2686
INDUSTRIAL AND ENGINEERING CHEMISTRY
(9) ZbkZ., 361, 113-65 (1908). (10) Einhorn, A,, and Hamburgei, A , , Ber., 41,24 (1908). (11) Flory, P. J., Chem. Reas., 39, 137 (1946). (12) Gams, A., Widmer, G., arid Fisch, I\‘.,Brit. Plastics, 14, 508-20 (1943). (13) Gams, A , , W-idmer, G., and Fisch, W., H e h . Chim. A c t e , 24,302E (19411. --, (14) Hirt, R. C., unpublished work. (15) Hodgins, T. S., Hovey, A. G., Hewitt, S., Barrett, W.R., and Meeske, C. J., IXD.ESG. CHEM.,33, 769 (1941). (16) Hughes, E. W., J. Am. C h e m SOC.,63, 1737 (1941). (17) Kadowaki, H., BUZZ.Cherrb. SOC.Japan, 11,248 (1936). (18) Klotz, I. hl., and Askounis, T., J . Am. Chem. SOC.,69, 801 (1947). (19) Knudsen, P., Ber., 47, 2698-701 (1914). (20) Kohler, R., KoZZoid Z., 103, 138 (1943). (21) Kumler, W. D., and Fohlen, G. bf., J . Ana. Chem. SOC.,64, 1944 (1942). (22) Landes, C. G., and Maxwell, C . S.,Paper Trade J . , T A P P I , 121, 51-60 (1945). U. 8.Patent 2,559,220 (1945). (23) Lundberg, L. *4., Ibid., 2,475,846 (1949). (24) Marvel, C. S., Elliott, 3. R., Roettner, F. E., and Yuska, Henry, J . Am. Chem. SOC..6 8 , 1681 (1946). (25) Ostrogovich, L4,,Gazt. ital., 65, 566 (1934). \ - -
Yol. 44, No. 11
(26)
Pauling, L., Brockway, L. O., aiid Beach, J. Y., ,J, A m . Cliena.
(27) (28)
Pulvermacher, G., Ber., 25, 307-10 (1892). Scheibler, H., Trostler, F., and Scholz, E., 2 . 3nge.w. Cliem., 41,
SOC.,57, 2705 (1935). 1305 (1928).
Smythe, L. E., J . Phgs. a?id Colloid Chem., 51,369 (1947). Taylor and Baker, “Sidgwick’sOrganic Chemistry of Nitrogen,” p. 280, New York, Clarendoii Press, 1937. (31) Thurston, 3. T., Gibson Island Conference. .July 1441 (unpublished paper). (32) Vogel, R. E., Kunststofe, 31, 309 (1941). (33) Walter, G., Trans. Faraday Soc., 32, 377-95 il936); K c d o i d Z., (29) (30)
57, 229-34 (1931). (34) (35) (36) (37)
Walter, G., Trans. Faradnu SOC.,32, 396 (1936). Walter, G., and Lutwak, R., Kolloid Beihefte, 40, 158 (1934). Wheland, George W., ”Theory of Resonance.” S e w York, . Johu Wley & Sons, 1944. Wohnsiedler, H. P., and Thomas, W.A I , , I-. ,5 Patents 2,345,543 (1944); 2,485,079, 2,485,080 (1949).
RECEIVED for review April 13, 1931. ACCEPTED.June 18, 19.52. Presented before the Division of Paint, Varnish, and Plastics Chemistry, Symposium o n Urea, Melamine, and Related Resina, a t the !19th lfeeting Of the .4MERICAh- CHEMICAL S O C I E T Y , Boston, 3Iasa.
Chloromethylation of Pol-ystvrene J
J
4
GIFFIN D. JONES Physical Research Laboratory, The Dow Chemical Co., Midland, Mich.
EARLY all of the common reactions of aromatic substitution have been applied to polystyrene. The chloromethylation of styrene-divinylbenzene copolymer and subsequent amination with tertiary amines has been described ( I , 3, 4). This paper deals with the chloromethylation of polystyrene. As a rule a solvent is necessary to carry out a reaction with a polymer. Chloromethylation a i t h chloromethyl ether is an ideal case from this point of view because both polystyrene and chloromethylated polystyrene are soluble in chloromethyl ether. The catalyst, too, dissolves in the reaction mixture even though, as in the case of zinc chloride, it may not be soluble in chloromethyl ether itself. As a Friedel-Crafts reaction chloromethylation requires less driving force than alkylation. If this were not so it would be impossible to isolate the substituted benzyl chloride that is produced in chloromethylation. The alkylation reaction is encountered as a secondary reaction in most chlorompthylations as pictured in the following equation:
Iln
, ClCHA OCH -+
Catalyst
f
a
R /
tion can be carried to a higher might per cent of chlorine at the gel point if it is carried out in a more dilute solution in chloromethyl ether. The use of a lower viscosity grade of polystyrene permits a higher degree of chloromethylation prior to gelation. This is shown in Table I where data are given for rhloromethylations carried t o the point of gelation. As a further illustration it was found th3t soluble samples of 10 t o 14% chlorine veere obtained by chloromethylating polystyrene of viscosity grade 87 in 8.7oJ, concentration or viscosity grade 2 in 22% concentration. The term “viscosity grade” is defined in Table I. A \yay of observing the progress of chloromethvlation is provided by the measurement of the viscosity rise which occurs slowly at first and abruptly as the gel point is approached. This is shomn in Figures 1 to 3. In Figure 1 the ordinate is a measure of viscosity as obtained fiom a recordlug ytirrer-viscosimeter. The data from which this graph was plotted were obtained from an experiment carried out in a resin pot of 3-liter capacity a hich was filled with 2 liters of a 14% by neight solution of polystyrene (commercial molding grade) in chloromethyl ether. Zinc R ~ C H , C I chloride (50 grams) was added and the solution stirred by a syn__ chromotor driven electrically by a synchrogenerator that was turned a t constant speed by an electric motor. The viscosity was indicated by the current required t o drive the synchromotor. The voltage drop across
R15
14.8 15.9
F~~& given ooncentration (2.67%) of Z D C in ~ ~solution.
90
80
16.a
November 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
2687
60
50
40 CPS
30
20
IO . 0
0.5
1.5
I
2
2.5
100
0
200
Figure 2.
a resistor is plotted as the ordinate in the figure. It is a measure of viscosity for the temperature (32" to 34" C.) and density of the solution a t the moment. The dip in the curve was caused by withdrawal of a sample. I n the experiment of Figure 2 more samples were withdrawn for analysis, and the data so obtained are replotted in Figure 3. The last sample, still soluble, was isolated very near to the gel points and a t a conversion of 64y0. As one goes to lower concentration of polystyrene it is necessary to increase the proportion of catalyst to the quantity of polystyrene used as shown in Table 11. The rate is quite dependent, however, on the purity of the chloromethyl ether. While dissolved hydrogen chloride is not objectionable, the presence of methylal makes it necessary to use a larger amount of catalyst. Methylal is a reaction product of chloromethyl ether with the methanol-a by-product of chloromethylation.
300
400
600
500
MINUTES
Figure 1. Viscosity Rise during Chloromethylation
Viscosity Rise during Chloromethylation First chloromethylation described
TABLE IV. Copolymer,
G. 20 160 160
CHLOROMETHYLATION OF STYRENE-ISOBUTYLENE COPOLYMER Chloromethyl Ether, M1. 200 416 416
Ligroin, Zinc Time, M1. Chloride, G. Hr. 1 8 1340 40 23 1340 53 23
C1, 7%
1.83 2.04 4.05
TABLE 11. CATALYSTCONCENTRATIONS FOR APPROXIMATELY
EQUAL RATEOF CHLOROMETHYLATION
Catalyst Zinc ohloride
Polystyrene Concn., %
7 16 30 11.7
Aluminum chloride
Weight Ratio of Catalyst to Polystyrene 0.4 0.16 0.08 0.045
The progress of chloromethylation can be judged by conductivity measurements as shown in Table 111.
IN CONDUCTIVITY DURING TABLE 111. INCREASE
CHLOROMETHYLATION
(Cell constant 0.093 a t 25O C.) Experiment Ad Experiment Bb Time, ReRistance, Temp. Time, Resiatance, T t m e , min. ohms C. mtn. ohms 2 38 85 730 33 100 38 680 34 3 10.5 38.5 660 34 4 120 39 670 34.5 6 40 135 670 (gel) 35 8 40.5 ... ... 15 ... .. 20 a 2.5 grams of zinc chloride in 100 ml. of 10% solution of polystyrene in redistilled chloromethyl ether. b 30 grams of ainc chloride in 2 liters of 10% solution of polystyrene in chloromethyl ether.
..
... ...
A convenient q-ay of arresting the chloromethylation was the addition of wet dioxane t o bleach the red color of the reaction
0
50
too
X CONVERSION
Figure 3. Viscosity Rise as a Function of Conversion From data of Figure 2
mixture. For ease in control, conditions giving very fast reaction were avoided. The chloromethylated polystyrene could be precipitated with methanol as a white powder To ensure complete removal of zinc chloride it was sometimes redissolved in dioxane and reprecipitated by spraying into water. If the zinc chloride was not removed completely the polymer became insoluble on drying even a t room temperature. Poly-or-methylstyrene can be chloromethylated with entirely similar results, as shown in Figure 4. Samples of styrene-isobutylene copolymer were chloromethylated also.
CPS -
15.47
-
15
for work a i t h chloromethyl ether mho are known to have sensitivities, asthma, or lung disorder. Where diluents such as tetrachloroethylene, methylene chloride, and paraffinic hydrocarbons have been used, the effect on gel point conversion is not pronounced. The paraffinic hydrocarbons reduce the catalyst solubility. Methylene chlorido is not really inert, of course, and it is interesting that a solution of polystyrenp in methylene chloride with stannic chloride added undergoes gelation when a drop of benzyl chloride is added as an activator. The reaction of a substituted benzyl chloride Kith a tertiary amine produces a quaternary ammonium chloride. In the case of chloromethylated polystyrene this amination reaction has been carried out by adding the amine t o a dioxane solution of the polymer. hniination m-ithout the presence of an organic solvent or swelling agent tciided t o givc a cross-linked aminated product, perhaps because of the formation of ether cross linke as shown in the folloa ing equation:
16.71
t
1 13.69
10
-
5
75G -CATALYST
10.47
t
0
I
ADDfTfON
I
0
1
100
,
200
I
1
-1
R ~ C € L C I
300
-+ T I ~ C H ~ O C H ,
€120
MINUTES
\Then amination is carried out with a dioxane solution of chloromethylated polystyrene there occurs coinplete precipitation a t partial conversion. Water is then added and amination is completed under homogeneous conditions. The solubility
I-
I
7 -
I
5
I-
90 GI
4
-
20
NCM
t
51 0
I
I
25
50
I 75
3
% CONVERSION
Figure 4. Chloroinethylatioii of Poly-a-methylstyrene Top. Chlorine content of samples shown Bottom. Polymer of viscosity grade 13.5 (measured at 25' C.) 7 9% concentration i n chloromethyl ether, catalyst ratio 0.4, temperature 30° C. was chloromethylated i n
Tests with laboratory aniinals have shown the liquid chloromethyl ether to be capable of causing very severe burns of the skin and eyes. Tests have also shown that vapors of this material are painful to the eyes, nose, and throat and are capable of causing serious injury to the lungs. The experience of human wbjects apparently confirms this finding. Although the vapors are quite painful, it is possible to breathe them in excessive amounts. The injury in the lungs may be slow to develop and may lead t o pneumonia. Until the quantitative toxicity is definpd more precisely it appears advisable to consider the vapor hazard coniparable to that presented by phosgene and the hazard of local injury from contact with liquid comparable t o that presented by strong acid or caustic. It i p advisable not t o employ pcrsons
10
2
I
0
0
0
50
100
% CONVERSION
Figure 5 . Calculated Relationship hetween Degree of Chloromethylation and Chlorine Content, Chloride Ion Content, Nitrogen Content, and Basic Groups i n Reaction Product Per cent conversion is &\en as mole per ccnt or per cent of benzene ring substituted Chlorine content (C1) of chloromethslated polymer i n weight per
--___ Chloride ion 0'l"t
content (Cl-) in reaction nroduct with trimethvlamine i n weight per rent Nitrogen content (N)of reaction product with trimethylamine in weight per cent &lillimoles per gram ( R I ) , dry wcight, of hasic groups in reaction product with trimethj lamine
November 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
turbidity. Nevertheless the dry polymer will not dissolve in water containing less than 20% acetone by volume. Such behavior has been reported by Signer and Demagistri (6) with reference to partially sulfonated polystyrene. This water-insoluble grade can be regarded as a n anion exchange resin which can be fabricated in film or fiber form, The film is colorless but fragile when dry unless a plasticizer is used. The swellability by water increases with conversion and this explains the maximum shown in the curve of Figure 6, which gives ionexchange capacity in terms of wet volume. For comparison the milligrams of chloride ion per gram of dry resin and the nitrogen percentage are shown for the trimethylamine derivative, The ion exchange capacity in terms of wet volume is lower when measured for the hydroxide form because the resin swells more in the hydroxide form. For example, the trimethylamine derivative of 33.5% chloromethylated polystyrene swelled two and o n e
X
-
12
50
0
2689
A-25 CC. 8-25 C.C. C-250 C.C.
II
100
% CONVERSION
Figure 6. Effect of Degree of Chloromethylation on Capacity and on Nitrogen Content of Reaction Product with Trimethylamine Per cent conversion given as mole per cent or per cent of benzene rings substituted C. Millimoles of basic group per unit volume (ml.) of waterswelled resin M . Millimoles of basic group per gram of dry resin N. Nitrogen content i n weight per cent
io 9
8
properties of the completely aminated product depend on the degree of chloromethylation. (The relationship of percentage conversion and percentage chlorine is given in Figure 5 . ) If 20 to 30% of the benzene rings have been chloromethylated, then the product of amination, for example with trimethylamine, is soluble in aqueous acetone but not in water or acetone. With over 40% of the benzene rings chloromethylated there is obtained from the soluble chloromethylated polymer an aminated product that is soluble in water. An interesting behavior shown by the aminated resin made from 30% chloromethylated polystyrene is that it cannot be precipitated with water nor does dilution of the aqueous acetone solution with water produce a very noticeable
:u
4
-2
0
4
I
I
I
8
I2
16
CC
N/I
I 20
,I 24
I 26
HCI
Figure 7. Titration of Anionic Polyelectrolyte Made with Amination of Chloromethylated Polystyrene by Dimethylethanolamine
7
6
1c.c.1.0 N
HCI
I
5
0 Figure 8.
2
8 10 Titration of Samples of Table V 4
6
half times in the chloride form and ten times in the hydroxide form. This fact in itself is proof of the quaternary nature of the product, because weakly basic polyelectrolytes are less hydrophilic in the free base than in salt form. Regeneration of waterinsoluble strongly basic polyelectrolyte with caustic is carried out as with conventional ion exchange resin except that as the excess caustic is washed away the resin becomes highly swelled. The titration curve of Figure 7 is characteristic of a quaternary ammonium base. Another way of regenerating these resins is to force the solution of the salt form through a bed of commercial, strongly basic anion exchange resin that has been converted to the hydroxide form. This is a continuous countercurrent exchange which is favored by the fact that the selectivity of chloride ion versus hydroxide ion is greater in the cross-linked resin of the same type (6). The samples of Table V are successive portions of effluent obtained by such a regeneration. The titration curves (Figure 8) are of these samples. It will be noted from Table V that the viscosity of the hydroxide form is more than twice that of the chloride form obtained from it by neutralization with acid. Other amines have been used for amination as shown in Table VI.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2690
TABLE 1'.
REGENERATION O F SOLUBLE POLYELECTROLYTE IONEXCHANGE RESIK
(Polystyrene,
BY
33.5 cp.; chloromethylation to 64 mole % conversiona;
amination with trimethylamine 14.79% C1-; regeneration 96% complete t o hidroxide form) Viscosity of Effluent, Cp. Concn., G./100 ml. Chloride form Hydroxide form .4 22.4 0.957 46.5 B 43.;145 3.65 C 0,652 8.50 .. a Sample 10 of Figure 1.
TABLE VI. AMIKATIOX OF CHLOROMETHYLATED POLYSTYRENE^ WITH SEVERAL TERTI.4RY AMINES TO GIVE WATER-SOLUBLE PRODUCTS Amines Nitrogen, ?'To Viscosity, Cp.b Trimethylamine 4.0 23.3 Benzyldimethylemine 3.85 7.9c Methylmor holine 5.01 22 Dimeth yletganolarnine 5.28 14.8 Triethylamine 2.16 9.ZC Containing 17.17% C1 and made f r o m polystyrene with a viscosity of 37 cp. in toluene solution. b 0.5% in water, 25' C. Slight residue on dissolving in water.
Traces of amine gave an odor to the product unless considerable attention was paid to eliminating it. One method used was the addition of hydrogen peroxide. The color of the aminated polymer was tan, although color was not noticeable in coatings made of the material. The viscosity concentration behavior of anionic strong polyelectrolytes described in this report is similar to that of those described by Fuoss and Strauss ( 2 ) and is shown in Figures 0, I O . and 11. 3.00 1
I
Vol. 44, No. 11
used, for example as an invisible ink for writing on glass or paper, the dry coating could be dyed with ordinary bluing, and the dyeing was resistant t o boiling with a common detergent. The m-ater-soluble grade of aminated chloromethylated polystyrene was used for the test, yet there was no evidence of diffusion of the resin from the original location. Other dyeinga were made, for example, with chromate and with ferricyanide solutions. The dye of the formula following was effectively mordanted in the case in which the extra sulfonic group was present but not in the case in which it was absent. I n general the higher viscosity of the polyelectrolyte the bettrr CsH- CH2C6H4S03for the applications in-11 volving the formation of insoluble salts. The polyelectrolytes herein described acted also as coagulants for polymer latices made with anRlordanted ionic emulsifiers. In the case of a styrenebutadiene latex (X446) made with a rosin acid soap and having 46.9% solids, the addition of chloride form of the trimethylamine derivative caused complete coagulation when CeHj C CeH4SCHzCeH4SOaNa 0.74 millimole (based on chloride analyses) Kot mordanted was added to 10 ml. of latex. The sample of quaternary ammonium polyelectrolyte used was that described in Table V as solution B. EXPERIMENTAL
CmoRohmrHYL ETHER. Chloromethyl ether is somewhat difficult to purify. While methylal is an objectionable impurity in regard to chloromethplation, hydrogen chloride is beneficial. For example, two chloromethylation experiments were made using
t I
20.0 I
oc C25 0 5
2
I
GRAMS
DcR
C
1OOcc
Figure 9. Viscosity of Water Solution of Pyridine Derivative of Chloromethylated Polystyrene
Applicat,ion ~ - ~ has r i i been of a cursory nature but several possibilities have been considered. Amination with ammonia or amines other than tertiary amines produces cross linking. Some adhesive teste were made by adding to a low viscosity chloromethylated polystyrene a plasticizer and a curing agent (ethanolamine). Film and filaments of high viscosity chloromethylated polymers were cured with diethylenetriamine and rendered solvent resistant. They were, however, fragile. The soluble aminated products were tested as precipitants and found t o function, for example, in coagulating a GR-S latex having an anionic stabilizer. In another test molasses was partially decolorized, the resin forming a filterable precipitate with some of the colored components. An interesting test F a s that of dye mordenting. If a solution of the polyelectrolytc was
,125
1
5.0 0
I
I
I
,250 0.500
1.000
2.000
PER 1 0 0 M L . Figure 10. Viscosity-Concentration Dependence GRAMS
Chloride form of resin used for experiment of Table V
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
November 1952
given polystyrene and two different samples of chloromethyl ether. I n the first experiment a purified sample was used: boiling point, 57" t o 58" C.; n v , 1.3908; dqs, 1.0533. In the second experiment a sample conhining excess hydrogen chloride was used: nv, 1.3942; dZ5, 1.0620. With a ratio of reactants of 10 grams of polystyrene, 95 ml. of chloromethyl ether, and 5 grams of zinc chloride, gelation occurred in 7 hours in the first experiment and 5 minutes in the second. A solution of 218. CHLOROMETHYLATION OF POLYSTYRENE. grams of polystyrene 33.5 cp.) in 2910 grams of chloromethyl ether (di5 1.07) was treated portionwise (half quantities) with a total of 77 grams of zinc chloride (anhydrous). The zinc chloride dissolved within 2 minutes with stirring, and the heat of solution produced a 3" C. rise in temperature. The temperature was brought back to 25' C., and the viscosity increased at 25" C. according to the curve of Figure 6. Samples were taken at t h e times indicated in the figure. The catalyst was added in two portions as indicated. No evidence of incipient gelation was observed. The samples were 50-ml. portions except for sample 10 which was the remainder. The samples were short-stopped with 10 ml. of aqueous dioxane and refrigerated prior to precipitation in methanol. The polymer was air dried and the yields are given below. The chlorine content is given in Figure 2; the zinc content was less than 0.006~0. Sample 1 2 4 5 6
7 8
9
269 1
amine. I n the case of the dimethylethanolamine the initial stage of amination was carried out in the absence of water. The products obtained with both amines were soluble in aqueous acetone (greater than 20% acetone) but not in acetone or water. The viscosity of the chloride form of the product made with dimethylethanolamine was measured in solution of equal volumes of water and acetone and found to be 9.64 cp. a t a concentration of 0.5 gram per 100 ml. and 59.3 cp. at a concentration of 10.0 grams per 100 ml. The aminated polymer was dried a t 50" C. in vacuum.
0.15
0.10
Polymer Yield, G. 3.8 4.2 4.26 4.3 4.5 4.6 4.6 4.6
Two further examples are cited in which a Pfaudler kettle was used. Polystyrene (25 pounds, viscosity of 10% solution in toluene 37 cp.) was dissolved in chloromethyl ether (30 gallons, d;5 1.08), producing an 8.5%solution. Zinc chloride (4 pounds) was dissolved in the stirred solution, and the reaction was allowed to proceed a t 40" to 50" C. for 9 hours. The reaction was then stopped by the addition of a solution of water (1 gallon) in dioxane (3 gallons). A portion of the polymer was precipitated in alcohol and found to contain 17.17% chlorine. I n all cases there was no opportunity for loss of yield; the problem was rather one of solvent recovery and drying the polymer. The samples were dried for analysis a t room temperature. A commercial molding grade of polystyrene was chloromethylated at 8.5% concentration in chloromethyl ether to 9.89% chlorine content. The quantities used were 25 pounds of polystyrene, 30 gallons of chloromethyl ether, and 4 pounds of zinc chloride. The reaction temperature was 23' C. for 11 hours and 48' C. for 8 hours. The viscosity of a 10% by weight solution of the chloromethylated polymer in toluene was found to be 56.6 cp. at 25" C. AMINATIONOF CHLOROMETHYLATED POLYSTYRENE. Chloromethylated polystyrene samples were immediately dissolved in dioxane after precipitation with methanol, and an excess of aqueous trimethylamine (25%) was added. The proportion of water t o dioxane was such that the polymer was soluble initially but precipitated during amination. Water was then added to redissolve the polymer and sufficient time (overnight) given for complete amination at room temperature. From sample 10 of the chloromethylation described first an aminated product was obtained that was soluble in water. The following data were obtained on this sample: nitrogen found, 5.61%; ionic chlorine found, 14.79%; and total chlorine found, 14.50%. Amination with tertiary amines of the polymer produced as described in the second example gave water-soluble products as described in Table VI. The chloromethylated polymer described as the third example was aminated with trimethylamine and with dimethylethanol-
0.05
0
0.5
I .o
Figure 11. Data of Figure 10 Plotted as in (2)
By the addition of silver nitrate i t was found to contain 1.47 meq. per gram of chloride ion. Most of the silver nitrate reacted at once. The last quarter of the quantity required about 10 minutes for complete reaction. The chloride form of the resin swelled 250% in water. The trimethylamine derivative was prepared also and found t o contain 1.78 meq. of chloride ion per gram. REQENERATION. It was difficult to convert the aqueous acetone, soluble quaternary chloride to the hydroxide form because, while swelling was relatively low prior t o and during treatment with aqueous caustic, i t became very high during washing of the hydroxide form. This made it difficult to wash out all of the excess caustic. Excess caustic and column operation are requisites for relatively complete conversion of a strong electrolyte resin to the hydroxide form, A 100-gram portion of the trimethylamine derivative just described was placed in a column and 1 gallon of 10% caustic passed through the resin bed over the period of an hour. Upon washing the resin swelled tenfold. A one-tenth portion of the washed resin was neutralized by 14 ml. of 1.0N acid. CHLOROMETHYLATION OF POLY-a-METHYLSTYRENE. POly-ffmethylstyrene (453 grams, viscosity of 10% solution in toluene 18.6 cp.) was dissolved in chloromethyl ether (1835 grams) and zinc chloride (30 grams) was added. After agitation for 61/2 hours, during which time the solution had become warm, the polymer was precipitated in alcohol (4 gallons). Even after air drying overnight the white powdery polymer amounted in weight t o slightly greater than the theoretical yield calculated from the chlorine content, 4.78%. The viscosity of a 10% solution in dioxane was 61.04 cp. CHLOROMETHYLATION AND AMINATION OF POLY-CY-METHYLSTYRENE. I n 3420 gmms of chloromethyl ether were dissolved 250 grams of poly-a-methylstyrene having a viscosity of 13.5
INDUSTRIAL AND ENGINEERING CHEMISTRY
2692
cp. measured in 10% toluene solution, and to the stirred solution was added 100 grams of anhydrous zinc chloride. The temperature and viscosity were checked, the latter with an Ostwald viscosimeter in a water bath a t 25" C. At the indicated point the reaction was short-stopped by the addition of a solution of 25 ml. of water in 75 ml. of dioxane. The polymer was precipitated in 4 gallons of alcohol by means of a Karing Blendor. After air drying overnight the white powdery product weighed 325
70
c
60
I-
z
w
0
LT
w
50
0, W 0
z a
40
I-
tH
30
(0
Z
4
LT I-
20
10
0 WAVELENGTH
IN M I L L I M I C R O N S
Figure 12. Decolorization of >lolasses with Soluble
Dowex 1 as Precipitant A . Untreated
B . Treated
grams. .4 small sample \vas removed for analysis (the chlorine content was found to be 16.9%) and the remainder dissolved in 1150 ml. of dioxane. To 600 grams of the solution ("6 aliquot) wa9 added 250 ml. of aqueous trimethylamine solution (257,) After agitating overnight the mixture was treated with 250 ml. of water and agitated overnight again. It was then dried dovcn and found to be water soluble. PREPARATION OF SAMPLE OF FIGURE 7 . The chloromethylation was conducted with aluminum chloride as a catalyst. The catalyst was used in the amount of 7.5 to 1430 grams of an 11.77, solution of polystyrene (commercial molding grade) in chloromethyl ether. The reaction time v a s 18 hours, and the precipitated polymer contained 4.9% chlorine. Amination was conducted a t room temperature with dimethylethanolamine in the ratio of 100 ml. of 54% aqueous %mine,250 ml. of dioxane, and 40 grams of chloromethylated polymer. After agitating foi 2 days there were added 150 ml. of mater to dissolve the po1ymc.r. The solution was dried in a vacuum oven a t 50" C. for 4 hours. The polymer was then placed in a column 2 inches in diameter, and a gallon of 10% caustic was passed through it during a halfhour period. A 250-ml. volume of the resin was then washed to negligible conductivity and titrated ith 1 hydrochloric arid. The resin occupied several times the volume when swelled with water as it did when dry. The titrated portion was evaporated to a 25-gram residue. PREPARATION OF SAXPLE OF FIGCRE 9. Polystyrene (viscosity grade 87) was chloromethylated to 14.5% chlorine. The quantities used were 200 grams of polystyrene, 2 liters of chloromethvl ether (ng 1.3958, d g 1.0525), and 100 grams of zinc chloride.
Vol. 44, No. 11
The time was 55 minutes. The yield (26T grams) was calculated from that obtained by drying a sample. The product was dissolved in dioxane and treated a-ith drv pyridine. On agitation for 15 hours a precipitate formed as a white coating on the walls of the vessel. This precipitate \vas water soluble and a water solution of it was dried to a clear film. Analysis showed it to contain 72.75% carbon, 6.85% hydrogen, and 1.93% nitrogen, CHLOROMETHYLATION WITH DILTER'T. I n dry tetrachloroethylene (1 liter) were dissolved polystyrene (710% 33.5 cp., 80 grams) and chloromethyl ether (64 grams). Stannic chloride (50 ml.) was added as a catalyst and the viscosity of the solution slowly increased from 24.4 to 26.5 ep. over a 4-hour period at 25" C. Gelation occurred within the next hour, and the crosslinked polymer that precipitated rq ab found to contain 8.5% chlorine. In a similar test zinc chloride (50 grams) instead of stannic chloride was added as the catalyst. The zinc chloride remained largely undissolved but the solution became red. After a week a t room temperature a sample of the polymer, still uncross-linked, was precipitated and found to contain 4.2% chlorine. APPLICATION TESTS. A preliminary test was made of the adheive properties of low viscosity chloromethylated polystyrene. Polystyrene of low viscosity (10% solution in toluene 2 cp.) mas chloromethylated to 13.3% chlorine content. A viscous composition of 7 parts of the product and 2 parts of dioxane was prepared. Ethanolamine was added as a curing agent in the amount of 1 to 5 ml. of the viscous composition, and the resulting solution was applied to a 1-square-inch surface of birch pi\-wood. After clamping overnight at 50% humidity the shear strength was determined a t a tear rate of 3 inches per minute and found to be 700 pounds per square inch. The wood itself parted at 1000 pounds per square inch. A film ims cast of a dioxane solution of chloromethylated polystyrene containing 9.9 7, chlorine and made from polystyrene of a commereinl molding grade. When drv it was immersed in diethylenetriamine overnight A4fterthis treatment it was resistant both to chlorinated solvents and water; however, it was of a fragile nature. A solution (5%) of the trimethylamine derivative made from chloromethylated polystyrene of 9.89% chlorine and 56.6 cp. viscosity (measured a t 10% concentration in toluene) was prepared in aqueous acetone (3 volumes of water to 1 volume of acetone). This solution was used as an invisible ink. It was applied with an ordinary pen to paper or cotton cloth and allowed to dry The paper or cloth wa? then immersed in a solution of Indigotinesulfonic acid (bluing) and rinsed in water. The writing appeared as a mordanted blue dye, and the bluing washed out of the rest of the material leaving the writing sharply defined. I n similar fashion a yellon- dyeing n a s produced with sodium dichromate and a grayish-brown dveing v1 ith sodium ferricyanide. A number of dyes were tried; those having an excess of sulfonic acid groups over the imino or amino groups were mordanted. Thus Light Green S.F. was more satisfactory than Guinea Green B and Brilliant Green. The dyes were used in 0.1% aqueous solution. Tests were made with GR-9 latices 5446 and X633, having ah stabilizers a rosin acid and a fatty acid soap, respectively. To 10 ml. of each latex were added v i t h stirring 5 ml. of solution I3 of Table V (chloride form). Complete coagulation occurred with X446 and a voluminous gummy precipitate formed. I n X633 small gel particles formed and precipitation was approximately half complete. A further effect of the soluble aminated material is that of precipitating colored acids present in molasses. A partial decolorization is achieved as shown in Figure 12. A solution of 10 grams of molasses in 40 ml. of water was divided into half portions. To one half was added 1.5 grams of a 7% solution of the trimethylamine derivative made from chloromethylated poly-a-methylstyrene containing ll.13yo chlorine Thp floc*-
November 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
culent precipitate was filtered and the light transmission of the two solutions compared. ACKNOWLEDGMENT
The sample of styrene-isobutylene copolymer was supplied through the courtesy of R. G. Newberg, Chemical ~ i ~ i Esso New Products Laboratory, Linden, N. J. LITERATURE CITED
(1) Dow Chemical Go., Brit. Patent applic. 28,871 and 28,876-8 (1949).
2693
(2) FUOSS, R.M., and Straws, U.P., Ann. N . Y . Acid Sci., 51, 836 (1949). (3) Hawdon, A. R.H., Marmio, N. D., Powell, G. R., and Thomas, S., paper presented at Ion Exchange Symposium, A.1.Ch.E. Meeting, Pittsburgh, Pa., April 1951. (4) McBurney, C. H., U. S. Patent 2,591,573 (April 1, 1952). ~ (5)i Skner, ~ ~ R., , and Demagistri, A., J. c h k . PhW., 47, 704 (1950). (6) Wheaton, R.,and Bauman, W., IND.ENG.Crrmf, 43, 1088 (1951). RECEIVED for review September 13, 1951. ACCEPTED August 19, 1952. Presented before the Division of Paint, Varnish, and Plastics Chemistry at the 121st meeting of the AMERICAN CHEMICAL SOCIETY, Milwaukee, Wis.. Maroh 30-April 3. 1952.
Fractionation of Cellulose Acetate A. J. ROSENTHAL AND B. B. WHITE Central Research and Development Department, Celanese Corp. of America, Summit, N . J .
c
ELLULOSE acetate is a polymer containing molecules of cal portions of a cellulose acetate in acetone solution by succesvarying chain length and chemical composition distribusive additions of n-heptane in one case and water in the other. tions. The distributions depend on the source of the cellulosic I n both cases the fractions varied in both acetyl value and visraw material as well as on the esterification and hydrolysis techcosity. When n-heptane was used as precipitant, the fraction niques employed. Because acetate yarn properties may be of highest viscosity had lowest acetyl value, whereas when water dependent on the distributions of both molecular weights and was used as precipitant, the fraction of highest viscosity had acetyl values, it is important that methods be available for their highest acetyl value. determination. DUAL DEPENDENCE OF SOLUBILITY ON The methods which have been used for fractionation of polyACETYL VALUE AND VISCOSITY meric substances have been reviewed by Cragg and Hammerschlag (2). For the most part, fractionations have been based on Schematically, a heterogeneous cellulose acetate with its spread the differential solubilities of the components of a polymer in of acetyl value and intrinsic viscosity can be represented by a solvent-precipitant mixtures. circle in Figure la. The actual distribution within the limits of The choice of solvent-precipitant system is worthy of emphasis the circle can be represented by intensity of shading. The shading is implied, but not included, in the subsequent diagrams for from several standpoints, Morey and Tamblyn (7)obtained variations in sensitivity to a molecular weight difference in two the sake of clarity. cellulose acetate fractions when using various combinations of If the solubility of the cellulose acetate in a solvent-precipitant mixture depends solely on its intrinsic viscosity, one would expect solvents and precipitants. Howlett and Urquhart (6) examined a number of solvent-precipifractions 1, 2, 3, and 4 to tant systems with a view to precipitate successively as extending the range of per shown in Figure lb. These cent precipitant over which fractions would be of concellulose acetate fractions stant average acetyl value could be obtained. Clement 3&; and would decrease remand Rivibre (1) characterlarly in intrinsic viscosity. ised cellulose acetate by Similarly, if the solventINTRINSIC precipitant combination fractional extraction with VISCOSITY could be chosen such that aqueous ethyl alcohol and found that the fractions the solubility of the cellulose varied in both viscosity and acetate depends solely on acetyl value. On the other its acetyl value, then frachand, Sookne, Rutherford, A.V. 4 3 2 I tions related as shown A.V.I{@, A.t[@' Mark, and Harris (8) fracschematically in Figure IC tionally precipitated cellu(b) (C) (d I would be expected. These lose acetate from an acetone fractions would have a consolution with ethyl alcohol I.v. I .v. I .v. stant average intrinsic vist o yield fractions of varying cosity and would differ prcviscosity with only slight gressively in acetyl value. acetyl value variations. Actually, the solubility of The importance of the A.V.1 a cellulose acetate molecule A .V. dual dependence of celluin a solvent-precipitant mixlose acetate solubility on ture is found in most cases (e) acetyl value and chain t o depend on both its inlength became apparent I .v. I.V. I.V. trinsic viscosity and its when McGoury and White Figure 1. Dual Dependence of Solubility of Cellulose acetyl value. Thus, in an (6) fractionated two identiAcetate on Acetyl Value and Intrinsic Viscosity acetone-water mixture low
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