Production of a polyacyloxalamidrazone
United States Patent [1 1 Wallrabenstein et al.  
 [451 Apr. 8, 1975 1 PRODUCTION OF A POLYACYLOXALAMIDRAZONE [75] lnventors: Michael Wallrabenstein, Worth;  
 Albert Schopf, Hering; Dieter Frank, Elsenfeld, all of Germany [73] Assignee: Akzona Incorporated, Asheville,  
 [22] Filed: Aug. 30, 1973 [21] Appl. No.: 393,017  
 Related U.S. Application Data [63] Continuation of Ser. No. 288,527, Sept. 13, 1972, abandoned. which is a continuation of Ser. No. 78,187, Oct. 5, 1970, abandoned.  
 [30] Foreign Application Priority Data Oct. 9, 1969 Germany 1950907 [52] U.S. Cl. 260/78 TF; 260/29.2 N [51] Int. Cl C08g 20/20; C09g 20/22 [58] Field of Search 260/78 TF [56] References Cited UNlTED STATES PATENTS 3,544,528 12/1970 Magcrlein et a1. 260/78 TF 3.573261 3/1971 Kersten et al...... 260/78 TF 3.583.953 6/1971 Rupp et al. 260/78 TF OTHER PU BLlCATlONS Chem. Abstracts, V01. 67, 1967, 11741 lj, Saga et al.  
 .1. of Polymer Science, pfB, Vol. 4, pp. 869-873, Saga et al., 1966, (Polymer Letters).  
 Primary Examinerl-l0ward E. Schain Attorney, Agent, or F irm-Johnston, Keil, Thompson &amp; Shurtleff 571 ABSTRACT Production of polyacyloxalamidrazones, especially a very high molecular weight polyterephthaloyloxalamidrazone having recurring units of the formula 6 Claims, No Drawings PRODUCTION OF A POLYACYLOXALAMIDRAZONE This is a continuation of application Ser. No. 288,527, filed Sept. 13, 1972, which is a continuation of Ser. No. 78,187, filed Oct. 5, 1970, both now abandoned.  
  lt has been previously been disclosed that polyacyloxalamidrazones can be produced by the reaction of oxalic acid bisamidrazone with a dicarboxylic acid dihalide in either a single phase or two-phase solvent system in the presence of an acid acceptor and with mixing at temperatures between about C. and 150C. Depending upon the solvents chosen for the polycondensation reaction and certain other conditions, it is possible to achieve some variation in the molecular weight of the resulting polycondensate. A two-phase solvent system is generally preferred in achieving higher molecular weight products, by means of a so-called interfacial polycondensation. For example, it is possible to employ a two-phase solvent system using water as one phase and a water-miscible organic liquid as the other phase, this organic liquid being inert to the dicarboxylic acid halide and having its miscibility with water substantially or completely suppressed by the addition of a salting-out agent. A suitable two-phase reaction medium of this type consists of water and tetrahydrofuran wherein a phase separation is achieved by the addition of soda as a salting-out agent. Also, since sodium carbonate is a basic substance. it is capable of simultaneously acting as an acid acceptor.  
  In these earliest developed processes for the production of polyacyloxalamidrazones, it was possible to achieve only relatively low molecular weight polycondensates as established by viscosity measurements. For example, depending upon the type of initial monomers, the reduced viscosity of the polycondensate did not excced a value of 0.5 to 2.5, measured as a solution of 1 gram of the polymer in 100 ml ofa percent aqueous potassium hydroxide solution at 20C.  
  In a further development of this polycondensation process, it has been possible to achieve somewhat higher molecular weight polymers by the reaction of oxalic acid bis-amidrazone with a dicarboxylic acid dihalide at temperatures between about 0C. and 60C. in a two-phase solvent mixture consisting essentially of water and a very pure tetrahydrofuran in a volume ratio of 3:1 to 1:3, preferably employing as the salting-out agent about 3 to percent by weight of sodium chloride or sodium sulfate (with reference to the amount of water). Also, alkali metal carbonates or bicarbonates are preferred as the acid acceptor. When following this special procedure, it has been possible to obtain polyacyloxalamidrazones with a reduced viscosity of &#39;from 3.3 to 5.4, again depending upon the initial monomers. The reduced viscosity in this case is also measured as noted above,.an&#39;d this particular measurement.  
 is employed throughout this specification.  
  Thus, the best results in the production of polyacyloxalamidrazones has been achieved in accordance with the earlier application of Magerlein et a1, Ser. No.  
  716,364, filed Mar. 27, 1968. Since this earlier application sets forth the general polycondensation reaction in considerable detail, it is incorporated herein by reference as fully as if set forth in its entirety. For the production of much lower molecular weight polycondensates, attention is further directed to the earlier work of Saga et al, Kogyo Kagaku Zasshi, 69, page 2225 1966); also compare Polymer Letters, page 869 (1966).  
  It is a primary object of the present invention to provide a process which leads to a polyterephthaloyloxalamidrazone having a substantially higher molecular weight than any previous polymer of this type, i.e., as evidenced by a considerably higher viscosity when measured under identical conditions in a 10 percent aqueous potassium hydroxide solution. Other objects and advantages of the invention will become more apparent upon consideration of the following detailed specification.  
  It has now been found, in accordance with the invention, that a polyterephthaloyloxalamidrazone of substantially higher viscosity can be obtained in the reaction of oxalic acid bisamidrazone and terephthalic acid dichloride at temperatures between about 0C. and C., using the two-phase solvent mixture of water and a substantially pure tetrahydrofuran, preferably in a volume ratio of 2:1 to 1:2, provided that the polycondensation reaction is carried out in this solvent mixture in the presence of a salting-out agent of lithium chloride or lithium sulfate in an amount of 7.5 to 30 percent by weight with reference to the amount of water and also in the presence of alkali metal carbonates or bicarbonates as the acid acceptor.  
  In order to obtain the polyterephthaloyloxalamidrazone product exhibiting substantially higher viscosities, it is essential to employ a very pure tetrahydrofuran. This pure tetrahydrofuran is preferably obtained by pretreatment with solid potassium hydroxide and then distilling it over-sodium boron hydride or potassium permanganate. After purification, the tetrahydrofuran is desirably stored prior to use under an oxygen-free atmosphere. Such precautionary measures should be followed to avoid an undesirable reduction in the viscosity of the final product.  
  As the acceptor for the acid set free in the polycondensation reaction, it has been found to be especially advantageous to employ alkali metal bicarbonates and particularly alkali,;metal carbonates. The sodium and potassium carbonates are especially preferred. The acid acceptor is employed in a conventional amount, i.e. in an amount sufficient to&#39;take up the hydrogen chloride split off during the reaction.  
  It is particularlyessential for purposes of the present invention to employ lithium chloride, lithium sulfate or mixtures thereof in an amount of about 7.5 to 30 percent by weight with reference to the amount of water. It is the presence of these added lithium chloride or sulfate salts in combination with the other reaction conditions which has a pronounced effect in the increase of the viscosity or molecular weight of the polyterephthaloyloxalamidrazone product. Especially good results are achieved when using these lithium salts in an amount of 10 to 25 percent by weight with reference to the amount of water. In general, the volume ratio of waterztetrahydrofuran should be within about 2:1 to 1:2, but it has been found that a volume ratio of about 3:2 to 1:1 is especially suitable, particularly when employing sodium carbonate or potassium carbonate as the acid acceptor. It is also preferable to carry out the polycondensation at a reaction temperature of about 10C. to 40C., these temperatures being maintained in a conventional manner by removing the heat of reaction. It is not essential to maintain a constant temperature throughout the reaction, and it will be generally understood that the recited temperature conditions refer to the temperature peak which occurs at the beginning of the reaction. As a matter of convenience, the  
 bisamidrazone in 500 ml. of oxygen-free distilled water and a solution of 15.9 grams 150 millimols) of sodium carbonate in 250 ml. of oxygen-free distilled water are brought to room temperature, combined with each reaction can be carried out at about room temperature other and placed in the mixing vessel of a Kotthoff or at slightly elevated temperatures which do not exmixer. While rapidly mixing at about 2.8X r.p.m. Ceed and which are Preferably lower than and cooling with water, a solution of 30.05 grams (150 In Carrying out the reaction. the various materials are millimols) of terephthalic acid dichloride in 500 ml. of brought together in usual mahheh but Preferably y pure tetrahydrofuran is added to the mixing vessel. The first dissolving the lithium chloride or lithium sulfate in 10 reaction i completed ft i i f about 20 to 25 Water and Separately P p g another Solution of the minutes. The polycondensate is filtered off on a suction acid acceptor in Water thereafter Combining the two filter, washed three times with water and finally washed Solutions at about room p The oxalic acid with methanol. Residual water is separated from the bisamidrazone is also Preferably dissolved together polycondensate by azeotropic distillation with ligroin. with the lithium salt, it being desirable in all cases to 5 The Product is then dried in a vacuum at 0 T p y a Substantially Oxygen-free distilled Watch The duced viscosity of this product is l 1.3 (measured as a terephthalic acid dichloride is dissolved in the pure tetl i f 1 gram f h polycondensate i 100 1, f rahydrofuran and then added together Wlllll IlllS organic a 10 percent potassium hydroxide aqueous lution at solvent under strong mixing conditions to the water 20C containing all of the other reaction components. At the 20 same time. the reaction mixture is cooled sufficiently EXAMPLES 2 by any conventional means, e.g., by indirect heat exchange with any suitable cooling fluid, so as to with- All of these examples are carried out in the same draw the heat of reaction and maintain the temperature manner as Example 1 with variations in materials and within the defined limits. After completion of the reacthe final results being set forth in the following table. tion, the polycondensate product can be separat d or The oxalic acid bisamidrazone and terephthalic acid isolated from the two-phase solvent medium by ondichloride monomers are used in equimolar amounts as ventional filtration or centrifuging, preferably followed listed in the second column of the table. The viscosity by washing with water and alcohol and then purifying of the polycondensate product is measured as in Examthe product by distillation. 3O ple 1.  
 TABLE Each Tetrahy- Lithium Salt Example monomer Water drofuran Acid Vis- No. (millimols) (ml) (ml) ((3/1 ()0 m1.H O) acceptor cosity 2 75 750 750 LiCl 15g Na CO 9.5 3 75 750 500 LiCl 15g 12.0 4 75 500 1000 LiCl 15g 9.3 5 75 750 500 LiCI l0g 8.6 6 75 750 500 LiCl g 11.1 7 150 750 500 LiCl 20g 10.2 8 225 750 500 LiCl 20g 8.2 9 225 750 500 LiCl g 7.8 10 75 750 500 LiCl 15g K C0 10.2 11 37.5 750 500 LiCl 15g Na CO;, 9.3 12 150 750 500 LiCl 15g NaHCO 7.3 13 75 750 500 LiCl 15g KHCO; 7.1 14 75 750 500 Li S() 15g Na CQ, 10.2 15 75 750 750 Li SO 25g Na CO; 8.4  
  When the process is carried out in accordance with Similar results can be achieved by using terephthalic the present invention, it is possible to obtain a polytereacid dibromide in place of the dichloride, and for purphthaloyloxalamidrazine with a reduced viscosity as poses of the present invention, these two halides are high as 12 (measured as a solution of 1 gram of the considered to be equivalent. polymer in 100 ml of a 10 percent by weight aqueous Although Saga et a1, supra, have disclosed a reaction solution of potassium hydroxide at 20C.). It is thus of oxalic acid bisamidrazone and terephthaloyl chlopossible to obtain essentially new and higher molecular 5S ride in dimethylformamide containing 5 percent by weight polycondensates with values for the aboveweight of lithium chloride, this solution polycondensadefined reduced viscosity of about 6 to 12 and preferation in a single solvent phase permits the production of bly more than 7 up to about 12. These high molecular only very low molecular weight polycondensates. For weight polycondensates can be dissolved in a dilute example, if one reacts oxalic acid bisamidrazone with aqueous alkali metal hydroxide solution and then spun terephthalic acid dichloride in dimethylacetamide as or formed in an acid bath in a conventional manner to taught by this reference, or in dimethylacetamide, N- produce filaments, films, foils or the like. methylpyrrolidine or hexamethylphosphoric acid tri- The invention is further illustrated by the following amide, in the presence of 5 percent lithium chloride, examples. the resulting polyterephthaloyloxalamidrazone has an EXAMPLE 1 inherent viscosity of only 0.20 to 0.76. As will be ap- A solution of 112.4 grams (2.65 mols) of lithium chloride and 17.4 grams millimols) of oxalic acid parent from experiments by these authors, the addition of lithium chloride, for example to hexamethylphosphoric acid triamide, fails to show any viscosity increasing effect. In fact, a comparative experiment carried out without the addition of lithium chloride actually gave a product with somewhat higher viscosity (note Table 1, Experiments 5 and 6 of Saga et al). Under these circumstances, it was quite surprising and unforeseeable that lithium chloride and/or lithium sulfate would exhibit a substantial viscosity increasing effect when employed in an interfacial polycondensation as required by the present invention.  
  The process of the present invention is therefore very advantageous in permitting one to achieve very high molecular weight polyterephthalolyloxalamidrazones. Furthermore, it has been noted that the solubility of the oxalic acid bisamidrazone in the aqueous lithium chloride phase is about three times greater than the solubility of this monomer in the aqueous phase employed in previous interfacial polycondensation reactions. This represents a further advantage of the invention, since one can react about three times the amount of oxalic acid bisamidrazone with the acyl dihalide when using the same amount of water as the aqueous phase. In  
 other words, it is possible to achieve a much higher drawing the heat of reaction, the improvement which comprises carrying out the polycondensation reaction at a temperature of about 0C. to 60C. in a solvent mixture of water and a substantially pure tetrahydrofuran with a volume ratio of waterztetrahydrofuran of about 2:1 to 1:2, in the presence of a salting-out agent selected from the group consisting of lithium chloride and lithium sulfate in an amount of 7.5 to 30 percent by weight with reference to the amount of water and in the presence of an acid acceptor selected from the group consisting of alkali metal carbonates and bicarbonates, the reaction period being sufficient to yield a polyterephthaloyloxalamidrazone having a reduced viscosity of about 7 to 12, measured as a solution of 1 gram of the polycondensate in ml. of a 10 percent potassium hydroxide aqueous solution at 20C.  
  2. A process as claimed in claim 1 wherein the reaction temperature is about 10C. to 40C.  
  3. A process as claimed in claim 1 wherein the volume ratio of waterztetrahydrofuran is about 3:2 to 1:], the salting-out agent is present in an amount of about 10 to 25 percent by weight with reference to the amount of water and the acid acceptor is a compound selected from the group consisting of sodium carbonate and potassium carbonate.  
  4. A process as claimed in claim 3 wherein the salting-out agent is lithium chloride.  
  5. A process as claimed in claim 3 wherein the saltingout agent is lithium sulfate.  
 6. A process as claimed in claim 3 wherein the reaction temperature is about 10C. to 40C.