tensile strength. S o t shown, however, is the fact that surface roughness and sandy feel of the paper were more noticeable in runs 59-1 5 and 59-16, Despite the improved tensile strength shown, it is felt that the better practice is to run the stocks to the paper machine within a very few hours after beating, because the other qualities are so much better and results are more predictable.
Conclusions
Acknowledgment
T h e authors thank the Diamond Ordnance Fuze Laboratories for sponsorship of the project on which this work was done and for permission to publish this work. The many helpful suggestions of Nathan Kaplan of Diamond Ordnance Fuze Laboratories and of C. E. Huckaba and \V. J. Nolan of the Chemical Engineering Department, University of Florida, and the aid of coworkers in this laboratory are hereby acknowledged.
Special-purpose paper can be made using glass microfibers and other inorganic fibers alone or in blends. S e w uses are being found for the paper, but high costs do not permit its use where cellulose paper suffices. The strength of inorganic paper does not approach that of cellulose paper, as shown by the fact that the conventional paper tester had to be modified to obtain readings. However, treatment with various binders. as is being done by some manufacturers, improves the strength. Procedures for the preparation of fibers for papermaking specify the desirable concentrations. length of time required. and beating conditions. The test results show that a laboratory paper machine produces paper with uniform basis weight and thickness. The ability of the paper machine to duplicate results of previous runs and to approach closely the target basis weights has been demonstrated.
literature Cited
(1) Badollet, M. S., Can. Mining M e t . Bull. 44, 237 (April 1960). (2) Chem. Eng. X e w s 3 8 , No. 8, 51, (1960). (3) , , Huckaba, C. E., Geddes, J. C., Jr.. IND.EXG. CHm. 5 2 , 569 (1960). (4) McKinley, M. D.. Bachelor’s high honors thesis, University of Florida. 1959. (5) O’Leary, M. J., Hobbs, R. B., Missimer. J. K., Erving, J. J., Tuppi 37, No. 10: 446 (1954). (6) O’Leary, M. J., Hubbard, D., J . Resfarch .\‘ail. Bur. Standards 5 5 , No. 1, 1 (1955). ( 7 ) O’Leary, M. J., Scribner, B. W., Missimer, J. K., Erving, J. J., Tub62 35. No. 7.289 (1952). (8) Sdhulmeyer, S. W.,‘Ibid.,’39, No. 9, 217.i (1956). (9) Walworth, C. B., Materials in Design Eng. 46, No. 5 , 124 (1957). RECEIVED for review September 28, 1961 ACCEPTED February 26, 1962 Peninsular Florida Section Tech. Meeting, .-lmerican Institute of Chemical Engineers, Daytona Beach, Fla.. May 1960.
CHARACTERIZATION OF AMBERLYST 15 Macroreticular Sulfonic Acid Cation Exchange Resin R O B E R T K U N I N , E R I C H F. M E I T Z N E R , J A M E S A . O L I N E , S A L L I E A. F I S H E R , ‘ A N D N O R M A N FRISCHZ Rohm
Haas Go., Philadelphia, Pa.
A new ion exchange structure entirely different from conventional homogeneous gels and having a rigid macroporous structure similar to those of conventional adsorbents, superimposed on the gel structure, has been developed. These resins have been designated as macroreticular (MR) ion exchangers. Typical i s Amberlyst 1 5, a sulfonic acid type based upon a slyrene-divinylbenzene copolymer. Whereas the specific surface area for conventional resins i s very small (.4L
Present address. Robinette Laboratories, Philadelphia, Pa. Present address, Princeton Chemical Research Corp.. Princeton, N. J. 140
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
cross links and chains of such gels vary considerably, depending upon such factors as electrolyte concentration, nature of solvent, nature of mobile and immobile ions, and temperature. The pore structure of such gels can only be considered as a n apparent molecular-type pore structure and the average porosity of such structures is dependent upon the distances between polymer chains and cross links under any particular set of conditions. The flexibility offered by the styrene-divinylbenzene system for controlling the above type of porosity has been useful during the past decade for many ion exchange applications. How-
ever, several limitations have become apparent. For example, if the degree of cross linking is decreased in order to accommodate larger ionic species, a considerable volume change is encountered during the exchange process and during changes in ionic strength, resulting in poor physical properties and in operational difficulties, particularly in chromatography. I n those systems featuring low degrees of cross linking, the rates of chemical degradation processes are accelerated. Further, the porosity associated with the conventional styrene-divinylbenzene is solely dependent upon the swelling characteristics of the gel structure. Therefore. in nonaqueous, nonpolar systems, these resins have but a negligible pore structure. These deficiencies of conventional ion exchange resins in certain applications have been apparent for several years. This paper describes the characterization of a new ion exchange resin, Amberlyst 15, prepared by a new polymerization technique that yields a cross-linked ion exchange structure entirely different from the conventional homogeneous gels and having a rigid macroporous structure similar to those of conventional adsorbents such as alumina, silica. and the carbons, which is superimposed on the gel structure. I n contrast to the conventional ion exchange resins, this resin has been designated as a macroreticular (MR) ion exchanger. T h e new ion exchange resin structure described in this study is of the sulfonic acid type and is based upon a styrene-diviny lbenzene copolymer. Physical Properties
In order to study adequately the pore properties of this new ion exchange structure, measurenients were made of the surface area by means of the BET method (nitrogen adsorption at -195OC.) (7), of the solvent uptake, and of the pore volume as characterized by the difference between the true density (helium displacement) and apparent density (mercury displacement) of the dry resin. From these measurements, the porosity was calculated by means of the following relationship : p=1-p” PS
where
P
(pore volume)/(pore volume polymer volume) pa = apparent density, grams per cc., by mercury displacement p. = skeletal density, grams per cc., by helium displacement
0
L
C
-
’
d=
4 (1014 P P A 1
-
P)
where
S
= specific surface area in sq. meters per gram of dry
2
= average pore diameter in angstroms
polymer
The data from these measurements have been summarized in Table I, with similar data for various conventional homogeneous sulfonic acid exchangers prepared by the sulfonation of styrene copolymers cross-linked with varying amounts of divinylbenzene. Included are the moisture-holding capacities as measured by the metbod described by Fisher and Kunin (2). Figures 1 and 2 describe, respectively, the low temperature nitrogen adsorption isotherm of Amberlyst 15 and the BET interpretation plot of the isotherm. Whereas the specific surface area for the conventional resins in the normal particle size range of 20 to 50 U.S. mesh size is very small (
