Table of Contents

Bicyclic acetals are cured using radiation polymerization. W. Reich and co-workers have developed a polymer (1) that is described as a suitable photoresist as the polymerization reaction is not sensitive to the presence of oxygen during radiation curing. The production of patterned coatings and moldings, such as printed circuits, is an industrially important process that makes use of photoresists, compounds that change solubility when irradiated with UV light. The photo polymerization reaction of acrylate compounds, however, is inhibited by oxygen. This newly patented process is based on the polymerization or copolymerization of monomer units derived from 2,7-dioxabicyclo[3.2.1]octane (2). The monomer is synthesized from the reaction between a butenediol derivative and a vinyl ether in the presence of a halogenating agent, followed by ring closing.

The ring-opening polymerization of 2 can then be done using either radical or cationic initiation. When polymerization is undertaken in the presence of a second monomer such as vinyl ethers, epoxides, unsaturated ketones, dienes, or styrene, a copolymer is obtained, preferably containing from 1 to 100 wt% of units of 1. The cationic polymerization requires the addition of photoinitiators to the monomer mixture. Because photoinitiators produce acids upon irradiation, this process should avoid photoinitiators that yield Brönsted acids. Ferrocenium salts are presented as suitable initiators for these reactions, with a preferred initiator concentration of 0.5–5 wt%. (BASF; U.S. Patent 6,077,932, June 20, 2000; LD)

A process for making electrets could lead to flexible electronic displays. Polymer spheres with “electrets”, or permanent charges (the name is analogous to magnets), and coincident colors are made in a process described by E. Kishi, T. Yagi, and T. Ikeda. Poly(methyl methacrylate) (PMMA) latex spheres were made that incorporate white pigment in each sphere. These spheres were dispersed in a poly(vinyl alcohol) (PVA) paste and coated at about the same thickness as the diameters of the spheres on an aluminum electrode. After drying, the PVA solution contracted, and half of each sphere— a hemisphere of PMMA—protruded from the film. The aluminum plate was connected to a power source, and a second metal plate was suspended just above the protruding hemispheres of polymer. The plates were given opposite charge, and the entire assembly was held at a temperature just above the softening point of the PMMA. The temperature of the assembly was gradually lowered to below the softening point. This process fixed the charges, one positive and one negative, on opposite sides of the polymer spheres. The upper electrode was removed at the end of the process, and carbon black was deposited on the hemispheres that protruded. At this point, the PVA was dissolved away from the finished spheres. The result was polymer spheres with hemispheres of opposing charges and different colors.

The spheres were assembled into a display device by first combining them with a highly viscous poly(dimethylsiloxane) (PDMS) polymer, coating the mixture, and curing the PDMS. The resultant piece of cured rubber sheet was soaked in a low-viscosity PDMS, which diffuses through the cured rubber and forms pockets around the embedded polymer balls, enabling them to spin. The sheet is then placed between indium –tin-oxide coated glass (transparent electrodes), and a charge is applied. By changing the direction of the charge, the balls can be made to spin and present either the black or white face.

The inventors also use black-pigmented polyethylene balls, which they treat similarly after painting one face white. In another example, they demonstrate the use of individually addressable sections of the clear electrodes, such as would be used in text or graphics. (Canon Kabushiki Kaisha; U.S. Patent 6,072,621, June 6, 2000; EGB)

A catalyst system that effectively enables carbonylation of ethylene oxide to give acrylic acid. Shell Oil has recently commercialized a process for making 1,3-propanediol that proceeds by the reaction of hydrogen and CO (hydroformylation reaction) with ethylene oxide (U.S. Patent 5,304,691). L. Slaugh and T. Forschner now disclose a catalyst system that allows ethylene oxide to be reacted with only CO (no hydrogen) to produce acrylic acid in high selectivity.

Several examples were given in the patent. The following conditions gave the highest selectivity to acrylic acid. In an autoclave purged of air, 0.34 mmol of cobalt octacarbonyl and 1.0 mmol of tin 2-ethylhexanoate were added to the solvent mixture (5 mL of MeOH and 27 mL of MTBE). After sealing the autoclave, ethylene oxide (43 mmol) was added under pressure of CO (1200 psig). After 6 h at 120 °C, the reaction contents were analyzed. Acrylic acid was produced in nearly 90% selectivity at 5.4% ethylene oxide conversion. Methyl 3-hydroxypropionate was formed in 7.8% selectivity. One experiment that omitted the tin 2-ethylhexanoate promoter did not give any acrylic acid. This kind of chemistry leverages Shell’s recent experience in 1,3-propanediol catalysis and back integration in ethylene oxide. (Shell Oil; U.S. Patent 6,084,124, July 4, 2000; JSP)

Ethylene glycol is produced in high yields via intermediate formation and decomposition of ethylene carbonate. Conventionally, ethylene glycol is produced commercially by the noncatalytic hydrolysis of ethylene oxide. This method, however, has some operational disadvantages. For example, ethylene oxide has a tendency to undergo oligomerization under hydrolysis conditions, which yields significant amounts of diethylene glycol (DEG) and triethylene glycol (TEG) as byproducts. Although a large excess of water can be used to minimize ethylene oxide oligomerization, this method increases the energy needed to separate the ethylene glycol from the water. One method, which has been explored by several companies, is to react ethylene oxide first with CO₂ to form ethylene carbonate, which, in turn, can be hydrolyzed to give ethylene glycol in very high selectivities and regenerate the CO₂.

In theory, this method avoids formation of ethylene oxide oligomers, but in practice, it suffers from slow reaction rates and potentially dangerous high exotherms. K. Kawabe has found that using a bubble column reactor in conjunction with a carbonation catalyst and water improves reaction rates and avoids hot spots, which makes for a much smoother and safer operation. A bubble column reactor is a reactor in which the reaction solution forms a continuous phase, and the gas phase (CO₂, in this case) is dispersed in the liquid phase by countercurrent introduction by means of a sparger at the bottom of the reactor. The examples reported in the patent used tributylmethylphosphonium iodide as the carbonation catalyst (4.5 kg/h). Feeds consisted of CO₂ (140 kg/h), ethylene oxide (62 kg/h), and water (50 kg/h). The feeds were reacted in the bubble column reactor at 150 °C and 20 kg/cm/g. The conversion of ethylene oxide was 99%; and selectivities to products were ethylene glycol (62.3%), ethylene carbonate (35.3%), DEG (2.3%), and TEG (0.1%). The reaction reportedly went smoothly and resulted in no hot spots. (Mitsubishi Chemical; U.S. Patent 6,080,897, June 27, 2000; JSP)

Preswelling membranes leads to an easier way to build fuel cells. Assembling fuel cells can be simplified by swelling the membrane electrolyte before applying the catalyst-containing electrodes. From a political, environmental, and economic perspective, the use of fuel cells offers an excellent alternative to fossil fuels that is natural and avoids using nonrenewable resources. A patent by J. Hulett of General Motors improves the manufacturing of one promising kind of fuel cell—the proton-exchange membrane–solid-polymer electrode (PEM–SPE) fuel cell.

Hydrogen, the main fuel in these cells, is burned with oxygen, typically from the air, and the result is water and energy. The “burning” is done by using a catalyst, typically platinum, which is supported on carbon black and bound with a resin: This mixture serves as the electrode. Two such electrodes are constructed on either side of a solid polymer electrolyte, which is most often composed of the same resin used in the electrodes. The solid electrolyte is a material such as Nafion from DuPont, which is a fluorinated sulfonic acid polymer. This sulfonic acid polymer transports protons or “holes”, rather than electrons, but the result is the same. The catalyst and this proton transport membrane are assembled into a unit called the membrane electrode assembly.

The patent addresses the problems encountered when applying the electrodes to either side of the central membrane. If each piece is cast independently, it can be difficult to make good contact. If the electrodes are dissolved or cast from a dispersion, the central membrane will often swell with the solvent and become dimensionally unstable. In the process described here, the membrane is first deliberately swollen in the solvent that will be used later in coating, then clamped in the x and y directions (z is perpendicular to the film). The swollen state, in which the polymer was clamped, becomes its stable, unstressed shape. Then the dry membrane is coated with a solution or dispersion of the electrolyte and dried. There is stress on the membrane in the dried state, but it cannot move. After the membrane is swollen with water, which is how it will be used, the stress is relieved. By contrast, coating a membrane that has never been swollen and clamped results in stress in the swollen, working state, but not in the dry state. This process manages to accommodate the swelling behavior of the membrane. (General Motors; U.S. Patent 6,074,692, June 13, 2000; EGB)