Note: Descriptions are shown in the official language in which they were submitted.
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AN IMPROVED FOAMABLE RESOLE RESIN COMPOSITION
BACKGROUND OF THE INVENTION
Foamable phenolic resole resin compositions are known
comprising a resole resin, a blowing agent and a surfactant.
U. S. P. 3,389,094 discloses such systems. Such compositions
have been optimized by the selection of the blowing agents and
surfactants to improve foamability and the structure of the
foams.
Such compositions are based on incompletely condensed
phenolic resole resins of phenol and formaldehyde. When such
compositions are mixed with an acid catalyst and a blowing agent,
an exothermic reaction with further condensation causes libera-
tion of gas by the blowing agent. The curing resin has an in-
creased viscosity which prevents the escape of said gases and
the composition expands to a foam with a substantially closed
cell structure. Finally, the resin cures completely to a rigid
foam of great utility for insulation uses. The cured phenol/al-
dehyde resole resins have fire and smoke retardant properties
which can be increased further with certain additives giving
added utility.
Acids are used to foam and cure such foams, hence, leave
the cured foam with ~4 pH below about 3 which is corrosive to
metal building materials when the foams are used as building in-
sulation. It is the objective of the present invention to pro-
vide foamable resole resin compositions that are curable to non-
corrosive foams.
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The invention relates to an improved foamable resole
resin composition curable to a non-corrosive foam, comprising
a resole resin, a blowing agent and a surfactant, wherein the
improvement comprises, having present in said composition dis-
persed metal powders selected from the group consisting of
zinc, iron, magnesium, calcium and barium and mixtures thereof.
The invention also relates to an improved process
for preparing a foamable resole resin composition, curable to
a noncorrosive foam, comprising blending a resole resin, a
blowing agent and a surfactant wherein the improvement com-
prises dispersing in said composition a metal powder selected
from the group consisting of zinc, iron, magnesium, calcium
and barium and mixtures thereof.
The invention also relates to an improved process
for foaming foamable resole resin composition, the improvement
comprising: adding an acid catalyst to the above composition
and allowing said composition to foam forming a cellular
material.
Any conventional water soluble resole resin can be
used. During the normal manufacture of single stage resole-
type liquid phenolic resins a basic catalyst is utilized. To
stabilize the finished resin, the base is usually neutralized
at the end of the manufacturing process. The neutralization
results in the formation of either a soluble or insoluble
salt depending on the base catalyst and neutralizing acid
employed. Since the presence of excess salt can be deleter-
ious to certain end use properties, it is often removed from
the resin by techniques such as insoluble salt filtration
or ion exchange. From both a cost and pol-
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C-06-12-0522
lution criteria, it is desirable to avoid removing the salt from
the resin. The aqueous resole resin solutions preferably are
those that have been neutralized so as to provide particular in-
ert salts that do not need to be removed but enhance the proper-
ties of the aqueous resole resin solutions.
The resole resins are formed using bases containing poly-
valent cations such as calcium and barium. The cation is con-
verted to a highly insoluble oxalate salt at the end of the manu-
facturing process. The cation so inerted does not interfere with
key application properties of the resole resin.
The calcium or barium oxalate is formed in situ in the
resin as very fine insoluble particles which results in very
stable dispersions with no tendency to settle or coagulate. The
highly insoluble nature of these salts make them, in principle,
a highly inert dispersed filler with little tendency to adversely
affect key properties, e.g. moisture resistance. Because the
dispersions are colloidal, in nature, the resins can be pumped,
sprayed and generally handled like salt free resins.
The combination of the fine particle calcium or barium
oxalate dispersion with a phenolic resole resin produces an un-
expected enhancement in the viscosity of the foaming composi-
tion. The use of the dispersed salt gives an alternative to
viscosity control which is normally controlled by varying the
molecular weight and solids content of the resin itself.
Aqueous resole resin solutions containing dispersed oxa-
late salts are basically resole resins prepared using calcium or
barium hydroxide and neutralized with oxalic acid or ammonium
oxalate.
The base catalyzed reaction of from 1.3 to 2.8 mols of
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formaldehyde with one mol of phenol is carried out in the pres-
ence of calcium or barium hydroxide. Additional bases such as
sodium hydroxide or organic amines may be added as cocatalysts
and pH regulators for the resin system. Typically, between 0.02
and 0.30 mol equivalents of total base per mol of original phenol
are utilized. The reaction is carried out at a temperature range
of from 40 to 80C.
The resole reaction is preferably carried out with
aqueous formalin solution of between 30-70% formaldehyde with
completed reaction solids adjusted to 60-99% by vacuum stripping
to remove water or by addition of water.
Aqueous resoles containing dispersed salts can be used
in the presence of variety of formaldehyde scavengers and resole
co-reactants. Suitable formaidehyde scavengers and resole co-
reactants include nitrogen containing organic compounds solublein the resole, or molecular weight less than 300, containing at
least one NH group per molecule reactive with formaldehyde. Ex-
amples include ammonia, primary and secondary amines, urea, sub-
stituted ureas, primary amides, dicyandiamide, guanidines and
aminotriazines such as melamine, guanamine and benzoguanamine.
Depending on the advancement of the resole it may be preferably
to add the scavengers and resole coreactants just prior to end
use to avoid storage stability problems such as rapid loss of
resole water tolerance or the precipitation of resin components.
Alternatively, the formaldehyde scavenging reaction is carried
out at the end of the resole reaction, prior to neutralization
with oxalate, preferably at a temperature in the range of 20 to
60C., to minimize oligomerization of the resole. The amount of
coreactant added can vary within very wide limits up to 1.0 mol
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per mol of phenol in the original reaction mixture. It is pre-
ferred to use between 0.5 and 1.5 mol equivalents of scavenger
per mol of free formaldehyde present at the end of the resole
reaction.
The preferred catalyst for resole stage is barium or cal-
cium hydroxide. Supplementary bases which can be used with the
main catalyst include alkali metal hydroxides such as lithium
hydroxide, sodium hydroxide and potassium hydroxide, alkali metal
carbonates such as sodium carbonate and potassium carbonate,
aqueous ammonia and amines of molecular weight less than 300.
The process can be carried out wherein said catalyst comprises
said alkaline earth hydroxides used in combination with a com-
pound selected from the group consisting of lithium hydroxide,
sodium hydroxide, potassium hydroxide, sodium carbonate, potas-
sium carbonate, organic amines, aqueous ammonia and mixtures
thereof wherein about 0.02 to 0.30 mol equivalents of combined
catalyst are used per mol of phenol charged, said alkaline earth
catalysts constituting about 50 to 95% of the mol equivalents
provided by said combined catalyst.
At the end of the reaction the barium and calcium hydrox-
ide are neutralized with sufficient oxalate to yield a highly
insoluble dispersed salt and adjust the pH within the range of
3.0 to 8.5. The supplementary bases are partially neutralized
as necessary and function to control the resin pH between 3 and
8.5. Preferably, the pH is adjusted between 6.0 and 8Ø
The formation of the insoluble oxalate can conveniently
be done by adding solid oxalic acid (usually oxalic acid dihy-
drate) ammonium oxalate or water solutions of these to the re-
sole system. Factors such as agitation and temperature are im-
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portant in obtaining a fine particle dispersion. Neutralization
is carried out in the range of 25 to 75C., preferably 30-60C.,
wherein precipitation of the inert salts occur. Generally, the
higher the temperature the finer the precipitated particle.
Agitation should be consistent with the mixing required for a
given vessel and known engineering practices for stirred tanks.
Generally, the higher the agitation the smaller the particle
size and can be adjusted to an intensity consistent with the
particle size required by simple experimentation for a specific
stirred tank.
The oxalate salt formed in water dispersion are charac-
terized by excellent stability with regard to sedimentation and
shear. Particle size is extremely small being below 2~4 and
normally averaging from about 0.01 to 1.0,4 , preferably 0.02 to
0.8~ .
The inert salts unexpectedly do not flocculate or pre-
cipitate and are stable in water solutions of the resole resins
of this invention if the resole resin content is from about 40
to 98% by weight. If the solutions are diluted to lower than
about 40% solids then flocculation and precipitation of the
salts can occur. Hence, although the resole resins as resins
are highly dilutable, and have a water tolerance greater than
500% the aqueous resole solutions containing the inert salts are
not since the inert salts will flocculate in solutions contain-
ing less than about 40% by weight of resole resins solids. Theresole resin solutions having dispersed inert salts can be made
dilutable by the addition of an anionic dispersing agent to in-
hibit the flocculation of the salts.
The preparation of the resole resin solutions preferably
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C-06-12-0522
used in the present composition have been disclosed in U. S.
Patent No. 4,011,186.
The resole resins then are solutions having varying
amounts of water with a resin solids content of 60 to 99%. How-
ever, in foamable compositions, the preferred resole resin solu-
tions have water contents of less than 10%. A water-content of
more than 10% in the resin is detrimental in that it absorbs too
much exothermic heat in the acid catalyzed blowing step and thus
less expansion takes place whereby undesirably high apparent
density products of non-uniform texture and large voids are ob-
tained. When cellular structures of very low apparent density
(0.2 to 2.0 pounds per cubic foot) are to be made, a water-con-
tent less than 5% in the "A" stage reaction product is preferred.
The resoles may have a viscosity of from about lO0 to
200,000 centipoise preferably 200 to 4000 cps. If the viscosity
is too low, there is a tendency for the foaming agents to vola-
tilize in the form of large bubbles. Foams thus produced are
characterized by an open cellular structure and large voids
which are not desired in foams used for insulating purposes.
The viscosity range required for the particular foaming agent
used can be determined by one skilled in the art. The size of
the cells in the above-described foaming materials is determined
by a number of other factors: the size of the cells depends for
one thing on the nature and quantity of the blowing atent used,
the reaction temperature, and the hardening characteristics of
the resin. Thus, by changing the type and quantity of the foam-
ing or interlacing agent, the temperature employed and the compo-
sition of the resin, it is possible to produce foams of different
density, hardness and rigidity, i.e., foams having pores of dif-
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ferent sizes.
The resoles preferably used in the present composition
are the reaction product of a phenol and an aldehyde. Generally,
from about 1.3 to 2.8 mols of aldehyde per mol of phenol are em-
ployed. The lowest density foamed structures (0.2 pound percubic foot) have been obtained when condensation products were
used based on 1.3 to 1.6 mols of formaldehyde reacted per mol of
phenol. Phenolic condensation products in which more than 1.6
mols and up to 3 mols of formaldehyde have been reacted with the
phenol tend to release loosely bound formaldehyde during the
acid-catalyzed reaction. Since this release of formaldehyde is
an endothermic type of reaction, it correspondingly reduced the
amount of exothermic heat of reaction caused by the acid cata-
lyst. Therefore, there is less heat available for vaporizing the
volatile matter in the reaction mixture whereby a lower degree of
expansion occurs resulting in cellular structures of higher ap-
parent densities, e.g., 2 to 20 pounds per cubic foot. On the
other hand, "A" stage condensation products having a reacted
formaldehyde ratio between 1.0 and 1.2 mols per mol of phenol
tend to harden before maximum expansion can occur and have less
exothermic heat; this is reflected by a somewhat higher density
of the foamed structures made therefrom.
Typical of the phenols that are useful in producing
suitable resole resins are those represented by the formula
OH
R' ~ R'
R ~ R
I
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C-06-12-0522
wherein at least two groups represented by R' are hydrogen atoms
and the groups represen-ted by R and any remaining group repre-
sented by R' are hydrogen atoms or groups which do not impede the
condensation of the phenol with an aldehyde (e.g., a substituent
such as halogen atom or a hydroxy, alkyl or aryl group). Illus-
trative of suitable phenols are phenol, cresols (particularly
m-cresol), xylenols (particularly 3,5-xylenol) and dihydroxyben-
zenes (particularly resorcinol). Typical of the aldehydes that
can be useful in producing suitable resole resins are formalde-
hyde (including the oligomers and polymers of formaldehyde suchas trioxane), furfural, sugars and cellulose hydrolyzates. Such
aldehydes can be employed without dilution or dissolved in suit-
able solvents including aqueous alcohols (e.g. aqueous methanol,
n-propanol, isobutanol or n-butanol).
FOAM PREPARATION
The manufacture of the foams is generally performed by
thoroughly mixing a phenolic resole resin with a surface active
substance, a metal powder to form said foamable resole resin com-
position. When uniformly mixed an acid curing agent is uniformly
mixed with said composition and the composition allowed to foam
and cure using the reaction exotherm or applied heat. The tem-
perature of the reaction is generally kept under 100C. if a
closed cell foam is desired. Higher temperatures can be used to
form open-celled foams.
The foaming of the phenolic resin is performed after the
individual components have been mixed together, the blowing agent
being transformed to the gaseous state. Depending on the compo-
sition of the mixture to be foamed, the foaming takes place at
temperatures between 0 and 100C., preferably at 15 to 60C.
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The resin can be foamed either in open or in closed molds to pro-
duce bodies of a shape corresponding to the shape of the open or
closed mold selected.
It is also possigle to perform the foaming process con-
tinuously in a double band press. In this case the componentsare proportioned and mixed by means of a known automatic pro-
portioning and mixing apparatus and the mixture is fed continu-
ously to the bands of a double band press by means of a charging
device moving crosswise to the direction of movement. Then the
mixture is passed through a gap of selectable thickness formed
between one roll and a support which may, if desired, also be a
roll. The rolls can be preheated if desired. By this process
boards of selectable thickness are obtained.
The hardening is generally so controlled that, as soon
as the desired foam volume is reached, the foam structure has
solidified to such an extent as to forestall collapse.
SURFACTANTS
Improvements in foam cell uniformity and size are se-
cured by the use of a surface active agent. Particularly useful
are the non-ionic types such as polyethers and polyalcohols, such
as condensation products of alkylene oxides (such as ethylene
oxide and propylene oxide) with alkyl phenols, fatty acids, alkyl
silanes and silicones and like materials, as is exemplified by
such products as octadecyl phenol-ethylene oxide, decyl phenol-
ethylene oxide sulfate and the low polymers of such materials aspolyoxyethylene dodecyl phenol, octyl phenol polyethylene glycol
ether, ricinoleic acid polyethylene glycolate, stearic acid
polyoxyethylene, glycolates and similar polyoxyethylates fatty
acids and vegetagle oils as well as polyoxyethylated fatty acid
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esters as polyoxyethylene sorbitan monolaurate, polyoxyethylene
sorbitan tristearate, polyoxypropylene sorbitan monolaurate,
polyoxy(propylene-ethylene) sorbitan monolaurate and polyoxy-
ethylene sorbitan pentaoleate; polyoxyethylene sorbitan mono-
palmitate and siloxane-oxyalkylene block copolymers such as those
containing a Si-0-C linkage between the siloxane and oxyalkylene
. , .
;i ~ moieties and those containing a Si-C linkage between the silox-
~ ane and oxyalkylene moieties. Typical siloxane-oxyalkylene
,. :
block copolymers contain a siloxane moiety composed of recurring
; lO dimethylsiloxy groups end-blocked with monomethylsiloxy and/or
trimethylsiloxy groups and an oxyalkylene moiety composed of re-
curring oxyethylene and/or oxypropylene groups end-blocked with
s~ alkoxy groups. Similarly useful are the quaternary ammonium
compounds with at least 2 alkyl groups attached to the nitrogen
atom like cetyl dimethyl benzyl ammonium chloride, octadecyl
` dimethyl benzyl ammonium chloride, octadecanol-9-dimethyl ethyl
ammonium bromide and diisobutylphenoxyethoxy ethyl dimethyl
benzyl ammonium chloride and sorbitan fatty acid esters such as
sorbitan monolaurate, sorbitan monopalmitate sorbitan mono-
stearate, sorbitan trloleate and like esters.
- When present, these surface active agents can be em-
-~ ployed in any desired amount depending on what results are de-
sired. They serve to aid the generation of smaller and more
uniform cells. Best results seem to be secured in using amounts
from 0.3 to about S% by weight of the agent based on the weight
of resole resin with preferred results at between about 0.5 to
3% by weight. Certain surfactants may cause collapse of the
foam if employed in too great a concentration and optimum con-
centration may vary with the individual surfactant selected.
.
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BLOWING AGENTS
The foaming agents which may be used to foam the resins
of this invention include carbon dioxide liberating materials,
low boiling aliphatic hydrocarbons, polyhalogenated saturated
fluorocarbons and ethers. Exemplary of carbon dioxide, liberat-
ing compounds are alkali and alkaline earth carbonates such as
sodium bicarbonate or calcium carbonate which, in the presence
of an acid, liberate carbon dioxide. Another group of blowing
agents comprises low-boiling organic compounds, such as carbon-
tetrachloride, ethylene dichloride, n-butyl ether, methylal,
n-pentane, chlorofluoromethane or the like. These latter mate-
rials are vaporized by the heat evolved in the condensation of
the resin or by additionally supplied heat, thereby bringing
about foaming of the liquid phenolic resin. Simultaneously with
the foaming process, the hardèner present in the mixture pro-
duces an increasing solidification and finally a hardening of
the foam.
Fluorocarbon foaming agents which may be used include
dichlorodifluoromethane, 1,2-dichloro-1,1,2,2-tetrafluoro-
ethane, 1,1,1-trichloro-2,2,2-trifluoroethane, 1,2-difluoro-
ethane and trichlorofluoromethane. The compounds should have
boiling points ranging from about -30 to 125C. The blowing
agents are employed in an amount sufficient to give the result-
ant foam the desired bulk density which is generally between
0.5 to 10 and preferably between 1 and 5 pounds per cubic foot.
The blowing agent generally comprises from 1 to 30, and prefer-
ably comprises from 5 to 20, weight percent of the composition.
When the blowing agent has a boiling point at or below ambient,
it is maintained under pressure until mixed with the other com-
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ponents. Alternatively, it can be maintained at subambient
temperature until mixed with the other components.
ACID CATALYSTS
As hardeners both liquid and pulverulent substances may
be utilized. The quantity required partially depends on the
foaming agent used. If the foaming agent consists of a solid
salt which evolves gases, part of the acid is used to release
the gases. If low-boiling solvents are employed as foaming
agent, the proportion of hardener is lower in accordance there-
with. In addition to mineral acids such as HCl, H2S04 and the
like, water-soluble sulfonic acids are particularly well suited
as water-soluble acids, i.e., those sulfonic acids where the
sulfonic acid group is directly linked to an aromatic ring which
may be substituted. Examples thereof include benzene sulfonic
acid, p-toluene sulfonic acid., phenol sulfonic acid, cresol sul-
fonic acid and the like. The aqueous solutions of these acids
are mainly utilized as 40 to 70% by weight solutions. Some
acids, such as p-toluene sulfonic acid, may also be used in the
pulverulent foam as hardener. The quantity O r the hardener used
varies between about 1 and 15% by weight, calculated as 100%
acid, based on phenol-resole resin.
The preferred sulfonic acid is a mixture of equal parts
by weight of toluene sulfonic acid and xylene sulfonic acid, as
described in Mausner et.al. U. S. Patent No. 3,458,449. Another
foaming catalyst which has been found to give excellent results
are novolac sulfonic acids, described in British Patent No.
1,283,113.
The catalyst is generally present in the minimum amount
that will give the desired cream times of 10 to 50 seconds and
_ 14 -
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firm times of 40 to 500 seconds to the reacting mixture. The
catalyst, however, generally comprises foam 0.5 to 20, and
preferably comprises from 1.0 to 15 weight percent based on the
weight of the resole resin.
The following examples will further illustrate the
present invention, however, it is to be understood that the
scope of the invention is not limited by the examples.
METAL POWDERS
Corrosion resistance for the foamable composition and
the cured foam is gained by dispersing particular powdered
metals in the foamable resole composition. The powdered metals
are selected from the group consisting of zinc, iron, magne-
sium, calcium and barium or mixtures thereof. The particle
size of such metal powders have been found to be most effective
if they have a particle size of about -lOO mesh size, prefer-
ably -140 mesh size, i.e., all particles pass through a 100 or
preferably a 140 mesh screen. Larger particles may be used,
however, larger particles detract from the appearance and
physical properties of the foam. The mesh or sieve sizes dis-
closed refer to U. S. Sieve Series of the U. S. Bureau of
Standards.
The powdered metals can be dispersed in the resole com-
position by conventional means such as stirred tanks or mixers,
continuous ribbon blenders or mixers wherein the mixing agita-
tion is sufficient to disperse the metal powder uniformly in
the resole composition in amounts of 1 to 15% by weight, pre-
ferable 2 to 10% based on the amount of acid used.
Phenolic foams are prepared by adding a strong acid
catalys-t to a resole resin composition generally having 1 to
_ 15 -
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C-06-12-0522
20% by weight of a blowing agent and 0.3 to 5% by weight of a
surfactant all based on said resole resin composition. Said
acid catalyst is present in an amount of 0.5 to 20% by weight
based on the weight of said resole composition. The acid cata-
lyst brings the pH of the resole composition to generally less
than a pH of 3 giving an exotherm to aid in blowing said foam
and causing rapid methylene bridge formation to crosslink and
cure the foam. The strong acids remain in the foam and are
water leachable leading to corrosion problems.
Most basic materials if added to the resole composition
before catalyst addition, e.g., metal oxides, hydroxides and
carbonates react preferentially and rapidly with the acid cata-
lyst reducing its effectiveness as a catalyst. It has been
found that metal powders will unexpectedly allow the resin com-
`~ lS position to foam and cure with acid catalysts yet yield a cured
foam having a ph of about 5 to 10. Corrosion tests showed the
` foam to be non-corrosive as disclosed in the Examples.
`~ EXAMPLE 1
A base catalyzed aqueous resole resin solution is pre-
pared by reacting 1.57 mol of aqueous formaldehyde (50%) per 1
mol of phenol in the presence of 0.035 mol of sodium hydroxide
and 0.032 mol of calcium hydroxide, initially below 60C., to
control reaction exotherm. The reaction is then conducted at
60-70C. range until the unreacted formaldehyde content drops
below 0.5%. The reaction is cooled to 40C. and 0.033 mol of
oxalic acid is added with agitation. The resulting resin has
a viscosity of 450 cps.
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EXAMPLE 2
A base catalyzed resole resin solution is prepared by
reacting 2.54 mol of aqueous formaldehyde (50%) per l mol of
phenol in the presence of 0.035 mol of sodium hydroxide and 0.14
mol of calcium hydroxide, initially below 60C., to control re-
action exotherm. The reaction is then conducted at 70C., re-
flux until the unreacted formaldehyde content drops to 2.3%.
The reaction is cooled to 50C., and 0.14 mol of oxalic acid
is added rapidly with agitation. The viscous dispersion
(Brookfield viscosity 3800 cps) is stable to storage at 0-10C.,
with no bottom settling.
EXAMPLES 3 - 28
To 100 parts of resole resin of Example 2 were added 10
parts of Freon 113(a) and 2 parts DC-193(b) surfactant and
mixed. The Ultra TX(C) acid (50% in glycerine) was mixed in.
The latent acid neutralizers (metal powders) when used, were
added before the acid. The following examples show the effect
of latent acid neutralizers of this invention upon foam forma-
tion, pH of foamed composition and corrosion of iron metal
tabs in foamed composition.
- 17 -
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