June, 1928
I S D G S T R I d L =1SD ESGI,\-EERISG' CHEMISTRY
597
Resins from Chlorinated Cymene',' P. H. Groggins BL-REAUOF CHEMISTRY A N D SOILS, WASHINGTOND. C.
24@244" C.) and unchanged H E S c h l o r i n e is A new type of chlorinated resins has been prepared p-cymene were also present. from p-cymene by chlorination in the presence of a b u b b l e d i n t o pNo reference in the literature metal catalyst. Varieties of the resin can be obtained cymene (l-methylwas found r e g a r d i n g t h e by previously incorporating other materials with 4-isopropylbenzene) a t tempossibilities of treating chlop-cymene. The resins are insoluble in acids, alkali, peratures above 100" C., subrinated chain derivatives of and alcohol. They cannot be brought to the infusible stitution takes place essenp - c y m e n e with a condenstially in the side chains. If state by heat and pressure treatment. The intering catalyst, or chlorinating mediate compounds are lethal to small animal and metallic aluminum, iron, or it a t higher temperatures in zinc is present during the vegetable organisms. the presence of a metal which chlorination the cymyl chlocould be activated by the rides thus formed condense in a manner similar to the Friedel-Crafts reaction. As the re- liberated hydrogen chloride. action proceeds dark resins are formed. Since chlorination Preliminary Experiments takes place simultaneously in the p-cymene ring as well as As a preliminary experiment, chlorine was led into a flask in its three methyl groups, no definite information can be given regarding the exact constitution of the intermediate containing p-cymene a t 50" C., using iron rods as a catalyst. products. The first steps in the condensation may, however, Hydrochloric acid vapors were liberated during the reaction, and in a short time the contents of the flask darkened. The be most simply represented as follows: chlorination was stopped when the density of the liquid was 1.035 at 20" C. On analysis the liquid was found to conCHgC1 tain 24.07 per cent of chlorine. When some of this material CHI was treated with aluminum chloride and heated, a black 2 4c1 + 2 resin was immediately formed. Similar results were obtained when naphthalene, o-dichlorobenzene, chloroform, or pcresol was added to the chlorinated p-cymene and subseH . C/CH3 quently heated in the presence of aluminum chloride. 'CHs The resins produced in these experiments are insoluble The formation of' resins by this reaction has also been in hot and cold acids, alkali, and boiling ethyl alcohol. They accomplished with mixtures of p-cymene and other soluble are readily taken up with warm p-cymene, o-dichlorobenzene, or miscible aliphatic and aromatic compounds. Under such turpentine, carbon disulfide, and to a lesser degree with peconditions the process consists in the progressive condensa- troleum distillates. They are not brought to an infusible tion of cymyl chloride, with the other constituents of the state by heat and pressure treatment. reaction mass, to form more complex reaction products. Constitution of Chlorinated p-Cymene The foregoing equation is subject to modification, since the resins prepared contained from 10 to 30 per cent chlorine. From analogys it was expected that p-cymene would reThis fact makes it evident that either some substitution act similarly to toluene and that a high chlorinating temperatakes place in the cymene ring or the resinous state is reached ture would be conducive to chain substitution, with the before all the side-chain chlorine has been liberated. The formation of the highly reactive cymyl chloride. Experidata presented below will show that both factors are respon- ment's had also shown t'hat, under conditions otherwise idensible for this chlorine content, and that the contribution tical, no resinification was effected a t temperatures under of each is governed by the temperature of chlorination. 25" C.; whereas such action took place readily a t 100" C. The mechanism of the reaction depends on the presence (Table 111) This, however, would not preclude the possiof metallic chlorides which are formed by the action of the bility of chain substitution in the former, for any cymyl liberated hydrogen chloride on the particular metal used. chloride present would not react a t the low temperature The presence of traces of water has been found beneficial of chlorination. in starting the reaction, since dry hydrogen chloride does Five samples of chlorinated p-cymene, prepared as described not readily combine with the metal to form the metallic below, mere selected for analysis t o determine the position chloride which is the true active catalyst. of the chlorine. These were washed with dilute sodium Lubs and Young3 found that when the chlorination of carbonate and then with water to insure the absence of any p-cymene was carried out under 35" C. in the presence of inorganic halide. They were dried, first a t 110" C. and iron filings the substitution was effected in the ortho position. then over calcium chloride, and gave no test for chlorine They obtained by fractionating a t reduced pressures a com- when tested with 0.1 N silver nitrate. pound which boils between 215" and 218" C. When the The samples investigated were products obtained by: chlorination is conducted a t a temperature between 10" and (1) Low-temperature chlorination, in which 4000 grams of 12" C. in the presence of iodine, Hintikka4 ascertained that p-cymene were chlorinated a t 20' C. in the presence of silica gel the product was essentially 2-chlorocymene (b. p. 213-216" until 690 grams of chlorine were absorbed. C.), and that considerable amounts of dichlorocymene (b. p. (2) High-temperature chlorination, in which 3000 grams of
(i+
Received February 6, 1928. Contribution 142 from the Color and Farm Waste Division, Bureau of Chemistry and Soils. Patents applied for. 8 J. IND.ENG. CHEM., 11, 1130 (1919). 4 Ann. acad. s c i . Fennicae, 19A, S o . 10, 6 pp. (1923). 1
p-cymene were chlorinated a t 100" C. until 808 grams of chlorine were absorbed. (3) High-temperature chlorination, in which 3000 grams of 5
Jackson and Fields, Am. Chem. J . , 2, 1 (1880).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
598
#-cymene were chlorinated at 140 O C. until 2550 grams of chlorine were absorbed. (4) Low-temperature chlorination, in which samples were chlorinated at 20" C. in the presence of aluminum. (See Table 111, series C and D.) (5). Low-temperature chlorination, in which sample was chlorinated at 35" C., and then partially distilled to remove any free p-cymene.
The analytical data show conclusively that the amount of side-chain substitution increases with the temperature of chlorination. The results also show that, under ordinary conditions, isomers will form the substitution taking place in the cymene ring as well as in the chains. No attempt was made to obtain either the pure chlorocymene or cymyl chloride as the mixture of both derivatives was considered a desirable characteristic in the final resins. It was important for the purposes of this investigation only to know that the position of the substituted chlorine could be regulated by properly controlling the temperature of chlorination. Table I-Constitution of Chlorinated p - C y m e n e CHLORINATION TOTAL SIDE-CHAIN
SAMPLE
TEMPERATURE
c.
CHLORINE~ Per cent 17.63 27-60 .46.95 40.00
CHLORINEb
P e r cent 3.28 18.95 36.23 20 11.81 35 4.44 Total chlorine determined by sodium peroxide method in a Parr
20 100
bomb. b Side-chain chlorine determined by hydrolysis with 10 per cent sodium carbonate solution.
Effect of Metal Catalyst
Chlorine was bubbled into three flasks, each containing 2000 grams of p-cymene. Aluminum rods were put into one flask, iron rods into another, and one was kept as a control. The results are recorded in Table 11. Table 11-Effect of Catalyst i n Producing R e s i n s (Temperature, 50-65' C.; time, 22 hours)
CATALYST Control Iron rods Aluminum rods
SPECIFIC
INCRGASE
CHLORINE
IN WEIGHT
ABSORBED Per CC4f
Grams ~. 1035 1070 880
34.10 34.s5 30.55
GRAVITY AT 200 c.
1.150 1.155 1,205
Vol. 20, No. 6
Table 111-Loss of Catalyst d u r i n g Chlorination CHLORINATION CHLORINE$ ALUMINUMALUMINUM CONDITION os
SERIES TEMP. ABSORBED TAKEN CONSUMEDREACTION MASS C. Grams Grams CmmrA" 100 64 11.0 0.2 Black sirup 50 73 10.0 Trace Dark solution 20 73 11.0 Trace Clear solution
__
B"
100 50 20
C
100 50 20
D
100 50 20
81 73 106
26.0 24.0 29.0
0.1
Black sirup Dark solution Clear solution
0.8 0.2 0.1
Tarry Black sirup Clear solution
Trace None
AFTER CHLORINATION ~.
60 81
8
10.8 10.0 11.0
6 44 72
25.9 24.0 29.0
Tarry Black sirup Clear solution a Two hundred grams of $-cymene were used in each test; series C and D are continuations of these runs.
0.6 0.2 0.1
Table IV-Loss of Catalyst in Preparation of Resins (Temperature between llOo and 130' C.) ALUMINUM AFTER
ALUMINUM
CHLORINE
CHLORINBALUMINUM CHLORIN-AFTER ALUMINUM IN FINAL RESIN ABSORBEDAT START ATION HEATING LOST RESIN Grams Grams Grams Grams Grams P e r cent
1 2 3
754 620 687
36 38 37
31 33 33
25 25 28
11 13 9
20.35 20.12 28.82
The catalyst was weighed a t the close of the chlorination process and finally at 160" C., when it was removed from the resin during the heating process. The continued loss of catalyst during the heating period shows that the condensation reaction continues after chlorination. The lower aluminum loss in the preparation of the o-dichlorobenzene resin is attributed to the fact that its soft resin is rather gummy and cannot be heated as long as the other two, Chlorination of p-Cymene Mixtures
When aliphatic or aromatic compounds are chlorinated with p-cymene, the rate of polymerization is retarded, unless such added components possess side chains. The incorporation of such products with the p-cymene is made in order to produce resins with speciiic characteristics. The addition of o-dichlorobenzene produces a resin with a higher chlorine content, which is believed to give added resistance to weather and water in coating compositions. The inclusion of naphthalene produces a harder resin which is not readily attacked by petroleum distillates. Multiple chlorination finally makes possible the utilization of other products which have little commercial value. It is therefore apparent that this method of producing resins can be of farreaching importance in the utilization of waste products.
It is interesting to note that, despite the lower chlorine absorption, the most viscous solution was produced in the flask containing the aluminum rods. During the course of the reaction it was observed that hydrogen chloride fumes were given off and that some of the acid condensed on the walls of the flasks. The control remained clear throughout the entire run. The aluminum rods were cemented together by the resins formed, and when a glass rod was moProperties and Application mentarily immersed in the solution it was covered with a The resins are insoluble in acids, alkali, and ethyl alcohol, heavy glossy coat of soft black resin. the first and are not affected by hot 15 per cent sodium chloride LOSS OF CATALYST DURING REACTION-During stages of the process there is practically no loss of metal, solution. The resins produced from low-temperature chlorinregardless of the temperature of chlorination. As the re- ations, in which ring-chlorine substitution is the primary action proceeds the metal becomes etched, and at temperatures action, are more stable than those which contain a preponabove 50" C. (Table 111) the loss becomes appreciable. It derance of side-chain chlorine. The cymyl chlorides formed is significant to note that the amount of resinification is as intermediate products have toxic properties and are known proportional to the aluminum losses. By comparing A to be lethal to small animal and vegetable organisms. Their and B with C and D one can also observe that increase in vapors are distinctly irritating to the mucous membranes weight, owing to chlorination a t 100' C., takes place up to a of the eyes, nose, and throat. By incorporating the proper certain point, approximately two atoms, after which prac- ingredients with p-cymene during chlorination it is possible tically no more chlorine is retained as it immediately enters to give specific properties to the final resin. It appears that a market for coating compositions derived into the condensation reaction and is liberated as hydrofrom such resins could be used to advantage in marine work chloric acid. The loss of catalyst sustained in the preparation of a set and chemical plants. The resin solutions may be advantaof three resins is given in Table IV. In these tests the follow- geously used in the treatment of railroad ties and telephone ing ingredients were used: (1) 2000 grams p-cymene, (2) poles. Stains, varnishes, and Iacquers have been prepared 1200 grams p-cymene, and 800 grams naphthalene, (3) 1500 from these resins, using o-dichlorobenzene and p-cymene as a thinner. The utility of such coating compositions has grams p-cymene, and 500 grams of o-dichlorobenzene.
June, 1928
I-VDUSTRIAL AIVD E S G I N E E RIiYG CHEMISTRY
already been reported.6 When incorporated in lacquers it appears that a satisfactory black, pliable coating composition can be prepared without the use of extraneous pigments. Certain modifications of these resins may find use in the 8
Groggins, Ckem. Met. Eng., 34, 291 (1927).
599
electrical industry. A sample submitted to the Bureau of Standards was found by H. C. Curtiss to possess the following factors: dielectric constant, 2.5; power factor, 3.0 per cent; resistivity, l O I 4 ohm centimeters; dielectric strength, 20 kilovolts per millimeter.
Acetone Condensation Resins’ H. A. Gardner and C. A. Knauss THEINSTITUTE OF PAINT
AND V A R N I S H
I
N T H E preparation of cellulose lacquers resins are used to a considerable extent, Some of the resins which manufacturers have desired to apply in this direction, because of alkali resistance or other favorable properties, do not always work well with the type of solvents used for the cellulose compounds. Precipitation and “blushing” have been the main defects. When this investigation was started, it was believed that resins produced from acetone might be found entirely soluble in most lacquer solvents. It has been known for some time that acetone forms solid condensation products with certain types of compounds, and, as acetone is a good solvent for nitrocellulose and miscible with practically all other solvents, it seemed to be a lead in the proper direction. Werner2 in 1904 mentioned acetone resins produced by the condensation of acetone with formaldehyde solution in the presence of alkali; he obtained an orange-colored powder which was soluble in alcohol and acetone. Muller3 and Ellis4 and others have studied similar products, using various alkalies as condensing agents. The work of these investigators seemed to indicate the possibilities of producing materials that could be applied in the direction mentioned above. Their work was not repeated, however, as it seemed more desirable to condense the acetone with some of the higher aldehydes that are becoming available in large quantities. Some of those tried were acetaldehyde, paraldehyde, aldol, and furfural. Preliminary Experiments
The procedure in the preliminary experiments consisted of refluxing a mixture of 58 grams (1 mol) of acetone with 88 grams (1mol) of aldol in the presence of a 10 per cent caustic potash solution for several hours, or until a viscous liquid layer separated from the aqueous layer. The resinous liquid thus produced was then treated with dilute acetic acid to neutrality. The product was then heated to about 150” C. for 30 minutes to drive off occluded water. I n this work paraldehyde did not condense with the acetone. This was to be expected, since paraldehyde does not give the common aldehyde reactions. The products obtained with the other aldehydes, however, were soluble in acetone and toluene, and possessed peculiar aldehydic odors. An equal quantity by weight of these products was then fused with rosin and dissolved in acetone to form 50 per cent solutions. Metal panels were coated with these solutions, and exposed on the testing racks along with panels coated with ester gum and dammar. The color of the products thus obtained from the synthetic resinous materials was considerably darker than dammar, being of deep amber tints. The durability, however, 1 Received March 28. 1928. Presented before the Division of Paint and Varnish Chemistry at the 75th Meeting of the American Chemical Society, St. Louis. Mo., April 16 to 19, 1928. J . Ckem. SOC.( L o n d o n ) , 196, 20 (1904). B n . , 64, 1192 (1921). 4 “Synthetic Resins and Their Plastics,” p. 226.
*
RESEARCH, W A S H I N G T O N , D.
c.
compared favorably in many cases with dammar, although in some instances early checking was observed. Hardened Resin Form
To prevent the formation of gummy products, it was decided to add rosin directly to the reaction mixtures. In order to have the rosin combine with the condensation products, it was necessary to use a weak acid condensing agent in place of the caustic potash solution previously employed. To 1 part of acetone there were added 2 parts by weight of rosin. This mixture was refluxed until the rosin had completely dissolved. The aldehydes were then added in quantity equivalent to 1 mol of aldehyde to 1 mol (58 grams) of acetone present in the acetone-rosin mixture. Hydrochloric acid (0.25 N ) was then added and the mixture refluxed for about 6 hours. The resinous mass produced was washed and neutralized with sodium carbonate, and then heated to drive off the water. The finished products were hard, of dark color, and rather brittle. Furfural and aldol were the aldehydes used in these experiments, as they gave greater promise of success than the others. The one produced from the furfural aldehyde was darker than that produced from aldol. These were dissolved t o a 50 per cent concentration in solvents, coated out upon metal panels, and exposed upon the testing racks on the roof. The type of failure seemed to be early checking, but the durability was fair. Solubility in acetone, toluene, and butyl acetate in practically any ratio was observed. The resin solutions were then combined with nitrocellulose, using as a formula 100 parts of 32-ounce (907 grams) solution of l/Z-second nitrocellulose in butyl acetate as the base. To this were added 60 grams of a 50 per cent solution of the aldehyde resin dissolved in toluene. Five grams of tricresyl phosphate and 40 grams of acetone were also employed. These lacquers were coated out upon panels and exposed. The durability was fairly comparable to that of the resins produced from ester gum and dammar, but the color was considerably darker. Cellulose Resins
An attempt was next made to produce a solid resin containing cellulose compounds. Since aldol and nitrocellulose or cellulose acetate are soluble in acetone, it was believed that a solution of these products could be condensed to obtain a compound which might be of general interest in lacquer work. To 464 grams (8 mols) of acetone, and 254 grams (3 mols) of aldol were added 40 grams of dry nitrocellulose. When the nitrocellulose dissolved, the mixture was slowly refluxed while dry hydrochloric acid gas was passed into the mixture. After refluxing for an hour and a half, 15 grams of rosin were added and heating was continued for about 2 hours. A viscous, reddish yellow, clear solution was formed, which became hard when the excess acetone was evaporated. A lacquer was made with this resin, and exposed for 28
