A method of fabricating an integrated circuit which maintains global planarization throughout the process flow is achieved. Trenched isolation regions are formed within a silicon substrate. Trenched polysilicon gate electrodes are formed within the silicon substrate and within the trenched isolation regions. Source and drain regions are formed within the silicon substrate wherein the top surfaces of the trenched isolation regions, the trenched polysilicon gate electrodes, and source and drain regions form a planarized top surface of the silicon substrate. A pre-metal dielectric layer is deposited over the planarized top surface. Contact openings are formed by etching through the dielectric to the trenched polysilicon gate electrodes and to the source and drain regions. The contact openings are filled with tungsten plugs wherein the top surfaces of the pre-metal dielectric and the tungsten plugs form a planarized top surface of the silicon substrate. A first metal layer is deposited over the planarized top surface. Oxygen ions are implanted into the first metal layer whereby the first metal layer is transformed into an insulator layer except where the layer is covered by photoresist wherein the top surface of the first metal layer forms a planarized top surface of the silicon substrate. The inter-metal dielectric layer and second metal layer are deposited, patterned, and planarized .

(1) Field of the Invention
This invention relates to the fabrication of integrated circuit devices and more particularly to a method of trenched polysilicon gate formation, tungsten-plug contact completion, and implant-induced inter-metal dielectric for improved integrated circuit devices.
(2) Description of the Prior Art
The conventional multi-level metallization process in the fabrication of Very Large Scale Integrated (VLSI) circuits suffers from a lack of planarization of the interlevel dielectric. The definition of sub-micron lines requires short wavelength photolithography at the cost of reduced depth of focus. Because of this reduced depth of focus, planarization of the layer to be exposed to photolithography is essential. An unplanarized layer requires a range of depths of focus which are not available in the sub-micron technology.
The step coverage of a metal layer formed by physical vapor deposition (PVD) is closely related to the morphology of the underlayer. More material is deposited on the "hump" than is deposited in the "valley." The larger the aspect ratio of the contact/via openings, the smaller the thickness of the metal sputtered onto the sidewalls and bottoms of the openings. For contact/via openings with a high aspect ratio larger than one, keyholes or voids naturally form in the openings and usually result in circuit failure of the contact/via opening.
In order to fill the contact/via openings with high aspect ratio of larger than one by a PVD method, a high deposition temperature or post-deposition thermal treatment is required. However, these methods suffer from difficulty of process control and sometimes the keyhole or void in the opening is inevitable. Because of these problems, the tungsten-plug process was introduced. The tungsten film can be deposited by chemical vapor deposition (CVD) with conformal step coverage. After blanket tungsten CVD and etchback, it is easy to obtain a planarized contact/via filling. Other candidates for this kind of filling include selective tungsten CVD, copper or silver CVD, as well as aluminum CVD. "An Advanced Four Level Interconnect Enhancement Module for 0.9 Micron CMOS" by C. A. Bollinger et al, VMIC Conference Proceedings, Jun. 12-13, 1990, c. 1990 by IEEE, pp. 21-27 discusses the use of a tungsten plug for contact window filling.
Even after the metal layer is deposited to an acceptable planarized surface, the morphology still shows a moderate ruggedness after metal pattern definition. The metal thickness cannot be reduced because of circuit performance considerations, but the metal line width and spacing have been reduced considerably in high density VLSI circuits. The aspect ratio of metal line spacings for the deposition of the intermetal dielectric layer is typically larger than one in sub half-micron devices. The planarization of the intermetal dielectric has become an important issue.
Many kinds of intermetal dielectric formation have been adopted to obtain an acceptable planarization. One method is to deposit dielectric conformally and etchback anisotropically many times. Its drawback is throughput and lack of productivity. Another method is to form a layer of spin-on-glass between two CVD oxide layers. The presence of aluminum limits the cure temperature and the uncured moisture in spin-on-glass always results in poisoned via as well as poor adhesion between the CVD oxides. Recently, chemical mechanical polishing (CMP) has been developed to planarize this kind of dielectric layer as well as for the conducting layer. However, the CMP method suffers from many drawbacks such as a complex process, more particles, serious loading effect, long learning time, cost of ownership, maturity, etc.
Local oxidation of silicon is the conventional lateral isolation scheme. The conventional local oxidation process (LOCOS) is described in VLSI Technology, International Edition, by S. M. Sze, McGraw-Hill Book Company, NY, N.Y., c. 1988 by McGraw-Hill Book Co., pp. 473-474. A layer of silicon nitride is deposited over a pad oxide overlying a silicon substrate. The pad oxide is a thin thermal oxide which allows better adhesion between the nitride and silicon and acts as a stress relaxation layer during field oxide formation. The nitride and oxide layers are etched to leave openings exposing portions of the silicon substrate where the local oxidation will take place. A boron channel-stop layer is ion implanted into the isolation regions. The field oxide is grown within the openings and the nitride and pad oxide layers are removed. This completes the local oxidation.
A major drawback of conventional local oxidation is a lack of planarization of the oxidized surface of the substrate. Trench isolation methods solve this problem. Typically, deep narrow trenches are used to isolate one device from another. Shallow trenches are used to isolate elements within a device, and wide trenches are used in areas where interconnection patterns will be deposited. U.S. Pat. No. 5,294,562 to Lur et al teaches one method of trench isolation with global planarization. Co-pending patent applications Ser. Nos. 08/127,061, 08/126,872, and 08/127,052, now U.S. Pat. No. 5,294,562 all filed on Sep. 27, 1993 teach other methods of trench isolation.
The articles, "Simulation of Sub-0.1-.mu.m MOSFET's with Completely Suppressed Short-Channel Effect," by Junko Tanaka et al, IEEE Electron Device Letters, Vol. 14, No. 8, August 1993, pp. 396-399 and "A New 0.25-.mu.m Recessed-Channel MOSFET with Selectively Halo-Doped Channel and Deep Graded Source/Drain," by W. H. Lee et al, IEEE Electron Device Letters, Vol. 14, No. 12, December 1993, pp. 578-580, discuss the improved performance and reliability of deep sub-micron devices afforded by trenched gates.
U.S. Pat. No. 4,814,285 to Matlock et al teaches the transformation of doped polysilicon or aluminum into an insulator by ion implanting oxygen or nitrogen for the purpose of selective deposition of tungsten or gold in contact/via openings. This method requires the use of a base layer, such as polysilicon. The contact/via formation is by selective deposition using the contact/via stud as a mask.


There is provided a heater which includes a vessel in which liquid is contained, and a heater to heat the liquid, the vessel having an inlet by which liquid can be fed into the vessel, and an outlet through which liquid may flow to a point of delivery. The inlet comprises a supply conduit connected to a liquid supply, and liquid flowing along the supply conduit is mixed with a gas. A gas trap is provided to collect gas passing with the liquid from the supply conduit within the vessel, and includes an opening to release collected gas into the vessel, whereby at least when the liquid flow along the supply conduit is stemmed, the released gas provides an expansion space in the vessel into which liquid can expand during subsequent heating, the expansion space being vented from the vessel. An air control valve restricts the amount of gas available for mixing with the liquid as the liquid flow rate through the supply conduit increases, thereby preventing aeration of the liquid.

This invention relates to a heater of the kind, hereinafter referred to as "the kind specified" including a vessel in which liquid is contained, means being provided to heat the liquid in the vessel. More particularly, but not exclusively, the invention has been devised for use as a water heater.

Electric water heater utilizing trapped air to provide expansion space


Methods and apparatus, including computer program products, for shaping amplitude contours of musical notes. A method for shaping amplitude contours of musical notes in time of particular pitch and duration includes processing musical notes to modify a contour of an amplitude shape curve of each note differently in accordance with its relationship to its succeeding note, the processing including calculating an initial amplitude shape curve, modifying a first portion of the calculated initial amplitude shape curve to be more convex or more concave, and independently modifying a second portion of the calculated initial amplitude shape curve to be more convex or more concave, the resulting modifications improving a timbre quality.

The present invention relates to data processing by digital computer, and more particularly to shaping amplitude contours of musical notes.
In music, musical notes, i.e., tones, may be struck, like they are on a piano, giving a limited opportunity for changing an amplitude shape once a note has been struck by a piano hammer that strikes the strings. A similar limitation applies to notes plucked on a harpsichord or struck on percussive instruments. Greater expressiveness on a violin is achieved as the two arms and fingers are used to control one note at a time, which enables a note to rise and decay gradually, with near unlimited variability, giving rise to the possibility of great eloquence, as well as providing difficulty of control. The human voice, the best instrument of all, has this ability, but can only sing one note at a time.
All instruments that can shape a single tone as a function of time require, for a musical effect, that it be done with appropriate discrimination and control. Only then can the emotional quality and meaning of the music be realized. The shapes of notes are individually and differentially controlled. While this is not the only parameter that serves the expressive needs of music, it is one of the important ones. Small changes in shape of single notes of a melody, or of several notes, can alter the meaning of music. Moreover, the amplitude shapes of notes, varying individually, do so in a way to achieve musical meaning.

Shaping amplitude contours of musical notes


In order to reduce the noise the exhaust of an internal-combustion engine, especially for off-road vehicles, there is utilized an absorption silencer comprising: a housing (1) made up of a plurality of mountable elements (10, 18), built from heat-resisting material and intended to be fitted and fixed in a removable way on the perforated exhaust pipe (50). Stuffing material (13) of deadening and heat-resisting material is interposed using two annular joints, a front one (20) and a rear one (21) built from partially elastic and highly heat-resisting material such as silicone or viton, and which also ensure the housing seal to the exhaust gases.. Advantageously, said the housing (1) is built from heat-resisting material, such as nylon or PPS, according to the rotary molding process.

It is known that the exhaust systems for motor vehicles are essentially made up of an exhaust pipe and of a silencer, also called "muffler", which is mainly intended to reduce the exhaust noise down to a legally set limit. To this end, the shapes and dimensions both of the exhaust pipe and the silencer are decisive factors. However, these dimensions and shapes affect negatively and heavily the performance of the engine itself by preventing the free flow of output exhaust gases especially in two-stroke engines, as mostly used in off-road vehicles.
The currently known silencers are made up of a metal housing which delimits the expansion chamber of substantially cylindrical shape and has a diameter greater than that of the exhaust pipe but with limited overall dimensions. These may be of two types: the first one, operating by "resonance or reflection", comprises more chambers fitted in series and in parallel to the outlet pipe of the gases which acoustically filter the more relevant portions of exhaust noise; and the second one, operating by "absorption", comprises a deadening material such as rock wool, placed between the pierced exhaust pipe and the housing, which dissipates the exhaust gases energy into heat by its vibration.
Such currently known silencers share the characteristic of having the housing built from metal in one or more parts fixed to each other and to the exhaust pipe by welds and this causes a string of non-negligible drawbacks; in fact, owing to the high performance required to the engine, the stresses imposed to the exhaust system are heavy and the direct transmission of heat and vibrations to the silencer cause a thermal loss, fast wear and favor the breaking of the housing at the weld points. Whenever a component breaks, it is necessary to replace the whole exhaust system and this implies a relevant expanse. In addition to this, laws which limit the noise produced by the exhaust gases in motor vehicles, especially in off-road vehicles, make these silencer arrangements unsuitable to meet technical as well as economical requirements.

Absorption silencer for internal-combustion engines, especially for off-road vehicles

Acerbis Plastica Italia s.p.a., Via Volta 5


The present disclosure relates to a device for use in ligament reconstruction surgery. The device includes a handle, a tube coupled to the handle, and a locking mechanism coupled to the handle. A method for use during ligament reconstruction surgery is also disclosed.

1. Field of Technology
The present disclosure relates to ligament reconstruction surgery, and more specifically, a device and method for determining lengths during reconstruction surgery.
2. Related Art
The creation of reconstruction tunnels in the femur for ligament reconstruction surgery is required for the attachment of a soft tissue graft, such as a patellar tendon or a semitendinosis tendon. The lengths of the femoral tunnels needs to be determined and calculations need to be made to determine the appropriate lengths for the implants that are used to fixate the grafts in the tunnels. Currently, manual calculations are used to determine these lengths. These manual calculations are often inaccurate and time consuming. Therefore, a device and method for calculating these lengths are needed.

Device and method for use during ligament reconstruction surgery


Processes for preparing a carbon black product having an organic group attached to the carbon black. In one process at least one diazonium salt reacts with a carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt. In another process at least one diazonium salt reacts with a carbon black in a protic reaction medium. Carbon black products which may be prepared according to process of the invention are described as well as uses of such carbon black products in plastic compositions, rubber compositions, paper compositions, and textile compositions.

This invention relates to a process for the preparation of carbon black products. The process involves reacting a diazonium salt with a carbon black to yield a carbon black product having an organic group attached to the carbon black. The invention also relates to new carbon black products and their uses.
Much effort has been expended over the last several decades to modify the surface chemistry of carbon black. While it is possible to deposit physically adsorbed material onto the surface of carbon black, permanently changing the surface chemistry of carbon black is substantially more difficult.
Some processes for chemically changing the surface of carbon black are known and used commercially. For example, it is well known that a carbon black surface can be oxidized with a variety of treating agents. Surface oxidation is used to make some commercial products. Sulfonation using sulfuric acid or chlorosulfuric acid and halogenation of a carbon black surface are also known. Some known methods for grafting polymers to the carbon black surface are reviewed by Tsubakowa in Polym. Sci., Vol. 17, pp 417-470, 1992. See also U.S. Pat. No. 4,014,844 which grafts polymers onto carbon black by contacting the carbon black with the polymer and heating.
U.S. Pat. No. 3,479,300 describes carbon catalyst compositions and a process for their production. The catalyst compositions are prepared by treating carbon particles with an alkali or alkaline earth metal and subsequently treating the resulting carbon/metal composition with a solvating ether. The carbon portions of the catalytic compositions can be reacted with various reagents, including organic compounds, to produce carbon compositions.
U.S. Pat. No. 3,043,708 describes modified carbon blacks having hydrocarbon groups chemically attached to the surface of the carbon black. The modified carbon blacks are prepared by reacting carbon black with an alkylating agent in the presence of a Friedel-Crafts type reaction catalyst. The hydrocarbon groups which reportedly can attach to the surface of the carbon black include aliphatic and aromatic groups. A modified carbon black containing aryl groups attached to the surface of a carbon black is reported as being preparable by reacting a halogenated carbon black with an aromatic hydrocarbon in the presence of a Friedel-Crafts type catalyst. U.S. Pat. No. 3,025,259 describes rubber compositions containing the modified carbon blacks of U.S. Pat. No. 3,043,708.
U.S. Pat. No. 3,335,020 describes modified carbon blacks where the carbon black is treated with benzene which is then polymerized on the carbon black. To prepare these modified carbon blacks, benzene and carbon black are mixed with a Lewis Acid catalyst under anhydrous conditions for about ten minutes. The benzene on the carbon black is then polymerized to parapolyphenyl by means of a combination co-catalyst-oxidizing agent and is reportedly thereby bonded to the carbon black.
U.S. Pat. Nos. 2,502,254 and 2,514,236 describe the manufacture of pigments containing carbon black. U.S. Pat. No. 2,502,254 reports that highly dispersed pigments suitable for mass pigmentation of viscose can be obtained by generating an azo pigment in the presence of carbon black.
The pigment is produced by coupling a diazotized amine and another usual intermediate for a yellow, orange, or red pigment in the presence of carbon black in one or the other of the aqueous solutions of which the mixing brings about the coupling. U.S. Pat. No. 2,514,236 reports that this process can also prepare a chocolate brown pigment by coupling one molecular proportion of a tetrazotized benzidine with two molecular proportions of an arylmethyl pyrazolone in the presence of carbon black.
PCT Patent Application No. WO 92/13983 describes a process for modifying the surfaces of carbon-containing materials by electrochemical reduction of diazonium salts. The process is reportedly applicable, in particular, to carbon plates and carbon fibers for composite materials. Carbon-containing materials modified by the process are also described. Electrochemical reduction of diazonium salts containing functionalized aryl radicals to covalently modify carbon surfaces is also described in Delmar et al., J. Am. Chem. Soc. 1992, 114, 5883-5884.
According to WO 92/13983, the process for modifying the surface of a carbon-containing material consists of grafting an aromatic group to the surface of this material by electrochemical reduction of a diazonium salt including this aromatic group. The carbon-containing material is placed in contact with a diazonium salt solution in an aprotic solvent and is negatively charged with respect to an anode which is also in contact with the diazonium salt solution. Use of a protic solvent is reported to prevent the electrochemical process from producing the intended product as a result of reducing the diazonium triple bond to yield a hydrazine.
Despite the technology discussed above, there remains a need to modify the surface chemistry of carbon black and impart desired properties to the carbon black.
Accordingly, the present invention relates to processes for preparing a carbon black product having an organic group attached to the carbon black. One process comprises the step of reacting at least one diazonium salt with a carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt. Another process comprises the step of reacting at least one diazonium salt with a carbon black in a protic reaction medium.
Other embodiments of the invention relate to novel carbon black products, which may be prepared according to a process of the invention. The carbon black products may be used in the same applications as conventional carbon blacks. Such uses include, but are not limited to, plastic compositions, aqueous inks, aqueous coatings, rubber compositions, paper compositions, and textile compositions.
The description which follows sets out additional features and advantages of the invention. These functions will be apparent from that description or may be learned by practice of the invention as described. The objectives and other advantages will be realized and attained by the processes, products, and compositions particularly pointed out in the description below and the appended claims.
A first embodiment of the invention provides processes for preparing a carbon black product having an organic group attached to the carbon black. One process involves the reaction of at least one diazonium salt with a carbon black in the absence of an externally applied current sufficient to reduce the diazonium salt. That is, the reaction between the diazonium salt and the carbon black proceeds without an external source of electrons sufficient to reduce the diazonium salt. Mixtures of different diazonium salts may be used in the process of the invention. This process can be carried out under a variety of reaction conditions and in any type of reaction medium, including both protic and aprotic solvent systems or slurries.
In another process, at least one diazonium salt reacts with a carbon black in a protic reaction medium. Mixtures of different diazonium salts may be used in this process of the invention. This process can also be carried out under a variety of reaction conditions.
Preferably, in both processes, the diazonium salt is formed in situ. If desired, in either process, the carbon black product can be isolated and dried by means known in the art. Furthermore, the resultant carbon black product can be treated to remove impurities by known techniques. The various preferred embodiments of these processes are discussed below and are shown in the examples.
Any carbon black may be used in the processes of this invention. The resulting carbon black products are useful in applications known for conventional carbon blacks. The properties of the carbon blacks are selected based upon the intended application. More importantly, the processes of this invention can be used to provide carbon black products having advantageous properties not associated with conventional carbon blacks.
The processes of the invention can be carried out under a wide variety of conditions and in general are not limited by any particular condition. The reaction conditions must be such that the particular diazonium salt is sufficiently stable to allow it to react with the carbon black. Thus, the processes can be carried out under reaction conditions where the diazonium salt is short lived. As the examples below illustrate, the reaction between the diazonium salt and the carbon black occurs, for example, over a wide range of pH and temperature. The processes can be carried out at acidic, neutral, and basic pH. Preferably, the pH ranges from about 1 to 9. The reaction temperature may preferably range from 0xc2x0 C. to 100xc2x0 C.
Diazonium salts, as known in the art, may be formed for example by the reaction of primary amines with aqueous solutions of nitrous acid. A general discussion of diazonium salts and methods for their preparation is found in Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 973-983, (Allyn and Bacon, Inc. 1987) and March, Advanced Organic Chemistry: Reaction, Mechanisms, and Structures, 4th Ed., (Wiley, 1992). According to this invention, a diazonium salt is an organic compound having one or more diazonium groups.
In the processes of the invention, the diazonium salt may be prepared prior to reaction with the carbon black or, more preferably, generated in situ using techniques known in the art. In situ generation also allows the use of unstable diazonium salts such as alkyl diazonium salts and avoids unnecessary handling or manipulation of the diazonium salt. In particularly preferred processes of this invention, both the nitrous acid and the diazonium salt are generated in situ. Each of these variations is shown in the examples below.
A diazonium salt, as is known in the art, may be generated by reacting a primary amine, a nitrite and an acid. The nitrite may be any metal nitrite, preferably lithium nitrite, sodium nitrite, potassium nitrite, or zinc nitrite, or any organic nitrite such as for example isoamylnitrite or ethylnitrite. The acid may be any acid, inorganic or organic, which is effective in the generation of the diazonium salt. Preferred acids include nitric acid, HNO3, hydrochloric acid, HCl, and sulfuric acid, H2SO4.
The diazonium salt may also be generated by reacting the primary amine with an aqueous solution of nitrogen dioxide. The aqueous solution of nitrogen dioxide, NO2/H2O, provides the nitrous acid needed to generate the diazonium salt.
Generating the diazonium salt in the presence of excess HCl may be less preferred than other alternatives because HCl is corrosive to stainless steel. Generation of the diazonium salt with NO2/H2O has the additional advantage of being less corrosive to stainless steel or other metals commonly used for reaction vessels. Generation using H2SO4/NaNO2 or HNO3/NaNO2 are also relatively non-corrosive.
In general, generating a diazonium salt from a primary amine, a nitrite, and an acid requires two equivalents of acid based on the amount of amine used. In an in situ process, the diazonium salt can be generated using one equivalent of the acid. When the primary amine contains a strong acid group, adding a separate acid may not be necessary in the processes of the invention. The acid group or groups of the primary amine can supply one or both of the needed equivalents of acid. When the primary amine contains a strong acid group, preferably either no additional acid or up to one equivalent of additional acid is added to a process of the invention to generate the diazonium salt in situ. A slight excess of additional acid may be used. One example of such a primary amine is para-aminobenzenesulfonic acid (sulfanilic acid). Others are shown in the examples below.
In general, diazonium salts are thermally unstable. They are typically prepared in solution at low temperatures, such as 0-5xc2x0 C., and used without isolation of the salt. Heating solutions of some diazonium salts may liberate nitrogen and form either the corresponding alcohols in acidic media or the organic free radicals in basic media.
However, to accomplish the process of the invention, the diazonium salt need only be sufficiently stable to allow reaction with the carbon black. Thus, the processes of the present invention can be carried out with some diazonium salts otherwise considered to be unstable and subject to decomposition. Some decomposition processes may compete with the reaction between the carbon black and the diazonium salt and may reduce the total number of organic groups attached to the carbon black. Further, the reaction may be carried out at elevated temperatures where many diazonium salts may be susceptible to decomposition. Elevated temperatures may also advantageously increase the solubility of the diazonium salt in the reaction medium and improve its handling during the process. However, elevated temperatures may result in some loss of the diazonium salt due to other decomposition processes.
The processes of the invention can be accomplished by adding the reagents to form the diazonium salt in situ, to a suspension of carbon black in the reaction medium, for example, water. Thus, a carbon black suspension to be used may already contain one or more reagents to generate the diazonium salt and the process of the invention accomplished by adding the remaining reagents. Some permutations of such processes are shown in the examples below.
Reactions to form a diazonium salt are compatible with a large variety of functional groups commonly found on organic compounds. Thus, only,the availability of a diazonium salt for reaction with a carbon black limits the processes of the invention.
The processes of this invention can be carried out in any reaction medium which allows the reaction between the diazonium salt and the carbon black to proceed. Preferably, the reaction medium is a solvent-based system. The solvent may be a protic solvent, an aprotic solvent, or a mixture of solvents. Protic solvents are solvents, like water or methanol, containing a hydrogen attached to an oxygen or nitrogen and thus are sufficiently acidic to form hydrogen bonds. Aprotic solvents are solvents which do not contain an acidic hydrogen as defined above. Aprotic solvents include, for example, solvents such as hexanes, tetrahydrofuran (THF), acetonitrile, and benzonitrile. For a discussion of protic and aprotic solvents see Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 228-231, (Allyn and Bacon, Inc. 1987).
The processes of this invention are preferably carried out in a protic reaction medium, that is, in a protic solvent alone or a mixture of solvents which contains at least one protic solvent. Preferred protic media include, but are not limited to water, aqueous media containing water and other solvents, alcohols, and any media containing an alcohol, or mixtures of such media.
According to the processes of the invention, the reaction between a diazonium salt and a carbon black can take place with any type of carbon black, for example, in fluffy or pelleted form. In one embodiment designed to reduce production costs, the reaction occurs during a process for forming carbon black pellets. For example, a carbon black product of the invention can be prepared in a dry drum by spraying a solution or slurry of a diazonium salt onto a carbon black. Alternatively, the carbon black product can be prepared by pelletizing a carbon black in the presence of a solvent system, such as water, containing the diazonium salt or the reagents to generate the diazonium salt in situ. Aqueous solvent systems are preferred. Accordingly, another embodiment of the invention provides a process for forming a pelletized carbon black comprising the steps of: introducing a carbon black and an aqueous slurry or solution of a diazonium salt into a pelletizer, reacting the diazonium salt with the carbon black to attach an organic group to the carbon black, and pelletizing the resulting carbon black having an attached organic group. The pelletized carbon black product may then be dried using conventional techniques.
In general, the processes of the invention produce inorganic by-products, such as salts. In some end uses, such as those discussed below, these by-products may be undesirable. Several possible ways to produce a carbon black product according to a process of the invention without unwanted inorganic by-products or salts are as follows:
First, the diazonium salt can be purified before use by removing the unwanted inorganic by-product using means known in the art. Second, the diazonium salt can be generated with the use of an organic nitrite as the diazotization agent yielding the corresponding alcohol rather than an inorganic salt. Third, when the diazonium salt is generated from an amine having an acid group and aqueous NO2, no inorganic salts are formed. Other ways may be known to those of skill in the art.
In addition to the inorganic by-products, a process of the invention may also produce organic by-products. They can be removed, for example, by extraction with organic solvents. Other ways may be known to those of skill in the art.
The reaction between a diazonium salt and a carbon black according to a process of this invention forms a carbon black product having an organic group attached to the carbon black. The diazonium salt may contain the organic group to be attached to the carbon black. Thus, the present invention relates to carbon black products having an organic group attached to the carbon black, particularly those prepared by a process of this invention. It may be possible to produce the carbon black products of this invention by other means known to those skilled in the art.
The organic group may be an aliphatic group, a cyclic organic group, or an organic compound having an aliphatic portion and a cyclic portion. As discussed above, the diazonium salt employed in the processes of the invention can be derived from a primary amine having one of these groups and being capable of forming, even transiently, a diazonium salt. The organic group may be substituted or unsubstituted, branched or unbranched. Aliphatic groups include, for example, groups derived from alkanes, alkenes, alcohols, ethers, aldehydes, ketones, carboxylic acids, and carbohydrates. Cyclic organic groups include, but are not limited to, alicyclic hydrocarbon groups (for example, cycloalkyls, cycloalkenyls), heterocyclic hydrocarbon groups (for example, pyrrolidinyl, pyrrolinyl, piperidinyl, morpholinyl, and the like), aryl groups (for example, phenyl, naphthyl, anthracenyl, and the like), and heteroaryl groups (imidazolyl, pyrazolyl, pyridinyl, thienyl, thiazolyl, furyl, indolyl, and the like). As the steric hinderance of a substituted organic group increases, the number of organic groups attached to the carbon black from the reaction between the diazonium salt and the carbon black may be diminished.
When the organic group is substituted, it may contain any functional group compatible with the formation of a diazonium salt. Preferred functional groups include, but are not limited to, R, OR, COR, COOR, OCOR, carboxylate salts such as COOLi, COONa, COOK, COOxe2x88x92NR4+, halogen, CN, NR2, SO3H, sulfonate salts such as SO3Li, SO3Na, SO3K, SO3xe2x88x92NR4+, OSO3H, OSO3xe2x88x92 salts, NR(COR), CONR2, NO2, PO3H2, phosphonate salts such as PO3HNa and PO3Na2, phosphate salts such as OPO3HNa and OPO3Na2, Nxe2x95x90NR, NR3+Xxe2x88x92, PR3+Xxe2x88x92, SkR, SSO3H, SSO3xe2x88x92 salts, SO2NRRxe2x80x2, SO2SR, SNRRxe2x80x2, SNQ, SO2NQ, CO2NQ, S-(1,4-piperazinediyl)-SR, 2-(1,3-dithianyl) 2-(1,3-dithiolanyl), SOR, and SO2R. R and Rxe2x80x2, which can be the same or different, are independently hydrogen, branched or unbranched C1-C20 substituted or unsubstituted, saturated or unsaturated hydrocarbon, e.g., alkyl, alkenyl, alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkylaryl, or substituted or unsubstituted arylalkyl. The integer k ranges from 1-8 and preferably from 2-4. The anion Xxe2x88x92 is a halide or an anion derived from a mineral or organic acid. Q is (CH2)w, (CH2)xO(CH2)z, (CH2)xNR(CH2)z, or (CH2)xS(CH2)z, where w is an integer from and x and z are integers from 1 to 6.
The carbon black product can comprise a carbon black and at least one organic group having a) an aromatic group and b) a cationic group, wherein at least one aromatic group of the organic group is attached to the carbon black. The organic group can be, for example Xxe2x88x92 R3N+CH2COAr, wherein R is a substituted or unsubstituted C1-C10 alkyl, Ar is phenylene or naphthylene, and Xxe2x88x92 is a halide or an anion derived from a mineral or organic acid.
A preferred organic group is an aromatic group of the formula AyArxe2x80x94, which corresponds to a primary amine of the formula AyArNH2. In this formula, the variables have the following meanings: Ar is an aromatic radical such as an aryl or heteroaryl group. Preferably, Ar is selected from the group consisting of phenyl, naphthyl, anthracenyl, phenanthrenyl, biphenyl, pyridinyl, benzothiadiazolyl, and benzothiazolyl; A is a substituent on the aromatic radical independently selected from a preferred functional group described above or A is a linear, branched or cyclic hydrocarbon radical (preferably containing 1 to 20 carbon atoms), unsubstituted or substituted with one or more of those functional groups; and y is an integer from 1 to the total number of xe2x80x94CH radicals in the aromatic radical. For instance, y is an integer from 1 to 5 when Ar is phenyl, 1 to 7 when Ar is naphthyl, 1 to 9 when Ar is anthracenyl, phenanthrenyl, or biphenyl, or 1 to 4 when Ar is pyridinyl.
In the above formula, specific examples of R and Rxe2x80x2 are NH2xe2x80x94C6H4xe2x80x94, CH2CH2xe2x80x94C6H4xe2x80x94NH2, CH2xe2x80x94C6H4xe2x80x94NH2, and C6H5.
Another preferred set of organic groups which may be attached to the carbon black are organic groups substituted with an ionic or an ionizable group as a functional group. An ionizable group is one which is capable of forming an ionic group in the medium of use. The ionic group may be an anionic group or a cationic group and the ionizable group may form an anion or a cation.
Ionizable functional groups forming anions include, for example, acidic groups or salts of acidic groups. The organic groups, therefore, include groups derived from organic acids. Preferably, when it contains an ionizable group forming an anion, such an organic group has a) an aromatic group and b) at least one acidic group having a pKa of less than 11, or at least one salt of an acidic group having a pKa of less than 11, or a mixture of at least one acidic group having a pKa of less than 11 and at least one salt of an acidic group having a pKa of less than 11. The pKa of the acidic group refers to the pKa of the organic group as a whole, not just the acidic substituent. More preferably, the pKa is less than 10 and most preferably less than 9. Preferably, the aromatic group of the organic group is directly attached to the carbon black. The aromatic group may be further substituted or unsubstituted, for example, with alkyl groups. More preferably, the organic group is a phenyl or a naphthyl group and the acidic group is a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, or a carboxylic acid group. Examples of these acidic groups and their salts are discussed above. Most preferably, the organic group is a substituted or unsubstituted sulfophenyl group or a salt thereof; a substituted or unsubstituted (polysulfo)phenyl group or a salt thereof; a substituted or unsubstituted sulfonaphthyl group or a salt thereof; or a substituted or unsubstituted (polysulfo)naphthyl group or a salt thereof. A preferred substituted sulfophenyl group is hydroxysulfophenyl group or a salt thereof.
Specific organic groups having an ionizable functional group forming an anion (and their corresponding primary amines for use in a process according to the invention) are p-sulfophenyl (p-sulfanilic acid), 4-hydroxy-3-sulfophenyl (2-hydroxy-5-amino-benzenesulfonic acid), and 2-sulfoethyl (2-aminoethanesulfonic acid). Other organic groups having ionizable functional groups forming anions are shown in the examples below.
Amines represent examples of ionizable functional groups that form cationic groups. For example, amines may be protonated to form ammonium groups in acidic media. Preferably, an organic group having an amine substituent has a pKb of less than 5. Quaternary ammonium groups (xe2x80x94NR3+) and quaternary phosphonium groups (xe2x80x94PR3+) also represent examples of cationic groups. Preferably, the organic group contains an aromatic group such as a phenyl or a naphthyl group and a quaternary ammonium or a quaternary phosphonium group. The aromatic group is preferably directly attached to the carbon black. Quaternized cyclic amines, and even quaternized aromatic amines, can also be used as the organic group. Thus, N-substituted pyridinium compounds, such as N-methylpyridyl, can be used in this regard. Examples of organic groups include, but are not limited to, (C5H4N)C2H5+, C6H4(NC5H5)+, C6H4COCH2N(CH3)3+, C6H4COCH2(NC5H5)+, (C5H4N)CH3+, and C6H4CH2N(CH3)3+.
An advantage of the carbon black products having an attached organic group substituted with an ionic or an ionizable group is that the carbon black product may have increased water dispersibility relative to the corresponding untreated carbon black. As shown in the Examples, water dispersibility of a carbon black product increases with the number of organic groups attached to the carbon black having an ionizable group or the number of ionizable groups attached to a given organic group. Thus, increasing the number of ionizable groups associated with the carbon black product should increase its water dispersibility and permits control of the water dispersibility to a desired level. It can be noted that the water dispersibility of a carbon black product containing an amine as the organic group attached to the carbon black may be increased by acidifying the aqueous medium.
Because the water dispersibility of the carbon black products depends to some extent on charge stabilization, it is preferable that the ionic strength of the aqueous medium be less than 0.1 molar. More preferably, the ionic strength is less than 0.01 molar.
When such a water dispersible carbon black product is prepared by a process of the invention, it is preferred that the ionic or ionizable groups be ionized in the reaction medium. The resulting product solution or slurry may be used as is,or diluted prior to use. Alternatively, the carbon black product may be dried by techniques used for conventional carbon blacks. These techniques include, but are not limited to, drying in ovens and rotary kilns. Overdrying, however, may cause a loss in the degree of water dispersibility.
In addition to their water dispersibility, carbon black products having an organic group substituted with an ionic or an ionizable group may also be dispersible in polar organic solvents such as dimethylsulfoxide (DMSO), and formamide. In alcohols such as methanol or ethanol, use of complexing agents such as crown ethers increases the dispersibility of carbon black products having an organic group containing a metal salt of an acidic group.
Aromatic sulfides encompass another group of preferred organic groups. Carbon black products having aromatic sulfide groups are particularly useful in rubber compositions. These aromatic sulfides can be represented by the formulas Ar(CH2)qSk(CH2)rArxe2x80x2 or Axe2x80x94(CH2)qSK(CH2)rArxe2x80x3 wherein Ar and Arxe2x80x2 are independently substituted or unsubstituted arylene or heteroarylene groups, Arxe2x80x3 is an aryl or heteroaryl group, k is 1 to 8 and q and r are 0-4. Substituted aryl groups would include substituted alkylaryl groups. Preferred arylene groups include phenylene groups, particularly p-phenylene groups, or benzothiazolylene groups. Preferred aryl groups include phenyl, naphthyl and benzothiazolyl. The number of sulfurs present, defined by k preferably ranges from 2 to 4. Particularly preferred aromatic sulfide groups are bis-para-(C6H4)xe2x80x94S2xe2x80x94(C6H4)xe2x80x94 and para-(C6H4)xe2x80x94S2xe2x80x94(C6H5). The diazonium salts of these aromatic sulfide groups may be conveniently prepared from their corresponding primary amines, H2Nxe2x80x94Arxe2x80x94Skxe2x80x94Arxe2x80x2xe2x80x94NH2 or H2Nxe2x80x94Arxe2x80x94Skxe2x80x94Arxe2x80x3.
Another preferred set of organic groups which may be attached to the carbon black are organic groups having an aminophenyl, such as (C6H4)xe2x80x94NH2, (C6H4)xe2x80x94CH2xe2x80x94(C6H4)xe2x80x94NH2, (C6H4)xe2x80x94SO2xe2x80x94(C6H4)xe2x80x94NH2.
The carbon black products of this invention may be used in the same applications as conventional carbon blacks. The organic groups attached to the carbon black, however, can be used to modify and improve the properties of a given carbon black for a particular use. If desired these organic groups attached to the carbon black may also be chemically changed using means known in the art into other groups for a particular use. For example, an acid group can be converted to its salt or its amide.
Carbon black products according to the invention have been prepared and evaluated in a number of end use applications. These uses include, for example, plastic compositions, aqueous inks, aqueous coatings, rubber compositions, paper compositions and textile compositions. The following paragraphs describe these uses generally and examples of each are shown below.
The carbon black products of this invention may be used as pigments or colorants in a plastic material. The carbon black products of the invention can also be used to impart conductivity to a plastic material. The carbon black products of the invention may give an increased rate of dispersion or improved quality of dispersion over the corresponding untreated carbon blacks. These improvements offer an economic advantage in plastic manufacture and in value of the finished product, respectively. As shown in Examples 47-62, using carbon black products of the invention may improve impact strength of the plastic. Thus, the invention relates to an improved plastic composition comprising a plastic and a carbon black, the improvement comprising the use of a carbon black product according to the invention.
As with conventional carbon blacks, the carbon black products can be used with a variety of plastics, including but not limited to plastics made from thermoplastic resins, thermosetting resins, or engineered materials, for example, composites. Typical kinds of thermoplastic resins include: (1) acrylonitrile-butadiene-styrene (ABS) resins; (2) acetals; (3) acrylics; (4) cellulosics; (5) chlorinated polyethers; (6) fluorocarbons, such as polytetrafluoroethylene (TFE), polychlorotrifluoroethylene (CTFE), and fluorinated ethylene propylene (FEP); (7) nylons (polyamides); (8) polycarbonates; (9) polyethylenes (including copolymers); (10) polypropylenes (including copolymers); (11) polystyrenes; (12) vinyls (polyvinyl chloride); (13) thermoplastic polyesters, such as polyethylene terephthalate or polybutylene terephthalate; (14) polyphenylene ether alloys; and blends and alloys of the above with rubber modifiers. Typical thermosetting resins include: (1) alkyds; (2) allylics; (3) the aminos (melamine and urea); (4) epoxies; (5) phenolics; (6) polyesters; (7) silicones; and (8) urethanes.
Generally, the carbon black product is added like any other pigment to the plastic used to form a plastic premix. This can be done, for example, in a dry mix or a melt stage. The carbon black products of the invention may be used in combination with other conventional additives in plastic compositions. According to the invention, the term plastic composition includes, but is not limited to, any plastic material, article, goods, surface, fabric, sheet, and the like For example, plastic materials include automotive parts, siding for homes, liners for swimming pools, roofing materials, packaging materials, and any variety of other household or industrial items.
The carbon black products of this invention are also useful in aqueous ink formulations. The water-dispersible carbon black products discussed above are particularly preferred for this use. Thus, the invention provides an improved ink composition comprising water and a carbon black, the improvement comprising the use of a carbon black product according to the invention. Other known aqueous ink additives may be incorporated into the aqueous ink formulation.
In general, an ink consists of four basic components: (1) a colorant or pigment, (2) a vehicle or varnish which functions as a carrier during printing, (3) additives to improve printability drying, and the like, and (4) solvents to adjust viscosity, drying and the compatibility of the other ink components. For a general discussion on the properties, preparation and uses of aqueous inks, see The Printing Manual, 5th Ed., Leach et al, Eds. (Chapman and Hall, 1993). Various aqueous ink compositions are also disclosed, for example, in U.S. Pat. Nos. 2,833,736, 3,607,813, 4,104,833, 4,308,061, 4,770,706, and 5,026,755.
The carbon black products of the invention, either as predispersion or as a solid, can be incorporated into an aqueous ink formulation using standard techniques. Use of a water dispersible carbon black product of the invention provides a significant advantage and cost savings by reducing or eliminating the milling steps generally used with other conventional carbon blacks.
Flexographic inks represent a group of aqueous ink compositions. Flexographic inks generally include a colorant, a binder, and a solvent. The carbon black products of the invention, particularly the water-dispersible carbon products, are useful as flexographic ink colorants. Example 101 shows the use of a carbon black product of the invention in an aqueous flexographic ink formulation.
The carbon black products of the invention can be used in aqueous news inks. For example, an aqueous news ink composition may comprise water, the carbon black products of the invention, a resin and conventional additives such as antifoam additives or a surfactant.
The carbon black products of the invention may also be used in aqueous coating compositions such as paints or finishes. The use of the water dispersible carbon black products discussed above in such coating compositions is preferred. Thus, an embodiment of the invention is an improved aqueous coating composition comprising water, resin and a carbon black, the improvement comprising the use of a carbon black product according to the invention. Other known aqueous coating additives may be incorporated the aqueous coating compositions. See, for example, McGraw-Hill Encyclopedia of Science and Technology, 5th Ed. (McGraw-Hill, 1982). See also U.S. Pat. Nos. 5,051,464, 5,319,044, 5,204,404, 5,051,464, 4,692,481, 5,356,973, 5,314,945, 5,266,406, and 5,266,361.
The carbon black products of the invention, either as a predispersion or as a solid, can be incorporated into an aqueous coating composition using standard techniques. Use of a water dispersible carbon black product provides a significant advantage and cost savings by reducing or eliminating the milling steps generally used with other conventional carbon blacks. Examples 102 and 103 below show the use of carbon black products according to the invention in aqueous automotive topcoat formulations.
The carbon black products of the invention may also be used in paper compositions. Preferred carbon black products for this use are the water dispersible carbon black products discussed above. Accordingly, the invention relates to an improved paper product comprising paper pulp and a carbon black, the improvement comprising the use of a carbon black according to the invention.
The carbon black products of the invention, either as a solid or a predispersion, can be incorporated into paper pulp using standard papermaking techniques as with conventional carbon blacks. Use of a water dispersible carbon black product discussed above may provide a significant advantage and cost savings by reducing or eliminating the steps generally used to disperse other conventional carbon blacks. Example 100 shows a paper product using a carbon black product according to the invention.
The paper products of the invention may incorporate other known paper additives such as sizing agents, retention aids, fixatives, fillers, defoamers, deflocculating agents, and the like. Advantageously, the water dispersible carbon black products discussed above are retained more efficiently at low loading levels when compared to the untreated carbon black when retention aids and acidic or alkaline sizing agents are used.
The carbon black products of the invention may also be used, as with conventional carbon blacks, as pigments, fillers, and reinforcing agents in the compounding and preparation of rubber compositions. Accordingly, the invention relates to an improved rubber composition containing rubber and a carbon black, the improvement comprising the use of a carbon black product according to the invention. The properties of the carbon black are important factors in determining the performance of the rubber composition containing a carbon black.
Carbon blacks, for example, are useful in the preparation of rubber vulcanizates such as those in tires. It is generally desirable in the production of tires to utilize carbon blacks which produce tires with satisfactory abrasion resistance and hysteresis performance. The treadwear properties of a tire are related to abrasion resistance. The greater the abrasion resistance, the greater the number of miles the tire will last without wearing out. The hysteresis of a rubber compound means the difference between the energy applied to deform a rubber compound, and the energy released as the rubber compound recovers to its initial undeformed state. Tires with lower hysteresis values reduce rolling resistance and therefore are able to reduce the fuel consumption of the vehicle utilizing the tire. Thus, it is particularly desirable to have carbon black products capable of imparting greater abrasion resistance and lower hysteresis in tires.
The carbon black products of this invention are useful in both natural and synthetic rubber compositions or mixtures of natural and synthetic rubbers. Carbon black products containing aromatic sulfides as the organic group, which are discussed above, are preferred for this use. Particularly preferred for use in rubber compositions are carbon black products having an attached aromatic sulfide organic group of the formula xe2x80x94(C6H4)xe2x80x94Skxe2x80x94(C6H4)xe2x80x94, where k is an integer from 1 to 8, and more preferably where k ranges from 2 to 4. The carbon black products of the invention can be used in rubber compositions which are sulfur-cured or peroxide-cured.
The carbon black products may be mixed with natural or synthetic rubbers by normal means, for example by milling. Generally, amounts of the carbon black product ranging from about 10 to about 250 parts by weight can be used for each 100 parts by weight of rubber in order to impart a significant degree of reinforcement. It is, however, preferred to use amounts varying from about 20 to about 100 parts by weight of carbon black per 100 parts by weight of rubber and especially preferred is the utilization of from about 40 to about 80 parts of carbon black per 100 parts of rubber.
Among the rubbers suitable for use with the present invention are natural rubber and its derivatives such as chlorinated rubber. The carbon black products of the invention may also be used with synthetic rubbers such as: copolymers of from about 10 to about 70 percent by weight of styrene and from about 90 to about 30 percent by weight of butadiene such as copolymer of 19 parts styrene and 81 parts butadiene, a copolymer of 30 parts styrene and 70 parts butadiene, a copolymer of 43 parts styrene and 57 parts butadiene and a copolymer of 50 parts styrene and 50 parts butadiene; polymers and copolymers of conjugated dienes such as polybutadiene, polyisoprene, polychloroprene, and the like, and copolymers of such conjugated dienes with an ethylenic group-containing monomer copolymerizable therewith such as styrene, methyl styrene, chlorostyrene, acrylonitrile, 2-vinylpyridine, 5-methyl 2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine, alkyl-substituted acrylates, vinyl ketone, methyl isopropenyl ketone, methyl vinyl either, alphamethylene carboxylic acids and the esters and amides thereof such as acrylic acid and dialkylacrylic acid amide; also suitable for use herein are copolymers of ethylene and other high alpha olefins such as propylene, butene-1 and pentene-1.
The rubber compositions of the present invention can therefore contain an elastomer, curing agents, reinforcing filler, a coupling agent, and, optionally, various processing aids, oil extenders, and antidegradents. In addition to the examples mentioned above, the elastomer can be, but is not limited to, polymers (e.g., homopolymers, copolymers, and terpolymers) manufactured from 1,3 butadiene, styrene, isoprene, isobutylene, 2,3-dimethyl-1,3 butadiene, acrylonitrile, ethylene, propylene, and the like. It is preferred that these elastomers have a glass transition point (Tg), as measured by DSC, between xe2x88x92120xc2x0 C. and 0xc2x0 C. Examples of such elastomers include poly(butadiene), poly(styrene-co-butadiene), and poly(isoprene).
Advantageously, the carbon black products of the present invention can impart improved abrasion resistance and/or reduced hysteresis to rubber compositions containing them. Examples 104-116 show the use of carbon black products of the invention in various rubber compositions and various properties of those compositions.
The carbon black products of this invention may also be used to color fibers or textiles. Preferred carbon black products for this use are the water dispersible carbon black products discussed above. Accordingly, the invention relates to improved fiber and textile compositions comprising a fiber or textile and a carbon black, the improvement comprising the use of a carbon black according to the invention. Fibers suitable for use comprise natural and synthetic fibers such as cotton, wool, silk, linen, polyester and nylon. Textiles suitable for use comprise natural and synthetic fibers such as cotton, wool, silk, linen, polyester and nylon. Preferably natural fibers and textiles comprising cotton, wool, silk and linen are used.
The carbon black products of the present invention may be colored by means known in the art to color fibers and textiles with, for example, direct and acid dyes. For a general discussion of coloring with dyes, see Kirk-Othmer Encyclopedia of Chemical Technology, Vol 8 pp 280-350 xe2x80x9cDyes, Application and Evaluationxe2x80x9d (John Wiley and Sons, 1979). Use of a water dispersible carbon black product discussed above provides a method for coloring these materials with a lightfast colorant.
The following examples are intended to illustrate, not limit, the claimed invention.

Reaction of carbon black with diazonium salts, resultant carbon black products and their uses


A paint dispersing training grenade includes a grenade body having dispersing passages extending between a central bore and an external surface of the grenade body, a plug threadedly received in one end of the bore, a piston resiliently urged by a spring toward the plug, a rupturable colorant containing capsule positioned between the piston and the plug, a separable release lever releasably pivotal on the grenade body and engaged with an abutment disk on a shaft extending from the piston, and an inertial delay mechanism engaged between the grenade body and the piston. The delay mechanism includes pivotable delay levers engaged with the piston at one end and having wheels rollably engaging a surface of the grenade body at another end. When the release lever is separated, movement of the piston by the spring is resisted by startup inertia of the wheels in rotating. When the inertia is overcome, the piston forceably ruptures the capsule and propels the colorant out of the grenade body through the dispersion passages.

In the past, war games in military training were often judged or scored by umpires based on troop strength and tactical position and statistical analysis thereof. More currently, special training weapons are often employed in such training to sharpen combat skills and to provide a mechanism for objectively scoring proficiency in such skills. For example, rifles having the look and feel of currently employed combat rifles are fitted with laser emitters, and combatants wear laser receivers which record a "kill" when a laser signal is received. Such an arrangement develops the aiming skill of the shooter while providing an objective indication of a "casualty".
In recent years, a combat type sport has developed in which the principal equipment or weapon is a gun which shoots paintballs. The propellant in the gun is compressed air or carbon dioxide cartridges. The paintballs are substantially spherical capsules, often formed of pharmaceutical capsule type gelatin, filled with a washable, pigmented liquid, resembling latex type paint in some respects. Currently, the principal participants are civilians grouped in teams who execute strategies and tactics, according to established rules, in competition with an opposing team. If a player is shot by a paintball, the player is considered a casualty and is unable to further assist his team. Because of the bright colors of the paints used and the difficulty of removing the results of a hit in the field, scoring of hits or casualties can be accomplished objectively.
In the area of anti-personnel weapons, such as grenades, mines, and the like, it has generally been difficult to devise safe simulation devices with which casualties can be objectively scored. Generally, devices which emit a loud report and/or smoke are employed, and scoring is done on a basis of survival statistics within a given radius of the weapon simulated.
At least one toy grenade is known which disperses a dye liquid upon detonation. The grenade body is filled with the dye liquid and compressed air and has a valve controlling flow of the liquid to dispersion orifices. The valve is controlled by a trigger mechanism which extends from the lower end of the grenade when armed. The grenade body is weighted so that, at least theoretically, when the grenade is thrown, it lands on the lower end and actuates the trigger. One inherent problem with this grenade is that the liquid releasing valve is at the top of the liquid chamber such that if the grenade lands as intended, when the valve opens, the compressed air escapes first and is unavailable for propelling a major portion of the liquid. And unless the grenade lands lower side down, actuation of the trigger mechanism is not assured.


The smokeless ignitor of the present invention prevents visible emissions upon cold or hot start-up of coal-fired or oil-fired utility boilers. The smokeless ignitor satisfies flame stability and combustion requirements by establishing a flame with 15-30% mass recirculation rate, a recirculation zone length of 0.75-1.5 effective throat diameters, a spray SMD of less than 120 microns and a STU value of .+-.50% or less.

One type of boiler, which can be found at Brandon Shores Station of Baltimore Gas and Electric Company, is a pulverized coal fired boiler having rows of burners situated on opposing furnace walls, for example, five rows of five burners. Ignitors, identified as "lighters", are installed in each burner. The ignitors are used to warm up the boiler and ignite the pulverized coal flames. Combustion air is distributed to the burners by a compartmented windbox. As generically illustrated in FIG. 1, the burner rows 1 are grouped in compartments 2 with air flows controlled by dampers 3 and measured using air foils 4 at both ends. This design permits balancing of air flows between compartments without changing burner register or vane settings, thus, effectively uncoupling air flow re-distribution between burners from burner aerodynamics.
During start-up, all burner inlet dampers are open and a minimum air flow of 25% of full load air is established. The minimum air flow specification is categorized as a "safe operating practice". It is generally referred to as a purge requirement to flush-out pockets of combustible (even explosive) mixtures of gases from within the boiler enclosure. This practice has been adopted by most utility boiler operations in the U.S. and is based on recommendations from insurance underwriters.
The principal features of the burners are illustrated in FIG. 2. Coal from the pulverizer is transported to the burner in a primary air flow (normally 10-20% of the total combustion air requirement) and is directed into the furnace through a central coal pipe 5. A distributor 6, mounted at the inlet, is intended to minimize flow mal-distributions within the coal pipe. Additional combustion air enters the burners through two cylindrical registers 6.1 outer and 6.2 inner. The register dampers can be rotated from a fully closed to an almost radial direction. The dampers are intended to be used to establish the relative air flows between the inner and outer annular regions of the burner.
A set of "spin vanes" 6.3 are located in the annular space between the coal pipe and the inner register sleeve. These vanes rotate around radial axes and can induce flow directions from clockwise to counterclockwise. The midpoint of the vane's rotation provides axial flow. While the functions of the spin vanes is to provide only enough turbulence to the inner air to establish an ignition zone and maintain stable combustion, their location and design alone provides a means for independently controlling the swirl in the inner annulus while maintaining a desired inner/outer air flow ratio.
The control rods for the registers and spin vanes are connected to levers outside the burner faceplate. The lever positions are set by engaging notches in a fixed plate 6.4. Once determined (during the initial start-up of the unit) the register and vane positions are designed to be kept at these "proper" settings under all operating conditions including; purge, light-off and firing cycles.
As illustrated in FIGS. 3a and 3b, the ignitors consist of an air atomized light oil fired burner 7, a high energy spark probe 8, and a "lighter shield" 9 incorporated into a drive and support assembly 10. A separate pneumatic drive for the spark probe allows the electrode to be retracted after the lighter flame is established. This provision is intended to avoid overheating the high energy electrode. Also shown are a high energy ignitor power supply unit 11, power supply cable 12, atomizing air/steam supply 15, oil supply 16, and oil atomizer 17.
The operating sequence for start-up is unit specific and depends on the configuration of burners and pulverizers and the operating philosophy of the company using the burner. One type of operating sequence for start-up of the ignitors is illustrated in FIG. 4. The critical step in the light-off sequence is the trial for ignition. At the end of this 15 second period the spark probe is de-energized and retracted. At this time all five ignitors in a row must be proven by the flame detectors. If not, the control system terminates ignition and initiates the purge and shutdown sequence. Multiple shut-downs and re-attempts to light and prove lighter flames are a typical occurrence during cold start-ups.
In addition to oil sprays which do not ignite, it is not unusual for the flame detectors to fail to prove an existing flame. FIGS. 3a and 3b, the atomizer 17 is an air-atomized, light-oil, 5 orifice y-jet design. These atomizers produce flames with 5 distinct "fingers". With an 80.degree. spray angle for the atomizer, the distance between flame "fingers" is generally the same as the axial distance from the atomizer at which the flame is viewed. For example, there is a 12-inch gap between flame "fingers" 12 inches from the ignitor. The orientation of the atomizer exit holes with respect to the flame detector is random. Therefore, it is possible that the failure of a flame detector to prove an established flame results from the detector sighting in on the gap between adjacent flame "fingers".
In either case (ignition failures or failure to prove lit flames), approximately 0.4-0.5 gallons of light oil is sprayed into the boiler for each unlit ignitor. A further contribution results from purging fuel from all five ignitors (including those that had been firing). This unburned oil can deposit on boiler surfaces, particularly in the convective passes and the air heater. As temperatures rise, oil retained in the boiler will re-vaporize into the gas flow. Therefore, failures to light and prove ignitor flames, can affect opacity at the time of attempted light-off and for several hours later. Typical opacity levels for cold start-ups are greater than 40% for up to several hours.
In addition to opacity resulting from lighter start-up problems, smoke is consistently observed in the furnace after the lighter flames are established. As shown in FIG. 5 (the opacity chart record for a prior cold start) the combined affects of both mechanisms results in opacity exceeding 10% for approximately 4 hours of the 4 hour and 50 minute period between the start of lighter fuel flow and the energization of the precipitator.


The present invention relates to a laser including a laser amplifier and a laser resonator. The laser amplifier includes a disk-shaped active medium having a reflector. The active medium rests on a cooling means for cooling said active medium and said reflector. The reflector embodies a mirror of said laser resonator. The laser amplifier includes an optical means for refocusing a pumping light configured for repeatedly deviating said pumping light and refocusing said pumping light onto the active medium for causing a multiple passage of said pumping light through said active medium. Such a thin-disk laser is not prone to thermal lensing. According to the invention, the laser resonator is formed as a ring resonator. Two optical waves can travel around within the ring resonator in different directions. An optical selection means is provided for giving preference to propagation of one of the both optical waves traveling around that can be coupled out as an output laser beam. The laser according to the invention is highly stable and can be adjusted and tuned easily. Intra-cavity frequency-multiplication can be achieved easily.

FIG. 1 shows such a solid-state laser according to the prior art, which is distributed by the applicant under the name "VersaDisk". The laser 100 comprises a laser amplifier 2 and a linear laser resonator 101. The laser amplifier 2 comprises a disk-shaped active medium 3 having a reflector, which is either deposited onto a back surface of the active medium 3 as a highly reflective coating, or which is formed as a separate mirror and connected with the active medium 3. The active medium 3 with the reflector rests on a cooling means 4 formed as a cooling finger, which cooling means dissipates heat from the active medium substantially perpendicular to a surface thereof.
The linear laser resonator 101 is formed by the above reflector and the concave mirror 11 serving as an output mirror for coupling out the output laser beam 19. Within the laser resonator 101 are provided an etalon 14, a Brewster plate 15 or selectively a Lyot filter 16 for enabling a selection of the wavelength, polarization and mode within the laser resonator 101. The active medium 3 is disposed at the focus of a parabolic or concave mirror 7 serving as an optical means for refocusing a pumping light. The pumping light is imaged via the glass fiber 5 and an input coupling mirror 6 disposed at a side thereof onto a mirror segment of the concave mirror 7, which images the pumping light onto the active medium 3 and focuses it. Pumping light 9b that is reflected by the reflector of the active medium 3, is reflected back onto another location or another segment of the concave mirror 7, where the pumping light is deviated onto another location or another segment of the concave mirror 7 and imaged and focused again onto the active medium 3. Thus, the pumping light is deviated repeatedly by the concave mirror 7 and is focused again onto the active medium 3 so that a multiple beam passage of the pumping light through the active medium 3 is accomplished. Thus, the effective absorption length within the active medium can be substantially larger than the thickness of the active medium 3. With regard to further details of the pumping geometry reference is made to U.S. Pat. No. 6,577,666 B2 and US 2003/25987 A1, the contents of which are hereby explicitly incorporated in the present application. A standing optical wave is formed within the laser resonator 101, which propagates through the opening 8 of the concave mirror 7.
The laser according to FIG. 1 is characterized by a high pump efficiency. Due to the homogeneous heat flow within the cooling finger 4, which serves at a heat sink, which heat flow is substantially co-linear to the optical axis of the laser resonator 101, thermal lensing effects are practically neglectible. The output laser beam 19 exhibits a nearly perfect Gaussian-shaped beam profile at all power levels so that the output laser beam 19 can be focused to small beam spots. Using a Yb:YAG crystal as the active medium 3, output powers of 10 W to 100 W at an output wavelength of 1030 nm can be achieved. The Lyot filter 16 provides for the ability of tuning the wavelength between approximately 1000 nm and approximately 1060 nm. The etalon 14 provides for a longitudinal single mode operation. The laser according to FIG. 1 can be operated in a perfect TEM00 laser operation.
However, with the laser according to FIG. 1, a stability range, where laser oscillation can be maintained reliably, is relatively narrow. In particular, the laser resonator 101 is relatively prone to tilting of both end mirrors of the linear laser resonator relative to each other. Furthermore, adjusting the laser for a stable laser operation is relatively critical with regard to the locations and angular positions of the optical elements of the laser resonator. Furthermore, disposing a frequency-multiplying crystal within a standing wave resonator according to FIG. 1 is relatively complicated, as the conditions for frequency multiplication are highly sensitive to instabilities of the linear standing wave resonator.
US 2002/0172253 A1 discloses a solid-state laser comprising a plurality of thin-disk laser amplification modules in a so-called active mirror configuration, each comprising an amplification medium, a cooling means for cooling the amplification medium and a mount for the amplification medium. A coolant flows through the cooling means. Use of an optical means for refocusing a pumping light is not disclosed. This laser is intended for very high output laser powers, but is not suitable for tuning an output wavelength. Although use of a ring resonator is disclosed, wherein a plurality of amplification modules are disposed, such a ring resonator is instable. For suppressing higher TEM laser modes, a beam extension telescope comprising two concave mirrors, is provided; an opening is disposed at a focus thereof.
DE 100 54 289 A1 discloses a solid-state laser comprising a laser amplifier disposed outside of the laser resonator. An output beam of the solid-state laser enters the external laser amplifier via an opening of a parabolic mirror, said external laser amplifier being formed by a crystal disk that is mounted on a cooling finger and is optically pumped by a pumping light beam. The pumping light beam is repeatedly imaged onto the crystal disk by the parabolic mirror in order to increase the pump efficiency of the external laser amplifier.
U.S. Pat. No. 6,577,666 B2 discloses a laser amplification system comprising a solid-state laser and a pumping light source, a pumping light beam thereof repeatedly passing through the amplification medium of the solid-state laser by means of an optical means for refocusing the pumping light. The solid-state body rests with the rear flat side on a reflector, which itself is seated on a front end of a cooling finger. A mirror disposed below an opening of the optical means for refocusing forms an end mirror of a linear laser resonator. Due to its similar configuration this laser is subject to comparable limitations, which have been discussed previously with reference to FIG. 1.
U.S. Pat. No. 5,856,996 discloses an end-pumped laser system having a linear resonator or a double z-shaped resonator.
DE 197 22 943 A1 discloses a non-planar ring laser.
U.S. Pat. No. 5,206,868 discloses a resonant non-linear laser beam converter. Furthermore, various resonator geometries are disclosed.


The present invention provides an automatic transmission for a motor vehicle having a compact single mode transfer gear continuously variable transmission (CVT) with a compound planetary gear carrier for use in front wheel drive vehicles. The automatic transmission includes an input shaft, a variator or other, similar device which provides a continuously variable input to output speed ratio over a limited range, a compound planetary gear assembly having a sun gear, a planet gear carrier with compound gear sets and a ring gear, a friction brake, a friction clutch and a plurality of transfer gears and layshafts.

The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Because of performance and packaging benefits, particularly the elimination of the propeller (prop) shaft, front wheel drive (FWD) vehicles have proven popular with consumers. Such elimination not only generally reduces the weight of the powertrain and thus of the vehicle but also reduces and can essentially eliminate the driveline hump on the floor of the passenger compartment. These benefits are especially pronounced in smaller size vehicles.
The placement of the engine, transmission, differential and drive axles, as well as steering components, all in the forward portion of the motor vehicle does, however, present design and packaging challenges which are greater than those encountered in rear wheel drive vehicles.
For example, certain transmission configurations, because of their tandem gear arrangements, occupy significant length along the torque flow path, i.e., from input to output. The incorporation of such transmissions in front wheel drive powertrains, oriented either transversely or longitudinally, may impact design and engineering choices about the particular vehicle in which certain transmissions may be used. Alternatively, passenger compartment volume may necessarily be slightly reduced to accommodate a particular transmission.
From the foregoing, it is apparent that the length as well as the overall size of a transmission will typically impact the design as well as the identity of a particular vehicle with which it is used. In turn, this renders it apparent that a more compact transmission will, all other things being equal, be more adaptable and usable in a wider variety of vehicles than a less compact transmission.
It is thus apparent that improvements, especially those directed to reduction of the overall size of an automatic transmission, are desirable and the present invention is so directed.

Compound planetary front wheel drive continuously variable transmission


A kingpin adapter is provided having an upper wall and a lower wall that are affixed to each other through side walls. The upper and lower walls have a kingpin aperture and a hitch ball aperture that is spaced from and parallel to the kingpin aperture. The kingpin aperture receives a kingpin and the adapter is affixed to the kingpin using pins that extend through the side walls and extend through a portion of the undercut in the kingpin. The upper wall has jack screws that extend through to contact a skid plate that is affixed to the kingpin. The jack screws affix optional adjustable fences that rotationally constrain the skid plate by contacting lateral edges of it.

Traditional kingpin and fifth wheel hitches used on recreational vehicles are similar to those used on tractor trailer combinations and have the same disadvantages. The kingpin must be at a very specific height for its entry into the fifth wheel hitch. Further, the operator of the vehicle must back into the kingpin when it is at its proper height. Performing this task can be nearly impossible in locations other than a large, level, and smooth surface.
Another problem with traditional kingpin and fifth wheel hitches is the constraint of the trailer to rotate in a single plane. In a traditional fifth wheel hitch, the kingpin is locked with a jaw that restrictively limits the out of plane movement with respect to the hitch. While this may work for a tractor trailer combination, it is extremely undesirable for smaller vehicles. Traveling over uneven terrain will necessitate out of plane movement. A previous attempt to provide out of plane movement with a fifth wheel hitch has been to provide a pivot pin below the fifth wheel plate. This allows the entire fifth wheel plate to pivot, but adds significant weight and complexity to the hitch. A more flexible system is needed for an ordinary recreational user that may lack the requisite skill to align a kingpin in a fifth wheel hitch. Further, a device is needed to allow an existing trailer having a kingpin to be adapted to the new flexible system.


The present disclosure provides an alert device and an alert method. The alert device includes an image capturing unit, an input/output unit and a processing unit. The image capturing unit is configured to capture at least one image of a wafer transportation system. The processing unit is configured to: retrieve the at least one image from the image capturing unit; define a first boundary in the at least one image; identify a wafer chuck of the wafer transportation system in the at least one image; determine whether the wafer chuck intersects the first boundary in the at least one image; and transmit an alert signal to the wafer transportation system via the input/output unit when the wafer chuck is determined to intersect the first boundary in the at least one image.

In the semiconductor industry, technologies of automated wafer transportation are introduced. However, during the automatic transportation of wafers, damage to the wafer may be caused if the wafer transportation apparatus is not operated smoothly. Accordingly, to prevent the wafer from being damaged during the automatic transportation, a device and a method for detecting the possible failures and alerting the wafer transportation apparatus are needed.
This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure.


Adjustments during assembly of an illuminating unit having a conventional light pipe in order to position the light pipe and a light guide plate are laborious. Further, a minute prism group having a pitch on the order of 100 μm must be provided to a side surface of the light pipe in order to uniformly guide illuminating light to the light guide plate. An illuminating unit of the present invention is provided with a light guide plate having an illuminating surface that is illuminated by light from a point light source, and a light pipe having an incident surface to which light from the point light source is made incident and an emerging portion from which the light emerges to the light guide plate. The emerging portion and the light guide plate are integrally joined.

1. Field of the Invention
The present invention relates to a display device used in a cellular telephone, a portable small television, a portable game player, a personal digital assistant (PDA), a small size laptop computer, and the like. In particular, the present invention relates to an illuminating unit called a back light or a front light, and to a display device that uses the illuminating unit.
2. Description of the Related Art
Light emitting diodes (hereinafter called LEDs) are often used as light sources having good turn-on characteristics, with little generated heat or noise, in display devices employed in electronic equipment. In general, a transmitting type color liquid crystal display device displays color images by illuminating liquid crystal display elements provided with a red (R), green (G), or blue (B) filter using a back light illuminating unit that uses a white color LED light source. However, ideal white color LED light sources capable of emitting white light do not exist, and devices have been contrived in order to achieve very natural color representation.
A method disclosed in JP 2002-57376 A, for example, is known as a typical recent method. This method is one in which blue color light emitted from a blue color LED light source provided with a fluorescent material excites the fluorescent material, thus obtaining light from green color light to red color light according to wavelength conversion. The light obtained by wavelength conversion is added to the blue color light, thus obtaining quasi-white color light. At the same time, red color light emitted from a red color LED light source is further added to the quasi-white color light, thus obtaining nearly ideal white color light. The white light is guided to a light guide plate, and illuminates liquid crystal display elements. Using this method, the nearly ideal white color light can be obtained simply by only performing output adjustments on the red color LED light source. A liquid crystal display device capable of clear color display can thus be achieved. It is necessary to mix the quasi-white color light and the red color light very efficiently, without color shifting, in order to obtain the nearly ideal white color light. However, a method may be used for mixing in which the blue color LED light source, which is provided with the fluorescent material, and the red color LED light source are disposed at both ends of a light pipe as a first LED light source, which is provided with the fluorescent material, and a second LED light source, respectively. The quasi-white color light and the red color light may be uniformly mixed within the light pipe.
On the other hand, with an illuminating unit such as a back light or a front light, a light source is disposed opposing an end surface of a light guide plate so that light emitted from the light source becomes incident from one end surface of the light guide plate. An illuminating unit having this type of light source arrangement is called a side light type illuminating unit. The side light type illuminating unit having LEDs thus disposed is easier to make smaller and thinner, and has a high light utilization efficiency. A plane emission configuration (refer to JP 3301752 B, for example) is known in which a light pipe is disposed on a side surface of a light guide plate, and light emitted from a light source is guided to the light guide plate through the light pipe. As disclosed in JP 3301752 B, a minute prism group may also be provided in a surface of the light guide plate of an illuminating unit that uses a side light type light pipe. The minute prism group is aligned in parallel with a longitudinal direction of the light pipe in order to make light illuminating an object to be illuminated more uniform. In addition, a minute prism group may also be provided to the light pipe itself, thus unifying the intensity distribution of light emitted from the light pipe and at the same time increasing the utilization efficiency of the light.
However, it is necessary to separately align the positions of the light pipe and the light guide plate when performing illumination with a conventional side light type illuminating unit, that is, when performing illumination with a unit in which the light pipe is disposed in a side light style from one side of the light guide plate. Consequently, there is a problem in that it is labor intensive to make adjustments during assembly.
In addition, it is necessary to provide the minute prism group on the side surface of the light pipe at a pitch of about 100 μm in order to guide the illuminating light to the light guide plate side.

Illuminating unit and display device using the unit


In a method of measuring humidity by using an electrochemical cell, the method comprises applying a voltage across the pair of electrodes to obtain a characteristic curve between the voltage applied and electrical current. The characteristic curve starts with a first flat portion in which a first diffusion limit current remains generally constant within a predetermined voltage range and passes through a point of inflection in which a second differential derivative of the characteristic curve falls on zero at certain voltage, and ends up with a second flat portion in which a second diffusion limit current remains generally constant within a predetermined voltage range. The point of the inflection is uniquely determined regardless of a humidity level of the gas at a constant temperature and oxygen concentration. The humidity level in the gas is obtained by reading the point of the inflection, and the intensity of the first and second diffusion limit current and then comparing the diffusion limit current with the inflection as a reference current.

1. Field of the Invention
This invention relates to a humidity measurement device in which humidity in an atmosphere is measured by using an electrochemical cell.
2. Description of the Prior Art
In a humidity measurement device of this type, there have been devices known in Japanese Provisional Publication Patent Nos. 60-222761, 62-150151 and 62-150152.
In the Japanese Provisional Publication Patent No. 60-222761, partial pressure of oxygen component in a gas is measured with the function of limit currents, each value of which is obtained before and after removing aqueous vapor component from the gas.
The Japanese Provisional Publication Patent No. 62-150151 teaches that the limit currents due to gas diffusion are obtained depending on an oxygen density and an aqueous density in the gas. The difference between values of the limit currents leads to humidity measurement.
Further, the Japanese Provisional Publication Patent No. 62-150152 suggests that a first limit current due to the oxygen density and a second limit current due to the aqueous density are obtained. Then a third limit current based on a dehumidified gas is obtained The humidity is measured based on the difference between the third limit current and at least one of the first and second limit currents.
In each device according to the Japanese Provisional Publication Patent Nos. 60-222761, 62-150151 and 62-150152, however, a dryer device is required to desiccate so as to remove aqueous vapor from the gas atmosphere, simultaneously a measurement device is required to measure the limit current. Thus necessitates a large scale measurement system as a whole resulting in a slow operation of the humidity measurement.
Therefore, the invention has its object to provide a humidity measurement device which is capable of eliminating all the drawbacks mentioned above.
It is an object of the invention to provide a humidity measurement device which is capable of measuring humidity level with a high accuracy.
It is an object of the invention to provide a compact humidity measurement device which is capable of measuring humidity with a quick response.

Method of measuring humidity using an electrochemical cell


The invention relates to an endocellulase catalytic domain comprising the sequence of SEQ ID NO: 1 or a functionally equivalent variant of said catalytic domain that substantially maintains or improves its catalytic activity. The invention also relates to a polypeptide, a nucleic acid, an expression cassette, a vector or a host cell. Additionally, the invention relates to the use of an endocellulase catalytic domain or the polypeptide of the invention for hydrolysing cellulose, producing bioethanol or as a detergent. The invention also relates to a method for hydrolysing cellulose and for producing bioethanol.

Over the past years, cellulose enzymes have attracted the interest of the scientific community as well as the industry due to their many biotechnological applications. Their production has increased exponentially and has encountered an important source of application in the production of bioethanol. Second-generation bioethanol made from lignocellulosic biomass is considered one of the most promising biofuels. However, the enzymatic hydrolysis of the cellulose component to liberate glucose for ethanol fermentation is one of the major barriers for the process to be economically competitive because of the cell wall recalcitrance of feedstock.
Efficient degradation of cellulosic biomass requires the synergistic action of the cellulolytic enzymes endocellulase, exocellulase and β-glucosidase. In order to increase bioethanol production, interest has been focused on the identification and optimization of fungal, yeast and bacterial cellulases and cellulolytic strains. Aside from traditional mutagenesis for improving the secretion level and enzymatic activities of cellulases, genetic engineering of strains and protein engineering on cellulase molecules enabled an increased yield. Bacterial and yeast cellulases are often preferred as these organisms have higher growth rates, although bacterial cellulases are able to deal better with the harsh conditions of industrial settings than eukaryotic ones, allowing higher rates of enzymatic hydrolysis, fermentation and product recovery.
Nevertheless, current cellulases have limited efficiency under industrial conditions. Therefore, there is still a need in the art for cellulases and endocellulases, in particular, with improved physicochemical and/or functional properties over existing naturally occurring and engineered cellulases.

Asociación Centro de Investigación Cooperativa en Nanociencias “CIC nanoGUNE”