Phenolic foams having a cell structure that is resistant to rupture under pressure and a slow deterioration of thermal insulation value are claimed. These foams can be cured to achieve dimensional stability without substantial adverse affect on their structure.

BACKGROUND OF THE INVENTION 
This invention relates to phenolic foams and particularly to closed-cell 
foams of a phenol/formaldehyde resin. 
The use of foam materials as insulation is an already well-established 
expedient. However many foam materials that are currently in use have 
certain inherent problems such as flammability or the production of 
noxious gases on partial combustion. For this reason there have been a 
number of attempts to develop a foam with an inbuilt resistance to burning 
and at the same time high insulation value. 
One of the resins explored as having the desired characteristics for 
producing a flame-resistant foam is a phenolic resin produced by 
copolymerization of phenol with formaldehyde using a basic catalyst. Such 
resins are usually called resoles. 
The first stage of the production of a phenolic resole is the formation of 
intermediates with the formula: 
##STR1## 
and the ratio of x/phenolic ring gives the approximate combined 
phenol/formaldehyde (F/P) ratio of the resin. 
These intermediates may then react to give structures with the following 
crosslinking groups: 
##STR2## 
structure II then, at high temperatures, reacting to split off 
formaldehyde and give crosslinking groups like structure (I). Further 
reaction leads to chain extension and crosslinking via reaction at other 
locations on the aromatic ring. 
The process of crosslinking and chain extension is not complete at the end 
of the foaming process but has progressed to such an extent that the foam 
has hardened and may be cut into pieces. The degree of cure, in the 
absence of added crosslinking agents, is a function of temperature and, to 
some extent, the time of exposure to that temperature. Thus foams that are 
exposed to only low temperatures have a low degree of cure. 
Unfortunately the problems of producing a phenolic foam are substantial in 
that, if good thermal conductivity is to be maintained, substantially all 
the cells must be and remain closed-cells. This is not easy since the 
reaction of phenol with formaldehyde generates water as a by-product and 
this can easily blow open the cells and so diminish the effectiveness of 
the foam as a thermal barrier. 
DISCUSSION OF THE PRIOR ART 
While it has been shown possible, as disclosed in British Pat. No. 
1,580,565, to produce a closed-cell phenolic foam by keeping the reaction 
temperature low, this results in foams with a low degree of cure and hence 
high residual formaldehyde and poor dimensional stability. Such foams are 
also subject to partial disruption if the cell structure is not strong 
enough to resist the forces to which the foam is exposed during curing 
and/or thermal cycling. 
In the attempt to generate phenolic foams with a fine uniform cell 
structure it has long been recognized that the nature of the resole itself 
is an important factor. In U.S. Pat. No. 3,389,094 the importance of using 
a resole with a water content of less than 10% is disclosed and in U.S. 
Pat. No. 2,845,396, for low density foams less than 5% water is stressed. 
Low water content is desirable because during curing any water present in 
the foam or generated during cure can vaporize and blow open the cells. 
This point is made in British Pat. No. 1,580,565. Low water content is 
also important since it leads to higher viscosity in the resin and better 
control over the foaming operation. 
The art teaches that a closed-cell foam can be made from a resole with the 
correct rheological properties and methods of adjusting the rheological 
properties of a resole during foaming by the incorporation of a suitable 
surfactant as described in U.S. Pat. Nos. 2,933,461; 2,845,396; 3,953,645; 
4,140,842 and 4,133,931 amongst others. 
Both the viscosity limitations and surfactant usage are reflections of the 
fact that to achieve adequate closed-cell content it is necessary that the 
cell walls be strong enough to withstand the stresses encountered when the 
resin is foamed. As the cells expand, the cell walls must be able to 
stretch without rupturing. They must in practice demonstrate the 
well-known Marangoni Effect described for example in "Plastic Foams" by 
Frisch and Saunders (Marcel Decker Inc. 1972) Part I, pp. 31-35. The 
Effect refers to the tendency of a surfactant-containing resin film, on 
stretching, to correct any tendency to depletion of the surfactant 
concentration on the surface of the film by feeding resin and surfactant 
into the stretched area and thus restore the film thickness. This 
"self-healing" effect therefore aids in preventing the fracture of cell 
walls during the foam formation. 
A phenolic foam useful as an insulating material requires a low thermal 
conductivity and clearly closed-cell foams are much preferred since they 
minimize heat transfer and loss by gas convection. Additionally it is 
desirable that the gas filling the closed-cells have as low a thermal 
conductivity as possible. Gases which have been found useful as blowing 
agents for phenolic foams include hydrocarbons and halogenated 
hydrocarbons (U.S. Pat. No. 2,933,461) and fluorocarbons (U.S. Pat. No. 
3,389,094). 
Other desirable characteristics of phenolic foams are dimensional stability 
and low residual formaldehyde. Both these characteristics can be provided 
by heating the foam but as indicated above this leads to foam disruption 
with the conventional foams of the prior art. 
Thus prior art phenolic foams have been produced at temperatures typically 
below about 80.degree. C. and have been subjected to cure operations at 
temperature of only up to about 80.degree. C. This produces a foam having 
a low degree of cure as distinguished from those with a higher degree of 
cure such as is desirable for many commercial applications. 
SUMMARY OF THE INVENTION 
Now, however, improvements have been developed to minimize such prior art 
shortcomings. 
Accordingly, it is a principal object of this invention to provide a 
partially cured phenolic foam that can withstand high temperature cures to 
give it dimensional stability while at the same time retaining good 
closed-cell content and good thermal insulation characteristics. 
Another object of this invention is to provide a process capable of 
producing such aforesaid partially cured phenolic foam. 
The present invention provides a partially cured resole foam with a density 
of from 30 to 70 kg/m.sup.3 and a closed-cell content of at least 85 
percent, said foam being derived from a composition comprising a phenolic 
resole with a formaldehyde to phenol mole ratio of from 1.2:1 to 2.5:1, a 
blowing agent having a thermal conductivity less than 0.016 
watts/m.degree. C. and a surfactant in sufficient quantity for the resole 
to exhibit the Marangoni Effect during foaming; said foam characterized in 
that: 
(A) the thermal conductivity of the foam after 100 days is less than 0.020 
watts/m.degree. C. and the value of .DELTA.k/ .DELTA.lnt is less than 
0.5.times.10.sup.-3 where .DELTA.k in watts/m.degree. C. is k.sub.100 
minus k.sub.1 and .DELTA.lnt in days is lnt.sub.100 minus lnt.sub.1 ; and 
(B) the isotropic pressure required to reduce the closed-cell content of 
the foam by at least 10% is in excess of 1.75 kg/cm.sup.2. 
The foam is characterized by its closed-cell content of at least 85% and 
preferably at least 90%. These levels of closed-cell content are 
substantially retained even after the partially cured foam has been heated 
to 90.degree. C. or even higher to effect cure. This feature is unusual 
because, as indicated above, cure temperatures tend to rupture cell walls.

DETAILED DESCRIPTION OF THE INVENTION 
FOAM COMPOSITION 
The resole from which the foam is prepared is essentially a conventional 
phenol/formaldehyde resole preferably with less than 10% by weight of any 
ring-substituted phenolic components such as cresol, xylenol and the like. 
The F/P mole ratio of the resole is from 1.2:1 to 2.5:1 though ratios at 
the higher end of this range are not preferred because the excessive 
amount of formaldehyde prolongs the cure process. However if too small a 
ratio is used, complete reaction to form the foam may be difficult to 
achieve. The most preferred F/P ratios are from 1.5 to 2.2:1. As used 
herein throughout, F/P ratio means the mole ratio of chemically combined 
formaldehyde to phenol in the resole. Such ratio can be determined by 
carbon 13 nuclear magnetic resonance (.sup.13 C-NMR). In a specific 
technique which has been used, .sup.13 C-NMR quantitative spectra were 
recorded using a JEOL FX-900 spectrometer (supplied by Jeol Co., 235 
Birchwood Ave., Cranford, N.J.) at ambient temperature on 50-70% weight 
percent solutions of resins in methanol solvent. Samples were run in a 10 
mm diameter tube with 2% added tetra methyl silane as a chemical shift 
reference. The spectrometer was equipped with an external lithium 7 
isotope lock. The analyzed spectra were the result of 1-5000 accumulations 
at a tip angle of 90.degree.. Optimized quantitative conditions were 
employed with gated decoupling (proton decoupling on only during 
accumulation) and a pulse delay between accumulations of &gt;5 T.sub.1 
(relaxation time). Integrated spectra were used to calculate combined F/P 
at an accuracy generally better than 4%. 
The density of the foam is from 30 to 70 kg/m.sup.3 but preferred foams 
have densities of from 40 to 60 kg/m.sup.3. The density is obtained by 
cutting a core sample 3.6 cm in diameter and 2.9 cm in length; the core is 
weighed accurately and the density calculated. 
The viscosity of the resole measured at room temperature of 25.degree. C. 
is from about 50,000 to 1,000,000 cps, with the best results obtained at a 
viscosity of from 80,000 to 600,000 cps and most preferably 80,000 to 
300,000 cps. At such viscosities, the resole can be foamed to produce a 
substantially closed-cell foam using foaming conditions according to the 
present invention that are relatively easily controlled. The reactivity of 
the resole is also very important since if it is too reactive the 
temperature of the foaming composition rises too high with the result that 
water vapor uncontrollably blows the foam and control over density and 
closed-cell content is lost. On the other hand, if reactivity time is too 
low processing times are long and uneconomical. A suitable test for resole 
reactivity is set forth hereinafter in Example 13. 
A resole is usually produced by the conventional base-catalyzed reaction 
using an acid subsequent to formation of the resole to neutralize the base 
and stabilize the resin. This of course results in the production of salt 
by the reaction of acid and base. The resole may be neutralized using 
sulfuric acid or carbon dioxide to give large insoluble salt particles 
which can easily be filtered out before the resole is used to produce a 
foam. It may also be possible to use unfiltered resins if no settling 
problems are encountered in the foaming process employed. In general, 
where salt particles are present, it is preferred that they be very large 
or very small, that is, substantially larger in diameter than that of the 
cell or smaller than the thickness of the cell wall. If smaller than the 
cell wall thickness the particle will not adversely affect the window 
integrity whereas if larger than a cell the number of cells that are 
disrupted should be low. Resoles in which neutralization produces a 
soluble salt are usually not employed because of the water sensitivity 
such resoles often display in that the insulating properties and 
dimensional stability of the resulting foam can be adversely affected by 
ambient humidity. However, resoles containing soluble salts which are not 
water sensitive, such as the calcium salt of an alkyl or aromatic sulfonic 
acid, or have low water sensitivity can be used. 
A preferred option is the use of the so-called "dispersed-salt" resoles in 
which the neutralizing acid is oxalic acid and the oxalate salts formed 
are highly insoluble and in colloidal form with substantially no tendency 
to settle. These resins and foams made from them are described for example 
in U.S. Pat. Nos. 4,060,504 and 4,216,295. 
The composition from which the foam is prepared comprises a surfactant 
material in an amount sufficient for the resole to exhibit the Marangoni 
Effect during foaming and thus have the capacity to produce cells with 
windows (the membranes between contiguous cells) that remain intact as the 
cell grows to its final size. The amount of surfactant that can be used 
varies somewhat with the surfactant but in general it has been observed 
that closed-cell foams are difficult to achieve with less than 0.5% by 
weight of surfactant and that over 6.0% by weight produces no advantage 
and may even be deleterious. The most useful amount of surfactant is found 
to be from 1 to 5% by weight. All surfactant percentages given are based 
on resole weight. 
The surfactant can be any one of those that have been shown effective with 
foamable resoles in the past. These include non-ionic surfactants such as 
polyethers, polyalcohols, particularly the condensation products of 
alkylene oxides with alkyl phenols, fatty acids, silanes and silicones, 
fatty acid esters of polyhydroxyl compounds such as sorbitan or sorbitol, 
polysilyl phosphonates, polydimethylsiloxane and the capped surfactants 
described in U.S. Pat. Nos. 4,133,931, 4,140,842 and 4,247,413, the 
disclosures of surfactants of which are incorporated herein by reference. 
Ionic surfactants such as alkylated quaternary ammonium derivatives may 
also be used. 
The presence of the surfactant as indicated above allows the foam/cure 
operation to proceed reasonably rapidly without cell structure disruption. 
However excessive speed, as a result for example of the use of resoles of 
high reactivity, may still cause disruption to occur. It is advisable 
therefore to select a resole of moderate reactivity and a foaming catalyst 
amount that will result in only a moderate exotherm. The combination of 
resole reactivity and foaming catalyst level can be expressed in terms of 
a reactivity number defined in Example 13 hereinafter and which can be 
between about 2 to about 12. 
Foaming is catalyzed by an acid and those commonly used include boric acid, 
sulfuric acid and sulfonic acids such as toluene and xylene sulfonic 
acids. Other catalytic acids however are known in the art and may be used. 
The level of catalyst used in the foaming mixture may widely vary 
depending on the particular resole and catalyst used. Levels between about 
0.5 to about 3.0 and preferably between 1.0 to 2.0 weight percent based on 
the weight of the resole can be used. 
The blowing agent used must have a thermal conductivity less than 0.016 and 
preferably less than 0.014 watts/m.degree. C. Typically this range 
includes blowing agents such as methylene dichloride, and various 
chlorofluorocarbons such as monofluorotrichloromethane, 
difluorodichloromethane, monofluorodichloromethane, 
difluoromonochloromethane, trifluorotrichloroethane, and 
tetrafluorodichloroethane. Freon 114, (1,2 dichlorotetrafluoroethane 
available from DuPont Company under the above trade designation) is 
particularly preferred. The level of blowing agent used in the foaming 
mixture is dependent on the molecular weight of the blowing agent and the 
density of the foam. Levels between about 5 to about 25 and preferably 
between 10 to 20 weight percent for Freon 114 based on the weight of the 
resole can be used for foams of about 30 to 70 kg/m.sup.3. 
In addition to catalyst residues formed in neutralizing the base catalyzing 
the reaction forming the resole, the resole may comprise latent 
neutralizing additives to remove traces of residual curing acid and leave 
a neutral foam. Suitable latent neutralizers are described for example in 
U.S. Pat. Nos. 4,207,400 and 4,207,401, the disclosures and teachings of 
latent neutralizers of which are incorporated herein by reference. 
In addition to the components described above, the foam can further 
comprise other additives such as anti-punking additives and particulate or 
fibrous fillers such as glass fibers, talc and the like, to improve the 
fire safety or physical characteristics of the resulting foam. It may also 
comprise components added after the resole formation such as lignin 
materials, urea, or melamine as extenders or formaldehyde scavengers. 
Hydrated alumina as taught in commonly owned U.S. application Ser. No. 
219,165 filed Dec. 22, 1980, now U.S. Pat. No. 4,419,460 issued Dec. 6, 
1983, is effective in increasing the closed-cell content and is therefore 
a desirable component of the foam. 
THE FOAMING PROCESS 
The process by which closed-cell phenolic foams are produced is very 
sensitive to variations in conditions and formulations. The basic process 
described in the prior art entails the extrusion of a foamable mixture 
under such conditions that the resole foams and hardens at compatible 
rates. However within these broad parameters it has not heretofore proved 
possible to obtain a foam that has the outstanding performance of the 
foams of the invention. 
In the production of the foams of the invention the components from which 
the foam is to be made comprise a resole, a surfactant, an acid catalyst 
and a blowing agent. These components are selected according to the 
principles outlined above and are mixed at a temperature and pressure 
calculated to ensure rapid expansion at the extrusion head. The mixing can 
be carried out in any mixer device capable of giving effective, fine (less 
than 10 micron) and uniform dispersion of the blowing agent in the 
mixture. A suitable mixer device for this stage of the operation is a high 
shear pin-type mixer with a short residence time such as an Oakes mixer. 
The preferred blowing agents are conventionally supplied under air or 
nitrogen pressure to the mixer. 
From the mixer the foamable mixture is passed to an extrusion head. 
Expansion from the head is rapid and results in a stream of foaming 
material that is deposited on a substrate. The extrusion head may be in 
the form of a slit so as to lay down a continuous sheet of foam. In a 
preferred process however the extrusion head is a valved pipe that 
reciprocates transverse to the direction of extrusion so as to lay down on 
a moving substrate a continuous ribbon of foam in parallel lines that 
coalesces as foaming proceeds. In a further preferred feature shaping 
members provide limitations to the expansion and result in the production 
of a uniform shaped board of the foamed resin. The shaping members may 
apply to the surface a suitable facing material though it may be 
convenient to apply such facing after hardening of the expanded foam. 
As foaming proceeds the foam is conventionally held at a constant 
temperature of about 60.degree. C. This is done by passing the foamed 
sheet through an oven at that temperature such that on leaving the oven 
after about twenty minutes it has hardened enough to be cut into board 
pieces which are then stored at 60.degree. C. for 18 hours. After this the 
board is in the partially cured state. The term "partially cured" as used 
herein means foam exposed to at least 60.degree. C. for at least 18 hours. 
Though other low temperature cure conditions can be used--e.g. longer 
times at lower temperatures, foams of the invention have at least the 
degree of partial cure achieved after such 18 hours at 60.degree. C. 
After curing for an appropriate period, it is often desirable to apply a 
facing to the surface. This may comprise cardboard, asphalt/asbestos 
composites, aluminum foil, plastic vapor barrier or glass fiber sheet 
material optionally impregnated with resin or asphalt. These facings may 
improve the surface of the foam and afford some dimensional stability. It 
should however be noted that cured foams have inherent three-dimensional 
stability up to about the temperature at which they were cured. Since the 
foams of the invention can be cured at temperatures in excess of those 
likely to be encountered in use, any facing selected need not be chosen 
with the problems of dimensional change in mind. 
While the process has been described in terms of the production of a 
continuous sheet it is of course possible to operate on a batch process 
and produce a single block of foam by extruding the foamable mixture into 
a mold. 
FOAM PROPERTIES 
Since the foam material is primarily useful as an insulating material, it 
is essential that it provides a good barrier to heat transfer. However it 
is not sufficient that the fresh foam have good thermal barrier 
properties; those properties must be retained for a prolonged period after 
installation. 
The thermal insulation characteristics of a closed-cell foam are largely 
determined by the rate at which heat is transferred through the foam via 
conduction through the cell skeleton and the gas filling the cells and via 
radiation through the cell structure. Thus the nature of the gas is a 
critical element in determining conductivity as is the extent to which it 
is retained in the cells. It will also be appreciated that stronger and 
thicker cell windows will be more capable of retaining a more desirable 
gas composition for a longer period than weaker, thinner windows. 
As the foam ages, air diffuses in and blowing agent diffuses out. Since air 
generally has a much higher thermal conductivity than the blowing agent, 
the thermal barrier properties are substantially diminished. This is a 
common experience with most insulating foams and has led to the use of 
barrier films on the major surfaces to inhibit escape of blowing agent. 
Such films however lose their utility when punctured. 
The decrease in thermal barrier properties takes place gradually but it is 
found that a useful indicator of long term performance is the thermal 
conductivity, "k", after 100 days storage at 23.degree. C. and 50 percent 
relative humidity. If the cell windows in the foam are fractured or very 
thin, the blowing agent will have been diluted by sufficient air to 
increase significantly the value of "k". 
The "k" after 100 days (k.sub.100) referred to in this specification is the 
thermal conductivity one hundred days after the production of the 
partially cured foams of the invention. The partially cured foams of the 
invention have a k.sub.100 of less than 0.020 watts/m.degree. C. 
A measure of the rate of increase of thermal conductivity with time of the 
partially cured foams of the invention can be expressed as the value 
(known as k-retention) of the expression .DELTA.k/.DELTA.lnt where 
.DELTA.k is k.sub.100 minus k.sub.1 and .DELTA.lnt is the natural log of 
t.sub.100 minus the natural log of t.sub.1 where k is the thermal 
conductivity of a 2.54 cm thick sample measured in watts/m.degree. C. 100 
days (k.sub.100) and one day (k.sub.1) after manufacture and t is elapsed 
time in days. The partially cured foams of the invention have a 
k-retention value of not more than 0.5.times.10.sup.-3. 
The k.sub.100 value gives a good indication of the barrier properties of 
the foam structure but it does not necessarily adequately indicate the 
strength of that structure, i.e. its ability to withstand internal 
pressures. This indication is provided by the "burst pressure" which is 
the isotropic pressure at which the closed-cell content is decreased by at 
least 10%. Good insulating foams need to be able to withstand high 
pressures such as are generated during cure or even such thermal cycling 
as may be experienced in use. In the foams of the invention a burst 
pressure in excess of 1.75 kg/cm.sup.2 is required. This, together with 
the k.sub.100 value, adequately defines a new type of partially cured foam 
not provided by the prior art with potential for the production of a high 
quality, fully cured foam. 
The invention is now described with reference to specific compositions 
which are intended for illustration only. It should not be inferred that 
they imply any limitation on the scope of the invention. 
The closed-cell content was measured by an air pycnometer using the 
technique described in ASTM D-2856 (Procedure C) to obtain open-cell 
content, the closed-cell content being 100 minus the open-cell content. 
The thermal conductivity of the foams was measured using the technique 
described in ASTM C-518-76 on a sample with a 2.54 cm thickness having at 
least 20.3 cms of width and length. The top face of the sample was at 
32.degree. C. and the bottom at 15.5.degree. C., thereby providing a mean 
temperature of 24.degree. C. for the entire sample. A heat flow meter 
thermal conductivity instrument constructed in accordance with such method 
and available as Rapid-K from Dynatech R/D Co., 99 Erie St., Cambridge, 
Mass. 02139 was used. 
The resole used in each example was dehydrated to below 3% by weight of 
water and bodied at 50.degree.-60.degree. C. for a time sufficient to 
provide the desired viscosity which was measured using a Brookfield 
viscometer Model HBT. Since viscosity variation with temperature is 
significant, a Brookfield thermocell was used for the resoles of the 
examples following hereafter which comprised a thermo container along with 
an SCR controller, Model HT-64, an SC4-27 spindle and an HT-2 sample 
container. Measurements were made at 25.degree. C. All viscosities given 
were obtained by this technique. 
The burst pressure of the cells of any particular foam was determined by 
measuring the closed-cell content of a foam sample, then placing that 
sample in a pressure tube and applying a small incremental isotropic 
pressure. After being subjected to that pressure for five (5) minutes the 
closed-cell content was remeasured. The sample was then replaced in the 
tube and pressurized at a slightly higher isotropic pressure for five (5) 
minutes before being measured for closed-cell content again. This 
procedure was repeated at even higher pressures and a graph was plotted of 
closed-cell content against pressure. It was found that at a 
characteristic isotropic pressure for each foam the closed-cell content 
dropped dramatically by at least 10% and continued to drop thereafter. 
This pressure is called the "burst pressure". 
EXAMPLE 1 
This Example illustrates the very high burst pressure of foams according to 
the invention. 
The following components were mixed together using a high shear short 
residence, pin-type mixer supplied by Oakes Machinery Co. and commonly 
called an "Oakes mixer". 
______________________________________ 
Resole (1) F/P ratio 1.89:1 
96 parts 
Viscosity at 25.degree. C. 
100,000 cps 
Blowing Agent Freon 114 (2) 16.5 parts 
Surfactant DC-193 (3) 4 parts 
Foaming Catalyst (4) 2.24 parts 
All Parts Being by Weight 
______________________________________ 
(1) RI-5100 (Monsanto Company) a resole containing a dispersed oxalate salt 
as a result of the neutralization of the calcium hydroxide catalyst using 
oxalic acid. 
(2) A fluorocarbon (1,2-dichloro-tetrafluoroethane) available from DuPont 
Company under that description. 
(3) A silicone based surfactant available from Dow Corning Company under 
that designation. 
(4) A 2:1 (weight ratio) blend of diethylene glycol and Ultra TX acid (a 
mixture of toluene and xylene sulfonic acids available from Witco Chemical 
Company under that trade designation) expressed in terms of acid component 
content. 
The blowing agent was supplied under air pressure and the resulting 
formulation was passed directly to an extrusion head in the form of a 
nozzle fitted with a torpedo valve to control the rate of expansion of the 
foamable mixture from the head. 
The temperature of the mixture at the extrusion head was between 40.degree. 
and 42.degree. C. and the pressure at the valve was kept at 3.74 to 4.42 
atmospheres. 
The extrusion head was reciprocated in such a way as to lay down a 
continuous ribbon of the foaming mixture on a moving sheet of Kraft paper. 
The mixture was deposited in essentially parallel lines forty centimeters 
in length such that, as foaming occurred, the lines coalesced to form a 
continuous sheet. 
The foam was allowed to stand for about 10 minutes at 60.degree. C. at 
which time it had hardened sufficiently to be cut using a saw into 
convenient pieces. Those pieces were than stored at 60.degree. C. for 18 
hours. 
Samples 1-A through 1-G were taken from different parts of the foam sheet 
produced by the above process and were tested for density, closed-cell 
content and thermal conductivity initially (k.sub.1) and after 100 days 
(k.sub.100). The results are set forth in Table 1. 
TABLE 1 
__________________________________________________________________________ 
FOAM PROPERTIES 
Thermal 
Conduct. 
(watt/m .degree.C.) 
Sample Initial 
Burst k.sub.100 
Invention)(A-G 
(kg/m.sup.3)Density 
cell (%)closed- 
(kg/cm.sup.2)Pressure 
(Initial)k.sub.1 
(-days)100 
##STR3## 
__________________________________________________________________________ 
1-A 47.9 94.2 2.81+ 
.0161 
.0164 
.065 
1-B 47.9 90.7 2.81+ 
.0161 
.0164 
.065 
1-C 47.9 92.4 2.81+ 
.0161 
.0164 
.065 
1-D 47.9 94.6 2.81+ 
.0161 
.0164 
.065 
1-E 47.9 95.1 2.81+ 
.0161 
.0164 
.065 
1-F 47.9 91.1 2.81+ 
.0161 
.0164 
.065 
1-G 48.2 95.0 2.74 .0161 
.0164 
.065 
__________________________________________________________________________ 
*.DELTA.k is k.sub.100 -k.sub.1 and .DELTA.lnt is lnt.sub.100 -lnt.sub.1. 
EXAMPLE 2 
This Example illustrates the use of a resole having an F/P ratio of 1.6:1 
to produce a foam according to the invention. 
The resole was a dispersed salt resole of the same type used in Example 1 
but made at the lower F/P ratio. As before the resole was dehydrated and 
bodied to a viscosity of 106,000 centipoise. 
The surfactant, blowing agent and catalyst used were those described in 
Example 1 and the weight proportions were as follows: 
______________________________________ 
Resole 96 parts 
Blowing Agent 16.5 parts 
Surfactant 4 parts 
Foaming Catalyst 
1.54 parts (expressed in terms 
of the acid compon- 
ent of the catalyst) 
______________________________________ 
The components were mixed, foamed and cured exactly as shown in Example 1 
except that the viscosity of the resole was 106,000 cps at 25.degree. C. 
and the temperature in the extrusion head 49.2.degree. C. 
When evaluated in the same manner as the foams produced in Example 1 it was 
found that the foam had a density of 39.4 kg/m.sup.3, an initial 
closed-cell content of 91.6%, an isotropic burst pressure of 2.46 
kg/cm.sup.2, a k.sub.1 of 0.0181 watts/m.degree. C. and a k.sub.100 of 
0.187 watts/m.degree. C. This gives a k-retention value of 
0.13.times.10.sup.-3 for the expression k.sub.100 -k.sub.1 /lnt.sub.100 
-lnt.sub.1. 
EXAMPLES 3-10 
Examples 3 to 10 illustrate the sensitivity of the process to variations in 
components and conditions. The Examples used a resole having a nominal F/P 
ratio of 2:1 dehydrated to different degrees to give different 
viscosities. The surfactant and the foaming catalyst were the same but the 
amount of surfactant and catalyst (expressed as the amount of the Ultra TX 
acid component) were varied. Additives (based on the total weight of the 
foamable composition) intended to enhance foam flexibility were used as 
indicated. For Examples 6, 7, 8 and 9 only, from the extrusion head the 
foam was cast into 25.4.times.30.5 .times.4.8 cm aluminum foil trays and 
then placed in a batch oven for 18 hours at 40.degree.-45.degree. C. Other 
differences from Example 1 are set forth in Table 2. 
TABLE 2 
__________________________________________________________________________ 
COMISON OF PROCESS VARIABLES 
Variable 
Example 
Examples 3-10 
Condition 
1 3 4 5 6 7 8 9 10 
__________________________________________________________________________ 
Viscosity 
100,000 
190,000 
100,000 
86,000 
93,100 
23,000 
74,000 
74,000 
30,000 
of Resin 
(cps at 25.degree. C.) 
+pph 4 4 2 4 4 4 4 4 4 
Surfactant 
Blowing Freon 
Freon 
Freon* 
Freon 
Freon* 
Freon* 
Freon* 
Freon* 
Freon 
Agent 114 114 11 114 11 11 11 11 114 
% Blowing 
13.7 19.4 
12.9 
16.5 
11.8 
8.2 7.5 11 13 
Agent 
+pph Acid 
2.24 2.01 
1.40 
2.02 
1.80 
1.90 
2.06 
2.00 
2.07 
Temperature 
40-42 
52.5 
54.1 
48.8 
-- -- -- -- 65.5 
at Extrusion 
(.degree.C.) 
Temperature In 
38-40 
51.5 
53.1 
47.0 
39.0 
42.0 
38.0 
38.0 
-- 
Mixer (.degree.C.) 
Additive 
None None 
None 
None 
8% 8% 4% 4% None 
TBEP.sup.1 
EVC.sup.2 
TBEP.sup.1 
TBEP.sup.1 
__________________________________________________________________________ 
*A fluorocarbon (trichloromonofluoromethane) available from DuPont under 
that designation. 
+ Based on 100 parts of resin 
.sup.1 Tributoxy ethyl phosphate from Monsanto Industrial Chemical Co. 
.sup.2 Ethylene vinyl chloride latex as Airflex 4514 from Air Products an 
Chemicals Inc. 
The foams produced by Examples 3 to 10 were characterized in the same 
manner as those of Example 1 and the results are set forth in Table 3. 
TABLE 3 
__________________________________________________________________________ 
FOAM PROPERTIES 
Thermal 
Closed- 
Burst 
Conductivity 
Example 
(kg/m.sup.3)Density 
Content (%)Cell 
(kg/cm.sup.2)Pressure 
k.sub.1k.sub.100(watts/m .degree.C.) 
##STR4## 
__________________________________________________________________________ 
3 30.0 (91.0) 1.41 .0132 
.0246 
2.48 
4 41.7 77.5 1.34 .0158 
.0331 
3.76 
5 38.5 (90.5) 1.90 (1) 
.0167 
.0331 
3.56 
6 52.9 (88.0) 0.84 .0173 
.0317 
3.13 
7 49.7 71.0 0.49 .0158 
.0331 
3.76 
8 70.5 60.0 0.98 .0317 
.0317 
-- (2) 
9 51.3 60.0 0.14 .0317 
.0317 
-- (2) 
10 46.0 94.3 -- .0167 
.0331 
3.56 
__________________________________________________________________________ 
(1) This result appears to be anomalous in view of the results obtained 
with the other comparative samples. 
(2) The foams were substantially air-filled from the start. 
Examples 1 and 2 above and 12 and 13 below set forth the materials and 
process conditions which were found to produce the foams of this 
invention. Changes in the various materials and process conditions from 
those used in Example 1 to produce the foams results in unsatisfactory 
foams as is evidenced by the results in Table 3 above. The relationship of 
these variables is complex and not readily understood at this time. It 
would appear that when one variable is changed the other variables must be 
reviewed and changes made as required to obtain the foams of this 
invention. Those of ordinary skill in the art will appreciate the 
interaction of these variables upon reading the present specification. 
EXAMPLE 11 
A sample of a closed-cell resole foam of unknown formulation and unknown 
cure history but apparently superior performance by comparison with 
phenolic foams available in commerce, was received from a third party and 
testing was begun on Aug. 15, 1978. The sample at that prior time was 
tested by the techniques described in Example 1. 
Results were as follows: 
______________________________________ 
Density 35.2 kg/m.sup.3 
Closed-Cell Content 97% 
Thermal Conductivity 
0.0132 watts/m.degree. C. 
(as received) 
Thermal Conductivity 
0.0176 watts/m.degree. C. 
(after 100 days) 
.DELTA.k/.DELTA.1nt 0.96 .times. 10.sup.-3 
______________________________________ 
On Jan. 13, 1981 burst pressure on the foregoing sample was run after the 
sample was heated for 18 hours at 60.degree. C. to ensure that it had 
received at least as good a cure as those described in Example 1. The 
result obtained was as follows: 
Burst Pressure: 1.55 kg/cm.sup.2. 
The above results show that although the foam has a fair retention after 
100 days of its low initial thermal conductivity, it did not match that of 
the invention, as set forth for example, in Table 1 nor was the rate of 
loss as determined by the k-retention value as low as that of the 
invention foam of Example 1. Additionally this retention is not alone an 
adequate indication of utility since a foam should be able to withstand 
high cure temperatures. The low isotropic burst pressure of the foam 
indicates that the foam cannot withstand cure without cell rupture. In 
fact when a foam sample from the same source received one month later and 
otherwise untreated was heated for 1 hour at 120.degree. C., the 
closed-cell content after ten minutes in the pycnometer was reduced to 
17.5% from 92.2%. This foam is not therefore adequately strong to 
withstand a curing operation or even the thermal cycling it could expect 
installed in a conventional built-up roof. By contrast when foam formed 
according to the conditions recited in Example 1 was subjected to a 
further 2 hours at 120.degree. C., the closed-cell content was only 
reduced to 94.4 from 95.5%. 
EXAMPLE 12 
This Example demonstrates the use of a salt-free resole to produce the foam 
of the invention. 
The resole used was prepared using the same proportions and components as 
were used to produce the resole used in Example 1. The calcium oxide 
catalyst in the resole was however neutralized using carbon dioxide in 
place of oxalic acid. Calcium carbonate was precipitated and filtered off 
and the salt-free resole was dehydrated to a suitable viscosity and mixed 
with the blowing agent surfactant and catalyst specified in Example 1. 
Two foams were obtained from two different runs and the process and 
proportions used in the runs were as given in Example 1 except as shown 
below in Table 4. 
TABLE 4 
______________________________________ 
FOAM PRODUCTION 
Sample 1 
Sample 2 
______________________________________ 
Resole 96 parts 96 parts 
Viscosity (cps) 75,200 82,400 
Blowing Agent 17.2 parts 
17.2 parts 
Surfactant 4.0 parts 4.0 parts 
Catalyst 2.01 parts 
1.98 parts 
Extrusion Head Temperature 
46.degree. C. 
-- 
Extrusion Head Pressure 
3.53 4.22 
(atmosphere) 
______________________________________ 
The two foams were evaluated in the same manner as the Example 1 foams and 
the results are set forth in Table 5. 
TABLE 5 
______________________________________ 
FOAM PRODUCTION 
Property Sample 1 Sample 2 
______________________________________ 
Density 
kg/m.sup.3 39.57 39.73 
Closed-Cell 
Content 96.1% 97.7% 
Thermal Conductivity 
initial (k.sub.1) 
0.0153 watts/m.degree. C. 
0.0153 watts/m.degree. C. 
after 100 days 
0.0167 watts/m.degree. C. 
0.0162 watts/m.degree. C. 
(k.sub.100) 
Burst Pressure 
1.90 2.18 
kg/cm.sup.2 
.DELTA.k/.DELTA.1nt 
0.30 .times. 10.sup.-3 
0.20 .times. 10.sup.-3 
(from k.sub.1 to k.sub.100) 
______________________________________ 
EXAMPLE 13 
This Example further illustrates the use of a resole having a nominal F/P 
ratio of 2:1 to produce a foam according to the invention. All parts are 
by weight. 
The following components were mixed together using a jacketed, continuous 
mixer, Model 4MHA available from Oakes Machinery Co., 235 Grant Ave., 
Islip, N.Y. 11751. 
______________________________________ 
Resole F/P ratio 1.93:1 
(1) 96 parts 
Viscosity at 25.degree. C. 
263,000 
cps 
Blowing Agent 
Freon 114 (2) 15 parts 
Surfactant DC-193 (3) 4 parts 
Foaming Catalyst (4) 2.2 parts 
______________________________________ 
(1) The liquid resole contained a dispersed oxalate salt as a result of the 
neutralization of calcium hydroxide catalyst using oxalic acid. The F/P 
ratio was obtained by nuclear magnetic resonance (NMR) analysis described 
previously. 
(2) A fluorocarbon (1,2-dichloro-tetrafluoroethane) available from DuPont 
under that description. 
(3) A silicone based surfactant available from Dow Corning Company under 
that description. 
(4) A 2:1 weight ratio blend of diethylene glycol and Ultra TX acid which 
is a mixture of toluene and xylene sulfonic acids available from Witco 
Chemical Company under that trade designation, expressed in terms of acid 
component content. 
The blowing agent was held in a bomb-like container and saturated with air 
by bubbling air at about 15 atmospheres into it for about 4 to 6 hours. 
This was to promote uniform nucleation of the blowing agent on reduction 
of the pressure during a subsequent phase of the foaming process. 
The resole, stored at about 5.degree. C. to minimize advancement, was 
initially brought to room temperature (25.degree. C.) and a laboratory 
test for reactivity performed thereon. This test was run at three acid 
levels (for Example 1, 1.5 and 1.8% acid as described in (4) above and 
based on resole weight) in order to measure the sensitivity of the resole 
reactivity to acid level. 150 grams of the resole and 3 grams of the 
DC-193 surfactant were charged to a 1 pint paper cup and mixed for one 
minute with a high speed mixer (720 rpm). 22.5 grams of Freon 113 blowing 
agent were then added and the contents mixed for an additional minute. The 
acid catalyst solution of toluene sulfonic acid and diethylene glycol was 
then added and mixed for an additional 30 seconds. 100 grams of the mixed 
formulation was quickly charged to a cylindrical cell about 5.7 cms high 
and 20.3 cms diameter fitted with a thermocouple attached to a recorder. 
The capped cell was placed in an oven set at 60.degree. C. and the peak 
temperature and time to reach same noted. The reactivity number, defined 
as the rate of temperature rise between the oven temperature and the peak 
temperature reached by the foaming composition, has the dimensions 
.degree.C./minute and was calculated at 3.2.degree. C./minute. This number 
is dependent on a number of resole characteristics--e.g. F/P ratio, water 
component, molecular weight, etc. and can therefore vary widely. Resoles 
with reactivity numbers of between about 2 to about 12 and preferably 
between 3 to 7 at a concentration of acid catalyst of 1.5% have been used. 
If the reactivity number is too high, water is added to the particular 
resole to reduce it whereas if the reverse is true the acid concentration 
is adjusted upwardly. 
The resole and surfactant were initially mixed together at about 
25.degree.-40.degree. C. in a jacketed, paddle mixer for about 30 minutes 
under an absolute pressure of 5 mm. of mercury to avoid entraining air. 
The resole and surfactant, foaming catalyst and blowing agent were 
continuously charged to the Oakes mixer in the foregoing noted ratios 
through suitable flow metering devices. Turbine meters obtained from Flow 
Technology Inc., Sacramento, Calif. were used on the Freon and an oval 
gear meter obtained from Brooks Instrument Division of Emerson Electric 
was used on the resole-surfactant acid-catalyst streams. The Oakes mixer 
was operated at about 93 rpm and had tempered water at about 40.degree. C. 
flowing through its jacket. The charge line carrying the resole was traced 
with hot water at about the same temperature. The blowing agent and 
catalyst were metered to the mixer at 25.degree. C. The temperatures of 
the foam composition entering the mixer was about 30.degree.-40.degree. C. 
while at the discharge of the mixer it was about 45.degree.-50.degree. C. 
The pressure in the mixer was 6.8 atmospheres. The temperature increase in 
the high shear mixer should be minimized to limit reaction therein which 
tends to foul the mixer. Likewise the pressure in the mixer should be 
above the vapor pressure of the foaming agent to avoid premature foaming 
and with the Freon 114 of this Example, such pressure should be kept at 
between about 3.4-6.8 atmospheres. 
The resulting formulation passed from the mixer through a finite length of 
insulated transfer tube consisting of a 91 cms long by 1.27 cms diameter 
pipe where foaming commenced, to an extrusion head in the form of a 0.64 
cm diameter nozzle just upstream of which was a bladder torpedo-control 
valve (Tube-O-Matic B-310208 available from Schrider Fluid Power Inc., 
P.O. Box 1448-71 Woodland St., Manchester, Conn. 06040). This air pressure 
controlled valve controlled the back pressure in the mixer and delivery 
tube and the rate of expansion of the foamable mixture issuing from the 
head. The mass flow rate of the foaming composition through the system was 
about 430-440 gms/minute. 
The temperature of the mixture at the nozzle was 49.degree. C. while the 
pressure there was 0.68 atmospheres; the pressure at the inlet to the 
control valve was 3.9 atmospheres whereas the temperature at such inlet 
was 50.9.degree. C. 
The extrusion head was reciprocated through about 55.9 cms in 2-4 seconds 
in such a way as to lay down a continuous ribbon of the foaming mixture on 
a sheet of natural Kraft paper 0.254 mm. thick having a weight of 205 
kg/1000m.sup.2 advancing at the rate of about 24.4 cms/min. 
The distance of the nozzle from the moving paper was kept at a minimum to 
minimize entrainment of air. 
The mixture was deposited in essentially parallel lines such that as 
foaming occurred the lines coalesced to form a continuous sheet. In this 
regard, the nature of the foam deposited on the moving paper web is a 
function of the pressure drop across the control valve. If the pressure 
upstream of the valve is too high a soupy deposit is obtained which 
results in discernible knit lines at the juncture of the ribbon-like 
formations issuing from the head which eventually produce undesirable 
large cells along such knit lines. On the other hand if such pressure is 
too low shearing of the foam in the control valve and delivery tube occurs 
which means that the cells are ruptured and the blowing agent escapes. The 
stream issuing from the nozzle should have the consistency of a froth such 
that rapid expansion without significant entrapment of air occurs as the 
composition is deposited on the paper substrate. 
Immediately downstream of the extrusion nozzle a protective Kraft paper 
covering was applied to the upper surface of the advancing foam sheet. 
Such covering (same characteristics as the paper substrate) passed around 
a fixed roller about 30.5 cms beyond the nozzle into contact with the 
rinsing developing foam sheet. The covered foam sheet was then brought 
into forcible compressive engagement with a succession of six immediately 
adjacent 3.8 cms diameter freely floating steel rolls interposed across 
the path of the advancing foam in order to iron out any irregularities in 
the foam surface and promote good wetting by the foam of the protective 
upper paper layer. The rollers serve to exert a constant pressure on the 
advancing foam and were vertically positioned so as to come into contact 
with about the upper 0.64 cms of thickness. This is important since 
warping of the foam product can occur in the absence of good adhesion with 
the top and bottom paper layers brought about by such compressive rolling 
contact. 
The foam sheet covered on its upper and lower faces with the Kraft paper 
was then passed through a hot air curing tunnel in the form of an oven 
obtained from Kornylak Co., 400 Heaton St., Hamilton, Ohio, described as a 
25 foot Air Film Principle Foam Containment Conveyor. This tunnel oven 
consisted of a section about 7.6 m long having a succession of five pairs 
of perforated platens vertically spaced 15.2 cms apart, one of each pair 
of which was above and below the advancing foam and each of which was 
about 1.5 m long. A film of hot air controlled at 53.degree. C. issued 
from the first pair of platens closest to the extrusion nozzle against the 
paper-covered upper and lower surfaces of the foam. A succession of about 
eight 3.8 cms diameter, immediately adjacent floating rollers were also in 
the oven under the first platen for contact with covered upper surface 
portion of the foam sheet. Air issuing from the remaining platens was kept 
at temperatures in the range of about 45.degree.-55.degree. C. The 
residence time of the foam in such oven was about 31 minutes at which time 
it had been hardened sufficiently to be cut with a saw into convenient 
pieces. These pieces were then stored at 60.degree. C. for 18 hours. 
Periodically (about once every 30 minutes) a thermocouple was inserted into 
the foam adjacent the extrusion nozzle and allowed to travel down the 
tunnel to measure the internal temperature of the foam formulation. The 
peak exotherm temperature was maintained at about 60.degree.-65.degree. C. 
and was controlled by adjusting the temperature of the hot air in the 
curing oven and/or the acid curing catalyst concentration in the mixture. 
Samples 5-1 through 5--5 were taken from different parts of the foam sheet 
produced by the foregoing process and were tested as previously described 
for density, closed-cell content, thermal conductivity initially (k.sub.1) 
and after 100 days (k.sub.100). The results are set forth in Table 6. 
TABLE 6 
__________________________________________________________________________ 
EXAMPLE 13 - FOAM PROPERTIES 
Initial Thermal Conductivity 
Time.sup.(4) 
Density 
Closed Cell 
Burst Pressure 
k.sub.1 
k.sub.100 
k-reten- 
Sample 
(hour) 
(kg/m.sup.3) 
(%) (kg/cm.sup.2) 
(watts/m .degree.C.) 
(watts/m .degree.C.) 
tion* .times. 10.sup.3 
__________________________________________________________________________ 
5-1.sup.(1) 
1344 
45.9 95.5 -- 0.0160 0.0240 1.72 
5-2.sup.(1) 
1402 
46.7 97.0 3.5 0.0164 0.0260 1.88 
5-3.sup.(2) 
1401 
47.7 98.4 3.0 0.0160 0.0171 0.19 
5-4.sup.(3) 
1355 
46.5 98.4 3.5 0.0163 0.0173 0.24 
5-5.sup.(1) 
1459 
47.1 97.6 3.2 0.0160 0.0168 0.19 
__________________________________________________________________________ 
*k.sub.100 - k.sub.1 /ln 100 - 1 i.e. .DELTA.k/.DELTA.ln (time) for time 
(t) = 1 to 100 
.sup.(1) Sample taken at outlet of Kornylak oven and immediately precured 
@ 60.degree. C. for 18 hours. 
.sup.(2) Sample taken at outlet of Kornylak oven, held overnight at 
insideambient room temperature conditions, then precured @ 60.degree. C. 
for 18 hours the next day. 
.sup.(3) As for (1) except that additional cure @ 90.degree. C. for 2 
hours before testing begun. 
.sup.(4) Of the day when run occurred when sample was taken. 
The above data overall illustrates partially cured foam according to the 
invention which had a density between 30 to 70 kg/m.sup.3, a closed-cell 
content of at least 85%, a thermal conductivity after 100 days less than 
0.020 watts/m.degree. C., a k-retention value less than 
0.5.times.10.sup.-3 and an isotropic burst pressure in excess of 1.75 
kg/cm.sup.2. The reason for the high k.sub.100 and k-retention values for 
Samples 5-1 and 5-2 is not known. 
EXAMPLE 14 
This example further illustrates the use of a resole having a nominal F/P 
ratio of 2:1 and a less than preferred viscosity to produce a foam. All 
parts are by weight. 
The following components were mixed together using a jacketed continuous 
mixer, Model 4MHA available from Oakes Machinery Co., 235 Grant Ave., 
Islip, N.Y. 11751: 
______________________________________ 
Resole F/P ratio 2.07:1 
(1) 96 parts 
Viscosity at 25.degree. C. 
77,000 cps 
Blowing Agent 
Freon 114 (2) 13 parts 
Surfactant DC-193 (3) 4 parts 
Foaming Catalyst (4) 1.34-1.64 
parts 
______________________________________ 
(1) The liquid resole contained in a dispersed oxalate salt as a result of 
the neutralization of calcium hydroxide catalyst using oxalic acid. The 
F/P ratio was obtained by nuclear magnetic resonance (NMR) analysis 
described previously. 
(2) A fluorocarbon (1,2-dichloro-tetrafluoroethane) available from duPont 
under that description. 
(3) A silicone based surfactant available from Dow Corning Company under 
that description. 
(4) A 2:1 weight ratio blend of diethylene glycol and Ultra TX acid which 
is a mixture of toluene and xylene sulfonic acids available from Witco 
Chemical Company under that trade designation, expressed in terms of acid 
component content. 
The blowing agent was held in a bomb-like container and saturated with air 
by bubbling air at about 15 atmospheres into it for about 4 to 6 hours. 
This was to promote uniform nucleation of the blowing agent on reduction 
of the pressure during a subsequent phase of the foaming process. 
The resole, stored at about 5.degree. C. to minimize advancement, was 
initially brought to room temperature (25.degree. C.) and a laboratory 
test for reactivity performed thereon. This test was run at three acid 
levels (for Example 1, 1.5 and 1.8% acid as described in (4) above and 
based on resole weight) in order to measure the sensitivity of the resole 
reactivity to acid level. One hundred fifty grams of the resole and 3 
grams of the DC-193 surfactant were charged to a 0.57 litre (1 pint) paper 
cup and mixed for one minute with a high speed mixer (720 rpm). 22.5 grams 
of Freon 113 blowing agent were then added and the contents mixed for an 
additional minute. The acid catalyst solution of toluene sulfonic acid and 
diethylene glycol was then added and mixed for an additional 30 seconds. 
100 grams of the mixed formulation was quickly charged to a cylindrical 
cell about 5.7 cms high and 20.3 cms diameter fitted with a thermocouple 
attached to a recorder. The capped cell was placed in an oven set at 
60.degree. C. and the peak temperature and time to reach same noted. The 
reactivity number, defined as the rate of temperature rise between the 
oven temperature and the peak temperature reached by the foaming 
composition has the dimensions .degree. C./minute and was calculated at 
8.0.degree. C./minute. This number is dependent on a number of resole 
characteristics--e.g. F/P ratio, water content, molecular weight, etc. and 
can therefore vary widely. Resoles with reactivity numbers of between 
about 2 to about 12 and preferably between 3 to 7 at a concentration of 
acid catalyst of 1.5% have been used. If the reactivity number is too 
high, water is added to the particular resole to reduce it whereas if the 
reverse is true the acid concentration is adjusted upwardly. 
The resole and surfactant were initially mixed together at about 
25.degree.-40.degree. C. in a jacketed, paddle mixer for about 30 minutes 
under an absolute pressure of 5 mm. of mercury to avoid entraining air. 
The resole and surfactant, foaming catalyst and blowing agent were 
continuously charged to the Oakes mixer in the foregoing noted ratios 
through suitable flow metering devices. Turbine meters obtained from Flow 
Technology Inc., Sacramento, Calif. were used on the Freon and an oval 
gear meter obtained from Brooks Instrument Division of Emerson Electric 
was used on the resole-surfactant acid-catalyst streams. The Oakes mixer 
was operated at about 115 rpm and had tempered water at about 40.degree. 
C. flowing through its jacket. The charge line carrying the resole was 
traced with hot water at about the same temperature. The blowing agent and 
catalyst were metered to the mixer at 25.degree. C. The temperatures of 
the foam composition entering the mixer was about 30.degree.-40.degree. C. 
while at the discharge of the mixer it was about 45.degree.-50.degree. C. 
The pressure in the mixer was 4.1 atmospheres. The temperature increase in 
the high shear mixer should be minimized to limit reaction therein which 
tends to foul the mixer. Likewise the pressure in the mixer should be 
above the vapor pressure of the foaming agent to avoid premature foaming 
and with the Freon 114 of this example, such pressure should be kept at 
between about 3.4-6.8 atmospheres. 
The resulting formulation passed from the mixer through a finite length of 
insulated transfer tube consisting of a 91 cms long by 1.27 cms diameter 
pipe where foaming commenced, to an extrusion head in the form of a 0.64 
cm diameter nozzle just upstream of which was a bladder torpedo-control 
valve (Tube-O-Matic Valve B-310208 available from Schrider Fluid Power 
Inc., P.O. Box 1448-71 Woodland St., Manchester, Conn. 06040). This air 
pressure controlled valve controlled the back pressure in the mixer and 
delivery tube and the rate of expansion of the foamable mixture issuing 
from the head. The mass flow rate of the foaming composition through the 
system was about 420 gms/minute. 
The temperature of the mixture at the nozzle was about 42.degree. C. while 
the pressure there was about 0.5 atmospheres; the pressure at the inlet to 
the control valve was about 1.5 atmospheres whereas the temperature at 
such inlet was about 44.degree. C. 
The extrusion head was reciprocated through about 42 cms in 2-4 seconds in 
such a way as to lay down a continuous ribbon of the foaming mixture on a 
sheet of natural Kraft paper 0.254 mm. thick having a weight of 205 
kg/1000m.sup.2 advancing at the rate of about 20-30 cms/min. 
The distance of the nozzle from the moving paper was kept at a minimum to 
minimize entrainment of air. 
The mixture was deposited in essentially parallel lines such that as 
foaming occurred the lines coalesced to form a continuous sheet. In this 
regard, the nature of the foam deposited on the moving paper web is a 
function of the pressure drop across the control valve. If the pressure 
upstream of the valve is too high a soupy deposit is obtained which 
results in discernible knit lines at the juncture of the ribbon-like 
formations issuing from the head which eventually produce undesirable 
large cells along such knit lines. On the other hand if such pressure is 
too low shearing of the foam in the control valve and delivery tube occurs 
which means that the cells are ruptured and the blowing agent escapes. The 
stream issuing from the nozzle should have the consistency of a froth such 
that rapid expansion without significant entrapment of air occurs as the 
composition is deposited on the paper substrate. 
Immediately downstream of the extrusion nozzle a protective Kraft paper 
covering was applied to the upper surface of the advancing foam sheet. 
Such covering (same characteristics as the paper substrate) passed around 
a fixed roller about 30.5 cms beyond the nozzle into contact with the 
rising developing foam sheet. The covered foam sheet was then brought into 
forcible compressive engagement with a succession of six immediately 
adjacent 3.8 cms diameter freely floating steel rolls interposed across 
the path of the advancing foam in order to iron out any irregularities in 
the foam surface and promote good wetting by the foam of the protective 
upper paper layer. The rollers serve to exert a constant pressure on the 
advancing foam and were vertically positioned so as to come into contact 
with about the upper 0.64 cms of thickness. This is important since 
warping of the foam product can occur in the absence of good adhesion with 
the top and bottom paper layers brought about by such compressive rolling 
contact. 
The foam sheet covered on its upper and lower faces with the Kraft paper 
was then passed through a hot air curing tunnel in the form of an oven 
obtained from Kornylak Co., 400 Heaton St., Hamilton, Ohio, described as a 
25 foot Air Film Principle Foam Containment Conveyor. This tunnel oven 
consisted of a section about 7.6 m long having a succession of five pairs 
of perforated platens vertically spaced 15.2 cms apart, one of each pair 
of which was above and below the advancing foam and each of which was 
about 1.5 m long. A film of hot air controlled at 53.degree. C. issued 
from the first pair of platens closest to the extrusion nozzle against the 
paper-covered upper and lower surfaces of the foam. A succession of about 
eight 3.8 cms diameter, immediately adjacent floating rollers were also in 
the oven under the first platen for contact with covered upper surface 
portion of the foam sheet. Air issuing from the remaining platens was kept 
at temperatures in the range of about 60.degree. C. The residence time of 
the foam in such oven varied from 20-50 minutes at which time it had been 
hardened sufficiently to be cut with a saw into convenient pieces. These 
pieces were then stored at 60.degree. C. for either 18 hours, or 4 hours, 
or they were not heated at all. 
Periodically (about once every 30 minutes) a thermocouple was inserted into 
the foam adjacent the extrusion nozzle and allowed to travel down the 
tunnel to measure the internal temperature of the foam formulation. The 
peak exotherm temperatures was maintained at about 60.degree.-70.degree. 
C. and was controlled by adjusting the temperature of the hot air in the 
curing oven and/or the acid curing catalyst concentration in the mixture. 
Runs 1 through 26 were taken at different times from the foam sheet 
produced by the foregoing process and were tested as previously described 
for density, closed-cell content and thermal conductivity after 100 days. 
The results are set forth in Table 7. 
All samples were made under nearly identical conditions. The major 
difference being the amount of batch oven cure. As can be seen from the 
data, it is extremely difficult to control foam properties utilizing this 
viscosity resin. Although 10 of the 26 samples had greater than 85% closed 
cell, none of those measured had a k retention value stability, 
.delta.k/.delta. In t, less than 0.5.times.10.sup.-3. The cell structure 
was marginally effective. 
TABLE 7 
______________________________________ 
k Retention Value 
Sample 
Density(Kg/m.sup.3) 
Closed Cell % 
.delta.k/.delta. 1nt 
______________________________________ 
14-1 49.5 67.5 
14-2 50.4 67.4 
14-3 57.5 80.7 
14-4 51.5 88.0 
14-5 52.7 86.4 1.56 .times. 10.sup.-3 
14-6 56.0 57.1 
14-7 51.9 72.1 
14-8 54.1 88.8 
14-9 54.6 79.3 
14-10 54.1 86.9 
14-11 46.7 67.7 
14-12 46.6 8.2 
14-13 53.8 89.6 1.37 .times. 10.sup.-3 
14-14 50.4 93.7 0.66 .times. 10.sup.-3 
14-15 52.3 91.8 
14-16 53.8 91.6 
14-17 47.5 3.7 
14-18 47.7 15.6 
14-19 48.8 96.0 0.66 .times. 10.sup.-3 
14-20 43.2 18.0 
14-21 45.4 39.9 
14-22 45.6 42.7 
14-23 41.6 13.6 
14-24 33.6 2.7 
14-25 37.9 15.6 
14-26 42.9 92.2 0.75 .times. 10.sup.-3 
______________________________________ 
EXAMPLE 15 
This example illustrates the use of a high viscosity resole having a 
nominal F/P ratio of 2:1 to produce a foam according to the invention. All 
parts are by weight. 
The following components were mixed together using a jacketed, continuous 
mixer, Model 4MHA available from Oakes Machinery Co., 235 Grant Ave. 
Islip, N.Y. 11751. 
______________________________________ 
Resole F/P ratio 1.93:1 
(1) 96 parts 
Viscosity at 25.degree. C. 
472,000 
cps 
Blowing Agent 
Freon 114 (2) 13.8 parts 
Surfactant DC-193 (3) 4 parts 
Foaming Catalyst (4) 1.3 parts 
______________________________________ 
(1) The liquid resole contained a dispersed oxalate salt as a result of the 
neutralization of calcium hydroxide catalyst using oxalic acid. The F/P 
ratio was obtained by nuclear magnetic resonance (NMR) analysis described 
previously. 
(2) A fluorocarbon (1,2-dichloro-tetrafluoroethane) available from duPont 
under that description. 
(3) A silicone based surfactant available from Dow Corning Company under 
that description. 
(4) A 2:1 weight ratio blend of diethylene glycol and Ultra TX acid which 
is a mixture of toluene and xylene sulfonic acids available from Witco 
Chemical Company under that trade designation, expressed in terms of acid 
component content. 
The blowing agent was held in a bomb-like container and saturated with air 
by bubbling air at about 15 atmospheres into it for about 4 to 6 hours. 
This was to promote uniform nucleation of the blowing agent on reduction 
of the pressure during a subsequent phase of the foaming process. 
The resole, stored at about 5.degree. C. to minimize advancement, was 
initially brought to room temperature (25.degree. C.) and a laboratory 
test for reactivity performed thereon. This test was run at three acid 
levels (for Example 1, 1.5 and 1.8% acid as described in (4) above and 
based on resole weight) in order to measure the sensitivity of the resole 
reactivity to acid level. 150 grams of the resole and 3 grams of the 
DC-193 surfactant were charged to a 0.57 litre (1 pint) paper cup and 
mixed for one minute with a high speed mixer (720 rpm). 22.5 grams of 
Freon 113 blowing agent were then added and the contents mixed for an 
additional minute. The acid catalyst solution of toluene sulfonic acid and 
diethylene glycol was then added and mixed for an additional 30 seconds. 
100 grams of the mixed formulation was quickly charged to a cylindrical 
cell about 5.7 cms high and 20.3 cms diameter fitted with a thermocouple 
attached to a recorder. The capped cell was placed in an oven set at 
60.degree. C. and the peak temperature and time to reach same noted. The 
reactivity number, defined as the rate of temperature rise between the 
oven temperature and the peak temperature reached by the foaming 
composition has the dimensions .degree. C./minute and was calculated at 
6.4.degree. C./minute. This number is dependent on a number of resole 
characteristics--e.g. F/P ratio, water content, molecular weight, etc. and 
can therefore vary widely. Resoles with reactivity numbers of between 
about 12 and preferably between 3 to 7 at a concentration of acid catalyst 
of 1.5% have been used. If the reactivity number is too high, water is 
added to the particular resole to reduce it whereas if the reverse is true 
the acid concentration is adjusted upwardly. 
The resole and surfactant were initially mixed together at about 
25.degree.-40.degree. C. in a jacketed, paddle mixer for about 30 minutes 
under an absolute pressure of 5 mm. of mercury to avoid entraining air. 
The resole and surfactant, foaming catalyst and blowing agent were 
continuously charged to the Oakes mixer in the foregoing noted ratios 
through suitable flow metering devices. Turbine meters obtained from Flow 
Technology Inc., Sacramento, Calif. were used on the Freon and an oval 
gear meter obtained from Brooks Instrument Division of Emerson Electric 
was used on the resole-surfactant acid-catalyst streams. The Oakes mixer 
was operated at about 130 rpm and had tempered water at about 40.degree. 
C. flowing through its jacket. The charge line carrying the resole was 
traced with hot water at about the same temperature. The blowing agent and 
catalyst were metered to the mixer at 25.degree. C. The temperatures of 
the foam composition entering the mixer was about 30.degree.-40.degree. C. 
while at the discharge of the mixer it was about 50.degree. C. The 
pressure in the mixer was 9.0 atmospheres. The temperature increase in the 
high shear mixer should be minimized to limit reaction therein which tends 
to foul the mixer. Likewise the pressure in the mixer should be above the 
vapor pressure of the foaming agent to avoid premature foaming and with 
the Freon 114 of this example, such pressure should be kept above 5.0 
atmospheres. 
The resulting formulation passed from the mixer through a finite length of 
insulated transfer tube consisting of 91 cms long by 1.27 cms diameter 
pipe where foaming commenced, to an extrusion head in the form of a 0.64 
cm diameter nozzle just upstream of which was a bladder torpedo-control 
valve (Tube-O-Matic Valve B-310208 available from Schrider Fluid Power 
Inc., P.O. Box 1448-71 Woodland St., Manchester, Conn 06040). This air 
pressure controlled valve controlled the back pressure in the mixer and 
delivery tube and the rate of expansion of the foamable mixture issuing 
from the head. The mass flow rate of the foaming composition through the 
system was about 420 gms/minute. 
The temperature of the mixture at the nozzle was 57.degree. C. while the 
pressure there was 1.4 atmospheres; the pressure at the inlet to the 
control valve was 3.5 atmospheres whereas the temperature at such inlet 
was 57.degree. C. 
The extrusion head was reciprocated through about 25 cms in 3 seconds in 
such a way as to lay down a continuous ribbon of the foaming mixture on a 
sheet of cardboard advancing at the rate of about 25.4 cms/min. 
The distance of the nozzle from the moving cardboard was kept at a minimum 
to minimize entrainment of air. 
The mixture was deposited in essentially parallel lines such that as 
foaming occurred the lines coalesced to form a continuous sheet. In this 
regard, the nature of the foam deposited on the moving cardboard is a 
function of the pressure drop across the control valve. If the pressure 
upstream of the valve is too high a soupy deposit is obtained which 
results in discernible knit lines at the juncture of the ribbon-like 
formations issuing from the head which eventually produce undesirable 
large cells along such knit lines. On the other hand if such pressure is 
too low shearing of the foam in the control valve and delivery tube occurs 
which means that the cells are ruptured and the blowing agent escapes. The 
stream issuing from the nozzle should have the consistency of a froth such 
that rapid expansion without significant entrapment of air occurs as the 
composition is deposited on the cardboard substrate. 
The foam deposited on the cardboard was placed in a hot air circulatory 
oven for 16 hours at 60.degree. C. After 16 hours the closed cell content 
was measured. 
______________________________________ 
Density 
Closed Cell Content 
______________________________________ 
Sample 15-1 47.5 89.9% 
15-2 40.3 87.2% 
______________________________________ 
EXAMPLE 16 
This example further illustrates the use of a high viscosity, resole having 
a nominal F/P ratio of 1.6:1, to produce a foam according to the 
invention. All parts are by weight. 
The following components were mixed together using a jacketed, continuous 
mixer, Model 4MHA available from Oakes Machinery Co., 235 Grant Ave., 
Islip, N.Y. 11751. 
______________________________________ 
Resole F/P ratio 1.6:1 
(1) 96 parts 
Viscosity at 25.degree. C. 
230,000 
cps 
Blowing Agent 
Freon 114 (2) 13.6 parts 
Surfactant DC-193 (3) 4 parts 
Foaming Catalyst (4) 2.1 parts 
______________________________________ 
(1) The liquid resole contained a soluble sodium salt as a result of the 
neutralization of sodium hydroxide catalyst using Ultra TX acid(5). The 
F/P ratio was obtained by nuclear magnetic resonance (NMR) analysis 
described previously. 
(2) A fluorocarbon (1,2-dichloro-tetrafluoroethane) available from duPont 
under that description. 
(3) A silicone based surfactant available from Dow Corning Company under 
that description. 
(4) A 2:1 weight ratio blend of diethylene glycol and Ultra TX acid which 
is a mixture of toluene and xylene sulfonic acids available from Witco 
Chemical Company under that trade designation, expressed in terms of acid 
component content. 
(5) Ultra TX is a mixture of toluene and xylene sulfonic acids available 
from Witco Chemical Co. 
The blowing agent was held in a bomb-like container and saturated with air 
by bubbling air at about 10 atmospheres into it for about 4 to 6 hours. 
This was to promote uniform nucleation of the blowing agent on reduction 
of the pressure during a subsequent phase of the foaming process. 
The resole, stored at about 5.degree. C. to minimize advancement, was 
initially brought to room temperature (25.degree. C.) and a laboratory 
test for reactivity performed thereon. This test was run at three acid 
levels (for Example 1, 1.5 and 1.8% acid as described in (4) above and 
based on resole weight) in order to measure the sensitivity of the resole 
reactivity to acid level. 150 grams of the resole and 3 grams of the 
DC-193 surfactant were charged to a 0.57 litre (1 pint) paper cup and 
mixed for one minute with a high speed mixer (720 rpm). 22.5 grams of 
Freon 113 blowing agent were then added and the contents mixed for an 
additional minute. The acid catalyst solution of toluene sulfonic acid and 
diethylene glycol was then added and mixed for an additional 30 seconds. 
100 grams of the mixed formulation was quickly charged to a cylindrical 
cell about 5.7 cms high and 20.3 cms diameter fitted with a thermocouple 
attached to a recorder. The capped cell was placed in an oven set at 
60.degree. C. and the peak temperature and time to reach same noted. The 
reactivity number, defined as the rate of temperature rise between the 
oven temperature and the peak temperature reached by the foaming 
composition, has the dimensions .degree. C./minute and was calculated at 
19.7.degree. C./minute. This number is dependent on a number of resole 
characteristics--e.g. F/P ratio, water content, molecular weight, etc. and 
can therefore vary widely. Resoles of this type with reactivity numbers of 
between about 5 to about 45 and preferably between 15 to 25 at a 
concentration of acid catalyst of 1.5% have been used. If the reactivity 
number is too high, water is added to the particular resole to reduce it 
whereas if the reverse is true the acid concentration is adjusted 
upwardly. 
The resole and surfactant were initially mixed together at about 
25.degree.-40.degree. C. in a jacketed, paddle mixer for about 30 minutes 
under an absolute pressure of 5 mm. of mercury to avoid entraining air. 
The resole and surfactant, foaming catalyst and blowing agent were 
continuously charged to the Oakes mixer in the foregoing noted ratios 
through suitable flow metering devices. Turbine meters obtained from Flow 
Technology Inc., Sacramento, Calif. were used on the Freon and an oval 
gear meter obtained from Brooks Instrument Division of Emerson Electric 
was used on the resole-surfactant acid-catalyst streams. The Oakes mixer 
was operated at about 180 rpm and had tempered water at about 40.degree. 
C. flowing through its jacket. The charge line carrying the resole was 
traced with hot water at about the same temperature. The blowing agent and 
catalyst were metered to the mixer at 25.degree. C. The temperatures of 
the foam composition entering the mixer was about 30.degree.-40.degree. C. 
while at the discharge of the mixer it was about 52.degree. C. The 
pressure in the mixer was 8 atmospheres. The temperature increase in the 
high shear mixer should be minimized to limit reaction therein which tends 
to foul the mixer. Likewise the pressure in the mixer should be above the 
vapor pressure of the foaming agent to avoid premature foaming and with 
the Freon 114 of this example, such pressure should be kept at between 
about 6-10 atmospheres. 
The resulting formulation passed from the mixer through a finite length of 
insulated transfer tube consisting of a 91 cms long by 1.27 cms diameter 
pipe where foaming commenced, to an extrusion head in the form of a 0.64 
cm diameter nozzle just upstream of which was a bladder torpedo-control 
valve (Tube-O-Matic Valve B-310208 available from Schrider Fluid Power 
Inc., P.O. Box 1448-71 Woodland St., Manchester, Conn 06040). This air 
pressure controlled valve controlled the back pressure in the mixer and 
delivery tube and the rate of expansion of the foamable mixture issuing 
from the head. The mass flow rate of the foaming composition through the 
system was about 720 gms/minute. 
The temperature of the mixture at the nozzle was 53.degree. C. while the 
pressure there was about 0.5 atmospheres; the pressure at the inlet to the 
control valve was 3.4 atmospheres whereas the temperature at such inlet 
was about 54.degree. C. 
The extrusion head was reciprocated through about 110 cms in 4-6 seconds in 
such a way as to lay down a continuous ribbon of the foaming mixture on a 
sheet of natural Kraft paper 0.254 mm. thick having a weight of 205 
kg/1000m.sup.2 advancing at the rate of about 29 cms/min. 
The distance of the nozzle from the moving paper was kept at a minimum to 
minimize entrainment of air. 
The mixture was deposited in essentially parallel lines such that as 
foaming occurred the lines coalesced to form a continuous sheet. In this 
regard, the nature of the foam deposited on the moving paper web is a 
function of the pressure drop across the control valve. If the pressure 
upstream of the valve is too high a soupy deposit is obtained which 
results in discernible knit lines at the juncture of the ribbon-like 
formations issuing from the head which eventually produce undesirable 
large cells along such knit lines. On the other hand if such pressure is 
too low shearing of the foam in the control valve and delivery tube occurs 
which means that the cells are ruptured and the blowing agent escapes. The 
stream issuing from the nozzle should have the consistency of a froth such 
that rapid expansion without significant entrapment of air occurs as the 
composition is deposited on the paper substrate. 
Immediately downstream of the extrusion nozzle a protective Kraft paper 
covering was applied to the upper surface of the advancing foam sheet. 
Such covering (same characteristics as the paper substrate) passed around 
a fixed roller about 30.5 cms beyond the nozzle into contact with the 
rising developing foam sheet. The covered foam sheet was then brought into 
forcible compressive engagement with a succession of six immediately 
adjacent 3.8 cms diameter freely floating steel rolls interposed across 
the path of the advancing foam in order to iron out any irregularities in 
the foam surface and promote good wetting by the foam of the protective 
upper paper layer. The rollers serve to exert a constant pressure on the 
advancing foam and were vertically positioned so as to come into contact 
with about the upper 0.64 cms of thickness. This is important since 
warping of the foam product can occur in the absence of good adhesion with 
the top and bottom paper layers brought about by such compressive rolling 
contact. 
The foam sheet covered on its upper and lower faces with the Kraft paper 
was then passed through a hot air curing tunnel in the form of an oven 
obtained from Kornylak Co., 400 Heaton St., Hamilton, Ohio, described as a 
25 foot Air Film Principle Foam Containment Conveyor. This tunnel oven 
consisted of a section about 7.6 m long having a succession of five pairs 
of perforated platens vertically spaced 15.2 cms apart, one of each pair 
of which was above and below the advancing foam and each of which was 
about 1.5 m long. A film of hot air controlled at 53.degree. C. issued 
from the first pair of platens closest to the extrusion nozzle against the 
paper-covered upper and lower surfaces of the foam. A succession of about 
eight 3.8 cms diameter, immediately adjacent floating rollers were also in 
the oven under the first platen for contact with covered upper surface 
portion of the foam sheet. Air issuing from the remaining platens was kept 
at temperatures in the range of about 55.degree.-65.degree. C. The 
residence time of the foam in such oven was about 21 minutes at which time 
it had been hardened sufficiently to be cut with a saw into convenient 
pieces. These pieces were then stored at 60.degree. C. for 18 hours. 
Periodically (about once every 30 minutes) a thermocouple was inserted into 
the foam adjacent the extrusion nozzle and allowed to travel down the 
tunnel to measure the internal temperature of the foam formulation. The 
peak exotherm temperature was maintained at about 65.degree.-70.degree. C. 
and was controlled by adjusting the temperature of the hot air in the 
curing oven and/or the acid curing catalyst concentration in the mixture. 
Samples 16-1 through 16-3 were taken from different parts of the foam sheet 
produced by the foregoing process and were tested as previously described 
for density, closed-cell content, thermal conductivity initially (k) and 
after 100 days (k.sub.100). The results are set forth in Table 8. 
TABLE 8 
__________________________________________________________________________ 
EXAMPLE 16 - FOAM PROPERTIES 
__________________________________________________________________________ 
Thermal Conductivity 
Initial (3) Estimate 
Time (2) 
Density 
Closed Cell 
Burst Pressure 
k.sub.1 
k.sub.100 
k-reten- 
Sample (1) 
(hour) 
(kg/m.sup.3) 
(%) (kg/cm.sup.2) 
(watts/m .degree.C.) 
(watts/m .degree.C.) 
tion* .times. 10.sup.3 
__________________________________________________________________________ 
16-1 1407 41.3 97.4 -- .0163 .0169 0.13 
16-2 1437 42.05 
96.5 2.9 .0160 .0166 0.13 
16-3 1534 41.7 98.3 2.9 .0157 .0163 0.13 
__________________________________________________________________________ 
*k.sub.100 - k.sub.1 /ln 100 - 1n 1 - i.e. .DELTA.k/.DELTA.ln for time 
(t) = 1 to 100 
(1) Sample taken at outlet of Kornylak oven and immediately pre-cured @ 
60.degree. C. for 18 hours 
before testing begun. 
(2) Of the day when run occurred when sample was taken. 
(3) These samples were aged at 140.degree. F. instead of 73.degree. F. 
Because of increases in diffusion, 
the aging rate at 140.degree. F. is known to be 3 times the rate at 
73.degree. F. The data @ 140.degree. F. 
follows: 
k.sub.1 
k.sub.100 @ 140.degree. F. 
k.sub.100 Estimate @ 73.degree. F. 
16-1 
0.0163 
0.0180 0.0169 
16-2 
0.0160 
0.0177 0.0166 
16-3 
0.0157 
0.0176 0.0163 
The above data overall illustrates partially cured foam according to the 
invention which had a density between 30 to 70 kg/m.sup.3, a closed-cell 
content of at least 85%, a thermal conductivity after 100 days less than 
0.020 watts/m.degree. C., a k-retention value less than 
0.5.times.10.sup.-3 and an isotropic burst pressure in excess of 1.75 
kg/cm.sup.2. Even the k retention value aged at 140.degree. F. is less 
than 0.5.times.10.sup.-3. 
Although this invention has been described with respect to specific 
modifications, the details thereof are not to be construed as limitations, 
for it will be apparent that various equivalents, changes and 
modifications may be resorted to without departing from the spirit and 
scope thereof and it is understood that such equivalent embodiments are 
intended to be included herein.