EP2038478B1 - Method for finishing paper and paper products - Google Patents

Abstract

Process for finishing paper and paper products by treating the surface of paper or paper products with at least one finishing agent, at least one finishing agent being applied in the form of a pattern on the top and/or bottom of paper or paper products, and the papers and paper products obtainable by the process.

Description

The invention relates to a process for finishing paper and paper products by treating the surface of paper and paper products with at least one finishing agent and the finished papers and paper products obtainable by the process.

To improve the properties of paper and paper products, for example, the surface of paper or paper products is treated with finishing agents such as hardeners, water repellents, hydrophilicizing agents and / or paper coating slips. The finishing agents are always applied over the entire surface of the top and / or bottom of the paper or paper products.

From the older one DE application 10 2005 050 658.5 For example, a method of reducing the absorption of water and water vapor and increasing the dimensional stability of paper and paper products is known. In this one first compresses cellulose fibers or a paper product obtained therefrom by dewatering on a sieve, then brings the compressed paper product with an aqueous solution and / or dispersion of the reactive material in contact, then lifts under further action of the aqueous solution and / or dispersion, the compression The paper product dries and heats to a temperature at which the reactive material reacts with itself and / or with the cellulose fibers to crosslink. Suitable reactive materials are, for example, thermally curable binders such as urea-formaldehyde adducts, one- or two-component systems based on epoxy resins, polyacrylates and polymethacrylates. Also in this process, the entire top or bottom of the paper is treated with at least one reactive material.

The US 2004/013 1842 teaches a method of making tissue papers by printing a hydrophobic composition in places on the surface of a tissue sheet. The hydrophobic composition causes softness of the tissue paper with good absorption properties.

US 3,667,422 discloses an apparatus for applying adhesive materials to a panel.

The DE 3707480 teaches a paper towel, which is sprayed in places with an oily or greasy agent as a care product. For towels, just the softness is an important feature.

The EP 333 417 describes a method for coating paper products by applying substrates to the surface of the paper products which improve the surface strength and thus the printability.

The US 4968 534 relates to a method for impregnating paper products by means of a device which applies the impregnating agent in the form of a pattern.

The invention has for its object to improve the properties of paper and paper products, in particular their stiffness, printability, laminability and biocidal activity against microorganisms to the effect that in comparison with known methods already achieved a sufficient effect with a smaller amount of finishing agents.

The object is achieved according to the invention with a method for finishing paper and paper products by treating the surface of paper or paper products with at least one finishing agent, if at least one finishing agent in the form of a pattern is applied to the top and / or bottom of paper or paper products and one as a finishing agent at least one agent that increases the stiffness of paper. The finishing agent is preferably applied to the top and / or bottom of paper or paper products by means of a printing process applied. Such printing processes belong to the state of the art. They are commonly used to print on sized or coated papers or textiles with printing pastes other than paper finishing equipment. The finishing agent can z. B. after the screen printing, ink-jet printing, flexographic printing or offset printing process on the top and / or bottom of paper or paper products to be printed.

Preferably, the finishing agent is printed on the top of paper or paper products by the ink-jet printing process. For example, the paper may be unsized or a bulk sized paper or paper product. Suitable engine sizes are, for example, alkyldiketenes, alkenylsuccinic anhydrides or rosin size.

The invention also relates to papers and paper products which are each obtainable by the process according to the invention. These are essentially writing and printing papers, packaging papers, corrugated cardboard, wallpaper, cardboard, filters and laminates, for example, of a composite of cardboard or paper and at least one film of a thermoplastic material, for example polyethylene, polypropylene, polyamide, polyester or polycarbonate ,

The finishing agent according to the invention, for example, in the form of a grid, a rhombus, spiral, circular, sheet-like, strip-shaped or punctiform printed on the top and / or bottom of paper or paper products, the arrangement of the pattern in an orderly or random (stochastic) can. The finishing materials are always applied according to the pattern. In contrast to known application methods of finishing compositions for paper in which the finishing agent is applied to the entire top or underside of paper, in the method according to the invention the finishing agent is applied to the surface of paper that does not coat the entire surface with it is. For example, the proportion of the total surface area printed with a finishing agent is 0.1 to 90, preferably 1 to 70%, and most is in the range of 10 to 50%. The other part of the surface of the paper not treated with a finishing agent remains untreated. After printing, the printed paper or paper product is dried and optionally heated to a temperature at which the finishing agents crosslink, e.g. to temperatures in the range of 35 to 200 ° C.

The effect achieved with the aid of the method according to the invention, for example the rigidity of a paper, depends on a number of factors, in particular on the composition and amount of finishing agent, on the structure of the finishing agent printed on the paper and on the orientation of the paper, ie the stiffness of the paper depends on the orientation of the cellulose fibers from. It is different for a paper sheet in the machine direction than transverse to it. The finishing agent is in the form of a pattern and may be printed eg on the top and / or bottom of paper or paper products in the form of a grid, a rhombus, a polygon (eg hexagon, octagon), spiral, circular, sheet, strip or dot. The individual strips of a grid or rhombus can have different dimensions, for example a thickness of 0.1 to 100 mm, preferably 1 to 10 mm and a length of 0.1 to 100 mm, preferably 1 to 10 mm. The distance between the individual strips of a grid, ie the unprinted areas, may for example have a spacing of 0.1 to 100 mm, preferably 1 to 10 mm. The grid can be square, rectangular or rhombic. If you print the paper strip-shaped, so the strips can extend over the entire length or width of the paper.

The paper can also be punctiform printed with a variety of points or area, which is to be understood by sheet-like that a larger area is provided with a finishing agent, for. B. an area with the dimensions 2 x 2 to 10 cm or 4 x 1 to 10 cm. For example, circular areas printed on a paper may have a diameter of 1 mm to 10 cm.

The method according to the invention can be integrated into the papermaking process. Thus, for example, it is possible to print the still wet paper with a finishing agent and then dry the paper thus treated and optionally heat it to a higher temperature (170 to 200 ° C) to crosslink the printed finishing agent. However, it is also possible to print on the paper during the drying process or afterwards with a finishing agent, to dry the printed material and, if necessary, to crosslink it. The paper products may be similarly printed during or after manufacture with at least one finishing agent.

As papers which are equipped according to the invention, preferably all types of paper, in particular base papers into consideration. By paper products are meant, for example, packaging papers, corrugated board, wallpaper, cardboard and laminates, for example, from a composite of cardboard or paper and at least one film of a thermoplastic material. For example, cellulose fibers of all kinds, both natural and recovered, in particular recycled paper fibers, which are mostly used in admixture with virgin fibers, can be used to make the papers and paper products. Fresh fibers or fresh fibers are to be understood as meaning cellulose fibers which have hitherto not yet been processed into a paper product or which have not yet been dried. Suitable pulps for the production of the pulps are all qualities customary for this purpose, for example wood pulp, bleached and unbleached pulp and pulps from all annual plants.

Wood pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure groundwood, semi-pulp, high yield pulp, and refiner mechanical pulp (RMP). As pulp, for example, sulphate, sulphite and soda pulps come into consideration. Preferably, unbleached pulp, also referred to as unbleached kraft pulp, is used. Suitable annual plants for the production of pulps are, for example, rice, wheat, sugar cane and kenaf.

The paper or paper products according to the invention are printed according to the pattern with a finishing agent. As a finishing agent, at least one agent is used which increases the stiffness of paper. These agents usually also increase the dry and / or wet strength of paper and paper products at the same time. Other finishing agents are conventional dry strength agents and / or wet strength agents for paper.

In order to increase the rigidity of paper and paper products, the invention preferably uses a thermally curable binder from the group of urea-formaldehyde adducts, urea-glyoxal adducts, melamine-formaldehyde adducts, phenol-formaldehyde adducts, one- and two-component systems based on epoxy resins, polyurethanes or isocyanates, polyacrylates, polymethacrylates, styrene- (meth) acrylate copolymer dispersions and / or styrene-butadiene- (meth) acrylic acid copolymer dispersions. In some cases, the use of mixtures of at least two reactive materials of interest e.g. Mixtures of melamine / urea-formaldehyde condensates. The reactive materials may be present as an aqueous solution or as an aqueous dispersion. In this case, transitions between solution and dispersion are possible. When using dispersions, for example, the average particle diameter of the polymer particles dispersed in water is below 1 μm, preferably below 500 nm and most in the range of 10 to 100 nm.

1. (i) mindestens einer reaktiven Substanz, die ein Polymer bildet,
2. (ii) gegebenenfalls mindestens einem C_1-5-Alkohol, mindestens einem Polyol oder deren Gemischen und
3. (iii) mindestens einem Katalysator

bestehen kann.The aqueous solution and / or dispersion thus contains, for example, a group of a reactive, crosslinkable material which consists of

1. (i) at least one reactive substance which forms a polymer,
2. (ii) optionally at least one C _1-5 -alcohol, at least one polyol or mixtures thereof and
3. (iii) at least one catalyst

can exist.

Examples of (i) a reactive substance forming a polymer are urea-glyoxal adducts and derivatives thereof, eg, 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (hereinafter called "DMDHEU"). When printing on paper or paper products, it can be used either alone or together with (ii) at least one C _1-5 -alcohol, a polyol or mixtures thereof. If one uses 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinon-2 together with an alcohol and / or a polyol as a finishing agent, correspondingly modified 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 arise (hereinafter referred to as "mDMDHEU"). Such compounds are for example from the US-A 4,396,391 and the WO 98/29393 known. These are reaction products of 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 with at least one C _1-5 -alcohol, at least one polyol or mixtures thereof.

The compounds of group (ii) include C _1-5 -alcohols, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and n-pentanol, preferably methanol, and polyols, such as Ethylene glycol, diethylene glycol, 1,2- and 1,3-propylene glycol, 1,2-, 1,3- and 1,4-butylene glycol, glycerol, trimethylolpropane and polyalkylene glycols such as polyethylene glycol, polypropylene glycol, block copolymers of ethylene glycol and propylene glycol. Preference is given to polyethylene glycols of the formula HO (CH ₂ CH ₂ O) _n H where n is from 3 to 20 and diethylene glycol.

To prepare modified 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (DMDHEU), DMDHEU and the monohydric alcohol and / or the polyol are mixed, the monohydric alcohol and / or the polyol being in an amount of each 0.1 to 2.0 molar equivalents, based on DMDHEU, are used. The mixture of DMDHEU, monohydric alcohol and / or polyol is reacted, for example, at temperatures of 20 to 70 ° C and a pH of 1 to 2.5, wherein the pH after the reaction is adjusted to 4 to 8.

Under (i) a reactive substance which forms a polymer, both urea-formaldehyde adducts and urea-glyoxal adducts and their derivatives are to be understood. The following compounds may be mentioned by way of example: dimethylolurea, bis (methoxymethyl) urea, tetramethylolacetylenediurea, methylolmethylurea and 1,3-dimethyl-4,5-dihydroxyimidazolidinone-2, 1,3-bis (hydroxymethyl) imidazolidinone-2 or mixtures thereof. These compounds of group (i) may also be used as finishing agents in the presence of (ii) at least one C _1-5 -alcohol, at least one polyol or mixtures thereof. Suitable alcohols and polyols have already been mentioned above. Preference is given to methanol, diethylene glycol or mixtures thereof.

The aqueous solution of the finishing agent contains the reactive compounds of group (i) and the compounds of group (ii), for example, in one concentration from 1 to 70 wt .-%, preferably 10 to 60 wt .-% and in particular 20 to 60 wt .-%. The impregnating agent preferably contains 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (DMDHEU) as a compound of group (i).

The finishing agent always contains a catalyst (iii) apart from (i) and optionally (ii). Suitable catalysts (iii) are, for example, metal salts from the group of metal halides, metal sulfates, metal nitrates, metal tetrafluoroborates, metal phosphates or mixtures thereof. Specific examples of (iii) are magnesium chloride, magnesium sulfate, zinc chloride, lithium chloride, lithium bromide, boron trifluoride, aluminum chloride, aluminum sulfate, zinc nitrate and sodium tetrafluoroborate. The compounds mentioned can be used either alone or in admixture as a catalyst.

Further suitable catalysts (iii) are ammonium salts such as ammonium chloride, ammonium sulfate, ammonium oxalate, diammonium phosphate or mixtures thereof. In addition, as a catalyst organic and / or inorganic acids can be used. Examples of these are maleic acid, formic acid, acetic acid, propionic acid, citric acid, tartaric acid, oxalic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, boric acid or mixtures thereof.

The compounds of group (iii) used are preferably magnesium chloride, zinc chloride, magnesium sulfate, aluminum sulfate or mixtures of these compounds. Particularly preferred is magnesium chloride.

The catalyst (iii) is, for example, in a concentration of 0.1 to 10 wt .-%, preferably 0.2 to 8 wt .-%, particularly preferably 0.3 to 5 wt .-%, based on the components (i ) - (iii) of the reactive material.

Of the products described above, which contain condensed formaldehyde, in particular low-formaldehyde condensation products are used. Low-formaldehyde should be understood in the present context that the reactive materials do not contain significant amounts of free formaldehyde and that no substantial amounts of formaldehyde are released during drying or curing of the cellulose fibers or paper products treated therewith. In general, such reactive materials contain <100 ppm formaldehyde.

Other reactive materials which react with themselves and / or cellulose fibers with crosslinking are formaldehyde-free, thermally curable binder into consideration. Such binders are described, for example, in the following documents, namely US 4,076,917 . EP-A 0 445 578 . EP-A 0 583 086 . EP-A 0 651 088 . WO 97/31036 , Page 4, line 12 to page 12, line 14, WO 97/31059 , Page 2, line 22 to page 12, line 5, WO 97/31060 , Page 3, line 8 to page 12, line 36,

DE-A 199 49 591 , Page 3, line 5 to page 7, line 38, WO 01/27163 , Page 5, line 34 to page 22, line 2 and the off DE-A 199 17 965 known radiation-curable binder.

Thermally curable binders other than the binders described in the above-mentioned references are all curable binders which are described, for example, for solidifying fibrous webs in the literature and / or which are used for this purpose in practice, such as thermosetting resins based on phenol and formaldehyde, the abovementioned melamine-formaldehyde and urea-formaldehyde resins, urea-glyoxal resins and in particular formaldehyde-free one and two-component systems based on epoxy resins or polyurethanes, polyacrylates, polymethacrylates, polyvinyl acetates, styrene-acrylate copolymer Dispersions, styrene-methacrylate copolymer dispersions, styrene-butadiene (meth) acrylic acid copolymer dispersions and mixtures of said dispersions with a mixture of a polycarboxylic acid and a polyhydric alcohol as a crosslinking component.

1. (a) einem Polymerisat, das durch radikalische Polymerisation erhältlich ist und das zu 5 bis 100 Gew.-% eines ethylenisch ungesättigten Carbonsäureanhydrids oder einer ethylenisch ungesättigten Dicarbonsäure, deren Carbonsäuregruppen eine Anhydridgruppe bilden können, einpolymerisiert enthält und
2. (b) mindestens einem Alkanolamin, das mindestens zwei Hydroxylgruppen im Molekül und/oder mindestens einem mehrwertigen Alkohol enthält.

Examples of preferred finishing agents are thermally curable binders in the form of blends of

1. (A) a polymer which is obtainable by free-radical polymerization and which contains from 5 to 100 wt .-% of an ethylenically unsaturated carboxylic acid anhydride or an ethylenically unsaturated dicarboxylic acid whose carboxylic acid groups can form an anhydride group, in copolymerized form, and
2. (B) at least one alkanolamine containing at least two hydroxyl groups in the molecule and / or at least one polyhydric alcohol.

Specific examples of such mixtures are aqueous solutions containing about 40 to 60% by weight of solids and / or dispersions of a copolymer of 80% by weight of acrylic acid and 20% by weight of maleic acid having a molecular weight M _w of 15,000 to 900,000 μm Combination with triethanolamine or aqueous solutions of a copolymer of 55% by weight of acrylic acid and 45% by weight of maleic acid in combination with triethanolamine. These binders may optionally contain an esterification catalyst and / or a bound phosphorus-containing compound such as hypophosphorous acid as a reaction accelerator.

• 50 bis 99,5 Gew.-% mindestens einer ethylenisch ungesättigten Mono- oder Dicarbonsäure,
• 0,5 bis 50 Gew.-% wenigstens einer ethylenisch ungesättigten Verbindung aus der Gruppe der Ester von ethylenisch ungesättigten Monocarbonsäuren und den Monoestern und den Diestern ethylenisch ungesättigter Dicarbonsäuren mit einem mindestens eine Hydroxylgruppe aufweisenden Amin und
• bis zu 20 Gew.-% eines anderen Monomeren.

The copolymer (a) described above may, for example, also be composed of

• From 50 to 99.5% by weight of at least one ethylenically unsaturated mono- or dicarboxylic acid,
• 0.5 to 50 wt .-% of at least one ethylenically unsaturated compound from the group of esters of ethylenically unsaturated monocarboxylic acids and the monoesters and the diesters of ethylenically unsaturated dicarboxylic acids having at least one hydroxyl-containing amine and
• up to 20% by weight of another monomer.

Thermally curable, aqueous compositions containing at least one copolymer (a) and at least one alkanolamine or higher-functional β-hydroxyalkylamine and / or at least one polyhydric alcohol may optionally additionally contain at least one surfactant.

• Polycarbonsäuren wie Polyacrylsäure, Polymethacrylsäure, Copolymerisaten aus Acrylsäure und Maleinsäure, Copoylmerisaten aus Methacrylsäure und Maleinsäure, Copolymerisaten aus Ethylen und Maleinsäure, Styrol und Maleinsäure, oder Copolymerisaten aus Acrylsäure oder Methacrylsäure und Estern von Acryl- oder Methacrylsäure mit vorzugsweise einwertigen 1 bis 24 C-Atome enthaltenden Alkoholen, wobei die Polycarbonsäuren einen K-Wert von 50 bis 100 (gemessen in nicht neutralisierter Form der Polycarbonsäuren nach H. Fikentscher in Dimethylformamid bei 25°C und einer Polymerkonzentration von 0,1 Gew.-%) und
• mehrwertigen Alkoholen wie Trimethylolpropan, Glycerin, 2-Hydroxymethylbutandiol-1,4 oder Polyvinylalkohol und/oder mehrwertigen Aminen und/oder Alkanolaminen.

Other thermosetting binders useful as finishing agents are based on aqueous mixtures of

• Polycarboxylic acids such as polyacrylic acid, polymethacrylic acid, copolymers of acrylic acid and maleic acid, copolymers of ethylene and maleic acid, styrene and maleic acid, or copolymers of acrylic acid or methacrylic acid and esters of acrylic or methacrylic acid with preferably monovalent 1 to 24 carbon atoms containing alcohols, wherein the polycarboxylic acids have a K value of 50 to 100 (measured in unneutralized form of the polycarboxylic acids according to H. Fikentscher in dimethylformamide at 25 ° C and a polymer concentration of 0.1 wt .-%) and
• polyhydric alcohols such as trimethylolpropane, glycerol, 2-hydroxymethylbutanediol-1,4 or polyvinyl alcohol and / or polyhydric amines and / or alkanolamines.

Polycarboxylic acids, polyhydric alcohols, alkanolamines and polyhydric amines are preferably used in amounts such that the number of acid function of the total number of alcoholic hydroxyl and amine functions is equivalent, see. EP-A 0 445 578 , Also useful are crosslinkable materials consisting of an aqueous solution of a polycarboxylic acid (homo- or copolymer) preferably having a molecular weight M _w of 10,000 or lower and a polyol such as triethanolamine and in which the ratio of equivalents of hydroxyl groups to equivalents of carboxyl groups in the Range from 0.4: 1 to 1.0: 1, cf. EP-A 0 990 727 ,

In the process according to the invention reactive materials are used with particular advantage as finishing agents, which are marketed under the trademark Acrodur® by BASF Aktiengesellschaft. An example of this is an aqueous styrene-acrylate polymer dispersion modified with a polycarboxylic acid and a polyhydric alcohol crosslinking component. It already cross-links at a temperature of 130 ° C. However, in order to achieve high production rates, the crosslinking is preferably carried out at temperatures of 180 to 200 ° C. Another formaldehyde-free binder is commercially available, for example, as a colorless to slightly yellowish, clear, aqueous solution of a modified polycarboxylic acid with a polyhydric alcohol as crosslinking component. It crosslinks e.g. at drying temperatures of about 160 to 180 ° C.

Particularly preferred are formaldehyde-free reactive materials containing at least one polycarboxylic acid and at least one polyhydric alcohol and / or alkanolamine or polyhydric amine. Compositions containing these reactive agents may optionally contain other formaldehyde-free polymers, for example polyacrylates sold under the trademark Acronal® by BASF Aktiengesellschaft. The aqueous solutions and / or dispersions of a reactive material used for printing contain the reactive material, for example, in an amount of 1 to 70 wt .-%, preferably 10 to 60 wt .-% and usually 30 to 50 wt .-%.

Compared with the known impregnation processes, the process according to the invention has the advantage that significantly lower amounts of finishing agent are required with approximately comparable properties of the papers and paper products, and thus less expensive manufacture of papers and paper products.

Unless otherwise indicated in the context, the percentages in examples represent percent by weight.

Examples Determination of rigidity

An A4 sheet was printed according to the invention with a finishing agent, dried and air-conditioned for 24 hours at 25 ° C and 60% humidity. The measurements were made at room temperature under the prevailing air pressure. From the center of the DIN A4 sheet printed with a finishing agent according to the invention, a test piece having the dimensions 100 × 100 mm was cut. The test piece was then fixed between two blocks of wood so that 50% of the test piece protruded. The part of the test piece protruding from the blocks was then loaded with weights of 1 to 50 g by placing the weights in the middle of the test piece at a distance of 10 mm from the outer edge. As soon as the end of the test piece protruding from the block reached 25 mm or the weight fell off the paper, the required load in g was measured as a measure of the stiffness.

• Ausrüstungsmittel 1: Mischung aus einer Polycarbonsäure und einem mehrwertigen Amin in Form einer 35%igen wässrigen Lösung (Acrodur® 950L)
• Ausrüstungsmittel 2: Mischung aus einer Polycarbonsäure und einem mehrwertigen Amin in Form einer 35%igen wässrigen Dispersion (Acrodur® D3515)
• Ausrüstungsmittel 3: 70%ige wässrige Lösung eines wärmehärtbaren Harnstoff-Formaldehyd-Harzes (Fixapret® ECO)

The following equipment was used:

• Finishing Agent 1: Mixture of a polycarboxylic acid and a polyvalent amine in the form of a 35% aqueous solution (Acrodur® 950L)
• Finishing Agent 2: Mixture of a polycarboxylic acid and a polyvalent amine in the form of a 35% aqueous dispersion (Acrodur® D3515)
• Finishing Agent 3: 70% aqueous solution of a thermosetting urea-formaldehyde resin (Fixapret® ECO)

Examples 1 to 36 and Comparative Examples 1 to 16

A4 size sheets were each printed with the amounts of finishing agents shown in the following table using the ink jet printing method with the patterns also shown in the table. The sheets printed with finishing agents 1 to 3 were each stored at 140 ° C for 15 minutes to crosslink the polymers. Thereafter, the stiffness of the paper was determined by the method described above. The results are given in the table.

In the table, "line (MD)" means lines printed on the A4 sheet, which are in the machine direction of the sheet in papermaking, and "line (CD)" lines which are transverse to the machine direction.

In Comparative Examples 1 to 6, water in the print patterns indicated in the table was printed on the sheet, and the thus-treated sheet was dried each before the determination of rigidity. table Example no. Equipment Agent No Solids content [%] Printed pattern Printed quantity [g / m ² ] Stiffness in the machine direction Stiffness across machine direction 1 1 12.5 Line (MD) 5 15 1 2 1 12.5 Line (CD) 5 1 20 3 1 12.5 spiral 5 7 6 4 1 12.5 Concentric circles 5 7 7 5 1 12.5 square 5 10 1 6 1 12.5 diamond 5 20 9 7 1 25 Line (MD) 15 18 1 8th 1 25 Line (CD) 20 1 16 9 1 25 spiral 15 12 12 10 1 25 Concentric circles 15 12 12 11 1 25 square 20 12 1 12 1 25 diamond 15 22 22 13 2 12.5 Line (MD) 5 17 1 14 2 12.5 Line (CD) 5 2 23 15 2 12.5 spiral 5 14 12 16 2 12.5 Concentric circles 4 17 17 17 2 12.5 square 5 25 6 18 2 12.5 diamond 4 7 12 19 2 25 Line (MD) 12 12 7 20 2 25 Line (CD) 15 1 24 21 2 25 spiral 14 19 19 22 2 25 Concentric circles 20 21 19 23 2 25 square 14 > 30 4 24 2 25 diamond 8th 27 9 25 3 12.5 Line (MD) 4 7 1 26 3 12.5 Line (CD) 5 1 5 27 3 12.5 spiral 4 6 7 28 3 12.5 Concentric circles 4 6 6 29 3 12.5 square 4 8th 1 30 3 12.5 diamond 4 8th 4 31 3 25 Line (MD) 20 16 1 32 3 25 Line (CD) 16 1 17 33 3 25 spiral 17 12 12 34 3 25 Concentric circles 15 9 8th 35 3 25 square 11 19 2 36 3 25 diamond 8th 10 4 Comparative Examples 1 water Line (MD) 0 6 1 2 water Line (CD) 0 6 1 3 water spiral 0 6 1 4 water Concentric circles 0 4 1 5 water square 0 5 1 6 water diamond 0 5 2 7 1 entire area 5 5 1 8th 1 entire area 20 7 2 9 1 entire area 100 22 20 10 2 full surface 5 4 1 11 2 entire area 20 7 2 12 2 entire area 100 25 23 13 3 entire area 5 5 1 14 3 entire area 20 6 3 15 3 entire area 100 20 23 16 Unprinted and uncoated test paper 6 1

Claims (12)

1. A process for finishing paper and paper products by treating the surface of paper or paper products with at least one finishing agent, wherein at least one finishing agent is applied in the form of a pattern to the top and/or bottom of paper or paper products, and wherein the finishing agent used is at least one agent which increases the stiffness of paper.
2. The process according to claim 1, wherein the finishing agent is applied with the aid of a printing process to the top and/or bottom of paper or paper products.
3. The process according to claim 1 or 2, wherein the finishing agent is printed on the top and/or the bottom of paper or paper products by the screen printing, inkjet printing, flexographic printing or offset printing process.
4. The process according to any of claims 1 to 3, wherein the finishing agent is printed on the top of paper or paper products by the inkjet printing process.
5. The process according to any of claims 1 to 4, wherein an engine-sized paper or paper product is used.
6. The process according to any of claims 1 to 5, wherein the finishing agents are printed in the form of a grid or of a rhombus or in spiral, circular, two-dimensional, strip or dot form on the top and/or bottom of paper or paper products, the pattern printed on being present in each case in ordered or in random form.
7. The process according to any of claims 1 to 6, wherein the finishing agent used is a strength agent.
8. The process according to any of claims 1 to 7, wherein the finishing agent used is a dry strength agent and/or a wet strength agent for paper.
9. The process according to any of claims 1 to 8, wherein the finishing agent used is at least one heat-curable binder from the group consisting of the urea-formaldehyde adducts, urea-glyoxal adducts, melamine-formaldehyde adducts, phenolformaldehyde adducts, one- and two-component systems based on epoxy resins, polyurethanes or isocyanates, polyacrylates, polymethacrylates, styrene/(meth)acrylate copolymer dispersions and/or styrene/butadiene/(meth)acrylic acid copolymer dispersions.
10. The process according to any of claims 1 to 8, wherein the finishing agent used is at least one heat-curable binder comprising a mixture of

    (a) a polymer which is obtainable by free radical polymerization and which comprises from 5 to 100% by weight of an ethylenically unsaturated carboxylic anhydride or of an ethylenically unsaturated dicarboxylic acid whose carboxyl groups can form anhydride groups, incorporated in the form of polymerized units, and

    (b) at least one alkanolamine which comprises at least two hydroxyl groups in the molecule and/or at least one polyhydric alcohol.
11. The process according to any of claims 1 to 8, wherein the finishing agent used is at least one heat-curable binder comprising an aqueous mixture with at least one polycarboxylic acid and at least one polyhydric alcohol and/or at least one polyfunctional amine and/or an alkanolamine.
12. A paper or paper product which in each case is obtainable by the process of claims 1 to 11.