A multistage catalytic partial oxidation (CPO) process for oxidizing a hydrocarbon feedstream comprising C1-C4 hydrocarbons, with an oxygen-containing feedstream to produce a product comprising CO and H2, also known as synthesis gas or syngas. The process employs a CPO catalyst, and controlled process features, including: (A) the total oxygen requirement for the process is introduced incrementally, in more than one reaction stage, using an oxygen-containing feedstream at more than one feed point in the process, each stage including a catalyst; (B) the oxygen-containing feedstream, hydrocarbon feedstream and, in reaction stages after the first of said multiple stages, the intermediate product produced in the prior stage, are mixed for a period of time, after they are brought into contact with one another, of less than about 1 millisecond to form a substantially uniform mixture, wherein the mixture is then contacted with the catalyst; (C) the oxygen-containing feedstream and the hydrocarbon feedstream are preheated prior to entry into the first stage, to a temperature of from about 450xc2x0 C. to less than about 1,000xc2x0 C.; and (D) the mixture temperature of the product in each stage following the first stage is from greater than about 600xc2x0 C. to less than about 1,000xc2x0 C. Preferably, the process comprises less than or equal to about five stages, the first stage preheat temperature recited in step (C) is greater than about 550xc2x0 C. and the mixture temperature of the product in each stage following the first stage is at least 700xc2x0 C.

Catalytic partial oxidation (CPO) of low carbon number hydrocarbon feed streams, such as methane, to produce useful products, such as mixtures of hydrogen and carbon monoxide, the latter mixture also known as synthesis gas or syngas. Syngas is useful for the preparation of a variety of other valuable chemical compounds, such as by application of the Fischer-Tropsch process.
The combustion of methane gas at elevated temperature, e.g., 1000xc2x0 F. (538xc2x0 C.) is highly exothermic and produces CO2 and H2O according to the following stoichiometry:
CH4+2O2xe2x86x92CO2+2H2O (xe2x88x92190.3 kcal/g mol CH4)
The gases formed in such a reaction are not directly useful for the production of valuable chemical compounds, and the high temperatures generated present problems with respect to reactors, catalysts and other process equipment if efforts were made to produce valuable products from water and carbon dioxide.
Conversely, it is known to produce a chemically useful mixture of CO and H2 gases, also known as synthesis gas or syngas, from methane and other light hydrocarbon gases, by various reactions, including partial oxidation, steam- or CO2-reforming, or a combination of these chemistries. The partial oxidation reaction of methane is a less highly exothermic reaction which, depending upon the relative proportions of the methane and oxygen and the reaction conditions, can proceed according to the following reaction paths:
It is most desirable to enable the partial oxidation reaction to proceed according to the last reaction scheme. This results in certain advantages: including (1) producing the most valuable syngas mixture; (2) minimizing the amount of heat produced (thereby protecting the apparatus and the catalyst bed); and (3) reducing the formation of steam (thereby increasing the yield of hydrogen and carbon monoxide). Any incidentally produced, or added, steam can be further converted by the steam-reforming reaction into additional useful syngas components.
Jacobs et al., U.S. Pat. No. 5,510,056 (Shell) discloses that successful operation of a CPO process on a commercial scale requires high conversion of the hydrocarbon feedstock at high space velocities, using mixtures of an oxygen-containing gas and methane in a preferred O2 to carbon atom ratio (in the region of the stoichiometric ratio of about 1:2, or 0.5), which mixtures are preferably preheated and at elevated pressures. The advance described in Jacobs is directed to the specifics of the catalyst support.
It is disclosed in EP 303 438 (assigned to Davy McKee Corp.), to conduct a CPO process using previously formed mixtures of high temperature, high pressure methane and oxygen gases and, optionally, steam at space velocities up to 500,000 hrxe2x88x921, using a mixing and distributing means in order to thoroughly premix the gases prior to introduction to the catalyst. It is the objective in this disclosure to operate the CPO process in a mass-transfer-controlled regime and to introduce the gas mixture at or above its autoignition temperature.
EP 842 894 A1 discloses a process and apparatus for catalytic partial oxidation of a hydrocarbon wherein the use of several stages is proposed. The reference states that in each stage there is used xe2x80x9ca small fraction of the stoichiometric amount of oxygen required for the reactionxe2x80x9d to prevent the generation of high temperatures in the reactor as a consequence of xe2x80x9cexcessivexe2x80x9d concentrations of oxygen. Furthermore, it is disclosed that the hydrocarbon feed is mixed with oxygen and preheated to a temperature in the range of 300-400xc2x0 C. and the reaction is performed at substantially the same temperature in all stage by cooling the reaction mixture in each stage.
GB Patent Application 2311790 discloses a two stage process and the use of a specifically defined catalyst whereby in a second stage a second synthesis gas is produced utilizing a first synthesis gas, as feed gas, with oxygen to cause partial oxidation of unreacted methane.
Staged oxygen addition has been disclosed as providing possible improvements solution to some of the difficulties encountered in CPO processes. xe2x80x9cCO2 Reforming and Partial Oxidation of Methane,xe2x80x9d Topics in Catalysis 3 (1996) 299-311, recommends a staged addition of O2 to the reactor during methane oxidation in a two stage process, including total methane oxidation followed by reforming in the presence of the formed CO2 and H2O. Oxygen staging is said to lead to a flattening of the temperature profile along the reactor. However, it is also stated that xe2x80x9clowering the O2/CH4 ratio will make carbon deposition thermodynamically more favorable and thus lead to deactivation of the catalyst.xe2x80x9d (Id., p.308). The experimental results reported in this reference are expressed as a function of the catalyst-bed exit temperature rather than feed temperature.
xe2x80x9cPartial Oxidation of Methane to Synthesis Gas via the Direct Reaction Scheme Over Ru/TiO2 Catalyst,xe2x80x9d Catalysis Letters 40 (1996) 189-195, discusses achieving an increase in selectivity to syngas in the presence of oxygen over a Ru/TiO2 catalyst by multi-feeding oxygen. The increase is attributed to suppression of deep oxidation of H2 and CO. Based on observations therein, the authors imply that xe2x80x9cif oxygen is fed along the length of the catalyst bed instead of only at the entrance . . . and its local partial pressure is maintained at low levels, CO selectivity via the direct reaction scheme may be increased by attenuating oxidation of methane to CO2.xe2x80x9d (Id., p.194).
xe2x80x9cMethane Conversion to Ethylene and Acetylene: Optimal Control with Chlorine, Oxygen and Heat Flux,xe2x80x9d Ind. Eng. Chem. Res. 35 (1996) 683-696, discloses conversion of methane to ethylene with controlled oxygen and heat flux. The process was conducted in the gas phase, i.e., the reference is directed to a non-catalytic gas phase methane reaction. Furthermore, oxygen is not present in the reactor initially; rather it was used as a manipulative variable.
xe2x80x9cKinetic-Transport Models of Bimodal Reaction Sequences-1. Homogeneous and Heterogeneous Pathways in Oxidative Coupling of Methane,xe2x80x9d Chemical Engineering Science, 48 (1993) 2643-2661, discloses a reaction transport model. Staging oxygen introduction along the reactor length is found to minimize secondary oxidation reactions by lowering the local O2 pressures, which leads to a slight increase in maximum yield, but also requires much larger reactor volumes. However, oxidative coupling differs from the technology disclosed by the present inventors in that it has as its objective the production of ethane and ethylene, rather than CO and H2 (i.e., syngas).
xe2x80x9cPartial Oxidation of Methane to Syngas Using Fast Flow Membrane Reactors,xe2x80x9d ACS Div. Fuel Chem. Reprints 42(2) Apr. 13, 1997, discloses the use of a double bed reactor wherein both beds can be operated autothermally if oxygen is used as the downstream feed instead of carbon dioxide. The temperature of the second bed rapidly increases upon introduction of the downstream oxygen feed.
While the above references disclosed certain aspects of CPO and staged oxygen addition, there still exists a need for a CPO process that avoids undesirable gas phase reactions and maximizes yield and selectivity.
A multistage catalytic partial oxidation (CPO) process for oxidizing a hydrocarbon feedstream comprising C1-C4 hydrocarbons, with an oxygen-containing feedstream to produce a product comprising CO and H2, said process conducted under CPO conditions in the presence of a CPO catalyst, wherein:
(A) the total oxygen requirement for said process is introduced incrementally from an oxygen-containing feedstream, the first of said incremental additions taking place in a first reaction stage, and subsequent said incremental additions taking place in at least one subsequent reaction stage, each said stage including said catalyst;
(B) in said first reaction stage said oxygen-containing feedstream and said hydrocarbon feedstream are mixed, and in said subsequent reaction stages, said oxygen-containing feedstream and the intermediate product produced in the prior stage are mixed; said mixing in said first stage occurring in a mix time of less than about 10 milliseconds and in said subsequent stages said mixing of said oxygen-containing feedstream and said intermediate product occurring in a mix time of less than about 1 millisecond, wherein said mix time is defined as the time when said hydrocarbon and said oxygen-containing feedstreams or said intermediate product and said oxygen-containing feedstream are brought into contact with one another and up to the time said mixture is contacted with said catalyst, to form a mixture, wherein said mixture is contacted with said catalyst;
(C) said oxygen-containing feedstream and said hydrocarbon feedstream are preheated prior to entry into said first stage, to a mixture temperature of from about 450xc2x0 C. to less than about 1,000xc2x0 C.; and
(D) the mixture temperatures of said product in each stage following said first stage is from greater than about 600xc2x0 C. to less than about 1,000xc2x0 C.
Preferably, the process comprises less than or equal to about five stages, the first stage preheat temperature recited in step (C) is greater than about 550xc2x0 C. and the temperature of the product mixture in each stage following said first stage is at least about 700xc2x0 C.
It is believed that CPO proceeds primarily by very fast metal-catalyzed steps that are only mildly exothermic. A key challenge in CPO is the need to operate at extremely high space velocities in order to suppress the contribution from non-selective gas-phase oxidation reaction pathways; this problem becomes particularly difficult to overcome at high temperatures and pressures.
In the operation of a staged CPO process it is desirable to reduce gas phase reactions to the maximum extent possible (and most preferably to eliminate such reactions) and, instead, to operate under conditions wherein all partial oxidation reactions occur on a highly active catalyst surface. In this way, the hydrocarbon feed is converted catalytically at such a high rate or low dwell time, that gas phase reactions or undesirable combustion stoichiometry (e.g., poor selectivity), do not have an opportunity to occur. In order to accomplish these objectives it is also necessary that the gases fed to a CPO catalyst be thoroughly premixed and the process be operated under specifically controlled conditions. Avoidance of gas phase reactions will also avoid damage to the catalyst, including physical damage as well as reduced activity and undesirable combustion reactions. Also, CPO catalysts generally do not exhibit such high levels of steam or CO2 reforming activity that would permit them to reform over-oxidized gas compositions at the high space velocities employed in CPO processes.
It is especially important to provide the premixed feed under controlled preheat conditions as well as controlled interstage temperature conditions and at high space velocity to enable the desired catalytic reaction of the premixed gases to occur at short contact times. An appropriately controlled catalytic partial oxidation process has the potential to provide extraordinary reactor productivity in view of the extremely high space velocities of the throughput if the aforementioned problems are avoided or at least significantly reduced.
It is an objective of the present invention to improve the selectivity and efficiency of the catalytic partial oxidation process, resulting in higher methane conversion and higher H2 and CO concentrations in the syngas.
The hydrocarbon and oxygen reaction mixture utilized in the instant invention to produce partial oxidation products need not be pure. H2O and CO2, may be present in the hydrocarbon stream introduced in relatively large amounts, such as from about 0.0 to 1.0 mole of H2O or CO2 per carbon atom of hydrocarbon to be oxidized. Other components, for example, H2, CO, Ar, N2, NH3, HCN, H2S, COS, CS2, organic sulfur-containing compounds, organic oxygenates, methane, and C2+ hydrocarbons may be present in lower concentrations, typically less than 0.10 mole of the component per carbon atom of the hydrocarbon being oxidized. The stream comprising oxygen may likewise contain components other than oxygen. These components are typically N2, CO2, H2O, and Ar. Some of these components, especially N2, CO2, and H2O, may be present in amounts, from 0.0 to 4.0 mole per mole of oxygen (O2). Other components (for example, as identified above) are typically present in amounts normally less than 0.1 mole of component per mole O2.
In one embodiment of the present invention, the principal component being oxidized is light hydrocarbon gas comprising methane. Typical hydrocarbon feeds that are used in catalytic partial oxidation include methane, natural gas, individual and mixtures of light (C2-C4) hydrocarbons, individual and mixtures of heavier (C5+) hydrocarbons, as well as olefins, aromatics, and oxygenates. More typically, saturated hydrocarbons are used as feed, and the partial oxidation products comprise synthesis gas, unsaturated hydrocarbons, oxygenated hydrocarbons, and combinations thereof.
In the CPO process, a well-mixed reaction gas mixture comprising an oxygen-containing feed and a feed comprising one or more hydrocarbons selected from the group consisting of C1-C4 compounds is contacted with a fixed bed of particulate or monolithic catalyst, wherein conversion occurs at extremely high rates. When the process is operated at high pressure and at very high gas hourly space velocities, or GHSV; velocities as high as 1,000,000 hr.xe2x88x921 or more, e.g., velocities of 10,000,000 hr.xe2x88x921 or more can be encountered. For purposes of the present disclosure, GHSV is calculated as the flow rate of the gases at xe2x80x9cstandardxe2x80x9d temperature and pressure, i.e., 1 atm/101.3 kPa and 68xc2x0 F./20xc2x0 C., divided by the total volume of the catalyst; for purposes of this definition, the total catalyst volume refers to the same aspect of the process as does GHSV, e.g., the overall process or one or more stages being considered in a multistage process. Furthermore, the use of active catalysts is preferred, among other process control variables, in order to avoid gas phase chemical reactions. Applicants have discovered that staged introduction of the oxygen feed during the CPO process and specific control of the temperature profile of the feed and the stages results in a more efficient process and improved selectivity, i.e., production of the desired syngas components, H2 and CO in high yields.
The process of the present invention is not limited by the pressure employed in the process and may be operated at any suitable pressure, including from about one atmosphere (0.1 MPa) and higher. For certain commercial operations, elevated pressures, that is pressures significantly above atmospheric pressure, may be preferred, but the nature of the application will dictate the pressure to be utilized in the operation of the invention disclosed herein. The process may be operated at pressures in the range of up to about 50 atmospheres (about 5.0 MPa) or more. When employed in lower pressure applications, the process is operated at pressures in the range of from about 1 to about 10 atmospheres (about 0.1 to about 1.0 MPa); for example, from about 1 to about 5.0 atmospheres (about 0.1 to about 0.5 MPa). In higher-pressure applications, pressures of from greater than about 5 to about 50 atmospheres and higher (about 0.5 to about 5.0 MPa and higher) may be encountered; for example from greater than about 10 to about 30 atmospheres (about 1.0 to about 3.0 MPa). In various commercial applications, it is not uncommon for a CPO process to be integrated within a broader operation or process, e.g., in the processing of a hydrocarbon stream and/or in a petrochemical process. Generally, pressure in the CPO process may be determined by economic and/or process factors relating to its use as an element in an overall process.
Catalyst compositions suitable for use in the catalytic partial oxidation of hydrocarbons are known in the art. Preferred catalysts for use in the process of the present invention comprise, as the catalytically active component, a metal selected from the group consisting of Group VIII of the Periodic Table of the Elements. References in this specification to the Periodic Table of the Elements are to the CAS version, as published in the CRC Handbook of Chemistry and Physics, 69th Edition. Preferred catalysts for use in the process comprise at least one metal selected from the group consisting of nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. Catalysts comprising at least one of ruthenium, rhodium or iridium as the catalytically active metal are most preferred for use in the process; in particular, a catalyst comprising at least rhodium is preferred.
The catalytically active metal is most suitably supported on a carrier. Suitable carrier materials are well known in the art and include the refractory oxides such as silica, alumina, titania, zirconia and mixtures thereof. Mixed refractory oxides, that is, refractory oxides comprising at least two cations, may also be employed as carrier materials for the catalyst.
The catalytically active metal may be deposited on a refractory oxide carrier by techniques well known in the art. A particularly suitable technique for depositing the metal on the carrier is impregnation, which technique typically comprises contacting the carrier material with a solution, dispersion or suspension of a compound of the catalytically active metal, followed by drying and calcining the resulting material. The catalytically active metal, for example rhodium, can be applied as part of a washcoat, for example, an alumina-based washcoat. Generally, the rhodium content will be from about 2 to about 20% by weight; preferably from about 4 to about 12% by weight in the washcoat. The washcoat loading, expressed as grams of washcoat per cubic inch of catalyst bed, will be from about 0.1 to 2.0; preferably from about 0.2 to about 1.0 g/cubic inch. Similarly, a preferred monolithic support such as ceramic foam is selected so to obtain a desired property, e.g., the number of pores per inch, ppi. Generally, a ceramic foam support will have from about 25 to about 150 ppi; preferably from about 30 to about 100 ppi.
As used in the process of the present invention, the catalyst preferably is retained in form of a fixed arrangement. The fixed arrangement may comprise a fixed bed of catalyst particles. Alternatively, the fixed arrangement may comprise the catalyst in the form of a monolith structure. The fixed arrangement may consist of a single monolith or particulate structure or, alternatively, may comprise a number of separate monolith and/or particulate structures combined to form the fixed arrangement in one or more stages. A preferred monolith structure comprises ceramic foam. Suitable ceramic foams for use in the process of the present invention are available commercially.
By practicing the process of the present invention, staged-oxygen CPO can provide higher yields and selectivities than conventional (co-fed or single-stage) CPO, provided that several specific process conditions are incorporated into the process in order to provide a workable process capable of higher yields and selectivities. It has surprisingly been found that the chemistry of the catalyst in a staged-oxygen CPO process becomes substantially more selective at higher temperatures, and that specific requirements for feed preheat and inter-stage cooling must be met in order to preserve the high yields and selectivities. In particular, the reactivity behavior of the gaseous premix for intermediate stages of a staged-oxygen CPO process leads to an unexpected need to carefully manage the inter-stage mixing time, and leads to an unexpected preference for an intermediate number of stages. These key features are further described in detail below.
A significant advantage of staged-O2 CPO is its ability to provide higher yields and selectivities than can be achieved with co-fed CPO (in which the oxygen-containing feed and the hydrocarbon feed are introduced concurrently in a single stage process). Pursuant to the present invention, the inventors have also found that higher yields and selectivities are significantly related to maintaining high interstage temperatures. Following the first stage, mixture temperatures between stages (i.e., the temperature at the inlet to the catalyst bed, representing the temperature of the mixed stream) should be kept above about 600xc2x0 C., and more preferable above about 700xc2x0 C. It is also desirable to keep such interstage mixture temperatures below about 1,000xc2x0 C.; preferably interstage mixture temperatures should be from about 600xc2x0 C. to about 1,000xc2x0 C.; more preferably, from about 650xc2x0 C. to about 950xc2x0 C.; most preferably, from about 700xc2x0 C. to about 900xc2x0 C. Interstage cooling may be employed, but only to the extent that temperatures remain within these specified ranges. Generally, it will be understood that the temperatures of individual streams, e.g., initial feedstreams to the process, an intermediate oxygen-containing feedstream or an intermediate product within the process, can differ from one another and from the temperature of a mixture of one or more of such streams specified at a point in the process.
An important economic driver in syngas generation is product (CO, H2) yield. Yield may be diminished by low conversion (unreacted CH4), or by low selectivity (e.g., production of undesirably high levels of H2O and/or CO2). For the range of catalysts under consideration herein, yields improve as interstage mixture temperature rises to above about 600xc2x0 C., and especially to above about 700xc2x0 C. Two coincident effects are involved. First, thermodynamic equilibrium shifts with increasing temperature to higher yields of syngas. Second, the ability of the catalyst to preferentially oxidize methane in the presence of CO and H2 increases with temperature. The latter effect is particularly important in between stages, leading to a requirement for interstage mixture temperature that is higher than the requirement for initial feed mixture temperature (stage 1). The feed mixture temperature (stage 1) should be above about 450xc2x0 C.; preferably above about 500xc2x0 C., more preferably above about 550xc2x0 C.; in each instance, the stage 1 feed mixture temperature should be less than about 1,000xc2x0 C. When convenient to the overall process to provide a higher feed mixture temperature, a particularly preferred feed mixture temperature range is from about 600xc2x0 C. to about 800xc2x0 C.
For purposes of the present invention, several process criteria can be calculated and used as measures of performance. One such measure is xe2x80x9cproratedxe2x80x9d conversion, expressed as moles of CH4 converted per xc2xd mole of 02 in the feed. It is calculated as:
Prorated CH4% conversion=xc2xd(CH4 inxe2x88x92CH4 out)xc3x97100/(O2 in)
Prorated conversion provides a convenient means of characterizing the performance of each stage of a multistage process. In contrast, overall CH4 conversion achieved in the process can be expressed as:
Overall conversion=(CH4 inxe2x88x92CH4 out)xc3x97100/CH4 in
Furthermore, selectivity for the production of hydrogen and carbon monoxide from methane in the feed is expressed as:
% CO Selectivity=(CO outxe2x88x92CO in)xc3x97100/(CH4 inxe2x88x92CH4 out)
% H2 Selectivity=xc2xd(H2 outxe2x88x92H2 in)xc3x97100/(CH4 inxe2x88x92CH4 out)
Compared to prior art processes, practice of staged CPO technology as taught herein can result in high levels of both methane conversion and product selectivity; e.g., levels of both characteristics concurrently approaching or even exceeding 95%.
A conventional justification for employing a staged oxygen CPO scheme is the expectation that dividing the oxygen between many stages will result in lower oxygen concentration between stages, and thus reduce the possibility, or prevent, gas-phase reaction leading to high temperatures. (e.g., EP 0 842 894 A1 at page 2, col. 2, line 14). However, it has been found that the reactivity of gaseous mixtures between stages in a multistage CPO process as disclosed herein can actually be much higher that the reactivity of similar feed mixtures in a co-fed (or single-stage) CPO process. For example, at interstage temperatures such as above 600 xc2x0 C., gas mixtures containing moderate concentrations of both oxygen and synthesis gas are highly reactive.
Consider, for example, the induction times for reaction as calculated using a kinetic model; shorter induction times reflect higher reactivity. Induction times, as defined here, represent the time for the reaction to achieve 50% oxygen conversion, as calculated using a kinetic model under perfect plug-flow adiabatic conditions. It is known that fuel/oxidizer mixtures under these conditions will spend a large fraction of the induction time slowly building up heat and radicals, until some critical level is achieved and combustion then proceeds very quickly. The chemical mechanism used for the calculation is taken from Mims, et. al. (J. Phys. Chem., 98 (1994) 13357-13372). While the absolute values of the induction times are sensitive to the specific models used, the general magnitude of the values, and the key trends could be developed with alternate gas-phase mechanisms for methane oxidation. (Induction times for actual systems are typically shorter than those calculated using a kinetic model, as herein, due to diffusion, dispersion, and recirculation effects that carry heat and radicals upstream from downstream locations).
For a 0.5:1 O2/CH4 mixture at practical conditions of 500xc2x0 C. preheat temperature and 25 atm pressure, the calculated induction time would be 384 milliseconds. In contrast, using an oxygen/syngas mixture at a lower oxygen concentration (e.g., based on stage 2 of a two stage process, idealized as: {fraction (2/9)} CH4, {fraction (2/9)} CO, {fraction (4/9)} H2, {fraction (1/9)} O2) but at controlled interstage conditions of 700xc2x0 C. and 25 atm, would result in an induction time of only 1 millisecond. As can be seen, the reactivity of the hydrocarbon/O2 mixture rises significantly faster with temperature than any attenuation of reactivity due to reduced oxygen concentration. Indeed, the presence of the syngas in the interstage mixture limits the attenuation of reactivity that is due to reduced oxygen concentration, by providing a highly reactive hydrogen component to the hydrocarbon mixture.
It will be recognized by those skilled in the art, that the gaseous premix formed when the hydrocarbon stream and the oxidant stream are introduced into the mixing zone will not be perfectly mixed at the point of initial contact. In any real physical device, some time or distance will be required before perfect mixing is achieved. As used herein, the term xe2x80x9cfeed streamxe2x80x9d means the individual streams, such as hydrocarbon or oxygen containing gas, that are being fed to the mixing zone, and the term xe2x80x9cmixturexe2x80x9d means the physical combination of these feed streams in a state that is highly mixed. It is important that the feed streams achieve a high degree of mixing in a minimum amount of time, and before gas phase or catalytic reactions begin to occur at any substantial level. In order to quantify this degree of mixing, the measure xe2x80x9cEfficiency of Mixingxe2x80x9d, abbreviated as Em, is used.
Em is calculated from the composition profile of the mixture stream. Composition profiles can be obtained by sampling the stream at many locations, or by use of other diagnostic tools. For example, imaging the Rayleigh-scattered light of a laser beam can, under properly controlled conditions, provide composition variations across partially mixed streams. Typically, a xe2x80x9cslicexe2x80x9d in a plane substantially perpendicular to the gas flow, i.e., across the reactor, is sampled. In particular, such samples will be measured in the region just prior to entry of the gas mixture into the catalyst. The composition data is used to calculate how much of each feed stream is present at each location in the sampled plane. For example, if one were mixing air with methane, the oxygen and nitrogen mole fractions would be combined to represent the mole fraction of the air stream.
For the case where hydrocarbon-containing (abbreviated HC) and oxygen-containing (abbreviated OX) feed streams are being mixed, Em is defined using the following equation:
Em=((XHC/XOX)MIN/(XHC/XOX)MAX)05
where XHC and XOX represent mole fractions in the mixture of hydrocarbon-containing gas and oxygen-containing gas, and the subscripts xe2x80x9cMINxe2x80x9d and xe2x80x9cMAXxe2x80x9d designate that these are the minimum and maximum ratios found in the mixture. Thus, (XHC/XOX)MIN represents the minimum HC/OX mole fraction ratio found in the composition profile. As so defined, Em reaches a value of 1.0 when the gases are perfectly mixed, and will have a value of 0.0 if the stream has any locations that are completely unmixed (a location where the composition is equal to that of either feed stream). Since the final, limited amount of oxygen is added in the last stage it is preferred that Em in that stage be better, i.e. higher, than in earlier stages (or for the overall process) in order to avoid formation of H2O and CO2. For example, while Em for the early stages of the process may be about 0.7 to about 0.8, it is preferred that Em in the last stage be greater than about 0.9. The process described herein can also be operated in a rapid injection mode, such as described in U.S. Pat. No. 5,883,138 (F. Hershkowitz et al.), the disclosure of which is incorporated herein by reference thereto.
For purposes of the present invention, the mixing time is defined as the duration of time after addition of O2 and up to the time of entry of the mixture of hydrocarbon and oxygen into the catalyst. In contrast, the total time in a stage is measured from the time the hydrocarbon feed first enters the reactor, or a product mix, including unreacted hydrocarbon, if any, leaves the catalyst from a prior stage, until the time a product mixture first begins to exit the next catalyst (the total time is not a critical performance variable for the present invention). Therefore, as defined, mixing time begins upon first contact of O2 with the flowing stream (either the initial hydrocarbon feed or the product stream from a prior stage), and ends when the mixed stream enters the catalyst. Necessarily, mixing requires a finite time and, for the purposes of the present invention, such mixing time in stages after the first stage should be less than about 1.0 millisecond; preferably less than about 0.5 millisecond; more preferably less than about 0.2; for example, from greater than zero to about 0.1 millisecond. Under practical operating conditions, a range of from about 0.05 to about 0.5 milliseconds is useful; particularly 0.05 to about 0.2 milliseconds; for example, about 0.1 milliseconds. The achievement of such short mixing times, and mixing times of even less than about 0.1 milliseconds, may be achieved by use of injector technology such as that described in U.S. Pat. No. 5,883,138, identified above. These short mixing times reflect the need to utilize relatively high interstage temperatures, as well as the high reactivity of the gases under these conditions. As such, mixing times may be longer for the first-stage feed, which is less reactive (since no hydrogen is present) and which may be at lower temperature. Finite mixing times of less than about 10 milliseconds should be achieved for the first stage feed; preferably, from about 0.05 milliseconds to about 5 milliseconds; more preferably from about 0.10 to about 2 milliseconds; generally, mixing times in the first stage of about 5 milliseconds or less are useful.
It has surprisingly been found that the short interstage mixing times referred to above result in a further requirement for a staged-O2 CPO process, which is the requirement of using a moderate number of stages. In a staged-oxygen CPO process, it is important for the gas mixture (in the first stage, the oxygen-containing feedstream and hydrocarbon, e.g., methane, and in later stages, also including the syngas and intermediate reaction products produced in prior stages) to contact the catalyst as a well-mixed stream. If a well-mixed stream is not achieved, O2-rich zones will exist leading to high temperature regions with concurrent poorer selectivity. To accomplish rapid mixing as well as thorough mixing requires substantial cross-stream or intra-stream dispersion. Where interstage mixing time is e.g., 0.1 millisecond, then gas flow even at a speed as high as sonic velocity (e.g., about 331 m/s in air at 0xc2x0 C. and ambient pressure) can be afforded a mixing distance only in the range of centimeters. Thus, physical mixing devices (such as static mixers) have limited applicability, and mixing energy must come from the momentum of the streams being mixed. The momentum of a stream is defined as the product of the velocity of the stream as it is injected into the mixing zone of the stage (the region preceding the catalyst) multiplied by the stream""s mass flow rate. As the number of stages in the staged-O2 CPO process is increased, the amount of oxygen introduced (and, consequently, its mass flow rate) at any one stage is thereby diminished. Thus, for systems with many stages, the volume ratio of the oxygen-containing stream to the continuing fuel stream will be very low. Therefore, the use of an excessive number of stages, each having very low volume ratios of oxygen to fuel (or hydrocarbon) in the gaseous stream, results in an impediment to required rapid and thorough mixing particularly as a consequence of diminished momentum of each oxygen stream. Thus, it also should be appreciated that the momentum of an oxygen stream in a stage in which a relatively low mass flow rate of oxygen is being used, can be increased by mixing the oxygen with a quantity of at least one gas that is inert or substantially inert under the process conditions taught herein, e.g., nitrogen and steam. The use of such a method should be tempered by the knowledge that introduction of a significant volume of inert gas will require increased size of gas handling, and possibly gas recycling, equipment. Without undue experimentation, one skilled in the art can determine a balance between increased momentum and the increased burden on process equipment and operations.
A useful parameter in defining the preferred number of stages is the Oxygen to Fuel-Carbon ratio, or O/FC ratio. The O/FC ratio is herein defined as the ratio of the number of moles of oxygen (as O2) to the number of moles of combustible carbon. In counting moles of combustible carbon, oxygenates are counted, as long as the carbon atom in question can still be further oxidized. Pursuant to this definition, methane counts as one carbon, ethane as two, CO as one, and CO2 counts as zero combustible carbon. This definition differs from an oxygen to carbon ratio, or O/C ratio, cited elsewhere, that excludes carbon atoms bound to oxygen regardless of whether they can be further oxidized. However, such an O/C ratio fails to capture the interstage aspect of having a large mass of continuing partially oxidized components capable of being further oxidized. Thus, for the purposes of the present invention, the O/FC ratio is meaningful both at feed and at interstage conditions. For staged-O2 CPO to be effectively carried out, the O/FC ratio at all stages should be greater than about 0.05; preferably, the O/FC ratio should be greater than about 0.10.
For the reaction:
CH4+xc2xdO2xe2x86x922H2+CO
the stoichiometric ratio for an idealized feed of pure methane and pure oxygen would be 0.5; if the addition of oxygen were staged so that the ratio was 0.25 in each stage, two stages would be required (barring undesirable reactions/reaction products). Partial oxidation for syngas generation will have a preferred overall feed stoichiometry (for the process as a whole) in the range of 0.3 to 0.8, preferably 0.4 to 0.8, more preferably 0.4 to 0.7 oxygen molecules per carbon atom of hydrocarbon feed (excluding any carbon atoms bound to oxygen, as well as pursuant to the definition of O/FC defined herein). However, as disclosed hereinabove, the ratio is also dependent on achieving acceptable levels of mixing by utilization of the momentum-accompanying the oxygen stream. In the present invention, it is not necessary to introduce equal amounts of the oxygen-containing feedstream into each stage; whether based on the amount of oxygen per se or the O/FC ratio for each stage, using the measured concentration of fuel carbon present in that stage. Furthermore, some catalysts disclosed as useful herein might provide better results with the introduction of more O2 in earlier stages, or vice versa. Alternatively, different catalysts can be employed at different stages to take advantage of the changed concentration of fuel carbon in each stage; and the preferred oxygen concentration may differ for each catalyst employed. Optimizing the concentration of oxygen for each stage will not require excessive experimentation for those skilled in the art, particularly in view of the limited number of stages that the present invention discloses as preferred. In the practice of the present invention, the O/FC ratio for each stage will be less than about 0.50 in all stages, more preferably less than about 0.40, most preferably less than about 0.30. In summary, in the practice of the present invention, the O/FC ratio for each stage will be greater than about 0.05; in other words from about 0.05 to about 0.50; preferably from about 0.05 to about 0.40; most preferably from about 0.10 to about 0.30. Correspondingly, the operation of the process of this invention, particularly when conducted to obtain high product yield (indicative of achieving high selectivity at high conversion), will be carried out in from about 2 to about 12 stages; preferably from about 2 to about 8 stages; most preferably from about 2 to about 5 stages (in each instance, inclusive of the number of stages recited).
The partial oxidation products generated in the instant process can be recovered and utilized in further synthesis processing, such as Fischer Tropsch synthesis, methanol synthesis, hydrocarbonylation, polymerization, water-gas shift, hydrogen separation, etc. According to a further embodiment of the present invention, the formed useful syngas is cooled, recovered and treated for use in further synthesis processing. Such treatment may include purification to remove low amounts of ammonia and hydrogen cyanide that may be produced in the partial oxidation process. Suitable processes for removing ammonia and hydrogen cyanide from gaseous streams are well known in the art. The removal of ammonia and hydrogen cyanide may be effected in a single step or in a plurality of steps. The cooling steps may be effected before or after the purification treatment steps, as appropriate to accommodate preferred temperatures of the treatment process. Small amounts of hydrogen may be separated from the syngas for use in a hydrocarbon upgrading process.
The treated syngas may be used, e.g., in processes that produce methanol and methanol based products, hydrocarbon synthesis (HCS) products such as liquid hydrocarbons, olefins, alcohols and aldehydes, oxo-synthesis products, ammonia and ammonia based fertilizers and chemicals, town gas and reduction gas used for the production of sponge iron, etc.
In a conventional HCS process, liquid and gaseous hydrocarbon products are formed by contacting the present syngas comprising a mixture of H2 and CO with a suitable Fischer-Tropsch type HCS catalyst, under shifting or non-shifting conditions. Suitable Fischer-Tropsch catalysts comprise one or more Group VIII catalytic metals such as Fe, Ni, Co, Ru, and Re. In one embodiment, the catalyst comprises catalytically effective amounts of Co and one or more of Re, Ru, Fe, Ni, Th, Zr, Hf, U, Mg, La on a suitable inorganic support material, preferably one which comprises one or more refractory metal oxides. Preferred supports for cobalt-containing catalysts comprise titania, particularly when employing a slurry HCS process in which higher molecular weight, e.g., C10+ products, primarily paraffinic liquid hydrocarbon products, are desired.
The hydrocarbon products produced by an HCS process according to an embodiment of the present invention are typically upgraded to form suitable products such as, synthetic crude oil, liquid fuels (e.g., jet and diesel), lubricating industrial or medicinal oil, waxy hydrocarbons, olefins (by, e.g., catalytic cracking or steam cracking), etc. Details of these processes are well known to those skilled in the art and need not be described here. All or a portion of the HCS products can be fractionated and then converted in one or more steps with or without a suitable catalyst or in the presence of hydrogen or both. Hydroconversion is usually preferred and includes mild hydrotreating (resulting in minimal branching) to make pumpable liquids, hydroisomerization (somewhat more branching, e.g., 25 to 85% and, preferably mono-methyl branching) for making distillates such as jet fuels and diesel fuels, and more severe hydroisomerization (where virtually all, e.g., less than 10 wt. % and preferably less than 5 wt. % of the feed remains unconverted) to make lube oils. These processes are also well known and reported in the literature in so far as catalysts and reaction conditions are concerned.
The ranges and limitations provided in this specification and claims are those that are believed to particularly point out and distinctly claim the instant invention. However, it is understood that other ranges and limitations that perform substantially the same function in substantially the same way to obtain the same or substantially the same result are intended to be within the scope of the instant invention as defined by this specification and claims.
The process of the present invention is further described by way of the following illustrative examples which are not intended to limit the scope of the invention in any manner whatsoever.

Catalytic partial oxidation using staged oxygen addition


A circular cut-off saw blade with a circular body having a peripheral edge, a plurality of curved slots spaced along the peripheral edge, each slot having an open outer end connecting with the peripheral edge, and defined by essentially parallel, continuously-curved sidewalls leading away from the peripheral edge, and cutting segments fixed to the peripheral edge between each pair of adjacent slots.

This invention relates to a circular saw blade.
Diamond blades are used to cut a variety of hard, abrasive, difficult-to-cut materials, such as concrete, stone, asphalt, and brick. The cutting portion of the blade, called a xe2x80x9csegmentxe2x80x9d is comprised of diamond abrasive grit particles held in place by a metallic matrix or xe2x80x9cbond.xe2x80x9d In use, the diamond abrasive grit particles act like tiny cutting points; they are forced through the material being cut by the power of the saw machine, causing fracture of the parent material which produces the cutting action. As the diamond abrasive particles do the work, they slowly wear away and become dull or fractured. For the blade to keep cutting, the bond material must also wear away to expose new diamond particles. If the bond and diamond are correctly designed and matched to the material being cut, the blade will continue to cut until the entire segment is worn away.
There are two primary performance measures for a diamond blade:
1. Lifexe2x80x94how much cutting can be done before the segment is gone; measured in inch-feet or square inches of cut. Life will vary depending on the material being cut.
2. Speed of Cutxe2x80x94how quickly the blade moves through the material; measured in inch-feet per minute or square inches per minute. Speed of cut also varies with the material being cut.
Increased life is typically achieved by using a bond material that is more wear resistant and/or increasing the amount (concentration) of diamond grit. Increased speed of cut is typically achieved by using a xe2x80x9csofterxe2x80x9d or faster wearing bond material and/or decreasing the amount (concentration) of diamond grit. Thus these two performance requirements compete with each otherxe2x80x94to get longer life one must give up speed of cut, and vice-versa. This trade-off is generally accepted by the industry. However, the invention is a break-through in that it achieves increased speed of cut without sacrificing life through the physical design of the blade geometry.
This invention includes the geometry and spacing of the slots and segments around the periphery of a circular cut-off saw blade. The slots are designed to produce maximum airflow and cooling of the saw in use. The segments are designed to work with the slots to maximize the airflow and cooling effect of the slots. This blade design is intended primarily for dry-cutting applications. It may also offer advantages for wet-cutting applications.
Design features of the slots include the curvature of the slot and the angle of the outer opening of the slot with respect to a radial line. The radius of curvature of the slots generally ranges from 1xe2x80x3 to 3xe2x80x3. The curvature of the slots is optimized to work with a specific combination of saw diameter, number of slots/segments, saw operating speed, and other design parameters to produce the maximum airflow and cooling. The curvature of the slot imparts more energy to the surrounding fluid (air) than does a straight slot.
The curvature and angle of the slots works with the rotation of the blade to produce outward airflow. There are many variations of the various parameters of the slot design. The slots may open to the periphery of the blade at an angle with respect to a radial line of from about 0xc2x0 to about 30xc2x0. The center of curvature of the slots is preferably ahead of the leading edge of the sidewall relative to the correct direction of rotation of the saw blade, but is alternatively behind the leading edge. The direction of rotation works with the angle and curvature of the slots to produce outward airflow. This orientation of slots also produces a more stable blade during cutting. Other variations include the number of slots (preferably from 4-75); the width of the slots (preferably from about 0.125xe2x80x3 to about 0.250xe2x80x3); the depth/length of the slots (preferably from about 0.5xe2x80x3 to about 2xe2x80x3); the radius of curvature of the slots (preferably from about 1xe2x80x3 to about 3xe2x80x3); and the use of more than one slot configuration on the same blade (for example, a mixture of longer and shorter or narrower and wider slots).
In the preferred embodiment of the invention, the curvature of the slots is such that as the blade advances (rotates) into static air, the innermost portion of the slot advances first, and is curved so that the direction of the slot is close to parallel with the direction it is traveling relative to the air. The air flows into the slot to fill the vacuum that would otherwise occupy the slot. As the blade continues to advance, the angle of the slot gradually changes toward a more radial angle; and the air is accelerated in a progressively more radial direction. Finally, as the slot exits the steel, the direction of the slot is radial, and the direction of the air flow is nearly radial.
Of the total circumference of the blade, a portion is covered by segments and a portion is used by the slots. The segments are in contact with the workpiece; in the slot area there is no contact. The total contact area can be expressed as a portion or percentage of the total peripheral area. Typical contact area values are in the range of 80-90% (of the full circumference). Blades with a lower contact area (in the range of 80-85% or less) typically act xe2x80x9csofterxe2x80x9d, meaning that they cut faster and wear quicker, all other things being equal. Conversely, blades with a higher contact area (85-90% or above) typically act xe2x80x9charderxe2x80x9d, meaning that they cut slower and wear faster. With the lower contact area, there is more power per square inch of cutting area applied by the machine; this results in higher load per abrasive particle, which makes that particle bite into the work-piece more, but it also causes the abrasive to wear and break-down faster.
The preferred configuration of the inventive blade is toward the low end of the xe2x80x9cconventionalxe2x80x9d range on peripheral contact areaxe2x80x94approximately 80%. By keeping the peripheral contact area toward the low end of the range, there is a good amount of room for slots. The bigger the slot, the more air it can move. However, if the slots are too big, the peripheral area is too low, and the blade will wear too quickly. The aim is to have enough area for good life, and also achieve fast cut. Accordingly, in one respect, the size of the slots is optimized to give the best blend of a large slot for air-flow combined with adequate peripheral contact area for blade life.
The length and curvature of the slot is also optimized to give the largest slot possible without reducing the strength and stiffness of the core below an acceptable level. Obviously, the more material that is removed by making the slot larger, the weaker and more flexible the core will become. The preferred inventive design is a compromise on size of the slot versus strength and stiffness of the core.
The number and size (length) of the segments is also optimized to give fast cut, with efficient flushing of fines, without inducing excessively fast wear or choppy cut. Standard segment lengths that are common in the diamond blade industry are 2 inches (50 mm) and 40 mm (1.575 inch), though a wide variety of segment lengths have been used. Shorter segments can be used to reduce the peripheral area and increase the speed of cut; the tradeoff is shorter blade life and a xe2x80x9cchoppyxe2x80x9d cut if the slots between the segments are excessively large. The length of the segments of the preferred embodiment herein is 1.250 inches, which provides for a high number of segments to yield the correct peripheral area and slots that are big enough to give the desired airflow effect without being so large as to produce a choppy cut. Variations contemplate segments in the 1.000-1.500 inch length range.
The invention also includes cutting segments in which the angle on the end of the segments is aligned either with radii of the blade (i.e., straight-edged segments), or aligned with the angle of the slot at the periphery, so that the edges of the segment effectively continue the slot sidewalls. There can be from 4 to 75 segments, depending on the blade diameter and the number of slots. Each segment is from about 1xe2x80x3 to about 2xe2x80x3 long. The invention can apply to blades having a nominal diameter of from about 4xe2x80x3 to about 36xe2x80x3.
The invention provides several operating advantages, including:
1. Cooler operation: The airflow cools the segments and the product being cut. This inhibits heat-induced damage to the diamond superabrasive, which would otherwise degrade the diamond particles and cause the blade to stop cutting. Current diamond blades perform very poorly in certain applications where a lot of heat is generated; and cooler-running blades generally cut faster and last longer.
2. Removal of fines: The increased airflow produces more effective removal of the fine material in the cut. Removal of the fines gives the diamond abrasive more direct contact with the parent material, which produces better cutting action. This results in faster cutting and/or longer blade life.
3. Longer blade life: The cooler running and better removal of fines make the blades last longer. This is particularly true in demanding applications where heat buildup and/or fines buildup are problems.
4. Faster cutting: The cooler running allows lower grade diamond to be used in the segments without fear of thermal degradation; lower grade diamond generally produces a faster cut.
5. Audible warning if mounted backwards: The curved slots make a different sound when operated in the opposite rotating direction; the sound of a blade that is mounted backwards is distinguishable from one that is mounted correctly.
6. Unique appearance: The design of the blade provides a unique appearance which makes the blades more easily visually distinguished from existing blades, which provides a clear product identity.


The present invention is a dough board assembly including an outer frame having top and bottom edges, an inner perimeter with the inner perimeter having at least one shoulder, at least one inner board sized to rest on the at least one inner shoulder within the inner perimeter so that at least one of the top and bottom edges extend above the inner board as it rests on the at least one shoulder. The inner perimeter has at least one perimeter length and at least one perimeter width. In an alternate embodiment, the assembly further includes a insert defining at least one orifice. In a second embodiment, the invention further comprises a rolling pin.

Baking dough is used to make a variety of baked goods including, but not limited to, cookies, pie crusts, breads, pretzels, and pizza. Typically, dough is produced by mixing the various ingredients until a relatively soft, malleable mixture is produced. The dough may then, for example, be formed into a specific shape, as in a pretzel, formed into a particular shape as for a bread loaf, or rolled into a flat sheet and cut into a desired shape, such as a shaped cookie.
When baking dough is rolled into a flat sheet, flour is often used to prevent the dough from sticking on the working surface, the rolling pin, or other item in the work area. The flour often is inadvertently spread throughout a large portion of the kitchen, bakery, or other work station which leads to dirty conditions and even the unwanted introduction of flour into other foods or ingredients.
This problem of unwanted flour distribution is aggravated by the breaking off of small pieces or crumbs of dough while it is being processed. In a typical large flat working surface, such as a kitchen or bakery counter, these dough crumbs are often dispersed over wide areas. Therefore, it would be helpful if both flour and dough crumbs were confined to a small, specific space where the dough is actually processed.
Another difficulty often found in working or processing baking dough is the need to achieve a uniform desired thickness of the final product. As dough is rolled, different amounts of pressure may be placed on different parts of the dough so that some parts of the resulting sheet of dough are thinner than other parts. Typically, the perimeter of the sheet is thinner than the interior of the sheet. As a result, forms, such as cookies, that are cut out of the perimeter of the sheet are thinner and often require lower baking temperatures or shorter baking times than thicker forms. In the same vein, the thinner edge portion of a larger piece, such as a pie crust may require a shorter cooking time and/or lower temperature than the thicker interior of the pie crust. Obviously, determining correct baking times becomes more difficult and problematic when pieces with different thicknesses are baked at the same time. It would be advantageous, therefore, to produce pieces having a more closely uniform thickness to allow for more consistent baking times and temperatures.
An additional factor to be considered in processing baking dough is the desirability of keeping the dough chilled as long as possible. Mixed dough is usually stored in a refrigerator and rolled or otherwise processed on surfaces such as marble or granite that will help to maintain the chilled temperature as long as possible. Inevitably, the longer the dough is processed, the warmer it becomes. When warm, the shortening component in the dough breaks down and the dough them becomes sticky and harder to work. Therefore, it would be beneficial to provide a device or apparatus that would keep the dough in a chilled condition or at least slow the rate of warming of the dough.
A dough board seen at http://armchair.com/store/gourmet/baking/doughboard1.html includes a frame and a board assembly (the "armchair assembly") that is described as adjustable to provide for rolling dough sheets with different thicknesses. Similarly, U.S. Pat. No. 6,607,187 to Adler discloses a board for rolling dough, preferably fabricated from wood in which an outer frame is provided with a plurality of grooves and tongues onto which a board may be positioned at different heights within the frame. Neither of these prior art devices addresses the problem of maintaining the dough at a chilled temperature while it is being processed. In addition, both the armchair assembly and the board disclosed in the '187 patent are made with a non-integral construction from different pieces of wood fastened together providing numerous grooves, joints and cracks where pieces and crumbs of dough can lodge making thorough cleaning difficult and often uncertain. This is compounded in the dough board seen in the '187 patent by the use of numerous tongue and groove combinations each of which is a place where dough crumbs, flour, and dirt may lodge without being successfully removed.
Thus, there is a need in the field for a device that will enable the user to reduce the distribution of processing waste such as flour and crumbs when dough is processed, is easy to clean, and also enable the dough to be maintained at a lower temperature for a longer period of time while it is being processed.


The method of laser surface treating pre-prepared zirconia surfaces provides for applying an organic resin in a thin, uniform film to a zirconia surface; maintaining the resin-coated zirconia surface in a controlled chamber at approximately 8 bar pressure at a temperature of approximately 175 degrees Centigrade for approximately 2 hours; heating the resin-coated zirconia surface to approximately 400 degrees Centigrade in an inert gas atmosphere, thereby converting the organic resin to carbon; and irradiating the carbon-coated zirconia surface with a laser beam while applying nitrogen under pressure, thereby forming a zirconium carbonitride coating.

1. Field of the Invention
The present invention relates to ceramics, and particularly to a method of laser surface treating pre-prepared zirconia surfaces, including yttria-supported zirconia, in order to harden the surfaces.
2. Description of the Related Art
Carbonitriding is a metallurgical surface modification technique that is used to increase the surface hardness of a metal, thereby reducing wear. During the process, atoms of carbon and nitrogen diffuse interstitially into the metal, creating barriers to slip, and increasing the hardness and modulus near the surface. Carbonitriding is often applied to inexpensive, easily machined low-carbon steel to impart the surface properties of more expensive and difficult to work grades of steel. Surface hardness of carbo-nitrided parts ranges from 55 to 62 HRC. An economical carbonitriding process applicable to zirconia might also address surface hardness issues for zirconia.
Laminates or composites produced by zirconia and yttria powders contain fine pores, which affect the structural homogeneity of the laminates and composites. Zirconia (ZrO2) is usually doped with small fraction (2-3%) of yttria (Y2O3) to conserve ZrO2 cubic (c-ZrO2) or tetragonal (t-ZrO2) high temperature phases down to room temperature. Surface treatment of yttria-stabilized tetragonal zirconia enhances the surface properties, such as corrosion and wear resistance, and improves the structural integrity at the surface through re-melting. The use of high energy lasers for surface treatment of such materials would offer considerable advantages, including local treatment, short processing time, and precise operation. Laser nitrogen gas-assisted processing of the surface could provide for the formation of zirconia nitride (ZrN) in the surface region. This would further improve the wear resistance of the surface, which would make it possible to use the treated surface in the cutting tool industry and hardness required other applications. Injecting particles during laser gas assisted processing modifies the surface chemistry and microstructure at the surface. The formation of zirconium carbide (ZrC) at the surface is desirable, since it is non-oxide ceramic with mixed ionic and metallic bonding, as well as high hardness.
Thus, a method of laser surface treating pre-prepared zirconia surfaces solving the aforementioned problems is desired.

Method of laser surface treating pre-prepared zirconia surfaces

King Fahd University of Petroleum and Minerals


An apparatus to use waste heat from an internal combustion engine in a vehicle, wherein the apparatus has an exhaust gas line to remove exhaust gases from the internal combustion engine, the exhaust gas line is thermally connected to a high-temperature side of a thermoelectric generator, and a latent heat accumulator is thermally connected to the high-temperature side of the thermoelectric generator.

1. Field of the Invention
The invention relates to an apparatus for utilizing the waste heat of an internal combustion engine in a vehicle, in particular in a railway vehicle, in which the apparatus has an exhaust gas line for removing exhaust gases from the internal combustion engine and the exhaust gas line is thermally connected to a high-temperature side of a thermoelectric generator. The invention further relates to a process for operating an internal combustion engine in a vehicle, in particular in a railway vehicle, in which exhaust gases from the internal combustion engine are diverted off through an exhaust gas line and the waste heat from the internal combustion engine that is diverted off with the exhaust gases is fed into a high-temperature side of a thermoelectric generator, and the thermoelectric generator utilizes the waste heat to generate electrical energy.
2. Description of Related Art
An apparatus of this type and a process of this type are disclosed in US 2005/0268955 A1. As also described in this publication, the internal combustion engine may in particular be the traction motor of a vehicle, for example a railway vehicle. In particular, in this case the internal combustion engine generates energy (in particular by driving a mechanically driven electric generator) for the traction of the vehicle and optionally also for other devices on the vehicle. The internal combustion engine is usually thermally connected to at least one coolant circuit.
The invention relates in particular to the field of railway vehicles, in which much more powerful internal combustion engines typically are used than is the case with highway vehicles. The railway vehicle may in particular be a locomotive, for example a diesel-electric locomotive. However, use of the invention in other vehicles, such as ships, is also conceivable.
In the apparatus that is described in US 2005/0268955 A1, high fluctuations are encountered in the generation of electrical power by the thermoelectric generator. In particular, the electrical power of the generator is low when the internal combustion engine generates low mechanical power. The problem is intensified by the fact that the efficiency with which a thermoelectric generator generates electrical energy from heat depends, among other things, on the temperature level on the high-temperature side of the generator. When waste heat from the exhaust gas line of the internal combustion engine is used, though, the temperature of the exhaust gas varies greatly within a very wide temperature range.

Operation of an internal combustion engine


A window retention system includes a door frame having an exterior panel, an interior panel, an opening therethrough defining an inner peripheral channel, the exterior panel includes an upright portion extending along the channel so as to be directed toward the interior panel; and a resiliently flexible window retainer strip yieldably interlocked with and thereby detachably mounted on the door frame. The retainer strip has a longitudinal axis and a first upright portion spaced from and in opposing relation with the upright portion of the exterior panel so as to delimit a first track in the channel and retain the window element therein. The strip includes a second upright portion laterally spaced from the first upright portion. The second upright portion is biased towards and yieldingly interlocks with the channel. A flange extends from the first upright portion of the strip to engage one of the door frame panels and thereby secure the first upright portion of the strip against rotation in a vertical plane. The retainer strip can be adapted to achieve full view, self-storing, and triple track window mountings in a variety of door frames, some of which utilize snap-in liners.

The present invention relates to the field of doors, more particularly to doors commonly referred to as xe2x80x9cstorm doorsxe2x80x9d for exterior entryways. Such doors typically include one or more window elements (glass-like plates, screens, vents, blinds and the like) which must be retained in the door frame during use, but whose removal may be desired for cleaning or other purposes. This invention provides a unique and versatile window retention system for doors.
Conventional storm doors often provide one or more window elements which are movable within a single door frame. Certain storm doors even provide window elements which are removable and interchangeable. The same is true for windows that are not included in a storm door. However, storm doors have some inherent problems that have heretofore been difficult to overcome. For instance, the window elements tend to deflect easily in the wind because of their relatively large surface. Typically, large amounts of weather stripping must be applied to the window elements and/or the door frame to fill the gaps.
Another problem is that movable window elements in conventional storm doors are typically rectangular and are supported or held only at their four corners. Thus, the intervening edges extend unsupported and are subjected to deflection due to the wind. In addition to the obvious problem of energy inefficiency, the unsupported edges may rattle against the door frame or other adjacent structures. Furthermore, moving the window elements can be precarious and unpredictable. A pair of swivel pins typically protrude from the upper corners of the movable window element and a pair of spring loaded latches are laterally extensible from the bottom corners. Both the pins and latches utilize a pair of vertical slots with a series of vertically spaced apertures extending through the liner, if one is present, and into the door frame. When the latches are withdrawn from the slots in order to move the window element, only the pins at the top secure the window element. The bottom of the window element tends to swing out of its track and toward the user. As a result, the top of the window and the pins therein can unexpectedly slide downwardly. Because the window element is supported in only four places and the contact areas are relatively small, the movement of the window element in its track tends to be sudden and unpredictable.
A primary objective of this invention is the provision of a universal system for detachably retaining window elements in a door.
Another objective of this invention is the provision of a window retention system which allows window elements to be snapped/released into place from one side of the door.
Another objective of this invention is the provision of a window retention system which allows window elements to be inserted into the door without the use of tools.
Another objective of this invention is the provision of a universal snap-in jamb liner which can accommodate either a self-storing or triple track window element set.
Another objective of this invention is the provision of a retainer strip which removably interlocks with a door frame or liner to retain a window element such that deflection of the window element by wind forces is minimized.
Another objective of this invention is the provision of a window retention system in which the window elements can be slidably raised and lowered without releasing any portion of the window element from horizontal retention.
Another objective of this invention is the provision of a window retention system which has fewer component parts while still providing a broad spectrum of products.
Another objective of this invention is the provision of a window retention system which is economical to manufacture, durable, flexible and reliable in use.
These and other objectives will be apparent from the description and claims which follow in view of the drawings.
The present invention relates to a window retention system for doors. The system adapts to various door frames and allows components, including window elements, to be installed and removed without tools. The system includes: a door frame having a window opening therethrough; a set of liners for the window opening; and retainer strips which are interposable between the window elements, the liners, and/or the frame so as to retain the window elements in the door frame.
Some opposing liners can be spring-loaded to yieldingly retain and center the window elements therebetween. This adjustable tension system yields more predictable sliding action for the window elements while greatly simplifying assembly. Window elements can be installed, removed and interchanged with greater ease.
Another aspect of this invention is the structure of the retainer strip which springingly and removably interlocks with the liner or the door frame to retain the window element(s) thereon. Once released against the liner or the door frame, the retainer strip provides a counter-acting force against the wind which might otherwise deflect the window element. The configuration of the retainer strip and its placement are adaptable to a variety of applications with minor changes. Similar strips can be used in door frames with liners, without liners, with single window elements, and with multiple window elements.

Strip for retaining storm door window elements


A method for processing an audio signal in accordance with a room impulse response is described. The audio signal is separately processed with an early part and a late reverberation of the room impulse response, and the processed early part of the audio signal and the reverberated signal are combined. A transition from the early part to the late reverberation in the room impulse response is reached when a correlation measure reaches a threshold, the threshold being set dependent on the correlation measure for a selected one of the early reflections in the early part of the room impulse response.

Spatial audio coding tools are well-known in the art and are standardized, for example, in the MPEG-surround standard. Spatial audio coding starts from a plurality of original input, e.g., five or seven input channels, which are identified by their placement in a reproduction setup, e.g., as a left channel, a center channel, a right channel, a left surround channel, a right surround channel and a low frequency enhancement channel. A spatial audio encoder may derive one or more downmix channels from the original channels and, additionally, may derive parametric data relating to spatial cues such as interchannel level differences in the channel coherence values, interchannel phase differences, interchannel time differences, etc. The one or more downmix channels are transmitted together with the parametric side information indicating the spatial cues to a spatial audio decoder for decoding the downmix channels and the associated parametric data in order to finally obtain output channels which are an approximated version of the original input channels. The placement of the channels in the output setup may be fixed, e.g., a 5.1 format, a 7.1 format, etc.
Also, spatial audio object coding tools are well-known in the art and are standardized, for example, in the MPEG SAOC standard (SAOC=spatial audio object coding). In contrast to spatial audio coding starting from original channels, spatial audio object coding starts from audio objects which are not automatically dedicated for a certain rendering reproduction setup. Rather, the placement of the audio objects in the reproduction scene is flexible and may be set by a user, e.g., by inputting certain rendering information into a spatial audio object coding decoder. Alternatively or additionally, rendering information may be transmitted as additional side information or metadata; rendering information may include information at which position in the reproduction setup a certain audio object is to be placed (e.g. over time). In order to obtain a certain data compression, a number of audio objects is encoded using an SAOC encoder which calculates, from the input objects, one or more transport channels by downmixing the objects in accordance with certain downmixing information. Furthermore, the SAOC encoder calculates parametric side information representing inter-object cues such as object level differences (OLD), object coherence values, etc. As in SAC (SAC=Spatial Audio Coding), the inter object parametric data is calculated for individual time/frequency tiles. For a certain frame (for example, 1024 or 2048 samples) of the audio signal a plurality of frequency bands (for example 24, 32, or 64 bands) are considered so that parametric data is provided for each frame and each frequency band. For example, when an audio piece has 20 frames and when each frame is subdivided into 32 frequency bands, the number of time/frequency tiles is 640.
In 3D audio systems it may be desired to provide a spatial impression of an audio signal as if the audio signal is listened to in a specific room. In such a situation, a room impulse response of the specific room is provided, for example on the basis of a measurement thereof, and is used for processing the audio signal upon presenting it to a listener. It may be desired to process the direct sound and early reflections in such a presentation separated from the late reverberation. This involves determining where the early reflections end and where the late reverberation starts.

Method for processing an audio signal in accordance with a room impulse response, signal processing unit, audio encoder, audio decoder, and binaural renderer

Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.


A method for fabricating an AMOLED display device is provided. A substrate is provided. A device layer having multiple active devices is formed on the substrate. A flat layer is configured on the device layer. A first, a second and a third color photoresistant layers are respectively configured on the flat layer and are patterned to form a first, a second and a third color filter layers. The first, the second and the third color filter layers respectively define a first, a second and a third pixel areas and are used for etching masks to etch the flat layer for exposing parts of the active devices. A first, a second and a third pixel electrode are respectively configured in the mentioned pixel areas and are electrically connected with the active devices. A first, a second and a third organic light emitting layers are respectively configured on the mentioned pixel electrodes.

1. Field of the Invention
The present invention relates to a method for fabricating an Active Matrix Organic Light Emitting Diode (AMOLED) display device and a structure of such device, and particularly to a method for fabricating an AMOLED display device and a structure thereof, in which color filter layers are processed by a half-tone mask.
2. Description of Related Art
An Organic Light Emitting Diode (OLED) is a semiconductor device capable of efficiently converting electrical energy into optical energy. OLEDs are wildly used as luminous elements in indication lights, display panels and optical reading/writing heads. Wherein, OLED display devices, having advantages such as free-viewing angles, simple processing, low production cost, fast response, wide operation temperature range and full color displaying, meet the demands of modern display devices in the multimedia field. So, in recent years, OLEDs are being enthusiastically researched and developed.
An AMOLED display device having a structure of color filter on array (COA) has been proposed. The fabricating methods and structures related to the AMOLED are also developed and proposed by many scholars. FIGS. 1A through 1F are schematic cross-sectional views illustrating a process for fabricating a conventional AMOLED display device having a structure of COA.
Referring to FIG. 1A, a substrate 100 is prepared. The substrate 100 has a device layer 110 configured thereon. The device layer 110 includes a plurality of thin film transistors (TFT) 120 (only one exemplarily shown), a plurality of scan lines (not shown) and a plurality of data lines (not shown). The TFTs 120 are driven by the scan lines and the data lines.
Referring to FIG. 1A, each TFT 120 includes a silicon island 121, a gate-insulating layer 122, a gate electrode 123, a source electrode 124a, a drain electrode 124b, an inter-layer dielectric (ILD) layer 125, and a source/drain contact metal 126. The ILD layer 125 has an opening 125a configured for exposing the source electrode 124a and the drain electrode 124b of the TFT 120. The source/drain contact metal 126 is electrically connected with the source electrode 124a and the drain electrode 124b. The source/drain contact metal 126 is adapted for electrically connecting the TFT 120 with a sequentially formed transparent conductive layer 150.
Referring to FIG. 1B, the ILD layer 125 is taken as a buffer layer for making a color filter array, that is the foregoing mentioned COA structure. Three times of procedures including coating color light resistant, exposing and photolithography are processed for respectively forming a red color filter layer 130, a green color filter layer (not shown) and a blue color filter layer (not shown) on the ILD layer 125. It is to be noted that the positions of the red color filter layer 130, the green color filter layer and the blue color filter layer are respectively corresponding to the subsequently formed pixel areas 162.
Now referring to FIG. 1C, a flat layer 140 is then formed on the substrate 100. The flat layer 140 covers the red color filter layer 130, the green color filter layer (not shown) and the blue color filter layer (not shown). Then, the flat layer 140 is patterned for forming a contact window opening 142, which exposes the source/drain contact metal 126.
Referring to FIG. 1D, a transparent conductive layer 150 is formed on the flat layer 140. The transparent conductive layer 150 is electrically connected with the source/drain contact metal 126 via the contact window opening 142.
Referring to FIG. 1E, a pixel defining layer 160 is then formed on the transparent conductive layer 150, for defining a plurality of pixel areas. The pixel defining layer 160 is generally formed by either coating an organic photoresistant layer, followed by exposure and photolithography; or coating an inorganic layer and then processing procedures of photolithography and etching.
Then referring to FIG. 1F, an organic light emitting layer 170 is formed in the pixel area 162 and thus completing the fabrication of the AMOLED display device 200. The organic light emitting layer 170 is controlled to emit light by switching actions of the TFT 120 to apply voltages on the transparent conductive layer 150. Light emitted from the organic light emitting layer 170 is therefore filtered by the color filter array layer (as the red color filter layer 130 shown in the drawings) to be color light.
It is to be noted that the process for fabricating the color filter array layer of the foregoing AMOLED display device 200 having COA structure requires three times of procedures including coating color photoresistant layer, exposing and photolithography. Further, a process of patterning the flat layer 140 to configure the contact window opening 142 is needed for electrically connecting the TFT 120 with the transparent conductive layer 150. Furthermore, another procedure including coating and patterning processes is also needed for configuring a pixel defining layer 170, which is required for defining the pixel areas 162, in which the organic light emitting layers 170 are to be coated.
According to the foregoing, the fabrication of the conventional AMOLED display device 200 having COA structure is complicated and the production cost thereof is unlikely to be lowered.

Method for fabricating active matrix organic light emitting diode display device and structure of such device


A multichannel electrical power amplifying system constructed and arranged to distribute electrical power of amount P to a total load coupled thereto. The system includes a plurality n of power amplifier channels, coupling the power amplifying system to a portion of the electrical load. Each of the amplifier channels distributes a portion of the electrical power P to a portion of the electrical load. Each power amplifier channel has a power distribution capacity, at least one of the power amplifier channels having a power distribution capacity significantly greater than       P    n    .

The invention relates to power amplifiers, and more particularly to multichannel power amplifiers. The power distribution capacities of multichannel amplifiers are typically xe2x80x9crated,xe2x80x9d on a xe2x80x9cper channelxe2x80x9d basis, usually on an xe2x80x9call channels drivenxe2x80x9d basis; that is, each of the four channels has a power distribution capacity of the per channel rating when all the channels are driving an electrical load. The total power distribution capacity of the amplifier system (often unspecified in a conventional multichannel amplifier) is the sum of the xe2x80x9cper channelxe2x80x9d ratings. For example, a four channel amplifier may be rated as 100 watts per channel, that is, each channel has a power distribution capacity of 100 watts, and the total rating, or power distribution capacity of the multichannel amplifier is 400 watts. To use all 400 watts of power distribution capacity, each channel would have a total load of 100 watts, but no more.
It is an important object of the invention to provide an improved multichannel power amplifier.
According to the invention, a multichannel electrical power amplifying system is constructed and arranged to distribute electrical power of amount P to an electrical load coupled thereto. The system includes a plurality n of power amplifier channels, coupling the power amplifying system to a portion of the electrical load, each of the amplifier channels for distributing a portion of the electrical power P to a portion of the electrical load. Each power amplifier channel has a power distribution capacity, and at least one of the power amplifier channels is constructed and arranged to have a power distribution capacity significantly greater than   P  n
and the sum of the capacities of the plurality of amplifier channels is significantly greater than P.
In another aspect of the invention, a multichannel electrical power amplifying system is constructed and arranged to provide a total amount of electrical power P. The amplifying system includes a plurality of electrically powered devices, the plurality of devices representing an electrical load. The amplifying system also includes a number n of power amplifier channels, each amplifier channel coupled to a portion of the electrical load, each of the plurality of power amplifier channels for providing a portion of the total amount of electrical power P to the portion of the electrical load. One of the portions significantly exceeds       P    n    .
The amplifying system also includes a plurality of input channels for receiving a plurality of input signals and circuitry to selectively route the input signal from any of the plurality of input channels to any one of the power amplifier channels.
Other features, objects, and advantages will become apparent from the following detailed description, which refers to the following drawing in which:

Abstract: The sum of the capacities of the plurality of amplifier channels is significantly greater than P.


Systems and methods for building and/or simplifying structured-document path-language expressions are described. One of these systems or methods enables a user to graphically select structured-document path-language functions and addresses. With these addresses and functions, a structured-document path-language expression can be built without a user having to fully understand or type in syntax for the expression. Another of these systems or methods simplifies structured-document path-language address and function syntax. This simplification can aid a user in building and easily understanding a structured-document path-language expression.

Extensible markup language (XML) is increasingly becoming the preferred format for electronic documents. XML is a tag-based hierarchical language that is extremely rich in terms of the information that it can be used to represent. For example, XML can be used to represent information spanning the spectrum from semi-structured information (such as one would find in a word processing document) to generally structured information (such as that which is contained in a table). For more information on XML, the reader is referred to the XML 1.0 Second Edition Specification which is the work of and currently available from the W3C (World Wide Web consortium).
To locate and process data in XML documents, another language, called the XML Path Language ("XPath"), can be used. XPath includes an addressing syntax for locating nodes in an XML document's hierarchical structure and functions performable on or with the nodes. XPath is a W3C standard. For more information, the reader is referred to the W3C's website, where information about XPath is currently located.
Using XPath, however, can be tedious and require a significant understanding of XPath and XML. To write XPath expressions, for instance, a user often needs lengthy training in how the XPath syntax is constructed and which functions it can perform. Even with this training, writing XPath expressions can be tedious and time consuming. XPath is also unforgiving; a small syntactical error, like a period or comma out of place, can make an XPath expression fail. If the expression fails, XPath is often not helpful in showing the user how to fix the error.
Assume, for example, that a user wishes to write an XPath expression to add the data in two of the "cost" nodes listed below. The namespaces listed below represent names for hierarchically arranged nodes of an XML document.
NS1:myfields                NS1:items                    NS1:item                            NS1:quantity                NS1:price                NS1:cost                                    NS1:item                            NS1:quantity                NS1:price                NS1:cost                                    NS1:item                            NS1:quantity                NS1:price                NS1:cost                                    NS1:item                            NS1:quantity                NS1:price                NS1:cost
If the user understands XML and XPath, he or she can write the XPath expression by: 1) determining what syntax is needed to address the first cost node; 2) typing in that syntax; 3) determining what syntax is needed to perform the function of addition; 4) typing in that syntax; 5) determining what syntax is needed to address the third node; and 6) typing in that syntax.
Thus, to construct an XPath expression that can add data within the first and third "cost" nodes, the user has to determine the syntax to address the first cost node and type it in:
/NS1:myfields/NS1:items/NS1:item/NS1:cost[1]
Next, the user has to determine the syntax for the function of addition, which is the "+" symbol. While this symbol is intuitive, many other XPath functions are not intuitive and so can require training to understand. The user then types the "+" symbol in:
/NS1:myfields/NS1:items/NS1:item/NS1:cost[1]+
Next, the user must determine the syntax to address the third cost node and type it in:
/NS1:myfields/NS1:items/NS1:item/NS1:cost[1]+/NS1:myfields/NS1/items /NS1:item/NS1:cost[3]
As this example shows, writing even a simple XPath expression can require training in XML and XPath, and can be tedious and time consuming as well. Also, even a small error in an XPath expression's syntax can cause the expression to fail, potentially requiring the user to find and fix the error or retype the expression.
Given the foregoing, there is a need for a user-friendly and/or non-technical way to create XPath expressions.

Structured-document path-language expression methods and systems


The present invention provides a thermal recording material, which is easy to manufacture and has excellent productivity, water resistance, heat resistance (running stability) and chemical resistance, by solving various problems caused by using a crosslinking agent for a protective layer.

1. Field of the Invention
The present invention relates to a thermal recording material, and more specifically to a thermal recording material which, by using a protecting layer made from a coating solution not having a crosslinking agent combined therewith, can contribute greatly to improvement in productivity, and solves various problems caused by the crosslinking agent, and at the same time, has improved heat resistance, water resistance and chemical resistance.
2. Description of the Related Art
Generally, a recording material which comprises a recording layer formed on a support and mainly composed of an electron donating colorless or lightly colored basic dye and an electron accepting organic or inorganic substance and having a binder, a filler, a sensitizer, a lubricant and the like blended therewith, are well known as a thermal recording material by a color reaction through a fusion contact between functional units by heat. (Japanese Examined Patent Publication Nos. 43-4160, 45-14039 and the like).
Such a thermal recording material is widely used for an output sheet for a variety of printers including facsimiles, a terminal for industrial instrumentation, a terminal for medical care, a handy terminal, a POS system and a ticket vending system because recording function is beforehand effected with the support (a paper, a synthetic paper, a synthetic resin film and the like). Thus, an image can be obtained by simply heating it with a thermal head, a thermal pen, a laser beam and the like, a complicated development process is not required, and an output device having a relatively simple and compact structure, and easy maintenance can be used.
In recent years, as the application of these thermal recording materials is expanding, the environments in which they are used have are also diversifying. However, there are the following prevalent problems in their ordinary use.
Specifically, the recording layer often peels off when the thermal recording materials are brought into contact with water, the recorded images fade or discolor when the thermal recording materials are brought into contact with a plastic film or sheet comprising plasticizers, the recorded images develop color when the thermal recording materials are brought into contact with organic solvents, and the like, and thus the thermal recording materials do not sufficiently satisfy storage stability.
Therefore, as means for solving the above-mentioned problems, various methods in which a protective layer is provided on a heat-sensitive recording layer have been proposed and carried out. However, these methods require that the protective layer be crosslinked in order to highly protect the heat-sensitive recording layer under various environments. For this purpose, the protective layer is prepared by curing it with combinations of various aqueous resins and various crosslinking agents, and the like. For example, the protective layer having improved oil resistance and heat resistance (adhesion of gases to a thermal head) by using glycidyl type crosslinking agents (Japanese Unexamined Patent Application Publication No. 57-188392) has been proposed, but it has poor reactivity and water resistance.
A protective layer having an amino compound together with a glycidyl-based crosslinking agent (Japanese Unexamined Patent Application Publication No. 64-61287) has excellent water resistance and chemical resistance, but it is not suitable for labels for foods because it generates formalin. Although an aziridine-based crosslinking agent has a high reaction rate, it is unstable in an aqueous solution, which makes it difficult to handle. A method using an isocyanate-based compound (Japanese Unexamined Patent Application Publication No. 57-19036) is similarly not satisfactory. Proposals of using an epoxy-based crosslinking agent (Japanese Unexamined Patent Application Publication Nos. 49-36343, 60-68990, and 5-318926) still have problems in that a crosslinking agent having an aromatic ring is insufficient in providing resistance to plasticizers and that a crosslinking agent based on glycidyl ether of polyhydric alcohol causes a skin color development. A known polyamine-amide-epichlorohydrin modified crosslinking agent is not preferred in view of environmental conservation because it contains chlorine.
As such, the methods using crosslinking agents make it possible to solve the above-mentioned problems to some extent, but the methods are still insufficient in overcoming the problems.
Further, since these crosslinking agents are crosslinked at low temperatures, it is difficult to ensure the stability of a coating solution (variation over time) after mixing it with a resin as a main ingredient, and heat required for the crosslinking agents for sufficient crosslinking of the thermal recording material, cannot be applied thereto during the production process, in view of the properties of the thermal recording materials. For these reasons, there are problems in the process wherein after coating, the thermal recording materials must be aged over a long time period, which cause problems in its productivity.
In view of the circumstances explained above, an object of the present invention is to provide a thermal recording material, which is easy to manufacture and has excellent productivity, and also excellent in water resistance, heat resistance (running stability) and chemical resistance, by solving various problems caused by using a crosslinking agent for a protective layer.

Abstract: The thermal recording material of the present invention comprises a protective layer mainly composed of a resin emulsion (a) comprising a copolymer resin emulsion (b) containing (meth)acrylonitrile and a vinyl monomer copolymerizable therewith, and having an SP value (solubility parameter) of 12.0 or more, a glass transition temperature (Tg) of 10 to 70° C., and a minimum film-forming temperature (MFT) of 5° C. or less, and a polyolefin copolymer resin emulsion (c).