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Патент USA US3022282

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United States
r.
atent
1
l€€
c
_
3,022,272
Patented Feb. 20, 1962
2
lysts, according to the processes as described in the co.
3,022,272
pending US. patent applications Ser. Nos. 461,938, 557,
Hermann Schnell, Krefeld-Uerdinger, and Gerhard Fritz,
256, 572,793, 572,802, 583,382 and 596,398, so far as
those applications refer to inter-esteri?cation processes,
PROCESS FOR THE PRODUCTION OF HIGH
MOLECULAR POLYCARBONATES
Krefeld-Bockum, Germany, assignors to Farhenfahri
ken Bayer Aktiengesellschaft, Leverkusen, Germany, a
corporation of Germany
N0 Drawing. Filed Oct. 8, 1956, Ser. No. 614,340
Claims priority, application Germany Dec. 21, 1955
,
14} Claims.
(Cl. 260-47)
For the production of polyesters from dicarboxylic
can ‘be overcome if these basic catalysts are neutralised
towards the end of the inter-esteri?cation by adding base
binding materials to the melt.
The process according to the invention can be used
with advantage for the production of polycarbonates from
e.g. aliphatic dihydroxy compounds such as diethylene
glycol, triethylene glycol, polyethylene glycol, thiodigly
acids and dihydroxy compounds, the free acids can be
col and the di- or poiy-glycols produced from propylene
esteri?ed with dihydroxy compounds with separation of
oxide-l,2,butanediol-l,4, hexanediol-1,6, octanediol-l,8,
decanediol-1,10, m-, p-xylylene glycol; from cycloali
High molecular ?lm
and ?bre-forming products are only obtainable accord 15 phatic dihydroxy compounds such as cyclohexane diol-l,
4, 2,2-di-(p-hydroxycyclohexyl)propane and 2,6-dihy
ing‘to this process with di?iculty. For the production of
roxy-decahydronaphthalene; from aromatic dihydroxy
high molecular polyesters it has therefore been preferred
compounds such as hydroquinone, resorcinol, 4,4'-dihy
to inter-esterify dihydroxy compounds with dicarboxylic
water at elevated temperatures.
'
droxydiphenyl, l,4-dihydroxynaphthalene, 1,6-dihydroxy
naphthalene, 2,6-dihydroxynaphthaiene, 1,5-dihydroxyan
general necessary in inter-esteri?cation to use basic cata
monohydroxyarylene-alkanes, like di-(p-hydroxyphenyl
carbonates of volatile aliphatic or aromatic compounds,
no high molecular ?lm or ?bre products are formed in
droxyphenylene) -pentane,
acid esters of volatile hydroxy compounds with separa
u-n>~sxg ji
tion of the volatile compound.
'
20 thracene and m-, p-hydroxybenzyl alcohol or mixtures of
Although the esteri?cation can normally be carried out
even without catalysts with considerable speed it is in 1 ,such dihydroxy compounds, but especially such as di
ene)-methane, 2,2-di-(p~hydroxyphenylcne)-propane, 1,1_
lysts. According to the conventional inter-esteri?cation
process the added catalysts remain in the end product. 25 di- (p-hydroxyphenylene ) -cyclohexane, 1,1-di- (p-hydroxy
m-methylphenylene)-cyclohexane, 3,4~di-(p-hydroxyphen
If alkali catalysts are added in the inter-esteri?cation
ylene ) hexane, 1,1-di-(p-hydroxyphenylene)-1-phenyl-eth
of aliphatic or aromatic dihydroxy compounds with di
ane, 2,2-di-(p-hydroxyphenylene)-butane, 2,2-di-(p-hy
3,3-di-(p-hydroxyphenylene) -
general because these catalysts decompose high molecu 30 pentane, 2,2-di-(p-hydroxyphenylene)~3-methyl-butane, 2,
2 - di - (p - hydroxyphenylene) - hexane, 2,2 - di - (p
lar polycarbonates.
hydroxyphenylene ) -4-methyl-pentane, 2,2-di- (p-hydroxy~
Processes have therefore hitherto been operated by
'phenylene)-heptane, 4,4'di-(p-hydroxyphenylene)-heptane
beginning the reaction of aliphatic dihydroxy compounds
and 2,2-(p-hydroxyphenylene)-tridecane.
I
with the carbonates of mono-hydroxy compounds in the
As suitable dicarbonates for inter-esteri?cation with
presence of non-volatile, only slightly water soluble, car 35
the dihydroxy compounds there are mentioned aliphatic
boxylic acids and a more than equivalent amount of an ‘_
alkali metal, dissolving the low molecular product ?rst' ‘ diesters such as diethyl-, dipropyl-, dibutyl-, diamyl-, di~
octyl—, methylethyl-, ethylpropyl- and ethylbutyl-carbon
formed in a solvent, removing the alkali metal by extrac
ates; cycloaliphatic diesters such as dicyclohexyl~ and
tion with dilute acid, e.g. aqueous hydrochloric acid, with
out removing the carboxylic acid and then after distilling 40 dicyclopentyl-carbonate, preferably however, diarylesters,
such as‘ diphenyl- and ditolylcarbonate; furthermore
off the solvent, completing the reaction to form a high
mixed esters such as methylcyclohexyl-, ethylcycloh'exyll,
:molecular ?lm- and ?bre-forming product.
methylphenyl-, ethylphenyl- and cyclohexylphenyl-car
This process is unduly involved. The added non-vola
bonate.
tile carboxylic acid which is not water soluble remains
If desired, one also can start from compounds such
in the high molecular polyester.- Acid and basic com 45
as dialkyl-, dicycloalkyl-, diaryl- or mixed dicarbonates
ponents alike tend during the Working up, especially of
high melting high molecular polycarbonates from the
of aromatic dihydroxy compounds which inter-esterify
when heated by themselves with separation of the cor
melt, to spoil the structure with the formation of gaseous
responding dicarbonates or when heated with dihydroxy
carbonic acid. This gas blowing makes the production
of good shaped bodies such as ?lms, ?bres and bristles 50 compounds with separation of the mono-hydroxy com
from the melt practically impossible. Mou'dings from
pounds, e.g. according to the process described in the
polycarbonates made in this way are seriously lacking in
copending US. patent application Ser. No. 596,398. '
As basic catalysts there can be added: alkali metals,
fastness to water especially at high temperatures.
such as lithium, sodium, potassium; alkaline earth met
Aromatic dihydroxy compounds however, can indeed
be converted during the complete inter-esteri?cation pe 55 als, such as magnesium, calcium, barium; alcoholates of
the alkali- or alkaline earth metals, such as sodium
riod in the presence of suitable basic catalysts into the
methylate and calciumethylate; phenolates, such as so
high molecular ?lm- and ?bre-forming state. But the
catalysts remaining in the end product spoil the structure
dium phenolate; sodium salts of dimonohydroxyarylene
pounds, in the presence of basic inter-esteri?cation cata- '
'benzoyl chloride, and toluene sulphochloride, organic
alkanes; hydrides of the alkali- and alkaline earth met
during working up in this case also with formation of
carbonic acid. Blown melts are thus obtained which 60 als such as lithium hydride and calcium hydride, oxides
--of the alkali- and alkaline earth metals such as lithium
make working up di?’icult or impossible. Mouldings pro
oxide and sodium oxide, amides of the alkali and alkaline
duced from these melts show a reduced stability to ele
earth metals, such as sodium amide and calcium amide,
vated temperatures and to water, ‘especially to hot water.
basic reacting salts of the alkali- and alkaline earth met
It has now been found that this drawback, in the inter
als with organic or inorganic acids such as sodium acetate,
esteri?cation of aliphatic, cycloaliphatic or aromatic di 65 sodium benzoate and sodium carbonate.
hydroxy compounds with dicarbonates of ' aliphatic or
In order to neutralise these basic catalysts a large va
aromatic mono-hydroxy compounds or in the polycon
riety of base-binding organic or inorganic substances can
densation of diary1-, dialkyl- or dicycloalkyl-dicarbonates
be added in accordance with the invention e.g. aromatic
of aromatic dihydroxy ‘compounds of thcmselveslor with 70 sulphonic acids such as p-tolyl sulphonic acid, organic
aliphatic, cycloa'liphatic or aromatic dihydroxy com
acid halides such as stearyl chloride, butyryl chloride,
3,022,272
4
or
into extendable ?bres and ?lms.
lies about 60° C.
chlorocarbonates such as phenyl chloroformate, p-hy~
droxydiphenyl chloroformate, and bischloroformates of
The softening point
Example 2
di-monohydroxy arylene alkanes, dialkylsulphates such
as dimethyl sulphate and bibutyl sulphate, organic
chlorine compounds such as benzoyl chloride and w-chlo~
A mixture of
45.6 parts of 2,2-di-(p-hydroxyphenylene)-propane
47.1 parts of diphenylcarbonate, and
0.008 part of lithium hydride
roacetophenone as well as acid salts of polycondensa
tion inorganic acids such as ammonium hydrogen sul
phate.
Base-binding substances which are volatile under
greatly reduced pressure at esteri?cation temperatures are
especially suitable since an incidental excess over that
required to neutralise the basic catalysts can be easily
are melted together under a nitrogen atmosphere with
stirring at 110~l50° C. The phenol which separates is
distilled off by further heating to 210° C. under a pres
The pressure is then
reduced to 0.2 mm. mercury gauge and the temperature
chloroformate and benzoyl chloride are examples of sub—
raised for one hour to 250° C., and for two further
stances of this group.
15 hours to 280° C. At the end of the condensation the
removed from the melt.
sure of 20 mm. mercury gauge.
Dimethyl sulphate, phenyl
In order to operate the process the inter-esteri?cation
is brought about between the dihydroxy compounds and
catalyst is neutralised by stirring 0.05 part of dimethyl
sulphate into the melt. The excess of neutralising agent
is ?nally removed by further heating under reduced pres
the di-carbonates of mono-hydroxy compounds, or the
polycondensation of the bis’phenyl-alkyl- or cycloalkyl
sure.
A viscous melt is obtained which solidi?es to a
carbonates of the aromatic dihydroxy compounds is 20 thermoplastic material melting at 240° C. which is suit
brought about with the' aforementioned basic catalysts
able, e.g. for the production from the melt or from
in a customary manner, preferably at temperatures of
solutions, for example in methylene chloride, of injection
from 50 to 330° (3., especially between 100—300‘’ C. and
mouldings and bristles, ?lms and ?bres which can be
orientated by stretching. The K-value measured in
or the neutral carbonate of the mono-hydroxy com 25 m-cresol is 51. Mouldings of the material are stable
pounds, at elevated temperature, preferably in vacuo, and
at working temperatures up to more than 300° C. with~
with introduction of nitrogen, until the desired degree
out decomposition or evolution of carbonic acid. Moulded
of condensation is completely or nearly attained.
bodies produced from the melt withstand elevated tem
According to the present invention the base-binding
peratures, even in the presence of water, for long periods.
continued by distilling off the volatile hydroxy compounds
substances are now introduced into the viscous melt. 30
This can be done by stirring into the viscous melt the
Example 3
A mixture of 550 parts of the bis-(phenylcarbonate)
exactly calculated quantity for neutralising the basic
of 2,2-di-(p-hydroxyphenylene)~propane, 228 parts of
catalysts or by introducing, optionally together with an
2,2-di-(p-hydroxyphenylene)-propane and 0.015 part of
indifferent gaseous carrier such as nitrogen, a volatile
baseébinding substance in vapour form. When volatile 35 the sodium salt of 2,2-di-(pshydroxyphenylene)-propane
are melted together with stirring under nitrogen. At
base-binding substances are used an excess over the quan
tity used to neutralise the basic catalyst can be removed
later by evacuation.
After the neutralisation of the catalysts, the inter
temperature between 120~200=° C. the phenol which sep
arates is distilled off at 20 mm. mercury gauge.
Finally
by further three hours’ heating at 280° C. under a pres
esteri?cation can if necessary be further continued to a 40 sure of 0.5 mm. mercury gauge a highly viscous melt is
limited extent for the attainment of a desired molecular
weight.
obtained. The alkali remaining in the catalyst is then
neutralised by the addition of 0.3 part of dimethylsul
phate to the melt and the excess of neutralising agent re
After the end of the poly-condensation the polycar
moved in vacuum. A highly colourless melt is obtained
bonate melt formed is converted by conventional meth
ods into granular form or directly into moulded bodies, 45 which solidi?es to a material with a K-value measured
in m-cresol of 53 and possessing the properties described
?lms, ?bres or bristles or the like. The polycarbonates
in Example 1.
obtained may be worked up from the melt without in
Example 4
volving the destructive in?uence of carbonic acid blow
ing, since even with prolonged heating over their melt
A mixture of 550 parts of 2,2-di-(p-hydroxyphen
ing points, they develop no carbonic acid. Shaped bodies 50 ylene)-butane, 650 parts of diphenyl carbonate and 0.025
produced from the melt display an especially good sta
part of the potassium salt of 2,2-di-(p-hydroxyphen
bility to elevated temperatures even in the presence of
ylene)-propane are melted together with stirring at 120°
water.
C. under nitrogen. The phenol which separates in the
The following examples are given for the purpose of
inter-esteri?cation distils oil‘ almost completely at the
55 temperatrue (of the melt) of 120-180” C. in the course
illustrating the invention, the parts being by weight.
.
Example 1
A mixture of
40 parts of hexanediol-l,6
42 parts of diethylcarbonate, and
0.003 part of sodium ethylate
are heated for half an hour to IOU-130° C. under re
of 30 minutes at 20 mm. mercury gauge. After further
stirring and heating to 280° C. at 0.5 mm. mercury
gauge the polycondensation is completed. The alkali
contained in the catalyst is then neutralised by introduc
60 ing 0.8 part of dimethylsulphate vapour with nitrogen
as a carrier.
Finally the melt is stirred for a further
half an hour at 0.5 mm. mercury gauge at 280° C. where
by the excess of dimethylsulphate is distilled off. The
polycarbonate is obtained with a K-value of 48 measured
ethyl alcohol separated by esteri?cation is distilled otf. 65 in m-cresol which melts at 210° C. and which can be
After a further 3 hours’ stirring at 200° C. under a pres
Worked up Without evolution of carbonic acid at tem
sure of 30 mm. mercury gauge the sodium ethylate used
peratures up to over 300° C. into injection moulds, ex
?ux with stirring and with introduction of nitrogen. The
as catalyst is neutralised by stirring 0.1 part of phenyl
pendable ?bres, ?lms and the like. The shaped bodies
chloroformate into the melt. Finally, the condensation
produced from the polycarbonate display an unusual sta~
is completed within 3 hours by heating to 250° C. under 70 bility to elevated temperatures, even in the presence of
a pressure of 0.5 mm. mercury gauge. The excess of
moisture.
neutralising agent is then distilled off. A viscous melt
Example 5
is obtained which solidi?es to a colourless high-polymeric
A mixture of 45 parts of 2,2-di-(p~hydroxyphenylene)body, which possesses the K-value of 65.4 measured in
m-cresol and which may be worked up from the melt 75 propane, 50 parts of di-o-cresylcarbonate,v 0.007 part of
3,022,272
calciumhydride and 0.01 part of sodium benzoate are
melted together with stirring under nitrogen. The greater
part of the phenol which separates distills oft at tempira
'tures of 140-200° C. at 20 mm. mercury gauge. A ter
a further 3 hours heating at 280° C. at 0.5 mm. mercury
gauge, 0.1 part of ammonium hydrogen sulphate are
stirred into the highly viscous melt obtained. The melt
is then stirred for a further half an hour at 280° C. and
0.5 mm. mercury gauge whereby the excess ammonium
hydrogen sulphate is removed. A highly viscous melt is
obtained of a polycarbonate with the K-value of 49
measured in m-cresol and with the properties described
in Example 2.
,
the melt a base-neutralizing compound selected from the
group consisting of phenylchloroformate, aromatic sul
fonic acid halide, w-chloroacetophenone, dialkyl sulphate
Example 6
A mixture of 46.8 parts of bis-phenylcarbonate of 2,2
-di-(p-hydroxyphenylene)-propane, 0.008 part of calcium
6
group consisting of aliphatic, cycloaliphatic and aromatic
dihydroxy compounds, (b) bis-carbonates selected from
the group consisting of bis-alkyl, bis-cycloalkyl and bis
aryl carbonates of aromatic dihydroxy compounds and
said organic dihydroxy compounds, and (c) said bis-car
bonates of aromatic dihydroxy compounds with them
selves, at temperatures from about 50 to about 330° C. in
‘the presence of a basic interesteri?cation catalyst until
highly polymeric polycarbonates are obtained, the im
provement
which comprises neutralizing the basic catalyst
10
‘at the end of the interesteri?cation reaction by adding to
and ammonium hydrogen sulphate in an amount at least
15 equivalent to the amount of the basic catalyst employed
in said interesteri?cation reaction.
2. In the process of producing highly polymeric ?ber
and ?lm-forming polycarbonates by interesterifying reac
hydride and 0.008 part of sodium benzoate is melted 'to
gether under nitrogen and with stirring. The diphenyl
carbonate split o?" is distilled off at 200° C. under a
tion mixtures selected from the group consisting of (a)
pressure of 2 mm. mercury gauge. After further heat 20 dicarbon'ates selected from the group consisting of ali
ing to 280° C. at a pressureof 0.2 mm. mercury gauge
phatic, cycloaliphatic and aromatic diesters of carbonic
the alkali catalyst is neutralised by stirring in 0.05 part
of dimethyl sulphate. The mixture is then stirred for a
acid and organic dihydroxy compounds selected from the
group consisting of aliphatic, cycloaliphatic and aromatic
further half an hour at 280° C. at 0.2 mm. mercury
dihydroxy compounds, (b) bis-carbonates selected from
gauge pressure, whereby the excess of dimethyl sulphate 25 the group consisting of bis-alkyl, bis-cyclo'alkyl and bis
is removed and a colourless high molecular weight ther
aryl carbonates of aromatic dihydroxy compounds and
moplastic polycarbonate is obtained which softens at
- said organic dihydroxy compounds, and (c) said bis-car
about 230° C., possesses a K-value of 52 measured in
~bonates of aromatic dihydroxy compounds with them
m-cresol and can be worked up from solutions, e.g. in
methylene chloride or from the melt, into stretchable ?le
ments or ?bres and injection mouldings.
30
Example 7
A mixture of 38 parts of the bis-phenylcarbonate of
selves, at temperatures from about 50 to about 330° C. in
the presence of a basic interesteri?cation catalyst and con
densing until highly polymeric polycarbonates are ob
tained, the improvement which comprises neutralizing the
basic catalyst after the liberation of substantially all of
the theoretically obtainable monohydroxy component of
2,2-di-(phydroxyphenylene)propane and 0.8 part of the 35 the carbonate by adding to the melt a base-neutralizing
compound selected from the group consisting of phenyl
pane and 0.001 part of the sodium salt of 2,2-di-(p-hy
chloroformate, aromatic sulfonic acid halide, w-ChlOl'O
droxyphenylene)-propane is melted together under a ni
acetophenone, dialkyl sulphate and ammonium hydrogen
trogen atmosphere with stirring. The neutral carbonate
sulphate, in an amount at least equivalent to the amount
bis-ethylcarbonate of 2,2 - di-(p-hydroxyphenylene)-pro
formed is distilled o?’ at 200° .C. under a pressure of 5
mm. mercury gauge. By further heating to 260-280° C.
under a pressure of 0.2 mm. mercury gauge, a highly vis
cous melt is obtained into which 0.05 partpof phenyl
of the basic catalyst employed in said interesteri?cation
reaction, and continuing the condensation until the desired
molecular weight of the polycarbonates is obtained.
3. The process of claim 2 wherein the base-neutraliz
chlorocarbon'ate are stirred to neutralise the alkali. The
ing compound is volatile at a temperature below the de
excess of phenylchlorocarbonate is then removed by half 45 composition temperature of the resulting polycarbonate,
an hour’s stirring at 280° C. and at 0.2 mm. mercury
and excess base-neutralizing compound is removed by
gauge pressure. The colourless high molecular Weight
distillation.
,
resin so produced with a softening point of about 230° C.
4.
In
the
process
of
producing
highly polymeric ?ber
and the K-value of 51 measured in m-cresol shows the
and ?lm-forming polycarbonates by interesterifying reac
same properties as the product described in Example 1. 50 tion mixtures selected from the group consisting of (a) di
Example 8
carbonates selected from the group consisting of aliphatic,
15 parts of the bis-(phenyl carbonate) of the resorcinol
(melting point 124-125° C.) and 0.01 part of the sodium
cycloaliphatic and aromatic diesters of carbonic acid and '
melted together under nitrogen and with stirring.
hydroxy compounds, (b) bis-carbonates selected from the
group consisting of bis-alkyl, bis-cycloalkyl and bis-aryl
carbonates of aromatic dihydroxy compounds and said
organic dihydroxy compounds, and (c) said bis-car
bonates of aromatic dihydroxy compounds with them
organic dihydroxy compounds selected from the group
salt of the 2,2-(4,4’-dihydroxy-diphenylene)-propane are 55 consisting of aliphatic, cycloaliphatic and aromatic di
At
200° C. and under a pressure of 12 mm. mercury gauge
the splitting o?f of the diphenyl carbonate begins. After
half an hour the pressure is reduced to 12 mm. mercury
‘gauge and the melt is stirred for 2 hours at 220° C. The 60
selves, at temperatures from about 50 to about 330° C. in
melt slowly becomes high viscous and is heated for fur
the presence of a basic 'interesteri?cation catalyst and
ther 2 hours at 250° C. and ?nally for a further hour at
condensing until highly polymeric polycarbonates are ob
270° C. under 0.5 mm. mercury gauge. Then 0.05 part
tained, the improvement which comprises neutralizing the
of phenylchlorocarbonate is mixed in and the excess of
this compound is distilled off in vacuo. A yellowish ther 65 basic catalyst after the liberation of substantially all of
the theoretically obtainable monohydroxy component of
moplastic polycarbonate is obtained which melts at about
210° C. It may be worked up from solutions of from
the melt into mouldings.
We claim:
1. In the process of producing highly polymeric ?bre 70
and ?lm forming polycarbonates by interesterifying reac
tion mixtures selected frcm the group consisting of (a)
dicarbonates selected from the, group consisting of ali
the carbonate by adding to the melt a base-neutralizing
compound selected from the group consisting of phenyl
chloroformate, aromatic sulfonic acid halide, w~chloro~
acetophenone, dialkyl sulphate and ammonium hydrogen
sulphate in an amount at least equivalent to the amount
of the basic catalyst employed in said interesteri?cation
reaction.
'
5. The process of claim 4 wherein the base-neutraliz
phatic, cycloaliphatic and aromatic diesters of carbonic
acid and organic dihydroxy compounds selected from the 75 ing compound is volatile at a temperature belowthe de~
3,023,272
8
7
composition temperature of the resulting polycarbonate,
and excess base-neutralizing compound is removed by
distillation.
6. The process for the production of a high molecular
?bre- and ?lm-forming polycarbonate which comprises
heating a mixture of hexanediol-1,6,diethylcarbonate and
a catalytic amount of sodium ethylate at temperatures of
from about 50 up to 250° C. under stirring and under re
duced pressure, adding phenylchloroformate in excess of
9. The process for the production. of: ‘a high molecular
?bre- and ?lm-forming polycarbonate whichscomprises
heating a mixture of bis-(phenylcarbonate) of, 2,2-di-(p
hydroxyphenylene)propane and a catalytic amount of
calcium hydride and sodium benzoate under stirring’ to
temperatures of from about 50 up to 280° C. and under
reduced pressure, adding (ii-methyl sulphate in excess of
that required for neutralizing said catalyst to. the melt, and
removing excess. neutralizing agent under‘ reduced. pres»
that required for sodium ethylate- neutralization to the 10 sure.
melt before the polycouclensation. is completed, and, dis
10. The process for the production of a high molecu
tilling off excess phenylchloroformate under reduced
iar ?hre- and ?lm-forming polycarbonate, which com
7. The process for the production of a high molecular
prises heating a mixture of the bis-(phenylcarbonate) of
resorcinol and a catalytic "amount of the sodium salt of
‘fibre and ?lm-forming polycarbonate which comprises
2,2-di-(p-hydroxyphenylene)-propane under stirring at
heating a mixture of bis-(phenylcarbonate) of 2,2-di-(p—
temperatures of from about 50 upv to 270° C., adding
phenylchlorocarbonate in excess of that required for neu
tralizing said sodium saltto the melt at the end of the
polycondensation reaction and removing excess neutral
pressure.
a
hydroxyphenylene)~propane, 2,2 — di - (p-hydroxyphenyl
ene)-propane and a catalytic amount of the sodium salt
of 2,2-di-(p-hydroxyphenylene)-propane under stirring at
temperatures of from about 50 up to 280° C.- and under 20 izing agent under‘ reduced pressure. '
reduced pressure, adding di-methyl sulphate in excess of
that required for neutralizing said sodium salt to the melt
atv the end of the "polycondensation reaction and remov
ing excess di-methyl sulphate under reduced pressure.
8. The process for the production of a high molecular
?bre- and ?lm-forming polycarbonate, which comprises
heating a mixture of 2,2-di-(p-hydroxyphenylene)—pro
pane, di-o-cresylcarbonate and a catalytic amount’ of cal-v
cium hydride and sodium benzoate under stirring to tem
peratures of from about 50 up to 280° C. and under re 30
References Cited in the tile of this patent
UNITED STATES PATENTS
1,995,291
2,210,817
2,739,957
2,789,968
2,808,390
Renolds et a1. ________ __ Apr. 23, 1957
Caldwell ______________ __ Oct. 1, 19,57
FOREIGN PATENTS
duced pressure, adding ammonium hydrogen sulphate in
excess of that required for neutralizing said catalyst to
the melt and removing excess neutralizing agent under re
duced pressure.
Carothers ____________ _.. Mar. 26, 1935
Peterson _______________ __ Aug. 6, 1940
Billica et al. _________ __ Mar. 27, 1956
650,002
546,377
Great Britain __________ __ Feb. 7, 1951
Belgium _____________ __ Mar. 23, 1956
L.
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