The assignee for this patent, patent number 8721937, is Research Foundation of The
Reporters obtained the following quote from the background information supplied by the inventors: "Polymeric microparticles (e.g., micron and sub-micron particles) have attracted increased attention over the past several years. Compared to conventional bulk polymeric structures, polymeric microparticles can have improved mechanical strength, and greater control of transport properties, material property adjustability, and dimensional stability. Because of these properties, polymeric microparticles are useful in a variety of applications such as, catalysts, coatings, controlled release formulations for pharmaceuticals, biostructural fillers, electronics devices, and polymeric composites.
"In addition, hydrophilic polymer microparticles and, in particular, polyamide (PA) microparticles, typically have a greatly enhanced water absorption capacity compared to their bulk counterparts. For example, although the water absorption of bulk nylon fibers is only 10% by weight, nylon microparticles provide both improved water absorbing ability, as well as spill and wear resistance, due to their greatly increased surface area and the accessibility of water to their submicron void.
"Polymers are a family of important synthetic materials, which have broad applications in biology, chemistry, medicine and engineering, including their use as fibers, plastics, and coatings. These products are useful but can be further improved by controlling the formation of polymeric nanostructures thereof. There is a continuing need for improved methods for the preparation of polymeric microparticles that are cost-effective, and amenable to synthesis on an industrial scale. In particular, there is a need for methods that allow for bulk polymeric materials to be converted to their corresponding polymeric microparticles using simple and energy-efficient method and apparatus."
In addition to obtaining background information on this patent, NewsRx editors also obtained the inventors' summary information for this patent: "This disclosure is based on the unexpected discovery that a spray drying process can be used to prepare polyamide (e.g., nylon-6) particles with small particle size (e.g., from about 0.5 .mu.m and about 10 .mu.m) and having a narrow size distribution. The particles thus obtained can be used in a wide variety of applications, such as abrasive materials, catalysts, coatings, controlled release formulations for pharmaceuticals, electronics devices, and polymeric composites. The spray drying process can reduce the energy consumption at least by 50% compared to the known powder forming processes and produces negligible waste when designed as a closed loop process.
"In one aspect, the disclosure features a method that includes spray drying a solution containing a polyamide to form polyamide particles having an average diameter of between about 0.5 .mu.m and about 10 .mu.m and at least about 85% of the polyamide particles having a diameter distribution of no more than about 1.5 .mu.m.
"In another aspect, the disclosure features a method that includes (1) spraying a solution containing between about 1 wt % and about 8 wt % of a polyamide to form a plurality of droplets; and (2) drying the droplets by an inert gas (e.g., nitrogen) having a temperature between about 140.degree. C. and about 210.degree. C. to form polyamide particles.
"In still another aspect, the disclosure features a composition that includes polyamide particles having an average diameter of between about 0.5 .mu.m and about 10 .mu.m (e.g., between about 0.5 .mu.m and about 4 .mu.m) and at least about 85% (e.g., at least about 90%) of the polyamide particles having a diameter distribution of no more than about 1.5 .mu.m.
"Embodiments can include one or more of the following optional features.
"The polyamide can include a nylon (e.g., nylon-6, nylon-11, nylon-12, nylon-6,6, nylon-6,9, nylon-6,10, nylon-6,12, or a mixture thereof).
"The solution can further include a solvent (e.g., a solvent having a boiling point less than about 120.degree. C.). Exemplary solvents include formic acid, dichloromethane, or a mixture thereof.
"The polyamide can be about 1 wt % to about 8 wt % of the solution.
"The spraying drying can include spraying the solution to form a plurality of droplets having an average diameter of from about 5 .mu.m to about 30 .mu.m. The solution can be sprayed through at least one nozzle (e.g., a high pressure nozzle, a spinning disk, or a piezoelectric nozzle).
"The spray drying can further include drying the droplets to form the polyamide particles. In some embodiments, the drying can include mixing the droplets with an inert gas having a temperature of between 140.degree. C. and about 210.degree.
"The inert gas can have a temperature of between about 140.degree. C. and about 190.degree. C. (e.g., between about 170.degree. C. and about 175.degree. C.) when introduced into the evaporation chamber. In such embodiments, the inert gas can have a temperature of between about 50.degree. C. and about 100.degree. C. at the bottom of the evaporation chamber, the polyamide can be about 1 wt % to about 6 wt % of the solution, and the polyamide particles can have a porosity of from about 0% to about 55%.
"The inert gas can also have a temperature of between about 175.degree. C. and about 210.degree. C. (e.g., between about 190.degree. C. and about 200.degree. C.) when introduced into the evaporation chamber. In such embodiments, the inert gas has a temperature of between about 50.degree. C. and about 100.degree. C. at the bottom of the evaporation chamber, the polyamide can be about 4 wt % to about 6 wt % of the solution, and the polyamide particles can have a porosity of from about 45% to about 85%.
"Embodiments can provide one or more of the following advantages.
"Without wishing to be bound by theory, it is believed that, when the inert gas and solvent are recycled during the process described above, the process produces negligible waste, which is environmentally friendly and significantly reduces the manufacturing costs. Further, without wishing to be bound theory, it is believed that the process described above can use at least about 50% less energy to produce one pound of polyamide particles than the most economical known method (i.e., cryogenic grinding).
"Other features and advantages of the invention will be apparent from the description, drawings, and claims."
For more information, see this patent: Couzis,
Keywords for this news article include: Electronics, Research Foundation of The
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