Note: Descriptions are shown in the official language in which they were submitted.
~038994
This invention relates to epoxy novolac resins
and a process for preparing them. More particularly, the
invention relates to an epoxy novolac resin having a narrow
molecular weight distribution represented by the general
formula
~O~CH l_CH2_CH_CH2 O-CH2-CH-CH2
~ C~l ~ ,C~j~
wherein each R is independently hydrogen or an alkyl
group having from 1 to 5 carbon atoms, each R' is
independently hydrogen, chlorine, bromine, an alkyl
group having from 1 to 6 carbon atoms or a glycidyloxy
group and n has an average value greater than 0.1 and
such that the viscosity in centistokes at 70C to average
EgW ratio is less than 11:1 when the weight average
molecular weight of the resin is below 2000 and a plot
lS of Mw vs Mw:Mn falls on or within the area bounded by
A, B, C, D in Figure 1 when the weight average molecular
weight is above 2000.
The process of the present invention comprises
q (A) dissolving an epoxy novolac resin having a wide
. 20 molecular weight distribution in xylene, toluene, methyl
isobutyl ketone, a solvent having a solubility parameter
of 8.0-9.0 with low to mèdium hydrogen bonding, a solvent
having a solubility parameter >11.5 and any hydrogen
bonding value, or a mixture of such solvents, at a tem-
perature between 50C and the boiling point of the
, solvent, wherein the quantity of solvent is from 30% to
,:
~ ' ~ .
~ 9~ '; ~' ' .'
l7,296-F ra~
1038994
90~ by weight of the combined weight of solvent and resin,
(B) cooling the resultant solution to a temperature below
50C and the freezing point of the solvent for a period of
time sufficient to cause a separation into two distinct
phases, (C) separating the two phases one from the other,
and (D) removing the solvent from each of the phases;
thereby producing (1) an epoxy novolac resin wherein the
weight average molecular weight is below 2000 and the
viscosity in centistokes at 70C to average EEW ratio is -.
below 11:1 and (2) an epoxy novolac resin wherein the - -
weight average molecular weight is above 2000 and wherein
a plot of MW vs Mw:Mn falls on or within the boundary of ~-
A, B, C, D in Figure 1.
The epoxy novolac resins which are suitably
employed in the process of the present invention are . ~ -
prepared by conventional means such as, for example, by ~ .
reacting in the presence of an acidic catalyst, e.g.,
oxali.c acid, an aldehyde such as formaldehyde and an
aromatic hydroxyl-containing compound such as phenol in
an aldehyde:phenol or like compound molar ratio suitable
in preparing a novolac of intermediate molecular weight
such as from 0.4:1 to 0.8:1 and preferably from 0.46:1 to
0.75:1. The excess phenol and water is then removed by .
any conventional means such as by flashing under vacuum.
Then the resultant novolac resin is reacted with an excess .
of an epihalohydrin such as epichlorohydrin or glycerine
dichlorohydrin in the presence of a basic catalyst such
as, for example, benzyl trimethyl ammonium chloride. t '
Then the resultant product is dehydrohalogenated with a
base such as, for example, sodium hydroxide, sodium
17,296-F -2-
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~38994
carbonate, or mixtures thereof. After washing with
water until neutral and filtering, excess epihalohydrin
is removed by flashing under vacuum thereby producing
an epoxy novolac resin.
In this process, the top layer or phase con-
tains the epoxy novolac resin having a relatively low
average molecular weight, whereas the bottom layer or
phase contains the epoxy resin having a relatively high
average molecular weight.
Aldehydes which may be suitably employed to
prepare the epoxy novolac resins employed in the present
invention include those aliphatic aldehydes having from
1 to 6 carbon atoms such as, for example, formaldehyde,
acetaldehyde, propionaldehyde, butyraldehyde, and
mixtures thereof.
Aromatic hydroxyl-containing compounds which
may be suitably employed to prepare the epoxy novolac
resins employed in the present invention include those
represented by the formula
~R
wherein R is hydrogen, a halogen such as bromine or
chlorine, a hydroxyl group or an alkyl group having
from 1 to 6 carbon atoms. Suitable such compounds `;
include, for example, phenol, methyl phenol, ethyl
phenol, propyl phenol, hydroquinone, resorcinol,
catechol, and mixtures thereof.
. .. ....
17,296-~ ~3~
~038994 :
Suitable solvents which may be employed in -
the process of the present invention include, for
example, xylene, toluene, methyl isobutyl ketone,
solvents having solubility parameters of 8.0-9.0 ~-
with low to medium hydrogen bonding and those with
solubility parameters >11.5 and any hydrogen bonding
value as described in an article entitled "Quanti-
fication of the Hydrogen Bonding Parameter" by E. P.
Lieberman, Official Digest, published by the Federation
of Societies for Paint Technology, Easton, Pa., Jan. -
1962, pp. 30-50, and mixtures thereof.
The accompanying Figure 1 is a graph or a -
plot for determining those epoxy novolac resins having -
weight average molecular weights above 2000 which are
encompassed by the present invention. The area bounded
by the points A, B, C, D is that which is encompassed
by the present invention. The labeled points are those
resins which illustrate the present invention and com-
parative experiments with respect to those resins
having weight average m~lecular weights above 2000.
The weight average molecular weight (Mw) is plotted
as the ordinate and the weight average molecular
weight:number average molecular weight (Mw:Mn) is
plotted as the abscissa. The coordinates for point A
are Mw = 2000; Mw:Mn = 2. The coordinates for point B
are Mw = 6500; Mw:Mn = 5. The coordinates for point C
are Mw = 11000; Mw:Mn = 5. The coordinates for point D
are Mw = 11000; Mw:Mn = 2.
.
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1038994
For resins having a weight average molecular
weight below 2000 that are encompassed by the present
invention the ratio of the viscosity in centistokes
at 70C to average epoxy equivalent weight (EEW) is
below 11:1.
Throughout this specification the molecular
weights are as determined by gel permeation chromato-
graphy.
The epoxy novolac resins of the present
invention which are of relatively low molecular weight
may be suitably employed as adhesives, laminates, coat-
ings and castings. They have a weight average molecular
weight below 2000 and viscosity in centistokes at 70C:
average EEW of <11:1. When compared to a conventionally
prepared epoxy novolac resin having an average molecular
weight of below 2000 they possess an improvement in one
or more of the properties such as a reduction in
viscosity, reduction in average EEW,
.
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17,296-F 5 -
~0~8994
increased heat distortion temperature, or increased
flexural properties.
The epoxy novolac resins of the present
invention which are of relatively high lecular
weight may be suitably employed as electrical var-
nishes, encapsulants, and molding powders. They have
a weight average molecular weight above 2000 and a
plot of Mw vs Mw:Mn falling on or within the area
bounded by A, B, C, D in Figure 1. When compared
to a conventionally prepared epoxy novolac resin
having an average molecular weight above 2000 and a
plot of Nw vs Mw:Mn falling outside the area bounded
by A, B, C, D they possess an improvement in one or
more of the properties such as a reduction in solu-
tion viscosity, increased heat distortion temperature,
increased flexural properties, a sharper melting
point and improved flow properties, or a higher melt-
ing point (i.e. a grindable solid such that the resin
can be ground without the particles sticking together).
The epoxy novolac resins of the present in-
vention can be employed alone or they may be employed
in admixture with other epoxy resin compositions. The
resins of this invention can be cured by any of the
conventional epoxy curing mechanisms, e.g. by employ-
ing such curing catalysts as teritary amines, Lewis
acids and the like or ~uch coreactive crosslinking
agents as primary and secondary amine-containing
compounds, polycarboxylic acids and anhydrides, ~ -
mercaptans, dicyandiamide, and the like.
17,296-F -6-
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~0~8994
The epoxy novolac resins of the present
invention may be admixed with inert materials such
as, for example, pigments, fillers, extenders, flexi-
bilizers, mold release agents, solvents and flow con-
trol agents as well as witl~ reactive diluents, accel-
erators, and fire retardand agents.
The following examples further illustrate
the present invention.
In the following examples, the molecular
weight data was obtain by gel permeation chromato-
graphy.
EXAMPLE I
A novolac resin having a 96C Durran's soften-
ing point was prepared using a 0.75:1 mole ratio of
formaldehyde to phenol.
Formaldehyde was fed into phenol (contain-
ing 0.6 wt. % oxalic acid) at 100C over approx. 1 ;~- -
.,;
hour period. This was reacted 1 hour and then the - -
excess phenol and water were removed under vacuum to
180C. The resulting novolac was dissolved in 5 moles
epichlorohydrin per equivalent of novolac or about
4.5:1 wt. ratio. 60~ aqueous benzyltrimethyl am-
monium chloride (about 3% of novolac wt.) was added ;~
and reacted at 60C for 4 days. The resulting novo-
lac polychlorohydrin ether was dehydrochlorinated ~ - ;
at about 20-25C using 50% excess aqueous solution
containing 15% NaOH and 10% Na2CO3 for 90 and 60
minutes respectively. This was washed with water
until neutral and the excess epichlorohydrin and
water were removed under vacuum to 160C to yield
.,
:, .
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1;~38994
an epoxy novolac having a 170 epoxide equivalent
weight, 5.4 average functionality, a 52C Durran's
softening point, a weight average molecular weight
of 2850, and a weight to number average molecular
weight ratio (Mw:Mn) of 3.098 (this resin is de-
signated as I in Figure 1). This epoxy novolac
was mixed at 20 weight percent solids in xylene and
heated to 80C to effect solution. This was then
cooled to 40C until separation into two phases oc-
curred. The phases were separated and the solvent
re ved from each phase. The low molecular weight
or soluble phase (45% of original resin weight) had
a 166.7 epoxide equivalent weight, 3.67 functionality,
a neat viscosity of 1177 cs at 70C, a weight average
molecular weight of 1112, and a viscosity in centi-
stokes at 70C : average EBW ratio of 7.06:1. The
higher molecular weight or insoluble phase (48.8~ of -
original resin weight) had an epoxide equivalent
weight of 181.4, 9.5 functionality, an 85C Durran's
softening point, a weight average molecular weight ~
of 4978, a weight average molecular weight to num- -
ber average molecular weight ratio of 2.891:1, and
a 50 weight percent acetone solution viscosity at
25C of 11.95 c8.
Samples of the low molecular weight fraction
were cured with stoichiometric quantities of methylene
dianiline for 16 hours at 125C plus 2 hours at 175C.
These samples are designated as I-l-A.
Additional samples were cured as above plus -
an additional 2 hours at 225C. These samples are
designated as I-l-B.
17,296-F -8-
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1038994
~he physical properties of samples I-l-A and
I-l-B as well as the properties of the uncured resin
designated as I-l are given in Table I.
Samples of the high molecular weight frac-
tion were cured with stoichiometric quantities of
4,4'-methylene bis(o-chloroaniline) for 16 hours at
140C plus 2 hours at 175C plus 2 hours at 250C.
These samples are designated as I-2. The physical
properties of these cured samples, as well as the prop-
erties of the uncured resin, also designated as I-2,
are given in Table II.
EXAMPLE II
An epoxy novolac was prepared as in Example I ~ -
from a novolac with a 101C Durran's softening point. The
epoxy novolac had a 176.2 epoxide equivalent weight, 5.45
functionality, a 57C Durran's softening point, a weight
average molecular weight of 2869, and a weight to number
average molecular weight ratio of 2.990 (this resin is
designated as II-A in Figure 1). This resin was frac- ~
tionated at 20 weight percent solids in xylene. The ~-
low molecular weight fraction (46.3% of original resin
weight) had a 166.7 epoxide equivalent weight, 3.53
functionality, a neat viscosity of 1683 cs at 70C, a
weignt average molecular weight of 869, and a viscosity
in centistokes at 70C : average EEW ratio of 10.1:1.
The higher molecular weight fraction (52.9% of original
resin weight) had a 180.2 epoxide equivalent weight, 9.5
funtionality, an 87C Durran's softening point, a weight
average molecular weight of 4463, a weight average mole-
cular weight to number average molecular weight ratio of
17,296-F -9-
~)38994
2.605:1, and a 50 weight percent acetone solution viscosity
at 25C of 11.84 cs (this resin is designated as II-B in
Figure 1).
EXAMPLE III (COMPARATIVE)
Preparation of Low Molecular Weight Conventional Epoxy
Novolac
A novolac resin was prepared using 0.46:1
formalin to phenol mole ratio. Each equivalent of novolac
was dissolved in 5 moles epichlorohydrin. This was
heated to 100C and 10% excess aqueous 50% NaOH was
added slowly over approximately 2 hours. The excess
epichlorohydrin was removed under vacuum to 150C.
This was then diluted with toluene to 15~ solids and
water washed to remove NaCl. The toluene was flashed
under vacuum to 150C to yield an epoxy novolac having
the following properties:
weight average molecular weight 1081
number average molecular weight 609
EEW, average 179.2
Functionality 3.4
Viscosity at 70C, cs (centistokes) 2542
Viscosity in centistokes at 70C
to EEW ratio 14.19:1
Cured samples were prepared employing stoichio-
metric quantities of methylene dianiline and curing at - -
125C for 16 hours plus 2 hours at 175C. The samples
were designated as III-A.
Cured samples were also prepared as above
excep~ that they were cured an additional 2 hours at
225C. These samples are designated as III-B.
The properties of these samples as well as
the properties of the uncured resin designated as III
are given in Table I.
17,296-p -10-
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1~38994
EXAMPLE IV (COMPARP.TIVE)
Preparation of High Molecular Weight Conventional Epoxy
Novolac
A novolac resin was prepared using a 0.72:l
mole ratio of formaldehyde to phenol.
Formaldehyde was fed into phenol (contain-
ing 0.6 wt. % oxalic acid) at 100C over approx. 1
hour period. This was reacted 1 hour and then the ex- -
cess phenol and water were removed under vacuum to ---
180C. The resulting novolac was dissolved in 5 moles
epichlorohydrin per equivalent of novolac or about a -~ -
- 4.5:1 wt. ratio. 60~ aqueous benzyl trimethyl am-
monium chloride (about 3~ of novolac wt.) was added
and reacted at 60C for 4 days. The resulting novo-
lac polychlorhydrin ether was dehydrochlorinated at
about 20-25C using a 50~ excess aqueous solution
containing 15~ NaOH and 10 Na2CO3 for 90 and 60 min- ~ ~
utes respectively. This was washed with water until ~ ;
neutral and the excess epichlorohydrin and water
were removed under vacuum to 160C to yield an epoxy
novolac having a 173.3 epoxide equivalent weight, a `
; 6.14 average functionality, a 62.5C Durran's soften-
ing point, a weight average molecular weight of 4386
and a weight average molecular weight to number ave-
rage molecular weight ratio of 4.124:1 (this resin -
i8 designated as IV in Figure 1). `
Cured samples were prepared using a stoici-
ometric quantity of 4,4'-methylenebis~o-chloroaniline)
and curing for 16 hours at 140C plus 2 hours at
~75C plus 2 hours at 250~C.
'; `' '
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17,296-F -11-
1038994
These samples are designated as IV and
- these properties as well as the properties of the
uncured resin are reported in Table II. .-
,296-F -12-
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1~)38994
- TABLE II
., ' ', , .
SAMPLE NUM~ER
Present
Invention Comparative
PROPERTY (UNCURED) I-2 IV
'' :
Wt. avg. mol. wt. 4978 4386
No. avg. mol. wt. 1722 1064
MW:Mn 2.891 4.124
EEW 181.4 173.3
Functionality (avg.) 9.5 6.14
Durran's softening point, C 85 62.5
PROPERTY (CURED) I-2 IV
Heat distortion temp. >250 >250
Flexural Strength, psi 12,250 10,200 -
(kg./sq. cm) (858) (714)
Flexural modulus, psi 485,000 460,000
(kg./sq. cm) (33,950) (32,200)
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17,296-F -14-
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1~38994
EXAMPLE V
A. An epoxy novolac was prepared as in Example
I from a novolac with a 104C Durran's softening point.
The resulting epoxy novolac had a 170.6 epoxide equiva-
lent weight 5.44 functionality, a 56C Durran's sof-
tening point, a weight average molecular weight of
2688, and a weight to number average molecular weight
ratio of 2.897 (this resin is designated as V-A in ~-
Figure 1).
B. After fractionation according to the pro-
cedure of Example I, the higher molecular weight
fraction (45.8~ of original weight) had a 175.5 epox- -
ide equivalent weight, 9.9 functionality, an 88C
Durran's softening point, a weight average molecular
weight of 4580, a weight average molecular weight to `
number average molecular weight ratio of 2.633:1,
and a 50% acetone solution viscosity at 25C of
12.56 cs (this resin is designated as V-B in Figure :
1). ' .
EXAMPLE VI
: A. An epoxy novolac was prepared as in Exam-
ple I from a 90C Durran's softening point novolac, .
had a 172 epoxide equivalent weight, 4.88 function- :
ality, a 51C Durran's softening point, a weight - .~ .
average molecular weight of 2101, and a weight to
number average molecular weight ratio of 2.504 (this
. resin is designated as VI-A in Figure 1). .:
; a. The higher molecular weight portion from
fractionation (43.4% of original weight) as in Ex-
ample I had a 182.2 epoxide equivalent weight, 8.2
17,296-F -15-
1~38994
: functionality, an 82C Durran's softening point, a
weight average molecular weight of 3671, a weight
average lecular weight to number average molecu-
lar weight ratio of 2.453, and a 50% acetone solu-
tion viscosity at 25C of 10.50 cs (this resin is
designated as VI-B in Figure 1).
EXAMPLE VII
An epoxy novolac resin similar to that of
Example II-A was fractionated on a larger scale and
resulted in a higher molecular weight portion with
a 183.8 epoxide equivalent weight, 9.22 functiona-
lity, an 84C Durran's softening point, a weight
average molecular weight of 4752, and a weight ave-
: rage molecular weight to number average molecular
weight ratio of 2.804. 52% of the original resin
: weight was recovered as the higher lecular weight
product (this resin is designated as VII in Figure
1) .
- EXAMPLE VIII
An epoxy novolac resin having a 179.2 epox-
ide equivalent weight, 3.40 functionality, a Durran's
softening point of less than 50C, a weight average
molecular weight of 1081, and a weight to number ave-
rage molecular weight ratio of 1.774 was fraction-
ated as in Example I. The unfractionated resin is
designated as VIII-A in Figure 1. The resulting
resin had a 207.7 epoxide equivalent weight, 5.18
functionality, a 67.5C Durran's softening point, a
weight average molecular weight of 2154, and a weight
average molecu~ar weight to number average molecular
17,296-F -16-
~/~38994
weight ratio of 2.002. The 504 acetone solution vis-
cosity at 25C was 7.9 cs (this resin is designsted
- as resin VIII-B in Figure l). -
EXAMPLE IX ( COMPARATIVE ) :
213.6 grams of 88~ phenolic solution and
162.4 grams of water were charged into a reactor.
5.8 grams of concentrated sulfuric acid (95.0-98.0%)
was added. The acidified solution was heated to
80C, then 80.6 grams of 37.2% formaldehyde was
added to the stirred acidified solution o~er a - -
period of 4 hours while the temperature was main-
tained at 80C.
Upon the completion of the addition of
- the formaldehyde solution, the temperature was main-
tained at 80C for an additional period of a half
hour, after which 8.0 grams of sodium carbonate was
added to neutralize the acid. ~
The system was then placed under vacuum --
at a pressure of 35 mm mercury and water distilled
by heating until the temperature reached 80C. Then,
; additional water was slowly added to the system at a
rate such that the distillation temperature was held - -
approximately constant at 80C. The addition of
water was continued until the total distillate col-
: ~ .
lected amounted to 630 grams.
The still residue was then used, it being
the no~olac resin. 50 grams of the resin was then
dissol~ed in 75.0 grams of methyl ethyl ketone and
81.0 grams of epichlorohydrin. The resulting solu~
tion was then heated; 40.0 grams of 50% sodium
:,,
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17,296-F -17- -
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1~38994
hydroxide solution were added gradually with Rtirring
over a 4-hour period to the warmed solution at about
80C. After the NaOH solution had been added the tem-
perature was maintained at 80C for an additional 1/2
hour.
The aqueous layer containing salt was then
withdrawn from the reactor. The organic layer con-
taining the resin was washed twice with 100 ml of
H20 to complete the removal of salt. The washed
organic layer was then distilled to remove most of
the methyl ethyl ketone. The remaining solution was
then stripped under vacuum to remove the remaining
solvent.
- The resultant resin was a very viscous
liquid at room temperature and was a clear amber
color. The resin had the following properties:
~ epoxide = 19.98
average EEW = 215
viscosity ~ 1360 centistokes at 70C
MW = 240
Mn = 616
Mw:Mn - 3.905
The plot of MW vs Mw:Mn is designated as
IX i~ Figure 1.
17,296-F -18-
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