FLAME RETARDANT BLEND FOR INTUMESCENT FLEXIBLE POLYURETHANE FOAM

Abstract: A flame and dripping ember retardant blend, for use in a polyurethane foam, comprises: (a) a predominant amount of a blend of (i) a major amount of an oligomeric halogenated organophosphorus flame retardant and (ii) a minor amount of a monomeric halogenated organophosphorus flame retardant; (b) a water or alcohol soluble urea-formaldehyde resin; and (c) a dialkyl-N,N-bis (hydroxyalkyl) aminomethylphosphonate.

Description: FLAME RETARDANT BLEND FOR INTUMESCENT FLEXIBLE POLYURETHANE FOAM Background of the Invention This invention relates to improvements in flexible, resilient polyurethane foams , and in particular to improvements in the characteristics of such foams when subjected to fire. A primary objective of this invention is to provide polyurethane foams having significantly enhanced resistance to combustion even when they are exposed to an intense ignition source. Flexible, resilient, polyurethane foams are made by the reaction of polyol and organic polyisocyanates in the presence of one or more blowing agents, one or more surfactants and one or more catalysts. Uses for these foams include carpet underlay, packaging, textile innerlining, mattresses, pillows, furniture paddings, cushions, automobile crash pads and sound and thermal insulation. Polyurethane foams burn readily when ignited. Various flame-retardant chemicals have been added to polyurethane foams including halogenated esters of phosphorus . This has resulted in some improvement in the flammability properties , the extent of burning after ignition by a low intensity source being reduced and the foams may even be made self-extinguishing to some degree in small-scale laboratory tests . However, when combustion does occur the foam can melt and drip flaming embers that can ignite other flammable materials in the vicinity causing the fire to spread. Such so-called "self-extinguishing" foams are generally not resistant to ignition by anything other than a low intensity ignition source. Other additives have been added to polyurethane foams to aid in overcoming this problem and to render the finished foams intumescent, or capable of producing a char, once having been ignited. These foams develop less flaming, dripping embers during combustion and produce a char that can act as a thermal insulating barrier and thus slow or prevent the spread of the fire. One approach to producing flexible, resilient polyurethane foams that are capable of passing the UL 94 HF-1 test is described in U.S. Patent No. 4,514,524 to G. Fesman. In this patent, a polyether polyol-based foam is treated with an additive combination of: a polyester polyol; a halogenated flame retardant (such as tris(l,3- dichloropropyl) phosphate) ; and a water or alcohol soluble urea-formaldehyde resin. A process for preparing flexible, polyurethane foams having reduced tendency to form burning embers when ignited and burned would be advantageous . Flexible , polyether urethane foams are better for many applications , for example furniture cushioning, than polyester urethane foams. The dry-char flexible, polyester urethane foams cannot be used where high-resiliency cushioning is required. Therefore, users would prefer a dry-char property for polyether foams that can satisfy certain flammability classifications, for example Underwriter's Laboratories UL-94 HF-1 classification. There is also concern about the resiliency of polyurethane cushioning foam incorporating polyester resins . Polyester foams are poorer in resiliency, an important factor for comfort cushioning. It would be advantageous to prepare a flexible, polyether urethane foam capable of meeting UL-94 HF-1 flammability classifications. It would be even more advantageous to formulate a flexible foam meeting the above classi ication and that is high in resiliency. Other objects and advantages of the present invention are shown throughout this specification. Summary of the Invention In accordance with the present invention, an improved flexible, resilient, polyether polyurethane foam with char- forming, or intumescent, properties, and a method of making such a foam has now been discovered. The process for preparing a flexible, resilient, flame-retardant and intumescent polyurethane foam by the reaction of a polyether polyol and an organic polyisocyanate comprises : adding to the polyurethane forming reactants at least one blowing agent, at least one surfactant, at least one catalyst and a flame and dripping ember retardant effective amount of an additive combination comprising: (i) a halogenated organophosphorus flame retardant, which contains a major amount of an oligomeric species and a minor amount of a monomeric species, (ii) a water or alcohol soluble urea-formaldehyde resin; and (iii) a dialkyl- ,N-bis (hydroxyalkyl) aminomethylphosphonate . This invention also comprises a composition for enhancing the flame retardance and dripping ember retardance of polyurethane foams which contains components (i) , (ii) , and (iii) as just described. Description of the Preferred Embodiments The process of this invention can be practiced by conventional polyurethane flexible, foam-forming technology. Polyurethane oams, according to this invention, having a density of from about 16 to about 48 kilograms per cubic meter are prepared by known methods , such as the prepolymer, quasi-polymer , or one shot systems. Foams can be prepared by batch or continuous processes . The foam-forming mixtures should include as basic ingredients : (A) a polyol (which in accordance with the present invention is preferably a polyether polyol) , (B) organic isocyanate, (C) blowing agent, (D) polyurethane catalyst, (E) surfactant, and (F) a combination of a halogenated flame retardant, which contains a major amount of an oligomeric species and a minor amount of a monomeric species , water or alcohol soluble urea-formaldehyde resin additive, and dialkyl-N,N-bis (hydroxyalkyl) aminomethylphosphonate . The preferred polyether polyol ingredient (A) can be selected from any of the wide variety of polyhydric polyether compounds available and conventionally used by the art for the preparation of flexible ether-type polyurethane foams. The most common polyether polyol compounds, the polyoxyalkylene polyether polyols, are generally prepared by the reaction of an alkylene oxide, such as 1,2-propylene oxide, with a polyhydric initiator or starter. The polyhydric initiator or starter can be, for example, glycerol, trimethylolmethane , trimethylolpropane , triethanolamine or a polyethylene glycol . The alkylene oxides used in preparing the polyethers preferably are those which contain from 2 to 4 carbon atoms, for example ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, trimethylene oxide and tetramethylene oxide. Also useful are the poly- (aralkylene ether) polyols that are derived from the corresponding aralkylene oxides such as, for example, styrene oxide, alone or mixed with an alkylene oxide. Generally, propylene oxide, that is, the 1,2-propylene oxide, and mixtures of 1,2-propylene oxide with ethylene oxide, are preferred for the preparation of the polyether polyol reactant. Also useful as polyols in the practice of this invention are the so-called graft polymers , that is polyether polyols which have been modified with acrylonitrile and/or styrene in such a way that some is grafted onto the backbone of the polyether polyol (but not on the functional , hydroxyl group) and some is present as a polymer dispersed in the polyol . The polyethers for use in the present invention preferably have molecular weights of from about 2000 to about 6000 and optimally from about 3000 to about 4500 and an average hydroxy functionality of from about 2 to about 3. An example of a commercially available polyether is F- 3020 brand polyether polyol, a product of Dow Chemical. If desired, however, component (A) can comprise the combination of a polyether and polyester polyol, as described in U.S. Patent No. 4,514,524 to G. Fesman, which is incorporated herein or even a polyester polyol without polyether polyol . Such an optional polyester polyol ingredient can be selected from one or a mixture of polyols conventionally used for the preparation of flexible polyurethane foams . Polyester polyols suitable for the preparations of these lexible polyurethane foams typically have a molecular weight between 500 and 5000 and hydroxyl number of from about 15 to about 150. Suitable polyols include the linear polymeric polyesters prepared from glycols and saturated polycarboxylic acids. For example, difunctional polyester polyols can be prepared by the reaction of diethylene glycol with adipic acid. A particularly preferred polyester polyol is the FOMREZ 53 brand product, from Witco Corporation . The organic polyisocyanate ingredient (B) of the foam- forming process can be selected from conventional isocyanates used for such purposes . Preferably, the isocyanate has an isocyanate functionality of from 2 to 3. Useful isocyanates include aromatic, aliphatic, cycloaliphatic , heterocycliσ types and mixtures thereof. Suitable organic isocyanates include toluene diisocyanate and phenylene diisocyanates, with toluene diisocyanate being preferred because of cost and availability. The blowing agent (C) ingredient can comprise water alone or water in combination with other conventional blowing agents , such as methylene chloride, or hydrocarbons or fluorocarbons having a boiling point from about -30°C to 60°C. The polyurethane catalyst ingredient (D) is selected from materials conventional for such purpose. Suitable catalysts include amines such as tertiary amines and metal compounds such as stannous octoate, dibutyltin dilaurate, etc. The surfactant ingredient (E) employed in the process of the invention can be selected from surfactants conventionally used or such purposes . Although a variety of surfactants are operative in the process of this invention, it has been found that a particularly desirable uniform cell structure and appearance is given to the foam if a silicone surfactant is used, e.g., Union Carbide Corporation TM L5810 and L5740 non-hydrolyzable silicone surfactants . The flame and dripping ember retardant additive combination (F) of this particular invention comprises a halogenated flame retardant, which contains a major amount of an oligomeric species and a minor amount of a monomeric species , water or alcohol soluble uncrosslinked urea- formaldehyde resin and a dialkyl-N,N-bis (hydroxyalkyl) aminomethylphosphonate . The halogenated flame-retardant ingredient used in the process and foam of the invention comprises a major amount (e.g., from about 88% to about 96%, by weight) of a halogenated flame-retardant oligomeric species and a minor amount (e.g., from about 12% to about 4%, by weight) of a halogenated flame-retardant monomeric species . For example, the oligomeric component can comprise a chlorinated oligomeric phosphate, such a commercially available as FYROL 99 brand from Akzo Nobel Functional Chemicals LLC, and the monomeric component can be a tris (haloalkyl) phosphate, preferably a chlorinated monomeric phosphate containing from one to four carbon atoms in the alkyl group, such as in FYROL FR-2 brand from Akzo Nobel Functional Chemicals LLC, which is tris (1,3- dichloropropyl) phosphate. A commerically available oligomeric/monomeric flame retardant additive for use in this invention is available under the trademark FYROL EFF from Akzo Nobel Functional Chemicals LLC. It contains 66 wt% of the oligomeric FYROL 99 product, 32.5 wt% of the monomeric FYROL FR-2 product, with an optional, but preferred anti-scorch package (1 wt% epoxy resin ,available as ERL-4221 brand, and 0.5 wt% of phenothiazine, based on the weight of the entire formulation) . The amino resin ingredient of this invention is a liquid water or alcohol soluble uncrosslinked (non- thermoset) urea-formaldehyde or urea-formaldehyde derivative precondensate resin which is unreactive with the organic isocyanate (under foam-forming conditions) . The term "water or alcohol soluble urea-formadehyde resin" is used in this specification to describe this essential ingredient. Preferred urea-formaldehyde resins for this invention are the butylated and the methylated urea- formaldehyde resins such as CYMEL U-80 and CYMEL 65 brand resins, which are products of Cytec Industries Inc. The amount of flame and dripping ember retardant additive combination used in the foam is an amount effective to give the combined reduction of flame retardant and dripping embers properties desired by the user. A useful standard for determining suitable levels of additive is the Underwriters' Laboratories UL-94 test. Urethane foam samples passing the HF-1 standard of the UL-94 test are considered to contain effective levels of additive for the purpose of this invention. The combined weight of the additive combination of oligomeric/monomeric halogenated organophosphorus flame retardant, water or alcohol soluble uncrosslinked urea- formaldehyde resin and a dialkyl-N,N-bis (hydroxyalkyl) aminomethylphosphonate is typically from about 5 to about 50 weight percent of the total weight of the foam formulation ingredients or of the final flexible polyurethane foam product. The ratio of polyol to halogenated flame retardant component to water or alcohol soluble urea-formaldehyde resin to dialkyl-N,N- bis (hydroxyalkyl) aminomethylphosphonate is from about 100:22:2.25:0.75 to about 100:14:1.5:0.5. It is preferred that the dialkyl groups contain from about one to about four carbon atoms therein as exemplified by diethyl or diisopropyl . The hydroxyalkyl group is preferably 2- hydroxyethyl . The additive combination of this invention can be a premixed storage-stable composition of matter suitable for addition to a foam-forming reaction system to impart enhanced flame retardance and dripping ember retardance to a flexible, resilient, polyurethane foam product. The essential ingredients of this additive combination comprises a polyol, an halogenated flame retardant, a water or alcohol soluble uncrosslinked urea-formaldehyde resin and the dialkyl-N, -bis (hydroxyalkyl) aminomethylphosphonate . However , a variety of optional ingredients may be added to the additive combination . For example , the combination can include the polyether polyol . Other optional ingredients can be selected from solvents, diluents, colorants, stabilizers, cell openers, lubricants, biocides , etc . The isocyanate foam reactant cannot be included. The additive combination can be used by mixing it in any order with the polyurethane foam-forming ingredients either prior to or at the time of reaction . The individual ingredients comprising the additive combination can be individually metered into the foam formulation as in the "one shot" method. The following Examples describe various embodiments of the invention. Other embodiments will be apparent to the skilled in the art from a consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the claims which follow the Examples . EXAMPLES Flame Retardant Blend Mixture: The flame retardant mixture that is employed in the following Examples comprises FYROL EFF flame retardant at 94.0 wt%, CYMEL U-80 resin (butylated urea formaldehyde resin) from Cytec Chemicals at 5 wt%, and FYROL 6 flame retardant (diethyl bis (hydroxyethyl) aminomethyl phosphonate) at 1 wt%. The FYROL EEF product is, in turn, a blend of 66 wt% FYROL 99 flame retardant (chlorinated oligomeric phosphate - CAS# 109640-81-5, 32.5 wt% FYROL FR-2 flame retardant (tri (l,3-dichloropropyl-2) phosphate - CAS# 13674- 87-8) , 1 wt% epoxy resin (ERL-4221 brand - CAS# 2386-87-0) , and 0.5 wt% phenothiazine (CAS# 92-84-2). Flame Retardant Blend Specifications : Typical Analysis Appearance amber % Phosphorus 10.93% % Chloride 30.55 % Acid No. 0.2 ma . Specific Gravity 1.41 Viscosity (cps) 25°C 1400 Flash point 220°F Fogging Properties (110°C/6hr/38°) 83 Vapor Pressure (400° F) 105 (See Below) -- — ASTM D2879 The following flame retardant test data were generated using a typical polyether polyurethane foam that was tested at a nominal density of 1.8 pounds per cubic foot (pcf) . The formulation used to form the foam comprised: a polyether polyol having a hydroxyl number of 56; a water level of 3.55; an amine level of 0.22; and a NCO index of 110. The flame retardant of this invention allowed this polyether polyurethane foam to meet the UL-94 HF-1 test criteria. UL-94HF- Test Criteria: Classification Criteria HF-1 HF-2 HBF Conditions Afterflame 4/5 is < 2sec. 4/5 is < 2 sec. Not have any specimen with a burning time 1/5 is < lOsec. 1/5 is < 10 sec. exceeding 40 mm per minute over a 100 mm span or Afterglow Have each specimen cease to burn be ore time for each flaming or glowing reaches the 125 mm individual gauge mark specimen < 30sec. < 30sec. BR (burn rate) = mm/min. Cotton indicator ignited by flaming particles or drops No Yes Damaged length for each individual specimen < 60 mm < 60 mm Notes: 4/5- Four out of a set of five specimens. 1/5- One out of a set of five specimens. Polyurethane Application Data Results : UL 94HF-1/ HF-2 and HBF Flammability Test Results for Sample 1 UL 94HF-1/ HF-2 and HBF Flammability Test Results for Sample 2 94HF-1/ HF-2 and HBF Flammability Test Results for Sample 3 UL 94HF-1/ HF-2 and HBF Flammability Test Results for Sample 4 Materials shall be classified HF-1, HF-2 or HBF on the basis of five specimens test results . If only one specimen from ia set of five does not comply with the requirements , another set of five specimens, subject to the same conditions, will be tested. 0 The following Table sets forth a polyurethane foam formulation that was made containing various lame retardants , including the blend of the present invention (which is coded "ULM") : 5 The following table shows the results for the U-94HF testing of a series of polyurethane foams containing such flame retardants as the blend of the present invention ("ULM"), tris (trichloroethyl) phosphate ("FR-2"), or melamine ("APP") : 0 The following Table provides UL-94HF test results for the indicated foam formulations after aging (for four hours at 25°C) : The following Table provides UL-94HF test results for the indicated foam formulations before aging (for seven days at 70°C) : The following table shows the results for the U-94HF testing of a series of polyurethane foams containing blends of tris (trichloroethyl) phosphate ("FR-2") and melamine ("APP") : The foregoing is provided merely to exemplify certain embodiments of the present invention and should not be construed in a limiting sense. The scope of protection desired is set forth in the Claims that follow.

Claims: I Claim : 1. A flame and dripping ember retardant blend, for use in a polyurethane foam, comprising: (a) a predominant amount of a blend of (i) a major amount of an oligomeric halogenated organophosphorus flame retardant and (ii) a minor amount of a monomeric halogenated organophosphorus flame retardant; (b) a water or alcohol soluble urea-formaldehyde resin; and (c) a dialkyl-N,N-is (hydroxyalkyl) aminomethylphosphonate. 2. The blend of Claim 1 wherein oligomeric halogenated organophosphorus flame retardant is a chlorinated oligomeric phosphate . 3. The blend of Claim 1 wherein the monomeric halogenated organophosphorus flame retardant is a chlorinated monomeric alkyl group-containing phosphate with from one to four carbon atoms in the alkyl group. 4. The blend of Claim 1 wherein the water or alcohol soluble urea- ormaldehyde resin is selected from the group consisting of the butylated and methylated urea-formaldehyde resins . 5. The blend of Claim 1 wherein the dialkyl-N,N- bis (hydroxyalkyl) aminomethylphosphonate contains from about one to about four carbon atoms in the alkyl groups therein and where the hydroxyalkyl group is 2-hydroxyethyl . 6. The blend of Claim 1 wherein the oligomeric halogenated organophosphorus flame retardant is a chlorinated oligomeric phosphate, the monomeric halogenated organophosphorus flame retardant is a chlorinated monomeric alkyl group-containing phosphate with from one to four carbon atoms in the alkyl group , the water or alcohol soluble urea- formaldehyde resin is selected from the group consisting of the butylated and methylated urea-formaldehyde resins, and the dialkyl-N,N-bis (hydroxyalkyl) minomethylphosphonate contains from about one to about four carbon atoms in the alkyl groups therein and where the hydroxyalkyl group is 2-hydroxyethyl . 7. The blend of Claim 6 wherein the monomeric halogenated organophosphorus flame retardant is tris (1,3- dichloropropyl) phosphate, the water or alcohol soluble urea- formaldehyde resin is a butylated urea-formaldehyde resin, and the dialkyl-N,N-bis (hydroxyalkyl) aminomethylphosphonate is diethyl-N,N-bis (hydroxyethyl) aminomethylphosphonate. 8. A polyurethane foam comprising any of the blends of Claims 1-7.

Inventors: PINZONI EMANUEL, PINZONI, EMANUEL
Applicants: AKZO NOBEL NV, PINZONI EMANUEL, AKZO NOBEL N.V., PINZONI, EMANUEL
Application year: 2001
Main classification: C08K5
IPC codes: C08G18, C08J9, C08K5, C08L61, C08L75, C09K21, D06M13, D06M15, D06M23