Process for producing flexible polyurethane foam using hexahydro-S-triazine catalysts

Hexahydro-s-triazines, and in particular hexamethylenetetramine (HMT), can be used in high water (5.0 or more parts per hundred parts of polyol) flexible polyurethane foams formulations in place of conventional gellation catalysts to produce open celled molded foams with excellent surfaces and with cores free of discoloration.

BACKGROUND OF THE INVENTION 
1. Field of The Invention 
The present invention relates to the use of hexahydro-s-triazine catalysts 
in the preparation of flexible polyether polyurethane foams. More 
particularly, the instant invention relates to the use of 
hexamethylenetetramine as a catalyst. 
2. Description of the Prior Art 
Catalysts for flexible polyurethane foams generally fall into two 
categories: the metal salts that promote the isocyanate polyol (gellation) 
reaction and the tertiary amines that promote the isocyanate-water 
(blowing) reaction. 
Of course none of these catalysts are specific and each catalyst within a 
given category has catalytic activity for both competing reactions which 
must be balanced to achieve optimum polyurethane foam. For example, tin 
salts such as stannous octoate are very specific for the gellation 
reaction but also catalyze the reaction between isocyanates with water to 
form ureas and carbon dioxide. Bis(2 dimethylaminoethyl) ether is highly 
specific for the blowing reaction but it also catalyzes the reaction 
between isocyanates with polyols. Triethylenediamine (TEDA) is an example 
of a tertiary amine that is relatively effective in both the gellation 
reaction and the blowing reaction. 
With high resiliency (HR) foams, where more reactive polyols are generally 
employed, very little tin catalysts can be used because the foam cell 
walls are less prone to rupture than with conventional foams, and this can 
result in shrinkage problems. In fact, most HR foams have to be 
mechanically crushed to prevent this problem. Accordingly, most or all of 
the tin catalyst is replaced with triethylenediamine to achieve the 
reaction required for final cure. Also, auxiliary tertiary amine catalysts 
such as pentamethyldipropylenetriamine that are significantly active for 
both the blowing and gellation reactions are used to decrease the overall 
levels of the more expensive and specific amines. 
Achieving the optimum catalytic balance is particularly difficult for rapid 
cure, low density HR Foams which are currently of significant commercial 
importance. 
Density reduction in such foams is achieved by either increasing the water 
level, and thus carbon dioxide evolution, or by the use of 
chlorofluorocarbons. Because of environmental concerns with the 
chlorofluorocarbons, the former approach is preferred. However, as the 
water level is increased, the exotherm increases creating a large 
temperature gradient between the foam core and the mold surface. Using a 
conventional amine catalyst like TEDA, this results in foam surface 
densification that extends significantly towards the core of the foam. In 
addition, at very high water levels, e.g. 6.5 or more parts per hundred 
parts of polyol, the center of the foam is discolored (scorched), 
presumably because of the very high exotherm and the basicity of the 
catalyst. 
It has surprisingly been found that hexahydro s-triazine compounds, and 
preferably hexamethylenetetramine (HMT), when substituted for conventional 
amine catalysts, greatly minimizes the densification and discoloration 
problems associated with low density foam employing high water levels. 
Hexahydro-s-triazine compounds, and hexamethylenetetramine (HMT) in 
particular, are known to the art and the latter has been widely used as 
crosslinking agents for organic rubbers and phenolic resins. U.S. Pat. No. 
4,275,169 discloses the use of HMT in the manufacture of polyester based 
flexible polyurethane foam with improved combustibility resistance. HMT is 
also disclosed in U.S. Pat. No. 3,689,440 with aromatic polyols to impart 
thermal stability to rigid urethane foams. The use of HMT, dispersed in 
waxy materials, such as stearic acid, to form large voids in polyurethane 
foams is disclosed in Japanese Pat. No. 67020798. 
The patent literature is also replete with examples of the use of 
hexahydro-s-triazines in polyurethane foams, particularly to induce 
isocyanurate formation and thus improve combustibility resistance. The 
most commonly cited triazine is 1,3,5 tris(3 
dimethylaminopropyl)-s-hexahydrotriazine (F-DMAP) which is used to promote 
isocyanaurate formation. Patents that describe these uses are: U.S. Pat. 
Nos. 4,228,310, 4,141,862; 4,066,580, 3,981,829, and 3,723,366. None of 
these patents describe the use of HMT alone in polyether flexible 
polyurethane foams or in blends with F-DMAP. 
OBJECTS OF THE INVENTION 
The primary object of the present invention is to prepare flexible 
polyurethane foams using a new class of catalysts. 
Another object of the present invention is to have the flexible 
polyurethane foams be of the low density, high resilency-type. 
Yet another object of the present invention is to avoid the use of 
chlorofluorocarbons in preparing these low density, high resilency foams. 
Another object of the present invention is to solve the densification and 
discoloration problems generally associated with high water, low density 
HR foams. 
Other objects of this invention will become apparent from the description 
and examples set forth hereafter. 
SUMMARY OF THE INVENTION 
It has been found that hexahydro-s-triazine compounds, preferably 
hexamethylenetetramine (HMT), greatly minimize the densification and 
discoloration problems associated with low- density HR foams made from 
high water formulations. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a process for producing HR polyurethane 
foams which include reacting: (a) a polyol or polymer/polyol and (b) an 
organic polyisocyanate in the presence of (c) a catalyst for the reaction 
of (a) and (b) to produce the polyurethane foam. The reaction is generally 
carried out in the presence of a blowing agent and a foam stabilizer. The 
reaction and foaming operations can be performed in any suitable manner, 
preferably by the one shot technique. 
The Hexahydro-s-triazine Catalysts 
The hexahydro-s-triazines compounds useful in this invention are 
hexamethylenetetramine: 
##STR1## 
and 1,3,5 tris (N,N-dialkylaminoalkyl) s-hexahydrotriazines of the 
following generic structure: 
##STR2## 
wherein R is alkylene group having from two to four carbon atoms, and 
R.sup.1 is an alkyl group having from 1 to 6 carbon atoms, preferably 
methyl or ethyl. 
The hexahydro-s-triazines useful in the present invention are generally 
prepared by the reaction between formaldehydes and amines or ammonia as 
taught in U.S. Pat. No. 4,025,469. 
Some of the hexahydro-s-triazines are solids that remain insoluble in 
polyols. Thus, the use of solvents may be required. The preferred 
material, HMT, is soluble in both water and glycerine. Glycerine is the 
preferred solvent since it has the additional advantage of delaying the 
blowing reaction and thus assist in balancing these two competing 
reactions. Generally, when a solvent is employed the hexahydro-s-triazine 
solution should be on the order of 1 to 40%, preferably 10 to 25% 
catalyst. 
Most preferably, a solution of 15% HMT in glycerine provides a liquid 
component for convenient addition to the foam formulation. The ratio of 
these two components is the ideal range for their use levels (1 to 3%) in 
the present invention. 
The hexahydro-s-triazines of this invention can be used from about 0.05 to 
5% based on the reacting mixture. Most preferably, they are used in the 
range of 0.1 to 0.5%. Hexamethylenetetramine can be used as the sole 
hexahydro-s-triazine of this invention while the other 
hexahydro-s-triazines must be used with HMT to achieve the desired 
effects. When mixtures are employed the HMT must be present in an amount 
equal to at least 25% of the total hexahydro-s-triazine catalyst charge. 
Polyol 
The polyol, or blends thereof, employed depends upon the end use of the 
polyurethane foam to be produced. The molecular weight or hydroxyl number 
of the polyol is selected so as to result in flexible foams when the 
polyol is converted to a polyurethane. The hydroxyl number of the polyols 
employed can accordingly vary over a wide range. In general, the hydroxyl 
number of the polyols employed may range from about 20 (or lower) to about 
70 (and higher). As a further refinement, the specific foam application 
will likewise influence the choice of the polyol. As an example, for 
molded foam, the hydroxyl number of the polyol may be on the order of 
about 20 to about 40, and for slabstock the hydroxyl number may be on the 
order of about 25 to about 70. 
The hydroxyl number limits described above are not intended to be 
restrictive, but are merely illustrative of the large number of possible 
combinations for the polyols used. 
The hydroxyl number is defined as the number of milligrams of potassium 
hydroxide required for the complete hydrolysis of the fully phthalated 
derivative prepared from one gram of polyol. The hydroxyl number can also 
be defined by the equation: 
EQU OH=(56.1.times.1000.times.f)/m.w. 
where 
OH=hydroxyl number of the polyol 
f=functionality, that is, average number of hydroxyl groups per molecule of 
polyol 
m.w.=number average molecular weight of the polyol. 
Substantially any of the polyols previously used in the art to make 
polyurethanes can be used as the polyol in this invention. Illustrative of 
the polyols useful in producing polyurethanes in accordance with this 
invention are the polyhydroxyalkanes, the polyoxyalkylene polyols, or the 
like. Among the polyols which can be employed are those selected from one 
or more of the following classes of compositions, alone or in admixture, 
known to those skilled in the polyurethane art: 
(a) alkylene oxide adducts of polyhydroxyalkanes; 
(b) alkylene oxide adducts of nonreducing sugars and sugar derivatives; 
(c) alkylene oxide adducts of phosphorus and polyphosphorus acids; 
(d) alkylene oxide adducts of polyphenols; 
(e) the polyols from natural oils such as castor oil, and the like. 
Illustrative alkylene oxide adducts of polyhydroxyalkanes include, among 
others, the alkylene oxide adducts of ethylene glycol, propylene glycol, 
1,3-dihydroxypropane, 1,3 dihydroxybutane, 1,4 dihydroxybutane, 1,4, 1,5 
and 1,6 dihydroxyhexane, 1,2-, 1,3- 1,4,1, 6-, and 1,8 dihydroxyoctane, 
1,10 dihydroxydecane, glycerol, 1,2,4-trihydroxybutane, 
1,2,6-trihyroxyhexane, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, 
pentaerythritol, polycaprolactone, xylitol, arabitol, sorbitol, mannitol, 
and the like. 
A further class of polyols which can be employed are the alkylene oxide 
adducts of the nonreducing sugars, wherein the alkylene oxides have from 2 
to 4 carbon atoms. Among the nonreducing sugars and sugar derivatives 
contemplated are sucrose, alkyl glycosides such as methyl glucoside, ethyl 
glucoside, and the like, glycol glycosides such as ethylene glycol 
glucoside, propylene glycol glycoside, glycerol glucoside, 
1,2,6-hexanetriol glucoside, and the like, as well as the alkylene oxide 
adducts of the alkyl glycosides as set forth in U.S. Pat. No. 3,073,788. 
The alkylene oxide adducts of phosphorus and polyphosphorus acids are 
another useful class of polyols. Ethylene oxide, 1,2-epoxypropane, the 
epoxybutanes, 3-chloro-1,2 epoxypropane, and the like are preferred 
alkylene oxides. Phosphoric acid, phosphorus acid, the polyphosphoric 
acids such as tripolyphosphoric acid, the polymetaphosphoric acids, and 
the like are desirable for use in this connection. 
Indeed, any material having an active hydrogen as determined by the 
Zerewitinoff test may be utilized as the polyol. For example, amine 
terminated polyether polyols are known and may be utilized, if desired. 
The most preferred polyols employed in this invention include the 
poly(oxypropylene) glycols, triols, and higher functionality polyols, and 
the like that are capped with ethylene or propylene oxide as dictated by 
the reactivity requirements of the particular polyurethane application. 
Generally, the nominal functionality of such polyols will be in the range 
of about 3 to 4 or so. These polyols also include 
poly-(oxypropylene-oxyethylene) polyols; however, desirably, the 
oxyethylene content should comprises less than 80 percent of the total and 
preferably less than 60 percent. The ethylene oxide, when used, can be 
incorporated in any fashion along the polymer chain. Stated another way, 
the ethylene oxide can be incorporated either in internal blocks, as 
terminal blocks, or may be randomly distributed along the polyol chain. 
In addition to these conventional polyols, polymer/polyols may be used 
alone or blended with other polyols. Polymer/polyols are well known in the 
art. The basic patents in the field are U.S. Pat. No. Re. 28,715 (reissue 
of U.S. Pat. No. 3,383,351) and U.S. Pat. No. Re. 29,118 (reissue of U.S. 
Pat. No. 3,304,273). Such compositions can be produced by polymerizing one 
or more ethylenically unsaturated monomers dissolved or dispersed in a 
polyol in the presence of a free radical catalyst to form a stable 
dispersion of polymer particles in the polyol. These polymer/polyol 
compositions have the valuable property of imparting to polyurethane foams 
produced therefrom higher load bearing properties than are provided by the 
corresponding unmodified polyols. Also included are the polyurethane and 
polyurea polymer/polyols as taught in U.S. Pat. Nos. 3,325,421 and 
4,374,209. 
Conceptually, a wide variety of monomers may be utilized in the preparation 
of the polymer/polyol compositions in accordance with the invention. 
Numerous ethylenically unsaturated monomers are disclosed in the prior 
patents. Any of these monomers should be suitable. 
The selection of the monomer or monomers used will depend on considerations 
such as the relative cost of the monomers and the polyurethane product 
characteristics required for the intended application. To impart the 
desired load-bearing to the foams, the monomer or monomers used in 
preparing the polymer/polyol should, of course, desirably be selected to 
provide a polymer which has a glass transition of at least slightly higher 
than room temperature. Exemplary monomers include styrene and its 
derivatives such as para-methylstyrene, acrylates, methacrylates such as 
methyl methacrylate, acrylonitrile and other nitrile derivatives such as 
methacrylonitrile, and the like. Vinylidene chloride may also be employed. 
The preferred monomer mixtures used to make the polymer/polyol compositions 
are mixtures of acrylonitrile and styrene or acrylonitrile, styrene and 
vinylidene chloride. 
The monomer content will be typically selected to provide the desired 
solids content required for the anticipated end-use application In 
general, it will usually be desirable to form the polymer/polyols with as 
high a resulting polymer or solids content as will provide the desired 
viscosity and stability properties. 
For typical HR foam formulations, solids content of up to about 45 weight 
percent or more are feasible and may be provided. In slabstock 
applications, the tendency is to utilize as high a solids content as 
possible, contents of 45 weight percent to about 50 weight percent or more 
being desired commercially for some applications. 
Isocyanates 
The organic polyisocyanates that are useful in producing polyurethane foam 
in accordance with this invention are organic compounds that contain at 
least two isocyanato groups. Such compounds are well-known in the art. 
Suitable organic polyisocyanates include the hydrocarbon diisocyanates 
(e.g., the alkylene diisocyanates and the arylene diisocyanates), as well 
as known triisocyanates and polymethylene poly (phenylene isocyanates). 
Examples of suitable polyisocyanates are 2,4-diisocyanatotoluene, 
2,6-diisocyanatotoluene, methylene bis(4 cyclohexyl isocyanate), 
1,8-diisocyanatooctane, 1,5-diisocyanato 2,2,4-trimethylpentane, 
1,9-diisocyanatononane, 1,10-diisocyanatopropyl)ether of 1,4 butylene 
glycol, 1,11-diisocyanatoundecane, 1,12-diisocyanatododecane 
bis(isocyanatohexyl) sulfide, 1,4-diisocyanatobenzene, 
3,5-diisocyanato-o-xylene, 4,6-diisocyanato-m-xylene, 
2,6-diisocyanato-p-xylene, 2,4-diisocyanato-l-chlorobenzene, 2,4 
diisocyanato-l-nitrobenzene, 2,5-diisocyanato-l-nitrobenzene, 
4,4'-diphenylmethylene diisocyanate, 3,3'-diphenyl-methylene diisocyanate, 
and polymethylene poly (phenyleneisocyanates), and mixtures thereof. The 
preferred polyisocyanates are TDI (80% 2,4-tolylene diisocyanate and 20%, 
2,6-tolylene diisocyanate), MDI (diphenylmethane diisocyanate alone or 
mixtures with its polymeric forms) and mixtures of TDI with MDI. 
Other Catalysts 
In addition to the hexahydro-s-triazine catalysts, any known catalysts 
useful in producing polyurethanes may be employed. The tertiary amines may 
be used as secondary catalysts for accelerating the gellation reaction 
and/or the blowing reaction in combination with one or more of the 
above-noted hexahydro-s-triazine catalysts. Metal catalysts, or 
combinations of metal catalysts, may also be employed as the secondary 
catalysts. The catalysts are employed in small amounts, for example, from 
about 0.001 percent to about 5 percent, based on the weight of the 
reaction mixture. Representative catalysts include: (a) tertiary amines 
such as bis(2,2'-dimethylamino)ethyl ether, trimethylamine, triethylamine, 
N methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, 
N,N-dimethylethanolamine, N,N,N',N'-tetramethyl-1,3-butanediamine, 
pentamethyldipropylenetriamine, triethanolamine, triethylenediamine, 
pyridine oxide and the like; (b) strong bases such as alkali and alkaline 
earth metal hydroxides, alkoxides, and phenoxides; (c) acidic metal salts 
of strong acids such as ferric chloride, stannic chloride, stannous 
chloride, antimony trichloride, bismuth nitrate and chloride, and the 
like; (d) chelates of various metals such as those which can be obtained 
from acetylacetone, benzoylacetone, trifluoroacetylacetone, ethyl 
acetoacetate, salicylaldehyde, cyclopentanone-2-carboxylate, 
acetylacetoneimine, bis-acetylacetone-alkylenediimines, 
salicylaldehydeimine, and the like, with the various metals such as Be, 
Mg, Zn, Cd, Pb, Ti, Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co, Ni, or such ions 
as MoO.sub.2 ++, UO.sub.2 ++, and the like; (e) salts of organic acids 
with a variety of metals such as alkali metals, alkaline earth metals, Al, 
Sn, Pb, Mn, Co, Bi, and Cu, including, for example, sodium acetate, 
potassium laurate, calcium hexanoate, stannous acetate, stannous octoate, 
stannous oleate, lead octoate, metallic driers such as manganese and 
cobalt naphthenate, and the like; (f) organometallic derivatives of 
tetravalent tin, trivalent and pentavalent As, Sb, and Bi, and metal 
carbonyls of iron and cobalt. 
Among the organotin compounds that deserve particular mention are 
dialkyltin salts of carboxylic acids, e.g., dibutyltin diacetate, 
dibutyltin dilaureate, dibutyltin maleate, dilauryltin diacetate, 
dioctyltin diacetate, dibutyltin bis(4 methylaminobenzoate), dibutyltin 
bis(6 methylaminocaproate), and the like. Similarly, there may be used a 
trialkyltin hydroxide, dialkyltin oxide, dialkyltin dialkoxide, or 
dialkyltin dichloride. Examples of these compounds include trimethyltin 
hydroxide, tributyltin hydroxide, trioctyltin hydroxide, dibutyltin oxide, 
dioctyltin oxide, dilauryltin oxide, dibutyltin-bis(isopropoxide), 
dibutyltindilaurylmercaptide, dibutyltin-bis(2 -dimethylaminopentylate), 
dibutyltin dichloride, dioctyltin dichloride, and the like. 
Blowing Agents 
When the polyurethane foam is formed, a small amount of a blowing agent is 
employed in the reaction mixture. For the purposes of the present 
invention, the primary blowing agent is water from about 0.5 to about 20, 
preferably 5 to 8, parts per hundred parts of polyol, based upon total 
weight of the polyol composition, alone or with other suitable blowing 
agents which are vaporized by the exotherm of the reaction. Illustrative 
polyurethane blowing agents include halogenated hydrocarbons such as 
trichloromonofluoromethane, dichlorodifluoromethane, 
dichloromonofluoromethane, dichloromethane, trichloromethane, 
1,1-dichloro-l-fluoroethane, 1,1,2-trichloro-1,2,2-trifluoroethane, 
hexafluorocyclobutane, octafluorocyclobutane, and the like. Another class 
of blowing agents include thermally unstable compounds which liberate 
gases upon heating such as N,N'-dimethyl N,N'-dinitrosoterephthalamide, 
amine formates, formic acid and the like. The generally preferred method 
of foaming for producing HR flexible foams is the use of water, or a 
combination of water plus a fluorocarbon blowing agent such as 
trichloromonofluoromethane. The quantity of blowing agent employed will 
vary with factors such as the density desired in the foamed product. 
The scorch-free advantages of the foams are most evident at water levels of 
5 or more parts per hundred parts of polyol. This results in a foam having 
a density less than 1.5 pounds per cubic foot. 
Stabilizers 
It is also within the scope of the invention to employ, when applicable, 
small amounts, e.g., about 0.001 percent to 5.0 percent by weight, based 
on the total reaction mixture, of a foam stabilizer. Suitable foam 
stabilizers or surfactants are known and may vary depending upon the 
particular polyurethane application. Suitable stabilizers for slabstock 
applications include "hydrolyzable" polysiloxane-polyoxyalkylene block 
copolymers such as the block copolymers described in U.S. Pat. Nos. 
2,834,748 and 2,917,480. Another useful class of foam stabilizers are the 
"non-hydrolyzable" polysiloxane-polyoxyalkylene block copolymers such as 
the block copolymers described in U.S. Pat. Nos. 3,505,377 and 3,686,254 
and British patent specification No. 1,220,471. The latter class of 
copolymers differs from the above mentioned polysiloxane-polyoxylakylene 
block copolymers in that the polysiloxane moiety is bonded to the 
polyoxy-alkylene moiety through direct carbon-to-silicon bonds, rather 
than through carbon-to-oxygen to-silicon bonds. These various 
polysiloxane-polyoxyalkylene block copolymers preferably contain from 5 to 
50 weight percent of polysiloxane polymer, with the remainder being 
polyoxyalkylene polymer. Yet another useful class of foam stabilizer is 
composed of the cyanoalkyl-polysiloxanes described in U.S. Pat. No. 
3,905,924. 
The polyurethanes so produced may be utilized in flexible foam applications 
where any conventional type of flexible polyurethane is or can be 
utilized. The polyurethanes find particular utility in the production of 
high resiliency foams for use in arm rests, mattresses, automobile seats, 
and the like, as well as in slabstock foams for use as carpet 
underlayment, and the like. 
Whereas the exact scope of the instant invention is set forth in the 
appended claims, the following specific examples illustrate certain 
aspects of the present invention and, more particularly, point out methods 
of evaluating the same. However, the examples are set forth for 
illustration only and are not to be construed as limitations on the 
present invention except as set forth in the appended claims. All parts 
and percentages are by weight unless otherwise specified. 
DEFINITIONS 
As used in the Examples, the following designations, symbols, terms and 
abbreviation have the following meanings: 
Polyol A--A polyol made by reacting propylene oxide with glycerine in the 
presence of potassium hydroxide catalyst, capping with ethylene oxide and 
refining to remove catalyst. The polyol contains about 16.5 weight percent 
ethylene oxide as a cap and has a hydroxyl number of about 28. 
Polyol B--A polyol made by reacting propylene oxide with glycerine in the 
presence of potassium hydroxide catalyst, capping with ethylene oxide and 
refining to remove catalyst. The polyol contains about 19 weight percent 
ethylene oxide as a cap and has a hydroxyl number of about 35. 
Polyol C--A polyol made by reacting propylene oxide with glycerine in the 
presence of potassium hydroxide catalyst, capping with ethylene oxide and 
refining to remove catalyst. The polyol contains about 9 weight percent 
ethylene oxide as a cap and has a hydroxyl number of about 31. 
Polyol D--A polyol made by reacting propylene oxide with glycerine in the 
presence of potassium hydroxide catalyst, capping with ethylene oxide and 
refining to remove catalyst. The polyol contains about 19 weight percent 
ethylene oxide as a cap and has a hydroxyl number of about 28. 
Polymer/Polyol A--A polymer/polyol sold by Union Carbide Corporation as 
"NIAX Polyol E-650". It contains 33 weight percent polymer and has a 
hydroxyl number of 24. 
Polymer/Polyol B--A polymer/polyol sold by Union Carbide Corporation as 
"NIAX Polyol E-654". It contains 28 weight percent polymer and has a 
hydroxyl number of 25. 
Polyol E--A propylene/ethylene oxide adduct of butanol sold by Union 
Carbide as "UCON Fluid 50HB5100". 
Graft A--A 10 percent by weight graft of acrylic acid on Polyol E. 
Polyol F--A polyol comprising 90 percent by weight of Polyol A and 10 
percent of Graft A neutralized with a 33 percent solution of KOH. 
Polyol G--A nine mole adduct of ethylene oxide on nonyl phenol. 
HMT--hexamethylenetetramine 
F--DMAP--1, 3, 5 tris (dimethylaminopropyl)-s-hexahydrotriazine 
HMT--G--a 15 percent solution of HMT in glycerine 
Catalyst A--A polyurethane foam triethylenediamine catalyst sold as "NIAX 
Catalyst A 33" by Union Carbide Corporation. 
Catalyst B--a polyurethane foam pentamethyldipropylenetriamine catalyst 
sold as "Polycat 77" by Air Products Corporation. 
Catalyst C--A polyurethane foam bis (2-dimethylaminoethyl)ether catalyst 
sold as "NIAX Catalyst A-1" by Union Carbide Corporation. 
Catalyst D--dibutyltin dilauryl mercaptide 
Surfactant A--A silicone surfactant sold for use in high resiliency foam by 
Union Carbide Corporation as "Silicone Surfactant Y-10,459". 
Surfactant B--A silicone surfactant sold for use in high resiliency foam by 
Union Carbide Corporation as "Silicone Surfactant Y-10,515". 
TDI--A mixture of 80 weight percent 2,4-diisocyanatotoluene and 20 weight 
percent 2,6-diisocyanatotoluene. 
Cream Time--is the time from the addition of the isocyanate during mixing 
of the components until the visible movement or expansion of the foam 
mixture begins. 
Exit Time--is the time when the foaming mixture first begins to extrude 
from the vent holes in the mold. 
Vent Collapse--is the sum of the area of the large cells or voids that can 
occur in the foam at the four 1/16" vent holes in the rectangular mold. 
PROCEDURE 
Prior to preparing the foaming mixture it was necessary to prepare the mold 
properly. The mold was heated to above 165.degree. F. in a forced air oven 
(250.degree. F.), then removed from the oven and sprayed with mold 
release. The mold was then cooled to 130.degree. F. to 160.degree. F. 
depending on the optimum temperature for a given formulation. The 
preparation of the foaming mixture was timed so that the mold was at or 
near optimum temperature at the time of pour. 
Each formulation was prepared by first mixing all of the ingredients except 
the TDI at 4000 rpm for 55 seconds. After mixing was stopped the correct 
level of TDI was added quickly. Then the mixer was started and the mixing 
at 4000 rpm was continued for 5 seconds. After the mixing was completed 
the contents of the mixing container were immediately poured into a waxed, 
heated (130.degree.-160.degree. F.) aluminum mold (15".times.15".times.5") 
provided with a lid hinged to the mold and four vent holes of 1/16 inch in 
diameter drilled close to each corner of the lid. The lid is provided with 
a latch for holding it in closed position. After pouring the resultant 
mixture into the mold the lid was closed and latched. The mixture in the 
mold was allowed to foam and fill the mold. Some of the foam extruded 
through the four vent holes. The foam was allowed to set for 2 minutes 
from pour and then placed in a 250.degree. F., forced air oven for 3 
minutes. The foam was demolded after a total of 2 to 5 minutes from pour. 
The form part was immediately hand crushed and then passed 3 times through 
crushing rollers (90% crush). After the crushing step the foam part was 
placed in a forced air oven at 250.degree. F. for a 30 minute postcure 
period. The parts were then placed in a constant temperature (72.degree. 
F.) constant humidity (50% RH) room and conditioned for 24 hours before 
testing for physical properties.