CA2121329A1 - Spray drying method for preparing kaolin as pigment extender - Google Patents
Spray drying method for preparing kaolin as pigment extenderInfo
- Publication number
- CA2121329A1 CA2121329A1 CA002121329A CA2121329A CA2121329A1 CA 2121329 A1 CA2121329 A1 CA 2121329A1 CA 002121329 A CA002121329 A CA 002121329A CA 2121329 A CA2121329 A CA 2121329A CA 2121329 A1 CA2121329 A1 CA 2121329A1
- Authority
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- Canada
- Prior art keywords
- kaolin
- tio2
- particles
- cationic
- slurry
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
- C04B14/20—Mica; Vermiculite
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/346—Clay
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/0081—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound
- C09C1/0084—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound containing titanium dioxide
- C09C1/0087—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound containing titanium dioxide only containing titanium dioxide and silica or silicate
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/40—Compounds of aluminium
- C09C1/42—Clays
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
- C01P2004/36—Spheres fragmented
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
- C01P2006/82—Compositional purity water content
Abstract
Composite white pigments composed of titanium dioxide (TiO2) and kaolin are prepared by subjecting kaolin slurry to spray drying with injected gas to promote droplet fluffing and fragmentation.
The slurry contains a hydrocolloid suspending agent and a cationic reagent for making the kaolin particles cationic. The frangible dry material thus produced can be blended with TiO2 particles to produce an extended TiO2 pigment.
The slurry contains a hydrocolloid suspending agent and a cationic reagent for making the kaolin particles cationic. The frangible dry material thus produced can be blended with TiO2 particles to produce an extended TiO2 pigment.
Description
W093/08t33 2 1 ~ 9 PCT/US~1/07734 SPRAY DRYING METHOD FOR PREPARING
K~OLIN AS A PIGMENT EXTENDER
FIELD OF INVENTION
The general field of the invention is mineral particles that are used as white pigments in the manufacture sf paper, plastics, and paints. This invention is particularly concerned with titanium dioxid (Tio2) pigments is used in the manufacture of plastics.
BACKGROUND OF INVENTION
Mineral particles such as calcium carbonate, kaolin, and titanium dioxide are widely used as white pi~ents in paper, plastics, and paints. Titanium dioxide (TiO2) piyments are the most exp~nsive of the white ~ineral pi~ments. TiO2 pigment are ~sed in pr~ference to other white pigments because of their outstanding propQrties for providing whiteness and Dpacity. In plastics, only low levels (viz. 1-2%) of Tio2 pigments are needed, but this adds signifi-cantly to the cost of manufacture. To reduce Tio2 pigm~nt cost, there has been an ex~ensive ~earch for additives or extender~ of Tio2 in plastics.
Tio2 pigments are also u-ced in papermaking. U.S. Patent 3,458,395 describes the prsparation of coated titanium dioxide pigments using a coating of aminated polysaccharide. The coated titaniu~ dioxide is described as providing improved retention in paper making.
Calcined clay (kaolin clay) has been used as an extender of Tio2 in papermaking, and in paints.
Fox exampl~, the Engelhard Coxporation in a publication entitled "ANSILEX 93 in Paperfilling w~ g3/08l33 2 ~ 2~ PCr/USg1/07734 ~
Application~" recommends combining 16 pounds of ANSILEX 93 (calcined clay) with 48.5 pounds of Tio2 to obtain comparable brightness and opacity to the use of 57 pounds of Tio2 in a paper furnish.
Particulate calcium carbonate has been pro-po ed as an extender for Tio2 as a whitening and brightening agent in the manufacture of paper: Chang and Scott, "An investigation into the mechanism of titaniumdioxide extension by calcium carbonate", Tappi Journal, October, ~988, pages 128-131. This study concluded that although calcium carb~nate particles can enhance the light-scattering behavior of Tio2, there is no specific interaction between the particles of CaCO3 and TiO2.
It has also been proposed to pretreat a mineral filler ~e.g., calcium carbonate~ with an organic polymeric material (e.g., an acrylate polymer) to improve performance of the CaC03 particles. As described in British Patent 1,405,751, a slurry is formed from the mineral particles and an acrylate polymer emulsion, and the slurry is spray dried to produce a powdery product. This patent describes ordinary spray drying. It is also known to spray dry a slurry injected with a gas to produce porous or fluffy spray-dxied products. (See, for example, U.S.
patents 3,222,193 and 4,180,593.) In the manufacture of plastics both rutile and anastase titanium dioxide are used as whitening pigments. They can be used alone or in combination with colorants. For maximum effectiveness, rutile tit~nium dioxide is preferred because of its high re ractive index (2.7), but anastase Tio2 is cheaper. Titanium dioxide particles are typically irregular particles with their largest dimension in a WO93/08133 ~1 213 2 9 PCT/US91/077 size range of 0.2 to 0.3 microns. The level of opacity of a plastic part is determined by the amount of added material that has a refractive index different than that of the substrate. Consequently, if more opacity is needed in a particular application, more titanium dioxide must be used to accomplish this where a white or }ight pastel color is desired. This adds to the manufacturing cost.
The requirements for a whitening agent in plastics are different than in paper making. Between paper and plastics are sufficient differentials between the refractive indices of the medium and inorganic fillers which determine light reflection effects. In papermaking titanium dioxide pigments used alone or with fillers such as kaolin clay can provide brightness, whiteness, opacity, and light scattering to the paper. Titanium dioxide extenders in paper making such as kaolin or calcium carbonate ~an help deagglomerate titanium dioxide particles by filling in the spaces between the Tio2 particles.
No specific interaction or particle bonding has been observed.
Unlike paper, however, the refractive indices of plastic polymers are relatively high and are close or equal to those of most inorganic fillers such as kaolin. Consequently, with kaolin particles, for xample, there i5 little or no light reflected and no benefit optically to their use as a plastic filler.
When used as extenders for titanium dioxide, inorganic fillers have heretofore been limited to alfew percent substitutions for the Tio2. Higher loading has resulted in losses in reflectivity, opacity, and brightness. Kaolin clay heretofore has not been a significantly effective extender for Tio2 in 2 1213 2~ PCT/US91/07734 -~1 plastics.
For a mineral filler to function as an extender for titanium dioxide, it must possess a combination of properties which have proven Yery difficult to achieve. As an initial requirement, the extender must be substantially less expensive than the Tio2 pigments, while having a high refractive index and being usable in the plastic without ad~erse effects. When combined with the TiO2 the resulting color and opacity should be substantially as good as where an eguivalent amount of Tio2 is used alone.
As far as is known, up to the present invention no inorganic filler has been developed which satisfies the commercial requirements for effectively extending Tio2 in plastics.
SUMM~RY OF INVENTIO~
Heretofore kaolin clay has not been functionally effective as an appreciable extender of titanium dioxide pigments in plastic formulations.
When as little as 5 to lO parts of kaolin ar~ combined with 90 to 95 parts of TiO2, the resulting whiteness and opacity of the the plastic are significantly reduced. By the method and product of this invention calcined kaolin particles can be combined in substantially larger proportions with ~iO2 without appreciable loss of whiteness and opacity.
For purposes of the present invention, the kaolin particles are first prepared as a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic polymer, or a reagent capable of binding or coating the kaolin particles and making them cationic. The prepared slurry of the kaolin particles is subjected to drying in a spray ~ ~ WO93/08133 2 1 21~ 2 9 PCT/US91/077~
drier. Gas injection-type spray drying is preferred. With this method, air or other gas under pressure is combined with the slurry as it is atomized. The added gas promotes droplet fluffing and fragmentation, which tends to prevent the formation of dense, hard agglomerates of the kaolin particles. By using gas injection spray drying, the resulting product can be a fluffed, fragmented material in which the invidual particles of kaolin are loosely agglomerated. The surface charga properties of the kaolin have been modi~ied from essentially anionic to essentially cationic.
The fluffy, dry material comprising the coated cationic kaolin particles is in a loosely aggregated form. It can be directly dry blended with titanium dioxide pigment particles. An ordinary mixer can be employed for this blending, such as a ribbon blender. The kaolin material is broken up to s~all aggregates or to largely individual kaolin particles which can be brought into intimate contact with individual Tio2 particles. Since the Tio2 particles have predominately anionic surface charges, a cationic-anionic interaction may occur between the particles. Whatever the mechanism, experimental evidence indicates that a specific bonding interaction occurs between the Tio2 and the modified clay particles. Since dry blending for~s the TiO2/clay aggregates, Van der Waal's forces may also be operative.
~ The kaolin particles are of substantially larger size than the Tio2 particles. A multiplicity o~ Tio2 particles can surround and interactively bind to the modified kaolin particles or aggregates of kaolin particles. It iB the resulting composite of W093/~8133 2 ~1 3 2 9 PCT/US91J077~
the kaolin and Tio2 which functions as an effective extender of TiO2. Present experimental results indicate that as much as l0 to ~5% of the Tio2 can be replaced with the chemically-modified, spray-dried kaolin.
Pre-blending or dry mixing of the modified kaolin with the titanium dioxide can be carried out as one way of practicing the present invention. The re-sulting composite can then be used as a pigment addi-tive in the mànufacture of plastics. A common method of adding colorants to plastics utilizes pre-formed solid pellets. The pre-formed composites of this invention can be used as an ingredient of these pellets, or, alternatively, a modified clay can be combined with the Tio2 in the formation of these pellets, which, as a first step, involves dry-blending the pellet components, including resin, titanium dioxide, optional added color, and usually a ~ dispersant or a wax. It appears to be optivnal :~ whether the composites of this invention are preformed or are formed n situ during the preparation of the color pellets. In either procedure, modified spray dried particles or clay particle aggregates can csmbine with the Tio2 particles to form the omposites of~this invention.
THE DRAWINGS
One preferred method of preparing the composite white pigment product of this invention is illustrated by the accompanying diagrammatic drawing~s. Fig. l is a flowsheet illustrating ~: ~ processing of kaolin to produce a dry fluffy material or blending with Tio2 as illustrated in Fig. 2.
DETAILED DESCRI~TION
For purpose of this invention, the preferred , :
~ ~WO93/08133 2 1213 2 9 PCT/US91/07734 kaolin clay to be used is a purified anionic kaolin usable as a white pigment. Water-washed calcined kaolin is especially suitable. Kaolin clays are aluminum polysilicates and are primarily anionic in charactPr. After water-washing, the natural kaolins may be spray-dried~ Particles of kaolin may be separated by delamination. Kaolins which have been purified and calcined at high temperatures are known commercially as "calcined kaolins" and are available from commercial sources. For example, a ~-alcined kaolin is sold under the trade name "ANSILEX 93" and is available from Engelhard Corporation, Edlson, New Jersey. The ~aolin particles are plate-like in form, and are sometimes referred to as platelets. They may range in their longest dimension from 0.5 to lO
microns. Typical long dimension size for the kaolin particles is from about l to 3 microns.
Commercially, two types of titanium dioxide are available, anastase and rutile, which have slightly different crystal structures that result in di~ferent refractive indexes. Anastase has a refractive index of 2.52 and rutile 2.76. Anastase is less abrasive than rutile, but rutile has the advantage of providing the higher refractive index.
Either anastase or rutile titanium dioxides can be used in the present invention. For optimum whiteness and opacity, it is preferred to employ rutile TiO2.
The Tio2 particles may range in long dimension size from O.l to 0.5 microns. Typical average long dimension size is from 0.2 to 0.3 microns~
In practicing the method of this invention for comparing a composite white pigment product, a spxaya~le slurry is prepared comprising an aqueous hydrocolloid suspension of calcined anionic white 3 -2 ~ X ~ PCT/US91/077 ~aolin particles in admixture with a cationic polymer or cationic agent for modifying the kaolin particles and making their surfaces essentially cationic. The hydrocolloid used as a suspending agent may be cooked starch, such as potato starch or corn starch. The starch may be unmodified, or it may be cationic starch such as a starch containing tertiary amine or quaternary ammonium groups. When a cationic starch is emplQyed, it can perform both the functions of a hydrocolloid suspension and a cationic polymer.
However, it is preferred to employ a separate cationic polymer in addition to a non-ionic hydrocolloid.
Starch is the preferred hydrocolloid since it is effective for suspending the kaolin particles and has a relatively low cost compared to other commercially available hydrocolloids. However, other hydrocolloids can be used, such as natural or synthetic ~ s like gelatin, dextran, sodium carboxymethylcellulose, or hydroxyethyl cellulose.
Such hydrocolloids are characterized by being polysaccharides and by being hydrophilic and water-adsorbing. As a class, these are recognized as suspending agents for fine solid particles in an aqueous medium.
- A sufficient amount of the hydrocolloid should be used to suspend the kaolin particles.
However, a large excess is not desirable. For example, from 0.3 to 53 parts by weight of the starch sr other hydrocolloid may be employed per 100 parts of kaolin. Using starch, a typical pr~ferred level is from abou~ 0.5 to 2.0 parts by weight of dry starch per 100 parts of kaolin.
The cationic polymer or agent should be ~wo g3/n8l33 2 1 2 1 ~ 2 9 Pcr/us9l/07734 water-soluble or water-dispersible. It preferably contains a plurality of amide, tertiary amine, or quaternary ammonium groups. For example, poly(acrylamides), poly(aminopolyamids) and poly(alkylpolyamides) can be used. Polyacrylamides are preferred cationic reagents. These polymers may be substituted with quaternary ammonium or tertiary amine groups but quaternary groups are preferred as being more strongly cationic. The degree of substitution on a weight basis can be from l to 10% of ' the substituted polymer. Polymer lengths can vary but high molecular weight poly(acrylamides) are preferred. Average molecular weight can range from 200 r 000 to 20,000,000. Polymers with average molecular weights above 500,000 are preferred, such as the 1,000,000 to 10,000,000 range.
In general, a sufficient amount of the cationic polymer or reagent should be employed to react with the anionic surfaces of the kaolin and make them essentially cationic. For example, from 0.1 to 5 parts by weight of the cationic polymer or reagent may be employed per lO0 parts of kaolin. With polyacrylamide and other similar cationic polymers, a ypical range is from about 0.2 to 1.0 parts by weight per 100 parts of kaolin.
The slurry as prepared for spray drying can be relatively concentrated. ~or example, it may contain a total of lO to 50 parts by we~ght of total solids per 100 parts water. The solids include the kaolin, the hydrocolloid suspending agent, and ~ationic polymer or reagent on a dry basis.
Typically, the slurry may contain from 30 to 45%
solids per 100 parts of water. The primary requirement i5 that the slurry be sprayable and that WO93~08133 2 1 2 1 3 2 9 PCT/USglfO7734 ) the kaolin particles are substantially homogeneously dispersed and suspended. In general, relatively hiigh concentration slurries are preferred in order to reduce the amount of water to be removed in the spray drying.
Standard commercial spray drying èquipment can be employed for carrying out the spray drying step. One suitable type of spray dryer is referred to as a two-fluid inlets or nozzle, providing mixing of two streams or entrances to the spray dryer. For xample, one nozzle can be used for introducing the slurry and the other for introducing the gas into the slurry.
~ he slurry is pumped into its spray dryer nozzle under sufficient pressure to produce an atomized spray, as is~well known in the spray dryer art. The gas, which is preferably air, but may be nitrogen or other gas, is in~ected into the slurry under pressure through the other inlet nozzle. For example, in a pilot spray unit, nitrogen or air was injected under pressures of 25 to 75 psig, and the slurry was pumped at pressures of lO0 to 150 psig.
T~e purpose of using gas injection is to minimize the formation of the hard spherical a7gregates which can result from drying atomized spherical droplets. The mixture of the slurry and the gas results tend to form droplets which are porous and which easily fragment. The gas serves to fluff and fragment the atomized droplets. The resulting dry material has a soft frangible character, and can easily be reduced to a finer particulate size by mechanical working, such as by ordinary mixing or blénding. With a product of this character, it is not necessary to pre-grind or otherwise prepare the ' .~WO~3/OX133 ~ PCT/US91/07734 spray-dried material for dry mixing with the titanium dioxide.
After the irregular fluffy dry material has been collected from the spray dryer, it can be directly combined with the anionic titanium dioxide pigment particles. For example, the spray dried material in a proportioned amount may be introduced into a batch or continuous mixer. In the mixer, the Tio2 and the spray dried material are brought into intimate contact. The average size of the sprayed material is also reduced which promotes contacting of individual particles or small aggregates. The mixing may be carried out so that essentially individual kaolin particles are brought into contact with a plurality of individual Tio2 particles. Dry mixing can promote surface bonding between the two types of parti~les. Further, the kaolin particles are of considerably larger size than the Tio2 particles, it may be visua}ized that the individual kaolin partiales associated with a plurality, probably a multiplicity, of the Tio2 particles. Clusters ar~ formed in which Tio2 particles surround a central modified clay particle or aggregate of clay particles, but the exact binding mechanism involved is not known with c ertainty.
The pre-blend can be used as a white pigment additive for plastics. The amount of the composite an ~e at the same level as Tio2 alone, viz. in amounts of from O. 5 to 3% of the plastic formulation.
: : For white or pastel colored plastics, Tio2 can be used in amounts of l to 2%.
For purpose of the present invention, the pre-blend product should contain at least 5% by weight of the modified kaolin particles, such as from 5 to WO93/08133 2 ~ 2 ~ 2~ PCT/US~1/077~ `~`~
40%. For example, the pre-blend can contain from 5 to 40% by weight of modified kaolin particles together with 60 to 95% Tio2 particles. In preferred embodiments, the blend is composed by weight of from lO to 30~ modified kaolin particles with from 70 to 90% of Tio2 particles.
While the pre-blend product comprising the composite white pigment of this invention has been developed especially for use as a white pigment in plastics, it is believed that it may have other uses t where it is desired to replace or extend a Tio2 pigmant, such as in certain paints or for certain purposes in papermaking.
There are two forms of colorants that are used in plastics: liguid color dispersions and solid~
color pelle~s. The composite TiO2/clay pigments of his invention are believed to be most useful as a co~ponent of the solid pellets colorants. Liquid . ~
colorants use chemical dispersants and high speed mixers which may tend to break up the composites of this invention and thereby reduce the effectiveness of the composites. Further, it is believed that the composites can be formed in situ during the production .
of the color pellets but probably cannot be effectively formed if the Tio2 and the modified clay are added separately to the liquid colorants.
Where it is desired to add the Tio2 to the mix used to form color pellets without preblending of the Tio2 and the modified clay, this can be done when the initial step of color pellet production is !
dry blending. When the Tio2 and modified clay are added to the dry blender, the composites can be formed situ and can then be combined into the color pellets in accordance with known procedure~. In such ~ W093/08133 ` 2 1 2 1 3 2 ~ PCT/US91/07734 color pellet production, the resin corresponding to that to which the pellets are to be added is employed as one of the in~redients, and the resin after admixture with the titanium dioxide, clay, and other ingredients is extruded to form the pellets which are then used as the colorant for the plastic before it is molded or otherwise formed.
FLOWSHEET E~AMPLE
One method for preparing the pre-blend composite product of this invention is illustrated in Figs. 1 and 2 of the accompanying drawing. As there shown, the ingredients for preparing the slurry are charged to a mixer/cooker wherein they are heated by steam injection. The added ingredients comprise the particulate anionic kaolin, the cationic polymer, water, and the hydrocolloid suspending agent. When the suspending agent is granule starch, it can be cooked or gelatinized in formation of the slurry. If coo~ing is not required, the slurry can be formed by mixing without heating.
After the slurry has been formed in th~
mixer/cooker ~10), it is passed to an agitated holding tank ~11). Sufficient agitation is provided in tank 10 to maintain a substantially homogeneous dispersion of the kaolin in the c90ked aqueous st~rch slurry.
From the holding tank 11, the slurry is transferred through a conduit equipped with a pump 12, and i5 introduced under pump pressure into one inlet of a two-fluid nozzle 13 positioned at the top of a spray dryer 14. ~ompressed air is introduced into the other inlet nozzle for combining with the slurry. The slurry/air mixture is atomized into the top of spray dryer 14. Heated air passes upwardly in the dryer, as indicated.
WO93/08133 21213 2 9 PCT/US91/07734 ~ ~
From the spray dryer the fluffed, fragmented, frangible product is passed to a cyclone ~eparator 15. From the separator there is discharged frangible, fluffy aggregates of cationic kaolin, which is ready for combining with particulate titanium dioxide.
In Fig. 2, the cationic kaolin material produced as described with reference to Fig. l, is introduced into 2 ribbon blender 16 together with a proportioned amount of Tio2. The ribbon blender 16 may be operated as a continuous flow-through blender to discharge a pre-blended composite product, consisting of kaolin/TiO2 clusters. Within the ribbon blender, the cationic kaolin material is broken up to a finer particulate form for bonding interaction (viz. clustering) with the smaller TiO2 particles.
Where it is desired to form the TiO2/clay composites during praparation of colorant pellets, a similar blending operation can be carried out using, for example, a ribbon blender like Blender 16. The Tio2 is added to the blender together with the other ingredients, including the resin, and optional added color, and a dry dispersant such as zinc stearate or a suitable wax (e.g., Acrowax). The Tio2 and spray-dried clay material will be proportioned as previously described, but the total amount of Tio2 used will be reduced by lO to 30%. The amount of added color such as ultramarine blue may also be reduced from lO to 30%. During the dry blending of these ingredients and before forming of the pellets, the composites of this invention are produced in situ and thereby serve the same purpose as when pre-formed, as described above. The cationic spray-dried kaolin aggregates and the finer particles prepared therefrom can be directly added to a blender in which the ~ W O 93/08133 2 1 2 1 3 2 ~ P(~r/US91/07734 ingredients are being combined for forming colorant pellets. The TiO2/clay composites of this invention are formed n situ. The following procedural description is illustrative.
PreParation of Colorant Additives Color pellet production involves dry blending the dry components; namely, resin, titanium dioxide, optional added color such as ultramarine blue, or other colorants used in plastics, and a dry dispersant such as zinc stearate or a suitable wax. The composite TiO2/clay pigments of this invention are substituted for the titanium dioxide. From 10 to 30%
less of the composite is used on a Tio2 basis. The added color may also be reduced by 10 to 30%. The ingredients are dry blended in commercial dry blending equipment,- such as a ribbon blender, which may be provided with high shear intensifier bars to delump the components and produce a fine powder blend. The blend can then be fed to an extruder which heats the mixture, melting the resin, with sufficient shear to fully disperse the color and pigment with the resin before being pelletized. The pellets may vary in size but typically range in diameter from 1/32" to 1/8" and ab~ut 1/8" in length.
The resulting pellets can be used in a variety of plastic fabrication methods, such as injection molding, blow molding, etc. The choice of resin depends on the end use. Polypropylene would be used with pellets made with polypropylene, polyethylene pellets with polyethylene, etc. The pellets can be fed to an injection molder, for example, which is basically an extruder. There the pellets are melted with the uncolored resin pellets.
Sufficient chear is used to fully disperse the . , WO~3/08133 2 1 2 1 3 2 9 PCT/US91/077~ ~
colorant in the resin before the finished product is formed.
Where hot mixing is employed as the means for forming a colorant additive, it is believed essential to use the preformed composite of this invention rather than to add the Tio2 and the spray-dried, modified clay separately. Various procedures are used in the plastics industry involving hot mixing, where the equipment may comprise a Bamberry mixer followed by an extruder, or, alternatively, using the extruder t without the Bamberry mixer. In all such procedures, instead of charging the Tio2 as is done in present practice to the hopper of the mixer or the extruder, a pre-blend composite prepared as described in this application will be substituted.
With regard to colorant additives as described above, it should be understood that the additive is a concentrate, and may contain the Tio2 in concentrations a~ high as 40 to 60~. Therafore, as little as 40 to 60% of the colorant additive may comprise the resin corresponding with the resin with which the additive is to be used.
The method of this invention and the results `~ obtained can be further understood and appreciated from the following experimental examples.
EXANPLE I
~- 985 lbs of "Astra-paque", calcined clay, and lO lbs of unmodified potato starch were slurried in l500 lbs of water and heated to 205-F for 30 minutes in a high ! ' shear mixer. 5 lbs of an emulsified high molecular weight cationic polyacrylamide with a low charge density of quaternary groups, "Polyplus" 695, was added to the hot dispersion. the dispersion was then ~ ~ W093/0~133 2 1 2 1 3 2 ~ PCr/US91/077~
pumped to a spray drier using a high pressure pump and a two fluid spray nozzle. Bottled nitrogen was connected to the gas line feeding directly to the spray nozzle at a pressure of 75 psi. The compressed nitrogen had the effect of blowing the otherwise spherical particles into aggregates having a fluffy appearance and having a moisture content of l D 8% and an oil absorption of 97.8~.
The resulting cationically ~harged calcined clay was then dry blended in proportions of 0.45 grams clay to l.82 grams of "Tioxide" RFC-6 rutile titanium dioxide and homopolymer polypropylene ~227 grams).
The dry materials were placed in a vessel and mixed on a paint shakPr for 60 seconds. The blended material ~as then molded on an injection moldiny machine and made into stepped chips. Two controls were also processed as described. The first was a dry blend of 1~ titanium dioxide and polypropylene and the other was a blend of polypropylene and a 20% reduction of titanium dioxide. The chips were then evaluated based on tint strength, reflectivity and color. The extended 80% Tio2/20% clay gave comparable results to the 100% TiO2.
EXAMP~ II
"Astro" X-200 cationic potato starch în an amount of 0.2 lbs. was dispersed in 35 lbs of water and heated to 205-F before 14.6 lbs of "Astra-Paq~e", calcined clay, was dispersed with a lightening mixer.
O.l lbs of Polyplus 695, a high molecular weight cationic polyacrylamide with a low charge density of quaternary groups was added to the dispersion.
Increased agitation was required to break up the flocs of clay and produce a smooth dispersion. The dispersion was then spray dried in a pilot dryer using WO93/08133 2 1 2 1 ~ 2 9 PCT/US91/07734 a two fluid nozzle and compressed air fed directly to the spray nozzle at a pressure of 25 psi. The resulting material had a mois~ure below 1% and had a light fluffy appearance.
EXAMPLE III
An unmodified potato starch in an amount of 0.2 lbs. was dispersed in 3S lbs of water and cooked at a temperature of 205F before 14.7 lbs of calcined clay was dispersed with a lightening mixer. O.l lb of l'Polyplus" 1275, a moderate molecular weight ~ationic polyacrylamide with a low charge density of tertiary amine groups was added to the dispersion. The dispersion was mixed until smooth and fed to a pilot spray drier with a two fluid nozzle and compressed air being directly fed to the nozzle at a pressures of 25 psi. The resulting powder had a liqht fluffy appearance and a moisture below 1%.
Sources of Commerçial Products The sources of the commercial products referred to in Examples I to III are: "Astra-paque"
is the trade name for calcined clay manufactured by Georgia Xaolin, Union, New Jersey. "Polyplus'l ~95 and "Polyplus" 1275 are trade names of products manufactured by Betz PaperChem, Inc., Jacksonville, Florida. Polypl~s 69S is a polyacrylamide substituted with quaternary ammonium groups which has an average molecular weight of around lO,000 daltons. Polyplus 1275 is a tertiary amine substituted polyacrylamide having an average molecular weight of 250,000 to 400,0Q0 daltons. ;
UNmodified potato starch can be obtained from Roguette Corporation, Gurnee, Illinois. Cationic potato starch, "Astro" X-200, is manufactured by Penford Products Company, Inc., Cedar Rapids, Iowa.
`WO93/08133 2 1 2 1 ~ 2 9 PCT/US~1~07734 Examination of Composite Piqment Treating fillers, particularly calcined clay, with cationic reagents or polymers renders the normally anionic clay to have cationic charges.
Titanium dioxide has a strong anionic charge. When dry blended it was hypothesized that there was chemical bonding between clay and titanium dioxide particles in the dry state. Samples of a dry blend prepared as detailed in Example I were examined with a scanning electron microscope. Separate samples of titanium dioxide and calcined clay prepared as described in Example I were also separately examined.
The results of the examination of the dry blended materials was that the clay at a 20% addition to the Tio2 could not be found as separate discrete particles. Attempts to use back scanning as a method of identifyin~ the individual particles based on atomic number ~molecular weight) were negative. The field of view showed no differentiation between particles and the results were as though the entire sample was homogeneous. Scanning electron microscope (SEM) photographs were taken of what appears to be calcined clay shaped particles completely covered with titanium dioxide particles. The flat, plate-like shaped particles of clay could barely be picked out of the entire field of the aggregated particles.
The dry blended filler/pigment was added to plastic at about 1% addition. Consistently, ~, reflectivity curves, Hunter color values, on plastic chips made both with straight titanium dioxide and resin and those made with 80% Tio2, 20~ modified calcined clay, and resin appeared nearly identical.
There does appear to be a slight color shift to the yellow side with the modified clay.
WO93/08133 2 1 2 1 3 2 9 P~T/US91~07734 ~
Samples of plastic chips containing the clay/TiO2 aggregates described above were prepared and examined using the SEM. Plastic slivers were cut away from the ships to expose the clay/pigment by separating it from the plastic resin. ~The plastic ~' resin inhibited efforts to identify particulates embedded within the resin with surface examinations.) A streak of titanium dioxide/clay particles was found and SEM photographs were made~ It was clear that the titanium dioxide particles that were revealed were bonded to the clay. The clay was pocked with Tio2 particles. For some clay/TiO2 aggregates, it appears that there were fewer TiO2 particles adhered to the clay than the dry state. However, no free floating TiO2 particles were observed. Possibly some Tio2 particles were off of the clay particles during the injection molding. Nevertheless, the observation confirmed they hypothesis that the Tio2 remains chemically bonded with the clay. This aggregation form of the dual pigment is believed to explain the high optical performance of the blend compared with straight Tio2~
~; ~
K~OLIN AS A PIGMENT EXTENDER
FIELD OF INVENTION
The general field of the invention is mineral particles that are used as white pigments in the manufacture sf paper, plastics, and paints. This invention is particularly concerned with titanium dioxid (Tio2) pigments is used in the manufacture of plastics.
BACKGROUND OF INVENTION
Mineral particles such as calcium carbonate, kaolin, and titanium dioxide are widely used as white pi~ents in paper, plastics, and paints. Titanium dioxide (TiO2) piyments are the most exp~nsive of the white ~ineral pi~ments. TiO2 pigment are ~sed in pr~ference to other white pigments because of their outstanding propQrties for providing whiteness and Dpacity. In plastics, only low levels (viz. 1-2%) of Tio2 pigments are needed, but this adds signifi-cantly to the cost of manufacture. To reduce Tio2 pigm~nt cost, there has been an ex~ensive ~earch for additives or extender~ of Tio2 in plastics.
Tio2 pigments are also u-ced in papermaking. U.S. Patent 3,458,395 describes the prsparation of coated titanium dioxide pigments using a coating of aminated polysaccharide. The coated titaniu~ dioxide is described as providing improved retention in paper making.
Calcined clay (kaolin clay) has been used as an extender of Tio2 in papermaking, and in paints.
Fox exampl~, the Engelhard Coxporation in a publication entitled "ANSILEX 93 in Paperfilling w~ g3/08l33 2 ~ 2~ PCr/USg1/07734 ~
Application~" recommends combining 16 pounds of ANSILEX 93 (calcined clay) with 48.5 pounds of Tio2 to obtain comparable brightness and opacity to the use of 57 pounds of Tio2 in a paper furnish.
Particulate calcium carbonate has been pro-po ed as an extender for Tio2 as a whitening and brightening agent in the manufacture of paper: Chang and Scott, "An investigation into the mechanism of titaniumdioxide extension by calcium carbonate", Tappi Journal, October, ~988, pages 128-131. This study concluded that although calcium carb~nate particles can enhance the light-scattering behavior of Tio2, there is no specific interaction between the particles of CaCO3 and TiO2.
It has also been proposed to pretreat a mineral filler ~e.g., calcium carbonate~ with an organic polymeric material (e.g., an acrylate polymer) to improve performance of the CaC03 particles. As described in British Patent 1,405,751, a slurry is formed from the mineral particles and an acrylate polymer emulsion, and the slurry is spray dried to produce a powdery product. This patent describes ordinary spray drying. It is also known to spray dry a slurry injected with a gas to produce porous or fluffy spray-dxied products. (See, for example, U.S.
patents 3,222,193 and 4,180,593.) In the manufacture of plastics both rutile and anastase titanium dioxide are used as whitening pigments. They can be used alone or in combination with colorants. For maximum effectiveness, rutile tit~nium dioxide is preferred because of its high re ractive index (2.7), but anastase Tio2 is cheaper. Titanium dioxide particles are typically irregular particles with their largest dimension in a WO93/08133 ~1 213 2 9 PCT/US91/077 size range of 0.2 to 0.3 microns. The level of opacity of a plastic part is determined by the amount of added material that has a refractive index different than that of the substrate. Consequently, if more opacity is needed in a particular application, more titanium dioxide must be used to accomplish this where a white or }ight pastel color is desired. This adds to the manufacturing cost.
The requirements for a whitening agent in plastics are different than in paper making. Between paper and plastics are sufficient differentials between the refractive indices of the medium and inorganic fillers which determine light reflection effects. In papermaking titanium dioxide pigments used alone or with fillers such as kaolin clay can provide brightness, whiteness, opacity, and light scattering to the paper. Titanium dioxide extenders in paper making such as kaolin or calcium carbonate ~an help deagglomerate titanium dioxide particles by filling in the spaces between the Tio2 particles.
No specific interaction or particle bonding has been observed.
Unlike paper, however, the refractive indices of plastic polymers are relatively high and are close or equal to those of most inorganic fillers such as kaolin. Consequently, with kaolin particles, for xample, there i5 little or no light reflected and no benefit optically to their use as a plastic filler.
When used as extenders for titanium dioxide, inorganic fillers have heretofore been limited to alfew percent substitutions for the Tio2. Higher loading has resulted in losses in reflectivity, opacity, and brightness. Kaolin clay heretofore has not been a significantly effective extender for Tio2 in 2 1213 2~ PCT/US91/07734 -~1 plastics.
For a mineral filler to function as an extender for titanium dioxide, it must possess a combination of properties which have proven Yery difficult to achieve. As an initial requirement, the extender must be substantially less expensive than the Tio2 pigments, while having a high refractive index and being usable in the plastic without ad~erse effects. When combined with the TiO2 the resulting color and opacity should be substantially as good as where an eguivalent amount of Tio2 is used alone.
As far as is known, up to the present invention no inorganic filler has been developed which satisfies the commercial requirements for effectively extending Tio2 in plastics.
SUMM~RY OF INVENTIO~
Heretofore kaolin clay has not been functionally effective as an appreciable extender of titanium dioxide pigments in plastic formulations.
When as little as 5 to lO parts of kaolin ar~ combined with 90 to 95 parts of TiO2, the resulting whiteness and opacity of the the plastic are significantly reduced. By the method and product of this invention calcined kaolin particles can be combined in substantially larger proportions with ~iO2 without appreciable loss of whiteness and opacity.
For purposes of the present invention, the kaolin particles are first prepared as a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic polymer, or a reagent capable of binding or coating the kaolin particles and making them cationic. The prepared slurry of the kaolin particles is subjected to drying in a spray ~ ~ WO93/08133 2 1 21~ 2 9 PCT/US91/077~
drier. Gas injection-type spray drying is preferred. With this method, air or other gas under pressure is combined with the slurry as it is atomized. The added gas promotes droplet fluffing and fragmentation, which tends to prevent the formation of dense, hard agglomerates of the kaolin particles. By using gas injection spray drying, the resulting product can be a fluffed, fragmented material in which the invidual particles of kaolin are loosely agglomerated. The surface charga properties of the kaolin have been modi~ied from essentially anionic to essentially cationic.
The fluffy, dry material comprising the coated cationic kaolin particles is in a loosely aggregated form. It can be directly dry blended with titanium dioxide pigment particles. An ordinary mixer can be employed for this blending, such as a ribbon blender. The kaolin material is broken up to s~all aggregates or to largely individual kaolin particles which can be brought into intimate contact with individual Tio2 particles. Since the Tio2 particles have predominately anionic surface charges, a cationic-anionic interaction may occur between the particles. Whatever the mechanism, experimental evidence indicates that a specific bonding interaction occurs between the Tio2 and the modified clay particles. Since dry blending for~s the TiO2/clay aggregates, Van der Waal's forces may also be operative.
~ The kaolin particles are of substantially larger size than the Tio2 particles. A multiplicity o~ Tio2 particles can surround and interactively bind to the modified kaolin particles or aggregates of kaolin particles. It iB the resulting composite of W093/~8133 2 ~1 3 2 9 PCT/US91J077~
the kaolin and Tio2 which functions as an effective extender of TiO2. Present experimental results indicate that as much as l0 to ~5% of the Tio2 can be replaced with the chemically-modified, spray-dried kaolin.
Pre-blending or dry mixing of the modified kaolin with the titanium dioxide can be carried out as one way of practicing the present invention. The re-sulting composite can then be used as a pigment addi-tive in the mànufacture of plastics. A common method of adding colorants to plastics utilizes pre-formed solid pellets. The pre-formed composites of this invention can be used as an ingredient of these pellets, or, alternatively, a modified clay can be combined with the Tio2 in the formation of these pellets, which, as a first step, involves dry-blending the pellet components, including resin, titanium dioxide, optional added color, and usually a ~ dispersant or a wax. It appears to be optivnal :~ whether the composites of this invention are preformed or are formed n situ during the preparation of the color pellets. In either procedure, modified spray dried particles or clay particle aggregates can csmbine with the Tio2 particles to form the omposites of~this invention.
THE DRAWINGS
One preferred method of preparing the composite white pigment product of this invention is illustrated by the accompanying diagrammatic drawing~s. Fig. l is a flowsheet illustrating ~: ~ processing of kaolin to produce a dry fluffy material or blending with Tio2 as illustrated in Fig. 2.
DETAILED DESCRI~TION
For purpose of this invention, the preferred , :
~ ~WO93/08133 2 1213 2 9 PCT/US91/07734 kaolin clay to be used is a purified anionic kaolin usable as a white pigment. Water-washed calcined kaolin is especially suitable. Kaolin clays are aluminum polysilicates and are primarily anionic in charactPr. After water-washing, the natural kaolins may be spray-dried~ Particles of kaolin may be separated by delamination. Kaolins which have been purified and calcined at high temperatures are known commercially as "calcined kaolins" and are available from commercial sources. For example, a ~-alcined kaolin is sold under the trade name "ANSILEX 93" and is available from Engelhard Corporation, Edlson, New Jersey. The ~aolin particles are plate-like in form, and are sometimes referred to as platelets. They may range in their longest dimension from 0.5 to lO
microns. Typical long dimension size for the kaolin particles is from about l to 3 microns.
Commercially, two types of titanium dioxide are available, anastase and rutile, which have slightly different crystal structures that result in di~ferent refractive indexes. Anastase has a refractive index of 2.52 and rutile 2.76. Anastase is less abrasive than rutile, but rutile has the advantage of providing the higher refractive index.
Either anastase or rutile titanium dioxides can be used in the present invention. For optimum whiteness and opacity, it is preferred to employ rutile TiO2.
The Tio2 particles may range in long dimension size from O.l to 0.5 microns. Typical average long dimension size is from 0.2 to 0.3 microns~
In practicing the method of this invention for comparing a composite white pigment product, a spxaya~le slurry is prepared comprising an aqueous hydrocolloid suspension of calcined anionic white 3 -2 ~ X ~ PCT/US91/077 ~aolin particles in admixture with a cationic polymer or cationic agent for modifying the kaolin particles and making their surfaces essentially cationic. The hydrocolloid used as a suspending agent may be cooked starch, such as potato starch or corn starch. The starch may be unmodified, or it may be cationic starch such as a starch containing tertiary amine or quaternary ammonium groups. When a cationic starch is emplQyed, it can perform both the functions of a hydrocolloid suspension and a cationic polymer.
However, it is preferred to employ a separate cationic polymer in addition to a non-ionic hydrocolloid.
Starch is the preferred hydrocolloid since it is effective for suspending the kaolin particles and has a relatively low cost compared to other commercially available hydrocolloids. However, other hydrocolloids can be used, such as natural or synthetic ~ s like gelatin, dextran, sodium carboxymethylcellulose, or hydroxyethyl cellulose.
Such hydrocolloids are characterized by being polysaccharides and by being hydrophilic and water-adsorbing. As a class, these are recognized as suspending agents for fine solid particles in an aqueous medium.
- A sufficient amount of the hydrocolloid should be used to suspend the kaolin particles.
However, a large excess is not desirable. For example, from 0.3 to 53 parts by weight of the starch sr other hydrocolloid may be employed per 100 parts of kaolin. Using starch, a typical pr~ferred level is from abou~ 0.5 to 2.0 parts by weight of dry starch per 100 parts of kaolin.
The cationic polymer or agent should be ~wo g3/n8l33 2 1 2 1 ~ 2 9 Pcr/us9l/07734 water-soluble or water-dispersible. It preferably contains a plurality of amide, tertiary amine, or quaternary ammonium groups. For example, poly(acrylamides), poly(aminopolyamids) and poly(alkylpolyamides) can be used. Polyacrylamides are preferred cationic reagents. These polymers may be substituted with quaternary ammonium or tertiary amine groups but quaternary groups are preferred as being more strongly cationic. The degree of substitution on a weight basis can be from l to 10% of ' the substituted polymer. Polymer lengths can vary but high molecular weight poly(acrylamides) are preferred. Average molecular weight can range from 200 r 000 to 20,000,000. Polymers with average molecular weights above 500,000 are preferred, such as the 1,000,000 to 10,000,000 range.
In general, a sufficient amount of the cationic polymer or reagent should be employed to react with the anionic surfaces of the kaolin and make them essentially cationic. For example, from 0.1 to 5 parts by weight of the cationic polymer or reagent may be employed per lO0 parts of kaolin. With polyacrylamide and other similar cationic polymers, a ypical range is from about 0.2 to 1.0 parts by weight per 100 parts of kaolin.
The slurry as prepared for spray drying can be relatively concentrated. ~or example, it may contain a total of lO to 50 parts by we~ght of total solids per 100 parts water. The solids include the kaolin, the hydrocolloid suspending agent, and ~ationic polymer or reagent on a dry basis.
Typically, the slurry may contain from 30 to 45%
solids per 100 parts of water. The primary requirement i5 that the slurry be sprayable and that WO93~08133 2 1 2 1 3 2 9 PCT/USglfO7734 ) the kaolin particles are substantially homogeneously dispersed and suspended. In general, relatively hiigh concentration slurries are preferred in order to reduce the amount of water to be removed in the spray drying.
Standard commercial spray drying èquipment can be employed for carrying out the spray drying step. One suitable type of spray dryer is referred to as a two-fluid inlets or nozzle, providing mixing of two streams or entrances to the spray dryer. For xample, one nozzle can be used for introducing the slurry and the other for introducing the gas into the slurry.
~ he slurry is pumped into its spray dryer nozzle under sufficient pressure to produce an atomized spray, as is~well known in the spray dryer art. The gas, which is preferably air, but may be nitrogen or other gas, is in~ected into the slurry under pressure through the other inlet nozzle. For example, in a pilot spray unit, nitrogen or air was injected under pressures of 25 to 75 psig, and the slurry was pumped at pressures of lO0 to 150 psig.
T~e purpose of using gas injection is to minimize the formation of the hard spherical a7gregates which can result from drying atomized spherical droplets. The mixture of the slurry and the gas results tend to form droplets which are porous and which easily fragment. The gas serves to fluff and fragment the atomized droplets. The resulting dry material has a soft frangible character, and can easily be reduced to a finer particulate size by mechanical working, such as by ordinary mixing or blénding. With a product of this character, it is not necessary to pre-grind or otherwise prepare the ' .~WO~3/OX133 ~ PCT/US91/07734 spray-dried material for dry mixing with the titanium dioxide.
After the irregular fluffy dry material has been collected from the spray dryer, it can be directly combined with the anionic titanium dioxide pigment particles. For example, the spray dried material in a proportioned amount may be introduced into a batch or continuous mixer. In the mixer, the Tio2 and the spray dried material are brought into intimate contact. The average size of the sprayed material is also reduced which promotes contacting of individual particles or small aggregates. The mixing may be carried out so that essentially individual kaolin particles are brought into contact with a plurality of individual Tio2 particles. Dry mixing can promote surface bonding between the two types of parti~les. Further, the kaolin particles are of considerably larger size than the Tio2 particles, it may be visua}ized that the individual kaolin partiales associated with a plurality, probably a multiplicity, of the Tio2 particles. Clusters ar~ formed in which Tio2 particles surround a central modified clay particle or aggregate of clay particles, but the exact binding mechanism involved is not known with c ertainty.
The pre-blend can be used as a white pigment additive for plastics. The amount of the composite an ~e at the same level as Tio2 alone, viz. in amounts of from O. 5 to 3% of the plastic formulation.
: : For white or pastel colored plastics, Tio2 can be used in amounts of l to 2%.
For purpose of the present invention, the pre-blend product should contain at least 5% by weight of the modified kaolin particles, such as from 5 to WO93/08133 2 ~ 2 ~ 2~ PCT/US~1/077~ `~`~
40%. For example, the pre-blend can contain from 5 to 40% by weight of modified kaolin particles together with 60 to 95% Tio2 particles. In preferred embodiments, the blend is composed by weight of from lO to 30~ modified kaolin particles with from 70 to 90% of Tio2 particles.
While the pre-blend product comprising the composite white pigment of this invention has been developed especially for use as a white pigment in plastics, it is believed that it may have other uses t where it is desired to replace or extend a Tio2 pigmant, such as in certain paints or for certain purposes in papermaking.
There are two forms of colorants that are used in plastics: liguid color dispersions and solid~
color pelle~s. The composite TiO2/clay pigments of his invention are believed to be most useful as a co~ponent of the solid pellets colorants. Liquid . ~
colorants use chemical dispersants and high speed mixers which may tend to break up the composites of this invention and thereby reduce the effectiveness of the composites. Further, it is believed that the composites can be formed in situ during the production .
of the color pellets but probably cannot be effectively formed if the Tio2 and the modified clay are added separately to the liquid colorants.
Where it is desired to add the Tio2 to the mix used to form color pellets without preblending of the Tio2 and the modified clay, this can be done when the initial step of color pellet production is !
dry blending. When the Tio2 and modified clay are added to the dry blender, the composites can be formed situ and can then be combined into the color pellets in accordance with known procedure~. In such ~ W093/08133 ` 2 1 2 1 3 2 ~ PCT/US91/07734 color pellet production, the resin corresponding to that to which the pellets are to be added is employed as one of the in~redients, and the resin after admixture with the titanium dioxide, clay, and other ingredients is extruded to form the pellets which are then used as the colorant for the plastic before it is molded or otherwise formed.
FLOWSHEET E~AMPLE
One method for preparing the pre-blend composite product of this invention is illustrated in Figs. 1 and 2 of the accompanying drawing. As there shown, the ingredients for preparing the slurry are charged to a mixer/cooker wherein they are heated by steam injection. The added ingredients comprise the particulate anionic kaolin, the cationic polymer, water, and the hydrocolloid suspending agent. When the suspending agent is granule starch, it can be cooked or gelatinized in formation of the slurry. If coo~ing is not required, the slurry can be formed by mixing without heating.
After the slurry has been formed in th~
mixer/cooker ~10), it is passed to an agitated holding tank ~11). Sufficient agitation is provided in tank 10 to maintain a substantially homogeneous dispersion of the kaolin in the c90ked aqueous st~rch slurry.
From the holding tank 11, the slurry is transferred through a conduit equipped with a pump 12, and i5 introduced under pump pressure into one inlet of a two-fluid nozzle 13 positioned at the top of a spray dryer 14. ~ompressed air is introduced into the other inlet nozzle for combining with the slurry. The slurry/air mixture is atomized into the top of spray dryer 14. Heated air passes upwardly in the dryer, as indicated.
WO93/08133 21213 2 9 PCT/US91/07734 ~ ~
From the spray dryer the fluffed, fragmented, frangible product is passed to a cyclone ~eparator 15. From the separator there is discharged frangible, fluffy aggregates of cationic kaolin, which is ready for combining with particulate titanium dioxide.
In Fig. 2, the cationic kaolin material produced as described with reference to Fig. l, is introduced into 2 ribbon blender 16 together with a proportioned amount of Tio2. The ribbon blender 16 may be operated as a continuous flow-through blender to discharge a pre-blended composite product, consisting of kaolin/TiO2 clusters. Within the ribbon blender, the cationic kaolin material is broken up to a finer particulate form for bonding interaction (viz. clustering) with the smaller TiO2 particles.
Where it is desired to form the TiO2/clay composites during praparation of colorant pellets, a similar blending operation can be carried out using, for example, a ribbon blender like Blender 16. The Tio2 is added to the blender together with the other ingredients, including the resin, and optional added color, and a dry dispersant such as zinc stearate or a suitable wax (e.g., Acrowax). The Tio2 and spray-dried clay material will be proportioned as previously described, but the total amount of Tio2 used will be reduced by lO to 30%. The amount of added color such as ultramarine blue may also be reduced from lO to 30%. During the dry blending of these ingredients and before forming of the pellets, the composites of this invention are produced in situ and thereby serve the same purpose as when pre-formed, as described above. The cationic spray-dried kaolin aggregates and the finer particles prepared therefrom can be directly added to a blender in which the ~ W O 93/08133 2 1 2 1 3 2 ~ P(~r/US91/07734 ingredients are being combined for forming colorant pellets. The TiO2/clay composites of this invention are formed n situ. The following procedural description is illustrative.
PreParation of Colorant Additives Color pellet production involves dry blending the dry components; namely, resin, titanium dioxide, optional added color such as ultramarine blue, or other colorants used in plastics, and a dry dispersant such as zinc stearate or a suitable wax. The composite TiO2/clay pigments of this invention are substituted for the titanium dioxide. From 10 to 30%
less of the composite is used on a Tio2 basis. The added color may also be reduced by 10 to 30%. The ingredients are dry blended in commercial dry blending equipment,- such as a ribbon blender, which may be provided with high shear intensifier bars to delump the components and produce a fine powder blend. The blend can then be fed to an extruder which heats the mixture, melting the resin, with sufficient shear to fully disperse the color and pigment with the resin before being pelletized. The pellets may vary in size but typically range in diameter from 1/32" to 1/8" and ab~ut 1/8" in length.
The resulting pellets can be used in a variety of plastic fabrication methods, such as injection molding, blow molding, etc. The choice of resin depends on the end use. Polypropylene would be used with pellets made with polypropylene, polyethylene pellets with polyethylene, etc. The pellets can be fed to an injection molder, for example, which is basically an extruder. There the pellets are melted with the uncolored resin pellets.
Sufficient chear is used to fully disperse the . , WO~3/08133 2 1 2 1 3 2 9 PCT/US91/077~ ~
colorant in the resin before the finished product is formed.
Where hot mixing is employed as the means for forming a colorant additive, it is believed essential to use the preformed composite of this invention rather than to add the Tio2 and the spray-dried, modified clay separately. Various procedures are used in the plastics industry involving hot mixing, where the equipment may comprise a Bamberry mixer followed by an extruder, or, alternatively, using the extruder t without the Bamberry mixer. In all such procedures, instead of charging the Tio2 as is done in present practice to the hopper of the mixer or the extruder, a pre-blend composite prepared as described in this application will be substituted.
With regard to colorant additives as described above, it should be understood that the additive is a concentrate, and may contain the Tio2 in concentrations a~ high as 40 to 60~. Therafore, as little as 40 to 60% of the colorant additive may comprise the resin corresponding with the resin with which the additive is to be used.
The method of this invention and the results `~ obtained can be further understood and appreciated from the following experimental examples.
EXANPLE I
~- 985 lbs of "Astra-paque", calcined clay, and lO lbs of unmodified potato starch were slurried in l500 lbs of water and heated to 205-F for 30 minutes in a high ! ' shear mixer. 5 lbs of an emulsified high molecular weight cationic polyacrylamide with a low charge density of quaternary groups, "Polyplus" 695, was added to the hot dispersion. the dispersion was then ~ ~ W093/0~133 2 1 2 1 3 2 ~ PCr/US91/077~
pumped to a spray drier using a high pressure pump and a two fluid spray nozzle. Bottled nitrogen was connected to the gas line feeding directly to the spray nozzle at a pressure of 75 psi. The compressed nitrogen had the effect of blowing the otherwise spherical particles into aggregates having a fluffy appearance and having a moisture content of l D 8% and an oil absorption of 97.8~.
The resulting cationically ~harged calcined clay was then dry blended in proportions of 0.45 grams clay to l.82 grams of "Tioxide" RFC-6 rutile titanium dioxide and homopolymer polypropylene ~227 grams).
The dry materials were placed in a vessel and mixed on a paint shakPr for 60 seconds. The blended material ~as then molded on an injection moldiny machine and made into stepped chips. Two controls were also processed as described. The first was a dry blend of 1~ titanium dioxide and polypropylene and the other was a blend of polypropylene and a 20% reduction of titanium dioxide. The chips were then evaluated based on tint strength, reflectivity and color. The extended 80% Tio2/20% clay gave comparable results to the 100% TiO2.
EXAMP~ II
"Astro" X-200 cationic potato starch în an amount of 0.2 lbs. was dispersed in 35 lbs of water and heated to 205-F before 14.6 lbs of "Astra-Paq~e", calcined clay, was dispersed with a lightening mixer.
O.l lbs of Polyplus 695, a high molecular weight cationic polyacrylamide with a low charge density of quaternary groups was added to the dispersion.
Increased agitation was required to break up the flocs of clay and produce a smooth dispersion. The dispersion was then spray dried in a pilot dryer using WO93/08133 2 1 2 1 ~ 2 9 PCT/US91/07734 a two fluid nozzle and compressed air fed directly to the spray nozzle at a pressure of 25 psi. The resulting material had a mois~ure below 1% and had a light fluffy appearance.
EXAMPLE III
An unmodified potato starch in an amount of 0.2 lbs. was dispersed in 3S lbs of water and cooked at a temperature of 205F before 14.7 lbs of calcined clay was dispersed with a lightening mixer. O.l lb of l'Polyplus" 1275, a moderate molecular weight ~ationic polyacrylamide with a low charge density of tertiary amine groups was added to the dispersion. The dispersion was mixed until smooth and fed to a pilot spray drier with a two fluid nozzle and compressed air being directly fed to the nozzle at a pressures of 25 psi. The resulting powder had a liqht fluffy appearance and a moisture below 1%.
Sources of Commerçial Products The sources of the commercial products referred to in Examples I to III are: "Astra-paque"
is the trade name for calcined clay manufactured by Georgia Xaolin, Union, New Jersey. "Polyplus'l ~95 and "Polyplus" 1275 are trade names of products manufactured by Betz PaperChem, Inc., Jacksonville, Florida. Polypl~s 69S is a polyacrylamide substituted with quaternary ammonium groups which has an average molecular weight of around lO,000 daltons. Polyplus 1275 is a tertiary amine substituted polyacrylamide having an average molecular weight of 250,000 to 400,0Q0 daltons. ;
UNmodified potato starch can be obtained from Roguette Corporation, Gurnee, Illinois. Cationic potato starch, "Astro" X-200, is manufactured by Penford Products Company, Inc., Cedar Rapids, Iowa.
`WO93/08133 2 1 2 1 ~ 2 9 PCT/US~1~07734 Examination of Composite Piqment Treating fillers, particularly calcined clay, with cationic reagents or polymers renders the normally anionic clay to have cationic charges.
Titanium dioxide has a strong anionic charge. When dry blended it was hypothesized that there was chemical bonding between clay and titanium dioxide particles in the dry state. Samples of a dry blend prepared as detailed in Example I were examined with a scanning electron microscope. Separate samples of titanium dioxide and calcined clay prepared as described in Example I were also separately examined.
The results of the examination of the dry blended materials was that the clay at a 20% addition to the Tio2 could not be found as separate discrete particles. Attempts to use back scanning as a method of identifyin~ the individual particles based on atomic number ~molecular weight) were negative. The field of view showed no differentiation between particles and the results were as though the entire sample was homogeneous. Scanning electron microscope (SEM) photographs were taken of what appears to be calcined clay shaped particles completely covered with titanium dioxide particles. The flat, plate-like shaped particles of clay could barely be picked out of the entire field of the aggregated particles.
The dry blended filler/pigment was added to plastic at about 1% addition. Consistently, ~, reflectivity curves, Hunter color values, on plastic chips made both with straight titanium dioxide and resin and those made with 80% Tio2, 20~ modified calcined clay, and resin appeared nearly identical.
There does appear to be a slight color shift to the yellow side with the modified clay.
WO93/08133 2 1 2 1 3 2 9 P~T/US91~07734 ~
Samples of plastic chips containing the clay/TiO2 aggregates described above were prepared and examined using the SEM. Plastic slivers were cut away from the ships to expose the clay/pigment by separating it from the plastic resin. ~The plastic ~' resin inhibited efforts to identify particulates embedded within the resin with surface examinations.) A streak of titanium dioxide/clay particles was found and SEM photographs were made~ It was clear that the titanium dioxide particles that were revealed were bonded to the clay. The clay was pocked with Tio2 particles. For some clay/TiO2 aggregates, it appears that there were fewer TiO2 particles adhered to the clay than the dry state. However, no free floating TiO2 particles were observed. Possibly some Tio2 particles were off of the clay particles during the injection molding. Nevertheless, the observation confirmed they hypothesis that the Tio2 remains chemically bonded with the clay. This aggregation form of the dual pigment is believed to explain the high optical performance of the blend compared with straight Tio2~
~; ~
Claims (8)
1. A method for preparing kaolin for use as a pigment extender, comprising:
(a) preparing a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic reagent capable of binding to said kaolin particles and making them cationic;
(b) subjecting said slurry to drying in a spray dryer by atomizing droplets of a pressurized mixture of said slurry with an added gas to promote droplet fluffing and fragmentation; and (c) collecting a frangible dry material from said spray drying which material is cationic and which binds in dry condition to anionic titanium dioxide.
(a) preparing a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic reagent capable of binding to said kaolin particles and making them cationic;
(b) subjecting said slurry to drying in a spray dryer by atomizing droplets of a pressurized mixture of said slurry with an added gas to promote droplet fluffing and fragmentation; and (c) collecting a frangible dry material from said spray drying which material is cationic and which binds in dry condition to anionic titanium dioxide.
2. The method of claim l in which the aqueous hydrocolloid is a cooked starch suspension and said cationic reagent is poly(acrylamide).
3. The kaolin pigment extender material produced by the method of claim l or claim 2.
4. The method of preparing a composite white pigment product composed of titanium dioxide (TiO2) and kaolin, comprising:
(a) preparing a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic reagent capable of binding to said kaolin particles and making them cationic;
(b) subjecting said slurry to drying in a spray dryer by atomizing droplets of a mixture of said slurry with pressurized air injected therein to promote droplet fluffing and fragmentation;
(c) collecting a frangible dry material from said spray drying which material is cationic; and (d) blending portions of said cationic material with anionic titanium dioxide (TiO2) pigment particles by mechanically mixing to bring the dry kaolin material into intimate contact with TiO2 particles, said mixed blend containing composites of TiO2 and kaolin particles and being composed by weight of from 5 to 40% of kaolin together with from 60 to 95% of TiO2.
(a) preparing a sprayable slurry comprising an aqueous hydrocolloid suspension of calcined anionic white kaolin particles in admixture with a cationic reagent capable of binding to said kaolin particles and making them cationic;
(b) subjecting said slurry to drying in a spray dryer by atomizing droplets of a mixture of said slurry with pressurized air injected therein to promote droplet fluffing and fragmentation;
(c) collecting a frangible dry material from said spray drying which material is cationic; and (d) blending portions of said cationic material with anionic titanium dioxide (TiO2) pigment particles by mechanically mixing to bring the dry kaolin material into intimate contact with TiO2 particles, said mixed blend containing composites of TiO2 and kaolin particles and being composed by weight of from 5 to 40% of kaolin together with from 60 to 95% of TiO2.
5. The method of claim 4 in which the aqueous hydrocolloid suspension is a cooked starch suspension and said cationic reagent is poly(acrylamide).
6. The mixed blend produced by the method of claim 4 or claim 5.
7. The method of claim 1 or claim 4 in which said cationic reagent is poly(acrylamide) having a molecular weight of at least 200,000 and containing cationic quaternary ammonium groups, said kaolin particles having a longest dimension of from 0.5 to 4 microns and said slurry containing from 0.1 to 2 parts by weight of said poly(acrylamide) per 100 parts of kaolin.
8. The method of claim 4 or claim 5 in which said mixed blend contains by weight from 10 to 30% kaolin together with 70 to 90% TiO2.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/470,926 US5078793A (en) | 1990-01-26 | 1990-01-26 | Spray drying method for preparing kaolin as a pigment extender |
| EP9292906309A EP0608228A4 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as a pigment extender. |
| CA002121329A CA2121329A1 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as pigment extender |
| PCT/US1991/007734 WO1993008133A1 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as a pigment extender |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/470,926 US5078793A (en) | 1990-01-26 | 1990-01-26 | Spray drying method for preparing kaolin as a pigment extender |
| CA002121329A CA2121329A1 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as pigment extender |
| PCT/US1991/007734 WO1993008133A1 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as a pigment extender |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2121329A1 true CA2121329A1 (en) | 1993-04-29 |
Family
ID=25677188
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002121329A Abandoned CA2121329A1 (en) | 1990-01-26 | 1991-10-17 | Spray drying method for preparing kaolin as pigment extender |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5078793A (en) |
| EP (1) | EP0608228A4 (en) |
| CA (1) | CA2121329A1 (en) |
| WO (1) | WO1993008133A1 (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5152835A (en) * | 1991-05-08 | 1992-10-06 | Engelhard Corporation | Composite titania-calcined kaolin opacifying pigments and method for making and using same |
| DE4211560A1 (en) * | 1992-04-07 | 1993-10-14 | Merck Patent Gmbh | Composite pigment prodn. - by spraying drying aq. suspension of substrate particles and fine pigment free from additive, used in plastics, lacquer, ink and cosmetics |
| GB9211822D0 (en) * | 1992-06-04 | 1992-07-15 | Tioxide Group Services Ltd | Composite pigmentary material |
| GB2267503B (en) * | 1992-06-04 | 1996-07-24 | Tioxide Group Services Ltd | Composite pigmentary material comprising particles of opposite surface charge |
| US5551975A (en) * | 1994-06-23 | 1996-09-03 | J. M. Huber Corporation | Structured pigment compositions, methods for preparation and use |
| US5584922A (en) * | 1994-09-14 | 1996-12-17 | Ciba-Geigy Corporation | Stir-in organic pigments |
| JP2636186B2 (en) * | 1994-09-26 | 1997-07-30 | 科学技術庁無機材質研究所長 | Polysaccharide or polysaccharide-clay composite porous body and method for producing the same |
| GB9602221D0 (en) * | 1996-02-03 | 1996-04-03 | Tioxide Group Services Ltd | Composite pigmentary material |
| GB9504962D0 (en) * | 1995-03-11 | 1995-04-26 | Tioxide Group Services Ltd | Composite pigmentary material |
| US5650003A (en) * | 1995-12-18 | 1997-07-22 | Nord Naolin Company | Cationized pigments and their use in papermaking |
| DE10007484C2 (en) * | 2000-02-18 | 2001-12-13 | Schoeller Felix Jun Foto | Substrate for recording materials |
| GB0209355D0 (en) * | 2002-04-24 | 2002-06-05 | Imerys Minerals Ltd | An opacified polymer composition |
| WO2007022022A2 (en) * | 2005-08-11 | 2007-02-22 | Basf Catalysts Llc | Volumizing agents |
| TW200843903A (en) * | 2007-05-03 | 2008-11-16 | Univ Nat Central | Abrasives with function of sliding grinding and its manufacturing method |
| CN103890106B (en) * | 2011-08-15 | 2016-04-20 | 巴斯夫公司 | The kaolin based paint pigment extender of a new generation |
| US8876965B2 (en) | 2012-05-09 | 2014-11-04 | J.M. Huber Corporation | Blended opacifier for coatings and polymeric matrices |
| CN105163950A (en) * | 2013-04-24 | 2015-12-16 | 惠普发展公司，有限责任合伙企业 | Printable recording media |
| CN110105803A (en) * | 2019-05-17 | 2019-08-09 | 南宁聚钙新材料科技有限责任公司 | A kind of coating alkaline-resisting aqueous titanium dioxide slurry and preparation method thereof |
| CN111471325A (en) * | 2020-05-11 | 2020-07-31 | 华东理工大学 | Method for improving fluidity of titanium dioxide for chinlon chemical fiber |
| CN113105759B (en) * | 2021-04-15 | 2022-04-15 | 攀枝花学院 | Surface treatment method of titanium dioxide |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3117883A (en) * | 1960-09-23 | 1964-01-14 | Glidden Co | Pigment for aqueous latex emulsion paints |
| US3222193A (en) * | 1962-09-12 | 1965-12-07 | Francis P Hanrahan | Method of spray drying liquid food products |
| GB1025960A (en) * | 1963-07-10 | 1966-04-14 | British Titan Products | Coated titanium dioxide pigments |
| US3453131A (en) * | 1966-01-05 | 1969-07-01 | Oxford Paper Co | Composite colloidal pigment particles,their formation and suspensions thereof |
| US3726700A (en) * | 1971-03-19 | 1973-04-10 | Du Pont | Composite pigments and their preparation |
| GB1405751A (en) * | 1971-07-27 | 1975-09-10 | Bpb Industries Ltd | Paper filler |
| US4180593A (en) * | 1977-04-29 | 1979-12-25 | Cohan Allan N | Process for producing round spherical free flowing blown bead food products of controlled bulk density |
| IE47019B1 (en) * | 1977-07-12 | 1983-11-30 | Blue Circle Ind Ltd | Producing dispersions of polymeric material and preflocculated fillers for use in papermaking |
| US5006574A (en) * | 1989-02-10 | 1991-04-09 | Engelhard Corporation | Cationcally dispersed slurries of calcined kaolin clay |
| DE69030020T2 (en) * | 1989-05-04 | 1997-10-02 | Engelhard Corp | Cationic treatment of ores |
-
1990
- 1990-01-26 US US07/470,926 patent/US5078793A/en not_active Expired - Lifetime
-
1991
- 1991-10-17 WO PCT/US1991/007734 patent/WO1993008133A1/en not_active Application Discontinuation
- 1991-10-17 EP EP9292906309A patent/EP0608228A4/en not_active Withdrawn
- 1991-10-17 CA CA002121329A patent/CA2121329A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0608228A1 (en) | 1994-08-03 |
| US5078793A (en) | 1992-01-07 |
| WO1993008133A1 (en) | 1993-04-29 |
| EP0608228A4 (en) | 1994-11-02 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Discontinued |