I&EC REPORTS & COMMENTS New light on photosensitive polymers
A new agricultural product Resin-enriched concrete tiles
c
LIGHT-SENSITIVE POLYMERS Modern theories explain old techniques Modern polymer research is producing some theories to help the understanding of photochemical processes used since the days of ancient Babylon. At a recent seminar, Dr. J. L. R . Williams of Kodak Research Laboratories summarized the history of photosensitive polymers and analyzed some of the techniques in terms of modern polymer theory. He also described experiments carried out with model organic compounds to study reactions that occur when photosensitive polymers are exposed to light. All polymers can be modified if they are exposed long enough to light of short enough wave lengthsfor example, polyethylene, especially when sensitizers are included in the system. Polymers which have major
ultraviolet absorptions in the range from 250 to 600 mp, or beyond contain chromophores, usually ethylenic unsaturation. Exposure to light causes cross-linking of the polymer molecules, which decreases polymer solubility and makes the exposed portions hard and acid-resistant. Efficiency of cross-linking depends upon the sensitivity of the photosensitive groups to the wave lengths of light used and the number and proximity of the groups along the polymer chain. A solubility difference between exposed and nonexposed polymer is produced. Images are developed into patterns by dissolving the unexposed portions. Cross-linked or modified exposed areas remain fixed. The Babylonians first used polymers to make photographic images by exposing coatings of pitch to the
Kodak Photo-Resist is used in the production of these very thin metal parts. Such shapes, used in electronic circuits, electric motors, and cameras, are produced by photo milling-a process which uses photo-sensitive polymer coatings
sun. Similar images were prepared in France in the 19th Century. Later applications of the technique used polychalcones. The first polymer designed to have image-forming properties was polyvinyl cinnamate, as reported in 1959. Dimerizations such as the reaction of cinnamate to form truxillate were known to produce cross-links. Polymers with increased light sensitivity can be made by attaching photosensitive groups along the polymer chain or by adding sensitizing materials which absorb in the long wave length region and transfer their energy to the photosensitive groups. Adding sensitizers can greatly extend the spectral range to which the polymer is sensitive. I n the Kodak Research Laboratories, a great deal of attention has been given the study of the synthesis and light-induced reactions of a group of low molecular weight photosensitive polymers-the 2-styrylpyridines. Better understanding of the mechanisms of photosensitive polymers has led to materials which are much faster photographically and are sensitive to a wide range of wave lengths of light. When styrylpyridine polymers are prepared with variations in substituent groups, for instance, great changes in the polymer’s light absorption and spectral sensitivity are produced. Now some polymeric materials-styrylpyridine polymers containing a dimethylamino group - have roughly the spectral sensitivity of panchromatic photographic film, although they are still many times slower photographically. J . H. OLIN
(Continuid on page 72) VOL. 5 5
NO. 5 M A Y 1 9 6 3
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I&EC R E POR TS
Try this for high-quality CH, 0
I
II
/O\
R-C-C-0-CH,-CH
-CH
I
R' Cardura'b E Ester
c
is the glycidpl ester c 91 1 Acid, a syntheti Cn-C,, tertiary carboxylic acid. Thi ester can be used to produce high-qua ity nondrying alkyd resins throug con 'iren t i o n a 1 cook i n g tech n i q u e! Films of these resins offer excellent rt sistance to chemicals, over-bake an1 U.V light and have good color, glos and flow, Y A R D U R A : ~E VERSATIC"'
Typical reaction
CARDURA E
+ R'COOH -+
OH
i
RCOOCH I -CH -CH ,-OCOR' Properties Formula weight B o i l i n g Point Color Water s o l u b i l i t y , 20'C. Viscosity, 2O0Cc.
214-242 275'C. Water w h i t e 0.03% w 8.0 c s .
PADS FOR ORCHARD HEAT1NG A convenient packaged heater gives imp r o u ed eJiciency Development work on a new idea in agricultural chemicals has been described to us by E. A. Cadwallader, a Washington, D. C.,chemicalengineer. While interested in the problem of efficiently transferring thermal energy to growing fruits and blossoms, he showed the possibilityof combining all of the features desirable in a small heater into one pad, called a smudge pad. Development of the best and most economical material if not yet complete, though workable models have been tested. Orchard heating requires a maximum number of heaters, which should be as small as practical, and of the simplest possible design. The inventor has reduced the design to a single block of solid material, containing fuel and oxidizer, held together by a binder. The fuel comprises the largest part of the pad, and 'ivould be a carbon-base material, Sufficient chosen for low cost. oxidizing agent is added to provide the desired rate of reaction and to insure smooth and complete burning. Nitrates of sodium and potassium, perchlorates of sodium, potassium or ammonium, or organic peroxides are suggested. The fuel may also act as the binder, or a material such as starch, polyvinyl chloride, or ethyl or methyl celluloses may be incorporated. Other ingredients add other desirable characteristics. Some fuels
For product literature and a sample, write to: Product Development Department, I n dustrial Chemicals Division, Shell Chemica Company, 110 West 5 1 s t St., N e w York 20 N e w Yorli. :%Shelltrademark IGHITOR
Fuel for protecting trees from frost can be incorporated into a solid block, hung near the tree by means of support holes Circle No. 12 on Readers' Service Card
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INDUSTRIAL A N D ENGINEER1
CHEMISTRY
burn to form a surface ash, which then slows burning rate. Adding a gas-producing chemical as a deashing agent prevents this problem. Alkali bicarbonates remove the ash by production of carbon dioxide, while hydrated chemicals clean the surface by producing steam. For further convenience, an ignitor is applied to one surface of the pad. I n operation, this material flashes across the surface of the pad, igniting the entire surface. Providing an electrical spark for ignition could lead to automatic operation. Every year, when temperatures drop to the freezing point, grov, ers of fruit crops liqht smudge fires and try to "heat up all out-of-doors.'' According to the Department of Agriculture, heat from these fires does indeed save a major portion of the fruit in protected orchards. but smoke serves no purpose. Smudge fires require considerable investment in heaters and fuel storage, and need continuous labor while firing. Because of stratification of warm and cool air, damage may occur only at one level of the tree, or at one part of the orchard. Yet heaters can rarely be placed where they will do the most good. This is costly in either fuel or lost crop. I n comparison, the proposed smudge pads can be placed around the trees in the best possible pattern. Minimum labor is required, and no equipment cost or heater maintenance cost need be considered. By using an automatic ignition system, the pads could be fired immediately when temperatures drop to the danger point. T h e smudge pads may be of greatest value to citrus fruit growers who must protect their trees when the fruit is almost ready for market, when an oily residue cannot be allowed to form. Proper distribution of small, clean-burning pads could solve their problems of soot deposition, and prevent tlic danger of over-heating the trees. (Continued on page 14)
he n/m from Houdry has a firm grip on catalytic problems I
His wide background in this highly specialized field can be of invaluable service to you. If your problem involves catalysis, you'll want to talk first with The Man from Houdry. He can make recommendations-support them with figures on probable operating costs and quality of performance. Take Houdry KAO-SPHERES@,for example. The Man from Houdry ean tell you that this cracking catalyst has extremely high stability. That there is virtually no loss of activity in going from fresh catalyst to equilibrium. That it is extremely hard, very sulfur resistant, and can be used well with both sweet and sour crudes for any moving-bed cracking operations.
In fact, he can give you the cost and performance story on any of the many Houdry catalysts. A t Houdry, catalysis is a way of life. For literature on any Houdry catalyst, write giving details of your requirements. Or ask to have The Man from Houdry call on you.
r3yl
PROCmSS AWD CHEMICAL COMPANY
1528 Walnut Street, Philadelphia 2, Pa. r i m c i s m cnwicus. Inc.
n i v i t i ~II AIR
*Houdv mmam P~ODRU.
..lhrrwsh C W d y h
Circle N,. 31 II Rmlen' Senin C a d
VOL. 5 5
NO. 5
M A Y 1963
13
I&EC R E P O R T S
When does computer process control Dav out? 1
A
r/
and we mean real dollar profits ! What can you expect from EA1 PC-12 computer control in terms of payout?
$2000 in 20 days-A for itself in 20 days.
PC-12 computer controlling a single distillation column paid
$60,000 in 4 m o n t h s - A PC-12 multiple column control system is expected to payout in 4 months. 2000% Profit-Reports indicate $100,000 annual saving from a $5000 analog computer control investment. These are just a few examples of the value of dynamic process control installations: Batch process feedweight computation Variable end point oxygen steelmaking prediction Data reduction in frequency response testing Distillation column controls Nonlinear control computations Economic dispatching of utilities Universal pilot plant control system
FLUOROELASTOMER FITS NUCLEAR APPLICATION Containers f o r making radioisotobes Europe’s atomic energy program has led to a new market for one of the fluorocarbon elastomers. Small and specialized though this market may be, it illustrates once more how the chemical industry develops uses from specific product properties. In Euratom‘s nuclear reactor at Ispra, Italy, for example, radioisotopes are produced by direct irradiation of materials enclosed in capsules. These containers are transported through the reactor pneumatically through aluminum tubes. And to avoid damage to the tubes, the capsules must be made of a soft, )-ielding material. But inside the reactor, the gamma radiation flux is 1 X l o 6 roentgens per hour, with a thermal neutron flux of 2 X per square centimeter and a temperature at the point of irradiation of about 400’ F. Most plasticswhich are preferred because they are soft and yielding-can’t withstand the high temperature and the high radiation levels. But Viton, Du Pont’s linear copolymer of vinylidene fluoride and hexafluoropropylene, re(Continued on page 77)
Ask for more information on the growing use of EAl’s solid state, multi-variable control computers-for on-line control and other important computations.
EA1
ELECTRONIC ASSOCIATES. INC. Long Branch, New Jersey
ADVANCED SYSTEMS ANALYSIS AND COMPUTATION SERVlCES/ANALOG COMPUTERS/HYBRID ANALOG-DIGITAL COMPU. TATION EQUIPMENT/SIMULATION SYSTEMS/SCIENTIFIC AND LABORATORY INSTRUMENTS/ INDUSTRIAL PROCESS CONTROL SYSTEMSjPHOTOGRAMMETRIC EQUI PMENTI RANGE INSTRUMENTATION SYSTEMS/TEST AND CHECK.OUT SYSTEMS/MILITARY AND INDUSTRIAL RESEARCH AND DEVELOPMENT SERVICES/FIELD ENGINEERING AND EQUIPMENT MAINTENANCE SERVICES.
A typical Viton catsule for irradiation of materials in a nuclear reactor
Circle No. 54 on Readers’ Service Card
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Circle NO. 11 on Readers’ Service Card
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