AU726536B2

AU726536B2 - Roll printing paper suitable for cold set and process for its production

Info

Publication number: AU726536B2
Application number: AU10196/97A
Authority: AU
Inventors: Hans-Peter Hofmann; Hartmut Wurster
Original assignee: Haindl Papier GmbH and Co KG
Current assignee: UPM Kymmene Papier GmbH and Co KG
Priority date: 1996-01-16
Filing date: 1997-01-16
Publication date: 2000-11-09
Anticipated expiration: 2017-01-16
Also published as: EP0785307A2; JPH09291497A; DE59708150D1; EP0785307A3; KR100489984B1; PT785307E; KR970059376A; NO323580B1; NO970150D0; EP0785307B1; AU1019697A; DK0785307T3; NZ314045A; ES2180827T3; NO970150L; ATE223986T1; DE19601245A1

Abstract

A coated roll printing paper suitable for printing with cold-set offset printing inks is based on paper containing paper fibres and mineral filler and has a coating containing ground calcium carbonate (CaCO3) pigment in a synthetic binder. The novel features are that: (a) not less than 50 wt.% of the pigment is a natural ground CaCO3; (b) all the pigment has a fineness of not less than 80% being less than 2 mu m; and (c) the dry binder fraction is less than 13 wt.% with respect to the pigment. Also claimed is a method of making the paper.

Description

p S F Ref: 363645

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

9 9~ 9 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Haindl Papier GmbH Georg-Haindl Strasse 9 86153 Augsburg

GERMANY

Hartmut Wurster and Hans-Peter Hofmann.

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Roll Printing Paper Suitable for Cold Set and Process for its Production The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 1 Roll Printing Paper Suitable for Cold Set and Process for its Production Introduction and Background The invention concerns a coated roll printing paper suitable for printing with cold-set offset printing inks using a base paper as the carrier paper which is formed from paper fibre material and mineral filler, with a coating containing ground calcium carbonate in the coating pigment and a synthetic binder as a binding agent. The invention further concerns use of such a paper and a process for its production.

At present, newspapers are nearly all printed by the offset process, using cold set inks. In contrast to heat-set inks they need not be exposed to heat for drying.

Instead, they dry as the water of the printing ink emulsion, as well as the oil in the ink, are absorbed into the carrier, ie., the paper, as soon as possible, with the e pigments of the ink remaining on the paper surface. Oxidative drying is also said to S 15 occur here.

eeooe Although the print quality improves with increasing smoothness of the carrier, and the consumption of ink decreases, smoother papers are generally less .oooo) absorbent, so that the absorption of the ink emulsifiers is slower. That causes smearing on the printing press guides and deposits in the folder and in the stack of copies. On the other hand, excess absorption causes the ink to penetrate more into the paper, giving an inadequate impression, ie., poor dot separation and printthrough of the print onto the back. Standard newsprint meet the conditions for adequately rapid drying of cold set inks but, as is well known, the quality of the image on newsprint is limited. Standard newsprint is an uncoated natural paper.

25 Thus its pore volume is not covered by a coating which could prevent absorption of the ink emulsion.

6 Rotary presses for newspapers are usually operated only during a limited portion of the day. It would be reasonable, then, to use such expensive equipment for other printing work, especially job printing, during the idle periods. Such jobs, though, which may be brochure enclosures or the like, generally require a higher quality of the printed image than is possible with standard newsprint. Because of that, there has been much discussion and experimentation with the purpose of making improved newsprint papers available for those applications. They could penetrate into the quality area of the SC (super-calendared) papers, ie., highly glazed papers such as are used for headset offset printing. As coated papers, they could also penetrate into the area of the LWC (low weight coated) papers. Previous experiments, though, did not succeed in being accepted by the market. European Patent Application o 377 983 describes a coated newsprint paper in which suitability for cold-set use is said to be achieved by a certain minimum content of acicular or needle-shaped pigments in the coating pigment, and which is said to exhibit at least a certain oil absorption value. It is not yet known that such a paper has found entry into the market. Acicular pigments, such as Satin White, precipitated calcium carbonate, and delaminated or structured kaolins, such as are recommended in the publication, are generally very expensive. Furthermore, because of their structure they require high usage of bonding material, which also increases the production costs.

Accordingly, it is an object of the invention at least in preferred embodiments to make available a coated roll printing paper which can be produced economically, which is suitable for printing with cold-set inks, is visually distinguished from the standard newsprint, and which can also be processed at printing speeds such as are common in offset printing of newspapers, or on the machines intended for such printing.

Summary of the Invention In attaining the above and other objects, one feature of the invention is a coated roll printing paper including as substrate a base paper containing paper-making fibres and mineral filler, and a coating which includes in its pigment ground calcium carbonate and in its binder a synthetic binder, characterised in that the surface wettability of the paper determined as the wetting angle (angle of contact) according to a Fibro-Test (as hereinbefore defined) after 2 seconds has a value of less than Another feature of the invention is a process for producing a roll printing paper P 20 suitable for printing with cold-set printing inks, in which a base paper is made from a i paper composition containing a paper fiber material and mineral filler and this base paper is coated with a coating color containing as the coating pigment a ground calcium carbonate and as the binder a synthetic binder, wherein a coating preparation is used for the coating, the coating pigment of which contains at least 50% by weight of a natural calcium carbonate, and the entire coating pigment of which has an average fineness of at least 65% 2 m, and in which the proportion of binder, based on the coating pigment, is less than 13% by weight, and wherein the amount of binder and calcium carbonate are selected so that the resulting coated paper has a surface wettability determined as the wetting angle (angle of contact) according to a fibro-test (as hereinbefore defined) after 2 seconds of less than Detailed Description of the Invention It was found, surprisingly, that the printability of a coated roll printing paper can be RA/ attained with cold-set printing inks if the coating has adequate microcapillarity and affinity for the emulsifiers of the cold-set printing inks. With respect to suitability of a [R:\LIBFFJ09027speci d c: j c 2a paper for cold-set ink printing, extensive studies were done to determine which measurable paper characteristics determine the suitability of a paper. It was found that particularly the surface wettability is critical. These properties can for example be attained if the coating pigment has a certain minium proportion, namely, 50%, of a natural ground (not acicular) calcium carbonate, the overall fineness of the coating pigment is such that at least 65% by weight of the pigment is made up of particles having a size 2 gim, and the proportion of binder, based on the dry weight, less than 13% by weight of the coating pigment. Sufficiently fine grades of kaolin are known to give a high pigment porosity, but they require high usage of binders because of their high specific surfaces.

That is particularly the case for delaminated and otherwise pretreated kaolins. Calcium carbonate, on the other hand, has an inert hydrophobic surface, requiring less binder in the coating.

Preferably, the desired result can be achieved when the surface wettability of the paper is less than 550, the calcium carbonate is a ground natural carbonate which makes 15 up at least 50% by weight of the coating pigment, the total coating pigment has a fineness of at least 9 [R:\LlBFF]09027speci.doc:njc 2 gim, and the proportion of binder, as dry weight based on the coating pigment is less than 13%.

Use of ground calcium carbonate in the coating is known from European Patent Application 0 377 983. There, though, the calcium carbonate is used only as a blending pigment along with the claimed acicular pigments.

According to an embodiment of the present invention, the calcium carbonate used should have medium to high fineness in order for the coating layer applied to have high microcapillarity to assure rapid drying of cold-set printing inks. The finer the capillaries, the higher the capillary pressure and thus the faster the phase separation of the printing inks, which are emulsified in more or less water. For high requirements, the coating pigment has to 100% by weight of calcium carbonate with a fineness of at least 80% 2 im, or at least 75% to about 85% by weight of a calcium carbonate with a fineness of about 2 imn. The ink absorption time and, especially, the water absorption capability of the paper surface appear to be critical for satisfactory drying of the cold-set printing inks. That is discussed further in the following. To be sure, certain minimums should be maintained for both properties to get satisfactory printing, but one property can to a certain extent be compensated by the other. The ink absorption time decreases with increasing fineness of the coating pigment, while the water absorption capability increases. At the same time, the specific surface of the pigment increases with the fineness, and thus the requirement for S. 20 binder increases. That reduces the favourable print properties. The person skilled in the •technology must find an optimal match between the fineness of the coating pigment and the proportion of binder used.

Aluminium hydroxide is a particularly suitable blending pigment because of its morphology and fineness. It can be used in proportions up to about 20% by weight of the S 25 coating pigment. Otherwise, kaolin with a fineness of 65% or more 2 gm can also be used as a blending pigment, if the printability properties allow it. Talc, titanium dioxide and 4. gypsum are also suitable blending pigments in small proportions as long as they do not counteract the desired capillarity of the coating.

A sodium bentonite has also proved good as a blending pigment with high water absorption capacity. Up to 25% by weight of a grade having a specific surface of 600m2/g can be used, limited by its effect on the rheology of the coating pigment.

It is desirable to use highly active binders in order that the cold-set ability of the coating not be reduced by too much binder. The following types of binders are generally used for paper coating. They are listed in order of decreasing binding [1:\DayLib\LIBUU]25709.docmcc action: polymeric dispersions styrene-butadiene, acrylate, styrene-acrylate), polyvinyl alcohol, protein or casein, starch. In order to get high binding action with the lowest possible proportion of binder, based on the coating pigment, polymeric binders and polyvinyl alcohol (PVA) are used preferably according to the invention.

PVA has, along with its binding ability, the property of attaching irreversibly to surfaces having relatively inert reactivity, such as calcium carbonate. Therefore it is preferably used in combination with a plastic binder. According to the invention it is preferable to use less than 12% binder, based on the coating pigment and, if possible in the combination above, less than 9.5% by weight. Typically the proportion of binder used is actually only about 6.5% by weight. If starch is also used, the proportions of binder are near the upper limit. More or less hydrophilic binder, starch or CMC (carboxymethyl cellulose), depending on the pigment mixture, is used with PVA to control the ink absorption time.

An example binder combination comprises 1.0 to 4.0 percent by weight PVA 15 and 4.5 to 5.5 percent by weight of a synthetic binder, including but not limited to a .i butadiene-styrene binder or a styrene-acrylate binder. In the meaning of this description, the polymeric dispersions, also combined with PVA, are considered highly active binders. Addition of a cross-linking agent can be necessary for certain binders.

20 The coating pigments according to the invention can, for example, have the following typical components: 0 0 0.

CaCO 3 65% <2pm 50-100% CaCO 3 90% <2p[m 50-90% Kaolin 65% <2pm 0-50% Kaolin 80% <2gm 0-50%

AI(OH)

3 98% <2pim 0-20% Sodium bentonite 600 mz/g 0-25% Polymeric binder 3-10% PVA Protein Starch The coating pigments used can also contain the usual additives, such as up to 1.5% by weight melamine-formaldehyde resin as a wet-strength agent, up to 0.4% carboxymethyl-cellulose (CMC) as a solution, optical brighteners, and/or chemicals for pH adjustment, such as NaOH.

Ground natural calcium carbonates which are suitable for the invention and are commercially available in large quantities include, for instance, Types and C90HS from ECC International. The C60HS grade has a proportion of 63 by weight <2jm with not more than 2% by weight 10pm and not more than 0.01% by weight >45pm. The C90 grade contains 90±3% by weight <2gm, not more than 1% by weight >10tm and not more than 0.01% by weight These grades are provided as slurries with solids contents of 78+1% by weight.

Omya is another producer of suitable grades of calcium carbonate. The coating pigments according to the invention are processed in an aqueous slurry with solid contents of 30-65% by weight based on dry weight. Applicable coating processes include doctor blade coating processes such as the inverted blade, jet flow, rollcoating systems such as the Massey coater, film presses such as the Jagenberg film press, the Speedsizer or the Metering Size Press from Beloit. Thus the process of the invention and the paper it produces are essentially independent of the nature of the coating process, although under given conditions one coating method or 1o another may give better results than others. As is well known, doctor blade coating processes smooth the paper surface, giving a coating thickness that varies with location, while roll-coating systems give a more even coating thickness which can be advantageous for ink absorption under some circumstances. Gentle drying of the coating can also be important so that undesirable migration of binder do not 15 injure the desired evenly distributed microcapillarity of the coating.

The invention considers coating weights for singly coated papers as a weight of more than 4g/m 2 for each side on the base paper. Coating weights of 7-12g/m 2 per side, typically about 8g/m 2 per side, are preferred.

The invention is not, however, limited to singly coated papers. It is also applicable to double-coated papers. Double coatings have coating weights per unit area of at least 15g/m 2 per side, and typically 20g/m 2 per side, with the coating weight divided about equally between the two coatings. The top coat is critical for the properties of the paper according to the invention. If this description speaks of a coating without specifying exactly, it means the single coating for singly coated papers, and, generally, the top coating of doubly coated papers; but in separate definitions it means the total coating.

this description, the first coat of a double coat is always expressly called the first coat.

The top coat is largely critical for the properties of a double-coated paper according to the invention. Thus it must meet the requirements and conditions which were described above essentially with respect to application to singly coated papers. The first coat does not absolutely have to have the same fineness or microcapillarity as the preferred embodiments of the previously described coatings.

But even the first coat should contain at least 50% by weight of ground natural calcium carbonate and it should also meet the requirements of the total coating pigment having a fineness of at least 65% <2pm, and the proportion of binder as dry weight, based on the coating pigment, being less than 13%. These minimum requirements as stated above are valid for purposes of definition both for singly and doubly coated papers. This is even more the case to the extent that a top coat which represents a preferred embodiment in its composition and fineness exceeds the minimum requirements set forth herein, when the first coat, considered by itself, does not absolutely have to meet these minimum requirements.

It may be practical to pre-smooth the base paper before applying the single coating or the first coating, as in a smoothing machine at the end of the paper machine, which can also be equipped with a'Soft-Nip'.

The invention is not limited to use of a particular base paper. Both papers with and without mechanical wood can be used, as well as those with a substantial proportion of recycled paper fibre. For instance, a mechanical-wood-free base paper from raw materials in the proportions (as dry weight) of about 78% chemical pulp; about 20% mineral filler, made up of 15% calcium carbonate, 2.5% kaolin and talc; and about 1% starch and about 1% other additives is suitable.

For cost reasons alone, though, paper containing mechanical wood pulp and a proportion of recycled wastepaper is preferred. As a rule, too, base papers containing mechanical wood pulp have advantages for printing, such as higher oeoo opacity. The fibre content of a base paper containing mechanical wood pulp and wastepaper, based on total fibre, as dry material, can be about 20% chemical pulp, mechanical pulp, and 60% wastepaper. The material can also contain up to about 50% mineral filler, based on the fibre content, so that the filler is about 3 of the material. As is well known, this proportion of filler does not entirely remain in the o 20 paper; some gets into the wastewater.

When mechanical wood fibres are mentioned in this description as fibre components, the term applies to all the materials which are usually meant by that term in paper technology, such as groundwood pulp, thermomechanical; pulp (TMP), chemothermomechanical pulp (CTMP), etc.

Another important prerequisite for acceptable printing with cold-set inks, along with satisfactory ink drying, is the dimensional stability of the paper. As the water from cold-set inks penetrates not only into the coating but also into the base paper, that affects the bonding between fibres the dimensional stability of the paper. This effect is greater than with normal newsprint. When a coated paper having a weight per unit area comparable with the coating is used as a carrier for the coating, the paper makes up a correspondingly smaller proportion by weight. That is, the base paper is thinner. The dimensional stability of a paper exposed to moisture can be improved by additives, such as starch. Thus it is common to add about 0.5% starch to the material going into base paper. Papers made on an open Fourdrinier machine or on the "hybrid formers," in which the upper dewatering screen accompanies the Fourdrinier screen only after the sheet has been formed, may perhaps have -adequate dimensional stability for use in cold-set printing without addition of starch to the paper. Because of the production process, they have relatively favourable fibre orientation with transverse to longitudinal ratios of about 1:2 to a maximum of 1:2.5. As the fibres are oriented principally in the production 7 direction, ie., the long direction of the paper, the deficiency in dimensional stability appears essentially in transverse shrinkage, with is increased by the tension of the paper in the printing machine.

Currently, papers for large-scale printing are produced only on very highspeed Fourdrinier machines, which, at the present state of the technology, use solely the so-called "Gap Formers", in which the sheet is formed in the running gap between two screens. Papers made on such modern machines have substantially poorer transverse/longitudinal fibre orientation, in the range of about 1:3 to 1:4.

That causes such papers to have considerably poorer transverse stability. Now, as part of the invention, it has been found that the dimensional stability of papers produced on gap formers can be improved adequately by adding more than 1% starch, up to a maximum of and typically about to the input materials.

The surprising feature is not the effect of the starch on the paper, but the fact that paper with such a high starch content can be produced at all on a gap former. That 15 had not been considered possible. It has been made possible, as part of the invention, with a modified, highly cationic, starch. The surprising effect was that when 1.5% starch was added to the input materials, about 1.4% could be found in the base paper, indicating an astonishingly high retention of the starch in sheet formation. Higher proportions of starch in the input do not have a significant effect on the base paper and, at best, increase the wastewater loading and costs. In a itest run with highly cationic starch, the base paper could be produced without reducing the machine speed, at about 1220 metre/minute.

With respect to suitability of a paper for cold-set ink printing, extensive studies were done to determine which measurable paper characteristics determine the suitability of the paper. It was found that certain limits in ink absorption and, particularly, in the surface wettability, are critical. A modified absorption test is used in the inventor's company to determine the ink absorption. It uses the multipurpose test printer, Dr. Darner System, from the company "Prifbau Dr. Ing. Herbert Darner" in Peisenberg. The surface wettability is generally determined by the timedependent decrease in contact angle of a liquid drop placed on the surface. The FIBRO 1100 Dynamic Absorption Tester from FIBRO-System AB in Stockholm was used for that. Summaries of the test procedures are attached to this description as Appendices A and B.

In the absorption test, a proof print is made with a standard printing ink under defined conditions. After a specified period it is pressed together with a backing paper. The ink intensity transferred to the backing paper is measured with a densitometer. The following data show the densitometer values for the backing paper after 30 seconds.

Distilled water was used in the contact angle measurements to determine surface wettability. The contact angles measured with the FIBRO tester after 2 seconds are reported in the following.

It has been found that the ink absorption is important for suitability for the cold-set printing process. It should definitely be and preferably The contact angle measured with the FIBRO tester after 2 seconds should be <700 and preferably <550. For example, standard newsprint has a value of only about 420 after 2 seconds. Such a natural paper has a high wettability. The two paper properties mentioned above partially balance each other. For instance, excellent printing is produced with a 2-second contact angle of 450 and an absorption, for both sides of the paper, of 0.5. Papers with contact angles of less than 500 and absorption values of <0.7 are outstandingly well suited for cold-set printing.

The papers according to the invention that are of concern here, which have the properties stated above, are essentially unglazed or only very slightly glazed 15 papers with Bekk smoothness values between about 10 and 50 seconds. These are matt grades. A high glaze on papers according to the invention would not only reduce the picking resistance of the surface, which is required for printability, but it might also result in loss of the microcapillarity required for drying the cold-set inks.

If not otherwise specified in this description, percentages are always weight 20 percentages, even if not expressly so stated. Also, if not specifically stated otherwise, the percentages and other quantities always refer to the components considered as dry. In this relation, the term "otro" refers to the oven-dry state.

Example embodiments of the invention follow.

Example 1 25 The following raw materials were used to produce base paper on a highspeed Fourdrinier machine with a double-screen former (gap former) at a machine speed of about 1200 meters/minute: Base paper raw materials Groundwood 12.3% Chemical pulp 13.0% Wastepaper 40.0% Filler 33.0% Highly cationic starch Retention agent 0.2% Base paper test data Weight per unit area 40.3g/m" Proportion of filler 15.2% Longitudinal breaking stress 41.8N Transverse breaking stress 11.8N riDire orientation, 1:3.5 transverse/longitudinal Brightness 73.5/ o 9 Volume 1.538cm /g

S

9 9* 9 9 5* 9 Example 2 The base paper made according to Example 1 was coated with a coating having the following composition: Natural CaCO 3 95% <2pm

AI(OH)

3 98% <2tm 100% Binders and additives based on the coating pigments Styrene-acrylate binder Starch solution 3% CMC (carboxymethyl cellulose) solution 0.25% Melamine-formaldehyde resin 0.8% Optical brightener 1.3% The coating had a weight per unit area of about 8g/m 2 per side. The following measurements were made on the finished paper: Weight per unit area 56.5g/ml Ash on ignition at 600 0 C 35.3% Volume 1.18 cm /g Bekk smoothness, upper side 22 seconds Bekk smoothness, lower side 15 seconds 2-second contact angle, FIBRO test 580 Absorption at 30 seconds 0.42 The cold-set suitability, ie., adequate ink drying of this paper in the practical test, was satisfactory.

Example 3 The base paper according to Example 1 was coated with a coating having the following composition: Coating pigment Natural CaC03, 90% <2gm 100% Binders and additives, based on the coating pigment Butadiene-styrene binder PVA solution Melamine-formaldehyde resin 1.3% Optical brightener 1.3% The paper had the following surface characteristics: 2-second contact angle, FIBRO test 450 Absorption value after 30 seconds 0.50 The other test data are the same as for the paper of Example 2. The paper made in this example showed outstanding cold-set suitability in the practical test.

Example 4 The base paper made as in Example 1 was coated with a coating pigment which differed from that of Example 3 only in the fact that, instead of a polyacrylate dispersing agent, the pigment was made into a cationic pigment slurry with a highamine-content cationic dispersing agent, and a cationic polymeric binder was used to prepare the coating pigment. The finished paper had the following surface characteristics: 2-second FIBRO contact angle 500 Absorption after 30 seconds 0.39/0.47 The printability of this paper in the cold-set process was also very good.

Example 5 (Comparison example) The base paper made as in Example 1 was coated with a coating pigment having the following composition: Natural CaCO 3 90% <2pm Kaolin, 80% <2pim 100% Binders and additives, based on the coatina Diament

S..

S *5 5

U

5** a,

C

SP

U

Styrene-acrylate binder Starch solution CMC solution 0.25% Melamine-formaldehyde resin 0.8% Optical brightener 1.3% The paper coated with this coating pigment had the following surface properties: 2-second FIBRO contact angle 720 Absorption after 30 seconds 1.11/1.19 Ink drying on printing with cold-set inks was not satisfactory. That is already expressed by the surface properties, and was due to the high proportion of binder.

A paper with a pigment coating differing from that above only in having

AI(OH)

3 98% <2pm, instead of 20% kaolin in the coating pigment gave similarly poor print results. The composition and proportion of binder were the same.

The papers made as in Examples 3 and 4 could be processed on cold-set printing presses at the usual production rates, and gave accurate image reproduction with normal ink drying. At the same time, the ink consumption was less than for newsprint. Water usage was reduced. The higher whiteness, compared with normal newsprint, gave a more contrasty print that was quite comparable with that of low-weight-coated matt grades.

Appendix A FIBRO 1100 DAT is the name of an instrument from Fibro system AB, Box 9081, S-12609 Stockholm, Sweden. The letters DAT stand for "Dynamic 11 Absorption Tester". The instrument is used to measure surface wettability. This is a paper characteristic which must be accurately measured and adjusted for process such as coating, printing etc. It works on the principle of contact angle measurement, and is based on a method development by the Swedish Paper Research Institute.

The instrument comprises a medical dropper system and a CCD (charge-coupled device) camera, that the drop size is adjustable from 0.1 to 9.9ptL, and that changes in the drop deposited on the paper sample, which are characteristic for the wettability, can be documented in storable video images with a cycle time of 20 milliseconds. The change of the contact angle with time can be plotted, so that the wetabilities of different paper samples can easily be compared with each other.

In this case, distilled water was used for wetting, and the wetting was determined after 2 seconds.

Appendix B In the counter printing test, also called a smear test or absorption test, a specified quantity of printing ink is placed on a paper strip. Sections of the strip are then rolled on backing paper strips at specified time intervals. The quantities of ink transferred to the backing paper strips is determined optically. They allow conclusions about the ink absorption and stakability of the sample strips.

Details of the test procedure can be found in a detailed description of multipurpose 20 test printing presses from Prufbau, Dr.-Ing. Herbert Dumer, Aich 17-23, D-82380 Peissenberg/Munich, dated 26 September 1972. See, in particular, Figures 10.5 and 14.2.

The instructions recommend 0.3cm 3 ink for coated papers, an ink-distribution time of 9 30 seconds in the ink-distributing rollers and 30 seconds for the printing form. The pressure for printing as well as for counter-printing should both be 200N/cm, ie., 800N for printing S 25 form width of 4cm. The absorption test No. 52 0068 of the Michael Huber Ink Factory, Munich, should be used. The counterpressure should be applied after 30, 60, 120 and 240 seconds. The recommended press speed is 0.5m/second. A standard paper called APCO H/II from the Scheufelen company is used as the test printing paper.

In this case, the test was done with the values stated, but with twice the printing speed.

The ink transfer to the baking strips caused by counter-pressure for 30 seconds, was evaluated in particular.

Further variations and modifications of the foregoing will be apparent to those skilled in the art and are intended to be encompassed by the claims appended hereto.

German priority applications 196 01 245.7 and 296 01 859.7 are relied on and incorporated herein by reference.

[o:\DayLib\LIBUU25709.doc:mcc [IA:DayLib\LIBUJ]25709.doc:mcc

Claims

1. A coated roll printing paper including as substrate a base paper containing paper-making fibers and mineral filler, and a coating which includes in its pigment ground calcium carbonate and in its binder a synthetic binder, characterised in that the surface wettability of the paper determined as the wetting angle (angle of contact) according to a Fibro-Test (as hereinbefore defined) after 2 seconds has a value of less than

2. A coated roll printing paper according to claim 1 wherein the surface wettability of the paper is less than

3. A coated roll printing paper according to claim 1 or claim 2 wherein the calcium carbonate is a ground natural calcium carbonate which makes up at least 50% by weight of the coating pigment.

4. A coated roll printing paper according to any one of claims 1-3 wherein the total coating pigment has a fineness of at least 65% <2jim. A coated roll printing paper according to any one of claim 1-4 wherein the proportion of binder, as dry weight based on the coating pigment, is less than 13%.

6. A coated roll printing paper according to any one of claims 1-5, characterised by the fact that the coating pigment comprises 50 to 60% by weight of a calcium carbonate having a fineness of at least 60% <2ptm, with the rest being pigments having an average fineness of at least 80% 2ptm. 20 7. A coated roll printing paper according to any one of claims 1-6, characterised by the fact that the average fineness of the coating pigment is at least 80% <2pgm.

8. A coated roll printing paper according to any one of claims 1-7, characterised by the fact that the coating pigment contains up to 20% by weight of an aluminium hydroxide having a fineness of at least 95% <2[tm. 25 9. A coated roll printing paper according to any one of claims 1-8, characterised by the fact that the coating pigment comprises, along with calcium carbonate, a proportion of up to 50% by weight kaolin having a fineness of >65% by weight <2pum and/or up to by weight aluminium hydroxide having a fineness of 95% <2ptm and/or 25% by weight of a sodium bentonite.

10. A coated roll printing paper according to any one of claims 1-9, characterised by a composition of the binder, in terms of dry weight, in the coating, in percent by weight of the coating pigment, of 3-10% synthetic binder 0-5% polyvinyl alcohol (PVA) 0-5% protein and/or casein 0-5% starch.

11. A coated roll printing paper according to any one of claims 1 to R characterised by the fact that the proportion of binder, based on the coating pigment, is less han 12% by weight. [I:\DayLib\LiBUU]25709.doc:mcc 13

12. A coated roll printing paper according to any one of claims 1-10, wherein the proportion of binder, based on the coating pigment, is less than 9.5% by weight.

13. A coated roll printing paper according to claim 11 or claim 12 wherein the binder, as a percentage of the coating pigment, comprises essentially 1.0 to 4.0% by weight PVA and 4.5 to 5.5% by weight of a synthetic binder, including but not limited to a butadine-styrene binder or a styrene-acrylate binder.

14. A coated roll printing paper according to any one of claims 1-13, wherein the weight per unit area of the coating is more than 5g/m 2 per side. A coated roll printing paper according to claim 14, wherein the weight per unit area of the coating is 7-12g/m 2 per side.

16. A coated roll printing paper according to claim 15, wherein the weight per unit area of the coating is at least 15g/m 2 per side.

17. A coated roll printing paper according to claim 15, wherein the weight per unit area of the coating is about 20g/m per side.

18. A coated roll printing paper according to any one of claims 1-17, wherein it is machine-smooth or slightly glazed, having a smoothness, according to Bekk, between and 50 seconds.

19. A coated roll printing paper according to any one of claims 1-18, wherein the :ink absorption test (as hereinbefore defined) gives a value <1.1. 2o 20. A coated roll printing paper according to any one of claims 1-18, wherein the ink absorption test (as hereinbefore defined) gives a value <0.8. o°

21. A coated roll printing paper according to any one of claims 1-20, wherein the base paper contains up to 18% by weight mineral filler, based on oven-dried paper fibre.

22. A coated roll printing paper according to any one of claims 1-21, wherein the base paper contains at least 1.0% of highly cationic starch by weight.

23. A coated roll printing paper according to any one of claims 1-21, wherein the base paper contains at least 1.3% by weight of highly cationic starch.

24. A process for producing a roll printing paper suitable for printing with cold- set printing inks, in which a base paper is made from a paper composition containing a paper fiber material and mineral filler and this base paper is coated with a coating color containing as the coating pigment a ground calcium carbonate and as the binder a synthetic binder, wherein a coating preparation is used for the coating, the coating pigment of which contains at least 50% by weight of a natural calcium carbonate, and the R entire coating pigment of which has an average fineness of at least 65% 2 tm, and in Swhich the proportion of binder, based on the coating pigment, is less than 13% by weight [R:\LIBFF]O9027speci.doc:n 14 and wherein the amount of binder and calcium carbonate are selected so that the resulting coated paper has a surface wettability determined as the wetting angle (angle of contact) according to a fibro-test (as hereinbefore defined) after 2 seconds of less than A process according to claim 24 wherein the ink absorption test (as hereinbefore defined) of the coated paper gives a value <1.1.

26. A process according to claim 24 wherein the ink absorption test (as hereinbefore defined) of the coated paper gives a valued <0.8.

27. A process according to any one of claims 24 to 26, wherein the base paper is produced with a gap-former with a transverse-to-longitudinal fiber orientation ratio of 1 1 0 to 2.5 and that at least 1.0% by weight of a particularly highly cationic starch is added to the paper fiber material, based on oven-dried paper fiber. •28. A process according to any one of claims 24 to 26, wherein the base paper is produced with a gap-former with a transverse-to-longitudinal fiber orientation ratio of 1 to 2.5 and that at least 1.5% by weight of a particularly highly cationic starch is added 15 to the paper fiber material, based on oven-dried paper fiber.

29. A process according to any one of claims 24 to 26, wherein the base paper is produced with a gap-former with a transverse-to-longitudinal fiber orientation ratio of 1 to 2.5 and that at least 2.0% by weight of a particularly highly cationic starch is added to the paper fiber material, based on oven-dried paper fiber.

30. A process according to any one of claims 24-29, wherein at least 25% by weight oven-dry mineral filler, based on oven-dry paper fiber material, is added to the mixture of materials for the base paper.

31. A process according to any one of claims 24-30, wherein a coating color is used in which the average fineness of the coating pigment is at least 80% 2 Vtm.

32. A process according to any one of claims 24-31, wherein a coating color is used, the coating pigment of which contains up to 20% by weight of aluminium hydroxide having a fineness of at least 95% 2am.

33. A process according to any one of claims 24-31, wherein a coating color is used, the coating pigment of which contains, along with calcium carbonate, up to 50% by weight kaolin having a fineness of 65% by weight 2 am and/or up to 20% by weight aluminium hydroxide having a fineness of 95% 2 tm and/or 25% by weight of a sodium bentonite.

34. A process according to any one of claims 24-33, wherein a coating pigment having a binder composition, in percent by weight, based on dry weight of coating W y\ pigment, of 3-10% synthetic binder [R:\LIBFF]09027speci.doc:njc polyvinyl alcohol (PVA) protein and/or casein starch. A process according to any one of claims 24-34 wherein a coating color having a binder content of not more than 9.5% by weight, based on coating pigment, is used.

36. A process according to claim 35, wherein, based on the coating pigment, essentially 3.0 to 4.0% by weight PVA and 4.5 to 5.5% by weight of a synthetic binder is used as the binder.

37. A process according to claim 35, wherein, based on the coating pigment, essentially 3.0 to 4.0% by weight PVA and 4.5 to 5.5% by weight of a synthetic binder including a butadiene-styrene binder or a styrene-acrylate binder, is used as a binder.

38. A process according to any one of claims 24-37, wherein a coating weight per unit area greater than 4g/m 2 is coated on each side of the paper. o 15 39. A process according to claim 38, wherein a coating weight per unit area of 7- 12g/m 2 is coated on the base paper per side.

40. A process according to claim 38, wherein a precoat and a top coat are applied in quantities giving a coating weight per unit area of at least 15g/m 2 in the finished paper.

41. A process according to claim 38, wherein a precoat and a topcoat are applied 20 in quantities giving a coating weight per unit area of about 20g/m 2 in the finished paper.

42. Use of a roll printing paper according to any one of claims 1-23 for cold-set offset printing.

43. Roll printing paper produced by the process of any one of claims 24-41.

44. Use of a coated roll printing paper for cold-set offset printing, the roll printing paper including as substrate a base paper containing paper-making fibers and mineral filler, and a coating which includes in its pigment ground calcium carbonate and in its binder a synthetic binder, wherein the surface wettability of the paper determined as the wetting angle (angle of contact) according to a Fibro-Test (as hereinbefore defined) after 2 seconds has a value of less than

45. A coated roll printing paper including as substrate a base paper containing paper-making fibers and mineral filler, and a coating which includes in its pigment ground calcium carbonate and in its binder a synthetic binder, said coated roll substantially as hereinbefore described with reference to any one of the examples but _RT excluding the comparative example. [RALIB FFJ 09027speci.doc:nj c 16

46. A process for producing a roll printing paper suitable for printing with cold- set printing inks, in which a base paper is made from a paper composition containing a paper fiber material and mineral filler and this base paper is coated with a coating color containing as the coating pigment a ground calcium carbonate and as the binder a synthetic binder, said process substantially as hereinbefore described with reference to any one of the examples but excluding the comparative example.

47. Use of a coated roll printing paper according to one or more of claims 1-23 or 43 for cold-set offset printing. Dated 8 September, 2000 Haindl Papier GmbH Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON a a a a o** [R:\LIBFF]09027speci doc:njC