CA1205597A - Partial hydrolysis of poly(iminoimidazolidinediones) - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Poly(iminoimidazolidinedione) of the general structure whelein one X is O and one X is NH, R is an organic moiety such as methylenediphenyl (PIPA-M) which are partially hydrolyzed to produce copolymers containing about 3 to 25% of the unhydrolyzed units:

and about 75 to 95% of the hydrolyzed units:

are stable crosslinkable polymers which exhibit such properties as adherence to metal when crosslinked.
The partial hydrolysis is obtained with a stoichio-metric amount of a Br?nsted acid such as HCl for the desired conversion or with sulfuric acid under narrow process conditions.

Description

~Z~ 7 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:

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.

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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.

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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

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:

" ,C

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~

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.

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1 In one of its aspects, the present invention is a 2 process for producing copolymer containing units of the 3 structures:

~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~

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.
. .

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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~

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.

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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

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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.

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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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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.

Claims (22)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A crosslinkable copolymer having the repeating unit:
wherein in said repeating units Q are from about 3 to 25% imidazolidinedione-1,3-diyl rings of the structure:

wherein one X is O and one X is NH and from about 75 to 97% imidazolidinetrione rings of the structure:

R in said repeating units is an organic moiety which may be aliphatic, alicyclic, aromatic or mixtures thereof and n is sufficiently large to produce a solid product.

2. The stable meltable composition according to claim 1 wherein the R group is methylenediphenyl.

3. The stable meltable composition according to claim 1 wherein the R group is oxydiphenyl.

4. The stable meltable composition according to claim 1 wherein the R group is a mixture of methyl-enediphenyl and 4-methyl-1,3-phenylenyl groups.

5. The stable meltable composition according to claim 1 wherein the R group is a mixture of methyl-enediphenyl and bitolylenediyl groups.

6. A crosslinked copolymer having the repeating unit:
wherein in said repeating units Q is from about 3 to 25% imidazolidinedione-1,3-diyl rings of the structure:

wherein one X is O and one X is NH and from about 75 to 97% imidazolidinedione rings of the structure:

R in said repeating units is an organic moiety which may be aliphatic, alicyclic, aromatic or mixtures thereof and n is sufficiently large to produce a solid product.

7. The stable meltable composition according to claim 6 wherein the R group is methylenediphenyl.

8, The stable meltable composition according to claim 6 wherein the R group is oxydiphenyl.

9. The stable meltable composition according to claim 6 wherein the R group is a mixture of methyl-enediphenyl and 4-methyl-1,3-phenylenyl groups,

10. The stable meltable composition according to claim 6 wherein the R group is a mixture of methyl-enediphenyl and bitolylenediyl groups.

11. A process for producing copolymer containing units of the structure:

and wherein one X is O and one X is NH comprising contacting a polymer of the repeating unit:

wherein one X is O and one X is NH, R in said repeating is an organic moiety which may be aliphatic, alicyclic, aromatic or mixtures thereof and n is sufficiently large to produce a solid product, with a monobasic Br?nsted acid in an amount less than 99 percent of the moles of iminoimidazoledinedione-1,3-diyl rings in said polymer at an initial temperature of about 20-25°C in the presence of water and allowing the reaction to proceed without cooling for a sufficient time to convert a substantially stoichiometric amount, based on the acid present, of said iminoimidazoledinedione-1, 3-diyl rings of said polymer to imidazolidinetrione rings.

12. The process according to claim 11 wherein said monobasic acid is selected from hydrochloric or hydrobromic.

13. The process according to claim 12 wherein said monobasic acid is hydrochloric.

14. The process according to claim 13 wherein an aqueous solution of acid is used.

15. The process according to claim 11, wherein from 1 to 99 molar percent of said acid is present based on the iminoimidazoledinedione-1, 3-diyl rings present in said polymer.

16. The process according to claim 12, wherein from 1 to 99 molar percent of said acid is present based on the iminoimidazoledinedione-1,3-diyl rings present in said polymer.

17. The process according to claim 13, wherein from 1 to 99 molar percent of said acid is present based on the iminoimidazoledinedione-1,3-diyl rings present in said polymer.

18. The process according to claim 15, 16 or 17 wherein from 25 to 97 molar percent of said acid is present based on the iminoimidazoledinedione-1,3-diyl rings present in said polymer.

19. A process for producing copolymer containing units of the structure:

and wherein one X is O and one X is NH comprising con-tacting a polymer of the repeating unit:

wherein one X is O and one X is NH, R in said repeating unit is an organic moiety which may be aliphatic, alicyclic, aromatic or mixtures thereof and n is sufficiently large to produce a solid, with from about 0.5 to 49.5 mole percent of sulfuric acid based on iminoimidazoledinedione-1,3-diyl rings in said polymer at a temperature in the range of 80 to 110°C, with 6 moles or less of water per mole of imioimidazoledinedione-1,3-diyl ring, for a period of time only sufficient to convert a substantially stoichiometric amount of said iminoimidazoledinedione-1, 3-diyl rings to imidazolidinetrione rings.

20. The process according to claim 19 wherein the temperature is no higher than 90°C.

21. The process according to claim 19 wherein there are 2 moles or less of water per mole of iminoimidazoledinedione-1,3-diyl ring present.

22. The process according to claim 19, 18, or 19 wherein the time of reaction is such as to result in an inherent viscosity of the product copolymer being no less than 94% of that of the poly-mer from which it was made.