MXPA00003122A - Stabilized polyether polyol and polyurethane foam obtained therefrom - Google Patents

Abstract

Disclosed is an isocyanate-reactive composition comprising an isocyanate-reactive compound having an equivalent weight of from about 400 to about 12000, and a stabilizing amount of methyl 3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate with optional costabilizers selected from another phenolic, an amine, a phosphite, a thioether, or a lactone stabilizer to form a stabilizer package which may be further used in a process for preparing a flexible polyurethane foam comprising reacting together an organic polyisocyanate with an isocyanate-reactive composition in the presence of a blowing agent to form the polyurethane foam.

Description

STABILIZED POLYETHYL POLYOL AND POLYURETHANE FOAM OBTAINED FROM THE SAME BACKGROUND OF THE INVENTION This invention relates to methods for stabilizing organic materials that are prone to deterioration by thermal and / or oxygen mechanisms and to the resulting stabilized materials. More particularly, the invention relates to such methods and compositions employing methyl 3- (4-hydroxy-3,5-bi-tert-butylphenyl) propionate as a stabilizer [also known in alternating nomenclature as 3- (3,5- methyl bi-tert-butyl-4-hydroxyphenyl] propionate and identified herein as MBPP.] Methods for the stabilization of polyether polyols and other polymeric materials with antioxidants or other stabilizers and the use of stabilized polyols are well known. the preparation of polyurethane foams to inhibit burns Polyether polyols, used in the manufacture of thick flexible and semi-flexible polyurethane foams, are typically stabilized with antioxidant packages consisting of phenolic antioxidants and amine which may also contain synergists such as phenothiazine or various compounds containing phosphite residues Polyurethane foams have been conventionally prepared to the tion of an isocyanate-reactive compound of high equivalent weight and a polyisocyanate in the presence of a blowing agent. Useful blowing agents include, for example, water, low boiling liquids, such as chlorofluorocarbon, methylene chloride and liquid carbon dioxide, or mixtures thereof. A persistent problem, however, in the preparation of flexible polyurethane foams, especially in thick-type foams, is the degradation of foam polymer which results in discoloration (also referred to herein as "burn"). The burn is a well-known thermal-oxidant process caused by the heat released from exothermic reactions, especially the exothermic reaction between water and isocyanate. This thermal-oxidizing process can be further exacerbated by the ambient heat and humidity conditions and can reach self-ignition levels of the foam. Consequently, the burn is considered one of the most serious issues since it represents a potential fire risk for the foam manufacturers. The burn is normally expressed as a function of the coloration of the foam which is expressed as delta E. The higher the delta E, the higher the burn of the foam. Although the phenol of 2,6-bi-tert-butyl-4-methyl, also referred to as butylated hydroxytoluene, or BHT has been widely used for many years as a stabilizer for polymers, it is subject to various drawbacks including its relatively high volatility, its ability to sublimate and its ability to form highly colored chromophores which can cause discoloration in polymers, polymer foams and materials in contact with polymers. In accordance with the above, many investigations have been commissioned to modify the chemistry of the BHT to eliminate or mitigate the aforementioned drawbacks or to replace the BHT completely with some other stabilizer of equivalent or superior efficacy.

SUMMARY OF THE INVENTION According to the present invention, there is described a process for preparing a flexible polyurethane foam comprising the reaction of an organic polyisocyanate together with an isocyanate-reactive composition, characterized in that one of the reactants has mixed therewith a stabilizing amount of methyl 3- (4-hydroxy-3,5-bi-tert-butylphenyl) propionate, in the presence of a blowing agent and under conditions sufficient to form the polyurethane or polyisocyanurate foam. An isocyanate-reactive composition comprising an isocyanate-reactive compound having an equivalent weight of from about 400 to about 12,000 is also disclosed., and a stabilizing amount of methyl 3- (4-hydroxy-3,5-bi-tert-butylphenyl) propionate. Additionally, a method is provided for stabilizing an organic material that is subject to thermal deterioration and / or oxidant which comprises the incorporation into such material of a stabilizing amount of 3- (4-hydroxy-3,5-bi-tert- methyl butylphenyl), optionally with another phenolic stabilizer and / or an amine and / or phosphite or thioether or lactone to form a stabilizer package of polyols, polyurethanes and other oxidically degradable polymeric materials.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a graph of experimental results for mixtures of amine and phenolic stabilizers showing a lower Delta E color for the MBPP of the invention. Figure 2 illustrates a graph of experimental results for mixtures of amine and phenolic stabilizers showing a lower Delta E color for the MBPP of the invention. Figure 3 illustrates a graph of experimental results for mixtures of amine and phenolic stabilizers showing a lower Delta E color for the MBPP of the invention. Figure 4 illustrates a graph of experimental results for mixtures of amine and phenolic stabilizers showing a lower Delta E color for the MBPP of the invention. Figure 5 illustrates a graph of experimental results for mixtures of amine and phenolic stabilizers showing a lower Delta E color for the MBPP of the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The essential stabilizing composition of this invention is methyl 3- (4-hydroxy-3,5-bi-tert-butylphenyl) propionate made by known processes. This essential stabilizer can be complemented with one or more suitable co-stabilizers and oxidants such as those set forth in the U.S. Patent. No. 5,516,920 which is incorporated for reference. The most common co-stabilizers are listed below with a few materials representative of the commonly available class. In carrying out the method of the invention, a stabilizing amount of the stabilizing composition is added to an organic material which is susceptible to thermal and / or oxidative degradation. In particular, synthetic organic polymeric substances such as vinyl resins formed from the polymerization of vinyl halides or from the copolymerization of vinyl halides with unsaturated polymerizable compounds can be stabilized with the mixtures of the functionalized esters of this invention. Specifically, these vinyl compounds would include vinyl esters, unsaturated acids alpha, beta, esters, aldehydes, ketones and unsaturated hydrocarbons such as butadiene or styrene. The method of this invention is also applicable to the stabilization of poly-alpha-olefins such as pofietylene, polypropylene, polybutylene, polyisoprene, and the like and copolymers of poly-alpha-olefins, polyamides, polyesters, polycarbonates, polyacetals, polystyrene and polyethylene oxide . Also included are high impact polystyrene copolymers such as those obtained by the copolymerization of butadiene and styrene and those formed by copolymerizing acrylonitrile, butadiene, and styrene. Other organic materials stabilized according to the present invention include aliphatic ester lubricating oils, oils of animal and vegetable origin, hydrocarbon materials such as gasoline, both natural and synthetic, diesel, mineral oil, fuel oil, drying oil, cutting fluids , waxes, resins and fatty acids such as soaps.

A particularly advantageous application of the method of this invention is the stabilization of the polyether and the polyether polyols which then react with isocyanates to produce rigid and flexible polyurethane and polyiscyanurate foams. The stabilization compositions of this invention provide protection against burn (both physical and color) to polyurethane foams which are used in such end uses as reinforcement of carpets, bedding, furniture, automobiles (both insulating materials and seats). ) and packaging. The occurrence of burn is of prime concern to manufacturers of polyurethane foam since the burn adversely affects the appearance of the product, causes physical damage and can result in a fire. Accordingly, foam manufacturers require improved protection against burning during the production of flexible thick foam. The role of antioxidants can be critical in providing increased protection against burnout in urethane foams without diminishing the other properties desired by the industry. The stabilizing composition of this invention can be incorporated into the organic material to be stabilized by known and conventional methods. In particular, the stabilizing composition of this invention can be pumped or introduced into the organic material in predetermined amounts. The specific amounts of stabilizing composition employed can vary widely depending on the particular organic material that is being stabilized. In general, the addition of from about 0.01 to about 5, preferably from about 0.02 to about 1 and more preferably from about 0.05 to about 0.25 percent, of the weight stabilizing composition of the organic material to be stabilized generally gives good results. If a co-stabilizer is used, it can be presented in the same amount as the previously established primary stabilizer. In the case of a polyurethane foam, such amounts of stabilizing composition can be added directly to a component of the composition forming the polyurethane foam, for example, the polyol, or the isocyanate component or the foam-forming composition itself same Phenolic Coestabilizer Suitable clogged phenols which may also be used in the composition herein include 2,4-dimethyl-6-octylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl -4-nonylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-n-butylphenol, 2,6-di-t-butyl-4-sec-butylphenol , 2,2'-methyleneobis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,4-dimethyl-dt-butylphenol, 4-hydroxymethyl -2,6-di-t-butylphenol, n-octadecyl-β (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 4,4'-dihydroxydiphenol, 4,4'-thiobis (6-t- butyl-o «cresoI), p-butylphenol, p-isopropylphenol, p- (1,1, 3,3-tetramethyl) phenol, 2,6-dioctadecyl-4-methyl phenol; 2,4,6-trimethyl phenol; 2,4,6-triisopropylp phenol; 2,4,6-tri-tert-butyl phenol; 2-tert-butyl-4,6-dimethyl phenol; 2,6-methyl-4-didodecyl phenol; actadecyl-3,5-di-tert-butyl-4-hydroxy hydrocinnamate; tetrakis [methylene (3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)] methane; 2,2'-oxamido bis- [ethyl-3- (3,5-di-tert-butyl-4-hydroxyl) i) propionate; 1, 3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) -s-triazine-2,4,6- (1 H, 3 H, 5 H) trione; 1 d-trimethyl-Ae-trisyl S-di-tert-buty-hydroxybenzyl) benzene; tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate; thymol, cresol mixed with m- and p-, p-nonylphenol, other phenols, cresols having alkyl substituents and mixtures thereof. The mixed phenolic ester stabilizer composition herein may be made entirely from the product phenolic esters but may also contain substantial amounts of one or more other stabilizers, eg, other phenolic stabilizers, amine-containing stabilizers, thioester stabilizers, phosphite stabilizers. , etc. Clogged Amine Coestabilizer The amine-containing stabilizers that can be used herein include the complex mixture of substituted diphenylamines containing a significant proportion of butylated and oxylated species which is obtained by reacting isobutylene and diphenylamine. Another diphenylamine, N-allyldiphenylamine, 4-isopropoxydiphenylamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthiamine, octylated diphenylamine, for example p, p'-di-tert-octyldiphenylamine, 4-n-butylaminophenol, 4 butylaminophenof, a mixture of tert-butyl / tertoctyldiphenylamines mono and dialkylated, a mixture of mono- and dialkylated isopropyl / isohexyldiphenylamines, mixtures of diphenylamines substituted with mono- and dialkylated tert-butyldiphenylamines are commercially available. Still other amine stabilizers include phenylenediamines and mixtures of phenolic and phenylenediamine stabilizers such as are known in the art.

Optional Thioether / Phosphite Stabilizer Examples of thioether stabilizers that can be used herein include 1.5. hydroxylated thiodiphenyl ethers, for example 2,2-thiobis (6-tert-butyl-4-methylphenol), 2,2'-thiobis (4-octylphenol), 4,4'-thiobis (6-tert-butyl) 3-methylphenol), 4,4'-thiobis (6-tert-butyl-2-methylphenol), 4,4'-thiobis- (3,6-di-sec-amylphenol), 4,4'-bis disulfide - (2,6-dimethyl-4-hydroxyphenol), as well as Cyanox 711 (American Cyanamid), Aarhus DMTDP (Aarhus Chemical Co.) and Evanstab 14 and Carstab DMTDP (Evans) commercially available. Other useful stabilizers that may be added to the mixed phenolic ester stabilizer composition of this invention include the thiophenols, dimethylacridane, phenothiazine and phosphites including but not limited to such as phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite and, more recently, tris (2,4-di-t-butylphenyl) phosphite which has become the industrial standard for hydrocytic stability. Polyurethane foams. Flexible polyurethane foams are generally prepared by reacting an organic polyisocyanate and a polyol in the presence of a blowing agent, a catalyst and optional auxiliary additives. Component of Foam Polyol. In producing the soft, flexible foams herein, substantially any organic compound containing more than two hydroxyl groups can be used as the polyol component. Such compounds generally have molecular weights of from about 400 to about 12,000, preferably from about 1,000 to about 8,000, and more preferably from about 1,500 to about 7,000. The functionality of the hydroxyl group containing the compound is generally in excess of 2 and preferably has an average functionality of from 2.5 to no more than 4. Preferred compounds include polyesters, polyethers, polythioethers, polyacetals, polycarbonates and polyester amides containing a average of more than 2, and preferably from 2.5 to 4 hydroxyl groups. When the polyisocyanate is MDI or based on MDI, the isocyanate-reactive compound advantageously has an average functionality of from about 1.5 to about 3.5, and more preferably from about 1.8 to about 2.1. With respect to the isocyanate-reactive compound, and chain extenders and extenders used in this invention, the term "functionality" refers to the average number of groups per molecule that contain one or more active hydrogen atoms. Polyesters containing hydroxyl groups suitable for the present invention are reaction products of polyhydric alcohols with polybasic carboxylic acids. Instead of using the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof to produce the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and can be optionally substituted (eg, by halogen atoms) and / or can be unsaturated. Polyesters suitable for use in accordance with the present invention are known to those in the art. These polyesters can be obtained by polymerizing epoxides, such as ethylene oxide or propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin in the presence of Lewis catalysts, such as BF3. The polymerization can also be carried out by the addition of epoxides (preferably ethylene oxide and propylene oxide) either in admixture or successively, to compounds containing reactive hydrogen atoms such as water, ammonium, alcohols or amines. Examples of such compounds containing reactive hydrogen are ethylene glycol, 1,3-propylene glycol. 1, 2-propylene glycol, trimethylolpropane, glycerol, sorbitol, 4,4'-dihydroxydiphenylpropane, aniline, ethanolamine and ethylenediamine. Polyesters of sucrose and polyesters that initiate with formitol or formosa can also be used in accordance with the present invention. Polyhydroxyl compounds containing urethane or urea groups, optionally modified natural polyols (such as castor oil) and carbohydrates (eg, starch) can also be used as the isocyanate-reactive compound of the present invention. Additional products of alkylene oxides with phenol / formaldehyde resins or with urea / formaldehyde resins can also be used. According to the present invention, it is also possible to use polyhydroxyl compounds containing high molecular weight polyadducts and polycondensates or polymers in finely dispersed or dissolved form. Such polyhydroxyl compounds can be obtained by polyaddition reactions (eg, reactions between polyisocyanates and aminofunctional compounds) and polycondensation reactions (eg, between formaldehyde and phenols and / or amines) in situ in the compounds. above mentioned that contain hydroxyl groups. It is also possible to obtain such a polyhydroxyl compound by mixing an aqueous polymer dispersion with a polyhydroxyl polymer and subsequently removing the water from the mixture. Also suitable are so-called polymer polyols which are prepared by polymerizing one or more ethylenically unsaturated monomers in an organic compound of relatively high molecular weight containing at least two hydroxyl groups or polycarbonate polyols, to be used in the process according to the present invention. Plastics that have particularly low combustibility are obtained by using polyether polyols modified by graft polymerization with vinyl phosphonic acid esters and, optionally, (meth) acrylonitrile, (meth) acrylamide or esters of (meth) acrylic acid Functional OH Polyhydroxyl compounds in which carboxyl groups have been introduced by radical grafting for polymerization with unsaturated carboxylic acids and, optionally, other olefinically unsaturated monomers are particularly advantageous when used in combination with mineral fillers. The polymer polyols mentioned above and useful herein are known and commercially available. Isocyanate-reactive compounds generally useful in the present invention include compounds containing active hydrogen, such as, for example, polyols, compounds ending in amine, secondary amines and amines. Suitable polyols include, for example, polyester polyol, or a polyether polyol containing at least 50 weight percent oxyalkylene units, an amine terminating derivative of such a polyester or polyether polyol, or a polymer polyol. based on such polyester or polyether polyol. Such polyols are generally well processed to provide a polyurethane foam having good properties. Of these, polyether polyols by themselves, derivatives terminating in amine thereof, and polymer polyols based on polyether polyol are preferred. The most preferred materials used as the isocyanate reactive compound herein are propylene oxide polymers having an average functionality of about 2.0 to about 3.5 and an equivalent weight of about 900-2000, which are optionally copolymerized about 1 to 80. , preferably 10 to 30 weight percent of ethylene oxide are covered at the end with up to about 30, preferably up to about 20 weight percent ethylene oxide, as well as derivatives that end in amine thereof and polymer polyols prepared from them, and mixtures thereof. The amine-terminating derivatives of the polyether polyols can be prepared in the reductive amination of the polyether polyol using ammonia or a primary amine. Alternatively, the derivative terminating in amine can be prepared by amidating the polyol deductively with ammonia and then reacting the resulting primary amine with an ethylenically unsaturated compound such as acrylonitrile, to form the corresponding secondary amine. The aromatic terminating polyether can be prepared by reacting the polyol with a diisocyanate, followed by hydrolyzing the free isocyanate groups to the amine groups. Alternatively, the polyal can react with a material such as o- or p-chloronitrobenzene to form an ether, followed by reduction of the nitro groups to the corresponding amine groups. Various types of polymer polyols based on polyether or polyester polyols are useful as the isocyanate-reactive compound in this invention. In this invention, a polymer polyol refers to a dispersion of a polymer in a continuous polyol phase. The dispersed polymer can be a polymer of one or more ethylenically unsaturated monomers, an epoxy resin, a polyurethane or a polyurea. Of these, polymer dispersions and styrene and / or acrylonitrile copolymers, so-called polyurea dispersions ("PHD polyols") and polyurea-polyurethane dispersions (the so-called PIPA polyols) are preferred. Component of Foam Isocyanate Substantially any organic polyisocyanate may be used in the production of flexible foams of the present invention. Aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates can be used. Among the polyisocyanates described herein are those corresponding to the general formula: Q (NCO) n wherein n represents 2-4, preferably 2; and Q represents an aliphatic hydrocarbon radical containing from 2 to 18 (preferably from 6 to 10) carbon atoms, a cycloaliphatic hydrocarbon radical containing from 4 to 15 (preferably from 5 to 10) carbon atoms, a radical of aromatic hydrocarbon ranging from 6 to 15 (preferably from 6 to 13) carbon atoms; or an araliphatic hydrocarbon radical containing from 8 to 15 (preferably from 8 to 13) carbon atoms. Examples of compounds corresponding to this formula are ethylene diisocyanate; 1,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 1, 12-dodecane diisocyanate; Cyclobutane-1,3-diisocyanate, cyclohexane-1, 3- and 1,4-diisocyanate and mixtures of these isomers; 1-Isocyanato-3,3,5-trimethyl-5-isocyanato-methyl cyclohexane; 2,4- and 2,6-hexahydrotolylene diisocyanate and mixtures of these isomers; hexahydro-1, 3- and / or 1,4-phenylene diisocyanate; 2,4'- and / or 4,4'-diphenylmethane perhydro diisocyanate; diisocyanate 1, 3- and 1, 4-phenylene; 2-4- and 2,6-tolylene diisocyanate and mixtures of these isomers; diphenylmethane -2,4'- and / or 4,4'-diisocyanate; and naphthylene-1,5-diisocyanate. Other examples of suitable polyisocyanates are; triphenylmethane-4,4 ', 4"-triisocyanate, polyphenylene polymethylene polyisocyanates of the type obtained by condensing aniline with formaldehyde followed by phosgenation; (m-) and p-isocyanates, phenylsulfonyl isocyanates; polyisocyanates containing carbodiimide groups; Norbonne, polyisocyanates containing allophanate groups; polyisocyanates containing isocyanurate groups; polyisocyanates containing urethane groups; polyisocyanates containing acylated urea groups; polyisocyanates containing biuret groups; polyisocyanates produced by telopolymerization reactions; polyisocyanates containing ester groups; reaction products of the aforementioned diisocyanates with acétalos and polyisocyanates containing polymeric fatty acid esters. It is also possible to use the distillation residues containing the isocyanate group obtained in the commercial production of isocyanates, optionally in solution in one or more of the polyisocyanates mentioned above. It is also possible to use mixing of the polyisocyanates mentioned above. Generally, it is preferred that commercially available polyisocyanates are used in the present invention. Such readily available materials include 2,4- and 2,6-toluene diisocyanate, also mixtures of these isomers ("TDI"); polyphenylene polymethylene polyisocyanates of the type obtained by condensing aniline with formaldehyde; followed by phosgenation ("crude MDI"); and polyisocyanates containing carbodimide groups; urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"). Preferred polyisocyanates for use in accordance with the invention include tolylene diisocyanate in the form of an 80:20 mixture of the 2,4- and 2,6-isomers ("TDI 80"), tolylene diisocyanate in the form of a mixture. 65:35 of the 2,4- and 2,6-isomers ("TDI 65") and prepolymers of tolylene diisocyanate. Blowing Agents Suitable blowing agents include water, optionally, with additional easily volatile inorganic or organic substances in an amount of 0.1 to 25 parts by weight up to 100 parts by weight of polyol. Suitable additional, organic blowing agents are acetone, ethyl acetate, halogen-substituted alkanes, such as methylene chloride, chloroform, ethylidene chloride, vinylidene chloride, monofluorotrichloromethane; chlorodifluoromethane; dichlorodifluoromethane; cyclopentane, fluorinated hydrocarbons, ethers of butane, hexane, heptane or diethyl. The inorganic blowing agents that can be used are air, CO2 and N2O. A blowing effect can also be achieved by adding compounds that decompose at the reaction temperature to emit a gas (eg, nitrogen, emitted by azo compounds, such as azodicarbonamide or azobutyronitrile). Another definition of blowing agents is any material that is capable of generating a gas under the conditions of the reaction of a polyisocyanate and an isocyanate-reactive compound. Such materials include air, carbon dioxide, nitrogen, water, formic acid, low boiling allogenated alkanes, finely divided solids, the so-called "azo" blowing agents such as azo-bis (formamide) and the like. Preferred are water, low boiling allogenated alkanes or mixtures thereof. The blowing agents are advantageously employed in an amount sufficient to provide the foam with a bulky density from about 0.5, preferably about 0.9, more preferably about 1.0 to about 6 or less, preferably about 4, more preferably about 3 pounds per cubic foot. Halogenated alkanes, including methylene chloride, dichlorodifluoromethane, monochlorodifluoromethane, monochlorotrifluoromethane and the like, generally provide the desired density when employed in amounts of from about 5 to about 50 parts per 100 parts of the isocyanate-reactive compound. The smaller amounts are useful when used in conjunction with another blowing agent, such as water. Catalyst v Degradants A catalyst for the reaction of the isocyanate-reactive compound and the polyisocyanate is also advantageously used in the manufacture of foam according to this invention. Although a wide variety of materials are known to be useful for this purpose, the most widely used and preferred catalysts are the tertiary amine catalysts and the organometallic catalysts. Exemplary tertiary amine catalysts include, for example, triethylene diamine, methyl morpholine, ethyl morpholine, diethyl ethanol amine, N-coconut morpholine, 1-methyl-4-dimethylaminoethyl piperazine, 3-methoxy N-dimethylpropylamine, N, N-diethyl-3-diethylaminopropylamine, dimethylbenzyl amine, bis (2-dimethylaminoethyl) ether, and the like. The tertiary amine catalysts are advantageously employed in an amount of from about 0.01 to about 5, preferably about 0.05 to about 2 parts per 100 parts by weight of the isocyanate-reactive compound. Exemplary organometallic catalysts include organic salts of metals such as tin, bismuth, iron, mercury, zinc, lead and the like, with organotin compounds being preferred. Suitable organotin catalysts include dimethyltin dilaurate, dibutyltin dilaurate, stannous octoate and the like. Advantageously, about 0.0001 to about 0.5 part by weight of an organometallic catalyst is used per 100 parts of the isocyanate-reactive compound. Degrants can be used, particularly in thick, high-resilience foam in order to improve processing and the presence of charge. Suitable degradants include alkalonamines and other compounds of about 200 or lower molecular weights having about 3-8, preferably about 3-4, active hydrogen-containing groups per molecule. Examples of such compounds are glycerin and trimethylolpropane, as well as other alkylene thiols. However, alkanolamines such as diethanolamine, triisopropanolamine, triethanolamine, diisopropanolamine, adducts of 4-8 moles of ethylene oxide and / or propylene oxide with ethylene diamine and the like, ammonia and the like are preferred. Based on its optimal reactivity, diethanolamine is more preferred. When used, from about 0.1 to about 4 parts of the degradant are advantageously employed per 100 parts of the isocyanate-reactive compound. Chain extenders can also be used to improve foam loading support. The "chain extenders" for the purpose of this invention, include compounds having two groups containing active hydrogen per molecule and an equivalent molecular weight from about 31 to about 300, preferably about 31 to about 150. The chain extenders containing hydroxyl include the alkylene glycols and glycol ethers such as ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, diethylene glycol, triethylene glycol, duprophenyl glycol, tripropylene glycol, 1,4-cyclohexanedimethanol and the like. Amine chain extenders include toluene diethyl diamine, phenylene diamine, methylene bis (o-chloroaniline), methylene bis (aniline) blocked with NaCl, toluene diamine, aromatic diamines which are substituted by at least one of the carbon adjacent to the amine groups with a lower alkyl group, and the like. Such chain extenders, when used, are advantageously employed in a minor amount, ie, from about 2 to about 30 parts per 100 parts of the isocyanate-reactive compound. However, it is usually preferable to prepare the foam in the substantial absence of a chain extender. EXAMPLES The following examples are illustrative of the invention. The laboratory research of antioxidants for flexible polyurethane foam is basically done by adding antioxidants in a minimally stabilized flexible thick polyether polyol and by making hand-mixed samples of polyurethane foam. The basic treatment The thermal degradation of flexible polyurethane foam takes place in the center of the large blocks during the manufacturing process. The core block temperature continues to increase within the first four hours of processing. This increase in temperature is not observed in small foam blocks because the insulating effect of the foam mass is not sufficient. The effect of temperature is simulated by placing a hand-blended bread made recently in a microwave oven. Exposure to heat is often prolonged by placing the hot foam in a convection oven. Careful selection of convection oven and microwave conditions to expose freshly made foam blocks is effective in predicting the relative performance of different polyurethane polyol antioxidant packages in large-scale foam making equipment. Antioxidants Evaluated The comparative data given in the examples refer to the following antioxidants: P-1: Butylated Hydroxytoluene (BHT); a highly volatile antioxidant, of relatively low molecular weight. P-2: 3,5-di-t-butyl-4-hydroxy-hydrocinnamic acid, C1-C9 branched alkyl ester. This is a liquid phenolic of intermediate molecular weight. It is substantially less volatile than BHT. P-3: octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate This is a di-tertiary butylphenol of high molecular weight with a long aiiphatic chain to reduce its volatility. A-1: butylated diphenylamine, octylated. This is a clogged, liquid aromatic amine. MBPP: methyl 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate; the composition of this invention. This is a solid phenolic with high yield of lower volatility than BHT. Preparation of the Polyol Sample The minimally stabilized polyol containing traces of butylated hydroxytoluene (BHT) is used as the basis for the evaluation of the stabilizer. The antioxidants to be evaluated are added from concentrated solutions in this polyol. All solutions are prepared in an identical manner, with heating and stirring under nitrogen. Preparation and Evaluation of the Foam Sample The following ingredients are mixed together and poured into an 8"x 8" x 4"cake box: Components Weight (grams) Polyether Triol 3000 mw 150.0 Water 7.5 Niax L silicone surfactant -6201 2.0 DABCO 33LV2 Amine Catalyst 0.5 DABCO Tin Catalyst T-92 0.4 Toluene Diisocyanate (80/20) Index 1 10 OSi Specialties, Inc. Air Products and Chemicals, Inc.

A 900-watt microwave oven is used to thermally overload these hand-mixed foams. A voltage and current power conditioner is used to ensure that the AC power going to the microwave oven does not fluctuate over time. The oven is pre-conditioned at the beginning of a series of foaming by placing 500 milliliters of drinking water in the center of the oven and heating it for 10 minutes at 30% energy. This also serves as a calibration step in the procedure. This volume of water increases 60 ° C in temperature after exposure in the microwave oven. The calibration ensures that the power generated from the furnace remains standard from one experiment to the next. Rinsing and curing periods are recorded for each foam. This is an additional verification in the consistency of the procedure. After the foam has been completely rinsed, it is cured in the emanation hood for 5 minutes carefully regulated. After 3 minutes of this period of time, the sides of the box come off to leave only the bottom intact. The foam is then placed in a microwave oven calibrated for 5 minutes and 10 seconds at 30% energy in this particular oven. The first foam of the day is discarded because the unbalanced microwave will not give data compatible with the rest of a series. The thermally exposed foam is removed from the microwave oven and placed in a convection oven at 120 ° C for 5 minutes. Finally, the foam is removed to a bell and allowed to cool. For all foams made after the first discarded foam and immediately after obtaining the foam rinse time, 500 milliliters of cold drinking water is placed in the center of the microwave oven and heated for 5 minutes at 30% energy . This period of 5 minutes coincides with the curing time for the foam that has just been poured and that is waiting to enter the microwave oven. This complete procedure of hand-mixed foam is repeated for each foam in the series. As a final check on the bread-to-bread consistency in the foaming and curing process, air flows are measured for each bread made. The variability of ± 1 cubic foot per minute of air flow is considered acceptable. The average air flow for the foams is 6 cmf. Each foam is cut into% "pieces to determine the darker color area.For proper operation of the microwave oven and suitably prepared foams, this location should be identical for each foam, and ideally in the center of the bread. The color developed during the thermal exposure is compared to a standard blank in a Hunter spectrophotometer The color analysis chosen is the Delta E index The Delta E is a measure that refers to how the eye perceives the color. Aspects of color: light-dark (L), reddish-green (a) and yellowish-blue (b) Delta E then becomes a mathematical expression that calculates the difference in each of these aspects between the sample and the standard: AE =? ¡AL2 + Aa2 + Áb2 A change unit one (1) in the Delta E value is a statistically significant difference. The heat exposure conditions for this study were more severe than what would be found in a real foam production line. The core temperature of a hand-mixed bread immediately after microwave exposure is approximately 190 ° C. These conditions were chosen to provide sufficient diffusion in the color data in order to aid in the discrimination of the antioxidant package and assist in obtaining the most efficient proportion of the various antioxidants. Polyol manufacturers can then reduce the total concentration to meet their needs. There were nine experiments designed, in total 166 individual foams in the studies reported in the present. Experimental Design There are a large number of factors that influence the results of a program to optimize the antioxidant package in polyether polyols. Among these are: the inconsistency of the operator, the variability between batches of polyol stabilized to the minimum and the variations of temperature and humidity during a series that is being foamed. There may also be unforeseen interactions between the antioxidants that are being selected. In addition, the complete number of permutations necessary to evaluate a number of antioxidants in their various combinations is practically insurmountable.

One solution to this problem is to use statistical techniques to provide prediction of the variables of interest. A statistical software package is used to generate experimental designs in order to minimize the number of foams required to produce a reasonable estimate of the most promising packages. The designed experiments maximize information while minimizing the experimental effort required to determine valid conclusions. The statistical design method allows the alteration of one, two or more variables from one experiment to the next and gives good estimates of the effects of the variables from considerably fewer experiments. The bonus is that the magnitude of the interactions is measured, if they exist. This was the technique used in the studies reported here. The variables in these statistically designed experiments are the type and concentration of antioxidant. Statistical software packages adapt the data to a linear model or a quadratic polynomial model. A standard analysis of variance (ANOVA) tells if the adaptation is statistically significant. In many cases, a linear model worked well to predict the results. Some of the antioxidant packages contain second order terms to improve adaptation. The simpler the model, the better. The experimental designs were chosen in order to allow prediction on a limited region of antioxidant concentrations. A statistical estimate of the linear effects and the interaction between antioxidants at varying concentrations is predicted in this work.

A useful statistical quantity to evaluate the predictability of a model is the value of R2. This quantity, known as the "coefficient of determination", indicates what percentage of the variation present in the data is taken into account by the model. How much variation in the data can be explained by the model. R2 varies from 0 to 1, and generally as long as it is closer to one, the model will explain the data better. The values of R2 for all these experimental designs are between 0.81 and 0.97. The analysis of the statistically predicted results is visually available to the experimenter as two-dimensional contour plots and three-dimensional graphs of the variables against Delta E. The examination of these contour plots allows for the determination of the best performance package in the reduction of color, as the relative concentration required for each antioxidant package to reach a Delta E. It is important to note that these Delta E predictions are based on laboratory-stressed foams and are therefore useful for relative performance predictions. These are not the absolute values of Delta E that one would get in a foam line. One can determine the performance of a specific anti-oxidant package with which one has experience in the foam line, by finding that package in the contour plot. From this, one can determine what could make a better or more economical antioxidant package. It is also recalled that these results are specific to the foam formulation chosen for the microwave burn.

RESULTS Data from nine statistically designed experiments are used in this study, giving a total of 166 foams. The designs were evaluations of both two and three variables (for example, two-component antioxidant packages or three-component antioxidant packages.) Each of these models produces Delta E contour plots over a range of antioxidant concentrations. amine and a phenolic, the concentration range of each is 1000-4000 ppm.When a third component is evaluated in terms of its importance in the antioxidant package, it is generally evaluated at 100-1500 ppm. it can be examined in two ways The results of each of the individual designed experiments can be examined independently from each other and the conclusions derived Another valid technique with reproducible microwave burn results, consistent, is to evaluate Delta E data through all designed experiments. Both approaches are used in the present. I. Two-component Antioxidant Packages: One Amina + One Phenolic The ability to interpret between multiple contour plots presents a new way to obtain a good comparative evaluation. When finding a suitable replacement package for BHT (P-1), it is initially necessary to determine the effectiveness of replacement candidates at the same concentration of all candidates. Figure 1 shows the efficacy of blocked amine A-1 at a concentration of 4000 ppm together with a phenolic concentration of 1000 ppm. It is notable that MBPP shows equal or better to P-1. Phenolics of much higher molecular weight are less effective. In general, higher molecular weights are less effective because they have a lower molar concentration of active phenolic hydroxyls. Figure 2 is a similar graph in which the concentrations were adjusted to 3000 ppm of A-1 and 2000 ppm of each respective phenolic. Here, the reduced amine level causes P-1 to be the best, but MBPP is quite close, with the others less effective. When the amount of A-1 is examined at the 3500 ppm level, the MBPP is again more effective than P-1. In Figure 3 an intermediate concentration of A-1 of 3500 ppm is used and the phenolic concentration was determined from the contour plots to produce identical Delta E's of 45. A Delta E of 45 was selected as a comparison point due to that was obtainable in all the experiments. MBPP performs better at this level of amine A-1 than BHT. One can assume that a higher phenolic content of MBPP over higher molecular weight phenolics may have combined with lower volatility in this very severely obstructed foam evaluation to give this good result. This assumption is made more logical by examining Table I. This table illustrates the relative volatility of the antioxidants examined when analyzed in a Thermal Gravimetric Analyzer (TGA). An evaluation method is to program the instrument to raise the temperature at a rate of 10PC per minute and determine the loss of weight against temperature. P-1 loses half of its weight by 182 ° C. The other antioxidants have significantly less volatility. Another method to assess volatility by TGA is to determine the isothermal weight loss. Here, each sample was maintained at 160 ° C under a nitrogen atmosphere for 250 minutes. This temperature is representative of the core temperature of commercially produced foam bread. The 20% and 50% weight loss times are given in Table I. H- Three-component Antioxidant Packages This section examines the effect on components A and B when component C is at specific levels in a designed experiment of three components. This was done by computer-generated isobar graphs of Delta E, from the statistical data and plotting the change in Delta E to four different concentrations of the third variable component. (Note: These graphs could be generated at any concentration of the third component, within the concentration range studied). This example evaluated MBPP as a third component in a designed experiment. The effectiveness of the interaction of the third component was determined by the following: P-3 remained constant and three levels of A-1 and three levels of MBPP were chosen to investigate its range of efficacy in the improvement of the total antioxidant package. In this design, MBPP was evaluated up to 1500 ppm. The microwaves induced discoloration at three levels of A-1 with 1500 ppm, P-1 was determined when this anti-oxidant package was fortified with three levels of MBPP. The results are shown in Figure 4. MBPP is beneficial with high concentrations of A-1 and lower concentrations (ie, 1500 ppm) of P-3 in the 500 ppm range of RB-515. An expanded design could be carried out to evaluate the effect of MBPP when it contains a P-3 constant at 1500 ppm. The 2D contour plots were examined again to determine if there was any additional benefit to be found when switching to high P-3 with only 1500 ppm of A-1 (see figure 5). The analysis of these points of data clearly shows that the MBPP is beneficial, shows again that the optimum level of MBPP is approximately 500 ppm. The examination of the above graphs shows that the development of the appropriate formulation through the use of designed experiments can significantly help in the development of an antioxidant package for polyols that will give good results at a minimal cost. The interactions and synergistic effects are elucidated in designed experiments, if they occur. Here we see the regions within which a third component can be added to total performance, clearly demonstrating the value of MBPP as an amplifier of polyol antioxidant performance.

TABLE 1

Claims (14)

1. CLAIMS 1. An isocyanate-reactive composition comprising an isocyanate-reactive compound having an equivalent weight of from about 400 to about 12,000 and a stabilizing amount of 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate. of methyl.
2. 2. The composition according to claim 1, characterized in that the isocyanate-reactive compound has an equivalent weight of from about 1,000 to about 2,500.
3. 3. The composition according to claim 2, characterized in that the isocyanate-reactive compound is a polyester or polyether polyol.
4. 4. The composition according to claim 1, characterized in that the methyl 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate is present in amounts of from 0.01 to 5.0 weight percent of the isocyanate-reactive compound. .
5. 5. The composition according to claim 1, characterized in that the methyl 3- (4-hydroxy-3,5-di-tert-butyl! Pheny!) Propionate is mixed with 0.01 to 5.0 weight percent of one or more co-stabilizers. selected from the group consisting of clogged phenols, blocked amines, lactones, thioethers and phosphites.
6. 6. The composition according to claim 5, characterized in that said co-stabilizer is selected from the group consisting of hydrophenyl propionate, ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and 3- (3, Propyl 5-di-t-butyl-4-hydroxyphenyl) propionate.
7. 7. The composition according to claim 5, characterized in that said coestabilizer is an obstructed amine selected from the group consisting of diphenylamine, p, p'-di-tert-oct-l-diphenylamine, p, p'-di-a-phenylethyldiphenylamine, p -tert-octyl-p'-phenylethyl-diphenylamine, p-tert-octyldiphenylamine, p-phenylethyldiphenylamine, tri-t-octyldiphenylamine, p-tert-butyldiphenylamine, p, p'-di-tert-butyldiphenylamine, p-tert-octyl -p'-butyldiphenylamine, p-tert-butyl-p'-phenylethyldiphenylamine, phenyl-beta-diphenylamine, the dilylamines, phenyltolilamines, the dinaphthylamines, dianilinodiphenyl-methane, p-hydroxyldiphenylamine, p-amino-diphenylamine, N, N'- diphenyl-p-phenylenediamine, p-chlorodiphenylamine, p-isopropoxydiphenylamine and mixtures thereof.
8. The composition according to claim 5, characterized in that said co-stabilizer is a clogged phenol selected from the group consisting of 2,4-dimethyl-6-octylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6 -di-t-butyl-4-nonylphenol, 2,6-di-t-butyl-4-n-butylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl -4-sec-butylphenol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,4-dimethyl-6 -t-butylphenol, 4-hydroxymethyl-2,6-di-t-butylphenol, n-octadecyl-b (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 4,4'-dihydroxydiphenol, 4.4 '-thiobis (6-t-butyl-o-cresol), p-butylphenol, p-isopropylphenol, p- (1,1-, 3,3-tetramethylbutyl) phenol, thimo !, cresol mixed with m- and p-, p-nonylphenol and mixtures thereof.
9. 9. A process for preparing a flexible polyurethane foam comprising the reaction of an organic polyisocyanate together with an isocyanate-reactive composition, wherein one of the reactants has a stabilizing amount of 3- (4-hydroxy-3) in admixture therewith. , 5-di-tert-butylfemyl) methyl propionate, in the presence of a blowing agent and under conditions sufficient to form the polyurethane foam.
10. The process according to claim 9, characterized in that the isocyanate-reactive compound has an equivalent weight of from about 1,000 to about 2,500.
11. 11. The process according to claim 9, characterized in that the isocyanate-reactive compound is a polyether or polyether polyol.
12. The process according to claim 9, characterized in that the methyl 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate is present in amounts of from 0.01 to 5.0 weight percent of the isocyanate-reactive compound .
13. The process according to claim 9, characterized in that the methyl 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate is mixed with 0.01 to 5.0 weight percent of one or more co-stabilizers selected from the group which consists of clogged phenols, blocked amines, lactones, thioethers and phosphites.
14. 14. The process according to claim 9, characterized in that the blowing agent is water.