Svnthesis of Disulfide Cross Links in Polyvinyl Alcohol and Cellulose J
Derivatives E. F. IZARD AND ,P. W. MORGAN E. Z. du Pont de Nemours & Company, Znc., Buffalo, N. Y . a,oc'-Dithiodiacetyl and (methy1enedithio)diace tyl cross links were introduced into polyvinyl alcohol and cellulose esters by reaction of substituent chloroacetyl groups with sodium thiosulfate, followed by mild oxidation or treatment with formaldehyde. Disulfide crow links, attached directly to the polymer chain, were synthesized in cellulose esters by the reaction of substituent p-toluenesulfonyl groups with sodium thiosulfate, thiourea, or pyridine and hydrogen sulfide, followed by oxidizing aftertreatments. The thiourea reaction was also applied to polyvinylp-toluenesulfonate. These cross-linking reactions were sufficiently mild so that little polymer degradation occurred. The cross-linked products in the form of films and fibers were insoluble in organic solvents and dsd not fuse below their decomposition points. The cellulose derivatives were not embrittled by degrees of cross linking 3s high as one link per five anhydroglucose units. The presence of the disulfide linkage was demonstrated by reduction of the cross-linked polymers to the soluble thiol form with thioglycolic acid and reoxidation to insoluble structurea. Thioacetal cross links could not be reduced in this way.
in the case of formaldehyde, to the very short length of the cross link. I n the present study cross links containing disulfide units were introduced into polyvinyl alcohol and cellulose derivatives by a series of nondegradative reactions. Two of these reactions are well known syntheses for simple mercaptans or disulfides. Bunte (4) found that alkyl halides react with sodium thiosulfate to form S-alkyl thiosulfate salts, which can be decomposed to disulfides a t moderate temperatures. A similar decomposition can be brought about by mild oxidation (69): 0
RX
+ Na&!JnOa+RS-SONa // + N a X O\
0 2RS-b-ONa il, I/ 0
+ Hz0 +
[O]
----f
-t- 2NaHSO4
R--5-S-R
Stoner and Dougherty (29) used these reactions for the synthesis of a variety of dithiodibasic acids. We have found that polyvinyl chloroacetate and cellulose acetate chloroacetate react readily, and quantitatively with sodium thiosulfate in methyl Cellosolve to yield the Bunte salt, which occurs also with simpler halides (16). The polyvinyl hydro-thiosulfatoacetate derivatives were water soluble in the range of 15 to 100% substitution. The cellulose acetate hydro-thiosulfatoacetate salts were highly swollen by water in the range of 0.4 mole per anhydroglucose unit when the acetyl substitution was also low, but none were completely water soluble. The polymeric thiosulfate derivatives (polymeric Bunte salts) were easily oxidized by mild reagents, such as iodine solutions, to insoluble cross-linked products. Very high degrees of cross linking in the polyvinyl derivative did not yield films which were brittle, but all these films exhibited the peculiar property of disintegrating' upon contact with water. Cellulose derivative yarns with as high as one dithiodiacetyl cross link per five anhydroglucose units were not appreciably more brittle or inflexible than the uncross-linked parent derivative':
T
RE formation of covalent cross links between the main chains of high polymeric substances has been generally accepted as the best explanation of the physical properties resulting from certain aftertreatments of polymers and as the mechanism involved in the formation of many insoluble synthetic polymers. There have been very few instances of the stcpwise synthesis or chemical demonstration of the existence of such cross links. Harris and eo-workers (IO,$6) showed by a n interesting series of reactions that wool contains disulfide cross links, and t h a t some of the physical and chemical properties, such as solubility, elasticity, and reaction with enzymes, are related to the presence: of these cross links. The disulfide groups were reduced with thioglycolic acid to free thiol groups, and these were recombined by mild oxidation. When the thiol groups were reacted with dihalides, the resulting cross link, containing two monosulfide groups, was no longer reducible. Vulcanized rubber is cross-linked through sulfur, and a number of studies have been made to determine what types of structures may be present ( I , 8,1.4., 23,26,31). Cellulose or its derivatives have been submitted to a variety of reactions which probably produce covalent cross links. Of these we may cite reactions with dibasic acids (go),formaldehyde ( 7 , 1 3 ) ,glyoxal ( 3 ) ,alkoxymethylureas (18), and melamine derivatives ( 5 ) . Heuser ( l a ) reviewed some of these reactions. All of these treatments are accompanied by a n increase in the softening temperature and a decrease or loss of solubility. It is well known that increasing degrees of vulcanization in rubber increaso the modulus of elasticity or hardness. With cellulose derivatives, particularly with formaldehyde treatments, a resulting brittleness has often been reported. This is probably due to the degradation of the cellulose molecule b$ w i d catalysts or acidic by-products or possibly,
HC-0-C-C-S-S-C-
HAH
I
H
H H
l
HiH H
-0
HAH
I
These polymeric Bunte salts were also cross-linked readily by reaction with formaldehyde in the presence of a n acid catalyst. Other aldehydes or ketones could be used but would not affect t h e length of the cross lirik. 1 The degrees of cross linking reported are maximum values calculated from sulfur analyses. It is recognized that, because of factors of diatribution and decreasing mobility of polymer chain aegmenta within the forming network structure, such maxima are probably not attainable.
617
618
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 3
beeii established, and this experiment with sodium thiosultate has not beun shown to have reached equilibrium
Another route to dieuliides is through the synthesis of mercaptans from thiourea and an active halogen compound (30):
H
s
7
1
The intormediate isothiourea derivative r i i u b t be decomposed with alkali, and so the use of this reaction for the synthesis of cross links is restricted to those polymers and their derivatives which are stable to alkali. Thiourea reacted readily with polyvinyl chloroacctate and cellulose acetate cliloroncetate. The products were highly ionic and therefore precipitated from the reaction media. They were soluble in solvents such as ketones or alcohols containing large amounts of water. Because of the sensitivity of the ester linkage, they could not be converted t o mercaptans intact:
HCH
H p-Toluenesulfonyl (tosyl) est'ers and other sulfonic esters have been used by various workers, especially in the field of Carbohydrates, as intermediates in the replacement of hydroxyls by other substituents. The best known of these reactions is the replacement of tosyloxy (TsO) groups by iodine from sodium iodide (6, 9, 24), though such replacements have also been accomplished wit8h chlorine (IW), fluorine ( I I ) , thiocyanate groups (W%), etc. I n these react>ionsthe sulfonyl ester group acts as if it were a halogen:
ROTs
+ Kal
--+
RT
+ NaOTs
Three new variations of this replacement reaction were effected and used to produce disulfide cross links in polymeric structures. In each casc tmhedisulfide link v-as directly attached to the main polymeric chain (16). Cellulose acetate p-tolueiiesulfonate was reacted with sodium thiosulfate, and the product in t'he form of yarn was cross-linked by mild oxidation. The change in sulfur content indicated t,hat about 25% of the tosyloxy groups (5.67, of the nonacetylated groups) had been replaced by disulfide links. This is considerably lo.cr-er than might be expected from the work of Cramer, Gardner, and Purves (6, 9) on replacement of tosyloxy groups by iodine. Purves found that tosyl groups on primary cellulosic hydroxyls were replaced by iodine, and that in a secondary cellulose acetate (cellulose triacetate which has been subjected to partial hydrolysis) about 3591, of the hydroxyl groups were primary. The course of other,possible replacement reactions has not
The oxidized yarns prepared Iron1 this product contained one cross link per thiyteen anhydroglucose units. They were not brittle and were only swollen by organics solvents. The tosyloxy groups in polyvinyl toluenesulfonate were replaced by isothiourea groups. Upon subsequent treatment m-ith alkali and oxidation, the polymer became insoluble:
H ~ H I
HbH
!
A similar reaction was carried out with cellulose acetate p-toluenesulfonate by impregnating gel yarns with thiourea and baking them. The alkaline treatment removed all acetyl groups and produced a, yarn containing thiol and tosyl subst,ituents, which was Cross-linked by oxidation. -4positive color test, with sodium nitroprusside showed the presence of thiol groups in the yarn before oxidation (19, 26). None of the possible by-products gave this color test. The degree of replacement (68..!17~ of the tosyloxy groups or 44.4y0of the nonacetylated groups) is of the order t o be expected from the studies of Cramer, Gardner, and Purves (6, 9), if thiourea reacts in the same way as sodium iodide. Chlorine has been introduced into cellulose in place of tosyloxy groups by tbe use of pyridine hydrochloride (6, I d ) . By an analogous reaction with pyridine and hydrogen sulfidc, part of the tosyloxy groups in cellulose acetate p-toluencsulfonate was replaced by thiol groups, and the resulting polymer cross-linked by oxidation (21) :
Analysis indicated that 8O'h of t,he tosyloxy groups had beell replaced by thiol groups. This is equivalent to 50y0 of the unesterified hydroxyl groups in the original seconda,ry cellulose acetate. These values may be somewhat high because several of the possible errors (incomplete renioval of sulfur-containing byproducts, fractional removal of any noncross-linked polymer, or de-esterification) could easily produce a high sulfur content. Very few sulfur derivatives of simple carbohydrates have been described (22, 27). The three preceding reactions provide methods by which such derivatives can be prepared. I n order to demonstrate more conclusively the presence of disulfide cross links in the polymeric structures, reductions with thioglycolic acid were carried out on several insolubilized derivatives. In every case a soluble polymer was obtained which gave a positive color test for thiol groups, and which was readily reoxidized t o the insoluble form. Such a cleavage to a soluble form was not possible when the polymer contained (methylen4 dithio)diacetyl cross links from the reaction of formaldehyde on the polymeric Bunte salt.
March 1949
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
DERIVATIVES OF POLYVINYL ALCOHOL
POLYVINYL CHLOROACETATE. A polyvinyl chloroacetate of low molecular weight was prepared by polymerizing the monomer in the presence of benzoyl peroxide. An ester of higher molecular weight was prepared by chloroacetylating polyvinyl alcohol, as follows: A mixture of 44 grams of high viscosity polyvinyl alcohol (Elvanol 91A-65), 200 grams chloroacetic acid, and 100 grams acetic acid was heated on a steam bath with stirring for 3 hours, a t which time a clear, homogeneous solution was obtained. The product was coagulated in water, washed, and dried. Thirty-five per cent of the hydroxyl groups was esterified, and the product was soluble in methyl Cellosolve, pyridine, and acetic acid. It contained 13.1yochlorine and had a saponification value of 5.08 ml. of 0.1 N sodium hydroxide per 100 mg., which correspond to 0.25 chloroacetyl and 0.10 acetyl group per vinyl unit. SODIUM SALT O F P O L Y V I N Y L HYDRO-THIOSULFATOACETATE. A solution of 120 grams ( I mole) polyvinyl chloroacetate (prepared from vinyl chloroacetate) in 490 grams methyl Cellosolve was mixed with a solution of 236 grams (0.95 mole) sodium thiosulfate hydrate in 236 grams water at 80" C. The mixture was homogeneous in 5 minutes and was immediately cooled t o room temperature. Such a solution contained no sodium thiosulfate, and the polymeric salt was soluble in water and in methyl Cellosolve. Similar polymeric salts were water soluble throughout the range of 15 t o 100yosubstitution. When completely oxidized, the thiosulfate groups in the polymeric salts were converted to disulfide linkages, and these oxidized products contained the calculated quantities of sulfur, as indicated in the following paragraph. Films of the sodium salt of polyvinyl hydro-thiosulfatoacetate (100% substitution) were prepared by spreading a 10% aqueous solution on glass plates with a doctor knife and allowing them to air-dry. Such films were then cross-linked and insolubilized by baking a t 100" C. for 2 hours and by oxidation with 2Y0 alcoholic iodine a t 50" C. for 30 minutes. IIydrogen peroxide (lOyG)and nitric acid (1540%) were also used as oxidizing agents. I n every case except with nitric acid, all of the thiosulfate groups were completely converted to disulfide linkages as indicated by the residual sulfur content. Calculated sulfur content for the above derivative after cross linking, 27.3%; found, 27.2% (after iodine oxidation), 27.0% (after hydrogen peroxide oxidation), and 24.0y0 (after nitric acid oxidation). The low value with nitric acid could result from the formation of some sulfonic acid groups. A film of the sodium salt of polyvinyl hydro-thiosulfatoacetate (92% substituted) was soaked in a 37y0 solution of formaldehyde to which had been added 291, hydrochloric acid. It became insoluble in water after a few minutes. POLYVINYL ~-(ISOTRIOUREA)ACETATE HYDROCHLORIDE. Thiourea (40 grams, 0.5 mole) was added with rapid stirring to a solution of polyvinyl chloroacetate (60 grams, 0.5 mole) in 180 grams of methyl Cellosolve at room temperature. Heat was evolved, and the solution set to a gelatinous mass in a few minutes. Excess solvent was poured off, and the product was washed with methanol and dried. It was soluble in water and contained 14.11% nitrogen and 16.00% sulfur; calculated for complete substitution, 14.25y0 nitrogen; 16.30% sulfur. POLYVINYL ~-TOLUENESULFONATE. A solution of 190 grams of p-toluenesulfonyl chloride in 500 grams of dry pyridine was added with stirring t o a slurry of 88 grams of polyvinyl alcohol in 500 grams pyridine at room temperature. The mixture was heated t o 65" C., and became clear and homogeneous. Heating was continued 3 hours. The product was precipitated in cold water, washed, and dried. It was soluble in methyl Cellosolve and contained 9.05% sulfur, equivalent to 22y0 substitution. POLYIINYI,' ISOTHIOUREA. The polyvinyl p-toluenesulfonate was dissolved in 600 grams of methyl Cellosolve, 40 grams of thiourea were added, and the solution was heated with stirring a t 90" C. for 12 hours, at which time the product was water soluble.
619
Addition of 3% sodium hydroxide coagulated the polymer as polyvinyl isothiourea. It was soluble in aqueous hydrochloric acid. Coagulation with concentrated alkali yielded a polymer which was insoluble in water, alcohol, or acids. CELLULOSE DERIVATIVES
CELLULOSEACETATE CHLOROACETATE. Methods for the chloroacetylation of cellulose described in the literature were found to cause excessive degradation (3, 68). The following two methods produced useful degrees of substitution in secondary cellulose acetate without great degradation. The second procedure is the milder. A secondary cellulose acetate [lo grams, 1.66 acetyl groups per anhydroglucose unit (g.u.)] was dried at 100" C. and dissolved in 60 grams chloroacetic acid a t 70". The process of solution required 30 minutes. The solution was then heated at 110' C. for 1 hour, cooled to 80 ', and poured into cold water with stirring. The washed flake was dissolved in acetone and reprecipitated. The product contained 4.98ojO chlorine and had a saponification value of 7.84 ml. of 0.1 N sodium hydroxide per 100 mg. [determined by the procedure of Malm and Clarke ( I 7 ) l . Saponification of sodium monochloroacetate by the same procedure gave negative values. Therefore these results correspond t o a n introduction of 0.36 chloroacetyl group per anhydroglucose unit without the loss of acetyl groups. Fairly tough, flexible films were cast from methyl Cellosolve. The chloroacetic acid used in this experiment contained a trace of iron salts. Pure acid failed to chloroacetylate cellulose acetate under these conditions. Results similar to t h a t described above were obtained with a variety of other cellulose acetate samples. Cellulose acetate (300 grams, 2.44 acetyl groups per anhydroglucose unit) was dried and suspended in 1.5 liters of dry, pure benzene. A solution of 300 grams pure chloroacetic anhydride in 1 liter of benzene a t 50" C. was added, and the mixture heated a t reflux temperature with stirring for 7 hours. The cellulose ester became highly swollen and stuck together in balls, but did not dissolve. It was isolated by decantation of the benzene liquors, dissolved in acetone, and precipitated in water. It contained 3.81y0chlorine and had a saponification value of 9.53 ml. of 0.1 N sodium hydroxide per 100 mg., which corresponds t o 0.31 chloroacetyl and 2.44 acetyl groups per anhydroglucose unit. The polymer was undegraded (vag. of 0.1% solution in glacial acid was 0.18 at 25" C.) and formed excellent films from the usual solvents for cellulose acetate. This reaction has been carried out with equal succcss in homogeneous solutions in dry acetone as well as on chloroform solutions of ethylcellulose. BUNTE SALT FROM CELLULOSE ACETATE! CHLOROACETATE. Cellulose acetate chloroacetate (2 grams, 1.66 acetyl and 0.38 chloroacetyl groups per anhydroglucose unit) was dissolved in 40 ml. of methyl Cellosolve, and 1 gram of sodium thiosulfate hydrate was added. Sufficient water was added with stirring a t 60" C. t o form a homogeneous solution. The solution was stirred a t 80" C. for 1 hour and then coagulated in alcohol. The wet flake was dissolved in pyridine, the insoluble salts were filtered out, and the solution was added to alcohol. The vacuum-dried flake contained no chlorine and 7.75% sulfur, which represents complete replacement of the chlorine groups by thiosulfate groups. The product was soluble in many organic solvents containing some water. Alcoholic iodine oxidized it rapidly t o the insoluble disulfide and, on standing in the air, i t slowly became insoluble. Cellulose acetate chloroacetate (80 grams, 2.44 acetyl and 0.31 chloroacetyl groups per anhydroglucose unit) was dissolved in 90 grams of 95-5 methyl Cellosolve-water and blanketed with nitrogen. Sodium thiosulfate hydrate (14 grams, 0.2 mole per
620
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 3
anhydroglucose unit) was added, and the r e a d o n mixture stirred stirred wat'er. The product, dried a t 65" C,, contained 4.28% a n d heated at 80" C. under a slow flow of nitrogen for 4 hours. sulfur which corresponds t o the introduction ob Q.075 thiosulT h e solution was filtered through a simple cloth filter under nifate group per anhydroglucose unit. trogen pressure, deaerated 18 hours, and spun into yarn, which The derivative had the solubilities of standard cellulose acehad a tenacity of 0.70 gram per denier a t 22.6% elongation. tate, was not unduly water sensitive, and formed tough, flexible The washed air-dried fibers contained 3.58y0 sulfur and were infilms. An acetone solution was spun into filaments which had conipletely soluble in aqueous acetone. After treatment with a tenacity of 1.0 gram per denier a t 3000 elongation. 2yo alcoholic iodine a t 50" C. for 30 minutes and washing, the The yarns m r e readily cross-linked by soaking in a 0.5y0solufibers Contained .2.26%, sulfur, which corresponds to 0.20 disultion of iodine in 25% aqueous alcohol at 50" C. Iodine was fide link per anhydroglucose unit. The cross-linked fibers were st,rongly absorbed, but this t,reatment did not damage the fibers mot brittle and were only slightly swollen in aqueous acet,one. when 25Y0 alcohol was used. Cross-linked filaments were not When hung over a heated metal bar under slight tension, they brittle and mere insoluble in all common solvents for cellulose showed only slight suftening at 210" C., were highly discolored derivatives. at 220 ', but did not break below 250". REACTIONO F CELLULOSE ACETATE p-TOLUENEsULFONATE A sample of unoxidized yarn was soaked in 10% formaldehyde WITH THIOUREA. Gel wet-spun filaments of cellulose acetate solution containing 1% p-toluenesulfonic acid, air-dried, and p-toluenesulfonatJe (2.44 acetyl and 0.34 p-toluene~iilfonylgroups baked 15 minutes at 100' C. The filaments were insoluble. per anhydroglucose unit) were soaked in 5% aqueous t)hiourea C:ELLULOSE ACETATE cY-(IsoTHIOUREA)AChTATE HYDROCHLO-solution for 1 hour, air-dried, and baked 5-1 hours a t 1.00" C. RIDE. Cellulose acetate chloroacetate ( L O grams, 1.66 acetyl After washing and drying, the yarn contained 2.01% nitrogen and 0.36 chloroacetyl groups per anhydroglucose unit) was heated and 5,22y0 sulfur. The calculated values for 0.24 isothiourea in 100 mi. acetone with 0.5 grani thiourea at 40" C. for 1 hour. group per anhydroglucose unit are Z.Olyo nitrogen and 5.53% A precipitate formed in 5 minutes and gradually became harder. sulfur. The product was highly swollen by water, was insoluble in dry The above yarn was soaked in 0.1 N sodium hydroxide for 24 acetone, but was soluble in a considerable range of aqueous acehours. When the alkali-wet yarns were dipped in 200 sodium tone. It contained 3.51% nitrogen, which is equivalent to comnitroprusside, they t,urned a bright reddish-violet, color, an indicaplete substitution of chlorine by isothiourea groups. tion of free thiol groups. Oxidation with 2% alcoholic iodine The polymer formed acidic solutions in aqueous acetone solution at 50" C. cross-linked the yarns, and they no longer gave which evolved carbon dioxide upon addition of sodium bicara positive test for thiol groups. bonate. A soluble cellulose derivative was isolated after this REACTIOS OF CELLULOSEACETATE~-TOLWT~ESTJLFOXATS treatment which contained no sulfur, nitrogen, or chlorine. WITH HYDROGEN SULFIDE. Cellulose acetate p-toluenesulfonat,c REACTION O F CELLULOSE -4CETATE cHLOR0AClCTATE YARNS (5 grams, 2.44 acetyl and 0.35 toluenesulfony~graups per arahydroglucose unit; % sulfur, 3.47, 3.49) was dissolved in 100 mi. of WITH SODIUM THIOSULFATE. A skein of cellulose acetate chloroacetate yarn (2.44 acetyl and 0.31 chloroacetyl groups per and r y pyridine, and the solution was kept saturated with hydrogen hydroglucose unit) was placed in an excess of 5% sodium thiosulfide a t 35 t o 40 O C. for 8 hours. Then t'he reaction vessel was sulfate dissolved in 50% aqueous alcohol. After 2 hours at stoppered and allowed to stand a t room temperature for 5 0 hours. 40' C., sufficient reaction had taken place so that the yarn was At 24 hours the product could be insolubilized by iodine oxidareadily insolubilized to acetone by alcoholic iodine. tion. The final product was acetone soluble, but was readily insolubilized by iodine or by exposure to air. I n order to retain At 24 hours a sample was oxidized, washed, and ana!yzed, and found to contain 2.45% sulfur, which is equivalent to 0.17 disulacetone solubility, the product was coagulated and washed under pure nitrogen in previously boiled water or the product was cofide cross link per anhydroglucose unit. Gel webspun yarns of the same derivative were soaked in lo%, agulated in nonsolvent organic solvents. Thin films were cast from the pyridine reaction mixture, partly sodium thiosulfate solution for 1 hour, air-dried, baked 4 hours at dried in air, and then washed thoroughly with water. These 100" C., washed, and again air-dried. The yarns were then oxidized in 2y0 alcoholic iodine for 30 minutes, washed wit,h alcohol, films x w e incompletely soluble in aceton?, but st,ill gave a positive t,est for free thiol groups with sodium nitroprusside. T h e and mater, and air-dried. The sulfur content \vas 0.59y0, which test was negative after iodine oxidation or longer exposure to corresponds to 0.05 disulfide cross link per anhydroglucose unit. air, and the films were no longer soluble. They were as flexible CELLULOSE ACETATE P-TOLUENESULFON~TE, Cellulose aceand tear resistant as films from the start,ing material. f a t e (400 grams, 1.66 acetyl groups per anhydroglucose unit), For the preparation of :t sample for analysis, the pyridine dried a t 100" C., was dissolved in 1500 ml. of dry pyridine. preaction mixture was filtered, and the product coagulated in Toluenesulfonyl chloride (400 grams) was dissolved in 300 ml. rapidly stirred water. It v a s washed thoroughly with water of pyridine. The two solutions were cooled to 15' C. and mixed. and then extracted a t room temperature with 95% ethanol, The solution was stirred a t room temperature for 4 hours, diluted benzene, and ether in succession (three I-hour leachings in each with an equal volume of acetone, and poured slowly into a large solvent with accompanying filtrat,ion and rinsing steps). T h e volume of rapidly stirred water a t 50" C. in order to precipitate final product was slightly colored, had no odor, and gave a negathe product. tive test for free thiol groups. The sulfur content (yosulfur, The product contained 3.3500 sulfur which is equivalmt to 4.01, 4.02; nitrogen, none) was equivalent t o 0.07 toluenesul0.29 p-toluenesulfonyl group per anhydroglucose unit. Other fonyl group and 0.28 disulfide cross link per anhx-droglucose unit. p-toluenesulfonyl derivatives used in this study were prepared in OF DISULFIDECROSSLISKS WITH THIOCILYCOLIC REDUCTION a similar way. ACID. Oxidized and insoluble yarns prepared from the sodium REACTIOX O F CELLULOSE ACETATE P-TOLUENESULFONhTE salt of cellulose acetate hydro-thiosulfatoacetate (0.2 mole sulfur WITH SODIUMTHIOSULFATE. Cellulose acetate p-toluenesulper anhydroglucose unit) were immersed in 80% aqueous acetone fonate (450 grams, 1.66 acetyl and 0.29 p-toluenesulfonyl groups containing 5% thioglycolic acid. After 30 hours a t 50" C. the per anydroglucose unit) was dissolved in a mixture of 1 liter of fibers were dissolved while a control without the thioglycolic acetone, 1 liter of methyl Cellosolve, and 100 ml. of water. The acid was unchanged. The polymer was coagulated in water, solution was warmed to 60" C., and 250 grams of sodium thiowashed thoroughly with alcohol and water, and cast into a film sulfate hydrate were added together with 100 ml. of methyl from aqueous, acetone. This film became insoluble upon oxidaCellosolve and 125 ml. of water. Stirring and heating at 60 t o tion with alcoholic iodine. 65" C. were continued for 2.5 hours. The solution was left at Cellulose acetate p-toluenesulfonate-sodium thiosulfate prodroom temperature 18 hours and then precipitated in rapidly
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1949
ucts were similarly reduced arid reoxidized. Thiosulfate derivatives cross-linked with formaldehyde withstood this reducing treatment for 100 hours without losing their fibrous form. The washed yarns did give a positive sodium nitroprusside test, a n indication t h a t not all the sulfur cross links contained methylene bridges. LITERATURE CITED
Bloomfield, G. F., J . Polymer Sci., 1,312-17 (1946). Borglin, J. N., U. S. Patent 2,392,359 (Jan. 8, 1946). Broderick, A. E., Ibid., 2,329,741 (Sept. 21, 1943). Bunte, H., Ber., 7,646-8 (1874). Coolidge, C., and Reese, J. S.,U. 8. Patent 2,375,838 (May 15, 1945).
Cramer, F. B., and Purves, C. B., J . Am. Chem. SOC.,61,3458-62 (1939).
Dillenius, H., Jentgen’s Kunstseide u. Zellwolle, 24, 520-33 (1942).
Farmer, E. H., and Shipley, F. W., J . Polymer Sci., 1, 293-304 (1946).
Gardner, T. S., and Purves, C. B., J . A m . Chem. SOC.,64, 153942 (1942).
Harris, M., Mirell, L. R., and Fourt, L., J . Research Natl. Bur. Standards, 29,73-86 (1942). Helferich, B., and Gnuchtel, A., Ber., 74B,1035-9 (1941). Hess, K., and Stenael, H., Ibid., 68,981-9 (1935). Heuser, E., Paper Trade J., 122, No. 3 , 4 3 (1946). Hull, C. M., Olsen, S. R., and France, W. G., IND. ENG.CHEM., 38,1282-8 (1946). Izard, E. F., U. 8.Patents 2,418,938-40 (April 15, 1947).
621
Irard, E. F., and Howk, B. W., Ibid., 2,418,941 (April 15, 1947).
Malm, C. J., and Clarke, H. T., J . Am. Chem. SOC.,51, 275 (1929).
Maxwell, R. W., U. S.Patent 2,373,135 (April 10, 1945). Morner, K. A. H., 2.phvsiol. Chem., 28, 594-615 (1899). Monorieff, R. W., and Bates, H., Ibid., 2,372,386 (March 27, 1945).
Morgan, P. W., U. 9. Patent, 2,418,942 (April 15, 1947). Muller, A., and Wilhelms, A., Ber., 74B, 698-705 (1941). Naylor, R. F., J . Polymer Sci., 1, 305-11 (1946). Oldham, J. W. H., and Rutherford, J. K., J . Am. Chem. SOC.,54, 366-78 (1932).
Olsen, 5 . R., Hull, C. M., and France, W. G., IND. ENG.CHEM., 38,1273-82 (1946).
Patterson, W. I., Geiger, W. B., Mirell, L. R., and Harris, M., J . Research Natl. BUT.Standards, 27, 89-103 (1941) ; Geiger, N. B., Kobayashi, F. F., and Harris, M., Ibid., 29, 381-9 (1942).
Raymond, A. L., in H.Gilman’s “Organic Chemistry,” 2nd ed., Vol. 11, p. 1612, New York, John Wiley & Sons, 1943. Rudy, H., Cellulosechem., 13, 49-58 (1932). Stoner, G. G., and Dougherty, A., J . A m . Chem. Sac., 63, 987-8 (1941).
Urquhart, G. G., Gates, J. W.,,?., and Connor, R., in N. L. Drake’s “Organic Syntheses, Vol. 21, p. 36, New York, John Wiley & Sons, 1941. Westlake, H. E., Jr., Chem. Rev., 39,230 (1946). RECEIVED December 8, 1947. Presented before the Division of Cellulose Chemistry at the 111th Meeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J.
Pure Hydrocarbons from Petroleum COMPOSITION OF C, FRACTION OF CATALYTIC GASOLINE JOHN GRISWOLD‘ AND J. E. WALICEY2 University of Texas, Austin, Tex.
A
hexane-hexene fraction from a Thermofor catalytic gasoline was separated into paraffinic and olefinic portions by the Distex operation. The two portions were analyzed by fractional distillation with refractive indexes, aniline points, bromine numbers, and specific dispersions on the small cuts. The percentages of &%dimethylbutane and of n-hexane were small, but the ratios of other isomeric hexanes corresponded approximately to equilibrium at the cracking temperature. Although a complete analysis as percentage of each individual hexene was not obtainable, many of the known isomers were present.
T
H E bulk of synthetic aliphatic chemicals is made from olefins, and at least one concern manufactures a variety of products from pentenes. As yet there is no corresponding utilization of the hexenes. This is in part due t o the relative numbers of individual compounds and the difficulty of separating mixtures of CSisomers as compared t o mixtures of Cg isomers. There are three pentanes and six pentenes with two pairs of pentenes boiling 1O C. apart. There are five hexanes, and seventeen noncyclic hexenes have been reported. Most of the latter fall into narrow boiling groups, whose complete resolution by fractionation would require a column containing several hundred theoreti1
Present address, Illinois Institute of Technology, Chicago 16, Ill.
* Present address, California Research Corporation, Richmond, Calif.
cal plates. On the other hand, chemical utilization does not require in all cases a material consisting of a single pure isomer. This investigation was undertaken t o shed light o n the hexenes which can be made available from the abundant supply of catalytic gasoline by application of the Distex operation. Laboratory studies showed t h a t activity coefficients for olefins are substantially the same as those for naphthenes of the same molecular weight wheri the solvent is aniline. Hence, the Distex operating conditions and type separation of paraffin-olefin mixtures are comparable to the same factors for paraffin-naphthene separation. EQUIPMENT AND ANALYTICAL TESTS
The development of the Distex pilot plant and its application t o the separation of paraffin-naphthene-aromatic hydrocarbons in straight-run fractions have been reported (6, 7 , 8). For the present work, the apparatus described ( 6 ) was used with the addition of a Brown Instrument Company 12-point temperature recorder (Figure 1). Analytical distillations were made with t h e 11-mm. diameter Podbielniak Heligrid column, and densities (dz5) were determined with the apparatus and techniques given in earlier articles. Aniline points were determined with 1 ml. each of sample and of aniline sealed into glass tubes which were suspended and rotated in a water bath. Refractive indexes (n%5 and were determined with B
