A coating composition comprising a solution of an electrically-conductive polymer and an organic solvent media wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent. Such a coating composition provides a means to protect an imaging element against the accumulation of static electrical charges before and after image processing while also providing the element with improved manufacturability and physical properties.

This invention relates to a coating composition useful in preparing imaging elements such as photographic, electrophotographic, and thermal imaging elements. More specifically, this invention relates to a coating composition containing an electrically-conductive polymer and an organic solvent media, where the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures, and the media has less than twelve weight percent water.
The problem of controlling static charge is well known in the field of photography. The accumulation of charge on film or paper surfaces leads to the attraction of dirt which can produce physical defects. The discharge of accumulated charge during or after the application of the sensitized emulsion layer(s) can produce irregular fog patterns or xe2x80x9cstatic marksxe2x80x9d in the emulsion. Static problems have been aggravated by increases in the sensitivity of new emulsions, increases in coating machine speeds, and increases in post-coating drying efficiency. The charge generated during the coating process may accumulate during winding and unwinding operations, during transport through the coating machines and during finishing operations such as slitting and spooling. Static charge can also be generated during the use of the finished photographic film product by both the customer and photofinisher. In an automatic camera, the winding of roll film in and out of the film cartridge, especially in a low relative humidity environment, can result in static charging. Similarly, high speed automated film processing can result in static charge generation. Sheet films (e.g., x-ray films) are especially susceptible to static charging during removal from light-tight packaging.
It is generally known that electrostatic charge can be dissipated effectively by incorporating one or more electrically-conductive xe2x80x9cantistaticxe2x80x9d layers into the film structure. Antistatic layers can be applied to one or to both sides of the film base as subbing layers either beneath or on the side opposite to the light-sensitive silver halide emulsion layers. An antistatic layer can alternatively be applied as an outermost coated layer either over the emulsion layers or on the side of the film base opposite to the emulsion layers or both. For some applications, the antistatic agent can be incorporated into the emulsion layers. Alternatively, the antistatic agent can be directly incorporated into the film base itself.
A wide variety of electrically-conductive materials can be formulated into coating compositions and thereby incorporated into antistatic layers to produce a wide range of conductivities. These can be divided into two broad groups: (i) ionic conductors and (ii) electronic conductors.
Most of the traditional antistatic layers comprise ionic conductors. Thus, charge is transferred in ionic conductors by the bulk diffusion of charged species through an electrolyte. The prior art describes numerous simple inorganic salts, alkali metal salts of surfactants, ionic conductive polymers, polymeric electrolytes containing alkali metal salts, and colloidal metal oxide sols stabilized by metal salts. Conductivity of most ionically conductive antistatic agents is generally strongly dependent upon temperature and relative humidity of the environment as well as the moisture in the antistatic layer. Because of their water solubility, many simple ionic conductors are usually leached out of antistatic layers during processing, thereby lessening their effectiveness.
Antistatic layers employing electronic conductors have also been described in the art. Because the conductivity depends predominantly upon electronic mobilities rather than ionic mobilities, the observed electronic conductivity is independent of relative humidity and other environmental conditions. Such antistatic layers can contain high volume percentages of electronically conductive materials including metal oxides, doped metal oxides, conductive carbon particles or semi-conductive inorganic particles. While such materials are less affected by the environment, a lengthy milling process is often required to reduce the particle size range of oxides to a level that will provide a transparent antistatic coating needed in most imaging elements. Additionally, the resulting coatings are abrasive to finishing equipment given the high volume percentages of the electronically conductive materials.
Electrically-conductive polymers have recently received attention from various industries because of their electronic conductivity. Although many of these polymers are highly colored and are less suited for photographic applications, some of these electrically-conductive polymers, such as substituted or unsubstituted pyrrole-containing polymers (as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654), substituted or unsubstituted thiophene-containing polymers (as mentioned in U.S. Pat. Nos. 4,731,408; 4,959,430; 4,987,042; 5,035,926; 5,300,575; 5,312,681; 5,354,613; 5,370,981; 5,372,924; 5,391,472; 5,403,467; 5,443,944; 5,463,056; 5,575,898; and 5,747,412) and substituted or unsubstituted aniline-containing polymers (as mentioned in U.S. Pat. Nos. 5,716,550 and 5,093,439) are transparent and not prohibitively colored, at least when coated in thin layers at moderate coverage. Because of their electronic conductivity instead of ionic conductivity, these polymers are conductive even at low humidity. Moreover, these polymers can retain sufficient conductivity even after wet chemical processing to provide what is known in the art as xe2x80x9cprocess-survivingxe2x80x9d antistatic characteristics to the photographic support they are applied onto. Unlike metal-containing semiconductive particulate antistatic materials (e.g., antimony-doped tin oxide), the aforementioned electrically-conductive polymers are less abrasive, environmentally more acceptable (due to the absence of heavy metals), and, in general, less expensive.
However, it has been reported that the mechanical strength of a binderless antistat layer comprising substituted or unsubstituted thiophene-containing polymers is not sufficient and can be easily damaged unless a water-soluble or water-dispersible binder is used in the antistat layer (U.S. Pat. Nos. 5,300,575 and 5,354,613). Alternatively, the mechanical strength of an antistat layer comprising only substituted or unsubstituted thiophene-containing polymers can be improved by applying an overcoat layer of a film-forming polymeric material from either an organic solvent solution or an aqueous solution or dispersion (U.S. Pat. No. 5,370,981). A preferred polymeric material for use as an aqueous dispersible binder with such polythiophene containing antistatic layers, or as a protective overcoat layer on such polythiophene-containing antistatic layers is polymethyl methacrylate (U.S. Pat. Nos. 5,354,613 and 5,370,981). However, these binders or protective overcoat layers may be too brittle for certain applications, such as motion picture print films (as illustrated in U.S. Pat. No. 5,679,505).
Alternative polymeric materials for overcoats include cellulose derivatives, polyacrylates, polyurethanes, lacquer systems, polystyrene or copolymers of these materials (as discussed in U.S. Pat. No. 5,370,981). However, according to U.S. Pat. No. 5,370,981, the use of an alkoxysilane is required in either the binderless polythiophene containing antistatic layer, the overcoat layer, or both layers to provide layer adhesion in such a two layer structure.
A variety of water-soluble or water-dispersible polymeric binder materials have been used in polythiophene containing antistat layers. In addition to the aforementioned polymethylmethacrylate, water dispersible materials include hydrophobic polymers with a glass transition temperature (Tg) of at least 40xc2x0 C. such as homopolymers or copolymers of styrene, vinylidene chloride, vinyl chloride, alkyl acrylates, alkyl methacylates, polyesters, urethane acrylates, acrylamide, and polyethers (as discussed in U.S. Pat. No. 5,354,613). Other water dispersible materials include polyvinylacetate (U.S. Pat. No. 5,300,575) or latex (co)polymers having hydrophilic functionality from groups such as sulphonic or carboxylic acid (U.S. Pat. No. 5,391,472). Water soluble binders include gelatin and polyvinylalcohol (U.S. Pat. No. 5,312,681). Polythiophene containing antistat layers, both in the presence and absence of water-soluble or water-dispersible polymeric binder materials, have been shown to tolerate the addition of water-miscible organic solvents (U.S. Pat. No. 5,300,575). However, the prior polythiophene antistat art only teaches the use of polythiophene in combination with water-soluble or water-dispersible polymeric binder materials prepared via solutions containing a minimum water content of approximately 37 wt % (as seen in U.S. Pat. No. 5,443,944, column 7, lines 1-17, magnetic and antistat layer 6.3 in Example 6). For the case of a binderless polythiophene antistat layer, the prior art (U.S. Pat. Nos. 5,300,575; 5,370,981; and 5,443,944) teaches the use of polythiophene solutions containing water contents of at least 25 wt %. As seen in U.S. Pat. No. 5,443,944, column 3, lines 64-68, 2.2 Antistatic solution 2, the lowest water content of a coating composition shown to form a binderless polythiophene antistatic layer is approximately 12 wt %.
Prior art for substituted or unsubstituted pyrrole-containing polymers (as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654) describes the use of these materials dispersed in a film-forming binder. While a broad range of binders useful in antistatic layers is described, examples from these patents only teach the use of aqueous coatings containing polypyrrole and water-dispersible or water-soluble binders.
Prior art for substituted or unsubstituted aniline-containing polymers (as discussed in U.S. Pat. No. 5,716,550) describes the use of the polyaniline complex dissolved in a first solvent and a film-forming binder dissolved in a second different solvent. The solvent systems taught in U.S. Pat. No. 5,716,550, such as solvent blends containing chlorinated solvents, are environmentally undesirable.
What is needed in the art is a more environmentally friendly solvent system in a coating composition that provides process-surviving antistatic characteristics as well as resistance to abrasion and scratching and improved manufacturability, without adding significant coloration to the imaging element.
The problems noted above are overcome with a coating composition comprising a solution of an electrically-conductive polymer and an organic solvent media wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent and preferably a maximum of 10 weight percent.
Another aspect of the invention discloses an imaging element comprising;
a support;
at least one image forming layer superposed on the support; and
a layer superposed on said support, wherein the layer is derived from a coating composition comprising a solution of an electrically-conductive polymer and an organic solvent media, wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent and preferably a maximum of 10 weight percent.
The coating composition of the present invention comprises an electrically-conductive polymer in an organic solvent media with reduced water content, and may optionally further comprise a film-forming binder and or other components, and thereby provides certain advantages over the teachings of the prior art. An organic solvent rich coating composition provides improved drying, a reduction in coating blush, enhanced compatibility with polymeric binders, and elimination of additional subbing layers on imaging supports.
In the known art, when water is not used as the second solvent for the film-forming binder (See, U.S. Pat. No. 5,716,550, for example), non-environmentally friendly chlorinated solvent systems such as dichloromethane, either by itself or in combination with methanol or acetone, are required for the film-forming binder. In the present invention, coating compositions employing more environmentally friendly solvent systems, such as acetone, can be used for the film-forming binder. Hence, the use of a chlorinated solvent is not required for the binder.
The present invention improves the manufacturability of imaging elements containing antistatic layers by employing novel coating compositions. For example, in certain manufacturing environments, drying capacities are limited, and the use of more volatile organic solvent rich coating formulations is required. Thus, to accommodate such manufacturing environments coating compositions employing low water contents are preferred. In addition, organic solvent rich coating compositions can eliminate the requirement of additional subbing layers on imaging supports and thereby lead to a simplification of the manufacturing process for the imaging element. Therefore, an aim of the present invention is to formulate coating compositions employing organic solvents in combination with a minimal amount of water that can provide electrically-conductive layers.
The coating compositions and imaging elements of this invention can be of many different types depending on the particular use for which they are intended. Such imaging elements include, for example, photographic, electrostatographic, photothermographic, migration, electrothermographic, dielectric recording and thermal-dye-transfer imaging elements.
Photographic elements which can be provided with an antistatic layer in accordance with the coating composition of this invention can differ widely in structure and composition. For example, they can vary greatly in regard to the type of support, the number and composition of the image-forming layers, and the kinds of auxiliary layers that are included in the elements. In particular, the photographic elements can be still films, motion picture films, x-ray films, graphic arts films, paper prints or microfiche, especially CRT-exposed autoreversal and computer output microfiche films. They can be black-and-white elements, color elements adapted for use in a negative-positive process, or color elements adapted for use in a reversal process.
Photographic elements can comprise any of a wide variety of supports. Typical supports include cellulose nitrate film, cellulose acetate film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, poly(ethylene naphthalate) film, polycarbonate film, polyethylene films, polypropylene films, glass, metal, paper (both natural and synthetic), polymer-coated paper, and the like.
The image-forming layer or layers of the element typically comprise a radiation-sensitive agent, e.g., silver halide, dispersed in a hydrophilic water-permeable colloid. Suitable hydrophilic vehicles include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic, and the like, and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers, and the like. A particularly common example of an image-forming layer is a gelatin-silver halide emulsion layer.
In order to promote adhesion between the conductive layer of this invention and the support, the support can be surface-treated by various processes including corona discharge, glow discharge, UV exposure, flame treatment, electron-beam treatment, as described in U.S. Pat. No 5,718,995 or treatment with adhesion-promoting agents including dichloro- and trichloro-acetic acid, phenol derivatives such as resorcinol and p-chloro-m-cresol, solvent washing or overcoating with adhesion promoting primer or tie layers containing polymers such as vinylidene chloride-containing copolymers, butadiene-based copolymers, glycidyl acrylate or methacrylate-containing copolymers, maleic anhydride-containing copolymers, condensation polymers such as polyesters, polyamides, polyurethanes, polycarbonates, mixtures and blends thereof, and the like. In a preferred embodiment of the present invention, no additional treatment of the support surface is necessary to promote adhesion between the conductive layer of this invention and the support because of the solvent mixture employed in the coating composition. The additional functionality of the coating composition of the present invention leads to a simplification of the manufacturing process for imaging elements.
Further details with respect to the composition and function of a wide variety of different imaging elements are provided in U.S. Pat. No. 5,300,676 and references described therein which are incorporated herein by reference. All of the imaging processes described in the ""676 patent, as well as many others, have in common the use of an electrically-conductive layer as an electrode or as an antistatic layer. The requirements for a useful electrically-conductive layer in an imaging environment are extremely demanding and thus the art has long sought to develop improved electrically-conductive layers exhibiting the necessary combination of physical, optical and chemical properties.
The coating composition of the invention can be applied to the aforementioned film or paper supports by any of a variety of well-known coating methods. Handcoating techniques include using a coating rod or knife or a doctor blade. Machine coating methods include skim pan/air knife coating, roller coating, gravure coating, curtain coating, bead coating or slide coating. Alternatively, the coating composition of the present invention can be applied to a single or multilayered polymeric web by any of the aforementioned methods, and the said polymeric web can subsequently be laminated (either directly or after stretching) to a film or paper support of an imaging element (such as those discussed above) by extrusion, calendering or any other suitable method, with or without suitable adhesion promoting tie layers.
The coating composition of the present invention can be applied to the support in various configurations depending upon the requirements of the specific application. As an abrasion resistant layer, the coating composition of the present invention is preferred to be applied as an outermost layer, preferably on the side of the support opposite to the imaging layer. However, the coating composition of the present invention can be applied at any other location within the imaging element, to fulfill other objectives. In the case of photographic elements, the coating composition can be applied to a polyester film base during the support manufacturing process, after orientation of the cast resin, and on top of a polymeric undercoat layer. The coating composition can be applied as a subbing layer under the sensitized emulsion, on the side of the support opposite the emulsion or on both sides of the support. Alternatively, it can be applied over the imaging layers on either or both sides of the support, particularly for thermally-processed imaging element. When the coating composition is applied as a subbing layer under the sensitized emulsion, it is not necessary to apply any intermediate layers such as barrier layers or adhesion promoting layers between it and the sensitized emulsion, although they can optionally be present. Alternatively, the coating composition can be applied as part of a multi-component curl control layer on the side of the support opposite to the sensitized emulsion. The present invention can be used in conjunction with an intermediate layer, containing primarily binder and antihalation dyes, that functions as an antihalation layer. Alternatively, these could be combined into a single layer. Detailed description of antihalation layers can be found in U.S. Pat. No. 5,679,505 and references therein which are incorporated herein by reference.
Typically, an antistatic layer may be used in a single or multilayer backing layer which is applied to the side of the support opposite to the sensitized emulsion. Such backing layers, which typically provide friction control and scratch, abrasion, and blocking resistance to imaging elements are commonly used, for example, in films for consumer imaging, motion picture imaging, business imaging, and others. In the case of backing layer applications, the antistatic layer can optionally be overcoated with an additional polymeric topcoat, such as a lubricant layer, and/or an alkali- removable carbon black-containing layer (as described in U.S. Pat. Nos. 2,271,234 and 2,327,828), for antihalation and camera- transport properties, and/or a transparent magnetic recording layer for information exchange, for example, and/or any other layer(s) for other functions.
In the case of photographic elements for direct or indirect x-ray applications, the antistatic layer can be applied as a subbing layer on either side or both sides of the film support. In one type of photographic element, the antistatic subbing layer is applied to only one side of the film support and the sensitized emulsion coated on both sides of the film support. Another type of photographic element contains a sensitized emulsion on only one side of the support and a pelloid containing gelatin on the opposite side of the support. An antistatic layer can be applied under the sensitized emulsion or, preferably, the pelloid. Additional optional layers can be present. In another photographic element for x-ray applications, an antistatic subbing layer can be applied either under or over a gelatin subbing layer containing an antihalation dye or pigment. Alternatively, both antihalation and antistatic functions can be combined in a single layer containing conductive material, antihalation dye, and a binder. This hybrid layer can be coated on one side of a film support under the sensitized emulsion.
It is also contemplated that the coating composition described herein can be used in imaging elements in which a relatively transparent layer containing magnetic particles dispersed in a binder is included. The coating composition of this invention functions well in such a combination and gives excellent photographic results. Transparent magnetic layers are well known and are described, for example, in U.S. Pat. No. 4,990,276, European Patent 459,349, and Research Disclosure, Item 34390, November, 1992, the disclosures of which are incorporated herein by reference. As disclosed in these publications, the magnetic particles can be of any type available such as ferro- and ferri-magnetic oxides, complex oxides with other metals, ferrites, etc. and can assume known particulate shapes and sizes, may contain dopants, and may exhibit the pH values known in the art. The particles may be shell coated and may be applied over the range of typical laydown.
Imaging elements incorporating coating compositions of this invention that are useful for other specific applications such as color negative films, color reversal films, black-and-white films, color and black-and-white papers, electrophotographic media, thermal dye transfer recording media etc., can also be prepared by the procedures described hereinabove. Other addenda, such as polymer latices to improve dimensional stability, hardeners or crosslinking agents, and various other conventional additives can be present optionally in any or all of the layers of the various aforementioned imaging elements.
The coating composition of the present invention comprises an electrically-conductive polymer, such as a substituted or unsubstituted pyrrole-containing polymer (as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654), a substituted or unsubstituted thiophene-containing polymer (as mentioned in U.S. Pat. Nos. 4,731,408; 4,959,430; 4,987,042; 5,035,926; 5,300,575; 5,312,681; 5,354,613; 5,370,981; 5,372,924; 5,391,472; 5,403,467; 5,443,944; 5,463,056; 5,575,898; and 5,747,412), and/or a substituted or unsubstituted aniline-containing polymer (as mentioned in U.S. Pat. Nos. 5,716,550 and 5,093,439). Typically a polyanion is used with the electrically-conductive substituted or unsubstituted pyrrole or thiophene-containing polymer. Polyanions of polymeric carboxylic acids or of polymeric sulfonic acids, are described in U.S. Pat. No. 5,354,613 for thiophene based polymers. The relative amount of the polyanion component to the substituted or unsubstituted thiophene-containing polymer may vary from 85/15 to 50/50. The polymeric sulfonic acids are those preferred for this invention. The molecular weight of the polyacids providing the polyanions is preferably between 1,000 and 2,000,000, and is more preferably between 2,000 and 500,000. The polyacids or their alkali salts are commonly available, e.g., polystyrenesulfonic acids and polyacrylic acids, or they may be produced based on known methods. Instead of the free acids required for the formation of the electrically-conductive polymers and polyanions, mixtures of alkali salts of polyacids and appropriate amounts of monoacids may also be used. The electrically-conductive polymer and polyanion compound may be soluble or dispersible in water or organic solvents or mixtures thereof. The preferred electrically-conductive polymer for the present invention is a substituted thiophene-containing polymer known as poly(3,4-ethylene dioxythiophene styrene sulfonate).
An optional component further comprising the coating composition of the present invention is a film-forming binder. The presence of a film-forming binder, in such a solvent rich coating composition, aids in the abrasion resistance of the antistatic layer and the adhesion of the antistatic layer to the support. The choice of the film-forming binder is determined by the solvent system employed in the coating composition. Suitable binders are therefore limited to those which are soluble or dispersible in the solvent mixture of the coating composition.
U.S. Pat. Nos. 5,665,498 and 5,674,654 describe the use of a dispersion of poly(3,4-ethylene dioxypyrrole/styrene sulfonate) or polypyrrole/poly(styrene sulfonic acid) in a film-forming binder. A wide variety of useful binders in antistatic layers are mentioned in these patents. However, neither of these patents teaches the use of solvent rich coating compositions and binders appropriate for such solvent systems, nor is the use of solvent rich coating compositions with an electrically-conductive polymer and binder anticipated based on the purely aqueous coating compositions containing water-soluble or water-dispersible binders disclosed in these patents.
U.S. Pat. No. 5,354,613 describes the use of a polythiophene with conjugated polymer backbone in the presence of a polymeric polyanion compound and a hydrophobic organic polymer having a glass transition value (Tg) of at least 40xc2x0 C. However, this patent never teaches the use of solvent rich coating compositions and hydrophobic organic polymer binders appropriate for use in such solvent systems with polythiophene and a polymeric polyanion. Also, the use of a solvent rich coating composition containing polythiophene and a binder for use as an antistatic layer is new teaching herein because U.S. Pat. No. 5,354,613 teaches only the use of an aqueous dispersion of the hydrophobic organic polymer in a primarily aqueous coating composition.
U.S. Pat. No. 5,300,575 describes a solution of a polythiophene and a polyanion with water or a mixture of water and a water-miscible organic solvent as the dispersing medium. While this patent teaches the use of binders such as polyvinylalcohol, polyvinylacetate, and polyurethane with the polythiophene to obtain good surface conductivities, these binders are either water-soluble or water-dispersible binders and are employed in primarily aqueous coating compositions containing a minimum water content of approximately 87 weight percent (see Example 8 in column 8, lines 5-13, of U.S. Pat. No. 5,300,575). The use of a polyurethane binder with polythiophene and a polyanion is also taught in combined magnetic and antistat layer 6.3 of Example 6 in column 7, lines 1-17, of U.S. Pat. No. 5,443,944. This coating composition employs a water content of approximately 37 weight percent, and is the minimum amount of water employed in the prior art for coating compositions containing polythiophene, a polyanion, and a binder. High electrical resistance or insufficient antistatic effects were observed with Example 6 of U.S. Pat. No. 5,443,944. Thus, the ability to utilize polythiophene and binder coating compositions with extremely low water contents and still obtain sufficient antistatic effects is unexpected based on the teachings of the prior polythiophene art.
U.S. Pat. Nos. 5,300,575 and 5,443,944 also teach the use of a binderless polythiophene antistatic layer, as does U.S. Pat. No. 5,370,981. A coating composition with a minimum water content of approximately 29 weight percent is shown for Antistatic layer 2a in Table 1, column 14, lines 55-67, of U.S. Pat. No. 5,300,575 and also for Antistatic layers 1-5 in Table 1, column 11, lines 50-60, of U.S. Pat. No. 5,370,981. Antistatic solution 2 in column 3, lines 64-68, of U.S. Pat. No. 5,443,944 employs a water content of approximately 12 weight percent, and is the minimum amount of water employed in the prior art for coating compositions containing only polythiophene and a polyanion.
U.S. Pat. No. 5,716,550 describes a coating composition comprising a solution of a complex of a polymeric polyaniline and a protonic acid dissolved in a first solvent having a Hansen polar solubility parameter of from 13 to about 17 MPaxc2xd and a Hansen hydrogen bonding solubility parameter of from about 5 to about 14 MPaxc2xd, and a film-forming binder dissolved in a second solvent. The first solvent for the polyaniline-protonic acid complex is dimethylsulfoxide, a gamma-butyrolactone/lower alcohol blend, a propylene carbonate/lower alcohol blend, an ethylene carbonate/lower alcohol blend, a propylene carbonate/ethylene carbonate/lower alcohol blend, or a mixture thereof, wherein said lower alcohol has up to 4 carbon atoms. The second solvent for the film-forming binder is water, a chlorinated solvent, or a mixture of a chlorinated solvent with a lower alcohol or acetone, wherein said lower alcohol has up to 4 carbon atoms. The weight ratio of the second solvent to the first solvent is from about 5:1 to about 19: 1. With the solvent ratios of the first claim of U.S. Pat. No. 5,716,550, and as seen in Examples 17-22, when water is present in the electrically-conductive coating composition it will be present at levels between approximately 83 and 95 weight percent. Thus, lower water content coating compositions are not anticipated from this patent.
In addition, the present invention teaches that the electrically-conductive polymer can first be prepared in a simple, more environmentally friendly solvent mixture of methanol and low levels of water. Examples of the present invention utilize a solvent mixture of methanol and water with weight percentages of 76 and 24, respectively, for first preparing the poly(3,4-ethylene dioxythiophene styrene sulfonate). Such a solvent system has a Hansen polar solubility parameter of 13.0 MPaxc2xd and a Hansen hydrogen bonding solubility parameter of 26.3 MPaxc2xd and therefore lies outside of the range taught in U.S. Pat. No. 5,716,550 for the polyaniline-protonic acid complex. Once prepared in a methanol/water blend, the poly(3,4-ethylene dioxythiophene styrene sulfonate) solution can then be added to a solvent system, with or without a film-forming binder in the solvent system, to further reduce the overall water content of the final coating composition.
When water is not used as the second solvent for the film-forming binder in U.S. Pat. No. 5,716,550, non-environmentally friendly chlorinated solvent systems such as dichloromethane, either by itself or in combination with methanol or acetone, are required for the film-forming binder. As will be seen in the working examples of the present invention, coating compositions employing more environmentally friendly solvent systems, such as acetone, can be used for the film-forming binder. Hence, the use of a chlorinated solvent is not required for the binder in the present invention.
As the non-aqueous, organic solvent portion of the coating composition of the present invention, solvents such as alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures are preferred. However, more preferred organic solvents for the practice of the present invention include acetone, methyl ethyl ketone, methanol, ethanol, butanol, Dowanol(trademark) PM (1-methoxy-2-propanol or propylene glycol monomethyl ether), iso-propanol, propanol, toluene, xylene, methyl isobutyl ketone, n-propyl acetate, cyclohexane and their mixtures. Among all the organic solvents, acetone, methanol, ethanol, iso-propanol, Dowanol(trademark) PM, butanol, propanol, cyclohexane, n-propyl acetate and their mixtures are most preferred. The relative amount of water in the final solvent mixture for the coating composition of the present invention is less than 12 weight percent of the total solvent and preferably a maximum of 10 weight percent of the total solvent.
In the present invention, the electrically-conductive polymer, polyanion compound and other components further comprising the coating composition, such as the film-forming binder, may be soluble or dispersible in the organic solvents and mixtures with minimal amounts of water. Examples of film-forming binders suitable for the present invention include, but are not limited to the following or mixtures of the following: cellulosic materials, such as cellulose esters and cellulose ethers; homopolymers or copolymers from styrene, vinylidene chloride, vinyl chloride, alkyl acrylate, alkyl methacrylate, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl ether, and vinyl acetate monomers; polyesters or copolyesters; polyurethanes or polyurethane acrylates; and polyvinylpyrrolidone. The preferred film-forming binder for the present invention is a cellulose ester and most preferred is cellulose diacetate.
According to the present invention, when a film-forming binder is included in the coating composition, it can be optionally crosslinked or hardened by adding a crosslinking agent to the coating composition. The crosslinking agent reacts with functional groups present in the film-forming binder, such as hydroxyl or carboxylic acid groups. Crosslinking agents, such as polyfunctional aziridines, carbodiimides, epoxy compounds, polyisocyanates, methoxyalkyl melamines, triazines, and the like are suitable for this purpose.
In a preferred embodiment of this invention, the relative amount of the electrically-conductive polymer can vary from 0.1-100 weight % and the relative amount of the film-forming binder can vary from 99.9-0 weight % in the dried layer. Most preferred is when the amount of electrically-conductive polymer is between 2 and 70 weight % and the film-forming binder is between 98 and 30 weight % in the dried layer.
In addition to film-forming binders, other components that are well known in the photographic art may also be present in the coating composition. These additional components include: surfactants and coating aids, dispersing aids, thickeners, coalescing aids, soluble and/or solid particle dyes, antifoggants, biocides, matte particles, lubricants, pigments, magnetic particles, and others.
The coating composition of this invention generally contains a limited amount of total solids including both the required components and the optional components. Usually the total solids is less than or equal to about 10 weight percent of the total coating composition. Preferably the total solids is between 0.01 and 10 weight percent.
The coating composition for the present invention is preferably coated at a dry weight coverage of between 0.005 and 10 g/m2, but most preferably between 0.01 and 2 g/m2.

Coating composition containing electrically-conductive polymer and solvent mixture


A method for reducing or preventing the formation of scale in a municipal or industrial waste water treatment facility comprising introducing an antiscalent composition which comprises:

The present invention relates to a novel method of treatment for the prevention, reduction of removal of scale in municipal and industrial waste water treatment facilities. The invention employs a new anti-scaling composition which is especially useful for the treatment of waste treatment plants prone to struvite scaling.
The precipitation of struvite is a recurring problem, especially in anaerobic sludge digestion systems. Soluble magnesium combines with ammonia and phosphate, released during the aerobic digestion to form magnesium ammonium phosphate (MgNH4PO4.6H2O) which is frequently referred to as struvite. Struvite is a hard, tenacious solid that is extremely difficult to remove from equipment surfaces and pipelines. It is generally encountered in sludge lines and downstream processes following biological phosphate removal and subsequent anaerobic digestion, although it can form wherever the solubility limit is exceeded. This can also be related to pH changes caused by sludge degassing. Deposits tend to form in pipes where waste waters stand between intermittent flows, but also in areas where there is turbulent flow, pressure change or where cavitation occurs. Thus struvite deposition occurs most frequently in pipes, pipe elbows, valves, centrifuge weir overflows, pumps etc.
Struvite deposition is becoming an increasingly widespread problem for a great many waste water treatment plants, since it reduces throughputs, which could adversely affect subsequent sludge processing. In extreme cases the struvite can reduce the throughput so significantly that the plant operation has to be stopped and then the blocked pipework and other equipment must be cleaned. Generally struvite deposits can only be removed completely by treatment with acid. This can be expensive and involve potentially dangerous handling and disposal of cleaning products (acidic solutions) which can also cause excessive wear to the equipment. In addition the plant closure time during the cleaning operation can also be costly.
Various proposals have been made in order to deal with this problem, many with some degree of success, but none of them have successfully overcome this problem completely.
For instance it is known to attempt to control the release of phosphate biologically. In an article by Nic Booker CSIRO, Molecular Science, entitled, xe2x80x9cStruvite formation in wastewater treatments plants: an accident waiting to happen?xe2x80x9d, the issue of nutrient removal from wastewater discharges is discussed. The study claims that Biological phosphorus removal plants can reduce phosphorus concentrations to less than 1 mg/L. However there is a tendency for some plants with insufficient ready assimilable carbon in the feedwater to have difficulty in consistently achieving this level. In addition the biological phosphorus plants involve a number of different stages of treatment, including anaerobic, aerobic and anoxic zones and require long liquid residence times of around 24 hours.
There have also been suggestions to prevent struvite formation by removing ammonia and phosphate chemically by the addition of magnesium to raise the pH. However, in practice this was found to be unsuccessful on the whole.
Another proposal has been to add 20 mg/L ferric salts and 0.25 mg/L anionic polymer. However, the addition of such large amounts of ferric salt could have a detrimental effect on the plant equipment.
In JP-A-08-099091 it is proposed to prevent the generation of struvite scale in piping by chemical reaction/crystallisation employing special separation equipment to recover the crystals of struvite. However, installing such struvite precipitating equipment adds an additional burden to the operation of the waste water treatment plant.
There has also been a proposal to combine a sequesterant with a polymeric dispersant. However, to our knowledge we are not aware of the commercial success of such a system.
Thus there exists a need to simply and conveniently prevent or significantly reduce the formation of struvite in waste water treatment facilities. Furthermore there is also a need to find a simple and convenient treatment of aqueous systems containing struvite deposits.
Thus according the present invention we provide a method for reducing or preventing the formation of scale in a municipal or industrial waste water treatment facility comprising introducing an antiscalent composition which comprises:
A) A water soluble polymer of molecular weight below 20,000 and containing anionic groups, and
B) A sequesterant compound containing at least one phosphonate group and salts thereof.
We have found that the special combination of low molecular weight anionic water soluble polymer and phosphate sequesterant give surprisingly effective results in reducing or preventing scale, especially struvite in waste water treatment systems. Thus it is essential to the present invention that the sequesterant comprised in the antiscalent composition of the present invention is a compound containing at least one phosphonate group.
The antiscalent composition may be used for the treatment of any scale deposits in a water treatment facility. The method is of particular relevance when the scale deposits comprise crystalline precipitate formed by the combination of phosphate, ammonia and magnesium, which may exist as magnesium ammonium phosphate (MgNH4PO4.6H2O) which is generally referred to as struvite.
The method may be applied to any waste water treatment facility in which scale deposit are a particular problem, especially where the scale deposit is struvite. We have found the method is especially valuable in removing, reducing or preventing scale deposition in sewage treatment plants. Hence in a particularly preferred form of the invention we provide a method in which struvite deposition is removed, reduced or prevented in a sewage treatment plant employing as a treatment aid the aforementioned antiscalent composition.
A further aspect of the invention relates to the treatment of any aqueous system containing struvite deposit. Thus we provide the use of a composition comprising
A) A water soluble polymer of molecular weight below 20,000 and containing anionic groups, and
B) A sequesterant compound containing at least one phosphonate group and salts thereof,
for the treatment of aqueous systems containing struvite.
The antiscalent composition employed in the present invention preferably comprises 25 to 75% by weight of the water soluble polymer (component A) and 25 to 75% by weight of the sequesterant (component B). Generally we have found that for many treatments it is preferred that the antiscaling composition comprises 30 to 70% by weight, most preferably 40 to 60%, of the water soluble polymer and between 30 and 70% by weight, most preferably 40 to 60%, of the sequesterant.
The water soluble polymer component of the antiscalent composition comprises anionic groups. The polymer is desirably formed from ethylenically unsaturated anionic monomer or anionic monomer blend in which the monomer blend comprises at least one of the anionic monomer. Typically the anionic monomer or anionic monomer blend can be formed from at least one ethylenically unsaturated carboxylic acid, sulphonic acid or phosphonic acid monomer. The monomers include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, crotonic acid, vinyl phosphonic acid, vinyl sulphonic acid, allyl sulphonic acid, 2-acrylamido-2-methylpropanesulphonic acid. When more than one monomer is employed in a blend, the monomer blend may comprise any of the aforementioned anionic monomer or alternatively a suitable ethylenically unsaturated nonionic monomer, for instance acrylamide or methacrylamide. The polymers may exist in the free acid form or more preferably they are partially or fully neutralised. A particularly preferred water soluble polymer is the homopolymer of acrylic acid, homopolymer of maleic acid, hompolymer maleic anhydride or a copolymer of acrylic acid with either maleic acid or maleic anhydride.
Typically the water soluble polymer is polymerised to a relatively low molecular weight. By low molecular weight we mean that the polymer will have a molecular weight as determined by GPC of below 20,000. However, the molecular weight of the polymer may desirably be in the range 1,500 to 10,000, preferably 2,000 to 5,000.
One way of preparing the water soluble polymer is by solution polymerisation of an aqueous solution of the monomers. Generally the aqueous monomer solution should be between 20 to 40% concentration, preferably around 30 to 35%. The monomer solution may also include a chain transfer agent, for instance sodium hypophosphite, 2-mercaptoethanol or isopropanol. If sodium hypophosphite is used as the chain transfer agent, the amount can be as much as 2000 ppm by weight, but is preferably in the range 10 to 500 ppm by weight, particularly 10 to 50 ppm. Where isopropanol is used as the chain transfer agent it is usual to use this as a part of the solvent system. Thus the monomers would be mixed with an isopropanol/water mixture and then polymerised.
A suitable initiator system, for instance aqueous ammonium persulphate, sodium metabisulphite or tertiary butyl hydroperoxide, optionally with other initiators is introduced. When preparing gel polymers by solution polymerisation the initiators are generally introduced into the monomer solution. Optionally a thermal initiator system may be included. Typically a thermal initiator would include any suitable initiator compound that releases radicals at an elevated temperature, for instance azo compounds, such as azobisisobutyronitrile. The temperature during polymerisation should rise to at least 70xc2x0 C. but preferably below 95xc2x0 C. Depending upon the molecular weight and the concentration of polymer in solution the formed polymer may be a sightly viscous but pourable aqueous solution or could be a rigid gel. Polymer gels may be further processed in a standard way by first comminuting the gel into smaller pieces, drying to the substantially dehydrated polymer followed by grinding to a powder. Pourable solutions of the polymer do not need further processing and would normally be supplied in this form where they may be further diluted on application.
Alternatively the polymers are produced as beads by suspension polymerisation or as a water-in-oil emulsion or dispersion by water-in-oil emulsion polymerisation, for example according to a process defined by EP-A-150933, EP-A-102760 or EP-A-126528.
Although to the invention in some instances beneficial results may be obtained when the polymer has a narrow polydispersity. Thus such polymers would contain a narrow molecular weight distribution. Typically such polymers may have a polydispersity of below 1.5. They may be prepared in accordance with the teachings of EP-A-127388, EP-A-129329 and EP-A-185458.
According to the invention the antiscalent composition comprises as component B a sequesterant compound containing at least one phosphonate group and salts thereof. The invention embraces any phosphonate sequesterant compound that in combination with the water soluble anionic polymer of component A produces a beneficial effect in the removal, reduction and prevention of scale deposits, especially struvite. Preferably the phosphonate sequesterant comprises at least two phosphonate groups which at least one nitrogen atom. Desirably the phosphonate sequesterant can be desirably a compound of the formula I
wherein M is hydrogen, alkali metal or ammonium and R is selected from the group consisting of xe2x80x94H, xe2x80x94CH2CH2N(CH2 PO3M2)2. xe2x80x94N(CH2 PO3M2)CH2CH2N(CH2 PO3M2)2 and xe2x80x94(CH2)6N(CH2 PO3M2)2. A particularly preferred sequesterant is the compound of formula II,
known as diethylenetriamine penta (methylene phosphonic acid) and including the corresponding alkali metal or ammonium salts, most preferred are the sodium salts.
The phosphonate sequesterant may be any one of a number of commercially available sequesterant products, for example DequestRTM 2066 which is a post acidified sodium salt of diethylenetriamine penta (methylene phosphonic acid) available from Solutia.
The antiscalent composition is generally prepared by missing an aqueous solution of the anionic water soluble polymer component with an aqueous solution of the phosphonate sequesterant.
The antiscalent composition may be applied at any point in the waste water treatment process. Desirably though it may be applied more effectively shortly before where the scale or struvite deposits have formed or are prone to form. Struvite tends to form in pipes where waste waters stand between intermittent flows, or in areas of turbulent flow, for instance where a pressure change or cavitation occurs. Thus since struvite deposition occurs most frequently in pipes, pipe elbows, valves, centrifuge weir overflows, pumps etc., it may be desirable to dose at or prior to these points. For instance it may be preferred to apply the antiscalent composition up to 200 meters prior to the area where scaling occurs. Thus it may be preferred to add the antiscalent such that it will thoroughly mix into the substrate before reaching the point where scaling occurs.
The antiscalent composition may be added in any amount, for instance up to 100 ppm. This dose is based on active sequesterant/polymer content per volume of waste water/substrate to be treated i.e. mg active antiscalent composition per liter of waste water. Generally though effective scale prevention/reduction may be achieved with much smaller doses, for instance 5 to 10 ppm, but may be as low as 2 or 3 ppm. We have found that scale/struvite can be effectively reduced or removed by an initial treatment of the antiscalent composition, for instance in the range 10 to 60 ppm, more preferably in the range 20 to 40 ppm. Following this initial treatment we have surprisingly found that sustained scale/struvite prevention can be achieved using reduced doses of the antiscalent composition, for instance between 5 or 10 ppm lower than the initial dose.
The following examples illustrate the invention.

Abstract: B) A sequesterant compound, selected from the group consisting of phosphonates, phosphates, metaphosphates and orthophosphates including derivatives and salts thereof. Preferred antiscalent compositions include a blend of A) a polymer of acrylic acid and/or maleic acid and B) diethylentriamine penta (methylenephosphonic acid) or salts thereof. The invention is of particular value for the treatment of struvite scale in sewage treatment works.

Ciba Specialty Chemicals Water Treatments Ltd.


A colloid mill utilizes a motor-driven shaft configuration that connects to the rotor of the colloid mill to the electric motor rotor. In this way, the mill rotor shaft is directly driven. Complex gear or belt drive arrangements between a separate electric motor and the fluid processing components of the colloid mill are thus avoided. Moreover, the gap between the mill rotor and mill stator can be adjusted simply by axially translating the motor-driven shaft. Such translation is provided by a timing belt-based arrangement to limit backlash. As a result, a simple hand-operated knob or stepper motor arrangement can be used to control the gap.

Industrial-grade mixing devices are generally divided into classes based upon their ability to mix fluids. Mixing is the process of reducing the size of particles or inhomogeneous species within the fluid. One metric for the degree or thoroughness of mixing is the energy density per unit volume that the mixing device generates to disrupt the fluid particles. The classes are distinguished based on delivered energy densities. There are three classes of industrial mixers having sufficient energy density to consistently produce mixtures or emulsions with particle sizes in the range of 0 to 50 microns.
Homogenization valve systems are typically classified as high energy devices. Fluid to be processed is pumped under very high pressure through a narrow-gap valve into a lower pressure environment. The pressure gradients across the valve and the resulting turbulence and cavitation act to break-up any particles in the fluid. These valve systems are most commonly used in milk homogenization and can yield average particle sizes in the 0-1 micron range.
At the other end of the spectrum are high shear mixer systems, classified as low energy devices. These systems usually have paddles or fluid rotors that turn at high speed in a reservoir of fluid to be processed, which in many of the more common applications is a food product. These systems are usually used when average particle sizes of greater than 20 microns are acceptable in the processed fluid.
Between high shear mixer and homogenization valve systems, in terms of the mixing energy density delivered to the fluid, are colloid mills, which are classified as intermediate energy devices. The typical colloid mill configuration includes a conical or disk rotor that is separated from a complementary, liquid-cooled stator by a closely-controlled rotor-stator gap, which is commonly between 0.001-0.40 inches. As the rotor rotates at high rates, it pumps fluid between the outer surface of the rotor and the inner surface of the stator, and shear forces generated in the gap process the fluid. Many colloid mills with proper adjustment achieve average particle sizes of 1-25 microns in the processed fluid. These capabilities render colloid mills appropriate for a variety of applications including colloid and oil/water-based emulsion processing such as that required for cosmetics, mayonnaise, or silicone/silver amalgam formation, to roofing-tar mixing.
Existing colloid mills have suffered from a number of performance- and ease-of-use-related problems.
One such problem relates mechanical complexity and stability. In the past, colloid mills have had mill housings for the rotor/stator and separate electrical motors with direct drive, reduction gear-, or belt-drive systems connecting the motors to the mill rotors. Elaborate mechanical isolation is required because both the mill rotor and the electric motor have separate bearing systems. Furthermore, the mechanisms used to enable rotor-stator gap adjustment, worm gear arrangement in one commercial device, have been mechanically complex and potentially dynamic during operation primarily due to thermal expansion effects.
In the present invention, these problems are avoided by relying on a motor-driven shaft configuration. That is, the shaft that drives and connects to the rotor of the colloid mill extends to the electric motor stator of the electric motor. In this way, the mill rotor shaft is directly driven.
The benefits resulting from this configuration primarily concern simplicity. Complex gear or belt drive arrangements between a separate electric motor and the fluid processing components of the colloid mill are avoided. Moreover, the gap between the mill rotor and mill stator can be adjusted simply by axially translating the motor-driven shaft. The small movements, of typically less than a 0.1 inches, have no or negligible effect on the electromagnetic field generation in the electric motor. Moreover, in this configuration, only one set of thrust bearings are required, and these are located very close to the rotor, thus minimizing any thermal expansion effects on the mill rotor-stator gap.
In general, according to one aspect, the invention features a colloid mill comprising a mill stator, a mill rotor, an electric motor stator, and a motor-driven shaft. This motor-driven shaft functions as an electric motor rotor that operates in cooperation with the electric motor stator, but also extends from the electric motor stator to the mill rotor, providing a direct drive arrangement.
In specific embodiments, a gap adjustment system is provided that changes a gap between the mill stator and the mill rotor by axially translating the motor-driven shaft relative to the electric motor stator. Further, the electric motor driven shaft is axially supported to counteract forces generated between the mill stator and mill rotor by at least one thrust bearing, preferably an angular contact bearing set, that is located on the side of the electric motor stator proximal to the mill rotor. As a result, mere radial support bearings are needed on the distal side of the electric motor stator relative to the mill rotor.
Another problem that arises in existing colloid mill designs is related to the stability of the mill rotor-stator gap and specifically the system used to adjust the gap. One of the most common configurations utilizes a worm-gear arrangement. This system, however, is hard to calibrate and can jam or freeze in response to the forces generated between the mill rotor and stator.
This problem is solved in the present invention by providing a timing belt-based arrangement for adjusting the gap. Such a timing belt system provides for no backlash. As a result, a simple hand-operated knob or stepper motor arrangement can be used to control the gap.
Specifically, a thrust bearing is supported in a threaded sleeve that mates with the colloidal mill body. The timing belt engages the sleeve to rotate it relative to the body, thus adjusting the thrust bearings axially and thereby controlling the gap between the mill stator and mill rotor.
In general, according to another aspect, the invention features a gap adjustment system for a colloid mill. The system comprises at least one thrust bearing that supports a shaft carrying a mill rotor in proximity to a mill stator. A threaded sleeve in turn carries the thrust bearing, its threads mating with complimentary threads of a body of the colloid mill. A timing belt, which is supported by the colloid mill body, engages the threaded sleeve to enable rotation relative to the body to thereby translate the thrust bearings, yielding axial movement of the shaft. This changes the gap between the mill stator and mill rotor.
In specific embodiments, a knob is used to manually adjust the timing belt.
In other embodiments, an adjustment motor, such as a stepper motor is used to adjust the timing belt under microprocessor control.
Another problem that arises in existing mills concerns what happens when a customer requires a new colloid mill for a given manufacturing process to handle higher fluid processing rates. In the past, manufacturers have offered larger and smaller-sized colloid mills to meet customer demand. The problem, however, has been that typically when moving to colloid mills of a higher throughput the manufactures have simply offered larger versions of a geometrically similar mill rotor-stator configuration. Put another way, a colloid mill with a higher throughput had a rotor and stator that looked like the colloid mill with a lower throughput but were simply larger. This technique for modifying colloid mill rotor/mill stator configurations to handle higher fluid volumes yields different processing effects on those fluids. The larger colloid mills tended to process the fluid at different energy densities, typically higher than the smaller colloid mills. This was a problem to the customer since it required recalibration of the processing parameters of the fluid in order to maintain a consistent product.
The present invention uses the recognition that the energy density delivered to the fluid or the characteristics that provide a uniform particle size at the output is related to the third power of the rotor speed and the second power of the rotor diameter. As a result, when scaling mill rotor/mill stator configurations to higher fluid throughput and consequently larger rotors, it is necessary to decrease the rotor speed. In order that the fluid has a consistent residence time and velocity gradient in the mill rotor-stator gap, the surface angle or rotor pitch, however, is increased with increases in the size of the rotor to counteract the effects of the slower rotor speeds. This provides kinematic similarity, or similar changes in velocity as the product traverses the mill rotor-stator gap of different sizes of the colloid mill.
In general, according to another aspect, the invention features a family of colloid mills in which the rotor surface pitch angles increase with increases in colloid mill throughputs. Said another way, the mill rotor surface angles and rotor surface lengths are controlled between colloid mills having different throughput in order to standardize the energy input into the processed fluids.
Another problem with existing mills has been colloid mill rotor configurations. Some mills have long slots that extend down the entire face of the mill rotor, whereas other configurations utilize relatively smooth conical- or disk-shaped rotor configurations. Each configuration has its relative advantages and disadvantages. The smooth rotor configuration tends to generate high and consistent shear forces in the processed fluid. The configuration with the long axially and radially running slots provides high fluid throughput rates, while establishing good turbulence.
The present invention utilizes a largely smooth rotor configuration in order to generate uniformly high shear forces, and thus consistency with correspondingly low variance in the particle size in the processed fluid. The inventive rotor, however, adds an annular region extending around the circumference of the rotor that provides an increased mill rotor/mill stator gap between upstream and downstream, relatively smooth, processing surfaces. This region of increased gap is designed to establish a cavitation field to compliment the largely shear-based fluid processing performed by the adjacent smooth rotor surfaces.
In general, according to another aspect, the invention features a colloid mill rotor that comprises a primary processing surface extending annularly around the rotor, and a secondary processing surface, also extending annularly around the rotor downstream of the primary processing surface. An intermediate, annular processing surface is located axially between the primary and secondary processing surfaces and is depressed relative to those surfaces. During operation, the relative operation of the primary and secondary processing surfaces establishes a low pressure region in the enlarged gap created by the intermediate processing surface. This establishes in many cases a cavitation field that compliments the shear processing of the fluid.
In specific embodiments, radially and axially extending slots are provided in the primary processing surface to facilitate the movement of the processed fluid through the gap. These slots in the primary processing surface cooperate with slots in the associated mill stator to facilitate pre-maceration of the fluid.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.


Methods and apparatus are provided for selecting advertisements and other information from a computer network database based on user defined preferences and transmitting the selected advertisement in background mode over a communications link between the computer network and a local computer with minimal interference with other processes communicating over the communications link. This method includes monitoring the communications link and transmitting portions of the advertisement when the communications link line utilization is below a preestablished threshold. Methods and apparatus are also provided for displaying or otherwise presenting the selected advertisements on the user""s computer. Additional methods and apparatus are provided for selecting and presenting information stored on a local storage media based on user defined preferences.

This invention relates generally to advertisement computer display systems and more particularly to a method and system for displaying advertisements and other information on a computer based on general user selected criteria and transmitting such information from a remote network to the local computer.
There are two major forms of advertising which are currently being employed on the Internet and commercial on-line services. One form is the use of a small advertisement on WEB pages which are commonly accessed. For example, a portion of the screen display for WEB pages used to access Internet searches may include a corporate logo or other advertisement material. Typical of this style of advertising is the Netscape(trademark) Internet Browser software available from Netscape Communications Corporation of Mountain View Calif., which presents a box containing logos for various corporations on the computer display when the user performs a search. This form of advertising, however, is not very sophisticated and does not encourage user interaction.
Another form of advertising on the Internet is the creation of WEB xe2x80x9cpagesxe2x80x9d or sites by advertisers. One variant of the use of a WEB page displays advertisements in a portion of the viewing area. A second variant, often used by corporate or other advertisers, is the use of WEB sites which employ attractive graphics in the hope of having the user interact with various advertising schemes. In addition, product ordering is usually available from these WEB sites. In most cases, users access these WEB sites by one of the following methods: knowing the Internet address; keyword searching; linking from a different WEB site; through an electronic shopping mall type site; through other advertisements on the Internet; or through the use of programs known as search browsers.
Current advertisers have attempted to improve the attractiveness of these WEB pages by including the use of sound, animated or rotating logos or pictures, and scrolling information. One system, Hot Java, available from Starwave Corp of Bellevue, Wash., supports the execution of small applications programs written in a specific programming language executing within the browser on the local computer. This allows the WEB pages to provide richer content, such as animation or scrolling sports scores across a user""s computer display, and better interaction with users. These effects, however, are only available while the user is viewing the specific WEB page incorporating the Hot Java technology.
Despite the fast and furious growth in this advertising sector, WEB sites are still regarded as xe2x80x9cpassivexe2x80x9d advertising used predominantly for a corporate image rather than for selling products. Specifically the following drawbacks describe the current state of advertising on the Internet: transmitting the advertising information consumes a large amount of the bandwidth of the communications link between the user""s computer and the network; access is initiated by the user rather than the advertiser; the user rather than the advertiser pays for access; accessing a site is a time consuming xe2x80x9chit or missxe2x80x9d process; and the process may improve the corporate image but creates little product demand.
U.S. Pat. No. 5,105,184 to Pirani et al. (xe2x80x9cPiranixe2x80x9d) discloses a system integrating commercial advertisements with computer software. The system discloses integrating commercial advertisements with different types of screens. Pirani, however, does not provide for any user input at the local computer as to the types of advertisements which are to be displayed. Thus, users would be forced to view numerous advertisements of which they are likely to have no interest. This will attenuate the users attention to the advertisements and decrease their effectiveness.
As noted above, a significant problem with current methods for advertising on computer networks is the consumption of significant portions of the bandwidth of the communications link between the user""s computer and the computer network. Prior systems have attempted to utilize essentially unused time in telephone networks to deliver advertising or other information. U.S. Pat. No. 5,321,740 to Gregorek, et al. (xe2x80x9cGregorekxe2x80x9d) discloses a marketing system over an existing telephone network which modifies a portion of the call processing system to play an informational announcement in place of the usual ringback or busy signals. Gregorek differs from the present invention in a number of ways, including the fact that it does not provide any means for interacting with computers over a computer network. Also, Gregorek delivers the informational announcement only during a short splice of time when the user is waiting for callback information.
Current file transfer protocols, such as the File Transfer Protocol (xe2x80x9cFTPxe2x80x9d) and the Trivial File Transfer Protocol (xe2x80x9cTFTPxe2x80x9d), for transferring files from a remote network, such as the Internet, via a communications link to a local computer are designed to transfer files as quickly as possible. Each computer process executing such a protocol attempts to make maximum use of the available communication resources. This leads to interference and an inevitable slowing down of other computer processes attempting to communicate over the communications link. There exists a need, therefore, for a file transfer process which is designed to behave as a background task and have a minimal impact on foreground communications.
There also exists a need to utilize the computer to display locally stored advertisements. Several software products provide xe2x80x9cyellow pagesxe2x80x9d on CD-ROMs or other media such as floppy disks. The user may use these yellow pages to search for products or advertisers by name or description. This system of advertising is limited, however, in that it requires the user to actively search for advertisers or products and therefore do not spontaneously display products to the user.
Microsoft Windows interface provides a rudimentary form of spontaneous advertising by incorporating a Microsoft Windows logo as an option in its screen saver utility. This system, however, offers only a single advertisement in response to a user""s response and therefore does not offer a variety of periodically changed advertisement content based on a user""s interests.
The object of the present invention is to provide a process for transmitting an information file between a local computer and a remote computer network over a communications link with minimal interference to other processes executing on the computer which are also transmitting over the communications link.
It is a further object of the present invention to provide a method and system of presenting individualized advertisements and other informational messages on a computer by allowing a user to select from a variety of advertisement or informational categories.
It is a further object of the present invention to provide a method and system of downloading and presenting individualized advertisements and other informational messages from a network to a local computer from a remote network to a local computer based on a user""s selection of advertisement or informational categories.
It is a further object of the present invention to provide such a method and system of downloading and presenting individualized advertisements and other informational messages from a network to a local computer with minimal interference with other data being transmitted between the network and the local computer.
In one variant of the present invention, all advertisements or other informational messages originate on a network server which is accessed via the Internet or alternate on-line method. Select advertisements are transparently downloaded from the network server and stored locally on the user""s local computer using a novel type of software referred to herein as a xe2x80x9cPolite Agent.xe2x80x9d In a second variation, the entire advertisement database is locally stored on the local computer or a removable media such as CD-ROM. Manipulation and display of the advertising message is performed by software residing on the user""s PC in accordance with preconfigured user preference information.
The advertisement is preferably displayed during idle time as a screen saver utility when the computer is not receiving keyboard input or updating the user""s display. Other techniques for displaying the advertisement, such as periodic audio-only messages, screen background wallpaper, cursor modifications, and display in a window on the user""s computer display are also available.
Users may enter their preferences by directly choosing categories of advertising or other informational content which most interest them or through interactive games and quizzes. Users may directly respond to advertising messages by participating in contests, requesting further product information, or ordering the advertised product. The advertisements are made attractive to the user by employing a variety of video, animation, sound or any other multimedia effects. Content may be based on an interactive theme such as a contest or special discount offers for on-line customers.
The system monitors the user""s interaction with the advertisements and produces raw data on how many times a particular advertisement was accessed as well as the user""s response to advertisements. All pertinent information is stored and sent back to a network server where it is made available to the advertisers. User requests for additional information may be directed to the advertiser itself or to the advertiser""s WEB site on the network.
The system further comprises the use of a background software process, the Polite Agent, for transferring information between the network and the local computer. The Polite Agent monitors the communications link between the network and the local computer and transfers small portions of the information when the communications link utilization rate is low. In this manner the Polite Agent avoids significant interference with other communications applications transmitting over the communications link. The Polite Agent may also be utilized to transmit other types of information content, such as news, weather, stock quotes, sports scores, software updates or trip reservation information.

Method and apparatus for transmitting and displaying information between a remote network and a local computer