FIELD OH 7 HI:.- J NVEN I" I UN
1'his invention re L-rl es to pol yiimd*-; films and to a (iroce:i!;? for
producing such films.
BACr'BRUUNO OF THE 1NWN I" TON
It is known to prepare poly i. m icie b'! e i id ¦;;:¦ in the si't. The proctss
i
qf.'OPrnlly t'lnp loyei.1 for such s prRpsr-tiLiDn is::- mainly solution
blending i !< Liang et si.) Polym. S'c.! .. Part fi; Polym,, Phys. , 30,
¦'¦165.....476 (1-fVl1) „ A s :i. m i 1 a.r niethod i s rpc i fpd in US Hatent ^6VS8014
(1997) to Ekiner.
Fur tii cm-, US P stent No . 5 2 7798 I. of 1994 to Haider and Lheneney
disclose ii in el'hod of 'jolution Dlendinq for the pre par-at ion of
polyimide <:ilms. The other process viz,, iiie.lt f?>; I".' us.i. on is
disclosed in US Patent No. :.:i43-v987 of i 9S'!b to Scott, Meyer,
Breeding and Owpris; US Patent No. 5346969 of ]994 to K'aku and
Luise. However, the po.l y im:i de blends of the prior- art suffer f rom
the drawback of having poor mutual '-olub :i 1 i ty and compatibility
of the component polymers in the blend. Another ilia ior disadvan-
tage assoc i. a ted with sue.!' blends is that the preparation of such
blends from the respective r'jmppnpnts in their fully imidirpd
'form is either d.i fficult or impossible. Further-, ttie component
polymers rsre expensive and therefore the blends are also e::pen.....
Hive. The methods of melt extrusion and solution blending neces.....
sitate the preparation of two polymers separately followed by
further- steps to obtain the blend.
OBJECTS OF THE INVENT IUN
It is therefore an object of this invention ho propose a pro*"ess
for- the prep.:! rat ion of polyimide blends- i, bcn:ophcnone teti'acarhonyl ic
di snhydnde (BTDA), biphenyl te t rac arboxy I. i c dianhydnde and diphenyl suiphone — 3 , 3 ' ., 4 , 4 '-tet i-a<: ar~
and the like are used.
bo>:y.l ic di anhydride (DSDA>A The additive i.ised .is generally a
monomer i c: lactam, such as for example, C-caprolactam, <::¦¦ jjyrro I. .1......
d i n o n e , o m e g a.....e n a r» t i > o 1 a c: t a. m, c a p r y 1 1 ;:; c t am., om e g a.....a m i n o u n d e c a n o i c
a c 1 d,, d o cl e c a 11 o 1 a c t a m .
Trie soJvpnt nspd for the first =;tpp of the resction is qenerally
a polar spro^ic solvi-nt which is basic in i". i=.; t- i.» r- *¦:.. „ A numbpr of
so I ven ts may be used ts-ut: h as, for example, dimethyl formami.de
(DMFK, MMP, DHAc and HMPA.
'The diamine i s trusted with the d i anhyci ride in a :l it mo!. e propcn--
o
t i on a I- a te mpera burp of 5.....:!. S C at inert atmosphere of dry pure
ni hrMjUfi, argon or helium.
The monomeric additive .i & uned in a proportion of 1 to 40 wjight
pi.-Ti: t-nt with respect to the polyimi.de and is added at room
terupt..-rat'.try .
The f i. 1 ms according to the invention are prepared by ra^finq the
blends on a su.itab.le substrate such as a plate, smJ drying the
o
same at a temperature of 3b' to 4v» C under vacuum. "I be dried films
o
are subsecjuen t i. y cured at temperature o* ov* to 300 !'.'¦ to obtmn
t h e p o 1 y i m i d p h .1 e n d f i '! m.
During the step of curing, eye .1 od eh yd rat ion takes place after 1 >:0
o
and uii:;tc?r goes ot.it up to 300 C „ The water mo 1 ecu In- ^njf'S f com !he
imi. d i f :i c at i on reaction of polyamic acid and is consiimed in the
polymerisation of £.....c ap ro.l. ac t am to Nyion-A, i'his phenomenon helps
in reducing the poro,::-1 ty of the f .i i m as the inatpr molecules are
<::: o n s u m e d w i t h i n t h e f i I en m a 1r- i .:¦:.
The invention will nom be explained in greater detail mi th the
help of the following non.....limiting example,,
EXAMPLE
P r e p a r a t i o n (::< f P A A ".
Penzophenune !, e tracarh o* y I ic d i anhyijr i. de (Efl'DAi n-iu I f Oil Corp,
USA!.'! was pi.irif ted by rec rys ta.l .i l z at :i on trom boiling a<.f-t:i<: anhy.....
c.l rids and ac I, .i viitpd charcoal and hoi" f i J t^'Bd. When co<"il ed,
crystals were filtered m suction gnd then washed thorough 1/ with
o
dry dichInromethane ;;,nri dried in vecui.kh oven st isboi.it 1 >''>v4 C for
1.5h. CJ>;ydi ;?-m 1. iru.- (OOA) [. F- I. u U. 3 ,, Sm i tz e rl and .1 was purified by
recryst a .1. I i 2 at :i on from alcohol and water m:i>:ture in rt'dnc i nij
ahcio&phere were cast on clean arid smooth glass plates
with the help of a doctor's blade (Mitufcoyo, Japan).
CyciodeI"iyd"'¦ a t :i c:¦ 1") of films :
The glass plates containing the films were kept if! vacuum oven at
35 0 for 2h and then at 4h.....50 !...: for another 1h during which
period the films on the glass plates became non-sticky in nature.
Then the films were taken out from vacuum oven and were pi aci'd in
and ijir c i re. 11 I s t. i. nc.j o1-' en ., Next the fol. lowinq thermal eye 1 odeh--.....
drabion 'scheidnh? wss followed

i'efi'|.ipr£ ture s^ias rs.i5t?rl from one stacje to the ne>:t st;',qe in ,!>0
//sin,. "!":i me no led in the psr-en the si s denote rest dene p time at the
resppctive tempersture. After this i, i ¦ e? r^frt ;;u !l eye lodehyclr -at i on , the
films on Ihe glass pistes were left within the oven for snout
t-"n?lve hours to attain room temperature. After that t.l-,e qj. esr
o
pistes were immersed in warm water (.....50 C) lor 30 mirs.. tar the
easy removal of thp f i I. ms from the g 1 a ss surface .
The PAA blend films prepared according to the invention with the
(itonDiPpric. additive are found to be clearer, smoothes1., transparent
and glossy compared to The films without the additive which are
slightly brownish 'in 1:0Tom p.
Charac: teri sa t :i on - Ail the films (control and blend* were charac—
tens^iJ by d e n s :i t y measurement, elemental analysis, IR, ' H and C
solid state NMR and X-ray diffraction.
Elemental Analysis ..... The calculated and the observed values of
the elemental analysis of the f i lni--> agree we.I i. „
TR Study ..... TR spectra of a J 1 the films confirm the presence of
the new polymer Nylon-6 farmed from the monomeric addtive £.....cap -
ro 1 sc t am „
Density of Films -¦¦ The densities of all the blend films are
higher than that of the control film for the PHD A based blend
system hut the BTDA based BB2 and BB3 f J. 1ms snow lower- density
.!. e aob :i. ng test for -the ad'! 1.1 i ve ' and ( n)
leaching test i'ar- the polymer in appropriate. bo 3. vents were
carried out. 7'his alorigw i. th the i.R, elemental data conclusively
proves that the polymer is forming in s'ltu from trie monomer and
it is forming a semi.....i. n terpens tr a': i. nq type of [intyn^'i' network
syst em.
Thermal Study...... Thermal s t ah i 1 i t -j of ttie films were r-ii-nerl out
C.i O O
by isothermal study at S\.& C in air, at 4i;H'-.f C ai'nJ at b0»} !..'.¦ both
in 33r and in inert atmosphere. Such study shows comparable
stab i. 1 .i. ty o f b 1 end f i 1ms .
Thermal Study (TGA/DIAJ ..... "I tie theriiiogra vimet r ic analysis ^ I tort)
sI'idwe that blend film:?, are more stable than the control films.
0 .i f f e r en -t i a 1 Sc: aim i r'g C a 1 o r i. iv-e t r y ..... Th e d s. f fpcen 11 a I s'~ ann i ng
cs1orimetry of all the films in air shows that the degradation
pattern of all the blended films ai-^ different and they have
e it tier more numbers of degradation peaks or have different
(|-i i g h e i ¦ energy v a 1u e s f o i d e g r a d a t i. (?n .
Mc-i'ih.'-in iC'i] Propert>..... The tensili? strength of t.lie b 1 end 1i Jms are
slight] y higher- fc-r the B'l'DA biased f :i. J ms ;:siw:i slightly lumer- (Less
than 1 Vt) l"or the PMDA based *: .i. 1 tits . Hi 11, m -:s I i c -ise& , the stress
at 1 ouier e .1 ong;:?t :i on i & higher- for hhe blend <: i I ms,.
f -. 1 e i" t (¦ i c a 1 Property - The b.! end film's show vnlnme resistivity of
the order of 10 ohm cm. The d.i. e 1 e<: t<*i r: rons-tent of i lie blend
f i. 1 m s i n c r e a b es »i a r g i n a 1 1 y .
We Claim:
1. A process for the preparation of polyimide blend films comprising
preparing a solution of a diamine compound in a solvent;
adding a dianhydride compound to a solution of the diamine compound in
a 1:1 mole proportion with stirring to obtain the polyamic acid solution;
adding a monomeric additive such as herein described to the polyamic
acid solution to obtain a blend, casting said blend to obtain a film, drying
said film and curing the dried film to obtain the polyimide blend film.
2. The process as claimed in claim lwherein said diammine compound is
selected from oxydianiline (ODA), 4,4 -diaminodi-phenyl methane
(DADOPM), 4,4 -diaminodi-phenyl sulphone (DADPS), p-phenylene
diammine, m-phenylene diammine and hexamethylene diammine.
3. The process as claimed in claim 1 wherein said dianhydride compound is
selected from pyromellitic dianhydride (PDMA), benzo-phenone
tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride
(BPDA), 4,4 -oxydiphthalic dianhydride, 4,4 -isophthalyl diphthalic
anhydride (ID PA), 4,4 -(hexafluoroiso-proplylidene) diphthalic
dianhydride (6FDA) and diphenyl sulphone - 3,3,4,4 -tetracarboxylic
dianhydride (DSDA).
4. The process as claimed in claim 1 wherein said solvent is a polar aprotic
solvent which is basic in nature.
5. The process as claimed in claim 1 wherein said solvent is selected from
dimethyl formamide (DMF), N,N-dimethylacetamide (DMAC), hexamethyl
phosphoric triamide (HMPA), NMP and the like.
6. The process as claimed in claim 1 wherein said additive is selected from
monomenc lactams such as -caprolactam, 2 pyrroli-dinone, omega-
enantho lactam, capryllactam,omega-amino undecanoic acid,
dodecanolactam.
7. The process as claimed in claim 1 wherein the proportion of the said
diammine and dianhydride compound is selected to form 18 to 25% of
the solid content in the solution after mixing.
8. The process as claimed in claim 1 wherein for the addition of said
dianhydride compound, the diammine compound solution is maintained at
a temperature of 5 to 15°C in the beginning and 20 to 25°C towards the
end of addition.
9. The process as claimed in claim 1 wherein the addition of dianhydride
compound to the diammine solution is done in an inert atmosphere using
a gas such as pure nitrogen, argon or helium.
10. The process as claimed in claim 1 wherein said addition of dianhydride is
done under slow stirring over a period of 2 to 3 hours.
11. The process as claimed in claim 1 wherein the monomeric additive is used
in a proportion to of 1 to 40 percent with respect the polyimide.
12. The process as claimed in claim 1 wherein said blend is cast on any
suitable substrate such as a plate.
13. The process as claimed in claim 1 wherein said film is dried at a
temperature in the range of 35 to 4Q°C under vacuum.
14. The process as claimed in claim 1 wherein said dried film is cured at a
temperature in the range of 50 to 300°C.

A process for the preparation of polyimide blend films comprising preparing a
solution of a diamine compound in a solvent;
adding a dianhydride compound to a solution of the diamine compound in a
1:1 mole proportion with stirring to obtain the polyamic acid solution;
adding a monomeric additive such as herein described to the polyamic acid
solution to obtain a blend, casting said blend to obtain a film, drying said film
and curing the dried film to obtain the polyimide blend film.