FI123224B - Fiber product and process for its manufacture - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a fiber product containing a pulp or wood fiber, and to a process for the manufacture of this product in which filler particles are attached between the pulp or wood fibers and fibrils, followed by the production of pulp or paper.

Description of Prior Art

The fillers or pigments used in the manufacture of paper and board are typically smaller than 5 µm in average particle size and are light in color. The most typical excipients are kaolins, talc, powdered calcium carbonate and precipitated calcium carbonate. In addition, there are more expensive so-called special pigments such as precipitated aluminum silicates, satin white and titanium dioxide. The exact demarcation between fillers and coating pigments is difficult, but roughly the fillers are coarser in size than the pigments used in the coating. The optimum particle size for most common fillers and coating pigments would be 0.4 to 0.5 µm to maximize light scattering. Typically, the coating pigments are 0.5 to 1 µm and the filler materials are 1.5 to 4 µm in average particle size.

A problem with fillers commonly used in the manufacture of paper and board products is that they weaken the final product. Paper grades with high filler content, such as copy paper and certain magazine papers, in particular, would need

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o 25 generally better stiffness compared to the current situation. The need for rigidity is also emphasized by the need for lighter basis weights for paper and board making. The stiffness of the co paper generally decreases as more filler is in the paper or if x basis weight is reduced. This reduction in stiffness, together with the decrease in strength, is therefore one of the major quality problems in the use of fillers in printing papers. This problem has traditionally been solved either by adding a separate strength enhancing additive or by reducing the amount of filler. However, due to the price and properties of pulp, this is not profitable.

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The most common clay mineral used as a filler in paper and board production is kaolin, which consists mainly of kaolinite. The kaolin mineral has a two-layer, plate-like structure with a tetrahedral silica layer and an octahedral alumina layer. The layers are interconnected by oxygen atoms. Because of the silanol groups 5 of the kaolin surface, the kaolin mineral surfaces are negatively charged and the edges positively charged when slurried in water. Kaolin can be produced by the dry or wet process, of which the wet process can chemically influence the final brightness of the kaolin at different stages of the process. The most common commercial grades of kaolin are water-washed, delaminated, calcined and chemically structured kaolin. The water wash often contains 10 several kaolin plates adhered to one another on their surfaces. In the delaminated grades, kaolin surfaces are separated by milling into smaller groups and individual kaolin plates. The calcined kaolins are prepared by partially melting kaolin plates having a suitably small particle size at about 1000 ° C. At temperatures above 450 ° C, the structure of kaolin crystals begins to change. Metakaolin is called 500 kaolin crystals heated at a temperature of about 15 ° C to about 800 ° C. The benefits of metakaolin and calcined kaolin are particularly visible in the improvement of brightness and opacity compared to water-washed and delaminated kaolin. This is based on the fact that the kaolin calcined between the kaolin plates has air-kaolin interfaces which scatter light efficiently. In addition, the pores formed in the structure of the structured kaolins help the ink to settle. The formation of the same interfaces is based on the production of chemically structured kaolins, but in this case the interfaces can be chemically bonded to each other - not by means of high temperatures. The luminous potency of chemically structured kaolins is usually between delaminated and calcined kaolins.

c \ j δ 25 The main disadvantage of using kaolin, like other fillers, is paper or cardboard.

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σ> deterioration of the strength of the tonic structure, especially when replacing the chemical pulp with a filler. This is because the fillers prevent the formation of hydrogen bonds between the fibers by adhering to the fiber surface.

□ _ 00 $ 5 30 EN 20020566 has shown that using an average particle size? structured aggregate agglomerates larger than 5 micrometers are achieved at the same time

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with a filler content, a higher street network strength is achieved than with normal fillers of less than 5 micrometers. FI publication 20085227 further demonstrates that by improving the hydrogen bonding capacity of the 3 surfaces of aggregate aggregates over 5 micrometers, further improvement in the strength and stiffness of the street network is achieved.

In this way, filler particles have been obtained which are of a size suitable for filling the gaps between the pulp fibers. In this way, the necessary strength of the fiber product has been achieved while a part of the pulp has been replaced. In general, however, in the prior art, attaining strength has been sufficient. However, another purpose of fillers and additives is retention, which is very difficult to improve while improving the strength of the product.

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In the manufacture of paper or board, it is known to form a paper or board product by removing water from the solids slurry. Water is by far the largest raw material by volume, with the aim of eliminating it as quickly as possible through wire, press and drying parts of the final product. Dehydration is one of the most important factors influencing the economics of papermaking, which is sought to be affected chemically by various flocculant and coagulants. Wire, press and dryer parts are used to mechanically dehydrate. More efficient dewatering also results in a reduction in the amount of drying energy required by the drying section.

20 Various fillers also bind water less than fiber, which in turn contributes to the economic benefits of their use through accelerated dewatering. The lower water-binding capacity is reflected in the wire, press and dryer sections for faster dewatering and thus lower energy costs in drying using a filler.

c \ i 0 25 Fillers and fibers are generally anionic in charge. Therefore, in order to improve filler retention g, it is generally necessary to introduce a cationic charge in the form of ions or polymers co into its fiber mass to attach the filler to the fiber network. In printing papers, the filler contents are about 30% based on dry fiber. Retention can be divided into mechanical

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and the chemical, of which the chemical is definitely more significant. Mechanical retention is more significant for high basis weight cartons, o δ C \ |

The reduction in the strength and stiffness of a paper or board product when replacing the fiber with a filler is mainly due to the fact that the fillers weaken the formation of hydrogen bonds between the fibers since the surface of the fillers does not form hydrogen bonds. Today, filler 4 is added directly to the fiber pulp. With the wire section, only a portion of the added filler adheres to the finished paper or board web. The remainder of the filler material eventually passes through the circulating water system into part of the finished paper or board structure, but the risks of various runnability problems have increased due mainly to the adhesion of various hydrophobic substances to the circulating water system fillers. The resulting runnability problems are usually manifested in paper or board machines, for example, in the form of stains or breaks in wires and blankets. Some of the filler material in the circulating water system also eventually loads on the wastewater treatment plant, as it is not always transported with the finished paper or board out of the process.

Thus, there would be a need for a fiber product having a filler adhere more effectively to the fiber while providing the product with advantageous strength properties, preferably further improved compared to known solutions.

Brief Description of the Invention

It is an object of the present invention to provide a novel paper or board product having high strength and high opacity.

In particular, it is an object of the present invention to provide a novel paper or board product containing filler adhering granules as well as carbonates adhering to fibrils.

The object of the present invention is to utilize aqueous carbonate contents

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o 25 salt compositions for the production of structured kaolin slurries in the manufacture of paper and board products.

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cö work. This ensures the fastest dewatering with a high wire retention cp co wire section and an improvement in certain paper and board quality properties. For bonding kaolin sheets, inter alia, latexes may be used as binders,

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Q_line sheets and stacks can be joined together to form granules or agglomerates of kaolin slurry co $ 5 30 tea by blending technique or spray drying. The object is to provide structured kaolin with an average particle size of more than 5 micrometres. The thus-dried structured kaolin can be further converted into calcined kaolin or metakaolin by heating in an oven. The improvement is achieved by using the aqueous solution of structured kaolin slurried in accordance with the invention in paper or board manufacture, whereby the wire section utilizes faster dewatering and higher retention. From the kaolin slurry prepared for aqueous salt preference, the carbonate filler is precipitated into the fiber structure by raising the pH, pressure or temperature, preferably downstream and / or after the press section. The aim is to obtain the desired amount and distribution of precipitated carbonate filler in the lumen and fibrils of the fibrous structure, whereby the anti-rigidity of structured kaolin can be prevented. At the same time, the resulting carbonate filler enhances the brightness, opacity and printability achieved with structured kaolin alone. In an ideal paper or board structure, the carbonate filler in the fiber fibrils would, among other things, increase stiffness, and the structured kaolin would be in the gaps in the fiber network, resulting in less fillers or pigments.

The present invention thus relates to a fibrous product containing a pulp or wood fiber, which product is preferably paper or paperboard, and to a process for the manufacture of this product in which filler particles are fixed between the pulp or wood fibers and fibrils followed by producing said paper or board.

More specifically, the fiber product of the present invention is characterized in what is set forth in the characterizing part of claim 1.

The process for producing a fiber product according to the invention, in turn, is characterized by what is stated in the characterizing part of claim 10.

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o 25

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σ> The present invention is multifunctional and improves a number of features: both the quality properties of paper and i co carton and the economic performance of the manufacturing process. By combining the carbonates of the appropriate size with the structured kaolin particles of the appropriate size,

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Among other things, the invention allows for improved brightness, opacity and printability while accelerating dewatering and retention? the wire section. An additional benefit of using kaolin is the fiber content of the precipitated carbonate filler.

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further enhancing the stiffness, opacity, lightness and printability of the structure. At the same time, part of the fiber of the end product has been replaced by a filler without loss of strength properties.

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Detailed Description of Preferred Embodiments of the Invention

The present invention relates to a fiber product containing cellulosic or wood fiber having filler particles attached between the fibers and the fibrils, some of which are structured, agglomerates or granules of kaolin, metakaolin or calcined kaolin, and some of the carboxylic acid salts or salts thereof, different states.

The present invention demonstrates that using an aqueous salt composition for preparing a structured kaolin slurry and raising the pH of the paper or board pulp diluted with the composition with a base and / or raising the temperature, optionally simultaneously increasing the solids content of the pulp, results in precipitated carbonate additive. This precipitated carbonate filler has a positive effect on the lightness, opacity, printability (ink absorption properties), thickness and stiffness of the paper or board product.

Structured kaolin particles can be present in the product up to 25% by weight of dry matter, at least 5% by weight of fiber. They are substantially spherical in size and are > 5 µm, preferably 10 to 40 µm, more preferably 20 to 40 µm. They are chemically structured kaolin agglomerates or granules, optionally treated such that their portion, preferably the surface, has been calcined or converted to metakaolin. The kaolin filler is preferably delaminated, water washed, dry graded or treated by two or more of the above processing methods.

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The carbonate, in turn, contains at least 0.01% by weight of dry matter in the product, for example 0.01-5% by weight, especially 0.01-3% by weight. The carbonic acid salts are at normal pressure x carbonate or bicarbonate salts, preferably bicarbonate and colloidal carbonate.

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They may have an average particle size <0.3 nm, preferably <0.1 nm. oo £ 30

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In the present application, I- '' colloidal carbonate particle '

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nitrates having a small average particle size of less than 300 nm, preferably less than 100 nm.

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The carbonic acid salts or esters are preferably formed from the corresponding oxide or hydroxide and are an inorganic or organic salt or a composite or mixture of several salts, preferably a calcium or magnesium salt or a mixture thereof.

According to a preferred embodiment of the invention, the filler particles are bonded to each other and to the fibers by a binder, preferably latex, silica, alum or aldehyde or a mixture thereof, preferably in an amount of 0.5 to 50% by weight.

The product may further contain other retention agents or flocculating or coagulating microparticulate or mixtures thereof, preferably at least microparticles, preferably in combination with conventional retention agents.

Various synthetic and natural polymers serve as retention agents in the invention. Polymers of nature are commonly called polysaccharides. An example of this is starch-15, which is the most commonly used natural polymer in the manufacture of paper and board, if fibers are not taken into account. Synthetic polymers include polyacrylamides. In particular, the polymer is selected from the group consisting of polyacrylamide, polyethyleneimine, starch, polydadmac, polyacrylamide, polyamine, a starch-based coagulant, a copolymer of the foregoing, or a mixture of two or more such polymers or copolymers. Most preferably, the polymer is polydadmac, polyamine, polyacrylamide, or a copolymer of two or more of these.

Inorganic so-called microparticles are preferably used in combination with these polymeric retention agents to improve dewatering, retention and formation. Of these non-organic microparticles, colloidal silica (polysilicic acid, silica wart, <i> microgel, etc.) and bentonite are particularly well suited for this purpose. Other exchange conditions include other bentonite or silica sols, gels, microgels, silicas and polysilicic acids, or mixtures thereof.

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The product may also contain one or more chemicals known per se selected from aluminum compounds, mass adhesives, surface adhesives, mucilage agents, dyes, starches, optical brighteners, dispersants, antifoams, plastic pigments and conventional fillers.

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The present invention also relates to a process for the preparation of such a fiber product, comprising: - adding an oxide or hydroxide to a hydroxide slurry in an aqueous solution and lowering the pH of the solution to 6.0-8.3 by passing carbon dioxide into a solution such that the whole solution, based on the weight of the solids, to form a salt composition, slurry the kaolin sheets or stacks or both together with the binder in water to form the kaolin composition, - to produce the to form structured kaolin particles or to form these structured kaolin particles by slurry in the salt composition described above or in 15 - optionally mixing the spray-dried structured kaolin particles with the salt composition or solubilized portion thereof described above, mixing the formed structured kaolin particles with the salt composition or the solubilized portion thereof, and 20 - precipitating the carbonate from the salt composition into a dispersion into particles while filtering, compressing and drying the dispersion into paper or board.

Briefly, in the process of the present invention, a solid of paper or board pulp is diluted with a kaolin composition slurried in a salt composition of the invention.

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The salt composition consists of carbonate states, i.e. carbonates and bicarbonates, and calcium or magnesium ions or a mixture thereof, added and produced in an aqueous solution at a pH of less than 8.3 throughout the production step. These carbonate forms may include, but are not limited to, colloidal size carbonate particles, bicarbonate ions, carbonate ions, and carbonic acid formed in aqueous solution at a pH below 8.3. o δ

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In the invention, a slurry of structured kaolin is added to a salt composition as described above in the step of making a paper or board product prior to the headbox of a paper machine, or structured particles are formed in this salt composition.

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Structured kaolin slurry is very useful, for example, in accelerating dewatering and improving retention in the wire section of a papermaking machine. For example, drying paper or board yields carbonate precipitated from the salt composition of the fiber structure, which in turn increases the light scattering capacity of the kaolin, thereby increasing opacity and brightness with the same amount of filler. In addition to increasing the temperature during the drying of paper and board, it is possible to precipitate the carbonate either by raising the pH (e.g. using a base) or by increasing the pressure with the wire, press and dryer sections. However, it is essential that the pH of the paper or board manufacture is maintained at the lower half of the hap-10 in a long and short cycle. The kaolin slurries are naturally acidic in the aqueous solution, while the sodium carbonate and talc slurries are basic. If the pH of the circulating water is to be raised by raising the temperature or pressure, or by raising the pH by addition of a base, this is done at the earliest in the headboard or wire section of the paper or board machine.

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Said '' aqueous solution '' may be any aqueous solution.

However, according to a preferred embodiment of the invention, the aqueous solution is raw water, chemically or mechanically purified water, tap water, purified water of various purities or other paper mill water or a mixture thereof, preferably filtrate water or process water from which the solids are separated or separated.

According to another preferred embodiment of the invention, said aqueous solution is a chemical pulp (sulphate or sulphite pulp), mechanical or chemimechanical.

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o 25 pulp, alkaline fibrous pulp, recycled fiber, deinked fiber (washing or floatation purified), nanocellulose pulp, coated wreck, uncoated wreck, or a mixture thereof.

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In particular, according to this second preferred embodiment, the aqueous solution is first made into a pulp in which the pulp solids are mixed with the solution, followed by the above process steps.

The "salt composition" thus contains, in addition to said aqueous solution, salts of carbonic acid. The salt composition preferably consists of magnesium or calcium carbonates or bicarbonates, or a mixture thereof, and is preferably prepared by adding a slurry of the oxide or hydroxide to the aqueous solution and introducing carbon dioxide into the solution so that the pH of the aqueous solution is substantially below 8.3 to form bicarbonate and colloidal carbonate having an average particle size of <0.3 nm, preferably <0.1 nm.

Paper and board machines usually aim to maintain the pH of the circulating water system in the range of 6-8. This utilizes, for example, the chemistry of carbonate ions and the pH buffering it provides.

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At acidic pH, soluble carbon dioxide (CO2) and to a lesser extent carbonic acid (H2CO3) are the major forms of carbonate. In the neutral (on both sides of pH 7) and basic range, bicarbonate or hydrogen carbonate (HCO3 ") is the predominant form of carbonate up to about pH 10." Principal "means that at least 15 to 50% by weight of the forms are carbonate. In the very basic range (pH> 10), carbonate (CO 32 ") is the predominant form. By moving from the basic region to the acidic region, substantially all of CO 32 'has been converted to HCCl 3 at about pH 8.3. Thus, the most important pH range for the production of paper and board, pH 6-8, is the predominant form of bicarbonate (HCO3 ').

20 '' Structured kaolin particles' are produced from kaolin plates or stacks of a kaolin composition, optionally further processed such that at least a portion of the kaolin, preferably the kaolin surface, is converted to metakaolin or calcined kaolin.

The granules or agglomerates of structured kaolin are prepared by spray drying the kaolin slurry with the aid of a binder. For spray drying, a rotary atomizer, pressure nozzles, bipolar nozzle, ultrasound or a combination of the above may be used.

cc □ _ From these granules or agglomerates, meta-kaolin or calcined Kao-30 line can be made by oven-drying or blending using a binder. slipped kaolin granules or agglomerates. In the production of 'structured' kaolin, i.e. spray drying, other raw materials than kaolin can be used. For example, prior to spray-drying or mixing techniques, calcium carbonate, titanium dioxide, talc or silica or more may be added to the kaolin slurry in aqueous solution prior to the preparation of granules or agglomerates.

In addition to these granules and agglomerates, the '' fiber dispersion '' includes a fiber source, a si-5 agent and the salt composition mentioned above. In the present invention, the fibers may be chemical pulp or mechanical pulp. For example, sulfate and sulphite cellulose fibers, soluble cellulose, nanocellulose, chemimechanical pulp (CTMP), thermomechanical pulp (TMP), pressure pulp (PGW), pulp, recycled fiber or refined pulp fibers may all function as fibers. Here, the binder is deposited on the surface of the formed kaolin particles, and acts by bonding the particles together, and in particular by bonding the particles to the fibers.

Flocculants, coagulants or microparticles, or a mixture thereof, or a copolymer thereof, may be added to the aqueous solution or fiber dispersion in an amount of at least 0.01%, particularly about 0.01% to 3% by weight of the total solution or dispersion, preferably at least microparticles. , preferably in combination with conventional flocculants or coagulants.

One or more chemicals known per se, selected from the group consisting of aluminum compounds, bulk adhesives, surface adhesives, dyes, starches, optical brighteners, plastic pigments, natural and synthetic polymers, and fillers and coatings may also be added to the fiber dispersion.

During the drying step of the production of paper or board or by raising the pH, the bicarbonate ions in the salt composition or mixed with the fiber dispersion are converted to carbonate carbonate particles. Similarly, as the temperature rises, carbon dioxide is released and the bicarbonate reacts with free calcium or magnesium ions according to the following reaction equ.

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Ca2 + + (HC03) 2 - CaCO3 | + CO 2 | + Η20 |.

Raising the pH at 30 ° C with a base such as NaOH or Ca (OH) 2 gives the carbonate C ...

particles precipitated according to the following reaction equations:

Ca2 + + (HC03-) 2 + 2NaOH - * CaCO3 | + Na 2 CO 3 + 2H 2 O.

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Ca2 + + (HC03) 2 + Ca (OH) 2 - »· 2CaCO3 j + 20H \ The carbonate particles so formed fit between the fibrils and the fiber, keeping the fibrils 5 outwardly oriented and bringing opacity, lightness, stiffness and thickness to the paper or board ( bulkiness). In particular, carbonates on the surface of paper or paperboard improve the adsorption of ink. Some of the precipitated carbonate is also inside the lumen and pores of the fibers. The structured kaolin, in turn, fills the gaps between the fibers of the fiber network, thereby reducing strength and stiffness to a lesser extent than, for example, using fillers of an average particle size of 3 microns or less.

The dispersion formed with these ingredients is then blended into a pulp which, in the final step of the process of the invention, is filtered, compressed and dried to a paper or board product. At this point, gaps of about 10 micrometres are usually left between the fibers. However, the kaolin agglomerates of the order of about 10 micrometers utilized in the present invention migrate to these apertures during the dewatering of the pulp and thereby increase the area where hydrogen bonds can be formed. With commercial fillers, the loss of strength is more pronounced because there is less inter-fiber space available for the formation of hydrogen bonds. For this reason, the present invention employs structured kaolin of about 15 µm average particle size.

The following examples illustrate certain preferred embodiments of the present invention. They are intended to illustrate the advantages and benefits of the invention and not to limit the scope of the invention,

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The results below show that the best results in terms of brightness, opacity, printability, strength and stiffness are obtained by combining structured kaolin and carbonate from carbonated salts precipitated in dispersion.

The addition of kaolin to acidic water and its use among the pulp increases the rate of dewatering and improves retention with screen press and dryer sections.

Example 1. Preparation of Structured Kaolin and Acid Water

The salt composition, hereinafter referred to as acidic water (hereinafter also referred to as "HV"), was prepared in this example in deionized water. A sealable plastic canister (30 liters volume) was first weighed with 25 kg of deionized water each. To this was added 15,170 grams of calcined lime (CaO), which had been quenched prior to addition to 600 grams of 45 ° C deionized water. By adding carbon dioxide to this dilute calcium hydroxide slurry, Ca (OH) 2, the pH was reduced from about 12 to 6.3. This solution was allowed to sediment for 12 hours, after which the colloidal, non-sedimented portion was separated from the canister. The sediment on the bottom was not used in the tests.

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Dry Covergloss (Kamin LLC) kaolin powder was slurried in deionized water to 20% solids. DispexN40 (BASF) dispersant 0.2% and latex (Acronal S505, BASF) based on the weight of kaolin were used for the dissolution. The slurry was then spray dried (Niro, mobile minor). The feed rate of the slurry was 50 ml / min,

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0 25 ° C rotation speed approximately 25 000 rpm, drying air temperature 250 ° C and o) outlet air temperature 110 ° C. The dried structured kaolin (hereinafter "struk") was cooled to room temperature and slurried in acidic water to a 20% slurry. The structured kaolin (struk + HV) thus prepared had an average particle size of 15 µm.

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rometers (Sedigraph 5120, Micromeritics).

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Example 2. Effect of the addition of structured kaolin slurry on the properties of the pulp paper.

In this series of experiments, a mixture of bleached pine pulp and bleached 5 birch pulp was first milled to an SR of 30 in a Valley grinder. The pine pulp was 30% by weight and the birch pulp 70%. The pulverization was carried out according to the standard method SCAN-C 25:76. This mass was diluted with deionized water of the invention to 0.2% consistency to which was added 0, 20 or 40% dry fiber based on 20% structured kaolin and acidic water slurry (struk + HV) prepared according to the previous example. In addition, for the comparison of the results, stock solutions diluted in 0.2% deionized water alone were added to which calcium carbonate (PCC, Precarb FS-240, Shaefer Finland Oy) precipitated at 0, 20 or 40% calculated on dry fiber was added, Covergloss (Kamin LLC) or Alphatexia (Imerys). All of these were made into a 20% slurry in deionized water before being added to the stock. The test points are called struk + HV, struk, PCC, Covergloss 15 and Alphatex.

Abbreviations: "struk" means structured kaolin, "PCC" means precipitated calcium carbonate, 20 '' Covergloss 'is a filler containing conventional, unstructured kaolin, and' 'Alphatex' is conventional, unstructured, calcined kaolin.

Slurries of each of these were prepared in either acidic water (where HV is also used for the test point) or deionized water alone, and this slurry was added to the pape-oo slurry to form the pulp of the test points.

80% m / m sheets of 0.2% consistency were thus prepared in sheet x mold without recycled water according to SCAN-C 26:76 (SCAN-M 5:76).

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10 sheets of each test point were prepared using 30 acrylamide (Praestaret PK 435) as cationic dust retention agents. Polyacrylamide was added at 250 g / h without shear under stirring. The sheets were then wet pressed and dried in a tumble dryer (120 ° C, 2 hours) as described in Pertti Aaltonen's 1986 publication (Pertti Aaltonen: Test Methods for Fiber Raw Materials and Paper, Otakustanta, 1986). All 15 sheets produced were subjected to air conditioning for 48 hours at 23 ° C and 50% relative humidity. The sheets were then checked for basis weights and the following properties were determined: • filler content (525 ° C and 2 hours) • ISO brightness (L&W Elrepho Spectrophotometer SE070), ISO 2470 5 · Opacity (L&W Elrepho Spectrophotometer SE070), ISO 2471 • Scott bond (Internal bond) Tester Huygen), Pin-UM403 • Rigidity (L&W paper bending Tester SE160), ISO 2493 / SCAN-P 29:95

The sheets had a basis weight of ± 0.6 g / m with an accuracy of 80 g / m in the target basis weight.

10 The evaluation of sheet printing properties was performed in this experiment as an optical density measurement. The sheets were printed on a Universial Testprinter (Testprint B.V.) using Cold set black (Sun Chemical, viscosity 7.3 Pas) at 10 milligrams of color on the sheet side. Optical densities were measured on densitometric (Macbeth) air-conditioned and dried samples after 24 hours of printing. The Universial test printer used a pressure of 630 N and a speed of 1 15 m / s.

Based on the filler content (525 ° C and 2 hours) determined from the sheets, the results are linearly normalized to the same 10% filler content. 95% confidence means 95% confidence interval.

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Table 1. 80 g / m2 sheet normalized to 10% filler content.

Test Point Opacity, Brightness, Scott Bond, Stiffness, Optical Density,%% J / m2 pNm 10 g cyi Covergloss 85 ^ 5 82 ^ 2,242 78 C3Ö § Alphatex 87 ^ 83 ^ 4 26Ö 65Ϊ42 § PCC 87J 8Ϊ3 267 68 \ £ 4 ”struk 8M 83 ^ 0 312 85 Ϊ52

En struk + HV 89 ^ 2 85 ^ 3 315 Ϊ38 1 ^ 56 Q_ 5 5 5 co 95% confidence ± 0.4 ± 0.2 ± 12 ± 6 ± 0.06 cd CO v o o δ c \ j

As the results show, adding structured kaolin (struk ± HV) suspended in acidic water to the pulp and combining the structured kaolin with the thus precipitated carbonate improves the brightness, opacity, strength, stiffness and printability (optical density) more than the use of structured kaolin. or use of PCC alone (PCC) Strength (Scott bond) also increases with about 15 micrometers of circular structured kaolin weakening the formation of inter-fiber hydrogen bonds less than with smaller size fillers (Covergloss, Alphatex and PCC).

Example 3. Effects of Conventional Kaolin Slurried in Acid Water on Paper Properties 10 In this example, dry Intrafil C (Imerys), a conventional kaolin, is slurried in acidic water or deionized water to a dry matter content of 20%. The acid water used is prepared as in Example 1.

In the Valley mill, the blend of bleached pine pulp and bleached birch pulp was first milled to SR 35. Pine pulp was 30% by weight and birch pulp 70%. The pulverization was carried out according to the standard method SCAN-C 25:76. This mass was diluted to 0.2% consistency to which 0, 20 or 40% Intrafil C (Intra) slurried in deionized water or Intrafil C (Intra + HV) slurried in acidic water was added.

The 0.2% consistency pulps thus prepared were made into sheets of 80 g / m 2 in sheet form without recycled water according to SCAN-C 26:76 (SCAN-M 5:76). 10 sheets of each test point were prepared using cationic polyacrylamide (Praestaret PK 435) as retention agents. Polyacrylamide was added at 250 g / t without shear

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o 25 mi while stirring. The sheets were then wet pressed and dried in a tumble dryer (120 ° C, 2 hours),

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x All sheets prepared were air conditioned for 48 hours at 23 ° C and 50% relative

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0_ to humidity. The sheets were then checked for basis weights and the following 30 properties were determined: co o £ · filler content (525 ° C and 2 hours) C l • ISO brightness (L&W Elrepho Spectrophotometer SE070), ISO 2470 • Opacity (L&W Elrepho Spectrophotometer SE070), ISO 2471 17 • Rigidity (L&W Thickness Tester SE160), ISO 2493 / SCAN-P 29:95 • Thickness (L&W Thickness Tester SE51), ISO 534

Table 2. 80 g / m2 sheet normalized to 10% filler content.

Test point Opacity,% Brightness,% Thickness, pm Rigidity, pNm

Intra 82Ä 132 74

Intra + HV 86 ^ 5 84 ^ 6 173 TO9 95% ± Ö4 ± Ö2 ± 2 ± 8 reliability 5

As these results show, opacity and brightness in particular are not as significantly improved with conventional kaolin as with structured.

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Claims (18)

Fiber product containing cellulose or wood fibers, characterized in that filler particles, some of which are chemically structured kaolin agglomerates or granules, and some of which are carbonate, are attached between the fibers and the fibrils. A product according to claim 1, wherein a binder, preferably latex, silica, soluble aluminum or aldehyde, or a mixture thereof, between the fibers, between the fibers and the filler particles, and between the fiber fibrils and the filler particles, is preferably in an amount of 0.05 to 20% by weight. -%. Product according to claim 1 or 2, containing structured kaolin particles up to 25% by weight of fiber, preferably at least 5% by weight of fiber. The product according to any one of the preceding claims, wherein the structured particles are substantially spherical and have a size of> 5 µm, preferably 10 to 40 µm, more preferably 20 to 40 µm. A product according to any one of the preceding claims, wherein the kaolin of the structured filler 20 is delaminated, water washed, dry graded or treated by two or more of the above processing methods, preferably converted at least from the outer surfaces of the particles to metakaolin or calcined kaolin. The product according to any one of the preceding claims, wherein the carbonic acid salts are carbonate or bicarbonate salts, preferably bicarbonate and colloidal carbonate, more preferably with an average particle size of <0.3 nm, most preferably <cp 0 0.1 nm, at normal paint pressure. X CC CL A product according to any one of the preceding claims, wherein the carbonate or bicarbonate salt formed from the corresponding oxide or hydroxide or a mixture thereof is a precipitated inorganic or organic salt or a composite of several salts, or a mixture of which the salt is preferably a calcium or magnesium salt or mixture. A product according to any one of the preceding claims, further comprising retention agents or microparticles flocculating or coagulating, or a mixture thereof. The product of any one of the preceding claims, further comprising one or more chemicals known per se selected from the group consisting of aluminum compounds, mass adhesives, surface adhesives, dyes, starches, optical brighteners, plastic pigments, natural and synthetic polymers, and fillers and coatings. A process for the preparation of a product according to any one of claims 1 to 9, characterized in that - adding the oxide or hydroxide as a hydroxide slurry to an aqueous solution and lowering the pH of the solution to 6.0-8.3 by passing carbon dioxide into the solution such that carbon dioxide and carbon dioxide slurry the salts have a concentration of at least 0.01% by weight of the total solids of the solution to form a salt composition, slurry the kaolin sheets or stacks or both together with the binder into water to form the kaolin composition, - produce the kaolin sheets or stacks or both kaolin droplets in a spray dryer, whereupon the excess water is also evaporated to form structured kaolin particles, or these structured kaolin particles are slurried to form the salt described above the kaolin sheets or stacks of the composition or its dissolved portion with the binder, or both, - mixing the formed structured kaolin particles together with the salt composition or dissolved portion into a paper or board stock to form a fibrous dispersion, and i co - precipitating the carbonate particles while x dispersion is filtered, compressed and dried into paper or board. □ _ 00 ^ 30 The method of claim 10, wherein the aqueous solution is raw water,? chemically or mechanically purified water, tap water, filtered water of various purities, or other paper mill water or a mixture thereof, preferably filtrate water or process water from which the solids are separated or separated. The process according to claim 10, wherein the aqueous solution is a chemical pulp (sulphate or sulphite pulp), a mechanical or chemimechanical pulp, a base pulp, a recycled fiber, a refined fiber, a nanocellulose pulp, a coated or uncoated sheath. 5 A process according to any one of claims 10 to 12, wherein the aqueous solution is first made into a pulp, wherein the solids of the pulp are mixed with the solution, followed by the steps of claim 9. The process of any one of claims 10 to 13, wherein the salt composition is prepared from magnesium or calcium carbonates or bicarbonates or a mixture thereof by adding a slurry of the oxide or hydroxide to the aqueous solution and introducing carbon dioxide into the solution such that the pH in the aqueous solution is substantially during the formation of bicarbonate and colloidal carbonates with an average particle size <0.3 nm. The process according to any one of claims 10 to 14, wherein the particles of structured kaolin are granules or agglomerates that have been converted by heating to at least their outer surfaces to metakaolin or calcined kaolin. The process according to any one of claims 10 to 15, wherein the binder is added to the kaolin slurry with stirring, whereby the binder settles on the surface of the kaolin, in particular on the surface of the structured particles formed from kaolin. c \ j o 25 The method of any one of claims 10 to 16, wherein one or more chemicals known per se are selected from the group consisting of aluminum compounds, mass adhesives, surface adhesives, dyes, starches, optical brighteners, plastic pigments, natural fibers, to the fiber dispersion. and synthetic polymers, as well as fillers and coatings. CL 00 T- 30 The process according to any one of claims 10 to 17, wherein the aqueous retention agents or microaggregating or flocculating microparticles, or a mixture thereof, or a copolymer thereof, of at least 0.01%, in particular about 0.01% to 3%, based on the weight of the total solution or dispersion solids, are added to the fiber dispersion.