Note: Descriptions are shown in the official language in which they were submitted.
t ~64~
The present invention relates to a method making
novolak resins. Ilovolaks are well known thermoplastic
phenol-aldehyde type and phenol-ketone type resins ob-
tained primarily by the use of the acid catalyst and excess
phenol. Tl~ese resins are generally alcohol soluble, and
typically require reaction with furfuryl alcohol, hexamethy-
lenetetramine, para-formaldehyde, etc., for conversion to
cured, crosslinked structures by heating, for example to
200-~00 F. The result of the acid-catalyzed reaction be-
tween a phenol and an aldehyde or ketone when an excess ofphenol is present, is a completed reaction in which the in-
dividual polymers have no ability to continue growin~ in
molecular weight once the aldehyde or ketone in the batch
has been consumed. Consequently, because of this stability
it has been regarded as of no importance that the catalyst
which is used in the manufacture of novolak reSi!lS be allow--
ed to remain ul?neutrali~ed in the reaction mixture so that
at the time that the water which is present in the reaction
mixture is stripped off, the pH of the reaction mixture is
between 2~5 and 1Ø ~rpically, upon stripping of the water
from the reaction mixture and cooling of the resulting resin,
a very high viscosity liquid or a solid novolak results. It
has been well known to use these resins, for example, by
grinding the resulting solid novolak resin and then mixing
them with furfuryl alcohol for use as foundry bindcrs, and
the like. Such mixtures are well known to be acid-curable
1 ~ 6Ql~l
-- 2 ~
and provide the advantage of a "high-solids" resin mixture.
In addition, novolak resin, when cured, ls recog-
nized to provide high perce~tage of carbon residue so that
it ranks approximately at the same level as cured furfuryl
alcohol resin with respect to efficiency in generation of
high carbon residue.
One of the disad~antages of one of the widely used
methods of manufacture of novolak resins heretofore avail-
able has been the requirement of the intermediate step of
converting the resin into a solid by cooling, e.g. in a fla-
king step, and then grindijng the resulting solid and admix-
ing the resulting powdered ~ovolak with a suitable solvent.
In order to make the "solid" novolaks grindable the resins
had to be stripped drastically during original manufacture
to remove substantially all traces of unreacted phenol. It
has been regarded as good ~ommercial practice for stripping
to continue until the melti~g point is elevated to at least
100C. to facilitate grlndi~g. Traces of phenol would ren-
der the powdery ground material fusable on storage, and the
resulting fused or lumpy solid resins were difEicult to
work with. Such problems are only partially alleviated by
an alternative method commonly using, methyl or ethyl alco-
hol, for example, to dissolve the stripped, but unneutrali-
zed novolak polymer in the reactive vessel. However, such
a solution is not 100% rea~ctive, and cannot normally be
used unless or until the inert solvent is volatilized in-
to the atmosphere at the point of use.
Another object of the present invention is the
elimination of the manufacturing steps in the manufacture
of novolak resins in which the novolak resin is converted
into an intermediate solid and in which an intermediate
grinding step is required.
The present invention provides a method of manu-
facturing a novolak resin comprising the steps of reacting,
at an elevated reaction temperature, an excess of a phenol
with aldehyde or ketone under acidic conditions, allowing
the reaction to continue until substantially all the al-
dehyde or ketone is reacted, stripping most of the water
and unreacted phenol from the reaction mixture after the
.,
~ 164~
-- 3
presence of aldehyde or ketone has substantially disappeared,
neutralizing the resulting novolak resin to provide a pH above
5.5, and adding to the resulting neutralized, novolak resin in
the reaction vessel, either before or immediately after strip-
ping, while the resin is still liquid and at a temperature ofabout 100C, a furan-containing solvent which is at ambient
room temperature, said solvent being selected from furfuryl
alcohol, furfural, or mixtures thereof, said solvent being
added in an amount sufficient to maintain the resulting novo-
lak resin solution as a liquid having a viscosity of lO0 000cps or less at 20C. In accordance with the present invention, a stream-
lined method of the manufacture of a 100% reactive liquid no-
volak resin is provided, which method results in a novolak re-
sin which is acid curable in addilion to being curable in theconventional manner, e.g. with hydroxymethylaminetetramine,
and in preferred embodiments is either acid or base curable,
and which provides high carbon residues, and from which no
inert organic solvent must be used at point of application or
use.
An advantage flowing from the present invention is
the fact that in the original manufacture reactor, the pro-
duct of the invention has reduced viscosity thus speeding up
and otherwise facilitating the removal of the resin from the
novolak reactor, or other containers.
In carrying out the present invention of a furan-
containing solvent selected from the group consisting of fur-
furyl alcohol and furfural and mixtures thereof is admixed
with the freshly prepared novolak resin after it has been neu-
tralized and either before or after it has been stripped,while it is still in the liq~id condition. In accordance
with a preferred embodiment ~f the present invention the
quantity of furan-containing solvent which is admixed with
the neutralized, stripped novolak resin is sufficient to
provide a fluid novolak resi~ at room temperature such as for
example a solution having a viscosity lO0 000 cps or less
at 20C., when the hot novolak solution is cooled to ambient
room temperature within 30 minutes of the time at which the
furfuryl alcohol is first added.
" ,, ~
- 3a -
When the levels of furfuryl alcohol are admixed to
provide the resulting novolak resin solution with approximate~
ly 10% furfuryl alcohol the resulting solution can be char-
~ 16414~
acterized as a gummy viscous mass. On the other hand, gen-
erally speaking, when levels of furfuryl alcohol are used
that would provide between 25 and 30~ monomeric furfuryl
alcohol in the resulting novolak resin solution, viscosi-
ties less than 100,000, usually less than 50,000 cps at
20 C. are normally encountered. Generally speaking the
amount of the furan-containing solvent which can be used
in accordance with the present invention can be relatively
high levels, e.g. up to 50~ and higher. It is preferred
that sufficient solvent be added to result in a solution
which has at least 15% solvent, based on the weight of the
solution.
Furthermore, it is highly desirable in order to
achieve maximum benefit of the present invention to apply
positive cooling means to quickly drop the temperature of
the novokal solution as soon as it is formed, so that am-
bient room temperature conditions are quickly achieved.
The furfuryl alcohol or furfural is added while the novolak
resin is still hot enough to be in a liquid, readily mixed
condition, although the temperature can be decreased sub-
stantially from the strippin~ temperature, e.g. by cooling,
or by addition of incremented portion of the cold furfuryl
alcohol or furfural, before the solution is completely form-
ed by addition of the rest of the furan-containing solvent.
In the manufacture of novolak resins, a phenol,
(this term is discussed more fully hereinafter), is allow-
ed to react with an aldehyde, or ketone typically in the
presence of water, at acid pH's, under reflux conditions.
For example, oxalic acid is used in quantities sufficient
to provide a pH of about 2.5-4.0 in the aqueous system.
Typically the reactions are allowed to proceed at reflux
conditions until the aldehyde or ketone is determined to be
(by conventional titration) absent from the reaction mixture,
and at least a slight excess of phenol is allowed to remain.
Up to this point the methods by which novolak resins are
produced are entirely conventional, and the method of the
present invention relates to an improvement in the subse-
quent steps. Consequently any conventional method for re-
acting phenol with an aldehyde in an acid medium with an ex-
l 164~
-- 5 --cess of phenol are contemplated as within the purview of
the practice improved by the present invention.
After the conventional manufacturing titrations
have determined that the aldehyde or ketone level has been
reduced substantially to zero, the reaction is regarded as
"terminated". In typical conventional practice heretofore,
the novolak-water mixture containing sufficient acid to pro-
vide a pH in the range of 2.~-4.0, for example, is immedi-
ately stripped usually under reduced pressure conditions
with the result that the free unneutralized acid is typic~l-
ly allowed to remain in the novolak resin upon the comple-
tion of its manufacture.
However, ln acc~rdance with the practice of the
present invention, the novolak is neutralized prior to fur-
ther processing. This can be achieved, in accordance with
the present invention, for example, by addition to the re-
action mixture of any suitable basic material such as, for
example, a solution of sodium hydroxide. Alkali metal hy-
droxides, and carbonates, and other non-reactive alkaline
materials can be employed. The amount of sodium hydroxide
which is added, or other basic neutralizing material, is
an amount sufficient to bring the p~l of the resulting resin
to ~t least 5.5 and preferably substantially above 6Ø The
preferred neutralizcd pH range is between 6.0 and 7. Neu-
tralizing to a p~ above 7 i5 permissable unless the furfural
cyclohexanone mixture is used as a solvent, in which case
the pH should be below 7Ø The neutralization preferably
takes place while there is a substantial amount of water
still in the reaction mixture, although the novolak resin
can be stripped to remove the water, either before or after
the addition of the basic material to neutralize the reaction
mixture.
The furan-containing solvent can be added either
before or after the stripping is completed. However, it is
preferred that it be added after stripping. Thus, in a pre-
ferred embodiment, after the stripping step has been complet-
ed and most of the water has been removed from the reaction
mixture (for example up to 4~ or so water can remain, typic-
ally) the furan-containing solvent is added. In a preferred
t ~64141
embodiment the hot novolak resin is cooled substantially be-
fore addition of the furan-containing solvent, e.g. to a
temperature below 150 F. but at which the resin is still a
liquid. Also, the furfuryl alcohol can be added incremental-
ly so that the fluidity is maintained during cooling, with
a large portion of the solvent being added near ambient
temperature conditions. This is to maximize the effect of
the solvent with respect to imparting fluidity. As used
herein the term "cooling" is intended to denote a positive
application of cooling means, such as, for example, con-
tacting the liquid with a heat exchange surface maintained
at temperatures substantially lower than the temperature of
the liquid, resulting in a` rapid reduction in temperature
of the liquid. "Cooling" does not necessarily indicate
that temperatures below ambient room temperatures are
achieved. Another positive application of cooling means in-
cludes the addition of "cold" furan-containing solvent, e.
g. solvent at ambient room temperature. Addition of a sub-
stantial quantity of cold solvent abruptly drops the tem-
perature of the liquid, and because of increased flui~ity,increased cooling efficiency at the heat exchange surfaces
are achieved, as well. As used herein, "cold" is intended
to refer to a temperature which is at least 50 F. below the
temperature of the liquid to which the "cold" material is
added. For example, ambient oom temperature furan-con-
taining solvent is "cold" as used herein for the purpose of
addition of the solvent to the hot resin liquid resulting in
abrupt drop of its temperature. The total amount of furan-
containing solvent which is added is an amount sufficient to
liquify the resulting novolak resin at room temperature, e.
g. 20 C. The preferred levels of furfuryl alcohol or furfur-
al solvent which are included, however, are at least 15~
based on the weight of the resulting solution, and amounts
sufficient to provide between 25 and 35~ of furan-containing
solvent is preferred.
Generally speaking, as used herein, the term
"novolak" and "novolak resin" denote a condensation product
such as is obtained by causing a phenol to condense with less
than an equimolar portion of an aldehyde or a ketone, in an
l 16~
-- 7
acidic environment. Structurally the molecules of a novo-
lak consist essentially of alkyl-substituted or unsubsti-
tuted phenylol nuclei connected together by methylene or
substituted methylene links. Although phenol and formal-
dehyde are preferred condensation reactants, other sub-
stances may be used. For example, phenol may be substi-
tuted with cresol, xylenols, mixtures of cresols and xylen-
ols, and epoxy resins such as the condensation products of
bis-phenol with epichlorohydrin; and formaldehyde can be
substituted with other water-soluble and phenol-reactive
aldehydes such as acetaldehyde and propienealdehyde. In
fact, the manufacture of any phenolic resin of the novolak
type can he improved in accordance with the present inven-
tion. Such resins, for example, are produced by condensing
phenol such as phenol itself, m-cresol, p-cresol, o-cresol,
3,5-xylenol, 3,4-xylenol, 2,5-xylenol, p-ethylphenol, p-ter-t-
butylphenol, p-tert-amylphenol, p-tert-oxtylphenol, p-
phenylphenol, 2,3,5-trimethylphenol, resorcinol, and the
like.
In the following examples, unless otherwise indi-
cated, all percents are expressed in percent by weight, parts
are parts by weight, and temperatures are expressed in F.
Example 1
A mixture of phenol and aqueous formaldehyde is
prepared at a ratio of 1.15 phenol to 1.00 moles of for-
maldehyde. A sufficient quantity of oxalic acid is admixed
therewith to provide a pH of about 3.0 and the reaction mix-
ture is allowed to react under atmospheric reflux tempera-
ture conditions until all of the formaldehyde disappears.
~0 Thereafter, a sufficient quantity of aqueous sodium hydro-
xide is added to the reaction mixture to elevate the pH of
the reaction mixture to approximately 6.3. Thereafter the
refluxing condensor is removed and most of the water and un-
reacted phenol is allowed to be removed from the reaction
mixture in the conventional reduced pressure distillation
stripping step. ~hen the water removal, stripping step is
substantially completed, sufficient furfuryl alcohol is ad-
ded to the stripped novolak resin which is at an elevated
temperature of about 100 C. to provide a resulting solution
~ 1641~4~
-- 8 --
having about 20 percent of furfuryl alcoholO Immediately
after admixing the solution is cooled to room temperature
within 30 minutes. The resulting neutralized solution is
storage stable.
Example 2
The procedure of Example 1 is repeated, except
that, instead of furfuryl alcohol, the same quanitity of
furfural is added to the hot, neutrallzed, stripped, nov-
olak liquid resin. Likewise a liquid solution result which
has similar fluidity at ambient temperature conditions.
This resulting novolak resin solution is storage stable.
Example 3
The procedure of Example 1 is repeated except
that instead of furfuryl alcohol, the same amount of a sol-
ution of 66% furfural and 33% cyclohexanone is added to the
hot novolak resin. Likewise a similarly fluid solution of
novolak resin is obtained. The resulting resin solution is
found to be readily curable under either acidic or basic
conditions, but is storage stable, as produced in accordance
with this invention.
Example 4
Relatively fine particulate carbon is admixed with
a pre-catalyzed novolak resin mixture comprising catalyst
and resin, the catalyst being a 50:50 mix oE maleic anhy-
dride and furfural, the resin being produced in accordance
with Example 1. The catalyst and resin were used in respec-
tive amounts sufficient to provide about 4% maleic anhydride
based on the weight of the resin and about 24% weight of
resin based on the weight of the particulate carbond. The
resulting admixture is shaped into the form of an electrode,
and heated to about 200 F. Upon heating the binder- cures in-
to a solid, and a strong carbon form in the shape of an elec-
trode is produced.
E_ ple 5
Particle board ingredients comprising wood chips,
saw dust, wood dust, and the like, are admixed with a pre-
catalyzed novolak resin mixture comprising catalyst and
resin, the catalyst being a 50:50 mix of maleic anhydride
l 16~14~
g
and furfural, the resin being produced in accordance with
Example 1 the catalyst and resin were used in respective
amounts suffi`cient to provide approximately 5% maleic an-
hydride based on the weight of the resin and 6% by weight
of the resin solution based on the weight of the wood par-
ticulate ingredients. The resulting mass is pressed into
the shape of a board and heated to 300 F. to trigger the
curing of the resin. A hiyh-strength particle board re-
sults from the curing step.
Example 6
Calcined magnesite is admixed with a pre mixture
of triethanolamine, and th~ liquid novolak resin solution
produced in Example 1 (in which furfural-cychlohexanone
mixture was used instead of furfuryl alcohol). The trie-
thanolamine catalyst is used in an amount sufficient to
provide between 5--10% based on the weight of the resin,
and the amount of resin solution which is used is sufficient
to provide 6% by weight based on the weight of the basic
magnesite. qhe resulting mixture is formed into a de-
sired brick form, heated, and the resin cures into a solid.The resulting magnesite brick can be used under very high
temperature conditions. At high temperatures the binder
is carbonized and the carbon formed improves the perfor-
mance and prolongs the life of the brick.
Example 7
Furfuryl alcohol, novolak resin, and the novolak
resin solution produced in accordance with Example 1 and 3
are respectively tested to determine carbon residue using
the Conradson Carbon Residue Test identified as follows:
In this test a weighed quantity of the material, or solu-
tion to be tested, is admixed with a known quantity of
catalyst, and placed in a crucible containing glass boiling
beads. The assembly is then weighed and post cured by
heating 2 hours at 180 F., 2 hours at 200 F., and 16 hours
at 300 F. The resulting post cured assembly is then placed
in a Conradson apparatus which comprises a second crucible
1 ~B~
-- 10 --
partially filled with a coke flour. The entire unit is
heated to temperatures set forth in the ASTM Procedure,
about 900 C. The cured material or solution then thermal-
ly disinter~rates. The weight loss is finally determined
and the residue (carbon) is calculated. The results of
the test are summarized in Table I.
TABLE I
Material Tested C rbon Residue
Straight Furfuryl Alcohol (acid cured 48
10 Novolak Resin (hexamethyltetramine-
acid cured . 48
The product of Example 1 (acid cured) 48
The Product of Example 3 (base cured) 33
The Product of Example 3 (acid cured) 45
Example 8
The tests oE Example 1 were repeated, except that
in Example 8, sufficient furfuryl alcohol was used to pro-
ide about 2a% by weight in the resulting novolak resin.
The resulting solution was found to be acid curable, and
20 had a stable viscosity of about 40,000 cps at room tem-
perature.
Example 9
This example provides a comparison of the effect
of pH, solvent concentration and effect of hot-holding time
on the viscosity of the novolak resin produced in accordance
with the invention.
TEST A
In a laboratory glassware kettle, the novolak
resin was prepared in accordance with the general method
30 described in Example 1. TTowever, the novolak was neutrali-
zed to a pH of 5.7 with a sodium hydroxide solu-tion while
refluxing, the resin was then stripped and furfuryl alcohol
in an amount sufficient to provide 30% furfuryl alcohol in
t 1641~
the resulting solution was addecl. The urfuryl alcohol was
added while cold, i.e. at ambient room temperature. The
stirring was allowed to continue, and the temperature of the
resulting solution was allowed to gradually achieve ambient
room temperature condition without further cooling other
than ambient air cooling. The viscosity of the resulting
product was found to be 39,000 cps at 20 C.
TEST B
In this test, the novolak resin was again pre~
pared by the identical procedure used in Test A above, and
in a pilot plant reactor equipped with a water cooling
jacket. After the phenol ormaldehyde reaction was com-
plete, the novolak was neutralized to a pH of 6.9, with a
sodium hydroxide solution while refluxing, the resin was
then stripped, and furfuryl alcohol in an amount sufficient
to provide 30~ furfuryl alcoho] in the resulting solution
was added. The furfuryl alcohol was added cold, and im-
mediately upon completion of the addition of the furfuryl
alcohol, cooling was applied rapidly by means of cold water
in the water jacket. The resulting solution was found to
have a viscosity of 3,500 cps at 20 C.
TEST C
In this test, the procedure of producing the
novolak resin of Tests A and B above was repeated in sep-
arate production runs, except that after stripping, the hot
liquid neutralized resin was sampled and six separate sam-
ples of each respective resin batch were aliquoted into
glass laboratory beakers which were placed on a laboratory
hot plate and maintained at 200 F. Into each of the re
spective beakers of each series of samples, different
quantities of furfuryl alcohol were added, to provide in
the respective beakers resulting solutions having 20, 25,
30, 35, 40 and 45% furfuryl alcohol respectively for each
series. The alcohol in this test, however, was added at
the same high temperature as the resin namely 200 F. After
thorough sti`rring, the resins were allowed to gradually be
l 16~14~
- 12 -
cooled with ambient air cooling to ambient room temperature
condi`tlons.
- The results of the two serles of tests of Test C
are reported on Table II.
TABLE II
_.
Viscosity (cps/room temp.)
% Furfuryl Alcohol pH 6.9 pH 5.7
5,000,0007.000,000
1,600,000
`246,0001,500,000
79,000 512,000
36,000 83,000
40 (100 C/8 hr.) 71,000 141,000
It is noted that in Test A and B, cold furfuryl al-
cohol was- added, and this resulted in a substantial decrease
in temperature immediately. In Test A, in which the resin
was allowed to be maintained at elevated temperature prior
to addition of the furan-containing solvent, and were main-
tained at elevated temperature for a long time as a result
of inefficient ambient air cooling, however, the result-
ing viscosities were relatively high, e.g. almost ~0,000
compared to the relatively low viscosity i.e. 3,500 cps
at 20 C. which was achieved in Test B in which the mixture
was cooled quickly to ambient temperature conditions.
~lso, it is apparent from Table II that neutralization to
the pH of 5.7 produced viscosities which are generally
speaking, almost twice that achieved by corresponding di-
lutions of novolak resin which had been neutralized to the
pH of 6.9. Nonetheless, in Test C in which hot furfuryl al-
cohol is added to the novolak resin, and in which the re-
sulting solutions are not cooled quickly, the viscosities
for corresponding levels of furfuryl alcohol are vastly
higher than the viscosities which are achieved with sudden
cooling of the solution by addition of cold (ambient tempera-
t 16~4~
- 13 -
ture~ furan-containing solvent thereto.
We know of no chemical or physical explanation
of this phenomenon at this time.
Thus, it will be appreciated from the above dis-
closure that the method of manufacturing liquid novolak
resin in accordance with this invention has been sub-
stantially streamlined with no significant adverse impact
with respect to the production of high carbon -residue acid
curable binders. Also this invention gives an alkaline
10 curable binder, e.g. with furfural cyclohexanone solvent,
which ranks very high among alkaline curable resins, with
respect to relatively high carbon residues.
The convention of the novolak resin to an inter-
mediate solid, with the inherent requirement of grinding
and other processing of the solid material, has been elimin-
ated, in accordance with the present invention. An easily
handled, readily applied liquid novolak resin solution is
produced.
