Reduction of discoloration in flame retarded polyurethane foams

Abstract: Polyurethane foams containing halogenated phosphorus-based flame retardants are protected from scorching by the incorporation therein of an anti-scorch package which comprises a diaryl arylenediamine, the reaction product of a diarylamine and a lower alkyl ketone, and a hindered phenol.

Description: The present invention relates to reduction of discoloration in flame retarded polyurethane foams. In U.S. Patent No. 4,130,513, a mixture of diphenyl p-phenylenediamine and the reaction product of diphenylamine and acetone is described as an additive package to prevent the discoloration of polyurethane foams which are rendered flame retardant by use of a halogenated phosphorus flame retardant. In U.S. Patent No. 4,178,420, it is disclosed that the discoloration of low density polyurethane foams produced with certain flame retardants can be reduced by incorporating certain amine antioxidants into the foam. It is shown that this cannot be achieved with certain di-t-butyl group-containing phenols. The instant invention concerns itself with an improvement in the general type of anti-scorch, two-component package described in the aforementioned U.S. Patent No. 4,130,513. The instant invention relates to a three-component, anti-scorch package for polyurethane foams which have been rendered flame retardant by the use of halogenated phosphorus-based flame retardants. The package comprises a diaryl arylenediamine, the reaction product of a diarylamine and a lower alkyl ketone, and, as a novel third component, a hindered phenol. The present invention is concerned with low density polyurethane foams that have been rendered flame retardant by the use of a halogenated phosphorus-based flame retardant and, more particularly, to the reduction of scorching when the curing operation is performed in the presence of such flame retardants. The flame retardant compositions which can be used in the low density polyurethane foams include such halogenated phosphorus-based flame retardants as poly(haloethyl-ethylene oxy) phosphoric acid esters, mixtures of such esters with other flame retardants, and such other flame retardants as the tris(haloalkyl)phosphates, such as tris(dibromo propyl)phosphate, tris(beta-chloroethyl) phosphate, and tris(beta-chloropropyl)phosphate, among others. Generally speaking, such halogenated, phosphorus-based flame retardants are employed in a flame retardant effective amount, generally from about 3% to about 20% by weight of the polyol used in the foam formulation. The polyurethane foam formulation which can be used in conjunction with the present invention includes the numerous conventional foam formulations for such low density polyurethane foams. The selection of various ingredients and process conditions for making such foams can easily be determined by a person of ordinary skill in the art. The three-component, anti-scorch package which is the subject of the present invention comprises the following components: (a) a diaryl arylenediamine; (b) the reaction product of a diarylamine and a lower alkyl ketone, such as acetone; and (c) as a novel third component, a hindered phenol. The diaryl arylenediamines which are deemed useful in accordance with the present invention include those of the formula Ar(NHAr)2, where Ar is a substituted or unsubstituted aryl group. A representative example of a suitable diaryl arylenediamine which can be used in accordance with the present invention is diphenyl para-phenylenediamine, which is a preferred additive. Generally speaking, the amount of such component can range anywhere from about 20% to about 40% by weight of the three-component anti-scorch package. The second component of the anti-scorch package of the present invention is a reaction product of a diarylamine and a lower alkyl ketone, such as acetone. A preferred reaction product from this class of compounds is the reaction product of diphenylamine and acetone which is described in U.S. Patent No. 3,798,184 as a stabilizer for polyurethane compositions against dry-heat degradation. Generally speaking, the amount of this component which can be used in the three-component, anti-scorch package of the present invention ranges from about 20% to about 40% by weight of the package. The third, and final, component for the anti-scorch package of the present invention comprises a hindered phenol. In order to insure good processability for the foam formulation, the hindered phenol (as well as the two previously mentioned anti-scorch components) should be readily soluble in the foam formulation components. For example, if the scorch inhibitor package of the present invention is intended to be marketed in combination with the flame retardant, it should be soluble in that component for best results. Liquid or readily dissolvable solid phenols are useful. This class of compound is known and includes phenol compounds having a plurality of substituents, e.g., of the alkyl-type. In order to insure solubility in the foam compositions, the alkyl groups should not be so bulky as to inhibit solubility. Polar substituents, if present, may tend to be acceptable, since they likely will not detract from the preferred solubility desired. For example, such phenols include compounds having from 2 to 4 alkyl substituents, particularly those that have some degree of bulk to them. Branched alkyl groups at the ortho positions serve to give the desired degree of steric hindrance. Included are such groups as secondary-butyl and tertiary-butyl. A representative phenol from this class of compound is a tributylated phenol such as 3,6'-di-tert-butyl-4-sec-butyl phenol. Generally speaking, the weight amount of hindered phenol which can be used in the anti-scorch package of the present invention can vary from about 20% to about 40% by weight of the three-component package. It has been found that the additional presence of the hindered phenol enables the type of two-component package shown in U.S. Patent No. 4,130,513 to function more effectively as an anti-scorch composition. Generally speaking, the weight amount of such anti-scorch composition in the polyurethane foam formulation can range anywhere from about 0.3% to about 7.5% by weight of the polyol used in the formulation. The following Example illustrate certain embodiments of the present invention, but should not be construed in a limiting sense. EXAMPLE The following general type of polyurethane foam formulation was prepared: Ingredient Parts by Weight Polyether Polyol (3000 mw) (NIAX 16-56 brand) 100 Halogenated Phosphoric Acid Ester Flame Retardant 15.0 Tolylene Diisocyanate 63.2 Water 5.0 Silicone Surfactant Stabilizer (L 5740 brand) 1.1 Diazobicyclo-(2,2,2)-octane Catalyst 0.3 N-ethylmorpholine Catalyst 0.2 Stannous Octoate Catalyst 0.4 The formulation was combined with the various types of additives mentioned in the Table given below and poured into a 20.32 cm x 20.32 cm x 12.70 cm box and allowed to rise freely. The foam was then placed in an AMANA TOUCHMATIC RADARANGE in microwave oven and heated for 105 seconds. The foam was removed and allowed to cool for 30 minutes. The foam bun was then sliced in the center perpendicular to the direction of rise and a 2.54 cm thick slice was cut from the bun. A 5.08 cm by 5.08 cm sample from the slice was removed for foam evaluation. The foam was evaluated, as more fully described in U.S. Patent No. 4,477,600, using a Pacific Scientific Spectrogard Colorimeter (XL 835 designation) to give a numerical rating to three color characteristics compared to a foam prepared without flame retardant. The color difference was calculated as more fully described in A Rapid Predictive Test for Urethane Foam Scorch, by Michael J. Reale and Barry A. Jacobs in Journal of Cellular Plastics, November/December 1979 (which is also incorporated herein by reference). A smaller color difference value indicates less discoloration and is indicative of superior performance. The Table sets forth the data. The numbers below anti-scorch additives A-D refers to the gram amounts present:

Claims: An anti-scorch composition for use in polyurethane foams containing a halogenated phosphorus-based flame retardant, which comprises: (a) a diaryl arylenediamine compound having the formula Ar(NHAr)2, wherein Ar is a substituted or unsubstituted aryl group; (b) the reaction product of a diarylamine and a lower alkyl ketone; and (c) a hindered phenol. A composition as claimed in Claim 1 wherein the diaryl arylenediamine compound is present at from 20% to 40% by weight of (a), (b) and (c), the reaction product is present at from 20% to 40%, by weight of (a), (b) and (c), and the hindered phenol is present at from 20% to 40%, by weight of (a), (b) and (c). A composition as claimed in Claim 1 or 2 wherein the diaryl arylenediamine is diphenyl para-phenylenediamine. A composition as claimed in Claim 1 or 2 wherein the reaction product is a reaction product of diarylamine and acetone. A composition as claimed in Claim 1 or 2 wherein the hindered phenol is 3,6'-di-tert-butyl-4-sec butyl phenol A polyurethane foam containing a halogenated phosphorus-based flame retardant which contains a composition according to any one of the Claims 1-5 in an amount of from 0.3% to 7.5%, by weight of polyol used in making the foam.

Inventors: FESMAN GERALD, JACOBS BARRY ALAN, WILLIAMS BARBARA ANN, FESMAN, GERALD, JACOBS, BARRY ALAN, WILLIAMS, BARBARA ANN
Applicants: AKZO NOBEL NV, AKZO NOBEL N.V.
Application year: 1989
Main classification: C08K5
IPC codes: C08K5, C08L75, C08G18, C08G101