Note: Descriptions are shown in the official language in which they were submitted.
, ~9L9533
In recent years, maleimides have acquired considera~le
importance as starting materials for the manufacture of high
polymers. They can be polymerised by themselves ~r in com-
bina-tion with other suitable monomers, by warming or catalyti-
cally. A polyaddition reaction of polymaleimides with organic
polyamines is also known. Given this importance of the male- -
,~,:: ... .
imides, it is necessary for the chemical raw materials indus-try -
to develop advantageous processes for the manufacture of
maleimides. -
It is already known to manufacture bis-maleimides by
reaction of the corresponding bis-maleamic acids with a lower ;
carboxylic acid anhydride (for example acetic anhydride) in the
presence of an organic dlluent and of a soluble nickel deriva- ~ -
tive. Such a process is described, and claimed, in DT-OS
2,040,094. This Offenlegungsschrift refers to US Patent - -
:. . :
Specifications 2,444,536, 3,018,290, 3,018,292 and 3,127,414
which relate to further known processes for the manufacture of
maleimides. -
. . . . . .
~ WhiIst the process according to DT-OS 2,040,094 repre-
sents a technical advance compared to the known processes men-
tioned in the same specification, it still suffers from con-
siderable disadvantages. m usj for example, the kettle yield
is very low (even in industrial installations). Kettles of
capacity approximately 2,000 1 must be employed for the pro-
duction of 70 kg of maleimide. Apart from the fact that the
nickel salts used as catalysts are relatively expensive, their
use is also very disadvantageous for ecological reasons. Since
the effIuents contain 100 times as much nickel salts as is
. .
,:.: .,
- 2 - ~
: ' -
.. . .
1049533
permitted at the present time and the removal of the~e salts from the efflu-
ent is extremely costly, the process according to DT-OS 2,040,094 has found
virtually no industrial acceptance.
British Patent No. 1,137,592 describes a multi-stage process for
the manufacture of bis-maleimides in which a sodium salt of a carboxylic
acid is used as the catalyst both for the manufacture of the bis-maleamic .. -~
acid and for the cyclising dehydration thereof to the imide. However, this .
process is disadvantageous inasmuch as the catalyst must be employed.lin .
high concentration (that is to say up to 3 mols per mol of the diamine ~: :
employed), which requires a costly washing operation of the end product to
remove the catalyst. Furthermore, the yields obtained in carrying out this .
known process (82 to 88% of theory) are too low.
Accordingly, it is the object of the invention to discover a
process which operates with a better space yield, which presents no problems
with regard to the effluents (in respect of amount and toxicity) and which
is thus overall substantially more economical in operation than the processes
: according to the state of the art.
The subje~t of the Invention is a process for the manufacture of
monomaleimides or polymaleimides by cyclising dehydration of monomaleamic '. :` .
20 : : acids or polymaleamic acids~selected from a) phenyl maleamic acid, b) a , ~.
.,.,~
polymaleamic acid of the general formula
CH COOH HOOC CH `.
~! NH - R -NH !l
CH CO CO CH ~ -
in whlch R denotes a braliched or unbranched aliphatic radical with a total ~. .
of 10 C-atoms, a cycloaliphatic radlcal on aromatic radical or an araliphatic .~- ~
radical, c) a polymaleamic acid of the formula ` .; ;
: HO-CO-CH=CH-CO-NH NH_CO_CH=CH_CO_OH
HO-CO-CH=CH-CO-NI ~ ~I-CO-CH=CH-CO-OH
and d) a polymaleamic acid of the formula i`
~ - 3 - :
1~ - , ~
.
. ~ 5", ' ', " '", '
l~9S33 ~
HO~CO-CH=CH-CO-NH NH-CO-CH=CH-CO-OH
~ ~Vl)
in the presence of lower, dehydrating, car~oxylic acid anhydrides, catalysts
and tertiary amines and in the presence or absence of organic solvents, : :
:, :,- .
characterised in that the catalyst employed iS an alkaline earth metal com- :.
pound in a concentration of 0.005 to 0.2 mol per mol of the monomaleamic acid . .
or polymaleamic acid.
"'.''..-'',~
' `":'-' ' :
',':'. ' :., ':.
. ~ ..... .
. .: .
~, :,
~ ,''" ''
~: ; ~.. ~ . . '
!,., '
', ,'; :,
,' .
~;
i~ .~,.,''
f. ' ':' .
.` ' ~:,
,~
. ~ " '
,' ~', '
~: '
.',"' ' ~ ,.
'`' ' ~' "'., '
- 3a - ~ . ~
,,~,~ ` '.' ,' ' ' '
r ~ ~0~S~3
The preferred range of catalyst concentration is 0.01
to 0.1 mol per mol of the maleamide!-carboxylic acid.
Particularly suitable catalysts according to the inven-
, ,: . .
tlon are alkaline earth metal oxides and alkaline earth metalacetates. Calcium compounds and barium compounds are employed
preferentially. The following substances should be mentioned
as examples of the catalysts: calcium acetate, calcium oxide,
barium acetate, barium oxide and strontium oxide. Alkaline
earth metal alcoholates or corresponding complex compounds are
also suitable.
- .
The dehydrating carboxylic acid anhydride used according
to the invention is preferably acetic anhydride. Preferably, -
2 to 3 mols of acetic anhydride should be used per mol of male- ~-
amic acid.
According to the invention it is possible to employ, for
; ~ example, trialkylamines and N,N-dialkylbenzylamines with 1 to 12
C atoms as tertiary amines. Triethylamine is employed prefer-
.. . .
entially. me preferred concentration of the tertiary amines
is between 0.3 and 1 mol per mol of maleamic acid.
me cyclising dehydration i9 carried out at temperatures ~
between 40C and 100C, preferably at atmospheric pressure. ~ ;
Preferably, it is carried out at temperatures between 40 and
,
~0C and in the presence of organic solvents.
Amongst the ~olvents ~hich can be used there may be men-
-tioned solvents of elevated polarity, such as, for example,
dimethylformamide, dimethylacetamide, dimethylsulphoxide, N- ;-
methylpyrrolidone and N-methylcaprolactam. It is also possible
to use cyclic ethers, such as, for example, tetrahydrofurane
_
~j
. ~ .
0~95~33
. ~ -,, :
and dioxane. The dialkyl ketone~" such as, for example,
acetone and methyl ethyl ke-tone, can be used with particular
advantage. Amounts by weight of solvents equivalent to
between 1.5 and 2.5 times the weight of the maleamic acid
: . . . .
employed are in general very suitable.
In addition to monomaleimides and polymaleimides with
more than 2 imide groups (especially 3 and 4 imide groups) in
the molecule, bis-maleimides can be manufactured particularly
advantageously by the process according to the invention. ~-
Starting products for the synthesis of these bis_maleimides
are, in particular, bis-maleamic acids of the general form~la
, ~ . ..... . .. . ...
CH - COOH HOOC ~ CH ;
N~ R - NH ll (I) !. ' '
CH - CO CO - CH - -
,
in which R denotes a branched or unbranched aliphatic radical
with a total of 10 C atoms, a cycloaliphatic radical, an aro~
,
B matLc radical, _ or an araliphatic radical.
Very suitable starting products are those bis-maleamic
- ::
acids of the formula (I) in which R denotes a radical of the
i .. . . ..
general formula
: .
~ ~ _ R1 ~ (II) ~ ~
. .
CH3 ~,'. ~,,
wherein Rl represents one of the radicals -CH2, -~- , -SO2-,
CH~
:
-SO-, -S-, -CO- and -O-. -
-- 5 --
~ , ' ::
:, :
,
' -': '" ~' . ''" ' ' ' :'' '' '' '." ' ' ' ' `, ~ ' ,'' .' " "' ' ' ' "'' " ' ''
4~3~S~3
N,N'-4,4'-Diphenylmethane-bis-maleamlc acid and N,N'-
4,4'-diphenylsulphone-bis-maleamic acid are particularly pre-
ferred for use. In addition it is in principle also possible
to employ all the bis-maleamic acids which are listed in DT-OS
2,04Q,094.
Furthermore, a polymaleamic acid of the formula
,`,~. ,,
HO CO CH=CH CO ~l - NH.CO-CH=CH.CO OH ~
~ - - (IV) ~ ;
.. . , . .,, , ., . . ; ,
is also very suitable for use according to the invention. ~ ;
An example of starting products for the manufacture of
tetramaleimides accord m g to the invention is the polymaleamic
acid of the formula
. .,, . . ..... . . . . . .. ., . . , . .. , .. . . _ . .. . . _ _ . . . . . . _ . ..
- ~
HO CO~CH=CH CO-NH NH CO CH=CH CO OH
HO CO~CH=CH CO NH ~ NH.CO CH=CH CO-OH
.. ........ _ _ . _ ., _ ,, _ __ ' .,, . . .. . .. . - - ._ .. ... . . _ . __ _ _ r , '
~:,
;~ :
~ Phenylmaleamic acid can be used, for example~ for the
... .
manufacture of a monomaleimide. It is produced by reaction
of aniline with maleic anhydride. ~
The monomaleamic acids and polymaleamic aclds used ~;
as starting materials for the process according to the invention
can be manufactured according to known processes which are des-
cribed in detail in the abovementioned patent specifications,
-, ~ ,
which quote the relevant literature,
Particularly suitable starting materials for the process -
: :,
- 6 -
~ ,,
;~ .
~0~533 :: :
according to the inVention are~ however, monomaleamic acids or
polymaleamic acids which have been manufactured by reaction of -
maleic anhydride with primary monoamines or polyamines in the
presence of organic solven~s and in the presence of 0.005 to
0.2 mol of an alkaline earth metal compound per mol of the mono-
amine or polyamine.
In manufacturing these preferred starting materials,
maleic anhydride is reacted with the particular monoamine or
polyamine in a ratio such that 0.8 to 1.2, preferably 0.95 to -
l.1, mols of maleic anhydride are present per equivalent of
amlne. , ,,
If the process according to the invention is carried
out in 2 stages in the manner described, yet a further advantage
surprisingly results. This is that~the maleamic acid produced
.. .. .. .
in the 1st stage proves to be stable to heat and to polymerisa- ~ -
tion. The consequence of this is that ~he organic solvent
.
present from the 1st stage can be removed wholly or partially,
,
preferably by distillation, prior to the cyclising dehydration,
ithout;producing sign1ficant amounts of by-products result1ng -~
2Q from degradation or polymerisation. This stabilising effect
is particularly marked and the success of the two-stage process
is opt~imal if, after carrying out the 1st stage of the process,
the organic sol~ent is removed except for 50 to 75~ by weight;
in this remark, the reactants are not to be understood as
solvents.
The maleimldes which can be~manufactured by the process -
`according to~the inventlon are in general obtained in the form
of a suspension in the particular organic solvent, and a part
. -
`, ' '
~,::
', ', . :':
';'': :
-7- ~
~' .:' ` ':
~ 10~9~i33
of the particular maleimide can also be present in solution.
Complete precipitation of the desired end p~oduct is then -
achieved by adding non-solvents such as, for example, water.
. . .
In most cases, -thorough washing (preferably with water) of the
maleimide obtained after filtration suffices to give an ade-
quately pure, industrlally usable product.
The technical advance achieved by the process according
to the invention can be summarised as follows. The kettle
yield is, surprisingly, substantially greater than with the pro-
cess according to DT-OS 2,040,09L~, kettles of appr~ximate
.
capacity 1,000 1 suffice for the production of 70 kg of male-
imide. The alkaline earth metal compounds used as the catalyst
a priori eliminate ~e ecological problems. As compared to the
.
use of alkali metal compounds as catalysts according to known
processes, the use of the alkaline earth metal compounds accord- `~
ing to the invention gives the ~ollowing advantages. Costly
washing operations are not necessary since the concentration
, ~ . . .
required according to the invention is much lower. It is sur-
prising that higher yields (preferably 95 - 97% of theory) are
achieved.
The maleimides manufactured ln accordance with the pro-
cess of the invention are, surprisingly, substantially more
active with regard to thermal polymerisation than the products
manufactured according to known processes. This behaviourls~s~c~
WlYdesirable inasmuch as fillers and additives can be added to ~~
the reaction mixtures to be polymerised~ in order to improve
the materials to be manu~actured and cheapen them, without
thereby making the reactivity too low. This unexpected
- 8 -
. ,
-
~ . : ' ' ::' . . : ''.: ~",' ' ' : ' '' '' ~' .:
~1(~4953~3
. .
behaviour of the maleimides manufactured by the process accord~ing to the invention, though they have the same analytical
data as maleimides manufactured according to known processes,
particularly underlines the inventive level of the process
claimed.
' ' ,',,
30.9 g of maleic anhydride (0.315 mol) and 118.0 g of
acetone are initially introduced into a flask equipped with a
reflux condenser and the mixture is stirred at 25C until com-
plete solution is achieved.
002 g of calcium oxide (0.00356 mol) -is added to this
solution and stirring is continued for 15 minutes. The mixture
is warmed to 60C and a solution of 29.7 g of 4,4'-diaminodi-
phenylmethane (0.149 mol) in 59.2 g of acetone is added dropwise
at this temperature over the course of approx. 1 hour. -~ -
87 g of acetone are distilled from the reaction mixture
at a bath temperature of 60C, whilst stirring and under vacuum
(approx. 40 - 100 mm Hg). A yellow crystal mass results.
2.0 g of glacial acetic acid, 48.6~ g of acetic anhydride
(0.476 mol) and 5.25 g of triethylamine (0.057 mol) are added to
this crystal mass. The reaction mixture is warmed to 60C and
stirre~ for 2 hours at this temperature. A brown solution
results. This solution is filtered warm (60C) through a fil-
ter covered with silica powder and the latter is rinsed with
6.0 g of acetone. me solution is cooled to 25C. 450 ml -
of water are addeu dropwise at this temperature over the course ;
! . . .
of 2 - 3 hours. A crystal suspension results. This crystal ~-
suspension is cooled to 10C and stirred at this temperature
;: ~ . '
9 ~ . -
.:, . .. ~ :, .
.. ~ .
: . ' ~ ' ":'
' ., ' '-," , `:,:, ~ ' ' ' ' . ' ' ., , . ' ,.' ' . , ' , ' ' ;; , ': :~', ,""
9533
for 1 hour. It is then filtered and the crystalline residue
is rinsed with 150 ml of cold (10C) water in portions. The
crystals are dried in a vacuum drying cabinet in vacuo at 80C
- Yield: 48.2 g of N,N'-4,4'-diphenylmethane-bis-male-
imide, corresponding to 90.0% of theory relative to 4,4'-diamino_ -
diphenylmethane (theory = 53.5 g), mel-ting point: 1~2 - 157~. -
Example 2
me procedure followed is exactly as in Example 1 except
that instead of 0.2 g of calcium oxide 0.3 g of calcium acetate
. . .
(0.0019 mol) is employed. The result of this experiment vir-
tually corresponds to the result of Example 1.
Example 3 -
The procedure followed is exactly as in Example 1 except
.
that instead of 0.2 g of calcium oxide 0.2 g of barium oxide
(0.00118 mol) is employed. The result corresponds to that of
-:
Example 1.
- Example 4
' ,'
me procedure followed is exactly as in Example 1, except
- that instead of 0.2 g of calcium oxide 0.3 g of barium acetate
(0.00118 mol) is employed. The result corresponds to that of
Example 1.
Example
48.6 g of acetic anhydride, 5.25 g of triethylamine
and 3.0 g of calcium acetate (0.019 mol) are initially intro- ;
duced into a flask equipped with a reflux condenser.
The mixture is warmed to 60C whilst stirring. A solu-
tion, warmed to 60C, of 59.1 g of N,N'-4,4'-diphenylmethane-
bis-maleamic acid (0.15 mol) and 144.0 g of dimethylformamide
~ . .
- 10 -
` ~:, . ':
-~ 109L~ii3;3~ -
is added dropwise to the above mixture over the course of 1
hour at 60C. The mixture is st,rred for a fur-ther 2 hour at ~-
60C. A viscous solution results.
This solution is allowed to cool to 30C and is run -
, :, ~: . .
over the course of 1 hour into a mixture of 225 g of ice and
225 g of water (maximum temperature during the addition: +10C). -
After completion of the addi-tion, the crystals are fil- ~
tered off and rinsed with 200 g of cold (10C) water. me -
crystals are dried in vaGuo at 80C in a vacuum drying cabinet.
Yield: 51.0 g of N,N'-4,4'-diphenylmethane-bis-male-
imide, corresponding to 95.4% of theory, relative to N,N'-4,4'-
diphenylmethane-bis-maleamic acid. (Theory = 53.5 g).
Melting point: 156 - 159C.
Example 6 ;
28.42 g of maleic anhydride (0.29 mol) and 73 g of -:
dimethylformamide are initially introduced into a flask equipped
with a reflux condenser, the mixture is warmed to 60C (~hich
produces a solution) and a solution, warmed to 60C, of 29.7 g s ~
of 4,4'-diaminodiphenylmethane (0.15 mol) in 73 g of dimethyl- ;
formamide is added dropwise to the above solution over the
course of 1 hour at 60C. 5.25 g of triethylamine are added
to the reaction mixture. The mixture is then stirred at 60C
until a solution is produced. The latter is allowed to cool
to 4bc and is added dropwise over the course of 1 hour to a
mixture of 48.6 g of acetic anhydride and 3.0 g of calcium
acetate (0.019 mol) at 60C.
The reaction mixture is kept for 1 hour at 50C, whilst ~;
-,
stirring. A viscous solution results. This solution is
, ~''
.
.
i; ~049533
allowed to cool to 30C and is added dropwise over the course of
approx. 1 hour to a mixture of 225 g of ice and 225 g of water
(with the temperature not exceeding 10C during the addition). :!: - :
After completion of the ad~ition, the crystals are fil~
tered off and rinsed with 200 g of water at 10C. The crystals
are dried ln vacuo at 80C in a vacuum drying cabinet.
Yield: 50.6 g of N,N'-4,4'-diphenylmethane-bis-male- J
, .
imide, corresponding to 94.6% of theory, relative to 4,4'-di-
aminodiphenylmethane. ( méory = 53.5 g). Melting point:
I59 - 162C. ~ '~
,
Example 7
~ , :
29.7 g of 4,4'-diaminodiphenylmethane (0.15 mol),
59.0 g of acetone and 23.7 g of benzyldimethylamine are
initially introduced into a flask equipped with a reflux conden-
ser. The mixture is stirred at 25C until a solution results.
,
ThlS solution is cooled to 10 - 15C. A solution of 28.42 g '
of maleic anhydride (0.29 mol) in 119 g of acetone is added ~ ~'
dropwise to the above~solution over the course of 1 hour at
10 - 15C.~ Thereafter, the resulting solution is added drop~
wise to a mixture of 48.6 g of acetic anhydride and 3.0 g of
calcium acetate (0.019 mol)' over the course of 1 hour at 60C.
me reaction mixture is warmed to 65 - 70C. 45 g of acetone
are then distilled off under normal pressure. - ;~
The viscous solution which remains is allowed to cool to
, ~ ,
30 - 35C and is run, over the course of 1 hour, into a mixture '~
of 225 g of ice &nd 225 g of water. After completion of the ~'
addition, the crystals are filtered oPf and rinsed with 200 g `~
of water at 10 C. ' The crystals are dried in vacuo at 80C
- 12 -
. " ' ~, ~, '., ,',;..'. ,"' ';.' '''' '" """ '`"'"'' `' "''' "'":"' "' '
4~S33
in a vacuum drying cabinet.
Yield: 52.0 g o~ N,N'-4,4'-diphenylmethane-bis-male-
imide, corresponding to 97.2% of theory, relat~ve to 4,4'- -
diaminodiphenylmethane. (Theory = 53.5 g). Melting point: !'
158 - 160C.
Example 8 ;
25.0 g of 3,3'-4,4'-biphenyltetramine (0.116 mol) and
72.0 g of dimethylformamide are initially introduced into a
flask equipped with a reflux condenser. The mixture is stirred
at 25C until a solution results. This solution is warmed to
60C and a solution of 48.05 g of maleic anhydride (0.49 mol) in
72.0 g of dimethylformamlde is added dropwise to the above solu~ --
tion over the course of 1 hour at 60 - 65C. The reaction mix-
-. . .
ture is kept at 60 - 65C for 1 hour, whilst stirring. The
mixture is cooled to 25C and 71.6 g of acetic anhydride
~....
(0.701 mol), 2.3 g of calcium acetate (anhydrous; 0.0145 mol)
and 5.9 g of triethylamine (0.058 mol) are added in succession.
e reaction mixture is warmed to 60 - 65C and is kept at this ;
temperature for 2 hours, whilst stirring. A solution of medium
viscosity results. This is allowed to cool to 30 - 35C and~9~Ogof
distill~d water are run in over the course of one hour. mere-
after, the resulting crystal/liquid mixture is cooled to
.
0 - 5C and is kept at this temperature for one hour, whilst ~ -
stirring. It is then filtered and the cryst~ls are rinsed ~-
with 300 g of distilled water at 10C. The crystals are i
dried in vacuo at 80C in a vacuum drying cabinet.
Yield: 48.8 g of 3,3'-4,4'-biphenyltetramaleimide, -
.
corresponding to 78.2% of theory, based on 3,3'-4,4'-biphenyl-
~ ~,
- 13 - ;
.,~ , , . : .
: , ,
11~4~9533
tetramine (theory = 62.35 g). Melting point: not character_
istic, product does not melt below 250C. N content (Kjehldal
method): 88.95% of the theoretical content free amine (by ti-
.
tration with sodium nitrite):~ 0 3%.
- Example 9
45.0 g of aniline (0.483 mol) and 100.0 g of dimethyl-
,: ,
formamide are introduced into a flask equipped with a reflux
condenser. The mixture is stirred at 25C until a solution
results. This solution is warmed to 60C. A solution of
49.7 g of maleic anhydride (0.506 mol) in 74.0 g of dimethyl-
formamide is added dropwise to the above solution over the
course of 1 hour at 60 - 65C. me reaction mixture is kept
~t 60 - 65C for 1 hour, whilst stirring. It is then cooled
to 25C and 7~.9 g of acetic anhydride (0.723 mol), 9.5 g of
calcium acetate (anhydrous; o.o60 mol) and 14. 6 g of triethyl-
amine (0.144 mol) are added in succession. me reaction mix- --
ture is warmed to 60 - 65C and kept at this temperature for ~ -
2 hours, whllst stirring. A solution of medium viscosity
results, which is cooled to 30 - 35C. 1,000.0 g of distilled
water are allowed to run in over the course of 1 hour. The ~ -
mixture containing the crystals is then cooled to 0 - 5C and
stirred at this temperature for 1 hour. It is then filtered
and the crystals are rinsed with 400 g of distilled water at
10C. The crystals are dried in vacuo at 50C in a vacuum
drying cabinet.
Yield: 73.0 g of phenylmaleimide, corresponding to
88.2% of theory, relative to aniline (theory = 83.67 g). Melt- ;
ing point: 76 - 78C. N content (Kjehldal method): 94.1~%.
- 14 -
: , .'.. ' ''
. ~
~4953~
Free amine: ~ 0.2%.
Example 10 - -
45.0 g of 4,4'-dia~inodiphenylsulphone (0.1812 mol) and
100.0 g of dimethylformamide are introduced into a flask eq~ipped -
with a reflux condenser. The mixture is stirred at Z5C until
a solution results. This solution is warmed to 60C. A
solution of 37.1 g of maleic anhydride (0.378 mol) in 68.0 g of
dimethylformamide is added dropwise to the above solution over
the course of 1 hour at 60 - 65C. The reaction mixture is -
stirred for 1 hour~ at 60 - 65C. It is then cooled to 25C
and 55.8 g of acetic anhydride (0.5465 mol), 3.57 g of calcium
acetate (anhydrcus; 0.0225 mol) and 5.49 g of triethylamine
(0.0543 mol) are added in succession. The reaction mixture is
warmed to 60 - 65C and kept at this temperature for 2 hours, ;
whilst stirring. A solution of medium viscosity results, which
is allowed to cool to 30 - 35C. 1,000 g of distilled water ;
are run in over the course of one hour. The mixture is then
cooled to 0 - 5C and stirred at this temperature for 1 hour.
It is then filtered~and the crystals are rinsed with 300 g of ;
distilled water at 10C. The crystals are dried in vacuo at
100C in a vacuum drying cabinet.
Yield: 71.6 g of N,N'-4,4'-diphenylsulphone-bis-
maleimide,corresponding to 96,7% of theory, relative to 4,4'-
- , .
diaminodiphenylsulphone (theory = 74.01 g). Melting poin-c: `
154 - 148C. N content (Kjehldahl method): 84.25%. Free
amine (by titration with sodium nltrite) ~ 0.3%. S content
~determined gravimetrically via Ba504): 92.0% of the theoretL- `
cal content.
-
~' ::
.,,-.
, . ' ' ' ', . . '
53 3
Example 11
35.0 g of 3,6-diaminodiphenylene oxide (0.1765 mol) and
200.0 g of dimethylformamide are initially introduced into a
flask equipped with a reflux condenser. me mix-ture is warmed
to 60C and the product is dissolved at this temperature.
Thereafter a solution of 36.3 g of maleic anhydride (0.370 mol)
in 70.0 g of dimethyl~ormamide is added dropwise to this solu- ;
tion over the course of 1 hour at 60 - 65C. The reaction
mixture is stirred for 1 hour at 60 - 65C and then cooled to -
25C. 54.1 g of acetic anhydride (0.5299 mol), 3.62 g of
calcium acetate (anhydrous; 0.0228 mol) and 5.35 g of triethyl-
amlne (0.0529 mol) are introduced in succession. The reaction ; ;
mixture is warmed to 60 - 65C and kept at this temperature for
2 hours, whilst stirring. A solution of medium viscosity `
results, which is allowed to cool to 30 - 35C. 1,300 g of
distilled water are run in over the course of one hour. The
mixture is then cooled to 0 - 5C and kept at this tempera-
ture for 1 hour whilst stirring. The resulting crystals are `
then filtered off and rinsed with 300 g of distilled water at
10C. The crystals are dried in vacuo at 100C in a vacuum
drying cabinet.
Yield: 59.53 g o~ N,N-3,6-dimaleimide-diphenylene oxide,
corresponding to 93.60/o of theory, relative to 3,6-diaminodi-
phenylene oxide (theory = 63.61 g). Melting point: 179 -
181C. N content (Kjehldal method): 92.76%. Free amine
. .
(by tLtration with sodium nitrite): < 0.3%.
. ;. :
- 16
:` . '~'.', : ,: .
