ter-ba~ed polyurethane foam, even without the addition of adhesives.
Typical reinforcing or decorative covering~, which may be optionally pigmented or printed, comprise woven or nonwoven material~ of gla~s, carbon, plastic~, or textile fibers, metal foilæ, for example, aluminum, copper, bra~s, gold, or ~teel up to 0.3 mm thick, polymers ~uch as poly-vinyl chloride, acrylo-butadiene-styrene polymer~, poly-amide, polyester, polyethylene, polypropylene, ~awdust-filled polypropylene, cellulose esters, and cellulose mixed esters, and cardboard or paper.
In a preferred embodiment of the invention the cover layers may be partially cured prepregs of un~aturated polyester resins, which are then fully cured during thermo-forming a~ temperature3 from 140 to 200C. Such prepregs are preferably 1 to 5 mm thick and in addition to the unsaturated polyester reæin, contain the u3ual monomers, for example, styrene, reinforcing material~, e.g., gla3~q fibers, fillers, e.g., chalk; thickener~, e.g., magnesium oxide, and po~sibly polymeric additive~, e.g., diene rubbers, as well a~ conventional inhibitor~, peroxides, and release agent~.
The cellular polyurethane shaped object~ in accordance with the invention are prepared exclusively from thermoformable flexible, ~emi-rigid, or rigid polyurethane foams baqed on polye~ter polyol~ or mixtures of polye~ter and polyether polyols, and polymeric MDI, or, in ~ome cases, modified polymeric MDI, whereby the semi-rigid blends are preferred due to their excellent deadening and recovery propertie3.
Polyester polyol~ having a functionality from 2 to 4, preferably from 2.3 to 4.0, and hydroxyl numbers from 45 to 380, preferably from 50 to 220, are preferred as starting component~ for the polyurethane foam~ which can be used in accordance with the invention. Hydroxyl numbers of from 50 to 80 are generally u~ed for the preparation of flexible foams, hydroxyl numbers of 85 to 150 are u~ed for the preparation of semi-rigid foams, and hydroxyl numbers of from 150 to 380 are preferable for the rig~d foam~.
The polye~ter polyols can be prepared using known method~, for example, by condensation poly~erization at temperatureq from 100C to 250C, preferably from 130C to 220C, in ~ome caseq in the pre~ence of esterification cataly~ts ~uch a~ organic compounds of titanium, vanadium, or tin. Inert qolvents or water entrainers ~uch as benzene toluene, xylene, or chlorobenzene may ~e utilized for the ~2~

azeotropic di~tillation of water of condenAation, preferably under reduced pre~sure. Suitable monomers include dicarbox-ylic acids; preferably aliphatic dicarboxylic acid~ having from 4 to 6 carbon atoms in the alkylene residue, and polyfunctional alcohol~, preferably diol~. Some typical aliphatic dicarboxylic acid~ are glutaric acid, pimelic acid, ~ebacic acid, and, preferably, adipic acid and mixtures of guccinic acid, glutaric acid, and adipic acid, and aromatic dicarboxylic acid~ ~uch a~ phthalic acid. In addition, les3er amounts of high molecular weight monocar-boxylic acids ~uch as fatty acid~ may be u~ed. Exampleq for di- and polyfunctional alcohol~, in particular difunctional alcohol~, are: ethylene glycol, diethylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butylene glycol, 1,5-pentamethylene glycol, 1,6-hexame~hylene glycol, glycerine, and trimethylolpropane. Diethylene glycol, 1,3 propylene glycol, mixtures of 1,4-butylene glycol, 1,5-pentamethylene glycol, and 1,6-hexamethylena glycol in weight ratio~ of from 10 to 30:40 to 60:15 to 35, glycerine, and trimethylolpropane arc preferred. Eqpecially preferred are polyester polyols ba~ed on adipic acid-diethylene glycol-glycerine; adipic acid-propylene glycol; adipic acid ethylene glycol diethylene glycol, mixture~ of ~uccinic, glutaric, and adipic acid-diethylene glycol-glycerine or trimethylolpropane; adipic acid mixtures of l,4-butylene, 1,5-pentamethylene, and 1,6-hexamethylene glycol, and, in particular, polye~ter polyols prepared from adipic acid-diethylene glycol-trimethylolpropane, adipic acid-phthalic acid-1,3-propylene glycol-trimethylolpropane, adipic acid-phthalic acid-oleic acid-trimethylolpropane, and adipic acid-glutaric acid-succinic acid-diethylene glycol and trimethylolpropane. The polyester polyols can be utilized individually or in the form of mixtures. Preferred are mixtures comprising a) 20 part3 to 85 part~, preferably 20 parts to 60 part~, by weight, of a polye~ter polyol of adipic acid-diethylene glycol-trimethyolpropane, b) 10 parts to 20 parts, preferably 10 partq to 30 part~, by weight, of a polyester polyol compri~ing adipic acid phthalic acid-1,3-propylene glycol-trimethylolpropane, and/or c) from 5 parts to 80 part~, preferably 5 part~ to 30 parts, by weight, of a polye~ter polyol comprising adipic acid phthalic acid-oleic acid-trimethylolpropane, or mixture~ comprising ~2~9~

d) 50 parts to 95 part~, preferably 60 parts to 90 parts, by weight, of a polyester polyol compri~ing adipic acid-diethylene glycol-trimethylolpropane, and e) 5 part3 to 50 parts, preferably 10 parts to 40 parts, by weight, of a polye~ter polyol compriQing adipic acid-glutaric acid-succinic acid-diethylene glycol-tri-methylolpropane.

The polyester polyol~ which can be utilized in accordance with the invention exhibit vi~co~ities of approximately 6000 mPa.s to 30,000 mPa.~, preferably 10,000 mPa. to 25,000 mPa.s, at 25C.
In order to prepare polyurethane foamq having special mechanical propertie~, the polyester polyols can al~o be mixed with le3ser amount~ of conventional polyether polyol~. Suitable polyester-polyether polyol mixtures, must be comprised of at least 55 percent by weigh~ of the aforementioned polyester polyols, preferably from 60 percent to nearly 100 percent by weight polye~ter polyol based on the total weight.
Mixtures of diphenylmethane diisocyanates and polyphenyl-polymethylene polyisocyanates (polymeric MDI) having a diphenylmethane diisocyanate i~omer content of from 40 to 85 weight percent, preferably from 40 to 65 weight percent~ and more preferably from 40 to 55 weight percent, are usQd a the aromatic polyisocyanate~. Also ~uitable i~
polymeric MDI modified by the presence of carbodiimide group~ and/or, preferably, urethane groups. In addition, for ~peclal applications, it may be de~irable to incorporate le~er amounts, for example, up to a maximum of 10 weight percent, ba~ed on the polymeric MDI, of carbodiimide- and/or urethane-modified 4,4'- and/or 2,4'-diphenylmethane dii~ocy~
anate.
Preferably, thermoformable polyurethane ~lab foam~
are prepared without the use of chain extender~ or cro~s-linking agent~. Depending on the mechanical propertie~
which are de~ired for the polyurethane foamA, however, the addition of chain extender~ or cros~-linking agent~ having molecular weight~ of from 60 to 300 can produce desirable re~ult~. Aliphatic diols having from 2 to 6 carbon atoms are suitable for this purpOQe, for example, ethylene glycol, 1,4-butylene glycol, and 1,6-hexamethylene glycol. Triol~
are al~o suitable, for example, glycerine and trimethylol-propane, alkanolamine~ ~uch a~ ethanolamine, dialkanolamines such a~ diethanolamine and trialkanolamine~ such as tri~
ethanolamine and trii30propanolamine. The co-utilization of triisopropanolamine with one or more of the above-mentioned chain extending or cros~-linking agent~ i~ preferred. The weight ratio of the chain extender or cro~-linking agent to ~LZlS~

the polyester polyol depends on the mechanical propertie~
desired in the final produc~ and can range from O to 10 weight percent, preferably from O to 5 weight percent ba~ed on the polye~ter polyol weight.
Water, which react~ with isocyanate groups to form carbon dioxide, is among the blowing agents which may be used to prepare the polyurethane foam. Preferred amount~ of water which can be uqed are from 0.01 to 5 weight percent, preferably from 2 to 4 weight percent based on the polyeRter polyol weight.
Other blowing agents which can be used, and which may be used in addition to, or to the exclusion of water, are liquids with low boiling pointQ which evaporate as a result of the exother~ic polyaddition reaction. Suitable liquid~ are those which are inert relative to the organic polyisocyanate~ and whose boiling points are not greater than 100C at atmospheric pre~sure, and which preferably range from -40 to +50C. Examples of quch preferably used liquid~ are: halogenated hydrocarbon~ such as methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, dichlorotetrafluoroethane, and 1/1,2-trichloro-1,2,2-trifluoroethane. Mixtures of the~e low-boiling-point liquids together and/or with other ~ub~tituted or un~ub~tituted hydrocarbon~ can also be used.

The mo~t desirable amount of low-boiling-point liquid to be u~ed to prepare the polyurethane foams depend~
on the de~ired den~ity as well as on the amount of water u~ed. In general, amounts from 0.1 to 20 weight percent, preferably from 5 to 15 weight percent ba~ed on the weight of the polye~ter polyol offer good results. ~est results are obtained when mixtures of water and trichlorofluoro-methane are used as the blowing agent.
In addition, ca~alysts may be incorporated in the reaction mixture to accelerate the formation of poly-ure~hane, and auxiliarie~ and additives generally uqed to produce polyurethane foams can also be incorporated. Such sub4tances include, for example, surfactants, flame retar-dants, reinforcing agents, porosity control agent3, anti-oxidant~, agents to protect again~t hydrolysis, colorants, pigments, filler3, and other additive~.
Suitable catalysts for accelerating the reaction betw~en the polyester polyols and, in some case~, the chain extender~, water, and the organic polyisocyanate~ are, for example: tertiary amines such as dimethylbenzylamine, N,N,N',N'-tetramethyldiaminoethylether, bis(dimethylamino-propyl)urea, N-methyl- or N-ethylmorpholine, dimethylpiper-azine, 1,2-dimethylimidazole, 1-aza-bicyclo-[3.3.0]-octane and, preferably triethylenediamine and 2-tdimethylamino-ethoxy)ethanol, which are u~ed in amounts from 0.1 to 30 ~

weight percent/ preferably from 0.5 to 25 weight percent ba~ed on the polye~ter polyol weight.
Surfactant3 can al~o be used, for example, to support the homogenization of the ~tarting material3 and, in ~ome ca~es, to regulate ~he cell ~tructure in the poly-urethane foam~. Typical examples are siloxane~oxyalkylene heteropolymer~ and other organic polysiloxane~, oxyethylated alkylphenolR, oxyethylated fatty alcohols, paraffin oil~, castor oil or castor oil acid esters and turkey red oil, which are used in amount~ from 0.2 to 6 parts by weight per 100 part~ by weiqht polye~ter polyol.
In order to improve the flame resistance of the polyure~hane ~lab foam~, fire retardance can be incor-porated. Typical examples are phosphorou3- and/or halogen-containing compound3 such a~ tricre~yl phosphate, trist2-chloroethyl]phosphate, tri~chloropropyl~phosphate, and tri~[2,3-dibromopropylene]phosphate; inorganic flame retardants ~uch as antimony trioxide, arsenic oxide, ammonium phosphate, ammonium polypho~phate~, ammonium sulfate, etc.; as well as cyanic acid derivative~ ~uch as dicyandiamide, guanidine, guanidine salt~, and melamine. In general, it has been found to be desirable to u~e from 5 to 50 part3 by weight of he cited flame retardant~ for each 100 parts by weight of the polye~ter polyol.

~21S~

Typical reinforcing material~ are: carbon fiber~, gla~s bead~, and, preferably, glass fibers and glas~ fiber powder. Such reinforcing material~ can be incorporated in the expandable polyurethane mixture in amount~ up to 25 weight percent based on the polye~ter polyol weight.
Additional information on the other standard auxiliaries and additives cited above can be found in the literature, for example, in the monograph by J. H. Saunder~
and K. C. Frisch, "High Polymers, n Vol. XVI, ~
pp. 1 and 2, Inter~cience Publishers, 1962, 1964.
In order to prepare the polyurethane ~lab foams, the organic polyi~ocyanates and pQlyester polyols or mixtures of polye3ter polyola and, in ~ome ca~e~, polyether polyol~ and/or chain extenders are reacted in ~uch amounts that the OH-:NCO-group ratio is from 1:(0.7-1.3), preferably from 1:(0.8-1.1). The preferred method of preparing flexible polyurethane foam3 utilizes OH-:NCO-group ratios of Prom 1:(0.8-0.95), while the preferred method for ~emi-rigid polyurethane foam~ u~e~ OH-:NCO-group ratio~ of from 1:(0.95-1.05) and the method for rigid polyurethane foams u~e~ OH-:NCO-group ratios of from 1:(1.05-1.1).
Preferably, the polyurethane foam~ are prepared utilizing the one-~hot proces~, either continuou~ly on ~lab foam equipment forming large foam ~lab~, or di~continuously in open mold~. When u~ing a mixing chamber with several feed nozzles, the starting components may be fed in sep-arately for vigorous mixing in the mixing chamber. It has been found to be particularly advantageous to work with a three-component sy~tem, whereby the polyeqter polyol~ or mixtures of polye~ter polyols, polyether polyols and/or diols are u~ed as the A component, the polymeric or modified MDI is uAed as the B component, and a premix comprising blowing agents, catalyst~, and, po3sibly, chain extenders or cross-linking agents, auxiliaries, and/or additive~ is used as the C component. Here, depending on the initial compo-nents used, it may be desirable to add a low-viscosity polyether polyol having a functionality of from 2 to 3 and a hydroxyl number of from 30 to 85 as a solubilizing agent in component C. Said Qolubilizing agent can be added in amounts ranging up to 45 weight percent ba~ed on the total weight of the blowing agent, catalyst and chain extender~, auxiliaries, and additives.
In order to prepare the polyurethane slab foams, the described starting ~ubqtances are vigorou~ly mixed in the aforementioned ratios at temperatures from 15C to 60C, preferably from 20C to 3~C, and then the reaction mixture i8 allowed to expand in open, optionally temperature-controlled, mold~.
The resulting thermoformable polyurethane foams having densities from 15 to 40 Kg/m3 posseqs, depending on 9~Q6 the selection of the polyester polyol and the OH-:NCO-equivalency ratios, ~uperior phy~ical propertie~ such as resistance to hydrolysis~ formability, cushioning ability and recovery, and thermal insulation and sound absorption capabilities.
The thermoformed cellular polyurethane shaped object~ prepared in accordance with the invention have densities from 15 Kg/m3 to 400 Kg/m3, preferably from 20 Kg~m3 to ao Kg/m3. The low-density ~haped object~ in particular, for example tho~e having densities up to 40 Kg/m3, have important commercial significance for increasing the "interior safety" in automotive and aircraft de~ign. The polyurethane shaped objects are preferably used in the railway, auto~otive, and aircraft industries a~
headliners, door and wall trim panels, instrument panels, dashboards, and engine compartment covers. However, the~e products are also used in the furniture industry, audio and television de~ign, and in the construction industry as protective materials to achieve sound absorption or thermal insulation.
The following polye~ter and polyether polyol~ are used to prepare the thermoformable polyurethane foams:

Polye~ter polyol I:
A polye3ter polyol having a functionality of 2.6 and a hydroxyl number of 60, prepared by the conden~ation polymerization of adipic acid with diethylene glycol and trimethylolpropane.

Polye~ter polyol II:
A polyester polyol having a functionality of 3.0 and a hydroxyl number of 215, prepared by the conden~ation polymerization of adipic acid, phthalic acid anhydride, 1,3-propylene glycol, and trimethylolpropane.

Polyester polyol III:
A polyester polyol having a functionality of 3.8and a hydroxyl number of 350, prepared by the conden~ation polymerization of adipic acid, phthalic acid anhydride, oleic acid, and trlmethylolpropane.

Polyeqter polyol IV:
A polye~ter polyol having a functionality of 2.6 and a hydroxyl number of 63, prepared by the conden~ation po~ymerization of a dicarboxylic acid mixture COmpri~iQg 50 part~ by weight adipic acid, 30 part~ by weight glutaric acid, and 20 part~ by weight ~uccinic acid, with diethylene glycol and trimethylolpropane.

Polyether polyol I:
A trifunctional polyether polyol having a hydroxyl number of 35 prepared by oxyalkylating glycerine with 1,2-propylene oxide and ethylene oxide in an 85:15 weight ratio.

Polyether polyol II:
A tetrafunctional polyether polyol having a hydroxyl number of 480 prepared by oxyalkylatin~ ethylene-diamine with l,2-propylene oxide.

Polymeric MDI:

A mixture compri~ing approximately 50 part3 by weight diphenylmethane diisocyanate3 and 50 parts by weight polyphenyl-polymethylene polyi~ocyanates.

Example 1 Preparation of a ~emi-rigid, thermoformable polyurethane ~lab foam from the following ~tarting compo-nent~:

parts by weight polye~ter polyol I, part~ by weight polyester polyol II, parts by weight polye~ter polyol III, part~ by weight polyether polyol I,

3.2 part3 by weight trii~opropanolamine, 1.7 parts by weight N,N-dimethylbenzylamine,

4.0 part3 by weight water and 97.8 parts by weiqht polymeric MDI.

In the one-~hot proces~ the ~tarting component~
are mixed together vigorously in a multiple-component mixing head at room temperature (23C) and are allowed to expand on a continual polyurethane ~lab line.
The following mechanical propertieq were measured in the resulting polyurethane foam:

Den~ity per DIN 53 420 38 kg/m3 Heat distortion ~emperature under flexural load per DIN 53 424 134C
Compression ~trength per DIN 53 421 80 KPa Flexural strength per DIN 53 423170 KPa Ten~ile strength per DIN 53 455161 N/mm2 Elongation per DIN 53 45517 percent ~e~
Preparation of a flexible, thermoformable poly-urethane slab foam from the following starting component~:

part~ by weight polyester polyol I, parts by weight polyeqter polyol IV, 1.2 part~ by weight N,N-dimethylbenzylamine, 1.2 partq by weight foam ~tabilizer based on polyether-poly~iloxane (Niax0 L 532, Vnion Carbide Corp.), 4.9 parts by weight water, 20.0 part~ by weight monofluorotrichloromethane and 62.4 parts by weight polymeric MDI.

The starting component~ were mixed and expanded a~
de~cribed in Example 1 to form a polyurethane slab ~oam in which the following mechanical propertie~ were observed:

Density per DIN 53 420 20 kg/m3 Tensile strength per DIN 53 571114 N/mm2 Load at 40 percent compres~ion per DIN 53 577 3.5 k.Pa Elongation per DIN 53 571 68 percent Example 3 Preparation of a tough, rigid, flame-resistant, ~hermoformable polyurethane slab foam from the following ~tarting components:

part~ by weight polyester polyol I, parts by weight polyester polyol II, parts by weight polyester polyol III, parts by weight polye~her polyol II, part~ by weight ammonium polyphosphate, parts by weight trichloroethyl phosphate, 3.2 parts by weight triisopropanolamine, 1.2 parts by weight dimethylbenzylamine, 4.0 parts by weight water, and 98.4 part~ by weight polymeric MDI.

12~9~

The starting component~ were mixed and expanded a~
described in Example 1 to form a polyurethane slab foam in which the following mechanical properties were observed:

Density per DIN 53 420 40 kb/m3 Heat di~tortion temperature under flexural load per DIN 53 424 138C
Compression strength per DIN 53 421 140 kPa Flexural ~trength per DIN 53 423 231 kPa Flexural stre~s ae conventional deflection per DIN 53 423 229 kPa Ten~ile strength per DIN 53 455 202 N/mm2 Elongation per DIN 53 455 13 percent The polyurethane ~lab foam met the following fire resi~tance requirements:

per DIN 4201: B 2 per FAR 25.853 (a through 1) per UL 94 HF 1 and per U.S.-FMVSS 302 The ~ound absorption efficiency 1(-) a~ a function of frequency, f, exhibited the curve ~hown in the figure for a foam qheet of denqity 40 kgfm3 and thicknes~ 17 mm in an ~L2~ 6 impedance tube. Curve 1 wa~ 0easured with the sound directed normal to the sheet while curve 2 was measured at a stati3tical angle of incidence.

Exampl0 4 The polyurethane ~lab foam prepared in accordance with E~ample 3 was cut into 20 mm-thick foam sheets. These ~heet were heated ~lightly and compressed to a sheet thickne~s of 10 mm in a forming tool at 180C and at a pressure of 1.5 bar.

The following mechanical properties were ob~erved in the resulting shaped objects:

Density per DIN 53 420 80 kg/m3 Flexural stress at conventional deflection per DIN 53 423 376 k.Pa Heat distortion temperature under flexural load per DIN 53 424 138C
Tensile strength per DIN 53 455 302 N/mm2 Elongation per DIN 53 455 16 percent Example 5 A polyurethane foam sheet of 10 mm thicknes~
prepared from the polyurethane slab foam of Example 2 was heated, covered with a 2 mm-thick prepreg of an unsaturated polyester resin, and molded in a molding tool at 150C.

- 2~ -1~9~

The resulting cellular qhaped sandwich wa3 u~ed a~
an engine compartment ~over for an automotivs application.

Claims (13)

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A cellular polyurethane having a density of 15 Kg/m3 to 400 Kg/m3 prepared by: thermoforming in a molding device at a temperature of from about 140°C to 200°C
and at a compression factor of from 1 to 10, a polyurethane foam having a density of from 15 Kg/m3 to 40 Kg/m3, wherein said polyurethane foam is prepared by reacting an isocyanate component comprising a member selected from the group consisting of;
(a) polymeric MDI;
(b) carbodiimide modified MDI;
(c) urethane modified MDI: and (d) mixtures thereof, with a polyol component selected from the group consisting of:
(e) a polyester polyol mixture containing one or more polyester polyols; and (f) a polyester/polyether polyol mixture comprising one or more polyester polyols and one or more polyether polyols, provided that the polyester polyols comprise at least 55 percent by weight of said polyol component, in the presence of catalysts, blowing agents, and optionally chain extenders, cross-linking agents, additives, and auxiliaries.

2. The cellular polyurethane part as recited in claim 1 wherein said part comprises a cellular foam core and a skin of higher density.

3. The cellular polyurethane part as recited in claim 2, wherein a degree of compression of from 2 to 10 is used.

4. The cellular polyurethane part as recited in claim 1, wherein said polyurethane foam has a thickness of 2 mm to 20 cm.

5. The cellular polyurethane part as recited in claim 1, wherein coverings are applied to one or more sides of said polyurethane foam prior to thermoforming.

6. The cellular shaped polyurethane part as recited in claim 5, wherein said coverings comprise curable, unsaturated polyester prepregs.

7. The cellular polyurethane part as recited in claim 6, wherein said prepregs contain glass fibers or fillers.

8. The cellular polyurethane part as recited in claim 1, wherein said polyester polyol component has a functionality of from 2 to 6 and a hydroxyl number of from 45 to 250.

9. The cellular polyurethane part as recited in claim 1 wherein said polyester polyols are selected from the group consisting of:
(a) adipic acid-diethylene glycol-tri-methylolpropane copolymers;
(b) adipic acid-phthalic acid-propylene glycol-trimethylolpropane copolymers;
(c) adipic acid, phthalic acid-oleic acid-trimethylolpropane copolymers;
(d) adipic acid-glutaric acid-succinic acid-diethylene glycol-trimethylol propane compolymers; and (e) mixtures of two or more of compolymers (a), (b), (c), or (d).

10. The cellular polyurethane part as recited in claim 8 wherein said polyester polyols are selected from the group consisting of:
(a) adipic acid-diethylene glycol-tri-methylolpropane copolymers;
(b) adipic acid-phthalic acid-propylene glycol-trimethylolpropane copolymers;

(c) adipic acid, phthalic acid-oleic acid-trimethylolpropane copolymers;
(d) adipic acid-glutaric acid-succinic acid-diethylene glycol-trimethylol propane compolymers; and (e) mixtures of two or more of copolymers (a), (b), (c), or (d).

11. A cellular polyurethane self-supporting trim panel, headliner, engine compartment cover or instrument panel as recited in claim 1.

12. A cellular polyurethane self-supporting trim panel, headliner, engine compartment cover or instrument panel as recited in claim 6.

13. A cellular polyurethane self-supporting trim panel, headliner, engine compartment cover or instrument panel as recited in claim 7.