Granulated papermaking sludge is combined with plastic to form composite materials that may be shaped into structural and non-structural articles.

The present invention relates to a composite formulation useful as a feedstock in the manufacture of composite end products, such as structural and non-structural construction materials, roofing tiles, fences, door panels, sound barriers, decking materials, decorative wall coverings and the like, and methods of formulating the composite.
Composite materials based on thermoplastic polymers and wood fiber-typically in the form of milled wood products or sawdust-mixed (compounded) with each other and with additives (lubricants, adhesives, compatibilizers, etc.), and manufactured using a high volume process such as extrusion or injection molding, have been known for many years. These materials, extruded or molded into suitable profiles, can replace wood in some applications, and offer the advantages of high resistance to moisture, insects and rot, good appearance, and the absence of knots and splinters.
The prior art includes thermosetting molding compounds containing cellulose fiber as filler. For example, U.S. Pat. No. 3,367,917 describes a thermosetting melamine-formaldehyde-benzoguanamine resinous molding composition containing a fibrous filler, such as alpha-cellulose pulp, in an amount between about 25% and 42% by weight. U.S. Pat. Nos. 3,407,154 and 3,407,155 describe thermosetting urea-formaldehyde and aminoplast resinous molding composition comprising fusible reactive urea-formaldehyde and aminotriazine-formaldehyde resin, respectively, and purified alpha-cellulose fibers (14%-25% by weight) as a filler. More recent innovations in this area are described in U.S. Pat. Nos. 4,282,119 and 4,362,827. In accordance with these patents, particle boards were produced employing a binding agent which was a combination of a polyisocyanate with a aminoplast resin containing 0.25 to 0.65 mole of formaldehyde per mole equivalent of amino groups. U.S. Pat. No. 3,546,158 describes a flooring composition involving a terpolymer, a non-fibrous filler (calcium carbonate, silica, clay, kaolin, carbon black, and the like) and a fibrous filler, such as wood flour, cellulose fibers, asbestos, and the like. Compositions may include 25% to 53% by weight of non-fibrous filler and 17% to 40% by weight of fibrous filler, with the fillers accounting for 50% to 80% of the total composite weight. U.S. Pat. No. 3,720,641 describes a process of blending an aromatic polyamide molding resin with reinforcing fillers, such as glass fibers, asbestos, cellulose fibers, cotton fabric paper and the like with the fillers ranging from 2% to 70% by weight based on the total molding composition. U.S. Pat. No. 5,288,775 describes moldable thermoset acrylic polymer composites containing 3% to 15% of cellulose fibers, fillers and water; the composite is a hard, high molecular cross-linking type that requires a chemical hardener. U.S. Pat. No. 5,767,177 describes a thermosetting composition comprising 33% to 43% of a thermosetting polyester resin, 5% to 15% of cellulose fiber of wood or cotton origin, 15% to 21% of mineral fillers (calcium carbonate or hydrated alumina) and 12.5% to 22.5% of reinforcement fibers such as glass, carbon, or Kevlar. U.S. Pat. No. 5,767,178 describes a thermoset (or a cold-set) composition of a phenol-aldehyde, a urea-aldehyde or a polyurethane, mixed with cellulose fibers and latex, containing magnesium oxychloride or magnesium oxysulphate to improve fire resistance of the resulting composite. A thermosetting composition, comprising both polyvinylchlorides and polyester resins along with sawdust and mineral fillers, is also described in U.S. Pat. No. 5,783,125.
Cellulose fiber has also been used as a reinforcing ingredient in thermoplastic compositions. U.S. Pat. No. 3,856,724 describes a composite based on polypropylene or low-density polyethylene (density 0.92) and 5% to 45%, preferably 20%, by weight of alpha-cellulose (100-mesh flock) along with some additives. U.S. Pat. No. 3,875,088 describes a composite material comprising 50% to 75% of a thermoplastic resin binder (ABS or rubber-modified polystyrene) and 20%-40% of wood flour (40-mesh and 100-mesh), with the ratio of plastic to wood flour being between 1.5 and 3.0. U.S. Pat. No. 3,878,143 describes a composite material comprising 63% by weight of polyvinyl chloride or polystyrene or ABS, and 30% of wood flour along with some minor additives. U.S. Pat. No. 3,943,079 describes a composite material comprising thermoplastic polyvinyl chloride polymer and cellulose fiber as major components, the cellulose fiber being wood pulp or cotton linters in amounts ranging from 16% to 30% by weight of the total. U.S. Pat. No. 4,165,302 describes filled thermoplastic resin compositions comprising low-density polyethylene, polypropylene and other resins (in amounts ranging from 95% to 50% by weight), organic fillers (such as wood flour) and inorganic fillers (such as fly ash or calcium carbonate). The ""302 patent is concerned primarily with increasing the melt flow index of filled thermoplastic resin compositions rather than their mechanical properties.
It became recognized that fillers, particularly cellulose fibers, do not disperse easily throughout the plastic formulations during mixing and molding. Accordingly, the finished products typically do not exhibit the desirable physical characteristics ordinarily associated with fiber-reinforced plastic composites. This problem has been dealt with in a number of patents. For example, U.S. Pat. No. 4,250,064 describes usage, along with low-density organic fibers (such as polyester fiber or cellulosic fiber), of a combination of coarse and fine inorganic filler such as calcium carbonate (20% to 50% by weight), which makes the organic filler more easily and uniformly dispersed in a plastic matrix (preferably chlorinated polyethylene or a vinyl chloride/vinyl acetate copolymer), avoiding visible clumps of fiber. U.S. Pat. No. 4,339,363 describes a thermoplastic resin composition involving crushed wastepaper (40% to 60% by weight), polyethylene, polypropylene or other thermoplastic resin and their combinations, and optionally an inorganic filler, such as calcium carbonate, talc, barium sulfate or the like (8% to 12% by weight). The ""363 patent indicates that such compositions provide higher heat resistance, flame retardancy and mechanical strength compared with those made of synthetic resins, pure or blended with woodmeal or having incorporated inorganic filler. U.S. Pat. No. 4,343,727 describes a thermoplastic compounded injection molding material comprising polyvinyl chloride and cellulosic fiber (Solca-Floc, 5% to 20% by weight) along with epoxidized soybean oil, hydrocarbon extenders, and stearic acid as a lubricant.
Another method of improving the dispersibility of cellulose fibers in a thermoplastic matrix is described in U.S. Pat. No. 4,414,267, according to which cellulose fibers (hardwood kraft, from 1% to 40% by weight of the final composite) are pretreated by slurrying them in water, contacting them with an aqueous suspension of a mixture of a vinyl chloride polymer and a plasticizer, and drying the thus-treated fibers. Yet another approach to improving cellulose filler dispersibility is described in U.S. Pat. No. 4,559,376, according to which cellulose or lignocellulose material is subjected to a hydrolytic pretreatment using diluted hydrochloric or sulfuric acid. Essentially, the treatment converts cellulose or lignocellulose material to a fine powder of microcrystalline cellulose, which exhibits better dispersibility in a polymer matrix such as high-density polyethylene (HDPE).
Attention in the fiber-plastic composite area has been increasingly paid to improving the physical properties, such as mechanical strength, stiffness, resistance to thermal deformation, etc., of the composite products. U.S. Pat. Nos. 4,687,793 and 4,783,493 describe elimination of moisture from cellulosic fiber (wood flour, rice hulls, waste paper, pulp, etc.) before blending them with a thermoplastic polymer (polypropylene, polyethylene, ABS, polyvinyl chloride, etc.), by heat-treating (80 to 150xc2x0 C.) the cellulosic material with glyoxal (0.5% to 12% by weight of the untreated cellulose). The patentees indicate that this treatment produces a cellulosic filler largely free of moisture, results in molded products free of the cavities or blisters typically caused by moisture-generated steam at molding temperatures of 160xc2x0 C. (320xc2x0 F.) and higher, and improves the physical properties of molded products (containing 10% to 65% of this cellulose filler by weight). U.S. Pat. No. 4,833,011 describes an approach to reducing the water content of cellulose fibers (bleached chemical or thermomechanical pulp) prior to mixing them with the thermoplastic resin (particularly an unsaturated polyester resin, such as an epoxy resin, with a crosslinking accelerator). The disclosed drying method involves thermal treatment (heating the fibers) or the chemical treatment (treating the fibers with alcohols, such as ethanol, polyvinyl alcohol, butanol or heptanol). The mix is heated and pressed in a mold, causing its crosslinking and curing. U.S. Pat. No. 4,717,743 discloses polyolefin-based resin compositions comprising newspaper sheets cut to small pieces (3 to 6 mm in size, 20% to 60% by weight of total composite, with 20% to 40% by weight given in the examples) and thermoplastic polymer such as low-density or high-density polyethylene, polypropylene and the like. U.S. Pat. No. 4,737,532 describes a thermoplastic resin composition comprising polyvinyl chloride, an ABS resin, and a high amount of wood flour (up to 60% by weight, as given in the examples), pressed at 200xc2x0 C. to obtain composite sheets.
Attention has also been paid to improving the compatibility of the filler with the polymer matrix, by providing an interaction between the filler and the polymer. xe2x80x9cCompatibilizersxe2x80x9d can be chemically attached either to cellulose fibers, or to a polymer, or can form a covalent chemical bond between the two, or can help to form a sort of uniform xe2x80x9calloyxe2x80x9d between two or several polymeric components ordinarily not very compatible with each other. Generally, compatibilizers markedly improve physical properties of the polymeric composite, its weatherability, and overall performance. U.S. Pat. No. 4,376,144 discloses a thermoplastic composite in which cellulose fiber (hardwood pulp, from 1% to 40% by weight) is attached to the polyvinyl chloride matrix with an isocyanate bonding agent (a cyclic trimer of toluene diisocyanate). A similar approach that uses alkyl isocyanates to bind cellulose fibers (from 1% to 50% by weight of the composite) to thermoplastic polymers such as polyethylene is described in U.S. Pat. No. 4,791,020. In both cases the patentees suggest that cellulose fibers treated in such a way have improved dispersability into the polymer and improved adhesion thereto. As the ""020 patent indicates, the precise mechanism by which the bonding occurs is not known, but the active isocyanate moieties in the bonding agent apparently react with the hydroxyl groups on the cellulose fibers, forming a chemical bonding with the latter. Another compatibilizer, a silylating agent, is described in U.S. Pat. Nos. 4,820,749 and 5,008,310, along with a series of isocyanate bonding agents, such as polymethylene polyphenylisocyanate, 1,6-hexamethylene di-isocyanate, and others. These patents disclose a reinforced composite material comprising a thermoplastic or thermosetting polymer, such as low density polyethylene, polypropylene or polystyrene, ground wood pulp (10% to 40% by weight), inorganic filler, such as clay, calcium carbonate, asbestos, glass fibers and the like (10%-30% with respect to wood pulp), maleic anhydride (0-5%) and gamma-aminopropyltriethoxysilane or similar silylating agents (0.1% to 8% by weight) or isocyanates (0.1% to 20% by weight). The patentees indicate that the silane or isocyanate grafting and bonding process results in better flowability of molten polyethylene and better physical properties of the finished composite product. U.S. Pat. No. 5,120,776 also discloses using of maleic anhydride (0-4%) to improve the bonding and dispersibility of an extruded mixture of 60%-90% of high-density polyethylene and 40% to 10% of wood flour (or chemithermomechanical pulp). U.S. Pat. No. 5,153,241 discloses composites made of thermoplastic polymers such as low density polyethylene, polypropylene or polystyrene (90% to 60%) and wood pulp or sawdust (10% to 40% by weight) grafted with a titanium coupling agent (isopropyltri[n-ethylaminoethylamino]titanate) in acetone, along with some inorganic fillers, such as calcium carbonate and Portland cement. U.S. Pat. No. 4,851,458 describes a composite material comprising polyvinyl chloride and cellulose filler (cellulose fiber or wood meal, preferably from 3% to 20% by weight of total) along with an xe2x80x9cadhesion promoterxe2x80x9d of undisclosed chemical structure or composition; the adhesion promoter is applied (coated or sprayed) to the fibers prior to incorporation thereof into the polymer. The patentees claim that the disclosed composite exhibits less shrinkage at elevated temperatures compared with polyvinyl chloride itself or filled with calcium carbonate; in particular, in a test at 110xc2x0 C. for one hour, the patentees indicate that PVC exhibits shrinkage of 2% to 4% of the original length, while the disclosed PVC-cellulose composite shows shrinkage below 1% at the same conditions. U.S. Pat. No. 5,981,631 describes achieving compatibility of the ingredients in a thermoplastic composition by extruding a polymer (polyethylene, polypropylene or polyvinyl chloride), wood fibers, and a coupling agent containing fatty acids and rosin acids, both having at least 16 carbon atoms.
Numerous patents issued in the 1990s concern composite materials comprising polyethylene (high- or low-density, HDPE and LDPE, respectively) and cellulose fibers. U.S. Pat. Nos. 5,082,605, 5,088,910 and 5,096,046 disclose a composite made of 40% to 60% of plastic (LDPE, or a combination of 60% LDPE and 40% HDPE, or having 10-15% of polypropylene of the total amount of plastic) and about 60% to 40% of wood fiber. U.S. Pat. No. 5,474,722 describes a composite material 20% to 80% of which a cellulosic material (ground wood, sawdust, wood flour, rice hulls, etc.) and polyethylene. U.S. Pat. No. 5,480,602 discloses a composite comprising polypropylene, polyethylene, or their combination along with lignocellulosic particles (50% to 70% by weight) and a polyurethane coupling agent (15 to 3% by weight of the mixture). U.S. Pat. No. 5,516,472 discloses a composite having approximately 26% HDPE and 65% wood flour, extruded in the presence of zinc stearate (2%) as a lubricant along with phenolic resin and polyurethane as minor additives and cross-linking agents (4% and 1.3%, respectively). U.S. Pat. Nos. 5,827,462, 5,866,264, 6,011,091 and 6,117,924 describe extruded thermoplastic composites comprising 20% to 40% HDPE or polyvinyl chloride, and 50% to 70% of wood flour, along with 0.5%-2% of lubricants (zinc stearate or calcium stearate) and other minor additives. The foregoing four patents contain an example of the composite (Recipe A and B) showing HDPE and PVC at 26% by weight, wood flour at 66%, and the above-indicated amount of lubricants and other minor additives. U.S. Pat. No. 5,863,480 discloses a thermoplastic composite of polyethylene, polypropylene, vinyls or other extrudable plastics, cellulosic fiber such as saw dust, wood flour, ground rice hulls, etc., fillers and lubricants. The patentees describe the extrusion occurring through a die at a temperature below the melting point of the polymer, so that the deformation of the polymer takes place in the solid phase, making the product biaxially oriented. Canadian Patent No. 2,278,688 discloses a thermoplastic composite material 50% to 60% of which is polyethylene or polypropylene, 10% to 30% of which is wood powder, and 10% to 35% of which is a silicate (mica). U.S. Pat. No. 5,952,105 describes a thermoplastic composition comprising sheared poly-coated paper (50% to 70% by weight) and polyethylene (30% to 50%). An example provided in the patent describes making an 80 g batch of a compression molded composite comprising HDPE (39%), a poly-coated paper (scrap milk jugs, 59%) and a coupling agent (Polybond 3009, 2%). U.S. Pat. No. 5,973,035 by the same authors describes a similar thermoplastic composition comprising sheared paper (50% to 70% by weight) and polyethylene (30% to 50%). An example provided in this patent describes production of an 80 g batch of a compression-molded composite comprising HDPE (39%), sheared scrap newspapers or magazines (59%), and a coupling agent (Fusabond 100D, 2%). U.S. Pat. No. 6,207,729 describes a similar thermoplastic composition comprising shredded and sheared cellulosic materials (33%-59% by weight) such as old newspapers, magazines, kenaf, kraftboard, etc., HDPE (33% to 50%), calcium carbonate (11% to 17%), and a coupling agent (Fusabond 100D, 2%). U.S. Pat. No. 6,153,293 discloses a thermoplastic composite comprising wood fiber (40%-60% by weight) and polyethylene (60%-40%) along with a powdered endothermic foaming agent. The patentees suggest that the foaming agent causes a greater degree of expansion of the composite, conferring a lower specific gravity (1.0xc2x10.2 g/cm3) with no significant loss of overall strength (modulus of rupture of 1,676 psi).
Recently attention has again been paid to alternative thermoplastic materials (e.g., other than polyethylene). U.S. Pat. No. 5,288,772 discloses a cellulose fiber-reinforced thermoplastic composition for compression molding, where thermoplastic material is polypropylene, or a mixture of polypropylene, polystyrene and polyethylene (40% to 90% of plastic by weight), and the cellulosic material (10% to 60% by weight) was milled scrap newspaper with an initial moisture content of at least 30% by weight. The patentees suggest that lignin present in the cellulosic scrap provides a coherent mass of thermoplastic and cellulosic material. A biodegradable thermoplastic composition comprising polyvinyl alcohols, polyurethanes or polyacrylates, cellulose fibers and chitosan is disclosed in U.S. Pat. No. 5,306,550. Canadian Patent Nos. 2,100,320, 2,178,036, 2,242,326, and U.S. Pat. Nos. 5,486,553, 5,539,027, 5,585,155, 5,827,607, 5,948,524, 6,015,611 and 6,015,612 describe a composite material comprising a polyvinyl chloride polymer (50% to 70%) and wood fiber (sawdust, 30% to 50%). Canadian Patent No. 2,250,161 and U.S. Pat. No. 5,738,935 disclose a thermoplastic composite comprising polyvinyl chloride (45% to 90%), cellulose fiber (10% to 55%), a porosity aid (0.01% to 5%) and an interfacial agent (0.01% to 2%). U.S. Pat. Nos. 5,635,125 and 5,992,116 describe a molded composite of wood sawdust particles (34% to 44%) and ground-up recycled polyvinyl chloride particles (55% to 65%). U.S. Pat. No. 5,783,505 discloses a biodegradable composition involving a blend of cellulose acetate and cotton for the manufacture of a non-woven products such as diapers. Biodegradable thermoplastic composite, comprising aliphatic polyester urethanes or polyester amides and wood flour as a reinforcing material, are described in U.S. Pat. No. 5,827,905.
Another recent innovation involves compounding of thermoplastic polymers and cellulosic materials along with other ingredients into a feedstock in the form of durable, easy to transport, and non-friable pellets. U.S. Pat. Nos. 5,746,958 and 5,851,469 disclose production of a wood-thermoplastic composite material comprising a wood component (40% to 65% by weight, and preferably 52%) and polyethylene (60% to 35%), preferably HDPE and preferably 48% by weight. U.S. Pat. No. 5,938,994 describes a wood-plastic composite material produced as feedstock pellets in a twin screw extruder, and comprising wood flour (about 20% to 80%) and polyethylene (80% to 20%) as a preferred plastic. U.S. Pat. Nos. 5,948,524, 6,015,612 and 6,210,792 disclose a wood-plastic composition manufactured as feedstock pellets comprising polyvinyl chloride and wood fiber.
Accordingly, although the prior art includes various thermoplastic composites based on waste materials, few of these materials are readily available on a widespread and cost-effective basis. Moreover, their proportion in the overall composite mixture tends to be somewhat low, since high proportions of non-plastic components can compromise mechanical properties. As a result, the environmental benefits offered by these compositions is limited.
We have found that high levels of granulated papermaking sludge (e.g., up to 70%-75%) can be mixed with plastic and, if desired, cellulose fiber to form composite materials that may be shaped into structural and non-structural articles. Surprisingly, despite relatively low levels of plastic (e.g., 20% to 40%), these composites exhibit worthwhile mechanical properties (having high strength, high modulus, high impact resistance, and good resistance to decay), can be made non-flammable, and show other useful properties making them economically attractive and beneficial to the environment.
In one aspect, the present invention relates to a composite formulation useful as a feedstock in the manufacture of composite end products, such as structural and non-structural construction materials, roofing tiles, fences, door panels, sound barriers, decking materials, decorative wall coverings and the like. In a representative embodiment, the feedstock composite contains granulated papermaking sludge and plastic. The feedstock may also contain cellulose fiber (e.g., agricultural by-products in a short-fiber form, such as rice hulls, cotton linters, ground cotton and other plant fibrous materials, fibers from textile manufacturing, pulping and paper converting operations, recycling of paper and wood products, etc.), and, if desired, additives such as reinforcing agents, lubricants, colorants, compatibilizers, and/or flame retardants. An advantage of the invention is the ecological benefit of utilizing papermaking sludge that would otherwise be disposed of as industrial waste; indeed, further ecological benefit can be realized by combining the granulated sludge with recycled plastic in formulating the composite.
The environmental benefits of productively utilizing papermaking sludge and avoiding its disposal are considerable. Pulp and paper sludge (a byproduct of primary pulping operations, recycle streams or waste paper pulping and the like) represents an environmental and disposal problem for manufacturers of pulp and paper. Generally, pulp and paper sludge is unsuitable for paper making, although it generally contains the same componentsxe2x80x94cellulose, lignin, hemicellulose, calcium carbonate, clay, and other inorganic componentsxe2x80x94as those present in the paper pulp itself.
Paper sludge has traditionally been disposed of by landfilling, composting, incorporation into cement, and incineration. The latter option, in turn, creates another problem, namely, disposal of the resulting ash, which often makes up to 50% (and sometimes as much as 80% or higher) of the volume of the sludge itself.
The principal components of ash are calcium carbonatexe2x80x94in the form of precipitated calcium carbonate (PCC) or ground calcium carbonate (GCC)xe2x80x94that typically constitutes 20% and up to 75% of dry sludge content, and clay. These two minerals are typically loaded into paper as a coating and filler to improve the mechanical characteristics as well as the appearance of paper. The resulting papermaking sludge, particularly mixed office paper sludge, consists primarily of two major components, i.e., fiber and minerals finely mixed with each other.
A typical recycling mill processes 600 tons of wastepaper per day, yielding 450 tons of pulp and producing 150 tons of papermaking sludge. The 228 mills currently under operation in North America produce 9 million tons of pulp residue, approximately 5 million tons of which is cellulose. The 154 European pulp and paper mills produce about 8 million tons of pulp residue, approximately 4 million tons of which is cellulose. The conversion of such waste material into value-added products has, therefore, long been desired.
GranTek Inc. (Green Bay, Wis.) manufactures controlled size dust-free granules, made of pulp and paper sludge, under the brand name BIODAC. The granules are a tight composite of organic and inorganic materials, i.e., cellulose fiber and minerals, and possess a developed porous structure. This granulated papermaking sludge is described, for example, in U.S. Pat. No. 5,730,371, the entire disclosure of which is hereby incorporated by reference. The granules have a controlled size and possess a developed porous structure; they are composed of organic and inorganic materials, i.e., cellulose fiber and minerals. It has been found that granulated pulp and paper sludge absorbs oil or other hydrophobic fluids to a high extent; for example, the particles described in the ""371 patent can absorb more than their own weight.
It is also found that granulated pulp and paper sludge, compared with loose cellulose fiber, greatly improves the properties of fiber-plastic composites. Moreover, while reinforcement of polymer matrices by incorporation of cellulose fiber is well-known, the incorporation of cellulose fiber into polymer hot melt is difficult. Intensive prolonged mixing is ordinarily required to disperse the fiber. It is particularly difficult to obtain high-strength fiber-plastic composites, since fibers typically possess a high degree of fiber-fiber interaction, tending to stick together in bundles of fibers and resisting dispersion of the individual fibers. It has been found, however, that granulation of pulp and paper sludge, approximately half of which is typically cellulose fiber, reduces fiber-to-fiber interaction prior to incorporating it into the matrix, and improves the mechanical properties of the composite.
The composites of the present invention preferably utilize granulated pulp and paper sludge. A preferred material is the BIODAC product described above. Since BIODAC granules have a very developed porous infrastructure, and are able to absorb a high amount of liquid, both hydrophilic and hydrophobic, such as oil (generally more than 100% by weight), they may be employed as a major ingredient in thermoplastic composites. In the preferred embodiment, organic material comprises a majority of the composition by weight, and desirably represents at least 60% (ideally 70-75%) by weight of the composition. The organic material preferably comprises granulated sludge, alone or in combination with cellulose fibers (e.g., rice hulls); the latter may be added to reduce overall material costs, but is by no means necessary to the invention. The composition also includes a polymer composition comprising a synthetic polymer resin, either alone or in the form of a plastic (i.e., combined with additives such as colorants, plasticizers, etc.) such as virgin and/or recycled HDPE, or LDPE, LLDPE, polypropylene, polyvinyl chloride, nylon 6, nylon 66 or other suitable material, at levels preferably ranging from 20-40% by weight. If desired, the composition may include additives such as reinforcing agents, lubricants, colorants, compatibilizers, and/or flame retardants at levels consistent with well-known applications of these components in conventional thermoplastic compositions. The final product is desirably extrudable, injection moldable and/or compression moldable.
The following examples illustrate various compositions that were formulated and then used to manufacture specified end products. The listed components were blended on a weight basis to form a homogeneous mix, then fed to a twin-screw compounding extruder. The resulting compounded material was pelletized, and fed to a single-screw extruder to form the end product.
The end products were tested according to ASTM D6109 (load at failure, flexural strength, flexural modulus), D6108 (load at failure, compressive strength), modified D3763 (puncture resistance), El (termite resistance), D1929 (self-ignition), D1037 (specific gravity, water absorption, moisture content), D635 (rate of burning).

Cellulose-reinforced thermoplastic composite and methods of making same


A display system for an appliance incorporates an electronic interface screen, such as an LCD touch screen, through which a wide range of information concerning operational, diagnostic and other data concerning the appliance can be displayed. The screen is divided into a number of panels for displaying different sets of information. Selecting one of the panels results in the panel becoming enlarged so as to fill the entire LCD screen while, at the same time, displaying an additional layer of detailed information.

1. Field of the Invention
The present invention pertains to the art of appliances and, more particularly, to a system for displaying information through an electronic interface system of an appliance.
2. Discussion of the Prior Art
Automatic commercial washing machines have traditionally been operated from stored programs based on the positioning of various manually actuated buttons. Currently, most washing machines incorporate electronic control systems used to establish wash temperatures and time settings for the various operations performed by the washing machine. It is also known to employ a menu driven display, such as an LCD touch screen, in a washing machine or other appliance through which desired cycle information can be inputted.
One major advantage of utilizing a menu driven display over more conventional, manually actuated buttons, is that the display can be used to advantageously prompt a user for programming inputs, as basic as the type of fabric to be cleaned to the degree or level of soiling, or as complex as the desired water extraction speed and temperature. In addition to prompting the user for necessary programming information, the washing appliance can visually display a wide range of information to the user, including washing instructions and tips, as well as help information for operating and programming the washing machine. Furthermore, there is at least the potential to display diagnostic information which can be beneficial for service personnel or the like.
Given the available mounting area, a visual display on an appliance will typically need to be fairly small. For displaying basic programming information, this size is not considered problematic. However, if the system is to display other types of information, such as washing instructions and diagnostic records, there can be a considerable amount of data which needs to be presented in order to adequately convey the desired information. Under such circumstances, the available display area may simply not be adequate enough to make that information available, at least without scrolling through the information. This problem is further amplified by the fact that known displays typically designate certain areas for particular kinds of information. Under such circumstances, the entire field of the display is simply not available for relaying the wealth of information which needs to be conveyed.
Based on the above, there exists a need for a menu display system in an appliance which overcomes the problems of the prior art. More particularly, there exists a need for an interactive appliance display which can present a wide range of information in a limited amount of space, while enhancing the manner and amount of information that can be accessed.

Information display system for an appliance incorporating electronic interface screen


A packaging container is provided for a large-caliber cartridge having a thin-walled cartridge case and a projectile, whose projectile head projects out of the front of and is connected to the cartridge case. The packaging container has an outer container and an inner container, which receives the cartridge. To secure the projectile of the cartridge inside the packaging container, with respect to a possible displacement of the projectile toward the rear end of the container, the projectile head of the cartridge is disposed in the inner container in a frictional lockup. For this purpose, the inner container has a one-piece projectile-head shaped receptacle at the front, to which a first half-shell that partially surrounds the cartridge case is connected, and a second half-shell, that is hinged to the first half-shell and can be secured to it.

This application claims the priority of German Patent Application No. 101 27 645.1 filed Jun. 7, 2001, which is incorporated herein by reference.
The invention relates to a packaging container for a large-caliber cartridge having a thin-walled cartridge case and a projectile, whose projectile head projects out of the front of the cartridge case and is connected to it.
German published Patent Application No. DE 195 14 988 A1 discloses a packaging container for large-caliber cartridges having a cartridge case and a small-caliber projectile. Because the projectile in large-caliber cartridges, especially those with a combustible cartridge case, is typically much heavier than the drive component, the projectile must be supported inside a support tube by corresponding, form-fitting plastic or fibrous elements to prevent damage to the cartridge case if the packaging container falls toward the casing bottom.
In large-caliber full-caliber projectiles, the projectile head typically has a smooth surface, in contrast to small-caliber projectiles, so in corresponding packaging containers, form-fitting support elements cannot securely fix the projectile head inside the container at a justifiable cost.
German published Patent Application No. 198 12 633 A1 discloses a packaging container in which the use of an inner case, which is supported against the rear side of the case and is connected at its front end to a spreader ring having radial, resilient claws, prevents a full-caliber projectile from being displaced toward the rear end of the container if the packaging container falls toward the casing bottom. When a cartridge is located in the packaging container, the claws press against the outside wall of the projectile head and create a frictional connection between the inner case and the projectile head.
The primary drawback of this packaging container is that the frictional lockup of the spreader ring impedes both the insertion and removal of the cartridge in the axial direction. The geometry and material of the spreader ring must be selected to assure a sufficient pressing force for effecting a diversion of the force of the projectile head across the packaging parts and into the casing bottom if the packaging falls axially, despite the relaxation of the ring material after a certain length of time.
It is the object of the invention to provide a packaging container in which the projectile of the respective cartridge is securely supported with respect to a possible displacement of the projectile toward the rear end of the container, even if the projectile is a full-caliber projectile whose head has a smooth surface.
In accordance with the invention, the above object generally is achieved by a packaging container for a large-caliber cartridge having a thin-walled cartridge case and a projectile, whose projectile head projects out of and in connected to the front of the cartridge case, with the container comprising an outer container and an inner container, which receives the cartridge and can be axially inserted into and withdrawn from the outer container. The inner container includes a projectile-head receptacle at the front, with the receptacle being connected at its rear to a first half-shell, which partially surrounds the cartridge case, and a second half-shell, which is hinged to the first half-shell and can be secured to it. The end region of the projectile-head receptacle facing the first half-shell, and the end region of the second half-shell facing the projectile-head receptacle are formed as complementary retaining shells (or are connected to complementary retaining shells) that surround the rear region of the projectile head in a frictional lockup or a form-fit during use of the packaging container for a projectile. Further, particularly advantageous embodiments of the invention likewise are disclosed.
The invention is essentially based on the concept of disposing the cartridge in an inner container for producing a frictional lockup for the projectile bead, the container having a projectile-head receptacle at the front, to which a first half-shell that partially surrounds the cartridge case is connected, and a second half-shell, which is hinged to the first half-shell and can be secured to it, with the end region of the projectile-head receptacle that faces the first half-shell and the end region of the second half-shell that faces the projectile-head receptacle being formed as complementary retaining shells, and/or being connected to retaining shells that surround the rear region of the projectile head in a frictional lockup and/or a form-fit in the intended use of the packaging container.
In the packaging container of the inventions therefore, the direction of force for moving the cartridge and the axial force deflection are decoupled from one another when the packaging container falls toward the casing bottom, so the latching in the circumferential direction and the axial force absorption can be optimized extensively independently of one another.
To assure a frictional lockup with the aid of the retaining shells, it has proven advantageous for the shells to comprise a deformable material, particularly an elastomer plastic, because the retaining shells can adapt precisely to the projectile contour during the latching process, which produces a correspondingly good frictional connection between the projectile and the retaining shells.
Further details about and advantages of the invention ensue from exemplary embodiments described below with reference to drawing figures.

Packaging container for a large-caliber cartridge


Disclosed herein is a method for preparing a blended gasoline composition comprising: a) providing an automotive gasoline; and b) blending the automotive gasoline with an octane enhancer and with a pressurant, thereby making the blended gasoline composition; wherein the blended gasoline composition comprises an oxygen content, contributed by ethanol, in an amount that ranges from 0% by weight to 0.75% by weight, based on the total weight of the blended gasoline composition and the total oxygen content weight contribution of ethanol present in the blended gasoline composition; wherein the blended gasoline composition comprises an oxygen content, contributed by methanol, in an amount that ranges from 0% by weight to 0.1% by weight, based on the total weight of the blended gasoline composition and the total oxygen content weight contribution of methanol present in the blended gasoline composition; and wherein the blended gasoline composition comprises lead in an amount that ranges from 0 grams per gallon to 0.05 grams per gallon of the blended fuel composition. Also disclosed herein is the blended gasoline composition.

Over the past century, General Aviation (GA), which includes all flying except for military and scheduled airline operations, has become a significant and integral part of the U.S. economy creating millions of jobs and making a positive impact on the U.S. balance of trade. The United States continues to be one of the world leaders in the design, manufacture, and use of GA airframes, engines, avionics, and supporting technologies. GA is a key catalyst for economic growth and has a profound influence on the quality of life in the United States. GA today touches nearly every aspect of our daily lives, and its continued success will shape American society and the American economy over the next century. Often, GA is thought of as recreational aviation, but there are many commercial and governmental operations that fall within this category of flying.
Consequently, aviation gasoline (AVGAS), which is a vital element in the operation of aircraft, which are powered by piston-driven engine, is vital within GA. There are approximately 167,000 aircraft in the United States GA fleet, the vast majority of which rely upon, and are currently fueled with 100 low lead (100LL) AVGAS, which is the only readily available gasoline for these aircraft.
Unfortunately, the 100LL AVGAS of today contains the additive tetraethyl lead (TEL), which has been used as an aviation gasoline additive for decades in order to meet the very high octane levels required to prevent detonation (engine knock) in high compression and high performance aircraft engines, and to satisfy the valve train lubricity needs of these engines.
It must be understood however, that of all the aircraft in the US and world-wide fleet of GA, as many as 80 percent are not powered by high compression or high performance engines; rather, they are powered by lower compression and lower performance engines, and which consequently could be fueled with lower performance aviation gasoline, if such a fuel was made readily available. That is, if a suitable lesser performance aviation gasoline was introduced into the marketplace, 80 percent of the GA fleet could operate on it; whereas, the balance of the fleet (20 percent of the aircraft) would continue to operate on the 100LL AVGAS (or an Unleaded replacement for 100LL AVGAS). Complicating matters, there are serious problems with 100LL AVGAS. Petitions and potential litigation from environmental organizations regarding lead-containing 100LL AVGAS, citing the adverse health impacts to humans and the environment from exposure to lead, have called for the US Environmental Protection Agency (EPA) to consider regulatory actions to eliminate or reduce lead emissions from aircraft. Similar regulatory actions are under consideration globally.
These activities raise concerns about the continued availability and use of leaded 100LL AVGAS. With the current number of aircraft that are powered by piston-driven engines in the US alone, which is more than 200 times larger than annual new aircraft production, the turnover rate of the existing fleet is very low. This low turnover rate leaves existing aircraft owners particularly vulnerable to devaluation of their aircraft should an unleaded replacement AVGAS be incompatible with the existing fleet. This vulnerability, combined with the stagnation of new aircraft sales and an overall deteriorating economic condition within the aviation industry, has created a sense of urgency regarding the development and deployment of an unleaded replacement for 100LL AVGAS. However, while efforts are under way towards developing an unleaded 100LL AVGAS replacement, these efforts are focusing on a replacement AVGAS that meets the performance demands of the entire GA fleet, not simply the 20 percent that actually needs it. As mentioned above, 80 percent of the GA fleet does not need 100LL AVGAS or an unleaded replacement for 100LL AVGAS to operate safely and efficiently.
Regardless, in response to the rapidly increasing concerns expressed by the GA community, the Unleaded AVGAS Transition Aviation Rulemaking Committee (UAT ARC) was chartered on Jan. 31, 2011, by the Federal Aviation Administration (FAA) Administrator to investigate, prioritize, and summarize the current issues relating to the transition to an unleaded replacement for 100LL AVGAS; and to recommend the tasks necessary to investigate and resolve these issues. The UAT ARC confirmed that an unleaded replacement fuel that meets the needs of the entire fleet does not currently exist.
As such, there remains a need for an inexpensive, suitable, and unleaded aviation fuel to relieve the pressures involved with transitioning GA towards the elimination of lead in aviation fuel.


A portion of a frame body is fixed on a surface of a heat-radiating plate, and on frame body, a semiconductor chip is die-bonded. Next, a prescribed electrode of semiconductor chip and corresponding lead terminal and the like are electrically connected by a prescribed wire. Next, the lead frame is set in a metal mold such that the semiconductor chip is covered with resin from above the semiconductor chip. Thermoplastic resin is introduced into the metal mold, and semiconductor chip and the like are sealed. By taking out the resulting body from the metal mold, a semiconductor is formed. Thus, a semiconductor device can be provided with reduced manufacturing cost.

1. Field of the Invention
The present invention relates to a semiconductor device and manufacturing method thereof and, more specifically, to a semiconductor device including a power semiconductor element and to a method of manufacturing the same.
2. Description of the Background Art
A switching element such as an IGBT (Insulated Gate Bipolar Transistor) is applied to a semiconductor device used, for example, for driving an inverter of industrial equipment. Such a switching element is mounted as a semiconductor chip on a prescribed ceramic substrate. The ceramic substrate having such a semiconductor chip mounted thereon is placed on a heat-radiating plate for radiating heat generated from the semiconductor chip. Around the heat-radiating plate, an insert case is arranged to surround the ceramic substrate. The insert case is formed of resin such as PET-PBT (PolyEthylene Terephetalate)-(PolyButylene Terephtalate), PBT or PPS (PolyPhenylene Sulfide).
A terminal base for connecting the semiconductor device to external equipment is provided on the insert case. The terminal base has a portion provided for supporting (fixing) a nut and a main electrode terminal extending from the ceramic substrate. At this portion, a terminal such as a bus bar connected to the external equipment is to be fixed by a bolt or the like. A semiconductor device of this type is disclosed, for example, in Japanese Patent Laying-Open No. 2002-314038.
The conventional semiconductor device, however, has the following problem. While reduction in manufacturing cost of the semiconductor devices has been demanded, the insert case of the semiconductor device described above is relatively expensive, and it is one factor that hinders reduction of manufacturing cost.

Semiconductor device and manufacturing method thereof


The invention relates to a pasty washing agent for use in commercial laundering which contains a non-ionic surfactant, an organic and/or inorganic builder, a bleaching agent based on peroxygen, and optionally contains other common constituents. The inventive pasty washing agent is characterized in that it contains 30 wt. % to 60 wt. % of non-ionic surfactant, 0.5 wt. % to 5 wt. % of a fatty acid and/or fatty acid alkaline-salt, 5 wt. % to 15 wt. % of citrate and/or citric acid and 15 wt. % to 35 wt. % of an inorganic peroxygen compound. In addition, the pasty washing agent does not contain alkali metasilicate nor a bleach activator. In addition to exhibiting a good cleaning efficiency, the inventive agent has a disinfecting action.

This invention relates to paste-form detergents for use in institutional laundries, to a process for their production and to a disinfecting washing process for institutional laundries.
Detergents used in the home are adapted to domestic requirements. Thus, they are normally powders or are sufficiently liquid to lend themselves to problem-free pouring and dosing. Since liquid detergents are also expected to be stable in storage over relatively broad temperature ranges, organic solvents and/or hydrotropes are often added to them although they do not themselves make any contribution to the washing/cleaning result and, for this reason, are not wanted. One way of avoiding possible dosing problems with insufficiently liquid detergents is proposed in European patent application EP 253 151 A2. This document describes liquid and, in some cases, highly viscous detergents based on nonionic and anionic surfactants which contain polyethylene glycol as hydrotrope and which do not have to be dosed in liquid form by the user, but instead are packed in portions in bags of water-soluble material, for example polyvinyl alcohol.
The paste-form detergent described in European patent EP 295 525 B1 consists of a liquid phase of nonionic surfactant which is liquid at temperatures below 10xc2x0 C. and xe2x80x94dispersed thereinxe2x80x94a solid phase with a certain particle size consisting of washing alkalis, sequestering agents and optionally anionic surfactants. The surfactants or surfactant mixtures used must have a pour point (solidification point) below 5xc2x0 C. to avoid solidification of the paste at low transportation and storage temperatures. This detergent paste is intended for institutional laundries and has such good flow properties that it can be pumped through a suction line by a conventional delivery pump. However, it has been found that pastes of the type in question are not always able satisfactorily to guarantee the homogeneity of their ingredients during the production process and often tend to separate, even in storage. This separation involves not only the separation of solid from liquid ingredients, but also phase separation of the liquid ingredients.
Another paste-form detergent which contains as nonionic surfactant from 40 to 70% by weight of ethoxylated C10-20 fatty alcoholxe2x80x94liquid at room temperaturexe2x80x94with an average degree of ethoxylation of 1 to 8, 20 to 50% by weight of ethoxylated and propoxylated C10-20 fatty alcoholsxe2x80x94liquid at room temperaturexe2x80x94with an average degree of ethoxylation of 2 to 8 and an average degree of propoxylation of 1 to 6 and 1 to 10% by weight of soap is described in International patent application WO 95/09229. This paste-form detergent is so pseudoplastic that it does not flow under the effect of gravity at room temperature, but assumes a distinctly lower viscosity on shearing and then flows under the effect of gravity. This paste-form detergent is preferably dosed by shearing to reduce its viscosity and then dosing the flowable product using feed pumps.
International patent application WO 98/10049 describes a paste-form detergent for use in institutional laundries containing nonionic surfactant, organic and/or inorganic builder, alkalizing agent and optionally bleaching agent, enzyme, redeposition-inhibiting polymer and/or other typical ingredients, characterized in that it contains 5% by weight to 30% by weight of an ethoxylated alcohol corresponding to the general formula R1xe2x80x94(OC2H4)mxe2x80x94OH (I), in which R1 is an alkyl or alkenyl group containing 9 to 15 carbon atoms and the average degree of ethoxylation m can assume values of 1 to 8, 1% by weight to 20% by weight of an ethoxylated alcohol corresponding to the general formula R2xe2x80x94(OC2H4)nOH (II), in which R2 is an alkyl or alkenyl group containing 12 to 22 carbon atoms and the average degree of ethoxylation n can assume values of 3 to 14, with the proviso that n is greater than m by at least 1.0, 20% by weight to 80% by weight of alkalizing agent, more particularly alkali metasilicate, 1% by weight to 20% by weight of medium-chain to long-chain alcohol or alkyl ether corresponding to the general formula R3xe2x80x94Oxe2x80x94R4 (III), in which R3 is an alkyl or alkenyl group containing 6 to 22 carbon atoms and, more particularly, 8 to 22 carbon atoms and R4 is hydrogen or an alkyl group containing 1 to 6 carbon atoms, and up to 15% by weight of organic builder of the polymeric polycarboxylate type. Polymeric polycarboxylates in this context are understood to be polymerization products of unsaturated mono- and/or dicarboxylic acids which, apart from carboxyl groups, have no other functionalities.
Institutional washing processes differ from household washing inter alia in the fact that, although different types of fabrics and variously soiled fabrics also accumulate, the material simultaneously arriving for washing contains largely the same bulk laundry which allows a washing technique specially adapted to the particular cleaning problem. However, there is a greater demand for high-performance cleaning processes in institutional laundries than in domestic washing because heavily soiled washing and infected hospital laundry can accumulate. To keep detergent consumption as low as possible, institutional laundries almost exclusively use water freed from hardness ions for washing. A detailed overview can be found in the article by H. Krxc3xcxcex2mann and H. G. Hloch entitled xe2x80x9cWaschverfahren in der gewerblichen Wxc3xa4schereixe2x80x9d, Tenside Surfactants Detergents 24 (1987), 341-349 and the literature cited therein.
The detergents known from the documents cited above have high cleaning performance and are particularly suitable for the institutional washing of soiled laundry. However, in cases where laundry contaminated with microorganisms, possibly even pathogenic microorganisms, accumulates, they are unable to meet the need for simultaneous disinfection so that disinfecting preparations have to be used with them.
Accordingly, there was a need for a detergent of simple composition which would combine high cleaning performance with a disinfecting effect when used in the wash cycle of conventional institutional washing machines.
The present invention, which is intended to satisfy that need, relates to a paste-form detergent for use in institutional laundries containing nonionic surfactant, organic and/or inorganic builder, peroxygen-based bleaching agent and optionally other typical ingredients, characterized in that it contains 30% by weight to 60% by weight of nonionic surfactant, 0.5% by weight to 5% by weight and more particularly 0.5% by weight to 3% by weight of fatty acid and/or fatty acid alkali metal salt, 5% by weight to 15% by weight of citrate and/or citric acid and 15% by weight to 35% by weight of inorganic peroxygen compound and is free from alkali metasilicate and bleach activator. It must be regarded as surprising that, despite the absence of bleach activators, i.e. precursor compounds forming percarboxylic acids under perhydrolysis conditions, such as esters and amides, a detergent with a disinfecting effect is obtained.
The present invention also relates to a process for the washing and disinfection of laundry in institutional laundries using a corresponding paste-form detergent. The detergent is preferably used in the 60xc2x0 C. wash program, i.e. at a washing temperature of about 60xc2x0 C. In one preferred embodiment of the process according to the invention, not all the ingredients of the paste-form detergent according to the invention need be used together in one detergent paste, instead one or more of the ingredients, particularly the inorganic peroxygen compound, can be separately used, in which case a paste-form detergent corresponding to a detergent according to the invention except for the missing ingredient(s) is additionally used. In this particular embodiment, it is possible where a multiple-chamber washing installation is used to introduce the ingredient used separately, particularly the inorganic peroxygen compound, into the same chamber as or into a different chamber from the paste-form detergent. The word xe2x80x9cseparatelyxe2x80x9d as used above is merely intended to describe the property xe2x80x9cseparately from the paste-form detergentxe2x80x9d, i.e. the ingredient to be introduced separately may also be used in combination or admixture with other typical detergent ingredients which do not undesirably interact with it.
The liquid phase of the paste-form detergent according to the invention is essentially formed by nonionic surfactants. A detergent according to the invention contains preferably 32% by weight to 55% by weight and more preferably 35% by weight to 50% by weight of nonionic surfactant in the form of one or more ethoxylated and/or propoxylated alcohols, preferably those corresponding to the above formula I or II. Mixtures of these nonionic surfactants are particularly preferred. Alcohols or ethers corresponding to formula III above and optionally additional surfactants corresponding to general formula IV:
R5xe2x80x94(OC2H4)xxe2x80x94(OC3H6)yxe2x80x94OHxe2x80x83xe2x80x83(IV)
in which R5 is an alkyl or alkenyl group containing 9 to 15 carbon atoms and, more particularly, 12 to 15 carbon atoms and the average degree of ethoxylation x can assume a value of 3 to 7 and the average degree of propoxylation y a value of 2 to 8, may also be present in detergents according to the invention. The viscosity of the detergent according to the invention can be adjusted by combining ethoxylated alcohols corresponding to formulae I and II. In the compounds corresponding to formulae I, II and IV, the substituents R1, R2 and R5 may be linear or branched, for example methyl-branched in the 2-position, linear chains containing primary etherified alcohol functions being preferred. The nonionic surfactant corresponding to formula I preferably has a carbon chain length of 8 to 14 carbon atoms and, more particularly, 12 to 14 carbon atoms and an average degree of ethoxylation m of 1 to 8 and, more particular, 1 to 5. The nonionic surfactant corresponding to formula II has a broader carbon chain length distribution towards longer chains with 12 to 22, preferably 12 to 18 and more preferably 16 to 18 carbon atoms and a higher average degree of ethoxylation n of 3 to 14 and, more particularly, 6 to 12. The ethoxylated alcohols corresponding to formula I and the ethoxylated alcohols corresponding to formula II are preferably present in ratios by weight of 2:1 to 1:1.8. The detergent according to the invention may contain other nonionic surfactants typically used in detergents such as, for example, alkyl polyglycosides and/or fatty acid polyhydroxyamides. However, the surfactant component is preferably free from alcohols which have only been propoxylated.
So far as the substituent R3 is concerned, the foregoing definitions of the substituents R1 and R2 largely apply to the alcohols or ethers corresponding to general formula IlI which contribute towards the particularly favorable low-temperature stability of the detergents according to the invention, which are responsible for the substantial absence of foam and for the reduction in surfactant deposits on the washed laundry and which additionally contribute to the washing performance. Besides hydrogen, R4 is preferably a methyl, ethyl, propyl or butyl group, hydrogen and the methyl group, more especially hydrogen, being particularly preferred. In one preferred embodiment of the invention, the detergents contain up to 15% by weight and preferably from 2% by weight to 10% by weight of compounds corresponding to general formula III.
Fatty acids or alkali metal salts thereof, the so-called soaps, or mixtures of fatty acids and soaps are present in detergents according in quantities of preferably 0.75% by weight to 2.5% by weight and more preferably 1% by weight to 2% by weight. Suitable soaps are, in particular, the alkali metal salts of saturated and/or unsaturated C12-18 fatty acids, for example coconut oil fatty acid, palm kernel oil fatty acid or tallow fatty acid; the corresponding acids may also be used as such. It is particularly preferred to use an optionally saponified carboxylic acid mixture ofxe2x80x94based on the carboxylic acid mixture as a wholexe2x80x942% by weight to 8% by weight of C14 carboxylic acid, up to 1% by weight of C15 carboxylic acid, 18% by weight to 24% by weight of C16 carboxylic acid, up to 3% by weight of C17 carboxylic acid, 20% by weight to 42% by weight of C18 carboxylic acid and 30% by weight to 44% by weight of C20-22 carboxylic acid. In fatty acid/soap mixtures, the ratio by weight of fatty acid to fatty acid alkali metal salt is preferably in the range from 1:99 to 50:50 and more preferably in the range from 5:95 to 25:75.
The detergent may optionally contain as further surfactants up to 10% by weight, preferably up to 5% by weight and, more preferably, from 0.5 to 3% by weight of synthetic anionic surfactants selected in particular from alkyl benzenesulfonates, alkyl or alkenyl sulfates and/or ether sulfates. Suitable synthetic anionic surfactants, which are preferably incorporated in the detergent according to the invention in solid, fine-particle and substantially water-free form, include in particular those of the sulfonate or sulfate type which are normally present as alkali metal salts and preferably as sodium salts. However, the above-mentioned surfactants of the sulfonate type in particular may also be used in the form of their free acids. Besides C9-13 alkyl benzensulfonates, suitable anionic surfactants of the sulfonate type are linear alkane sulfonates containing 11 to 15 carbon atoms which are obtainable by sulfochlorination or sulfoxidation of alkanes and subsequent saponification or neutralization, salts of sulfofatty acids and esters thereof which are derived from saturated C12-18 fatty acids sulfonated in particular in the xcex1-position and lower alcohols, such as methanol, ethanol and propanol, and olefin sulfonates which are formed, for example, by sulfonation of terminal C12-18 olefins and subsequent alkaline hydrolysis. Suitable surfactants of the sulfate type are, in particular, primary alkyl sulfates with preferably linear alkyl chains containing 10 to 20 carbon atoms which have an alkali metal, ammonium or alkyl- or hydroxyalkyl-substituted ammonium ion as countercation. Derivatives of linear alcohols containing in particular 12 to 18 carbon atoms and branched-chain analogs thereof, so-called oxoalcohols, are particularly suitable. Accordingly, the sulfation products of primary fatty alcohols with linear dodecyl, tetradecyl or octadecyl groups and mixtures thereof are particularly suitable. Particularly preferred alkyl sulfates contain a tallow alkyl group, i.e. mixtures essentially containing hexadecyl and octadecyl groups. The alkyl sulfates may be prepared in known manner by reaction of the corresponding alcohol component with a typical sulfating agent, more particularly sulfur trioxide or chlorosulfonic acid, and subsequent neutralization with alkali metal, ammonium or alkyl- or hydroxyalkyl-substituted ammonium bases. In addition, the sulfated alkoxylation products of such alcohols, so-called ether sulfates, may be present in the detergents. Ether sulfates such as these preferably contain 2 to 30 and, more particularly, 4 to 10 ethylene glycol groups per molecule.
The solid phase of the detergent according to the invention is essentially formed by the alkalizing agents, the inorganic peroxygen compounds and the builders, although other particulate auxiliaries may optionally be present. The solid phase should be homogeneously dispersed in the liquid surfactant phase. The ingredients of the paste-form detergent present as solid phase should be fine-particle materials and should have a mean particle size of 5 xcexcm to 200 xcexcm, at most 15% of the particles being larger than 200 xcexcm in size. It is surprisingly possible to incorporate relatively coarse-particle solids, for example those in which 20 to 50% of the particles are larger than 100 xcexcm in size, in the paste-form detergents according to the invention without any disadvantages. The mean particle size of the particles forming the solid phase is preferably 10 xcexcm to 80 xcexcm and more preferably 10 xcexcm to 60 xcexcm, the maximum particle size being below 300 xcexcm and, more particularly, below 250 xcexcm. In a preferred embodiment, 90% by weight of the solid powder-form ingredients are smaller than 200 xcexcm in size and, more particularly, smaller than 150 xcexcm in size. The mean particle size may be determined by known methods (for example by laser diffraction or Coulter Counter).
The alkalizing agents present as an additional component are often also referred to as washing alkalis. They may largely be assigned to the solid phase. Under the conditions under which the detergents according to the invention are used, they provide for a pH value in the alkaline range which is normally from 9.5 to 11.5 and, more particularly, from 10 to 11 (as measured on a 1% by weight solution of the detergent in ion-exchanged water). The preferred alkalizing agent is alkali metal carbonate which may also be used in admixture with alkali metal hydrogen carbonate. Alkali metasilicates as strong alkalizing agents are not present in the paste-form detergents according to the invention. The detergents generally contain 20% by weight to 80% by weight, preferably 30% by weight to 70% by weight and more preferably 40% by weight to 60% by weight of alkalizing agent. If the presence of phosphate is ecologically acceptable in the use of the detergents according to the invention (for example where the wastewater is subjected to phosphate-eliminating treatment), polymeric alkali metal phosphates, such as sodium tripolyphosphate, may optionally be present in the paste-form detergents according to the invention. Their percentage content is preferably up to 70% by weight and more preferably from 15% by weight to 40% by weight, based on the detergent as a whole, the percentage content of other solids, for example the alkali metal carbonate and/or alumosilicate optionally present, being reduced accordingly. In one preferred embodiment, the detergents according to the invention contain 5% by weight to 15% by weight and more particularly 6% by weight to 10% by weight of alkali metal carbonate and/or alkali metal hydrogen carbonate.
A detergent according to the invention contains citric acid, alkali metal citrate or mixtures thereof as organic builder. Other monomeric polycarboxylic acids and hydroxycarboxylic acids, such as gluconic acid and salts thereof, and also typical co-builders or complexing agents from the class of aminopolycarboxylic acids and polyphosphonic acids, are also suitable. Aminopolycarboxylic acids include nitrilotriacetic acid, ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid and higher homologs thereof, N,N-bis-(carboxymethyl)-aspartic acid preferably being used. Suitable polyphosphonic acids are 1-hydroxyethane-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediamine tetra(methylenephosphonic acid) and higher homologs thereof such as, for example, diethylene tetramine tetra-(methylenephosphonic acid). The acids mentioned above are normally used in the form of their alkali metal salts, particularly their sodium and potassium salts. Other suitable builders include homopolymeric and/or copolymeric carboxylic acids and alkali metal salts thereof, the sodium or potassium salts again being particularly preferred. Builders of this type which have proved to be particularly suitable are polymeric carboxylates and polymeric carboxylic acids with a relative molecular weight of at least 350 in the form of their water-soluble salts, more particularly their sodium and/or potassium salts, such as the oxidized polysaccharides according to International patent application WO 93/08251, polyacrylates, polymethacrylates, polymaleates and, in particular, copolymers of acrylic acid with maleic acid or maleic anhydride, preferably those of 50 to 70% acrylic acid and 50 to 10% maleic acid which are characterized, for example, in European patent EP 022 551. The relative molecular weight of the homopolymers is generally between 1,000 and 100,000 while the relative molecular weight of the copolymers is between 2,000 and 200,000 and preferably between 50,000 and 120,000, based on free acid. A particularly preferred acrylic acid/maleic acid copolymer has a relative molecular weight of 50,000 to 100,000. Suitable but less preferred compounds of this class are copolymers of acrylic acid or methacrylic acid with vinyl ethers, such as vinyl methyl ethers, vinyl esters, ethylene, propylene and styrene, in which the acid makes up at least 50% by weight. Other suitable water-soluble organic builders are terpolymers which contain two unsaturated acids and/or salts thereof as monomers and vinyl alcohol and/or an esterified vinyl alcohol or a carbohydrate as the third monomer. The first acidic monomer or its salt is derived from a monoethylenically unsaturated C3-8 carboxylic acid and preferably from a C3-4 monocarboxylic acid, more especially (meth)acrylic acid. The second acidic monomer or its salt may be derivative of a C4-8 dicarboxylic acid, maleic acid being particularly preferred, and/or a derivative of an allyl sulfonic acid substituted in the 2-position by an alkyl or aryl group. Polymers such as these may be produced in particular by the methods described in German patent DE 42 21 381 and German patent application DE 43 00 772 and generally have a relative molecular weight of 1,000 to 200,000. Other preferred copolymers are those described in German patent applications DE 43 03 320 and DE 44 17 734 which preferably contain acrolein and acrylic acid/acrylic acid salts or vinyl acetate as monomers. The polyacetal carboxylic acids described, for example, in U.S. Pat. No. 4,144,226 and U.S. Pat. No. 4,146,495 which are obtained by polymerization of esters of glycolic acid, introduction of stable terminal groups and saponification to the sodium or potassium salts are also suitable, as are polymeric acids obtained by polymerization of acrolein and Canizzaro disproportionation of the polymer with strong alkalis. They are essentially made of acrylic acid units and vinyl alcohol units or acrolein units. A detergent according to the invention preferably contains 8% by weight to 12.5% by weight of citrate and/or citric acid. Besides citrate and/or citric acid, it contains preferably 2% by weight to 12% by weight and more preferably 5% by weight to 10% by weight of other organic builders in the form of polymeric polycarboxylate.
Besides the phosphate mentioned above, organic builders suitable for use in the detergents according to the invention are crystalline alkali metal silicates and fine-particle alkali metal alumosilicates, more particularly zeolites of the NaA, X and/or P type. Suitable zeolites normally have a calcium binding capacity of 100 to 200 mg CaO/g which may be determined in accordance with DE 24 12 837. Their particle size is normally in the range from 1 xcexcm to 10 xcexcm. They are used in dry form. In the present case, the water present in combined form in the zeolites is not problematical. Preferred crystalline silicates, which may be present either on their own or together with the alumosilicates mentioned, are crystalline layer silicates with the formula NaMSixO2+x.yH2O, where m is hydrogen or sodium, x is a number of 1.9 to 4 and y is a number of 0 to 20. Preferred values for x are 2, 3 and 4. Crystalline layer silicates such as these are described, for example, in European patent application EP 163 514. Both xcex2- and xcex4-sodium disilicates Na2Si2O5.yH2O are particularly preferred, xcex2-sodium disilicate being obtainable, for example, by the process described in International patent application WO 91/08171. Suitable crystalline silicates are commercially available under the names of SKS-6 (manufacturer: Hoechst) and Nabion(copyright) 15 (manufacturer: Rhxc3x4ne-Poulenc). The content of inorganic builder in the paste may be up to 35% by weight and is preferably up to 25% by weight and, more preferably, between 10% by weight and 25% by weight.
In addition, the paste-form detergent according to the invention may contain an oxygen-containing oxidizing agent in the form of inorganic peroxygen compounds preferably selected from the group consisting of alkali metal perborate, alkali metal percarbonate and mixtures thereof, sodium perborate tetrahydrate and sodium perborate monohydrate being particularly important alongside sodium percarbonate. Other suitable oxidizing agents are, for example, persulfates and peroxypyrophosphates. Inorganic peroxygen compounds may be present in detergents according to the invention in quantities of preferably 20% by weight to 30% by weight and more preferably 22.5% by weight to 27.5% by weight. The disinfecting strength of the detergents according to the invention at temperatures around 60xc2x0 C. is developed without the presence of bleach activators so that the detergents according to the invention are normally free from bleach activators which typically improve the oxidizing powder of such oxidizing agents.
In addition, a detergent according to the invention may contain other washing aids which are normally present in quantities of up to about 15% by weight, based on the detergent as a whole. Examples of such washing aids include enzymes, redeposition inhibitors, soil release agents, dye transfer inhibitors, such as homopolymers and/or copolymers of vinyl pyrrolidone and/or vinyl imidazole, optical brighteners, foam regulators and/or dyes and perfumes. Where perfumes which are generally liquid are present, they blend into the liquid phase of detergents according to the invention. By virtue of the small quantities in which they are used, however, they have no significant influence on the flow behavior of the pastes.
The paste-form detergents according to the invention are preferably substantially free from water. By xe2x80x9csubstantially free from waterxe2x80x9d is meant a state in which the content of free water, i.e. water which is not present in the form of water of hydration and water of constitution, is up to 5% by weight and preferably below 3% by weight. It is worth remarking that, despite the presence of the peroxyen-containing bleaching agent, higher water contents than in normal paste-form substantially water-free detergents are entirely possible. Organic solvents, which include the low molecular weight and low-boiling alcohols and ether alcohols normally used in liquid concentrates, and hydrotropic compounds may optionally be present in quantities of up to 6% by weight, but are preferably absent.
Enzymes optionally present in the detergents according to the invention include, in particular, enzymes from the class of proteases, lipases, cutinases, amylases, pullulanases, xylanases, hemicellulases, cellulases, peroxidases and oxidases and mixtures thereof, the use of protease, amylase, lipase and/or cellulase being particularly preferred. The percentage content of enzymes is preferably from 0.2% by weight to 1.5% by weight and more preferably from 0.5% by weight to 1% by weight. The enzymes may be adsorbed onto supports and/or encapsulated in membrane materials in the usual way or may be incorporated in the pastes as concentrated water-free liquid formulations. Suitable proteases are known, for example, from International patent applications WO 91/02792, WO 92/21760, WO 93/05134, WO 93/07276, WO 93/18140, WO 93/24623, WO 94/02618, WO 94/23053, WO 94/25579, WO 94/25583, WO 95/02044, WO 95/05477, WO 95/07350, WO 95/10592, WO 95/10615, WO 95/20039, WO 95/20663, WO 95/23211, WO 95/27049, WO 95/30010, WO 95/30011, WO 95/30743 and WO 95/34627. Enzymes stabilized against oxidative damage, for example the proteases and amylases known under the commercial names of Durazym(copyright) or Purafect(copyright)OxP and Duramyl(copyright) or Purafect(copyright)OxAm, are preferably used.
Suitable redeposition inhibitors and soil release agents are cellulose ethers, such as carboxymethyl cellulose, methyl cellulose, hydroxyalkyl celluloses and cellulose mixed ethers, such as methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose and methyl carboxymethyl cellulose. Sodium carboxymethyl cellulose and mixtures thereof with methyl cellulose are preferably used. The soil release agents normally used include copolyesters containing dicarboxylic acid units, alkylene glycol units and polyalkylene units. Soil-release copolyesters of the type mentioned and their use in detergents have been known for some time. For example, DE-OS 16 17 141 describes a washing process using polyethylene terephthalate and/or polyoxyethylene glycol copolymers. DE-OS 22 00 911 relates to detergents containing nonionic surfactant and a copolymer of polyoxyethylene glycol and polyethylene terephthalate. DE-OS 22 53 063 mentions acidic textile finishes containing a copolymer of a dibasic carboxylic acid and an alkylene or cycloalkylene polyglycol and optionally an alkylene or cycloalkylene glycol. European patent EP 0 066 944 relates to textile treatment compositions containing a copolyester of ethylene glycol, polyethylene glycol, aromatic dicarboxylic acid and sulfonated aromatic dicarboxylic acid in certain molar ratios. Methyl- or ethyl-end-capped polyesters containing ethylene and/or propylene terephthalate and polyethylene oxide terephthalate units and detergents containing such a soil-release polymer are known from European patent EP 185 427. European patent EP 241 984 relates to a polyester containing substituted ethylene units and glycerol units in addition to oxyethylene groups and terephthalic acid units. The percentage content of redeposition inhibitors and/or soil-release agents in detergents according to the invention is generally not more than 2% by weight and is preferably between 0.5% by weight and 1.5% by weight.
The dye transfer inhibitors suitable for use in detergents according to the invention include in particular polyvinyl pyrrolidones, polyvinyl imidazoles, polymeric N-oxides, such as poly-(vinylpyridine-N-oxide), and copolymers of vinyl pyrrolidone and vinyl imidazole and mixtures thereof. The percentage content of dye transfer inhibitors in detergents according to the invention is preferably between 0.1% by weight and 2% by weight and more preferably between 0.2% by weight and 1% by weight.
The detergents according to the invention may contain, for example, derivatives of diaminostilbene disulfonic acid and alkali metal salts thereof as optical brighteners, more particularly for textiles of cellulose fibers (for example cotton). Suitable optical brighteners are, for example, salts of 4,4xe2x80x2-bis-(2-anilino-4-morpholino-1,3,5-triazin-6-yl-amino)-stilbene-2,2xe2x80x2-disulfonic acid or compounds of similar structure which contain a diethanolamino group, a methylamino group or a 2-methoxyethylamino group instead of the morpholino group. In addition, brighteners of the optically substituted dibenzofuranyl biphenyl type or the optionally substituted 4,4xe2x80x2-distyryl diphenyl type, for example 4,4xe2x80x2-bis-(4-chloro-3-sulfostyryl)-diphenyl, may also be present. Mixtures of brighteners may also be used. Brighteners of the 1,3-diaryl-2-pyrazolone type, for example 1-(p-sulfamoylphenyl)-3-(p-chlorophenyl)-2-pyrazoline and compounds of similar structure are particularly suitable for polyamide fibers. The percentage content of optical brighteners (or mixtures of optical brighteners) in the detergent according to the invention is generally not more than 1% by weight and is preferably from 0.05% by weight to 0.5% by weight.
Typical foam regulators which may be used in the detergents according to the invention are, for example, mixtures of polysiloxane and silica, the fine-particle silica present therein preferably being silanized. The polysiloxanes may consist both of linear compounds and of crosslinked polysiloxane resins and mixtures thereof. Other foam inhibitors are paraffin hydrocarbons, more particularly microparaffins and paraffin waxes with melting points above 40xc2x0 C., saturated fatty acids or soaps containing in particular 20 to 22 carbon atoms, for example sodium behenate, and alkali metal salts of phosphoric acid monoesters and/or dialkyl esters in which the alkyl chains contain 12 to 22 carbon atoms. Of these foam inhibitors, sodium monoalkyl phosphate and/or dialkyl phosphate containing C16-18 alkyl groups are preferably used. The percentage content of foam regulators is preferably between 0.2% by weight and 2% by weight. In many cases, there is no need at all for the additional use of foam inhibitors.
In order to increase the physical stability and the chemical stability of xe2x80x94in particularxe2x80x94the enzymes optionally present, dehydrating agents, for example in the form of salts which bind water of crystallization, such as water-free sodium acetate, calcium sulfate, calcium chloride, sodium hydroxide, magnesium silicate, or metal oxides, such as CaO, MgO, P4O10 or Al2O3, may also be used. Dehydrating agents such as these, with which the water content of detergents according to the invention can be reduced to particularly low values, are present in the detergents according to the invention in quantities of preferably 1% by weight to 10% by weight and, more preferably, 2% by weight to 8% by weight.
Paste-form detergents according to the invention are preferably produced by initially introducing the nonionic surfactant(s), optionally adding the alcohol or ether corresponding to formula III and optionally mixing the whole with the mixture of fatty acid alkali metal salt and fatty acid and optionally the foam regulator and the synthetic anionic surfactant to form a homogeneous premix. A premix such as this is largely stable in storage and flowable at temperatures in the range from room temperature to 40xc2x0 C., even if the ingredients of the premix are not always completely liquid or dissolved at those temperatures. The powder-form constituents, including the citric acid/citrate, of the paste-form detergent are added to the premix thus formed, preferably after heating to temperatures of around 80xc2x0 C. and are dispersed in the premix, more particularly by stirring. The mixture thus obtained is then preferably subjected to wet grinding which gives the product the required consistency and homogeneity. Other ingredients, more particularly temperature-sensitive or shearing-sensitive ingredients, such as perfume oils and enzymes, are then added and should be uniformly incorporated as carefully as possible in order not to destroy the structure of the paste. Immediately after their production, the detergents according to the invention are flowable and pumpable under the effect of shear forces and can thus be packed in conventional supply containers.
A paste-form detergent according to the invention has a viscosity at 25xc2x0 C. of 60,000 mPa s to 100,000 mPa s and, more particularly, in the range from 70,000 mPa s to 90,000 mPa s, as measured with a Brookfield rotational viscosimeter (spindle No. 7) at 5 revolutions per minute. These viscosity figures are read off after a measuring time of 3 minutes in order to allow for any thixotropic effect the paste may have. In one particular embodiment of the invention, the paste-form detergent preferably has such a viscosity at room temperature that it does not flow under the effect of gravity. It is then preferably particularly thixotropic and pseudoplastic, i.e. it has a distinctly lower viscosity on shearing and flows under the effect of gravity. In a particularly preferred embodiment, the paste has an apparent viscosity of about 80,000 mPa s to 120,000 mPa s at 25xc2x0 C. and at a shear rate of 0.0001 sxe2x88x921, as measured with a Bohlin CS rheometer (manufacturer: Bohlin) with a plate/plate measuring system, plate interval 4 mm. On exposure to adequate shear forces, for example a shear rate of 10xe2x88x921 for otherwise the same measuring conditions, a detergent according to the invention preferably has a considerably lower viscosityxe2x80x94generally 100 to 1,000 times lower. The reduction in viscosity on shearing is largely reversible, i.e. on removal of the shear forces, the detergent returns to its original physical state without separating. It is important in this connection to bear in mind the fact that the viscosities mentioned are not measured immediately after production of the paste, but instead are the viscosities of stored pastes so to speak in equilibrium because the shear forces acting in the course of the production process lead to a lower paste viscosity which only gradually increases to the critical viscosity. Storage times of one month are generally sufficient for this purpose.
A detergent according to the invention normally has a density of 1.3 kg/l to 1.6 kg/l. The detergent according to the invention can be dosed using conventional paste dispensers, as described for example in International patent application WO 95/29282, German patent application DE 196 05 906, German patent DE 44 30 418 and European patents EP 0 295 525 and EP 0 356 707. A dispenser particularly suitable for dosing pseudoplastic paste-form detergents is known, for example, from International patent application WO 95/09263 and is preferably used for dosing pseudoplastic pastes according to the invention. The detergents according to the invention may optionally be packed in portions in films, particularly water-soluble films. Such films are described, for example, in European patent application EP 253 151. A detergent according to the invention is preferably used in institutional laundries for washing and disinfecting soiled washing. It is used in concentrations of preferably 2 g/l to 5 g/l in the wash liquor.


In some embodiments, a non-transitory processor-readable medium stores code representing instructions to cause a processor to smooth a current image of a scene to produce a smoothed image and subtract pixel values of a background image of the scene from corresponding pixel values of the smoothed image to produce an altitude difference image. Pixel values of the altitude difference image are weighted to produce a weighted difference image. The weighted difference image is convolved to produce a convoluted difference image. A threshold is applied to each pixel of the convoluted difference image to produce a thresholded difference image. Pixels having a value less than the threshold are removed from the thresholded difference image and classified as background pixels. Foreground pixels are determined based on the thresholded difference image.

Disclosed embodiments relate to video monitoring and interpretation by software-aided methodology, and more particularly, to a system and method for improving the utility of video images in systems handling video, such as, for example, for system-interpreted analysis of video images for security purposes.
Video analytics is an industry term for the automated extraction of information from video. Video analytic systems can include a combination of imaging, computer vision and/or machine intelligence applied to real-world problems. Its utility spans several industry segments including video surveillance, retail, and automation. Video analytics is distinct from machine vision, machine inspection, and automotive vision. Known applications of video analytics can include, for example, detecting suspicious objects and activities for improved security, license plate recognition, traffic analysis for intelligent transportation systems, and customer counting and queue management for retail applications. Advantages of automated video surveillance systems include increased effectiveness and lower cost compared to human-operated systems.
Some known surveillance systems can accurately detect changes in a scene. Changes in a scene lead to changes of pixel values in a camera image. Scene changes can be induced by global or local illumination changes (e.g. sun light, car headlights, street lights), by environmental motion (e.g. blowing debris, shaking trees, running water), or by moving objects (e.g. moving people, cars, and pets). One of the challenging tasks of a surveillance system is to discriminate changes caused by moving objects from illumination changes.
Changes in pixel values for a given image can be computed relative to pixel values in a reference image of the same scene. A reference image, which can be referred to as a background image, generally depicts motionless objects (e.g. buildings, trees, light posts, roads, and parked cars) in a scene. To discriminate changes caused by illumination and environmental conditions (also called clutter motion) from changes caused by moving foreground objects of interest (e.g., moving objects), one known technique assumes that a small pixel and/or illumination change in an image corresponds to static objects, and a large pixel and/or illumination change in an image corresponds to moving objects. A pixel and/or illumination difference threshold can be used to differentiate static objects from moving objects. In a given scene, pixel differences below a threshold can be classified as static objects and pixel differences above the threshold can be classified as moving objects. Defining a threshold that accurately separates moving objects from clutter and background motion can be difficult. The more accurate the threshold, the greater the number of pixels corresponding to moving objects can be detected. Such an assumption is often violated by drastic and/or non-uniform illumination changes, such as regions of brightness and regions having shadows resulting from, for example, headlights or clouds, respectively. Pixel differences associated with such regions can be large, and thus, the regions are classified as moving objects rather than background. In addition to illumination change, large pixel differences can be associated with clutter motion (e.g. moving leaves, moving water, fountains). Pixels corresponding to clutter motion often do not correspond to objects of surveillance interest. As such, it is desirable to exclude such regions from the moving object detection.
Known systems can group pixels corresponding to moving objects into blobs for analysis. During blob analysis, some blobs can be rejected from consideration as moving objects while other blobs can be passed to high level post processing (e.g. recognition, classification). By employing moving object detection, a surveillance system reacts immediately with a lesser chance for a false alarm (i.e. the surveillance system almost instantly detects a moving object and quickly analyzes its behavior).
FIG. 1 illustrates the flow of moving object detection. Collectively, these steps can be referred to as background subtraction or background maintenance. The initial step can be to build a background image, representing an observed scene (e.g. by acquiring a frame of video input), at 100. This step can be performed at startup. Steps 2-4 can be repeated for each subsequent frame. The second step, for each "current" frame, can be to determine illumination differences between the current scene image and the background image (e.g., compute a background difference image), at 105. The third step can be to filter out noise (e.g., illumination changes due to static objects) in the background difference image using a pixel difference threshold, at 110. The pixels can then be grouped into blobs, at 115, and the blobs analyzed, at 120. The background image can be updated with objects that are deemed to be part of the background. Each step includes algorithms of different complexity, and the performance of moving object detection is dependent on the performance of such algorithms. The ultimate goal of a background subtraction algorithm is to provide accurate moving object detection while maintaining a low rate of false alarms from clutter or illumination changes.
The performance of the background subtraction algorithm can bound the performance and capabilities of a surveillance system because downstream processing such as recognition and classification depend on the quality and accuracy of blobs. Therefore, there is a constant demand for improving the performance of the background subtraction algorithm. Background subtraction is a key step for moving object detection in the presence of either static or dynamic backgrounds. To understand what occurs in a scene, the background subtraction algorithm can be used jointly with object tracking, recognition, classification, behavior analysis, and statistical data collection. Background subtraction is suitable for any application in which background removal is a guide for both reducing the search space and detecting regions of interest for further processing.
Many known approaches to background subtraction include modeling the color value of each background pixel by a Gaussian I(x, y)≈N (μ(x, y),Σ(x, y)) The parameters of the Gaussian distribution are determined from a sequence of consecutive frames. Once the background model is built, a likelihood function is used to decide whether a pixel value of a current frame corresponds to the Gaussian model, N(μ(x,y),Σ(x,y)).
Another approach uses a mixture of Gaussians to model color pixel values in outdoor scenes. Another approach uses not only color information but spatial information as well. That is, each pixel of a current frame is matched to both the corresponding pixel in the background image and pixels neighboring the corresponding pixel. Another approach uses a three-component system: the first component predicts pixel value in a current frame, the second component fills in homogeneous regions of foreground objects, and the third component detects sudden global changes. Yet another approach aggregates the color and texture information for small image blocks.
Existing techniques use a mathematical model for the background or foreground blobs using scene statistics. However, they fail to address some challenges that occur in real-world usage. In many scenes, the assumption that a pixel value can be modeled by a Gaussian distribution is only true part of the time, which makes it difficult to build a robust algorithm. Additionally, the temporal updating of the background image or model is an unsolved issue that can instantly and drastically decrease the performance of the whole system. Accordingly, improvement is still required to complement existing algorithms. Some drawbacks of various known approaches are identified below in connection with real-world situations.
Pixel Difference Thresholding
The illumination of outdoor scenes cannot easily be controlled. Accordingly, the pixel difference between an image and its corresponding background image cannot be modeled robustly (i.e. the values of the background image can fluctuate drastically, chaotically and non-uniformly). Shadows, glares, reflections and the nature of object surfaces are examples of factors that can cause unpredictable behavior of pixel values and, as such, the pixel difference. Observing that pixel differences corresponding to groups of pixels behave more predictably and/or less chaotically, models were developed to calculate pixel differences by considering groups of pixels around a particular pixel. Such models assume that a pixel difference calculated using spatially close pixels behave more predictably than differences calculated using individual pixels. Although spatial modeling of a pixel difference provides some improvement, clutter motion (e.g., moving leaves on trees) remains a problem when values of the grouped pixels change both simultaneously and unpredictably. As a consequence, clutter motion regions can be identified as moving objects and can cause a surveillance system to generate false alarms.
Clutter Motion
One known solution for eliminating illumination changes caused by clutter motion regions is based on complex modeling of a background image. Multiple models, rather than a single model, can be used. Complex modeling assumes that the pixel value may fluctuate around several average values. Theoretically, the assumption is quite valid and indeed imitates real life scenarios. One or more thresholds can be applied to the difference between current and average pixel values. However, complex modeling can be sensitive to weather conditions (e.g. snow, rain, wind gusts), and the required processing power makes its implementation impractical due to the need for continuous moving object detection at a high frame rate. Complex modeling relies on continuous moving object detection and the accurate updating of individual models, which depends on the natural environment and specifics of the surveillance scene. Accordingly, statistics of a pixel model of the background image are updated after each input frame has been processed. An error in updating the background image or model directly affects the pixel difference threshold, and problems related to illumination change can accordingly reappear. One solution is to manually mask out the clutter motion regions, which results in the system failing to detect objects in the masked-out regions. However, artifacts of video compression (e.g., blockiness and ringing) can raise problems similar to those caused by clutter motion regions. Hence, manual masking is frequently not an acceptable solution.
Choosing a Threshold
Applying thresholds to pixel differences between an image and a corresponding background discards pixels assumed to be in the background. Once the pixels are discarded from the process (i.e., pixels are classified as background pixels), it can be difficult to re-classify them as object pixels. Moreover, estimating and updating the threshold value can be difficult. In some systems, for example, thresholds depend on the specifics of the surveillance scene, and hence, require tuning during the installation phase. Additionally, different thresholds can be used for different parts of the scene. Such tuning increases the cost of installation without guaranteeing high performance in an uncontrolled outdoor environment. Tuning may require a human to manually re-tune the system under unpredictable weather conditions. The process of choosing thresholds is unpredictable and depends strongly on aspects of background modeling. In systems based on Gaussian modeling, the threshold is uniform and constant for the entire scene. However, in some outdoor scenes each pixel cannot be modeled and updated using the same parametric model.
There is therefore a need to improve the performance of background subtraction so that it is robust to global and local illumination change, clutter motion, and is able to reliably update the background image/model.

System and method for motion detection in a surveillance video