FI57145C - FOERFARANDE FOER FRAMSTAELLNING AV BESTRUNA PAPPER - Google Patents

Description

© SUOMI — FINLAND patent publication — patentskrift 5714 5 o o © © Kv.lk./Int.CI. D 21 H 1/22 © Patent application - Patentansökning 752622 © Filing date - Ansökningsdag 19 · 09 «75 @ Start date - Giltighetsdag 19.09.75 © Published public - Bllvit offentllg 19.04.76 @ Date of publication and publication

Ansökan utlagd och utl.skriften pubi ice rad 29.02.80

National Board of Patents and Registration © Patent granted - Patent meddelat 10.06.80

Patents and registries

Requested privilege - Begärd priority 18.10.7 ^

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2449616.0 Verified-Styrkt (73) Degussa Aktiengesellschaft, Weissfrauenstrasse 9 »6000 Frankfurt 1,

Federal Republic of Germany (Förbundsrepubliken Tyskland (DE) (72) Wilhelm Berndt, Frankfurt a.M., Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (74) Oy Kolster Ab (54) Method for producing coated papers - Förfarande för fram-ställning

The invention relates to a process for the production of coated papers having a basis weight of between 45 and 100 g / m 3 and improved printing properties by applying to one side a coating composition comprising a coating pigment, a binder, water and chemical additives from cellulose and possibly wood pulp and filler. formed on the base paper and finally finishing.

Double-sided coated papers are used as printing media for magazines, cover pages of most picture magazines, etc., especially the so-called LWC papers («light weight coated). These are coated papers with a basis weight of between 45 and 100 g / m 2, which are primarily used for gravure printing and also for offset printing. They usually comprise a base paper containing wood chips, which is coated on each side with about 10 g / m 2. These are pulp papers, i.e. grades of paper that are produced in large quantities.

Of particular interest to the method of the invention set forth below are LWC papers for gravure printing. These papers must have a particularly smooth surface to obtain a good print on all 57145 raster dots on the printing plate. Instead, only minor requirements are placed on surface strength. Accordingly, the coating dyes used for the papers contain kaolin as coating pigments, and they avoid the addition of pigments, such as calcium carbonate, which could adversely affect the yeast and the ban. The proportion of binder may remain low in response to a low strength requirement. Starch and latex (butadiene-styrene or styrene-acrylic acid ester) are most often used as binders. Recently, self-thickening latexes are also preferred, which make the addition of a natural binder (starch, CMC, casein) unnecessary. Other common additives are Ca-stearates and possibly dyes.

A typical LVC coating composition used for gravure printing paper may have the following configurations of kaolin 100 parts solids dispersant 0.3 "" self-thickener latex 5 - 7 ""

Ca stearate 0.8 ""

Lubrication is most often done with blade coulters at speeds between 400 and 800 m / minute.

As already mentioned, very smooth paper is required for gravure printing. Although the papers currently offered are of high quality, there are still defects, especially in the half-tone value of the printed product, due to incomplete or incomplete discoloration in the individual cavities of the printing plate. These missing dots »Commonly referred to as" missing dots ", give a restless image impression. Surfaces, which should be similar, then appear coarse-grained. In order to reduce the proportion of "missing dots" to the smallest possible, the intaglio printing papers are accurately and also treated vigorously mechanically with a polishing calender. However, by hitherto known means it is not possible to avoid errors in the desired amount And with corresponding certainty. In addition to this, still suffer from intense satin absorption-ability and opacity.

The object of the invention was thus to provide a process for the production of coated papers having a coating unit weight of between 45 and 100 g / m 3, having improved printing characteristics, by applying to both sides a mixture of after that satin, as a result of which the occurrence of "missing dots" is optimally avoided without the need for extreme bonds for satinization 3 5 714 5.

It is characterized in the invention that 3 to 30% by weight, preferably 5 to 13% by weight, based on the coating pigment, of a synthetically obtained amorphous product, consisting of aluminum and / or calcium silicic acid rf, is dispersed in the brush mass. licate, having an average primary particle size of less than 150 nm, preferably between 10 and 60 nm, an average secondary particle size of less than 10 μm, preferably 2-4 μm, and having a specific surface area measured by the BET method of less than 300 m 2 / g, preferably between 20-150 m2 / g.

The flocculant pigment is obtained by escorting aqueous water glass solutions with acidic Al and / or Ca salts or acids alone. These are thus amorphous Na-aluminum bridges or Ca-silicates or silicic acids. Essential to the success of their use is not only their coalition but also, and above all, their structure. All of the precipitation systems shown give products consisting of primary precipitation components,

With a diameter of less than 150 nm, However, these primary particles are bound in a cloudy order to the secondary structures, with an average diameter of 2 to 4 μm. These destructive secondary structures are crucial for the application. Measures that interfere with these structures, such as strong shear stress, are also detrimental to the desired effect. Sodium aluminum silicate, which has the following parameters, has proven to be excellent:

Si02 * 71 #

AlgOj »8 #

Na 2 O - 7 # annealing loss (including HgO 13 # primary particle size - 25 to 35 nm p BET surface »110 m / g plus calcium silicate, Having the following parameters:

Si02 - 80 #

CaO - 4 #

Na 2 O - 2 # annealing net (including H 2 O> 13 # particle size> 85 nm BET surface area> 35 m2 / g as well as silicic acid, Having the following parameters:

SiO2 - 87 # annealing loss (including HgO) 11 # particle size 18 nm Λ BET surface> 210 m / g 4,571 45

The improvement in printability must be seen as a result of the increased flexible volume of the coating layer. As hitherto, on ordinary surfaces, the kaolin sheets, when glued against each other and pressed next to each other, form a surface », the system becomes curly and compressible under the influence of flexible silicate-filled Alne secondary structures. The surface thus comes into contact with the raster of the deep-grained plate with even a slight press head. At the same time, the color transfer improves due to the increased absorbency of the surface.

The amounts of synthetic precipitation product required to achieve a good effect are 3-30 i »of the total weight of the coating pigment. In practice, 5-15 is common. Excessive application rates (above 30 56) increase the absorbency of the surface more than is beneficial and are therefore detrimental. In addition, the quantities available are limited by economic considerations. It should also be mentioned that the need for a binder in the precipitation product is considerably higher than with kaolin and that the viscosity of the paint becomes higher. These factors also limit the amounts of use to the aforementioned 5-15 mothers.

The use of synthetic precipitation products obtained from water glass solutions in paper coating compositions is already known. Until now, however, it has only come into question with papers »for which the gloss is desired or for which gloss does not form the basis of quality. It is still known to use titanium dioxide as an extender, an agent for increasing whiteness and providing a high oil absorption capacity.

It is a special feature that the precipitation products used according to the invention, when used alone, impart a matt surface to the coated papers. This property remains the same when using the usual amounts of binder for efflux coating and when calcium carbonate is the coating pigment. For these reasons, it was suggested «that pigments in this class be used in the manufacture of coated matte effet paper» whereby improved printability was observed.

However, in addition to good printability, high gloss is required for LVC-type deep-grained paper. Contrary to all suggestions, it has now become apparent that the use of the additions according to the invention in the LVC manufacturing instructions does not cause a reduction in gloss. Even a small improvement in gloss is achieved. Thus, only the method according to the invention becomes possible at all.

In the following, the invention will be illustrated in more detail by means of an example

Example a) Wood-containing coating raw paper for LVC was brushed on a Yoith-Blide coating machine at a speed of 700 m / min. The coating composition contained 10 # of total pigment amorphous Na aluminosilicate.

The sodium aluminosilicate consisted of 71 SiO 2, Θ $: eta Al 2 O 2, 0.2?

CaQ, $ 7: eta Na 2 O, $ 6: eta HgO and 13 # of annealing losses including water - 5,571 45 na # Primary particle diameter ranged from 25 to 35 nm, secondary structures had a maximum amount of 2-4 μm · The product appeared as a dried, ground powder . When dispersing in the coating composition, severe shear stress was avoided.

The coated paper was etinated 11 times on a calendar by running at a compression pressure of 200 kp / cm. To evaluate printability, a roll of this paper was printed on a Testaoolor gravure press. Gloss, smoothness and whiteness were further measured.

h) The same coating raw paper was coated with a coating composition with a pigment part of 100 Often kaolin. The color corresponds to the value of the prior art. Satinating and evaluation take place in the same way as in example a).

Example ah SS + OS ++ SS + OS ++ 1 kaolin 90 100 - 2 Na-Al silicate 10 3 dispersant 0.3 0.3 4 self-thickening latex 7 6.5 5 Ca stearate 0.8 0.8 6 solid alum content 52.7 54.6

7 viscosity cP

(Brookfield 100 5 / min) 1460 1200 8 application weights (coating) g / m 12 10 12 10 9 paper properties: 9.1 smoothness (contact part in 25 Kp) 34 43 28 30 9.2. gloss 60 ° / 60 ° (orientation angle: angle of reflection) 0.90 0.88 0.83 0.82 9.3. whiteness (Elrepho H 46) 78.4 78.3 77.4 77.4

9.4 * opacity DIN

53 146 0.968 0.966 0.963 0.966 9.5 »printability only single numerous" missing "missing points" via points "

The paper of Example (a) has a significantly higher gloss than that of (b) and gives an image that appears substantially smoother when printed due to the absence of "missing dots".

+ - wire side ++ - top side

Claims (6)

1. A process for producing coated paper having a basis weight of from 45 to 100 g / m and having improved printing properties by double-coating one of the coating pigments, coatings, water and chemical additives comprising coating coatings on one of cellulose and any abrasive pulp base paper and subsequent smoothing in supercalender, characterized in that in the coating mass, 3-30 wt. fo, preferably 5-15 wt. 56, calculated as the coating pigment, of a synthetically obtained amorphous product consisting of a silicate of aluminum and / or calcium and / or silicic acid having an average primary particle size less than 150 nm, preferably between 10 and 80 nm, an average secondary particle size less than 10 µm, preferably 2-4 µm, and a specific surface, measured according to The BET method, less than 300 m / g, preferably between 20 and 150 n / g. 2. A process according to claim 1, characterized in that as a silicate a sodium-aluminum silicate having the following parameters is used: SiO 2 = 71% Al 2 O 2 = 8 $ 1 Ta 2 = 7 1 ° glow loss (incl. HgO) = 13 $ = 25-35 nm PET surface = 110 m2 / g 3. Process according to claim 1, characterized in that a calcium silicate is used as silicate with the following parameters: SiO 2 = 80 $ CaO = 4 $ Nag0 = 2 $ glow loss (incl. HgO) surface area = 35 m2 / g 4 · Process according to claim 1, characterized in that a silicic acid having the following parameters is used: