FLAME RETARDANT INTERNALLY CURED POLYURETHANE FOAM HAVING IMPROVED PROPERTIES

Abstract: Flexible polyurethane foam forming compositions comprising a polyether polyol, and organic isocyanate compound, a blowing agent, and a curing agent, preferably melamine, in an amount effective to rapidly cure the resultant foam and improve the compression set properties of the foam, the amount of curing agent generally ranging from about 0.25 up to about 4 parts by weight based on 100 parts polyether polyol. Also, flame retardant polyether polyurethane foam prepared from foam forming components of a polyether polyol, an organic isocyanate compound, water, a liquid phosphorus ester in an amount of about 4 to 10 parts by weight and melamine in an amount of 1 to 5 parts by weight, each based on 100 parts by weight of the polyether polyol in the composition. Between 15 and 500 percent by weight melamine is used to replace a minor portion of the amount of ester (i.e., less than half) which would normally be used to achieve substantially the same degree of flame retardance in the foam. Also, the compositions of polyurethane foams and methods of forming same from such foam-forming compositions.

Description: FLAME RETARDANT INTERNALLY CURED POLYURETHANE FOAM HAVING IMPROVED PROPERTIES Technical Field: The invention relates to polyurethane foam-forming compositions and methods of forming flexible polyurethane foam therefrom in which a curing agent, preferably melamine, is added to the foam-forming components to rapidly cure the foam after formation as well as to concurrently improve the compression set properties of the foam. When flame retardant foams are desired, the amount of melamine can be used to replace a portion of conventional liquid phosphorus ester flame retardant additives without loss of the necessary flame retardant properties of the foam. Background Art: Polyurethane foam is prepared commercially in the form of large blocks that are subsequently cut into the desired shape for use in the manufacture of various articles that require a foam padding. It is well known that polyurethane foam requires time to cure and develop its full physical properties. In typical polyurethane foam formulations, a polyhydroxy material ("polyol") , water as a blowing agent and an organic isocyanate compound are reacted in the presence of catalysts or other additives. Much of the time, a small percentage of terminal isocyanate groups are left unreacted in the foam structure. If the foam is distorted or compressed in this condition, it fails to recover its original dimensions when the distortive or compressive force is released. Normally, the terminal isocyanate groups that are left unreacted in the foam structure will react with the residual water in the foam structure or with the water vapor I in the atmosphere over a period of several hours or days, and the foam will ultimately achieve its full physical proper¬ ties. As pointed out in the Encyclopedia of Polymer Science and Technology (John Wiley and Sons, New York 1969) in the section on Polyur thanes, polyethers are commercially the • * _ most important of the polyols used to prepare polyurethanes. At the present time most of the polyethers used in the production of flexible polyurethane foams are derived from propylene oxide and ethylene oxide. In this preparation, propylene oxide is reacted with glycerol in the presence of a basic catalyst to form a poly(oxypropylene) homopolymer which is further reacted with ethylene oxide to form a block copolymer. According to the prior art, melamine in relatively large quantities, i.e., above 20 to as high as 200 parts by weight based on 100 parts polyol, has been used in both flexible and rigid foams as a fire retardant additive, either alone or in combination with other materials such as silica, alumina, halogenated phosphorus ester compounds, and the like. For example, British Patent Specification No. 2,094,315 discloses an intumescent, highly resilient polyether urethane foam prepared by reacting a polyether polyol, an organic polyisocyanat , a catalyst, a surface active agent, a blowing agent, an intumescent material, a carbonific element for forming a carbonaceous char by reaction with the acid libera¬ ted from the intumescent material, and optionally, a spumific element for generating non-flammable gases which contribute to the intumescence and to a reduction of the effects of flame on the surface of the resulting foam. Melamine is disclosed as a suitable spu ific element, and the examples show the use of 10 or 20 parts melamine based on 100 parts polyol. Another example of the use of melamine in flame resist¬ ant flexible polyurethane foams is found in U.S. Patent No. 4,258,141. These foams generally contain a specific aromati isocyanate compound, a polyol, flame inhibitors, and blowing agents, with optional additions of chain extenders and other additives. The amount of melamine (or other cyanic acid derivative) ranges from 10 to 70 weight percent, preferably 20 to 50 weight percent, based on the weight of the aromatic polyisocyanates or mixtures of aromatic polyisocyanates. Melamine has also been used as an additive to the foam forming components of other foams, such as polyester poly¬ urethane foams and rigid foams. U.S. Patent No. 4,317,889 discloses flexible, resilient polyester polyurethane foams with substantially improved charforming or intumescent properties, obtained by adding to a conventional polyester polyurethane foam forming reaction mixture at least one melamine derivative, at least one flame retardant, and hydrated alumina. The amount of melamine derivative generally ranges from about 10 to 30 parts by weight based on 100 parts by weight of the polyester polyol. Also, U.S. Patent No. 3,897,372 discloses polyurethane foam compositions having flame retardancy and reduced smoke density formed by reacting specific polyisocyanate capped polyoxethylene glycol resin reactants with water. Melamine is added to these foam-forming compositions in an amount of between 1 and 200 parts by weight based on 100 parts by weight of the resin reactant, along with between 50 and 400 parts by weight of aluminum hydrate. Rigid polyurethane foams which include melamine powder in an amount of between 20 and 100 parts by weight based on " the weight of the polyhydroxyl compound are described in U.S. Patent No. 4,221,875. Also, West German Patent No. 2,348,838 discloses a method for flameproofing synthetic polyurethane • materials by adding to a mixture of polyisocyanates, catalysts, polyols, foaming agents, and auxiliary agents, melamine as a flameproofing agent in an amount of between 2.5 and 50% by weight based on the total weight of the reaction mixture. Rebond polyurethane foam compositions having melamine or urea incorporated therein are described in U.S. Patent No. 4,385,131. These additives are included in an amount of between about 40 to 100 parts per 100 parts of polyurethane foam chips. The additives and foam chips are joined by a liquid binder to form flame retardant rebond foam articles. U.S. Patent No. 3,726,835 discloses that melamine or dicyandiamide can be utilized as a stabilizer for poly¬ urethane prepolymers which are thereafter cured to form elastomeric polymers. In these compositions, 10 parts melamine or dicyandiamide is added to 100 parts prepolymer. U.S. Patent No. 4,374,207 discloses flexible, resilient, polyurethane foam having improved flame retardancy and intumescent properties prepared from a reaction mixture comprising a polyether polyol, an organic polyisocyanate, a blowing agent, a surfactant, a catalyst, a flame retardant and hydrated alumina, optionally with a char former of a melamine derivative. U.S. Patent Nos. 4,139,501 and 4,197,373 disclose poly¬ ether polyurethane foams containing, as a flame retardant additive, a melamine derivative, usually in amounts ranging from one to 20 weight percent of the polyol (in the , 501 patent) and from 0.25 to 30 parts by weight based on 100 parts polyol in the '373 patent. The '501 patent also utilizes conventional halogenated esters in amounts ranging from 4 to 30 percent by weight of the polyol to further increase the flame retardance. Post-curing of polyether derived foam by exposure to a mixture of water vapor and gaseous ammonia, primary or secondary amines at temperatures of about 50 to 150 β F for a period of at least one minute is disclosed in U.S. Patent No. 4,537,912. While this process effectively and rapidly cures the foam, it constitutes an additional step beyond those normally used in the foam manufacturing process. This process also requires storage of the foam prior to the post curing treatment. It is more desirable to cure the foam as it is manufactured to reduce or even eliminate such storage time and to prepare a fully cured foam material which can be immediately shipped to the end users after cutting to the desired shapes. None of these references disclose the possibility of using melamine or other curing agents for rapidly curing polyether polyurethane foam while concommittantly improving the compression set properties, nor do they disclose the benefits of substituting small amounts of these agents for a portion of the conventional liquid phosphorous esters to maintain the desired flame retardance of the foam. The present invention provides a one-step foaming and curing process which achieves a rapid and full post cure of the foam so that low compression set values as measured by ASTM standard test D-3574 (Constant Deflection Compression Set Test) are obtained, with the elimination of post curing steps, and with a reduction of conventional liquid phosphorus flame retardant esters while retaining the same degree of flame retardance of the foam. Summary of the Invention The present invention relates to a flexible polyurethane foam forming composition comprising a polyether polyol; an organic isocyanate compound; water; a curing agent, prefer¬ ably melamine, in an amount effective to rapidly cure the resultant foam and improve the compression set properties thereof up to abou -4 parts by weight; and optionally, between about 4 to 10 parts by weight of a liquid phosphorus ester flame retardant agent, said amounts based on 100 parts by weight of the polyether polyol. An embodiment of the invention relates to a method for rapidly curing and improving the compression set properties of a polyurethane foam which comprises adding a curing agent, again preferably of melamine, to a polyurethane foam-forming composition containing a polyether polyol, an organic isocyanate compound, and water, the curing agent being added in an amount sufficient to rapidly cure the resultant foam and improve the compression set properties and up to about 4 parts by weight based on 100 parts by weight of the polyether polyol, and thereafter forming the polyurethane foam from the foam-forming composition. Another embodiment of the present invention also relates to a method for maintaining the flame retardant properties of a polyether polyurethane foam prepared from a polyurethane foam-forming composition comprising a polyether polyol, an organic isocyanate compound, water, and a liquid phosphorous ester flame retardant additive. This method includes the steps of replacing a minor portion of the liquid phosphorous ester with an amount of melamine which is less than that which would normally be necessary to achieve similar flame retardance if melamine alone is used. Melamine alone is not effective unless about 20 parts by weight based on 100 parts by weight polyol is used, while the effective amounts of ester generally ranges from about 5 to 10 parts. In this invention, we have found that generally, between 1 and 6 parts of the ester can be replaced with between 1 and 5 parts melamine with no loss of flame retardant properties of the foam. Thus, the amount of melamine which is to replace part of the ester ranges from about 15 to 500 percent of the minor portion of the ester which is to be replaced. Preferably, the amount of melamine ranges from about 50 to 300 percent of the minor portion of the ester. "Minor portion" is used to mean less than half of the amount of flame retardant ester additive which would normally be used. Preferably, less than 33%- or even less than 25% by weight of the total amount of ester additive is replaced with melamine. Thereafter, the foam is formed from the melamine containing foam-forming composition. As noted above, about 1 to 6 parts of the ester, which is usually used in an amount of from 8 to 10 parts based on 100 parts polyol, are replaced with between about 1 and 5 parts of melamine. Optimum results are achieved when equal amounts of ester are replaced by the melamine, usually in an amount of about 1 to 3 parts and most preferably 2 parts i.e., 2 parts melamine for 2 parts ester. Another aspect of the invention relates to a flexible polyether derived polyurethane foam forming composition comprising a polyether polyol; an organic isocyanate compound; water as a blowing agent; and between about 0.1 and 4 parts by weight based on 100 parts by weight of the polyether polyol of a curing agent of a compound of the formula wherein R.1 is hydrogen or an alkyl. alkenyl, cycloaliphatic, or aryl moeity having between one and twelve carbon atoms; 2 is an alkyl, alkenyl, cycloaliphatic or aryl moeity having between one and twelve carbon atoms and at least one hydroxyl moeity; and x is between about 0.5 to β, inclusive. Preferably, the polyether polyol is a conventional unmodified polyether polyol; R. is hydrogen; R_ is a hydroxy alkyl moeity having between 2 and 4 carbon atoms; and x is between 2 and 3. This curing agent is preferably used in an amount of between about 0.4 and 1.4 parts by weight based on 100 parts by weight of the conventional polyether polyol. Detailed Description o ' f the Invention The objectives of this invention are accomplished by incorporating into the foam forming components of a flexible polyether polyurethane foam composition a small amount of a curing agent, preferably of melamine. Then, during the foam-forming reaction, the melamine rapidly cures the foam, i.e., improves the resulting compression set properties of the foam. This amount of melamine also replaces a portion o the conventional liquid phosphorus ester flame retardant agent without reducing the flame retardant properties of the foam. The term "polyether polyurethane" as used throughout this application generally refers to conventional, unmodifie polyurethanes derived by polyether polyols. This class would include the poly(oxytetramethylene) glycols which are prepared by the polymerization of tetrahydrofuran. Poly(oxypropylene) triols are another important group of polyethers used in the manufacture of polyurethanes which are included in this class. These triols are prepared by the same general reactions as poly (oxypropylene) glycols. The polyurethanes derived from polyesters do not normally present post-curing problems and thus do not form part of this inven¬ tion. The term "organic isocyanate compound" is used to describe the isocyanate or polyisocyanate compounds that are suitable for use in this invention. Such organic isocyanate compounds include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof. Representative of these types are the diisocyanates such as m-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate (and isomers) , naphthalene- 1,5-diisocyanate, l-methoxyphenyl-2,4-diisocyanate, 4,4,-diphenylmethane diisocyanate, 4,4'-biphenylene diisocyanate, 3,3-dimethoxy- 4,4 -biphenyl diisocyanate, 3,3 , -dimethoxy-4,4-'-biphenyl diisocyanate, .3,3'-dimethyl-4,4'-biphenyl diisocyanate and 3,3 -dimethyldiphenylmethane-4,4'-diisocyanate; ' the triisocyanates such as 4,4'4"-triphenylmethane triiso- cyanate, and toluene 2,4,6-triisocyanate; and the tetraiso- cyanates such as 4,4 / -dimethyldiphenylmethane-2,2 / -5,5''- tetraisocyanate and polymeric polyisocyanates such as poly- methylene polyphenylene polyisocyanate. Especially useful due to their availability and properties are toluene diiso¬ cyanate, 4,4'-diphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanate. Crude polyisocyanates may also be used in the composi¬ tions of the present invention, such as crude toluene diisocyanate obtained by the phosgenation of a mixture of toluene diamines or crude diphenylmethane isocyanate obtained by the phosgenation of crude diphenylmethane diamine. The preferred, crude isocyanates are disclosed in U.S. Pat. No. 3 f 15,65 . The polyurethane foams employed in the present invention are generally prepared by the reaction of the polyether polyol with the organic isocyanate compound in the presence of a blowing agent, i.e., water and, optionally, in the presence of additional polyhydroxyl-containing components, chain-extending agents, catalysts, surface-active agents, stabilizers, dyes, fillers and pigments. The preparation of cellular polyurethane plastic foam is well known in the art. Corresponding quantities of excess isocyanate compound are used to react with the water, generally used in an amount of less than about 6 parts, to produce carbon dioxide. It is also possible to proceed with the preparation of the polyurethane by a prepolymer technique wherein an excess of the organic isocyanate compound is reacted in a first step with the polyol of the present invention to prepare a prepolymer having free isocyanate groups which is then reac¬ ted in a second step with water and/or additional polyols to prepare a foam. Alternatively, the components may be reacted in a single working step commonly known as the "one shot" technique of preparing polyurethanes. Flexible, one shot polyurethane foam is formed by two principal reactions: 1. The reaction of hydroxyl groups in a polymeric polyol with an isocyanate group to form a urethane linkage. Because of difunctional isocyanates, oligomers are formed. As the reaction proceeds, the viscosity increases to a point that the mixture is said to have "creamed". R-OH + R'NCO =- R-0-C-N-R' (urethane group) 0 H 2. Water reacts with an isocyate group to form an unstable carbamic acid. The acid decomposes to generate C0_ and an amine. The amine in turn reacts with an isocyanate to form a urea group. 2R -NCO + H-0 -- R'-N-C-N-R" (urea group) + C0 2 i II I H O H The presence of excess isocyanate groups in the formula¬ tion promotes cross-linking by reacting with the previously formed urethane and urea linkages to form allophonates and biurets. This begins to occur at about 80"C. . While the use of excess isocyanate is important for stabilizing the foam as I I it forms and improving physical properties, this excess can also lead to isocyanate groups being physically trapped within the matrix after foam formation. As the -OH's and -NH's are consumed by the reaction, those remaining biurets and allophonates also became fixed in some locations. The result is that unreacted isocyanate groups remain in the foam. Poor compression sets are said to result when unreacted isocyanate groups on a cell wall are forced by compression against another wall. If these isocyanate groups react when compressed, the deformation is permanent; hence, poor compression set properties of the foam are obtained. The problem then becomes how to provide enough isocyan¬ ate to form the foam without also obtaining poor compression set properties. Two solutions are known. I. Atmospheric moisture, which is always present in the foam slab, can eventually react with the excess isocyanate-groups. This moisture is present primarily due to diffusion of the humidity from the atmosphere, while some moisture may be present due to the use of excess water in the foam forming ingredients. Whatever the source, this moisture is available in the foam for reaction with the excess isocyanate. Because of the size of the foam slab and the uncooperativeness of nature in providing reliable relative humidity, this.reaction can take three days to six weeks and is not a practical solu¬ tion. In addition, it is not possible to predict when the reaction is substantially complete, so the foam must be tested periodically with a test that takes 24 hours. / 3 2. The forced cure process described in U.S. Patent No. 4,537,912 can be used: ammonia and moisture vapor are brought to the isocyanate to effect an essentially instant cure. While this extra process- ing adds to the cost of the foam and presents logis¬ tical problems, it at least makes it possible to plan on reliable compression set properties while eliminating the need for excessive storage areas for holding the foam as it cures. We have now discovered that it is indeed possible to use high enough isocyanate indices for foam formation and still not interfere with rapidly obtaining good compression sets. Melamine powder, added in small amounts into the polyol provides an inexpensive solution. Melamine is easy to disperse, does not react with the foam-forming components, does not interfere with the foaming process, and does not detract from the physical properties of the foam. In fact, melamine even marginally improves the physical properties of the foam and provides some flame retardant properties as well. Melamine appears to work very much like ammonia, i.e., as a catalyst for the reaction of the remaining isocyanate groups with the moisture that is present in the foam. On the surface, melamine appears quite different. It is a white crystalline powder which melts at 350°C and dissociates at 610"F. It has very little solubility in most common solv¬ ents. In comparison, ammonia, a gas, is much more basic than melamine and has less steric hindrance, so would be a much stronger catalyst. Because of the high reactivity of ammonia, it cannot be introduced to the foam until the chemistry is essentially complete. It cannot be added to the formulation and, in fact, cannot be introduced until the foam is several hours old. When it is introduced with moisture, it catalyzes the almost instantaneous reaction of the remaining isocyanate groups with water. Melamine is a weak base having more steric hindrance than ammonia. It is essentially insoluble in both the start¬ ing ingredients and the foam. This would suggest that the reaction with isocyanate would be very slow and that its catalytic effect would be weaker than ammonia. Because of this, melamine can be added to the foam forming ingredients. There also appears to be no effect on cream time. As the temperature rises there appears to be some effect on the rate of rise. This shortening of rise time is an indication that the water/isocyanate reaction is being catalyzed. When the rise is complete, the unreacted isocyanate appears to be at least partially complexed by melamine. As the gases in the open cell foam are exchanged with the atmosphere, the mois¬ ture in the humidity of the surrounding air enters the bun. This moisture finds the reactive complex and reacts to elimi¬ nate the isocyanate group, thus removing this source of poor compression set properties. The actual reaction with isocyanate appears to be mostly restricted to this intermediate complex. There is evidence, both factory and laboratory, that melamine is not becoming permanently involved in the polymer formation. Another useful curing agent is a composition of the formula Throughout the specification, this formula will be abbrevi¬ ated as C_N r (R) ιr . Preferably, the R moeities are ' the combination of (R.) 6- . v (- R 2 ^x wherein R. is hydrogen or an alkyl, alkenyl, cycloaliphatic, or aryl moeity having between one and twelve carbon atoms; R is an alkyl, alkenyl, cycloaliphatic, or aryl moeity having between one and twelve carbon atoms and at least one hydroxyl moeity; and x is between about 0.5 to 6, inclusive. Preferably, R is hydrogen; R_ is a hydroxy alkyl moeity having between 2 and 4 carbon atoms; and x is between 2 and 3, inclusive. This curing agent is preferably used in an amount of between about 0.01 and 4, preferably between 0.4 and 1.4 parts by weight based on 100 parts by weight of the polyether polyol. The most preferred material is known in the trade as Melpol ® , and is available from American Cyanamid. The formula for this material is C_ JNO-H_J . D_(CH Z_CH0HCH_->),_____. D_, since this material is a combination of about 5% by weight C_N c H c ( CH- CHOHCH_ ) , 40% C-N-H . ( CH. CHOHCH. ) . and 55% 3 6 5 λ 2 3 ' 3 6 4 2 3 2 C 3 N 6 H 3 (CH 2 CHOHCH 3 ) 3 . It has also been found that the Melpol ® compound is sufficiently soluble in conventional polyether polyols to allow suitable quantities of the compound to be added to the foam forming formulations by incorporation in the polyol. Thus, the preferred compounds of formula I are those which are soluble in the polyol or other foam forming components. / <r As noted above, the curing aqent is added to the form- forming composition to cure the foam immediately after foam formation so that greatly improved (i.e. lower) compression set values are obtained, as determined according to ASTM test method D-3574. The most preferred curing agent is melamine in the form of a powder, and any amounts in the range of about 0.1 to 4 parts by weight and preferably between 1 and 2 parts by weight based on 100 parts by weight of polyether polyol are suitable. Amounts of 5 parts by weight or higher based on 100 parts by weight of polyol do not improve and, in fact, detrimentally affect the compression set properties of the resulting foam and therefore should not be used. The particle size of the melamine powder is not critical and any particle size ranges between 1 and 100 microns is suitable. Two standard melamine powders, have been found to be suitable: Pluragard ® melamine powder by BASF, which has a particle size distribution of 60% of less than 44 microns, and finely ground melamine powder by MCI, which has a particle size distribution of 90% less than 10 microns. In addition to melamine, other curing agents having as an active moeity an amine or hydroxyl group are also useful; however, the active moeity must not enter into the early stages of the foam forming reaction. This can be determined in the compound by its basic nature. The specific require¬ ments for suitable curing agents are: a reactive moeity in the form of primary or second¬ ary amine, or an alcohol, or the melamine structure; n 2. a dissociation constant of between about 1.8 x 10 -5 3. insolubility and/or immiscibility of the compound in the reaction media; i.e., the foam-forming compon¬ ents. Therefore, predictability of success of the compound is limited to knowing its dissociation constant, its Lewis base strength and how available the moeity is for reaction with the isocyanate. At the same base strength or dissociation constant, soluble materials will react fast, miscible materials (liquids) rapidly and insoluble solids very slowly. For example, aniline is a weaker base than melamine. However, it is a liquid that either dissolves or mixes with the preferred isocyanate, TDI. Aniline provides a rapid cure, but if sufficient aniline enters the foam reaction early enough, it can interfere with the polymerization process. As a result the physical properties of the foam will suffer. As noted above when the Melpol ® compound is used as the curing agent, an amount of between 0.1 and 4 parts by weight, preferably between 0.4 and 1.4 parts by weight, has been found to be suitable. Since the Melpol ® compound is somewhat soluble in the normal polyether polyols which are utilized, a particularly convenient way to add the Melpol ® compound to the foam forming components, is in solution with a portion of the polyol. Heating the polyol to, for example, 100°F can increase the solubility of the compound therein. Thus, a 25% by weight solution of Melpol ® compound in the polyol can be used in an amount of about 2 parts so that, effectively 0.5 parts by weight are added to the foam. The amount of polyol can be decreased to 98.5 parts so that the resultant formulation contains a total of 100 parts by weight of the polyol. The solubility of the Melpol ® compound in the polyol does not affect the polymerization process, and provides an additional advantage in that a lower amount of Melpol ® compound (compared to the insoluble melamine) is used to achieve similar physical properties and flame retardance in the foam. In accordance with the preceding, additional curing agents include cyanuric acid, 2,6-diaminopyridine, dicyan¬ diamide, formamide, 2-hydroxy benzimidazole, 3-amino- 1,2,4- triazole, hypoxanthine, caprolactam, 3-amino-l,2,4_ triazine, 4,4,-m thylene dianiline and aniline, and these are contem¬ plated as being within the scope of the present invention. It is believed that melamine derivatives having the basicity values described above and which are relatively insoluble in the foam-forming components or which do not affect the foam forming reaction should help cure the foam while also providing improvement to the resulting compression set values when used in the above-stated ranges. Thus, such melamine derivatives are contemplated as being within the scope of this invention. As noted above, due to its relatively low cost and availability, melamine powder is the most preferred additive. While a single curing agent is added for ease of formulation of the foam, it is understood that two or more of these agents may be used in combination, and such combinations are contemplated by this invention. It has also been found that melamine is capable of replacing a portion of the more expensive conventional flame retardant(s) in small amounts without reducing the flame retardant characteristics of the foam. i f In this embodiment, the most preferred amounts of melamine range from about 1 to 5 parts by weight and prefer¬ ably between 1 and 3 parts by weight based on 100 parts by weight of polyether polyol. These amounts are suitable for replacing between 1 and 6 parts of conventional liquid phos¬ phorus ester flame retardant agent. Amounts higher than 5 parts by weight of melamine based on 100 parts by weight of polyol used in conjunction with the reduced amounts of liquid phosphorus ester additive do not provide any further benefits since the cost of the formulation is increased and flame retardance is only slightly increased within acceptable limits. Generally, 4 parts melamine maximum are used to avoid detrimentally affecting the compression set properties of the foam. Suitable flame retardants for use in the composition of the invention include those which are conventionally used in the art of making flexible, flame retardant polyurethane foams, such as tri-esters of phosphoric acid, halogenated triesters of phosphoric acid, halogenated hydrocarbons, and the like. Specific examples of such suitable flame retardants are: tris(1,3-dichloropropyl)phosphate, tris(2,3-dibromopropyl)- phosphate, 2,2-bis(chloromethyl)-1,3 propylene bis[di(2- chloroeth 1) hosphate] , t is(2-chloroethyl)phosphate, tris(2-chloroprophyl)phosphate, bis(dichloropropyl) tribro- moneopentyl phosphate, tetrakis(2-chloroethyl) ethylene diphosphate (sold by Olin Chemical,s as THERMOLIN ® 101), FYROL ® EFF(oligomeric chloroalkyl phosphate, sold by Stauffer Chemical Co.), tricresyl phosphate, cresyl diphenyl phos¬ phate, chlorinated paraffin, and brominated paraffin. Halo¬ genated phosphates are generally preferred as flame retardant additives in polyether polyurethane foams of the invention, Zo especially tris(1,3-dichloropropyl)phosphate, tris(2-chloro¬ ethyl)phosphate, FYROL ® EFF, and tetrakis(2- chloroethyl)ethylene diphosphate, with the first and last- named being particularly preferred. It is also possible to utilize in this invention liquid flame retardants similar to those described above but which also contain reactive hydroxyl groups in their structure, such as Vircol ® 82. Although a single flame retardant is preferred from the standpoint of simplicity of formulation, mixtures of two or more of the same type or of different types may be found to give improved performance in some cases, and such mixtures may be included in the foams of this invention. The amount of flame retardant additive or mixture according to the prior art generally ranges from about 8 to about 10 parts by weight per 100 parts by weight of polyol in the foam forming composition, however, depending upon the specific compound used, the amounts could range from 5 to 20 parts by weight based on 100 parts by weight polyol or even more. In this invention, it is found advantageous to use from about 4 to about 8 parts by weight of the ester along with between 1 and 3 parts of melamine to achieve the desired flame retardance. Other additives for forming the foam which may be incorporated into these form foaming compositions are well known to those skilled in the art, and would include, for example, catalysts, chain extending agents, and surfactants or surface active agents. Chain-extending agents which may be employed in the preparation of the polyurethane foams of the invention include those compounds having at least two functional groups zι bearing active hydrogen atoms such as water, hydrazine, primary and secondary diamines, amino alcohols, amino acids, hydroxy acids, glycols, or mixtures thereof. A preferred group of chain-extending agents includes water, ethylene glycol, 1,4-butanediol and primary and secondary diamines which react more readily with the prepolymer than does water such as phenylene diamine, l,4-cyclohexane-bis-(methylamine) , ethylenedia ine, diethylenetriamine, N-(2-hydroxypropyl) ethylenediamine, N,N-di(2-dydroxypropyl)ethylenediamine, piperazine, and 2-methylpiperazine. Any suitable catalyst or combination of catalysts may be used including tertiary amines such as, for example, triethy- lenediamine, N-methylmorpholine, N-ethylmorpholine, diethyl- ethanolamine, N-cocomorpholine, l-methyl-4-dimethylamino- ethylpiperazine, 3-methoxypropyldimethylamine, N,N,N'- trimethylisopropyl propylenediamine, 3-diethylaminopropyl- diethylamine, dimethylbenzylamine, and the like. Other suit¬ able catalysts include, for example, stannous octoate, stannous chloride, dibutyltin di-2-ethyl hexanoate, stannous oxide, as well as other organometallic compounds such as are disclosed in U.S. Pat. No. 2,846,408. A surfactant or surface-active agent is generally necessary for production of high grade polyurethane foam according to the present invention, since in the absence of same, the foams may collapse or contain very large uneven cells. Numerous surface-active agents have been found satis¬ factory, with nonionic surface active agents being preferred. Of these, the well-known silicones have been found to be particularly advantageous. Other surface-active agents which are operative, include polyethylene glycol ethers of long chain alcohols, tertiary amine or alkanolamine salts of long chain alkyl acid sulfate esters, alkyl sulfoniσ esters, and alkyl arylsulfonic acids. Examples The scope of the invention is further described! in connection with the following examples which are set forth for the sole purpose of illustrating the preferred embodi- ments of the invention and which are not to be construed as limiting the scope of the invention in any manner. In these examples, all parts given are by weight unless otherwise specified, while the density values are reported in pounds per cubic feet, the porosity values in cubic decimeters per second and the compression set values in percent loss as defined in ASTM D-3574. Also, unless noted otherwise, all references to melamine powder refer to the BASF Pluragard ® material described above. Example 3: (Comparative) Three control samples were prepared from the following formulation: Component parts by weight polyether polyol* (3000 mw) 100.0 toluene diisocyanate (80/20) 49.7 water 4.0 stannous octoate catalyst 0.27 silicone surfactant 1.0 amine catalyst 0.4 conventional fire retardant additives 8.0 *Polyol 3010 from Dow Chemical Six samples were prepared at 70°F, three were allowed t age for 24 hours and three were aged for one week. The following properties (averaged from the samples) were measured: Property Value compression set (24 hours) 30.7 compression set (1 week) 8.9 porosity 4.2 density 1.59 Examples 2-8: To the control formulation, 0.25, 0.5, 1, 2, 3, 4 and 5 parts melamine powder, respectively, were added t prepare the foams of Examples 2-8. Three samples of each foam were prepared and tested in the same manner as in Example I. Results averaged from three samples of each Example were as follows: Value of Example Property 2 3 4 5 6 7 8 compression set (24 hours) 20.7 21.-. 8.4 8.0 9.2 13.5 32.1 compression set (1 week) 8.6 8.5 8.2 8 . 2 9 . 1 12 . 7 27 . 4 porosity 4.4 4.0 4.4 4 . 5 4 . 2 4 . 1 4 . 5 density 1.61 1.60 1.61 1. 61 1 . 62 1. 63 1. 6 The results show improvement over the control for Examples 2-7, with maximum efficiency for the addition of 1 to 2 parts melamine powder (Examples 4-5) . Also, the addition of 5 parts melamine powder gave worse compression set results than the control without melamine powder. Example 9: (Comparative) Nine control samples (A through I) were prepared from the following formulation: Component parts i by weight polyether polyol* (3000 mw) 100. . 0 toluene diisocyanate (80/20) 49 . . 7 water 4 . . 0 stannous octoate catalyst 0 . . 27 silicone surfactant 1. , 0 amine catalyst 0 . , 35 conventional fire retardant additives 8.21 *Polyol 3010 from Dow Chemical Foam samples were prepared at ambient temperature (i.e., 74-78°F) , and the following properties were measured: Compression Set 87.8 87:4 86.3 81.7 86.6 82.4 87.4 85.9 84.3 85.5 These properties were determined from the middle section of foam samples which were wrapped while aging. The proper¬ ties of foam sample A properties were determined 3 hours after foam formation, foam samples B and C at 4 hours, and the remaining foam samples at 2.5 hours. Example 10: To the control formulation of Example 9, 1.8 parts of melamine powder were added to prepare nine foam samples (J through R) . These samples were prepared at temperatures between 74 and 78°F, and the following properties were measured. Example Property J K L M N 0 P Q R Average Density 1.56 1.52 1.54 1.63 1.53 1.59 1.57 1.50 1.53 1.55 Porosity 5.2 5.4 5.2 5.3 5.1 4.1 4.2 5.9 4.9 5.0 Compression Set 6.0 4.-5 4.7 4.3 3.3 5.6 4.2 5.2 5.1 4.8 The properties of foam sample J were measured 3 hours after foam formation, the properties of foam samples K and L were measured at 4 hours, while the remaining foam samples were tested at 2.5 hours. These data show that, at an addition of about 1.8 parts melamine powder, optimum properties are obtained. Example 11: (Comparative) Another foam formulation was prepared as follows: Component parts by weight polyether polyol* (3000 mw) 100.0 toluene diisocyanate (80/20) 49.7 water 4.0 stannous octoate catalyst 0.25 silicone surfactant 1.1 amine catalyst 0.28 conventional fire retardant additives 8.21 *Polyol 3010 from Dow Chemical A foam sample was prepared at 70°F and the following properties were measured three hours after foam formation from the middle section of the sample. ■ lo Property Value Density 1.65 Porosity 4.2 Compression Set 17. A Example 12: To the formulation of Example 11, 1.8 parts melamine powder were added. The foam was formed at 70°F and the following properties were determined under the same conditions as Example 11. Property Density Porosity Compression Set Example 13-26: (Comparative) Four control samples were prepared from the following fo'rmulation: Component parts by weight polyether polyol* (3000 mw) 100.0 toluene diisocyanate (80/20) 49.7 water 4.0 silicone surfactant 1.0 amine catalyst 0.35 stannous octoate catalyst 0.28 conventional fire retardant additives 8.0 *Polyol 3010 from Dow Chemical For Examples 13, 14 and 17 through 26, an amine catalyst in an amount of 0.35 parts, a stannous octoate catalyst in an amount of between 0.25 and 0.28 parts and conventional fire retardant additives in an amount of 8.21 parts were added, Hi while Examples 15 and 16 utilized 8.0 parts conventional fire retardant additive, 0.32 parts of the amine catalyst and 0.46 parts of the stannous octoate catalyst. Foams were prepared at ambient temperatures (i.e., 66- 76°F), and the following properties were measured from a sample taken from the middle of the foam 2.5 hours after aging. Property Example Density Porosity Compressi 13 1.53 2.2 79.7 14 1.58 2.9 79.4 15 1.62 4.2 87.0 16 1.57 4.6 86.7 17 1.52 3.1 78.1 18 1.57 3.0 85.2 19 1.55 2.6 85.3 20 1.61 3.1 82.5 21 1.59 3.1 80.5 22 1.59 3.2 78.5 23 1.54 4.2 78.4 24 1.57 3.8 85.2 25 1.60 2.8 82.8 26 1.57 2.2 86.3 Average e D / 83 . 3 Examples 27-30: To the control formulations of Examples 13 and 14, 1.8 parts of caprolactam were added to prepare the foams of Examples 27 and 28, respectively, and 1.8 parts of melamine powder were added to prepare the foams of Examples 29 and 30, respectively. These samples were prepared at 73 c and the following properties were measured from the middle section of the foams after aging for 2.5 hours. Example Property 27 28 29 30 Density 1.72 1.65 1.50 1.54 Porosity 3.0 3.2 3.2 3.1 Compression Set 6.5 7.6 4.9 4.6 Examples 31-36: To the control formulations of Examples 15, 16 and 17, 1.8 parts of anililne were added to prepare the foams of Examples 31, 32 and 33, respectively, while 1.8 parts of melamine powder were added to prepare the foams of Examples 34, 35 and 36, respectively. Each of the cyanuric acid and melamine containing foams were prepared at 66, 75 and 76°F, respectively, and the following properties were again measured 2.5 hours after foam formation from a middle section of the foam as in the preceding examples. Example Property 31 32 33 34 35 36 Density 1.54 1.49 1.51 1.56 1.59 1.49 Porosity 5.6 5.7 5c0 5.8 5.6 5.0 Compression Set 3.5 4.2 5.1 3.3 4.5 5.5 Examples 37- -42: To the control formulations Of Examplees 18, 19 and 20, 1.8 parts of 2=6 diaminopyridine were added to prepare the foams of Examples 37-39, respectively, while 1.8 parts melamine powder were added to the same control formula¬ tions to form the foams of Examples 40-42, respectively. Each of the 2-6 diaminopyridine and melamine containing foams were prepared at 66, 76 and 73 β F, respectively and the following properties were measured 2.5 hours after foam formation from a middle section of each foam as in the preceding examples. 2? Example Property 37 38 39 40 41 42 Density 1.50 1.53 1.51 1.49 1.55 1.57 Porosity 4.3 1.7 3.1 6.7 3.6 4.5 Compression Set 9.2 44.0 14.6 4.8 3.5 4.8 Examples 43-48: To the control formulations of Examples 21, 22 and 23, 1.8 parts of dicyandiamide were added to prepare the foams of Examples 43-45, respectively, while 1.8 parts melamine powder were added to the same control formulations to form the foams of Examples 40-42, respectively. These foams were prepared at 73°F and the following properties were measured as in the preceding examples: Example Property 43 44 45 46 47 48 Density 1.51 1.52 1.51 1.56 1.57 1.55 Porosity 2.9 2.8 2.9 4.4 4.1 4.1 Compression Set 6.5 6.5 7.9 4.7 3.2 3.9 Examples 49-52: To.the control formulations of Examples 20 and 24, 1.8 parts of the Pluargard ® melamine powder, were added to prepare the foams of Examples 49-50, respectively, while 1.8 parts finely ground melamine powder, (particle size 90% less than 10 microns) were added to prepare the foams of Examples 51-52, respectively. Each of the large and small particle size melamine containing foams were prepared at 66 and 73°F, respectively, and the following properties were measured as in the preceding examples. Example Property 49 50 51 52 Density 1.61 1.57 1.51 1.55 Porosity 5.5 4.5 5.0 5.2 Compression Set 3.6 4.8 4.0 4.9 The data shows essentially no difference for the use of fine or standard particle size melamine powder in these foams. Examples 53-56: To the control formulations of Examples 25 and 26, 1.8 parts of formamide were added to prepare the foams of Examples 53-54, respectively, while 1.8 parts mela¬ mine powder were added to prepare the foams of Examples 55- 56, respectively. These samples were prepared at 73°F and the following properties were measured as in the preceding examples. Example Property 53 54 55 56 Density 1.69 lo64 1.52 1.57 Porosity 3.1 2.7 3 3 2.8 Compression Set 6.0 5.4 4.2 4.9 Examples 57-60: To the control formulations of Examples 25 and 26, 1.8 parts of 2-hydroxy benzimidazole were added to prepare the foams of Examples 57-58, respectively, while 1.8 parts melamine powder were added to prepare the foams of Examples 59-60, respectively. These samples were prepared at 73 β F and the following properties were measured as in the preceding examples. 3/ Example Property 57 58 59 60 Density 1.58 1.59 1.52 1.57 Porosity 3.5 2.9 3.3 2.8 Compression Set 5.9 6.5 4.2 4.9 Examples 61-66: To the control formulations of Examples 16, 17 and 19, 1.8 parts of hypoxanthine were used to prepare th foams of Examples 61-63, respectively, while to the same control formulations, 1.8 parts melamine powder were added t prepare the foams of Examples 64-66, respectively. These foams were prepared at 75-76"F and the following properties were measured as in the preceding examples. Example Property 61 62 63 64 65 66 Density 1.52 1.59 1.55 1.59 1.49 1.55 Porosity 5.1 4.9 3.6 5.6 5.0 3.6 Compression Set 3.8 4.9 4.6 4.6 5.5 3.5 Example 67- 70: (Comparative) Four control samples were prepared from the following formulation: Component parts by weight polyether polyol* (3000 mw) 100.0 toluene diisocyanate (80/20) 49.7 water 4.0 silicone surfactant 1.0 amine catalyst 0.35 stannous octoate catalyst 0.28 conventional fire retardant additives 8.0 *Polyol 3010 from Dow Chemical $ Z Foams were prepared at ambient temperatures (i.e., 73-74 β F), and the following properties were measured from a sample taken from the middle of the foam 2.5 hours after aging. Property Example Density Porosity Compression Set 67 1. ■58 3.1 85. .4 68 1« .55 3.2 84. ,2 69 1. ,50 3.1 81. ,4 70 1. ,58 3.0 70. ,4 Average 1.55 3.1 80.4 Examples 71-74: To the control formulations of Examples 67 and 68, 1.8 parts of 3-amino-l,2,4-triazine were added to prepare the foams of Examples 71 and 72, respectively, and 1.8 parts of melamine powder were added to prepare the foams of Examples 73 and 74, respectively. These samples were prepared at 73°F and the following properties were measured from the middle section of the foams after aging for 2.5 hours. Example Property 67 68 69 70 Density 1.52 1.55 1.57 1.55 Porosity 5.1 3.4 4.1 3.9 Compression Set 4.6 4.4 5.2 3.6 Examples 75-78: To the control formulations of Examples 69, and 70, 1.8 parts of aniline were added to prepare the foams of Examples 75 and 76, respectively, while 1.8 parts of melamine powder were added to prepare the foams of Examples 77 and 78, respectively. The foams of Examples 75 and 77 were prepared at 74 β F, while the foams of Examples 76 and 78 were prepared at 75°F, with the following properties measure 2.5 hours after foam formation from a middle section of the foam as in the preceding examples. 5 Example Property 75 76 77 78 Density 1.59 1.58 1.54 1.51 Porosity 3.8 4.0 3.9 2.9 Compression Set 5.6 5.7 3.8 4.7 10 These examples illustrate the improvement in the compression set of the foam by the addition of melamine or melamine equivalent compared to the control samples without these additives. 15 In the following examples, the flame retardant proper¬ ties of various foams are illustrated, with burn test values given in inches per minute. 20 Examples 79-83: (Comparative) A control sample (Example 79) was prepared from the following formulation: Component parts by weight polyether polyol* (3000 mw) 100.0 „ 5 toluene diisocyanate (80/20) 49.25 water 4.0 stannous octoate catalyst 0.22 silicone surfactant 1.0 amine catalyst 0.32 30 *Polyol 3010 from Dow Chemical 35 To this formulation, 5, 10, 15 and 20 parts melamine were added to form the foams of Examples 80-83, respectively. These foams were prepared at room temperature, and then tested for fire retardance with the following results. Example Property 79 80 81 82 83_ Density 1.59 1.58 1.58 1.60 1.61 Porosity 4.8 4.7 4.5 4.4 4.4 MVSS-302 Burn test: Top 8.1 8.0 6.4 4.0 1.3 SEO Middle 8.2 8.0 6.3 4.1 1.7 SEO Bottom 8.1 8.0 6.0 3.8 1.4 SEO The burn test samples denote those taken from the top, middle and bottom portions of the foam. The SEO rating is as defined in MVSS-302, i.e., a self-extinguishing zero burn material. Other ratings, such as SE-NBR, indicate a self- extinguishing no burn rate material. Where a letter designation is not used, the numbers in the table represent the burn rate of the sample in inches. As is evident from these results, melamine alone as a flame retardant is not effective unless used in an amount of at least about 20 parts based on 100 parts polyol. Examples 84-86 To a control formulation similar to that of Example 79, except that 49 parts of toluene diisocyanate were used, 2 parts melamine and 5, 8 and 10 parts DE-60F (penta-bromo diphenyl oxide) , respectively, were added to prepare the foams of Examples 84-86. These foams were prepared and tested in the same manner as Examples 79-83. The results are illustrated below. ≤ Example Property 84 85 86 Density 1.60 1.57 1.65 Porosity 5.1 4.0 4.5 MVSS-302 Burn test :*: Top 1.4 .8 .7 Middle 1.0 .7 .8 Bottom .9 .7 .8 * all SE- ■ 0 Examples 87-89 Examples 84-86 were repeated except that a different flame retardant compound, Anti-blaze 80 ® tris (beta-chloro- propyl) phosphate ("AB-80") , was used in the same amounts as Examples 84-86 along with the two parts of melamine. Results are as follows: Example Property 87 88 89 Density 1.68 1.63 1.75 Porosity 4.9 5.1 4.6 MVSS-302 Burn test*: Top 1.2 1.1 1.1 Middle 1.1 1.1 1.1 Bottom 1.1 1.2 1.0 * all SE-0 3C Examples 90-92 Examples 84-86 were repeated except that a different flame retardant compound. Anti-blaze 150 ® tetrakis (2-chloro ethyl) ethylene diphosphate ("AB-150") , was used along with the two parts of melamine. Results are as follows: Example Property 90 91 92 Density 1.62 1.70 1.67 Porosity 4.0 4.1 3.5 MVSS-302 Burn test*: Top 1.4 .8 .8 Middle 1.2 .8 .6 Bottom LO .8 .7 * all SE-0 xa ples 93-95 Examples 84-86 were repeated except that a different flame retardant compound, Thermolin 101 ® tetrakis (2-chloro ethyl) ethylene diphosphate ("T-101") , was used along with the two parts of melamine. Results are as follows: 31 Example Property 93 94 95 Density 1.61 1.63 1.67 Porosity 3.9 4.1 3.5 MVSS-302 Burn test*: Top .8 .6 .7 Middle .9 .7 .7 Bottom 1.0 .7 .7 * all SE-0 Examples 96-98 Examples 84-86 were repeated except that a different flame retardant compound, D-836 (Great Lakes Chemical Corp . ) a brominated-chlorinated phosphate ester, was used along with the two parts of melamine. Results are as follows : Flame Retardant Parts by weight in Example Additive 99 100 101 102 103 104 105 106 107 108 AB- 80 10 8 TM- 101 AB-150 D-836 DE 60 F 6 Melamine 2 3? These foams were prepared at room temperature, and then tested for fire retardance with the following results. Example Property 99 100 101 102 103 104 105 106 107 108 Density 1.60 1.61 1.63 1.64 1.59 1.60 1.60 1.59 1.58 1.58 Porosity 4.1. 4.0 4.2 4.1 4.0 4.0 4.1 4.0 4.3 4.2 MVSS 302 Burn test*: Top 1.3 - 1.2 1.3 1.2 1.4 1.2 1.4 1.2 1.5 1.4 Middle 1.0 1. 1 i . r 1.0 1.2 1.1 1.2 1.1 1.3 1.2 Bottom 1.0 1.0 1.1 1.0 1.2 1.1 1.2 1.2 1.3 1.2 * All SEO Example 109: (Comparative) A control sample was prepared fro the following formulation: Component parts by weight polyether polyol* (3000 mw) 100.0 toluene diisocyanate (80/20) 51.7 water .0 stannous octoate catalyst 0.25 silicone surfactant 1.0 amine catalyst 0.35 Vircol 82 6.0 *Polyol 3010 from Dow Chemical This foam was prepared at 72 β F and then tested for fire retardance with the following results: 31 Property Example 109 Density 1.56 Porosity 3.0 MVSS-302 Burn test*: Top 1.3 Middle 1.4 Bottom 1.2 * all SE-0 Example 110: To a control formulation similar to that of Example 109, except that 51 parts of toluene diisocyanate were used, 10 parts melamine and 4 parts Vircol 82 were added. This foam was prepared and tested at 74°F in the same manner as Example 109. The results are illustrated below. Property Example 110 Density 1.72 Porosity 4.02 MVSS-302 Burn test*: Top 1.0 Middle 1.3 Bottom 1.4 * all SE-0 A slightly lower amount of toluene diisocyanate was used in Example 110 because of the lower amount of Vircol 82 which was used. This example shows the utility of the invention when melamine is substituted for a portion of a reactive flame retardant additive. to Since the Vircol 82 is reactive with the isocyanate component, a greater amount of melamine is required compared to that used with substantially non-reactive flame retardant additives. Generally, 4 to 10 parts melamine are necessary to replace between 2 to 4 parts of the reactive esters. Thus, the percentage of melamine replacement ranges from about 200 to 500 percent for this embodiment of the inven¬ tion. If desired, one skilled in the art could utilize react¬ ive flame retardant additives in combination with non-react¬ ive flame retardant additives, and such mixtures can be treated similarly under the teachings of this invention, i.e., a portion of one or both of the additives in the mixture can be replaced with melamine in the amounts previ¬ ously described. As is evident from the results of examples 84 to 110, melamine used in combination with the other flame retardant additives is more effective than the use of the same amount of the single flame -retardant additive alone, or the use of melamine alone. As demonstrated by examples 79-83, melamine must be used in an amount of about 20 parts by weight (based on 100 parts polyol) to be effective as a flame retardant additive, while the esters, when used alone, require between 5 to 10 parts or more to impart acceptable flame retardance properties to the foam. Examples 111-115: The following foam-forming formulation was prepared: Component parts by weight for Example 111 112 113 114 115 polyether polyol* (3500 mw) 100 98.5 98.5 98.5 98.5 toluene diisocyanate (80/20) 46.7 45.0 46.0 45.0 46.0 water 3.5 3.5 3.5 3.5 3.5 stannous octoate catalyst 0.4 0.35 0.35 0.46 0.45 silicone surfactant Id 1.1 1.1 1.1 1.1 amine catalyst 0.27 0.27 0.27 0.27 0.27 Melpol ® blend** - 2.0 2.0 2.0 2.0 AB-80 3.0 8.0 8.0 8.0 8.0 AB-150 5.0 — — — — *Polyol 3800 from Dow Chemical ** Solution of 25% Melpol ® compound and 75% Polyol 3800 Example 111 is a control, while the foams of Examples 112-115 effectively contain 0.5 parts of the Melpol ® compound and 100 parts polyether polyol. These foams were prepared at room temperature. Example Property 111 112 113 114 115 Density 1.7 1.8 1.72 1.71 1.7 Porosity 3.8 4.1 4.3 4.0 3.5 90% Compression 5.52 4.45 3.37 6.06 5.72 Set (24 hr) (72 hr) MVSS-302 Burn test:* Top - 3.0 2.2 SE Middle - 2.1 2.4 SE Bottom - 2.5 2.4 SE * All samples SEO *z The burn test samples denote average results from those taken from the -top, middle and bottom portions of three samples of the foam. The SEO rating is as defined in MVSS- 302, i.e., a self-extinguishing zero burn material. The other rating of SE indicates that some of the samples were self- extinguishing with no burn rate. The numbers in the table represent the burn rate of the sample in inches. As is evident from the compression set results, the foams containing the Melpol ® compound achieved similar values in one day to that achieved by the control in 3 days. Examples 116-118: The following foam-forming formulations were prepared. Component parts by weight for Example 116 117 118 polyether polyol* (3500 mw) 100.0 98.5 98.5 toluene diisocyanate (80/20) 39.4 38.0 38.7 water 2.9 3.0 3.0 stannous octoate catalyst 0.42 0.42 0.42 silicone surfactant - 1.2 1.2 1.2 amine catalyst 0.44 0.44 0.44 Melopol ® blend** - 2.0 2.0 flame retardant additive 3.0 3.0 __. *Polyol 3800 from Dow Chemical **Solution of 25% Melpol ® Compund and 75% Polyol 3800 The following properties were determined: • Example Property 116 117 118 Density 1.7 1.68 1.68 Porosity 4.9 3.5 3.0 90% Compression 3.53 5.6 5.24 Set (24 hr) Again, the data illustates that the foams of the inven¬ tion achieve better compression set properties than the control. While it is apparent that the invention herein disclosed is well calculated to fulfill the desired results, it will be appreciated that numerous modifications and embodiments may b devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodi¬ ments as fall within the true spirit and scope of the present invention.

Claims: CLAIMS What is claimed is: 1. A flexible polyether derived polyurethane foam-forming composition comprising a polyether polyol, an organic isocyanate compound, water in an amount effective to act as a blowing agent, and a curing agent of an organic compound having at least one ' amine or hydroxyl moiety and a dissociation constant of between about 1.8 x 10 —5 and 2.5 x 10 —12 and which is substantially non-reactive with the foam- ' forming components but which acts as a catalyst to the reaction of remaining isocyanate groups with moisture in the form after formation thereof, said curing agent added in an amount effective to cause the reaction of a sufficient number of said remaining isocyanate groups with said moisture to improve the compression set properties of the resulting flexible foam. 2. The composition of claim 1 where the curing agent is melamine in an amount of between 0.25 and 4 parts by weight based on 100 parts by weight of the polyether polyol, and wherein the water is present in an amount of less than 6 parts by weight based on 100 parts by weight of the polyether polyol. 3. The composition of claim 2 wherein the amount of melamine is between 1 and 2 parts by weight based on 100 parts by weight of the polyether polyol. 4. The composition of claim 1 wherein the curing agent is cyanuric acid, ,6-diamino pyridine, dicyandiamide, formamide, 2-hydroxy benzimidazole, 3-amino-l,2,4-triazole, hypoxanthine, caprolactam, 3-amino-l,2,4-triazine, 4'4'- methylene dianiline, aniline, or mixtures thereof in an amount of less than about 4 parts by weight based on 100 parts by weight of the polyether polyol, and wherein the water is present in an amount of less than 6 parts by weight based on 100 parts by weight of the polyether polyol. 5. The composition of claim 4 wherein the amount of curing agent ranges from between 1 and 2 parts by weight based on 100 parts by weight of the polyether polyol. 6. The composition of claim 1 further comprising a liquid phosphorous ester flame retardant additive in an amount sufficient to impart flame retardance to the resulting foam. 7. The composition of claim 6 wherein the amount of flame retardant agent ranges from about 4 to 8 parts and the amount of melamine ranges from about 1 to 3 parts. 8. The composition of claim 1 wherein the polyether polyol is a conventional, unmodified polyether polyol and the curing agent is substantially insoluble in the foam-forming components. 9. A flexible polyurethane foam formed from the foam-forming composition of any one of claims 1-8. 10. A method for rapidly curing and improving the compression set properties of a flexible polyether derived foam which comprises: adding to a polyurethane foam-forming composition containing a polyether polyol, an organic isocyanate compound, and water in an amount effective to act as a blowing agent, a curing agent of an organic compound having at least one amine or hydroxyl moiety and a dissociation constant of between about 1.8 xlO -5 It and 2.5 x 10 —12 whi .ch is substanti .ally non-reacti .ve with the foam-forming components but which acts as a catalyst to the reaction of remaining isocyanate groups with moisture in the foam after formation thereof, said curing agent added in an amount effective to cause the rapid reaction of a sufficient number of said remaining isocyanate groups with said moisture to improve the compression set properties; and forming the polyurethane foam from said foam- forming composition, whereby said curing agent cures substantially all the resultant foam. 11. The method of claim 10 wherein the curing agent is present in an amount ranging from between about 0.25 and 4 parts by weight based on 100 parts by weight of the polyether polyol, and wherein the blowing agent is water in an amount of * less than 6 parts by weight based on 100 parts by weight of the polyether polyol. 12= The method of claim 11 wherein the amount of curing agent ranges from between about 1 and 2 parts by weight based on 100 parts by weight of the polyether polyol. 13. The composition of claim 10 wherein the polyether polyol is a conventional, unmodified polyether polyol and the curing agent is substantially insoluble in the foam-forming components. 14. The method of claim 10 wherein the curing agent is melamine, cyanuric acid, 2,6-diamino pyridine, dicyandiamide, formamide, 2-hydroxy benzimidazole, 3-amino- 1,2,4-triazole, hypoxanthine, caprolactam, 3-amino-l,2,4- triazine, '4 '-methylene dianiline, aniline, or mixtures thereof, and wherein the blowing agent is water in an amount of less than 6.parts by weight based on 100 parts by weight of the polyether polyol. 15. A method for maintaining the flame retardant properties of a flame retardant polyether polyurethane foam prepared from a polyurethane foam-forming composition comprising a polyether polyol, an organic isocyanate compound, water in an amount effective to act as a blowing agent, and a liquid phosphorous ester flame retardant additive which would normally be used in an amount of between 4 and 10 parts by weight based on 100 parts by weight of the polyether polyol, which method comprises: replacing a minor portion of the amount of liquid phosphorous ester flame retardant additive with an amount of melamine which is between about 15 to 500 percent of the minor portion of the additive to be replaced, said replacement amount being 10 parts by weight or less based on 100 parts by weight of the polyether polyol; and thereafter forming the form from the melamine containing foam-forming composition to obtain a foam having substantially the same flame retardance as one wherein a portion of the liquid phosphorus ester is not replaced with melamine. 16. The method of claim 15 wherein the minor portion of the flame retardant additive is an amount of less than about 33 weight percent of the total amount of the additive. 17. The method of claim 15 wherein the amount melamine ranges from 50 to 300 percent of the minor portion of the flame retardant additive to be replaced, and wherein the minor portion of the flame retardant additive is an amount of less than about 25 weight percent of the total amount of the additive. 18. The method of claim 15 wherein the polyether polyol is a conventional, unmodified polyether polyol; the blowing agent is water in an amount of less than ' 6 parts by weight; the minor portion of the flame retardant additive ranges from between about 1 and 6 parts by weight; and the replacement amount of melamine is between about 1 and 5 parts by weight, said amounts all based on 100 parts by weight of the conventional, unmodified polyether polyol. 19. The method of claim 15 wherein the predetermined amount of the flame retardant ranges from between about 1 and 2 parts by weight and wherein the replacement amount of melamine is between about 1 and 3 parts by weight, said amounts based on 100 parts by weight polyol. 20. The method of claim 15 wherein the flame retardant additive is reactive with the isocyanate compound, and wherein between about 4 and 10 parts melamine are used to replace between about 2 and 4 parts of the reactive ester. 21. The flexible flame retardant polyether derived polyurethane foam formed by the method of any one of claims 10 to 20. 22. A flexible polyether derived polyurethane foam forming composition comprising a polyether polyol; an organic isocyanate compound; water in an amount effective to act as a blowing agent; and between about 0.01 and 4 parts by weight based on 100 parts by weight of the polyether polyol of a curing agent of a compound of the formula C. gCR.) C R 2 ) 6 - wherein R. is hydrogen or an alkyl, alkenyl, cycloaliphatic or aryl moeity having between one and twelve carbon atoms; R 5 is an alkyl, alkenyl, cycloaliphatic or aryl moeity having between one and twelve carbon atoms and at least one hydroxyl moeity; and x is between about 0.5 and 6.

Inventors: HOWARD GREGORY WAYNE, MURPH RONALD LANCE, RICCIARDI MICHAEL ANTHONY, TEUMAC FRED NORMAN, HOWARD, GREGORY, WAYNE, MURPH, RONALD, LANCE, RICCIARDI, MICHAEL, ANTHONY, TEUMAC, FRED, NORMAN
Applicants: REEVES BROS INC, REEVES BROTHERS, INC.
Application year: 1988
Main classification: C08G18
IPC codes: C08G18, C08G101, C08J9, C08K5