Note: Descriptions are shown in the official language in which they were submitted.
RD-8971
The present invention relates to film forminy poly-
formal resins having an intrinsic viscosity of at least
0.3 dl/g. More particularly, the present invention relates
to the reaction of methylene halide and bisphenol is a
mixture having an excess of methylene halide and alkali
hydroxide.
Prior to the present invention, as shown by Barclay
U.S. Patent 3,069,386 dated December 18, 1962, polyformal `
resins were prepared by reacting a disodium diphenolate and
a methylene halide in the presence of a polar organic solvent
under substantially anhydrous conditions. As taught by
Barclay, the reaction was sensitive to small amounts of
water and other impurities containing hydrxyl groups which
caused undesirable side reactions. As a result, the poly-
formal resins made by the method of Barclay had an extremely .
low reduced viscosity. It was found that the polyformal
was unsuitable as a thermoplastic because it was extremely
brittle and has very little strength. As a result,
Barclay used the polyformal as an intermediate for making a ~ :
polycarbonate-polyformal copolymer by a standard phosgenation
procedure.
The present invention is based on the discovery that
film forming polyformals having an intrinsic viscosity as .
high as 2.0 dl/g in chloroform at 25C and consisting -~
essentially of chemically combined units of the formula,
(1) -OROCH2- ,
where R is a divalent C(6_30) aromatic radical, can be made
by effecting a reaction under substantially anhydrous con-
ditions between methylene halide and a bisphenol of the formula,
7 ~
RD-8971
(2) H0-R-OH
where R is defined above, in the presence of an alkali hydroxide,
an~ the alkali hydroxide and methylene halide are maintalned
during the intercondensation reaction at greater than stoichio-
metric concentrations. Unlike Barclay's polyformals, havingintrinsic viscosities less than 0.2 dl/g and undesirable physical
properties, such as brittleness, ~he polyformals of the present
invention have been found to possess intrinsic viscosities greater
than 0.3 and even as high as about 2.0 dl/g. Polyformals derived
from bisphenol-A, for example, can have tensile strengths o
about 7000 psi with 110% elongation and Gardner impac~ values
greater than 320 in. lbs. In addition, the polyormals of the
present invention can be converted to copolymers by standard
phosgenation techniques and can be blended with various thermo-
plastic materials to impart improved properties thereto.
Radicals included by R of formulas 1 and 2 are, orexample, phenylene, tolylene, xylylene, naphthalene, etc.;
halogenated derivatives of such divalent aromatic hydrocarbon
radicals, such as chlorophenylene, bromotolylene, etc., divalent
radicals, such as
-RQR- ,
O O
where Q can be cyclohexyl, fluorenyl, -0-, -S-, -C-, -S-, -C-,
Cl~ ~Cl
and -CyH2y~ and y is equal to 1 to 5 inclusive.
There is provided by the present invention a method
for making aromatic polyformal resin consisting essentially of
chemically combined units of ~ormula (1), where prior to the
present invention aromatic polyformals were made by reacting
an alkali diphenolate and a methylene halide in the presence
of a polar organic solvent under substantially anhydrous con-
2~7
RD-8971
ditions resulting in a reaction mixture highly sensitive -to
water and other impurities containing hydroxy groups, tending to
cause undesirable side reactions and producing polyformals having
an intrinsic viscosity of less than 0.2 dl/g, the improvement
which comprises agitating under substantially anhydrous conditions
a reaction mixture comprising methylene halide, bisphenol
of formula (2), alkali hydroxide and a member selected from
the class consisting of a phase transfer catalyst and a dipolar
aprotic solvent, where there is utilized in the reaction mixture
per mole of bisphenol more than 1 mole of methylene halide and
more than 2 moles of alkali hydroxide resulting in a reaction
mixture less sensitive to water and other impurities containing
hydroxy groups, and capable of providing film-forming moldable
aromatic polyformals having an intrinsic viscosity greater
than 0.3 dl/g.
Some of the bisphenols of formula (2) are compounds
such as:
2,2-bis(4-hydroxyphenyl)propane (bisphenol-A);
2,4'-dihydroxydiphenylmethane;
bis-(2-hydroxyphenyl)methane;
1,1-bis-(4-hydroxyphenyl)ethane;
1,1-bis-(4-hydroxyphenyl)propane;
2,2-bis-(4-hydroxyphenyl)-pentane;
3,3-bis-(4-hydroxyphenyl)pentane;
4,4'~dihydroxybiphenyl;
4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl; ~:
2,4'-dihydroxybenzophenone;
4,4'-dihydroxydiphenylsulfone;
2,4'-dihydroxydiphenylsulfone;
4,4'-dihydroxydiphenyl sulfoxide;
- 3 -
RD-8971
4,4'-d-~h~droxydiphenyl sulfide;
hydroquinone;
resorcinol;
9,9-bis(4-hydroxyphenyl)-fluorene
3,4'-dihydroxydiphenylmethane;
4,4'-dihydroxybenzophenone;
4,4'-dihydroxydiphenylether;
1,1-dichloro-2,2~bis(4-hydroxyphenyl)ethylene, and
1,1,1-trichloro-2,2-bis(4-hydroxyphenyl)ethane.
Methylene halides which can be used in the practice
of the invention, are, for example, methylene chloride, methylene
bromide, chlorobromo methane, etc. Alkali hydroxldes which can
be employed in the practice of the invention are, for example,
potassium hydroxide whi~h can be in the form of pellets, powder,
etc., sodium hydroxide, etc.
The polyformal resins having units of ormula (1~ are :~
thermoplastic injection moldable materials which can be con-
verted to films and fibers. Preferably, the poly~ormal resins
are transparent injection moldable film forming and fiber form~
ing thermoplastic materials. In particular instances, the poly-
formal resins of the present invention may bP translucent or
cloudy materials, depending on the degree o crystallization of
the resulting polymer.
The polyformal resins of the present invention also
can be phosgenated to produce polyformal~polycarbonate copolymers.
The polyformals of formula (13 and the polyformal-polycarbonate
copolymers can be further blended with other thermoplastic
organic resins, such as Lexan ~ resin, PPO ~D resin, Valox ~
resin, all products of the General Electric Company, over wide
proportions by weight, such as from 1% ~o 99% of the polyformal
RD-8971
resin to 9g% to 1% of the high perfo~mance thermoplastic
organic resin. The polyformal reslns of the present invention
also can be blended with various fillers, such as glass fiber,
silicon carbide whiskers, silica fillers, etc., stabilizers,
pigments t flame retardants , etc.
In the practice of the inventi.on, the polyformal
resin can be made by effecting contact at a temperature of 0C
to 100C and preferably 40C to 100C between methylene halide
and blspheno' in the presence of alksli hydroxide. Reaction
can be conducted between excess methylene halide and blsph~nol
until the latter has been completely reacted.
Reaction between the methylene halide and the bisphenol
can be effected under substantially anhydrous conditions.
Reflux temperatures at atmospheric pressure or above atmospheri.c
pressure can be used along with agitation of the mixture. Re2c-
tion between methylene halide and bisphenol in the presene of
excess alkali hydroxide can be accel~rated by using a substan-
tially inert organic solvent in combination with methylene halide,
such as a nonpolar or dipolar aprotic organic solvent. Nonpolar
organic solvents which can be employed in the methylene halide
are, for example, chlorobenzene, dichlorobenzene, benzenQ, toiuene,
etc. In addition, there can be used dipolar aprot:ic solvents,
such as N-methylpyrrolidone, tetrahydrofuran, dimethylsulfoxide,
etc.
Experience has shown that when methylene halide is
employed in the absence of a dipolar aprotic solvent, effec~ive
results are achieved if a phase transfer catalyst is used to
facilitate in situ formation of the alkali salt of the bisphenol
and the subsequent condensation reaction with the methylene
halide. Suitable phase transfer catalysts are, for examPle,
3.~ 4~7
R~-8971
quaternary ammonium and phosphonlum salts, such as describ~d in
JACS 93, 195 (1971) by C.M. Starks. A proportion o~ from about
0.01 to 0.5 mols of the phase transfer catalyst pe.r mol of the bls
phenol has been found to provide for effective results, and
preferably from 0.02 to 0.10 mols of phase transfer catalyst per
mol o bisphenol can be employed.
The intercondensation reaction can be conduc~ed over
a period of from 0.1 hours to 24 hours cr greater depetld^ing upor
such factors as the nature of the methylene halide, whether an
organic solvent is employed in combination with the methylel~e
halide,the type of such organi.c solvent, temperature of the reao~
tion, the degree o~ agitation, etc. In particular instances,
for example, the more hignly reactive methylene bromide carL b~
substituted for methylene chloride or a mi~ture OL Ctll.OrO~enZen?,
with methylene chloride will reflux at a higher temperature. '.
In addition, the reaction can be conducted at elevated pressu-res,
or in a closed system to permit the methylene halide ~o xeact
with the bisphenol at a higher temperature. Those skilled :in
the art would know, for example, that the methylen.e halide
itself, when used in excess amo~nts, can serve as a suitab`le
organic solven~ as well as a reactant.
The foll.owing examples are given by way of :illustr~
tion and not by way of limitation. All parts are by w~i~ht,
unless otherwise speceified.
Example 1.
A mixture of 114 parts ~a. 5 mol) of bisphenol-A,
95 parts (1.7 mol) KOH pellets, 23.3 parts (.05 mol) of
~`~ Aliquat 336 (95% ac~ive monomethyltrlcaprylyl ammonium chloride),
a phase transfer catalys~ of the General Mi.lls Co~pany, and
1,009 par~s of methylene chloride was refluxed and s~irred
~-8971
for a period of 21 hours under a nitrogen atmosphere. Wate-r
was then added to the mixture and the organic phase was separ-
ated and washed with water. A 70% yield of polymer was obtained
by adding the organic layer to methanol and filterin~ and dry-
ing the resulting precipitate at 60C. ThP polymer was found tohave a Tg of 85C and an intrinsic viscosity o 0.60 dl~g in
chloroform at 25C. The polymer was compression molded at 160C
to produce a tough colorless, f~exible transparent film. It also
can be cast from chloroform. Eased on elemental anal~sis and
~MR spectrum, the pol~mer was a poly~ormal having t~e formllla
~ Q ~ C ~ CH2~-
where n has an average value of 65.
The polyformal had the following p~ysical propert.ies:
Tensile strength, p.s.i. at yield 7-8000
Tensile strength, p. 5. i. at break 7100-7S00
Elongation % 110
Density g/cm3 1.10
Flexural strength p.s.i. 14,3~0
Flexural modulus 105 p.s.i. 73F 4 1
Gardner impac~ stre~gth ~320 in. lb.
Example 2.
A mixture o dimethylsulfoxide, me-thyl~ne chloride,
potassium hydroxide, bisphenol-A, and Ali~ at ~7as stirred at a
temperature of 60C for 4 hours under substantially anhydrous
conditions. The mixture had a weight percent solids oE ~2~/~ and
a ratio of aboutllOparts of dimethyl sulfoxide per 90 par~s of
methylene chloride. In addition, there was utilized in the
mixture a ratio of 2.6 mols of potassium hydroxide per mol of
-7
~ Y24~ RD-8g71
the bisphenol-A while the Aliquat was employed in a proportion
of about 0.1 mol of Aliquat per mol of the bisphenol-A. There
was obtained a polyformal having an intrinsic Yiscosiky o~
0.548 dl/g in chloroform at 25C. Based on method o~ prepara
tion, the polymer consisted essenti.ally of chemically combined
blsphenol-A units and formaldehyde units. A tough flexible film
was obtained by compression molding, following the ~rocedure of ~
~:xam~le 1, or by casting from a chloroform solution. ~.
Example 3.
A mixture of chlorobenzene, rnethylene chloride, potas-
sium hydroxide pellets, bisphenol-A, tetrabutylammonium bromlde
and 1.9% by weight of water was stirred at 75C or a period
of about 40 minutes. The mixture had a 19% solids content by
weight, where the chlorobenzene was utilized in a proportion o:E
about 3 parts o~ chlorobenzene per part of methylene chloride 9
while there was employed about 2.6 mols of potassium hydroxide
per mol cf bisphenol-A. In addition, the tetrabutyla~mvnium
bromide was present in the mixture in a proportion of ,~bout 0.1
mol of the phase transfer catalyst per mol of bisphenol-A.
There was obtained a 36% yield of polyformal from
the above mixture having an intrinsic viscosity of 0.519 dl/g
in chloroform at 25C and consisting essentially of chemically
combined bisphenol-A units and formaldehyde units. A ~ough
flexible film was obtained by casting or compression molding
the ~lymer following the procedure previo~sly described. `:
Example 4.
A mixture of N-methylpyrrolidone, methylene chloride,
potassium hydroxide pellets and bisphenol-A was stirred for 39
minutes at 70C under substan~ially anhydrous conditions. The
N-methylpyrrolidone and the methylene chloride was used in abou~
equal proportions by weight in the polymerization ~ixture having
--8--
,. ,,... ....... .. , , ...... ,,,, ~ . . .. ...
Rl)- 8 g 71
about 19% by weight of solids. The mixture also had a ratio of
2.6 mols of potassium hydroxide per mol of bisphenol-A.
polyformal was obtained consisting of chemically combined bis-
phenol-A units and formaldehyde units having an lntrlnsic vis-
cosity of about 0.50 dl/~. A tough flexible film was obtained
from the polyformal following the abovP described casting or
compression molding techniques.
Example 5.
The procedure of Example 4 was repeated, except that
in place of the potassium hydroxide there was utili~ed 2.1 mols
sodium hydroxide per mol of bisphenol-A. After approximately
one hour, there was recovered a 66% yield of a pol~formal ~aving
an intrinsic viscosity o 0.80 dl/g.
Example 6.
The procedure of Example 4 was repeated, except t~lat
there was utilized in the mixture 1% by weight of p t-butyl-
phenol, based on the weight of bisphenol A and the mi~ture ~;!as
heated for 105 minutes at 70C. No Aliqtlat phase transfPr
catalyst was used. There was obtained a polyformal ha-~ing an
~0 i.ntrinsic viscosity of 0.352 in chloroform at 2SC and consi.stlng
essentially of chemically combined bisphenol-A uni~ and or-
maldehyde units and chain stopped with p-t--butylphenol urlits.
The resulting polyformal was cast or compression molded to a
tough flexible film.
The above procedure was repeated, except tha-~ 2V/~ by
weight of the chain stopper wa5 used in the intercondensatio
mixture. Tt was found that the intrinsic viscosity of the
polyformal had been reduced to 0.273. A further interconden-
sation reaction was attempted, free of chain-s~.opper ~sing
stoichiometric amounts of potassium hydroxide and ~he bis
phenol-A. It was found that even though ~he mixture had been
, . , : . . ,.:. , ., , , - . :
.. . .. .. . . . .. .
~ 4~Y RD~8971
heated and stlrred for two hours at 70C, the intrin~lc vls-
cosity of the resulting polyformal was 0.22.7. ~he low ln~rin-
sic viscosity of the polyformal indicated that even though
the intercondensation reaction mixture was freP of chain s~opper
and it had been heated for two hours, more than a stoichio~
metric amount of potassium hydroxide was needed to produce
polyformal having an intrinsic viscoslty of at leas~ 0.3 dl/g. ;
Example 7.
A mixture of methylene bromide, potassium hydroxide
pellets, bisphenol-A and Aliquat phase transfer catalyst ~as `~
heated for 10 minutes at 96C under substanti.ally anhydrous
conditions while the mixture was stirred. The mixture con~ained
11% by weight of solids and the potassium hydroxide was utllized
in a proportion of 4 mols of potassium hydroxide per mol of
bisphenol-A while the phase transfer catalyst was employe~ in
a proportion of 0.1 mol of catalyst per mol of bisphenol-A
There was obtained a polyformal consisting essentially of chem-
ically combined bisphenol-A units and formaldehyde lmirs
having an intrin~ic viscosity in chlorofo~m of 1.9 at 25C.
The polymer was cast or compression mold~d to a tough 1exlble
film.
Example 8.
A mixture of methylene bromide, 1,1-~ichloro-2,2-bis
(4-hydroxyphenyl)ethylene, potassium hydroxide pellets and
Aliquat phase transfer catalyst was heated and stirxed at 96C
for a period of 75 minutes under substantially anhydrous con-
ditions. There was obtained a polyformal consistirlg essen~ially
of formaldehyde units chemically combined with units of the
formula,
-0 ~ C ~ o_
~C~
Cl Cl
-10-
.. . .
~ ~ 7 ~ ~ ~ RD-8971
and having an intrinsic viscosity o 0.441. The polymer was
readily converted to a tough flexible film by casting from
chloroform solution or by compression molding. It had a Tg of
115C. .
S The above film exhibits valuable dlelectrlc and fl~me
retardant properties qualifying it as a Elame retardant addi~ive
in injection moldable plastics. The film o~gen inde~ i8 37.
Example 9.
A mixture of 16 parts (0.05 mol) of 2,2-bis(p-hydroxy-
phenyl)-l,l,l-trichloroethane, ll parts ~O.lg5 mol) o:E K0~1
pellets, 56 parts of methylene bromide and 66 parts of N--methyl~
pyrrolidone was stirred at reflux (70~C). A vigorous reactio
with obvious exotherm and increased reaction mixture viscosity
was apparent after 13 minutes. After 51 minutes the reac~io
mixture was poured into methanol and the polymer was isolated
in the usual manner. There was obtained a 75% yield or a poly-
formal consisting essentially of formald~hyde units chemically
combined with units of the formula,
-o~ C~ O , `' `'''
Cl~ ~Cl
and having an intrinsic viscosity of ~.745 dl/g.
Example 10.
A mixture of methylene chloride, N-methylpyrrolidone,
potassium hydroxid~e pellets and 9,9-bis(4-hydroxyphenyl)flllorene,
or "BPF", was stirred for 66 minutes at 70C under sub3tantially
anhydrous conditions. There was obtained a polyformal having
an intrinsic viscosity of 0.638 and consisting essentially of
chemically combined formaldehyde units and ur~its o the formula3
Z~7
RD-8971
_o~ ~0- ~'~
The polyformal was obtained at a 63% yield and formed a tough
flexible film by casting or com~ression molding. I~
had a Tg of 221C. `
Example 11.
A mixture of 2.3 parts (0.01 mol) of bis~henol-A, 1.7
parts (0.026 mol) of 85% pulverized potas3ium hydroxide, 0.47
part (0.001 mol) of Aliquat 336 and about 53 ~arts o~ methylene
; chloride were stirred at room temperature un~er substantially
anhydrous conditions for 18 hours. The r~action mixture was
then washed with water until it was neutral. Methanol was then
added to the mixture resulting in the precipitation or product.
There was obtained a 49% yield o polyformal having an intrinsic
viscosity of 0.31 dl/g, consisting essentially of chemically
combined bisphenol-A units and formaldehyde units.
Example 12.
A mixture was stirred in a closed system at 50~ con-
sisting of 3600 parts of methylene chloride, 119 parts (0.238
mol~ of Ali~uat 336, 542 parts (2.37 mols) o~ bisphenol-A and
400 parts (6.2 mols) of potassium hydroxide pellets. The mix-
ture w~s stirred for about 115 minute~. There was obtained a
polyformal, consisting essentially of chemically combined
bisphenol-A units and formaldehyde units having an intrinslc
viscoisty of 0.551 di/g.
Example 13.
z~
RD-8971
.
: A mixture of methylene chloride, N-methylpyrrolidone,
potassium hydroxide pellets and 2,2-bls(4-hydroxyphenyl~-butane
was stirred at 70C under substantially anhydrous conditiolls
for 30 minutes. The mixture had a solids content of about
15% by weight and there was used a proportion of about 52 parts ~ :
of methylene chloride per 60 parts of N-methylpyrrolidone and
a ratio of 2.6 mols of potassium hydroxide per mol of ~he
2,2-bis(4-hydroxyphenylj-butane. There was obtained a poly-
formal consisting essentially of chemically combined formalde-
hyde units and units of the formula,
- O ~ C ~ O-
CH3
and having an intrinsic viscosity of 1.48 and a Tg of 86~C.
Example 14.
A mixture of methylene chloride, N-methylpy~olidone,
bisphenol-A, 0-hydroxyethylresorcinol and potassium hydroxlde
pellets was stirred at a temperature of 70C for 90 m:Lnlltes
under substantially anhydrous conditions. The mix~ur~ had a
solids content of l9~/~ by weight and there was utilized a pro~
portion of about 78 parts of methylene chloride per 91 parts
of the N-methylpyrrolidone, and a ratio of about 2.6 mols vf
potassium hydroxide per mol of bisphenol-A and a proportion
of about 35 mols o-f bisphenol-A per mol o 0-hydroxyethyl-
resorcinol. There was obtained a polyformal consistiIlg ~ssen
tially of chemically combined bisphenol-A units and fnrmalde-
hyde units and chain terminated with units of the formul~,
HO~H2CH2
~0- .
.
13-
: : . .- . ~ . , .
RD 8971
having an intrinsic viscosi-ty o~ 0.471 dl/g
Example ~ .
A mixture was ~.irr~d under sub~tanti.ally anhydrou~
conditions consisting of methyl~ne chloride, N-methylpyrroli
done, potassium hydroxide pellets, and 3,3-bis(p-hydroxy~hPnyl)
pentane for a period of about 42 minutes at a temperature of
70C. The mixture had a solid~ content of aboutl8 % by weight
and a ratio of about 52 parts of methylene chloride per 60
parts of N-methylpyrrolidone and a proportion o about 2.6
mols of potassium hydroxide per mol of the 3,3~bis~p~h~drs~xy-
phenyl)-pentane. There was obtaine.d a polyvr~1al h~Villg a'L~
intrinsic viscosity of 0.831 dl/g, a T of ~1C and conslsting
g .
essentially of chemically combined rormaldehyde ~mits and ~mi~3
of the formula,
CH3
-o ~ C ~ 0
CH3
Example 16.
A mixture of methylene chloridP, ~hlorobenze~e,
potassium hydroxide pellets, bisphenol-A and Ali~uat, the phase
transfer catalyst o~ Example l, manufactured by the General
Mills Company, Chemical Division, was heat~d and stirred fcr
a period o 7.4 hours at a temperature of 60C unde~ a
nitrogen atmosphere. The sollds content of the mixture was
about 20% by weight and there was u~ilized a mol -ra~io o~ 2.
mols of potassium hydroxide per mol o~ bisphenol-.A. There wa3
also utilized in the mixture, a proportion of about 11~0 part~
of chlorobenzene to 901 parts of methylene chloride. In addi.tion J
RD-8971
the Allquat was employed in the mixtur at a proportion of
0.1 mol of Aliquat per mol of bisphenol-A.
Following the procedure of Exa~ple 1, there was
recovered a 58 % yield of a polyformal havi~g an inkrinsic
viscosity of 0.735 dl/~ in chloroform at 25. A c]ear fllm was
obtained by casting the polymer from a chloroform solution or
compression molding it at 160C. The film is tough and flex-
ible and exhiblts a Gardner impact value of ~r~ater than 320 in. lb.
~xample 17.
The procedure of Example 16 was repeated, except ~hat
ln place of the potasslum hydroxlde there was util.i~ed 4 mols of
sodium hydroxide. In additionl there was utlliæed a proporti~n
of about 68 parts of chlorobenzene to 20 parts of the mPthylene
chloride. The intercondensation reactioll was conducted at a tem-
perature of 75C and it was completPd within ~ h3urs~ There was
obtained a 75% yield of a polyformal consisting essentially of
chemically combined formaldehyde units and bisphenol-~ units,
as shown by Example 1, having an intrinsic viscoslty of 0.422
dl/g. A tough flexible film was obtained by castin~ the pol~mer
from chloroform or compression molding it in accordance wlth the
procedure of Example 1.
Example 18,
The procedure of Example 7 utilizlng methylene
bromide was repeated except that in place o blspheno`l-A thare
was used
CH ~ CH3
CH3 CH3
-15~
,
.
. , ; : .;. :. . :
RD-8971
There was obtained a polyformal having a Tg of 175C and con-
sisting essentially of chemically combined ~mit~ of th~ formula,
_oH ~ S ~ OCH2-
H3 CH3
Example 19.
.
A mixture of 30 parts ~0.1 mol) of 3,4-bis(p-hydroxy-
phenyl~-3,4-hexanediol, 14.6 parts (0.26 mol) KOH pellets, 81
part~ methylene chloride and 93 parts of N-meth~lpyrrolidone
was stirred and heated at reflux (70C~. A~ter 81 minutes,
11 parts (0.2 mol) more of KOH pellets was added. AEter 92
minutes the very thick reaction mixture was pourecl into methanrJl
to recover the polymer. A film formlng polyforrnal was ob~alnecl,
consisting of formaldehyde units chemically comblned with units
of the structure
C,H3
A CH~
-O ~ C-OH
f~~
HOC ~ O-
,CH2
~H3
The polymer had an intrinsic viscosity of 0.5~4 dl/g, and ~g
of 67C. ,
. Although N-methylpyrrolidone was used to r.nake the ~ `~
a~Dove polyformal,the present invention provides ~or ~he use o
a broad variety of dipolar aprotic solvents which can be used
in the poly~ormal reaction mixture at 25C to lQOC, and a~
5% to 95,JO by weight, based on the ~.otal weight of the nixture.
Although the above examples are limi.~ed to only a ~ -
~ew of the very many variables whlch can be e~plvyed in the
-16-
RD-8971
practice of the present invention, it should be understood
that the present invention is directed to a much broader class
of polyformals included by formula (1~ as well as procedures
used in making these materials as shown in the description
S preceding these examples.
.. .. ~ ....
