Note: Descriptions are shown in the official language in which they were submitted.
~Z~ 7
-- 1 --
1 Field of the Invention
2 The present invention relates to novel copolymers
3 and the method of their production.
4 Related Art
Extensive development has been directed to the
6 preparation of poly(parabanic acids). The poly(parabanic
7 acids) also designated as poly(l,3-imidazolidine-2,4,5-tri-
8 ones) may be prepared, for example, by the acid hydrolysis
9 of poly(iminoimidazolidinediones) and contain the imidazo-
lidinetrione ring in the repeating unit:
11 0
13 - ~' ~ N
14 0=C - C=O
Both the poly(iminoimidazolidinediones) and poly
16 (parabanic acids) ana their method of preparation are known
17 and described in detail in commonly assigned U.S. Pat. No.
18 3,661,859. The poly(parabanic acids) may also be prepared
19 by other processes, such as shown in U.S. Pat. No.
3,609,113.
21 The poly(iminoimidazolidinediones) may be formed
22 by the reaction of hydrogen cyanide with a diisocyanate or
23 mixture of diisocyanates, the reaction of a dicyanoformamide
24 with a diisocyanate or mixtures of diisocyanates, or the
polymerization of a cyanoformamidyl isocyanate and contain
26 a 1,3-imidazolidinedione-1,3-diyl ring of the following
27 structure in the repeating units:
28 1~
29 ,, C ~ C
N Nl - and/o~ N N~
31 0=C - C=NH HN=C - C=0
32 wherein NH is in the 4 or 5 position.
33 U.S. Pat. No. 3,661,859 discloses the extent of
34 hydrolysis may be controlled by the quantity of acid used
and specifically taught that complete hydrolysis requires
36 a molar quantity of acid equivalent to the molar quantity
37 of imino groups to be hydrolyzed.
~X~
1~?5~7
1 Commonly assigned U.S. Pat. No. 4,028,311 of the
2 present inventor disclosed that when sulfuric acid was used
3 for the hydrolysis of poly(iminoimidazolidinediones) that a
4 stoichiometric amount of sulfuric acid could be used only
at high temperatures, e.gO, 80-110C, because at lower tem-
6 peratures the ammonium bisulfate which formed slowly and in-
7 completely changed to ammonium sulfate and sulEuric acid.
8 The ammonium bisu].fate was not acid enough to cause the de-
9 sired hydrolysis. Therefore, the reaction was deprived of
sufficient acid at lower temperatures. However, at the
11 higher temperatures the bisulfate was rapidly converted to
12 ammonium sulfate and sulfuric acid. The effect of using
13 the stoichiometric amount of sulfuric acid at a maximwn tem-
14 perature of only 45C was the production of a product which
contained some g;-oups which had not been hydrolyzed; i.e.,
16 the extent of hydrolysis was not controlled under these con-
17 ditions.
18 It has now been found that parabanic acid/imino-
19 imidazolidinedione copolymers, that is copolymers contain-
ing both iminoimidazolidinedione-1,3-diyl and imidazolidine-
21 trione-1,3-diyl rings in a specific range of ratios have
22 special and desirable properties not heretofore known.
23 Some of the parabanic acid polymers have been found
24 to have high glass transition temperatures, and thus are
especially suitable as magnetic tapes (where good dimension~
26 al stability at high temperatures is required), films for
27 use in flexible printed circuits, cable wraps, etc., for
28 fibers such as tire cord fibers (where tensile strength and
29 modulus are required), for moldings for electrical connec-
tors, bearings, magnetic wire insulation, coatings for cables,31 cookware, glas.s fabrics, industrial belts (where high tem-
32 peratures are required) and the like. Generally these poly-
33 mers are very resistant to thermal decomposition. However,
34 the poly(parabanic acid) polymers are subject to attack by
some solvents and in many applications these polymers cannot
36 be used as such but must be thermally crosslinked to enhance
37 their solvent resistance.
~2~SS~
-- 3
1 The poly(iminoimidazolidinedione) polymers i.e.,
2 the poly(parabanic acid) polymer precursors, have very poor
3 thermal stability, however, it has been found that these
4 polymers wili crosslink more readily to become insoluble in
solvents which normally attack the parabanic acid polymers.
6 A preferred aspect of the present invention re-
7 sides in crosslinkable coplymers having the repeating unit:
8 ~ Q R ~
9 n
wherein said repeating units Q is from 3 to 25~ imidazoli-
11 dinedione-1,3-diyl rings (PIPA) of the structure:
12 ~~
1.3 ", C
14 N N
X=C C=X
16 wherein one X is 0 and one X is ~H and from about
17 75 to 97% imidazolidinetrione rings (PPA) of the
18 structure:
19 0
" ,C
21 N N -
22 O=C - C=O
23 R in said repeating units is an organic moiety which may be
24 aliphatic, alicyclic, aromatic or mixtures thereof, and n is
sufficiently large to produce a solid product.
26 A further aspect of the present invention is the
27 crosslinked product of above defined polymer. The cross-
28 linking is obtained by heating the polymers at 200 to 300C
29 usually for 10 minutes to 24 hours. The crosslinked products
are insoluble in the normal solvents for the polymer and are
31 useful as wire coatings, electric motor winding varnishes
32 and the like where solvent resistance or imperviousness are
33 necessary or desirable.
34 The R is the organic moiety of the diisocyanate
when the polymer is produced according to the procedure in
36 U.S. Pat. No. 3,661,859. Thus, the diisocyanates may be
37 selected from a broad group having a large variety of organ-
38 ic moieties. The organic moieties of the diisocyanate may
~z~ss~
-- 4
1 be substituted with groups such as alkyl, aryl, halogens,
2 sulfoxy, sulfonyl, alkoxy, aryloxy, oxo, ester, alkylthio,
3 arylthio, nitro an~ the like wnich do not react with the
4 isocyanate group. Functional groups which have active hy-
drogen atoms, (e.g., carboxylic acids, phenols, amines, etc.)
6 should not be present. Specific diisocyanates which may be
7 used are set out in U.S. Pat. No. 3,661,859, other patents,
8 articles or organic textbooks as known in the art. Some
9 preferred R groups are methylenediphenyl, oxidiphenyl, a mix-
ture of methylenediphenyl and 4-methyl-1,3-phenylenyl, and a
11 mixture of methylenediphenyl and bitolylenediyl.
12 It has been found by partially hydrolyzing the
13 poly(iminoimidazolidinedione) polymers (PIPA) to produce co-
14 polymers containing both PIPA and PPA rings in the polymer in
the ranges of 3 to 25% PIPA and 50 to 97% PPA that thermally
16 stable, readily crosslinkable polymers are produced. The
17 crosslinked products are solvent resistant, i.e., they are
18 insoluble in solvents which normally dissolve the PIPA or
19 PPA polymers. The PPA polymers will also crosslink to be-
come solvent resistant, however, harsher heat treatment is
21 required than for the presently claimed, partially hydro-
22 lyzed PIPA/PPA copolymers. The claimed partially hydrolyzed
23 polymers of the present invention also exhibit superior ad-
24 herence to other substrates such as metals.
The ease of crosslinking is directly related to
26 the increase in PIPA units in the copol~mer chain, however,
27 the reduction in the number of hydrolyzed units (PPA units)
28 concurrently produces a less thermally stable polymer and
29 polymers containing less than about 75% of the PPA units are
considered undesirable because of their instability. More-
31 over those polymers containing less than about 3% of the
32 PIPA do not exhibit the improved properties and are sub-
33 stantially the same as completely hydrolyzed PPA polymers,
34 in regard to crosslinking and adherence to metal.
A further aspect of the present invention is a
36 method for using sulfuric acid for the hydrolysis of the
37 imidazolidinedione-1,3-diyl rings.
~. "
55~
1 In one of its aspects, the present invention is a
2 process for producing copolymer containing units of the
3 structures:
4 0 O
~1 11
5 ~ ~ N _ and _,, C
7 X=C C=X O=C C=O
8 ~iminoimidazolidinedione ring) (i~idazolidinetrione ring)
9 l~herein one X is O and one X is NH comprising con-
tacting a polymer of the le~eating unit:
11 _ _
13 - N ~ - N R -
14 X=C C=X .
n
16 wherein one X is O and one X is NH, R in said repeating uni.t
17 is an organic moiety which may be aliphatic, alicyclic, aro-
18 matic or mixtures thereof and n is sufficiently large to
19 produce a solid polymer, with a monobasic Bronsted acid in
an amount less than a molar amount equivalent to the imino-
21 imidazolidinedione-1,3-diyl rings in said polymer (prefer-
22 ably less than 99 percent of the moles of said rings) in the
23 presence of water to hydrolyze said NH groups, allowing said
24 hydrolysis reaction to proceed for a sufficient time to con-
vert a substantially stoichiometric amount, based on the
26 acid present, of the iminoimidazolidinedione-1,3-diyl rings
27 of the polymer to imidazolidinetrione rings. The initial
28 temperature of the xeaction mixture is preferably room tem-
29 perature (i.e., about 20-25C).
Thus the amount of monobasic acid employed is less
31 than the amount which will convert all of the iminoimidazo-
32 lidinedione-1,3-diyl rings of the PIPA preferably at least
33 about 1~ up to about 99~ of the iminoimidazolidinedione-l,
34 3-diyl rings in the PIPA. One of the uses of these partially
hydrolyzed copolymers is the preparation of aminohydrations
36 by the hydrogenation of the C = NH groups using the proce-
37 dure disclosed by Tad L. Patton, "J. of Organic Chemistry,"
38 32, 383-388 (1976), which form~ a new class of polymeric
lZ~
-- 6 --
1 materials for use as such or for use as intermediates in
2 the preparation other polymers by reaction of the amino groups
3 by various procedures as known in the art.
4 The conversion of PIPA to PPA requires one mole
of hydrogen ion per mole of iminoimidazolidinedione ring (or
6 repeat unit). Thus, by controlling the mole r2tio of acid
7 to iminoimidazolidinedione rings substantially stoichiome-
8 tric conversions can be obtained.
g The hydrolysis reaction may be carried out by con-
tacting the precursor heterocyclic polymer characterized by
11 the imino-1,3-imidazolidinedione rings with aqueous solu-
12 tions of Bronsted acids, such as hydrochloric, hydrobromic,
13 sulfuric, formic, and the like, or with anhydrous hydrogen
14 chloride or hydrogen bromide such that when the polymer is
contacted with water or precipitated in water, hydrolysis
16 of the imino groups will occur to produce the desired par-
17 tially hydrolyzed polymer containing both the PIPA and PPA
18 rings.
19 The PIPA precursor polymers produced by any of
the methods described in the art may be precipitated from
21 the reaction solution during formation because of choice of
22 reaction solvent or may be precipitated in an isocyanate-
23 reactive or nonreactive solvent after completion of the poly-
24 merization. The solid precursor polymer (PIPA) may then be
hydrolyzed either a.s a solid suspension or redissolving it
26 in a suitable solvent. The solid PIPA precursor may be sus~
27 pended in an aqueous solution of Bronsted acid to carry out
28 the desired hydrolysis. However, the solid PIPA precursor
29 may be contacted with anhydrous hydrogen chloride in the
appropriate molar ratio, for example, and thereafter con-
31 tacted with water to complete the partial hydrolysis.
32 The solution of the precursor polymer (PIPA) may
33 be the original polymerization solution in which it was made
34 so the partial hydrolysis may be carried out in situ imme-
diately after formation of the PIPA by any of the known meth-
36 ods noted above. A solution may also be formed by redis-
37 solving the isolated precursor polymer in a preferred sol-
38 vent.
. .
~Z~5~
1 The partial hydrolysis has been found to result
2 in some degradation of the polymer as observed by lower in-
3 herent viscosities. This degradation has been particularly
4 noted with sulfuric acid, under some conditions. It is pre-
ferable to use aqueous solutions of monobasic acids for the
6 partial hydrolysis. The monobasic acids may be used at low-
7 er temperatures to carry out the partial hydrolysis than sul-
8 furic acid. The polymer degradation observed to occur dur-
9 ing partial hydrolysis is in marked contrast to complete
hydrolysis where the PPA polymer products have substantially
11 the same inherent viscosity as the PIPA precursor.
12 Although techniques have been developed to use
13 sulfuric acid for the partial hydrolysis so as to minimize
14 the degradation, the monobasic acids are preferred. The
preferred procedure using a monobasic acid is to start the
16 partial hydrolysis at ambient room temperature (about 20-
17 25C) and usually the temperature of the reaction mixtures
18 rises to around 45C by the exothermic heat of reaction.
19 Sulfuric acid can be used in the same manner, and since on-
ly one hydrogen will readily be available one mole of sul-
21 furic acid will hydrolyze about 0.5 mole of the imino groups
22 in a PIPA in the first 15 minutes of hydrolysis. However,
23 the sulfuric acid hydrolysis will continue slowly as the
24 ammonium bisulfate is slowly converted to sulfuric acid and
the degree of conversion (as is disclosed in US Pat. No.
26 4,028,311) will depend on temperature and the length of the
27 hydrolysis reaction. In contrast to this the monobasic
28 acids are totally used up and the product has a controllable
29 and predicable degree of hydrolysis.
It has been found that utilizing the appropriate
31 molar amount of sulfuric acid at 80 to 110C preferably no
32 higher than 90C with short reaction times, e.g., ten min-
33 utes or less and/or 6 moles or less of water per mole of
34 imino groups, preferably two moles or less of water per mole
of imino the degradation of the polymer inherent viscosity
36 was limited and remained within acceptable limits. For the
37 purposes of the present invention a decrease in the inherent
38 viscosity of the polymer of 6% or less is acceptable to pro-
~z~ss~
1 duce a useful product. However, with the monobasic acids no
2 special considerations along these lines were required and
3 ~Tery little degradation was observed. Stoichiometrically
4 at least one mole of water per mole of imino group will be
present to effect the hydrolysis with monobasic acid; prac-
6 tically, at least 2 are added.
7 Very generally, PIPA's and PPA are solu~le in mod-
8 erate hydrogen bonding dipolar, aprotic solvents. Suitable
g solvents include dimethylformamide, dimethylacetamide, di-
methlsulfoxide, hexamethylphosphoramide and N-methylpyrro-
11 lidone. These may be used in admixture with each other or
12 with other aprotic solvents such as benzene, toluene/ xylene,
13 methylacetate, ethylacetate, anisole, phenotole, butyl ben-
14 zoate, chlorobenzene, etc.
For purposes of illustration, the examples illus-
16 trating the invention will be described in specific with
17 respect to a particular polymer. That is, a polyiminoimi-
18 dazolidinedione prepared from diphenylmethane diisocyanate
19 in accordance with proprietary techniques well described in
patents assigned to Exxon Research and Engineering Company
21 to result in a polymer having the repeating unit shown be-
22 low. _ _
23 ~01
24 _ ,,, C ~ CH2 ~ n
28 wherein one X is O and one X is NH, which is the
29 precursor to the completely hydrolyzed product thereof,
a high performance polymer having the repeating unit
31 shown below:
32 0~
36 ._ 0=C - C=0 CH2 ~ ~~- n
37 which is also designated as poly[l,4-phenylenemethylene-1,
38 4-phenylene-1,3-(imidazolidine-2,4,5-trione)] which is also
3LZ~5~
g
1 designated in chemical abstracts as poly[(2,4,5-trioxo-1,3
2 imidazolidinediyl)-1,4-phenylenemethylene-1,4-phenylene].
3 It has a high glass transition temperature of greater than
4 275C and cannot be extruded or molded.
For purposes of convenience, these polymer spe-
6 cies will be referred to as PIPA-M and PPA-M, respectively.
7 It will be recognized that other polyiminoimidazolidinedi-
8 ones (PIPA) and the partially hydrolyzed product (PIPA-PPA
9 can be prepared from other monomers so that the diphenyl
methane group may be replaced by other organic moieties.
11 In addition to the polymer, it is contemplated
12 that other appropriate additives which are not detrimental
13 to the polymer such as plasticizers, antioxidants, UV sta-
14 bilizers, flame retardants pigments, fillers and the like
may be present in the present compositions.
16 Examples
17 The inherent viscosities were determined at 25C
18 using a concentration of 0.5 g. of polymer in 100 ml solu-
19 tion using dimethylformamide as the solvent~
Example 1
21 This example describes the hydrolysis of PIPA-M
22 with various quantities of hydrochloric acid and shows the
23 effect of incomplete hydrolysis on the thermal crosslinking
24 properties of the products. When less than the stoichio-
metric quantity of acid was used to hydrolyze the PIPA-M,
26 the repeating units contained iminoimidazolidinedione rings
27 as well as imidazolidinetrione (parabanic acid) rings.
28 A solution which contained 0.064 moles of PIPA-~
29 repeating units per 100 g. solution was used; the solvent
was dimethylformamide (DMF). To 160 gram portions of the
31 solution were added measured quantities of 37.9% hydrochlor-
32 ic acid with stirring. After 45 minutes at room temperature
33 the polymers were precipitated by mixing with water. The
34 quantities of acid used, the percent of the imino groups
hydrolyzed by the quantity of acid used, the inherent vis-
36 cosities of the polymers, and the solubilities of the powder
37 products in dimethylformamide after they had aged 24 hours
38 in air at 200C are recorded below. All of the products
.
5~
-- 10 ~
1 were soluble in dimethylformamide before they were aged.
2 37.9% HCl,
3 Reaction Moles(~) % Hydrolyzed~b) ~inh Solubility~C)
4 A 0.112 109.4 1.06 sol
B 0.104 106.4 1.06 sol
6 C O.lQ4 lQl.5 .1 04 sol
7 D 0,Q87 85 Q 1.04 insol
8 E O . 05856, 6 0,37 insol.
9 F 0.01~ 11.7 1.04 insol.
(a) Moles of HCl per 0.1024 mole of PIPA-M repeating unit.
11 (b) % hydrolyzed = molOels24cL X 100
12 (c) Solubility of the polymer powder in dimethylformamide
13 at room temperature after aging 24 hours at 200 C. The
14 size of the insoluble gels increased from 3 (finely
divided gels) to E to F (very coarse, large gels). All
16 of the polymers were soluble before they were heated.
17 Example 2
18 This example describes the hydrolysis of PIPA-M
19 with 85% of the molar quantity of acid re~uired for the com-
plete conversion of the PIPA-M to PPA-M.
21 To 1082 g. of a dimethylformamide solution which
22 contained 192.5 g. ~o.695 mole of repeating unit) of PIPA-M
23 ~ninh = 1.01) was added a solution of 58.4 g. of 37% hydro-
24 chloric acid tO.592 mole HCl), 27 g. water, and 200 ml. di-
methylformamide. ~he solution was stirred without heating
26 for 30 minutes. The solution was then filtered to remove
27 the ammonium chloride which precipitated. The polymer was
28 precipitated from the filtrate by mixing it with water. The
29 dry product weighed 185 g. and had an inherent viscosity of
0.98. The infrared spectrum of a thin film of the product
31 had a weak band at 5.98y (C=N) which is characteristic of
32 the iminoimidazolidinedione ring system (and is a strong
33 band in the spectrum of PIPA-M) and a strong band at 5.74y
34 which is characteristic of the carbonyl groups in the imi-
dazolidinetrione ring.
36 Nitrogen analysis: found, 10.8%; calculated,
37 10.82% ~based on the theoretically expected hydrolysis of
38 85.2% of the imino groups in the PIPA-M) . A film of this
39 copolymer was cast from dimethylformamide. After drying in
a vacuum oven at 120C the film was soluble in dimethylfor-
41 mamide. However, after aging one hour at 260C the film
lZ~5S~
1 was insoluble in the solvent. A film of PPA-M aged under
2 the same conditions remained soluble in dimethylformamide.
3 Example 3
4 To 1086 g. of dimethylformamide solution which
contained 193~3 g. (0.698 mole of repeating unit) of PIPA-M
6 (ninh = 1.01) was added a solution of 64.8 g. of 37% hydro-
7 chloric acid (0.657 mole HC1), 30.2 g. water, and 200 ml di-
8 methylformamide. The procedure was identical to that in
g Example 2. The yield of polymer was 190 g.; it had an in-
herent viscosity of 0.98. The infrared spectrum had absorp-
11 tion peaks characteristic of both iminoimidazolidinedione
12 and imidazolidinetrione rings. Nitrogen analysis: found
13 10.28~; calculated, 10.37% (based on the theoretically ex-
14 pected hydrolysis of 94.1~ of the imino groups in the PIPA-
~.5 ~).
16 A 2 mil film of the copolymer was cast from di-
17 methylformamide. The dry film was soluble in dimethylform-
18 amide and remained soluble after aging one hour at 260C.
19 It became insoluble in the solvent after aging 2 hours at
260 C. For comparison, a film of PPA-M similarly treated
21 was still soluble after aging 2 hours at 260C.
22 Example 4
23 To 1062 g. of a dimethylformamide solution which
24 contained 189 g. (0.682 mole of repeating unit) of PIPA-M
(ninh - 1.01) was added a solution of 66.31 g. of 37% hy-
26 drochloric acid (0.672 mole HCl), 34.6 g. water, and 200 ml.
27 dimethylformamide. The procedure was identical to that in
28 example 2. The yield of polymer was 180 g.; it had an in-
29 herent viscosity of 1.01. Nitrogen analysis: found, 10.12%;
calculated, 10.14% (based on the theoretically expected hy-
31 drolysis of 98.5% of the imino groups in the PIPA-M).
32 Example 5
33 This example describes the hydrolysis of PIPA-M
34 with an excess of the molar quantity of acid re~uired for
the complete conversion of the PIPA-M to PPA-M~
36 To 1134 g. of a dimethylformamide solution which
37 contained 201.8 g. (0.729 mole of repeating unit) of PIPA-M
38 (ninh = 1.01) was added a solution of 75.5 g. or 37% hydro-
~Z~5~
- 12 -
1 chloric acid (0.765 mole ~Cl), 31 g. water and 200 ml. di-
2 methylformamide. The procedure was identical to that used
3 in Example 2. The polymer yield was 200 g.; it had an in-
4 herent viscosity of 1.01. Nitrogen analysis: found, 10.13%;
calculated for PPA-M, 10.07~.
6 Example 6
7 This example compares the crosslinking and adhe-
8 sion of films cast from the polymers in Examples 2, 3, 4,
g and 5 onto copper foil. The latter was 1 oz. treated RA
(rolled annealed) copper foil.
11 Solutions of the polymeric products described in
12 Examples 2, 3, 4, and 5 were prepared by dissolving 10 g.
13 of each polymer in 65 ml. dimethylformamide. Then strips
14 (1" x 6") of the copper foil were coated with the solutions.
Evaporation left films of the polymers which were finally
16 dried at 150C.
17 Sections of each coated foil were cut. When creased
18 the films did not break nor separate from the copper. When
19 the coated sections were soaked in dimethylformamide all of
the films dissolved. Therefore, none of the films wer
21 crosslinked.
22 After the coated foils were aged 1 hour at 260C
23 they all remained tightly adhered to the copper and did not
24 break or crack when creased. When soaked in dimethylform-
amide the films from the polymers made in Examples 3, 4, and
26 5 all dissolved; however, the film formed from the polymer
27 made in Example 2 did not dissolve and could not be delam-
28 inated from the copper.
29 After aging 2~ hours at 260C the film coatings
made from the polymers described in Example 2 and 3 were in-
31 soluble in dimethylformamide and remained tightly adhered to
32 the copper even after soaking 48 hours in solvent. The other
33 two film coatings (made from polymers described in Examples
34 4 and 5) were insoluble in dimethylformamide but floated off
of the copper when they were soaked in the solvent. These
36 results reveal that there is a difference~in the adhesion of
37 the films to copper. The difference appears to be due to
38 the presence and concentration of iminoimidazolidinedione
~2~?5S~
l rings in the polymers, apparently the concentration of these
2 rings in the polymer described in Example 4 was too low to
3 enhance adhesion to copper. The above results also show
4 that the rate of crosslinking is directly related to the con~
centration of the iminoimidazolidinedione rings in the poly-
6 mer.
7 Example 7
8 A solution of 650 g. (2.34 moles repeating units)
9 PIPA-M (ninh 1.07) in 3250 g. dimethylformamide was heated
with stirring to 60C. Then 107.3 g. (1.05 mole) of 96.3%
11 sulfuric acid was added followed immediately by a solution
12 of 253 g.water in 253 g. dimethylform~de. The temperature was in-
13 creased to 85C. After 15 minutes the reaction solution was cooled
14 to 30C, filtered to remove the insoluble ammonium sulfate,
lS and then precipitated in water. The product had an inher-
16 ent viscosity of 0.58. Nitrogen analysis: found, 10.43%;
17 calculated, 10.59% (based on the theoretically expected hy-
18 drolysis of 89.7% of the groups in the PIPA-M.
19 Example 8
A solution of 688 g. (2.48 moles repeating units)
21 PIPA-M (ninh = 1.07) in 3445 g. dimethylformamide was heated
22 to 60C. Then 120.2 g. (1 18 mole) of 96.3% sulfuric acid
23 was added followed immediately by a solution of 268.5 g. wa-
24 ter in 268.5 g. dimethylformamide. After heating 15 min-
utes at 85C the product was isolated by the same procedure
26 used in Example 7. The inherent viscosity of the product
27 was 0.65. Nitrogen analysis: found, 10.31~; calculated,
28 10.32% (based on the theoretically expected hydrolysis of
29 95.1%).
Films (2 mil) of this copolymer and PPA-M were
31 cast from dimethylformamide solutions. The following mechan-
32 ical properties before and after aging one hour at 240C re-
33 veal that the elongation of the copolymer film was signifi-
34 cantly decreased and its tensile strength at break increased
by the heat treatment. The PPA-M film did not undergo chan-
36 ges to significantly change these properties.
-" lZ~?SS~
- 14 -
1 Before Agin~: Ey,~ Ty,psi Eb,~ Tb,psi
~ PPA-?5: 1415,200 27 14,~00
3 Example 8 Film: 14 14,950 16 14,650
4 A~ter 24 Hrs at 240C:
?PA-M: 13 16,g50 32 15,900
6 Example 8 Film: ~ --- 11 18,200
7 Ey% = elongation at yield, Ty = tensile strength at
8 yield, Eb - elongation at break, Tb = tensile strength
9 at b~eak.
Note the improvement in tensile property occurred even
11 though the suifuric acid had produced a partially hy-
12 drolyzed polymer which had a significantly lower in-
13 herent ~iscosity than the PPA from which it was made.
14 Example g
To a solution of 721 g. (2.60 moles of repeating
16 units) PIPA-M (~inh 0.99) in 3240 g. dimethylformamide was
17 heated to 60C. Then 129.9 g. (1.276 moles) of 96.3~ sul-
18 furic acid was added followed immediately by a solution of
19 281 g. water in 281 g. dimethylformamide. After stirring
at 85C for 15 minutes the polymer was isolated by the same
21 procedures used in Example 7. The polymer had an inherent
22 viscosity of 0.83. Nitrogen analysis: found 10.14% calcu-
23 lated, 10.16% (based on the theoretically expected hydroly-
24 sis of 98.1~ of the imino groups in the PIPA-M).
Films (2 mil) of the copolymer and PPA-M were cast
26 from dimethylformamide solutions. The following mechanical
27 properties reveal that heating the films 1 hour at 240C had
28 no significant effects on their mechanical properties. The
29 concentration of imino groups in the film of the copolymer
was apparently too low to make it different from PPA-M.
31 Be~ore A~in~ Ey,% Ty, psi Eb,% Tb,~si
2 PPA-M: 1415,200 27 14,400
33 Example 9 Film: 1415,300 49 15,400
34 After 24 Hrs at 240C:
365 PPA-M 1316,950 32 15,900
Example 9 Film: 1314,300 15 14,650
37 Example 10
38 To 1215 g. of a dimethylformamide solution which
39 contained 200 g. ~0.722 moles of repeat units) PIPA-M
~2~5~
- 15 -
1 (~inh = 0.99) was added 36.9 g. (13.47 g.; 0.369 moles HCl)
2 of 36.5~ hydrochloric acid followed by a solution of 78 g.
3 water in 220 g. dimethylformamide. The heat liberated by
4 the reaction raised the temperature from 23 to 36 C, after
stirring 30 minutes the solution was filtered to remove the
6 precipitated ammonium chloride. Polymer was precipitated
7 from the filtrate by mixing it with water. The polymer had
8 an inherent vlscosity of 0.98. Nitrogen analysis: found,
9 12.54%; calculated 12.56% (based on the theoretically ex-
pected hydrolysis of 51.1~ of the imino groups inthe PIPA-M).
11 Although the polymer was r~adily soluble in di-
12 methylformamide, it became insoluble when it was heated for13 30 minutes at 260C.
14 Example 11
To a solution of 161.5 g. (0.583 moles of repeat-
16 ing unit) PIPA-M (ninh = 0.99) in 820 g. dimethylformamide
17 was added a solution of 53.2 g. (19.95 g., 0.S46 mole HCl)
18 of 37.5% hydrochloric acid in 160 ml. dimethylformamide. The
19 maximum reaction temperature was 35C; after 30 minutes the
solution was filtered to remove the ammonium chloride which
21 precipitated. Polymer was precipitated from the filtrate
22 by mixing it with water. It had an inherent viscosity of
23 1.03. Nitrogen analysis: found, 10.38%; calculated, 10.39
24 (based on the theoretically expected hydrolysis of 93.6% of
the imino groups in the PIPA-M).
26 Example 12
27 A solution of 55.4 g. (0.20 moles of repeating
28 units) PIPA-M (ninh = 1.06) in 280 g. dimethylformamide was
29 heated to 60C. Then 9.16 g. (0.90 mole) of 96.3% sulfuric
acid was added followed immediately by a solution of 36 g.
31 water and 72 g. dimethylformamide. The solution was stirred
32 and heated at 90-95C for 30 minute~. It was then cooled
33 and filtered. The clear filtrate was mixed with water to
34 precipitate the product which had an inherent viscosity of
0.44.
36 Based on the quantity of acid used for the hydrol-
37 ysis, 90% of the imino groups in the PIPA-M should have been
38 hydrolyzed.
l~S~
- 16
1 A film of the product was cast from dimethylforma-
2 mide. After aging 3 hours at 260C it was insoluble in di-
3 methylformamide while a similarly cast film of PPA-M was
4 still soluble after the same heat expos-lre.
Example 13
6 This example compares the results of 14 reactions
7 to hydrolyze 95% of the imino groups in PIPA-M with sulfuric
8 acid. The reactions differed in the concentrations of PIPA-
g M in solution, the concentration of water in the reaction
solution and the reaction times. The general procedure was
11 to heat the PIPA-M solution tc 60 C, then add the sulfuric
12 acid and water. For each mole of imino group in solution
13 0.475 moles of sulfuric acid (0.95 moles of hydrogen ion)
14 was added. The quantity of water added was varied. The
solutions were heated at 85-88C for the various times (10,
16 20, or 30 minutes) indicated in the table below. The reac-
17 tion solutions were cooled quickly in an ice water bath. Then
18 the polymers were precipitated from solution with water. me
19 inherent viscosities of the polymers were determined.
The infrared spectra of the products formed by all
21 of the reactions were identical to each other and to the
22 product made in Example 8 (95.1~ hydrolyzed).
23 The concentration of reagents, reaction times and
24 inherent viscosities of the polymeric products are summarized
in the table below.
26 The inherent viscosity of the products, relative
27 to the inherent viscosity of the original PIPA-M, varied
28 from 0.67 to 1.03. Since the inherent viscosity of PPA-M
29 resin (made by hydrolyzing 100~ of the imino groups) is es-
sentially the same as that of the PIPA-M from which it is
31 made inherent viscosities lower than 1 in the above experi-
32 ments indicate that molecular weight degradation occurred
33 during the partial hydrolysis of PIPA-M.
34 Molecular weight degradation was not related to
the concentration (moles per kg. DMF) of sulfuric acid in
36 the reaction solution.
37 Molecular weight degradation was encouraged by
38 long reaction times (compare the inherent viscosities of
~z~ss~
1 products in runs C with M and D with N).
2 Molecular weight degradation increased as the con-
3 centration of water increase. This is particularly obvious
4 if the reactions in the 20 and 30 minute reaction times are
compared, i.e., compare E, F, G, H, I, and ~ with each other
6 and K, L, M, and N with each other. The concentration of
7 water had less effect on polymer degradation during a 10 min-
8 ute reaction period.
9 The molecular weight degradation which occurred in
the reactions described in this example and in Examples 7,
11 8, 9, and 12 were unexpected since degradation was not ob-
12 served in Examples 1-5. The difference between the two sets
13 of experiments are in the acid used for hydrolysis. Heat is
14 not required when hydrochloric acid is used. When sulfuric
acid is used, heat is required if both acid hydrogen ions
16 are to be utilized in the hydrolysis reaction as clescribed
17 in U.S. Pat. No. 4,028,311.
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-- 19 --
1 Example 14
2 To a solution of 17 g. (0.0614 mole repeating unit)
3 of PIPA-M (~inh = 1.34) in 83 g. dimethylformamide was added
4 1.64 g. of 96.9% su furic acid (0.0162 mole) which would pro-
vide 52.8~ theoretical conversion of the PIPA rings. Then a
6 solution of 9 g. water in 25 ml dimethylformamide. The so-
7 lution was not heated. Portions of the solution were mixed
8 with water to precipitate polymer after 0.5, 2, 6, 24 and 72
9 hours and the inherent viscosity of each polymer was deter-
mined. The results (below) show that the inherent viscosity
11 of the polymer in solution slowly decreased.
12 Run Reaction time, hrs. ninh
13 A 0.5 1.21
14 B 2 1.22
C 6 1.14
16 D 24 1.05
17 E 7~ 0.85
18 A thin (approx 0.1 mil thick) film of each product
19 was cast and its infrared spectrum obtained. The intensity
of the absorption peak at 1670 cm 1 (characteristic of the
21 C=N group) slowly decreased relative to the other absorption
22 peaks; this indicated that either the hydrolysis continued~
23 although at a very slow rate, during the last 70 hours ox
24 the imino group was disappearing by decomposition of some of
the iminoimidazolidinedione rings. The latter would result
26 in a decxease of the inherent viscoslty of the polymer. Prob-
27 ably both reactions were occurring. This example demon-
28 strates the rather substantial degradation (compare to ex-
29 ample 1 run for 45 minutes with HCl) and is the result of
the incomplete utilization of the sulfuric acid under exo-
31 thermic (low about 45C maximum) conditions.
