A ramp-shaped intervertebral implant is disclosed. The implant has a body having a first end, a second end, a top surface and a bottom surface. At least one of the top and bottom surfaces is tapered and converges towards the second end of the body. An opening extends through the body and has one end opening onto the top surface of the implant and the other end opening onto the bottom surface of the implant. The implant can be formed from the diaphysis or metaphysis of a long bone, wherein the intramedullary canal of the long bone defines the opening. Alternately, the implant can be made from any biocompatible material having the requisite strength requirement.

1. Technical Field
The present disclosure relates generally to intervertebral implants for spinal fusion and, more particularly, to a ramp-shaped intervertebral implant having a top surface and a bottom surface and at least one opening extending between the top and bottom surfaces.
2. Background of Related Art
Surgical procedures for fusing adjacent vertebrae together to treat back pain in patients with ruptured or degenerated intervertebral discs, spondylolisthesis or other pathologies are well known. Typically during such a procedure, a spinal implant is placed into the intervertebral space in a position to engage adjoining vertebrae. The implant is constructed from a biocompatible material which is adapted to fuse with the adjacent vertebrae to maintain proper spacing and lordosis between the adjacent vertebrae, i.e., maintain the disc space.
A variety of different types of intervertebral implants have been developed to perform this function including spinal fusion cages, threaded bone dowels and stepped bone dowels. Exemplary implants are disclosed in U.S. Patent Applications filed on even date herewith, under Certificate of Express Mail Label Nos. EL260888080US and EL071686220US, and entitled xe2x80x9cIntervertebral Implantxe2x80x9d and xe2x80x9cKeyed Intervertebral Dowelxe2x80x9d, respectively, the entire disclosures of which are incorporated herein by reference.
One type of intervertebral implant has a wedge configuration. U.S. Pat. No. 5,425,772 to Brantigan discloses a wedge-shaped implant having an anterior end, a posterior end, front and rear walls, top and bottom walls and sidewalls. The implant is constructed from biocompatible carbon reinforced polymer or alternately of traditional orthopedic implant materials such as chrome cobalt, stainless steel or titanium. The top and bottom walls are tapered from the anterior end of the implant to the posterior end such that the anterior end of the implant has a height greater than the height of the posterior end of the implant. The top and bottom of the implant are continuous and unslotted and include a series of transverse teeth or serrations extending thereacross. A slot configured to receive bone graft material extends through the implant between the sidewalls.
During insertion of Brantigan""s implant into the intervertebral space, the adjoining vertebrae are tensioned and a portion of disc tissue between the vertebrae is cut and removed to form channels between the vertebrae. The implant is positioned in the channel such that the teeth formed on the top and bottom surfaces of the implant engage the adjoining vertebrae. During a surgical spinal fusion procedure, two of Brantigan""s implants are inserted between the adjoining vertebrae to be fused.
U.S. Pat. No. 5,443,514 to Steffee also discloses a wedge-shaped implant having upper and lower toothed surfaces, a pair of parallel side surfaces, a pair of end surfaces and a plurality of openings extending between the side surfaces. The implant is constructed from an injection molded chopped carbon fiber reinforced polymer. The openings facilitate blood flow and bone growth from one side of the implant to the other. Steffee""s implant is adapted to receive an insertion tool which during insertion of the implant between adjoining vertebrae rotates the implant from a horizontal to a vertical orientation. During a surgical procedure, two of Steffee""s implants are positioned between adjoining vertebrae.
Conventional wedge-shaped intervertebral implants, including those described above, have several drawbacks. For example, although autograft wedges are known, e.g., iliac crest wedges, typically, conventional wedge-shaped implants are constructed from materials which do not remodel but rather remain in place forever or until removal is necessitated, i.e., at least some or all of the implant is not replaced by new bone, but rather the implant itself is incorporated into the body. Since the implants usually become adherent to the adjoining vertebrae, if removal of the implant is ever necessitated, the procedure to effect removal is complicated and dangerous to the patient. Moreover, in conventional wedge-shaped implants, the opening(s) to facilitate bone ingrowth extend transversely through the implant and as such do not open in communication with the adjoining vertebrae. Thus, bone ingrowth and eventual fusion will occur more slowly.
Accordingly, a need exists for an improved wedge-shaped intervertebral implant which can be easily manufactured from a material which will be remodeled within the body and will more quickly become adherent to adjoining vertebrae.
In accordance with the present disclosure, a ramp-shaped intervertebral implant which is constructed from animal or human cadaveric bone or bone composites, or from any biocompatible material having the requisite strength requirements suitable for implantation, is provided. The ramp-shaped implant includes a body having a first side, a second side and upper and lower surfaces. An opening extends through a central portion of the body between the upper and lower surfaces and a series of ridges are formed over at least a portion of at least one of the upper and lower surfaces. The implant decreases in height from the first end of the implant to the second end of the implant.
In a preferred embodiment, the implant is formed from the diaphysis or metaphysis of a long bone. More particularly, the implant is formed by first cutting a cortical ring from a long bone. Next, the cortical ring is secured within a holding fixture and the sidewalls of the cortical ring are machined to provide the implant with a desired shape. As such, the implant may retain its natural configuration or some or all of the sidewalls can be machined to form the implant to any configuration including rectangular, circular, C-shaped, etc. The intramedullary canal of the cortical ring defines an opening which extends from the top surface to the bottom surface of the implant. The implant is then placed in a second holding fixture and the top surface is machined to provide the appropriate taper and the ridges. These steps can be performed simultaneously using, for example, a three-dimensional computer operated milling machine. Alternately, the steps can be performed consecutively. Next, the implant is repositioned in the holding fixture and the bottom surface of the implant is machined to provide the appropriate taper and the ridges. The side surfaces may also be machined to vary the width of the implant along the longitudinal axis of the implant. A C-shaped implant can be formed by making a cut across the medial lateral plane of the cortical ring to expose the intramedullary canal. Thereafter, a ramp or taper can be provided in the anterior/posterior plane. Because the implant is constructed of bone, after insertion into the body of a patient, the implant will remodel within the body. New bone of a patient will eventually replace some or all of the implant. Thus, if removal of the implant is ever necessitated, the implanted bone and/or the remodeled bone can be easily reamed out. Moreover, since the opening extends between the top and bottom surfaces of the implant, bone growth material which is packed into the opening directly contacts the adjoining vertebrae. Thus, fusion of the implant and adjoining vertebrae will occur more quickly.
Alternately, the ramp-shaped intervertebral implant can be formed from any biocompatible material having the requisite strength requirements via any known process including but not limited to molding and machining.


A method for removing ammonia from fly ash employs water mist (a water fog) or a flowing warm humid air stream to rid the fly ash of ammonia. Ozone alone or with other co-oxidants such as hydrogen peroxide are also used to rid fly ash of ammonia.

The herein disclosed invention finds applicability in the field of coal combustion flue gas purification and more particularly in the field of fly ash purification.
Ammonia vapor comes into contact with fly ash in connection with several processes for NOx reduction or particulate capture in pulverized coal combustion, including selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), and electrostatic precipitator conditioning [Castle, 1980, Golden, 2001]. Typically some portion of the vapor phase ammonia adsorbs or deposits on fly ash with the potential to cause problems in ash utilization, handling, and disposal [Larrimore, 2000]. Of particular concern for disposal is the possibility for high ammonia contents in surface and groundwater near ash ponds [Golden, 2001] and at landfill sites in runoff, leachate and surrounding atmosphere [Lowe et al., 1989; Golden, D., 2001]. Problems in utilization arise not from degradation of concrete properties [Novak and Rych, 1989; Golden, 2001] but rather from worker exposure to odor, especially during enclosed concrete pours. Ammonia odors are perceived as a sufficiently serious nuisance that levels of 300 ppm or more by weight in ash (not uncommon in untreated fly ash streams from units with SCR systems), can effectively destroy the ash utilization market. Acceptable ammonia levels to avoid problems in utilization and disposal have been cited by different sources as less than 50, 60, or 100 ppm [Novak and Rych, 1989; Necker, 1989].
There are few publications in the archival scientific literature on ash/ammonia interactions, exceptions being the work of Janssen et al. [1986] which focused on catalysis of the NO/NH3 reaction and most notably the work of Turner et al. [1994], which focused on the mechanism of adsorption and its potential impact on the operation of flue gas treatment technologies. Recently, however, there has been a flurry of applied studies reported in the conference literature, patent literature, and in industry reports, motivated by current projections of widespread SCR unit installation in the U.S. in the coming years [Muzio et al., 1995; Hinton, 1999; Larrimore, 2000; Golden, 2001; Brendel et al., 2001; Levy et al., 201; Rubel et al., 2001; Ramme and Fischer, 2001; Bittner et al., 2001]. These sources discuss many aspects of the ammonia/ash problem and present a number of new ideas for remediation processes. The factors governing the extent of ammonia contamination are not fully understood, but are believed to depend on the concentration of unreacted ammonia leaving the SCR unit (the xe2x80x9cammonia slipxe2x80x9d), duct temperatures/time history, ash composition [Muzio et al., 1995], and SO3 concentration in the flue gas [Larrimore, 2000, Turner et al., 1994, Muzio et al., 1995]. Ammonia associated with fly ash can be in the form of ammonium sulfate or more commonly bisulfate particles [Golden, 2001; Rubel et al., 2001], or ammonia species adsorbed on carbon sites [Rubel, 2001], likely on carbon surface oxides, or mineral surfaces [Turner, et al. 1994]. Ammonia is well known to chemisorb on acidic surface sites [Sahu, et al., 1998], and indeed is extensively used as a titrant to characterize surface acidity [Gedeon et al., 2001].
Relevant Patents
1. U.S. Pat. No. 6,136,089, xe2x80x9cApparatus and Method for Deactivating Carbon in Fly Ashxe2x80x9d. This patent describes the use of ozone to improve the air entrainment behavior of fly ash by modifying the surface chemistry of unburned carbon, e.g., carbon passivation vs. ammonia reduction.
2. U.S. Pat. No. 6,077,494, xe2x80x9cMethod for Removing Ammonia from Ammonia Contaminated Fly Ashxe2x80x9d. This recent patent covers the use of very small amounts of water ( less than 5%), in the so-called semi-dry state. The patent makes no mention of method of water addition, requires intense mechanical agitation of the ash, and does not mention humid air, or ozone.
3. Japanese patent JP8187484A describes a process for removing ammonia that involves a humidifier. The process involves intense mechanical agitation and there is no mention of using warm humid air, which holds sufficient moisture that upon cooling in contact with co-flowing ash will deliver a uniform and controlled moisture level.
4. U.S. Pat. No. 5,069,720, U.S. Pat. No. 5,211,926, International patent 99/48563 describe the use of water to remove ammonia, but in large amounts that classify these as truly xe2x80x9cwetxe2x80x9d techniques.
Experimental Background
There is almost no information in the archival scientific literature on methods of ammonia removal from fly ash, despite great commercial interest in a variety of competing techniques [Larrimore, 2000, Golden, 2001], including thermal methods [Levy et al., 2001], combustion-based methods [Giampa, 2001], and water-based methods [Gasiorowski and Hrach, 2000; Katsuya et al., 1996; Hwang, 1999]. An objective of the present invention is to investigate the chemistry of room temperature methods for ammonia removal from fly ash using moisture and oxidizing agents, alone or in combination. In a study, special emphasis was placed on controlled addition of small amounts of moisture to avoid wet ash handling, so-called xe2x80x9csemi-dry processingxe2x80x9d, which is the basis for several industrial patents [Gasiorowski and Hrach, 2000; Katsuya et al., 1996], and on the use of ozone, which has recently been found to passivate unburned carbon surfaces in fly ash and thus improve air entrainment properties of problem ash streams [Gao et al., 2001].
Objects of the Invention
A main object of this invention is to remove ammonia from fly ash employing a minimum amount of water.
An important object of this invention is to remove ammonia from fly ash without sensibly wetting the fly ash with water.
A further object of the invention is to effectively use ozone for ammonia removal from fly ash, alone or in combination with moisture.
A still further object of this invention is to carry out the process of ammonia removal at temperatures under 150xc2x0 C.
These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed drawings.
The herein disclosed invention involves a process for ridding fly ash of ammonia that avoids the use of sensible moisture; but instead uses a water fog (water mist) or warm humid air.
The terms water fog and water mist are used interchangeably in this disclosure.
Also, disclosed by the invention is the use of ozone to rid the fly ash of ammonia.
A method of this invention for removing ammonia from fly ash comprises subjecting ammonia containing fly ash to a water mist wherein the water mist contacts the ammonia containing fly-ash and removes the ammonia from the fly ash. The water mist can be applied to the fly ash in a warm air environment or the mist can be applied in humid air. In a specific method of the invention, the fly ash is a basic fly ash and/or the water mist has a high pH. In another specific method for removing ammonia from fly ash, a water mist is applied to a co-flowing fly ash stream in controlled amounts to produce fly ash with uniform 1-5 wt-% moisture with water droplets being fine enough to remain suspended as an aerosol for uniform wetting of the dispersed ash after mist/ash mixing and afterwards the co-flowing suspension is subjected to gas/particle separation to yield a reduced-ammonia ash suitable for disposal/utilization and an ammonia-laden waste gas stream.
Another method for removing ammonia from fly ash comprises subjecting ammonia containing fly ash to a water fog (water mist) wherein the water fog or mist contacts the ammonia containing fly ash and removes the ammonia from the fly ash. The water fog can be applied in a warm environment. As a further embodiment, the fog is produced with an ultrasonic nebulizer in a flowing humid air stream flowing through an agitated fly ash bed. In the water fog process, the treated ash can be a basic ash or when the ash is an acid ash, it should be treated to make it basic. The fly ash can be mixed with additives, such as, Ca(OH)2 to make it basic. As an added feature of the water fog method, ozone, ozone-containing air or ozone-containing oxygen is used as the fog carrier gas, or is used as an additional step to further reduce the ammonia level in ash as well as to rid the fly ash of residual evolved ammonia and residual moisture. In a specific embodiment, a co-oxidant, such as, H2O2 solution is used as the liquid feed for fog generation.
A still further method for removing ammonia from fly ash comprises subjecting ammonia containing fly ash to warm humid air wherein the warm humid air contacts the ammonia containing fly-ash and dissolves and removes the ammonia from the fly ash. The method can be carried out by passing a stream of humidified air through a fixed bed of fly ash in up-flow configuration. The method for removing ammonia from fly ash can be based on the addition of warm humid air to a co-flowing fly ash stream of lower temperature. The temperature and flow rate of the humid air are controlled so that when the suspension is mixed and cooled to ambient temperature, water vapor condenses in an amount that constitutes 1-5 wt-% moisture in the solid ash for optimal semi-dry ammonia removal. After mixing of the fly ash and warm humid air, the co-flowing suspension is subjected to gas/particle separation to yield a reduced-ammonia ash suitable for disposal or utilization and, also, an ammonia-laden waste gas stream.
An additional important method of this invention is for reducing ammonia in fly ash comprising applying effective amounts ozone to the fly ash to reduce ammonia therein. In the ozone treating process, the fly ash can be in the dry or semi-dry state. The ozone application can be done in a co-flowing suspension, fluidized bed, or a mechanically agitated bed. As specific examples of the method, the ozone is applied at a concentration of about 2 Vol % and at a temperature of about 150xc2x0 C. in an amount of from 0-500 gm ozone/per Kg ash.
An important process of this invention for removing ammonia from fly ash comprises treating the fly ash with both low moisture and ozone treatment to accomplish dry or semi-dry ( less than 5 wt-% moisture) ammonia reduction at temperatures below 150xc2x0 C. A further method for ridding fly ash of ammonia comprises applying a mixture of effective amounts of hydrogen peroxide (H2O2) and ozone as co-oxidizing agents in a flowing fog
Materials and Experimental Procedures
Samples with reference to Tables 1-3 below
Four commercial ash samples were selected for this study from among the 80 ash samples in the Brown University ash sample bank [Kulaots, 2001]. Properties of the selected samples are shown in Tables 1 and 2. FA1 and FA2 are ammoniated ash samples, one with high and one with low pH, from two power stations in the New England region operating SNCR units and burning bituminous coals. FA3 and FA4 are typical non-ammoniated ashes from eastern and western U.S. coals respectively, and are used in experiments in which ammonia is loaded on the ash under a variety of laboratory conditions. Note that both the carbon content and the ammonia content of FA1 is unusually high. At 1060 ppm this ash has more than ten times the amount of ammonia that is commonly cited as the desired amount to avoid ash utilization problems [Larrimore, 2000]. The basic nature of FA1 is unusual for a class F ash whose alkaline and alkaline earth components sum to only 6.2 wt-% on a carbon-free basis (see Table 2). It can be shown by simple equilibrium calculations for the reaction NH3+H2Oxe2x86x92NH4++OHxe2x88x92 that this basicity is in part due to its very high ammonia content. Consider 1 gm of ash in 30 ml of water, as used in our pH measurement procedure. If the 1060 ppm of ammonia is completely desorbed from the surfaces into solution in the aqueous phase, a pH of 10.3 would be observed before significant volatilization occurred if the remainder of the ash constituents (mineral phases and carbon surfaces) were neutral. Thus part of the basicity of the ash can be attributed to the ammonia itself.
Experimental Procedures
Fly Ash Characterization
The ammonia content of a test fly ash sample was determined by mixing two grams of ash with 3 ml of 2 v/v-% H2SO4 and 37 ml distilled water. The suspension was dispersed in an ultrasonic bath for 5 minutes, and the solid ash was separated from the solution by a 10-minute centrifugation. The supernatant solution was then filtered and 30 ml used to measure ammonium ion concentration by specific ammonium ion electrode and Corning pH/ion analyzer model 455. Potassium ion is known to interfere with the accurate measurement of ammonia, but the potassium levels in the samples tested were too low for the interference to be significant (Table 2).
The acid/base character of test fly ash samples were measured by mixing 1 gm of ash with 30 ml distilled water and dispersing the particles in an ultrasonic bath for 5 minutes. After centrifugation and filtration as above, the pH of the solution was measured by a Corning pH/ion analyzer 455. The thermal desorption results were obtained with an Autosorb vapor adsorption apparatus used in out gassing mode to desorb NH3 from 3-5 gm ash samples as a function of temperature and time under vacuum.
Experiments in Static Humid Air
Ash samples were enclosed in a laboratory desiccator adjacent to calibrated aqueous solutions designed to provide gas environments of known H2O and/or ammonia partial pressure. In the first type of experiment, 5 gms of an ammonia-containing fly ash was placed in a 50xc3x979 mm dish and loaded into a 150 mm desiccator. A separate 90xc3x9750 mm dish was prepared with 40 ml of standard salt solutions designed to provide fixed relative humidity according to the procedure of Wexler et al. [1991]. Using 20 gm salt in 40 ml of water at 25 C. the relative humidity (RH) values are 75% (NaCl), 84% (KCl), 92% (KNO3). Both the ammonia content and the moisture content of the ash samples were measured before and after exposure.
The second type of experiment is identical to the first, except that calibrated solutions of ammonium salts were used instead of KCl, NaCl, or KNO3. Dilute ammonium hydroxide solutions were prepared at various concentrations and the ammonia vapor concentration measured in the desiccator for calibration [Fujisaki, 2000]. These experiments create vapor environments with both H2O and NH3 and, although designed to load NH3 onto ash, in fact are capable of producing a net adsorption or net desorption of ammonia on/from ash, depending on ash type and conditions.
Experiments in Flowing Humid Air
A fixed/fluidized bed reactor was used to contact ash with a continuous stream of air at a fixed relative humidity. Ten grams of ash were placed in a 25 mm diameter glass tube fitted with a porous glass distributor disc at the bottom with 0.15-0.18 mm pores and subjected to continuous mechanical vibration. The air flow to the reactor bottom was set at either 0.3 lit/min or 0.8 lit/min and was pre-humidified in a series of two water-filled tubes, while the humidity was measured at the reactor inlet using a digital hygrometer with an accuracy of xc2x12% RH. Ash moisture and ammonia contents were measured before and after treatment by ion electrodes as described above.
Experiments with Flowing Fog
These experiments were similar to those in humid air, but an ultrasonic nebulizer was used to introduce ultrafine water droplets to the humidified air upstream of the contact vessel, and some mechanical stirring was carried out manually or with a magnetic stir bar. Here 10 gm of ash was placed in a 40 mm diameter reactor fitted with the same porous distributor (0.15-0.18 mm pore size) and exposed to a fog-containing upward airflow of 0.7 lit/min. After water addition the sample was removed and the ammonia content measured. Half of the sample (5 gm) was returned to the glass reactor and dried in flowing air without water mist at a flow rate of 0.3 lit/min. The time between the end of the fog treatment and the beginning of the drying stage was always 1 minute. All experiments were at ambient temperature.
Additional experiments were conducted for acidic ashes in which basic additives, NaOH or Ca(OH)2, were introduced into the liquid feed for fog generation. As an alternative, the basic additives can also be added as a dry powder to the ash prior to treatment. In another variant on the basic experiment, ozone-containing air or oxygen was used in place of pure air as the dry-off gas or fog carrier gas. In yet another variant of the basic experiment 30 wt-% H2O2 solution was employed as the liquid feed for fog generation in place of water. Joint treatment with ozone and H2O2 is the xe2x80x9cperoxonexe2x80x9d route to aqueous ammonia oxidation [Kuo et al., 1991]. Experiments were also carried out in which dry ozone-containing air or oxygen were passed through the fixed bed of ash without moisture addition.
Results and Discussion
FIGS. 1-4, 6-11 and Table 3 summarize the experimental results. FIG. 1 describes vacuum thermal desorption behavior of two ammonia containing ash samples from the field. FIG. 1 shows that 200xc2x0 C. is insufficient to remove significant ammonia, but that a majority of the ammonia in these ash samples can be removed by thermal treatment alone at 300xc2x0 C. FIG. 1 also shows that the required desorption times are long at 300xc2x0 C., either due to desorption/decomposition kinetics or to slow diffusion through the deep sample beds. This simple thermal desorption experiment does not provide sufficient information to positively identify the ammonia form or forms, but significant evolution does occur at temperatures characteristic of ammonium bisulfate compositions (decomposition onset 214xc2x0 C. in inert [Rubel et al., 2001]).
FIGS. 2-8, 10, 11 and Table 3 summarize a large set of ammonia-removal experiments using controlled amounts of moisture at ambient temperature. FIG. 2 presents results from the earliest set of experiments, those using static humid air in closed desiccators. The plot shows that ammonia can be completely removed from the high-pH ash, FA1, simply by placing it near a dish with an aqueous salt solution to create an atmosphere of controlled humidity, i.e., under conditions where no liquid water is added directly to the ash sample.
Exposure to static humid air is observed to increase ash moisture content from about 0.8% initially to values ranging form 1.3-1.9%. It is believed that slight condensation in and around the individual ash/carbon particles causes the ammonia species to desorb, enter solution, and be converted to the highly volatile NH3 form according to:
NH3(aq)+H2O (liq)⇄NH4+(aq)+OHxe2x88x92(aq)xe2x80x83xe2x80x83(1a)
NH3(aq)⇄NH3(vap)xe2x80x83xe2x80x83(1b)
NH3 is highly volatile so equilibrium 1b favors partitioning to the vapor phase, while equilibrium 1a is highly dependent on solution pH. The combined reaction system (1a and 1b) leads to NH3 as the predominant species and thus, leads to extensive ammonia volatilization whenever pH values are greater than about 10 in the condensed film. Water vapor is always below saturation in the FIG. 2 experiments, so partial condensation occurs by adsorption on surfaces and capillary condensation in pores and fine intraparticle spaces. It is notable that ammonia removal can occur with the addition of so little liquid water (1.3-1.9 wt-%) that ash handling characteristics are not greatly affected.
FIG. 2 describes results of experiments on ammonia removal in static humid air. Initial ash moisture contents were 0.82 wt-% for FA1, and 0.80 wt-% for FA2. Moisture contents of selected treated ash samples shown on this figure were as follows: 1.3% for FA2 at RH84 (20 hrs); 1.6% for FA2 at RH94 (20 hrs); 1.6% for FA1 at RH84 (20-60 hrs); and 1.9% for FA1 at RH92 (20 hrs). FIG. 2 also shows that the process is not effective for the low-pH ash, FA2. The critical role of solution pH is further illustrated in FIG. 3, which presents results for two acidic and two basic ashes placed in proximity to aqueous ammonia solutions. The standard solutions were designed to create vapor environments with known partial pressures of ammonia. Although the original goal of these experiments was to load ammonia onto ash, it was found that this exposure can either increase or decrease ash ammonia content depending on ash type. Both acidic ashes (FA2,3) adsorbed ammonia from the solutions, as expected (see FIG. 3). but the basic ash, FA1, experienced a large ammonia loss. Further, adding a basic additive to the acidic ash, FA3, eliminated the uptake completely. Additional experiments on other ash samples show the same trends with pH [Fujisaki, 2001]. We conclude that in the presence of near-saturated humid air, we can remove but not add ammonia to basic ashes, and conversely we can add but not remove ammonia from acidic ashes.
FIG. 3 illustrates effect of pH on the removal or addition of ammonia in static mixtures of humid air and ammonia vapor (700 ppm) established with a calibrated ammonium hydroxide solution. The basic additive was CaO as a dry powder added to the ash. Similar results were obtained when CaO was added in solution, or using Ca(OH)2 either as a dry powder or in solution. These results combinedly show that the ammonia release is governed by solution chemistry as embodied by Eq. 1, despite the very low moisture levels. It appears that above 1-2% moisture, a water film forms in and around individual particles and is sufficiently continuous to dissolve the adsorbed or deposited ammonia and to mediate its release in a way that is at least qualitatively similar to bulk solution behavior. This is not an obvious result considering the dry physical appearance of the ash and the lack of macroscopic evidence of a continuous water phase. The effectiveness of small amounts of water is claimed in several process patents [Gasiorowski and Hrach, 2000; Katsuya et al., 1996] where the authors quote the advantages of rapid ammonia release and quasi-dry ash handling. We demonstrate here that even exposure to static humid air can bring about these effects.
A more effective contacting scheme employs a continuous stream of humidified air passed through a fixed bed of ash in upflow configuration. FIG. 4 shows the results of ammonia removal experiments in flowing humid air (RH 93%) passed upward through 10 gm fixed beds of ash at one of two different flowrates. Sample: basic fly ash, FA1. FIG. 4 also illustrates that this contacting method is effective at removing ammonia from the basic ash at moisture levels of less than 3 wt-%. The rate of removal increases with increasing moisture content, but the total contact times are still long. The long times are believed to be the result of (1) the slow rate of water addition due to the limited carrying capacity for water vapor in room temperature air (0.023 mole fraction), (2) the low driving force for water addition to the solid phase, which at these subsaturated conditions is driven by adsorption and capillary condensation, and (3) slow diffusion of dissolved species within the microscopic water film.
The structure and properties of the water film can be appreciated by several simple calculations. For example, FIG. 5 describes the thickness of uniform water film on collection of ideal, nonporous, monodisperse spherical particles of typical mineral density, 2.2 g/cmxe2x88x923. This calculation demonstrates that the water film produced by most humid air and flowing fog experiments (moisture contents 1-5%) have sub-micron mean dimensions. FIG. 5 further shows the geometric relationship between moisture content and water film thickness for an ideal ensemble of monodisperse, non-contacting spheres of density 2.2 gm/cm3, similar to the density of mineral phases in fly ash. The small amounts of water employed here give rise to a nominal film thickness well below 1 mm. For the humid air experiments, we further expect the water film to be highly non-uniform, consisting of very thin mono- or multi-layer adsorbed films on external particle surfaces or large pore surfaces in carbon, coexisting with bulk moisture in fine pores and fine neck regions lying at points of particle contact. The Kelvin equation describes this sub-saturation condensation, and for the simple case of spherical geometry yields a maximum size of filled pores (or filled particle interstitial regions) of 1.5 nm at 50% RH, 5 nm at 80% RH, and 21 nm at 95% RH under these conditions. We therefore expect bulk water only in nanometric (meso) pores and nanometric interstitial regions. We expect much of the ash surface to be covered only by a multi-layer adsorbed film, making the water phase only semi-continuous and leading to slow diffusion of dissolved species. On the other hand, desorption may be aided by the fact that ammonium salts and adsorbed ammonia species may serve as attractive sites for preferential water adsorption or condensation.
Flowing Fog.
In an attempt to reduce required contact times, experiments were performed in which 2-3 wt-% water is introduced quickly to the ash using an ultrasonic nebulizer to create a fine fog in the flowing humid air stream. The ultrafine water droplets remain in a quasi-stable aerosol as they pass through the porous distributor disk and enter the agitated ash bed. FIG. 6 shows the effect of the fog on ammonia removal under a variety of conditions and further describes results of ammonia removal with flowing fog followed by air drying to remove untreated mist or fog from the ash (sample: basic ash, FA1). The extent of moisture addition is varied by varying the total fog generation time from 2-8 minutes. Moisture-in-ash measurements are shown on graph at the end of the fog addition prior to the start of air drying. FIG. 7 describes ammonia removal by flowing fog. Plot shows time resolved values of both ash moisture and ammonia content during fog addition and air drying. Multiple points at 3 minutes represent duplicate experiments. These experiments take place in two parts: a fog addition stage lasting 2-8 minutes followed by a drying stage in air lasting 4-30 minutes. The labeled data points give the ash moisture content at the end of the fog stage and prior to the onset of drying. As moisture levels rise above 2 wt-%, ammonia liberation becomes very rapid.
Adding 3.3 wt-% water in 2 minutes drives off over half of the adsorbed ammonia with no drying time. FIG. 7 shows the time resolved measurements of both ammonia and ash moisture in another flowing fog experiment. At moisture levels above 3 wt-% ammonia removal is rapid, but the rate falls off quickly when moisture levels drop to about 2% during the subsequent drying stage. These combined results show promise for practical processes involving rapid uniform addition of small amounts of moisture followed by limited air drying to achieve high levels of ammonia removal.
Flowing fog treatment produces rapid ammonia release, but was observed in separate experiments to be ineffective for acidic ashes which represent a technologically important fly ash class. Several industrial patents [Gasiorowski and Hrach, 2000; Katsuya et al., 1996] and the results of FIG. 2 in static humid air suggest that acidic ashes can be successfully treated after introduction of inexpensive basic additives. FIG. 8 and Table 3 confirm this behavior for the flowing fog treatment using NaOH solutions for fog generation (Table 3) or Ca(OH)2 added as a dry powder to the ash.
FIG. 8 describes the effect of dry Ca(OH)2 as basic additive on ammonia removal from acidic ash (FA2) with flowing fog. Moisture levels in the ash were similar in the 5 experiments, ranging from 3.3% to 3.9% directly after fog addition, and ranging from 2.1% to 2.7% after drying.
Experiments with Ozone.
FIG. 9 describes reduction in fly ash ammonia content by dry ozone treatment (sample: 8 gm bed of basic fly ash, FA1). Flowrate: 2 lit/min; contact time: 30 minute. FIG. 9 shows the effect of ozonation on ammonia under dry conditions as a function of ozone concentration and temperature. Ozone reduces ash ammonia content under all conditions, but the truly significant reductions are observed at higher concentration (2 vol-%) and temperature (150xc2x0 C.). The primary measurement in these experiments is residual ammonia on ash, and thus the data do not directly distinguish between removal and destruction, although direct oxidative attack leading to destruction of on ammonia species is the most likely mechanism. The experiment in oxygen alone proves that gas stripping is not responsible for the loss of ammonia.
The cumulative amount of ozone fed to the reactor in these FIG. 9 experiments ranged from 64 to 320 gm-ozone/kg ash and is a factor of 15-100 higher than the minimum theoretical stoichiometric requirement for complete NH3 oxidation to nitrate and water. This high ozone usage is likely due to kinetic limitations of the ozone/ammonia reaction and to competition from the fast ozone/carbon chemisorption reaction [Gao et al., 2001]. The ozone/carbon chemisorption reaction is known to improve the air entrainment behavior of these high carbon ashes by reducing hydrophobic surface area [Gao et al., 2001], but here the reaction rapidly consumes ozone that would otherwise be available for ammonia destruction. The extent of ammonia removal/destruction by ozone increases with increasing temperature to 150xc2x0 C., further suggesting kinetic limitations for this reaction.
Several experiments were conducted to explore whether ozone has a beneficial effect during the drying stage of wet ammonia removal processes, which could eliminate the need for off-gas treatment. FIG. 10 shows experiments in which 3 vol-% ozone was substituted for the drying air in the flowing fog experiment. This plot shows that the ammonia removal is sensitive to the moisture content directly after fog addition (as observed previously), and that ozone has no substantial enhancing effect on ammonia release. It is likely that the release of ammonia from the liquid phase is too fast under these conditions to allow the aqueous reaction with ozone to be effective.
In acidic ashes by contrast the ammonia species remain in solution where they may be available for aqueous oxidative attack. FIG. 11 shows the effect of H2O2 and ozone as joint (peroxone) oxidizing agents during the semi-dry treatment of the acidic ash FA2 with flowing fog. FIG. 11 teaches the effect of H2O2/O3 fog on ammonia removal/destruction from acidic ash (FA2). Fog contained 30 wt-% H2O2 and was transported using 0.7 lit/min of 3% ozone in oxygen. The drying stage used 0.3 lit/min of 5% ozone in dry oxygen. Moisture levels in the ash were similar in the 4 experiments, ranging from 12.7% to 13.7% directly after fog addition, and ranging from 6.1% to 7.2% after drying. Only modest reductions in ammonia are observed over a 60 minute treatment interval. Ammonia ozonation is heavily favored by thermodynamics, so this result implies slow kinetics, again with likely competition from the ozone carbon reaction. Peroxone oxidation is known to attack dissolved ammonia preferentially to ammonium ion, and the kinetics are thus sharply pH dependent [Kuo et al., 1991]. Under these conditions the peroxone kinetics are too slow to achieve substantial ammonia reductions, likely due to low concentrations of dissolved ammonia at the prevailing low pH. Perversely, at high pH ammonia is rapidly evolved, so rapid peroxone destruction of ammonia would require careful control of intermediate pH, if indeed it is possible at all.
FIG. 10 shows the effect of ozone addition during the drying stage of ammonia removal (sample: basic fly ash, FA1). The ozone containing stream was 3 vol-% ozone in air.
The disclosed invention demonstrates that ammonia species can be removed from fly ash at or near room temperature by a variety of dry and semi-dry techniques. Rapid ammonia removal occurs from a microscopic water film on surfaces, in fine pores, and in ash particle interstitial regions whenever the film pH is highxe2x80x94achieved either by dissolution of the natural basic components of the ash or by the separate introduction of soluble basic additives. Flowing humid air and flowing water aerosol (fog) as used in this invention are promising methods for the uniform addition of small amounts of water to fly ash for semi-dry ammonia removal. Ozone is capable of destroying ammonia on ash in the dry state, but is less effective under semi-dry conditions due to kinetic limitations on the aqueous phase reaction.
The use of ozone has an advantage in that no chemical residue is left in the ash since ozone decomposes shortly after use into molecular oxygen.
In the past a variety of processes have been proposed for removing or destroying ammonia in fly ash, but they involve either large amounts of water, intense mechanical agitation, high temperature, or aggressive chemical agents that remain in the ash. The herein disclosed invention suggests methods for dry or semi-dry reduction in ash ammonia contents at or near room temperature without the need for intense mechanical agitation or long-lived chemical additives.
The herein disclosed invention describes a method for removing ammonia from fly ash. Ammonia on fly ash is a by-product of the combustion of coal. When fly ash is used as a concrete additive, it is desirable to have the ammonia removed from the fly ash. Applying water to the ammonia-bearing fly ash causes the ammonia to detach and to be dissipated into the atmosphere. The addition of high pH liquid will cause the release of ammonia. The amount of ammonia on the fly ash can be up to 2,000 ppm. The amount of water aerosol relative to total ammonia containing fly ash can be 1 to 5%. The overall temperature of the process is not critical. Ambient temperature would be operative. A temperature which is too high would not allow for the effective removal of ammonia. The process can be carried out in a fly ash stream. Note, also, that a high pH can be used to convert the ammonia salt to ammonia.
The invention seeks to optimize the amount of water relative to the overall amount of fly ash. It is desirable not to use any excess amount of water. The small amount of water can be applied as an aerosol or a fog. A film is formed around the particles of the fly ash. The process can be carried out with all components in suspension. The particles are fine. The process can be carried out in a fluid bed or in a pneumatic system. During the moisture treatment, the particles of fly ash release ammonia. Note that ammonia gas is poorly soluble in water.
The invention also involves simultaneously adding ozone and water fog (mist) to the fly ash to achieve enhanced ammonia removal/destruction.
Examples of the Process
1. A process for removing ammonia from fly ash based on addition of fine water mist to a co-flowing fly ash stream in controlled amounts to produce fly ash with uniform 1-5 wt-% moisture. The water droplets must be fine enough to remain suspended as an aerosol for uniform wetting of the dispersed ash. After mist/ash mixing, the co-flowing suspension is subjected to gas/particle separation to yield a reduced-ammonia ash suitable for disposal or utilization and an ammonia-laden waste gas stream.
2. A process for removing ammonia from fly ash based on addition of warm humid air to a co-flowing fly ash stream of lower temperature. The temperature and flow rate of the humid air are controlled so that when the suspension is mixed and cooled to ambient temperature, water vapor condenses in an amount that constitutes 1-5 wt-% moisture in the solid ash for optimal semi-dry ammonia removal. After mixing of the fly ash and warm humid air, the co-flowing suspension is subjected to gas/particle separation to yield a reduced-ammonia ash suitable for disposal or utilization and an ammonia-laden waste gas stream.
3. A process for reducing the ammonia content of fly ash by contacting an ozone-containing gas with fly ash in the dry or semi-dry state. A variety of contacting methods can be used, including co-flowing suspension, fluidized beds, and mechanically agitated beds.
4. A process that combines two or more of the above features to accomplish dry or semi-dry ( less than 5 wt-% moisture) ammonia reduction at temperatures below 150xc2x0 C.

Dry and semi-dry methods for removal of ammonia from fly ash


The invention relates to a process for repairing coated substrate surfaces comprising the following successive steps:

The invention relates to a process for repairing coated substrate surfaces by means of radiation-curable coating compositions. The process may find application particular for repairing small coating blemishes in automotive and industrial coating.
It is known to use coating compositions curable by high-energy radiation in automotive coating and likewise in automotive repair coating. Coating compositions based on free-radically polymerizable binders are in particular used in such applications. This application also utilizes the advantages of radiation-curable coating compositions, such as, the very short curing times, the low solvent emission of the coating compositions and the good hardness and scratch resistance of the resulting coatings.
When repairing coating blemishes, it is often unnecessary to completely recoat an entire vehicle or vehicle part, for example, a bonnet. In the case of small coating blemishes, it is usually sufficient to recoat the area immediately surrounding the blemished area (spot repair). The preparation, coating and clean-up effort expended by the finisher is here largely independent of the size of the coating blemish to be repaired. For example, operations, such as, preparing the coating material and spray gun, putting on the breathing mask, applying the coating with a spray gun, cleaning the spray gun and other equipment or containers must always be carried out.
There is accordingly a requirement in repair coating for a simplified processes to repair small coating blemishes, in particular also in those cases in which only a top coat is to be repaired.
Prior art processes are known in which, as an alternative to conventional spray application, coated films are applied onto the substrate to be treated, for example, an automotive body. The films may here be provided on one side with one or more coating layers and may have on the same or the other side an adhesive layer so that the film can be fixed to the substrate. Where appropriate binders are used, the coating and/or adhesive layers may also be cured by ultraviolet light (UV) radiation. Such films and corresponding application processes have often been described in the literature, for example in WO-A-00/08094, WO-A-00/63015, EP-A-251 546 and EP-A-361 351. In general, the film is laminated onto the substrate, where it remains. DE-A-196 54 918 describes coating film usable for decorative purposes that comprises a xe2x80x9cfree coating filmxe2x80x9d. The coating film comprises an adhesive layer and at least one coating layer. It is possible to dispense with a stabilizing backing film in this case.
The process according to the invention provides a process for repairing coated substrate surfaces by means of radiation-curable coating compositions, which process is in particular suitable for repairing small blemished areas, for example, in the context of repair coating in automotive original coating or in a repair bodyshop and permits the performance of the repair to the required quality quickly and straightforwardly without major preparation and clean-up effort.
The present invention relates to a process for repairing coated substrate surfaces comprising the following successive steps:
a) optionally preparing a blemished area to be repaired,
b) providing a backing film coated on one side with an uncured or at least partially cured coating layer of a coating composition curable by means of high energy radiation,
c) applying the backing film with its coated side onto the blemished area to be repaired,
d) irradiating the coating applied in this manner onto the blemished area to be repaired with high energy radiation and
e) removing the backing film, wherein
the coating is irradiated through the backing film and/or after removing the backing film.
It has surprisingly been found that, using the process according to the invention, it is possible quickly and straightforwardly to repair in particular small coating blemishes without any reduction in quality in comparison with conventional processes. Smooth, optically faultless surfaces are obtained which have the good hardness and solvent resistance typical of UV cross-linking systems.
Steps d) and e) are preferably performed in such a manner that irradiation proceeds through the backing film, the backing film is removed after irradiation and irradiation is optionally performed again after removal of the backing film. It is also possible, but less preferred, to irradiate the coating only after removal of the backing film.
The individual steps of the process according to the invention are explained in greater detail below.
In general, the blemished area to be repaired is prepared prior to the repair. In this case, the process according to the invention begins with step a), namely preparation of the blemished area to be repaired. This involves preparing the damaged coating in accordance with the requirements of the repair. Normally, the coating is initially thoroughly cleaned, for example, with a silicone remover. The surface may then be sanded lightly with rubbing compound or sandpaper and optionally cleaned once again. If necessary, a putty composition, for example, may be applied and appropriately post-treated. Alternatively, the blemished area may also be prepared by laser treatment.
Step b) of the process according to the invention comprises the provision of a backing film coated on one side with an uncured or at least partially cured coating layer of a coating composition curable by means of high energy radiation. The backing film comprises films made from any desired, in particular thermoplastic, plastics that meet certain requirements with regard to UV transmittance and heat resistance. In the case of the preferred embodiment of irradiation in which high energy radiation is passed through the backing film, the films must transmit UV radiation and be resistant to the temperatures that arise in the film material on irradiation with UV radiation. The films must also be resistant to the temperatures optionally required for partially gelling/tackifying the applied coating layer. Suitable film materials are, for example, polyolefins, such as, polyethylene, polypropylene, polyurethane, polyamide and polyesters, such as, polyethylene terephthalate and polybutylene terephthalate. Films may also consist of polymer blends and also may be optionally surface-treated. It is also possible for the films to have a textured surface, for example, a micro- and/or macrotextured surface. The thickness of the films may, for example, be between 10 and 1000 xcexcm, preferably, between 10 and 500 xcexcm, particularly preferably, between 20 and 250 xcexcm and is determined by practical considerations of processability. The films selected should preferably be those that are elastic and extensible and cling effectively to the substrate by electrostatic forces.
The backing films are coated on one side with liquid or pasty coating compositions curable by means of high energy radiation. The coating compositions may be aqueous, diluted with solvents or contain neither solvents nor water. The coating compositions curable by irradiation with high energy radiation are cationically and/or free-radically curable coating compositions known to the person skilled in the art, wherein free-radically curable coating compositions are preferred.
Cationically curable coating compositions that are to be applied onto the backing film in the process according to the invention contain one or more cationically polymerizable binders. These may comprise conventional binders known to the person skilled in the art, such as, polyfunctional epoxy oligomers containing more than two epoxy groups per molecule. These comprise, for example, polyalkylene glycol diglycidyl ethers, hydrogenated bisphenol A glycidyl ethers, epoxyurethane resins, glycerol triglycidyl ether, diglycidyl hexahydrophthalate, diglycidyl esters of dimer acids, epoxidised derivatives of (methyl)cyclohexene, such as, for example 3,4-epoxycyclohexylmethyl (3,4-epoxycyclohexane) carboxylate or epoxidized polybutadiene. The number average molar mass of the polyepoxy compounds is preferably below 10,000. Reactive diluents, such as, cyclohexene oxide, butene oxide, butanediol diglycidyl ether or hexanediol diglycidyl ether, may also be used.
The cationically curable coating compositions contain one or more photoinitiators. Photoinitiators that may be used are onium salts, such as, diazonium salts and sulfonium salts.
Free-radically curable coating compositions that are preferably to be applied onto the backing film in the process according to the invention contain one or more binders with free-radically polymerizable olefinic double bonds. Suitable binders having free-radically polymerizable olefinic double bonds that may be considered are, for example, all the binders known to the skilled person that can be cross-linked by free-radical polymerization. These binders are prepolymers, such as, polymers and oligomers containing, per molecule, one or more, preferably on average 2 to 20, particularly preferably 3 to 10 free-radically polymerizable olefinic double bonds. The polymerizable double bonds may, for example, be present in the form of (meth)acryloyl, vinyl, allyl, maleate and/or fumarate groups. The free-radically polymerizable double bonds are particularly preferably present in the form of (meth)acryloyl groups.
Both here and below, (meth)acryloyl or (meth)acrylic are respectively intended to mean acryloyl and/or methacryloyl or acrylic and/or methacrylic.
Examples of prepolymers or oligomers include (meth)acryloyl-functional poly(meth)acrylates, polyurethane (meth)acrylates, polyester (meth)acrylates, unsaturated polyesters, polyether (meth)acrylates, silicone (meth)acrylates, epoxy (meth)acrylates, amino (meth)acrylates and melamine (meth)acrylates. The number average molar mass Mn of these compounds may be, for example, 500 to 10,000 g/mole, preferably 500 to 5,000 g/mole. The binders may be used individually or as a mixture. (Meth)acryloyl-functional poly(meth)acrylates and/or polyurethane (meth)acrylates are preferably used.
The prepolymers may be used in combination with reactive diluents, i.e., free-radically polymerizable low molecular weight compounds with a molar mass of below 500 g/mole. The reactive diluents may be mono-, di- or polyunsaturated. Examples of monounsaturated reactive diluents include: (meth)acrylic acid and esters thereof, maleic acid and semi-esters thereof, vinyl acetate, vinyl ethers, substituted vinylureas, styrene, vinyltoluene. Examples of diunsaturated reactive diluents include: di(meth)acrylates, such as, alkylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, vinyl (meth)acrylate, allyl (meth)acrylate, divinylbenzene, dipropylene glycol di(meth)acrylate, hexanediol di(meth)acrylate. Examples of polyunsaturated reactive diluents are: glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate. The reactive diluents may be used alone or in mixture.
Preferred free-radically curable coating compositions contain one or more photoinitiators, for example, in quantities of 0.1 to 5 wt-%, preferably of 0.5 to 3 wt-%, relative to the sum of free-radically polymerizable prepolymers, reactive diluents and photoinitiators. Examples of photoinitiators are benzoin and derivatives thereof, acetophenone and derivatives thereof, for example 2,2-diacetoxyacetophenone, benzophenone and derivatives thereof, thioxanthone and derivatives thereof, anthraquinone, 1-benzoylcyclohexanol, organophosphorus compounds, such as, acylphosphine oxides. The photoinitiators may be used individually or in combination.
It is possible, although less preferred, for the coating compositions curable by means of high energy radiation to contain, in addition to the binder components free-radically and/or cationically polymerizable by means of high energy radiation, or in addition to the free-radically and/or cationically polymerizable functional groups, further binder components or further functional groups that are chemically cross-linkable by an additional curing mechanism. Further chemically cross-linking binders that may preferably be used are one-component binder systems, for example, based on OH-functional compounds, amino resins and/or blocked polyisocyanates and those based on carboxy-functional and epoxy-functional compounds. Moisture-curing binder components are also possible, for example, compounds with free isocyanate groups, with hydrolyzable alkoxysilane groups or with ketimine- or aldimine-blocked amino groups. In the event that the coating compositions contain binders or functional groups that cure by means of atmospheric humidity, certain conditions must be maintained during preparation of the coating backing films in order to avoid premature curing. This issue is addressed in greater detail below in the description of the form of the coated backing film. The additional functional groups and the free-radically and/or cationically polymerizable functional groups may be present in the same binder and/or in separate binders.
The coating compositions that may be used in the process according to the invention for coating the backing film may be pigmented or unpigmented coating compositions. Unpigmented coating compositions are, for example, coating compositions formulated in conventional manner as clear coats. Pigmented coating compositions contain colour-imparting and/or special effect-imparting pigments. Suitable colour-imparting pigments are any conventional coating pigments of an organic or inorganic nature. Examples of inorganic or organic colour-imparting pigments are titanium dioxide, micronized titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone or pyrrolopyrrole pigments. Examples of special effect-imparting pigments are metal pigments, for example, made from aluminium or copper; interference pigments, such as, metal oxide coated metal pigments, titanium dioxide coated mica.
The coating compositions may also contain transparent pigments, soluble dyes and/or extenders. Examples of usable fillers are silicon dioxide, aluminium silicate, barium sulfate, calcium carbonate and talc.
The coating compositions may also contain conventional coating additives. Examples of conventional coating additives include levelling agents, rheological agents, such as, highly disperse silica or polymeric urea compounds, thickeners, for example, based on partially cross-linked, carboxy-functional polymers or on polyurethanes, defoamers, wetting agents, anticratering agents, catalysts, antioxidants and light stabilizers based on HALS products and/or UV absorbers. The additives are used in conventional amounts known to the person skilled in the art.
The coating compositions may contain water and/or organic solvents. The latter comprise conventional organic coating solvents known to the person skilled in the art.
The coating compositions curable by means of high energy radiation may be applied onto the backing film by conventional methods, for example, by brushing, roller coating, pouring, blade coating or spraying. The coating composition may be applied as a melt or in the liquid phase, for example, as a solution. The coating compositions may, for example, be blade coated as a solution. In the subsequent drying process, the solvent is allowed to evaporate, optionally, with gentle heating. The coating must in no event be completely cross-linked during the drying process. The dried, uncross-linked coating should advantageously be slightly tacky at room temperature in order to ensure good adhesion onto the substrate to be repaired. The coating may either be intrinsically tacky due to specially formulated binders or tackiness may be achieved by slight partial cross-linking/gelling of the dried coating, for example, by heating and/or by UV irradiation. The coating compositions curable by means of high energy radiation are generally applied in layer thickness of 1 to 100 xcexcm, preferably of 5 to 60 xcexcm.
It is in principle possible, although not preferred, for the backing film to be provided with more than one coating layer, for example, with a pigment base coat and a transparent clear coat. In the latter case, the clear coat would first be applied onto the backing film and then the base coat would be applied onto the clear coat, for example, wet-on-wet and optionally, after a flash-off phase.
One possible development of the coating backing film consists in applying the coating with a layer thickness that reduces towards the edges of the film so that, when it is subsequently applied, edge marks in the existing coating are avoided.
In order to facilitate subsequent removal of the backing film from the substrate to be repaired, it may be advantageous to leave at least one edge zone of the backing film uncoated. It may also be advantageous to provide a special finish on the side of the backing film that is to be coated, for example, a release coating, or to use special surface-treated films, for example, films surface-modified with silicate layers, in order, on removal of the backing film, to facilitate detachment from the coating that is fixed to the substrate to be repaired.
It may also be advantageous to provide the coated backing film with a temporary protective film to provide protection. The protective film may here be present only on the coated side of the backing film, but it may also be applied onto both sides and completely enclose the entire coated backing film. The latter possibility would in particular be advisable in the event of presence of the above-described moisture-curing binder or functional groups in order to exclude atmospheric humidity. In order to protect the coating on the backing film from premature polymerisation brought about by UV radiation, a transparent or colored, for example, a black film material that does not transmit UV radiation may be used advantageously. For example, a black polyethylene film may be used. In order to facilitate detachment of the protective film, it too may also be provided with non-stick properties, as described above.
The coated films, optionally provided with protective film or protective envelope, may be prefabricated and stored in the most varied shapes and sizes, for example, in sizes of 0.5 cm2 to 400 cm2, preferably of 1 cm2 to 100 cm2. The films may also be stored as a reel of continuous film.
After provision of a coated backing film and removal of an optionally present protective film or protective envelope, the backing film is applied with its coated side onto the blemished area to be repaired in accordance with step c) of the process according to the invention. Favourably, a film sheet size is selected that perfectly fits over the blemished area, taking account of any uncoated edge zones or layer thicknesses that reduce towards the edges. As already mentioned, the blemished area may be sanded lightly or roughened before application of the coated backing film in order to ensure good adhesion. The film then is laminated onto the substrate, preferably with exposure to pressure and, optionally, heat, so fixing the coating onto the substrate to be coated. This can be carried out, for example, with a heatable roller, such as, a rubber roller. Coating layers comprising a blemished area to be repaired that may be considered are, for example, electrodeposition coated substrates, putty, primer, filler and base coat layers, but in particular, clear coat and single layer top coat layers. The coated backing film may here be applied either onto the damaged coating layer or onto an underlying layer. The latter case arises, for example, if the blemished area is sanded down to one of the underlying coating layers, for example, during preparation for the repair.
After application of the coated backing film with its coated side onto the blemished area to be repaired, the coating applied in this manner is irradiated with high energy radiation, preferably with UV radiation. Irradiation may here be performed through the backing film and/or the coating is directly irradiated after removal of the backing film.
The preferred source of radiation comprises UV radiation sources emitting UV light in the wave length range from 180 to 420 nm, in particular from 200 to 400 nm. Examples of such UV radiation sources are optionally doped high, medium and low pressure mercury vapour emitters, gas discharge tubes, such as, low pressure xenon lamps and UV lasers.
Apart from these continuously operating UV radiation sources, however, it is also possible to use discontinuous UV radiation sources. These are preferably so-called high-energy flash devices (UV flash lamps for short). The UV flash lamps may contain a plurality of flash tubes, for example, quartz tubes filled with inert gas such as xenon. The UV flash lamps have an illuminance of at least 10 megalux, preferably from 10 to 80 megalux per flash discharge. The energy per flash discharge may be, for example, 1 to 10 kJoule.
The irradiation time with UV radiation when UV flash lamps are used as the UV radiation source may be, for example, in the range from 1 millisecond to 400 seconds, preferably from 4 to 160 seconds, depending on the number of flash discharges selected. The flashes may be triggered, for example, about every 4 seconds. Curing may take place, for example, by means of 1 to 40 successive flash discharges.
If continuous UV radiation sources are used, the irradiation time may be in the range from a few seconds to about 5 minutes, preferably less than 5 minutes. The distance between the UV radiation sources and the surface to be irradiated may be, for example 5 to 60 cm.
When the coatings are irradiated by means of UV radiation, in particular with UV flash lamps, temperatures may be generated on the coating that are such that, in the event that the coating compositions cure by an additional cross-linking mechanism as well as polymerisation, they give rise to at least partial curing by means of this additional cross-linking mechanism.
In order to cure the coating compositions by means of the additional cross-linking mechanism, the coatings may, however, also be exposed to relatively high temperatures of for example 60 to 140xc2x0 C. to cure completely. Complete curing may take place by conventional methods, for example, in an oven or in a conveyor unit, for example, with hot air or infrared radiation. Depending upon the curing temperature, curing times of 1 to 60 minutes are possible. It is, of course, also possible to perform the additional thermal curing prior to irradiation. An appropriately heat-resistant film material must be selected depending upon the curing temperatures required for the additional thermal curing. The temperature sensitivity of the substrate to be repaired must also be taken into consideration when selecting the curing temperature.
For coating compositions that are curable by UV radiation but not enhanced by an additional crosslinking mechanism, it is preferred to supply additional thermal energy, for example, with an infra-red lamp, to support the polymerisation (hardening) of the composition.
In the preferred case of irradiation with UV radiation though the backing film, the film is removed after irradiation. In the case of additional thermal curing, the coating is first allowed to cool before the film is removed. When removing the backing film, it is favourable if the film is uncoated on at least one edge zone so as to facilitate detachment of the film.
One development of the invention consists in effecting a partial cure of the coating by UV irradiation through the film and performing final curing in a second irradiation step after removal of the film. In other words, the radiation dose required for complete cure (by means of free-radical and/or cationic polymerisation) is supplied in at least two separate irradiation steps. In the event that the coating contains binders that cure by an additional cross-linking mechanism, it also possible in a first step completely or partially to cure the coating with regard to the free-radical and/or cationic polymerisation by means of UV radiation and, after removal of the film, firstly to perform any outstanding final curing with regard to free-radical and/or cationic polymerisation by means of UV radiation and then to supply thermal energy for further curing by means of the additional cross-linking mechanism.
After removal of the backing film and optional subsequent final curing and preferably a cooling phase, the repaired area may be polished.
It is, in principle, also possible to apply more than one coated backing film, for example two coated backing films, in succession onto the blemished area to be repaired. Depending upon requirements, this may, for example, comprise one backing film coated with a base coat and one coated with a clear coat or one backing film coated with a filler and one coated with a one-layer top coat.
If a backing film provided with a textured surface is coated and applied according to the invention, repair coated surfaces provided with the corresponding negative textures are obtained after removal of the backing film. This may, for example, prove necessary when repairing per se textured substrate surfaces.
Substrates which are suitable for the process according to the invention are any desired substrates, for example, metal, plastic, or composite substrates made from metal and plastic components.
The process according to the invention may find application for repairing any desired coated substrates, for example, in industrial and automotive coating, for example, in repair coating of automotive bodies in automotive original coating (end-of-line repair) or in a repair bodyshop. The process according to the invention may particularly advantageously be used for repairing small blemished areas (spot repairs). In particular, clear coats or pigmented one-layer top coats may be applied onto an existing multilayer coating for repair purposes by the process according to the invention.
The following example is intended to illustrate the invention in greater detail.

Process for repairing coated substrate surfaces

Abstract: e) removing the backing film, wherein


A switch contact for a wireless communication device is disclosed which is comprised of a generally U-shaped spring contact positioned between a printed circuit board and a planar inverted F antenna in a compressed state for electrically connecting the printed circuit board to a feed point on the planar inverted F antenna. The leg portions of the spring contact are provided with spring extensions which are overlapped and which are biased towards one another.

1. Field of the Invention
This invention relates to internal antennas for hand-held mobile telephones and wireless communication devices. More particularly, the present invention relates to a switch contact for connecting a planar inverted F antenna in the device to a printed circuit board therein.
2. Description of the Related Art
Internal antennas for wireless communication devices are becoming more popular due to their ease of integration into the housing of the device, lower cost, and smaller profile. A popular internal antenna is the planar inverted F antenna (PIFA). A major difficulty encountered in mass production of a PIFA is the method used to inexpensively provide a connection between the signal on the printed circuit board (PCB) to the feed point on the PIFA. The simplest method is to insert spring contacts that apply pressure between the PCB and the PIFA. The proper amount of pressure is crucial for making a consistent, reliable electrical connection.
Spring contacts of the type described above may be configured in different ways. One way is to use what is called a xe2x80x9cpogoxe2x80x9d pin. The pogo pin is made of a spring housed inside two closed end concentric tubes. The spring provides pressure to the tubes to press against both the PCB and the PIFA. The tubes hold the spring, provide an electrical path, and enclose the spring to eliminate the inductance of the spring. However, pogo pins are usually too expensive for use in mass production.
Another method of configuring the spring contact is to form metal strips into beams that perform all the functions mentioned hereinabove. The beams are necessary to prevent deformation of the metal strips due to flexing the metal during switching. Deformation reduces the spring force of the metal. Unfortunately, the spring portion of the contact is not enclosed to eliminate the induction. In most cases, the additional induction causes the electrical size of the PIFA to be smaller to compensate for the inductance. Smaller electrical size in general means the gain will be lower.
A switch contact is disclosed for a wireless communication device including a printed circuit board having a planar inverted F antenna arranged parallel thereto and spaced therefrom. For purposes of description, the printed circuit board will be described as being positioned below the planar inverted F antenna. The spring contact is generally U-shaped and is positioned between the printed circuit board and the planar inverted F antenna in a compressed state for electrically connecting the printed circuit board to a feed point on the planar inverted F antenna. The spring contact includes a base portion having spaced-apart first and second leg portions extending therefrom. The first leg portion of the spring contact curves laterally and upwardly from the PCB, bends 180 degrees over a relatively large radius (base portion), with the second leg portion curving laterally and upwardly to the PIFA. The first leg portion is in electrical contact with the printed circuit board with the second leg portion being in electrical contact with the feed point on the planar inverted F antenna. The spring contact forms the mechanical portion of the contact that provides upward and downward spring force to ensure good electrical connection between the surface of the PIFA and the contact. The first leg portion has a first spring extension extending therefrom towards the printed circuit board while the second leg portion has a second spring extension extending therefrom towards the planar inverted F antenna. The first and second spring extensions are biased towards one another so that the spring extensions are in electrical contact with one another. The spring extensions provide an electrical path that bypasses the inductive path of the spring portion of the contacts. The inductance of the spring is short-circuited by the bypass.
The distance between the PCB and the PIFA has a dimensional tolerance which must be included in the overlap between the spring extensions and the lateral spring forces. The overlap between the extensions compensates for dimensional tolerance stack-up.
The spring contact of this invention may be used in other types of antennas such as microstrip patch antennas.
It is therefore a principal object of the invention to provide an improved switch contact for a wireless communication device including a printed circuit board and a planar inverted F antenna arranged parallel to the printed circuit board and spaced therefrom.
Yet another object of the invention is to provide a switch contact of the type described which include spring extensions at the ends thereof which provide an electrical path that bypasses the inductive path of the spring portion of the contact.
Yet another object of the invention is to provide a switch contact for a wireless communication device which has the ability to compensate for dimensional tolerance stack-up.
These and other objects will be apparent to those skilled in the art.

Switch contact for a planar inverted F antenna


Disclosed is a disposable dialysis cassette which is flat, flexible, self-closing and applicable to solutions containing proteins, DNA, RNA, or other molecules. The dialysis cassette embodies a first and second semi-permeable dialysis membrane, or tubular dialysis membrane, sealed by a flexible frame to form a dialysis chamber having a self-closing channel for the introduction of a dialysis sample by either a pipette or other dispensing mechanism.

Not applicable.
The present invention relates to a holder for a dialysis membrane used in osmotic separation. More specifically, the present invention discloses a dialysis support frame.
Dialysis separation is an effective means of separating molecules according to their ability to diffuse through a semi-permeable membrane. The dialysis solution is placed within a dialysis chamber containing one or more walls formed by a semi-permeable membrane. The membrane, by virtue of its composition and porosity, allows molecules equal to or less than a particular molecular weight to pass through and into a dialysis bath in which the chamber is submerged. The driving force behind dialysis separation lies within the osmotic flow created by the concentration differential between the dialysis solution and the dialysis bath.
Although dialysis separation is an effective means of separating molecules of variable sizes, it is cumbersome and generally requires great care to avoid contamination or the loss of a sample. A commonly applied method involves sealing the top and bottom ends of a tubular dialysis membrane with clips or collars to form a dialysis chamber. If the ends of the tubing are not carefully sealed, the dialysis chamber will leak and the sample may be lost. In addition, the lack of support for the generally flaccid membrane results in significant difficulty in loading and unloading samples. Because of the nature of the clips and collars used to seal the dialysis chamber, it is often necessary to handle the membrane which may effect the integrity of the membrane thus causing inefficient dialysis separation.
Finally, this method does not provide ample space for labeling the chamber to indicate the enclosed sample. Therefore, labeling must be written on the small clamp or collar, or on an object which is inconveniently attached to the tubing with material such as string.
U.S. Pat. No. 5,788,075 describes an apparatus containing a floating support ring comprising a central opening surrounded by a downwardly extending tube used to support a dialysis membrane. The walls of the apparatus and the floor of the dialysis membrane converge to create the dialysis chamber. In its operation, the assembled apparatus is suspended over a dialysis bath and the sample loaded into the dialysis chamber.
Although this solution offers advantages, it introduces new problems. First, the sample is open to the air which allows it to be easily contaminated. Secondly, because the vessel is open, it is easy for the sample to spill into the dialysis bath as it floats. Loading and unloading are greatly simplified, but assembly of the device requires some skill by the user.
U.S. Pat. No. 5,503,741, describes a dialysis cassette which embodies a hermetically sealed sample chamber formed by fixing two dialysis membranes to a gasket. The gasket is impermeable to the sample being dialyzed, but is penetrable by a hypodermic needle. Upon assembly, the sealed sample chamber is contained within a rigid housing containing windows exposing the dialysis membranes. In its operation, a hypodermic needle is inserted through the gasket and into the chamber so as to insert or withdraw the dialysis solution. The cassette is then placed within a dialysis bath where dialysis separation occurs.
Unfortunately, this product also has several drawbacks. One such drawback is the fact that the device requires the use of a hypodermic needle to introduce the dialysis solution into the dialysis chamber. The use of a hypodermic needle may be unacceptable when the dialysis cassette is used to separate DNA or RNA fragments as high shear forces are created in the liquid passing through the needle such as may damage larger molecules. The shear forces may also disrupt and inhibit the dialysis of whole mammalian cells, algal cells, protists (i.e., amoebas, water bears, etc.), and colonial organisms.
The dialysis cassette has a further drawback in that it requires greater skill in the loading and unloading of samples, as compared to the methods described above. Furthermore, in view of its construction, the dialysis cassette is likely to carry a greater expense in its use.
What is needed is a simplified device providing minimal risk of contamination or sample loss. This device should allow for the dialysis of delicate samples which include proteins, DNA or RNA.
The present invention provides a simplified disposable dialysis cassette in which a flexible frame supports and exposes a dialysis membrane for simplified filling and handling.
The dialysis cassette embodies a first and second semi-permeable dialysis membrane, or tubular dialysis membrane sealed by a flexible frame to form a dialysis chamber having a self-closing channel for the introduction of samples by either a pipette or other dispensing mechanism. The dialysis cassette is assembled by the combination of a first and second flexible polymeric sheet bonded together to form a semi-rigid frame, wherein the bottom end of the dialysis chamber is preferably affixed and sealed within the semi-rigid frame and the top end of the dialysis chamber is extended within and to the edge of the semi-rigid frame to create a self-closing channel which provides access to a portion of the dialysis chamber exposed by a window formed by central apertures contained within the first and second polymeric sheets. In its use, the frame may be flexed to allow the opening and closing of the self-closing channel for the introduction of a sample into the dialysis chamber.
In a further embodiment of the invention, an instrument guide is affixed within the channel to allow for the easy insertion of a pipette or other dispensing mechanism used to deposit the dialysis sample.
It is an object of the present invention to provide a disposable dialysis cassette which is less bulky, flexible, self-closing and capable of separating sensitive molecules such as protein, DNA, RNA or other large, linear polymers not of biological origin that can be broken by shear force. It is also an object of the present invention to provide a flexible dialysis cassette, wherein the semi-rigid frame allows the dialysis chamber to be self-closing.
It is another object of the invention to provide a flexible cassette which is useful in culter systems designed for certain tissues, algaes, and microbial organisms.
Other objects, advantages, and features of the present invention will become apparent after examination of the specification, claims, and drawings.