EP0754260A1

EP0754260A1 - Web printing paper coated on both sides and process for its manufacture

Info

Publication number: EP0754260A1
Application number: EP95916612A
Authority: EP
Inventors: Dieter Horand; Adam GÜRTLER; Bernd Pelech; Paul-Heinz DÄHLING
Original assignee: Stora Feldmuehle AG
Current assignee: Stora Publication Paper AG
Priority date: 1994-04-08
Filing date: 1995-04-07
Publication date: 1997-01-22
Anticipated expiration: 2015-04-07
Also published as: ES2123976T3; CA2187182C; EP0754260B1; FI963942A; FI963942A0; DE59503785D1; WO1995027824A1; JPH09511552A; ATE171743T1; DK0754260T3; DE4411987A1; US5952091A; DE4411987C2; CA2187182A1

Abstract

PCT No. PCT/EP95/01283 Sec. 371 Date Sep. 30, 1996 Sec. 102(e) Date Sep. 30, 1996 PCT Filed Apr. 7, 1995 PCT Pub. No. WO95/27824 PCT Pub. Date Oct. 19, 1995A web printing paper, including a coating base paper which contains mineral filler and at least one of wood pulp and cellulose as fiber components. The coating base paper has a grammage of 30 to <58 g/m2, and a filler content, relative to its grammage, equal to 15 to 35% by weight. The coating base paper selectively contains, in addition to the at least one of wood pulp and cellulose, up to <50% by weight recycled fibers, all weight parts adding up to 100% by weight. The printing paper further includes a coating applied to both sides of the base paper by a film press so as to absorb printing ink. The coating contains pigment and binder. The coating on each side of the base paper has a grammage of 2 to 12 g/m2, and the pigment of the coating has a grain size, 40 to 60% by weight, of <2 mu m.

Description

Roll paper coated on both sides and process for its production

The present invention relates to a roll-coated paper coated on both sides, consisting of a coating base paper which contains mineral filler and, as fiber components, wood pulp and / or cellulose, the line used to hold the printing ink and containing pigment and binder being applied by means of a film press. The invention further relates to a method for producing the roll printing paper.

Web printing papers of the type specified at the outset are used for the production of magazines, in particular illustrated magazines, magazines, catalogs and advertising brochures, as are usually attached to daily newspapers or illustrated magazines.

Numerous attempts have already been made to reduce the manufacturing costs of the papers in question, in particular by reducing the Basis weight of the coating base papers to be used or by exchanging the pulp and / or wood pulp fibers used for recycling fibers.

An overview of wood-containing offset papers, as is common in Europe, can be found in the article: "Study on binder systems for LLWC and MFP papers", published in "Wochenblatt für Papierfabrikation" 9 (1988), pages 337 to 344 This study also describes a film press used to apply preparations for the paper types in question. The one described

The pigment composition consisted of a mixture of 60 parts of English China Clay and 40 parts of a fine American kaolin. In summary, the authors of this reference come to the conclusion that when using an SD coater (short residence coating device) 20 parts by weight of binder are required for an application of 5 g / m ² or 30 parts for a 3 g / m ² application are. However, if a film press is used instead of an SD coater, an increase in the binder level is considered necessary in order to achieve the same printing gloss, but with reduced opacity.

In "Wochenblatt für Papierfabrikation" 16 (1990), pages 701 to 708 and the identical reference "Pulp and Paper Canada" 92: 4 (1991), pages 52 to 58, reports on the surface treatment of newsprint using a film press. A raw paper with only an ash content of 0.4% by weight was used in these investigations. There is no information on the fineness of the pigments used for the surface treatment. In the recipes used for surface pigmentation, the extraordinarily high binder content of 70% by weight, based on pigment, is striking. The investigations are essentially limited to a coat weight of 5 g / m ² and page.

EP-0 377 983 A2 relates to a newsprint paper coated by means of an air brush or a roller coating device, which has an improved ink acceptance,

Surface strength and opacity should have. Line weights between 1 and 12 g / m ² , preferably between 3 and 8 g / m ² and the side to be printed are disclosed, a total area weight of 60 g / m ² not to be exceeded. The filler content of the known coating base paper is in the usual range between 0.5 and 10% by weight, but preferably less than 0.5% by weight.

In "Wochenblatt für Papierfabrikation" 1 (1988), pages 1 to 6, the article "Surface-coated SC papers, a challenge for LWC papers" relates to the coating of SC papers with a filler content of 15 to 25%. The SDTA application system (short dwell time applicator) is specified as the application device. The application weights are in the range up to 3.5 g / m ² and page, while for coating base papers with a lower filler content of less than 10% by weight, higher application weights are required, such as. B. in the so-called LWC papers, up to a coat weight of about 9 g / m ² 'and page.

According to the essay: "Possibilities for on-line coating of filled, wood-containing papers, published in" Wochenblatt für Papierfabrikation "13 (1992), pages 507 to 515, highly filled, improved SC papers are first made available by means of a film press with a pigmentation of calcium carbonate and at least 30% by weight of binder, based on the pigment, pretreated so that the papers have sufficient strength to be able to provide them with the actual top coat in a second operation by means of a knife coater. The top coats consist of mixtures of Kaolin and fine calcium carbonate, with 12 parts by weight of binder per 100 parts by weight of pigment mixture.The minimum application quantity for the top coat is 7 g / m ² and side, for example application weights of up to 19 g / m ² , while for the primer 4 to 5 g / m ² specified become. Although some of the papers produced, which represent a new type of coated paper, have excellent properties, there are disadvantages in that the required double-coat application and the high coat weight result in a paper which, due to the costs involved, must remain closed to essential areas of application. The disadvantages of film splitting at the exit of a film press are shown in detail in this article.

In the article: "Surface treatment of AP-containing printing papers - a challenge on the way to new paper qualities", published in "Wochenblatt für Papierfabrikation" 2 (1993), pages 53 to 61, is about various coating devices, including the under The name "speedsizer" became known film press reports. With regard to the surface treatment of SC paper, a pigment layer of 4 to 5 g / m ^{2 is} considered sufficient for achieving a good gravure printing quality, although it is found restrictively that a higher coating weight improves the coverage and whiteness when using a speedsizer pronounced film splitting results and a drastic drop in smoothness results. There is therefore a second coating step with a

Doctor blade coater for the purpose of achieving good gravure printing properties considered appropriate, Admittedly, a high level of machine expenditure and additional operating costs and thus an increase in the price of the product must result.

Finally, in the article: "Operating experience with Twin-HSM in the surface finishing of raw paper based on waste paper", published in "Wochenblatt für Papierfabrikation" 21 (1993), pages 886 to 890, reports on the problems with the use of a film press and also high ones Application weights mentioned, but only revealed regarding the type of coating colors applied that these were pigmented compositions.

The object of the present invention is to provide a roll paper coated on both sides which can be produced under inexpensive conditions, in the production of which a double coat in particular is not required, the fibrous material of which may consist of recycled fibers and the appearance and printability of which are comparable with the commercially available roll printing paper is. In particular, the invention aims to provide a web printing paper capable of gravure printing.

To achieve the object, the invention provides a web printing paper coated on both sides, which consists of a coating base paper, the mineral filler and Fibrous components contain wood pulp and / or cellulose, the line used to hold the printing ink containing pigment and binder and applied by means of a fil press, the paper being characterized in that

the coating base paper has a basis weight of 30 to <58 g / m ² ,

- The filler content of the base paper - based on its basis weight - is 15 to 35% by weight,

the coating base paper contains, apart from wood pulp and / or cellulose, optionally up to <50% by weight of recycled fibers, all parts by weight adding up to 100% by weight,

- The line has a basis weight of 2 to 12 g / m ² per side and

- The pigment of the coating to 40 to 60 wt.% Has a grain size <2 microns.

Before the advantages of the present invention, its further preferred embodiments and the method for producing the roll printing paper according to the invention are explained in more detail, the terms used in the description and claims are explained:

Among the roll printing papers according to the invention, only single-ply papers are different from z. B. to understand cardboard.

Under filler are to be understood the mineral pigments that the fiber suspension in the - 8th -

Papermaking can be added. No distinction is made here between freshly added fillers and fillers which are fed to the paper production process together with fibrous materials which may have been recovered from waste paper.

Recycled fibers are fiber materials recovered from waste paper, according to the invention particularly preferred are those which are obtained from waste paper type D31 in accordance with the list of German standard types.

Deinkt recycled fibers are fibers from which the printing ink is largely removed.

Wood pulp is understood to mean mechanically shredded wood fibers, i.e. both the so-called Schuff grades and the grades obtained with the help of refiners. A list of the different types of coagulum is given in the literature reference: "Zellstoff und Papier" 37 (1988), page 212. Of these types of wood materials listed there, the so-called TMP material (thermo-mechanical refiner wood material) is particularly preferred according to the invention.

Wood pulp or pulp is to be understood as "fresh" fibers, in contrast to the recycling fibers based on wood pulp or cellulose. The term film press is used here to identify all devices in which the coating color is pre-dosed by means of metering rollers, doctor blades and a smooth or grooved doctor blade on a transfer roller, from which the pre-dosed coating ink is "indirectly" transferred to the base paper web to form the coating. More detailed explanations can be found in the literature discussed above: "Wochenblatt für Papierfabrikation" 13 (1992), pages 507 to 515; also the reference: "Wochenblatt für Papierfabrikation" 6 (1992), pages 193 to 197.

Hot-soft calenders are also referred to in the professional world as soft-compact calendars, the nip consisting of a heated chilled cast iron roller and an associated roller with elastic plastic, see. a. "Wochenblatt für Papierfabrikation" 16 (1990), pages 701 to 708.

All weight information on fiber materials, coating base papers and coated papers or coatings refer to "oven-dry" weight information. Information on the binder relates to the solids content of the binder.

One of the known sedimentation methods, e.g. B. Andreas pipette, Sedigraph or Shimadzu centrifuge. The pigments present in the coating according to the invention are preferably exclusively mineral pigments. As a result of their relatively coarse particle size distribution, such pigments have hitherto been added as fillers to the pulp pulp in papermaking. The inventors had now recognized that when using these coarse-grain pigments as coating pigments for a coating color to be applied by means of a film press, the so-called film splitting did not occur, or at least to a significantly lesser extent, and this resulted in a substantially smoother coating surface. The invention therefore also enables problem-free application of significantly higher coat weights even with highly pigmented coating colors. Good coverage of the surface of the coating base paper is possible with a single stroke. The measures known from the prior art, such as the application of a primer by means of a film press and the subsequent application of a line serving to receive the printing ink by means of a doctor blade coater, can therefore be dispensed with. The pigment of the coating preferably has a grain size of <2 μm to 40 to 55% by weight. Possibly. can the coating pigment up to max. 10% by weight, based on the total pigment content, of one or more non-mineral pigments, such as, for. B. undissolved starch granules.

In connection with the high filler content of the base paper from 15 to 35% by weight arises especially with line application weights of more than 5 g / m ² and page, a roll printing paper of high opacity and good surface structure, which can be printed in both offset and gravure printing. It is preferred that the pigment content of the coating is not less than 80% by weight, based on the total solids content of the coating

Coating paint auxiliaries in a minor amount of max. 1.5% by weight can be present. The use of a film press as a coating device not only enables the coating base paper to be reduced to 30 g / m ² , it also makes it possible, in conjunction with the pigment composition according to the invention, for the coating used to hold the printing ink, apart from wood pulp and / or cellulose <50% by weight of the base paper from recycled fibers, preferably from deinked recycled fibers.

From an economic point of view, the present invention thus offers the advantage of saving material costs by accessing the coating pigments according to the invention, which are less expensive than the conventional fine-particle coating pigments, and furthermore there is the advantage of reducing the production costs with just a single coating process and finally offering them Invention also has the advantage of being able to use recycled fibers to a considerable extent. The invention is not limited to the use of recycled fibers, rather considerable economic advantages already result from the reduced material and manufacturing costs, even if the fibrous material of the base paper consists of only wood pulp and cellulose.

In order to ensure a uniform coating surface, it has furthermore proven to be expedient for the coating pigments to have an average grain size in the range from 1.3 to 2.5 μm and for their BET surface area to be between 6.5 and 9 m ² / g. Kaolin, calcium carbonate and talc are preferably suitable as coating pigments. According to a further preferred embodiment, the coating pigment to be used according to the invention consists of more than 80% by weight of kaolin, calcium carbonate, talc or a mixture of these coating pigments in the stated particle size distribution, while the rest of the coating pigment consists of pigments of the same type, but in a finer distribution or of other pigments , such as B. may consist of aluminum hydroxide, bentonite or titanium dioxide.

To achieve particularly good coverage of the base paper, a coat application of more than 5 g / m ² and page is preferred, but the application weight should not exceed 10 g / m ² and page. The binder content of the coating depends on the intended use of the web printing paper according to the invention, a binder content of 12 to 20% by weight, based on pigment, being preferred for web printing paper to be printed in dry offset, while a binder content of 10 to 15% is preferred for wet offset printing. % is sufficient. According to the invention, a binder content of 4 to 7% by weight, based on pigment, is provided for a web printing paper to be printed using the gravure printing process.

The usual synthetic latices based on acrylate and butadiene styrene are particularly suitable as binders, and furthermore - especially in the case of offset printing formulations - starch-based binders, it being generally preferred that the binder as a whole consists predominantly of a synthetic latex. Only in the case of offset printing recipes with binder proportions of more than 10% by weight can more than 50% by weight, but not more than 65% by weight, consist of a starch-based binder.

For the production of the roll printing paper according to the invention, a coating base paper has proven to be particularly suitable, to which cationic starch has been added as a mass additive to improve the strength during production. The fillers of the base paper preferably consist predominantly of kaolin, Calcium carbonate and talc or a mixture of these substances.

According to the invention, the roll printing paper can be produced online, i. H. After it has dried, the coating base paper is fed directly to the film press for application of the coating and, if necessary, smoothed directly by means of a calender after application and drying of the coating. A supercalender or a hot-soft calender can be used as the calender.

The following examples illustrate the invention:

In Examples 1 and 2 below, a wood-based coating base paper with a basis weight of 52 g / m ² and a filler content of 31% by weight was coated in an experimental coating device equipped with a film press - application weight: 6 g / m ² and side - dried and applied a super calender satin.

Coating color 1 (example 1):

Kaolin: 45% by weight <2 μm 100 parts by weight of self-thickening acrylate latex: 5 parts by weight

Na stearate: 0.5 part by weight

Solids content: 40% by weight Coating color 2 (example 2):

Kaolin as in coating color 1: 60 parts by weight of talc: 44% by weight <2 μm 40 parts by weight of other components and solids content as in coating color 1.

A visual evaluation of the web printed in gravure printing showed an excellent printing result.

Claims

claims

Roll paper coated on both sides, consisting of a coating base paper, the mineral filler and as

Fibrous components contain wood pulp and / or cellulose, the line used to hold the printing ink and containing pigment and binder being applied by means of a film press, characterized in that

the coating base paper has a basis weight of 30 to <58 g / m ² ,

- the filler content of the base paper - based on its surface area - is 15 to 35% by weight,

- The line has a basis weight of 2 to 12 g / m ² per side and

- The pigment of the coating to 40 to 60 wt.% Has a grain size <2 microns.

2. Coated printing paper coated on both sides according to claim 1, characterized in that the pigment of the coating has 40 to 55% by weight of a grain size <2 μm.

3. Double-sided coated printing paper according to one of claims 1 or 2, characterized in that the pigment of the coating has an average grain size in the range from 1.3 to 2.5 microns.

4. Coated printing paper coated on both sides according to one of claims 1 to 3, characterized in that the pigment of the coating consists predominantly of kaolin, calcium carbonate, talc or a mixture of these pigments.

5. Coated printing paper coated on both sides according to one of claims 1 to 4, characterized in that the pigment of the coating consists of more than 80% by weight of kaolin, calcium carbonate, talc or a mixture of these pigments.

6. Roll printing paper according to one of claims 1 to 5, characterized in that the line has a basis weight> 5 g / m ² per side.

7. Coated printing paper coated on both sides according to one of claims 1 to 6, characterized in that the line has a surface mass of not more than 10 g / m ² and side.

8. Coated printing paper coated on both sides according to one of claims 1 to 7, characterized in that the coating 12 to 20 wt.% Binder - based on the pigment of the coating

- contains.

9. Double-sided coated printing paper according to one of claims 1 to 7, characterized in that the line 10 to 15 wt.% Binder - based on the pigment of the line

- contains.

10. Coated printing paper coated on both sides according to one of claims 1 to 7, characterized in that the coating 4 to 7 wt.% Binder - based on the pigment of the coating

- contains.

11. A method for producing a roll printing paper coated on both sides according to one of claims 1 to 10, characterized in that

- on a coating base paper which has a basis weight of 30 to <58 g / m ² and a mineral filler content of 15 to 35% by weight, the coating base paper optionally containing up to <50% by weight recycled fibers in addition to wood pulp and / or cellulose and all parts by weight add up to 100% by weight,

- On each side of the coating base paper using a film press a coating color to achieve a coat weight with a basis weight of 2 to 12 g / m ² and page applied, the applied coating color is dried and the dried paper is smoothed by means of a calender, the pigment of the coating being 40 to 60% by weight with a grain size of <2 μm.