PT86510B - PRODUCTION PROCESS OF A STRUCTURED CAULINE PIGMENT - Google Patents

Abstract

Kaolin pigments with enhanced light-scattering and opacifying properties, when incorporated in paper, are produced by mixing finely divided kaolin with (a) urea or an organic amine and (b) an aggregation-enhancing agent (I), which is an alkali metal carbonate or an alkaline earth metal carbonate or hydroxide. (I) is used in an amt. corresp. to 5-120 mmoles of the metal ion per 100 parts by weight (sic) of kaolin.

Description

This invention relates in general to a process for the production of kaolin products and, more specifically, refers to a structured kaolin pigment. The pigment is useful as a filler for paper products and allows the preparation of paper coating formulations which give coated skin products with surprisingly improved properties.

Background of the Invention

It is well known that in the course of making paper and similar products, including cardboard and the like, quantities of inorganic materials are incorporated into the fibrous fabric to improve the quality of the resulting product. In the absence of such charges, the resulting paper may have a relatively poor texture, due to the discontinuities of the fibrous mesh. Said loads are also important in improving the printing qualities of the paper, that is, by improving the surface characteristics of the paper. The use of such appropriate fillers, moreover, greatly improves the opacity and brightness of a sheet of paper with a certain weight.

Various inorganic materials have long been known to be effective for many of the purposes mentioned above. Among the best of these materials is titanium dioxide that can be incorporated into paper in the form of anatase or rutile. However, titanium dioxide is among the most expensive usable materials. Thus, despite the effectiveness of such material as a load, its use is limited and subs have been in high demand. satisfactory titles.

Among the materials that have found increasing acceptance as fillers for paper, are calcined kaolin. Materials of this type are generally prepared by calcining a raw kaolin that may have been initially subjected to previous beneficiation steps, to remove certain impurities, for example, in order to improve the gloss of the product.

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-3 final. Conveniently, reference can be made to Proctor, US patent 3 014 836 and Fanselow et al., US patent 3 586 823, whose disclosures are representative of the ari terior technique related to calcined kaolin.

These properties that make kaolin pigment particularly valuable as a filler are also well known. They include a low abrasion index and high gloss and opacification characteristics. Low abrasion is significant in order to ensure that the resulting paper product can be manufactured and processed using conventional equipment, without prejudice to mBsmo. Gloss and opacification characteristics are important in producing an acceptable sheet of paper that has whiteness, high opacity, good printing properties and low weight.

Both the brightness characteristics of a given kaolin and its opacification properties, when incorporated into the paper as filler or filler, can be quantitatively related to a filler property identified as the diffusion coefficient S. The said parameter, that is, the diffusion coefficient S of a given charge pigment is a well-known and widely used property in paper technology, and has been the subject of numerous technical and similar publications. The first interpretation of such measures was made by Kubelka and Munk, and was presented in Z. Tech Physik 12: 539 (1931). Other citations of applicable measurement techniques and detailed definitions of said diffusion coefficient are presented in numerous sites, in the patent literature and in the technique. Reference can be made in this regard, for example, to US patents 4 026 726 and 4 026 173. In addition to the citations presented in those patents, reference can also be made to Pulp and Paper Science Technology, volume 2 of Paper, chapter 3, by HC Schwalbe (McGraw-Hill Book Company, NY).

*

It is well known that, in order to obtain high light diffusion and opacity, most of the charge must be in the 1 micron range. However, it is not possible to achieve a good light diffusion only by using a kaolin that has the aforementioned character.

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- dimensional dimension; Another essential feature required is that the kaolin is structured, that is, formed by a set of interconnected or joined platelets to give aggregates that include a platelet network.

Aggregation may be of interest for other reasons.

In particular, many of the reserves of crude kaolin are considerably thinner than preferred for the paper industry; that is, they have an excessively high proportion of particles with an equivalent spherical diameter (D.E.E.) of less than 0.25 micron. Typical cretaceous kaolins include 25 to 50% by weight of particles less than 0.25 microns, and tertiary kaolins can include 50 to 60% by weight of particles less than 0.25 micron DEE. large amounts of very fine particles can have detrimental effects on the strength of the paper and other aspects. and are undesirable for paper manufacturers. Although said extremely fine particles can be removed by various separation processes, such as high speed centrifugation, such removal is very expensive and requires a high capital investment; in addition, there is a possible loss of high proportions of fed material.

One process to achieve aggregation is to use calcination. Thus, in US patent 4,381,948 to A.D. McConnell et al., A calcined kaolin pigment and a process for making it are disclosed. Said pigment consists of porous aggregates of kaolin platelets and exhibits high light diffusion characteristics when incorporated into paper as a filler. This pigment, which adequately corresponds to the commercially available product ALPHATEX ©, from the present transferee Anglo-American Clays Corporation (Atlanta, Georgia), is prepared first by kneading and dispersing a suitable crude kaolin to form an aqueous dispersion thereof. The kneaded and dispersed aqueous paste is subjected to a particle size separation from which a clay paste with a very small particle size is recovered; for example, substantially all particles can be smaller than

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-51 microns of D.E.E .. The paste is dried to give a clay relatively free of moisture, which is then fully pulverized to break the agglomerates. This material is then used as the feed material for a calciner; such material is calcined under carefully controlled conditions at typical temperatures of at least 900 ° C. The resulting product is cooled and pulverized, to provide a pigment of the porous, very light diffusing aggregates of kaolin platelets, as described.

calcined kaolin has also found use in paper coating applications. Reference can be made to the publication of Hollingsiuorth, Jones and Bonney, The Effect of Calcined Clays on the Printability of Coated Rotogravure and Offset Printing Papers, TAPPI Proceedings, pages 9-16, 1983, Coating Conference, discussing the advantages of incorporating p, and small amounts of calcined kaolin in conventional kaolin-based coating formulations. The gloss and opacity of the paper increase with the increase in the calcined kaolin content, as can be expected from a pigment with high light diffusion, and in some formulations the gloss may show a slight increase with the increase in the calcined kaolin content.

It is found that the calcined kaolin products, including those of the type ALPHATEX ®, mentioned above, are manufactured by relatively complex techniques, which involve several steps, including, specifically, a calcination step, plus several preparatory calcination steps and later stages calcination. Thus, said product is relatively expensive to produce and requires considerable investment in complex and similar devices, for example, calciners with many settings and the like. It can be stressed that the conditions of preparation of these materials must be controlled very carefully, in order to maintain abrasion in the products. calcined surfaces acceptably low. For example, the calcination operation itself tends to produce an abrasive product - as a result of overheating - if great care is not taken to avoid such a result.

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-6It should also be noted that, to produce a calcined product with low abrasion, the particle size of the calciner's feed material must be carefully controlled; even a relatively small increase in the size of such material can have very marked detrimental effects on Valley abrasion.

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It is known to use non-calcined kaolin (sometimes called hydrated) both as fillers for paper and for coating paper. As the non-calcined material does not normally have good light diffusion qualities or good opacity, its usefulness, especially as a filler, is limited; and this (in addition to improving the gloss) is in fact the particular advantage of calcined products of the type ALPHATEX ®; that is to say, as a result of its sacred structures, very good light diffusing properties and good opacity are provided.

Still with respect to the terminology, it turns out that in li. terature of the prior art, including numerous patents of the prior art, relating to the field of kaolin products and their processing, the term hydrated is often used to refer to kaolin that has not been subjected to calcination; more specifically, it has not been subjected to temperatures above 450 ° C, temperatures that damage the basic crystalline structure of kaolin. These so-called hydrated clays may have been produced from crude kaolin that has undergone processing, such as, for example, flotation such as foam, magnetic separation, mechanical delamination, grinding or similar comminution, but not the aforementioned heating that could harm the crystalline structure.

In a precise technical sense, the description of these materials as hydrated, however, is incorrect. More specifically, molecular water is not really present in the structure of kaolinite. Thus, although the composition can be (and often is) arbitrarily written as 2Η,? 0.Al ₂ .2Si, it is, it is now well known, that kaolinite is a hydrocarbon silicate.

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-7 aluminum oxide with the approximate composition A12 (0H) ^ SÍ205 (which matches the hydrated formula just mentioned). Once the kaolin is subjected to calcination which, for the purposes of this description, means to be heated to 450 ° C or more, for a period of time that eliminates the hydroxyl groups, the crystalline structure of the kaolinite is destroyed. Therefore, such a material, thus calcined, cannot be correctly called kaolin. Thus, it should be noted that hereinafter, in this description, when the expression kaolin or kaolinite is used, such expression necessarily implies that the original structure of the material remains intact. Thus, the expression kaolin, when used here, can be considered to be equivalent to the previous use, technically imprecise (but often used) hydrated kaolin or, sometimes. zes, simply, hydrated clay.

From time to time, it has been proposed to provide structured kaolin clusters, by processes unrelated to calcination, the aim being to produce a pigment with high light diffusion, and good opacification properties, without the need for calcination.

Thus, in US Patent 4,346,171 to Peter Economou, a structured kaolin agglomerate is shown in which the clay platelets are stabilized or frozen in position, in addition to those of a urea-formaldehyde prepolymer.

Another relevant technique includes U.S. Patent 4,072,537 to F.L.Kurrle. It contains a composite silicate pigment prepared by a precipitation reaction in which hydrated spherical metal particles are precipitated on the flat surfaces of the clay particles, which have a platelet-like structure. The metal silicate pigment component consists of the reaction product of an alkali metal silicate, soluble in water, such as sodium silicate, and a polyvalent metal salt, soluble in water, such as calcium chloride.

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- In US patents 3,853,574, 3,864,140 and 3,856,545, all by Thomas H. Ferrigno, pigment compositions are presented in which comminuted minerals, such as kaolin, are combined. inorganic binders and formed with agglomerates that, when calcined, produce compositions that include numerous particles of the minerals, joined together, and presenting internal voids and multiple light reflection surfaces. The resulting pigmentary compositions are useful in applications that require high reflectance of visible light. These products, however, are, as indicated, produced by calcination and based on inorganic binders such as glassy material, for example, an alkali metal silicate or the like.

According to what has been said, it can be considered an objective of the invention to supply a structured kaolin product that has improved light diffusion characteristics and is thus useful as an opacifying and light diffusing filler for paper and paper, and that can similarly be used in other papermaking applications, including coating it.

It is also an object of the invention to provide coated papers and cardboard products for printing purposes, such as offset printing, engraving and other types of printing, using a structured kaolin pigment.

Another objective of the present invention is to provide a pigment product with the above characteristics which is prepared without calcination and, therefore, without subjecting the kaolin to high temperatures and thus having low abrasiveness, according to the kaolin feed material. from which it is produced.

Yet another object of the invention is to provide a pigment product of the above type, which is composed of structured aggregates of tiny kaolin particles, which are chemically bonded together, that is, without the use of calcination or other high temperature techniques.

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-9 Yet another object of the invention is to provide a process, such as the one mentioned above, that allows low abrasion structured kaolin pigments to be produced from process feed materials larger than those that can normally be used in calcination, to produce a comparable, low abrasion product.

Yet another object of the invention is to provide coating compositions based on kaolin pigments and respective processes which, in comparison with conventional coating compositions based on kaolin pigments, improve the coating structure and the hiding power in papers coated with such compositions, as shown by the optical properties, such as brightness and opacity, and as shown by the printability properties, such as offset composition brightness, ink responsiveness, better K & N, less flecked and less dot failure. engraving ink.

Summary of the Invention

In accordance with the process of the present invention, a small particle size kaolin feed material is reacted, in particle form, with a metallic chloride, such as silicon tetrachloride, to form a chemically aggregated structured kaolin pigment . The free moisture present in the particulate feed material is sufficient to initiate at least a partial hydrolysis of the chloride, or metallic chlorides. However, if the humidity level is too high, it can decrease or impair the efficiency of the aggregation process. Thus, in cases where silicon and / or titanium chlorides are used, if the humidity level is too high in relation to the metal chloride (s), then the hydrolysis products of the metal chlorides will precipitate, predominantly as metal oxides, ie as silica and / or titanium gel. In the case of aluminum trichloride, if the humidity level is very high in relation to metallic chloride then the dilution of the resulting aluminum hydroxide, in the end, (in the presence of ammonia) can be so high that it causes ine67 aggregation 105

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-10 effective. In the case of silicon and titanium chlorides, the molar ratio of water to metallic chloride should be at least 0.23 and generally less than 50, with a preferable molar ratio of about 1 to 10. When using trichloride aluminum, the lower humidity limits are as indicated for silicon chloride and titanium chloride; the upper limits, in this case, are not critical, except that when the humidity level is higher than 10/6 by weight of the feed material (corresponding to a molar ratio of water to metallic chloride of about 8.2) processing as a product is increasingly difficult and may require additional drying steps.

The indicated steps are carried out under conditions such that the crystalline structure of basic kaolinite (when determined by X-ray or electron diffraction) is not altered; that is, kaolinite does not become substantially amorphous, as occurs in conventional high temperature calcination, as described, for example, in the patents of Fanselow and collators and McConnell and collaborators, Proctor. Heating can optionally be used to shorten the reaction time. However, temperatures will generally not exceed about 150 ° C. To complete the polymerization and condensation that is believed to occur, it is preferable, according to the invention, to age the resulting product, typically for at least three days.

The fed kaolin is preferably dry milled before the reaction step with the metal chloride.

metal chloride used in the invention can be one or more of the chlorides having the general formula MC1 *, where M is Si, Ti or Al, and x is 3 or 4, according to Μ. The amount of heat of metal straight used is preferably about 9,08 to 15,89 kg / ton of dry mixture. More generally, at least 4.54 kg of metallic chloride can be used per ton., Depending on the chosen level of the desired diffusion improvement, unless a level of 15.89 to 18.16 kg / ton is reached, above the which additional dissemination numbers are of limited value considering

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-lio increasing costs of the additive.

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It is preferable, in order to obtain high light diffusion characteristics, to use a small particle size kaolin in the process of the invention, preferably one in which the particle size distribution is such that about 70 to about 100% by weight of the even have less than 1 micron of DEE. When the pigment is primarily of interest for use as a filler (as opposed to use for paper coating) and when light diffusing qualities are not the primary consideration, thicker feed, for example, up to 70% by weight with at least 2 microns of DEE.

In another aspect of the invention, it is preferable to mix small amounts of an aggregation enhancing agent with the kaolin fed. Such an agent is chosen from one or more members of the group consisting of alkaline earth metal carbonates or hydroxides, or lithium carbonate.

Aggregation-improving agent mixed with kaolin should preferably supply about 5 to 120 moles of alkaline earth metal or lithium ions per 100 parts by weight of kaolin. This is equal to about 0.5 to 12% by weight of the alkaline earth metal carbonate, or hydroxide, particulate or lithium carbonate kaolin. When calcium carbonate or hydroxide, which is particularly preferred, is used, a preferred addition range is about 1.5 to 4% by weight of kaolin.

In addition, ammonia is desirably added at levels of about 3.63-7.26 kg / ton of feed mixture, with ammonia being added to kaolin and metal chloride previously combined. It appears that other improvements in the products occur when the steps of adding metallic chloride and ammonia are repeated in sequence, after the initial sequence just mentioned. However, when the pigments produced are to be used as a skin coat, it is preferable to use the ammonia treatment only after application.

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-12second sequential addition of metallic chloride.

According to the invention, urea or an organic amine, for example, a liquid or solid amine, such as a polyfunctional amine containing 2 to 6 carbon atoms, is added and can be used in place of ammonia.

It is found that the aggregate products of the invention have a pore volume that is greater than that of the kaolin / feed used to form the same, although less than that of a kaolin. in the calcined obtained from the same batch of feed. It is noted that the void void volume of the products of the present invention, when prepared from feed materials with small particle size, vary from 0.4 to 0.8 cmVg ·

It is thus found that the products of the invention have a higher oil absorption compared to the non-aggregated food material, although the oil absorption is not as high as that of a calcined kaolin prepared from the same material. The improved oil absorption characteristics provide improved printing qualities on papers in which the product is incorporated.

Essentially the process of the invention aims at the aggregation of the very fine particles (that is, less than 0.25 microns) present in very fine feed streams, of the type discussed above. These tiny particles can, in fact, serve, in the aggregates, as bridges between the larger particles (for example, with micron size) to which they are chemically bonded. Thus, an important advantage for the paper manufacturer is that the otherwise large percentages of unwanted extremely fine particles have actually been removed as separate entities, but without the need for separation steps, along with the expensive equipment required by such operations.

Unexpectedly it was found that the structured kaolin pigments produced by the previous process allow for the preparation of surprisingly improved coated papers, as well as cardboard products. More specifically, by using 'Λ

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From said pigment coating formulations are obtained which provide a dense structured coating, giving improved coverage, gloss, opacity and particularly improved appearance, for certain coating weights. In relation to the final paper product, these benefits can be obtained in the form of either improved sheet properties, or for example. coating gaps significantly reduced. The resulting coated papers are found to have properties suitable for offset, engraving, print and similar contact printing.

When used in paper coating applications, the structured kaolin pigments of the invention comprise from about 5 to 60%, preferably from about 10 to 30% by weight of the total pigment component of the coating composition. The pigment balance can comprise any of the known coating pigments, such as coating grade kaolin, calcium carbonate, titanium dioxide, plastic pigments and the like. The coating compositions, in addition to the pigment component, include conventional components such as adhesive binders, dispersants and other known additives.

Brief Description of Drawings

Figure 1 is a graph showing the effect of using a filler comprising a kaolin treated with calcium carbone, ethylenediamine, silicon tetrachloride and ammonia, on opacity compared to the use of Alphatex (a calcined kaolin) and clay load; and figure 2, similarly, shows the effect on the crossing by ink.

Detailed Description of the Invention

In a presently preferred process, said pigment is; trutured can be produced by the chemical reaction of a classified and pulverized kaolin to which about 0.4 to 12% by weight of calcium carbonate or hydroxide has been incorporated,

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-14 as an aggregation enhancer, with silicon tetrachloride, the latter being intermixed with clay at room temperature (259C) and in the proportion of 9.08-15.89 kg / ton of dry feed material.

content of the feed material in free moisture is preferably such that it provides a water to metal chloride molar ratio of about 1:10. These levels are sufficient to hydrolyze SiCl3, to initially produce monosilicon acid, without, however, being sufficient to precipitate free silica.

Silicon tetrachloride can be intermixed in liquid or vapor form.

want fast and intimate mixing apparatus between low shear end devices.

is made by the contact of the mixers

A suitable intermix is capable of reagents. The, including known mixing paddle mixers, are suitable

The mixture of mechanical and other feed material for this and silicon tetrachloride can then be exposed to ammonia, for example, by addition. gaseous ammonia in the proportion of about 3.63 per ton of feed material, neutralize

Ammonia the acid by-products and contributes to the 7.26 kg serves for the binding, possibly by the formation of process-type polymers

Si _n - (NH)

Organic, for example, a liquid or solid amine used in place of ammonia; in this case, the conditions to be employed are similar, except that the addition of base and metallic chloride is more flexible, urea, generally it can be added before the mixture of silicon tetrachloride, generally not hurting to add before lice addition, amines an amine can be

When • it can be done before or preferably before, it is from 3.63 to 9.08 kg / ton if using liquid mines, or with after;

In the case of organic amines, pre after the tetrachloride itself. A useful addition range for feed material is 3.63-7.26 kg / ton

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of feed material. Urea is preferably added in the range of 4.53-9.08 kg / ton of feed material. Such amines include ethylenediamine, hexamethylenetetramine and triethylenetetramine. Similarly, aminosilanes, for example, 3-aminopropyltrimethoxysilane, can be used in the invention.

During mixing, a rapid initial reaction occurs between the kaolin particles and the reagents. The subsequent aggregation and bonding process is relatively slow and is completed in about three days. Heating to temperatures up to 15 ° C, after incorporating the reagents into the feed mixture, can help expel undesirable volatile products, but such heating is not a necessary condition for the present process which is carried out effectively without the need for any heating.

Other processing steps can be used in the process, silicon, characteristics

For example, if the depending on the intended use of raw material, characterize the initial before the intermixture of the clay with tetrachloride. prejudicial to such improvement or it will be minimal; that is, in many size classes it should be noted that, as it uses heating to elect cases, it will be sufficient to simply particle the process of the present invention not

Among other things, and because there will be no high temperatures, as occurs during calcination, the presence of impurities that are considered highly undesirable in calcination processing, such as glass-forming oxides, is not of fundamental importance in present invention. This is, in fact, one of the main advantages of the present process, since a minimum improvement of the crude clay is necessary. As heating at high temperatures is not used, the product of the invention exhibits an abrasion value that is in accordance with the feed kaolin used in the process. In fact, the typical abrasions of the products of this invention are basic.

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-16th less than 15, while all abrasions are l / alley abrasions determined by the Institute of Paper Chemistry, procedure 65.

Especially when the objective is to achieve a very high diffusion coefficient in the product, the classification of the raw kaolin starting material can be an important consideration in the present invention, since in the case of the US patent N9.

381 948 by McConnell and colleagues, the resulting aggregates have light diffusing qualities (and consequent opacity when used on paper) partially with a function of the fineness and uniformity of the particles that make up the aggregates. Thus, for example, the use of a thin, classified clay fraction, for example, one in which a very high percentage of it is less than 1 micron in equivalent spherical diameter (DEE) produces an unusually good product in the present invention. , for the same reasons that are presented in the patent of McConnell and collaborators. Classification in such a fine degree, however, may not be necessary or appropriate, when the desired final product does not need to have unusually good opacifying properties or light diffusers. Thus, more generally, when the classification of crude kaolin is considered desirable, a feed fraction for the present process can be provided in which at least 88% by weight of the particles have less than 2 microns of DEE. (Except as mentioned above, when the product is intended for paper coating applications, the feed fraction should preferably be at least 94% by weight of particles with less than 2 microns DEE). Classification can be conducted by several techniques known in the art, including air classification or aqueous classification techniques.

brightness of the pigments provided by the invention is mainly influenced by the raw starting kaolin and the processing, if any, to which the kaolin was subjected before being processed according to the present invention. Depending on the particular end use of the pigments produced by the envy, the final GE gloss can vary from 75 to more than 90.

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-17 pigments are used for coating applications, feeding the kaolin to the pigment production process. streaks can have a GE gloss in the range of about 80 to 92.

chemical reaction step, consisting of the intermixing of the kaolin feed with silicon tetrachloride, is carried out by the addition of silicon tetrachloride while the mixture is being processed. Once the intermix is completed, the resulting product is aged, preferably for a period of at least 3 days, to improve the diffusion properties of the aggregated kaolin particles.

The quality of the resulting products, made by proces. The invention depends, in part, on the physical and chemical properties of the raw kaolin used as raw materials. A wide range of raw kaolin can be used in the invention. The raw material can be processed by conventional procedure in the field, including so-called dry processing and / or so-called wet processing. When proces is used. itchy to wet, it can, in some cases, be limited to aqueous classification. In other cases, depending on the nature of the raw material and the desired product, additional known processing techniques can be used to remove unwanted elements or contaminants from the kaolin. Similarly, classification can be carried out as part of the wet processing treatment. In a typical sequence known to pa. In wet processing, for example, the raw material can be kneaded and dispersed and then subjected, for example, by centrifugation, to separation by particle size, as an aqueous solution or dispersion, from which a clay suspension is recovered. where a desired percentage of particles is below a specified limit. This suspension can be dried to give a clay that has a very low moisture content, usually one in which less than 1 / wt.% moisture is present. Drying, in this case, is preferably done by spraying. The addition of carbonate or calcium hydroxide. calcium is preferably carried out by mixing in said material, before spray drying.

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-18 Because of its relatively low cost and easy availability, silicon tetrachloride is a present reagent, preferred for use in the process of this invention. However, other metal chlorides can be used effectively in the invention. More specifically, the metal chlorides that have the general formula MC1, where x can be 3 or 4, according to M, and M is Si, A1 and / or Ti. The hydrolyzed products of the indicated metal chlorides have an appropriate structure that will allow them to adapt within the kaolin tetrahedral crystal structure. Similarly, although calcium carbonate is a preferred aggregation-enhancing agent for use in the process of the invention, other alkaline earth aX metal carbonates or hydroxides, or lithium carbonate, are usable in the invention.

A preferable addition range for the aggregation improving agent is 1.5 to 4.0% by weight of the feed mixture.

Coarse calcium carbonates or hydroxides are less effective in the present invention, where it is preferable, instead, to use the so-called types for paper of fine, ground or precipitated calcium carbonates, that is, the same types that are used as fillers for paper and for paper coating. A suitable material for use in the process of the invention is CARBITAL 50 or CARBITAL 90, products of Atlantic Carbonates of Baltimore, Maryland. These products have, respectively, particle size distributions such that 50 and 90% by weight, of them, have less than 2 microns of D.E.E ..

Although the applicant does not wish to be attached to any specific theory of the present invention, it is hypothesized that the effectiveness of the present invention may result in part from the hydrolysis of silicon tetrachloride, which leads to monosilicic acid which reacts immediately with the surface of the kaolin, or polymerizes and then reacts with the kaolin particles. However, the immediate reaction is believed to be more likely. The addition of ammonia or urea, or an amine, helps to neutralize the acid resulting from the first reaction indicated above and improves the condensation reactions of monosilic acid.

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conical. Ammonia, urea or amine can also form silicon-amine polymers that would improve and bind the particles more. The improvement of the present process is carried out by the addition of the metal ion of the improving agent which is believed to result in the formation of metal silicates which function as binding agents, giving stronger aggregates, and which also help to neutralize acid by-products.

As shown above, ammonia, a gaseous base, can be used to neutralize acid by-products of the chemical reactionulinite and metal chlorides easily hydrolyzed between z

viable. Also described is a process of chemical aggregation and effective neutralization of acid by-products with solid or liquid organic bases.

das tion

up

The solid or liquid bases are preferred, given their ease of handling associated with i --- * ------- ~~~ with the hazardous gasses also verified that they are aggregation, as well as that, the organic bases phyllic and elimination with the handling of gaseous ammonia. There is a reduction of one step in the proces. repeated application of the base and in addition tend to make the aggregate more oil

Oil absorption is further improved by applying pigments to printing papers, which is useful. Improvement in ink crossing is achieved.

The inuence is further illustrated by the examples that follow, which should only be seen as illustrative of the present invention and not limiting it.

General Process of Preparation of Feed Clays for

Examples I to VI

The feed clay was prepared by applying a fine kaolinite derived from northeastern Georgia and which comprised a material of very fine particle size, having a GE shine in the range of 82 to 87 (in all cases of this description, it is understood -the brightness values are obtained according to the standard specification established by TAPPI, procedure T-646 os-75); or a mix of small particle kaolin from northeast Georgia with a GE shine of around 87.

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-20The crude clays were processed according to the general practice used in the kaolin processing industries. you. The processed clays were classified by centrifugation until 96% had less than 2 microns of D.E.E .. The classified clays were flocculated using 0.25% by weight of aluminum sulfate and adjusting the pH to 5.5 with sulfuric acid. The flocculated kaolinites were filtered. The significantly dried kaolinites (remaining about 20% moisture) were then redispersed with 0.25% by weight of sodium polyacrylate and with adjustment from pH to 7.0. Kaolinites redispej? These were then spray dried. The humidity of the dry products was about 1.0% by weight.

Example I

Chemical Aggregation in the Presence of Organic Base with Short Chain, Urea;

spray dried kaolin product was sprayed by means of a laboratory spray, and is referred to herein as Control-I. The pulverized clay was mixed with 3.0% by weight of ground calcium carbonate, supplied by Atlantic Carbonates Corporation, in a suspension at 75% by weight. The mixture was dried in an oven at 150 ° C for 15 minutes and sprayed again, referred to as Control-II. The dry product was then mixed with 1.5% by weight of finely ground urea, supplied by Fisher Scientific Products. The resulting kaolinite is called Feed Clay-I.

g of Feed Clay-I were mixed with 1.0% by weight silicon tetrachloride in a high speed Waring mixer. The mixture was subjected to a light vacuum for 5 minutes and the process was repeated. The final product was dried at 150 ° C for 15 minutes, giving Product-I. The Product-I was allowed to age for 3 days and tested for optical diffusion property on paper. The results are shown in Table I. It should be noted that there is a gain of 74 fusion units compared to Control-I.

In this and subsequent examples, all data from di67 105

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-21 fusion are normalized by comparison with the sample diffusion coefficient of the Alphatex ® mentioned above. Ideally, in a study of this nature, the same batch of beaten pulp should always be used. As this is not practical, the process adopted was to load a group of sheets, in each series of tests, using the same Alphatex from series to series. Statistically, samples loaded with Alphatex at 1D% load, had a strain. diffusion factor of 700 cm / g, and in each series where Alphatex differs from 700, the diffusion coefficients of the experimental samples were correspondingly adjusted proportionally to the adjustments that the paper containing Alphatex requires. to bring its value to 700 cm ^ / g. This procedure is sometimes referred to here as normalizing the diffusion coefficients.

Example II

Chemical aggregation in the presence of short chain aliphatic amine, ethylenediamine;

Feed clay-II was prepared using Contro. lo-II, described in Example I, the control-II was treated with 1.0% by weight of ethylene diamine, supplied by MCB - Company, the product being referred to as Feed Clay-II.

g of Feed Clay-II were mixed with 1.0% by weight silicon tetrachloride in the high speed Waring mixer. The mixture was subjected to a slight vacuum and exposed to about 1.0 / 4 by weight of ammonia gas. These steps were repeated. The resulting Product-II was then opened in the air and allowed to age for three days. The aged samples were tested as in Example I. The results are shown in Table I. Note that the diffusion at 10/4 load levels is 80 units higher than for Control-I. In addition, the simple mixture of Control-I with 3/4 of ground calcium carbonate (which was of the type for paper coating, 90/4 by weight of which it had less than 2 microns of DEE) and 1/4 of ethylenediamine gave a gain of 53 units of diffusion.

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The products of the invention also exhibited oil absorption, increased when compared to the control clays. This is illustrated in the data in Table II which compares oil absorption for a series of samples, including Control I and Control I reacted with SiCl ^ above, and in which several short chain amines are used, together with SiCl ^. The amines, although preferably added before the metal chloride, can also be added during the reaction, including after the addition of metal chloride to the mixture. The oil absorption values were in all cases determined by the TAPPI procedure.

Figures 1 and 2 show the ‘comparison

favorable product-II with Alphatex, in opacity and crossing of paint. TABLE I • Standardized diffusion of aggregate kaolinites chemically with application of urea and ethylenediamine Diffusion of light Material to 10 / o of charge Control-I 516 Control-II 543 Feed Clay-I 545 Feed Clay-II 569 Product-I 590 Product-II 596

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-23TABELA II

Effect of the addition of organic amines on the absorption of chemically added kaolin pigment oil

Material

Oil absorption g / 100 g clay

Control-I52.0

I-Control + 1% SiCl ^ 61.0

Control-I + 0.4% Diethylenetriamine followed by 1% SiCl ^ 74.2

Control-I + l / o SiCl ^ followed by

0.4% Diethylenetriamine72.4

Control-I + 1% 3-Aminopropyl-tri-methoxy-silane followed by 1% SiCl ^ 74.2

Control-I + 1% SiCl ^ followed by 1.0 / 3-Aminopropyl-trimethoxy-silane67,6

Product-I (as defined above) 66.3

Product-II (as defined above) 65.3 oil was linseed oil and was used according to the TAPPI procedure. The process was a common scraping process with a spatula. The specific gravity of the oil was 0.95 g / ml.

Example III

Chemical aggregation in the presence of cyclic amine, hexamethylenetetramine initial process is similar to the preparation of Control-II, described in Example I. Control-II was then mixed with 0.4% by weight of hexamethylene-tetramine, to give Arpi la Power Supply-III.

g of Feed Clay-III were treated with 1 wt% silicon tetrachloride, evacuated for 5 minutes and again treated with 1.0 wt% silicon tetrachloride. The mixture was exposed to air and dried at 150 ° C for 15 ml

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..... Ί; * «-24nutos, to give Product-III. The dry Product-III was aged for three days and tested as in Example I. The results are given in Table III. Note that there is an increase of 57 diffusion units, after chemical aggregation. It should also be noted that simply mixing Control-II with hexamethylenetetramine leads to an increase of 31 diffusion units.

Example IV

Preparation of Control-III Control-III was prepared from Control-I by mixing with 0.4% by weight of hexamethylenetetramine and drying at 150 ° C for 15 minutes; that is, it does not contain calcium carbonate. Control-III shows an increase of almost 13 diffusion units, without any other chemical treatment. The result is given in Table III.

Example V

In this example, Feed Clay-III was treated with a sequence of 1.0 wt% silicon tetrachloride and 0.4 wt% ammonia, according to the procedure described in Example II. The product IV was dried at 150 ° C for 15 minutes and aged for three days, and tested according to Example I. The result is shown in Table III. Note that the increase in diffusion units was 61 units, compared to Control-I. Note also that the difference in diffusion units between Product-ΠΙ and Product-IV is only four units, which is within the measurement limitation. These results indicate that a solid organic base, instead of gaseous ammonia, can be used in the chemical aggregation

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-25TABELA III

Normalized diffusion of kaolinites chemically aggregated with

application of hexamethylenetetramine Diffusion of light Material at 10% load Control-I 520 Control-III 533 Feed Clay-HI 551 Product-IH 577 Product-IV 581

Control-I, using ground calcium carbonate and ethylenediamine.

Feed Clay-IV: Control-I was mixed with 0.8% by weight of ethylenediamine.

Feed Clay-V: Control-I was mixed with 2% by weight of calcium carbonate and 0.4% by weight of ethylene mine.

Feed Clay-VI: Control-I was mixed with 2.0% by weight of calcium carbonate and 0.8% by weight of ethylenediamine.

The Food clays above were added as follows:

Product-V: Control-I was treated with 1.0 wt% silicon tetrachloride, evacuated for 5 minutes and exposed to 0.4 wt% ammonia. The above process was repeated and the final product was dried at 150 ° C for 15 minutes and aged for 3 days.

Product-VI: the overall process was identical to the production of Product-V, but this time 75 g of

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Power Supply-IV.

Product-VII: the feed clay and the process were f

the same as for Product-VI, but ammonia was not used.

Product-VIII: the process was identical to that used in the preparation of Product-V, but 75 g of Feed Clay -! / Were used.

Product-IX: the process was identical to that used in the preparation of Product-VIII, but no ammonia was used.

Product-X: the production process was identical to that used in the preparation of Product-VIII, but 75 g of Feed Clay VI were used.

Product-XI: the production process was identical to that used in the preparation of Product-IX, but 75 g of Feed Clay-VI were used.

All products, feed clays and controls were tested for performance, as described in Example I. The results are provided in Table IV. Note that the effect of organic amine on aggregation is much weaker in the absence of ground calcium carbonate. However, when calcium carbonate was present, chemical aggregation was as effective as in the presence of ammonia gas.

FOLLOW TABLE IV

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-27 TABLE IV

Normalized diffusion of chemically aggregated kaolinites with the application of ethylenediamine

Material Light diffusion at 10% load Control-I 521 Feed Clay IV 540 Feed Clay V 549 Feed Clay VI 561 Product-V 575 Product-VI 549 Product-VII 572 Product-VIII 593 Product-IX 587 Product-X 588 Product-XI 579

Example VII

Chemical aggregation in the presence of urea:

A series of experiments similar to that of Example VI were performed, using urea as a solid organic base. The results are shown in Table V.

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-28TABELA V

Chemically normalized kaolinite diffusion aggregated, with urea application Diffusion of light Material at 10% load Feed-A, Control-I + 1.0% urea 525 Feed-B, Control-I + 1.5% urea 529 Power-C, Control-I + 2.0% 540 Calcium carbonate + 1.0% urea Feed-D, Control-I + 2.0% 539 Calcium carbonate + 1.5% urea Feed-A handled by process-1 575 C-feed treated by process-1 566 Feed-B treated by process-1 565 Feed-B treated by process-2 575 D-feed treated by process-1 563 D-feed treated by process-2 570

process-1 refers to a chemical treatment in which no reaction was used.

process-2 refers to a chemical reaction in which 0.4% by weight of ammonia was used after each treatment with silicon tetrachloride.

Although the present invention has been particularly presented in terms of its specific embodiments, it should be understood, in view of the present disclosure, that numerous variations of the invention are now made possible to those skilled in the art, which are within the scope of the present teachings. Therefore, the invention must be widely seen, and limited only by the scope and spirit of the attached claims.

Claims (20)

1 - Production process of a structured kaolin pigment, with improved light diffusion and opacification properties, when incorporated into paper, characterized by the fact that it comprises the steps of: (a) forming a kaolin feed mixture with a fine particle size; and (b) aggregation of the kaolin particles to form the structured pigment, by combining said particulate feed mixture, with a metallic chloride that has the general formula MC1, where M is Si, A1 or Ti, ex is 3 or THE 4, in accordance with M, and with urea or an organic amine; the moisture level present in said feed mixture being reacted in step (b) sufficient to hydrolyze, at least partially, the metal chloride; and steps (a) and (b) being conducted under conditions such that the basic crystalline structure of kaolinite is not altered. Process according to claim 1, characterized in that urea is used. Process according to claim 1, character. used by the use of a liquid or solid polyfunctional amine containing 2 to 6 carbon atoms. 4 - Production process of a structured kaolin pigment, having improved light diffusion and opacification properties, when incorporated into paper, characterized by the fact that it comprises the steps of: (a) forming a feed mixture of a kaolin with a fine particle size together with an aggregation-improving agent selected from one or more elements in the group consisting of alkaline earth metal carbonate or hydroxide and lithium carbonate, the improving agent being present in amounts that provide about 5 to 120 millimoles of metal ion as the improving agent for 67 105 SK-862 Portugal 100 parts by weight of kaolin; and (b) aggregation of the kaolin particles to form the structured pigment, by combining said feed mixture in the form of particles, with a metallic chloride that has the general formula MCl, where M is Si, AI or Ti, ex is 3 or 4, according to M, and with urea or with an organic amine; the moisture level present in said feed mixture, reacted in step (b), sufficient to hydrolyze, at least partially, the metal chloride; and steps (a) and (b) being conducted under conditions such that the basic crystalline structure of kaolinite is not altered. Process according to claim 4, characterized in that said metal chloride comprises silicon tetrachloride and in that the moisture level in said feed material is lower than that in which the hydrolysis predominant product is silica. Process according to claim 4, characterized in that step (b) includes the step of heating the reagents to temperatures not exceeding 150 ° C. Process according to claim 4, characterized in that it includes the steps of aging the product of step (b) for at least three days, to improve the diffusion properties of the aggregated kaolin particles. Process according to claim 4, characterized in that said particulate kaolin such that it has a size distribution of 70 to 100% by weight is less than 2 microns of equivalent spherical diameter. Process according to claim 4, characterized in that the feed mixture, submitted to step (b), has a moisture content such that it provides a water-to-metal chloride ratio of about 1 to 10. 67 105 SK-862 Portugal Process according to claim 4, characterized in that the feed mixture subjected to step (b) has a free moisture content such that it provides a water to metal chloride molar ratio of less than 50. Process according to claim 4, characterized in that said kaolin used in step (a) is the product of the air classification of a raw kaolin clay to a size at least ^ so thin that 88 / less than 2 microns. Process according to claim 4, characterized in that said aggregation-improving agent comprises from 0.5 to 12%, by weight of the kaolin, of a particulate alkaline earth metal carbonate or hydroxide. Process according to claim 12, characterized in that said improving agent comprises calcium carbonate. Process according to claim 13, characterized in that the feed mixture of kaolin and calcium carbonate is dry milled before step (b). Process according to claim 4, characterized in that said organic urea or amine is added at levels of 3.63 to 9.08 kg per ton of said feed mixture. 16 - Process for the production of a structured kaolin pigment, having improved light diffusing and opacifying properties, when incorporated into paper, characterized by the fact that it comprises the steps of: (a) forming a kaolin feed mixture, with a fine particle size with an aggregation-improving agent selected from one or more elements in the group consisting of alkaline earth metal carbonate or hydroxide and lithium carbonate, the improving agent being present 67 105 SK-862 Portugal -32 in amounts that provide about 5 to 120 millimoles of metal ion as the improving agent per 100 parts by weight of kaolin; and (b) aggregation of the kaolin particles, to form the structured pigment, by reacting said feed mixture in the form of particles with a metallic chloride that has the general formula MC1, where M is Si, A1 or Ti, ex is 3 or 4, X in accordance with M, and in the presence of urea or an organic amine; the moisture level being present in said alj mixture. mentation reacted in step (b) sufficient to hydrolyze, at least partially, the metal chloride; and steps (a) and (b) being conducted under conditions such that the basic crystalline structure of kaolinite is not altered. Process according to claim 16, characterized in that ammonia is added to the reagents. according to said urea or 18 - Process, performed by the fact that there is nothing to the feed mixture. claim 16, that the organic amine is added Process according to claim 16, characterized in that an organic amine is used which is added to the reactants in step (b). character is postponed. 20. The process according to claim 16, characterized in that an organic amine is used which is an amino-silane. ·