Composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide in which particles of the latter and other particulate pigmentary, subpigmentary and nonpigmentary components are cemented intrinsically with the aid of in-situ synthesized complex microgels.

1. Field of the Invention
This invention relates to novel composite pigment products comprising from 4.5% up to 50%, by weight, of particulate titanium dioxide.
More specifically, this invention relates to composite pigment products in which particles of titanium dioxide and other pigmentary and subpigmentary components, as well as disperse and soluble nonpigmentary components, are coflocculated and cemented intrinsically with the aid of in-situ synthesized complex (multicomponent) functional microgels.
2. Discussion of the Relevant Art
White pigments encompass a class of particulate materials which are essentially colorless, insoluble, nontoxic, reasonably nonabrasive, and have dimensions favoring a diffuse reflection, or scattering, of light constituting the visible portion of the electromagnetic spectrum with wavelengths ranging from 420 nm for violet to 660 nm for red.
In accordance with the laws of physical optics, maximum scattering of light occurs when a propagating light wave encounters in its path an obstacle, a pigment particle as the case in point, whose dimensions are equal to one-half of the length of the impinging wave. At equal particle dimensions, pigmentary materials with higher refractive indexes, whose values may range from 1.41 for silica to 2.73 for rutile, scatter the light more efficiently than analogous materials with lower refractive indexes.
The most elementary physical model of light scattering may be considered one in which monochromatic light is diffracted by a single spherical particle. Maximum diffraction of the blue, green and red portions of the light spectrum (additive primary components of light) is obtained with particle diameters of about 150 nm, 200 nm and 250 nm, respectively. By integrating the comprehensive spectral response of a single spherical particle scattering polychromatic light, mapped as a function of particle diameter, one can calculate that the maximum light scattering occurs with a particle of about 200 nm in diameter.
A universally useful model of light scattering by pigments must, however, be applicable both to any arbitrary pigment shape (virtually all inorganic pigments, other than TiO.sub.2, are nonspherical) as well as to integral end-use formations containing these pigments, such as paper-coating and paint films, filled paper or pigmented plastics. Let us consider, for example, a single, highly anisometric particle of kaolin clay in the form of a hexagonal platelet. The light waves of different lengths impinging upon such a multifaceted platelet scatter with different intensities depending on how closely the dimensions of a particular facet of a clay platelet approximate one-half of the length of the impinging light wave. Among the multitude of facets by which the impinging light may be scattered are, for example, platelet faces (in the x,y plane) or edges and protrusions from platelet's surfaces (in z direction). Moreover, the impinging light waves are scattered independently by each of the six triangular tips of the hexagonal platelet, the shorter waves being scattered more efficiently closer to the tips, across shorter distances, and, correspondingly, the longer waves being scattered more efficiently farther from the tips, across longer distances.
The ability to scatter light is a universal property both of particulate and extensive matter. Hence, even an "infinitely" large, most precisely polished mirror also scatters light, though only to a very negligible extent. In general, all light waves, regardless of length, will scatter with different intensities across all physical obstacles encountered in their path, such as individual particles or parts of aggregated matter, grain boundaries, or sites of localized stress concentrations giving rise to elastooptical effects.
As far as white pigments are concerned, it should be emphasized that the latter represent a pragmatic class of particulate materials, useful in the trade, whose features are defined by a convention. In the very minimum, pigments must consist to a predominant extent of particles whose dimensions uniquely favor the scattering of light, not so much with regard to the performance of individual particles but primarily with regard to the performance of the resultant end-use formations containing these particles. The latter requirement necessitates that pigments additionally possess certain specific features and performance properties, though the scope of the latter is not fixed but expands steadily in keeping pace with the scientific and technological advancements in the field of pigments.
Whether a solid particle can be classified as pigmentary depends not only upon raw physical dimensions but also upon the particle's morphology. Hence, monolithic, spherical, virtually perfectly isometric, single-faceted particles of TiO.sub.2, or organic pigments, cease to be pigmentary for all practical purposes when their particle diameters exceed about 1 .mu.m. Overall, a spherical shape for mineral pigment particles is disadvantageous in many respects. Spheres, being perfectly isometric, single-faceted geometric bodies, scatter the light more selectively, hence, less efficiently, than analogous anisometric particles of an equivalent mass. Moreover, spheres have an inherent tendency to form dense, closely packed structures with a low void volume, characterized by a low light-scattering efficacy. Closely packed ensembles of monodisperse populations of spheres have a maximum void volume of only about 26%, which, for polydisperse populations of spheres, can fall below 15%, or even 10%.
The formation of closely packed ensembles of pigment particles, the closest such packing occurring with spherical ones, is unavoidable in paper coating and filling or in paints, causing many potential light-scattering sites to become inaccessible to the impinging light waves. Hence, the magnitude of integral light scattering of a formation of closely packed spherical particles is invariably much less than the sum of potential light-scattering effects attainable with the individual component particles scattering the light as discrete spheres.
Multi-faceted pigment particles, such asintrinsically aggregated clusters of elementary, ultrafine (sub-pigmentary) particles of precipitated silica or metal silicates, on the other hand, can be as large as 10 .mu.m, or even 20 .mu.m, e.s.d. (equivalent spherical diameter) and still be pigment worthy. Regardless of morphological features, however, all particulate materials with dimensions finer than 0.1 .mu.m e.s.d. are not pigment worthy, being classified as "subpigmentary." It should be pointed out, though, that inherently fine-particle-size pigment products, such as titanium dioxide or high-glossing kaolin clay, may contain a substantial proportion of subpigmentary particles.
White pigments traditionally have been divided in the art into "primary," with a refractive index of about 2.0 or higher, and "secondary," with a refractive index ranging from about 1.4 to 1.65. Following the example of lithopone, introduced on the market around 1875, interspacing of particles of high-refractive-index primary pigments with particles of low-refractive-index secondary ones has become a standing practice in the paint and paper industries. As the first composite pigment ever, obtained by coprecipitating birefringent zinc sulfide (refractive indices 2.356 and 2.378), used in proportions of from 30 to 60%, by weight, with barium sulfate (refractive index 1.64), lithopone represents a classical example of a virtually perfect interspacing of a primary pigment with a secondary one. As titanium dioxide (TiO.sub.2) was introduced on the market in 1919, quickly becoming the dominant high-refractive-index white pigment on the market, it became instantly clear that the most economical performance is obtained when TiO.sub.2 is used in blends with less expensive, low-refractive-index co-pigments (extenders). It was also recognized, however, that a great deal of detrimental selective fractionation and flocculation occurs in practical applications involving the use of such loose pigment blends. Hence, various composite pigments were developed in which the primary pigments, such as titanium dioxide or zinc sulfide (ZnS), were first intimately blended with, and subsequently affixed to, secondary pigments (extenders), to achieve a permanent immobilization of both particulate species relative to each other.
The initial main approaches used in the prior art to manufacture composite pigments containing particulate titanium dioxide involved either a precipitation of the latter in a slurry of a secondary pigment (barium sulfate or calcium sulfate), or a simultaneous coprecipitation of both the titanium dioxide and secondary pigment, followed by dewatering, calcining and pulverization. The above TiO.sub.2 -based composite pigments, whose manufacture was based in part on a simulation of the lithopone process, were called "coalesced" composite pigments. The intrinsic cementation of TiO.sub.2 /extender aggregates, ensuring their mechanical integrity, was obtained by thermal sintering.
The subsequent approaches toward synthesizing analogous composite pigments were based on various methods of treatment of aqueous slurries of extraneously prepared primary and secondary pigments to obtain maximum mutual interspacing and a permanent immobilization of the primary and secondary particulate species relative to each other. Accordingly, the in-situ coprecipitated, TiO.sub.2 -based composite pigments of the prior art can be classified as "intrinsic" composite pigments, to distingush them from the "derivative" ones, synthesized from extraneous pigmentary components.
It should not be overlooked, however, that the secondary pigments (extenders, co-pigments) used along with titanium dioxide are, as a rule, highly polydisperse systems characterized by a wide spread of particle dimensions. Hence, while the use of co-pigments is, overall, beneficial to the resultant optical-performance efficacy of titanium dioxide, the oversized particles in co-pigments have a well-documented adverse effect upon the flocculation characteristic of the relatively small TiO.sub.2 particles, this adverse effect being particularly strongly pronounced in dilute and non-optimally dispersed slurries.
The effect of larger particles on the flocculation tendency of smaller particles was first described by V. D. Samygin et al. in the article titled "Mechanism of Mutual Flocculation of Particles Differing in Size" (translated from Kolloidnyi Zhurnal, Vol. 30, No. 4, pp. 581-586, July-August, 1968), dealing with the flocculation phenomena in flotation processes. According to the above article, the rate of adhesion of fine particles to coarser ones may be higher by a factor of 10.sup.3 -10.sup.4 than the rate of cohesion between finer particles. Applicant's subsequent experimental work showed that the above phenomenon is rather universal and is encountered in both dry and wet disperse systems. For example, coarser and more abrasive particle aggregates were obtained by calcining (thermal sintering) of high-glossing clay feeds with particle dimensions ranging from 0.1 to 2.0 .mu.m e.s.d. than by calcining of analogous feeds from which essentially all particles larger than about 1.5 .mu.m e.s.d. were removed by centrifugal separation.
The first of the above-mentioned novel approaches to the manufacture of derivative composite pigments, based on flocculation (coflocculation) of pigmentary components suspended in aqueous media, was disclosed by Alessandroni in U.S. Pat. Nos. 2,176,875, 2,176,876 and U.S. Pat. No. 2,176,877. In one case, for example, the coflocculation was carried out by adding an extraneous flocculant to an aqueous slurry containing both the primary, high-refractive-index pigment (titanium dioxide or zinc sulfide) and the secondary, low-refractive-index extender pigment. In another case, the coflocculation of pigmentary components was attained when a separately prepared aqueous slurry of titanium dioxide, or zinc sulfide, dispersed with one type of dispersant, was blended with a separately prepared slurry of an extender pigment dispersed with another type of dispersant "antipathetic" to the former one. In both of the above cases, the flocculated media were filtered, dewatered, dried and pulverized without the calcining step being employed.
Based on the present colloid-chemical experience and in view of the preceding discussion of the article by Samygin, however, it is clear that a high degree of detrimental separation and selective aggregation of the particulates, according to both species and size, could not have been avoided with the slow and inefficient flocculation mechanisms employed by Alessandroni. Moreover, the approaches used by Alessandroni are lacking a viable adhesion mechanism capable of imparting an adequate mechanical integrity to the resultant composite pigments.
Another approach toward the synthesis of white and colored derivative composite pigments was disclosed in U.S. Pat. No. 3,453,131 to Fadner. According to the latter, single and/or multiple species of functional colloidal particles of ". . . carbon black, acetylene black, iron oxide, Mannox blue, azobisisobutyronitrile, zinc oxide, methyl zimate, sulfur, titanium dioxide, polystyrene, or antimony oxide or mixtures thereof" with diameters ranging from 0.01 .mu.m to 1.0 .mu.m were attached by means of a "coupling agent" to platy clay particles, ranging from 0.5 .mu.m to 3.0 .infin.m in diameter, used as a carrier medium.
The above composite pigments were synthesized by adding 0.5% to 25%, by weight, of an aliphatic acid (coupling agent) into an aqueous slurry of pigmentary components and ". . . mixing the composite suspension for a sufficient time to form the composite colloidal particles." The resultant "composite particle suspensions" were considered as the final products intended for use in various commercial formulations in which the individual component materials have traditionally been employed in a loose (nonaggregated) state.
U.S. Pat. No. 3,453,131 to Fadner also teaches that, "Alternately, the composite particles can be separated from the aqueous medium, for instance, by freeze-drying or by spray-drying, and utilized subsequently in formulating aqueous, non-aqueous or non-liquid composition."
Unlike Alessandroni, who relied on a direct flocculation of composite slurries, Fadner employs compounding of the particulates present in composite (multicomponent) slurries with the above-mentioned coupling agents. As far as the mechanism of this compounding, or the action of the coupling agent, is concerned, Fadner explicitly states that "The scientific factors governing the formation of composite particles according to this invention are not completely understood." Moreover, Fadner does not provide any information with regard to the mechanical integrity of the dried composite particles, but an analysis of the functional aspects of the composite pigment systems in question clearly points to the lack of any practically significant adhesion mechanism capable of providing such an integrity.
Another approach to synthesizing composite pigments from blends of TiO.sub.2 and a coarse calcined clay, or a coarse delaminated clay, was disclosed in U.S. Pat. No. 3,726,700 to Wildt. It should be pointed out that although a flocculation of the particulates present in the reaction medium is unavoidable under the reaction conditions described in the above-mentioned patent, an intentional flocculation was not specified as an element of the strategy of the approach elected by Wildt. Instead, Wildt's approach was based on compounding the pigmentary raw materials present in the furnish with in-situ formed alumino-silicate or similar gels, of the type used routinely in the TiO.sub.2 industry for the application of surface coatings to TiO.sub.2 particles.
The mechanical integrity of Wildt's composite pigments was provided by thermally curing the in-situ-formed gels, called in the above patent ". . . hydrous oxide of aluminum, silicon, titanium, and mixtures thereof."
In analyzing the colloidal and kinetic aspects of Wildt's process, it is readily understood by those skilled in the art that a detrimental fractionation and selective flocculation of the pigmentary components employed, both according to species and size, are impossible to avoid in the lengthy synthesis process in which just a single step of digestion takes from 30 to 60 minutes. Furthermore, the above fractionation and selective flocculation were undoubtedly facilitated even more through the use of the dispersion-destabilizing alum. Although a permanent immobilization of TiO.sub.2 particles relative to the extender particles was indeed attained in Wildt's composite pigments, there is also virtually no doubt that the latter immobilization was realized through the attachment of "blobs" of badly flocculated TiO.sub.2 particles to the coarse extender (carrier) particles.
Perhaps the most fundamental point to be raised with regard to Wildt's composite pigments is that, in accordance with the relative proportions of TiO.sub.2 and coarse-particle-size extenders employed, the number of available extender particles was far too low to approach even remotely an effective interspacing of TiO.sub.2 particles present in the system, the oversized dimensions of the extender particles notwithstanding.
Since Wildt does not provide any numerical light-scattering data for the composite pigments in question, e.g., in a head-to-head comparison with rutile pigment used as the raw material for their synthesis, no unambiguous conclusion can be reached as to the true source of the claimed improvement of the hiding efficacy of paint systems formulated with the aid of the composite pigments in question. As is well known to those skilled in the art, however, an increased hiding efficacy of TiO.sub.2 -based paints can also be obtained by a simple addition of extraneous loose particles of high-oil-absorption silicates, of the same type as were synthesized in situ in Wildt's composite pigment.
In summary, the principal goal of keeping TiO.sub.2 particles apart by interspacing them with particles of secondary pigments (extenders) and immobilizing both species relative to each other was approached in the prior art by synthesizing both intrinsic as well as derivative TiO.sub.2 -based composite pigments, further referred to also as "extended-TiO.sub.2 " composite pigments, with the aid of three fundamentally different approaches presented schematically in the following:
(1) In-situ coprecipitation of both titanium dioxide as well as extender particles in an aqueous medium, or precipitation of titanium dioxide particles in aqueous slurries of extraneous extender particles, the choice of extenders being limited in practice, in both of the above cases, to essentially only barium sulfate or calcium sulfate. PA1 (2) Coflocculation of extraneously prepared titanium dioxide and extender pigments present in composite (multicomponent) aqueous slurries, using either extraneous flocculants or an in-situ interaction between two antagonistic (incompatible) dispersing agents in accordance with U.S. Pat. Nos. 2,176,875, 2,176,876 and 2,176,877 to Alessandroni. PA1 (3) Compounding composite aqueous slurries of extraneously prepared titanium dioxide and extender pigments with coupling agents (aliphatic acids), in accordance with U.S. Pat. No. 3,453,131 to Fadner, or with (in-situ-formed) gel-like precipitates of hydrous oxides of silicon, aluminum and titanium, in accordance with U.S. Pat. No. 3,726,700 to Wildt. PA1 (a) A maximum homooenization of the composite, well-dispersed pigment furnishes by inducing a statistically uniform spatial distribution of all particulates present in the aqueous reaction medium with the aid of suitable (high-performance) dispersants and intensive agitation regimes. PA1 (b) Instantaneous immobilization ("freezing") of the dynamically induced and maintained, statistically uniform spatial distribution of all particulates present in the furnish to permanently preserve an equivalent statistically uniform distribution of these particulates in the resultant composite pigments. PA1 (c) Intrinsic cementation of the resultant composite-pigment aggregates to impart adequate mechanical integrity to the composite pigment products, enabling them to withstand the shearing regimes to which they are routinely exposed in handling and end-use applications. PA1 (a) from 0.5% to 95%, by weight, of at least one mineral particulate subpigmentary material; PA1 (b) from 0.5% to 25%, by weight, of at least one high-oil-absorption particulate material with a specific surface area larger than 100 m.sup.2 /g; PA1 (c) from 0.25% to 20%, by weight, of at least one organic, particulate non-film-forming material; PA1 (d) from 0.25% to 5%, by weight, of at least one disperse and/or soluble organic polymer adhesive; PA1 (e) from 0.001% to 0.5%, by weight, of at least one organic, cationically active compound with at least two reactive groups in each molecule; PA1 (f) from 0.005% to 5%, by weight, of at least one color dye; PA1 (g) from 0.005% to 0.2%, by weight, of carbon black; and PA1 (h) from 0.1% to 2%, by weight, of synthetic and/or cellulosic microfibrils .
Regardless of the type of the approach employed, the three key processing elements which are indispensable to a successful synthesis of derivative composite pigments of an extended-TiO.sub.2 type are as follows:
As is readily understood by those skilled in the art, the in-situ coprecipitated, coalesced intrinsic composite pigments (TiO.sub.2 /BaSO.sub.4 and TiO.sub.2 /CaSO.sub.4) of the prior art conform to all of the above-listed requirements. For example, the requirements specified under (a) and (b) were satisfied by virtue of the intrinsic coprecipitation, providing a perfect homogenization and mutual interspacing of the primary and secondary particulate species. The requirement specified under (c), on the other hand, was satisfied by sintering the intrinsically interspaced particulate species.
Although the coalesced, extended-TiO.sub.2 composite pigments were manufactured for many years (until about 1970), their commercial demise was brought about by the inherently limited selection of viable extenders, narrowed down essentially to the unattractive barium sulfate and calcium sulfate.
Neither of the above-mentioned approaches satisfies the requirements (a) or (b) when applied to the synthesis of derivative TiO.sub.2 -based composite pigments of the prior art, as will become clear from the considerations to follow, and only Wildt's approach provides an adequate mechanical integrity to the resultant composite pigment products in accordance with the requirement (c).
First of all, a truly optimized pigment dispersion, such as is indispensable for a successful manufacture of derivative composite pigments in accordance with the requirement (a), mentioned above, can only be attained with a single monodisperse particulate species. In a slurry of a polydisperse pigment, for example, one can distinguish three distinct classes of particulates, namely, pigment fines, with particles smaller than 0.15-0.2 .mu.m e.s.d.; intermediate fractions, with particles ranging from about 0.2 .mu.m to about 0.5-0.7 .mu.m e.s.d.; and "coarse" fractions, with particles larger than 0.7-1 .mu.m e.s.d., differing significantly with regard to their behavior in aqueous media. Hence, while commercial slurries of polydisperse pigments of the above type are often referred to in the art as being "optimally" dispersed, in reality, each individual particle-size fraction is characterized by a different dispersion stability and, conversely, different resistance to flocculation.
The overall picture becomes yet more complicated with pigment slurries that are both polydisperse and heterodisperse (consisting of two or more different pigment species), such as are used for the synthesis of derivative composite pigments. It is thus impossible, for all practical purposes, to obtain an optimized dispersion of polydisperse composite slurries, in that each of the above-mentioned fractions and species has a different optimum dispersant demand, both quantitatively and qualitatively, and a different equilibrium between the dispersant adsorbed on the pigment and dissolved in the carrier medium (water). Hence, even if "optimally" dispersed slurries of individual pigments were prepared separately and then blended, a progressive destabilization of the disperse state would immediately set in. As a consequence, the polydisperse and heterodisperse phases present in the system (pigment furnish) would commence to separate (fractionate) and selectively flocculate according to species and size, starting with the relatively least stable disperse fraction and progressing toward the relatively more stable ones.
Ironically, the better the initial dispersion of a composite pigment slurry, the more pronounced are the phenomena of fractionation and selective flocculation when the slow and inefficient flocculation processes of the prior art are employed in making composite pigments.
It is thus obvious that an instantaneous immobilization of all particulate components of both heterodisperse and polydisperse pigment furnishes is indispensable for synthesizing TiO.sub.2 -based composite pigments in which the individual particles of TiO.sub.2 are either intimately interspaced with extender particles, if the latter are present in sufficient numbers and have proper dimensions, or are at least distributed in a statistically uniform fashion within the flocculated composite pigment furnish and the resultant pigment aggregates. It is also obvious, however, that the abovementioned instantaneous immobilization can only be achieved with the aid of a truly instantaneous, indiscriminate and complete flocculation mechanism.
A flocculation mechanism having the latter attributes was unknown in the prior, art, however, before it was disclosed in U.S. Pat. No. 5,116,418 to Kaliski ("Process for Making Structural Aggregate Pigments," and the co-pending patent application Ser. No. 07/919,831 ("Functional Complex Microgels with Rapid Formation Kinetics"), Filed Jul. 27, 1992, both above applications being incorporated herein by reference. According to the above disclosures, composite pigments characterized by a statistically uniform distribution of all particulate components can be synthesized only with the aid of both well-dispersed pigment furnishes and an instantaneous, indiscriminate and complete flocculation process.
It is worth pointing out, though, that while an optimized pigment dispersion, attainable only with the use of highly efficient modern dispersants, is necessary for a successful synthesis of derivative composite pigments, the weak and slow flocculating processes of the prior art are incapable of effectively overriding the powerful action of the latter dispersants. It is not at all surprising, therefore, that Alessandroni makes no references with regard to any dispersion optimization of the composite raw material slurries to be flocculated, the dispersants listed being very inefficient or outright mediocre. Fadner, on the other hand, explicitly concedes in U.S. Pat. No. 3,453,131 (col. 5, lines 1-5): "The dispersant for the functional colloidal particles should be present in minimal amounts and should not be of a type that is so strongly adsorbed to the functional particles that it cannot be replaced by, or its function overcome by, the organic acid coupling agent."
The process for synthesizing TiO.sub.2 -containing composite pigments according to U.S. Pat. No. 3,726,700 to Wildt does not make any use of dispersants, as is clear from the following description:
"1. Titanium dioxide cooler discharge and the selected clay in the desired proportions are slurried in water (the term "slurrying in water" implies in the trade that no dispersants are being used - applicant) at 100-300 g/l of total solids.
2. While vigorously agitating the slurry, a solution of sodium silicate (400 g/l SiO.sub.2) is added to the slurry in an amount necessary to give the desired weight percent of SiO.sub.2, based on total pigment solids.
3. A solution of aluminum sulfate (100 g/l Al.sub.2 O.sub.3)) is added in sufficient quantity to give the desired proportion of Al.sub.2 O.sub.3.
4. The slurry is, optionally, then heated to 50.degree.-70.degree. C.
5. Since the pH is usually less than 5 at this point, sodium hydroxide is added to the agitated slurry until the pH reaches 7.8-8.3.
6. After a digestion for 30-60 minutes, with occasional additions for pH adjustments, the slurry is filtered, washed, dried and fluid energy milled."
As is well known to those skilled in the art, it is impossible to obtain a satisfactory deaggregation, let alone dispersion, of the composite pigment furnish in the above step (1) by simply slurrying the pigmentary components in water at 10-30% solids. As a matter of fact, a satisfactory deaggregation and dispersion of a pigment, or blend of pigments, cannot be attained in a diluted slurry even with the aid of the best dispersants available.
Although sodium silicate used in step (2) has some moderate dispersing action when used in concentrated pigment slurries at very low dosages (a few tenths of one percent on the weight of pigment), it acts as a flocculant, specifically, micro-flocculant, at the high proportions specified in Wildt's patent. The above flocculating action is still further compounded by the addition of aluminum sulfate in step (3), the optional heating in step (4), and the lengthy digestion of 30-60 minutes in step (6).
It is thus obvious that the principal goal of the above-discussed synthesis procedure, clearly defined by the following quotation from U.S. Pat. No. 3,726,700 to Wildt (col. 2, ln. 5-9), has not been attained: "It would be advantageous, therefore, if the titanium dioxide could be affixed to the inexpensive extender in such a manner that the optimum spacing could be maintained throughout the various processes of paint preparation, pigment dispersion and drying."
Wildt also states (col. 2, lines 13-19) that "A process for affixing pigment particles of colloidal size to particles of a non-swelling clay by coupling with organic acids is described in Fadner U.S. Pat. No. 3,453,131 but there is no suggestion that in using TiO.sub.2 as the pigment it is possible to achieve a composite pigment of outstanding superiority in terms of light scattering efficiency."
While the above statement regarding the context of Fadner's disclosure is basically correct, Wildt himself has not offered any direct evidence that his composite pigments do indeed provide such a superior light-scattering efficiency. As previously indicated, the increased hiding in paints, claimed by Wildt, can also be obtained by indirect means without increasing the intrinsic light-scattering efficacy of the composite pigment itself. As a matter of fact, neither Wildt, nor Fadner, nor Alessandroni have offered any objective evidence that the immobilized TiO.sub.2 particles in the composite pigments in question have indeed acquired steric configurations favoring increased light scattering, even though such an evidence can be secured readily in terms of light-scattering data or electronphotomicrographs.
In an analogy to the path of reasoning pursued by Fadner, Wildt postulates as follows: "That the product thus obtained consists of particles of TiO.sub.2 which are dispersed on, and adhered to, the larger clay particles is shown by the lack of selective sedimentation when dispersed in water, the unchanged composition after fluid energy milling, and the markedly improved hiding power conferred to latex paints when compared to a mechanical mixture of equivalent TiO.sub.2 -clay composition."
As is readily understood by those skilled in the art, however, the above "proofs" constitute conditions which are merely necessary, but not sufficient, to reach the above conclusion in that (a) the thermally cured alumino-silicate cement formed in situ in Wildt's process is sufficiently strong to permanently affix TiO.sub.2 and extender particles (regardless of whether their steric configurations are overall favorable or not), to prevent any subsequent separation in handling and end-use applications; and (b) a permanent, durable, cementation of the individual particulate ingredients of composite pigments does not prove that affixing TiO.sub.2 particles ". . . to the inexpensive extender in such a manner that the optimum spacing could be maintained throughout the various processes . . . ," postulated in the patent in question, has been even remotely approached.
The issue of extending TiO.sub.2 pigments, treated extensively in the literature in the last several decades, has been most fittingly summarized by J. H. Brown in the article titled "Crowding and Spacing of Titanium Dioxide Pigments," issued in the Journal of Coating Technology, Vol. 60, No. 758, Pages 67-71March 1988, dealing with hiding properties of nonporous paints. In the above article Brown dismisses the usefulness of particulate extenders, opting, instead, for coatings deposited on the surface of TiO.sub.2 particles. Brown finally concludes that, under the best of circumstances, the hiding power of coated TiO.sub.2 pigments in paints with a pigment-volume concentration greater than 20% could be as much as 10% higher than that of a conventional (uncoated) rutile, which is not a major improvement by any means.
While the industrial experience with derivative composite pigments of the extended-TiO.sub.2 type, obtained by co-flocculation or compounding with extraneous or in-situ synthesized agents, has been consistently negative, it should be emphasized that the principal reason for the above lack of a practically acknowledged success was that the approaches known in the prior art, based on slow and inefficient flocculation processes, were incapable of preventing the detrimental segregation and selective flocculation of pigmentary components during the course of the synthesis process.
It is also worth noting that while all composite pigments are, de facto, aggregates, the aggregation as such, specifically, a controlled aggregation, was never intentionally employed in the prior art as an independent tool for enhancing the optical properties of composite pigments. Instead, the latter enhancement has always been attempted through interspacing of TiO.sub.2 particles with particles of extender pigments, steadfastly ignoring the fact that pigments (extenders) with particle dimensions small enough to be suitable for a truly effective interspacing have never been available on the market. It must thus be stated unequivocally that, with the exception of the intrinsic, coprecipitated TiO.sub.2 /BaSO.sub.4 (CaSO.sub.4) composite pigments, mentioned previously, the prior-art references relating to interspacing of TiO.sub.2 particles with extender particles are a clear evidence of the prevailing confusion with regard to the above subject matter.
The fact that light-scattering properties of entire pigment populations can be improved by aggregating in situ pigment fines, whose dimensions in a discrete state are too small for efficient light scattering, was first discovered by the applicant and published in the Journal of the Technical Association of the Pulp and Paper Industry (TAPPI), Vol. 53, No. 11, November 1970, Pages 2077-2084 ("Performance of Some Clays in Starch-Containing Paper-Coating Films; Part I. Black Glass Plates as Model Substrates"), preceded by a presentation at the TAPPI Coating Conference held in Houston, Tex., May 3-4, 1970.
The above publication shows plots of light-scattering coefficients at the wavelengths of 457 and 577 nm as a function of the binder-volume fraction (FIGS. 6 and 7), assessed for three different clay pigments made into coating colors and deposited as films on optically flat black glass plates as coating substrates. The slopes of the curves representing the light-scattering coefficients of No. 1 and No. 2 clays ascend initially with the increasing binder-volume fractions and, after reaching the maximum values at a binder-volume fraction corresponding to about 5 parts of starch per 100 parts of clay, by weight, descend as the binder level is further increased.
This initial increase of the light-scattering coefficients is explained in the above publication ". . . by an aggregation of clay fines effected by the initial addition of binder. The aggregates of ultrafine particles, which are understood here as assemblies of a very few such particles, should scatter the light more effectively than the individual components." The subsequent steady decline of the magnitude of the light-scattering coefficients is explained as follows: "An increase of the binder content of the coating systems beyond the F.sub.bv (binder-volume fraction-explanation added by the applicant) value of 0.080 (5 parts starch per 100 parts clay, by weight) appears to cause a further growth of the assemblies of pigment particles, so that the optimum dimensions of the light-scattering sites are exceeded."
With the relatively coarse mechanically delaminated clay, having a low proportion of particles with equivalent spherical diameters in the 0.1 .mu.m to 0.2 .mu.m range, the light-scattering coefficients of the coatings declined from the very first incremental addition of binder because of the scarcity of ultrafine particles amenable to a beneficial aggregation. The relatively coarser intrinsic structure of coating films containing the mechanically delaminated clay, compared to those containing No. 1 and No. 2 clays, has been verified with the aid of the empirical parameter called "Rho" (after the Greek letter .rho.), defined in the above publication as the ratio of light-scattering coefficients determined at 577 nm and 457 nm for the same coating film.
With coating films characterized by intrinsic structures that are relatively fine, such as binderless coatings or coatings having a low binder-volume fraction, the magnitudes of the corresponding "Rho" parameters are low. As the intrinsic coating structures become coarser, as was the case with all coatings discussed in the above publication in which the binder content was increased, the magnitude of Rho increases accordingly.
It becomes apparent on the basis of the above considerations, backed by practical experience, that the light-scattering efficacy of end-use formations containing pigments depends not only upon the original shapes and dimensions of pigment particles but, to a major extent, also on how these particles aggregate (flocculate) into the resultant end-use formations. The publication by Kaliski (TAPPI Journal, Vol. 53, No. 11, November 1970, pages 2077-2084) thus established scientific foundations for a new pigment technology opening the way to designing and manufacturing entirely new lines of derivative pigment products with improved optical and functional performance properties, synthesized by a controlled aggregation of extraneous pigmentary raw materials by themselves or combined with a variety of subpigmentary and/or nonpigmentary particulates.
Indeed, the first patent pertaining to the manufacture of aggregate pigments with an improved optical performance (U.S. Pat. No. 4,075,030: High Bulking Clay Pigments and Methods for Making the Same) was issued in 1978 to Bundy et al., with related patents by other inventors to follow. It should be pointed out, though, that none of the patented aggregate pigments was synthesized under conditions allowing a satisfactory control of the aggregation process, since the later control can only be achieved with the aid of an instantaneous, indiscriminate and complete flocculation. A flocculation process of the above-mentioned type was unknown in the prior art, however, before the previously mentioned disclosure by the applicant. Moreover, as documented amply by industrial experience, the problem of imparting an adequate mechanical integrity to aggregate pigments, while simultaneously generating in a controlled manner beneficial aggregate structures, has never been resolved satisfactorily in the technology of aggregate pigment products of the prior art.
Novel methods for the manufacture of practically countless types of aggregate pigments with exotic compositions, enhanced optical properties, excellent mechanical integrity, and unique functional properties, have been disclosed in U.S. Pat. No. 5,116,418.
It is intended hereinafter, therefore, to demonstrate how novel derivative composite pigment products can be synthesized by a controlled aggregation of primary and secondary (extender) pigments dispersed in aqueous media (furnishes), optionally including various subpigmentary and nonpigmentary particulates and auxiliary soluble media. It is also intended to provide an unambiguous classification of derivative aggregate composite pigment products of the extended-TiO.sub.2 type to clearly distinguish between those intrinsically interspaced ones and those of a "pseudo-interspaced" type characterized merely by a statistically uniform distribution of the particulate components.
In accordance with the foregoing and disclosures to follow, it is an object of the present invention to provide formulations for novel composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, synthesized by the general method disclosed in the previously mentioned U.S. Pat. No. 5,116,418, the optical-performance efficacy of the composite pigments under discussion being superior to that of the equivalent loose blends of titanium dioxide and raw materials employed for their synthesis.
In particular, it is an object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, encompassing both rutile and the slightly less efficient anatase, derived from commercial titanium dioxide pigment products in the state "as is," or comminuted beyond the limits of comminution practiced in the prior art.
It is also an object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide combined with extraneously prepared, low-refractive-index inorganic and/or organic pigments.
It is a further object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, also containing extraneously prepared particulate materials which are subpigmentary and/or nonpigmentary.
It is a yet further object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, also containing carbon black to impart extra-high opacifying properties to the latter pigment products, thus rendering them especially well suited for applications such as the manufacture of lightweight newsprint or paints and lacquers with superior hiding properties.
It is a still further object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, also containing from 0.005% to 5%, by weight, of color dyes to eliminate the residual yellow hue inherent to all commercial TiO.sub.2 pigments and/or render the resultant composite pigments directly applicable to coloring of paints, plastics and synthetic fibers.
It is a yet further object of the invention to provide formulations for composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide, also containing from 0.001% to 0.5%, by weight, of chemically built-in organic, cationically active compounds with at least two reactive groups in each molecule to impart controlled levels of organophilic properties to the resultant pigment products, thus rendering them uniquely compatible with, and dispersible in, organic media such as plastics, synthetic fibers and solvent-based lacquers and paints.
It is a yet further object of the invention to provide formulations for composite pigment products containing, in addition to extender pigments and other auxiliary materials, from 4.5% up to 50%, by weight, of particulate titanium dioxide, in which the particulate ingredients are coflocculated into aggregates whose intrinsic structure and spatial distribution of the light-scattering sites and functional sites provide optical- and functional-performance efficacies that are superior to those of the equivalent loose blends of TiO.sub.2 and other raw materials employed.
It is also a particularly special object of the invention to provide general principles of qualitative, quantitative and functional formulating to enable one to custom design composite pigment products containing from 4.5% up to 50%, by weight, of particulate titanium dioxide in combinations with other particulate components, having overall optical and functional-performance characteristics superior to those attainable with the aid of the equivalent blends of loose (nonaggregated) particulate raw materials.

TiO.sub.2 -containing composite pigment products


A system and circuit for pin fault testing is disclosed. The system includes an external tester and a circuit designed to be tested. The external tester is coupled to pins of the circuit and is configured to enter test data into the circuit. The external tester is also configured to receive continuity data from the circuit and to determine pin faults from a comparison of the test data to the continuity data. The circuit includes a plurality scan cells which are coupled in a chain fashion. When testing input pins, the external tester places a test pattern onto the input pins, stores a continuity pattern into the scan cells that are electro-mechanically coupled to the input pins, serially scans the continuity pattern out of the circuit, and compares the continuity pattern to the test pattern. When testing the output pins, the external tester serially scans a test pattern into the scan cells coupled to the output pins and compares the continuity pattern generated on the output pins to the test pattern.

The present invention relates generally to application specific integrated circuits (ASIC's), and more particularly to a system and apparatus for ASIC pin fault testing.
In an application specific integrated circuit (ASIC), one general problem encountered in the manufacturing testing process is that the electro-mechanical connections used to get signals into and out of the ASIC logic from external devices may be defective. Consequently, test circuitry is typically built into an ASIC to verify continuity of input and output pins to the ASIC logic (i.e. detecting ASIC pin faults).
As illustrated in FIG. 1, ASIC 100 includes test circuitry for detecting ASIC pin faults. The test circuitry includes a boundary scan register 103, test logic 120, a test data in signal pin (TDI) 130, test data out signal pin (TDO) 132, test mode select signal pin (TMS) 134, and test clock pin (TCK) 136. The boundary scan register 103 includes input boundary scan cells (BSCs) 104A-104D and output boundary scan cells 105A-105D. The input boundary scan cells 104A-104D are placed between the ASIC logic 110 and all the ASIC data input pins 101A-101D and the output boundary scan cells 105A-105D are placed between the ASIC logic 110 and all the ASIC data output pins 102-102D. Here, "data input pins" refers to the pins that provide input signals to the ASIC logic 110 and "data output pins" refers to the pins that receive output signals from the ASIC logic 110.
Test logic 120 includes a test access port (TAP) 122, various registers 124, 126, 128, and control logic 129. The test logic 120 drives control lines for the boundary scan cells 104-104D and 105-105D and typically conforms to IEEE 1149.1 standard for boundary scan. The IEEE 1149.1 standard for boundary scan enables testing of the ASIC 100 for a variety of manufacturing tests beyond just simple ASIC pin fault testing.
A typical structure for an input boundary scan register cell (BSC) 203A and a typical structure for an output boundary scan register cell 203B are illustrated in FIGS. 2A and 2B, respectively. Input boundary scan cells 104A-104D are identical and are represented by cell 203A (FIG. 2). Output boundary scan register cells 105A-105D are also identical and are represented by cell 203B (FIG. 3). Moreover, the basic structure of cells 203A and 203B is the same. The only difference in cells 203A and 203B is the source of the input signal for the cell and the use of the output signal from the cell.
Each cell 203A, 203B includes two two-to-one multiplexers 211A, 214A and 211B, 214B and two D-type flip-flops 212A, 213A and 212B, 213B. Test logic 120 drives five control lines which are used by cells 203A, 203B. If the signal on control line MODE is active, the input signal to cell 203A, 203B is not simply passed through the cell. Rather, multiplexer 214A, 214B passes the signal generated by D-type flip-flops 212A, 213A and 212B, 213B to the cell output line.
In normal operation of ASIC 100, cells 203A and 203B add two two-to-one multiplexers signal propagation time delays between the input and output pins of ASIC 100. This time delay is in addition to the time delay of ASIC logic 110. In addition to the time delay, cells 203A and 203B increase the gate count of ASIC 100. The size of a logic section in ASIC 100 is measured by the number of "equivalent gates" required to build the logic section. Herein, the number of equivalent gates is the number of the two input NAND gates required to duplicate the function of the logic section. Using an equivalent gate count, different designs can be compared on an equal basis. Table 1 gives the equivalent gate count for one BSC, either an input BSC 203A or an output BSC 203B.
TABLE 1 ______________________________________ # Equivalent Total # Gate Type Gates Equivalent Gates ______________________________________ 2 Input Mux 3 2 6 D Flip-Flop 8 16 Total Equivalent Gates in Cell 22 ______________________________________
Thus, in view of Table 1, the boundary scan register cells require an additional 44 equivalent gates for each input pin-output pin pair, or in general: Additional BSC Gate Count=(# Input Pins)*22+(# Output Pins)*22.
The physical size and cost of ASIC 100 is proportional to the number of gates in ASIC 100. Thus, adding test circuitry directly increases the physical size and component cost of ASIC 100. Furthermore, any test circuitry placed in series with ASIC logic 110 between an input pin and an output pin adds signal propagation delay time as the signals are routed through the additional test circuitry. This additional signal propagation delay occurs even when the ASIC is not being tested, thus impairing the normal operation of the ASIC 100.
Therefore, boundary scan adds both excessive logic gates to ASIC 100 and excessive propagation delay for signals as the signals travel through the additional test circuitry. Both of these effects are detrimental to the ASIC performance and cost. Unfortunately, as ASICs are used in higher speed systems, the time delay which the ASIC can tolerate and still operate properly diminishes. Only minimal additional time delays can be tolerated.
What is needed therefore is a method and apparatus which enables testing for ASIC pin faults while not substantially adding to the signal propagation delay time and physical size of the ASIC.

System and circuit for ASIC pin fault testing


Systems and methods are provided for detecting and correcting address errors in a memory system. In the memory system, a memory device generates an error-detection code based on an address transmitted via an address bus and transmits the error-detection code to a memory controller. The memory controller transmits an error indication to the memory device in response to the error-detection code. The error indication causes the memory device to remove the received address and prevent a memory operation.

The present disclosure relates generally to memory systems. More particularly, the present disclosure relates to detection and correction of errors within a memory system.
As the data transfer rate in computer systems becomes progressively faster, modern memory systems are more prone to transmission errors. Noise, crosstalk, inter-symbol interference, among other factors, can significantly impair signal quality, especially as data rates approach multiple Gbps.
The following description is presented to enable any person skilled in the art to make and use embodiments disclosed herein, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present disclosure is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the disclosure.


An improved desolventizer toaster and methods are provided wherein a solvent vapor recycle system may be employed to recycle solvent vapor throughout a portion of the desolventizer portion of the apparatus housing. In other embodiments of the invention, a water vapor recycle system may be employed to recycle water vapor throughout a portion of the toaster portion of the apparatus housing. The solvent vapor recycle system may comprise an appropriate meal dust separator, blower and superheater. The water vapor recycle system may comprise an appropriate ejector or blower and superheater. Water vapor recovered in the solvent extraction process may be used as a water vapor feed to the heated water vapor recycling system.

Oilseed crushing, the production of vegetable oil and animal feed from oilseeds, nearly always entails a solvent extraction step in which particulate, oilseed material is contacted with an organic solvent such as but not limited to hexane and its isomers to separate the liquid fraction from the solid fraction. The resultant liquid fraction is known in the trade as "miscella", a solution of vegetable oil in the organic solvent, and the resultant solid fraction is known in the trade as "spent material", the extraction residue soaked with organic solvent. After evaporating the solvent from the miscella, the crude vegetable oil is further processed to produce edible oil products. After evaporating the organic solvent present in the spent material, an oilseed meal is produced that is primarily used as a high protein animal feed ingredient.
The spent material from the solvent extraction process is generally soaked with twenty-five to thirty-five percent (25-35%) solvent by weight. The downstream process of evaporating the solvent from said spent material is known in the trade as "desolventizing", whose primary purpose is to remove the organic solvent to as low a residual solvent content as possible for both feed safety and environmental purposes.
Most oilseeds contain anti-nutritional factors (ANF) that prevent key amino acids in oilseed meals from being digested by mono-gastric animals such as poultry and swine. Said ANF generally consist of heat labile peptides such as the trypsin inhibitors present in soybeans. Accordingly, heating the oilseed meal to a sufficiently high temperature with adequate moisture present for a sufficiently long period inactivates these ANF by denaturing said peptides. The term used in the trade for this process is "toasting".
Toasting the meal simultaneously denatures the protein present in the meal. Denaturing the protein lowers the availability of the protein to be digested by mono-gastric animals such as poultry and swine, which therefore lowers the feed value of the meal in these markets. The degree of protein digestibility is often characterized in the trade by the protein digestibility index (PDI) expressed in percent. Higher PDI means higher availability of the protein to be digested. The majority of soybean meal in the trade today has a PDI in the range of twenty to thirty-five percent (20-35%).
The prior art, as exemplified by U.S. Pat. No. 5,992,050, employs equipment whereby spent material is treated in an apparatus that is known in the trade as a "desolventizer-toaster" (DT). The solvent content of the spent material is generally twenty-five to thirty-five percent (25-35%) by weight, with a moisture content of ten to twelve percent (10-12%) by weight and a temperature of 50-60° C.
The spent material continuously enters the DT vessel and drops onto a tray inside, known in the trade as a "pre-desolventizing" (PD) tray, which is an indirect steam-heated horizontal disc with a surface temperature typically 135-155° C. A shallow layer of spent material is stirred above the surface of the PD tray by stirring blades extending from a rotating centrally located shaft. Upon contacting the PD tray surface, the temperature of the spent material is increased to the boiling range of the solvent, typically 60-70° C., where the organic solvent begins to evaporate. A typical DT has two to four PD trays stacked vertically in series, where approximately ten to twenty percent (10-20%) of the initial solvent is evaporated, while the temperature remains 50-60° C. and the moisture remains relatively constant at ten to twelve percent (10-12%).
After the spent material exits the PD trays, the spent material continuously enters the next chamber of the DT vessel. The spent material drops onto a tray inside, known in the trade as a "counter-current" (CC) tray, which is an indirect steam-heated horizontal disc with a surface temperature typically 135-155° C. that has special apertures therein that allow ascending superheated water vapor to rise through. A deep layer of spent material is stirred above the surface of the CC tray by stirring blades extending from a rotating centrally located shaft. Soon after falling to the material surface of spent material supported above the CC tray, rising superheated water vapor from below condenses into the spent material layer providing latent heat to evaporate the majority of the remaining solvent from the spent material. When the spent material exits this first CC tray it will typically contain less than one percent residual solvent by weight with a moisture content of eighteen to twenty-two percent (18-22%) by weight and a temperature of 95-100° C. These moisture and temperature conditions allow for destruction of ANF and reduction of protein digestibility in the spent material.
A typical DT has two to four CC trays stacked vertically in series. After the first CC tray, the temperature and moisture remain relatively constant. The primary purpose of the remaining CC trays is to allow time for further stripping of the remaining traces of residual solvent by rising superheated water vapor and time for adequate destruction of the ANF. Reduction of the protein digestibility of the spent material continues on the remaining CC trays.
After the spent material exits the final CC tray, the spent material continuously enters the next chamber of the DT vessel. The spent material drops onto a tray inside, known in the trade as a "sparge" (SP) tray, which is a hollow horizontal disc with perforated upper surface for even distribution of superheated water vapor into the DT. A deep layer of spent material is stirred above the surface of the SP tray by stirring blades extending from a rotating centrally located shaft. The evenly distributed superheated water vapor rises through the spent material to achieve efficient removal of the remaining residual solvent to acceptable levels. Final destruction of ANF and reduction of protein digestibility also occur on the SP tray. When the desolventized, toasted meal exits the DT vessel it will typically contain less than 0.05% solvent by weight with a moisture content of eighteen to twenty-two percent (18-22%) by weight and a temperature of 105 to 110° C. The ANF of the desolventized, toasted meal as measured by urease delta pH is typically less than 0.15 and the protein digestibility as measured by PDI is typically 20-30%.
The solvent evaporated from the spent material along with an equilibrium quantity of water vapor typically exits the upper roof of the DT vessel. This vapor stream is generally 67-75° C. temperature and is composed of 90-95% solvent vapor in equilibrium with 5-10% of water vapor. This vapor stream often contains traces of meal dust and therefore passes through a vapor scrubbing apparatus before passing on to heat recovery.
In summary, it is known in the trade that the DT operates at or near atmospheric pressure and therefore the temperature of the spent material reaches a temperature just above the boiling point of water, 105-110° C. It has been found that with a typical DT apparatus and process that the amount of superheated water vapor condensation required to evaporate the remaining solvent in the spent material after the PD trays typically increases the moisture of the spent material to 20-22% by weight. It also been found that to achieve a residual solvent content in the desolventized, toasted meal at the exit of the DT of less than 500 parts per million (ppm), and preferably less than 250 ppm solvent by weight, that the spent material must remain in the CC and SP trays of the DT collectively for 20 minutes or greater with a minimum rising superheated water vapor flux rate of 300 kg/hr water vapor per m2 tray surface area. It is further known that the combination of 20-30 minutes residence time at 105-110° C. and 20-22% moisture produces a meal with a protein digestibility as measured by PDI of 20-30%. This represents the present state-of-the-art apparatus, process and results in the trade.
Accordingly, there is a need in the art to provide a DT process and apparatus wherein the resultant desolventized and toasted spent material meets the industry requirements for residual solvent content and destruction of ANF, while simultaneously providing a meal product with significantly high protein digestibility as measured by PDI.

Desolventizer toaster with vapor recycle


A method includes, in a mobile communication terminal that is camped on a serving cell, evaluating signals of one or more neighbor cells, and permitting the terminal to switch to a neighbor cell when a signal of the neighbor cell meets a reselection criterion for at least a predefined reselection interval. Acquisition of one or more configuration parameters of the neighbor cell is initiated at least partly in parallel with the reselection interval of the neighbor cell. Following the reselection interval, a switch is made to camp on the neighbor cell using the acquired configuration parameters.

Cellular communication systems typically support reselection processes, in which wireless communication terminals reselect the cells via which they communicate. In order to communicate via a newly-selected cell, the wireless communication terminal typically needs to acquire System Information (SI) parameters of the new cell.
Cell reselection and SI acquisition in Global System for Mobile communications (GSM) are specified, for example, by the Third Generation Partnership Project (3GPP), in "Technical Specification Group GSM/EDGE Radio Access Network; Multiplexing and multiple access on the radio path (Release 8)," TS 45.002, version 8.1.0, March, 2011; and in "Technical Specification Group GSM/EDGE Radio Access Network; Radio subsystem link control (Release 8)," TS 45.008, version 8.14.0, March, 2012, which are incorporated herein by reference.
Cell reselection and SI acquisition in Universal Mobile Telecommunications System (UMTS) are also specified by 3GPP, for example in "Technical Specification Group Radio Access Network; Requirements for support of radio resource management (FDD) (Release 8)," TS 25.133, version 8.15.0, September, 2011; and in "Technical Specification Group Radio Access Network; Radio Resource Control (RRC); Protocol specification (Release 8)," TS 25.331, version 8.14.0, March, 2011, which are incorporated herein by reference.
For Evolved Universal Terrestrial Radio Access (E-UTRA) systems, also referred to as Long Term Evolution (LTE), Cell reselection and SI acquisition are also specified by 3GPP, for example, in "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) procedures in idle mode (Release 8)," TS 36.304, version 8.10.0, June, 2011; in "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); Protocol specification (Release 8)," TS 36.331, version 8.8.0, December, 2009; in "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for support of radio resource management (Release 8)," TS 36.133, version 8.17.0, March, 2012; and in "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC); User Equipment (UE) conformance specification; Part 1: Protocol conformance specification (Release 10)," TS 36.523-1, version 10.2.0, September, 2012, which are incorporated herein by reference.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.

Inter-rat reselection in mobile communication systems


A solder which can form a soldered joint of good bonding strength on a Ni layer containing a small amount of P formed from electroless Ni plating with a P-containing plating solution comprises 60–64 mass % of Sn, 0.002–0.01 mass % of P, 0.04–0.3 mass % of Cu, and a remainder of Pb. The solder is particularly suitable for forming a solder bump on a Cu electrode which has been coated with Ni by electroless plating.

Portions to be soldered, such as electrode pads which are formed on the surface of a substrate of an electronic part such as a BGA (ball grid array) package or on the surface of a printed circuit board (PCB), are often made of copper (Cu), since Cu is wettable by molten solder as easily as are noble metals such as gold (Au) and silver (Ag) and it is much less expensive than these noble metals. However, there are cases in which the advantage of Cu that it has good wettability by molten solder is developed excessively so that the formation of an intermetallic compound of Cu with Sn (contained in the solder) takes place during soldering more than is required for the solder to form soldered joints of sufficient bonding strength. The formation of such an intermetallic compound, which is inherently brittle, continues to develop even during aging of the soldered joints.
Therefore, when Cu is used to form portions to be soldered such as electrode pads, it is found that soldered joints formed on such portions are susceptible to brittle fracture due to the formation of a Cu—Sn intermetallic compound in an excessive amount.
In contrast, as is well known to those skilled in the art, if nickel (Ni) is used to form portions to be soldered and soldering is performed under appropriately controlled conditions, it is possible to attain sufficient wettability by molten solder while the amount of an intermetallic compound formed is controlled to a reasonable level required to provide the resulting soldered joints with sufficient bonding strength. However, due to the cost advantage of Cu that it is less expensive than Ni, Cu is preferred as the most versatile nonferrous conductive metal in many applications including electronic parts.
In order to exploit the advantages of Cu and Ni together, substrates for electronic parts having portions to be soldered which are made of Cu and coated with Ni by plating have recently been employed increasingly. Thus, portions to be soldered such as electrode pads have a body of Cu, and only their surface which must be wetted by molten solder is formed by Ni plating so as to prevent the formation of an intermetallic compound in an excessive amount.
Ni plating can be performed either by electroplating or electroless plating. Electroplating forms a metal layer on the surface of a cathode by an electrolytic reaction. When a substrate such as a substrate of a BGA package or of a PCB is subjected to electroplating to form a Ni layer on portions to be soldered (i.e., electrode pads) of the substrate, there are many problems such as the necessity of electrical connection to each of the tiny electrode pads so as to allow them to act as cathodes, a limitation on the current density for electrolysis, and corrosion of metallic portions in a plating bath. A soluble anode, which is burdensome in replacement when it has been consumed and which is wasteful since it cannot be consumed completely, is generally used in electroplating with Ni. Furthermore, the rate of Ni deposition by electroplating is not uniform, and it is decreased particularly in those areas which are far from the anode or which form recesses.
In contrast, electroless Ni plating is advantageous in that a Ni layer having a uniform thickness can be formed, regardless of the type or shape of a material to be plated, by merely immersing the material in a plating solution without passing an electric current therethrough. Therefore, electroless plating is predominantly employed in Ni plating of substrates.
A typical plating solution which is used in electroless Ni plating is a solution called a Ni—P plating solution, which contains nickel sulfate as a Ni ion source and sodium hypophosphite as a reducing agent. An Ni—P plating solution also contains sodium hydroxide to maintain the pH of the solution at a predetermined value. A nickel coating formed by electroless plating with a Ni—P solution usually contains phosphorus (P) in an amount of 2–15 mass %.
After a substrate of a BGA package (hereunder referred to as a BGA substrate) is subjected to electroless Ni plating to form a Ni layer on the electrode pads of the substrate, flash plating with Au is applied in most cases in order to protect the Ni-plated layer from a chemical reaction such as oxidation and improve the wettability by or affinity for molten solder. Thereafter, solder bumps are formed on the Ni-plated electrode pads of the BGA substrate. When the BGA package is mounted on a PCB (printed circuit board), the solder bumps are allowed to melt to solder the BGA substrate to the PCB. The PCB also has electrode pads, which are typically made of Cu. The Cu electrode pads of the PCB may also be plated with Ni, and the resulting Ni layer may be subjected to flash plating with gold or another noble metal.
The formation of solder bumps on the electrode pads of a BGA substrate is performed by a process comprising applying a sticky flux to the electrode pads, then placing a solder ball on each electrode pad, and heating the BGA substrate having the solder ball on each electrode pad in a reflow furnace at a temperature sufficient to melt the solder ball and convert it into a solder bump bonded to the electrode pad.
The solder balls used to form solder bumps on a BGA substrate are generally made of a solder having a composition which is close to an Sn—Pb eutectic alloy, i.e., a composition consisting essentially of 60–64 mass % of Sn and a remainder of Pb. Such a eutectic or nearly eutectic Sn—Pb solder has a relatively low melting point of at most 190° C., so it is possible to minimize thermal effect on the BGA substrate and the electronic device mounted on the substrate during heating to form the solder bumps and/or subsequent heating for soldering the substrate to a PCB. Another advantage of the Sn—Pb alloy is that it generally exhibits good wetting power.
When solder bumps made of the eutectic or nearly eutectic Sn—Pb solder are formed by the above-described process on Ni-plated electrode pads which have been treated by flash plating with Au, it is expected that in the final heating step in the process, the solder balls which have melted can wet the underlying electrode pads smoothly and form solder bumps firmly secured to the electrode pads due to the Ni plating and flash Au plating and in view of the nature of the solder.
In fact, however, with electronic products having assembled therein a PCB on which a BGA package having solder bumps formed in this manner on its substrate is mounted, the BGA substrate is sometimes detached from the PCB by accident. For example, electronic products such as cellular phones and notebook computers may receive mechanical shocks when a cellular phone put in a pocket of ones clothing slips out of the pocket or when one drops a bag containing a notebook computer from his grasp. In such situations, detachment of soldered joints formed from the above-described solder bumps to connect the BGA substrate to the PCB may occur, leading to failure of electrical connection between these two parts and malfunction of the electronic product.

Solder for use on surfaces coated with nickel by electroless plating


Fouling components within a fluid may be prevented from accumulating when an additive contacts the fluid, e.g. by coating the wellbore with the additive prior to the production of the fluid or adding the additive directly to the fluid, etc.. The additive may include, but is not limited to, a block copolymer having at least two components. The first component may be a charged monomer, and the second component may be a long chain fatty alcohol acrylate monomer. In one alternative embodiment, the fluid may be an oil-based fluid produced through a wellbore or an oil-based wellbore fluid, and the fouling components may be or include, but are not limited to, wax, paraffins, asphaltene, resins, and combinations thereof.

Fuel oils, crude oils, refinery fluids, lubricants and/or petroleum products may often contain fouling components, e.g., paraffins, waxes, etc. that may agglomerate or precipitate, particularly at low temperatures, as large crystals in such a way that may cause the oil to lose its ability to flow, i.e. the pour point becomes higher because of the fouling components within the fluid. The 'pour point' of a fluid is the temperature at which a fluid ceases to pour. One test to determine the pour point is the ASTM D-97 pour point test where the oil ceases to flow at a given temperature (the pour point) when the sample is held at 90 degrees to the upright for five seconds. Higher pour points are typically associated with crude oils having significant paraffin or wax content because these fouling components begin precipitating as the temperature of the fluid decreases. At some point, the precipitates may accumulate and/or agglomerate to the point where the fluid will no longer flow. 'Fouling component' is defined herein to be any component that may agglomerate or precipitate in a fluid.
As the temperature of the fluid falls and approaches the pour point, difficulties arise in transporting the fuel or lubricant through lines and pumps. Further, the wax crystals tend to plug fuel lines, screens, and filters at temperatures above the pour point. These problems are well recognized in the art, and various additives have been proposed, many of which are in commercial use, for depressing the pour point of fuel oils and lubricants. Similarly, other additives have been proposed and are in commercial use for reducing the size and changing the shape of the wax crystals that do form. Smaller size crystals are desirable since they are less likely to clog a filter, but these smaller crystals may still agglomerate and form larger crystals and subsequently pose the same problem of plugging or clogging various types of well equipment. Thus, it would be beneficial to also prevent the smaller crystals from agglomerating and/or precipitating, or otherwise accumulating.
Such well treatment agents may be placed in contact with the oilfield fluids contained in the formation before such fluids enter the wellbore where deleterious effects are commonly encountered. Various well treatment agents are often used in production wells to prevent the deleterious effects caused by such formations and precipitates. For instance, pour point depressants and wax crystal modifiers have been used to change the nature of wax crystals that precipitate from the petroleum fuel, lubricant or crude oil, thereby reducing the tendency of wax crystals to plug equipment
It would be desirable if the aforementioned fluid compositions and methods for using such fluids could be tailored to prevent the agglomerating and/or precipitating of these types of fouling components within the fluid, and thereby reduce the pour point of the fluid.

Charged block co-polymers as pour point depressants


A wafer boat on which semiconductor wafers are placed is inserted into a process tube, and a process gas is supplied into the process tube to perform heat treating. In this case, prior to the heat treating, the process tube is evacuated to have a pressure lower than a pressure in the heat treating while a temperature in the process tube is kept to be higher than a temperature in the heat treating. After the heat treating is performed, the process tube is purged with an N.sub.2 gas.

1. Field of the Invention
The present invention relates to a method of heat treating an object to be processed such as a semiconductor wafer.
2. Description of the Related Art
In the conventional steps in manufacturing a semiconductor device, a heat-treating apparatus comprising a cylindrical process tube is used. The heat-treating apparatus performs predetermined heat treating to a semiconductor wafer serving as an object to be processed at a predetermined pressure and a predetermined temperature in the process tube. In recent years, as a heat-treating apparatus, a vertical type apparatus in which a process tube is vertically arranged has been popularly used in place of a conventional horizontal type apparatus in which a process tube is horizontally arranged.
In the vertical heat-treating apparatus, the process tube is formed of quarts or fused silica, the lower end of the process tube is open, and a semiconductor wafer serving as an object to be processed is loaded/unloaded in/from the lower opening. In this case, a plurality of wafers are placed on a wafer boat such that the surfaces of the wafers are kept horizontal, the wafers in this state are loaded/unloaded in/from the process tube. A heater and a heat insulator are arranged around the process tube to heat interior of the process tube, and a discharge pipe and a process gas supply pipe are connected to the lower portion of the process tube.
In the heat-treating apparatus, the wafer boat with the wafers is loaded in the process tube, the process tube is evacuated from the discharge pipe, and a predetermined process gas is supplied from the process gas supply pipe. In this state, a predetermined process, e.g., a CVD process, is performed to the semiconductor wafers at a predetermined process temperature and a predetermined process pressure.
In recent years, semiconductor devices tend to be highly integrated, and circuit patterns of the semiconductor devices tend to be further micropatterned accordingly. For this reason, in each processing step in the manufacture of a semiconductor device, the accuracy of each processing step must be improved. In heat treating, a heat-treated layer rarely containing an impurity must be obtained by improving the processing accuracy. For this purpose, improvement of the purity of a process gas and an increase in degree of vacuum in heat treating are considered.
However, even when the purity of the process gas is improved, and the heat treating is performed at a predetermined degree of vacuum, a gas is produced from semiconductor wafers and the inner wall of a process tube during the heat treating. For this reason, a small amount of impurity mixes in the atmosphere, thereby degrading the purity of a heat-treated layer.
In addition, improvement of processing accuracy easily causes a considerable decrease in throughput, and high-purity annealed layers must be formed while the decrease in throughput is suppressed.

Method of heat treating semiconductor wafers by varying the pressure and temperature


A controlling section controls an image forming section to form a calibration pattern on an object. The calibration pattern includes a plurality of first patterns and a plurality of second patterns. Each of the first patterns includes at least one pair of marks. Each of the at least one pair of marks has different colors and overlaps with each other in a first direction. The first patterns have different degrees of overlapping from each other. Each of the second patterns is formed between one of the first patterns and another one of the first patterns in the moving direction. The detecting section detects the first and second patterns formed on the object. The correcting section corrects the image forming position in the first direction based on detection results of the first patterns, and corrects the image forming position in a second direction based on detection results of the second patterns.

Conventionally, so-called tandem-type image forming apparatuses are known. This type of image forming apparatus includes a plurality of photosensitive members for each color (yellow, magenta, cyan, and black, for example) that is arranged in a direction in which a paper conveying belt moves. Images in each color borne on a corresponding photosensitive member are sequentially transferred onto a paper on the belt.
In such a tandem-type image forming apparatuses, if image forming positions on paper for each color are deviated (shifted) from the correct positions, color images with color registration errors are formed undesirably. Hence, one of these image forming apparatuses has a function to correct image forming positions of each color (Japanese Patent Application Publication No. 2004-61876). When performing this correcting function, first the image forming apparatus forms a registration pattern (position alignment pattern or calibration pattern) including a plurality of marks on the belt. The registration pattern includes reference color marks and correction color marks, and includes a plurality of pairs of marks having different degrees of overlapping between both marks in a main scanning direction or in a sub-scanning direction. Density of each pair of marks differs depending on the degree of overlapping of the pair of marks. It can be considered that the both marks constituting the pair of marks having density in an extremal value are aligned with each other (the degree of overlapping is maximum). Hence, density of each pair of marks is sequentially measured, and the pair of marks showing an extremal value of those densities is identified. Then, the positional deviation amount that is originally assumed by the image forming apparatus for the pair of marks is determined as the deviation amount of image forming positions of the correction color relative to image forming positions of the reference color in the main scanning direction or in the sub-scanning direction. The timing of forming images is corrected by offsetting the deviation amount.


A cell balancing circuit includes a plurality of battery cells coupled in series, balancing switches, each balancing switch being coupled in parallel to a respective battery cell, balancing resistors, each balancing resistor being coupled in series to the respective battery cell, a balancing controller that individually controls the balancing switches such that the battery cells are discharged through the balancing resistors, and positive temperature coefficient (PTC) elements, each PTC element being positioned adjacent to a respective balancing resistor and electrically coupled to the respective balancing switch coupled in series to the respective balancing resistor.

Studies on rechargeable secondary batteries have been actively conducted with the development of portable electronic devices such as cellular phones and notebook computers. Particularly, various kinds of secondary batteries have been developed, such as a nickel-cadmium battery, a lead storage battery, a nickel metal hydride (NiMH) battery, a lithium polymer battery, a metal lithium battery and a zinc-air storage battery. Such a secondary battery is combined with a circuit so as to constitute a battery pack, and charging and discharging are performed through an external terminal of the battery pack.

Cell balancing circuit and battery pack having the same


A test system includes a communications channel that terminals in a probe, which contacts an input terminal of an electronic device to be tested. A resistor is connected between the communications channel near the probe and ground. The resistor reduces the input resistance of the terminal and thereby reduces the rise and fall times of the input terminal. The channel may be terminated in a branch having multiple paths in which each path is terminated with a probe for contacting a terminal on electronic devices to be tested. Isolation resistors are included in the branches to prevent a fault at one input terminal from propagating to the other input terminals. A shunt resistor is provided in each branch, which reduces the input resistance of the terminal and thereby reduces the rise and fall times of the input terminal. The shunt resistor may also be sized to reduce, minimize, or eliminate signal reflections back up the channel.

The present invention is generally applicable to any system in which data is driven down one or more communications channels. One example of such a system is a test system for testing electronic devices, such as semiconductor devices. FIG. 1 illustrates a simplified block diagram of a test system 100 for testing electronic devices. The test system 100 of FIG. 1 may test the dies of an unsingulated semiconductor wafer, singulated dies (packaged or unpackaged), or multi-chip modules. Such a system 100 may be configured to test other types of electronic devices, such as printed circuit boards, as well. As shown, the system 100 includes a tester 102, communications connection 104 (e.g., a coaxial cable, fiber optic link, wireless communications link, etc.), probe head 107, and a probe card 108 for communicating test signals between the tester 102 and the electronic device 112 under test ("DUT"). The test system 100 also includes a housing 106 with a moveable chuck 114 for supporting and moving the DUT 112. Probes 110 of the probe card make contact with the DUT 112 and thereby form electrical connections with the DUT.
The tester 102 generates test data, which is driven through communications channels comprising electrically conductive paths through communications connection 104, probe head 107, and probe card 108 to the input terminals (not shown in FIG. 1) of the DUT 112. Response data generated by the DUT 112 are output through output terminals of the DUT and travel to the tester 102 through compare channels (also comprising electrically conductive paths, through the probe card 108, probe head 108, and communications connection 104). Typically, the tester 102 then compares the response data generated by the DUT 112 to expected response data to determine whether the DUT 112 is good or bad. (Such testing may additionally or alternatively be used to rate operation of the DUT.)
FIG. 2 illustrates an exemplary DUT 112 with two input terminals 208 and 210, two output terminals 204 and 206, one power terminal 212, and one ground terminal 202. (A typical DUT may have many more terminals, but six terminals are shown in FIG. 2 for ease of illustration and discussion.) As shown in FIG. 2, power is provided from tester 102 to power terminal 212 through a power channel 224, which comprises electrically conductive paths through communications connection 104, probe head 107, and probe card 108, which includes probe 110f that contacts power terminal 212. A ground connection is similarly provided from tester 102 through ground channel 214, which terminates in probe 110a. Drivers 228 and 230 in tester 102 drive test data through drive channels 222 and 224, which terminate respectively in probes 110d and 110e, to input terminals 208 and 210. Response data generated by DUT 112 and output via output terminals 204 and 206 are received by comparators 232 and 234 in tester 102. (Comparators 232 and 234 may compare the response data with expected response data.) Control module 226 controls overall operation of the tester 102, provides power and ground, generates test data, acquires the results of comparing the actual response data with the expected response data, and/or generates timing signals, among other things.
FIG. 3 illustrates a partial view of tester 102, showing only drivers 228 and 230, which drive channels 222 and 220. In FIG. 3, resistor 308 represents the output impedance of a driver (228 or 230), and resistor 310 represents the characteristic impedance of a communications channel (220 or 222). In FIG. 3, it is assumed that DUT 112 is a complementary-metal-oxide-semiconductor (CMOS) device. As is known, an input terminal (e.g., 208 or 210) of a CMOS device (e.g., 112) is primarily capacitive. A simplified equivalent circuit for input terminals 208 and 210 is shown in FIG. 3 as a resistor 302 (representing an input resistance of an input terminal (e.g., 208 or 210)) in series with a capacitor 304 (representing the primarily capacitive nature of the input terminals 208 and 210). (306 represents ground.)
As is known, a change from a low to a high signal at an input terminal 208 or 210 does not register in DUT 112 until a sufficient charge builds up on capacitor 304. Similarly, a change from a high to a low signal at an input terminal 208 or 210 does not register in DUT 112 until the charge on capacitor 304 dissipates. The time needed to charge capacitor 304 is often referred to as rise time, and the time needed to discharge capacitor 304 is fall time.
As is known, the rise time of a resistor and a capacitor in series is proportional to the product of the resistance and capacitance. The time constant (τ) of the rise time is as follows: τ=R*C (where τ is the time constant of the rise time or the fall time, R is the resistance of the resistor, C is the capacitance of the capacitor, and * refers to multiplication). The voltage across the capacitor 304 is as follows: vc(t)=C*vd*(1−e−t/τ) where:                vc(t) is the voltage across capacitor 304 at time t,        vd is the output voltage of driver 228 or 230,        t is the time from the rising edge of vd (from a low to a high voltage level),        τ is the time constant, and τ=R*C,        R is the total resistance between each driver 228 and 230 and the capacitance 304 of each input terminal 208 and 210 (R is thus the sum of the output impedance 308 of a driver, the characteristic impedance 310 of a drive channel, and the input resistance 302 of an input terminal of DUT 112), and        C is the capacitance of capacitor 304.
The fall time of a resistor and capacitor in series is also proportional to the product of the resistance and the capacitance, and the same time constant (τ) is applicable. The voltage across the capacitor 304 is as follows: vc(t)=C*vo*e−t/τ where vo is the initial charge on the capacitor and the other parameters are as defined above.
As should be apparent, the rise time and fall time of the input terminals 208 and 210 limit the frequency at which input signals to DUT 112 may be switched. As should also be apparent, the test system 100 may add to the rise and fall times of the input terminals 208 and 210 of DUT 112. This is because, for each driver 228 and 230 and drive channel 220 and 222, the output impedance 308 of the driver 228 and 230 and the characteristic impedance 310 of the channels 220 and 222 effectively increase the input resistance 302 of the input terminals 208 and 210 of DUT 112.
Another potential limit on the frequency at which DUT 112 may be switched arises from signal reflections on channels 220 and 222. A test signal driven by driver 228 or 230 down channel 222 or 220 will reflect (at least partially) off of input terminal 210 or 208 and travel back up the channel 222 or 220 toward the driver 228 or 230. If the driver output impedance 308 matches the characteristic impedance 310 of the channel (222 or 220), the reflected signal is absorbed by the driver output impedance 308 and is not further reflected back down the channel (222 or 220) toward the DUT 112. Such a configuration in which the output impedance of the driver (or source of the signal) matches the characteristic impedance of the channel is often referred to as "source termination." Even if the system shown in FIG. 3 is source terminated, the reflections that travel back up the channels 222 and 220 may cause jitter, noise, or inter-symbol interference that limits the frequency at which the input terminals 210 and 208 may be switched.
In many test applications, it would be advantageous to increase the frequency at which a DUT may be tested.

Method and apparatus for increasing operating frequency of a system for testing electronic devices


Systems and methods for switching from a first Internet context to a second Internet context without process shutdown are described. Internet context data, such as cookies, history and user-defined data, is stored in containers unique to each user on a system. Internet content is stored in a common location so redundant downloaded information is not stored. Content information is found or stored by hashing a URL and indexing the memory location according to the resulting hash value. If content data is specific to a particular user, a hash is performed on a combination of the URL and an ordinal associated with the user's unique identity to obtain a hash value unique to the user. The user-specific content is then stored and the memory location is indexed according to the unique hash value.

When a user browses the Internet using a browser on a computer, the user builds up an Internet context for her browsing activity, e.g., through cookies, history and personalized data. As the popularity of Internet browsing has grown, it is not uncommon to have more than one person using a single computer. When different people use the same computer for Internet browsing, Internet contexts can become confused. As a result, one user may no longer know which websites he has visited, and users' preferences for the same website may conflict.
To accommodate multi-user arrangements, operating systems support "profiles" for different users, each profile defining a particular work environment configured for a particular user. Each user of a computer can maintain his or her own profile, which accommodates the particular user. However, switching from one Internet context to another requires a system-wide process shutdown, meaning that a current user must end any tasks that are in progress and log off before a new user can log in. In addition, most families do not go to the trouble to enable profiles on their home computers and, therefore, they cannot switch contexts at all.

Systems and methods for switching internet contexts without process shutdown