CHEMICALS
Nonaqueous Foams Enter Aerosols Glycols used in place of water give stable foams with widely varying properties Aerosol makers have a new type of foam to think about—nonaqueous. Foamed products based on water formulations, marketed since early 1950, are one of the major groups of aerosol products. But because water foams have limited stability, chemists have long toyed with the idea of waterless foams. Now a study made at Du Pont's Freon products laboratory (C&EN, Oct. 31, page 39), released at the Montreal meeting of the Canadian Manufacturers of Chemical Specialties, gives the aerosol industry some of the technical background needed to launch nonaqueous foam products. Du Pont's work, headed by Dr. Paul Sanders, is based on replacing water with polyhydric alcohols, mainly glycols and glycol derivatives. By varying the type and amount of glycol, propellant, and surface active agent in the system, foam characteristics can be varied over a wide range. Some foams break down in less than
a minute; others are stable up to two weeks. One reason for the stability of nonaqueous foams is the low volatility of glycols compared to water. Dr. Sanders finds that these foam cells are smaller and much more uniform than those of water-based foams. While it is too early to pinpoint applications for the new foams, Dr. Sanders suggests they should be particularly useful for drug and cosmetic products such as insect repellents, suntan lotions, burn ointments and antiperspirants. Preferred Materials. The basic system used by Dr. Sanders contains 86% glycol, 4% propylene glycol monostearate as the emulsifying agent, and a mixture of 40% Freon-12 and 60% Freon-114 as the propellant. The preferred glycols, he says, are propylene glycol and polyethylene glycol 200 or 400. In general, glycols that are the least soluble in the propellant system give the best foams.
SMALL CELLS. Propylene glycol foam (left) exhibits the smaller, more uniform cellular structure that makes many nonaqueous aerosol foams more stable than water based foams (right). Stability of nonaqueous foams may make them useful in a variety of topical drug and cosmetic products 64
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Soluble glycols give unstable foams or do not foam at all. Over-all, propellant concentrations of 8 to 107c give the best type of discharge and foam, Dr. Sanders finds. Increasing the amount of propellant results in very coherent foams, although discharge is sputtery. At high concentrations—60 to 90%—the product comes out as a dry, frozen foam which expands into a stable foam after it warms up. The choice of surface active agent for nonaqueous systems is critical. The most satisfactory agent of those tested by Dr. Sanders is propylene glycol monostearate. It appears to be necessary, he says, to use an agent that is not completely soluble in either the glycol or the propellant. Finely divided particles of undissolved emulsifier may act as an auxiliary emulsifier and stabilizer, Dr. Sanders believes. One exception to the solubility effect is cetyl alcohol. When this is used as the emulsifying agent the system is clear and homogeneous, yet still yields a satisfactory foam. The discharge with cetyl alcohol is almost liquid, but expands immediately into a foam. The amount of surface active agent in the system affects foam stability. At less than 2% concentration the foam stands up for less than an hour. Above 4%, very stable foams result. But Dr. Sanders cautions that the chance of valve clogging is increased considerably when the concentration of the surface active agent is increased above 4 % . Pressure Sensitive. Ethyl alcohol, used as a solvent in many cosmetic and drug formulations, can be tolerated in nonaqueous systems up to about 10% concentrations. Higher amounts, Dr. Sanders says, may have an adverse effect on foam stability. Adding ethyl alcohol to the emulsion also can produce foam which breaks down immediately when pressure is applied. The Du Pont investigations are just one of the steps toward putting nonaqueous foams on the market. No work has been done on storage stabilities or the effect of glycol systems on container linings and valve parts. Also, work must be done to find how storage effects activity of the product. This is particularly important, Dr. Sanders points out, where pharmaceuticals and other topical products are involved.
BRIEFS Epinephrine and arterenol derivatives,
metabolic precursors, and catabolites are now available from California Corp. for Biochemical Research, Los Angeles, Calif. The compounds are metabolic products of methylation, deamination, and oxidation, Calbiochem says. The compounds: 3-0methylepinephrine, 3-O-methylnorepinephrine, 3,4-dihydroxymandelic acid, 3-methoxy-4-hydroxymandelic acid, 3-methoxy-4-hydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid, 3-hydroxytyramine, and 3methoxytyr amine. C1
Semicommercial quantities of 1,2,3,trichioropropene come from Dow Chemical, Midland, Mich. The chemical is similar structurally to allyl chloride, Dow points out, and thus should find similar uses. C2
Seven fatty acid methyl esters and
two high molecular weight hydrocarbons have been added to its line of purified chemicals by Applied Science Laboratories, State College, Pa. The esters and their per cent purities: methyl linolenate, 99 plus; methyl isomyristate, 99 plus; methyl hexacosanoate, 99 plus; methyl triacontanoate, 95 plus; methyl erucate, 99 plus; dimethyl brassylate, 99 plus; and elaidyl alcohol, 98 plus. The hydrocarbons are ??-tetratriacontane (C 3 4 ) and 7i-dotetracontane ( C 4 2 ) , both 99% pure. The chemicals are useful standards and quantitative aids for gas chromatography, Applied Science says. C3
Cylinders of sulfur tetrafluonde, vinyl fluoride, and aliène have been added to its line of compressed gases by The Matheson Co., East Rutherford, N.J. Sulfur tetrafluoride is a selective fluorinating agent; vinyl fluoride reacts like an olefin, will form homo- and copolymers; aliène can be used in various organic syntheses. C4
Hydrazine diborane (N.>H 4 B2H G ) can
be obtained in developmental quantities from Callery Chemical, Pittsburgh, Pa. The compound is suitable for rocket propellants, Callery says. Prop-
w a s there... testing and retesting wire insulation. Through sound research and solid experience, RC Plasticizers and Insular Resins provide your wire and cable with three vital prerequisites: high insulation resistance, ease of processing and maximum durability. Local or long distance — RC research and the experts who provide it are always at your disposal. We invite your inquiries for advice, technical bulletins and samples. Whether we provide an experience-tested solution or create a custom made formulation, your product's plus in performance and profit will prove . . . RC was there !
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C&EN
65
Spotlights pH Meters
HARSHAW SCIENTIFIC
W i t h our comprehensive line of p H meters—ranging from the ultra-sensitive Beckman Model GS to the inexpensive Beckman Pocket M o d e l — w e offer the proper instrument for your particular need. Representative models are described briefly below. W e welcome your requests for more detailed information.
erties listed by Callery: white, crystalline, free-flowing powder; molecular weight, 59.7; density, 0.91 gram per c c ; heat of formation, 30 kcal. per mole. C5
Research quantities of 5-methoxytryptamine ( C 1 1 H 1 4 N 2 0 ) are available from Regis Chemical, Chicago, 111. The chemical is useful in melatonin studies and the synthesis of methoxyharmans, Regis says. Form is white to pale yellow crystal; melting point is 120° to 122° C. C6
Intermediate that increases crosslinking in rigid urethane foams has been developed by Union Carbide Chemicals, New York, N.Y. Niax hexol LS-485 is derived from propylene oxide, has molecular weights around 700, Carbide says. Other possible uses listed by Carbide: preparing resins, emulsifiers, surfactants, pharmaceuticals, biocides, adhesives, and plasticizers. C7
Family of cellophanes coated with polymers has been introduced by Olin Mathieson Chemical, New York, N.Y. The films seal rapidly at low temperatures; they are moistureproof, can be printed and machined, the company says. Suggested uses include packaging for foods, textiles, and paper products. C8
Tylac series 3 5 0 0 has been added to its line of latex adhesives by International Latex, New York, N.Y. The modified butadiene-styrene latex improves adhesion, wet rub resistance, smoothness, and gloss of coated papers, the company says. C9
Service-facilities and complete electrode stocks a r e maintained a t all Harshaw Scientific Branches
Rigid, foamed-plastic pipe insulation has been developed by Armstrong Cork, Lancaster, Pa. Rigid Armaflex is designed to complement Armstrong's flexible foamed plastic, Armaflex, in areas where the insulation is subject to compression set, the company says. C 10
H À R S H AW S C I E NT I F I C Division of The Harshaw Chemical Co. · Cleveland 6, Ohio SUPPLYING THE NATION'S LABORATORIES FROM COAST TO COAST OAKLAND 1, CAL. HOUSTON 11, TEXAS SALES BRANCHES CINCINNATI 13, OHIO 5321 East 8th Street 6265 Wiehe Road 6622 Supply Row AND WAREHOUSE^ PHILADELPHIA 48, PA. LOS ANGELES 22, CAL. CLEVELAND 6, OHIO DETROIT 28, MICH. Jackson & Swanson Sts. 3237 So. Garfield Ave. 9240 Hubbell Ave. 1945 East 97th Street SALES OFFICES · Atlanta 5, Ga. · Baton Rouge 6, La. · Buffalo 2, N.Y. · Hastings-On-Hudson 6, N.Y. · Pittsburgh 22, Pa.
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Further useful information on keyed Chemical items mentioned is readily available . . . Use handy coupon on page 82 ^
