Process for preparing flexible CFC-free polyurethane foams using an encapsulated blowing agent

The present invention relates to a process for producing a flexible polyurethane foam by reacting, at a reaction temperature within a temperature range of between about 70.degree. F. and about 150.degree. F., a reaction mixture comprised of a polyol, an organic isocyanate, water, an encapsulated blowing agent, and a reaction catalyst, wherein the encapsulated blowing agent comprises a shell and a core, said shell comprising a polymer having a melting point above the initial reaction temperature, and said core comprising a gaseous blowing agent or blowing agent precursor for blowing said reaction mixture at said reaction temperature. In another aspect, the present invention relates to a process for cooling a hot polyurethane foam utilizing encapsulated water contained in the foam forming reaction mixture.

FIELD OF THE INVENTION 
This invention relates generally to polyurethane foams, and, more 
specifically, to the preparation of CFC-free flexible polyurethane foams 
using an encapsulated blowing agent. 
BACKGROUND OF THE INVENTION 
In the production of polyurethane foams, a polyol is reacted with a 
polyisocyanate in the presence of a polyurethane catalyst and a blowing 
agent. Unfortunately, certain blowing agents, namely chlorofluorocarbons 
(so-called "CFCs"), are hazardous to the environment, specifically the 
ozone layer of the stratosphere. Hence, alternatives to the use of CFC's 
are being actively sought by the polyurethanes community. 
Certain alternatives to the use of CFC's in the preparation of flexible 
polyurethane foams are known in the art. By way of illustration, methylene 
chloride has been used in conjunction with water as blowing agents to 
produce the desired foam. Unfortunately, methylene chloride has been 
determined to be a volatile organic acid, and therefore it is not 
desireable for use as a blowing agent. Other alternatives to the use of 
CFC's that do not involve the use of volatile organics or carcinogens 
would be highly desired by the flexible urethanes community. In the past, 
CFC-free, so-called "all-water-blown" foams tend to scorch and/or be 
firmer than might otherwise be desired at relatively low densities. 
Heretofore, suitable alternatives have not been known based upon the 
knowledge of the present inventors. 
SUMMARY OF THE INVENTION 
In one aspect, the present invention relates to a process for producing a 
flexible polyurethane foam by reacting, at an initial reaction temperature 
selected from within a temperature range of between about 70.degree. F. 
and about 150.degree. F. (preferably 70.degree. F.-120.degree. F.), a 
reaction mixture comprised of a polyol, an organic isocyanate, water, an 
encapsulated blowing agent, and a reaction catalyst, wherein the 
encapsulated blowing agent comprises a shell and a core, said shell 
comprising a polymer having a melting point above the inital reaction 
temperature (preferably between about 100.degree. F. and about 250.degree. 
F.) and said core comprising a gaseous blowing agent or blowing agent 
precursor for blowing said reaction mixture at said reaction temperature. 
Preferably, the core of said encapsulated blowing agent is a gas selected 
from the group consisting of carbon dioxide, nitrogen, air, and 
combinations thereof. 
In another aspect, the present invention relates to a process for producing 
a flexible polyurethane foam which comprises the steps of: 
(a) reacting, at an initial reaction temperature selected from within a 
temperature range of between about 70.degree. F. and about 150.degree. F. 
(preferably 70.degree. F.-120.degree. F.), a reaction mixture comprised of 
a polyol, an organic isocyanate, water, an encapsulated blowing agent, and 
a reaction catalyst, wherein the encapsulated blowing agent comprises a 
shell and a core, said shell comprising a polymer having a melting point 
above the inital reaction temperature (preferably between about 
100.degree. F. and about 250.degree. F.) and said core comprising a 
gaseous blowing agent, said water forming carbon dioxide in said reaction 
mixture at said reaction-temperature to cause partial foaming of said 
reaction mixture, and 
(b) rupturing the shell of said encapsulated blowing agent by heating said 
shell to within said temperature range to release the gaseous blowing 
agent or blowing agent precursor and cause blowing by said blowing agent 
in order to complete the foaming of said reaction mixture to form a 
polyurethane foam having a desired softness as measured by an indentation 
force deflection of between about 8 and about 30 pounds per fifty square 
inches at 25% deflection as measured by ASTM 3574-86. 
In another aspect, the present invention relates to a composition 
comprising a polyol and an encapsulated blowing agent or encapsulated 
blowing agent precursor. 
In yet another aspect, the present invention relates to a process for 
forming and cooling a polyurethane foam which comprises the steps of: 
(a) reacting a reaction mixture comprised of a polyol, an organic 
isocyanate, a water blowing agent, a reaction catalyst and encapsulated 
water, said encapsulated water comprising a polymer shell and a water 
core, said reaction mixture releasing heat by means of a reaction exotherm 
during the polyurethane-forming reaction to provide a hot polyurethane 
foam, and 
(b) melting said polymer using said reaction exotherm (preferably at a 
temperature of between about 150.degree. F. and about 350.degree. F.) in 
order to rupture said shell, thus releasing said water into said hot 
polyurethane foam, thus cooling said hot foam by virtue of the 
vaporization of said water to provide a cooled polyurethane foam. 
These and other aspects will become apparent upon reading the following 
detailed description of the invention. 
DETAILED DESCRIPTION OF THE EMBODIMENT 
It has now been surprisingly found in accordance with the present invention 
that flexible polyurethane foams are suitably produced utilizing 
encapsulated gaseous blowing agent(s) to supplement the primary blowing 
action provided by water (which reacts to form a carbon dioxide blowing 
agent during the urethane-forming reaction) in the manufacture of 
water-blown polyurethane foam wherein the water is typically employed in 
an amount of up to 6 parts per hundred parts of polyol ("phr"). The 
supplemental blowing agent facilitates the production of a foam having the 
desired density and degree of softness without the use of undesireable CFC 
or other volatile organic blowing agents and also moderates the reaction 
temperature. Alternatively, when using encapsulated water as a coolant in 
making an all-water blown foam, the amount of water used to blow the foam 
can be up to 8 phr without excessive reaction exotherm. 
The present invention is particularly significant since it provides 
methodology for avoiding the use of chlorofluorocarbon or other volatile 
organic blowing agents while achieving scorch free foam having a desired 
density. 
Thus, the use of the encapsulated gaseous blowing agent in accordance with 
the present invention enables the production of a soft foam having a 
desired density of no greater than 2 pounds per cubic foot ("pcf"), 
preferably between 0.9 and 1.5 pcf, without any significant scorching of 
the foam which tends to occur when an "all-water-blown" foam is fabricated 
at very low density. 
The "softness" of the foam is suitably measured in accordance with ASTM D 
3574-86, and preferably the foams made in accordance with the present 
invention have a softness as measured by this ASTM test of between about 8 
and about 30 pounds per fifty square inches of foam at a 25% deflection. 
In another aspect, it has also been surprisingly found that encapsulated 
water can suitably be incorporated into a polyurethane-forming reaction 
mixture in order to provide cooling of the reaction exotherm via water 
evaporation upon rupture of the water-containing capsules after the 
urethane-forming reaction is complete. 
Although a wide range of capsule sizes are suitably utilized in accordance 
with the present invention, the capsules are preferably individually less 
than 10 microns in diameter, and more preferably they are microcapsules 
having a submicron particle size. The capsules suitably employ a polymer 
shell having a melting point preferably within the range of between about 
100.degree. F. and about 250.degree. F. for the encapsulated gaseous 
blowing agents, and a preferred temperature of between about 150.degree. 
F. and about 350.degree. F. when using encapsulated water. A preferred 
polymer for use in the preparation of the shell is a urea-formaldehyde 
copolymer, although a wide variety of other polymers having the desired 
melting point can suitably be used, such as for example a natural polymer 
such as methylcellulose, succinylated gelatin, waxes, paraffin etc., a 
synthetic polymer such as polyvinyl alcohol, polyethylene, polyvinyl 
chloride etc., or a synthentic elastomer such as neoprene, acrylonitrile, 
polysiloxane and combinations thereof. 
In a preferred embodiment, a "one-shot" method of foam fabrication is 
employed, whereby the isocyanate containing stream (commonly referred to 
as the "A-side") and the polyol-containing and catalyst-containing stream 
(commonly referred to as the "B-side") are mixed. Each of these streams 
are preferably liquids in which all of the various additives (except the 
CO.sub.2 microcapsules) are preferably soluble, although dispersions 
utilizing solid components can be employed if desired. In accordance with 
a more preferred embodiment of the present invention, the B-side contains 
polyol, encapsulated blowing agent, water, and a surfactant to assist in 
foam cell formation. 
A typical "B-side" formulation is prepared by blending: 
POLY-G 32-56, a product of Olin Corporation; 100 grams L-620 (a silicone 
surfactant), a liquid product of Union Carbide Corporation; 1.1 grams 
Dimethylethanolamine (catalyst), a product of Air Products; 0.18 grams 
Water in an amount of 0.1 to 8 parts per 100 parts of polyol 
Encapsulated gaseous blowing agent in an amount equal to the amount of 
blowing agent being replaced. 
After thorough mixing of this blend at room temperature, the blend forms a 
dispersion having a viscosity of about 300 cps at room temperature. 
The polyols which are used in the subject invention are well known in the 
art and are preferably those referred to as polyether polyols and/or 
polyester polyols or a combination thereof. The polyether polyols are 
prepared by the reaction of an alkylene oxide with polyhydric or 
polyamine-containing compounds, or mixtures thereof. Alkylene oxides which 
may be employed in the preparation of the polyols of the present invention 
include ethylene oxide, propylene oxide, butylene oxide, styrene oxide and 
the like. Halogenated alkylene oxides may also be used such as 
epichlorohydrin, 3,3,3-trichlorobutylene oxide, etc. Mixtures of any of 
the above alkylene oxides may also be employed. The preferred alkylene 
oxide is propylene oxide, or a mixture of propylene oxide with ethylene 
oxide. 
Polyoxyalkylene polyether polyols are preferred and generally contain 
either primary or secondary hydroxyl groups, or mixtures thereof. These 
polyols are suitably prepared by reacting an active-hydrogen containing 
compound, such as polyhydric compounds or polyamines, with the 
above-described alkylene oxides. Useful polyhydric compounds include 
ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 
glycerol, pentaerythritol, sorbitol, sucrose, methyl glucoside, glucose, 
etc. Polyamine compounds which may be reacted with the alkylene oxide to 
prepare amine-based polyols include mono-, di-, and triethanol amine, 
ethylene diamine, diethylene diamine, toluene diamine, etc. These 
polyhydric alcohols and polyamine compounds can be reacted separately with 
alkylene oxides or they can be pre-mixed in the preparation of polyether 
polyol mixtures or blends. Preferred polyester polyols are those based on 
terephthalic, phthalic, isophthalic, adipic, succinic, glutaric, fumaric 
acid(s), and combinations thereof, and the like. 
Preferably, the polyol is employed in a proportion corresponding to between 
about 0.8 and about 1.1 equivalents per equivalent of polyisocyanate. 
By "equivalents" of polyol is meant the molecular weight divided by the 
number of hydroxyl groups present in the molecule. The equivalent weight 
is expressed in whatever units, i.e., grams, pounds, tons, etc., are used 
to designate the amounts of the other components of the reaction mixture. 
Similarly, the term "equivalent" used in relation to the polyisocyanate 
has its usually accepted meaning, namely, the molecular weight of the 
polyisocyanate, in whatever units are used to designate the amounts of the 
various components of the reaction mixture, divided by the number of 
isocyanate groups present in the molecule. 
The polyisocyanate employed in the preparation of the cellular polymers of 
the invention can be any of the polyisocyanates, organic and inorganic, 
known to be useful in the art of polymer formation. Such polyisocyanates 
are commonly employed in the preparation of polyurethanes by reaction with 
compounds containing two or more active hydrogen-containing groups. 
Illustrative of such polyisocyanates are 2,4-tolylene diisocyanate, 
2,6-tolylene diisocyanate, 4,4'-methylenebis(phenyl isocyanate), 
dianisidine diisocyanate, tolidine diisocyanate, hexamethylene 
diisocyanate, m-xylene diisocyanate 1,5-napthalene diisocyanate, 
p-phenylene diisocyanate 1,5-napthalene diisocyanate, p-phenylene 
diisocyanate, 1,4-diethylbenzene diisocyanate and the like. Mixtures of 
two or more of the above isocyanates can be used, such as mixtures of the 
2,4- and 2,6-isomers of tolylene diisocyanate, mixture of the 2,4'- and 
4,4'-isomers of methylenebis(phenyl isocyanate) and the like. In addition 
to the 4,4'-methylenebis (phenyl isocyanate) or mixtures of the 
2,4'-isomer and 4,4'-isomer thereof which are employed as the isocyanate 
component, there can also be used modified forms of these isocyanates. For 
example, there can be used 4,4'-methylenebis(phenyl isocyanate), or an 
admixture thereof with a minor amount of the 2,4'-isomer, which has been 
treated to convert a minor proportion, generally less than 15 percent by 
weight of the starting material, to an artifact of said starting material. 
For example, the polyisocyanate component can be methylenebis(-phenyl 
isocyanate) which has been converted to a stable liquid at temperatures of 
about 15.degree. C. or higher. 
Illustrative of another modified form of 4,4'-,methylenebis(phenyl 
isocyanate) which can form the polyisocyanate component is the product 
obtained by treating the former compound, or mixtures thereof with small 
portions of 2,4'-isomer, with a minor portion of a carbodimide such as 
diphenylcarbodiimide. In accordance with said process, a minor proportion 
of the methylenebis(phenyl isocyanate) is converted to the corresponding 
isocyanato-carbodiimide and there is obtained a mixture of a major 
proportion of unchanged starting material and a minor proportion of said 
isocyanato-substituted carbodimide. 
Preferred as the polyisocyanate component is TDI. 
Amine catalysts useful in the polyurethane-forming reaction include 
tertiary amines such as: N,N-dialkylpiperazines such as 
N,N-dimethylpiperazine, N,N-diethylpiperazine and the like; trialkylamines 
such as trimethylamine, triethylamine, tributylamine and the like; 
1,4-diazabicyclo(2--2--2) octane, which is more frequently referred to as 
triethylene diamine, and the lower-alkyl derivatives thereof such as 
2-methyl triethylene diamine, 2,3-dimethyl triethylene diamine, 
2,5-diethyl triethylene diamine and 2,6-diisopropyl triethylene diamine; 
N,N',N"-trialkylaminoalkylhexahydrotriazines such as 
N,N'N"-tris(dimethylaminomethyl)-hexahydrotriazine, 
N,N',N"-tris(dimethylaminoethyl)hexahydrotriazine, 
N,N'N"-tris(dimethylaminopropyl)hexahydrotriazine, 
N,N',N"-tris(diethylaminoethyl) hexahydrotriazine, 
N,N'N"-tris(diethylaminopropyl) hexahydrotriazine and the like; mono-, 
di-, and tri-(dialkylaminoalkyl) monohydric phenols or thiophenols such as 
2-(dimethylaminomethyl)phenol, 2-dimethylaminobutyl)phenol, 
2-(diethylaminoethyl)phenol, 2-(diethylaminobutyl)phenol, 
2-(dimethylaminomethyl)thiophenol, 2-(diethylaminoethyl)thiophenol, 
2,4-bis(dimethylaminoethyl)phenol, 2,4-bis(dipropylaminobutyl)phenol, 
2,4-bis(dipropylaminoethyl)phenol, 2,4-bis(dimethylaminoethyl)thiophenol, 
2,4-bis(diethylaminopropyl)triophenol, 
2,4-bis(dipropylaminoethyl)-thiophenol, 
2,4,6-tris(dimethylaminoethyl)phenol, 2,4,6-tris(diethylaminoethyl)phenol, 
2,4,6-tris(dipropylaminomethyl)phenol, 
2,4,6-tris(diethylaminoethyl)thiophenol, 2,4,6-tris(dimethylaminoethyl) 
thiophenol and the like; N, N, N'N'-tetraalkylalkylenediamines such as 
N,N,N',N'-tetramethyl-1,3-propane diamine, 
N,N,N',N'-tetramethyl-1,3-butanediamine, 
N,N,N',N'-tetramethylethylenediamine and the like; 
N,N-dialkylcyclohexylamines such as N,N-dimethylcyclohexylamine, 
N,N-diethylcyclohexylamine and the like; N-alkylmorpholines such as 
N-methylmorpholine, N-ethylmorpholine and the like; 
N,N-dialkylalkanolamines such as N,N-dimethylethanolamine, 
N,N-diethylethanolamine and the like; N,N,N',N'-tetraalkylguanidines such 
as N,N,N',N'-tetramethylguanidine, N,N,N',N'-tetraethylguanidine and the 
like. The tertiary amines are suitably used as an intermediate in the 
preparation of the desired acid blocked catalyst, and are also suitably 
optionally employed to supplement the acid blocked amine catalyst. 
If desired, any organometallic compound known to be a catalyst in the 
reaction between an isocyanato group and an active hydrogen-containing 
group can be employed as a supplemental catalyst in the compositions of 
the present invention. Such catalysts include the organic acid salts of, 
and the organometallic derivatives of, bismuth, lead, tin, iron, antimony, 
uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, 
cerium, molybdenum, vanadium, copper, manganese, and zirconium. 
The preferred group of said organometallic derivatives is that derived from 
tin. Examples of this preferred group are: dibutyltin diacetate, 
dibutyltin dilaurate, stannous octoate, stannous oleate, and the like. 
Commercial blends of tin catalyst with an amine catalyst are available, 
for example, as DABCO 33-LV, a product of Air Products Corporation. 
Optional additives such as dispersing agents, cell stabilizers, 
surfactants, flame retardants, and the like, which are commonly employed 
in the fabrication of polymer foams, can be employed in the process of the 
invention. For example, the well-known phosphorus-based flame retardant 
additives may be used if flame retardancy is desired. These phosphate 
additives generally do not adversely affect the physical properties of the 
foam even if they are hydrolyzed and/or physically removed from the foam 
since these additives are not part of the foam backbone. As another 
illustration, a finer cell structure may be obtained if organosilicone 
polymers are used as surfactants in the reaction mix. 
Other optional additives, such as inorganic and organic fillers, can be 
employed in the process of this invention. Illustrative inorganic fillers 
are calcium carbonate, barium sulfate, silica, glass, antimony oxides, 
etc. Illustrative organic fillers are the various polymers, copolymers of 
vinyl chloride, vinyl acetate, acrylonitrile, styrene, melamine, partially 
oxyalkylated melamine, etc. Organic esters can also be employed if 
desired. Particularly preferred esters are those derived from dicarboxylic 
acids such as oxalic, malonic, succinic, glutaric, maleic, phthalic, 
isophthalic and terephthalic acids. The use of an organic filler, 
particularly isophthalic and/or terephthalic esters, is preferred in the 
composition of the present invention since these organic fillers are 
liquid and soluble in the "B-side". 
It is preferred in preparing the polyurethane foams of the invention to 
include in the foam forming reaction mixture a small proportion of a 
conventional surfactant in order to improve the cell structure of the 
resulting foam. Typical such surfactants are the silicones and the 
siloxaneoxyalkylene block copolymers. U.S. Pat. No. 2,834,748 and T. H. 
Ferrigno. Rigid Plastic Foams (New York:Reinhold Publishing Corp., 1963), 
pp. 38-42, disclose various surfactants which are useful for this purpose. 
The surfactant choice, while not essential to the present invention, does 
have an effect upon the cell structure in the resulting polyurethane foam, 
and the recently-introduced "high efficiency" surfactants are desireably 
employed. 
Preferred surfactants are the following: 
______________________________________ 
##STR1## 
##STR2## 
##STR3## 
##STR4## 
##STR5## 
##STR6## 
B-8021 GOLDSCHMIDT 
______________________________________ 
Generally up to 2.5 parts by weight (preferably 0.8-1.5 parts) of the 
surfactant are employed per every 100 parts of the polyol reactant. 
The cellular products of the invention can be employed for all the purposes 
for which the currently produced cellular products are conventionally 
employed, but as noted above are particularly suitable when using 
polyether polyols for applications where excellent softness and low scorch 
is required.

The following examples are intended to illustrate, but in no way limit, the 
scope of the present invention. 
COMATIVE EXAMPLE A 
Preparation of a Foam Using Methylene Chloride as a Blowing Agent 
To 100 grams of Poly-G.RTM. 32-56 in a one quart plastic cup is added 9.5 
grams of methylene chloride, 5.2 grams of water, 0.18 grams of DMEA, and 
1.1 grams of silicone surfactant. The contents are stirred with a high 
speed high shear mixer for approximately 20 seconds. 0.64 grams of Dabco 
T-10 is added to the mixture and it is mixed again for approximately 10 
seconds. The stirrer is then started again for approximately 10 seconds. 
The stirrer is then started again and 67.6 grams of TDI-80 is added while 
the mixture was still being stirred. After eight seconds the contents of 
the cup was poured into a cake box. The anticipated foam density is 1.0 
pcf; however, the methylene chloride is an undesirable blowing agent from 
an environmental and toxicity standpoint. 
EXAMPLE 1 
Proposed Example Using an Encapsulated Blowing Agent 
The same procedure as is used in example 1 is proposed for Example 1 above. 
Encapsulated CO.sub.2 (7.03 GM) is substituted for the methylene chloride. 
The resulting foam has a density of 1.1 pcf. 
EXAMPLE 2 
Proposed Example Using a Reduced Amount of Water 
The same procedure as is used in example 1 above. Encapsulated CO.sub.2 is 
substituted for all of the methylene chloride and 1.0 phr of water. Water 
concentration is reduced from 5.2 phr to 4.2 phr of water. Water 
concentrations is reduced from 5.2 phr to 4.2 phr and encapsulated 
CO.sub.2 concentration is increased to 10.5 phr. TDI-80 concentration is 
reduced to 55.18 phr to compensate for the lower water in the formula. 
Foam density is 1.0 pcf. 
EXAMPLE 3 
Cooling of the Reaction Exotherm Using Encapsulated H.sub.2 O 
The same procedure as in Example 1 is used. The formulation is changed: 
water is increased from 5.2 gm to 7.2 gm and corresponding TDI is 
increased to 86.93 gm, methylene chloride is reduced to zero, and 7.4 gm 
encapsulated water is added. The 7.4 gm encapsulated water does not 
include the wt. of capsules, and the encapsulated water serves to cool the 
high temperature generated by the reaction exotherm. The foam has a 
density of 1.0 pcf and same maximum exotherm temperature as in Example 1. 
While the invention has been described above with references to specific 
embodiments thereof, it is apparent that many changes, modifications and 
variations in the materials, arrangements of parts and steps can be made 
without departing from the inventive concept disclosed herein. 
Accordingly, the spirit and broad scope of the appended claims is intended 
to embrace all such changes, modifications and variations that may occur 
to one of skill in the art upon a reading of the disclosure. All patent 
applications, patents and other publications cited herein are incorporated 
by reference in their entirety.