Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates -to a novel method for preparing
improved polyethersulfones~
Polyethersulfones are important and useful polymers
in the manufacture of films, sheets and molded parts Such
polymers are normally prepared by reacting an alkali metal
salt of a dihydric phenol with a 4,4'-dihalodiphenyl sulfone
compound. The alkali metal salt is usually obtained by re-
acting a strong base, such as potassium or sodium hydroxide with
a dihydric phenol U.K Patent 1~078J234 describes the above
method where the dihydric phenol may be BiSphenol A~ It is
also known from U.K. Patent 1,264,900 to react a Bisphenol A
~ or a blend of Bisphenol A and an unsubstituted biphe.nol with
:; an equal molar amount of a 4,4'-dihalodiphenyl sulfone in the
presence of potassium carbonate I'his reference teaches-that
in order to obtain polymers of desirable moleculax weight the
molar amount of potassium carbonate employed should no-t be .
less than the combined amount on a molar basis of the dihydric
phenol and 4,4'-dihalodiphenyl sulfone present ~t i~ further
known to polymerize the potassium diphenoxide salt of 3,3'5,5'- .
tetramethyl-4,4'-biphenol with 4,4'-dichlorodiphenyl sulfona --
: Schultze, Th0 Klnetics of Solu.tion Polycondensation of Aromatic
Pol~ethers. Advances in Chemistry Series (ACS), 1969, Vol~ 91,
pages 692-702
However, there is no disclosure in the prior ar-t that
polyether sulfones having controllable molecular weights ranging
from within 20,000 to 125,000 may be prepared from 3,3',5,5'-
~ tetraalkyl-4,4'-dihydroxybiphenyl using a stoichiometric excess
of 0 to 30 perecent of an alkali metal carbonate or bicarbonate,
nor has there been any suggestion of polymeric polyethersulfones
derived from 3,3',5,5'-tetraalkyl-4,4'-dihydroxybiphenyl and
-- 2
L551~7
having a density o no more than 1.20 gm/cc
It has now been discovered that when a 3,3'5,5'-
tetraalkyl-4,4'-dihydroxybiphenyl is reacted with a substanti-
ally equal molar amount of a 4,4'-dihalodiphenyl sulfone com-
pound and from about 0 to 30 percent of stoichiometric excess
of an alkali metal carbonate or bicarbonate in khe presence
of a dipolar aprotic solvent, improved polymers are formed,
Not only do the polymers exhibit excellant high heat dis-
tortion temperatures and other advantageous properties, but
surprisingly the polymers or products made therefrom possess ~:
unusually low densities. Such lower densities provide obvious
economic savings in the manufacture of films; sheets, or
molded parts
According to the invention there is therefore pro-
vided a process for preparing a polyathexsulfone polymer having
a molecular weight from between 20,~000 to 125~000 which com-
prises the substantially equimolar reaction of a 3,3'-5~5'- ::
: tetraalkyl-4,4'-dihydroxybiphenyl with a 4,4'-dihalodiphenyl
:~ sulfone compound and from about 0-30 percent stoichiometric ;~
20 excess of an alkali metal carbonate or bicarbonate in the
presence of dipolar apr~otic liquid solvent
Accor~ing to the invention ther~ is al~o prov~d~fl
a polyethersulfone polymer derived from a 3,3',5,5'-tetra- ~ .
alkyl~4,4'-dihydroxybiphenyl having a molecular weight of
: from 20,000 to 125,000 and a density of no more than 1 20 gm/cc~
The reactants which may be utilized and which are
critical to the present invention are described. in detail
....
below.
The 3,3',5,5'-tetraalkyl-4,4' dihydroxybiphenyl
which may be employed in carrying out the present invention has
the following formula
;' ' .
S97
Rl ~3
~\
HO - ~ OH
R2 R4
wherein Rl, R20 R3and R4 are alkyl and may be the same or
different,
As used herein, the term alkyl refers to any mono
valent radical derived from a saturated aliphatic hydrocarbon
by removal of one hydrogen atom therefrom~ The term includes
both straiyht chain and branch chain materials containing from
1 to about 12 carbon atoms. Preferred results are achieved
with the alkyl substituents containing from 1 to about 5 carbon
atoms. In the compositions of the present invention it is
preferred to employ symmetrical biphenyls - i.e, thos~ in
which the substituent Rl equals R3 and R2 equals R4. A spec;fic
starting compound which is most preferred is tetramethylbi- -
phenol (TMBP), wherein the alkyl substituents are all methyl~
other biphenols which may be useful inclu~e those where ~he
alkyl substituent may be ethyl, propyl and secondary butyl.
sy the term molecular weight is meant, ~nless otherwise
specifically indicated, weight average molecular weight,
The tetraalXyl biphenols utilized in the process
; of the invention are commercially availahle or may be prepared
according to the teaching of U.S, patent 3,804,865,
'rhe halogen atoms in the dihalodiphenyI sulfone
~ compound are preferably chlorine for economic reasons~
; The fluorine derivative is more expensive but will cause the
formation of polymer to proceed at à faster rate, 'rhe bromine
derivatives are more comparable to the chlorine derivatives
but may require adjustment of reaction tempera-ture, Iodine
derivatives genera~ly react slower,
-- 4 --
~'
3L5~7
The alkali metal carbonate or bicarbonate, is prefer-
ahly potassium carbonate although other alkali metal carbonates
such as sodium carbonate may also be useful~ Similarly the
bicarbonates such as potassium bicarbonate will also have
utility in the process of the invention. ~t has been dis-
covered that the amount of carbonate or hicarbonate is critical
to the formation of the desired polymers. Specifically a ~ ;
stoichiometric excess of from about 0 to 30 per cent has been
found essential to provide the polymers having the desired
properties~ Amounts less than 0 percent stoichiometric excess
yield polymers having undesirable low moleculax weight and -~
correspondingly, amounts in excess o 30 percent provide polymers
having molecular weights above 125,000 which polymers are
difficult to process. By stoichiometric is meant one equivalent
of base per chlorine atom. The desirability of the polyether-
,.~ . ,
sulfone product is directly related to a combination of pro-
perties including density, molecular weight, hardness, glass
transition temperatureO solvent resistance, fIexural and~ -
tensile strength, While properties such as low density,
.~ ~
high glass transition temperatures and solvent resistance
characterize all the polymers of the present invention,
higl;e~ mol~cula;- we ght p-~lyniers tend to show an incre~se
in the toughness. Optimum flexural and tensile properties
will be found in polymers having from 30,000 to 80,000
molacular weight,
Polymerization reaction times may vary and will
be dependent on the molecular weight desired. For example
to produce a polymer with low molec~ular weight (e.g. 20,000)
it is suggested to allow the reaction to proceed for about
2 hours at 130 - 150 and for about 4-5 hours at 150-170.
:
~'
/
,
Higher molecular weight polymer wi.ll require longer reaction
times generally from 24 to ~8 hours at 130 - 150C, ~ollowed
by further polymerization at 150-170C, Shorter times at
higher temperature are possible but are not reco~nended in
view of possible deleterious results such as polymer deterio-
ration and undes.irable color formation, Lower temperatures
such as 100-125C, may slow the rate of reaction considerably
Preferred temperature ranges are from 140-160C, with reaction
times of between 4 to 100 hours, Another consideration af-
fecting the temperature of the reaction is the boiling point
of the solvent, For obvious reasons the temperature of the
reaction should never substantially exceed the boiling point .
at atmospheric pressure, The polymerization is de~irably
allowed to proceed at two temperature stages to acilitate the
removal of any azeotrope that may be present during the re-
action, For example, the azeotrope containing water may be
distilled in the lower temperature stage to remove the water
after which the solvent may be reused. To avoid oxidative side
: reactions, the polymerization is expediently carried out in
~- 20 an in~rt atmosphere, for example under nitrogen, The reaction
is preferably carxied out under conditions to remove any sub-
stanti~ anount of ~.t~ for~e~,
The polymerization reaction requires the presence of
a dipolar aprotic reaction solvent. Specific solvents found
useful in the process of the invention include dimethylacetamide~
;~ hexamethylphosphoramide, sulfolane, dimethylsulfoxide and
tetramethylurea. A particularly preferxed solvent is dimethyl-
acetamide, Sufficient solvent should be used to enable
adequate stirring of the xeaction mixture during the polymeriza-
tion process particularly as the reaction mix-ture becomes moxe
~,i!
~3lS9~
viscous Usually a ratio of 5-8 parts of solvent for ~ne
part of the biphenyl and the 4,4'-dihalophenyl sulfone mix-
ture will be adequateO More solvent should be used for the
formation of hiyher molecular weight pol~ners
The polymerization reaction tends to produce waterO . .
When water is produced in quantities exceeding 5 to 1 percent ~ ~
by weight of the reaction mixture, it is advisable to re- ~ -
move this water, preferably by the distillation of a water-
containing azeotrope present in the system. While a variety
of inert azeotrope-forming organic liquids such as benzene,
-~ xylene and chlorobenzene may be utilized for this purpose,
a preferred azeotroper is toluene. In general, the amount
of azeotropex required is determined by the amount o~ water
relsased during the reaction. Amounts of 25 to 33 percent
by weight of the amount of solvent medium are expectea t~ be
adequate to keep the system sufficiently anhydrous
. If desired, polyethersulfone polymers may be prepared
using a blend of starting biphenol monomers For exa~ple
polymers may be prepared from a blend of tetralkylbiphenol ~:
with bisphenol A or thiodiphenol The polyethersulfones
prepared from such a blend tend to have lower glass tran5i-
tion tempereratures ar-d hiyher densities
The polymer resulting from the process of this
invention can be isolated, recovered and , if desired~ puri-
fied according to conventional techniques For example,
solid polymer may be isolated ~y high-speed mixing of the
polymer solution (prior filtration of the polymer solution
is optional) with excess water or an organic nonsolventO
such as methanol or acetone Filtration, thorough washing
of the filter cake with water, and vacuum drying will yield
substantially sal-t-free polymerO Methanol and acetone are
also useful washing reagents for the removal of colored and
low molecular weight impurities. Due to their high volatility,
their use will also facilitate drying o~ the so~id polymers.
Reprecipitation techniques may include the use of t in addi-
tion to the reaction solvents, selected polymer solvents,
such as dimethylacetamide, chloroform or pyridine, in combi-
nation with nonsolvents, such as water, methanol or acetone.
A particularly preferred purification technique involves
spontaneous reprecipation from cyclic ethers with near-
qUantLtatiVe yields o~ purified amorphous polymer Polymers
subjected to this purification technique show after compression
molding not only increased tensile and flex strength but exhibit
increased thermal stability and a narrowing of the molecular
weight range.
Cyclic ethers which are suitable for spontaneous
reprecipitation include, dioxane, tetrahydrofuran, 2-methyl-
tetrahydrofuran, tetrahydropyran, epichlorohydrin, 1,3-dioxo-
lane, 1,2-epoxypropane and 4,4'-dimethyl-m dioxane.
Thermal stability of the polymer may be improved
alternatively or in addition to spontaneous reprecipitation
hy an aclditiv~ such ~s for sx~mple tris(r.onylpheny ) phosp~.it~
or by extraction and subsequent reprecipitation. Measurement
of thermal effects by differential scanning calorimetry (DSC)
and visual inspection of compression molded polymers indicated
that thermal stability may be improved by 25C
The following examples are included t~ further
illustrate the naturs of the inventi~on~ In the examples all
percentages are by weight unless otherwise indicated Densities
have been calculated by the air displacement method using a
' ' .
,
~.
.
,
Beckman Air Compression Pycnometer, Model 930. Glass transi-
tion values (Tg) were obtained by analyzing a sample in the
"990 Differential Scanning Thermal Analyzer" available from
Du Pon-t Instruments. Analysis was performed in a nitrogen
- atmosphere using a standard heating rate of 10C/min
EXAMPLE 1
(Stoichiometric Amount o~ K2C03)
Into a three neck reaction flask equipped with
a 1 foot Vigreux column, having attached thereto a Dean-
Stark water separator and vertical condenser was placed
6.05 gm ( 025 mj terramethylbiphenol, lO0 ml. dimethyl-
~; acetamide, 7.18 g. (0.025 m) of 4,~'-dichlorophenylsulfone,
3~45 g. (~025 m) of potassium carbonate, and 30 ml of toluene.
The charge was heated while in a nitrogen atmosphere at 138-
145C for 64 hours while toluene was refluxed at 105-133C.
and the water of reaction was collected. Toluene was then allowed
to distill at pot temperatures of 150-165C for 3 5 hours -~
After cooling, the product was precipitated with water (1.6
liters) in a blender. The product was filtered and washed
with water until substantially free of Cl The product was
an off-white spongy solid wLth low bulk density
,; .
- .
;' ,
...
,''
,
. ;~, .
59~7
Q) . '
,
o
~ o ~ n o ~ In
C) ~ d, ~ ','
~ . .
. .
o .:
t`l ~ oq ~a ~ g o ~ ~ ,
N a) O I I I ~ ~ ~ t~
~ ~ æ ~
. .
C)
O ~ O
. tO ~ o o u~
~ ~ ~ ..
.~ . ~ ~ ~ O ~ ~
,
O ~
nl o tO ~ ~q 00 0 ~ O
r~
o ~ : -
H O : :
: o C~) o
~ ~ a) I a) I I ~ ' t`
':; ~~ tn O ~ ~:
a: ~
O : ,:
E~ ~) ¦ ou~ N O
~ o 1
, , O' ~ , ~ '
o r~ O
~ o
.:~ ~` I L~ ) r~
. ~ o ~
~ ~q o O : ,
U U~ o ::-
I a ,~ O ~ ~ ~,, L
rl u~ ~ F F. rl Fl rl O F. ~ tJ` O 1'~ C)
OO u~ ~ tq 1~ 0 U O r~) h ,a rdO O rl rl o :
r-l~ O ~ I ~ ~ ~ ~rl ~1 O ~: r~U O ~I C) ~
QI~ u3 U ~~ a) ~ ~ S~
~3o x ~ u~ a) u ~4 ~ ~ ,5~ 1 o ~1 C.)
~au ~ o ,~ ~ ~ p~ U ~
' ~ ~1~ O
-- 10
~1&~597
EXAMPLES 2-7
Example~ 2-7 prepared according to -the procedure of
Example 1 with varying amounts of KsCO3 show the properties
outlined in Table I. Certain oE the examples as seen in
Table I have additionally been washed with methanol or
acetone. In those examples one part of product was washed
with 10 parts of either methanol or acetone per 1 part polymer.
Example 5 was reprecipitated from 5% pyridine solution by adding
10 parts of water, Example 6 was reprecipitated from a 5%
solution of polymer in chloroform by adding 3 parts methanol.
Both the additional washing and reprecipitation techniques
will improved the purity of the polymer by removi~g low mole-
cular weight and coloured by-products.
.
Example 8 is a comparative example using NaHO instead
of K2CO~.
COMPAR~TIVE EX~MPLE 8
(Prior Art Process)
24,22 g (0.1 m) of TMBP was dissolved in a mixture of
49 g (44.5 ml) dimethylsulfoxide (DMSO) and 140 g (127 ml)
chlorobenzene in a 4-neck 500 ml. flask, fitted with paddle
stirrer, thermometer, N2 sparge, dropping funnel and fraction-
ating column which column was connected to a water separator
and condensor. The clear amber solution was heated under a
nitrogen atmosphere a-t 63-83C while 17.5 g of a 46,5% NaOH
solution (0,20 equivalentc) was added over a 7 minute pe,riod~
The resulting thin slurry was heated at 114-134 and water
removed azeotropically (1 hr,1. Additional DMSO (44,5 ml) was
added while chlorobenzene wa5 distilled at 134-160 ~1 hr.),
A slurry was obtained. A heated solùtion of 28~72 g ~0.1 m)
'~ 30 4,4'-dichlorophenylsulfone in chlorobenzene (30%) was added to
the slurry at 155-158 over a 15 minutes period, A further
amount of DMSO (44,5 ml) was added -- -
.
-- 11 --
~'
'~h
97
_ . . . ~ '
. . ~ ,, .
. . . ..
~ -~
r~
h t'~l
0 ~ I I i ' '
~1 ;i
C) , '~:
~:~ O
~ 1
O O N ~r) 1` GO .
. C`l O I ~) I It) ''
t`l o I tn
~1 `. ~ ~ I
~ a ~ ~
: u~
U~
.
~, I
H I a) ~ U : :
O o ~ U ~ G) ,
O O
I ~I ~O O C`l
I. ~ l h 0: ~ : ~ -
U U O ' : : ~ ,:
'' U 0 U ~ - .
.~
I ~ g o ~ ~ a) -
O u~
, ~ '
0 ~
:,-: ~) a)a~: :
0 ~ ~ . ,
~1 ~ s a)
I I , I ~a ~ ,:: ,,
0 . ~ :
S
, ,~
:' ~ ~ a
O p ~
0
~
0
~ t"3 `~ , ~
.. ,1 _ ,1 5 0
X U
0 o ~
~IJ U ~ 1 ~ aJ U a)~1 0
~1 ~1 U ~ m
~ u7 ~ ~ a) X aJ ~ ~
k S~ 1 0 h 5`1 m
0 ~ ~ ~ ~ ~ 0~ ~
x a E~ X ~ N ~
-- 12
.,
,; ' ~ ' '
LS517
T A B ~, E ~TI
.
~ Comparisons of Dioxane~Treated and Untreated Polyme~
~: '
Examle 3 Example 10
Untreated Dioxane-treated ,
.~ Mn 15,800 25,900
Mw 62,200 63, aoo
.~ Mw ;:::
Mn 3.94 2.47 ::~
RV (CllC1.3) 0.824 0,872
. Tg (C) . 270 275 : . ~ ~
~; Cl (%) . 0.38 0.14 ~ : :
:`: ~ : -' ~'`
Compression ~ ~ : :
Moldinq: ~
~ ~ . ~
Tensile Strength (psi) 11,600 12,400
Modulus~(106 psi) ~ 0.35 : ~ ~ 0,30
Flexural Strength ~
.. (psi) 14,:000~ : 21,000~ :
: Modulus (106 psi) ~ 0,39 ~ 0.40 : ~:
Elongation (%) 5.85 4.0
Clarity fair very good
. Color amber light amber .,.
~'
,:j. :
;,, ~
''',' ~ '
: 13
, .:
~'.' \ '.
."''~ ' .
~'':: :
' ' .
;~
5~
while the precipitated solids dissolved. The final stage of
reaction was carried out at 156-160 ~or 4,5 hours during
which the viscosity built up, The product was cooled and
treated with 2 ml methyl iodide at 125 for 10 minutes to
methylate residual phenolic hydroxyl groups, Upon cooling
the product was obtained as a moist solid, It was mixed well
with 1500 ml H20, filtered, and washed with water until
chloride ion free, The moist. filter cake was then transferred
into 1 liter of methanol, stixred well and filtered, The
. 10 product was washed with methanol, air-dried and then vacuum
; dried at 120C and 1 mm Hg pressure for 3 hours, The yield
of polymer, was 45,3 g (99O3%),
Several polyethersulfone polymers were compression
molded in the form of 3" diam., usin~ a 50 ton press (Pasadena :
Hydraulics, Inc.). Electrically heated platens were used
with the top platens having a temperature of 600F and the
bottom platen a temperature of 570-590F. The weight o~ each ~ ~
polysulfone polymer sample was 10 g, The mold release agent :.:
was Fluoroglide (TM), available from Chemplast: Company, The
.~ 20 samples were heated for 10 minutes at 600F at zero pressure
followed by 10 minutes at 600F and 7,000 psi. The molded
part~ ~r~^ r~.ov~. at 185F,
The properties of the molded parts prepared by the
: above procedure are shown in Table II,
The polymers of the present invention are also useful
in the manufacture of films and extruded sheetq~ Standard
solvent casting and extrusion techniques such as described in
~ the Enc~cloPerdia of PolYmer Science~and Technolo~y, Inter-
:~
: science Publi,shers, Vol, 6, pages 764~777 may be employed,
~he following ~xample 9 illustrates a method to
~olvent-cast a film,
- 14
, .
Examples 10, 11 and 12 illustrate three techniques
to improve thermal stability. Other improved properties
ara shown in Table III.
E,X~MPLED 9
1,6 g of polymer prepared according to the method
of Example 2 was dissolved in 65 ml of pyridine and filtered,
The clarified solution was cast on a glass plate within a
Teflon (TM) frame in a dry and dust free atmosphere, A clear
film of ~,5 mils thickness was obtained after 24 hours at a
temperature of 65C. The film was tested and showed a tensile
strength of 8900 psi, a modulus of 0.33 x 106 psi and an
elongation of 4.5%.
EXAMPLE 10
Purlfication by Dioxane (spontaneous reprecipitation)
A sample of TMBP polyethersulfone (50 g) which has,
been prepared according to Example 3 and which has been
purified by a solvent treatment st~ep with acetone at room~
temperature is mixed with 930 ml dioxane and stirred~for 20
minutes. After 20 minutes when most of the polymer has dis-
solved, the solution is filtered through Whatman ~o. 4 filterpaper and a layer of Super Cel filter aid~ The filtration is
completed within 20-30 minutes. The filter cake is washed
with 250 ml dioxane. The combined filtrate is then stirred
gently for 24 hours at room temperature, During this time
.
spontaneous re-precipitation of purified polymer occurs,
The product is filtered, washed with 300 ml dioxane and 500 ml
methanol, and is then dried at 65/16 hours at atmospheric
pressure and at 80/~ 1 mm for 68 hours. The product is re-
covered in 72% yield as a light yellow powder, Properties
of the untreated and dioxane-treated product (as amorphous
g7
powder and compression-molded specimen) are gi~en in the
attached Table III,
EX~MPLE 11
Tris(nonylphenyl)phosphite Additive
A sample of 15 g TMBP polysulfone with R,V, = 0.69,
acetone-washed and prepared as in Example 2 of the invention,
was mixed with 150 ml acetone, containing 0,15 g tris(nonyl
phenyl)phosphite, The slurry is stirred and the solvent is
gradually allowed to evaporate at room temperature, The
product is then dried at 75/C 1 mm for 2-5 hours. A com- ;
pression molding of this polymer was made at a temperature
25C higher than a control without additive, No thermal
deterioration is noted in the treated sample, Some deteri-
oration is seen at the edge of the control sample, DSC
. .
showed a 25 higher onset of thermal effects in the treated
sample versus control. -
EXaMPLE 12
Extraction Followed bv Re~reci~itation of Polymer
~, ; .
14.5 g of a sample of acetone-washed polyether-
sulfone prepared according to Example 2 was dissolved in 300 ml
chloroformO The solution was extracted three times with 50 ml
0.23 N H2S04, followed by six extractions with 75 ml water,
The chloroform solution was then filtered through a layer
of filter aid. Polymer was precipitated by adding one part
thé chloroform solution to two parts of rapidly stirred
methanol, The polymer precipitates as a white solid and is
filtered and washed with methanol and acetone, The polymer
is dried at 95/~ 1 mm for 4 hours~ The product has excellent
color, A compression molding of this polymer made at a tem-
perature 25~C higher than a control had better color and
- 16
' ''
~1S97
showed no thermal deterioration. The control sample showed
some deterioration at the edges, DSC analysis showed a 25
higher onset of thermal effects in the treated sample versus
control.
~,
,` ~ . ~ ' :'
:~ '
- 17
.
