Method for determining the hardness of fragrance containing polyurethane foams

A method is disclosed for controlling the hardness of a polyurethane foam by introducing an aroma chemical into the reaction mixture to form a polyurethane foam according to a desired hardness to be attained. The aroma chemical can be selected based on the empirical formula: EQU log.sub.e (hardness of foam)=1.87(polarity/molecular weight).sup.0.27

INTRODUCTION AND BACKGROUND 
The present invention relates to a method for predicting the structure and 
integrity of a polyurethane foam by means of the particular fragrance 
ingredient added to the reactant mixture. In another aspect, the present 
invention relates to a method for controlling the hardness of a 
polyurethane foam having a fragrance ingredient to produce a foam product 
with a desired degree of hardness ranging from soft to hard depending upon 
the selection of an aroma chemical which is introduced into the reaction 
mixture to form the polyurethane foam. 
It is known in the past to produce polyurethane foams by introducing a 
fragrance component into the reactants to produce the polyurethane foam. 
Such methods however have not been able to devise a way to predict and 
control the relative hardness of the resulting foam product by selecting 
and using a particular aroma chemical for incorporation into the foam 
producing formulation. 
SUMMARY OF THE INVENTION 
The present invention provides a method for predicting in advance the 
structure and integrity of a polyurethane foam by establishing a table of 
previously tested aroma chemicals according to observed relative hardness 
based on a given polyurethane foam forming composition and then selecting 
an aroma chemical based on the data in the table for inclusion into a 
selected formulation for producing a polyurethane foam of desired 
predictable properties. 
In another aspect the invention provides a method of selecting an aroma 
chemical depending upon its polarity on a scale of 1 to 10 and actual 
molecular weight and predicting the approximate hardness of the resulting 
polyurethane foam based on establishing a range of hardness on a scale of 
from 1 to 10 for the resulting foam product, the maximum value of 10 
indicating the highest degree of foam hardness. 
In another aspect, the present invention provides a method for controlling 
the hardness of a polyurethane foam by selecting an aroma chemical, 
calculating the resulting hardness to be achieved according to an 
empirical formula and introducing the aroma chemical into the reaction 
mixture containing the polyurethane foam forming reactants to form the 
polyurethane foam according to the desired hardness to be attained. The 
empirical formula of the present invention is: 
EQU log.sub.e (Z)=1.87(X/Y).sup.0.27 
wherein 
Z=hardness of foam on a scale of 1 to 10 
X=polarity of aroma chemical on a scale of 1 to 
Y=actual molecular weight of aroma chemical

DETAILED DESCRIPTION OF THE INVENTION 
The polyurethane foams of the present invention are made by reacting an 
active-hydrogen containing compound, usually a polyol or mixtures of 
polyols, with a polyisocyanate or mixture of polyisocyanates. Optionally, 
extenders, blowing agents and the like which are conventional ingredients 
for preparing polyurethane foams also can be introduced into the reactant 
mixture. The polyisocyanates which can be used for purposes of the present 
invention are modified and unmodified polyisocyanates which are well known 
to those skilled in art. 
For the purposes of this invention the term polyisocyanate is used to 
describe compounds containing at least two isocyanate groups. Unmodified 
polyisocyanates included aliphatic or cycloaliphatic and aromatic 
polyisocyanates. Examples include 2,4- and 
2,6-methylcyclohexylenediisocyanate, tetramethylene diisocyanante, 
cyclohexane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene 
diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, 
naphthalene-1,5-diisocyanante, 1-mexthoxyphenyl-2,4-diisocyanante. 
Preferred isocyanates include 4,4'-diphenylmethane diisocyanate (MDI), 
mixtures of 4,4- and 2,4-diphenylmethane diisocyanate, and polymeric 
polyisocyanates such as polymethylene polyphenylenes polyisocyanates 
(polymeric MDI). 
These polyisocyanates are prepared by conventional methods known in the 
art, e.g. phosgenation of the corresponding organic amine. 
For purposes of the present invention isocyanates other than the preferred 
isocyanates may be present in minor amounts. 
In the preparation of the polyurethanes of the present invention the 
isocyanate is reacted with isocyanante reactive hydrogen-containing 
compounds (polyols are preferred). Hydroxyl group-containing compounds 
(polyols) useful in the preparation of polyurethanes are described in the 
Polyurethane Handbook in chapter 3, Section 3.1 pages 42-61; and in 
Polyurethanes; Chemistry and Technology in Chapter II, Sections III and 
IV, pages 32-47. Many hydroxyl-group containing compounds may be used, 
including simple aliphatic glycols, dihydroxy aromatics, bisphenols, and 
hydroxyl-terminated polyethers, polyesters, and polyacetals, among others. 
Extensive lists of suitable polyols may be found in the above references 
and in many patents, for example in columns 2 and 3 of U.S. Pat. No. 
3,652,639, columns 2-6 of U.S. Pat. No. 4,421,872; and columns 4-6 of U.S. 
Pat. No. 4,310,632; these three patents being hereby incorporated by 
reference. 
Preferably used are hydroxyl-terminated polyoxyalkylene polyols. The former 
are generally prepared by well known methods, for example by the base 
catalyzed addition of an alkylene oxide, preferably ethylene oxide 
(oxirane), propylene oxide (methyloxirane) or butylene oxide 
(ethyloxirane) to an initiator molecule containing on the average two or 
more active hydrogens. Examples of preferred initiator molecules are 
dihydric initiators such as ethylene glycol, propylene glycol, butylene 
glycol, neopentyl glycol, 1,6-hexanediol, hydroquinone, resorcinol, the 
bisphenols, aniline and other aromatic monoamines, aliphatic monoamines, 
and monoesters of gylcerine; trihydric initiators such as glycerine, 
trimethylolpropane, trimethylolethane, N-alkylphenylenediamines, mono-, 
di, and trialkanolamines; tetrahydric initiators such as ethylene diamine, 
propylene diamine, 2,4-, 2,2'- and 4,4'-methylenedianiline, 
toluenediamine, and pentaerythritol; pentahydric initiators such as 
diethylenetriamine; and hexahydric and octahydric initiators such as 
sorbitol and sucrose. 
Addition of alkylene oxide to the initiator molecules may take place 
simultaneously or sequentially when more than one alkylene oxide is used, 
resulting in block, heteric, and block-heteric polyoxyalkylene polyethers. 
The number of hydroxyl groups will generally equal the number of active 
hydrogens in the initiator molecule. Processes for preparing such 
polyethers are described both in the Polyurethane Handbook and 
Polyurethanes; Chemistry and Technology as well as in many patents, for 
example U.S. Pat. Nos. 1,922,451; 2,674,619; 1,922,459; 3,190,927; and 
3,346,557. 
Polyester polyols also represent polyurethane-forming reactants. Such 
polyesters are well known in the art and are prepared simply by 
polymerizing polycarboxylic acid derivatives, for example the 
corresponding acid chlorides or anhydrides, with a polyol. Numerous 
polycarboxylic acids are suitable, for example malonic acid, citric acid, 
succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, 
sebacic acid, maleic acid, fumaric acid, terephthalic acid, and phthalic 
acid. Numerous polyols are suitable, for example the various aliphatic 
glycols, trimethylolpropane and trimethylolethane, 
.alpha.-methylglucoside, and sorbitol. Also suitable are low molecular 
weight polyoxyalkylene glycols such as polyoxyethylene glycol, 
polyoxypropylene glycol, and block and heteric 
polyoxyethylene-polyoxypropylene glycols. These lists of dicarboxylic 
acids and polyols are illustrative only, and not limiting. An excess of 
polyol should be used to ensure hydroxyl termination. Methods of 
preparation of such polyester polyols are given in the Polyurethane 
Handbook and in Polyurethanes; Chemistry and Technology. 
Illustrative polymerization initiators which may be employed are the 
well-known free radical types of vinyl polymerization initiators such as 
the peroxides, persulfates, perborates, percarbonates, azo compounds, etc. 
These include hydrogen peroxide, dibenzoyl peroxide, acetyl peroxide, 
benzoyl hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, lauroyl 
peroxide, butyryl peroxide, diisopropylbenzene hydroperoxide, cumene 
hydroperoxide, paramenthane hydroperoxide, diacetyl peroxide, di-o-cumyl 
peroxide, dipropyl peroxide, diisopropyl peroxide, isopropyl-t-butyl 
peroxide, butyl-t-butyl peroxide, difuroyl peroxide, bis(triphenylmethyl) 
peroxide, bis(p-methoxybenzoyl) peroxide, p-monomethoxybenzoyl peroxide, 
rubene peroxide, ascaridol, t-butyl peroxybenzoate, diethyl 
peroxyterephthalate, propyl hydroperoxide, t-butyl hydroperoxide, 
cyclohyexyl hydroperoxide, trans-decalin hydroperoxide, 
.alpha.-methylbenzyl hydroperoxide, .alpha.-methyl-.alpha.-ethyl benzyl 
hydroperoxide, tetralin hydroperoxide, triphenyl-methyl hydroperoxide, 
diphenylmethyl hydroperoxide, .alpha.,.alpha.'-azobis-(2-methyl 
heptonitrile), 1-t-butylazo-1-cyanocyclohexane, persuccinic acid, 
diisopropyl peroxy discarbonate, 2,2'-azobis-(2-4-dimethylvaleronitrile), 
2-t-butylazo-2-cyano-4-methoxy-4-methylpentane,2,2'-azo-bis-2-methylbutane 
nitrile, 2-t-butylazo-2-cyanobutane, 1-t-amylazo-l-cyanocyclohexane, 
2,2'-azobis-2,4-dimethyl-4-methoxyvaleronitrile, 2,2'-azobis- 
2-methylbutyronitrile, 2-t-butylazo-2-cyano-4-methylpentane, 
2-t-butylazo-2-isobutyronitrile, and the like; a mixture of initiators may 
also be used. The preferred initiators are 
2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(isobutyronitrile), 
2-2'-azobis(2,4-dimethylvaleronitrile), 
2-t-butylazo-2-cyano-4-methoxy-4-methyl pentane, 
2-t-butylazo-2-cyano-4-methylpentane, 2-t-butylazo-2-cyano-butane and 
lauroyl peroxide. Generally, from about 0.1 percent to about 10 percent, 
preferably from about 1 percent to about 4 percent, by weight of initiator 
based on the weight of the monomer will be employed in the process of the 
invention. 
Any suitable catalyst or mixture of catalysts may be used including 
tertiary amines such as, for example, triethylenediamine, 
N-methylmorpholine, N-ethylmorpholine, diethylethanolamine, 
N-cocomorpholine, 1-methyl-4-dimethylamino-ethylpiperazine, 
3-methoxypropyldimethylamine, N,N,N'-trimethylisopropyl propylenediamine, 
3-diethylaminopropyldiethylamine, dimethylbenzylamine, and the like. Other 
suitable catalysts are, for example, stannous chloride, 
dibutylin-di-2-ethyl hexonate, potassium hexanoate, stannous oxide, as 
well as other organometallic compounds such as are disclosed in U.S. Pat. 
No. 2,846,408. 
In some instances, a surface-active agent is necessary for production of 
polyurethane foam. Numerous surface-active agents have been found 
satisfactory. Of these, the nonionic surface-active agents such as the 
well known silicones have been found particularly desirable when use of a 
surfactant is necessary. Other surface-active agents which are operative, 
although not preferred, include polyethylene glycol ethers of long chain 
alcohols, tertiary amine or alkanol amine salts of long chain alkyl acid 
sulfate esters, alkyl sulfonic esters, and alkyl arylsulfonic acids. Use 
of a surfactant in the present invention is optional. 
A chain extender and/or crosslinker is used as well in the present 
invention These include those compounds having at least two functional 
groups bearing active hydrogen atoms such as, hydrazine, primary and 
secondary diamines, amino alcohols, amine acids, hydroxy acids, glycols, 
or mixtures thereof. Glycerin is an example of a preferred compound used 
as a crosslinker. 
Other optional additives which fall within the scope of the present 
invention include known pigments, such as carbon black, dyes, stabilizers 
against aging and weathering, fungistats, bacteriostats, fillers, or flame 
retarding agents. 
The following examples serve to illustrate the present invention and are 
not considered limiting thereof. 
Suitable methods of preparation include the prepolymer technique wherein an 
excess of organic polyisocyanate is reacted with a polyol to prepare a 
prepolymer having free isocyanate reactive groups, which is then reacted 
with a mixture of water, surfactant, aroma chemical, and catalyst to 
obtain foam. Another option is to prepare a foam by reacting all the 
components in a single working step known as the "one-shot" method. In the 
one-shot method, the components may be mixed in a mix head or by 
impingement mixing. 
The polyurethane components combined by any one of the above-mentioned 
techniques may be poured or sprayed into an open mold, which is 
subsequently closed and clamped, if necessary, to allow the components to 
fully react, after which the part is demolded and allowed to cure. 
Alternatively, the polyurethane components may be injected into an open or 
closed mold, which is subsequently closed if the components were initially 
injected into an open mold; and the components are allowed to fully react 
after which the part is demolded and set aside to cure. 
The mixed polyurethane components may also be poured, injected, or sprayed 
into open cavities or molds and allowed to free rise instead of reacting 
in a closed mold, such as in the production of slab stock which is cut 
into a desired shape, a pour-in-place method of applying rigid 
polyurethane between panels used as the final part, or a pour-behind 
method of foaming. 
A typical polyurethane formulation is as follows: 
60 parts by weight of an ethylene oxide-propylene oxide adduct of a mixture 
of vicinal toluene diamine and dipropylene glycol containing a 
polyoxypropylene polyether cap and having an hydroxyl number of 450 and is 
commercially available from BASF Corporation as Pluracol.RTM.1132 polyol. 
35 parts by weight of a glycerine initiated all proylene oxide adduct 
having a theoretical hydroxyl number of 398 and is commercially available 
from BASF Corporation as Pluracol.RTM. GP 430 polyol. 
5 parts by weight of diethylene glycol having a theoretical hydroxyl number 
of 1016. 
6.79 parts by weight water 
1.5 parts by weight tetramethylhexanediamine, a urethane-promoting 
catalyst. 
1 part by weight of a silicone surfactant commercially available from Union 
Carbide. 
231.9 parts by weight of ISO A, a solvent free polymethylene 
polyphenylisocyanate having a functionality of about 2.7 and an NCO 
content of about 31.8 weight percent. 
The following aroma chemicals can be incorporated into a typical 
polyurethane formulation an explained above in the loading of 15% by 
weight of the total of the polyurethane forming components. 
##STR1## 
By preparing a polyurethane foam of a given polyol/isocyanate formulation 
with each aroma chemical and then measuring hardness of the resulting 
foam, it is possible to prepare a chart or panel of values providing an 
indication of relative hardness keyed to structure of the aroma chemical. 
Therefore, choosing any one of the above fragrances and a suitable 
polyisocyanate/polyol combination enables one to make a fragrant 
polyurethane foam. Based on a range of 1 to 10, the following chart shows 
the relative hardness of the products obtained in accordance with the 
present invention. Hardness can be measured by instrument or manually as 
is known in the art. 
______________________________________ 
Hardness of 
Aroma Chemical 
Molecular weight 
Polarity Foam 
______________________________________ 
Andrane 220 1 4 
Benzyl acetate 
150 2 3 
Benzyl benzoate 
212 9 9 
Citralva .RTM. 
149 2 5 
Diethyl phthalate 
126 2 10 
Diola 116 2 10 
Dipropylene glycol 
150 8 1 
Ethyl butyrate 
116 6 7 
Ethyl methyl phenyl 
202 2 1 
Glycolate 
Eucalyptol USP 
154 3 6 
Eugenol 164 7 5 
Fructone 174 6 5 
Geraniol RG 154 4 2 
cis-3 Hexenyl 
220 2 4 
salicylate 
Hexyl cinnamic 
216 4 8 
aldehyde 
ISO E Super .RTM. 
234 3 4 
Kharismal 200 2 4 
Kohinool .RTM. 
186 4 7 
Koavone .RTM. 
182 6 4 
Lemsyn GB 152 9 4 
Lilial 190 3 8 
Limonene VAH 136 2 10 
Lyral .RTM. 210 3 1 
Methyl anthranilate 
151 9 5 
Methyl Lavender 
172 9 2 
Ketone 
MUSQ 1-2-1 .RTM. 
258 3 8 
Peach Aldehyde 
184 5 2 
Coeur 
Phenafleur .RTM. 
204 3 9 
Phenoxanol .RTM. 
178 7 2 
Prismantol 178 4 2 
Sanjinol .TM. 
186 4 6 
Tetrahydro muguol 
158 3 5 
Coeur 
Tabacarol 218 5 5 
______________________________________ 
In making the fragrant polyurethane foams of the present invention one 
first selects suitable polyols and polyisocyanates for reaction to make a 
foam having the characteristics that would be predictable based on the 
knowledge in the prior art of the expected properties of a polyurethane 
foam made from such ingredients. These general parameters are well known 
in the art and persons skilled in the art would be able to predict the 
general characteristics of the resulting polyurethane foam depending upon 
the polyol and polyisocyanate that was chosen. The aroma chemical is then 
chosen and introduced in an amount which may range from 5 to 20% by 
weight, preferably 15%, of the total ingredients. The type of aroma 
chemicals selected and therefore the nature of the final properties of the 
product can be determined by routine experimentation and by calculation 
using the empirical formula described below. It is possible to specify in 
advance what the final general nature of the foam product will be 
depending upon the aroma chemical that is selected. By making a series of 
foams employing selected aroma compounds and using the same basic foam 
formulation, it is then possible to establish a table according to the 
chemical structure of the aroma compound correlating hardness obtained 
with the specific aroma compound. Thereafter, the skilled worker can then 
make a selection of an aroma chemical from that table for combination with 
and introduction into any other polyol and polyisocyanate formulation for 
foam production whereby the general degree of hardness of the final 
polyurethane foam could be predicted. 
As will be apparent, the polyurethanes produced in accordance with the 
present invention can be molded into any shape or configuration as is the 
case with other polyurethane formulations. 
To control and thereby determine the hardness of the resulting polyurethane 
foam the following empirical formula can be used to obtain an 
approximation of relative hardness for a given aroma chemical 
EQU log.sub.e (Z)=1.87(X/Y).sup.0.27 
wherein 
Z=hardness of foam 
X=polarity of aroma chemical 
Y=actual molecular weight of aroma chemical 
As a first step after choosing a particular aroma chemical and determining 
its actual molecular weight, it is necessary to establish a value for the 
polarity of the molecule based on a scale of 1 to 10. The above table of 
representative aroma chemicals provides ample guidelines for persons 
skilled in the art to establish a value for polarity of selected aroma 
chemicals based on their known structure in comparison to known chemicals 
for which a polarity value is set forth above. Then using the above 
formula, an approximate relative hardness can be calculated whereby a 
value will be arrived at ranging from 1 to 10 and can be compared to the 
above list. 
In lieu of using the formula, a series of experiments can also be carried 
out as described above to prepare a table of representative data. 
Further variations and modifications of the foregoing will be apparent to 
those persons skilled in the art and are intended to be encompassed by the 
claims appended hereto.