CA2006698A1

CA2006698A1 - Process for the preparation of flame resistant, elastic polyurethane flexible foams while using at least one polyoxyalkylene polyamide and melamine

Info

Publication number: CA2006698A1
Application number: CA002006698A
Authority: CA
Inventors: Manfred Genz; Reinhard Leppkes; Willibald Schoenleben; Heinz-Dieter Lutter; Gerhard Ramlow; Erhard Reich; Peter Hettinger
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-12-28
Filing date: 1989-12-27
Publication date: 1990-06-28
Also published as: EP0377868A2; DE3844048A1; EP0377868A3

Abstract

PROCESS FOR THE PREPARATION OF FLAME RESISTANT
ELASTIC POLYURETHANE FLEXIBLE FOAMS WHILE USING
AT LEAST ONE POLYOXYALKYLENE POLYAMINE AND MELAMINE

ABSTRACT OF DISCLOSURE

The present invention deals with a process for the preparation of flame resistant elastic polyurethane flexible foams, comprising reacting:
a) organic polyisocyanates and/or modified organic polyisocyanates with;
b) higher molecular weight compounds having at least 2 reactive hydrogen atoms;
c) optionally lower molecular weight chain extending agents;
in the presence of d) catalysts;
e) blowing agents;
f) flame retardants;
as well as with or without g) auxiliaries and/or additives;
whereby as starting component (b) a mixture having an average functionality of 2 to 4 and an average molecular weight of 2200 to 8000 is used which preferably comprises bi) 40 to 94 parts by weight of at least one polyoxyalkylene polyol having a functionality of 2 to 4 and an average molecular weight of 250 to 8000;
bii) 3 to 25 parts by weight of at least one polymer modified polyoxyalkylene polyol having an average functionality of 2 to 4 and an average molecular weight of 1200 to 8000 selected from the group consisting of graft polyoxyalkylene polyols and polyurethane polyalkylene polyols containing in bonded form polyurea groups, polyhydrazide groups and/or tertiary amino groups;
biii) 3 to 25 parts by weight of at least one polyoxyalkylene polyamine having a functionality of 2 to 4 and an average molecular weight of 1800 to 8000; and using melamine or mixtures of melamine and other flame retardants as flame retardant (f).

Description

i9~

PROCESS FOR THE PREPARATION OF FLAME
RESISTANT, ELASTIC POLYURETHANE FLEXIBLE
FOAMS WHILE USING AT LEAST ONE POLYOXYALKYLENE
POLYAMINE AND MELAMINE

~ACKGROUND OF THE INVENTION

The preparation of elastic polyurethane flexible foams is disclosed in numerous patent and literature publications. Typical examples are: The Plastics Handbook, volume VII, Polyurethanes, Carl-Hanser Puhlishers, Munich, 1st edition, 1966, edited by Dr. R. Vieweg and Dr. A.
Hochtlen, and the 2nd edition 1983, edited by Dr. G. Oertel;
and the monograph, Integral Skin Foams,by Dr. H~ Piechota and Dr. ~. Rohr, 1975, Carl-Hanser Publishers.
Normally, in the preparation of polyurethane flexible foams commerically available toluene diisocyanates are used as polyisocyanates; polyoxyalkylene polyols based on lr2-propylene oxide and/or ethylene oxide, as well as mixtures of polyoxyalkylene polyols and graft polyoxyalkylene polyols are used as the polyfunctional higher molecular weight compoundq; and alkane diols or hydroxyl group containing and/or amino group containing ~O~ 9~

compounds having a functionality greater than 2, such as, for example, glycerin, trimethylolpropane or alkanolamines are used as the chain extending agents.
~ he aforesaid polyurethane flexible foams are not flame resistant and a disadvantage is particularly their high flamability. To overcome this disadvantage, flame retardant, preferably halogen- and/or phosphorous-containing compounds are incorporated into the foamable polyurethane mixture. However, adding these products often has a negative impact on the mechanical properties of the resulting polyurethane foams. Numerous experiments were aimed at developing novel flame retardants and at replacing the halogen- and/or phosphorous-containing compounds completely or at least partially by these in polyurethane foams.
A typical compound, for example, is the polyfunctional melamine having a melting point of 354C.
According to DE-A-23 4B 838, ~elamine is suspended in the polyol and/or the polyisocyanate component and then the resulting suspension is immediately processed into isocyanurate group containing, flame resistant polyurethane plastics. United ~tates patent 4,221,875 (DE-A-28 09 084) discloses flame resistant polyurethane rigid foams prepared ~o~

by reacting organic polyisocyanates and polyoxyalkylene polyols in the presence of blowing agents and silicones as surfactants 20 to 100 parts by weight of melamine as a flame retardant per 100 parts by weight of polyoxyalkylene pGlyol.
EP-A-0 004 618 (U5 Patent 4,258,141) discloses a process for the preparation of low flame resistant polyurethane flexible foams while using a mixture of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates ~polymeric MDI) having a content of diphenylmethane diisocyanate isomers of from 40 to 90 weight percent based on the total weight as the polyisocyanate; and cyanic acid derivatives, preferably melamine as flame retardants.
Although according to this process the flame resistance of the polyurethane foams is significantly improved, the strong sedimentation of the melamine in the polyol which occurs after a short period of storage is regarded as a dis,advantage. EP-B-023 9B7 (US patent 4,293,657~ discloses stable melamine polyol dispersions in which the melamine is reduced in size to a particle size less than 10 microns in situ in the polyol in the presence of at least one stabilizer employing a local energy density of from 10 to 3000 kW/m3. This additional processing step requires additional equipment and is more costly.

~O~

Attempts were also made to improve processing of p~lyurethane formulation containing melamine by adding suitable additive~ but without reducing the flame retardancy o~ the resulting foams. According to DE-A-35 30 519 (GB-A-2] 63 762A) a mixture of melamine and an addition product of an alkanolamine and an isocyanate are used as a flame retardant additive which is dispersed in the polyol. GB-A-21 77 405A and GB-A-21 77 406A disclose mixtures of melamine and styrene acrylonitrile graft polyoxypropylene polyoxyethylene polyols dispersed in conventional polyoxypropylene polyoxyethylene polyols as well as optionally phosphorous-and/or halogen-containing compounds as flame retardant additives. Foams prepared according to this proce~s indeed demonstrate good flame retardancy, however, their mechanical properties often do not satisfy specific requirements. Another disadvantage is that the formulations must be processed using multiple component mi:~ing equipment since the componen~s containing melamine have an inadequate storage stability.
The object of the present inven~ion was to prepare flame resistant elastic polyurethane foams, preferably mo].ded foams, having good mechanical properties, while using me]amine as a flame retardant preferably according to the 2 component process. In addition conventional processes ~hould at least be improved and the starting materials optionally could be modified to achieve storage starting mixtures.
This object was surprisingly met by using a mixture of polyoxyalkylene polyols and polyoxyalkylene po].yamines as higher molecular weight compounds having at least 2 reactive hydrogen atoms in conjunction with melamine or melamine containing mixtures as flame retardants.

SUMI~ARY OF THE INVENTION
Accordingly, the subject of the invention is a process for the preparation of flame resistant elastic polyurethane flexible foams, comprising reacting~

a~ organic polyisocyanates and~or modified organic polyisocyanates having NCO contents of fr~m 34 to 2.B weight percent based on the total weight; with b) higher molecular weight compounds having at least 2 reactive hydrogen atoms; and c) with or without lower molecular weight chain extending agents;
in the presence of ~o~

d) catalysts;
e) blowing agents;
f) flame retardants;
and with or without g) auxiliaries and/or additives, whereîn a mixture having an average functionality of from 2 to 4, more preferably 2.0 to 3 and an average molecular weight of from 2200 to 800Q, more preferably 3600 to 6500 is used as starting component b) which comprises:

bi) at least one polyoxyalkylene polyol, preferably at least one polyoxyalkylene polyol having an average functionality of 2 to 4, more prefera~ly 2.0 to 2.4 and an average molecular weight of from 250 to 8000, more preferably 3600 to 6500;
bii) at least one polymer modified polyoxyalkylene polyol, preferably at least one graft polyoxyalkylene polyol, having an average functionality 2 to 4, more preferably 2 to 3 and an average molecular weight of from 1200 to BC00, more preferably 2200 to 6500; and ~iii) at least one polyoxyalkylene polyamine, preferably at least one polyoxyalkylene polyamine havlng an average functionality of from 2 to 4, more preferably 2 to 3 and an average mGlecular weight of from 1800 to 8000, more preferably 2500 to 6500;
and melamine or mixtures of melamine and other flame retardants as said flame retardant (f).

The higher molecular weight compounds (b) used according to the present invention efficaciously are used in such quantities so that the 100 parts by weight of the mixtures comprises:
40 to 94 parts by weight, more preferably 60 to 87 parts ~y weight of a polyoxyalkylene polyol Ibi) or a polyoxyalkylene polyol mixture;

3 ~o 25 parts by weight, more preferably 3 to 15 parts by weight of a polymer modified polyol, preferably selected from the group consisting of graft polyoxyalkylene polyols, polyurea, polyhydrazide or tertiary amino group containing polyurethane polyoxyalkylene polyol dispersions or mixtures of such polymer modified polyols; and 3 to 35 parts by weight, more preferably 10 to 25 parts by weight of a polyoxyalkylene polyamine or a polyoxyalkylene polyamine mixture.

Surprisingly, a storage stable mixture, the so-called (A) component which after six months of storage at room temperature exhibited practically no melamine sedimentation was able to be made from the above-mentioned mixture of components (bi) through ~biii), the catalysts (d), blowing agent (e) the melamine or melamine containing mixture as flame retardant (f) as well as with or without the lower molecular weight chain extending agents (c) and auxiliaries and/or additives (g~. The (A) component processes extremely well on conventional hign pressure machines since its viscosity surprisingly decreases with an increasing pressure, i.e., the (A) component is thixotropic. Polyurethane flexible foams, more preferably molded foams prepared according to the process of the present invention have very good flame retardancy and are characterized by a high mechanical property level. Also noteworthy is the rapid curing ability of the reaction mixture and the high green strength of the resulting polyurethane flexible foam molded articles which can very easily be demolded after short mold residency times so that molded articles can be efficiently prepared industrially.
The following should be noted with respect to the starting components used according to the process of the present invention:

~o()~

a) conventional organic, for example, aliphatic, cycloaliphatic, araliphatic, cycloaliphatic-aromatic and preferably aromatic di- and/or polyisocyanates are suitable in the preparation of the flame resistant elastic polyurethane flexible foams preferably polyurethane molded flexible foams. Individual examples of aromatic polyisocyanates are mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates (MDI); mixtures of MDI isomers and polyphenyl polymethylene polyisocyanates, so-called polymeric MDI having an MDI isomerir content of at least 50 weight percent, more preferably 60 to 90 weight percent and more based on the total weight of the mixture; 2,4- and 2,6-toluene diisocyanate as well as the corresponding commercially available isomeric mixture; mixtures of toluene diisocyanates and MDI
and/or polymeric MDI, for example, those having a MDI content of 30 to 90 weight percent, more preferably 40 to eo weight percent based on the total weight of the polymeric MDI's.

~o(~

Also suitable are the so-called modified multivalent isocyanates, that is products which are obtained by the chemical reaction of organic di-and/or polyisocyanates. Individual examples are ester, urea, biuret, allophonate, isocyanurate and preferably carbodiimide, uretonimine and/or urethane group containing di- and/or polyisocyanates. Individual examples are urethane group containing prepolymers having an NCO content of 14 to 2.8 weight percent, more preferably 12 to 3.5 weight percent or quasi-prepolymers having an NCO content of 35 to 14 weight percent, more preferably 34 to 22 weight percent whereby polyisocyanates of toluene diisocyanates modified with urethane groups preferably have an NCO content of 34 to 28 weight percent and those of 4,4'-MDI, 4,4'- and 2,4'-MDI isomeric mixtures or polymeric MDI preferably have an NCO content of 28 to 22 weight percent based on the total weight; and are prepared by reacting diols, oxalkylene glycols and/or polyoxyalkylene glycols having molecular weights of 62 to 6000, preferably 134.18 to 4200 with toluene diisocyanates, 4,4'-MDI, MDI isomeric ' ,.

~Ot)~;~5~

mixture.s and/or polymelic MDI, for example, at temperatures of from 20 to 110C, more preferably 50 to 90C~ whereby the following can be used individually or as mixtures thereof as the oxalkylene glycols and polyoxyalkylene glycols:
diethylene glycol, dipropylene glycol, polyoxyethylene, polyoxypropylene glycol and polyoxypropylene-polyoxyethylene glycol;
carbodiimide group and/or isocyanurate group containing polyisocyanates, for example, based on MDI isomers and/or toluene diisocyanate.

However, the following have proven particularly useful and thus are preferably used~ 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate and urethane group containing polyisocyanates having an NCO
content of 34 to 28 weight percent, more preferably 34 to 30 weight percent prepared from 2,4- and 2,6-toluene ,iiisocyanate mixtures efficaciously in a weight ratio of 80:20; and polyoxypropylene-polyoxyethylene glycol~ having a molecular weight of 2800 to 4200.

--11~

>Ot~

b) To prepare a storage stable ~elamine containing (A~
component, as already established, according to the present invention the mixture comprises higher molecular weight compounds having at least 2 reactive hydrogen a~oms (b), said mixture has an average functionality of from 2 to 4 and an average molecular weight of from 2200 to 8000 and contains:

bi) at least one polyoxyalkylene polyol;
bii) at least one polymer modified polyoxyalkylene polyol;
and biii) at least one polyoxyalkylene polyamine.

Suitable polyoxyalkylene polyols ~bi) have an average functionality of 2 to 4, more preferably 2.0 to 2.4 and an average molecular weight of 250 to 8000, more preferably 3600 to 6500 and can be prepared according to conventional processes, for example, by the anionic polymerization with alkali hydroxides, such as sodium or potassium hydroxide;

~o~

or alkali alkylates, such as, for example, sodium methylate, sodium or potassium ethylate or potassium isopropylate as catalysts; or by the cationic polymerization with Lewis acids such as antimony pentachloride, boron triflo~ride etherate, etc.; or using bleaching earth as catalysts; or from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical and an initiator molecule which contains 2 to 4, more preferably 2 to 3 reactive hydrogen atoms ir. bonded form.

Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- and/or 2,3~butylene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, in alteration one after the other or as mixtures. Examples of suitable initiator molecules are: water, organic dicarboxylic acids, such as, for example, succinic acid, adipic acid, phthalic acid, terphthalic acid, aliphatic and aromatic, optionally N-mono-, N,N-and N,N'-dialkyl substituted diamines having 1 to 4 ~)0~

carbon atoms in the alkyl radical such as, optionally, mono- and dialkyl substituted ethylene diamine, diethylene triamine, triethylene tetraamine, 1,3-propylene diamine, 1,3- and/or 1,4-butylene diamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylene diamine, phenylene diamines, 2,4- and 2,6-toluene diamine and 4,4'- and 2,4'- and 2,2'-diamino-~iphenylmethane.

Typical initiator molecules are: alkanolamines, such as ethanolamine, diethanolamine, N-methyl- and N-ethyl ethanolamine, N-n,ethyl- and N-ethyldiethanolamine, triethanolamine, and ammonia. Preferably used are multivalent, most preferably divalent and/or trivalent alcohols, such as ethanediol, 1,2- and 1,3-propylene diol, diethylene glycol, dipropylene glycol, 1,4-butane diol, 1,6-hexanediol, glycerin, trimethylolpropane and pentaerythritol.

The polyoxyalkylene polyols can be used individually or in the form of mixtures whereby those products are preferred which contain both ~O~ t~

ethylene oxide units as well as 1,2-propylene oxide units in the oxalkylene chain in bonded form and in addition, these units can be arranged either statistically or in block fashion. Most preferably used are polyoxypropylene-polyoxyethylene polyols having more than 50% of terminally positioned primary hydroxyl groups having a functionality of 2 to 3 and a molecular weight of from 3600 to 6500.
Polyoxy~etramethylene glycols efficaciously are those having molecular weights of from 250 to 3000, more preferably 800 to 2200 or mixtures of the aforesaid polyols.

Preferably graft polyoxyalkylene polyols are used as a polymer modified polyoxyalkylene polyols (bii) having an average funtionality of 2 to ~, more preferably 2 to 3 and an average molecular weight of ~rom 1200 to 8000, more preferably 2200 to 6500. 'rhese can be prepared by the in situ polymerization of ole~inic unsaturated monomers or mixtures thereof, ~uch as, for example, styrene acrylonitrile or styrene acrylonitrile mixtures, in polyoxyalkylene polyols, for example, from the ~ 0 O~ t~

above described polyoxyalkylene polyols analogous to the teaching of Federal Republic of Germany patents 11 11 394, 12, 22 669 (US patents 3,304,273~ 3,383,351, 5,523,093), 11 52 536 (Great ~ritain 1 040 452) and 11 52 537 (Great Britain 987 61B); or by dispersing graft polymers obtained previously by the radical polymerization in solvents, in polyoxyalkylene polyols analogous to the teachings of US patents 3,391,092, 4,014,846 and 4,093,573. Eor the preparatisn of the graft polyoxyalkylene polyols both the above-mentioned saturated polyoxyalkylene polyols are suitable which according to US reissue patent 28,715 are essentially free of ethylenically unsaturated units; and also olefinic unsaturated polyoxyalkylene polyols as disclosed, for example, in US patent 3,652,659 and in US reissue patent 29,014. Also suitable ~s polymer modified polyoxyalkylene polyols are polyurea, polyhydrazide or tertiary amino group containing polyurethane polyoxyalkylene polyol dispersions as disclosed in, for example, EP-B-O 011 752 (US 4 304 708), US
4,374,209 and DE-A-32 31 497. The polymer modified v~o()~

polyoxyalkylene polyols (bii) which efficaciously possess 2 to 35 weight percent, more preferably 3 to ~5 weight percent b~sed on the total weight of polymer particles just as the polyoxyalkylene polyols (bi) and the polyoxyalkylene polyamides ~biii~, they can be used individually or in the form of mixtures.

Typical polyoxyalkylene polyamines ~biii), preferably having an average functionality of 2 to 4, more preferably 2 to 3, and an average molecular weight of preferably l800 to 8000 and most preferably 25 to 6500, are efficacio~sly those whose amino yroups are in bonded form on the aliphatic radicals and which contain up to at least 70~, more preferably more than 90~ of primary amino groups. In place of mixtures of polyoxyalkylene polyols (bi) and polyoxyalkylene polyamines (biii) or in conjunction with one of these compounds (bi~
or tbii.i) optionally also partially aminated polyoxyalkylene polyols can be used with the proYiso that the sum of the characteristic data of the individual components fulfills the novel ~()ç~

characteristi~s of the mixtures of (bi) through t b'i i i ) .

The polyoxyalkylene polyamines having amino groups in bonded form on the aliphatic radicals used according to the present invention can be prepared according to conventional processes, for example, by the cyanoalkylation of the above-mentioned polyoxyalkylene polyols and subsequent hydrogenation of the nitrile formed (US patent 3,257,050), or by the amination of polyoxyalkylene polyols with ammonia in the presence of hydrogen and catalysts (DE-A-12 15 373~.

c) Optionally it can be useful to modify the mechanical properties of the flame resistant elaqtic polyurethane foams, preferably the flexible molded foams by adding lower molecular weight chain extendillq agents (c) in addition to the novel mixture (b) comprising components ~bi) through (biii~. Such agents are, for example, polyfunctional, more preferably di- and trifunctional compounds, having molecular weights f~,oo~

of from 17 to about 400, more preferably 62 to about 300. Typical examples are di- and/or trialkanolamines, Ruch as, for example, diethanolamine and triethanolamine; aliphatic diols and/or triols having 2 to 6 carbon atoms in the alkylene radicals, such as, for example, ethanediol, 1,4-butane- diols, 1,5-pentanediol, 1,6-hexanediol, glycerin and/or trimethylolpropane, and lower molecular weight ethoxylation and/or propoxylation products prepared from the above-mentioned dialkanolamines, trialkanolamines, diols and/or triols; as well as aliphatic and/or aromatic diamines, such as for example, 1,2-ethane- diamine, 1,4-butanediamine, 1,6-hexanediamine, 2,4- and/or 2,6-toluenediamine, 4,4'-diamino diphenylmethane, 3,3'-di-, and/or 3,3',5,5'-tetraalkyl substituted 4,4'-diphenylmethanes as initiator molecules and alkylene oxides or mixtures thereof.

Dialkanolamines, diols and/or triols and most preferably 1,6-hexanediol, diethanolamine, trimethylolpropane and glycerin or mixtures thereof are preferably used as said chain extending agent (c) .

The chain extending agents which are used in the preparation of the polyurethane flexible foams are efficaciously used in such weight quantities so that per mole of higher molecular weight compound (b~ from 0.01 to 8 moles, more preferably 0.1 to 3 moles of chain extending agent (c) is present in the reaction mixture.

d) To accelerate the reaction between mixture ~b) comprising higher molecular weight compounds comprising (biJ through (biii), water is added as a blowing agent (e) and op~ionally chain extending agent ~c), and in addition conventional polyurethane catalysts are added to the reaction mixture to accelerate the reaction with the organic polyisocyanates and/or modified polyisocyanates (a). Preferably basic polyurethane catalysts are used, for example, tertiary amines, such 25 dimethylben~ylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N'N'-tetramethyldiamino-diethylether, bis~dimethylaminopropyl)urea, N-methyl- and/or N--2~-ethylmorpholine, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, l-azabicyclo[2.2.01octane, dimethylaminoethanol, 2-~N,N-dimethylamin~ethoxy)ethanol, N,N',N"-tris-(dialkylaminoalkyl)-hexahydrotriazine, e.g., N,N'N"-tris-(dimethylaminopropyl)-s-hexahydrotriazine and most preferably triethylenediamine. Howe~er, also suitable are metal salts such as iron(II) chloride, zinc chloride, lead octoate and preferably tin salts, such as, tin dioctoate, tin diethylhexoate, and dibutyltin dilaurate as well as preferably, mixtures of tertiary amines and organic tin salts. Efficaciously used is from 0.1 to 10 weight percent, more preferably 0.3 to 3 weight percent of catalysl:s based on the tertiary amine and~or 0.01 to 0.5 weight percent, more preferably 0.03 to 0.25 weight percent of metal salt based on the weight of the mixture of starting components (bi) through (biii).

e) Water is among the blowing agents (e) which can be used in the preparation of polyurethane flexible foams which reacts with the isocyanate groups to form carbon dioxide. The amount of water which is efficaciously used is from 0.1 to 5 parts by weight, more preferably 1.0 to 3.5 parts by weight and most preferably 2.5 to 3.0 parts by weight based on 100 parts by weight of mixture (b) comprising components (bi) through (biii).

In addition, physically active blowing agents can be used mixed with water. Suitable liquids are those which are inert to the organic optionally modified polyisocyanates (a) and which have boiling points below 100C, more preferably below 50C, and most preferably between -50 and 30C at atmospheric pressure so that they evaporate under the influence of the exothermic polymerization reaction.
E~amples of such preferably used liquids are hydrocarbons such as pentane, n- and isobutane, and propane; ethers such as dimethylether and diethylether; ketones such as aeetone and methylethyl ketone, ethylacetate and preferably ~o()~

halogenated hydrocarbons, such as methylene chloride, trifluorochloromethane, dichlorodifluoromethane, dichloromonofluoromethane, dichlorotetrafluoroethane and 1,1,2-trichloro-1,2,2-trifluoroethane. In addition, mixtures of these low boiling point liquids can be used with one another or with other substituted or unsubstituted hydrocarbons.

The amount of physically effective blowing agent required in addition to the water depends on the desired foam density and can be simply determined. The amount is from about O to 25 parts by weight, more preferahly O to 15 parts by weight per 100 parts by weight of mixture ~b) comprising components (bi) through (biii). It can also be efficacious to mix the physically effective blowing agent with the optionally modified polyisocyanates (a) and thereby to decrease the viscosity.

f~ According to ~he present invention melamine is used as flame retardant (f). A commercial form of melamine can be used and normally it has an average ;~oo~

particle size of from S to 50 microns and possesses the following particle size distribution:

10 weight percent of the particles are greater than 30 microns;
30 weight percent of the particles are greater than 24 microns;
50 weight percent of the particles are greater than 20 microns;
70 weight percent of the particles are greater than 16 microns;
90 weight percent of the particles are greater than 11 microns.

~elamine which has proven most useful and therefore preferably used has an average particle size of from 20 to 50 microns and a bulk density of from 300 to 800 grams per liter, more preferably 500 to 650 grams per liter. The melamine is best used in a quantity of from S to 130 parts by weight, and more preferably 70 to 100 parts by weight per 100 parts by weight of mixture (b) comprising components (bi) through (biii).

Efficaciously, melamine is exclusively used as said flame retardant. However, it can also be advantageous in achieving special effects, for example, homogenation and stabilization of the Rtarting component mixture, reducing smoke development in a fire, specific improvement of mechanical properties of the polyurethane foams prepared, etc., to combine the melamine with other organic or inorganic flame retardants so that the melamine can be used in a reduced quantity.
Mixtures of flame retardants ~f) which have proven most suitable in improving flame retardancy comprise:

fl) 70 to 100 parts by weight of melamine;

f2) 0 to 30 parts by weight, more preferably 3 to 15 parts by weight of starch, preferably selected from the group consisting of corn starch, rice starch, potato ~tarch, wheat starchr mixtures thereof and optionally chemically modified starch derivatives;

-~5- -f3) 0 to 30 parts by weight, more preferably 3 to 15 parts by weight of at least one additional flame retardant selected from the group consisting of tricresyl phosphate, tris-(2-chloroethyl)-phosphate, tris(2-chloropropyl)phosphate, tris(l,3-dichloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, tetrakis-(2-chloroethyl)ethylene diphosphate, aluminum hydrsxide, ammonium sulfate, ammonium, phosphate, and ammonium polyphosphate, whereby the parts by weight are each based on 100 parts by weight of mixture (b) of higher molecular weight compounds (bi~ through ~biii).

~lso effective are mixtures of flame reta~dants (f~
comprising:

fl) 70 to llDO parts by weight of melamine; and f2) 3 to 30 parts by weight of at least one of the above mentioned starches or the corresponding ~tarch derivative; or f3~ 1 to 30 parts by weight of ammonium polyphosphate whereby the parts by weight are each based on 100 parts by weight of mixture (b) comprising higher molecular weight compounds of (bi) through (biii)~

Most preferred as ammonium polyphosphate is the finely divided, difficultly soluble, modified form having the following general formula:

H~n-m)+2 ~NH4)mPn3n~1 in which n is a number having an average value of from 20 to 800, more preferably about 700 and the ratio of m to n is about 1 and the modified ammonium polyphosphate comprises about 80 to 99.5 mass percent of ammonium polyphosphate and about 0.5 to ,20 mass percent of a hardened epoxy resin having an epoxy equivalent weight of about 170 to about 220 which envelops the individual ammonium polyphosphate particles. Such ammonium polyphosphate, for example, can be purchased from Hoechst AZ as Exolit0.

g) Auxiliaries and/or additives Ig~ can also be added to the reaction mixture. Typical examples are surfactants, stabilizers, agents to protect against hydrolysis, cell regulators, fungistatic and bacteriostatic substances, dyes, pigments and fillers.

~ypical surfactants are those which serve to support the homogenation of the starting materials and which also possibly regulate the cell structure of the foam. Typical examples are siloxane-oxyalkylene mixed polymers and other organopolysiloxanes, oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils, castor oil and~or ricinoleic acid esters and Turkey red oil used in quantities of from 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight per 100 parts by weight of mixture (b) comprising (bi) through (biii).

The additives and auxiliaries can be found in the technical literature, for example, the monograph of J.H.
Saunders and K.C. Frisch, Hiqh Polymers, volume XVI, Polyurethanes, parts 1 and 2, Interscience Publishers, 1962 and/or 1964, or in the Plastics Handbook, Polyurethanes, volume VII, Carl-Hanser Publishers, Munich, Vienna, 1st and 2nd editions, 1966 and 1983.
When preparing the polyurethane flexible foams, the organic optionally modified polyisocyanates (a), the higher molecular weight compounds having at least 2 reactive hydrogen atoms (b), and optionally chain extending agents (c) are reacted in the presence of catalysts (d), blowing agents (e), flame retardant (f) and optionally auxiliaries andjor additives (g) at temperatures of from 0 to 100C, more preferably 15 to 80C in such quantity ratios so that per NCO group from 0.5 to 2, more preferably 0.8 to 1.3 and moæt preferably about 1 reactive hydrogen atom is and/or are present in bonded form from starting components (b) and optionally (c).
~ he polyurethane flexible foams are efficaciously prepared according to the one shot process by mixing two components namely, (A) and ~B). Here starting components ~b), ~d), (e), (f) and optionally (c) and (g) are added to the so-called (~) component and as the l~) component starting component (a) optionally mixed with (f), (g) and inert physically active blowing agents are used. Since the (A) component is storage stable for at least 6 months the (A~ and (~) components need only to be mixed intensively before the preparation of the polyurethane flexible foams.
The reaction mixture can be foamed in open or closed molds and is also suitable for the preparation of slab stock foams.
As previously stated, the process of the present invention is preferably used for the preparation of polyurethane flexible foams. The reaction mixture is normally introduced into a preferably heated metal mold at a temperature of from 15 to 80C, more preferably 30 to 65C. The mold temperature generally is from 20 to 90C, more preferably 35 to 70C. The reaction mix~ure can cure under compression, for example, with a degree of compression of from 1.8 to 8, more preferably 2 to 6, and most preferably 2.2 to 4 in a closed mold.
The po].yurethane flexible foams prepared according to the present invention have densities of from 35 to 120 g/l, preferably 40 to 80 g/l. They possess good flame resistance, passed the kerosene burner test (FAR 25.853C) and have a good mechanical property level. The molded foams are preferably used as cushioning elements, for example, as seat cushions, arm rests, head rests, sun visors and safety coverings in the interior of motor vehicles, preferably automobiles and airplanes, whereby most preferably airplane seats are prepared having densities of from 35 to 100 9/1.
The parts in the examples refer to parts by weight.

Example 1 A Component: a mixture comprising:

75 parts by weight of a polyoxypropylene-polyoxyethylene polyol initiated with glycerin having an average molecular weight of 6000;
10 parts by weiyht of a graft polyoxypropylene-polyoxyethylene polyol initiated with trimethylolpropane having an average molecular weight of about 6000 and a graft polymer content of 20 weight percent based on the total weight prepared while using an acrylonitrile styrene mixture in grafting;
20 parts by weight of a polyoxypropylene polyoxyethylene diamine having an average molecular weight of about 39D0 prepared by the amination of a polyoxypropylene polyoxyethylene glycol initiated with dipropylene glycol;
1.2 parts by weight of a silicone stabilizer (~ilicone DC 5043 from Dow Corning Corporation);
2.4 parts by weight of water;
10.0 parts by weight of trichlorofluoromethane;

0.42 parts by weight of a 33 weight percent solution of triethylene diamine in dipropylene glycol;
0.2 parts by weight of 2-(dimethylaminoethyoxy)ethanol;
0.12 parts by weight of bis~dimethylaminoe~hyl)ether;
1.2 parts by weight of diethanolamine; and 100.0 parts by weight of melamine B Component:

95 parts by weight of a urethane group containing quasi-prepolymer having a NCO content of 31 weight percent and a viscosity of 52 m-Pas at 25C prepared from a 2,4- and 2,6-toluene diisocyanate isomeric mixture in a weight ratio of B0.20 and from a polyoxypropylene-polyoxyethylene glycol having a molecular weight of 3900 and S parts by weight of trichloroethylpho~phate.
100 parts by weight of A component and 22 parts by weight of the ~ component corresponding to a ~CO index of 100 were intensively mixed together then the reaction mixture at a temperature of 23C was introduced into the hollow cavity of an airplane seat mold in such a quantity SQ

3~

that in the closed mold there was a degree of compression of 1.~.
The molded part was demolded after 12 minutes and stored 24 hours at room temperature.
The flame resistant molded article had the following mechanical properties:

Density lg/l]: 65 Tensile ~trength according to DIN 53 571 ~Pa]: 70 Elongation according to DIN 53 571 1%]: 75 Tear propagation strength according to DIN 53 575 IN/mm]: 0.36 Compression permanent set according to DI~ 53 572 ¦%]: 6 Example 2 A Component:

Anal~gous to example 1, but in place of the melamine as a flame retardant a mixture comprising the following was used:
85 parts by weight of melamine;
10 parts by weight of wheat starch; and 5 parts by weight of ammonium polyphosphate (Exolit~ 422 from Hoechst AG) B Component:

A urethane group containing quasi prepolymer having a NCO content of 31 weight percent, a visco~ity of 52 m-Pas at 25C prepared from a 2,4- and 2,6-toluene diisocyanate isomeric mixture (weight ratio 80:20) and a polyoxypropylene-polyoxyethylene glycol initiated with dipropylene glycol, having a molecular weight of 3900.
100 part6 by weight of the A component and 21 part~ by weight of the B component were reacted analogous to the disclo~ure in example 1 to form a flexible polyurethane molded foam.

.

The mechanical properties of the resulting flexible flame resistant polyurethane molded foam corresponded essentially to those of the product obtained according to example 1.

Examp1e 3 A Component:

Analogous to example 1, howeve~, in place of the melamine as a flame retardant a mixture of the following was used:
75 parts by weight of melamine and 25 parts by weight of ammonium polyphosphate (Exolit~ 422 from Hoechst AG).

B Component:

A urethane group containing quasi-prepolymer having a NCO content of 31 weight percent prepared from a 2,4- and 2,6-toluene diisocyanate isomeric mixture ~weight ra~io 80:20) and a polyoxypropylene/polyoxyethylene polyol initiated with trimethylolpropane having a molecular weight of 6200.
100 parts by weight of the A component and 21 parts by weight of the B component were reacted analogous to the teachings of examples 1 into a flexible polyurethane molded foam.

~o~

The flame resistant molded article obtained had the following mechanical properties:

Density 19/1~: 70 Tensile strength according to DIN 53 571 [KPa]: 70 Elongation according to DIN 53 571 [%]: 70 Tear propagation strength according to DIN 53 575 lN/mm]: 0.4 Compression permanent set according to DIN 53 572 [%~: 7 ~t~ .{~

Example 4 A Component:

Analogous to example 1, however in place of the melamine is a flame retardant a mixture of the following was used.
85 parts by weight of melamine; and 15 parts by weight of potato s~a~ch.

B Component:

A mixture of 2,4-- and 2,6-toluene diisocyanate in a weight ratio of 80~20.
100 parts by weight of the A component and 15 parts by weight of the B component were reacted analogous to the teachings of example 1 into a flexible polyurethane molded foam.
The flame resistant molded article obtained had the following mechanical properties:

Density [9/1~: 75 Tensile strength according to DIN 53 571 ~KPa]: ~8 Elongation according to DIN 53 571[%j: 75 Tear propagation strength according to DIN 53 575 [N/mm]; 0.35 Compression permanent set according to DIN 53 572 [~]: 7 The molded articles prepared according to examples 1 through 4 passed the kerosene burner test (FA 25.823 C) with less than a 10~ weight loss and accordingly fulfill the &trictest fire re~uirements today for polyurethane flexible foams.
By using the other flame retardants suitable according to the present invention the melamine content was reduced and so were the smoke gas densities.

Claims

1. A process for the preparation of flame resistant, elastic polyurethane flexible foams, comprising reacting:

a) organic polyisocyanates and/or modified organic polyisocyanates with;
b) higher molecular weight compounds having at least two reactive hydrogen atoms; and c) optionally lower molecular weight chain extending agents in the presence of;
d) catalysts;
e) blowing agents;
f) flame retardants;
as well as optionally g) auxiliaries and/or additives;
wherein a mixture having an average functionality of from 2 to 4 and having an average molecular weight of from 2200 to 8000 is used as starting component (b) which comprises bi) at least one polyoxyalkylene polyol;
bii) at least one polymer modified polyoxyalkylene polyol; and biii) at least one polyoxyalkylene polyamine; and melamine or a mixture of melamine and other flame retardants is used as flame retardant (f).

2. The process of claim 1 wherein the mixture of starting component (b) comprises:
bi) at least one polyoxyalkylene polyol having a functionality of from 2 to 4 and having an average molecular weight of 250 to 8000;
bii) at least one polymer modified polyoxyalkylene polyol having a functionality of from 2 to 4 and having an average molecular weight of from 1200 to 8000 selected from the group consisting of graft polyoxyalkylene polyols, and polyurethane-polyoxyalkylene-polyol-dispersions containing in bonded form polyurea groups, polyhydrazide groups and/or tertiary amino groups; and biii) at least one polyoxyalkylene polyamine having a functionality of from 2 to 4 and having an average molecular weight of 1800 to 8000.

3. The process of claim 1 wherein the mixture used as starting component (b), based on 100 parts by weight, comprises:
bi) 40 to 94 parts by weight of at least one polyoxyalkylene polyol having a functionality of from 2 to 4 and having an average molecular weight of 250 to 8000;
bii) 3 to 25 parts by weight of at least one polymer modified polyoxyalkylene polyol having a functionality of from 2 to 4 and having an average molecular weight of 1200 to 8000; and biii) 3 to 35 parts by weight of at least one polyoxyalkylene polyamine having a functionality of from 2 to 4 and having an average molecular weight of 1800 to 8000.

4. The process of claim 1 wherein the following is used as the polyoxyalkylene polyol (bi) for the mixture of starting component (b):
polyoxypropylene-polyoxyethylene polyols having more than 50 percent terminal primary hydroxyl groups, having a functionality of from 2 to 3 and having a molecular weight of 3600 to 6500; and polyoxytetramethylene glycols having a molecular weight of from 250 to 3000, or mixtures of the aforesaid compounds.

5. The process of claim 1 wherein 5 to 130 parts by weight of melamine per 100 parts by weight of mixture (b) of starting component (bi) through (biii) is used as flame retardant (f).

6. The process of claim 1 wherein the following mixture is used as flame retardant (f):

f1) 70 to 100 parts by weight of melamine;

f2) 0 to 30 parts by weight of starch; and f3) 0 to 30 parts by weight of at least one additional fire retardant selected from the group consisting of tricresyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tris (1,3 dichloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, aluminum hydroxide, ammonium sulfate, ammonium phosphate, and ammonium polyphosphate, whereby the parts by weight are each based on 100 parts by weight of mixture (b) of higher molecular weight compounds (bi) through (biii).

7. The process of claim 1 wherein a mixture of the following is used as fire retardant (f):

f1) melamine; and f3) modified ammonium polyphosphate, whereby the ammonium polyphosphate has the general formula H(n-m)+2(NH4)mPnO3n+1 in which n is a whole number having an average value of from about 20 to 800, the ratio of m to n is about 1, the modified ammonium polyphosphate comprises approximately 80 to 99.5 mass percent of ammonium polyphosphate, and approximately 0.5 to 20 mass percent of a hardened epoxy resin having an epoxy equivalent weight of about 170 to about 220, which envelopes the individual ammonium poly-phosphate particles.

8. The process of claim 1 wherein a mixture of the following is used as fire retardant (f):

f1) 70 to 100 parts by weight of melamine; and f2) 3 to 15 parts by weight of starch and/or f3) 3 to 15 parts by weight of at least one additional fire retardant selected from the group consisting of tricresyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tris(1,3-dichloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, aluminum hydroxide, ammonium sulfate, ammonium phos-phate, and ammonium polyphosphate, whereby the parts by weight are each based on 100 parts by weight of mixture (b) of higher molecular weight compounds (bi) through (biii).

9. The process of claim 1 wherein a mixture of the following is used as flame retardant (f):

f1) 70 to 100 parts by weight of melamine; and f3) 1 to 30 parts by weight of ammonium poly-phosphate, wherein the parts by weight each are based on 100 parts by weight of mixture (b) of higher molecular weight compounds (bi) through (biii).

10. The process of claim 1 wherein a mixture of the following is used as fire retardant (f);

f1) 70 to 100 parts by weight of melamine; and f2) 3 to 30 parts by weight of at least one starch selected from the group consisting of corn starch, rice starch, potato starch and wheat starch, wherein the parts by weight each are based on 100 parts; by weight of mixture (b) of higher molecular weight compound (bi) through (biii).

11. The process of claim 1 wherein 2,4-toluene diisocyanate, 2,6-toluene diisocyanate mixtures of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, and urethane group-containing polyisocyanate mixtures having a NCO content of 34 to 28 weight percent based on the aforesaid toluene diisocyanate isomers are used as the organic and/or modified organic polyisocyanates (a).

12. The process of claim 1 wherein a chain extending agent (c) is used in the preparation of the flame resistant elastic polyurethane flexible foams selected preferably from the group consisting of 1,6-hexanediol, diethanolamine, glycerin, and trimethylolpropane.

13. The process of claim 1 wherein melamine (f) has a bulk density of 300 to 800 gram per liter and an average particle size of 20 to 50 microns.

14. The process of claim 1 wherein the reaction is carried out in a closed mold under compression employing a degree of compression from 1.1 to 8.

15. A process for the preparation of airplane seats from the flame resistant elastic polyurethane flexible foams of claim 1 wherein said seats have a density of from 35 to 100 grams per liter.