Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
94~3
--1--
PROCESS FOR PREPARING
ADVANCED EPOXY RESINS EMPLOYING
A PHOSP~ONIUM TRIFLUOROACETATE CATALYST
Epoxy resins have heretofore been advanced
in the presence of phosphonium catalysts disclosed by
Mark F. Dante et al. in U.S. 3,477,990 dated
November 11, 1969; William O. Perry in Canadian 893,191
dated February 15, 1972, and William O. Perry in U.S.
3,948,855 dated April 6, 1975. However, the quantities
of catalyst employed were that which would provide a
resin having a percent epoxide value sufficiently close
to the theoretical epoxide value that no improvement in
properties were envisioned.
U.S. Patents 4,325,918 (Donald A. Luke, et al.
dated April 20, 1982) and 4,370,465 (Ross C. Whiteside,
Jr., et al. dated January 25, 1983) disclose the prepara-
tion of advanced epoxy resins having improved physical
properties by employing a sufficient quantity of a phos-
phonium catalyst such that the resultant advanced epoxy
resin had a percent epoxide lower than the theoretical
percent epoxide value
The process of the present invention produces
advanced epoxy resins having a percent epoxide value
lower than the theoretical percent epoxide and a desir-
ably lower color than the color produced by those
advanced epoxy resins produced by the process described
in US. Patents 4,325,918 and 4,370,465. The difference
O
30,527A-F l
--2--
obtained by subtracting the percent epoxide obtained by
analysis from the theoretical percent epoxide i5 from
0.5 to 4, often from 1 to 2. The advanced epoxy resins
prepared by the process of this invention are suitable
for use in preparing electrical laminates.
The present invention pertains to a process
for advancing epoxy resins in molecular weight by
reacting (A) an epoxy resin which is a glycidyl ether
of a dihydric phenol or thiophenol having an average of
more than one glycidyl ether group per molecule with
(B) a dihydric phenolic or thiophenolic compound in the
presence of catalytic quantities of (C) a phosphonium
catalyst, wherein the improvment comprises employing as
the catalyst, component O a phosphonium ~rifluoro-
acetate salt.
Suitable glycidyl ethers of a dihydr1c phenolwhich can be employed in the present invention include
those represented by the formula
H2C-CH-CH2 (A)x Z-CH2-CH-CH Z
X X n
X O
~}( A ) ~s~Z-CH2 CH2
X
wherein A is a divalent hydrocarbon group having from 1
O O
to 8 carbon atoms, -So, -S-S-, -O-, -C-, US-, or
30,527A-F -2-
3~3
--3--
-S-; each X is independently hydrogen, chlorine, bromine
0
or a hydrocarbon group having from 1 to 10 carbon
atoms; each Z is independently 0 or S; x has a value
of zero or one and n has a value such that the EEW is
from 156 to 400, preferably from 177 to 190, calculated
on the basis of X being hydrogen.
Particularly suitable are the diglycidyl
ethers of bisphenol A and tetrabromobisphenol A.
Suitable dihydric phenolic or thiophenolic
compounds include, or example, catechol, hydrog~linone,
resorcinol and bisphenols such as those represented by
the formula
; HZ Ax 2H
wherein A, I, Z and x are as defined above.
Particularly suitable dihydric phenolic
compounds are bisphenol A and tetrabromo bisphenol A.
The phosphonium trifluoroacetate salt catalysts
employed herein can be in essentially pure form or they
can be prepared in situ without purification other than
filtration of solid precipitated by-products of the
reaction between a tetrahydrocarbyl phosphonium compound
and trifluoroacetic acid or a salt thereof.
.
.
30,527A-F -3-
3943
_g _
Suitable phosphonium compounds which can be
employed herein include, for example, those compounds
having at least one phosphonium cation group repre-
sented by the formula
R
R P-R
R
wherein each R is independently a hydrocarbyl or substi-
tuted hydrocarbyl group having from 1 to 20, preferably
from 1 to 6, carbon atoms or substituted hydrocarbyl
groups. It is preferred that at least one, preferably
two and most preferably three, of the R groups be an
aromatic group i.e., an aryl group or an alkaryl group
such that the phosphorus atom is attached directly to
the aromatic ring of such aryl or alkaryl group.
By the term hydrocarbyl, it is meant that the
groups can be alkyl, aryl, alkaryl, or aralkyl and the
:~ 20 alkyl can ye either cyclic or acyclic. By substituted
hydrocarbyl it is meant that the hydrocarbyl groups can
contain one or more substituent groups such as, for
: example, Cl, Br, I, NO2, and mixtures thereof.
I; The R groups can contain any substituent
group which will not deactivate the catalyst under the
conditions in which they are employed.
It is preferred that the phosphonium cation
contain at least one aromatic ring and at least one
alkyl group attached directly to a phosphorous atom.
30, 527A-F -4-
., I,
39~3
--5~
Suitable anions include the halides, such as,
for example, Cl, Br, and I, as well as carboxylates,
dicarboxylates, phosphates, nitrates, sulfates, nitrites,
sulfites, borates, chromates, and mixtures thereof.
The dihydric phenol and the glycidyl ether of
a dihydric phenol are employed in quantities such that
the theoretical percent epoxide of the resultant product
has the desired value.
.. . .
The quantity of catalyst will of course vary
depending upon the particular catalyst employed; however,
for most catalysts, from 0.1 to 1.5, preferably from
0.2 to 0.8l parts ox catalyst by weight per 100 parts
by weight of glycidyl ether of dihydric phenol can be
employed.
The reaction conditions employed to prepare
:~ the advanced epoxy resins can vary, but temperatures of
rom 100C to 200C, preferably from 1~0C to 160C,
are suitable Lower temperatures usually require
longer reaction times whereas higher temperatures
usually require shorter reactlon times.
:; The pressure employed is not particularly
important and can be from about 1 mm Hg vacuum to 100
I: : psig (O.l to 791 kPa). however, it is usually preferxed
to employ~pressures of from 5 psig to 20 psig (136 to
: 25 239 kPa~.
: Any of the well known curing ayents can be
employed in the pr.esent invention to cure the epoxy
resins. Such curing agents include, for example,
amines, amides, guanidines, phenollc hydroxyl-containing
30,527A-F -5-
--6--
materials, carboxylic acids, carboylic acid anhydrides,
imidazoles, biguanides, and mixtures thereof.
Particulary suitable curing agents include,
for example, guanidines such as for example, dicyan-
diamide and tetramethyl guanidine and biguanides suchas 1,6-xylene biguanide, polyhydric phenols, and mix-
tures thereof.
The quantity of curing agent employer depends
upon the particular curing agent employed and the
properties desired in the resultant cured resin, all of
which is well known by those persons reasonably skilled
in the art and discussed in HANDBOOK OF EPOXY RESINS,
by Lee and Neville, McGraw Hill, 1967.
The theoretical percent epoxide is calculated
by the following formula
THEORETICAL PERCENT EPOXIDE =
EqER = epoxide equivalents from the epoxy resin.
EqDHP = phenolic hydroxyl equivalents from the dihydric
phenol.
WtER = weight of epoxy resin employed.
WtDHP = weight of dihydric phenol employed.
The actual percent epoxide was determined
experimentally by titration with perchloric acid in
glacial acetic acid by the liberation of hydrogen
bromide generated by the addition of tetraethylammoni
bromide in glacial acetic acid using crystal violet as
an indicator. The epoxy groups react stoichiometrically
with hydrogen bromide generated from the reactlon of
30,527A-F -6-
,,
~L~:03~3
--7--
perchloric acid with te-trae-thyl ammonium bromlde. When
the epoxy groups haze been reacted, the free hydrogen
bromide causes the crystal violet to change color.
The phosphonium trifluoroaceta~e salts employed
as epoxy advancement catalysts in the examples (Table It
were prepared by the synthetic procedures described
. schematically below.
Procedure A ...
CF3CO2H''
03P-Alkyl - 03P Alkyl + H20 + C02
~3 5
HC03 CF3C02
Procedure B
DOWER ion exchange resin
03P Alkyl r~Sln [eQH~ >~3P-Alkyl CF3CO2H
Bre CH30H L OH
f
03P-Alkyl H20
20 - CF3Co29
Procedure C
:
CF3C02H _ _
03P-Alky~ >03P-Alkyl + 2CH3C2H
e CH30H
: 25 CH3C02 CH3C02H CF3C0
: Procedure D
al 2AgO2CCF3 0 ~3
03P-CH2CH2P03 > 03PCH2CH2P03 -t 2AgBr~
e CH30H
302 Br 2CF3C0
.
Trademark o The Dow Chemical Company
30, 527A-F -7
--8--
The procedure (A) described above was employed
to prepare the catalyst employed in Examples 1-5.
The procedure (B) described above was employed
to prepare the catalyst employed in Examples 6, 7, 8,
10, 11 and 12.
The procedure (C) described above was employed
to prepare the catalyst employed in Comparative Experi-
menus A, B and C.
The procedure (D) described above was employed
to prepare the catalyst employed in Example 9.
GENERAL PROCEDURE FOR RESIN PREPARATION
To a reaction vessel equipped with a means of
pressure regulation, stirring, temperature control and
indication of nitrogen purge was chargPd the desired
weight of the specified low molecular weight diglycidyl
ether of a dihydric phenol and the desired weight of
the specified dihydric phenol or thiophenol. The
mixture was heated at a rate of 5C/minute (0.083C/s)
with a constant 1Ow ox N2 over the reactants, unless
otherwise indicated. When the temperature of the
mixture reached 60C, the desired amount of the speci-
fied phosphonium salt dissolved in methanol was added.
The mixture was heated at the desired reaction condi-
tions (specified as A or B in Table I) to give the
resultant product. The reaction condition (A) consists
of heating the reaction mixture for one hour (3600 s)
at the temperatures of 130C, 140C, 150C and finally
at 160C for 2 hours (7200 s). The reaction (B) was
heated directly to 150C with an exotherm occurring
followed by post heating at 160C for 3 hours (10800 s).
30,527A-F -8-
~L203943
REACTANTS FOR RESIN ADVANCEMENT
EPOXY RESIN A was a liquid diglycidyl ether of
-
bisphenol-A having an average epoxide equivalent weight
of 179.9, percent epoxide of 23.90.
EPOXY RESIN B was a liquld diglycidyl ether of
bisphenol-A having an average epoxide equivalent weight
of 18~.6, percent epoxide of 22.8.
EPOXY RESIN C was a liquid diglycidyl ether of
2,2' diallyl bisphenol-A having an average epoxide
equivalent weight of 227.5, percent epoxide of 18.9.
i~CH2C~1~2 1
CH2cH=cH2 - 2
.
DIHYDRIC PHENOL ox THIOPHENOL A was tetrabromobis-
phenol-A, a dihydric phenol, having a phenolic hydroxyl
equivalent weight of 272 and percent bromine content of
58.85 percent.
DIHYDRIC PHENOL or THIOPHENOL B was bisphenol-A, a
dihydric phenol, having a phenolic hydroxyl equivalent
: weight of 114.
DIHYDRIC PHENOL_or THIOPHENOL C was 2,2'diallyl
bisphenol-A, a dihydric phenol, having a phenolic
hydroxyl equivalent weight of 155.
:
30,527A-F ~9-
.,~
3~3
--10--
O OH
i
L C~2cH=cH2 _ 2
DIHYDRIC PHENOL or THIOPHENOL D was 4,4'-phenoxybenzene
_ .... ..
dithiol, a dihydric thiophenol, having a thiophenolic
thiol equivalent weight of 118.
O SH
DI~YDRIC PHENOL or THIOPHENOL E was 4,4'sulfonyldiphenol,
a dihydric phenol, having a phenolic hydroxyl equivalent
weight of 125.
.
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30, 5271~-F -15-
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30, 527A-F -17-
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