FI117870B - Coated fiber web and method of making it - Google Patents

Abstract

The present invention relates to a coated fibrous web and a method for producing it. According to the present invention, a coated fibrous web comprises a filler-containing base web that has a pigment-containing coating layer on at least one surface. The filler of the base web consists at least partially of cellulose or lignocellulose fibrils, on the surface of which light scattering material particles have been deposited. The filler comprises cellulose or lignocellulose fibrils having an average thickness less than 5 mum produced from plant fibres by refining and screening. Considerable advantages are achieved with the present invention. With the help of the composite filler, the formation of the fibrous web can be improved significantly without impairing the retention, which makes is possible to achieve an extremely smooth substrate for the coating. The smoothness of the surface can also be improved. Furthermore, the fines-based carrier fraction of the filler compresses the surface of the base paper so that the coating does not penetrate too much into the fibre network. Due to these reasons even a small amount of coating produces good coverage and quality improving cost-efficiency.

Description

, 117870 Coated fiber track and method for its manufacture

The present invention relates to a coated fiber web according to the preamble of claim 1.

Such a fiber web generally comprises a filler-containing base web having a pigment-containing coating on at least one surface thereof.

The invention also relates to a method for producing a coated fiber web according to the preamble of claim 12.

The printability of the paper and board - the properties of the printing surface and the printing process - is improved by coating the paper with various mineral coatings. The purpose of the coating is to cover the fibers and fibrous flocs of paper or cardboard, thereby reducing the roughness of the surface 15 and reducing the pore size of the surface. Coatings usually consist of pigments and binders, and various additives.

The ability of the base paper to be coated, i.e., the ability of the base paper to become coated, has become increasingly important as demand for lighter grades of paper increases. Although. The coating properties and the method of coating, including the base paper, can influence the opacity. Due to the properties of the base paper, good formability and smoothness, as well as appropriate air permeability and porosity are more important factors in the application of the coating, especially when good quality is sought with a small amount of coating. The fiber web to be coated usually contains a filler. The filler improves the paper's • · * * * 25 formation by filling the spaces between the fibers. The filler can also improve the opacity of the web.

♦ ·· * FI Patent Publication No. 100729 discloses a papermaking filler which,. | * comprises * · · 30 porous aggregates of calcium carbonate particles precipitated on the surface of the fines. It is characteristic of this novel filler, according to the patent, that calcium carbonate is precipitated on cellulose fibers and / or mechanical pulp fibrils made from pulp. The fines fraction corresponds predominantly to the P100 fraction of the mesh screen.

117870 2

According to said patent, the filler can be used to increase the content of calcium carbonate in the paper, thereby reducing the basis weight of the paper without changing the "other important" properties of the paper. The results of the publication are based on the results of the laboratory 5 sheets as measured by SCAN-C 26:76 and SCAN-M 5:76 respectively. No mention of paper coating can be found in the publication.

According to the present invention, it has now surprisingly been found that by filling the paper or cardboard web or similar fibrous web with the filler described above, not only the other important properties of the paper remain unchanged, but the fiber web can be substantially improved.

It has further been found in the invention that other excipients may be used, which at least in part consist of cellulose or lignocellulosic fibrils on which light scattering material particles have been deposited. These particles are typically aqueous phase precipitated inorganic salts such as calcium carbonate, calcium sulfate, barium sulfate and calcium oxalate.

More specifically, the method according to the invention has essentially the # # φ ·. 20 is characterized in what is stated in the characterizing part of claim 1.

• · * * · · • · · * * · *

The process according to the invention is characterized by what is stated in the patent claims. mus 12 features.

• · • * · ····· • · · ** '; There are considerable advantages to the invention. Thus, a composite filler composed of fibrils and mineral pigments has been found to impart to the base paper properties such as 1 ·,. which are better in terms of coating than can be achieved with commercially available fillers currently available. Because the composite filler used in the invention can, surprisingly, significantly improve the formation of the fiber web by retention. ***. 30, the invention provides a very smooth coating substrate. Surface smoothness can also be improved. In addition, the fines-based carrier fraction of the filler compactes the pulp ···. and the surface of the paper so that the coating does not over-penetrate the fiber network. For these reasons, even a small amount of coatings • produces good coverage and coating quality, which improves cost-effectiveness.

3 1 1 7870

The invention will now be explored in more detail with the aid of a detailed description and a few embodiments.

In the examples below, the filler used in the invention is based on fibrils obtained from chemical pulp. Chemical pulp, as used herein, refers to pulp treated with cooking chemicals to delignify cellulosic fibers. According to a preferred embodiment, the fibrils are obtained by grinding a pulp prepared by a sulphate process or by another alkaline process. In addition to chemical pulps, kek-10 is also suitable for modifying fibrils derived from chemimechanical and mechanical pulps. . . .

Typically, the average thickness of the cellulose or lignocellulosic fibrils is less than 5 µm, usually less than 1 µm. Fibrils are characterized by one or both of the following criteria: a. They correspond to a fraction which passes through a 50 (or preferably 100) mesh sieve; and b. having an average thickness of 0.01 to 10 µm (preferably up to 5 µm, most preferably up to 1 µm) and an average length of 10 to 1500 µm.

, 20 The starting material for the fibrils, i.e. the cellulose or other fiber-based fines, is fibrillated with a pulverizer ♦ · * • »*. If desired, the desired fraction can be separated with a screen, but the fine material does not always have to be sorted. Suitable fibril fractions are the wire sorting fractions P50 - • * ·, ·· ^ P400. Preferably, refiners with grooved blades are used.

The light scattering material particles of the filler are inorganic or organic salts, which can be formed from their starting materials by precipitation in an aqueous medium. Such compounds include calcium carbonate, calcium oxalate, calcium sulfate, barium sulfate *, and mixtures thereof. The particles of material are deposited on the fibers. The amount of the inorganic salt compound in relation to the amount of fibrils is from about 0.0001 to about 95% by weight, preferably from about 0.1 to about 90% by weight, preferably from about 60 to about 80% by weight, based on the amount of filler • · * * * • t thirst 0.1 to 80% by weight. preferably about 0.5 to 50% by weight of the paper.

• · Φ * • · * t ···. ' • · • · • · · '4 117870

In the following, the invention is considered in particular on the basis of the product according to F1 patent 100729, but it is clear that the invention can be applied to the other products mentioned above by suitable modification of the light scattering pigment starting materials.

The filler is prepared by precipitating a mineral pigment on the surface of fine cellulosic fiber and / or mechanical pulp fibers. For example, the precipitation of calcium carbonate can be accomplished by introducing into the fibrils water slurry an aqueous mixture of calcium hydroxide, optionally containing solid calcium hydroxide, and at least partially dissolved in water containing carbonate ions. Carbon dioxide gas which produces calcium carbonate in the presence of calcium hydroxide can also be introduced into the aqueous phase. Pearl-like calcium carbonate crystal aggregates held together by fibrils, i.e. fine strands, are formed in which the calcium carbonate particles are deposited on the fines. The fines strands, together with calcium carbonate, form pearl-like straps that resemble the pearl strands closest to the pile. The effective volume to mass ratio of aggregates in water (in sludge) is very high compared to the corresponding ratio of conventional filler calcium carbonate. By effective volume is meant the volume required by the pigment.

The diameter of the calcium carbonate particles in the aggregates is from about 0.1 to about 5 µm, typically from about 0.2 to about 3 µm. In particular, the fibrils correspond to the P50 (or P100) to P400 of the screen sorter.

In the filler, at least 80%, preferably up to 90%, of the alloyed light-scattering pigment particles are adhered to the fibrils.

The paper pulp is pulverized in a manner known per se to a suitable consistency (typically about 0.15% solids) and spread on a wire. • * • · min in the headbox of a paper or board machine, preferably the above filler, usually about 1 - # φφ #. 100 wt.% of the weight of the fibers in the pulp, in other words, the filler amount may be as high or equal. - than the actual amount of fiber pulp. It is also possible in principle to · · · · · · · · · · · · · * · The fibrous material of the base track.

♦ • · · ···· »· • * * ♦ ♦ ·» · 5 1 1 7870

In a paper or board machine, the pulp is webbed to form a paper or board web. The fiber web is dried and coated and optionally post-treated e.g.

5 Coating can be performed as single coat or double coat, whereby coating pastes can be used as single coat pastes and so-called pre-coat and top coat pastes. Triple coatings are also possible. In general, the coating composition of the invention contains 10 to 100 parts by weight of at least one pigment or mixture of pigments, 0.1 to 30 parts by weight of at least one binder, and 1 to 10 parts by weight of 10 other additives known per se.

A typical composition of the pre-coating composition is as follows: * Coating sponge 15 (e.g., coarse calcium carbonate) 100 parts by weight binder 1-20% by weight of pigment additives and excipients 0.1 to 10% by weight of pigment water remaining, 20 water is added so that the dry matter content is generally 40-70%.

• · · • · · «· * ··« ·

According to the invention, the composition of the surface coating composition or the disposable coating composition is, for example, as follows: 25 coating pigment I.

• • 4 (eg fine carbonate) 10 to 90 parts by weight

coating pigment II

4 ·· t (e.g. fine kaolin) 10 to 90 parts by weight pigment total 100 parts by weight 30 binder 1 to 20 parts by weight.

* · · Additives and excipients 0.1 to 10 parts by weight water remainder · · · · · Water is added to such a coating composition so that the dry matter content is typically 50 to 75%.

6 117870

According to the invention, pigments having a steep particle size distribution can be used in the above coating compositions, wherein at most 35% of the pigment particles are less than 0.5 µm, preferably no more than 15% are less than 0.2 µm.

The invention is applicable to any pigment. Examples of pigments include precipitated calcium carbonate, powdered calcium carbonate, calcium sulfate, calcium oxalate, aluminum silicate, kaolin (hydrous aluminosilicate), aluminum hydroxide oxide, magnesium silicate, talc (hydrous silicate), magnesium silicate, and the like. Synthetic pigments may also be considered. The main pigments of the above-mentioned pigments are kaolin, calcium carbonate, precipitated calcium carbonate and gypsum, which generally make up more than 50% of the dry weight of the coating composition. Calcined kaolin, titanium dioxide, satin white, aluminum hydroxide, sodium silicoaluminate and plastic pigments are additional pigments and are generally present in amounts less than 25% of the dry weight of the mixture. Special pigments include special kaolins and calcium carbonates as well as barium sulphate and zinc oxide.

The invention is particularly preferably applied to calcium carbonate, calcium sulfate, aluminum. For nisilicate and aluminum hydroxide, magnesium silicate, titanium dioxide and / or barium sulphate, and mixtures thereof, with calcium carbonate or gypsum and lithium oxide as the main pigment being the main pigment. or mixtures of gypsum and kaolin.

• · * * * »• · · · · *. ···. Any known binders commonly used in papermaking may be used as binders for the coating composition. In addition to the individual binders, i *. #> Binder mixtures may also be used. Examples of typical binders include synthetic latexes, which are composed of polymers or copolymers of ethylenically unsaturated compounds, e.g. butadiene-styrene copolymers, where possible. 30 is a carboxyl-containing comonomer, such as acrylic acid, itaconic acid or • · * * * \ maleic acid, and polyvinyl acetate containing carboxyl-containing monomers. Further, binders may be used with the above materials, e.g. water-soluble polymers, starch, CMC, hydroxyethyl cellulose and polyvinyl alcohol.

7 117870 Conventional additives and adjuvants such as dispersants (e.g., sodium salt of polyacrylic acid), agents for viscosity and water retention (e.g., CMC, hydroxyethylcellulose, polyacrylates, n-benzoates) can be used in the coating composition. lubricants, hardeners used to improve water resistance, optical aids, antifoams, pH adjusters and anti-pollution agents. Lubricants may include sulfonated oils, esters, amines, calcium or ammonium stearates, glyoxal as water resistance enhancers, diaminostilbene disulfonic acid derivatives as optical excipients, antifoam phosphate esters, silicones, alcohols, ethers, of the anti-pollution agents formaldehyde, phenol, quaternary ammonium salts.

The coating composition may be applied to the material web in a manner known per se. The method of coating the paper and / or board according to the invention can be carried out with a conventional coating apparatus, i.e., a blade coating, or by film coating or by surface spraying (JET application).

When coating at least one surface of the paper web, preferably both surfaces, a coating layer having a surface weight of 5 to 30 g / m 2 is formed. The uncoated side t 20 can be treated with eg surface sizing.

• · ♦ • · * ...

* 1 • · · ·

The invention can produce coated and optionally calendered * ·. * 1 *. cellulosic material webs with excellent printability, good «· · ·; 1 ·! smoothness and high opacity and brightness. "Cellulosic material" means: ***; 25 generally containing paper or paperboard or similar cellulosic material derived from lignocellulosic material, in particular wood or perennial or perennial. plants. The material in question may be wood-based or wood-free and may be • · · made from mechanical, semi-mechanical (chemimechanical) or chemical pulp. Pulp and mechanical pulp may be bleached or unbleached. The material may also include • · ^: ***; 30 recycled fibers, especially recycled paper or recycled paperboard. Material web • - ·

The soot typically ranges from 35 to 500 g / m 2, in particular from about 50 to 450 g / m 2.

φ * ··· ♦ · · · · · ·

Generally, the base paper has a basis weight of 20 to 250 g / m 2, preferably 30 to 80 g / m 2. Coating this type of base paper with a weight of about 50-70 g / m210-20 g 117870 8 l / m / side and calendering the paper to a product with a weight of 70-110 g / m, at least 90% brightness and opacity is at least 90%. A particularly preferred product is coated offset paper, which combines high gloss with high opacity and bulk. The invention is also suitable for the production of coated fine, possibly mechanical pulp families.

The following non-limiting examples illustrate the invention. The measurement results for paper properties reported in the examples are determined using the following standard methods:

Surface Roughness: SCAN-P76: 95>

Porosity: SCAN-P60 Air Permeability Resistant: SCAN-M8, P19 15 Example 1 Preparation of Filler

Pulp milling 20 Birch sulfate pulp was milled with a Valmet JC-01 refiner to produce a filler suitable for preparing the pulp. The refining consistency was about 4% and the total energy consumption i * 343 kWh / t and the specific edge load 0.5 J / m.

* * * * · * 4 · * «*» · * · * ··· * The product characteristics are shown in Table 1.

* * · * · 25 • · • ·

Table 1. Fiber Properties Before and After Grinding # ♦ ... Before Grinding After Grinding 1 * * ·, 30 Fiber Length (Length), mm 0.86 0.58 * * * * 1] ···. Fiber Length (Weight), mm 1.00 0.77 • * • · · SR0 16 86 35 '• · • * 1 V Fiber Carbonization 117870 9

Carbonation was carried out in tap water as disclosed in FI Patent Publication No. 100729.

An aqueous slurry was obtained with a solids content of 2.22% and a total volume of 248 m. The final product had a CaC03 content of 69.7% and a specific surface area of 10.6 m 2 / g, * 1 · 1 *. * 1 «* · · · · * 1 • · · 1 • 1 ♦ · * · 1 ·« · •….

• · · • -1, * • · 1 * 1 1 1 • 1 1 * ···· * · • 1 «* 1 1« • 1 1 · · • · 1 • · «• · 10 1 1 78 70

Example 2

Manufacture of base paper

The product described in Example 1 was used as a filler for coated fine papers. The following table shows the results of a fine-grain pilot run on a STFI pilot machine (FEX) in Stockholm:

Table 2. Surface Properties of Fine Paper Filler Filler Formation, Porosity, Air Permeability Roughness, Concentration,% ml / min Resistance, s ml / min ___% __ (Bendtsen) (Gurley) __ (Bendtsen) PCC_18,8 10,6_761 ___ JJ6_814 PCC_2lfi_JU_ 799_ \ 6A_J62_

SuperFill 17.8_JM_ 543_26J_771_

Superfill 22.4 [9.5 [439 32.3 611 10

From the table values, it can be noted that the fines-based filler described in this invention improves the formation and smoothness of the base paper with commercial PCC filler to such an extent that it has a surprisingly good effect on the paper coating. The effect is greater the more filler is used. The filler also has a higher density (SuperFill), which can be dynamically enhanced, especially on lightweight papers, through better coating of the paste.

* a * · * a * a · • a

Example 3 a * · * ... * 20 Factory Test * * 1 • •• aa • ·: AI. Preparation of Filler Base Paper For coating, a base paper having a basis weight of 56 x 25 g / m 2 was manufactured under factory conditions. The stock consisted of a mixture of birch pulp (74%) and pine pulp (24%). After milling ·; *, the SR number of the pine was 32-34 ° and that of the birch 22-25 °. SR mass of mass in headbox! * ": Was 35 -40 °.

The paper machine wire section had a Valmet hybrid screen (Sym-former), and the wet press section included a Valmet Sym-Press II with a triple press and a standard drying section.

Π 117870

Three different fillers were used in the base paper, namely the products Finntalc F 15 SL (Mondo Mineralsm Talc), Albacar HO (Specialty Mineralsm PCC) and the composite filler described in Example 1, hereinafter also referred to as "SuperFill".

Talc was used as filler at 10% and 15% and PCC and SuperFil at 10%, 15% and 20%.

The retention chemicals used were nanoparticles and cationic starch (Compozil Plus: EKA NP 780 nanoparticle and EKA PL 1510 C-PAM, supplied by EKA Chemicals). For Talc and PCC, the dosage amounts were: nanoparticle 280 g / t, polymer 10 70 g / t, and SuperFil: nanoparticle 280 g / t, polymer 50 g / t. The application rates of cationic starch and resin size were 8 kg / t and 5.2 kg / t. Alum was dosed with talc at 13 kg / t and 19 kg / t with PCC and SuperFil.

A2. Results 15

Coulter-oil porosity was measured from base paper samples. At low filler concentrations, no significant differences in pore size distribution were observed with the different fillers. 75% of all pores were within the range of 1.2 to 1.8 µm (around the maximum point). However, when the filler concentration was increased to 20%, significant differences were obtained. For PCC, the median pore size 20 increased with the amount of filler. At the same time, the pore size distribution widened. In this case, 75% of the values of the · · ** "'were in the range of 2.3 µm. With the SuperFill filler the median decreased and the distribution decreased by 75% of the values in the range of 0.8 µm. the effect can also be seen with * · · .. * · · Talc but on a smaller scale with a filler content of 20% Super- * *

For Fill, the median pore size of the filler was only 60% of the corresponding value for PCC and the pore size, ···. At 25, the width of the distribution (75% of the values) was only 34% of the values achieved with the PCC.

* * ·

Thus, it can be concluded from the results that SuperFill produces paper with a surface that is * '** · more closed than PCC-filled paper, which facilitates the coating and improves the quality of the paper. due to better coverage. In other words, the coating pigments cannot penetrate «

»•» I

. * ··. 30 earth base paper just as easily, resulting in a smoother and smoother surface.

* · * * · «*** '. B1 Online Coating • * * · · «·

The base paper described above was coated with one side, the other side with surface glue. The 117870 12 was bladed using a BTG single-blade ABC coater. The surface sizing was done in the same unit by film transfer on the back roll of the coating. The machine speed was 750 m / min and the track width was 252 cm. The on line coating was done after the fourth drying group and the coating was dried with drying cylinders (5th drying group).

5

On-line coating was performed on base papers containing 15% talc or SuperFil as fillers. Only the wire side (13 g / m2) was coated, the surface side was glued (0.5 g / m2).

10 The on-line coater had good runnability with SuperFill. The coating conditions were kept constant in the experiment and are shown in Table 3. The composition or solids content of the coating paste did not change during the experiment.

Table 3. Coating Conditions __Beam SuperFill

Ground weight, 53.8 53.0 g / m2

Gross weight of roll, g / m2 70.1 68.5 Gross weight of coating, 13.1 12.6 g / m2

Humidity of base paper,% 1.5 1.7,, ·. Humidity of roller,% 5.9 5.4 * ··· * Blade pressure, kPa 188.7 182.9

Thickness, pm 86.0 94.0 15 • · · * * • · *! «* # * The properties of the coated and calendered papers were determined.

* ·••••••••••

SuperFilk coated, calendered and calendered paper had about 5 percentage points: ·. 20 better gloss 0.1 pps better smoothness than equivalent talc-filled paper *. ***. counter. This is a very good result, considering that the cover quantities for SuperFill papers were slightly smaller. The light scattering factor and brightness were also • • t ... # much better with SuperFill papers.

• · • * * '' j.

·· *** · 25 Based on the results, it can be concluded that composite pigments can effectively reduce the penetration of the coating paste into the base paper for a better coating of the coating.

Claims (16)

A coated fiber web comprising: - a filler-containing base web having at least one surface having a pigmented coating layer, characterized in that - the base-web filler consists at least in part of cellulose or lignocellulosic fibrils on which light scattering material particles have been deposited. Fiber web according to Claim 1, characterized in that the filler comprises cellulose or ligno-cellulosic fibrils made from milling and screening of vegetable fibers having an average thickness of less than 5 µπι. Fiber web according to claim 2, characterized in that the light scattering material particles are deposited on fibrils corresponding to a fraction passing through a 50 mesh screen and / or having an average thickness of 0.01 to 5 µm and an average length of 10 µm. - 1500 pm. Fiber web according to one of Claims 1 to 3, characterized in that the light-scattering material particles are inorganic salts which can be formed from their starting materials by precipitation in an aqueous medium. Fiber track according to claim 4, feeling 11 u that the light scattering particles are calcium carbonate, calcium oxalate, calcium sulfate, barium. • · ... 25 sulphates or mixtures thereof. • · • n m Fiber web according to one of Claims 1 to 5, characterized in that * *. ···. particles of material are deposited on the fibrils. ··· ··· ”Il 30 The fiber web according to claim 6, characterized in that the amount of light scattering material particle relative to the amount of fibrils is 0.0001 to 95% by weight, preferably about; * * * 0.1 to 90% by weight, preferably about 60 to 80% by weight, based on the amount of filler, and from about 0.1 to 60% by weight, preferably about 0.5 to 50% by weight -% of paper. 117870 Fiber web according to one of the preceding claims, characterized in that it is coated with calcium carbonate, gypsum, aluminum silicate, kaolin, aluminum hydroxide, magnesium silicate, talc, titanium dioxide, barium sulphate, zinc oxide or a synthetic pigment thereof. 5 Fiber web according to one of the preceding claims, characterized in that the filler comprising cellulose or lignocellulosic fibrils on which light scattering material particles have been deposited, constitutes 10-100% by weight of the filler of the base web. Fiber web according to one of the preceding claims, characterized in that the filler material comprising cellulose or lignocellulose fibrils on which light scattering material particles have been deposited, constitutes from 1 to 100% by weight of the fibrous material of the base web. Fiber web according to one of the preceding claims, characterized in that it comprises coated, wood-containing or wood-free paper. 12. A method of producing a coated fiber web comprising applying a pigment-20-containing coating layer to at least one surface of a fibrous substrate, characterized in that the substrate is formed from a stock of fibrous material to which a product comprising cellulose or lignocellulose is added. ·. fibrils on which light scattering material particles have been deposited. • · · • • • • * * * • * * e ·. ;; The method according to claim 12, characterized in that full *** is used. 25 materials comprising cellulose or lignocellulosic fibrils manufactured by milling and screening vegetable fibers with an average thickness of less than 5 µm. • · • ·· 13 1 1 7 870 to and gloss. This is probably because the paper has small pores, the pores have a narrow size distribution, and the base paper has a very good smoothness. * • · • · «* · · * ···« • M • * 1 * · * * 4 * «4 * * · 4 4 • · • 4 4 • 4 · 4 4« • · * 4 4 4 * 4 4 4 4 * * 4 4 4 • 44 4 4 444 '4 * 4 4 4 4 44 * 4 4 4' • * 4 4 4 4 4 4 '4 4 4 «« 4 4' 4 4 * 4 44 4 4, 117870 14. A method according to claim 13, characterized in that a filler material is used in which light scattering material particles are deposited on such fibrils. 30 corresponding to the fraction passing through a 50 mesh sieve and / or having an average packing of ··· *. the mouth is 0.1 to 10 µm and the average length is 10 to 1500 µm. • · · · «· · • * *« «♦ 16 1 1 7870 Method according to one of Claims 12 to 14, characterized in that a filler is used in which at least 80% of the precipitated light-scattering pigment particles are attached to the fibrils. Method according to one of Claims 12 to 15, characterized in that the base web is coated with a pigment-containing coating composition on a paper machine. • · • »· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· · ··· • · * «» «· # ·« • · ♦ 1 1 ··· '. • · ♦ · • · 1 ···· '· * 1 • t · ♦ · 2 ♦ · ♦ ♦ «♦ · • · ♦ • ♦ 117870