About Chemical Innovation - Subscription Information
August 2001
Vol. 31, No. 8, pp 39–42.
Patent Watch

Table of Contents

Elizabeth G. Burns
Laura Deakin
Jeffrey S. Plotkin

A resin that combines the best and worst of laboratory odors makes a better tire tread. E. J. Blok and co-inventors describe a polymeric resin that is made from limonene (essence of citrus), dicyclopentadiene (one of the worst smelling olefins around), and tert-butylstyrene. The resinous material was made by combining the olefins in a ratio of 1 part limonene to 1 part dicyclopentadiene to 2 parts tert-butylstyrene. These monomers were diluted in hydrocarbons and treated with anhydrous AlCl3 to effect polymerization at room temperature over a few hours. The resulting solution was precipitated by adding it to i-PrOH–H2O, washed further with i-PrOH, and steam distilled to remove low-molecular-weight matter. The polymer that was left behind was cooled on aluminum pans; the resulting hard resin had a capillary tube melting point of 120–156 °C. Gel permeation chromatography with columns designed for small molecule analysis showed that ~85% of the material is in the 2400-Da range.

Tire tread was made by combining this resin (80 parts) with styrene–butadiene rubber (100 parts) in a Banbury mixer. The material was evaluated against commercially available coumarone–indene and phenolic resins. Dry traction of the compounded rubber was measured by tan Δ (energy loss per cycle) and loss compliance measured at 40% strain. Durability was measured by G´ (shear storage modulus) at 40% strain, 300% modulus, and tensile strength limit. The rubber compounded with phenolic resin showed good dry traction but a loss in durability. The coumarone–indene material was stiff and showed good durability but little improvement in dry traction. The rubber made with the limonene–dicyclopentadiene– tert-butylstyrene resin showed good dry adhesion with only a small sacrifice of durability. (Goodyear Tire & Rubber; U.S. Patent 6,221,990, April 24, 2001; EGB)

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A process that converts crude cyclopentadiene and methanol to p-xylene and light olefins is being explored by ExxonMobil. The olefins business is highly competitive, and any processing twist that can upgrade steam cracker byproducts to higher-value products can provide an economic advantage. Many approaches are currently being developed; examples are metathesis of C4 olefins with ethylene to boost propylene output and so-called selective cracking of C4–C5 olefins to ethylene and propylene.

J. Beck, S. Brown, and W. Weber have now disclosed a process that reacts C4+ dienes and certain oxygenates, such as MeOH or Me2O, over a zeolite catalyst to give p-xylene, ethylene, and propylene. They demonstrated the efficacy of the process by preparing a feedstock composed of 75 wt % H2O, 1.25 wt % dicyclopentadiene (which converts to cyclopentadiene upon heating), 1.25 wt % toluene, and 22.5 wt % MeOH. This mixture is intended to model a typical C4+ feedstream that contains C5 dienes and aromatics. The model feedstream was passed through a fixed bed of catalyst in a 1/2-in. o.d. quartz reactor. The catalyst was prepared by slurrying H3PO4, kaolin clay, and SiO2–Al2O3 (450:1) ZSM-5 in water, followed by spray drying. The catalyst was calcined in air at 510 °C to give a composition of 40 wt % ZSM-5 and 4.5 wt % phosphorus.

The feed was reacted at 430 °C and 1 atm. Dicyclopentadiene conversion was complete at 20% MeOH conversion and 10% toluene conversion. GC analysis revealed that the hydrocarbon product was composed of 30% p-xylene, 25% ethylene, and 22% propylene. The remaining hydrocarbon products were mostly C4+ olefins and C8+ aromatics. The inventors assert that with this process, ~18 lb of MeOH and 2 lb of cyclopentadiene can be converted to 3 lb of p-xylene, 2.5 lb of ethylene, 2.2 lb of propylene, and 2.4 lb of byproducts. (Mobil Oil; U.S. Patent 6,187,982, Feb 13, 2001; JSP)

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New colorimetric sensors are made from polydiacetylene-immobilized liposomes. D. H. Charych and A. Reichert have developed a novel colorimetric sensor and propose that it could provide a cheaper alternative to currently used immunoassays requiring monoclonal antibodies. Currently, many biosensors use fluorescent labels, in which the onset of fluorescence or a decrease in fluorescence intensity is an indication that analyte binding has taken place. The newly discovered sensor operates on a colorimetric principle and is composed of immobilized liposomes. The sensor can be used to detect the presence of a variety of analytes: inorganic, organic, and biological. The liposomes are bound to a polymeric organic matrix by modifying the lipid monomers to contain a polymerizable group, diacetylene, and a head group for specific binding of the analyte.

The liposomes are generated using known sonication methods and are immobilized in polydiacetylene by exposing the solution to UV light (254 nm) to effect radical polymerization of the monomer. The resulting blue polymer can then be coated onto beads; this flow-through system permits samples to be screened very rapidly. The alternating double and triple bonds of polydiacetylenes are known to absorb visible light intensely. Color variation from blue to red is achieved with changes in conformation, temperature, or pH. When polydiacetylenes are used as a biosensor matrix, analyte binding causes small but detectable changes in the local polymer electronic environment. This results in an observable change in the polymer matrix UV–vis absorption profile, making this polymer ideal for simple analyte binding detection. When the analyte binds to the head group on the liposome surface, the color change is immediate and the color intensity determines analyte concentration quantitatively.

Binding the influenza virus to liposomes modified with sialic acid head groups and trapped in a Langmuir–Blodgett polydiacetylene film produced an intense color change (see Charych, D. H.; Nagy, J. O.; Spevak, W.; Bednarski, M. D. Science 1993, 261, 585–588). The 3-D polymer network reported here displayed a dramatic color change, from deep purple to orange, upon the binding of the influenza virus. This suggests that very low quantities of analyte can be monitored. Virus quantities as low as 11 hemagglutinating units, ~1.1 × 108 particles, can be detected. Modification of the binding site will determine which compounds can be measured effectively. By choosing broader-binding groups, the sensor could be used to detect the presence of species from large families of biological molecules or the presence of several different metal ions. In this fashion, the sensor is particularly useful for the detection of molecules for which antibodies cannot be readily obtained. (The Regents of the University of California; U.S. Patent 6,180,135, Jan 30, 2001; LD)

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A jacket might keep you warmer if it could store your body heat more effectively. Most thermal insulation works by trapping layers of warm air, but air has a limited heat capacity. J. L. Zuckerman and co-inventors describe a better way to incorporate microencapsulated waxes that store energy effectively in coated fabrics. The waxes chosen are C10–C30 hydrocarbons, molecules most of us haven’t thought about since we learned IUPAC nomenclature way back when. These materials, when purified, have melting points that range from just below 0 to >60 °C.

A microencapsulated wax is a particle coated with gelatin or another substrate. The wax, when molten, cannot flow outside its shell and will resolidify when cooled. The microencapsulated waxes are added to a coating solution that includes a polymer dispersion, thickener, and surfactants. The coating is applied to a fabric using a knife-over-roll coater and dried at 127 °C. The waxes n-octadecane (C18) and n-eicosane (C20) are particularly suited for use in garments; they have melting temperatures of 28 and 38 °C, respectively—below and at body temperature. Higher melting point waxes might be useful in heat-protective garments. The authors note that these microencapsulated waxes serve as antiblocking additives and heat sinks.

Fabrics made using these coating compositions exhibited no loss of waterproofing or breathability relative to control samples made without wax particles, but the amount of heat flow across the coated fabric did decrease. (Gateway Technologies; U.S. Patent Application 20010000517, April 26, 2001; EGB)

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Production of methacrylic acid by selective isobutane oxidation is a challenging goal for industrial chemists and engineers. The conventional route to methacrylic acid (MAA), or its more commercially valuable ester, methyl methacrylate (MMA), is through acetone cyanohydrin, produced by the reaction of Me2CO and HCN, followed by several finishing steps, to finally yield MMA. Because HCN is very toxic and expensive to make as a primary product (low-cost HCN is available as a byproduct of acrylonitrile production, but safe transportation then becomes an issue), other routes to MAA and MMA have been explored. In Japan, isobutylene is used to make MAA and MMA, and in an effort to lower production costs, much research has been devoted to developing catalysts capable of selectively oxidizing low-cost isobutane to MAA.

Most of the previous work in this area suffered because good selectivities could only be achieved at low isobutane conversions per pass or vice versa. A. Motoyama and I. Nakamura have invented catalysts that provide good selectivities at commercially feasible isobutane conversion levels. The catalysts comprise a sparingly water-soluble salt of a heteropoly acid and a mixed oxide containing phosphorus, molybdenum, and vanadium. The oxidation was performed in a stainless steel flow reactor. The gas feed was composed of isobutane, air, and steam in a ratio of 7.5:67.5:25.0; a space velocity of 2800– 5600 h–1 was used. The reactor was heated to 340–350 °C. Various catalyst compositions were tried, and MAA selectivities as high as 48.4% were achieved at an isobutane conversion of 11.4%. At an isobutane conversion of 25.8%, MAA selectivity was reasonably constant at 41.5%. (Nippon Shokubai, European Patent Application 1,092,702 A2, April 18, 2001; JSP)

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This pressure-sensitive paper is its own release liner. Pressure-sensitive labels usually come with a release liner—that slippery shiny stuff that you have to throw away. M. J. Sanchez and co-inventors have disclosed a thermal paper that doubles as its own liner. This product can provide economic and environmental benefits: less to buy, less to dispose of. Thermal papers are those that create images where heat is applied. For example, thermal paper is often used in inexpensive fax machines and for receipts at pay-at-the-pump gas stations. This technology is also used to make bar-code labels, and it is this type of application that needs a pressure-sensitive thermal paper.

The inventors coat classic release materials—such as General Electric’s epoxy-based silicone systems—with Teflon-derived wax particles. This combination is coated and cured on one side of a thermal paper. The paper is then extrusion-coated on the other side with a pressure-sensitive adhesive. Now the single layer—sticky on only one side—can be wound on itself and dispensed like Scotch Tape. This may present some interesting challenges to the engineers who build thermal printers: How to print on a label that is its own tape? This invention is demonstrated on thermal, rather than printable, labels for an obvious reason: Release liners are not very printable. In thermal paper, the ink is already in the paper, waiting for its cue to become visible with heat.

The single example describes how to make such a label but does not disclose what kind of blocking test was used to decide whether the release liner was going to last. The authors also do not show any printing of the label, which may require special equipment. (Moore Business Forms; U.S. Patent 6,221,485, April 24, 2001; EGB)

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Graffiti-resistant coatings can be made using a UV-curable composition, including fluorinated monomers. Molded plastic objects, such as benches, polycarbonate kiosk windows, and the like are often subject to the depredations of graffiti artists. Because graffiti makes a location appear to lack maintenance, it drives customers and street traffic away.figure

In response to the need for an easily maintained coating, M. Mueller and R. Neeb disclose a family of compositions that comprise multifunctional methacrylates, fluoromonomers (see example), UV-curing photoinitiators, and what the inventors term “customary additives”, a category that includes UV stabilizers and coating aids.

The coating solution is made simply by mixing the necessary ingredients. The examples in the patent disclose coating solutions containing 39 parts by weight pentaerythritol tetraacrylate, 59 parts hexanediol diacrylate, and 2 parts Darocur 1116 (a thermoplastic bisphenol A polycarbonate from Ciba Specialty Chemicals), plus varying amounts of monomer. A specified amount of the acrylate or methacrylate monomer was added to the base coating mixture. The coating was applied to plates of Makrolon 281 (a thermoplastic bisphenol A polycarbonate from A. Brodacz) by means of a spiral “doctor” applicator to give a wet film thickness of 12 µm. After 1 min settling time, the coating was hardened using a high-pressure mercury lamp, at 1 m/min advance speed, under a nitrogen atmosphere. The inventors don’t tell us much about the settling time, but it is probably sufficient to allow the fluoromonomers to rise to the surface. A graph of time-to-cure versus contact angle would have been informative.

The antigraffiti properties were evaluated by spraying coated samples with ordinary commercial acrylic automotive paint and evaluating the wetting and ease of removal of the paint. In coatings with at least 0.5 wt % fluoromonomer, the paint beaded immediately and could be removed without solvents. Ease of removal correlated roughly with the contact angle of water on the surface. Abrasion resistance, measured with a Taber abrader, also improved with the addition of fluoromonomer. (Roehm; U.S. Patent 6,221,988, April 24, 2001; EGB)

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A new polymeric decolorizer creates erasable images on paper. The image-forming material developed by S. Takayama and co-inventors permits sharp images to be imprinted onto polymer-coated paper and subsequently erased by treatment with heat or solvent. The three important components of the material are the dye precursor, the developer, and the polymeric decolorizer. Direct interaction between the dye precursor (color former) and the developer is required to obtain a color image on the page. The color formers used in this process are electron-donating molecules such as fluorans or diarylphthalides—oxygen-bridged triarylmethine derivatives that frequently contain halogen or amino substituents. The electron-accepting molecules used as developers, such as phenols, carboxylic acids, and benzophenones, are chosen to promote strong interactions, in some cases via a hydrogen bond with the color former. Bonding between these components leads to the formation of an image, or the colored state.

After the image is formed, it can be erased with a decolorizer. This is typically a polymer with electron-donating groups such as poly(vinylaniline) or polyacrylonitrile, or a polymer with a sugar skeleton, such as a derivative of starch or cellulose. The decolorizer competes with the color former for bonding with the developer. Conditions that favor decolorizer–developer interactions result in image erasure; the formation of the colored state is blocked. Although the decolorizer could also be a small molecule, the reaction with the polymeric decolorizer is driven by the high concentration of functional groups on the polymer, resulting in effective image removal.

The image can also be erased by temperature changes, effectively reducing the color intensity to <5% of its value in the colored state. When the coated paper is exposed to temperatures greater than the melting temperature of the polymeric decolorizer, excess decolorizer functional groups cause the decolorizer and developer to interact. Cooling the polymer rapidly from the melt stabilizes these interactions; the colorless state is then maintained at room temperature for at least 300 h. This erasure procedure is only suited to polymeric decolorizers with Tg values above room temperature. The image can similarly be erased by exposing the paper to organic solvents such as alcohols, THF, and dioxane.

The image-forming and -erasing components can be attached to the paper in several ways. Generally, the paper is treated first with styrene–butadiene or ethylene–vinyl acetate copolymer; this matrix improves adhesion of the other compounds. When the mixture of color former, developer, and decolorizer is sprayed onto the matrix surface, the image appears immediately. Alternatively, the color former and developer can be deposited inside polymethacrylonitrile microcapsules. These 10-µm particles are then broken when passed through a press roller. Although the process of writing on the same page is not detailed, this likely requires that more color-forming and decolorizing agents be layered onto the page. The writing and erasing process using a pen-type tool is also described. (Kabushiki Kaisha Toshiba; U.S. Patent 6,203,603, March 20, 2001; LD)

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A heterogeneous catalyst with excellent selectivity for oligomerizing ethylene to commercially valuable C4–C10 α-olefins has been developed by scientists at SABIC. Commercial processes for producing α-olefins characteristically produce a fairly broad range, from C4 to C20 or higher. Unfortunately, this broad product slate does not match market demand for these products. Various processing tricks are used to modify the extent of ethylene oligomerization or to further process the less desirable α-olefins into more useful products.

The Shell Higher Olefin Process (SHOP) uses the second approach. In this process, unwanted higher α-olefins are isomerized to yield a range of internal olefins, which can then undergo metathesis with ethylene or butylene to afford olefins of intermediate molecular weight. If a catalyst could be developed that only gives α-olefins in the C6–C10 range without the need for extra processing, it would be an important advance.

M. Zahoor and co-inventors have disclosed a heterogeneous catalyst system that has very good selectivities for oligomerizing ethylene to C4–C10 α-olefins. The catalyst system consists of a chelating agent, a nickel precursor compound, an activator, and a silica support. The preferred catalyst is made with 2-diphenylphosphinobenzoic acid as the chelating agent, NiCl2, and NaBH4. These three materials were dissolved in EtOH, and calcined silica was added to the solution and stirred for 40 min. The slurry was then freeze-dried. The resulting supported catalyst (63 mg) was slurried in EtOH (20 mL) and transferred via syringe to a pressure reactor. The reactor was pressurized with ethylene to 725 psig and heated to 100 °C for 120 min. Analysis of the reactor contents showed that ethylene conversion was 49%; selectivities to C4, C6, C8, and C10 α-olefins were 31, 33, 19, and 13%, respectively. Selectivities to the α-olefins in each fraction were 99.9, 99.2, 98.2, and 96.9%, respectively. As a further benefit, the catalyst is not air-sensitive and is easily handled. (Saudi Basic Industries; U.S. Patent 6,184,428, Feb 17, 2001; JSP)

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