Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
6816
`:
:
6-10525/+/B
Polyamide, PolyaMide-imide and Polyimide Polymers and Process for
their Manufacture
The present invention relates to new polyamide, polyamide-imide
and polyimide polymers and a process for their manufacture.
It is known that, in general, polyamides, polyamide-imides and
polyimides, and above all aromatic polymers of this type, can be pro-
cessed only with difficulty. It is also known that the solubility of
such polymers can be somewhat improved if bulky diamines or dianhydri-
des containing 3 or more aromatic rings are used for their manufacture
(compare, for example, DT-AS 1,595,733 and DT-OS 2,009,739, 2,153,829,
2,257,996 and 2,321,513). However, these polymers have the disadvantage
that they cannot be processed from the melt, or can be processed from
the melt only with difficulty. Moreover, the stability to heat and/or
- chemical stability of these polymers is inadequate in some cases.
It has been found that polyamides, polyamide-amide-acids and
polyamide-acids, and corresponding cyclised (imidised) derivatives,
which are readily soluble and can be processed easily and have egcel-
lent thermal, electrical and/or mechanical properties can be manufac-
tured by using new aromatic diamines.
The present invention therefore relates to new polyamides,
polyamide-amide-acids or polyamide~acids which consist of 1 to 100 mol%
of structural elements of formula I
C ~ COOHm~ H ~ (I)
HOOCn_l C~ . ;o
.~ O \-=o/ _
,~
6~6
. .
and of O to 99 mol% of structural elements of formula II
- O ~ I
11
_ _ C ~ COOHm_l (II)
HOOC 1 C - NH - Rl - NH - _
~
in which the NH groups in formula I independently of one another are
bonded to the benzene nucleus in the o-, m- or p-position and the indi-
vidual m, n, R and Rl independently of one another have the following
meanings: m and n denote the number 1 or 2, R denotes an aliphatic
radical with at least two carbon atoms or a cycloaliphatic, carbocyclic-
aromatic or heterocyclic-aromatic radical, the carbonamide groups and
carboxyl groups being bonded to different carbon atoms and, if R deno-
tes a cyclic radical and at least one of m and n denotes the number 2,
the carboxyl groups each being in the ortho-position relative to a
carbonamide group, and Rl denotes an aliphatic radical with a~ least
two carbon atoms or a cycloaliphatic, araliphatic, carbocyclic aromatic
or heterocyclic-aromatic radical, and also to the corresponding deriva-
tives which have been cyclised to the imide.
These polyamides, polyamide-amide-acids or polyamide-acids and
the corresponding derivatives which have been cyclised to the imide
; can be manufactured by subjecting 1-100 mol% of a diamine of formula III
'`:
H2
o_ ~
.~ ~. \O
. H ~ o=-
. 2
:; in which the NH2 groups independently of one another are in the o-,
m- or p-position of the benzene nucleus, and 0-99 mol% of a diamine
. .
61~
of formula I~
H2~ ~ Rl NH2 (IV)
to a condensation reaction with essentially stoichiometric amounts of a
compound of formula V
YOC COX
m-l (V)
in which what has been stated under formulae I and II applies in respect
of m, n, R and Rl and X, when m and/or n = 2, together with Y, forms
the -O- grouping and Y represents a chlorine atom, a hydroxyl group,
an unsubstituted or substituted phenoxy group or an alkoxy group with
1-18, and especially 1-12, carbon atoms, or, if m and/or n = 2, Y, to-
gether with ~, forms the -O- grouping, the groups -COY and -COX being
bonded to different carbon atoms and, if R represents a cyclic radical
and m and/or n - 2, the -COY group or groups being in the ortho-posi-
tion relative to a -COX group, and optiona].ly subsequently cyclising
the resulting polymers, in which m and/or n = 2, to the imide.
The polyamides, polyamide-amide-acids and polyamide-acids accord-
ing to the invention in general have an intrinsic viscosity in N,N-di-
methylacetamide (DMA) at 25C of about 0.04 to 4.0 d Vg and especially
of 0.1 to 2.5 d Vg. The intrinsic viscosity of the cyclised derivatives,
that is to say the polyamide-imides and polyimides, in concentrated
H2S04 or DMA at 25C is of the same order of size.
The intrinsic viscosity /~ i t i i is calculated according to
the following equation
ln ~
intrinsic = ~
Jqll6~
.
~ 4 --
In this equation: ln denotes the natural logarithm, ~ denotes the visco~
sity of the solution ~0.5% by weight of the polymer in suitable sol-
vents, preferably N,N-dimethylacetamide or concentrated sulphuric acid),
~ denotes the viscosity of the solvent and c denotes the concentra-
tion of the polymer solution in g of polymer~100 ml of solvent.
The viscosity measurements are carried out at 25C.
The polymers according to the invention can be homopolymers or
copolymers which have statistical distribution of the indivicual struc-
tural elements of formulae I and II. In the individual structural
elements, the m, n, R and Rl can also have different meanings. However,
the polymers can also be homopolymers or copolymers which have any
desired, and at least in part a block-like arrangement of polyamide,
po].ya~.ide amide-acid or polyamide-acid structural elements, according
to the definition, of formulae I and II. Homopolymers or copolymers
of this type can be obtained, for example, by first allowing a diamine
of formula III to react with a slight excess of a specific di-, tri-
or tetracarboxylic acid derivative of formula V, for example with a
dicarboxylic acid derivative, and then adding another di-, tri- or
tetra-carboxylic acid derivative of formula V, a diamine of formula IV
and/or further diamine of the formula III to the reaction mixture.
:~ ;
An additional advantage of the invention is that it is, in
general, possible to manufacture copolymers which have the desired
improved properties by the addition of relatively small amounts of
diamine of formula III.
:
Preferably, the individual m, n, R, Rl, ~ and Y have the same
meaning and the NH and NH2 groups in formulae I and III, respectively
are both in the same position, especially in the o-position and above
all in the p-position of the ben~ene ring.
~IL0~i86
According to a further preference, the polyamides, polyamide-
amide-acids or polyamide-acids according to the invention, and the
corresponding cyclised derivatives, consist only of structural ele-
ments of formula I. However, polymers, accorcLing to the definition,
which consist of 5-80 mol% of structural elements of formula I and of
20-95 mol% of structural elements of formula II, and the corresponding
cyclised derivatives, are particularly preferred.
If Y represents a substituted phenoxy group, these groups are,
in particular, phenoxy groups substituted by nitro groups or alkyl
or alXoxy groups with 1 or 2 carbon atoms or by halogen atoms, above
all chlorine or fluorine, such as the 2-, 3- or 4-nitrophenoxy group,
2,4- or 3,5-dinitrophenoxy group or 3,5-dichlorophenoxy group or the
pentachlorophenoxy, 2-methylphenoxy or 2-methoxyphenoxy group.
Alkoxy groups Y can be straight-chain or branched. Examples
which may be mentioned are: the methoxy, ethoxy, n-propoxy, isopropoxy,
n-butoxy, tert.-butoxy, hexyloxy, octoxy, decyloxy, dodecyloxy, tetra-
decyloxy and octadecyloxy group. Unsubstituted phenoxy groups or alkoxy
groups with 1-12, and especially 1-4, carbon atoms are preferred.
If R represents an aliphatic radic~l, these radicals are,
preferably, unsubstituted, straight-chain or branched alkylene groups
with 2-10 carbon atoms.
Cycloaliphatic radicals represented by R are, above all, 5-mem-
bered or 6-membered cycloalkylene groups.
If R denotes a carbocyclic-aromatic radical, this preferably
contains at least one 6-membered ring; such radicals are, in particu-
lar, monocyclic radicals, fused polycyclic radicals or polycyclic
radicals which have several cyclic, fused or non-fused systems which
cah be linked to one another direct or via bridge members. Examples
~,
of suitable bridge members which may be mentioned are -O-, -CU2CH2-,
Q
-CH~-, -CH-, -C-, -S-S-, -SO-, -SO2-, -SO2NH-, -CO-, -CO-, -C-C-,
.. .. ..
Q Q O O O
Q Q
-CONH-, -NH-CO-NH-, -Si- or -O-Si-O-, in which Q denotes an alkyl group
Q Q
with 1-6, and preferably 1-4, carbon atoms or a phenyl group.
. .
If R denotes a heterocyclic-aromatic radical, possible radicals
are, in particular, 5-membered or 6-membered heterocyclic-aromatic,
optionally benzo-condensed ring systems containing O, N and/or S.
Carbocyclic-aromatic or heterocyclic-aromatic radicals repre-
sented by R can also be substituted, for example by nitro groups,
alkyl groups with 1~4 carbon atoms, trifluoromethyl groups, halogen
~ atoms, especially chlorine, or silyl, sulphonic acid or sulphamoyl
: groups.
: .
Aliphatic, araliphatic, cycloaliphatic, carbocyclic-aromatic
or heterocyclic-aromatic radicals represented by Rl can be unsubsti-
tuted or substituted, for example by halogen atoms, such as fluorine,
chlorine or bromine, or by alkyl or alkoxy groups, each with 1-4
carbon atoms.
~- Possible aliphatic radicals Rl are, above all, straight~chain
or branched alkylene groups with 2-12 carbon atoms, it being possible
for the alkylene chain also to be interrupted by hetero atoms, such as
O, S or N atoms.
In the meaning of a cycloaliphatic radical, Rl represents, for
example, the 1,3- or 1,4-cyclohexylene group, the 1,4-bis-(methylene)-
cyclohexane group or the dicyclohexyl-methane group, whilst possible
araliphatic radicals are, above all, 1,3-, 1,4- or 2,4-bis-alkylene-
benzene radicals, 4,~ bis-alkylene-diphenyl radicals and ~,4'-bis-
alkylene-diphenyl ether radicals.
If Rl represents a carbocyclic-aromatic radical, such radicals
are, preferably, monocyclic aromatic radicals, fused polycyclic aroma-
tic radicals or non-fused bicyclic aromatic radicals and in the case
of the latter the aromatic nuclei are bonded to one another via a
bridge member. Possible bridge members are the groups mentioned in the
preceding text when discussing R.
If Rl denotes a heterocyclic-aromatic radical, such radicals
are, in particular, heterocyclic-aromatic of 5-membered or 6-membered
rings containing 0~ N and/or S. ~dvantageously, R represents an unsub-
stituted alkylene group with 4-10 carbon atoms or an unsubsti.tuted
monocyclic, a fused bicyclic or a non-fused bicyclic aromatic radical
and i.n the case of the latter the aromatic nuclei are bonded to one
another via the bridge member -0-, -C0- or -S02-, whilst Rl denotes
an unsubstituted alkylene group with 2-10 carbon atoms, a bis-(methy-
lene)-cyclohexane group or a monocyclic or non-fused bicyclic aromatic
radical which is unsubstituted or substituted by halogen atoms or
alkyl or alkoxy groups, each with 1-4 carbon atoms.
Polyamides, polyamide-amide-acids or polyamide-acids, as well as
the corresponding derivatives which have been cyclised to the imide,
which consist only of structural elements of formula I, in which R
denotes a benzene ring or an unsubstituted alkylene group with 4-10
carbon atoms when m and n = 1, a benzene ring when m = ]. and n = 2 and
a benzene ring or the benzophenone ring system when m and n = 2, but
especially polyamides, polyamide-amide-acids or polyamide-acids, as
well as the corresponding derivatives which have been cyclised to the
imide, which consist of 5-80 mol% of structural elements of formula I
and 20-95 mol% of structural elements of formula II and in which m and
n each denote the number l, R denotes a benzene ring or an unsubsti-
6~36
tuted alkylene group with 4-10 carbon atoms and Rl denotes an unsubsti-
tuted alkylene group with 2-12 carbon atoms, but above al] the 1,3- or
1,4-phenylene group, the 4,4'-diphenylmethane radical or the 4,4'-di-
phenyl ether radical; m denotes the number 1 and n denotes the number 2,
R denotes a benzene ring and Rl denotes an unsubstituted alkylene
group with 2-12 carbon atoms, but especially the 1,3- or 1,4-phenylene
group, the 4,4'-diphenylmethane radical or the 4,4'-diphenyl ether
radical; or m and n denote the number 2, R denotes a benzene ring or
the benzophenone ring system and Rl denotes an unsubstituted alkylene
group with 2-12 carbon atoms, but preferably the 1,3- or 1,4-phenylene
group, the 4,4'-diphenylmethane radical or the 4,4'-diphenyl ether
radical, are preferred.
Polymers, accordlng to the definition, and the corresponding
derivatives which have been cyclised to the imide, which consist of
5-50 mol% of structural elements of formula I and 50-95 mol% of ~truc-
tural elements of formula II and in which Rl denotes the 1,3-phenylene
group, the 4,4'-diphenylmethane radical or the 4,4'-diphenyl ether
radical, m denotes 1, n denotes 2 and R denotes a benzene ring, or m
and n denote 2 and R denotes a benzene ring or the benzophenone ring
system, but above all polyamide copolymers which consist of 5-50 mol%
of structural elements of formula I and 50-95 mol% of structural
elements of formula II and in which m and n denote the number l, R
denotes a benzene ring and Rl denotes an unsubstituted alkylene group
with 4-10 carbon atoms, the 1,3-phenylene group, the 4,4'-diphenyl-
methane radical or the 4,4-diphenyl ether radical, are very parti-
cularly preferred.
In the above-mentioned preferred polymers, the NH g.oups in
formula I are preferably each bonded to the benzene nucleus in the
ortho-position and in particular each bonded to the benzene nucleus
in the para-position.
~Q~6
The diamines of formula IV and the di-, tri- and tetra-carboxylic
acid derivatives of formula V are known or can be manufactured according
to methods which are in themselves known. Examples which may be
mentioned are:
Diamines of the formula IV
o-, m- and p-phenylenediamine, diaminotoluenes, such as 2,4-di-
aminotoluene, 1,4-diamino-2-methoxybenzene, 2,5-diaminoxylene, 17 3-di-
amino-4-chlorobenzene, 4,4'-diamino-diphenylmethane, 4,4'-diaminodi-
phenyl ether, 4,4'-diamino-diphenyl thioether, 4,4'-diaminodiphenyl-
sulphone, 2,2'-diaminobenzophenone, 4,4'-diaminodiphenylurea and 1,~-
or 1,5-diaminonaphthalene; 2,6-diaminopyridine, 1,4-piperazine, 2,4-
diaminopyrimidine, 2,4-diamino-s-triazine, di-, tri-, tetra-, hexa-,
hepta-, octa- and deca-methylenediamine, 2,2-dimethylpropylenediamine,
2,5-dimethylhexamethylenediamine, 4,4-dimethylheptamethylenediamine,
3-methylheptamethylenediamine, 3-methoxyhexamethyldiamine, 2,11-diamino-
dodecane, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 1,2-bis~(3-
aminopropoxy)-ethane, N,N'-dimethylethylenediamine and N,N'-dimethyl-
1,6-diaminohexane as well as the diamines of the formulae
2 2 3 2 2 ( 2)3NH2 and ~2N(CH2)3S(CH2)3NH2; 174-diamin
hexane, 1,4-bis-(2-methy1-4-aminopentyl)-benzene and 1,4-bis-(amino-
methyl)-benzene.
Compounds of the formula V
Malonic acid, dimethylmalonic acid, succinic acid, glutaric
acid, adipic acid, suberic acid, sebacic acid and dodecanedicarboxylic
acid, 1,3-cyclopentane-dicarboxylic acid, hexahydroisophthalic acid,
hexahydroterephthalic acid, terephthalic acid, isophthalic acid,
4,4'-dicarboxydiphenylethane, naphthalene-2,6-dicarboxylic acid, thio-
phene-2,5-dicarboxylic acid and pyridine-2,3-dicarboxylic acid as well
as the corresponding dichlorides and diesters according to the defini-
tion; trimellitic acid 1,2-anhydride-chloride (1,3-dioxo-benzo[c]
oxalane-5-carboxylic acid chloride), trimellitic acid anhydride and
6~36
- 10 -
trimelli-tic acid as well as esters according to the definition; pyro-
mellitic acid dianhydride, 3,3',4,4'-benzophenone-tetracarboxylic acid
dianhydride, 2,3,3',4'-benzophenone-tetracarboxylic acid dianhydride,
2,2',3,3'-benzophenone-tetracarboxylic acid dianhydride, 393',4,4l-di-
phenyl-tetracarboxylic acid dianhydride, bis-(2,3-dicarboxyphenyl)-
methane dianhydride, bis-(2,5,6-trifluoro-3,4-dicarboxyphenyl)-methane
dianhydride, 2,2-bis-(2,3-dicarboxyphenyl)~propane dianhydride, bis-
(3,4-dicarboxyphenyl) ether dianhydride, bis-(3,4-dicarboxyphenyl)-
sulphone dianhydride, N,N-(3,4-dicarboxyphenyl)-N-methylamine dian-
hydride, bis-(3,4-dicarboxyphenyl)-diethylsilane dianhydride, 2,3,6,7-
and 1,2,5,6-naphthalene-tetracarboxylic acid dianhydride, 2,6-dichloro-
naphthalene-l~4~5~8-tetracarboxylic acid dianhydride, thiophene-2,3,4,5-
tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic
acid dianhydride and pyridine-2,3,5,6-tetracarboxylic acid dianhydride.
Preferred compounds of the formula IV are alkylene-diamines
with 2-12, and especially 4-10, carbon atoms and especially 1,3- or
1,4-phenylenediamine, 4,4'-diaminodiphenyl ether and 4,47-diaminodi-
phenylmethane.
Acid dichlorides, acid chloride-anhydrides or dianhydrides, and
especially those in which R denotes a benzene ring or the benzophenone
ring system, are advantageously used as the compounds of the formula V.
The polycondensation reaction of the compounds of the formula
III with one or more compounds of the formula V and, optionally, one
or more compounds of the formula IV is carried out in a manner which
is in itself known, appropriately at temperatures of about -50C to
~300C. The reaction can be carried out in the melt or, preferably,
in an inert organic solvent or a solvent mixture. Temperatures of
-20C to +50C are preferred for the polycondensation reaction in solu-
tion.
' '
:
Examples of suitable organic solvents are: chlorinated aromatic
hydrocarbons, such as chlorobenzene and dichlorobenzenes, chlorinated
aliphatic hydrocarbons, such as methylene chloride, chloroform, tetra-
chloroethane and tetrachloroethylene, aliphatic and cycloaliphatic
ketones, such as acetone, methyl ethyl ketone, cyclopentanone and cyclo-
hexanone, cyclic ethers, such as tetrahydrofurane, tetrahydropyrane
and dioxane, cyclic amides, such as N methyl-2-pyrrolidone, N-acetyl-2-
pyrrolidone and N-methyl-~ -caprolactam, N,N-dialkylamides of aliphatic
~onocarboxylic acids with 1-3 carbon atoms in the acid part, such as
N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide and
N,N-dimethylmethoxy-acetamide, hexamethylphosphoric acid triamide
(hexametapol), N,N,N',N'-tetramethylurea, tetrahydrothiophene dioxide
(sulpholane) and dialkylsulphoxides, such as dimethylsulphoxide and
diethylsulphoxide.
Preferred solvents are N,N-dialkylamides of aliphatic mono-
carboxylic acids with 1-3 carbon atoms in the acid part9 especially
N,N-dimethylacetamide, as well as cyclic amides, such as N-methyl-2-
pyrrolidone.
The hydrochloric acid obtained during the condensation reaction
with compounds of the formula V in which Y represents chlorine can be
removed by neutralisation with basic substances, such as calcium
hydroxide or triethylamine, or by reaction with an epoxide compound,
such as ethylene oxide or propylene oxide, and by washing out with
suitable solvents.
The condensation reactions are appropriately carried out with
the exclusion of moisture, for example in an inert gas atmosphere,
such as nitrogen.
As already mentioned initially, the reaction of the di-, tri-
or tetra-carboxylic acid derivatives of the formula V with the diamines
-
~ l2 -
of the formula I~ and~or III can also be carried out stepwise in order
to manufacture poly~ers which, at least in part, have a block-type
distribution of the structural elements of the formula I or II. It is
also possible to link polyamides, polyamide-amide-acids or polyamide-
acids which have structural elements of the formula I or VI and have
been manufactured separately, with one another and so-called block
copolymers are formed by this means. In all of these cases, the reac-
tion is carried out in a manner which is in itself l~nown using a
slight excess of one or the other reactant in order to obtain prepoly-
mers which have end groups suitable for the further reaction, for
example amino end groups, acid chloride groups and/or anhydride groups.
.
The optional cyclisation of the polyamide-acids or polyamide-
amide-acids (m and/or n = 2) obtained after the condensation reaction
is carried out in a manner which is in itself known by chemical means
or by means of heat.
The chemical cyclisation is appropriately carried out by treat-
ment with a dehydrating agent on its own or as a mixture with a ter-
tiary amine. Reagents which can be used are, for example, acetic an-
hydride, propionic anhydride and dicyclohexylcarbodiimide or mixtures
of acetic anhydride and triethylamine.
The cyclisation by means of heat is carried out by heating to
temperatures of about 50C to 300C and preferably of about 150C to
250C and optionally with the addition of an inert organic solvent.
The polyamides, polyamide-amide-acids and polyamide-acids
according to the invention, as well as the correspondillg cyclised
derivativesJ are suitable for the manufacture of shaped articles of
.
very diverse types, such as fibres~ films, sheets, coating composi-
tions, foams, laminating resins, composite materials, moulding powders,
pres3ed areicles and ehe like, in a mamler which is in ieself hnown,
. ~
'
.
86
- 13 -
if desired with the use of customary additives, such as pigments, fil-
lers and the iike. The polymers according to t:he invention can also be
processed easily from the melt and are distinguished by good mechani-
cal, electrical and thermal properties as well as, in general, by good
solubility in organic solvents, such as N,N-dimethylacetamide, N,N-di-
methylformamide and N-methyl-2-pyrrolidone.
The new diamines of formula III can be manufactured, for example,
by either reacting a compound of formula VIa
O\M
. (VIa)
=~ .=-
O M
in a molar ratio of at least 1:2 with a compound of formula VIIa
l \ _./ (VIIa)
or reacting a compound of formula VIb
~ D_~ (VIb)
= O ~ = -
Z2
in a molar ratio of at least 1:2 with a compound of formula VIIb
M+O- ~ ~ 2 (VIIb)
in which M denotes a hydrogen, alkaline earth metal or alkali metal
cation, a trialkyl-ammonium cation with 3-24, and especially 3-12,
carbon atoms, or a quaternary ammonium cation, Zl denotes a halogen
atom or, if the nitro group is in the ortho-position relative to Zl'
also denotes a nitro group and Z2 denotes a halogen atom, to give a
compound of formula VIII
6~3~
1~ -
~ ~ 2
o\ ~ \ /
D ~
0~ . (VIII)
/
O
N02 =.
in which the two nitro groups independently of one another are in the
o-, ~- or p-position of the benzene ring, and subsequently converting
the compound of formula VIII into a compound of formula III. Mixtures
of two different compounds of the formula VIIa or VIIb can also be
used in the above process.
Possible halogen atoms Zl and Z2 are bromine atoms, but especial-
ly chlorine atoms and fluorine atoms.
':
If M represents an alkaline earth metal cation or an alkali
metal cation, this cation is, for example, the Ba7 Mg, Ca, Li, ~a or
K cation. Examples of suitable trialkylammonium cations ~ are the
trimethyl-ammonium, triethyl-ammonium, methyldiethyl-ammonium and
tri-n-octyl ammonium cation, whilst possible quaternary ammonium
cations are, for example, the benzyltrimethyl-ammonium cation and the
tetramethyl-ammonium cation. M preferably represents the hydrogen, Na
or K cation.
The reaction of the compounds of formula VIa and VIb with the
compounds o Eormula VIIa und VIIb can be carried out in an aqueous-
organic or organic medium or, alternatively, in the melt.
If M in formula VIa or VIIb represents hydrogen, the reaction
is advantageously carried out in an aqueous-organic or organic medium
; and optionally in the presence of an acid-binding agent. Examples of
acid-binding agents which can be used are inorganic and organic bases,
such as alkaline earth metal hydroxides and carbonates and alkali metal
hydroxides and carbonates, especially the hydroxides or carbonates of
`'-'
:.
.' , . .
'' '
- 15 -
:.
~a or K, and tertiary amines, such as triethylamine, pyridine or pyri-
dine bases.
.
The inert organic solvents used are, appropriately, polar aprotic
solvents, for example dialkylsulphoxides, such as dime~hylsulphoxide
and diethylsulphoxide, tetra~ethylenesulphone or dimethylsulphone.
Compounds oE formula IVa and VIIb in which M represents an
alkaline earth metal cation, an alkali metal cation, a trialkyl-
ammonium cation or a quaternary ammonium cation are preferred for the
reaction in the melt.
The reaction temperatures are generally between about 50C and
150C for the reaction in an organic or aqueous-organic medium and
between about 100C and 200C, preferably between about 130C and
160C, for the reaction in the melt.
Compounds of formulae VIb and VIIb, but especially compounds
of formulae VIa and VIIa in which M represents the hydrogen cation or
an alkali metal cation, especially the sodium cation or potassium
cation, and Zl and Z2 represent chlorine or fluorine are preferably
used.
'
The compounds of formulae VIa, VIb, VIIa and VIIb are prefer-
ably employed in stoichiometric amounts. However, the reaction can
; also be carried out with a slight excess of one or the other reactant.
, .
The reduction (hydrogenation) of the compounds of formula VIII
can be carried out in a manner which is in itself known, for example
with iron in an acid medium by the Béchamp method, optionally in the
presence of neutral salts, such as iron-II sulphate, CaC12 or sodium
hydrogen sulphate; with tin or tin-II chloride in the presence of HCl;
with zinc in an acid or neutral medium9 optionally with the addition
686
.~
- 16 -
- of neutral salts, such as CaCl2 and NH4Cl; with lithium aluminium
hydride; with hydraæines, such as hydraæine hydrate and phenylhydra
zine, if necessary with the addition of Raney nickel catalysts, and
with sodium dithionite (Na2S204).
Catalytic reduction is preferred. Examples of suitable catalysts
are palladium, palladium-on-charcoal, platinum, platinum black, plati-
num oxide and, above all, Raney nickel. The catalytic reduction is
appropriately carried out in a suitable inert organic solvent, such as
dioxane or methylcellosolve.
The compounds of formulae VIa, VIb9 VIIa and VIIb are known
or can be manufactured easily in a manner which is in itself known.
The compounds of formula VIII are also new. Both these compounds
and the diamines of the formula III can, after the reaction, be isola-
ted, and purified, in a customary manner, for e~ample by washing with
water or diethyl ether or by filtering and recrystallising from suit-
able solvents, such as methanol or ethanol. The compounds of the for-
mulae III and VIII are obtained in the form of white to slightly
yellowish crystals.
. :
,
. ,
.- ' '
6~3~
- 17 -
Example I
HO\ ~2 \ ~ NO
. + 2 i 1 I DMSO
=- H2
OH Cl NO -- ~ O Raney-Ni
=.
~ -NH2
. _ . . _ . , = .
. _ . . = . . _ .
.=.
37.2 g (0.2 mol) of 2,2'-dihydroxy-biphenyl and 63 g (0.4 mol)
of p-nitrochlorobenzene are dissolved in 160 ml of dimethylsulphoxide
(DMSO) in a sulphonation 1ask and the solution is warmed to 80C.
A solution of 26.4 g (0.4 mol) oE 85% strength potassium hydroxide in
20 ml of water is then added dropwise, whilst stirring, and the reac-
tion solution is subsequently further stirred for 3 hours at 100-110C.
After coollng, the reaction solution is poured into ice water and the
resulting precipitate is washed several times with water. The resulting
crude product is then dried for 20 hours under a high vacuum at 70C
and unconverted nitrochlorobenzene sublimes away during drying. The
residue is recrystallised twice from ethanol. 12.4 g (15% of theory)
of 2,2'-di-(p-nitrophenoxy)-biphenyl are obtained in the form of
slightly yellowish crystals; melting point 158C.
Analysis for C24H1606N2 (molecular weight 428.41):
calculated C 67.3% H 3.72% N 6.55%
found C 67.1% H 3.8 % N 6.4 %.
82.5 g of the above 2,2'-di-(p-nitrophenoxy)-biphenyl are hydro-
genated with 24 g of Raney nickel in 900 ml of dioxane at 40-50C.
`:
:'
.
'.', ' ' ' ''
- 18 -
After filtering off the catalyst and evaporating the solvent, 70 g
(99% of theory~ of crude 2,2'-di-(p-aminophenoxy)-biphenyl are obtained
and this is recrystallised twice from ethanol. After recrystallisation,
51.6 g (73% of theory) of pure 2,2'-di-(p-aminophenoxy)-biphenyl are
obtained in the form of slightly yellowish crystals, melting point
15~C.
Analysis for C24H2002N2 (molecular weight 368.44):
calculated C 78.24% H 5.~7% N 7.61%
found C 7~.1 % ~ 5.6 % N 7.~ %
Example 2: 74.4 g (0.4 mol) of 2,2'-dihydroxy-biphenyl are sus-
pended in 400 ml of distilled water in a round-bottomed flask and 53.5
g (0.8 mol) of 84% pure solid potassium hydroxide are then added in
portions at 20-25C, whilst stirring. The reaction mixture is stirred
further until all of the 2,2l-dihydroxy biphenyl has dissolved. The
reaction solution is then evaporated to dryness in a rotary evaporator.
315 g (2 mols) of p-nitrochlorobenzene are added to the residue (the
dipotassium salt of 2,2'-dihydroxy-biphenyl), the round-bottomed flask
is provided with a riser and the reaction mixture is heated to 150C
for 2 hours, whilst stirring. After cooling to about 100C, the result-
ing melt is poured into 2 litres of chloroform. The resulting solution
is extracted twice with water, dried over potassium carbonate and eva-
~- porated in a rotary evaporator. In order to remove excess p-nitrochloro-
benzene, the residue is suspended in 2 litres of diethyl ether and the
suspension is warmed under reflux for a short time. The reaction mix-
ture is then filtered and the material on the filter is rinsed with
diethyl ether and, after decolourising with active charcoal, the pro-
duct is recrystallised from ethanol. This gives 38.9 g (23% of theory)
of the 2,2'-di-(p-nitrophenoxy)-biphenyl (of analytical purity)
characterised in Example 1.
`:
The hydrogenation to 2,2'-di-(p-aminophenoxy)-biphenyl is
carried out as described in Example 1.
- , :
-- 19 --
Example 3: Analogously to the procedure described in Example 2,
37.2 g (0.2 mol~ of 2,2'-dihydroxy-biphenyl are converted into the
corresponding dipotassi~m salt using 26.8 g (0.4 mol) of 84% pure solid
potassium hydroxide in 200 ml of water. This salt is reacted in the
melt with 157 g ~1 mol) of o-chloronitroben~ene, in the manner described
in Example 2. The crude product which is obtained after removal of th~
chloroform is dissolved hot in methanol, the solution is decolourised
with active charcoal and the product is crystallised. The product is
then recrystallised once more from ethanol and 20.3 g (24% of theory)
of 2,2'-di-(o-nitrophenoxy)-biphenyl are obtained in the form of pale
yellowish crystals; melting point 154C.
Analysis for C24H1606N2 (molecular weight 428.41):
calculated C 67.3% H 3.72% N 6.55%
found C 67.3% H 3.8 % N 6.5 %
27 g of 2,2'-di-(o~nitrophenoxy)-biphenyl are hydrogenated with
3 g of Raney nickel in 270 ml of dioxane at 35-40C. After filtering
oEf the catalyst and evaporating the solvent, 23 g (99% of theory)
of crude diamine results and this is recrystallised twice from ethanol.
This gives 16.2 g (70% of theory) of 2,2'-di-(o-aminophenoxy)-biphenyl
in the form of colourless crystals; melting point 175C.
Analysis for ~24H20o2N2 (molecular weight 368.44):
calculated C 78.25% H 5.47% N 7.61%
found C 78.28% H 5.53% N 7.66%
.
Example 4: 18.62 g (0.1 mol) of 2,2'-dihydroxy-biphenyl and 28.22 g
(0.2 mol) of p-nitrofluorobenzene are dissolved in 80 ml of dimethyl-
sulphoxide in a sulphonation flask and the solution is warmed to 80C.
A solution of 13.2 g (0.2 mol) of 85% pure potassium hydroxide in
lO ml of water is then added dropwise, whilst stirring, and the reac-
tion solution is subsequently further stirred for 3 hours at 100-110Co
During this time a yellow precipitate forms and after the reaction
mixture has cooled this is separated off by decanting off the super-
- 20 -
natant liquor and is then washed several times with water. ~fter drying,
the crude product is recrystallised from ethanol. 32.86 g (77% oE
theory) of 2,2'-di-(p-nitrophenoxy)-biphenyl of analytlcal purity are
obtained in the form of slightly yellowish crystals with a melting
point of 158C.
Hydrogenation of the above product by the method described in
Example 1 and recrystallisation of the resulting crude product from
ethanol gives 2,2'-di-(p-aminophenoxy) biphenyl which is of analytical
purity and has a melting point of 157-158C.
;''
Example 5: 18.62 g (0.1 mol) of 2,2~-dihydroxydiphenyl, 23.22 g
(0.2 mol) of o-nitrofluoroben~ene, 13.2 g (0.2 mol) of 85% pure solid
potassium hydroxide and 10 ml of water are reacted in 80 ml of di-
methylsulphoxide according to the procedure described in Example 4.
After washing and recrystallising the resulting precipitata, 28.82 g
(67% of theory~ of 2,2'-di-(o-nitrophenoxy)-biphenyl of analytical
purity are obtained in the form of slightly yellowish crystals with
a melting point of 153-154C.
~ ydrogenation of the above product by the procedure described
in Example 3 and recrystallisation of the crude product from ethanol
gives 2,2'-di(o-aminophenoxy)-biphenyl which is of analytical purity
and has a melting point of 174-175C.
..
Example 6: 5.526 g (0.015 mol) of the 2,2'-di-(p-aminophenoxy)-
.,
biphenyl prepared according to Example 1 are dissolved in 90 ml of
;` anhydrous N,N-dimethylacetamide (DMA) in a sulphonation flask, under
a nitrogen atmosphere, and the solution is cooled to 0-5C. 4.83 g
(0.015 mol) of 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride
in solid form are added in portions to this solution, whilst stirring.
~ The resulting viscous solution is then stirred for a further 30 minu-
; tes at 0-5C and subsequently for a further 2 hours at 20-25C. The
.:
:
~' ' :
P61~1~
intrinsic viscosity of the polyamide-acid thus formed is 0.75 dl/g
(0.5% by weight in DMA at 25C).
Part of this polyamide-acid solution is spread to give a film.
The film is dried in vacuo as follows: l hour at 60~, 1 hour at 100C,
1 hour at 150C and 16 hours at 200C~ A transparellt, flexible film is
obtained.
A mixture of 45 ml of acetic anhydride and 30 ml of pyridine is
added dropwise to the remainder of the above polyamide-acid solution.
Subsequently, the reaction mixture is stirred for 16 hours at 20-25C
and then poured into water. The precipitate thus formed is washed
several times with water and dried in a vacuum drying cabinet for
20 hours at 150C/20 mm Hg and for 20 hours at 200C/0.1 mm Hg. 7.8 g
of polyimide in the form of a yellow powder are obtained.
For processing by the compression moulding process, the above
polyimide is introduced into a compression mould for circular sheets,
which has been prewarmed to 320C, and compression moulded at this
temperature for 3 minutes under the contact pressure and for 5 minutes
under a pressure of 225 kp/cm2. Strong, transparent mouldings which
have good mechanical and electrical properties even at elevated tem-
peratures are obtained.
Example 7: Analogously to the procedure described in Example 6,
1.842 g (0.005 mol) of the 2~2'-di-(o-aminophenoxy)-biphenyl prepared
according to Example 3, in 37 ml of anhydrous DM~, are reacted with
1.611 g (0.005 mol) of 3,3',4,4'-benzophenone-tetracarboxylic acid di-
anhydride. The resulting polyamide-acid has an intrinsic viscosity of
0.20 dl/g (0.5% by weight in DMA at 25C).
. .
.
6~1~
- 22 -
Example 8: 3.68 g (0.01 mol) of 2,2'-di-(p-aminopheno~y)-biphenyl
are dissolved in 50 ml of anhydrous D~ in a sulphonation flask, under
a nitrogen atmosphere, and the solution is cooled to -15C. 2.03 g
(0.01 mol) of isophthalic acid dichloride in the solid form are then
added in portions, whilst stirring, in such a way that the temperature
of the reaction mixture does not rise above -5C. The reaction mixture
is then rinsed with 10 ml of D~ and stirred for a further 1 hour at
-5C and then for a further 1 hour at 20-25C. Finally, the reaction
mixture is cooled and a solution of 2.02 g (0.02 mol) of triethylamine
in 10 ml of DMA is added dropwise at -5C. ~fter stirring for 1 hour
at 20-25C, the triethylamine hydrochloride which has precipitated is
filtered off.
~- Part of the resulting polyamide solution is cast to give a film
and the film is dried in a vacuum oven for 1 hour at 60C, for 1 hour
at 100C and for 16 hours at 150C. A transparent film is obtained.
The remainder of the polyamide solution is poured into water.
Thereupon, the polyamide precipitates in the form of a powder and this
is dried in vacuo at 150C. The polyamide is soluble in D~ and is
pressed in a platen press at 260C to give small, transparent, flexible
sheets.
.,,:
- Example 9: 2.210 g (0.006 mol) of 2,2'-di-(p-aminophenoxy)-bi-
phenyl and 2.804 g (0.014 mol) of 4,4'-diaminodiphenyl ether are dis-
solved in 100 ml of anhydrous D~ in a sulphonation flask, under a
nitrogen atmosphere, and the solution is cooled to 15C. 6.445 g
(0.02 mol) of 3~3',4,4'-benzophenone-tetracarboxylic acid dianhydride
in the solid form are then added in portions and the reaction mixture
is stirred for 1 hour at 15C and then for 2 hours at 20-25C.
~'
Part of the resulting highly viscous polyamide-acid solution
is spread on a glass plate to give a film and the film is dried in a
'~. ' ''
_ ~3 -
vacuum drying cabinet for 1 hour at 60C, for 1 hour at lOO'C and for
16 hours at 200C. A transparent flexible film with good mechanical
properties is obtained.
A mixture of 90 ml of acetic anhydride and 60 ml of pyridine is
added dropwise to the remainder of the above polyamide-acid solution
and the reaction mixture is stirred for 16 hours at 20 25C. The reac-
tion mixture is then poured into water. The copolyimide which has pre-
cipitated is washed with water and dried for 20 hours at 120C and for
20 hours at 200C in a vacuum drying cabinet. The polymer has an in-
trinsic viscosity of 0.48 dl/g ~0.5% by weight in concentrated H2S04
at 25C). Pressing in a platen press at 320C gives transparent flexible
sheets with good mechanical properties.
At 320C, it was no~ possible to press a known polyimide, which
was prepared by the process described above from 4,4'-diaminodiphenyl
ether and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride
(molar ratio 1:1), to flexible sheets.
Example 10: In accordance with the procedure described in Example 9,
2.947 g (0.008 mol) of 2,2'-di-(p-aminophenoxy)-biphenyl in 110 ml of
anhydrous DMA are reacted with 2.37 g (0.012 mol) of 4,4'-diaminodi-
phenylmethane and 6.445 g (0.02 mol) of 3,3',4,4'-benzophenonetetra-
carboxylic acid dianhydride and tlle resulting polyamide-acid is pro-
cessed to give films and a polyimide powder. The films are transparent,
tough and flexible. The powder has an intrinsic viscosity of 0.4 dl/g
(0.5~ by weight in concentrated H2S04 at 25C) and can be pressed at
280C in a platen press to give transparent flexible sheets.
Example 11: In accordance with the procedure described in Example
9, 2.210 g (0.006 mol) of 2,2'-di-(o-aminophenoxy)-biphenyl in 110 ml
of anhydrous DMA are reacted with 2.804 g (0.014 mol) of 4,4'-diamino-
diphenyl ether and 6.445 g (0.02 mol) of 3,3',4,4'-benzophenonetetra-
- 24 -
carboxylic acid dianhydride. The resulting polyamide-acid is processed
to give a powder. The copolyimide has an intrinsic viscosity of 0.37
d Vg (0.57~ by weight in concentrated H2S04 at 25C) and can be pressed
to transparent sheets at 260C in a platen press.
Example 12: In accordance with the procedure described in Example
~, 1.84 g (O.OQ5 mol) of 2,2'-di-(p-aminophenoxy)-biphenyl are reacted
with 4.00 g (0.02 mol) of 4,4'-diaminodiphenyl ether and 5.45 g
(0.025 mol) of pyromellitic acid dianhydride in 160 ml of anhydrous
DMA and the copolyamide-acid is processed to give transparent flexible
films.
Example 13: 3.68 g (0.01 mol) of 2,2'-di-(p-aminophenoxy)-biphenyl
and 7.93 g (0.04 mol) of 4,4'-diaminodiphenylmethane are dissolved in
110 ml of anhydrous DMA in a sulphonation flask, under a nitrogen
atmosphere, and the solution is cooled to -20C. 10.53 g (0.05 mol)
of trimellitic acid anhydridechloride in the solid form are then added,
whilst stirring, and the reaction solution is stirred for 15 minutes
at -20C and then for 2 hours at 20-25C. Subsequently, the reaction
solution is cooled again and a solution of 10.22 g (0.10 mol) of tri-
ethylamine in 20 ml of DMA is then added dropwise at -15C. After
stirring for 2 hours at 20-25C, the triethylamine hydrochloride which
has precipitated is fi]tered off. 60 ml of acetic anhydride are added
dropwise to the filtrate. The reaction mixture is stirred for a further
16 hours at 20-25C and is then poured into water. The copolyamide-
imide which has precipitated is washed with water and ethanol and
dried for 24 hours at 200C/0.1 mm Hg. This gives 18.24 g of the co-
polyamide-imide in the form of a yellow powder which is soluble in
dimethylacetamide.
For processing by the compression moulding process, the powder
is introduced into a compression mould for standard bars, which has
been preheated to 300C, and compression moulded at this temperature
- 25 -
for 5 minutes under a pressure of 500 kp~cm . Transparent strong
mouldings with good mechanical properties are obtained.
Example 14: 7.37 g ~0.02 mol) of 2,2'-di--(p-aminophenoxy)-biphenyland 19.46 g (0.18 mol) of m-phenylenediamine are dissolved in 350 ml
of anhydrous D~ in a sulphonation flask, under a nitrogen atmosphere,
and the solution is cooled to -20C. 40.6 g (0.2 mol) of isophthalic
acid dichloride in the solid form are then added, whilst stirring. The
reaction mixture is stirred for a further lS minutes at -20C and then
for a further 2 hours at 20-25C and cooled again and a solution of
40.47 g (0.4 mol) of triethylamine in S5 ml of DMA is added dropwise
at -15C. The reaction mixture is again stirred for 2 hours at 20-25C.
The resulting highly viscous reaction mixture is then diluted with
300 ml of DMA. The triethylamine hydrochloride which has precipitated
is filtered off. The reaction solution is poured into water. The co-
polyamide which has precipitated is washed with water and ethanol and
dried for 4 hours at 150C/20 mm Hg and for 24 hours at 200C/0.1 mm Hg.
This gives 48 g of copolyamide, which is soluble in dimethylacetamide.
The intrinsic viscosity is 1.24 d Vg (0.5% by weight in DMA at 25C)
and the glass transition temperature is 266C.
A 20% strength solution of this polyamide in N,N-dimethylaceta-
mide is cast to give films and the films are dried as follows: 3 hours
at 80C/20 mm Hg, 1 hour at 150C/0.1 mm Hg and 16 hours at 250C/
0.1 mm Hg. Tough, transparent flexible films are obtained.
For processing by the compression moulding process, the copoly-
amide is introduced into a compression mould which has been preheated
to 320C and compression moulded at this temperature for 3 minutes
under the contact pressure and for 5 minutes under a pressure of
500 kp/cm . Transparent, firm bars or sheets which have excellent
mechanical and electrical properties (flexural strength 231 ~Vmm ,
modulus of elasticity 4,000 N/mm ) are obtained. In comparison with
`6~i
- 26 -
this, a homopolyamide obtained from m-phenylenediamine and isophthalic
acid dichloride from the melt cannot be compression moulded to give
shaped articles. Moreover, it is soluble in dimethylacetamide only
when lithium chloride is added.
Example 15: In accordance with the procedure described in Example
-
14, 14.74 g (0.04 mol) of 2,2'-di-(p-aminophenoxy)-biphenyl in 440 ml
oE anhydrous DMA are reacted, in the presence of 40.47 g (0.4 mol) of
triethylamine with 17.30 g (0.16 mol) of m-phenylenediamine and 40.6 g
(0.2 mol) of isophthalic acid dichloride and the polymer is precipitated.
This gives 54 g of copolyamide, which is soluble in DMA. The intrinsic
viscosity is 1.11 dl/g (0.5% by weight in D~ at 25C) and the glass
transition temperature is 260C (determined by DSC = Differential
Scanning Calorimetry).
A 20~ strength solution of this copolyamide in N,N-dimethylacet-
amide is processed to f ilms in accordance with E~ample 14. Transparent
flexible films with very good mechanical and electrical properties are
obtained.
Part of the copolyamide is also processed according to Example
14 by the compression moulding process to transparent shaped articles
which have good stability to heat and good mechanical properties.
Example 16: In accordance with Example 147 22.11 g (0.06 mol) of
2,2'-di-(p-aminophenoxy)-biphenyl, 15.14 g (0.14 mol) of m-phenylene-
diamine, 40.6 g (0~2 mol) of isophthalic acid dichloride and 40.47 g
(0.4 mol) oE triethylamine are reacted in 470 ml of anhydrous D~L~.
The resulting copolyamide is processed to give a powder. The copoly-
amide is soluble in DMA; intrinsic viscosity 1.03 dl/g (0.5% by weight
in DMA at 25C).
6~
- 27 -
A 20% strength solution of this copolyamide in N,N-dimethyl-
acetamide is processed according ~o Example 14 to give transparellt
flexibl~ films. The films have good stability to thermo-oxidation and
good mechanical properties.
Example 17: In accordance with Example 14, 3.68 g (0.01 mol) of
2,2'-di-(p-aminophenoxy)-biphenyl, 20.55 g (0.19 mol) of m-phenylene-
diamine, 40.6 g (0.20 mol) of isophthalic acid dichloride and 40.76 g
(0.4 mol) of triethylamine are reacted in 300 ml of anhydrous DMA.
The resulting copolyamide (47 g) is processed to a powder; intrinsic
viscosity 1.01 d Vg (0.5% by weight in DMA at 25C).
A 20% strength solution of the copolyamide in D~ is processed
to give transparent flexible films which have good mechanical proper-
ties and good stability to thermo-oxidation.
Compression moulding of the copolyamide by the compression
moulding process at 320C, as described in Example 14, gives strong
mouldings which have good mechanical and electrical properties.
Example 1~: In accordance with Example 14, 1.47 g (0.004 mol) of
2,2'-di-(o-aminophenoxy)-biphenyl, 3.89 g (0.036 mol) of m-phenylene-
diamine, 8.12 g (0.04 mol) of isophthalic acid dichloride and 8.09 g
(0.08 mol) of triethylamine are reacted in 80 ml of anhydrous DMA.
The resulting copolyamide is processed to a powder. This gives 9.6 g
oE copolyamide, which is soluble in DMA. The intrinsic viscosity is
0.4 dL/g (0.5% by weight in DMA at 25C).
The copolyamide is compression moulded by the compression mould-
ing process at 320C, in accordance with the procedure described in
Example 14, to give strong mouldings which have good electrical proper-
ties.
686
..~
- 28 -
Example 19: In accordance with the proceclure described in Example 8,
. .
3.68 g ~0.01 mol) of 2,2'-di-(p-aminophenoxy)-biphenyl, 1.16 g (0.01 mol)
of hexamethylenediamine, 4.06 g (0 02 mol) of terephthalic acid di-
chloride and 4.04 g (0.04 mol) of triethylamine are reacted in 40 ml
of anhydrous DMA. The reaction solution is then poured into water.
The product which has precipitated is washed and dried and then pressed
in a platen press at 280C to give transparent sheets.
Example 20: In accordance with the procedure described in Example
8, 5.89 g (0.016 mol) of 2~2'-di-(p-aminophenoxy~-biphenyl, 0.80 g
(0.004 mol) of 4,4'-diaminodiphenyl ether, 4 78 g (0.02 mol) of sebacic
acid dichloride and 4.05 g (0.04 mol) of triethylamine are reacted in
50 ml of anhydrous DMA. Part of the resulting polyamide solution is
cast to give a film and the film is dried in a drying cabinet for
16 hours at 70C/20 mm Hg, for 1 hour at 100C/0.1 mm Hg, for 1 hour
at 150C/0.1 mm Hg and for 1 hour at 200C/0.1 mm Hg and also for
2 hours at 250C/0.1 mm Hg. Very Elexible films are obtained.
The remainder of the polyamide solution is poured into water.
The polyamide which has precipitated is then dried in vacuo at 80C
and pressed in a platen press at 200C to give transparent, very
flexible small sheets.
:
.
